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Features

Deforestation in the Tropics

Government policies that encourage exploitation-in particular excessive logging and clearing for ranches and farms-are largely to blame for the accelerating destruction of tropical forests

By Robert Repetto

The Unusual Origin of the Polymerase Chain Reaction

A surprisingly simple method for making unlimited copies of DNA fragments was conceived under unlikely circumstances-during a moonlit drive through the mountains of California

By Kary B. Mullis

Impact Cratering on the Earth

The explosion of the world's nuclear arsenal could not match the power released when a kilometer-size meteorite hits the earth. Have impacts even more powerful altered biological as well as geologic evolution?

By Richard A. F. Grieve

Advanced Light-Water Reactors

New designs that include "passive" safety features can make nuclear power more attractive, but only if attention is paid to economics, effective management and rigorous training methods

By Neil E. Todreas and Michael W. Golay

What the Brain Tells the Eye

A circadian clock adjusts the sensitivity of the horseshoe crab's eyes. Study of the mechanism opens a window on the brain's control of sensory organs in other animals as well

By Robert B. Barlow Jr.

The Transformation of the Kalahari !Kung

Why after centuries of stability has this society, an apparent relic of ancient hunting and gathering groups, abandoned many of its traditional ways?

By John E. Yellen

Departments

  • 50 and 100 Years Ago: April 1990

  • Right to Lie?

  • Slow Boat to Mars

  • Acid Test

  • Science Behind the Wall

  • Zap!

  • All about Eve

  • Gone in a Flash

  • Green Thumbs

  • Net Result: Folded Protein

  • Space Invaders

  • Tone of Relief

  • Mandelbrot Set-To

  • What is Happening at the Center of Our Galaxy?

  • Milliken & Co.

  • Of Mice and Men

  • Atmosphere of Uncertainty

  • Breakup?

  • Cashcowosaurus

  • Ancient Glazes

  • Letters

    Letters to the Editors, April 1990

  • Recommended

    Books, April 1990

  • Amateur Scientist

    The Amateur Scientist, April 1990

  • Departments

    The Analytical Economist: Budgeting Smoke and Mirrors

  • Essay: A New Initiative to Save the Planet

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April 1990

Think Outside the Gift Box