SCIENCE

Added to water in the proper proportion, the particles formed a quivering crystal.

When the researchers brought a magnet close to the liquid, they found they could compress or expand the crystal's invisible lattice by altering the strength of the magnetic field.

The distance between layers of particles varied from 169 to 274 nanometers -- a lot, in this world. It allowed enough change in the diffraction and reflectance properties of the crystal that the liquid could be made to take on every hue from violet to red.

This property of "tunable" color in liquid may prove useful in sensing devices, electronic display screens, even disappearing inks. The research appears in Angewandte Chemie International Edition.

-- David Brown

Antidepressants, Suicide Tries

Two new studies in the American Journal of Psychiatry this month show that fewer people attempt suicide in the month after they start antidepressant treatment than in the month before they start taking the drugs. The studies add a new layer of evidence to the controversy over whether medications such as Prozac and Paxil cause people to become suicidal.

The studies examined the records of more than 330,000 patients in Group Health Cooperative, aSeattle-based health-care system, and of veterans who received care through the Department of Veterans Affairs.

Greg Simon of the Seattle health-care system and Robert Gibbons of the University of Illinois at Chicago, who analyzed the records of veterans, said the decline in suicide attempts following the start of treatment was seen among all age groups. Similar benefits were also detected after the introduction of other kinds of treatment, including psychotherapy.

The Food and Drug Administration has asked the makers of antidepressants to place "black box" warnings on the drugs, following evidence from placebo-controlled trials that suggested that patients getting the drugs displayed more suicidal behavior than patients who got sugar pills. Antidepressant prescription rates have fallen steeply since the warnings went into effect. Some experts have wondered whether the drugs might increase suicidal behavior among some individuals while lowering the risk among others.

-- Shankar Vedantam