Showing papers in "American Scientist in 1996"

Biological invasions as global environmental change

Abstract: In recent years the difficult question "what constitutes scientific misconduct?" has troubled prominent ethicists and scientists and tied many a blue-ribbon panel in knots. In teaching an ethics class for graduate and undergraduate students over the past few years, we have identified what seems to be a necessary starting point for this debate: the clearest possible understanding of how science actually works. Without such an understanding, we believe, one can easily imagine formulating plausible-sounding ethical principles that would be unworkable or even damaging to the scientific enterprise.

Can technology spare the earth

Abstract: Evolving efficiencies in global use of resources suggests that technology can restore the environment even as the population grows. This article discusses secular trends in what technology does with four paramount resources: energy, materials, land and water, called `factors of production,` along with labor and capital by economists. 46 refs, 11 figs.

How a Scientific Discovery Is Made: A Case History

Abstract: This extensive article looks at the initiation and development of a scientific discovery, using the discovery of high-temperature superconductivity. The study demonstrates that scientific innovation depends on a mixture of basic and applied research, on interdisciplinary borrowing, on an unforced pace, and on personal motivations beyond the administrators rule book. 24 refs., 9 figs.

You Can't Hear the Shape of a Drum

Abstract: Around the middle of the last century, the French philosopher Auguste Comte speculated that knowledge of the chemical composition of stars would be forever beyond the reach of science. Scarcely a decade later, however, the new science of spectroscopy was born?and with it the ability to determine the chem? ical makeup of stellar atmospheres. This development precipitated a revolution in physics. The second most abundant ele? ment in the universe, helium, was first discovered spectroscopically in the solar atmosphere, and eventually an enor? mous database accumulated, perrr?tting the identification of molecules in inter?

The maturation of a cell

Abstract: Many of the cells in a human body are disposable. That is, many are meant to be used briefly, and when they become used up, to be discarded. Con? sider skin cells, which are abraded in vast numbers daily, only to be replaced by other skin cells. Or blood cells, which reside in the body for only a few weeks before being replaced. Bone cells are also being used and replaced, either as the bone is remodeled in response to the changing demands it receives through a person's lifetime, or when it is broken and must be repaired. Skin, blood and bone cells represent the mature or differentiated stages of each cell type. In order for the body to replenish these mature cells when nec? essary, it must manufacture an ample supply of precursor cells. Precursors are the immature varieties of the fully func? tional cells that have the capability to divide and make more precursors or differentiate into the mature and func?

The timing of birth

Abstract: In the fifth century Bc, the Greek philosopher, physician and scientist Hippocrates suggested that a baby de? cides the timing of its own birth: "When the child has grown big and the mother can no longer support him with food, he struggles and breaks forth into the world, free from all bonds/' Hip? pocrates believed that the signal that begins the process is a failure of the pla? centa to keep up with the increasing nutritional needs of the fetus More than 2,300 years later, in the 1930s, Sir Joseph Barcroft at Cambridge University in England was the first to attempt direct experiments with preg? nant sheep to assess various functions of the fetus while the fetal lamb was

The critical mass

Abstract: This article discusses in detail the historical background leading to different lines of scientific thinking in the Allied and in the German scientific communities around the feasibility and development of an atomic bomb. An extensive, parallel time table is given along with discussions of the basic theories of the major players during the conception and development of a nuclear program in both arenas. 35 refs., 11 figs., 5 tabs.

Architecture and Evolution

Abstract: ments. By analogy, Gould and Lewontin criticized arguments about evolution that emphasize immediate biological utility and pay little attention to other attributes of form. They decry, for ex? ample, the various "untestable specula? tions based on secondary utility" of? fered to explain the stunted front legs of a Tyrannosaurus; it makes far more sense, they contend, to accept its ab? normal form as "the reduced product of conventionally functional homo logues in ancestors/' In other words, adaptationsim places so much faith in natural selection as an optimizing agent that an organism "is broken into unitary 'traits' and an adaptive story for each is proposed separately." In some cases, a viable explanation based on adaptation cannot be devised and should not be, Gould and Lewontin wrote. Gould and Lewontin's principal metaphor, based on the so-called deco? rated spandrels of Saint Mark's Cathe

Communal Breeding in Burying Beetles

Abstract: When a young chipmunk dies in the woods, a wide variety of or? ganisms?from mammalian scav? engers to insects, fungi and microbes? compete for this sudden food bonanza. In New England, burying beetles rank as one of the most successful competi? tors. A chipmunk is a relatively large carcass for these 1.5 centimeter-long insects, and such a food source may be discovered and buried by various com? binations of adult burying beetles. As they bury the carcass, they shave it and roll it into a ball, readying it to become food for a single large brood of young, or grubs. Once finished, some of the adults may remain in the brood cham? ber to tend to the carcass and to feed and defend the larvae until their devel?

Fractal Image Compression

Abstract: In spite of the 20-year hiatus since a satellite from Earth last orbited the Red Planet, Mars continues to exert a powerful attraction on the human psy? che?not only on the popular imagina? tion but perhaps even more so on the curiosity of those who are carrying out its exploration. Consider the surprising parallel between our current incomplete understanding of the planet and the even more sparse comprehension of sci? entists and the public 100 years ago. Like the imaginative and well-publi? cized astronomers and fiction writers of

The shapes of planetary nebulae

Abstract: In about 5 billion years our sun will mount a spectacu ar show of violent seismic activity that will eject nearly all of its gaseous layers into space. The event will take place on the eve of its decline, a last gasp before death. Dust and gas cast off by the dying star will be reshaped by a million-mile-per-hour wind and heated by a searing radiation from a hot white remnant lying at its center. Any survivor in the solar system will see the glowing gas as a colorful specter 500 times larger than Pluto's or? bit?a planetary nebula. Our sun's destiny is not unique; nearly 99 percent of all stars will share a similar finale. (Many of the rest will end their lives in a supernova explo? sion, a spectacular event in its own right.) Previous generations of stars have already met such a fate. Their ejected nebulae can be seen in modest telescopes, scattered here and there among the stars in our galaxy. By some estimates there may be more than 100,000 planetary nebulae in the Milky Way galaxy. More than 1,000 of these have been catalogued. The typical planetary nebula has a Hfetime of no more than 30,000 years or so?a brief moment in the 10-billion

Bubbles and double bubbles

Abstract: land, Dido had the skin cut into a long thong, and she laid it out in a circle that surrounded Byrsa Hill, which would become Carthage. Like Dido, ancient farmers enclosing fields and lords building walls around castles must have wondered: Given a fixed length of material, what shape encloses the largest area? Equivalently, we can ask what shape uses the small? est length to enclose a given area. The Greeks dubbed that the isoperimetric (same-perimeter) problem. Although Dido made the best choice, because a circle encloses area more efficiently than any other two-dimensional shape, it took a long time for mathematicians to generate a proof. In the third or fourth century B.c., the ancient Greek mathematician Zenodorus apparently made the first mathematical stab at

Curing the Incurable

Abstract: Americans, it seems, have an abiding faith in the power of science and technology to remedy environmental degradation. Take, for example, the nation's war on lake eutrophica tion. This federally funded effort sprang from the belief that a massive lake-restoration program could erase the damage inflicted on the nation's lakes by decades of abuse and mismanagement. Many millions of dollars and many years later, it appears that this faith was sadly misplaced. More than 20 years ago, in American Scientist's Marginalia department (May-June 1973), Yale University professor G. Evelyn Hutchinson ex? pounded on the subject of lake eutrophication, the process by which lakes deteriorate as they be? come increasingly productive with age. Referring to eutrophication as a "contemporary practical problem," Hutchinson explained how all lakes evolve naturally in a manner corresponding to ecological succession. Newborn lakes are typical? ly oligotrophic?deep, clean and unproductive. As lakes mature, however, they become more eu trophic. A eutrophic lake is typically shallow? the result of long-term sedimentation?and in? fested with aquatic vegetation, including rooted plants and phytoplankton. People accelerate eutrophication by polluting lakes with sewage, fertilizers and other materials enriched with nitrogen and phosphorus, which stimulate excessive vegetative growth. Deforesta? tion, road construction, real-estate development, agriculture and other cultural disturbances in wa? tersheds are major sources of sediment. Thus eu? trophication can proceed at a natural rate or be cul? turally accelerated; either way the process is more or less continuous and irreversible. Bogs, swamps and marshes?the climax stage of eutrophication?are often sites of former lakes that are nearly extinct. Ironically, just as Professor Hutchinson, the world's most renowned limnologist, was inform? ing the scientific community and others about the inevitable nature of lake eutrophication, the U.S. Environmental Protection Agency was em? barking on an ambitious project to halt eutrophi? cation and restore highly eutrophic lakes to pris? tine conditions. The Clean Lakes Program, authorized under the Clean Water Act of 1972, proceeded to fund lake-restoration projects in 1976. By 1993, EPA had awarded grants totaling about $150 million and had spent hundreds of millions of additional dollars administering the program. Thousands of first-rate scientists and engineers participated in countless limnological studies and lake-cleanup efforts nationwide. Congressional funding for the program was slashed almost to zero in fiscal year 1995, and the future of Clean Lakes along with other EPA pro? grams is in doubt in the current political climate. Many, many lakes are in urgent need of help. But perhaps not the sort of help that came from the Clean Lakes Program. Unfortunately, this heroic effort may have cost us the opportunity to pro? tect and improve lakes that can be saved.

The Petronas Twin Towers

Abstract: For two decades, the 110-story Sears Tower stood as the tallest building in the world. Topping out at 1,454 feet above ground lev? el?almost as tall as a string of five football fields would be long?the bundle of nine steel tubes standing just outside Chicago's Loop could be said to have cast a shadow over all other sky? scrapers since its completion in 1974. New York's World Trade Center, the 1,368and 1,362-foot-tall twin towers completed only a year earlier, held the record as tallest buildings for only a brief time. Before that, the Empire State Building, at 1,250 feet tall even without its broadcasting towers?which, like those of the Sears Tower, do not count as part of the building proper?held the world height record for over four decades. Completed in 1931, the Empire State then surpassed the one-year-old Chrysler building, which at 1,046 feet tall had been the first to break the magical 1,000-foot mark. Before then, the Woolworth building, a 792-foot tall Gothic cathedral of commerce paid for in cash by the profits from its namesake's chain of five and ten-cent stores, had stood as the world's tallest building for almost two decades. Skyscrapers?so named since the 1880s, when Chicago's 100-foot-tall buildings were marvels of contemporary structural engineering?seem to have sprouted up in temporal and spatial clus? ters, with Chicago and New York proving espe? cially hospitable to the form and its financing. Throughout most of the 20th century, the sky? scraper was considered a particularly American genre, growing with the economy and optimism of cities such as Atlanta, Houston, Los Angeles and Seattle. In the last decade of the century, however, the frontier of the skyscraper has moved across the Pacific Ocean to the Far East.

Competition between two weeds

Abstract: Every gardener knows that plants compete with ach other?e pecial? ly if one of the plants is a weed. Al? though gardeners help their plants win competitive interactions by removing or poisoning weeds, plants in nature must fight on their own?finding ways to de? feat rival plants. The question is: What causes competing plants to win or lose? Competition between plants repre? sents one of the best-documented inter? actions between biological species. Hundreds of examples show that plant species affect one another through the use of shared resources, including light, nutrients and water. A tomato seedling in your garden, for instance, may grow poorly in the shade cast by a mature oak tree. Another tomato plant may sur? vive better in the shade, because some individual plants have different com? petitive abilities. The outcome of com? petition between plants may also de? pend on the composition of the local community and debris or chemicals left by plants from earlier generations. Although botanists have assembled a virtual catalogue of examples of com? petition, we know very little about the mechanisms that govern differences in competitive ability. I shall describe a se? ries of experiments that reveal an intri? cate^?and somewhat surprising?web