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On the Cover

July-August 2001 Volume 89, Number 4

Titanium silicon carbide is a member of a recently discovered class of ceramics with remarkable properties. The compounds discussed by Michel W. Barsoum and Tamer El-Raghy in "The MAX Phases: Unique New Carbide and Nitride Materials" may one day help increase the efficiency of jet engines and industrial chemical processes, among other applications. ...


FEATURE ARTICLES

The MAX Phases: Unique New Carbide and Nitride Materials *

Michel Barsoum, Tamer El-Raghy

Ternary ceramics turn out to be surprisingly soft and machinable, yet also heat-tolerant, strong and lightweight


Iris Recognition *

John Daugman

The colored part of the eye contains delicate patterns that vary randomly from person to person, offering a powerful means of identification


Protostars

Thomas Greene

"Stellar embryology" takes a step forward with the first detailed look at the youngest Sun-like stars


The Nature of Emotions *

Robert Plutchik

Human emotions have deep evolutionary roots, a fact that may explain their complexity and provide tools for clinical practice


Science and Uncertainty in Habitat Conservation Planning *

Laura Watchman, Martha Groom, John Perrine

A review of 43 habitat conservation plans reveals numerous ways to reduce uncertainty for landowners and imperiled species alike


* access restricted to members and subscribers


DEPARTMENTS

COMPUTING SCIENCE

Randomness as a Resource

Brian Hayes

Prospecting for the mother lode of disorder

MACROSCOPE

Infecting Other Worlds

Richard Greenberg, B. Randall Tufts

Should space explorers observe "planetary protections"?

MARGINALIA

Hi O Silver

Roald Hoffmann

The beautiful chemistry of oxidation states

ENGINEERING

China Journal II *

Henry Petroski

A visit to China's Three Gorges Dam

SCIENCE OBSERVER

Moonbounce

David Schneider

Measuring Earth's reflectivity by observing the Moon

It Came From . . . The Atmosphere

Michael Szpir

Strange sounds from atmospheric radio waves

FROM THE PRESIDENT


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