Friday, June 24, 2011
Monday, June 20, 2011
AN ENIGMATIC (SYNAPSID?) TOOTH FROM THE EARLY CRETACEOUS OF NEW SOUTH WALES, AUSTRALIA1. WILLIAM A. CLEMENS (a)2. GREGORY P. WILSON (a)3. RALPH E. MOLNAR (b)a. Museum of Paleontology and Department of Integrative Biology, University of California Berkeley, California 94720-4785, firstname.lastname@example.org. Queensland Museum, P.O. Box 3300, South Brisbane QLD 4101, Australia, and Museum of Northern Arizona, Flagstaff, Arizona 86011Abstract:Largely fragmentary fossils from sites in New South Wales, Victoria, and Queensland, Australia document terrestrial and marine vertebrate faunas of Aptian–Albian age. The natural cast of a large tooth from the Griman Creek Formation, Lightning Ridge, New South Wales, records the presence of a hitherto unknown member of the fauna. Although reference to one of the groups of crocodyliforms that evolved complex, mammal-like postcanine teeth cannot be excluded, the fossil more likely represents a species of synapsid. In some respects it is similar to lower postcanines of traversodontids. Greater morphological similarities to upper molars of dryolestids make reference of this tooth to this group more likely. Current Mesozoic Laurasian and Gondwanan fossil records include mammals with cheek teeth of similar large size.
Link to paper in title.
On rare occasion, the light-sensing photoreceptor cells in the eye misfire and signal to the brain as if they have captured photons, when in reality they haven't. For years this phenomenon remained a mystery. Reporting in the June 10 issue of Science, neuroscientists at the Johns Hopkins University School of Medicine have discovered that a light-capturing pigment molecule in photoreceptors can be triggered by heat, as well, giving rise to these false alarms.
"A photon, the unit of light, is just energy, which, when captured by the pigment rhodopsin, most of the time causes the molecule to change shape, then triggering the cell to send an electrical signal to the brain to inform about light absorption," explains King-Wai Yau, Ph.D., professor of neuroscience at Johns Hopkins and member of its Center for Sensory Biology. "If rhodopsin can be triggered by light energy," says Yau, "it may also be occasionally triggered by other types of energy, such as heat, producing false alarms. These fake signals compromise our ability to see objects on a moonless night. So we tried to figure it out; namely, how the pigment is tripped by accident."
"Thermal energy is everywhere, as long as the temperature is above absolute zero," says neuroscience research associate Dong-Gen Luo, Ph.D. "The question is: How much heat energy would it take to trigger rhodopsin and enable it to fire off a signal, even without capturing light?" says Johns Hopkins Biochemistry, Cellular and Molecular Biology graduate student Wendy Yue.
For 30 years, the assumption was that heat could trigger a pigment molecule to send a false signal, but through a mechanism different from that of light, says Yau, because it seemed, based on theoretical calculations: that very little thermal energy was required compared to light energy.
But the theory, according to Yau, was based mainly on the pigment rhodopsin. However, rhodopsin is mainly responsible for seeing in dim light and is not the only pigment in the eye; other pigments are present in red-, green- and blue-sensitive cone photoreceptors that are used for color and bright-light vision. Although researchers are able to measure the false events of rhodopsin from a single rhodopsin-containing cell, a long-standing challenge has been to take measurements of the other pigments. "The electrical signal from a single cone pigment molecule is so small in a cone cell that it is simply not measurable," says Luo. "So we had to figure out a new way to measure these false signals from cone pigments."
By engineering a rod cell to make human red cone pigment, which is usually only found in cone cells, Yau's team was able to measure the electrical output from an individual cell and calculate this pigment's false signals by taking advantage of the large and detectable signals sent out from the cell.
As for blue cone pigment, "Nature did the experiment for us," says Yau. "In many amphibians, one type of rod cells called green rods naturally express a blue cone pigment, as do blue cones." So to determine whether heat can cause pigment cells to misfire, the team, working in the dark, first cooled the cells, and then slowly returned the cells to room temperature, measuring the electrical activity of the cells as they warmed up. They found that red-sensing pigment triggers false alarms most frequently, rhodopsin (bluish-green-sensing pigment) triggers falsely less frequently, and blue-sensing pigment does so even less.
"This validates the 60-year-old Barlow's hypothesis that suggested the longer wavelength the pigment senses—meaning the closer to the red end of the spectrum—the noisier it is," says Yau. And this finding led the team to develop and test a new theory: that heat can trigger pigments to misfire, by the same mechanism as light.
Pivotal to this theory is that visual pigment molecules are large, complex molecules containing many chemical bonds. And since each chemical bond has the potential to contain some small amount of thermal energy, the total amount of energy a pigment molecule could contain can, in theory, be enough to trigger the false alarm.
"For a long time, people assumed that light and heat had to trigger via different mechanisms, but now we think that both types of energy, in fact, trigger identical changes in the pigment molecules," says Yau. Moreover, since longer wavelength pigments have higher rates of false alarms, Yau says this may explain why animals never evolved to have infrared-sensing pigments.
"Apart from putting to rest a long-standing debate, it's a wake-up call for researchers to realize that biomolecules in general have more potential thermal energy than previously thought," says Luo.
Link in title.
Wednesday, June 15, 2011
Friday, June 10, 2011
Wednesday, June 08, 2011
The study, published yesterday in the journal Ecology Letters, analyzed the species richness and the structure of their communities throughout the different regions of the European territory from the Ural Mountains to the Iberian Peninsula. The selection of this family of insects was motivated by their high dispersal ability and because their food sources (mainly cattle and sheep dung) are present throughout the continent.Research by the Spanish National Research Council reveals that the large impacts occurred during the last ice age maintain their effects on the current distribution of dung beetles of the scarab family. The presence of these beetles in Europe seems to be more influenced by the climate of that glaciation than by the present one.Scarabs are insects of tropical origin that cannot survive below 0 ° C mean annual temperature, "so it could be expected that their presence gradually decreases as temperatures drop down northwards " says the researcher from the National Museum of Natural Sciences, CSIC, Joaquín Hortal. However, the analysis of the relationship between the magnitude of climate change since the last glaciation and the distribution of scarabs evidences that these insects are not evenly distributed according to this gradient, but rather show two different patterns, one in the north and one in the south. Horton said: "The border defining the two areas is almost similar to the limit of 0 °C of mean annual temperature at the time of the last ice age." (See Figure 1)Although scarab species richness is actually lower in the north that in the south, another two characteristics can be explained under the hypothesis of the influence of the last ice age.The first one is based on the species present throughout Europe. Data show that all scarab species living in the northern territory above the border defined by the 0 ° C limit in the last glaciations are also present in the south, and there is no species exclusive to the northernmost area. According to Hortal, "this is an effect of the difficulty of adapting to cold climate that still exists, as the north does not hold unique species adapted to the cold."This feature is consistent with the second observation, based on the age of the species present in each area. The study results show that the species that have been able to re-colonize the north are also those that have evolved most recently." Although the adaptation to cold climates started before the last glaciation, these species belong to the newer phylogenetic branches of the Scarabaeidae," says the researcher from CSIC.
Thursday, June 02, 2011
Japanese researchers are working on a solar-sail spacecraft with 10 times the surface area of the Ikaros testbed launched toward Venus last year, after achieving all of their technical objectives with the testbed.This spacecraft will launch on a five-year mission instead of the six-month span allotted to Ikaros. Lofted as a piggyback payload with the Venus Climate Orbiter Akasuki on May 21, 2010, Ikaros passed Venus on Dec. 8.Researchers hoped to demonstrate automatic sail deployment, power generation with thin-film solar cells on the sail surface, verification that the pressure of photons from the Sun caused the sail to accelerate, and guidance and navigation with the sail. The sail met its intended acceleration of 100 meters per second and veered off the ballistic trajectory it would have followed without the Sun’s pressure, says Yuichi Tsuda, an assistant professor in the Japan Aerospace Exploration Agency (JAXA) Space Exploration Center, in an English-language report on the experiment’s outcome.The deployment and power generation were demonstrated early on. To control the 14 x 14-meter (46 x 46-ft.) spin-stabilized sail, the Ikaros team used a non-toxic “gas-liquid equilibrium thruster” for attitude control, and an attitude-detection system that combined a Sun sensor and Doppler measurements from the low-gain antenna.To tilt the spin axis of the spacecraft, the team powered a liquid-crystal variable-reflectivity element mounted as a thin polyimide film around the edges of the sail off and on to throw the spinning sail off balance and tilt it as it spun. As it happened, the spacecraft required almost no fuel to keep its sail facing the Sun, even though it turned a full 180 deg. over the six months, according to Tsuda.
Wednesday, June 01, 2011
Mammoths were a diverse genus that roamed across Eurasia and North America during the Pleistocene era. In continental North America, at least two highly divergent species have long been recognized – woolly mammoths (Mammuthus primigenius) and Columbian mammoths (M. columbi). But new genetic evidence published in BioMed Central's open access journal Genome Biology suggests that these species may have been closely related enough to mate when they had the chance.Remains of woolly mammoths have been found across the glacial tundra-steppe of Eurasia and northern North America, while the much physically larger Columbian mammoths inhabited the savannah environments of temperate southern and central North America. The differences between the species have long been considered as unique adaptations to the environments where they evolved. But by piecing together trace fragments of DNA from an 11 thousand year-old Columbian mammoth from Fairview, Utah, a team of Canadian, American and French researchers found that surprisingly the mitochondrial genome from this mammoth was nearly indiscernible from that of its northern woolly counterparts.But the group does not suspect that this requires a re-write of North American mammoth evolution. "We think this individual may have been a woolly-Columbian hybrid," says Jacob Enk of the McMaster Ancient DNA Centre, the group that led the research. "Living African elephant species interbreed where their ranges adjoin, with males of the bigger species out-competing the smaller for mates. This results in mitochondrial genomes from the smaller species showing up in populations of the larger. Since woolly and Columbian ranges periodically overlapped in time and space, it's likely that they engaged in similar behaviour and left a similar genetic signal." The team goes on to suggest that interbreeding may explain some mammoth fossils that have intermediate physical characteristics, between woollies and Columbians, sometimes assigned to the species M. jeffersonii.They do not rule out other explanations however, and note that the only way to know for sure whether their mammoth was a hybrid is to sequence nuclear DNA from it and other mammoths. For poorly-preserved remains like those of southern-ranging Columbians, this will be a challenge. But they expect that by exploiting new cutting-edge sequencing technologies, the nuclear genomes of these amazing animals are within reach.
Recent research by a team of physicists reveals a surprise at this fundamental level. ETH-Professor Renato Renner, and Vlatko Vedral of the Centre for Quantum Technologies at the National University of Singapore and the University of Oxford, UK, and their colleagues describe in the scientific journal Nature how the deletion of data, under certain conditions, can create a cooling effect instead of generating heat. The cooling effect appears when the strange quantum phenomenon of entanglement is invoked. Ultimately, it may be possible to harness this effect to cool supercomputers that have their performance held back by heat generation. «Achieving the control at the quantum level that would be required to implement this in supercomputers is a huge technological challenge, but it may not be impossible. We have seen enormous progress is quantum technologies over the past 20 years,» says Vedral. With the technology in quantum physics labs today, it should be possible to do a proof of principle experiment on a few bits of data.