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Ultracold Neutrons

Neutrons moving so slowly that they cannot penetrate a solid surface can be confined in a metal bottle. By storing them for long intervals it may be possible to measure fundamental properties of the neutron

By J. M. Pendlebury, P. Ageron, R. Golub and W. Mampe

The Year without a Summer

In 1816 in New England it snowed in June, and then killing frosts continued through August. The cause was the explosion ofa volcano in Indonesia. The economic and social consequences are instructive

By Elizabeth Stommel and Henry Stommel

The Theory of Knots

A piece of knotted string with its ends joined is a good physical model of an abstract mathematical knot. The theory of knots seeks to analyze the different ways of tracing a knotted curve in space

By Lee Neuwirth

The Nerve-Growth Factor

This protein plays a key role in the formation of the nervous system. It has also been employed as an "Ariadne's thread" to explore mechanisms of nerve-cell growth and differentiation

By Pietro Calissano and Rita Levi-Montalcini

The History of the Atlantic

The ocean is 165 million years old. Its growth and the topography of its bottom are explained by plate-tectonic theory, deep probes of the bottom and measurements of heat flow and magnetism

By Christopher Tapscott and John G. Sclater

External Human Fertilization

The procedure whereby a new human being is conceived in a glass dish has raised issues that must be faced by investigators and by the public. The debate needs to be informed by known facts of human development

By Clifford Grobstein

Automatic Control by Distributed Intelligence

Microelectronics makes it possible to run an industrial plant with a multitude of "chips" interconnected in a hierarchy extending from the control of one machine to the integration of the entire plant

By Charles Rose, Irving Lefkowitz and Stephen Kahne

A Neolithic Flint Mine

The start of farming in prehistoric Europe increased the demand for flint tools. Excavation at one flint-rich valley in the Netherlands shows how miners dug up flints by the ton more than 5,000 years ago

By Peter W. Bosch

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