Blade of Grass

Social history often returns to the theme of the lawn versus crabgrass. Properly nurtured, suburban sod serves as a symbol of gentility and social superiority. Dominance over the encroachments of chickweed, par-tridgeberries, plantains, rushes and innumerable other undesirable forms of vegetation proclaims the orderliness, the rightness of an existence distanced from the rigors of urban living. F. Herbert Bormann, an emeritus professor of forest ecology at the Yale University School of Forestry...

These huge swift creatures were the dominant carnivores of the continent for millions of years until competitors drove

Phorusrhacos Longissimus

It is a summer day on the pampas of central Argentina some five million years ago. A herd of small, horselike mammals are grazing peacefully in the warm sun. None of the animals is aware of the vigilant creature standing 50 meters away in the tall grass. Most of the watcher's trim, feathered body is concealed by the vegetation. Its eyes, set on the sides of a disproportionately large head perched on a long and powerful neck, are fixed on the herd. The head moves from side to side in short,...

Users and HIV Infection

Are infected with the human immunodeficiency virus, but it is unclear how many of them were infected through injection or through sex with a drug user. In the U.S., however, one third of all AIDS cases can be attributed to drug injection. of American culture from T-shirts and blue jeans to fast food many different countries have adopted the practice. The fact that cocaine, heroin and related drugs are illegal encourages the use of injection. Severe statutory restrictions greatly increase the...

Liquid Mirror Telescopes at Work

Homemade Telescope Liquid Mirror

A mirror, three meters in diameter, made recently by the National Aeronautics and Space Administration bottom left will search for space debris. The diagram top shows how the mirror works. The mirror and bearing rest on a three-point mount the axis of rotation is aligned vertically using two adjustable screws. A synchronous electric motor, connected by pulleys and a belt, drives the turntable under the mirror's container. An AC power supply, stabilized with a crystal oscillator, controls the...