Astronomy
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Milky Way’s New Neighbor: A Giant Dwarf
Ever since astronomers discovered our universe’s accelerating expansion, tension has rippled between theory and observations, especially in studies of our galaxy’s neighborhood.
The standard model of cosmology, which suggests that dark energy and “cold” dark matter govern the universe’s evolution, predicts many more small galaxies near the Milky Way than what we’ve observed so far. Dwarfs should be the building blocks of larger galaxies like our own, so the lack has puzzled astronomers — are they not there, or are we just not seeing them?
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Now, the list of known dwarfs has just added one of its largest members: Crater 2. You’d think large dwarfs would be easy to find, but this one’s stars are spread out and easily entangled with the stars of the Milky Way. It took a sensitive survey to pick out the small galaxy hidden behind the galaxy’s stars.
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Gabriel Torrealba (University of Cambridge, UK) led a team that discovered the Crater 2 dwarf galaxy in survey data collected at the Very Large Telescope in Chile. The team used specialized software to spot over-crowding among stars, searching for dim stellar clumps. But identifying a clump isn't enough. Only Crater 2 contained red giant stars and horizontal branch stars — both old, evolved stars that mark an ancient stellar population separate from the youthful Milky Way disk.
Torrealba and colleagues estimate that Crater 2 lies 391,000 light-years from Earth. That makes it one of the most distant dwarf galaxies known. It’s also one of the largest: at 6,500 light-years across, it comes in fourth among our galaxy’s neighbors, after the Large and Small Magellanic Clouds, and the torn-apart Sagittarius dwarf galaxy. Moreover, it’s incredibly diffuse, its stars spread out over several square degrees. So despite its size, Crater 2 is much fainter than those Milky Way companions, nearly 100 times fainter than Sagittarius and almost 10,000 times fainter than the LMC.
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Curiosity Leaves Rough Terrain For Smoother, Science Rich Lakebed
NASA's Curiosity Mars rover has nearly finished crossing a stretch of the most rugged and difficult-to-navigate terrain encountered during the mission's 44 months on Mars.
The rover climbed onto the Naukluft Plateau of lower Mount Sharp in early March after spending several weeks investigating sand dunes. The plateau's sandstone bedrock has been carved by eons of wind erosion into ridges and knobs. The path of about a quarter mile (400 meters) westward across it is taking Curiosity toward smoother surfaces leading to geological layers of scientific interest farther uphill.
The roughness of the terrain on the plateau raised concern that driving on it could be especially damaging to Curiosity's wheels, as was terrain Curiosity crossed before reaching the base of Mount Sharp. Holes and tears in the rover's aluminum wheels became noticeable in 2013. The rover team responded by adjusting the long-term traverse route, revising how local terrain is assessed and refining how drives are planned. Extensive Earth-based testing provided insight into wheel longevity.
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The next part of the rover's route will return to a type of lake-deposited mudstone surface examined previously. Farther ahead on lower Mount Sharp are three geological units that have been key destinations for the mission since its landing site was selected. One of the units contains an iron-oxide mineral called hematite, which was detected from orbit. Just above it lies a band rich in clay minerals, then a series of layers that contain sulfur-bearing minerals called sulfates. By examining them with Curiosity, researchers hope to gain a better understanding of how long ancient environmental conditions remained favorable for microbial life, if it was ever present on Mars, before conditions became drier and less favorable.
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Biology
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Researcher Studies How Animals Puncture Things
If shooting arrows from a crossbow into cubes of ballistics gelatin doesn’t sound like biological science to you, you’ve got a lot to learn from University of Illinois animal biology professor Philip Anderson, who did just that to answer a fundamental question about how animals use their fangs, claws and tentacles to puncture other animals.
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The study is the first step of an effort to understand how nature, “red in tooth and claw,” as the poet Alfred Tennyson wrote, uses tooth, claw, tentacles and even tools to capture food or defend against an enemy, competitor or predator.
“There are a lot of animals that have to puncture in order to survive,” Anderson said. “You have snakes that puncture with their fangs during strikes to inject venom. Some mantis shrimp, a group of marine crustaceans, use their very fast, power-amplified appendages to harpoon things like fish out of the water column and pull them down into their burrows to feed.”
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“[Stinging sea creatures like the Portuguese man-of-war] sting using single-celled organs on their tentacles called nematocysts, which are basically little hydrostatic, pressurized harpoons that inject venom,” he said.
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“What’s really cool from the evolutionary point of view is that it’s not often that you have the ability to look at biomechanical systems across such a wide range of animals that are all trying to achieve a similar performance,” Anderson said.
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A 'Tropical' Parasitic Disease Emerges In The Canadian Arctic
An outbreak of an intestinal parasite common in the tropics, known as Cryptosporidium, has been identified for the first time in the Arctic. The discovery was made in Nunavik, Quebec, by a team from the Research Institute of the McGill University Health Centre (RI-MUHC), in collaboration with the Nunavik Department of Public Health, Institut National de Santé Publique du Québec and Health Canada. The discovery, which was documented in the journal PLoS Neglected Tropical Diseases, could have long-term implications for the health of children in Nunavik and Nunavut's communities.
"We were very surprised to discover this strain of Cryptosporidium in the Artic, which is more typically seen in low-income countries than elsewhere in North-America," says the study's senior author, Dr. Cédric Yansouni, who is Associate Director of the J.D. MacLean Centre for Tropical Diseases at the MUHC and Professor of the Division of Infectious Diseases in the Department of Medical Microbiology at McGill University.
Cryptosporidium is a microscopic parasite that lives in the intestine of mammals, including humans, and is transmitted by the fecal-oral route from ingestion of contaminated food or water or contact with infected individuals. The parasite causes an illness known as Cryptosporidiosis which is characterized by diarrhea, cramps and vomiting. The disease can last several weeks and can be fatal for young children and those with weakened immune systems, such as people with AIDS, transplant recipients, or patients undergoing cancer treatment. The researchers examined an outbreak of Cryptosporidium that occurred between April 2013 and April 2014 across 10 villages in Nunavik. In close collaboration with the clinical teams on site, the researchers were able to identify that the strain was Cryptosporidium hominis, which is spread from human to human and usually found in tropical countries.
"We are being particularly vigilant because it is known in low-income countries that repeated Cryptosporidium infections can cause growth delays and difficulty at school in children. In the Nunavik outbreak, children under the age of five were the group most affected by the infection," explains Dr. Yansouni.
Chemistry
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Mixed Outlook For Ethanol–Petrol Blends
As part of the world’s switch toward renewable fuels, ethanol from biomass is being blended with gasoline in increasing proportions. UK petrol typically contains 5% ethanol. This will rise to 10% by 2020, but other countries, like Brazil, already use much higher proportions. In addition to reducing fossil fuel consumption, ethanol blends can cut emissions of some air pollutants such as carbon monoxide and particulate matter.
However, scientists from the University of Leeds and the University of York have now shown that ethanol blended fuels could also have environmental drawbacks. The team sampled London’s air during 2012 and found significantly higher levels of atmospheric ethanol, and its related oxidation product acetaldehyde, than those predicted by the NAEI, the UK’s national emissions estimate. In fact, current models underestimated acetaldehyde levels by up to a factor of 40.
Despite their importance in the urban atmosphere, ethanol and acetaldehyde are seldom studied. ‘Because they’re not part of air quality regulations, they’re not routinely measured,’ explains Rachel Dunmore from the University of York, who led the study. ‘We know that they can have adverse health effects or other air quality effects such as ozone production, so the fact that we observed high levels of them piqued our interest.’
Acetaldehyde is a respiratory irritant and a suspected carcinogen. Engines can generate acetaldehyde, as can ethanol being photo-oxidised in the air. In addition, both ethanol and acetaldehyde are active in other photochemical processes such as ozone production, long after they are emitted. Because ethanol is long-lived, increased emissions from somewhere like London could result in increased ozone production in downwind areas.
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How Lead Ended Up In Flint’s Tap Water
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Cities no longer install lead pipes. But older cities such as Flint still rely on them, usually as service lines that connect water mains in the street to a home’s water meter. A 1990 report from the American Water Works Association estimates there are millions of lead service lines in the U.S. To limit how much lead leaches into the water from these pipes and some homes’ plumbing, EPA’s Lead & Copper Rule requires water utilities serving more than 50,000 people to establish a plan to monitor and control corrosion.
As part of these plans, utilities treat their water to maintain a mineral crust on the inside surfaces of their pipes. This so-called passivation layer protects the pipes’ metal from oxidants in the water. The coatings consist, in part, of insoluble oxidized metal compounds produced as the pipe slowly corrodes.
If the water’s chemistry isn’t optimized, then the passivation layer may start to dissolve, or mineral particles may begin to flake off of the pipe’s crust. This exposes bare metal, allowing the iron, lead, or copper to oxidize and leach into the water. Environmental engineers that C&EN contacted say that, on the basis of how Flint treated the river water, the water chemistry was not optimized to control corrosion.
Most important, the treated Flint River water lacked one chemical that the treated Detroit water had: phosphate. “They essentially lost something that was protecting them against high lead concentrations,” Giammar says. Cities such as Detroit add orthophosphate to their water as part of their corrosion control plans because the compound encourages the formation of lead phosphates, which are largely insoluble and can add to the pipes’ passivation layer. [...]
The entire Flint water crisis could have been avoided if the city had just added orthophosphate, Edwards says. He bases his opinion, in part, on experiments his group ran on the treated Flint River water. The researchers joined copper pipes with lead solder and then placed the pieces in either treated Flint River water or treated Detroit water. After five weeks in the Flint water, the joined pipes leached 16 times as much lead as those in the Detroit water, demonstrating just how corrosive the treated Flint water was. But when the scientists added a phosphate corrosion inhibitor to the Flint water, the factor went down to four.
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Ecology
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Long-Eared Bat Denied Habitat Protection Under The Endangered Species Act
Although northern long-eared bat populations have declined by 90 percent in their core range, the U.S. Fish and Wildlife Service today said it will not protect any of its critical habitat, saying it would not be “prudent” for the species. Under the Endangered Species Act, the government can opt not to designate critical habitat if there is factual evidence that a species would be placed at greater risk of extinction from poachers, collectors or vandals. But in the case of the northern long-eared bat, which is listed as “threatened” under the Endangered Species Act, there is almost no evidence that the species is at risk from these types of threats. Instead its dramatic decline has been driven mostly by disease and habitat loss.
“This is a terrible turn of events for the northern long-eared bat,” said Tanya Sanerib, an attorney at the Center for Biological Diversity. “If you don’t protect the places endangered species live, it becomes that much harder to save them. This is yet another instance where the Fish and Wildlife Service has gone out of its way to appease special interests rather than protecting our most vulnerable animals.”
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Despite scientific research showing that species with critical habitat are twice as likely to be on a path toward recovery as species without designated habitat, only half of endangered species have received critical habitat to date. Although Congress intended that the overwhelming majority of endangered species would receive critical habitat, the “not prudent” loophole has been repeatedly abused to avoid giving species the vital protections they need. In the case of the northern long-eared bat, the Fish and Wildlife Service has justified limits on the protections for the bat, arguing that white-nose syndrome is the only threat to the species that puts it at risk of extinction.
The Service tailored the protections of the bat only to those areas within a quarter-mile of known wintering hibernacula, like caves, and to known maternity roosts where bats raise their young. Critical habitat designations provide an additional layer of protections for endangered species by prohibiting federal agencies from taking actions that would adversely modify those areas. Critical habitat also guides conservation and recovery planning by identifying the most important areas for a species that need extra protection. However, unless an activity on private lands is funded or permitted by the federal government, a critical habitat designation has little impact on purely private actions.
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Long-Term Exposure To Particulate Air Pollutants Associated With Numerous Cancers
The study between the University of Birmingham and University of Hong Kong, published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research, adds to growing concern around the health risks of prolonged exposure to ambient fine particulate matter.
Particulate matter is the term for particles found in the air, including hydrocarbons and heavy metals produced by transportation and power generation, among other sources. This study focused on ambient fine particulate matter, or matter with an aerodynamic diameter of less than 2.5 micrometers (PM2.5).
For every 10 microgram per cubic meter (µg/m³) of increased exposure to PM2.5, the risk of dying from any cancer rose by 22 percent.
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After adjusting for smoking status, and excluding deaths that had occurred within three years of the baseline to control for competing diseases, the study showed that for every 10 µg/m³ of increased exposure to PM2.5, the risk of dying from any cancer rose by 22 percent. Increases of 10 µg/m³ of PM2.5 were associated with a 42 percent increased risk of mortality from cancer in the upper digestive tract and a 35 percent increased risk of mortality from accessory digestive organs, which include the liver, bile ducts, gall bladder, and pancreas.
For women, every 10 µg/m³ increase in exposure to PM2.5 was associated with an 80 percent increased risk of mortality from breast cancer, and men experienced a 36 percent increased risk of dying of lung cancer for every 10 µg/m³ increased exposure to PM2.5.
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Physics
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Light-Powered 3-D Printer Creates Terahertz Lens
From visible light to radio waves, most people are familiar with the different sections of the electromagnetic spectrum. But one wavelength is often forgotten, little understood, and, until recently, rarely studied. It's called terahertz, and it has important applications in imaging and communications.
"Terahertz is somewhat of a gap between microwaves and infrared," said Northwestern University's Cheng Sun. "People are trying to fill in this gap because this spectrum carries a lot of information."
Sun and his team have used metamaterials and 3-D printing to develop a novel lens that works with terahertz frequencies. Not only does it have better imaging capabilities than common lenses, but it opens the door for more advances in the mysterious realm of the terahertz.
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There are two major factors that made this new lens possible. First, it is made from a novel metamaterial that exhibits properties not readily available in nature. "Such properties originate from its tiny structures that are much smaller than the terahertz wavelength," said Fan Zhou, the paper's first author and member of Sun's laboratory. "By assembling these tiny structures, we can create specific refractive index distribution."
Second, the lens was manufactured with a 3-D printing technique called projection micro-stereo-lithography. The technique enables a scalable, rapid, and inexpensive way to produce the tiny features that are needed for the lens to operate at the terahertz frequency band. The printing technology allowed the researchers to fabricate the metamaterial to precisely fit their designs.
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Personal Cooling Units On The Horizon
Firefighters entering burning buildings, athletes competing in the broiling sun and workers in foundries may eventually be able to carry their own, lightweight cooling units with them, thanks to a nanowire array that cools, according to Penn State materials researchers.
"Most electrocaloric ceramic materials contain lead," said Qing Wang, professor of materials science and engineering. "We try not to use lead. Conventional cooling systems use coolants that can be environmentally problematic as well. Our nanowire array can cool without these problems."
Electrocaloric materials are nanostructured materials that show a reversible temperature change under an applied electric field. Previously available electrocaloric materials were single crystals, bulk ceramics or ceramic thin films that could cool, but are limited because they are rigid, fragile and have poor processability. Ferroelectric polymers also can cool, but the electric field needed to induce cooling is above the safety limit for humans.
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Their vertically aligned ferroelectric barium strontium titanate nanowire array can cool about 5.5 degrees Fahrenheit using 36 volts, an electric field level safe for humans. A 500 gram battery pack about the size of an IPad could power the material for about two hours.
The researchers grow the material in two stages. First, titanium dioxide nanowires are grown on fluorine doped tin oxide coated glass. The researchers use a template so all the nanowires grow perpendicular to the glass' surface and to the same height. Then the researchers infuse barium and strontium ions into the titanium dioxide nanowires.