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Iron Deficiency

One of the most common health problems worldwide and potentially one of the most treatable, iron deficiency can have devastating effects. It can jeopardize a child's mental and physical development...

By Nevin S. Scrimshaw


These cagelike molecules constitute the third form of pure carbon (the other two are diamond and graphite). C 60 , the archetype, is the roundest molecule that can possibly exist...

By Richard E. Smalley and Robert F. Curl

End of the Proterozoic Eon

Some 800 million years ago the earth entered a period of major tectonic and environmental change. An increase in oxygen levels probably occurred at this time, which in turn may have opened the door to large animals...

By Andrew H. Knoll

How the Immune System Learns about Self

The immature immune system produces cells that would attack every tissue in the body. Within the thymus, however, it learns which cells would be harmful, useless or useful

By Harald von Boehmer and Pawel Kisielow

Natural Selection and Darwin's Finches

The finches of the Galápagos—the classic example of how natural selection works over millions of years-have now been observed to evolve in real time. A single drought can change a population...

By Peter R. Grant

The Origins of the Asteroids

Once regarded as "vermin of the skies," asteroids are now known to offer important clues to the birth of the solar system. They are the remnants of a planet that failed to form

By Richard P. Binzel, M. Antonietta Barucci and Marcello Fulchignoni

Focused Ion Beams

Liquid-metal sources, their conical shape generated by electrostatic fields, produce charged atoms that can cut away and rebuild circuits on a microscopic scale

By Jon Orloff

Soiled Shores

Cleanup technologies, from hot-water washing to fertilizer, were applied to the mess left by the Exxon Valdez oil spill. But nature, it seems, fared better on its own.

By Marguerite Holloway


  • 50 and 100 Years Ago: October 1991

  • Howls of Dismay

  • Greenhouse Gusher

  • Sol's Plumage

  • Spin Cycle

  • The Danger from Kuwait's Air Pollution

  • Crossed Lines

  • Sharper Image

  • Word Games

  • Sharing Germplasm

  • Digital Dyslexia

  • The Satisfaction of Delayed Gratification

  • The Light Fantastic

  • Don't Change the Channel, Rearrange that Face

  • Secret Garden

  • Body Heat

  • How's My Driving?

  • Letters

    Letters to the Editors, October 1991

  • Recommended

    Book Reviews, October 1991

  • Mathematical Recreation

    Concentration: A Winning Strategy

  • Departments

    An Illusion of Economic Stability?

  • Quantum English

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