When people suffer severe brain damage — as a result of car crashes, for example, or falls or aneurysms — they may slip into a coma for weeks, their eyes closed, their bodies unresponsive.

Some recover, but others enter a mysterious state: eyes open, yet without clear signs of consciousness. Hundreds of thousands of such patients in the United States alone are diagnosed in a vegetative state or as minimally conscious. They may survive for decades without regaining a connection to the outside world.

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Scientists have developed a new weapon against H.I.V.: a molecular mimic that invades a cell and steals essential proteins from the virus.

A study published in Science on Thursday reported that this viral thief prevented H.I.V. from multiplying inside of monkeys.

The new therapeutic approach will soon be tested in people, the scientists said. Four or five volunteers with H.I.V. will receive a single injection of the engineered virus. “This is imminent,” said Leor Weinberger, a virologist at the University of California, San Francisco, who led the new study.

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A new study describes 700,000-year-old teeth and arm bones from one of our most enigmatic relatives: a toddler-size “hobbit” who lived on a small island between the Indian and Pacific Oceans.

The study, published on Tuesday in the journal Nature Communications, suggests that the species, Homo floresiensis, sometimes nicknamed hobbits, could be even smaller than previously thought. But the results still left scientists divided over how such exceptional humans evolved.

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There is no rose without thorns, the old saying goes. But to botanists, there is no rose with thorns: The spiky outgrowths of a rose stem are called “prickles,” and are biologically distinct from the stiff, woody thorns of other plants.

Prickles are a remarkable example of evolution repeating itself. In the past 400 million years, plants evolved them 28 different times. Roses grow prickles on their stems, whereas others grow them on their leaves or their fruits. Grasses grow tiny prickles on their flowering tufts. Solanum atropurpureum, a wild relative of potatoes that grows in Brazil, has prickles so nasty that they’ve earned it two fearsome nicknames: “Purple devil” and “Malevolence.”

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For generations, physicists have puzzled over life. Their theories about matter and energy have helped them understand how the universe produced galaxies and planets. But physicists have struggled to understand how lifeless chemical reactions give rise to the complexity stored in our cells.

In a new book, “Life as No One Knows It: The Physics of Life’s Emergence,” out on Aug. 6, Sara Walker, a physicist at Arizona State University, offers a theory that she and her colleagues believe can make sense of life. Assembly theory, as they call it, looks at everything in the universe in terms of how it was assembled from smaller parts. Life, the scientists argue, emerges when the universe hits on a way to make exceptionally intricate things.

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