Issue for the week of August 27th, 2011

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Big fish return to Mexican marine park

A 1.2-meter-long gulf grouper (Mycteroperca jordani) is among the large predators that have returned to Cabo Pulmo National Marine Park after a fishing ban.Octavio Aburto/iLCP

Within 14 years of a national marine park in Mexico’s Gulf of California closing its borders to fishing, the total mass of its denizens more than quintupled, a new study finds. Over the same period, the share of top predators — sentinels of a healthy ecosystem — also soared. Both trends countered those for fish in unprotected regions of the Gulf.

“People who object to marine protected areas, especially to strong protection like here, often say there is no proof that they work,” says Elliott Norse of the Marine Conservation Biology Institute in Bellevue, Wash., who was not involved in the new study. “Well, this is the proof.”

A group of bigeye trevally (Caranx sexfasciatus) forms a spawning aggregation. Such populations have returned to the waters of the Cabo Pulmo National Marine Park after a fishing ban.Octavio Aburto/iLCP

The 71-square-kilometer Cabo Pulmo National Marine Park sits close to where the Gulf opens into the Pacific. Its coral reef makes it a tourist destination for diving and snorkeling. Since 1995, 35 percent of the park’s waters have been off limits to fishing, but local communities informally extended the no-take zone to the rest of the park, says Octavio Aburto-Oropeza of the Scripps Institution of Oceanography in La Jolla, Calif. He and his colleagues surveyed the reef’s fish populations in 1999 and again in 2009. They report the results of those surveys August 12 in PLoS ONE.

Fishers typically first target meaty predators such as giant groupers and snappers. Absent in 1999, such big fish — some a meter or more long — again inhabit Cabo Pulmo, Aburto-Oropeza says. He even witnessed Pacific tunas visiting to dine on the park’s reef fish.

Sharks remain notable for their virtual absence. Owing to heavy exploitation for the fin trade and slow rates of reproduction, this family of predators remains rare inside Cabo Pulmo and out, Aburto-Oropeza says.

Norse says there’s no reason to believe that the new study’s findings should prove unique to the Gulf of California. “I suspect that what they found would occur anywhere people who fish exercise the admirable restraint that the people have at Cabo Pulmo.”

Found in: Environment, Life and Science & Society

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Sparing the rare earths

A potential shortage of several rare earth metals (some shown) has spurred research into technologies that don’t require them.Images-of-elements.com

The Toyota Prius isn’t exactly a muscle car. But the magnets under the hood certainly pack a punch.

Pound for pound, these permanent magnets are some of the most powerful on the planet. They generate fields 10 times stronger than those of typical refrigerator magnets, helping the hybrid car’s motor and generator to turn the wheels and charge the battery. The secret to the magnets’ intense fields? About three pounds of alloy made with rare earth elements.

Rare earths, 17 chemical elements found mostly in an appendage to the periodic table, have long been the darlings of solid-state physics and the electronics industry. Without these materials, hard drives wouldn’t be able to store so much information and smartphones wouldn’t be so pocket-friendly.

“Take away the small rare earth magnets inside the earbuds for your iPod, and you’re back to traditional-looking over-the-ear headphones,” says Alex King, director of the U.S. Department of Energy’s Ames Laboratory in Iowa.

But some people, particularly in the United States and Japan, have begun to worry about potential shortages in the supply of rare earths. Although the elements are not rare in themselves, they are concentrated in just a few locations. Last year, China produced about 97 percent of the rare earths mined on the planet. In recent years that country has been cutting back on the amount of rare earths it exports, reducing quotas by almost 40 percent in 2010.

Rising prices and a looming potential shortage have now ignited searches for alternatives to magnet technologies that chew up large amounts of rare earths.

Rare indeedChina contains about half the world’s reserves of rare earth elements,and it far outstrips other countries in producing them from mining operations. SOURCE: USGSJanel Kiley

For some applications, rare earth elements may be simply irreplaceable. The phosphors used in color televisions and other displays with cathode-ray tubes get their brilliant reds from europium compounds. This rare earth’s electrons jump between energy levels and emit light in ways that can’t be mimicked by any other element in the periodic table.

Magnets, which account for about one-fifth of global rare earth consumption, may be a different story. With DOE funding, materials scientists in the United States are reviving the study of magnets, a field that hasn’t seen a major breakthrough in nearly three decades. Meanwhile, Japan — second only to China in global magnet production — has dedicated more than $150 million of its 2011 budget to research that would reduce its need for rare earths.

Some scientists plan to make the strongest rare earth magnets stronger with blends that use less of these materials. Others hope to ditch the elements in favor of common metals that might be good enough to get the job done.

“A lot of old problems in permanent magnetism are being revisited with new tools,” says Oliver Gutfleisch, a materials scientist who studies magnets at the Leibniz Institute for Solid State and Materials Research in Dresden, Germany. “We have to produce a next-generation magnet.”

Revisiting the iron age

The strength of a magnet — its ability to tug on iron — starts with its electrons. Every electron spins around its axis, like a planet or a figure skater. In most substances, electrons pair off, spinning in opposite directions. But some elements have unpaired electrons that spin in a way that makes their atoms into tiny bar magnets, with a north and a south pole. Expose a group of these atoms briefly to a magnetic field, and they line up with one another straight as soldiers, working together to make one big magnet.

HYBRID VIGORView larger image | A vehicle such as the Toyota Prius contains rare earth elements throughout its various advanced technologies, including more than 20 pounds of lanthanum in the battery pack.© Owaki/Kulla/Corbis

Iron is one of the most magnetizable materials on Earth, but there’s a good reason why magnets aren’t usually made of pure iron. At the slightest provocation, such as a tiny electric field or change in temperature, iron’s atoms break rank and swing out of alignment, ruining the magnet. Iron is thus considered magnetically soft.

Metallurgist Iver Anderson, who spent years purifying rare earth metals in the crucibles of the Ames Laboratory, now hopes to harden soft iron alloys to create a magnet free of rare earths. The goal isn’t to make something that can rival today’s best magnets, just something with a better bottom line.

“For many applications, we don’t have to reach the same magnetic strength levels as rare earth magnets,” he says. “For hybrid cars, we need something maybe 50 percent or so as strong.”

Anderson and his colleagues plan to harden a blend of iron and cobalt by changing the shape of its crystal structure. The cube-shaped atomic lattices that make up iron cobalt give atoms too much freedom to wiggle around. Other crystal structures, such as hexagons and tetrahedrons, are better at keeping atoms in line, so “we’re trying to figure out a way to distort the cubic structure and make it tetrahedral,” says Anderson. Computer simulations he presented at an Energy Department meeting in May suggest that this goal could be achieved by peppering the usual iron cobalt recipe with other atoms: tungsten, maybe, or nitrogen.

The Ames team is also dusting off “alnico” magnets, commercialized in the 1940s. Made mostly of aluminum, nickel, cobalt and iron, these magnets are reasonably hard but only about one-fifth as strong as the best rare earth magnets. Tweaking the structure of these magnets to line up the iron cobalt grains might up the oomph.

“We’re at least a year away from knowing whether this will work,” Anderson says. “Whether it makes sense from an economic standpoint is another step beyond that.”

What rare earth elements are good for

Another scientist who wants to work with magnets from the iron age is Migaku Takahashi of Tohoku University in Japan. He is experimenting with combinations of iron and nitrogen because thin films made out of these elements are the most magnetizable material known. In March, Takahashi’s collaboration announced a method to create powders that retain this property, though they still lack the hardness needed to be useful for rare earth–free magnets.  Like Anderson, Takahashi is taking the long view; he doesn’t expect to be able to make a commercial magnet out of this material until at least 2023.

Rare attraction

Uncertain that these well-explored traditional materials will yield new surprises anytime soon, Ames scientists and other groups are trying to reinvent rare earth magnets from the bottom up.

The best rare earth magnets used today date to 1983, when scientists at General Motors and the Sumitomo Special Metals Co. in Japan independently created the first alloy of iron, boron and the rare earth metal neodymium. This breakthrough was driven by economics; the best magnets at the time were made of cobalt and the rare earth samarium, and the price of cobalt was rising rapidly.

Adding neodymium atoms smothers some of the iron’s magnetic strength but greatly improves its ability to resist demagnetization. Neodymium magnets can achieve about 56 megagauss-oersteds, or MGOe, a unit of magnetic field strength. That compares with more than 10 MGOe for the best non–rare earth magnets, and less than 5 MGOe for the stuff used in refrigerator magnets.

“It’s hard to imagine making a more perfect magnetic material than neodymium-boron-iron,” says George Hadjipanayis, a materials scientist at the University of Delaware in Newark, whose research was crucial to the invention of the first neodymium magnets.

POWER UPView larger image | Magnets containing rare earth elements, such as neodymium and samarium, achieve far higher measures of magnetic field strength than older magnets based on iron alloys.O. Gutfleisch et al/Advanced Materials 2011

Confident that no single material could do a better job, Hadjipanayis and his colleagues have turned to composite neodymium magnets. The researchers are grinding magnetically hard and soft materials into pellets and trying to bind them like candies stuck in a ball. The soft stuff, perhaps iron cobalt, should boost the magnet’s pull. The hard stuff, rare earth compounds, should preserve the strength.

For the materials to play well together, though, these pellets must be extremely small, small enough to qualify as a “nanocomposite” material. When hard chunks and soft chunks are arranged in a kind of patchwork quilt, the hard bits stay connected over distance by the equivalent of magnetic springs. If stretched too far over the soft bits, the springs snap, and the nanocomposite stops behaving as a single material.

A magnet structured as a nanocomposite could achieve some 120 MGOe — more than twice as strong as anything on the market today, according to calculations published in 1993 by Ralph Skomski and Michael Coey of Trinity College Dublin. It would also use significantly less rare earth material.

“Nanocomposite magnets are the holy grail for rare earth magnets,” says John Burba, executive vice president and chief technology officer at Molycorp Minerals in Greenwood Village, Colo.

New teamwork

Thanks to advances in nanotechnology in the years since nanocomposites were first proposed, Hadjipanayis’ team can now create suitably tiny and uniform bits of hard and soft magnetic materials — while also preventing oxygen from damaging their surfaces, a key problem in making nanocomposite magnets. So can a team at General Electric’s Global Research Center in Niskayuna, N.Y.

GE is pursuing nanocomposite magnets because it’s the largest manufacturer of wind turbines in the United States. New turbine designs incorporate huge magnets that can better handle fluctuations in wind speed and provide more torque than older designs. But a turbine capable of powering about 2,400 homes uses as much as a ton and a half of rare earth permanent magnets.

Last year, in response to a steep increase in the price of the metal rhenium (which is not a rare earth), GE scientists made a very strong replacement “superalloy” out of very small grains of nickel. Using techniques similar to those developed for that and other work, the researchers now aim to improve the strength of rare earth magnets by about 40 percent while decreasing the amount of rare earths in the magnets by 80 percent. What these magnets will be made of, though, is still anyone’s guess.

“We’re exploring several different hard and soft materials but haven’t selected a specific chemistry yet,” says materials scientist Frank Johnson of GE.

Choosing the right stuff for a nanocomposite isn’t easy. In 2002, physicist Ping Liu, now at the University of Texas at Arlington, and colleagues published a paper in Nature describing experiments that mixed magnetically hard and soft particles made of iron and platinum. His team fused the particles, and the resulting magnetic fields were more than 50 percent stronger than the hard material on its own.

But Liu hasn’t figured out how to get all of the grains lined up before fusing, which would allow the nanocomposite to reach its full potential. And the platinum may make this approach too expensive to be viable for everyday magnets.

Dyspros and cons

If they ever live up to their promise, nanocomposite magnets should reduce the demand for both neodymium and for another rare earth element called dysprosium.

Dysprosium hardens magnets against heat by reshaping their magnetic fields. Every neodymium magnet intended for a hybrid car, a wind turbine or another application in which temperatures soar to hundreds of degrees must be spiked with a bit of the pricey dysprosium. It costs more than seven times as much as neodymium and is currently mined in only one place in the world: clays in southern China. So some researchers are exploring pragmatic ways to cut down on its use.

Changing the microstructures of magnets could help, as neodymium magnets made of smaller grains are naturally more resistant to demagnetization. Working with the magnet company Intermetallics, materials scientist Satoshi Sugimoto of Tohoku University and colleagues recently developed fine-grained magnets that require 40 percent less dysprosium.

The best fine-grained magnets completely free of dysprosium may belong to Kazuhiro Hono, a researcher at the National Institute for Materials Science in Tsukuba, Japan, and colleagues. These magnets, to be described in September in Scripta Materialia, are 60 percent more resistant to demagnetization than commercial neodymium magnets that lack dysprosium. But Hono’s magnets are still not quite good enough for cars and wind turbines.

Despite recent advances, neither Japan nor the United States appears to be counting on magnet breakthroughs anytime soon. Geologists from the University of Tokyo and their colleagues recently proposed dredging the Pacific Ocean for rare earths (SN: 8/13/11, p. 14). Several Japanese companies have also started “urban mining” programs meant to reclaim the rare earths buried in cell phones and other devices. Hitachi is working to reclaim 80 percent of the rare earths from the magnets of discarded hard drives and air conditioners.

In the United States, Molycorp Minerals has reopened a mine on the edge of California’s Mojave Desert that was once a profitable source of europium and cerium. Last year, the company began processing previously mined ore for rare earths, including neodymium.

But these efforts to dig out of a difficult situation may not prove economical, and the combined creativity of scientists on both sides of the Pacific may fall short. So Toyota has launched a program to rid its cars altogether of permanent magnets —  rare earth or not — by developing a new motor that would run on electromagnets, which generate fields by passing current through coils of wires and have traditionally been considered too bulky for hybrid and electric cars.

If Toyota engineers succeed, these new motors could push forward the next generation of hybrid vehicles without the need for any rare earths.

Found in: Chemistry, Earth, Matter & Energy, Science & Society and Technology

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Book Review : The Bleeding Disease: Hemophilia and the Unintended Consequences of Medical Progress by Stephen Pemberton

A historian shows how advances in treatment made hemophilia manageable — yet led to many deaths from HIV-tainted plasma.

Johns Hopkins Univ. Press, 2011, 377 p., $50

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When birds go to town

Paris crows feast on some human leftovers. They’re not the only birds that have learned to like garbage.WITT/SIPA/Associated Press

Anne Clark and Kevin McGowan are discussing, perfectly seriously, how a crow might be able to recognize a car. Not tell a car from, say, a cat, but pick out the red Subaru from other cars in the parking lot.

Clark, an animal behaviorist at Binghamton University in New York, is sitting in her own red Subaru with McGowan, of Cornell’s Laboratory of Ornithology in Ithaca. Neither bothers to mention — it’s apparently so routine — that when Clark pulled into the lot, two crows flapped over to nearby trees. Country crows often back away from human doings, but these birds lingered as if people-watching.

Clark and McGowan are running a long-term study of what urban life is like for a group of Ithaca’s crows, tagging and following them as they grow up, take over or lose territories, and succeed or not in raising the next generation of research subjects. Even in a university town, the birds probably aren’t lured to the Subaru by the thrill of scientific discovery, but rather by the scientists’ occasional ploy of flinging peanuts and dog food out the window to engineer some bird activity.

“They know us,” McGowan says. There isn’t another Subaru in the lot to test the birds’ discriminatory abilities, but McGowan has inadvertently conducted his own experiment. He sold his car and bought a new one. McGowan was temporarily invisible automotively, but the birds caught on eventually. And the old car’s new owner reported that a crow appeared to be following him to work. It was OK; the driver just provisioned the car with peanuts for an occasional fling.

New food sources are just one of the opportunities that organisms of all kinds — including ants, birds and cockroaches on down to zoysia grass — encounter when they take up life around people. As human populations boom, more and more plants and animals are becoming city dwellers, a shift that intrigues biologists fretting over the practical problems of nuisance critters as well as theoreticians musing over how organisms adapt to new environments. For even a green town presents plenty of novelty unknown in any species’ evolutionary history.

Dropping dietary clues View larger image | Glaucous gulls living around the town of Deadhorse, Alaska, get much of their food in the form of human garbage, researchers recently found. This part of the diet proved particularly important to the gulls during chick rearing. Rural birds studied in Simpson, Alaska, appeared to get their dinner elsewhere.E.l. Weiser and A.N. Powell/Condor 2010

The considerable number of birds that now share cities and suburbs offer as good a focus as any for scientists trying to understand what happens when animals go to town. Though some birds are seizing new opportunities, the lifestyle often comes with costs. Biologists are now beginning to see how birds respond to some of the major facts of city life, from discarded french fries to relentless low-pitched noise.

And other studies are showing how, by encouraging species that can cope and filtering out those that can’t, urban areas are creating mix-and-match combos of inhabitants that have never had to deal with each other in quite the same way before. Odd juxtapositions of predators, competitors, prey and, oh my, people become a challenge in themselves.

Feed me

Clark and McGowan didn’t intentionally train Ithaca’s crow population to car watch, and the researchers throw food only when other attempts to coax a bird to cooperate have failed. Still, Team Crow’s adventures in the parking lot turn out to be a classic example of the new crow-human dealings that emerge where people abound. One of the big attractions of these urban environments is all the leftover and left-outside human food just waiting for the enterprising forager.

Clark, McGowan and Binghamton graduate student Jennifer Campbell-Smith are searching for this year’s nests so McGowan or another tree climber can band nestlings. The nestlings will be included in a database of crow families going back more than two decades. Crow family territories in Ithaca are smaller and nestle together much more densely than they do in rural New York, and the family sagas are complex. A day riding around on a spring nest survey is like dropping in from Mars and having to pick up the plotlines of The Sopranos, Lost and a lot of Shakespeare, all with feathers.

Urban birds deal with new surroundings in innovative ways. This hummingbird nest is in a power plant’s boiler feed return pipe.Jon Ridler, Cornell Lab of Ornithology, www.CelebrateUrbanBirds.org

All morning Clark has proved almost clairvoyant at driving in traffic along Ithaca roads and suddenly veering onto the shoulder after glimpsing the dark form of a nest among the many dark forms in conifers half a block away. The woods by the parking lot are tough even for the clairvoyant, though. A crow pair nested here last year, but the team never determined which tree held the young.

Crows are nesting in the same clump of trees this year, and the dilemma calls for flinging food in hopes that the birds it draws will take some back to the nest. They readily flap down to the asphalt to pick up the goodies and fly off with bulging beakfuls. A few loads get ferried into the dense tangle of branches in an uphill corner of the pines, but again, spotting which tree has the nest proves tricky.

There’s another handful of peanuts. And another. After more than an hour of observation from the parking lot, the woods and two vantage points in a cemetery across the street, there’s still no obvious tree. The crows have gotten a fine lunch but have managed to keep their nesting address private. One might ask who trained whom.

For birds such as these Ithaca crows, which can balance a natural wariness with some strategic boldness, the world is their garbage dump. A 2010 study of glaucous gulls found that birds in northern Alaska towns rely heavily on human garbage, with up to 85 percent of regurgitated pellets and breeding-season bird remains including human leftovers. In Seattle it’s “roadkills, Cheetos and french fries, and Kentucky Fried Chicken — all the favorites,” says John Marzluff of the University of Washington.

In an upcoming article in Studies in Avian Biology, Marzluff discusses classic studies of three bird populations that picked up the knack of opening, and drinking from, milk bottles delivered to people’s doorsteps in the morning. He says Seattle’s crows even know what time the keepers at the zoo throw fish to the penguins, and the birds show up to vie for the handouts.

OVER THE GRUMBLEThe sounds of the city can drown out the lower ranges of a bird’s songs (figures show a great tit song in a quiet forest and the same song masked by urban rumblings). Recent studies suggest birds try to accommodate in various ways.H. Slabbekoorn

On the other side of the Pacific, birds known as jungle crows have visited a shrine in Kyoto and helped themselves to some of the thousands of fat-rich, potentially crow-edible candles set out along the paths. Video recordings revealed that the crows don’t shrink from flames, says Hiroyoshi Higuchi of the University of Tokyo. Crows carried still-smoldering candles away, suggesting an explanation for puzzling fires in fields nearby.

Human food, even when it’s not aflame, may not be so good for birds, though. In a 2009 study comparing the effects of available food on chick rearing in suburban and rural places, Clark, McGowan and Rebecca Heiss, a graduate student at Binghamton at the time, reported evidence that nutrient deficits in suburbia may be limiting the growth of young crows there. Suburban crows lag behind country cousins in size, and offering suburbanites high-protein, high-calcium supplements boosted nestling growth. What startled the researchers, though, was what happened when they set out supplemental nestling food in the countryside. Crows that took home the best nutritional formula used by specialists in nursing orphan chicks ended up with noticeably punier youngsters than neighbors relying entirely on wild food. Even the best food that humans could concoct fell short of a natural diet.

What human nutrition does for birds seems to depend on the species, meaning some dive and others thrive. Abundant human garbage, for example, is proposed as one of the drivers behind population booms in urban gulls worldwide over the last 50 years. The garbage in the diets of those glaucous gulls in northern Alaska turned out to be important in successfully raising chicks, according to an analysis in the fall 2010 issue of the Condor.

Yet the glaucous gulls also hunt other birds. Work done at the University of Alaska Fairbanks by Emily Weiser and Abby Powell has confirmed that remains of more than a dozen at-risk bird species turned up along with the garbage in gull nest debris. While garbage may be a boon for the gulls, their rising numbers may lead to more predation on rare birds — changing the circumstances for these already stressed populations.

Even the abundant food that human enthusiasts set out on their feeders comes with complications, writes Darryl Jones of Griffith University in Nathan, Australia, in the spring 2011 issue of Emu. Evidence so far suggests that feeding birds during the winter increases their chance of survival and advances the timing of nesting and egg laying come spring, meaning more time for raising young. Yet feeding can also push birds out of sync with natural food supplies and may encourage migratory species to stick around all year, possibly competing with winter residents.

BEWARE THE CAVEMANBirds seem to be capable of recognizing threatening people, and can pass that concern on to others. The map below shows sites in Seattle where researchers in caveman masks captured crows and locations where the same masks elicited scolding from birds more than two years later.H.N. Cornell et al/Proceedings of the Royal Society B 2011, adapted by T. Dubé

“There is absolutely no doubt that this amount of human provisioning is having massive and widespread influences on bird populations,” Jones says, “and we really need to know what is happening.”

Sounds of the city

Fine urban dining options often come with unnatural noise. But oddly enough, studies in the 1990s didn’t find that rumbling traffic affected the way city birds sing, says Hans Slabbekoorn of Leiden University in the Netherlands.

Unaware of those negative results at the time, Slabbekoorn went about carefully checking noise in male great tit territories. The more traffic noise competing with a male’s arias, the higher their minimum frequency, Slabbekoorn’s team reported in 2003. Much of the cacophony of urban environments, the cars and air conditioners and leaf blowers and such, growl and grind in the lower frequencies. Studies now suggest that birds can show some musical accommodation.

The frequency change that human hubbub prompts in great tits doesn’t come from singing the same songs at a different pitch, Slabbekoorn and graduate student Wouter Halfwerk announced in 2009. In a study designed to get at the mechanism of the song accommodation, the team experimented with individual birds, analyzing their normal songs and then playing some recorded urban rumble-grumble. Great tits have individual repertoires of up to nine songs. “Peta peta peta,” Slabbekoorn sings, a song heard from the same bird that also does “petati petati.” Lower pitches, prone to get drowned out, dominate some of these songs but not others. During the sessions of recorded urban noise, males sang fewer of the songs with substantial lower notes, showing off more of the high end of the repertoire.

As an additional test, the researchers played what they call reverse urban noise, an artificially created opposite to traffic sounds that puts most of the sound energy at the higher frequencies instead of the lower ones. Confronted with this vexation, the males abandoned the higher-pitched tunes in their repertoire and returned to the lower ones.

Song switching may be the great tit way, but researchers are finding it’s not the only way birds get around extra sound. Nightingales tend to sing louder in loud places, and European robins grow more likely to sing at the formerly unrobinlike hours of the relatively quiet urban night.

While birdsong may be music to human ears, to the birds themselves it’s, “Get your foul feathered rump out of my territory right now,” “Choose me, baby” or some other vital communication. Disrupting such important messages or sabotaging some other aspect of sound could be exacting costs even for birds that readily live in the din. It’s a tricky matter to test, but Slabbekoorn’s group has some evidence. Great tits nesting at various distances from a Dutch motorway fledged fewer offspring in noisier territories, his team reported in the February Journal of Applied Ecology. Though tits persist, they’re paying a price for their urban homes.

And, like any other bit of city living, noise can affect different dwellers differently. Investigating that variability has been challenging because shrubbery, food, pollution, people and plenty of other factors vary along with city noise. For a cleaner test, one team turned to another kind of noisy environment: land around natural gas wells. In piñon-juniper forests of the southwestern United States, some wells run thundering compressors around the clock while others in the same kind of woodlands don’t. Loud compressor zones had about the same number of bird nests as quiet sites, but only 21 nesting species instead of 32, says Clinton Francis of the National Evolutionary Synthesis Center in Durham, N.C.

One of the species conspicuously rare around compressors was the Western scrub jay, which raids nests of a variety of species and eats the eggs. Low risk of jays may have had something to do with why several species such as black-chinned hummingbirds appeared to favor noisy sites. And low numbers of jays likewise might explain why the bird community that tolerates relentless compressor roars overall reproduces more successfully than the quiet community. Ability to cope or not has rejiggered the dynamics of the bird mix.

The living city

The inevitable species in all of these mixes is Homo sapiens. Humans, for all their generosity with garbage, have a dark side as far as a bird is concerned. They’re not just predators, they’re opinionated predators with technology.

Crow shooting, for example, used to be much more common around Ithaca. McGowan hypothesizes that crows living in the city now descend from those that were willing to take a chance and move closer to people as shooting waned. Several decades ago, old-timers told him that crows hardly ever appeared in town. These days, he and Clark have banded more than 2,000.

Crows may have gotten cozier with people, but the birds don’t forget insults. Crows even appear to recognize and remember the faces of upsetting humans, Marzluff and his colleagues reported in Animal Behaviour in 2010. Marzluff and other experimenters trapped wild Seattle crows just once while wearing rubber masks sold on the Internet as caveman faces. More than two years after the incident, people of various genders and ages and with different body sizes and walking gaits attracted shrieking, dive-bombing crows when wearing the masks. Yet the same people could walk unmasked with hardly any attention from crows.

Crows can even learn grudges from other crows, the Marzluff team reported in June online in the Proceedings of the Royal Society B. Five years after the original trapping episode, crows that weren’t among the offended birds — and crows that weren’t even hatched at the time of trapping — now scold people wearing the masks. The tendency to mob someone wearing the dangerous face has become twice as common at some Seattle sites and spread at least a kilometer from the original study area, apparently via crow information networks.

Crows are celebrated as clever birds, but some capacity for distinguishing among individual people has even turned up among birds of more humble reputation: free-ranging pigeons. When two similar-looking people wearing coats of different colors routinely set out food in a park in Paris, the pigeons could still tell the friendly one from the one that chased them even when the people switched coats, Ahmed Belguermi of Université Paris Ouest and colleagues reported online in Animal Cognition in June. Birds hopping around sidewalks and city parks know about more than human clothing. When Clark is viewing an especially edgy bird, she sometimes puts it at ease by facing off at an angle and pulling out her cell phone for a mimed conversation. Crows seem to assume that people on cell phones ignore their surroundings.

Such studies of urban birds are telling a nuanced tale of animal reactions to previously unencountered environs. A casual observer might assume that animals thriving in the city are just the oblivious, bold species that don’t happen to notice or care if people tramp among them. But that doesn’t appear to be the case.

Instead, Clark says, “living in a city is probably very cognitively complicated.” A bird in the country seems to flourish with just a few simple rules about humans. “People — bad! Fly away!” as she puts it. To survive among the urban wonders and terrors, though, metropolitan animals are using their native cognitive abilities to distinguish the opportunities from the perils. In the city, it’s caveman — bad, Subaru driver — good.

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Science & the Public: Growing need for space trash collectors

Greenhouse gas, solar slowdown are lengthening the lifetime of space debris — increasing its threat to satellites and astronautsWeb edition : Monday, August 15th, 2011 Hovering hazardsThe yellow cloud marks orbiting aerospace debris in low Earth orbit. The longer the debris remains in orbit, the longer it can threaten spacecraft.H. Lewis/Univ. of Southampton

On April 2, for the fifth time in less than three years, the International Space Station fired its engines to dodge a piece of orbital debris that appeared on a collision path. Other spacecraft also regularly scoot out of the way of rocket and satellite debris. Such evasive action will be needed increasingly frequently, a new study finds.

Friction between the atmosphere and materials passing through it, known as drag force, offers the only natural means for culling detritus left in orbit by space launches. But the thermosphere is cooling. A resulting drop in its density is cutting this portion of the atmosphere's drag force, thereby increasing the lifetime of orbiting trash (including pieces in that heavily populated band at 800 to 1,000 kilometers).

Space agencies around the world have been discussing a need to actively remove aerospace debris. One reason: The number of pieces has been steadily rising, driven in part by collisions between orbiting pieces of trash or trash and spacecraft. Among the biggest debris multipliers: a spectacular 2009 crash between the dead Russian Kosmos 2251 spacecraft and the U.S. Iridium-33 telecommunications satellite.

Two years ago, aerospace engineer Hugh Lewis of the University of Southampton, England, and his colleagues calculated that within a few decades, space agencies would have to begin culling perhaps five major pieces of debris annually to slow this collision-enhanced growth in the number of orbiting trash particles. But in a paper in the Journal of Geophysical Research, posted online Aug. 10, the Southampton team now doubles that number, pointing out that the thermosphere’s falling density renders the old trash-pickup requirements obsolete.

Climate impacts

The thermosphere does not behave as a gas, explains Lewis. Molecules originating on or near Earth’s surface are propelled upward based on their energy, he observes. With cooling, fewer of them reach satellite (and associated debris) heights.

Growing emissions of carbon dioxide, a greenhouse gas, contribute to the thermosphere’s cooling, the Southampton team points out. The mechanism, Lewis says, appears to be collisions between CO2 and atomic oxygen at high altitudes. Those collisions release heat in the form of infrared energy, which radiates out into space — removing warmth from Earth’s atmosphere.

A drop in the sun’s activity will also cool the thermosphere. Although the new JGR analysis assumed that solar cycles during the next 70 years would roughly match those seen over the past 30, this may prove an overly conservative assumption, Lewis acknowledges. This spring and summer, scientists have been reporting that the current solar cycle is particularly anemic. And solar activity might remain lackluster for the indefinite future.

Upper atmospheric increases in carbon dioxide “is the primary cooling agent of the thermosphere,” observes thermosphere climate scientist John Emmert of the Naval Research Laboratory in Washington, D.C. The Southampton team’s new analyses, he says, “demonstrate for the first time that space climate change has significant consequences for orbital debris proliferation and for debris mitigation strategies.”

Trash collection realities

Although actively removing space trash from orbit “is absolutely desirable,” focusing on how many pieces to remove annually “is sort of a moot point, since we don’t know how to clean up even one,” says Nicholas Johnson, chief scientist of NASA’s Orbital Debris Program Office, at the Johnson Space Center in Houston.

There’s also the issue of relative risk, he says. “Although there is a sort of sandblasting going on in space all of the time, both from man-made and natural debris, we’ve only had two operational spacecraft ever hit by man-made debris (that we know of) that sustained any major damage.” One was the Iridium-33 catastrophe, the other a French satellite hit in 1996 which was temporarily disabled. While not wishing to dismiss the risk of a possible catastrophic impact, Johnson notes that the risk of a spacecraft-killing collision remains rare — and that “even two times a small number is still a small number.”

But even if space engineers were given the go ahead to develop a waste-collection service for space, succeeding would likely take a very long time. “There is nothing on the horizon that either DOD or NASA believes can do the job [space-trash removal] from either a technical standpoint or from a financial one,” Johnson notes. Still, that won’t stop U.S. researchers from formally brainstorming solutions — and on Uncle Sam’s dime.

Johnson notes that the President’s new national space policy, announced last year, for the first time directs NASA and the Defense Department to develop technologies for removing threatening debris. Their challenge is complicated by the fact that no one has decided which trash to target first. And the issue isn’t as simple as it might at first seem.

There is debris in low Earth orbit — between 400 km and perhaps 1,000 km — where the Hubble Space Telescope, International Space Station and some other satellites reside. Then there’s the geosynchronous Earth orbit regime at altitudes of perhaps 36,000 km. Protecting craft orbiting at such vastly different altitudes will require different strategies.

Engineers also will have to decide whether to focus on protecting today’s operational spacecraft over the next decade or two or protecting craft that may orbit a century from now.

If the focus is going to be on protecting future generations, Johnson says, then the priority should be ridding the skies of big pieces of trash — perhaps the car-size multi-ton behemoths that can break up into hundreds (if not thousands) of shards. Shifting the emphasis to current-generation spacecraft, he says, will argue for getting rid of small debris. “If we’re going to lose spacecraft in the next two decades,” he explains, “statistically, we’re going to lose them to small things we can’t track.”

Government agencies are already tracking thousands of large debris particles in low Earth orbit. Another half million smaller ones, between 1 and 10 centimeters, also pose threats. Uncertainties in their paths currently prompt satellite managers to be overly conservative, maneuvering spacecraft to new paths more frequently than is truly necessary, Johnson notes. The only way to limit that, he says, is to improve the tracking of trajectories for small, but potentially spacecraft-killing debris.

Found in: Atom & Cosmos, Climate Change, Earth Science, Environment, Matter & Energy, Planetary Science, Science & Society and Technology

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JediBot uses Kinect to control lightsaber

Stanford University graduate student Ken Oslund reveals that he is the JediBot's father.

(Credit: Video screenshot by Amanda Kooser/CNET)

You spent countless hours locked in lightsaber battles with your buddies while growing up. What happens when there's no one left to play with you because they all have jobs and babies? You make your own Star Wars playmate.

Students at Stanford University programmed a robotic arm dubbed the JediBot. The bright orange arm swings a red foam lightsaber against a human opponent. It gets off surprisingly snappy attacks with some decent robotic muscle behind it.

It's one thing to create an arm that goes on the offensive, but another to build one capable of defense as well. That's where the Microsoft Kinect comes in. The opposing lightsaber is green so that the Kinect sensors can pick up on where it is in space. The JediBot uses that information to plan its defensive maneuvers.

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The robotic arm--which can swing its sword about once every two to three seconds--was created for a 3.5-week Experimental Robotics course. The class also produced a robot that grills hamburgers and even adds the ketchup. The only thing that would make the JediBot better is if it battled you to a draw and then offered you a tasty cheeseburger.

It's about time someone came up with a Star Wars action figure that truly brings the action. All that's missing are the awesome sound effects. Good thing you've been practicing. Wuumph! Zzzsh! Zzzsh!

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