Revving Up Fuel Cells
Progress toward hydrogen-powered cars depends on less expensive but greater capacity fuel-cell systems [see “On the Road to Fuel-Cell Cars”; SciAm, March 2005]. Researchers have taken big steps on both the cost and storage challenges. A team from Quebec came up with a recipe that uses iron instead of expensive platinum to catalyze the electricity-making reaction of hydrogen and oxygen. The key was carbon structures containing microscopic pores, which were filled with iron to provide plenty of active sites for chemical reactions. The iron-based substance, described in the April 3 Science, produced catalytic activity within 10 percent of the best platinum versions and 35 times better than previous, nonprecious metal catalysts.
Pores are also driving the search for materials that can store hydrogen for delivery to fuel cells. A team from the University of Michigan at Ann Arbor says it has made a material that has a record-high surface area for holding gases. This hydrogen sponge consists of zinc oxide clusters linked by an organic material; one gram has the surface area of 5,000 square meters, nearly the size of a football field. Details of the substance, dubbed UMCM-2, appear in the April 1 Journal of the American Chemical Society.
New Heart Cells from the Atomic Age
Aboveground nuclear testing in the 1950s spewed radioactive carbon 14 and other isotopes worldwide. Plants soaked up the compounds, animals ate the plants, and humans ate both, inadvertently creating an experimental opportunity for Jonas Frisén of the Karolinska Institute in Stockholm and his colleagues. They have used the decay of atomic age carbon 14 as a biological marker to determine how frequently the body replaces its cells [see “Cold War Clues”; SciAm, December 2005]. With the data, they have settled a long-standing question by showing that humans can indeed produce new heart cells, or cardiomyocytes. The annual turnover rate is 1 percent at age 25, decreasing to 0.45 percent by age 75; all told, about 40 percent of cardiomyocytes are replaced by age 70. The finding, in the April 3 Science, suggests that stimulating the turnover mechanism could repair damaged hearts.
Not So Lifesaving
For years researchers have questioned the value of a blood test for prostate cancer, called a PSA test [see “Does Screening for Prostate Cancer Make Sense?”; SciAm, September 1996]. After all, most prostate cancers progress slowly, sometimes never posing a problem, and treatment could cause impotence and incontinence. First results from large, ongoing U.S. and European studies, published in the March 26 New England Journal of Medicine, suggest that the PSA test does not save many lives. The U.S.trial found no reduction in death from prostate screening in men followed for about 11 years. The European study, which had different protocols, saw a 20 percent drop in death rates, which translated to seven fewer deaths per 10,000 men screened and tracked for nine years. Expect follow-up work to resolve some of the differences between the two studies.
Storms could become more intense as the world warms [see “Warmer Oceans, Stronger Hurricanes”; SciAm, July 2007]. Researchers studying 58 hurricanes found that an increase in lightning tended to precede the strongest winds by a day. For instance, monitors tracking Hurricane Dennis in 2005 recorded a surge in lightning flashes—from 600 a day to 1,500—nearly 24 hours before wind speeds doubled and peaked at 150 miles per hour. The correlation, reported online April 6 in Nature Geoscience, needs more data before lightning can be considered a definitive predictor of storm intensity.
Note: This article was originally published with the title, "Updates".