Blocking Sound with Holes
Anyone kept awake by a neighbor’s television may be surprised to learn that a few holes drilled through a wall could lower the volume on sound. Francisco Meseguer of the Polytechnic University of Valencia in Spain and his colleagues placed a series of 20-centimeter-thick aluminum plates in a tank of water and found that perforated plates could diminish ultrasound waves passing through by up to another 10 decibels as compared with solid plates. This reduction was greatest when the spacing between the holes roughly equaled the sound’s wavelength. Evidently, the incoming sound interacts with regularly spaced holes, generating acoustic waves on the plate’s surface that destructively interfere with waves going through the plate. The findings, in the August 22 Physical Review Letters, could help soundproof machines while allowing cooling air through, remarks Meseguer, who says his team is now experimenting with audible sound.
—Charles Q. Choi
More Fluid Mileage
Electric fields can boost a car’s gas mileage by up to 20 percent, thanks to a well-known effect in which electric fields reduce the viscosity of a liquid [see “Electrorheological Fluids”; Scientific American, October 1993]. Reduced fuel viscosity means that much smaller droplets can be injected into the engine, leading to more efficient combustion. Investigators at Temple University thinned fuel by attaching an electrically charged tube to a diesel engine’s fuel line near the fuel injector. In road tests, the attachment, which consumed less than 0.1 watt, increased highway fuel economy from 32 to 38 miles per gallon. The researchers, who describe the boost in the November 19 Energy & Fuels, expect the device will find use in all kinds of internal-combustion engines.
—Charles Q. Choi
Every night the Brazilian ant Forelius pusillus takes selflessness to a whole new level. At dusk, as the ants defend their homes by sealing off the entrances with sand, up to eight workers remain outside to finish the job. Left behind, they die by the next day—the first known example of a suicidal mission that is preemptive rather than a response to immediate danger.
Behavioral ecologist Adam Tofilski of the Agricultural University of Kraków in Poland and his colleagues found that these ants were not just stragglers trapped outside. They were deliberately helping to cover the entrances, spending up to 50 minutes kicking sand into the holes until the entrances were indistinguishable from the surroundings. In experiments, the scientists found that only six of 23 ants left behind were alive the next morning, showing that their act was a sacrifice. Just why the ants died is unclear—the species is fragile, but the researchers also suspect that the outside individuals could be old or sick. The findings, in the November American Naturalist, could elucidate the evolution of altruism.
—Charles Q. Choi
The 2008 Nobel Prizes
This month the king of Sweden will honor these 10 people of science for their achievements.
Three of them—Luc Montagnier, Yoichiro Nambu and Paul Krugman—have written for Scientific American.
Physiology or Medicine: Harald zur Hausen of the German Cancer Research Center in Heidelberg, for his discovery that the human papillomavirus causes cervical cancer, and Françoise Barré-Sinoussi of the Pasteur Institute in Paris and Luc Montagnier of the World Foundation for AIDS Research and Prevention in Paris, for their discovery of the human immunodeficiency virus (HIV). In making its choice, the Nobel committee snubbed Robert C. Gallo of the University of Maryland, who proved that HIV causes AIDS.
Physics: Yoichiro Nambu of the University of Chicago, for the discovery of the mechanism of spontaneous broken symmetry, which helps to explain the masses of subatomic particles and the forces acting on them, and Makoto Kobayashi of the High Energy Accelerator Research Organization (KEK) in Tsukuba, Japan, and Toshihide Maskawa of Kyoto University, for the discovery of the origin of broken symmetry, which predicts the existence of at least three families of quarks.
Chemistry: Osamu Shimomura of the Marine Biological Laboratory in Woods Hole, Mass., Martin Chalfie of Columbia University and Roger Y. Tsien of the University of California, San Diego, for their discovery of the green fluorescent protein and its development as a visual tag in bioscience.
Economics: Paul Krugman of Princeton University, for his theories on international trade patterns and geography, which explain why cities are growing and why similar industries clump together.
Vanishing Act for Mammals
A new survey of the world’s 5,487 mammal species reveals that one in four is in danger of dying out—including some species of bats, the most numerous of mammals. The International Union for Conservation of Nature (IUCN) concludes that at least 1,139 mammals around the globe are threatened with extinction and that the populations of 52 percent of all mammal species are declining. South and Southeast Asia are home to the most threatened mammals. Deforestation and hunting are the prime causes of the rapid declines in land mammals, such as elephants in Asia; most endangered marine mammals, such as the vaquita porpoise in Mexico’s Gulf of California, have succumbed to fishing nets, ship strikes or pollution.
Concerted efforts have brought some mammals, such as the black-footed ferret, back from the brink, but long-term success depends on tackling the root problems, the IUCN warns in its report published in the October 10 Science.
For the budget-conscious terrorist, fertilizer has been the ingredient of choice—because it contains ammonium nitrate, the chemical foundation of many kinds of bombs. Honeywell International—the Morristown, N.J.–based company famous for thermostats—has now patented a blast-free alternative. The company’s fertilizer adds in ammonium sulfate, which binds to the ammonium nitrate and makes it unable to burn quickly. In tests, the fertilizer does not detonate even when mixed with diesel or other fuels. What remains to be seen is whether it performs well as plant food; target crops would be those that need both nitrate and sulfate, such as tomatoes, cabbages and potatoes. Honeywell plans to offer the product by the end of 2009. Farmers will likely pay more for the so-called Sulf-N 26 fertilizer, but those who use it will have some assurance that the Department of Homeland Security won’t come calling when they buy in bulk. —David Biello
The actual benefits of intensive psychotherapy have long been controversial. Now investigators report that such therapy can be effective against chronic mental problems such as anxiety and depression. They looked at 23 studies involving 1,053 patients who received long-term psychodynamic therapy, which seeks clues into the unconscious roots of disorders and focuses on the relationship between patient and therapist. Psychotherapy that lasted a year or longer appeared significantly more beneficial for complex mental problems than shorter-term therapies and seemed cost-effective. Analyze more in the October 1 Journal of the American Medical Association.
—Charles Q. Choi
The Deadly Dozen
The Wildlife Conservation Society (WCS) has issued a report of 12 diseases that are likely to spread and get worse as the world warms up and precipitation patterns change, providing more opportunities for these outbreaks. They are bird flu (H5N1 influenza), babesiosis (a malarialike disease), cholera, Ebola, infections by animal parasites (such as the worm Baylisascaris procyonis), Lyme disease, plague, poisonings from algal blooms called red tides, Rift Valley fever, sleeping sickness, tuberculosis, and yellow fever. To prevent some of these ailments from becoming the next Black Death or 1918 flu pandemic, the WCS suggests monitoring wildlife to detect signs of these pathogens before a major outbreak erupts.
Successful Rock Tracking
For the first time, investigators tracked a small asteroid (a few meters in size) before it hit the earth. A telescope that is part of the Catalina Sky Survey, based near Tucson, Ariz., is part of an effort to locate near-earth objects that could pose a collision hazard. It picked up the body, dubbed 2008 TC3, on October 6. Researchers then correctly predicted that the space rock would enter the atmosphere at 12.8 kilometers per second over northern Sudan at 5:46 A.M. local time the next day, releasing approximately one kiloton of energy. Objects of this size strike the earth once every few months.
Note: This article was originally published with the title, "News Scan Briefs".