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The Rise of a Maya Merchant Class

The centuries just before the Spanish conquest are usually viewed as a time of Maya decline and decadence. A review of the evidence suggests instead that new leaders were pursuing new objectives

By Jeremy A. Sabloff and William L. Rathje

The Final Steps in Secretion

Precisely how does the living cell secrete substances? It seems that such substances are packaged in a membrane that releases its contents when it fuses with the outer membrane of the cell

By Birgit Satir

The Debate over the Hydrogen Bomb

A recently declassified report sheds light on the original U.S. decision to develop the "Super." The unanimous opposition of the Oppenheimer committee, overruled then, appears now to have been basically correct

By Herbert F. York

Quarks with Color and Flavor

The particles called quarks may be truly elementary. Their "colors" explain why they cannot be isolated; their "flavors" distinguish four basic kinds, including one that has the property called charm

By Sheldon Lee Glashow

Natural-Uranium Heavy-Water Reactors

In the U.S. power reactors are fueled with enriched uranium and are cooled by ordinary water. The Canadian "Candu" system, working with unenriched uranium and heavy water, offers interesting alternatives

By Hugh C. McIntyre

Musical Illusions

Presenting certain sequences of tones simultaneously to both ears produces paradoxical auditory illusions. Surprisingly, right-handed subjects and left-handed subjects perceive the illusions differently

By Diana Deutsch

Image Reconstruction from Projections

A mathematical technique makes it possible to use a series of X-ray exposures made from different angles to reveal the internal organs of the body in cross section instead of superimposed on one another

By Richard Gordon, Gabor T. Herman and Steven A. Johnson

Active Animals of the Deep-Sea Floor

Baited automatic cameras dropped to the bottom of the ocean reveal a surprising population of large fishes and other scavengers that find and consume dead animals that fall from the waters far above

By John D. Isaacs and Richard A. Schwartzlose

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