Astronomy
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Ancient Volcanos Point To Extensive Ice On Mars
Volcanoes erupted beneath an ice sheet on Mars billions of years ago, far from any ice sheet on the Red Planet today, new evidence from NASA's Mars Reconnaissance Orbiter suggests.
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Sheridan Ackiss of Purdue University, West Lafayette, Indiana, and collaborators used the orbiter's mineral-mapping spectrometer to investigate surface composition in an oddly textured region of southern Mars called "Sisyphi Montes." The region is studded with flat-topped mountains. Other researchers previously noted these domes' similarity in shape to volcanoes on Earth that erupted underneath ice.
"Rocks tell stories. Studying the rocks can show how the volcano formed or how it was changed over time," Ackiss said. "I wanted to learn what story the rocks on these volcanoes were telling."
When a volcano begins erupting beneath a sheet of ice on Earth, the rapidly generated steam typically leads to explosions that punch through the ice and propel ash high into the sky. For example, the 2010 eruption of ice-covered Eyjafjallajökull in Iceland lofted ash that disrupted air travel across Europe for about a week.
Characteristic minerals resulting from such subglacial volcanism on Earth include zeolites, sulfates and clays. Those are just what the new research has detected at some flat-topped mountains in the Sisyphi Montes region examined with the spacecraft's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), providing resolution of about 60 feet (18 meters) per pixel.
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New Tech Will Pin Down Earth's Position In Space And Time
Earlier this year, NASA and several partners successfully tested new technology that will make it easier to measure Earth's position in space and time. The work will improve navigation of space missions and geophysical studies of Earth, agency officials said.
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Specifically, NASA is working on improvements to very long baseline interferometry (VLBI), a technique that allows multiple radio telescopes to work together simultaneously to make more precise measurements.
A signal from a radio-emitting object, such as a quasar (the region around a galaxy's central supermassive black hole), is collected by several telescopes. Then, researchers calculate the distance between the telescopes by comparing the times at which the radio signal arrived at different receivers. The new system allows scientists to determine that timing more precisely, making measurements of the Earth's rotation and orientation more accurate, NASA officials said.
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One improvement is the size of the dishes. At 39 to 42 feet (12 to 13 meters) wide, the new dishes are significantly smaller than the 65- to 100-foot-wide (20 to 30 m) ones used in the older network. The smaller dishes can move more quickly and do 100 observations per hour, compared with about 12 per hour for the older system. This smaller dish type is also less expensive than the older, larger ones, NASA officials said. In addition, VGOS can use broadband capability to perform more sensitive observations, thus allowing for more precise measurements with less interference from other radio sources, NASA officials said. It can work in four frequencies (bands) at the same time, allowing data-transfer rates of 8 to 16 gigabits per second (1,000 times the data-transfer rate of HDTV). The older system, by contrast, uses only two frequencies and has a data-transfer rate of 256 megabits per second, NASA officials said.
In addition, VGOS can use broadband capability to perform more sensitive observations, thus allowing for more precise measurements with less interference from other radio sources, NASA officials said. It can work in four frequencies (bands) at the same time, allowing data-transfer rates of 8 to 16 gigabits per second (1,000 times the data-transfer rate of HDTV). The older system, by contrast, uses only two frequencies and has a data-transfer rate of 256 megabits per second, NASA officials said.
Biology
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First Gene Linked To Temperature Sex Switch
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In crocodiles, alligators, and certain lizard and turtle species, an embryo can become either a male or a female depending on the temperatures it experiences while in the egg. Rapid climate change may threaten the future of some of these species by skewing the sex ratio. For example, by some estimates temperature rises over the next century will cause painted turtles to produce only females. Such species may also evolve in response to climate change. Biologists are trying to understand how these animals will be affected by and adapt to rising global temperatures.
But little is known about how this temperature-dependent switch between ovaries and testes is regulated. To look for clues to the molecular mechanisms behind this process, study leader Turk Rhen (University of North Dakota) and his colleagues investigate how genes influence sex determination in common snapping turtles. The advantage of focusing on this rugged-looking North American native is that sex is determined in a brief five-day window during the 65-day egg incubation: the temperature-sensitive period. If the incubation temperature during the temperature-sensitive period is changed from a "male-producing temperature" (26.5°C or 79.7°F) to a "female-producing temperature" (31°C or 87.8°F), all the eggs will hatch into females.
In previous work, the team identified a gene -- CIRBP -- that is activated within 24 hours of such a temperature shift. Two days later, several genes known to be involved in ovary or testes development are either activated or repressed. The new study confirmed that CIRBP is expressed at the right time (very early in the temperature-sensitive period) and the right place (the gonads) to be involved in specifying sex.
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Remarkably, this CIRBP variant may partly explain a curious fact about snapping turtles: the sex ratio in populations from different latitudes responds differently to temperature. For example, if you collect eggs from snapping turtles in Minnesota and Louisiana and incubate them all at 27°C (80.6°F) in the lab, the eggs collected in the North will produce nearly all males, while those from the South will produce mostly females. This variation suggests subpopulations of the species have evolved and adapted to their local climate.
The team found that the "C" version of CIRBP was more common in turtles from northern Minnesota than those from 250 miles away in southern Minnesota, and it was not detected in a population from even further south, in Texas. Though this is only a small sample of locations, the trend is consistent with the sex determination pattern in each population: the "A" version (which makes turtles more likely to be female) was more common in populations that produce females at a lower temperature.
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Crocodile Eyes Are Optimized For Lurking
Crocodiles aren’t terrifying just because they have huge teeth and a deadly bite, though. It’s that an attack appears to come from nowhere. The animals lurk just beneath the water, with only their eyes keeping a lookout for something tasty — like one of us. Now, new research shows that, while a croc may not see as well as you or I, its eyesight is quite good and well adapted for lying in wait at the water’s surface.
Nicolas Nagloo and colleagues from the University of Western Australia in Crawley took a detailed look at eyes from three young saltwater and two young freshwater crocodiles. “Both Australian species possess a bright yellow iris, a slit pupil and a relatively large lens,”[...]. Such features, which were known before this study, are helpful for seeing in dim light. (The animals, though, don’t have great vision underwater.) Crocs are also equipped with a “mobile slit retina” that helps the animals control how much light reaches the eye during daylight.
Dissections and examinations of the cells of the eyes revealed that both species have three types of single cones, a type of double cone and one type of rod. This means that the animals can see colors well. But the freshwater crocs appear to be a bit more sensitive to red than their saltwater counterparts (known as “salties” in Australia); that may help the freshies see in streams and rivers where there is more red light. Both species also have a horizontal streak of high spatial acuity, which allows the reptiles to scan back and forth for prey without ever moving their heads.
That the two species have eyes that are so similar is somewhat surprising given that they are separated by some 12 million years of evolution, live in different habitats and prefer different prey, with the freshwater crocs preferring smaller animals and more fish. But both species have adopted a similar hunting style in which the animals hide just beneath the water and scan the flat environment for a suitable meal. Their eyes, this study shows, are specialized to aid in such attacks.
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Chemistry
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Rechargeable First For Promising Battery Tech
Sodium–carbon dioxide batteries can theoretically store 10 times as much energy weight for weight as commercial lithium–ion batteries. They work similarly to lithium–air batteries but use cheaper, more abundant sodium and carbon dioxide. Moreover, many electrolytes react with the compounds formed during discharge in a lithium–air battery – a problem that doesn’t occur in sodium–carbon dioxide batteries, which only produce sodium carbonate and carbon.
However, the few existing metal–carbon dioxide batteries are non-rechargeable. As they discharge, solid products deposit on the cathode and block the gas channels that allow carbon dioxide to interact with the electrolyte, meaning the electrochemical reaction can’t be reversed. Jun Chen and his team at Nankai University in China overcame this flaw using an ether-based electrolyte and a carbon nanotube cathode. ‘We tried different kinds of carbon – active carbon, graphite – but carbon nanotubes performed best because they have a highly porous, three-dimensional structure,’ says Chen. This means the cathode stores the discharge solids without the gas channels becoming blocked.
With an energy density of about 1000Wh/kg, Chen’s battery already surpasses its commercial counterparts. ‘Lithium-ion batteries that are used in Tesla electric cars have only about 180Wh/kg,’ says Chen. And, he adds, even after 200 discharge–recharge cycles, they saw almost no drop in the battery’s capacity.
However, there are still challenges to overcome before a sodium–carbon dioxide battery will see the inside of an electric car. Chen admits that water is detrimental to the battery, it only works with pure carbon dioxide and their coin-sized setup is currently too small to power anything more than a tiny light emitting diode.
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Wasabi
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The pistachio-green paste on your plate might be called wasabi, but it’s most likely just a mix of European horseradish, mustard, and food coloring. Even in Japan, the home of wasabi, the real thing is in short supply.
“Real” wasabi comes from the rootlike stem, or rhizome (think of fresh ginger), of Wasabia japonica. As a member of the Cruciferae family, it is related to such plants as cabbage, cauliflower, broccoli, and mustard. Its distant cousin European horseradish (Armoracia rusticana) often pinch-hits for it in culinary uses.
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Unlike horseradish-based stand-ins, the heat of real wasabi dissipates quickly because of the volatility of the flavor components. “If you take imitation wasabi powder and add water, you can leave that almost overnight and it will still be hot,” says Brian Oates, president and chief scientific officer of Pacific Coast Wasabi, in Vancouver, British Columbia. “With wasabi, when you grate it up, it’s only good for, at most, 15 minutes.” The components of both wasabi and horseradish can be stabilized by acids, such as vinegar or lemon juice.
The key chemicals that give wasabi its characteristic heat and flavor aren’t present until the wasabi is macerated. When the cell wall is disrupted, it releases the enzyme myrosinase, which hydrolyzes glucosinolates, a group of sulfur-containing glucose derivatives, to produce isothiocyanates that provide wasabi’s spicy zing. The most abundant of these is allyl isothiocyanate.
“Horseradish has a different profile of isothiocyanates, and it is possible to taste the difference,” says Geoffrey P. Savage, an associate professor in the food group at Lincoln University, in Canterbury, New Zealand. “The problem is that not many people have tasted the original taste of wasabi, so they don’t know what they are tasting.”
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Ecology
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Clues Found In Crater Left By Dinosaur-Killing Asteroid
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After weeks of drilling from an offshore platform in the Gulf of Mexico, they have reached rocks left over from the day the Earth was hit by a killer asteroid.
The cataclysm is believed to have wiped out the dinosaurs. "This was probably the most important event in the last 100 million years," says Joanna Morgan, a geophysicist at Imperial College in London and a leader of the expedition.
Since the 1980s, researchers have known about the impact site, located near the present-day Yucatan Peninsula. Known as Chicxulub, the crater is approximately 125 miles across. It was created when an asteroid the size of Staten Island, N.Y., struck the Earth around 66 million years ago. The initial explosion from the impact would have made a nuclear bomb look like a firecracker. The searing heat started wildfires many hundreds of miles away.
After that, came an unscheduled winter. Sulfur, ash and debris clouded the sky. Darkness fell and, for a while, Earth was not itself.
"I think it was a bad few months really," Morgan says.
That's an understatement: Scientists believe 75 percent of life went extinct during this dark chapter in Earth's history, including the dinosaurs.
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Study Finds Ice Isn't Being Lost From Greenland's Interior
Scientists studying data from the top of the Greenland ice sheet have discovered that during winter in the center of the world's largest island, temperature inversions and other low-level atmospheric phenomena effectively isolate the ice surface from the atmosphere -- recycling water vapor and halting the loss or gain of ice.
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Near Greenland's coasts, Berkelhammer said, "it's relatively warm, and the ice melts faster and faster. But in the center of the ice sheet, it's 25 below zero Celsius (-13 F), so it's always freezing, even if it warms. It's a very rare occurrence to go above freezing," he said. The authors note that "despite rapid melting in the coastal regions of the ice sheet, a significant area -- approximately 40 percent -- rarely experiences surface melting."
Solid ice can be lost not only by melting into liquid water. Under certain conditions, it can vaporize by sublimation, a one-step transition from solid to gas. Such conditions exist at the high-altitude, dry, frigid, glacial surface of Greenland's interior.
"Sublimation is common there, unlike other places," Berkelhammer said. "We looked at the exchange of water between the ice sheet and the air above it through condensation, evaporation, and sublimation."
"We expected sublimation to increase with temperature, but we find no net loss" of ice over time, Berkelhammer said, again referring just to the interior of the ice mass. "You could say, if this process changes, you'd lose ice significantly faster. Or, if (recycling) becomes even more efficient, you would conserve even more ice mass.
"We can't predict," he said. "And we don't know from the ice-core records what the history is."
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Physics
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Engineers Create A Better Way To Boil Water—With Industrial, Electronics Applications
Engineers at Oregon State University have found a new way to induce and control boiling bubble formation, that may allow everything from industrial-sized boilers to advanced electronics to work better and last longer.
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The concept could be useful in two ways, researchers say - either to boil water and create steam more readily, like in a boiler or a clothing iron; or with a product such as an electronics device to release heat more readily while working at a cooler temperature.
"One of the key limitations for electronic devices is the heat they generate, and something that helps dissipate that heat will help them operate at faster speeds and prevent failure," said Chih-hung Chang, a professor of electrical engineering in the OSU College of Engineering. "The more bubbles you can generate, the more cooling you can achieve.
"On the other hand, if you want to create steam at a lower surface temperature, this approach should be very useful in boilers and improve their efficiency. We've already shown that it can be done on large surfaces and should be able to scale up in size to commercial use."
The new approach is based on the use of piezoelectric inkjet printing to create hydrophobic polymer "dots" on a substrate, and then deposit a hydrophilic zinc oxide nanostructure on top of that. The zinc oxide nanostructure only grows in the area without dots. By controlling both the hydrophobic and hydrophilic structure of the material, bubble formation can be precisely controlled and manipulated for the desired goal.
This technology allows researchers to control both boiling and condensation processes, as well as spatial bubble nucleation sites, bubble onset and departure frequency, heat transfer coefficient and critical heat flux for the first time.
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Researchers investigate Chladni Patterns In A Liquid At Microscale
A team of researchers with Université Grenoble Alpes in France has discovered that there are differences in patterns created in tiny particles immersed in water over a vibrating drum head, than in dry sand particles dropped on a metal plate and vibrated. In their paper published in Physical Review Letters, the researchers describe their experiments and the differences they found between the submerged particles, the patterns that developed and the mechanisms behind them.
Several centuries ago, it was noted that covering a plate with flour and causing the plate to vibrate resulted in the flour forming into different patterns, depending on the frequency of the vibration. Later it was noted that sand poured over the back of violin demonstrated the same types of properties—such patterns have subsequently been called Chladni Patterns and they have been used in designing musical instruments and other applications over the years. In this new effort, the researchers wondered if the same types of patterns would emerge in particles that exist in a water solution.
To find out, the researchers placed an amount of multi-sized microbeads into a container that had a membrane stretched across a base at the bottom, similar to a drum. They next filled the container with water and then watched (and filmed) what happened when the membrane was caused to vibrate at different frequencies.
The researchers found that the beads did migrate to form patterns, very similar to those in a dry environment, and they could be changed by adjusting the vibration frequency—but they also found that there were some differences. First, the patterns were not created the same way, instead of the finer grains getting pushed to nodes, they actually moved in the opposite direction, piling up at antinodes, forming what might be described as inverse Chladni patterns—due to a phenomenon known as acoustic streaming. But perhaps, more amusing, the team also found that under the right circumstances, i.e. causing vibrations that were off the resonant frequency, the microbeads could be caused to move in clusters around an outer circle, much like, they note, dancers engaged in a farandole.
The researchers note that their findings could have practical applications, like using vibrations to move particles in a fluid across a surface to a desired location in industrial applications, or more exotically, to move cells on a surface into a desired pattern before allowing them to grow.