Two controversial studies suggest antiviral mechanism called RNA interference may exist in vertebrates after all.

Organisms including plants, fungi and flies fight viruses using an elegant mechanism involving RNA snippets that mammals apparently ditched at some point in their evolutionary history. At least, that is what scientists thought - but two controversial reports published today suggest otherwise.

The RNA defence mechanism hinges on the fact that most viruses copy their RNA when they replicate. Invaded cells recognize viral RNA and automatically launch RNA interference, or RNAi, to stop the virus from multiplying and spreading to other host cells.

The RNAi process begins when an enzyme known as DICER chops a long strand of the virus RNA into chunks that are about 22 genetic letters long. Next, another one of the host cell's molecules ships the fragments off to the invading virus where they cling to the viral RNA, preventing its replication.

"It's an incredible system because it can be adapted to any virus," says Olivier Voinnet, a molecular biologist at the Swiss Federal Institute of Technology in Zurich, Switzerland, and an author of one of the papers, which are published in Science^{1, 2}.

More than 1,000 old concrete buildings in Los Angeles and hundreds more throughout the county may be at risk of collapsing in a major earthquake, according to a Times analysis.

By the most conservative estimate, as many as 50 of these buildings in the city alone would be destroyed, exposing thousands to injury or death.

A cross-section of the city lives and works in them: seamstresses in downtown factories, white-collar workers in Ventura Boulevard high-rises and condo dwellers on Millionaires' Mile in Westwood.

Despite their sturdy appearance, many older concrete buildings are vulnerable to the sideways movement of a major earthquake because they don't have enough steel reinforcing bars to hold columns in place.

Los Angeles officials have known about the dangers for more than 40 years but have failed to force owners to make their properties safer. The city has even rejected calls to make a list of concrete buildings.

In the absence of city action, university scientists compiled the first comprehensive inventory of potentially dangerous concrete buildings in Los Angeles.

The scientists, however, have declined to make the information public. They said they are willing to share it with L.A. officials, but only if the city requests a copy. The city has not done so, the scientists said.

About 46 million years ago, a mosquito sunk its proboscis into some animal, perhaps a bird or a mammal, and filled up on a meal of blood. Then its luck turned for the worse, as it fell into a lake and sunk to the bottom.

Normally this wouldn't be newsworthy, and nobody would likely know or care about a long-dead insect in what is now northwest Montana. But somehow, the mosquito didn't immediately decompose - a fortuitous turn of events for modern-day scientists - and became fossilized over the course of many years, said Dale Greenwalt, a researcher at the National Museum of Natural History in Washington, D.C. Greenwalt discovered the mosquito fossil after it was given to the museum as a gift, and he immediately realized the specimen's rarity.

It is, in fact, the only blood-engorged mosquito fossil found, Greenwalt told LiveScience. The fossil is even stranger because it comes from shale, a type of rock formed from sediments deposited at the bottom of bodies of water, as opposed to amber, the age-old remains of dried tree sap, in which insect remnants are generally better preserved.

"The chances that such an insect would be preserved in shale is almost infinitesimally small," Greenwalt said.

In their study, Greenwalt and his collaborators bombarded the mosquito fossil with molecules of bismuth, a heavy metal, which vaporizes chemicals found in the fossil. These airborne chemicals are then analyzed by a mass spectrometer, a machine that can identify chemicals based on their atomic weights, Greenwalt said. The beauty of this technique, called time-of-flight secondary ion mass spectrometry, is that it doesn't destroy the sample - previously, similar techniques required grinding up portions of fossils, he added. The analysis revealed hidden porphyrins, organic compounds found in hemoglobin, the oxygen-carrying protein in blood, hidden in the fossilized mosquito's abdomen.

Show up ISON! You have got the green light! The latest images of ISON show the 'Comet of the Century' shining green! October 8 2013This stunner was captured by Adam Block on Ocotober 8 2013, just before sunrise, atop Mount Lemmon. This beautiful image features ISON's greenish coma, trailed by a long, straight tail.

Austrian scientists have found that 19 Tyrolean men alive today are related to Oetzi the Iceman, whose 5,300-year-old frozen body was found in the Alps.

Their relationship was established through DNA analysis by scientists from the Institute of Legal Medicine at Innsbruck Medical University.

The men have not been told about their connection to Oetzi. The DNA tests were taken from blood donors in Tyrol.

A particular genetic mutation was matched, the APA news agency reports. Oetzi's body was found frozen in the Italian Alps in 1991.

• Scientists found that three Alpine swifts travelled 1,240 miles non-stop

• The birds were found to eat and drink while in the air by Swiss researchers

• Instead of resting at night, data collected suggested they carried on
  gliding
  
  
  

  Record breakers: Scientists say that a 1,240-mile flight carried out by three Alpine Swifts is the longest recorded flight made by any bird
  Researchers who tracked a group of migrating birds have discovered that they flew for 200 days non-stop between Africa and Europe.
  
  Scientists say that the 1,240-mile flight carried out by three Alpine Swifts is the longest recorded flight made by any bird.
  
  Although experts have speculated that a related species, the common swift, remains airborne for much of the year, the latest research is the first to provide data over such a long period.

Something is not quite right inside the Earth's core. When seismic waves from earthquakes ripple through its solid center, they hit a speed bump.

The seismic vibrations should zip along about 30 percent faster than their actual speed, according to experiments and computer models recreating the conditions inside the inner core. Scientists have tried to explain this odd observation by playing around with the core's properties - adding metal such as nickel, or suggesting that iron acts strangely deep inside the planet.

Now, a new computer model of Earth's inner core explains the seismic wave slowdown via changes in iron's strength just before the metal melts. The findings were published Oct. 10 in the journal Science.

Scientists think the Earth's outer core is liquid, but the heart is solid iron and nickel, plus traces of elements such as sulfur and gold. Seismic waves passing through the core provide a snapshot view, similar to a CT scan, of its structure. The planet's magnetic field and the rotation of the Earth also offer clues to the core's composition and structure.

Only two species in nature have the ability to make hooks for use as tools - humans and the New Caledonian crows. But many thought that the crows' use of hooked twigs to take out insects from holes was just trial and error that they went through. But new research shows that's not the case. The crows pay close attention to the features of each tool, ensuring that the hooked end is oriented correctly for snagging prey.

In a paper to be published as part of a special issue of journal Philosophical Transactions of the Royal Society B, scientists at the University of St Andrews discovered that New Caledonian crows do not rely on guesswork when deploying one of their most complicated tool types, hooked stick tools.

New Caledonian crows are one of the world's most proficient animal tool users. The species is restricted to the tropical islands of New Caledonia in the South Pacific, where it is known to use several different tool types to obtain beetle grubs and other concealed prey.

The study investigated hooked stick tools, which wild crows manufacture by using their bills to snip a forked stick out of a shrub. This stick is then 'crafted' by the careful removal of wood and bark, leaving a curved twig with a neat hook at the end. The crows use these tools to extract prey items such as insects from their hiding places in holes and crevices.

A near-Earth asteroid about a fifth the size of the space rock thought to have killed the dinosaurs has been discovered by a Russian-operated observatory in New Mexico

The kilometer-wide asteroid, dubbed 2013 TB80, was first spotted on Wednesday by the remotely run ISON-NM observatory and was later confirmed by US and Japanese astronomers, the International Astronomical Union said in an online statement.

The asteroid, believed to be the 704th largest with an orbit that comes relatively near Earth, does not pose a danger of crashing into our planet, said the head of the observatory that made the discovery.

"It's a big asteroid, but it poses no danger for us," Leonid Elenin, who lives in the Moscow Region, told RIA Novosti on Friday.

A new study shows that changes in the environment caused by people are helping animals to evolve bigger brains.

Well, chalk one up for homo-sapiens, sort of. While we've known for some time that humans have been affecting the enviroment on a global scale, one aspect of our evolutionary impact on other species might not be all bad.

In a recent study, University of Minnesota biologist Emilie C. Snell-Rood found evidence suggesting that our direct changes to the natural habitats of animals (through technologies advances, antibiotics and revised food pyramids) have caused some animals to evolve with bigger brains.

Dr. Snell-Rood studied dozens of individual animal skulls, some as old as a century, from ten different species including bats, gophers and mice. In two of the species, the white-footed mouse and the meadow role, the brains of the animals plucked from metropolitan areas or suburbs were about 6% bigger than those of the animals taken from farms or other rural areas. Dr. Snell-Rood's hypothesis after assessing the first wave of results was that brains become significantly bigger when they move to cities or bustling towns, where the animals must learn to find food in places that they're not biologically trained to encounter or expect.