Hard lesson

I read with interest “Coronary calcium may predict death risk” (SN: 9/13/03, p. 174: Coronary calcium may predict death risk). Can you tell me what contributes to these deposits in arteries?

Julie Winslett
Dahlonega, Ga.

It’s not ingestion of calcium, at least in people with normal kidney function, says Paolo Raggi of Tulane University in New Orleans. Rather, the condition stems from damage to vessel walls wrought by high blood pressure, high cholesterol, smoking, and other factors.–N. Seppa

Subsonic booms

There is a striking similarity in the wave patterns of the ash plume on the cover of the Sept. 13 issue (for “Danger in the Air: Volcanoes have a long reach,” SN: 9/13/03, p. 168: Danger in the Air) and those in the gas of the Perseus Cluster (“A Low Note in Cosmos: Sounding out a new role for black holes,” SN: 9/13/03, p. 163: A Low Note in Cosmos: Sounding out a new role for black holes). Could it be that volcanoes produce sound waves we can’t hear but can see in the plume?

Paul Heins
Gainesville, Fla.

Volcanoes do indeed produce abundant pressure waves that have frequencies below the threshold of human hearing. In fact, because these pulses can travel thousands of kilometers, they can reveal distant, major eruptions.–S. Perkins

Who’s to know?

It’s very appealing to think that a noninvasive test could pick up the earliest signs of cancers or cardiovascular disease (“To Your Health? Controversy surrounds whole-body scans–a costly screen for silent threats,” SN: 9/20/03, p. 184: To Your Health?). Despite passionate testimonials of how whole-body CT scanning “saved my life,” we don’t know what the tumors found really would have done. We don’t know that these patients’ lives were improved, much less saved. In medicine today, intelligence doesn’t always prevail when it comes to clinicians ordering laboratory tests. How can we expect patients to do any better?

Alfredo A. Sadun and
Rebecca E. Sadun
Keck-USC School of Medicine
Los Angeles, Calif.


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