Secrets of the singing dunes

The dunes at Sand Mountain in Nevada sing a note of low C, two octaves below middle C. In the desert of Mar de Dunas in Chile...

The dunes at Sand Mountain in Nevada sing a note of low C, two octaves below middle C. In the desert of Mar de Dunas in Chile, the dunes sing slightly higher, an F, while the sands of Ghord Lahmar in Morocco are higher yet, a G sharp.Since at least the time of Marco Polo, desert travellers have heard the songs of the dunes, a loud—up to 115 decibels—deep hum that can last several minutes. While the songs are steady in frequency, the dunes do not have perfect pitch. Scientists already knew that the sounds were generated by avalanches, but were not sure how. Now, after five years of research, visiting sand dunes in Morocco, Chile, China and Oman, a team of scientists from the United States, France and Morocco say they have the answer.

In a paper that will appear in Physical Review Letters, the scientists say that collisions between sand grains cause the motions of the grains to become synchronised. The outer layer of the dune vibrates like the cone of a loudspeaker. The particular note depends primarily on the size of the grains. Indeed, no dune was required at all. The scientists shipped sand from a Moroccan desert to a Paris laboratory and reproduced the singing by pushing the sand around with a metal blade. ‘‘It’s not at all like any other instrument we know,’’ said one of the scientists, Stephane Douady of the National Center for Scientific Research in Paris. The most beautiful dune tune comes from the sands of Oman. ‘‘Very pure sound,’’ Douady said. ‘‘This one is really singing.’’ The least musical bits of silicon were those from China, which hardly sang at all.

Lefties and Righties

Is left-handedness less common in women? Studies of populations usually find that left-handedness is somewhat less common in women, but perhaps because left-handedness is hard to define, the difference varies by several percentage points. One large study in 1971 used a standard called the Edinburgh Handedness Inventory, which asks which hand is used for different tasks, and found that 90 percent of women were right-handed, as against 86 percent of men. But a smaller 1988 study using the same inventory found no significant difference by sex, and a large Internet study done for the BBC for another purpose found sex differences that varied by ethnic group. Anthropologists’ studies of traditional cultures in Africa and elsewhere found a wide range of differences, from no left-handed women at all to levels approximating those in Western studies. Some researchers have suggested that the trend for more men to be left-handed is not universal or may be affected by social norms, with left-handed men stubbornly clinging to left-handedness while left-handed women are more easily persuaded to join the majority. Reasons suggested for rates of left-handedness that differ by sex include an innate difference in the structure of the hemispheres of the brain; effects of a gene or genes; prenatal hormonal influences, especially that of testosterone; or some other process in the womb. (NYT)

Women gain in medicine

More women appear to be taking leadership roles in medical research, but they still lag behind men, according to a new study. Reshma Jagsi of the University of Michigan Medical School and colleagues analysed the number of women who were the lead or senior author of papers in six leading US journals: the New England Journal of Medicine, the Journal of the American Medical Association, Obstetrics and Gynecology, the Annals of Internal Medicine, the Annals of Surgery and the Journal of Pediatrics. The number of female lead authors increased from 6 percent in 1970 to 29 percent in 2004. The number of female senior authors increased from 4 percent in 1970 to 19 percent in 2004. The researchers noted that the rate of increase might be reaching a plateau, with an apparent slowdown from 2000 to 2004. Similar increases were found in the number of women invited to write editorials. In 1980, no invited editorial in JAMA were written by women, while almost 19 percent were written by women in 2004. Only 1.5 percent of the editorials in the New England journal were written by women in 1970, a share that rose to 20 percent in 2000 but dropped to 11 percent in 2004. ‘‘Women have come a long way, but there is still a long path ahead,’’ said Jagsi, whose study was published in Thursday’s New England Journal of Medicine. (LAT-WP)

Bengaluru family feared dead in Kurnool bus fire

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A family of four from Andhra Pradesh, residing in Bengaluru, are suspected to be among the 20 people reported dead in a fire that gutted a Hyderabad-Bengaluru bus near Kurnool in the early hours of Friday.

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