Scientific American Magazine Vol 222 Issue 4

Scientific American Magazine

Volume 222, Issue 4

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Features

The Delivery of Medical Care

Medical care in the U.S. is expensive and poorly distributed, and national health insurance will make things worse. What is needed is an innovative system in which the sick are separated from the well

Sidney R. Garfield

Repeated Segments of DNA

In cells of higher organisms a significant fraction of the genetic material appears in as many as a million identical or very similar copies. The origin and function of repetitive DNA remain unknown

Roy J. Britten, David E. Kohne

The Red Sea Hot Brines

Three pools of very salty hot water have accumulated at the bottom of the Red Sea. The sediments in these pools are rich in minerals deposited from the brines

Egon T. Degens, David A. Ross

Chemistry by Computer

Computed quantum-mechanical models of the electronic structure of atoms and molecules can provide a reliable and comprehensive alternative to the traditional experimental approach to chemistry

Arnold C. Wahl

Pesticides and the Reproduction of Birds

High concentrations of chlorinated hydrocarbon residues accumulate in such flesh-eaters as hawks and pelicans. Among the results are upsets in normal breeding behavior and eggs too fragile to survive

David B. Peakall

How is Muscle Turned On and Off?

Work with muscle fiber of a giant barnacle supports the hypothesis that a flow of calcium ions in response to a nerve signal gives rise to contraction, and that withdrawal of the ions results in relaxation

Graham Hoyle

Hyperactive Children

Certain children are more than usually restless, noisy, destructive and distractible. Their behavior appears to be a distinct disease syndrome that may well be innate

Mark A. Stewart

Liquid-Crystal Display Devices

Liquid crystals (fluids that have certain crystalline properties) respond to an electric field by becoming cloudy or changing color. Effects of this kind can be used for the presentation of images

George H. Heilmeier

Departments

Letters to the Editors, April 1970

50 and 100 Years Ago: April 1970

The Authors

Science and the Citizen: April 1970

Mathematical Games

The Amateur Scientist

Books

Bibliography