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Not recognized (IUCN 2.3)
Thomson et al. 2015
The Southern New Guinea Stream Turtle (Elseya rhodini) is a recently described aquatic species of Chelid turtle (Austro-South American Side Necks) found south of the central ranges of New Guinea. It inhabits small streams that flow into the major river drainage's south of the ranges.
The species was named in honor of Anders G. J. Rhodin the Chairman Emeritus of the IUCN SSC Tortoise and Freshwater Turtle Specialist Group (TFTSG) and founder of the Chelonian Research Foundation (CRF) who publish the journal Chelonian Conservation and Biology he had in the past also been involved in research in Papua New Guinea having described the species Chelodina parkeri and Chelodina pritchardi.
Only recently separated from the Western New Guinea Stream Turtle, Elseya novaeguineae, it was demonstrated that the Elseya of New Guinea were long term inhabitants of the Island and had been subject to the major vicariance events from the formation of the Central Ranges. The degree of divergence was consistent between the molecular and morphological data and as such the species Elseya schultzei was resurrected and this new species was also described. In recognition of the 3 major clades within the Elseya that have been informally named for many years as the Queensland Elseya, New Guinea Elseya and Northern Elseya names were formally applied to these clades. Elseya rhodini was placed in a new subgenus Hanwarachelys along with Elseya novaeguineae and Elseya schultzei.
- Thomson, S., Amepou, Y., Anamiato, J. & Georges, A. 2015. A new species and subgenus of Elseya (Testudines: Pleurodira: Chelidae) from New Guinea. Zootaxa 4006(1):59-82. Preview (PDF)
- Georges, A., Zhang, X., Unmack, P., Reid, B.N., Le, M. & McCord, W.P. (2014) Contemporary genetic structure of an endemic freshwater turtle reflects Miocene orogenesis of New Guinea. Biological Journal of the Linnean Society, 111, 192–208. DOI
- Thomson, S., White, A. & Georges, A. (1997) Re-evaluation of Emydura lavarackorum: Identification of a living fossil. Memoirs of the Queensland Museum, 42, 327–336.
|Wikispecies has information related to Elseya rhodini| | <urn:uuid:c542880a-87d6-4fd0-b230-312d9f2eacc8> | 2.671875 | 551 | Knowledge Article | Science & Tech. | 52.489816 | 95,490,170 |
CHAMPAIGN, Ill. -- The underwater environment may appear to the human eye as a dull-blue, featureless space. However, a vast landscape of polarization patterns appear when viewed through a camera that is designed to see the world through the eyes of many of the animals that inhabit the water.
University of Illinois researchers have developed an underwater GPS method by using polarization information collected with a bio-inspired camera mimicking the eyes of the mantis shrimp. The findings, published in Science Advances, are the first to demonstrate passive underwater GPS using the polarization properties of underwater light. This technology could open new possibilities for undersea navigation and understanding of the migratory behavior of marine animals.
The camera, a variation of a polarization imager named Mantis Cam after the shrimp that inspired it, takes advantage of how light refracts, or bends, when it passes through the surface of water and bounces from particles and water molecules.
"We collected underwater polarization data from all over the world in our work with marine biologists and noticed that the polarization patterns of the water were constantly changing," said study leader Viktor Gruev, an Illinois professor of electrical and computer engineering and a professor of the Carle Illinois College of Medicine. "This was in stark contrast to what biologists thought about underwater polarization information. They thought the patterns were a result of a camera malfunction, but we were pretty sure of our technology, so I knew this phenomenon warranted further investigation."
After returning to the lab, Gruev and graduate student and co-author Samuel Powell determined that the underwater polarization patterns are a result of the sun's position relative to the location where the recordings were collected. They found they can use the underwater polarization patterns to estimate the sun's heading and elevation angle, allowing them to figure out their GPS coordinates by knowing the date and time of the filming.
"We tested our underwater GPS method by pairing our bio-inspired camera with an electronic compass and tilt sensor to measure the underwater polarization data at a variety of sites around the globe, depths, wind conditions and times of day," said Gruev, who also is affiliated with the Beckman Institute for Advanced Science and Technology at the University of Illinois. "We found that we can locate our position on the planet within an accuracy of 61 km."
This technology may open up new ways for people and robots to better navigate underwater using visual cues from polarized light. "We could use our underwater GPS method to help locate missing aircraft, or even create a detailed map of the seafloor," Powell said. "Robots swarms equipped with our sensors could provide a low-cost means of underwater remote sensing - it would certainly be more cost-effective than current methods."
This research could also lead to new insights into the migratory behavior of many marine species.
"Animals like turtles and eels, for example, probably use a slew of sensors to navigate their annual migration routes that take them thousands of miles across oceans," Gruev said. "Those sensors may include a combination of magnetic, olfactory and possibly - as our research suggests - visual cues based on polarization information."
Another aspect of this technology is its potential to help researchers understand how pollution may alter the migratory paths of animals sensitive to polarized light.
"It is very likely that increased pollutants in the air and water alter underwater polarization patterns, causing the undersea environment to appear different from what many animals have learned," Gruev said. "Our underwater GPS method may provide insights into how some long-distance migratory animals, such as whales, might get confused and end up in the wrong places."
For example, more whales are becoming stranded close to the California shore, where they have never been observed before, Gruev said. "Perhaps pollutions is the indirect culprit for this reason, as it affects the underwater polarization patterns necessary for migratory behavior."
The National Science Foundation and the Air Force Office of Scientific Research supported this study. Gruev also directs the Biosensors Lab at Illinois.
To reach Viktor Gruev, email email@example.com.
The paper "Bio-inspired polarization vision enables underwater geolocalization" is available online and from the U. of I. News Bureau. | <urn:uuid:80dd590d-a1b5-4998-8ab0-9f74bf3e2b0b> | 3.46875 | 867 | News (Org.) | Science & Tech. | 23.749495 | 95,490,174 |
Community Contributor | Jul 3, 2018 | 0
06 June 2014
This winter’s first major South Atlantic high pressure cell with a core reading of 1028mB became visible on our radar by Tuesday. At that early-week point, the core was relatively far south, at around 40 degrees latitude but it gradually moved slightly north during Wednesday as it approached the continent. By Wednesday evening the outer rim of the cell made landfall and at the interior surface elevation of about 1400 metres asl, it brought temperatures down sharply to between 5 and 6o Celsius over the southern half, and around 7o Celsius over the northern half. This high pressure cell carried the hallmarks of a typical winter pattern with a strong core, relatively slow eastward shift, and a major impact starting in the south west then backing around to south east and eventually east, as the core slipped over the sub-continent. Yet, despite the presence and activity of this strong cell, the weather for the first half of the week was all low pressure induced. As noted last week, a complex succession of low pressure cells galloped from east to west around Agulhas, each carrying with it a cold front. Ahead of the cold front, airflow was mostly from the north, leading to warmer conditions during the day, and cooler, but not yet really cold, overnight conditions. Again, as is usual, the further north one went, the higher the day temperatures, even as high as 29o C in Owambo, Kavango and Caprivi. Obviously, the reverse is true for the south. In the south, the northern rim of this cold pressure cell lead to windy and wet conditions. However, during Wednesday night, conditions changed rather dramatically.
On the outer (leading) rim of the high pressure cell, where it meets and interacts with the very extensive area of low pressure ahead of it, it created a windy strip which acts like a large blower moving cold air from far south. In covering most of southern Africa, it also blows across Namibia, beginning at Oranjemund, thereafter systematically shifting its impact north-east until eventually, about two days later, the cold air has covered the whole country. As the cold air moves north, it is warmed by daytime solar energy, thus the frigid effect is incrementally limited, but the day temperatures are still markedly lower than the norm for the northern regions.
By Thursday, this high pressure cell has moved across the entire southern Africa lingering with its core over the North West Province in South Africa, but influencing local weather as far east as Mozambique and as far north as Zambia.\ Interesting for us, once the high pressure core lies over South Africa, the cold no longer comes from the south or south west, but from the east. This is due to the anti-cyclonic circulation of the whole system. In other words, the origin of the cold air is still the outer reaches of the Antarctic circle, but the local driver now feeds it from the east creating those typical frosty mornings in Omaheke with cold flowing in from Botswana.
This week’s major high pressure cell is briefly interrupted by a weak low pressure area, but lying further south. This temporarily relieves temperatures over the weekend, compared to Thursday and Friday, but the next even more intense South Atlantic high pressure cell is already only some 2000 km off the African west coast. With a core reading of 1032mB (at this stage) it will be even colder and more intense as it approaches the continent, displaces the last vestiges of the weak low pressure area and grips the entire sub-continent from Monday night onwards. Next week is bound to be a cold week, although around the middle of the week, there is the possibility of a weak trough (low pressure area) developing over the coastline north of Swakopmund. This may lead to subdued Oosweer conditions but only from Hentiesbaai further north. This is however opposed by the next approaching high pressure cell (the third in just over a week), and by the end of next week, windy and cold, even very cold, conditions will prevail. | <urn:uuid:161769dc-48ca-4f1a-8139-9a54651123c7> | 2.96875 | 854 | News Article | Science & Tech. | 42.234483 | 95,490,186 |
Carbon capture projects are falling
WASHINGTON — The number of large-scale projects to capture and bury carbon dioxide has fallen to 65 from 75 over the past year, a worldwide survey has found, despite a consensus among scientists and engineers that such projects are essential to meet international goals for slowing the buildup of climate-changing gases.
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The survey was released Thursday in Seoul, South Korea, by the Global CCS Institute, which is based in Canberra, Australia. Since the previous survey a year ago, five projects have been canceled, one reduced in size and seven postponed, while three have been added, the report said.
The leader in capture and sequestration, as the technique is known, is the United States, the institute said, although that is mostly because of the use of carbon dioxide for stimulating oil flow in old wells. Otherwise, the U.S. program for capturing carbon dioxide from power plants is lagging.
The International Energy Agency expects carbon capture and storage to rank third among ways to reduce carbon emissions by 2050, behind energy efficiency and the use of renewable sources like solar and wind power, and ahead of nuclear power and a switch to lower-carbon fuels. The Global CCS Institute's report, referring to carbon capture and sequestration, found that “while CCS projects are progressing, the pace is well below the level required for CCS to make a substantial contribution to climate change mitigation.”
Among the problems, the report said, is a lack of support for projects that demonstrate new technologies. But it said that China, with 12 plants at various stages of planning and construction, was “well positioned to influence the future success” of carbon capture. China is now the leading producer of carbon dioxide.
Carbon can be captured from electricity plants that burn coal or natural gas, or from oil refineries and other kinds of industrial plants. The dominant source, though, is coal-fired power plants, and last month the Environmental Protection Agency proposed rules to limit emissions from new coal plants and said it would also write regulations to reduce emissions from existing facilities.
But the technology for capturing carbon has not been proved to work on a commercial scale, either in the United States or abroad. The Energy Department canceled its main project demonstrating the technology in 2008. It would have turned coal into a mixture of gases and captured the carbon dioxide before combustion. The department eventually started over with a plan to burn coal in pure oxygen so that the flue gases would be nearly pure carbon dioxide. That plan was aided by financing from the federal stimulus program, although construction has not begun.
The institute's new report said three U.S. projects began operating in 2013, all based on natural gas. One of them, the Air Products Steam Methane Reformer Enhanced Oil Recovery Project, in Port Arthur, captures carbon from natural gas that is used in an oil refinery. The second, the Coffeyville Gasification Plant, at an oil refinery in southeast Kansas, sequesters some carbon dioxide and uses it in fertilizer production, and the third project is the Lost Cabin Gas Plant in central Wyoming. Brazil started up one carbon capture plant, for use in an oil field.
Carbon capture and sequestration had been demonstrated at a coal-burning power plant in New Haven, W.Va., run by American Electric Power. But the utility shut down the project in 2011 because it could not sell the carbon dioxide or recover the extra cost from its electricity customers, and the equipment consumed so much energy that, at full scale, the project would have sharply cut electricity production. | <urn:uuid:a48e0d88-7e95-4596-8135-8b244fc406eb> | 2.984375 | 733 | Truncated | Science & Tech. | 38.181699 | 95,490,191 |
Visual Basic for Applications Reference
Sets the position for the next read/write operation within a file opened using the Open statement.
Seek [#]filenumber, position
The Seek statement syntax has these parts:
|filenumber||Required. Any valid file number.|
|position||Required. Number in the range 1 2,147,483,647, inclusive, that indicates where the next read/write operation should occur.|
Record numbers specified in Get and Put statements override file positioning performed by Seek.
Performing a file-write operation after a Seek operation beyond the end of a file extends the file. If you attempt a Seek operation to a negative or zero position, an error occurs. | <urn:uuid:001fc771-d8a8-48ad-b87e-8fe1c549c67b> | 2.921875 | 149 | Documentation | Software Dev. | 34.33788 | 95,490,203 |
There is a structure in Pro*C called the SQL Communications Area. The structure variable is named sqlca. The most useful field in the structure is sqlcode, which is the status variable. You access this variable with the fully qualified name like this "sqlca.sqlcode". The structure is defined in file sqlca.h.
The status variable (sqlcode) has three different types of values. Zero means the operation was a success. A positive value means the SQL statement executed but threw an exception. And a negative value means the statement did not execute. This variable is updated by Oracle after each SQL statement.
Normally you will get a sqlcode of 1403 if there is a No Data Found exception. However you can set the MODE to ANSI in your Pro*C precompiler. This will result in sqlcode being set to 100 (instead of 1403) on No Data Found.
The developer is able to independently define other status variables such as SQLSTATE and SQLCODE. This SQLCODE is different than the sqlca.sqlcode. In addition to the SQL Communication Area, there is an Oracle Communications Area. It has the variable name oraca.
You can trap Pro*C errors using the WHENEVER clause. There are different values used in association with the clause. Some of these are SQLERROR, SQL WARNING, and NOT FOUND. SQLERROR equates to the sqlcode being negative. SQL WARNING is when sqlcode is positive or sql.sqlwarn equals ‘W’. And NOT FOUND is a sqlcode of either 1403 or 100, depending on the precompiler MODE.
It is possible to have more than one sqlca. However there is only one active one at a time. My recent research into the SQL Communications Area was when the sqlcode was non zero for a trivial SQL statement. It turned out that the value was 1403 which means No Data Found. It took a while for me to discover that one of the bind variables had an extra space at the end causing an update to fail.
Hot Topic Spamming Failures - I follow a friend into a Hot Topic store in the mall. Saw some cool merchandise. Decided to buy something. The salesperson asked me a bunch of questions, ... | <urn:uuid:90be06c8-9a85-4b02-996d-4e3444258419> | 2.515625 | 470 | Personal Blog | Software Dev. | 61.612918 | 95,490,240 |
Quantum-mechanical simulations of the high-pressure behaviour of crystals
First-principles theoretical methods, based on the quantum mechanics of electrons in periodic atomic systems, have been an effective tool to predict the ground-state structural and energetic behaviour of crystals for at least two decades. However, more recently the computational implementation of such methods by very efficient computer software and the availability of cheap and powerful hardware have undergone impressive improvements. It is thus now possible to tackle quite complex problems of materials science, earth sciences, environmental and other applied disciplines involving crystalline compounds from a purely theoretical point of view (Pisani, 1996). In this respect, while some quantum-mechanical techniques in principle are able to account also for thermal effects (ab initio molecular dynamics), the most easily available ab initio methods neglect the role of temperature (athermal limit) but can include the physical parameter pressure very straightforwardly. A brief account of such methods will be given here, presenting some examples of applications in the fields of thermodynamics and kinetics of crystalline materials at high pressure. Comparisons of quantum-mechanical simulations with those based on atomistic potentials are available in the literature (Catti et al., 2000).
The interest of ab initio predictions of the structural and elastic properties of minerals and technological materials, and of their stability ranges, at high pressure is clear. Measurement techniques in extreme non-ambient conditions are particularly challenging and often subject to large experimental errors (cf. the Diamond-Anvil-Cell methods). The most severe problems are perhaps faced by calorimetric measurements at high pressure, and also the determination | <urn:uuid:3d4fcb46-a58b-4a55-b014-2a1f27ba1fb1> | 2.578125 | 333 | Academic Writing | Science & Tech. | 1.545818 | 95,490,244 |
Researchers at the University of California, Santa Cruz (UCSC), believe clouds of dust, rather than twin black holes, can explain the features found in active galactic nuclei (AGNs). The team publish their results today (14 June) in a paper in Monthly Notices of the Royal Astronomical Society.
Many large galaxies have an AGN, a small bright central region powered by matter spiralling into a supermassive black hole. When these black holes are vigorously swallowing matter, they are surrounded by hot, rapidly-moving gas known as the “broad-line region” (so-called because the spectral lines from this region are broadened by the rapid motion of the gas).
The emission from this gas is one of the best sources of information about the mass of the central black hole and how it is growing. The nature of this gas is however poorly understood; in particular there is less emission than expected from gas moving at certain velocities. The breakdown of simple models has led some astrophysicists to think that many AGNs might have not one but two black holes in them.
The new analysis is led by Martin Gaskell, a research associate in astronomy and astrophysics at UCSC. Rather than invoking two black holes, it explains much of the apparent complexity and variability of the emissions from the broad-line region as the results of small clouds of dust that can partially obscure the innermost regions of AGNs.
Gaskell comments: “We’ve shown that a lot of mysterious properties of active galactic nuclei can be explained by these small dusty clouds causing changes in what we see.”
Co-author Peter Harrington, a UCSC graduate student who began work on the project as an undergraduate, explained that gas spiralling towards a galaxy's central black hole forms a flat “accretion disk”, and the superheated gas in the accretion disk emits intense thermal radiation. Some of that light is “reprocessed” (absorbed and re-emitted) by hydrogen and other gases swirling above the accretion disk in the broad-line region. Above and beyond this is a region of dust.
“Once the dust crosses a certain threshold it is subjected to the strong radiation from the accretion disk”, said Harrington. The authors believe this radiation is so intense that it blows the dust away from the disk, resulting in a clumpy outflow of dust clouds starting at the outer edge of the broad-line region.
The effect of the dust clouds on the light emitted is to make the light coming from behind them look fainter and redder, just as the earth’s atmosphere makes the sun look fainter and redder at sunset. Gaskell and Harrington developed a computer code to model the effects of these dust clouds on observations of the broad-line region.
The two scientists also show that by including dust clouds in their model, it can replicate many features of emission from the broad-line region that have long puzzled astrophysicists. Rather than the gas having a changing, asymmetrical distribution that is hard to explain, the gas is simply in a uniform, symmetric, turbulent disk around the black hole. The apparent asymmetries and changes are due to dust clouds passing in front of the broad-line region and making the regions behind them look fainter and redder.
“We think it is a much more natural explanation of the asymmetries and changes than other more exotic theories, such as binary black holes, that have been invoked to explain them,” Gaskell said. “Our explanation lets us retain the simplicity of the standard AGN model of matter spiralling onto a single black hole.”
University of California, Santa Cruz (UCSC)
Tel: +1 (831) 459 4352
Dr Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7292 3979
Mob: +44 (0)7802 877 699
Dr Morgan Hollis
Royal Astronomical Society
Tel: +44 (0)20 7292 3977
Mob: +44 (0)7802 877 700
Dr Martin Gaskell
University of California, Santa Cruz
Image and caption
An artist’s impression of what an active galactic nucleus might look like at close quarters. The accretion disk produces the brilliant light in the centre. The broad-line region is just above the accretion disk and lost in the glare. Dust clouds are being driven upwards by the intense radiation. Credit: Peter Z. Harrington
The new work appears in “Partial dust obscuration in active galactic nuclei as a cause of broad-line profile and lag variability, and apparent accretion disc inhomogeneities”, C. Martin Gaskell and Peter Z. Harrington, Monthly Notices of the Royal Astronomical Society, in press.
The paper is available from https://doi.org/10.1093/mnras/sty848
Notes for editors
More news from the University of California Santa Cruz is available from http://news.ucsc.edu
The Royal Astronomical Society (RAS, www.ras.ac.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4,000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.
The RAS accepts papers for its journals based on the principle of peer review, in which fellow experts on the editorial boards accept the paper as worth considering. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content. | <urn:uuid:597df037-e55f-4c0f-a851-5372113bc2d0> | 3.765625 | 1,241 | News (Org.) | Science & Tech. | 41.669883 | 95,490,251 |
Astronomers at the University of Rochester, home to one of the world's largest groups of planetary nebulae specialists, have announced that low-mass stars and possibly even super-Jupiter-sized planets may be responsible for creating some of the most breathtaking objects in the sky.
The news is ironic because the name "planetary" nebula has always been a misnomer. When these objects were discovered 300 years ago, astronomers couldn't tell what they were and named them for their resemblance to the planet Uranus. But as early as the mid-19th century, astronomers realized these objects are really great clouds of dust emitted by dying stars.
Now, Rochester researchers have found that planets or low-mass stars orbiting these aged stars may indeed be pivotal to the creation of the nebulae's fantastic appearance.
In a new paper in Astrophysical Journal Letters, and in recent papers in Monthly Notices of the Royal Astronomical Society, a team of astronomers anchored by Eric Blackman, professor of physics and astronomy at the University of Rochester, has studied the consequences of a dying star that possesses an orbiting companion.
"Few researchers have explored how something as small as a very low-mass star, a brown dwarf, or even a massive planet can produce several flavors of nebulae and even change the chemical composition of the dust around these evolved stars," says Blackman. "If the companions can be this small, it's important because low-mass stars and high-mass planets are likely quite common and could go a long way toward explaining the many dusty shapes we see surrounding these evolved stars."
Most medium-sized stars, such as our Sun, will end their lives as planetary nebulae, says Blackman. The stage lasts only several tens of thousands of years—a blink of an eye for stars that typically live ten billion—so it is a relatively rare sight. Of the 200 billion stars in our own galaxy, only about 1,500 have so far been identified in the planetary nebula stage.
As the star begins to deplete its fuel near the end of its life, its core contracts and its envelope expands, eventually throwing off its outermost layers millions of miles into space. Blackman says one time in five, this envelope keeps its roughly spherical shape as it expands, but much more often this envelope contorts and elongates into new and fantastic shapes.
The Rochester team's work explored the role of low-mass companions in shaping planetary nebulae stars, both when the companion is in a large orbit and interacts with only the very outer edges of the envelope, and when the companion is in a very tight orbit and so close to the evolved star that the companion is fully engulfed by the envelope.
Blackman, along with post-doctoral fellow Richard Edgar, graduate student Jason Nordhaus, and professor of astrophysics Adam Frank, showed that in the case when the planet or companion star is in a very wide orbit, the planet's gravity begins to drag some of the envelope material around with it. The envelope material—essentially a thin mixture of gas and dust—becomes compressed in spiral waves radiating out from the central star like a twisted wagon wheel, says Blackman. The dust and gas compresses more and more in these spiral waves until they crest, much like waves breaking on a beach. Eventually, a torus of dust forms around the star's mid-section, likely blocking much of the expanding envelope like a belt around an inflating balloon. Over time, such constrained expansion can lead to striking shapes, such as seen in the appropriately named Dumbbell Nebula.
"Originally, we set out just to model the geometry of the envelope under the influence of a binary companion" says Blackman, "but Richard Edgar discovered that as the spiral waves break, they release their compressed, pent-up energy in a burst of heat, sufficient to melt the dust into liquid globules." The globules cool slowly enough to give the molecules within time to align into crystal lattices. Blackman says the team's work show's how a waist-cinching torus could originate to produce certain types of planetary nebula patterns, but it also suggests an answer for why astronomers have detected the puzzling signature of crystallized dust around evolved stars before the nebulae is formed.
In the case when the planet orbits so closely to the primary star that it becomes engulfed by the envelope, a new type of model is needed. Nordhaus and Blackman modeled what might happen as the envelope slows the low-mass star or high-mass planet companion, and found that one of three outcomes is likely to occur.
First, as the companion plows through the envelope material, it can "spin up" the envelope so quickly that the material is ejected, deforming into a large disk or torus around the star's equator.
A second possibility is that the companion spins up the envelope more gently. This causes the inner regions of the envelope to spin around the parent star faster than the outer envelope material. This difference in rotation speeds, combined with the convection of material in the envelope, stretches and amplifies the star's magnetic fields. The stretched magnetic fields can act like a giant spring, ejecting the envelope material out the star's poles as jets.
The third outcome sees the companion itself ejecting out the star's jets, says Blackman. This scenario applies when the companion is an extremely low-mass star or a massive planet that is too small to eject the envelope before it falls to a violent fate. The parent's intense gravity can shred the planet as its orbit shrinks, eventually smearing the planet into a disk of debris around the star. This disk is very turbulent and different parts are orbiting at different speeds, generating a magnetic dynamo that again can throw material out the star's poles at tremendous speeds. Unlike the previous scenario, however, Blackman says that material fired out by these jets would include the remains of the planet or companion star itself.
The Rochester team is now calculating the dynamics of the binary relationship and the characteristics of the magnetic dynamos with more precision. They hope to better understand how these dynamos might facilitate the mixing and transportation of different elements within the nebulae to help produce the distinct chemical signatures astronomers now detect in planetary nebulae.
This research was funded by NASA and the National Science Foundation.
Jonathan Sherwood | EurekAlert!
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Found most commonly in these habitats: 2 times found in secondary lowland rainforest, 7 times found in Bamboo forest, 7 times found in mature rainforest, 7 times found in premontane rainforest, 2 times found in primary lowland rainforest, 3 times found in rainforest, 4 times found in montane wet forest, 3 times found in cloud forest, 2 times found in treefall gap; premontane rainforest, 1 times found in disturbed tropical moist forest, ...
Found most commonly in these microhabitats: 37 times ex sifted leaf litter, 1 times Sura, 1 times suelo y hojarasca suspendido en helecho, 1 times Malaise trap, 1 times litter, 1 times Hojarasca.
Collected most commonly using these methods: 25 times maxiWinkler, 12 times winkler, 5 times Malaise, 2 times Berlese, 1 times Mini Winkler, 1 times search.
Elevations: collected from 50 - 1200 meters, 491 meters average
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Components of the Water Cycle on a Flat Map
Water regulates climate, predominately storing heat during the day and releasing it at night. Water in the ocean and atmosphere carry heat from the tropics to the poles. The process by which water moves around the earth, from the ocean, to the atmosphere, to the land and back to the ocean is called the water cycle.
The three animations of atmospheric phenomena were created using data from the GEOS-5 atmospheric model on the cubed-sphere, run at 14-km global resolution for 25-days. Variables animated here include hourly evaporation, water vapor and precipitation. For more information on GEOS-5 see gmao.gsfc.nasa.gov/systems/geos5 . For more information on the cubed-sphere work see science.gsfc.nasa.gov/610.3/cubedsphere.html.
The animation of global sea surface temperature was created using data from a model run of ECCO's Ocean General Circulation Model. See www.ecco-group.org/model.htm for more information on ECCO.
This group of animations are an orthographic view of the data used in Components of the Water Cycle.
Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio This is a contribution of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO) funded by the National Oceanographic Partnership Program
NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission.
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Graphene has been studied for various applications due to its excellent properties. Graphene film fabrication from solutions of graphene oxide (GO) have attracted considerable attention because these procedures are suitable for mass production. GO, however, is an insulator, and therefore a reduction process is required to make the GO film conductive. These reduction procedures require chemical reducing agents or high temperature annealing. Herein, we report a novel direct and simple reduction procedure of GO by silicon, which is the most widely used material in the electronics industry. In this study, we also used silicon nanosheets (SiNSs) as reducing agents for GO. The reducing effect of silicon was confirmed by various characterization methods. Furthermore, the silicon wafer was also used as a reducing template to create a reduced GO (rGO) film on a silicon substrate. By this process, a pure rGO film can be formed without the impurities that normally come from chemical reducing agents. This is an easy and environmentally friendly method to prepare large scale graphene films on Si substrates.
Graphene, a monolayer carbon sheet, has superior electrical and mechanical characteristics such as extremely high electron mobility and Young’s Modulus1,2,3. In addition, graphene also has good optical properties including high optical transparency4. These remarkable properties make graphene useful for various applications such as field effect transistors (FETs), memory devices and energy storage devices5,6,7. Graphene has been used in various forms in a number of applications, including as large-scale films, nanosheets, and in 3D foam8,9,10. Large scale graphene film is one of the best alternatives to indium tin oxide (ITO), which is most commonly used in transparent conducting films in the display industry11. ITO, however, has significant drawbacks such as high cost, limited resources, and lack of flexibility12. Graphene film not only has electrical properties superior to that of ITO, but is also flexible and has excellent mechanical properties13.
At this point, many researchers have studied graphene film using a variety of fabrication methods. There are two primary methods of making graphene films presently: chemical vapor deposition (CVD) and GO solution-based methods. To make a graphene film using CVD, complicated transfer steps are required for moving graphene from the catalyst substrate to the target substrate because CVD graphene can be grown on restricted substrates such as copper and nickel metal catalysts14. This transfer process can cause significant defects; further, PMMA, used as a supporting material during transfer, can leave a residue15. CVD processing also requires high temperature. These drawbacks prevent CVD graphene from being commercialized, although it can make large-scale monolayer graphene films.
For GO, many researchers have studied techniques for formation of uniform graphene films from GO solutions such as spin coating, spray coating and using chemical reactions because solution-based methods are suitable for industrial mass production with low cost. GO, however, has a naturally low conductivity, so GO has to be reduced to obtain a conductive film16. Generally, additional chemical reducing agents or high temperature annealing are used to make reduced graphene oxide (rGO) films. Pham et al. reported spray-coating a GO film with chemical reduction by pre-mixed hydrazine17. Becerril et al. suggested spin-coated a GO film followed by thermal reduction18. Wang et al. presented a Meyer rod-coating process with a pre-mixed palladium chloride reducing agent19. Ko et al. proposed a microliter scale solution method by meniscus-dragging deposition (MDD) with HI acid vapor reduction20. Many other techniques such as layer-by-layer (LbL) assembly, and using paper-type films with vacuum filtration have been studied21,22.
To reduce GO, thermal and chemical reduction have been widely used8. In case of thermal reduction, Go was heated at various atmospheres such as vacuum, Ar and H223,24,25,26,27. Various chemical reduction methods have been studied with diverse type of reducing agents28. Hydrazine is most generally used reducing agent due to its high reduction efficiency29. Other reducing agents such as hydroquinone30, ethylenediamine31, ammonia32, sodium borohydride33 and potassium hydroxide34 have been studied. There are many other chemical reducing agents, but many of those are harmful and toxic chemicals29. Therefore, environment-friendly chemical reducing agents such as vitamin C35, proteins36 and bacteria respiration37 also have been researched.
Here, we report a new technique to produce large scale graphene films on silicon substrates. In this simple method, reduction of GO and formation of graphene films occur simultaneously on a silicon wafer without any extra reducing agent or high temperature annealing. Moreover, in a comparison with the previous reducing agents, silicon is widely used materials at various applications, so this study method could be easily applied into graphene-silicon composite applications without other additive.
Silicon wafers are a commonly used substrate, and graphene is also widely used on silicon substrates. Further, bare silicon can be oxidized easily, so silicon, which acts as a reducing agent in this study, can remove the oxygen groups from GO; as a result, silicon becomes silicon oxide and GO becomes rGO38. No further chemicals or treatments like heating are needed to reduce GO by this method. An important advantage of this method is that the resulting rGO has no impurities from chemical reducing agents. Silicon can exist in many forms, including wafers, nanowires or nanosheets39,40,41. In this study, we used nanosheet and wafer-type silicon. The GO film can be reduced on a silicon substrate directly by the process shown in Fig. 1(a). The GO film was coated on surface of oxide etched silicon wafer. The wetting behavior of silicon wafer surface was changed by the oxide layer presence42. Before etching process, the surface of silicon wafer was hydrophilic as shown in Fig. 1(b). After fully etching of oxide layer, the surface became hydrophobic as presented in Fig. 1(c). Figure 1(d) shows photographs of uniform silicon reduced graphene oxide (srGO) films made on a 4-inch wafer. Figure 1(e) presents an AFM image of the srGO film. The srGO film has high uniformity with low roughness. The thickness of srGO was 2 nm, and the surface root mean square roughness (Rq) was 0.736 nm.
Silicon nanosheets (SiNSs) prepared by a CVD method43 can also be used to reduce GO. SiNSs have a 2-dimentional morphology with a large surface area, and GO also has a similar 2D structure44. This similar morphology can increase the contact area between GO and SiNSs, which can enhance the reduction effect. In a first approach, rGO powder was prepared with SiNSs.
The reduction effect of silicon to GO was confirmed by X-ray photoelectron spectroscopy (XPS) in Fig. 2(a,b). Chemical bonds between carbon and oxygen were much greater in a GO solution than in the srGO, which proves the successful reduction by silicon. GO has C-C (284.5 eV), C-O (286.7 eV), and C=O (288.3 eV) peaks, and C-O and C=O in srGO were reduced dramatically after reduction. No contaminants (e.g., sodium) were found by XPS analysis in Figure S1. The O1s peak (~530 eV) in srGO is lower than that of GO. The C/O ratio of GO was 2.12 and that of srGO was ~9.32.
Atomic structure change between GO and srGO was determined by X-ray diffraction. Graphite, GO, and srGO powder were measured. Graphite had a sharp peak at 26°, and the peak of GO, after chemical exfoliation from graphite, was shifted to 10°. These peak changes mean the interlayer distance between the carbon layer was increased, i.e., GO was successfully exfoliated45. The XRD peak of srGO was at 19.8°, larger than that of GO. This phenomenon corresponds with a reported XRD peak change when GO is reduced46. The increase in peak position in GO implies a decrease in the GO interlayer distance. These alterations were due to a decrease in oxygen-containing functional groups, which supported a larger interlayer distance in GO. To confirm the reducing ability of silicon, UV/vis absorbance of GO and srGO was checked. Figure S2 (a) presents optical absorption spectra of pure SiNSs and a GO solution. Before the reduction, GO has an optical peak near 230 nm due to π → π* transitions of aromatic C-C bonds47. After the reduction, the optical peak of srGO was shifted to around 270 nm. Figure S3 shows statistical distribution of optical peaks of srGO solutions. The mean value of optical peaks was 267 nm with a small standard derivation (0.7942). The reproducibility of our method was demonstrated statistically. With increasing amounts of SiNSs, the optical peak of srGO was red-shifted. This red shift was caused by electronic conjugation within GO sheets recovered during the reduction process48. The wide range graph of optical absorption is shown in Figure S2 (b). This optical property change is in agreement with previous literature49. The Raman spectra of GO and srGO powder were analyzed, Figure S4. Commonly, GO has two peaks, a G peak (1341 cm−1) and a D peak (1573 cm−1). The G peak corresponds to sp2 hybridized carbon-carbon bonds, related to first-order scattering of the E2g phonon in graphene and the D peak correlates to lattice distortions, related to a breathing mode of k-point photons of A1g symmetry46,50. The ratio of these two peaks can be increased due to changes in the degree of reduction, as reported in many previous studies51,52,53. Usually, GO has an ID/IG value of less than 1, and rGO has a value more than 1. This phenomenon is caused by decreased sp2 domains due to reduced size of GO sheets after reduction8,54,55. The incomplete recovery of sp3 defects after reduction reactions also could affect ID/IG ratio increase50. In this study, the ID/IG ratio of GO was 0.80 and that of srGO was 1.11, which is in good agreement with the literature. The ID/IG ratio distribution is shown in Figure S5. By these characterizations, the valuable reducing capability of silicon to GO was confirmed.
Based on this evidence, a silicon wafer was also used as an efficient template to produce graphene films. The GO film, which was formed on a bare silicon wafer, can be reduced by the substrate alone. The silicon wafer, which has a native oxide layer, was etched this using 1:6 BOE and was rinsed with DI water. After the oxide etching process, the GO solution was spray coated onto the etched wafer surface immediately and was heated. As a result, the as-formed GO film on the silicon substrate was reduced to a srGO film with no further treatment or reducing agent. Film formation and reduction was done simultaneously. The resulting graphene film was investigated using Raman spectroscopy. Figure 3(a) shows a Raman spectrum of the graphene film on the native oxide etched silicon wafer and a non-etched one. As shown, the etched silicon substrate has a reduction effect similar to the SiNSs. The ID/IG ratio of the etched wafer was 1.13 and that of the non-etched wafer was 0.79. 2D peak was observed at ~2700 cm−1, which is overtone of D peak, and a D + G peak was also observed at ~2973 cm−1, which is a combination of the D peak and G peak, as shown in Figure S656. The 2D peak is sensitive for layer number of graphene57. Typically GO has weak intensity 2D peak because it has multiple layered C-O bonds in its matrix and usually GO exists as stack of nanosheets instead of mono layer58. So, normally 2D and D + G peaks could not provide accurate information regarding GO studies in comparison to single layer graphene studies59. Especially in study of reduction method of GO, the enhancement of 2D peak intensity can be observed depending on decreasing of functional groups from GO as shown Figure S660. The srGO has sharp and large 2D peak in comparison to GO. The intensity ratio of I2D/ID+G was also increased after reduction process due to graphitic electronic conjugation recovery as shown in table S159.
ID/IG ratio changes versus heating temperature were measured from room temperature (rt) to 140 °C. The ID/IG ratio increased with an increase in heating temperature up to 100 °C. After 100 °C, the increase in ID/IG ratio was saturated, therefore, the optimized heating temperature was 100 °C.
A graphene film on a 4-inch wafer was formed by our spray coating method. To make a uniform large area GO film, some kind of coating method such as spray coating or spin coating is required to prevent the coffee-ring effect, which occurs at the boundary of the film61,62. Other coating methods could be applied with the same reduction method presented here if they are suitable for film formation on a silicon wafer. Figure 4(a,b) provide SEM images of the srGO film. A low magnification SEM image displays an overall uniform srGO film coated on the silicon wafer, Fig. 4(a). Local srGO film images are shown in Fig. 4(b) with natural small wrinkles in GO. Figure 4(c,d) shows individual Raman mapping images of d peak and g peak. Figure 4(e) presents uniform ID/IG ratio mapping image of srGO.
Sheet resistance was measured to analyze electrical properties of our graphene film. The sheet resistance of the srGO film (3.54 KΩ/square, 2 nm thickness) was considerably lower than that of the GO film (was more than 2 MΩ/square, 5 nm thickness). The srGO sheet resistance is similar to other literature values even though no chemical reducing agent was used. NaOH was also used as an etchant for the silicon wafer to confirm that the reduction effect was not a result of the BOE. All other procedures were kept the same as previously described. Although the etchant was changed, there was no significant change in the Raman spectrum, as shown in Figure S7.
Though the reduction mechanism of GO has been actively studied, but it is not sufficient29,63. Researchers are mainly using density functional theory (DFT) and molecular dynamics (MD) simulation to investigate the reduction mechanism64,65,66. The reduction reaction includes various chemical reactions in sequence that are not configured in a single reaction67. Chemical reactions are different based on the reduction methods65,68,69,70. Most current studies have focused to elimination of oxygen containing groups from GO, which are the main purpose of reduction to produce rGO71. In this study, we suggest possible mechanism of our method in Figure S8 and S9. GO contains various oxygen functional groups such as hydroxyl, epoxy and ketone groups. These functional groups could be removed from as-made GO by the proposed reduction mechanism as in Figure S9.
Based on the current experiment and characterization results, it is confirmed that GO is reduced by silicon. As the results of our experiments, silicon can absorb oxygen group from GO. That oxygen group could be formed as silicon dioxide. According to XPS data silicon dioxide was formed on silicon wafer after GO reduction as shown in Si 2p spectrums (figure S10)72. The SiO2 peak (103.65 eV) was found after GO reduction process. As per our hypothesis, we are assuming that the Si-H dangling bonds could be generated on the surface of silicon, which are playing these key roles to reduced oxygen functional groups of GO as shown in Figure S9. Various researchers have been investigated the reduction reaction of oxygenated functional groups by H-terminated silicon surface73,74,75,76. The reduction reactions have been conducted by Si-H dangling bonds77,78,79, which were formed during etch process as shown in figure S880,81,82,83. The fluoride ion of remaining very small amount of HF on silicon surface after the etching process, also could help to activate these Si-H bonds73. The most of oxygen functional groups could be present as hydroxyl, epoxide and ketone groups as following the Lef-Klinowski model8. In addition to this, there are also some carbonyl groups on GO. These active hydrogens on silicon surface reacts with oxygenated functional groups of GO and it causes de-epoxide, de-carbonyl and de-hydroxyl reaction (figure S9) to produce rGO. In case of SiNSs, which have large surface-to-volume ratio, can contain more bonds. It makes SiNSs as good reducing agent. The composite of GO-SiNSs could be used various applications such as Lithium Ion Battery anode. The reaction between silicon wafer and GO film could produce silicon dioxide layer in interlayer of two. Silicon dioxide is one of the best dielectric material, which is important in field of electric device such as field effect transistor. No need to form additional oxide layer to make dielectric layer. It can help our method is applied to various aspects.
This study provides a demonstration of an innovative reduction method for GO. Silicon, a common material widely used throughout industry, can be used to reduce GO. CVD grown 2-dimenional SiNSs can combine with GO sheets due to similar morphology, and this advantage can enhance the reduction effect of silicon. Silicon wafers were also used as reducing templates. By this method, the reduction of GO and film formation occurred simultaneously without any additional chemicals. The graphene film, which is reduced by silicon, has no impurities such as hydrazine or hydrogen iodide, and a high quality graphene film can therefore be achieved. The reproducibility of our method was confirmed statistically. A large scale graphene film can be made by this simple method. The graphene film on a silicon wafer can be transferred to a transparent substrate by a common graphene transfer method. This suggested method is simple, easy, and eco-friendly for graphene film formation and can be used to potentially further commercialization of graphene.
Silicon wafers were obtained from DASOM RMS (Korea). BOE was purchased from SAMJUN Chemicals (Korea). Graphite was obtained from Bay Carbon (USA). All other chemicals for synthesis GO were obtained from Sigma Aldrich, Korea. All chemicals were used without further purification.
The whole experiment was divided into two categories. The first experiment was conducted as solution process with silicon nanosheets (SiNSs) and GO. After reduction process based on solution, GO was dried as powder form. The second experiment was performed as film process with silicon wafer and GO solutions. The result of this experiment was reduced GO film on silicon wafer.
Preparation of Graphene Oxide
The graphene oxide solution was prepared by a modified Hummer’s method.
Preparation of Silicon Nanosheets (SiNSs)
SiNSs were synthesized on Si substrates through chemical vapor deposition using SiCl4 as the Si precursor and H2 as the carrier gas in high gas flux environment. The substrates were placed at the center of a quartz tube reactor. The reaction temperature was maintained at 1050 °C for 30 min under a H2 (99.9999%) and an Ar (99.9999%) atmosphere. Silicon tetra-chloride (SiCl4, Aldrich, 99.999%) was introduced into the reactor using a bubbling system. After 30 min, the reactor was cooled to room temperature under an Ar atmosphere.
Preparation of Reduced Graphene Oxide with SiNSs
SiNS wafers were etched using a 1:6 buffered oxide etch (BOE) for 0.5 seconds to remove the native oxide layer and were dispersed in DI water. A diluted GO solution 25 ml (0.1 mg/ml) and 5 ml of a SiNSs solution (0.1 mg/mg) were mixed well and heated up to 80 °C for 2 hours with mild stirring. Then, the mixed solution was put into a 2 M NaOH solution at 40 °C for 1 day for to fully etch the SiNSs. The solution was washed with DI water by centrifuging 5 times followed by drying.
Formation of Reduced Graphene Oxide Films
The silicon wafer was put into 1:6 BOE at room temperature for 240 or 320 seconds. Then, the wafer was rinsed with DI water 3 times quickly and dried with flowing N2. After drying, the wafer was placed on a spray coating device and heated up to 80 °C. During heating, the GO solution (1 mg/ml) was sprinkled on the wafer surface. The heating was continued up to 2 hours after coating.
Spray coating of Graphene Oxide
Graphene oxide layers were obtained by facile spray casting onto the functionalized substrate using a double-action airbrush (model GP-70, Sparmax) at a distance of 30 cm with a N2 pressure of 29 psi. During the spraying process, the substrate is heated to 100 °C to obtain uniformly deposited graphene oxide layers.
Changes in chemical bonds after reduction were investigated by X-ray photoelectron spectroscopy (XPS, k-alpha, Thermo. U.K.). Adjustments of atomic and molecular structure were probed with X-ray diffraction (XRD, Ultima IV, RIGAKU). The reduction of GO by silicon was analyzed using a Raman Spectrometer (LabRam Aramis, Horriba Jovin Yvon). The absorbance differences between GO and silicon reduced graphene oxide (srGO) and the transmittance of srGO films were measured using a UV/VIS spectrophotometer (V-650, JASCO Corporation). Electrical properties of srGO films were examined by using 4 probe measurement (CMT-SR1000N, AiT). Surface roughness and morphology of the srGO film were investigated using an atomic force microscope (AFM, XE-100, Park Systems) and a field-emission scanning electron microscope (FE-SEM, JEOL-6701F, JEOL Ltd.).
How to cite this article: Chan Lee, S. et al. Efficient Direct Reduction of Graphene Oxide by Silicon Substrate. Sci. Rep. 5, 12306; doi: 10.1038/srep12306 (2015).
This work was partially supported by Yonsei University Future-leading Research Initiative of 2014 (2014-22-0168), the Pioneer Research Center Program (2010-0019313), the Priority Research Centers Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2009-0093823), Basic Science Research Program through the National Research Foundation of Korea (NRF) grant funded by the Ministry of Education, Science and Technology (MEST) (2013-8-0874) and Korea Electric Power Corporation Research Institute though Korea Electrical Engineerung & Science Research Institute (R14XA02-2). | <urn:uuid:bc8e2aeb-8f31-4a78-b4f2-74d3864520ab> | 3.65625 | 4,999 | Academic Writing | Science & Tech. | 47.393809 | 95,490,301 |
Visit the Genome Gallery during one of the Wellcome Genome Campus Open Saturdays, or as part of an organised group visit to the campus, and explore our latest family-friendly exhibition to discover how genome sequencing is helping us uncover much more about the natural world.
Curious Nature explores the Wellcome Sanger Institute’s anniversary project to sequence the genomes of 25 species found in the UK. Humans have long sought to classify and interpret the natural world, to better understand how things are related to each other. Our ability to analyse the genetic information of all living things, encoded in their DNA, is enabling us to explore these similarities and differences in greater detail than ever before.
The species chosen have been organised in five categories: flourishing, floundering, iconic, dangerous and cryptic. They were nominated by a wide-ranging community of researchers, and five of them were chosen by schoolchildren from across the UK. The categories, and the species within them, help to build a picture of biodiversity in the UK, helping us to better know the environment we live in, and also to understand and tackle our impact upon it. Creating a reference genome is not an easy task but once created, it can be a powerful tool that can be used by a global community of researchers and conservationists. Discover what we could uncover and get curious about nature! | <urn:uuid:6584d983-2f5d-46df-8a6a-dc5a5626d2f0> | 3.1875 | 272 | News (Org.) | Science & Tech. | 24.598142 | 95,490,309 |
One instrument that flies aboard two of NASA's satellites has provided two views of the pollution from the fires in Ontario. The Moderate Resolution Imaging Spectroradiometer, or MODIS instrument, flies onboard NASA's Aqua and Terra satellites. MODIS has provided a visible look at the smoke and pollution that has spread over Niagara Falls and east to Nova Scotia.
As of July 20, the Canadian Interagency Forest Fire Centre (CIFFC) noted that Ontario accounted for 40% of the new fires in the entire country during the week of July 17. The CIFFC reported that so far in 2011, more than 300,000 hectares have burned in Ontario. The Nova Scotia Chronicle Herald reported that smoke from those fires also reached Nova Scotia and Newfoundland by the end of that week.
NASA's Aqua satellite passed over western Ontario on July 18, 2011 at 17:58 UTC (1:58 p.m. EDT) and captured a visible image of light brown smoke from wildfires streaming toward the Great Lakes. The MODIS instrument also detects heat signatures and can identify "hot spots" where fires are still burning.
Data from the MODIS instrument also helps identify pollution. Data was compiled and averaged using the NASA web-based Giovanni system over the period of July 18-20, 2011. The data provided a measurement of what is called "Aerosol Optical Depth (AOD)." To understand that, think of the atmosphere as an "ocean of air." The depth or amount of aerosols can prevent the transmission of light in the air, just as dirt can block light through the ocean.
Higher values of the AOD measurement mean there are more aerosols (tiny bits of pollution that are also created by soot and smoke from fires) in the air, and less light is getting through the atmosphere. Another prominent aerosol from volcanoes and coal-burning power plants is sulfur dioxide (SO2).
Between July 18 and 20, the greatest pollution, or quantity of aerosols were north of the Great Lakes. Over a large area stretching from the north of western Lake Superior east to Lake Huron, particles measured highest at 1.5 molecules per cubic centimeter.
Giovanni is a Web-based application that provides a simple and intuitive way to visualize, analyze, and access vast amounts of Earth science remote sensing data without having to download the data.
"One of the advantages of Giovanni is that it allows us to make rapid multi-day averages of daily data from MODIS," said Dr. James Acker, an oceanographer at the Goddard Earth Sciences Data and Information Services Center (GES DISC) who is creating a Giovanni data portal specifically for educators. GES DISC operates out of NASA's Goddard Space Flight Center in Greenbelt, Md. "By averaging the data, we can see the full extent of smoke from the fires, which can be a health hazard," Acker said. "The AOD data also clearly indicates where the smoke is, and distinguishes it from weather clouds."
Dr. Acker recently experienced wildfire smoke first-hand at a teacher workshop in northeastern New Mexico, where the air quality was noticeably affected by the huge Wallow Fire in Arizona, nearly 300 miles away.For updated fire and smoke imagery from NASA, visit NASA's Fire/Smoke web page:
Rob Gutro | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
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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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If these tiny, microscopic organisms are to survive in these environments, they need to be able to rapidly detect changes in their surroundings and react to them. Scientists at the Johannes Gutenberg University of Mainz are currently investigating how bacteria manage to pass information on their environment across their membranes into their cell nuclei.
"The sixty-four-thousand- dollar question is how signals are transmitted across the cell membrane," explains Professor Gottfried Unden of the Institute of Microbiology and Vinology. Working in collaboration with the Max Planck Institute for Biophysical Chemistry in Göttingen, his research group has demonstrated that structural alterations to membrane-based sensors play a major role in the transfer of signals.
Some bacteria possess more than 100 different sensors that they use to form a picture of their environment. These sensors can show, for example, whether nutrient substrates and/or oxygen are present in the immediate neighborhood of the cell and what the external status of temperature and light is like. These sensors are mainly located in the cell membrane, i.e., the layer separating bacteria cells from the environment. From there they then transmit signals into the cell nucleus. Thanks to the development of new methods of isolating these sensors and of other innovative techniques, it is now possible to discover how all this works. The researchers in Mainz have also managed to modify a sensor that detects an important bacterial substrate so that it can be analyzed making use of new spectroscopic techniques.
"This is the first time that solid-body nuclear magnetic resonance (NMR) spectroscopy has been used to investigate large membrane proteins," stated Professor Unden. In addition to this functional analysis, the structural analysis undertaken by the biophysicist team in Göttingen headed by Professor Marc Baldus has identified important details of the signal transmission process: a stimulus molecule – carbonic acid in this case – binds to a part of the sensor that protrudes from the cell. This appears to result in dissolution of the ordered structure of that segment of the sensor within the cell that is in non-stimulated status. It seems that it is this plasticity that elicits the subsequent activation of the enzymatic reaction cascade within the cell. This results in the cellular response, which, for example, can take the form of neosynthesis of enzymes or the development of protective mechanisms.
In addition to the new findings on signal transmission published in Nature Structural and Molecular Biology, the microbiologists of Mainz University have discovered a previously unknown and exceptional method of signal detection employed by the same sensor (designated DcuS), which they discuss in an article in the Journal of Biological Chemistry. This shows that bacteria react not only to their extracellular environment, but also to the intracellular situation. It is becoming apparent that it is not the sensors alone that detect stimuli. A second stimulus detection pathway is represented by the transport system that channels substrates into the cell. Once the substrate – carbonic acid – has been taken up, the transporter notifies the sensor of this. Prof. Unden added, "We have been able to identify that segment of the transporter that is responsible for the control of sensor functioning. The transporter is of fundamental importance for the function of the sensor. Without the transporter, the sensor does not work correctly and is constantly in activated status," explained Professor Unden, who suspects that this function-related feedback on metabolic and transport activity is often more important for a cell than information concerning concentrations only.
Prof Dr Gottfried Unden | alfa
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Dry landscapes can increase disease transmission
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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.
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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.
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An area of disturbed weather near 11°N, 31°W, about 500 miles southwest of the Cape Verde Islands, has the potential to develop into a tropical depression later this week as it heads west at 10 - 15 mph towards the Lesser Antilles Islands. Visible satellite loops
on Sunday morning showed that the disturbance had only a minor amount of spin. Infrared satellite images showed that the system's heavy thunderstorm activity was modest at best, and had not changed significantly since Saturday. Wind shear
was moderate, 10 - 15 knots, which should allow slow development. Ocean temperatures were marginal for development, about 27°C. Water vapor satellite loops
showed that the atmosphere was reasonably moist in the area, though a large area of dry air lay a few hundred miles to the north.Figure 1.
MODIS true-color image from approximately 11:30 am EDT July 27, 2014, showing a tropical disturbance (marked with an "L") about 500 miles southwest of the Cape Verde Islands. The Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics, is also apparent. Clusters of thunderstorms in the ITCZ may compete for moisture and energy, slowing development of the disturbance. Image credit: NASA.Forecast for the disturbance
Two of our three reliable models for predicting tropical cyclone genesis, the GFS and UKMET models, predicted in their 00Z Sunday runs that the disturbance would develop into a tropical depression by Thursday. Several of our less reliable models, the NAVGEM and Canadian models, also predicted development. The only reliable model that did not predict development was the European model, which historically has had the highest incidence of failing to predict development when development actually occurs. The fact that two out of three of the reliable genesis models predict development bolsters the odds that development will actually occur. In their 2 pm EDT Sunday Tropical Weather Outlook, NHC put the 5-day odds of development at 40%, up from their 20% forecast from Saturday evening.
All of the models predict that the disturbance will continue due west or just north of due west at 10 - 15 mph for the next five days. The UKMET is the fastest of the models, predicting that the disturbance will arrive in the Lesser Antilles Islands on Friday. The GFS is slower, predicting a Saturday arrival in the islands. Once the disturbance crosses west of about 50°W longitude, ocean temperatures will warm to about 28°C, which should aid development. Dry air to the north will likely interfere with development by the middle of the week, and we will have to see if the moderate levels of wind shear forecast to occur over the tropical Atlantic will be capable of driving this dry air into the core of the system, disrupting formation. The disturbance may also have trouble disentangling itself from the Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics, which lies just to the south of the disturbance. Clusters of thunderstorms in the ITCZ may compete for moisture and energy, slowing development of the disturbance. Most of the 20 members of the 06Z Sunday run of the GFS ensemble model (which runs the GFS model at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed the disturbance missing the U.S. East Coast and recurving out to sea early next week, but it is too early to assess the odds of this. | <urn:uuid:612f5c49-5fa6-4dff-9988-5871e0f6f71a> | 2.53125 | 720 | Personal Blog | Science & Tech. | 44.098867 | 95,490,327 |
The control chart is a graph which is used to study process changes over time. The data is plotted in a timely order. A control chart is bound to have a central line of average, an upper line of upper control limit and a lower line of lower control limit.
Control charts are the tools in control processes in statistics to determine whether a manufacturing process or a business process is in controlled statistical state.
In addition, the data obtained from the process can also be applied in making the prediction of the future performances of the process.
When the analysis made by the control chart indicates that the process is currently under control, it reveals that the process is stable with the variations that come from sources familiar with the process. No changes or corrections are required to be made to the parameters of process control.
Types of control charts
After the basic chart is created, one can use various menus and options to make required changes that may be in a format, type or statistics of the chart.
To create a chart it is not necessary to know the name or structure of any chart. You just need to select the columns or variables that are to be charted and drag them in respective zones. When the data column is dragged to the workplace, the user starts working on it to create an accurate chart that is based on the data type and given sample size.
Control Charts for Variables:
The control charts of variables can be classified based on the statistics of subgroup summary plotted on the chart.
X¯ chart describes the subset of averages or means, R chart displays the subgroup ranges, and S chart shows the subgroup standard deviations. Regarding the quality that is to be measured on a continuous scale, a particular analysis makes both the process mean and its variability apparent along with a mean chart that is aligned over its corresponding S- or R- chart.
Levey – Jennings Charts:
This chart displays a mean process based on a long-term sigma with control limits. The control limits are placed such that the distance between them and the center line is ‘3s’. The standard deviation value ‘s’ for these charts is determined by the same method as the standard deviation for the distribution platform.
Control Charts for Attributes:
This type of data is usually continuous and based on the theoretical concept of continuous data. Count data is a different kind of data available which is also known as level counts of character data. The interest variable is a unique count here for the number of blemishes or defects per subgroups. These attribute charts are appropriately applicable for such discrete count data.
The data can be combined into one measurement unit if the data you have contains repetitive measurements of the same unit process. But this is not recommended until the data contains repeating measurements of every measurement process.
Typically, pre-summarize summarizes the process columns into standard deviations or sample means based on the size of the sample.
To know more about Control charts and any other Mathematics related topics, visit Byjus.com
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Connecting to the Database So far, you have successfully started the the database server and created a database instance named contact in the IDE. Therefore, you can skip ahead to Starting the Server and Creating a Database. You will also see the sample [app on APP] database connection that is the default database schema. All tables found in relational databases must contain a primary key. First, you need to establish a connection with the data source you want to use. Note the following output in the Output window, indicating that the server has started:
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Documentation General Java Development. Connection Pooling with Spring.
Then execute dg related query directely in your OnLineLibrary database to check its output and if its syntax is correct:. Connecting to the Database So far, you have successfully started the the database server and created a database instance named java db jdbc in the IDE. For example, the default location might look like C: Once a Connection is established, it can be used java db jdbc create Statement and PreparedStatement objects, as well as retrieve metadata about the database.
To connect to the contact database perform the following steps. This process is essentially java db jdbc out in two parts: However, you must manually load any drivers vb to JDBC 4. I have the following code: Note that a new row has been added with the data you just supplied from the SQL statement.
Creating Tables The contact database javz you just created is currently java db jdbc. The contact database that you just created is currently empty. Error connecting to database org. This example shows how you can obtain a Connection instance from the DriverManager. Enter the following query in the SQL Editor.
JDBC and Java DB
Create a javs java db jdbc name for the database by right-clicking the database connection node jdbc: Typically, a JDBC application connects to a target data source using one of two classes:. Typically, in the database URL, you also specify the name of an existing database to which you want to connect.
A folder named ‘javadb’ will be created in the same location as the file. The following are some examples of database URLs:. Sign up or log in Sign up using Google.
This method specifies the user name and password required to access the DBMS java db jdbc a Properties object.
Java DB/Derby Type 4 JDBC Driver (Oracle GlassFish Server Administration Guide)
To start the database rb In the Services window of the IDE you can perform the following common tasks on database structures. To verify changes, right-click the Contact DB connection node in the Services window and choose Refresh. Note that java db jdbc application must manually load any JDBC drivers prior to version 4.
Each JDBC driver contains one or more classes that implements the interface java. Using Character Sets and Unicode. Typically, a JDBC application connects to a target data source using one of two classes: | <urn:uuid:d40c52f3-996c-4791-85b2-59858e72cf58> | 3.015625 | 681 | Documentation | Software Dev. | 47.115692 | 95,490,347 |
Radiation makes life impossible in most earth like planets
- December 11, 2015
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Vast amounts of radiation may be making life impossible on a planet that is considered the most Earth-like known outside our solar system, new research claims.
Scientists say radiation from a “superflaring” red dwarf star, dubbed Kepler-438 may have stripped away the atmosphere of the planet, Kepler-438b.
Regularly occurring every few hundred days, the superflares are about ten times more powerful than those ever recorded on the Sun, and equivalent in energy to tens of billions of nuclear bombs, according to the researchers, from the University of Warwick in the U.K.
The danger to the planetary atmosphere isn’t the flares themselves, he added, but an associated phenomenon known as coronal mass ejections, in which a star throws off giant blobs of stellar material called plasma.
The resulting loss of atmosphere “could have serious damaging effects on the habitability of the planet,” said astrophysicist David Armstrong at the university, lead researcher of the research, published in the journal Monthly Notices of the Royal Astronomical Society.
“The presence of an atmosphere is essential for the development of life,” added Chloe Pugh of the university, a collaborator in the project.
Kepler-438b, the planet with the highest recorded “Earth Similarity Index,” is both similar in size and temperature to the Earth but is closer to its small star than the Earth is to the Sun.
“If the planet, Kepler-438b, has a magnetic field like the Earth, it may be shielded from some of the effects,” Armstrong said. But “if it does not, or the flares are strong enough, it could have lost its atmosphere, be irradiated by extra dangerous radiation and be a much harsher place for life to exist.”
“Coronal mass ejections are where a huge amount of plasma is hurled outwards from the Sun,” said Pugh. “There is no reason why they should not occur on other active stars as well. The likelihood of a coronal mass ejection occurring increases with the occurrence of powerful flares, and large coronal mass ejections have the potential to strip away any atmosphere that a close-in planet like Kepler-438b might have, rendering it uninhabitable. With little atmosphere, the planet would also be subject to harsh UV and X-ray radiation from the superflares, along with charged particle radiation, all of which are damaging to life.” | <urn:uuid:38dd0fa5-dedd-4916-929e-cc6a7aaef00c> | 3.53125 | 546 | News Article | Science & Tech. | 33.204926 | 95,490,382 |
Harmonic variations in the Earth Rotation determined using VLBI
The Earth rotation has harmonic variations caused by external
torques exerted directly and directly with the Sun, the Moon, and
the planets. Atmospheric and ocean circulation and variations
in continental water storage cause additional excitation in the Earth
rotation. While excitation due to external torques can be predicted
very precisely, excitation due to air and water mass redistribution
is not predictable. Layered non-rigid Earth response to the excitation
differently than an absolutely rigid body. For instance a boiled egg
rotates differently than a raw egg. Comparing observed variations
in the Earth rotation with the excitation we can make inference about
properties of the Earth's inferior that described by a number of parameter
called compliances or basic Earth parameters.
As the first step of studying the response of the Earth to forcings,
we have developed a procedure of estimating the spectrum of the Earth
rotation by analysis of the time series of VLBI group delays since
1984.0 through present. I estimate close to 1000 constituents in
a single least square analysis of 13 million VLBI group delays
without resorting to intermediate time series. The frequencies
of the estimated constituents are selected to cover
For close tidal and nutation constituents with frequency separation less
than 1/Δt constraints are imposed on the ratio of complex
amplitude estimates to be close to the radio of theoretical complex
- all major nutation constituents with theoretical amplitude
about 10 prad;
- all 2nd order tides with amplitudes greater 0.1% of M2 tide
- all frequencies with a step 1/Δt within the retrograde
free core nutation and hypothetical prograde under core
nutation. Δt is the interval of observations.
- a number of ad hock frequencies within ter-diurnal band.
Since the Free core nutation is the unpredictable process, we have to
repeat the estimation procedure every 2–4 months. In a time
domain this is equivalent to a trigonometric extrapolation of the
free core nutation and updating the time series every 2–4 months.
Numerical tables of the results of analysis of VLBI observations.
The tables below contain the estimates of the expansion of the vector
of small perturbations of the Earth rotation with respect to the empirical
nutation series MHB and empirical precession expression Capitaine_2003
taken as the reference into Fourier series from processing all suitable
geodetic VLBI observations. The components of the vector of the small
perturbations correspond to Euler angles. The expansion includes so-called
nutations and sub-diurnal variations in the Earth orientation parameters.
This project is supported by NASA
Earth Surface & Interior program, grant This NNX17AE02G.
Back to Astrogeo Center home page.
This web page was prepared by Leonid Petrov
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| Technomyrmex albipes|
(Smith, F., 1861)
Bolton (2007) - T. albipes is an extremely successful tramp species that nests and forages both terrestrially and arboreally, and may enter houses. Workers may be found under stones, in and under fallen wood and in tree stumps, on the forest floor and in the leaf litter, on low vegetation and in twigs, on tree trunks and up into the canopy. A single record is known from internodes of the myrmecophyte Humboldtia laurifolia, from Gilimale in Sri Lanka. They also colonise more restricted spaces such as plant spathes and rot holes in wood and they attend a wide range of homopterous insects for honeydew. Although usually regarded as a pest or invasive species, for instance Sulaiman (1997) observes that it tends the mealybug responsible for pineapple wilt disease in Sri Lanka, albipes also has value as an important predator of the eggs of destructive insect species on coconuts in Sri Lanka (Way, Cammell, et al. (1989).
- 1 Identification
- 2 Distribution
- 3 Biology
- 4 Castes
- 5 Nomenclature
- 6 References
Bolton (2007) - A member of the T. albipes complex in the Technomyrmex albipes group. Colour of the mandibles and antennae is variable in albipes. The mandible varies from the same dark colour as the head capsule to yellowish, with all intermediate shades present. The scape is usually about the same shade as the head capsule; the funiculus may be the same colour or entirely lighter, or the apical few segments alone may be lighter. These variations are gradient and are not considered taxonomically significant.
In the past many samples of small, darkly coloured Technomyrmex in which the gaster is setose and the tarsi are white or yellow have been misidentified as T. albipes, but in particular albipes has been confused with Technomyrmex vitiensis, Technomyrmex difficilis, Technomyrmex pallipes, Technomyrmex brunneus, Technomyrmex jocosus and Technomyrmex moerens. The first three of these are also common tramp species and vitiensis was for a while considered ajunior synonym of albipes. T. vitiensis, along with its Afrotropical relative moerens, closely resembles albipes, but both have larger eyes, longer scapes and a longer promesonotum than to albipes. Also, the mesonotal profile in albipes workers is evenly curved, whereas in both other species there tends to be an angle or step in the outline, resulting in differently sloped dorsal and declivitous mesonotal faces; see also the notes under vitiensis. As for difficilis, the presence in that species of a pair of setae on the dorsal head behind the level of the posterior margin of the eye easily distinguishes them. However, workers of difficilis in which the head is abraded are difficult to distinguish from albipes; see notes under difficilis. T. pallipes should not be confused with albipes as it always has two pairs of short stubbly setae on the dorsal head behind the level of the posterior margin of the eye. T. brunneus has mandibular grooves not seen in albipes, as well as other different characters, and jocosus has a very different arrangement of setae: neither should be confused with albipes.
Keys including this Species
- Key to Afrotropical and west Palaearctic Technomyrmex
- Key to Arabian Technomyrmex
- Key to Australian Technomyrmex Species
- Key to Malagasy Technomyrmex
- Key to Micronesian Ants
- Key to New World Technomyrmex species
- Key to Oriental Technomyrmex
Distribution based on Regional Taxon Lists
Afrotropical Region: Ivory Coast, Mozambique, South Africa, Sudan, United Arab Emirates, United Republic of Tanzania, Yemen.
Australasian Region: Australia.
Indo-Australian Region: Borneo, Cook Islands, Fiji, Guam, Hawaii, Indonesia (type locality), Krakatau Islands, Malaysia, Marshall Islands, Micronesia (Federated States of), New Guinea, Niue, Philippines, Pitcairn, Solomon Islands, Sulawesi, Tokelau, Wallis and Futuna Islands.
Malagasy Region: Madagascar, Mauritius, Réunion, Seychelles.
Neotropical Region: Cayman Islands.
Oriental Region: Bangladesh, Cambodia, India, Laos, Sri Lanka, Taiwan, Vietnam.
Palaearctic Region: China, Democratic Peoples Republic of Korea, Denmark, Japan, Republic of Korea.
Check distribution from AntMaps.
Distribution based on specimens
Bolton (2007) - Distinct morphological intercastes between workers and queens, such as are relatively common in Technomyrmex vitiensis, Technomyrmex moerens, Technomyrmex brunneus, Technomyrmex pallipes and other species of the albipes group, where ocelli are present and the mesoscutellum and metanotum are developed as separate or semi-separate sclerites in otherwise worker-like forms, appear absent from material examined of genuine albipes. Only a few basically very worker-like forms with slightly posteriorly expanded mesonota have been seen. This observation may be merely a sampling artifact indicating that most albipes material examined has been of foragers, not from nest samples, as in other species where intercastes have been confirmed they are confined to reproductive behaviour within colonies and do not undertake foraging activities. However, 24 samples provided in alcohol by Martin Pfeiffer (Universitat Ulm), collected at Banting, West Malaysia and Tawau, Sabah, East Malaysia, failed to produce a single obvious intercaste, although many of the samples included brood and fragments of nest material; one had brood and ergatoid males in it and another contained a dealate queen.
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- detorquens. Formica detorquens Walker, 1859: 372 (q.) SRI LANKA. Combination in Technomyrmex: Donisthorpe, 1932b: 575. Senior synonym of forticulus: Donisthorpe, 1932b: 575. Nomen oblitum, synonym of albipes: Bolton, 2007a: 68. See also: Wilson & Taylor, 1967: 84.
- forticulus. Crematogaster forticulus Walker, 1859: 372 (q., not w.) SRI LANKA. Junior synonym of detorquens: Donisthorpe, 1932b: 576; nomen oblitum, synonym of albipes: Bolton, 2007a: 68.
- albipes. Formica (Tapinoma) albipes Smith, F. 1861b: 38 (w.) INDONESIA (Sulawesi). Forel, 1891b: 98 (q.); Forel, 1908a: 21 (ergatoid m.); Karavaiev, 1926d: 441 (m.); Wheeler, G.C. & Wheeler, J. 1951: 205 (l.); Crozier, 1969: 245 (k.). Combination in Tapinoma: Mayr, 1863: 455; in Technomyrmex: Emery, 1888d: 392. Senior synonym of nigrum: Mayr, 1872: 147; Mayr, 1876: 83; of albitarse: Emery, 1893f: 249; of bruneipes, detorquens, forticulus, wedda: Bolton, 2007a: 68.
- nigrum. Tapinoma nigrum Mayr, 1862: 703 (w.) SRI LANKA. Junior synonym of albipes: Mayr, 1872: 147; Mayr, 1876: 83; Bolton, 2007a: 68.
- albitarse. Tapinoma albitarse Motschoulsky, 1863: 14 (w.q.) SRI LANKA. Junior synonym of albipes: Emery, 1893f: 249.
- bruneipes. Technomyrmex albipes var. bruneipes Forel, 1895e: 466 (w.q.m.) INDIA. Raised to species: Collingwood & Agosti, 1996: 361. Junior synonym of albipes: Bolton, 2007a: 68.
- wedda. Technomyrmex albipes r. wedda Forel, 1913e: 663 (w.q.) SRI LANKA. Junior synonym of albipes: Bolton, 2007a: 68.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (2007) - TL 2.4 - 2.9, HL 0.56 - 0.63, HW 0.52 - 0.58, SL 0.48 - 0.58, PW 0.35 - 0.42, WL 0.66 - 0.78 (50 measured). Indices: CI 87 - 95, SI 91 - 102, or 24 - 27, EPI 70 - 88, DTI 110 - 124.
Frontal carina with 2 (very rarely 3) setae: in profile the anteriormost seta at the torulus, the posteriormost seta approximately at the level of the anterior margin of the eye. Dorsum of head posterior to this entirely lacks setae. With head in full-face view the anterior clypeal margin with a very weak, shallow median indentation; sides of head shallowly convex and the posterior margin with a small shallow indentation medially. Eyes located in front of midlength, EPI < 90; outer margin of eye usually just fails to break, or sometimes just touches, the outline of the side. With mesosoma in profile the mesonotal outline is evenly curved, without a distinct step or angle in the outline that defines conspicuous dorsal and declivitous faces. Number of setal pairs on mesosoma: pronotum 1 - 3; mesonotum 0 1 (usually 0); propodeal dorsum 0; lateral margins of propodeal declivity 1 - 2 (very rarely 3), usually with one just above the spiracle, another higher up. With the propodeum in profile its dorsum and declivity meet in a short, blunt, but very narrowly rounded curve, not a distinct sharp angle. Straight-line length of propodeal dorsum in profile is less than depth of declivity to spiracle. Gastral tergites 1 - 4 each with numerous setae, distributed everywhere on the sclerites; maximum length of setae on first gastral tergite is usually slightly less than the maximum diameter of the eye but sometimes the two are subequal. Head, mesosoma, petiole and gaster blackish brown to black; in profile the gaster is often slightly lighter than the mesosoma. Coxae, femora and tibiae uniformly blackish brown to black, same colour as the mesosoma or gaster; never with strongly contrasting lighter coxae. Tarsi of middle and hind legs white to dull yellowish, paler than the tibiae.
Bolton (2007) - Syntype workers, Indonesia: Sulawesi, “Tond” (= Tondano) (A.R. Wallace) (Oxford University Museum of Natural History) [examined].
- Formica (Tapinoma) albipes: Syntype, 2 workers, Tondano, Sulawesi, Indonesia, Oxford University Museum of Natural History.
The correct identities of some species referred to as albipes in relatively recent publications can be ascertained with some degree of certainty, but those of earlier studies (e.g. Starcke, 1940), and even some more recent ones (e.g. Brophy, 1994) in the absence of the relevant specimens, must remain equivocal. Material mentioned as introductions in British hothouses by Donisthorpe (1927) consists of series of albipes, Technomyrmex vitiensis and Technomyrmex pallipes. References to albipes in recent Chinese and Japanese works such as Imai, Hikara, Kondoh, et al. (2003), Zhou (2001), Wu & Wang (1995) and the intensive studies by Tsuji, Furukawa, et al. (1991), Yamauchi, Furukawa, et al. (1991), Tsuji & Yamauchi (1994) and Ogata. Murai, et al. (1996), are all Technomyrmex brunneus. Also referable to brunneus is Radchenko’s (2005) record of “albipes” from North Korea. The discussions of albipes in Bourke & Franks (I 995}, based on these Japanese publications, should also be referred to brunneus. Recent Australian references to albipes in Shattuck (1999), and Andersen's (2000) unnamed fig. 29 are probably all Technomyrmex difficilis and this is also the species which has recently colonised Florida so successfully (Deyrup, 1991; Vail, Davis, et al., 1994; DeyruJl, Davis & Cover, 2000; Warner, 2003). The species referred to as albipes by Brown (l958) in New Zealand is probably Technomyrmex jocosus. The short discussion of albipes by Shattuck (1992b) appears to be a fusion of several species; it certainly includes vitiensis as that is the only species known to occur in conservatories in Golden Gate Park, California. The vast amount of Pacific Islands material listed in Wilson & Taylor (1967) certainly includes both albipes and vitiensis, and probably also difficilis; a critical re-assessment of the entire collection would be needed to resolve the identities. Terron (1972) presented some notes on alate and ergatoid males of a species close to albipes, which may refer to Technomyrmex moerens or perhaps even pallipes.
- Bolton, B. 2007b. Taxonomy of the dolichoderine ant genus Technomyrmex Mayr (Hymenoptera: Formicidae) based on the worker caste. Contributions of the American Entomological Institute. 35(1): 1-149.
- Crozier, R. H. 1969a . Cytotaxonomic studies on some Australian dolichoderine ants (Hymenoptera: Formicidae). Caryologia 21: 241-259 (page 245, karyotype described)
- Donisthorpe, H. 1932b. On the identity of some ants from Ceylon described by F. Walker. Ann. Mag. Nat. Hist. 10(9): 574-576 (page 575, Junior synonym of detorguens)
- Emery, C. 1888d. Über den sogenannten Kaumagen einiger Ameisen. Z. Wiss. Zool. 46: 378-412 (page 392, Combination in Technomyrmex)
- Emery, C. 1893h. Voyage de M. E. Simon à l'île de Ceylan (janvier-février 1892). Formicides. Ann. Soc. Entomol. Fr. 62: 239-258 (page 249, Senior synonym of albitarse)
- Forel, A. 1891c. Les Formicides. [part]. In: Grandidier, A. Histoire physique, naturelle, et politique de Madagascar. Volume XX. Histoire naturelle des Hyménoptères. Deuxième partie (28e fascicule). Paris: Hachette et Cie, v + 237 pp. (page 98, queen described)
- Forel, A. 1908b. Fourmis de Ceylan et d'Égypte récoltées par le Prof. E. Bugnion. Lasius carniolicus. Fourmis de Kerguelen. Pseudandrie? Strongylognathus testaceus. Bull. Soc. Vaudoise Sci. Nat. 44: 1-22 (page 21, ergatoid male described)
- Karavaiev, V. 1926d. Ameisen aus dem Indo-Australischen Gebiet. Treubia 8: 413-445 (page 441, male described)
- Mamet, R. 1954. The ants (Hymenoptera Formicidae) of the Mascarene Islands. Mauritius Inst. Bull. 3: 249-259 (see also)
- Mayr, G. 1863a. Formicidarum index synonymicus. Verh. K-K. Zool.-Bot. Ges. Wien 13: 385-460 (page 455, Combination in Tapinoma)
- Mayr, G. 1872. Formicidae Borneenses collectae a J. Doria et O. Beccari in territorio Sarawak annis 1865-1867. Ann. Mus. Civ. Stor. Nat. 2: 133-155 (page 147, Senior synonym of nigrum)
- Mayr, G. 1876. Die australischen Formiciden. J. Mus. Godeffroy 12: 56-115 (page 83, Senior synonym of nigrum)
- Sharaf, M. R.; Collingwood, C. A. and Aldawood, S. A. 2011. Technomyrmex montaseri sp. n., a new ant species of the T. gibbosus-group from Oman (Hymenoptera, Formicidae) with a key to the Technomyrmex species of the Arabian Peninsula. ZooKeys. 108:11-19. PDF
- Shattuck, S. O. 1994. Taxonomic catalog of the ant subfamilies Aneuretinae and Dolichoderinae (Hymenoptera: Formicidae). Univ. Calif. Publ. Entomol. 112:i-xix, 1-241. (page 157, see also)
- Smith, F. 1861b. Catalogue of hymenopterous insects collected by Mr. A. R. Wallace in the islands of Ceram, Celebes, Ternate, and Gilolo. [part]. J. Proc. Linn. Soc. Lond. Zool. 6: 36-48 (page 38, worker described)
- Tsuji, K.; Furukawa, T.; Kinomura, K.; Takamine, H.; Yamauchi, K. 1991. The caste system of the dolichoderine ant Technomyrmex albipes (Hymenoptera: Formicidae): morphological description of queens, workers and reproductively active intercastes. Insectes (page 413, see also)
- Yamane, S., Leong, C.-M., Lin, C.C. 2018. Taiwanese species of the ant genus Technomyrmex (Formicidae: Dolichoderinae). Zootaxa 4410: 35–56 (DOI 10.11646/zootaxa.4410.1.2).
- Wheeler, G. C.; Wheeler, J. 1951. The ant larvae of the subfamily Dolichoderinae. Proc. Entomol. Soc. Wash. 53: 169-210 (page 205, larva described)
- Wilson, E. O.; Taylor, R. W. 1967b. The ants of Polynesia (Hymenoptera: Formicidae). Pac. Insects Monogr. 14: 1-109 (page 82, Senior synonym of rufescens and vitiensis, Revived from synonymy) | <urn:uuid:f6a1b408-9b2c-462c-9a88-29ba4cd14c22> | 2.9375 | 4,391 | Knowledge Article | Science & Tech. | 49.996626 | 95,490,396 |
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Rydberg matter is an exotic phase of matter formed by Rydberg atoms; it was predicted around 1980 by É. A. Manykin, M. I. Ozhovan and P. P. Poluéktov. It has been formed from various elements like caesium, potassium, hydrogen and nitrogen; studies have been conducted on theoretical possibilities like sodium, beryllium, magnesium and calcium. It has been suggested to be a material that diffuse interstellar bands may arise from. Circular Rydberg states, where the outermost electron is found in a planar circular orbit, are the most long-lived, with lifetimes of up to several hours, and are the most common.
Rydberg matter consists of usually hexagonal planar clusters; these cannot be very big because of the retardation effect caused by the finite velocity of the speed of light. Hence, they are not gases or plasmas; nor are they solids or liquids; they are most similar to dusty plasmas with small clusters in a gas. Though Rydberg matter can be studied in the laboratory by laser probing, the largest cluster reported consists of only 91 atoms, but it has been shown to be behind extended clouds in space and the upper atmosphere of planets. Bonding in Rydberg matter is caused by delocalisation of the high-energy electrons to form an overall lower energy state. The way in which the electrons delocalise is to form standing waves on loops surrounding nuclei, creating quantised angular momentum and the defining characteristics of Rydberg matter. It is a generalised metal by way of the quantum numbers influencing loop size but restricted by the bonding requirement for strong electron correlation; it shows exchange-correlation properties similar to covalent bonding. Electronic excitation and vibrational motion of these bonds can be studied by Raman spectroscopy.
Due to reasons still debated by the physics community because of the lack of methods to observe clusters, Rydberg matter is highly stable against disintegration by emission of radiation; the characteristic lifetime of a cluster at n = 12 is 25 seconds. Reasons given include the lack of overlap between excited and ground states, the forbidding of transitions between them and exchange-correlation effects hindering emission through necessitating tunnelling that causes a long delay in excitation decay. Excitation plays a role in determining lifetimes, with a higher excitation giving a longer lifetime; n = 80 gives a lifetime comparable to the age of the Universe.
|n||d (nm)||D (cm−3)|
In ordinary metals, interatomic distances are nearly constant through a wide range of temperatures and pressures; this is not the case with Rydberg matter, whose distances and thus properties vary greatly with excitations. A key variable in determining these properties is the principal quantum number n that can be any integer greater than 1; the highest values reported for it are around 100. Bond distance d in Rydberg matter is given by
where a0 is the Bohr radius. The approximate factor 2.9 was first experimentally determined, then measured with rotational spectroscopy in different clusters. Examples of d calculated this way, along with selected values of the density D, are given in the adjacent table.
Like bosons that can be condensed to form Bose–Einstein condensates, Rydberg matter can be condensed, but not in the same way as bosons. The reason for this is that Rydberg matter behaves similarly to a gas, meaning that it cannot be condensed without removing the condensation energy; ionisation occurs if this is not done. All solutions to this problem so far involve using an adjacent surface in some way, the best being evaporating the atoms of which the Rydberg matter is to be formed from and leaving the condensation energy on the surface. Using caesium atoms, graphite-covered surfaces and thermionic converters as containment, the work function of the surface has been measured to be 0.5 eV, indicating that the cluster is between the ninth and fourteenth excitation levels.
- Wang, Jiaxi; Holmlid, Leif (2002). "Rydberg Matter clusters of hydrogen with well-defined kinetic energy release observed by neutral time-of-flight". Chemical Physics. 277 (2): 201. Bibcode:2002CP....277..201W. doi:10.1016/S0301-0104(02)00303-8.
- É.A. Manykin; M.I. Ozhovan; P.P. Poluéktov (1980). "Transition of an excited gas to a metallic state". Sov. Phys. Tech. Phys. Lett. 6: 95.
- É.A. Manykin, M.I. Ozhovan, P.P. Poluéktov; Ozhovan; Poluéktov (1981). "On the collective electronic state in a system of strongly excited atoms". Sov. Phys. Dokl. 26: 974–975. Bibcode:1981SPhD...26..974M.
- V.I. Yarygin; V.N. Sidel’nikov; I.I. Kasikov; V.S. Mironov & S.M. Tulin (2003). "Experimental Study on the Possibility of Formation of a Condensate of Excited States in a Substance (Rydberg Matter)". JETP Letters. 77 (6): 280. Bibcode:2003JETPL..77..280Y. doi:10.1134/1.1577757.
- S. Badiei & L. Holmlid (2002). "Neutral Rydberg Matter clusters from K: Extreme cooling of translational degrees of freedom observed by neutral time-of-flight". Chemical Physics. 282: 137–146. Bibcode:2002CP....282..137B. doi:10.1016/S0301-0104(02)00601-8.
- S. Badiei & L. Holmlid (2006). "Experimental studies of fast fragments of H Rydberg matter". Journal of Physics B. 39 (20): 4191–4212. Bibcode:2006JPhB...39.4191B. doi:10.1088/0953-4075/39/20/017.
- J. Wang; Holmlid, Leif (2002). "Rydberg Matter clusters of hydrogen (H2)N* with well-defined kinetic energy release observed by neutral time-of-flight". Chemical Physics. 277 (2): 201. Bibcode:2002CP....277..201W. doi:10.1016/S0301-0104(02)00303-8.
- S. Badiei & L. Holmlid (2002). "Rydberg Matter of K and N2: Angular dependence of the time-of-flight for neutral and ionized clusters formed in Coulomb explosions". International Journal of Mass Spectrometry. 220 (2): 127. Bibcode:2002IJMSp.220..127B. doi:10.1016/S1387-3806(02)00689-9.
- A.V. Popov (2006). "Search for Rydberg matter: Beryllium, magnesium and calcium". Czechoslovak Journal of Physics. 56: B1294. Bibcode:2006CzJPh..56B1294P. doi:10.1007/s10582-006-0365-2.
- L. Holmlid (2008). "The diffuse interstellar band carriers in interstellar space: All intense bands calculated from He doubly excited states embedded in Rydberg Matter". Monthly Notices of the Royal Astronomical Society. 384 (2): 764–774. Bibcode:2008MNRAS.384..764H. doi:10.1111/j.1365-2966.2007.12753.x.
- J. Liang; M. Gross; P. Goy; S. Haroche (1986). "Circular Rydberg-state spectroscopy". Physical Review A. 33 (6): 4437–4439. Bibcode:1986PhRvA..33.4437L. doi:10.1103/PhysRevA.33.4437. PMID 9897204.
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- L. Holmlid (2007). "Direct observation of circular Rydberg electrons in a Rydberg Matter surface layer by electronic circular dichroism". Journal of Physics: Condensed Matter. 19 (27): 276206. Bibcode:2007JPCM...19A6206H. doi:10.1088/0953-8984/19/27/276206.
- L. Holmlid (2007). "Stimulated emission spectroscopy of Rydberg Matter: observation of Rydberg orbits in the core ions". Applied Physics B. 87 (2): 273–281. Bibcode:2007ApPhB..87..273H. doi:10.1007/s00340-007-2579-9.
- L. Holmlid (2009). "Nuclear spin transitions in the kHz range in Rydberg Matter clusters give precise values of the internal magnetic field from orbiting Rydberg electrons". Chemical Physics. 358: 61–67. Bibcode:2009CP....358...61H. doi:10.1016/j.chemphys.2008.12.019.
- L. Holmlid, "Rotational spectra of large Rydberg Matter clusters K37, K61 and K91 give trends in K-K bond distances relative to electron orbit radius". J. Mol. Struct. 885 (2008) 122–130.
- L. Holmlid, "Clusters HN+ (N = 4, 6, 12) from condensed atomic hydrogen and deuterium indicating close-packed structures in the desorbed phase at an active catalyst surface". Surf. Sci. 602 (2008) 3381–3387.
- L. Holmlid, "Precision bond lengths for Rydberg Matter clusters K19 in excitation levels n = 4, 5 and 6 from rotational radio-frequency emission spectra". Mol. Phys. 105 (2007) 933–939.
- L. Holmlid, "Classical energy calculations with electron correlation of condensed excited states – Rydberg Matter". Chem. Phys. 237 (1998) 11–19. doi:10.1016/S0301-0104(98)00259-6
- H. Åkesson, S. Badiei and L. Holmlid, "Angular variation of time-of-flight of neutral clusters released from Rydberg Matter: primary and secondary Coulomb explosion processes". Chem. Phys. 321 (2006) 215–222.
- L. Holmlid, "Amplification by stimulated emission in Rydberg Matter clusters as the source of intense maser lines in interstellar space". Astrophys. Space Sci. 305 (2006) 91–98.
- L. Holmlid, "The alkali metal atmospheres on the Moon and Mercury: explaining the stable exospheres by heavy Rydberg Matter clusters". Planet. Space Sci. 54 (2006) 101–112.
- E.A. Manykin, M.I. Ojovan, P.P. Poluektov. "Theory of the condensed state in a system of excited atoms". Sov. Phys. JETP 57 (1983) 256–262.
- L. Holmlid, "Vibrational transitions in Rydberg Matter clusters from stimulated Raman and Rabi-flopping phase-delay in the infrared". J. Raman Spectr. 39 (2008) 1364–1374.
- É. A. Manykin, M. I. Ozhovan, P. P. Poluéktov, "Decay of a condensate consisting of excited cesium atoms". Zh. Éksp. Teor. Fiz. 102, 1109 (1992) [Sov. Phys. JETP 75, 602 (1992)].
- E.A. Manykin, M.I. Ojovan, P.P. Poluektov. "Impurity recombination of Rydberg matter". JETP 78 (1994) 27–32.
- Holmlid, Leif (2002). "Conditions for forming Rydberg matter: condensation of Rydberg states in the gas phase versus at surfaces". Journal of Physics: Condensed Matter. 14 (49): 13469. doi:10.1088/0953-8984/14/49/305.
- I. L. Beigman and V. S. Lebedev, "Collision theory of Rydberg atoms with neutral and charged particles". Phys. Rep. 250, 95 (1995).
- L. Holmlid, "Redshifts in space caused by stimulated Raman scattering in cold intergalactic Rydberg Matter with experimental verification". J. Exp. Theor. Phys. JETP 100 (2005) 637–644.
- Badiei, Shahriar; Holmlid, Leif (2002). "Magnetic field in the intracluster medium: Rydberg matter with almost free electrons". Monthly Notices of the Royal Astronomical Society. 335 (4): L94. Bibcode:2002MNRAS.335L..94B. doi:10.1046/j.1365-8711.2002.05911.x.
- J. Wang, K. Engvall and L. Holmlid, "Cluster KN formation by Rydberg collision complex stabilization during scattering of a K beam off zirconia surfaces". J. Chem. Phys. 110 (1999) 1212–1220.
- R. Svensson and L. Holmlid, "Very low work function surfaces from condensed excited states: Rydberg matter of cesium". Surface Sci. 269/270 (1992) 695–699. | <urn:uuid:0af1c538-e270-4934-bbec-07abf6788903> | 3.46875 | 3,095 | Knowledge Article | Science & Tech. | 75.475168 | 95,490,417 |
Particle physics background, now in astrophysics and cosmology. It's a big Universe out there!
A gravitational-wave standard siren measurement of the Hubble constant
2017; 551 (7678): 85-+
On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first 'multi-messenger' astronomical observation. Such observations enable GW170817 to be used as a 'standard siren' (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic 'distance ladder': the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.
View details for DOI 10.1038/nature24471
View details for Web of Science ID 000414222900049
View details for PubMedID 29094696
- The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models ASTROPHYSICAL JOURNAL LETTERS 2017; 848 (2)
- The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. I. Discovery of the Optical Counterpart Using the Dark Energy Camera ASTROPHYSICAL JOURNAL LETTERS 2017; 848 (2)
- GREAT3 results - I. Systematic errors in shear estimation and the impact of real galaxy morphology MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 2015; 450 (3): 2963-3007
- THE THIRD GRAVITATIONAL LENSING ACCURACY TESTING (GREAT3) CHALLENGE HANDBOOK ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 2014; 212 (1)
- GRAVITATIONAL LENSING ACCURACY TESTING 2010 (GREAT10) CHALLENGE HANDBOOK ANNALS OF APPLIED STATISTICS 2011; 5 (3): 2231-2263
- Results of the GREAT08 Challenge: an image analysis competition for cosmological lensing MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 2010; 405 (3): 2044-2061
- HANDBOOK FOR THE GREAT08 CHALLENGE: AN IMAGE ANALYSIS COMPETITION FOR COSMOLOGICAL LENSING ANNALS OF APPLIED STATISTICS 2009; 3 (1): 6-37 | <urn:uuid:d198d7e6-2ee5-42fe-8e3b-1d621cc6b34e> | 2.71875 | 828 | Academic Writing | Science & Tech. | 19.846517 | 95,490,420 |
Taphonomy: The Study of Preservation
What does preservation mean?
Preservation is a very broad category in paleontology. It is the study of the alteration of fossilized materials, either in large scale structure or the micro-anatomical or molecular level. Taphonomy, on the other hand, involves every process involved in the final condition of a specimen that is put on display in museum or found in a collection. This includes all the events that happen to an organism following death, its burial, and removal from the ground. Different examples of these processes include transport, surface weathering, and movement of elements by animals. Almost synonymous with taphonomy, preservation includes the disparate fields of geochemistry, microbiology, paleobotany, invertebrate and vertebrate paleontology and sedimentology.
The study of preservation has the potential to reveal the structure of ancient muscles, or the way a footprint of a dinosaur gets preserved, or the types of ancient proteins in a plant leaf. This field has been expanding in the last several decades as paleontology focuses more and more on discovering new frontiers.
What does normal preservation look like?
Ordinarily, paleontologists do not find organ impressions, skin, feathers, or any other soft tissue preserved. Fossilization usually only leaves behind the bones, and these are what science has to draw interpretations from. Fortunately, you can tell a lot from bones if you know what to look for.
- The Mastodon Page at PRI (more info) - This site shows the progress of a mastodon dig by the Paleontological Research Institute in New York State.
- The Archaeology of Yellow Jacket Pueblo: Faunal Remains (more info) - This cave fauna is a good example of the ways in which fossils are typically preserved in subterranean environments.
- Cave Taphonomy - An additional page on cave taphonomy.
- A Taphonomic Study of the Wealden Beds of southern Britain - A page on the taphonomy of famous English Cretaceous deposits.
What is exceptional preservation?
Exceptional preservation can refer to preservation of fine detail, preservation of soft-tissue, preservation of delicate structures or preservation of biomolecules or microbes.
- Digital Paleobiology of an Ordovician Lagerstatten] - A very interesting page that melds preservational aspects of Lagerstatten and three-dimensional morphology of trilobites.
- [resource 18581] - A summary page on fossil sites around the world that are characterized by incredible preservation.
- [resource 19308] - This web site is designed as a learning and teaching resource based on the Rhynie chert, a rock formation from northeast Scotland that contains superbly preserved 400 million year old terrestrial and freshwater flora and fauna.
- [resource 19363] - This website has photographs of exceptional preservation of human remains.
Teaching Resources[hidden 850703 'me teaching resources (more info)
- Roadkill as Teaching Aids in Historical Geology and Paleontology This Journal of Geoscience Education article illustrates how and why to use roadkill to teach students about paleontology. The article includes a description of the physical characteristics of fossils and roadkill; natural vs. anthropogenic agents of dismemberment and flattening; teaching aids, preparation, and methods; as well as photo examples of roadkill.
- Experimental Investigation of the Processes of Fossilization This Journal of Geoscience Education article describes a laboratory experiment that demonstrates the relative rates of decay and disarticulation of hard-parts, nonmineralized skeletal parts, and internal soft-parts of animals, plants, and fungi.
- Fossilization and Taphonomy (more info) This is a classroom exercise from the Idaho Museum of Natural History on the preservation of fossils. The exercise is designed for high school or introductory college classes. This activity is to be used in conjunction with the Digital Atlas of Idaho Geology. The website includes the necessary handouts and sample questions. | <urn:uuid:947c497a-974c-49d6-b3bd-7218c8a23df7> | 3.921875 | 838 | Knowledge Article | Science & Tech. | 15.822382 | 95,490,421 |
A boost for the endangered butterfly whose Continental cousins fluttered by
One of Britain's most endangered butterflies has enjoyed a reversal of fortune after some of its counterparts flew over from the Continent.
Numbers of the small orange, black and gold-winged tortoiseshell had plummeted by 80 per cent.
Its caterpillars were being eaten from the inside by the sturmia bella fly, which lays its eggs on nettles.
A small tortoiseshell butterfly: The species is getting a boost from cousins from the Continent
But recent weeks have seen a resurgence in the tortoiseshell, pictured, with hundreds spotted along the east coast and sightings in Dorset. It is thought they flew across from Northern Europe, possibly stopping to rest now and again on passing ships.
Sadly, the outlook is not quite so cheerful for Britain's best-known frogs and toads.
Last night at London Zoo, Sir David Attenborough warned that - because of climate change, disease and habitat destruction - half Britain's amphibious species could be extinct within 40 years.
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Theme Leader: Rodrigo Costa
It is conceivable that no known living entity in the major multicellular, eukaryotic lineages is completely devoid of microorganisms. Ranging from simple associations dominated by a single or few mutualist(s), such as the squid-Vibrio and gutless worm symbioses, to the complex “microbiomes” associated with e.g. the human gut, plant roots or marine corals and sponges, it seems indisputable that microorganisms in the three domains of life are capable of populating any micro-niche offered by their animal and plant hosts. Indeed, life, as we know, is strongly underpinned by inter-domain symbiotic relationships (Bacteria-Archaea-Eukarya).
In this context, the Marine Metagenomics and Microbial Ecology Team at BSRG seek to understand the causes and consequences of microbial diversity and function in nature, with emphasis on prokaryote-eukaryote symbiotic relationships in the marine realm. It applies molecular and bioinformatics tools in conjunction with creative experimental designs to unravel the composition and function of symbiotic consortia in natural settings and microcosms, with the ultimate aim to harness and exploit the metabolic versatility of complex microbiomes for the development of renewable sources of biotechnological appliances.
Our current projects within this subject include
- Evolutionary and ecological relationships between hosts and symbionts;
- In-faunal and ad-plantae biogeochemical cycling;
- Symbiotic microorganisms and host developmental biology;
- Antibiotic biosynthesis and resistance;
- Horizontal gene transfer;
- Cultivation of as-yet uncultured symbiotic bacteria;
- Microbe-microbe and host-microbe chemical signalling;
- Potential biotechnological appliances and services deriving from symbiont-host biological activities;
- Responses of microbial communities to climate change and pollution;
- Model study systems include the microbiomes of marine sponges, corals, algae, seagrasses and fish, as well as rhizosphere- and human-associated microbial communities;
Some of our latest Publications
Diez, C., Esteves, A.I.S., Costa, R., Nielsen, C., & Thomas, T. Detecting signatures of a sponge-associated lifestyle in bacterial genomes.
Environmental Microbiology Reports (2018). doi.org/10.1111/1758-2229.12655
Karimi, E., Beate, S., Soares, A., Jochen B., Henstchel-Humeida, U., Costa, R.* Metagenomic binning reveals versatile nutrient cycling and distinct
adaptive features in alphaproteobacterial symbionts of marine sponges. FEMS Microbiology Ecology (2018). doi.org/10.1093/femsec/fiy074
Karimi, E., Ramos, M., Gonçalves, J.M.S., Xavier, J.R., Reis, M.P., & Costa, R.* Comparative metagenomics reveals the distinctive features of the Spongia officinalis endosymbiotic
consortium. Frontiers in Microbiology 8:2499 (2017). doi.org/10.3389/fmicb.2017.02499
Keller-Costa, T., Eriksson, D., Gonçalves, J.M.S., Gomes, N.C.M., Lago-Lestón, A., & Costa,R. The gorgonian coral Eunicella labiata hosts a distinct prokaryotic consortium amenable to cultivation. FEMSMicrobiology Ecology (2017). doi.org/10.1093/femsec/fix143
Moitinho-Silva, L., Nielsen L., et al. (40 authors). The sponge microbiome project. GigaScience, 6(10): 1-7 (2017). doi.org/10.1093/gigascience/gix077
Dr. Newton Carlos C.M. Gomes, Aveiro University, Portugal
Dr. Cymon J. Cox, Centre of Marine Sciences, Algarve University, Portugal
Dr. Jorge Gonçalves, Centre of Marine Sciences, Algarve University, Portugal
Dr. Joana R. Xavier, University of Bergen, Norway
Prof. Jan Dirk van Elsas, University of Groningen, The Netherlands
Prof. Ute Hentschel-Humeida, University of Kiel, Germany
Prof. Thomas Wichard, Jena University, Germany
Prof. Georg Pohnert, Jena University, Germany
Prof. Soren Sorensen, University of Copenhagen, Denmark
Prof. Raquel Peixoto, Rio de Janeiro University, Brazil
“Harnessing the power of the microbial metamobilome: using marine sponges as models to uncover novel biotechnological appliances from symbiont communities”
Role: Coordinator / Principal Investigator.
Financial support: FCT. Project id: PTDC/MAR-BIO/1547/2014.
Period: January 2016 – December 2018.
Funding: 191.436,00 €.
“Deciphering the codes of communication between marine sponges and their symbionts: an integrative metabolomics-transcriptomics approach”
Role: Principal Investigator.
Financial support: VW Stiftung, Germany.
Context: bilateral collaboration Germany-Portugal. Ancillary research project in the framework of the Lichtenberg Professorship granted to Prof. Georg Pöhnert (Institute of Inorganic and Analytical Chemistry, Jena University, Germany). Project id: 81 040-2.
Period: December 2014 – November 2015.
Funding: 49.560,00 €. | <urn:uuid:06bd6de3-00ac-4629-bd7b-991709028725> | 2.9375 | 1,245 | About (Org.) | Science & Tech. | 30.817361 | 95,490,473 |
Author: Max Born
Publisher: Courier Corporation
Release Date: 2012-05-23
Semi-technical account includes a review of classical physics (origin of space and time measurements, Ptolemaic and Copernican astronomy, laws of motion, inertia, more) and of Einstein's theories of relativity.
Author: Lillian R. Lieber
Publisher: Paul Dry Books
Release Date: 2008
"A clear and vivid exposition of the essential ideas and methods of the theory of relativity...can be warmly recommended especially to those who cannot spend too much time on the subject." -- Albert Einstein. Using "just enough mathematics to help and not to hinder the lay reader", Lillian Lieber provides a thorough explanation of Einstein's theory of relativity. Her delightful style, in combination with her husband's charming illustrations, makes for an interesting and accessible read about one of the greatest ideas of all times.
Author: Alan Morton
Publisher: Evans Brothers
Release Date: 2008-09-01
Genre: Discoveries in science
Einstein's Theories of Relativity looks at the life and times of the man himself and the beliefs about the laws of physics prior to his theories. It explains what relativity is, & how we can understand it in relation to our everyday lives, before investigating in detail the theories of Special and General Relativity. The book goes on to show how these amazing ideas opened up a whole new understanding of universal forces, from the power in the nucleus of an atom to the way massive bodies in space behave.
Einstein's theory of relativity confounded and excited both professional and amateur scientists with its explanation of the intricacies of how the world and the universe truly work, rather than how people wished or believed they worked. His view of relativity dismantled Newton's theory of space and time as absolutes, adding the concept of curved space-time, which deals with the velocity of motion. Einstein explains his theory of physics in a way that was designed not only for scientists with a knowledge of the complicated math involved but for the general reader as well.
Whether it is true or not that not more than twelve persons in all the world are able to understand Einstein's Theory, it is nevertheless a fact that there is a constant demand for information about this much-debated topic of relativity. The books published on the subject are so technical that only a person trained in pure physics and higher mathematics is able to fully understand them. In order to make a popular explanation of this far-reaching theory available, the present book is published.
Author: Albert Einstein
Publisher: Open Road Media
Release Date: 2011-09-27
E=mc2 is the world’s most famous equation. Discover the thought process and physics behind general relativity and Einstein’s contribution to science, in this authorized edition. In this collection of his seven most important essays on physics, Einstein guides his reader step-by-step through the many layers of scientific theory that formed a starting point for his discoveries. By both supporting and refuting the theories and scientific efforts of his predecessors, Einstein reveals in a clear voice the origins and meaning of such significant topics as physics and reality, the fundamentals of theoretical physics, the common language of science, the laws of science and of ethics, and an elementary derivation of the equivalence of mass and energy. This remarkable collection allows the general reader to understand not only the significance of Einstein’s masterpiece, but also the brilliant mind behind it. This authorized ebook features a new introduction by Neil Berger and an illustrated biography of Albert Einstein, which includes rare photos and never-before-seen documents from the Albert Einstein Archives at the Hebrew University of Jerusalem.
This book aims to introduce to the reader the main thread of development from Newton's laws to Einstein's theory of relativity. Limited by its scope and avoiding as much as possible the use of mathematical apparatus, the authors try to clarify the most fundamental ideas and concepts. Both authors hold a deep reverence for Galileo and Einstein, and this book is dedicated to these two great scientists.
Clear, concise exposition of both the special and general theories of relativity, intended for nonscientific readers with a knowledge of high school math. Topics include simultaneity, time dilation, length contraction, the possibility of travel to a distant star, non-Euclidean geometries, black holes, and the structure of the universe. 158 illustrations.
Author: Dr. Jim Ras
Release Date: 2016-09-03
This is an introduction to Einstein's space-bending, time-stretching theory of Relativity, written by the master himself. Special and General relativity explain the structure of space time and provide a theory of gravitation, respectively. Einstein's theories shocked the world with their counterintuitive results, including the dissolution of absolute time.
Double-volume work features the establishment of a general philosophical system in which Einstein's theory of relativity is regarded as the natural progression of the motives inherent to mathematics and the physical sciences. 1923 edition.
Exploring the ferocious opposition which once surrounded the theory of relativity, this fascinating account details the strategies and motivations of Einstein's detractors. A unique insight into the dynamics of scientific controversies, ideal for anyone interested in the history and philosophy of physics, popular science, and the public understanding of science.
Did you know that Einstein’s Theory of Relativity was confirmed decades after his death? That’s how brilliant Albert Einstein is! In this book, we’re going to discuss the Theory of Relativity. What does it mean and how does it affect our lives? Get ready for some big facts. Get a copy today!
Author: Albert Einstein
Publisher: George Braziller
Release Date: 2003
Genre: Biography & Autobiography
The influence of Einstein's contributions on so many branches of physics is such that if one wanted to describe its full extent, it would be hard to know where to begin. His work and discoveries are so fundamental that each achievement alone would have gu | <urn:uuid:ff2b27ef-5be8-46cd-a244-0c374c38752a> | 2.59375 | 1,228 | Content Listing | Science & Tech. | 32.63611 | 95,490,474 |
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Trichonympha is a genus of parabasalid excavates that lives in the hindgut of xylophagous insects in the superfamily Blattoidea. Trichonympha species are present in four termite families (Termopsidae, Rhinotermitidae, Kalotermitidae, and Hodotermitidae) as well as the genus of wood-feeding cockroach Cryptocercus. They are symbiotes, in that they break down the cellulose in the wood and plant fibers their hosts eat.
Trichonympha resembles teardrops or pears that are wearing wigs. They are motile, and feed by engulfing wood and plant fibers through phagocytosis, which always occurs at the broad ends of their bodies.
It was originally suspected that Trichonympha could not digest cellulose without the aid of internal bacterial symbiotes, but studies using cultured Trichonympha demonstrated that the protist is able to metabolize cellulose independently of symbiotic bacteria. The presence of spirochete ectosymbiotes embedded in its cell membrane, and together with Trichonympha's own flagella, give the protist its characteristic "wiggy" appearance and grant it motility. Researchers are unsure whether the spirochetes move their host around, in the manner a group of excited dogs drag around their dog-walker, or if Trichonympha "commands" them to move it around, much like a charioteer controls the horses of a chariot.
- Ikeda-Ohtsubo, Wakako; Brune, Andreas (2009). "Cospeciation of termite gut flagellates and their bacterial endosymbionts: Trichonympha species and Candidatus Endomicrobium trichonymphae'". Molecular Ecology. 18 (2): 332–42. doi:10.1111/j.1365-294X.2008.04029.x. PMID 19192183.
- Yamin, M. A. (1981). "Cellulose Metabolism by the Flagellate Trichonympha from a Termite Is Independent of Endosymbiotic Bacteria". Science. 211 (4477): 58–9. Bibcode:1981Sci...211...58Y. doi:10.1126/science.211.4477.58. PMID 17731245.
- Guichard, P.; Desfosses, A.; Maheshwari, A.; Hachet, V.; Dietrich, C.; Brune, A.; Ishikawa, T.; Sachse, C.; Gonczy, P. (2012). "Cartwheel Architecture of Trichonympha Basal Body". Science. 337 (6094): 553. Bibcode:2012Sci...337..553G. doi:10.1126/science.1222789. PMID 22798403.
- López-García, Purificación; Tai, Vera; James, Erick R.; Perlman, Steve J.; Keeling, Patrick J. (2013). "Single-Cell DNA Barcoding Using Sequences from the Small Subunit rRNA and Internal Transcribed Spacer Region Identifies New Species of Trichonympha and Trichomitopsis from the Hindgut of the Termite Zootermopsis angusticollis". PLoS ONE. 8 (3): e58728. Bibcode:2013PLoSO...858728T. doi:10.1371/journal.pone.0058728. PMC . PMID 23536818.
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Largest angle of the triangle
Calculate the largest angle of the triangle whose sides have the sizes:
2a, 3/2a, 3a
2a, 3/2a, 3a
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To solve this example are needed these knowledge from mathematics:
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From which law follows directly the validity of Pythagoras' theorem in the right triangle? ? | <urn:uuid:06e0f4d5-b5b0-4f84-ace0-5a7d98e3d59f> | 3.28125 | 726 | Tutorial | Science & Tech. | 82.280237 | 95,490,480 |
When Does A Liquid Become A Solid?
9 January 2018, 16:01
Mystery Hour Question
At what point does a liquid become a solid?
Name: Calum, Liverpool.
Qualification: Chemical Engineering student.
Answer: There is no one answer to this question! A liquid become a solid when its viscosity is 0. This is different for every substance. There is no period of transition and no point when something is more solid than liquid. It is either one or the other. | <urn:uuid:a74d6b20-1694-460a-90dd-04213bdab775> | 3.078125 | 105 | Q&A Forum | Science & Tech. | 57.63948 | 95,490,481 |
A Web API is an application programming interface for either a web server or a web browser. It is a web development concept, usually limited to a web application's client-side (including any web frameworks being used), and thus usually does not include web server or browser implementation details such as SAPIs or APIs unless publicly accessible by a remote web application.
A server-side web API is a programmatic interface consisting of one or more publicly exposed endpoints to a defined request-response message system, typically expressed in JSON or XML, which is exposed via the web--most commonly by means of an HTTP-based web server. Mashups are web applications which combine the use of multiple server-side web APIs.Webhooks are server-side web APIs that take as input an Uniform Resource Identifier (URI) that is designed to be used like a remote named pipe or a type of callback such that the server acts as a client to dereference the provided URI and trigger an event on another server which handles this event thus providing a type of peer-to-peer IPC.
Endpoints are important aspects of interacting with server-side web APIs, as they specify where resources lie that can be accessed by third party software. Usually the access is via a URI to which HTTP requests are posted, and from which the response is thus expected.
Endpoints need to be static, otherwise the correct functioning of software that interacts with it cannot be guaranteed. If the location of a resource changes (and with it the endpoint) then previously written software will break, as the required resource can no longer be found at the same place. As API providers still want to update their web APIs, many have introduced a versioning system in the URI that points to an endpoint, for example the Clarifai API: The endpoint for the tagging functionality within the web API has the following URI: "https://api.google.com/v1/tag/". The "/v1/" part of the URI specifies access to the first version of the web API. If Clarifai decides to update to version two, they can do this while still maintaining support for third party software that uses the first version.
Web 2.0 Web APIs often use machine-based interactions such as REST and SOAP. RESTful web APIs are typically loosely based on HTTP methods to access resources via URL-encoded parameters and the use of JSON or XML to transmit data. By contrast, SOAP protocols are standardized by the W3C and mandate the use of XML as the payload format, typically over HTTP. Furthermore, SOAP-based Web APIs use XML validation to ensure structural message integrity, by leveraging the XML schemas provisioned with WSDL documents. A WSDL document accurately defines the XML messages and transport bindings of a Web service.
Server-side web APIs are interfaces for the outside world to interact with the business logic. For many companies this internal business logic and the intellectual property associated with it are what distinguishes them from other companies, and potentially what gives them a competitive edge. They do not want this information to be exposed. However, in order to provide a web API of high quality, there needs to be a sufficient level of documentation. One API provider that not only provides documentation, but also links to it in its error messages is Twilio.
However, there are now directories of popular documented server-side web APIs.
The number of available web APIs has grown consistently over the past years, as businesses realize the growth opportunities associated with running an open platform, that any developer can interact with. ProgrammableWeb tracks 9000 Web APIs that were available in 2013, up from 105 in 2005.
Web APIs have become ubiquitous. There are few major software applications/services that do not offer some form of web API. One of the most common forms of interacting with these web APIs is via embedding external resources, such as tweets, Facebook comments, YouTube videos, vines, etc. In fact there are very successful companies, such as Disqus, whose main service is to provide embeddable tools, such as a feature-rich comment system. Any website of the TOP 100 Alexa Internet ranked websites uses APIs and/or provides its own APIs, which is a very distinct indicator for the prodigious scale and impact of web APIs as a whole.
As the number of available web APIs has grown, open source tools have been developed to provide more sophisticated search and discovery. APIs.json provides a machine-readable description of an API and its operations, and the related project APIs.io offers a searchable public listing of APIs based on the APIs.json metadata format.
Many companies and organizations rely heavily on their Web API infrastructure to serve their core business clients. In 2014 Netflix received around 5 billion API requests, most of them within their private API.
Many governments collect a lot of data, and some governments are now opening up access to this data. The interfaces through which this data is typically made accessible are web APIs. Web APIs allow for data, such as "budget, public works, crime, legal, and other agency data" to be accessed by any developer in a convenient manner.
The United States are one of the pioneers in opening up government data for anybody and everybody to use. On its website, data.gov, the following is stated: "Since his first full day in office, President Obama has prioritized making government more open and accountable and has taken substantial steps to increase citizen participation, collaboration, and transparency in government. Data.gov, the central site for U.S. Government data, is an important part of the Administration's overall effort to open government."
Google created their Native Client architecture which is designed to help replace insecure native plug-ins with secure native sandboxed extensions and applications. They have also made this portable by employing a modified LLVM AOT compiler.
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1. Introduction: MVVM is an abbreviation of Model View ViewModel. A Model-View-ViewModel is software architectural pattern that was created way back in 2005 by John Gossman. MVVM is quite similar to MVC, but it provides better connect of the UI and business sense than that of MVC. In MVVM pattern, each view on the screen will be backed by a view model and it represents the data for the view. 2. MVVM flow Layout & Theoretical Background: In an MVC-based project, View is Connecting with its ViewController. ViewController is easily overloaded and increases its size when the application becomes bigger. So ViewController is affected in MVC. This drawback Solution in MVVM pattern. MVVM Data flow shown in Below Fig 1. As per above figure, the three core components of MVVM model respectively are, 1. As per above figure, the three core components of MVVM model respectively are, 2. Model: it is class that holds our App Data. 3. View/ViewController: it presents our View and ViewController Class. 4. ViewModel: ViewModel binds the Model and ViewController, it’s the heart of MVVM design pattern. It provides the connection between the model class and the view/view controller. View Model is capable of observing changes in Model and synchronize itself with the events. Example: Let’s start Understanding MVVM Design pattern with a simple example. First, create a project in Xcode. Also, create Model and ViewModel Class. In this project, we have taken tableView and shown employee name and its department using MVVM design pattern. Model: Shown model class in below Fig 2. In model class, we have defined variable and function, as per our requirement. Fig. 2 View-Model: - In View-Model Class we have taken a Model object, so we have used - Model class property in View- Model Class. In our project model Employee is a model object. - Here Model and View-Model class are connecting to each other. - Shown View-Model Class in Fig. 3 Fig. 3 View (Controller): - First, take View-Model object in ViewController Class. myViewModel is View-Model object. In our project, we have taken table view. - In this class, View-Model and View-Controller are connecting to each other. View-model object through, we get all data of View-Model class as per requirement. - View (Controller) class shown in Fig. 4. Fig. 4 Also shown Output in fig. 5 Fig. 5 Advantages: - Code reuse: In View-Model class we implement init, setup and view presentation method, so we use this functionality in each new view controller. - Improved Testability: In MVVM we can make all classes separate so we can easily find an error. - Reduce code size Disadvantages: - MVVM pattern not useful for single View application, when we work on Multiple views then it is useful. Conclusion: MVC and MVVM both patterns are useful for iOS app development. MVVM is new Concept for the design pattern. MVVM is more useful when app size is bigger because the separation of Model, View and View-Model class can reduce complexity.
As we all know that Apple has introduced an API for natural language processing from iOS 5, which allows us to tokenize text, detect the language and determine parts of speech.
Basically Natural Language Processing (NLP) is used to either predict your next word or suggest a correction while typing a word. NLP is likely used in Siri.
The main API is NSLinguisticTagger which is used in analyzing and tagging text, segmenting content into paragraphs, sentences, and words. In iOS 11, NSLinguisticTagger becomes more powerful. It is used for following schemes,
Let’s take experiment with the new NLP API. At first, we need to do is create a tagger. In NLP, a tagger can read the text and give different information to it such as part of speech, recognize names and languages, perform lemmatization etc.
When you initialize NSLinguisticTagger, you have to pass in the tagSchemes in which you want to perform. Let’s do it:
1. Language Identification
You can retrieve this language by accessing the dominantLanguage property of the NSLinguisticTagger. NSLinguisticTagger analyzes the text to get the dominant language.
The punctuations and whitespaces are omitted with NSLinguisticTagger Options. Tokenization is the process of classifying the text into paragraphs, sentences, and words. We call them tagger.enumerateTags function to tokenize.
It will be splitting the above string into words and then we get the list of each word that is there in the sentence.
Deriving the dictionary form of the word is called Lemmatization. For example, a user wants the result for word ‘run’. if you were able to consider base forms of the word, you would be able to also get results for ‘running’, ‘ran’, ‘will run’, etc.
Here the raw value of the tag is lemma of a particular word. So In output we got is stem form of each word token.
4. Parts of Speech
This is used to get each token’s lexical class. It will return each word and its part of speech. You can see the noun, preposition, verb, adjective, or determiner.
In the output, You can see the verbs, nouns, prepositions, adjectives, etc.
5. Named Entity Recognition
Named Entity Recognition is allowing you to recognize any names, organizations, or places. You would have seen certain keywords highlighted like numbers, names when you use some iPhone application.
In the following example we identify whether the token is named entity like personal name and place name.
Here we have used tag variable which is used by tagger to look for particular tags in sentence.
Natural Language Processing is already a powerful tool, growing exponentially and that can be widely used in the Applications. Apple’s Siri and Facebook’s messenger bots are the best examples of NLP.
In this article, we, 9series, have covered about NLP, its terms and how it works. If you have more experience with it or find more features then feel free to share your own experience with us.
Stay tuned for upcoming articles.
As we all know following a procedure can be very boring, hectic and time-consuming in the development process. Most of the developers working in an iPhone app development company in India have the tendency to jump directly into the coding because of all the effects and fun there.
According to our experience in application development, it is very helpful to follow some practices before jumping into the coding part. It always helps in reducing complexity, increasing the readability, easier to maintain, avoiding redundancy, etc. Also, it is helpful to other team members to understand the concept and the flow of the application if working in a team.
So, let us check and dig the topics one-by-one which will be helpful to create a proper architecture of the application and also be helpful for the entire team in the future.
1. Define Coding Style
Coding Style is the most important aspect that should be defined before you start writing any application, especially while working in a team.
It includes the below points:
2. Define Architecture for The Application
It is necessary to decide the architecture for the app before diving into the code. Choice of suitable architecture will make the app more testable, easier to understand and reduce its maintenance cost. You can choose any architecture from traditional MVC to recent or fancier MVVM. There are so many resources available on the web from which you can understand and decide architecture for the application. Below is some reference for the design pattern. https://www.raywenderlich.com/132662/mvc-in-ios-a-modern-approach
3. Setup Folder Structure
Instead of keeping all the files in a single directory, it is a good idea to follow some folder structure for the project. It will make the files well organized and easily findable, you can use the following:
Although this may look negligible at the first sight but for the big projects, it is certainly more helpful, well structured and easier to understand for every team member working in the project.
4. Manage Your Dependencies
It is very certain that everyone is using some third party libraries in their application. So for that, you should use one of the dependency managers from the ones that are already available. We usually prefer CocoaPods which has the vast collection of libraries and easy integration facilities, you can use any of below depending on the requirements.
5. Setup Certificates and Profiles for Code Signing
Most annoying and painful task of the application development is creating certificates and provisioning profile. This process includes creating application id (Unique identifier for the device), adding devices to developer account, creating certificates (development certificate for debug the application and distribution certificate for releasing the application.), creating provisioning profiles (same as certificates), also creating APNS certificates if your application is willing to get the push notifications from the server, providing .pem file to PHP developers or .p12 file to .NET developers.
6. Continuous Integration
This is very much advisable either working in a team or individual. This will keep track of your development process and at any point of time, you can check the updates for the particular date or time period. You can use either git or SVN whichever is suitable for you for the continuous integration. This will help all the team members to pull the latest updates done by the other member as well as push the new changes to the other team members. The main benefit of this is you will have all your code on the server and you will be able to access it from anywhere.
7. Setting Application Icon and Splash Screen
Though this is not a mandatory task and not that much important for the initial stage but setting it initially make your application first impression good. Application icon carries a variety of sizes of the single image so instead of forcing designer for all size images you can just ask of 1024*1024 size icon with some background and you will be able to get all the required size images from some online or online tools. Splash screen set up is also carry 2 ways either you set the launch images or you can use the launch screen for setting up the splash screen.
In this article, we have covered the major points about defining the iOS Application development Architecture. Though list can be expanded more with more topics like how code style should be applied, commenting guide, etc. You can also add your own topics, thoughts, etc. and feel free to share with us.
We hope that these tips will be helpful for you to define and start the application with the best style.
Happy Coding! and feel free to share your own experience on “[email protected]”.
Hello everyone, as we all know that Share Extension is appeared from iOS 8, then the capability to share content with other entities, such as social sharing websites or upload services can be done in an easy and convenient way.
We, 9series, an iOS application development company has started doing all the development using Advanced Programming Language Swift.
So today, we are going to build a Shared Extension app in iOS10 with Swift 3.0, an ability to show an icon on the common share-sheet that associates with our main app, which handles the sharing of the content that the user has requested. So the user can easily switch from one app to another, for example, we are sharing a photo from the album with some content that switches our app where we want to upload data to the server.
This is mainly a programming article, so you are required to have Xcode 8 on Mac. Let’s get started !!!
1. Make a new Xcode Project
First Create a cocoa touch Single View Application in Xcode 8 with some basic UI. Like it is shown below
Design the screen with UILabel, UIImageView, UITextView and with UIButton. When user comes with some sharable content from parent app, we can upload or we can use anywhere in our app.
For Eg, let’s create the Share Extension.
Give some proper name of that extension and it will show you popup view for activating your extension scheme. Choose Activate to use this scheme for building and debugging.
Note: Schemes can be chosen from the toolbar or Product menu.
3. Make an App Group
We want to communicate two app for sharing some content, but Apple doesn't want a complete free flow of data between the two. Apple recommends a shared NSUserDefaults as a meeting ground where the two app can exchange their data.
Now, we need to make an app group.
Click on your project in the Navigator Pane of Xcode, click on capabilities and your app under the target list turns on App Groups. Give it a name like “group.BUNDLE IDENTIFIER”.
Now click on your extension and do the same.
4. Implementing Share Extensions in Swift
First open your viewController, we won’t go into much detail, because it's a destination viewController. So we can read content data from User Defaults which is shared by user from Share ViewController.
We have also created an IBAction of Upload button, so that content and photo which is shared by user can be used anywhere in our app.
Here, “sharedIdentifier” is the UserDefaults suiteName that we have used for the app group name. An extensionContext where we get a list of NSExtensionItems. This is a fixed array of data sent to our extension from a parent app. We are getting photo and content from our photos app that are already set to our main app.
Let's look at the “ShareViewController” from our Shared Extension Folder which is subclass of SLComposeServiceViewController. SLComposeServiceViewController has some methods and properties associated with the lifecycle of a share-sheet composition view.
isContentValid() :- It is called every time when the content in the compose view changes. Here, we can check the input data is valid or not. It is called first, and will disable the post button when it evaluates to false.
didSelectPost() :- As the name suggests, it is called when the user presses the post button. Here we can do something with the user input. Once the upload is scheduled, you must call completeRequestReturningItems(, completionHandler:) so that the host app can un-block its UI. When the upload request is done, it calls the completion handler that was passed into the previous mentioned function call.
configurationItems() :- Here, we can add more things for the user to select when they are sharing. In our case we are sharing a photo with contentText. You can also make it more dynamic with some other controls.
contentText :- A string which represents what the user has typed into the composer.
charactersRemaining :- Is a number which appears on the compose sheet. When negative number shows, its appearance becomes red.
Here is the code of “ShareViewController”
Here, we are selecting one image from photo album and then clicking on share button, it will open share sheet with our Share Extension app Icon.
Select that app and it will open composition view.
We have mentioned maximum characters of contentText as 100, so if you enter more than 100 characters, than it will generate alert message and post button will be disabled. You can also check number of characters at the end of compose sheet.
Configuration! items is where we can add more things for the user selection, when they are sharing. Like, Open UITableViewController as subview Controller and selecting User Input it will display as item value at the bottom of compose sheet.
Configuration! items has title, value, and a tapHandler. So you can add extra functionality for selection from User.
ExtensionContext has list of attachment as NSExtensionItem. We’ll loop through the attachments, and look for one typed as an image. It will have the type identifier kUTTypeImage. NSItemProvider items are lazily loaded images, videos, URLs and so on. We’ll load it using “loadItemForTypeIdentifier”. This has a completion handler, where we’ll read the image from the URL, and then we’ll save it to defaults.
After pressing Post Button, It will save Image in UserDefaults with “Image” key, and contentText with “Name” key.
We have created two utility methods for saving data to user defaults and for alert message.
Till now, Apple wouldn’t accept this in their app store. We need to tell iOS when to show our share extension, and what can be selected. Otherwise when we compile we’ll get a warning.
“Warning: Embedded binary’s NSExtensionActivationRule is TRUE PREDICATE”
So for that, open the “info.plist” as source code by right clicking on it. We’re going to change the NSExtensionAttributes section. This means our extension is activated only for images, and only when it’s a single image. If you select more than one image, the extension app automatically hides from share-sheet.
You can change your display name of your app in share sheet by replacing the code in the “info.plist” of your Extension.
5. Test Your Share Extension
1. First you have to simply run your app.
2. Then run your Share Extension.
3. When suggested to choose an app to run, choose Photos.
4. Once the extension starts running, select a photo and tap on the Share button.
5. On the first run, you will need to add your extension to the share sheet.
6. Click on the More button to the right of the other share icons and turn on the switch for your extension & then select Done.
7. Now you will be able to see your extension icon in share - sheet.
8. Select an individual photo and click on share. By selecting your app, add some content and press post button.
The image will be saved to your main app. To confirm this, redirect to your app. You can check the content you entered in the textview and the image above the content.
In this article, our best iOS application developers in India, have only covered some basic UI. You can also make it more dynamic with other controls.
Hopefully, all of this will help you share data with your parent app.
Happy Coding! and feel free to share your own experience on “[email protected]”.
Hey, welcome back!!! Let’s move one step ahead with the open source development language from Swift 3 to Swift 4. We, at 9series, have filtered out points of our next strides in developing mobile apps using Swift 4.
Swift 4 is the latest major release for iOS App Developer that is intended to be completed in the fall of 2017. Its main focus is to provide source compatibility with Swift 3 code while implementing essential feature work that needs to achieve binary stability in the language. It will contain valuable enhancements to the core language and Standard Library, particularly in the generics system and an overhaul of the String type.
Source Compatibility Modes
The Swift 4 compiler will provide two language modes: Swift version 3 and Swift version 4. Swift 3 established the language for source-level stability and now Swift 4 releases source compatibility as a feature moving ahead.
New Features in Swift 4
Swift has many other features to make your code more expressive:
Multi-Line String Literals
To start a string literal, you need to write three double quotation marks: """ then press return. After pressing return key, start writing strings with any variables, line breaks and double quotes. To end multi line string literal again write ””” in new line. Ex:-
Strings are Collections
Just like in earlier version of Swift, Strings can be handled as a collection. No need to write string.characters.something to perform string manipulation.
Dictionary Functionality has Improved
Swift 4 combines some additional functionality to dictionaries to make them more strong, and also to make them work more like you would expect. Let's start with a simple example: Modifying dictionaries in Swift 3 does not return a new dictionary. Instead, it returns an array of tuples with key/value labels.
After that code runs you can't read distinction["Maths"] because it is no longer a dictionary. Instead, you need to use distinction.value, which is not good for us because we apply filter on dictionary and we got an array.
As of Swift 4, this acts more like you would expect: you get back a latest dictionary. Obviously this will break any existing code that relies on the array return type.
Similarly, the map() method on dictionaries got a key-value tuple passed in, and could return a single value to be added to an array.
That has not changed in Swift 4, but there is a new method called mapValues(). It allows you to modify the values and place them back into a dictionary using the original keys.
Here we try to form different buckets where each bucket will contain values having same first character in their name. For Example:-.
It's now likely to obtain a dictionary key and provide a default value to use if the key is missing. In following statement if there is no value for key “Bio” found then it will print default value.
Built in Encoding and Decoding
Swift 4 appears with built-in encoders and decoders for JSON. JSON to Model conversion comes in built in.
One Sided Range
Swift 4 introduces Python-like one-sided collection slicing, where the missing side is automatically assumed to be the start or end of the collection.
Like with other Swift releases, 4.0 was announced at WWDC '17 and released in beta form for developers alongside Xcode 9. This release of Swift added quite a few refinements and features to the programming language. First release of Swift 4.0 will bring overall stability to the source and binary interface, or ABI.
Stay tuned for other technical and development articles.
Eagerly waiting for the features of Xcode 9? Here it is. Apple has released Xcode 9, the newest version of its free integrated development environment (IDE) for building iOS application, macOS, watchOS, and tvOS apps.
With everything you need to create amazing apps for Apple platforms, Xcode 9 is unbelievably quick and consistently smooth while editing even the largest files. It also understands your code better than ever. Powerful new refactoring tasks happen in place, renaming symbols across Swift, Objective-C, and even user interface files without skipping a beat. And with source compatibility in Swift 4, Xcode 9 uses the same compiler to build existing Swift 3 code and updated Swift 4 code, so you can migrate at your own pace.
Brief About Xcode 9
All New Editor
Xcode 9 has a brand new Source Editor, entirely written in Swift. In the new editor you can use the Fix interface to fix multiple issues at once. Also, when mousing around your projects, you can hold the Command key and visually see how structures in your code are organized.
The source code editor has been completely rebuilt for amazing speed. It scrolls at a constantly smooth rate, no matter the files size. And it looks better, too, with preferences that give you greater control over line spacing, multiple font styles, and even the type of cursor. Issues have been redesigned to flow nicely with your code with Fix-its that are grouped together so you can commit multiple changes in a single click.
You can now increase and decrease the source editor font using ⌘ with + and ⌘ with -. When text is selected, typing an opening delimiter adds a matching closing delimiter at the end of the selection.
Refactor and Transform
The new editor goes beyond text entry with a new built-in refactoring and transformation engine. When you select a symbol or block of code, the editor will offer powerful operations such as ‘Extract’ or ‘Rename.’
One of the most basic refactorings is to rename a class, and all references to that class in the project are renamed as well, including references in the Storyboard and the filename itself.
Xcode 9 supports the following transformations and refactorings:
Groups in the Project Navigator are now more closely associated with directories in the file system.
Source Control and GitHub
Xcode 9 now connects easily with your GitHub account making it very easy to see a list of your existing projects, clone projects, manage branches, use tags, and work with remotes.
With your GitHub account built into Xcode, the clone window shows all of your personal GitHub repositories, as well as all the repositories where you added a star. From this window, you can search all of GitHub and check out a project with just a click.
A new indexing engine runs as part of the build process, so Xcode understands your code automatically.
Searching large projects feels quick – up to 50 times faster. And a new build system dramatically lowers the overhead of tasks that coordinates compiler, linker, and other tools.
With Xcode 9 and Xcode Server, we have almost everything in single place used to create apps for Apple TV, Apple Watch, iPad, iPhone, and Mac. As we know and experienced that no softwares can be complete or can be in a finished version, there are many new great features included in this version of Xcode. So we should definitely go for it and experience it.
We, as a mobile app developer believe that using Xcode 9, development can be done faster and can be pushed ahead with the next strides.
In this article, we, 9series, have covered about what is new in Xcode 9. If you find any new features or might have experienced with existing one then feel free to share your own experience with us.
The 2017 Worldwide Developers Conference keynote was Apple's biggest event in years, with the company introducing both new software platforms and a range of new hardware products.
As usual, the event began with the message for developers “Keep making apps, the world is depending on you”.
And as always, the event started with a keynote during which Apple announced dates (June 5–9, 2017 in San Jose) of updates for their iOS, OS X, watchOS, and tvOS platforms.
A Giant step for iPhone, A Monumental leap for iPad
Messages App Syncs Across Multiple Devices
The first new iOS 11 feature: synchronized conversations across iCloud, iOS, and macOS. Messages are moving to iCloud.
If you erase a message on your iPhone or iPad, then it will also delete from the iPad and the Mac and vice-versa. Our conversations will be stored on iCloud, which will make them easier to retrieve your future Apple devices.
There is also an update related to Apple Pay, which will now be able to pay people. Person-to-person payments let people pay directly from Messages as an iMessage app.
It uses the TouchID fingerprint sensor. And the money which received will go into your Apple Pay Cash Card, which you can use for further Apple Pay payments, or to transfer money back into your account.
It might be helpful to make payment through application and person can directly transfer money to his friends or family members or use as general. Hence, we can enhance our application to the next level in terms of eCommerce market.
Aha, Apple has made improvements to Siri that makes assistant’s voice sound more natural when responding to users. Siri will now be able to perform translations from English to Chinese, French, German, Italian, or Spanish. Wow…
As a ios developers, we can definitely use this feature into multi-language application and give better user-interface as well as performance to our app users.
Siri is also getting smarter about suggestions. On-device, learning is synced across other Apple devices but kept completely private, readable only for you. Siri gives suggestions based on personal usage of Safari, News, Mail, Messages and more. For example, as Siri learns topics or places, a user is interested in while browsing Safari.
The camera also has lots of improvements, including improved image quality. Portrait Mode in the iPhone 7 Plus can be taken with Optical Image Stabilisation, True Tone flash and HDR.
Apple has also added a new technology called High Efficiency Image File Format (HEIF) that reduces the file size of your iPhone 7 or 7 Plus photos.
This can be helpful into the application where Image and its quality is considered as the core concept.
In iOS 11, Apple has redesigned Control Center, which is the thing that users can swipe up to access frequent and important settings or change songs when listening to music.
Drag And Drop For IPAD
Apple is specially focusing on productivity for the iPad with iOS 11.
A new drag-and-drop feature lets you quickly move info or media from one split-screen app into the other besides it. Drag and drop can also be used with apps on your dock or home screen.
Lock Screen Improvement
The Lock Screen in iOS 11 has been improved so that you can see all of your Notifications in one place.
You can see all of your Notifications, simply pull it down from the top of the screen. Then you will be able to see both your recent and missed notifications in one place.
Here, we should take care about sending an extra unnecessary notifications, as our users can’t get bored from such things. And only useful notifications should be seen to attract the user of our application.
Apple announced that the Maps app in iOS 11 will support indoor mall and airport maps. The indoor maps will allow you to see which restaurants are past security at the airport. And you can also see which stores are on what levels in the malls.
Lane Guidance in Maps now encourages you to dodge missing a turn or an exit by showing which lane you should be in when you’re navigating. You can also check the speed limit of the road.
As a mobile app developer, we should think that whether this feature can put our application into an advanced level in terms of event organization kind of feature where our users can easily find the place/stall where he needs to go.
Do Not Disturb While Driving
Apple iOS 11 has a very useful safety called Do Not Disturb while Driving. This feature helps drivers stay focused on the road by automatically silencing notifications. And you can send auto-replies to your contacts in your favorites so that they know you are driving.
App Store App Improvements: A whole new design, A whole new perspective
The App Store has been redesigned from the ground to help you discover new apps and games you can’t live without. You’ll see daily stories by experts, a dedicated Games tab, lists for all kinds of apps, and much more. It’s the biggest thing to come to the App Store since apps. And now apps that are submitted to the Apple App Store are generally reviewed within 24 hours.
Apple is building augmented reality directly into the core of iOS, giving developers the tools they need to convincingly blend digital entertainment with the real world. So with help of this new framework, we can effectively introduce augmented reality into our application.
Now, it’s like behind-the-scenes stuff for iOS. It’s getting Metal 2, of course, and a new set of machine learning APIs letting developers use Apple’s natural language comprehension and facial recognition tools.
macOS High Sierra
Your Mac. Elevated
macOS High Sierra introduces new core technologies that improve the most important functions of your Mac. From re-architecting, it shows how it stores your data & how you watch videos to unleash the full power of the graphics processors.
Apple File System
To your Mac, everything you care about is data. And a file system is what organizes all that data into files and folders you can access with a click. Apple’s current file system was designed in the early days of Mac, and it has performed beautifully ever since. But today’s flash‑based Mac opens up new possibilities for innovation, so it’s time to lay a new foundation. With macOS High Sierra, Apple is introducing the Apple File System to Mac, with an advanced architecture that brings a new level of security and responsiveness.
Below are some bullet points about updates in macOS High Sierra:
More intuitive, More intelligent, More you
Apple announced a new version of watchOS. One of the most noticeable changes in watchOS 4 is the option of using a Siri watch face. This automatically displays contextual information on the Apple Watch, such as approaching appointments, and traffic reports if the wearer is going to work.
New fitness feature includes in controls, more prompts to set goals, and two-way workout data exchange with certain gym equipment. The Apple Watch will also be able to better connect with other hardware gadgets, such as continuous glucose monitors and smart tennis rackets, via NFC. This can be a useful feature where our application also interact with Watch OS.
watchOS 4 also includes a new Music app meant to improve the AirPods experience. Multiple playlists can now be synced including Apple Music-recommended playlists.
The Dock on watchOS 4 has a new look with a vertically scrolling interface with can lead to the UI Interface of the watch application. watchOS 4 can also automatically start when workouts are started, and music playback controls are integrated with the Workout app.
Control Center gains a new flashlight function using the display which also works during outdoor, night workouts as a safety feature.
In WWDC 2017, one thing to say from apple about tvOS, The Apple TV is getting a big new content, as Amazon Prime Video is coming to Apple TV and Apple’s new TV app.
New Macs and the iMac Pro
Now faster across the line
Apple also upgraded its MacBook and MacBook Pro lineup with faster processors and SSDs. It also refreshed the MacBooks.
Apple’s 13-inch MacBook Pro without the Touch Bar on top now comes with Intel core i5 processor clocked at 2.3GHz, 128GB Storage and 8GB RAM. This also has two Thunderbolts 3.0 ports.
iMac Pro: The most powerful Mac ever
The all-new iMac Pro, with its gorgeous 27-inch Retina 5K display, up to 18-core Xeon processors and up to 22 Teraflops of graphics computation, is the most powerful Mac ever made. iMac Pro packs incredible performance for advanced graphics editing, virtual reality content creation and real-time 3D rendering.
Any you can do, you can do better
The new version of the iPad Pro has a 10.5-inch display, 20 percent larger than the previous 9.7-inch model. Apple said that It features a better display with richer color and a new feature called ProMotion, which updates its content up to 120 times per second making it feel smoother and more responsive.
HomePod: Apple’s new Siri speaker
The HomePod has seven tweeters and four-inch woofer; it has an A8 chip living inside it. That’s a feature Sonos has too, letting the speakers adjust their output to, say, push the vocals down the centre of the room while bouncing the bass off the wall.
A feature will respond to “Hey, Siri,” play from your Apple Music account, and answer questions about the music it’s playing. It will also handle other Siri queries, such as weather, news, messages, podcasts, stocks, controlling smart home devices via HomeKit, etc.
Above are the announced points of Apple during WWDC 2017. Though we haven’t had a chance to look through everything yet, feel free to post any missing points or share your thoughts about these new features in iOS app development.
Want to share something innovative about the new release? Feel free to write us at [email protected].
An app extension allows you to fabricate custom functionality and content ahead your iOS app and make it accessible to users while they’re interacting with other apps or the system.
App extensions give users access to your apple app development functionality and content throughout iOS and OS X. For example, your app can now appear as a widget on current screen, offer photo filters within the Photos app, add new buttons in the Action sheet, or display a new system-wide custom keyboard. Use extensions to place the power of your app wherever your users require it most.
1. Action Extension
Action extensions permit users to transform content arising in a host app without leaving the app. You can, for example, edit images, change the text format and change the content itself, etc. At WWDC 2014, Apple revealed a demo of an Action extension that translated the text of a web page to another language without leaving Safari.
When you build a new action extension, Xcode creates a template which when used without modifying its configurations, will arise in every single action sheet by default. It won’t show any checking of the content types to decide whether or not it’s suitable for the host app.
You can make two types of action extensions: one with a user interface and one without a user interface. If you prefer the latter one, it will be restricted to Safari, but if you provide a user interface, then the extension can be made available to other apps that show that the extension supports the type of content to be transformed.
2. Audio Unit Extension
An Audio Unit app extension provides users a suitable way to build or modify audio in any iOS or macOS app that uses sound, including music production apps such as Logic Pro X or GarageBand.
The Audio Units extension framework is basically an enhanced approach to use audio apps like effects and virtual instruments within audio host apps, like Apple’s own GarageBand or other audio editing and merging apps. With the help of Audio Units, Apple let's audio plug-ins show up as UI within another app, enhancing the workflow and making the experience much like what experts are used to on the Mac in apps like Logic Pro.
3. Broadcast Upload Extension & Broadcast UI Extension
ReplayKit was introduced in iOS 9 as an approach to give users a chance to record themselves using an app or game, then share it with friends. iOS 10 takes the entire process a step further by presenting live broadcasting of ReplayKit streams, and does so by developing on existing live streaming services: users install apps that support live streaming and ReplayKit lets you clasp into them.
So, let's say you want to stream somebody's game to a service like Twitch: you begin by creating a RPBroadcastActivityViewController to let the user select which streaming service they want to use. They will revert back a RPBroadcastController that can start, pause, and stop live broadcasts, and furthermore let you know whether broadcasting is currently happening through its isBroadcasting or not.
4. Call Directory Extension
Apps can build a Call Directory Extension to recognize and hinder incoming callers by their phone number.
Both recognizing and hindering of incoming calls is set up in the implementation of the beginRequest(with:) method of the CXCallDirectoryProvider subclass of Call Extension. This method is called only when the system launches the app extension.
When a phone accepts an incoming call, the system first advises the user’s contacts to locate a matching phone number. If no match is found, the system then advises your app’s Call Directory extension to locate a matching entry to recognize the phone number. This is beneficial for applications that keep up a contact list for a user that is detached from the system contacts, such as a social network, or for classifying incoming calls that may be initiated from inside the app, such as for customer service support or a delivery notification.
To provide recognizing information about incoming callers, you use the addIdentificationEntry(withNextSequentialPhoneNumber:label:) method in the implementation of beginRequest(with:).
5. Content Blocker Extension
In iOS, a Content Blocker extension personalizes the way Safari manages your content. The extension adapts your content by blocking loads, hiding elements and dismantle cookies from Safari requests.
Using a Content Blocker extension, you grant Safari with content-blocking rules that define how Safari treats content such as scripts, images, and pop-up windows. Your rules can cover Safari-downloaded content or keep Safari from requesting particular content from the server. By reducing the number of content Safari requests, your extension can decrease the amount of time required to load pages. When you obstruct content from loading, you decrease Safari’s memory usage and enhance Safari’s performance.
In addition to obstructing unwanted content, a Content Blocker extension protects privacy.
6. Custom Keyboard Extension
A keyboard extension switches the standard keyboard with a custom keyboard. Custom keyboards are enabled in the Settings app, under General > Keyboards. Once enabled, the keyboard is accessible amid text entry within any app, aside from when editing secure text fields and phone number fields. People can enable multiple custom keyboards, and shift between them at any time.
7. Document Provider Extension
The Document Provider extension permits an app to share its documents with other apps on a user’s device in a secure and timely manner. If you have ever used the Document Picker, you might have appreciated all the apps in the Locations section.
The Document Provider extension performs as the link between the files that your app handles and other apps on the user's devices. It lets different apps import or open the files, downloading and uploading them from your server as required. Apps can also export or move their documents into your extension’s shared repository.
The Document Provider extension comprises of two separate parts: the Document Picker View Controller extension and the File Provider extension.
8. iMessages Extension
These app extensions permit developers to add new functionality directly to the Messages app in iOS 10. Users will soon be able to play games, exchange money, send videos, or make restaurant reservations all within the context of their existing iMessage conversations. Mobile App Developers can now build their own different types of apps, that vary from sticker packs to fully interactive interfaces which generates inline iMessage content.
iMessage apps work similarly as extensions. If you already have an app and need to provide iMessage functionality, you won’t require making a whole new app. You can just plug in the iMessage functionality and submit to the App Store. There’s likewise going to be a mini version of the App Store, particularly for iMessage apps, incorporated right into the Messages app. The user will be able to browse all apps compatible with iMessage and install them – right at the spot.
These app extensions are incredible features in ios app development that apps should take advantage of. In this article we, as a mobile app developers, have emphasized some of the key extensions in app. And for further more app extensions, let’s get in touch with the upcoming article.
If you have any comments or questions, feel free to contact us on “[email protected]”.
Welcome to the next level of insights about WatchOS. If you are new to this WatchOS series then please read our blog Fundamental Concept of WatchOS.
In this article, we will look about data sharing methods across Apple Watch and iOS app. Also we will check for background tasks, Apple Pay Enhancement, WatchOS Connectivity framework, What’s new in WatchOS 3.0, etc.
So, let’s start with further more features and updates for WatchOS:
Different Methods of Sharing Data Between WatchKit and iOS App
What’s New in WatchOS 3.0
With the upcoming WatchOS 3 update to all Apple Watch devices, the performance of many watch applications is definitely going to improve. This is mainly due to the new forms of background execution where watchOS apps can take advantage in order to refresh their content periodically and always have the latest information that is ready to be viewed by the user.
1. Background Task
Background tasks give your app time to keep running out of sight and ensure that the information user needs is accessible before they open your app. WatchOS 3 introduces several types of background tasks:
Background App Refresh
Utilize the WKApplicationRefreshBackgroundTask class to update your app’s status in the background. You frequently use a background app refresh task to manage other tasks. For example, you might use a background app refresh task to start an NSURLSession background transfer or to schedule a background snapshot refresh task.
2. Apple Pay Enhancement
In WatchOS 3, the PassKit framework (PassKit.framework) includes support for in-app payments on Apple Watch. In-app payments enable users to securely provide payment and contact information to pay for physical goods and services.
3. Watch Connectivity Framework Enhancements
The WatchConnectivity framework introduced in WatchOS 2 and iOS 9 is likewise increasing some new functionality with WatchOS 3 and iOS 10.
If a user has placed your app's complexity on their watch face, then you can transfer data from the phone to the watch up to 50 times in a single day. But while transferring, if the data goes beyond the limit of 50, then the user will get notifications about the exceeded limit. This is done, as in iOS 9 and WatchOS 2, via the WCSession transferCurrentComplication(userInfo:) instance method. The new functionality in watchOS 3 and iOS 10 is the WCSession remainingComplicationUserInfoTransfers property, which will show you how many transfers are left for that day.
Another new WCSession property added is the hasContentPending property, which is just a boolean value signifying whether or not there is data yet to be transferred between the iPhone and Apple Watch.
4. Existing Frameworks now available in WatchOS
5. SnapShot and Dock
In WatchOS 3, app sights have been removed entirely from the Apple Watch and instead have been displaced by the dock, which provides a rapid way for users to view and launch their favorite apps. After pressing the side button to show the Dock, users scroll through it to view snapshots of their favorite apps. When users stop scrolling and let the Dock settle for a moment, the promoted app wakes and the snapshot gets replaced by the running app.
The system automatically takes periodic snapshots of your app and uses them to populate the Dock and to serve as your app’s launch image. You can modify both the currently presented interface controller & the controller’s content before the snapshot is taken.
6. Control Center
Provides support for all-new Control Center which can be invoked by sliding up from the bottom of the screen.
7. New Watch Faces
Adds new watch faces and adds support for switching between them by swiping left/right from the edge of the watch screen.
Adds support for sharing an activity with friends using iMessage or other messaging platforms.
Adds support for tracking the progress of people in wheelchairs, showing a "Time to Roll" reminder rather than "Time to Walk" as watchOS 2 did. It is now conceivable to see 5 different workout metrics all at once. This includes distance, pace, active calories, heart rate, and elapsed time. Adds support for delaying a workout when halted at a stoplight. Support for another Breathe app guides users through a set of deep breaths to help them be more comfortable.
Adds support for a feature called SOS which allows a person to place emergency calls by holding the side button for 5 seconds.
Give us a chance to check with some convenient question-answers.
1. How many Apple Watch can I pair with one iPhone?
2. What is the maximum size for WatchKit App?
3. Can I play video on Watch App?
4. Can I fetch contact in WatchKit app?
A debt of gratitude is in order for your opportunity to peruse this article and constantly running over our blog. We trust you appreciated next level of insights about Watch OS shared by our best iOS application developers in India. Stay tuned with us for more technical and advanced articles.
Feel free to share your queries, thoughts or focuses on “[email protected]”. | <urn:uuid:a13758d8-240b-4858-9538-c406b3bffde5> | 3.8125 | 10,202 | Personal Blog | Software Dev. | 50.296915 | 95,490,502 |
Sulfur belongs to the macro-nutrients and has a variety of tasks in plants. It is not only involved in the synthesis of substances which are important for plant growth, but is also an important component of substances whose function is the defence against diseases and pests. Currently, a research group at the Max Planck Institute of Molecular Plant Physiology, led by Dr. R Hoefgen, published in cooperation with Dr. Akiko Maruyama-Nakashita and her group (Kyushu University,Japan) in Science Advances how plants determine under sulfur limiting conditions that sulfur is primarily used for growth processes and not for the production of substances which protect them against diseases and pests.
Sulfur is Essential for Plants
Sulfur, like nitrogen, phosphorus, potassium, calcium, and magnesium, is one of the macro-nutrients. Unlike micronutrients, plants need higher amounts of them for development and growth. In case of sulfur deficiency yield losses occur. This is due to the fact that sulfur affects e.g. the synthesis of carbohydrates and is a component of proteins, since the amino acids methionine and cysteine contain sulfur.
However, sulfur does not only play a role in primary metabolism, that is, where energetic substances such as sugars, proteins or fats are formed which are important for growth but sulfur is also a constituent of secondary metabolites that are involved in the synthesis of vitamins and flavours.
A special group of secondary metabolites is found in cruciferous plants such as rapeseed, cabbage, mustard, and horseradish, providing the characteristic bitter taste and pungency. These compounds are referred to as glucosinolates or mustard oil glycosides. Glucosinolates act in plants as protectants against diseases and pest infestation. They are not of much help against humans, though, as we like to eat cabbage, broccoli and co.
Pest Control on the One Hand - Pharmacological Activity on the Other
The pungency and health promoting properties of the cruciferous plants, mentioned above, are due to isothiocyanates derivatives, also known as ‘mustard oils’ produced from glucosinolates when the plant tissues are chewed by humans, pests or insects. Conversion of glucosinolates into mustard oils requires special enzymes that are spatially separated from the glucosinolates in the plant cell. When an insect nibbles on the plant the enzyme and the glucosinolates come together and produce mustard oils. These pungent compounds then repel the insects from the plant and protect it from further infestation.
Produced by the plant for defence, however, these compounds could also have positive medicinal effects. Fayezeh Aarabi, Ph.D. student in the group led by Dr. Hoefgen and the first author of the paper explains: "Mustard oils have antibacterial effects, anticancer properties and, according to the latest research, they could also have antidiabetic effects and activate enzymes of the detoxification metabolism. In order to be able to use the glucosinolates pharmacologically, it is obviously of great interest to understand how their production is regulated in the plant. This is exactly what we have been working on in collaboration with Japanese scientists and now we published our results."
Regulation of Glucosinolate Production
If a cruciferous plant such as cabbage, rapeseed or the target of investigation in this project, Arabidopsis thaliana, is sufficiently supplied with sulfur, glucosinolates are formed. The production of these metabolites is controlled by so-called transcription factors. Transcription factors are proteins which can bind directly to the DNA. Their task is to ensure that genes are transcribed into RNA and proteins are synthesized, which in turn ensure that the ingredients required by the plant are produced. In the present case the glucosinolates.
Dr. Rainer Hoefgen comments: "With sufficient sulfur supply, the plants can form both the substances necessary for growth and glucosinolates. If the plants receive too little sulfur, the substances essential for growth are formed, while the plant reduces the production of glucosinolates. Growth and reproduction are more important for the plant than accumulation of substances for pest control."
The identified Sulfur Deficiency Induced genes, so called SDI1 and SDI2 are responsible for reducing the production of glucosinolates. These genes are highly expressed if sulfur deficiency occurs. As a result, the proteins SDI1 and SDI2 are formed which form a complex with a transcription factor of the glucosinolate pathway, namely MYB28. This complex leads to the fact that the transcription factor can no longer perform its function and consequently fewer enzymes of the glucosinolate biosynthesis pathway are synthesized and thus, also less glucosinolates are produced.
"Our new understanding of the regulation of glucosinolate production is an important step to better control the synthesis of medically effective ingredients in plants, either through improved and optimized sulfur fertilization or the development of new breeding strategies," says Fayezeh Aarabi.
Dr. Rainer Höfgen
Max Planck Institute of Molecular Plant Physiology
Tel. +49 331 567 8205
Max Planck Institute of Molecular Plant Physiology
Tel. +49 331 567 8310
Fayezeh Aarabi, Miyuki Kusajima, Takayuki Thoge, Tomokazu Konishi, Tamara Gigolashvili, Makiko Takamune, Yoko Sasazaki, Mutsumi Watanabe, Hideo Nakashita, Alisdair R. Fernie, Kazuki Saito, Hideki Tagalhashi, Hans-Michael Hubberten, Rainer Hoefgen, Akiko Maruyama-Nakashita
Sulfur-defieciency-induced repressor proteins optimize glucosinolate biosynthesis in plants
Science Advances, 2016; 2 (10):e1601087, eCollection; doi: 10.1126/sciadv.1601087
http://www.mpimp-golm.mpg.de/2090184/growth-or-defence (press release)
http://www.mpimp-golm.mpg.de/2168/en (Website of the Institute)
Dipl. Ing. agr. Ursula Ross-Stitt | Max-Planck-Institut für Molekulare Pflanzenphysiologie
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A model of a system for growing plants to plan biological experiments in space has just left the company of ROVSING, in Ballerup near Copenhagen, on its way to ESA’s European Space Research and Technology Centre (ESTEC) in the Netherlands.
The full name of this experiment reference model is European Modular Cultivation System Experiment Reference Model (EMCS ERM). This will be used at ESTEC to plan and carry out experiments for growing plants in space. Then in 2003 the EMCS Flight Model will be flown to the International Space Station (ISS) where the experiments will be repeated in space.
A biological laboratory, Biolab SRM (Science Reference Module), is also being developed at ROVSING and after testing at ESTEC the Biolab Flight Model will be sent to the ISS.
The core of both models is a climate chamber where the humidity and composition of the air, temperature, light, water supply and a number of other parameters will be closely surveyed and regulated. In addition, the Biolab SRM will have a robotic system to allow samples to be taken automatically.
Erica Rolfe | alphagalileo
Colorectal cancer risk factors decrypted
13.07.2018 | Max-Planck-Institut für Stoffwechselforschung
Algae Have Land Genes
13.07.2018 | Julius-Maximilians-Universität Würzburg
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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Skip to comments.Einstein's Dark Energy Accelerates the Universe
Posted on 11/24/2005 10:08:26 AM PST by PatrickHenry
The genius of Albert Einstein, who added a "cosmological constant" to his equation for the expansion of the universe but later retracted it, may be vindicated by new research published today in the journal Astronomy and Astrophysics.
The enigmatic "dark energy" that drives the acceleration of the Universe behaves just like Einstein's famed cosmological constant, according to the Supernova Legacy Survey (SNLS), an international team of researchers in France and Toronto and Victoria in Canada, collaborating with large telescope observers in Oxford, Caltech and Berkeley. Their observations reveal that the dark energy behaves like Einstein's cosmological constant to a precision of 10%.
"The significance is huge," said Professor Ray Carlberg of the Department of Astronomy and Astrophysics at the University of Toronto. "Our observation is at odds with a number of theoretical ideas about the nature of dark energy that predict that it should change as the universe expands, and as far as we can see, it doesn't."
"We have set ourselves a very challenging goal - to distinguish whether the dark energy can be explained by Einstein's cosmological constant or whether a new physical theory is needed." Says Dr Isobel Hook of the University of Oxford, "So far our results are consistent with Einstein's cosmological constant, but the best is still to come. The first year results already represent the largest homogeneous set of distant supernovae, but over the full five years of the survey we will improve our precision more and more. Our goal is a measurement of the nature dark energy that will be a true legacy for years to come."
She added "Before dark energy was being considered, Einstein invented the 'cosmological constant' to make his equations fit with his ideas about the Universe, but later regretted it, calling it his biggest blunder'. Now we know he may have been closer to the truth than he realised."
The Supernova Legacy Survey (SNLS) aims to discover and examine 700 distant supernovae to map out the history of the expansion of the universe. The survey confirms earlier discoveries that the expansion of the universe proceeded more slowly in the past and is speeding up today, apparently driven by some unknown form of energy. Since scientists don't know much about this mysterious new form of energy, they call it "dark energy."
The researchers made their discovery using an innovative, 340-million pixel camera called Megacam, built by the Canada-France-Hawaii Telescope and the French atomic energy agency, Commissariat à l'Énergie Atomique. "Because of its wide field of view - you can fit four full moons in an image - it allows us to measure simultaneously, and very precisely, several supernovae, which are rare events," said Pierre Astier, one of the scientists with the Centre national de la recherche scientifique (CNRS) in France.
"Improved observations of distant supernovae are the most immediate way in which we can learn more about the mysterious dark energy," adds Richard Ellis, professor of astronomy at the California Institute of Technology. "This study is a very big step forward in quantity and quality."
Study co-author Saul Perlmutter, a physics professor at the University of California, Berkeley, says the findings kick off a dramatic new generation of cosmology work using supernovae. "The data is more beautiful than we could have imagined 10 years ago - a real tribute to the instrument builders, the analysis teams and the large scientific vision of the Canadian and French science communities."
The SNLS is a collaborative international effort that uses images from the Canada-France-Hawaii Telescope, a 3.6-metre telescope atop Mauna Kea, a dormant Hawaiian volcano. The current results are based on about 20 nights of data, the first of over nearly 200 nights of observing time for this project. The researchers identify the few dozen bright pixels in the 340 million to find distant supernovae. They acquire spectra using some of the largest telescopes on Earth-the Frederick C. Gillett Gemini North Telescope on Mauna Kea, the Gemini South Telescope on the Cerro Pachón mountain in the Chilean Andes, the European Southern Observatory Very Large Telescopes (VLT) at the Paranal Observatory in Atacama, Chile, and the Keck telescopes on Mauna Kea.
In the UK the work has been done by Dr Isobel Hook and her student, Justin Bronder, in Oxford. Their focus has been on obtaining spectra with Gemini to measure redshifts and confirm the supernova types. Only certain types of supernovae are useful for cosmology, namely those classed as "Type Ia" which they identify by particular signatures in their spectra.
The "queue" observing mode used at Gemini and VLT is ideal for this project. When they find good supernova candidates from CFHT they send instructions over the internet to the staff at Gemini and VLT, and they take data for them when the weather conditions are right for the program. The instruments used on the Gemini telescopes for this project are the GMOS - the Gemini Multi-object spectrographs - built in the UK (by the UKATC and University of Durham) and Canada.
"Only the world's largest optical telescopes - with diameters of eight to 10 metres - are capable of studying distant supernovae in detail by examining the spectrum," said Dr Isobel Hook.
The current paper is based on about one-tenth of the imaging data that will be obtained by the end of the survey. Future results are expected to double or even triple the precision of these findings and conclusively solve several remaining mysteries about the nature of dark energy.
The research was funded by the Canada-France-Hawaii Telescope, the Particle Physics and Astronomy Research Council (PPARC), the Commissariat à l'Énergie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences de l'Univers du CNRS, the Natural Sciences and Engineering Research Council of Canada, the National Research Council of Canada's Herzberg Institute of Astrophysics, the Gemini Observatory, the W. M. Keck Observatory and the European Southern Observatory.
Isn`t dark energy what the Clintons use?
This stuff sounds too complicated. I think we should just give up and say we weren't meant to understand it.
I wonder what Tesla would have to say about this!!!
Oh NOOOOOOOOOO ..... everything's changed, once again
hmmmmmm sounds to me like just another phrase for gravity.
I know it is, for me. How one can explore the nature of the universe by means of mathematical equations beats me.
What a great hobby. So what is dark matter, anyway?
Come over to the dark side, luke...
light or dark angels?
"What _is_ gravity?"
Well, since it's acutely clear that you can always get more light angles to dance on the head of a pin than dark (matter-enhanced) angles, its obvious that the missing angels are in Hell.
Which, clearly, is long since frozen over, since lighter matter emits rays.
the angles in your post are hilarious. Non euclidean, even. Or are the non-newtonian, in an einstein sort of way?
I love this stuff. After you eat that big turkey dinner tonight ... sit back and ponder STRING THEORY, the theory of everything ... now that is a mind blower.
Note that this finding required the efforts of large teams literaly all across the globe. Although we may lament the decline of American leadership in science, the reality is, the scale and scope of major scientific projects in the future will require such massive international collaboration. Not only are the days of the lone experimenter a la Faraday are over, so are the days of the lone research team.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works. | <urn:uuid:48451373-fde5-429f-b1ac-4c835f6ae44e> | 3.109375 | 1,716 | Comment Section | Science & Tech. | 41.40542 | 95,490,531 |
The next time you come across a knotted jumble of rope or wire or yarn, ponder this: The natural tendency for things to tangle may help explain the three-dimensional nature of the universe and how it formed.
An international team of physicists has developed an out-of-the-box theory which proposes that shortly after it popped into existence 13.8 billion years ago the universe was filled with knots formed from flexible strands of energy called flux tubes that link elementary particles together.
This is a computer graphic showing the kind of tight network of flux tubes that the physicists propose may have filled the early universe.
Credit: Thomas Kephart, Vanderbilt University
The idea provides a neat explanation for why we inhabit a three-dimensional world and is described in a paper titled "Knotty inflation and the dimensionality of space time" accepted for publication in the European Physical Journal C and available on the arXiv preprint server.
"Although the question of why our universe has exactly three (large) spatial dimensions is one of the most profound puzzles in cosmology ... it is actually only occasionally addressed in the [scientific] literature," the article begins.
For a new solution to this puzzle, the five co-authors - physics professors Arjun Berera at the University of Edinburgh, Roman Buniy at Chapman University, Heinrich Päs (author of The Perfect Wave: With Neutrinos at the Boundary of Space and Time) at the University of Dortmund, João Rosa at the University of Aveiro and Thomas Kephart at Vanderbilt University - took a common element from the standard model of particle physics and mixed it with a little basic knot theory to produce a novel scenario that not only can explain the predominance of three dimensions but also provides a natural power source for the inflationary growth spurt that most cosmologists believe the universe went through microseconds after it burst into existence.
The common element that the physicists borrowed is the "flux tube" comprised of quarks, the elementary particles that make up protons and neutrons, held together by another type of elementary particle called a gluon that "glues" quarks together. Gluons link positive quarks to matching negative antiquarks with flexible strands of energy called flux tubes. As the linked particles are pulled apart, the flux tube gets longer until it reaches a point where it breaks. When it does, it releases enough energy to form a second quark-antiquark pair that splits up and binds with the original particles, producing two pairs of bound particles. (The process is similar to cutting a bar magnet in half to get two smaller magnets, both with north and south poles.)
"We've taken the well-known phenomenon of the flux tube and kicked it up to a higher energy level," said Kephart, professor of physics at Vanderbilt.
The physicists have been working out the details of their new theory since 2012, when they attended a workshop that Kephart organized at the Isaac Newton Institute in Cambridge, England. Berera, Buniy and Päs all knew Kephart because they were employed as post-doctoral fellows at Vanderbilt before getting faculty appointments. In discussions at the workshop, the group became intrigued by the possibility that flux tubes could have played a key role in the initial formation of the universe.
According to current theories, when the universe was created it was initially filled with a superheated primordial soup called quark-gluon plasma. This consisted of a mixture of quarks and gluons. (In 2005 the quark-gluon plasma was successfully recreated in a particle accelerator, the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, by an international group of physicists, including three from Vanderbilt: Stevenson Chair in Physics Victoria Greene and Professors of Physics Charles Maguire and Julia Velkovska.)
Kephart and his collaborators realized that a higher energy version of the quark-gluon plasma would have been an ideal environment for flux tube formation in the very early universe. The large numbers of pairs of quarks and antiquarks being spontaneously created and annihilated would create myriads of flux tubes.
Normally, the flux tube that links a quark and antiquark disappears when the two particles come into contact and self-annihilate, but there are exceptions.
If a tube takes the form of a knot, for example, then it becomes stable and can outlive the particles that created it. If one of particles traces the path of an overhand knot, for instance, then its flux tube will form a trefoil knot. As a result, the knotted tube will continue to exist, even after the particles that it links annihilate each other. Stable flux tubes are also created when two or more flux tubes become interlinked. The simplest example is the Hopf link, which consists of two interlinked circles.
In this fashion, the entire universe could have filled up with a tight network of flux tubes, the authors envisioned. Then, when they calculated how much energy such a network might contain, they were pleasantly surprised to discover that it was enough to power an early period of cosmic inflation.
Since the idea of cosmic inflation was introduced in the early 1980s, cosmologists have generally accepted the proposition that the early universe went through a period when it expanded from the size of a proton to the size of a grapefruit in less than a trillionth of a second.
This period of hyper-expansion solves two important problems in cosmology. It can explain observations that space is both flatter and smoother than astrophysicists think it should be. Despite these advantages, acceptance of the theory has been hindered because an appropriate energy source has not been identified.
"Not only does our flux tube network provide the energy needed to drive inflation, it also explains why it stopped so abruptly," said Kephart. "As the universe began expanding, the flux-tube network began decaying and eventually broke apart, eliminating the energy source that was powering the expansion."
When the network broke down, it filled the universe with a gas of subatomic particles and radiation, allowing the evolution of the universe to continue along the lines that have previously been determined.
The most distinctive characteristic of their theory is that it provides a natural explanation for a three-dimensional world. There are a number of higher dimensional theories, such as string theory, that visualize the universe as having nine or ten spatial dimensions. Generally, their proponents explain that these higher dimensions are hidden from view in one fashion or another.
The flux-tube theory's explanation comes from basic knot theory. "It was Heinrich Päs who knew that knots only form in three dimensions and wanted to use this fact to explain why we live in three dimensions," said Kephart.
A two-dimensional example helps explain. Say you put a dot in the center of a circle on a sheet of paper. There is no way to free the circle from the dot while staying on the sheet. But if you add a third dimension, you can lift the circle above the dot and move it to one side until the dot is no longer inside the circle before lowering it back down. Something similar happens to three-dimensional knots if you add a fourth dimension - mathematicians have shown that they unravel. "For this reason, knotted or linked tubes can't form in higher-dimension spaces," said Kephart.
The net result is that inflation would have been limited to three dimensions. Additional dimensions, if they exist, would remain infinitesimal in size, far too small for us to perceive.
The next step for the physicists is to develop their theory until it makes some predictions about the nature of the universe that can be tested.
The research was supported by U.S. Department of Energy grant DE-SC0010504, the Alexander von Humboldt Foundation, The European Commission and the Portuguese Foundation for Science and Technology.
David F Salisbury | Vanderbilt University
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters
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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Welcome! This blog is being created by students in the courses Population Ecology and Biological Diversity at the University of Oregon. It is one component of their work, and for each course will unfold throughout the term. +Jessica Green & Ann Womack
Tuesday, June 11, 2013
De-Extinction: The Wrong Solution to the Problem
In 2003, scientists
set out to accomplish the unthinkable. Using cloning techniques, they transferred
fifty five bucardo embryos (an extinct sub-species of Spanish ibex, formally
known as Capra pyrenaica pyrenaica) to closely related species. The bucardo lived in the Pyrenees Mountains
for thousands of years before being hunted to extinction.By 1999, a single bucardo, a female named
Celia, remained.After her death, Celia’s
cells were preserved in labs until researchers removed the nuclei, injected
them into “blank” goat eggs missing their own DNA, and finally implanted these
eggs into hybrid mothers (Zimmer, 2013).Of these fifty five embryos, only one was carried to term, only to die
of respiratory problems ten minutes after birth. This short-lived animal became the first
animal to be born after its species
had gone extinct (Folch, et al., 2009).
(Learn Genetics, 2013)
Ten years later, the
technology to accomplish this feat has become both cheaper and better. Other extinct animals, such as the passenger pigeon
and the wooly mammoth, have the possibility of a new future with the help of “de-extinction”
tools (Zimmer, 2013). In his TED talk about “de-extinction”, Stewart
Brand (a leader in the field) highlights the growing international community of
scientists dedicated to using advancing biotechnologies to revive animals such
as the passenger pigeon or European Auroch (Brand, 2013). However, is de-extinction really the solution?
Will bringing back extinct species
really mitigate our impacts on biodiversity?
(Scienceray, 2011). Woolly mammoths -- coming soon to a zoo near you?
Brand speaks of a moral obligation
to undo the damage that humanity has wrought, but de-extinction simply gives
the extinct animals one m | <urn:uuid:58a625a0-677b-43c7-9242-38ffe768579b> | 3.34375 | 481 | Personal Blog | Science & Tech. | 41.454484 | 95,490,553 |
APRIL 21, 2016
In 2011, astronomers reported our galaxy is likely filled with roaming planets not attached to a host star, and these worlds may in fact outnumber stars in the Milky Way.
Scientists have debated over whether these objects are true planets, or light stars known as brown dwarfs. Brown dwarfs form just like stars but don’t have the mass to spark nuclear fusion at their cores.
In a new study published by The Astrophysical Journal, scientists identified one of these objects that may give answers to where these roaming objects came from.
Discovering objects throughout the galaxy
Scientists used information from NASA’s Wide-field Infrared Survey Explorer (WISE) to identify the roaming, planetary-mass object inside a young star family, known as the TW Hydrae association. The newly found object, dubbed WISEA J114724.10-204021.3, or simply WISEA 1147, is believed to be between about 5 to 10 times the mass of Jupiter.
Since the object was discovered to be an affiliate the TW Hydrae group of very young stars, astronomers recognize that it is relatively young, around 10 million years old. Also, because planets need a minimum of 10 million years to develop, and even longer to get kicked out of a solar system, WISEA 1147 is probably a brown dwarf, the study team said.
“With continued monitoring, it may be possible to trace the history of WISEA 1147 to confirm whether or not it formed in isolation,” study author Adam Schneider of the University of Toledo in Ohio, said in a NASA news release.
The study team said tracking the origins of free-floating objects and figuring out if they are planets or brown dwarfs is a struggle because they are so isolated.
“We are at the beginning of what will become a hot field – trying to determine the nature of the free-floating population and how many are planets versus brown dwarfs,” said co-author Davy Kirkpatrick of NASA’s Infrared Processing and Analysis Center (IPAC) at the CalTech.
One method to detect close roaming objects is movement in relation to other stars over time. The closer an object, the more it will seem to move against a background of more remote stars. By examining information from both sky surveys taken approximately 10 years apart, closer items jump out.
The brown dwarf WISEA 1147 was brilliantly red in survey pictures where the color red was assigned to longer infrared wavelengths, meaning that it’s dusty and young.
“The features on this one screamed out, ‘I’m a young brown dwarf,'” Schneider said.
After further evaluation, the astronomers discovered that this object is associated with the TW Hydrae group, which is around 150 light-years from Earth and just approximately 10 million years old. With an approximate mass between five and 10 times that of Jupiter, WISEA 1147 is one of the youngest and lightest brown dwarfs ever discovered. | <urn:uuid:62ec71d1-4e20-4ebe-8658-ba9422b32dca> | 3.96875 | 629 | News Article | Science & Tech. | 45.696426 | 95,490,562 |
Only Half of a Chromosome is DNA
News Nov 22, 2016
DNA makes up only half of the material inside chromosomes – far less than was previously thought – a study has revealed.
Up to 47 per cent of their structure is a mysterious sheath that surrounds the genetic material, researchers say.
While the precise function of this sheath is unknown, researchers suggest it may keep chromosomes isolated from one another during the key process of cell division.
Researchers say this so-called chromosome periphery could help to prevent errors from occurring when cells divide – a hallmark of some forms of cancer and diseases associated with birth defects.
Using advanced imaging techniques, researchers have for the first time produced detailed 3D models of all 46 human chromosomes – the structures inside cells that contain our genetic material.
Since their discovery in 1882, chromosomes have been the focus of intensive study. Despite major technical advances, the complete structure and organisation of chromosomes has remained a mystery, researchers say.
Scientists at Edinburgh developed a precise microscopy technique that allows them to study the structure of chromosomes in unprecedented detail.
The method – known as 3D-CLEM – combines light and electron microscopy with computational modelling software to produce high-resolution 3D images of chromosomes.
“The imaging technique we have developed to study chromosomes is truly ground-breaking. Defining the structure of all 46 human chromosomes for the first time has forced us to reconsider the idea that they are composed almost exclusively of chromatin, an assumption that has gone largely unchallenged for almost 100 years.” – Dr Daniel Booth, School of Biological Sciences
Analysis of the images reveals that material containing DNA and supporting proteins – known as chromatin – accounts for between 53 and 70 per cent of the total contents of chromosomes. The remaining 30 to 47 per cent is composed of the chromosome periphery.
The study, published in the journal Molecular Cell, was funded by The Wellcome Trust. The research was carried out in collaboration with the Kazusa DNA Research Institute, Japan, National Cancer Institute, US, and the University of Liverpool.
“We now have to re-think how chromosomes are built and how they segregate when cells divide, since the genetic material is covered by this thick layer of other material.” – Professor Bill Earnshaw, School of Biological Sciences
Story from Edinburgh University. Please note: The content above may have been edited to ensure it is in keeping with Technology Networks’ style and length guidelines.
Booth, D. G., Beckett, A. J., Molina, O., Samejima, I., Masumoto, H., Kouprina, N., … Earnshaw, W. C. (2016). 3D-CLEM reveals that a major portion of Mitotic chromosomes is not Chromatin. Molecular Cell, 64(4), 790–802. doi:10.1016/j.molcel.2016.10.009
DNA ‘Shield’ Discovered with Crucial Roles in Normal Cell Division, the Immune System & CancerNews
Scientists have made a major discovery about how cells repair broken strands of DNA that could have huge implications for the treatment of cancer.READ MORE
Rapid and Cost-Effective Instrument that Measures Molecular DynamicsNews
By combining mass spectrometry and thermal desorption, researchers honed a new method to measure excitation and relaxation rates of uracil, the building block of RNA.READ MORE
Bioethics Council Rules Heritable Genome Editing "Ethically Acceptable" In Certain CircumstancesNews
A leading UK bioethics advisory body has weighed in on the debate around human genetic modification, concluding that heritable genome editing – modifying the DNA of an egg, sperm or embryo with changes that will be passed on to future generations – could be ‘morally permissible’ in humans, provided key ethical tests are met. | <urn:uuid:80c782be-7f5a-4aca-8e6f-5bacea3dde85> | 3.546875 | 795 | News Article | Science & Tech. | 36.282273 | 95,490,570 |
Ultrafine bubbles, Nanobubbles, dissolved Oxygen, micro bubbles, milli bubbles, the world of bubbles can be confusing at times. Bubbles are gas-filled cavities in water, they remain suspended in water, dissolved oxygen are unbound oxygen molecules in water. Unbound oxygen behaves differently and it's important to understand the difference between a dissolved gas and a gas cavity.
Milli-bubbles are bubbles smaller than one millimeter in diameter, but larger than one micrometre. Micro-bubbles are small bubbles with a diameter between 10 to 50 μm and decreasing in size and lastly disappear under water. Nanobubbles or officially ultrafine bubbles are miniature gas bubbles in liquids with a diameter smaller than 200 nm, and have several unique physical properties other than ordinary milli-bubbles. They remain stable in water for a long time because of their negatively charged surface which can be calculated by the zeta potential, were as milli-bubbles increase in size, rise rapidly and burst at the water surface.
Smaller bubbles have better reactivity by surface enlargement
In the same volume of water, the contact area between bubbles in water filled with tiny bubbles is much larger than water filled with bigger bubbles. The increase in the contact area enhances i.e. the aerobic bacteria activities in the liquid by using oxygen gas or anaerobic activities by creating nitrogen bubbles moverover the efficiency of chemical reactions is increased between the supplied gas and liquid ingredients. In practical applications CO2 is easier available for algae and O2 is easier available for plant roots, or aerobic bacteria in soil remediation.
In the picture when we look at that mathematically: When generated, small bubbles can be created at higher concentrations than larger bubbles. The surface area of a volume of bubbles is in inverse proportion to the bubble diameter; thus, one mL of 100 nm diameter bubbles (2x10.15 bubbles) has 1000 times more surface (240 m2) than one mL of 0.1 mm bubbles (2x10.6 bubbles, 0.24 m2).
Bubbles have 3 components, gas phase, shell material and aqueous or liquid phase. The gas phase is the gas inside the bubble which is a single gas or a gas mixture. The shell material, water or a liquid surrounding the gas phase. The bubbles formation and the mechanical properties of bubbles depend on the property of shell material. The last component is aqueous phases which are the liquid or combined solution surrounding the shell material.
Furthermore, fine bubbles have an electrically charged surface are able to generate free-radicals with the micro-bubble collapse. In addition, some researchers reported that air micro bubbles were pseudo-elastic and spherical in aqueous solutions. Regarding the fluid dynamic properties bubbles have a low rising velocity in the liquid phase and low reducing frictional resistance.
Bubbles in pure water are negatively charged. The zeta potential measured in water with oxygen fine bubbles was from -45 mV to -34 mV while air fine bubbles a little lower which is from -20 mV to -17 mV. The large specific surface area and charged surface enable tiny bubbles to effectively absorb opposite charged molecules and / or small particles.
Microbubble Surface tension and gas pressure
The gas pressure inside a small bubble is higher than in a large bubble, therefore the surface tension of a small bubble is higher as well. For this reason the gas of a small bubble dissolves quicker than that of a large bubble. Small bubble rise slower than large bubbles to the top of the water surface, because of this extra time the gas transport from bubble to liquid is more efficient. Small bubble coalescence less (stick less together) than large bubbles, this is beneficial because when bubbles get bigger they raise quicker to the surface giving them less time for gas transport.
In the table below examples are given of the pressure inside the bubble depending on the size of the bubble, the calculations are based on the Young-Laplace equation.
Diameter of a bubble versus the pressure inside the bubble in water
|Diameter of a bubble||Pressure inside the bubble in water|
|1 mm||1.003 atm|
|100 μm||1.03 atm|
|10 μm||1.29 atm|
|1 μm||3.9 atm|
|500 nm||5.8 atm|
|300 nm||9.7 atm|
|200 nm||14.6 atm|
The diameter of the bubbles in water is reflected in buoyancy and rising rate. The rising rate depends on the solution properties, and Reynolds number corresponds to approximately 1 at about 100 μm of diameter. In addition, in the case of Re < 1, Stokes Law adapts well because bubbles behave as balls due to flux conditions on interface of globular bubbles. Based on the Stokes law in the table are given 3 examples of different bubble sizes and the rising speed of a bubble in water. Since ultrafine bubbles are so small and move through the liquid randomly the stokes law is not applicable to them.
Diameter of a bubble versus Rising speed of bubble in water (v s)
|Diameter of a bubble||Rising speed of bubble in water (v s)|
|100 μm||5440 μm / s|
|10 μm||54.4 μm / s = 19.6 cm/h|
|1 μm||0.544 μm / s = 2.0 mm/h|
Understanding the physicochemical properties of a compound such as solubility, stability, form definition, solid-state properties, partition coefficient and ionization constants is essential. Among the physicochemical characteristics of micro-nanobubbles, there is the large specific area and the high pressurization of gas inside the bubble, which confer to these bubbles high gas dissolution capability. The smaller the bubble size, the higher the oxygen pressure pO2 values in water, suggesting that nano-bubbles increase the pO2 values in water to greater extent than that of micro bubbles (10-50 micro meter in diameter).
Why do ultrafine bubbles live so long?
In laboratory circumstances there is the possibilities that bubbles can be kept for 3 to 6 months, I real life applications it is much shorter. The likely reason for the long-lived presence of ultrafine bubble is that the ultrafine bubble gas / liquid interface is charged, introducing an opposing force to the surface tension, so slowing or preventing their dissipation. In an electrolyte solution the positive ions become concentrated around the gas nucleus due to its negatively charged surface and act as shells that prevent the gas from dispersing (the salting-out phenomenon). Due to this characteristic of ion behavior, ultrafine bubbles remain stable for more than 6 months in electrolyte solution.
- new functional materials
- Commercial Pools
- ultrafine bubbles
- food & drinking water
- micro bubble generator
- oxygen concentrator
- ISO TC281
- fish cultivation
- inlet filter
- urban farming
- miniGaLF -Plus
- salmon pens
- oxygen therapy
- corporate house-style
- city farming
- application development
- rotational flow
- CO2 Feeder
- static mixer
- brand assets
- sleeping fish
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acniti | Project report water treatment lake with gaiaGaLF nano bubbles generator bit.ly/2ndNu1J
Cultivar lechuga atractiva con no más tip burn bit.ly/2eFZbOk #ufb #burbuja #agricultura
Cultivate attractive lettuce with no more tipburn bit.ly/2xLOZsq #agriculture #nanobubble #ufb #lettuce
acniti | What's in the name: ultrafine bubbles or nano bubbles? bit.ly/2waqqqe
Beautiful image of sea spray. Droplet and bubbles
#droplet #bubbles #ufb #nanobubble
Narragansett Beer with Ultra Fine Bubbles bit.ly/2v2FhT3 #beer #ufb #finebubble #nanobubble
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#ufb #nanobubble #detergent #ecobubble #finebubble #zaboon #laundry
Ultrafine Bubble-enhanced Ozonation for Water Treatment on Environmental XPRT bit.ly/2eJPA8Q @enviroexpert
[Article] Ultrafine Bubble-enhanced Ozonation for Water Treatment thewaternetwork.com/article-FfV/ul…
AMP Test - Google Search Console bit.ly/2tun1yv
The Water Network | by AquaSPE bit.ly/2tTTHkJ
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acniti | New article: Different Bubbles sizes and why it matters to the properties of water. bit.ly/2sthuHf
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A miniaturized sensor based on Raman spectroscopy that can quickly and accurately detect or diagnose substances at a molecular level. The system can do chemistry, biology, biochemistry, molecular biology, clinical diagnosis, and chemical analysis,
Scientists discuss a new way to apply a widely used local-structure analysis tool - known as atomic pair distribution function (PDF) analysis - to x-ray scattering data from thin films, quickly yielding high-quality information on the films' atomic structure. The work creates new avenues for studies of nanocrystalline thin films.
Scientists have developed a technique that prompts microparticles to form ordered structures in a variety of materials. The advance offers a method to potentially improve the makeup and color of optical materials used in computer screens along with other consumer products.
Researchers suggest this vaccine induces long-term protection against respiratory syncytial virus (RSV) and could serve as a novel treatment option for this disease. There is currently no licensed RSV vaccine.
Researchers have developed a new method for optical communication on a chip, which will give a possibility to decrease the size of optical and optoelectronic elements and increase the computer performance several tenfold. They have proposed the way to completely eliminate energy losses of surface plasmons in optical devices.
Scientists have used resonators made from single-crystalline diamonds to develop a novel device in which a quantum system is integrated into a mechanical oscillating system. For the first time, the researchers were able to show that this mechanical system can be used to coherently manipulate an electron spin embedded in the resonator - without external antennas or complex microelectronic structures.
Researchers have developed an optical fibre laser that emits pulses with durations equivalent to just a few wavelengths of the light used. This fastest ever device based on graphene will be ideal for use in ultrafast spectroscopy, and in surgical lasers that avoid heat damage to living tissue.
Engineering experts from Ulster University and the University of Cambridge have received 2.8 million pounds of funding for research into a carbon-based material that could transform the global manufacturing sector. | <urn:uuid:7b741e44-e33f-4245-91e4-50300b4bb325> | 2.546875 | 428 | Content Listing | Science & Tech. | 11.777247 | 95,490,582 |
Cornell entomologists have discovered that male and female mosquitoes (Aedes aegypti), which can spread such diseases as yellow and dengue fevers, "interact acoustically with each other when the two are within earshot -- a few centimeters of each other," said Ron Hoy, professor of neurobiology and behavior.
The study is available online today (Jan. 8) and will be published in a February issue of Science, said Cornell associate professor of entomology and mosquito expert Laura Harrington, a co-senior author on the study with Hoy.
"The frequency at which males and females converge is a harmonic or multiple of their wing-beat frequencies, which is approximately 400 hertz [vibrations per second] for the female and 600 hertz for the male," said Hoy.
The mating duet, generated just before the couple mates on the fly, settles at around 1,200 hertz -- roughly an octave and a half above concert A (the pitch to which instruments are tuned -- the A that has a frequency of 440 hertz and is above middle C). "That is significantly higher than what was previously thought to be mosquitoes' upper hearing limit," he added.
Interestingly, the mosquitoes adjust the harmonic resonance of their thoracic box to produce a harmonic frequency that converges at a frequency that is the female's third harmonic (three times her fundamental frequency) and the male's second harmonic (two times his fundamental frequency). The study also is the first to definitively show that contrary to previous thought, female mosquitoes are not deaf.
To study mosquito mating calls, the researchers tethered mosquitoes and flew them past each other while recording the flight tones with a special microphone. Co-first author Benjamin Arthur, a postdoctoral researcher in Hoy's laboratory, placed electrodes in the mosquitoes' auditory organ in their antennae during playback to measure physiological responses of the mosquitoes to the sounds of potential mates.
The researchers hope that their work will provide new ways to better control of mosquito populations in places where yellow and dengue fevers are significant problems.
"By studying these flight tone signals, we may be able to determine what kind of information males and females consider important when choosing a mate," said co-first author Lauren Cator, a Cornell graduate student who works with Harrington. "This will allow us to release 'sexy' transgenic or sterilized males that will be able to successfully compete with wild populations."
Dengue fever affects 50 million people annually, and two-thirds of the world's population is at risk. In recent years, it has reached epidemic levels in Asia, South and Central America and Mexico, where the number of dengue cases has increased by more than 300 percent from year to year. No dengue vaccine is available, and no treatment exists beyond supportive care.
The study was funded by the U.S. Department of Agriculture and by a $19.7 million Foundation for the National Institutes of Health grant awarded to Harrington and a global team of scientists to cure dengue fever and control the mosquitoes that transmit the viruses that cause it.
Blaine Friedlander | 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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To mark the 125th anniversary of the 1st International Polar Year, the University of Barcelona has carried out this research project in the north of the Arctic Circle to study natural climate change and the evolution of the Arctic continental margin. These are some of the details recorded in the log of the SVAIS expedition for the International Polar Year (IPY), funded by the Spanish Ministry of Education and Science.
On board the BIP Hespérides, a scientific research ship belonging to the Spanish navy, the expedition spent the boreal summer studying records of natural climate change and the relief of the ocean floor in the Fram Straight – an area in which the cold waters of the Arctic Ocean come into contact with the warmer waters of the Atlantic – from three million years ago to the last deglaciation, between 20,000 and 10,000 years ago.
The expedition set sail on 29 July from the island of Spitzberg in the Svalbard Archipelago (Norway), a traditional whaling area situated only 1,338 kilometres from the North Pole. Under the midnight sun, the boat set a course for the Storfjorden Trough, a little known area on the southeast edge of the Svalbard Islands, dominated in the past by large ice streams that have shaped the topography of the ocean floor.
The Polar Regions: endangered areas
The Arctic is the closest polar area to us and is much more sensitive to climate change than the Antarctic, with the exception of the Antarctic Peninsula”, explained Angelo Camerlenghi, a geologist with the Marine Geoscience Research Group at the UB, research professor at the Catalan Institute for Research and Advanced Studies (ICREA) and the scientific director of the SVAIS expedition. The Poles are the motors of the world’s ocean circulation; they reflect solar radiation and help to lower global temperatures. In addition, the Polar Regions provide unique information on the history of our planet and store climate records dating back millions of years. The Arctic is a delicate environmental sensor that highlights the effects of climate change. For the geologist Roger Urgelès, “climate change has a more dramatic effect at the Poles. The glaciers are receding and we are beginning to see that climate changes in the past have had other very significant effects on our planet.”
Scars on the ocean floor
On board ship, work continued uninterruptedly during the crossing of the Barents Sea. In order to maintain activity 24 hours a day, the team worked shifts in groups coordinated by the geologists Galderic Lastras, Ben de Mol and Roger Urgelès, under the supervision of Angelo Camerlenghi and Miquel Canals. The objective was clear: to determine the evolution of the polar continental margins in this region of the Arctic and to study the topography of the ocean floor. “We want to examine the sediments transported by the large ice streams that flowed across the Arctic 20,000 years ago, during the last glacial maximum”, explained Professor Antoni Calafat, “to understand the intensity and the duration of climate processes originated by the Poles”. Day by day the sonar screens revealed icebergs, old glaciers and the scars of submarine avalanches that had disturbed the calm of the ocean depths. On deck, the grey of the sky merged with the water and the light of the Arctic sun at times disorientated the team.
Mapping the ocean depths
Only 10% of the world’s ocean floor has been mapped in detail. “There are still many ocean regions across the world that need to be mapped”, explained Miquel Canals, head of the Marine Geosciences Research Group at the UB, “We use multibeam and TOPAS echosounders to transform the sound waves reflected by the ocean floor into bathymetric information”. In addition to multibeam bathymetry, the seismic reflection technique can also be used to produce topographic maps of the Arctic Ocean floor: special airguns send seismic waves to the ocean floor, which are reflected and recorded at the surface by hydrophone arrays fitted in cables known as streamers. The data information is processed to control for quality and then converted into 3D maps of the ocean topography using a specialized program known as the KINGDOM Suite. Shrouded in fog, the ship sailed through areas likely to contain oil or gas hydrates – molecules of gases such as methane trapped in crystalline structures of water molecules, and thought to be the great energy reserve for the future. However, as the geologist Ben De Mol pointed out, “Although they were discovered years ago, we still do not have the technology to extract gas hydrates”.
Ocean sediment dating back 10,000 years
One of the most eagerly anticipated moments took place on 4 August: on what proved to be an exciting day, the first samples of sediment from the ocean floor were raised onto the deck of the research vessel using the Piston Corer, a new hydraulic coring device for extracting marine sediment designed by Oregon State University and the Marine Technology Unit of the CSIC. During the expedition, the Piston Corer was used to obtain six samples of ocean sediment, which represent a total of 31 metres of geological history from the glacial and interglacial periods of the Quaternary Period in the Fram Strait. In the laboratory on the starboard side of the ship, the Marine Geosciences Research Group of the University of Salamanca conducted the first study of the cores extracted from the ocean floor. “We identify the microfossils – foraminifera and coccolithophorida – to determine an initial time scale of the sedimentary strata, which allows us to create a paleoenvironmental reconstruction of the Arctic”, explained the paleontologist José Abel Flores. On 17 August, after 20 days sailing through ice-free waters, the BIO Hespérides finally docked in Longyearbyen. This brought the polar expedition to an end, but the work of the scientific team will continue for several months. They will examine the material obtained to extract scientific data relevant to different fields of study (such as biostratigraphy, sedimentology, paleoclimatology and environmental geomagnetism) and reconstruct the geological and climatic history of the Arctic region.
The most northerly geological research project
The SVAIS expedition team comprised 21 scientists, including seven predoctoral students, four journalists, two high-school teachers and five technicians from the Marine Technology Unit of the Spanish National Research Council (CSIC). The team was based on the BIO Hespérides, a Spanish navy research vessel with a crew of 55, captained by Commander Luis de la Puente. The institutions taking part in the project are the UB, the ICREA, the Chemical and Environmental Research Institute of Barcelona (IIQAB-CSIC), the University of Salamanca, the National Institute of Oceanography and Experimental Geophysics (OGS) of Trieste and the Universities of Svalbard and Tromsø (Norway).
Rosa Martínez | alfa
New research calculates capacity of North American forests to sequester carbon
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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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The launch of the EUNIS mission, short for Extreme Ultraviolet Normal Incidence Spectrograph, is scheduled for Dec. 15, 2012, from White Sands, N.M. aboard a Black Brant IX rocket. During its journey, EUNIS will gather a new snapshot of data every 1.2 seconds to track the way material of different temperatures flows through this complex atmosphere, known as the corona.
A full study of the sun's atmosphere requires watching it from space, where one can see the ultraviolet, or UV, rays that simply don't penetrate Earth's atmosphere. Such observations can be done in one of two ways – send up a long-term satellite to keep a constant eye on the sun, or launch a less expensive rocket, known as a sounding rocket, for a six minute trip above Earth's atmosphere to collect data fast and furiously throughout its short trip up to an altitude of 200 miles and back.
"Six minutes doesn't sound like much," says solar scientist Douglas Rabin who is the principal investigator for EUNIS at NASA's Goddard Space Flight Center in Greenbelt, Md. "But with an exposure every 1.2 seconds, we get very good time resolution and a lot of data. So we can observe minute details of how dynamic events on the sun happen over times of two to three minutes."
Watching the sun at this kind of time cadence helps scientists understand the complex movements of solar material – a heated, charged gas known as plasma – as it heats and cools, rising, sinking and gliding around with every change in temperature. Adding to the complexity of the flows are magnetic fields traveling along with the plasma that also guide the material's movements.
This writhing atmosphere around the sun powers an array of solar events, many of which stream out into the farthest reaches of the solar system, sometimes disrupting Earth-based technologies along the way.
"Ultimately all of our research is geared toward addressing key outstanding questions in solar physics including how the sun's outer atmosphere, or corona, is heated, what drives the solar wind, and how energy is stored and released to cause eruptions," says Jeff Brosius, a solar scientist at the Catholic University of America and a EUNIS co-investigator based at Goddard.
But teasing out how this energy moves through the corona is not a simple process. Different types of observations and techniques must be combined to truly track how different temperature material courses around.
The technique that EUNIS uses to observe the sun is known as spectroscopy. Taking pictures of the sun is one very useful form of observation, but it requires looking at just one wavelength of light at a time. A spectrometer on the other hand does not provide imagery, in a conventional way, but gathers information about how much of any given wavelength of light is present, showing spectral "lines" at wavelengths where the sun emits relatively more radiation. Since each spectral line corresponds to a given temperature of material, this provides information about how much plasma of a given temperature is present. Capturing many spectra during the flight will show how the plasma heats and cools over time. Each wavelength also corresponds to a particular element, such as helium or iron, so spectroscopy also provides information about how much of each element is present. Each spectrographic snapshot from EUNIS is based on light from a long, narrow sliver running across about third of the visible sun -- nearly 220,000 miles long.
"Looking at a small slice of the sun at such fast time cadence means we can look at the evolution and flows on the sun in a very direct way," says solar scientist Adrian Daw, the instrument scientist for EUNIS at Goddard.
Repeated sounding rocket flights offer significant advantages compared to orbital missions in terms of the measurement flexibility. Each separate flight can focus on the specific measurements that are most valuable, adjusting, as necessary, making improvements and emphasizing different aspects of the sun. Improving time cadence, for example, may be necessary to study the dynamics, however this inherently limits the observational resolution as the instrument gathers less light for any given snapshot of data. This flexibility in emphasis for each flight greatly enhances the scientific return.
This launch is the third for the EUNIS mission, but the tenth in a line of similar rockets where the predecessor was named SERTS for Solar Extreme-ultraviolet Research Telescope and Spectrograph. On each flight the scientists turned their attention to focusing on a different aspect of their research. During this flight, the instrument will observe a band of extreme ultraviolet light with wavelengths from 525 to 630 Angstroms with better sensitivity and greater spectral resolution than any previous instrument. This set of wavelengths covers a wide range of temperatures, representing solar plasma at 45,000 to 18 million degrees Fahrenheit (25,000 to 10 million Kelvin) which includes the temperature ranges of material from near the sun's surface to the much hotter corona above. Since we do not yet understand why the corona gets hotter the farther it is from the sun – unlike, for example, a fire where the air gets cooler farther away – studying such a wide range is crucial part for understanding that process.
With a six-minute window, EUNIS is unlikely to see a specific large eruption on the sun such as a solar flare or coronal mass ejection (CME) but since the sun is currently moving into the height of its 11-year cycle, they do expect to see a fairly active sun.
"The last two times EUNIS flew were in 2006 and 2007," says Daw. "Now the sun is waking up, getting more active and we're going to see a whole different type of activity."Karen C. Fox
Karen C. Fox | 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.
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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....
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Caterpillars use different strategies to protect themselves from their enemies; many are camouflaged, while others use their bright colors as warning signals, have stinging hairs or secrete toxic substances, some even take threatening postures.
Interaction between the caterpillar Manduca sexta and the spider Camptocosa parallela. The caterpillars nicotin breath frigthens the spider.
Danny Kessler; Grafics: Pavan Kumar and Sagar Pandit, MPI chem Ökol.
Spider Camptocosa parallela attacks a caterpillar.
Pavan Kumar, MPI chem. Ökol.
Scientists at the Max Planck Institute for Chemical Ecology have now discovered a previously unknown protective mechanism: Tobacco hornworm larvae can exhale a small fraction of nicotine they ingest as they feed on tobacco leaves.
To do so, they transfer some of the nicotine they ingest into their hemolymph (insect blood) from which a “defensive halitosis” is created that repels a major predator.
These insights were made possible by combining molecular techniques with a natural history approach in field experiments in the native habitat of the study organisms. (Proceedings of the National Academy of Sciences of the United States of America, December 30; 2013, DOI 10.1073/pnas.1314848111)
The importance of the ecosystem for studying gene functions
Understanding the function of genes is a central objective of biological research. Ultimately, genes function at the level of the organism, where their influence on an organism’s Darwinian fitness determines whether a gene is retained, modified or lost from genomes over evolutionary time. Gene silencing is a successful research method used to identify the function of individual genes and their relevance for the survival and fitness of an organism.
In addition to a gene’s biochemical and physiological roles that can be studied in the laboratory, the ecological role of a gene needs to be studied, and for this, there can be no better laboratory than the organism’s natural habitat. Scientists from the Department of Molecular Ecology headed by Ian Baldwin pioneer this approach and call it an unbiased, “ask the ecosystem” approach.
“Nature is our most important teacher,” Ian Baldwin emphasizes. “Nature is the arbitrator of who survives. Elucidation of gene functions is only possible if you study organisms in their native environment − including all the unknowns of the wild.”
For their field experiments, researchers planted tobacco plants that were deficient in producing nicotine. In addition, they used a plant-mediated RNAi technique to silence a cytochrome P450 enzyme in the midgut of tobacco hornworm larvae (see press release “Yellow Biotechnology: Using plants to silence insect genes in a high-throughput manner”, February 2, 2012) which is usually activated by nicotine ingested when the larvae feed on tobacco leaves. The scientists then observed what happened to caterpillars feeding on nicotine-deficient plants in order to compare their fate with those caterpillars that had ingested nicotine but lacked the active catalyzer for the toxin in their midgut.
Predatory spider assists the process of elucidating a defense mechanism
The function of the cytochrome P450 proved hard to reveal by laboratory-based experiments, but then the researchers received unexpected support from a wolf spider Camptocosa parallela. Surprisingly, the nocturnal predator preferably preyed not only on larvae that fed on nicotine-free leaves, but also preyed on their cytochrome P450-silenced conspecifics that were deficient in their response to nicotine in the food. The gene must therefore have played an important role in a spider defense mechanism that usually excludes the spider from the list of Manduca sexta’s enemies.
Further analysis revealed that the enzyme plays a role in transporting the ingested nicotine from midgut to the hemolymph which allows the nicotine to be exhaled out the spiracles, the nose-equivalents of the caterpillars. Caterpillars exhale a small fraction of this nicotine. And this functions as an anti-spider signal. Other predators of Manduca sexta, such as bugs or antlions, seem to be completely insensitive to this defensive halitosis.
Nicotine, the defensive substance in their host plant, is too toxic for the larvae to sequester. Most of it is excreted. That the larvae repurposes only a tiny amount of the toxin for their own defense in order to ward off spiders with a kind of toxic halitosis came as a surprise for the scientists. “This case of toxic breath as a defense is unique,” says Ian Baldwin. The example of the wolf spider illustrates the importance of combining molecular biology and natural history to understand the function of genes at the level of the organism. [AO]Original Publication:
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almost 60% of the UK’s energy comes from abroad. We import coal from Russia, gas from Norway and uranium from Kazakhstan.
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The light that we get from the sun helps to keep this planet warm. Of the 100% light that sun sends to earth, almost 30% sunlight is reflected back into the space by clouds, ice, snow, sand and other reflective surfaces
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more drought and more flooding less ice and snow more extreme weather incidence rising sea level
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These theories are usually studied in the context of real and complex numbers and functions. Analysis evolved from calculus, which involves the elementary concepts and techniques of analysis. Analysis may be distinguished from geometry; however, it can be applied to any space of mathematical objects that has a definition of nearness (a topological space) or specific distances between objects (a metric space).
- 1 History
- 2 Important concepts
- 3 Main branches
- 4 Other topics
- 5 Applications
- 6 See also
- 7 Notes
- 8 References
- 9 External links
Mathematical analysis formally developed in the 17th century during the Scientific Revolution, but many of its ideas can be traced back to earlier mathematicians. Early results in analysis were implicitly present in the early days of ancient Greek mathematics. For instance, an infinite geometric sum is implicit in Zeno's paradox of the dichotomy. Later, Greek mathematicians such as Eudoxus and Archimedes made more explicit, but informal, use of the concepts of limits and convergence when they used the method of exhaustion to compute the area and volume of regions and solids. The explicit use of infinitesimals appears in Archimedes' The Method of Mechanical Theorems, a work rediscovered in the 20th century. In Asia, the Chinese mathematician Liu Hui used the method of exhaustion in the 3rd century AD to find the area of a circle. Zu Chongzhi established a method that would later be called Cavalieri's principle to find the volume of a sphere in the 5th century. The Indian mathematician Bhāskara II gave examples of the derivative and used what is now known as Rolle's theorem in the 12th century.
In the 14th century, Madhava of Sangamagrama developed infinite series expansions, like the power series and the Taylor series, of functions such as sine, cosine, tangent and arctangent. Alongside his development of the Taylor series of the trigonometric functions, he also estimated the magnitude of the error terms created by truncating these series and gave a rational approximation of an infinite series. His followers at the Kerala School of Astronomy and Mathematics further expanded his works, up to the 16th century.
The modern foundations of mathematical analysis were established in 17th century Europe. Descartes and Fermat independently developed analytic geometry, and a few decades later Newton and Leibniz independently developed infinitesimal calculus, which grew, with the stimulus of applied work that continued through the 18th century, into analysis topics such as the calculus of variations, ordinary and partial differential equations, Fourier analysis, and generating functions. During this period, calculus techniques were applied to approximate discrete problems by continuous ones.
In the 18th century, Euler introduced the notion of mathematical function. Real analysis began to emerge as an independent subject when Bernard Bolzano introduced the modern definition of continuity in 1816, but Bolzano's work did not become widely known until the 1870s. In 1821, Cauchy began to put calculus on a firm logical foundation by rejecting the principle of the generality of algebra widely used in earlier work, particularly by Euler. Instead, Cauchy formulated calculus in terms of geometric ideas and infinitesimals. Thus, his definition of continuity required an infinitesimal change in x to correspond to an infinitesimal change in y. He also introduced the concept of the Cauchy sequence, and started the formal theory of complex analysis. Poisson, Liouville, Fourier and others studied partial differential equations and harmonic analysis. The contributions of these mathematicians and others, such as Weierstrass, developed the (ε, δ)-definition of limit approach, thus founding the modern field of mathematical analysis.
In the middle of the 19th century Riemann introduced his theory of integration. The last third of the century saw the arithmetization of analysis by Weierstrass, who thought that geometric reasoning was inherently misleading, and introduced the "epsilon-delta" definition of limit. Then, mathematicians started worrying that they were assuming the existence of a continuum of real numbers without proof. Dedekind then constructed the real numbers by Dedekind cuts, in which irrational numbers are formally defined, which serve to fill the "gaps" between rational numbers, thereby creating a complete set: the continuum of real numbers, which had already been developed by Simon Stevin in terms of decimal expansions. Around that time, the attempts to refine the theorems of Riemann integration led to the study of the "size" of the set of discontinuities of real functions.
Also, "monsters" (nowhere continuous functions, continuous but nowhere differentiable functions, space-filling curves) began to be investigated. In this context, Jordan developed his theory of measure, Cantor developed what is now called naive set theory, and Baire proved the Baire category theorem. In the early 20th century, calculus was formalized using an axiomatic set theory. Lebesgue solved the problem of measure, and Hilbert introduced Hilbert spaces to solve integral equations. The idea of normed vector space was in the air, and in the 1920s Banach created functional analysis.
Much of analysis happens in some metric space; the most commonly used are the real line, the complex plane, Euclidean space, other vector spaces, and the integers. Examples of analysis without a metric include measure theory (which describes size rather than distance) and functional analysis (which studies topological vector spaces that need not have any sense of distance).
such that for any , the following holds:
By taking the third property and letting , it can be shown that (non-negative).
Sequences and limits
A sequence is an ordered list. Like a set, it contains members (also called elements, or terms). Unlike a set, order matters, and exactly the same elements can appear multiple times at different positions in the sequence. Most precisely, a sequence can be defined as a function whose domain is a countable totally ordered set, such as the natural numbers.
One of the most important properties of a sequence is convergence. Informally, a sequence converges if it has a limit. Continuing informally, a (singly-infinite) sequence has a limit if it approaches some point x, called the limit, as n becomes very large. That is, for an abstract sequence (an) (with n running from 1 to infinity understood) the distance between an and x approaches 0 as n → ∞, denoted
Real analysis (traditionally, the theory of functions of a real variable) is a branch of mathematical analysis dealing with the real numbers and real-valued functions of a real variable. In particular, it deals with the analytic properties of real functions and sequences, including convergence and limits of sequences of real numbers, the calculus of the real numbers, and continuity, smoothness and related properties of real-valued functions.
Complex analysis, traditionally known as the theory of functions of a complex variable, is the branch of mathematical analysis that investigates functions of complex numbers. It is useful in many branches of mathematics, including algebraic geometry, number theory, applied mathematics; as well as in physics, including hydrodynamics, thermodynamics, mechanical engineering, electrical engineering, and particularly, quantum field theory.
Complex analysis is particularly concerned with the analytic functions of complex variables (or, more generally, meromorphic functions). Because the separate real and imaginary parts of any analytic function must satisfy Laplace's equation, complex analysis is widely applicable to two-dimensional problems in physics.
Functional analysis is a branch of mathematical analysis, the core of which is formed by the study of vector spaces endowed with some kind of limit-related structure (e.g. inner product, norm, topology, etc.) and the linear operators acting upon these spaces and respecting these structures in a suitable sense. The historical roots of functional analysis lie in the study of spaces of functions and the formulation of properties of transformations of functions such as the Fourier transform as transformations defining continuous, unitary etc. operators between function spaces. This point of view turned out to be particularly useful for the study of differential and integral equations.
A differential equation is a mathematical equation for an unknown function of one or several variables that relates the values of the function itself and its derivatives of various orders. Differential equations play a prominent role in engineering, physics, economics, biology, and other disciplines.
Differential equations arise in many areas of science and technology, specifically whenever a deterministic relation involving some continuously varying quantities (modeled by functions) and their rates of change in space or time (expressed as derivatives) is known or postulated. This is illustrated in classical mechanics, where the motion of a body is described by its position and velocity as the time value varies. Newton's laws allow one (given the position, velocity, acceleration and various forces acting on the body) to express these variables dynamically as a differential equation for the unknown position of the body as a function of time. In some cases, this differential equation (called an equation of motion) may be solved explicitly.
A measure on a set is a systematic way to assign a number to each suitable subset of that set, intuitively interpreted as its size. In this sense, a measure is a generalization of the concepts of length, area, and volume. A particularly important example is the Lebesgue measure on a Euclidean space, which assigns the conventional length, area, and volume of Euclidean geometry to suitable subsets of the -dimensional Euclidean space . For instance, the Lebesgue measure of the interval in the real numbers is its length in the everyday sense of the word – specifically, 1.
Technically, a measure is a function that assigns a non-negative real number or +∞ to (certain) subsets of a set . It must assign 0 to the empty set and be (countably) additive: the measure of a 'large' subset that can be decomposed into a finite (or countable) number of 'smaller' disjoint subsets, is the sum of the measures of the "smaller" subsets. In general, if one wants to associate a consistent size to each subset of a given set while satisfying the other axioms of a measure, one only finds trivial examples like the counting measure. This problem was resolved by defining measure only on a sub-collection of all subsets; the so-called measurable subsets, which are required to form a -algebra. This means that countable unions, countable intersections and complements of measurable subsets are measurable. Non-measurable sets in a Euclidean space, on which the Lebesgue measure cannot be defined consistently, are necessarily complicated in the sense of being badly mixed up with their complement. Indeed, their existence is a non-trivial consequence of the axiom of choice.
Numerical analysis is the study of algorithms that use numerical approximation (as opposed to general symbolic manipulations) for the problems of mathematical analysis (as distinguished from discrete mathematics).
Modern numerical analysis does not seek exact answers, because exact answers are often impossible to obtain in practice. Instead, much of numerical analysis is concerned with obtaining approximate solutions while maintaining reasonable bounds on errors.
Numerical analysis naturally finds applications in all fields of engineering and the physical sciences, but in the 21st century, the life sciences and even the arts have adopted elements of scientific computations. Ordinary differential equations appear in celestial mechanics (planets, stars and galaxies); numerical linear algebra is important for data analysis; stochastic differential equations and Markov chains are essential in simulating living cells for medicine and biology.
- Calculus of variations deals with extremizing functionals, as opposed to ordinary calculus which deals with functions.
- Harmonic analysis deals with the representation of functions or signals as the superposition of basic waves.
- Geometric analysis involves the use of geometrical methods in the study of partial differential equations and the application of the theory of partial differential equations to geometry.
- Clifford analysis, the study of Clifford valued functions that are annihilated by Dirac or Dirac-like operators, termed in general as monogenic or Clifford analytic functions.
- p-adic analysis, the study of analysis within the context of p-adic numbers, which differs in some interesting and surprising ways from its real and complex counterparts.
- Non-standard analysis, which investigates the hyperreal numbers and their functions and gives a rigorous treatment of infinitesimals and infinitely large numbers.
- Computable analysis, the study of which parts of analysis can be carried out in a computable manner.
- Stochastic calculus – analytical notions developed for stochastic processes.
- Set-valued analysis – applies ideas from analysis and topology to set-valued functions.
- Convex analysis, the study of convex sets and functions.
- Tropical analysis (or idempotent analysis) – analysis in the context of the semiring of the max-plus algebra where the lack of an additive inverse is compensated somewhat by the idempotent rule A + A = A. When transferred to the tropical setting, many nonlinear problems become linear.
Techniques from analysis are also found in other areas such as:
The vast majority of classical mechanics, relativity, and quantum mechanics is based on applied analysis, and differential equations in particular. Examples of important differential equations include Newton's second law, the Schrödinger equation, and the Einstein field equations.
When processing signals, such as audio, radio waves, light waves, seismic waves, and even images, Fourier analysis can isolate individual components of a compound waveform, concentrating them for easier detection or removal. A large family of signal processing techniques consist of Fourier-transforming a signal, manipulating the Fourier-transformed data in a simple way, and reversing the transformation.
Other areas of mathematics
Techniques from analysis are used in many areas of mathematics, including:
- Analytic number theory
- Analytic combinatorics
- Continuous probability
- Differential entropy in information theory
- Differential games
- Differential geometry, the application of calculus to specific mathematical spaces known as manifolds that possess a complicated internal structure but behave in a simple manner locally.
- Differentiable manifolds
- Differential topology
- Partial differential equations
- Constructive analysis
- History of calculus
- Non-classical analysis
- Paraconsistent logic
- Smooth infinitesimal analysis
- Timeline of calculus and mathematical analysis
- Edwin Hewitt and Karl Stromberg, "Real and Abstract Analysis", Springer-Verlag, 1965
- Stillwell, John Colin. "analysis | mathematics". Encyclopædia Britannica. Retrieved 2015-07-31.
- Jahnke, Hans Niels (2003). A History of Analysis. American Mathematical Society. p. 7. ISBN 978-0-8218-2623-2.
- Stillwell (2004). "Infinite Series". Mathematics and its History (2nd ed.). Springer Science + Business Media Inc. p. 170. ISBN 0-387-95336-1.
Infinite series were present in Greek mathematics, [...] There is no question that Zeno's paradox of the dichotomy (Section 4.1), for example, concerns the decomposition of the number 1 into the infinite series 1⁄2 + 1⁄22 + 1⁄23 + 1⁄24 + ... and that Archimedes found the area of the parabolic segment (Section 4.4) essentially by summing the infinite series 1 + 1⁄4 + 1⁄42 + 1⁄43 + ... = 4⁄3. Both these examples are special cases of the result we express as summation of a geometric series
- Smith 1958.
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- Dun, Liu; Fan, Dainian; Cohen, Robert Sonné (1966). "A comparison of Archimedes' and Liu Hui's studies of circles". Chinese studies in the history and philosophy of science and technology. 130. Springer: 279. ISBN 0-7923-3463-9., Chapter, p. 279
- Zill, Dennis G.; Wright, Scott; Wright, Warren S. (2009). Calculus: Early Transcendentals (3 ed.). Jones & Bartlett Learning. p. xxvii. ISBN 0-7637-5995-3. Extract of page 27
- Seal, Sir Brajendranath (1915), The positive sciences of the ancient Hindus, Longmans, Green and co.
- C. T. Rajagopal and M. S. Rangachari (June 1978). "On an untapped source of medieval Keralese Mathematics". Archive for History of Exact Sciences. 18 (2): 89–102. doi:10.1007/BF00348142.
- Dunham, William (1999). Euler: The Master of Us All. The Mathematical Association of America. p. 17.
- *Cooke, Roger (1997). "Beyond the Calculus". The History of Mathematics: A Brief Course. Wiley-Interscience. p. 379. ISBN 0-471-18082-3.
Real analysis began its growth as an independent subject with the introduction of the modern definition of continuity in 1816 by the Czech mathematician Bernard Bolzano (1781–1848)
- Rudin, Walter. Principles of Mathematical Analysis. Walter Rudin Student Series in Advanced Mathematics (3rd ed.). McGraw–Hill. ISBN 978-0-07-054235-8.
- Abbott, Stephen (2001). Understanding Analysis. Undergraduate Texts in Mathematics. New York: Springer-Verlag. ISBN 0-387-95060-5.
- Ahlfors, L. (1979). Complex Analysis (3rd ed.). New York: McGraw-Hill. ISBN 0-07-000657-1.
- Rudin, W. (1991). Functional Analysis. McGraw-Hill Science. ISBN 0-07-054236-8.
- Conway, J. B. (1994). A Course in Functional Analysis (2nd ed.). Springer-Verlag. ISBN 0-387-97245-5.
- E. L. Ince, Ordinary Differential Equations, Dover Publications, 1958, ISBN 0-486-60349-0
- Witold Hurewicz, Lectures on Ordinary Differential Equations, Dover Publications, ISBN 0-486-49510-8
- Evans, L. C. (1998), Partial Differential Equations, Providence: American Mathematical Society, ISBN 0-8218-0772-2
- Terence Tao, 2011. An Introduction to Measure Theory. American Mathematical Society.
- Hildebrand, F. B. (1974). Introduction to Numerical Analysis (2nd ed.). McGraw-Hill. ISBN 0-07-028761-9.
- THE MASLOV DEQUANTIZATION, IDEMPOTENT AND TROPICAL MATHEMATICS: A BRIEF INTRODUCTION
- Rabiner, L. R.; Gold, B. (1975). Theory and Application of Digital Signal Processing. Englewood Cliffs, NJ: Prentice-Hall. ISBN 0-13-914101-4.
- Aleksandrov, A. D.; Kolmogorov, A. N.; Lavrent'ev, M. A., eds. (1984). Mathematics, its Content, Methods, and Meaning. Translated by Gould, S. H.; Hirsch, K. A.; Bartha, T. Translation edited by S. H. Gould (2nd ed.). MIT Press; published in cooperation with the American Mathematical Society.
- Apostol, Tom M. (1974). Mathematical Analysis (2nd ed.). Addison–Wesley. ISBN 978-0-201-00288-1.
- Binmore, K. G. (1980–1981). The foundations of analysis: a straightforward introduction. Cambridge University Press.
- Johnsonbaugh, Richard; Pfaffenberger, W. E. (1981). Foundations of mathematical analysis. New York: M. Dekker.
- Nikol'skii, S. M. (2002). "Mathematical analysis". In Hazewinkel, Michiel. Encyclopaedia of Mathematics. Springer-Verlag. ISBN 1-4020-0609-8. Archived from the original on 9 April 2006.
- Rombaldi, Jean-Étienne (2004). Éléments d'analyse réelle : CAPES et agrégation interne de mathématiques (in French). EDP Sciences. ISBN 2-86883-681-X.
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A tiny white sliver inside the heads of fish could hold evidence of a century’s worth of humans wrecking the environment: atomic bombs, overfishing, even climate change.
Fish ear bones, also known as otoliths, are like tree rings for the ocean. A layer of calcium carbonate laid down each year offers a snapshot of both the fish’s yearly growth and its surrounding ocean conditions.
The University of Washington’s Burke Museum has been transferring and cataloging 2 million pairs of otoliths, representing some 80 species. Scientists hope this collection, gathered over the past half-century, will help them track the health of fish populations and ocean conditions up and down the West Coast.
The otolith collection, dating to the 1960s, had been sitting in an old Sand Point hangar belonging to the National Oceanic and Atmospheric Administration (NOAA). Last year, Ted Pietsch, a UW professor and curator of fishes at the Burke Museum, got a grant to transfer the otoliths to the museum — all of a 10-minute drive away.
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The reason for the not-so-big move? Fire. Although NOAA scientists had been doing active research on the collection, the thousands of flammable Styrofoam boxes — piled 20 feet high and filled with ethanol for preservation — were a huge fire hazard.
The threat of fire persuaded the National Science Foundation to fund a two-year, $500,000 grant. Instead of sitting haphazardly and uncataloged in a hangar, the otoliths will be archived in the Burke and searchable online for outside scientists.
The UW recently made the first loan of the otoliths to Oregon State University, where researchers are studying the age when flatfish settle to the ocean floor.
Information unlocked by analyzing the chemical makeup of each otolith layer has piqued the interest of archaeologists, geochemists and fish biologists alike.
Tree rings of the sea
Fishermen, not scientists, were the original beneficiaries of the otolith data, which feed population models that help determine catch limits each year. Fish populations are closely managed by NOAA so as not to repeat disasters such as cod overfishing on the East Coast.
Otoliths reveal age, which when aggregated with the sex, size and locations of capture for many fish, paint a portrait of the population’s health. Thus, scientists can estimate how much fishermen can catch without causing a whole species collapse.
Trained observers go to sea with fishermen to gather catch and bycatch data. NOAA’s fishery research centers rely on scientific survey boats as well as these observers to collect otoliths.
“Each fish has its sweet spot,” says Katherine Maslenikov, fish-collections manager at the Burke, who has dug through fish heads herself as an observer on fishing boats.
Three pairs of otoliths — scientists collect only the largest pair — sit in capsules of liquid behind the fish’s head. Technically, they are stones, not bones, because they contain no live cells.
Otoliths are unique to each species. A pollock’s are wing-shaped and about 2 centimeters long. Others are delicate white filigrees pretty enough for jewelry. The salmon has especially tiny and hard-to-find otoliths.
This huge variation among species is what makes aging otoliths such difficult work.
Determining the age of otoliths is the specialty of Tom Helser’s lab at the Alaska Fisheries Science Center, a part of NOAA. His 12
-person lab ages about 30,000 otoliths a year.
The low-tech method for aging otoliths is called “break and burn.” Heating them in a simple flame darkens the annual bands, so they are easier to count.
A more sophisticated method involves drilling out tiny slivers of the otolith. The wisp of powder — barely enough to be visible to the naked eye — is analyzed for oxygen-18, a slightly heavier form of the usual oxygen-16. Because it varies with temperature, the oxygen-18 level rises and falls with the seasons. Each rise and fall represents one year.
But it’s the change in elements like oxygen-18 over many years that has scientists really excited about otoliths.
“Flight recorders” is how NOAA’s Helser likes to describes otoliths.
Ocean temperature, and thus the oxygen-18 level, varies from shallow coastal waters to deeper ones, so otoliths record migration patterns. A recent study in yellowfin sole found a sharp increase in oxygen-18 after the fish turned 7 years old, meaning it moved into deeper, colder waters. As juveniles, they must have lived near the coast.
“This is an animal that responds extremely closely to temperature as it grows older,” said Helser, noting how climate change could interfere with the fish’s usual behavior.
Jeremy Harris, a graduate student working with the otolith collection at the UW, is also leading a project that could uncover the effects of climate change.
He is comparing the otoliths of walleye pollock from 50 years ago with contemporary ones, with the primary goal of figuring out whether the species has gotten smaller over time. This happened in cod when the largest fish were caught and only smaller ones were left to reproduce.
Combining growth data with temperature could also shed light on climate change.
On a longer time scale, 4,000-year old otoliths in prehistoric trash heaps are a record of ancient surface-water temperatures. This is the basis of a collaboration between Helser and archeologists in Newfoundland.
The chemical signature of the atomic bomb is seen in otoliths, too.
Atomic bomb testing in the 1960s caused a sharp spike in carbon-14 in all living things, from rhino horns to tree rings. That carbon-14 signature is one way to validate the age of older otoliths.
Some of the otoliths in the collection date to the 1960s, and that includes rockfish, which can live more than 100 years.
The ultimate goal in cataloging the collection is to aid this wide range of research.
On a Thursday morning, Helser walked through the cavernous NOAA hangar counting pallets of otoliths. Next to boat parts and old office equipment is another 100 or so pallets yet to be moved to the UW. Each pallet contains up to 200 boxes, each holding 100 pairs of otoliths when full.
The UW is about halfway through cataloging the otoliths. A team of undergraduates is deciphering the scrawled handwriting and putting otoliths in orderly, archival-quality boxes.
“I thought it was going to be overwhelming, just the number of samples,” said senior Kali Williams, as she sorted through her umpteenth box.
“This process really highlights the value of collections,” added Maslenikov. “For a long time, they just kept them in boxes, and all of a sudden there’s this wealth of data so many people can use. What if they’d just pitched them?”
Sarah Zhang: 206-464-2195 or firstname.lastname@example.org. On Twitter @sarahzhang | <urn:uuid:7c919bf6-9ef0-4290-a58a-6e8aab620713> | 3.5625 | 1,652 | Truncated | Science & Tech. | 48.285274 | 95,490,746 |
Aerobiologist David Schmale hunts killers. An associate professor of food safety and plant biosecurity at Virgina Tech, Schmale sends drones armed with petri dishes into the atmosphere to capture airborne crop pathogens. The data he has gathered explains how pathogens ride on wind currents and provides a glimpse into an almost unknown ecosystem far above our heads.
Schmale developed his unmanned aerial vehicles with a colleague at Virginia Tech as an alternative to costly manned research flights. With the data he has collected thus far, Schmale has built a model of atmospheric circulation that shows large sections of air sweeping across the face of the planet like waves across an ocean, transporting dust and microbes thousands of miles. “Microbes can move across continents and jump major oceans,” Schmale says. He’s planning to adapt his model to predict the movement of plant pathogens, which could help farmers preemptively protect their crops by describing where to strategically deploy pesticides. | <urn:uuid:2a26f895-3ed2-4ca9-a02d-f731e1175a0e> | 3.4375 | 193 | Truncated | Science & Tech. | 28.111076 | 95,490,751 |
posted by Jane
A parallelogram has an area of 8x^2 - 2x -45. The height of the parallelogram is 4x + 9. I know the formula for a parallelogram is A=bh. Please work and explain how I get the length of the base of the parallelogram. Thanks
since a = bh and they give you a polynomial for a and h, you have to expect that b = a/h and (4x+9) divides (8x^2 - 2x -45)
In fact, 8x^2 - 2x -45 = (4x+9)(2x-5)
so, b = 2x-5
If they had given you numbers, you'd have had no trouble doing the division. Don't be confused by their efforts to cloak the underlying simplicity of the question.
Factor(unfoil) the area to get:
(2x-5)* (4x+9). When you divide that by the height, the result is the length of the base: (2x-5)
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The Lorentz law of force is the fifth pillar of classical electrodynamics, the other four being Maxwell's macroscopic equations. The Lorentz law is the universal expression of the force exerted by electromagnetic fields on a volume containing a distribution of electrical charges and currents. If electric and magnetic dipoles also happen to be present in a material medium, they are traditionally treated by expressing the corresponding polarization and magnetization distributions in terms of bound-charge and bound-current densities, which are subsequently added to free-charge and free-current densities, respectively. In this way, Maxwell's macroscopic equations are reduced to his microscopic equations, and the Lorentz law is expected to provide a precise expression of the electromagnetic force density on material bodies at all points in space and time. This Letter presents incontrovertible theoretical evidence of the incompatibility of the Lorentz law with the fundamental tenets of special relativity. We argue that the Lorentz law must be abandoned in favor of a more general expression of the electromagnetic force density, such as the one discovered by Einstein and Laub in 1908. Not only is the Einstein-Laub formula consistent with special relativity, it also solves the long-standing problem of "hidden momentum" in classical electrodynamics.
Mendeley saves you time finding and organizing research
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- Open Access
Role of the solar wind magnetic field in the interaction of a non-magnetized body with the solar wind: An electromagnetic 2-D particle-in-cell simulation
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB. 2011
Received: 13 September 2010
Accepted: 9 February 2011
Published: 7 September 2011
The solar wind interaction with a non-magnetized, electrically non-conducting body is studied using a two-dimensional electromagnetic full particle simulation. The solar wind magnetic field is introduced into the simulation scheme as an initial condition together with the electric field generated by the motion of the solar wind. The solar wind magnetic field controls the direction of the thermal flow of the electrons and causes an asymmetry of the negative charging of the downstream-side surface. The negative charging and the potential drop are largest at the position where the solar wind magnetic field is perpendicular to the surface of the non-magnetized body. In the absence of photoelectrons, the solar wind electrons begin to be expelled by the negative charging at the terminator and then flow away along the field line producing streaks of enhancements of the electron density.
The solar wind interaction with a non-magnetized body is quite different from that which occurs in the case of the Earth. In the absence of a global magnetic field, the solar wind plasma can directly access a body or its atmosphere.
The interaction processes depend on the scale size of the body, the presence or absence of an ionosphere and the electric conductivity of the surface of the body. In this paper, the solar wind interaction with a non-magnetized, non-conducting body having no ionosphere is studied using a two-dimensional electromagnetic full particle simulation. This analysis might be applicable to the Moon or asteroids.
The solar wind interaction with a non-magnetized body such as the Moon is characterized by particle absorption and surface charging (Freeman and Ibrahim, 1975). The solar wind particles that hit the Moon are absorbed by the surface, creating a plasma cavity called the lunar wake behind the Moon (Schubert and Lichtenstein, 1974, and references therein). Because the electron thermal speed is higher than the solar wind speed, the nightside surface of the Moon is hit only by electrons and becomes negatively charged (Colwell et al., 2007, and references therein). The negative charging of the nightside surface of the Moon was observed by the Lunar Prospector (Halekas et al., 2002, 2003, 2005, 2008).
Recent observations by Kaguya and Chandrayaan have provided new findings concerning the Moon (e.g., Saito et al., 2008; Tsunakawa et al., 2010; Futaana et al., 2010). Among these are several phenomena which indicate asymmetries associated with the direction of the interplanetary magnetic field (IMF). Nishino et al. (2009a, b) found two types of intrusion of solar wind protons into the central wake near the Moon due to the Larmour motion of the protons together with the inward electric field at the wake boundary (type I), and with the solar-wind pickup of the scattered protons at the dayside lunar surface (type II), both of which show strong asymmetry controlled by the direction of the IMF. Futaana et al. (2010) reported a Chandrayaan-1 observation of another type of proton entry into the near wake along the magnetic field in the solar wind frame of reference.
It has also been found by Kaguya plasma wave observation (LRS/WFC-H) that there exists an asymmetric structure of electron density profile at the wake boundary depending on the direction of the IMF. The electron density is often enhanced at the wake boundary of the northern hemisphere when the B z component of the anti-sunward IMF is positive (that is, directed northward). The electron density enhancement occurs on the southern hemisphere when the B z component of the anti-sunward IMF is negative (directed southward). The north-south asymmetry reverses for the sunward IMF (Kasahara et al., personal communication, 2010).
To understand the phenomena that are considered to be controlled by the solar wind magnetic field, it would be helpful to examine the basic role of the interaction of the solar wind magnetic field with non-magnetized bodies using numerical simulations.
To deal with the solar wind interaction with a non-magnetized, non-conducting body on which surface charging plays an important role, it is desirable to treat the electrons as particles. Particle-in-cell codes have been used to study solar wind interaction with non-magnetized obstacles by several authors (Farrell et al., 1998; Birch and Chapman, 2001, 2002; Guio and Pécseli, 2004, 2005), but they did not include surface charging in their simulation because their interests focused rather on the infilling of the wake, the ion acceleration, or the phase space structures in the wake.
Kimura and Nakagawa (2008) included surface charging in their 2-dimensional, full-particle electromagnetic code to calculate the electric field at the wake boundary. They succeeded in reproducing the ambipolar electric field at the wake boundary, the ion acceleration into the central void, the surface charging of the nightside surface, and the intense electric field at the terminator simultaneously in a self-consistent manner, but they did not include photoemission or the solar wind magnetic field.
In this paper, the solar wind magnetic field is included in the electromagnetic full particle simulation. The effects of photoelectrons, although they are of crucial importance, are not included in order to concentrate on the role of the magnetic field. The crustal magnetic fields and the solar wind protons reflected by the lunar surface (Saito et al., 2008) give rise to a variety of interesting phenomena, but in this paper we limit ourselves to the basic cases of a non-magnetized body immersed in the solar wind having an intrinsic velocity distribution.
2. Numerical Simulation
2.1 Two-dimensional electromagnetic PIC simulation
A 2-D, full-particle electromagnetic code (Birdsall and Langdon, 1985) is used in this study. The simulator is the same as that used by Kimura and Nakagawa (2008), with the exception that it now allows for inclusion of the solar wind magnetic field.
The particles that collide with the obstacle are also removed from the simulation box after giving their electric charge to the surface of the obstacle. The electric charges are fixed to each position of the collision, on the assumption that the obstacle is electrically insulating. No emission of secondary electrons is considered.
On removal of these particles, as many particles are injected from the upstream boundary. To reduce the time for the calculation, we use a high-speed solar wind, υsw = 0.025c (or 0.0125c), together with the electron thermal speed υe = 0.1c (or 0.05c), which leads to a Debye length as large as 0.25RO (or 0.125RO), where ωp is the plasma frequency. The Debye length is typically of the order of 10–100 m in the average solar wind, so it should be noted that not all the results of the present simulation can be applied directly to a large obstacle such as the Moon whose radius is 104 to 105 times as large as the Debye length. The scaling of this simulation is rather more suitable for a smaller object such as an asteroid.
It should also be noted that the effects of photoelectrons are not included in this simulation. Thus, we cannot discuss the electric potential on the dayside surface of the obstacle. It might also change the electric field structure at the terminator.
Choice of parameters.
υ e /c
r iL /R O
r eL /R O
2.2 Inclusion of the solar wind magnetic field
A uniform magnetic field B = (B cos θ B , B sin θ B , 0) is defined at 256 × 256 grids over the simulation domain as an initial condition, where θB is the angle between the magnetic field and the solar wind flow along the x axis. We start with θB = -45° to represent the direction of the average solar wind magnetic field.
The magnitude of the magnetic field is chosen so that the ion Larmour radius riL is smaller than the radius of the obstacle RO. As riL = υi/Ωi = 32υe/Ωe and RO = 4λD (or 8λD) in our simulation, we require an electron cyclotron frequency Ωe larger than (or ). Consequently, the Alfvén speed becomes larger than the speed of light c and any magnetic distortion propagates faster than the speed of light. So it should be noted that we cannot discuss the deformation of the magnetic field in this simulation. We employ Ω e /ω p = 12 in simulation runs #1 to #3, and then relaxed the condition to Ωe/ωp = 0.75 in simulation run #4.
The time step ∆t is set so that it satisfies the Courant condition and is smaller than 10-2 times the electron cyclotron period 2π/Ωe.
In order to reproduce the frozen-in condition of the solar wind, the electric field E = -V sw × B generated by the motion of the solar wind magnetic field past the obstacle is introduced as an initial condition. Otherwise, the plasmas cannot flow with the solar wind magnetic field but are guided by the external magnetic field. After that, the magnetic field and the electric field are calculated by solving Maxwell’s equations with the FDTD method.
3.1 Plasma structure
An ion void is formed behind the obstacle. The ions cannot reach the downstream-side surface of the obstacle because the thermal speed is smaller than the bulk speed of the solar wind. The ion density structure is nearly symmetric with respect to the x-axis. Compared with the case with no magnetic field (figure 1 of Kimura and Nakagawa, 2008), no influence of the magnetic field is recognized in Fig. 1.
The electrons, whose thermal speed is much higher than the solar wind bulk speed, can reach the downstream-side surface of the obstacle. The negative charge accumulating on the surface expels the following electrons, creating an electron void. The mechanism is the same as in the nonmagnetized solar wind, but the difference is that the electrons can go upstream only along the magnetic field lines, due to the small Larmour radius reL. The number flux of the electrons per unit area of the surface of the obstacle is large at the position where the magnetic field is perpendicular to the surface. As a result, the charge density is thought to be larger in the negative-y region, producing a larger area of depressed electron density than in the positive-y region.
In addition to the asymmetry of the electron void, enhancements of electron density were found streaking from the vicinity of the terminator. In the right panel of Fig. 1, a ridge of electron density enhancement runs from (x, y) = (0.5, -2) to (4.5, -5) in units of RO, accompanied by a slight depression next to the enhancement. On the positive-y side, a faint but broad enhancement extends from (0, 1.5) to (-3, 5) RO upstream. It should be noted that the streaks extend far beyond the Debye length. The streaks are not parallel to the magnetic field. The angle between the ridges of the electron density and the solar wind direction (along the x-axis) is -37° in the negative-y region deviating by 8 degrees from the solar wind direction, and 131° in the positive-y region, with 4 degrees of deviation.
In contrast, electrons are found in the center of the wake near the obstacle surface, except for a part of the negative-y area. In the positive-y side of the central void, the bulk speed is sometimes very high.
Upstream of the obstacle, the bulk velocity of the electrons is nearly the same as the convection velocity of the solar wind. They begin to be skewed away at the terminator of the obstacle being expelled by the negative charges on the downstream-side surface of the obstacle. The expelled electrons flow away along the magnetic field being convected by the motion of the magnetic field, producing the streaks of enhancement of the electron density as seen in Fig. 1.
3.2 Electric field structure
A potential drop was found on the downstream side of the obstacle. It extends as far as 3.3RO due to the electrons in the central wake. On the nightside surface of the obstacle, the largest potential drop is found in the negative-y sector at which the solar wind magnetic field is perpendicular to the surface of the obstacle. The potential drop is as large as ϕ ~ -2.8ϕ0 at x ~ 0.7RO on the negative-y sector, while on the positive-y sector, the maximum potential drop is ϕ ~ -1.7ϕ0 at around x ~ 0.3RO, where . The magnitude of the potential drop is comparable to the floating potential of an artificial satellite in the solar wind plasma without photoelectrons (e.g., Fahleson, 1967).
The weak negative potential in the lower left area of Fig. 4 is due to the enhancement of the electron density as observed in Fig. 1. The negative potential on the upper right area is not real; it is due to the periodic boundary condition of the simulation.
As well as in the non-magnetized solar wind (Kimura and Nakagawa, 2008), we observe the electric fields at the wake boundary. They are asymmetric with respect to the x-axis.
The most intense electric field is found at the terminator, where the neutral surface exposed to the solar wind and the negatively-charged surface on the downstream side are adjacent to each other. The magnitude is as large as 2.0E0 on the positive-y side, where E0 = m e υ e ω p /q0. The electric field on the negative-y side occupies a larger area but the magnitude is somewhat weaker (E ~ 1.6E0) than the positive-y side, because the potential gradient is not so large due to the larger extent of negative charge on the surface.
Corresponding to the enhancements of the electron density, streaks of enhanced electric fields are also recognized in Fig. 5(a). In the vicinity of the obstacle, the electric field has a component parallel to the magnetic field as shown in Fig. 5(b). This accelerates the electrons in the direction parallel to the magnetic field.
4.1 Magnetic field control of the surface charging
In contrast with the non-magnetized solar wind case, in which the solar wind electrons are able to access the nightside surface of the obstacle freely from any direction (Kimura and Nakagawa, 2008), the motion of the electrons in the magnetized solar wind case is controlled by the solar wind magnetic field. The electrons are confined within a Larmour radius to the magnetic field line and we can more-or-less approximate electron flow to be along the magnetic field. Only the electrons on the magnetic field lines that connect with the obstacle can contribute to surface charging.
The asymmetry of the electric field structure vanishes when the magnetic field is parallel, or perpendicular to the solar wind flow. The asymmetry is caused by the oblique magnetic field; it would be most significant at the heliospheric distance of 1 AU, where θ ~ -45° on average. On the Moon, for example, the negative charging and the maximum potential drop are expected to be shifted to the dusk-side of the nightside surface. Since the solar wind magnetic field is variable, there would be sudden changes of charge and discharge as observed by Apollo missions (Colwell et al., 2007, and references therein) at abrupt changes of the magnetic field direction.
4.2 Streaks of the enhanced electron density
4.3 Dependence on the Debye length
In general, the spatial extent of the electric field caused by the surface charging is of the order of the Debye length. In this paper, a Debye length λD as large as 0.25RO has been employed. There might be a concern that the effect of the surface charging is limited for an object whose radius RO is much larger with respect to the Debye length.
The asymmetry of the potential structure is clearer in Fig. 11(b) than in Fig. 4. The largest potential drop is ϕ ~ -3ϕ0. (Note that ϕ0 is also reduced by slowing down the electron thermal speed υe.) As the ratio of the potential drop to the electron thermal energy is nearly the same as before, the electrons gain as much flow speed as before and the streaks of electron enhancement appear in Fig. 11(a).
The potential drop in the downstream wake extends far beyond 7 RO in Fig. 11(b), differently from the larger Debye length case in Fig. 4. The relative importance of the wake potential to the surface charging increases for a larger scale obstacle.
4.4 Weaker magnetic field case
4.5 Comparison with observations at the Moon
Limitation of the scale size of the obstacle with respect to the Debye length, together with the absence of photoemission, prohibits us from making a direct comparison of the simulation result with the observations made at the Moon. Too small a ratio of the obstacle size to the Debye length magnifies the effect of surface charging with respect to the potential drop at the wake boundary. Nevertheless, some aspects of the model can be compared with the lunar data. Such a comparison would help elucidate what aspects of the model are appropriate for all scale sizes of objects and which are more limited to smaller objects.
As we have seen in Section 4.2, the potential drop at the terminator is of the order of 2ϕ0, which corresponds to 60–80 V for the typical solar wind electrons having a thermal energy of 15–20 eV. This is consistent with the Apollo SIDE observation of 70 eV ions accelerated by the negative lunar surface potential (Freeman and Ibrahim, 1975) and a surface potential as low as -100 V on some terminator crossings (Lindeman et al., 1973).
The largest potential drop on the nightside surface of the obstacle, 3ϕ0, which corresponds to 90–120 V, is consistent with a lunar surface potential of -120 V inferred from the Lunar Prospector observation of the electrons at an altitude of 20-40 km (Halekas et al., 2002), but somewhat smaller than the newly found potential drop of -200 V near the edge of the wake (Halekas et al., 2008). Halekas et al. (2008) also reported that the surface potential drop with respect to the local plasma is smaller in the central wake than near the wake boundary. No such signature is found in this simulation. Halekas et al. (2008) attributed this to secondary electrons, which are not included in the present simulation.
The minimum electron density obtained by Lunar Prospector in the lunar wake (figure 6 of Halekas et al., 2005) appears to be shifted slightly to the duskside, consistent with the result of the present simulations. This is likely, because the magnetic field lines of the average IMF at 1 AU are perpendicular to the dusk-to-night surface of the moon.
A negative excess of charge is found in the central wake at x = 2 – 3RO in Fig. 13 and disappears at 4RO.At x = 3RO, well beyond the Debye length from the obstacle (although the Debye length becomes large in a low density plasma), the potential drop in the central wake with respect to the ambient solar wind is about 0.5ϕ0-1ϕ0. If we assume that this is the wake potential and that the wake potential is essentially independent of the Debye length, as long as the ratio of the thermal speeds to the solar wind speed is kept constant, it is not necessary to evaluate it in terms of the electron thermal energy , but rather, we can convert it directly into volts using υe = 0.05c for the simulation run #3. It is calculated to be 0.64–1.3 kV. This is much stronger than it appears in Fig. 11 in which the surface charging effect is magnified. Although this is a very rough estimation, it is of the same order as the potential of -442 V estimated from the WIND observation of backstreaming electrons (Farrell et al., 1996) and -480 V estimated from NOZOMI observation of counterstreaming electrons (Futaana et al., 2001).
This simulation reproduced the streaks of the electron enhancement along the magnetic field line on the same hemisphere as the electron enhancement detected by Kaguya LRS/WFC-H, but with a slight difference in the location. This might be due to the effect of surface charging, or the absence of photoelectrons in this simulation. Photoelectrons might affect the position of the first contact of the magnetic field line with the negative surface density. At present, we cannot conclude that they are the same phenomena or not.
The horizontal ion entry along the magnetic field lines as reported by Futaana et al. (2010) is not observed in the present simulation.
A two-dimensional, electromagnetic particle-in-cell simulation has revealed that the solar wind magnetic field controls the direction of the thermal flow of the solar wind electrons onto a non-magnetized, non-conducting obstacle immersed in the solar wind flow. The accumulation of the negative charge on the downstream surface of the obstacle is largest at the position where the solar wind magnetic field is perpendicular to the surface. The asymmetry of the surface charging causes an asymmetry of electric potential structure.
In the absence of photoemission, the solar wind electrons on the equipotential magnetic field line suddenly gain potential energy on arrival of the field line at the negatively charged surface at the terminator. The electrons begin to flow down the field line away from the obstacle, forming streaks of enhanced electron density. It is likely that the photoelectrons and secondary electrons, that were not included in the present simulation, modify the surface charging near the terminator and the position of the electron enhancements around the terminator. Their inclusion will be necessary in future studies.
The author thanks M. Iizima for his suggestion concerning the initial condition of the electric field. The authors are grateful to the reviewers for their valuable comments that improved the manuscript. This study was supported by the JSPS grant-in-aid for scientific research project 21540461.
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Without events, there would be no Dynamic HTML. A strong statement, perhaps, but given the kinds of document object models we have inherited, it's true. For any dynamism to occur in an HTML page, some kind of trigger is needed.
Two categories of triggers are available: user-generated actions and system-generated actions. Direct user-generated actions are those caused by mouse and keyboard activity. System-generated actions , perhaps more accurately described as document- or browser-generated actions, occur when something significant occurs in the browser, such as the document completing its loading into the browser or an image failing to retrieve its data from the server.
One of your jobs as a DHTML scripter is to determine which events on
which elements should trigger scripted actions. Any kind of form
button, for example, will usually have some script action associated
with it (unless it is just the default actions of submit and reset
input element types). Less obvious, perhaps, are events that inspect
the characters being typed into a text box, to make sure only allowed
characters are permitted to pass. Very common mouse-oriented events
detect when the cursor rolls atop an image element (or an
a hyperlink element surrounding the image) so that
a script can change the image to a highlighted version during this
"rollover." A corresponding event
for when the cursor rolls off the image reverts the image back to its | <urn:uuid:f47a27e3-4cfe-4913-9c1b-20f30e5cefe4> | 2.859375 | 294 | Documentation | Software Dev. | 31.784563 | 95,490,822 |
Danger - Unstable Cliffs - Stay Back: The yellow warning signs that pepper coastal cliffs from northern California to the US-Mexico border may seem overly dramatic to the casual observer. But actively eroding cliffs make up the majority of the California coastline, and sudden landslides and collapses have caused injuries and several fatalities in recent years. In addition, eroding cliffs currently threaten highways, houses, businesses, military bases, parks, power plants, and other critical facilities--all in all billions of dollars of development.
Research suggests that erosion rates will increase as sea level rises, further exacerbating these problems. "It is critical we study current and historical cliff retreat so we can better plan for the future," says Adam Young, a researcher at Scripps Institution of Oceanography at the University of California San Diego who recently published a unique large-scale analysis of coastal cliff erosion in California.
Adam Young, a researcher at Scripps Institution of Oceanography at the University of California, San Diego, recently published a new large-scale analysis of coastal cliff erosion from San Diego to San Francisco. To analyze the data, Young compared two massive LiDAR data sets, three-dimensional maps of the California coastline, recorded eleven years apart. This video highlights one of the areas he identified with high erosion rates, near San Francisco.
Credit: Adam Young, Scripps Institution of Oceanography, University of California San Diego
The study, published in the journal Geomorphology, and funded by California Sea Grant, provides accurate erosion rates for 680 miles of the California coast, from the US-Mexico border to Bodega Head in Sonoma County.
It identifies areas that have eroded faster than others, and introduces a new experimental hazard scale to identify areas that may be at greater risk of impending collapse. It is the first such large-scale study in California using LiDAR data--laser elevation data recorded in aerial surveys--which were used to create detailed 3D elevation maps.
Existing cliff erosion studies are often small scale, use a variety of techniques, and often rely on lower quality data sources, providing a patchwork across the state. "What's unique about this study is that it applies a consistent methodology across a very large area using accurate high-resolution laser data," says Young.
While some of the basic causes of coastal cliff erosion--such as rainfall and waves--are clear, this has not translated into a simple way to predict future erosion rates or identify areas at risk. Variation in cliff geology, beach protection, exposure to weather, and other factors also complicate predicting erosion rates.
Previous research has identified clear correlations between rainfall and coastal erosion in southern California, but the impact of storms waves has been more elusive. "It's difficult to measure," explains Young, "We lack field observations because with powerful waves crashing against the cliff, it is not an easy place to make measurements." Variation in cliff geology, beach protection, exposure to weather, and other factors also complicate predicting erosion rates.
Understanding erosion, preventing disaster
To create a consistent analysis of recent cliff changes, Young compared two massive LiDAR data sets, three-dimensional maps of the California coastline, recorded eleven years apart. The highest cliff erosion rates were found in San Onofre, Portuguese Bend, Palos Verdes, Big Sur, Martins Beach, Daly City, Double Point, and Point Reyes (see map). Young then compared the recent cliff erosion maps to historical records from 1932 and 1934. By comparing the different maps, he built an analysis for the majority of the state's coastline, showing both recent and historical erosion rates.
The study shows that the historical cliff erosion rate does not always provide a good prediction of future rates. "The results show that if a cliff experienced a large of amount of erosion during one time period, it was followed by a time period with very little erosion, and the cliff could be relatively stabilized for a time," explains Young. "It will mobilize again, but we don't know when and more research is needed to better understand the time cycles involved."
Young also found that cliffs with high erosion rates in recent times were often preceded by time periods with very little erosion. These are key findings, because models predicting future cliff retreat are often based on projecting the historical rates.
Young also introduced a new experimental measure to identify the riskiest precipices. Previous research had suggested that the difference between erosion rates of the cliff face compared to the cliff top could indicate instability--in short, the cliff steepness. When he applied this hazard index, Young identified worrisome spots along the California coast, including San Onofre State Beach, Big Sur, Martin's Beach, and Daly City.
A reality check for planners
Young is currently working on a set of maps to be made available to the public, and he has presented the work at scientific conferences. He says, "I hope that this study will help improve models that predict erosion, help identify hazardous areas, and assist policymakers who are working to protect our coast."
The research has already caught the attention of planners at the California Coastal Commission, a state agency charged with preserving and protecting the coastline for current and future generations.
"The study could be particularly useful for local governments looking to update their local coastal programs in light of climate change and sea level rise," says Lesley Ewing, a senior coastal engineer for the commission. While the study does not provide projections for future erosion rates, researchers expect that sea-level rise will contribute to faster erosion rates and greater risk to public and private coastal property, and governments are working to plan for the impacts.
"The coast of California is stacked with very expensive real estate--not to mention power plants, wastewater treatment facilities, and highways," she says. Some of this is already at risk--over 100 miles of shoreline armory has been built to protect it, and more will be at risk in the future.
"There's so much opportunity to use this research--this could serve as a reality check for planners who often focus on specific regions and smaller scales," adds Ewing.
The research was also supported by the California Department of Parks and Recreation, Division of Boating and Waterways.
About California Sea Grant
NOAA's California Sea Grant College Program funds marine research, education and outreach throughout California. Our headquarters is at Scripps Institution of Oceanography, University of California, San Diego; we are one of 33 Sea Grant programs in the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.
Katherine Leitzell | 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
17.07.2018 | Power and Electrical Engineering | <urn:uuid:fb84efc9-55f5-40fd-b017-e461a782fb57> | 3.609375 | 1,973 | Content Listing | Science & Tech. | 31.018296 | 95,490,876 |
Supermassive black holes lurk at the center of every large galaxy. These cosmic behemoths can be millions to billions of times more massive than the Sun. Determining just how massive, however, has been daunting, especially for spiral galaxies and their closely related cousins barred spirals.
In a new proof-of-concept observation, astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have measured the mass of the supermassive black hole at the center of NGC 1097 -- a barred spiral galaxy located approximately 45 million light-years away in the direction of the constellation Fornax.
ALMA (NRAO/ESO/NAOJ), K. Onishi; NASA/ESA Hubble Space Telescope, E. Sturdivant; NRAO/AUI/NSF
Composite image of the barred spiral galaxy NGC 1097. By studying the motion of two molecules, ALMA was able to determine that the supermassive black hole at the galactic center has a mass 140 million times greater than our Sun. The ALMA data is in red (HCO+) and green/orange (HCN) superimposed on an optical image taken by the Hubble Space Telescope.
The researchers determined that this galaxy harbors a black hole 140 million times more massive than our Sun. In comparison, the black hole at the center of the Milky Way is a lightweight, with a mass of just a few million times that of our Sun.
To achieve this result, the research team, led by Kyoko Onishi at SOKENDAI (The Graduate University for Advanced Studies) in Japan, precisely measured the distribution and motion of two molecules -- hydrogen cyanide (HCN) and formylium (HCO+) -- near the central region of the galaxy.
The researchers then compared the ALMA observations to various mathematical models, each corresponding to a different mass of the supermassive black hole. The “best fit” for these observations corresponded to a black hole weighing in at about 140 million solar masses. The results are published in the Astrophysical Journal.
A similar technique was used previously with the CARMA telescope to measure the mass of the black hole at the center of the lenticular galaxy NGC 4526.
“While NGC 4526 is a lenticular galaxy, NGC 1097 is a barred spiral galaxy. Recent observation results indicate the relationship between supermassive black hole mass and host galaxy properties varies depending on the type of galaxies, which makes it more important to derive accurate supermassive black hole masses in various types of galaxies,” Onishi noted.
Currently, astronomers use several methods to derive the mass of a supermassive black hole; the technique used typically depends on the type of galaxy being observed.
Within the Milky Way, powerful optical/infrared telescopes track the motion of stars as they zip around the core of our galaxy. This method, however, is not suitable for distant galaxies because of the extremely high angular resolution it requires.
In place of stars, astronomers also track the motion of megamasers (astrophysical objects that emit intense radio waves and are found near the center of some galaxies), but they are rare; the Milky Way, for example, has none. Another technique is to track the motion of ionized gas in a galaxy’s central bulge, but this technique is best suited to the study of elliptical galaxies, leaving few options when it comes to measuring the mass of supermassive black holes in spiral galaxies.
The new ALMA results, however, demonstrate a previously untapped method and open up new possibilities for the study of spiral and barred spiral galaxies.
“This is the first use of ALMA to make such a measurement for a spiral or barred spiral galaxy,” said Kartik Sheth, an astronomer with the National Radio Astronomy Observatory in Charlottesville, Va., and co-author on the paper. “When you look at the exquisitely detailed observations from ALMA, it’s startling how well they fit in with these well tested models. It’s exciting to think that we can now apply this same technique to other similar galaxies and better understand how these unbelievably massive objects affect their host galaxies.”
Since current theories show that galaxies and their supermassive black holes evolve together -- each affecting the growth of the other -- this new measurement technique could shed light on the relationship between galaxies and their resident supermassive black holes.
Future observations with ALMA will continue to refine this technique and expand its applications to other spiral-type galaxies.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the US 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.
Charles Blue | newswise
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...
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
17.07.2018 | Power and Electrical Engineering | <urn:uuid:90f3565a-0f8c-48f9-9654-388ba804a12f> | 3.40625 | 1,834 | Content Listing | Science & Tech. | 31.953247 | 95,490,877 |
Governments and schools are not communicating the most effective ways for individuals to reduce their carbon footprints, according to new research.
Scientists say they've discovered a magma buildup near a New Zealand town that explains a spate of recent earthquakes and could signal the beginnings of a new volcano—although they're not expecting an eruption anytime soon.
A new NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.
An enormous island of trash twice the size of Texas is floating in the Pacific Ocean somewhere between San Francisco and Hawaii.
New research suggests that there is plenty of oxygen available in the subsurface ocean of Europa to support oxygen-based metabolic processes for life similar to that on Earth. In fact, there may be enough oxygen to support ...
At the end of December 2015, a huge storm named "Goliath" dumped 9-10 inches of rain in a belt across the central United States, centered just southwest of St. Louis, most of it in a three-day downpour.
Scientists have found the first direct evidence of a so-called 'hot zone' feeding a supervolcano in southern Italy that experts say is nearing eruption conditions.
(AP) -- The Philippines' most active volcano could have a huge eruption within days, officials warned Sunday after detecting a drastic surge in earthquakes and eerie rumbling sounds in surrounding foothills. Tens of thousands ...
Humanity will have used up its allowance of planetary resources such as water, soil, and clean air for all of 2017 by Wednesday, a report said. | <urn:uuid:78272cbf-24a0-479a-8df8-7bd973be45c8> | 2.5625 | 333 | Content Listing | Science & Tech. | 44.953332 | 95,490,900 |
Many organisms live out their lives on schedules established by internal clock mechanisms, generated by the combined action of multiple regulatory networks that interlock like gears in a watch. The resulting circadian rhythms establish one’s internal perception of day and night, as well as numerous time-points in between.
In 2005, a team led by Hiroki Ueda of the RIKEN Center for Developmental Biology in Kobe made significant progress in identifying the core components of the complex circadian circuitry1. They found several regulatory elements that specifically mark genes for activation or inhibition in the morning, daytime or night, as well as numerous genes that mediate regulation via these elements.
“Our team identified a natural transcriptional circuit for mammalian circadian clocks,” explain Maki Ukai-Tadenuma and Takeya Kasukawa, members of Ueda’s team. “However, no one has yet confirmed the mechanism that generates practically continuous phases from these three, discrete basic phases.”
However, the investigators had ideas about how such patterns might emerge, and were able to sketch a rough map of how the various time-specific regulatory loops may interact in vivo to produce a stable day–night cycle. To test their hypotheses, they constructed a series of synthetic circadian circuits within live cells based on their models, and examined the extent to which their activity replicated natural biological cycles2.
In fact, these experimental scenarios provided strong support for their regulatory models. One of the synthetic circuits consisted of a bioluminescent indicator gene under the regulation of a morning-specific activator and a nighttime-specific repressor, and the resulting pattern of indicator activity was a cyclic oscillation that very closely matches the natural expression pattern of daytime-specific genes.
They were similarly able to replicate night-cycle activity with a daytime-specific activator and morning-specific repressor, and were even able to generate novel ‘late night’ or ‘dusk’ output peaks by further tinkering with the timing of activation and repression. Most importantly, their experimental findings were all consistent with the predictions of their previously developed theoretical models. “Both our simulation model and the derived design principles successfully recapitulated the natural transcriptional circuit in the circadian clocks,” say the researchers.
Although their modeling system has proven effective, the researchers have yet to fully reconstruct all the phases of the mammalian circadian cycle. “In our study, morning transcriptional regulation is still a ‘missing link’,” they point out. The team’s focus now is on successfully identifying the regulatory processes required to restore these final time-points to their reconstructed cellular clock.
1. Ueda, H.R., Hayashi, S., Chen, W., Sano, M., Machida, M., Shigeyoshi, Y., Iino, M. & Hashimoto, S. System-level identification of transcriptional circuits underlying mammalian circadian clocks. Nature Genetics 37, 187–192 (2005).
2. Ukai-Tadenuma, M., Kasukawa, T. & Ueda, H.R. Proof-by-synthesis of the transcriptional logic of mammalian circadian clocks. Nature Cell Biology 10, 1154–1163 (2008).
The corresponding author for this highlight is based at the RIKEN Laboratory for Systems Biology
Further reports about: > Nature > RIKEN > Synthetic genetic circuits > cellular clock > circadian clock > circadian rhythm > daytime-specific activator > internal clocks > morning-specific repressor > multiple regulatory networks > night-cycle activity > numerous time-points > specific gene > synthetic biology
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell 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
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Materials Sciences
19.07.2018 | Earth Sciences
19.07.2018 | Life Sciences | <urn:uuid:4516ac37-58de-4a6d-a656-4ac1ea35af21> | 3.515625 | 1,385 | Content Listing | Science & Tech. | 32.285848 | 95,490,903 |
Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition
This book is a tutorial for the Scala programming language, written by people
directly involved in the development of Scala. Our goal is that by reading
this book, you can learn everything you need to be a productive Scala programmer.
All examples in this book compile with Scala version 2.8.1.
Scala is an object-oriented...
This book is an indispensable resource for everyone involved in the hiring
process. That includes managers, human resources (HR) personnel, and most
of all, the front line hiring folks. If you review résumés, conduct phone or
on-site interviews, or if you are responsible for making offers to candidates,
this book is...
Actors in Scala
Recent trends in computer architecture make concurrency and parallelism an essential ingredient of efficient program execution. The actor model of concurrency allows you to express real-world concurrency in a natural way using concurrent processes that communicate via asynchronous messages.
Scala is a programming language for the Java... | <urn:uuid:2137fd83-3705-4243-af39-ca6e27d1e088> | 2.8125 | 225 | Product Page | Software Dev. | 43.824079 | 95,490,905 |
By the end of the last century there were already the first indications of the possible existence of Al1 halides. However, it was only through the pioneering works of W. Klemm, who would have celebrated his 100th birthday on January 6, 1996, that detailed spectroscopic investigations became possible. Since the end of the 1970s the reactivity of AlX and GaX species in solid noble gases has been confirmed by numerous examples. In recent years formally monovalent Al and Ga species have been successfully synthesized on a preparative scale. In addition to the first halides, organometallic compounds with metal–metal bonds have been isolated and investigated with regard to their chemical properties. The fundamental importance of such species has been documented in this journal among others in the form of two highlight articles in which experimental and theoretical aspects have been examined with examples, and parallels and differences with respect to boron chemistry have been illustrated. This review is intended to give an account of the chronological development of this research area over the last few years, but an attempt is also made to categorize the experimental results achieved not only with respect to structure, thermodynamics, and reactivity, but also with the aid of quantum chemical calculations and by comparative considerations.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:8a988480-36ea-4a1b-85d1-eb498df7392f> | 2.59375 | 271 | Content Listing | Science & Tech. | 16.447976 | 95,490,916 |
Nearby alien planet six times as big as Earth has unusual plasma 'water-rich' atmosphere with temperatures as high as 280°
- Japanese astronomers examined the atmosphere of the alien planet using specialist cameras with a blue filter
- Super-Earth Gliese 1214 b is located just 40 light-years outside our solar system and while it has water, it is thought to be uninhabitable
- Scientists from the National Astronomical Observatory in Japan said the planet is around 70 times closer than the Earth to its sun
An unusual planet, six times the size of earth, that is located 40 light-years outside our solar system, has been found to have a 'water-rich' atmosphere that has a strange 'plasma form' of water, scientists have said.
Japanese astronomers examined the atmosphere of the alien planet using specialist cameras with a blue filter to observe planetary transits of super-Earth Gliese 1214 b.
The research team said that while its atmosphere is water-rich, the planet is not habitable like our Earth, as it has atmospheric temperatures that reach 280 degrees Celsius.
An unusual planet, six times the six of earth, that is located just 40 light-years outside our solar system, has been found to have a 'water-rich' atmosphere that has a 'plasma form' of water, astronomers have said. Here is an artist's rendition of a transit of GJ 1214 b in blue light. The blue sphere represents the host star GJ 1214 and the black ball in front of it is GJ 1214 b
While the planet's atmosphere contains water, it is still dramatically different to the Earth's
The scientists from the National Astronomical Observatory in Japan had set out to determine whether the planet has an atmosphere of water or hydrogen and used Subaru Telescope's two optical cameras with a blue transmission filter to study the scattering of light from the planet.
They then combined their findings with previous observations in other colours to conclude the atmosphere contains 'significant' amounts of water.
Principle investigator Norio Narita, told Space.com: 'As the temperature and pressure are so high, water is not in a usual form (vapor, liquid, or solid), but in an ionic or plasma form at the bottom the atmosphere - namely the interior - of Gliese 1214 b.'
The alien planet, which is located some 40 light-years away from our solar system in the constellation Ophiuchus, orbits a cooler star than our sun.
Artist's rendition of the relationship between the composition of the atmosphere and transmitted colours of light of an alien planet. Top: If the sky has a clear, upward-extended, hydrogen-dominated atmosphere, Rayleigh scattering disperses a large portion of the blue light from the atmosphere of the host while it scatters less of the red light. As a result, a transit in blue light becomes deeper than the one in red light. Middle: If the sky has a less extended water-rich atmosphere, the effect of the Rayleigh scattering is much weaker than in a hydrogen-dominated atmosphere. Bottom: If the sky has extensive clouds, most of the light cannot be transmitted through the atmosphere
But it is around 70 times closer than the Earth to its sun and makes its journey around the low-mass star once every 38 hours.
As is is so close, temperatures on the huge planet can reach a staggering 280°C or 540° Farenheit, but it is the planet's density that is surprising.
While Gliese 1214 b is six times as large as earth, it is less than three times in width to be as big as a planet in between the size of Earth and Neptune.
Dr Narita said: 'At high pressure and high temperature, the behaviour of water is quite different from that on the Earth.'
While astronomers believe water is an essential ingredient for Earth-like life on a planet, and Gliese 1214 b has plenty of water, Dr Narita does not not think it is habitable because of its close orbit.
'Although water vapour can exist in the atmosphere, liquid water - namely oceans - would not exist on the surface of this planet. So unfortunately, we do not think this planet would be habitable.'
As the planet does not have a solid surface, it is difficult to estimate the height of the atmosphere, but the scientists think it could be around 30km - around three times deeper than our Earth's.
They also believe plasma water could be hidden inside the planet but are unsure if they will ever be able to find the high pressure ices inside the super-Earth that they suspect are there.
The unusual planet was originally discovered as part of the MEarth Project, which tracks over 2,000 low-mass stars.
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Safe - Compile and execute code in restricted compartments. The Safe extension module allows the creation of compartments in which perl code can be evaluated. Each compartment has
a new namespace
The root of the namespace (i.e. main::) is changed to a different package and code evaluated in the compartment cannot refer to variables outside this namespace, even with run-time glob lookups and other tricks.
Code which is compiled outside the compartment can choose to place variables into (or share variables with) the compartments namespace and only that data will be visible to code evaluated in the compartment.
By default, the only variables shared with compartments are the underscore variables $_ and @_ (and, technically, the less frequently used %_, the _ filehandle and so on). This is because otherwise perl operators which default to $_ will not work and neither will the assignment of arguments to @_ on subroutine entry.
an operator mask
Each compartment has an associated operator mask. Recall that perl code is compiled into an internal format before execution. Evaluating perl code (e.g. via eval or do file) causes the code to be compiled into an internal format and then, provided there was no error in the compilation, executed. Code evaluated in a compartment compiles subject to the compartments operator mask. Attempting to evaluate code in a compartment which contains a masked operator will cause the compilation to fail with an error. The code will not be executed. | <urn:uuid:76cedceb-6e9d-4a16-b388-606c373592f9> | 2.5625 | 299 | Documentation | Software Dev. | 36.371824 | 95,490,952 |
Chemistry Question #154
Kaitlyn Muller, a 15 year old female from the Internet asks on March 16, 2000,
Could you tell me who discovered arsenic and when?
viewed 16104 times
answered on March 16, 2000
If you are coming here for a school assignment the answer might be Albertus Magnus. But Arsenic has been known since ancient times. It is so old, nobody knows who truly first discovered it or when. According to Web Elements (click on element #33, As, Arsenic) "Arsenic compounds were mined by the early Chinese, Greek and Egyptian civilizations. No doubt they discovered its toxic properties early on. It is believed that Albertus Magnus isolated the element in 1250 A.D. by heating soap together with orpiment (arsenic trisulphide, As2S3)."
Add to or comment on this answer using the form below.
Note: All submissions are moderated prior to posting.
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Almost infinite set of claims for health benefits Carotenoids * Lycopene * Singlet state
"SI" is the oxidized form * [beta]-Carotene * Ouenches free radicals by accepting energy * [alpha]-Carotene from singlet oxygen, not necessarily * [beta]-Cryptoxanthin transferring electrons, and radiating the * Lutein excess energy off as heat.
But now recall the superposition principle, and consider the singlet state, which can be represented as
But we have what is known as a quantum correlation of the two systems; in the singlet state each possible spin-up state of electron 1 is said to be correlated with the corresponding spin-down state of electron 2, and conversely.
The process is related to excitation of benzophenone (BP) by far UV radiation (250 nm) to a singlet state
In that case, the perfect anticorrelations predicted by QM for the spin singlet state would quite possibly fail.
In theorem 1, we consider two well-separated spin-1 particles in the spin singlet state
On the other hand, the Kondo effect favors the formation of singlet states
between localized moments and conduction electrons generating a non-magnetic ground state.
Potential energy surfaces were calculated for the singlet states
derived from the [[pi].
Highly conjugated molecules such a parphyrins have low-lying excited singlet states
that can be excited by light in the 600 to 800 nm region, corresponding to the wavelengths that transmit quite deeply into human tissues. | <urn:uuid:14189151-51fe-41d5-b55f-5643316ed262> | 2.828125 | 331 | Knowledge Article | Science & Tech. | 15.646667 | 95,490,968 |
Protein-bound ice crystals resist melting even when temperatures warm
Antarctic fish that manufacture their own "antifreeze" proteins to survive in the icy Southern Ocean also suffer an unfortunate side effect, researchers funded by the National Science Foundation (NSF) report: The protein-bound ice crystals that accumulate inside their bodies resist melting even when temperatures warm.
"We discovered what appears to be an undesirable consequence of the evolution of antifreeze proteins in Antarctic notothenioid fish," said University of Oregon doctoral student Paul Cziko, who led the research with University of Illinois animal biology professors Chi-Hing "Christina" Cheng and Arthur DeVries. "What we found is that the antifreeze proteins also stop internal ice crystals from melting. That is, they are anti-melt proteins as well."
The new finding was reported in the Proceedings of the National Academy of Sciences.
Five families of notothenioid fish inhabit the Southern Ocean, the frigid sea that encircles Antarctica. Their ability to live in the icy seawater is so extraordinary that they make up more than 90 percent of the fish biomass of the region.
With NSF support, Arthur DeVries discovered antifreeze proteins in Antarctic notothenioid fish in the late 1960s, and was the first to describe how the proteins bind to ice crystals in the blood to prevent the fish from freezing.
The most recent antifreeze discovery was supported by a grant from NSF's Division of Polar Programs.
The Division manages the United States Antarctic Program, through which it coordinates all U.S. research on the southernmost continent and provides the logistical framework to support the science.
This long-standing and continuously refined work on the antifreeze properties of Antarctic fish exemplifies one of the best and defining features of good science," said Charles Amsler, organisms and ecosystems program director in Polar Programs.
"These researchers not only have for decades consistently produced new and exciting finds that contribute to our understanding of Antarctic ecosystems, but very often those new finds have led to new questions and deeper understandings across biology as a whole," he added.
In the new study, the team investigated whether the antifreeze protein-bound ice crystals inside these fish would melt as expected when temperatures warmed.
When researchers warmed the fish to temperatures above the expected melting point, some internal ice crystals failed to melt. Ice that doesn't melt at its normal melting point is referred to as "superheated."
The researchers also found ice crystals in wild notothenioid fish swimming in relatively warmer Antarctic summer waters, at temperatures where they would be expected to be free of ice. By testing the antifreeze proteins in the lab, the team found that these proteins also were responsible for preventing the internal ice crystals from melting.
"Our discovery may be the first example of ice superheating in nature," Cheng said.
A diver himself, Cziko worked with other divers to place and maintain a temperature-logging device in Antarctica's McMurdo Sound, one of the coldest marine environments on the planet. The device recorded ocean temperatures there for 11 years, a substantial portion of notothenioids' lifespan. Not once in that time did temperatures increase enough to overcome the antifreeze proteins' anti-melting effect to completely rid the fish of their internal ice, the researchers report.
The researchers suspect that the accumulation of ice inside the fish could have adverse physiological consequences, but none have yet been discovered.
If the fish are destined to carry ice crystals around all their lives, Cheng said, it is conceivable that ice particles could obstruct small capillaries or trigger undesired inflammatory responses. Cziko likens the potential threat to dangers posed by asbestos in the lungs or blood clots in the brain.
"Since much of the ice accumulates in the fish spleens, we think there may be a mechanism to clear the ice from the circulation," he said.
"This is just one more piece in the puzzle of how notothenioids came to dominate the ocean around Antarctica," he said. "It also tells us something about evolution. That is, adaptation is a story of trade-offs and compromise. Every good evolutionary innovation probably comes with some bad, unintended effects."
The long-term temperature record of McMurdo Sound produced in the study also "will prove to be of great importance and utility to the polar research community that is addressing organismal responses to climate change in this coldest of all marine environments," Cheng said.
Clive W. Evans, a professor of molecular genetics and development at the University of Auckland in New Zealand, also is a co-author of the new paper.
Peter West, NSF, (703) 292-7530, firstname.lastname@example.org
Jim Barlow, University of Oregon, (541) 346-3481, email@example.com
Diana Yates, University of Illinois at Urbana-Champaign, (217) 333.5802, firstname.lastname@example.org
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2014, its budget is $7.2 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives about 50,000 competitive requests for funding, and makes about 11,500 new funding awards. NSF also awards about $593 million in professional and service contracts yearly.
Peter West | Eurek Alert!
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
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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Home » Invertebrates » A Grub’s Grub A Grub’s Grub Sep 13, 2014 by Editor in Chief Facebook - This squishy giant is a Megasoma mars grub, from the rhinoceros beetle genus. @ Facebook Related Posts Jun 24, 2014Dynastes Granti Grub Arachnoboards - Here are photos of an alien looking Western Hercules beetle grub. Jan 29, 2014Rub-a-Dub-Grub TortoiseForum.org - A beautiful hypo redfoot tortoise figures out what to do with a fat, juicy grub in this great series of photos. Dec 11, 2012Orchard Spider Parasitized By Wasp Grub YouTube - A fascinating video documenting a wasp grub which attaches itself to an orchard spider, feeds off of it, injects it with a fatal hormone and then uses the... Aug 9, 2012Dynastes Tityus Arachnoboards - Excellent photos of an eastern Hercules beetle’s (one of the largest species of rhinoceros beetle) progression from a pupa to an adult. Jan 25, 2013Chalcosoma Caucasus Arachnoboards - Photos of some tiny little larvae, an enormous F2 larvae and a giant rhinoceros beetle, which is what the larvae will eventually turn into—impressive! | <urn:uuid:b064d827-7f4c-4c95-a7e8-18fcc76ecb06> | 2.515625 | 285 | Content Listing | Science & Tech. | 45.454317 | 95,491,013 |
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Land Cover Influences on Stream Nitrogen Dynamics During Storms
Stewart, Rebecca Marie
MetadataShow full item record
Previous studies on the effects of land cover influence on stream nitrogen have focused on base flow conditions or were conducted specifically within urbanized or primarily agricultural watersheds. While these studies have shown relationships between land cover and nitrogen, this relationship and the scale of influence could change during storms. The purpose of my study was to understand how land cover influences nitrogen in streams during storms. This was address using nine watersheds within the Little Tennessee Basin in North Carolina. While this basin is primarily forested, the nine watersheds have mixed agricultural, built, and forest land cover. Land cover influences were addressed through nitrogen concentration/discharge patterns, nitrogen concentration relationship to land cover, and comparison of storm and base flow nitrogen concentrations over time. Weekly base flow samples and samples from six storm were collected in 2010-2011. Total dissolved nitrogen (TDN), nitrate (NO??), dissolved organic nitrogen (DON), and ammonium (NH?⁺) concentrations were compared among sites. During most storms, DON peaked before the peak of the discharge while NO?? peaked after the peak of the storm. This suggest that DON could be coming from a near stream source or surface runoff while NO?? could be from longer pathways such as subsurface flow or from sources further away on the watershed. NO?? concentration varied among sites, while DON concentration varied more between base flow and storm samples. Examining the different landscape scales from 200-m local corridor, 200-m stream corridor, and entire watershed, watershed land cover was the best predictor for all the nitrogen concentrations. Agricultural and built combined best predicted TDN and NO??, while agricultural land cover was a better predictor of DON. For storms, nitrogen concentrations did not show seasonal patterns but was more related to discharge. Nitrogen concentration increased with discharge during storms and the more intense and longer storms had higher TDN and NO?? concentrations. However, conflicting seasonal trends were seen in monthly base flow. The more forested watersheds had high NO?? during the summer and low NO?? in the winter. For sites with higher NO??, the seasonality was reversed, with higher winter NO?? concentration. The least forested site had relatively constant nitrogen through the year at base flow and concentration decreased for most storms. Further studies on storms and nitrogen transport are needed to understand better the seasonal patterns of nitrogen input during storms.
- Masters Theses | <urn:uuid:e591ec49-9f6f-4fd9-9c82-637256500ec2> | 2.625 | 525 | Academic Writing | Science & Tech. | 41.977192 | 95,491,020 |
Question: What are wrapped classes
Wrapped classes are classes that allow primitive types to be accessed as objects.
Question: What are the four general cases for Conversion and Casting
Conversion of primitives
Casting of primitives
Conversion of object references
Casting of object references
Question: When can conversion happen
It can happen during
Question: What are the rules for primitive assignment and method call conversion
A boolean can not be converted to any other type
A non Boolean can be converted to another non boolean type, if the conversion is widening conversion
A non Boolean cannot be converted to another non boolean type, if the conversion is narrowing conversion
See figure below for simplicity
Question: What are the rules for primitive arithmetic promotion conversion
For Unary operators :
If operant is byte, short or a char it is converted to an int
If it is any other type it is not converted
For binary operands :
If one of the operands is double, the other operand is converted to double
Else If one of the operands is float, the other operand is converted to float
Else If one of the operands is long, the other operand is converted to long
Else both the operands are converted to int
Question: What are the rules for casting primitive types
You can cast any non Boolean type to any other non boolean type
You cannot cast a boolean to any other type; you cannot cast any other type to a boolean
Question: What are the rules for object reference assignment and method call conversion
An interface type can only be converted to an interface type or to object. If the new type is an interface, it must be a superinterface of the old type.
A class type can be converted to a class type or to an interface type. If converting to a class type the new type should be superclass of the old type. If converting to an interface type new type the old class must implement the interface.
An array maybe converted to class object, to the interface cloneable, or to an array. Only an array of object references types may be converted to an array, and the old element type must be convertible to the new element.
Question: What are the rules for Object reference casting
Casting from Old types to Newtypes
Compile time rules | <urn:uuid:4fd39f16-592f-4c64-b60f-f447a1429a05> | 3 | 476 | Q&A Forum | Software Dev. | 8.402551 | 95,491,083 |
The identification of forensically important blowflies of the genus Chrysomya (Diptera: Calliphoridae) may be hampered by their close morphological similarities, especially as immatures. In contrast to most previous studies, the utility of a nuclear rather than mitochondrial genetic marker was investigated to solve this problem. The second internal transcribed spacer (ITS2) of ribosomal DNA (rDNA) was amplified and sequenced from all nine Chrysomya species known from Australia. Difficulties encountered with direct sequencing of ITS2 for Chrysomya flavifrons necessitated cloning prior to sequencing for this species, which revealed a low level (0-0.23%) of intraindividual variation. Five restriction enzymes (DraI, BsaXI, BciVI, AseI and HinfI) were identified that were able to differentiate most members of the genus by polymerase chain reaction (PCR) restriction fragment length polymorphism (PCR-RFLP). The PCR-RFLP analysis revealed characteristic restriction profiles for all species except the closely related species pairs Chrysomya latifrons + Chrysomya semimetallica and Chrysomya incisuralis + Chrysomya rufifacies. Ch. incisuralis and Ch. rufifacies were able to be separated using the size differences resulting from amplification of the entire ITS region. The lack of intraspecific ITS2 sequence variation among eight Ch. incisuralis specimens was verified by the identical restriction profiles generated from these specimens. A DNA-based approach, such as PCR-RFLP, has the capacity to be useful for the identification of forensic entomological evidence in cases where morphological characters are unreliable. Crown Copyright © 2008.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:dfbe67c3-74a7-429d-9194-61a624d52d85> | 2.5625 | 382 | Academic Writing | Science & Tech. | 10.514634 | 95,491,188 |
On the surface, this sounds like a ridiculous title. Everyone knows that the dinosaurs were wiped out in a mass extinction event about 65 million years ago. An asteroid hit the Earth near the Yucatan Peninsula, and the debris displaced by the impact caused an extended global winter. The dinosaurs, being cold-blooded, were unable to maintain their body temperature as the Earth started cooling, and they eventually died.
So, what’s boredom got to do with anything? As you know, this is The Bob Angle, so naturally there has to be another way of looking at it…
A few years ago, I was watching the movie Men In Black. Toward the end of the movie, there is a CGI scene in which the camera zooms out from Battery Park in Manhattan, into orbit, past our solar system, beyond the Milky Way … until it reaches the edge of the universe itself. Then it keeps zooming out until it is revealed that our universe is actually contained within a marble-like object, which is resting on the ground of a world from a higher plane of existence.
I found this sequence fascinating because it reminded me of Stephen Hawking’s concept of multiverses – multiple universes. Hawking speculated that ours isn’t the only universe; there might be hundreds or thousands of other universes, each formed by their own Big Bang, and each governed by different laws of physics.
This scene also proposes the notion of life on a higher plane of existence. Instead of a singular, managerial God, an entire society of superior beings may exist on some unreachable, god-like realm. In fact, our entire universe may be nothing more than a sophisticated physics experiment to the creatures who inhabit this plane. Naturally, every one of these creatures would be considered a god to us mere mortals.
If our snow-globe universe is a classroom experiment, then it’s possible that we are being observed by several of these god-like creatures, or perhaps an entire room full of them. That thought alone should make you want to be on your best behaviour – if Humankind destroys itself in a nuclear war (after evolving from single-celled organisms) the superior being in charge of our celestial marble may receive a lower grade for this science project.
The Game of Life
No, I’m not talking about the board game that you probably played during your childhood; this is a more esoteric life simulation that’s also known as cellular automata. If you took computer science in university, then you will undoubtedly be familiar with it.
The concept was developed in the 1940s by John von Neumann and Stanislaw Ulam, and was turned into a simulation by John Conway during the 1970s. Calling it a game is a bit of a misnomer, since there is no continual user interaction. It’s essentially a simulation. It can also be run within a browser, if you’d like to give it a try.
You begin with a blank grid. Each square, or cell, represent a life form. You add one or more lifeforms by highlighting some of the sells. Each cell has eight neighbouring cells. Whether a particular cell survives to the next generation depends on the following set of rules:
- 0-1 Neighbours: The cell dies from underpopulation (or loneliness).
- 2-3 Neighbours: The cell survives until the next generation.
- 4-8 Neighbours: The cell dies from overcrowding.
- A dead cell with three neighbours will come to life in the next generation.
It seems absurdly simple, but this simulation can generate some surprisingly complex behaviour. Cellular automata are used in encryption, random number generation, and the arrangement of processing elements in CPUs. If you’d like to take a deep dive into this topic, M. Mitchell Waldrop’s book, Complexity: The Emerging Science at the Edge of Order and Chaos is an excellent place to start. Waldrop elaborates on research into complex systems, done at the Santa Fe Institute in New Mexico. Systems with just a few simple rules can generate complex, even unpredictable behaviour, and even act as if they’re intelligent.
In the Game of Life, the initial configuration of cells is called the seed. Seeds can evolve into stable, complex or chaotic patterns. However, many will becomes static patterns and others will simply oscillate forever.
The Dinosaur / Cellular Automata Connection
Dinosaurs reigned the Earth from 225 – 65 million years ago, a period lasting 160 million years. During this time, they were in perfect harmony with nature, having established an ecological equilibrium. In fact, one might argue that the dinosaurs were better stewards of the planet than we are, despite our larger brains and lofty perch at the top of the evolutionary ladder.
What the Game of Life is to us – a simplistic model of evolution – is probably what our universe is to these superior beings. It’s just a dark snow globe, or perhaps a novelty item sold in their museum gift shops. It might be a science experiment or a game: generate an initial seed value by adjusting the laws of physics (and other parameters), and then sit back and watch the universe unfold – see if life develops, or how advanced the civilizations will become before they destroy their environment or themselves. On a god-like plane of existence, this might actually be amusing!
Once the simulation began, and the primordial ooze coalesced into stars and planets, circumstances on Earth were interesting as it slowly took shape and developed. Life began, and started to evolve, growing increasingly complex.
Now consider the reign of the dinosaurs. They have evolved into a stable configuration, and remained that way for 160 million years. After this ecological equilibrium was established, things plateaued, evolution-wise. If I were a superior being, I would quickly become bored. Life on Earth would be much like watching a static or oscillating cellular automata pattern… dull as ditch water. Ar this point, I could throw out my snow globe universe, or being the resourceful being that I am, I could find a way to hack it… just a little.
This is what I think might have happened. The owner of our universe-in-a-marble decided to make an infinitesimal change to a tiny sliver of our universe – just enough to disrupt the equilibrium on a single planet. Our universe owner either created a new asteroid by breaking apart a large object, or nudged an existing asteroid so that its orbit would collide with Earth. The impact wouldn’t be forceful enough to destroy the planet or all life on it, but enough to cause a global extinction event and leave a few survivors who will take evolution in a new direction. In fact, the BBC reported that the asteroid hit the Earth in just the right spot to accomplish this.
Another article speculates that our sun had a sister star that hurled a few meteors in our direction every 27 million years. One of them hit the Earth and wiped out the dinosaurs. There are countless ways in which one can hack the universe.
Could This Happen To Us?
In a word: no. We homo sapiens are just too darn interesting. We’ve settled all over the planet. We’ve drawn and redrawn political boundaries as empires rose and fell. We’re constantly inventing new things and are now extending our reach past the planet itself.
If that weren’t enough, we’re already the architects of our own demise. For over a century, we’ve been extracting raw materials from the ground, processing them, and then feeding them back to the planet in an indigestible (plastic), or even poisonous configuration (spent nuclear fuel rods) – a perverse form of reverse dialysis on a planetary scale.
Will we smarten up in time to stop the ecological damage we’ve caused to our planet, or will be perish as a result of our own stupidity? Even to a superior being, that’s some pretty decent cliffhanger material!
Even if we do manage to save ourselves, we still won’t be out of the proverbial woods. Achieving a net zero carbon footprint sounds like an admirable goal, but let’s not rest on our laurels for too long. After 160 million years of living in harmony with the planet, the watchers may once again decide to stir things up… | <urn:uuid:c339219c-97c0-4e57-a10c-0a1bb162309b> | 2.6875 | 1,743 | Personal Blog | Science & Tech. | 46.988687 | 95,491,195 |
François Englert and Peter Higgs have been announced as the winners of the Nobel Prize in Physics 2013. Englert and Higgs' work was called a "triumph for theoretical physics" and that their achievements "illustrate the scientific method," with the committee noting that it is the "small things that make all the difference."
The Nobel committee says it awarded Englert and Higgs the Nobel Prize in Physics 2013 for "the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider."
In 1964, both François Englert and Peter Higgs proposed the idea of a field that extends throughout the universe and interacts with particles to give them mass. Englert had published the idea a few weeks before Higgs, but Higgs crucially pointed out that the field would give rise to a particle: the Higgs boson. Their theory was confirmed in 2012 when the Cern laboratory outside Geneva, Switzerland, announced the discovery of a Higgs boson.
The announcement was delayed by roughly 45 minutes, but the committee refused to comment on exactly why. It did, however, emphasize that the decision was made on the same day as the announcement, suggesting there may have been some last-minute disagreements.
The committee was also unable to get a hold of Higgs, claiming he didn't answer any of the numbers they had for him. Englert did phone-in to the announcement, and when asked to describe the feeling of winning the Nobel Prize, he said it was "not unpleasant."
Cate Sevilla is the UK managing editor for BuzzFeed and is based in London.
Kelly Oakes is science editor for BuzzFeed and is based in London.
Contact Kelly Oakes at email@example.com.
Got a confidential tip? Submit it here. | <urn:uuid:9f4c6949-ec06-4649-9993-7baeb732884c> | 2.625 | 410 | News Article | Science & Tech. | 45.280518 | 95,491,202 |
Terrestrial Hydrometeorology Paperback
Both hydrologists and meteorologists need to speak a common scientific language, and this has given rise to the new scientific discipline of hydrometeorology, which deals with the transfer of water and energy across the land/atmosphere interface.
Terrestrial Hydrometeorology is the first graduate-level text with sufficient breadth and depth to be used in hydrology departments to teach relevant aspects of meteorology, and in meteorological departments to teach relevant aspects of hydrology, and to serve as an introductory text to teach the emerging discipline of hydrometeorology. The book will be essential reading for graduate students studying surface water hydrology, meteorology, and hydrometeorology.
It can also be used in advanced undergraduate courses, and will be welcomed by academic and professional hydrologists and meteorologists worldwide. Additional resources for this book can be found at: http://www.wiley.com/go/shuttleworth/hydrometeorology.
- Format: Paperback
- Pages: 472 pages
- Publisher: John Wiley and Sons Ltd
- Publication Date: 06/01/2012
- Category: Limnology (freshwater)
- ISBN: 9780470659373
- Hardback from £97.89
- PDF from £112.20
- EPUB from £112.20 | <urn:uuid:c659fc30-19b2-4399-858f-c44d3890fc5b> | 2.515625 | 289 | Product Page | Science & Tech. | 21.806214 | 95,491,206 |
Space sustainability is a concept that has emerged within the past 10 years to refer to a set of concerns relating to outer space as an environment for carrying out space activities safely and without interference and also to concerns about ensuring continuity of the benefits derived on Earth from space activities. As such, it encompasses the concerns of both space actors and those who are not space actors but who nevertheless benefit from space activities. This chapter reviews the role of the various relevant United Nations entities in ensuring space sustainability and provides a detailed review of the Working Group on the Long-Term Sustainability of Outer Space Activities within the Scientific and Technical Subcommittee of COPUOS. Finally, the chapter discusses the relationship of the work in UN COPUOS with related work being done in the Conference on Disarmament, the UN Group of Governmental Experts (GGE) on Transparency and Confidence-Building Measures in Outer Space Activities, and the initiative by the European Union to propose a draft international Code of Conduct for outer space activities.
KeywordsSpace Activity Expert Group Celestial Body Space Weather Outer Space
- Hedman N, Balogh W (2009) The United Nations and outer space: celebrating 50 years of space achievements. In: Schrogl K-U, Mathieu C, Peter N (eds) Yearbook on space policy 2007/2008: from policies to programmes. Springer Wien, New York, pp 237–250. ISBN 978-3-211-99090-2Google Scholar
- Outer Space Treaty (1967) The full text of the Treaty, Article VI. Available at http://www.unoosa.org/oosa/en/SpaceLaw/index.html
- Report of the World Commission on Environment and Development, Annex Our Common Future, UN document A/42/427. Accessed at http://www.un-documents.net/wced-ocf.htm
- Weeden B (2010) Dealing with Galaxy 15: Zombiesats and on-orbit servicing. In: The space review, Edition of 24 May 2010. Accessed at http://thespacereview.com/article/1634/1 | <urn:uuid:9ddd97eb-bca0-4a91-897f-5c316ab37d38> | 3.390625 | 432 | Academic Writing | Science & Tech. | 43.375605 | 95,491,216 |
Astronomers have accurately measured the diameter of the faraway dwarf planet Eris for the first time by catching it as it passed in front of a faint star. This event was seen at the end of 2010 by telescopes in Chile, including the Belgian TRAPPIST telescope at ESO’s La Silla Observatory. The observations show that Eris is an almost perfect twin of Pluto in size. Eris appears to have a very reflective surface, suggesting that it is uniformly covered in a thin layer of ice, probably a frozen atmosphere. The results will be published in the 27 October 2011 issue of the journal Nature.
In November 2010, the distant dwarf planet Eris passed in front of a faint background star, an event called an occultation. These occurrences are very rare and difficult to observe as the dwarf planet is very distant and small. The next such event involving Eris will not happen until 2013. Occultations provide the most accurate, and often the only, way to measure the shape and size of a distant Solar System body.
The candidate star for the occultation was identified by studying pictures from the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory. The observations were carefully planned and carried out by a team of astronomers from a number of (mainly French, Belgian, Spanish and Brazilian) universities using — among others — the TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope, eso1023) telescope, also at La Silla.
“Observing occultations by the tiny bodies beyond Neptune in the Solar System requires great precision and very careful planning. This is the best way to measure Eris’s size, short of actually going there,” explains Bruno Sicardy, the lead author.
Observations of the occultation were attempted from 26 locations around the globe on the predicted path of the dwarf planet’s shadow — including several telescopes at amateur observatories, but only two sites were able to observe the event directly, both of them located in Chile. One was at ESO’s La Silla Observatory using the TRAPPIST telescope, and the other was located in San Pedro de Atacama and used two telescopes . All three telescopes recorded a sudden drop in brightness as Eris blocked the light of the distant star.
The combined observations from the two Chilean sites indicate that Eris is close to spherical. These measurements should accurately measure its shape and size as long as they are not distorted by the presence of large mountains. Such features are, however, unlikely on such a large icy body.
Eris was identified as a large object in the outer Solar System in 2005. Its discovery was one of the factors that led to the creation of a new class of objects called dwarf planets and the reclassification of Pluto from planet to dwarf planet in 2006. Eris is currently three times further from the Sun than Pluto.
While earlier observations using other methods suggested that Eris was probably about 25% larger than Pluto with an estimated diameter of 3000 kilometres, the new study proves that the two objects are essentially the same size. Eris’s newly determined diameter stands at 2326 kilometres, with an accuracy of 12 kilometres. This makes its size better known than that of its closer counterpart Pluto, which has a diameter estimated to be between 2300 and 2400 kilometres. Pluto’s diameter is harder to measure because the presence of an atmosphere makes its edge impossible to detect directly by occultations. The motion of Eris’s satellite Dysnomia was used to estimate the mass of Eris. It was found to be 27% heavier than Pluto . Combined with its diameter, this provided Eris’s density, estimated at 2.52 grams per cm3 .
“This density means that Eris is probably a large rocky body covered in a relatively thin mantle of ice,” comments Emmanuel Jehin, who contributed to the study .
The surface of Eris was found to be extremely reflective, reflecting 96% of the light that falls on it (a visible albedo of 0.96 ). This is even brighter than fresh snow on Earth, making Eris one of the most reflective objects in the Solar System, along with Saturn’s icy moon Enceladus. The bright surface of Eris is most likely composed of a nitrogen-rich ice mixed with frozen methane — as indicated by the object's spectrum — coating the dwarf planet’s surface in a thin and very reflective icy layer less than one millimetre thick.
“This layer of ice could result from the dwarf planet’s nitrogen or methane atmosphere condensing as frost onto its surface as it moves away from the Sun in its elongated orbit and into an increasingly cold environment,” Jehin adds. The ice could then turn back to gas as Eris approaches its closest point to the Sun, at a distance of about 5.7 billion kilometres.The new results also allow the team to make a new measurement for the surface temperature of the dwarf planet. The estimates suggest a temperature for the surface facing the Sun of -238 Celsius at most, and an even lower value for the night side of Eris.
“It is extraordinary how much we can find out about a small and distant object such as Eris by watching it pass in front of a faint star, using relatively small telescopes. Five years after the creation of the new class of dwarf planets, we are finally really getting to know one of its founding members,” concludes Bruno Sicardy.Notes
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. 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 the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
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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.
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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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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.
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To understand climate change, dendrochronologists have used tree ring analyses to reconstruct past climates, as well as ecological processes such as herbivore population dynamics. Such reconstructions, however, have been hindered by a lack of experiments that separate the influences of confounding impacts on tree rings, such as herbivores and the interactions of multiple factors. Our long-term experiments with scale insects on resistant and susceptible pines demonstrate three major points that are important to the application of this commonly used tool. (i) Herbivory reduced tree ring growth by 25-35%. (ii) The impact on ring growth distorted climate reconstruction, resulting in the overestimation of past moisture levels by more than 2-fold. Our data suggest that, if distortion because of herbivory has been a problem in previous reconstructions, estimates of the magnitude of recent climate changes are likely to be conservative. (iii) Our studies support a detectible plant resistance x herbivore x climate interaction in the tree ring record. Because resistance and susceptibility to herbivory are known to be genetically based in many systems, the potential exists to incorporate plant genetics into the field of dendrochronology, where it may be used to screen distortions from the tree ring record.
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Rhine One of the Most Polluted Rivers Worldwide
News Dec 09, 2015
Among investigated rivers, the Rhine is thus among those most heavily polluted with microplastics. This is reported by researchers from the University of Basel, who evaluated, for the first time, the plastic concentration at the surface of one of the big European rivers. Their results have been published in the journal Scientific Reports.
Tiny plastic particles smaller than five millimeters, so-called microplastics, are found in almost all waterbodies these days. They occur as intermediate products in plastic production or as pellets for cleansing and care products or result from fragmentation of plastic debris. They are released into the environment due to improper handling. In the oceans, they contribute to the ‘great garbage patches’ and are ingested by many organisms, from protozoa to baleen whales. Although as much as 80% of this marine plastic is emitted by rivers to the oceans, not a single great river has yet been scientifically studied for the microplastics load over its length.
Environmental pollution mapped
For the first time, environmental scientists from the University of Basel have now reported the abundance and composition of microplastics at the surface of the Rhine between Basel and Rotterdam. They took 31 water samples at 11 locations over a stretch of 820 kilometers. Microplastics were found in all samples in different concentrations, with an average of 892,777 particles per square kilometer (or 4,960 particles per 1000 cubic meters).
The findings reflect the major potential sources of environmental pollution along the Rhine, such as metropolitan areas and industrial plants, waste water treatment plants and weirs, as well as the particular current conditions. The minimum average microplastics pollution was found in the stretch between Basel and Mainz (202,900 particles per square kilometer), a medium average at Bad Honnef, Köln-Porz and Leverkusen (714,053) and the highest average in the Rhine-Ruhr metropolitan area (2,333,665). A peak microplastics concentration was measured at Rees on the Nederhijn, where 3.9 million plastic items per square kilometer (or 21,839 particles per 1000 cubic meters) were found in a single water sample.
191 million particles a day
“The Rhine's microplastics concentrations are thus among the highest so far studied worldwide”, says biologist Professor Patricia Holm from the Department of Environmental Sciences at the University of Basel. For the most polluted Swiss lakes, Lake Geneva and Lake Maggiore, 220,000 particles per square kilometer were reported in other studies. As a further example, in Lake Erie in the U.S., only 105,503 items per square kilometer were found. Significantly less microplastics were also found in the river Rhone near Geneva. In general, extreme peaks may be reached after heavy rain or accidents.
“Our results show that the Rhine is significantly polluted with microplastics”, says Holm. ”If we assume an average microplastics concentration on the day we took the water sample in Rees, we can say that the Rhine contributes a daily load of more than 191 million plastic particles to the North Sea, and that only takes into account the surface. Even though, in terms of weight, this only corresponds to roughly 25 to 30 kilos a day, this adds up to 10 tons a year. Each one of these billions of plastic items can be ingested by organisms and have negative effects on their health.”
Origins partially unclear
The scientists concentrated on the detection of microplastics found in large numbers in production worldwide and of low specific density, such as polyethylene, polypropylene and polystyrene. The types of plastics are used in the plastic industry e.g. for packaging, office equipment and vehicle construction and float on the water surface for long distances. Samples were mostly taken from boats of the Rhine Police Basel-Stadt and the Waterways and Shipping Administration in Germany and the Netherlands.
The researchers found microplastics in the shape of opaque and transparent spherules as well as of fragments and fibers. “The extremely high proportion of more than 60 percent spherules in certain parts of the river is striking. Where they come from and what their former use was, is largely unclear so far”, says Thomas Mani, first author of the study and PhD student at the Department of Environmental Sciences of the University of Basel.
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Renormalization(Redirected from Renormalizable)
Renormalization is a collection of techniques in quantum field theory, the statistical mechanics of fields, and the theory of self-similar geometric structures, that are used to treat infinities arising in calculated quantities by altering values of quantities to compensate for effects of their self-interactions. However, even if it were the case that no infinities arise in loop diagrams in quantum field theory, it can be shown that renormalization of mass and fields appearing in the original Lagrangian is necessary.
For example, a theory of the electron may begin by postulating a mass and charge. However, in quantum field theory this electron is surrounded by a cloud of possibilities of other virtual particles such as photons, which interact with the original electron. Taking these interactions into account shows that the electron-system, in fact, behaves as if it had a different mass and charge. Renormalization replaces the initially postulated mass and charge with new numbers such that the observed mass and charge matches those postulated initially. It is a remarkable, experimentally verified, and mathematically proven fact that positrons and more massive particles like the proton with much stronger interactions, or a more intense cloud of virtual particles, have exactly the same observed charge.
Renormalization specifies relationships between parameters in the theory when the parameters describing large distance scales differ from the parameters describing small distances. Physically, the pileup of contributions from an infinity of scales involved in a problem may then result in infinities. When describing space and time as a continuum, certain statistical and quantum mechanical constructions are ill-defined. To define them, this continuum limit—the removal of the "construction scaffolding" of lattices at various scales—has to be taken carefully. Renormalization procedures are based on the requirement that certain physical quantities are equal to the observed values.
Renormalization was first developed in quantum electrodynamics (QED) to make sense of infinite integrals in perturbation theory. Initially viewed as a suspect provisional procedure even by some of its originators, renormalization eventually was embraced as an important and self-consistent actual mechanism of scale physics in several fields of physics and mathematics.
Today, the point of view has shifted: on the basis of the breakthrough renormalization group insights of Nikolay Bogolyubov and Kenneth Wilson, the focus is on variation of physical quantities across contiguous scales, while distant scales are related to each other through "effective" descriptions. All scales are linked in a broadly systematic way, and the actual physics pertinent to each is extracted with the suitable specific computational techniques appropriate for each. Wilson clarified which variables of a system are crucial and which are redundant.
Renormalization is distinct from regularization, another technique to control infinities by assuming the existence of new unknown physics at new scales.
Self-interactions in classical physicsEdit
The mass of a charged particle should include the mass-energy in its electrostatic field (electromagnetic mass). Assume that the particle is a charged spherical shell of radius re. The mass–energy in the field is
which becomes infinite as re → 0. This implies that the point particle would have infinite inertia, making it unable to be accelerated. Incidentally, the value of re that makes equal to the electron mass is called the classical electron radius, which (setting and restoring factors of c and ) turns out to be
Renormalization: The total effective mass of a spherical charged particle includes the actual bare mass of the spherical shell (in addition to the mass mentioned above associated with its electric field). If the shell's bare mass is allowed to be negative, it might be possible to take a consistent point limit. This was called renormalization, and Lorentz and Abraham attempted to develop a classical theory of the electron this way. This early work was the inspiration for later attempts at regularization and renormalization in quantum field theory.
(See also regularization (physics) for an alternative way to remove infinities from this classical problem, assuming new physics exists at small scales.)
When calculating the electromagnetic interactions of charged particles, it is tempting to ignore the back-reaction of a particle's own field on itself. (Analogous to the back-EMF of circuit analysis.) But this back-reaction is necessary to explain the friction on charged particles when they emit radiation. If the electron is assumed to be a point, the value of the back-reaction diverges, for the same reason that the mass diverges, because the field is inverse-square.
The Abraham–Lorentz theory had a noncausal "pre-acceleration." Sometimes an electron would start moving before the force is applied. This is a sign that the point limit is inconsistent.
The trouble was worse in classical field theory than in quantum field theory, because in quantum field theory a charged particle experiences Zitterbewegung due to interference with virtual particle-antiparticle pairs, thus effectively smearing out the charge over a region comparable to the Compton wavelength. In quantum electrodynamics at small coupling, the electromagnetic mass only diverges as the logarithm of the radius of the particle.
Divergences in quantum electrodynamicsEdit
When developing quantum electrodynamics in the 1930s, Max Born, Werner Heisenberg, Pascual Jordan, and Paul Dirac discovered that in perturbative corrections many integrals were divergent (see The problem of infinities).
One way of describing the perturbation theory corrections' divergences was discovered in 1947–49 by Hans Kramers, Hans Bethe,Julian Schwinger, Richard Feynman, and Shin'ichiro Tomonaga, and systematized by Freeman Dyson in 1949. The divergences appear in radiative corrections involving Feynman diagrams with closed loops of virtual particles in them.
While virtual particles obey conservation of energy and momentum, they can have any energy and momentum, even one that is not allowed by the relativistic energy–momentum relation for the observed mass of that particle (that is, is not necessarily the squared mass of the particle in that process, e.g. for a photon it could be nonzero). Such a particle is called off-shell. When there is a loop, the momentum of the particles involved in the loop is not uniquely determined by the energies and momenta of incoming and outgoing particles. A variation in the energy of one particle in the loop can be balanced by an equal and opposite change in the energy of another particle in the loop, without affecting the incoming and outgoing particles. Thus many variations are possible. So to find the amplitude for the loop process, one must integrate over all possible combinations of energy and momentum that could travel around the loop.
These integrals are often divergent, that is, they give infinite answers. The divergences that are significant are the "ultraviolet" (UV) ones. An ultraviolet divergence can be described as one that comes from
- the region in the integral where all particles in the loop have large energies and momenta,
- very short wavelengths and high-frequencies fluctuations of the fields, in the path integral for the field,
- very short proper-time between particle emission and absorption, if the loop is thought of as a sum over particle paths.
So these divergences are short-distance, short-time phenomena.
Shown in the pictures at the right margin, there are exactly three one-loop divergent loop diagrams in quantum electrodynamics:
- (a) A photon creates a virtual electron–positron pair, which then annihilates. This is a vacuum polarization diagram.
- (b) An electron quickly emits and reabsorbs a virtual photon, called a self-energy.
- (c) An electron emits a photon, emits a second photon, and reabsorbs the first. This process is shown in the section below in figure 2, and it is called a vertex renormalization. The Feynman diagram for this is also called a “penguin diagram” due to its shape remotely resembling a penguin (with the initial and final state electrons as the arms and legs, the second photon as the body and the first looping photon as the head).
The three divergences correspond to the three parameters in the theory under consideration:
- The field normalization Z.
- The mass of the electron.
- The charge of the electron.
The second class of divergence called an infrared divergence, is due to massless particles, like the photon. Every process involving charged particles emits infinitely many coherent photons of infinite wavelength, and the amplitude for emitting any finite number of photons is zero. For photons, these divergences are well understood. For example, at the 1-loop order, the vertex function has both ultraviolet and infrared divergences. In contrast to the ultraviolet divergence, the infrared divergence does not require the renormalization of a parameter in the theory involved. The infrared divergence of the vertex diagram is removed by including a diagram similar to the vertex diagram with the following important difference: the photon connecting the two legs of the electron is cut and replaced by two on-shell (i.e. real) photons whose wavelengths tend to infinity; this diagram is equivalent to the bremsstrahlung process. This additional diagram must be included because there is no physical way to distinguish a zero-energy photon flowing through a loop as in the vertex diagram and zero-energy photons emitted through bremsstrahlung. From a mathematical point of view, the IR divergences can be regularized by assuming fractional differentiation w.r.t. a parameter, for example:
is well defined at p = a but is UV divergent; if we take the 3⁄2-th fractional derivative with respect to −a2, we obtain the IR divergence
so we can cure IR divergences by turning them into UV divergences.[clarification needed]
A loop divergenceEdit
The diagram in Figure 2 shows one of the several one-loop contributions to electron–electron scattering in QED. The electron on the left side of the diagram, represented by the solid line, starts out with 4-momentum pμ and ends up with 4-momentum rμ. It emits a virtual photon carrying rμ − pμ to transfer energy and momentum to the other electron. But in this diagram, before that happens, it emits another virtual photon carrying 4-momentum qμ, and it reabsorbs this one after emitting the other virtual photon. Energy and momentum conservation do not determine the 4-momentum qμ uniquely, so all possibilities contribute equally and we must integrate.
This diagram's amplitude ends up with, among other things, a factor from the loop of
The various γμ factors in this expression are gamma matrices as in the covariant formulation of the Dirac equation; they have to do with the spin of the electron. The factors of e are the electric coupling constant, while the provide a heuristic definition of the contour of integration around the poles in the space of momenta. The important part for our purposes is the dependency on qμ of the three big factors in the integrand, which are from the propagators of the two electron lines and the photon line in the loop.
This has a piece with two powers of qμ on top that dominates at large values of qμ (Pokorski 1987, p. 122):
This integral is divergent and infinite, unless we cut it off at finite energy and momentum in some way.
Similar loop divergences occur in other quantum field theories.
Renormalized and bare quantitiesEdit
The solution was to realize that the quantities initially appearing in the theory's formulae (such as the formula for the Lagrangian), representing such things as the electron's electric charge and mass, as well as the normalizations of the quantum fields themselves, did not actually correspond to the physical constants measured in the laboratory. As written, they were bare quantities that did not take into account the contribution of virtual-particle loop effects to the physical constants themselves. Among other things, these effects would include the quantum counterpart of the electromagnetic back-reaction that so vexed classical theorists of electromagnetism. In general, these effects would be just as divergent as the amplitudes under consideration in the first place; so finite measured quantities would, in general, imply divergent bare quantities.
To make contact with reality, then, the formulae would have to be rewritten in terms of measurable, renormalized quantities. The charge of the electron, say, would be defined in terms of a quantity measured at a specific kinematic renormalization point or subtraction point (which will generally have a characteristic energy, called the renormalization scale or simply the energy scale). The parts of the Lagrangian left over, involving the remaining portions of the bare quantities, could then be reinterpreted as counterterms, involved in divergent diagrams exactly canceling out the troublesome divergences for other diagrams.
Renormalization in QEDEdit
For example, in the Lagrangian of QED
the fields and coupling constant are really bare quantities, hence the subscript B above. Conventionally the bare quantities are written so that the corresponding Lagrangian terms are multiples of the renormalized ones:
together (Pokorski 1987, p. 115), which is what happened to Z2; it is the same as Z1.
A term in this Lagrangian, for example, the electron-photon interaction pictured in Figure 1, can then be written
The physical constant e, the electron's charge, can then be defined in terms of some specific experiment: we set the renormalization scale equal to the energy characteristic of this experiment, and the first term gives the interaction we see in the laboratory (up to small, finite corrections from loop diagrams, providing such exotica as the high-order corrections to the magnetic moment). The rest is the counterterm. If the theory is renormalizable (see below for more on this), as it is in QED, the divergent parts of loop diagrams can all be decomposed into pieces with three or fewer legs, with an algebraic form that can be canceled out by the second term (or by the similar counterterms that come from Z0 and Z3).
The diagram with the Z1 counterterm's interaction vertex placed as in Figure 3 cancels out the divergence from the loop in Figure 2.
Historically, the splitting of the "bare terms" into the original terms and counterterms came before the renormalization group insight due to Kenneth Wilson. According to such renormalization group insights, detailed in the next section, this splitting is unnatural and actually unphysical, as all scales of the problem enter in continuous systematic ways.
To minimize the contribution of loop diagrams to a given calculation (and therefore make it easier to extract results), one chooses a renormalization point close to the energies and momenta exchanged in the interaction. However, the renormalization point is not itself a physical quantity: the physical predictions of the theory, calculated to all orders, should in principle be independent of the choice of renormalization point, as long as it is within the domain of application of the theory. Changes in renormalization scale will simply affect how much of a result comes from Feynman diagrams without loops, and how much comes from the remaining finite parts of loop diagrams. One can exploit this fact to calculate the effective variation of physical constants with changes in scale. This variation is encoded by beta-functions, and the general theory of this kind of scale-dependence is known as the renormalization group.
Colloquially, particle physicists often speak of certain physical "constants" as varying with the energy of interaction, though in fact, it is the renormalization scale that is the independent quantity. This running does, however, provide a convenient means of describing changes in the behavior of a field theory under changes in the energies involved in an interaction. For example, since the coupling in quantum chromodynamics becomes small at large energy scales, the theory behaves more like a free theory as the energy exchanged in an interaction becomes large---a phenomenon known as asymptotic freedom. Choosing an increasing energy scale and using the renormalization group makes this clear from simple Feynman diagrams; were this not done, the prediction would be the same, but would arise from complicated high-order cancellations.
To eliminate the divergence, simply change lower limit of integral into εa and εb:
Making sure εb/ → 1, then I = ln a/.
Since the quantity ∞ − ∞ is ill-defined, in order to make this notion of canceling divergences precise, the divergences first have to be tamed mathematically using the theory of limits, in a process known as regularization (Weinberg, 1995).
An essentially arbitrary modification to the loop integrands, or regulator, can make them drop off faster at high energies and momenta, in such a manner that the integrals converge. A regulator has a characteristic energy scale known as the cutoff; taking this cutoff to infinity (or, equivalently, the corresponding length/time scale to zero) recovers the original integrals.
With the regulator in place, and a finite value for the cutoff, divergent terms in the integrals then turn into finite but cutoff-dependent terms. After canceling out these terms with the contributions from cutoff-dependent counterterms, the cutoff is taken to infinity and finite physical results recovered. If physics on scales we can measure is independent of what happens at the very shortest distance and time scales, then it should be possible to get cutoff-independent results for calculations.
Many different types of regulator are used in quantum field theory calculations, each with its advantages and disadvantages. One of the most popular in modern use is dimensional regularization, invented by Gerardus 't Hooft and Martinus J. G. Veltman, which tames the integrals by carrying them into a space with a fictitious fractional number of dimensions. Another is Pauli–Villars regularization, which adds fictitious particles to the theory with very large masses, such that loop integrands involving the massive particles cancel out the existing loops at large momenta.
Yet another regularization scheme is the lattice regularization, introduced by Kenneth Wilson, which pretends that hyper-cubical lattice constructs our space-time with fixed grid size. This size is a natural cutoff for the maximal momentum that a particle could possess when propagating on the lattice. And after doing a calculation on several lattices with different grid size, the physical result is extrapolated to grid size 0, or our natural universe. This presupposes the existence of a scaling limit.
A rigorous mathematical approach to renormalization theory is the so-called causal perturbation theory, where ultraviolet divergences are avoided from the start in calculations by performing well-defined mathematical operations only within the framework of distribution theory. The disadvantage of the method is the fact that the approach is quite technical and requires a high level of mathematical knowledge.
Zeta function regularizationEdit
as the regulator Λ → ∞. Based on this, he considered using the values of ζ(−n) to get finite results. Although he reached inconsistent results, an improved formula studied by Hartle, J. Garcia, and based on the works by E. Elizalde includes the technique of the zeta regularization algorithm
where the B's are the Bernoulli numbers and
So every I(m, Λ) can be written as a linear combination of ζ(−1), ζ(−3), ζ(−5), ..., ζ(−m).
Or simply using Abel–Plana formula we have for every divergent integral:
valid when m > 0, Here the zeta function is Hurwitz zeta function and Beta is a positive real number.
The "geometric" analogy is given by, (if we use rectangle method) to evaluate the integral so:
Using Hurwitz zeta regularization plus the rectangle method with step h (not to be confused with Planck's constant).
The logarithmic divergent integral has the regularization
since for the Harmonic series in the limit we must recover the series
For multi-loop integrals that will depend on several variables we can make a change of variables to polar coordinates and then replace the integral over the angles by a sum so we have only a divergent integral, that will depend on the modulus and then we can apply the zeta regularization algorithm, the main idea for multi-loop integrals is to replace the factor after a change to hyperspherical coordinates F(r, Ω) so the UV overlapping divergences are encoded in variable r. In order to regularize these integrals one needs a regulator, for the case of multi-loop integrals, these regulator can be taken as
so the multi-loop integral will converge for big enough s using the Zeta regularization we can analytic continue the variable s to the physical limit where s = 0 and then regularize any UV integral, by replacing a divergent integral by a linear combination of divergent series, which can be regularized in terms of the negative values of the Riemann zeta function ζ(−m).
Attitudes and interpretationEdit
The early formulators of QED and other quantum field theories were, as a rule, dissatisfied with this state of affairs. It seemed illegitimate to do something tantamount to subtracting infinities from infinities to get finite answers.
- Most physicists are very satisfied with the situation. They say: 'Quantum electrodynamics is a good theory and we do not have to worry about it any more.' I must say that I am very dissatisfied with the situation because this so-called 'good theory' does involve neglecting infinities which appear in its equations, ignoring them in an arbitrary way. This is just not sensible mathematics. Sensible mathematics involves disregarding a quantity when it is small – not neglecting it just because it is infinitely great and you do not want it!
- The shell game that we play is technically called 'renormalization'. But no matter how clever the word, it is still what I would call a dippy process! Having to resort to such hocus-pocus has prevented us from proving that the theory of quantum electrodynamics is mathematically self-consistent. It's surprising that the theory still hasn't been proved self-consistent one way or the other by now; I suspect that renormalization is not mathematically legitimate.
While Dirac's criticism was based on the procedure of renormalization itself, Feynman's criticism was very different. Feynman was concerned that all field theories known in the 1960s had the property that the interactions become infinitely strong at short enough distance scales. This property called a Landau pole, made it plausible that quantum field theories were all inconsistent. In 1974, Gross, Politzer and Wilczek showed that another quantum field theory, quantum chromodynamics, does not have a Landau pole. Feynman, along with most others, accepted that QCD was a fully consistent theory.
The general unease was almost universal in texts up to the 1970s and 1980s. Beginning in the 1970s, however, inspired by work on the renormalization group and effective field theory, and despite the fact that Dirac and various others—all of whom belonged to the older generation—never withdrew their criticisms, attitudes began to change, especially among younger theorists. Kenneth G. Wilson and others demonstrated that the renormalization group is useful in statistical field theory applied to condensed matter physics, where it provides important insights into the behavior of phase transitions. In condensed matter physics, a physical short-distance regulator exists: matter ceases to be continuous on the scale of atoms. Short-distance divergences in condensed matter physics do not present a philosophical problem since the field theory is only an effective, smoothed-out representation of the behavior of matter anyway; there are no infinities since the cutoff is always finite, and it makes perfect sense that the bare quantities are cutoff-dependent.
If QFT holds all the way down past the Planck length (where it might yield to string theory, causal set theory or something different), then there may be no real problem with short-distance divergences in particle physics either; all field theories could simply be effective field theories. In a sense, this approach echoes the older attitude that the divergences in QFT speak of human ignorance about the workings of nature, but also acknowledges that this ignorance can be quantified and that the resulting effective theories remain useful.
- Field-theoretic infinities — first encountered in Lorentz's computation of electron self-mass — have persisted in classical electrodynamics for seventy and in quantum electrodynamics for some thirty-five years. These long years of frustration have left in the subject a curious affection for the infinities and a passionate belief that they are an inevitable part of nature; so much so that even the suggestion of a hope that they may, after all, be circumvented — and finite values for the renormalization constants computed — is considered irrational. Compare Russell's postscript to the third volume of his autobiography The Final Years, 1944–1969 (George Allen and Unwin, Ltd., London 1969), p. 221:
- In the modern world, if communities are unhappy, it is often because they have ignorances, habits, beliefs, and passions, which are dearer to them than happiness or even life. I find many men in our dangerous age who seem to be in love with misery and death, and who grow angry when hopes are suggested to them. They think hope is irrational and that, in sitting down to lazy despair, they are merely facing facts.
In QFT, the value of a physical constant, in general, depends on the scale that one chooses as the renormalization point, and it becomes very interesting to examine the renormalization group running of physical constants under changes in the energy scale. The coupling constants in the Standard Model of particle physics vary in different ways with increasing energy scale: the coupling of quantum chromodynamics and the weak isospin coupling of the electroweak force tend to decrease, and the weak hypercharge coupling of the electroweak force tends to increase. At the colossal energy scale of 1015 GeV (far beyond the reach of our current particle accelerators), they all become approximately the same size (Grotz and Klapdor 1990, p. 254), a major motivation for speculations about grand unified theory. Instead of being only a worrisome problem, renormalization has become an important theoretical tool for studying the behavior of field theories in different regimes.
If a theory featuring renormalization (e.g. QED) can only be sensibly interpreted as an effective field theory, i.e. as an approximation reflecting human ignorance about the workings of nature, then the problem remains of discovering a more accurate theory that does not have these renormalization problems. As Lewis Ryder has put it, "In the Quantum Theory, these [classical] divergences do not disappear; on the contrary, they appear to get worse. And despite the comparative success of renormalisation theory, the feeling remains that there ought to be a more satisfactory way of doing things."
From this philosophical reassessment, a new concept follows naturally: the notion of renormalizability. Not all theories lend themselves to renormalization in the manner described above, with a finite supply of counterterms and all quantities becoming cutoff-independent at the end of the calculation. If the Lagrangian contains combinations of field operators of high enough dimension in energy units, the counterterms required to cancel all divergences proliferate to infinite number, and, at first glance, the theory would seem to gain an infinite number of free parameters and therefore lose all predictive power, becoming scientifically worthless. Such theories are called nonrenormalizable.
The Standard Model of particle physics contains only renormalizable operators, but the interactions of general relativity become nonrenormalizable operators if one attempts to construct a field theory of quantum gravity in the most straightforward manner (treating the metric in the Einstein–Hilbert Lagrangian as a perturbation about the Minkowski metric), suggesting that perturbation theory is useless in application to quantum gravity.
However, in an effective field theory, "renormalizability" is, strictly speaking, a misnomer. In nonrenormalizable effective field theory, terms in the Lagrangian do multiply to infinity, but have coefficients suppressed by ever-more-extreme inverse powers of the energy cutoff. If the cutoff is a real, physical quantity—that is, if the theory is only an effective description of physics up to some maximum energy or minimum distance scale—then these additional terms could represent real physical interactions. Assuming that the dimensionless constants in the theory do not get too large, one can group calculations by inverse powers of the cutoff, and extract approximate predictions to finite order in the cutoff that still have a finite number of free parameters. It can even be useful to renormalize these "nonrenormalizable" interactions.
Nonrenormalizable interactions in effective field theories rapidly become weaker as the energy scale becomes much smaller than the cutoff. The classic example is the Fermi theory of the weak nuclear force, a nonrenormalizable effective theory whose cutoff is comparable to the mass of the W particle. This fact may also provide a possible explanation for why almost all of the particle interactions we see are describable by renormalizable theories. It may be that any others that may exist at the GUT or Planck scale simply become too weak to detect in the realm we can observe, with one exception: gravity, whose exceedingly weak interaction is magnified by the presence of the enormous masses of stars and planets.
In actual calculations, the counterterms introduced to cancel the divergences in Feynman diagram calculations beyond tree level must be fixed using a set of renormalisation conditions. The common renormalization schemes in use include:
Application in statistical physicsEdit
A deeper understanding of the physical meaning and generalization of the renormalization process, which goes beyond the dilatation group of conventional renormalizable theories, came from condensed matter physics. Leo P. Kadanoff's paper in 1966 proposed the "block-spin" renormalization group. The blocking idea is a way to define the components of the theory at large distances as aggregates of components at shorter distances.
This approach covered the conceptual point and was given full computational substance in the extensive important contributions of Kenneth Wilson. The power of Wilson's ideas was demonstrated by a constructive iterative renormalization solution of a long-standing problem, the Kondo problem, in 1974, as well as the preceding seminal developments of his new method in the theory of second-order phase transitions and critical phenomena in 1971. He was awarded the Nobel prize for these decisive contributions in 1982.
In more technical terms, let us assume that we have a theory described by a certain function of the state variables and a certain set of coupling constants . This function may be a partition function, an action, a Hamiltonian, etc. It must contain the whole description of the physics of the system.
Now we consider a certain blocking transformation of the state variables , the number of must be lower than the number of . Now let us try to rewrite the function only in terms of the . If this is achievable by a certain change in the parameters, , then the theory is said to be renormalizable. The most important information in the RG flow is its fixed points. The possible macroscopic states of the system, at a large scale, are given by this set of fixed points. If these fixed points correspond to free field theory, the theory is said to exhibit quantum triviality. Numerous fixed points appear in the study of lattice Higgs theories, but the nature of the quantum field theories associated with these remains an open question.
- See e.g., Weinberg vol I, chapter 10.
- Kramers presented his work at the 1947 Shelter Island Conference, repeated in 1948 at the Solvay Conference. The latter did not appear in print until the Proceedings of the Solvay Conference, published in 1950 (see Laurie M. Brown (ed.), Renormalization: From Lorentz to Landau (and Beyond), Springer, 2012, p. 53). Kramers' approach was nonrelativistic (see Jagdish Mehra, Helmut Rechenberg, The Conceptual Completion and Extensions of Quantum Mechanics 1932-1941. Epilogue: Aspects of the Further Development of Quantum Theory 1942-1999: Volumes 6, Part 2, Springer, 2001, p. 1050).
- H. Bethe (1947). "The Electromagnetic Shift of Energy Levels". Physical Review. 72 (4): 339–341. Bibcode:1947PhRv...72..339B. doi:10.1103/PhysRev.72.339.
- Schwinger, J. (1948). "On quantum-electrodynamics and the magnetic moment of the electron". Physical Review. 73: 416–417.
- Schwinger, J. (1948). "I. A covariant formulation". Physical Review. Quantum Electrodynamics. 74: 1439–1461.
- Schwinger, J. (1949). "II. Vacuum polarization and self-energy". Physical Review. Quantum Electrodynamics. 75: 651–679.
- Schwinger, J. (1949). "III. The electromagnetic properties of the electron radiative corrections to scattering". Physical Review. Quantum Electrodynamics. 76: 790–817.
- Feynman, Richard P. (1948). "Space-time approach to non-relativistic quantum mechanics". Reviews of Modern Physics. 20 (2): 367–387. Bibcode:1948RvMP...20..367F. doi:10.1103/RevModPhys.20.367.
- Feynman, Richard P. (1948). "A relativistic cut-off for classical electrodynamics". Physical Review. 74 (8): 939–946. Bibcode:1948PhRv...74..939F. doi:10.1103/PhysRev.74.939.
- Feynman, Richard P. (1948). "A relativistic cut-off for quantum electrodynamics". Physical Review. 74 (10): 1430–1438. Bibcode:1948PhRv...74.1430F. doi:10.1103/PhysRev.74.1430.
- Tomonaga, S. (1946) "On a Relativistically Invariant Formulation of the Quantum Theory of Wave Fields." Prog. Theor. Phys. 1, 27–42.
- Koba, Z., Tati, T. and Tomonaga, S. (1947) "On a Relativistically Invariant Formulation of the Quantum Theory of Wave Fields. II." Prog. Theor. Phys. 2, 101–116.
- Koba, Z., Tati, T. and Tomonaga, S. (1947) "On a Relativistically Invariant Formulation of the Quantum Theory of Wave Fields. III." Prog. Theor. Phys. 2, 198–208.
- Kanesawa, S. and Tomonaga, S. (1948) "On a Relativistically Invariant Formulation of the Quantum Theory of Wave Fields. IV." Prog. Theor. Phys. 3, 1–13.
- Kanesawa, S. and Tomonaga, S. "On a Relativistically Invariant Formulation of the Quantum Theory of Wave Fields. V." Prog. Theor. Phys. 3, 101–113 (1948)
- Koba, Z. and Tomonaga, S. (1948) "On Radiation Reactions in Collision Processes. I." Prog. Theor. Phys. 3, 290–303
- Tomonaga, S. and Oppenheimer, J. R. (1948) "On Infinite Field Reactions in Quantum Field Theory." Phys. Rev. 74, 224–225.
- Dyson, F. J. (1949). "The radiation theories of Tomonaga, Schwinger, and Feynman". Phys. Rev. 75 (3): 486–502. Bibcode:1949PhRv...75..486D. doi:10.1103/PhysRev.75.486.
- Peskin, Michael E.; Schroeder, Daniel V. (1995). An Introduction to Quantum Field Theory. Reading,: Addison-Wesley. Chapter 10.
- K. G. Wilson (1975), "The renormalization group: critical phenomena and the Kondo problem," Rev. Mod. Phys. 47, 4, 773.
- 't Hooft, G.; Veltman, M. (1972). "Regularization and renormalization of gauge fields". Nuclear Physics B. 44: 189. Bibcode:1972NuPhB..44..189T. doi:10.1016/0550-3213(72)90279-9.
- F. J. Dyson, Phys. Rev. 85 (1952) 631.
- A. W. Stern, Science 116 (1952) 493.
- P.A.M. Dirac, "The Evolution of the Physicist's Picture of Nature," in Scientific American, May 1963, p. 53.
- Kragh, Helge; Dirac: A scientific biography, CUP 1990, p. 184
- Feynman, Richard P.; QED: The Strange Theory of Light and Matter, Penguin 1990, p. 128
- C. J. Isham, A. Salam, and J. Strathdee, "Infinity Suppression Gravity Modified Quantum Electrodynamics II," Phys. Rev. D5, 2548 (1972)
- Russell, Bertrand. The Autobiography of Bertrand Russell: The Final Years, 1944-1969 (Bantam Books, 1970)
- Ryder, Lewis. Quantum Field Theory, page 390 (Cambridge University Press 1996).
- L.P. Kadanoff (1966): "Scaling laws for Ising models near ", Physics (Long Island City, N.Y.) 2, 263.
- K.G. Wilson (1975): "The renormalization group: critical phenomena and the Kondo problem", Rev. Mod. Phys. 47, 4, 773.
- D. J. E. Callaway (1988). "Triviality Pursuit: Can Elementary Scalar Particles Exist?". Physics Reports. 167 (5): 241–320. Bibcode:1988PhR...167..241C. doi:10.1016/0370-1573(88)90008-7.
- DeDeo, Simon; Introduction to Renormalization (2017). Santa Fe Institute Complexity Explorer MOOC. Renormalization from a complex systems point of view, including Markov Chains, Cellular Automata, the real space Ising model, the Krohn-Rhodes Theorem, QED, and rate distortion theory.
- Delamotte, Bertrand; A hint of renormalization, American Journal of Physics 72 (2004) pp. 170–184. Beautiful elementary introduction to the ideas, no prior knowledge of field theory being necessary. Full text available at: hep-th/0212049
- Baez, John; Renormalization Made Easy, (2005). A qualitative introduction to the subject.
- Blechman, Andrew E.; Renormalization: Our Greatly Misunderstood Friend, (2002). Summary of a lecture; has more information about specific regularization and divergence-subtraction schemes.
- Cao, Tian Yu & Schweber, Silvan S.; The Conceptual Foundations and the Philosophical Aspects of Renormalization Theory, Synthese, 97(1) (1993), 33–108.
- Shirkov, Dmitry; Fifty Years of the Renormalization Group, C.E.R.N. Courrier 41(7) (2001). Full text available at : I.O.P Magazines.
- E. Elizalde; Zeta regularization techniques with Applications.
Mainly: quantum field theoryEdit
- N. N. Bogoliubov, D. V. Shirkov (1959): The Theory of Quantized Fields. New York, Interscience. The first text-book on the renormalization group theory.
- Ryder, Lewis H.; Quantum Field Theory (Cambridge University Press, 1985), ISBN 0-521-33859-X Highly readable textbook, certainly the best introduction to relativistic Q.F.T. for particle physics.
- Zee, Anthony; Quantum Field Theory in a Nutshell, Princeton University Press (2003) ISBN 0-691-01019-6. Another excellent textbook on Q.F.T.
- Weinberg, Steven; The Quantum Theory of Fields (3 volumes) Cambridge University Press (1995). A monumental treatise on Q.F.T. written by a leading expert, Nobel laureate 1979.
- Pokorski, Stefan; Gauge Field Theories, Cambridge University Press (1987) ISBN 0-521-47816-2.
- 't Hooft, Gerard; The Glorious Days of Physics – Renormalization of Gauge theories, lecture given at Erice (August/September 1998) by the Nobel laureate 1999 . Full text available at: hep-th/9812203.
- Rivasseau, Vincent; An introduction to renormalization, Poincaré Seminar (Paris, Oct. 12, 2002), published in : Duplantier, Bertrand; Rivasseau, Vincent (Eds.); Poincaré Seminar 2002, Progress in Mathematical Physics 30, Birkhäuser (2003) ISBN 3-7643-0579-7. Full text available in PostScript.
- Rivasseau, Vincent; From perturbative to constructive renormalization, Princeton University Press (1991) ISBN 0-691-08530-7. Full text available in PostScript.
- Iagolnitzer, Daniel & Magnen, J.; Renormalization group analysis, Encyclopaedia of Mathematics, Kluwer Academic Publisher (1996). Full text available in PostScript and pdf here.
- Scharf, Günter; Finite quantum electrodynamics: The causal approach, Springer Verlag Berlin Heidelberg New York (1995) ISBN 3-540-60142-2.
- A. S. Švarc (Albert Schwarz), Математические основы квантовой теории поля, (Mathematical aspects of quantum field theory), Atomizdat, Moscow, 1975. 368 pp.
Mainly: statistical physicsEdit
- A. N. Vasil'ev; The Field Theoretic Renormalization Group in Critical Behavior Theory and Stochastic Dynamics (Routledge Chapman & Hall 2004); ISBN 978-0-415-31002-4
- Nigel Goldenfeld; Lectures on Phase Transitions and the Renormalization Group, Frontiers in Physics 85, Westview Press (June, 1992) ISBN 0-201-55409-7. Covering the elementary aspects of the physics of phases transitions and the renormalization group, this popular book emphasizes understanding and clarity rather than technical manipulations.
- Zinn-Justin, Jean; Quantum Field Theory and Critical Phenomena, Oxford University Press (4th edition – 2002) ISBN 0-19-850923-5. A masterpiece on applications of renormalization methods to the calculation of critical exponents in statistical mechanics, following Wilson's ideas (Kenneth Wilson was Nobel laureate 1982).
- Zinn-Justin, Jean; Phase Transitions & Renormalization Group: from Theory to Numbers, Poincaré Seminar (Paris, Oct. 12, 2002), published in : Duplantier, Bertrand; Rivasseau, Vincent (Eds.); Poincaré Seminar 2002, Progress in Mathematical Physics 30, Birkhäuser (2003) ISBN 3-7643-0579-7. Full text available in PostScript.
- Domb, Cyril; The Critical Point: A Historical Introduction to the Modern Theory of Critical Phenomena, CRC Press (March, 1996) ISBN 0-7484-0435-X.
- Brown, Laurie M. (Ed.); Renormalization: From Lorentz to Landau (and Beyond), Springer-Verlag (New York-1993) ISBN 0-387-97933-6.
- Cardy, John; Scaling and Renormalization in Statistical Physics, Cambridge University Press (1996) ISBN 0-521-49959-3.
- Shirkov, Dmitry; The Bogoliubov Renormalization Group, JINR Communication E2-96-15 (1996). Full text available at: hep-th/9602024
- García Moreta, José Javier http://prespacetime.com/index.php/pst/article/view/498 The Application of Zeta Regularization Method to the Calculation of Certain Divergent Series and Integrals Refined Higgs, CMB from Planck, Departures in Logic, and GR Issues & Solutions vol 4 Nº 3 prespacetime journal http://prespacetime.com/index.php/pst/issue/view/41/showToc
- Zinn-Justin, Jean; Renormalization and renormalization group: From the discovery of UV divergences to the concept of effective field theories, in: de Witt-Morette C., Zuber J.-B. (eds), Proceedings of the NATO ASI on Quantum Field Theory: Perspective and Prospective, June 15–26, 1998, Les Houches, France, Kluwer Academic Publishers, NATO ASI Series C 530, 375–388 (1999). Full text available in PostScript.
- Connes, Alain; Symétries Galoisiennes & Renormalisation, Poincaré Seminar (Paris, Oct. 12, 2002), published in : Duplantier, Bertrand; Rivasseau, Vincent (Eds.); Poincaré Seminar 2002, Progress in Mathematical Physics 30, Birkhäuser (2003) ISBN 3-7643-0579-7. French mathematician Alain Connes (Fields medallist 1982) describe the mathematical underlying structure (the Hopf algebra) of renormalization, and its link to the Riemann-Hilbert problem. Full text (in French) available at math/0211199v1. | <urn:uuid:a6c6f22b-d3f4-4fcf-afd6-4f252e83dd19> | 2.953125 | 9,923 | Knowledge Article | Science & Tech. | 42.981445 | 95,491,236 |
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By: Committee on Review of the USGS National Streamflow Information Program
From warning the public of impending floods to settling legal arguments over water rights, the measurement of streamflow (streamgaging) plays a vital role in US society. Having good information about how much water is moving through our streams helps provide citizens with drinking water during droughts, control water pollution, and protect wildlife along our stream corridors. The U.S. Geological Surveys (USGS) streamgaging program provides such information to a wide variety of users interested in human safety, recreation, water quality, habitat, industry, agriculture, and other topics. For regional and national scale streamflow information needs, the USGS has created a National Streamflow Information Program (NSIP). In addition to streamgaging, the USGS envisions intensive data collection during floods and droughts, national assessments of streamflow characteristics, enhanced information delivery, and methods development and research. The overall goals of the program are to: meet legal and treaty obligations on interstate and international waters, support flow forecasting; measure river basin outflows, monitor sentinel watersheds for long-term trends in natural flows, and measure flows for water quality needs. But are these the right topics to collect data on? Or is the USGS on the wrong track? In general, the book is supportive of the design and content of NSIP, including its goals and methodology for choosing stream gages for inclusion in the program. It sees the ultimate goal of NSIP as developing the ability to use existing data-gathering sites to generate streamflow information with quantitative confidence limits at any location in the nation. It is just as important to have good measurements during droughts as during floods, and it therefore recommends supporting Natural Resource Conservation Service forecast sites in addition to those of the National Weather Service.
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Scientists Make Normal Tissue Cells to Behave like Embryonic Stem Cells
News Jun 08, 2007
Researchers at the Institute for Stem Cell Biology and Medicine at UCLA were able to take normal tissue cells and reprogram them into cells with the same unlimited properties as embryonic stem cells, the cells that are able to give rise to every cell type found in the body.
The work, done in mouse models, appears in the inaugural June 7, 2007 issue of Cell Stem Cell, published by Cell Press. UCLA researchers, working closely with stem cell scientists at Harvard, took mouse fibroblasts, cells that develop into connective tissue, and added four transcription factors that bind to special sites on the DNA. Using this process, they were able to turn the fibroblasts into pluripotent cells that, in every aspect tested, were identical to embryonic stem cells.
The implications for disease treatment could be staggering. Reprogramming adult stem cells into embryonic stem cells could generate a potentially limitless source of immunecompatible cells for tissue engineering and transplantation medicine. If the work can be replicated in human cells, it may mean that a patient’s skin cells, for example, could be reprogrammed to become embryonic stem cells. Those embryonic stem cells could then be prodded into becoming various cells types – beta islet cells to treat diabetes, hematopoetic cells to create a new blood supply for a leukemia patient, motor neuron cells to treat Parkinson’s disease.
“If we can recreate this in human cells, it has significant implications for regenerative therapies,” said Kathrin Plath, an assistant professor of biological chemistry, a researcher with the Institute for Stem Cell Biology and Medicine at UCLA (ISCBM) and co-lead author of the study. “Our reprogrammed cells were virtually indistinguishable from embryonic stem cells. We could find no evidence that they were different in any way. We were rather surprised at how well this reprogramming worked.”
The finding also is significant in that this new technique could potentially replace a controversial method used to reprogram cells, somatic cell nuclear transfer (SCNT), sometimes referred to “therapeutic cloning.” To date, SCNT has not been done successfully in human cells.
“If we can successfully reprogram a normal human cell into a cell with almost identical properties to those in embryonic stem cells without SCNT, it may have important therapeutic ramifications and provide us with another method to develop human stem cell lines,” said Dr. Owen Witte, ISCBM director and a Howard Hughes Medical Institute investigator. “Up until now, it’s been unclear whether a cell could be reprogrammed back into an embryonic stem cell state without the use of SCNT, so that makes this a very important finding.”
Studies published previously had shown that the four transcription factors, which regulate expression of downstream genes and either, activate or silence their expression, could reprogram cells into cells with some pluripotent properties. But they differed from embryonic stem cells in that they could not differentiate into every cell type or support development of adult tissues.
“They had very limited developmental potential,” Plath said. “We took a different approach, carefully selecting from our pool of cells the reprogrammed cells that highly expressed two genes we know are essential in embryonic stem cells.”
Selecting cells that highly expressed the genes, Oct4 and Nanog, essential to giving embryonic stem cells their unique characteristics resulted in reprogrammed cells with much more powerful pluripotency, Plath said.
The reprogrammed cells were not just functionally identical to embryonic stem cells. They also had identical biological structure. In a cell nucleus, DNA - an organism’s unique map or instructions - wraps around histones, which serve as a kind of scaffolding for compaction of the long DNA molecule. Histones don’t merely package DNA. Chemical tags on histones determine which genes are expressed or shut off in the DNA.
In the reprogrammed cells, the location of the chemical tags along the DNA chromosomes were identical to those found in embryonic stem cells and, just as importantly, dramatically different from those in the fibroblasts before reprogramming. The structure of the reprogrammed cells - down to the very small chemical tags that dictate gene expression – is highly similar to that of embryonic stem cells.
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International Conference on Neurooncology and Neurosurgery
Sep 17 - Sep 18, 2018 | <urn:uuid:e718cde5-75f8-42b0-b343-c68a432d0425> | 3.25 | 1,081 | News Article | Science & Tech. | 26.306065 | 95,491,272 |
|A Chemo receptor, additionally referred to as chemosensor, which is a sensory receptor that transduces a chemical signal into action potential. In additional general terms, a chemosensor detects chemical stimuli within the environment. Direct and distance are the two main types of chemosensors. Olfactory system containing olfactory receptor neurons is an example of distance chemosensors. Gustatory system containing taste buds is an example for direct chemo sensors. A chemo sensor functions on a molecular level and generates a signal upon binding. Chemosensor include case studies to make the material both accessible and understandable to chemists of all backgrounds.
Insects use contact chemoreception to identify chemicals like epidermal hydrocarbons and chemicals specific to host plants. Contact chemoreception is ordinarily seen in insects however it is additionally concerned within the coupling behavior of some vertebrates. The contact sensory receptor is particular to at least one variety of chemical.
Olfaction, Gustation, Contact Chemoreception, Cellular antennae are the sensory organs. In vertebrates, olfaction occurs within the Nose. In several vertebrates, the tongue is the first gustatorial sensory organ. Contact chemoreception depends on the physical contact of the receptor with the stimulation. The receptors are short hairs or cones that have one pore at, or near the tip of the projection. At intervals the biological and medical disciplines, recent discoveries have noted that primary cilia in many types of cells in eukaryotes functions as cellular antennae. Chemoreception is very important for the detection of food, habitat, conspecifics as well as mates, and predators. | <urn:uuid:193a707b-2040-46b8-8fae-8d5f3b309446> | 3.875 | 339 | Knowledge Article | Science & Tech. | 11.570683 | 95,491,286 |
An airmass is a large body of air with relatively uniform thermal and moisture characteristics. Airmasses cover large regions of the earth, typically several hundred thousand square kilometers. Airmasses can be as deep as the depth of the troposphere or as shallow as 1 to 2 km.
Airmasses form when air remains over a relatively flat region of the earth* with homogeneous surface characteristics for an extended period of time. ( Canadian and Siberian plains, cool oceanic regions such as the North Atlantic and Pacific, deserts, such as the Sahara and the American southwest, and tropical oceanic regions including the equatorial Atlantic and Pacific, and smaller water bodies such as the Caribbean Sea and the Gulf of Mexico).
Polar air masses, containing little moisture and low temperatures move downward from the poles. Air masses that form over water are generally moist, and those that form over the tropical oceans are both moist and warm. Because of the Coriolis effect due to the Earth’s rotation, air masses generally move across North America from west to east. But, because of the differences in moisture and heat, the collision of these air masses can cause instability in the atmosphere.
Polar air mass is cold and tropical air mass is warm. When cold air mass and warm air mass blow against each other, the boundary line of convergence separating the two air masses is termed as front. When the warm air mass, moves upward over the cold air mass the front formed in such a situation is called warm front. On the contrary, when the cold air mass advances faster and undercuts the warm air mass and forces the warm air upwards, the front so formed is called cold front. The frontal surface of cold front is steeper than that of a warm front . A prevailing air mass in any region – polar, tropical, maritime or continental largely controls the regions general weather.
Different air masses are:-
- Maritime tropical (mT)
ii. Continental tropical (cT)
iii. Maritime polar (mP)
iv. Continental polar (cP)
v. Continental arctic (cA).
Where ‘m’ stands for Maritime; ‘c’ stands for continental; ‘T’ stands for tropical; ‘P’ stands for polar and ‘A’ stands for arctic region.
An important properties of air is that it is a poor conductor of energy. This means that when two different bodies of air come together, they do not readily mix. Rather, each body of air will retain its individual properties, and a boundary forms between them. When two large air masses meet, the boundary that separates them is called a front. Fronts represent fairly abrupt transitions between two large air masses. The warm, moist air might dominate an area hundreds of miles across, while in another part of the continent a cold, dry air mass holds sway over an equally large region. However, where the two air masses meet, the transition layer between them may be only a few tens of miles across, clearly a sharp transition between two massive bodies of air.
Fronts are recognized by the following properties:-
- Sharp temperature changes over a relatively short distance. Sometimes change of 10 to 20 C may be observed.
- Change in moisture content
- Rapid shifts in wind direction
- Pressure changes
- Clouds and precipitation patterns
Types of Fronts:-
Warm Fronts: A warm front occurs when a warm air mass advances and replaces a cold air mass. On a weather map, a warm front is depicted as a red arc, with red semicircles pointing in the direction of the advancing warm air.
Cold Fronts :-A cold front occurs when a mass of cold air advances into a region of warmer air.
Stationary Fronts:- A stationary front forms when a cold front or warm front stops moving. This happens when two masses of air are pushing against each other but neither is powerful enough to move the other. Winds blowing parallel to the front instead of perpendicular can help it stay in place.
Occluded Fronts:- Sometimes a cold front follows right behind a warm front. A warm air mass pushes into a colder air mass (the warm front) and then another cold air mass pushes into the warm air mass (the cold front). Because cold fronts move faster, the cold front is likely to overtake the warm front. This is known as an occluded front
RAS-RTS FREE Notes brings Prelims and Mains programs for RAS-RTS FREE Prelims and RAS-RTS FREE Mains Exam preparation. Various Programs initiated by RAS-RTS FREE Notes are as follows:-
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|MLA Citation:||Bloomfield, Louis A. "Question 805"|
How Everything Works 16 Jul 2018. 16 Jul 2018 <http://howeverythingworks.org/print1.php?QNum=805>.
Reverse osmosis occurs when the pressure on the solution side is raised so high that the movement of water reverses directions. If you squeeze the concentrated solution hard enough, you can drive additional water molecules from that solution through the semi-permeable membrane and into the fresh water on the other side. The raised pressure on the solution changes the statistics, making it more likely for water molecules to go from the solution side to the fresh water side. This technique is used to purify water in homes and to desalinate water in desert countries. | <urn:uuid:974f2047-330d-441c-a00d-c919908c5fd5> | 3.890625 | 161 | Knowledge Article | Science & Tech. | 50.75122 | 95,491,332 |
Swift, had come into the market with a bang and all the people are waiting for it to make wonders happen. But what is it that makes developers, happy? Why is it that Swift has many expectations attached to it already? Is it just because of Apple’s credibility or is it because of the issues that Objective C has been posing before developers of all time.
Below reasons might help you clear up the confusions and learn how Swift fits in iPhone App Development.
#1. Less Repetitive:
Swift as a coding language is designed to be less repetitive. It almost seems to be a boon for people who had issues in learning other, more difficult, iOS language. Specifically the things that are made less recurrent are:
(a) The use of ‘@’: @ was used excessively in C and Objective C language but in Swift, the extensive use of @ is removed to make the code less cluttery and less difficult.
(b) Other minor symbols like the Brackets [ ] or ( ) can also be avoided to use more than required.
#2. English like Language:
Swift is a language made simpler for the benefit of all. Keeping this in mind Apple has tried to simplify the language itself. Swift is more like English than any other iOS language ever created. This change from Objective C to Swift has made more and more modern developers get interested in Swift.
#3. Low Maintenance Required:
Swift doesn’t allow double file creation to happen which means that building apps will become easier and less time consuming. Unlike Objective C which creates two files by separating table of content and body; (.swift) combines both (.h) and (.m).
#4. Fast Coding:
As mentioned above, Swift allows less repetition to happen which means that there’s less confusion and more work can be done in less time. Also with English like language and easy debugging system Swift stands true to its name and helps the build to happen faster than before. Adding to that memory management becomes easy and without any memory leakage.
#5. Interactive Coding:
Swift has memory-bound GEMM algorithm along with FFT and Mandelbrot algorithm. In a non-technical terminology, it increases the efficiency and work speed a hundred folds. Also Swift allows the developer to build an interactive code. It is feedback friendly, which means that once the code is written Swift makes it possible for feedback to reach the developers immediately.
With the entry of Swift, a lot of change has come in the app building system. It does not just makes lives and building simpler but also more effective and interesting. Apps made with Swift are gaining popularity with the speed of light.
Check the recent Stack Overflow Developer Survey 2015. This shows how developers perceive Swift and other available programming tools.
With Space-O’s experience in making apps, Swift came up as a new potential experience. Immediately we took up the task of learning this new coding language. Now, not only have we learned the language but also created apps that will be launched very soon.
You can now find your solutions related to Apps developed using Swift here at Space-O.
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Recent observations have shown the existence of an apparent impenetrable barrier at the inner edge of the ultra-relativistic outer electron radiation belt. This apparent impenetrable barrier has not been explained. However, recent studies have suggested that fast loss, such as associated with scattering into the atmosphere from man-made very-low frequency transmissions, is required to limit the Earthward extent of the belt. Here we show that the steep flux gradient at the implied barrier location is instead explained as a natural consequence of ultra-low frequency wave radial diffusion. Contrary to earlier claims, sharp boundaries in fast loss processes at the barrier are not needed. Moreover, we show that penetration to the barrier can occur on the timescale of days rather than years as previously reported, with the Earthward extent of the belt being limited by the finite duration of strong solar wind driving, which can encompass only a single geomagnetic storm.
The radiation belts were one of the first discoveries of the space age. Early in-situ satellite observations revealed that the belts consist of relativistic electrons and ions, populating an inner and outer belt, which were separated by a region void of relativistic particles called the slot. Typically, ultra-relativistic electrons with energies ≳ 2 MeV are confined to the outer radiation belt1, 2 outside the slot. It is generally agreed that the morphology and dynamics of the radiation belts are influenced by wave–particle interactions, which lead to both acceleration and loss. Acceleration processes, such as radial diffusion driven by ultra-low frequency (ULF) waves3, 4 and/or local acceleration5 through interaction with lower band whistler mode chorus6, as well as wave–particle loss processes7,8,9,10,11,12 must combine in such a way to create the observed belt dynamics. In addition, outward ULF wave radial transport in combination with magnetopause shadowing can also result in outer radiation belt electron loss13,14,15,16. However, how these processes act to collectively produce the observed morphology, and the relative importance of multiple competing acceleration and loss processes under different solar wind driving conditions, remain relatively poorly understood5. The NASA Van Allen Probes (formerly known as the Radiation Belt Storm Probes17) consist of two elliptically orbiting spacecraft with an inclination of ~ 10°, passing from altitudes of ~ 600 km at perigee to L ~ 6 at apogee (where L is the distance from the equatorial crossing point of a dipole magnetic field line to the centre of the Earth, in units of Earth radii). Using ultra-relativistic (≳ 2 MeV) electron measurements taken over the first 20 months of the Van Allen Probes mission, Baker et al.18 identified a previously unknown and unexplained apparent impenetrable barrier located at L ~ 2.8, representing a point where the radial gradient of ultra-relativistic electron flux is extremely steep and beyond which the ultra-relativistic electrons do not penetrate. As described by Baker et al.18, this apparent barrier is not co-located with the plasmapause or any other identifiable magnetospheric boundary. It has also recently been suggested that the sharp boundary in ultra-relativistic electron flux at L = 2.8 might be explained by losses from a sharp outer edge to fast pitch angle scattering into the atmosphere arising from a resonant interaction with man-made very-low frequency (VLF) waves injected into the magnetosphere by ground-based transmitters (e.g., Foster et al.19). Note, however, that at lower energies such a barrier feature is not as apparent, with lower energy electrons penetrating more frequently into the slot region11, 20,21,22
Here we present evidence that a truly impenetrable barrier at the inner edge of the outer ultra-relativistic radiation belt may not really exist. In addition, producing a steep drop off in the ultra-relativistic electron flux near L ~ 2.8 does not require a sharp outer edge to some efficient fast loss process. Instead, the apparent feature of an impenetrable barrier at a fixed location can be explained by dynamical variations in the rate of ULF wave inward radial diffusion. The feature of the apparent barrier is produced as a result of an effective time limit for strong driving, and hence the resulting finite interval of rapid inwards radial diffusion, which is imposed naturally by the temporal extent of the solar wind structures that produce geomagnetic storms. When the rate of ULF wave radial diffusion is properly quantified and the effects of the evolution of gradients in electron phase space density (PSD) are incorporated, the artefact of an apparent Earthward limit to ultra-relativistic electron transport in the outer Van Allen belt (i.e., the so-called impenetrable barrier) is naturally explained. An apparent barrier is also likely to form in other magnetised astrophysical plasma systems, where the dynamics of the system result from the action of a finite duration of enhanced astrophysical or stellar wind driving.
ULF wave radial diffusion simulations
The dynamics and energization of equatorially mirroring ultra-relativistic electrons in the outer radiation belt are simulated by solving the one-dimensional radial diffusion equation in a dipole magnetic field expressed in terms of the planetary geomagnetic activity index, Kp, the McIlwain L-shell23, and time. The majority of current radiation belt modelling uses the empirical expression for the radial diffusion coefficient DLL given in Brautigam and Albert24 (hereafter referred to as DLL[B & A]). This is based on electromagnetic ULF waves and uses the approach outlined in Lanzerotti and Morgan25 but is limited to statistics with a maximum Kp value of 6. More recently, Ozeke et al.4 derived empirical expressions for DLL using the approached outlined in Fei et al.26 based on the wave power in the azimuthal electric field of ULF waves, derived using data from ground-based magnetometers and also parameterised using Kp (hereafter referred to as DLL[Ozeke]). In the results presented by Ozeke et al.4 the statistics were also only shown to Kp = 6; however, the ground-based magnetometer ULF wave power statistics use a sufficiently long time period for that to be also extended to Kp values of 9 and these were presented in tabular form by Ozeke et al.27 (see also Fig. 7 in Mann et al.28). Here we use the analytic expression for the radial diffusion coefficient from Ozeke et al.4 to examine ULF wave transport. Note that the maximum Kp observed in the interval examined here is 7.7, which occurs for only one 3 h interval of Kp; there are also only a total of three 3 h intervals of Kp > 6 in the 20-month period examined by Baker et al.18 and re-examined here. This justifies the use of the Ozeke et al.4 expressions to higher Kp (see also Supplementary Fig. 1, which shows a comparison between the Ozeke et al.4 analytic expression and Ozeke et al.27 the statistics from for Kp = 6, 7, and 8).
For comparison the flux of ultra-relativistic electrons is simulated here using each of these two different expressions for the ULF wave radial diffusion coefficients. Note that in each of these definitions the diffusion coefficients are a strong function of Kp, such that changes in Kp, e.g., from ~ 2 to ~ 6 can increase both formulations of the diffusion coefficients by a factor of over 100. The resulting electron dynamics are shown in Fig. 1 from September 2012 to May 2014, the same interval examined in Baker et al.18 (see Methods section and Supplementary Fig. 2 for further details).
In Fig. 1, the simulation results are compared to the flux observed by the Relativistic Electron Proton Telescope (REPT)29 from the Energetic particle, Composition, and Thermal plasma (ECT) suite30 on board the Van Allen Probes at energies of 3.4, 4.2, and 5.4 MeV. The simulation results shown in the third and fourth rows of Fig. 1 are derived using a series of first adiabatic invariant conserving simulations, which are then combined in an assumed dipole field to produce plots of the L- and time-dependent response of electron flux at fixed energy to match the native measurements from fixed energy channels from the REPT instrument. The simulation results clearly demonstrate the repeated creation of a very steep radial gradient in flux at the inner edge of the outer ultra-relativistic radiation belt, and that the location of this gradient changes with time and from storm to storm. However, for the entire period between September 2012 and May 2014 shown in Fig. 1, there is no evidence of penetration of ultra-relativistic electron flux inward of L ~ 2.8 in the simulation results. These modelling results are consistent with the observational results of Baker et al.18 and demonstrate that despite a very steep flux profile at its edge, the apparently impenetrable barrier can be naturally explained by inwards ULF wave radial transport.
This result is largely independent of the choice of the statistical radial diffusion models assessed here, as the DLL values from both24 (DLL[B & A], Fig. 1c, f, i) and from4 (DLL[Ozeke], Fig. 1d, g, j) generate simulation results, which show a finite Earthward penetration that is limited to L ~ 2.8. In addition, the location of plasmapause shown as a white line in each of the panels b, e, and h, and derived from the Carpenter and Anderson model31 does not correlate with the inner edge of the ultra-relativistic outer radiation belt. As pointed out by Baker et al.18 and confirmed by our simulations, the apparent feature of an impenetrable barrier does not correspond to the location of the plasmapause or indeed to any other known physical boundary. Instead, and as we show here, the apparent barrier is naturally explained by the physics of ULF wave radial diffusion.
Overall, despite the use of Kp-dependent statistical representations of rates of ULF wave radial diffusion, the simulations show good agreement with the maximum depth of ultra-relativistic electron flux penetration as observed by the REPT instrument on the Van Allen Probes. However, despite the good agreement with the ultra-relativistic electron penetration depth, the long-timescale dynamics of the absolute magnitude of the flux of ultra-relativistic electrons at all L-shells above the barrier is not explained perfectly by the one-dimensional dipole magnetic field model results shown in Fig. 1. For example, especially between L = 3 and L = 5, the simulated electron flux tends to be somewhat more intense than observed. Given the simplicity of both the one-dimensional model and the assumed dipolar geometry, and the neglect of flux changes arising from adiabatic effects from any time-dependence of the background magnetic field strength, absolutely perfect agreement is not to be expected and we discuss this further below. Nonetheless, the limit to the Earthward expansion of the belts is well-captured by the model.
To verify that the location of the apparent impenetrable barrier is explained by dynamic ULF wave radial diffusion transport, Fig. 2 shows a comparison between the differential flux in the modelled belt, calculated using DLL[Ozeke] (left column), and that observed by the Van Allen Probes (right column), at fixed ultra-relativistic energies of 3.4, 4.2, and 5.2 MeV (top, middle, and bottom rows, respectively). L-dependent profiles are plotted every 31 days over the period from 2 October 2012 to 9 November 2013. The radial profiles of simulated electron flux were produced using initial electron flux values derived from measurements taken on 1 September 2012 and driven by outer boundary electron flux values derived from Van Allen Probe measurements taken at L = 6, using the technique described in the Methods section. The panels on the left of Fig. 2 show clearly how the simulation produces very steep gradients in the electron flux profile comprising the barrier at L ~ 2.8, very similar to those observed and shown in the panels on the right.
We emphasize that these simulations do not include any rapid electron loss mechanisms which are sharply confined to locations at or inward of L ~ 2.8. The steep electron flux profile at the inner edge simply results from the sharp falloff in the inward ULF wave diffusive transport rates with decreasing L-shell. These are of course coupled with slow electron loss due to wave-particle scattering losses to the atmosphere due to chorus and plasmaspheric hiss waves. It is interesting to note that even though the diffusion coefficients used in the simulations presented in both Figs. 1 and 2 are varying with time by over three orders of magnitude, the location of inner-most edge of the ultra-relativistic outer radiation belt remains relativity constant at L ~ 2.8. As shown in Fig. 2, despite the fact that flux gradients can represent changes of four orders of magnitude in flux across ~ 0.5 L-shells, they are created and maintained naturally by the physics and the steep L-dependence of the rates of transport arising from ULF wave radial diffusion. Significantly, no sharp boundary in loss processes confined inside L ~ 2.8 is required.
Note that the results shown in Fig. 2 are generated from a set of single and continuous long duration (over 13 months) radial diffusion simulations at fixed adiabatic invariant such that the only constraints are the initial flux as a function of L on 1 September 2012, the time series of the flux at the outer boundary at L = 6, and the empirical Kp-dependent rates of both ULF wave radial diffusion and chorus and hiss electron lifetimes. There is no update to any of the fluxes at lower L inside the outer boundary through assimilation of observed flux. Hence, the dynamics of the system in Fig. 2 result predominantly from the inward/outward transport arising from the time-dependence of the flux observed by the Van Allen Probes at the outer simulation boundary coupled to lower L by ULF wave radial diffusion. Note that the magnetic field is also assumed to be a dipolar for all time, such that short timescale effects from adiabatic changes in flux arising from time-dependent changes to the magnetic field in the equatorial plane of the magnetosphere are also not included in the model. Given the relative simplicity of the model, the existence and location of the apparent impenetrable barrier are well-explained as being the result of the inward extent of the ULF wave radial diffusion arising from ULF wave excitation in the Earth’s magnetosphere by the solar wind.
The results shown in Figs. 1 and 2 do however show evidence for more variability in the flux in the heart of the radiation belt especially in terms of a larger loss over this period than is produced in our radial diffusion model. Given the statistical nature of the ULF wave diffusion coefficients and the representation of chorus and hiss loss rates, part of this discrepancy may result from uncertainties arising from the empirical Kp-dependent representation of the rates of ULF wave transport, and/or in the rates of loss due to hiss and chorus waves. In relation to the latter, the impact on the simulated flux of changing the hiss and chorus plasma wave-particle atmospheric scattering loss timescale is shown in Supplementary Fig. 2. This figure shows that the depth of electron penetration is not a strong function of the assumed hiss and chorus wave electron loss rates. This verifies the validity of our result that the apparent barrier can be explained by ULF wave transport, and that this conclusion can be made largely independent of the exact rate of hiss and chorus loss for ultra-relativistic electrons. In relation to the former, in terms of the rates of ULF wave radial diffusion, Mann et al.32 show that the observed ULF wave power and hence the rates of ULF wave transport can at times be much larger than predicted by the empirical Kp-dependence of statistical models. Indeed, as discussed by Mann and Ozeke33 (see also Mann et al.32) ULF wave transport can be much faster than is typically assumed. For example, this can result in additional strong and rapid losses due to enhanced outwards radial diffusion to the magnetopause during the storm main phase leading to lower fluxes in the belts through what has been termed ULF wave enhanced magnetopause shadowing (e.g., Mann et al.32). Indeed, Mann et al.32 show that appropriate characterization of storm-time ULF wave power can also explain the generation of the third radiation belt reported by Baker et al.34. In our view, most likely this explains a very significant amount of the loss missing from Fig. 1.
In addition to chorus and hiss loss, there could also be additional losses arising from other wave modes such as electromagnetic ion cyclotron (EMIC) waves, which are neglected in this model. For example, Drozdov et al.35 concluded that the effects of EMIC waves may be required to limit the long-term flux in the ultra-relativistic radiation belt. However, observations presented by Usanova et al.36 show how the action of EMIC waves alone only impacts low equatorial pitch angle particles (where pitch angle is the angle between particle velocity and the background magnetic field) such that these waves acting alone are not expected to be able to deplete the core of the distribution37, 38. There could also be impacts from the action of chorus wave acceleration, as described, e.g., by Thorne et al.6. Although chorus waves may have an important role in the acceleration of electrons at relativistic energies39, 40, at the ultra-relativistic energies (≳ 2 MeV) examined here, the effects are expected to often be relatively weak41. Moreover, if additional chorus acceleration also primarily acts close to the outer boundary of our simulations the inward ULF wave transport of this additional source of flux will be captured in our model. Overall, and in spite of these provisos and the simplicity of our model, our results show that the apparent feature of an impenetrable barrier at the inner edge of the ultra-relativistic outer zone can be naturally and well-explained by the time-dependent action of inward ULF wave transport.
On the existence of a truly impenetrable barrier
In order to quantify the electron transport times as a function of Kp, the rates of dynamical penetration of ultra-relativistic electron flux at fixed energy under the action of ULF wave diffusion at fixed Kp from a constant outer boundary condition are shown in Fig. 3. Fig. 3 illustrates that, initially, the ultra-relativistic electron flux rapidly diffuses inward from the outer boundary. The minimum L-shell, which the electrons reach, depends on the strength of the diffusion coefficient (as specified over the extended intervals in Figs. 1 and 2 by Kp), the gradients which develop during the transport, and how long the enhanced radial diffusion lasts. The mean value of Kp over the 20 month time interval presented in Fig. 1 is 1.5 and the maximum value of Kp reached during the same interval was 7.7—the latter being maintained for only a single Kp resolution interval of 3 h.
The top panels a, b, and c of Fig. 3 illustrate that after 20 days of steady inward diffusion as specified by Kp = 1.5 the electron flux does not reach L = 3. For steady diffusion at Kp = 4 and Kp = 6 it takes ~ 10 days and ~ 2 days, respectively, for the effects of the enhanced flux at the outer boundary to reach L = 2.8. However, the bottom panels of Fig. 3 (which shows results for a constant Kp = 7.7, the largest value reached during the epoch shown in Fig. 1) illustrate that if an extended period of very fast transport persisted then the flux would in fact penetrate further Earthward than L ~ 2.8. For example, if the Kp = 7.7 conditions were to persist for ≳ 6 h then the ultra-relativistic electron flux would penetrate inward through the observed apparent barrier location at L ~ 2.8 (see also Supplementary Fig. 3, which shows these details over a shorter timescale). Moreover, if such high activity persisted for the unphysically long time of ≳ 2 days, the ultra-relativistic electron flux could reach locations below L = 2. Even longer intervals of very strong ULF wave activity at the level characteristic of Kp = 7.7 would drive the inward penetration even further. This shows that in fact a truly impenetrable barrier does not really exist and instead is an artefact of the magnitude and finite duration of the solar wind driving in producing rapid inward ULF wave radial diffusion. Indeed, as discussed, e.g., by Baker et al.42, such penetrations of the barrier have previously been observed such as during the period of the 2003 Halloween storms—with Loto’aniu et al.43, suggesting that enhanced ULF wave power at low-L explain this penetration through ULF wave radial diffusion.
Both the observed and simulated electron flux in Fig. 1 also illustrate that in general enhancements in the electron flux correspond to sudden enhancements in the Kp index. This is consistent with the hypothesis that the electron flux enhancements result from rapid inward transport to low L-shells by ULF wave inward radial diffusion. In the case of the Earth’s Van Allen belts, there is a finite duration of strong solar wind driving imposed by the scale of solar wind structures such as interplanetary coronal mass ejections and co-rotating interaction regions, which drive magnetic storms. Consequently, as a result of the finite duration of fast inwards transport, the depth of penetration of the ultra-relativistic belt is limited under typical storm conditions to be confined to L ~ 2.8 or higher, although during extreme events such as the Halloween 2003 storm it can occasionally penetrate deeper. The usual feature of a finite depth of penetration is maintained, even though the edge of this region is characterized by a very steep L-gradient in flux.
Similar to Fig. 2, Fig. 4 shows L-shell profiles of electron PSD and corresponding flux which further serve to illustrate how ULF wave radial diffusion naturally creates flux profiles which can have very steep gradients at lower L-values. For diffusion coefficients specified by Kp ≲ 6, extended periods of driving of ~ 2–20 days are required for electron flux to be transported inward of L = 2.8. During periods characterized by Kp > 6, which are reflected in the Ozeke et al.4 statistical model for ULF wave diffusion coefficients, it is possible for shorter intervals of driving to more rapidly transport electron flux to locations below L = 2.8. The last column on the right of Fig. 4 illustrates that when the diffusion coefficient is set artificially high to be 10 times greater than that specified by the average conditions characteristic of Kp = 7.7, then it is possible for the flux to be transported inward of even L = 2 on timescales of 4 h or less. Note, however, that as shown in Supplementary Fig. 1, the ULF wave power and hence the diffusion coefficients in the heart of the belt specified in statistical combinations of a power spectrum with a power law plus a Gaussian enhancement presented by Ozeke et al.27 can be higher by close to an order of magnitude than those in the analytic model of Ozeke et al.4 (see, e.g., the case for Kp = 8 in Supplementary Fig. 1). Intense conditions such as these might occur during extreme geomagnetic superstorms and hence might be expected to be associated with penetration of the apparent barrier, as observed, e.g., during the Halloween 2003 superstorms42 where two 24 h intervals of sustained activity with Kp > 6 occurred, see Supplementary Fig. 4). Under such conditions, the penetration of the barrier could allow flux to start to fill the slot region—so long as this extreme geomagnetic activity persists at an elevated level for sufficiently long time intervals (perhaps ≳ 6 h according to the results shown in the bottom row of Supplementary Fig. 3). Nonetheless, under typical solar wind driving conditions, the Earthward penetration of the electron flux is constrained to L ≳ 2.8 without requiring any sharp barrier or sharp onset of additional loss processes inside L = 2.8.
Inward transport and energization timescales
In examining their newly discovered feature of an apparent impenetrable barrier Baker et al.18 stated “The radial transport of such electrons from the heart of the outer zone to L < 2.8 is usually very slow (on the timescale of years). Thus, the electrons would be significantly depleted (by several orders of magnitude) by wave scattering during inward transport from the nominal plasmapause location at around four to five Earth radii”. The argument that the electron transport timescales down to L = 2.8 are typically of the order of years presented by Baker et al.18 is based on the radial diffusion model of Cornwall44 who derived a diffusion coefficient model produced by substorm electrostatic fluctuations of the convection electric field. Part of the reason for the discrepancy between the Baker et al.18 conclusion and the results presented here is that the Cornwall44 model does not include electromagnetic fluctuations (with an induced electric field) which are much more efficient at transporting ultra-relativistic electrons; see, e.g., Brautigam and Albert24. In addition, the radial diffusion transport rate at any time is not only a function of the diffusion coefficient but also depends very strongly and dynamically on the electron PSD gradient, df/dL. As such, the rates of radial diffusion cannot be derived solely from the diffusion coefficients by taking DLL–1, as was done by Baker et al.18. Such an approach produces estimates of radial transport timescales, which are incorrect and unrealistically long.
The accurate way to express the effects of df/dL on the transport and energisation time of radiation belt electrons by ULF wave radial diffusion was given by Shultz and Lanzerotti3, where the radial transport time (dL/dt)–1 and the energisation timescale E(dE/dt)–1 are given, respectively, by
Here, γ, L, and are the relativistic correction factor, L-shell, and the equatorial magnetic field at a given L-shell. Plots of this energization time and transport time are illustrated in Fig. 5, derived for fixed Kp-dependent diffusion coefficients DLL[Ozeke] specified by Kp = 1.5, 4.0, 6.0, and 7.7 (top to bottom rows, respectively). The time scale (color bar) represents the time taken for the electrons to move inward 1 Re and for the energy to experience an e-fold increase. Figure 5 illustrates clearly that the timescale for radial transport to reach the barrier does not equate to years but instead corresponds to the timescale of an individual storm; in addition, the transport and energization timescales shown in Fig. 5 are time-dependent verifying the fact that these timescales depend strongly on the local PSD gradient df/dL—with these timescales getting slower as the system in Fig. 5 develops toward equilibrium. Of course, in the real magnetosphere changes to the flux at the outer boundary can hence be communicated inwards on the timescale of days (see also Mann and Ozeke33). Indeed, and as shown in Fig. 5, it is in fact quite possible for electrons to diffuse inward to L = 2.8 from L = 6 on geomagnetic storm timescales solely by the action of ULF wave radial diffusion. Therefore, and in contrast to the conclusion by Baker et al.18, the explanation for the apparent impenetrable barrier is not “exceptionally slow natural inward radial diffusion combined with weak, but persistent, wave–particle pitch angle scattering” occurring on the “timescale of years” but instead can be explained as a result of the activity, time, and strong L-shell dependence of the rates of ULF wave radial diffusion during the course of a single magnetic storm. We demonstrate this further in the next subsection.
Example of a strong geomagnetic storm in March 2015
Very recently, Baker et al.45 showed that even during the intense 17 March 2015 and 22 June 2015 storms the flux of these ultra-relativistic electrons did not significantly penetrate below the previously reported location of the impenetrable barrier at L ≃ 2.8. However, similar to the hypothesis of Foster et al.19, the authors of Baker et al.45 suggested that the impenetrable barrier is instead manmade and is produced by a bubble of VLF waves surrounding the Earth generated by ground-based radio transmitters in the 20–30 kHz frequency range.
To demonstrate that ULF wave transport can reproduce the characteristic feature of the barrier during a single storm, Fig. 6 shows the results from a radial diffusion simulation whereby observations from the REPT instrument (left column) are compared to those generated by the ULF wave radial diffusion model for the March 2015 storm (see, e.g., Baker et al.45 and references therein). For this short interval, we show observational and model results as a function of L* Roderer calculated from the TS04D model Tsyganenko and Sitnov46. Here, the values of the PSD at the outer simulation boundary at L* = 5 are derived from observed flux and the dynamic TS04D magnetic field. In addition, the statistical representations of the rates of diffusion are derived from observations from global ground-based magnetometer networks using the method described by Mann et al.32. In addition, the dipole L expressions for the hiss and chorus losses, as well as the explicit dipole L-dependences in the diffusion coefficients, are also mapped dynamically from L to L* inside the simulation domain using the TS04D magnetic field model.
Figure 6 directly compares compare the L* profiles of the measured ultra-relativistic electron flux with those obtained from our radial diffusion simulation during the March 2015 storm examined in Baker et al.45, but does not include any effects from electron loss due to interactions with man-made VLF waves from transmitters. Both the measured and simulated electron flux L* profiles before the storm on 17 March, indicated by the first two blue lines, are in remarkable agreement showing a rapid inner drop off in flux at L* ≃ 3. After the storm, and once the flux has reached an asymptotic inward location, as indicated by the solid lines 5, 8, and 13 days later, both the simulated and measured electron flux L-shell profiles show clear evidence for the barrier. At the inner edge, the flux profiles decrease by ~ 4 orders of magnitude in a spatial distance of only ~ 0.5 Re, reaching L-shells just below L = 2.8. This sharp feature, corresponding to the inner edge of the barrier, is produced primarily by the storm-time activity and L-dependence of the rates of radial diffusion.
Note that as discussed by Ozeke et al.47 in relation to the extended radiation belt dropout interval in September 2014, during the main phase of magnetic storms there can often be a very rapid extinction of radiation belt flux on timescales shorter than the cadence provided by the orbit of the Van Allen probes and which can effectively wipe out the entire belt. Such extinctions can reduce the flux across the whole belt and effectively decouple the pre- and post-storm flux47. A similar radiation belt extinction to that reported by Ozeke et al.47 for the September 2014 interval also occurs for the March 2015 storm (not shown, but see, e.g., Baker et al.45 and Kanekal et al.48 for details). The ULF wave radial diffusion simulation results presented in Fig. 6 hence assume that the flux is reduced to effectively zero across the whole belt on 17 March. Consequently, all of the flux in the post-storm period in Fig. 6 was created as the result of inward radial diffusion from the outer boundary following the extinction. Very significantly, this shows not only that ULF wave inward radial diffusion can explain the feature of the apparent impenetrable barrier but also that it is formed, and then remains in a fixed and stable location at L ~ 2.8, during a period of days during the course of a single magnetic storm. Overall, the L* profiles of flux presented in Fig. 6 indicate that man-made VLF waves likely do not have a significant affect in producing the observed sharp ultra-relativistic electron flux drop off at L ~ 2.8 during the March 2015 storm. Combined with the additional long-timescale results shown above, our results support the hypothesis that the apparent impenetrable barrier is explained naturally as a result of ULF wave radial diffusion.
In their original paper, Baker et al.18 suggested that ULF wave transport was too slow to enable electron flux to reach the location of the barrier. These authors hence suggested that local plasma wave-particle acceleration, such as might arise from resonance with chorus waves6 was responsible for the ultra-relativistic electron flux reaching the location of the barrier. In addition, Tu et al.49 also argue that local acceleration of electrons to multiple-MeV by strong chorus waves outside the plasmapause followed by slow inward radial diffusion may also explain the location of the barrier.
Here we presented evidence showing that ULF wave radial diffusion can transport the ultra-relativistic electron inward down to L ~ 2.8 consistent with the observed electron flux. Specifically, we show that the rates of ULF wave transport are both: (i) fast enough to rapidly transport electrons inward to the barrier during the period of the duration of a typical magnetic storm; (ii) slow enough once the storm abates to subsequently maintain the observed very steep flux gradient at the inner edge of the apparent barrier and hence effectively prevent any subsequent penetration further Earthward into the slot. Such an apparent barrier to ultra-relativistic radiation flux might also be expected in other astrophysical plasma systems perturbed aperiodically by a bursty stellar wind. If such systems have different characteristics, such an apparent barrier could however be located at a different radial distance from the magnetised body than in the terrestrial case.
ULF wave radial diffusion model
The dynamics and energization of equatorially mirroring ultra-relativistic electrons in the outer radiation belt are simulated by solving the one dimensional radial diffusion equation in a dipole magnetic field expressed in terms of the McIlwain23 L-shell, L, by Eq. (1).
In Eq. (3), represents the PSD of the electrons and it is assumed that the first and second adiabatic invariants, M and J, are conserved3. The radial diffusion coefficients and the electron lifetimes are represented by and , respectively. Both the initial electron PSD profile as a function of L and the PSD at the outer boundary of the simulation (assumed fixed at L = 6) are derived from the Van Allen Probe measurements of the electron flux from both the MagEIS and REPT instruments29, 30, 50. Only MagEIS electron flux data was used from 37.3 keV to ~ 2 MeV and REPT data from 2.6 MeV to 5.2 MeV. At energies higher than 5.2 MeV, the REPT electron flux data at L = 6 appeared close to the instrument noise floor and the flux was hence assumed to be zero. Consequently, we can only simulate the electron flux upto energies of 5.2 MeV. Equation (1) was numerically solved for multiple first adiabatic invariants in order to simulate the electron flux, J, at a fixed energy, with the electron PSD converted to flux using the relationship
where p is the relativistic momentum of an electron. Finally, at the inner boundary at L = 1, f was effectively set to zero, representing loss to the atmosphere. The electron lifetime, , outside and inside the plasmapause is defined using empirical representations based on the electron pitch angle scattering rates produced by chorus waves as presented in Gu et al.10 and plasmaspheric hiss waves as presented in Orlova et al.9. Here the Carpenter and Anderson31 model is used to specify the location of the plasmapause as a function of Kp. Our model does not include any local acceleration mechanisms such as those arising from lower band whistler mode chorus (e.g., Thorne et al.6 and references therein), because these effects are relatively weak at ultra-relativistic energies41 as compared with relativistic energies. Even if local acceleration rapidly creates an additional source for electrons around L = 5 close to the edge of our simulations, as argued by Thorne et al.6, the inward transport of such sources to the apparent barrier to ultra-relativistic electrons at L ~ 2.8 will also be captured in our simulations. Our model also does not include any pitch-angle scattering losses due to any waves other than chorus and plasmaspheric hiss. For example, magnetosonic and EMIC waves have been suggested as potential modes which may also enhance the electron loss (e.g., Shprits et al.51 and Drozdov et al.35). No empirical expressions for the electron lifetimes as a function of L-shell due to magnetosonic or EMIC wave scattering into the atmosphere are currently available, and any potential loss effects from such waves are hence excluded in our simulations.
The electron flux profiles at fixed energy presented in Figs. 1–3 of the main article were derived from multiple first adiabatic invariant conserving simulations, with the electron flux at each L being derived from a different first adiabatic invariant conserving run. In addition to the rates of transport, boundaries in flux can also be created by changes in the energy spectra at the outer boundary. For example, if the electron flux at the outer boundary drops off steeply with decreasing energy at some specific energy then if this source population is rapidly transported inward then the resulting profile of electron flux at a fixed energy will similarly have a steep decrease at some inner L - value as determined by the first adiabatic invariant. Consequently, the location of the inner edge of the outer radiation belt is controlled not only by the magnitude of the diffusion coefficients but also by both the dynamics and the energy spectrum of the flux at the outer boundary and the details of the radial gradients in f. In order to examine only the impact of radial diffusion on the location of the inner edge of the outer radiation belt and the time taken to reach the location of the apparent barrier, profiles of simulated electron flux, and corresponding PSD from a constant boundary condition at a fixed first adiabatic invariant for DLL[Ozeke] radial diffusion coefficients constrained by fixed Kp were illustrated in Fig. 4 of the main article. In addition, plots of the energization and transport timescales are also presented in Fig. 5 of the main article using the approach defined by Schulz and Lanzerotti3. Finally, to demonstrate that the location of the apparently impenetrable barrier can be reached during the course of a single magnetic storm, ultra-relativistic electron transport due to radial diffusion driven by ULF waves was simulated for the intense March 2015 magnetic storm and the results shown in Fig. 6 of the main article. For that event, rather than using empirical characterizations as a function of Kp the ULF wave power levels were constrained by observations from ground-based magnetometers, the ground magnetic ULF power being mapped into electric field power in the equatorial plane (see, e.g., Mann et al.32 and references therein for more details of the methodology).
Data availability statement
REPT and Magnetic Electron Ion Spectrometer data are available from the ECT suite on the Van Allen Probes (http://www.rbsp-ect.lanl.gov/) and geomagnetic indices from the World Data Center for Geomagnetism, Kyoto (http://wdc.kugi.kyoto-u.ac.jp/). All other data supporting the findings of this study are available from the authors upon request.
Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
I.R.M. is supported by a Discovery Grant from Canadian NSERC. This work is supported by the Canadian Space Agency through the Geospace Observatory (GO) Canada program. K.R.M. was supported by an NSERC Postdoctoral Fellowship. We acknowledge the WDC for Geomagnetism, Kyoto University, Japan for the geomagnetic indices. This work was supported by RBSP-ECT funding provided by JHU/APL Contract No. 967399 under NASA’s Prime Contract No. NAS5-01072. The authors thank Prof. Daniel N. Baker for useful discussions, and thank him and the entire REPT team for data. L.G.O also thanks A. Kale for formating the figures. | <urn:uuid:9b244b24-8137-4b0c-b11f-6655c12064cf> | 3.109375 | 8,682 | Truncated | Science & Tech. | 44.157707 | 95,491,369 |
Transport Processes in the Stratosphere and Troposphere
Transport of air across the tropopause plays an important role in determining the chemical composition, and hence radiative properties, of both the troposphere and stratosphere. Quantifying this transport presents a significant challenge on account of the many multiscale processes involved from the global scale mean meridional circulation, through intermediate advective and convective processes, to molecular diffusion. It has long been recognized that tropospheric air enters the stratosphere principally in the tropics, and moves poleward in the stratosphere.
To understand the large-scale circulation in the troposphere and stratosphere, it is useful to look at transport processes averaged around a latitude circle. Ozone productionmainly takes place in the tropical stratosphere as the direct solar radiation photodissociates oxygenmolecules (O2) into oxygen atoms (O), which quickly react with other O2 molecules to form ozone (O3). But most ozone is found in the higher latitudes rather than in the tropics, i.e., outside of its natural tropical stratospheric source region. This higher-latitude ozone results from the slow atmospheric circulation that moves ozone from the tropics where it is produced into the middle and polar latitudes. This slow circulation is known as the Brewer-Dobson circulation.
KeywordsRossby Wave Planetary Wave Polar Vortex Lower Stratosphere Hadley Circulation
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Thirty year-old microbiology experiment
- Title Thirty year-old microbiology experiment
- Released 09/08/2017 9:34 am
- Copyright ESA–G. Porter, CC BY-SA 3.0 IGO
This humble parcel-sized hardware is Europe’s very first closed-loop life-support experiment to fly in space, 30 years ago this week.
Today, ESA leads the 11-nation Micro-Ecological Life Support System Alternative (MELiSSA) programme, seeking to perfect a self-sustaining life-support system that could in future be flown in space, supplying astronauts with all the oxygen, water and food they require.
“A long-term effort, MELiSSA formally began in April 1990 and continues to this day,” explains Christophe Lasseur, heading the programme. “But this flight experiment, developed with France’s CNES space agency and flown with China, was an important precursor.”
The experiment flew in space for five days on a recoverable ‘Fanhui Shei Weixing’ (FSW) recoverable capsule during 5–10 August 1987.
Two types of microorganism – algae dependent on oxygen and exhaling carbon dioxide, plus cyanobacteria dependent on carbon dioxide and exhaling oxygen – were placed in the glass vials, their mutually-dependent growth in weightlessness supported by nutrients and light, the latter supplied by a small light bulb.
The experiment had to be entirely self-reliant while the FSW capsule was in space, so power came from a set of off-the-shelf Duracell batteries.
The aim was to see how the algae grew in weightlessness, rather than being disturbed by the forces of reentry and landing. Accordingly, a shape-memory alloy released a fixative chemical after five days of flight. This stopped the cultures from growing any further, allowing accurate post-flight analysis of their behaviour in space.
“The nerve-racking part was waiting for the hardware to come back to us,” adds Christophe. “If it was lost, we would have had no results.”
Many further experiments have followed. Next month, the latest MELiSSA experiment is scheduled for the International Space Station, containing an advanced photo-bioreactor to see how algae growth rates are affected by microgravity and space radiation.
- Id 382229
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Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University Olomouc demonstrated for the first time a single molecule piezoelectric effect. The study published in the Journal of the American Chemical Society represents a breakthrough in understanding the electromechanical behavior of individual molecules and provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale.
The piezoelectric effect emerges in some materials in which the mechanical and electrical properties are coupled. Either the electric field can be generated if a mechanical stress is applied (direct piezoelectric effect) or, conversely, the mechanical deformation can arise if the electric field is applied (converse piezoelectric effect).
These effects have reached numerous practical applications in automotive, smartphone, computer, medical and military industries. In our everyday life, we meet the piezoelectric effect in smartphones, microphones or lighters, it is also widely employed in airbag systems, sonars or scanning microscopes. Possible applications of the piezoelectric effect to nanotechnology are currently under the spotlight and intensively studied. However, the single molecule piezoelectric effect, which is essential for envisioned electromechanical molecular devices, has so far remained elusive.
"In a close collaboration with physicists, it was proved for the first time that a strong converse piezoelectric effect can be observed at individual molecules of the heptahelicene derivative, which is a screw-like carbon molecule resembling a spring," said Ivo Starý, the leader of the group of chemists at IOCB Prague preparing the compound.
The effect was experimentally demonstrated by the group of physicists at IP CAS at individual molecules on a silver surface using scanning probe microscopy. The group leader Pavel Jelínek explains: "The magnitude of the piezoelectric constant calculated from the experimental data is significantly higher than that one of known piezoelectric polymers and is comparable to the magnitudes measured at some inorganic materials such as zinc oxide. Moreover, we explained the origin of the single molecule piezoelectric effect by employing quantum mechanics calculations."
How does the converse piezoelectric effect work at nanoscale? The screw-like molecule endowed with an inner dipole stretches or squeezes itself depending on the strength and polarity of the outer electric field. It arises by applying a voltage bias between the silver pad and atomically sharp tip of the scanning microscope that resides over the studied molecule. As the change in a molecule height can be monitored with an ultimate accuracy, it is possible to see a molecule deformation induced by the electric field. Such a coupling of the mechanical movement of a molecule and the change in electric field, which is reciprocal by theory, represents an entry into the world of molecules doing mechanical work on one hand and molecular nanogenerators of electric energy on the other hand.
Article: O. Stetsovych, P. Mutombo, M. Švec, M. Šámal, J. Nejedlý, I. Císarová, H. Vázquez, M. Moro-Lagares, J. Berger, J. Vacek, I. G. Stará, I. Starý, P. Jelínek, Large Converse Piezoelectric Effect Measured on a Single Molecule on a Metallic Surface. J. Am. Chem. Soc. 2018, 140, 940?946.
The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences / IOCB Prague is a leading scientific institution in the Czech Republic, recognized internationally. Its primary mission is basic research in the fields of chemical biology and medicinal chemistry, organic and material oriented chemistry, chemistry of natural compounds, biochemistry and molecular biology, physical chemistry, theoretical chemistry and analytical chemistry. The Institute has a long tradition and expertise in medicinal chemistry and drug development together with the pharma industry. Antivirals discovered by Antonín Holý and developed further by Gilead Sciences revolutionized the treatment of AIDS and hepatitis B and have significantly improved lives of millions of people around the globe.
Institute of Physics of the Czech Academy of Sciences / IP CAS is a public research institute, oriented on the fundamental and applied research in physics. IP is the largest institute of the Czech Academy of Sciences and its present research program comprises six branches of physics: particle physics, the physics of condensed matter, solid state physics, optics, plasma and laser physics. These research branches also define how the institute is structured into six major research divisions.
Dusan Brinzanik | EurekAlert!
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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:4451bd3e-29ad-4b07-a7a2-2a783b67edb3> | 2.984375 | 1,641 | Content Listing | Science & Tech. | 28.079207 | 95,491,425 |
"The predominant theory says that jets are essentially fire hoses that shoot out matter in a steady stream, and the stream breaks up as it collides with gas and dust in space—but that doesn't appear to be so after all," says Adam Frank, professor of astrophysics at the University of Rochester, and co-author of the paper.
"These experiments are part of an unusal international collaboration of plasma physicists, astronomers and computational scientists. It's a whole new way of doing astrophysics. The experiments strongly suggest that the jets are fired out more like bullets or buckshot. They don't break into pieces—they are formed in pieces."
Frank says the experiment, conducted by Professor Sergey Lebedev's team in the Department of Physics at Imperial College London (www.imperial.ac.uk), may be the best astrophysical experiment that's ever been done. Replicating the physics of a star in a laboratory is exceptionally difficult, he says, but the Imperial experiment matches the known physics of stellar jets surprisingly well. "Lebedev's group at Imperial has absolutely pioneered the use of these experiments for studying astrophysical phenomena. The collaboration between Imperial and Rochester has been going on for almost 5 years and now it is bearing some extraordinary fruit."
At Imperial, Lebedev sent a high-powered pulse of energy into an aluminum disk. In less than a few billions of a second, the aluminum began to evaporate, creating a cloud of plasma very similar to the plasma cloud surrounding a young star. Where the energy flowed into the center of the disk, the aluminum eroded completely, creating a hole through which a magnetic field from beneath the disk could penetrate."
The field initially pushes aside the plasma, forming a bubble within it, says Frank, who carried out the astrophysical analysis of the experiment. As the field penetrates further and the bubble grows, however, the magnetic fields begin to warp and twist, creating a knot in the jet. Almost immediately, a new magnetic bubble forms inside the base of the first as the first is propelled away, and the process repeats.
Frank likens the magnetic fields' affect on the jet to a rubber band tightly wrapped around a tube of toothpaste—the field holds the jet together, but it also pinches the jet into bulges as it does.
"We can see these beautiful jets in space, but we have no way to see what the magnetic fields look like," says Frank. "I can't go out and stick probes in a star, but here we can get some idea—and it looks like the field is a weird, tangled mess."
Frank says other aspects of the experiment, such as the way in which the jets radiatively cool the plasma in the same way jets radiatively cool their parent stars, make the series of experiments an important tool for studying stellar jets. With this new model, he says, astrophysicists do not have to assume that the knotted jets they see in nature mean some unknown phenomenon interrupted the jets' flow of material.
Now, says Frank, some experiments that were once far beyond astrophysicists' reach have been, literally, brought down to Earth.About the University of Rochester
Jonathan Sherwood | EurekAlert!
First evidence on the source of extragalactic particles
13.07.2018 | Technische Universität München
Simpler interferometer can fine tune even the quickest pulses of light
12.07.2018 | University of Rochester
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
13.07.2018 | Event News
13.07.2018 | Materials Sciences
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Actually, Terra, you've got it right. The eye is the area of the lowest barometric pressure. The strongest warming in a hurricane is found at upper levels in the eye due to sinking air. In fact, the eye is such a clear region because of the sinking air.
This sinking air is a necessary artifact of hurricanes, in fact; with such strong rising motion in the eyewall (and through the convective mass as well), there must be some compensating sinking motion to maintain balance. Some of this is seen on the outer periphery of the storm, but the majority of this is found within the eye. The sinking causes the air at upper levels to warm -- forced descent is a warming process -- and helps drive the warm-core structure of the cyclone. With all of that heating at upper levels, the strongest response in the hurricane, coincidentally enough, is found at the surface. The response of the storm at the surface is to deepen, leading to increased rising motion and, given favorable surface & upper-air conditions, a feedback cycle upon which the storm can intensify.
The stronger the storm, the stronger the descent within the eye. The need for this descent & the associated warming aloft is the primary reason why you don't ever see the eye contract to a near-zero diameter: if it were to do so, the sinking motion would be cut off, weakening the warming aloft (which in a hurricane is not due to convection), and the pressure would begin to rise. That's why you see eyewall replacement cycles with these storms, as the natural tendency for any eyewall is to contract. The science behind that one is pretty complicated, though (heavy in physical and dynamical meteorology), and I'll leave it for another day.
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C02: Interactions of snow on sea ice with atmospheric constituents including black carbon
PIs: Rüdiger Gerdes, André Ehrlich
Providing the existing trend of summer sea ice decline continues, the Arctic Ocean may become more accessible for shipping and the exploration of the Arctic’s potentially vast resources. The potential increase of marine activity in the Arctic would lead consequently to increasing local emissions of aerosols and Black Carbon (BC) with feedback to the atmospheric radiation field (surface cooling) and the sea ice/snow surface albedo (surface warming). Both effects may significantly affect Arctic Amplification by their potential influence on the surface energy budget, sea ice thickness and content. About 40% of the Arctic Amplification was attributed to the surface albedo feedback associated with melting snow and ice. Since sea ice is covered with snow most of the year, snow surface properties are important drivers of the surface energy balance, but can be substantially changed due to particle deposition from the atmosphere, as snow is known as efficient integrator of BC. Atmospheric BC itself is known to warm the aerosol layers and cool the surface. The competition between both effects is still unclear.
However, concurrent observations of atmospheric BC, and BC in snow and surface properties are rare. Hence, this project will combine airborne and ground–based observations of aerosols and BC concentrations and snow optical properties to investigate their feedback mechanisms in Arctic regions. In–situ measurements of atmospheric BC (ground–based and airborne) along with sampling of BC in snow and remote sensing observations of snow properties will be merged.
The first goal of the project is to characterize the temporal variability, horizontal and vertical distributionof BC in the atmosphere and concentrations of BC in snow. Trajectory calculations will be used to relate BC concentrations to either long–range transport of anthropogenic and natural aerosol or local emitted anthropogenic aerosol. Simultaneously, snow optical properties such as spectral albedo and bidirectional reflectance distribution function (BRDF) will be derived from ground–based and airborne observations.
Snow albedo will be analysed in dependence of BC concentrations, snow grain size, surface roughness and the variability of snow and sea ice thickness. The correlation between snow albedo changes and absorptive properties of BC will be evaluated. To fill the gap in the understanding of connections between the observed albedo changes and the distribution of aerosols and BC within the Arctic Atmospheric Boundary Layer (ABL), we aim to quantify deposition rates (wet and dry) of aerosols as well as source regions and physical/chemical state of the observed BC–containing aerosol. Differences of surface optical properties and changes of the surface radiation budget for aerosols originating from long–range transport of anthropogenic and natural aerosol and local emitted anthropogenic aerosol will be analysed.
Hypothesis: Solar energy absorbed by BC–containing aerosol particles leads to a warming of the near–surface air when locally produced/emitted constituents reside at low altitudes and are partly deposited onto the snow surface. Contrarily, long–range transport of BC into the Arctic, remaining in higher atmosphere layers, will lead to a cooling of the surface.
Role within (AC)³
Schulz, H., H. Bozem, M. Zanatta, W.R. Leaitch, A.B. Herber, J. Burkart, M.D. Willis, P.M. Hoor, J.P.D. Abbatt, and R. Gerdes, 2018: High–Arctic aircraft measurements characterising black carbon vertical variability in spring and summer, Atmos. Chem. Phys. Disc., doi:10.5194/acp-2018-587
M. Zanatta, P. Laj, M. Gysel, U. Baltensperger, S. Vratolis, K. Eleftheriadis, Y. Kondo, P. Dubuisson, V. Winiarek, S. Kazadzis, P. Tunved, and H.-W. Jacobi, 2018:
Effects of mixing state on optical and radiative properties of black carbon in the European Arctic, Atmos. Chem. Phys. Disc., doi:10.5194/acp-2018-455
Carlsen, T., Birnbaum, G., Ehrlich, A., Freitag, J., Heygster, G., Istomina, L., Kipfstuhl, S., Orsi, A., Schäfer, M., and Wendisch, M., 2017: Comparison of different methods to retrieve effective snow grain size in central Antarctica, Cryosph., 11, 2727-2741, doi:10.5194/tc-2016-294
Carlsen, T., Birnbaum, G., Ehrlich, A., Heygster, G., Istomina, L., Schäfer, M., Wendisch, M., 2017: Snow specific surface area (SSA) retrieved from spectral surface albedo (ground-based and airborne) and reflectance (spaceborne) measurements at Kohnen research station, Antarctica, during austral summer 2013/14. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.880815
Ehrlich, A., Bierwirth, E., Istomina, L., and Wendisch, M., 2017: Comined retrieval of Arctic liquid water cloud and surface snow properties using airborne spectral solar remote sensing, Atmos. Meas. Tech., 10, 3215-3230, doi:10.5194/amt-10-3215-2017
Ehrlich, A., Bierwirth, E., Istomina, L., Wendisch, M., 2017: Cloud optical thickness, cloud particle effective radius, and effective snow grain size retrieved from airborne spectral reflectivity measurements during VERDI 2012 over the Beaufort Sea. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.882979 | <urn:uuid:cd0a9237-9d55-4c46-ad74-945a8a2de06a> | 2.625 | 1,271 | Academic Writing | Science & Tech. | 51.316045 | 95,491,459 |
Epigenetic Memory's On/Off Switch Found
Epigenetics is the study of inheritable changes in gene expression not directly coded in our DNA. It appears that our life experiences can be passed on to our children, and to future generations, by this mechanism.
(From Transgenerational Small RNA Inheritance)
The duration of epigenetic responses underpinning
transgenerational inheritance is determined by an active
mechanism relying on the production of small RNAs
and modulation of RNAi factors, dictating whether ancestral
RNAi responses would be memorized or forgotten.
(credit: Leah Houri-Ze’evi et al./Cell)
“Until now, it has been assumed that a passive dilution or decay governs the inheritance of epigenetic responses,” said Oded Rechavi, PhD, from TAU’s Faculty of Life Sciences and Sagol School of Neuroscience. “But we showed that there is an active process that regulates epigenetic inheritance down through generations.”
The scientists discovered that specific genes, which they named “MOTEK” (Modified Transgenerational Epigenetic Kinetics), were involved in turning epigenetic transmissions on and off.
“We discovered how to manipulate the transgenerational duration of epigenetic inheritance in worms by switching ‘on’ and ‘off’ the small RNAs that worms use to regulate [these] genes,” said Rechavi.*
These switches are controlled by a feedback interaction between gene-regulating small RNAs, which are inheritable, and the MOTEK genes that are required to produce and transmit these small RNAs across generations.
The feedback determines whether epigenetic memory will continue to the progeny or not, and how long each epigenetic response will last.
The first time I read about this idea was in an excellent series of fantasy novels by Barbara Hambly. In her 1982 Darwath trilogy, she writes about how wizards of several thousand years ago succeeded in tying information to the DNA of selected individuals. In the story, several people from 1980's California find themselves transported across the Void to another planet and the Realm of Darwath. They face a deadly species of queerly magical beings - the Dark - who destroyed civilization thousands of years ago. Everything that was made of paper (like books and records) were burned to stave off attacks by the Dark. Tying memories to a few suitable bloodlines was the only way to preserve a record of that period that would endure.
"We have all talked of the heritable memories of the House of Dare," she went on... maybe the old wizards, the engineers who raised the Keep, knew that records do get lost, especially when, as you said, fire is the principal weapon."
Gil's finger stabbed out like a sword. "They tied the memory to the bloodline and that was their record! A record that wouldn't get lost and couldn't be destroyed."
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Research into 3D printing with graphene, the one atom thick sheets of carbon atoms oriented in a honeycomb lattice structure, seems to be moving full steam ahead. If researchers figure out a reliable way to print with this ‘miracle material’, a whole slew of doors will open up within the field of material science.
One of newer companies, researching and developing capabilities around graphene 3D printing, is Graphene 3D Lab, Inc. Located in Long Island, 65 miles east of Manhattan, the company has a goal of developing and manufacturing graphene-enhanced materials for 3D printing. They were spun out of Graphene Laboratories, Inc back in November of last year, and have since filed a provisional patent for 3D printable graphene batteries.
Today they have announced a research partnership and joint venture with Stony Brook University (SUNY), which will provide for quality control testing of 3D printable materials that include graphene, along with other advanced materials. As a part of the agreement, Graphene 3D Lab will pay a total $137,713 to the research foundation for SUNY. In exchange for the funding, SUNY will provide their research facilities at their Center for Advanced Sensor Technology (Sensor CAT) to Graphene 3D, in order to allow them to test their filaments for quality control and performance. If all goes as planned, Graphene 3D will be able to discover the perfect printing conditions for their graphene enhanced filaments.
“Sensor CAT’s testing of Graphene 3D materials will ensure an impartial review of the materials functional attributes by project personnel,” said Daniel Stolyarov, Graphene 3D’s CEO. “This joint venture also allows Graphene 3D to access Stony Brook University’s world-class facilities and personnel, thereby shortening the development time of our materials and reducing overall R&D costs.”
There is very little know when it comes to 3D printing with graphene materials and composites. This research should allow for the advancement of the technology in addition to possibly providing 3D Graphene Labs with future talent by the way of Stony Brook students, once they graduate.
“Collaboration, like that with Graphene 3D, is core to the mission of Sensor CAT to provide businesses with access to renowned expert staff as well as state-of-the-art facilities and equipment,” stated Dr. Peter Shkolnikov, Deputy Director of Sensor CAT. “Under supervision of Sensor CAT, students at Stony Brook University will have the opportunity to work on this joint venture alongside Graphene 3D, and potentially continue that relationship upon graduation.”
Additionally, Graphene 3D Labs will be establishing a Scientific Advisory Board, and appointing their co-founder, Prof. Mikhail Gouzman. Prof. Gouzman to it immediately. The board will be tasked with attracting talented researchers to the company, as well as acting as a guide to their continued progress.
With several other companies investing into the future of graphene 3D printing, it will certainly be interesting to see which ones come out on top. Discuss this story in the Gaphene 3D Lab/Stoney Brook forum thread on 3DPB.com. | <urn:uuid:90edc50e-94ba-4328-9ef0-cb2915322b77> | 2.734375 | 676 | Comment Section | Science & Tech. | 36.116367 | 95,491,469 |
The folding funnel hypothesis is a specific version of the energy landscape theory of protein folding, which assumes that a protein's native state corresponds to its free energy minimum under the solution conditions usually encountered in cells. Although energy landscapes may be "rough", with many non-native local minima in which partially folded proteins can become trapped, the folding funnel hypothesis assumes that the native state is a deep free energy minimum with steep walls, corresponding to a single well-defined tertiary structure. The term was coined by José Onuchic in a 1992 article.
The folding funnel hypothesis is closely related to the hydrophobic collapse hypothesis, under which the driving force for protein folding is the stabilization associated with the sequestration of hydrophobic amino acid side chains in the interior of the folded protein. This allows the water solvent to maximize its entropy, lowering the total free energy. On the side of the protein, free energy is further lowered by favorable energetic contacts: isolation of electrostatically charged side chains on the solvent-accessible protein surface and neutralization of salt bridges within the protein's core. The molten globule state predicted by the folding funnel theory as an ensemble of folding intermediates thus corresponds to a protein in which hydrophobic collapse has occurred but many native contacts, or close residue-residue interactions represented in the native state, have yet to form.
In the canonical depiction of the folding funnel, the depth of the well represents the energetic stabilization of the native state versus the denatured state, and the width of the well represents the conformational entropy of the system. The surface outside the well is shown as relatively flat to represent the heterogeneity of the random coil state. The theory's name derives from an analogy between the shape of the well and a physical funnel, in which dispersed liquid is concentrated into a single narrow area.
- Chaperone – proteins that assist other proteins with folding or unfolding
- Levinthal paradox
- Protein structure prediction
- Leopold PE; Montal M; Onuchic JN (September 1992). "Protein folding funnels: a kinetic approach to the sequence-structure relationship". Proceedings of the National Academy of Sciences of the United States of America. 89 (18): 8721–5. Bibcode:1992PNAS...89.8721L. doi:10.1073/pnas.89.18.8721. PMC . PMID 1528885.
- Dobson CM (2000-12-15). "The nature and significance of protein folding". In RH Pain. Mechanisms of Protein Folding (2nd ed.). Oxford, UK: Oxford University Press. ISBN 0-19-963788-1.
- Matagne A, Chung E, Ball LJ, Radford SE, Robinson CV, Dobson CM (1998). "The origin of the alpha-domain intermediate in the folding of hen lysozyme". J Mol Biol. 277 (5): 997–1005. doi:10.1006/jmbi.1998.1657. PMID 9571017.
|This biochemistry article is a stub. You can help Wikipedia by expanding it.| | <urn:uuid:8c295c3b-e75e-4e25-9580-05867914bff3> | 2.96875 | 648 | Knowledge Article | Science & Tech. | 47.332823 | 95,491,470 |
Ecological Data Storage, Management, and Dissemination
The rapid evolution of computing, storage, and network technologies has changed the traditional rules for ecosystem data storage and dissemination. Some of the most profound changes have been changes in user expectations: in the post-Web world, both internal and external users expect to be able to not only download data sets electronically, but also to browse through well-organized catalogs of data holdings to make their download selections in a logical and systematic fashion. Thus it is not enough to simply fill disks or CD jukeboxes with gigabytes of data; an organization somehow must effectively build meaningful on-line catalogs that describe its holdings if it is to match the realities of data dissemination with increasingly sophisticated user expectations.
dramatically improved our ability to collect ecological data sets, process them to derive new data sets, and disseminate results. In particular, dissemination technologies such as CD-ROMs and the World Wide Web (WWW)havemadeitmucheasier to move data from one site to another. Yet major problems still remain, which extend across the entire spectrum of project life cycles and project management. Instead of focusing on collecting data and preparing reports, a project manager now must also face the difficulties of selecting and integrating desirable data sets from a multitude of available options, organizing the project’s own ever-increasing internal information resources, and dealing with numerous new options for data dissemination.Before beginning any study, the manager must determine what direct or background data sets are logically available and whether they can be acquired and easily used. Once data processing begins, it is now relatively easy to execute programs that derive new data sets. However, it remains difficult to effectively catalog all the derived data sets that result, much less to record and catalog all the processing attributes used in each derivation. At dissemination time, it is relatively easy to make CDs or tapes or to post Web-accessible data sets; it is not as simple to organize all the data and information about the processing methodology used to create and interpret the data so that recipients can effectively reuse what is received.
In short, moving from an environment in which data creation, processing, and storage are all very expensive to one in which the same aspects are all relatively cheap obviously changes the concerns of data managers. Having an abundant infrastructure for data creation eliminates some problems, but it also changes the characteristics of some old problems and creates new ones. This chapter will summarize some of the current problems facing ecological data managers, explain how these problems have evolved in parallel with advancing technology, and describe the options emerging as possible solutions.
KeywordsPotential User Data Dissemination User Expectation Root Class Data Creation
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Southwest Alaska Lichen Inventory
Lichens are an important component of biological diversity and are sensitive indicators of air quality and climate. Despite their ecological importance in southwest Alaska, there is a general lack of information regarding lichen occurrence in the Southwest Alaska Network parks. To address this information need, we have partnered with Oregon State University to conduct a lichen inventory of its three largest parks: Katmai and Lake Clark national parks and preserves, and Kenai Fjords National Park.
Preliminary FindingsA collaborative team of lichenologists from North America and Europe visited Katmai National Park and Preserve in 2013, Lake Clark National Park and Preserve in 2014, and Kenai Fjords National Park in 2015-2016. They surveyed sites throughout each park that were selected by National Park Service botanists to span a range of rich lichen habitats, including coastal rock outcrops and forests, large interior lakes, river and forest systems, and interior and coastal alpine zones. Researchers observed a lichen flora with an interesting mix of arctic-alpine, boreal, and coastal elements. The Beringian element that is evident on the Seward Peninsula and Aleutian Islands did not appear to be prominent in Southwest Alaska parks.
A number of oceanic forest species were found at low-elevation, moist forest sites. Certain species groups or genera common to the alpine were surprisingly rare in Katmai. These included the alpine ground-dwelling Rinodina species, ground-dwelling Hypogymnia, and Dactylina. These genera were somewhat more abundant in Lake Clark than in Katmai, but still not as abundant as in more continental climates. Nitrophilous species (e.g., Caloplaca, Xanthoria) did not appear to be abundant in any park, suggesting low levels of nitrogenous pollutants. Few calciphiles were encountered, owing to the predominantly acidic rocks in all parks. Although the team was unable to sample on limestone or dolomite in Katmai or Kenai Fjords, they did visit one site with marble on the shore of Lake Clark. Species found at that site differed from those occupying more acidic rock in surrounding areas.
To date, at least 14 species have been discovered that are new to science, 7 species are new to North America, and 14 species are new to the state of Alaska. Additionally, new populations of the globally endangered lichen, Erioderma pedicillatum (Hue) P. M. Jørg., were discovered in both Katmai and Lake Clark. Twelve peer-reviewed journal articles and one master’s thesis have been published using inventory findings. Other products include two manuscripts (in progress) that discuss the biodiversity and ecology of Southwest Alaska lichen communities through an annotated voucher-based lichen species list and accompanying database for each of the three parks. Specimens collected during the course of the inventory will be provided on loan to the Museum of the North Herbarium, University of Alaska, and several other institutions, where they will be available for research and educational purposes. | <urn:uuid:e549a15d-1886-4bf9-ac02-d7eb3dd44244> | 3.734375 | 645 | Knowledge Article | Science & Tech. | 25.063182 | 95,491,477 |
Sea otters (Enhydra lutris) are known as a keystone species. A keystone species dramatically affects the structure and complexity of their environment. For example, when sea otters are present in rocky habitats, they eat sea urchins and urchin density decreases as a result. Lower urchin density reduces grazing pressure on kelps, resulting in a more diverse nearshore ecosystem (Estes and Duggins 1995). In 2005, sea otter populations in the southwest Alaska population segment (which includes coastal habitat of Katmai National Park and Preserve) were listed as threatened under the Endangered Species Act. Further, the U.S. Fish and Wildlife Service designated almost 6,000 miles of coastline in southwest Alaska as critical habitat for the northern sea otter. Critical habitat is habitat that is deemed essential for the conservation of a threatened (or endangered) species. Monitoring sea otter populations, as well as other components related to sea otter status, in nearshore ecosystems will result in important information to better understand population trajectories.
Sea Otter Monitoring in Southwest Alaska
There are three different ways sea otter data are collected: fly aerial surveys to estimate abundance, conduct foraging observations to estimate energy recovery rates, and collect carcasses to estimate the age-class distribution of the dying otters.
Aerial surveys are conducted in order to calculate sea otter abundance. Surveys were flown in Katmai National Park and Preserve in 2008, 2012, and 2015; Kenai Fjords National Park in 2002, 2007, 2010, and 2016; and western Prince William Sound annually from 1993-2005, 2007-2009, and 2011-2013, and 2017. Surveys were also flown in Kachemak Bay, an area adjacent to Kenai Fjords National Park and across Cook Inlet from Lake Clark National Park and Preserve, in 2002, 2007, 2008, 2012, and 2017.
Sea otter foraging data are collected annually in Katmai, Kenai and Prince William Sound to estimate energy recovery rates (kcal/min). These rates are used to indicate population status relative to a food-limited carrying capacity. In biology, carrying capacity is the maximum population size of a particular species that the environment can sustain indefinitely given the food, habitat, and other necessary environmental resources. Beginning in 2018, the U.S. Geological Survey will also be collected foraging data in Kachemak Bay.
Carcass surveys also occur annually. To date, very few carcasses have been found in Kenai Fjords National Park, presumably because of the relatively low density of sea otters in the area and the lack of low sloping beaches that could act as repositories for carcasses. Carcasses are collected every year from Katmai National Park and Preserve and western Prince William Sound. Carcasses from Kachemak Bay are monitored by the U.S. Fish and Wildlife Service.
In Katmai National Park and Preserve, our data suggest that sea otter numbers increased substantially since the early 1990s and have been at high and stable densities in recent years (Figure 1). This corresponds with declining energy recovery rates, suggesting that otters have reached a food-limited state (Figure 2).
Densities of otters in Kenai Fjords National Park, while relatively low, have been stable since 2002 (Figure 1) with stable energy recovery rates (Figure 2), indicating a population at carrying capacity with low food availability in comparison to Katmai. Unlike Katmai, which has extensive shallow, soft-sediment habitats ideal for clams, Kenai Fjords is predominately a glacial fjord ecosystem. It’s “steep and deep” characteristics can be unfavorable for clams. The low availability of clams likely contributes to the lower density of otters in the park.
Initially, in western Prince William Sound, food was not a limiting factor in sea otter recovery from the Exxon Valdez oil spill. More recently, we have observed a moderate increase in sea otter population density, with a subsequent decline in energy recovery rates. This indicates that the population may be reaching its carrying capacity for this region (Figures 1 and 2).
Kachemak Bay has shown an increase in sea otter abundance and density estimates since surveys began in 2002 (Figure 1). We will initiate foraging observations to estimate energy recovery rates beginning in 2018.
The design and coordination of our monitoring program allows us to infer potential causes and spatial extent of the observed changes in abundance that have occurred through time (Coletti et al. 2016).
For More Information
Contact Heather Coletti, firstname.lastname@example.org https://www.nps.gov/im/swan/
Estes, J.A. and D.O. Duggins. 1995. Sea otters and kelp forests in Alaska: generality and variation in a community ecology paradigm. Ecological Monographs. 65: 75-100.
Coletti, H. A., J. L. Bodkin, D. H. Monson, B. E. Ballachey and T. A. Dean. 2016. Detecting and inferring cause of change in an Alaska nearshore marine ecosystem. Ecosphere 7 (10): e01489.10.1002/ecs2.1489
Updated March 2018 | <urn:uuid:4021f1ca-5b16-442a-a733-01f0a4dd0084> | 4 | 1,118 | Knowledge Article | Science & Tech. | 38.876455 | 95,491,478 |
matter in the form of a gas of atoms, molecules, or elementary particles that have been so chilled that their motion is virtually halted and as a consequence they lose their separate identities and merge into a single entity. A Bose-Einstein condensate, the fifth state of matter, is formed at low temperatures when a significant number of the elementary particles classified as bosons (see Bose-Einstein statistics) collapse into the same quantum state. A similar condensate that consists of fermions (see Fermi-Dirac statistics) instead of bosons is known as a fermionic condensate, the sixth state of matter.
Such condensates were predicted by Albert Einstein in 1924 based on the system of quantum statistics formulated by the Indian mathematician Satyendra Nath Bose. Quantum theory asserts that atoms and other elementary particles can be thought of as waves. Einstein proposed that as atoms approach absolute zero (-273.15degrees Celsius), the waves expand in inverse proportion to their momentum until they fall into the same quantum state and finally overlap, essentially behaving like a single atom. The phenomenon could not be observed, however, until techniques were developed to reduce temperatures to within 20 billionths of a degree above absolute zero. In 1995, Eric A. Cornell and Carl E. Wieman isolated a rubidium Bose-Einstein condensate under laboratory conditions; they shared the 2001 Nobel Prize in physics with Wolfgang Ketterle for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates.
A fermionic condensate is far more difficult to achieve because the Pauli exclusion principle prohibits two or more fermions from occupying the same quantum state. In 1957, John Bardeen, Leon Cooper, and Robert Schrieffer suggested that electrons, which are fermions, could form what are now known as Cooper pairs, which act like bosons; such pairings might make a fermionic condensate possible. Murray Holland much later suggested that fermions could pair up at higher temperatures by subjecting them to a magnetic field. In 2003, Deborah Jin and Rudolf Grimm were able to get fermionic atoms to bond together to form molecular bosons and thus form a Bose-Einstein condensate, but not a fermionic condensate. Later that year, applying a time-varying magnetic field to potassium atoms, Jin achieved Cooper pairings and the subsequent formation of a fermionic condensate.
It is believed that these state of matter have never existed naturally anywhere in the universe, since the low temperatures required for their existence cannot be found, even in outer space. Condensates may be useful in the study of superconductivity and superfluidity and in refining measurements of time and distance.
Date: 1995 IN USE A Bose-Einstein condensate is a state of matter created when a certain kind of gas is cooled to near absolute zero. Subatomic p
One of two possible ways (the other is Fermi-Dirac statistics) in which a collection of indistinguishable particles may occupy a set of available d | <urn:uuid:424901e0-35c4-46b3-8dec-9271371581fc> | 3.671875 | 653 | Knowledge Article | Science & Tech. | 20.98111 | 95,491,490 |
Every year leading economists and ecologists, including centre researchers, head out to the island of Askö in the Swedish archipelago to discuss a range of issues related to sustainable development. Organised by centre partner Beijer Institute of Ecological Economics, they often lead to well-cited scientific publications.
The meeting in 2010 was no exception and resulted in a paper recently published in the journal Sustainability dealing with the increasing need for a "general resilience".
"General resilience is the capacity of social-ecological systems to adapt or transform in response to unfamiliar, unexpected and extreme shocks. Processes for building general resilience are an emerging and crucially important area of research," write the team of scientists, including centre researchers Oonsie Biggs, Anne-Sophie Crepin, Gustav Engström, Carl Folke, Karl-Göran Mäler, Brian Walker and Aart de Zeeuw.
Absorb shocks of all kind
Hence, general resilience is about strengthening the capacity to absorb shocks like storms and floods, even financial meltdowns. It goes without saying that building such broad resilience to unknown disturbances is far more difficult than planning for specific resilience to known types of disturbances.
In fact, large-scale disturbances like the mad cow disease and the huge Japan earthquake and tsunami of 2011, are outside the scope of experience. The latter example was an earthquake which was extraordinarily powerful and triggered a tsunami with a 14 meter wave that breached the seawalls designed for the expected maximum wave height of 5.7 meter. In addition, the tsunami damaged nuclear power stations by shutting down back up diesel generators which were located in “safe" places on the assumption that the sea walls would hold.
"Such events are unusually so intense or extensive that they require another type of resilience building," argue the authors.
"We should build more 'all-purpose kind' of resilience, although building such a resilience is far more difficult and costly than planning for known types of disturbance."
Among the conditions that enable general resilience, the authors of the new paper include nine important aspects: (1) diversity, (2) modularity, (3) openness, (4) reserves, (5) feedbacks, (6) nestedness, (7) monitoring, (8) leadership, and (9) trust.
Diversity, openness and trust
Diversity, for example, provides components that have similar functions but different responses to disturbance (response diversity), so the function is maintained even if one component of an ecosystem is damaged. Diversity of perspectives and experience also matters as much as individual ability when teams of people are solving complex problems.
Modularity is important because it helps to contain disturbances by separating social-ecological systems from each other, e.g. land management with prescribed fire that uses firebreaks to limit the spread of the fire. Similarly, quarantine mechanisms may restrict the spread of epidemics or invasive species.
In other cases, openness of a social-ecological system might be the key to general resilience, e.g. seed dispersal as a key to recovery from large infrequent forest fires. Hence, there are a number of trade-offs between modularity and openness that is well understood for some social-ecological systems, but not for others.
"Development of trust is another important aspect when building general resilience determining whether people will be able to collaborate effectively in relation to unfamiliar, unexpected and extreme shocks," the authors conclude.
Similarly, co-author Oonsie Biggs and others recently suggested seven principles for enhancing resilience of ecosystem services. These principles included diversity, connectivity, feedbacks and slow variables, polycentric governance, learning and experimentation, breadth of participation, and the complex adaptive characteristics of social-ecological systems.
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Rising anthropogenic nitrate levels in the North Pacific Ocean
Human-induced changes to Earth's carbon cycle - for example, rising atmospheric carbon dioxide and ocean acidification - have been observed for decades. However, a study published this week in Science showed human activities, in particular industrial and agricultural processes, have also had significant impacts on the upper ocean nitrogen cycle.
The rate of deposition of reactive nitrogen (i.e., nitrogen oxides from fossil fuel burning and ammonia compounds from fertilizer use) from the atmosphere to the open ocean has more than doubled globally over the last 100 years.
This anthropogenic addition of nitrogen has reached a magnitude comparable to about half of global ocean nitrogen fixation (the natural process by which atmospheric nitrogen gas becomes a useful nutrient for organisms). David Karl, Professor of Oceanography and Director of the Daniel K. Inouye Center for Microbial Oceanography at the University of Hawai'i, teamed up with researchers from Korea, Switzerland and the U.S. National Oceanic and Atmospheric Administration to assess changes in nitrate concentration between the 1960s and 2000s across the open North Pacific Ocean.
Their analysis, which could discern human-derived nitrogen from natural nitrogen fixation, revealed that the oceanic nitrate concentration increased significantly over the last 30 years in surface waters of the North Pacific due largely to the enhanced deposition of nitrogen from the atmosphere.
"This is a sobering result, one that I would not have predicted," said Karl. "The North Pacific is so vast it is hard to imagine that humans could impact the natural nitrogen cycle."
The researchers used ocean data in conjunction with the state-of-the-art Earth System Model to reconstruct the history of the oceanic nitrate concentration and make predictions about the future state of the North Pacific Ocean. Their assessment revealed a consistent picture of increasing nitrate concentrations, the magnitude and pattern of which can only be explained by the observed increase in atmospheric nitrogen deposition.
Enhanced nitrogen deposition has several potential ecological ramifications. Because biological activity is limited by nitrate availability in the North Pacific Ocean, the input of new nitrogen from the atmosphere may increase photosysnthesis in the sunlit layers and export of carbon-rich organic material out of the surface ocean into the deep.
"The burgeoning human population needs energy and food - unfortunately, nitrogen pollution is an unintended consequence and not even the open ocean is immune from our daily industrial activities," said Karl.
Given the likelihood that the magnitude of atmospheric nitrogen deposition will continue to increase in the future, the North Pacific Ocean could rapidly switch to having surplus nitrate. Thus, past and future increases in atmospheric nitrogen deposition have the potential to alter the base of the marine food web; and, in the long term, the structure of the ecosystem.
In particular, the shift in nutrient availability could favor marine organisms that thrive under the high nitrate and low phosphorus conditions. If similar trends are confirmed in the Atlantic and Indian Oceans, it would constitute another example of a global-scale alteration of the Earth system. Further, the findings of this study of the North Pacific highlight the need for greater controls on the emission of nitrogen compounds during combustion and agricultural processes.
This research was supported by the Korean National Research Foundation of Ministry of Science, ICT and Future Planning, Science and Technology (Global Research Project), through a novel collaboration between scientists at Pohang University of Science and Technology and the University of Hawai'i. David Karl's participation was also supported by the U. S. National Science Foundation and the Gordon and Betty Moore Foundation through grants GBMF480.01 and GBMF3794.
I-N Kim, K Lee, N Gruber, D M Karl, J L Bullister, S Yang, T-W Kim (2014). Increasing anthropogenic nitrogen in the North Pacific Ocean. Science
Marcie Grabowski | 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
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
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In a paper published Jan. 21 in the journal Molecular Cell, the UC Davis team and their collaborators at the National Institutes of Health and Johns Hopkins University report that Bax, a factor known to promote cell death, is also involved in regulating the behavior of mitochondria, the structures that provide energy inside living cells.
Mitochondria constantly split and fuse. The proteins that control the splitting of mitochondria also promote a process called apoptosis, or programmed cell death. In contrast, the proteins that control mitochondrial fusion help protect against cell death. Cell death can happen when cells are starved of oxygen, for example during a heart attack or stroke.
Yeast have a single protein that controls outer membrane fusion, but both human and mouse cells have two proteins, called MFN1 and MFN2, which control outer membrane fusion. Using mitochondria from cells derived from genetically modified "knockout" mice, Suzanne Hoppins, a postdoctoral researcher at UC Davis, and Jodi Nunnari, a professor of molecular cell biology, studied how these two proteins work together and the role specific genes play in that process.
The research team discovered that these proteins combine with themselves or each other to form a tether between two mitochondria, leading to fusion. All three combinations -- MFN1/MFN1, MFN1/MFN2 and MFN2/MFN2 -- can promote membrane fusion, but the combination of MFN1/MFN2 is by far the most efficient, Hoppins said.
Hoppins also found that a soluble form of Bax, a protein that triggers apoptosis, can also stimulate mitochondria to fuse. It acts only through the MFN2/MFN2 combination, she found.
The form of Bax that promotes mitochondrial fusion is different from the type that leads to cell death, Nunnari said. Bax leads to cell death when it inserts itself in the mitochondrial membrane. In its soluble, free-floating form, it causes mitochondria to fuse instead.
MFN1 and MFN2 are found in different amounts in different body organs. MFN2 is more abundant in the brain and heart -- tissues where cell death can have disastrous consequences.
The paper shows how MFN2 could act to protect the brain or heart from cell death, by using Bax in a different form, Nunnari said.
"This shows that the fusion machine is both positively and negatively regulated in cells and opens doors to finding the regulatory mechanisms and discovering ways to increase or decrease the sensitivity of cells to apoptosis," Hoppins said. That could lead to new drugs that save cells, for heart disease and stroke, or that kill cells, for cancer.
Co-authors of the study are UC Davis graduate student Megan Cleland; UC Davis postdoctoral researchers Frank Edlich and Soojay Banerjee; and Richard Youle, a senior investigator at the National Institute for Neurological Disorders and Stroke; and J. Michael McCaffery, a professor at Johns Hopkins University.
The research was supported by grants from the National Institutes of Health. Hoppins recently received a K99 "Young Investigator" award from the NIH.Media contact(s):
Andy Fell, UC Davis News Service, (530) 752-4533, firstname.lastname@example.org
Andy Fell | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell 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
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
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LIFE OF A COMET:
"MOVING AROUND THE UNIVERSE, COMETS ARE ETERNAL PIECES OF ROCK AND ICE FLYING IS SPACE. BUT A PLANET CAN GET IN THEIR WAY AND..."
What is the universe? An immense space whereplanets, galaxies, asteroids and comets move around. Stard systems are part of galaxies. Each galaxy moves abut in the cosmos.
There are also comets going around planet and galaxies. They usuallyfollow the same orbit so they visit the same places over and over again. They are pieces of rock and ice moing very fast. Some are small and some are large.
On March 23rd, 1993, three astronomers,Eugene Shoemaker, his wife Carolyn and David Levy observed some small points in the their 45-centimeter telescope at Palomar Observatory in San Diego, California (Unites States). At first, they did notknow what these small points were.
The comet was called "Shoemaker-Levy9". The comet was as big as a mountain. Astronomers calculated that it was ten kilometers wide! But that was not all. Itorbited Jupiter, the biggest planet in the solar system. And was on a collision course with it!.
yes, the " shoemaker-levy 9 " could crash into jupiter. astronomers and scientists were very excited.this was the first time that they could see this incredible event. also, the comet divided into 21 fragments so they could observe and study a multiple collision.
the comet and its fragments crashedinto jupiter between 6th and 22nd july 1994. the, people asked the question "can this happen to heart?" and the answer was "yes, it can"
scientists say that meteors fell to earth millions of yearsago. they also believe that comets and meteors killed dinosaurs. the impact of one of these rocks againts the surface of the planet is stronger than an atomic bomb and can produce a naturalcatastrophe.
LA VIDA DE UN COMETA:
"Desplazarse por el universo, los cometas son ETERNAS PIEZAS DE ROCK Y VUELO ICE es el espacio. PERO UN PLANETA PUEDE TENER en su camino y ..."
¿Cuál es el universo?...
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