1. Trang chủ
  2. » Khoa Học Tự Nhiên

scientific american - 1999 01 - revolution in cosmology

96 509 0

Đang tải... (xem toàn văn)

Tài liệu hạn chế xem trước, để xem đầy đủ mời bạn chọn Tải xuống

THÔNG TIN TÀI LIỆU

Thông tin cơ bản

Định dạng
Số trang 96
Dung lượng 7,51 MB

Nội dung

JANUARY 1999 $4.95 THE FLU: NEW DRUGS BEAT KILLER VIRUSES • Y2K BUG: HOW TO FIX IT, WHAT TO EXPECT SPECIAL REPORT: Revolution in Cosmology New observations have smashed the old view of our universe. What now? Copyright 1998 Scientific American, Inc. January 1999 Volume 280 Number 1 FROM THE EDITORS 6 LETTERS TO THE EDITORS 10 50, 100 AND 150 YEARS AGO 14 THE 1998 NOBEL PRIZES FOR SCIENCE NEWS AND ANALYSIS IN FOCUS Computer “hacktivists” fight for human rights with the Internet. 21 SCIENCE AND THE CITIZEN More genetic support for an African Eve Unexpected cosmic rays Whence whales? Space geriatrics. 24 PROFILE James R. Flynn ponders the strange rise in IQ scores. 37 TECHNOLOGY AND BUSINESS Conscious Cog A racial and economic health gap Food frenzies. 39 CYBER VIEW The U.S. military defends itself against the World Wide Web. 44 2 Surveying Space-time with Supernovae 46 Craig J. Hogan, Robert P. Kirshner and Nicholas B. Suntzeff Light from stars that exploded as much as seven billion years ago suggests that, con- trary to expectations, the universe’s rate of ex- pansion is speeding up. Cosmological Antigravity 52 Lawrence M. Krauss Albert Einstein’s notorious cosmological constant could of- fer the antigravitational push needed to explain the accelera- tion that astronomers see. Inflation in a Low-Density Universe 62 Martin A. Bucher and David N. Spergel Even if the universe holds too little matter, inflation theory isn’t dead yet. Condi- tions “before” the big bang might have given the universe unforeseen properties. SPECIAL REPORT REVOLUTION IN COSMOLOGY 45 Cosmologists thought inflation theory could ex- plain all the basic processes that shaped the universe —until new observations violated a central prediction. For the past year, the- orists have scrambled to make sense of the latest data. Either the uni- verse is dominated by a bizarre form of energy or our uni- verse is just one strangely curved bubble of space- time in an infinite continuum. 16 Copyright 1998 Scientific American, Inc. Scientific American (ISSN 0036-8733), published monthly by Scientific American, Inc., 415 Madison Avenue, New York, N.Y. 10017-1111. Copyright © 1998 by Scientific American, Inc. All rights reserved. No part of this issue may be repro- duced by any mechanical, photographic or electronic process, or in the form of a phonographic recording, nor may it be stored in a retriev al system, transmitted or otherwise copied for public or private use without written permission of the publisher. Periodicals postage paid at New York, N.Y., and at additional mailing offices. Canada Post International Publications Mail (Canadian Distribution) Sales Agreement No. 242764. Canadian BN No. 127387652RT; QST No. Q1015332537. Subscription rates: one year $34.97 (outside U.S. $49). Institutional price: one year $39.95 (outside U.S. $50.95). Postmaster: Send address changes to Scientific American, Box 3187, Harlan, Iowa 51537. Reprints available: write Reprint Department, Scientific American, Inc., 415 Madison Avenue, New York, N.Y. 10017-1111; fax: (212) 355-0408 or send e-mail to sacust@sciam.com Subscription inquiries: U.S. and Canada (800) 333-1199; other (515) 247-7631. Child Care among the Insects Douglas W. Tallamy Photographs by Ken Preston-Mafham Many insects are not the cold, careless parents that one might assume. When environmental condi- tions set a premium on the survival of young, in- sects will sometimes watch over their broods, guide hatchlings to food and fend off predators. If a virulent strain of influenza appeared unexpect- edly, millions could die before vaccines would be ready. But better drugs that stop the virus from mul- tiplying in the body could soon be available. They would contain all strains of influenza. Disarming Flu Viruses W. Graeme Laver, Norbert Bischofberger and Robert G. Webster 72 78 88 94 100 THE AMATEUR SCIENTIST Monitoring the earth’s magnetism. 106 MATHEMATICAL RECREATIONS How uneven divisions can leave everyone happy. 110 3 Salmon are an economic mainstay of the Pacific Northwest and British Columbia, but the numbers of some species are dropping. Research groups con- tend with the mysterious disappearance. Expeditions To Save a Salmon Glenn Zorpette, staff writer Photographs by F. Stuart Westmorland Sprinkled throughout the genetic material of cells are short, repetitive sequences called microsatellites. Mislabeled as “junk DNA,” they foster mutations that allow bacteria (and perhaps higher organisms) to evolve faster in challenging environments. DNA Microsatellites: Agents of Evolution? E. Richard Moxon and Christopher Wills With just 12 months until the Year 2000 comput- er problem erupts, only automated fixes can begin to head off trouble. This Y2K expert describes why a simple date adjustment is so devilishly hard to accomplish and realistically assesses how much chaos this glitch will bring in the next millennium. Y2K: So Many Bugs So Little Time Peter de Jager About the Cover Quantum particles fluctuating in and out of existence might, on a cosmic scale, counterbalance gravity’s tug on ordinary matter and push the universe outward. Painting by Don Dixon. THE SCIENTIFIC AMERICAN WEB SITE www.sciam.com Watch a solar flare re-created in the laboratory: www.sciam.com/exhibit/111698 sun/index.html Then browse this month’s articles and departments linked to other science resources on the World Wide Web. REVIEWS AND COMMENTARIES Blood money: a sanguine history of transfusions, contamination and commerce. 112 The Editors Recommend Books on animal intelligence, mum- mies, invisible computers and more. 113 Connections, by James Burke Pendulums, radioactivity and the Suez Canal. 115 Wonders, by the Morrisons The giant serpent and the lake of air. 116 WORKING KNOWLEDGE What makes the piano so grand? 118 Copyright 1998 Scientific American, Inc. 6Scientific American January 1999 T he fate of the universe used to be so simple. It was either fire or ice. Either the combined gravity of the universe would bring its expansion to a halt, compelling the cosmos to replay the big bang in reverse, or else gravity would steadily weaken and the universe would expand forever, slowly and inexorably pulling planets, stars and galaxies apart until it became a barren, frigid void. Now cosmologists realize that things aren’t so straightforward. The uni- verse may not be governed by the gravity of ordinary matter after all. If the latest observa- tions of the distant universe (as discussed in our special report, beginning on page 45) are borne out, matter has little say in its own fate. Instead the universe may be controlled by the so-called cosmological constant, a surreal form of energy that imparts a gravitational re- pulsion rather than the usual attraction. The idea of the constant has been embraced and renounced more than once since Albert Einstein initially proposed it 80 years ago. This time it may be here to stay. At first glance its shadowy reinforcement of cosmic expansion suggests that, as the ultimate fate, ice will have to suffice. But that judgment is premature. Because physicists know so little —“nothing” would be a fair approximation—about the constant, the fate of the universe is back where it started: in the realm of uncertainty. O ne implication is that science writers who have been using Robert Frostian fire-and-ice allusions will have to find a new metaphor. An- other is that the cosmos might be undergoing a second round of “inflation,” a resurgence of the process that, 12 billion or so years ago, caused space to go bang. Just as that earlier period of explosive growth ended —giving form and light to what had been void—so, too, might the rekindled inflation. If so, the universe will expand to unimaginable propor- tions, the constant will fade away and physical possibilities will unfold that are only dimly perceived in today’s theories. If there is a story to be seen in cosmic history, it is the march from the utter simplicity of the big bang to ever increasing complexity and diversi- ty. The near-perfect uniformity of the primordial fireball, and of the laws that governed it, has steadily given way to a messy but fertile heterogene- ity: photons, subatomic particles, simple atoms, stars, complex atoms and molecules, galaxies, living things, artificial things. Understanding how this intricacy is immanent in the fundamental laws of physics is one of the most perplexing philosophical puzzles in science. The basic rules of nature are simple, but their consummation may never lose its ability to surprise. A perpetual trend toward richness, the outcome of which cannot be foreseen, may be the true fate of the universe. Getting Complicated ® Established 1845 F ROM THE E DITORS GEORGE MUSSER, Staff Editor editors@sciam.com John Rennie, EDITOR IN CHIEF Board of Editors Michelle Press, MANAGING EDITOR Philip M. Yam, NEWS EDITOR Ricki L. Rusting, SENIOR ASSOCIATE EDITOR ASSOCIATE EDITORS: Timothy M. Beardsley; David A. Schneider; Gary Stix W. Wayt Gibbs, SENIOR WRITER Kristin Leutwyler, ON-LINE EDITOR EDITORS: Mark Alpert; Carol Ezzell; Alden M. Hayashi; Madhusree Mukerjee; George Musser; Sasha Nemecek; Glenn Zorpette CONTRIBUTING EDITORS: Marguerite Holloway; Steve Mirsky; Paul Wallich Art Edward Bell, ART DIRECTOR Jana Brenning, SENIOR ASSOCIATE ART DIRECTOR Johnny Johnson, ASSISTANT ART DIRECTOR Bryan Christie, ASSISTANT ART DIRECTOR Dmitry Krasny, ASSISTANT ART DIRECTOR Bridget Gerety, PHOTOGRAPHY EDITOR Richard Hunt, PRODUCTION EDITOR Copy Maria-Christina Keller, COPY CHIEF Molly K. Frances; Daniel C. Schlenoff; Katherine A. Wong; Stephanie J. Arthur; Eugene Raikhel; Myles McDonnell Administration Rob Gaines, EDITORIAL ADMINISTRATOR David Wildermuth Production Richard Sasso, ASSOCIATE PUBLISHER/ VICE PRESIDENT, PRODUCTION William Sherman, DIRECTOR, PRODUCTION Janet Cermak, MANUFACTURING MANAGER Silvia Di Placido, PREPRESS AND QUALITY MANAGER Georgina Franco, PRINT PRODUCTION MANAGER Norma Jones, ASSISTANT PROJECT MANAGER Madelyn Keyes, CUSTOM PUBLISHING MANAGER Carl Cherebin, AD TRAFFIC Circulation Lorraine Leib Terlecki, ASSOCIATE PUBLISHER/ CIRCULATION DIRECTOR Katherine Robold, CIRCULATION MANAGER Joanne Guralnick, CIRCULATION PROMOTION MANAGER Rosa Davis, FULFILLMENT MANAGER Business Administration Marie M. Beaumonte, GENERAL MANAGER Alyson M. Lane, BUSINESS MANAGER Constance Holmes, MANAGER, ADVERTISING ACCOUNTING AND COORDINATION Electronic Publishing Martin O. K. Paul, DIRECTOR Ancillary Products Diane McGarvey, DIRECTOR Chairman and Chief Executive Officer John J. Hanley Co-Chairman Rolf Grisebach President Joachim P. Rosler Vice President Frances Newburg Scientific American, Inc. 415 Madison Avenue New York, NY 10017-1111 (212) 754-0550 PRINTED IN U.S.A. STUART LEVY National Center for Supercomputing Applications AND TAMARA MUNZER Stanford University Geometry of space-time? Copyright 1998 Scientific American, Inc. ATTENTION, PLEASE I t was a pleasure reading Russell A. Barkley’s article, “Attention-Deficit Hyperactivity Disorder,” in your Sep- tember issue. There is no doubt that Barkley’s work has been tremendously valuable. But I have trouble with Barkley’s assertion that ADHD is purely a neurological “disorder,” best treated with stimulant medication. Before we rush to the pharmacist, I propose we cast a broader perspective. The criteria for a diagnosis of ADHD are so general that any one of us could be diagnosed with it at some point in our lives. This accounts for a high false- positive rate when we attempt to classi- fy people with many common com- plaints of impulsivity, agitation and difficulty focusing. Compounding this is the tremendous overlap between the criteria used for an ADHD diagnosis and those for other, more common dis- orders such as anxiety and depression. We must recognize that no previous generation of children has been as hurried, overstimulated and subjected to powerful social challenges as to- day’s American child- ren have. It would be great if there were a magic pill to provide the cure —but the real- ity is that our clinics remain crowded with ADHD children, al- ready on medications, who continue to seek help with navigating the demands of a stressful, frenetic childhood. ANTHONY V. RAO Department of Psychiatry Harvard Medical School Barkley disappointed this reader in several ways. The article implies a com- plete picture but ignores attention-deficit disorder (ADD), without hyperactivity. There are those who have quiet trouble channeling their attention; because they may procrastinate, forget or hyperfocus but don’t disrupt, their difficulties are of- ten overlooked. Barkley also doesn’t dis- cuss the originality and energy that can characterize ADD/ADHD. Often cre- ativity is ADD/ADHD gone right. PRISCILLA L. VAIL Bedford, N.Y. Barkley’s article on ADHD was very informative; however, he does parents a disservice when he characterizes special education as an option of last resort. Par- ents should not be dis- couraged from seek- ing special education services at an early point in their child’s education, as it could help the child avoid years of frustration. Barkley seems to be under the impression that special education means separate class- es. This is not the case: more and more students across the U.S. receive special education services while being included in regular classes. Information centers in each state can help parents learn about special educa- tion support for students with ADHD. Call the Technical Assistance Alliance for Parent Centers at 888-248-0822 for the location of the center nearest you. DEBORAH LEUCHOVIUS PACER Center Minneapolis, Minn. Barkley replies: People with ADHD undoubtedly have many fine personal attributes, as parents of ADHD children can testify. But no study has ever shown that having ADHD results in enhanced creativity, intelligence and the like. In fact, some studies have shown that ADHD can reduce IQ scores by an average of seven to 10 points and diminish certain forms of creativity. Rao is mistaken —I did not suggest medication alone as a treatment for ADHD. Rather it is part of a package that should include special education and other accommodations as needed, as Leuchovius’s letter emphasizes. Twin studies show that environmental fac- tors such as a hectic society do not cause ADHD. Furthermore, the criteria for ADHD are surely not so broad as to diagnose everyone with the disorder: studies find that only 3 to 7 percent of children meet the diagnostic criteria. Vail mentions ADD involving only inattention, without hyperactivity; space constraints on the article precluded my addressing this possibly distinct disorder. Inattentiveness in ADD patients may be qualitatively different, resulting in a low- er risk for antisocial behavior and a dif- ferent pattern of cognitive deficits. SPACE CONSTRAINTS R onald White is correct that NASA re- search on “Weightlessness and the Human Body” [September] is good news for denizens of the International Space Station and for future interplanetary mis- sions. The evidence suggests, however, that such research is of limited value to those of us here on Earth. Twenty years of microgravity research on Mir and ear- lier space stations have yielded some in- Letters to the Editors10 Scientific American January 1999 LETTERS TO THE EDITORS P arents responded in large numbers to Russell A. Barkley’s “Attention- Deficit Hyperactivity Disorder” in the September issue. Many echoed the sentiments of Lynne Scholl from Cincinnati, Ohio, who wrote that “my daughter has many wonderful qualities that are a direct result of her ADHD. She is incredibly creative and inquisitive. Yes, there are differences in how she responds to her environment —some are good; some are not. Does this mean I should try to change her? I would not want to do that, so I choose to help her deal with her ADHD-related difficulties, just as I would teach her to cope with any of life’s difficulties.” Kathleen G. Nadeau, director of the Chesapeake Psychological Services of Maryland, suggested that “the high activity level, low boredom tolerance and impulsivity of people with ADHD bother teachers and challenge parents. These same traits, once the school years are through, translate very often into creativity, entrepreneurial ca- pacity and high energy.” Additional comments are included below. YAN NASCIMBENE MANAGING ADHD often requires a combination of medication and special education. Copyright 1998 Scientific American, Inc. Letters to the Editors Scientific American January 1999 11 teresting insights but no major break- throughs. Space medicine cannot justify its enormous cost when the National In- stitutes of Health can fund only about 25 percent of the deserving research applica- tions it receives. The staggering $1.3-bil- lion annual cost of keeping four Ameri- can researchers in orbit could pay for 5,000 or more grants for cutting-edge re- search at laboratories and universities. Surely the best way to study aging and to improve medical care is to spend our lim- ited resources on Earth. DALE BUMPERS U.S. Senator, Arkansas White replies: The decision to build the Internation- al Space Station and to continue human space flight was based on many factors, not just on the benefits that might result from biomedical research in space. Thus, it is grossly misleading to weigh the benefits of such research against the entire cost of the human space flight program. I hope my article did not lead readers to believe that space biomedical research would somehow replace NIH- supported research on aging, osteopo- rosis or anything else. The NASA bio- medical research program is much smaller than the NIH program. The two approaches are complementary, not mutually exclusive. Judging by our ex- perience so far, I believe that space bio- medical research will make unique and important contributions to health on Earth at the same time as it improves the health of space travelers. Letters to the editors should be sent by e-mail to editors@sciam.com or by post to Scientific American, 415 Madison Ave., New York, NY 10017. Letters may be edited for length and clarity. OTHER EDITIONS OF SCIENTIFIC AMERICAN Le Scienze Piazza della Repubblica, 8 20121 Milano, ITALY tel: +39-2-29001753 redazione@lescienze.it Spektrum der Wissenschaft Verlagsgesellschaft mbH Vangerowstrasse 20 69115 Heidelberg, GERMANY tel: +49-6221-50460 redaktion@spektrum.com Investigacion y Ciencia Prensa Científica, S.A. Muntaner, 339 pral. 1. a 08021 Barcelona, SPAIN tel: +34-93-4143344 precisa@abaforum.es Pour la Science Éditions Belin 8, rue Férou 75006 Paris, FRANCE tel: +33-1-55-42-84-00 Majallat Al-Oloom Kuwait Foundation for the Advancement of Sciences P.O. Box 20856 Safat 13069, KUWAIT tel: +965-2428186 Swiat Nauki Proszynski i Ska S.A. ul. Garazowa 7 02-651 Warszawa, POLAND tel: +48-022-607-76-40 swiatnauki@proszynski.com.pl Nikkei Science, Inc. 1-9-5 Otemachi, Chiyoda-ku Tokyo 100-8066, JAPAN tel: +813-5255-2821 Svit Nauky Lviv State Medical University 69 Pekarska Street 290010, Lviv, UKRAINE tel: +380-322-755856 zavadka@meduniv.lviv.ua Ke Xue Institute of Scientific and Technical Information of China P.O. Box 2104 Chongqing, Sichuan PEOPLE’S REPUBLIC OF CHINA tel: +86-236-3863170 NEW YORK Kate Dobson, PUBLISHER tel: 212-451-8522, kdobson@sciam.com 415 Madison Avenue New York, NY 10017 fax: 212-754-1138 Thomas Potratz, ADVERTISING DIRECTOR tel: 212-451-8561, tpotratz@sciam.com Timothy W. Whiting, SALES DEVELOPMENT MANAGER tel: 212-451-8228, twhiting@sciam.com Kevin Gentzel tel: 212-451-8820, kgentzel@sciam.com Randy James tel: 212-451-8528, rjames@sciam.com Stuart M. Keating tel: 212-451-8525, skeating@sciam.com Wanda R. Knox tel: 212-451-8530, wknox@sciam.com Laura Salant, MARKETING DIRECTOR tel: 212-451-8590, lsalant@sciam.com Diane Schube, PROMOTION MANAGER tel: 212-451-8592, dschube@sciam.com Susan Spirakis, RESEARCH MANAGER tel: 212-451-8529, sspirakis@sciam.com Nancy Mongelli, PROMOTION DESIGN MANAGER tel: 212-451-8532, nmongelli@sciam.com ASSISTANTS: May Jung, Beth O’Keeffe DETROIT Edward A. Bartley, MIDWEST MANAGER 3000 Town Center, Suite 1435 Southfield, MI 48075 tel: 248-353-4411, fax: 248-353-4360 ebartley@sciam.com OFFICE MANAGER: Kathy McDonald CHICAGO Randy James, CHICAGO REGIONAL MANAGER tel: 312-236-1090, fax: 312-236-0893 rjames@sciam.com LOS ANGELES Lisa K. Carden, WEST COAST MANAGER 1554 South Sepulveda Blvd., Suite 212 Los Angeles, CA 90025 tel: 310-477-9299, fax: 310-477-9179 lcarden@sciam.com ASSISTANT: Stacy Slossy SAN FRANCISCO Debra Silver, SAN FRANCISCO MANAGER 225 Bush Street, Suite 1453 San Francisco, CA 94104 tel: 415-403-9030, fax: 415-403-9033 dsilver@sciam.com ASSISTANT: Rosemary Nocera DALLAS The Griffith Group 16990 Dallas Parkway, Suite 201 Dallas, TX 75248 tel: 972-931-9001, fax: 972-931-9074 lowcpm@onramp.net International Advertising Contacts CANADA Fenn Company, Inc. 2130 King Road, Box 1060 King City, Ontario L7B 1B1 Canada tel: 905-833-6200, fax: 905-833-2116 dfenn@canadads.com EUROPE Roy Edwards, INTERNATIONAL ADVERTISING DIRECTOR Thavies Inn House, 3/4, Holborn Circus London EC1N 2HB, England tel: +44 171 842-4343, fax: +44 171 583-6221 redwards@sciam.com BENELUX Reginald Hoe Europa S.A. Rue des Confédérés 29 1040 Bruxelles, Belgium tel: +32-2/735-2150, fax: +32-2/735-7310 MIDDLE EAST Peter Smith Media & Marketing Moor Orchard, Payhembury, Honiton Devon EX14 OJU, England tel: +44 140 484-1321, fax: +44 140 484-1320 JAPAN Tsuneo Kai Nikkei International Ltd. 1-6-6 Uchikanda, Chiyoda-ku Tokyo 101-0047, Japan tel: +813-5259-2690, fax: +813-5259-2679 KOREA Jo, Young Sang Biscom, Inc. Kwangwhamun, P.O. Box 1916 Seoul, Korea tel: +822 739-7840, fax: +822 732-3662 HONG KONG Stephen Hutton Hutton Media Limited Suite 2102, Fook Lee Commercial Centre Town Place 33 Lockhart Road, Wanchai, Hong Kong tel: +852 2528 9135, fax: +852 2528 9281 Advertising and Marketing Contacts ERRATA “The Asymmetry between Matter and Antimatter” [October] contains an error on page 77 regarding the handedness of neutrinos. The article should have stated that as far as we know, there are no right-handed neu- trinos: they are always left-handed. In “Cryptography for the Internet” [October], the screen shots shown were from the program QuickMail Pro. We apologize for the confusion. Copyright 1998 Scientific American, Inc. JANUARY 1949 NUCLÉAIRE—“The first self-sustaining chain reaction to be produced outside of the English-speaking nations has just been achieved by French physicists. Frederic Joliot-Curie, di- rector of the French Atomic Energy Commission, announced that a uranium pile went into operation last month at Fort de Châtillon, on the outskirts of Paris. To U.S. workers, who have taken great pains to refine the uranium used in their re- actors, the ability of the Châtillon pile to sustain itself on im- pure uranium (uranium oxide) is something of a surprise.” OEDIPUS COMPLEX —“Freud knew the Oedipus myth from Sophocles’ tragedy King Oedipus. The question is whether Freud was right in assuming that this myth confirms his view that unconscious incestuous drives and resulting hate against the father-rival are an intrinsic part of any male child’s equipment. If we examine the myth more closely, however, doubts arise. There is no indication whatsoever in the myth that Oedipus is attracted by or falls in love with Jo- casta. The myth has to be understood as a symbol, not of the incestuous tie between mother and son, but of the rebellion of the son against the authority of the father in the patriar- chal family; the marriage of Oedipus and Jocasta is a symbol of the victory of the son who takes over his father’s place and with it all the privileges. —Erich Fromm” JANUARY 1899 POLONIUM AND RADIUM—“Two of us have shown that, by purely chemical processes, a strongly radio-active substance can be extracted from pitchblende. We therefore came to the conclusion that pitchblende might contain a new element, for which we proposed the name of polonium. Subsequently, we have met with a second substance, strongly radio-active, and entirely differing from the first body in its chemical proper- ties. The new radio-active substance has the properties of almost pure barium; its chlorides, however, having a radio- activity 900 times greater than that of uranium. We believe that the new radio-active substance contains a new element, to which we propose to give the name of radium. —M. P. Curie, Mme. P. Curie, and M. G. Bémont” BAD AIR —“Dr. G. B. Grassi for a long time had doubts on the connection between mosquitoes and malaria, owing to the absence of malaria from certain districts where mosquitoes abound. A careful classification of the various species of gnat has now led him to the conclusion that the distribution of cer- tain kinds coincides very closely with the distribution of the disease. The common Culex pipiens is to be regarded as per- fectly innocuous. On the other hand, a large species (Anophe- les claviger, Fabr.) known in Italy as ‘zanzarone,’ or ‘moschi- no,’ is constantly found associated with malaria, and is most abundant where the disease is most prevalent.” JANUARY 1849 BIOCIDES FOR AGRICULTURE—“The London Lancet mentions a practice which is common among the English farmers, of steeping their wheat in a solution of arsenic be- fore sowing it, to prevent the ravages of the worm on the seed, and of birds on the plant when grown. The plan is stated to have proved eminently successful, and of course exerts no deleterious effects on the plant. In Hampshire, Lincolnshire, and many oth- er districts where the practice prevails, numbers of partridges and pheasants have been found dead in the wheat fields, poisoned by eating the seed. This is certainly a practice to be condemned. We can af- ford to feed both men and birds.” MAINSTREAM NICOTINE —“Prout, in his Trea- tise on Disease, says about tobacco, ‘Although con- fessedly one of the most virulent poisons in nature, yet such is the fascinating influence of this noxious weed, that mankind resorts to it in every mode that can be devised to insure its stupefying and pernicious agency. The severe and dyspeptic symp- toms sometimes produced by inveterate snuff-tak- ers are well known; and I have seen such cases ter- minate fatally with malignant diseases of the stomach and liver. Surely, if the dictates of reason were allowed to prevail, an article so injurious to the health and so offensive in its mode of employment would speedily be banished from common use.’” A GREAT DIAMOND —“Koh-i-noor—or, ‘mountain of light.’ A diamond of inestimable value has been taken by the British troops in India, from one of the native princes. It is proposed to insert it in the centre of Queen Victoria’s diadem.” 50, 100 and 150 Years Ago 50, 100 AND 150 YEARS AGO 14 Scientific American January 1999 Oedipus, king of Thebes, with Jocasta, his queen Copyright 1998 Scientific American, Inc. The 1998 Nobel Prizes in Science Here follow explanations of the mechanisms and processes that underlie the world’s top awards for physics, chemistry and physiology — and an excerpt from a Scientific American article by the economics laureate Special Briefing AP/WIDE WORLD PHOTOS PHYSICS HOW ELECTRONS SPLIT HORST L. STÖRMER Bell Laboratories DANIEL C. TSUI Princeton University ROBERT B. LAUGHLIN Stanford University T he humming, beeping, well-lit modern world could not have been built without the knowl- edge that electric current is a parade of electrons and that those particles are not ricocheting billiard balls but fuzzy clouds of probability that obey odd rules of eti- quette as they maneuver in a dance of mutual repulsion. Discoveries about how electrons behave can thus have far-reach- ing consequences, although they may seem little more than curiosities at the time. Superconductivity was one exam- ple. One day it may turn out that the dis- covery for which Horst L. Störmer of Bell Laboratories, Daniel C. Tsui of Princeton University and Robert B. Laughlin of Stanford University received the 1998 Nobel Prize in Physics is another. Störmer and Tsui tortured electrons for their secrets. They squeezed electrons into a layer so thin that particles could move neither up nor down. They zapped the electrons with high magnetic flux. And they chilled the whole assembly to within a hair of absolute zero. Then physicists saw something unexpected. The electrical resistance across the thin current of electrons rose in steps rather than a straight line as they turned up the magnetic field. The plateaus suggest that ELECTRON’S-EYE VIEW shows how the thin layer of particles sandwiched between two pieces of semiconductor ( light-blue balls) might look to a typical electron (a). The electron’s cloud of possible positions spreads out (turquoise sheet) like a liquid to fill the layer ex- cept for spots where bits of magnetic flux (violet lines) zip through the ceiling. The electron avoids those spots, so vortices in its cloud open there. Other electrons in the area (green balls), repulsed by the first electron and by one another, naturally drift into the holes. As they do, they become bound to the lines of magnetism. If an electron is bumped out of the layer, it leaves behind an unoccupied vortex that can then split into smaller holes (b). Three rays of magnetic flux anchoring a single electron can thus become three separate “quasiparticles” (red lines), each carrying one third of the original charge. Similarly, if the magnetic field is reduced slightly, a ray of flux may disappear, causing one vortex to shrink (black lines) and creating an apparent excess of one-third electron charge at that point. 16 Scientific American January 1999 The 1998 Nobel Prizes in Science a SEMICONDUCTOR ATO M ELECTRON “FLUID” LAYER MAGNETIC FLUX VORTEX JOHN W. KARAPELOU b Copyright 1998 Scientific American, Inc. The 1998 Nobel Prizes in Science Scientific American January 1999 17 CHEMISTRY REACTIONS ON A COMPUTER WALTER KOHN Unversity of California, Santa Barbara JOHN A. POPLE Northwestern Unversity P redicting how chemicals will re- act is not an easy business, even for computational chemists, who study virtual reactions on comput- ers rather than mixing chemicals in beakers. Chemical reactions involve the breaking and reformation of bonds be- tween atoms; whether or not a bond will form depends on the position and energy of the atom’s electrons. This year’s Nobel Prize in Chemistry recog- nizes advances in computational tech- niques that predict reactions more quickly and accurately. Nobel recipient Walter Kohn devel- oped the computational method known as density-functional theory. It can be used to determine a molecule’s struc- ture and other properties; more impor- tant, it greatly simplifies essential calcu- lations. Instead of tracking the motion of each individual electron in a given molecule (large molecules can contain hundreds or even thousands of elec- trons), Kohn’s technique uses quantum mechanics to consider the overall densi- ty of electrons throughout the mole- cule. With density-functional theory, chemists today can often perform struc- ture calculations on desktop computers instead of mainframes. One program popular among chem- ists that incorporates Kohn’s density- functional theory in addition to many other computational techniques was developed by the co-recipient of this year’s prize, John A. Pople. He designed the program GAUSSIAN, first released in 1970. More than 10,000 scientists now use the latest version of it. ENERGY REACTION PROGRESS STARTING MATERIAL TRANSITION STATE FINAL PRODUCTS ClO O 2 Cl O 3 Cl O 3 + + E = E T + E V + E J + E XC where E J = 1 / 2 ∫∫ ρ(r 1 )(∆r 12 ) –1 ρ(r 2 )dr 1 dr 2 E XC (ρ) = ∫f(ρ α (r),ρ β (r),∇ρ α (r),∇ρ β (r))d 3 r Orbital Symmetries: Alpha Orbitals: Occupied (A')(A')(A')(A')(A')(A')(A")(A')(A')(A') (A')(A')(A')(A")(A')(A')(A")(A')(A")(A') (A') Atomic-Atomic Spin Densities. 12 34 O 0.001726 0.081746 -0.082306 0.000000 O 0.081746 –0.719714 0.000037 0.000000 O –0.082306 0.000037 0.719049 0.000003 # B1LYP/6-31G(d) opt=(calcfc,ts,noeigentest) scf=qc Ozone + Cl. TS Search 0 2 O O 1 rOO1 O 1 rOO2 2 aOOO Cl 2 rOCl 1 aOOCl 2 0.0 rOO1 2.150442 rOO2 1.256937 rOCl 2.833787 aOOO 38.654298 aOOCl 173.306808 1998 Nobel Prizes some new kind of particle was carrying fractions — 1 / 3 , 2 / 5 , 3 / 7 and so on—of a sin- gle electron charge. Electrons are funda- mental particles: they do not split. So what was going on? It took Laughlin a year to work out a theoretical explanation, which fur- ther experiments have since support- ed. Cramped and cold, the usually fre- netic electrons condense into a kind of fluid. Vortices in the fluid match up bits of magnetism with electrons. If there are not enough magnetic lines to share equally, some of the vortices can sepa- rate from their electrons and dance about independently, carrying fractions of positive charge (opposite page). The fractional quantum Hall effect, as it is called, occurs in rare conditions. But that does not mean it will lack applica- tions. When quantum wells were discov- ered, they were equally rare and curious. Today they are built into nearly every compact-disc player sold. JOHNNY JOHNSON; SOURCE: DOUGLAS J. FOX Gaussian, Inc. STEP 1: GAUSSIAN program can analyze reactions such as the one between ozone (O 3 ) and the highly reactive form of chlorine called a chlorine radical (Cl–). This reaction occurs in the earth’s stratosphere and leads to the fa- mous ozone hole over Antarctica. Input into the program includes information on the atoms in the compounds to be studied. The programmer must provide basic data on the structures of the chemicals, such as the bond lengths and angles between atoms. STEP 2: The program takes the provided information and per- forms quantum-mechanical calculations that predict how the two chemicals will react. GAUSSIAN can also display intermediate steps in the chemical reaction, called transition states. The equations of density-func- tional theory simplify the analysis. STEP 3: The final output provides information ranging from the exact structure of the products to the occupied elec- tronic orbitals of the atoms and more. For a simple reaction such as this one, the program can produce results in a matter of minutes. As the number of atoms involved increases, so does the time required: a study of a protein structure with 100 or more atoms can take hours or even days to complete. Copyright 1998 Scientific American, Inc. 18 Scientific American January 1999 1998 Nobel Prizes PHYSIOLOGY OR MEDICINE A VERSATILE GAS ROBERT F. FURCHGOTT State University of New York Health Science Center at Brooklyn LOUIS J. IGNARRO U.C.L.A. School of Medicine FERID MURAD University of Texas Medical School at Houston C areers that seek to counter the conventional wisdom may ei- ther founder in obscurity or garner the highest accolades. Robert F. Furchgott, Louis J. Ignarro and Ferid Murad received the 1998 Nobel Prize in Physiology or Medicine for discoveries related to the biological function of a molecule that was once primarily known as an air pollutant. The three were her- alded for elucidating nitric oxide’s role in initiating cellular events that dilate blood vessels. “Signal transmission by a gas that is produced by one cell, penetrates through membranes and regulates the function of another cell represents an en- tirely new principle for signaling in bio- logical systems,” noted the Nobel As- sembly at the Karolinska Institute in Sweden. (Actually, a letter published in Science subsequent to the Nobel an- nouncements pointed out that ethylene gas had been recognized as a signaling molecule in plants since 1934.) Nevertheless, many scientists original- ly dismissed the notion that a gas like ni- tric oxide (NO) could be an intercellular messenger. The typical signal molecules are proteins, peptides or smaller organic molecules. NO, a highly reactive gas, is so unstable that reactions with oxygen or water will convert it into nitrites or nitrates within 10 seconds. But as Furchgott, Ignarro and Murad showed, NO is essential to keeping blood vessels wide open to maintain blood flow and pressure (below). In atherosclerosis, in which plaque oc- cludes the coronary arteries, the cells lining the blood vessels produce less NO. The work that led to the Nobel explains why patients with chest pain (angina pectoris) caused by atheroscle- rosis get relief from pills containing ni- troglycerin: the compound, once it has entered the smooth muscle cells, releas- es NO. Ironically, dynamite, invented by Alfred Nobel, the founder of the prizes, contains nitroglycerin as its ac- tive ingredient. In recent years, scientists have found that NO serves other vital roles in phys- iology. The gas is a signaling molecule for the nervous system. White blood cells use it to kill bacteria, fungi, para- sites and tumor cells. When white blood cells release too much NO in response to a bacterial in- fection, a patient goes into shock. An understanding of the biochemical pathways that in- volve NO led to the development of the anti-impo- tence medication Viagra (sildenafil). 3 GC converts guanosine triphos- phate (GTP) to cyclic guanosine monophosphate (cGMP). 2 NO molecules from the endotheli- um travel into smooth muscle cells, where they activate an en- zyme, guanylyl cyclase (GC). 5 Smooth muscle cells relax. 1 Neurotransmitter or hormone binds with receptors on endo- thelial cells lining the artery, which in response releases nitric oxide (NO). 4 cGMP causes calcium ions to enter storage areas of the cell. The lowered con- centrations of calcium ions (Ca ++ ) set off a cas- cade of cellular reactions that cause the cell’s con- tractile filaments (myosin and actin) to slide apart. JOHN W. KARAPELOU 6 Blood vessel dilates. NUCLEUS CONTRACTED SMOOTH MUSCLE CELL MYOSIN ACTIN SMOOTH MUSCLE CELL RECEPTOR ENDOTHELIAL CELL CONSTRICTED ARTERY NEUROTRANSMITTER OR HORMONE DILATED ARTERY STORAGE AREA GC GC GC GTP cGMP Ca ++ NO NITRIC OXIDE (NO) Copyright 1998 Scientific American, Inc. [...]... attitude” while watching, contains data collected by the radio antenna at Arecibo Obserfor example, the Enterprise crew explain in one case the chem- vatory in Puerto Rico During idle periods of the user’s machine, istry of life while fending off attacks from soil-dwelling, non-car- the screensaver would comb through the data, looking for sigbon-based organisms The key was active watching—stopping nals that... the Greisen-ZatsepinKuzmin cutoff After traveling 150 million light-years, no ordinary particle could still have the observed energies Yet astronomers have seen no plausiNews and Analysis January 1999 Copyright 1998 Scientific American, Inc 34 Scientific American A N T I G R AV I T Y Taste Matters I f we are indeed what we eat, then Americans can rest assured that they actually have something that some... conducted by the American been scientifically validated No state gives strong privacy proManagement Association shows that more than 40 percent en- tection to workers using e-mail, voice mail or the telephone, nor gaged in some kind of intrusive employee monitoring Such does any state prohibit intrusive psychological testing The map monitoring includes checking of e-mail, voice mail and tele- illustrates... an all-time high of 76.1 years But some people—namely, the poor and certain minority ethnic groups—are still being left behind For instance, life expectancy for white Americans is 76.8 years, but for black Americans it stands at just 70.2 years In an effort to remedy the problem, the federal budget for 1999 includes just over $220 million to eliminate inequities in health by 2010 But even as the initiative... mechanisms are at work in both cases The shuttle experiments involving Glenn were more like a doctor’s examiNews and Analysis January 1999 Copyright 1998 Scientific American, Inc JOHN GLENN SUITS UP at the Kennedy Space Center in preparation for his nineday shuttle flight In Brief, continued from page 30 AP PHOTO Tag-Team Voting The Minnesota gubernatorial election of former pro-wrestler Jesse “The... threads empty space Finally, a pair of cosmologists offer another interpretation that extends the theory of in ation to times “before” the big bang —The Editors Revolution in Cosmology Scientific American January 1999 Copyright 1998 Scientific American, Inc 45 Surveying Space-time with Exploding stars seen across immense distances show that the cosmic expansion may be accelerating— a sign that the... thereby offering predictions for concrete things that astronomers can actually measure Before the publication of Einstein’s theory in 1916 and the first observations of cosmic expansion during the following decade, most scientists 46 Scientific American PETER CHALLIS Harvard-Smithsonian Center for Astrophysics T Surveying Space-time with Supernovae January 1999 Copyright 1998 Scientific American, Inc Supernovae... information.” 22 Scientific American News and Analysis January 1999 Copyright 1998 Scientific American, Inc AND THE ANTHROPOLOGY OUT OF AFRICA, INTO ASIA Controversial DNA studies link Asian hunter-gatherers to African pygmies S cientists may have pinpointed direct descendants of the first humans to migrate out of Africa into Asia They could be the aboriginal inhabitants of the Andaman Islands in the Bay... restrictmodern times—by determined opposi- ed by many countries (in this case, India) tion to all seafarers who attempted to for fear that the genetic information they land To this day, one group of An- contain will be misused—specifically, put damanese, inhabiting tiny North Sentinel to commercial use So it will be a while Island, attacks with arrows any ap- before the intriguing links between Andamanese... don’t look as cost-effective,” Dennis explains That clean bill of health for the country may be a while in —Sasha Nemecek coming about 15 years of food scares in Britain—including salmonella in eggs; listeria in cheese; Escherichia coli, antibiotics and hormones in meat; and pesticide residues and phthalates (benzene-related compounds) in just about everything And of course, most infamous was the scare . an in nite continuum. 16 Copyright 1998 Scientific American, Inc. Scientific American (ISSN 003 6-8 733), published monthly by Scientific American, Inc., 415 Madison Avenue, New York, N.Y. 1 001 7-1 111 0 2-6 51 Warszawa, POLAND tel: +4 8-0 2 2-6 0 7-7 6-4 0 swiatnauki@proszynski.com.pl Nikkei Science, Inc. 1-9 -5 Otemachi, Chiyoda-ku Tokyo 10 0-8 066, JAPAN tel: +81 3-5 25 5-2 821 Svit Nauky Lviv State Medical. 48 4-1 320 JAPAN Tsuneo Kai Nikkei International Ltd. 1-6 -6 Uchikanda, Chiyoda-ku Tokyo 10 1-0 047, Japan tel: +81 3-5 25 9-2 690, fax: +81 3-5 25 9-2 679 KOREA Jo, Young Sang Biscom, Inc. Kwangwhamun, P.O. Box

Ngày đăng: 12/05/2014, 15:51