12 Mayıs 2008 Pazartesi
Table of Contents; April 2004; Scientific American Magazine; by Staff Editor; 2 Page(s)
SA Perspectives: Breaking Out of Orbit; April 2004; Scientific American Magazine; by Staff Editor; 1 Page(s)
Shortly after 11:30 p.m. Houston time on December 13, 1972, the commander of Apollo 17, Gene Cernan, took one final look across Mare Serenitatis, climbed into the lunar module and closed the hatch. It was the last time anyone has had his boots planted in alien soil. Since then, the human space program has been adrift. Lacking an overarching mission, astronauts putter around in orbit doing make-work.
This past January 14, President George W. Bush gave them something big to shoot for: a return to the moon by 2020 and a human mission to Mars sometime after that. His plan phases out the shuttle by 2010, replaces it by 2014 and abandons the space station in 2016. A presidential commission headed by aerospace veteran Edward C. "Pete" Aldridge, Jr., has started to flesh out the details, and NASA is already ramping up a technology development effort. Meanwhile the European Space Agency has laid out similar goals with a similar timetable and initial budget. Plenty of blanks need to be filled in, but that is natural in the early stages of a multigenerational project.
How to Contact Us and On the Web; April 2004; Scientific American Magazine; by Staff Editor; 1 Page(s)
Letters to the Editors; April 2004; Scientific American Magazine; by Staff Editor; 2 Page(s)
In the December 2003 issue's cover story, "Does Race Exist?" authors Michael J. Bamshad and Steve E. Olson predicted that new genetic studies of matters related to race will lead to "a much deeper understanding of both our biological nature and our human connectedness." In the same issue, Scientific American's Board of Editors recognized 50 visionaries whose work in research, technology and policy left the world a bit better at the close of the year. While geneticists work on the microscopic explanations of our human connectedness, the particularly international character of the responses to the "Scientific American 50" was heartening macroscopic evidence of our interrelations. The letters come together on the following pages.
I was disappointed to learn from "Racing to Conclusions" [SA Perspectives] that the Food and Drug Administration is proposing that "racial" data be collected as part of clinical trials. Your article did not state strongly enough that the current racial/ethnic classifications promoted by the Census Bureau are archaic, inaccurate and confounding. Data derived from such classification are of extremely limited value, the main result being the perpetuation of outdated concepts about the human race.
50, 100 and 150 Years Ago; April 2004; Scientific American Magazine; by Staff Editor; 1 Page(s)
SEX FOR PLEASURE - "Social, political and public health leaders in many countries are now seriously concerned with the population question and are taking active steps to disseminate family planning information in an effort to bring about a better balance between resources and populations. In attempting to introduce family planning measures, however, they are confronted with a major problem: the need for a contraceptive method which is simple, practical and within economic reach of everyone."
TRITIUM - "Until less than a decade ago men did not know tritium existed. It was discovered first as a synthetic product of nuclear transformation in a reactor; then it was detected in nature. The finding of tritium in nature was not easy. The total amount on our planet is about two pounds, and most of that is in the oceans, so diluted as to be beyond detection. Why bother to hunt down this infinitesimal substance? The answer is that tritium (radiohydrogen), like radiocarbon, may be an excellent tracer for studying natural processes. With it we can date plant products, and tritium in the earth's precipitation may tell us a good deal about the great movements of air and moisture over the face of the globe. - Willard F. Libby" [Editors' note: Libby won the 1960 Nobel Prize in Chemistry for his work on carbon 14.]
Fly Me to the Moon; April 2004; Scientific American Magazine; by Mark Alpert; 2 Page(s)
When President George W. Bush declared in January that NASA would set its sights on returning astronauts to the moon by 2020, scientists quickly lined up on opposing sides. Although Bush's plan promises more funding for researchers studying the moon and Mars, other branches of space science are already feeling the pinch. The most prominent loser by far is the Hubble Space Telescope. Just two days after the president presented his initiative, NASA announced that it would cancel a shuttle flight to install new gyroscopes, batteries and scientific instruments to the Hubble. If NASA does not reverse the decision, its premier space observatory will cease operating when its current equipment fails in the next few years.
The problem arises from the Bush administration's strategy of financing the moon effort through the early retirement of the space shuttle. During the phaseout, targeted for 2010, much of the shuttle's $4-billion annual budget will be shifted toward designing a crew exploration vehicle that could take astronauts to the moon. In the meantime, shuttle missions will focus on assembling the International Space Station.
Sobering Shift; April 2004; Scientific American Magazine; by Sally Lehrman; 2 Page(s)
Since the first "alcoholism gene," dubbed DRD2, was found in 1990, researchers have hunted for DNA sequences that might predispose someone to a drinking problem. But DRD2's role in alcoholism has remained extremely controversial, and despite many efforts, no better candidates have emerged.
Many investigators are now taking a different tack. Instead of searching in families and populations of alcoholics for genes that might broadly confer a high risk for dependence, they are attempting to understand alcohol's effects and why they differ among people. In an explosion of studies, scientists have used rodents, fruit flies, zebra fish and roundworms to study characteristics such as sensitivity to intoxication and severity of withdrawal. By exploring alcohol's interaction with genes and the associated biological pathways, they hope to find clues to alcohol's addictive qualities.
Missing Movement; April 2004; Scientific American Magazine; by Wendy M. Grossman; 2 Page(s)
In mid-February the U.S. government gave up on its search for the herd mates of the first known U.S. case of bovine spongiform encephalopathy (BSE), popularly known as mad cow disease. The end of the trace-back effort, which began after the sick animal was uncovered in December 2003, means that the whereabouts and disposition of 52 of the 81 cattle that entered the country with the infected cow from Canada will remain uncertain. Of those 52, 11 were born at about the same time as the BSE cow and may have eaten the same contaminated feed that is presumed to have been the vector for the sickness.
The problem lies with the antiquated method of keeping tabs on animals - important not just for BSE but for other illnesses among livestock, such as foot-and-mouth disease, and for food poisoning resulting from Escherichia coli or Salmonella contamination. Unlike Canada, the U.K., the European Union and Australia, the U.S. does not mandate livestock tracking nationally. Moreover, there are significant regional differences in how animals are handled. Reliance on paper records contributes to slowness and inefficiency. And because only sick animals and their herd mates are followed, success in wiping out some livestock diseases (such as brucellosis) has, ironically, acted in the past few years to reduce the number of animals being tracked.
Magnetic Moods; April 2004; Scientific American Magazine; by Emily Harrison; 1 Page(s)
A 20-minute spell in an MRI tube is nobody's idea of a good time. So when several depressed patients exited a novel scanning session laughing, joking and exhibiting generally jovial behavior, researchers led by imaging physicist Michael Rohan and imaging center director Perry F. Renshaw at McLean psychiatric hospital in Belmont, Mass., quickly decided to investigate. What their preliminary study suggests is that the unique induced electrical fields associated with that particular type of magnetic resonance imaging session could improve the mood of patients with bipolar disorder.
The scan used in the study was an echo-planar magnetic resonance spectroscopic imaging (EP-MRSI) procedure, a fairly new method of MRI that McLean researchers were using to observe the effects of certain pharmaceuticals on bipolar subjects at the time of the serendipitous observation. Of the 30 individuals who received the EP-MRSI scans, 23 reported immediate mood improvement, the team says in the January issue of the American Journal of Psychiatry. The scans did not affect healthy individuals, eliminating the unsettling possibility that such electromagnetic therapy could be used to get a one-shot hit of happiness.
Shattered Glass; April 2004; Scientific American Magazine; by David Appell; 3 Page(s)
Physicists investigating heavy-particle collisions believe they are on the track of a universal form of matter, one common to very high energy particles ranging from protons to heavy nuclei such as uranium. Some think that this matter, called a color glass condensate, may explain new nuclear properties and the process of particle formation during collisions. Experimentalists have recently reported intriguing data that suggest a color glass condensate has actually formed in past work.
Particles such as protons and neutrons consist of smaller particles called quarks and gluons. Just as electrons have an electrical charge and transmit their force via photons, quarks have a "color" charge and transmit their force via gluons. But one major difference is that gluons, unlike photons, interact strongly with one another. As protons or heavy nuclei, such as gold, are accelerated to nearly the speed of light, the quarks and gluons inside flatten into a pancakelike structure, a relativistic effect called Lorentz contraction. The energy of acceleration also produces more gluons. The flattened multitude of gluons then begins to overlap, falling into the same quantum state, similar to the way atoms in a low-temperature Bose-Einstein condensate overlap and behave collectively as one gigantic atom.
Double Distress; April 2004; Scientific American Magazine; by Rebecca Renner; 1 Page(s)
Amphibians are in decline, and the causes remain controversial. Among the earliest suspected culprits were pesticides, but the role of those toxic substances is not so obvious. Only a few reports have linked amphibian declines to pesticides. And even in those few studies, the pesticide concentrations appear to be too low to kill amphibians.
But University of Pittsburgh biologist Rick A. Relyea suggests that standard toxicology may greatly underestimate the power of pesticides on frogs in the wild. In the December 2003 Ecological Applications, he shows that carbaryl, a common pesticide sold as Sevin, is much more lethal to tadpoles - up to 46 times - when the pesticide is combined with another stressor: the presence of a predator.
By the Numbers: A Surplus of Women; April 2004; Scientific American Magazine; by Rodger Doyle; 1 Page(s)
In 19th-century America, men of marriageable age outnumbered women, in part because the immigrant stream was heavily male and because many young women died in childbirth. Changes in immigration and mortality now mean that the reverse is true. In 1890 there were 107 males for every 100 females in the 20- to 44-year-old group, but in 2002 the ratio had dropped to 98 per 100.
The present imbalance has led to exaggerated reports of female marriage prospects. For example, a widely publicized report in 1986 claimed that a white college-educated woman still single at 35 had a 5 percent chance of marrying; at 40, her chances declined to 1 percent. The conclusion seemed credible because it fed the stereotype that women who have a college degree have trouble finding a husband - a notion apparently originating in the late 19th century when marriage by female college graduates was low. A far more reliable forecast, based on more sophisticated analyses, comes from two Princeton University demographers, Joshua R. Goldstein and Catherine T. Kenney, who estimate that 97 percent of white female college graduates born between 1960 and 1964 will eventually marry.
News Scan Briefs; April 2004; Scientific American Magazine; by Charles Choi, JR Minkel; 2 Page(s)
Land mines kill or injure some 26,000 people every year, and roughly 110 million remain unexploded in about 64 countries. Genetically engineered vegetation could help detect these hidden bombs. Biotechnology firm Aresa Biodetection in Copenhagen has modified the common garden weed thale cress (Arabidopsis thaliana). If their roots detect chemicals common to explosives, such as nitrogen dioxide, that leak out as mines corrode, the plants react as if it were autumn and change from green to red in three to six weeks. Aresa plans to test its plant, whose pollen has been rendered sterile, in small, restricted areas in Sri Lanka, Bosnia and other war-torn places. The hope is to clear mine-ridden land safely and cheaply so that farmers can resume cultivation. The company, which announced the plants creation on January 24, is also working on plants to detect and remove heavy metals in polluted soil.
When physicist Hans J. Herrmann of the University of Stuttgart in Germany heard a 1985 talk about tectonic plates sliding past each other with unexpectedly low friction, he began mulling over the nature of space-filling groups of ball bearings. He soon found theoretical arrays of two-dimensional disks that all turn in harmony, but a three-dimensional version proved elusive - no matter the arrangement, some balls would slip and rub, instead of turning against their neighbors. The physicist and his colleagues have now solved the problem theoretically. Imagine a sphere with six smaller spheres placed inside like the corners of a regular octahedron. The remaining space inside the big sphere can be completely filled with ever smaller spheres in a fractal pattern by a mathematical technique called inversion. Turn one sphere, and the rest turn without rubbing. A real bearing based on this model must consist of finitely many spheres, which Herrmann says would still be frictionless unless the balls were somehow forced out of place. Turn to the January 30 Physical Review Letters for the head-spinning result.
Innovations: Making Proteins without DNA; April 2004; Scientific American Magazine; by Gary Stix; 2 Page(s)
Emil Fischer experimented with making polypeptides - chains of at least three amino acids - during the opening years of the 20th century. Fischer received the Nobel Prize in 1902 for his work on the synthesis of sugars and purines. But he never reached his goal of concocting a complete protein. Nearly 90 years later chemists were not doing that much better. The only practical methods of producing synthetic polypeptides had reached about the 50amino acid mark, the size of the smallest proteins. But much of the attention had switched to recombinant-DNA methods that copied a gene and then inserted the clone into a cell that could pump out protein.
A few diehards, however, could still see the promise of synthetic chemistry. In 1989 biochemist Stephen B. H. Kent, along with colleagues from the California Institute of Technology used a synthetic process to make the HIV protease - the enzyme needed to make the virus fully functional. Then, along with collaborators from the National Cancer Institute, the team went on to determine the crystalline structure of the protein. "Some of us were too old-fashioned to stop making things by chemistry," Kent says. "We beat out people in the pharmaceutical industry who were trying to clone and express proteins."
Staking Claims: Patent Enforcement; April 2004; Scientific American Magazine; by Gary Stix; 1 Page(s)
The U.S. intellectual-property system has distinguished itself in the past several years for such gems as patents on privatizing government, a method for using a playground swing, and a computerized system that handles reservations for going to the toilet. But patenting the obvious is by no means confined to the land of reality shows and SUVs.
In recent years, Costa Rica has given new meaning to the legal term "patent enforcement." It all has to do with the country's popular canopy tours, in which visitors strapped in a harness slide along a cable between treetop platforms. For Costa Rica, decade-old canopy tours are big business, generating a reported $120 million annually. It is estimated that a quarter of the more than a million tourists who come here every year patronize one of the 80-plus tour operations.
Skeptic: Magic Water and Mencken's Maxim; April 2004; Scientific American Magazine; by Michael Shermer; 1 Page(s)
Henry Louis Mencken was a stogie-chomping, QWERTY-pounding social commentator in the first half of the 20th century who never met a man or a claim he didn't like ... to disparage, critique or parody with wit that would shame Dennis Miller back to Monday Night Football. Stupidity and quackery were favorite targets for Mencken's barbs. "Nature abhors a moron," he once quipped. "No one in this world, so far as I know ... has ever lost money by underestimating the intelligence of the great masses of the plain people," he famously noted. Some claims are so preposterous, in fact, that there is only one rejoinder: "One horselaugh is worth ten thousand syllogisms." I call this "Mencken's maxim," and I find that it is an appropriate response to preposterous claims made about magic water sold on the Web. I offer as a holotype of Mencken's maxim the following: Golden 'C' Lithium Structured Water (www.luminanti.com/goldenc.html).
This "is pure water infused with the energies of the Golden 'C' crystal, a very special and extremely rare stone mined near San Diego at the turn of the 20th century." The stone "contains more lithium than any other stone on the planet" and "emits a signature one-of-a-kind healing energy." How does the Golden 'C' water get these magical qualities? Crystal and water are placed in a ceramic container in a "dark and quiet space" for 24 hours, then the water is poured into "violet glass bottles" that "energize it." Finally, "each violet bottle is placed precisely within a special copper pyramid, specially designed to have the exact Sacred Geometry to create a Pillar of Light Jacob's Ladder vortex."
Insights: Draining the Language out of Color; April 2004; Scientific American Magazine; by Philip E. Ross; 2 Page(s)
Would a rose by any other name really smell as sweet? Do our words shape our thoughts, so that "we dissect nature along lines laid down by our native languages," as the linguist Benjamin L. Whorf asserted half a century ago? Is language a straitjacket?
Perhaps to some extent, allows Paul Kay, 69, emeritus professor of linguistics at the University of California at Berkeley. Those are hardly fighting words, and Kay, dressed in fuzzy shoes and a fuzzy sweater, his feet up on his desk, doesn't seem a pugnacious fellow. Yet he and his former colleague, Brent Berlin (now at the University of Georgia), have been at the center of a 35-year running debate concerning Whorfs hypothesis, called linguistic relativity. "Our work has been interpreted by some people as undermining linguistic relativity, but it applies only to a very restricted domain: color," Kay remarks.
The Other Half of the Brain; April 2004; Scientific American Magazine; by R. Douglas Fields; 8 Page(s)
The recent book Driving Mr. Albert tells the true story of pathologist Thomas Harvey, who performed the autopsy of Albert Einstein in 1955. After finishing his task, Harvey irreverently took Einstein's brain home, where he kept it floating in a plastic container for the next 40 years. From time to time Harvey doled out small brain slices to scientists and pseudoscientists around the world who probed the tissue for clues to Einstein's genius. But when Harvey reached his 80s, he placed what was left of the brain in the trunk of his Buick Skylark and embarked on a road trip across the country to return it to Einstein's granddaughter.
One of the respected scientists who examined sections of the prized brain was Marian C. Diamond of the University of California at Berkeley. She found nothing unusual about the number or size of its neurons (nerve cells). But in the association cortex, responsible for high-level cognition, she did discover a surprisingly large number of nonneuronal cells known as glia - a much greater concentration than that found in the average Albert's head.
The Hidden Members of Planetary Systems; April 2004; Scientific American Magazine; by David R. Ardila; 8 Page(s)
Does our solar system represent the rule or the exception? Do similar collections of worlds surround other stars in the galaxy, or is the sun peculiar? Although this is one of the fundamental questions driving modern astronomy, the answer remains elusive. Over the past nine years, astronomers have discovered at least 111 planets around sunlike stars by looking for the slight back-and-forth motion that these bodies impart to their parent suns. Yet this technique detects only the most massive and tightly orbiting objects. If extraterrestrial astronomers applied the same method to our solar system, they might manage to identify Jupiter, and maybe Saturn, but they would completely miss the smaller bodies that make the suns family so rich and varied: asteroids, comets and the terrestrial planets.
How can astronomers detect those smaller bodies and paint a more complete picture of the diversity of planetary systems? A clue appears in the western sky in the spring, right after sunset. If you watch closely, you might see the zodiacal light, a faint triangle of light extending up from the horizon. The zodiacal light is produced by sunlight bouncing off interplanetary dust particles in our solar system. The triangle of light stretches along the suns path in the sky, indicating that the dust forms a disk in the plane of Earths orbit. What makes the dust interesting is that it should not be there. The individual dust particles are so small - about 20 to 200 microns across, judging from the color of the zodiacal light - that sunlight quickly causes them to spiral into the sun and burn up. Dust particles that are even smaller are quickly blown away from the solar system by radiation pressure. Therefore, for dust to be present it must be replenished continuously.
The Tyranny of Choice; April 2004; Scientific American Magazine; by Barry Schwartz; 6 Page(s)
Americans today choose among more options in more parts of life than has ever been possible before. To an extent, the opportunity to choose enhances our lives. It is only logical to think that if some choice is good, more is better; people who care about having infinite options will benefit from them, and those who do not can always just ignore the 273 versions of cereal they have never tried. Yet recent research strongly suggests that, psychologically, this assumption is wrong. Although some choice is undoubtedly better than none, more is not always better than less.
This evidence is consistent with large-scale social trends. Assessments of well-being by various social scientists - among them, David G. Myers of Hope College and Robert E. Lane of Yale University - reveal that increased choice and increased affluence have, in fact, been accompanied by decreased well-being in the U.S. and most other affluent societies. As the gross domestic product more than doubled in the past 30 years, the proportion of the population describing itself as "very happy" declined by about 5 percent, or by some 14 million people. In addition, more of us than ever are clinically depressed. Of course, no one believes that a single factor explains decreased well-being, but a number of findings indicate that the explosion of choice plays an important role.
The First Nanochips; April 2004; Scientific American Magazine; by G. Dan Hutcheson; 8 Page(s)
For most people, the notion of harnessing nanotechnology for electronic circuitry suggests something wildly futuristic. In fact, if you have used a personal computer made in the past few years, your work was most likely processed by semiconductors built with nanometer-scale features. These immensely sophisticated microchips - or rather, nanochips - are now manufactured by the millions, yet the scientists and engineers responsible for their development receive little recognition. You might say that these people are the Rodney Dangerfields of nanotechnology. So here I would like to trumpet their accomplishments and explain how their efforts have maintained the steady advance in circuit performance to which consumers have grown accustomed.
The recent strides are certainly impressive, but, you might ask, is semiconductor manufacture really nanotechnology? Indeed it is. After all, the most widely accepted definition of that word applies to something with dimensions smaller than 100 nanometers, and the first transistor gates under this mark went into production in 2000. Integrated circuits coming to market now have gates that are a scant 50 nanometers wide. That's 50 billionths of a meter, about a thousandth the width of a human hair.
Evolution Encoded; April 2004; Scientific American Magazine; by Stephen J. Freeland and Laurence D. Hurst; 8 Page(s)
On April 14, 2003, scientists announced to the world that they had finished sequencing the human genome - logging the three billion pairs of DNA nucleotides that describe how to make a human being. But finding all the working genes amid the junk in the sequence remains a further challenge, as does gaining a better understanding of how and when genes are activated and how their instructions affect the behavior of the protein molecules they describe. So it is no wonder that Human Genome Project leader Francis S. Collins has called the group's accomplishment only "the end of the beginning."
Collins was also alluding to an event commemorated that same week: the beginning of the beginning, 50 years earlier, when James D. Watson and Francis H. Crick revealed the structure of the DNA molecule itself. That, too, was an exciting time. Scientists knew that the molecule they were finally able to visualize contained nothing less than the secret of life, which permitted organisms to store themselves as a set of blueprints and convert this stored information back into live metabolism. In subsequent years, attempts to figure out how this conversion took place captivated the scientific world. DNA's alphabet was known to consist of only four types of nucleotide. So the information encoded in the double helix had to be decoded according to some rules to tell cells which of 20 amino acids to string together to constitute the thousands of proteins that make up billions of life-forms. Indeed, the entire living world had to be perpetually engaged in frenetic decryption, as eggs hatched, seeds germinated, fungus spread and bacteria divided.
Blastoffs on a Budget; April 2004; Scientific American Magazine; by Joan C. Horvath; 6 Page(s)
Well into the 1860s, the American West remained divided from the East by the harsh terrain of the country's broad, untamed interior, particularly the steep peaks of the Sierra Nevada. Then four Sacramento merchants began raising money to fund a seemingly impossible project: to build a railroad across the high Sierras and thus unite the continent. Derided by the press, the moneymen, top engineers and politicians, the ambitious enterprise nonetheless overcame daunting technical obstacles and eventually succeeded. The so-called Big Four investors, Collis P. Huntington, Mark Hopkins, Charles Crocker and Leland Stanford, became enormously rich as settlers arrived in the newly opened lands. Railroads prospered from the short-haul traffic for a burgeoning population they helped to create.
" Today a group of entrepreneurs has a comparable but loftier aim: to provide cheap, reliable transportation to low Earth orbit. Their high-flying goal comes with similarly steep challenges. Like the rail pioneers, private rocket builders are trying to create a market where none currently exists while keeping costs affordable. Further, they must develop a regular taxi service to space that is sufficiently safe to attract customers. (It will be some time before any flights to space will be as safe as passenger airline flights, though.) Finally, the entrepreneurs must surmount evolving governmental regulatory hurdles."
Working Knowledge: Complete Burn; April 2004; Scientific American Magazine; by Mark Fischetti; 2 Page(s)
"Hey, this sporty model is hot," the auto salesman raves. "It's got sequential multipoint fuel injection!" Yeah, well, so does virtually every other passenger vehicle now in production.
For decades, the good old carburetor acted like a funnel that allowed gasoline and air to be sucked into a car engine's cylinders. Spark plugs ignited the mixture in mini explosions that drove the pistons. The carburetor worked well enough but struggled to finely control the fuel-to-air ratio or even to deliver gasoline equally to each cylinder, limiting fuel economy and creating pollutants and rough engine operation.
Technicalities: Plug-and-Play Robots; April 2004; Scientific American Magazine; by W. Wayt Gibbs; 3 Page(s)
"Could this be the place?" I wonder as I stand before a nondescript storefront, formerly a tattoo parlor, in the tiny borough of Youngwood, Pa. The windows are covered by blinds; the door bears forbidding bars. The building lacks a sign or even a house number. It seems an odd location from which to launch an ambitious new species of robot.
But when Thomas J. Burick opens the door and I see three prototype "PC-Bots" sitting on his small workbench, I realize that this 34-year-old entrepreneur is no ordinary inventor. The half-meter-high robots look like R2-D2 droids that have been redesigned by Cadillac. Burick says that he spent a year honing their appearance, something almost unheard of in serious robotics, where function usually trumps form.
Reviews: The Brain in Love; April 2004; Scientific American Magazine; by Barbara Smuts, Staff Editors; 2 Page(s)
A male baboon named Sherlock sat on a cliff, unable to take his eyes off his favorite female, Cybelle, as she foraged far below. Each time Cybelle approached another adult male, Sherlock froze with tension, only to relax again when she ignored a potential rival. Finally, Cybelle glanced up and met his gaze. Instantly Sherlock flattened his ears and narrowed his eyes in what baboon researchers call the come-hither face. It worked; seconds later Cybelle sat by her guy, grooming him with gusto.
After observing many similar scenarios, I realized that baboons, like humans, develop intense attractions to particular members of the opposite sex. Baboon heterosexual partnerships bear an intriguing resemblance to ours, but they also differ in important ways. For instance, baboons can simultaneously be "in love" with more than one individual, a capacity that, according to anthropologist Helen Fisher, most humans lack.
Puzzling Adventures: Bluffhead; April 2004; Scientific American Magazine; by Dennis E. Shasha; 1 Page(s)
In my gambling years, between the ages of eight and 12, I played roulette, poker, blackjack and any other game that had a three-cent ante. One of my favorite games, though, was one we called "Bluffhead." Each person takes a card from a shuffled deck and holds it, face out, to his or her forehead. In other words, players see everyone elses cards but not their own. The best card wins. Ace is high and suits don't matter, so ties are possible.
This puzzle has to do with inferring information about the cards people hold by hearing what the players say. To be concrete, suppose that we have three players. Caroline always speaks first, then David, then Jordan, and back to Caroline and so on. Each player makes one of the statements listed at the bottom right of this page. Assume the players are perfect logicians and reveal information only through these phrases; also, they say the strongest thing they can - that is, they choose the statement that is true and highest on the list.
Anti Gravity: Visiting Royalty; April 2004; Scientific American Magazine; by Steve Mirsky; 1 Page(s)
There are many compelling vistas for the traveler heading west of Mexico City on Route 15. The extinct Nevado de Toluca volcano, for example, dominates the scene to the left. Within its now quiet caldera lie two lakes, which, at an altitude of more than 15,000 feet, are among the highest places in the world where people scuba dive. The volcanos lakes thus offer the opportunity to get altitude sickness and the bends at the same time.
Then there are the views to the right as Route 15 turns from a busy highway into a twisting, two-lane mountain road. Pondering the sheer drops from the switchbacks my bus is negotiating can be the cause of - or cure for, depending on one's particular physiology - the gastrointestinal problems this part of the world is famous for inadvertently inflicting on gringos like me.
Ask the Experts; April 2004; Scientific American Magazine; by Staff Editor; 1 Page(s)
Dimples reduce drag and improve lift, so golf balls fly farther. A smooth golf ball hit by a professional would travel only about half as far as one with dimples.
Engineers and scientists in the golf industry study the impact between a golf club and a ball to determine the so-called launch conditions. The impact, which typically lasts just 1D2,000 of a second, establishes the ball's velocity, launch angle and spin rate. Gravity and aerodynamics then take over the ball's trajectory (no matter how much the golfer hopes or curses). As a result, aerodynamic optimization - achieved through dimple-pattern design - is critical.
Fuzzy Logic; April 2004; Scientific American Magazine; by Roz Chast; 1 Page(s)
22 Şubat 2008 Cuma
Position-specific entropy profiles created from scanning 306 human and 95 avian influenza A viral genomes showed that 228 of 4,591 amino acid residues yielded significant differences between these 2 viruses. We subsequently used 15,785 protein sequences from the National Center for Biotechnology Information (NCBI) to assess the robustness of these signatures and obtained 52 "species-associated" positions. Specific mutations on those points may enable an avian influenza virus to become a human virus. Many of these signatures are found in NP, PA, and PB2 genes (viral ribonucleoproteins [RNPs]) and are mostly located in the functional domains related to RNP-RNP interactions that are important for viral replication. Upon inspecting 21 human-isolated avian influenza viral genomes from NCBI, we found 19 that exhibited ≥1 species-associated residue changes; 7 of them contained ≥2 substitutions. Histograms based on pairwise sequence comparison showed that NP disjointed most between human and avian influenza viruses, followed by PA and PB2.
Pandemic influenza A virus infections have occurred 3 times during the past century; the 1957 (H2N2) and 1968 (H3N2) pandemic strains emerged from a reassortment of human and avian viruses. Recently, all 8 genome segments from the 1918 (H1N1) influenza A virus were completely sequenced. The results indicate that the 1918 pandemic virus may not have emerged by a reassortment of avian and human virus as did the 2 other pandemic strains. Although the 1918 H1N1 is not considered an avian virus, it is the most avianlike of all mammalian influenza viruses.[2,3] The recent circulation of highly pathogenic avian H5N1 viruses in Asia from 2003 to 2006 has caused ≥90 human deaths and has raised concern about a new pandemic. Therefore, we need to understand what genetic variations could render avian influenza virus capable of becoming a pandemic strain. Genomewide comparison of human versus avian influenza A viruses would show the evolutionary similarities and differences between them and thus provide information for studying the mechanism of influenza viral infection and replication in different host species.
Although many research efforts have focused on the molecular evolution of specific genes of influenza viruses, comprehensive comparisons among the nucleotide sequences of all 8 genomic segments and among the 11 encoded protein sequences have not been extensively reported. In this study, we used several computational approaches for finding specific genetic signatures characteristic of human and avian influenza A viral genomes. We subsequently validated the robustness of those signatures with human and avian protein sequences downloaded from Influenza Virus Resources at the National Center for Biotechnology Information (NCBI) (http://www.ncbi.nlm.nih.gov/genomes/FLU/FLU.html).
Throat swabs from patients with influenzalike syndromes were collected from the Clinical Virology Laboratory, Chang Gung Memorial Hospital. The specimens were inoculated in MDCK cells. Typing for influenza A virus was then performed with immunofluorescent assay by type-specific monoclonal antibody (Dako, Cambridgeshire, UK). Subtyping was conducted by reverse transcription (RT)-PCR with subtype-specific primers.
The RT-PCR product was purified by using the QIAquick Gel Extraction Kit (Qiagen, Valencia, CA, USA). The nucleotide sequence was determined with an automated DNA sequencer. Sequence editing and processing were performed with Lasergene, version 3.18 (DNASTAR, Madison, WI, USA). Multiple sequence alignment was performed with ClustalW version 1.83 (ftp://ftp.ebi.ac.uk/pub/software/unix/clustalw). Global sequence comparison that yielded pairwise sequence identities used in histogram analysis was done with the program Needle in the EMBOSS package. Amino acid sequences were translated from coding sequences and aligned by BioEdit. An entropy value was defined at an aligned amino acid position according to the formula ΣPi*log(Pi), in which i is the observed probability for each of the 20 amino acids (aa). A graphic tool was developed in Java for displaying the entropy plot used in this work. All amino acid numberings are based on influenza virus A/Puerto Rico/8/1934 (PR8).
Sequences Used in Study
To show the host-associated amino acid signatures, we retrieved full genome sequences (as of August 22, 2005) from the genome browser at Influenza Sequence Database (ISD). To differentiate between avian and human influenza viruses, we excluded human-isolated avian influenza viruses from the human dataset and examined those sequences separately. Altogether, we had 95 avian and 306 human influenza viral genomes, henceforth termed "primary dataset." All 11 viral proteins encoded by the 8 genomic RNA segments were compared: PB2, PB1, PB1-F2, PA, HA, NP, NA, M1, M2, NS1, and NS2.
Avian influenza viruses from human influenza patients were separately retrieved from NCBI as well as from ISD. Altogether, we had 417 protein sequences from 60 avian influenza strains, in which 21 strains contain sequences (full or nearly full length) from all 8 genomic RNA segments.
For validating the signatures obtained from analyzing the primary dataset, we further retrieved 15,785 human or avian influenza A viral protein sequences from NCBI's Influenza Virus Resources. Details for the sequences used can be found in Appendix, Supporting Materials and Methods, as well as in Appendix Table 1 and Appendix Table 2. Eleven Taiwanese genomes produced in this work have been deposited in GenBank with accession numbers DQ415283 through DQ415370.