In This Issue
ENVIRONMENTAL SCIENCES
Global warming could lead to increased severe thunderstorms
Scientists anticipate intensified precipitation by the end of the century as increased anthropogenic greenhouse gas concentrations are expected to raise average temperatures by 2–6°C around the world. Robert Trapp et al. used global and high-resolution regional climate models to examine whether the intensified precipitation will arise from severe thunderstorms. The authors evaluated two quantitative measures of thunderstorm environments: the convective available potential energy (CAPE), a measure of a storm's energy, and the storm's wind shear. High CAPE and shear values in localized areas are known to promote damaging storms that produce large rainfall rates, hailstones, destructive surface winds, and tornadoes. The authors discovered that under greenhouse gas emission scenarios predicted by the Intergovernmental Panel on Climate Change, the number of days on which meteorological conditions occur that would support the formation of severe thunderstorms increases >100% in the United States. The increase will be particularly notable in densely populated regions of the southern and eastern United States, including cities such as Atlanta and New York. Reduced emissions, the researchers say, could reduce the increases they have projected. — F.A.
Anomaly in severe thunderstorm environment days (NDSEV) in spring (Left) and summer (Right).
“Changes in severe thunderstorm environment frequency during the 21st century caused by anthropogenically enhanced global radiative forcing” by Robert J. Trapp, Noah S. Diffenbaugh, Harold E. Brooks, Michael E. Baldwin, Eric D. Robinson, and Jeremy S. Pal (see pages 19719–19723)
ANTHROPOLOGY
Prehistoric Asian jade linked to Taiwan
The ratio of elements in jade and its inclusions can pin it to the locality where it was quarried. In previous work, Hsiao-Chun Hung and Yoshiyuki Iizuka developed a database for jade sites around the Pacific Rim. Now, assisted by their coauthors, they have analyzed a set of artifacts dated from 3000 B.C. to 500 A.D. and shown that, although jade artifacts can be found across a broad swath of southeast Asia, most of them can be traced to a singlegeological origin: Fengtian, in Taiwan. The authors used a low-vacuum scanning electron microscope with an energy dispersive x-ray spectrometer to identify the relative amounts of iron, magnesium, and silicon, together with the inclusion minerals, in the jade. Two types of ear ornament were chosen for the study: the three-pointed “lingling-o” and a two-headed animal pendant, both of which were popular in southeast Asia between 500 B.C. and 500 A.D. The authors analyzed 144 artifacts, including some Neolithic specimens, from Taiwan, the Philippines, Malaysia, Vietnam, and Thailand. Based on elemental composition, 116 were identified as originating in Fengtian. The source of the others remains unknown. This work, the authors say, reveals one of the most extensive prehistoric trading networks in semiprecious stone. — K.M.
2,000-year-old jade earrings.
“Ancient jades map 3,000 years of prehistoric exchange in Southeast Asia” by Hsiao-Chun Hung, Yoshiyuki Iizuka, Peter Bellwood, Kim Dung Nguyen, Bérénice Bellina, Praon Silapanth, Eusebio Dizon, Rey Santiago, Ipoi Datan, and Jonathan H. Manton (see pages 19745–19750)
MEDICAL SCIENCES
High folate levels are linked to exacerbation of vitamin B12 deficiency
The metabolism of the vitamins folic acid and B12 is linked and deficiency in either can lead to anemia and macrocytosis. Deficiency in vitamin B12, but not folate, may also be associated with neurological and neuropsychiatric abnormalities. Previous research has shown, among participants in a United States survey, that prevalence of anemia and cognitive impairment is approximately five times higher in people who have low vitamin B12 status and high blood folate levels, compared with those who had low vitamin B12 status but normal blood folate levels. These data seem to suggest that high blood folate is associated with amplifying clinical manifestations of vitamin B12 deficiency. Jacob Selhub et al. show that high folate may worsen clinical manifestations of B12 by altering the activity of two enzymes that require B12 to function. In people with vitamin B12 deficiency, high blood folate levels are linked to higher levels of homocysteine and methylmalonic acid, biomarkers of B12 status, versus individuals with B12 deficiency and normal blood folate levels. These data relating high folate and low B12 to clinical and biochemical outcomes were obtained from a sample of the elderly population in the United States after foods such as flour and cereal were mandated by the U.S. Food and Drug Administration to be fortified with folic acid in 1998. The authors conclude that the levels of folate associated with adverse effects are only attainable through folic acid supplements and fortified foods, not from natural folate. — B.T.
“In vitamin B12 deficiency, higher serum folate is associated with increased total homocysteine and methylmalonic acid concentrations” by Jacob Selhub, Martha Savaria Morris, and Paul F. Jacques (see pages 19995–20000)
NEUROSCIENCE
Touch of a vanished hand
The lack of feedback provided by touch typically limits amputees' use of prosthetic arms. This limitation could be partially alleviated if sensors in artificial fingertips could connect to nerve endings on an amputee's body. Todd Kuiken et al. have taken a step toward this solution by rerouting the major hand nerves to the pectoral muscle in a 54-year-old man and a 24-year-old woman who had lost arms. This surgery allowed the nerves to reinnervate the chest skin, where they established sensation of the missing hand. Although signals from the transferred hand nerves overlapped in some areas with those from the chest, no confusion arose; the patients reported feeling being touched in two places simultaneously. The authors characterized the results of the surgery by measuring thresholds for touch, heat/cold, and electrical-induced pain, and noting which areas of the patient's chest corresponded to which region of the phantom hand. Despite the fact that the transferred hand nerves were integrated over the new area in a complex manner, the transferred hand sensation thresholds did not differ much from normal skin in all modalities. With appropriate hardware connections, the authors say, this type of surgery could allow patients more sophisticated use of prostheses. — K.M.
Sensation in the patients' reinnervated chest skin referred to the missing hand.
“Redirection of cutaneous sensation from the hand to the chest skin of human amputees with targeted reinnervation” by Todd A. Kuiken, Paul D. Marasco, Blair A. Lock, R. Norman Harden, and Julius P. A. Dewald (see pages 20061–20066)
