Researchers report initial success in promising approach to prevent tooth decay

Sizin üçün oyun:

Google Play'də əldə edin

Yüklə 257.11 Kb.
ölçüsü257.11 Kb.
1   2   3   4   5   6   7   8


Find offers a new way to track how species evolved

PHILADELPHIA -- Ohio State University geologists have isolated complex organic molecules from 350-million-year-old fossil sea creatures -- the oldest such molecules yet found.

The molecules may have functioned as pigments, but the study offers a much bigger finding: an entirely new way to track how species evolved.

Christina O'Malley, a doctoral student in earth sciences at Ohio State, found orange and yellow organic molecules inside the fossilized remains of several species of sea creatures known as crinoids. The oldest fossils in the study date back to the Mississippian period.

She reported the find Wednesday at the meeting of the Geological Society of America in Philadelphia.

Crinoids still exist today. Though they resemble plants, they are marine animals. They cling to the seafloor and feast on plankton that float by.

The crinoids in this study had flower-like fronds capping skinny stalks about six inches high -- a look resembling "starfish on a stick," said William Ausich, professor of earth sciences and O'Malley's co-advisor with Yu-Ping Chin, also a professor of earth sciences.

Today's crinoids display a range of colors, some variegated shades of red, orange, and yellow, so the geologists weren't surprised that some of those colors turned up in the 350-million-year-old crinoids, Ausich said.

"People have suspected for a long time that organic molecules could be found inside fossils," he added. "This is just the first time that scientists have succeeded in finding them."

Though the organic molecules could be classified as pigments, nobody can be sure that they functioned as pigments inside these ancient animals, the geologists emphasized. They may have served some other purpose besides coloration -- perhaps to defend the animal from predators by making it less palatable.

Because the molecules appear to be a little different for each species of crinoid, scientists can now use the pigments as biomarkers to map relationships on the creatures' family tree. Until now, they could only infer crinoid lineage based on the size and shape of key features on the animals' skeletons.

"This could be a new tool for figuring out how long-dead creatures became so prolific and successful. We can't travel back in time, but now we can look for clues about these creature's lives in a way that hasn't been attempted or taken advantage of before," O'Malley said.

Scientists can only view fossilized plants and animals in the grays and tans of sedimentary rock, such as the limestone fossils in this study. Rock is inorganic, and replaces organic molecules such as pigments during fossilization. What O'Malley and her colleagues discovered is that some organic molecules occasionally survive the process.

"Crinoid skeleton is very porous, and we think that when inorganic molecules filled in the spaces of the skeleton during preservation, some of the organic molecules were trapped inside the fossil," she said.

O'Malley found pigments in every crinoid specimen that she sampled from three fossil sites, one in Switzerland and two in Indiana.

The Indiana samples date back to 350 million years ago, during the Mississippian period, when much of North America was covered by a shallow inland sea. The Switzerland fossils date back to 60 million years ago, during the Jurassic period. The sites preserved the crinoids exceptionally well, probably because a sudden storm buried them in sediment.

Should pigments be found in other fossils, the technique could prove to be a reliable way to trace species' evolution. So far, the crinoid biomarkers mesh well with scientists' concepts of how those species are related.

O'Malley isolated the pigments by grinding up small bits of fossil and dissolving the organic molecules into a solution. Then she injected a tiny sample of the solution into a machine called a gas chromatograph mass spectrometer. The machine vaporized the solution so that a magnet could separate individual molecules based on electric charge and mass. Computer software then identified the molecules.

Orange and yellow organic molecules emerged, along with several other molecules that the geologists have yet to identify. The off-the-shelf software was only designed to identify common laboratory compounds, O'Malley explained. She would like to generate her own database of fossil organic molecules, and also extract pigments from other marine fossils, including some from sites in Iowa.

The Geological Society of America supported this work with a Graduate Student Research Grant. Other funding was provided by the National Science Foundation.

Moon and rain could mean quakes

A full moon may have triggered the Indian Ocean earthquake that caused the tsunami on 26 December 2004, a new study concludes.

Between October 2004 and August 2005 Robin Crockett from the University of Northampton, UK, and his colleagues monitored tremors and collected tidal data along the Java/Sumatra trench. They found that major quakes were 86 per cent more likely around new and full moons, when tides are at their greatest.

"At new and full moons the biggest mass of water is being loaded and unloaded at the plate boundary," Crockett says. That might be the final push that initiates a quake.

Meanwhile Sebastian Hainzl from the University of Potsdam, Germany, and his colleagues have noticed that rain can also trigger quakes. In 2002 they monitored tremors, rainfall and groundwater pressure in south-east Germany.

They found that water from a heavy rainstorm can reach spots underground where masses of rock are trying to move past each other but are stuck together by friction. The water can ease the friction, releasing pent-up tension so that the rocks jerk past each other and initiate tremors as deep as 4 kilometres underground (Geophysical Research Letters, DOI: 10.1029/2006GL027074 and 10.1029/2006GL027642).

Telescopes can tune in to alien TV

Radio telescopes designed to study the primordial universe could also eavesdrop on extraterrestrial civilisations similar to our own. "By a happy accident," says abraham Loeb of Harvard University, "the telescopes will be sensitive to justthe kind of radio emission that our civilisation is leaking into space."

The next generation of radio telescopes are designed to pick up radio waves emitted by neutral hydrogen molecules in the early universe. These signals originally had a wavelength of 21 centimetres, but the universe has expanded since they were emitted, stretching the waves in the process. Today, these signals have a wavelength of several metres, corresponding to a frequency of tens or hundreds of megahertz. "This overlaps with our civilisation's radio emissions, which are in the range 50 to 400 megahertz," says Loeb.

Loeb and his Harvard colleague Matias Zaldarriaga say that the most powerful emissions from our own planet come from military radars, and TV and FM radio transmitters. They span a small range of frequencies, and if ET is producing similar signals, these "spikes" in the radio spectrum will be discernible by telescopes such as the Low- Frequency array (LoFaR) which is now being built in the Netherlands ( "This is radio SETi, but at wavelengths that SETi experiments haven't probed in the past," says Seth Shostak of the SETi institute in Mountain View, California. "That by itself is reason enough to recommend it."

The ability of telescopes such as LoFaR to detect spectral spikes means they will also be able to detect the doppler shift in wavelength as an ET planet orbits its parent star. according to Loeb and Zaldarriaga, this will make it possible to deduce the shape of the orbit, the tilt of the planet as it spins on its axis, and the planet's distance from the star. "This in turn will allow an estimate of the planet's surface temperature, indicating whether liquid water is a possibility," he says.

Loeb and Zaldarriaga say that the technique would pick up radio leakage from alien civilisations within about 1000 light years of Earth. By some estimates, there could be as many as 100 million stars with planets within this volume of space. Of course, the success of Loeb and Zaldarriaga's proposal depends crucially on how many of these planets have civilisations that are roughly at the same stage of development as ours. "This is very difficult to quantify," says Loeb.

There are practical difficulties, too. "By looking in the bands that we humans fill with signals – radar, TV and so on – the SETi researchers are guaranteed to encounter enormous terrestrial interference," Shostak says. Sorting out ET from the BBC will be a substantial challenge."
Women's education is strongly related to husband's income

Much has been written about the income returns to education, but women have been largely ignored by this literature, having historically spent significant periods of time outside the formal labor market. In a thought-provoking new study, economists from Brigham Young University correlate women's education to future quality of life through an examination of husband's earnings. Specifically, the researchers find that a woman's college completion predicts an average increase in her husband's earnings of more than $20,000 relative to women who only attended some college.

"Women's education does not have a strong effect on the probability of being married but dramatically increases husband's income," write Lars Lefgren and Frank McIntyre in the current issue of the Journal of Labor Economics.

Consistent with the observation that school has become an increasingly important place to meet potential partners, women who attended college are much more likely to marry college-educated husbands. Education may also change a woman's social circles, or make them more desirable to high-ability men. It has also been well established in other literature that married men earn more than unmarried men.

However, given that women who choose to invest heavily in education may be systematically different than women who invest less, Legren and McIntyre wanted to even more firmly establish a causal relationship between education and marriage outcomes.

Using Census data from 1980 broken down by birth quarter, the researchers analyzed how enrollment cutoff dates and differences in the amount of compulsory schooling can affect husband's earnings. They found that an extra year of schooling – that is, the difference in compulsory schooling between a child born in mid-December, just before the cutoff, and a child born a month later in mid-January, just after the cutoff – increases husband's earnings by about $4,000.

"Inasmuch as marriage generates nonpecuniary benefits as well, the marriage market could be an even more important avenue through which education increases women's welfare," the authors write.


Since 1983, the Journal of Labor Economics has presented international research that examines issues affecting the economy as well as social and private behavior. Lars Lefgren and Frank McIntyre. "The Relationship between Women's Education and Marriage Outcomes," Journal of Labor Economics 24:4.

Vitamin C and water not just healthy for people -- healthy for plastics, too

New manufacturing techniques may lead to cheaper, 'greener' plastics

Two new laboratory breakthroughs are poised to dramatically improve how plastics are made by assembling molecular chains more quickly and with less waste. Using such environmentally friendly substances as vitamin C or pure water, the two approaches present attractive alternatives to the common plastic manufacturing technique called free radical polymerization (FRP).

"The methods both present novel and complementary ways to dramatically improve efficiency, product control, and cost for the polymer industry," said Andy Lovinger, the National Science Foundation program director who oversees funds for the two projects. "Each of these approaches could have a very significant impact on polymer manufacturing."

Plastics are polymers, long, potentially complex, molecule chains crafted from an array of smaller chemical units. Using FRP, chemical engineers can create the right plastic for a range of applications, such as a specific trim for a car door or soft foam for a pillow.

For some plastics, the building-block molecules do not easily link together. To surmount this problem, researchers from Carnegie Mellon University in Pittsburgh, Pa., devised a process called atom transfer radical polymerization (ATRP), which provides creative ways to coax the chemical subunits into chains. However, this method comes with certain costs, such as the need for a copper catalyst that can become unwanted waste.

Now, the Carnegie Mellon researchers have discovered that adding vitamin C, glucose, or other electron-absorbing agents to the ATRP process can reduce the amount of copper catalyst by a factor of 1000. Because the catalyst often needs to be removed from the end products, less copper means far less waste and drastically reduced removal costs. Mass manufacturing could become more affordable for a range of items such as advanced sensors, drug delivery systems, paint coatings, and video displays.

The research is described in a paper in the Oct. 17, 2006, issue of the Proceedings of the National Academy of Sciences.

At the University of Pennsylvania (UPenn), researchers are using a different approach to improve FRP. Called single electron transfer-living radical polymerization, the new method relies upon relatively low-energy reactions, uses elemental copper (copper metal, as opposed to copper in a chemical solution) as a catalyst to limit byproducts and allows manufacturers to use one of the most environmentally friendly solvents in the arsenal, water. The entirely new method of polymerization builds upon existing mechanisms to craft large molecules very quickly.
Nuclear security: Diaster waiting to happen

SPONTANEOUS combustion is not high on most people's list of worries, but when it happens to materials at one of the world's oldest and largest storage centres for weapons-grade uranium, it is a different matter.

On 22 September, the plastic wrapping around some uranium at the Y-12 National Security Complex in Oak Ridge, Tennessee, burst into flames as a technician was removing it inside a glovebox. Exposed to air, the uranium had heated up and ignited the plastic.

The fire took place in a large wooden warehouse built in 1944 to help the Manhattan Project, set up to develop nuclearweapons. The warehouse is one of the facility's main stores for its 400 tonnes of highly enriched uranium, and is now officially rated as a fire hazard, according to an assessment in 1996 by the US Department of Energy (DoE).

In this case the incident was contained, but a major fire would have catastrophic consequences. The DoE says a fire could result in uranium containers breaking open and releasing their contents in a plume of toxic, radioactive smoke. About 700,000 people live within a 160-kilometre radius of Y-12, including 174,000 in Knoxville 25 km away and 28,000 in Oak Ridge itself. In the worst case, the DoE estimates that the local population could receive radiation doses of up to 900 millisieverts, enough to cause nausea, hair loss and in some cases death.

The dangers at Y-12, revealed in a study this week, are not unique. Worldwide more than 1750 tonnes of highly enriched uranium have been produced over the last 62 years to supply bombs, submarines and research reactors. "Significant amounts are stored at dozens of sites in Russia and other countries, often inadequately accounted for, protected and controlled," says Morten Bremer Mærli, a nuclear expert from the Norwegian Institute of International Affairs in Oslo. "Many of the stores are old, some pose environmental threats and some may be at risk from terrorists. International standards are currently too weak to ensure safety and security." But what is surprising about Y-12 is that the world's richest nation has allowed it to deteriorate to such a poor state.

It has been "festering for decades", says Robert Alvarez, a senior environmental adviser to the Clinton administration now with think tank the Institute for Policy Studies in Washington DC.

"While a considerable amount of attention has been drawn to dubious storage conditions in Russia and former Soviet states, long standing nuclear weapons material storage problems in this country pose unacceptable risks to workers and the public," he says. Alvarez is the author of the detailed study of safety at Y-12 due to appear in a forthcoming issue of the journal Science and Global Security, published by Princeton University. He reveals that the incident on 22 September is just the latest of 22 fires and explosions that have beset the Y-12 complex since 1997, a rate of about two a year.

COLUMBUS , Ohio – In the long run, a drink or two a day may be good for the brain.

Researchers found that moderate amounts of alcohol – amounts equivalent to a couple of drinks a day for a human – improved the memories of laboratory rats.

Such a finding may have implications for serious neurodegenerative diseases like Alzheimer's, said Matthew During, the study's senior author and a professor of molecular virology, immunology and cancer genetics at Ohio State University .

“There is some evidence suggesting that mild to moderate alcohol consumption can protect against diseases like Alzheimer's in humans,” said During. “But it's not apparent how this happens.”

He and his colleague, Margaret Kalev-Zylinska, a postdoctoral researcher at the University of Auckland, in New Zealand, uncovered a neuronal mechanism that may help explain the link between alcohol and improved memory.

“We saw a noticeable change on the surface of certain neurons in rats that were given alcohol,” During said. “This change may have something to do with the positive effects of alcohol on memory.”

The researchers presented their findings at the annual Society for Neuroscience conference in Atlanta.

During and Kalev-Zylinska designed a special liquid diet for the rats. One formulation included a low dose of alcohol, comparable to two or three drinks a day for a human, while the other diet included a much higher dose of alcohol, comparable to six or seven drinks a day for a human. A third group of rats was given a liquid diet without alcohol. All animals were given their respective diets daily for about four weeks.

The researchers measured the rats' blood-alcohol levels three times throughout the study. Toward the end of the study, they subjected the rats to two different memory tasks.

For the first task, the rats were given several minutes to examine two identical, square plastic objects. After a certain amount of time, a researcher replaced one of the objects with a new, round object made of glass. The researchers measured the amount of time that each rat spent checking out the new object – an indication that the animal recognizes it as a new object.

Rats given low doses of alcohol spent about three times longer examining the new object than did rats on the alcohol-free diet. Rats given the high dose of alcohol spent equivalent amounts of time checking out both objects, suggesting that they were unable to differentiate the old object from the new one.

For the second task rats were placed in a box with two chambers separated by a door. One chamber was well-lit, while the adjacent chamber was dark. After placing a rat in the well-lit chamber and then lifting the door, the researchers timed how quickly the rats entered the dark chamber (rats are nocturnal, and naturally prefer dark spaces.) Once inside the dark chamber, the rat received a mild electric shock to its feet.

The researchers repeated this same experiment 24 hours later, and kept track of how long it took the animal to enter the dark chamber. Many of the animals re-entered the dark area, yet the rats given alcohol waited anywhere from 2.5 to 4.5 times longer to enter the dark chamber than did the animals given the alcohol-free diet.

“The results suggest that both doses of alcohol moderately improved the animals' ability to remember this negative event, since they seemed hesitant to go into the dark area,” During said. “It also suggests that high levels of alcohol can reinforce bad memories.

“People who drink to forget bad memories may actually be doing the opposite by reinforcing the neural circuits that control negative emotional memory,” he continued.

At the end of the study, the researchers analyzed brain and liver tissue from each animal.

They found that low levels of alcohol increased the expression of a particular receptor, NR1, on the surface of neurons in a region of the brain, the hippocampus, that plays a role in memory. Researchers think that NR1 plays a role in memory and learning.

In a separate set of experiments, During and Kalev-Zylinska increased the number of NR1 receptors in another group of rats, and found that this boost improved the animals' memories to an extent similar to the improvement seen in the rats given low doses of alcohol. They also they used a new gene transfer technique to knock down the NR1 receptors in a group of rats given alcohol – alcohol had no memory-enhancing effects on these animals.

“These experiments suggest that the effect of alcohol works through the NR1 receptor, at least where memory and learning are concerned,” During said.

“We didn't see any toxic effects of low-level alcohol consumption on the brain or the liver,” During said. “It didn't damage neurons nor did it cause liver damage during the short study. But the higher dose of alcohol damaged both.”
Erotic images prove useful in coaxing out unconscious brain activity

When your eyes are presented with erotic images in a way that keeps you from becoming aware of them, your brain can still detect and respond to the images according to your gender and sexual orientation, a team of University of Minnesota psychologists has found. The team, led by graduate student Yi Jiang and his adviser, psychology professor Sheng He, found that even when unaware of erotic images in their field of vision, research subjects shifted the focus of their visual attention according to whether they were straight males, gay males, straight women or gay/bisexual women. The researchers, who have published their findings in the Proceedings of the National Academy of Sciences online, stressed that while differences among the groups are clear, individual differences are not and so could not be used to determine a person's sexual orientation.

The purpose of the work was to uncover mechanisms by which the brain processes visual information that is not consciously perceived by the subjects. When subjects become conscious of images, the sequence of steps in brain processing becomes very complicated because neurons engage in all sorts of feedback and crosstalk--especially with emotionally charged information. The researchers were studying the flow of visual information at an earlier stage, while it is still traveling along a one-way path.

"We're trying to reveal what happens when one doesn't have a conscious visual perception. That is, how the brain processes visual information independent of consciousness," said He.

The researchers chose to generate brain activity by using erotic pictures because they promised to elicit strong responses and clear patterns in the data. But the researchers believe the mechanisms by which the brain processes such images are universal.

"This definitely doesn't just work for erotic pictures," said He. "But erotic images stand out in terms of potency to generate a response."

In the experiments, subjects were seated at a stereoscope, which allows different images to be simultaneously displayed to the left and right eyes. Each eye was presented with a square screen that was divided into two patches sitting side by side. One eye was presented with an intact picture of a nude person in one patch and the same picture scrambled in the neighboring patch. The other eye was presented with twin patches containing moving, high-contrast noise patterns similar to "snow" on a TV screen. As seen by the subjects, the screens from both eyes overlapped. The moving images had the effect of suppressing the information coming from the other eye, rendering the intact pictures invisible.

The subjects were then tested to see if their visual attention had shifted toward or away from the part of the visual field where the intact erotic image had appeared.

The strongest shift in attention toward the area where the image had been was in heterosexual men who had been shown nude female images. Those subjects also tended to be repelled by nude male images. Among heterosexual women, nude male images induced a less strong attention shift toward the image site but no significant shift in response to nude female pictures. Gay men behaved similarly to heterosexual women, and gay/bisexual women performed in between heterosexual men and women.

The divergent results among the groups of study subjects provide evidence that the subjects' brains were processing the visual information in a selective manner.

"Selective attention helps us to quickly process what is important while ignoring the irrelevant," the researchers write. "In this study, we demonstrate that information that has not entered observers' consciousness, such as [invisible] erotic pictures, can direct the distribution of spatial attention. Furthermore, invisible erotic information can either attract or repel observers' spatial attention depending on their gender and sexual orientation."

The images in the study were likely processed by the amygdala, a brain center that plays a critical role in processing emotional information, said He. But the researchers believe that the information about the images is probably destroyed at an early stage of processing by the cerebral cortex, where information from our two eyes is combined.

Dostları ilə paylaş:
1   2   3   4   5   6   7   8
Orklarla döyüş:

Google Play'də əldə edin

Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur © 2017
rəhbərliyinə müraciət

    Ana səhifə