2 Scientific American, August ienti meri an olume um er ugust u lished monthl ienti meri an a di ision of ature meri a n. e or la a uite e or. August , Volume No 2 pp Letters; 50, and Years Ago: Innovation and Discovery as Chronicled in Scientific American PDF (1, KB) . Scientific American (August ), , Published online: 14 July | doi /scientificamerican
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Scientific American is the essential guide to the most awe-inspiring advances in science and technology, explaining how they change our understanding of the. 52 Scientific American, October NEUROSCIENCE. Your nightly rest turns out to affect your mind and health more than anyone suspected. Scientific American (ISSN ), Volume , Number 1, January , published monthly by Scientific American, a division of Nature.
These discrete sounds exhibit geographical variation like. Evgeniy S. But if the gene copy contains disabling typos or is missing pieces of the original, such as the promoter, it will become a pseudogene. One of the primary issues with the gaine. Like many physicists, Connes hopes that the Higgs particle will show up in detectors.
This result is surprising entanglement and wormholes might in fact be equivalent and because entanglement. In a gas. Joseph Polchinski and James agitation of molecules. We also hole connecting the black hole to another system. December The scopic constituents that collectively are capable of adopting vari.
Einstein and N. Donald Marolf. They discovered a paradox tures. When the amount of entanglement becomes for the first hole. Burning Rings of Fire. A further look at black holes points the way to the answer.
Each has would not follow our usual notion of geometry. July 1. September In such situations. We believe that the seemingly unrelated phenomena of nection between the two black holes. The fact that black holes radiate implies that they have a ing work in on the connection between entanglement and temperature—a notion with important ramifications.
Cool Horizons for Entangled Black Holes. There was also interest- plistic. May Susskind Now. In summary. In point toward it. In this picture. But the two distant black holes in this description of quantum spacetime—and a long-awaited unifica- case are physically connected through their interior and brought tion of general relativity and quantum mechanics. Although the medical know-how for transplanting organs has expanded rapidly. Investigators have struggled.
A few years ago scientists thought that they could do that by using stem cells. Re- replacement search continues on this approach. Global fig- ures are hard to come by. Such an achieve. That virtuoso performance sports the head and wings of an eagle and the body of a lion. We believe After sacrificing the animal. My colleagues and I believe that it may be possible to cluded. Evolution has already created an exquisite process man cells—in an animal such as a pig or cow.
A normal pig heart would. A small but increasing number of investigators. Our occurs in the weeks and months after a fertilized egg gives rise dream is to create a chimera by injecting human stem cells into to an embryo that grows and—without having to rely on an arti. The idea might sound far-fetched.
Sev- would overwhelmingly reject a direct cross-species implant. These so-called chimeric embryos would then gestate in surrogate animals until the organs Pdx1 can be harvested.
After a few weeks of gestation. The resulting ani- for turning a handful of identical cells into all the specialized or. For starters. Pig eral different teams injected custom-designed mouse embryos heart valves are suitable substitutes for human tissue only after with rat stem cells and then allowed the resulting chimeras to de- they have been chemically treated to prevent this immune reac. Relying on human origin. We still have much to learn about how taken from animals and human stem cells grown in cell cul- best to prepare human stem cells and animal embryos so that tures.
This around the world. Gestation in pigs normally lasts about four months. We fertilize a pig egg with pig sperm. Waiting lists could become a thing of the once identical cells soon start to move and behave differently as past as we develop a bountiful supply of replacement parts they divide. Each of these cells organs. The cells make and release special- to four weeks.
We are nowhere near ready to take that final step of produc. Liver Gallbladder iPSCs begin to develop Dorsal into pancreas cells Ventral pancreatic pancreatic bud bud mice—except that they had the pancreas of a rat. A lot later the combined cell. Within a few days several hundred cells have from farm animals for tens of thousands of suffering people formed a kind of ball within a ball.
After completing several more intermediate exper. But even if we are unable to create fully formed two and then four seemingly identical cells. If success.
Thanks to the complex interplay of genes and proteins. Provided these experiments are successful—and this still incomplete understanding and a lot of trial and error. Then we transferred the chimeric embryos into ed by the precise location of different cells at various times with- surrogate sows.
The raw materials we use include porcine eggs and sperm ing chimeric piglets. We also recognize how much this growth is guid- mature normally. Experimenting on human ent potential problems. To date. Pigs also have Closer study of the human iPSCs created to date. They are already so far along to becom- velop fully. If the added cells develop appropriately. Previous work has demonstrated. Using iPSCs would offer the added ad- concentrated our efforts on creating pig embryos.
As the embryo grows. The fact that a single gene. By deleting the was transplanted in Because mice are too small to generate or. If we wait any longer. Recent- gan unless we inject enough human stem cells that contain the ly researchers led by George Church of Harvard University have missing gene.
Because normal human embryos require nine months to de. More recently. A few cells located in the middle layer. Because these iPSCs do not human cells to the somewhat longer pig timeline should require respond correctly. Other organs. Adapting tell them to grow into something else. My colleagues and I stopped the experimental em- means that emptying the niche for these organs will require de.
Hiromitsu Nakauchi. Biologists refer to this physiological state as be- sity of Tokyo. The result would ic of Barcelona. August September 3. There are additional concerns. Truly naive stem cells.
I believe the knowledge and techniques we dis- Moxie Foundation for supporting this early work when no one cover along the way will prove enormously valuable. The best way to prevent such a troubling outcome is to make our lab would not be able to accomplish such a task by our. Together with embryologists. One of the thought our approach was even feasible.
The tantly related species such as pigs. We have also begun tracing the way the hu. But we must pay special attention to three types— velop a little longer—until they are six weeks old.
Imagine the ethical nightmare. But the preliminary re- best number of human iPSCs that need to be implanted for the sults I have described in this article make me cautiously opti- embryo to develop successfully and the time at which we need mistic that we may generate human organs from chimeric ani- to implant them.
I knew mal. Studies To date. At that point. We began injecting pig All bets are off. I vividly remember his advice: If we cannot figure out a bio. Scientists are people. And we can be overly ments have helped us to gain some basic knowledge about the optimistic about what our discoveries may imply—not just for development of chimeric embryos. We are starting to learn the our own fields but also for humankind. So far we have allowed the chimeric embryo to grow into a fetus. Although it is a long shot.
The guidelines that we and tell them when to stop growing—the better they may be able have worked out with regulatory authorities require us to sacri. We get excited about Overall. November 5.
We can forestall that problem by delet- mans and pigs are not as closely related. I am especially grateful to surmountable. Allowing these animals to then breed only way to determine whether human iPSCs can cross species could lead to the ethically disastrous case in which a fully human barriers and contribute to the formation of a human organ in a fetus the result of a humanized sperm from one pig fertilizing a pig is to role up your sleeves and do the experiment.
Yet even if we fail to create functional organs for the San Antonio Catholic University of Murcia in Spain and the transplantation. Wayt Gibbs Photographs by Chris Mueller. The shiny. Even if it succeeds. Warning lights start flashing. For decades academic On the video feed overhead. Preliminary results have ic hurdles. The second discouraging example is ITER.
The temperature inside that chamber will rise. There they collide and form a hot. In April. The warning lights switch off. The current energizes the ring magnets and nearly inexhaustible and have no carbon. Such fusion power plants would run on morning using power from the local grid. This reactor is an early prototype for a power plant balize its parts for a more advanced reactor—dubbed C-2W—to be completed in mid I click it.
The system stant. It will rely on giant superconducting magnets to control a team all the data it needed to move on. When you fire as many as pulled the plug on designing a prototype power plant. Two years ago Livermore Just another shot at fusion. They also would zap to come. One example is the million kilometers an hour. Clouds of hydrogen ions form at the opposing ends of the that have clarified some fusion science but are not on track to vacuum cylinder and are propelled toward the center at nearly a pump electricity into the grid by midcentury.
Sitting in the control room W. A power plant room had dropped a wrench onto the concrete floor. I see workers out on the floor of scientists have designed gargantuan machines intended to solve this nondescript warehouse near Irvine. The plants would charges up banks of beefy capacitors. ITER will make no electricity.
All the new pioneers need to do is solve some of the hardest over loudspeakers. The backers are placing high-risk. That typically disruptive electric currents and magnetic fields. The tremes: Equally important.
In this design. Frustrated senators voted 90—8 to cut off U. ITER aims for a low plasma density. Congress was. Most of the newcomers are searching for sweeter spots that lie in the less explored middle ground. NIF and ITER are at opposite ends of a spectrum of plausible designs that spans a huge range of plasma densities and energy- confinement times a measure of how long heat stays inside the plasma.
Forewarned by the glacial progress of the giants. Tri Alpha claims to have raised hundreds of millions of greater than about seconds per cubic centimeter. That pleases their investors. Fission reactors. A big opportunity. But after a subsequent though guarded vote of confidence by the U. A get the candle lit. Another fast-moving group is ITER. Two atomic nuclei. Department of Energy. As of May. As a rule of thumb. To deliver. Any show-stopping flaws in these schemes most likely will plenty of space to have a bad surprise—or a good one.
Full operation will not come until at the earliest. In a power reactor.
But the tests plasma. The fusion converts the missing mass into energy. Just three scale reactor that powers itself as well as the grid. The blobs remained stable and hot for five milliseconds. The designs shown here are for commercial-style reactors. Neutral beam injector 8 total Beams run along tube. Laberge describes the stability problem. They have essentially solved tall. With each beat. The entire neutral atoms into the edges of the tube process would repeat once every second.
The liquid chamber degrees Celsius for fusion reactions to metal captures the neutrons and heat take off.
A brief. Eight injectors shoot beams of released by the fusion. If all goes well. But the Sandia system is. The team is trying to improve the sides. The machine imposes a covers the open end of the fuel target may be scattering the separate magnetic field to keep the resulting plasma from light. Laberge argues. It has in experiments thus far. The thin window that ionizes the fuel as it starts to implode. Sandia researchers calculate that it might be.
That is more than 20 times for late Daniel Sinars.
But if But competition could change that sentiment. Half a continent away in New Mexico. According to Slutz. Is that enough to achieve General Fusion must struggle with unproved physics. A brief trillion-watt laser blast nearly as much as their models predict. For a squirting out the ends of the cylinder.
But a laser may simply be the wrong tool for the job. It is an elegant solution on a whiteboard, but no one has ever built such a system. And Laberge worries that as shock waves from the pistons pass through the lead-lithium mixture, some of the metal could spray into the plasma, squelching the fusion.
The start-ups Currently that race in the U. Federal money for alternative paths to fusion has been face numerous practical challenges. Scientists Maybe, maybe not. Tri Alpha is pursuing proton-boron fusion precisely to avoid Is it worth taking a few more shots?
Plasma Physics: The Fusion Upstarts. But that technology does not yet exist. We once believed that the continents were fixed on the surface of Earth; now we know they move. We thought margarine was healthier than butter and that hormone-replacement therapy was the right treatment for vast numbers of postmenopausal women; now we know better.
But while scientists do not know everything, there is plenty they. And especially during this political season, it is dispiriting to see how many people—including political candidates—bizarrely reject some of the most basic, evidence-based truths that underlie modern science.
Psychological research has shown that being confronted with that mounting evidence can actually harden the positions of the truth deniers, so we do not pretend that the essays that follow will fix the problem. Nevertheless, we feel it is our duty to point out that some things actually are true, even in the constantly growing and evolving world of science. Because of a convergence of evidence from many lines of inquiry. Darwin came to this conclusion: Not only are the dates consistent.
It is not as if one scientist finds that a fossil hominin is 1. If new species are created naturally—not supernatu- rally—what place. No wonder that more than a cen- tury and a half later people of some religious faiths still find the theo- But in those intervening years scientists ry so terribly threatening.
Nobody knows where this have never been shown to be dangerous. For example: The ages are given in estimates. And of course. Dobzhansky famously noted. The consistency of dating techniques also gives us confidence that the theory is true. Explanation for vinced quite contrary to opinion I started with that species are not it is like confessing a mur- the Diversity der immutable. Trilobites and mammals are separated by many millions of years.
A product called Oscillococcinum is sold based on the unscientific thinking of a single mis. They consult two books. That means Muscovy duck the heart and liver. The el Hahnemann. What are you afraid of? You do have to replace fluids lost to urine and perspira no access to healthy food or a balanced diet. If any of that makes sense to you. It is active ingredient.
They ask way to explain homeopathic theory is with this example: If coffee a laundry list of irrelevant questions What color are your eyes? What keeps you awake. Any chemis- and Its Kindred Delusions. It is inconsistent with our basic knowledge of physics. All that remains is the quack. We have learned plenty since then. The cabal would also have to fake all the data from past climates that tells us there is no magic mechanism clouds or otherwise that will save us from the well-established warming effects of carbon dioxide acting in concert with water vapor.
Our understanding of the connection between greenhouse gases and global warming rests on the same principles that underlie heat-seeking missiles. Some of my favorites: Berlin wall. Likewise the carbon isotope and car- bon budget data that prove that the carbon dioxide accumulating in the atmosphere really does come from deforestation and burning fossil fuels.
If it is a conspiracy. Global warming is a problem. Homeopathy was bunk in Earth is not flat. It would have to fake the observed conjunction of strato- 0 spheric cooling with tropospheric warming. Irish-born physicist John Tyndall have used homeopathy instead of effective drugs.
Science rewards those who overturn previous dogma think quantum theory versus classical mechanics. People have died. I wish they radiation emitted back into space.
As Edzard Ernst. It adds up to an awful lot of stuff to fake and makes faking the moon landing look like a piece of cake. It would take quite a conspiracy to fake all that. Energy is conserved. And so on and so forth. People temporary Gustav Kirchhoff. You know it. By now There were many later developments in the 20th century. The Conspiracy Theories ed that it works no better than placebos. Austrian Ludwig Boltzmann in the mids and his German con- strates the inability of the general public to think critically.
At the time. As a consequence. Animal tests But despite a handful of suspicious-looking studies. If the disorder is genetic. For the most part. Frederick Banting and Charles Best discovered insulin.
It is nice to be able to point a finger at an evil force causing autism. Another possibility is that the notion that vaccines cause autism is comforting—certainly far more comforting than studies that have shown a genetic basis. Until a clear cause and cure for autism emerge.
The most encouraging aspect of the vaccine-autism controversy has been the emergence of academics. If autism is caused by events occurring out- side the womb. Criminal activity does not increase during the full moon. There are several plausible rea- sons why they feel this way. Conspiracy theorists argue that the only reason studies have shown that vaccines do not cause autism is that a vast international con- spiracy is hiding the truth.
Although only a small group of parents hold this belief. And everyone loves a bogeyman. Since then. That should tell you something: Assuming an aliens- without-borders effort. Even aside from the formi- dable technical challenges of interstellar travel. If aliens have been here weekly radio program.
Aurum Press. Seth Mnookin. The Panic Virus: If despite nonprofit organization the lack of good evidence. I think the United Nations would notice. Most of these can be explained as aircraft. Unless the extraterrestrials come from a very close star system. Unless extraterrestrials prefer Americans and exceptionalism aside.
There remains no scientifically validated evidence that extraterrestrials have been here. The He also co-hosts a Roswell incident was nearly 70 years ago.
Many people believe the latter. The History of a Modern Myth. Global Weirdness. The majority of the evidence is composed of sightings—eyewitness accounts. They say Evidence of Alien that the government knows the aliens are here Visitations Exists but keeps the evidence under wraps at Area 51 or some other top-secret venue. Viking Adult. Why are they here now? Big Picture Science. The pyramids. Climate Central.
The killer whale findings raise ques- emergence of new species. Whatever the motivation behind it. His research focuses on the mechanisms that create. If so. The sun has burned off most of the morning mist. Exactly why the creatures engage in this scraping behavior. Despite their name. Plumper and Kaikash gently scrape their bodies against the small. British Columbia. Observations made since the s have diversification: These cultural and physical differences. J ust offshore from the pebble beaches of Bere Point on Malcolm Island.
I watch from the boat as three killer whale brothers named Cracroft. That is. University of London. Physical traits. In the favored scenario. Soon they will leave to hunt for salmon or look for mates. It is part of the distinctive cultural fabric of the northern resident killer whales. The brothers have already spent the better part of an hour here absorbed in this activity.
The northern resident killer whales are not the only ones Intriguingly. Mounting evidence indicates that cul. Documented examples specialize in hunting Antarctic minke whales. For the facial features and fingerprints to identify individual humans. Were the populations already living in the same whales live side by side without fraternizing. One type. There research begun in the early s inconclusive for many Northern Hemisphere killer whales.
Bigg and his colleagues. Biologists can use those traits to sity in England and his collaborators hint that these ecotypes identify individual killer whales. Burdin of the Russian Academy found only in isolated springs in California and Nevada shows of Sciences. For its part humans. Current evidence is mostly the Northeast Pacific. Andrew sary for speciation to occur. Yet scientists have now shown that in various marine the killer whales. Resident ent environmental conditions. If this separation persists long enough.
Deecke of the University of Cumbria in England. Ford and graphical barrier of some kind—perhaps a mountain range. In the parlance of The Southern Hemisphere hosts geographically overlapping biologists.
B Type 1 Preferred prey: They also differ in their physical features. These separate groups. Their cultural traditions probably differ depending on their preferred prey. The whales choose mates that share their customs rather than foreigners from other eco- types. Yet studies show that in var- ious regions distinct forms.
Culture appears to keep the ecotypes apart. Whether the northern Pacific halibut ecotypes began to diverge while living and sleeper sharks in the same region or whether they started to differentiate at a time D Transient earlier in the evolutionary history Preferred prey: E Type 2 Preferred prey: Patagonian toothfish J Type C Preferred prey: Antarctic toothfish November For example.
Scientists have observed this behavior in two groups records maintained and occasionally published by SeaWorld. In May of this year. A pod of the killer whales will herd a Because these and other behaviors are found only in certain school of herring into a tight ball close to the water surface. But the most dramatic specializations have dubbed carousel feeding—to hunt the herring that form the occurred in cultural behaviors related to food acquisition. But the ice-pack whales are diversifying by exploiting different food sources and killer whales have learned to create waves that wash the seals evolving various traits that presumably help them get those over the ice float and into the water.
Some of these distinguishing features are physical. Rather mounting evidence suggests that submerged until they are just meters away from their quarry.
What is keeping them separate now? Breeding the beach. In Antarctica. G-clan and R-clan for the tions that live side by side. Do other is. These discrete sounds exhibit geographical variation like. Although all sequently evade capture. That have diversified. The challenges the ecotypes face. Then individual so suggests that culture is keeping these ecotypes apart. Fish-eating killer have also played a role in driving speciation among those early whales do not have the same problem.
January Not only do the pulsed calls and whistles differ thropologists thought that most selective pressures that shaped among killer whales from different geographical regions.
Killer lations were during all phases of their diversification. Might culture the time they swim and hunt in stealth mode. There is no evidence to suggest that killer whale ecotypes? Some preliminary studies hint that the killer whales use these signals in any way that really resembles oceans around Africa might. With the advent of and ecotype variation.
April Rather the southern Asia come to mind. But they also often vary among social modern tools for studying genomes. The drug is illegal in the U. Photographs ScientificAmerican. The windows of your bed- room disappear into blackness. This scene bleeds into a darker one of demons. You are Shea Prueger. Thunderclouds cover the bedroom ceiling. Clinic op- and other treatments. You cov- er your eyes. You cannot wake up—you cannot move your body. In the U. The year-old used to live in New York spread.
Renegade Science. Today she is recall. So for two days in erators claim that a dose can curb addictive behavior. The walls around you bend and twist. Narcotics Anonymous wide. The increase in needle what no other recovery treatment could do. She stayed clean ed remedy for an exploding problem.. An audience somewhere is clapping. Nothing worked. Sweats drips from your forehead. You want to get away. You have trouble breathing. In diction with a psychoactive drug called ibogaine..
After all adverse events. Around that time the late Howard Lotsof. Lex Kogan. Many seek help but do so in vain. During treatment patients often suffer from car. From to a French pharmaceutical compa- works on many neural pathways at the same time. The stimu- panies.
Many of from addictions to alcohol. It is illegal to use ibogaine as medicine in damage. Because withdrawal symptoms. Prueger is now chief administrator ing one in every treatments. About 80 per. Buoyed by these ideas. Word spread. Some animal studies of ibogaine and addiction came out times death. That is why heroin addict. Published medical reports tie ibogaine to 19 in the late s. Not if it there is a toxic part. Animal studies suggest that of Envision Recovery.
The overseas clinics began to open. In small amounts of around eight milligrams. During the previous two days. Schen- five years. Kogan says.
That could indi- here and ready. Mallek swallowed the pill. Carefully monitoring heart health will help spot arrhythmias in case treat- ment is needed. Schen- an electrolyte solution to keep his body hydrated while he fasted berg reports that he conducted phone interviews and corrobo- on fruit and water. Operators create mystical rituals cliff in a suburban neighborhood. When I interviewed Mallek.
It is a manipulation. His study. An IV line was tied to his right arm. After a patient ingests ibogaine. Brown says he and his colleagues ence behind them. He had tried to get sober suffering and the pain of human beings and offer magical solu- dozens of times already. Mallek has been using heroin for the past 15 years connected to ibogaine clinics: He had been taking small ibogaine doses search led by neuroscientist Eduardo Schenberg of the Federal to test his physical responses for risky reactions.
After testing. Just like Mallek. Envision purchas- es the white. He had not taken any opiates for 12 hours and had just entered the first stages of with- drawal—sweats and chills.
He was ready to be- gin treatment. This double effect than half of the patients stayed clean a year after the treatment. In Deborah Mash. They worry chief of drug abuse research at the fda. More cravings and stems withdrawal symptoms. In the body. With funding from private ments in social well-being.
Ibogaine works. Mash has not been able to November When a strong opioid such as her- aspects of motor function. Vocci argues. From a molecular perspective. When researchers done does. But when Mash sought funding from nida to conduct research on higher doses and to begin a larger study. The study did not follow them further. One of the primary issues with the gaine. The initial results were positive: There is also the po. The preliminary data showed that all patients benefited gram with those kinds of risks.
Using follow-up data on patients after treatment. Food and Drug Administration approval to begin a safety study of ibogaine in cocaine-dependent volunteers. The safety data are just so bad. There was no observed effect on the cerebellum. If a per- of brain and spinal cord cells. Mash says. In a University of Arkan. The heart risks have been well documented. In the s several animal studies at ing across billions of nerve cells in the reward centers of the brain.
In people. Counseling and Mash is not far behind. Researchers believe the serotonergic system is years of ibogaine trials on Saint Kitts. Noribogaine incites these cells to send more serotonin to the substantia nigra.
Research in the s with damage or any other neurotoxicity. Results of an un- potential and its dangers in the s. This chemical inhibits Cingulate the activity of dopamine neurons of the brain chemical dopamine. Inspired by the results of her eight tonergic system. In itus in the department of neuroscience and experimental thera.
Acetylcholine But Deborah Mash. MARCH Private pharmaceutical companies noribogaine. Nestler and Robert C. In their wake, found that the number of meth users during many others followed: SAMHSA found, howephedrine or pseudoephedrine; the last are ever, that the proportion of these users medications available without prescription.
That translates into , peomethamphetamine; Mexican gangs bring ple who are at particular risk of violence into the country most of the remainder. They fabricated a touch sensitivity.
Future touch sensors for robots based on this work will most likely rely not on light signals but rather on electrical impulses, researcher Ravi Saraf explains. For a few million years, the North Pole felt downright Floridian thanks to the presence of greenhouse gases released by some unknown geologic process.
The warmth as recorded by the core data is 10 degrees Celsius higher than climate models had predicted. Virtually all these chestnuts were killed within 50 years by a fungus introduced to the U. He notes that the chestnut-killing fungus may not have thrived on the dry, rocky mountaintop where this stand dwells. The American Chestnut Foundation announced May 19 it would breed the trees with blight-resistant Chinese chestnuts in the hopes of eventually developing a hardier, mostly American hybrid.
Marine biologists had noticed that in this typically social crustacean, sickly looking lobsters, infected with a lethal and contagious virus called PaV1, usually become isolated from the pack.
To determine if the avoidance is purposeful, scientists set up two adjacent dens in a tank of seawater, tied either a sick or healthy lobster in one den and then introduced a second lobster. If the second creature was already infected, it bunked with its sick or healthy tank-mate equally often.
But healthy lobsters were one fourth as likely to share dens with infected lobsters than with healthy ones — even before the sickies became contagious — probably because of chemical signals. A double-blind study, however, shows that a three-day treatment is just as effective. Though abundant in the centrosomes, few to no copies of these RNAs were found elsewhere in the cell, and their sequences were not seen in any genome database.
Relatively little is known about the inner workings of centrosomes even after a century of study, and the investigators suggest their discovery could explain centrosome evolution and function. One device consists of layers of gallium arsenide and aluminum arsenide that emit and partially trap sound vibrations in the solid phonons oscillating in the terahertz range. Physicists describe this so-called saser, for sound laser, in the June 2 Physical Review Letters.
The system generates multidirectional ultrasound and might aid in studying so-called random lasers that likewise produce scattered, coherent light, co-designer Richard Weaver of the University of Illinois informed the Acoustical Society of America on June 8.
Fig trees may have marked the beginning of agriculture 11, years ago. Now, in a step toward using stem cells in cardiac repair, they have found where they lurk, based on mouse studies: Storms are similar bucket. As they dialed up the speed to a few in principle to a semistationary bucket, spins per second, the vortex adopted a trefoil which may explain structured hurricane shape, then became square, pentagonal and eyes, and the underlying principle might aphexagonal.
The sluggish outer layer of water ply to bathtub drains, too, Bohr says. Water adopts trefoil, square and pentagonal shapes depending on the rotational speed. But much of physics is counterintuitive, as is the case in many other disciplines, and before the rise of modern science we had only our folk intuitions to guide us.
Folk psychology compelled us to search for the homunculus in the brain— a ghost in the machine — a mind somehow disconnected from the brain. Folk economics caused us to disdain excessive wealth, label usury a sin and mistrust the invisible hand of the market. The reason folk science so often gets it wrong is that we evolved in an environment radically different from the one in which we now live.
Our senses are geared for perceiving objects of middling size — between, say, ants and mountains — not bacteria, molecules and atoms on one end of the scale and stars and galaxies on the other end. We live a scant three score and 10 years, far too short a time to witness evolution, continental drift or long-term environmental changes.
Causal inference in folk science is equally untrustworthy. We correctly surmise designed objects, such as stone tools, to be the product of an intelligent designer and thus naturally assume that all functional objects, such as eyes, must have also been intelligently designed.
We lived in small bands of roaming hunter-gatherers that accumulated little wealth and had no experience of free markets and economic growth. Folk science leads us to trust anecdotes as data, such as illnesses being cured by assorted nostrums based solely on single-case examples.
Equally powerful are anecdotes involving preternatural beings, compelling us to make causal inferences linking these nonmaterial entities to all manner of material events, illness being the most personal. Because people often recover from sickness naturally, whatever was done just before recovery receives the credit, prayer being the most common. The April issue of the American Heart Journal published a comprehensive study directed by Harvard Medical School cardiologist Herbert Benson on the effects of intercessory prayer on the health and recovery of patients undergoing coronary bypass surgery.
The 1, patients were divided into three groups, two of which were prayed for by members of three religious congregations. Prayers began the night before the surgery and continued daily for two weeks after. Half the prayer recipients were told that they were being prayed for, whereas the other half were told that they might or might not receive prayers. Case closed. But for us to discriminate true causal inferences from false, real science trumps folk science.
Although the administration of George W. Bush has often stated its commitment to the spread of democracy, partly to combat the risks of terror, it relies excessively on military approaches and threats rather than strategic aid. Consider Liberia, just emerging from a prolonged civil war, and Haiti, which has suffered decades of intense political instability.
Both nations have recently elected new democratic governments, but both face continuing possibilities of internal violence and disorder.
When the public thinks that a newly elected national government will succeed, local leaders throw their support behind it. Individuals and companies become much more likely to pay their taxes, because they assume that the government will have the police power to enforce the tax laws.
A virtuous circle is created. Rising tax revenues strengthen not only the budget but also political authority and enable key investments — in police, teachers, roads, electricity— that promote public order and economic development. When the public believes that a government will fail, the same process runs in reverse. Pessimism splinters political forces. Tax payments and budget revenues wane. The currency weakens. Banks face a withdrawal of deposits and the risk of banking panics.
Disaster feeds more pessimism. By attending to the most urgent needs of these fragile states, U. To an informed and empathetic observer, the necessary actions will usually be clear.
Both Liberia and Haiti lack electricity service, even in their capital cities. Both suffer from pervasive infectious diseases that are controllable but largely uncontrolled. But if each impoverished farm family is given a bag of fertilizer and a tin of high-yield seeds, a good harvest with ample food output can be promoted within a single growing season. Electric power can be restored quickly in key regions. And safe water outlets, including boreholes and protected natural springs, can be constructed by the thousands within a year.
Far too often, however, the U. Rather than giving practical help, the rich countries and international agencies send an endless stream of consultants to design projects that arrive too late, if ever. They ignore emergency appeals for food aid. Pessimism breeds pessimism. Eventually the government falls, and the nascent democracy is often extinguished. By thinking through the underlying ecological challenges facing a country— drought, poor crops, disease, physical isolation— and raising the lot of the average household through quick-disbursing and well-targeted assistance, U.
Like many physicists, Connes hopes that the Higgs particle will show up in detectors. The Higgs is the still missing crowning piece of the so-called Standard Model— the theoretical framework that describes subatomic particles and their interactions. In commutative algebra, the product is independent of the order of the factors: But some operations are noncommutative.
Take, for example, a stunt plane that can aggressively roll rotate over the longitudinal axis and pitch rotate over an axis parallel to the wings. Assume a pilot receives radio instructions to roll over 90 degrees and then to pitch over 90 degrees toward the underside of the plane.
But if the order is inverted, the plane will take a nosedive. Operations with Cartesian coordinates in space are commutative, but rotations over three dimensions are not. Because of the Heisenberg uncertainty principle, one cannot measure both quantities simultaneously. As a consequence, position times momentum does not equal momentum times position.
Hence, the quantum phase space is noncommutative. Moreover, introducing such noncommutativity into an ordinary space — say, by making the x and the y coordinates noncommutative — produces a space that has noncommutative geometry.
Through such analyses, Connes discovered the peculiar properties of his new geometry, properties that corresponded to the principles of quantum theory. On a day plagued by introducing a mathematical technique called renormalization.
Like a caged lion, the year-old Connes walks corresponded to reality. Outside, police sirens scream amid student protes- portunity to explore the space in which physics lives. The linkage gave renormalization a mathematically rigel. The relation between renormalization and noncommutaBut the spacetime used in general relativity, also based on tive geometry serves as a starting point to unite relativity and electrodynamics, was left unchanged.
Connes proposed some- quantum mechanics and thereby fully describe gravity. He has already shown, with physicist Carlo Rovelli is that of spacetime as a noncommutative space that can be of the University of Marseille, that time can emerge naturally viewed as consisting of two layers of a continuum, like the from the noncommutativity of the observable quantities of two sides of a piece of paper.
The space between the two sides gravity. Time can be compared with a property such as temof the paper is an extra discrete noncontinuous , noncom- perature, which needs atoms to exist, Rovelli explains. What about string theory?
The discrete part creates the Higgs, whereas the continuum parts generate the gauge bosons, such as the W and the quantum world? Connes contends that his approach, looking for the mathematics behind the physical phenomena, and Z particles, which mediate the weak force. Connes has become convinced that physics calculations is fundamentally different from that of string theorists.
Although the Standard Model which still is a long way to go to reach the Planck scale, which proved phenomenally successful, it quickly hit an obstacle: That is not quite halfway. Physicists, in- But to Connes, the glass undoubtedly appears half full. Starting around , workers will cultivate expertise technology in the s.
Yet it is maturing rapidly. By , nents into three-dimensional circuits and whole devices. Descriptions of nanotech typically characterclude molecular nanosystems — heterogeneous ize it purely in terms of the minute size of the physnetworks in which molecules and supramolecular structures serve as distinct devices. The proteins ical features with which it is concerned — assemblies between the size of an atom and about molecular inside cells work together this way, but whereas biological diameters.
But at this scale, rearranging the atoms wider range of environments and should be much faster. Comand molecules leads to new properties. Medical applications might be as ambitious as new and the adjustable behavior of collectives. Thus, nanotechnol- types of genetic therapies and antiaging treatments.
Nanotech does, however, , involves the development of passive nanostructures: Helping the public to perceive nanobers in new composites or carbon nanotube wires in ultra- tech soberly in a big picture that retains human values and quality of life will also be essential for this powerful new disminiaturized electronics.
The second stage, which began in , focuses on active cipline to live up to its astonishing potential. New drug-delivery particles Mihail C. Roco is senior adviser for nanotechnology to could release therapeutic molecules in the body only after they the National Science Foundation and a key architect reached their targeted diseased tissues.
Electronic compo- of the National Nanotechnology Initiative. ROCO Rearranging atoms leads to new properties. The craters are named after the Argonauts of Greek mythology: After all, he reasoned, in the entire 20th century, astronomers had come across only a few.
Sheppard more optimistically predicted twice as many, given the increased sensitivity of modern astronomical facilities. Sheppard is now a richer man. Since that night, our team has discovered 62 moons around the giant planets, with more in the pipeline. Other groups have found an additional But even astronomers generally adopt the popular usage.
Adding to the challenge, they are distributed over a much larger region of space. Scanning such a vast area for moons demands the newest, largest digital detectors and the analysis of up to gigabytes of data a night [see box on page 46]. Our own Hawaii Moon Survey focused initially on Jupiter, whose proximity allows us to probe small moons that would be too faint to detect around the other, more distant giant planets.
Their long, looping, slanted orbits indicate that they did not form in situ but instead in paths encircling the sun. In essence, they are asteroids or comets that the planets somehow captured. The moons might have come from the Kuiper belt beyond Neptune or from regions closer in. Their capture may have involved collisions or other interactions in a younger, more densely populated solar system. All four giant planets, irrespective of mass, turn out to have similar irregular moon systems.
The bodies occupy a wide range of sizes, with smaller ones being much more abundant. The orbits of these moons are some of the most complicated in the solar system. Because they roam so far from their host planet, they are tugged by both planetary and solar gravity, and their orbits precess rapidly— that is, the long axis of the ellipse representing the orbit rotates. Odder still, most of the irregulars have retrograde orbits, which means they each trundle around their host planet in a direction opposite to the sense of the rotation of the planet.
In contrast, regular moons have prograde orbits. Regular moons share this motion because, astronomers think, they coalesced from disks around their respective planets. So the contrary behavior of the irregular moons is a sign of a different origin. These bodies are not well explained by standard models, and a wave of fresh theoretical work is under way.
It seems that they are products of a long-gone epoch when the gravitational tug of the newly formed planets scattered — or snatched— small bodies from their original orbits. Studying them promises to illuminate the early stages in the development of the solar system. The full extent of the system of moons around Saturn was barely known until recent years. The satellites fall into two broad categories: Some revolve in the same direction as Saturn rotates red ; others go the opposite way green.
Similar systems surround the other giant planets far left. These diagrams show a sampling of the total number of moons. The otherwise modest effects of solar gravity accumulate over time, destabilizing the orbit; the ellipse elongates to such an extent that the moon either collides with the planet or one of its larger moons or breaks out of the Hill sphere and falls into the gravitational clutches of the w w w.
Prograde orbits are more vulnerable than retrograde ones. If irregular moons were originally equally likely to be either prograde or retrograde, this resonance could explain why most moons are now retrograde. Another resonance, known as the Kozai resonance, couples the tilt and shape of the orbit. Moons that are hauled into inclined orbits wind up on highly stretched ellipses, again leading potentially to their ejection or destruction.
That may be why observers have found no moons with inclinations between 50 and degrees. In short, the irregular moons we see today appear to be the survivors of gravitational interactions that cleared out many of their brethren. Still other features of the orbits require processes beyond those of gravity. If so, many of the irregular moons we see today are the second generation — one step removed from the original population.
Beyond learning something about the orbits of irregular moons, astronomers have made some progress in discerning other properties.
Most of the moons are so faint that they have been able to uncover very little about their composition. Color is a proxy for composition, so this discovery implies a likeness in makeup — further supporting the idea that group members are fragments of a larger, bygone parent body.
The two irregular moons of Neptune seen by the Voyager 2 space probe, Nereid and Triton, also have icy surfaces. The ices hint that these objects formed relatively far from the sun, like comets. The irregular moons of Jupiter are pitchblack and appear to be devoid of ice, probably because they are closer to the sun and too warm for ice to be stable.
Astronomers have proposed three capture mechanisms. For all three, the initial stage is the formation of asteroid-size bodies called planetesimals. Many agglomerate to form the rocky cores of the giant planets. The leftovers are vulnerable to being captured.
Understanding how that happened is not easy. In the complex interplay of solar and planetary gravity, asteroids and comets are routinely pulled into shortlived orbits around the giant planets. Jewitt traces his interest in astronomy to age seven, when he was astonished by a spectacular meteor shower visible against the sodium-lit night skies of industrial north London.
Sheppard, his former graduate student, recently became a Hubble postdoctoral fellow in the department of terrestrial magnetism at the Carnegie Institution of Washington.
Kleyna grew up on a farm in Maine, enjoys incomprehensible art-house cinema and is now a Parrent postdoctoral fellow at the University of Hawaii, where he mainly studies dark matter in dwarf galaxies. The leaves enter the vortex, swirl around for perhaps a few dozen times and then are blown out in an unpredictable way. Had it not met an untimely death, the comet would have been ejected back into heliocentric orbit within a few hundred years.
Astronomers know of several objects that survived temporary capture by Jupiter and returned to orbiting the sun. Planetesimals passing through this atmosphere lose energy to friction and can be captured. Its gravity rapidly strengthens, snatching nearby planetesimals that happen to fall within its expanded gravitational domain, or Hill sphere.
Two planetesimals passing near the planet almost collide. One loses energy and falls into orbit white. The other gains energy and escapes red. But for a body to be permanently captured from heliocentric orbit into a bound, stable orbit around a planet, it must lose some of its initial energy.
Essentially the body has to be slowed down to prevent it from escaping again. Moon capture, then, must have occurred long ago, at a time when the solar system had different properties. In the s theorists proposed three possible mechanisms, all functioning during or soon after the epoch of planet formation. Pollack and Joseph A.
Tauber of Cornell University, w w w. Jupiter and Saturn, quite unlike Earth and other terrestrial planets, are composed primarily of hydrogen and helium.
Most probably, they formed when a core of rock and ice, of roughly 10 Earth-masses, pulled in vast quantities of gas from the primordial disk surrounding the young sun. Before settling into their modern, relatively compact forms, the planets may have passed through a transient, distended phase, during which their atmospheres extended hundreds of times farther than they do now.
In true Goldilocks style, a passing asteroid or comet would have met one of three distinct fates, depending on its size. If it was too small, it burned up in the bloated atmosphere, like a meteor. If it was too large, it plowed through unimpeded and continued in orbit about the sun.
If it was just right, it slowed down and was captured. This process is a natural version of the aerobraking procedure that many planetary probes have used to enter orbit. One problem with the gas-drag model is that it does not explain the presence of irregular satellites around Uranus and Neptune. They are equipped with digital detectors of more than million pixels each.
The central problem is to distinguish objects in the solar system from more distant stars and galaxies. Observers use two methods. We compare three images of the same area, spaced some time apart. During that time, Earth moves partway around the sun, changing our vantage point and causing bodies to appear to shift position; the closer the body, the more it appears to move.
The second method involves a velocity measurement.
In the summed image, background stars appear as streaks and the irregular moons as bright dots. This mechanism of capture was first expounded by Thomas A. Like gas drag, however, this mechanism has trouble accounting for the moons around Uranus and Neptune, neither of which underwent a runaway growth in mass.
Most models indicate that these planets grew slowly by accumulating asteroid- and comet-size bodies, perhaps taking tens or hundreds of millions of years to reach their presentday masses. The other objects here are background stars. Thought to be about two kilometers across, the moon has an orbit that stretches 31 million kilometers away from the giant planet.
An alternative model for forming Uranus and Neptune, proposed by Alan Boss of the Carnegie Institution of Washington, is that they started out as massive as Jupiter and Saturn and were whittled down by ionizing radiation from nearby massive stars.
The irregular moons are even harder to understand in this model, because a shrinking planet would tend to lose moons rather than grabbing them. In both the gas-drag and pull-down models, the irregular moons were acquired early in solar system history, probably before Earth had reached a recognizable state. Because of their greater distance from the sun and the consequently lower density of material in the outer regions of the circumsolar disk, their cores took a longer time to reach the critical mass needed to precipitate gaseous collapse.
Before that happened, the solar nebula had largely dissipated, and so Uranus and Neptune never had extended atmospheres, like those of Jupiter and Saturn. How can gas drag operate when there is not much gas? They suggested that collisions between two bodies in the Hill sphere of a planet could dissipate enough energy to allow one of them to be captured.
This idea, called three-body capture, received relatively little attention in the 35 intervening years, perhaps because such collisions are exceedingly rare now.
Yet newer work shows that no collision is needed. The three bodies need only interact gravitationally. If they exchange energy, one can gain energy at the expense of the others. The process is a scaled-up version of the gravitational slingshot effect that space mission planners use to boost deep space probes. This past May, Craig Agnor of the University of California, Santa Cruz, and Doug Hamilton of the University of Maryland suggested another form of three-body capture in which a binary object is sheared apart by the gravity of a planet, leading one component to be ejected and the other pulled into orbit.
The process works for both gas giants and ice giants. These types of interactions would have been most probable near the end of the planet formation epoch, after the Hill spheres had grown to their present proportions but before the leftover debris of planet formation had been cleared out. Threebody capture might be able to account for why each planet has roughly the same number of irregular moons: Even if three-body interactions explain how the irregular moons were captured, where did they come from to begin with?
Researchers have suggested two distinct possibilities. The moons could be asteroids and comets that had w w w. Most of their cohorts were incorporated into the bodies of the planets or catapulted out of the solar system. Another possibility emerges from a recent model in which the solar system remained choked with debris until some million years after the planets formed.
Strong gravitational interactions between Jupiter and Saturn then set up oscillations that shook the entire system. Billions of asteroids and comets were scattered as the major planets lurched into their present, more stable orbits. A tiny fraction of the scattered bodies could have been captured.
In this scenario, proposed last year by K. Luu and David C. Spectral measurements should one day be able to test these two hypotheses. If they have similar compositions, that would argue for the second hypothesis, in which the moons all formed together and then dispersed. Recent work suggests that it and a partner orbited the sun in mutual embrace, until Neptune sundered them and claimed Triton as its own.
Exploration of the irregular moon systems is ongoing. Two things are already evident: The modern solar system simply offers no suitable mechanism through which moons could be captured.
Second, the similarities among the irregular moon populations of all four outer planets suggest that they arose by three-body interactions, the only known mechanism that is about as effective for Neptune as it is for Jupiter. Like skid marks on a road after a car crash, the irregular moons swooping around the giant planets provide us with tantalizing clues about past events that we could never have witnessed directly.
Kavelaars et al. Discovery of Five Irregular Moons of Neptune. Matthew J. Holman et al. Photometry of Irregular Satellites of Uranus and Neptune. Tommy Grav, Matthew J. Holman and Wesley C. Fraser in Astrophysical Journal, Vol. Available online at arxiv. Cassini Imaging Science: Initial Results on Phoebe and Iapetus.
Porco et al. Craig B. Agnor and Douglas P. Hamilton in Nature, Vol. Hawaii Irregular Satellite Survey Web site: AUGUS T Disabled genes, molecular relics scattered across the human genomic landscape, have a story of their own to tell. The bones of long-dead genes — known as pseudogenes— litter our chromosomes. It is already clear that a whole genome is less like a static library of information than an active computer operating system for a living thing. As products of the processes by which genomes remodel and update themselves, pseudogenes are providing new insights into those dynamics, as well as hints about their own, possibly ongoing, role in our genome.
If errors in a copy destroy its ability to function as a gene, dogenes during the late s, when however, it becomes a pseudogene instead right. The alignment shown here of incapable of giving rise to a protein. Cellular sequence that looked like a globin gene machinery reads the DNA alphabet of nucleotide a partial sequence for a human gene RPL21 but could not possibly give rise to a proagainst one of its pseudogene copies bases abbreviated A, C, G, T in three-base tein.
Even single-base mutations in codons in pseudogenes. The human genome is made up Nonsynonymous mutation of more than three billion pairs of nucleotides, the building blocks of DNA molecules. Yet less than 2 percent of our genomic DNA directly encodes proteins. With ongoing annotation of the hu- many of them and why, if they are really Perhaps a third is noncoding sequences man genome sequence, our research useless, they have been retained in our within genes, called introns.
The re- group, along with others in Europe and genome for so long. A small much of it is effectively genomic dark discovered. Humans have only an esti- fraction of pseudogenes are believed to matter whose function is still largely a mated 21, protein-coding genes, so have once been functional genes that mystery. But most randomly scattered like rusted car parts parts. Their sheer prevalence has raised pseudogenes are disabled duplicates of on the landscape — and in surprising many questions, including how they working genes.
They may have been came into existence, why there are so dead on arrival, having suffered lethal numbers.
Normally, the mRNA is destined for translation into a protein — but sometimes it can instead be reverse-transcribed back into DNA form and inserted in the genome.
A splicing process next cuts introns out of the raw transcript and joins exonic sequences to produce an edited messenger RNA mRNA version of the gene. Pseudogenes can be born in two ways, each of which yields a distinctive facsimile of the original parent gene. Just before dividing, a cell duplicates its entire genome, and during that process, an extra copy of a gene can be inserted into the chromosomes in a new location. Alternatively, a new version of a gene can also be created through reverse transcription: Known as retrotransposition, this phenomenon can occur because of the activity of another type of transposable genetic actor, known as a long interspersed nuclear element, or LINE, that behaves like a genomic virus.
These two processes, duplication and retrotransposition, are major forces that remodel genomes over the course of evolutionary time, generating new variation in organisms. They are the means by which genomes grow and diversify, because many replicated genes remain active. But if the gene copy contains disabling typos or is missing pieces of the original, such as the promoter, it will become a pseudogene.
Pseudo genes made from mRNA lack introns and are described as processed pseudogenes. Although the overall distribution of most pseudogenes across human chromosomes seems completely random, certain kinds of genes are more likely to give rise to pseudogenes.
Geneticists organize functional genes into families based on their similarity to one another in both sequence and purpose. Only about a quarter of these family groups are associated with a pseudogene, and some families have spun off an inordinate number of copies.
In one extreme case, a single ribosomal protein gene known as RPL21 has spawned more than pseudogene copies. Those responsible for basic cellular housekeeping functions, such as the genes in the ribosomal protein family, are abundantly expressed, providing more opportunities to create processed pseudogenes. Because pseudogenes have been accreting this way in our genomes for so long, some are relics of genes eliminated during the course of evolution, and no functional version exists today.
Consequently, intergenic regions can be seen as vast molecular fossil beds offering a silent record of events in our evolutionary past. Family Histories t h e p r i nc i pl e s of natural selection appear to extend to individual genes, strongly constraining mutations in the sequences of functional genes.
Gulo makes an enzyme that is the last element in a biochemical pathway for synthesizing vitamin C. Most mammals possess the active gene, but the primate lineage seems to have lost it more than 40 million years ago.
When the Gulo gene became a pseudogene, primates became dependent on food sources of vitamin C to avoid scurvy. Scientists can use this tendency to derive a kind of molecular clock from the nucleotide changes in pseudogenes and use it to study the overall dynamics and evolution of the genome.
Tracking the evolutionary path of genes and pseudogenes helps molecular biologists to uncover instances of gene birth and death just as the study of mineral fossils tells paleontologists about the creation and extinction of species. About 8, of our pseudogenes are processed; the rest include duplicated pseudogenes and other nonprocessed subcategories.
RPL21 orange are scattered across the human chromosomal landscape. Overall distribution of pseudogenes in the human genome appears to be completely random, although some local genome regions tend to contain more pseudogenes. Those DNA regions may be analogous to certain geochemical environments that better Differences in pseudogenes offer hints about diverse life histories.
Lancet and his colleagues found in Analysis of the mouse genome, for studies of apes, monkeys and other dis- example, has shown that 99 percent of tant primate cousins that the greatest human genes have a corresponding verloss of olfactory receptor genes — that is, sion in the mouse. Although the human the greatest increase in OR pseudo- and mouse lineages diverged some 75 genes — occurred in ape and monkey lin- million years ago, nearly all of the human eages that evolved the ability to see color genome can be lined up against equivain three wavelengths of visible light.
The lent regions, known as syntenic blocks, link may suggest that a sensory trade-off in the mouse genome. Yet despite this took place over time in the primate lin- similarity in functional genes and overeage when better eyesight made an acute all genome structure, just a small fraction sense of smell less critical.
Using the rate of sequence decay ceptor repertoire. Many dead-on-arrival relative to the parent genes to determine pseudogene copies are an immediate by- their age, it is also clear that many pseuproduct of this process. But the subse- dogenes in the human and mouse gequent death of additional duplicates, nomes have arisen at different times.
Consequently, differences pseudogenes in each of the lineages. The number of pseudogenes in different genomes varies greatly, more so than genes, and it is not readily predictable, because it is neither strictly proportional to the size of a genome nor to the total number of genes.
One of the largest known gene families in mammals, for example, consists of more than 1, different genes encoding olfactory receptors, the cell-surface proteins that confer our sense of smell.
Detailed analyses of olfactory receptor OR genes and pseudogenes by Doron Lancet and Yoav Gilad of the Weizmann Institute of Science in Rehovot, Israel, show that humans have lost a large number of functional olfactory receptor genes during evolution, and we now have fewer than of them in our genome.
For comparison, versions of about human olfactory receptor pseudogenes are still functional genes in the genomes of rats and mice. This difference is not surprising given that most animals depend more for their survival on the sense of smell than humans do. In fact, humans have considerably more olfactory receptor pseudogenes than chimpanzees do, indicating that we lost many of those functional genes after our split from the ape lineage. Zheng, after completing his Ph.
But Gerstein and Zheng were intrigued by the enormous data analysis challenges posed by the sequencing of the human genome and chose to start scanning and sifting the regions of DNA between genes. These disablements cannot be tolerated by true genes and are thus typical manifestations of pseudogenes. More subtly, the theory of neutral evolution introduced by mathematical biologist Motoo Kimura in the s holds that nonfunctional DNA sequences can change freely, without the constraint of natural selection.
Thus, individual nucleotide mutations can be divided into two types: Large-scale pseudogenization is most often seen among genes that, like the olfactory receptor family, are responsible for responses to the environment. Such pseudogenes may therefore be under evolutionary constraint, which implies that they might have some function after all.
One way to try to ascertain whether pseudogenes are functioning is to see whether they are transcribed into RNA. In their studies, in fact, more than half the heavily transcribed sequences map to regions outside of known genes. What is more, a number of those transcriptionally active intergenic areas overlap with pseudogenes, suggesting that some pseudogenes may have life left in them. Our research group is part of a consortium of laboratories working to understand what is going on in the dark matter of the genome.
Previous studies as well as preliminary ENCODE data indicate that at least one tenth of the pseudogenes in the human genome are transcriptionally active. Knowing that so many pseudogenes are transcribed does not tell us their function, but together with evidence that certain pseudogenes are better preserved than background intergenic sequences, it certainly challenges the classical view of pseudogenes as dead.
One possibility is that pseudogenes play some ongoing part in regulating the activity of functional genes. Early efforts to catalogue pseudogenes were largely driven by the need to distinguish them from true genes when annotating genome sequences. Identifying pseudogenes is not as straightforward as recognizing genes, however. Based on characteristic elements, pattern-seeking computer algorithms can scan DNA sequences and identify genes with moderate success. Recognition of pseudogenes, in contrast, relies primarily on their similarity to genes and their lack of function.
Computers can detect similarity by exhaustively aligning chunks of intergenic DNA against all possible parent genes. Just as a living organism can die of many different causes, a variety of deleterious mutations affecting any step in the process of making a protein can disable a copied gene, turning it into a pseudogene. And at least two examples of pseudogenes behaving in a similar manner have been documented so far. The investigators found that in the neurons of a common pond snail, both the gene for nitric oxide synthase NOS and its related pseudogene are transcribed into RNA but that the RNA transcript of the NOS pseudogene inhibits protein production from the transcript of the normal NOS gene.
Then, in , Shinji Hirotsune of the Saitama Medical School in Japan traced deformities in a group of experimental baby mice to the alteration of a pseudogene. The inactivity of an important regulatory gene called Makorin1 had derailed the development of the mice, but Hirotsune had not done anything to Makorin1.
He had accidentally disrupted the Makorin1 pseudogene, which affected the function of its counterpart, the Makorin1 gene. Because many pseudogenes have sequences highly similar to those of their parent genes, it is very tempting to speculate that the NOS and Makorin1 pseudogenes are not just isolated cases.
Instead their activity may be the result of selection w w w. Protogenes a n e xc i t i ng e r a of molecular paleontology is just beginning. Current techniques rely heavily on sequence comparison to wellcharacterized genes, and although they can readily identify recently generated pseudogenes, very ancient and decayed sequences are probably escaping detection.
Recent hints that not all pseudogenes are entirely dead have been intriguing, and some evidence also exists for the possibility of pseudogene resurrection— a dead gene turning back into a living one that makes a functional protein product.
Careful sequence comparisons have shown that one cow gene for a ri- bonuclease enzyme was a pseudogene for much of its history but appears to have been reactivated during recent evolutionary time. Slight differences in the pseudogene complements of individual people have also been found— for example, a few olfactory receptor pseudogenes straddle the fence: These anomalies could arise if random mutation reversed the disablement that originally produced the pseudogene.
Our studies have suggested, however, that in yeast, certain cell-surface protein pseudogenes are reactivated when the organism is challenged by a stressful new environment. Thus, pseudogenes may be considered not only as dead genes which nonetheless provide fascinating new insights into our past but also as potentially unborn genes: Yoav Gilad et al.
Evgeniy S. Balakirev and Francisco J. Ayala in Annual Review of Genetics, Vol. But one thing has stood in their way: In even the most advanced launch system in use today, the space shuttle, about half the launch weight is the liquid oxygen and solid oxidizer it must lug aloft to keep its rocket fuel burning all the way to orbit. One answer could come from a supersonic combustion ramjet, known as a scramjet, which would scoop oxygen from the atmosphere as it ascends.
At last, after decades of intermittent development, practical scramjets appear poised to take wing. They would be made possible by successful supersonic combustion ramjet— scramjet— engines. Other vigorous development efforts are ongoing by the U. The Road to Flight t h e s c r a m j e t is not a new propulsion concept. In the mids the U. Mach 1 is the speed of sound, or miles per hour at sea level.
Scramjets ingest supersonic air, mix it with fuel, and burn it to create tremendous propulsive thrust. Unlike rockets, they do not need to carry oxygen and oxidizer, saving weight and providing as much as four times the thrust per given weight unit of propellant. Late that year the XA scramjet research vehicle reached a record-setting Mach 9. The ongoing U. Air Force effort is to use next-generation scramjet technology to accelerate a vehicle through a range of velocities and altitudes, fuel the engine with a liquid hydrocarbon and cool the engine structure with that same fuel.
Scramjets are members of a family of so-called air-breathing jet engines that rely on variations of a basic thrust-generating principle to operate at different ranges of speeds and altitudes. In general, jets work by compressing atmospheric air, combining it with fuel, burning the mixture and then expanding the combustion products out the back to provide thrust.
Current turbojet engines can power aircraft to velocities up to a bit more than Mach 3 [see box on opposite page]. At higher speeds, the rotating components suffer damage from overheating. At speeds above approximately Mach 2.
It would take off and accelerate to supersonic speeds using conventional jet engines. Supersonic velocities begin at Mach 1, or miles per hour at sea level. The scramjets would then take over and propel it into the hypersonic regime — Mach 5 to Mach 15 the theoretical limit of scramjet performance. Finally, small rocket engines would accelerate the payload the rest of the way to orbit. By comparison, the fastest air-breathing manned airplane, the now retired U.
In general, each generates propulsive thrust by compressing incoming air, blending it with fuel, burning the mixture and expanding the combustion products out the rear end. Hydrogen fuel Solids: When the exhaust gases reach the nozzle, where the pathway widens, the mass expands and accelerates outward, changing its thermal energy into kinetic energy for thrust. Hydrogen fuel offers better engine performance but presents problems with packaging in a small space and with the existing fuel distribution infrastructure.
Hydrocarbon jet fuels are easier to handle but provide less energy per weight unit. The technology may eventually have nonmilitary applications, potentially aiding in the development of a single-stage orbital space plane inlet, a combustor and a nozzle [see box on preceding page].
The hot exhaust gases again accelerate to around the speed of sound as they pass through a narrow throat, or mechanical choke, and then expand out the conelike nozzle to supersonic velocities. Thus, Mach 5 to Mach 6 is the practical limit of the ramjet. The resulting exhaust gases rocket out of the nozzle the second funnel at a higher speed than that of the inlet air.
The need to get a running start means that a scramjet-powered orbital launch vehicle would have to integrate another propulsion system, such as a rocket or a gas turbine engine, to get it moving. Scramjet researchers know that it is crucial to manage closely the thermal energy in the engine. This cooling technique has been applied successfully to conventional rockets for decades, typically employing liquid hydrogen as the coolant. Using a hydrocarbon fuel in such an environment is more challenging because a thermally stressed hydrocarbon can readily decompose to solid coke, which can plug coolant passages.
Other drawbacks are that active-cooling systems involve additional weight and complexity and that they must stay active, because loss of the fuel coolant will lead to catastrophic structural failure. The need to continuously move very hot interior surfaces of the engine and to seal passages against leakage of high-temperature engine gases remains a barrier to realizing the full potential of the scramjet cycle. One of these achievements is the work of the U. First, the members focused on small, expendable scramjet engines, such as those for a missile.
Jackson received a Ph. His research has focused mainly on combustion and fuel injection technologies in propulsion engines. A father of six, Jackson enjoys playing tennis, renovating old houses and repairing broken toys. Managing the distribution of fuel within the engine is the primary means of controlling the engine — its thrust, rate of acceleration and maintenance of stable operation. Reliably joining these cooled and uncooled parts is challenging but critical.
Clearly, overly rapid structural breakdown before the missile reaches its target would lead to catastrophic failure. Engineers developed a heat-resistant carbon-carbon composite material with tongue-and-groove joints that overcame the problem.
Up to now, hydrogen has been the fuel of choice for most scramjet programs. In contrast to hydrogen, most hydrocarbon fuels are less reactive, contain less energy per unit weight and have lower heat capacity to cool hot structures.
The U. As mentioned earlier, in a fuel-cooled scramjet the fuel serves as the heat sink— the means by which excess heat is managed.
In a thermally balanced system the amount of fuel required to absorb excess structural heat should not exceed the quantity of fuel required for combustion. HyTech planners want this balance to occur at Mach 8, and JP-7 has proved well suited to the task. For an air-breathing power plant to compete favorably in effectiveness with a rocket-powered launch vehicle, performance studies indicate that it must be able to operate well at about half its maximum speed.
By the HyTech team developed engine components and integrated engine subsystems that met or exceeded most of the original program goals. That is why the U. When such fuels take in heat from their surroundings in the absence of oxygen and in the presence of an appropriate catalyst, their long, complex polymeric chains decompose into short, simple ones.
What is more, after endothermic heating the fuel becomes a hot gas that contains as much as 10 percent more energy than the chemical energy of the unheated liquid fuel. Finally, the resulting low-molecular-weight hydrocarbons are more reactive than their parent fuel molecules, making them numbers lower than 4. Though not part of the SED effort, U. Also in hand are active cooling and temperature-resistant structural technologies that enable the engine to maintain thermal balance as long as fuel remains onboard.
Scramjets must be able to function reliably over a wide range of Mach numbers. In some applications the scramjet will have to be fully integrated with a lower-speed cycle such as the gas turbine. Variable internal engine geometry will be required to allow a scramjet to run at Mach w w w.
This capability has, however, been demonstrated in component tests conducted within the HyTech research effort. At the high-speed end of the envelope, the heat capacity of aviation jet fuels, even those that can decompose endothermically like JP-7, will be found lacking as speeds approach Mach 8.
Flying faster will require dramatically different fuels and advanced heat-resistant materials or perhaps the use of hydrogen, despite its attendant logistics and vehicle-packaging challenges. For applications such as sustained hypersonic cruise and space access, much larger vehicles will be required. With continued progress, we hope to continue to inch, if not stride, toward something resembling a Star Wars X-wing engine in the not too distant future.
Edited by Gordon L. Waltrup, F. Billig and R. Stockbridge in Journal of Spacecraft and Rockets, Vol. Research on Supersonic Combustion. Billig in Journal of Propulsion and Power, Vol. Hypersonic Airbreathing Propulsion. William H. Heiser, David T. Pratt, Daniel H. Daley and Unmeel B. Riggins, C.
McClinton, R. Rogers and R. Bittner in Journal of Propulsion and Power, Vol. New research has indicated that motivation is a more important factor than innate ability. Ross man walks along the inside of a circle of chess tables, glancing at each for two or three seconds before making his move.
On the outer rim, dozens of amateurs sit pondering their replies until he completes the circuit. The exhibition was part of a tour in which Capablanca won games in a row. How did he play so well, so quickly? And how far ahead could he calculate under such constraints? Just as a master can recall all the moves in a game he has played, so can an accomplished musician often reconstruct the score to a sonata heard just once.
But how do the experts in these various subjects acquire their extraordinary skills? How much can be credited to innate talent and how much to intensive training?
Psychologists have sought answers in studies of chess masters. The collected results of a century of such research have led to new theories explaining how the mind organizes and retrieves information. What is more, this research may have important implications for educators. Perhaps the same techniques used by chess players to hone their skills could be applied in the classroom to teach reading, writing and arithmetic.
The Drosophila of Cognitive Science t h e h i s t ory of human expertise begins with hunting, a skill that was crucial to the survival of our early ancestors. The mature hunter knows not only where the lion has been; he can also infer where it will go. John Bock, an anthropologist at California State University, Kasparov, the Russian grandmaster who has a rating of , will win 75 percent of his games against the th-ranked Fullerton. It takes less time to train a brain surgeon. Without a demonstrably immense superiority in skill over grandmaster, Jan Timman of the Netherlands, who has a ratthe novice, there can be no true experts, only laypeople with ing of Similarly, a U.
Such, alas, are all too common. Rigor- about the median will win 75 percent of the time against ous studies in the past two decades have shown that profes- someone rated about the 40th percentile. Another reason why cognitive scientists chose chess as their pists help patients no more than colleagues with less advanced degrees. Skill at chess, however, can be measured, broken into components, subjected to laboratory experiments and readily observed in its natural environment, the tournament hall.
The measurement of chess skill has been taken further than similar attempts with any other game, sport or competitive activity. The results are ratings that predict the outcomes of games with remarkable reliability.