TUESDAY, AUGUST 10, 2010 SCIENCE NEWS


Depression may be seen in the eyes If depression has a color, it might be gray — at least in the


eyes of the depressed. This is because a study published in the July issue of Bio- logical Psychiatry found that depressed people seem to have more difficulty distinguishing contrast differences than oth- er people. Using a pattern electroretinogram, an electrocardiogram for the eyes, researchers compared the visual electrical activ- ity of 40 healthy people with 40 people who had received di- agnoses of major depressive disorder. Twenty of the de- pressed people were on medication and 20 were not; regard- less of medication, all the depressed participants suffered from symptoms of major depression.


At the begining of each test, researchers had subjects stare


at a bland checkerboard image on a computer screen. “It’s almost a gray-on-gray checkerboard,” said contribut- ing author Ludger Tebartz van Elst, a psychiatry and psycho- therapy professor at the University of Freiburg in Germany. The checkerboard flickered 12 times per second at this muted setting. Then researchers steadily increased the im- age’s contrast, morphing the dull checkerboard into a crisp black-and-white image. At each contrast setting, researchers recorded the electrical activity of the participants’ retinas. They found that increasing contrast correlated with in- creasing electrical activity in the retinas of the healthy peo- ple. The retinas of those with depression reacted far less to the changing image. “The more depressed, the more severe the depression, the lower the contrast gain,” Tebartz van Elst said. As indicated by the electrical activity of the cells of the eye, depressed par- ticipants had more trouble noticing the change from low contrast to high contrast. “We were lucky to find such an accessible, measurable in-


dicator,” he said. “It’s like a thermometer of the . . . sickness in the center of the brain at the level of the eye.” Currently, mental health professionals don’t have an ob-


jective test to determine if people are depressed, said Tebartz van Elst. To diagnose depression, he usually relies on what patients tell him and what he observes when patients de- scribe their symptoms.


Although more research is needed, Tebartz van Elst and his colleagues have opened the possibility that there might be an “objective measure for the subjective state of depres- sion.”


“If this is the case,” he said, “this might have consequences not only for research but also for clinical diagnostic pro- cedures.”


— Leslie Tamura Disease threatens bats in Northeast


One of the most common bat species could face extinction in the Northeast within decades due to white-nose syn- drome, a disease now rapidly spreading. While bats have a reputation for frightening people, they are vital in controlling insects that spread disease. The threatened little brown bat has been known to eat its weight in insects in a night.


Researchers led by biology professor Thomas H. Kunz of Boston University report in the journal Science that white- nose syndrome, caused by a fungus, could all but wipe out the little brown bat in the Northeast in 20 years. The syndrome was discov- ered near Albany, N.Y., in 2006, and since then bats have declined by 30 to 99 percent in some areas. The illness has been confirmed in 115 bat-hibernating loca- tions in Canada and the United States, ranging as far south as Tennessee and as


RICKY CARIOTI/THE WASHINGTON POST


Hibernating bats are dying from white-nose syndrome.


far west as Oklahoma, the researchers reported. Last month the U.S. Forest Service said it is barring entry


to caves in Colorado, Wyoming, Nebraska, Kansas and South Dakota to help prevent people from inadvertently spreading the disease. And the New Mexico-based Center for Biological Diversity has asked state wildlife officials across the country to consider closing state-owned caves to the public to pre- vent the spread of the illness. “This is one of the worst wildlife crises we’ve faced in


North America,” said Winifred F. Frick, a co-author of the re- port. “The severity of the mortality and the rapidity of the spread of this disease make it very challenging and dis- tressing.” The fungus grows on the nose, wing membranes and ears of bats while they hibernate in caves and mines dur- ing the winter. The researchers said this causes the bats to wake up frequently, burning up vital fat stores, with the re- sult that they starve to death before spring.


— Associated Press SCIENCE SCAN EXPLORATION


Nature vs. human nature “THE WILDEST DREAM: CONQUEST OF EVEREST” (NATIONAL GEOGRAPHIC ENTERTAINMENT) British mountaineer George Mallory is more famous for


something he said than the many remarkable things he did. When the New York Times asked him, in 1923, “Why climb Everest?” he answered, “Because it’s there.” The documen- tary “The Wildest Dream,” at the Johnson Imax Theater in the Smithsonian National Museum of Natural History, tries to determine if Mallory reached the summit of Mount Ever- est (before he died 800 feet below it) in 1924, three decades before the first official scaling of the peak. American climber Conrad Anker, who found Mallory’s body in 1999 in the so- called “death zone” above 26,000 feet, follows Mallory’s path, even wearing re-creations of his inadequate gabardine gear for parts of the climb. The icy vistas are surely stunning in Imax form (unfortunately, the press screening was held in a standard theater), but most remarkable is the primal drive of man to “conquer” nature and the sacrifices he will make to do so.


BEHAVIORAL RESEARCH You are now free


to crawl around the cabin “THE SMART SWARM” (AVERY, $26) Anyone who has crouched down to


watch ants work or gazed up at the sky and seen birds fly in a V formation has probably pondered swarm theory. Na- tional Geographic Senior Editor Peter Miller explains how creatures such as


ants, termites and honeybees can organize themselves and solve difficult problems. This is not new science: A major breakthrough in understanding how termites build mounds was uncovered in the 1950s by French biologist Pierre-Paul Grassé, for example. But Miller includes the latest research and then shows how humans are using the wisdom of swarms to improve communication and decision-making. For instance, Southwest Airlines analyzed behavioral sim- ulations of ants to determine the most efficient way to get passengers to board a plane.


— Rachel Saslow


KLMNO THE GREEN LANTERN How green is the nuclear option? by Nina Shen Rastogi


I thought nuclear reactors were an absolute no-go for environ- mentalists. But I keep hearing them touted as a clean energy source. What are nuclear en- ergy’s green credentials? Some environmentalists are in- deed coming around to nuclear energy. That’s because the nuclear fission process produces virtually no greenhouse gas emissions, un- like the burning of fossil fuels such as coal and natural gas. (Those two fossil fuels accounted for about 70 percent of U.S. elec- tricity in 2008. Nukes made 20 percent.) Also, fission produces neither sulfur dioxide nor nitro- gen oxides, the fossil-fuel pollu- tants that cause acid rain. Advocates are fond of noting


that nuclear power provides 70 percent of the country’s “carbon- free” energy. But nuclear energy isn’t really a zero-carbon system, since you still have to build power plants, mine and enrich uranium, and transport processed fuel, all of which typically rely on CO2


-


emitting fuel sources. Even when the entire life cycle is taken into account, however, nuclear energy warms the planet much less than coal or natural gas. The compari- son with renewables such as wind and solar (which also generate emissions in the manufacturing phase) is less cut and dried. While it’s commonly accepted


that nuclear energy has a rela- tively dainty footprint, the ques- tion of whether new reactors would be the most cost-effective way to lower electricity-related emissions is still hotly debated. The fuel itself is relatively in- expensive, at least for the time be- ing. But as noted in Time, recent price estimates for a large plant in Florida came in at $12 billion to $18 billion, and that’s before you consider the nuclear industry’s history of major cost overruns. Some analysts say alternative


methods would yield much more climate-saving bang for our buck than nuclear power. For example, Amory Lovins of the Rocky Moun- tain Institute argues that we should be investing in general effi- ciency measures and “micropow- er,” a catchall term that includes cogeneration of heat and electric- ity, plus renewables other than big hydropower operations. What about safety concerns? Admittedly, there’s a fright factor


Science


E3


MICHAEL SLOAN FOR THE WASHINGTON POST The Green Lantern is a weekly


environmental column from Slate. Read previous columns at www.slate.com/greenlantern.


with nuclear power. But in the 31 years since the partial meltdown at Three Mile Island, there haven’t been any emergencies in the Unit- ed States that remotely ap- proached the severity of that in- cident, though there have been some close calls. The government’s Nuclear Reg-


ulatory Commission has a set safety goal for every reactor in the country: The chance of an acci- dent that results in radioactivity being released to the environment must be no more than one in a million, as determined by prob- abilistic risk assessment. But even the longest of odds will never sat- isfy everyone, especially after the cataclysmic drilling accident in the Gulf of Mexico. In recent years, a number of leaks of radio- active water have stoked environ-


mentalist ire, although nearby residents were not exposed to dangerous doses of radiation. Meanwhile, nuclear prolifera- tion risks remain a prohibitive concern for many experts. And many environmentalists continue to give nukes the stink eye be- cause, as the Lantern noted in an earlier column, after 50 years we still don’t have a long-term plan for storing high-level commercial nuclear waste.


But long-term disposal is a problem we’re saddled with no matter what: Whether we ramp up nuclear energy production or shut down all our plants tomor- row, we’ll have at least 62,500 metric tons of used nuclear fuel to deal with.


Atomic energy also generates other environmental concerns. Like conventional power plants, a nuclear site cranks out electricity using steam-driven turbines. Cooling those operations often re- quires a whole lot of water, the drawing and releasing of which can affect aquatic wildlife. Uranium mining can also dam- age the environment. Mining and


milling operators must deal with mill tailings, the radioactive ma- terial left over after the uranium has been extracted from the ore, as well as waste rock and radiolog- ically contaminated equipment. For all this, it’s worth noting


that uranium is a very efficient en- ergy source: One ton of natural uranium can produce the same number of kilowatt-hours as 16,000 tons of coal or 80,000 bar- rels of oil. The Lantern doesn’t find her- self particularly freaked out by atomic energy. The long-term waste conundrum seems more pressing: After all, isn’t the notion that you don’t bequeath problems to your descendants a major tenet of environmentalism? At the same time, global warming is itself a dire legacy, and every energy tech- nology has its pitfalls. So if nu- clear power can play a role in cool- ing our planet, the Lantern thinks it deserves to stay on the table.


Is there an environmental quandary that’s been keeping you up at night? Send it to ask.the. lantern@gmail.com.


Designers sweat the details to let athletic clothes breathe HOW AND WHY


Leslie Tamura


advertisements claiming that this shirt has the textile technology to keep you dry, that those shorts can wick away your sweat, that this fabric will keep you feeling cool and comfortable during the most intense workouts. But what’s the science behind these promises? How do dry-wick textiles actually work? It comes down to two principles: percolation and evaporation. “Moisture-management” fabrics absorb the sweat from your body, propelling it away from your skin, then spread it throughout the garment so it can easily vaporize into the environment. But these products differ in how they use various fibers. A natural fiber may absorb more than a synthetic fiber, but a synthetic fiber may dry faster. Searching for the desired balance between wicking and drying, manufacturers mix different amounts of natural and synthetic fibers or transform an individual fiber’s silhouette. The fiber recipe determines how the overall garment copes with sweat. Natural fibers tend to love


M


water. They pick it up whenever they can. Synthetic fibers, however, do their best to avoid or repel water. Cotton is a natural fiber and a fantastic lover of water. When you sweat, cotton fibers will absorb the fluid, “wicking” the droplets away from your body. But because cotton fibers love liquid so much, they don’t give it up very easily. The cotton fabric will hold onto the water, absorbing moisture into its fibers, resisting evaporation. This is why it takes so long for your cotton T-shirts to dry. “With natural fibers, you get


what Mother Nature makes, and you have to live with it,” said Becky Rose, an activewear research and development fellow for Invista, the manufacturer of Coolmax fabric. “Sometimes it’s


ost of us are familiar with dry-wick athletic apparel. We see the


good, sometimes it’s not so good.” Wearing a cotton shirt during


a workout may feel cool because you’re essentially wearing a shirt drenched in your bodily fluids, but as your core body temperature comes down, you may experience post-workout chills. Your cotton shirt does not want to dry, and you’re left feeling cold and clammy. “For athletic wear,” said Yiqi


Yang, a professor of textile chemistry at the University of Nebraska at Lincoln, “you want [the fabric] to wick water as good as cotton, but you don’t want it soaked.”


At the other end of the


spectrum is polyester. Polyester wants nothing to do with water. Its synthetic fibers are not tempted to absorb the beads of sweat pooling along your skin. When you do sweat, a 100-percent polyester shirt will simply trap the beads of sweat against your skin, often forcing the liquid to just trickle down your body. Polyester may just leave you feeling wet. “Sweat is not just water on


your skin,” said Chris Moore, general manager of Optimer Brands, the manufacturer of DriRelease fabrics. “It is the transportation media of your body’s excess heat.” If the polyester fibers don’t remove the sweat, or heat, efficiently from your body, you may not cool as quickly as if you were wearing a cotton shirt. Nylon is an in-between fabric, sharing properties with cotton and polyester. When nylon gets wet, it absorbs moisture, but it is also more apt to give up the moisture through evaporation. It takes less energy to release the water into the environment because the fibers don’t really care if the water stays or goes. But many athletic garments are made of 100-percent polyester fibers. How are they able to keep you feeling dry? Some companies alter fibers’ chemistry or apply a laminate to the outer surface of the fibers so they are more absorbent. Other dry-wick garments are made of a blend of enough water-loving fibers to pull sweat


from the body and enough water-hating fibers to throw water out onto the surface of the fabric for evaporation. DriRelease, for example, uses a


patented mix of 85-percent polyester and 15-percent cotton fibers in its fabrics. Its fibers can be found in such brands as Asics, Hanesbrands, Nautica and Nike. Coolmax, the original moisture-management fabric developed by DuPont in 1986, features a unique 100-percent polyester fiber design. Unlike other polyester fibers, which are typically tubular, Coolmax polyester fibers have either scalloped-oval or four-leaf-clover cross sections that create tiny tunnels for the sweat to slide through to the outside of the fabric. “The smaller the diameter, or


the finer the tubes,” Yang said, “the more powerful the liquid transportation.” As more companies highlight their garments’ absorbent capillaries, fiber blend and dry-wick, moisture-wick or quick-dry abilities, the athletic apparel market can get confusing. “What’s very important to communicate to consumers is to really look at the tag,” Moore said.


If you want your garment to simply wick the sweat, 100-percent cotton would do well. If you want your garment to wick and dry, find a 100-percent polyester fabric with sufficient pores to allow for breathability. Or find a fabric with a blend of natural and synthetic fibers. Because there are no


industry-wide standards for rating moisture-management clothes, people have to make do with figuring out what they want from their workout attire and reading garment labels. “You want a material that


doesn’t wet itself,” Yang said, “but at the same time, it will transport water away from the body and not let the water in.”


ALAMY Cotton absorbs perspiration; polyester can channel it away. tamural@washpost.com


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