SNTF AERIC 46
November
Volume 7
Nuber 5
Health Care Reform Rashi Fein
If any national issue rivals emploment and the gr econoic outloo it is health care. More than mion mericans lac mecal srance even though the u spends more of its gross domestic product on health care than does any other developed nation. The solution the author proposes is a radically new strctre that provides universal nsurance and contas escalating costs.
4
The Exansion Rate and Size of the Uverse Wendy L Freedman
The holy grail of cosmology is an accurate determination of the Hubble constant the rate at wch the uverse is eanding. Present measrements dier by a factor of twoa door wide enough to accommodate several divergent hypothe ses about the ltimate fate of the nverse. New tecques that promise to ree the calcation should aect the ente eld of extragalactic astronomy.
62
The isk of Software Bev Littlewood and Lorenzo Strigini
Glitches n computer programs are aoyng when they cost an hour's wor. critical appications such as telephone networs nuclear power plants or missle gdance systems insious faults can spell disaster. ince even the best proof caot pinpot the extent of verabiity the authors arge that the use of computers should be restricted wherever safety is a prmary consideration.
SCIECE I PICE
Visualizing Biological Moleces Arthur] Olson and David S. Goodsell
The form of a proten strongly luences its ncon so creang accrate pictures of biological molecules is an portant goal. It has been magcently achieved by the power of the computer to create ages that combe art and engineerg.
The Big Bang of al Evolution Jefey S. Levinton
About 6 ilion years ago a remarable burst of evolutionar creativity simul taneously gave rise to the basic body plans of all mode mticelllar amals. y ndamentally new designs for livng creates seem not to have emerged from the evolutionary cauldron since then is one of the great mysteries of biolo g. everal possible elanations for the stabity come up short.
© 1992 SCIENTIFIC AMERICAN, INC
Scientifc American (lSSN 0036-8733) publshed monthly by Scientific American, Inc., 41 Madson Avenue, New York, N.Y. 100171111. Copyright © 1992 by Scientfic American, Inc. All rights reserved. Prnted in the U.S.A. No part of this ssue may be repoduced by any mechanical, photographc or eectronic process, or in the form of a phonogaphic ecordng, nor may t be stored n a retreva system, transmitted or otherwse copied for pubic or prvate use without wrtten permission of the publisher. Secondclass postage paid at New York, N.Y, and at addtional mail ing offices. Authorzed as second-class mal by the Post Oice Department, Ottawa, Canada, and for payment of postage in cash Canadan ST No. R 127387652. Subscripton rates: one year $36 (outside . and possessons add $11 per year for postage). Subscription inquiries: .S. and Canada 800-333-1199; other 51 5-2477631. Postmaster: Send address changes to Scien tific American Box 3187, Harlan, Iowa 51537. Reprints availabe: write Reprint Department, Scentfic American, Inc., 415 Madison Avenue New York, N.Y. 10017·1111, or fax: (212) 3550408.
94
nguistic Origins of Native Aericans Joseph H. Greenberg and Merritt Ruhlen
The st Native mericans to settle in the New World brought with them their genes and their langages. A comparative aysis of the many native tonges reveals tee distnct langage faes, inicatng that the mericas were origi nally poplated by three successive waves of igration from Asia. 100
Astronomy in the Age of Columbus Owen Gingerich
Colbus's discovery that a vast, unknown landmass lay between Europe and Asia vividly demonstrated that ancient knowledge of the world was woely in complete. The geograpic revolution that foowed paved the way for orthodox astronomical ideas, ncluding the sun-centered cosmology of Copecus. 06
TRED I MICROECHIC
Micron Machations Ga St, sta writer
Researchers are borrong cipmakng technology to produce an array of mo tors, gears and other mechaical parts so small as to be dwarfed by the pot of a p or held n the pncers of an ant More than displays of techical rtuOSity, these nuscule gadgets may have uses rangng from the fabrication of devices capable of extremely dense data storage to strments for icrosgery
DEPARTMENTS 6
Letters
Science and the Citizen For rent: Rus si spy ple .... How bacteria resist drugs .. Stear oscillations .. Too much industrial poli ? Sneaker spl . Controg chaos pumps up a laser. A cel trsplant controversy ... POF Posopher Karl Popper
Hubble's ehanced image .. Defendg expert itnesses
50 d 100 Years Ago 94: The price of success in medicine is ve years of life.
128
e ate Scienst Plottg the period of Cepheid variable stars
8
Science and Business 132 Makg ork work .. More nds for Sematech? . Biotecology tacles second messengers . Arcial tel gence n drg development ... A sound solution for refrigerators .. NIC CONOMIT When the poor are good redit risks
Books The st accountants . Bding cheistry . Structural failres
138
Essay Michael Schulhof Scientists, not M.B. A.'s, should be the captais of industry
5 © 1992 SCIENTIFIC AMERICAN, INC
THE COVER mage of an ant wth a ncke gear for a te machne wapped over a eg was taken wth a scag eectron mcroscope The mcrograph was made at the Karshe Nucear Research Center n Germany The gear mcrons n dameter and mcrons hgh was made by a process caed UGA the Ger man acronym for a thographc eectro patng and modng tecque that s used to make mcroscopc mcroscopc mechaca compo nents (see "Mcron Machinatons by Gary Stx page .
THE ILLUSTRATIONS Cover mage by the Insttute for Mcrostructure Tecnoogy Karsruhe Nucear Research Center Computerzed fase coorng by Jason Ker Page
Source
Page
Source
Jason Gotz; courtesy of Mount Sna Medca Center, New York Cty W and Den Mcntyre! Photo Researchers Inc. Jason Ker er Joy Joy Johnson (top) Jason Ker er (bottom) Connectcut Genera fe Isurance Jm Re Wendy L Freedman Kateen Katmes!JSD Jared Scedman Coutesy of Havard nversty Archves D Aubert/Sygma Nucear Eectrc rthur J Oson and Davd S Goodse Rchard E Dckerson, nversty of Cafora Los Angees (lef) Teresa Larsen, CLA (center) rthur J Oson and Davd S Goodse (right) Athur J Oson (top) Vctora A Roberts Research Insttte of Scrpps Cnc (bottom) Athur J Oson (top lef) Ezabeth D Getzo and Joh A. Taer Scrpps Cc (top center) Mchae Pque Scrpps Cc and Davd S Goodse (top right) thur J Oson and Davd S Goodse (bottom lef and center) Athur J Oson and I Sara Man Scpps Cc (bottom right) Patrca J. Wyne Jony Jonson (gph) Patrca J Wynne (drwings) Patrca J Wye
John A . Ender versty of Cafora Santa Barbara Mchae Goodman (lef) Arzona Hstorca Socety brary (center) N W Tera! Photo Researchers Inc
(right)
Jean de Dinteville and Georges de Selve ("The Ambassadors) by Hans Ho
bein reproduced courtesy of the Trustees Natona Gaey London Nuremberg Chronicle; cou tesy of Owen Gngerch Jana Brennng Freball, by Abrecht Ab recht Dler er by permsson of the Syn dcs of the Ftzwam Museum Cambrdge Cambrdge Eectroncs Desgn Center, Department of Eectrca Engneerng and Apped Physcs, Case Western Reseve versty Gabor Kss (top) Stephae Rauser (bottom lef) Berkey Sensor and Actuator Center nversty of Caforna Berkeey (center and bottom right)
Gabor Kss; based on gaph cs from the Department of Eectrca and Computer En gneerng versty of Ws consMadson (top) n versty of Wsconsn (bottom lef) Ne McDonad (bottom right)
Robert Procnow Insttute of Industra Sc ence, nversty of Tokyo (lef) Schoo of Eectrca Engneerng Corne n verty and the Natona Nanofabrcaton Facty (right)
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8
SCIENTIFIC ERICAN November
1992 © 1992 SCIENTIFIC AMERICAN, INC
Gerard Piel
LETTERS TO THE EDITORS
Hobbled Space Telescope
schedule calls for the train to make its 85-mile r in 8 minutestn rounding errors, the same speed as its namesake. Perhaps it is easier for society to make quantm improvements by adopt ing new tecnology, such as maglev, tan by accreting incremental improve ments in esting tecnologies
what alternative Huber has to oer to the legal tradition of calling on epert witnesses in court cases
After reading Eric J. Chaisson's pane gyric to the performance of the Hubble MARCOA J. SO Space Telescope ["Early Results from Rumney, N.H the Hubble Space Telescope, SCENTIFIC ERICAN, June], I was struck by his enthusiasm for that lawed piece of hardware. The Hubble project was a Huber replies: ndivdualsparticularly one such nancial, managerial and teccal as as Nace, who has spent many years lit co for NAA that resulted in the launch E OHEN of an epensive orbiting telescope that Binghamton, NY. igatng Bendectin casescan believe many things, often with sincere convc has a teccal capability far less than tion But if courts are to resolve sci plaed The place to ave found and entic controversies consistently and corrected the fundamental design and Science on the Stand accurately, they must rely less on indi construction errors was in the labora tory, not in orbit or in subsequent com n the essay "Junk Science in the vidual scientists, still less o ndividual Courtroom [SCENTIFIC ERICAN, lawyers and more on the published, puter enhancements peerreviewed, consensus conclusions NAA spent may llions of dollars Je], Peter W uber espouses that cit on Hubble, which ain't chopped liver izens are not capable of honestly evalu of scientic communties Readers nterested n the science of Unfortunately, Hubble' performance ating scientic evdence and deciding an't pt I woder ow much error or the most probable cause of an injury. Bendectn and cerebral palsy may re wisul tg is incorporated in the He essentially wants to stile scientic fer to the FDA' published pronounce computer enhacement of Hubble' thought and any opion that ight ments on Bendectn, to the Institute of Medicne's Medical Professional Liabili not be in the majority lawed imagery? Huber uses as a example the drug and the Delive of Obstetrical Care OBERT C E Bedectin He decnes to point out that (National Academy Press, 1989) and to many epideiologic sties have shon the large body of scientic literature El Tor, Calif a statisticaly signicant association be that those reports cite tween Bendectin and umerous birth defects In fact, the Food and Drg Ad Wi It R on Te? stration ever concluded tat Be Jubling the Genes As a scietist, am fascinated by dectn "id ot cause bth defects The There was a mutation in "Genetic magev tecnology ["i Trains, by truth is that every amal study ever Gary Stx; SCIENTIFIC ECAN, Au done by ayoe other than the manu Algorithms, by Jon H Holland [SCI gust] As a commuter, I remain un facrer showed eects, from heart de ENTIFC ERIC, July], a otherwise impressed The goal of transportation fects to hernias ad issng mbs. The fainatng introduction to computer planers should be to buid hgh-speed company's ow stdies also showed an programs desiged to evolve Chromo soma crossingover, wich leads to the conventiona rail systems capable of eect o rabbits moving commuters etween cities 300 suggest that it would e far better recombation of geetic material, does to 400 iles apart at 180 les per to have "juk science in a courtroom ot occur whe sperm and ova se, as houra reasoable compromse be than no science unless conrmed by stated in the article Rather crossing over occurs durig meiosis, the pro tween the lowcost, lowspeed automo govermental authorities. cess that produces ova or sperm Ts bile and the ig-cost, igspeed air system allows a much greater degree plane f I could ride such a train for B J ACE of genetic recombation, and hece di less tha $120, that is the option Pauson, Nace, Norwind & Sellinger versity, tha would crossg-over at the wuld choose. Maglev wod ave to be Washngton, DC time of ertilizatio equally successfu at balancig cost The relaton of inept practices by ob versus travel tie, ad I am not opti mistic about that prospect stetricians at the time of brth to later My L. AZITA erologic ad motor problems, nclud Department of Human Genetics MICHAEL RBERG ing cerebral palsy, is nown and accept Medical Colege of Virgiia Indianapolis, Id ed in the eld Naturally, in particular Virgia Coonwealth University cases, tere will be contention among Te August issue, wth its excellet experts The main source of "ju sci Al/ letters to the editor may be edit article on maglev, also reported in "50 ece is from those such as uber who ed for length and clari. Because of and 100 Years Ago that on July 4, make blaet pronouncements 1892, the Empire State Express made As a pediatrician and cld psyca the volume of mail, letters cannot be the 81mile r from Rochester to Syr trist with more than 20 years of eld acknowledged individual/y Unsolicited acuse i 74 iutes mtrak now as experience, have seen at rsthand the manuscripts must be accompanied y a a train of the same nae, ad its eects deed y Huber fai to see stamped, self-addressed envelope 10
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HE ONLY BE PED THAT MES A SPOS C GO FASTER.
The brake pedal in the new Mazda R-7 may be the lightest in the world. We made it out of aluminum, then drilled holes in it. W hy go to such extremes? We know what a handful of enthusiasts hav always known. In a pure sports car every ounce counts. That's why we started with a sequential twin turbo rotary engine that's 200 pounds lighter than a comparable piston engine. Which gave us a head start on a weight reduction program nothing short of obsessive (we even trimme the spar plug leads). The result is something that you may never see again. 2789
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SCIENCE A THE CITIZEN
Declassifed Russian geophysicists seek new ways of making a living ot so long ago a Russian spy plane bristg with detectors y ing into the heart of the U.S. air defense network would have sent ght er jets scramblng. But this past Sep tember 12, radar operators srugged when a massive Ilyushn 76-MD "ling laboratory touched down at Denver's Stapleton airport, just a few nutes' lying time from, among other places, the North American Aerospace Defense headquarters n Cheyenne Mountain and the spysatellite station at Bucey A National Guard Base. In case any further proof was need ed that the cold war is over, the 3 2 sci entists and 14 crew members, many of them former employees of the Sovi et miltary complex, then threw open the cargo doors, brought out the vodka and nvited all comers to crawl over the huge craft and inspect its gear. Cam eras welcome. The landmark visit was the cul nation of a seven-month eort by War ren T. Dewhurst, chef geophysicist of the coastal and geodetic srvey of the National Oceanc and Atmospheric Admstration NOA Dewhrst has been forging ls th his colleagues in the former evil empire for over a year and rst saw the lying laborato ry ts past February at the Gromov Flight Testg Institute near Moscow. It was then, Dewhurst says, that he conceived of bringing it to the U.S. as an advertisement for the Geophysical Tecology Transfer Initiative that he was planning with Norman Hartll, a geophysicist at the Colorado School of Mines in Golden, and Serguej N. Do maratsj, a researcher at the St. Peters bg Institte for Terrestrial Magnetism, Ionosphere and Radio Wave Propaga tion Tomas G. Musiniantz of the Insti tte for Precise Instrentaton in Mos cow suggested eisting Russian scien tists for the trip to Colorado. Dewhurst, Hartll and Domaratskj are connced that U.S. and Russian geophysicists have a lot to teach one an other because they have worked sepa rately for decades. The principal obsta cle to cooperation has been the sensing technologies they use, wich until re-
N
16
MILITARY AND CILN U.S. scientists examine Russian yushin 76-MD "fying laborato at Denver's Stapleton aiort Phoo: Har R. Olsson.
cently were classied. Although surveys of nute variations in the earths mag netic and gravitational elds can be used to locate inerals, oil and gas, magnetic-eld disturbances over the ocean can also reveal the presence of submarines. Gravity-eld maps can be used for accurate targeting and can pin pont ndergrond caverns that conceal issiles. The magnetometers on the specialy modied lyushin are of mitary deign, accorng to Hartl, who says the craft is "baically a Soviet military antisub marine warfare plane. The fourjet en gine acraft, which has a range of 8,200 ometers and can accoodate 40 tons of cargo, carries synthetic-aperture imaging radar as well as gravimeters. NOA' leet of sips and small aircraft carry no such nstruments "Our sips go out and measure depth, and thats it, Dewhurst says refully. Dewhurst says he does not embar rass s Russian counterparts by ask ing them about litary missions they may have lown. "If tis collaboration is mutually acceptable, we sould allow it to happen, he says. The U.S. military was not so eager, however. Securing landing rights for the Ilyshin in Den ver took a major eort, and Dewhurst
SCIEIFIC ERC November 1 992
also ran into "remnants of the cold war in the State Department. he day before the airplane left Moscow, many of the crew and scientists still had not received visas to enter the U.S Once on the ground at Stapleton, the Russian scientists spent the next four days at the Colorado School of Mines makng sales pitches to US geophysi cistsand to sharpeyed litary types from places like the Naval Surface War fare Center nd the Defense Mapping Agency. With military support drying up, the Russians were unabashed about making their appeas. "We have the ex perience, we have the means, we have the desire, said Musiantz, winding up an overview of the lng laborato ry "What we are a little short of is the money. Among the systems the Russians de scribed was a powerl LiA (a laser based radar that can be used to see be low the sea face) that employs a 300owatt coppervapor laser Accordng to Vktor I. Feigels of the nstitte of Fne Mechanics and Optics St. Peters burg, the system can provide usel in formation on depths down to 20 or 3 0 meters. Jon Davis of the Nava A War fare Center n Warster, Pa., says the US. av might cooperate wth the Rus
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sians on LD work because I hink hey are a lile beer han we are in his area." Mny of he observers agreed ha the Russians' relatively unsopisicaed elecroic equipmen had forced hem o solve problems in ngeious ways. They described many eciques for improing aboe graviy seys, for example. They have ousanding heoreticians," says Richard]. Wold of GWR Insumens in San Diego, which man ufacures gravimeers Soe observers were disapponed. lhough he isiors described onboard compung for processig synheticaperure radar daa, hey didn' show any really ice synheicaperure images," says ndrew Ochadlck of he Naval A Warfare Cen er. Bu he added, I'm going o lea o speak Russian." The Golden conference was he rs formal even under he rbric of he Geophysical Transfer iiaive. The nex be a coference 1993 n S Peersburg, where U.S. geophysiciss w describe heir research In addiion, Dew hrs and Domaraskj have creaed a permanen fondaion in S Peersbrg dedicaed o join geophysics projecs Alhough he foundaion is brand new, Dewhurs already has one proj ec for i in mind. He is rying o up support for acqiring (he is skechy on nancial deais) a Russian lying boa" designaed he Beriev A40 Two prooypes already exis The aircraf wold be equipped wh gravimeric, LAR and oher sens and wod be used for srveys n polar regions or anywhere else The arplane's long range and amphibious capabliy make i he idea choice, Dewhurs and Do maraskij beeve, because i cod sur vey from he air and hen land a sea o make grod rh" easuremens The researchers aeady have one sey mapped ou: he recen nomansland of he Berng Srai, where, hey agree, here is a unel jus waiing o be bui The srech is a mere 60 eswih an island in he ddleand he waer is shalow, Dewhrs says. I he meanime, Dewhrst wold be delighed o see he lyusn conducng geophysical surveys in he US s onboard LDs make i ideal for ar and waerqualiy moorg, Har ponts ou. And o anyone who nds ncreble he idea of he U.S. A Force's alowing he ulipurpose surey arplane o y fourkomeerspaced parllel es over Kansas h is sensors swched on, Dewhurs has a ready reply. A monh ago he miliary wasn't keen abou i landing Colorado," he says, gesuring o he airplane on he armac Bu here i is" Tim Beardsley 18
Paradise Lost? Microbes mount a comeback as drug resistance spreads y a few years afer pecil lin moved ino despread se drg he 1940s came he rs repors ha some baceria had grown resisan. nd as ore powerful ani bioics such as srepomycin, eracycline and chloramphecol were developed, baceria evolved resisance o hem, oo. Today baceria and gi ha are resisan o once eecive drugs are causng deahs and drig up he medi ca coss all over he world Drug resisance was mosly ignored n he U.S unil recenly because physi cians believed hey had access o all he anibioics hey gh need, says Suar B Levy, a researcher a Tufs Uni versiy They wee wrong Drug resisance has been found n raly every ye of microbe ha has been fough wih anibioics. Tha covers everyhing from foodborne pahogens sch as Salmonella o sexally ransmied organsms such as Neisseria gonorrhoeae Srgical paiens are now dying in US hospials from wond infecions caused by enerococcal baceria resisan o several dieren drugs These are people who should probably no be dying," says David Saes, a physician a he Veerans Adsraion Medical Cen er Cleveland hough an infecion ha is resis an o one drug can ofen be cured by wiching o a dieren (and sually more eensive) one, increasing num bers of pahogens are resisan o sever al drgs During he 1980s, obreaks of mlidrugresisan dysenery, chol era and pneumona, o name jus a few
O
examples, were recorded around he world. nd in he pas wo years he US medical esablishen has been shaken by he emergence of muidrugresisan Mycobacterium uberculos, a scourge ha many physicians assmed had been quashed in developed coun ries During 1991, uberclosis resis ance o one or more drus was repored 36 saes. Resisance of TB o drgs represens an alarng rea because, ke many oher serious infecions, he principal risk behaior for acquing TB fecion is breaing," sae Barry R. Bloom and Chrisopher]. L Murray in a recen is sue of Science Bloom, an invesigao a he Aber Ensein College of Medicine he Brox, and Mrray, who works a he Harvard School of Public Healh, ou ha TB is he leading case of deah from infecious disease worldwide, wih eigh million new cas es and 29 ion deahs every year. n he U.S., the nmber of TB cases has been increasing since 1985, wih more han 26,000 repored in 1991 And in New York Ciy, one hird of all cases esed in 1991 were resisan o one or more drugs Uncomplicaed TB can be cred wih a sxmonh corse of anibioics, bu he oulook for mli drgresisan cases is bleak Those re sisant o wo or more ajor anibioics have a faay rae of arod 50 percen; paiens infeced wih he hman uodeciency us (HV), he caus aive agen of ADS, sccumb in ony a few weeks Accordig o Bloom and Murray, aemps o rea people who are posiive may have pered he eergence of M. tuberculosis resisan o virually all aniTB drugs The dis ease is also spreading rapidly n people no infeced h H Many drugresisan baceria have
How Tuberculosis May Develop Drug Resistance SUSCEPTBLE 1 usceptiblty gene (red on plasmid (circle) produces enzyme (green).
RESSTNT
SCIENTIFIC ERICN November 1 992
2 Drug isoniazid (blue) is harmess untl enzyme breaks it nto active form
3 he active form of isoniazid destroys the bacteral cell.
usceptibility gene s deleted by mutaton, and so no enzyme is produced. soniazd remains in inactve form, and the cell survives
perfect addi tion or an ideal gi for friends family and colleagues.
It' ", <
y
at e bo.
genes that enable them to produce en zymes that either destroy paticar an tibiotics or pump them out of the bac teal cels. Because bactera pass genes not ony between members of the same speces but also between dierent spe ces, genes that confer esstance to a widely used dg spead rapidly. Until tis summe, the mechasm of dug resistance to TB was uown. Yg Zhang of the Hammesmith Hos pital in London and is colleages ds covered the basis fo resistance to a TB drug used fequently in treatment, iso nazid. Surpringly, resstance in this instance seems to result from te loss of a gene, one on a plasmd, or loop of DNA. The gene probably allows the TB bacterium to process isoazid into an active fom. That ding suggests some pomising avenues for esearch. But de veloping a new dug usually takes at least seven yeas, Saes points out. Yet drug companes have been scal ing back research on antibiotics and othe antimicrobials and turing in stead to anticancer and antval dgs. So when drug-esistant TB st came to national attenton n 1991, there was no U.S. source fo two TB drgs that were fomerly used to treat the dis ease, streptomycin and -amno sal cylate sodum homas L. Copman, head of bio
technology of the Pharmaceutical Man ufacters Assocation, places the bame on the "dismal amount being spent on drug resstance by the Natonal Insti tutes of Health. According to Jon R. La Montagne of the National Institute of Allergy and nfectous Diseases, the amount that institte spent on esearch related to drug resstance in 1991 was $9.7 illion up from $6.7 milion in 1988. But Slaes says much of that to tal is only peripheally related to the practcal problem. nd although the I has sponsoed two wokshops on drug resistance snce 1989, the agency declined to support a major new re search eort. "If people are going to take t seri ously, the I and the Centers for Ds ease Control will have to rebudget, Bloom says. He charges that the CDC knew of some cases of drugresistant B moe than two years ago and con sderedbut rejcteda progam to eliminate t. "f that had been done, we would have the infrastructre we need now, he says. "The tragedy is you have to have skeletons on the font page of the newspapers befoe people can be persuaded sometg must be done. Physcians are settng up informal networks for moitoring antibotic re sstance. Lev is seeking I funding for a voluntary international data base.
Thomas F. O'Bien and Jon M. Stellng of Harvard Medical School have devel oped a data management program that helps micobiology laboratories track drug-resistant organisms. That eort wch includes posting reports on an intenational network, is supported by the World Health Organization. HO is now helpng several coun tries set up T control programs. n the U.S., the CDC is starting to monitor drug resistance n dierent orgasms, including M. tberculosi De E. Sider of the CDC says the agency wants even tally to obtain data on drug suscepti blity for every case of TB n the U.S., but that moitoring system is not yet g. In the meantme, physicans could ze the spead of drg resistance by not using antibiotcs that are more power ta necessary, says orge Ja coby, an nfectious disease specalst at Massachusetts General Hosptal. About half of all antibiotic use in the U.S is inappropriate, asserts Calin M. Kun who chairs a coittee on antibiot ics for the Infectious Disease Socety of merica. Many pescribed antbotics, he says, are ether more powerful than necessary, used fo longer than neces sary or not needed at all. "Its a cacoph ony, Kuin declares. "We have a long way to go. Tm Beardsley
Brnging Scence to the Bottom Lne
T
he enthsiasm in Washington for steering research toward the bottom line has reached the National Science Fondation (NSF), the traditional mainstay of science nsllied by commercialism Walter E. Massey, the fondation's director, appointed a ble-ribbon com mission in September to "examine ways for NSF to accept an enhanced role in fostering connections between re search and technology The group's indstrial emphais is nderscored by the choice of Robert Galvin, former chief exective officer of Motorola, to serve as co-chair man with William H Danforth, chancellor of Washington University Some advocates of basic research are nwilling to give up withot a ght The American Physical Society is "deeply concerned that the NSF may be wavering in its commitment to basic science, according to spokesman Roert L. Park Physicists plan to make their obj ections lod and clear Massey has been pshing for changes at the NSF for more than a year He cites the end of the cold war, the in creasingly international character of science and the downtrn in U.S corporate research as reasons why the agency, which has a bdget of almost $2 billion, shold reexamine its operation Massey says he favors giving the agency "an expanded portfolio of programs that wold be integrated with ongoing activities and closely aligned with indstry and other government agencies When Massey presented his ideas this past Jne to the
20
SCIENIFIC AERIC
November 1 992
National Science Board, the NSF governing body, the board declined to approve that kind of mission shift with out irst getting it blessed by an otside group The com mission is being asked to nish its report by November, so that whichever administration is in the White Hose next year will have a blueprint for action The grop's recom mendations are likely to nd receptive ears on the Nation al Science Board and in Congress Both bodies have called for more applied research The NSF' navel contemplation comes hard on the heels of a similar effort to develop a strategic plan for the Na tional nstittes of Health, the principal avene of federal spport for basic biomedical research. The NH, with a bd get of some $9 billion, has traditionally spported a mix tre of pre basic research and stdies aimed at speciic diseases Development of the NH plan, which director Ber nadine P Healy initiated more than a year ago, engendered apprehension and otright hostility from some research ers NH sources say Healy's plan has also rn into troble with her political taskmasters at the Department of Health and uman Services, who view it as an attempt to jstify frther increases in the NH' bdget. According to some NH prognosticators, the long-gestat ing strategic plan will be published, with sitable bows to academic freedom as well as the need for commercial de velopment, and then ignored. The commission on the NSF will, presmably, be aiming to ensre that fate does not be fall Massey's plan -Tim Beardsley
lls fr Jrr's Kds Experts argue the merits and safe of human trials
AN INITATION TO SMIT NOMINATIONS FOR THE 99 KNG FAISA INTERNATIONAL PRIZE IN MEDICINE AND SCIENCE The Genera Secretariat of the King Faisal International Prize is pleased to invite universities and spialist research centers throughout the word to nominate quaified candidates for: the King Faisal Internationa Prize in Medicine in the topic of:
«MEDICAL APPLICATIONS OF GENETIC NGINEERING» and the King Faisal Internationa Prize in Science in the topic of:
«MATH� TICS» Nominations shoud meet the foowing requirements:
Nominees must have accompished an outstanding academic work on the Prize tpic benefitting mankind and enriching human progress
2.
Submitted work must be original and published
3.
Ony recognized educational or resrch institutions may make nominations
4.
Each nomination should include: a) a typed list of the nominee's nominated works b) a typed C V detaiing the nonee's academic background experience and publshed works c) ten copies of each submitted work d) three recent coour photos 4"x6" e) the nominee's maiing address including: (1) ofce address teephone number teex fax (2) home address and teephone number Nominations will be evaluated by a Seection C ommitt consisting of highy recognized spiaists in the topic
6
More than one person may share the prize.
The a) b) c)
The a) b) c) The a)
9.
10
nominee's submitted work will not be accepted if: it has been previousy awarded a prize by any internationa organization it is a university degree; it is unpubished
nomination will not be accepted if: t is nominated by individuas or politica parties; t does not meet a the prize conditions; it is received after the announced date prize consists of: a ceriicate in the winner's name containing an abstract of the work that quaifed him/her for the prize; b) a god mal; c) a sum of three hundred and fifty thousand Saudi Riyals ' ( approximatey US $93333 ). e winner(s) nae(s) wi be announced in February 1994 and the prize w be awarded in an officia ceremony at a later date
?
11
The latest date for receiving the complete nomination requirements wil be September 1, 1993
12
No nomination papers or wors wi be returned to the senders whether or not the nominee was awarded the prize.
13.
A correspondence must be sent by registered airmai to: The Gneral Secretariat, King Faisal International Prize P.O Box 22476, Riyadh 4 Kingdom of Saudi Arabia Tel: 4652255, Tlx: 44667 PRIZE , Fax: 46565 Cable JAEZAH
22
SCIENTIFIC ERICAN
Noeber 2
T
his past Labo Day on te Muscu la Dystopy Association (MDA) teleton, Jey Lewis endeed s aual update of te encouaging progess being made against cippling illnesses. Wat iewers migt not ae guessed is tat one area of teapeutic inestigationa form of cell tansplan tation called myoblast tansfeas saply diided muscula dystopy e seaces. Altoug some egad myo blast tansfe as a safe teciue, ot es woy tat expeiments of dubious scientic alue ae exposing young pa tients to unwaanted azards. People jumped too fast fom aimal models into umans" says Heny F. Epstein of te Baylo College of Medi cine a scientic adise to te MDA In a ecent letter to Science, e and more tan two dozen ote muscle eseac es and pysicians called for a geneal moatoium on myoblast tansfes in umans until cetain basic uestions ae been esoled in aimals. I truly beliee tei lette is popa ganda by molecula geneticists intend ed to smea cell tansplantaton" us Pete K Law of te Cell eapy Re seac Foundation in Memphis. Law as epoted te geatest successes wit myoblast tansfeand is wo as dawn te geatest e ey are op posed to it fo fea tat myoblast tans fe w become te teapy instead of gene teapy" e says e disease at te cente of te con toersy is Ducenne's muscula dys topy a genetic disode tat sties about one in eey 3500 boys and caus es pogessie wasting of te muscles ose alicted wit te disease begin to weaen sometime afte te age of e and gadually lose all stengt in tei limbs tey usually die by age 20 wen tei diapagms o eats fail. I te mid1980s geneticists leaned tat Ducene's dystopy is caused by a defectie gene for dystopin, a potein essential to muscle function. Since ten inestigators ae sougt to escue te sic muscles by esto ing te ssing protein. Molecula bi ologists, fo example, ae been tying to deelop a gene teapy tat would insert woing dystopin genes into te muscles Myoblast tansfe is an altenatie ap poac in whic wole cells not just genes ae used. peiments on rodents suggested tat if cells called myoblasts ae injected into dystophic muscles,
they can sometmes save the unhealthy muscle bers by usng wth them and mang dystrop 989 George Karpat o the Montreal Neurological Institute, Law (who was then at the Unversty o Tenessee at Mempis) and others intiated trals on human subects. To date, more than 60 boys have receved myoblast transers Generally, the results o those experments have been underwhelmng ew o the subects have demonstrated any mprovement. Ths past March n Cell Tnsplantation, though, Law announced the best results yet. Usng a patented techque, he and s colleagues nected myoblasts nto the leg muscles o dystropc boys and later measured their unctonal changes. Laws group clams that n the 3 boys tested so ar, 8 percent o the treated muscles became stronger or dd not lose strength Many muscular dystrophy researchers contend that Law's study s seriously lawed Ther prmary complaint s that Law did not use a control group to test whether the gans are llusory. But Law nssts that edcal ethcs prevented m from runnng the knds o con trols s crtcs wanted Law says he dd not nect a placebo nto patents because, n s experience, such nectons accelerate muscle degeneration. He also dd not nect myoblasts into ust one leg of a boy and use the other leg as a control because the mbalance n strength ight cause the boys to all and hurt themselves. The only acceptable control, Law says, was to compare a muscle aganst tsel ater the myoblast nectons. He lkens the comparison to the beoreandater pcures used n commercals or bald ness remedies "A experiment wthout controls s not an experment," Epsten responds. He argues that pharmaceutcal companes have establshed statistcal methods or conducting drug trals that protect human subects wthout nvaldatng the control procedures. Moreover, a control was crtical n Laws experments because some data suggest that cyclosporne, the mmunosuppressve drug given to the boys to prevent them rom reectng the transplanted myoblasts, can cause a transent ncrease n the strength o muscles. Law's s not the only work on myoblast transer that has been crtczed. This past Aprl a team headed by Hel en M. lau o the Stanord Unversty School o Medcne publshed a report n Natue conrmng the ablty o transplanted myoblasts to make dystropn or sck muscles. Yet Erc P. Homan o the Unversty of Pttsburgh
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Scool o edicine, one o te discovees o dystoi, agues tat Blaus esults may be less an tey seem: a enomenon called genetic evesion could cause sick muscle bes to look as oug tey ee making dyston. In any even, oman says, no moe tan about 1 ecent o te bes seemed to ave been eled by e teatment, an eciency too lo to ave teaeutic meaing. Is tis eally success?" e asks. Blau stands by te conclusions o e ae. She emasies a, unlike La's exeiment, es as a contolled, doubleblind sudy; se also agues tat e metods uled out alseositive esults om geneic evesion. Blau believes te etition o a moatoium is misguided bu acoledges tat because te eciency o te myoblast tanse as suisingly lo," e gou is delibeating abou ete uman exeimenaion is e ay to oceed a ts time." Deendes o myoblast tanse exeiments oint ou tat, accoding to te eots, no boy as eve been amed by te ocedue. stein is not eassued. It's extemely inconsistent t all evious exeience it cyclosoine tat no side eects ave been obseved," e says, adding tat ose side eects include kidney ailue and cance e ave no idea ete isks could be uncoveed," e says. e ad oman bot note tat myoblast tanse is imactical o xing at ac tually kills Ducenne's dystoy atienste degeneation o te eat and diaagm. e call o a moatoium, oeve eanest, caies no ocial eigt. e Food and Dug Administation as not yet asseed any juisdicion ove cell tanslantation. e National Institutes o ealt ae not cuently unding any myoblast tanse exeiments in umans. e DA, ic as unded exements, emans oenmded on te subect. e DA is in te business o nding causes and cues," assets Donald S. ood, te DA's diecto o science and ecnology. e association ould neve cut o suot to an aea as long as i eld ose." In ood's oinion, bot uman and aimal exeimens ave value today. e sees te conlict ove myoblas tanse as at o te going ains" all ne tecologies ace. It makes eveyone ok tat muc ade at get ting te ig anse," e says. But e also notes, You must be umble e ace o tis. You must go vey cautious ly od obid you sould do ayting to take even one day o te lie o a cild." -Joh Ree
Stellar Bels Quivering stars bare their inner secrets
T
he discovery that the sun rings like a bell, made early in the 960s at the California Institute of Technology, heralded the new eld of helioseismology. Astronomers who watch oscillations of the solar surface can measure conditions deep wit the sun, in the same way that sismologists monitor earthquake waves to stdy the interior of the earth. In the past few years, researchers have taken that remarkable achievement a step further: they are deducing the internal struc tures of distant stars from subtle vibrations on their surfaces, a techique called asteroseismology. By far the greatest successes in ths eld have come from observations of white dwarf stars, the compact remnants of sunlike stars. Instabilities in the outer layers of some dwarfs set up waves that travel along a star's surface so that the whole star shakes
and shimies," explains Steven D Kawaler of Iowa State Uiversity. Those waves compress the outer layers of the star as they travel, causing certain regions to grow hotter and hence to radiate more intensely. Oscillations therefore show up as complicated but wellordered changes in the brightnesses of wte dwarfs. In the most extreme cases, a star's luminosity can vary by 30 percent. One of the most crucial elements of stellar oscillation observation is that the record must be contuous. In 988 R Edward Nather of the Uiversity of Texas and a number of collaborators established the Whole Earth Telescope, a loose assocition of astronomers around the world dedicated to maintaning roundtheclock coverage of oscillating stars. The latest version of the Whole Earth Telescope, which began work on September 2 , incorporates 13 observing sites, the largest number yet. Some of the most impressive results from the enterprise concern a extreme ly hot white dwarf known oly as PG 1 159035. A group led by D E. Wnget of the University of Texas reported that
PG 59035 oscillates at 25 frequencies having periods from 385 to ,000 seconds long. Hidden wtn those frequencies is a bounty of information about the physical conitions of the star. The star's rotation, for example, causes oscillations that move west to east along the star's surface to exhibit a slightly dierent frequency than do os cillations movng from east to west. The magnitude of the frequency split indicates that the star completes a rotation every .38 days. That information provides clues regarding the evolution of red giants into white dwarfs. Ts is the rst piece of data on what the cores of red giants do," Kawaler says. Asteroseismology is also llnatng other important aspects of stellar evolution theory by revealing the compo sition of white dwarfs. Places where a star's temperatre, density or composition suddely change act to relect and trap internal waves Seismologists exploited the same phenomenon to de duce that the earth is divided into a core, mantle and crust. Silarly, Wnget and his colleaes succeeded in mea suring the trapped oscillations to de
Flotsam Footwear
S
the perpatetic shoes could provde a caibration point for erendipty often comes to the aid of science. An ama computer modes of ocean surface currents. teur astronomer spots a nova, a sherman captures a ngraham then ran a computer hindcast to retrace the coelacanth in his net, a pair of oceanographers map path of the shoes. It was "a perfect itte gettogether, as the ocan currents by monitoring the advance of an acci denta shoe spi . . . . he describes it. His mode showed that the 1 9 90 path of A shoe spil? On May 2 7, 1 9 90 , a freighter was buffeted drift was much farther south tan usua. n certain other by a severe gae n the northeast Pacic Ocean, and ve years, suc as 1 9 82, ocean curents associated with warm water in the tropical Pacic woud have caused most of shipping containers of Nike footgear went over the side. Lke a feet of message-bearing bottes, te 80,00 sneak te soes to dri toward Aaska. The scentc value of the spil has by no means dried ers began washing ashore in Britsh Coumbia, Wasing up. Some of the shoes recenty reached Hawaii, and oth ton and Oregon in eary 1 9 9 1 When Curtis C. Ebbesmeyer of EvansHamlton, a marine ers "shoud be reaching Japan shortly, Ebbesmeyer notes. instruments company in Seatte, and W James Ingraham,Jr., Any additonal shoes that wash ashore wi hep the re of the Nationa Marine Fisher searchers as they expand their study of ocean surface drift to ies Service eard news reports the western Pacc. of the soe spi, they immedi The great shoe spill of 1 99 0 atey realized they had stum as aso had some practica bed across a potentaly usefu efects. Artist Steve McLeod ocean dri experiment. " tried to nd the scientists who were of Oregon as earned $5 6 8 by colecting and seling the tracking down te shoes, but seafaring footwear. And bot nobody was, Ebbesmeyer re Ebbesmeyer and ngraam cas. "t surprised me. are sportng teir own recov Ebbesmeyer contacted his ered Nikes. Ebbesmeyer rec friend ngraham, who moni ommends giving the soes a tors surface currents to de hotwater wash before wear termine teir effects on sal mon migration. Wit the ea ing them; a ong period of drifting may be good for sci ger assistance of a network of ence, but it is bad for comfort. beachcombers, the researc "The shoes are rea stiff after ers recovered about 1 ,30 0 of two years n the ocean, he the shoes. Because the ocation FOOTLOOSE DRIFTER recently washed ashore in Califoia_ Photo: Jackie Cunningham. of te spi was we known, reports. -Corey S. Powell
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termine the interor structure of PG 1 159035. It seems t o have a threelayer composition: a blanket of hydrogen atop helium and carbon shells. More extensive observations will enable the researchers to deduce not only the density of the various layers but ther thcknesses as well. When applied to a whole range of wte dwarfs, that technque w make t possble to rene gcantly the theory of the internal transformatons that occur as stars evolve. Another noteworthy applcaton of asterosesmology s indicating the rate at which white dwarfs cool Such nformation " w tell you how old the oldest whte dwarfs arethat's our ultimate goal," Nather says. Knowng the ages of the oldest dwarfs w reveal the mnmum age of the Milky Way and also may make it possible to learn whether the galax formed all at once or f varous parts coalesced at substantally different tmes.
Accordng to theoretcal models, the coolest known wte dwarfs seem to be about 10 billon years old, another pece of evidence that the uverse caot be only eght bllon years old, as some cosmological observatons mply. Kawaler reports that the observed rate of change in the oscllaton perods caused by coolng is on the right tme scale" expected for hot white dwarfs He is still studying the signs of change on cooler starsa rather dcult task, snce he is looking for an effect amountng to a few seconds over 15 years of data," he notes. So far asteroseismology shows that the theory is right to a factor of two" Whte dwarfs are partcularly open to the techiques of asterosesomology, but astronomers are looking for osclatons among all inds of stellar populations Ideally, one would le to analyze the vbrations of stable, mddleaged stars and compare the propertes wth those of the sun. Oscillations alter the
brghtness of such stars by only a few parts per llon, however. A group led by Timothy M. Brown of the Hgh Altitude Observatory tentatvely dentied osciatons on the star Procyon, bu he readily confesses that there are a frightenng number of ways you can get fooled." Hs group w make another set of observatons ths winter to tr to mprove ther level of certanty. Meanwhle nobody s forgettng about the most proximate star. The Global Oscllaton Network Group, an nternatonal grouping of sx telescopes, provide several years of continuous observatons of solar oscillatons startng 1993 Helosesmology s already answering such seemingly mponderable questions as, What is the temperatre at the core of the sun, and what drves the 2 2year actvty cycle? Nather reects plosopcally on ths kind of work It's amazing that naure would allow us to do t, that it's possible at all" -orey S. Powell
Who Were the Indo-Europeans? id successive waves of ndo-European horsemen begin to galop from the steppes of southern Rus sia some 6,500 years ago, spreading their an guage as they subjugated farmers between Greece and the Ganges? Or did the vast ndo-European famiy of an guages expand from the Midde East beginning 2,500 years earier, when farmers moved outward in search of and, swamping any foraging cutures in their path? Rather than resolving this prehistoric puzze, a recent study of European genetic patterns by Robert R Soka and his coleagues at the State University of New York at Stony Brook has failed to veri either theory Neither can account for the observed correlation between the languages and genes of Europe Soka's team set out to test an earier model that Albert J Ammerman of the University of Parma and . . Cavalli Sforza of Stanford University had proposed to explain the spread of agriculture from the Fertie Crescent The re searchers argued that a genetic trend between the south eastern and northwestern extreme of Europe was the vestige of a population boom occasioned by the invention of agricuture in the Fertie Crescent In this view, farming had been propagated ess by cutural borrowing than by demographic repacement In 1 9 87 Coin Renfrew of the University of Cambridge appied the mode to his anaysis of the archaeoogica record to expain the spread of ndo European anguages Last year the Stony Brook researchers mapped Euro pean genetic patterns against the archaeologica record of eary farming cutures and conrmed the demographic eg of the theory At the end of the study, published in Na ture, the workers cautioned that further research was nec essary to test the inguistic leg, which posits 1 0 postagri cutura transitiona areas where the ndo-European sub families differentiated into their present f orm Now Sokal's latest study, pubished in the Proceedings of the National Aca demy of Sciences, eaves tha t leg hang-
D
28
SCIENTIFC ERICAN ovember 1992
ing in thin air, right next to the warrior theory of Mari ja Gimbutas, an archaeologist at the University of Caifor nia at Los Angees This time Sokal and his team anayzed the genetic patterns of many dierent European popua tions so they could t them into a famiy tree Then they compared that tree with one of 4 3 European anguag es assembled by Merritt Ruhen, a linguistic taxonomist. The workers found a 0 1 4 correlation between genes and anguages. The researchers then estimated how much of that cor reation could be explained by mere geographic distance, a factor that dierentiates genes and languages in tandem After hoding geography constant, the workers found an average residual correlation between anguages and genes of 006 This residuum remains unexpained Soka demonstrates the crux of the experiment by su perimposing irst Renfrew's theory, then Gimbutas's, on a map of Europe Each theory appears as a set of arrows, paced with the help of Renfrew and Gimbutas "f Ren frew's theory were true, Sokal says, "it shoud account for the rest of the correation, which shoud then drop to zero But there's no change It's stil 0 . 06 The same is true when you add Gimbutas0 06 correlation Such sma correlations may seem mere statistica stat ic, but Soka insists they are signicant "Not every genetic ocus wil dierentiate during the origins of various popu ations, he decares "n a comparison of modern, raciay diverse populationsItaians, Nigerians and Japanese talians differed from the other two popuations by as much as 0. 2 in ony 20 . 4 percent of the cases How, then, does Sokal account for the correation? He decines to offer a mode but says he has an inking of what might have happened f geography cannot expain the concurrence of anguages and genes, then both must have begun to evove in parael in some other pace, per haps outside of Europe n that case, they must have come with immigrants as yet unknown. -Philip Ross
Desert Dyamcs Competition is the rule in complex ecostems
T
o anyone who has watched birds jostling one another at a garden feeder, the idea that species com pete for valable resources ight seem obvious. But strange to say, ecoogists have often disagreed about how im portant competition actualy is in natu ral ecosystems. Some researchers argue that cliatic factors such as tempera tre and the amount of rainfall are lie y to be far more critical. Clashes over food, according to tis way of t , are signicant only during hard times, when there is a shortage f alternative foraging places. One reason the debate about compe tition has gone on for so long is that
counting amals in natura or near natral habitats is notoriously dicut. d because eld experents are usu ay done with grants that ast for ony a year or two, most studies have been shor t. A study run by James H. Brown, a professor at the University of New Mexico, is one of the few exceptions. Brown is conducting a ong-term inves tigation of the teractions between ro dents, birds and plants in the Chihua huan desert of southeastern Arizona. In a recent report, Brown concudes there is a persistent and steady competition beween species despite the portance of cimatic eects on the numbers of dividuals. Brown and his coaborators started their experiments 15 years ago by fenc ing o 24 plots, each 50 meters aong a side, in lat desert near Porta, Ariz. The fences, made of re mesh, extend 60 centimeters above ground and 20
centimeters below, to discourage the kangaroo rats, deer mice and other ro dents beg stdied fro m burrowg un der them. A few plots were left undis turbed. In some the experimenters ex cuded arger rodents by making holes in the fences that were too small for them to get trough. I other pots they removed dierent combinations of spe cies. Then the workers carefuy doc mented the numbers of various pants and animals in the plots and watched how they changed over time In the pots that Bro and is co leagues eft alone, the eight desert ro dents that they studied varied strik ingy in their responses to changing en viroenta conditions. Some species dispayed a veyear repeated pattern that Brown links to the El Nio South ern Oscillation, a climatic cycle that causes heavy winter rain in the soth western U.S. in some years. But other species showed no eecteven though all the rodents feed on seeds, wich pants produce in greater numbers in wet years than in dry years. The studies indicate that it woud have been impossibe to predict how each species would respond. Brown notes that his experiments provide no support for the ideabeloved o f biolo g textbooksthat ecoogical commu nities reach equiibria appropriate to their geograpic region. Nature is not so dull. In is experimental plots, equi librium was the oy tng that was nev er present. Rather, he says, "cou nity composition varied continuously over time. The experental removs of particu ar spec ies from plots provided frther evidence of compex dynamics even in a relativey simpe ecosystem. Remova of a species, Brown says, can lead to cas cading eects that take years to play out. When he removed the tree species of kangaroo rats from several pots, for example, he found that the habitat changed dramatically over the course of a few years. Severa species of grass es colonized the areas b etween shrubs and became far more abundant while other, short grasses became rare. Birds, like rodents, forage on seeds, so it woud not be surprising if remov ing the rodents from a pot made it more attractive to birds. But in fact
VGETAON CNGES markedy when kangaroo rats are removed from an ex perimenta pot (to left of fence) . Aer ve years, the annua Lesquerella gordoni ( yellow flowers) is more common (top). Aer a rther eight years, ta perennia and annua grasses dominate (bottom). Phots: James H. Brown. 32
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the opposite happens, rown's studies show. irds forage less in plots that have no rodents than they do in undis turbed plots Moreover, birds show a similar aversion to plots that have had a the ants removedeven though ants, le birds and rodents, forage on seeds. ro and his collaborators tink ro dents and ants make plots more at tractive to birds by making trails and creating areas of bare soil. irds ap parently avoided plots th denser veg etation because they would have to expend more eort to nd the same amount of food.
Yet despite the complexity, a sophis ticated statistical analysis proved that competitive interactions are still an im portant force. When rown, together with Mark L. Taper and Edward J Heske, exaed the colective eects of kanga roo rats on the other seed-eating ro dents in is plots over a long period, a clear signal emerged. The smaller ro dents consistently forage by preference where the larger kangaroo rats do not. And the eect was remarkably constant over time rown displays proper scientic cau tion about generalizing from is re
sults. The Arizona desert might not be typical of other ecosystems, for example. Nevertheless, he notes, "our experiment is virtually unique in be ing of sucient duration to assess long-term temporal variation in com petition. And in a paper submitted to the journal cology, entitled "Con stant Competition in a Variable En vironment, rown's conclusion about the role of competition is unambig ous: "Interspecic competition plays a major, sustained role in the structure and dyamics of this desert rodent community m Beardsley
Kicking Chaos out of Lasers
B
y eputation, lases emit "pue light of homogeneous wavelengths and consistent intensity In fact, the in tensity of light poduced by some lases often de velops chaotic fuctuatons At the Geogia Institute of Technology, Raja sh Roy and his gaduate students Zelda Gills and Chistina Iwata ae nding ways to tame lases that are chaotcally inclined In the pocess, they have found they can incease the stable powe output of ce tan lases by 1 5-fold The eseaches wok with a popula lasea solid-state neodymium-VAG lase, pumped, o poweed, by anothe diode lase For seveal years, wokes have used such la sers to poduce shot-wavelength green light by doublng the frequency (and halving the wavelength) of an infaed laser with the help of a nonlinea "doublng crystal Such fequency doubling is nonetheless plagued by the so-called geen poblem: as infared is converted to green, the ntensty of the light spontaneously degeneates into chaotic oscillations Tying to boost the output of light by pumpng in moe enegy also tigges chaos Two years ago Roy and his team found they could damp en such chaos by caefully oienting the doubling cystal, theeby skting the odd polaization effects that caused the geen poblem But what if parametes changed?
As the eseaches began lookng fo dynamic contols to stablize chaos, they tuned to a novel analog technique called occasional popotional feedback contol Statng wth a lase that emits light that fluctuates chaotcally n in tensity, they sampled the signal at egula intevals The dfeences between those measued values and a collec tion of efeence values were then tanslated into tiny kicks that nudged the signal into perodc behavior The contol was successfulto a degee Once the Geoga Tech eseaches tied boosting the powe input into thei lase, they povoked anothe onset of chaos Help was at hand, however, in the form of recent theoet cal wok by Ia B Schwatz and oana A Tandaf of the S Naval Reseach Laboatoy aimed at controlling un stable obts By using eocorecting codes, Schwartz and Tandaf had enabled algorithms that contol local sputs of chaos to handle a wide ange of changing paamete values As a esult, by tuning only one, easily accessble paamete (say, powe input), the mathematicians could tack the be havio of unstable obits Such an appoach could conse quently be used to compensate fo andom dift By ntegratng the e o-corecting codes into their con tol pog am, Roy and his students managed to squeeze out 1 5 tmes moe stab le light than the laser had peviously po duced for minutes at a time. The contols moeove, equied lttle addtonal energyonly 2 o 3 pe cent of the pumping powe ''The lase expeiment shows of te eal powe of applying math ematcs to nonlinea systems, observes Schwatz, who has al ready led a patent application He is looking forwad to tying out the appoach n othe aenas, ncluding obiting satellte plat foms, fuid and combustion con tol systems and cadiac pacemak es Roy, on the othe hand, wll contnue to exploe chaos in othe lase and ibe-optc systems Un coveing new souces of chaotic INTENSI OF LSER, shown on oscilloscope screen as chaoic burss over ime, behavio to tackle is not yet a is moniored by Georgia Insiue of Technology gduae suden Zelda Gills. Phoo Margare Barre, Georgia Insiue of Technology. poblem -Ezabeth Corcoran
36
SCIENTIFIC ERICAN ovember 1992
PROIE: KR R POPPER e teetu r
heory of falsiabiliy is ceraiy no scienic I belongs o meascience Popper used o banish sudens from Once seaed, he keeps daring away is seinar for asing such an "idioic am jus abou o mee he philoso quesion, bu he doesn' blame me for pher Karl R Popper, and 'm rying o forage for books or aricles ha can doing so; some oher plosopher, he buress a poin Sriving o dredge a o lower my expecaions Popper is name or dae from is memory, he suggess, probably pu me up o i far and away he mos inluenial pilo kneads is emples and grimaces as if "Yes, I lie. sopher of modern scienceamong sci in agony. A one poin, when he word I should have known beer han o eniss if no oher pilosophers He "muaion briely eludes he slaps ry o rip up Karl Popper For more is bes nown for s a sserion ha sci han 7 0 years, he has bee n debaing his enic heories can never be proved s forehead wih alarg force, shou ing, "Terms, erms, erms! hrough experimenal ess bu only cenry's greaes ideas wih is cenu During one of is brief pauses for disproved, or "falsied In counless ry's greaes inds And criicism, afer all, is Popper's credo He sees aricles and more han a criicism, and even conlic, dozen bookshe laes, a as essenial for progress of collecion of essays, pub all kinds Jus as scieniss lshed jus s yearhe has also held forh on quanu approach he ruh hrough wha he calls "conjecure and mechaics, deersm, he heory of evoluion, poliical refuaion, so do species oaiariasm and pracical evolve rough compeiion and socieies ough polii ly every oher issue of noe. Bu as Popper's assisan cal debae A "human socie y wihou colic, he once ushers me ino his house souh of London, she warns oe, "would be a sociey me ha "Sir Karl (he was no of friends bu of ans Popper was raised in Vien ghed in 1965) is ex na in an inellecual house haused and w probably hold; s faher was a profes only have he energy o alk for an hour or so He jus sor of law and his moher urned 90 in July, a monh an accomplished musician ago, and he has already en He races he genesis of s dured endless ineiews and plosophy, wch he calls congralaions For he pas criical raionalism, o s several days, he has been 1 7h year Afer a brief dal oiling over wo lecures he liance wih comunism, he inends o deliver when he became disgused by he receives he presigious Ky dogmaism of Marxiss, by oo Prize, also called Japan's heir uer cerainy ha Nobel, in November On op Marx was "righ A roughly of ha he has been ill and is he same ime, he learned sill aking medicaion ha obseaions of a re cen Then Popper makes s solar ecpse had boe ou a enrance Sooped, equipped predicion of a bizarre heo wih a hearing aid and sur ry of graiy proposed by a prisingly shor (I'd assumed young physicis named Al he auhor of such auocra AUS TN-BORN PHIOSOPHER Karl R. Popper has inveighed ber Einsein ic prose would be all), he The conras compelled against dogmatm in both science and politics throughout his is noneheless as ineic as Popper o wonder: Wha ex areer. Photo: Dad Levenson/Black Star. a banamweigh boxer He acly disinguished pseudo brandishes an aricle I wroe for cien- breah, I menion s asserion ha a scienic heories, such as Marxism or tic merican abou how quan me heory mus be falsiable o be consid asrology or ev en psychoanalysis, from chacs is inspiring some physiciss o ered scienic Is is falsiabiy heo scienic ones, such as Einsein's heo abandon heir view of subaoc pari ry, I ask falsiable? Popper places ry of relaiviy? The answer, he decid cles as wholy objecive eniies. "I don' s hand over mine and ransxes me ed, was ha he laer oered predic wih a radian smile "I don' wan o believe a word of i, he declares in a Vi ions speic enough o be experimen hur you, he says, his voice sofening, enneseaccened voice "Subjecivism ally esed-and hence falsied "bu i's a silly quesion. has no place in physics, quanum or A he ime, he posophy of science Sill smiling, he genly explains ha oherwise, he informs me "Physics, he was donaed by logical posiivism, "he funcion of falsiabiliy is o say wich assered ha scieniss can logi exclaims, grabbing a book from a able wheher a heory is scienic or no. My cally infer cerain lmied ruhs abou and slang i down, "is ha!
38
SCIENTIFIC MERICAN ovember 1 992
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the world through repeated empirical observatios Popper agreed with the positivists that a theory ca be true but he rejected their cotetio that we ca ever know it is true "We must disti guish betwee truth he says "which is obective ad absolute ad certaity which is subjective Moreover accordig to Popper sci ece caot be reduced to a formal log ical system or method as the positivists suggested A theory is a ivetio a act of creatio based more o a scie tist's iitio tha o preestig em pirical data "The history of sciece is everywhere specative Popper says "It is a marvelous history It makes you proud to be a huma beg If sciece is a truly creative eter prise however the the world must ufold i fudametally upredictable ways Recogzg ts fact Popper has waged a lifelog battle agaist deter miism "Determiism meas that if you have suciet kowledge of chem istry ad physics you ca predict what Mozart will write tomorrow he says. "Now this is a ridiculous hypothesis Popper realized early o that qua tum mechaics udercuts determiism by replacig classical certaity with "propesities But eve classical sys tems are ieretly upredictable a fact that Popper claims to have discovered log before moder chaos theorists I 9 5 he foud a theorem by a 9th cetury Frech mathematicia showg that a te umber of geodesics or shortest paths ca coect two poits o a twodimesioal surface called a hored plae This theorem demo strates that "the world is chaotic Pop per says Popper rst elucidated s ideas i 934 i what is still his bestkow book he Logic of cientic Discove. It was so well received that 1936 Pop per who was th teachig gh school was oered a philosophy professor ship at Caterbury Uiversity College i New Zealad After ridig out World War II i the atipodes Popper took a positio at the Lodo School of Eco ocs ad Political Sciece where he remas a profe ssor eeritus Popper's ideas more tha those of ay other posopher have bee warm ly received by scietists physicists i particular The British physicist er ma Bodi recetly praised Popp er's philosophy are as "st the touch stoe of whether oe's ideas are scie tically meagl The adatio is mua Popper keeps remidig me that he was persoally acquaited with such giats as Este Scdger ad Bohr "I kew him quite well Popper says of Bohr "e was a marvelous phys
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iist, one of the greatest of all time, but a miserable phlosopher Popper has generally been at odds wth his fellow philosophers, whatever their outlook His book h Opn c and ts ns, published i 1945 agered politcal phlosophers of all strpes with its attacks o Plato, Mar, Hegel and others whom Popper ac cused of political dogmatism Polt, even more than scence, Popper sist ed, requres the free play of ideas and critcism Dogmatsm inevtably leads not to utopia, as Marsts and fascsts alke have caimed, but to totalitaran repression Some studets of Popper, noting his o authoritarian demean or, referred to s book as h Opn c On f ts ns.) Popper also wrangled th those
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CINTIIC ICAN vb 1 2
postwar phlosophers who ared that plosophy is notng but tautological word games n hs autobiography, Unndd Qust, Popper recals s leg endary duel th a progetor of ts school, Ludwg Wittgenstein Popper was giving a lecture at Cambridge i 1 946 when Wttgenstein interrpted to proclaim the "noneistence of phlo sophical problems Popper demurred, sayg there were many such problems, such as establishing a bass for moral rules Wttgenstein, who was nervously playng wth a replace poker, tust it at Popper, demanding, "Gve an eam ple of a moral rule ! When Popper re plied, "Not to threaten vsting lectur ers th pokers, Wittgensten stormed out of the room Popper is repelled by the currently popuar view that sciece s ven more by politics and socal custom than by a rational pursuit of the trth He blames ts attitude on a plot by socal scen tists to overtow the traditonal peck ing order in science, whch accords physicists the most legitimacy and so cial scientists the least "Ths s a hor rible aair, Popper growls, "and it w go on probably and become more and more horrble Yet scietists, too, can fall short of Popper's deal The growng subsidza tion of science by the pubc sice World War has led to "a certa corrption, he says "Scetsts are not as crtcal as they should be There is a certa wish that people le you -he jabs a nger toward my chest-"should bring them
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SCIENTIFI
Halth ar Rorm
Medical costs are rising rapid, and millions of eople have no health car coverage. Te nation urgent needs a universal insurance program by Rash Fein
he us. faces two challenging health care problems The rst is that an estimated 35 illion ericans have no medical insurance and millions more have only limited coverage. Ts situation is compound ed by the fact that most Americans be lieve that medical care is a right people should not be denied necessary treat ment because of their income. Despite disagreements about particularssuch as what constitutes necessary or ade quate treatment and how much serc es should costthere is general agree ment that the us has faled to develop a system for the equitable distribution of health care The second, newer problem involves the eect of rising healthrelated costs on the nations longrn econoc pros pects. 1940 health care absorbed $4 billion, a mere 4 percent of our gross national product (GNP). In 1990 such expenditures equaled $666 billion, or 122 percent of the GNP; projections suggest that in 992 the country spend more than $800 billion on med ical care, or 3.4 percent of the GNP
RASHI FEIN is professor of the eco· nomics of medicine at Harvard Medical School. Although s work has incuded studies of manpower supply and the · nancing of medical education, his cur· rent work is directed at health care re form. Fein, who received his doctorate from Jons Hopkins Uiversity, served on President Jon F. Kenedy's Council of Economic Advisers He is the author of several books on the economics of health care and is a member of the nsti tute of Medicne
46
The ncreasing proportion of the GNP spent on health is associated with a de cliing share of the GNP spent on other needs such as education and repair of the infrastructure, as well as on re search and development. In 1990 busi nesses spent 61 percent of pretx prof its and 108 percent of aftertax prots on health care benets for employees (as opposed to 20 and 36 percent, re spectively, in 1970). Health paents were 15.3 percent of total federal ex penditures; 11.4 percent of state and local budgets went to health. hese allocations reduce the funds available for meetng other government comit ments and for investing in economic opportuties that contribute to long term growth. The US also spends more of its gross domestic product (GDP)the value of items produced solely wit US bor derson health care than any of the 23 other members of the Orgazation for Economic Cooperation and Devel opment (OECD). In 1989, for example, the US. spent 11.8 percent of its GDP on health In contrast, Canada spent 87 percent; 16 other nations spent less than 8 percent. The private sector nanced about 60 percent of the u.S ex penditures, as opposed to only 20 per cent in all OECD countries combined As a result, erican compaes have proportionately less capital to invest, thereby jeopardizing the countrys in ternational competitive position. Clearly, the development of a novel health care system is ethically and eco nocally imperative. Although build ing on the current foundation has a certain political appeal, that basis is severely lawed The country needs to
SCIEIC RIC November 1992
erect a new structure, one that provides universal, or national, health insurance and one that helps to contain health care expenditures.
D
iscussions about national health nsurance n the uS began more than 75 years ago. Prompted by the Progressive Movement and buildg on successl state iitiatives on work mens compensation, state legislatures began to discuss such plans Over time, sions of the goals, structures, admin istration and funding for such a pro gram have inevitably changed. Di crive Dictiona of Health are, pub lished in 1976 by Congress, hints at the ever chagng perceptions of health care reform. The deition given for national health surance is "a term not yet de ned the U.S" As the divergent bls now before Congress demonstrate, ts term remas udened Yet the major issue has remaned fair ly consistent. The rst arguments for national health insurance were framed in terms of equity: remove nancial barriers for people whose medical care costs were more than they could aord and who had inadequate coverage or no insurance at all. The source of these gaps n insurance has been the contin uing inability of private (as opposed to goverental) insurance to provide af fordable coverage equitably.
SG I COSTS teaten people who lack medical insurance-a group numbering more than 35 million in the U.S. To prevent a social and econoc crisis sweeping reforms in the current insurance system must be instituted
SCIEIC ERIC November 1992
47
groups with people at igher risk, such as the elderly, found that heir premi ums increased. Cost sharing therefore took place solely win particular groups or sub groupsbut not across groups. Inevi ably, as those with less risk moved away from those with gher risk, the average risk for those still in the com mnity group increased, as did their premium coss. turn, individuals who perceived hemselves as havng lower han average risk left the comun ty, causing a further escalation of costs for hose who stayed. A vicious circle was established.
T
COVERAGE FOR THE ELEY and the disabed is guaranteed by Medicare Before the creation of that program in 1965, many of the eldery were not covered by in surance or had to pay exorbitant premiums because they were considered bad risks. Medicare which does not discriminate against persons at high risk could serve as the model for a universa heath insurance program.
The insurance gap stems from the way private insrance changed during and after World War II. Durng the war, the government froze wages, and man agement and labor were encouraged to bargain over medical coverage. Em ployees desired insurance because of he greater ability of medicine to cure illness; employers oered this fringe benet because i was, a least a rst, relatively inexpensive. These condions led to growth for he insurance indus try, a patern tha continued after the war, when he National Labor Relations Board ed that employers ung to bargain over health care benets were guilty of an unfair labor practice. Con sequenly, employment-based private health insurance grew rapidly during the 1940s and 190s. Employerbased private insurance, however, fails o provide coverage for those who are not employed or who work temporarly or sporadically. It also isses people whose employers, for rea sons including the high costs of health nsurance, do not provide insurance benets Another problem emerged as 48
well. Initially, preums were based on a couniyrating principle: that is, payments relected the average cost of care for all subscribers. The amount paid by a group or individual did not depend on age, gender, health stats or the previous or anicipated use of healh services. Ts straeg mplied a subsidy from younger, healter members of the popation to its older, sicker members. Buyers considered he subsidy, a form of risk averagng, one of the desired at tributes of insurance. But commuty ratng did not survive for long in a compeitive world Privae insurance companies sought new mar kets by basg premiums on he health care costs incurred by speic sub groups of subscribers. Tis approach became nown as eerience rating, and it encouraged insurers to look for low errisk individuals or groups (includ ing employees of paricular rms) and o oer hem reduced rates. Tis tactic had wo unfortunae consequences it became advanageous for persons or groups wih lower risks to dissociate from persons wh gher risks, and
SCIEI IC November 1992
he detrimenal raications of experience rang are apparen to day. Because he costs of health care have exploded, he dierence in premiums between igh- and low-risk indivduals and between community and experience rating has increased. These escalaing costs have variably af fected businesses as well as individu als. particular, rms, such as he Ford Moor Company, that have older em ployees who use more health services, are at a compeitive disadvantage. Com paies such as Honda, whose employ ees tend o be younger and healtier, do no ncur igh costs. (Ths drawback is, of course, made even more severe by the fact that older rms provide cover age for early reirees, a category that does no exist in the younger rm.) Experience raing has also drawn aention to preexisting condiions health problems steng from a con diion hat an individual has before he or she is covered by a policy. Tis issue is likely o become more pervasive as genetic research enables more precise measurement of dividual risk factors: one's genes wll become the ultimate preexisting condition Uness the coun ry changes its current health insurance system, individuals at aboveaverage risk wll nd it ever more dicul o obain employment that includes su ciently comprehensive coverage. Many factors help to explain the ex plosion in medical costs tha has in creased the vulnerability of the Amer ican economy and exposed he weak nesses found in he experience-rating system. The population has gro (and i continues o do so) Elderly people, whose health care costs are igh, rep resent a burgeoning proporion of the population. The economy has suered from general inlation. In addition, be cause healh care is a service indus try, it is a secor of the economy wih low productivity gains and subsantial ly large increases in coss. d afer all, the base cost of provid-
ng medcal cae has gown. The teat of malpactce suts has nceased the pessue to pactce defensve med cne. Physcans outnely pefom tests and pocedues that have queston able medcal value but consdeable le gal consequences. Costs and expend tues have also sen fo the best of easons: medcnes mpoved ablty to help pople. Futhemoe, the health cae comu nty has neve opeated wtn any bud getay constants. Many patents ae shelteed fom costs because the n suance coves them. Physcans, awae that the patents ae potected, have been fee to set fees n an uegulat ed maket. ndeed, U.S. physcans ean substantally moe than doctos n any othe OECD county. Escalatng medca costs have also un dened the employebased pvate nsuance stuctue that emeged afte Wold Wa . The gh cost of cove age has encouaged employes to lm t the expendtues. They have made cutbacks n benets, nceased employ ee cost shang and educed coveage fo dependents. t has become obvous that employe based pvate nsuance opeatng wth n a system donated by expeence atng cannot each eveyone. Thee ae now, as thee wee n the 1950s, thee goups lkely to be undensued o n adequately nsued: unempoyed peo ple, those whose employes do not po de nsuance and applcants wth pe estng condtons. Access to nsuance has become an especally sgncant s sue as medcnes ablty to teat and pevent llnesses successully has m poved and as the costs of such lfe savng teventons have sen.
I
t s possble to eect a uve sal nsuance pogam that would avod the gaps and advese eects of the cuent system. The concept s staghtfowad evey peson would be enolled n the same nancng po gam, one sla to the Medcae mod e. Unde the Medcae pogam fo the aged, dsabled and people wth end stage enal dsease, benecaes seek cae fom dvese souces even though the same nsuance pogam coves them l Payments to Medcae ae not elat ed to an ndvduals health status o to cuent o pojected futue use of health sevces. No would t be nec essay to make them so n an expand ed system that enolled all U.S. ct zens. Expeence atng dsappeas and th t the atonale fo dscm natng aganst ghsk uses. The m petus to shft costs fom one pogam
u.s. Health Care Costs 20
z w u w
b;
5
a « z 0
z
U U
f
5 70 75 0 5 7 0 2*5*2000* YEAR
JC
SOURCE: Health Care Financing Administraon
Increase i Health Care Spending,
1980-1989
0
z w u w
40
�
« u w a
20
GERMANY
UK.
FRANCE
JAPAN
CANADA
s
SOURCE Organization for Economic Cooperation and Development
Comparison of Costs for Health Care, Defense and Education 2 z
HEALTH CARE
0 w
b;
a « z i 4 « z
EDUCATION
U U
2 0 5
70
75
0
5
0
YEAR SOURCE Cs s U.S. National Center for Education Statistics, Health Care Financing Administration, U.S. Oice of Management and Budget
SCIEIC ERIC November 1992
49
to another falls by the wayside when thee is only one program. Moreover, a single uversal program severs the lik to employment In con trast, pay-or-play proposals, often pre sented as a pragmatic compromise be tween a radically new system and cur rent practices, expad that age. Such policies would require employers to ei ther "pay (forward a specied amount to a government fund that would be used to provide insurance) or "play (provide their employees wth health isurance that meets a predetermied benet standard). But because pay-or-play proposals buld on the existig model of em ployment-based insurance, they would continue patterns of ineciency They would have to deal with coverage for parttime work and selfemployment. They would have to have separate mech anisms to provide contuty of cov erage for individuals who change em ployers or location. They wod have to account fo the diering ability of em ployers to nance isance and pro vide appropriate subsidies for "margi nal rms as we as for start-up enter prises. Pay-o-play policies wod also have to avoid propagating icentives to e idividuals with lower risks whose premiums would be less costly Although it is possible to design spe cial provisions to meet these dleas, each attempt to compensate for the complexities of an employment-based appoach comes at a price The system becomes more cumbersome and suf fers from increased admnstrative du ties and igher adistrative costs. Pay-oplay proposals would have to be caefuy tuned and retuned i order to maintn the desred balance between the private and the public provision of insuance. A relatively low pay provision (in other words, too low a tax) would make the play alternative unattractive and wod lead to the declie of private isurance Conversely, too high a pay prOvision would force some employers not oering insurance to playeven though that chOice might place an oner ous burden on them, in the form of low er prots, or on their employees, in the form of lower wages or uemployment If everyone is enrolled in the same program, however, a number of other wse complex nancing issues are au tomatically resolved Again, Medicae provides a helpl precedent. Medicare is nanced tough a combination of sources. In 1992 an estimated 58 per cent of total income to the fund ill be derived from payroll taxes, 25 percent from general revenues and 9 percent from dividual prems. Just as none of these payments are related to the 50
dividual's health status, the same would be true in an expanded uiversal pro gram that included all mericans Ex perience rating and its unfavorable ef fects would disappear. A universal program could rely on any of the nancing sources used in Medicare, or it might be anced by ad ditional revenues such as those from a value-added tax. The choice of ancg soces is vitally portant, and the tial political and economic diculties brought about by sfting a large pro portion of the estimated $460 billion of private health care funding into the public sector are considerable. Yet these are surmountable, one-time concerns and are eased by the recogition that on average the increase in taxes to ance versal coverage wod be balanced by the decle i private payments for surance premiums ad care. The pro gram woud require a sift, not an aug mentaton, in health care nancng
j
igle unvesal program has an othe positive featureone that becomes apparent when we compae Social Security th welfare and Medicare with Medicaid. Social Se curity and Medicare do not discri nate on the basis of income. Converse ly, welfare and Medicaid are solely for the poor. The rst two are strong pro grams that, by ncludng everyone, pro tect lowincome dividuals from the va garies of g; the fates of verse in come groups are exorably interted In contrast, we fund welfare and Mecaid for "themad we al now or tk we kow who "they are. These programs rely on the lk of human ndness, but ts milk sometimes cur dles. To ze the development of disparities i access and n quaty, it is important to erect programs that do not enroll persons according to socio economic characteristics and sources of dig. Yet tis is the risk we with strat egies, such as pay-or-play plans, that combe private and pubc approaches The publicly ded programs would have a disproportionate number of low come o ighisk people for whom employers pefer to pay. Their per cap ita medical costs would be gher be cause medical needs relect health sta tus, whch is, in turn, aected by hous ig, education and employment. nce agai, goverment plans would appear to be more expensive than pri vate intiatives, presumably because goverment is less eient, thereby prOvidig a rationale for cuttig public budgets and for underfunding. What ever level the publicly funded iitia tive begins at, over time a program for
SCIC RIC November 1992
the poor ll become a poor program. Enolling everyone i the same plan will certaiy not solve or even address all the shortcongs of the crent sys tem. But the approach wod enable us to tacle the issue of cost contaent in a drect way. A single erollment program means a single payer or, more appropriately, a single purchaser of services. Tis sit uation leads to the standardization of forms, to electronic billing and to vai ous measures that reduce conUion, delay and the costs of admiistation in today's system The purchaser would not oly pay the bill for sevces but also accept a broader esponsibility to focus on issues of quality of care, un necessay services and value fo mon ey Each of these activities contibutes to cost control In addition, a uiversal proga that raises funds trough taxes and pemi um paents caot survive fo long if it neglects cost considerations If it caot fund its obligations, it wll be forced to incease its revenues or shift costs to patientsand it wil fail. Be cause the single insuance approach caot sft costs to anothe insurer, it must acieve its goal witn a budget Therefore, the plan wod have to set an overall budget for health care as well as simlar budgets for physician and hospital sevices. As demonsated by many counties, such as Fance and Japan, negotiations between all aect ed parties, icludg govenent and health care pOviders, can give ise to a budget Ths political process weighs the costs of health cae agast alterna tive pubic progams ad private-sector expendires Measures such as pospective bud gets for institutional care, capitated (non-fee) payments for people enolled i Health Maitenance ganizations, and other approaches to managed care would assist i meeting budgetary con staint There is no tellectual chal lenge to developng the tools necessay to do the tas Great diculty may arise, as it does th all large govenment programs, in choosing a budget that relects the pubc view of competing consumption and ivestment opportuities (such as education). In the 1960s and early 1970s voters feared that the govern ment was poligate and that national health insuance would bakrupt the nationespecially a nation that asso ciated larger expendtures wth gher quality Today the fear is the everse, that legislators wil be parsimoious and that the nation will not spend as much as is essential to maintain the medical care inrastucte.
Of course, there can be no guarantee that underspendng w not occur. Nev ertheless, it is possible to structure na tional health insurance to reduce the likelihood of such a phenomenon. The most mportant protective device is versality-the fact that everyone is cov ered by the same ancing scheme. Al though individuals will be able to opt out of the publicly funded program in favor of private insurance, the incen tive to exercise that option can be re duced by requng payment of the uni versal tax even if one elects to receive privately funded care. Moreover, stipu lating that providers be entirely in or out of the program would guard aganst underspending To formulate workable health care budgets, policymakers must become more concerned about the supply of health resources The proliferation of ightechnology equipment and serices and the growth of nacially rewarding specialties-sgery, anesthesiology, ra diology and subspecialties of internal medicine-have contributed to expand ing costs. If the system does not solve the monetary and other incentives that have led to a decliing nterest in fami ly medicine, general medicine and pe diatrics, costs wll not be contained nor quality sustained. Not even the best national health in surance program can succeed in as suring access to care at a reasonable, responsible expenditure level if health restructuring is limted to insurance eollment, nancing and payment Medical education and training must be reformed. So also must the nanc ing of medical education. Its igh cost can lead to indebtedness and conse quently cause stdents to choose lucra tive specialties
M
any academic health analysts believe a remodeled US health care system would be able to deliver serces to all Americans for the $800 bllion now spent on care for oly some ericans These experts say the system could do so without denng anyone care that is medically neces sary. They point to the large savings that would accre if uneeded care were eliminated and patterns of ad nistration streamlined ndeed, some estimates suggest that as much as 25 percent of performed procedures are not required Nevertheless, the sangs wod occr oly over a number of years Deter ing what constitutes appropriate care wod requre resech nto and consen sus about the meang of unnecessary care Patterns of practice would have to be altered. We would have to pursue an
How Health Care Is Financed, in Billions PRIVAE INSURANCE OUT OF POCKE MEDCARE OTHER GOVERNMENT PROGRAMS MEDICAID OHER PRIVATE SOURCES SOURC Health Care Financing Administration 1990
Where Health Care Funds Are Spent, in Billions HOSPITALS PHYSICIAN SERVICES OHER PERSONAL EXPENSES MEDCA SUPPES (EG, DRUGS, EYEGLASSES) OTHER SPENDING (INCLUDES ADMINISTRATON) NURSNG HOMES RESEARC AN CONSRUCTON OF FACILIES SOURC Health Care Financing Administration, 1990
Comparison of Physicians' Incomes AVERAGE PHYSCAN'S NCOME IN US DOLLARS
RAIO OF PHYSCANS INCOME TO AVERAGE INCOME
PYSICANS PER ,000 POPULAON
-3
AUSTRALIA
34
22
CANAA
70,44
347
DENMARK
3,0
20
24
FINLAN
35,55
2
22
FRANCE
NO AVALABLE
327 (7
22
WEST GERMANY
,244
42
24
RELAN
730
0
2
AY
NO AVAIABLE
0 ()
3
JAPAN
5,437
24
4
NORWAY
3,4
3
20
SWEEN
NOT AVAILABE
0 (3)
24
SWZERLAD
50
40
UK
33,5
23
3
US
500
52
SOURC Organization for conomic Cooperation and Deelopment 1986
SCIETIFIC ERICA November 1992
51
ment A series of insurance packages adistered by the states, rather than one federal program, would not vio late the concept of uiversality. The de tas of the mesg of federal and state responsibilities would be important The federal government would have to dene benets and cost-contaiment goals as well as provide some funding But in my judgment, the gains associat ed th state admiistration and more direct citizen involvement would out weigh the additional complexiy discussing health care reform, oth er econoists and health care experts emphasize the naure of the deivery system and the role of managed care, the role assigned to cost sharing and the type of negotiation process used to de velop an appropriate fee stcture I do not deny the portance of these mat ters or suggest that the framework I have outed canot be altered n sever al respects ithout comproising the basic integrity of the proposals At the same me, I do mean to em phasize that we need to consider nda mental choices We must choose be tween ivers social nsance and the continuation of employment-based in surance, between comuniy and expe rience rating and between cost contain ment and cost escalation The approach I propose has some dis advantages In addition to beng noin cremental, it increases the role of gov erent It also requires concern about the eects of restrcuring, the fate of displaced workers and the consequenc es of sifting large sums from the pri vate to the public sector Yet a system analogous to an improved Medicare for all has the boon of SimpliCity It can be explained and can be understood and is workable. he plan spells out the eq uity and expenditure issues eciently
C
itizens should not adopt the pos ture that many analysts and pol iticians have chosen: to reject what they agree is an ecient and work able program because they presume it is too big a step and cannot pass the legislative hurdles The less ecient in cremental approaches that seem "bet ter may prove as challenging to enact as the single erollment program out lined here Noting will come easily, but on health insurance reform, as on other matters, the public may be ahead of the representatives A Kaiser/Louis Harris pol at the end of Jue foud that adlts preferred a single-payer plan over a pay-or-play program by a mar gin of 35 to 29 percent even though the latter has the endorsement of ma jor congressional gres and leaders in the busness commuity
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FE AIDENT HLH GROP NSRN AN NNTIS
CONNETICUT GENERAL ISURAC MAY
•
Hm INSNCE was readiy provided by employers during the 1940s and 1950s. Medical care was at tat me ess eensive, and mny people whose medical eenses had been paid by the federal government during World War II expected employers to provide similar coverage. Tis advertisement for insurance appeared n Forne magazine in September 1945
Wile the incremental pay-or-play program might be viewed as an "estab lishment proposal that has received considerable attention and publiCity, the more comprehensive Single-payer proposal was preferred by 4 to 29 percent of Democrats and 38 to 29 per cent of independents Republicans did favor the pay-orplay approach, but oy by 3 to 26 percent, despite the president's criticisms of the single-pay-
er approach as socialistic and leading to long lnes lection year is hardly the time to ac cept the pundits as the true experts on what is politically feasible It is certain ly not the moment to reject comprehen sive reform on the grounds that it is not doable Rather all of us must become more kowledgeable about and must debate each of the options that could improve the health of our sociey
UTH ING MDL C, MDL CO: T S O HL I POLY. as ein Harvard Universiy Press,
1986. B A, CO, D POL T COX O HL
SY RO. John Holahan, Marilyn Moon, W. Pee Welch and Sephen Zucker man Urban Insiue Press 1991. SO UL CODO HL C. Hey Aaron Broongs nsiuion, 1991.
SCIETIFIC ERICA November 1992
53
The Expsio Rte and ze of the Uiverse Te age, evolution and fate of the universe depend on just how fast it is expanding. By measuring the size of the universe using a varie of new techniques, astronomers have improved estimates of the expansion rate by Wdy L. Fd
O
ur Milky Way and all other gal galaes, leag to completely new esti aes are mog away from one mates of the expansion rate. At present, several lines of evidence another as a result of the big bang, the ery birth of the uverse. point toward a igh expansion rate, i During the 20th century, cosmologists plying that the uverse is relatively have discovered tis expansion, detect yong, perhaps oy 10 bion years od ed the microwave background radia They also suggest that the eansion of tion from the original exposion, de the uverse may continue indenitely duced the origin of chemical elements Yet for many reasons, my colleagues in the universe and mapped te large and I do not consider the edence de scale strcture and motion of galaes. nitive, and indeed we activey debate Despite tese advances and many oth the merits of our tecques ers, elementary questions remai unan An accurate measurement of the ex swered How long ago did the colossal pansion rate is essential not oly for de expansion begin? Wi the uiverse con teg the age of the verse and its tinue to expand forever, or the fate but also for constrang theories of verse evenually be halted by graity cosmology and models of gal forma tion Frtermore, it is portant for es and then collapse back on itself? For decades cosmoogists have been tiating ndamental quantities rang attempting to answer such questions ig from the amont of noous by measuring he size scae and expan mater n galaes to the size of clusters sion rate of te iverse. To accomplish of galaes nd because accurate mea ts task, astronomers must determine srements of distance are required for bot ow fast galaxies are moving and calculating he luminosity, mass and how ar away hey are Techniques or size of astronomical objects, the issue measuring the veociies of galaxies are of the cosmologica distance scale, or we established, but estating the dis determination of the expansion rate, tances to gaes as proved to be a far aects, to a greater or lesser extent, the more calenging ask During the pas entire eld of extragalactic asronomy tronomers began measurg the decade, severa independent groups of asronomers have deveoped beter eansion rate of the niverse some 60 meods for measuring te disances to years ago 1929 the enent astrono mer Edn P. Hubble of the Carnegie In stitution discovered that nearly all gal-
L
WENDY FREEDMAN is a member of the sta at the Carnegie Observaories Pasadena, Calif. Born in Toronto, she re ceived a Ph.D. in asronomy and astr physics from the University of Torono in She became a Carnegie postdoc toral fellow and, in was the rst woman o join the sta. She is now a member of the Hubble Space Telescope Key Project Team for he Extragalactic Distance Scale. Her interest, outside of asronomy, is spending ime with her faly: husband Barry, daugher Rachael, and son Dael,
4
54
7
4
ANDROMEDA G is a prime exam pe of why cacuatg the eansion rate of the universe is dicut Andromeda is ion ight-years away from the earth, but it sti fees the gravitationa p of our own gaaxy Consequenty, its reative motion has itte to do th the expansion of the verse By obserng more distant gaaes, astronomers can detect the expansion, but they do not ow its precis rate because it is dicut to measure distan es to remote gaaes
2
SCIENT IFIC ERICAN N ovember 1992
axies ae moing away from the earth at temendous elocities oreoe he made the emakable obseration that the elocity of ecession is popotion al to the distance to the galaxy His ob seations poided the st eidence that the entie unierse is expanding Hubble was the st to deteine the expansion ate Late tis quantity be came known as the Hubble constant: the ecession elocity of the galaxy di ided by its distance A ey ough es timate of the Hubble constant is 100 kilometers pe second pe megapasec (Astronomes commonly epesent dis tances in tems of megapasecs whee one megapasec is the distance light taels in 326 llion yeas) hus a
typical galaxy at a distance of 50 mega pasecs moes away at about 5,000 kilometes pe second A galaxy at 500 megapasecs therefoe moes at about 50,000 kilometes per second o moe than 100 illion iles pe hou! Fo six decades astonomes hae hotly debated the precise alue of the ex pansion ate Hubble oiginaly obtaed a alue of 500 ometes per second pe megapasec (km/s/pc) Afte Hubble's death 1953 is potg Alan R. Sand age also at Canegie continued the po gam of mapping he expansion of the unierse As Sandage and othes made moe accuate and extensie obsea tions they eentually resed Hubble's original alue doward consideably
into the ange of 50 to 100 /s/pc incating a iese far lge than sug gested by the ealiest measuements Duing the past two decades new estimates of the Hubble constant hae contued to fall it tis same ange but preferentially towad the two ex temes. Notably Sandage and his long te collaborato Gusta A aann of the Uniesity of Basel hae agued for a alue of 50 /s/pc wheeas Gad de Vaucouleurs of the Uniersi ty of exas has adocated a alue of 100 /s/Mpc he contoersy has ceat ed an unsatisfactoy situation in which scientists hae been free to choose any alue of the Hubble constant between the two extremes
the cycle, ts luminosty increases very rapidly, whereas during the remainder Why Cphd Vb P of the cycle, the lunosity of he Ce phed decreases sowy On average, Ce ePheid variable is a relatvey young star, severa times more massve pheid variables are about 10,000 tes than the sun, whose luminosity changes in a periodc way: a Ce brighter than the sun pheid brightens and then dims more sowly It pulsates because the emarkably, the dstance o a Cephe force of gravity acting on the atmosphere of the star is not quite baanced by id can be calculated from its period the pressure of the hot gases from the interior of the star (the length of its cycle) and its average The imbalance occurs because of changes in the atmosphere of a Cephe apparent brightness (its luminosity as d An important ingredient in the atmosphere s singy ionzed heium (that observed from the earth) 1908 Hen is, heium atoms that have lost a singe electron) As radiation fows out of retta S Leavitt of Harvard College Ob the interior of a Cepheid, singly ionized heum i the atmosphere absorbs seratory discovered that the perod of ad scatters radiation, and t may become doubly ionized (that is, each hei a Cephed is very tightly correlated with um atom releases a second eectron). Consequently, the atmosphere e its brightness She found that the long comes more opaque, making it diffcut for radiation to escape from the at er the period, the brghter the star This mosphere. Ths interaction between radation and matter generates a pres relaton arises from the fact that the sure that pushes out the atmosphere of the star As a result, the Cepheid brightness of a Cephed is proportona ncreases n size and brightness to its surface area Large, bright Cephe Yet as the atmosphere ids pulsate over a long period just as, expands, t aso cools, and for example, large bells resonate at a at ower temperatures the low frequency (long period ) helium returns to its si By observing the variations in lumi gy ionzed state Hence, nosity of a Cepheid over time, astrono the atmosphere allows ra mers can obtain its period and average diation to pass through apparent uiosity and thereby calcu more freely, and the pres late its absolute luinosity (that is, the sure on the atmosphere apparent brightness the star would have decreases Eventually, the if it were a standard distance of 10 par atmosphere collapses secs away) Frhermore, they now that back to its initia ize, and the apparent linosity decreases as the Cephed returns to its the distance t travels creases There original brghtness. The fore, the distance to the Cepheid can be cycle then repeats computed from the ratio of the absolute Astronomers have pre brightness to the apparent brightness dicted the behavior of CeCepheids are useful distance indi pheids wth great accura cators for many reasons In particular, cy using theoretica mod their cycic behavior and high lunosi els of the evolution of the ty make them relatively easy to nd interior of stars as well as and to measure simulations of the flow of In the 1920s Hubble used Cepheid radiation in stars Astron variables to establish that other gales omers have confidence n ested far beyond the M Way While Cepheids as distance in studig photographs of the Androm SEVEL CEPHEID VLES are apparent in dicators because they un eda nebula, also known as M31, Hubble the galy M33, a member of our own Local derstand the underying roup_ Individual Cepheids are marked by a identied faint starlike images whose physics of these young number and the letter V. Each dark point repre brightnesses vared slghtly over time stars and have observed sents a star whereas the white irregular patch He was able to show that ther behavior them in great detai es are regions lled with dust matched that of nearby Cepheid vari ables By measuring the apparent bright nesses and periods of the Cepheids in M31 he deduced that M31 was located In principle, determination of the lines are shifted to longer wavelengths more than several hundred thousand Hubble constant is simple, reqirng by an amout proporon to the velo lghtyears away from the sun, well out side the Milky Way From the 1930s to only a measurement of distance and t-an eect nown as redshift the 1960s, Hubble, Sandage and others velocity though measring the veloc To determine the distance to a gal ity of a galax is straightforward, how axy, astronomers have a choice of a made a tremendous eort to discover ever, gauging the distance is rather dif variety of complicated methods Each Cepheids in nearby galaxies They suc cult To obtain the velocity, astron has its advantages, but none, it seems, ceeded n measuring the distances to about a dozen galaes, thereby impov omers disperse the light cong from is perfect a galaxy and record its spectrum The ing the foundatons for deriving the spectum of a galaxy contans dscrete tronomers can most accurately Hubble constant spectra lines These occur at character One of the major diculties with the measure the distances to near istic wavelengths caused by emission or by gales by moitog a type Cephed method is that the apparent lu absorption by specic elements in the of star commonly referred to as a nosty can be shed by he dust gas and stars that make up the galaxy Cepheid variable Over te, the star found between stars The particles ab For a galaxy moving away from the changes in brightness in a periodic and sorb, scatter and redden the lght from earth, the positions of these spectral distinctive way Durng the rst part of all types of stars The eects of the dus
A
56
SCIEIC IC Novemer 1992
re most severe or be nd trviolet ight It is thereore necessry tht s tronomers either observe Cepheids t rred wvelengths where the eects re less sigcnt or observe them t mny dierent opticl wvelengths so tht they cn ssess the eects nd cor rect or them
T
o determine the dstnce to Ce pheids thereore stronomers need telescopes nd detectors tht re very sensitve to light t vr ety o wvelengths Hbble Sndge nd their contemporries sed photo grphic pltes tht responded primri ly to green nd ble ight nd hd n eciency o less thn tenth o per cent Tody stronomers se soldstte chrgecopled devices CCDs) mde ot o tin wers o slicon These de vices cn detect light o wvelengths rom ble to red nd re more thn 50 percent ecient When photon strikes CCD it libertes electrons n the sili con creting detectble sign CCDs oer n enormos increse in obserng ecency over photogrph ic pltes In ddition they record the brightness o ight sorce with mch greter cccy thn photogrpc m terils The CCDs thereore mke idel detectors or stdying Cepheids nd or deling with the eects o dst grins Dring the pst decde my collb ortor nd hsbnd) Brry F Mdore nd I t the Cliorni Institte o Tech nology hve crelly remesred the dstnces to the nerest glxies s ing CCDs nd the lrge relecting tele scopes t mny sites incding Mn Ke in Hwii Ls Cmpns in Chile nd Mont Plomr in Cliorni s rest we hve deterned the distnc es to nerby glxies with mch gret er ccrcy thn ever beore Uortntely the teciqe or me suring the distnces to gles contin ng Cepheids cot be sed drectly to obtin the Hbble constnt Cepheids re bright enogh to be observed oy in the nerest glxies not the distnt ones nd lthogh nerby glxies re prtcipting in the expnsion o the verse the grvittionl interctions mong the neighbors my be csing some to move mch ster or slower thn the rest o the iverse Conse qently to clclte the Hbble con stnt stronomers mst ccrtely de termine the dstnces to remote glx ies nd tht tsk is extremely diiclt Nevertheless sonomers hve devel oped sever methods or determiing distnces to remote glxies Becse mny o these techiqes mst be cli brted sing the Cepheid distnce scle they re considered secondry distnce
indctors The tecqes re bsed either on properties o certin types o bright objects witin glxies or on chrcterstics o glxies themselves Yet scientists cnnot rech consenss bot wich i ny secondry indi ctors re relble Frthermore they disgree bot how they shold pply mny o the methods nd then wheth er they shold djst the reslts to c cont or vrios eects tht ight bis the rests Dierences the choice o secondry methods re t the root o
lmost ll o the crrent debte bot the Hbble constnt One o the most promsing tech iqes or mesg gret istnces re lies on correltion between the bright ness o glxy nd the rte t which it rottes Highlumnosity glxies re typicly more ssive thn lowl m nosity glxies nd so bright glxies rotte more slowly thn dim glxies lthogh the existence o sch corre ltion ws known or some time it ws not ntil 1977 tht R Brnt Tlly o
0
08
w f Z( « � z i« « > (z «
1.2
L W
6
12
16
30
2
3 6
2
4 8
5
DAYS
GNITUDE OF A CEPHEID varies cycically over a period of days. Each colored ine corresponds to observations at dieren wavelengths of radiation (from tra violet to near infrared). The ampitude of the ight variation is largest toward blue and ultravioe wavelengths. Cepheids are therefore more easily discovered using deectors sensitive to ble light.
SCEFC ERC November 1992
57
Measuring Distances to Galaxies
A
stronomers can employ several diffeent techniques for measuring distances to gaaxies. Unfortunately, the accuracy of the measurements decreases as the distance to the galaxy in creases By observing stars known as Cepheid variables through ground-based teescopes, astronomers have accurately dete group, mined the distances to galaxies as far away as the
M
Hubble pace Telescope
some million light-years away Using the same technique and the they may be abe to measure the distance to the Virgo custer, approximately million light-years away. By measuring the brightness of a galaxy and the velocity at which it rotates, astronomers can curently determine the distance to galaxies some million light-yeas away Another promising
5
3
GALAXY CLUSTERS 0 MLLION LIGHTYEARS) ( 30
M8 1 GALAXY GROUP ( 10 MILLON LGHT-YEARS)
M8 1 GROUP (10 MILLION LIGHTYE ARS)
LOCAL GROUP (THREE MILLION LGHTYEARS)
VRGO (50 MILLIO LIGHTYEARS)
w
. ' . . . . . . .' . . . .. : . . . . .
18
20
22
" 32
3 2
10
100
w
24 M81
M31
22 NGC 20
M33 NGC 300
DAYS
PEROD of a Cepheid variable-the time it takes for the star to complete one cycle of brighteg and g-is related to its magnitude, or brightness. The measure ments were made at infrared wavelengths on Cepheids in the Large Magellac Cloud
he Uversiy of Hawaii and Richard isher of he Naional Radio strono my Observaory used he correlaion exensivey o measure disances he ullyisher relaion yields he mos accurae disance measuremens when observaions of he brighness of a galax are made a infrared wave lenghs here are wo reasons. irs he sars ha domnae he luminosiy of galaxies emi mos of her radiaon a nearinfrared waveenghs. Second as frared radaion traves ough sace scaers ess a onger wave enghs Jus over a decade ago he use of he uysher reaion a infrared waveenghs was ioneered by he ae Marc aronson of he Uiversy of Ar zona Jeremy R Mould of Caech Jon 58
VELOC at which a gal rotates is re lated to its magitude Tis socalled Tlly Fisher relaon is eemely precise, enabng accurate relave distances to be obtaed Cepheid distances to these galaxes were de terned usng detectors called CCDs
P Huchra of Harvard Uiversy and Gregory D. Bohun of he Universy of Oregon. Since hen severa ndeen den grous have esed he ulyish er mehod exensively Mos moran hey have shown ha he relaion does no aear o deend on enviroen; more secicaly s he same in he dense ars of rich clusers he ou er ars of such clusers and for rea ively isoaed galaxies. or hese reasons and ohers, asron omers generaly agree bu by no means uiversay acce ha he ulyish er reaion is one of he mos accurae secondar disance indicaors avaiable. I can be used o esmae disances as far away as 300 mion ghyears. n oher advanage of he mehod is ha
November 199
he Cehed ecnique can be used to cibrae he ulyisher mehod dis advanage is ha asronomers currenly ac a dealed heoreical undersand ing of he ulysher relaion
R
esearcers have receny deve oed wo oher sance measur ing ecques [see "Mrroring he Cosmos by Corey S Powe; November 991]. he rs mehod devsed by George Jacoby of he Naional Oical sronomy Ob servaores and is coleages nvolves objecs nown as laneary nebuae hese objecs are formed when sars ha are abou as massive as he sun aroach he end of heir fe cyce Jacoby and is coworers foud ha
wih disance because the task o resoing individua stars becomes increasingy dicult Hence, the stance o a gaaxy technque s based on the apparent peak bghtness of a can be gauged by how much kind of explodng star known as a type Ja supernova In the apparen brightness of the princple such exposions could be detected out to a ds ga uctuaes over is sur tance of about haf of the visible unverse. The supeno face. ter deeg he dis va technque s far less accurate than the Cephed ances o gaaes usg the method as the graphs beow suggest surface brighness echique, Tonry compared he esus VISIBLE UNIVERSE ( 10 BILLION LIGHT-YEARS) wih those obtaned usig he DISTANT SUPERNOVA planeay nebula and Tuly (FIVE BILLION Fishe methos and ound ex LIGHT-YEARS) cellen agreement. Consider ing he uncertanties ha have plagued measemes of ex ragaacic disances, ony's ndngs are exemey encour aging. Yet boh mehods cur reny have only smal num bers of Cepheid calibraors avaiabe. oher disance indicaor ha has great potenia is a paricular kind o supernova GALAXY CLUSTERS kown as ye Ia Supernovae (300 MILLION are catastropc exposions LIGHT-YEARS) tha mark the deah o certain kinds o stars ype Ia super novae, asronomers beieve oc 100 cur in doube star systems in wch one of the stars is a very dense objec known as a 8.5 we dwarf. The explosion is riggered when mass from the companion star is transferred 5.0 to he wite dwarf. Because su 3 3 0 15 pernovae release remendous DISTANCE (MILLIONS OF LIGHT YEARS) amots of radiaion, astrono mers should be able o obseve ABSOLUE BRGHESS of a type Ia supeovae peraps as far away upeova theory predicts is constant and as ve billion lighyears, hat ts apparent brightness is therefore related is, a distance spanng a radi o its distance om the earth. Yet astrono us of haf the isible universe. ners have been able to make only one Type Ia supernovae make neasurement to calibrate this stance scale good disance indicators be cause a the peak of their brighness, hey all are bethe losiies of panetary nebulae lieved to produce roughly he same do not exceed a well-deed, upper l amount o light. Usng tis nformaion, it. To deerine the disance to a gal astronomers can infer heir distance. ax, they simply measured the apparent Unforunately, supernovae are very luinosities of the brightest planetary rare evens, making both her discovery nebae in tha galax. To calibrate her and especially ther calibraion exreme method, they used gales with stanc y dicult. Because hey occur so re es detered by Cepheids. They found quently, the chance o a type Ia super that his technique produces disance novae ocg n a galax near enough measurements tha agree ver well with where Cepheids can also be measured is the Tully-Fisher mehod in cases where very low. In fact, it was ony during this boh mehods have been applied. pas year hat Sandage and s col The second method, developed by leages obaed, for the rs time, a di Jon L Tony of he Massachusets Insti rect distance o a gaaxy own to have tute of Tecology and his colleagues, harbored a ype Ia supernova. To do so, exploits he fac hat nearby gaaes ap Sandage's team made observaions of pear grainy, whereas remote gaaes are Cepheids using the Hubble pace Telemore uiform n the srface brightness scope. Alhough their work represents a disribution. he graininess decreases major advance, a sgle result is stl -
)
sucien to caibrate the supernova dis tance scale accurately.
T
wo other methods for deerin ing the Hubbe consan aso de serve mention because hey are completely independen o the Cepheid disance scale and they can be useul for measurg isances on vast cosmo ogica scales. Moreove, preliary ap plications of each o hese methods cur renty favor a owe vaue o he Hub ble consan The s of hese alernaive mehods relies on an eect caed graviaion a ensing: if ight rom some distant source traves near a galaxy on is way to the earth, he ligh can be delected. The igh akes many dierent pahs around he gaax, some shorter, some longer, and consequenly arrives a the ear at diferen imes. If the bright ness o he source vaies in some dis cive way the signal be seen st in he ligh ha akes he shores path and be observed again, some time aer, in he light tha raverses the long es path. The dierence in the arriva times reveals the derence in lengh be tween he two gh paths. By appying a heoreica model of the mass distribu ion of the gaaxy, astronomers can cal culate a value or the Hubbe consant. The second method makes use of a phenomenon know as e Sunyaev Zel'dovich (SZ) eect. When photons from he microwave background travel through galax clusters, they can gain energy as they scaer o he ho pas ma (xray) electrons found in he cus ers. The net reslt of the scatering is a decrease n the icrowave backgrond toward the posiion of he cluser. By comparing the microwave and x-ray distributions, a distance to the cluser can be inferred. To deermine the dis tance, however, asronomers mus also know the average density o the elec trons, heir disribuion and their em perature, and they mus have an accu rate measure of the decrement in the emperaure of the microwave back ground. By calculaing the distance to the cluser and measurg its recession al veOity, astronomers can hen obain the Hubble constant. The SZ method and he graviaion a-lening ecique are proising bu have not yet been tested rigorously. To assess the uncertainies in these ech niques, researchers mus nd more ob jecs wih the required characterisics The debate contues as to he best mehod for deterng distances to remote galaes. Consequenty, asron omers hold many conicing opions abou wha he best current esimate is for the Hubble constan. Sandage and
SCIEIFIC MERICA ovember 12
59
vr
HENETA S. of Harvard Col lege Observatory fond, a cor reaon between the period of a Cepheid variabe and its absolte brighess This correlation alows astronomers to mea· sre distances to the nearest galaes
1908,
his collaborators have reported a pre nary value of 45 km/s/Mpc using the type a supernova method. he SZ method and the gravitationallensing tecnique also support a low value for the Hubble constant. My colleages and I derived a best es ate by usng the most recent Cepheid measrements ndiidualy to cabrate the infrared ullyFisher relation the planetary nebula tecque and also the surface-brightness uctuation method hese three independent teciques give results that are in excellent agreement they yield a high value for the Hubble constant of about 80 m/s/Mpc
O
ur measurements and those of our colleagues have many im plications for the age evolution and fate of the verse. A low value for the Hubble constant implies an old age for the universe whereas a igh value suggests a young age n particular a Hubble constant of 100 /s/Mpc in dicates the uverse is about seven to 10 billion years old (depending on the amount of matter in the universe and the corresponding deceleration caused by that matter). A value of 50 /s/ Mpc suggests however an age of IS to 20 billion years. And what of the ultimate fate of the unverse? If the average density of mat ter in the universe is low as current ob servational estates indicate the cur rent standard cosmological model pre dcts that the eansion of the nverse will continue forever. Nevertheless the ory suggests that the universe contains 60
he controversy over the value for the more mass than that which can be at tributed to luminous matter. A very ac Hubbe constant may be settled as as tive area of cosmological research is tronomers continue to use the Hubble the search for this additional "dark pace Telescope In Aprl 1990 the tele matter in the universe. o answer the scope named n honor of Edwin Hubble question about the ultimate fate of the was launched into orbit around the universe unambigously however cos earth [see "Early Results from the Hub mologists require not only a nowledge ble Space elescope by Eric J. Chais of the Hubble constant and the average son; SCIEIFIC ERICA, June]. he mass density of the universe but also space telescope has the potential to re an independent measure of the age of solve indiidual stars at distances 10 the universe. hese three quantities are tmes arther than can be don from the needed to specify uquely the geome grond It therefore provides the oppor try and the evolution o the uverse. tity to discover Cepheids in a volume If the Hubble constant turns out to of space 1,000 times larger than the be high it would have profound impli region that can be routinely accessed cations for our understanding of the from ground-based telescopes. evolution of galaxies and the uverse One of the ighest priorities of Hub A Hubble constant of 80 km/s/Mpc ble is to discover Cepheids n galaes as yields an age estimate of from eight to far away as the rgo cluster (about 50 12 billion years (allowing for uncertain milion light-years). he Cepheids could ty in the value for the average density be used to determine the distances to of the universe). hese estimates are all those galaes thereby calibrating vari shorter than what theoretical models ous seconday stance ndicators. Such suggest for the age of old stellar sys obserations cold greatly prove mea tems own as globular clusters. Glob srements of the Hubble constant. ular clusters are believed to be among the rst obects to form in our galaxy ome time ago several colleagues and ther age is estated to be between and I were awarded sucient ob 13 and 1 bllion years. Obviously the sering time on Hubble to nd ages of the globular clusters cannot be new Cepheids in more distant galaes. older than the age of the verse itself. 1991 we began our rst obserations he age estimates for globular clus of the nearby galaxy M81 We identied ters are often cited as a reason for pre more than 20 new Cepheids and ob ferrg a priori a low vaue for the Hub tained a spectacular set of light ces. ble constant and therefore an older age Unfortunately the telescope has not for the uverse. Some astronomers ar performed as expected because of the gue however that the theoretical mod spherical aberration of the prary mir els of gobular clusters on wich these ror and most of the program has been estimates depend may not be complete delayed until the telescope optics have and may be based on inaccurate as been corrected (crrently planned to oc smptions For nstance the models rely cur in December 1993) Scientists have many reasons to be on nowng the precise ratios of certan elements present in globular clusters optistic that the upcoming decade particularly oxgen and iron. Moreover may alow us to resolve the current con accrate ages require accurate measres troversy over the age of the uverse of lunosities of globar cluster stars and to chart the course of its evolution which n turn require accurate measure· But the history of science suggests that ments of the distances to the globular we are unlikely to be the last genera clusters Considerg that both the mea tion to wrestle with these challenges. surements of the Hubble constant and the models and distances for globular FURTHER ING clusters may contain errors astrono AN DCOVER E GA. R. Be mers cnot easily udge the seriousness endzen R Hat and D Seeley Scence of the apparent age discrepancy between Hstoy bcatons, 76 the universe and globular clusters. E OOOGCA DACE LAER A high vaue for the Hubble constant DANCE AN E N E UNVERE raises another potentialy serious prob Mchael Rowan-Robnson. W. H. Fee· lem it disagrees with standard theories man and Company, of how galaes are formed and distrib E EPE DANCE CAE Bay F. uted n space. For example the theories Madoe and Wendy L Feedman n lications of the Astronomical Socie of make predictions about how much te the PaCic, Vol. No 667 pages is required to form the largescale clus 7; Septembe terg that has been observed n the dis LONEY EAR OF E OO E tribution of galaes. If the Hubble con CEFC QE FOR E ECRE OF stant is large (that is the uverse is E UNVERE Des Ovebye. Hape young) the models cannot reproduce Collns blshes, the observed distribution of galaxies.
SCIEIFIC ERICA November 1992
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NJ.
he Risks of oftware Programming bugs have disrupted telephone serce and delayed shuttle launches. An inherent uncertain in reabii may mean miting a computer's role, especial in systems where soware is critical for saf y B w z g
M
OSt of us have eerienced some nd of problem related to com puter failure: a bil mailed n er ror or a day's work destroyed by some mysterious gtch in a desktop comput er. uch nuisances, often caused by soft ware faults, or "bugs, are merely ncon venient when compared ith the conse quences of computer failures in critical systems. oftware bugs caused the se ries of large-scale outages of telephone service in the U A sofware problem may have prevented the Patriot issile system from tracing the raqi cud issile that led 8 American soldiers during the Gulf War Indeed, software faults are generally more nsiious and much more diclt to handle than are physical defects The problems essentially arise from complexity, wich increases the possi bility that design faults ill persist and emerge the al product Convention al engineering has made great strides n the understandng and control of phys ical problems. Although design faults are somemes present n material prod ucts that do not contan computers, the relative simplicity of such machines
BEV UTLEWOOD and LORENZO STRIGINI collaborate as members of the project Predictably Dependable Comput ing Systems (PDCS), a research eort on computer dependability that brings to gether researchers from European coun tries. Littlewood received is Ph.D. in computer science and statistics from the City iversity in London, where he is the director of the Centre for Software Reliability. Strigini, a researcher at the Institute fo Iformation Processing (IEI) of Italy's National Research Council (CNR) received s lr in electroc engineering from the versity of Pisa. The work of the authors in ths eld was partially funded by the Comssion of the European Comunties as part of the PDCS project. The authors thank the other workers in PDCS discussions ith whom have been valuabl e in forng the vews expressed here
6
has made design reliabili less serious than it has become for sofware The concerns expressed here, incdentally, go far beyond exotc military and aero space products Complex sofware is nding critical roles in more mundane areas, such as fourwheel steering and antilock braking in automobiles ts article we exame some major reasons for the uncertainty conceg software reliability and argue that our abity to mease it fls f short of he levels that are sometimes required In critical systems, such as the safey sys tems of a dangerous cheical plant, it may be that the appropriate level of safey be garanteed ony the roe of software is lited.
I
n theory at least, sofware can be made that is free of defects Unlike materials and machnery, sofware does not wear out design defects are present from the time the software is loaded into the computer In principle, these faults could be removed once and for all Furthermore, mathematica proof should enable prograers to guarantee correctness Yet the goal of perfect software re mains elusive Despite rigorous and sys tematic testing, most large programs contain some residual bugs when de livered The reason for this is the com plety of the source code A program of only a few hundred lines may con tain tens of decisions, lowing for hou sands of alternative paths of execu tion (programs for farly critica applica tions vary between tens and mllions of lines of code) A program can make the wrong decision because the particular inputs that triggered the problem had not been used durng the test phase, when defects could be corrected The situation responsible for such inputs may even have been sunderstood or unanticipated: the designer ei ther "cor rectly programed he rong reaction or failed to take the situaton into ac count altogether This pe of bug s the most dicult to eradicate
SCIETIFIC ERICA ovembe 1992
PATOT MISSI strea over Tel Aviv to intercept an coming Iraqi Scud s-
In addition, specications often change during system deveopment, as the intended purpose of the system is moed or becomes better derstood. Such changes may have impications that rppe through a parts f a sys tem, makng the previous design nade quate Furthermore, rea use may stl der from intended purpose. Faiures of Patriot misses to ntercept Scud ssies have been attributed to an ac cmuation of naccacies n the inter na time-keepng of a computer Yet the computer was performng accordng to specications: the system was meant
to be trned o and restarted often enough for the accumuated error never to become dangerous. Because the sys tem was used in an untended way, a minor inaccuracy became a serious probem. The intrinsic behavior of digita sys tems aso hinders the creation of com petey reabe software Many physica systems are ndamentay continuous in that they are descrbed by "webe haved functionsthat is, very sma changes n s produce very sma dierences n respones In contrast, the smaest possibe perturbaton to
sile during the G War On some occasions the soare conoing te atriot's tracng sstem ma have faed, pre
the state of a digita computer (chang ing a bit from 0 to 1, for insance) may produce a radica response. A singe in correct character the speCication of a contro program for an Atas rocket, carring the rst US interpanetary spacecraft, Maine 1 timatey caused the veice to veer o corse Both rock et and spacecraft had to be destroyed shorty after aunch In a other branches of engineering, smpcity and gradua change consti tute the man eements of trusworthy design But n software engineering the unprecedented degrees of novety and
venng the msses om locag and destrong ther Scud targets One such faure led to the deaths of 8 US solders. SCEC EC ovembe 1992
63
than are civan ones. Survval in com bat depends on hgh performance, a wch forbids conservative design, and -1600 a new computer system may mprove 500 U the airplane's chances even i it is less a safe than computers used n comme -160 � cial airplanes. Simlarly, in the design u 50 of a lybywre ciian arcraft, such as I the Arbus A320 or the Boeng 777, the U possibity that software may cause ac i cients has to be weighed agast the Z < kelhood that it may avoid some ms U -1.6 haps that would otherwise be caused 20 25 35 by plot error or equipment falure. 15 30 10 5 0 G U We believe that there are severe re strictions on the evels of condence 20 that one can justiably place in the re s abiity of softwae. To elain tis pot 088 5 of view, we need to consider the dier ( z a : 15 0.75 : � ent sources of evidence that support s condence n software. The most obvi 12 068 - � ous is testg: g the program, di ;5 ° recty obserg its behavior and remov 050 � 10 U< ing bugs whenever they show up. In z . 0.38 � ths process the reliability of the soft U 7.5 > ware grow, and the data collected i 5 025 can now generally be used, va sopis U 5 ticated statistical extrapoation tech013 � niques, to obtain accurate meases of ! o 0 how reliable the program has become. 70 80 90 100 10 120 130 50 60 40 Unfortunatey, this approach works U U ony when the reliability requrements SOF FATS persst even n welldebugged programs Edward N. Adams of are fairly modest (say, n the range of mM found that bugs that remained a sstem were prarl ",ear bugs one failure every few years) when com that s, each of them would produce a fale onl once in , ears p Such pared ith the requrements often set for critical applications. To have confi faults make debuggng an exercse n shng re: n the test of a tar commandand-conol sstem m, the tme needed to remove the bugs begs dence at a level such as 109 fare per to outpace b far the resultng mprovement n the estmated relabilt, measured hour, we wold need to execute the pro terms of estmated acheved mean tme to falure For vsual clart, the graphs gram for very many multipes of 109 have been plotted on derent tme scales. hours, or 100,000 years. Clearly, tis task is not possible. In the time spans for wch it is feasibe to test, assurance ebility that prograg aords tion requires specia consideraton that of the safet would fall many orders of tempt workers to ignore these prnci lies beyond the scope of tis article magnitude short of what is needed. The problem here is a law of d ples. Entirely new applications can be [see "Acheving Eectronic Privacy, by designed with apparent ease, giving a David Chaum; SCIC C, ishing returns. When we continue de fase sense of secity to developers d August]. buggg a program for a very long te, cients who are not faiar with prob Given that perfect software is a prac eventualy the bugs fond are so "sma ems specic to software Even the ad tical impossibity, how can we decide that xng them has virtualy no eect dtion of nove features to a program whether a program is as reliable as it is on the overal reliablity or safety. Ed may produce unexpected changes n supposed to be? Frst, safety require ward N. Adams of the Thomas . esting featres. ments must be chosen carefully to re Watson Research Center empircally an ect the nate of the applicaon. These ayzed "bug sizes over a worldwide he probems of embedding com reqirements can v amacay from data base that involved the equivaent plex decision rles in a design one application to another. For exam use of thousands of years of a particu and forecastg the behavior of pe, the U.S. reques that its new air ar software system. complex scontnuous systems are not trac conol system cot be unavail The most exaorda discove was imted to software. Designers of high able for more than three seconds a year. that about a td of a bugs found were ly compex digital integrated circuits In civilian airiners, the probabilty of ",OOO-year bugs: each of them pro encounter sar probems. Software, certain catastrophc failures must be duced a faure ony about once 5,000 no worse than 109 per ho. however, is st the predominant mei years of execution (the rates from other settng reliability requirements for bugs vared by several orders of magni um for embodying extremey compex, computers, we must also take to ac speciaized decision es. tde). These rare bugs made up a siz addition to unintentiona design cot any extra benets that a comput able portion of al faults because bugs bugs, aws deiberately introduced to er may produce, because not using a that caused igher faure rates were compromise a system can cause unac partcar system may itself c harm. encountered, and so removed, earlier. ceptabe system behavior. The issue of For example, itay aircraft are by Eventaly, only the ,OOOyear bugs computer securty, privacy an encryp necessity much more dangerous to y make the system unreliable, and remov( 5,000
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SCIC C November 1992
a of one of these bring negigibe improvement n reiabiity trapoatg from testng and debug gng aso mpies an unsubstantiated as sumptionnamey, that a bug, once en countered, is spy corrected In reai ty, an attempt to f a bug sometimes fas. It may even ntroduce an entirey nove faut Because nothing woud be known about the new bug, its eect on the reiabiity of the system woud be unbounded In particuar, the system ght not even be as reiabe as it was before the bug was found. Therefore, a prudent course woud be to discount competey the isto ry prior to the ast faiure Tis precau tion, criticay important in situations that invove safety, woud require an evauator to treat the software after the ast f as if it were a competey new program Ony the most recent period of errorfree working woud iuence judgment about the safety of the pro gram But even tis conservative course of action cannot provide much con dence Our research has shown that un der quite pausibe mathematica as sumptions, there is oy about a 5050 chance that the program function without faiure for the same ength of time as it had before. The probem of estating safety is actay even more serious To have any codence in the numerica resuts, we must subject the program to sitations it might encounter in reaity This ap proach ensures that nputs causing fai ures are encountered with the same frequency th wich they woud in fact arise In addition, the tester shoud aways be abe to decide whether the program's output is actuay correct The probems here are siar to those of designing and impementing the sofware itsef To constrct an accate test environment, we need to be sure
that we ave thought of a circumstanc es that the software meet Just as the unexpected often defeats us in sys tem design, so it is in test design. t woud be wise to retain an eement of skepticism about the representative ness of the testing and thus about the accuracy of the gures The probem in demonstratg ex treme reiabiity or safety for any in didua piece of software is py ack of the necessary owedge For compex software, the unpaatabe th seems to be that there are severe imi tations to the condence one can pace in a program. Merey observing a pro gram's behavior is not the way to be sure that it function propery for 100,000 years How ese might we ac quire such codence?
j
n obvious prerequisite for gh reiabity is that software be bt ith methods that are e y to achieve reiabiity One method uses "forma techques, which rey on mathematica proofs to garantee that a program function according to specication Indeed, forma techniques have become a topic of de interest Such methods, though currenty it ed by practica probems in the scope of appication, can eectivey avoid pro gramng errors arising in the transa tion from the specication to the actu a program Unfortatey, specications must a so be forma statements. In other words, the user's needs woud have to be ex pressed in a mathematica anguage. That task is not simpe it requires a carefu choice of those aspects of the rea word to be described in the forma anguage and an understandng of both the detaied practica probems of the appication and of the forma anguage Errors woud ey be ntroduced d
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DESIGN DIVERSITY helps to icrease the reability of soft ware systems Each program version, or replica, is developed independently by dierent design teams. The "adjudicator decides the actual output of the system by usg, for example,
ing this process, and we coud not rea sonaby caim the program wud nev er fa Another method now widey used (in aoc and rairoad contro appica tions, for instance) to acieve high rei abiiy is faut toerance, or protective redundancy A ypica way of appng redundancy is to have dieren design teams deveop severa versions of the program The hope is that if the teams make mistakes, the errors be er ent Each version of he program pro vides its "opion of the correct output The outputs pass to an adjudication phase, which produces a singe ouput that wod be correct the majority of versions gave the correct res Some evidence ests that such de sign diversity deivers gh reiabiiy in a costeective manner Different design teams, however, may make the same mistakes (perhaps because o commonaities n cutura background) or conceptuay different mistakes that happen o make the versions ai on the same faut The adjudicator woud therefore produce incorrect ouput To measure the reiabty of at-to erant software, it is necessary o gauge the staistica correation between fai ures of the different versions. Unforu natey, the task turns out to be as hard as trying to measure the reiabiiy by treating the whoe system as a singe entiyand we have seen the dicuy of dong that. So foma proofs do no enabe one to caim that a program never fai and if faut toerance cannot guarantee reiabiity, there seems no choice but to evauate reiabity drecty, using meh ods that are acknowedged to be of im ited adequacy How do the reguatory authoriies and sofware users dea with this uncertainy? There are three approaches The rst
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the median value produced by the replicas or the value "vot ed for by a majority The adjudicator could be another re dundant system or could consist of noncomputer technolo g such as hydraulic actuators
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assis dsignausd faius as "non quantiab os and avoids spify g quimnts fo th softwa This mthod is now in faiy wid us. Fo instan, in ivi aviation, th s Fd a Aviation Administation Advsoy Ciua 213091A dsibs "apt ab mans fo showing ompian with som fda aviation guations. It stats that atastop fai ondi tions (th wost atgoy) must b "so uniky that thy a not antiipatd to ou duing th nti opationa f of a aipans of on typ Th suggstd quantitativ pssion is th pobabiity of faiu of not mo
than 10 p hou of ight Softwa, howv, is piity udd fom this iua, "baus it is not fasib to assss th numb o kinds of soft wa os, if any, that may ma af t th omption of systm dsign, dvopmnt, and tst. Th widy usd doumnt of th Ra io Ta Cossion fo Aonau tis, RTCA/D178A, simiay avoids softwa masus. Th doumnt, whih givs guidins fo manufatu s who must sk tiation by avi ation authoitis, piiy uss to mandat quantitativ tms o mth ods fo vauating softwa iabiity o
safty. Instad th ommission gads a ot nging appoahtight managmnt, thoough viws and tsts, and anaysis of pvious os as mo itia than quantitativ mth ods. Th basi mssag of RTCA/D 178A "is that dsigns must tak a dis ipd appoah to softwa: qui mnts dtion, dsign, dvopmnt, tsting, ongation managmnt and doumntation. That is, th bst assu an of iabiity is to vify that ut most a was usd th dsign How good is suh assuan? A guaby, not vy good: th is no vi dn that supio dsign and podu
The Nature of Software Failure
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oware occasionally fails because it contains design fauts. Some have argued that such failures are sys tematic-that is, because writing software is a pure ly logical exercise, there is nothing intrinsicay uncertain about it. If enough is known about the inputs, the pro gram's behavior woud be completey deterministic. We believe, however, that soware faiures cannot be mathe maticay described ony in deterministic terms. n fact, we think that describing the nature of soware failures re quires a probabilistic treatment, just as we use statistics to describe how oen, on average, electrical or mechani cal devices fail. To see why, consider al the possible inputs (called the input space) that the software might encounter in its life (bv) An input for an operation of the soware is a set of digital data (numbers) read from the outside world and from information already stored in the computers mem ory. n the igure above, the input space is shown in the two dimensions of the printed page, but in practice the space would usualy consist of many dimensions. Here the input space contains three fault zones num bered to nput x ies in faut , that is, it woud cause the program to produce an unacceptable output. On the other hand, the program can successfully execute input y which does not ie in any fault zone. A program is tested by executing it with many inputs and checking whether the results are correct. f a right an swer is produced during testing, it wil also be produced
SCIC C November 1992
whenever the same input is presented. For most programs, testing for al possible inputs woud require bilions of bil lions of years-hence, the need to infer failure probabili ties from testing on a sample of inputs. We woud like to know when the program wil next fail, but that is not possibe because of the inherent uncertain ty in te process. First, uncertainty arises from the phYi ca mechanisms that determine the succession of inputs (caled the trajectory in the input space). We can never be sure which inputs will be selected in the future, and dier ent inputs wil ave different chances of being selected. Second, we are uncertain about the sizes and locations of the fault regions in the input space. Even if we knew the trajectory, we would still not know wen the program would encounter a faut. Therefore, we must describe our belief about the future failure behavior of the program in terms of probabiities. We might ask what is the probability that we can survive a particuar number of inputs before failure. Or we might ask what the probability is that a randomy selected input causes a failure. Both questions can oen easily be turned into a timebased measure of reliabiity-tat is, the prob ability that the program wil execute perfectly for a partic ular length of time. In conclusion, we are forced to consider the process of successive failures of a program to be just as "random as that of a hardware device. he use of a probabilitybased reliabiity measure is therefore inevitable.
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tion methods consistently yeld supe rior products. We cannot even be cer tain whether the best current methods ever produce sucient reliabiity for the more demanding appications Escheing the quantication of soft ware safety poses a serious iitation for many potential dangerous sys tems, especialy those that requie an overa probabilistic risk assessment before operation Probabilities can be predicted with reasonable accuracy for phsica faiures caused by stress and wear. But this accuracy caot be used in eorts to assess the risk that the en tire system (that is, hardware and soft ware) fai if nothing more precise can be said other than that the bes eort was made to avoid isakes. Sim py mandating the use of "best practice does not solve the problem. We hasten to add that it woud be foolish to aban don tecques own to improve reli abiy and safety just because we do not now exacly how much they help. Standards that encourage their use are certaiy benecial, but they do not sove the probem of owing that the software has the required safety The second-and we think, better approach woud require that the system be designed so the roe of software in it is not too critical "Not too critical here means that the required software reiabity is suciently modes so the reiability can be demonstrated before the system is deployed Ts approach has been taken for the new Sizewe B nucear reactor in the UK., where oy a 104 probablity of failure on demand is needed from the softwarebased pro tection system. There are weestabished meth ods for imiting the criticaity of any one component For exampe, an indus trial plant whose operations are con troled primariy by computers may be equipped with safety systems that do not depend on any software or other compex design. A safet or bacp sys tem usuay performs simper nctions than does the man contol system, so it can be built more reiaby. Safety is pos sibe if the backup systems are com peey separated from the main sys ems They coud be bit with dierent technoogy or use aternative sensors, actuators and power sources. Then the probabiity that both primay and back up (or safety) sstems fa sltane ousy may be justiably considered ow The third approach is simpy to ac cept the current imitations of software and live ith a more modest overa system safety ter al, society some imes demands extremely high safety for what may be irrationa reasons. Med ica systems are a good example Sur
SIZEWELL B wl be he s nuclear reacor he UK o conain boh convenional and sofwre-based proecon sysems for emergency shudowns. Crics argue ha he compley of he sofware sysemi relies on hundreds of microprocessors and more t nes of codemakes i dcul o ense eacor safey.
geons are knon to have fairy igh failure rates, and it would seem natu ral to accept a computerized alteative if the device is shown to be as good as or oy slighty better than the human physician. Indeed, in the near future robotic surgeons probaby perform operations that are beyond the capab ities of humans
T
he tree approaches to regulating software safety may seem rather disappOintng Each sets its on either the degree of safety in the system or the amount of compety in the pro gram Perhaps the ony way to learn more about the necessary compromis es between safety and complety is to study the failures (or lack hereof) of software in operation. Unfortunately, there is a paucit of daa from which to fashion statistical predictions Information on software faiure is sedom made public. Compa nies fear that sharing such knowedge woud harm their competitive stance They wory even more that publising it woud antagoize pubic opiion People ight see te detection of a software faut as an ndication of ow production standards, even though it may actually attest to a vey thorough procedure ap pied to vey igh quaity software But secrecy can ony allow expectations of safety to cimb to creasingly ueais tic eves. Some investigators have sug gesed that the government make man datoy he ogging and iscosng of fai e data n critical software systems. Such regulations would remove the fear that companies volunteering the ormation would be hurt
However it is obtained, an extensive colection of data woud in te hep to quantify the ecacy of dierent pro duction and vaidation techniques The information woud help estabish more realistic rues for gaugg the trustwor thiness of software systems Thus, for software that is not fu tested statisti caly, the acceptable claims of safety coud be tied to expiit upper bounds that wod depend on the complet of the progam Such an approach ight alow us to justify caims for the re iabiity and safety of software beyond what is now beievable In the meantime, we shoud remain way of any dramatic claims of reliabi ity. Considering the evels of compex ity that software has made pOie, we believe being skeptical is the safest course of action.
FRER ING EAA SA-A S A David L Parnas, Jo van Schouwen and Shu Po Kwan in icis f h M Vol 33, No6, paes 636648; June 1990. S SAY EM M SYM Nancy G Leveson in icis f h M Vol 34, No 2, paes 3446; Febrary 1991. FM R H uc M A SYM. oderated by Peter Neumann vailable as the usenet newsroup cmprisks, or by request on the internet rom risks request@cslsrcm H uc M SYM. Reular column edit ed by Peter Neuman in ic
is f h M
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SCIENCE IN PICTE
Visualizng Biologica Molecules Computer-generated images are aiding research in molecular structure and helpi to elucidate t he complex chemist of life b A ] Dv G
T
he eye, wich is caled the window of the soul, is the chief eans whereby te understanding ay ost uly and abundanty appreciate the inte works of nature." The words of Leonardo da Vnci eloquently capture the intiate relation between ision and coprehension Yet odern science often confronts objects that are invisible to the huan eye. Chests and biochests in particar have been thwarted by the fact that they cannot see the oecues they endeavor to study. The atoc detais of olecues can not be discerned even through electron icroscopes. In recent years, however, coputer tecnology as ade it possibe to suate conncing, scientically accrate pic tures of oecules Suc iages allow biochests and o ecuar bioogists to explore, in a failiar visual way, the coplex olecules built by ces. Copter grapics help to discose, for exape how antibodies seek out foreign oe cues and how enzyes provide exactly the rigt enroent to tiate a checal reacton. A cear picture of the strcture of a oecue can carry great conceptua weight. One such iage-the diagra of the doubehex shape of DNA pub ished by Jaes Watson and Francis Crick-revoutionized understanding of an heredity and genetic disease. Scientists gather the raw data for oecuar iages n sev eral ways. Xray crystaography is currently the ost suc cessful. A researcher irradiates a crysta coposed of a par ticuar olecule with an intense bea of xrays, whch scat ter into a distinctive pattern. The pattern is atheatically anayzed to revea the spatial distribution of eectrons and, by extension, the location of every ato in the olecue. Nucear agnetic resonance (NMR) spectroscopy oers an
ARTHUR J. OLSON and DAVID S. GOODSELL are working to expand the role of computer graphics for studying the functio and structure of large biological molecules. Olson received his Ph.D. from the University of California, Berkeley, in 1975 and conducted postdoctoral research at Harvard University, where he used x·ray crystallography to study the structure of viruses. In 1981 he founded the Molecular Graphics Laboratory at the Research Institute o Scripps Cliic in La Jolla, Calif. Olson's bio cheical lms and molecular images have appeared in many popular and tecical settings. Goodsell received is Ph.D. in 1987 from the University of Californa, Los Angeles, where he also studied x-ray crystallography. He then joined Olsons labo ratory, developing molecular rendering tecques nd compu tatioal methods for drug design. Goodsell recently returned to U.C.LA. to continue his work in crystallography.
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SCIEIFIC EC November 1992
alternative approach to detering the structure of a o ecule. A soution containing the oecue of interest is placed in a powerful agnetic eld. The saple is then exposed to puses of radio waves; nuclei of certain atos in the oecule respond by etting their own rado waves at frequencies de terined by their oca cheica enviroents. These fre quencies are terpreted to disclose the approate distanc es between atos in the olecule. By cobng those con stras with the known cheical properties of the oecule, one can deduce the positions of the constituent atos. SIMUITED IMAGES of the moecuar word were created y means of compuer grapics. A pice of the human immo deciency virus (below), ased on eectron microscope data from U Skogund of he Karoins Institute and S gund of Uppsaa Universiy, shows a coneshaped core containig genetic maeria surrounded y a spherica enveope. A view of a drug inding to DNA (right) was drawn using xray crys taographic data coected y R. E Dickerson of UC A The drug appears as a region of gh eectron densiy (green and yellow) lg he narrow groove of the DNA (dark spheres).
SCIETIFIC ERIC November 1992
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X-RAY CRYSTOGHY provides the information need ed to simuate a picture of a moecue A crysta of DNA scat ters xrays i a characteristic pattern (lef) Computer anaysis of the pattern can revea the distribution of eectrons i each DNA moecue A cage of ines drawn around regns of hgh
eectron density (right) ustrates the ocatons of the atoms in the moecue; an unusua guanineadenne mspar s seen here. A pixe-based mage (opposite page) gives a better ee ing for the threedmensiona arrangement of the atoms but requires more te to compute
Witin the ast few years, aterials scientists have devel oed a third ethod for observing the atos in oecules, caed scaning robe icroscoy A olecue is iobi lized on a at surface, and a neede whose ti is oly a few atos wide is scanned across the surface A feedback loo al ows the ti to folow the exact contour of each ato, tracing out its shae Reeated asses of the neede gradualy buid u a treediensiona contour of one side of the olecule. ll tee techniques yied vast aounts of data that are far easier to interret if recast into a visua for. Before the widesread use of couters, researchers laboriously sifted tough inforation on stri charts, sciloscoes and ho tograhs and then built brass or lastic odels based on the results Because of the huge aount of work nvolved, scien tists were eectivey liited to studying sa olecules containg no ore than a few dozen atos Researchers interested in biological olecules, wch con tain hundreds to hundreds of thousands of atos, were therefore avid users of the rst couters 1947 Raond Piinsky of Pensyvaia State University deveoed an ana og acine, XC, to transfor his xray crystaograic data into an intelligible olecular icture As couters have advanced, so too has the agtude of the scientic robles to wich they are aied Modern digita cout ers, used in conjunction th couter graics, enabe sci entists to roduce detailed ictures of enorous olecues, incuding enzyes, antibodies and even entire viruses wo concetuay distinct grahic aroaches are co oy used to create ictes of oecules One builds u an iage out of sets of lines drawn fro oint to oint he other ethod generates an iage fro a dense a of dots, or xels. Each tecnique has its ow advantages and draw backs Because a line can be described by erey two osi tions, linebased disays can draw and redraw an iage raidly, letting an investigator aulate the iage nterac tively Iages drawn on ixebased dislays (usually a col or onitor) take longer to generate, because each icture ele
ent ust be assigned a coor vaue; a tyica onitor con tans ore than one on xes But ixel disays can s ulate eects such as shadng and shadowg, wich add to the reais of the ictures o construct a olecar iage, researchers begn by co ecting foration on the structre of the olece, ost of ten by eans of xray crystalograhy Xrays scatter ost strongly where the electron density is ghestthat is, around the atos in the oecule Hence, regions that exibit high eectron densities are atos; regions having ow densities are ety sace. (Eectron icroscoy can fursh siar but coarser treediensiona as of eectron density that do not resolve individual atos.) ust as cartograhers draw ines of constant eevation on a a to segregate ills and valeys, crystallograhers use couter grahics to draw a boundary surface tough the data, searating atos fro ety sace. he surface ay be ortrayed as a tick esh of ines that resebes a bird cage Usg a graics rogra, the scientist then ts a chan of atos inside the surface, folowing the convouted con tours indicated by the electron density data Pxelbased iages rovide a clearer view of the crysta lograhic resuts For exale, one can assign secic co ors and otica roerties to various vaues of the data. In the DNA eectron density a shown on the reous age, arts of the oecue having igh values of electron density are rendered oaque and colored, whereas regions of ow density aear transarent rough a rocess known as volue rendering, the graics software fors an iage that suates how light woud trave trough an object os sessing those otical roerties. Unfortunatey, voueren dered iages require far ore tie to cacuate than do the inebased iages. Carity is gained at the cost of seed of aulating the view of the olecule Once the coordiates of the constituent atos are nown, the couter oers a host of techiques by wich to anayze a oecue. Molecar graics ca focus and si the ic
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SCEFC ERC November 199
ue of he olecule we ananng all he elevan nfo aon Bochess ofen n enghenng o look a he way a poen chan fols no a copac olecule ane S Rchason of Duke Unvesy populae a sple bu ef fecve gapc epesenaon ha follows he oveall fol ng of he poen bu elnaes he confusng angle of n vual aos he esulng bbon aga faclaes clas sfyng he any vese poen sucues no a le nube of snc folng ofs Copues also asss he suy of he shape of a bologcal olece wch n t eenes how neacs wh ohe olecules he eases way o epc he oue opogaphy of a olecule s o ceae a spacellng aga n hs poce ue he copue aws aos n he olecule as sphees whose a elec how close hey ay appoach one anohe Placng a he sphees n he pope locaons enes a gh ly luc age of he ene olecule Colong each ao ac cog o s checal nae conveys sll oe nfoaon Spacellng pcues show a olecule as gh appea f wee agne o vsble se B K. ee now a he
Naonal nsues of Healh an Feec M chas of Yale Unvesy ook a een appoach an calculae wha a olecule gh look lke o a wae olecule hey use a copue poga o oll an agnay wae ol ecule aoun all ses of a olecule nong whee he wae ouche n s way hey eve a pcue ha shows he olecule's suface bu os hose egons ha ae se quesee fo suounng wae olecules Such a pcue helps o elucae fo nsance how poens neac wh he wae always pesen n lvng syses. he geoec aangeen of aos s only one aspec of a olecules nae; he checal an physcal popees of each ao-s chage se an neacons wh ohe aos-ae also poan Pee]. Goofo of he Unve sy of Oxfo has evelope a eho o eene how a bologcal olecule checally neacs wh aos n oh e olecules He sequenally places a copuesulae pobe ao a vaous locaons aoun he olecule A each pon he copue calculaes he checal neacon beween pobe an olecule yelng a caalogue of places SCETFIC ERCA Novembe 1992
79
MOLEC DSIGN is a rapidy growing appcaion of mo ecuar compuer graphics. H proease (above) a moecue crucia o he mauraon of he virus, oers an aracve ar ge for drug design. The proen backbone is shown n bue; he sie of caayc aciviy is green. inhibor drug (purpe) binds a he acive sie of he proease, prevening norma vira funcio n. The daa for his mode are from A Wodawer of he Naiona Cancer Insiue. In anoher eermen work ers fabricaed a cusomized enzyme (ef) by grafing a se o bind a mea ion (sma red sphere) ono an anbody ha bnds o he chemica uorescein (bue doed region).
faoable and unfaoable to the pobe ato Pcues po duced usng ts tye of analysis can higight the cheical hot spots whee an ato is likely to bind Copute gapics can also captue the elusie dynaic behao of bological olecules In tllionths of a second olecules ibate twist and otate hei otions ae inisible to xay cystallogaphy d NMR spectoscopy because such expeents take hous o days to pefo Dynac co pute siulations howee can follow the otions of a ol ecule tough thousands of tie steps geneating a coe sponding nube of snapshots of the changing stcte he eseache ay then scoll tough the entie siulaton stoppng at leisue to exaine the ost nteesting te steps he best faes ay be cobined into a shot oie that depicts the olecule's dynaics 8
SCETFC ERCA Novmbr 1992
One of the ost exciting applications of the new gapics techniques lies in coputeaided olecula design s sci entists hae ipoed thei undestandg of biological ol ecules they hae inceasingly sought to odify specic ol ecules to suit a paticula need Designing antiiotic drgs constucting noel potes and engineeing useful icoo gass ae just a few of the goals bioenginees ae pusu ing to ipoe huan health and the quality of life Copute gapcs ae assisting in the design of dgs to teat diese disodes including hypetension ephysea glaucoa and aious fos of cance Reseaches use co pute gaphcs to test a wide ange of candidate dgs be foe be g the tieconsuing pocess of synthesis and laboatory testg One paticulaly poig eot inoles the design of antal agents to contol the eects of the hu an munodeciency is (H). Medical eseaches hae isolated a nube of potes fo the irus and deteined the stctures ong these poteins ae H eese tan scptase the olecule that tanslates ial to DN so that it can ncopoate itself in the host cell's DN and H potease a cucial olecule that allows the ius to atue and to cause futhe infection
MOLECULAR STRUCTURE AND FUNCTION can be studied easiy ceary and accuratey using computer graphics The top images were drawn on nebased devices the bottom ones on pixebased dispays. Researchers may exane the shape of an antibody using a dotted surface (tp lef) or a series of soidoong shaded spheres (boom lef) Computers can por tray the binding of an antigen by dispaying arrows that indi
cate the direction of the moecue's eectrostatic ed(top cen ter) or by using voumerendering techniques to dispay the strength of carbon interactions; green indicates regions favor abe to carbon (bottom center) The extremey rapid interna motions of an antibody may be depicted as a mutipe image (tp right) or as one in a series of snapshots of physicay in teresting moments (bottom right)
Workers have succeeded n crystazng V protease alone and bound wih various nibitor molecules, makng i possi ble to study them by x-ray crysallography. Computerbased analysis of the sctres of he molecles has helped identify a growng st of candidae drg compounds Several of them appear eective in laboratory chemical ests and can arrest the growth of HIV a cel culture. Athough issues of oci ty and ecacy in acual paients rema o be solved, at least one compuer-designed HIV proease ibiorR031-8959, fabricaed by HomanLa Roche in he UKhas shown sucient prose tha i is now beng esed in clcal trials. Encouraged by he many advances in the undersanding of protein strucure and funcion, Rchard A Lerner and is colleagues at he Reseach Instie of Scripps Cc have em barked on a particularly ambitious projec: desigg custom ized enzmes to caalyze, or faciliate, certan checal reac ions The researchers are modfying antioies to act as cat alyss Anibodies possess a remarkable abiliy o recogize and distguish between various molecles, so a caayic an ibody could be constructed to aid a carefully seleced reac ion [see "Catalytic Aibodies, by chard A Lerner and Al fonso Tramontano; SCIETIFIC ERICA, March 1988]. Spe ically designed caalyic antibodies could one day attack a virus or break up a blood clo without harming the paient's own healhy cells In colaboration wih Victoria A Robers, Jo A Taner d Elizabeh D Getzo, also at Scripps, Lerner has modied an anibody o create a chemical site where meta atoms can bind. Computer grapics helped o guide the researchers in consrcng the sie The ablity to add a metal o antibodies is an mporant step oward he goal of taor-made catalysts, because many reactions deped on metal atoms for caalysis The proise of molecular compuer graphics has barely begun o be realized The speed and memory capaciy of compuer hardware are doublg every 18 months, eading to commensurae improvements in he versatility of sofware Virtual-reality smulaors ha can merse he rsearcher n
a tangible molecular word are themselves becoing a rea ity. Video-display goggles change the view in response to head motions force-feedback mechaisms let he researcher "feel he forces acting on he moecule in ew In a prototye being developed at the Universiy of North Carolina under the direction of Frederick P Brooks, Jr., sci enists can use a compuerized simuator o tes candidae drugs by feeling how well they t into a targe molecule A novative project a hat same facility has inked a scang tuneing icroscope with a virtual-realiy sysem The goal is o enable the scientist o see and feel the atomic deas of a molecule beg probed by the icroscope. Such sysems may someday enable humans to nterac wh the subcroscopic word as easily as they do with the word of direc senses. Perhaps he geates vrtue of moleclar computer grapcs ies n its potential to mprove scientic commuication High speed data neworks wll eable workers in dierent parts of the world o examine imultaneousy the lates resuls in molecular research Ineracive video wl perit sdents at a levels o stdy moecuar sructure and function. And so pisticaed simulations coupled wih ristic grapcs wil allow laypeope o obain, for the rs time, a personal fee ing for the complex cheical world win themseves
FRTHER READNG MOLECUAR MODELING OFTWRE ND METHODS FOR MEDICINAL HEISTRY. N Claude Cohen, erey M. Blaney Christine Hum
blet Peter Gund and Dad C Barry in Journal of Medicinal Chemist, Vol 33, No.3 pages 883-894; March 990. OPlR RAPHICS: RNCIPLES AND RACTICE. ames D Foley Andries van Dam Steven K. Feiner and ohn F Hughes Addi sonWesley Pblisng, 990. MCROOLECR PHICS. A Olson and D Goodsell in Current Opinion in Structurl Biology, Vol 2 pages 93-20; April 992. JOURNAL OF MOLECULAR RAPHICS. Edited by W G Richards ButterworthHeinemann Publishers, quarterly
SCIETIFIC ERICA November 1992
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roy Gilcrist knows how it feels to be thorougly versed in a job and to be good at it A 22-yea veteran of the New York Telephone com pany and union member, Gilcrist has repared and spliced every nd of tele phone line from twisted copper pars to optical bers n budngs troughout New York City. "You get into a mind set, he says. "You say, Tis is the way I've been woring. So I don't want to hear anyting about changing it.' Yet for the past year, Gilchrist has been part of an eightman commando team charged ith doing just that: re tg how the telephone company goes about "provsionng, or providg customers with one of its most ad vanced products, and then radically re stcturing how the work gets done. At stake are hundreds of millions of dollars of business. Since the deregula tion of the telecommuications industy n the id1980s, New York Telephone's share of the Manhattan market for pri vately leased, igh-speed data gh ways, caed networks, slipped from 100 percent to about 64 percent tis year hese services are used by bus nesses from banks to longdistance commucations compaes to ship 1.5 llion bits of data per second between oces along a single private path. An alysts estimate that the U.S. market for leasing such lines tops $2 billion "We lost igcant market share n one of the premier products in our arsenal concedes Douglas] Mello, a goup ice president at New York elephone. Now Melo is betting that Gicrst and is collaborators have designed a plan for reversing that side "There's no reason why we shouldn't do bette, Mello nsists Seventyve to 80 percent market share would be "reasonable, he suggests. What is more, Mello hopes that the tecque of retg work practices will be applied more broadly witn the telephone company The eort puts New York Telephone at the forefront of a sweeping trend that promses to be as embracing as the 980s doctrine of quality. From the halls of the Massachusetts Institute of Tecnology to the conference rooms of 18
MEMBERS of the telephone company's Center, led b Eric Wilson (, ) are at the heart of an experiment in redesigning work practices. Phot: Dan Wagner
boutique consultancies, management rus are telling corporations to take a long, hard look at how work really gets done and f the process Such concerns it home at New York elephone's parent, Nynex, in early 1991 as its share of T business con tinued to melt away Mello toyed with iring consultants. "But you oy reay get disceble chge i the people clos est to the problem ae involved, he says. So, in a rst for the telephone company, Mello appointed a design team stafed jontly by "craft, or unon, workers and st-ne managers and set them to the task of sharpeng the way the compa ny handled orders for T es. When he learned that researchers in the Nynex Scence and Technology expert system laboratory wee already begining to model work processes, Mello pulled them into the project as "faciitators. Among the researchers was one con sultant, antropologist Patricia Sachs "Yes, we get a few smirks about the an tropologist, Melo says "But the bus ness is about people, and we had to un derstand how the job gets done Gilchrst and is teammates found a
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multitude of reasons why the phone company had stmbled126 to be pre cise "We looked at the process from A to Z," Gilchrist says, fom the central oce trough the eld construction. "I thi it was the rst time that anybody had an idea of what the whole process looked like, he adds. Flling an order, the group discovered, nvolved 126 worksteps and more than 40 people though many indivduals were re sponsible for some part of a T instal lation, no one saw the job tough ti the end For instance, customers spoke rst with a service representative The "rep would take don some details to start the order and suggest when the company might hook up sevice But that timetable was oy a best gessthe rep was uely to ow any of the engineerng details that would de termine how quicly seice could be connected And although the rep wod have recorded all the data needed to process the order, engineers would lke ly need other iformationa guarantee of future delays "We used to tk, If only those other guys could have done their ob right, then there would be no
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problem! problem! ' recalls Eric Wilson, a mem principle is that computer systems designed to help people learn ber of the design team nd a former should be designed rep "But we never never really knew knew what was to do their jobs rather than simply tak g over tasks such as scheduling goig on a that other end Within six months, the design team Orders from the sales reps were then routed to the Digital Facilities Quality was ready to oer seor managers its approach "We wanted four orga Center, wch wch passed jobs, jobs, lke so many new approach zations collapsed into one, Graham re soccer soccer balls, to service superviso supervisors, rs, who zations counts, and proposed proposed sifting respon in turn routed them to various tech counts, cians Schedulig was coordinated by sibilities so that one small group wold a computer, computer, which distributed distributed job tick be responsible for an entire T job Co ets Should one teccian teccian encounter ordinating the work would be a "T a snag, he might simply go on to the Center Most daring was a proposal next job as another worker was sent to eventually create a job that would out to solve the problem "So a custom bridge the traditional uion-maage er might see three dispatchers dispatchers march ment divide After the presentation "someone said, We asked asked ing in and out and still not have T ser Sachs recals, "someone vice, Gilchrist points out nd only you to organize a radical change, and rarely did the repswho talked with by God, you did it!' customersever talk ith engineers or Transforng the ideas into action with techcians turned out to be harder than the team g ood With the the help of the Science and and Tech Tech expected "We had a whole lot of good nology facilitators, facilitators, Mello's group began stu, Gilcist says, "but the only peo to probe the work practices more deep ple who new it were us nd wowthe wowthe ly, modeling modeling the work lows on a com rest of the world was bi g! Senior Senior man puter Some smple smple changes seemed ob agement decided to give the new plan vious: the design team quicky recom a sx months' trial in downtown Man mended rewriting the form lled out hattan but required one compromise: by the reps as they took orders to in rather than try to negotiate a new job clude more appropriate information title, New York Telephone would sim "Tis sounds simple, says Elizabeth R. ply brng three types of workersreps, Graham, who headed the facilitators' engineers and truk assignorsinto T Center and sit them down side group But it took almost a year to elic the T Center it and coordinate all the relevant ques by side "They'll do all the front-end tions for the new form, she adds work, Graham explains, and can call More fundamentally, the team ex on one another to handle questions plored paradigms, or descriptions, of From the T Center, the orders will how dierent groups interact interac t Led by low to a turf coordinator, responsible Sachs, the members talked about how for some section of the city That coor African bands function, how the tele dinator will track the progress of the phone company used to work and how job until completion, keeping in close they wod wod orgaize orgaize a start-up start-up company company touch with the the tecicians tecicians Accordng Accordng to that sold sold T services T services They visited oth the simulations rn by the Science and er divisions of the company and even a Tecnolo Tecnology gy research researchers, ers, the the plan should should branch of Cg, Inc, to watch how enable enable a team of a dozenrather than 40people to set up a new T service T service selfmanaged teams performed The group even tried imagining the in two or three days, down from more perfect perfect employ employee ee"Mel "Melw who ho could could than seven The coordination relies on do everything himself, then gradually commuication among people, people, rather gave Melvin Melv in perfectly adept assistants than on computer scheduling, pints By tg about what information out David M Torok, a facilitator Melv needed needed to get is job done, Sachs Sachs Late ts September the trial was notes, notes, it became became clear who needed to scheduled to wing into action Mello talk to whom to move ahead a job like will be watching for evidence that cus setting up a Tline "You thought you tomers are happier and that the time understood your job, but you were oly for settng settng up services services has dropped dropped The Tecology y researchers researchers will acting in a little box, Wison observes Science and Tecolog "We came out of that box, Gilchrist be motoring how people learn to col adds, "but reluctantl reluctantly y laborate and looking for clues about Over the weeks weeks the design design team ar how to design ture software systems ticulated a set of guiding guiding priniples, or Wilson, who will be acting manager of ways that the team members wanted to the T Center, plans to g e workers to work work Ensring Ensring that that people were were respon respon keep seeng ways to smooth the pro sible for an entire projectfrom order cess Gilchrist has retrned to s work to instalationwa instalationwas s on the list lso im as a splicer splicer and and is eady eady helpng helpng people people portant, Sachs adds, was the belief that sort out the new teamwork teamwork approach knowledgeable workers workers are valuable as "It's se been a real education, he says sets The practical implication of that with a smile smile -Eliabeth Corcon 120
SITIFI RI November 199 © 1992 SCIENTIFIC SCIENTIFIC AMERICAN, INC
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ter years spent developing whis per-qet refrigerators, refrigerators, appance makers may turn to noise to cool the next generation generation of iceboxes A physicist-turnedentrepreneur has de veloped a lubricant-free soc compres compres sor that proises to be more energy ef cient than standard standard compressors and can use use reigernt reigerntss not based based on ozone ozone depletg depletg cloroluo cloroluorocar rocarbons bons (CFCs) (CFCs) Timothy Timothy S Lucas, president of Sonic Son ic Compressors Systems in Glen Alen, Va, believes s compressor may prove to be the tonic the applianc industry needs to meet the upcoming stringent CFC regulations and energy efciency requirements Lucas says s start-up company company has bult worng prototypes prototypes and is negotiatng a contract with a ma jor refrigerator maker He hopes to demonstrate is device in a domestic refrigerator in early 1993 What makes the instrment promis ing is that it is a drop-in replacement for conventional compressors and so will not require retooling or other ex pensive procedures In addition, "we shod be able to to make the compr compress essors ors at a comparable comparable price, Lucas says says Cou pled with a projected improvement in energy eciency of 30 to 40 percent over esting compresso compressors, rs, manufactur manufactur ers may save on more expensive expensive tech niques for eiency, eiency, such as increas ing insulation or adding larger l arger heat ex changers and more powerl fans Standard compressors in refrigera tors generall y rely on pistons or rotors r otors to compress the cooling gas Because refrigerators are expected to function trouble free for for 15 to 20 years, the com presso pressors rs must must be lubricated to prevent excessive wear wear nd the refrigerant and the lubricant must be compatible The most ideal mx has been mineral oils and CFC 12, which is scheduled to be phased out out over the next next few years, pos pos sibly by 1996 As a replacement, the chemical industry is pusng hydro luorocarbon (HFC) 134a, a substitute that developers claim has no non ef fect on the ozone layer and should pro duce oly a imal greehouse eect Some refrigerator engineers worry that lubricants lubricants compatible compatible ith the new refrigerant refrigerant may not be developed in time The appliance appliance ndustry has been evaluating evaluating ester-base ester-based d oils, but tests so far have not been encouragg "The lu brication properties properties are not n ot as good as those of mineral oils, says Carl Outt, the general manager of engineering at
the Whrlpool Corporation. Further more, "funny tngs star happeing when you add other compounds to improve the lubricant's eectiveness, he remarks rema rks Over time the ester oils re act with HFC 134a and other oils used to manufacture components to form a waxy residue that plugs up the refriger ator tubes The oils, too, may react with water to corrode the internal parts, so that refrigerators would have to be made a moisture-free environment contrast, Lucas's compresso compressorr needs contrast, no lubrication, and that means "trow ing away oil restraints in nding an envonmentally envonmentally frieny frieny refrigerant, refrigerant, Lu cas says The soc compresor com presor is sim ply an oddly shaped tube that acts as a resonance cavity for the refrigerant. The entire resonator moves back and forth about 50 microns along its cylin drical axis at about 340 hertz The os cillation creates a standing stan ding wave in the cavity Because the cavity is designed so that the standing wave reiforces it self, the pressure changes achieved in the tube are large In terms of sound pressure, the amplitude is about 200 decibels, decibels, but the compre compressor ssor is nonethe nonethe less quiet because because the mass of the tube prevents any sound from escaping. A valve vents the pressurized refrigerant into tubing that circulates the luid. The biggest problem Lucas faced in is design was elinating shock waves that formed formed n the cavity, wastg wastg power power as heat and thereby limiting compres-
sion. Lucas spent a year at Los Ala mos National La boratory woring with acoustic and engine-cycle engine-cycle expert Grego ry W. Swift to nd a solutin. "The trick was the geometric design of the res onator, Lucas points out. The shape made the igher harmonics that caused the shock waves to interfere with one another, leaving oly the fundamental frequency in the cavity. To an ndustry no for extreme caution in introducin g new technology, a radically a radically redesigned compressor may seem ris Nor Nor have manufacters manufacters for gotten General Electric' Electric'ss debacle it its rotary compressor compressor in the 1980s. After rusing it into prodUction, GE discov ered the compressor was defective; the company spent an estimated $450 mil lion to recall the products But Lucas is unperturbed "It appeared to be more of a management problem rather than an engineerin g one, he notes Refrigerator compaies may have few other alteatives alteatives i they canot meet tough energy efciency standards cost eectively or nd an HFC 134acom patible oil Manufacturers should be able to meet 1993 eciency ecie ncy guidelines by tweaking existing parts But the oil compatibiity compatibiity issue remains, wll, sticky sticky One industry expert expert tinks manufac trers could end up shorteing shorteing the war ranted lifetimes of the macinery if the gumming is not solved. the more reason, perhaps, to cll out with a new compressor -Philip Yam
Refrigerating by Sound RESONATOR CAVITY
LOW-PRESSURE GAS FROM EVAPORATOR
NAKE VALVE
DSCHARGE VAVE
MAGNET
SPRNG
RESONATOR SUPPOR
The sonic compressor is driven like an ordinary oudspeaker. The osclation creates in the resonator cavty a high-ampitude standing wave, whch com presses the refrigerant gas. A one-way vave vents the gas to a condenser, which lquefies and cools it. The lquid circulates around the space to be cooled evaporating evaporating and thus absorbing heat The gas is then pulled back into the compressor to repeat the cyce.
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urphy's second corollary says everything takes longer than expected Saving the . semi conductor in dustry is no exception 1987, with neres sti jangling from watching Japanese competitors gobble up the market mar ket for dyamic random-ac cess memories (DMs), S S industry and goverment created Sematech, the Semiconductor Manufactring Tecol ogy research consortium. According to the founders, foun ders, Sematech Sematec h would woul d develop manufacturng teciques that any . chip maker could use, thereby hoing erica's overall competitive edge. To pay for the project, industry and gov ernment each agreed to spend $100 million anually for ve years. That time is up. Although .S. mem ory chip makers are not yet on rm ground, many believe Sematech has in stead helped stabilize the other half of the chip businessnamel business namely, y, the se conductor conduc tor manufacturin manufa cturing g equipment industry industry Now, Now, supporters supporters suggest suggest,, Sem atech can turn back to its original s sion of dectly addressing the needs of chip makers. makers. As a result, result, Sematech's leaders are pounding the pavement at Capitol Hil, aring that they have spent the money wisely and that the goverment should continue the con sortim's aowance "I don't t there there is anyone anyone who wl not say Sematech has done a lot of good things for S industry, says Richard A. Aurelio, an executive vice president with Varian Associates in Palo Alto, Calif Representatives of the Bush admnis tration are also enthusiastic. "We feel that Sematech's been extremely eec tive, says Arati Prabhakar, who directs the croelectroics technology oce at the Defense Advanced Research Research Proj Proj ects Agency (DARA). Yet as Sematech has reached reached the ve-year mark, DA'S obligation is over, she says "We're "W e're not in the business of perpetuating block funding, Prabhakar adds The Th e govern govern ment has proposed trimming funding to $80 mil on in scal 1993 (Observers (Observers nonetheless believe Congress Congress will re store Sematech's Sematech's $100 mllion) Measuring Sematech's performance precisely is tri c Earlier tis year mar ket research analysts estimated that the erosion of American rms' market shares in chips and equipment had stopped; some reports ndicated that at least the top few equipment makers gained some market share during 1991 But ndustry leaders caution that any
SCIETIFIC ERICA November 1992 © 1992 SCIENTIFIC AMERICAN, AMERICAN, INC
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such gains are short-lived at best For eral Signal and the Silicon Valley Group the equipment indusry, at least, "the to buy out faltering US toolmakers and claims that we're regaing market share have another go at bulding advanced against the Japanese aren't tre, Aure lithograpic steppers, the devices that lio says Japanese cip makers bought project integrated-circuit patterns onto ittle equipment last year, he points out semiconductor wafers The Silicon Val he recogition that cells receive "As soon as the Japanese start investing ley Group received sgnicant aid from again, we'll be down instrctions from hormones and IBM, in the form of a pledge to buy 20 Even so, equipment makers say the advanced steppers Yet ithout Sema growth factors provided a foun program has enabled them to under tech the deal wod have falen tough, dation for the biotecology industry in the 1970s At the time, few people stand better their customers' needs Der Torossian says Since they were brought together under In its sixth year Sematech's leaders categorized proteins such as inulin and the Sematech umbrella, tool and cp aim to refocus the consortium's atten erytropoietin as "rst messengers It producers speak more freely lthough tion on issues of immediate concern to was enough to now that such proteins dividual ms were woring on the cip makerssuch as computerinte nstigate celular change by binding to quality and reiability of t hei products, grated manufactng and ghtg con receptors in the membrane surroding the oly systematic cross-industy pro tamination in clean rooms At the same cellsand that making them in quanti gram that took hold was Sematech's time, Sematech plans to help cip man y would provide treatments for dia Partnering for Total Quality, obseves ufacters advance to ever more sopis betes and anemia Today the way that communication Papken Der Torossian, chairman of the ticated and densely patteed cips Equipment makers worry they l be proceeds insde the cell after a surface Silicon Valley Group in San ose, Calif Too and cip researchers also co left bend More complex cips, Bonke receptor is contacted is the rallng in aborated on standard tecniques for observes, w require new tools "'d like terest of a new group of botecology appromating the mean time between to see more direct investment in the compaes When a receptor is bound, failures and for estimating the cost of form of guaranteed loans to manufac its conguration sifts That action a new tool, says Neil R Boke, pres turers to de new tecnology, Au sumons a variey of so-called second messengers, wich in turn sgna other dent of General Signal's semiconductor relio adds Others suggest there are more roles chemical carriers nside the cell Tis equipment operations in Santa Clara, Calif "Before Sematech, buyers wouldn't for Sematech Der Torossi would like "psst, pass it on process, known as accept your gures, he explains They to see Sea tech serve as a clearng signal transduction, is opening path relied stead on homegrown models house for information about all the ways for treating astma, allergies, ar for calculating likely costs and failure governmentfunded research programs tritis, cancer, carovascular disease, rates "Now when asked, we're all using in microelectronics Sematech "should psoriasis and other sorders "It is now be used as a catalyst to organze and widey accepted that many diseases are the same sheets of music Sea tech also helped the industry maxmze the semiconductor R&D that the result of dysnction in signa trans duction pathways, pots out rthur G develop specic tools Even though Ap we do in the national labs, he says For now, Sematech has its eye on se Altschul, Jr, director of plannng for pled Materials is the top S semi conductor equipment maker, "we have curing the funding it believes it needs Sugen in Redwood City, Calif Firms incuding iad, Cadus, Onyx, huge R&D expenses It is dicult to go to move cip manufacturing to the it alone, says Dan Maydan, executve next generaton of devices The priority Spix and Sugen intend to manufac vice president at Applied Materials n of Sematech's rst ve years was to te small molecules that block or mi Santa Clara, Calif Tecnicaland nan catch up with Japanese competitors, ic the action of second messengers and cialad from Sematech accelerated says ' Prabhakar "Now, she ther followers All beleve that signal the development of a new etcing tool adds, "the issue s to provoke funda transduction oers numerous points for Support from Sematech enabled Gen- mental change -Elizabeth Corcon pharmaceutcal intervention, even i the pathways are poorly marked as yet "We're trying to gre out an incredi bly complex railroad and witcing sys tem by just having direct experimental From 1982 through 1992 Sema evdence for some of the parts, ex tech received $990 million. The plans Glenn L . Cooper, executive vice consortium spent $287 million (29 president of Spinx in Durham, NC percent) on external research and "How the conductors talk, what the development right). Another $214 common switch boxes are and what the million paid for on-site facilities overall timetable is are only now being and equipment, supplemented by pieced together $135 million for clean-room sup Spx's approach revolves around plies and $84 million on equip the lipids, or fats, that make up cell ment for specific projects. Labor membranes "It's a prcularly attractive costs consumed $185 million. place to work, Cooper says, noting that lipids reglate certain key second mes ITHOGRAPHY sengers, such as protein nase C (PKC), CENTERS OF EXCELENCE an enzyme that mediates cel nctions, AND NATIONAL ABORATORIES incuding inlammation and prolifera CONTAMINATION-FREE MUTILEVEL METAS MANUFACTURING tion When a growth factor bnds to a COMPUTER-INTEGRATED receptor on the cel surface, a lipid mol o OTHER D DISCRETIONARY FUND MANUFACTURING ecule lodged in the membrane s chem ically cleaved in two One of the fragSOURCE: General Accounting Ofice
T
Were Sematech Spent Its Money
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SITIFI RIA November 1992 © 1992 SCIENTIFIC AMERICAN, INC
Steps Intracellular Signal Transduction INDING PROEIN, SUCH ASA GROWH FACOR
RANSD UCING PROEIN
SOURCE: Ariad Pharmaceuticals
ments is released, activatngPKC side the cell and kickng o a cascade of cell division and lamation. "That's when al hell breaks loose, Cooper declares. Spx believes blocking the signal that stches on PKC may prove bene cia in treatng a spectrum of illness es, cludng psoriasis, a conic skn disorder that aects 2.5 million people in the U.S. Ts October psoriasis pa tients at the University of Califoria at Irne were scheduled to begn testing an ointment that interferes with the ac tion ofPKC. Meanwle Ariad Pharmaceuticals is exploring drugs for treating allergies and asta. Because patients with these iesses experience acute attacks, "you can test a drug and now whether it works in 15 miutes, observes Harvey Berger, the Cambridge, Mass., compa ny's chief executive oicer. In contrast, cancer drugs usually require lengthy trials in large nmbers of subjects. The rm began corporate life earlier this year with a private placement of $46 million, the largest yet garnered by a biotechnoloy company. riad's tia target is an interaction that results the release of istamine a phenomenon al too familiar to aler gy and asthma suerers, who experi ence the tchy, rritating results. When an alergen such as pollen enters the body, the une system dispatches an antibody to meet it. The complex then binds to a receptor waiting on the surface of a mast cell. The bindng al-
ters the receptors intracelular congu ration, an event that prompts the cell to spew out its stores of histame. "Its e a bolt of lighg ttng a tree and causing the root� o change, says Joan S. Brugge, riads scientic drector. A drug to prevent the altered roots of the mast cell receptor from contact ing the intracellular components that trigger releae of histane might be eective against alleries. Ariad says it intends to beg testing such a com pound i humans witn several years. The company expects that eort to help it devise other drugs. "What we learn from mast cels wl be relevant to other actors of the imune system, such as T and B cells, Berger observes. "here are a lot of slarities already that pro vide insights into rheumatoi arthritis and other diseases, he notes. Other researcers are interested in how cells pass messages by transfer rg electricaly charged groups of mol ecles from one prote to another. Sec ond messengers often spr these move ments, which are carried out by specc enzymes. For example, knases add negatively charged phosphate groups; phosphatases reverse that action. various nds of cancer, and possi bly non-nsuln-dependent diabetes, the culprit appears to be the enzme tyro sine knase. "Its a gas pedal for the specic functions of cell growth and glucose uptake, says ltschul of Sugen. The enzyme's ability to transfer phos phate groups is critical to the way
growth messages echo trough cells. ltschl notes that phosphatases can e thought of as brake pedals. At Sugen, researchers are screening diseased tissues to see if they nd re ceptors that are not present in or are somehow dierent from those in nor mal tissue. They presume these recep tors are a mechaism for the disease. If the receptors contain tyrose nas es, Sugen begins looking for matcing phosphatases or other means of g o the process. The company expects to begin testing drugs based on thes discoveries humans n two ears. Follong a simlar vein of inquiry, Cadus in New York City is seeking to inbit the transfer of moleclar groups that alter receptors coupled to socaed G protens. he receptors for light in the back of the eye act on G protein, explans Samuel D Waksa, chief execu tive oicer of Cadus and its parent com pany, !mClone. " the eye, one photon of light activates a receptor. Then G bidng proteins set o a cascade of messages that is amplied until you see the light, he notes. Inlammation and allergy and many other responses to sngle molecules may proceed the same way, Waksal says. But cronic s eases can develop when a signal does not stop. Cadus is intent on blocking transfer events known as methylation and prenylation that enable G proteins to couple to receptors. There are many regulatory proteins hard-red into the pathway from cell membrane to nuceus, reminds Frak McCormck, vice president of Onyx. The Richmond, Calif., spno of Chiron is devoted to desigg cncr drgs based on signal transducion. "We're gong for the rs pathway, which includes tyro sne and other kinases, he says. Muta tions in the ras gene (which is involved in the growth of normal cells) lock it into an active state in many cancers, causing signal transduction pathways to be hperacve. "tras drgs are kely to slow down the growh of tmorsfor how long is own, McCorick spec ulates. "Maybe the cels will die out or wl sit atent wle the g is present. McCormick acknowledges that shut tng down pathways used by normal cells raises conce about potenal i ef fects such drgs might have on healthy tissues. But experiments n ice with a variety of cancers indicate that remo ng the genes responsible for destruc tive pathways has not harmed the crea tures. "It seems that normal cells d a way arond, he says. The early prom ising results from signal transduction research are encouraging scientists to folow pathways they might otherse have avoided. -Deborah Eickson
SCIIFIC ARC November 99 © 1992 SCIENTIFIC AMERICAN, INC
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Iuv g fl ll hlp d k l wh wk
I
T b ! The Academic Decathlon is a national scholastic competition which provides recognition and reward for solid academic endeavor. Individual high school students compete in their grade point category: A, B or C and below. Teams compete across a range of events for important awards: scholar ships, medals, pride in temselves, their teams and their schools. e reatet aard r u peope eduata aeeent Te ade et eek reeed repet r ork at a ee trted ad utaed dur te prtat pre-ee ear pe t jut to te teetua ete but t pe tru o be tudet u pepe tk part Deatl pett uatn ext n Nata Fal
f at rst you don't succeed, then try, try again: such s the tration of drug development The sometmes intuitive, basically trial-and-error pro cess typcally involves screeg 20,000 to 40,000 compunds to nd a single promisng lead. For every 4,000 leads exaned, often no more than one be comes a marketable drg. To ren n ts randomness, medicinal chests have been attempting for the past 10 years to constuct drugs that t precise tar gets, such as receptors on cell surfaces. Computeraided approaches to "ra tionally desgng drugs have not yet worked as well as researchers had hoped. The methods tend to rely on an image of a molecule in what is pre smed to be ts ideal congurationfor nstance, at the moment of bindg. Be cause few computer design programs can acknowledge the mutual shape changes between a molecule and its re ceptor, drug designers may be misled nto creatg a "perfect compound that cnot nction in the body. Arris Pharmaceutcals believes artifi cial-intelligence () systems are a be· ter way of utilizg the strength of computers in drug discovery. Comput er algoritms smlar to the kind that enable U.S. military cuise missiles o
nd ther targets can also be written to recognize the shapes of molecules, ex plains Michae J Ross, president and chief executive ocer of the South San Francisco Silarly, programs de veloped by robotics researchers to move a mechanical arm without nocking down obstacles alow the computer to contemplate how a drug contacts its receptor. "We're not developing expert systems to replace medical chemists, Ross notes. "We're developing tools to augment the ntution The company is usg its systems n-house, tially to optimize dgs for astma and to create an orally active form of erythropOietin, the red blood cell stimulator. "The computer should help us decide early on what to synthe size, so we w make oy 10 percent of the molecules we would otheise have to, Ross declares. In the process, researchers program into the computer descriptions of mole cules and the results of their perfor mance in biological assays. The com puter analyzes the data to determine what all the compounds that work have in common and how they dier from those that do not work. The scientists apply the computer's observations n the next round of eerents, steady bldng a data base of eerience. "Peo ple just cannot reember all the data they've seen, says Toms Lozano-Prez, a researcher in computer sion and robotics at th Massachusetts Institute of Tecnology and an Arris consultant
inii min is
pleased to oin American Airlines, Te Krausz Companies, Inc., GTE, D.C. Heath, the Lenno oundation, Ronald Mc Donald's Cildren's Charities, orth rop, The Psycological Corporation, Raytheon, TRW and oters in sponsor ing the Academic Decathlon. All of us saute the many local companies and organizations which help their schools and their children participate.
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MOLEC SURACES analyzed in detail with arti(al intelligence, may prove to have paes that inuence the peoance of drugs. Photo: A Phaaceuicals
SCIIC ARIC November 1992 © 1992 SCIENTIFIC AMERICAN, INC
"Macine leg algorithms w find patterns that est in all the data. By relying on computers to track ex periments, ris hopes to be able to model molecules in much greater detai than is now comon. Most computer representations of drugs focus on a few points and the distance and angles between them, Lozano-Prez explains: "We're nding you need more like 100 data points to characterize a molecule properly. Attributes such as molecular charge and hydrophobicity add en sionality that is ct for humans but simple for computers to consider Arris scientists anticipate that map ping the surfaces of molecules in detal w free them of established notions concerng the way certain classes of molecules are inluenced by structur al features such as "backbones. Ross notes, "It's not just how much a sur face sticks out in one direction but also what's in beween that counts A key aspect of the Arris approach is that it takes advantage of negative data. "If you're kng up a mountain, you'd like to know where a mudslide has closed o a path, so you won't bother going that way. You'd at least like to mark your map for next time, reasons ichard H. Lathrop, seor scientist at rris. The system he and the compu tational group at Arris are creating w record the topography of molecules "It w tell you, whatever you do, don't have something pointy stickng out of the left side, he says The company believes it w be able to apply what it learns from one class of molecules, such as peptides, to oth er compounds, such as small organic drugs that can be taken orally "I think rris is going to make money, de clares Larry Hunter, director of the ma cine learning group at the National i brary of Medicne. "Small increments of improvement lead to bigger and bigger advantages, as the Japanese have dem onstrated with cars, he notes. Peter S K, a strucral biologist at the Howard Hughes Medical Institute at the Whitehead Institute, observes: "It's not trvial to bring the articialintelli gence people to the biology people and have them all xthat's starting to happen at Arris "If wha we have is as good as we it is, we won't be able to stop peo ple from followng us, Ross says ris has attracted the top academic resech ers in machine learnng and pattern recognition, but competitors could still tap a rich source of highly skiled peo ple. these postcold war days, classi fied weapons designers may nd them selves invited to join a new technology explosion. -Deboah Eickon
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THE ANALYTICAL ECOOMIST A Rsk Worth Tag
P
oor people have few assets. As a resut, few acial istitutios e eager to ed them moey. Ac cordig to covetioal ecooic s dom, poor borrowers lack the icome to pay o oas. Wors e, f they defaut there is o coateral to seize i lieu of repaymet, although oa sharks may circumvet tis problem by sezig bor rowers istead of their assets That o oe eds to the poor is geeray ac cepted as poof there is o moey to be made at it. Several baks ad acial groups are successy abadoig tis preju dice May poor peope, it turs out, are more tha creditworthy uder the right circumstaces. Cosequety, so cia bettermet ca be protabe-both i the Third World ad the U.S. "There really is a market che for these o vative forms of edig, says Michael Carter of the Uversity of Wiscosi "Capital markets ted ot to take care of peope very wel. The progrs th at work rely o sm oas, short repaymet periods ad, frequetly, group edig. The most famous is the Gramee (or "vilage) Bak of Bagadesh, whose average oas of $67, rougy equivaet to half a year's icome, must be paid back i oe year. Gramee reports that 98 percet of its loas are repaid-as op posed to the coutry's average rate of 30 to 40 percet. Ecoost Muhaad Yus foud ed Gramee Bak i 1976 after he de teried that ack of capita was the prary obstace to productive sefem poymet amog he poor. Ocialy es tabished i 1983, the ba ow has some 980 braches ad 12 o bor rowers. Nietytwo percet of the ciets are wome who sought to start their o busiesses. Vages where the b has et moey have registered im provemets i educatio, health care ad wome's status Gramee's sategy for success is peer edig To obtai a loa, a idividua must bad together ith four eigh bors. The group meets with a loa of cer ad the chooses oe or two of the ve to be eigibe for a itia oa. Be fore aother group ember ca receive a oa, the rst borrowers must make reguar repaymets A oas must be 126
repaid before ayoe becomes eligible for a secod, larger oa. Peer ledig solves several problems that are heret i al capita markets but are particulary thoy for the poor. The st is ack of iormao. I a ba does ot kow a cliet's istory, it ca ot adequatey assess the rsk of ed g. Athough the expected prot o a $io corporate e of cret ca justi detaied factg, the iterest o $67 for a year woud barely cover the teephoe cal for a computerized credi report-assug that a ladess Bagladesi farmer had a documeted credt stoy. I cotras, people from a viage or eighborhood kow oe aother I eect, they elimiate the costs that the eder would otherise have to pay to detere creditworthiess "It is hard for peope the hierarchy to have as good iformatio as peers
People considered "poor credit risks have loan repayment rates of nearly 100 percent. do, oes Joseph E. Sigitz of Staord Uiversity. additio, Stiglitz says, "peer moi torig addresses the heory of moral hazard. Accordig to tis theoy, bor rowers w repay loas to baks oy if they have sometg to ose that is more vauable tha what hey coud gai by keepg the cash Whe the ast recessio t the US., for example, thou sads of home oers abadoed hous es that were suddey worth less tha the baace o their mortgages. Whe peope's fates are ed, however, they ca create resposibe peer groups ad poice oe aother. " You are ted to the group as a whoe, Carter explais To some, the mode of the Gramee Bak woud ot seem to be oe that coud be successfuy traspated to the US. "A ot of Americas woud bak at it, Stiglitz says deed, some at tempts at peer edig i the US. have faled, perhaps i part because the eighborhoods are ot as homoge eous as they are Bagadesh. Never
S November 1992 © 1992 SCIENTIFIC AMERICAN, INC
theess, more t 20 US. orgaizatios use group ledig to d sma eter pises Some, such as the Wome's Self Employmet Proect i Ccago, have repaymet rates of eary 100 percet (The U.S studet loa default rate is curetly 1 9 perce t.) Despite the outstadig repymet records of these sma ledig orgaiza tios, some ecoosts questio wheth er they are realy protabe. Gramee, for exampe, sti requires a subsidy to meet its operatio costs. Ye Gramee "would't take much to become protable, argues J. D. Vo Piscke of the World Bak. exader M. Couts of RESULTS, a oprot group workig o word huger, co teds the bak w be i the back i a few years "It was ot protabe be ca use it was expadig rapidy util re cety, he expais. Bak Raat do esa, wich provides rra credit a tiowide, is already protable, otes Marguerite S. Robiso of the Harvard stitte for teatioa Deveopmet. The apparet success of Gramee, Raat ad similar istitios aso ex poses ecoosts' disregard of the i formal sector (smalscae sefempoy met) as a ege for deveopmet. As much as haf of the gross domestic product of L merica coutries, for exampe, comes from such activities, says Gabriea Romaow of ACCION teratioa, a oprot orgaizatio that has grated crooas sce 19 73 Meawhile traditioa ecooists fo cus o-ad the Word Bak teds to d-atal resource eoitatio ad frastructure deveopmet, such as road buildig Nor is ecouragemet of the iforma sector a developmet strategy suted oly to Thd Word coutries. I the U.S, more tha 100 orgaizatios cur rety assist icroeterprises by pro vd aig, grats or loas. Coess gave the Sma Busiess Adstratio $ 1 5 o this year for 3 5 icrooa demostratio projects. "Some baks are beng to see tis as a way to broade their orma operatig proce dure, says Bevery Sth of the As soci atio for Eterprise Opportity To propoets of Gramee, that bae y begis to tap the possibities. "There is o reaso we could't have a hou sad Gramees this coutry, Vo Pischke says. -Marguerite Holloway and Paul Wallich
THE AMATEUR S C lENTl S T
odd o so
ighting epheid Variabes
N
ot all stars sne as steadily as the sun A small percentage is ibly luctuate in brightness But far from being mere curiosities, vari able sts oer much iformation about themselves and the universe as a whole Among the most use are the socalled type I Cepheids, because they are good indicators of distance Ts property comes about because a deite relation exists between a Cepheid's period of variability and its lumnosity: the long er the period, the intrinsically bright er the star Finding a Cepheid's period and measing the apparent brightness enable astronomers to deduce its dis tance from the earth [see "The Expan sion Rate and Size of the Uiverse, by Wendy L Freedman, page 54J. etting accurate distance gures is usually not straightforward Because of the range of magnitudes in the peri odlunosity relation, distance calcu lations can be o by a factor of two or
tree To correct for this uncertainty, astronomers generally rely on observa tions of several Cepheids in proximity For example, I discovered 29 Cepheids in the galaxy NC 3 09 I t their ap parent magtudes at maximum light into the graph of the periodluosity relation [see bottom illustration on opposite pageJ. The t yielded a distance f 9 megaparsecs Even ts gure is oy approximate, since it is not cor rected for absorption by the interven ig interstellar matter Accurate dis tance measurements usually demand large telescopes, lters ad complicat ed tecques to extrapolate measure ments from one celestial body to an other As such, determinig distaces is a task best left to the profeional Yet the amateur is not left completely out in the cold You can readily deter mine a Cepheid's brightness over time ad display the information as a light curve One of the most usel resources
DELTA CEPH is in the constellation Cepheus, near the Little Dipper. Compare its brightness over time with that o f Beta and Epsilon Cephei Astronomers use the Greek alphabet to label stars in a constellation according brightness.
128
CIEIC ERIC November
© 1992 SCIENTIFIC AMERICAN, INC
i making observations of variable stars is the Astronomical Almanac Tis refer ence (availbl� from the Superitendent of Documents, US overnment Print ing Oce, Washigton, DC, 20402) ists the variable stars visible to the naked eye The iformation includes the names of the stars, their type and location and their period of variability The almanac also lists a recent time of maximum light, wich ca be used to predict future mmum brightness Stellar brightness is expressed in terms of the magtude scale Each unit on the scale corresponds to a lunosi ty dierence of 25 times Fainter stars have larger magnitude numbers; the brightest objects in the sky have nega tive numbers For instance, the sn shines at magnitude 26 The unaided eye can detect objects up to a magi tude of about sx The times given in the almanac are in Julian days, which is a g dec imal numer related to the dates and times of events Julian dates are much more convenient than ordinary calen dar dates To obtain the interval be tween events, you simply subtract the dates Section B of the almanac sts the equivalent calendar dates The general strategy for observing Cepheid variables is to measure the brightness of a Cepheid at many times over many cycles There are two ways to collect the data on light variation The rst is simply to use the unaided eye and make informed estimates The second is to photograph the star and determne the brightness by measuring the size of the image In either case, begin by making the rst set of measurements close togeth er over one or two cycles, so you can get a rough idea of the period Then wait for a few cycles and take a second set of measurements But do not wait too long: whe the number of cycles multiplied by the uncertaty in the pe riod equals one period, you woud be o in the cycle cot by one Pause for sev eral more cycles before taking a td
GEORGE A. CSON teaches astrono my phi chemistry and piano (music is his other passion) at Citrs College in Glendora Calif He is also a visiting as tronomer at the Carnegie Instittion. He received his Ph.D in physics from the University of Califoria Davis
set of observations. You can repeat this process indeitely. Kowing the n ber of cycles between the observations, you can "phase together your observa tions to produce an accurate value or the period. I use a computer program to perform the task; the box on the next page describes the algorit. The procedure to observe Cepheids with the naked eye is simple in princi ple and is attributed to the German as tronomer Friedrich W. A. Argelander. You select ordinary (nonvariable) stars to compare with the Cepheids. The ap parent magtudes of the comparison stars should cover the full range of the variable's brightness. The comparison stars should be located in the sky as closely as possible to the variable, so that each comparison star and the vari able are n the same eld of view. Ideal ly, the comparison stars should dier i steps of 0.3 to 0.5 in magnitude. I la bel each comparison star in an alpha betical order based on brightness, with "a being the brightest. At the time of observation, decide wich two comparison stars have mag nitudes that bracket those of the var iable. Then try to estimate to the near est tenth the relative brightness of the Cepheid in the bracketed interval. Thus, if you estimate that the magi tude of a variable is 0.4 between those of comparison stars b and c, rite b4c as the magitude (the Cepheid observ er's shorthand). You can convert to the actual value by interpolating between the kno magitudes of b and c. Of course, suitable comparison stars may not lie close enough to the vari able. In that case, you would need to shift your line of sight back and forth between the stars to estimate relative brightness. Visua memory is very short; when you concentrate on the second star, your eye has "forgotten how bright the rst one looked. In addition, the g of stars makes it more dicult to judge their brightness. Even so, with practice, your ability to esti mate brightness can improve. In fact, ith oly three levels of brghtness, the period of a variable can be found ith reasonable accuracy. Try the techque on Delta Cephei, wich has an apparent visual magitde of 3.48 at maximum and 4.37 at mi mum. Locate Beta Cephei (magitude 3.23) from a star chart and use it as comparison star a. Use Epsilon Cephei, at a magnitude of 4.19, as comparison star b. Observe Delta Cephei once a ight for a week or two, and write down its time and brightness as compared with a and b. If the brightness of Delta Cephei is in between those of a and b, simply rite a5b. These three values
w
Z C « :
o
DAYS
7
LIGHT CURV for Delta Cephei shows that the star varies by approximately a mag nitude in brightness over a period of about ve days.
can provide a crde estimate of the pe riod. With a ttle practice and some luck ith the weather, you should be able to rene your estmates. The almanac lists other Cepheids and suitable compari son stars if Delta Cephei is not easily seen from your location. A more accurate means to record Cephed variability is through photog raphy. Because lm can detect objects too faint for the naked eye, you can conduct a photographic study of Ceph eds not even isted n the almanac. You wl need a camera mounted to your telescope and a clock-drive it (a track ing mechanism that follows te appar ent motion of a celestial body). For a variable such as Delta Cephe, a typical exposure through a small telescope would be about 10 seconds. You should, however, take several pho tographs with dierent exposure times and select the best time. I recomend doing your own developing so that you can keep the processing consis w
tent from one roll of to the next. Film records the lght intensity of stars as sze: the brighter the star, the larger the image. Thus, you wl need to correlate the diameter of a stellar image with a star whose magnitude is kown (magtudes are printed n the almanac and other andbooks). n my astronomy course, I use the open clus ter NGC 6940 to teach my students how to perform the task. I use a 12power comparator (essentially a loupe) to measure the images of the 5 stars in the cluster on an enlarged print. The comparator contains a reticle that has a lnear scale with .ilimeter div sions (available from scientic-equip ment supply compaes). You should be able to estimate sizes to within a few hundredths of a eter. A plot of the magitdes of these stars agast the logart of the square of the diameters yields a straight line [see illustration on next page]. Once cal ibrated, you can nd the magitude of
-9
I - C « : -7 . « w I
. ( -4 « : -3 : x « :
LAHM PED (DAYS
PERIOD-LUMINOSITY RELAON for pe I Cepheids, shown here for visual wave lengths, helps astronomers deduce a Cepheid's distance. Each period has a range of possible magnitudes, which arise because of inherent dierences among Cepheids.
CIENTIFIC ERICAN November © 1992 SCIENTIFIC AMERICAN, INC
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7
:
! z
� �
+
+
+ - AHM d2 (MMEES
-0.4
CALBAON LNE for photogphed stars in the open cluster NGC the diameters of the images, to the apparent magnitudes
- 6940 relates
any star (including possible Cepheids) stars against stars whose magdes in the eld of view. Just measure the are listed. Tis secondary calibration star's diameter and use the calibration needs to be done oy once. You cn line to convert Each photograph wl then use these secondary standards against wich to measure the variable have to be calibrated in ts way To ensure accuracy in secondary cali Indeed, it may be that the magnitudes of the stars you need for cali brations, you should take certan pre bration are not listed in any handbook cautions. First, use the same exposure In that case, you must calibrate those time for all the photographs Second,
Finding the Period
I
use a program based on one written by Hugo G. Marraco and Juan C Muzzo of the National Universty of La Plata in Argentna The essential features of the algo rithm folow. The rst step s simply to take a guess; most type I Cepheds have periods of a few days. Then calcu late the phase for each data point that s, determine where n the cycle you observed the Cephed at that tme. Otherwise, you can easly get the wrong period, especaly if you have made ony a few observations To determne the phase, count the number of complete cycles, N start ing at your earliest observation Mathematically, N whole number part of t to/p, where to is the tme of rst observation (n Juian days); t s the time of a subsequent observation; and p is the tria period you guessed The fractional part eft over is the phase-that is, =
wher t is the phase at time t Now that you have the phase for each ata point, calculate the scat terng of the datain other words, the standard deviation of your data ponts Break up the total phase
3
range 0 to 1 cycle) into ntervals of, say, a tenth and see how many data points fall in that tenth For example, you might have three data points whose phase vaues fal in the inter val 0.1 to 0.2. You simply cacuate their standard deviation. Perform this task for each interval and then nd the average standard deviaton for al 10 intervas. Next you wi need to increment the period and repeat the phase and scattering calculations. But be care ful: if the ncrement is too large, you mght skip over the correct perod without noticng it. On the other hand, if the period increment s too small, t would take a very long time to nd the right vaue. Ater covering the period range, look at the values of the scatter ing and locate the minmum stan dard deviation. Select a small range of period around this value and search for a more precise period us ing a smaller period ncrement I usualy seect 0.01 day as my irst increment and decrease it by a fac tor of 10 for each teration You can tell when you are inished because the scattering parameter is the same for severa successve values of the perod Select the central value as your best period
SCINTIFIC ERICAN Noember © 1992 SCIENTIFIC AMERICAN, INC
shoot everything on the same roll of f, so that the images experience the same developer concentration and pro cessg time Third, work from nega tive prints; it is easier to measure dark images on a light background rather than vce versa (I make such prints from contact negatives of the original negatives) Finally, correct for the fact that you are looking along dierent op tical paths trough the atmosphere The most systematic method is to convert your magntdes to what they would be if you were looking straight up For visual wavelengths, the amount of correction is equal to about 4 (se cant - where is the angle between the zeith and photographed eld Once yo have calibrated your photographs, you can d the period by using the al gorithm in the box on this page You can construct light curves by plotting magnitude versus phase Remember to plot the smaller magitudes (brighter values) toward the top of the ordinate. The conventional way to dis play light crves is to show two com plete cycles. If you decide to pursue more ad vanced nds of observations, you can obtan scons and softare for data analysis from many sources One of the most usel is the mecan Association of Variable Star Observers (MVSO), wch can supply der charts for thou sands of variable stars as well as their corresponding comparison stars he associaton can recommend projects suitable to each observer's geograpc location, equipment, obsering condi tions and schedle. Interested read ers can contact the MVSO at Birch Street, Cambridge, 38 Amateur astronomy magazines also provide in formation on Cepheids For a sample data set and a coy of the program that nds the period (wrt ten in FORTR ), send a seladdressed, stamped business enelope to the Amateur Scientist, Sighting Cepheid Vari ables, Scientic American, Madison Aenue, New York, FURTHER REING THE M OF HE EBULAE.
Hubble Yale Uiversity Press, print 18)
Edwin P. 13 (re-
THE AURE OF ARIABLE SAR
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EPHEI: THEORY AN BERVAION
Edited by Barry F Madore. Proceedings of the AU Coloquium No. 8 Cam bridge Uiversity Press 185 THE AGALACIC DIANCE SCALE
Edited by Sidney van den Bergh and Chrisopher ] Pritche Astronomical Society of the Pacic Conference Series VoL ; 188
When Professor Jon Lien is not teaching class, he's saving schools off the coast of Newfoundland. Knife in hand, he sets out to sea to rescue whales rapped underwater by fishing nets. On the next Scientic American Frontiers on PBS: join Professor Lien as he looks a 60,-pound humpback in the eye so tat they both may live to tell abou it. Youll also see stories bou smart food, wheelchair racers, owler monkeys and tuberculosis. All fascinaing. All true. Not one fish stoy in te bunch. Sponsored by GTE
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Schmandt-Besserat Unversity of Texas Press, 1992 ($60)
H
undreds of clay tablets marked in cuneiform were found in the 1930s durig excavation of ay er of "the rst and foremost Sumeri an City, Urk (the Bilical Erech, in pre sent-day Iraq) The earest were itten in the decades before 3000 BC Those archaic texts are surprisingly mature, with few pictographs d many abstract symbols, not much dierent from texts of Sumer a llei or more later. The sign for "sheep, for instance, was a circled cross; for "metal, a crescent with ve ines Sopisticated rting had appeared suddenly, ready-made. The priest-poets of Sumer had their own explanations n one myth, snng nanna, the divine sister of mortal Gil gamesh, hero-founder of Urk, received from Father Enki, God of Wisdom, an imprudently generous gift "Swang with drink, he gave her the precious me the 100 elements of al civilzation. First on the list was the gh priest hood itself! After many indispensable older arts, icludng lovemaking, song, even treachery, there came eight mod ern crafts, one among them the craft of the scribe Inaa, rejoicing, ferried the me upriver to her holy srine at Uruk, where in time the mute clay would be made to speak by wel-tred sribes This new, scrupulous and exciting ar chaeological account of how writing came is given us by a brilliant scholar, a woman who of course makes no di vine claims at all. What snes here is the human mind, spnnng a tight web of iference from abundant evidence. Edence comes out of 100-odd sites disclosed by a century of the spade, ex cavations manly along the Jordan and the tree rivers that low to the head of the Persian Gulf. Not least terestig is the fact that the material she draws on is some 8,000 little hand-modeled pel lets of red clay, often rejected or ig nored even during excavation, now be come chef cornerstones of her power demonstration (Volume II, not seen or reviewed, is a teccal reference catalogue that lists and locates the to kens in their thousands.) Twenty years ago Professor Scmandt132
Besserat was a new postdoctoral fellow at the Radcie (now the Buntig) Insti tute. She wanted to study the uses of clay the Near East before pottery, bits of clay loors, hearth lngs, bricks and more "Wherever would go, in muse ms on fo contnents, these geometric kets were always present They were the oldest clay objects to have been re hardened The very earliest ones may have been "baked i domestic ovens, but the latest show perfectly controlled and much hotter rng Most archae ologists had ignored them; a few had jumped to the unsupported conclusion that they were amuets or game pieces. She came to call them tokens A Ro setta stone for the tokens had been fod by 1960, but not fully read A pe-
culiar empty "hollow tablet bore a late cuneiform inscription that described once enclosed counters that listed so many ewes, lambs d sheep. The cot i the textual lst matched the number of "stones reported to have been held in the holow tablet when the excavators had opened it. But the counters them selves were neither saved nor described A second hollow tablet was reported in 1966 by the author's teacher, Pierre et, at the Louvre. From Susa, it was much older, preiterate, and it still held its original contents, the very sort of geometric artifacts Scandt-Besserat would later d in abundance lying loose and out of context on museum shelves "In 1970, two pieces of the puz zle snapped together for me ... had not
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seen [the et article] since I began extend the token code to an urbanized collectg tokens. I cold not believe my society. The temple bureaucrats were no eyes when I saw the small clay cones, longer content with the sple tibutes spheres, and tetrahedrons" in et's of the farmer but rew the levies from ilustrations. The use of that multitude a variety of urban craftsmen. of tokens had been found. Quite another dimension lies withn Tokens were a common code. They this chronicle of the wellknown rise of are ideal smbols, save only for their tystate, class and the division of labor. three-dimensional natre They are dis t is the growing abstraction and com crete, recogizable, repeatable, durable, plety of the code Perhaps the rst re cheap, yet open-ended enough to allow corded counts came n the upper Paleo many new forms. They were a record itc, smple tallies of time passed, say, keeping device at vlage scale, one that one mak on a bone for each day of the swept across the Near East on the unar month Later came tokens, every coattais of agriculture" for 5,000 years, token form a threedimensional noun, remarkably free of any regional varia each commodity counted concretely by tions until cities began At rst there its set of identical tokens. Natre and were at most a dozen or two simple quantity were stl fused. foms. Then they entered a second, The new step is found on nscribed moe complex phase, to dindle once tablets of Sumer during the last centu writing had come ries before ritng: abstract count. Num The rst two hollow tablets reported ber was no onger embodied by a sgle have been followed by 115 more, most form class o tokens but stood in two ater than 4000 B.C. Now these are rec dimensions as a set of maks on clay. ogzed as envelopes of clay. Nearly The tablets bore mpessed numerals, at all the envelopes ae covered with re rst imple talies like the Roman nu peated seal impressions, a signature mera Adjog each such mpessed sometimes seveaauthenticatg the numera les an incised mark, often the secrity of the contents Oly a few have drawing of a complex token form, to been opened to check the contents (x identify what was counted Aritmetic ay techques have not yet given good had come, not merely a count of day s or esuts) The number of tokens witin of ducks but pure number itsef, that s never vey high; on the average there class of casses ae about ine These are no records of The accountants invented the rst large-scae tade but ather of villagers' numerals on cay around 3100 B.C. en contrbutions to pooled grain or live coding the concepts of oneness, two stock supluses, subject to some later ness, treeness" the city stage called redistbuton Step by step, such com Uuk it took one three-dimensona munties became raked societes, " i ovod token to recod one customary whch redistributon alows in the end jar of o. A little later, in the overlying for a tribute of oerngs, fees and taxes ayer called Uruk IVa, it took two mark Next come wel-marked envelopes. ings on the surface of a clay tablet. One For them, many tokens have been m impresson recorded a customary uit pressed nto the outer cay, to sgnal to measure, the jarful, using the outline the scibes just what is in the authen form of the old ovoid token A second tic record sealed wthn The match in single, strong mark conveyed the pue signicance between token types and numera 1: one oil jar By Uruk t farm products (rather than, say, days took tree sgs, one fo the numeral 1, o labor) rests on the subsequent cuei one for the standard jarul and a new form symbols These can often be traced sybol that denoted ol tsef With back n form to mpressons made on three signs, a leble written language clay tablets a few centuries beore sty had arrived lus-wrtten cuneifom proper appears. Once ndividual citizens needed to be hose eary mpressed signs match ice identied, the idea of names in ebus ly the old foms of the tokens and of was not far o Gven one mark or place ten enough t the epigrapher's judg ment convention, like the cartouche in ment of the origin of the later, more Egyptian hierogyphics, a string of sym styized cuneorm whose meanig s bols could stand no longer oly for kown from rich teray context. concept or comodity but mply fo After 4000 B.C industry gave a ma the sound connoted trough the spok jor boost to the token system" Hun en language: phonetics, that novelty, al dreds of new types are found, largely n most the last decisive one, depended Urk Some of them are qte grtive, less on the social milieu than on nter tny bowls, jas ith hanles, even little nal practice among specialist scribes. trussed ducks, a of them handmade Witin a few centuries they had invent cay pelets, easy caricatures, often in ed the way we now share the myth of csed with simpe dots and stripes. (A Inanna and the sustaned argument in few are even molded.) These changes this absorbing book 134
SCIENIFIC ERICAN vembe 1992 © 1992 SCIENTIFIC AMERICAN, INC
HE CHEMI BON: U AN DYAMIS, edited by Ahmed Zewail
Academic Press, 1992 ($4995).
C
ertainly chemistry is structre the double helix and the hexago nal benzene ring have become lo gos for the ente sence But chemistry ufods in tme as t dwells space. Re actions, the e of chemical struc tres, are equally at the roots of the science And there is a nal necessity those clever chests themslves Tis ne book introduces all three Its authors re ine celebrated chem ists from North Aerica and the Uit ed Kngdom Six of them are Nobel laureates one, Linus Pauling, is a ar ity indeed, a Double Noelist, once for cheity, once for peace. The attractive voume grew from a splendd occasion, the symposium in February of 1991 when Caltech celebrated Paulng's 90th birthday Personal reiniscences, col ol iagrams and photographs and bi ographies of the contributors welcome the general scientic reader to ine rel atively informal chapters Linus Pauling opens by recalling s eay interest in neals at age 2, when in wonder he colected the local agates At 18 he became an assistant n structor in quanttative cheica anal yss at Oregon Agricultura Coege, to gve one of the two senas that year One man spoke on the frozen sh in dustry young Pauling told of the elec tron theory of the chemica bond from the recent papers of G N. Lews and Ivng Langmur that had caught A ttle late he tried to deposit single cs tas of on in a magnetic eld: without success" But it was enough to spark ex pression of an nterest in crystaogra phy, and Professo rthur mos Noyes of Caltech proposed to the just-accepted teachng eow that he begn graduate research there wth xay diraction For a dozen years Pauling made and anayzed Laue photographs and thought deeply about structues. In 1934 the transton to moden xray crystallog raphy was beg by the ..Patterson ia gram." That boldly smplfyng appro mation to the location of atoms in lat tices was just what so good a cheist could use Paug also mastered the old quantu theory, found some of its itations, and made his way as a fresh PhD to a fellowsip i Munich with Sommefeld in the sprng of 926, just when Scrdnger published the st papers on the wave equation. The yog American returned a working quantm cheist, whose steady ow of sights ad approatons has become classc
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n 1939 Pauling published a famous series of lectres on the checal bond, the deepest view we then had. Nobelist Max F. Pertz read chemistry then in Vi enna That meant he ote down what the professor said, "or rather my girl friend who knew shorthand did, and learnt it by heart Pauling's book was not at all like that t included his opin ion that the easily formed, rather weak hydrogen bond, one proton lying be tween two somewhat negative atoms, would be more signcant for the mole ces of lfe than "y other sigle strc tural feature. Postwar, Pauling would add that hemoglob ight be the mol ecule whose mapping could tease out the full nature of protein structure, in spite of the prodigious mout of work Perutz read it all and says, " took ths admontion to heart, but it took me an other 30 years to do the job. Francis rick read the same book "t is almost true to say that's the ony chemistry ever learned. Paulng's insistence on the basic importance of quantum chemstry was decisive for rick. Physicist Max Delbrck, pioneer of molecular biology, thought, lke Niels Bo, that there would have to be new physics witn the giant molecules. When he saw the double helix of DNA, "he thought it was too much like a tin kertoy. But Pauling expected that di rectness of t He had a long string of profound structural ideas the alpha helx, pleated sheets, enzyme sites and coiled coils. But also he led an active group who worked hard at real and meanngful structures, the foundation of molecular biology. The topic of another Pauling admir er, Alexander ch, is the double helx in three forms. First is the DNA we ow, then the same DNA without solvent wa ter and, last, the lef-handed, less stable, ZDNA Grooves in the three molecules oer clues to how proteins recognize their instrctive sites. The chemsts were slow to split sec onds. 1947 the free radicals, transient intermediate steps in most reactions, seemed beyond direct chemical study. Microsecond chemistry was begn with a lash by another author, Lord George Porter, n 1949. Start a gas reaction with a brief lash, and probe the changes without delay by a second tailored lash, analyzed by apt spectrometry Step by step, that technque has been extended down nne orders of magn tude, most recently by editor Zewail, the Linus Pauling Professor of hemi cal Physics, at work in Pauling's old x ray lab at altech A photograph of his tamed beams zigzagging around a big loating optical table is included. The ingenious apparatus can record chem-
SCIENIFIC ERICAN vembe 1992 © 1992 SCIENTIFIC AMERICAN, INC
ical identications within tens of fem toseconds by use of ultrashort laser pulses, collisioless, polarized molecu lar beams, and well-timed pulse manp ulation. Such studies show directly "the ephemeral, but a-important, transition states in chemical reactions and spa tialy resolve atoc teractions down to a tenth or less of atomic dmensions hs own chapter, John Polanyi, the modern inventor of the transition state, elaborates the subtle idea helplly, and another chapter outlines the complex multidmensional energy srfaces many reactions imply (Here and a few oth er places the up-todate material makes demands mos nonchest readers wl not easily meet) Elder Pag does not avoid the fray. He cites new experiments ad theory to support hs view that the intermetalc quasicrystals of the experts, with their unendingly frstrated repetitions, are fact much simpler twed structures that oly smulate the vefold syme try denied al tre crystals. Acute, feity, as astonshng as ever, herochemist Li nus Paulg mayor may notbe right once again, at a ripe 9.
W BUIINGS DO w U , by Matthys Levy and
Mario Salvadori llustrations by Kevin Woest. W. W Norton and ompany, 1992 ($2495)
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n ts insiders' book, we are let in on a lot of delicious trade talk that frames the specic elanations. Us g drawings plenty, but not even one drop of algebra, the account brgs you to see why buings stand up and "yes, but once in a blue moon, [why] they fall down. These are two savvy old pros, distinguished structural architects and prinCipals in a New York consulting noted for detective skll in investi gating buildings that failed under cer tai newsworthy blue moons. Professor Salvadori years ago established s tal ent and verve as an expositor in a mem orable book or two on why buildings stand up; ths new volume has as much insight and moves with the swift action of the Johstow Flood (not ignored) across dozens of celebrated examples. Theirs is no new problem. Of the Sev en Wonders of the Ancient World, what with wars and earthquakes and vandals and neglect, six have fallen. Oy the Great Pyrad still stands. One early pyrad did n fact slough o l its two ton lmestone masonry casing blocks; its foundation design explains the failure, not repeated. Poor ing Kong of course
dd not overstress the Empre Stte Bldnghs trgedy ws oly specl eectsbut tht tll, redundnt steel frme lterly shook o the rel mpct of foglost bomber n 1945 Hedon collson t speed just bove the 79th loorlne klled the crew nd 10 people the buldng, mostly by burg gso lne. (The festy Lttle Flower cme up behnd the re ghters nd ws seen shkng s myorl st "nd mutterng: I told them not to ly over the cty. ) The mssve tower shook mldly un der the joltthe ton bomber brought oly hlf percent of the momentum of the desgn wnd lodnd fter one double swy, wtnesses reclled, the mo tons settled don. Msonrycld tow ers re well dmped by frcton be tween the steel elements nd the hevy wlls, but lghter modern towers v brte much more esly The beutful nd now truly sfe Hncock Tower, whose mrrored sunsets so vvfy the Boston skylne, n 1973 begn per lous wndowsheddng moton n re sponse to locl wndstorms. A cross re of ltgton, ll gnst ll, ended n legl greement of "nondsclosure n perpetuty, but the frternty of bulders, tghtlpped to outsders, s "rstrte grpevne to ts members. The tle leked here s not ll new, but t s prtculrly well told. Eveg went ttle wrong One mjor tsk ws to stblze the usuy shped tower gnst ts twstg response to nd. The strong glss ndows crcked s the frme swyed more thn 10,000 of them were replced wth subtly less verble ones More steel lone would not do the vbrtons hd to be dmped s well. The 58th loor of the tower ws gven over to two 300ton blocks of led, ech free to slde on n oly plt form The buldng eect slps under the mssve blocks, whose nert keeps them from quck response Bg sprngs, tuned to precsely the rght rhyts trnsfer the motons of the tower wlls to the two blocks the motonl energy the blocks gn s stedly drned out to become mere het wthn bg shock bsorbers. The buldng now swys oly lttle s the blocks wtn swng to nd fro through mny feet The seor uthors recountng of the tough Q nd pt A durng two of hs ppernces on the wtness stnd s en ggng. He hs come to dmre the ws dom of "uneducted jures more thn he smrts t the brbs of the trl lw yers. A rel expert lke Mro Slvdor knows tht "wht counts n court de bte s the whole mn rther thn the specst. Ts ppeng vole closes wth 40pge ppendx tht oers n dmrble prmer of structrl theory.
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