Building a Quasicrystal

Cover: New experimental evidence supports an unusual model of quasicrystal structure in some metal alloys. Such a material's complex atomic arrangement (inset) can be understood in terms of a single repeating cluster that shares atoms with neighboring clusters, like overlapping 10-sided tiles (background). (Images: Paul Steinhardt)

Electron Mix Binds Water Molecules
The first experimental evidence that hydrogen bonds are partly covalent bonds may open the door to a better understanding of the intermolecular links that determine water's distinctive properties.

Multiplied immune cells combat HIV
Immune cells called cytoxic T lymphocytes can be taken from a HIV-positive patient, massively replicated, and reinjected into the individual to temporarily fight the AIDS virus.

Scoping out the homes of gamma-ray bursts
Astronomers have begun to identify the galaxies where energetic gamma-ray bursts originate.

Which is healthier, the wining or the dining?
Wine drinkers tend to have more healthful diets and lifestyles than nondrinkers, suggesting that it is not the libation that lowers wine drinkers' risk of heart disease.

Cellular conversion turns brain into blood
Under the proper conditions, the unspecialized cells that normally give rise to various tissue types in the brain can also act as bone marrow, the crucial source of an adult body's blood cells.

A bug's kiss has chemistry in humans
A protein in the saliva of a blood-sucking insect uses nitric oxide in a unique way to open up blood vessels and prevent clotting.

Stinking beauty betrays dung beetles
A lovely purple flower in Borneo provides one of the rare examples of a specialized, pungent fragrance attracts dung beetles.

Infant temperament shows its flexibility
Early behavioral styles, such as shyness or sociability, among infants often undergo noticeable shifts by age 4 1/2.

Biology

Cancer drug reveals unexpected partner
The drug taxol may make tumor cells die by binding to a protein called Bcl-2, a more direct anticancer effect than anticipated.

Milking mice for mammary gland genes
In pregnant mice, so-called Hox genes help the animal's mammary gland prepare to secrete milk.

Environment

Beluga whales' mercurial status
Mercury pollution in the St. Lawrence River estuary may be playing a role in the high incidence of cancers among beluga whales.

Pesticides and breast cancer
Measurable levels in blood of two persistent pesticides appear to increase a woman's risk of developing breast cancer.

Astronomy

Plethora of quasars
Observing a quadrant of the sky at visible-light, infrared, and radio wavelengths, astronomers have discovered dozens of quasars, including the most distant one known.

Asteroid rendezvous: Better luck next year
Delayed by a year because of mishaps that occurred when the spacecraft lost radio contact with Earth, the Near Earth Asteroid Rendezvous mission is now scheduled to meet up with an asteroid called 433 Eros on Valentine's Day, 2000.

Food & Nutrition

E. coli can take flight
Fruit flies can carry a common food-poisoning agent into wounds on an apple, a study shows, but pretreating the fruit with rot-inhibiting microbes can prevent the infection.

Food poisoning: Sprouts linked to bouts
Sprouts of contaminated alfalfa seeds triggered a major North American Salmonella poisoning outbreak and illustrated why sprouts are liable to harbor food-borne pathogens.

Physics

Tiny satellite tests gravity's grip
The fall of a tiny glass block in a Colorado laboratory yielded a new measurement of gravity's strength, increasing confidence in the most widely accepted value for the elusive gravitational constant.

Fusion hopeful hits temperature high
The world's most powerful X-ray machine scorched plasmas to more than 2 million degrees and crushed fuel capsules, two milestones toward sustainable fusion.

More Than the Brain's Drain
Does cerebrospinal fluid help the brain convey messages?
The fluid that bathes the brain and spinal cord may be used by those organs to send signals for sleep, appetite, and sex.

A Quasicrystal Construction Kit
Picturing complex alloy structures as overlapping atomic clusters
A quasicrystal's atomic arrangement can be understood in terms of a single repeating cluster that shares atoms with neighboring clusters.

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