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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


SCIENTISTS’ BOOKSHELF

Apparatus and Acumen

Arthur Greenberg

A review of Instruments and Experimentation in the History of Chemistry, edited by Frederic L. Holmes and Trevor H. Levere.

See all book reviews for this issue.


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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