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Science  13 Jul 2007:
Vol. 317, Issue 5835, pp. 178

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    Enormous Detector Forces Rethink Of Highest Energy Cosmic Rays

    1. Adrian Cho

    MERIDA, MEXICO—When, a decade ago, physicists in Japan reported seeing far more ultrahigh-energy cosmic rays than expected, some theorists interpreted the excess as a hint of exotic new particles—perhaps supermassive relics from the big bang that could be part of the mysterious dark matter whose gravity holds the galaxies together. But the controversial excess of super-energetic particles from space has a simpler explanation, researchers with a far larger detector array now say: It doesn't exist.

    That conclusion, reported here* last week, may be the most important early result from the Pierre Auger Observatory, which sprawls across the Pampa Amarilla in western Argentina. It's also a disappointment for researchers in the field of ultrahigh-energy cosmic rays. “It is less sexy than before, that's for sure,” says Yoshiyuki Takahashi of the University of Alabama, Huntsville.

    Still, plenty of mystery remains. Auger and other arrays do see some cosmic rays with the energy of a large hailstone, and physicists still can't say how or where in the heavens a single subatomic particle might gain such energy. But now that researchers see that the number of cosmic rays dives as expected at very high energies, explanations will likely turn from exotic particles to the astrophysics of stars and galaxies.

    The purported excess sparked controversy years ago (Science, 21 June 2002, p. 2134). From 1990 to 2004, physicists with the Akeno Giant Air Shower Array (AGASA) west of Tokyo spotted roughly a dozen particles crashing to earth at energies of 100 exa-electron volts (EeV), about 100 million times higher than any particle accelerator has achieved. Physicists believe cosmic rays gain energy as they swirl in magnetic fields, and they couldn't think of any object in space both big enough and wielding a strong enough magnetic field to contain particles until they reach such staggering energies. So some speculated that the rays blast out of the decays of supermassive particles.

    Four eyes.

    All four of Auger's fluorescence detectors spotted this high-energy cosmic ray. The gigantic array sees no excess of highest energy rays.


    The excess also clashed with an energy limit predicted in the 1960s. If each ray is a proton, then at energies above about 40 EeV it should interact with the photons in the after-glow of the big bang, the cosmic microwave background, in a way that saps its energy to 40 EeV within a distance of 300 million light years. If AGASA was seeing rays with energies above this “GZK cutoff,” then they had to originate in the cosmic neighborhood.

    Moreover, another group saw no excess. Whereas AGASA researchers detected 11 rays with energies greater than 100 EeV, physicists with the High-Resolution Fly's Eye (Hi-Res) detector at the U.S. Army's Dugway Proving Ground in Utah saw only a couple. The two detectors are very different, however. When a high-energy cosmic ray strikes the atmosphere, it triggers a cascade of billions of particles called an extensive air shower. AGASA used 111 detectors spread over 100 square kilometers of ground to measure the showers. In contrast, Hi-Res used twin batteries of specialized telescopes to detect the light produced when the shower causes nitrogen molecules in the air to fluoresce.

    The Auger array uses both techniques. Covering 3000 square kilometers and comprising more than 1300 surface detectors and 24 fluorescence telescopes in four batteries, the almost-completed array has already collected enough data to rule out the excess. “If AGASA had been correct, then we should have seen 30 events [at or above 100 EeV], and we see two,” says Alan Watson of the University of Leeds, U.K., who is the spokesperson for the Auger collaboration. The Auger data also show that very few of the most energetic rays are photons. As supermassive particles ought to decay readily into photons, that finding undermines exotic-particle musings, says Glennys Farrar, a theorist at New York University who joined the 300-member Auger collaboration in September.

    Meanwhile, researchers working with Hi-Res, which stopped taking data last year, say the shape of their final spectrum of cosmic ray energies definitely proves the rays are running up against the GZK cutoff. “It looks very much like what everyone has been predicting,” says Pierre Sokolsky of the University of Utah in Salt Lake City. “It's the classic GZK signature.” Others aren't so sure. Auger's data suggests the highest energy rays comprise protons and heavier nuclei, which don't feel the GZK drag, Watson says. Instead of being slowed, the nuclei may never be accelerated to 40 EeV, he says.

    Whatever its cause, the fall-off leads some to question the need to build a bigger array, as the Auger team hopes to do in the Northern Hemisphere. “Once you see the cutoff—even if you disagree about what it is—then building a bigger detector hardly gets you anything,” because there are so few higher energy particles to capture, says Gordon Thomson, a Hi-Res member from Rutgers University in Piscataway, New Jersey. Members of the Hi-Res and AGASA teams are building a detector in Utah called the Telescope Array, which will be three-eighths the size of Auger. That may be just the right size, Thomson says.

    Others say that only a bigger array can amass enough data to trace the fall-off in detail. “Now we understand that above the GZK cutoff there are ten times less cosmic rays than we thought 10 years ago, so we may need a detector ten times as big as Auger,” says Masahiro Teshima of the Max Planck Institute for Physics in Munich, Germany, who worked on AGASA and is working on the Telescope Array.

    The few highest energy, straightest flying particles will be crucial for determining whether high-energy cosmic rays emanate from particular points or patches in the sky, says James Cronin of the University of Chicago, Illinois, who, with Watson, dreamed up the Auger array in the early 1990s. Such “anisotropy” might reveal the rays' origins, and “if we can show an anisotropy, then that's a brilliant breakthrough,” he says. Mapping the sky could take a decade—although Cronin and Watson hint they may have already seen something exciting that's not yet ready for release.

    • *30th International Cosmic Ray Conference, 3-11 July

  2. HIV/AIDS: India Slashes Estimate of HIV-Infected People

    1. Jon Cohen

    Contrary to previous estimates, India does not have more HIV-infected people than any country in the world, says a new analysis by government health officials. Improved and widened surveys of the country's massive population has led India's National AIDS Control Organization (NACO) to slash by more than half the estimated number of people infected, from 5.7 million to 2.5 million. NACO, which announced the new figures on 6 July, says HIV thus infects 0.36% of the country's adults, rather than 0.9%. “The figures are now much more realistic,” says N. K. Ganguly, the head of the Indian Council of Medical Research in New Delhi who chaired a meeting that reviewed the new NACO numbers. Ganguly, who long worried that epidemiologists had exaggerated the scale of India's epidemic, adds that he was “very happy” that a look back analysis also found that HIV was not gaining ground in this huge country.

    The Joint United Nations Programme on HIV/AIDS (UNAIDS), which advised NACO and earlier issued the higher estimate, supports the new figures. “We're much more confident that the estimates being put out are as accurate as they can be,” says epidemiologist Peter Ghys, who heads the UNAIDS branch that produces the oft-cited estimates for most countries.

    In the past, India's HIV estimates have relied heavily on a limited number of “sentinel” surveillance sites, like clinics for pregnant women. But such analyses capture more data from urban than rural areas and miss many high-risk groups such as injecting drug users or men who have sex with men. The new analysis includes data from 400 new sentinel sites added since 2006—there were just 764 in 2005—as well as voluntary blood samples taken from more than 100,000 people in a national household survey.

    View this table:

    Much wider sampling, including a national household survey that goes well beyond the “sentinel” surveillance sites, like the clinic above in Kolkata, has led to new, lower estimates of size of the AIDS epidemic in India.

    NACO's estimates of HIV-infected people still are far from exact, ranging from 2 million to 3.1 million. But that's more certainty than portrayed by UNAIDS in 2006, which estimated India's HIV-infected population at 3.4 million to 9.4 million. The range is “some indication that at the time we were not as confident as we are today about the estimates,” says UNAIDS's Ghys.

    The lowered estimates and the reanalysis of data back to 2002 indicate that the country has had a stable epidemic with a “marginal decline” last year, NACO says. This challenges the idea that India is on an “African trajectory”—with the virus moving from concentrated risk groups such as sex workers and truck drivers to the general population—a controversial assertion made by epidemiologist Richard Feachem, former head of the Global Fund to Fight AIDS, Tuberculosis and Malaria (Science, 23 April 2004, p. 504). India expert and epidemiologist Robert Bollinger of Johns Hopkins University in Baltimore, Maryland, co-authored a 9 October 2004 Lancet article with Indian colleagues that explicitly criticized Feachem's prediction. “Frankly, I wouldn't be surprised if there were 6.1 million or 5 million or 2.5 million infected people, but the point is the epidemic is different in India,” says Bollinger. A key distinction, he says, is outside of commercial sex workers, Indian women rarely have more than one sexual partner at the same time, a major driver of epidemics.

    Suniti Solomon, who runs a private clinic in Chennai, YRG Care, stresses that India still faces a formidable challenge. “Whatever the numbers, if we are complacent … the virus will spread faster,” says Solomon. And she says many infected people still do not have access to anti-HIV drugs. The country is also seeing “worrying” rates of people who fail to respond to treatment and need more expensive second-line drugs, she says.

    According to an April report issued by UNAIDS, the World Health Organization, and UNICEF, India had just over 55,000 people receiving anti-HIV drugs as of November 2006. The report, which relied on the old calculations of HIV prevalence, estimated that the number of people in need of immediate treatment ranged from 627,000 to 1.6 million. The new numbers mean “fewer people need treatment today and will need treatment in the future,” says Ghys. Yet he, too, cautions that this doesn't suddenly make scaling up treatment simple.

    UNAIDS's latest figures estimate that 39.5 million people worldwide are infected with HIV, which the revised Indian numbers would lower to 36.3 million. South Africa now has the unfortunate distinction of having more HIV-infected people—5.5 million as of 2005—than any country in the world.


    Science Wins Communication Award


    Science and Nature have jointly been named recipients of the prestigious 2007 Prince of Asturias Award for Communication and Humanities.

    The award is made annually by Spain's Prince of Asturias Foundation, formed in 1980 under the presidency of His Royal Highness Prince Felipe de Borbón, heir to the throne of Spain. The foundation honors accomplishments by individuals, groups, or organizations in eight categories: communication and humanities, social sciences, arts, letters, scientific and technical research, international cooperation, concord, and sports.

    In a statement, the foundation noted: “Some of the most important and innovative work of the last 150 years has appeared on the pages of Science and Nature, thus contributing to the birth and development of many disciplines, including Electromagnetism, Relativity, Quantum Theory, Genetics, Biochemistry and Astronomy. … In 2001, the international community learned of the description of the human genome from the pages of both publications.”

    This year's awardees in other categories are former Vice President Al Gore (international cooperation), Bob Dylan (arts), developmental geneticists Ginés Morata of the Spanish National Research Council and Peter Lawrence of Cambridge University in the United Kingdom (scientific and technical research), and Hebrew writer and professor Amos Oz of the Ben-Gurion University in Israel (letters). Awards for social sciences, sports, and concord have not yet been announced.

    “We are delighted and deeply honored that our journal's contributions to public discourse on science and technology have been recognized by Spain's Crown Prince Foundation,” said Science's Editor-in-Chief Donald Kennedy.

    The awards will be presented at a ceremony in Oviedo, Spain, in October.


    Record U.S. Warmth of 2006 Was Part Natural, Part Greenhouse

    1. Richard A. Kerr

    Too many voracious pine bark beetles are surviving milder western winters.


    Climate scientists usually hesitate to point to a single climate extreme and say, “That's the greenhouse at work.” Climate naturally swings to and fro so much that it can be tough to pick out the influence of the strengthening greenhouse on a hurricane season, say, or on one country's climate over the course of a year.

    But four National Oceanic and Atmospheric Administration (NOAA) climate scientists report in a paper in press at Geophysical Research Letters that the greenhouse was behind more than half of last year's record-breaking warmth across the contiguous United States. By their reckoning, global warming in 2006 was aggravating all manner of U.S. extremes: severe droughts, the rising cost of air conditioning, the cold-sensitive pine bark beetle ravaging once-cool western forests, and maybe even some midwinter daffodils.

    Last January, NOAA announced that 2006 was the warmest year for the lower 48 states since record-keeping began in 1895; temperatures even eclipsed the El Niño-fueled record of 1998. According to a NOAA press release, El Niño was contributing to 2006's unusual warmth, and the strengthening greenhouse was probably involved too. But NOAA couldn't say which climate phenomenon was more important in setting the new record.

    So climate dynamicists Mart in Hoerling, Jon Eischeid, Xiao-Wei Quan, and TaiYi Xu of NOAA's Earth System Research Laboratory in Boulder, Colorado, decided to find out what was behind the record. First, to gauge the influence of last year's El Niño, they checked on what 10 actual El Niño warmings of the tropical Pacific had done to U.S. temperatures. They found a slight overall cooling, not a warming, concentrated in the northern states. Then, in two climate models, they simulated the effect of a warmer tropical Pacific on U.S. temperatures. Again, they found a slight cooling. That “leads us to conclude that it was very unlikely that El Niño either caused or materially contributed to the record 2006 warmth,” they write.

    Next, the NOAA group checked on what greenhouse gases might have contributed. Because they had no prior examples of the recent run-up in greenhouse gases, the researchers were limited to analyzing simulations. They looked at 18 models that included greenhouse gases rising since the late 19th century to the present. Averaged over the models, the simulated greenhouse warming spanned the entire contiguous United States—much like the 2006 warmth, when every one of the lower 48 states was warmer than normal. The model average in 2006 accounted for “more than half of the observed warmth,” the researchers report. “The record 2006 warmth was primarily due to human influences.”


    All 48 of the contiguous states shared in the greenhouse-fueled warmth of 2006.

    “I could come up with a slightly different conclusion,” says meteorologist David Karoly of the University of Melbourne, Australia. Rather than blame half of the record warmth on the greenhouse, he would say that the new results show that added greenhouse gases have considerably upped the chances of a year like 2006. He agrees, however, that greenhouse gases made “a substantial contribution to the warmth of 2006.”

    Whatever the phrasing, the same greenhouse contribution is at work over the United States this year as last. But what are the chances that the natural jostling of the climate system will bring enough extra warmth to the year to set back-to-back records? It's possible, the NOAA group calculates, but not likely: The odds are only 16%. Still, the past spring was the fifth warmest on record for the contiguous United States. The heat is on again?


    Canadian Study Reveals New Class of Potential POPs

    1. Jocelyn Kaiser

    Dioxin, PCBs, the pesticide DDT—these pollutants are considered among the most dangerous on the planet because they don't break down easily, are highly toxic, and build up in the food chain. Because these chemicals stay put in our body fat, even tiny amounts in food can add up over time and contribute to health problems such as cancer. So worrisome are the risks that more than 140 countries have endorsed a 2001 international treaty that aims to banish a dozen of these substances from the environment.

    Now on p. 236, a Canadian team reports that efforts to crack down on persistent organic pollutants, or POPs, may have missed an entire set of them. The problem is that risk assessment experts now finger potential POPs based on whether they build up in fish food webs. That assumption, the authors argue, based on modeling and field data, could be missing chemicals that fish remove from their bodies but that become concentrated in the tissues of mammals and birds, which have a different respiratory physiology.

    One-third of the 12,000 or so organic chemicals on the market in Canada fit this new category, say the study's authors at Simon Fraser University in Burnaby, British Columbia. This study did not examine whether these chemicals are actually harming wildlife and people, they and others are quick to point out. Still, the work “is really raising a red flag and saying we've got to pay attention to this,” says ecotoxicologist Lawrence Burkhard of the U.S. Environmental Protection Agency in Duluth, Minnesota.

    Biomagnification means that the level of a toxin in animals' tissues rises as one moves up the food chain. For instance, as larvae eat algae, fish eat the larvae, and bigger fish eat smaller fish, the toxin present in the algae becomes increasingly concentrated; top predators like swordfish and polar bears end up with the highest doses in their tissues. This can happen with stable, fatsoluble chemicals that aren't easily excreted in urine or feces. Biomagnification was first studied in the late 1960s in aquatic food webs, explains Frank Gobas, professor at Simon Fraser University and leader of the study. To screen chemicals, scientists began using a property known as Kow, which indicates how readily a chemical dissolves in water compared with fat and thus predicts how easily it will move from a fish's blood lipids into water through its gills. Low-Kow, or more watersoluble, chemicals don't build up in the fish food chain and were assumed to be safe.

    Toxic web.

    This wolf devouring a caribou carcass may be ingesting toxic organic chemicals that the caribou picked up from eating lichen.


    Environmental chemists realized, however, that this assumption might not hold in food chains involving mammals and birds because their lungs are in contact with air, not water. This means that many chemicals that are relatively soluble in water and therefore don't accumulate in fish might remain in the tissues of land animals if they aren't volatile enough to easily move from the lungs into the air (predicted by a property called Koa). Supporting this idea, some organic chemicals that don't biomagnify in fish appeared to be doing so in other wildlife and humans.

    To explore this hypothesis, Gobas and graduate student Barry Kelly and colleagues collected plant and animal tissue samples—from lichens to beluga whales killed in Inuit hunts—in the Arctic, where, because of weather patterns and cold temperatures, organic pollutant levels are high. They tested the samples not only for known POPs but also for several chemicals with a low Kow but high Koa, which suggested they might biomagnify in air-breathing animals.

    The measured levels of contaminants for various animals in aquatic and land food webs were similar to those predicted from a bioaccumulation model incorporating Koa and Kow, suggesting the model was correct. Chemicals with low Kow and high Koa stood out as potentially risky. Several of the contaminants studied, such as the insecticide lindane, have been proposed for the POPs treaty already. But many others with similar properties have not been scrutinized, Gobas says. The bottom line: “We're missing a lot of chemicals” that may be building up in the food web, Gobas says.

    Canada and countries in Europe that are working through lists of industrial chemicals to identify new potential POPs will now need to revise their approach, says chemist Derek Muir of Environment Canada. He adds, however, that the model has limitations. For one thing, it assumes the chemicals aren't metabolized; many of them probably are, which may convert them to a form that is easily excreted. Procter & Gamble senior scientist Annie Weisbrod agrees: the Koa of chemicals “will matter in some cases,” she says, “but the number of chemicals [that bioaccumulate] will not be a third of those in commerce.”


    Making Dirty Coal Plants Cleaner

    1. Eli Kintisch

    A daunting task awaits the utility industry as it scrambles to catch the carbon spewing from today's generation of plants

    Burning issue.

    Coal's role in the future of U.S. energy production is growing despite its sizable contribution to global warming.


    PITTSBURGH, PENNSYLVANIA—American Electric Power (AEP), the biggest user of coal in the United States, has long supported research on ways to curb carbon emissions from its 26 generating plants. But this spring, Michael Morris, its CEO, surprised an audience of fossil fuel scientists, engineers, and business executives gathered here when he pronounced that techniques to extract carbon from flue gases could be developed soon—if consumers are willing to pay for them. “If we want cleaner air, it's going to cost something,” he declared. The fact that a power industry executive is even talking in these terms is a new departure, says Sarah Forbes of Potomac-Hudson Engineering Inc., a Bethesda, Maryland-based consulting firm. She sees it as a “bold” signal that the Columbus, Ohio-based utility, at least, is getting serious about carbon capture.

    Emissions from the world's 2100 coal-fired power plants are responsible for roughly a third of the CO2 generated by human activity. In the United States, roughly 600 plants produce about 30% of the 7 billion metric tons of greenhouse gases emitted by all U.S. humanmade sources, easily surpassing the amount produced by cars and all other industries combined. Additionally, the share of electricity generated by coal in the United States is expected to climb from 48% today to 55% by 2030. And the United States is not alone. Last year, China, which derives about 80% of its electricity from coal and recently surpassed the United States as the world's biggest CO2 emitter, brought online two major coal plants a week. “If we don't solve the climate problem for coal, we're not going to solve the climate problem,” says Princeton physicist Robert Williams, a coal expert.

    In practice, making coal plants cleaner means removing as much of the CO2 generated from flue gases as possible before they are vented into the atmosphere. One approach popular with industry and the federal government is called the Integrated Gasification Combined Cycle (IGCC), which creates hydrogen to burn and CO2 to be sequestered. (The U.S. Department of Energy [DOE] plans to spend $1 billion for a full-scale public-private plant called FutureGen that's scheduled to open in 2012.) Once extracted, the carbon dioxide would then be stored, most likely underground, at a cost and by an exact method that are still uncertain.

    But only a handful of such plants are running commercially worldwide, and none currently stores the CO2 underground. A second approach, applicable to most existing plants, would remove the CO2 from the flue stream after combustion. The industry standard, in limited use today, employs a molecule called monoethanolamine (MEA), which has been used for decades as a solvent to bind with CO2 and separate it from natural gas.

    Planners have long figured that building new facilities optimized for reduced emissions would be cheaper than retrofitting existing plants, in part because of the large amount of energy needed to extract the CO2. But the retrofit option is becoming more attractive. One reason is the growing support for near-term caps on carbon dioxide emissions (Science, 8 June, p. 1412). The recent U.N. Intergovernmental Panel on Climate Change report on mitigating greenhouse warming puts a premium on early action to curb carbon emissions. That means retrofitting existing plants may be more important than building cleaner ones that won't go on line for 20 years.

    The cost of retrofitting also seems likely to decline as scientists develop new technologies; at the same time, the projected cost of new construction, including IGCC plants, is sharply rising in step with prices for industrial materials like concrete and steel. “It's a big change,” says engineer Jonathan Gibbins of Imperial College, London. “For a long time carbon capture meant [methods like] FutureGen, which was something wonderful that was 15 or 20 years ahead.”

    Taking a sip

    Nestled among the green hills of coal country in Cumberland, Maryland, about 2 km from the Potomac River, the 7-year-old Warrior Run plant burns 652,000 metric tons of coal each year. That makes it one of the newest and smallest facilities operated by its owner, AES corporation. But what also sets it apart is its ability to collect some of the carbon dioxide from the emissions generated in its boiler and sell it commercially to beverage gas distributors. “If you've had a Coke today, you've probably ingested some of our product,” says plant manager Larry Cantrell.

    Cantrell's experience operating Warrior Run gives him some insight into the economics of capturing carbon, and the numbers aren't very encouraging. Warrior Run must generate 202 megawatts (MW) of power to meet its target of selling 180 MW. Roughly 4 MW of the gross total produced goes to provide the energy required for the MEA process to grab CO2, which captures only 5% of the plant's CO2 emissions. Grabbing more would divert much more energy; the cost of removing the carbon dioxide by pipeline, truck, or geological injection would drain profits even further.

    Although current off-the-shelf technologies for carbon capture are improving, they still have a long way to go. A 2001 DOE study of a 433 MW plant in Conesville, Ohio, calculated that adding an MEA unit to capture 96% of its CO2 emissions would cut the plant's net output by about 40%. And using the technology would raise electricity bills by 36% or more, according to a recent Massachusetts Institute of Technology study. Last year, DOE updated its Conesville study and found that the use of improved MEA technology, including more concentrated mixtures, more heat sharing, and larger and more tightly packed columns (see diagram), would allow the plant to capture 90% of CO2 with only a 30% reduction in power output. That's better, but it's still a big hit.

    How a retrofit works.

    (1) Most coal plants burn coal to create steam, running a turbine that produces electricity. After treatment for pollutants, the flue gas, a mixture of CO2 (blue) and other emissions (green), goes out a smokestack. To collect CO2 for storage, however, the mixture of gases is directed to an absorber (2), where a solvent like MEA (pink) bonds with the CO2 molecules. The bonded CO2-solvent complexes are separated in the stripper (3), which requires heat. More energy is needed for the next step (4), which produces a purified CO2 stream for ground storage as well as solvent molecules that can be reused. (Schematic not to scale.)


    Rearranging the inner workings of a plant's heat exchangers and turbines promises to make a bigger difference than simply siphoning steam off for a retrofit bolted onto the plant's edge, says engineer Wolfgang Arlt of Universität Erlangen-Nurnberg, Germany. His recent simulated retrofit with MEA produced a 9% loss in total plant efficiency instead of 11% without the reoptimizing tweaks. “That's a big difference” over years of operation and thousands of plants, says Arlt.

    Some scientists think that alternatives chemically similar to MEA offer greater hope. One uses a cooled stream of ammonium carbonate as the solvent to pull carbon dioxide from flue gas, releasing the gas when boiled. Data from a year-long experiment with chilled ammonia at the bench scale, run by the French energy giant Alstom, suggests that the method needs only 15% as much steam from the plant to capture the same amount of CO2 as an equivalent MEA effort. That's because the solvent grabs CO2 less tightly, requiring less energy to release it.

    Alstom is now building a 30-meter-tall unit to capture 15,000 metric tons of CO2 per year from a Pleasant Prairie, Wisconsin, coal plant operated by We Energies. AEP plans to try the technique at plants in West Virginia and Oklahoma, where engineers hope to use the gas to help extract additional oil from nearby fields. The main goal of the work is to quantify the energy demands, says Alstom's Robert Hilton, but he's also hoping to power the process with heat now wasted instead of precious steam.


    New plants are projected to be built in the U.S. soon, but the current fleet is going nowhere fast.


    A grab bag of approaches

    The reason solvents are needed at all is because CO2 makes up only a small fraction of the flue gas created and emitted by coal plants. Another retrofitting technique involves the seemingly paradoxical goal of producing flue gases that are richer in CO2. The method, called oxy-firing, burns coal in a pure oxygen stream, producing CO2 and little else. After only minor processing, the flue gas can be injected into the ground. Such equipment could be attached to existing boilers “more or less as is,” says University of Utah chemical engineer Eric Eddings.

    Last year, boilermaker Babcock and Wilcox ended a 7-year oxy-firing test in Alliance, Ohio, using a burner only 5% the size of those used in a typical coal plant. Preliminary results suggest that oxy-firing would raise a typical U.S. customer's electric bill by 44%—compared with more than 50% for MEA—without accounting for storage costs. Complicating the equation, says Babcock and Wilcox's Kip Alexander, is that “everyone is trying to get cost estimates on equipment that hasn't been built yet.”

    One drawback to oxy-firing, says University of Texas chemical engineer Gary Rochelle, is the need to make permanent changes to the boiler, the heart of a coal plant. By contrast, treating flue gas gives operators the option of changing the carbon-stripping technique by swapping equipment off the end of the plant. That flexibility could make emissions cuts easier for industry: The Conesville study, for example, suggested that capturing half the carbon emissions from the plant would cost half as much as capturing all of the CO2.

    Keeping options open for relatively new steam-powered plants is a big worry of coal experts, especially for those eyeing the Asian juggernaut. Gibbins hopes to spread the word about technical advances during a visit to China later this year. He plans to encourage Chinese utilities to include particular features—such as space for new equipment and certain steam fittings—on their prodigiously growing coal fleet so that they're ready if researchers, mostly in the West, succeed in making capture cheaper over the next decade.

    Other methods to grab CO2 from flue gas are still at the bench stage. They include giant molecules that can pluck out CO2 with spindly arms called dendrimers, cagelike molecules that capture the CO2, or biological catalysts (see sidebar). The initial barrier for each technology is the high cost of producing the molecules. But the methods also hint at some attractive benefits. One problem with MEA is its volatility, which requires a company to run a chiller plant on site to remove the evaporated solvent from the concentrated CO2. But ionic liquids, a relatively new class of chemicals that are liquid at room temperature, have low volatility, and chemists are finding they might be useful for removing carbon dioxide.

    The search for carbon-clutching tools is attracting researchers from a variety of fields previously unrelated to coal, like nanotechnology. Researchers at the University of Notre Dame, for example, were trying to use ionic liquids to make environmentally friendly solvents for the chemical industry when they discovered that the CO2 involved kept dissolving in the ionic liquid. “We didn't expect the carbon dioxide to be so soluble,” says Notre Dame chemical engineer Edward Maginn.

    Now, DOE is funding basic work with the chemicals for carbon capture, and Maginn's team is examining how to make cheap-to-synthesize solvents that grab CO2 just firmly enough. “It's a very small [but] growing field,” he says. And every little bit helps a community that's trying to tackle a problem from a virtual standing start, says Babcock and Wilcox's Alexander. “We need to demonstrate a lot of things,” he says.


    A Career CO2 Hunter Goes After Big Game

    1. Eli Kintisch

    For 30 years, Michael Trachtenberg, a fast-talking, 66-year-old former neuroscientist, has been working on an enzyme that removes carbon dioxide from various environments. Now, with the coal industry and government finally focusing on reducing greenhouse gas emissions, Trachtenberg is hoping to parlay his expertise and moxie into a commercial success.

    Using your noggin.

    Michael Trachtenberg's technique for carbon capture involves an enzyme found in the human brain.


    Improbably, Trachtenberg began his career as an epilepsy researcher, studying the connection between that disorder and the brain's ability to process carbon dioxide with an enzyme called carbonic anhydrase. While working at the University of Texas Medical Branch in Galveston, he learned that oil companies pump carbon dioxide into depleted wells to extract more crude. In 1991, Trachtenberg formed a company, Carbozyme, with the goal being to use the enzyme to grab carbon dioxide from coal plant emissions and sell it to oil firms. The venture flopped, but by then he was hooked on CO2. Applying his knowledge in work funded by NASA, Trachtenberg next created a device to maintain CO2 and moisture levels inside an astronaut's space suit that was smaller and cheaper than what the space agency was using at the time.

    Now that “everyone and their mother” are suddenly interested in capturing carbon, Trachtenberg predicts an industry consolidation in which “there won't be many of us little guys [left].” But he's hoping Carbozyme, reconstituted in 2003, can hold its own against the likes of Mitsubishi and General Electric. A $7.4 million grant this year from the Department of Energy (DOE)—the biggest award to one team from a $24 million pot—will allow the Monmouth Junction, New Jersey, company and its industry partners to carry out basic and applied research on post-combustion CO2 capture. (Carbozyme's technology uses the enzyme in membranes to catalyze the conversion of CO2 to bicarbonate ions, reversing the process with the same enzyme by altering the pressure.) He says that preliminary results show that his CO2 absorber is dozens of times more cost efficient than the current state-of-the-art technology using a molecule called monoethanolamine.

    Trachtenberg's schedule at a recent carbon capture conference in Pittsburgh, Pennsylvania, showed how far he's come since his days as an academic scientist: In addition to attending presentations, he juggled hushed sit-downs with some of the biggest names in the coal industry. A gregarious self-promoter, he's also learned how to protect his intellectual property. Scrutinizing slides before a public meeting with other DOE grantees, he explains: “I'm making damn sure that there's nothing proprietary in those presentations.”


    Prominent Researchers Join the Attack on Stem Cell Patents

    1. Constance Holden

    James Thomson's work deserves praise but no patents for doing what others could have achieved with the proper resources, critics say


    Some say Thomson (right) didn't invent anything.


    Four prominent stem cell scientists have filed “declarations” in support of a citizens' group that is trying to break the University of Wisconsin's hold on patents for human embryonic stem (ES) cells.

    Joining the fray are Harvard researchers Chad Cowan and Douglas Melton, as well as Alan Trounson of Australia's Monash University. A new statement was also submitted by Jeanne Loring of the Burnham Institute for Medical Research in San Diego, California, who has been advising the Foundation for Taxpayer and Consumer Rights, which filed the initial complaint last July.

    In April, the U.S. Patent and Trademark Office (PTO) issued a preliminary ruling upholding the taxpayer foundation's challenges to three existing patents (Science, 13 April, p. 182) covering primate and human ES cells, which are based on the work of University of Wisconsin, Madison, researcher James Thomson and held by the Wisconsin Alumni Research Foundation (WARF). WARF narrowed its claims in response to the ruling, excluding human ES cells from sources other than fertilized eggs, such as cloning. But WARF is standing pat in face of the latest onslaught. Spokesperson Andrew Cohn says it will have no response to the statements, which contain “nothing new.”

    The scientists' statements reiterate the taxpayer foundation's central arguments: that the feat by Thomson—who announced the first successful cultivation of human ES cells in 1998 (Science, 6 November 1998, p. 1145)—was “obvious” and therefore unpatentable since it was the outcome of using already-known technology.

    The four scientists emphasize that Thomson deserves all the accolades he has received. But they argue that he was just lucky in having access to abundant funding (from Geron Corporation in Menlo Park, California) and fresh frozen human embryos (from Israel). “I believe that had any other stem cell scientist been given the same starting material and financial support, they could have made the same accomplishment,” stated Melton.

    WARF argues that for 2 decades after the discovery of mouse ES cells, people “repeatedly tried and failed” to cultivate sustainable lines from other mammals including sheep, pigs, hamsters, cows, and humans. But none of these efforts was successful until Thomson reported the first monkey ES cell line in 1995. WARF cites Ariff Bongso at the National University of Singapore as a researcher who tried and failed to cultivate human ES cells pre-Thomson. Bongso derived a human cell line in 1994 but was unable to maintain it. WARF also emphasizes that Thomson was the first to report that Leukemia Inhibitory Factor, or LIF, although necessary for cultivating mouse ES cells, is not needed with human cells.

    The challengers counter that “not a single scientist in the field tried and failed to achieve Thomson's accomplishment”—not for lack of know-how but because they did not have the proper resources. They also cite Bongso's work, arguing that with a little more time he would have gotten it right. Trounson says he had “work in progress” cultivating human ES cells at the time Thomson reported his breakthrough (Trounson's work was published in 2000). Melton points out that his team in the past few years has successfully isolated human ES cells “by simply following … methods taught for deriving mouse, rat, pig, and sheep ES cells. We did so without recourse to Dr. Thomson's publications.…”

    Colin Stewart, a stem cell researcher at the Institute of Medical Biology in Singapore, is the only outside expert who has offered a declaration to the PTO in support of WARF's position. Stewart, co-discoverer of the role of LIF in mouse ES cell culture, basically argues that existing methods for cultivating mouse cells did not provide adequate guidance for cultivating human ones. (Stewart was not available for comment.)

    Some lawyers have gone to bat for WARF. In a blog posted on 4 July, Chicago, Illinois, biotech lawyer Kevin Noonan points out it is difficult to maintain that the invention was anticipated by “prior art” given the acknowledged “absence of appropriate starting materials”—human embryos. “The best the art could provide is a suggestion about how human stem cells might be produced,” he writes. Madison, Wisconsin, patent attorney Grady Frenchick is confident the patents will hold up. “Everybody's going to use [Thomson's] method of isolation and cultivation. That's truly the breakthrough,” he says.

    But it is difficult to find a stem cell researcher other than Stewart or Thomson who thinks WARF's patents are justified. “I know of no one other then the folks … associated with WARF and these patents who is in favor of how they are handling this,” says Fred Gage of the Salk Research Institute in San Diego, California.

    Johns Hopkins University stem cell researcher John Gearhart agrees with the challengers. “The procedure James [Thomson] used to generate human ES cells was one that had been basically reported [back in the '80s] for generating mouse ES cells,” says Gearhart. The LIF argument is a red herring, he adds. Even though Thomson found it was not necessary for growing human cells, its presence does not interfere with culturing them.

    Gearhart says he doubts “whether the patent office really understood what was going on” when it issued WARF's patents. “They were not very rigorous.” But with so many eyes now on it, the PTO is presumably giving the issue more than routine scrutiny.


    Exploring the Prehistory of Europe, in a Few Bold Leaps

    1. John Bohannon

    Archaeology's Renaissance man takes a new plunge—into the topic that made him leave a life of literature for a “$10-a-day” life


    NISSI BAY, CYPRUS—For the operator of the bungee jump here at the Olympic Lagoon Resort, it is a strange request. The Cypriot Department of Antiquities wants him to give a ride to a visiting American academic. A tall man in khaki trousers, Albert Ammerman steps over the coiled bungee cord and joins the operator in the metal cage. The crane hoists them 60 meters over the bay—the point at which most passengers are bound at the ankles and dive screaming into the air—and then Ammerman has the crane pivot farther, dangling the cage above the bone-white escarpment flanking the resort. Here Ammerman pulls out a camera and snaps shots of the land below.

    “People came here on boats 12,000 years ago. It's one of the most important archaeological sites on Cyprus,” Ammerman says, surprising the tattooed bungee operator. Most people consider it a waste area, full of jagged rocks that hurt the feet—there have been plans to bulldoze it for a hotel. As the bungee operator swings the cage back over the water, he asks, “Are you sure you wouldn't like to have a go?” Ammerman chuckles, and cocks his head to consider the plunge.

    Ammerman, 64, is no stranger to wild leaps into the unknown. Indeed, they have defined his career. But in spite of changing research areas—and even fields—about once a decade, Ammerman has made important advances again and again. “He is truly a Renaissance man of archaeology,” says Nicola Terrenato, an archaeologist at the University of North Carolina at Chapel Hill. A decade ago, Ammerman all but abandoned the topic that launched his career, the origins of agriculture. But after a chance discovery on Cyprus's shore a few years ago, he has come back with a radical hypothesis—that sea-going people dominated the coasts and islands of the Mediterranean for millennia before farming was established.

    Piccolo è bello

    The first time Ammerman took a leap into the unknown was as an undergraduate at the University of Michigan, Ann Arbor, in 1964, when he turned away from math and physics to literature. As the Vietnam War reached its apex, he put aside dreams of becoming a “rocket scientist” because, he says, he felt it would mean making weapons “in one way or another.” A newly declared English major, he scooped up the university's top prizes for essay writing and for original poetry. By 1966, he was an editor at a New York literary company, producing recordings of readings by famous actors and actresses.

    But in 1967, says Ammerman, “curiosity” drove him to jump again. He moved to England and enrolled in a Ph.D. program at the Institute of Archaeology, now part of University College London. “My friends told me I was crazy to consider being a student,” Ammerman recalls. His employer had just agreed to make him the new editor in chief of their European operation, with “my own London office and two secretaries.” Instead, Ammerman ended up “in Italy, searching for the origins of agriculture, living on $10 a day,” he says. “Those were the great years.”

    In the late 1960s, Ammerman says he and a like-minded group of “young turks” believed in a theory called “indigenism,” which held that crops were domesticated all over Europe by the people living there. The theory was wrong, Ammerman soon realized. But in searching for evidence to support it, he acquired a deep understanding of the continent's prehistoric landscape. According to Andrew Moore, an archaeologist at the Rochester Institute of Technology in New York state, Ammerman had “a knack for finding sites in areas that others had not thought worthy of exploration.”

    Ammerman demonstrated that the earliest signs of agriculture didn't overlap with late hunter-gatherer sites, and this was key evidence for a theory contrary to indigenism—the view that agriculture swept across Europe in a rapid revolution, imported by newcomers. But it would be nearly 2 decades before Moore and others proved definitively that Europe's crop plants were domesticated in the Near East.

    To find evidence of a farmer mass-migration, Ammerman crossed disciplines again. While he was in Italy in the late 1960s, he teamed up with Luca Cavalli-Sforza, a geneticist now at Stanford University in Palo Alto, California, who was studying human migrations. “Theirs was the first collaboration between an archaeologist and a geneticist to put together two totally distinct forms of scientific knowledge,” says Moore. Ammerman mapped out the location of the earliest known appearances of agriculture across Europe, while Cavalli-Sforza analyzed samples of blood from people living in Europe today, gauging genetic differences by comparing mutations in the genes for blood proteins.

    When they compared notes, a striking pattern emerged. Agriculture appeared steadily later the farther west they looked, and the degree of genetic difference between populations also grew steadily greater. “The best explanation for those patterns is that agricultural people moved into Europe from the east, displacing and mixing with hunter-gatherers as they went,” says Ammerman. By correlating geographic and genetic distance, the duo calculated the rate of the spread of agriculture across Europe at roughly 1 kilometer per year. “It created an entirely new field of archaeology,” says Curtis Runnels, an archaeologist at Boston University in Massachusetts.

    Striking similarity.

    Ammerman found stone tools near a rocky outcrop on Cyprus that he says resemble Neolithic tools from the mainland.


    The next leap came in 1985 while Ammerman was holding a temporary position at the University of Parma in Italy. While working on a dig in Rome, Ammerman teamed up with geophysicists to use techniques then foreign to archaeology, such as radar imaging and computer modeling of landscape evolution. In retrospect, says Terrenato, “establishing the solid contours and the geology of a site as it was when human occupation started” is an “obvious first step.” But archaeologists had rarely done so, “in part because of the difficulty of acquiring the necessary data,” he says.

    Ammerman wasn't the only archaeologist exploring these new methods, says John Cherry, an archaeologist at Brown University, “but he was one of the first, and his approach was very creative.”

    The geo-archaeological methods paid off well. From Rome, Ammerman went to ancient Athens and other cities, plying his quantitative methods. In Venice, says Moore, Ammerman produced “spectacular results, pushing back the date of the inception of the city and giving it a new founding history.” This work has also embroiled him in debates over the future of coastal cities in the face of climate change (Science, 25 August 2000, p. 1301).

    But staying out of the mainstream has often required Ammerman to work “as the proverbial army of one,” says Terrenato, stringing together small grants to do field work either alone or in small collaborations. Unlike colleagues at big research universities with troops of graduate students, Ammerman drifted between universities in Italy and settled at a small liberal arts college, Colgate University in Hamilton, New York. But if he has an underdog reputation, Ammerman is sanguine about it. “Piccolo è bello,” he says—small is beautiful.

    Neolithic redux

    In 2004, Ammerman spent a year as a Fulbright senior scholar in Cyprus. He was attracted to an archaeological mystery on the island.

    Ammerman and Cavalli-Sforza's rate of 1 kilometer per year for the spread of agriculture works well on the European mainland, but the picture is confusing along the Mediterranean coast. Cyprus, as the first big island off the Near Eastern coast, partly visible from mountains in Turkey, should have been colonized by farmers relatively early. To get there, however, they would have needed boats to traverse 60 kilometers of open water, and evidence for ancient seafaring in the Mediterranean is scant.

    Within the past decade, Edgar Peltenburg, an archaeologist at the University of Edinburgh, U.K., has pushed the date of Cypriot occupation back to 8200 B.C.E., making it one of the earliest arrivals of agriculture from the Near East. The discovery implies that seafaring technology must have been available by then, says Ammerman, and it also creates a paradox. “In a world of boats, agriculture should have spread far more quickly around the Mediterranean than on the mainland.” But the opposite is true. Traveling west, the next big island, Crete, is only days away by boat, but farmers do not seem to have left their mark there until 7000 B.C.E. The toe of Italy seems to have been foreign to farming until 1000 years after that. “What took them so long?” Ammerman wonders.

    A few months after arriving at Cyprus, Ammerman was strolling along the Aeolianite bluff at Nissi Bay when he saw something that stopped him in his tracks. He picked up a small, chipped stone and turned it over in his hand. It was a tool from before the Neolithic Period. “Then I started seeing them all over the place,” he says. He teamed up with a fellow Fulbright senior scholar on Cyprus, Jay Noller, a geologist at Oregon State University in Corvalis, to map out other Aeolianite outcrops on the island. Sure enough, a similar part of the coast to the west is peppered with stone blades and scrapers typical of the mainland about 12,000 years ago.

    Archaeologists have never noticed these sites, says Ammerman, “because no one would ever think of looking in such a place.” The Aeolianite seems like an unpleasant place to make a living, he says. But after several summers of fieldwork, “I now appreciate that it's awful for agriculturalists but wonderful for hunter-gatherers.” The Aeolianite's natural pits and shelves “are like Paleolithic furniture, perfect if you've got seafood you've captured down at the coast and need a sheltered place to process and cook it.”

    Ammerman believes he's found by far the oldest evidence of seafaring in the Mediterranean, and he thinks it could shed light on the agricultural transition itself. “The mistake that I think we have always made about the Neolithic is to assume that agriculture must have been perceived as a far superior lifestyle and was immediately embraced,” he says. “Agriculture can support far higher population densities,” and that is why the agriculturalists inevitably took over. But the coastal environment is not ideal for agriculture, says Ammerman, adding “I think agriculture didn't spread along the coasts because they were already frequented by a stable culture of voyaging foragers.”

    But Ammerman “desperately needs independent evidence to sustain the early dating of his sites,” says Peltenburg. Ammerman's first shot at that—getting a carbon date on a sample of charcoal from the surface—was disappointing. The sample turned out to be no older than the days of Napoleon. Now he plans to get carbon dates from samples of shells at lower levels.

    Back in the bungee cage, Ammerman decides to skip this plunge. But about his new research direction, he has no hesitation. “Sure, I could be wrong,” he says. “But this sure is fun.” That seems to be the motto of a scientist who has followed the beat of his own drum.


    Autism's Cause May Reside in Abnormalities at the Synapse

    1. Ken Garber

    New genetic evidence is leading researchers to home in on the cleft separating neurons as the site where the disorder may originate

    Environment counts.

    Despite the highly genetic nature of autism, which researchers are now deciphering, specialized school programs help.


    No one knows what causes autism, which in its broad definition affects about 1 in every 150 children. The impaired social interaction, communication deficits, and restricted and repetitive behaviors seen in people with the condition have confounded scientists since it was first identified in 1943. Because only a minority of autistic persons have severe intellectual disability, and some show exceptional cognitive talents, relatively subtle changes in the brain are probably responsible. Now a flurry of new discoveries is pointing to one possible site of autism's origin: the synapse.

    Synapses are junctions across which neurons communicate. They are essential for sensory perception, movement coordination, learning, and memory—virtually all brain function. “The synapse is like the soul of the brain,” says Huda Zoghbi, a pediatric neurologist at the Baylor College of Medicine in Houston, Texas. “It's at the root of everything.”

    Zoghbi was the first to propose, in 2003, that altered synapses might be responsible for autism. But direct evidence was thin. Now “there seems to be a confluence of data flowing,” says Stephen Scherer, a geneticist at the Hospital for Sick Children in Toronto, Ontario.

    Critical connection.

    Neurexins and neuroligins coming together in the synapse. Alterations in these proteins could change how neurons communicate and lead to autism.


    Until the mid-1980s, experts considered autism a strictly environmental disorder, with most of the blame falling on faulty parenting. Now we know that “autistic spectrum disorder,” the term specialists prefer, is overwhelmingly genetic. Based mostly on studies of fraternal and identical twins, University of Illinois at Chicago autism researcher Edwin Cook concludes that genetic factors contribute about 90% to autism, with environmental factors contributing no more than 10%. Autism is “the most heritable of neurodevelopmental disorders that are complex in origin,” says Scherer. (Biology is not destiny, of course, because the environment affects the form any genetic disorder takes, and autistic children often improve if placed in the right learning setting.)

    Abnormalities of chromosomes, many of them visible under the microscope, are thought to account for 10 to 20% of autism cases. The effect of multiple genes acting in combination probably accounts for most of the rest. Two groups recently reported that many autism patients have novel deletions and duplications in their genomes (Science, 20 April 2007, p. 445), probably arising when chromosomes cross over during meiosis. Researchers are honing in on the individual genes responsible.

    Because autism is a spectrum of disorders, different gene combinations will play a role in different individuals. What's generating excitement now is the discovery of mutations in single genes that, in rare instances, seem able to cause autism. These genes may be pointing directly at a general mechanism for the disorder, at the synapse.

    The first autism genes?

    Zoghbi's provocative 2003 synapse hypothesis rested partly on work that year by a group led by Thomas Bourgeron at the Pasteur Institute in Paris, France, that found mutations in proteins called neuroligins in two pairs of Swedish brothers with autism spectrum disorder. Neuroligins are proteins expressed on the surface of the postsynaptic neuron that bind to proteins on the presynaptic neuron called neurexins, spanning the synapse and forming a physical tether. Together, neuroligins and neurexins are thought to play key roles in the formation and functioning of synapses.

    Some researchers contested the Pasteur Institute findings, however, because no other reports of these mutations in other individuals with autism followed; some even questioned whether the Swedish brothers actually had autism. “If it wasn't [autism], it was pretty damn close,” says Scherer.

    These rare neuroligin mutations and other suggestive evidence linking some neuroligin-binding proteins to autism led Bourgeron to postulate a “neuroligin autism pathway” in which abnormalities in any of these dozen or more proteins could predispose their possessors to the disorder. Bourgeron buttressed his case this January, when his group identified mutations in one of these proteins, Shank3, in three autistic individuals. In such rare cases, mutations in this single gene seem to be sufficient to cause autism. Other groups, according to Scherer, are also reporting Shank3 mutations in autistic patients. “It's being replicated for sure,” he says. In the one published study so far, Shank3 mutations appear to account for about 1% of autism cases.

    Then, in March 2007, the Autism Genome Project Consortium, a group of over 50 institutions in North America and Europe, reported results of a 5-year study on the genetics of autism in 1600 families. In addition to several new chromosomal regions implicated in the disorder, the researchers found the neurexin-1 gene associated with autism. Since neurexins bind to neuroligins at the synapse, this finding boosted the neuroligin autism pathway idea, although the study's authors did not look for specific neurexin mutations. (Several groups are now sequencing the gene.) Shank3 abnormalities also turned up in some Autism Genome Project families, reports Scherer, the study's coprincipal investigator, again implicating the neuroligin pathway.

    Autism's origin?

    Neuroligins and neurexins, proteins crucial for aligning and activating synapses, have now been implicated in autism, along with the Shank3 scaffolding protein. An altered balance between excitatory synapses (left) and inhibitory (right) could affect learning and memory during development.


    Bourgeron now feels vindicated. “People in the field are really accepting that this is a pathway which is associated with autism,” he says. “When we published the neuroligin [report in 2003], nobody believed it.”

    Mutations in single synaptic genes, including neuroligins, neurexins, and Shank3, will probably explain only a small number of autism cases—5% at most, Scherer estimates. In the most convincing case so far, Shank3, “a single genecould cause this complex disease type,” says Scherer. “That's tremendously important,” Scherer explains, because it could provide clues to cellular defects underlying all autism. In Alzheimer's disease, for example, mutations in the β-amyloid precursor protein (APP) account for a tiny fraction (less than 0.1%) of all cases yet were crucial in revealing the likely disease mechanism: the abnormal deposit of amyloid plaques in the brain. “This field, autism, is probably about 7 years behind the Alzheimer's story,” says Scherer.

    Orchestrating the synapse

    Now the race is on to figure out how neuroligins and their binding proteins are contributing to autism. “What exactly do these proteins do at synapses?” asks Thomas Südhof, a neuroscientist at the University of Texas Southwestern in Dallas. “That's … crucial for understanding autism.”

    Südhof's lab discovered neurexins in 1992 and neuroligins in 1995. They have been studied intensely ever since, because they seemed to hold the key to how synapses form, and thus to brain development. At first their pairing was thought to physically tether the synapse, but it later became clear that they also promote the recruitment of neurotransmitter receptors and various structural molecules to the synapse—in fact, orchestrating a complete synapse. Neuroligins and neurexins “are unbelievably important proteins,” says Südhof. “They're life or death.”

    Clues to their possible role in autism are now appearing. One theory is that an abnormal neuroligin pathway upsets the balance of excitatory and inhibitory synapses in neurons, thereby affecting learning and memory, and thus language and social communication. Broadly speaking, synapses can be either excitatory, when the neurotransmitter glutamate is released, or inhibitory, with release of the neurotransmitter gamma-aminobutyric acid (GABA). The ratio of excitatory and inhibitory synapses on a neuron determines whether it will fire in any given situation. In the 21 June issue of Neuron, Südhof reported that in experiments in cells, overexpressing neuroligin-1 leads to excitatory transmission at synapses, whereas neuroligin-2 overexpression leads to inhibition. Südhof speculates that an alteration in either neuroligin could change the excitatory-inhibitory balance, subtly changing the number of neurons that are firing during brain development. Such disruptions could eventually produce the lasting symptoms of autism, he explains, because synapses change with use, becoming more or less sensitive to stimuli depending on experience. This “synaptic plasticity” is the basis of learning and memory.

    That's just one possibility. The synapse is extraordinarily complex, both chemically and structurally, and a lot could go wrong there as the brain develops. Studies in animals to understand the different components of the synapse and to determine mutation effects are just beginning.

    Many research groups are now focusing on finding links between synapse genes and autism. Cook argues for a broader approach, including whole genome scans for other genes that might have less individual effect but may account for more autism cases. (Some such studies are in progress.) “To say one or the other approach … is the right way to go is, I think, at this point naïve,” Cook says.

    Few genes or many?

    The hope is that most cases of autism are caused by just a few strongly acting genes, rather than many weak genes in concert. Simpler genetics would accelerate understanding of the disorder, as well as facilitate early diagnosis and genetic counseling, and provide more discrete targets for therapy. Bourgeron notes that a single abnormal gene—or even a single gene copy, as with Shank3—can, in rare instances, cause autism. But even Bourgeron doubts that altered synapses by themselves are enough to cause most cases. “Autism is not a single entity,” he stresses.

    He speculates that a combination of abnormal synapses and altered neural networks—the complex circuitry involving the billions of neurons that permits language and social interaction—could combine to cause most cases of autism. Factors that could alter neural networks include a global, as opposed to neuron-level, shift in the excitatory-inhibitory balance, increased neuron numbers (many autistic children have large heads), or high levels of the neurotransmitter serotonin, seen in about a quarter of autistic patients.

    Besides synapse abnormalities, many causes of autism have been postulated, from altered neuron migration during early development to chronic inflammation in the brain. Imaging and post-mortem studies suggest that “underconnectivity” between brain regions is at the heart of the disorder (Science, 24 June 2005, p. 1856). Underconnectivity and altered synapses are not mutually exclusive. “If you have regionally different synapse dysfunction, you're going to have differences in connectivity between different brain regions,” says Südhof. “That's exactly what you would predict.”

    In the end, it may all come down to the synapse.


    Last-Gasp Effort to Save Borneo's Tropical Rainforests

    1. Richard Stone


    One of the most ambitious attempts ever to safeguard tropical forests is taking shape in Southeast Asia. In February, the three nations—Brunei Darussalam, Indonesia, and Malaysia—that share Borneo agreed to conserve and jointly manage vast tracts of the world's third-largest island to protect its unparalleled biodiversity. At the meeting, scientists outlined their vision for the Heart of Borneo (HoB) initiative—to rave reviews. “It's phenomenal. A fantastic project,” says terrestrial ecologist Nigel Stork, head of the School of Natural Resource Management at the University of Melbourne in Victoria, Australia. Yet with many details still to be worked out, some worry whether the partners will follow through on all that's been promised.

    Under HoB, a third of the island—some 240,000 square kilometers straddling Brunei, Indonesia, and Malaysia—would be designated for varying degrees of protection, from conservation to uses ranging from tourism to sustainable logging. “This is the only place [in Southeast Asia] where tropical rainforest can still be conserved on a large-enough scale to remain permanently viable,” says Rahimatsah Amat, chief technical officer for Borneo with the World Wide Fund for Nature (WWF) in Malaysia. Famed for its orangutans, Borneo is a biodiversity wonderland with three new species described each month, on average, over the past decade. The richness of tree diversity “is greater than anywhere else in the Old World,” says Peter Ashton of Harvard University's Arnold Arboretum.

    Ashton, who has conducted fieldwork in Brunei for 50 years, calls HoB “spectacular.” The initiative, adds Carsten Brühl, an ecologist at the University Koblenz-Landau in Germany, is “the only chance that is left to do something meaningful to conserve the remaining forests of Borneo.” As a cautionary tale, Brühl points to deforestation on nearby Sumatra. Without HoB, he says, Borneo's ecosystems “might be lost in 20 years.”

    Like those of Sumatra, Borneo's forests are under siege. Palm oil plantations are spreading as sales of the biofuel soar, invasive acacia trees are on a rampage, and wild-fires ravage the island each year. The Heart of Borneo has come none too soon. “The project already appears to have been successful in deterring oil palm expansion in the HoB area, at least on paper,” says conservation biologist Matthew Struebig of Queen Mary, University of London, U.K.

    Withering heart.

    Although boundaries are not yet set, the Heart of Borneo initiative aims to keep remaining forests intact.


    Although the three governments are still crafting implementation plans, the multimillion-dollar HoB would integrate management of national parks and other protected areas with adjoining landscapes to ensure contiguous forest cover. The HoB concept “is not a total lock-away of land,” says the initiative's originator, WWF adviser Mikaail Kavanagh. Although about half of HoB land will continue to be utilized, the governments are expected to curtail unsustainable or damaging practices, such as clear-cutting and unbridled expansion of palm plantations. “We still have to provide livelihoods for people as well as protecting the biodiversity,” says Stork, who is not involved with the initiative.

    Scientists expect HoB will yield big, albeit vague, dividends in species protection. The project's scale “is very promising, since size does matter for biodiversity conservation in tropical forest habitats,” says Brühl, who studies Borneo's ants. “I expect that such an ambitious project will provide a safeguard against biodiversity loss. But how will that be measured?” asks Myron Shekelle, an expert on tarsiers at the National University of Singapore.

    Some scientists worry that the initiative could be detrimental to creatures outside project boundaries by distracting attention from them. “HoB looks like it would represent upland habitats in all states very well, but much of the diversity and the greatest conservation threats are in the lowlands,” argues Struebig, who points out that substantial orangutan populations are outside HoB, in the peat swamps of Indonesia's Kalimantan provinces. Although HoB “can't cover all of Borneo,” Struebig says, “it would be catastrophic if donor and government conservation interest was diverted from other flagship areas as a result.”

    The initiative's amorphousness also raises eyebrows. “Exactly what is covered and what commitments each country would take beyond publicity and tourism seem very uncertain at this stage,” says Struebig. Experts are lobbying the three Borneo governments to take a rigorous approach to sustainable forest management. Timber extraction should be highly selective, using systems like helicopters or cables, says Brühl, who adds that such techniques have been tested in Borneo.

    Despite the misgivings, experts laud WWF for conceiving HoB and persuading the politicians to adopt it. The initiative could become “a milestone in conservation,” says Brühl. Or, he warns, “It could also become a piece of paper with a catchy title.” The onus is now on Borneo's governments to carry the ball forward: to finalize HoB boundaries and lay out a mechanism for managing and funding it. A game plan is due by February 2008.


    Paradise Lost, Then Regained

    1. Richard Stone


    A half-century ago, invaders overran Cousine Island. Feral pigs denuded the tiny outpost in the Seychelles archipelago, and alien plants ran riot. Many ecologists wrote off the island. “It was so degraded, so disturbed. It was in a very, very sad condition,” says Michael Samways, an ecologist at the University of Stellenbosch in South Africa.

    Samways didn't give up on Cousine, however. He has since become the chief architect of what appears to have been a stunning ecological recovery. At the meeting, Samways enthralled participants with a vivid description of the “landscape triage” his team has performed over the past 15 years to restore Cousine to a facsimile of what it was like before humans arrived. “We call it 'Paradise Gained,'” says Samways. “It's a marvelous story,” says Paul Racey, a biologist at the University of Aberdeen, U.K.

    In important ways, few islands compare to Cousine. It is privately owned, and the current owner bankrolled the restoration. Crucially to its ecology, Cousine appears never to have suffered a rodent infestation. That is probably because the island has no jetty, so boats cannot easily moor and introduce vermin stowaways, Samways says. Sans rats (egg fanciers), creatures like the lesser noddy, a seabird, hung on.

    But ample devastation was inflicted by other mammals brought to Cousine in the first half of the 20th century. In 1977, Racey led a team to the island to assess its endangered brush warblers. They found no warblers—and “plenty of alien plants,” he says. Subsequent surveys revealed that the Seychelles magpie robin also had vanished.

    Ownership of Cousine changed hands, and in the early 1990s, Samways and Peter Hitchins, the island's manager, embarked on the restoration. First they enlisted “an army of people” to hunt down the feral pigs, cats, and chickens, Samways says. “There is nothing soft about conservation,” he explains. “It has to be undertaken with military discipline rather than with poetic wonder.”

    After vanquishing the aliens, Samways's forces planted mapou trees to restore the canopy and released a couple of dozen tortoises that had been held in captivity elsewhere. Four Seychelles magpie robins brought to Cousine have since begat 40, and there are now around 200 brush warblers. Lesser noddy numbers have skyrocketed from a smattering to an estimated 90,000 pairs. “The noddy brings back a functioning ecosystem” by defecating and dropping food items, which add nutrients to impoverished soils, Samways says. One downside: The island's vitality could attract poachers—a “particular worry,” he says, as they could be a conduit for rodents.

    Primeval vision.

    The lesser noddy's recovery has helped revitalize Cousine's ecosystems.


    The situation offshore is not so pretty. Cousine's coral reefs were hammered by the globe-girdling bleaching event of 1998. Since then, “there's been very little recovery,” Samways says. Ten years ago, the reefs were alive with organ corals and butterfly fish. His team found neither on a survey earlier this year.

    Although coral bleaching was beyond their control, Cousine's managers have implemented tough measures to safeguard the terrestrial revival. The approach might seem unorthodox: exclusive villas where celebrities and the super-rich pay 400 euros and up for a night's stay. “All that money goes into the conservation efforts,” Samways says. Guests are ferried in by helicopter and subjected to strict quarantine.

    Cousine will serve as an ark for such endemic species like the Seychelles giant millipede that are under threat elsewhere in the archipelago. But to Samways, the deeper value of Cousine's renewal can only be fathomed by visiting the island. “The animals are so unafraid of people. You sit on the beach next to a bird with its egg, and it literally won't bat an eyelid.” Many people, he says, have forgotten what it's like to truly experience nature. “Cousine rescues us from that extinction of experience.”

    Cousine may be exceptional, and “time will be the best judge of just what is in store for its natural systems,” says Christopher Filardi, a biodiversity expert at the American Museum of Natural History in New York City. But it shows, he says, that “active intervention or restoration can reinvent a place that is richer and more reflective of its organic history than would exist if we did nothing.”


    From Flying Foes to Fantastic Friends

    1. Richard Stone



    The Horsfield's fruit bat (Cynopterus horsfieldii) is found across Southeast Asia.


    The bell is tolling for Southeast Asia's bats. Pummeled by habitat erosion and hunting, some 20% of bat species may become extinct by the end of the century, experts predict. A concerted effort is now underway to save the furry critters with the establishment of a Southeast Asian Bat Conservation Research Unit.

    Throughout the region, bats are an animal of ill repute. “People think bats are scary: they get stuck in your hair, they drink your blood,” says Tigga Kingston, a biologist at Texas Tech University in Lubbock and head of the new research unit. “We want people to go from 'ugh' to 'aah.'” Since 2001, Kingston's team has reached out to Malaysian communities to publicize the high ecological value of the only mammals capable of powered flight. For starters, bats consume as much as their body weight in insects in a single night—” fantastic pest control,” Kingston says. And some species pollinate fruit, including durian, a $1.5 billion commodity. “Bat conservation can be boiled down to: no bats, no durian, we can all go home.” A chilling thought for fans of the pungent fruit.

    Besides preaching the bat gospel, Kingston's research unit, bankrolled by the British American Tobacco Biodiversity Partnership, will fund science and conservation. One urgent need is to curb appetites for flying foxes, a delicacy in Malaysia and other countries. “They're under severe hunting pressure,” Kingston says. A top research priority, meanwhile, is to establish a regional network of taxonomists. “There are more and more cryptic species being discovered,” Kingston says. “You can't conserve what you can't identify.” A taxonomy workshop is planned for the island of Java later this year.

    Experts are thrilled. “It's an absolutely superb initiative,” says University of Aberdeen, U.K., biologist Paul Racey, who studies bats on Madagascar.