Babies born to mothers with HIV have a much smaller risk of getting the virus themselves if medical personnel administer preventive drugs, such as nevirapine, at birth to the moms and their newborns. Nevertheless, a small percentage of those infants will end up getting the disease anyway. And without treatment, some 62 percent of HIV-positive children die before the age of two.
Editor's Note: Students from Dartmouth's Thayer School of Engineering are working in Tanzania to help improve sanitation and energy technologies in local villages. The student-led group , known as Humanitarian Engineering Leadership Projects (HELP), will file dispatches from the field during their trip. This is their eighth blog post for Scientific American.
More than a fifth of Africa's freshwater species are threatened with extinction , and their disappearance could threaten livelihoods across the continent, according to a new study by the International Union for Conservation of Nature (IUCN).
The study, conducted for the IUCN's Red List of Threatened Species, assessed 5,167 African freshwater species over a five-year period. Two hundred scientists contributed to the report, which covers fish, mollusks, crabs, aquatic plants and aquatic insects such as dragonflies and damselflies.
NEW YORK--When convincing someone to trade in a commodity that cannot be seen or touched, it's best to hold their hand--even if only by telephone. Standing while talking helps, too, at least for broker Lenny Hochschild, who specializes in convincing everyone from agribusiness to electric utilities to buy and sell in a market that doesn't exist yet--a U.S. market for the right to emit carbon dioxide, the most ubiquitous greenhouse gas changing the global climate.
This is possibly the newest market in the world, a would-be global attempt to create a trade in the greenhouse gas emissions from any nation's fleet of cars, household refrigerators, electric power plants, factories, even farms. It's an attempt to peel back the smothering blanket of global warming by giving people a financial incentive to reduce emissions under an economic concept known as cap and trade.
Always finding excuses to skip the gym? Congrats--you might be able to blame your genes. Because the mere desire to exercise may be inherited, at least in mice. So says a study in the journal Proceedings of the Royal Society B . [Theodore Garland Jr. et al, http://bit.ly/crWNGd ]
All our experience of the world, and ability to act on it, are channelled through our body. The pioneering computer scientist, Alan Turing, correctly realised the human mind is special not particularly because of its computing power, but because the body provides it with a unique interface to the world. Current research in psychology and neuroscience is probing how the brain represents the body. Recent advances have revealed that body representation is fundamentally multisensory, arising from the combination of many different sensory signals. These include classical “senses,” such as touch and vision, and also much more specific signals, such as the flexion or extension of each muscle, which define the body’s posture in space. This information is integrated to construct a multisensory representation of the current state of the body. Intriguingly, multisensory signals also affect what we perceive our body to be like, for example by making us feel like a rubber hand really is our hand! Our thoughts about what our body is are highly flexible, and track the multisensory inputs that the brain receives.
A common illustration of just how flexible the sense of our body is comes from changes in the brain’s representation of the body due to tool use. Humans, and some other animals, are able to use tools as additions to the body. When we use a long pole to retrieve an object we couldn’t otherwise reach, the pole becomes, in some sense, an extension of our body. Is this merely a poetic way of speaking, or does the brain actually incorporate the tool into its representation of the body? Studies of monkeys learning to use a rake to obtain distant objects show that this may be more than a mere metaphor. Multisensory brain cells respond both to touch on the hand or visual objects appearing near the hand. When the monkeys used the rake, these cells began to respond to objects appearing anywhere along the length of the tool, suggesting the brain represented the rake as actually being part of the hand.
One of the signature discoveries of cognitive neuroscience is that a structure called the hippocampus, deep within the brain, is intimately involved in creating memories. This fact was dramatically illustrated by a singular patient, Henry Molaison, who experienced severe epileptic seizures. In 1953, when Molaison was 27, doctors removed his hippocampus and nearby areas on both sides of his brain. The operation controlled his epilepsy, but at a price--from that time on, he was unable to remember the things that happened to him. He could learn skills, such as mirror writing, but would be puzzled by his expertise, because he could not recall having acquired it.
H.M., as he was known during his lifetime to protect his privacy, taught scientists three lessons. First, certain brain structures--the hippocampus and the amygdala, the brain’s emotion center--specialize in remembering. Second, there are different kinds of memory--the ability to recall facts, or personal experiences, or physical skills like riding a bike--each with its own properties. Third, memory is distinct from the brain’s intellectual and perceptual abilities.
The universe is a mighty big place, but there is no shortage of amazement right here in our celestial neighborhood. From Venus's searing surface temperatures, hot enough to melt lead, to Jupiter's Great Red Spot, a storm that has been raging for hundreds of years, to the cryovolcanoes of the Saturnian moon Enceladus , the solar system boasts plenty of extreme locales.
Turning the clock back by half a century could be the key to solving one of science’s biggest puzzles: how to bring together gravity and particle physics. At least that is the hope of researchers advocating a back-to-basics approach in the search for a unified theory of physics.
In July mathematicians and physicists met at the Banff International Research Station in Alberta, Canada, to discuss a return to the golden age of particle physics. They were harking back to the 1960s, when physicist Murray Gell-Mann realized that elementary particles could be grouped according to their masses, charges and other properties, falling into patterns that matched complex symmetrical mathematical structures known as Lie (“lee”) groups. The power of this correspondence was cemented when Gell-Mann mapped known particles to the Lie group SU(3), exposing a vacant position indicating that a new particle, the soon to be discovered “Omega-minus,” must exist.
In 1980, a scientist looking at bone fragments under an ultraviolet microscope noticed the bones were glowing green--a hallmark of the antibiotic tetracycline. The drug latches onto calcium and gets deposited in bone. Nothing unusual. Except these bones were from a Nubian mummy buried 1,600 years ago in Sudan--long before scientists discovered tetracycline, in 1948.
I suffer from eschatological obsession. That is, I spend lots of time brooding about ends. So the cover of the September Scientific American --which reads simply "the end."--made me all shivery, like when I hear the spooky sitar opening of The Doors' apocalyptic rock poem "The End." (I'm never more Freudian than when I hear Morrison's Oedipal yowl.)
Dmitri K. Belyaev, a Russian scientist, may be the man most responsible for our understanding of the process by which wolves were domesticated into our canine companions. Dogs began making for themselves a social niche within human culture as early as 12,000 years ago in the Middle East . But Belyaev didn’t study dogs or wolves; his research focused instead on foxes. What might foxes be able to tell us about the domestication of dogs?
Domesticated animals of widely different species seem to share some common traits: changes in body size, in fur coloration, in the timing of the reproductive cycle. Their hair or fur becomes wavy or curly; they have floppy ears and shortened or curly tails. Even Darwin noted , in On the Origin of Species, that “not a single domestic animal can be named which has not, in some country, drooping ears.” Drooping ears is a feature that does not ever occur in the wild, except for in elephants. And domesticated animals possess characteristic changes in behavior compared with their wild brethren, such as a willingness or even an eagerness to hang out with humans.
