SCIENCE
Notebook

Monday, August 7, 2006

Study Links Explicit Music, Teenagers' Sexual Activity

Teenagers who regularly listen to music lyrics with explicit references to casual sex are more likely to initiate sexual intercourse and take part in other sexual activity, compared with those who do not listen to such music, according to a study being released today.

The study is the first to document that music with "degrading" lyrics appears to trigger different kinds of behavior than other songs, including those that focus on romantic attachment, love and longing.

Lyrics about casual sex affected both male and female teenagers, whites and nonwhites, according to Rand Corp. researchers who published their findings in the journal Pediatrics. The study tracked 1,461 adolescents over three years and compared the music they said they listened to with self-reported sexual activity.

"Lyrics classified as degrading depicted sexually insatiable men pursuing women valued only as sex objects," the researchers wrote. Such lyrics, which were most prominent in rap music, might convey distorted notions about gender roles to both male and female teenagers, the researchers concluded.

Large numbers of sexually active teenagers told researchers that they wished they had delayed sexual initiation, the study said.

Early sex is associated with an increased risk of sexually transmitted diseases, the study noted -- more than a third of teenagers reported not using a condom the last time they had sex. About 900,000 U.S. teenagers get pregnant each year, which translates to one in five sexually active teenage girls.

-- Shankar Vedantam

Deep Oceans Called Home Of Diverse Microbial Life

Scientists fishing for genes in the deep oceans have netted a huge catch of surprisingly diverse genetic snippets, providing the best evidence yet that the seas are home to far more microbial diversity than researchers had thought.

The work indicates that the world's oceans, once thought to be virtually sterile on the microbial scale, are teeming with bacteria and related organisms that have been evolving and swapping genes for billions of years.

Mitchell Sogin of the Marine Biological Laboratory in Woods Hole, Mass., led the new work -- part of an ongoing census of marine microbial life. They knew that previous efforts to catalogue single-celled oceanic bugs, which involved trying to grow them in laboratory dishes, had led to vast underestimates because only a small portion of those life-forms can survive in standard nutrient broths.

Applying a sophisticated method of gene screening to seawater samples retrieved from deep North Atlantic and Pacific waters, Sogin's team compared genetic sequences in their samples -- released from dead microbes -- with the sequences of known microbial genes. Some of the samples came from areas around a volcanic vent deep in the northeast Pacific Ocean. They concluded that deep-sea bacterial communities are perhaps 100 times more genetically complex than previously appreciated.

That enhanced diversity -- large numbers of bacterial species, each of which is relatively rare -- is serving today as a precious reservoir of genetic material that could help keep the oceans productive as global climate change takes a toll on today's dominant microbial species, they concluded in last week's issue of Proceedings of the National Academy of Sciences.

-- Rick Weiss

Airflow Above Ionosphere May Cause Disruptive Plasma

Gigantic electrically charged gas bubbles that form in the upper reaches of the atmosphere -- sometimes disrupting radio, Global Positioning System and other transmissions -- are probably caused by a force similar to wind shear -- the meeting of winds traveling in opposite directions.

The bubbles, which can reach 1,200 miles high, were first identified in the mid-1970s as a cause for disruptions in satellite communications. But none of the proposed theories could explain why they formed.

New work by a NASA-funded research team, led by David L. Hysell of Cornell University, found that there is a westward flow of air just below the eastward-moving high ionosphere. The periodic meeting of the two is what is believed to set up a shear, which in turn produces waves that are the seeds of the bubbles.

The bubbles -- or, more formally, electrically charged plasma -- usually appear at night and occur somewhere above the globe on about 50 percent of evenings. They generally form about 250 miles above the Earth, almost always above the equator. Unlike more earthbound gas bubbles, these plasma formations do not burst but gradually diffuse into the atmosphere.

The researchers did their work on the Marshall Islands atoll of Kwajalein, in the Pacific Ocean near the equator, and used sounding rockets to measure wind speeds and directions in the ionosphere. Hysell said that the team's discovery could lead to better forecasting of the radio disruptions because "we now know what to look for."

The discovery was described in a series of papers published or submitted to geophysical journals, including the Journal of Geophysical Research.

-- Marc Kaufman