Wednesday, August 26, 2009
Chinese scientists put forward the theory that "Peking Man" had begun to "use fire" in 1930s, while oversea researchers doubted that the ashes found in the Peking Man site were remains of natural fire instead of man-made.
Remains of ashes, burned bones and carbon dust found from the excavation layer inside the "Peking Man Cave" provides more support for the theory of Chinese scientists, said Gao Xing, the team leader of the project and Vice Director of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), CAS.
On June 24, China formally starts a large-scale rescue excavation project in Zhoukoudian 50 kilometres southwest to Beijing's city center, 72 years after its last excavation efforts of comparable scale in 1937.
Anthropologists have unearthed nearly one thousand vertebrate fossils, most of which are small rodent, insectivores and birds. There are also broken teeth and limb bone fossils of large and medium size animals in the unearthed discoveries.
Besides, researchers also found 5 steinkerns, 37 flake tools, 5 hammerstones, 5 scrapers, 2 choppers, 6 broken stone tools with evident manmade character and 118 stoneworks that researchers reckon are artificial during the excavation.
The Chinese Academy of Sciences
Dartmouth College geography professor emeritus and geographer Vincent H. Malmström had a theory in 1973 that the shooting stars an ancient Native American tribe saw in the sky thousands of years ago was a sign that something important was about to happen.
"The shooting stars that will be observed this evening are part of a recurring celestial phenomena that heralded the beginning of recorded time in America exactly 3,367 years ago tonight, on August 13, -1358 (1359 B.C.)," said Malmström August 13.
In 1992, the Swift-Tuttle comet passed the Earth, a trip it makes once every 130 years. The Zoque, a Native American tribe in what is now southern Mexico, first noted it and initiated the earliest calendar in the Americas. The following day at noon, the sun passed directly overhead at their principal site, now known to archaeologists as Izapa, giving rise to a 260-day calendar that became the time-count subsequently adopted by most of the early peoples of Mesoamerica, including the Mayas and the Aztecs.
Malmström's book on the Mesoamerican calendar, "Cycles of the Sun, Mysteries of the Moon", was published by the University of Texas Press in 1997 and in 2008, using NASA data, he demonstrated how the Mayan people learned to predict lunar eclipses.
Since planets form out of the same swirling gas cloud that creates a star, they are expected to orbit in the same direction that the star spins. Graduate students David Anderson, of Keele University, and Amaury Triaud, of Geneva Observatory, were surprised to find that WASP-17 is orbiting the wrong way, making it the first planet known to have a ``retrograde'' orbit. The likely explanation is that WASP-17 was involved in a near collision with another planet early in its history.
WASP-17 appears to have been the victim of a game of planetary billiards, flung into its unusual orbit by a close encounter with a ``big brother'' planet. Professor Coel Hellier, of Keele University, remarks: "Shakespeare said that two planets could no more occupy the same orbit than two kings could rule England; WASP-17 shows that he was right.”
David Anderson added “Newly formed solar systems can be violent places. Our own moon is thought to have been created when a Mars-sized planet collided with the recently formed Earth and threw up a cloud of debris that turned into the moon. A near collision during the early, violent stage of this planetary system could well have caused a gravitational slingshot, flinging WASP-17 into its backwards orbit.”
The first sign that WASP-17 was unusual was its large size. Though it is only half the mass of Jupiter it is bloated to nearly twice Jupiter's size, making it the largest planet known.
Astronomers have long wondered why some extra-solar planets are far bigger than expected, and WASP-17 points to the explanation. Scattered into a highly elliptical, retrograde orbit, it would have been subjected to intense tides. Tidal compression and stretching would have heated the gas-giant planet to its current, hugely bloated extent. "This planet is only as dense as expanded polystyrene, seventy times less dense than the planet we're standing on", notes Prof. Hellier.
Professor Keith Mason, Chief Executive of the Science and Technology Facilities Council, which funded the research, said, “This is a fascinating new find and another triumph for the WASP team. Not only are they locating these far flung and mysterious planets but revealing more about how planetary systems, such as our own Solar System, formed and evolved. The WASP team has proved once again why this project is currently the World's most successful project searching for transiting exoplanets.”
WASP-17 is the 17th new exoplanet (planet outside our solar system) found by the Wide Area Search for Planets (WASP) consortium of UK universities. The WASP team detected the planet using an array of cameras that monitor hundreds of thousands of stars, searching for small dips in their light when a planet transits in front of them. Geneva Observatory then measured the mass of WASP-17, showing that it was the right mass to be a planet. The WASP-South camera array that led to the discovery of WASP-17 is hosted by the South African Astronomical Observatory.
Science and Technology Facilities Council
When bees sting, they pump poison into their victims. Now the toxin in bee venom has been harnessed to kill tumor cells by researchers at Washington University School of Medicine in St. Louis. The researchers attached the major component of bee venom to nano-sized spheres that they call nanobees.
In mice, nanobees delivered the bee toxin melittin to tumors while protecting other tissues from the toxin's destructive power. The mice's tumors stopped growing or shrank. The nanobees' effectiveness against cancer in the mice is reported in advance online publication Aug. 10 in the Journal of Clinical Investigation.
"The nanobees fly in, land on the surface of cells and deposit their cargo of melittin which rapidly merges with the target cells," says co-author Samuel Wickline, M.D., who heads the Siteman Center of Cancer Nanotechnology Excellence at Washington University. "We've shown that the bee toxin gets taken into the cells where it pokes holes in their internal structures."
Melittin is a small protein, or peptide, that is strongly attracted to cell membranes, where it can form pores that break up cells and kill them.
"Melittin has been of interest to researchers because in high enough concentration it can destroy any cell it comes into contact with, making it an effective antibacterial and antifungal agent and potentially an anticancer agent," says co-author Paul Schlesinger, M.D., Ph.D., associate professor of cell biology and physiology. "Cancer cells can adapt and develop resistance to many anticancer agents that alter gene function or target a cell's DNA, but it's hard for cells to find a way around the mechanism that melittin uses to kill."
The scientists tested nanobees in two kinds of mice with cancerous tumors. One mouse breed was implanted with human breast cancer cells and the other with melanoma tumors. After four to five injections of the melittin-carrying nanoparticles over several days, growth of the mice's breast cancer tumors slowed by nearly 25 percent, and the size of the mice's melanoma tumors decreased by 88 percent compared to untreated tumors.
The researchers indicate that the nanobees gathered in these solid tumors because tumors often have leaky blood vessels and tend to retain material. Scientists call this the enhanced permeability and retention effect of tumors, and it explains how certain drugs concentrate in tumor tissue much more than they do in normal tissues.
But the researchers also developed a more specific method for making sure nanobees go to tumors and not healthy tissue by loading the nanobees with additional components. When they added a targeting agent that was attracted to growing blood vessels around tumors, the nanobees were guided to precancerous skin lesions that were rapidly increasing their blood supply. Injections of targeted nanobees reduced the extent of proliferation of precancerous skin cells in the mice by 80 percent.
Overall, the results suggest that nanobees could not only lessen the growth and size of established cancerous tumors but also act at early stages to prevent cancer from developing.
"Nanobees are an effective way to package the useful, but potentially deadly, melittin, sequestering it so that it neither harms normal cells nor gets degraded before it reaches its target," Schlesinger says.
If a significant amount of melittin were injected directly into the bloodstream, widespread destruction of red blood cells would result. The researchers showed that nanoparticles protected the mice's red cells and other tissues from the toxic effects of melittin. Nanobees injected into the bloodstream did not harm the mice. They had normal blood counts, and tests for the presence of blood-borne enzymes indicative of organ damage were negative.
When secured to the nanobees, melittin is safe from protein-destroying enzymes that the body produces. Although unattached melittin was cleared from the mice's circulation within minutes, half of the melittin on nanobees was still circulating 200 minutes later. Schlesinger indicates that is long enough for the nanobees to circulate through the mice's bloodstream 200 times, giving them ample time to locate tumors.
"Melittin is a workhorse," says Wickline, also professor of medicine in the Cardiovascular Division and professor of physics, of biomedical engineering and of cell biology and physiology. "It's very stable on the nanoparticles, and it's easily and cheaply produced. We are now using a nontoxic part of the melittin molecule to hook other drugs, targeting agents or imaging compounds onto nanoparticles."
The core of the nanobees is composed of perfluorocarbon, an inert compound used in artificial blood. The research group developed perfluorocarbon nanoparticles several years ago and have been studying their use in various medical applications, including diagnosis and treatment of atherosclerosis and cancer. About six millionths of an inch in diameter, the nanoparticles are large enough to carry thousands of active compounds, yet small enough to pass readily through the bloodstream and to attach to cell membranes.
"We can add melittin to our nanoparticles after they are built," Wickline says. "If we've already developed nanoparticles as carriers and given them a targeting agent, we can then add a variety of components using native melittin or melittin-like proteins without needing to rebuild the carrier. Melittin fortunately goes onto the nanoparticles very quickly and completely and remains on the nanobee until cell contact is made."
The flexibility of nanobees and other nanoparticles made by the group suggests they could be readily adapted to fit medical situations as needed. The ability to attach imaging agents to nanoparticles means that the nanoparticles can give a visible indication of how much medication gets to tumors and how tumors respond.
"Potentially, these could be formulated for a particular patient," Schlesinger says. "We are learning more and more about tumor biology, and that knowledge could soon allow us to create nanoparticles targeted for specific tumors using the nanobee approach."
Beneath northern India’s irrigated fields of wheat, rice, and barley ... beneath its densely populated cities of Jaiphur and New Delhi, the groundwater has been disappearing. Halfway around the world, hydrologists, including Matt Rodell of NASA, have been hunting for it.
Where is northern India’s underground water supply going? According to Rodell and colleagues, it is being pumped and consumed by human activities -- principally to irrigate cropland -- faster than the aquifers can be replenished by natural processes. They based their conclusions -- published in the August 20 issue of Nature -- on observations from NASA’s Gravity Recovery and Climate Experiment (GRACE).
"If measures are not taken to ensure sustainable groundwater usage, consequences for the 114 million residents of the region may include a collapse of agricultural output and severe shortages of potable water," said Rodell, who is based at NASA’s Goddard Space Flight Center in Greenbelt, Md.
Groundwater comes from the natural percolation of precipitation and other surface waters down through Earth’s soil and rock, accumulating in aquifers -- cavities and layers of porous rock, gravel, sand, or clay. In some of these subterranean reservoirs, the water may be thousands to millions of years old; in others, water levels decline and rise again naturally each year.
Groundwater levels do not respond to changes in weather as rapidly as lakes, streams, and rivers do. So when groundwater is pumped for irrigation or other uses, recharge to the original levels can take months or years.
Changes in underground water masses affect gravity enough to provide a signal, such that changes in gravity can be translated into a measurement of an equivalent change in water.
"Water below the surface can hide from the naked eye, but not from GRACE," said Rodell. The twin satellites of GRACE can sense tiny changes in Earth’s gravity field and associated mass distribution, including water masses stored above or below Earth’s surface. As the satellites orbit 300 miles above Earth's surface, their positions change -- relative to each other -- in response to variations in the pull of gravity. The satellites fly roughly 137 miles apart, and microwave ranging systems measure every microscopic change in the distance between the two.
With previous research in the United States having proven the accuracy of GRACE in detecting groundwater, Rodell and colleagues Isabella Velicogna, of NASA’s Jet Propulsion Laboratory and the University of California-Irvine, and James Famiglietti, of UC-Irvine, were looking for a region where they could apply the new technique.
"Using GRACE satellite observations, we can observe and monitor water changes in critical areas of the world, from one month to the next, without leaving our desks," said Velicogna. "These satellites provide a window to underground water storage changes."
The northern Indian states of Rajasthan, Punjab and Haryana have all of the ingredients for groundwater depletion: staggering population growth, rapid economic development and water-hungry farms, which account for about 95 percent of groundwater use in the region.
Data provided by India's Ministry of Water Resources suggested groundwater use was exceeding natural replenishment, but the regional rate of depletion was unknown. Rodell and colleagues had their case study. The team analyzed six years of monthly GRACE gravity data for northern India to produce a time series of water storage changes beneath the region’s land surface.
They found that groundwater levels have been declining by an average of one meter every three years (one foot per year). More than 109 cubic km (26 cubic miles) of groundwater disappeared between 2002 and 2008 -- double the capacity of India's largest surface water reservoir, the Upper Wainganga, and triple that of Lake Mead, the largest man-made reservoir in the United States.
"We don’t know the absolute volume of water in the Northern Indian aquifers, but GRACE provides strong evidence that current rates of water extraction are not sustainable," said Rodell. "The region has become dependent on irrigation to maximize agricultural productivity, so we could be looking at more than a water crisis."
The loss is particularly alarming because it occurred when there were no unusual trends in rainfall. In fact, rainfall was slightly above normal for the period.
The researchers examined data and models of soil moisture, lake and reservoir storage, vegetation and glaciers in the nearby Himalayas, in order to confirm that the apparent groundwater trend was real. Nothing unusual showed up in the natural environment.
The only influence they couldn’t rule out was human.
"At its core, this dilemma is an age-old cycle of human need and activity -- particularly the need for irrigation to produce food," said Bridget Scanlon, a hydrologist at the Jackson School of Geosciences at the University of Texas in Austin. "That cycle is now overwhelming fresh water reserves all over the world. Even one region’s water problem has implications beyond its borders."
"For the first time, we can observe water use on land with no additional ground-based data collection," Famiglietti said. "This is critical because in many developing countries, where hydrological data are both sparse and hard to access, space-based methods provide perhaps the only opportunity to assess changes in fresh water availability across large regions."
(Photo: NASA/Matt Rodell)
A new study by researchers at Wake Forest University School of Medicine may reveal how long-lasting memories form in the brain.
The researchers hope that the findings, now available online and scheduled to appear in an upcoming issue of Neuroscience, may one day help scientists develop treatments to prevent and treat conditions such as post-traumatic stress disorder.
“Although many things are known about memories that form from repeat experiences, not much is known with regard to how some memories form with just one exposure,” said Ashok Hegde, Ph.D., an associate professor of neurobiology and anatomy and the lead investigator on the study.
Scientists do know that people tend to remember extremely happy or sad occasions vividly because of the emotional connection, Hegde said. Extreme emotions trigger the release of a chemical in the brain called norepinephrine, which is related to adrenaline. That norepinephrine somehow helps memories last a long time – some even a lifetime.
For example, he said, when a person asks, “Where were you when the 9/11 attacks happened?” most people can recall immediately where they were and what they were doing when they heard the news. They remember the moment as if it just happened because a national tragedy arouses emotion and emotion somehow makes memories last for a long time, Hegde explained.
For the current study, Hegde and colleagues looked at how norepinephrine helps female mice remember the scent of their male partners after being exposed to it just once during mating.
The researchers studied the neural circuitry in the accessory olfactory bulb, the part of the brain where memory of the male partner’s scent is stored. They found that norepinephrine, released in mice while mating, activates an enzyme called Protein Kinase C (PKC), specifically, the “alpha” isoform of PKC, in the accessory olfactory bulb. The PKC enzyme has about a dozen forms, or isoforms, that exist in the brains of mammals, including humans.
“The fact that PKC-alpha is activated through the release of norepinephrine is an important discovery,” Hegde said. “It explains how strong memories form for specific sensory experiences.”
In female mice, the information about the partner’s scent is carried by a chemical called glutamate and the fact that mating has occurred is conveyed by the release of norepinepherine, Hegde explained. Previous studies have found that glutamate and norepinephrine together, but not individually, cause strong memory formation for the male’s scent.
“No one knew how this happened,” Hegde said. “Our findings indicate that the PKC-alpha enzyme tells the nerve cells in the brain that these two chemicals have arrived together. PKC-alpha is like the bouncer who lifts the rope blocking the entrance to an exclusive club for strong memories when glutamate and norepinephrine arrive together. If they arrive alone, they can’t get past the velvet rope.”
Hegde explained that, when memory is stored in the brain, the connections between nerve cells, called synapses, change. Strong memories are formed when synapses become stronger through structural changes that occur at the synapse. PKC-alpha works with glutamate and norepinephrine to create those changes.
Hegde said that the next step in this line of research is to learn exactly how PKC-alpha can turn genes on in nerve cells. Understanding the precise sequence of molecules that are activated by PKC-alpha will help researchers block the function of these molecules and test whether they block memory formation. This future research will not only explain strong pleasant memories, but also how strong unpleasant memories form in instances like post-traumatic stress disorder.