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Scientists Find the Milky Way is Greasy
Scientists determined space is full of a grease-like substance. They estimate 10 billion trillion trillion metric tons of “space grease” floats in space. That’s enough for 40 trillion trillion trillion packs of butter. Professor Tim Schmidt said the substance is toxic and only exists in interstellar space. The team will next explore a mothball-like substance that exists in space. | <urn:uuid:122816bc-dd13-4158-a8d2-228d00b7868a> | 2.78125 | 89 | Truncated | Science & Tech. | 57.77693 | 95,477,707 |
Pristionchus nematodes come in two varieties: Most species consist of typical males and females, but in several species the females have evolved the ability to produce and use their own sperm for reproduction. Scientists from the Max Planck Institute of Developmental Biology in Tübingen, Germany, discovered that these so called hermaphrodites have shorter lifespans, with females frequently living over twice as long as closely related hermaphrodites.
The ways that males and females interact affects many biological processes, including the evolution of important traits like lifespan and the rate of ageing. While the male-female mating system is found in most vertebrates, and all mammals—many animal species employ alternative arrangements.
Professor Ralf Sommer and Dr. Cameron Weadick from the Max Planck Institute of Developmental Biology are doing research on the evolutionary consequences of such differences.
They wanted to find out if self-fertilizing hermaphrodite nematodes would evolve to live longer, healthier lives; or if they would evolve shorter life cycles, characterized by quick bursts of reproduction followed by senescent decay. By comparing species that utilize different mating systems, it’s possible to see how much of a role sexual interactions play in shaping life-history evolution.
The researchers measured adult lifespan in females and hermaphrodites from eleven different Pristionchus nematode (roundworm) species. They discovered that hermaphrodites, which fertilize their own eggs with their own sperm, live significantly shorter than their female relatives.
Importantly, lifespan did not correlate with the number of offspring, indicating that the lifespan differences between females and hermaphrodites aren’t simply due to a trade-off between living long and investing in reproduction.
There are various possible reasons for the differences in lifespan. Hermaphrodites start reproducing earlier in life, as they produce sperm before adulthood, but females have to invest time to find males to mate with. Another reason relates to the costs of mating: Males can damage females during mating, and the females may need to be built especially strong in order to tolerate this, leading to the evolution of females capable of living for a long time.
Finally, decreased lifespan in hermaphrodites may be a consequence of inbreeding, which can impede natural selection and lead to the accumulation of damaging mutations. These mechanisms are not mutually exclusive, and a key challenge for future work will be to determine the relative contributions of each process. "We want to investigate the connection between survival and the mating system.
Our results set the stage for future work on the genetic basis of differences in lifespan.”, says Weadick. Apart from Pristionchus nematodes, the relation between self-fertilization and lifespan has only been investigated in plants so far. The comparison with other species might help to identifying genes that are associated with the evolution of lifespan. (Adapted from: American Society of Naturalists)
Mating System Transitions Drive Life Span Evolution in Pristionchus Nematodes
Prof. Dr. Ralf Sommer
Phone: 07071 601- 441
Nadja Winter (PR Officer)
Phone: +49 7071 601- 444
Nadja Winter | Max-Planck-Institut für Entwicklungsbiologie
O2 stable hydrogenases for applications
23.07.2018 | Max-Planck-Institut für Chemische Energiekonversion
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks. Their study, published April 17 in the journal Nature, shows that the atmospheres of Mars and Earth diverged in important ways very early in the 4.6 billion year evolution of our solar system.
The results will help guide researchers’ next steps in understanding whether life exists, or has ever existed, on Mars and how water — now absent from the Martian surface — flowed there in the past.
Heather Franz, a former University of Maryland research associate who now works on the Curiosity rover science team at the NASA Goddard Space Flight Center, led the study with James Farquhar, co-author and UMD geology professor. The researchers measured the sulfur composition of 40 Mars meteorites — a much larger number than in previous analyses. Of more than 60,000 meteorites found on Earth, only 69 are believed to be pieces of rocks blasted off the Martian surface.
The meteorites are igneous rocks that formed on Mars, were ejected into space when an asteroid or comet slammed into the red planet, and landed on Earth. The oldest meteorite in the study is about 4.1 billion years old, formed when our solar system was in its infancy. The youngest are between 200 million and 500 million years old.
Studying Martian meteorites of different ages can help scientists investigate the chemical composition of the Martian atmosphere throughout history, and learn whether the planet has ever been hospitable to life. Mars and Earth share the basic elements for life, but conditions on Mars are much less favorable, marked by an arid surface, cold temperatures, radioactive cosmic rays, and ultraviolet radiation from the Sun. Still, some Martian geological features were evidently formed by water — a sign of milder conditions in the past. Scientists are not sure what conditions made it possible for liquid water to exist on the surface, but greenhouse gases released by volcanoes likely played a role.
Sulfur, which is plentiful on Mars, may have been among the greenhouse gases that warmed the surface, and could have provided a food source for microbes. Because meteorites are a rich source of information about Martian sulfur, the researchers analyzed sulfur atoms that were incorporated into the rocks.
In the Martian meteorites, some sulfur came from molten rock, or magma, which came to the surface during volcanic eruptions. Volcanoes also vented sulfur dioxide into the atmosphere, where it interacted with light, reacted with other molecules, and settled on the surface.
Sulfur has four naturally occurring stable isotopes, or different forms of the element, each with its own atomic signature. Sulfur is also chemically versatile, interacting with many other elements, and each type of interaction distributes sulfur isotopes in a different way. Researchers measuring the ratios of sulfur isotopes in a rock sample can learn whether the sulfur was magma from deep below the surface, atmospheric sulfur dioxide or a related compound, or a product of biological activity.
Using state-of-the-art techniques to track the sulfur isotopes in samples from the Martian meteorites, the researchers were able to identify some sulfur as a product of photochemical processes in the Martian atmosphere. The sulfur was deposited on the surface and later incorporated into erupting magma that formed igneous rocks. The isotopic fingerprints found in the meteorite samples are different than those that would have been produced by sulfur-based life forms.The researchers found the chemical reactions involving sulfur in the Martian atmosphere were different than those that took place early in Earth’s geological history. This suggests the two planets’ early atmospheres were very different, Franz said.
The exact nature of the differences is unclear, but other evidence suggests that soon after our solar system formed, much of Mars’ atmosphere was lost, leaving it thinner than Earth’s, with lower concentrations of carbon dioxide and other gases. That is one reason why Mars is too cold for liquid water today — but that may not always have been the case, said Franz.
“Climate models show that a moderate abundance of sulfur dioxide in the atmosphere after volcanic episodes, which have occurred throughout Mars’ history, could have produced a warming effect which may have allowed liquid water to exist at the surface for extended periods,” Franz said. “Our measurements of sulfur in Martian meteorites narrow the range of possible atmospheric compositions, since the pattern of isotopes that we observe points to a distinctive type of photochemical activity on Mars, different from that on early Earth.”
Periods of higher levels of sulfur dioxide may help explain the red planet’s dry lakebeds, river channels and other evidence of a watery past. Warm conditions may even have persisted long enough for microbial life to develop.
The team’s work has yielded the most comprehensive record of the distribution of sulfur isotopes on Mars. In effect, they have compiled a database of atomic fingerprints that provide a standard of comparison for sulfur-containing samples collected by NASA’s Curiosity rover and future Mars missions. This information will make it much easier for researchers to zero in on any signs of biologically produced sulfur, Farquhar said.
- Heather B. Franz, Sang-Tae Kim, James Farquhar, James M. D. Day, Rita C. Economos, Kevin D. McKeegan, Axel K. Schmitt, Anthony J. Irving, Joost Hoek, James Dottin III. Isotopic links between atmospheric chemistry and the deep sulphur cycle on Mars. Nature, 2014; 508 (7496): 364 DOI: 10.1038/nature13175
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This volume presents the results of the project "Ecology of Arable Land. The Role of Organisms in Nitrogen Cycling." The project was carried out during 1979-1988 with field studies concentrated to 1980-1985. The main project objective was to investigate and synthesize the contributions of the soil organisms to nitrogen and carbon circulation in four contrasting cropping systems. More than 25 scientists, from disciplines including soil hydrology, crop production ecology, soil microbiology, soil zoology, soil chemistry and systems analysis, were involved in the project.
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Python for Beginners: An Introduction to Learn Python Programming with Tutorials and Hands-On Examples
Free Python for Beginners: An Introduction to Learn Python Programming with Tutorials and Hands-On Examples
Python for Beginners: An Introduction to Learn Python Programming with Tutorials and Hands-On Examples by Nathan Metzler
English | 25 Oct. 2017 | ISBN: 1973108798 | ASIN: B076VSPJ81 | 71 Pages | AZW3 | 537.14 KB
Master the Python Environment and Become a Skilled Coder
When you open up Beginner’s Guide to Python, you’ll enter a new world of creative and lucrative possibilities. From executing Python scripts on various operating systems to learning identifiers and keywords, you’ll be up-and-running in no time. Now is the time – get ready for the ride of a lifetime as you discover the inner workings of a language on which much of the world’s newest devices depend.
With this book, you can learn what you need to know to get started with this popular and powerful coding platform:
Installing the necessary software
Setting up your programming environment
Learning the basic syntax of Python
Understanding variables, operators, and control structures
Absorbing the basics of Python functions
This comprehensive and easy-to-read introduction to Python programming includes a wealth of programming tutorials for writing your first lines of code. You’ll learn how to analyze and process raw data inputs and present useful information to users. With this guide, you can learn to calculate factorials, reverse numbers, and determine whether numbers are palindromes and even/odd.
You’ll even discover simple and straightforward methods for creating menu-driven programs with user-defined functions
Don’t pass up this opportunity to make a great salary as a programmer and leave your mark on the world. Get your copy of Beginner’s Guide to Python and take your first steps toward a bright future
Zero Day eBook | <urn:uuid:cd73830d-a3d5-4ba4-8235-3516070af791> | 3.046875 | 415 | Product Page | Software Dev. | 29.563718 | 95,477,743 |
Unique and irreplaceable Arctic wildlife and landscapes are crucially at risk due to global warming caused by human activities according to the Arctic Biodiversity Assessment (ABA), a new report prepared by 253 scientists from 15 countries under the auspices of the Conservation of Arctic Flora and Fauna (CAFF), the biodiversity working group of the Arctic Council.
"An entire bio-climatic zone, the high Arctic, may disappear. Polar bears and the other highly adapted organisms cannot move further north, so they may go extinct. We risk losing several species forever," says Hans Meltofte of Aarhus University, chief scientist of the report.
From the iconic polar bear and elusive narwhal to the tiny Arctic flowers and lichens that paint the tundra in the summer months, the Arctic is home to a diversity of highly adapted animal, plant, fungal and microbial species. All told, there are more than 21,000 species.
Maintaining biodiversity in the Arctic is important for many reasons. For Arctic peoples, biodiversity is a vital part of their material and spiritual existence. Arctic fisheries and tourism have global importance and represent immense economic value. Millions of Arctic birds and mammals that migrate and connect the Arctic to virtually all parts of the globe are also at risk from climate change in the Arctic as well as from development and hunting in temperate and tropical areas. Marine and terrestrial ecosystems such as vast areas of lowland tundra, wetlands, mountains, extensive shallow ocean shelves, millennia-old ice shelves and huge seabird cliffs are characteristic to the Arctic. These are now at stake, according to the report.
"Climate change is by far the worst threat to Arctic biodiversity. Temperatures are expected to increase more in the Arctic compared to the global average, resulting in severe disruptions to Arctic biodiversity some of which are already visible," warns Meltofte.
A planetary increase of 2 °C, the worldwide agreed upon acceptable limit of warming, is projected to result in vastly more heating in the Arctic with anticipated temperature increases of 2.8-7.8 °C this century. Such dramatic changes will likely result in severe damage to Arctic biodiversity.
Disappearing sea ice is affecting marine species, changing dynamics in the marine food web and productivities of the sea. Many unique species found only in the Arctic rely on this ice to hunt, rest, breed and/or escape predators.
Other key findings
• Generally speaking, overharvest is no longer a primary threat, although pressures on some populations remain a serious problem.
• A variety of contaminants have bioaccumulated in several Arctic predator species to levels that threaten the health and ability to reproduce of both animals and humans. However, it is not clear if this is affecting entire populations of species.
• Arctic habitats are among the least anthropogenic disturbed on Earth, and huge tracts of almost pristine tundra, mountain, freshwater and marine habitats still exist.
• Regionally, ocean bottom trawling, non-renewable resource development and other intensive forms of land use pose serious challenges to Arctic biodiversity.
• Pollution from oil spills at sites of oil and gas development and from oil transport is a serious local level threat particularly in coastal and marine ecosystems.
• Uptake of CO2 in sea water is more pronounced in the cold Arctic waters than elsewhere, and the resulting acidification of Arctic seas threaten calcifying organisms and maybe even fisheries.
• Shipping and resource development corridors are rapidly expanding and may dramatically increase the rate of introduction of alien species.
• There is an enormous deficit in our knowledge of species richness in many groups of organisms, and monitoring in the Arctic is lagging far behind that in other regions of the world.
• The multitude of changes in Arctic biodiversity – driven by climate and other anthropogenic stressors – will have profound effects on the living conditions of peoples in the Arctic.
Contact:Chief scientist and executive editor, senior advisor DSc. Hans Meltofte
DSc. Hans Meltofte | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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The scientific community’s focus on publishing positive results leaves a sizeable amount of research that is either incorrect or in some cases dangerous. If you want to form a conclusion based on an experiment, it is a basic rule in science that you include all data—both positive and negative. The same applies to the global collection of scientific knowledge that should include all scientific results, even when the results are unexpected. But this does not always happen, and a number of concerned scientists say that a large portion of research today is incorrect, which is particularly problematic and even dangerous within the health sciences, say the scientists. This problem is arguably part of a crisis within basic research, which has been described in a series of articles here on ScienceNordic. Other articles in the series include pressure on scientists to publish their results and a lack of reproducibility in science.
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The U.S. Army Corps of Engineers is gearing up for its biggest-ever planned spill of water over dams on the Columbia and Snake rivers.
It’s a controversial move that was ordered by a federal court to help endangered fish avoid extinction. To make sure it’s done right, dam managers tested their options first, using miniature models of Northwest dams way down in Vicksburg, Mississippi.
What are the miniature versions of Northwest dams doing in Mississippi?
Turns out, Vicksburg is home to a whole lot of miniature models. It all started back in 1927 with a massive flood on the Mississippi River. Congress created a lab to help manage future floods, and engineers dug a mini Mississippi River right into the dirt in Vicksburg.
“The mission is solving the most challenging problems,” said Jackie Pettway, chief of the Corps’ Coastal Hydraulics Lab in Vicksburg. “You know, the problems that are too big for engineering firms to tackle.”
One of those problems is figuring out how to spill more water through dams without disturbing the delicate balance of hydroelectric power generation, water storage and fish survival.
The Vicksburg lab has more than a million square feet of hangar space filled with miniature models based on dams across the country – including all eight major dams on the Columbia and Snake rivers.
Surrounded by mini dams
In the Northwest, dams are scattered along hundreds of miles of the Columbia and Snake rivers. But down in Vicksburg, you can see several under one roof.
Inside a massive hangar at the lab last fall, Rock Peters with the Northwest Division of the Corps of Engineers in Portland was surrounded by mini dams.
“Right now we’re standing between two models,” he said. “We have The Dalles general model on our right and on our left we have Lower Monumental.”
In the real world, it would have taken a three-hour drive through southeastern Washington to travel from one dam to the other. The laboratory versions look like very long kiddie pools, with just a couple feet of water flowing through a mini dam.
About a dozen people from Northwest agencies and tribes were gathered around The Dalles Dam model. Some were standing on top of the dam itself, which is roughly the size of a small footbridge.
"We're looking at new spill patterns and new spill levels as part of the court injunction," Peters said.
The court ordered as much spill as the law allows. State laws set limits on how much water can be spilled over dams before the gases produced in the process may become harmful to fish.
Meeting the legal limit at some dams will mean increasing the amount of planned spill by 50 to 100 percent.
'More spill is better'
Tucker Jones, Columbia River manager for the Oregon Department of Fish and Wildlife, is on the winning side of the judge’s order to spill more water through dams – instead of sending it through turbines to generate electricity.
“We know that more spill is better,” Jones said. “The turbines, that is the worst route. Blades that are spinning are not typically good for living things.”
Sending fish through spill bays instead can move them quickly on a straight path downriver – a much better route for juvenile fish headed to the ocean, he said.
While fish might survive a trip through the turbines, they could suffer or even die from it later. To save endangered fish, Jones says, we need to help more of them survive to adulthood.
Right now, for many runs of threatened and endangered salmon and steelhead, less than two percent of the juveniles that leave the Columbia River Basin return as adults.
In 2016, a federal judge rejected the latest plan for helping salmon survive dams in the Columbia River Basin. As a result, federal agencies are revamping their long-term dam management plans.
"While those things are playing out, we felt we needed to do something now," Jones said. “We’re looking for short-term: do something now for fish that are in real trouble.”
But dam managers say spilling more water is complicated. It can send fish in the wrong direction. It can create eddies and make baby salmon more vulnerable to predators like birds, sea lions or other fish. It can also cause erosion and damage the dams themselves.
Brad Bird, a senior hydraulic engineer with the Corps, said the miniature dam models are crucial to designing a spill plan that will help fish without creating problems to the rest of the hydro system.
"They're invaluable," he said. "I don't know how you'd do what we do without them. Nobody wants us experimenting with endangered species."
The models don’t generate electricity, and there aren’t any fish in the kiddie pools. But otherwise they're just like the real thing – only 50 to 80 times smaller.
The bottom of the pools surrounding the models are shaped exactly like the bottom of the river, so they offer an accurate picture of how water will move when it's spilled through the full-size dams.
Managers study where the water will go as it moves downstream by injecting hot pink dye into the mini dam and sprinkling confetti in the surrounding pool.
The water flows through the part of the dam that looks like a row of garages. Each section is called a spill bay. The direction the water flows can be adjusted by changing the amount of water flowing through each individual spill bay.
The trick is to make sure the spill sends water in the right direction for both baby salmon swimming downstream and adult salmon swimming upstream.
Surprisingly fish friendly
Mike Langeslay, a fish biologist with the Corps, is standing on the full-size version of The Dalles Dam, east of the Cascades.
“If you look downstream, see that little peninsula down there with rocks and land and little islands?” he said, pointing. “That’s pretty well-known predator habitat – for birds, gulls, small mouth bass, northern pike minnow.”
Out here, it’s half a mile across the river from Oregon to Washington. And you drive – rather than walk – across the top of the dam.
The dam has 23 spill bays, each with its own massive gate that opens to release water. Langeslay said they used to open all the spill bays in the spring, sending fish right into predator habitat.
They’ve used the mini dam to solve that problem. They now open fewer spill bays and they built a wall in the river to steer the water in the right direction.
“We wouldn’t have been able to do it without the model," Langeslay said. "I mean, can you imagine trial and error sticking a wall in there?"
Standing on top of an open spill bay is like standing on top of a waterfall. It's a huge drop down to the river.
“If you look at it, it doesn’t look like it’s very friendly to fish," Langeslay said. "It’s surprising that it actually is. The visual is, you know, certainly a person falling through this wouldn’t survive.”
Managers track fish survival through dam spillways, and the numbers are good. On average, Langeslay said, about 98 percent of the fish survive. The question is: for how long?
As the Corps starts spilling more water this spring, advocates are convinced it will help more fish survive to adulthood.
Critics like Terry Flores, director of the industry and commerce-backed group Northwest River Partners, say the science isn’t clear on whether more spill will mean more fish will survive longer.
"There is no proof that more spill will be better for fish," Flores said. "That’s why we’re so skeptical. We want things done based on good science."
Meanwhile, spilling water to meet the judge's orders could cost up to $40 million, according to an estimate from the Bonneville Power Administration. The agency has plans to add any extra costs to the region's electric bills in the form of a spill surcharge.
Dam managers could be wasting water on spill, Flores says, and sacrificing hydropower without getting any more fish. | <urn:uuid:827d49f6-9a0e-4c1a-815f-19ffe9b6895b> | 3.5625 | 1,741 | News Article | Science & Tech. | 60.054212 | 95,477,772 |
A new study on the Earth’s largest ice sheet has found that so-called ‘global warming’ has not caused the ice caps to melt.
The study, published in the journal Nature, completely debunks earlier studies that warned melting ice caps would cause sea levels to rise in the near future.
Westernjournal.com reports: Shakun’s study found that while portions of Antarctica’s ice sheets retreated, the eastern portion proved to be very resilient during the warm period between 2.6 million and 5.3 million years ago.
“Based on this evidence from the Pliocene, today’s current carbon dioxide levels are not enough to destabilize the land-based ice on the Antarctic continent,” Shakun said in a statement.
Shakun’s team analyzed ice cores, looking for isotopes that point to interaction between glacial sediment and cosmic rays. They only found trace amounts, suggesting ice cover persisted through past warm periods.
“This does not mean that at current atmospheric carbon dioxide levels, Antarctica won’t contribute to sea level rise,” Shakun said.
“Marine-based ice very well could and in fact is already starting to contribute, and that alone holds an estimated 20 meters of sea level rise.”
“We’re saying that the terrestrial segment is more resilient at current carbon dioxide levels,” he said.
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Jupiter is the fifth planet from the Sun and the largest in the Solar System, Jupiter is named after the Roman god of sky and thunder in fact Jupiter was the “King of the Gods” the equivalent of the Greek God Zeus. Jupiter is the fourth brightest object in our solar system is visible to the naked eye and was first recorded by the ancient Babylonians in around the 7th or 8th century’s BC. It couldn’t be more accurately named because Jupiter is massive, I mean really massive. In fact if Jupiter got any more massive, it would actually shrink due to the gravitational effects causing it to pull in on itself. Jupiter mass is incredibly two and a half times that of the combined mass of all other planets in the entire solar system. Jupiter is almost like its own mini solar system. It has four main large moons, Io, Europa, Ganymede, and Callisto, however Jupiter has 67 confirmed moons which are in turn split into three categories, Inner, Galilean and Outer. It even has a faint ring system around it. I will come back to these moons and ring system at another time to discuss in more detail.
A Jovian day takes just under 10 Earth Hours making it the fastest rotating body in our Solar System. However it will take 12 Earth Years for Jupiter to complete one orbit around the sun! This means Jupiter has only made two complete revaluations of the sun in my lifetime! Jupiter is more than five times farther than the sun than Earth. That’s 484 million miles (778 million kilometres) or 5.2 Astronomical Units. However its presence is felt throughout the solar system acting like a cosmic shield that eats up or sling shots away any would be comets or asteroid’s that would collide with earth. Jupiter’s gravity of is only 2 and a half times what it is on Earth, due to it being made up of gases. Jupiter is the first of the gas giants that live in the outer solar system composed 89.8 percent molecular hydrogen, 10.2 percent helium, minor amounts of methane, ammonia and water. Unlike the planets Mercury, Venus Earth and Mars it does not have a solid core the gaseous material it is made from simply gets denser with depth. The colourful cloud belts of Jupiter are arranged in dark and light zones created by strong east-west winds in the planet’s upper atmosphere which are made of ammonia crystals and sulphur traveling at speeds more than 400 miles an hour (640 kilometres per hour). The huge “Red Spot” that appears in the cloud belt is an enormous storm that has been raging for over 300 years. This storm is big that three Earth’s would fit inside of it.
There have been a lot of missions to Jupiter beginning with NASA’s Pioneer 10 spacecraft in December 1973 followed by then Pioneer 11 in December 1974. Voyager 1 and 2 in 1979 where the last until Ulysses arrived in February 1992. Cassini made a flyby in 2000, on its way to Saturn. And finally, NASA’s New Horizons spacecraft made its flyby in 2007. Below are a few links to the sites I gathered my information on but I would like to advise you to check out www.astronomycast.com and www.universetoday.com Photo Credit: Reto Stöckli, Nazmi El Saleous, and Marit Jentoft-Nilsen, NASA GSFC.
Thanks To: theplanets.org, solarsystem.nasa.gov, science.nationalgeographic.com, universetoday.com, space-facts.com, astronomycast.com, astronomyonline.org, planetfacts.org | <urn:uuid:8b3ebb70-e70d-44d7-9418-07296b5712e6> | 3.296875 | 766 | Personal Blog | Science & Tech. | 62.123783 | 95,477,797 |
Waste from textile and paint industries often contains organic dyes such as methylene blue as pollutants. Photocatalysis is an efficient means of reducing such pollution, and molybdenum trioxide (MoO3) catalyzes this degradation.
Researchers from Bangalore, India, led by C. N. R. Rao now report no less than four methods to produce nanosheets made of very few layers of MoO3. This material is more efficient as a photocatalyst than bulk MoO3, they write in Chemistry—An Asian Journal.
The n-type semiconductor molybdenum trioxide is used widely in heterogeneous catalysis. The Indian team prepared nanosheets of MoO3 by oxidation of MoS2 nanosheets, by using graphene oxide as a template, and by intercalation with LiBr into the bulk material or its ultrasonication.
When used as a photocatalyst in the degradation of methylene blue, a heterocyclic aromatic dye, the researchers found few-layered MoO3 to afford nearly complete degradation of the dye in less than 10 minutes, whereas only about one-third of the dye was degraded during this period with the bulk compound.
“As MoO3 holds great potential in applications ranging from gas sensing to energy storage, our study will likely spur further research on few-layer MoO3,” says Rao. Indeed, further results reported in their study suggest that a composite of this material with a borocarbonitride is promising as an electrode material for supercapacitors. It will be interesting to see what is coming next for this intriguing few-layer nanostructure.About the Author
Author: C. N. R. Rao, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore (India), http://www.jncasr.ac.in/cnrrao/
Title: Synthesis, Characterization, and Properties of Few-Layer MoO3
Chemistry - An Asian Journal, Permalink to the article: http://dx.doi.org/10.1002/asia.201300470
C. N. R. Rao | Wiley-VCH
Scientists uncover the role of a protein in production & survival of myelin-forming cells
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
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Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
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Aerosols and the imaging atmospheric Cherenkov technique
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The ability to extract energetic γ-rays from the overwhelming high energy cosmic ray back- ground has opened up a new window of observation on the non-thermal universe. By utilis- ing an atmospheric technique VERITAS, an array of four imagining atmospheric Cherenkov telescopes, detects astrophysical gamma radiation in the energy range 85 GeV to >30 TeV. As the atmosphere is an integral part of the detector understanding the effects of aerosols is important. This thesis reports on a novel aerosol extinction estimation technique that utilises an opti- mised and repurposed ceilometer. Taking advantage of water vapour absorption correction for the 905-910 nm laser and optimised ceilometer data quality cuts an independent mea- surement is provided for aerosol extinction pro le up to 5 km above ground level. The inherent uncertainties are as low as ± ∼5-7%, with a high duty cycle > 95% for dusk to dawn operation in the absence of clouds. From close to 6 years of ceilometer data (Decem- ber 2011 to June 2017) aerosol optical depth is now known to seasonally increase more than 4-fold regularly from mid-winter to mid-summer, with a corresponding increase in overall atmospheric aerosol extinction ∼7-8%. During rare episodes of heavy aerosol loading at- mospheric aerosol extinction increases by more than 15%. A historical aring episode, during a period of elevated aerosol loading, of the blazar Mrk 421 in April 2013 was analysed with new elevated aerosol extinction instrument response functions. For the elevated aerosol extinction analysis the following result was obtained; I = 6.8±0.6×10−10 cm−2s−1TeV−1, Γ = −1.75±0.06, Eo = 1.45±0.14, χ2/NDF = 42.86/31. This result lies within experimental accuracies for the result obtained with thenormal aerosol extinction analysis. However, it is noted that below 237 GeV the ele- vated aerosol analysis shows a marked decline in signi cance σ . The spectral plot deviates slightly from a power-law with exponential cutoff below 237 GeV, but the differences are small. An in depth examination of systematic uncertainty in reconstructed energy arising from el- evated aerosol loading has yielded a year-on-year value of ∼5%, while the Mrk 421 April 2013 aring episode yielded an uncertainty in reconstructed energy of ∼6-7%. This analy- sis was not carried out for the next source examined, PKS 1441 +25. A soft VHE γ-ray source from April 2015 was analysed, PKS 1441 +25, whose data set was partially taken during elevated aerosol loading. For the elevated extinction analy- sis the following result was obtained; I = 8.9×10−12±1.3×10−12 cm−2s−1TeV−1 , Γ = −5.81±0.57, χ2/NDF = 4.98/3. This result also lies within experimental accuracies for the result obtained with the normal aerosol extinction analysis. In conclusion, the aerosol extinction correction applied to the Mrk 421 and PKS 1441 +25 data sets do not bene t noticeably from the elevated aerosol correction developed in this thesis, implying that VERITAS data taken during periods of elevated aerosol loading is not in need of re-analysis.
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The following license files are associated with this item: | <urn:uuid:2a7bce1f-051d-4994-a175-532e81ed7b53> | 2.75 | 828 | Academic Writing | Science & Tech. | 47.456995 | 95,477,810 |
Authors: George Rajna
Stanford researchers have developed a water-based battery that could provide a cheap way to store wind or solar energy generated when the sun is shining and wind is blowing so it can be fed back into the electric grid and be redistributed when demand is high. Researchers at AMOLF and the University of Texas have circumvented this problem with a vibrating glass ring that interacts with light. They thus created a microscale circulator that directionally routes light on an optical chip without using magnets. Researchers have discovered three distinct variants of magnetic domain walls in the helimagnet iron germanium (FeGe). Magnetic materials that form helical structures—coiled shapes comparable to a spiral staircase or the double helix strands of a DNA molecule—occasionally exhibit exotic behavior that could improve information processing in hard drives and other digital devices. In a new study, researchers have designed "invisible" magnetic sensors—sensors that are magnetically invisible so that they can still detect but do not distort the surrounding magnetic fields. At Carnegie Mellon University, Materials Science and Engineering Professor Mike McHenry and his research group are developing metal amorphous nanocomposite materials (MANC), or magnetic materials whose nanocrystals have been grown out of an amorphous matrix to create a two phase magnetic material that exploits both the attractive magnetic inductions of the nanocrystals and the large electrical resistance of a metallic glass. The search and manipulation of novel properties emerging from the quantum nature of matter could lead to next-generation electronics and quantum computers. A research team from Lab) has found the first evidence that a shaking motion in the structure of an atomically thin (2-D) material possesses a naturally occurring circular rotation. Topological effects, such as those found in crystals whose surfaces conduct electricity while their bulk does not, have been an exciting topic of physics research in recent years and were the subject of the 2016 Nobel Prize in physics.
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The 17th century saw the beginning of the theory of continued fractions. The 18th century was really their golden age. It was marked by three outstanding mathematicians, Euler, Lambert and Lagrange, all belonging to the Berlin Academy of Sciences which was reorganized by Frederic the second (Berlin, 24.1.1712—Berlin, 17.8.1786). The 18th century was also that of the birth of Padé approximants, which are connected with continued fractions and played (and are still playing) an important rôle in applications. The century ended with the publication of the first encyclopaedias and mathematical dictionaries, which had great importance in the spreading of continued fractions among the mathematicians, thus preparing the formidable explosion of the subject during the 19th century.
KeywordsContinue Fraction Continue Fraction Expansion Divergent Series Pade Approximants Pade Approximation
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Nuclear radiation that is emitted from nuclear reactor has a high impact on environment, landscape and on health and lifestyle. Even in a normal situation without any calamity, the impact on the environment is very high because of the high usage of fossil fuels used in extracting and mining uranium that releases both carbon dioxide as well as greenhouse gases into the atmosphere. In the event of any calamity like what happened in Fukushima, the threat becomes much higher because the radioactive elements released into the atmosphere can have an impact on the flora and fauna and affect the ozone layer (Environmental Protection Agency, 2011). For example, drinking water in Tokyo and other major cities of Japan showed a percentage of presence of radioactive elements (Foodandwaterwatch.org, n.d). Therefore, the danger posed by nuclear power plant in light of the phenomenon of climate change is high. Post the massive earthquake and the ensuing Tsunami in Japan on March 11, 2011, one of the main threats that came out was the radiation threat from Japans Nuclear Power plants. Leaks of radioactive gas happened in three reactors at the Fukushima Nuclear Power Station because of partial meltdowns. In another reactor, the spent fuel rods caught fire and radioactive gases and materials were released directly into the atmosphere outside (Chang, 2011). This issue raised many concerns regarding the potential affects on various factors like environment and health and form the main reason for my selection
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NASA's Global Hawk 871 departed from NASA's Wallops Flight Facility, Wallops Island, Va. today, Sept. 17, at 10 a.m. EDT from Runway 04. This marked the twenty-fifth flight for NASA 871. Meanwhile, NASA 872 was returning to home base after making its seventy-fifth flight. These flights over Tropical Storm Humberto brought forth the one-hundredth flight of NASA's Global Hawks.
The AIRS instrument aboard NASA's Aqua satellite captured this infrared image of Humberto on Sept. 17 at 4:29 UTC/12:289 a.m. EDT. The image showed the highest storms and coldest cloud top temperatures (purple) northeast of the center.
Image Credit: NASA JPL, Ed Olsen
NASA's Global Hawk 872 unmanned aircraft took off at 10:42 a.m. EDT from Runway 22 at NASA's Wallops Flight Facility, Wallops Island, Va. on Sept. 16 to investigate Humberto and dispersed dropsondes throughout the storm. NASA 872 gathered data on the environment of the storm. Global Hawk aircraft are well-suited for hurricane investigations because they can fly for as long as 28 hours and over-fly hurricanes at altitudes greater than 60,000 feet (18.3 km).
Tropical storm Humberto had little deep convection and was classified by the National Hurricane Center (NHC) as a post-tropical cyclone on September 14, 2013. By September 16, Humberto was showing bursts of strong convection and thunderstorms were developing with heavy rainfall, so Humberto was again classified a tropical storm.
NASA's Tropical Rainfall Measuring Mission or TRMM satellite observed Humberto on September 15, 2013 at 1652 UTC (12:52 p.m. EDT) and on September 16, 2013 at 1557 UTC (11:57 a.m. EDT). A comparison of the two TRMM orbits showed significant changes that occurred within Humberto in less than 24 hours. In the first orbit on September 15, 2013 Humberto's center of circulation was rain free and only contained a small area of convective rainfall that was located well to the north of Humberto's surface location. Areas of strong convective rainfall were associated with rebounding Tropical Storm Humberto when TRMM viewed the same area on September 16, 2013.
The Atmospheric Infrared Sounder instrument aboard NASA's Aqua satellite captured an infrared image of Humberto on Sept. 17 at 4:29 UTC/12:289 a.m. EDT. The image showed the highest storms and coldest cloud top temperatures were still east and northeast of the center and were dropping the heaviest rainfall. .
At 11 a.m. EDT on Sept. 17 the center of Tropical Storm Humberto was located near latitude 29.4 north and longitude 42.5 west, about 1070 miles/1,720 km west-southwest of the Azores Islands. Humberto's maximum sustained winds were near 45 mph/75 kph and the National Hurricane Center expects some slight strengthening. Humberto is moving to the north at 10 mph/17 kph and is expected to turn to the northwest and slow down before heading north again on Sept. 18.
HS3 is a mission that brings together several NASA centers with federal and university partners to investigate the processes that underlie hurricane formation and intensity change in the Atlantic Ocean basin. Among those factors, HS3 will address the controversial role of the hot, dry and dusty Saharan Air Layer in tropical storm formation and intensification and the extent to which deep convection in the inner-core region of storms is a key driver of intensity change. The HS3 mission will operate between Aug. 20 and Sept. 23.
Humberto is forecast to again become a post-tropical low in about four days.Text credit: Rob Gutro
Rob Gutro | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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One-nanometer trimetallic alloy particles created
A researcher group of Tokyo Institute of Technology succeeded in developing precisely controlled alloy nanoparticles "multimetallic nanoclusters (MNCs)" made of three metals: copper, platinum, and gold. They also discovered that MNCs show catalytic activity that is 24 times greater than commercially available carbon-supported platinum catalysts in the oxidization of hydrocarbons using oxygen in the air.
The principal component of petroleum and natural gas are hydrocarbons and their mixtures, and are indispensable as resources supporting modern infrastructure as raw materials for the petrochemical industry. A technique which has been conventionally used to create beneficial chemical products from hydrocarbons was to use a large amount of metallic peroxides in hazardous organic solvents to oxidize hydrocarbon compounds. To use resources effectively and to reduce environmental impact, clean catalytic oxidization without solvents using the oxygen in the air has been a popular research subject in recent years. Research of noble metal nanoparticles supported on porous carbon materials or metallic oxides are especially prevalent, and they are viewed as promising catalysts. Vital elements determining the reactivity of such heterogeneous catalysts are the shape, size, and metallic composition of the metallic nanoparticles. Particles of a size less than 2 nm have especially gained attention in the development of new high-performance catalysts, since it has been found that reducing the diameter of the catalyst particle not only increases the surface area ratio but greatly changes the state of the electrons on the surface of the metals, greatly changing its reactivity. However, the method of synthesizing metallic nanoparticles of such a size while controlling both its diameter and composition had not been discovered.
The research group led by Kimihisa Yamamoto of Tokyo institute of Technology developed a method of synthesizing microscopic alloy nanoparticles using branched molecules "dendrimers" they themselves had developed in Yamamoto Atom Hybrid Projectouter on the ERATO program, the Exploratory Research for Advanced Technology, research funding program supported by Japan Science and Technology Agency (JST). Molecules called dendrimers have a regular branching structure with only one definite molecular weight although they are classified as macromolecules. The research group implemented many coordination sites for forming metal ions and complexes. By using a dendrimer with such coordination sites as a template for the nanoparticle, the group was able to synthesize a nanoparticle with a controlled number of atoms.
Further, they evaluated the activity of this alloy nanoparticle as an oxidization catalyst for hydrocarbons under ordinary pressures when using oxygen in the air as the oxidizing agent, and found that its activity was 24 times greater than that of commercially available catalysts for oxidization of organic compounds. They also found that, by adding a catalytic amount of organic hydroperoxide, this catalyst promotes the oxidization of hydrocarbon into aldehydes and ketones under ordinary temperatures and pressures. Further, by comparing the changes in activity due to alloy catalysts of different metallic compositions and examining the composition and other characteristics of the intermediates, ketones and organic hydroperoxides, the group was able to observe the process of reaction promotion due to the alloying of the catalyst.
The catalytic transformation of inactive hydrocarbons to substances with higher added value is a technology garnering much attention in recent times. The knowledge gained from this research is anticipated to become a design guideline for new high-performance catalysts. The method for synthesizing alloy nanoparticles developed in this research can be used generally and applied to other metals. For this reason, this could be said to be the technology uncovering the reactivity of other microscopic alloy nanoparticles, whose catalytic performance had not been known. Further study is required on the increase of catalytic activity at the interface of copper and other noble metals in the oxidizing transformations of other organic compounds, not only the oxidization of hydrocarbons. Application is anticipated for next-generation high-performance materials in the fields as diverse as optics, electronics, and energy.
Source: Tokyo Institute of Technology
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A planetary scientist explains that, with some adaptations, life-forms similar to Earth's could live on other planets' environments as well. | <urn:uuid:8a19c7cc-830e-4885-a6f0-6ebf225edc78> | 3.265625 | 441 | Content Listing | Science & Tech. | 41.784903 | 95,477,935 |
Pond is preferred breeding ground for frogs and some insects. Though terrestrial, adult frogs consume invertebrates such as annelids, gastropods and arthropods including mosquitoes present in pond water and form an important part of ecosystems as both predator and prey. They reflect back to us the environmental health of our planet. Their permeable skin makes them especially vulnerable to environmental contaminants, such as agricultural, industrial, and pharmaceutical chemicals, particularly endocrine disruptors. Studies have shown that 50 frogs can keep an acre of a rice paddy field free of insects and can keep a check on insect populations including mosquitoes. | <urn:uuid:9e141618-6085-4c1e-8ade-d47d7fa32941> | 3.234375 | 123 | Knowledge Article | Science & Tech. | 26.083455 | 95,477,936 |
This paper discusses some applications of the smear camera, one of the primary tools used to measure the velocity of rapid reaction fronts in an explosive or detonation reaction. Solid cylindrical explosive charges are normally initiated at a small area on the end of the axis. Due to the nature of propagation of a reaction front, the optical records, normally obtained from the periphery of a charge, are distorted and do not give a true measure of the front's velocity. For accurate measurement, long charges are ordinarily used and only a small portion of the total smear record is used to obtain the true velocity. A transformation equation has been derived whereby the data from smear camera records of the peripheral detonation of a short (L/D of 2.5) tetryl charge can be interpreted to obtain a detonation velocity measurement. The results are in excellent agreement with the values measured along the axis as well as with those published in the literature.
A. Robert Clairmont,
"Analysis of Optical Determination of Detonation Velocity in Short Charges," Optical Engineering 5(1), 050118 (1 November 1966). https://doi.org/10.1117/12.7971368 | <urn:uuid:e6ae960c-24f1-4abf-bb11-cb122d693fe0> | 3.203125 | 239 | Academic Writing | Science & Tech. | 38.579375 | 95,477,940 |
There's more to quantum tunneling than meets the eye – or rather, the visualization technique. Most quantum tunneling discussion focus on incoherent single-particle tunneling; on the other hand, quantum tunneling in the context of proton dynamics usually involves many hydrogen bonds at once, which leads to what is known as correlated many-body tunneling. (The many-body problem refers to the properties of microscopic systems that are described by quantum mechanics, comprising a large number of interacting particles – that is, ≥ 3 – which can become entangled.) The downside is that while single-particle tunneling is well understood, many-body tunneling is still shrouded in mystery. Recently, however, scientists at Peking University, Beijing reported the real-space observation of concerted proton tunneling in a cyclic water tetramer – a macromolecular nanocluster consisting of four water molecules arranged in a loop or ring – by using a cryogenic scanning tunneling microscope (STM). The scientists found that the presence of the Cl- chlorine anion (a negatively charged chlorine ion) at the STM tip apex may either enhance or suppress the concerted tunneling process based on the coupling symmetry between the ion and the protons, adding that their work may allow the control the quantum states of protons with atomic-scale precision.
Prof. Ying Jiang discussed the paper that he, Prof. En-Ge Wang and their colleagues published in Nature Physics, noting that one of the main challenges they encountered was directly visualizing the concerted tunneling of four protons in an individual hydrogen-bonded water tetramer adsorbed on a gold-supported halite film. "One basic requirement is to locate in real space the position of protons within the hydrogen-bonded network, such that the motion of the protons can be tracked," Jiang tells Phys.org. "This is extremely difficult for any microscopes due to the light mass and small size of protons – and even worse is that the travelling distance of the protons across the hydrogen bonds is less than one ångström (10-10m). As a result, attacking this problem ideally requires the ability to access the internal degree of freedom of water molecule. Fortunately, we developed a novel submolecular imaging technique last year1 that allows us to discriminate the orientation of water molecules as well as the hydrogen-bonding directionality." This technique is what paved the way for the scientists to address the proton dynamics within the hydrogen-bonded network.
"Furthermore," Jiang continues, "the concerted tunneling or many-body correlated tunneling of the protons is extremely sensitive to the atomic-scale environment, and can be easily disturbed or even killed by the probes." This is due to the fact that the concerted tunneling of protons is a coherent quantum process, which requires all the protons to have exactly the same phase – and the asymmetric coupling between the probes and the protons can destroy the phase correlation between the protons and quench the collective tunneling. "In other words, one may easily mess up such concerted tunneling process just because the STM tip is not in the correct position. Therefore, we need to position the STM tip very precisely inside the water tetramer to ensure the symmetric coupling, where the four protons are all equally coupled with the STM tip." To search for such a precise position requires a great deal of care and patience: If the STM tip is off by only 10 picometers (10-12m), the researchers may obtain completely different results.
Another issue was finding that the presence of the chlorine anion at the STM tip apex may either enhance or suppress the concerted tunneling process, depending on the details of the coupling symmetry between the Cl anion and the protons. "I have to emphasize that it is far more difficult to control the concerted tunneling of protons than to simply visualize this process – it means that one has to simultaneously manipulate several quantum particles in real space." That is, while the STM tip not only acts as a local probe, but can be used to manipulate the single atoms or molecules on surface with atomic-scale precision, manipulating many-body states is challenging. "It's essential to always keep the coupling geometry between the STM tip and four protons in a symmetric way during the manipulation," Jiang points out. "Otherwise, the concerted tunneling is easily suppressed or even quenched."
In addition, Jiang continues, the Cl anion at the tip apex is very important for achieving the efficient manipulation of the concerted proton tunneling. "To be honest, we actually learned this from an accident: For months, we tried to control the concerted tunneling process with a bare metal tip, but all attempts failed. One day the tip was crashed into the gold-supported sodium chloride film substrate due to a faulty operation. Unexpectedly, using this 'bad' tip, we were able to enhance the tunneling rate very efficiently." The scientists later determined that this occurred because the tip picked up a chlorine atom from the sodium chloride surface – and since the chlorine atom is electronegative in nature, the tip is negatively charged. The long-range electric interaction between the negatively charged chlorine atom and the positively charged protons then leads to the suppression of the tunneling barrier.
"Without the Cl- tip, the proton has to travel for a long distance from one water molecule to the other, and the energy barrier is quite high. Inserting a chlorine anion between the water molecules establishes a 'bridge' for the protons. The attraction of Cl- assists the protons, as it were, and thereby assists the proton transfer process," Jiang explains, "That's the physical analogy of why the energy barrier is suppressed by the tip/proton coupling."
After this accidental tip crashing, the researchers invested quite some time to explore a controllable and reproducible way to functionalize the tip apex with a single chlorine atom. "We discovered that chlorine atoms on the sodium chloride surface seemed very 'tip-friendly.'" Once they manipulated a bare tip to closely approach the NaCl(001) surface – that is, one in which crystalline cleavage occurs parallel to the faces of a cube – and then applied the proper voltage pulse, the chlorine atom readily translocated onto the tip end and became very stable.
Moreover, further lowering of the tip height leads to continuous decrease of the barrier because the electric interaction gets stronger – and if the tunneling barrier can be suppressed to such an extent that the zero-point energy of the protons exceeds the barrier height, an extreme quantum effect – that is, complete quantum delocalization – may occur. "In such a case," Jiang notes, "the protons are shared by two nearest-neighboring water molecules, and the originally asymmetric hydrogen bond then becomes symmetric. This is a much stronger quantum effect than quantum tunneling, which we are still struggling to explore."
A third challenge was tuning the Cl-/proton electric coupling in three dimensions with picometer precision. "It's no exaggeration to say that tuning the coupling of protons to the atomic-scale environment in three dimensions with picometer precision is not possible with any technique other than STM. With the combination of the tip height z and tip lateral position x, y, we can actually achieve any coupling geometry between the Cl anion and the protons." Due to the high stability of their STM, the precision for tuning the dimensions can get down to one picometer or better, which is essential for controlling the many-body quantum states of protons. "We were very surprised to see that 10 picometer change in the tip height (z direction) can lead to almost one order of magnitude difference in the tunneling rate. This again shows the extreme sensitivity of the many-body tunneling to the atomic-scale environment, which has never been observed before."
The paper details how the scientists explored the role of individual chlorine anions in influencing the correlated tunneling process by using the Cl--terminated tip, which if located at the exact center of the water tetramer, the Cl anion on the tip apex is equally coupled with the four protons and the cooperativity of the protons is reserved. (Cooperativity is a phenomenon displayed by systems involving identical or near-identical elements, which act non-independently of each other, relative to a hypothetical standard non-interacting system in which the individual elements are acting independently.) "The tunneling probability can be greatly enhanced by the Cl-/proton electric attraction – but if the tip is slightly moved off the center at, for example, the picometer scale, asymmetric coupling occurs. If that occurs, even if the Cl-/proton electric attraction is still present, the phase coherence between the protons can be easily destroyed due to inequivalent coupling between the protons and the chlorine anion. In such a case, the four protons can hardly move at the same pace and one would expect a rapid quenching of the correlated tunneling process."
When asked about the significant implications and potential applications of controlling the quantum states of protons with atomic-scale precision as made possible by their work, Jiang told Phys.org that the ability to control the quantum states of protons "can certainly improve our understanding of the role of quantum mechanics in proton dynamics, such as phase transition in ices of high-pressure phases. It may also provide completely new routes for the design of new energy, new medicine and new functional materials related to proton transfer."
Jiang adds that a less straightforward but very ambitious application is quantum computing. "The two many-body states of the four protons can be adopted to build a qubit, which is essential in quantum computing. If there is a way to decouple the water tetramer from the environment, we should be able to observe the superposition of the two many-body states. However, the biggest challenge lies in how to realize coherent control on and readout of the two many-body states. Since scattering by tunneling electrons from the STM tip tends to destroy the quantum coherence of protons, it seems that we need to develop new techniques other than STM to realize such control."
Moving forward with their research, the scientists are now trying to build larger hydrogen-bonded water clusters on substrates to explore more novel correlated quantum behaviors of protons. "We're also curious about the upper limit of the number of protons at which cooperativity and tunnel collectively" – that is, correlated many-body tunneling – "can be maintained. Another thing we're planning to do is using an accurately-engineered STM tip to further suppress the tunneling barrier such that the zero-point motion of protons can surpass the energy barrier. We then expect to visualize the complete quantum delocalization at single proton level."
One innovation the researchers are interested in developing is achieving coherent control on the many-body quantum states of protons, as described above; another is improving the temporal resolution of their STM system, such that they can closely follow the coherent evolution of the many-body states in real time. "These new techniques may well make it possible to observe the Rabi oscillation of proton states, which is a common phenomenon for photon- or spin-based two-level systems." The Rabi oscillation, or Rabi cycle, is the cyclic behavior of a two-state (with non-equal energies) quantum system important in quantum optics, nuclear magnetic resonance and quantum computing that, in the presence of an oscillatory driving field, can become excited when it absorbs a quantum of energy.
As to other areas of research that might benefit from the study, Jiang tells Phys.org
that "the improved understanding and the real-space control of
correlated proton tunneling may have great impact in an extremely broad
spectrum of research fields, such as phase transition, signal
transduction, topological organic ferroelectrics, photosynthesis, and
enzyme catalysis, to name just a few."
Explore further: Autonomous atom assembly of nanostructures using a scanning tunneling microscope
More information: Direct visualization of concerted proton tunnelling in a water nanocluster, Nature Physics (2015) 11:235–239, doi:10.1038/nphys3225
1Real-space imaging of interfacial water with submolecular resolution, Nature Materials (2014) 13:184–189, doi:10.1038/nmat3848 | <urn:uuid:043bf550-b75b-4206-b6cf-74fc37b05fdf> | 3.234375 | 2,594 | Truncated | Science & Tech. | 24.494796 | 95,477,947 |
Cleaner beaches must for greater protection to marine turtles
STAFF REPORT KHI: Clean environment along sea shores and at islands is prerequisite to provide safe, secure and nesting place for the turtles especially during the ensuing breeding season as this species is increasingly endangered with the rising sea water pollution and amount of litter at the shore. There is a grave need to create awareness among the sea shore visitors to avoid dropping food wrappers, shopping bags or other waste items as it badly affects the water quality as well as environment which, too, affects the whole ecosystem.
During the past some time, efforts to protect the endangered sea turtles along the coasts of Sindh and Balochistan have received a boost that could ensure cleaner sea sides significantly.
Most recently, the IUCN Pakistan in collaboration with International Centre Integrated Mountain Development (ICIMOD) has launched a USAID-funded Saving the Endangered Sea Turtles project at a ceremony in Karachi, which was attended by a large number of participants representing government, civil society, private sector and academic organizations.
The project was jointly organized to mark the World Turtle Day and International Day for Biological Diversity 2014 at Sandspit Beach Karachi.
The event commenced with Beach Cleaning Competition at the Sandspit Beach involving children from the five schools of the coastal areas. During this activity, approximately two tons of litter was collected and disposed of to create safe nesting place for the turtles during the ensuing breeding season.
Later, a turtle quiz programme was conducted to create awareness amongst the children about the turtles and the threats facing them. The event was attended by representatives of the Sindh Wildlife Department, WWF-Pakistan; ICI Pakistan; Fisherfolks of Kaka Pir village; and Women Moti Mala Tanzeem.
“Turtles are an important part of our biodiversity. The Sandspit and Hawksbay beaches are amongst the 11 most important turtle nesting grounds in the world. Around 6,000 Green Turtles used to visit these beaches during the breeding seasons, but their numbers have dwindled over the years due to various threats – including entanglement in fishing nets, habitat degradation and littering of the nesting beaches. Leftover food at the beaches results in increase of predators population that hunts on the hatched baby turtles while crawling towards the sea,” said Ghulam Qadir Shah, Mangrove for the Future Programme, National Coordinator in his opening remarks on the occasion.
On this occasion, in his message Dr. David Molden, the Director General ICIMOD related to the International Day for Biodiversity, stressed upon reinforcing global commitments for biodiversity conservation to ensure continuity of provisioning, regulating, cultural and supporting services of biodiversity resources.
Speaking on the occasion, Amar Guriro, President, National Council of the Environmental Journalists (NCEJ) emphasized on increasing the environmental reporting in the mainstream media.
Naveed Soomro, Manager Wetland Centre, WWF-P, highlighted the need to conserve sea turtles and other biodiversity resources.
IUCN Country Representative Mahmood Akhtar said, “This is not our first attempt to conserve these endangered species. IUCN has actively been engaged in the conservation, awareness-raising and monitoring of sea turtles and other marine species such as dolphins, whales, migratory birds along Sindh and Balochistan coasts”
The chief guest on the occasion, Rukhsana Saleem, Secretary, Climate Change Division, assured her full support to the cause.
The UN General Assembly has marked 2014 as the International Year of Small Island Developing States. Accordingly, the UN is focusing on the theme Island Biodiversity for this year. Due to their isolation, islands harbor a unique array of biodiversity, and many island species are endemic – they are found nowhere else on earth. Islands thus make a substantial contribution to global biodiversity. However, they are extremely vulnerable to loss of species diversity.
https://www.technologytimes.pk/cleaner-beaches-must-for-greater-protection-to-marine-turtles/Newsbeaches,Cleaner,greater,Marine,protection,turtles STAFF REPORT KHI: Clean environment along sea shores and at islands is prerequisite to provide safe, secure and nesting place for the turtles especially during the ensuing breeding season as this species is increasingly endangered with the rising sea water pollution and amount of litter at the shore. There...Technology TimesTechnology Times email@example.comAdministratorTechnology Times is Pakistan's First Newspaper on Science and TechnologyTechnology Times | <urn:uuid:521d2d84-dac9-4689-8c70-4bf9c478ef62> | 3.15625 | 918 | News Article | Science & Tech. | 18.86811 | 95,477,957 |
|시간 제한||메모리 제한||제출||정답||맞은 사람||정답 비율|
|1 초||256 MB||43||25||23||58.974%|
Just like humans enjoy playing the game of Hopscotch, Farmer John's cows have invented a variant of the game for themselves to play. Being played by clumsy animals weighing nearly a ton, Cow Hopscotch almost always ends in disaster, but this has surprisingly not deterred the cows from attempting to play nearly every afternoon.
The game is played on an R by C grid (2 <= R <= 15, 2 <= C <= 15), where each square is colored either red or blue. Cows start in the top-left square and move to the bottom-right square by a sequence of jumps, where a jump is valid if and only if
1) You are jumping to a square of a different color,
2) The square that you are jumping to is at least one row below the current square that you are on, and
3) The square that you are jumping to is at least one column to the right of the current square that you are on.
Please help the cows compute the number of different possible sequences of valid jumps that will take them from the top-left square to the bottom-right square.
The first line contains the two integers R and C. The next R lines will each contain C characters. Each character is either 'R' or a 'B', indicating a red square or a blue square.
Output the number of different ways one can jump from the top-left square to the bottom-right square.
4 4 RRRR RRBR RBBR RRRR | <urn:uuid:d114e933-73aa-4bff-8d9f-0790b3bea091> | 3.28125 | 397 | Tutorial | Science & Tech. | 73.477 | 95,477,977 |
Viewers are introduced to the building blocks of programming. They learn about five data types and how to use them to create and initialize a variable. Additionally, they learn how to print variables and combinations of text and variables.
1. Introduce Objective
2. Data Type Definition
3. 5 different Data Types
4. Define Variable
5. Create and initialize 5 variables each of a different data type
Java functions are among the best things for programmers to work with as Java sites can be very easy to read and prepare. Java especially simplifies many processes in the coding industry as it helps integrate many forms of technology and different d… | <urn:uuid:caa0fc8d-6edc-4c88-b728-a8cd3b513f8b> | 3.734375 | 130 | Truncated | Software Dev. | 43.193598 | 95,477,980 |
"Sea stars were assumed to be at the mercy of the sun during low tide," said the study's lead author, Sylvain Pincebourde of François Rabelais University in Tours, France. "This work shows that some sea stars have an unexpected back-up strategy."
The researcher is published in the December issue of The American Naturalist.
Sea stars need to endure rapid changes in temperature. During high tide, they are fully submerged in cool sea water. But when tides receded, the stars are often left on rocky shorelines, baking in the sun.
Clearly the stars had some way of beating the heat, but scientists were unsure how they did it. Pincebourde and his team thought it might have something to do with fluid-filled cavities found in the arms of sea stars. So he set up an experiment to test it.
The researchers placed sea stars in aquariums and varied the water level to simulate tidal patterns. Heat lamps were used to control temperature, with some stars experiencing hotter temperatures than others. The researchers found that stars exposed to higher temperatures at low tide had higher body mass after the high tide that followed. Since the stars were not allowed to eat, the increased mass must be from soaking up water.
"This reservoir of cool water keeps the sea star from overheating when the tide recedes again the next day, a process called 'thermal inertia,'" Pincebourde said.
What appears to be happening, the researchers say, is that a hot low tide serves as a cue telling the star to soak up more water during the next high tide. And the amount of water the stars can hold is remarkable.
"It would be as if humans were able to look at a weather forecast, decide it was going to be hot tomorrow, and then in preparation suck up 15 or more pounds of water into our bodies," said co-author Brian Helmuth of the University of South Carolina in Columbia.
The researchers are concerned, however, that climate change may put this novel cooling strategy in peril.
"This strategy only works when the sea water is colder than the air," said co-author Eric Sanford of the University if California, Davis. "Ocean warming might therefore break down this buffering mechanism, making this sea star susceptible to global warming. There are likely limits to how much this mechanism can buffer this animal against global change."
Sylvain Pincebourde, Eric Sanford, and Brian Helmuth, "An Intertidal Sea Star Adjusts Thermal Inertia to Avoid Extreme Body Temperatures." The American Naturalist 174:6 (December 2009).
Since its inception in 1867, The American Naturalist has maintained its position as one of the world's most renowned, peer-reviewed publications in ecology, evolution, and population and integrative biology research. The journal is published by The University of Chicago Press for the American Society of Naturalists.
Kevin Stacey | EurekAlert!
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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The steradian (symbol: sr) or square radian is the SI unit of solid angle. It is used in three-dimensional geometry, and is analogous to the radian, which quantifies planar angles. Whereas an angle in radians, projected onto a circle, gives a length on the circumference, a solid angle in steradians, projected onto a sphere, gives an area on the surface. The name is derived from the Greek στερεός stereos 'solid' + radian.
A graphical representation of 1 steradian.The sphere has radius r, and in this case the area A of the highlighted surface patch is r2. The solid angle Ω equals [A/r2] sr which is 1 sr in this example. The entire sphere has a solid angle of 4πsr.
|Unit system||SI derived unit|
|Unit of||Solid angle|
The steradian, like the radian, is a dimensionless unit, essentially because a solid angle is the ratio between the area subtended and the square of its distance from the center: both the numerator and denominator of this ratio have dimension length squared (i.e. L2/L2 = 1, dimensionless). It is useful, however, to distinguish between dimensionless quantities of a different nature, so the symbol "sr" is used to indicate a solid angle. For example, radiant intensity can be measured in watts per steradian (W⋅sr−1). The steradian was formerly an SI supplementary unit, but this category was abolished in 1995 and the steradian is now considered an SI derived unit.
A steradian can be defined as the solid angle subtended at the center of a unit sphere by a unit area on its surface. For a general sphere of radius r, any portion of its surface with area A = r2 subtends one steradian at its center.
The solid angle is related to the area it cuts out of a sphere:
Because the surface area A of a sphere is 4πr2, the definition implies that a sphere subtends 4π steradians (≈ 12.56637 sr) at its center. By the same argument, the maximum solid angle that can be subtended at any point is 4π sr.
Since A = r2, it corresponds to the area of a spherical cap (A = 2πrh) (where h stands for the "height" of the cap), and the relationship h/ = 1/ holds. Therefore, one steradian corresponds to the plane (i.e. radian) angle of the cross-section of a simple cone subtending the plane angle 2θ, with θ given by:
This angle corresponds to the plane aperture angle of 2θ ≈ 1.144 rad or 65.54°.
The solid angle of a cone whose cross-section subtends the angle 2θ is:
Solid angles over 4π steradians—the solid angle of a full Euclidean sphere—are rarely encountered.
|Look up steradian in Wiktionary, the free dictionary.|
- Stutzman, Warren L; Thiele, Gary A (2012-05-22). Antenna Theory and Design. ISBN 978-0-470-57664-9.
- Woolard, Edgar (2012-12-02). Spherical Astronomy. ISBN 978-0-323-14912-9.
- "Steradian", McGraw-Hill Dictionary of Scientific and Technical Terms, fifth edition, Sybil P. Parker, editor in chief. McGraw-Hill, 1997. ISBN 0-07-052433-5.
- Stephen M. Shafroth, James Christopher Austin, Accelerator-based Atomic Physics: Techniques and Applications, 1997, ISBN 1563964848, p. 333
- R. Bracewell, Govind Swarup, "The Stanford microwave spectroheliograph antenna, a microsteradian pencil beam interferometer" IRE Transactions on Antennas and Propagation 9:1:22-30 (1961) | <urn:uuid:dcba6d23-0e9c-4f30-916d-50b7d3d34286> | 4.03125 | 863 | Knowledge Article | Science & Tech. | 60.288091 | 95,477,992 |
mechanism whereby atoms combine to form molecules. There is a chemical bond between two atoms or groups of atoms when the forces acting between them are strong enough to lead to the formation of an aggregate with sufficient stability to be regarded as an independent species. The number of bonds an atom forms corresponds to its valence. The amount of energy required to break a bond and produce neutral atoms is called the bond energy. All bonds arise from the attraction of unlike charges according to Coulomb's law; however, depending on the atoms involved, this force manifests itself in quite different ways. The principal types of chemical bond are the ionic, covalent, metallic, and hydrogen bonds. The ionic and covalent bonds are idealized cases, however; most bonds are of an intermediate type.
The ionic bond results from the attraction of oppositely charged ions. The atoms of metallic elements, e.g., those of sodium, lose their outer electrons easily, while the atoms of nonmetals, e.g., those of chlorine, tend to gain electrons. The highly stable ions that result retain their individual structures as they approach one another to form a stable molecule or crystal. In an ionic crystal like sodium chloride, no discrete diatomic molecules exist; rather, the crystal is composed of independent Na+ and Cl- ions, each of which is attracted to neighboring ions of the opposite charge. Thus the entire crystal is a single giant molecule.
A single covalent bond is created when two atoms share a pair of electrons. There is no net charge on either atom; the attractive force is produced by interaction of the electron pair with the nuclei of both atoms. If the atoms share more than two electrons, double and triple bonds are formed, because each shared pair produces its own bond. By sharing their electrons, both atoms are able to achieve a highly stable electron configuration corresponding to that of an inert gas. For example, in methane (CH4), carbon shares an electron pair with each hydrogen atom; the total number of electrons shared by carbon is eight, which corresponds to the number of electrons in the outer shell of neon; each hydrogen shares two electrons, which corresponds to the electron configuration of helium.
In most covalent bonds, each atom contributes one electron to the shared pair. In certain cases, however, both electrons come from the same atom. As a result, the bond has a partly ionic character and is called a coordinate link. Actually, the only purely covalent bond is that between two identical atoms.
Covalent bonds are of particular importance in organic chemistry because of the ability of the carbon atom to form four covalent bonds. These bonds are oriented in definite directions in space, giving rise to the complex geometry of organic molecules. If all four bonds are single, as in methane, the shape of the molecule is that of a tetrahedron. The importance of shared electron pairs was first realized by the American chemist G. N. Lewis (1916), who pointed out that very few stable molecules exist in which the total number of electrons is odd. His octet rule allows chemists to predict the most probable bond structure and charge distribution for molecules and ions. With the advent of quantum mechanics, it was realized that the electrons in a shared pair must have opposite spin, as required by the Pauli exclusion principle. The molecular orbital theory was developed to predict the exact distribution of the electron density in various molecular structures. The American chemist Linus Pauling introduced the concept of resonance to explain how stability is achieved when more than one reasonable molecular structure is possible: the actual molecule is a coherent mixture of the two structures.
Unlike the ionic and covalent bonds, which are found in a great variety of molecules, the metallic and hydrogen bonds are highly specialized. The metallic bond is responsible for the crystalline structure of pure metals. This bond cannot be ionic because all the atoms are identical, nor can it be covalent, in the ordinary sense, because there are too few valence electrons to be shared in pairs among neighboring atoms. Instead, the valence electrons are shared collectively by all the atoms in the crystal. The electrons behave like a free gas moving within the lattice of fixed, positive ionic cores. The extreme mobility of the electrons in a metal explains its high thermal and electrical conductivity.
Hydrogen bonding is a strong electrostatic attraction between two independent polar molecules, i.e., molecules in which the charges are unevenly distributed, usually containing nitrogen, oxygen, or fluorine. These elements have strong electron-attracting power, and the hydrogen atom serves as a bridge between them. The hydrogen bond, which plays an important role in molecular biology, is much weaker than the ionic or covalent bonds. It is responsible for the structure of ice.
- See L. Pauling, The Nature of the Chemical Bond (3d ed. 1960).
- A. L. Companion, Chemical Bonding (2d ed. 1979).
The force that holds the atoms together in a molecule or the ions together in a crystalline solid. In general, atoms combine to form molecules...
Mechanism that holds together atoms to form molecules. There are several types which arise either from the attraction of unlike charges, or from...
An attractive force between atoms strong enough to permit the combined aggregate to function as a unit. A more exact definition is not possible beca | <urn:uuid:6f610555-53bf-4197-9764-a0206464ac59> | 4.375 | 1,104 | Knowledge Article | Science & Tech. | 37.672718 | 95,477,997 |
posted by Physics - URGENT
Water moves through a constricted pipe in steady, ideal flow. At the lower point shown in the figure below, the pressure is 1.70 ✕ 105 Pa and the pipe radius is 2.50 cm. At the higher point located at
y = 2.50 m, the pressure is 1.21 ✕ 105 Pa and the pipe radius is 1.70 cm.
(a) Find the speed of flow in the lower section.
(b) Find the speed of flow in the upper section.
(c) Find the volume flow rate through the pipe. | <urn:uuid:42661c6e-08db-419c-b471-a5decac81cf2> | 3.625 | 126 | Tutorial | Science & Tech. | 99.032866 | 95,477,999 |
12 July 2018
Unique star system can be used to test general relativity
Published online 8 January 2014
In space, the orbital interactions between three bodies have been studied for centuries since they can be used to measure the properties of stars and planets, such as mass and composition, as well as test our theories of gravity. The presence of a neutron star known as a millisecond pulsar, which rotates hundreds of times per second and emits radio waves much as a lighthouse emits light, can be used to study these types of astronomical systems.
So far, the only three-body system discovered with a millisecond pulsar had a companion planet, whose gravitational interactions were too weak to measure properly. Now, a team of international researchers, led by Scott Ransom from the National Radio Astronomy Observatory in Charlottesville, Virginia, and involving Mallory Roberts from the New York University at Abu Dhabi, have discovered a three-body system with a millisecond pulsar and two white-dwarf companions. The inner white dwarf has an orbital period of 1.6 Earth days while the outer one makes a full rotation of the pulsar in almost an Earth year.
The researchers found the system to be coplanar with nearly circular orbits. This unexpected finding suggests a complex and exotic evolutionary pathway that differs from those of known stellar systems. The strong gravitational pull of the outer star could allow researchers to make further measurements and test a key part of the general theory of relativity, the strong equivalence principle, which suggests that the orbital motions of bodies with strong self-gravity are the same as those with weak self-gravity.
- S. M. Ransom et al. A millisecond pulsar in a stellar triple system. Nature (2014) doi:10.1038/nature12917 | <urn:uuid:f83f9f17-8d76-4064-8dd5-459337320f55> | 3.84375 | 361 | Truncated | Science & Tech. | 37.469195 | 95,478,008 |
Calculate the solubility of silver chromate in 0.005 M Na2CrO4.
a. 1.4 ´10–4 M
b. 3.4 ´10–5 M
c. 1.1 ´10–5 M
d. 1.6 ´10–6 M
e. < 1.0 ´10–6 M
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Neutrons probe oxygen-generating enzyme for a greener approach to clean water
A new study sheds light on a unique enzyme that could provide an eco-friendly treatment for chlorite-contaminated water supplies and improve water quality worldwide.
An international team of researchers led by Christian Obinger from the University of Vienna used neutron analysis at Oak Ridge National Laboratory, x-ray crystallography and other techniques to study the chlorite dismutase enzyme. This naturally occurring protein can break down chlorite, an industrial pollutant found in groundwater, drinking water and soils, into harmless byproducts, but its catalytic process is not well understood. Understanding how the bacterial enzyme converts chlorite into chloride and oxygen could open possibilities for future applications in bioremediation and biotechnology.
The results, published in ACS Catalysis, also contribute to fundamental research on the enzyme's ability to produce oxygen. Oxygen generation is incredibly rare in nature, once thought possible only by photosynthesis, so the enzymatic activity of chlorite dismutase has attracted interest from the scientific community beyond its environmental applications for clean water.
Exactly how chlorite dismutase works at a molecular level to break down chlorite has been debated since the enzyme was discovered in 1996. The complexity of the enzyme's molecular structure and the difficulty of studying proteins with experimental methods present inherent challenges for researchers.
Like most enzymes, chlorite dismutase is a protein that catalyzes a highly specific reaction. The process is often environmentally dependent, meaning it works best within specific parameters, including temperature, concentration and pH ranges. Identifying the ideal parameters for the reaction is key to supporting bioengineering and large-scale production of chlorite dismutase to safely remove chlorite from the environment and potentially exploit the enzyme's oxygen generation.
The team isolated an unstudied Cyanothece strain of chlorite dismutase and examined the protein's crystal structure at specific pH values to determine the impact of pH on chlorite conversion.
The researchers used MaNDi, the macromolecular neutron diffractometer, beamline 11-B at the Spallation Neutron Source, a Department of Energy User Facility at ORNL, to collect unique data only obtainable through the use of neutrons.
"Different protein crystals have different degrees of symmetry, which will determine how we go about measuring them. This crystal is unusual in that it has very little symmetry, so an especially large number of reflections have to be recorded individually to get a complete data set," said Leighton Coates, MaNDi Lead Instrument Scientist. "This would be a challenging and lengthy task anywhere, and it was only achievable in this time frame due to the large area detector coverage of the MaNDi instrument."
On MaNDi, researchers were able to detect the protonation states of important amino acids thought to support the reaction. "Protonation" refers to a fundamental step in catalysis during which hydrogen attaches to molecules. "This is the important region of the protein, where the chemistry is happening and the chlorite is being broken down," said Coates.
Protonation states are not easily observed because they involve hydrogen, which is difficult to detect with x-rays or other techniques. In addition, a phenomenon called "photoreduction" occurs when exposing metal-containing enzymes like chlorite dismutase to x-rays, essentially changing the atomic structure of the sample.
Because neutron techniques do not have these limitations, they can give researchers key information that cannot be obtained by other methods. "Neutrons are nondestructive and sensitive to light elements like hydrogen, so they can provide exclusive information about the atomic structure of proteins, which are largely composed of hydrogen molecules," Coates explained.
"And unlike x-rays that can damage delicate proteins, neutron techniques allow you to collect data at room temperature on an unaltered protein in its active state without the impacts of ionizing radiation and photoreduction," said Coates. "This experiment really highlights the benefit of using neutrons to study proteins."
The journal article is published as "Molecular mechanism of enzymatic chlorite detoxification: insights from structural and kinetic studies." Coauthors include Irene Schaffner, Georg Mlynek, Nicola Flego, Dominic Pu?hringer, Julian Libiseller-Egger, Leighton Coates, Stefan Hofbauer, Marzia Bellei, Paul G. Furtmu?ller, Gianantonio Battistuzzi, Giulietta Smulevich, Kristina Djinović-Carugo and Christian Obinger.
The Spallation Neutron Source is a DOE Office of Science User Facility. UT-Battelle manages ORNL for the DOE Office of Science. The single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. | <urn:uuid:937f9578-92a9-4c15-83f7-5aa97c16bd1a> | 3.734375 | 1,026 | News Article | Science & Tech. | 11.95498 | 95,478,044 |
May 25 2011 Astronomy Newsletter
I thought it was about time I updated a very old article about Copernicus. A few weeks ago, I wrote about how his idea of a heliocentric system set off a revolution in astronomy. This week I've written a bit about his life - also his death. Considering he's one of the most famous names in the history of science, it was strange that no one knew where he was buried until quite recently. And identifying the remains was a story worthy of an episode of CSI! So here is this week's article from the Astronomy site at BellaOnline.
Nicolaus Copernicus - His Life
The day job of one reluctant revolutionary was as the canon of a cathedral. And the last resting place of the man who turned astronomy on its head, Nicolaus Copernicus, was unmarked. How did his student astronomy books help to identify his remains four and a half centuries later?
By the way, yesterday (May 24) was the 468th anniversary of the death of Copernicus.
I was out the other night and amazingly, it was clear. And what did I see in the east but the Summer Triangle – Vega, Altair and Lyra! Lovely. I don't really know why people called it the "summer" triangle, because it's visible for a good month before the solstice, then on into the autumn. Still it's a nice promise of summer.
For more about the Summer Triangle, have a look at the beginner's guide at http//www.bellaonline.com/articles/art27681.asp.
If you saw last week's article “Gravity – Cosmic Glue” http://www.bellaonline.com/articles/art2162.asp, you may remember that Einstein's theory was tested in a solar eclipse. This happened on May 29, 1919.
That's all for this now. Wishing you clear skies.
Please visit astronomy.bellaonline.com for even more great content about Astronomy.
To participate in online discussions, this site has a community forum all about Astronomy located here -
I hope to hear from you sometime soon, either in the forum or in response to this email message. I welcome your feedback!
Do pass this message along to family and friends who might also be interested. Remember it's free and without obligation.
Mona Evans, Astronomy Editor
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The pollen basket or corbicula (plural corbiculae) is part of the tibia on the hind legs of certain species of bees. They use the structure in harvesting pollen and carrying it to the nest or hive. Other species of bees have scopae instead.
Structure and function
Bees in four tribes of the family Apidae, subfamily Apinae: the honey bees, bumblebees, stingless bees, and orchid bees have corbiculae. The corbicula is a polished cavity surrounded by a fringe of hairs, into which the bee collects the pollen; most other bees possess a structure called the scopa, which is similar in function, but is a dense mass of branched hairs into which pollen is pressed, with pollen grains held in place in the narrow spaces between the hairs. A honey bee moistens the forelegs with its protruding tongue and brushes the pollen that has collected on its head, body and forward appendages to the hind legs. The pollen is transferred to the pollen comb on the hind legs and then combed, pressed, compacted, and transferred to the corbicula on the outside surface of the tibia of the hind legs.
In Apis species, a single hair functions as a pin that secures the middle of the pollen load. Either honey or nectar is used to moisten the dry pollen, producing the product known as bee pollen or bee bread. The mixing of the pollen with nectar or honey changes the color of the pollen. The color of the pollen can help identify the pollen source.
There was little formal description of the corbicula before Carl Linnaeus explained the biological function of pollen in the mid-18th century. In English the first edition of Encyclopædia Britannica described the structure in 1771 without giving it any special name. The second edition, 1777, refers to the corbicula simply as the "basket". By 1802 William Kirby had introduced the New Latin term corbicula into English. He had borrowed it, with acknowledgement, from Réaumur. Like other Latin anatomical terms, this had the advantages of specificity, international acceptability, and culture neutrality. By 1820 the term pollen-basket seems to have gained acceptance in beekeeping, though a century later a compendium of entomological terminology recognised pollen-plate and corbicula without including "pollen-basket". A century later, the authors of "Imms" included only the terms scopa and corbicula in the index, with "pollen basket" in the text.
Corbicula is a diminutive of corbis, a basket or pannier. It is the singular, with plural corbiculae, but since at least c. 1866 some authors have thought corbicula to be the plural of a non-existent neuter form corbiculum.
- George Gordh, Gordon Gordh, David Headrick, A Dictionary of Entomology, Science, 2003; 1040 pages; pg.713
- Bees (Hymenoptera: Apoidea: Apiformes) Encyclopedia of Entomology 2008. Vol. 2, pages 419–434
- Cedric Gillott, Entomology, Springer, 1995; 798 pages; pg. 79
- Dorothy Hodges, The Pollen Loads of the Honeybee, published by Bee Research Association, 1952
- Society of Gentlemen in Scotland (1771). Encyclopædia Britannica: Or, A Dictionary of Arts and Sciences, Compiled Upon a New Plan in which the Different Sciences and Arts are Digested Into Distinct Treatises Or Systems; and the Various Technical Terms, Etc., are Explained as They Occur in the Order of the Alphabet. Encyclopædia Britannica. p. 89.
- Bees. J. Balfour and Company W. Gordon. 1778. p. 440.
- William Kirby (1802). Monographia Apum Angliae; Or, An Attempt to Divide Into Their Natural Genera and Families, Such Species of the Linnean Genus Apis as Have Been Discovered in England: with Descriptions and Observations. To which are Prefixed Some Introductory Remarks Upon the Class Hymenoptera, and a Synoptical Table of the Nomenclature of the External Parts of These Insects. With Plates. Vol. 1. [-2.]. By William Kirby . p. 200.
- "The Honeybee". Murray's Magazine. II: 258. 1887. extracted in Bees: Extracts II.
- Smith, John. B. Explanation of terms used in entomology. Pub: Brooklyn Entomological Society 1906. May be downloaded from:
- Richards, O. W.; Davies, R.G. (1977). Imms' General Textbook of Entomology: Volume 1: Structure, Physiology and Development Volume 2: Classification and Biology. Berlin: Springer. ISBN 0-412-61390-5.
- Ainsworth, Robert; Eds: Morell, Thomas; Carey, John | An Abridgment of Ainsworth's Latin Dictionary, 13th ed. | London 1834
- Jaeger, Edmund Carroll (1959). A source-book of biological names and terms. Springfield, Ill: Thomas. ISBN 0-398-06179-3.
- William Young (1810). A new Latin-English dictionary: To which is prefixed an English-Latin dictionary. A. Wilson. pp. 22–.
- Alpheus Spring Packard (1868). Guide to the Study of Insects: And a Treatise on Those Injurious and Beneficial to Crops: for the Use of Colleges, Farm-schools, and Agriculturists. Naturalist's agency. p. 116.
- Frederick Augustus Porter Barnard; Arnold Guyot; A.J. Johnson & Co (1890). Johnson's universal cyclopædia: a scientific and popular treasury of useful knowledge. A.J. Johnson.
- George McGavin (1992). Insects of the northern hemisphere. Dragon's World. ISBN 978-1-85028-151-1.
- James L. Castner (2000). Photographic atlas of entomology and guide to insect identification. Feline Press. ISBN 978-0-9625150-4-0. | <urn:uuid:40fb7a99-8b4f-4e53-ae86-431206d18c51> | 3.921875 | 1,356 | Knowledge Article | Science & Tech. | 56.402095 | 95,478,087 |
posted by Kathy
The displacement vector for a 15.0 second interval of a jet airplane's flight is (3850, −2430) m. (a) What is the magnitude of the average velocity? (b) At what angle, measured from the positive x axis, did the airplane fly during this time interval? Express the angle as a number between −180° and +180°.
Thanks a lot. | <urn:uuid:e5a25c4e-d906-482f-bde1-2dd224e606e0> | 2.859375 | 86 | Q&A Forum | Science & Tech. | 74.904731 | 95,478,091 |
Challenges and opportunities in land surface modelling of savanna ecosystems
Hutley, Lindsay B.
De Kauwe, Martin G.
- Journal Article
Rights / licenseCreative Commons Attribution 3.0 Unported
The savanna complex is a highly diverse global biome that occurs within the seasonally dry tropical to sub-tropical equatorial latitudes and are structurally and functionally distinct from grasslands and forests. Savannas are open-canopy environments that encompass a broad demographic continuum, often characterised by a changing dominance between C3-tree and C4-grass vegetation, where frequent environmental disturbances such as fire modulates the balance between ephemeral and perennial life forms. Climate change is projected to result in significant changes to the savanna floristic structure, with increases to woody biomass expected through CO2 fertilisation in mesic savannas and increased tree mortality expected through increased rainfall interannual variability in xeric savannas. The complex interaction between vegetation and climate that occurs in savannas has traditionally challenged terrestrial biosphere models (TBMs), which aim to simulate the interaction between the atmosphere and the land surface to predict responses of vegetation to changing in environmental forcing. In this review, we examine whether TBMs are able to adequately represent savanna fluxes and what implications potential deficiencies may have for climate change projection scenarios that rely on these models. We start by highlighting the defining characteristic traits and behaviours of savannas, how these differ across continents and how this information is (or is not) represented in the structural framework of many TBMs. We highlight three dynamic processes that we believe directly affect the water use and productivity of the savanna system: phenology, root-water access and fire dynamics. Following this, we discuss how these processes are represented in many current-generation TBMs and whether they are suitable for simulating savanna fluxes. Finally, we give an overview of how eddy-covariance observations in combination with other data sources can be used in model benchmarking and intercomparison frameworks to diagnose the performance of TBMs in this environment and formulate road maps for future development. Our investigation reveals that many TBMs systematically misrepresent phenology, the effects of fire and root-water access (if they are considered at all) and that these should be critical areas for future development. Furthermore, such processes must not be static (i.e. prescribed behaviour) but be capable of responding to the changing environmental conditions in order to emulate the dynamic behaviour of savannas. Without such developments, however, TBMs will have limited predictive capability in making the critical projections needed to understand how savannas will respond to future global change Show more
Journal / seriesBiogeosciences
Pages / Article No.
Organisational unit03812 - Or, Dani
MoreShow all metadata | <urn:uuid:7ae89052-47e4-4cc5-984d-45269558162f> | 2.546875 | 579 | Academic Writing | Science & Tech. | 2.950758 | 95,478,096 |
Dwarf Salamander, Coastal Plain Dwarf Salamander
© 2012 Todd Pierson (1 of 21)
Country distribution from AmphibiaWeb's database: United States
Eurycea quadridigitata, Holbrook, 1842
Ronald M. Bonett1
1. Historical versus Current Distribution. Dwarf salamanders (Eurycea quadridigitata) were described (as Salamandra quadridigitata) by Holbrook (1842); the type locality was restricted by Schmidt (1953) to the vicinity of Charleston, South Carolina. Cope (1869) transferred this taxon to the genus Manculus (as M. quadridigitatus). Dunn (1923) considered Manculus a junior synonym of Eurycea, and Wake (1966) concurred. However, Mittleman (1947, 1967) supported recognition of the genus Manculus, and recognized three subspecies: M. q. quadridigitatus throughout the southeast and much of the Gulf Coastal Plain; M. q. paludicolus from Louisiana and eastern Texas; and M. q. uvidus from northeastern Texas, western Arkansas, and southwestern Missouri. Nearly all recent authors consider this taxon a single species, Eurycea quadridigitata. Molecular work supports inclusion of this taxon in Eurycea under the Linnean system of nomenclature (Chippindale et al., 2000; C. Hass and R. Highton, unpublished data; P.T.C., unpublished data). In the broad sense, dwarf salamanders have a wide range from North Carolina south into much of peninsular Florida, and west into eastern Texas and southern Arkansas; they occur primarily in the Atlantic and Gulf Coastal Plain regions (see map in Petranka, 1998). However, recent molecular work has revealed deep divergences within this "species," and also suggests that the taxon may not be monophyletic (Chippindale et al., 2000; C. Hass and R. Highton, unpublished data; P.T.C., unpublished data). Eurycea quadridigitata probably consists of at least four distinct species, some of which occur sympatrically but apparently do not interbreed (R. Highton, personal communication). In fact, Harrison and Guttman (2003) have recently described Chamberlain’s dwarf salamanders (Eurycea chamberlaini) from an isolated area in the western Piedmont of South Carolina, the lower Piedmont of North Carolina, the upper Coastal Plain of South Carolina, and the central portion of the Coastal Plain in North Carolina (see account, this volume). Even in the area of the type locality, at least two species are present and sometimes sympatric (R. Highton, personal communication). A formal taxonomic treatment of this complex is expected in the near future. Given this situation, the information for "E. quadridigitata" summarized here almost certainly represents a composite of data for several, perhaps distantly related, species.
2. Historical versus Current Abundance. Generally unknown, but numbers are undoubtedly lower in areas impacted by human activities (Petranka, 1998). Local abundance of adult members of the E. quadridigitata complex was monitored during a 16-yr study (1979–'94) of a Carolina bay in South Carolina (Semlitsch et al., 1996). Breeding adult numbers were not influenced by seasonal rainfall amounts, and recruitment of juveniles was not influenced by larval densities. Juvenile recruitment was, however, influenced by the number of breeding adults. Members of this complex appear to be common in suitable habitat (Petranka, 1998), but given the current confusion regarding species boundaries and the probable occurrence of multiple, sometimes sympatric species, estimates of distribution and abundance should be considered questionable.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. In South Carolina, E. quadridigitata migrate to breeding ponds from August–October (Gibbons and Semlitsch, 1991) and have been collected during migration until late November (McMillan and Semlitsch, 1980). South Carolina breeding populations can include ≤ 10,000 adults, with approximately equal representation of males and females (Gibbons and Semlitsch, 1991). In South Carolina, breeding migrations occur primarily at night, but individuals will also migrate crepuscularly and diurnally (Semlitsch and Pechmann, 1985; Gibbons and Semlitsch, 1991). It has been suggested that dwarf salamanders avoid predation and desiccation during diurnal migrations by traveling beneath the leaf litter (Semlitsch and Pechmann, 1985). Individuals were collected during apparent breeding migrations from late autumn to early winter in east-central Alabama (Trauth, 1983).
ii. Breeding habitat. In the Atlantic Coastal Plain of South Carolina, Eurycea quadridigitata use lentic habitats such as Carolina bays and ephemeral ponds (Gibbons and Semlitsch, 1991). Similarly, in Florida, dwarf salamanders were found only to be associated with ponds (Goin, 1951). In east-central North Carolina, however, adult dwarf salamanders and their eggs have been found along small streams (Brimley, 1923), suggesting that members of this complex will also breed in lotic habitats (Goin, 1951).
i. Egg deposition sites. Females attach their eggs singly to vegetation and other substrates such as twigs, rootlets, and debris. Eggs usually are laid so that they are associated with flowing water (Brimley, 1923; Carr, 1940a; Harrison, 1973; Trauth, 1983). Eggs may also be laid in shallow depressions beneath cover objects along wetland margins (Goin, 1951) or in dry depressions that will fill with spring rains (Taylor et al., 1988).
ii. Clutch size. Developmental data have been collected on members of the E. quadridigitata complex from several localities throughout the range. Clutches containing from 7–48 eggs are oviposited by South Carolina females from November–December when breeding ponds fill (Gibbons and Semlitsch, 1991). Females from east-central Alabama populations had previtellogenic follicles within their ovaries from March–September and enlarged ovarian follicles (14–59) from October–February; oviposition probably occurs over a broad time period in this region (Trauth, 1983). Numerous eggs have been discovered in the field in east-central North Carolina during early February (Brimley, 1923). In Florida, single clutches containing 20 eggs and 62 eggs were recovered from the field in November and February, respectively (Goin, 1951). This lack of synchrony in oviposition by populations in different locations may actually reflect interspecific differences among members of this complex. In the lab, eggs from Florida populations took approximately 3–4 wk to hatch, with hatchlings measuring from 7.5–8.3 mm in total length (Goin, 1951).
C. Larvae/Metamorphosis. As with all hemidactyliines, members of the E. quadridigitata complex have an aquatic larval stage (Petranka, 1998). Goin (1951) described larvae from Florida populations to be morphologically intermediate between typical pond-type and stream-type salamander larvae, with a dorsal caudal fin that extends anteriorly to the mid dorsum (pond characteristic) and relatively few gill filaments (stream characteristic). A photograph of a larval dwarf salamander from southeastern North Carolina (R.W. VanDevender, in Petranka, 1998) matches the description of dwarf salamander larvae from Florida by Goin (1951). Larvae of members of the Eurycea quadridigitata complex have been found to inhabit temporary ponds and Carolina bays in South Carolina (Semlitsch, 1980a; Taylor et al., 1988; Gibbons and Semlitsch, 1991). Additionally, it is likely that larvae develop in the aquatic habitats immediately adjacent to oviposition sites. This suggests that hammock ponds (Goin, 1951) and streams (Brimley, 1923) should also be included as larval habitats for members of this complex. It is unclear whether these reported differences in larval habitat reflect interspecific differences among members of this complex or the ability of larvae of these species to use a variety of aquatic habitats.
i. Length of larval stage. Most larvae metamorphose 2–6 mo after hatching (Brimley, 1923; Harrison, 1973; Semlitsch, 1980a; Petranka, 1998). Harrison (1973) and Semlitsch (1980a) found small larvae in January and February in South Carolina. Mount (1975; see also Petranka, 1998) noted small larvae in pools and ditches in March in Alabama.
ii. Larval requirements.
a. Food. According to Petranka (1998), larvae are benthic feeders. Prey include small invertebrates such as zooplankton, ostracods, and insect larvae (Taylor et al., 1988; see also Petranka, 1998).
b. Cover. Larvae are likely benthic.
iii. Larval polymorphisms. Unknown and unlikely.
iv. Features of metamorphosis. Newly metamorphosed dwarf salamanders have been found from April (Harrison, 1973) to early July (Semlitsch, 1980a; Taylor et al., 1988; see also Petranka, 1998).
v. Post-metamorphic migrations. Unknown and unlikely.
vi. Neoteny. Unknown.
D. Juvenile Habitat. Similar to adult habitat.
E. Adult Habitat. Most studies of adult members of the E. quadridigitata complex have involved individuals intercepted during migrations to and from breeding ponds. Therefore, aside from general notes on habitats where adult dwarf salamanders have been uncovered in the field, little is known about their terrestrial habitat characteristics outside of the breeding season. In general, members of the E. quadridigitata complex have been found beneath cover objects at the edges of ponds and swamps as well as in seeps and amongst leaf litter in springs (Mount, 1975; Petranka, 1998).
F. Home Range Size. Unknown. However, Carr (1940a) notes that dwarf salamanders from Florida can be found at considerable distances from aquatic habitats outside of the breeding season.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Aestivation is unknown.
I. Seasonal Migrations. The only known migrations for the species of the E. quadridigitata complex are apparently for breeding purposes.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. Studies in South Carolina have examined diel patterns of adult migratory activity (Semlitsch and Pechmann, 1985), and larval trophic relations of dwarf salamanders and other sympatric salamanders such as eastern newts (Notophthalmus viridescens) and various ambystomatids (Taylor et al., 1988). These studies have revealed a host of interspecific differences, but none that can be directly attributed to interactions between the species examined. Some members of the E. quadridigitata complex are known to occur sympatrically and are distinguishable based on both external morphology and molecular markers (R. Highton, personal communication). Other plethodontids that have been found syntopic with members of the E. quadridigitata complex in southern Mississippi and southeastern Louisiana include three-lined salamanders (Eurycea guttolineata), southern red salamanders (Pseudotriton ruber vioscai), and spotted dusky salamanders (Desmognathus conanti; R.M.B., personal observation).
L. Age/Size at Reproductive Maturity. In east-central North Carolina, dwarf salamanders are reported to hatch in March and transform 2–3 mo later (Brimley, 1923). Larval periods of approximately 5–6.5 mo are reported for South Carolina populations (Harrison, 1973; Semlitsch, 1980a), and both males and females reach sexual maturity about 8–9 mo after hatching (Semlitsch, 1980a). Semlitsch (1980a) proposes that males are likely to reproduce during their first year, while females likely take an additional year for ova to develop. There has been considerable variation in size at maturity reported among populations of this complex, and the different species that currently are considered E. quadridigitata may mature at different sizes. Monitoring natural populations in South Carolina, Semlitsch (1980a) found larval periods to last from 5–6 mo when individuals attain lengths of 20.7–25.6 mm SVL. Other measurements of newly metamorphosed individuals from South Carolina showed a smaller size at metamorphosis (17–20 mm SVL; Harrison, 1973).
M. Longevity. Unknown.
N. Feeding Behavior. In South Carolina, dwarf salamander larvae feed diurnally, with small individuals taking primarily zooplankton and large larvae consuming small invertebrates (Taylor et al., 1988). Metamorphosed individuals in South Carolina were found to feed upon acarinans, arachnids, coleopterans, collembolans, diplopods, dipterans, hemipterans, homopterans, hymenopterans, and pseudoscorpionids (McMillan and Semlitsch, 1980). Acarinans, arachnids, coleopterans, collembolans, hymenopterans, and larval insects were recovered from the stomachs of terrestrial individuals from southern Georgia (Powders and Cate, 1980). The individuals examined by Powders and Cate (1980) were from two distinct size classes, but showed no differences in preferred prey items. Individuals from Florida populations were found to feed upon coleopterans (larval and adult), annelids, and amphipods (Carr, 1940a).
O. Predators. Examination of stomach contents of 122 pig frogs (Rana grylio) from southwest Georgia revealed four dwarf salamanders (Lamb, 1984). This is the only evidence of predation on dwarf salamanders, although it has been speculated that birds, snakes, and large invertebrates are likely predators (Petranka, 1998).
P. Anti-Predator Mechanisms. Unknown.
Q. Diseases. Unknown.
R. Parasites. Unknown.
4. Conservation. Members of the Eurycea quadridigitata complex currently are given no special protective status. Given the existence of several putative, currently undescribed species in the group, their conservation status should be re-examined after species boundaries and geographic ranges have been accurately delineated.
1Ronald M. Bonett
2Paul T. Chippindale
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Jul 2018.
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In-Situ Aircraft Measurements of the Vertical Distribution of Black Carbon in the Lower Troposphere of Beijing, China, in the Spring and Summer Time
AbstractDue to rapid economic development in recent years, China has become a major global source of refractory black carbon (rBC) particles. However, surface rBC measurements have been limited, and the lower troposphere suffers from a complete lack of measurements, especially in heavily rBC-polluted regions such as China’s capital, Beijing (BJ). In this study, we present the first concentration measurements using an airborne Single Particle Soot Photometer (SP2) instrument, including vertical distributions, size distributions, and the mixing state of rBC particles in the lower troposphere in BJ and its surrounding areas. The measurements were conducted from April to June 2012 during 11 flights. The results show that the vertical rBC distributions had noticeable differences between different air masses. When an air mass originated from the south of BJ (polluted region), the rBC particles were strongly compressed in the planetary boundary layer (PBL), and showed a large vertical gradient at the top of the PBL. In contrast, when an air mass originated from the north of BJ (clean region), there was a small vertical gradient. This analysis suggests that there was significant regional transport of rBC particles that enhanced the air pollution in BJ, and the transport not only occurred near the surface but also in the middle levels of the PBL (around 0.5 to 1 km). The measured size distributions show that about 80% of the rBC particles were between the diameters of 70 and 400 nm, and the mean diameter of the peak rBC concentrations was about 180–210 nm. This suggests that the rBC particles were relatively small particles. The mixing state of the rBC particles was analyzed to study the coating processes that occurred on the surface of these particles. The results indicate that the air mass strongly affected the number fraction (NF) of the coated particles. As for a southern air mass, the local air pollution was high, which was coupled with a lower PBL height and higher humidity. Consequently, hygroscopic growth occurred rapidly, producing a high NF value (~65%) of coated rBC particles. The correlation coefficient between the NF and the local relative humidity (RH) was 0.88, suggesting that the rBC particles were quickly converted from hydrophobic to hydrophilic particles. This rapid conversion is very important because it suggests a shorter lifetime of rBC particles under heavily polluted conditions. In contrast, under a northern air mass, there was no clear correlation between the NF and the local humidity. This suggests that the coating process occurred during the regional transport in the upwind region. In this case, the lifetime was longer than the southern air mass condition. View Full-Text
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Zhao, D.; Tie, X.; Gao, Y.; Zhang, Q.; Tian, H.; Bi, K.; Jin, Y.; Chen, P. In-Situ Aircraft Measurements of the Vertical Distribution of Black Carbon in the Lower Troposphere of Beijing, China, in the Spring and Summer Time. Atmosphere 2015, 6, 713-731.
Zhao D, Tie X, Gao Y, Zhang Q, Tian H, Bi K, Jin Y, Chen P. In-Situ Aircraft Measurements of the Vertical Distribution of Black Carbon in the Lower Troposphere of Beijing, China, in the Spring and Summer Time. Atmosphere. 2015; 6(5):713-731.Chicago/Turabian Style
Zhao, Delong; Tie, Xuexi; Gao, Yang; Zhang, Qiang; Tian, Haijun; Bi, Kai; Jin, Yongli; Chen, Pengfei. 2015. "In-Situ Aircraft Measurements of the Vertical Distribution of Black Carbon in the Lower Troposphere of Beijing, China, in the Spring and Summer Time." Atmosphere 6, no. 5: 713-731. | <urn:uuid:7476bfc5-4662-4d17-9249-886b648cf30d> | 2.890625 | 825 | Academic Writing | Science & Tech. | 54.645869 | 95,478,121 |
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Temporal range: Middle Eocene – recent, 45–0 Ma
|Male European wool carder bee, Anthidium manicatum|
Megachilidae is a cosmopolitan family of mostly solitary bees whose pollen-carrying structure (called a scopa) is restricted to the ventral surface of the abdomen (rather than mostly or exclusively on the hind legs as in other bee families). Megachilid genera are most commonly known as mason bees and leafcutter bees, reflecting the materials from which they build their nest cells (soil or leaves, respectively); a few collect plant or animal hairs and fibers, and are called carder bees, while others use plant resins in nest construction and are correspondingly called resin bees. All species feed on nectar and pollen, but a few are kleptoparasites (informally called "cuckoo bees"), feeding on pollen collected by other megachilid bees. Parasitic species do not possess scopae. The motion of Megachilidae in the reproductive structures of flowers is energetic and swimming-like; this agitation releases large amounts of pollen.
The lifecycle of nonparasitic Megachilidae is typically that nests are built, divided into cells. Each cell receives a supply of food (pollen or a pollen/nectar mix) and an egg; after finding a suitable spot (often near where she emerged), a female starts building a first cell, stocks it, and oviposits. She builds a wall that separates the completed cell from the next one. The larva hatches from the egg and consumes the food supply. After moulting a few times, it spins a cocoon and pupates. It emerges from the nest as an adult. Males die shortly after mating, but females survive for another few weeks, during which they build new nests.
Nests are often built in natural or artificial cavities. Some embed individual cells in a mass of clay or resin attached to a wall, rock surface, or plant stem. Nest cavities are often linear, for example in hollow plant stems, but not always (snail shells are used by some Osmia, and some species readily use irregular cavities).
Some genera of megachilids are brood parasites, so have no ventral scopa (e.g. Stelis and Coelioxys). They often parasitize related taxa. They typically enter the nest before it is sealed and lay their eggs in a cell. After hatching, the parasite larva kills the host larva, unless the female parasite has already done so, and then consumes the provisions. Parasitic species are of equal size or smaller than their victims. In 1921, the journal American Museum Novitates published a preliminary report on parasitic megachilid bees of the western United States.
North America has an estimated 630 different megachilid species, including Megachile, Osmia, Anthidium, Hoplitis, and Chalicodoma. Most Megachilidae are native, and a few are introduced, accidentally and intentionally; globally the number of species identified exceeds 4,000. Thus Megachilidae represent 15% to 20% of named species of bees.
The scientific name Megachilidae refers to the genus Megachile, translating roughly as large lipped (Ancient Greek μέγᾰς (mégas, "big") + χεῖλος (kheîlos, "lip"); their "large lips" and strong jaws are well-suited for collection of nest building materials.
Most Megachilidae build their nests in above-ground cavities; they all are solitary bees. Their nesting habits means that in some studies of bee diversity, this bee family is most likely to be the one encountered, even though the many ground nesting bees are much greater in specie numbers (~70% are ground nesters). For example, in Krombein's trap-nesting survey (1967), almost all bees that nested in his offerings were Megachilid species—40 of 43 occupying bee species. (They were outnumbered in diversity by almost twice as many species of wasps (75) that utilized the nests).
Because they are (mostly) above-ground nesters and more commonly attracted to artificial nests, megachilid bees are also more commonly cultivated than ground nesting solitary bees. They accept nesting materials made from hollow stems, tubes, and blocks with preformed holes ("nest blocks"), and several megachilids have become important species for agricultural / horticultural pollination. In North America these cultivated bees include the introduced Megachile rotundata, (alfalfa leafcutter bees), used extensively in alfalfa pollination, and the western native and frequently raised Osmia lignaria (the orchard mason bee or blue orchard bee), used in orchard pollination. Other Osmia and Megachile species are also in commercial use in North America, Europe and Asia.
A suite of megachilid rely on plant resins for nest construction. These "resin bees" are typically smaller than honey bees, and effective pollinators, although the hard glue-like resins can complicate management of other tunnel nesting bees. Carder bees, Anthidium, are unique for using plant fibers; there are 80 to 90 species of them in North America. Ironically, a non-native is best known—A. manicatum, the European wool carder bee, was accidentally introduced to the Americas in the late '60s and has now spread across the continent. It has been described as "... perhaps the most widely distributed unmanaged bee species in the world." Like most Anthidium, rather than cutting leaves or petals, A. manicatum scrapes the hairs from leaves to use for nesting material. It is atypical because the male is larger than the female and constantly on patrol, protecting a "harem" by chasing and even attacking all interlopers including honey and bumble bees, its tail equipped with multiple prongs that can knife in between the segments of most any intruder.
Neither the introduced Anthidium nor its American cousins are considered parasites, only territorial and at times aggressive. But some Megachilidae are, including Coelioxys, a kleptoparasite mostly of leafcutter bees, and Stelis, a kleptoparasite of leafcutter and mason bees.
While some Megachilidae are extensively studied for their commercial possibilities (or impacts), others are studied by happenstance. Chalicodoma mason bees, not commonly cultivated, are known through extended observation and writings in the last half of the 19th century by Jean-Henri Fabre, with his writings made further famous by his English translator Alexander Teixeira de Mattos (The Mason Bee). Chalicodoma typically uses grit rather than mud in nest construction, along with other differences. (Fabre wrote many observations, including of other Megachilidae, from his home in France; his writings inspired many future researchers and enthusiasts, from Charles Darwin to Gerald Durrell.)
The fossil record for megachilid bees is poor, but a Middle Eocene dicotyledonous leaf shows definite semicircular cutouts along its margin, implying that leaf-cutting bees existed at that time. Multiply-cut leaves and rare body fossils from the Eocene of Germany and the Paleocene of France suggest that Megachilinae began cutting leaves early in their evolution. Phylogenetic analysis yields an age consistent with this Eocene origin for the group. | <urn:uuid:b74ac30f-75dd-43de-92b6-15e08b463051> | 3.484375 | 1,667 | Knowledge Article | Science & Tech. | 25.44695 | 95,478,202 |
Did supervolcanoes on Mars dramatically change its climate? Craters reveal how massive eruptions 3 billion years ago scarred red planet's surface
- Supervolcanoes are 1000s of times stronger than ordinary volcanoes
- Evidence of them has been found in craters on Mars' northern highlands
- Finding could change estimates of how habitable surface may have been
Mars may once have been rocked by titanic supervolcano eruptions that could have shaped the planet's climate, scientists believe.
Crater-like features which could be the footprints of the cataclysmic events have been discovered at several sites in the Martian northern highlands.
Scientists believe they were left behind by massive volcanic explosions that blasted ash and lava out of the planet's surface more than three billion years ago.
Mars may once have been rocked by titanic supervolcano eruptions that may have shaped the planet's climate. This image shows an area of Mars known as Eden Patera looking which is a 70-kilometre wide caldera formed by formed by the collapse of land. Scientists believe the collapse may have followed a supervolcanic eruption
Supervolcano eruptions are thousands of times stronger than those of ordinary volcanoes, and powerful enough to alter global climate and cause mass extinctions.
They have occurred in Earth's past, and a plugged supervolcano is said to be simmering beneath Yellowstone National Park
Rather than producing typical conical mountains of lava and ash, supervolcanoes erupt suddenly in huge explosions.
Because they do not build mountains, evidence of ancient supervolcanoes can be hard to detect.
But scientists think they may have formed a series of irregularly shaped craters in an area of Mars known as Arabia Terra.
If future work shows that supervolcanoes were present more widely on ancient Mars, it would completely change estimates of how the atmosphere formed from volcanic gases, how sediments formed from volcanic ash and how habitable the surface might have been
WHAT IS A SUPERVOLCANO?
A volcano becomes a 'supervolcano' if it erupts more than 1,000 cubic kilometres of magma.
Their eruptions are thousands of times stronger than those of ordinary volcanoes, and powerful enough to alter global climate and cause mass extinctions.
Supervolcanos occur when magma in the mantle rises into the crust from but is unable to break through.
Pressure builds in a large and growing magma pool until the crust is unable to contain it.
Yellowstone is one example of a supervolcano on Earth. The last eruption was 630,000 years ago, and was 1,000 times bigger than the Mount St Helens eruption in 1980.
The ancient, crater-pockmarked region is covered by layers of fine-grained material of unknown origin that could have been left by explosive eruptions.
One of the best examples of what might be a supervolcano remnant is Eden Patera, a depression in the Martian surface 85km wide and 1.8km deep.
It is linked to at least three other depressions in what scientists describe as a ‘caldera complex’.
Other supervolcano candidates include the 700 metre-deep Euphrates Patera, and Siloe Patera, a nest of deep craters extending up to 1,750 metres below the surrounding plains.
The volcanoes may have produced powdery deposits identified by Nasa rovers at two landing sites, Meridiani Planum and Gale Crater.
Many Martian volcanoes are easily recognised from their massive shield-shaped structure, similar to what we see in Hawaii. 'But these are relatively youthful features on Mars and we have always wondered where the ancient volcanoes are,' said Dr Joseph Michalski, from the Natural History Museum
Gases released by the eruptions would have altered the Martian climate, according to the scientists writing in the journal Nature.
‘Discovering supervolcanic structures fundamentally changes how we view ancient volcanism on Mars,’ said lead researcher Dr Joseph Michalski, from the Natural History Museum.
‘Many Martian volcanoes are easily recognised from their massive shield-shaped structure, similar to what we see in Hawaii.
‘But these are relatively youthful features on Mars and we have always wondered where the ancient volcanoes are.
‘It is possible that the most ancient volcanoes were much more explosive and formed structures similar to what we now see in Arabia Terra.’
He added: ‘It makes sense that supervolcanoes might have been more common on ancient Mars, particularly if the ancient crust was thinner than it is now.
‘This would allow magma to rise to the surface more quickly, before it could release gases within the crust.
‘If future work shows that supervolcanoes were present more widely on ancient Mars, it would completely change estimates of how the atmosphere formed from volcanic gases, how sediments formed from volcanic ash and how habitable the surface might have been.’
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The Ideal Gas Law relates an amount of gas to its pressure, temperature and the volume that it occupies. Changes that occur in the state of the gas are described by a variation of this law. This variation, the Combined Gas Law, lets you explore the state of the gas under different conditions. The Combined Gas Law reduces to the Gay Lussac Law when the gas volume is fixed. You can use the Gay Lussac Law to relate pressure changes to temperature changes.
Represent the initial state of the gas with an initial temperature T1 and an initial pressure P1. P1 is the pressure of the gas before the pressure drop occurs. T1 is the temperature of the gas before the temperature drops.
Calculate the proportionality constant (k) formed by the ratio of the initial temperature to the initial pressure. Use the formula: k = T1/P1. For example, if a gas at an initial temperature of 300 K and an initial pressure of 100 Pa, drops by 50 Pa, the proportionality constant k = 3 K/Pa = 300/100 = T1/P1.
Multiply the drop in pressure by the proportionality constant k to obtain the drop in temperature. For example, if a gas at an initial temperature of 300 K and an initial pressure of 100 Pa, drops by 50 Pa, the change in temperature = 150 K = (3 K/Pa) x (50 Pa) = (k) x (change in pressure). | <urn:uuid:6e365fbb-bf0c-4aa2-9709-484775a013b0> | 3.875 | 302 | Tutorial | Science & Tech. | 56.848677 | 95,478,231 |
We think of symbols as the standard types, arrays, classes, fields, functions, variables, parameters, and all of the related built-in standard functions and library functions as described in the documentation Programmers Reference.
In order to make it easy to insert these symbols in the source code, the IDE can generate a list of symbols which is presented when invoking the menu item Select Symbol from the Edit Menu or simply by pressing Ctrl+Space in the editor. The current editor position of the cursor represents the insertion point of where to insert a chosen symbol.
Symbols can be inserted by double-clicking a symbol, or selecting a symbol and pressing Enter or clicking the Select button. Insertion can also include the arguments of a function. Once a symbol is passed back to the insertion point of the editor, the form of symbols looses focus and is usually closed, however it can remain open, which may be convenient in certain situations - e.g. when multiple symbols are to be selected.
Which Symbols to Present.
The list of symbols is generated by the compiler in a context sensitive manner doing a quick syntax check to search for the relevant symbols dependent on the current position of the cursor. This is described in more detail for the compiler.
If any syntax errors interfere with the search for relevant symbols, then the list of symbols may be incomplete, in which case the form presents a small error log indicator in the upper right corner of the form (see example 2 below) to indicate errors have been reported to the Error Log.
When the form is opened it can either present all the relevant symbols, or it can use a filter to present only a subset.
Example 2. Notice the red error log indicator.
If the cursor doesn't touch any text, then the form is opened without a filter, presenting all the relevant symbols in a tree structure grouped by their origin and/or functionality making it easy to look for symbols in a context based manner.
If the cursor is positioned in a text with some of the text located to the left of the cursor, then this left part of the text is used as a filter, and only symbols containing this filter in some form are presented. The filter is not case sensitive.
If the cursor is positioned after a dot - e.g. like myTxt.| then the type of the expression left of the dot is used to identify which functions are relevant to present. For class objects - e.g. like myObj.| this could also include class-fields, class-functions and built-in standard functions. If some text exist between the dot and the cursor - e.g. like myTxt.trim| then this text trim is used as an additional filter to narrow down the presented symbols even more.
If the form is using a filter, it is presented and can be edited. If the filter is removed, the symbols are presented in the default tree structure. | <urn:uuid:518e4428-98ae-4763-9759-5a528fa77d4e> | 2.890625 | 601 | Documentation | Software Dev. | 55.692822 | 95,478,238 |
Clojure From the Ground Up
by Kyle Kingsbury
Publisher: Aphyr.com 2014
This guide aims to introduce newcomers and experienced programmers alike to the beauty of functional programming, starting with the simplest building blocks of software. You'll need a computer, basic proficiency in the command line, a text editor, and an internet connection. By the end of this series, you'll have a thorough command of the Clojure programming language.
Home page url
Download or read it online for free here:
by Rich Hickey
Very few people have seen a literate program so this is intended as a working example, published in book form. You can read this book like any other novel. At the end of it you will be familiar with the ideas and how they are expressed in the code.
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Clojure is a functional, dynamically typed language with a syntax influenced by LISP. Clojure programs run on the Java Virtual Machine. This guide branches out on topic to lead you to the appropriate topics based on what you're trying to accomplish.
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Clojure is a dialect of the Lisp programming language. It is a functional general-purpose language. We have collected a number of recipes which show how to accomplish specific tasks using the Clojure programming language.
by Daniel Higginbotham - braveclojure.com
The book gives you the tools and language details needed to start playing with real programs immediately. It assumes 0 experience with the JVM, functional programming, or lisp. It eschews 'real-world' examples in favor of more interesting exercises. | <urn:uuid:6f0fc6cf-93fa-437d-8b7d-6c901d321c6f> | 2.765625 | 337 | Product Page | Software Dev. | 45.677605 | 95,478,239 |
Infrared data from NASA's Terra satellite found the area of strongest storms in weakening Tropical Cyclone Sanba when it was over the island of Palawan.
Infrared light provides valuable temperature data to forecasters and cloud top temperatures give clues about highest, coldest, strongest storms within a hurricane.
On Feb.14 at 10:45 a.m. EDT (1435 UTC) the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA's Terra satellite analyzed Tropical Cyclone Sanba's cloud top temperatures in infrared light.
MODIS found a small area where cloud top temperatures of strongest thunderstorms, located in the Sargasso Sea, just southeast of Palawan. Those temperatures were as cold as or colder than minus 80 degrees Fahrenheit (minus 62.2 Celsius).
Cloud top temperatures that cold indicate strong storms that have the capability to create heavy rain.
The Joint Typhoon Warning Center noted at 10 a.m. EDT (1500 UTC) Sanba's maximum sustained winds had dropped to 28.7 mph (25 knots/46.3 kph). Sanba was moving into the South China Sea in a westerly direction at 5.7 mph (5 knots/9.6 kph).
Sanba was located about 480 nautical miles south-southwest of Manila, Philippines near 6.8 degrees north latitude and 119.2 degrees east longitude, about 480 nautical miles south-southwest of Manila, Philippines.
Sanba is crossing the southwestern part of the Sulu Sea, and will pass south of Palawan into the South China Sea. The system will not re-strengthen.
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A new report by Australian and Swedish marine scientists in the journal Frontiers in Ecology and the Environment suggests that it may be possible to restore living coral cover to a badly-degraded reef system – though not easy.
With 70 per cent or more of the world’s coral reefs now assessed as degraded, adopting a business-as-usual approach to how we use and manage reefs is no longer an option, says lead author of the report Nick Graham.
“We are unlikely to be able to keep many of the world’s reefs in a pristine state, but with good management we may be able to maintain them in a coral-dominated condition and in some cases we may be able to bring back reefs from a degraded state,” he explains.
The researchers have taken heart from examples on land in desertified landscapes; exceptional falls of rain, in combination with controls on grazing pressure, can result in widespread regrowth of natural vegetation.
They argue that coral reef managers may be able to take advantage of shocks like tropical storms, periods of cloudy weather or even strong seasonal effects on abundance to restore coral cover on degraded reefs.
“Normally we think of these shocks as damaging to coral reefs – but research suggests they are just as damaging to the organisms that can replace coral. In other words, they may act as a circuit-breaker that allows corals to regain control of a reef.”
The key to the new thinking is resilience: healthy corals reefs are naturally resilient to shocks – but damaged ones may become overgrown with sea weeds, and the corals vanish.
“Weed-dominated systems are pretty resilient too and, once established, it is very hard to restore the corals,” Dr Graham explains.Macroalgae dominated
“However a weed-dominated reef can be damaged by big storms too. Cloudy weather and seasonal changes in water temperature can also cause the weeds to die back.
“This dieback of weeds opens a window through which corals can re-establish.”
The key to bringing back corals is exactly the same as preventing coral cover being lost in the first place, Dr Graham says – reducing human impacts through regulation of fisheries and water quality. If reefs are prepared in this way, they may bounce back when a window for recovery opens.
Prof David Bellwood emphasized that “When it comes to saving our coral reefs, prevention is always better than cure and early action is important to slow or reverse degradation.”
The researchers emphasize that both protection and recovery of the world’s coral reefs call for a fundamental change in how people interact with and use reef ecosystems.
“Until now, the focus has mainly been on conserving small parts of a reef in marine protected areas,” said Prof Bellwood, “- we’re talking about broader approaches to change the relationship between humans and coral reefs to reduce human impacts across the whole ecosystem.”
The paper concludes, “Although the composition of coral reefs will likely continue to vary over time, it may be possible to maintain coral-dominated reefs and their associated ecosystem goods and services… Scientists and managers could take advantage of opportunities for change by harnessing shocks and natural variability as potential stimuli for beneficial shifts in ecosystem states.”
The paper “Managing resilience to reverse phase shifts in coral reefs” by Nicholas AJ Graham, David R Bellwood, Joshua E Cinner, Terry P Hughes, Albert V Norström and Magnus Nyström appears in the journal Frontiers in Ecology and the Environment.More information:
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Did climate change shrink the giant hippo?
1.8 million years ago, giant hippos were a common sight across Europe - even making it to the Norfolk Broads.
They were a prominent part of European wildlife, when mega-fauna such as woolly mammoths and giant cave bears bestrode the continent.
Now palaeontologists writing in Boreas, believe that the changing climate during the Pleistocene Era may have forced Europe's hippos to shrink to pygmy sizes before driving them to warmer climes.
An artist's impression of how the broads and fens of Norfolk would have looked in the Pleistocene age, with seven tonne hippos wallowing
NORFOLK'S GIANT HIPPOS
The ancient hippopotamus (Hippopotamus sp.) weighed about six to seven tonnes, much heavier than today's modern hippos weighing up to four tonnes.
The ancient hippos had prominent eyes that acted as periscopes when under water.
In 2004, the Natural History Museum found fossils of the animal in the Norfolk Broads.
The fossils were discovered on an inland site near Lowestoft by teams from the Natural History Museum and Queen Mary College, University of London.
'Species of hippo ranged across pre-historic Europe, including the giant Hippopotamus antiquus, a huge animal which often weighed up to a tonne more than today's African hippos,' said lead author Dr Paul Mazza from the University of Florence.
'While these giants ranged across Spain, Italy and Germany, ancestors of the modern Hippo, Hippopotamus amphibious, reached as far north as the British Isles.'
Hippos were a constant feature of European wildlife for 1.4 million years, during the climatically turbulent time of the Pleistocene era, which witnessed 17 glacial events.
The experience of such environmental changes would not have been without cost, and Dr Mazza and co-author Dr Adele Bertini, also from Florence, investigated the impact this changing climate may have incurred.
The research focused on fossils from across Europe, ranging from the German town of Untermaßfeld in Thuringia, to Castel di Guido, North of Rome, and Collecurti and Colle Lepre in Italy's Central Eastern Marche province.
The fossils were compared to a database of measurements taken from modern African and fossil European hippos.
'The German fossil from Untermaßfeld is the largest hippo ever found in Europe, estimated to weigh up to 3.5 tonnes,' said Mazza.
'The Collecurti specimen was also large, but interestingly even though it was close in both time and distance to the Colle Lepre specimen the latter specimen was 25% smaller.
'A final specimen, an old female from Ortona in central Italy, was smaller again.
'It was 17% smaller than the Collecurti fossil and approximately 50% lighter.'
The authors found that a clear size threshold separated hippo specimens which heralded from different parts of the Pleistocene age.
A baby hippopotamus stands next to its mother at Berlin zoo. Researchers believe climate change shrank the giant hippo to the size of today's animals.
The hippos from the early Pleistocene were the largest ever known while smaller specimens emerged during the middle Pleistocene.
Larger specimens briefly reappeared during the late Pleistocene.
'We believe the size difference was connected to the changing environmental conditions throughout the Pleistocene,' said Mazza.
'The Ortona hippo, the smallest of the specimens, lived in a climate where glacial cycles turned colder, while cold steppes replaced warm ones across the Mediterranean.'
The drop in temperature and rainfall during the Pleistocene caused significant changes to plant life across Europe resulting in an expansion of grassy steppes.
Being grazers hippos may have been expected to thrive in this new environment.
Unexpectedly they appeared to shrink, only re-attaining their past size during the warm periods of the late Pleistocene, when forests and woodland re-colonised the steppes.
During their time in Europe hippos were forced to live in habitats influenced by a general environmental trend towards cooler and drier conditions.
In response hippos achieved giant sizes during warmer and relatively more humid stages, but became smaller, and even very small, under non-ideal environmental conditions.
'While hippos are normally considered indicators of warm, temperate habitats this research shows that temperature was not only the controlling factor for their ancient ancestors," concluded Mazza.
'Our research suggests other factors, such as food availability, were equally important.
'Appreciating the importance of factors beyond temperature is of great significance as we consider how species may adapt to future ecological and environmental changes.'
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Morgan, Joanna; Lana, Cristiano; Kearsley, Anton; Coles, Barry; Belcher, Claire; Montanari, Sandro; Díaz-Martínez, Enrique; Barbosa, Antonio; Neumann, Virginio (2006): Analyses of shocked quartz from the K-P boundary. PANGAEA, https://doi.org/10.1594/PANGAEA.723777, Supplement to: Morgan, J et al. (2006): Analyses of shocked quartz at the global K-P boundary indicate an origin from a single, high-angle, oblique impact at Chicxulub. Earth and Planetary Science Letters, 251(3-4), 264-279, https://doi.org/10.1016/j.epsl.2006.09.009
Always quote above citation when using data! You can download the citation in several formats below.
The precise cause and timing of the Cretaceous-Paleocene (K-P) mass extinction 65 Ma ago remains a matter of debate. Many advocate that the extinction was caused by a meteorite impact at Chicxulub, Mexico, and a number of potential kill-mechanisms have been proposed for this. Although we now have good constraints on the size of this impact and chemistry of the target rocks, estimates of its environmental consequences are hindered by a lack of knowledge about the obliquity of this impact. An oblique impact is likely to have been far more catastrophic than a sub-vertical one, because greater volumes of volatiles would have been released into the atmosphere. The principal purpose of this study was to characterize shocked quartz within distal K-P ejecta, to investigate whether the quartz distribution carried a signature of the direction and angle of impact. Our analyses show that the total number, maximum and average size of shocked quartz grains all decrease gradually with paleodistance from Chicxulub. We do not find particularly high abundances in Pacific sites relative to Atlantic and European sites, as has been previously reported, and the size-distribution around Chicxulub is relatively symmetric. Ejecta samples at any one site display features that are indicative of a wide range of shock pressures, but the mean degree of shock increases with paleodistance. These shock- and size-distributions are both consistent with the K-P layer having been formed by a single impact at Chicxulub. One site in the South Atlantic contains quartz indicating an anomalously high average shock degree, that may be indicative of an oblique impact with an uprange direction to the southeast +/- 45°. The apparent continuous coverage of proximal ejecta in this quadrant of the crater, however, suggests a relatively high impact angle of >45°. We conclude that some of the more extreme predictions of the environmental consequences of a low-angle impact at Chicxulub are probably not applicable.
Median Latitude: 14.625017 * Median Longitude: 8.841790 * South-bound Latitude: -40.980000 * West-bound Longitude: -157.831700 * North-bound Latitude: 55.190000 * East-bound Longitude: 165.611795
Date/Time Start: 1990-01-31T00:45:00 * Date/Time End: 2003-03-29T00:00:00
130-803D * Latitude: 2.433000 * Longitude: 160.541000 * Date/Time Start: 1990-01-31T00:45:00 * Date/Time End: 1990-02-07T03:30:00 * Elevation: -3412.2 m * Penetration: 656 m * Recovery: 494.96 m * Location: North Pacific Ocean * Campaign: Leg130 * Basis: Joides Resolution * Device: Drilling/drill rig (DRILL) * Comment: 71 core; 656 m cored; 0 m drilled; 75.5 % recovery
198-1209 * Latitude: 32.651700 * Longitude: 158.505983 * Date/Time Start: 2001-09-18T00:00:00 * Date/Time End: 2001-09-23T00:00:00 * Elevation: -2387.3 m * Penetration: 865.1 m * Recovery: 766 m * Location: North Pacific Ocean * Campaign: Leg198 * Basis: Joides Resolution * Device: Composite Core (COMPCORE) * Comment: 83 cores; 759.4 m cored; 105.7 m drilled; 100.9% recovery
207-1258A * Latitude: 9.433330 * Longitude: -54.733310 * Date/Time Start: 2003-01-22T18:15:00 * Date/Time End: 2003-01-25T10:10:00 * Elevation: -3192.2 m * Penetration: 447.5 m * Recovery: 375.46 m * Location: North Atlantic Ocean * Campaign: Leg207 * Basis: Joides Resolution * Device: Drilling/drill rig (DRILL) * Comment: 50 cores; 447.5 m cored; 0 m drilled; 83.9 % recovery | <urn:uuid:03192aa6-9985-48d1-a0e9-eb163f9e5a82> | 2.78125 | 1,113 | Academic Writing | Science & Tech. | 61.303338 | 95,478,276 |
Name: Instructors’ name: Course: Date: Terrifying New Math of Climate Change In the article "Terrifying New Math of Climate Change" Bill Mcibben points out scary temperature data experienced in the spring of 2012 in the Northern Hemisphere. He quotes meteorologists who reported the mean temperature over May to have been the highest ever in U.S…
Bill then highlights three simple data about global warming that should act as a wakeup call for the fight. According to Bill, the Copenhagen summit of 2009 ended with no commitment at all to address global warming. However, the summit did point out that global warming should not go beyond 2 oC. Nevertheless, two degrees Celsius increase in temperature is far too lenient, when we consider that the effect being experienced now are the result of only under 0.8 0C. For instance, a third of the summer ice over the arctic has melted; this translates to five percent wetter atmosphere over the oceans- a devastating flood is looming. Gleaning from Scientists and countries against the two degrees accord, Bill maintains that the two-degree figure is very misguided and unattainable. The second number is “565 gigatons.” This is the estimated amount of carbon dioxide that a human being can release into the atmosphere by midcentury and still remain within the 2 OC of global warming. While this figure may not be very exact, Bill is quick to note that recent simulations of global warming confirm the validity of the figure. If this is the case, it then implies that we are more than half way to the limit. This can be explained by the fact that the while we are currently at 0.8 0C mark of warming the carbon dioxide already in the atmosphere will continue to heat up the atmosphere even further. In addition, computer simulations points out that we are about three quarters to hit the 2 0C limit of warming. Bill warns that even after the 2009 summit the trends for carbon dioxide release into the atmosphere only saw a one year lull and has ever since been on the rise. There have been increases in countries such as 3.2% in America, 9.3% in China, 2.4% in Japan. Bill warns that, at the current mean degree carbon emission rise of 3%, the 2 oC warming is only 16 years away. Despite all these scientists are shying off from providing evidence in details, we may be headed for a six degrees warming (Faith, IEA's chief economist). Bill then give reasons why campaigns against global warming have failed and continue failing both at individual level and through environment groups lobbying with the political systems. For instance, many Americans have not reduced their use of paper; prefer taking flights and driving energy consuming cars rather than hybrid cars. Bill commends president Obama for the energy efficiency mandate he achieved shortly after he got into power, but then goes on to criticize his current ambitions regarding oil and coal exploration. President Obama administration, for instance, has already indicated willingness to grant Shell permission to start drilling in the Arctic and support oil exploration in Oklahoma. What worries most as Bill points out is this is a trend all over the world for instance Canada and Venezuela have turned to want to go against the Kyoto protocol as they seek to dig out more coal from their soil. Bill warns that a very daring movement (acknowledging that the movement will have enemies) is needed to transform the trends of global warming to save our world. He points out to effects that we are experiencing already such as Colorado fires and failure of korn kernels in Kentucky at the expense of summer heat waves. Bill argues that we are losing the battle since the ...
Cite this document
(“The End of the Wild/Terrifying New Math of Climate Change/Are we Essay”, n.d.)
Retrieved from https://studentshare.net/english/114008-the-end-of-the-wild-terrifying-new-math-of-climate
(The End of the Wild/Terrifying New Math of Climate Change/Are We Essay)
“The End of the Wild/Terrifying New Math of Climate Change/Are We Essay”, n.d. https://studentshare.net/english/114008-the-end-of-the-wild-terrifying-new-math-of-climate.
Such circumstances have been hypothetically considered, keeping the growth potential and attractiveness of the South-African retail market in mind. It has also been considered that Topshop is most likely to use South Africa as the central base of expansion strategy on the African continent.
Between 1967 and 1988 the price of ticket changed by almost 1150%, whereas the cost of commercials also changed by the same percentage. But if we look at the index the inflation in this period was increased by only 250%, as the index during this period was around 354.
It has also been considered that Topshop is most likely to use South Africa as the central base of expansion strategy in the African continent. In the context of the present study it needs to be mentioned that while
There is a constant disappearance of the forests from activities such as deforestation; one can easily see industrial smokes rising up the sky; the exhaust fumes released from vehicles. All these are day to day causes of global warming. The opportune
In the changes, defects are expected to reduce to less than 5 defects in every 1,000 products. This will lead to the achievement of efficiencies and effectiveness required by the customers. Another metric is short time
Among the stakeholders, the most important objective to the business is to offer quality products and services to its clients.
BJB manufacturing can make vehicle cd changers much better by identifying the flaws and correcting | <urn:uuid:13cc0ff7-c196-478d-bcaf-e3f900050810> | 2.859375 | 1,178 | Truncated | Science & Tech. | 48.8145 | 95,478,279 |
A View from Emerging Technology from the arXiv
The Puzzle of the Half-Comet, Half-Asteroid
A mysterious object that ejects dust like a comet but orbits like an asteroid could be a new class of object in the solar system.
astronomers identified an extraordinary object orbiting the Sun between Mars
and Jupiter in a region best known for its asteroids. And yet this body, called
133P, defied description: it had the orbit of an asteroid yet emitted dust like
Clearly, this was a rare object. After centuries of observation, not a single other object in the asteroid belt had burped gas and dust in the same way.
So how could this have got there? According to Henry Hsieh at Queen’s University, Belfast in Northern Ireland, there can be only two explanations. The first is that 133P is a comet that has somehow recently become trapped in an asteroid-like orbit. This would have required a hugely unlikely combination of gravitational kicks from other planets as the comet travelled into the solar system from the Kuiper Belt or Oort cloud.
Hsieh says this is so fantastically unlikely that it is almost certainly a one-off event. So there’s almost no chance that we’d see another comet-like object in this kind of orbit.
The second explanation is that 133P is an asteroid formed partly of ice and that this is being released, perhaps by a collision with another asteroid. If this were the case, there would almost certainly be other asteroids with a similar makeup releasing dust. These we ought to be able to see.
So Hsieh set out to find one, making some 657 observations of 599 asteroids in the asteroid belt. The big news is that he has found one other object, called 176P/LINEAR, which is also emitting dust.
So it looks as if the mystery is solved. That more or less rules out the possibility that 133P is a captured comet. Instead, 133P and 176P are a new class of comet-like asteroids made up partly of ice, which is ejected whenever these objects are struck in the occasional unavoidable collision.
That’s an interesting new addition to the asteroid menagerie. The only question now is what to call these beasts that are half comet and half asteroid. Comsteroids? Asteromets? Hsiehroids?
Ref: arxiv.org/abs/0907.5505: The Hawaii Trails Project: Comet-Hunting in the Main Asteroid Belt
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:5581faee-4144-48ec-8079-7a186425d400> | 3.6875 | 554 | Truncated | Science & Tech. | 54.688462 | 95,478,286 |
Researcher in remote Chagos Islands says he saw crabs, previously thought to be scavengers, hunting and killing seabird
A large, land-dwelling crustacean known as a coconut or robber crab has been seen hunting and killing a seabird, the first time such behaviour has been observed in the species.
According to Laidre, the crab climbed a tree and attacked the seabird in its nest situated on a branch close to the ground. The crab broke the birds wing, causing it to fall out of its nest and then took to the bird with its claws, breaking its other wing and leaving it incapacitated.
Once the bird was unable to move, other coconut crabs arrived and pulled the bird apart in scenes Laidre described as pretty gruesome.
Coconut crabs are the largest land-dwelling invertebrate. They can weigh up to 4kg and grow up to one metre wide. They are common in coral atolls across the Indian and Pacific Oceans and can be the largest animal in their environment.
The crabs behaviour of actively hunting and killing a large, vertebrate animal has never been witnessed before and has significant implications for how the crabs may affect their island ecosystems.
Previously thought to be scavengers, Laidres discovery suggests the crabs may dominate their ecosystems and could discourage other animals, particularly seabirds, from inhabiting islands where they would be forced to nest on the ground.
Further research by Laidre goes some way to confirming this hypothesis. He conducted surveys that found that birds were less likely to live on islands where coconut crabs lived, and vice versa.
Whether this behaviour is a one-off or widespread remains to be seen. Laidre plans to set up remotely activated cameras at entrances to the crabs burrows to find out. | <urn:uuid:e5322799-6968-4c97-a353-5d97939bc253> | 3.203125 | 370 | News Article | Science & Tech. | 42.880385 | 95,478,288 |
The Museum’s highly-valued marine mammal collections and databases are the focus of much of the research undertaken by the Mammals group. Researchers also undertake post-mortems and detailed sample collection on carcasses collected by Museum staff, the Department of Environment, Water and Natural Resources (DEWNR), and volunteers. The information collected contributes to long-term studies of many aspects of marine mammal biology.
South Australia’s extensive database of whale and dolphin sightings is also managed by Dr Catherine Kemper, Senior Research Scientist, Mammals.
To find out more about this research you can listen to Dr Kemper's talk about the challenge of conserving whales and dolphins in the 21st century.
Examples of current research on marine mammals include:
- taxonomy and distribution of southern Australian dolphins in the genera Tursiops and Delphinus;
- biology of the Pygmy Right Whale, Caperea marginata;
- diet and life history of dolphins, whales and seals, including age estimation using teeth;
- causes of death, including investigations of human interactions leading to death;
- toxic contaminant concentrations and their relationship to pathology;
- diseases and parasites;
- morphology and anatomy;
- population genetics of Indo-Pacific bottlenose dolphins (Tursiops aduncus);
- conservation status and abundance of dolphins in South Australian waters; and
- long-term research on the abundance and distribution of the New Zealand Fur Seal (Arctocephalus forsteri) and Australian Sea Lion (Neophoca cinerea) in southern Australia to determine the potential threat to species and populations posed by human activities.
Dolphin Trauma Group
The Dolphin Trauma Group is a multidisciplinary team of specialists who investigate dolphin mortalities, disease and biology in South Australia. Overseen by Dr Catherine Kemper, Senior Research Scientist, Mammals, the specific aims of the group are to:
- determine as quickly as possible the cause and manner of dolphin deaths;
- ensure that injuries are adequately documented and evidence collected to facilitate prosecutions if potential perpetrators are found;
- assist in the collection of information on dolphin morbidity and mortality; and
- carry out scientific research that assists in conserving local dolphin populations.
Other members of the Group include Ikuko Tomo (Honorary Research Associate), Michael Bossley (Whale and Dolphin Conservation Society) and DEWNR staff of the Adelaide Dolphin Sanctuary. In association with Biosecurity SA (Department of Primary Industries and Resources of South Australia), the Dolphin Trauma Group researched the 2013 Dolphin Morbillivirus mortality event in Gulf St Vincent.
Marine Mammal Ageing Facility
The Museum’s Marine Mammal Ageing Facility was established in 2007 to facilitate the study of age estimation of whales, dolphins and seals. At present, it is focussing on methods involving teeth of marine mammals, particularly dolphins and seals, and is also available for use by non-Museum personnel.
The Mammals group also has an active program of research on Australian terrestrial mammal species and subfossil mammals.
Examples of current research projects include:
- taxonomy, distribution and identification of small marsupials, native rodents and bats;
- conservation of bat species in Australia;
- taxonomy of extinct rodents found in subfossil material (e.g. Pseudomys auritus, Notomys robustus);
- changes in the subfossil fauna and the relationship to time of deposition; and
- seasonal changes in the diet of barn owls from the arid zone as determined by studying pellets. | <urn:uuid:f6c9b614-c60c-40aa-b71c-8e4cc297a3fb> | 2.828125 | 748 | Knowledge Article | Science & Tech. | 3.810151 | 95,478,304 |
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Asteroid 253 Mathilde, a Near-Earth Asteroid photographed by NASA's NEAR (Near Earth Asteroid Rendezvous) mission in June 1997. Mathilde is about 60 km in diameter and orbits in the asteroid belt between Mars and Jupiter.
Gaspra, Asteroid #951.
Asteroid 4 Vesta, the brightest asteroid and the fourth largest. Vesta is the only asteroid that can be seen without a telescope (it is sixth magnitude).
The asteroid 243 Ida and its tiny asteroid moon, Dactyl. This is the first asteroid ever found with an orbiting moon. Ida's dimensions are about 56 x 24 x 21 kilometers (35 x 15 x 13 miles). Dactyl is only about 1.2 x 1.4 x 1.6 km (0.75 x 0.87 x 1 mile) across.
Trojan asteroids are asteroids that orbit in gravitationally stable Lagrange points in a planet's orbit, either trailing it or preceding it (these places are where the gravitational attraction of the Sun and of the planet balance each other). Jupiter has the most Trojan asteroids; Mars also has some. Achilles was the first Trojan asteroid found. The asteroids preceding Jupiter in its orbit were named for Greek heroes; those following Jupiter in its orbit were named for Trojan heroes.
Asteroid coloring page
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Asteroids Cloze: A fill-in-the-blanks activity on asteroids. Answers
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- Poster presentation
- Open Access
RNA-Seq methods for imperfect samples: development, evaluation and applications
© BioMed Central Ltd 2011
Published: 19 September 2011
Next-generation sequencing of RNA (RNA-Seq) is a powerful tool that can be applied to a wide range of biological questions. RNA-Seq provides insight at multiple levels into the transcription of the genome. It yields sequence, splicing and expression-level information, allowing the identification of novel transcripts and sequence alterations. We have been developing and comparing methods for samples that present a challenge: that is, those with low quantity and/or quality RNA.
RNA-Seq methods that start from total RNA and do not require the oligo(dT) purification of mRNA will be valuable for such challenging samples. Such methods use alternative approaches to reduce the fraction of sequencing reads derived from rRNA. We will present results from multiple approaches, including the use of not-so-random (NSR) primers for cDNA synthesis, low-C0t hybridization with a duplex-specific nuclease for light normalization and NuGEN’s Ovation RNA-Seq kit. We demonstrated that these three methods successfully reduce the fraction of rRNA to less than 13%, even when starting from degraded RNA. We compared the performance between these methods and with ‘gold standard’ RNA-Seq data (derived from samples with large quantities of high-quality RNA), using quantitative criteria that evaluate effectiveness for genome annotation, transcript discovery and expression profiling. The application of these methods to samples that contain degraded RNA and/or very low input amounts of RNA will also be presented. | <urn:uuid:c9ed6d4a-5085-4a48-b3ec-fe78647a0ae1> | 2.578125 | 341 | Academic Writing | Science & Tech. | 25.704364 | 95,478,315 |
posted by Roger
A sample of phosphorus of mass 3.654 g reacts with dichlorine to form 16.20 g of a molecular compound. What is the empirical formula of this compound?
Compound of P and Cl = mass 16.20 g
Started with 3.654 g P = -3.654
Amount chlorine added = 16.20-3.654 = 12.546.
moles P = 3.546/molar mass P
moles Cl = 12.546/atomic mass Cl
Then find the molar ratios of the two elements with the smallest being 1.00. The easy way to do that is to divide the smallest number by itself thereby producing 1.00 for that element. Then divide the other number by the same small number. The numbers you get will be the x and y of PxCly.
Post your work if you get stuck.
I don't understand when you say divide by the smallest numbers. For instnace, am I supposed to divide 3.546 (P) by 3.546 again?
No. Did you convert g P to moles. Then convert g chlorine to moles. You want to find the molar ratios of THOSE two numbers (the moles).
3.654 g P x (1 mol/30.97 g P) = .12 mol
12.546 g Cl x (1 mol/35.45 g Cl) = .35 mol
Therefore, the empirical formula will be PCl3? Is this correct?
Yes, but you rounded one of your numbers before you should have rounded.
3.546/30.97 = 0.1180 (don't round to 0.12--to two significant figures when you are allowed 4.
12.546/35.45 = 0.3539.
Your ratios are 0.12/0.12 = 1.00
0.35/0.12 = 2.92 so you rounded to P1Cl3 (PCl3) which is correct. Using my numbers, you would have obtained,
0.1180/0.1180 = 1.000
0.3539/0.1180 = 2.999
The final numbers are closer to whole numbers if you round correctly. In some cases it would make a difference in the formula obtained; in this case it did not. | <urn:uuid:816eb84b-b2b2-4469-93eb-4200bf5cf8cb> | 3.3125 | 495 | Q&A Forum | Science & Tech. | 111.852669 | 95,478,330 |
Jet Propulsion Laboratory Development Ephemeris
The name Jet Propulsion Laboratory Development Ephemeris (followed by a number), the abbreviation JPL DE(number), or just DE(number) designates one of a series of models of the Solar System produced at the Jet Propulsion Laboratory in Pasadena, California, primarily for purposes of spacecraft navigation and astronomy. The models consist of computer representations of positions, velocities and accelerations of major Solar System bodies, tabulated at equally spaced intervals of time, covering a specified span of years. Barycentric rectangular coordinates of the Sun, eight major planets and Pluto, and geocentric coordinates of the Moon are tabulated.
DE405, created in May 1997, include both nutations and librations, and is considered the fundamental planetary and lunar ephemerides of The Astronomical Almanac. It is very large at 62.4 Megabytes, so smaller, more targeted versions have been created based on DE405.
There have been many versions of the JPL DE, from the 1960s through the present, in support of both robotic and manned spacecraft missions. Available documentation is sketchy, but we know DE69 was announced in 1969 to be the third release of the JPL Ephemeris Tapes, and was a special purpose, short-duration ephemeris. The then-current JPL Export Ephemeris was DE19. These early releases were distributed on magnetic tape.
In the days before personal computers, computers were large and expensive, and numerical integrations such as these were run by large organizations with ample resources. The JPL ephemerides prior to DE405 were integrated on a Univac mainframe in double precision. For instance, DE102, which was created in 1977, took six million steps and ran for nine days on a Univac 1100/81. DE405 was integrated on a DEC Alpha in quadruple precision.
In the 1970s and early 1980s, much work was done in the astronomical community to update the astronomical almanacs from the theoretical work of the 1890s to modern, relativistic theory. From 1975 through 1982, six ephemerides were produced at JPL using the modern techniques of least-squares adjustment of numerically-integrated output to high precision data: DE96 in Nov. 1975, DE102 in Sep. 1977, DE111 in May 1980, DE118 in Sep. 1981, and DE200 in 1982. DE102 was the first numerically integrated so-called Long Ephemeris, covering much of history for which useful astronomical observations were available: 1141 BC to AD 3001. DE200, a version of DE118 migrated to the J2000.0 reference frame, was adopted as the fundamental ephemeris for the new almanacs starting in 1984. DE402 introduced coordinates referred to the International Celestial Reference Frame (ICRF).
Each ephemeris was produced by numerical integration of the equations of motion, starting from a set of initial conditions. Due to the precision of modern observational data, the analytical method of general perturbations could no longer be applied to a high enough accuracy to adequately reproduce the observations. The method of special perturbations was applied, using numerical integration to solve the n-body problem, in effect putting the entire Solar System into motion in the computer's memory, accounting for all relevant physical laws. The initial conditions were both constants such as planetary masses, from outside sources, and parameters such as initial positions and velocities, adjusted to produce output which was a "best fit" to a large set of observations. A least-squares technique was used to perform the fitting. . As of DE421, perturbations from 343 asteroids, representing about 90% of the mass of the main asteroid belt, have been included in the dynamical model.
The physics modeled included the mutual Newtonian gravitational accelerations and their relativistic corrections (a modified form of the Einstein-Infeld-Hoffmann equation), the accelerations caused by the tidal distortion of the Earth, the accelerations caused by the figure of the Earth and Moon, and a model of the lunar librations.
The observational data in the fits has been an evolving set, including: ranges (distances) to planets measured by radio signals from spacecraft, direct radar-ranging of planets, two-dimensional position fixes (on the plane of the sky) by VLBI of spacecraft, transit and CCD telescopic observations of planets and small bodies, and laser-ranging of retroreflectors on the Moon, among others. DE102, for instance, was fit to 48,479 observations.
The time argument of the integrated ephemerides is a relativistic coordinate time scale called Teph, necessary in precise work to account for the small relativistic effects of time dilation and simultaneity. In later ephemerides, Teph is essentially equivalent to the IAU definition of TCB.
Positions and velocities of the Sun, Earth, Moon, and planets, along with the orientation of the Moon, are stored as Chebyshev polynomial coefficients fit in 32-day-long segments. The ephemerides are now available via World Wide Web and FTP as data files containing the Chebyshev coefficients, along with source code to recover (calculate) positions and velocities. . Files vary in the time periods they cover, ranging from a few hundred years to several thousand, and bodies they include. Data may be based on each planet's true center or its barycenter.
The use of Chebyshev polynomials enables highly precise calculations for a given point in time. DE405 recovery (calculation) for the inner planets is about 0.001 arcseconds (equivalent to about 1 km at the distance of Mars); for the outer planets it is generally about 0.1 arcseconds. The 'reduced accuracy' DE406 ephemeris gives an interpolating precision (relative to the full ephemeris values) no worse than 25 metres for any planet and no worse than 1 metre for the moon.
Note that these precision numbers are for the interpolated values relative original tabulated coordinates. The overall precision and accuracy of interpolated values for describing the actual motions of the planets will be a function of both the precision of the ephemeris tabulated coordinates and the precision of the interpolation.
- JPL uses the ephemerides for navigation of spacecraft throughout the Solar System. Typically, a new ephemeris is computed including the latest available observations of the target planet(s), either for planning of the mission(s), or for final contact of the spacecraft with the target. See below, Recent ephemerides in the series.
- The Astronomical Almanac for 1984 through 2002 were based on JPL ephemeris DE200, and from 2003 to 2014 the Astronomical Almanac was based on JPL ephemeris DE405. The current Almanac is derived from DE430.
- The JPL ephemerides are widely used for planetary science; some examples are included in the Notes and References.
- Software is available to use the JPL ephemerides for the production of apparent ephemerides for any location and time; these are widely used by professional and amateur astronomers for reducing planetary observations and producing very precise observing guides.
- DE430 and DE431 can be used with the popular planetarium software Stellarium
Ephemerides in the series
DE430 was created in 2013 and Is intended for use in analyzing modern data. It covers the dates 1550 Jan 01 to 2650 Jan 22 with the most accurate lunar ephemeris. From 2015 onwards this ephemeris is utilized in Astronomical Almanac. Beginning with this release only Mars' Barycenter was included due to the small masses of its moons Phobos and Deimos which create a very small offset from the planet's center. . The complete ephemerides files is 128 megabytes but several alternative versions have been made available by JPL
DE431 was created in 2013 and is intended for analysis of earlier historical observations of the Sun, Moon, and planets. It covers a longer time span than DE430 (13201 BC to AD 17191) agreeing with DE430 within 1 meter over the time period covered by DE430. Position of the Moon is accurate within 20 meters between 1913-2113 and that error grows quadratically outside of that range. It is the largest of the ephemerides files at 3.4 gigabytes.
DE102 was created in 1981, includes nutations but not librations. Referred to the dynamical equator and equinox of 1950. Covers JED 1206160.5 (-1410 APR 16) to JED 2817872.5 (3002 DEC 22).
DE200 was created in 1981; includes nutations but not librations. Referred to the dynamical equator and equinox of 2000. Covers JED 2305424.5 (1599 DEC 09) to JED 2513360.5 (2169 MAR 31). This ephemeris was used for the Astronomical Almanac from 1984 to 2003.
DE202 was created in 1987; includes nutations and librations. Referred to the dynamical equator and equinox of 2000. Covers JED 2414992.5 (1899 DEC 04) to JED 2469808.5 (2050 JAN 02).
DE402 was released in 1995, and was quickly superseded by DE403.
DE403 was created 1993, released in 1995. F JPL ephemeris was expressed in the coordinates of the International Earth Rotation Service (IERS) reference frame, essentially the ICRF. The data crunched by JPL to derive the ephemeris began to move away from limited-accuracy telescopic observations and more toward higher-accuracy radar-ranging of the planets, radio-ranging of spacecraft, and very-long-baseline-interferometric (VLBI) observations of spacecraft, especially for the four inner planets. Telescopic observations remained important for the outer planets because of their distance, hence the inability to bounce radar off of them, and the difficulty of parking a spacecraft near them. The perturbations of 300 asteroids were included, vs DE118/DE200 which included only the five asteroids determined to cause the largest perturbations. Better values of the planets' masses had been found since DE118/DE200, further refining the perturbations. Lunar Laser Ranging accuracy was improved, giving better positions of the Moon. DE403 covered the time span Apr 1599 to Jun 2199.
DE404 was released in 1996. A so-called Long Ephemeris, this condensed version of DE403 covered 3000 BC to AD 3000. While both DE403 and DE404 were integrated over the same timespan, the interpolation of DE404 was somewhat reduced in accuracy and nutation of the Earth and libration of the Moon were not included.
DE405 was released in 1998. It added several years' extra data from telescopic, radar, spacecraft, and VLBI observations (of the Galileo spacecraft at Jupiter, in particular). The method of modeling the asteroids' perturbations was improved, although the same number of asteroids were modeled. The ephemeris was more accurately oriented onto the ICRF. DE405 covered 1600 to 2200 to full precision. This ephemeris was utilized in the Astronomical Almanac from 2003 until 2014.
DE406 was released with DE405 in 1998. A Long Ephemeris, this was the condensed version of DE405, covering 3000 BC to AD 3000 with the same limitations as DE404. This is the same integration as DE405, with the accuracy of the interpolating polynomials has been lessened to reduce file size for the longer time span covered by the file.
DE407 was apparently unreleased. Details in readily-available sources are sketchy.
DE408 was an unreleased ephemeris, created in 2005 as a longer version of DE406, covering 20,000 years.
DE409 was released in 2003 for the MER spacecraft arrival at Mars and the Cassini arrival at Saturn. Further spacecraft ranging and VLBI (to the Mars Global Surveyor, Mars Pathfinder and the Mars Odyssey spacecraft) and telescopic data were included in the fit. The orbits of the Pioneer and Voyager spacecraft were reprocessed to give data points for Saturn. These resulted in improvements over DE405, especially to the predicted positions of Mars and Saturn. DE409 covered the years 1901 to 2019.
DE410 was also released in 2003 covered 1901 - 2019, with improvements from DE409 in the masses for Venus, Mars, Jupiter, Saturn and the Earth-Moon system based on recent research. Though the masses had not yet been adopted by the IAU. The ephemerides were created to support the arrivals of the MER and Cassini spacecraft.
DE411 was widely cited in the astronomical community, but not publicly released by JPL
DE412 was widely cited in the astronomical community, but not publicly released by JPL
DE413 was released in 2004 with updated ephemeris of Pluto in support of the occultation of a star by its satellite Charon on 11 Jul 2005. DE413 was fit to new CCD telescopic observations of Pluto in order to give improved positions of the planet and its moon.
DE414 was created in 2005 and released in 2006. The numerical integration software was updated to use quadruple-precision for the Newtonian part of the equations of motion. Ranging data to the Mars Global Surveyor and Mars Odyssey spacecraft were extended to 2005, and further CCD observations of the five outer planets were included in the fit. Some data was accidentally left out of the fit, namely Magellan Venus data for 1992-94 and Galileo Jupiter data for 1996-97. Some ranging data to the NEAR Shoemaker spacecraft orbiting the asteroid Eros was used to derive the Earth/Moon mass ratio. DE414 covered the years 1599 to 2201.
DE418 was released in 2007 for planning the New Horizons mission to Pluto. New observations of Pluto, which took advantage of the new astrometric accuracy of the Hipparcos star catalog, were included in the fit. Mars spacecraft ranging and VLBI observations were updated through 2007. Asteroid masses were estimated differently. Lunar laser ranging data for the Moon was added for the first time since DE403, significantly improving the lunar orbit and librations. Estimated position data from the Cassini spacecraft was included in the fit, improving the orbit of Saturn, but rigorous analysis of the data was deferred to a later date. DE418 covered the years 1899 to 2051, and JPL recommended not using it outside of that range due to minor inconsistencies which remained in the planets' masses due to time constraints.
DE421 was released in 2008. It included additional ranging and VLBI measurements of Mars spacecraft, new ranging and VLBI of the Venus Express spacecraft, the latest estimates of planetary masses, additional lunar laser ranging, and two more months of CCD measurements of Pluto. When initially released in 2008, the DE421 ephemeris covered the years 1900 to 2050. An additional data release in 2013 extended the coverage to the year 2200.
DE423 was released in 2010. Position estimates of the MESSENGER spacecraft and additional range and VLBI data from the Venus Express spacecraft were fit. DE423 covered the years 1799 to 2200.
Notes and references
- See, for example, Lieske (1967). "JPL Development Ephemeris Number 28". JPL Technical Report 32-1206.; O'Handley; et al. (1969). "JPL Development Ephemeris Number 69" (PDF). JPL Technical Report 32-1465.; Standish; et al. (1976). "JPL Development Ephemeris number 96".; see also Newhall, Standish and Williams (1983).
- York (1971). "Estimated DE19 Lunar Ephemeris Errors for the Apollo 15 Mission" (PDF). NASA MSC Internal Note 71-FM-291.
- Newhall, Standish, and Williams (1983). "DE 102 - A numerically integrated ephemeris of the moon and planets spanning forty-four centuries". Astronomy and Astrophysics, vol.125, no.1, Aug.1983.
- See Standish and Williams in the Sources
- Standish (1989). "The observational basis for JPL's DE 200, the planetary ephemerides of the Astronomical Almanac". Astronomy and Astrophysics, vol. 233, no. 1, July 1990. Bibcode:1990A&A...233..252S.
- See US Naval Observatory (Naval Oceanography Portal), "History of the Astronomical Almanac" (accessed September 2017); see also Standish (1998) for details of DE405.
- Folkner, William (February 15, 2014). "The Planetary and Lunar Ephemerides, DE430 and DE431" (PDF).
- See Thornton and Border (2000). "Radiometric Tracking Techniques for Deep-Space Navigation" (PDF). Archived from the original (PDF) on 2012-02-18. for a good summary of spacecraft radio-navigation.
- See sources cited at [[Ephemeris time#JPL ephemeris time argument Teph|JPL ephemeris time argument Teph]].
- See the JPL FTP site with ephemerides (data files), source code (for access and basic processing of the data to recover positions and velocities), and documentation.
- See JPL Planetary and Lunar Ephemerides Export Information README.txt version of 12 Oct 2007. Also available is an older version README.txt version of December 6, 2005 Archived January 15, 2012, at the Wayback Machine..
- See the NASA SPICE system.
- Acton (2013). "README.txt". Archived from the original on January 16, 2014.
- "JPL PLANETARY AND LUNAR EPHEMERIDES : Export Information". April 30, 2014.
- Faulkner (April 30, 2014). "Planetary and Lunar Ephemerides, Export Information". JPL.
- "JPL Ephemerides Files".
- "Ephemerides". Jet Propulsion Laboratory. Retrieved 1 March 2016.
- "JPL Memorandum IOM 392R-14-003" (PDF). April 30, 2014.
- Standish; et al. (1995). "JPL Planetary and Lunar Ephemerides, DE403/LE403" (PDF). JPL Interoffice Memorandum IOM 314.10-127. Archived from the original (PDF) on August 11, 2011.
- Folkner (2011). "JPL PLANETARY AND LUNAR EPHEMERIDES : Export Information". Archived from the original on 2012-01-15.
- Standish and Newhall (1996). "New accuracy levels for solar system ephemerides (Lecture)".
- Standish (1998). "JPL Planetary and Lunar Ephemerides, DE405/LE405" (PDF). JPL Interoffice Memorandum 312.F-98-048. Archived from the original (PDF) on February 20, 2012.
- See, for instance, "IERS Annual Report 2004" (PDF). which mentions DE407 only very briefly.
- See "de408.cmt". at NASA's Navigation and Ancillary Information Facility website and Peale; et al. (2006). "Long-period forcing of Mercury's libration in longitude". Icarus. Bibcode:2007Icar..187..365P. doi:10.1016/j.icarus.2006.10.028. which states that DE408 covered 20,000 years.
- Standish (2003). "JPL Planetary Ephemeris DE409" (PDF). JPL Interoffice Memorandum IOM 312.N-03-007.
- Standish (2003). "JPL Planetary Ephemeris DE410" (PDF). JPL Interoffice Memorandum IOM 312.N-03-009.
- See, for instance, Standish (2004). "The Ephemeris of Pluto: DE413" (PDF). JPL Interoffice Memorandum IOM 343-04-008. which compares DE413 output with DE411.
- See, for instance, Champion; et al. (2010). "Measuring the Mass of Solar System Planets Using Pulsar Timing". The Astrophysical Journal Letters. which references DE412.
- Standish (2006). "JPL Planetary Ephemeris DE414" (PDF). JPL Interoffice Memorandum IOM 343.R-06-002.
- Folkner; et al. (2007). "Planetary and Lunar Ephemeris DE418" (PDF). JPL Interoffice Memorandum IOM 343.R-07-005.
- Folkner; et al. (2008). "The Planetary and Lunar Ephemeris DE421" (PDF). JPL Interoffice Memorandum IOM 343.R-08-003.
- Folkner (2011). "JPL Planetary and Lunar Ephemerides : Export Information". Archived from the original on January 15, 2012.
- Folkner (2010). "Planetary Ephemeris DE423 fit to Messenger encounters with Mercury" (PDF). JPL Interoffice Memorandum IOM 343.R-10-001.
- Folkner (2011). "README.txt". file at the JPL FTP website.
- Folkner's descriptions of most of JPL's DE series
- NRAO description of the format and uses of the JPL ephemerides
- IAU's Papers and Information Related to Ephemerides
- JPL Solar System Dynamics
- Information about JPL ephemerides and links to programs and source code
- Java source code that implements JPL ephemerides and other theories
- JPL FTP site with ephemerides (data files), source code (for access and basic processing of the data to recover positions and velocities), and documentation.
- JPL Interoffice Memoranda describing features of the ephemerides.
- US Naval Observatory (Naval Oceanography Portal), "History of the Astronomical Almanac" (accessed September 2017).
- Standish; Newhall; Williams; Yeomans (1992), "CHAPTER 5: Orbital Ephemerides of the Sun, Moon, and Planets", in Seidelmann, Explanatory Supplement to the Astronomical Almanac (1 ed.), Mill Valley, CA: University Science Books, ISBN 0-935702-68-7.
- Standish; Williams, CHAPTER 8: Orbital Ephemerides of the Sun, Moon, and Planets (PDF) an unpublished, updated version of the above source. | <urn:uuid:51c6aafb-efd3-49dd-8a97-82e3ece5c5ec> | 3.15625 | 4,763 | Knowledge Article | Science & Tech. | 47.968791 | 95,478,340 |
Authors: J.A. Azpeitia, A. Zepeda, L. Torres, Y. Verde
Affilation: Instituto Tecnologico de Cancun, Mexico
Pages: 433 - 435
Keywords: carbon nanotubes, lead, platinum, ruthenium, wastewater
Recently, remove Pb2+ ions from drinking water has been focused due to its high toxicity to our health, such as nausea, convulsions, coma, renal failure, cancer and subtle effects on metabolism and intelligence. Different approaches to remove Pb2+ ions from wastewater, including chemicals precipitation, ion exchange, reverse osmosis and adsorption have been used. Adsorption is the simplest and best cost-effective method. Various adsorbents such as activated carbon, iron oxides, filamentous fungal biomass and natural condensed tannin have been explored and the results are promising. Carbon nanotubes (CNTs) have attracted special attentions to many researchers since 1991 because they posses exceptionally morphologies and have showed excellent physical and chemical properties and great potential for environmental applications. CNTs are also good anion and cation adsorption materials for wastewater treatment and they exhibit large specific surface areas which are easy to decorate. For example, CNTs oxidized with nitric acid showed very good lead and cadmium (II) cation adsorption capability. Transition metals deposited on CNT had demonstrated to improve the heavy metals adsorption. In this work, a Pb2+ adsorption study using a Pt and Ru on Multiwall Carbon Nanotube (MWCNT) matrix is presented. Pt/MWCNT and Ru/MWCNT were synthesized using an aqueous deposition method follow by a H2 thermal reduction. Nanostructured materials were post-treated with nitric acid at different concentrations. Pb2+ synthetic solution and M/MWCNT (M= Ru or Pt) were placed in centrifugation process during several hours at room temperature. Samples of the synthetic solution were taken before and after centrifugation step and analyzed by atomic absorption spectroscopy (AAS) to determine lead concentration. AAS results show Pb adsorption of 41 +- 3% and 29 +- 1% from Pt/MWCNT and Ru/MWCNT respectively at 0.4 N HNO3 concentration. Scanning Electron Microscopy (SEM) shows lead adsorption on the MWCNT matrix by growing of Pb crystals (Figure 1). High Pb2+ adsorption on the synthesized M/MWCNT convert them in a good candidate to be use as wastewater treatment materials.
Nanotech Conference Proceedings are now published in the TechConnect Briefs | <urn:uuid:5b711a83-4cd2-49d5-814e-de28661247a0> | 2.8125 | 576 | Academic Writing | Science & Tech. | 30.048001 | 95,478,344 |
|Unit level:||Level 2|
|Teaching period(s):||Semester 2|
|Offered by||School of Mathematics|
|Available as a free choice unit?:||N
This module aims to engage students with a circle of algorithmic techniques and concrete problems arising in elementary number theory and graph theory.
Modern Discrete Mathematics is a broad subject bearing on everything from logic to logistics. Roughly speaking, it is a part of mathematics that touches on those subjects that Calculus and Algebra can't: problems where there is no sensible notion continuity or smoothness and little algebraic structure. The subject, which is typically concerned with finiteor at the most countablesets of objects, abounds with interesting, concrete problems and entertaining examples.
On completion of this unit successful students will be able to:
- Define what it means for two graphs to be isomorphic and determine, with rigorous supporting arguments, whether two (small) graphs are isomorphic.
- Explain what the chromatic number of a graph is, determine it for small graphs and apply the idea to scheduling problems.
- Say what it means for a graph to be Eulerian and determine whether small graphs or multigraphs are Eulerian.
- Say what it means for a graph to be Hamiltonian and use the Bondy-Chvátal theorem to prove that a graph is Hamiltonian.
- Construct the graph Laplacian and apply the Matrix-Tree Theorem to count the number of spanning trees or spanning arborescences contained in a graph.
- Construct the adjacency matrix of a graph and exploit the connection between powers of the adjacency matrix to count walks. Also, define the operations of tropical arithmetic, construct the weight matrix associated with a weighted graph and use its tropical matrix powers to find the lengths of shortest paths.
- Given a project defined by a set of tasks, along with their durations and prerequisites, use critical path analysis to determine how quickly the project can be completed.
- Say what it means for a graph to be planar; state and apply Kuratowski’s theorem and determine whether a graph is planar or not.
- Other - 20%
- Written exam - 80%
Assessment Further Information
- Coursework; Weighting within unit 20%. This will consist of a problem set due on the last Friday before Easter and handed out two weeks earlier.
- 2 hours end of semester examination; Weighting within unit 80%
Graph Theory & Applications:
The basic definitions about graphs should be familiar from the Mathematical Workshop MATH10001, so after a brief review we will treat the following topics:
• Basic notions & notations, trees
• Eulerian tours & Hamiltonian cycles
• The Principle of Inclusion/Exclusion and the Matrix-Tree Theorem
• Shortest paths & applications to scheduling
Planar graphs & map colouring
- Dieter Jungnickel, Graphs, Networks and Algorithms (Springer, 2005)
This book is available online through SpringerLink, a service to which the University subscribes.
Feedback tutorials will provide an opportunity for students' work to be discussed and provide feedback on their understanding. Coursework or in-class tests (where applicable) also provide an opportunity for students to receive feedback. Students can also get feedback on their understanding directly from the lecturer, for example during the lecturer's office hour.
- Lectures - 22 hours
- Tutorials - 11 hours
- Independent study hours - 67 hours | <urn:uuid:f07bde70-fd51-413f-9c4b-a209c4e2943f> | 3.6875 | 741 | Product Page | Science & Tech. | 31.182455 | 95,478,347 |
Genetics is the study of genes, heredity and variation in living organisms. It is concerned with the process of trait inheritance from parents to offspring. Given that all living organisms have genes; this study can be applied to almost any system containing living organisms. This modern science that we know today as genetics was founded by Gregor Mendel in the mid-19th century, who we usually refer to as the ‘Father of Genetics.’
In his studies, Mendel discovered that organisms can inherit traits from their parents through as he called them ‘discrete units of inheritance,’ which we now know today as a gene. With the use of modern analytical techniques, we know that a gene is a subunit of DNA which codes for a cellular function – for example, it can code for a certain protein such as an enzyme. DNA itself is made up of nucleotides, which are transcripted and translated by the cell’s machinery to form a chain of amino acids. The order of amino acids corresponds to the order of the genes; and thus the relationship between these two is referred to the genetic code – as our DNA codes for our cellular function.
However, not all genes are the same, mutations will always introduce variations into the genetic codes. Two homologous genes may not be identical, but may still code for the same protein. These are known as alleles. A mutation can also change the protein it codes for by changing the amino acid sequence that is generated. Thereby, it changes the function and it could potentially make the protein ineffective.
Thus, it can be seen that genetics can be examined from a macroscopic level where genetics play a role in behavior and appearance, or from a microscopic level where genetics play a role in the protein that gets produced. Thus, understanding genetics is important for understanding not only biology, but also human behavior.© BrainMass Inc. brainmass.com July 22, 2018, 3:11 am ad1c9bdddf | <urn:uuid:c148a3b2-225c-4708-b011-5027dad79a07> | 3.671875 | 408 | Knowledge Article | Science & Tech. | 42.038666 | 95,478,351 |
By Zdeněk Kopal
Read or Download Advances in Astronomy and Astrophysics: v. 7 PDF
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Additional info for Advances in Astronomy and Astrophysics: v. 7
Advances in Astronomy and Astrophysics: v. 7 by Zdeněk Kopal | <urn:uuid:0d485c74-47d7-482e-96df-1dcf04165098> | 2.53125 | 522 | Product Page | Science & Tech. | 19.846908 | 95,478,359 |
How long can you go without water? After only a few hours you will begin to get thirsty. Within a couple days without water you would get very sick.Without water, your body would die within about a week, possibly even sooner.
Living things need water to survive. But why is water so important? All lifeforms on Earth are comprised almost entirely of water. Your own body is about 66%water. Water in your blood helps transport food and chemicals to your cells. It helps remove waste products from your body. Water is used to cool you down, to warm you up, and to carry out the chemical reactions that allow you to move and grow. Another important use of water is to keep your body clean. Though you may not like it, taking a bath or shower is an important part of being healthy.
Plants use water to grow, to transport food, and to carry out chemical reactions. In addition, plants use water as part of photosynthesis, to create their own food. | <urn:uuid:3a6a692c-1085-4f42-90a4-e8c39e58e17d> | 3.28125 | 203 | Knowledge Article | Science & Tech. | 68.962193 | 95,478,411 |
Interaction of Nuclei with Electromagnetic Radiation
In the development of atomic physics the interaction of atoms with electromagnetic radiation has been of paramount importance for the understanding of atomic structure. In the case of nuclei, this interaction has not been so important a tool, since, unlike the atomic case, the wavelengths of interest are so short that they cannot be measured by the usual optical devices. The rather indirect methods which must be employed make the energy determination quite inaccurate compared to spectroscopic standards, and the available resolution low. Furthermore in most cases the radiation process is only one of many competing processes (such as particle emission or sometimes even beta-decay) and its probability is correspondingly lower.
KeywordsElectric Dipole Electromagnetic Radiation Compound Nucleus Internal Conversion Multipole Moment
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Presentation on theme: "Pierre-Johan CHARTRE email@example.com Java EE - JAX-RS - Pierre-Johan CHARTRE firstname.lastname@example.org."— Presentation transcript:
1 Pierre-Johan CHARTRE email@example.com Java EE - JAX-RS -Pierre-Johan CHARTRE
2 Web-services Definition: “A Web service is a method of communication between two electronic devices over the World Wide Web.”WikipediaWeb service is "a software system designed to support interoperable machine-to-machine interaction over a network.“W3C
3 Web-services Definition: A Web service has an interface described in a machine-processable format (specifically Web Services Description Language, aka WSDL).Other systems interact with the Web service in a manner prescribed by its description using SOAP messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards.
5 Service-Oriented Achitecture SOA is a set of principles and methodologies for designing and developing software in the form of interoperable services.These services are well-defined business functionalities that are built as software components that can be reused for different purposes.
8 Web-services Definition: W3C has identified 2 major classes of Web servicesREST-compliant Web servicesthe primary purpose of the service is to manipulate XML representations of Web resources using a uniform set of stateless operations;It’s the Web (2.0) APIa defined set of HTTP request messages along with a definition of the structure of response messages, typically expressed in JSON or XML. Arbitrary Web services the service may expose an arbitrary set of operations
10 REST Web-services REST: Representational State Transfert is a style of software architecture for distributed systems such as the WWW.REST has emerged as a predominant Web-service design model.REST was first described by Roy Fielding in 2000.It’s a resource-oriented Web-service
11 REST Web-services Architecture definition In a REST based architecture everything is a resource. A resource is accessed via a common interface based on the HTTP standard methods.In a REST based architecture you typically havea REST server which provides access to the resourcesand a REST client which accesses and modify the REST resources.REST is designed to use a stateless communication protocol, typically HTTP.REST allows that resources have different representations, e.g. text, xml, json etc. The rest client can ask for specific representation via the HTTP protocol (content negotiation).
12 REST Web-services HTTP methods GET defines a reading access of the resource without side-effects. The resource is never changed via a GET request, e.g. the request has no side effects (idempotent).PUT creates a new resource, must also be idempotent.DELETE removes the resources. The operations are idempotent, they can get repeated without leading to different results.POST updates an existing resource or creates a new resource.
13 REST Web-services Example base URI for the web service: http://example.com/resources/ResourceGETPUTPOSTDELETECollection URI, such asList the URIs and perhaps other details of the collection's members.Replace the entire collection with another collection.Create a new entry in the collection. The new entry's URL is assigned automatically and is usually returned by the operation.Delete the entire collection.Element URI, such asRetrieve a representation of the addressed member of the collection, expressed in an appropriate Internet media type.Replace the addressed member of the collection, or if it doesn't exist, create it.Not generally used. Treat the addressed member as a collection in its own right and create a new entry in it.Delete the addressed member of the collection.
14 JAX-RS JSR-311: “JAX-RS: The Java API for RESTful Web Services” Introduced in Java SE 5: annotation-basedObjective: simplify the development and deployment of web service clients and endpoints.Part of J2EE 6No configuration is necessary to start using JAX-RS
15 JAX-RS API Specifications Annotations to aid in mapping a resource class (a Plain Old Java Object) as a web resource.@Path specifies the relative path for a resource class or method.the HTTP request type of a resource.@Produces specifies the response MIME media types.@Consumes specifies the accepted request media types.Annotations to method parameters to pull information out of the request. All take a key of some form which is used to look up the value required.@PathParam binds the parameter to a path segment.@QueryParam binds the parameter to the value of an HTTP query parameter.@MatrixParam binds the parameter to the value of an HTTP matrix parameter.@HeaderParam binds the parameter to an HTTP header value.@CookieParam binds the parameter to a cookie value.@FormParam binds the parameter to a form value.@DefaultValue specifies a default value for the above bindings when the key is not found.@Context returns the entire context of the object. HttpServletRequest request) | <urn:uuid:3e77dc07-c557-462b-836f-0ceb9b0a1a25> | 3.421875 | 1,098 | Audio Transcript | Software Dev. | 35.589362 | 95,478,427 |
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How to Easily Convert Celsius to Fahrenheit
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What Is Urethane?
How to Make Slime Without Borax or Liquid Starch
How Oxygen Gas Is Produced During Photosynthesis?
How to Convert Milligrams Per Liter to Molarity
What Are Five Properties of Gases?
Science Fair Projects on Chewing Gum
How to Tell If Something Is Polar or Non-Polar
How to Calibrate an Outdoor Thermometer
How to Calculate the Amount of Reactant in Excess
How to Read Degrees on a Compass
Ideas for Controlled Variable Science Projects
Precautions When Using a Microscope
How Is a Photon Produced?
How Does a Plasma Ball Work?
Science Fair Project on Ripening Bananas
How to Calculate End Point
Ice Cubes Melting Process
How Do Plants Store Energy During Photosynthesis?
How to Mix Calcium Chloride and Water
How to Make Things Float in Water
How to Neutralize Food Coloring in Water
How to Raise the PH Level in Water
How to Tell Whether Something Is Reduced or Oxidized
What Is Gibbs Free Energy?
Do and Don't in the Science Lab
Six Types of Microscopes
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This resource is a simulation of an ideal Otto engine. The page explains the cycles of the engine, and the applet shows its cycles alongside a pressure vs. volume or temperature vs. volume diagram. The graph shows that net work is done by the piston.
This page is part of a collection of Java applets with tutorial questions developed for undergraduate physics students.
%0 Electronic Source %A Forinash, Kyle %D May 9, 2007 %T Indiana University Southeast Physics Applets: Ideal Otto Engine Simulation %V 2018 %N 21 July 2018 %8 May 9, 2007 %9 application/java %U http://pages.iu.edu/~kforinas/physlets/thermo/Otto.html
Disclaimer: ComPADRE offers citation styles as a guide only. We cannot offer interpretations about citations as this is an automated procedure. Please refer to the style manuals in the Citation Source Information area for clarifications. | <urn:uuid:a074e5d4-5c9c-42fd-bba4-7d8800dbca16> | 2.859375 | 192 | Knowledge Article | Science & Tech. | 46.70875 | 95,478,450 |
+44 1803 865913
Edited By: G A Schultz and E T Engman
483 pages, 188 figs
The book provides comprehensive information on possible applications of remote sensing data for hydrological monitoring and modeling as well as for water management decisions. It is intended to provide methods to support the readers in solving their own problems in hydrology and water management. Mathematical theory is provided only as far as it is necessary for understanding the underlying principles. The book is especially timely because of new programs and sensors that are or will be realized. ESA, NASA, NASDA as well as the Indian Space Agency and the Brazilian Space Agency have recently launched satellites or developed plans for new sensor systems that will be especially pertinent to hydrology and water management as are the new large-scale groundbased weather radar systems. New techniques will be presented whose structures will differ from conventional hydrological models due to the nature of remotely sensed data.
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+44 1803 865913
By: James R Pfafflin, Joseph M Lynch and Edward N Zeigler
Environmental science and engineering is a truly interdisciplinary field. From its origins in public health practice, concern for the well-being of our environment has embraced areas as diverse as chemistry, the earth sciences, biology, engineering and law. The specialist language of any discipline can be a barrier to co-operation and understanding in solving environmental problems.
It explains many important specialist environmental terms in a clear and concise way. It also provides an extensive guide to the many acronyms encountered in environmental science.
The dictionary describes many of the acts, organisations and requirements related to the legislation of the environment, giving particular emphasis to those of the United States of America. Thus, it will be particularly useful to those seeking a greater understanding of the US perspective on the environmental question.
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Researchers have genetically engineered trees that will be easier to break down to produce paper and biofuel, a breakthrough that will mean using fewer chemicals, less energy and creating fewer environmental pollutants.
"One of the largest impediments for the pulp and paper industry as well as the emerging biofuel industry is a polymer found in wood known as lignin," says Shawn Mansfield, a professor of Wood Science at the University of British Columbia.
Lignin makes up a substantial portion of the cell wall of most plants and is a processing impediment for pulp, paper and biofuel. Currently the lignin must be removed, a process that requires significant chemicals and energy and causes undesirable waste.
Researchers used genetic engineering to modify the lignin to make it easier to break down without adversely affecting the tree's strength.
"We're designing trees to be processed with less energy and fewer chemicals, and ultimately recovering more wood carbohydrate than is currently possible," says Mansfield.
Researchers had previously tried to tackle this problem by reducing the quantity of lignin in trees by suppressing genes, which often resulted in trees that are stunted in growth or were susceptible to wind, snow, pests and pathogens.
"It is truly a unique achievement to design trees for deconstruction while maintaining their growth potential and strength."
The study, a collaboration between researchers at the University of British Columbia, the University of Wisconsin-Madison, Michigan State University, is a collaboration funded by Great Lakes Bioenergy Research Center, was published today in Science.
The structure of lignin naturally contains ether bonds that are difficult to degrade. Researchers used genetic engineering to introduce ester bonds into the lignin backbone that are easier to break down chemically.
The new technique means that the lignin may be recovered more effectively and used in other applications, such as adhesives, insolation, carbon fibres and paint additives.
The genetic modification strategy employed in this study could also be used on other plants like grasses to be used as a new kind of fuel to replace petroleum.
Genetic modification can be a contentious issue, but there are ways to ensure that the genes do not spread to the forest. These techniques include growing crops away from native stands so cross-pollination isn't possible; introducing genes to make both the male and female trees or plants sterile; and harvesting trees before they reach reproductive maturity.
In the future, genetically modified trees could be planted like an agricultural crop, not in our native forests. Poplar is a potential energy crop for the biofuel industry because the tree grows quickly and on marginal farmland. Lignin makes up 20 to 25 per cent of the tree.
"We're a petroleum reliant society," says Mansfield. "We rely on the same resource for everything from smartphones to gasoline. We need to diversify and take the pressure off of fossil fuels. Trees and plants have enormous potential to contribute carbon to our society."
Heather Amos | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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23.07.2018 | Health and Medicine
23.07.2018 | Life Sciences | <urn:uuid:33d68cb8-bf9e-4c33-9610-0781159d60a2> | 3.78125 | 1,201 | Content Listing | Science & Tech. | 35.343611 | 95,478,486 |
Amount of carbon dioxide released into U.S. atmosphere at lowest level in 20 years
PITTSBURGH -- In a surprising turnaround, the amount of carbon dioxide being released into the atmosphere in the U.S. has fallen dramatically to its lowest level in 20 years, and government officials say the biggest reason is that cheap and plentiful natural gas has led many power plant operators to switch from dirtier-burning coal.
Many of the world's leading climate scientists didn't see the drop coming, in large part because it happened as a result of market forces rather than direct government action against carbon dioxide, a greenhouse gas that traps heat in the atmosphere.
Michael Mann, director of the Earth System Science Center at Penn State University, said the shift away from coal is reason for "cautious optimism" about potential ways to deal with climate change. He said it demonstrates that "ultimately people follow their wallets" on global warming.
"There's a very clear lesson here. What it shows is that if you make a cleaner energy source cheaper, you will displace dirtier sources," said Roger Pielke Jr., a climate expert at the University of Colorado.
In a little-noticed technical report, the U.S. Energy Information Agency, a part of the Energy Department, said this month that energy related U.S. CO2 emissions for the first four months of this year fell to about 1992 levels. Energy emissions make up about 98 percent of the total. The Associated Press contacted environmental experts, scientists and utility companies and learned that virtually everyone believes the shift could have major long-term implications for U.S. energy policy.
While conservation efforts, the lagging economy and greater use of renewable energy are factors in the CO2 decline, the drop-off is due mainly to low-priced natural gas, the agency said.
A frenzy of shale gas drilling in the Northeast's Marcellus Shale and in Texas, Arkansas and Louisiana has caused the wholesale price of natural gas to plummet from $7 or $8 per unit to about $3 over the past four years, making it cheaper to burn than coal for a given amount of energy produced. As a result, utilities are relying more than ever on gas-fired generating plants.
Both government and industry experts said the biggest surprise is how quickly the electric industry turned away from coal. In 2005, coal was used to produce about half of all the electricity generated in the U.S. The Energy Information Agency said that fell to 34 percent in March, the lowest level since it began keeping records nearly 40 years ago.
The question is whether the shift is just one bright spot in a big, gloomy picture, or a potentially larger trend.
Coal and energy use are still growing rapidly in other countries, particularly China, and CO2 levels globally are rising, not falling. Moreover, changes in the marketplace -- a boom in the economy, a fall in coal prices, a rise in natural gas -- could stall or even reverse the shift. For example, U.S. emissions fell in 2008 and 2009, then rose in 2010 before falling again last year.
Also, while natural gas burns cleaner than coal, it still emits some CO2. And drilling has its own environmental consequences, which are not yet fully understood.
"Natural gas is not a long-term solution to the CO2 problem," Pielke warned.
The International Energy Agency said the U.S. has cut carbon dioxide emissions more than any other country over the last six years. Total U.S. carbon emissions from energy consumption peaked at about 6 billion metric tons in 2007. Projections for this year are around 5.2 billion, and the 1990 figure was about 5 billion.
China's emissions were estimated to be about 9 billion tons in 2011, accounting for about 29 percent of the global total. The U.S. accounted for approximately 16 percent.
Mann called it "ironic" that the shift from coal to gas has helped bring the U.S. closer to meeting some of the greenhouse gas targets in the 1997 Kyoto treaty on global warming, which the United States never ratified. On the other hand, leaks of methane from natural gas wells could be pushing the U.S. over the Kyoto target for that gas.
Even with such questions, public health experts welcome the shift, since it is reducing air pollution.
"The trend is good. We like it. We are pleased that we're shifting away from one of the dirtiest sources to one that's much cleaner," said Janice Nolen, an American Lung Association spokeswoman. "It's been a real surprise to see this kind of shift. We certainly didn't predict it."
Power plants that burn coal produce more than 90 times as much sulfur dioxide, five times as much nitrogen oxide and twice as much carbon dioxide as those that run on natural gas, according to the Government Accountability Office, the investigative arm of Congress. Sulfur dioxide causes acid rain and nitrogen oxides lead to smog.
Bentek, an energy consulting firm in Colorado, said that sulfur dioxide emissions at larger power plants in 28 Eastern, Midwestern and Southern states fell 34 percent during the past two years, and nitrous oxide fell 16 percent. Natural gas has helped the power industry meet federal air pollution standards earlier than anticipated, Bentek said.
Last year the Environmental Protection Agency issued its first rules to limit CO2 emissions from power plants, but the standards don't take effect until 2014 and 2015. Experts had predicted that the rules might reduce emissions over the long term, but they didn't expect so many utilities to shift to gas so early. And they think price was the reason.
"A lot of our units are running much more gas than they ever have in the past," said Melissa McHenry, a spokeswoman for Ohio-based American Electric Power Co. "It really is a reflection of what's happened with shale gas."
"In the near term, all that you're going to build is a natural gas plant," she said. Still, she warned: "Natural gas has been very volatile historically. Whether shale gas has really changed that -- the jury is still out. I don't think we know yet."
Jason Hayes, a spokesman for the American Coal Council, based in Washington, predicted cheap gas won't last.
"Coal is going to be here for a long time. Our export markets are growing. Demand is going up around the world. Even if we decide not to use it, everybody else wants it," he said. Hayes also said the industry expects new coal-fired power plants will be built as pollution-control technology advances: "The industry will meet the challenge" of the EPA regulations.
The boom in gas production has come about largely because of hydraulic fracturing, or fracking. Large volumes of water, plus sand and chemicals, are injected to break shale rock apart and free the gas.
Environmentalists say that the fluids can pollute underground drinking water supplies and that methane leaks from drilling cause serious air pollution and also contribute to global warming. The industry and many government officials say the practice is safe when done properly. But there have been cases in which faulty wells did pollute water, and there is little reliable data about the scale of methane leakage.
"The Sierra Club has serious doubts about the net benefits of natural gas," said Deborah Nardone, director of the group's Beyond Natural Gas campaign.
"Without sufficient oversight and protections, we have no way of knowing how much dangerous pollution is being released into Americans' air and water by the gas industry. For those reason, our ultimate goal is to replace coal with clean energy and energy efficiency and as little natural gas as possible."
Wind supplied less than 3 percent of the nation's electricity in 2011 according to EIA data, and solar power was far less. Estimates for this year suggest that coal will account for about 37 percent of the nation's electricity, natural gas 30 percent, and nuclear about 19 percent.
Some worry that cheap gas could hurt renewable energy efforts.
"Installation of new renewable energy facilities has now all but dried up, unable to compete on a grid now flooded with a low-cost, high-energy fuel," two experts from Colorado's Renewable and Sustainable Energy Institute said in an essay posted this week on Environment360, a Yale University website.
How much further the shift from coal to natural gas can go is unclear. Bentek says that power companies plan to retire 175 coal-fired plants over the next five years. That could bring coal's CO2 emissions down to 1980 levels. However, the EIA predicts prices of natural gas will start to rise a bit next year, and then more about eight years from now.
Despite unanswered questions about the environmental effects of drilling, the gas boom "is actually one of a number of reasons for cautious optimism," Mann said. "There's a lot of doom and gloom out there. It is important to point out that there is still time" to address global warning. | <urn:uuid:e1e577c5-e6c7-4a17-9b28-884997ac2392> | 3.40625 | 1,839 | News Article | Science & Tech. | 53.700385 | 95,478,513 |
A doctoral student in biology at the University of Zurich has now carried out experiments proving that pigeons have a spatial map and thus possess cognitive capabilities. In unknown territories, they recognize where they are in relation to their loft and are able to choose their targets themselves.
Pigeon fitted with miniature GPS logger
Homing pigeons fly off from an unknown place in unfamiliar territory and still manage to find their way home. Their ability to find their way home has always been fascinating to us humans. Despite intensive research, it is not yet definitively clear where this unusual gift comes from.
All we know is that homing pigeons and migratory birds determine their flight direction with the help of the Earth’s magnetic field, the stars and the position of the sun. As Nicole Blaser, a doctoral student in biology at the University of Zurich demonstrates in the «Journal of Experimental Biology», homing pigeons navigate using a mental map.
Navigating like a robot or cognitive capabilities?
Research proposes two approaches to explain how homing pigeons can find their home loft when released from an unfamiliar place. The first version assumes that pigeons compare the coordinates of their current location with those of the home loft and then systematically reduce the difference between the two until they have brought the two points together. If this version is accurate, it would mean that pigeons navigate like flying robots. The second version accords the pigeons a spatial understanding and «knowledge» of their position in space relative to their home loft. This would presuppose a type of mental map in their brain and thus cognitive capabilities. Up until now, there has not been any clear evidence to support the two navigation variants proposed.
For their experiments, Blaser and her colleagues fitted homing pigeons with miniature GPS loggers in order to monitor the birds’ flight paths. Beforehand the researchers trained the pigeons not to obtain food in the home loft, as was normally the case otherwise. «We fed the pigeons in a second loft around thirty kilometers away, from where they each had to fly back to their home loft», says Blaser, explaining the structure of the experiment. The scientists then brought the pigeons to a third place unknown to the pigeons in completely unfamiliar territory. This release site was in turn thirty kilometers from the home loft and the food loft. Natural obstacles obscured visual contact between the release site and the two lofts. One group of the pigeons was allowed to eat until satiated before flying home. The other group was kept hungry before starting off. Blaser explained: «With this arrangement, we wanted to find out whether the hungry pigeons fly first to the home loft and from there to the food loft or whether they are able to fly directly to the food loft.»
Fed pigeons fly home, hungry pigeons fly to the food loft
«As we expected, the satiated pigeons flew directly to the home loft», explains Prof. Hans-Peter Lipp, neuroanatomist at UZH and Blaser’s supervisor for her doctoral thesis. «They already started on course for their loft and only deviated from that course for a short time to make topography-induced detours.» The hungry pigeons behaved quite differently, setting off on course for the food loft from the very beginning and flying directly to that target. They also flew around topographical obstacles and then immediately adjusted again to their original course. Based on this procedure, Blaser concludes that pigeons can determine their location and their direction of flight relative to the target and can choose between several targets. They thus have a type of cognitive navigational map in their heads and have cognitive capabilities. «Pigeons use their heads to fly», jokes the young biologist.Literature:
Nathalie Huber | Universität Zürich
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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18.07.2018 | Health and Medicine | <urn:uuid:420bd7ca-1f6a-4f51-8ed3-39c533b7a128> | 3.703125 | 1,409 | Content Listing | Science & Tech. | 40.416412 | 95,478,525 |
Open star clusters like the one seen here are not just perfect subjects for pretty pictures. Most stars form within clusters and these clusters can be used by astronomers as laboratories to study how stars evolve and die. The cluster captured here by the Wide Field Imager (WFI) at ESO’s La Silla Observatory is known as IC 4651, and the stars born within it now display a wide variety of characteristics.
The loose speckling of stars in this new ESO image is the open star cluster IC 4651, located within the Milky Way, in the constellation of Ara (The Altar), about 3000 light-years away. The cluster is around 1.7 billion years old — making it middle-aged by open cluster standards. IC 4651 was discovered by Solon Bailey, who pioneered the establishment of observatories in the high dry sites of the Andes, and it was catalogued in 1896 by the Danish–Irish astronomer John Louis Emil Dreyer.
The Milky Way is known to contain over a thousand of these open clusters, with more thought to exist, and many have been studied in great depth. Observations of star clusters like these have furthered our knowledge of the formation and evolution of the Milky Way and the individual stars within it. They also allow astronomers to test their models of how stars evolve.
The stars in IC 4651 all formed around the same time out of the same cloud of gas . These sibling stars are only bound together very loosely by their attraction to one another and also by the gas between them. As the stars within the cluster interact with other clusters and clouds of gas in the galaxy around them, and as the gas between the stars is either used up to form new stars or blown away from the cluster, the cluster’s structure begins to change. Eventually, the remaining mass in the cluster becomes small enough that even the stars can escape. Recent observations of IC 4651 showed that the cluster contains a mass of 630 times the mass of the Sun and yet it is thought that it initially contained at least 8300 stars, with a total mass 5300 times that of the Sun.
As this cluster is relatively old, a part of this lost mass will be due to the most massive stars in the cluster having already reached the ends of their lives and exploded as supernovae. However, the majority of the stars that have been lost will not have died, but merely moved on. They will have been stripped from the cluster as it passed by a giant gas cloud or had a close encounter with a neighbouring cluster, or even simply drifted away.
A fraction of these lost stars may still be gravitationally bound to the cluster and surround it at a great distance. The remaining lost stars will have migrated away from the cluster to join others, or have settled elsewhere in the busy Milky Way. The Sun was probably once part of a cluster like IC 4651, until it and all its siblings were gradually separated and spread across the Milky Way.
This image was taken using the Wide Field Imager. This camera is permanently mounted at the MPG/ESO 2.2-metre telescope at the La Silla Observatory. It consists of several CCD detectors with a total of 67 million pixels and can observe an area as large as the full Moon. The instrument allows observations from visible light to the near infrared, with more than 40 filters available. For this image, only three of these filters were used.
Although many of the stars captured here belong to IC 4651, most of the very brightest in the picture actually lie between us and the cluster and most of the faintest ones are more distant.
This quantity is in fact much larger than the numbers quoted by previous studies which surveyed smaller regions, leaving out many of the cluster’s stars that lie further from its core.
ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become "the world’s biggest eye on the sky".
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
This is a translation of ESO Press Release eso1534.
Richard Hook | ESO-Media-Newsletter
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
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A monster solar flare erupted early on Oct. 19 from a huge sunspot that may just be getting warmed up.
The sun fired off an X-class solar flare — the most powerful type — that peaked at 1:01 a.m. EDT (5:01 GMT). NASA's Solar Dynamics Observatory spacecraft captured photos and video of the intense sun storm, which researchers classified as an X1.1 flare.
The flare erupted from a sunspot called AR (Active Region) 2192, which has since grown to become 78,000 miles (125,000 kilometers) wide, according to Spaceweather.com — almost as big as the planet Jupiter.
"Since [Sunday's flare], the sunspot has almost doubled in size and developed an increasingly unstable 'beta-gamma-delta' magnetic field," Spaceweather.com's Tony Phillips wrote in an update. "It would seem to be just a matter of time before another strong explosion occurs."
AR 2192 has been pointing away from Earth, so its outbursts to date have not affected the planet much. But that could change soon; the sunspot is now rotating around toward Earth, Phillips added.
Solar flares are bursts of energetic radiation that can cause temporary radio blackouts and affect the precision of GPS satellite measurements. Scientists classify strong flares into three categories, with C being the weakest, M medium-strength and X the most powerful.
Flares are often accompanied by coronal mass ejections (CMEs), clouds of super-hot solar plasma that rocket through space at millions of miles per hour. Earth-directed CMEs can cause geomagnetic storms that can disrupt power grids and radio communications, and also amp up the beautiful auroral displays known as the northern and southern lights.
The flare on Oct. 19 was far from the strongest of the year; the sun blasted out an X4.9 flare in February. (X4 flares are four times more intense than X1 flares.)
The sun is currently near the peak of its 11-year activity cycle, which is known as Solar Cycle 24. But the current solar max is the weakest one in a century or so, scientists say.
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This article originally published at Space.com here | <urn:uuid:0db03950-9eaf-4429-9cf7-335429aa585f> | 3.203125 | 530 | Truncated | Science & Tech. | 57.595682 | 95,478,537 |
What they saw contradicts fundamental notions of how key biological molecules break up during the repair of sunburn – and that knowledge could someday lead to drugs or even lotions that could heal sunburn in humans.
In the Proceedings of the National Academy of Sciences, the Ohio State University researchers and their colleagues confirm what was previously known about the enzyme photolyase, which is naturally produced in the cells of plants and some animals – though not in mammals, including humans. The enzyme repairs DNA by tearing open the misshapen, damaged area of the DNA in two places and reforming it into its original, undamaged shape.
But the enzyme doesn’t break up the injury in both places at once, as researchers previously suspected from theoretical calculations. Instead, it’s a two-step process that sends an electron through the DNA molecule in a circuitous route from one breakup site to the other, the new study revealed.
The research was led by Dongping Zhong, the Robert Smith Professor of Physics and professor in the departments of chemistry and biochemistry at Ohio State.
Zhong and his team literally shed light on the process in the laboratory using a laser with a kind of strobe effect to take super-fast measurements of the enzyme in action.
What they saw surprised them.
The two key chemical bond sites broke up one after the other – the first in just a few trillionths of a second, and the next after a 90-trillionths-of-a-second delay.
The reason? The single electron ejected from the enzyme – the source of energy for the breakup – took time and energy to travel from one bond site to the other, tunneling along the outer edge of the ring-shaped damage site.
Also, it turns out that for the enzyme taking the long way around is the most efficient way for the electron to do the job, Zhong explained.
“The enzyme needs to inject an electron into damaged DNA -- but how?” he said. “There are two pathways. One is direct jump from the enzyme across the ring from one side to the other, which is a short distance. But instead the electron takes the scenic route. We found that along the way, there is another molecule that acts as a bridge to speed the electron flow, and in this way, the long route actually takes less time.”
Now that they have revealed how the enzyme actually works, the researchers hope that others can use this knowledge to create synthetic photolyase for drugs or even lotions that can repair DNA.
Ultraviolet (UV) light damages DNA by exciting the atoms in the DNA molecule, causing accidental bonds to form between the atoms. The bond is called a photo-lesion, and can lead to a kind of molecular injury called a dimer. Dimers prevent DNA from replicating properly, and cause genetic mutations that lead to diseases such as cancer.
The dimer in question is called a cyclobutane pyrimidine dimer, and it is shaped like a ring that juts out from the side of the DNA.
For those organisms lucky enough to have photolyase in their cells, the enzyme absorbs energy from visible light – specifically, blue light – to shoot an electron into the cyclobutane ring to break it up. The result is a perfectly repaired strand of DNA.
That's why photolyase-carrying insects, fish, birds, amphibians, marsupials, and even bacteria, viruses and yeast are all protected from cancer-causing UV rays from the sun. Meanwhile, humans and all other mammals lack the enzyme, and so are particularly vulnerable to UV.
A synthetic form of photolyase could make up for our enzymatic shortfall. But Zhong’s group will leave that discovery to other researchers; they have now set their sights on photoreceptors – the proteins that absorb light and initiate signaling for many biological functions.
This research was funded by the National Institutes of Health, the Packard Foundation, the American Heart Association, and the Ohio State University Pelotonia fellowship.
Coauthors on the paper include Zheyun Liu, Chuang Tan, Xunmin Guo, Ya-Ting Kao, Jiang Li, and Lijuan Wang, all of Ohio State; and Aziz Sancar of the University of North Carolina School of Medicine, Chapel Hill.Contact: Dongping Zhong, (614) 292-3044; Zhong.firstname.lastname@example.org
Pam Frost Gorder | Newswise Science News
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Hurricanes cannot form near the equator, or so meteorology textbooks maintain. But a storm named Typhoon Vamei upended scientists thinking when it swirled above the equator in the South China Sea near Singapore on December 27, 2001. It formed so close to the equator that its winds howled in both hemispheres.
The Modis satellite image shows Typhoon Vamei at 1.5 degrees North near Singapore on December 27, 2001, with circulation on both sides of the equator. The land areas are the Malay Peninsula and Sumatra to the west of the typhoon, and Borneo to the east.
Satellite Image Credit: CRISP/National University of Singapore
New research funded by the National Science Foundation (NSF) and the U.S. Navys Office of Naval Research reveals the unusual mechanism for the birth of such a storm.
Intense thunderstorms over expanses of warm ocean water roil the atmosphere. Earths rotation spins these storms through the Coriolis Effect, a deflection that results in storms whirling counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
Cheryl Dybas | NSF
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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19.07.2018 | Materials Sciences
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Researchers at Washington University in St. Louis and Arizona State University have sequenced the genome of a rare bacterium that harvests light energy by making an even rarer form of chlorophyll, chlorophyll d. Chlorophyll d absorbs “red edge,” near infrared, long wave length light, invisible to the naked eye.
In so doing, the cyanobacterium Acaryochloris marina, competes with virtually no other plant or bacterium in the world for sunlight. As a result, its genome is massive for a cyanobacterium, comprising 8.3 million base pairs, and sophisticated. The genome is among the very largest of 55 cyanobacterial strains in the world sequenced thus far, and it is the first chlorophyll d –containing organism to be sequenced .
Robert Blankenship. Ph.D., Lucille P. Markey Distinguished Professor in Arts & Sciences at Washington University, and principal investigator of the project, said with every gene of Acaryochloris marina now sequenced and annotated, the immediate goal is to find the enzyme that causes a chemical structure change in chlorophyll d, making it different from primarily chlorophyll a, and b, but also from about nine other forms of chlorophyll.
“The synthesis of chlorophyll by an organism is complex, involving 17 different steps in all,” Blankenship said. “Some place near the end of this process an enzyme transforms a vinyl group to a formyl group to make chlorophyll d. This transformation of chemical forms is not known in any other chlorophyll molecules.”
Blankenship said he and his collaborators have some candidate genes they will test. They hope to insert these genes into an organism that makes just chlorophyll a. If the organism learns to synthesize chlorophyll d with one of the genes, the mystery of chlorophyll d synthesis will be solved, and then the excitement will begin.
Blankenship and his colleagues from both institutions published a paper on their work in the Feb. 4, online edition of the Proceedings of the National Academy of Sciences. The work was supported by the National Science Foundation and also involved collaborators from Australia and Japan. Three Washington University undergraduate students and one graduate student participated in the project, as well as other research personnel.
Harvesting solar power through plants or other organisms that would be genetically altered with the chlorophyll d gene could make them solar power factories that generate and store solar energy. Consider a seven-foot tall corn plant genetically tailored with the chlorophyll d gene to be expressed at the very base of the stalk. While the rest of the plant synthesized chlorophyll a, absorbing short wave light, the base is absorbing “red edge” light in the 710 nanometer range. Energy could be stored in the base without competing with any other part of the plant for photosynthesis, as the rest only makes chlorophyll a. Also, the altered corn using the chlorophyll d gene could become a super plant because of its enhanced ability to harness energy from the sun.
That model is similar to how Acaryochloris marina actually operates in the South Pacific, specifically Australia’s Great Barrier Reef. Discovered just 11 years ago, the cyanobacterium lives in a symbiotic relationship with a sponge-like marine animal popularly called a sea squirt . The Acaryochloris marina lives beneath the sea squirt, which is a marine animal that lives attached to rocks just below the surface of the water. The cyanobacterium absorbs “red edge” light through the tissues of its pal the sea squirt.
The genome, said Blankenship, is “ fat and happy. Acaryochloris marina lies down there using that far red light that no one else can use. The organism has never been under very strong selection pressure to be lean and mean like other bacteria are. It’s kind of in a sweet spot. Living in this environment is what allowed it to have such dramatic genome expansion.”
Blankenship said that once the gene that causes the late-step chemical transformation is found and inserted successfully into other plants or organisms, that it could potentially represent a five percent increase in available light for organisms to use.
“We now have genetic information on a unique organism that makes this type of pigment that no other organism does,” Blankenship said. “We don’t know what all the genes do by any means. But we’ve just begun the analysis. When we find the chlorophyll d enzyme and then look into transferring it into other organisms, we’ll be working to extend the range of potentially useful photosynthesis radiation.’
Robert Blankenship | EurekAlert!
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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According to macaque-ulations... physics professor spots monkey who is the spitting image of Einstein
- Amateur photographer captured several photos of the adorable creature
- Tufty hair and wrinkles make baby macaque look just like the scientist
Would you accept a physics lesson from a monkey who claimed to be a professor?
Perhaps you would if it was this extraordinary-looking macaque - who bears a startling resemblance to genius scientist Albert Einstein.
The astonishing pictures were taken by another physics expert, 66-year-old Professor Mihail Nazarov, at Taiping National Park in Malaysia.
It's all relative: The Stump-tailed Macaque's big eyes, wrinkled brow and tufts of white hair make him look just like the famous professor
Intelligent life: The likeness is unmistakable - although one of these two might be better at sums
The amateur photographer noticed the likeness immediately and quickly took some shots to prove his theory.
From his receding white hair to his sprouting moustache, the baby monkey is a double for the man behind the legendary E=MC² equation.
The Stump-tailed Macaque looks even more like the genius German scientist because of his wrinkled face, which belies his tender years.
Totally bananas: Like Einstein, the baby monkey knows the smartest solution to any problem - including transport
'As soon as I saw the baby monkey, my very first thought was that it looked like Einstein and that I needed to get some shots of it to prove it,' said Prof Nazarov.
'When I got back home, I looked back through the shots and could see the similarities between the monkey and Einstein even more.
'I love these pictures and the feeling of capturing something which is so unusual and amazing.'
Einstein took his place in the history books in the early 20th century and is often regarded as the father of modern physics for his work on the idea of relativity.
Now his furrowed brow can be seen again - not bent over a pile of books but swinging through the branches of a tree.
EINSTEIN VS MONKEY: HOW THEY MEASURE UP
Name: Albert Einstein
Born: Ulm, Germany (later lived in the U.S)
Lifespan: 1879-1955 (died aged 76)
Job: Most influential physicist of 20th century
Best known for: His mass-energy equivalence formula E=MC², the world's most famous equation
He says: All religions, arts and sciences are branches of the same tree
Name: Stump-tailed macaque
Born: South China or northeastern India
Lifespan: Usually around 30 years
Job: Travelling and eating, mainly fruit
Best known for: Testing hair regrowth products for balding humans, because they too lose hair with age
He says: Not much, because his cheeks are filled with food. Will bare teeth at predators
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January 14 2014 Astronomy Newsletter
Here's the latest article from the Astronomy site at BellaOnline.com.
Galaxy or Star Cluster?
Galaxies and star clusters are collections of stars held together by gravity. What's the difference between them? For one thing, galaxies are really big. But how big is big? Even bigger than a million stars? Yes, that's small in astronomy.
I've also just updated an article pointing out the astronomy games, quizzes and jigsaws on BellaOnline with links to all of them.
Johann Bode born January 19, 1747
Bode's name lives on in what's known as “Bode's Law.” It's not a law, but a formula that gives the distance from the Sun to the planets – until it breaks down at Neptune. (Neptune was discovered the year after Bode's death.) However more than this, Bode was one of the founders of the Berlin Astronomical Yearbook. And his star atlas “Uranographia” was the greatest of the Golden Age of celestial atlases. You can read about Bode here: http://www.bellaonline.com/articles/art42694.asp
*Mission to Pluto and beyond*
NASA's New Horizons mission to Pluto and the Kuiper Belt was launched on Bode's birthday in 2005, though that probably wasn't why the date was chosen. What's the Kuiper Belt? Find out here: http://www.bellaonline.com/articles/art40059.asp
To participate in online discussions, this site has a community forum all about Astronomy located here - http://forums.bellaonline.com/ubbthreads.php?ubb=postlist&Board=323
Please visit astronomy.bellaonline.com for even more great content about Astronomy.
I hope to hear from you sometime soon, either in the forum or in response to this email message. I welcome your feedback!
Do pass this message along to family and friends who might also be interested. Remember it's free and without obligation.
I wish you clear skies.
Mona Evans, Astronomy Editor
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A shark researcher has discovered a new species that's found in the Pacific Ocean off the coasts of Costa Rica, Nicaragua, and Panama and glows in the dark.
Vicky Vasquez, who works at the Pacific Shark Research Center in Moss Landing, California, let her younger cousins name it: Ninja Lanternshark.
The animal's official title is Etmopterus benchleyi, a name Vasquez told BuzzFeed News is meant to honor Peter Benchley, who authored the novel Jaws and co-wrote the film adaptation with Stephen Spielberg.
But for the colloquial monicker, Vasquez recruited her first and second cousins, who are between 8 and 14 years old.
"They love animals and two of the girls have become especially obsessed with sharks," Vasquez told BuzzFeed News in an email. "This interest was all on their own."
According to Canadian science publication Hakai Magazine, Ninja Lanternshark measures about one-half meter (or a one and a half feet) long, and has black skin and "bulbous eyes."
Vasquez explained to her cousins that the cells in the shark's skin allow it to release a soft glow in the depths of the ocean. This characteristic allows it to blend into the limited amount of light down there, and sneak up on its prey without being noticed.
You know, like a ninja. | <urn:uuid:845df5c0-6866-45cf-ab78-3bad77ea5aeb> | 2.796875 | 280 | News Article | Science & Tech. | 52.136 | 95,478,576 |
Dinocampus coccinellae is a braconid wasp parasite of coccinellid beetles, including the spotted lady beetle, Coleomegilla maculata. D. coccinellae has been described as turning its ladybird host into a temporary "zombie" guarding the wasp cocoon. About 25% of ladybirds recover after the cocoon they are guarding matures.
In 1802, Schrank first described a female adult of this species as "Lady-bird killer 2155. Deep black, eyes green; head, front legs, and apex of the petiolate abdomen mussel-brown." (A petiolate abdomen is one whose basal segment is stalk-like, that is, long and slender.) Nearly all D. coccinellae are female offspring of unfertilized eggs, although males are also occasionally found. The male, when observed, has no ovipositor and is slimmer and darker than females.
The mature female wasp seeks out adult female ladybirds, although they will sometimes oviposit into a male adult or larval instar. One egg is planted in the host's soft underbelly. The wasp larva hatches after 5–7 days into a first instar larva with large mandibles and proceeds to remove any other eggs or larvae before beginning to feed on the ladybird's fat bodies and gonads.
The wasp larva inside the ladybird goes through four larval instars in 18–27 days. Meanwhile, the ladybird continues to forage and feed until the wasp larva, when it is ready to emerge, paralyzes the ladybird before tunneling out. It pupates in a cocoon attached to the leg of the living ladybird, whose brightly colored body and occasional twitching reduce predation. A growing D. coccinellae wasp nestled in its cocoon is extremely vulnerable, and other insects will devour it. If one of these predators tries to eat it, the ladybug retaliates, scaring it off. The ladybug becomes the parasites bodyguard, by protecting it from predators. However, wasp cocoons protected in this way develop into adults that produce fewer eggs, due to the energy demands of maintaining a living protector.
Ladybirds paralyzed, twitching, and attached to the cocoon of D. coccinellae have been compared to zombies by many writers. After 6–9 days, the wasp emerges from the cocoon. Remarkably, some 25% of ladybirds revive and emerge from paralysis once the cocoon has been emptied. The paralytic effect has been proposed to be associated with an RNA virus, Dinocampus coccinellae paralysis virus.
Dinocampus coccinellae can itself be parasitised by Gelis agilis, a hyperparasite that is known for its mimicry of ants. The wingless females of G. agilis oviposit into D. coccinellae cocoons; the egg immediately hatches and consumes the developing wasp. Cocoons hosting G. agilis usually take twice as long to emerge.
Because one ladybird can consume up to 5,500 aphids in a year, any ladybird parasite represents a potential threat to agriculture. In Britain, at least, the infestatation of seven-spotted ladybirds (Coccinella septempunctata) with D. coccinellae rose significantly during the 1990s, from about 20% to more than 70%, threatening to have a serious economic impact on British farmers.
- "Dinocampus coccinellae (Schrank 1802)". Fauna Europaea. Retrieved 23 June 2011.
- Cushman, R. A. (1922). "The identity of Ichneumon coccinellae Schrank (Hym.)". Proceedings of the Entomological Society of Washington. 24 (9): 241–242.
- Davis, Dexter S.; Sarah L. Stewart; Andrea Manica; Michael E. N. Majerus (2006). "Adaptive preferential selection of female coccinellid hosts by the parasitoid wasp Dinocampus coccinellae (Hymenoptera: Braconidae)" (PDF). European Journal of Entomology. 103 (1): 41–45. doi:10.14411/eje.2006.006. Archived from the original (PDF) on 2012-03-11.
- Geoghegan, Irene E.; Tamsin M. O. Majerus; Michael E. N. Majerus (1998). "A record of a rare male of the parthenogenetic parasitoid Dinocampus coccinellae (Schrank) (Hym.:Braconidae)". The Entomologist's Record and Journal of Variation. 110 (5–6): 171–172.
- Shaw, Scott Richard (1988). "A new Mexican genus and species of Dinocampini with serrate antennae (Hymenoptera; Braconidae; Euphorinae)" (PDF). Psyche. 95 (3–4): 289–298. doi:10.1155/1988/98545.
- Bruce, Anne. "Parasitoid wasp threatens Scottish Seven Spot ladybird". Microscopy UK. Retrieved 23 June 2011.
- "'Save our ladybirds' plea". BBC News. 17 January 2000. Retrieved 24 June 2011.
- Fanny Maure; Jacques Brodeur; Nicolas Ponlet; Josée Doyon; Annabelle Firlej; Éric Elguero; Frédéric Thomas (2011). "The cost of a bodyguard". Biology Letters. 7 (6): 843–846. doi:10.1098/rsbl.2011.0415. PMC . PMID 21697162. Archived from the original (PDF) on 2014-08-08.
- Zimmerm, Carl (November 2014). "Meet Natures Nightmare Mindsuckers". National Geographic.
- "Ladybird made into 'zombie' bodyguard by parasitic wasp". BBC News. 23 June 2011. Retrieved 23 June 2011.
- Braconnier, Deborah. "A real-life zombie story in the life of bugs". PhysOrg. Retrieved 25 June 2011.
- Pappas, Stephanie (21 June 2011). "The case of the wasp and the zombie ladybug". MSNBC. Retrieved 25 June 2011.
- Dheilly NM, Maure F, Ravallec M, et al. (2015), "Who is the puppet master? Replication of a parasitic wasp-associated virus correlates with host behaviour manipulation", Proceedings of the Royal Society B, 282 (1803): 20142773, doi:10.1098/rspb.2014.2773, PMC , PMID 25673681
- Anonymous (2015), "Wasp virus turns ladybugs into zombie babysitters", Science, doi:10.1126/science.aaa7844
- Connor, Steve (5 August 1998). "Ladybirds being wiped out by parasitic wasps". The Independent. Retrieved 24 June 2011. | <urn:uuid:2ef1a782-33cb-478c-b8af-55503c82d59f> | 3.328125 | 1,524 | Knowledge Article | Science & Tech. | 54.67131 | 95,478,602 |
Light is of fundamental importance. It allows us to see the world around us and record pictures of our environment. It enables communication over long distances through optical fibers. All current methods of detecting light share a common property: absorption and thus destruction of a photon.
Using a single atom trapped in an optical resonator, the presence of a reflected photon can be detected nondestructively. MPQ, Quantum Dynamics Division
It has been a long-standing dream to be able to watch individual photons fly by without absorbing them. A team of scientists in the Quantum Dynamics Division of Prof. Gerhard Rempe at the Max-Planck-Institute of Quantum Optics has now for the first time realized a device which leaves the photon untouched upon detection (Science Express, 14 November 2013).
In the experiment, the incoming photon is reflected off an optical resonator containing a single atom prepared in a superposition state. The reflection changes the superposition phase which is then measured to trace the photon. The new method opens up the perspective to dramatically increase the detection efficiency of single light quanta and has important implications for all experiments where photons are used to encode and communicate quantum information.
The key elements in the experiment are a single rubidium atom and an optical cavity. The latter is a resonator for light that is made of two highly-reflecting mirrors at a very small distance. The atom is trapped at the center of the cavity, where light forces strongly confine it in all three dimensions. It exhibits two different ground states, each characterized by its specific transition energy to the next excited state. To test the detector, the cavity is irradiated with a series of very faint lasers pulses that contain on average much less than a single photon.
In one of its ground states, the atom is off-resonant with both, the cavity and an impinging photon. In this case, the photon will enter the cavity, but not interact with the atom. Because of the special properties of the cavity, the photon will leave it on the same path it entered. In the other ground state, the atom is resonant with both, the cavity and the impinging photon.
In this case, atom and cavity represent a strongly coupled system with properties distinctively different from those of the individual systems. In contrast to the first case, a photon, which is on resonance with the cavity, has no chance to get into it. Instead, it is reflected from the first mirror. In either case, the fragile light quantum is reflected rather than absorbed and destroyed.
“However, the photon has left its trace in the atom,” Andreas Reiserer, doctoral student on the experiment and first author of the publication, explains. “The trick is that we prepare the atom in a superposition of the two ground states. The very moment the photon is reflected from the cavity, the resonant state experiences a phase shift relative to the off-resonant one. This phase shift can then be read out from the atom. In this way, the photon has survived its detection with its properties, for example its pulse shape or polarization, untouched.”
The phase shift of the atomic state is detected using a well-known technique: “Loosely speaking, the atom lights up when probed after reflection of a photon,” says Dr. Stephan Ritter, scientist at the experiment. In order to prove that the nondestructive detection works, the reflected photons are also registered by conventional photodetectors. “In this way, we detect the photon twice, which is impossible with destructive detectors alone. In our proof-of-principle experiment we have achieved a single-photon detection efficiency of 74 %, which is already more than the 60% of typical destructive detectors.” Ritter says. “The achieved value is not fundamentally limited, but due to some imperfections that we can work on in the future.”
The ability to observe single photons without destroying them or changing any of their degrees of freedom opens the perspective for a number of new experiments. A single photon can be detected repeatedly by combining several nondestructive devices. This also provides new possibilities for using single photons in quantum communication and quantum information processing. The successful transfer of a photon in a quantum network could be detected without destroying the fragile quantum information encoded in it. Based on the mechanism used for single-photon detection, it should also be possible to realize a deterministic, universal quantum gate between a reflected single photon and the single atom and even between two photons. Because quantum gates are the functional building blocks of a quantum computer, this is a long-standing dream in optical quantum computing. Olivia Meyer-StrengOriginal Publication:
Dr. Olivia Meyer-Streng | Max-Planck-Institut
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Deformation of volcanic materials by pore pressurization: analog experiments with simplified geometry
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The pressurization of pore fluids plays a significant role in deforming volcanic materials; however, understanding of this process remains incomplete, especially scenarios accompanying phreatic eruptions. Analog experiments presented here use a simple geometry to study the mechanics of this type of deformation. Syrup was injected into the base of a sand medium, simulating the permeable flow of fluids through shallow volcanic systems. The experiments examined surface deformation over many source depths and pressures. Surface deformation was recorded using a Microsoft® Kinect™ sensor, generating high-spatiotemporal resolution lab-scale digital elevation models (DEMs). The behavior of the system is controlled by the ratio of pore pressure to lithostatic loading \((\lambda =p/\rho g D)\). For \(\lambda <10\), deformation was accommodated by high-angle, reversed-mechanism shearing along which fluid preferentially flowed, leading to a continuous feedback between deformation and pressurization wherein higher pressure ratios yielded larger deformations. For \(\lambda >10\), fluid expulsion from the layer was much faster, vertically fracturing to the surface with larger pressure ratios yielding less deformation. The temporal behavior of deformation followed a characteristic evolution that produced an approximately exponential increase in deformation with time until complete layer penetration. This process is distinguished from magmatic sources in continuous geodetic data by its rapidity and characteristic time evolution. The time evolution of the experiments compares well with tilt records from Mt. Ontake, Japan, in the lead-up to the deadly 2014 phreatic eruption. Improved understanding of this process may guide the evolution of magmatic intrusions such as dikes, cone sheets, and cryptodomes and contribute to caldera resurgence or deformation that destabilizes volcanic flanks.
KeywordsAnalog experiments Volcanic pore pressurization Deformation Mechanical failure Flank destabilization Microsoft Kinect sensor
We thank Associate Editor Acocella, Dr. O. Galland, and two anonymous reviewers for their help in improving the manuscript.
The present work was funded by private donations to the University at Buffalo Foundation to study volcanism in the Southern Cascades, and by NASA grant number NNX12AQ10G. The views expressed in the present contribution are those of the authors alone.
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Type conversion in C ++ rather old, or rather a classic operation. In short and in Russian: Conversion type – it is considered an indication of a set of computer bytes integer or real. Or a pointer to a specific class.
At all, to understand the type conversion is necessary to consider the mechanism and structure variables. For example, PAC line integer multiple: short int, int, long int, not counting the unsigned. And computer places for them a different number of memory cells (bytes): 1, 2 and 4 respectively. Convert within these types of one class is called the standard conversion. at:
int a = 1;
short int b = 2;
b = a;
Take the next: take the two younger byte of a variable "a", simply transplanted in two bytes of variable «b». Since the value in and (unit) it is currently placed in these two bytes, the program will give the correct result, and C ++ will not be against such a conversion.
Why do I need to consider the size of the variable in the conversion?
What happens if you put in a variable "a" number 123456789? It is perfectly fit in 4 byte type int, but 2 byte type short int it no longer falls. too much. С , as expected, it just cuts the long number, taking only the tail of it, and put into a variable «b». We obtain course nonsense. And with a minus, if you bring it to the screen. Converting from the variable, which occupies a greater number of bytes in the memory will not be correct. If you convert the contrary from the short in long for example such problems will not, because the bytes in the variable recipient longer, and places data that stores short quite enough.
It is necessary to know. Teachers often catch students on this focus, especially in the training manual giving a similar pitfall with variable poorly compatible with each other in size.
As for the types of real conversion, It is engaged in a math coprocessor. There is no longer just the bytes distilled from cell to cell, and special instructions are executed, which convert the whole into a type of material with a mantissa and exponent, as it should be, and return value. This is not a conversion, it is converted. Anyway, It will deal with the processor.
int a = 123;
float b = 25.14;
a = b;
b = a;
cout << a << ' ' << b << endl;
In this example, the math co-processor converts the real to integer, and will drive to a variable, and then do the reverse operation: It will drive a whole in his special register (It called ST), and after he would get from a real integral part, equal to that, that in variable “and”.
If you want to convert from a real double (8 bytes) in float (4 bytes), here such problems, as a whole will not be a. Math coprocessor just round up to the real value, fits in 4 bytes, that does not lead to an incorrect value:
double b = 1234567891234565555.25;
a = b;
cout << a << '\n' << b;
The result will still be the number 1.234568e + 18, which means a 1.2-plus 18-degree. Another thing, what in “a” there will be rounded to the number of the 6th decimal place, instead 1.234567891234566e + 18. In general, inaccurate calculations it does not interfere, but it is recommended to use the program material of the same type, that did not happen here such rounding.
In addition to the type of transformation there is such a thing as the cast.
Visibility typecast can show such an example:
float b = 25.14;
a = (int)b;
cout << a << ' ' << b;
If the conversion – this decision C ++ (or rather compiler), in what type of result, it uses a type cast, rigidly specified by the programmer. In this example, the programmer tells the compiler, you need to convert it into a int, but not in short int. After all 25 and placed in int and short, that selects the compiler programmer may not know.
In everyday life such type conversions actually rare. And it's not necessary. The ideology of programming in a residential hints to avoid such frills, because they can be a rake (in the above example in the conversion of whole), therefore casts in C ++ should not be used everywhere.
:) Thank you for this article its author Stilet – Super Moderator programmers offline ProgrammersForum.
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By Neven Kresic,Zoran Stevanovic
Groundwater Hydrology of Water source Series - Water is a necessary environmental source and one who has to be thoroughly controlled. because the global areas extra emphasis on sustainable water provides, the call for for services in hydrology and water assets keeps to extend. This sequence is meant for pro engineers, who search an organization origin in hydrology and a capability to use this data to resolve difficulties in water source administration. destiny books within the sequence are: Groudwater Hydrology of Springs (2009), Groudwater Hydrology of River Basins (2009), Groudwater Hydrology of Aquifers (2010), and Groudwater Hydrology of Wetlands (2010).
First applied as a chief resource of ingesting water within the historic international, springs proceed to provide a few of the world's towns with water. lately their long term sustainability is stressed as a result of an elevated call for from groundwater clients. Edited through world-renowned hydrologists, Groundwater Hydrology of Springs: idea, administration, and Sustainability will supply civil and environmental engineers with a finished reference for coping with and maintaining the water caliber of Springs. With contributions from specialists from world wide, this e-book disguise some of the world's greatest springs, delivering a different international viewpoint on how engineers world wide are using engineering rules for dealing with difficulties equivalent to: mismanagement, overexploitation and their affects either water volume and caliber. The publication can be divided into elements: half one will clarify the idea and ideas of hydrology as they practice to Springs whereas half will supply an extraordinary look at the engineering practices used to regulate the most vital Springs from worldwide.
- Description of the spring and the aquifer feeding it
- Latest groundwater and contaminant delivery models
- Description of assets of aquifer use
- Understanding of infection and/or attainable contamination
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Every month on Earth Matters, we offer a puzzling satellite image. The May 2015 puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, what the image shows, and why the scene is interesting.
How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.
The prize. We can’t offer prize money, but, we can promise you credit and glory (well, maybe just credit). Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. In the credits, we’ll acknowledge the person who was first to correctly ID the image. We’ll also recognize people who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have played a role in molding the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you want us to recognize, please mention that as well.
Recent winners. If you’ve won the puzzler in the last few months or work in geospatial imaging, please sit on your hands for at least a day to give others a chance to play.
Releasing Comments. Savvy readers have solved some of our puzzlers after only a few minutes or hours. To give more people a chance to play, we may wait between 24-48 hours before posting the answers we receive in the comment thread.
Congratulations to reader Suzi for being the first to answer our April puzzler. As Suzi noted, the image shows South Korea’s Sisan Island. While Suzi (and several other readers) thought the offshore grid pattern was evidence of oyster or fish farming, our research suggests it is mainly seaweed farming. Severalsourcescited the western part of South Korea’s south coast as the main area of seaweed production, and aerial imagery of seaweed farms match the general appearance of our satellite image.
However, Suzi’s comment did prompt me to look more closely at the distribution of oyster farms and other types of aquaculture in South Korea, and it does seem possible that some of the patterns in the puzzler could be evidence of oyster aquaculture. Are there aquaculture experts or South Koreans reading this who are willing to share their opinion? Is this all seaweed or a mixture of seaweed and other types of aquaculture?
I suspect it may not be possible distinguish between seaweed farming and other types of aquaculture at Landsat’s resolution, but I would love to see somebody with more expertise prove me wrong. In the meantime, you can read what we published about this area as our Image of the Day on April 25, 2015.
Comments Off on April Puzzler Answer: Seaweed (and Oyster?) Farms
Columbia University climate scientist Kátia Fernandes appeared on the cover of the 2014 Climate Models wall calendar. The calendar, dreamed up by two science writers at Columbia University, offered a fresh look on the meaning of the term ‘climate model.” Read more about the calendar from AGU’s Plainspoken Scientist blog. Image credit: Charlie Naebeck.
Based on email and social media comments we receive, climate models are one of the least understood and most maligned tools used by Earth scientists.
What is a climate model? Putting aside the scientists from the Lamont-Doherty Earth Observatory who posed for a climate model calendar in 2014 (cover above), climate models are simply mathematical representations of Earth’s climate that are based on fundamental physical, biological, and chemical laws and theories. As NOAA explained in a story about the first general circulation model to include both the ocean and atmosphere, scientists divide the planet into a three-dimensional grid, use computers to solve the equations, and then evaluate the results when they “run” a climate model. As the story noted: “Models calculate winds, heat transfer, radiation, relative humidity, and surface hydrology within each grid and evaluate interactions with neighboring points.” The illustration below should help you visualize how the grids are laid out and some of the physical processes models include.
One of the first general circulation models was developed at Lawrence Livermore National Laboratory by Cecil “Chuck” Leith in the early 1960s. Unlike the NOAA model mentioned above, Leith’s model only simulated the atmosphere. What make Leith’s work so remarkable was that he was the first to produce a computer animation based on the model output. Watch the video below to see how these wobbling yet compelling animations looked.
From the very beginning, Leith’s animations attracted attention. “The one that I have is essentially a polar projection of the Northern Hemisphere, and you can see the patterns moving in mid-latitudes,” Leith explained during an oral history interview conducted by the American Institute of Physics. “I did it just because I knew we could do it, it would be interesting to look at, but it was almost too interesting. Whenever I’d go anywhere and give a talk about what I was doing, I would show the film and everybody was fascinated by the film, and they didn’t care what I said about the technical aspects of the model, as far as I could tell. And, in fact, Smagorinsky (another pioneer of climate modeling and the first director of NOAA) used to chide me about it a little bit. He says: ‘That’s just big plan showmanship. There’s no science there.’ But they started making movies too.” You can read more about Leith’s animation from Climate Central.
“The NASA authorization bill making its way through the House of Representatives guts our Earth science program and threatens to set back generations worth of progress in better understanding our changing climate, and our ability to prepare for and respond to earthquakes, droughts, and storm events.
NASA leads the world in the exploration of and study of planets, and none is more important than the one on which we live.
In addition, the bill underfunds the critical space technologies that the nation will need to lead in space, including on our journey to Mars.” | <urn:uuid:80ef6416-327d-48a4-b5f0-1ecd69ed9794> | 2.625 | 1,402 | News (Org.) | Science & Tech. | 45.018558 | 95,478,684 |
Precise reconstruction of regional climate changes in the past
Traces of volcanic ash originating from islandic volcanoes have been found in the sediments of Laker Tiefer See in the Nossentiner-Schwinzer Heide natural park in Mecklenburg-Vorpommern. This allows to more precisely date climate changes of the last 11500 years.
Microscope fotos of volcanic glass particles from two islandic eruptions of the Dyngjufjöll volcanic centre in North-eastern Iceland found in lakes Tiefer See (North-eastern Germany) and Czechowskie (Poland): Askja-S eruption from ca 11000 years ago and the Askja AD1875 eruption (photos: Sabine Wulf, GFZ)
An international team of geoscientists lead by the GFZ German Research Centre for Geosciences detected traces of in total eight volcanic eruptions on Island of which six could be precisely identified. The oldest eruption occurred 11400 years ago and the youngest from AD 1875 has been also described in historical documents.
Seasonally laminated lake sediments represent ideal geoarchives for reconstructing natural climate variability in the past. Achim Brauer from the Research Centre for Geosciences explained the particular importance of the identified volcanic ash deposits:
“Particles of three of the volcanic ashes detected in Lake Tiefer See have been also found 500 km further East in a lake in Poland. For the first time, this allows to synchronize both sediment archives to the year precise, which enables us to decipher even subtle regional differences of climate changes in the past. This information, in turn, provides the chance to better anticipate regional aspects of future climate change.“
The particular challenge of this approach was the fact that volcanic ash was not deposited as visible layers, but only as a few tiny volcanic glass particles scattered in the lake sediments. “These small glass particles commonly are smaller than 50 micrometer“, explained GFZ-scientist Sabine Wulf.
“We applied a novel combination of chemical and microscopic methods to detect these fine traces in the lake sediments and to separate them for further analyses.“ Geochemical analyses of individual glass shards and their comparison with volcanic ash from the source region on Island ideally allows to precisely tracing back the corresponding volcanic eruption.
Moreover, this approach allows reconstructing the distribution of volcanic ash clouds from eruptions in the past over large areas and thus provides new insights into past wind conditions.
This study was carried out within the frame of the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analyses, www.iclea.de) funded by the Helmholtz Association and are a contribution to the TERENO observatory for climate and landscape evolution an North-Eastern Germany coordinated by the GFZ.
Sabine Wulf, Nadine Dräger, Florian Ott, Johanna Serb, Oona Appelt, Esther Guðmundsdóttir, Christel van den Bogaard, Michał Słowinski, Mirosław Błaszkiewicz, Achim Brauer: “Holocene tephrostratigraphy of varved sediment records from Lakes Tiefer See (NE Germany) and Czechowskie (N Poland)”, Quaternary Science Reviews 132(2016), January 2016, DOI: http://dx.doi.org/10.1016/j.quascirev.2015.11.007
Dipl.Met. Franz Ossing | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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Summary and Keywords
The overwhelming majority of the scientific community agrees that climate change (CC) is occurring and is caused by anthropogenic, or human-caused, forcing. The global populace is aware of this phenomenon but appears to be unconcerned about CC and is slow to adopt potential mitigative actions. CC is a unique and complex phenomenon affected by various kinds of uncertainty, rendering communicative efforts particularly challenging. The compound and, potentially, conflicting uncertainties inherent in CC engender public ambivalence about the issue. The treatment of uncertainty in the Intergovernmental Panel on Climate Change’s (IPCC’s) reports have been shown to be confusing to policymakers and the general public, further confounding public outreach efforts. Given diverse communication styles and the multifaceted nature of CC, an assortment of strategies has been recommended to maximize understanding and increase salience. In particular, using evidence-based approaches to communicate about probabilistic outcomes in CC increases communicative efficiency.
Access to the complete content on Oxford Research Encyclopedia of Climate Science requires a subscription or purchase. Public users are able to search the site and view the abstracts and keywords for each book and chapter without a subscription.
If you have purchased a print title that contains an access token, please see the token for information about how to register your code. | <urn:uuid:1009eede-fd9c-4164-b1ee-9feb811a7571> | 3.1875 | 267 | Truncated | Science & Tech. | 11.794333 | 95,478,695 |
Eukaryotes are a very diverse group, and their cell structures are equally diverse. Many have cell walls; many do not. Many have chloroplasts, derived from primary, secondary, or even tertiary endosymbiosis; and many do not. Some groups have unique structures, such as the cyanelles of the glaucophytes , the haptonema of the haptophytes , or the ejectisomes of the cryptomonads . Other structures, such as pseudopods , are found in various eukaryote groups in different forms, such as the lobose amoebozoans or the reticulose foraminiferans .
Today, mitochondria are found in fungi, plants, and animals, and they use oxygen to produce energy in the form of ATP molecules, which cells then employ to drive many processes. Scientists believe that mitochondria evolved from aerobic , or oxygen-consuming, prokaryotes. In comparison, chloroplasts are found in plant cells and some algae, and they convert solar energy into energy-storing sugars such as glucose. Chloroplasts also produce oxygen, which makes them necessary for all life as we know it. Scientists think chloroplasts evolved from photosynthetic prokaryotes similar to modern-day cyanobacteria (Figure 4). Today, we classify prokaryotes and eukaryotes based on differences in their cellular contents (Figure 5). | <urn:uuid:48b7dcca-4b6b-47ab-8417-5f6a4506533b> | 4.1875 | 295 | Knowledge Article | Science & Tech. | 17.957359 | 95,478,700 |
The dust cycle is critically important for the current climate of Mars. The radiative effects of dust impact the thermal and dynamical state of the atmosphere [1,2,3]. Although dust is present in the Martian atmosphere throughout the year, the level of dustiness varies with season. The atmosphere is generally the dustiest during northern fall and winter and the least dusty during northern spring and summer . Dust particles are lifted into the atmosphere by dust storms that range in size from meters to thousands of kilometers across . Regional storm activity is enhanced before northern winter solstice (Ls~200 degrees - 240 degrees), and after northern solstice (Ls~305 degrees - 340 degrees ), which produces elevated atmospheric dust loadings during these periods [5,6,7]. These pre- and post- solstice increases in dust loading are thought to be associated with transient eddy activity in the northern hemisphere with cross-equatorial transport of dust leading to enhanced dust lifting in the southern hemisphere . Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles [8,9,10]. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading. | <urn:uuid:1af45575-631f-47c6-a623-736786706c94> | 3.8125 | 329 | Knowledge Article | Science & Tech. | 32.822727 | 95,478,701 |
The sudden increase in the temperature across most parts of the US seems to be impacting the acceptance of climate science for the Americans. There has been a study conducted in this regard which explains, the world is getting warmer due to one major factor and that is- human activity.
According to the longest-running surveys conducted on Americans and their attitudes regarding the climate change, more than 73% of the American public now thinks there is a solid evidence of global warming. 60% of the population in the US believes that the warming is caused due to human influences, in some parts. Both of the findings are estimated to be higher in the survey that was conducted by the University of Michigan and Muhlenberg College in the year 2008.
According to the National Ocean and Atmospheric Administration, the latest poll was held in May and it was recorded to be hotter than any other survey conducted in May in the last 124 years of record keeping. Chris Borick, the director of the Muhlenberg College Institute of Public Opinion was reported saying that there are several shreds of evidence that signify that weather is a contributing factor to understand the changing climate. However, there are numerous other factors to name. People complain that they are experiencing a different climate compared to the climate they used to experience in the past.
Americans are now becoming more confident to speak in this regard. According to the latest survey, while 90% of the Democrats believe that there is a solid evidence of change in climate, less than 50% of the Republicans believe the same. The hot climate has persisted in several parts of the U.S. this May with Los Angeles showing an overnight increase in temperature at 79°F on 7th of July. More than 80 million people from cities like Denver and Colorado have been shifted to safe locations in the recent weeks because of the dramatically increasing heat. | <urn:uuid:071512a3-36be-46e4-88b4-3b4f2a93bb9e> | 3.21875 | 370 | News Article | Science & Tech. | 37.879967 | 95,478,703 |
Precise 'weight check' of black hole
A research group led by Kyoko Onishi at the SOKENDAI (The Graduate University for Advanced Studies), including a researcher in the National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS), observed the barred spiral galaxy NGC 1097 with ALMA and found that the central supermassive black hole (SMBH) has a mass 140 million times the mass of the Sun.
This is the central region of NGC 1097 observed with ALMA. The velocity of the HCN gas is shown in the color and overlaid on the optical image taken by the Hubble Space Telescope. Red indicates gas is moving away from us while purple is coming closer to us.
Credit: ALMA (ESO/NAOJ/NRAO), K. Onishi (SOKENDAI), NASA/ESA Hubble Space Telescope
Since galaxies are believed to have co-evolved with SMBHs, SMBH mass is an important parameter in understanding their relation in the context of galaxy evolution. This research result is based on the ALMA observation data obtained within a two-hour observation, which demonstrates the outstanding capacity of ALMA in the SMBH mass measurement.
It is thought that a majority of the galaxies in the universe have a massive black hole in the galactic center. Since these black holes have masses of several millions to tens of billions of solar masses, they are called "supermassive black holes (SMBHs)".
Recent observation results suggest the correlation between the SMBH mass and the central bulge mass/luminosity of the host galaxy. Such correlation indicates that SMBHs may have a key role in the growth and evolution of galaxies.
SMBH mass is an essential parameter to reveal the correlation between the SMBH and the host galaxy. There are several methods to derive the SMBH mass, one of which is using proper motion of stars and megamasers (astrophysical objects that emit strong radio waves) around the SMBH to estimate the gravity of the SMBH applied to the observed objects.
This measurement method, however, is difficult and not suitable for the most galaxies because it requires observations of the regions around the SMBH with very high angular resolution (*1 and *2). Another method is using ionized gas dynamics distributed in the host galaxy bulge.
Ionized gas, however, is easily affected by non-circular motion such as inflow or outflow of gas, in addition to the gravity of the SMBH. This makes it difficult to accurately measure SMBH mass for a large number of galaxies. The method most commonly used to estimate SMBH mass is the one using stellar dynamics in host galaxies, although its application is rather limited to elliptical galaxies and thus it won't be a versatile SMBH mass measurement method applicable to wide ranging types of galaxies.
An alternative to these conventional methods is to derive the SMBH mass from molecular gas dynamics in the central region of a galaxy, which was formulated by Davis et al. at the European Southern Observatory (ESO). This method has the advantage that molecular gas is less susceptible to environmental conditions compared to stars and ionized gas, and therefore the motion affected by SMBH gravity can be measured more easily. Davis et al. made observations of a galaxy NGC 4526 for tens of hours with a radio telescope called CARMA and estimated the mass of the central SMBH.
Observations with ALMA:
A research team led by Kyoko Onishi, a doctoral student at the SOKENDAI (The Graduate University for Advanced Studies) doing her research at the National Astronomical Observatory of Japan (NAOJ), took on a challenge to derive the mass of the SMBH in the central region of the galaxy NGC 1097 (*3) using ALMA observation data. ALMA's high sensitivity enables the team to measure gas velocity with high accuracy.
"While NGC 4526, observed by a team led by Davis, is a lenticular galaxy, NGC 1097 is a barred spiral galaxy. Recent observation results indicate the relationship between SMBH mass and host galaxy properties varies depending on the type of galaxies, which makes it more important to derive accurate SMBH masses in various types of galaxies," Onishi said.
The research team made precise measurement of the distribution and kinematics of molecular gas by observing emission lines from hydrogen cyanide (HCN) and formyl cation (HCO+) with ALMA, and then examined the gravitational motion of the molecular gas by making some astrophysical models.
Since the gravity applied to the molecular gas differs depending on the SMBH mass as well as the density and distribution of stars in the bulge, the gas motion was calculated by making models assuming various cases in order to find a model which is best fitted for the observation data. As a result of the calculation, it was found that the central SMBH of NGC1097 has a mass 140 million times the solar mass. This is the first SMBH mass measurement using this method in late-type galaxies (e.g. spiral and barred spiral galaxies).
Onishi said, expressing her expectations for future ALMA observations, "We could obtain the kinematics data of the central molecular gas in NGC 1097 within a two-hour ALMA observation. To reveal the relation between the SMBH and the host galaxy, we need to derive more SMBH masses in various types of galaxies. ALMA will enable us to observe a large number of galaxies in a practical length of time."
Measuring the mass of SMBHs is the first step to solving the long-standing mysteries about how galaxies and SMBHs have been formed and co-evolved. This research assures ALMA's capability in this field.
*1) The method to derive the SMBH mass using the proper motion of stars around the SMBH is applicable only to the black hole at the center of our Milky Way galaxy. This method cannot be extended to other galaxies, which are too far to observe individual stars in the central region separately.
*2) In 1993, a high-velocity maser was observed in the central region of the galaxy NGC4258 with the 45-m radio telescope at the NAOJ Nobeyama Radio Observatory. This was the first observational evidence for the presence of a SMBH. However this method cannot be used to derive SMBH masses in a majority of galaxies because only a very scarce number of masers have been found around SMBHs.
*3) NGC 1097 is a barred spiral galaxy about 47 million light years away in the direction of the constellation of Fornax.
Paper / Research Team:
This observation result was published Onishi et al. "A Measurement of the Black-Hole Mass in NGC 1097 using ALMA" in the Astrophysical Journal, issued in June 2015.
This research was conducted by:
This research is supported by JSPS Grants-in-Aid for Scientific Research (No. 26*368).
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
Graduate student, SOKENDAI (The Graduate University for Advanced Studies), Japan
Chief Public Information Officer, National Astronomical Observatory of Japan
Masaaki Hiramatsu | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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I'll also walk you through some of the different scenarios and ways in which you can validate an XML document with an XSD schema programmatically (see Table 1). NET Framework 2.0 means you can perform XML data validation against a Document Type Definition (DTD) or an XML schema. XSD schema-based validation is the industry-accepted standard and will be the method of XML validation in this article.
You specify the validation settings as well as a Validation Event Handler method using the Xml Reader Settings object. I won't explain how to validate XML data using DTDs because those are not typically used outside legacy applications.
When a call to validate fails to parse the document, the error may be retrieved using last_error.
On errors not related to the XML parsing methods will throw exceptions. The Best Available backend type will check which backends are available and give you the "best" of those.
You also set a factory attribute to specify the parser language to use.
(For SAX parsing, on the other hand, you set a property on the parser generated by the factory).
To be notified of validation errors in an XML document, the following must be true: It is helpful to start by defining the constants you will use when configuring the factory.
These are the same constants you define when using XML Schema for SAX parsing, and they are declared at the beginning of the Because JAXP-compliant parsers are not namespace-aware by default, it is necessary to set the property for schema validation to work.
Let's review some XML basics before diving into how the new features in XML can help you validate XML data more easily. An XML document contains elements, attributes, and values of primitive data types.XML data is valid when the elements and the content of the individual elements in the XML data conform to the declared data types specified in the schema or DTD. NET is handled primarily by the classes present in a handful of namespaces: System. The classes that are commonly employed to validate the XML document are Xml Reader, Xml Reader Settings, Xml Schema Set, and Xml Node Reader. Xml namespace is probably the most significant of these namespaces if only because it includes classes such as Xml Document, Xml Node Reader, Xml Reader, and Xml Reader Settings, which are critical in validating XML data.(To learn more about XML Schema, you can review the online tutorial, XML Schema Part 0: Primer.At the end of this section, you will also learn how to use an XML Schema definition to validate a document that contains elements from multiple namespaces. | <urn:uuid:ffb01138-5ec8-4917-818b-79ab3ba1e418> | 2.703125 | 546 | Documentation | Software Dev. | 45.479679 | 95,478,710 |
The combustion of biomass for energy production is attracting a growing interest academically and industrially as a means to reduce the sector’s impact on climate forcing. Modelling will play a key role in the design of optimal biomass combustion systems, however there is a need to adapt currently adopted models for solid fuel combustion to take into account the unique challenges that biomass combustion introduces. Among these is the irregular shapes of biomass particles, which tend to depart significantly from the ideally spherical assumption that is widely adopted. Studies into investigating the impact of these shape irregularities on radiative transfer to the particle, the dominant mode of heat transfer at combustion temperatures, to better represent the ignition and combustion of biomass.
For further information please contact Professor Derek B Ingham on firstname.lastname@example.org | <urn:uuid:b1f525c4-e6f4-4b1c-a2da-06d4a7f95f33> | 2.671875 | 160 | Knowledge Article | Science & Tech. | 13.384216 | 95,478,721 |
Novel genetic engineered yeast strains (Saccharomyces cerevisae) have been established that produce increased ethanol yield while simultaneously reduce the production of the unwanted by-product glycerol. It is a strong industrial interest to reduce the glycerol formation during glucose catabolism and thereby increasing ethanol yield, also because glycerol disturbs the distillation process. Past approaches to reduce glycerol formation based e.g. on the deletion of either one or the two genes gpd1 and gpd2 of glycerol-3-phosphate dehydrogenase (GPDH), which is the rate-controlling enzyme in the glycerol formation pathway of the yeast Saccharomyces cerevisae. These isoenzymes play also a crucial role in osmoregulation and redox balance. While single deletion of either gpd1 or gpd2 does not noticeble decrease glycerol production, the gpd1∆gpd2∆ double deletion strain produces no glycerol, however with the negative side effect that growth and ethanol production is abolished under anaerobic conditions and strongly reduced under aerobic conditions.<br><br> In the novel genetic engineering approaches, a) the Gpd1 enzyme activity is only partly reduced in a gpd2∆-deleted CEN-PK113 yeast strain background by replacing the strong natural gpd1 promotor by a weak TEF1 promotor mutant or b) both enzyme activities of GPD1 and GPD2 are partly reduced. The strains with reduced GPD1 and GPD2 activity show an increase in ethanol production by 2-5% and a reduction in glycerol formation by 61-88% compared to wild type and a slight better growth rate than the TEFmut:GPD1 gpd2∆-strain (ethanol increase: 6,3%; glycerol formation reduction by 64%).
The technology was developed at the Technische Universität Berlin.
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firstname.lastname@example.org | TechnologieAllianz e.V.
New Lithium Salts of Pentafluorophenylamide Anions as Electrolytes in Lithium Ionic Batteries
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Gratings on glass surfaces
28.03.2017 | TechnologieAllianz e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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The power spectrum of a time series describes the distribution of power into frequency components composing that signal. According to Fourier analysis any physical signal can be decomposed into a number of discrete frequencies, or a spectrum of frequencies over a continuous range. The statistical average of a certain signal or sort of signal (including noise) as analyzed in terms of its frequency content, is called its spectrum.
When the energy of the signal is concentrated around a finite time interval, especially if its total energy is finite, one may compute the energy spectral density. More commonly used is the power spectral density (or simply power spectrum), which applies to signals existing over all time, or over a time period large enough (especially in relation to the duration of a measurement) that it could as well have been over an infinite time interval. The power spectral density (PSD) then refers to the spectral energy distribution that would be found per unit time, since the total energy of such a signal over all time would generally be infinite. Summation or integration of the spectral components yields the total power (for a physical process) or variance (in a statistical process), identical to what would be obtained by integrating over the time domain, as dictated by Parseval's theorem.
The spectrum of a physical process often contains essential information about the nature of . For instance, the pitch and timbre of a musical instrument are immediately determined from a spectral analysis. The color of a light source is determined by the spectrum of the electromagnetic wave's electric field as it fluctuates at an extremely high frequency. Obtaining a spectrum from time series such as these involves the Fourier transform, and generalizations based on Fourier analysis. In many cases the time domain is not specifically employed in practice, such as when a dispersive prism is used to obtain a spectrum of light in a spectrograph, or when a sound is perceived through its effect on the auditory receptors of the inner ear, each of which is sensitive to a particular frequency.
However this article concentrates on situations in which the time series is known (at least in a statistical sense) or directly measured (such as by a microphone sampled by a computer). The power spectrum is important in statistical signal processing and in the statistical study of stochastic processes, as well as in many other branches of physics and engineering. Typically the process is a function of time, but one can similarly discuss data in the spatial domain being decomposed in terms of spatial frequency.
- 1 Explanation
- 2 Definition
- 3 Estimation
- 4 Properties
- 5 Related concepts
- 6 Applications
- 7 See also
- 8 Notes
- 9 References
- 10 External links
Any signal that can be represented as a variable that varies in time has a corresponding frequency spectrum. This includes familiar entities such as visible light (perceived as color), musical notes (perceived as pitch), radio/TV (specified by their frequency, or sometimes wavelength) and even the regular rotation of the earth. When these signals are viewed in the form of a frequency spectrum, certain aspects of the received signals or the underlying processes producing them are revealed. In some cases the frequency spectrum may include a distinct peak corresponding to a sine wave component. And additionally there may be peaks corresponding to harmonics of a fundamental peak, indicating a periodic signal which is not simply sinusoidal. Or a continuous spectrum may show narrow frequency intervals which are strongly enhanced corresponding to resonances, or frequency intervals containing almost zero power as would be produced by a notch filter.
In physics, the signal might be a wave, such as an electromagnetic wave, an acoustic wave, or the vibration of a mechanism. The power spectral density (PSD) of the signal describes the power present in the signal as a function of frequency, per unit frequency. Power spectral density is commonly expressed in watts per hertz (W/Hz).
When a signal is defined in terms only of a voltage, for instance, there is no unique power associated with the stated amplitude. In this case "power" is simply reckoned in terms of the square of the signal, as this would always be proportional to the actual power delivered by that signal into a given impedance. So one might use units of V2 Hz−1 for the PSD and V2 s Hz−1 for the ESD (energy spectral density) even though no actual "power" or "energy" is specified.
Sometimes one encounters an amplitude spectral density (ASD), which is the square root of the PSD; the ASD of a voltage signal has units of V Hz−1/2. This is useful when the shape of the spectrum is rather constant, since variations in the ASD will then be proportional to variations in the signal's voltage level itself. But it is mathematically preferred to use the PSD, since only in that case is the area under the curve meaningful in terms of actual power over all frequency or over a specified bandwidth.
Mathematically, it is not necessary to assign physical dimensions to the signal or to the independent variable. In the following discussion the meaning of x(t) will remain unspecified, but the independent variable will be assumed to be that of time.
Energy spectral density
Energy spectral density describes how the energy of a signal or a time series is distributed with frequency. Here, the term energy is used in the generalized sense of signal processing; that is, the energy of a signal is
The energy spectral density is most suitable for transients—that is, pulse-like signals—having a finite total energy. In this case, Parseval's theorem gives us an alternate expression for the energy of the signal:
is the Fourier transform of the signal and is the frequency in Hz, i.e., cycles per second. Often used is the angular frequency . Since the integral on the right-hand side is the energy of the signal, the integrand can be interpreted as a density function describing the energy per unit frequency contained in the signal at the frequency . In light of this, the energy spectral density of a signal is defined as
As a physical example of how one might measure the energy spectral density of a signal, suppose represents the potential (in volts) of an electrical pulse propagating along a transmission line of impedance , and suppose the line is terminated with a matched resistor (so that all of the pulse energy is delivered to the resistor and none is reflected back). By Ohm's law, the power delivered to the resistor at time is equal to , so the total energy is found by integrating with respect to time over the duration of the pulse. To find the value of the energy spectral density at frequency , one could insert between the transmission line and the resistor a bandpass filter which passes only a narrow range of frequencies (, say) near the frequency of interest and then measure the total energy dissipated across the resistor. The value of the energy spectral density at is then estimated to be . In this example, since the power has units of V2 Ω−1, the energy has units of V2 s Ω−1 = J, and hence the estimate of the energy spectral density has units of J Hz−1, as required. In many situations, it is common to forgo the step of dividing by so that the energy spectral density instead has units of V2 s Hz−1.
This definition generalizes in a straightforward manner to a discrete signal with an infinite number of values such as a signal sampled at discrete times :
where is the discrete Fourier transform of and is the complex conjugate of The sampling interval is needed to keep the correct physical units and to ensure that we recover the continuous case in the limit ; however, in the mathematical sciences, the interval is often set to 1.
Power spectral density
The above definition of energy spectral density is suitable for transients (pulse-like signals) whose energy is concentrated around one time window; then the Fourier transforms of the signals generally exist. For continuous signals over all time, such as stationary processes, one must rather define the power spectral density (PSD); this describes how power of a signal or time series is distributed over frequency, as in the simple example given previously. Here, power can be the actual physical power, or more often, for convenience with abstract signals, is simply identified with the squared value of the signal. For example, statisticians study the variance of a function over time (or over another independent variable), and using an analogy with electrical signals (among other physical processes), it is customary to refer to it as the power spectrum even when there is no physical power involved. If one were to create a physical voltage source which followed and applied it to the terminals of a 1 ohm resistor, then indeed the instantaneous power dissipated in that resistor would be given by x2 watts.
The average power P of a signal over all time is therefore given by the following time average:
Note that a stationary process, for instance, may have a finite power but an infinite energy. After all, energy is the integral of power, and the stationary signal continues over an infinite time. That is the reason that we cannot use the energy spectral density as defined above in such cases.
In analyzing the frequency content of the signal , one might like to compute the ordinary Fourier transform ; however, for many signals of interest the Fourier transform does not formally exist.[N 1] Because of this complication one can as well work with a truncated Fourier transform where the signal is integrated only over a finite interval [0, T]:
In the latter form (for a stationary random process), one can make the change of variables and with the limits of integration (rather than [0,T]) approaching infinity, the resulting power spectral density and the autocorrelation function of this signal are seen to be Fourier transform pairs (Wiener–Khinchin theorem). The autocorrelation function is a statistic defined as
or more generally as
in the case that X(t) is complex-valued. Provided that is absolutely integrable (which is not always true),
Many authors use this equality to actually define the power spectral density.
The power of the signal in a given frequency band (or ) can be calculated by integrating over frequency. Since , an equal amount of power can be attributed to positive and negative frequencies, which accounts for the factor of 2 in the following form (such trivial factors dependent on conventions used):
More generally, similar techniques may be used to estimate a time-varying spectral density. In this case the truncated Fourier transform defined above over the finite time interval (0, T) is not evaluated in the limit of T approaching infinity. This results in decreased spectral coverage and resolution since frequencies of less than 1/T are not sampled, and results at frequencies which are not an integer multiple of 1/T are not independent. Just using a single such time series, the estimated power spectrum will be very "noisy", however this can be alleviated if it is possible to evaluate the expected value (in the above equation) using a large (or infinite) number of short-term spectra corresponding to statistical ensembles of realizations of x(t) evaluated over the specified time window.
This definition of the power spectral density can be generalized to discrete time variables . As above we can consider a finite window of with the signal sampled at discrete times for a total measurement period . Then a single estimate of the PSD can be obtained through summation rather than integration:
As before, the actual PSD is achieved when N (and thus T) approach infinity and the expected value is formally applied. In a real-world application, one would typically average this single-measurement PSD over many trials to obtain a more accurate estimate of the theoretical PSD of the physical process underlying the individual measurements. This computed PSD is sometimes called a periodogram. This periodogram converges to the true PSD as the number of estimates as well as the averaging time interval T approach infinity (Brown & Hwang).
If two signals both possess power spectral densities, then the #Cross-spectral density can similarly be calculated; as the PSD is related to the autocorrelation, so is the cross-spectral density related to the cross-correlation.
Properties of the power spectral density
Some properties of the PSD include:
- The spectrum of a real valued process (or even a complex process using the above definition) is real and an even function of frequency: .
- If the process is continuous and purely indeterministic[clarification needed], the autocovariance function can be reconstructed by using the Inverse Fourier transform
- The PSD can be used to compute the variance (net power) of a process by integrating over frequency:
- Being based on the fourier transform, the PSD is a linear function of the autocovariance function in the sense that if is decomposed into two functions , then
Given two signals and , each of which possess power spectral densities and , it is possible to define a cross-spectral density (CSD) given by
The cross-spectral density (or 'cross power spectrum') is thus the Fourier transform of the cross-correlation function.
where is the cross-correlation of and .
By an extension of the Wiener–Khinchin theorem, the Fourier transform of the cross-spectral density is the cross-covariance function. In light of this, the PSD is seen to be a special case of the CSD for .
For discrete signals xn and yn, the relationship between the cross-spectral density and the cross-covariance is
The goal of spectral density estimation is to estimate the spectral density of a random signal from a sequence of time samples. Depending on what is known about the signal, estimation techniques can involve parametric or non-parametric approaches, and may be based on time-domain or frequency-domain analysis. For example, a common parametric technique involves fitting the observations to an autoregressive model. A common non-parametric technique is the periodogram.
- The spectral density of and the autocorrelation of form a Fourier transform pair (for PSD versus ESD, different definitions of autocorrelation function are used). This result is known as Wiener–Khinchin theorem.
- One of the results of Fourier analysis is Parseval's theorem which states that the area under the energy spectral density curve is equal to the area under the square of the magnitude of the signal, the total energy:
- The above theorem holds true in the discrete cases as well. A similar result holds for power: the area under the power spectral density curve is equal to the total signal power, which is , the autocorrelation function at zero lag. This is also (up to a constant which depends on the normalization factors chosen in the definitions employed) the variance of the data comprising the signal.
- The spectral centroid of a signal is the midpoint of its spectral density function, i.e. the frequency that divides the distribution into two equal parts.
- The spectral edge frequency of a signal is an extension of the previous concept to any proportion instead of two equal parts.
- The spectral density is a function of frequency, not a function of time. However, the spectral density of small windows of a longer signal may be calculated, and plotted versus time associated with the window. Such a graph is called a spectrogram. This is the basis of a number of spectral analysis techniques such as the short-time Fourier transform and wavelets.
- A "spectrum" generally means the power spectral density, as discussed above, which depicts the distribution of signal content over frequency. This is not to be confused with the frequency response of a transfer function which also includes a phase (or equivalently, a real and imaginary part as a function of frequency). For transfer functions, (e.g., Bode plot, chirp) the complete frequency response may be graphed in two parts, amplitude versus frequency and phase versus frequency (or less commonly, as real and imaginary parts of the transfer function). The impulse response (in the time domain) , cannot generally be uniquely recovered from the amplitude spectral density part alone without the phase function. Although these are also fourier transform pairs, there is no symmetry (as there is for the autocorrelation) forcing the fourier transform to be real-valued. See spectral phase and phase noise.
The concept and use of the power spectrum of a signal is fundamental in electrical engineering, especially in electronic communication systems, including radio communications, radars, and related systems, plus passive remote sensing technology. Electronic instruments called spectrum analyzers are used to observe and measure the power spectra of signals.
The spectrum analyzer measures the magnitude of the short-time Fourier transform (STFT) of an input signal. If the signal being analyzed can be considered a stationary process, the STFT is a good smoothed estimate of its power spectral density.
Primordial fluctuations, density variations in the early universe, are quantified by a power spectrum which gives the power of the variations as a function of spatial scale.
- Noise spectral density
- Spectral density estimation
- Spectral efficiency
- Spectral power distribution
- Brightness temperature
- Colors of noise
- Spectral leakage
- Window function
- Whittle likelihood
- Some authors (e.g. Risken) still use the non-normalized Fourier transform in a formal way to formulate a definition of the power spectral density
- P Stoica & R Moses (2005). "Spectral Analysis of Signals" (PDF).
- P Stoica & R Moses (2005). "Spectral Analysis of Signals" (PDF).
- P Stoica & R Moses (2005). "Spectral Analysis of Signals" (PDF).
- Gérard Maral (2003). VSAT Networks. John Wiley and Sons. ISBN 0-470-86684-5.
- Michael Peter Norton & Denis G. Karczub (2003). Fundamentals of Noise and Vibration Analysis for Engineers. Cambridge University Press. ISBN 0-521-49913-5.
- Michael Cerna & Audrey F. Harvey (2000). "The Fundamentals of FFT-Based Signal Analysis and Measurement" (PDF).
- Alessandro Birolini (2007). Reliability Engineering. Springer. p. 83. ISBN 978-3-540-49388-4.
- Oppenheim; Verghese. Signals, Systems, and Inference. pp. 32–4.
- Stein, Jonathan Y. (2000). Digital Signal Processing: A Computer Science Perspective. Wiley. p. 115.
- Hannes Risken (1996). The Fokker–Planck Equation: Methods of Solution and Applications (2nd ed.). Springer. p. 30. ISBN 9783540615309.
- Fred Rieke; William Bialek & David Warland (1999). Spikes: Exploring the Neural Code (Computational Neuroscience). MIT Press. ISBN 978-0262681087.
- Scott Millers & Donald Childers (2012). Probability and random processes. Academic Press. pp. 370–5.
- The Wiener–Khinchin theorem makes sense of this formula for any wide-sense stationary process under weaker hypotheses: does not need to be absolutely integrable, it only needs to exist. But the integral can no longer be interpreted as usual. The formula also makes sense if interpreted as involving distributions (in the sense of Laurent Schwartz, not in the sense of a statistical Cumulative distribution function) instead of functions. If is continuous, Bochner's theorem can be used to prove that its Fourier transform exists as a positive measure, whose distribution function is F (but not necessarily as a function and not necessarily possessing a probability density).
- Dennis Ward Ricker (2003). Echo Signal Processing. Springer. ISBN 1-4020-7395-X.
- Robert Grover Brown & Patrick Y.C. Hwang (1997). Introduction to Random Signals and Applied Kalman Filtering. John Wiley & Sons. ASIN 0471128392. ISBN 0-471-12839-2.
- Storch, H. Von; F. W Zwiers (2001). Statistical analysis in climate research. Cambridge University Press. ISBN 0-521-01230-9.
- An Introduction to the Theory of Random Signals and Noise, Wilbur B. Davenport and Willian L. Root, IEEE Press, New York, 1987, ISBN 0-87942-235-1
- William D Penny (2009). "Signal Processing Course, chapter 7". | <urn:uuid:88e4d4ac-37ca-4167-8387-210eeccedfcc> | 3.703125 | 4,305 | Knowledge Article | Science & Tech. | 38.738411 | 95,478,743 |
Epsom-like salts believed to be common on Mars may be a major source of water there, say geologists at Indiana University Bloomington and Los Alamos National Laboratory. In their report in this weeks Nature, the scientists also speculate that the salts will provide a chemical record of water on the Red Planet.
"The Mars Odyssey orbiter recently showed that there may be as much as 10 percent water hidden in the Martian near-surface," said David Bish, Haydn Murray Chair of Applied Clay Mineralogy at IU and a co-author of the report. "We were able to show that under Mars-like conditions, magnesium sulfate salts can contain a great deal of water. Our findings also suggest that the kinds of sulfates we find on Mars could give us a lot of insight into the history of water and mineral formation there."
The scientists learned that magnesium sulfate salts are extremely sensitive to changes in temperature, pressure and humidity. For that reason, the scientists argue that information contained in the salts could be easily lost if samples were brought back to Earth for study. Instead, they say, future missions to Mars should measure the properties of the salts on site.
David Bricker | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
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Epoch of Reionisation
The quest to try and understand how the Universe came to look the way it does lies at the heart of astronomy. However when viewing the Universe from a historical perspective astronomers are immediately faced with fundamental unanswered questions. We believe the Universe has a finite age, and as a result, that there must have been an epoch when galaxies appeared for the first time. However we do not know how this first generation of galaxies formed. We do not know what they looked like, or how big they were. Indeed, we do not even know when galaxies first played an important role in the evolution of our Universe.
Over the last decade the composition of the Universe has been determined to high accuracy. Understanding the first galaxies now represents the next great challenge for observational cosmology. Currently, our knowledge of the first galaxies is currently limited to two primary facts. Astronomers believe that our Universe began with the “Big Bang”, after which the initially very hot Universe expanded and cooled. When the Universe cooled sufficiently that the gas of protons and electrons “recombined” to form atomic hydrogen, light was able to travel freely for the first time. We observe this light today as a diffuse glow on the sky known as the Cosmic Microwave Background, which describes the state of the Universe 380,000 years after the Big Bang. Small ripples of density observed at this time grew under the influence of gravity, forming the sites of modern-day galaxies some 13.7 billion years later. Some of the atomic hydrogen in the early Universe formed stars within galaxies, but most is located in the space between galaxies. The current belief is that the first galaxies appeared a few hundred million years after the Big Bang, resulting in a large UV flux that reionised hydrogen in the Universe. The time when galaxies first became important can be defined as the instant when the combined galaxies in the Universe had produced enough ultra-violet light to reionise all of the hydrogen. Astronomers refer to this as the end of the Dark Ages of the Universe.
There are several key observational areas in which substantial progress will be made in the study of the first galaxies during the coming decade. The first of these are forthcoming programs, with an emphasis on obtaining data beyond the current redshift, or distance frontier, using new surveys and instruments. Following the success of the Hubble Space Telescope (HST), the flagship James Webb Space Telescope (JWST) is scheduled for launch in 2014. JWST is a large infrared optimised telescope that will be used to search for the high redshift galaxies thought to be responsible for the reionisation of the intergalactic hydrogen.
The advent of 30-meter class optical/IR telescopes in the next decade, such as the Giant Magellan telescope (GMT), will open a new window on the Universe allowing spectra to be taken of the earliest forming galaxies discovered with JWST. Much emphasis is also based on experiments to measure the redshifted 21 cm radio signal (Furlanetto et al. 2006; Morales & Wyithe 2010), which may provide the first direct probe of the neutral hydrogen in the high redshift Universe.
Radio telescopes such as the Murchison Widefield Array (MWA, now beginning to take data in Western Australia), will lead efforts in this exciting new field. Next generation ground-based surveys such as SkyMapper (Keller et al. 2007), will discover high redshift quasars, thus providing valuable additional targets for studies of the intervening intergalactic hydrogen using quasar absorption spectroscopy.
Finally, the Planck surveyor and other cosmic microwave background experiments will provide tighter limits on fundamental cosmological and astrophysical parameters, providing better constraints on the integrated ionisation history of the IGM. The goal of these observations will be to elucidate the physical history and origin of the first galaxies, which can only be achieved within a sophisticated physical framework.
Within this context, the development of theoretical models that include detailed physics of galaxy formation and intergalactic hydrogen will therefore play a key role. At the highest redshifts astronomers have only theoretical predictions to guide knowledge of the first galaxies and their interaction with intergalactic hydrogen prior to reionisation. Further developing these theoretical models and utilizing them in combination with observational data to better understand the evolution of the IGM during the Epoch of Reionisation underpin the proposed science program within the Astrophysics group.
Supervisor Profiles & Available Research Projects
- First stars and galaxies (observations, modeling)
- Gamma Ray Bursts as tracers of star formation during the epoch of reionization
- Galaxy formation
- Large-scale structure and cosmology
- The first sources in the universe and reionization
- Cosmological H11 regions
- Constraints on the dark matter particle looking at results from both cosmological structure formation and the Large Hadron Collider
- TBA: Lucy Forman (Date TBC) Wed 15 August, 2018 @12:00 PM, level 7Dr Luc[...]
- TBA: Lisa Drummond Wed 1 August, 2018 @12:00 PM, level 7Lisa Drummond, PhD[...]
- Pulsars as gravitational wave sources Wed 25 July, 2018 @12:00 PM, level 7Dr Matthew Pitkin,[...]
- Titans of the Early Universe: The origin of the most massive, high-redshift quasars Wed 18 July, 2018 @12:00 PM, level 7 Dr. Tyrone Woods,[...]
- Detectability of 21cm signal during the Epoch of Reionization with 21cm-LAE cross correlation Wed 11 July, 2018 @12:00 PM, level 7Shintaro Yoshiura,[...]
- Science vs Cinema: Star Trek II - Wrath of Khan Sun 8 Jul, 2018 @3.30 PM, NOVA cinemaDr. Rachael Liverm[...]
- The most powerful radio-sources in the southern hemisphere Mon 2 July, 2018 @12:00 PM, level 7 Dr. Sarah White, Re[...] | <urn:uuid:50834b67-616b-4b4d-b370-686dd866d61b> | 3.90625 | 1,245 | Content Listing | Science & Tech. | 40.868462 | 95,478,755 |
|CNIDARIA : ACTINIARIA : Edwardsiidae||SEA ANEMONES AND HYDROIDS|
Description: The column of this burrowing sea anemone is similar to Edwardsia claparedii but even more elongated. There are 16-32 tentacles, arranged in 3 cycles. The colour of the disc, tentacles and scapulus is translucent pale orange, usually patterned with opaque white or cream, tentacles plain or with white tips. The column is up to 70mm long and 5mm diameter, span of tentacles to 40mm.
This species was described as a new species, Edwardsia callianthus by Rawlinson in 1935 and this detailed description is available online here.
Habitat: Burrows in sand or gravel in moderate tidal streams. Occurs in sheltered localities from lower shore to the shallow sublittoral: usually abundant when present.
Distribution: Known only from a few localities in the Irish Sea and from the northern coast of France. May be more widely distributed but easily overlooked unless deliberately sought. Please notify any new records.
Similar Species: Different coloration from other Edwardsia spp., similar to Edwardsiella carnea but this lives amongst rocks. There are a number of other Edwardsia species in Scandinavia and France and this group of anemones are little studied, so more species may be present in our area.
Key Identification Features:
Distribution Map from NBN: Interactive map : National Biodiversity Network mapping facility, data for UK.
WoRMS: Species record : World Register of Marine Species.
|Picton, B.E. & Morrow, C.C. (2016). Edwardsia timida de Quatrefages, 1842. [In] Encyclopedia of Marine Life of Britain and Ireland. |
http://www.habitas.org.uk/marinelife/species.asp?item=D13440 Accessed on 2018-07-19
|Copyright © National Museums of Northern Ireland, 2002-2015| | <urn:uuid:5aed0ce6-3091-4780-9bff-e1d99b2fbf07> | 2.6875 | 422 | Knowledge Article | Science & Tech. | 40.102518 | 95,478,775 |
Wind speed is caused by air moving from high pressure to low pressure, usually due to changes in temperature. Note that wind direction is usually almost parallel to isobars (and not perpendicular as one might expect), due to the rotation of the earth.
Factors affecting wind speed
Wind speed is affected by a number of factors and situations, operating on varying scales (from micro to macro scales). These include the pressure gradient, Rossby waves and jet streams, and local weather conditions. There are also links to be found between wind speed and wind direction, notably with the pressure gradient and terrain conditions.
Pressure gradient is a term to describe the difference in air pressure between two points in the atmosphere or on the surface of the Earth. It is vital to wind speed, because the greater the difference in pressure, the faster the wind flows (from the high to low pressure) to balance out the variation. The pressure gradient, when combined with the Coriolis effect and friction, also influences wind direction.
Rossby waves are strong winds in the upper troposphere. These operate on a global scale and move from West to East (hence being known as Westerlies). The Rossby waves are themselves a different wind speed from what we experience in the lower troposphere.
Local weather conditions play a key role in influencing wind speed, as the formation of hurricanes, monsoons and cyclones as freak weather conditions can drastically affect the flow velocity of the wind.
The fastest wind speed not related to tornadoes ever recorded was during the passage of Tropical Cyclone Olivia on 10 April 1996: an automatic weather station on Barrow Island, Australia, registered a maximum wind gust of 408 km/h (220 kn; 253 mph; 113 m/s). The wind gust was evaluated by the WMO Evaluation Panel who found that the anemometer was mechanically sound and the gust was within statistical probability and ratified the measurement in 2010. The anemometer was mounted 10 m above ground level (and thus 64 m above sea level). During the cyclone, several extreme gusts of greater than 300 km/h (160 kn; 83 m/s) were recorded, with a maximum 5-minute mean speed of 176 km/h (95 kn; 110 mph; 49 m/s), the extreme gust factor was in the order of 2.27–2.75 times the mean wind speed. The pattern and scales of the gusts suggest that a mesovortex was embedded in the already strong eyewall of the cyclone.
The now second highest surface wind speed ever officially recorded is 372 km/h (231 mph; 103 m/s) at the Mount Washington (New Hampshire) Observatory: 6,288 ft (1917 m) above sea level in the US on 12 April 1934, using a heated anemometer. The anemometer, specifically designed for use on Mount Washington was later tested by the US National Weather Bureau and confirmed to be accurate.
Wind speeds within certain atmospheric phenomena (such as tornadoes) may greatly exceed these values but have never been accurately measured. Directly measuring these tornadic winds is rarely done as the violent wind would destroy the instruments. A method of estimating speed is to use Doppler on Wheels to sense the wind speeds remotely, and, using this method, the figure of 486 km/h (302 mph; 135 m/s) during the 1999 Bridge Creek–Moore tornado in Oklahoma on 3 May 1999 is often quoted as the highest-recorded surface wind speed, although another figure of 512 kilometres per hour (318 mph) has also been quoted for the same tornado. Yet another number used by the Center for Severe Weather Research for that measurement is 486 ± 32 km/h (302 ± 20 mph). However, speeds measured by Doppler radar are not considered official records.
An anemometer is one of the tools used to measure wind speed. A device consisting of a vertical pillar and three or four concave cups, the anemometer captures the horizontal movement of air particles (wind speed).
Another tool used to measure wind velocity includes a GPS combined with pilot tube. A fluid flow velocity tool, the Pitot tube is primarily used to determine the air velocity of an aircraft.
Design of structures
Wind speed is a common factor in the design of structures and buildings around the world. It is often the governing factor in the required lateral strength of a structure's design.
In the United States, the wind speed used in design is often referred to as a "3-second gust" which is the highest sustained gust over a 3-second period having a probability of being exceeded per year of 1 in 50 (ASCE 7-05). This design wind speed is accepted by most building codes in the United States and often governs the lateral design of buildings and structures.
In Canada, reference wind pressures are used in design and are based on the "mean hourly" wind speed having a probability of being exceeded per year of 1 in 50. The reference wind pressure (q) is calculated in Pascals using the following equation: q=(1/2)pV² where p is the air density in kg/m³ and V is wind speed in m/s.
Historically, wind speeds have been reported with a variety of averaging times (such as fastest mile, 3-second gust, 1-minute and mean hourly) which designers may have to take into account. To convert wind speeds from one averaging time to another, the Durst Curve was developed which defines the relation between probable maximum wind speed averaged over t seconds, Vt, and mean wind speed over one hour V3600.
- Beaufort scale
- Fujita scale and Enhanced Fujita Scale
- Prevailing wind
- Saffir–Simpson Hurricane Scale
- TORRO scale
- Wind direction
- Knot (unit)
- International Building Code (promulgator of NBC 2005)
- American Society of Civil Engineers (promulgator of ASCE 7-05)
- C.Michael Hogan. 2010. Abiotic factor. Encyclopedia of Earth. eds Emily Monosson and C. Cleveland. National Council for Science and the Environment Archived 2013-06-08 at the Wayback Machine.. Washington DC
- "World record wind gust". World Meteorological Association. Retrieved 12 February 2017.
- "Documentation and verification of the world extreme wind gust record: 113.3 m s–1 on Barrow Island, Australia, during passage of tropical cyclone Olivia" (PDF). Australian Meteorological and Oceanographic Journal.
- "The story of the world record wind". Mount Washington Observatory. Retrieved 26 January 2010.
- "Massive Okla. tornado had windspeed up to 200 mph". CBS News. 20 May 2013. Retrieved 17 May 2014.
- "Historical Tornadoes". National Weather Service.
- "Highest surface wind speed-Tropical Cyclone Olivia sets world record". World Record Academy. 26 January 2010. Retrieved 17 May 2014.
- Wurman, Joshua (2007). "Doppler On Wheels". Center for Severe Weather Research. Archived from the original on 2010-09-07.
- Koen, Joshua. "Make and Use an Anemometer to measure Wind Speed". www.ciese.org. Retrieved 2018-04-18.
- "Wind and Structures". Korea Science (in Korean). Retrieved 2018-04-18.
- NBC 2005 Structural Commentaries - Part 4 of Div. B, Comm. I
- ASCE 7-05 commentary Figure C6-4, ASCE 7-10 C26.5-1
- Media related to Wind speed at Wikimedia Commons | <urn:uuid:1eb6d2b4-018e-471f-bcf9-b367db063732> | 4.3125 | 1,585 | Knowledge Article | Science & Tech. | 57.014055 | 95,478,780 |
|Acoustics and Sound|
Physics of Sound Waves > s.a. fluids; Phonon;
* Properties: Sound waves are longitudinal in fluids, but can be both longitudinal and transverse (in general with different propagation speeds) in solids.
* Propagation speed: In an elastic solid it is v = (c/ρ)1/2, where c is the elastic constant; In a fluid, v = λ/τ, the ratio of the mean free length to mean free time; In a medium with negative specific heat, it is imaginary; In air, v is proportional to T 1/2.
* Most intense sound: Macroscopically, up to 500 psi; Sonoluminescence has more.
@ General references: Lindsay TPT(63); Campbell & Greated 87; Rossing AJP(87)jul; Bregman 90; Raichel 00; Borovitskaya 15 [I]; Goldsmith 16 [I].
@ Differential geometric viewpoint: Zloshchastiev APPB(99)gq/98 [superfluid He]; Bilić CQG(99)gq; Visser et al ht/01-conf [BECs and Lorentz symmetry violation]; Fischer & Visser EPL(03)gq/02 [phonons]; Visser & Molina-París NJP(10)-a1001 [barotropic irrotational fluid flow]; Gibbons & Warnick CP(11)-a1102 [geometry of sound rays in a wind]; Bensoam a1304; > s.a. lorentzian geometry; wormholes.
@ Acoustic torsion: Garcia de Andrade gq/03 [and superfluids], PRD(04), gq/04 [turbulence], PLA(05)gq [vorticity], PLA(05) [and breaking of acoustic Lorentz invariance].
@ Propagation in various media: Fletcher AJP(74)jun [gas, adiabatic assumption]; Martynov TMP(06) [liquids and gases]; Bacon TPT(12) [speed of sound in air vs temperature]; Deckert et al a1406 [quantum gas of interacting bosonic atoms]; Peano et al PRX(15) [unidirectional propagation]; > s.a. spin models; wave phenomena.
@ Related topics: NS(90)jan20, p56; NS(91)jan19, 38-41; Stenflo PLA(96) [acoustic gravity waves]; news pw(05)nov, pw(07)jan [superluminal]; Aref et al ch(16)-a1506 [quantum acoustics with surface acoustic waves].
Applications and Effects > s.a. black-hole
electromagnetism [electroacoustics]; sonoluminescence.
* Photoacoustics: The process of producing sound with light (the opposite of sonoluminescence), discovered by Alexander G Bell in the XIX century; Applied to detect tiny gas leaks by heating the gas with a laser [@ news pn(00)jun].
* Thermoacoustics: 1997, Engines so far are not very efficient, but they are ecological refrigerators or prime movers with no moving parts.
* In geophysics and astronomy: Sound waves probe the interior of the Earth, Moon, Sun, and other objects.
* In cosmology: Relativistic sound waves propagating in the early universe left an imprint that is still discernible in the cosmic microwave background and in the large-scale distribution of galaxies.
* Acoustic Time Reversal Mirrors: Devices that record a sound wave from a source and generate a new one that behaves as if the original traveled backwards in time; They have been tested in water, air and solids (more complicated, since there are two types of sound waves there), and they can be applied to locating defects in solids (airplanes, kidney stones).
@ General references: Munk ThSc(93)sep [ocean warming]; Kuperman & Lynch PT(04)oct [in shallow water]; news pn(06)jul [sand dunes].
@ Thermoacoustics: Swift PT(95)jul, Garrett AJP(04)jan [engines]; news pn(07)jun [turning heat into electricity].
@ Time reversal: news pn(95)nov; Fink CP(96), PT(97)mar; Fink SA(99)nov.
@ In cosmology: Eisenstein & Bennett PT(08)apr; Corasaniti & Melchiorri PRD(08).
@ Acoustic cloaking devices: news pw(08)jan; Chan Phy(11)jan [for ultrasonic water waves]; Popa et al PRL(11) + news bbc(11)jun; news pw(12)jan; news sci(13)mar [3D]; Zhu et al PRX(14) [acoustic PT symmetry and one-way cloaking].
@ Related topics: Snieder & Wapenaar PT(10)oct [imaging with ambient noise]; Altfeder et al PRL(10) + news ns(10)oct + focus(10)oct ["phonon tunneling" or "propagation across a vacuum"]; Lepri & Casati PRL(11) + news msnbc(11)may [one-way acoustic mirrors]; Torrent & Sánchez-Dehesa PRL(12) + news pw(12)may [acoustic analog of graphene]; news sn(13)jul, sfg(14)jan [levitation]; news pw(14)jan ["one-way circulator"]; Denardo et al AJP(14)feb [acoustic radiation force]; news pm(14)may [acoustic tractor beam]; Marzo et al PRL(18) [acoustic trap]; > s.a. casimir effect [acoustic analog]; Lasers; metamaterials; music [including hearing, psychoacoustics, architectural acoustics]; physics teaching; technology.
* Idea: Sound whose frequency is either higher than those audible by humans, or high enough that molecules of the medium experience almost no collisions over one period of the wave.
* Applications: In medicine, destroying cancer cells; Stopping internal bleeding (ASA meeting, 06.1998); Ultrasound imaging (1999, without physical contact through impedance matching); RUS, Resonant Ultrasound Spectroscopy, developed in 1988 by A Migliori for elasticity measurements; Ultrasound amplification by self-excited resonance (uaser), an acoustic analog of lasers.
@ General references: Maynard PT(96)jan [RUS]; Povey CP(98) [and food]; Maris SA(98)jan [picosecond pulses]; Cheeke 12.
@ Medical applications: Crum & Hynynen PW(96)aug; Vaezy et al pw(01)aug, ter Haar PT(01)dec [surgery]; Novario et al RNC(03) [medical diagnostic]; Wang et al PRL(13) [measuring local blood flow speed in living tissue].
@ Other applications: Potter et al PRL(14) [acoustic imaging technique to reveal cracks in structures]; news pw(15)feb [twisted light]; news pt(15)dec, pt(16)feb [super-resolution imaging].
* Sources: Some large mammals, such as elephants, rhinoceros and whales use f just below 20 Hz for communication; Volcanoes, meteorites, ocean swell (f ~ 0.2–0.3 Hz), tornadoes and hurricanes (from a location not in the eye), explosions; A background of about 70 db with f ~ 0.1–1 Hz is normal; The Earth's solid interior produces a constant hum of a few mHz.
* Propagation: Infrasound can travel around the world, using the vsound(h) dependance and low dispersion to heat; Diatomic molecules in the air do absorb energy from acoustic waves in the sonic range, but not from infrasound.
* Effects: Frequencies above 1 Hz can be sometimes felt with our bodies; Infrasound at about 17 Hz has been shown to induce a sense of uneasiness, sadness and anxiety in an audience.
* Applications: Monitor location and nature of avalanches, tornadoes and atmospheric physics, meteorite impacts, volcanoes, nuclear weapons tests.
@ References: Bedard & Georges PT(00)mar [atmospheric]; Hedlin & Romanowicz pw(06)aug [review and global network].
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Genetic engineering is one of the most amazing advancements made in the scientific field in modern times. It can be defined as the process of manipulating the DNA in order to modify it. The DNA is the blueprint of every organism, the building block if you will. As you can imagine, the ability to modify this very structure gives man almost godlike powers. Being able to modify DNA means you can potentially create anything out of a creature. Naturally, thanks to its immense potential for both good and bad, the scientific community and the laymen have responded variously to genetic engineering. Like everything else, even this great advancement has its own share of pitfalls. In this article, we will look at both sides of the issue.
Positive effects of genetic engineering:
We will first see how genetic engineering can be put to good use.
The biggest advantage of genetic engineering is, of course, in the field of diseases. Genetic diseases can be completely eliminated by the implementation of genetic engineering. Sine genetic anomalies cause certain diseases, scientists can introduce mutations in the genes that would eradicate the possibility of such diseases from occurring, thus completely eradicating hereditary illnesses such as diabetes, heart diseases, and even some forms of cancer. Not only that; people who have contracted diseases from external influences can be cured by removing the gene that fell prey to the influence. Genetic engineering can also be use to make people healthier by introducing mutations that lead to stronger immunity and longer life spans.
Help in biotechnology
Biotechnology stands to gain immense benefits from genetic engineering. And this is not the stuff science fiction is made of; even today, scientists are actively deliberating the possibility of xenotransplantation, or the transplant of living tissues from one organism to another. Animals possessing organs with similar properties as those in humans are being debated for use in transplantation; for instance, pigs, which are similar in physiology and tissue structure to humans, are being actively considered for heart and lung transplants. Needless to say, this will have far reaching effects on human life; the wait for suitable organs will definitely become much shorter if animal organs can be harvested, and vice versa.
Eradicate world hunger
With an ever growing population, food shortage in the near future has become a worrying possibility. Genetic engineering can do a lot of good in this respect. Plants are already being modified to contain more nutrients and produce more crops, and this process can be accelerated further. If more and more genetically modified crops are produced, there will be a drive to make the process cheaper, and the wide availability of crops will bring down food prices all over the world. Needless to say, channeled properly, genetic engineering does have the propensity to permanently eradicate hunger and related diseases from the world map.
Negative effects of genetic engineering:
All said and done, there are some very distinctly worrying consequences of genetic engineering.
The biggest concern is of course the uncertainly that is born out of the unfamiliarity of the whole thing. Since this is a fairly new processes and mostly in the research stage, many people are worried that it might lead to unforeseen complications. The introduction of a mutation in the gene might give positive results, but it might turn the tables and turn into a rogue gene that will corrupt the entire system. It might give rise to new diseases that will have no cure for years to come.
On a bigger scale, the possibility of militant groups harnessing the process of genetic engineering is very real. Genetically engineered virus and bacteria can be created and unleashed on the world as very effective, and deadly, biological weapons. It will certainly not be a fun scenario to be in a world where there is the constant threat of being affected by a virus or bacteria that has been genetically engineered to resist all known attempts of killing them.
The newness of genetic engineering has caused it to meet with a lot of skepticism, and although not all of the criticism is grounded in solid facts or science, they are certainly worth giving a thought. The biggest point of contention against genetic engineering is that it is not man’s place to play God, that is, make changes that go against the natural order of things. However, this doesn’t really hold up, considering that humans and animals would have very short life spans if nature had been given free rein to run its course. There are of course some inherent dangers to genetic engineering, and it is up to the scientists to weigh the pros and cons before they embark on massive steps.Labels:positive impact of genetic engineer, genetic engineering negative effects, positive negative and interesting aspests of the genetic engineer, | <urn:uuid:fdaa37e2-efbd-408a-96f5-955dec006b50> | 3.078125 | 932 | Personal Blog | Science & Tech. | 28.057205 | 95,478,810 |
Energy has a vital prospect for sustainable modern daily life and industrial activities. Parallel to economic and population growth, the demand for energy production on a global scale as well as on a country basis is rapidly increasing. With current production technologies, energy is obtained by using fossil fuels such as hydrocarbon-containing oil, natural gas and coal. In the case of carbon-based technologies, CO2, NOx, SOx, particulate matter, etc., uncontrolled release of by-products into the atmosphere leads to a wide range of environmental problems. Compared to fossil fuels, H2 is an energy carrier that has gained much attention in recent years as a potential solution to problems of air pollution, climate change, energy security, and high fuel prices and H2 is a more efficient and clean energy source because of its high energy content and its ability to be easily converted to electricity.
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Microfragmentation concept explains non-positive environmental heterogeneity–diversity relationships
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Although recent studies have revealed that the relationship between diversity and environmental heterogeneity is not always positive, as classical niche theory predicts, scientists have had difficulty interpreting these results from an ecological perspective. We propose a new concept—microfragmentation—to explain how small-scale heterogeneity can have neutral or even negative effect on species diversity. We define microfragmentation as a community level process of splitting habitat into a more heterogeneous environment that can have non-positive effects on the diversity through habitat loss and subsequent isolation. We provide support for the microfragmentation concept with results from spatially explicit heterogeneity–diversity model simulations, in which varying sets of species (with different ratios of specialist and generalist species) were modeled at different levels of configurational heterogeneity (meaning that only the habitat structure was changed, not its composition). Our results indicate that environmental heterogeneity can affect community diversity in the same way as fragmentation at the landscape level. Although generalist species might not be seriously affected by microfragmentation, the persistence of specialist species can be seriously disturbed by small-scale patchiness. The microfragmentation concept provides new insight into community level diversity dynamics and can influence conservation and management strategies.
KeywordsSpecies diversity Environmental diversity Habitat fragmentation Modeling Community dynamics
This research was supported by the European Union 7th framework project SCALES, FP7-226852; European Union 6th framework project ECOCHANGE, FP6-036866; European Regional Development Fund, Centre of Excellence FIBIR, ERMOS program (Grant 14, co-funded by Marie Curie Actions), and Estonian Science Foundation (Grant 8323) and CSIC JAE DOC fellowship. The authors would like to thank the anonymous reviewers for their valuable comments and suggestions. Author contributions: L.L., R.T. and M.P. designed the study; L.L., M.P., I.H. and A.G. did the analysis; L.L., R.S.-K. and M.P. wrote the manuscript. All authors discussed the results and made substantial contributions to the manuscript.
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