May 21, 2008 -- The metaphorical gold standard of medical treatment might one day turn out to be a literal gold treatment.

By hacking off the ends of a failed HIV drug and sticking the resulting molecules onto gold nanoparticles, scientists have stopped HIV from infecting lab-cultured white blood cells. It is the first time gold nanoparticles have shown potential in therapies for HIV.

May 21, 2008 -- In a stroke of cosmic luck, astronomers for the first time witnessed the start of one of the universe's most fiery events: the end of a star's life as it exploded into a supernova.

On Jan. 9, astronomers used a NASA X-ray satellite to spy on a star already well into its death throes, when another star in the same galaxy started to explode. The outburst was 100 billion times brighter than Earth's sun.

May 21, 2008 -- Paleontologists are exchanging finely-chiseled blows over the mightiest rodent to bestride the Earth.

The rat-like beast, dubbed Josephoartigasia monesi, leapt into the headlines in January, when Uruguayan experts said it weighed just over a ton.

May 21, 2008 -- Herds of dinosaurs once wandered Arabia and have left behind some footprints in what's being called the first set of trackways discovered on the Arabian Peninsula.

The approximately 165 million-year-old tracks in Yemen appear to have been made by at least two types of dinosaurs, with young and old dinos traveling together along what was once a coastal mud flat.

May 21, 2008 -- Researchers say they have found about half of the universe's missing matter hidden in the spaces between billions of galaxies thanks to the Hubble telescope.

This normal matter, which is called baryons, was created during and after the Big Bang, and should not be confused with dark matter, researchers said.

May 21, 2008 -- A Japanese center which says it has trained a dog to sniff out human cancer cells is cloning the animal in South Korea, a Seoul-based biotechnology company and the dog's owner said Wednesday.

Cloned fetuses from the black labrador retriever named Marine were last month implanted into a surrogate mother dog, said Ra Jeong-Chan, president of RNL Bio.

May 20, 2008 -- A closer look at the remnants of mid-latitude glaciers on Mars has revealed signs of deep, icy rivers in the recent geologic past, say researchers who have published the discovery in the May issue of the journal Geology.

Mars glaciologist James Dickson of Brown University and his colleagues followed the trail of telltale glacial remnants at the edges of Mars' northern lowlands and were surprised to find signs that a glacier once traveled in a direction now uphill, toward a canyon's edge.

May 20, 2008 -- Countries thinking of joining the rush for biofuels run the risk of planting invasive plant species that could wreak environmental and economic havoc, biologists warned on Tuesday.

In a report issued on the sidelines of a major U.N. conference on biodiversity, an alliance of four expert groups urged governments to select low-risk species of crops for biofuels and impose new controls to manage invasive plants.

May 20, 2008 -- Strong, versatile little "nanotubes" made out of carbon are considered future stars in nanotechnology research in medicine and industry. Now a study finds that longer threads of the stuff mimic the toxic qualities of asbestos, renewing questions about how carbon nanotubes can be used safely.

Researchers with British institutes and the U.S.-based Project on Emerging Nanotechnologies injected mice with asbestos and with commercial samples of carbon nanotubes of varying sizes. When they examined the lining of the rodents' abdominal cavities, the researchers observed that longer nanotubes behaved like asbestos, provoking inflammation and lesions.

May 20, 2008 -- The function of tails has somewhat stumped scientists over the years, but now researchers have determined that female rats' tails play a very important role in the rodent mating process.

Female rats use their tails to direct, stimulate and balance their male partners, scientists determined.

May 20, 2008 -- Experts found a tiny gold combined toothpick and earwax spoon, believed to be more than 385 years old, during the search for a shipwrecked Spanish galleon off the Florida Keys.

The late 16th or early 17th century grooming tool, which weighs only about an ounce, was located by Blue Water Ventures diver Chris Rackley as he searched the area about 22 feet below the surface and 40 miles west of Key West. He says its value could exceed $100,000.

May 20, 2008 -- Scientists said Tuesday they had "resurrected" a gene from the extinct Tasmanian tiger by implanting it in a mouse, raising the future possibility of bringing animals such as dinosaurs back to life.

In what they describe as a world first, researchers from Australian and U.S. universities extracted a gene from a preserved specimen of the doglike marsupial -- formally known as a thylacine -- and revived it in a mouse embryo.

May 19, 2008 -- The wasting of food is wasting water -- a lot of it -- and there isn't much to spare.

A report released this week by the Stockholm International Water Institute says that as much as 50 percent of the calories grown globally don't make it to the table.