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Health Maintenance Organizations

A decade ago the Federal Government endorsed the concept of prepaid medical care. Today the number of HMO's is less than was envisioned then, but it is nevertheless increasing

By Ernest W. Saward and Scott Fleming

The Bizarre Spectrum of SS 433

Displaced emission lines found in the spectrum of this extraordinary stellar object suggest that it is spewing two narrow high-speed jets of matter in opposite directions. How can such behavior be explained?

By Bruce Margon

The Causes of Color

They are diverse, but they all stem from the same root: It is the electrons in matter, through their varied responses to different wavelengths of light, that make the world a many-colored place

By Kurt Nassau

The Southern Appalachians and the Growth of Continents

A large seismic-reflection survey suggests that for at least half of the history of the earth continents have evolved by the stacking and shuffling of relatively thin sheets of material at their margins

By Frederick A. Cook, Larry D. Brown and Jack E. Oliver

Positron-Emission Tomography

This technique displays the concentration of radioactively labeled substances in the living body with improved clarity. It holds much promise for both biological investigations and clinical diagnosis

By Michel M. Ter-Pogossian, Marcus E. Raichle and Burton E. Sobel

The Buoyancy of the Chambered Nautilus

The animal trims its weight and gains mobility by dividing its shell into compartments and removing their watery content. It succeeds in spite of the ocean's pressure, which tends to drive water back in

By Peter Ward, Lewis Greenwald and Olive E. Greenwald

Departments

  • 50 and 100 Years Ago, October 1980

  • Mathematical Games, October 1980

  • Monoclonal Antibodies

  • Science and the Citizen, October 1980

  • Oil Mining

  • Bibliography, October 1980

  • Letters

    Letters to the Editors, October 1980

  • Recommended

    Books, October 1980

  • Amateur Scientist

    The Amateur Scientist, October 1980

  • Departments

    The Authors, October 1980

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October 1980

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