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Features

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

By Roy J. Britten and 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

By Egon T. Degens and David A. Ross

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

By 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

By 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

By 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

By George H. Heilmeier

Departments

  • 50 and 100 Years Ago: April 1970

  • The Delivery of Medical Care

  • Science and the Citizen: April 1970

  • Chemistry by Computer

  • Mathematical Games

  • Letters

    Letters to the Editors, April 1970

  • Recommended

    Books

  • Amateur Scientist

    The Amateur Scientist

  • Departments

    The Authors

  • Bibliography

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April 1970

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