Postnatal neurodevelopmental disorders: meeting at the synapse?

We often think of neurodevelopmental disorders as beginning before birth, and many certainly do. A handful, however, strike many months after birth, following a period of apparently normal growth and development. Autism and Rett syndrome are two such disorders, and here I consider some of their similarities at the phenotypic and pathogenic levels. I propose that both disorders result from disruption of postnatal or experience-dependent synaptic plasticity.     

Biotechnology and the environment: What is at risk?

This paper argues that the new biotechnologies will affect the natural environment primarily in two ways: by bringing relatively wild areas, such as forests and estuaries, under domestication, and by forcing areas now domesticated, such as farms, out of production, because of surpluses. The problem of the safety of biotechnology—the risk of some inadvertent side-effect—seems almost trivial in relation to the social and economic implications of these intentional uses. The paper proposes that we should be more concerned about the successful uses of biotechnology than about the possible mishaps or failures.Mark Sagoff is Senior Research Associate and Acting Director of the Institute for Philosophy and Public Policy at the University of Maryland. His book,The Economy of the Earth: Philosophy, Law and the Environment (Cambridge University Press, 1988), deals with normative and conceptual issues in environmental law. Sagoff's work in ethical issues in biotechnology has received support from the National Science Foundation.     

General relativity at 75: how right was einstein?

The status of experimental tests of general relativity is reviewed on the occasion of its 75th anniversary. Einstein's equivalence principle is well supported by experiments such as the E?tv?s experiment, tests of special relativity, and the gravitational redshift experiment. Tests of general relativity have reached high precision, including the light deflection and the perihelion advance of Mercury, proposed by Einstein 75 years ago, and new tests such as the Shapiro time delay and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected to an accuracy of 1 percent on the basis of measurements of the binary pulsar. The status of the "fifth force" is discussed, along with the frontiers of experimental relativity, including proposals for testing relativistic gravity with advanced technology and spacecraft.     

1981N1: A Neptune Arc?

An object in the vicinity of Neptune detected in 1981 by simultaneous stellar occultation measurements at observatories near Tucson, Arizona, was interpreted as a new Neptune satellite. A reinterpretation suggests that it may have instead been a Neptune arc similar to one observed in 1984. The 1981 object, however, did not occult the star during simultaneous observations at Flagstaff, Arizona. This result constrains possible arc geometries.