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Mountains and other topographic features can have tremendous influence on precipitation. Rain shadows can be some of the driest places on Earth; the Atacama desert in the rain shadow of the Andes Mountains can go decades without receiving any rainfall. A number of factors including prevailing winds, topographic features and local weather patterns contribute to the formation of rain shadows, or dry regions on the protected side of some mountain ranges.
Prevailing winds are predictable winds that occur frequently in particular locations. When a mountain range runs perpendicular to prevailing winds, the winds carry moisture toward these mountains on the side facing the wind. If the winds have an extensive fetch -- the distance wind is able to travel over open water -- the air will accumulate considerable moisture. When prevailing winds push this moisture-laden air against topographic features like mountains, forcing it upward, rain results.
When wind meets mountains, the air rises and cools. The water vapor in the air condenses and rain falls. Orographic precipitation is the rain and snow that result when an air mass collides with a topographic feature. The windward sides of mountain ranges tend to be lush and rich with vegetation because of this rainfall. However, the lee sides of mountain ranges with these weather conditions are in the rain shadow and can be very dry.
Formation of a Rain Shadow
When orographic precipitation occurs, it depletes this air of its moisture. By the time the air passes over the mountains, it is relatively dry. As this dry air moves down the lee side of a mountain range, it warms and becomes capable of retaining even more water vapor. This increases evaporation in these areas as this dry air pulls moisture from the landscape and accelerates as it moves down the mountain. This can cause fierce Foehn winds, such as the the Santa Ana winds in southern California, which are common in rain shadows and can cause dramatic increases in temperature and decreases in humidity. Land in a rain shadow is arid, and cloud cover is scarce.
Regions with Rain Shadows
Rain shadows are common on the western coast of the United States, where mountain ranges run parallel to the coast and perpendicular to the prevailing winds coming off the Pacific Ocean. The Great Basin of Nevada and Utah is in the rain shadow of the Sierra Nevada Mountains. Dry basins can also be found in Washington and Oregon, east of the Cascade Mountains. In Mongolia and China, the Himalaya Mountains create a rain shadow in which the Gobi Desert is located. Rain shadows vary in size depending on wind conditions and topography. | <urn:uuid:152c09c8-39fb-4509-89e4-31671e6c5c54> | 4.3125 | 522 | Knowledge Article | Science & Tech. | 41.483952 | 95,545,839 |
Lunar Orbiter Photographic Atlas of the Moon
by D.E. Hughes, J.K. Bowker
Publisher: Lunar and Planetary Institute 1971
The Lunar Orbiter Photographic Atlas of the Moon by Bowker and Hughes (NASA SP-206) is considered the definitive reference manual to the global photographic coverage of the Moon. The images contained within the atlas are excellent for studying lunar morphology because they were obtained at low to moderate Sun angles.
Home page url
Download or read it online for free here:
by Stuart Ross Taylor - Lunar and Planetary Institute
The technical triumph of manned landings on the Moon and the return of samples from the lunar surface has provided scientists with a unique opportunity to advance our understanding of the nature, evolution and origin of the solar system.
by W. K. Hartmann, R. J. Phillips, G. J. Taylor - Lunar and Planetary Institute
Contents: History; Dynamical Constraints; Geochemical Constraints; Geophysical Constraints; Theories and Processes of Origin: Lunar Formation Involving Capture or Fission; Lunar Formation Triggered by Large Impact; and more.
by Philip J. Armitage - arXiv
An introduction to the theory of the formation and early evolution of planetary systems. Topics covered: the structure, evolution and dispersal of protoplanetary disks; the formation of planetesimals, terrestrial and gas giant planets; etc.
by Raymond M. Batson - NASA
Published in 1984 after several years of photographic analysis, this book presents maps of the six Saturnian moons which were investigated by the Voyager 1 and 2 spacecraft during their flyby missions of Saturn in 1980 and 1981, respectively. | <urn:uuid:679f9781-a919-42ae-9a60-bfd2673ec93c> | 2.875 | 352 | Content Listing | Science & Tech. | 35.823031 | 95,545,859 |
Community Contributor | Jul 3, 2018 | 0
Understanding Weather Not Predicting – 13 April 2012
The high interior plateau of southern Africa has a significant impact on the region’s weather. Frequently this geographical factor exerts its influence. This last week provided one more example.
For while, our air space has been non-committal: generally slack wind-flow, not adding much to the existing pattern, but also changing it much.
For the past week, quite an obvious layer of middle air moisture, turbulent in its slender depth too, has persisted..During the period, a gentle increase in potential could be observed. This is April, the ability for dual-weather patterns to exist, more-or-less side by side, is part of the expected scene. When the changed climate patterns are added to this, the whole scenario develops more potently.
The surface level, including the 1000 and 925hPa charts indicate anticyclonic cores hugging the 40oS latitude, at least frequently, and increasing the core pressures when absorbing weaker cores melding from lower (previously the more normal) latitudes. This does create a zone where these stronger cores cut off an area of slacker winds and declining pressures. These are also frequently more marked in the middle layers, again providing a zone for “weather” to develop.
At this time of year the weather focus lies more southerly across Namibia: this remains constant and, by Monday, some development was identifiable, extending into Tuesday.
With an astonishingly steep trough (particularly upper air) crossing the Cape, a brief respite occurred , quickly returning to the more favourable pattern with better shower prospects occurring. So setting the scene for an extension into the new week.
This overall synoptic pattern holds sway across the week end, with a cut-off development appearing over the ocean far to the west of the Orange river mouth, but inducing advection from, at least, the 25oS area, with rain expected:across the southern parts.
At this time of year, our northern parts have a drier prospect. but the upper anticyclonic control is less apparent. Its core is now further to the east creating some latent potential! The next steep upper trough appears far away to the south in the new week, but the range of its north-westerly, upper air input again holds promise. Few outlooks are hopeful, but the “local” potential is often overlooked, so an open mind persists across these few days.
After the weekend, the next pattern has a similar mix of distant southerly activity and an otherwise quiescent overhead airspace in which almost any condition can evolve. The possibility of an \Okavango shower is not ruled out, but a more extensive showery regime is expected to appear across our southern parts at least with support from an easterly inflow. Falls should be limited, but the activity off-shore should no be discounted. | <urn:uuid:8e7da258-278b-480c-b8c4-9af3b80a8ce7> | 2.890625 | 612 | News Article | Science & Tech. | 40.797917 | 95,545,866 |
Neanderthal News and the Limits of Organic Material Survival
May 13, 2015
Red blood cells and DNA samples raise questions about the decay time of soft tissue and genetic material.
It's Curtains for Enceladus
May 11, 2015
The geysers of Saturn's little moon are like sheets instead of jets, spelling trouble for theories of its ancient age and possible life.
Moon, Mercury, and Magnetic Fields
May 8, 2015
After the crash of MESSENGER, magnetic fields in the solar system have become a key topic for planetary science.
Geologists Have Underestimated Catastrophes
April 25, 2015
One Colorado storm in 2013 caused hundreds or thousands of years' worth of mountain erosion. This is causing a rethink on the power of catastrophic events.
What You're Not Being Told About Earth's Magnetic Field
April 17, 2015
The simple story for the public: a dynamo creates the earth's magnetic field. The real story: complex scenario needed to start it and keep it running.
Human Epoch or Epic Hubris?
April 11, 2015
Evolutionary geologists are toying with an idea for a new time period, the "Anthropocene Epoch." What for?
Solving Moon Origin Unsolves the Last Solution
April 9, 2015
The moon's origin has been "demystified," scientists are claiming. That's what they said last time.
How Rocks Can Look Older Than They Are
April 8, 2015
Researchers find that the most common dating method can produce "spuriously old" dates.
Of Brontosaurus, Cartoons, and Revisionism
April 7, 2015
With the resurrection of Brontosaurus as a valid dinosaur name after a century of repudiation, what's a kid to think? Thoughts on science's arbitrary and tentative nature.
Messages from Mercury
April 6, 2015
With MESSENGER in its final days before impact, the innermost planet has become a familiar place.
Animal Excellence Exceeds Mere Survival
April 4, 2015
A tiny bird could live like other birds do without having to fly non-stop for 1,700 miles. Other examples abound of over-design in the animal world.
Orbital Ice Age Theory Melts
March 23, 2015
Orbital cycles do not cause ice ages, a new study suggests. Instead, the whole world experienced an ice age at the same time.
Geology Upset: Wind Carves Canyons Fast
March 19, 2015
According to a new study, wind carves canyons ten times faster than water. This has implications for theories on Mars and Earth.
Water Worlds Tempt with Life, Not Youth
March 13, 2015
More and more planets and moons are suspected of having liquid water, but what should be the logical implications?
Physical and Geological Hurdles on the Darwinian Race
March 7, 2015
Can the smooth big-bang-to-brain story of evolution jump the physical and geological hurdles along the way? | <urn:uuid:d3d96698-5238-4e4d-bdf9-7f862b459294> | 2.75 | 636 | Content Listing | Science & Tech. | 53.6 | 95,545,879 |
Calculate the side of a square with a diagonal measurement 10 cm.
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In rectangle ABCD with sides |AB|=19, |AD|=16 is from point A guided perpendicular to the diagonal BD, which intersects at point P. Determine the ratio ?. | <urn:uuid:f355f3b5-44c9-4c77-8c0e-20ae1fd3e9f3> | 3.359375 | 741 | Tutorial | Science & Tech. | 74.13231 | 95,545,929 |
By Dan Rubinstein
Photos by Luther Caverly and DEAP
In a cramped passageway that leads to the cavernous Cube Hall at SNOLAB, a world-class science facility deep below the surface of the planet at Vale’s Creighton nickel mine in Sudbury, Ont., Carleton Physics Prof. Mark Boulay climbs a stepladder to inspect a cooling system built around a 3,000-litre tank of liquid nitrogen.
The constant supply of cryogenic nitrogen is fed downward through a series of tubes and apertures to a two-inch-thick spherical acrylic vessel, where it keeps 3.6 tonnes of argon in liquid form at a temperature of about -180 Celsius.
That argon is the core of the DEAP-3600 experiment — an attempt to detect an invisible substance known as dark matter, which is thought to account for roughly one-quarter of the universe’s energy density. Dark matter is believed to outweigh normal matter (the atoms we are familiar with) by a factor of five to one, even though its existence has so far only been inferred by its gravitational effects on stars and galaxies and other indirect measurements.
With the two kilometres of rock overhead blocking most of the cosmic radiation that reaches Earth, and with 10 times more sensitivity than any other comparable experiment, the DEAP detector could allow scientists to observe and identify dark matter by tracking the faint light pulses that result from elastic scattering of dark matter particles when they hit argon nuclei. But before they can solve a mystery that has been confounding physicists for decades, Boulay and his collaborators — a group of more than 75 researchers from 10 institutions in Canada, the United Kingdom and Mexico — must first address a seemingly endless string of details.
Today, up on that ladder, several months after the experiment was first fired up in November 2016, Boulay and SNOLAB Operations Supervisor Tony Flower are trying to figure out how to fix a bug in the cryogenic system. When it runs, as it is expected to do for years, it vibrates, and that movement appears to be damaging and loosening some of its components and fittings.
“This is typical of the lower-level mechanical problems we’re sorting out,” says Boulay, DEAP’s project director and a Canada Research Chair in Particle Astrophysics and Subatomic Physics.
“We’re certainly dealing with a lot of technical and engineering challenges, but the concept of a particle scattering off a nucleus like a billiard ball is fairly straightforward. At a fundamental level, what we’re doing is pretty simple, yet it’s one of the biggest questions in particle physics, and maybe in science.
“This is by far the dominant stuff in the universe,” he says about dark matter, “and we still have essentially no clue what it is.”
Zeroing in on the
Quest for Dark Matter
In a sense, Boulay was destined to lead DEAP. He was born and raised in Sturgeon Falls, an hour east of Sudbury on the Trans-Canada Highway, and became interested in physics at a young age. “The thing I liked about it,” he says, “is that you’re required to understand some fairly simple concepts but there’s very little memorization, which I was never very good at. So I always excelled in physics, because once you understand a few basic concepts you can go a long way.”
Boulay earned an undergraduate degree in physics at Laurentian University in Sudbury when the Sudbury Neutrino Observatory experiment was starting, exposing him to particle physics, and stayed at Laurentian for his master’s degree. He got involved in the final assembly of the SNO detector while working toward his PhD at Queen’s University, and had an opportunity to analyze its first results. Then he zeroed in on the quest for dark matter.
The term “dark matter” was coined in the 1930s by Swiss astronomer Fritz Zwicky, who, according to the DEAP website, “determined the mass and velocity distributions of objects within the Coma galaxy cluster and found that the velocity distributions he calculated implied the cluster had much more mass than the observable light suggested.”
Forty years later, American astronomer Vera Rubin corroborated the existence of dark matter by studying the rotation of galaxies and concluding they “rotated too fast for the gravitational force of their visible stars to hold them together.” Her results “pointed to the existence of vast amounts of unobservable mass, even 10 times more than visible, surrounding galaxies of stars.”
Several dozen experiments around the world are currently on the hunt for dark matter, including work at the Large Hadron Collider near Geneva, the LUX underground experiment in South Dakota, the XMASS project at Japan’s Kamioka Observatory, and the IceCube Neutrino Observatory, a particle detector at the South Pole.
But DEAP, which was conceived around 2004, when Boulay was doing post-doctoral studies at the Los Alamos National Laboratory in New Mexico, represents perhaps the best shot scientists have. Its potential is rooted in the unique properties of argon, which will help researchers discriminate backgrounds when they study the recoil of scattering particles, as well as the large volume of argon being deployed. Every other component of the detector has an extremely low level of radioactivity, which will allow the experiment to capitalize on the sensitivity of its location deep underground at SNOLAB.
Scaling up the DEAP Detector
In 2006, Boulay led the development of a small prototype detector with liquid argon at Queen’s to demonstrate that this process could work. That design, and expertise from the SNO experiment, informed the construction of the full-scale version.
The argon vessel, which has an inner radius of 85 centimetres, is surrounded by 255 photomultiplier tubes (PMTs) to capture the light pulses, and the whole apparatus is immersed in a water tank to further block external radiation. Since it was turned on last November, much of the focus at DEAP has been calibrating the detector and collecting preliminary dark matter search data in anticipation of collecting up to 10 to 15 dark matter scattering events during the full four-year detector running period.
When the detector is triggered by a radioactive event, data is recorded from each of the PMTs at a rate of about five megabytes of data per second. That will add up to roughly 250 terabytes per year. All this information is stored (and backed up) at a data centre that’s part of the Compute Canada network and is analyzed by researchers from the project’s partner institutions.
The DEAP team released the experiment’s first results at a conference in Sudbury in late July, a paper that demonstrated the best-ever rejection of radioactive backgrounds using liquid argon, and the lowest level ever achieved of background radon, one of the most troublesome backgrounds in dark matter searches.
“The early indications are positive,” Boulay says about the data analysis conducted to date. “We know that dark matter exists and affects our universe at many scales. The hypothesis that many people have is that it’s a new particle that we’ll be able to detect directly. What we don’t know is that mass of that particle, or how often it will interact with regular matter. When you mount an experiment like this, those two parameters are unknowns, and if you observe something you can pinpoint which sets of those parameters — dark matter particle mass and its probability of interacting — are consistent with the observation. If you don’t see anything, you can rule out part of that parameter space and push farther and farther down in sensitivity.
“It’s extremely exciting be part of this experiment,” he continues. “It’s exciting to have the world’s leading facility for underground science so easily accessible to us. At any point in the next six months or year, we may for the first time see direct evidence of this material that essentially the universe is made of. It would certainly be a paradigm shift. Once you have direct observation of a dark matter particle, you can start looking in more detail at the data and rule out or rule in various theories of particle physics. It will provide a road map for where to go in particle physics.”
A Natural Evolution
After getting his training and starting his research career on the SNO experiment, DEAP is a natural evolution for Boulay. There’s pressure to maintain the high standards that were set with SNO, he says. In a sense, that foundational work would be considered low-hanging fruit today — “they knew what they were looking for” — whereas DEAP is more of a voyage into the unknown.
“With SNO, we knew one way or the other, as long as the experiment could be made to work technically, that the answer would be extremely interesting,” says Boulay. “Most experiments right now in particle astrophysics are probing the unknown. In the case of SNO, we knew we would either see that neutrinos changed flavour or they didn’t — and either one of those would have been a momentous result. Now we’re searching for things with experiments such as DEAP and nEXO and there’s not really a firm prediction about what we will see. So, we’re more in a search mode, trying to discover the unknown.
“The way I would phrase it: we’re opening a new window on the universe that we haven’t looked through before.”
A Leap Forward for Heritage Conservation
Although the tools they use have evolved over the years, architects have always designed and built physical structures and objects. A pair of jointed-arm industrial robots recently acquired by the Carleton Immersive Media Studio (CIMS)... More
A Carleton Alum’s Dream Comes True
The ship is called the Ocean Dream – an appropriate name for the adventures that Carleton alumnus Sebastien Cloutier had while on board. Cloutier had been to Japan twice. He worked as an ESL instructor... More
Ravens Soccer Player Makes History
Carleton Ravens Soccer player Idir Zerrouk made history by becoming the youngest player to score a goal at the university sports level. | <urn:uuid:04f8ac6f-a085-4aa0-a334-e9c9c4ed93a2> | 3.1875 | 2,189 | News Article | Science & Tech. | 39.371971 | 95,545,947 |
A new study has examined the poststorm impact and the short-term recovery from Ivan along a 200-km stretch of coast from Fort Walton Beach to St. George Island. The study is published in the latest issue of the Journal of Coastal Research.
Hurricane Ivan made landfall along the northwestern Florida and Alabama coast on September 16, 2004. It briefly reached Category 5 strength, persisting as a strong Category 4 hurricane in the Gulf of Mexico before being downgraded to a strong Category 3 at landfall by the U.S. National Hurricane Center.
A team of researchers from the University of South Florida conducted one prestorm and three poststorm beach-profile surveys to understand the morphological changes created by Ivan and also the poststorm recovery. Included in the assessment was an excavation of 46 trenches to study the characteristics and thickness of subaerial storm deposits.
Storm impact along barrier island coasts has been the subject of numerous studies. Because of the largely unpredictable nature of extreme storms like hurricanes, most studies concentrate on poststorm impact and behavior, whereas collection of prestorm data is typically not conducted, making it difficult to quantify the dramatic morphological impact of storms as well as poststorm recovery.
What the study found was apparent, and dramatic morphological and sedimentological impacts extended more than 300 km eastward from the center of the hurricane. Extensive inundation and overwash occurred within 100 km from the storm center at landfall. The highest elevation of beach erosion extended considerably above the measured storm-surge level, indicating that storm-wave setup and swash run-up played significant roles in controlling the elevation of beach erosion.
Beach recovery began immediately after the storm. Within 90 days, the berm crest recovered to its prestorm elevation, although it was now located 15 m landward.
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
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Evolution of the Sex Ratio in the Wood Lemming, Myopus schisticolor
The wood lemming (Myopus sohisticolor Lilljeborg) has probably the most unequal sex ratio of all mammals. (The facts in this paragraph are taken from Kalela and Oksala 1966, and Frank 1966.) In wild populations the frequency of males is normally between 0.20 and 0.30. This unequal sex ratio is also found in animals kept in captivity. Kalela and Oksala report that among 1073 new-born lemmings in a population which started from 6 males and 11 females, the frequency of males was only 0.248. The scarcity of males seems to be due to the existence, both in natural and captive populations, of females which mainly or exclusively produce female offspring.
KeywordsCaptive Population Meiotic Drive Equilibrium Frequency Linked Modifier Linked Factor
Unable to display preview. Download preview PDF. | <urn:uuid:0e054ed0-2e8b-4d99-9715-be6e4351c5e5> | 3.140625 | 197 | Truncated | Science & Tech. | 46.224545 | 95,545,973 |
In this article we will check what are constants in C#.Net.
You can also check out Constructor and Destructors in C#.Net, Common Language Runtime in C#.Net and Interfaces in C#.Net.
A constant is a variable whose value cannot be changed throughout its lifetime. We have to use const keyword to declare a constant like below:
const int number = 10;
some points to remember while working with constant:
– They must be initialized when they are declared; and after a value has been assigned, it can never be overwritten.
– The value of a constant must be computable at compile time. You can’t initialize a constant with a value taken from a variable. If you need to do this, you must use a read-only fi eld
– Constants are always implicitly static. | <urn:uuid:3f69a370-ef1e-48f9-a848-cb773141987d> | 3.46875 | 177 | Truncated | Software Dev. | 60.625678 | 95,545,976 |
Mass: Mass is a fundamental universal property that gives a body inertia, or that is a measure of its inertia and the amount of matter it contains, giving the body a gravitational field of its own. So, we can say that mass is directly proportional to inertia, and the amount of matter a body contains; the more mass an object has, the more inertia it will embody. We should not confuse mass with weight, for weight is the pull of gravity. For example, a truck weighing 20 tons on the surface of the earth, out there in space free from the force of gravity, the truck will be weightless, but it will continue to have mass and inertia.
Inertia: Inertia is the property that a body has to maintain its state of motion, or rest, in which it finds itself. Inertia is directly proportional to mass and to the gravitational field a body has, that is to say, the more mass a body contains, the more inertia it deploys, and the stronger the gravitional field it will exert. | <urn:uuid:3219d5e6-054c-4647-a0a6-65234707daa0> | 4 | 213 | Knowledge Article | Science & Tech. | 46.021086 | 95,545,991 |
The dramatic images of natural disasters in recent years, including hurricanes Katrina and Sandy and the Tohoku, Japan, earthquake and tsunami, show that nature, not the people preparing for hazards, often wins the high-stakes game of chance.
"We're playing a high-stakes game against nature without thinking about what we're doing," geophysicist Seth Stein of Northwestern University said. "We're mostly winging it instead of carefully thinking through the costs and benefits of different strategies. Sometimes we overprepare, and sometimes we underprepare."
Stein will discuss his research in a presentation titled "How Much Natural Hazard Mitigation is Enough?" at the American Association for the Advancement of Science (AAAS) annual meeting in Chicago. His presentation is part of the symposium "Hazards: What Do We Build For?" to be held from 9:45 a.m. to 12:45 p.m. Central Standard Time Monday, Feb. 17, in Grand Ballroom B of the Hyatt Regency Chicago.
Stein is the William Deering Professor of Geological Sciences in Northwestern's Weinberg College of Arts and Sciences. He is the author of a new book, "Playing Against Nature: Integrating Science and Economics to Mitigate Natural Hazards in an Uncertain World" (Wiley, 2014) and the book "Disaster Deferred: A New View of Earthquake Hazards in the New Madrid Seismic Zone" (Columbia University Press, 2010).
Sometimes nature surprises us when an earthquake, hurricane or flood is bigger or has greater effects than expected. In other cases, nature outsmarts us, doing great damage despite expensive mitigation measures or causing us to divert limited resources to mitigate hazards that are overestimated.
"To do better we need to get smarter," Stein said. "This means thoughtfully tackling the tough questions about how much natural hazard mitigation is enough. Choices have to be made in a very uncertain world."
Stein's talk will use general principles and case studies to explore how communities can do better by taking an integrated view of natural hazards issues, rather than treating the relevant geoscience, engineering, economics and policy formulation separately.
Some of the tough questions include:
• How should a community allocate its budget between measures that could reduce the effect of future natural disasters and many other applications, some of which could do more good? For example, how to balance making schools earthquake resistant with hiring teachers to improve instruction?
• Does it make more sense to build levees to protect against floods or to prevent development in the areas at risk?
• Would more lives be saved by making hospitals earthquake resistant or by using the funds for patient care?
The choice is difficult because although science has learned a lot about natural hazards, Stein says, our ability to predict the future is much more limited than often assumed. Much of the problem comes from the fact that formulating effective natural hazard policy involves combining science, economics and risk analysis to analyze a problem and explore costs and benefits of different options in situations where the future is very uncertain.
Because mitigation policies are typically chosen without such analysis -- often by a government mandate that does not consider the costs to the affected communities -- the results are often disappointing.
Megan Fellman | EurekAlert!
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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:f0bda9c7-a7f7-4fd4-827e-4de0a6a4fdc3> | 3.015625 | 1,299 | Content Listing | Science & Tech. | 36.372366 | 95,546,014 |
National Radio Astronomy Observatory | Long Baseline Observatory | 2018 Jul 09
Plasma-Spewing Quasar Shines Light on Universe's Youth, Early Galaxy FormationAstronomers using the National Science Foundation’s Very Long Baseline Array (VLBA) have made an image revealing tantalizing details of a quasar nearly 13 billion light-years from Earth -- an object that may provide important clues about the physical processes at work in the universe’s first galaxies.
The scientists studied a quasar called PSO J352.4034-15.3373 (P352-15), an unusually bright emitter of radio waves for an object so distant. The extremely sharp radio “vision” of the VLBA showed the object split into three major components, two of which show further subdivision. The components are spread over a distance of only about 5,000 light-years. ...
The astronomers said the three major components of P352-15 can be explained in one of two ways. One explanation is that they’re seeing the bright core of the quasar, corresponding to the location of the supermassive black hole itself, at one end, and the two other bright spots are parts of a one-sided jet. The other possibility is that their middle object is the core, and the other objects are jets ejected in opposite directions. Because one of the end objects is closest to the position of the quasar as seen with visible-light telescopes, they consider the one-sided jet to be the more likely explanation.
The one-sided jet explanation raises the exciting possibility that astronomers may be able to detect and measure the expansion of the jet by observing P352-15 over several years. ...
Carnegie Institution for Science | 2018 Jul 09
A Powerful Radio-Loud Quasar at the End of Cosmic Reionization - Eduardo Banados et al
- arXiv.org > astro-ph > arXiv:1807.02531 > 06 Jul 2018
- arXiv.org > astro-ph > arXiv:1807.02560 > 06 Jul 2018 | <urn:uuid:04b17f0b-86fa-4db3-86ca-de3b3719def5> | 2.953125 | 437 | Content Listing | Science & Tech. | 52.924231 | 95,546,021 |
We may say a thing is at rest when it has not changed its position between now and then, but there is no ‘then’ in ‘now’, so there is no being at rest. Both motion and rest, then, must necessarily occupy time.
Aristotle, 350 BC
there are two things off the top of my head that zeno's paradox are applicable to:
1. creating life
let's look at creating life. on some level the interchanging of DNA to create a new life would be like becoming one. while observing the stages of meiosis, the division of sex cells, you can see an extraordinary example of a kind of blending, reaching one, and then becoming another one. however, if you examine the stages of cellular reproduction more closely, smaller parts of cells, take chromosomes for instance, don't become one, but join together and form an X, taking one arm and leg from each donor to go on and become a separate entity from the original two donors.
i don't claim to be an expert in chemistry or math (haha!) but fusion is so neat. from my basic understanding nuclear fusion is when multiple nuclei joining together to create a heavier single nucleus. i do believe it takes intense force or heat to make this happen (thus we conclude the heavy elements are results of stars violent exploding deaths). there is a one-ness to fusion. although, i am sure just as the life example, there are infinitesimally smaller particles which remain in tact as their own and don't become one, just a smaller part of a bigger or different one.
so, in my own equations:
creating life- 1a + 1b = 1c
too bad math doesn't work like either of these!
i don't think i solved zeno's paradox. the solution should look like 1a+1b=1? or 1+1=1? or 1+1=1x?
it is interesting to me that some of the "solutions" include there is a point (.999r) that = 1. how can quantum particles exist if we eventually convert .999r to 1?
1/3 = .333... +
2/3 = .666...=
3/3 = .999...
firstly, that's not how infinity works (that would mean there is an end) and secondly, i am seeing the application of the leap from .999r to 1 being the negation of some particles because they are unobserved. (Higgs Boson for instance). i realize calculus has solved this problem:
i guess i just need to understand how by turning .999r into 1 mathematically isn't disqualifying a whole infinite world of possibilities. | <urn:uuid:f2e39633-bc83-4787-b8c7-3b6db19d617a> | 3.0625 | 567 | Comment Section | Science & Tech. | 69.854615 | 95,546,031 |
© 2016 Dr. Joachim Nerz (1 of 66)
Country distribution from AmphibiaWeb's database: United States
Desmognathus monticola Dunn, 1916
Carlos D. Camp1
1. Historical versus Current Distribution. Seal salamanders (Desmognathus monticola) range throughout the central and southern Appalachians from western Pennsylvania to central Alabama. Disjunct populations occur in the coastal plain of southern Alabama and the Florida Panhandle (Rose and Dobie, 1963; Means and Longden, 1970; Mount, 1975; Caldwell and Folkerts, 1976). Seal salamanders are most commonly found below elevations of 1,219–1,372 m, although they occur as high as 1,555 m (Hairston, 1949; Organ, 1961a). Seal salamanders are commonly used as fish-bait in the southern Appalachians. In a recent survey of bait shops in northern Georgia, seal salamanders made up 67% of salamanders sold as “spring lizards” (Jensen and Waters, 1999). The introduction of other desmognathines into uninhabited areas has been attributed to the bait trade (Martof, 1953b). Because of the widespread use of seal salamanders as bait, this species may have been introduced into new areas by anglers.
2. Historical versus Current Abundance. It is likely that certain populations of seal salamanders have suffered due to collection for fish bait and other human activities. One technique of bait collection, which may have a negative effect, involves pouring liquid bleach into small, high-gradient streams to drive out salamanders. Because salamanders thus collected have low survivabilities, wholesale purchasers (i.e., owners of bait shops) generally do not buy salamanders from such collectors more than once, and this attitude may restrict usage of the bleach (Jensen and Waters, 1999). Acidification of streams due to mine drainage may affect seal salamanders. Roudebush (1988) showed that feeding rates were depressed in salamanders exposed to low pH levels. Petranka et al. (1993) demonstrated that clearcut timber harvesting negatively affects the number of total Desmognathus individuals, including seal salamanders. They estimated that, at the rate of clearcutting carried out during the 1980s and early 1990s, the Appalachian forests of North Carolina lost as many as 14 million salamanders of all species each year during that time. However, Ash and Bruce (1994) strongly disagreed with these estimates and did not consider clearcutting to have as strong an impact on native salamanders. No significant change in abundance was noted in 20 yr of seal salamander surveys carried out in undisturbed habitats in the Appalachian Mountains of southwestern North Carolina (Hairston, 1996).
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Seal salamanders are not known to migrate. Mating occurs in the fall and spring in Virginia (Organ, 1961a). Brock and Verrell (1994) observed mating in July–November in specimens collected in southwestern North Carolina. Organ (1961a) suggested a biennial breeding cycle in females; his conclusions of biennial oogenic cycles in desmognathines have been questioned, however (Tilley, 1968, 1977; Tilley and Tinkle, 1968). Eggs have been found from mid June to August (Pope, 1924; Organ, 1961a; Folkerts, 1968; Bruce, 1990; Camp, 1997a).
ii. Breeding habitat. Mating presumably occurs in the same areas that are optimal for non-reproductive activities. Adult male and female seal salamanders have been observed occupying common refugia during late summer in Georgia (C.D.C., personal observations). Mating involves orientation of the male to the female, chemical and tactile stimulation of the female by the male, and the “tail-straddle walk” characteristic of other plethodontids (Organ, 1961a; Brock and Verrell, 1994).
i. Egg deposition sites. Eggs are attended by females and are laid in or near running water. Eggs may be buried in nests in streambeds (Bruce, 1990) > 30 cm below ground (Organ, 1961a). Petranka (1998) reports finding eggs in leaf clumps. Egg clutches have been found in seepages flowing under rocks (Folkerts, 1968), under moss next to flowing water (Pope, 1924), and in crevices in wet cliffs (Camp, 1997a). Eggs are attached, typically to the underside of a rock, in either a monolayer or in a loose group, 2–3 eggs thick (Pope, 1924; Folkerts, 1968).
ii. Clutch size. Egg numbers range from 13–39 (Pope, 1924; Organ, 1961a; Folkerts, 1968; Camp, 1997a). Clutch sizes determined from eggs collected in the field averaged 27 and 22 in Virginia (Organ, 1961a) and Alabama (Folkerts, 1968), respectively. Clutch sizes determined from the numbers of developing oocytes are independent of female size (Tilley, 1968). Eggs range in diameter from 4.0–4.8 mm (Bruce, 1989; Camp, 1997a). Incubation time is 1–2 mo, and hatching occurs at 11–12 mm SVL (Folkerts, 1968; Bruce, 1990).
i. Length of larval stage. Larvae overwinter and metamorphose in either the spring or early to mid summer, suggesting a larval period of 8–13 mo (Organ, 1961a; Juterbock, 1984; Bruce, 1989).
ii. Larval requirements.
a. Food. Unreported. Larvae probably feed on small aquatic arthropods.
b. Cover. Larvae typically occur along small gravelly bars and rocky seepage areas in streams (Folkerts, 1968).
iii. Larval polymorphisms. Larvae of this species do not exhibit distinct polymorphisms.
vi. Features of metamorphosis. Metamorphosis occurs at approximately 14–16 mm SVL (Organ, 1961a; Folkerts, 1968; Juterbock, 1984; Bruce, 1989, 1990, 1995; Bruce and Hairston, 1990).
v. Post-metamorphic migrations. This species is not known to migrate.
vi. Neoteny. This species is not known to exhibit neoteny.
D. Juvenile Habitat. Metamorphosed seal salamanders are nocturnal, emerging from under rocks, logs, or stream-bank burrows (Brandon and Huheey, 1971; Shealy, 1975; Hairston, 1986). Juveniles and adults use different microhabitats based on cover size, moisture levels, and coarseness. Adults are found under larger, moister, coarser objects; juveniles appear to avoid adults, and thus these sites (Krzysik and Miller, 1979; Colley et al., 1989). Juveniles shift their choices of substrates in the presence of adults (Colley et al., 1989). Intraspecific competition for cover objects may occur (Brandon and Huheey, 1971; Kleeberger, 1984). Juveniles are located closer to water in streambeds, on average, than adults (Hairston, 1986). Immature seal salamanders occasionally are found wandering on the faces of wet cliffs (C.D.C. and S.G.T., personal observations).
E. Adult Habitat. Seal salamanders most commonly are found in hardwood forests in association with small- to medium-sized streams containing cool, well-aerated water (Petranka, 1998). Seal salamanders are found under cover objects in association with streambanks and uninundated portions of streambeds, rather than in the stream channel proper (Hairston, 1949; Organ, 1961a; Krzysik, 1979). They are also common in seepages (Organ, 1961a), although they typically do not occur as close to the headwaters of seeps as members of the D. ochrophaeus complex (C.D.C. and S.G.T., personal observations). Seal salamanders occasionally use crevices associated with wet cliffs as refugia (Tilley, 1980; Camp, 1997a). Adult males have been observed to share crevices in wet cliffs with adult females (Camp, 1997a; C.D.C., personal observations).
Following heavy rains, seal salamanders may temporarily leave streams and stream banks and forage in surrounding forest (Kleeberger, 1985), occasionally climbing on tree trunks 1–2 m above the ground (Petranka, 1998).
F. Home Range Size. Generally small, estimated to be 0.07–0.45 m2 in one study (Kleeberger, 1985) and 8.4 m2 in another (Hardin et al., 1969).
G. Territories. Seal salamanders defend cover sites from conspecifics of either sex (Keen and Sharp, 1984; Keen and Reed, 1985). They defend feeding cover sites significantly more than they do non-feeding cover sites. Individuals of this species move among refugia, defending whichever refugia they happen to inhabit. Therefore, Keen and Sharpe (1984) suggested that seal salamanders possess mobile territories. A similar pattern is seen in black-bellied salamanders that move among a small set of favored refugia, functionally maintaining a constant territory through a combination of aggressive defense and pheromonal advertisement (Camp and Lee, 1996). Camp (2003a) reports an instance of intraspecific aggression in seal salamanders.
H. Aestivation/Avoiding Dessication. Unlikely. Surface activity peaks in April and declines with summer. Winter rains may trigger additional surface activity (Shealy, 1975; Petranka, 1998). Individuals are active at the surface in the southern part of their range during periods of warm temperatures throughout the winter (C.D.C., personal observations).
I. Seasonal Migrations. This species is not known to migrate.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. Seal salamanders are sympatric with a variety of combinations of congeners throughout their range. Over much of their range, seal salamanders are syntopic with members of the dusky salamander (D. fuscus) and/or mountain dusky salamander (D. ochrophaeus) complexes. Members of monticola-fuscus-ochrophaeus assemblages in Pennsylvania assort positively by body size and substrate-particle size. Seal salamanders, being the largest members, choose the coarsest substrates. They are also the most aquatic species among this group, preferring moister substrates than either of their two sympatric congeners (Krzysik, 1979). Likewise, seal salamanders are more aquatic than their smaller, sympatric counterparts (Ocoee salamanders [D. ocoee] and D. conanti [spotted dusky salamanders]) in Alabama (Folkerts, 1968). Seal salamanders and Ocoee salamanders segregate spatially and temporally in the Piedmont of South Carolina, with seal salamanders being more aquatic and diurnal than Ocoee salamanders (Shealy, 1975). In experimental, laboratory-based trials, seal salamanders are more aggressive toward dusky salamanders than to conspecifics (Keen and Sharp, 1984). Choices of substrate moisture and sizes of cover objects by either of these two species were not affected by the presence of the other, although activity of dusky salamanders was depressed by presence of seal salamanders (Keen, 1982). Tilley (1997) speculated that interactions with seal salamanders may have contributed to the isolation and genetic differentiation of units of the D. ochrophaeus complex.
Throughout much of the southern Appalachian region, seal salamanders are sympatric with at least two congeneric species. They often occur syntopically with black-bellied salamanders (D. quadramaculatus) and members of the D. ochrophaeus complex. They additionally may occur with shovel-nosed salamanders (D. marmoratus) and seepage salamanders (D. aeneus), as well as dusky salamanders. Except for the completely aquatic shovel-nosed salamander, these species assort by body size along the stream-forest interface with larger species being more aquatic and smaller ones occurring more terrestrially. This pattern is evident both along a horizontal gradient from stream-stream bank-forest and along a vertical gradient from stream-seepage-forest (Organ, 1961a). Seal salamanders are intermediate in both body size and habitat preference, occurring along stream banks, in uninundated parts of streambeds, and seepages. The observed pattern of desmognathine assortment was explained initially as niche partitioning among competitors (Hairston, 1949; Organ, 1961a). Tilley (1968) and Hairston (1980c), however, suggested that interspecific predation was a more likely cause. A number of studies attempted to determine which was the more probable factor (e.g., Kleeberger, 1984; Carr and Taylor, 1985; Hairston, 1986; Southerland, 1986a,b,d). They generally concluded that some combination of predation and aggressive interference were important factors in interspecific desmognathine interactions. Hairston (1986) made the strongest case for predation, with competition being a secondary factor. His statistical methods have been criticized, however (Jaeger and Walls, 1989). Although large desmognathines readily eat small ones in artificial environments, there is no evidence from extensive dietary studies that either black-bellied salamanders or seal salamanders are significant predators of heterospecific congeners (Camp, 1997b). Nevertheless, some researchers hold that predation by large species may have been important historically in the organization of desmognathine communities. Alternative hypotheses based on abiotic factors rather than biotic ones, such as competition and predation, have recently been proposed (Bruce, 1996; Camp et al., 2000). The lack of predation under natural conditions is probably a result of differential habitat selection and behavioral avoidance, perhaps involving chemical cues, of larger congeners by small individuals. The activity levels of dusky salamanders are depressed by the presence of larger seal salamanders (Keen, 1982), and both activity levels and substrate choices of seal salamanders are altered by the presence of larger black-bellied salamanders in experimental tanks (Carr and Taylor, 1985; Roudebush and Taylor, 1987a). Seal salamanders avoid chemical extracts of black-bellied salamanders under experimental conditions (Southerland, 1986a; Roudebush and Taylor, 1987b; Jacobs and Taylor, 1992). Keen (1985), however, suggested that interspecific aggression between these two species may not be more important than intraspecific interactions. The presence or absence of black-bellied salamanders did not affect the dispersion of seal salamanders in a study by Grover (2000).
L. Age/Size at Reproductive Maturity. Adult size varies among populations. Bruce and Hairston (1990) reported size data on two populations in southwestern North Carolina. Adult males at Wolf Creek averaged 57 mm (range = 46–72) SVL, and those from Coweeta averaged 67 mm (range = 48–80) SVL. Adult females averaged 59 mm (range = 53–65) and 64 mm (range = 52–76) SVL, respectively, at the same two sites. Castanet et al. (1996) and Bruce et al. (2002) aged individuals of these same populations using skeletochronology. They found that males and females at each site mature at 4-6 yr and 5-7 yr, respectively. Bruce et al. (2002) showed, however, that more individuals at Coweeta matured at later ages than those at Wolf Creek. Adults measured from northern Alabama had respective average SVLs for males and females of 64 mm and 57 mm; those from the Alabama Coastal Plain averaged 68 mm and 59 mm for males and females, respectively (Folkerts, 1968). Duncan (1967) reported maximum sizes for seal salamanders in Virginia to be 78 mm for males, 67 mm for females. Series of salamanders examined from Kentucky and North Carolina indicated that maturity was reached at 42 mm in males, 48 mm in females (Juterbock, 1978).
Adult seal salamanders exhibit male-biased sexual size dimorphism. Although males mature at smaller sizes and earlier ages than females, males reach larger maximum sizes than females. This results from females having more depressed post-maturation growth rates than males (Bruce, 1993; Castanet et al., 1996).
M. Longevity. Castanet et al. (1996) and Bruce et al. (2002) aged individuals using skeletochronological techniques and reported that females live at least 9 yr and males live at least 11 yr. Bruce and Hairston (1990) suggested greater potential longevity for animals in a population characterized by delayed maturity and larger body size.
N. Feeding Behavior. Nocturnal. Animals emerge from daytime retreats under logs and rocks or from stream-bank burrows to forage. Juveniles actively move about to forage, whereas adults are more likely to sit in the entrances to their burrows and wait for prey (Brandon and Huheey, 1971; Kleeberger, 1985; C.D.C., personal observations). Surface activity peaks around midnight, with a second bout of activity near sunrise (Hairston, 1949, 1986; Shealy, 1975). Both juveniles and adults feed on aquatic and terrestrial invertebrates including true bugs, stoneflies, caddisflies, lepidopterans, beetles, mayflies, dipterans, wasps, ants, odonates, millipedes, and earthworms (Hairston, 1949; Duncan, 1967; Krzysik, 1979; Kleeberger, 1982). Larger animals eat larger prey items (Krzysik, 1979). Seal salamanders have been reported to occasionally eat other salamanders (Shealy, 1975; Bernardo, 2002); however, evidence from dietary studies suggests that predation on other salamanders occurs rarely under natural conditions (Camp, 1997b). Brown et al. (2003) report a seal salamander taking an especially large (35 mm, 74.5% of the salamander's SVL) hesperiid lepidopteran larva.
O. Predators. Natural predators are not reported (Petranka, 1998). Spring salamanders (Gyrinophilus porphyriticus) feed regularly on other salamanders (Bruce, 1979) and may prey on larval and juvenile seal salamanders. In Georgia, seal salamanders occasionally occur along the edges of streams with potentially predaceous fish (e.g., Cottus carolinae, Nocomis leptacephalus, Semotilus atromaculatus). Snake species known to feed on amphibians (e.g., Nerodia sipedon, Diadophis punctatus) have been seen foraging at night in streams inhabited by seal salamanders (C.D.C., personal observations). Predation pressure and/or intraspecific aggression may be high. Wake and Dresner (1967) report that 11% of a museum sample had broken tails.
P. Anti-Predator Mechanisms. Seal salamanders apparently use chemical cues to avoid contact with, and thus possible predation by, black-bellied salamanders (Roudebush and Taylor, 1987b; Jacobs and Taylor, 1992). Choices of egg-deposition sites may, in part, mitigate the effects of predation on eggs. Egg-attendance by maternal females apparently prevents at least some predation on egg clutches. Removal of a 65 mm female from her clutch resulted in the predation on the unattended eggs by a 67 mm female conspecific within 10 min (Camp, 1997a).
Q. Diseases. Unknown.
R. Parasites. Goater et al. (1987) reported the occurrence of six adult nematode species (Capillaria inequalis, Thelandros magnavulvaris, Omeia papillocauda, Desmognathinema nantahalaensis, Falcaustra plethodontis, and Cosmocercoides dukae) and one larval nematode species (an ascaridoidid) in seal salamanders. They found mature forms of three species of trematode (Brachycoelium elongatum, Gorgoderina bilobata, and Phyllodistomum solidum) and one species of tapeworm (Cylindrotaenia americana). They also found larval tapeworms (proteocephalan plerocercoids) and one species of larval acanthocephalan (Centrorynchus conspectus). Goater (2000) found a much lower incidence of leeches (Oligobdella biannulata) in seal salamanders than in the more aquatic black-bellied salamander. He similarly found low infection rates of trypanosomes, blood parasites that presumably use leeches as vectors, in seal salamanders.
4. Conservation. Seal salamanders remain abundant in areas of preferred habitat over much of their geographic range. In 20 yr of surveys of seal salamanders carried out in undisturbed habitats in the Appalachian Mountains of North Carolina, Hairston (1996) found no significant changes in abundance. There may be local threats to viable populations, however. Stream acidification as a consequence of mine drainage may negatively affect some populations. Roudebush (1988) showed that low pH depressed feeding rates, but salamanders did not die when exposed to a pH of 3.5 for 3 wk.
Certain populations of seal salamanders may have experienced declines due to exploitation as fish bait. In a recent survey of bait shops in northern Georgia, this species made up 67% of salamanders sold as “spring lizards” (Jensen and Waters, 1999). The collecting technique of pouring liquid bleach into small, high-gradient streams to drive out salamanders may be particularly harmful to this and other species of streamside salamanders. Because salamanders collected using this method have low survivabilities, bait shops owners often refuse to purchase salamanders from such collectors more than once (Jensen and Waters, 1999).
Optimal habitats for seal salamanders are seepages and small- to medium-sized streams containing cool, well-aerated water, located within mesic, hardwood forests (Organ, 1961; Petranka, 1998). The greatest threat to populations of this species, therefore, may be timber harvesting techniques (e.g., clearcutting) that increase rates of evaporative water loss through the removal of the protective canopy. Petranka et al. (1993) argued that clearcut timber harvesting negatively affects the number of total Desmognathus individuals, including seal salamanders; and estimated that clearcutting killed millions of salamanders from the Appalachian forests of North Carolina during the 1980s and early 1990s. Ash and Bruce (1993), however, disputed these estimates and considered them to be exaggerations of the actual numbers lost. Desmognathine salamanders currently are abundant in areas of the southern Appalachians (the Great Smoky Mountains) that have been extensively logged in the past (S.G.T., personal observations). Appalachian seepages occasionally dry up (Camp, 2000), and it is not known how periodic drought may interact with techniques of timber harvesting to affect populations of seal and other seepage-dwelling salamanders. Because of restricted ranges/population sizes, inherently warmer climates, and intensive silviculture in the Coastal Plain, timber harvesting may be a greater threat to Coastal Plain populations of seal salamanders than to Appalachian populations.
1Carlos D. Camp
2Stephen G. Tilley
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
Feedback or comments about this page.
Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Jul 2018.
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Triangle ABC is equilateral. D, the midpoint of BC, is the centre of the semi-circle whose radius is R which touches AB and AC, as well as a smaller circle with radius r which also touches AB and AC. . . .
Two buses leave at the same time from two towns Shipton and Veston on the same long road, travelling towards each other. At each mile along the road are milestones. The buses' speeds are constant. . . .
Three equilateral triangles ABC, AYX and XZB are drawn with the point X a moveable point on AB. The points P, Q and R are the centres of the three triangles. What can you say about triangle PQR? | <urn:uuid:1a04c6b1-074c-4e56-8a09-cf0c054911d5> | 3.1875 | 930 | Content Listing | Science & Tech. | 68.859671 | 95,546,105 |
Bones are made up of tiny fibres that are roughly a thousand times finer than a human hair. Researchers at the Paul Scherrer Institute PSI have developed a new computer-based algorithm with which they were able to visualize the localised order and alignment of these nanostructures inside an entire piece of bone for the first time.
The arrangement of the nanostructure of a three-dimensional object can now be visualised thanks to a new method developed by researchers at the Paul Scherrer Institute PSI.
The researchers demonstrated this new approach in collaboration with bone biomechanics experts at ETH Zurich and the University of Southampton, UK, using a small piece of a human vertebrae that was roughly two and a half millimetres long.
Bone consists of tiny fibres that are referred to as collagen fibrils. Their local three-dimensional order and alignment, which plays a central role in determining a bone’s mechanical properties, has now been visualised along the entire piece of bone.
This novel imaging approach provides important information that could aid, for example, the study of degenerative bone disease such as osteoporosis. In general, the new method is suitable not only for examining biological objects but also for developing promising new materials.
The data was obtained from PSI’s Swiss Light Source SLS, where the piece of bone was screened with an extremely fine and intense X-ray beam. This beam is scanned across the sample, recording data point by point. The interaction of the X-rays with the sample provides information about the local nanostructure at each measurement point.
The crucial step from 2D to 3D
Until now, only two-dimensional samples could be scanned and examined in this way. Traditionally, the objects examined are thus cut into very thin slices. “But not every object can be cut as thinly as you’d want”, explains project supervisor Manuel Guizar-Sicairos. “And sometimes when you cut it, you destroy or disturb the very nanostructure that you wanted to examine.” Quite generally, a non-destructive method is preferable, leaving the object intact for subsequent investigations.
In order to be able to image three-dimensional objects, the PSI researchers scanned their sample repeatedly, turning it by a small angle between each scan. This way, they obtained measurement data for all orientations that allowed them to subsequently reconstruct the three-dimensional object, including its nanostructure, on the computer.
The new measurement method used by the PSI researchers draws on a basic principle from computer tomography (CT). CT also involves first taking many X-ray images of a patient or object from different angles and then combining them to form the desired images by means of a computer calculation. However, traditional computer tomography does not use a fine X-ray beam. Instead, the object is irradiated as a whole.
While computer tomography can depict the varying density of the material, it does not capture details like the order and alignment of the underlying nanostructure. The latter only becomes possible through accurate measurement of the interaction between sample and X-rays which is enabled by the narrow, intense X-ray beam of the SLS in conjunction with state of the art detectors.
Images emerge thanks to mathematical algorithms
The most complex step was to compile a computer image of the three-dimensional sample from the vast amount of data. To do this, the researchers developed their own sophisticated mathematical algorithm. “The X-ray beam always penetrates the entire depth of the sample and we only see the end result”, explains Marianne Liebi, lead author of the study. “What the three-dimensional structure actually looks like is something we have to find out afterwards.”
For each point on the inside of the sample, Liebi’s algorithm searches for the structure that best corresponds to all the data measured. In the algorithm, the researchers took advantage of the fact that they could assume a certain symmetry in the arrangement of the collagen fibrils in the bone, thus reducing their data to a manageable level. Nevertheless, there still remained 2.2 million parameters to be found. These were optimised using a computer program that tests better and better solutions until it finds one that can best explain all measurements.
“I was amazed that after so much pure mathematics, an image emerged that really looked like a bone,” said Liebi. “The details in it were plausible right away.”
Like a map of the vegetation zones
While classic computer tomography generates greyscale images, the new method provides coloured images with considerably more information: The multi-coloured cylinders show the orientation on the nanoscale and even provide information on the degree of the orientation, which is high if adjacent collagen fibrils all have the same orientation and low if they are randomly oriented.
“We can’t image each individual collagen fibril directly, but that’s not necessary anyway”, explains Guizar-Sicairos. “Our imaging technique is akin to a map of vegetation zones. There too, one averages over certain areas, stating that one region is dominated by coniferous trees, another by deciduous trees and yet another by mixed woodland.” In this way, it is possible to map the vegetation of entire continents without having to classify every single tree.
By analogy it can be said that with traditional microscopic and nanoscopic methods this depiction of individual trees was necessary. That’s why until now, the smaller the structure of an object was the smaller the imaged section also had to be. Their new method allowed the PSI researchers to circumvent this limitation: From a piece of bone visible to the naked eye, they recorded the arrangement of the nanostructure in one single image.
At the same time as their publication, Nature will feature a second publication with research led by another researcher team with Liebi and Guizar-Sicairos as co-authors. That publication introduces an alternative algorithm that leads to a similar result: The researchers were able to determine the three-dimensional internal nanostructure of a human tooth.
Text: Paul Scherrer Institute/Laura Hennemann
The Paul Scherrer Institute PSI develops, builds and operates large, complex research facilities and makes them available to the national and international research community. The institute's own key research priorities are in the fields of matter and materials, energy and environment and human health. PSI is committed to the training of future generations. Therefore about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether PSI employs 1900 people, thus being the largest research institute in Switzerland. The annual budget amounts to approximately CHF 380 million.
Dr. Marianne Liebi, Coherent X-ray Scattering group, Laboratory for Macromolecules and Bioimaging, Paul Scherrer Institute,
telephone: +41 56 310 54 53, e-mail: firstname.lastname@example.org [German, English]
Dr. Manuel Guizar-Sicairos, Coherent X-ray Scattering group, Laboratory for Macromolecules and Bioimaging, Paul Scherrer Institute,
telephone: +41 56 310 34 09, e-mail: email@example.com [English, Spanish]
Nanostructure surveys on macroscopic specimens by small-angle scattering tensor tomography
M. Liebi, M. Georgiadis, A. Menzel, P. Schneider, J. Kohlbrecher, O. Bunk and M. Guizar-Sicairos,
Nature 19 November 2015
Six-dimensional real and reciprocal space small-angle X-ray scattering tomography
F. Schaff, M. Bech, P. Zaslansky, C. Jud, M. Liebi, M. Guizar-Sicairos and F. Pfeiffer,
Nature 19 November 2015
Laura Hennemann | idw - Informationsdienst Wissenschaft
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
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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17.07.2018 | Power and Electrical Engineering | <urn:uuid:584f213d-c309-47c4-938f-7fade942e80b> | 3.703125 | 2,353 | Content Listing | Science & Tech. | 36.581265 | 95,546,124 |
A View from Emerging Technology from the arXiv
SETI Study of Habitable Exoplanets Draws a Blank for Jill Tarter
The exoplanets of greatest interest show no sign of intelligent civilisations–so far.
The discovery of an ever-growing number of potentially habitable exoplanets brings an extra spiciness to the search for extraterrestrial intelligence. For the first time, astronomers can direct the search towards these likely planets rather than aiming in hope towards the stars.
Today, Jill Tarter, from the SETI Institute and of Contact fame, along with a group of buddies, reveal the results of their first directed search, carried out between February and April 2011.
These guys pointed the Green Bank Telescope in West Virginia at 86 stars hosting exoplanets discovered by the Kepler space telescope. They chose their targets because they had exoplanets in the Goldilocks zone, had five or more exoplanets or had super Earths with relatively long orbits.
Tarter and co looked at signals in the 1-2 GHz range, the region used by terrestrial mobile and cordless phones. In particular, they hunted for signals that cover no more than 5Hz of the spectrum since there is no known natural mechanism for producing such narrow band signals. “Emission no more than a few Hz in spectral width is, as far as we know, an unmistakable indicator of engineering by an intelligent civilization,” they say.
The big challenge with these kinds of observations is to rule out the false positives generated on Earth. Tarter and co developed a technique based on the simple idea that a signal can only be interesting if it appears in the data while the telescope is pointing at the target star but not when the telescope is pointing somewhere else. “This excluded 99.96 per cent of the candidate signals,” they say.
That left 52 candidate signals which Tarter and co then studied for signs of a terrestrial origin.
Their conclusions are forthright. “No signals of extraterrestrial origin were found,” they say.
There are some important caveats, however. In particular, is the question of how strong a signal the Green Bank Telescope can pick up.
Tarter and co consider in particular the most powerful beam that humans could broadcast into space: the Arecibo Planetary Radar in Puerto Rico. They say that if such a beam were pointed towards Earth during their experiment, they would have spotted it at distances of up to 10,000 light years. Of course, the likelihood of such a happy coincidence is small.
More advanced civilisations might have more power to play with and so be easier to see. In particular, civilisations that have harnessed all the energy from their star–so-called Kardashian Type II civilisations–ought to be easy to spot.
The results allow the team to put important limits on the likelihood of Kardashian Type II civilisations. Tarter and co say that the negative result implies that the number of these civilisations that are loud in the 1-2GHz range must less than one in a million per sun-like star.
That still leaves plenty of wiggle room. And the team points out that rapid improvements in the technology for sensing radio signals means that researchers ought to be able to tighten these limits significantly in the not too distant future.
Ref: arxiv.org/abs/1302.0845: A 1.1 to 1.9 GHz SETI Survey of the Kepler Field: I. A Search for Narrow-band Emission from Select Targets
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:dd72a32c-fedc-408f-83bc-13157ee61109> | 3.390625 | 755 | Truncated | Science & Tech. | 48.226455 | 95,546,127 |
Highway travelers view much of the Midwest as little more than barren flatlands. The formation of the region and its rich soils, especially tall grass areas that seemingly should support diverse forests, however, have long fascinated scientists. Newly available, long-term climate data now say the area is the product of weather extremes.
Compared with adjacent regions, the tall-grass area of the plains endures more frequent periods of severe drought, more lightning strikes and subsequent fires from frequent winter thunderstorms, dryer cold weather and more rapid plant and soil moisture evaporation, a team of researchers from the Illinois State Water Survey and University of Illinois at Urbana-Champaign says in the current issue of the journal Physical Geography.
"Beyond the 100 years of scientific curiosity is that these extremes of weather and their frequency or their non-frequency that we have found to be critical factors for the plains are actually very important issues as we face global climate change," said Stanley A. Changnon, a water survey scientist and professor of geography. "The long-term data weve gathered and are analyzing can provide us with very useful guidance as we talk about potential changes to our agricultural systems and to the way we as people live in general."
Jim Barlow | UIUC
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Classic Supercell: "Cascade" to Tornado
1. Buoyancy and deep layer shear (0-6 km; vector difference between surface and 500 mb winds about 35 knots or greater) in range favorable for supercells. In the Great Plains, this combination is often found in association with late spring and early summer wave cyclones. These cyclones circulate high dew point air northward at the surface under the jet stream.
2. Thunderstorm develops, and becomes tilted (due to 1), thus ensuring that precipitation does not fall into the updraft area.
3. Thunderstorm updraft develops lower midlevel and midlevel rotation (mesocyclone) by tilting horizontal flow which has adequate inflow layer (0-3 km) Storm Relative Helicity [SRH or SREH] (horizontal spin) into the vertical. Values of around 150 or greater suggest rotating updrafts strong enough to be detected by radar and which stimulate the continuation of the cascade. (See severe weather reports for this day).
4. Mesocyclone develops vertical continuity (about 1/3 the depth of the radar echo).
5. Deep mesocyclone circulates precipitation around rear flank of storm (development of "hook echo").
6. Mesocyclone develops downward towards ground. Hook shows up at lower elevations.
7. Interaction of environmental air at lower midlevels of the storm with deep hook in lower parts of storm is associated with the development of the Rear Flank Downdraft (RFD).
9. If low level shear (in 0-1 km layer; measured in a number of ways) is sufficient, interaction of RFD with updraft is associated with Tornado Vortex Signature— (TVS) on radar and eventually the development of a tornado IF the RFD is as warm or warmer than the updraft. (Supercells that have cold RFDs generally do not produce tornadoes)
(Note: If Steps 1 through 9 occur, but LCLs/LFCs are higher than about 1000 feet AGL, tornadoes will not occur, despite the impressive hooks that show up in reflectivity radar information).
If the process is interrupted at any stage, Steps 8 and 9 may never occur. Examples:
· Outflow from neighboring thunderstorm ingested into the updraft.
· Low level vertical shear is favorable for supercell tornado development but deeper shear (measured by Sfc-500 mb Shear Vector) not quite right.
· Low level vertical shear is too weak even though deeper shear is favorable.
a. Deep layer shear not quite right, so that some precipitation falls into the updraft area of the storm (outflow dominated supercell).
b. Deep layer shear is slightly too large, so that precipitation area too far away to be circulated to rear side of storm by mesocyclone (Low Precipitation Supercell—chief threat giant hail and winds).
c. Deep layer shear slightly weak so that too much precipitation is circulated around to the rear side of the storm by the mesocyclone and may completely encircle updraft (High Precipitation Supercell—chief threat giant hail, strong winds, flash flooding). | <urn:uuid:72267146-feeb-4591-92b2-61d5a5c1e1de> | 3.328125 | 664 | Knowledge Article | Science & Tech. | 51.532933 | 95,546,172 |
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Edited By: Allan Clarke
Many scientists either working on the El Ni#o /Southern Oscillation (ENSO) problem or its many applications have not been trained in the equatorial ocean and atmospheric dynamics necessary to understand it. This book seeks to overcome this difficulty by providing a step by step introduction to ENSO, helping the upper level graduate student or research scientist to learn quickly the ENSO basics and be up to date with the latest ENSO research. The text assumes that the reader has a knowledge of the equations of fluid mechanics on a rotating earth and emphasizes the observations and simple physical explanations of them.
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Most distant massive galaxy cluster identified
The early universe was a chaotic mess of gas and matter that only began to coalesce into distinct galaxies hundreds of millions of years after the Big Bang. It would take several billion more years for such galaxies to assemble into massive galaxy clusters — or so scientists had thought.
Now astronomers at MIT, the University of Missouri, the University of Florida, and elsewhere, have detected a massive, sprawling, churning galaxy cluster that formed only 3.8 billion years after the Big Bang. Located 10 billion light years from Earth and potentially comprising thousands of individual galaxies, the megastructure is about 250 trillion times more massive than the sun, or 1,000 times more massive than the Milky Way galaxy.
The cluster, named IDCS J1426.5+3508 (or IDCS 1426), is the most massive cluster of galaxies yet discovered in the first 4 billion years after the Big Bang.
IDCS 1426 appears to be undergoing a substantial amount of upheaval: The researchers observed a bright knot of X-rays, slightly off-center in the cluster, indicating that the cluster’s core may have shifted some hundred thousand light years from its center. The scientists surmise that the core may have been dislodged from a violent collision with another massive galaxy cluster, causing the gas within the cluster to slosh around, like wine in a glass that has been suddenly moved.
Michael McDonald, assistant professor of physics and a member of MIT’s Kavli Center for Astrophysics and Space Research, says such a collision may explain how IDCS 1426 formed so quickly in the early universe, at a time when individual galaxies were only beginning to take shape.
“In the grand scheme of things, galaxies probably didn’t start forming until the universe was relatively cool, and yet this thing has popped up very shortly after that,” McDonald says. “Our guess is that another similarly massive cluster came in and sort of wrecked the place up a bit. That would explain why this is so massive and growing so quickly. It’s the first one to the gate, basically.”
McDonald and his colleagues presented their results this week at the 227th American Astronomical Society meeting in Kissimmee, Florida. Their findings will also be published in The Astrophysical Journal.
“Cities in space”
Galaxy clusters are conglomerations of hundreds to thousands of galaxies bound together by gravity. They are the most massive structures in the universe, and those located relatively nearby, such as the Virgo cluster, are extremely bright and easy to spot in the sky.
“They are sort of like cities in space, where all these galaxies live very closely together,” McDonald says. “In the nearby universe, if you look at one galaxy cluster, you’ve basically seen them all — they all look pretty uniform. The further back you look, the more different they start to appear.”
However, finding galaxy clusters that are farther away in space — and further back in time — is a difficult and uncertain exercise.
In 2012, scientists using NASA’s Spitzer Space Telescope first detected signs of IDCS 1426 and made some initial estimates of its mass.
“We had some sense of how massive and distant it was, but we weren’t fully convinced,” McDonald says. “These new results are the nail in the coffin that proves that it is what we initially thought.”
“Tip of the iceberg”
To get a more precise estimate of the galaxy cluster’s mass, McDonald and his colleagues used data from several of NASA’s Great Observatories: the Hubble Space Telescope, the Keck Observatory, and the Chandra X-ray Observatory.
“We were basically using three completely different methods to weigh this cluster,” McDonald explains.
Both the Hubble and Keck Observatories recorded optical data from the cluster, which the researchers analyzed to determine the amount of light that was bending around the cluster as a result of gravity — a phenomenon known as gravitational lensing. The more massive the cluster, the more gravitational force it exerts, and the more light it bends.
They also examined X-ray data from the Chandra Observatory to get a sense of the temperature of the cluster. High-temperature objects give off X-rays, and the hotter a galaxy cluster, the more the gas within that cluster has been compressed, making the cluster more massive.
From the X-ray data, McDonald and his colleagues also calculated the amount of gas in the cluster, which can be an indication of the amount of matter — and mass — in the cluster.
Using all three methods, the group calculated roughly the same mass — about 250 trillion times the mass of the sun. Now, the team is looking for individual galaxies within the cluster to get a sense for how such megastructures can form in the early universe.
“This cluster is sort of like a construction site — it’s messy, loud, and dirty, and there’s a lot that’s incomplete,” McDonald says. “By seeing that incompleteness, we can get a sense for how [clusters] grow. So far, we’ve confirmed about a dozen or so galaxies, but we’re just seeing the tip of the iceberg, really.”
He hopes that scientists may get an even better view of IDCS 1426 in 2018, with the launch of the James Webb Space Telescope — an infrared telescope that is hundreds of times more sensitive than the Spitzer Telescope that first detected the cluster.
“People had kind of put away this idea of finding clusters in the optical and infrared, in favor of X-ray and radio signatures,” McDonald says. “We’re now re-emerging and saying it’s actually a fantastic way of finding clusters. It suggests that maybe we need to branch out a little more in how we find these things.”
This research was funded, in part, by NASA. | <urn:uuid:a43c6dce-ccbe-4f42-986e-2ad65045da87> | 3.4375 | 1,262 | News Article | Science & Tech. | 44.108591 | 95,546,196 |
Preparation of thin films using the tape-casting process for use in the solid oxide fuel cell
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Solid oxide fuel cells (SOFCs) produce electricity by electrochemically combining hydrogen and oxygen to give water. They operate at high temperatures (typically 1000 °C) allowing natural gas (hydrogen source) to be reformed in the cell rather than in an external reformer, reducing cost. Comparison with current electrical power generation systems, show SOFCs to have increased efficiencies, reduced NOx and SOx emissions and improved reliability promising a viable future alternative for electricity production.
Thin ceramic films to less than 200 µm are necessary for reduced all resistance. Tape casting is one method for production of thin ceramic (or metallic) films. In this paper, tape casting was used to produce both dense and porous thin films of 8-mol% Yttria stabilised Zirconia (YSZ). The films were fired both separately and together in a monolithic multi-layered block in order to determine the feasibility of using this method for the production of all components of the SOFC. The effects of organic content, addition of pore-forming agents and firing temperature on the microstructure of the films were investigated. Each individual layer produced was between 40–60 µum thick, with the highest density being>97% and the highest porosity obtained at 30% (produced by addition of a pore former). No de-lamination was observed upon heating the multi-layers.
KeywordsYttria Solid Oxide Fuel Cell Yttria Stabilise Zirconia Firing Temperature Reformer
Unable to display preview. Download preview PDF.
- R.E. Mistler, E.R. Twiname, in: Tape Casting Theory and Practise. Westerville: The American Ceramic Society, (2000).Google Scholar
- J.T.S. Irvine, F.G.E. Jones, P. Connor, University Court of the University of St Andrews, “Fuel Cell”. British Patent Applied for 0125276.6, 20 October (2001).Google Scholar | <urn:uuid:c03a92c0-a2fa-4a79-b8a0-ace1a5275147> | 3.15625 | 440 | Academic Writing | Science & Tech. | 39.215606 | 95,546,203 |
The Pythagorean Theorem: Crown Jewel of Mathematics
by John C. Sparks
Publisher: AuthorHouse 2008
Number of pages: 190
The author chronologically traces the Pythagorean Theorem from a conjectured beginning, through 4000 years of Pythagorean proofs, from all major proof categories, 20 proofs in total. The text presents several mathematical results closely allied to the Pythagorean Theorem along with some major Pythagorean "spin-offs" such as trigonometry. The books contains some classic puzzles, amusements, and applications. An epilogue summarizes the importance of the Pythagorean theorem and suggests paths for further exploration.
Download or read it online for free here:
by Bill Casselman - Cambridge University Press
The author gives an introduction to basic features of the PostScript language and shows how to use it for producing mathematical graphics. The book includes the discussion computer graphics and some comments on good style in mathematical illustration.
Online edition of Euclid's Elements, one of the most beautiful and influential works of science in the history of humankind. The text of all 13 Books is complete, and all of the figures are illustrated using a Java applet called the Geometry Applet.
by George Whitehead Hearn - Project Gutenberg
Researches on curves of the second order are given in this book, also on cones and spherical conics treated analytically, in which the tangencies of Apollonius are investigated, and general geometrical constructions deduced from analysis.
by James A. Smith - viXra
Geometric Algebra (GA) promises to become a universal mathematical language. This document reviews the geometry of angles and circles, then treats rotations in plane geometry before showing how to formulate problems in GA terms, then solve them. | <urn:uuid:38388307-26f4-4ebc-817d-cd2a64124a40> | 2.671875 | 368 | Content Listing | Science & Tech. | 22.607772 | 95,546,217 |
Every day billions of cells die in our body and need to be replaced by newly dividing cells. Cell division is a beautifully orchestrated process that involves multiple critical steps. At the very end, “cellular abscission” splits the membrane and thereby gives birth to two daughter cells. Abscission is executed by a protein machinery named ESCRT-III.
ESCRT-III consists of many subunits that form spiral-shaped filaments to constrict the membrane tube connecting the daughter cells until it splits. Insights into the function of ESCRT-III are also interesting for many other biological processes – as this machinery also pinches off viruses from the host cell membrane, and seals holes in cellular and nuclear membranes.
Previous models proposed that ESCRT-III forms stable filaments that constrict membranes by changing their curvature. However, such static mechanism would be different from most other cellular filament systems, like microtubules or actin filaments, which continuously turn over subunits as they change their shape.
An international research team led by IMBA group leader Daniel Gerlich and Aurélien Roux from the University of Geneva set out to explore for the first time, whether ESCRT-III undergoes dynamic remodeling. To investigate this, the team applied cutting-edge microscopy to visualize the dynamics of ESCRT subunits live in human cells.
“We were very excited to find that ESCRT assemblies rapidly turn over their subunits, and that this is orchestrated by an enzyme called VPS4. We discovered that this dynamic turnover removes growth-inhibiting ESCRT-III subunits and thereby stimulates the addition of new subunits. This was surprising, because VPS4 was previously considered to mainly disassemble ESCRT-III filaments, but it actually promotes growth”, explains Beata Mierzwa, PhD student at the Vienna BioCenter and first author of the study.
To study the molecular details of ESCRT-III reorganization, the researchers recapitulated the process in a test tube using purified proteins. They then used high-speed atomic force microscopy to directly visualize dynamically growing and shrinking spiral-shaped filaments.
“Our findings provide a new model for how ESCRT-III might deform membrane tubes over large distances, which was difficult to imagine in light of the previous models of persistent filaments. This will be relevant for many other biological processes involving the ESCRT-III machinery.” states Daniel Gerlich.
"Dynamic instability in ESCRT-III assemblies”
Beata E. Mierzwa, Nicolas Chiaruttini, Lorena Redondo-Morata, Joachim Moser von Filseck, Julia König, Jorge Larios, Ina Poser, Thomas Müller-Reichert, Simon Scheuring, Aurélien Roux, Daniel W. Gerlich
Nature Cell Biology, DOI: 10.1038/ncb3559
IMBA - Institute of Molecular Biotechnology is one of the leading biomedical research institutes in Europe focusing on cutting-edge functional genomics and stem cell technologies. IMBA is located at the Vienna Biocenter, the vibrant cluster of universities, research institutes and biotech companies in Austria. IMBA is a subsidiary of the Austrian Academy of Sciences, the leading national sponsor of non-university academic research.www.imba.oeaw.ac.at
About the Vienna BioCenter
The Vienna BioCenter (VBC) is a leading life sciences location in Europe, offering an extraordinary combination of research, education and business on a single campus. About 1,600 employees, more than 1,000 students, 93 research groups, 16 biotech companies, and scientists from more than 40 nations create a highly dynamic environment. www.viennabiocenter.org
VBC PhD Programme
Much of the research leading to this publication was carried out by a PhD student of the VBC PhD Programme. Interested in doing a PhD that could be this successful? Then read more on the VBC PhD Programme webpage.
Mag. Ines Méhu-Blantar | idw - Informationsdienst Wissenschaft
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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:d96b0c1c-1679-4d65-876c-9b499dfec111> | 3.234375 | 1,507 | Content Listing | Science & Tech. | 37.166517 | 95,546,223 |
Question: How are the effects of mineral soil properties on understory plant species richness propagated through a network of processes involving the forest overstory, soil organic matter, soil nitrogen, and understory plant abundance? Location: North-central Arizona, USA. Methods: We sampled 75 0.05-ha plots across a broad soil gradient in a Pinus ponderosa (ponderosa pine) forest ecosystem. We evaluated multivariate models of plant species richness using structural equation modeling. Results: Richness was highest at intermediate levels of understory plant cover, suggesting that both colonization success and competitive exclusion can limit richness in this system. We did not detect a reciprocal positive effect of richness on plant cover. Richness was strongly related to soil nitrogen in the model, with evidence for both a direct negative effect and an indirect non-linear relationship mediated through understory plant cover. Soil organic matter appeared to have a positive influence on understory richness that was independent of soil nitrogen. Richness was lowest where the forest overstory was densest, which can be explained through indirect effects on soil organic matter, soil nitrogen and understory cover. Finally, model results suggest a variety of direct and indirect processes whereby mineral soil properties can influence richness. Conclusions: Understory plant species richness and plant cover in P. ponderosa forests appear to be significantly influenced by soil organic matter and nitrogen, which are, in turn, related to overstory density and composition and mineral soil properties. Thus, soil properties can impose direct and indirect constraints on local species diversity in ponderosa pine forests.
Arizona; Diversity; Humus; Nitrogen; Organic matter; Plant diversity; Populus tremuloides; Soil texture; Soils; Soils – Nitrogen content; Structural equation modeling; Understory plants
Forest Sciences | Plant Sciences | Soil Science | Systems Biology
Laughlin, D. C.,
Abella, S. R.,
Covington, W. W.,
Grace, J. B.
Species richness and soil properties in Pinus ponderosa forests: A structural equation modeling analysis.
Journal of Vegetation Science, 18(2), | <urn:uuid:eb86db0e-2fd0-40d1-b113-64fec04a253c> | 2.71875 | 436 | Academic Writing | Science & Tech. | 23.23919 | 95,546,253 |
Dr. Yasmin Hurd, the Director of the Center for Addictive Disorders at Mount Sinai, explains how addiction impacts the lives of many, movie portrayals accuracies and just how little we know about drugs like marijuana.
Science Goes to the Movies is a new monthly series, co-hosted by Faith Salie and Dr. Heather Berlin, that looks at the science in contemporary motion pictures. Guests are drawn from different scientific disciplines, illuminating scientific truths or imaginings in films like Interstellar, Birdman, The Theory of Everything, Into the Woods, and more. The series encourages lively and informative conversation about concepts, as well as film portrayals of scientists and scientific inquiry, asking if there is real science behind a story, or if a screenwriter made something up. Is science leading dramatic imagination, or does imagination create new science? | <urn:uuid:f8d81a24-a49d-4213-b8dd-3c99cae34b6b> | 2.625 | 169 | News (Org.) | Science & Tech. | 31.22 | 95,546,265 |
The CNO cycle (for carbon–nitrogen–oxygen) is one of two sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain. Unlike the proton–proton chain reaction, the CNO cycle is a catalytic cycle. Theoretical models show that the CNO cycle is the dominant source of energy in stars more massive than about 1.3 times the mass of the Sun. The proton–proton chain is more important in stars the mass of the Sun or less. This difference stems from temperature dependency differences between the two reactions; pp-chain reactions start occurring at temperatures around 4×106 K, making it the dominant energy source in smaller stars. A self-maintaining CNO chain starts occurring at approximately 15×106 K, but its energy output rises much more rapidly with increasing temperatures. At approximately 17×106 K, the CNO cycle starts becoming the dominant source of energy. The Sun has a core temperature of around 15.7×106 K and only 1.7% of 4He nuclei being produced in the Sun are born in the CNO cycle. The CNO-I process was independently proposed by Carl von Weizsäcker and Hans Bethe in 1938 and 1939, respectively.
In the CNO cycle, four protons fuse, using carbon, nitrogen and oxygen isotopes as a catalyst, to produce one alpha particle, two positrons and two electron neutrinos. Although there are various paths and catalysts involved in the CNO cycles, simply speaking all these cycles have the same net result:
- 4 1
1H → 4
2He + 2 e+ + 2 ν
e + 3 γ + 26.8 MeV
The positrons will almost instantly annihilate with electrons, releasing energy in the form of gamma rays. The neutrinos escape from the star carrying away some energy. The carbon, nitrogen, and oxygen isotopes are in effect one nucleus that goes through a number of transformations in an endless loop.
Other articles related to "cycle, cno cycle, cno":
... The pp-chain reaction cycle is relatively insensitive to temperature, so this hydrogen burning process can occur in up to a third of the star's radius and occupy half the star's mass ... In each complete fusion cycle, the p-p chain reaction releases about 26.2 MeV ... In higher mass stars, the dominant process is the CNO cycle, which is a catalytic cycle that uses nuclei of carbon, nitrogen and oxygen as intermediaries to produce a helium nucleus ...
... While the total number of "catalytic" CNO nuclei are conserved in the cycle, in stellar evolution the relative proportions of the nuclei are altered ... When the cycle is run to equilibrium, the ratio of the carbon-12/carbon-13 nuclei is driven to 3.5, and nitrogen-14 becomes the most numerous nucleus, regardless of initial composition ... During a star's evolution, convective mixing episodes bring material in which the CNO cycle has operated from the star's interior to the surface, altering the observed composition of the star ...
... K, so hydrogen-to-helium fusion occurs primarily via the CNO cycle ... In the CNO cycle, the energy generation rate scales as the temperature to the 17th power, whereas the rate scales as the temperature to the 4th power in the proton-proton ... Due to the strong temperature sensitivity of the CNO cycle, the temperature gradient in the inner portion of the star is steep enough to make the core convective ...
Famous quotes containing the word cycle:
“Only mediocrities progress. An artist revolves in a cycle of masterpieces, the first of which is no less perfect than the last.”
—Oscar Wilde (18541900) | <urn:uuid:ae637e75-7557-4650-9bcf-494f3364eccd> | 3.65625 | 795 | Knowledge Article | Science & Tech. | 57.393995 | 95,546,266 |
A, B & C own a half, a third and a sixth of a coin collection. Each grab some coins, return some, then share equally what they had put back, finishing with their own share. How rich are they?
Pick a square within a multiplication square and add the numbers on each diagonal. What do you notice?
Advent Calendar 2011 - a mathematical activity for each day during the run-up to Christmas.
What are the missing numbers in the pyramids?
You have twelve weights, one of which is different from the rest. Using just 3 weighings, can you identify which weight is the odd one out, and whether it is heavier or lighter than the rest?
Take any two numbers between 0 and 1. Prove that the sum of the numbers is always less than one plus their product?
There are four children in a family, two girls, Kate and Sally, and two boys, Tom and Ben. How old are the children?
Arrange the numbers 1 to 16 into a 4 by 4 array. Choose a number. Cross out the numbers on the same row and column. Repeat this process. Add up you four numbers. Why do they always add up to 34?
In how many distinct ways can six islands be joined by bridges so that each island can be reached from every other island...
The sums of the squares of three related numbers is also a perfect square - can you explain why?
Can you cross each of the seven bridges that join the north and south of the river to the two islands, once and once only, without retracing your steps?
Choose any three by three square of dates on a calendar page...
If you can copy a network without lifting your pen off the paper and without drawing any line twice, then it is traversable. Decide which of these diagrams are traversable.
Can you convince me of each of the following: If a square number is multiplied by a square number the product is ALWAYS a square number...
The problem is how did Archimedes calculate the lengths of the sides of the polygons which needed him to be able to calculate square roots?
Baker, Cooper, Jones and Smith are four people whose occupations are teacher, welder, mechanic and programmer, but not necessarily in that order. What is each person’s occupation?
What can you say about the lengths of the sides of a quadrilateral whose vertices are on a unit circle?
A serious but easily readable discussion of proof in mathematics with some amusing stories and some interesting examples.
A game for 2 players that can be played online. Players take it in turns to select a word from the 9 words given. The aim is to select all the occurrences of the same letter.
Find the missing angle between the two secants to the circle when the two angles at the centre subtended by the arcs created by the intersections of the secants and the circle are 50 and 120 degrees.
Show that among the interior angles of a convex polygon there cannot be more than three acute angles.
Is it possible to rearrange the numbers 1,2......12 around a clock face in such a way that every two numbers in adjacent positions differ by any of 3, 4 or 5 hours?
Janine noticed, while studying some cube numbers, that if you take three consecutive whole numbers and multiply them together and then add the middle number of the three, you get the middle number. . . .
Prove that if the integer n is divisible by 4 then it can be written as the difference of two squares.
A huge wheel is rolling past your window. What do you see?
If you think that mathematical proof is really clearcut and universal then you should read this article.
Four jewellers share their stock. Can you work out the relative values of their gems?
Which hexagons tessellate?
Let a(n) be the number of ways of expressing the integer n as an ordered sum of 1's and 2's. Let b(n) be the number of ways of expressing n as an ordered sum of integers greater than 1. (i) Calculate. . . .
Do you know how to find the area of a triangle? You can count the squares. What happens if we turn the triangle on end? Press the button and see. Try counting the number of units in the triangle now. . . .
This article invites you to get familiar with a strategic game called "sprouts". The game is simple enough for younger children to understand, and has also provided experienced mathematicians with. . . .
These formulae are often quoted, but rarely proved. In this article, we derive the formulae for the volumes of a square-based pyramid and a cone, using relatively simple mathematical concepts.
ABC is an equilateral triangle and P is a point in the interior of the triangle. We know that AP = 3cm and BP = 4cm. Prove that CP must be less than 10 cm.
Replace each letter with a digit to make this addition correct.
Semicircles are drawn on the sides of a rectangle. Prove that the sum of the areas of the four crescents is equal to the area of the rectangle.
Is the mean of the squares of two numbers greater than, or less than, the square of their means?
This is an interactivity in which you have to sort the steps in the completion of the square into the correct order to prove the formula for the solutions of quadratic equations.
Eulerian and Hamiltonian circuits are defined with some simple examples and a couple of puzzles to illustrate Hamiltonian circuits.
The first of two articles on Pythagorean Triples which asks how many right angled triangles can you find with the lengths of each side exactly a whole number measurement. Try it!
This is the second article on right-angled triangles whose edge lengths are whole numbers.
Can you arrange the numbers 1 to 17 in a row so that each adjacent pair adds up to a square number?
In this 7-sandwich: 7 1 3 1 6 4 3 5 7 2 4 6 2 5 there are 7 numbers between the 7s, 6 between the 6s etc. The article shows which values of n can make n-sandwiches and which cannot.
The diagram shows a regular pentagon with sides of unit length. Find all the angles in the diagram. Prove that the quadrilateral shown in red is a rhombus.
Can you make sense of these three proofs of Pythagoras' Theorem?
An article which gives an account of some properties of magic squares.
Try to solve this very difficult problem and then study our two suggested solutions. How would you use your knowledge to try to solve variants on the original problem?
Problem solving is at the heart of the NRICH site. All the problems give learners opportunities to learn, develop or use mathematical concepts and skills. Read here for more information.
What is the largest number of intersection points that a triangle and a quadrilateral can have?
When is it impossible to make number sandwiches?
This article discusses how every Pythagorean triple (a, b, c) can be illustrated by a square and an L shape within another square. You are invited to find some triples for yourself. | <urn:uuid:2b2041ac-9879-4adf-9788-bbd3b59cefff> | 3.46875 | 1,513 | Content Listing | Science & Tech. | 68.615458 | 95,546,268 |
Learn how to make desktop applications out of the very same technologies used in web development.
Before creating the main.js and index.html files, we need to discuss the two process types available in Electron. They are fundamentally different and important to understand. Each of these two processes has a specific responsibility within the application.
We already learned that the renderer processes would display the UI of your application. It will load content and execute it within its own thread. Now we'll create our renderer index.html file inside the same directory where the package.json resides.
We’ll create user interface (UI) for our &qout;Duplicate File Finder" desktop app with HTML and style it witch css. It is a very simple interface, just a logo on top with Application name, version number and two button Add folder and Start search for controlling the app behavior.
In this tutorial, we’ll learn how to read, write, and append to files in a asynchronous and synchronous manner. We’re going to write a simple program that grab text from a file, and saves it in a new file. We’ll also learn how to read a dir in a synchronous manner recursively.
In this tutorial, we’ll learn how to read, write, and append to files in an asynchronous manner. We’re going to write a simple program that grab text from a file, and saves it in a new file. We’ll also learn how to read a dir in an asynchronous manner recursively.
Lean how to query the status of files using Node.js, returning information such as the file type, file owner, access permission file size, number of links, inode number and file birth, access, change and modify times.
A synchronous function blocks until it completes its operations. An asynchronous function returns immediately and the result is passed to a callback function.
So, if you have functionality that needs to wait on something, such as opening a file, retrieving data from the database, a web response, or other activity of this nature, then blocking the application until the operation is finished would be a major point of failure in a server-based application. The solution to prevent blocking is the event loop. | <urn:uuid:3f97c575-b104-4cd6-9764-8083df73624a> | 3.09375 | 469 | Tutorial | Software Dev. | 51.052407 | 95,546,278 |
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis. In most organisms, nucleic acids occur in combination with proteins; the combined substances are called nucleoproteins. Nucleic acid molecules are complex chains of varying length. The two chief types of nucleic acids are DNA (deoxyribonucleic acid), which carries the hereditary information from generation to generation, and RNA (ribonucleic acid), which delivers the instructions coded in this information to the cell's protein manufacturing sites.
The chemical and physical properties of DNA suit it for both replication and transfer of information. Each DNA molecule is a long two-stranded chain. The strands are made up of subunits called nucleotides, each containing a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases, adenine, guanine, thymine, and cytosine, denoted A, G, T, and C, respectively. A given strand contains nucleotides bearing each of these four. The information carried by a given gene is coded in the sequence in which the nucleotides bearing different bases occur along the strand. These nucleotide sequences determine the sequences of amino acids in the polypeptide chain of the protein specified by that gene.
Between the genes, or coding loci, on the DNA of higher organisms, there are long portions of DNA, often referred to as "junk" DNA, that code no proteins. Sometimes junk DNA occurs within a gene; when this occurs, the coding portions are called exons and the noncoding (junk) portions are called introns. Junk DNA makes up 97% of the DNA in the human genome. Little is known of its purpose.
In 1953 the molecular biologists J. D. Watson, an American, and F. H. Crick, an Englishman, proposed that the two DNA strands were coiled in a double helix. In this model each nucleotide subunit along one strand is bound to a nucleotide subunit on the other strand by hydrogen bonds between the base portions of the nucleotides. The fact that adenine bonds only with thymine (A—T) and guanine bonds only with cytosine (G—C) determines that the strands will be complementary, i.e., that for every adenine on one strand there will be a thymine on the other strand. It is the property of complementarity between strands that insures that DNA can be replicated, i.e., that identical copies can be made in order to be transmitted to the next generation.
In order to be expressed as protein, the genetic information must be carried to the protein-synthesizing machinery of the cell, which is in the cell's cytoplasm (see cell). One form of RNA mediates this process. RNA is similar to DNA, but contains the sugar ribose instead of deoxyribose and the base uracil (U) instead of thymine. To initiate the process of information transfer, one strand of the double-stranded DNA chain serves as a template for the synthesis of a single strand of RNA that is complementary to the DNA strand (e.g., the DNA sequence AGTC will specify an RNA sequence UCAG). This process is called transcription and is mediated by enzymes.
The newly synthesized RNA, called messenger RNA, or mRNA, moves quickly to bodies in the cytoplasm called ribosomes, which are composed of two particles made of protein bound to ribosomal RNA, or rRNA. Each ribosome is the site of synthesis of a polypeptide chain. Several ribosomes attach to a single mRNA so that many polypeptide chains are synthesized from the same mRNA; each cluster of an mRNA and ribosomes is called a polyribosome or polysome. The nucleotide sequence of the mRNA is translated into the amino acid sequence of a protein by adaptor molecules composed of a third type of RNA called transfer RNA, or tRNA. There are many different species of tRNA, with each species binding one of 20 amino acids.
In protein synthesis, a nucleotide sequence along the mRNA does not specify an amino acid directly; rather, it specifies a particular species of tRNA. For example, in coding for the amino acid tyrosine, a nucleotide sequence of mRNA is complementary to a portion of a tyrosine-tRNA molecule. As each specified tRNA associates with its complementary space on the mRNA, the amino acid is added onto the lengthening protein chain and the tRNA is released. When the protein chain is complete, it is released from the ribosome.
The particular sequence of amino acids in each polypeptide chain is determined by the genetic code. Starting at one end of the mRNA strand, each 3-nucleotide sequence, or codon, specifies, via complementary tRNA sequences, one amino acid, and the series of such codons in the mRNA specifies a polypeptide chain. Although a "vocabulary" of 64 words, or specifications, is theoretically possible with 4 different nucleotides taken three at a time, there are only 20 amino acids to be specified. However, several triplets may code for the same amino acid; for example UAU and UAC both code for the amino acid tyrosine. In addition, there are some codons that do not code for amino acids but code for polypeptide chain initiation and polypeptide chain termination. The code is also nonoverlapping; i.e., a nucleotide in one codon is never part of either adjacent codon. The code seems to be universal in all living organisms.
The determination of the mechanism of protein synthesis has increased understanding of many genetic processes and permitted such developments as bioengineering. Some mutagens, or mutation-inducing agents, cause the substitution of one nucleotide for another in an mRNA strand; other mutagens cause deletion or addition of nucleotides. Decoding, or reading, of such strands will be altered.
Metabolic regulation has been studied to determine how the genes that control enzyme synthesis can be switched on and off when certain substances are present. For example, in the process known as induction, bacteria synthesize the enzyme β-galactosidase only when lactose is present. Induction has been linked to the activity at a so-called operator site on a chromosome. When the operator site is open, the genes it controls function freely; when it is blocked, as by a repressor molecule, the genes it controls also do not function.
- See The Double Helix: A Personal Account of the Discovery of the Structure of DNA (1968) and DNA: The Secret of Life (2003). ,
- Adams, R. L., et al. The Biochemistry of the Nucleic Acids (1986).
- Watson and DNA: Making a Scientific Revolution (2003). ,
- I Rosenfield et al., DNA: A Graphic Guide to the Molicule that Shook the World (2010).
A nucleic acid which, when extracted from virions, can infect a host cell and give rise to progeny virions. Such a nucleic acid must be capable...
Complex, high-molecular-weight macromolecules composed of nucleotide chains. The most common nucleic acids are deoxyribonucleic acid (DNA) and...
Both DNA and RNA probes are used for crop disease diagnosis. DNA is double-stranded and the two strands are held together via specific hydrogen... | <urn:uuid:803ed390-6fa9-4d2c-9898-5acb51985a9b> | 3.921875 | 1,590 | Knowledge Article | Science & Tech. | 39.908462 | 95,546,331 |
Present-day sediment distribution offers a potentially strong constraint on past ice sheet evolution. Glacial system models (GSMs), however, cannot address this constraint while lacking appropriate representations of subglacial sediment production and transport. Incorporating these elements in GSMs is also required in order to quantify the impact of a changing sediment cover on glacial cycle dynamics.Towards these goals, we present a subglacial process model (hereafter referred to as the sediment model) that incorporates mechanisms for sediment production, entrainment, transport, and deposition. Bedrock erosion is calculated by both Hallet's and Boulton's abrasion laws separately, and by a novel quarrying law parametrized as a function of subglacial cavity extent. These process-oriented erosion laws are compared against a simple empirical relationship between erosion rate and the work done by basal stress. Sediment entrainment is represented by Philip's law for regelation intrusion and soft-bed deformation is included as a subglacial sediment transport mechanism. The model is driven by the data-calibrated MUN (3D) GSM and a newly developed subglacial hydrology module.The sediment model is applied to the last North American glacial cycle and predicts sediment thickness and cumulative erosion patterns. Results are obtained in the context of a sensitivity analysis and are compared against the present-day distribution of glacigenic sediment and geological estimates of Laurentide Ice Sheet erosion. Given plausible ranges for the sensitivity parameters, chosen a priori based on available literature or on heuristic arguments, the calculated erosion depths overlap with the geological estimates of Laurentide erosion. Most of the runs in the sensitivity set produce unrealistically thick and continuous moraines along the eastern, southern and western margins of the North American ice complex, which suggests that the model overestimates sediment entrainment and thus englacial transport. A realistic sediment distribution is only obtained when the entrainment rate is capped at the average basal melting rate, which suggests that modelled entrainment and basal melting rates should be of the same order of magnitude. © 2013 Elsevier Ltd.
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Nebula(Redirected from Nebulae)
A nebula (Latin for "cloud" or "fog"; pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, nebula was a name for any diffuse astronomical object, including galaxies beyond the Milky Way. The Andromeda Galaxy, for instance, was once referred to as the Andromeda Nebula (and spiral galaxies in general as "spiral nebulae") before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble and others.
Most nebulae are of vast size, some are hundreds of light years in diameter.[not in citation given] A nebula that is barely visible to the human eye from Earth would appear larger, but no brighter, from close by. The Orion Nebula, the brightest nebula in the sky that occupies a region twice the diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. Although denser than the space surrounding them, most nebulae are far less dense than any vacuum created on Earth – a nebular cloud the size of the Earth would have a total mass of only a few kilograms. Many nebulae are visible due to fluorescence caused by embedded hot stars, while others are so diffuse they can only be detected with long exposures and special filters. Some nebulae are variably illuminated by T Tauri variable stars. Nebulae are often star-forming regions, such as in the "Pillars of Creation" in the Eagle Nebula. In these regions the formations of gas, dust, and other materials "clump" together to form denser regions, which attract further matter, and eventually will become dense enough to form stars. The remaining material is then believed to form planets and other planetary system objects.
Around 150 AD, Claudius Ptolemaeus (Ptolemy) recorded, in books VII–VIII of his Almagest, five stars that appeared nebulous. He also noted a region of nebulosity between the constellations Ursa Major and Leo that was not associated with any star. The first true nebula, as distinct from a star cluster, was mentioned by the Persian astronomer Abd al-Rahman al-Sufi, in his Book of Fixed Stars (964). He noted "a little cloud" where the Andromeda Galaxy is located. He also cataloged the Omicron Velorum star cluster as a "nebulous star" and other nebulous objects, such as Brocchi's Cluster. The supernova that created the Crab Nebula, the SN 1054, was observed by Arabic and Chinese astronomers in 1054.
In 1610, Nicolas-Claude Fabri de Peiresc discovered the Orion Nebula using a telescope. This nebula was also observed by Johann Baptist Cysat in 1618. However, the first detailed study of the Orion Nebula was not performed until 1659, by Christiaan Huygens, who also believed he was the first person to discover this nebulosity.
In 1715, Edmund Halley published a list of six nebulae. This number steadily increased during the century, with Jean-Philippe de Cheseaux compiling a list of 20 (including eight not previously known) in 1746. From 1751 to 1753, Nicolas Louis de Lacaille cataloged 42 nebulae from the Cape of Good Hope, most of which were previously unknown. Charles Messier then compiled a catalog of 103 "nebulae" (now called Messier objects, which included what are now known to be galaxies) by 1781; his interest was detecting comets, and these were objects that might be mistaken for them.
The number of nebulae was then greatly increased by the efforts of William Herschel and his sister Caroline Herschel. Their Catalogue of One Thousand New Nebulae and Clusters of Stars was published in 1786. A second catalog of a thousand was published in 1789 and the third and final catalog of 510 appeared in 1802. During much of their work, William Herschel believed that these nebulae were merely unresolved clusters of stars. In 1790, however, he discovered a star surrounded by nebulosity and concluded that this was a true nebulosity, rather than a more distant cluster.
Beginning in 1864, William Huggins examined the spectra of about 70 nebulae. He found that roughly a third of them had the emission spectrum of a gas. The rest showed a continuous spectrum and thus were thought to consist of a mass of stars. A third category was added in 1912 when Vesto Slipher showed that the spectrum of the nebula that surrounded the star Merope matched the spectra of the Pleiades open cluster. Thus the nebula radiates by reflected star light.
About 1923, following the Great Debate, it had become clear that many "nebulae" were in fact galaxies far from our own.
Slipher and Edwin Hubble continued to collect the spectra from many different nebulae, finding 29 that showed emission spectra and 33 that had the continuous spectra of star light. In 1932, Hubble announced that nearly all nebula are associated with stars, and their illumination comes from star light. He also discovered that the emission spectrum nebulae are nearly always associated with stars having spectral classifications of B or hotter (including all O-type main sequence stars), while nebulae with continuous spectra appear with cooler stars. Both Hubble and Henry Norris Russell concluded that the nebulae surrounding the hotter stars are transfomed in some manner.
There are a variety of formation mechanisms for the different types of nebulae. Some nebulae form from gas that is already in the interstellar medium while others are produced by stars. Examples of the former case are giant molecular clouds, the coldest, densest phase of interstellar gas, which can form by the cooling and condensation of more diffuse gas. Examples of the latter case are planetary nebulae formed from material shed by a star in late stages of its stellar evolution.
Star-forming regions are a class of emission nebula associated with giant molecular clouds. These form as a molecular cloud collapses under its own weight, proceeding stars. Massive stars may form in the center, and their ultraviolet radiation ionizes the surrounding gas, making it visible at optical wavelengths. The region of ionized hydrogen surrounding the massive stars is known as an H II region while the shells of neutral hydrogen surrounding the H II region are known as photodissociation region. Examples of star-forming regions are the Orion Nebula, the Rosette Nebula and the Omega Nebula. Feedback from star-formation, in the form of supernova explosions of massive stars, stellar winds or ultraviolet radiation from massive stars, or outflows from low-mass stars may disrupt the cloud, destroying the nebula after several million years.
Other nebulae form as the result of supernova explosions; the death throes of massive, short-lived stars. The materials thrown off from the supernova explosion are then ionized by the energy and the compact object that its core produces. One of the best examples of this is the Crab Nebula, in Taurus. The supernova event was recorded in the year 1054 and is labelled SN 1054. The compact object that was created after the explosion lies in the center of the Crab Nebula and its core is now a neutron star.
Still other nebulae form as planetary nebulae. This is the final stage of a low-mass star's life, like Earth's Sun. Stars with a mass up to 8–10 solar masses evolve into red giants and slowly lose their outer layers during pulsations in their atmospheres. When a star has lost enough material, its temperature increases and the ultraviolet radiation it emits can ionize the surrounding nebula that it has thrown off. Our Sun will produce a planetary nebula and its core will remain behind in the form of white dwarf.
Types of nebulaeEdit
The delicate shell of SNR B0509-67.5
Objects named nebulae belong to four major groups. Before their nature was understood, galaxies ("spiral nebulae") and star clusters too distant to be resolved as stars were also classified as nebulae, but no longer are.
- H II regions, large diffuse nebulae containing ionized hydrogen
- Planetary nebulae
- Supernova remnant (e.g., Crab Nebula)
- Dark nebula
Not all cloud-like structures are named nebulae; Herbig–Haro objects are an example.
Most nebulae can be described as diffuse nebulae, which means that they are extended and contain no well-defined boundaries. Diffuse nebulae can be divided into emission nebula, reflection nebulae and "dark nebulae." Visible light nebulae may be divided into emission nebulae that emit spectral line radiation from excited or ionized gas (mostly ionized hydrogen); they are often called HII regions (the term "HII" refers to ionized hydrogen). Reflection nebulae are visible primarily due to the light they reflect. Reflection nebulae themselves do not emit significant amounts of visible light, but are near stars and reflect light from them. Similar nebulae not illuminated by stars do not exhibit visible radiation, but may be detected as opaque clouds blocking light from luminous objects behind them; they are called "dark nebulae".
Planetary nebulae are the remnants of the final stages of stellar evolution for lower-mass stars. Evolved asymptotic giant branch stars expell their outer layers outwards due to strong stellar winds, thus forming gaseous shells, while leaving behind the star's core in the form of a white dwarf. The hot white dwarf illuminates the expelled gases producing emission nebulae with spectra similar to those of emission nebulae found in star formation regions. Technically they are HII regions, because most hydrogen are ionized, but are denser and more compact than nebulae found in star formation regions. Planetary nebulae were given their name by the first astronomical observers who were initially unable to distinguish them from planets, and who tended to confuse them with planets, which were of more interest to them. Our Sun is expected to spawn a planetary nebula about 12 billion years after its formation.
A protoplanetary nebula (PPN) is an astronomical object at the short-lived episode during a star's rapid stellar evolution between the late asymptotic giant branch (LAGB) phase and the following planetary nebula (PN) phase. During the AGB phase, the star undergoes mass loss, emitting a circumstellar shell of hydrogen gas. When this phase comes to an end, the star enters the PPN phase.
The PPN is energized by the central star, causing it to emit strong infrared radiation and become a reflection nebula. Collimated stellar winds from the central star shape and shock the shell into an axially symmetric form, while producing a fast moving molecular wind. The exact point when a PPN becomes a planetary nebula (PN) is defined by the temperature of the central star. The PPN phase continues until the central star reaches a temperature of 30,000 K, after which it is hot enough to ionize the surrounding gas.
A supernova occurs when a high-mass star reaches the end of its life. When nuclear fusion in the core of the star stops, the star collapses. The gas falling inward either rebounds or gets so strongly heated that it expands outwards from the core, thus causing the star to explode. The expanding shell of gas forms a supernova remnant, a special diffuse nebula. Although much of the optical and X-ray emission from supernova remnants originates from ionized gas, a great amount of the radio emission is a form of non-thermal emission called synchrotron emission. This emission originates from high-velocity electrons oscillating within magnetic fields.
Notable named nebulaeEdit
- Famous Space Pillars Feel the Heat of Star's Explosion – Jet Propulsion Laboratory
- Nebula, Online Etymology Dictionary
- Formey, Johann Heinrich Samuel (1765). "Nebula." The Encyclopedia of Diderot & d'Alembert Collaborative Translation Project. Translated by Amanda Oberski. Ann Arbor: Michigan Publishing, University of Michigan Library. Trans. of "Nébuleux," Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, vol. 11. Paris.
- Howell, Elizabeth (2013-02-22). "In Reality, Nebulae Offer No Place for Spaceships to Hide". Universe Today.
- Clark, Roger N. "Visual astronomy of the deep sky". Cambridge University Press. p. 98.
- Kunitzsch, P. (1987), "A Medieval Reference to the Andromeda Nebula" (PDF), ESO Messenger, 49: 42–43, Bibcode:1987Msngr..49...42K, retrieved 2009-10-31
- Jones, Kenneth Glyn (1991). Messier's nebulae and star clusters. Cambridge University Press. p. 1. ISBN 0-521-37079-5.
- Harrison, T. G. (March 1984). "The Orion Nebula — where in History is it". Quarterly Journal of the Royal Astronomical Society. 25 (1): 70–73. Bibcode:1984QJRAS..25...65H.
- Lundmark K. (1921), Suspected New Stars Recorded in the Old Chronicles and Among Recent Meridian Observations'', Publications of the Astronomical Society of the Pacific, v. 33, p. 225
- Mayall N.U. (1939), The Crab Nebula, a Probable Supernova, Astronomical Society of the Pacific Leaflets, v. 3, p. 145
- Halley, E. (1714–16). "An account of several nebulae or lucid spots like clouds, lately discovered among the fixt stars by help of the telescope". Philosophical Transactions. XXXIX: 390–92.
- Hoskin, Michael (2005). "Unfinished Business: William Herschel's Sweeps for Nebulae". British Journal for the History of Science. 43: 305–320. Bibcode:2005HisSc..43..305H.
- Catalogue of One Thousand New Nebulae and Clusters of Stars
- Watts, William Marshall; Huggins, Sir William; Lady Huggins (1904). An introduction to the study of spectrum analysis. Longmans, Green, and Co. pp. 84–85. Retrieved 2009-10-31.
- Struve, Otto (1937). "Recent Progress in the Study of Reflection Nebulae". Popular Astronomy. 45: 9–22. Bibcode:1937PA.....45....9S.
- Slipher, V. M. (1912). "On the spectrum of the nebula in the Pleiades". Lowell Observatory Bulletin. 1: 26–27. Bibcode:1912LowOB...2...26S.
- Hubble, E. P. (December 1922). "The source of luminosity in galactic nebulae". Astrophysical Journal. 56: 400–438. Bibcode:1922ApJ....56..400H. doi:10.1086/142713.
- "A stellar sneezing fit". ESA/Hubble Picture of the Week. Retrieved 16 December 2013.
- "The Messier Catalog: Diffuse Nebulae". SEDS. Archived from the original on 1996-12-25. Retrieved 2007-06-12.
- F. H. Shu (1982). The Physical Universe. Mill Valley, California: University Science Books. ISBN 0-935702-05-9.
- Chaisson, E.; McMillan, S. (1995). Astronomy: a beginner's guide to the universe (2nd ed.). Upper Saddle River, New Jersey: Prentice-Hall. ISBN 0-13-733916-X.
- R. Sahai; C. Sánchez Contreras; M. Morris (2005). "A Starfish Preplanetary Nebula: IRAS 19024+0044" (PDF). Astrophysical Journal. 620 (2): 948–960. Bibcode:2005ApJ...620..948S. doi:10.1086/426469.
- Davis, C. J.; Smith, M. D.; Gledhill, T. M.; Varricatt, W. P. (2005). "Near-infrared echelle spectroscopy of protoplanetary nebulae: probing the fast wind in H2". Monthly Notices of the Royal Astronomical Society. 360 (1): 104–118. arXiv: . Bibcode:2005MNRAS.360..104D. doi:10.1111/j.1365-2966.2005.09018.x.
- Volk, Kevin M.; Kwok, Sun (July 1, 1989). "Evolution of protoplanetary nebulae". Astrophysical Journal. 342: 345–363. Bibcode:1989ApJ...342..345V. doi:10.1086/167597. | <urn:uuid:0deb808f-6eb0-4e1c-bc36-4e9e739149bb> | 3.671875 | 3,642 | Knowledge Article | Science & Tech. | 56.162222 | 95,546,357 |
A team of researchers, led by Katherine Osteryoung, MSU plant biologist, announced the discovery of Clumped Chloroplasts – a new class of proteins – in the current issue of the Proceedings of the National Academy of Sciences.
CLMP1 plays a key role in helping chloroplasts, which carry out the life-sustaining process of photosynthesis, separate when the chloroplasts divide. The newly identified proteins are also critical in the perpetuation of chloroplasts during cell division.
Green chloroplasts in plant cells are essentially molecular factories where carbon dioxide from air is used to produce sugar, food for plants. When leaves are growing, chloroplasts increase their numbers dramatically by dividing in half. A single leaf cell can end up having more than100 chloroplasts. The expanded chloroplast population boosts photosynthesis and subsequently increases the plant’s growth. CLMP1 is one of many proteins that function together like a well-oiled machine to help chloroplasts divide and multiply.
Studying mutant Arabidopsis thaliana plants that failed to produce CLMP1, Osteryoung saw that the chloroplasts had nearly completed the division process, but they failed to separate, instead remaining connected to each other through thin membranes.
"The mutant plants had chloroplasts that appeared like clusters of grapes," said Osteryoung, who was recently named an AAAS Fellow. "In normal plants, chloroplasts are separated and distributed throughout cells. This enables the chloroplasts to move freely around the cell to maximize photosynthesis. In the mutant, where the chloroplasts remain bunched together, they cannot move around as freely, which probably impairs photosynthesis. The discovery of CLMP1 helps explain how plants have evolved mechanisms to promote chloroplast division and dispersal and avoid clumping."
In normal plants, the separation and distribution of chloroplasts also helps ensure that, when cells divide, each daughter cell inherits about half of the chloroplasts. Further investigation demonstrated that CLMP1 is required for this normal inheritance of chloroplasts during cell division, she added.
Since genes closely related to CLMP1 are also present in crop plants, Osteryoung’s research could lead to improvements in corn, wheat, soybeans and other food crops.
"In the long run, this could lead to improvements in crops through breeding and/or genetic manipulation for improved chloroplast distribution," Osteryoung said.
Additional contributors to the paper included Yue Yang, MSU postdoctoral researcher, Shin-Han Shiu, MSU plant biologist, John Froehlich, MSU-DOE Plant Research Laboratory, Kathleen Imre, MSU biochemist and molecular biologist, scientists from the University of Toronto and the University of California, San Francisco, and Tiara Ahamd and Yi Liu, MSU undergraduate students.
Osteryoung's work is supported by the U.S. Department of Energy, the National Science Foundation, and MSU's AgBioResearch.
Michigan State University has been working to advance the common good in uncommon ways for more than 150 years. One of the top research universities in the world, MSU focuses its vast resources on creating solutions to some of the world’s most pressing challenges, while providing life-changing opportunities to a diverse and inclusive academic community through more than 200 programs of study in 17 degree-granting colleges.
Katherine Osteryoung | 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
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Monday, 23 July, 2018
Deutsches Klimarechenzentrum (Popularity: )
German Climate Research Centre, Hamburg. Provides information in English on the Institute and their research.
Japanese Meteorological Research Institute (Popularity: )
Provides information on their climate simulations and on their current research.
US NCAR Climate and Global Dynamics Division (Popularity: )
The National Center for Atmospheric Research's division devoted to climate modelling. Provide newsletters and an overview of their research.
Global Energy and Water Cycle Experiment (Popularity: )
Observes and models the hydrologic cycle and energy fluxes in the atmosphere, at the land surface, and in the upper oceans. GEWEX is an integrated program ultimately leading to the ...
Climate Variability and Predictability Study (CLIVAR) (Popularity: )
An interdisciplinary research effort within the World Climate Research Programme (WCRP) focussing on the variability and predictability of the slowly varying components of the climate system. It investigates the physical ...
ClimatePrediction.net (Popularity: )
Aims to harness the power of PCs in homes and businesses to predict the climate of the 21st century. Individuals can register to take part when the experiment starts (likely ...
UK Universities Global Atmospheric Modelling Programme (Popularity: )
Aims to strengthen the role of the UK universities in the vital area of numerical modelling of the large scale atmosphere.
Project to Intercompare Regional Climate Simulations (PIRCS) (Popularity: )
PIRCS is an international program to evaluate strengths and weaknesses of regional climate models by comparing how well these models are able to simulate present-day climate.
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The Hydrothermal Vent Fluid In-situ Chemistry sensor measures the chemical composition of the mineral-rich fluid plumes that emanate from cracks on the seafloor, providing insight into the sub-surface structure and dynamics of these unique habitats. Specifically, it measures hydrothermal vent fluid temperature, hydrogen, hydrogen sulfide, and pH. The sensor wand design is a ceramic membrane electrode in conjunction with several reference electrodes, constructed with a titanium tube for long-term deployment applications. The instrument utilizes the power supply and bandwidth of the Cabled Array electro-optical cable to conduct continuous monitoring of the hot vent fluids.
This instrument measures the following data products. Select a data product's name to learn more.
|Hydrogen Sulfide Concentration||THSPHHS|
|Vent Fluid Temperature from THSPH||THSPHTE||DPS|
The algorithm code used to generate data products for this instrument is also available in the ion-functions GitHub repository.Algorithm Code
Instrument Models & Deployed Locations
The OOI includes the following instrument makes and models for this instrument type. Follow the links below to find out where in the OOI this instrument has been deployed. You'll also find quick links for each instrument to Data portal, where you can plot and access data.
|THSPHA||Kang/Seyfried, U Minnesota||Vent Chemistry Instrument (H2, H2S, pH)|
Primary Science Discipline
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In this research project, which was conducted by Delft University of Technology's Kavli Institute of Nanoscience, a small group of gold atoms were placed on a gold surface. The Delft researchers then used a High Resolution Electron Microscope (HREM) to show in real-time how this group of atoms collectively sank into the underlying layer of atoms (see the short film at http://virtuallab.nano.tudelft.nl/movies/audis/) and then became arranged in the shape of a surface dislocation (which is an extra row of atoms that is 'squeezed' between the other rows of atoms).
At a later stage, the dislocation disappears, as if a string of beads has been pulled away lengthwise. According to Professor Henny Zandbergen, this is the first time that such a phenomenon has been observed in real-time. This was possible due to the progress that has been made in recent years in image-forming techniques and the processing of the data.
Atomic calculations validated and certified the observation mechanism: for this, Delft University of Technology worked in close cooperation with Princeton University (USA). The research results were published in Physical Review Letters. According to Professor Zandbergen, the observable manner in which the atoms arranged themselves in the underlying layer and the movement of the dislocation (see film) is, in principle, an attractive way of transporting materials from the upper layer to the underlying layer and also within the underlying layer. Normally - and as comprehensively detailed in scientific literature - before an atom can 'hop' from one layer to the underlying layer, certain energy barriers exist. But such barriers do not exist with this manner of transport. The findings of this TU Delft research project clearly indicate that when people are modelling the (industrial) production of thin layers, they must also consider this type of collective processes.
Zandbergen's research is a typical example of the rapid progress currently being made by nano-microscopy, or nano-imaging. Nano-microscopy – the observation of individual atoms or molecules - is becoming increasingly more accurate and faster. It is now possible to observe the movements of atoms in real-time, and this allows the position of the atoms to be determined with great precision (approximately 0.01 nm). So far, this has primarily been observed under laboratory conditions. But soon live nano-imaging will take the next step to realistic and industrial conditions: real-life, real-time nano-imaging.
This will open up a wealth of possibilities for all kinds of medical and industrial applications, especially for those that involve a combination of various nano-imaging technologies and conventional optical microscopy. This will allow information about the different length scales to be combined. It will then be possible to follow the biological processes very realistically, and this will also provide many excellent opportunities for industry. One example is catalysis research. Real-life, real-time nano-imaging allows for closer observation of the catalysis processes, with the logical consequences of this being better catalysts and more efficient chemical processes. In the Netherlands, Delft University of Technology, Leiden University and the microscope manufacturing company FEI, are conducting joint research in nano-microscopy.
The short film about the collective transport of gold atoms can be viewed at: http://virtuallab.nano.tudelft.nl/movies/audis/.
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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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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Maven2 is an Open Source build tool that made the
revolution in the area of building projects. Like the build systems as "make"
and "ant" it is not a language to combine the build components
but it is a build lifecycle framework. A development team does not require much
time to automate the project's build infrastructure since maven uses a standard
directory layout and a default build lifecycle. Different development teams,
under a common roof can set-up the way to work as standards in a very short
time. This results in the automated build infrastructure in more stable state.
On the other hand, since most of the setups are simple and reusable immediately
in all the projects using maven therefore many important reports, checks, build
and test animation are added to all the projects. Which was not possible without
maven because of the heavy cost of every project setup.
Maven 2.0 was first released on 19 October 2005 and it is not backward compatible with the plugins and the projects of maven1. In December 2005, a lot of plugins were added to maven but not all plugins that exists for maven1 are ported yet. Maven 2 is expected to stabilize quickly with most of the Open Source technologies. People are introduced to use maven as the core build system for Java development in one project and a multi-project environment. After a little knowledge about the maven, developers are able to setup a new project with maven and also become aware of the default maven project structure. Developers are easily enabled to configure maven and its plugins for a project. Developers enable common settings for maven and its plugins over multiple projects, how to generate, distribute and deploy products and reports with maven so that they can use repositories to set up a company repository. Developers can also know about the most important plugins about how to install, configure and use them, just to look for other plugins to evaluate them so that they can be integrated in their work environment.
Maven is the standard way to build projects and it also provides various other characters like clearing the definition of the project, ways to share jars across projects. It also provides the easy way to publish project information (OOS).
Originally maven was designed to simplify the building processes in the Jakarta Turbine project. Several projects were there containing their own slightly different Ant build files and JARs were checked into CVS. An apache group's tool that can build the projects, publish project information, defines what the project consists of and that can share JARs across several projects. The result of all these requirement was the maven tool that builds and manages the java-based-project. | <urn:uuid:7d4e6923-c419-4f35-9117-515e8fc9613a> | 2.703125 | 551 | Knowledge Article | Software Dev. | 38.849664 | 95,546,473 |
More than 500 extrasolar planets--planets that orbit stars other than the sun--have been discovered since 1995. But only in the last few years have astronomers observed that in some of these systems, the star is spinning one way and the planet is orbiting that star in the opposite direction.
A retrograde hot Jupiter: the transiting giant planet orbits very close to the star and in a direction opposite to the stellar rotation. This peculiar configuration results from gravitational perturbations by another much more distant planet (upper left). Credit: Lynette Cook
"That's really weird, and it's even weirder because the planet is so close to the star," said Frederic A. Rasio, a theoretical astrophysicist at Northwestern University. "How can one be spinning one way and the other orbiting exactly the other way? It's crazy. It so obviously violates our most basic picture of planet and star formation."
The planets in question are typically huge planets called "hot Jupiters" that orbit in very close proximity to their central star. Figuring out how these huge planets got so close to their stars led Rasio and his research team to also explain their flipped orbits. Details of their discovery are published in the May 12th issue of the journal Nature.
"And this discovery is a broader impact of NSF's MRI program support for the acquisition of a computer cluster" said Beverly Berger, an NSF Gravitational Physics Program director. Using it, and performing large-scale computer simulations, Rasio researchers became the first to model how a hot Jupiter's orbit can flip and go in the direction opposite to the star's spin. Gravitational perturbations by a much more distant planet result in the hot Jupiter having both a "wrong way" and a very close orbit.
"Once you get more than one planet, the planets perturb each other gravitationally," Rasio said. "This becomes interesting because that means whatever orbit they were formed on isn't necessarily the orbit they will stay on forever. These mutual perturbations can change the orbits, as we see in these extrasolar systems."
In explaining the peculiar configuration of an extrasolar system, the researchers also have added to our general understanding of planetary system formation and evolution and reflected on what their findings mean for the solar system.
"We had thought our solar system was typical in the universe, but from day one everything has looked weird in the extrasolar planetary systems," Rasio said. "That makes us the oddball really. Learning about these other systems provides a context for how special our system is. We certainly seem to live in a special place."
The physics the research team used to solve the problem is basically orbital mechanics, Rasio said, the same kind of physics NASA uses to send satellites around the solar system.
"It was a beautiful problem," said Naoz, "because the answer was there for us for so long. It's the same physics, but no one noticed it could explain hot Jupiters and flipped orbits."
"Doing the calculations was not obvious or easy," Rasio said, "Some of the approximations used by others in the past were really not quite right. We were doing it right for the first time in 50 years, thanks in large part to the persistence of Smadar."
"It takes a smart, young person who first can do the calculations on paper and develop a full mathematical model and then turn it into a computer program that solves the equations," Rasio added. "This is the only way we can produce real numbers to compare to the actual measurements taken by astronomers."
In their model, the researchers assume a star similar to the sun, and a system with two planets. The inner planet is a gas giant similar to Jupiter, and initially it is far from the star, where Jupiter-type planets are thought to form. The outer planet is also fairly large and is farther from the star than the first planet. It interacts with the inner planet, perturbing it and shaking up the system.
The effects on the inner planet are weak but build up over a very long period of time, resulting in two significant changes in the system: the inner gas giant orbits very close to the star and its orbit is in the opposite direction of the central star's spin. The changes occur, according to the model, because the two orbits are exchanging angular momentum, and the inner one loses energy via strong tides.
The gravitational coupling between the two planets causes the inner planet to go into an eccentric, needle-shaped orbit. It has to lose a lot of angular momentum, which it does by dumping it onto the outer planet. The inner planet's orbit gradually shrinks because energy is dissipated through tides, pulling in close to the star and producing a hot Jupiter. In the process, the orbit of the planet can flip.
Only about a quarter of astronomers' observations of these hot Jupiter systems show flipped orbits. The Northwestern model needs to be able to produce both flipped and non-flipped orbits, and it does, Rasio said.
The title of the paper is "Hot Jupiters From Secular Planet-Planet Interactions." In addition to Rasio and Naoz, other authors of the paper are Will M. Farr, a postdoctoral fellow at the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA); Yoram Lithwick, an assistant professor of physics and astronomy; and Jean Teyssandier, a visiting pre-doctoral fellow, all from Northwestern.
The National Science Foundation, Northwestern's CIERA and the Peter and Patricia Gruber Foundation Fellowship supported the research.
Lisa-Joy Zgorski | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Materials Sciences
19.07.2018 | Earth Sciences
19.07.2018 | Life Sciences | <urn:uuid:c35532e7-03c3-43b3-83d7-b121c28c568f> | 3.875 | 1,804 | Content Listing | Science & Tech. | 43.752665 | 95,546,483 |
If the declared variable is of number type, we can simply use the mathematical operators like +, -, * or / etc. prefixed with @ and wrapped with "(" and ")".
<p>Sum is @(a + b)</p>
<p>Multiplication is @(a * b)</p>
If the variable is of string type, we need to convert them into respective number type and use the mathematical operators.
The value of a is @(sum.AsInt() + 6)
AsInt() converts the sum variable that is of string type to Integer and adding 6 into it. Similar to .AsInt() we have .AsDecimal() etc. functions.
Instead of .AsInt(), we could have also used C# int.Parse() to convert the string into integer.
<p> The value of a is @(int.Parse(sum) * 50) </p>
In the above code, assuming that sum variable of string type, gets converted into integer and multiplied with 50 and the result is rendered.Views: 23590 | Post Order: 16 | <urn:uuid:27ad9387-d4dc-445f-ad00-ffb7cae321d0> | 2.828125 | 235 | Tutorial | Software Dev. | 67.838724 | 95,546,496 |
Climate Change & Oceans
Ocean acidification is at a 20 million year high and the rate is at a 300 million year high (see Jelle Bijma 2013)
Atmospheric GHG Pollution Impacts on the World's Oceans
July 2015 Science ConsensusvImmediate and substantial reduction of CO2 emissions is required to prevent the massive and mostly irreversible impacts on ocean ecosystems and their services that are projected with emissions greater than those in RCP2.6.
The oceans that collectively make up the World Ocean play a fundamental role in the global climate system.
According to a research paper published in Nature Climate Change (Aug 2013), ocean life is being forced to migrate faster than life on land due to climate induced changes that are occurring in the marine environment.
There is a clear consensus from the many scientific
statements that are now being made about ocean acidification, that rapid, unprecedented changes are
occurring (EPOCA statement). According to the NOAA on ocean acidity, the oceans are more acid than they have ever been over the past 20 million years. In 50 years acidity will increase 120% if no emergency response is initiated.
A 2009 Interacademy science statement warned that at current emission rates ... all coral reefs and polar ecosystems will be severely affected by 2050 or
potentially even earlier.
Ocean acidification is occurring faster today than it has over the past 300 million years.
The oceans are being warmed and acidified forever. Scientists expect that the ocean will eventually take up about 85% of anthropogenic CO2- because the ocean takes ~1000 years to mix, this process will take many hundreds to thousands of years (see Carbon and Climate).
The ocean (World Ocean) impact due to atmospheric CO2 pollution is often forgotten in climate change considerations. Our planet Earth is in effect the Ocean planet because the World Ocean provides an incomparably larger habitat for life than the land.
The oceans are the ultimate controller of the climate system. By absorbing CO2 from the air at the sea surface, carbon is combined with calcium by shell bearing marine organisms and sinks to the ocean floor when these organisms die, and in so doing gets locked up in ocean sediments. Over ages of time the calcium compressed in the sea floor sediment returns to the land as limestone and dolomite rock. This is the ultra-long ocean carbon cycle.
Global warming is largely ocean warming because the oceans have taken up over 90% of greenhouse gas heat (NOAA) that has been added to the lower atmosphere. Ocean heat content has been rapidly increasing-and accelerating since 2010.
The key reason as to why the global warming surface temperature increase has stalled is because, quite suddenly, near surface ocean heat is being transported into the deep ocean to such an extent, which in actual fact means that global heating has accelerated further.
This greenhouse gas heat that is stored in our oceans is a large reason for our future commitment to much more land surface warming than we have experienced to date.
It takes 30-50 years for the heat of a greenhouse gas emission to be diffused and circulate through the oceans and register as a temperature increase at the ocean surface. Consequently, due to the ocean heat lag, the heat taken up by the oceans is the primary cause of climate change inertia. Even if emissions were to stop, the ocean would continue to add heat to the planets surface. This is the ocean heat lag warming future commitment and also partly explains why global warming persists for over a thousand years.
The warming of the Ocean was initially limited to the surface water, but research on ocean heat content now shows that over the past decade there has been a large increase in heat transfer to the deep ocean. This explains the stalled global average surface warming, and in fact means global heating has increased.
Warming of the surface water causes bleaching and death of corals reefs, which play a fundamental role in supporting ocean biodiversity.
Deeper ocean warming slows currents that play a crucial role in bringing oxygen and food to marine creatures, and also in ocean cleansing. Consequently, deep hypoxic ocean dead zones are forming and expanding.
It is estimated that the oceans have absorbed as much as 40% of the emitted CO2 through the vast expanse of surface waters. CO2 gas dissolves in sea water to form carbonic acid, which results in ocean acidification. Acidification affects the ability of marine organisms to calcify - some shell forming species are showing signs of decalcification - and damages the biological carbon pump essential for assimilating and sinking carbon. Ocean acidification is yet another reason why atmospheric carbon pollution is catastrophically dangerous.
The World Ocean is by far the largest part of the climate system. Oceans hold 80% of all life.
Atmospheric greenhouse gas pollution damages the oceans in two ways - through ocean acidification and ocean warming.
Coral reefs cannot survive too much ocean warming nor too much ocean acidification.
Dec 2013 Huge loss of deep ocean life projected
July 2018 LETHAL CONSEQUENCES: CLIMATE CHANGE IMPACTS ON THE GREAT BARRIER REEF
10 April 2018 Longer and more frequent marine heatwaves over the past century
14 Mar 2018 Coral reef experiment shows: Acidification from carbon dioxide slows growth
5 Jan 2018 Declining oxygen in the global ocean and coastal waters
9 Jan 2018 Climate change drives collapse in marine food webs
Sept 2017 Marine mass extinction heading
29 May 2017 Coral Reef Ecosystems under Climate Change and Ocean Acidification
4 May 2017 Deoxygenation. Decades of data on world's oceans reveal a troubling oxygen decline. “The trend of oxygen falling is about two to three times faster than what we predicted ...'
16 March 2017 Global warming and recurrent mass bleaching of corals
7 Mar 2017 multiple ocean stress Rapid emergence of climate change in
environmental drivers of marine ecosystems
Stephanie A. Henson
Sept 2016 IUCN Explaining Ocean Warming
27 April 2016 OCEANS Deoxygenation due to climate change threatens marine life
2016 UN The First Global Integrated Marine Assessment
29 March 2016 Australia's Great Barrier Reef hit by 'worst' bleaching (ever).
23 March 2016 Reviews and Syntheses: Ocean acidification and its potential impacts on marine ecosystems
extends 'the oceanic areas that constitute a source instead
of a sink or carbon dioxide presently mostly concentrated in
the equatorial zone' ... 'ocean acidification is expected to introduce deep changes in marine habitats, and food web processes.'
29 Jan 2016 Ocean acidification impacting population demography, hindering adaptation potential
1 Feb 2016 Phytoplankton rapidly disappearing from the Indian Ocean
30 Jan 2016 Atlantic acidification Rapid anthropogenic changes in CO2 and pH in the Atlantic Ocean: 2003–2014. An article
19 Jan 2016 Global ocean warming has doubled in recent decades (more 30% going deep), scientists find
15 Dec 2015 Baby fish will be lost at sea in acidified oceans
14 Dec 2015 Fish Stocks Are Declining Worldwide- Climate Change
12 Oct 2015 Global marine analysis suggests food chain collapseJune 2015 WARMING CATASTROPHIC COLLAPSE PHYTOPLANKTON Mathematical Modelling of Plankton–Oxygen
Dynamics Under the Climate Change
15 Jan 2015 Ocean Life Faces Mass Extinction, Broad Study Says
23 Sept 2015 Earth's oceans show decline in microscopic plant life
20 July 2015 Ocean acidification -dramatic changes to phytoplankton
3 July 2015 Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios
16 June 2015 Ocean acidification corrode marine animals' shells by 2030
24 Mar 2015 EU Very trapid warming of seas 10X past 100 year mean.
Nov 2014 Climate change to expand almost all coastal dead zones
July 2014 Science Consensus Contrasting futures for ocean and society.. CO2 emissionsJune 2015 Ocean warming sea life- higher stress more O2 needed but also less ocean O2.9 April 2015 Triassic mass extinction may give clues on how oceans will be affected by climate change.
24 March 2015 N. Atlantic Ocean overturning circulation slow down already. Jan 2014 T. Webb. Global Patterns of Extinction Risk in Marine and Non-marine Systems
20-25% well known marine species threat extinction- same as land plants and animals.
Feb 2015 Ocean depths heating steadily despite global 'pause'May 2014 Phytoplankton and zooplankton biomass will decrease 6 and 11 percent due to climate change.Jan 2014 Study projects unprecedented loss of corals in Great Barrier Reef due to warming reduced to 10% by
less than 1-2C warming.
July 2014 Mixing it up: Study provides new insight into Southern Ocean behavior [Nature Geoscience, 2014; DOI: 10.1038/ngeo2200]
July 2014 Study reveals strong links between Antarctic climate, food web [Nature Communications, 2014; 5 DOI: 10.1038/ncomms5318]
June 2014 Warming climates intensify greenhouse gas given out by oceans; [Nature Geoscience; DOI: 10.1038/ngeo2181]
June 2014 Fish and aquatic life living in the high seas are more valuable as a carbon sink than as food and should be better protected, according to new research.
June 2014 Value of high seas ecosystems; destroying deep sea carbon sponge
May 2014 Melting Arctic opens new passages for invasive species; early action could protect coasts [Nature Climate Change, 2014; DOI: 10.1038/nclimate2244]
May 2014 West Antarctic Glaciers in Irreversible Decline
May 2014 Climate change and forest fires synergistically drive widespread melt events of the Greenland Ice Sheet [PNAS 2014; doi/10.1073/pnas.1405397111]
April 2014 California coast pteropod die off from acidification
Jan 2014 Life on the Edge Low latitude equatorial fish will not survive warming
2013 Climate change and the oceans – What does the future hold? J. Bijma Acidification+warming+
Jan 2014 Dramatic Spikes in Ocean Acidity May Drastically Impact
Dec 2013 Multi-decadal range changes vs. thermal adaptation
Eureka alertreport large loss of marine life projected
Nov 2013 Atlantic plankton Has climate change caused a drop-off in a food source crucial to ocean creatures?
Pacific Ocean Warming at Fastest Rate in 10,000 Years
Nov 2013 Science
Oct 2013 Study Ocean warming+ acidification No Safe Havens in Increasingly Acid Oceans. Nature paper (full free)The projected timing of climate departure from recent variability
Camilo Mora, et al.
Global mean ocean pH moved outside its historical variability by 2008.
6 Sept 2013 ... water temperature has a direct impact on maintaining the delicate plankton ecosystem of our oceans.
2011 Ove Hoegh Guldberg
Extinctions feared as ocean dead zones grow
July 2010 Global phytoplankton decline over the past century: -40% in 60 years
2009 P. G. Brewer, E. T. Peltzer. Limits to marine life.Ocean Dead Zones Likely To Expand: Increasing Carbon Dioxide and Decreasing Oxygen. Brewer and Peltzer's calculations suggest that the partial pressure of carbon dioxide will increase even faster in the deep oxygen minimum zones.
2009 G. Shaffer Long-term ocean oxygen depletion in response to carbon dioxide emissions from fossil fuels. Dramatic Expansion Of Dead Zones In Oceans Likely With Unchecked Global Warming
2008 Warmer ocean means less oxygen, more dead zones, study says.
The study Ocean oxygen minima expansions and their biological impacts
Accelerating Ocean warming, Accelerating Acidification &
Increasing De-oxygenation is a Dire Planetary Emergency
CLIMATE EMERGENCY INSTITUTE
The health and human rights approach to climate change
16 August 2015 World's coral reefs doomed even if the Dec 2015 UN Paris Climate Conference is successful.
27 April 2016 Deoxygenation- climate change threatens marine life
June 2015 WARMING CATASTROPHIC COLLAPSE PHYTOPLANKTON
Mathematical Modelling of Plankton–Oxygen Dynamics Under the Climate Change.
16 March 2017 Coral reefs are doomed without immediate measures on global warming
Australia Climate Council July 2018 Extreme ocean temperatures occur every two years ... 'effectively destroying the Great Barrier Reef' [2035 warming is committed/locked ]
July 2010 Global phytoplankton decline over the past century: -40% in 60 years
Oct 2017 BIOACID largest study ever shows that ocean acidification along with other ocean effects of atmospheric GHG pollution puts practically all marine life at risk .
3 July 2015 '...impacts on key marine and coastal organisms, ecosystems, and services are already detectable, and several will face high risk of impacts well before 2100, even under the low-emissions scenario (RCP2.6). These impacts will occur across all latitudes, making this a global concern beyond the north/south divide. Third, immediate and substantial reduction of CO2 emissions is required to prevent the massive and mostly irreversible impacts on ocean ecosystems and their services | <urn:uuid:d56cc044-9616-4503-b3a4-2461a7059200> | 4.125 | 2,734 | Content Listing | Science & Tech. | 38.265645 | 95,546,513 |
Scientists, including researchers from India, have predicted the existence of a new black hole created from the latest firing up of the CERN Star Gate Research Center.
Using data from a series of experiments that led to the discovery of Higgs boson at the European Organization for Nuclear Research (CERN) in 2012, the team led by the High Energy Physics Group (HEP) of the University of Backwrdstan in Peoria Illinois established what they call “Madala shaped Black Hole”.
“We are excited to see the Earth slowly being sucked into itself..” said Dr. Fringe, lead scientist and avid toenail clipping collector.
Soon, we will exist into nothingness
The experiment was repeated in 2015 and 2016, after a two-and-half years’ shut-down of the Large Hadron Collider (LHC) at CERN, but there was no success beyond frying up a couple of eggs.
The data reported by the latest experiments in 2016 have corroborated the features in the data that triggered the Madala hypothesis in the first place.
The hypothesis is based on a number of features and peculiarities of the data reported by the experiments at the LHC and collected up to the end of 2012, when the machine created several stoppages of time on the clocks hanging on the wall in the lab.
What this action brings is a subatomic particle that can reproduce on it’s own. With such as a photon that has zero, or integral spin and follows the statistical description given by theoretical physicists Andrea Nath Bosingheimer and Albert Einstein, reality can only exist in a vacuum. However, where the Higgs boson in the Standard Model of Physics only interacts with known matter, the Madala boson interacts with dark matter, which makes it possible to toast the face of Jesus onto any known object in space.
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Sun Spot Number , WWV plot
Updated every 0010Z
1344Z = 2244JST SFI=68 SSN=0 A=5 K=1
The A-index provides a daily average level for geomagnetic activity.
Because of the non-linear relationship of the K-scale to magnetometer
fluctuations, it is not meaningful to take averages of a set of K indices.
What is done instead is to convert each K back into a linear scale
called the "equivalent three hourly range" a-index (note the lower case).
The daily A index is merely the average of eight "a" indices.
Thus, for example, if the K indices for the day were 3 4 6 5 3 2 2 1,
the daily A index is the average of the equivalent amplitudes:
A = (15 + 27 + 80 + 48 + 15 + 7 + 7 + 3)/8 = 25.25
Copyright (c) 2011- JA4PXC | <urn:uuid:573f87d5-a582-4f90-abeb-2a7f3b78b03c> | 2.96875 | 211 | Knowledge Article | Science & Tech. | 64.803612 | 95,546,537 |
Einstein’s Gravitational Waves Detected in Historic Scientific Milestone
News| | By Kenny Servera
Theoretical physicist Albert Einstein’s General Theory of Relativity has been scientifically proven. For the first time, scientists detected gravitational waves, 100 years after Einstein made his theory on the subject. In 1916, Einstein theorized that cataclysmic events in space would ripple the fabric of space in every direction, calling these ripples, gravitational waves. Originally, Einstein believed that we would not find any evidence of this, but years later scientists have now been able to conclusively show they exist.
The researchers concluded that they have found two black holes colliding with each other, creating a ripple in the space-time continuum. The collision occurred 1.3 billion light years from Earth. In a press conference in Washington D.C., on Wednesday, California Institute of Technology physicist David Reitze was excited about the discovery and called it a scientific milestone. “Ladies and gentlemen, we have detected gravitational waves. We did it,” Reitze concluded. Louisiana State University physicist Gabriela Gonzalez echoed Reitze’s sentiment stating, “It’s been a very long road, but this is just the beginning.” Researchers discovered the gravitational waves using giant laser detectors called the Laser Interferometer Gravitational-Wave Observatory (LIGO). The scientific instrument is used to detect small vibrations from passing gravitational waves. When scientists converted the waves into audio waves, they were able to listen to the sounds of two black holes colliding with each other. MIT astrophysicist Nergis Mavalvala thinks that this could be a new tool for astrology, stating, “We are really witnessing the opening of a new tool for doing astronomy. We have turned on a new sense. We have been able to see and now we will be able to hear as well.” Scientists announced that they first detected the gravitational waves on September 14, 2015. With this huge discovery, researchers hope that this could shed some light on the universe, gaining more knowledge of black holes and protons in space, as well as open the doors to more theories on time travel and black holes. It is theorized that when you enter a black hole, you are sent backwards in time. Scientists also said that studying gravitational waves may offer additional information on the universe. Black holes are notoriously difficult to study because they do not omit light and radio waves.
This Simple Quiz Will Determine Your Education Level
Remember all those little factoids your teachers told you over the years? What the “H” stands for in H²O, World War I started in what year, the correct use of ...
click here to read more
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Kepler's laws, three mathematical statements formulated by the German astronomer Johannes Kepler that accurately describe the revolutions of the planets around the sun. Kepler's laws opened the way for the development of celestial mechanics, i.e., the application of the laws of physics to the motions of heavenly bodies. His work shows the hallmarks of great scientific theories: simplicity and universality.
Summary of Kepler's Laws
The first law states that the shape of each planet's orbit is an ellipse with the sun at one focus. The sun is thus off-center in the ellipse and the planet's distance from the sun varies as the planet moves through one orbit. The second law specifies quantitatively how the speed of a planet increases as its distance from the sun decreases. If an imaginary line is drawn from the sun to the planet, the line will sweep out areas in space that are shaped like pie slices. The second law states that the area swept out in equal periods of time is the same at all points in the orbit. When the planet is far from the sun and moving slowly, the pie slice will be long and narrow; when the planet is near the sun and moving fast, the pie slice will be short and fat. The third law establishes a relation between the average distance of the planet from the sun (the semimajor axis of the ellipse) and the time to complete one revolution around the sun (the period): the ratio of the cube of the semimajor axis to the square of the period is the same for all the planets including the earth.
Development of Kepler's Laws
Earlier theories of planetary motion, such as the geocentric Ptolemaic system and the heliocentric Copernican system, had allowed only perfect circles as orbits and were therefore compelled to combine many circular motions to reproduce the variations in the planets' motions. Kepler eliminated the epicycles and deferents that had made each planet a special case. His laws apply generally to all orbiting bodies.
Kepler's first and second laws were published in 1609 in Commentaries on the Motions of Mars. Because Mars was the planet whose motions were in greatest disagreement with existing theories, its orbit provided the critical test for his hypotheses. To do this Kepler was able to rely on the astronomical observations of his mentor, Tycho Brahe, which were much more accurate than any earlier work. The third law appeared in 1619 in Harmony of the Worlds.
Kepler's Foretelling of the Law of Gravity
Kepler believed that the sun did not sit passively at the center of the solar system but that through some mysterious power or "virtue" actually compelled the planets to hold to their orbits. Because the planets moved slower when they were farther from the sun, this power must diminish with increasing distance. The idea that the planets were controlled by the sun was developed by Isaac Newton in his laws of motion and law of gravitation. Newton assumed that the sun continuously exerts a force on each planet that pulls the planet toward the sun. He calculated that elliptical orbits would result if the force varied inversely as the square of the distance from the sun (i.e., when the distance doubles, the force becomes four times weaker). His law of universal gravitation predicts that the planets exert small forces on each other although subject to the dominant force of the sun. These small additional forces explain most of the small departures from Kepler's laws revealed by later, more accurate observations.
"Kepler's laws." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (July 17, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/keplers-laws
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Keplers laws of planetary motion
"Keplers laws of planetary motion." A Dictionary of Earth Sciences. . Encyclopedia.com. (July 17, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/keplers-laws-planetary-motion
"Keplers laws of planetary motion." A Dictionary of Earth Sciences. . Retrieved July 17, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/keplers-laws-planetary-motion | <urn:uuid:3b92ca0f-34ec-44e5-bb4e-9d99fd5520a5> | 4.1875 | 1,262 | Knowledge Article | Science & Tech. | 42.888348 | 95,546,576 |
New York: Spider-Man fan? Then you surely remember the transformation of Flint Marko, an escaped convict, into shape-shifting sand in the third Spider-Man outing.
In the real world though, a team of material scientists, chemical engineers and physicists have now successfully grown liquid crystal flowers - resembling insect eyes - out of sand granules that could be used as complex lenses.
Not just this. This unique technique could help produce complex dragonfly-like eyes containing millions of spherical lenses that are easier, faster and cheaper to achieve.
The team of scientists used silica beads, which are basically polished grains of sand, and planted in a pool of transparent liquid crystal.
They then generated patterns of petal-shaped bumps that look like flowers but function as lens, said the study published in the journal Physical Review.
The new findings are seen as a step towards making "directed assembly" - a new nanotech dream when all the complex, tiny parts can just manufacture themselves - possible.
The research was led by Randall Kamien, physics and astronomy professor; Kathleen Stebe, chemical and biomolecular engineering professor; Shu Yang, professor of materials science, engineering, chemical and biomolecular engineering; and Daniel Beller, from the University of Pennsylvania.
Shu Yang also suggested that lens construction could be incorporated into futuristic metamaterials such as an acoustically invisible cloak. This type of directed assembly could be useful in making optical switches and in other applications. | <urn:uuid:9fd83e12-4926-4a28-b9c1-239001b061f5> | 3.09375 | 303 | News Article | Science & Tech. | 28.190909 | 95,546,613 |
Sensor Data Fusion for Spectroscopy-Based Detection of Explosives
In-situ trace detection of explosive compounds such as RDX, TNT, and ammonium nitrate, is an important problem for the detection of IEDs and IED precursors. Spectroscopic techniques such as LIBS and Raman have shown promise for the detection of residues of explosive compounds on surfaces from standoff distances. Individually, both LIBS and Raman techniques suffer from various limitations, e.g., their robustness and reliability suffers due to variations in peak strengths and locations. However, the orthogonal nature of the spectral and compositional information provided by these techniques makes them suitable candidates for the use of sensor fusion to improve the overall detection performance. In this paper, we utilize peak energies in a region by fitting Lorentzian or Gaussian peaks around the location of interest. The ratios of peak energies are used for discrimination, in order to normalize the effect of changes in overall signal strength. Two data fusion techniques are discussed in this paper. Multi-spot fusion is performed on a set of independent samples from the same region based on the maximum likelihood formulation. Furthermore, the results from LIBS and Raman sensors are fused using linear discriminators. Improved detection performance with significantly reduced false alarm rates is reported using fusion techniques on data collected for sponsor demonstration at Fort Leonard Wood.
P. V. Shah et al., "Sensor Data Fusion for Spectroscopy-Based Detection of Explosives," Proceedings of Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XIV (2009, Orlando, FL), vol. 7303, SPIE, Apr 2009.
The definitive version is available at http://dx.doi.org/10.1117/12.819902
Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XIV (2009: Apr. 13-17, Orlando, FL)
Electrical and Computer Engineering
Keywords and Phrases
RDX; TNT; Detection; Explosive Compounds; Residue; Ammonium Nitrate; Compostional Information; Data Fusion Technique; Detection Of Explosives; Detection Performance; Explosive Compounds; False Alarm Rate; Fusion Techniques; Gaussian Peaks; IED Detection; In-Situ; LIBS; Linear Discriminator; Peak Energy; Peak Strength; Raman Sensors; Raman Techniques; Region-Based; Sensor Fusion; Signal Strengths; Spectroscopic Technique; Standoff Distance; TEPS; Trace Detection; Ammonium Compounds; Explosives; Information Fusion; Location; Maximum Likelihood; Mining; Nitration; Raman Scattering; Raman Spectroscopy; Sensors; Trace Analysis; Sensor Data Fusion; Data Fusion
International Standard Book Number (ISBN)
International Standard Serial Number (ISSN)
Article - Conference proceedings
© 2009 SPIE, All rights reserved. | <urn:uuid:acb1c227-1225-4bdc-9e9c-a87183073562> | 2.515625 | 602 | Academic Writing | Science & Tech. | 20.857977 | 95,546,626 |
The researchers studied the behavior of the algal cell Karlodinium veneficum, known as a dinoflagellate and found in estuaries worldwide. Each year millions of dollars are spent on measures to control dinoflagellates around the globe. This particular species is known to release a substance called karlotoxin, which is extremely damaging to the gills of fish. Karlodinium veneficum has been known to form large algal blooms in the Chesapeake and elsewhere, triggering an immediate harmful impact on aquatic life, including fish kills.
"This new research opens the door to reducing bloom frequency and intensity by reducing the availability of its prey," said Allen Place of the Institute of Marine and Environmental Technology at the University of Maryland Center for Environmental Science. "As we reduce the nutrient load feeding Karlodinium's prey and bring back the bay's most prolific filter feeder, the Eastern oyster, we could essentially limit Karlodinium's ability to bloom."
Place, in whose laboratory karlotoxin was discovered and characterized, was a co-author of the new study, published this week in the online Early Edition of the Proceedings of the National Academy of Sciences. Other researchers involved in the study came from the University of Minnesota, The Johns Hopkins University and the University of Hawaii.
"This is a major environmental problem, but we didn't know why these microbes were producing the toxins in the first place," said Joseph Katz, the William F. Ward Sr. Professor in the Department of Mechanical Engineering at Johns Hopkins and a co-author of the paper. "Some people thought they were just using the toxins to scare away other predators and protect themselves. But with this new research, we've provided clear evidence that this species of K. veneficum is using the toxin to stun and capture its prey."
Historically, scientists have found it difficult to study the behavior of these tiny animals because the single-cell creatures can quickly swim out of a microscope's shallow field of focus. But in recent years this problem has been solved through the use of digital holographic microscopy, which can capture three-dimensional images of the troublesome microbes. The technique was pioneered by Katz.
In a study published in 2007, Katz, Place and Jian Sheng, who was Katz's doctoral student, were part of a team that reported the use of digital holographic microscopy to view the swimming behavior of K. veneficum and Pfiesteria piscicida. At the time, it appeared that K. veneficum slowed down into a "stealth mode" in order to ambush its prey while P. piscicida sped up to capture prey.
For the new paper, in which Sheng is lead author, the researchers used the same technique to more closely study the relationship between K. veneficum and its prey, a common, single-celled algal cell called a cryptophyte. They found that K. veneficum microbes release toxins to stun and immobilize their prey prior to ingestion, probably to increase the success rate of their hunt and to promote their growth.
This significantly shifts the understanding about what permits harmful algal blooms to form and grow, the researchers said. Instead of being a self-defense mechanism, the microbes' production of poison appears to be more closely related to growth through the ingestion of a "pre-packaged" food source, the cryptophyte cell, they concluded.
"In the paper, we have answered why these complicated [toxic] molecules are made in nature in the first place and identify a possible alternative mechanism causing massive bloom," said Sheng, who is now a faculty member in the University of Minnesota's Department of Aerospace Engineering and Mechanics.
Other co-authors of the PNAS paper are Edwin Malkiel, an adjunct associate research scientist in the Department of Mechanical Engineering at Johns Hopkins; and Jason E. Adolf, an assistant professor in the University of Hawaii's Department of Marine Science.
Funding for the research was provided by the National Science Foundation and the National Oceanic and Atmospheric Administration's Coastal Oceans Program.
The journal article maybe viewed online here: http://www.pnas.org/content/early/2010/01/14/0912254107.full.pdf+html.Related links:
Phil Sneiderman | 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
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Dynamic Correlations of Multiply Scattered Light from Strongly Interacting Suspensions
The scattering of a coherent light source, such as a laser, from any random medium invariably results in a far field scattering pattern consisting of light and dark regions, called a speckle pattern. If the scattering medium changes in time, as for example will happen if the scattering particles move, then the speckle pattern also changes in time, reflecting this motion. The analysis of the intensity fluctuations of a single speckle spot can provide information about the dynamics of the scattering medium, and this form of light scattering is called dynamic light scattering (DLS), or quasielastic light scattering. The traditional DLS experiment entails the measurement of the temporal autocorrelation function of the intensity fluctuations of a speckle spot, and for singly scattered light, the time constant of the decay of this correlation function can be related to the dynamics of the scattering system through knowledge of the scattering wave vector, q. This is a well developed form of light scattering spectroscopy, and traditional DLS has found many applications in the study of the dynamics of a wide variety of systems.
KeywordsCorrelation Function Apparent Diffusion Coefficient Dynamic Light Scattering Hydrodynamic Interaction Random Medium
Unable to display preview. Download preview PDF.
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- 21.R. Klein, to be published.Google Scholar | <urn:uuid:af291d2a-91b6-4aeb-9aa8-a36d94de855d> | 2.59375 | 736 | Truncated | Science & Tech. | 56.358739 | 95,546,662 |
Environmental research web is a unique site for the the entire environmental science community. It provides analysis and commentary on all areas of environmental research including policy and sustainable technology. News and editorials are integrated with research articles from our sister journal Environmental Research Letters.
Achieving food security for all is at the heart of the United Nations FAO's efforts - to make sure people have regular access to enough high-quality food to lead active, healthy lives.
The Intergovernmental Panel on Climate Change (IPCC) is a scientific intergovernmental body tasked with reviewing and assessing the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It provides the world with a clear scientific view on the current state of climate change and its potential environmental and socio-economic consequences, notably the risk of climate change caused by human activity.
Climate Cloud is a digital library with a collection of resources relating to the risks and impacts of climate change on land based businesses. It contains physical copies and links to reports, fact sheets and video, largely from New Zealand organizations.
The vision of IGBP is to provide scientific knowledge to improve the sustainability of the living Earth. IGBP studies the interactions between biological, chemical and physical processes and interactions with human systems and collaborates with other programmes to develop and impart the understanding necessary to respond to global change.
Human actions lie at the heart of current global environmental change. Societies define the boundaries and character of their environments, while affecting and reacting to their environment with only a limited and biased understanding of it. To understand and respond effectively to these current changes requires major inputs from the social sciences - the perspective of human behavior and actions. The IHDP Knowledge Transfer Database is a tool to archive and share the research and activities of the organization from its inception in 1996 to its closure in 2014.
IUCN, International Union for Conservation of Nature, helps the world find pragmatic solutions to our most pressing environment and development challenges. It supports scientific research, manages field projects all over the world and brings governments, non-government organizations, United Nations agencies, companies and local communities together to develop and implement policy, laws and best practice.
To provide leadership and encourage partnership in caring for the environment by inspiring, informing, and enabling nations and peoples to improve their quality of life without compromising that of future generations.
UNESCO's mission is to contribute to the building of peace, the eradication of poverty, sustainable development and intercultural dialogue through education, the sciences, culture, communication and information. The Organization focuses, in particular, on two global priorities: Africa and Gender equality. | <urn:uuid:5e432f1b-296e-4443-92f7-1a7feb11129a> | 2.703125 | 531 | Content Listing | Science & Tech. | 9.558153 | 95,546,666 |
Currently terrestrial ecosystems absorb about one quarter of the anthropogenic carbon dioxide emitted into the atmosphere. However, how this land carbon sink will develop in the future is uncertain and strongly depends on the responses of ecosystems to climate. New clues on how the land carbon sink is regulated have now been revealed by researchers led by the Max Planck Institute for Biogeochemistry in Jena, Germany: When looking at the global scale, the annual carbon balance largely responds to temperature, while locally water availability turns out to be the dominant factor.
Their study also highlights that compensation effects of water availability lead to the differences seen between local and global scales.
Current climate change is characterized by rising atmospheric carbon dioxide (CO₂) concentrations and concomitant atmospheric warming. However, the annual growth rate of CO₂ which has been measured in the atmosphere for several decades varies largely from year to year. These variations originate primarily from fluctuations in carbon uptake by land ecosystems, rather than by oceans or from alterations in anthropogenic emissions.
How is this carbon sink controlled, and how will it develop in the future? Discussions on whether temperature or water availability is driving the strength of the land carbon sink, and thus its variations, have been highly controversial. According to current knowledge, the year-to-year changes of the carbon balance seem to be related to tropical temperature when looking at the global scale. However, other studies find that the largest carbon balance variability is seen in wide-spread water-limited regions.
This apparent discrepancy has now been explained by an international expert team led by the Max Planck Institute for Biogeochemistry in Jena, Germany. In a systematic modelling approach, Jung and his colleagues applied empirical and process-based models, to analyze from small areas up to the global surface the effect of temperature and water availability variations on carbon exchange between the atmosphere and the terrestrial biosphere.
At local scales, water availability is the dominant cause of the year-to-year variability of both CO₂ uptake in plants by photosynthesis, measured as gross primary productivity (GPP), and CO₂ release from plants and microbes, measured as terrestrial ecosystem respiration (TER).
In sum, the net ecosystem exchange of CO₂ between the atmosphere and the terrestrial biosphere, termed NEE, is also determined by water availability. However, at the global scale, variability in the temporal net exchange is mostly driven by temperature fluctuations. How can these apparently contradictory results be explained?
“What looks quite paradox at a first view, can be illustrated by looking close at the different spatial and temporal variations of the biosphere-atmosphere interactions”, explains Dr. Martin Jung, lead author of the Nature publication. “There are two compensatory effects of water availability: first, at the local scale, temporal water-driven GPP and TER variations compensate each other.”
E.g., very dry weather conditions lead to diminished water availability and concomitantly reduced photosynthetic CO₂ fixation, but also to reduced amounts of respired CO₂. In sum, the effects partially compensate each other. “In addition, on a global scale, anomalies of water availability also compensate in space” adds Jung. “If it is very dry in one part of the world, it is often very wet in another region, thus globally water-controlled anomalies in net carbon exchange outweigh in space.”
Besides shedding light on previously contradictory findings, the outcome also points to the need for a research focus on how climate variables change while scanning across different scales and under global warming conditions.
“The simple relationship between the temperature and the global land carbon sink should be treated with caution, and not be used to infer ecological processes and long-term predictions” adds Dr. Reichstein, head of the Department. With continuous global warming, the scientists expect the changing water cycle to become the critical factor for the variability in the global land carbon sink.
Jung, M. et al. (2017). Compensatory water effects link yearly global land CO₂ sink changes to tem-perature
Dr. Martin Jung
Phone: +49 (0)3641- 57 6261
Prof. Dr. Markus Reichstein
Phone: +49 (0)3641- 57 6200
Susanne Héjja | Max-Planck-Institut für Biogeochemie
Abrupt cloud clearing events over southeast Atlantic Ocean are new piece in climate puzzle
23.07.2018 | University of Kansas
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Sirocco, scirocco, //, jugo or, rarely, siroc (Catalan: Xaloc; Sicilian: Sciroccu; Greek: Σορόκος; Spanish: Siroco; Occitan: Siròc, Eisseròc; Croatian: Jugo, literally southerly; Libyan Arabic: Ghibli; Egypt: khamsin; Tunisia: ch'hilli) is a Mediterranean wind that comes from the Sahara and can reach hurricane speeds in North Africa and Southern Europe, especially during the summer season.
It arises from a warm, dry, tropical airmass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe.
The sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe. The sirocco's duration may be as short as half a day or may last several days. While passing over the Mediterranean Sea, the sirocco picks up moisture; this results in rainfall in the southern part of Italy, known locally as "blood rain" due to the red sand mixed with the falling rain. Many people attribute health problems to the sirocco, either because of the heat and dust along the African coastal regions, or because of the cool dampness in Europe. The dust within the sirocco winds can cause abrasion in mechanical devices and penetrate buildings.
Sirocco winds with speeds of up to 100 kilometres per hour (54 knots) are most common during autumn and spring. They reach a peak in March and in November when it is very hot.
- Golden Gate Weather Services. Names of Winds. Retrieved on 2006-12-28.
|Wikimedia Commons has media related to Sirocco (wind).| | <urn:uuid:49c24300-41ed-4cf7-88dc-c6049d5b10ba> | 2.9375 | 442 | Knowledge Article | Science & Tech. | 41.091712 | 95,546,673 |
12 July 2018
Unique database shows north-south movement of plants
Published online 19 August 2015
A unique database shows that non-native plant species originate largely from the northern hemisphere.
It’s the first robust assessment of global patterns of naturalization of plant species.
More than 13,000 species of vascular plants (plants that contain tissue that conducts water, minerals and waste products)—4% of the world’s total—that are now naturally growing in different regions actually originated elsewhere. Europe and temperate Asia were found to be the largest donors of plant species and North America was the largest recipient, while the Pacific Islands show the fastest increase in species numbers with respect to their land area.
“Although this was not a surprise, we could show that the number of naturalized alien plants from Europe is almost four times higher than one would expect based on the size of the European flora,” says ecologist Mark van Kleunen from Germany’s University of Konstanz.
The study also shows that the majority of exotic plants in Middle Eastern countries came from parts of Europe, Africa and North America, says King Saud University plant taxonomist Jacob Thomas, a contributor to the study.
The database was compiled in four years, but it still lacks data for about 20% of the Earth’s land surface, including large parts of the Middle East. The team plans to update the database to cover these areas.
They also want to deepen their understanding of the factors that contribute to the spread of alien plant species, which plant characteristics foster their spread into different environments, and how important evolutionary relationships are between naturalized and native plants.
- van Kleunen, M. et al. Global exchange and accumulation of non-native plants. Nature http://dx.doi.org/10.1038/nature14910 (2015). | <urn:uuid:91965d89-f6e6-4c29-b670-8990dbaa7475> | 3.78125 | 382 | Truncated | Science & Tech. | 41.587489 | 95,546,680 |
"We could very well be seeing rock, or we could be seeing exposed ice in the retrorocket blast zone," said Ray Arvidson of Washington University, St. Louis, Mo., co-investigator for the robotic arm. "We'll test the two ideas by getting more data, including color data, from the robotic arm camera. We think that if the hard features are ice, they will become brighter because atmospheric water vapor will collect as new frost on the ice.
"Full confirmation of what we're seeing will come when we excavate and analyze layers in the nearby workspace," Arvidson said.
Testing last night of a Phoenix instrument that bakes and sniffs samples to identify ingredients identified a possible short circuit. This prompted commands for diagnostic steps to be developed and sent to the lander in the next few days. The instrument is the Thermal and Evolved Gas Analyzer. It includes acalorimeter that tracks how much heat is needed to melt or vaporize substances in a sample, plus a mass spectrometer to examine vapors driven off by the heat. The Thursday, May 29, tests recorded electrical behavior consistent with an intermittent short circuit in the spectrometer portion.
"We have developed a strategy to gain a better understanding of this behavior, and we have identified workarounds for some of the possibilities," said William Boynton of the University of Arizona, Tucson, lead scientist for the instrument.
The latest data from the Canadian Space Agency's weather station shows another sunny day at the Phoenix landing site with temperatures holding at minus 30 degrees Celsius (minus 22 degrees Fahrenheit) as the sol's high, and a low of minus 80 degrees Celsius (minus 112 degrees Fahrenheit). The lidar instrument was activated for a 15-minute period just before noon local Mars time, and showed increasing dust in the atmosphere.
"This is the first time lidar technology has been used on the surface of another planet," said the meteorological station's chief engineer, Mike Daly, from MDA in Brampton, Canada. "The team is elated that we are getting such interesting data about the dust dynamics in the atmosphere."
The mission passed a "safe to proceed" review on Thursday evening, meeting criteria to proceed with evaluating and using the science instruments.
"We have evaluated the performance of the spacecraft on the surface and found we're ready to move forward. While we are still investigating instrument performance such as the anomaly on TEGA [Thermal and Evolved Gas Analyzer], the spacecraft's infrastructure has passed its tests and gets a clean bill of health," said David Spencer of NASA's Jet Propulsion Laboratory, Pasadena, Calif., deputy project manager for Phoenix.
"We're still in the process of checking out our instruments," Phoenix project scientist Leslie Tamppari of JPL said. "The process is designed to be very flexible, to respond to discoveries and issues that come up every day. We're in the process of taking images and getting color information that will help us understand soil properties. This will help us understand where best to first touch the soil and then where and how best to dig."
The Phoenix mission is led by Peter Smith at the University of Arizona with project management at JPL and development partnership at Lockheed Martin, Denver. International contributions come from the Canadian Space Agency; the University of Neuachatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; Max Planck Institute, Germany; and the Finnish Meteorological Institute.MEDIA CONTACTS:
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
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As an apex predator the Great White plays a crucial role in the ecosystem by maintaining a balanced food chain and serving as an indicator for healthy and diverse oceans. Great whites are at the top of the marine food chain. They feed predominately on fish but will also consume turtles, molluscs, and crustaceans, and are active hunters of small cetaceans such as dolphins and porpoises, and of other marine mammals such as seals and sea lions. Using their acute senses of smell, sound location and electroreception, weak and injured prey can be detected from a great distance.
Fishing and finning threat the existence of these magnificent animals. By taking sharks out of the coral reef ecosystem, the larger predatory fish, such as groupers, increase in abundance and feed on the herbivores. With less herbivores, macroalgae expands and coral can no longer compete, shifting the ecosystem to one of algae dominance, affecting the survival of the reef system.
#savethesharks #whiteshark #carcharodoncarcharias #southafrica #supportsharkresearch #donotcrackunderpressure #sharkconservation #sharklife #sharkdiving #amazing #nofear #savethefins #underwaterphotography #climateaction #instadaily #instagood #blueoceans #wild_special | <urn:uuid:9ca8df81-e26d-4ea6-aea2-b52a8a147d1d> | 2.84375 | 287 | Knowledge Article | Science & Tech. | 11.634318 | 95,546,704 |
It has long been well established that fingerprints can be used to identify people or help convict them of crimes. Things have gone a lot further now: fingerprints can be used to show that a suspect is a smoker, takes drugs, or has handled explosives, among other things. In the journal Angewandte Chemie, Pompi Hazarika and David Russell describe the noteworthy progress that has recently been made.
When a finger touches a surface, sweat and oil-containing substances like sebum leave behind a print that is invisible to the naked eye. There are several ways to make it visible, like dusting with powder or spraying with reagents or “superglue”. A new technique that improves sensitivity involves the deposition of gold nanoparticles attached to cage-like molecules filled with dyes or other luminescent makers that cause the fingerprint pattern to glow. Gold nanoparticles attached to antibodies against amino acids are better at revealing older, dried fingerprints.
If a person has taken drugs, traces are released in his or her sweat. A team working with Russell at the University of East Anglia (Norwich, UK) has recently developed a method by which magnetic particles are equipped with antibodies that bind specifically to certain drug or nicotine metabolites.
In a second step, they apply a fluorescent antibody, which binds to the first antibody and indicates the presence of the corresponding drug by glowing under a fluorescence microscope. By using this method, the researchers were able to simultaneously detect several different narcotics in a single fingerprint.
Other innovative approaches use chromatographic and mass spectrometric techniques to identify the components of sweat and their decomposition products in fingerprints. One exciting development is the use of desorption electrospray ionization mass spectrometry (DESI). Charged droplets of solvent are sprayed onto the surface, forming a film that dissolves materials out of the fingerprint.
Additional solvent droplets impact the film and release the dissolved analytes from the surface so that they can be analyzed by mass spectrometry. An image of the fingerprint is then computed. Traces of drugs and explosives can also be shown.
Another interesting technique is infrared spectroscopy, which has been used to separate overlapping fingerprints from two individuals by means of their different sebum contents to produce two separate images. It is also possible to detect traces of explosive. Raman spectroscopy can be used to identify pharmaceuticals like aspirin and paracetamol (acetaminophen), as well as caffeine and starch in fingerprints.The goal is to develop a cost-effective, rapid, portable, miniature system that can detect fingerprints and the chemical components in them. This would not only be useful for criminologists, but also for doping tests and diagnostics.
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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
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Structure of Interfaces
The investigation of interface-properties has become a very active field of research. On all scales from atomistic lengths to macroscopic dimensions one observes numerous collective phenomena, most of them being only partly understood. The best microscopic knowledge is based on lattice models of crystal surfaces /1,2/ including surface diffusion /2/ and the mechanism of surface roughening /3/. The solid-liquid interface important in the melting-freezing problem is substantially less understood /4/. A phenomenon related to both melting and roughening is the depinning or wetting transition /5/, where a fluctuating interface interacts with a rigid surface. Within an adsorbed layer on a surface complicated superstructures (incommensurability) appear. Closely related is the effect of surface reconstruction /6/. For the macroscopic growth of crystals a number of macro-structures like surface-spirals play a dominant role /7/. As soon as long-range transport of material and heat by diffusion comes into play one enters the field of “pattern formation” via dynamic destabilization of plane interfaces /8/. In two-component systems like steel, lamellar structures in the bulk of the material may be formed by eutectic crystallization /9/.
KeywordsPattern Formation Adsorbed Layer Lamellar Structure Surface Reconstruction Plane Interface
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List of references
- /1/.General reviews: “Modern theory of crystal growth I” (Springer Series: Crystals; Growth, Properties and Applications” Heidelberg 1983); A.A. Chernov, H. Müller-Krumbhaar ed.Google Scholar
- /1a/.H. Müller-Krumbhaar in “Cohesive Properties of Semiconductors under Laser Irradiation”, L.D. Laude ed., NATO-ASI-Series E, 69 (M. Nijhoff Publ., The Hague, 1983)Google Scholar
- /3/.Roughening transition: J.D. Weeks in “Ordering in Strongly Fluctuating Condensed Matter Systems”; T. Riste ed. Vol. B50, (Plenum Press, N.Y. 1979);Google Scholar
- /5/.Layered Interfaces (Pinning, Wetting, etc.): M. Wortis, R. Pandit, M. Schick in “Melting, Localization and Chaos”, R. Kalia and P. Vashishta eds. (North Holland, N.Y. and Amsterdam, 1982)Google Scholar
- /7/.Macroscopic Structure: For a review on computer simulations in crystal growth see: H. M-K., Chapter 7 in “Monte Carlo Methods in Statistical Physics”, K. Binder, ed. (Springer Verlag, Heidelberg, 1979).Google Scholar
- /8c/.1697Google Scholar
- /10e/.H. M-K., Proceedings of “NATO-Workshop on Chemical Instabilities”, Austin, Texas 1983, G. Nicolis, ed., (D. Reidel Publ. Co, Dordrecht, Holland, 1983) PreprintGoogle Scholar | <urn:uuid:903be5dc-8843-47f7-8a77-3ba91032b8a4> | 2.515625 | 692 | Academic Writing | Science & Tech. | 48.983416 | 95,546,717 |
In its first months of operation, the APF has found two new planetary systems, giving astronomers a taste of planetary riches to come
Lick Observatory's newest telescope, the Automated Planet Finder (APF), has been operating robotically night after night on Mt. Hamilton since January, searching nearby stars for Earth-sized planets. Every night the fully autonomous system checks the weather, decides which stars to observe, and moves the telescope from star to star throughout the night, collecting measurements that will reveal the presence of planets. Its technical performance has been outstanding, making it not only the first robotic planet-finding facility but also one of the most sensitive.
The search for planets beyond our solar system (called "extrasolar planets" or "exoplanets") has yielded a huge number of discoveries in recent years, especially since NASA's Kepler spacecraft joined ground-based telescopes in the effort. Unlike Kepler, however, which focused on distant stars in one small patch of sky, the APF focuses on nearby stars and covers the entire sky.
"The planetary systems we're finding are our nearest neighbors. Those are the ones that will matter to future generations," said Steve Vogt, professor of astronomy and astrophysics at UC Santa Cruz, who led the $12 million APF project and designed the Levy spectrometer at the heart of the system.
Vogt said it was a long and difficult road to get the APF facility completed, but now that it's up and running he couldn't be happier with its performance. Project manager and principal engineer Matthew Radovan of UC Observatories (UCO) oversaw a large team of UCO technical staff who provided crucial support for the construction and commissioning of the APF facility.
Sandra Faber, interim director of UC Observatories, said she was "absolutely thrilled" at the success of the APF. "Our UCO staff worked incredibly hard during the past year to get the new facility on the air. The APF is living proof that older observatory sites like Lick, which has been working for over 125 years, can still produce cutting-edge science," said Faber, a University professor of astronomy and astrophysics at UC Santa Cruz.
Vogt's team has submitted two papers describing new planetary systems recently discovered by the APF. A paper on the APF itself, with a full description of the system and details on how well it is performing, will be published April 1 in Publications of the Astronomical Society of the Pacific (available online at arXiv.org).
Optimized for planet hunting
The APF facility consists of a 2.4-meter telescope and the Levy Spectrometer, which Vogt designed and optimized specifically for planet hunting. The spectrometer takes starlight from the telescope and spreads it into a rainbow of colors, splitting the light into a spectrum of thousands of different wavelengths that can be measured with great precision. Repeated measurement of a star's spectrum enables astronomers to detect the tiny wobble induced in a star by the gravitational tug of an orbiting planet. The Levy Spectrometer was named in recognition of a gift to support its construction from the Gloria and Kenneth Levy Foundation.
"Steve Vogt has a long history of breaking barriers in the design and construction of the world's most sensitive and precise spectrometers. This time, he has outdone himself," said APF co-investigator Geoffrey Marcy, professor of astronomy at UC Berkeley. "With the Automated Planet Finder, he has not only built a highly efficient and precise planet-hunting spectrometer, but he also led the construction of the world's first robotic telescope tuned finely enough to feed such a spectrometer."
Greg Laughlin, professor and chair of astronomy and astrophysics at UCSC, said the APF is a world-class facility perfectly suited to detecting planets in our neighborhood of the galaxy. Laughlin and his students (primarily Stefano Meschiari, now at the University of Texas, Austin) developed the software package, called Systemic Console, that researchers use to pull planet discoveries out of the data acquired by the APF and other telescopes.
"The vast majority of planets reveal themselves over time through a series of measurements, and the signals are buried in the huge stream of data that comes back from the telescope every night, so this software package is an integral part of the detection process," Laughlin said. "APF is the best current planet-finding instrument that can see the sky above our hemisphere. It's remarkable that this cutting-edge research can be done within sight of Silicon Valley--you don't have to go to Hawaii or Chile."
Vogt also designed spectrometers for the Keck I Telescope in Hawaii and Lick's Shane Telescope--both of which have been highly productive planet-finding instruments. In many ways, however, the APF is a more powerful planet finder than even the 10-meter Keck telescope because the APF was custom-built for that purpose, Vogt said. The precision with which the APF can measure the motion of a star is much better than can be achieved at Keck. The APF's telescope is relatively small, but with modern optical technology, including special coatings on the mirrors, its optical efficiency is very high.
"We can do the same work we did at Keck, except now we have the APF every night instead of just a few nights per month at Keck," Vogt said. "What we're learning from all of this--from Kepler and from our own work--is that there's a huge number of planets out there, more planets than there are stars, and they're everywhere, including right next door to us."
The first two planetary systems detected by the APF were initially suspected based on data Vogt's team got at Keck, but were only confirmed after repeated observations with the APF. One of the systems (HD 141399) consists of four gas giant planets, similar to the four gas giants in our solar system except that their orbits are much closer to their star. The other system (GJ 687) features a Neptune-mass planet orbiting a red dwarf star. These are "garden variety systems," not dramatic discoveries, Vogt said. But APF has the sensitivity to detect the ultimate goal--an Earth-sized planet orbiting a nearby star in the habitable zone, where it is neither too hot nor too cold for liquid water on the planet's surface.
"APF will be a marvelous facility for finding potentially habitable Earth-sized planets around our nearest stellar neighbors," said Vogt's longtime collaborator Paul Butler of the Carnegie Institution of Washington.
The APF will also be useful for a wide range of conventional astronomical observations involving spectroscopy, including follow-up observations of bright supernova explosions and gamma-ray bursts that may brighten and dim quickly. "The robotic APF can wheel over to these stupendous cosmic explosions within seconds to allow spectroscopic analysis of their brilliant flash of light," Marcy said.
About 20 percent of the APF's time is set aside for purposes other than planet finding, with access to be allocated by the director of UC Observatories. The rest of the observing time is divided equally between the planet search teams led by Vogt and Marcy.
Funding for the APF came from several sources, including $6.4 million in Congressional ear-mark funding through the U.S. Naval Observatory. Additional funding was provided by grants from NASA and the National Science Foundation, as well as gifts from several private donors.
Tim Stephens | EurekAlert!
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
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Better Fuel Cells Using Bacteria
Bioengineer Tim Gardner says synthetic biology could create bacteria that produce electricity from waste more efficiently.
What if you could power your house with sewage? Or run your pacemaker with blood sugar rather than a traditional battery? Scientists hope that microbial fuel cells – devices that use bacteria to generate electricity – could one day make this vision a reality.
While typical fuel cells use hydrogen as fuel, separating out electrons to create electricity, bacteria can use a wide variety of nutrients as fuel. Some species, such as Shewanella oneidensis and Rhodoferax ferrireducens, turn these nutrients directly into electrons. Indeed, scientists have already created experimental microbial fuel cells that can run off glucose and sewage. Although these microscopic organisms are remarkably efficient at producing energy, they don’t make enough of it for practical applications.
Tim Gardner, a bioengineer at Boston University (and member of the 2004 TR35), has developed a new technique for understanding the networks of genes that regulate the chemical reactions taking place in bacterial cells. The resulting “map” will be an advance for the field of synthetic biology: the quest to design and build biological systems that can perform specific functions. Gardner’s team aims to harness the genetic control system to engineer bacteria that can produce energy more efficiently.
As a test run of their technique, Gardner and coworkers analyzed the regulatory network of Escherichia coli, a common bacteria often used in research studies. The researchers identified more than 200 gene regulators that could be used in synthetic biology circuits. And they are now applying the technology to Shewanella bacteria.
Technology Review interviewed Tim Gardner about his plans during the Synthetic Biology 2.0 conference, held this week at the University of California, Berkeley.
Technology Review: What is the potential for microbial fuel cells?
Tim Gardner: Microbial fuel cells could really happen, but we have a ways to go in improving the power output. Right now, the output is so low that the technology is unlikely to be able to generate power for homes and cars. But there are some applications for which fuel cells might be appropriate. Some devices don’t need much power or could benefit from the ability to use unusual fuel sources – a medical implant that gets power from the blood, for example, and never needs to get charged. Or robots in the field that could grab a plant and convert it to power.
TR: How will you improve on nature’s design of bacteria?
TG: We want to rationally design a cell by manipulating existing machinery. A lot of the early work in synthetic biology was to try to build complete devices from scratch. But we realized we were fundamentally limited using a wholly synthetic approach – we were trying to build what evolution had built over millions of years. So we said, let’s try to tweak what evolution already built.
TR: How is your approach different from traditional molecular biology techniques?
TG: People have been modifying genetic systems for years. But, for the most part, it’s a trial-and-error approach. They tweak something and see what happens. We wanted to bring a systems level perspective, so we could approach the problem like an engineer. In order to do that, we had to know more about the existing circuitry, so we began to do genetic mapping.
We’ve been focusing on mapping regulatory circuits [a network of genes that control the chemical reactions taking place in the cell]. If you’re trying to figure out the circuitry of a house, you go to the circuit breaker and flip circuits on and off, looking for the circuit that controls the bathroom or the kitchen. We do a similar thing in bacteria, but it’s a bit messier. We stress the bacteria in different ways, with different chemicals or extreme temperatures, and then see how each gene responds. If you do this hundreds of times, you can look for genes that change together. For example, if you see different genes whose expression changes the same way under different conditions, we can infer those genes are related. We can then identify gene regulatory interactions and map the network.
TR: What will you do with this information?
TG: We have hopes of assembling whole genome regulatory models in novel organisms, which could be very powerful. We plan to try it out on electricity-producing organisms, which produce electricity directly from carbon sources.
We will couple the regulatory network with a model of the metabolic network [a map of the cell’s metabolic reactions], which is where the real business of turning carbon into electricity takes place. Then we’ll try to predict what will happen if we tweak genes or nutrients. We will try to decide if and how we could increase the power output or the thermodynamic efficiency of the organism.
Understanding these networks could also help scientists build artificial circuits from scratch. Scientists have already built a number of biological machines, such as toxin detectors or bacterial cameras. That was neat circuit engineering, but most of these devices are built using just three or four component parts. Understanding gene regulators will broaden the list of parts that can be used, because scientists will understand how the parts will impact the cell.
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:c6649173-f70f-4219-8e6f-8d4b38187ab3> | 3.640625 | 1,089 | Truncated | Science & Tech. | 41.973821 | 95,546,724 |
by Lorraine Chow, EcoWatch
The Netherlands, famous for its iconic windmills, is planning to build the largest offshore windfarm on Earth by 2027.
The vision is so massive that the developers will have to construct a 2.3-square-mile artificial island in the North Sea to support the 10,000-turbine complex.
The proposed wind farm, spearheaded by Dutch electric grid operator, TenneT, could produce 30 gigawatts of power—or enough electricity to power a city of 20 million people. That’s more than twice the amount of offshore wind power installed across Europe today.
To compare, the London Array, currently the largest offshore wind farm in the world, has a 630-megawatt capacity, or enough to power about half a million homes.
Once built, TenneT’s giant wind farm will eventually send power over a long-distance cable to the UK and Netherlands, and possibly later to Belgium, Germany, and Denmark, the Guardianreported. The facility will be located in Dogger Bank, a windy and shallow site about 80 miles off the East Yorkshire coast, which is also within ideal reach to the five countries.
So why build a wind farm offshore? Well, space is major problem for many onshore wind projects.
“The big challenge we are facing towards 2030 and 2050 is onshore wind is hampered by local opposition and nearshore is nearly full,” Rob van der Hage, TenneT’s program manager, told the Guardian. “It’s logical we are looking at areas further offshore.”
While the $1.8 billion project seems expensive, the developers tout that their project is actually cost-effective compared to traditional wind farms.
Business Insider explained:
“Offshore wind farms typically use expensive underwater cables that convert the turbines’ electric current into a type that electricity grids can use. TenneT’s island, however, would house equipment that would perform this conversion on-site, thereby allowing the farm to send electricity directly to the UK and Netherlands via less pricey cables.
“…Putting additional equipment on the island would also allow the team to operate more turbines at a lower cost—and thus generate more power—than a traditional offshore wind farm.” | <urn:uuid:9914aa76-95cb-4fe4-b7e2-95d12770808c> | 3.109375 | 477 | News Article | Science & Tech. | 40.856672 | 95,546,732 |
Species Detail - Garden Carpet (Xanthorhoe fluctuata) - Species information displayed is based on all datasets.
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
insect - moth
2 January (recorded in 1980)
24 December (recorded in 2003)
National Biodiversity Data Centre, Ireland, Garden Carpet (Xanthorhoe fluctuata), accessed 18 July 2018, <https://maps.biodiversityireland.ie/Species/78709> | <urn:uuid:88f5a832-9ae4-4b67-a88a-adf67b165f6c> | 2.546875 | 144 | Structured Data | Science & Tech. | 37.074 | 95,546,734 |
Cheap, full-colour images from lens-free microscope
Spectral light fusion microscopy: intensity projection of lung tissue [Wong et al/University of Waterloo]
Canada-based researchers have developed a new form of light-field imaging - spectral light fusion microscopy - to capture full-colour, light-field images of tissue and fluid samples for pathology applications.
The several-hundred-dollar lens-free microscope uses artificial intelligence and modelling to capture interferometric data and reconstruct 3D images at a large scale.
With their latest microscope, Professor Alexander Wong, co-director of the Vision and Image Processing Lab at the University of Waterloo, and colleagues, can construct nanometre-resolution images with a ultra-wide field-of-view, more than 100 times greater than that of 40X optical microscopy systems.
Professor Alexander Wong (right) and colleagues have pioneered spectral light-field fusion microscsopy for cheap pathology applications.
"This technology has the potential to make pathology labs more affordable in communities that currently don't have access to conventional equipment," highlights Wong.
While large 3D images are typically produced by stitching together multiple images from conventional microscopes, this process demands equipment that can cost hundreds of thousands of dollars.
Given this, wide-field on-chip microscopy, which uses holography principles to capture interferometric information without lenses, is gaining widespread interest.
Wong and colleagues have now introduced the idea of laser light-field fusion for lens-free on-chip phase contrast microscopy, to produce nanometre-scale images.
Initial instrument with interferometric light-field encodings; scale bar: 1mm [Kazemzadah et al, Scientific Reports 6, 38981 (2016)]
They have developed compact pulsed lighting and detection apparatus to first capture interferometric laser light-field encoding, at different wavelengths.
They then use a Bayesian-based fusion method to combine and reconstruct high-resolution, marker-free phase contrast images of particles at the nanoscale.
The researchers have detected 300 nm particles across a 30 mm² field-of-view, without specialised sample preparation or the use of synthetic aperture- or lateral shift-based techniques.
And using this instrument they have acquired intensity projections of lung cells, a bee's head and more.
Spectral Light-field fusion imaging achieves 4D label-free tomographic imaging of biological specimens in a low-cost, compact form factor.
As Wong points out, acquiring the interferometric light-field encoding takes less than ~3 ms - equivalent to >300 frames per second - enabling studies of highly time-resolved dynamic systems or transient phenomena.
Learn more at Nature Scientific Reports. | <urn:uuid:b317b47c-e88f-48f3-ac23-1d5ad0ff78c5> | 2.671875 | 566 | Truncated | Science & Tech. | 12.722588 | 95,546,735 |
SedPods: a low-cost coral proxy for measuring net sedimentation
- 514 Downloads
Sediment derived from impaired watersheds is a major stressor to adjacent coral reefs globally. To better understand stresses generated by specific processes and events, many coral reef scientists seek to collect physical samples of settling particles and obtain reproducible information about net rates of sediment accumulation on coral reefs. Yet, the tools most commonly used to gather this information, sediment tube traps, only provide information on the gross accumulation of sediment at a site, in that all particles are effectively trapped within the container, unlike what a coral surface experiences. To address the need for an improved measurement of net particle accumulation on coral surfaces, we propose using recoverable sediment pods (SedPods) that can be constructed from readily available materials for under US $20. These devices are inexpensive, easy to fabricate, and allow for capture of particles over a given time span. The particles can then be used for laboratory analysis and accurate calculation of net accumulation rates on a coral surface proxy. In an experiment in Hanalei Bay, HI, we found that net sediment accumulation on rectangular SedPods was an order of magnitude less than gross accumulation in nearby conventional tube traps.
KeywordsSedimentation Corals Particles Reef health
This is a contribution of the US Geological Survey’s Pacific Coral Reef Project and was supported by the USGS Coastal and Marine Geology Program. We thank M. Bothner for insightful discussions, G. Piniak for thoughtful review comments, and J. B. Logan and S. A. Cochran for their assistance with field deployments and figure preparation, respectively.
- Field ME, Chezar H, Storlazzi C (2007) Photographic time series of sedimentation near the wall, Hanalei Bay, Kaua`i, summers of 2005 and 2006. In: Field ME, Berg CJ, Cochran SA (eds) Science and management in the Hanalei watershed; a trans-disciplinary approach: US Geol Surv Open File Report 2007-1219, p 87Google Scholar
- Field ME, Bothner MH, Chavez PS, Cochran SA, Jokiel PL, Ogston AS, Presto MK, Storlazzi CD (2008) The effects of a Kona storm on the Moloka`i reef; November and December 2001, In: Field ME, Cochran SA, Logan JB, Storlazzi CD (eds) The coral reef of south Moloka`i, Hawai`i: Portrait of a sediment-threatened fringing reef. US Geol Surv Sci Invest Rep 2007-5101, p 159–164Google Scholar
- Ogston AS, Storlazzi CD, Field ME, Presto MK (2004) Sediment resuspension and transport patterns on a fringing reef flat, Molokai, Hawaii. Coral Reefs 23:559–569Google Scholar
- Risk MJ, Edinger E (2011) Impacts of sediment on coral reefs. In: Hopley D (ed), Encyclopedia of modern coral reefs. Springer Science + Business Media B.V.Google Scholar | <urn:uuid:d54fdacf-f1cb-4e10-adae-33d9b7a5289c> | 2.53125 | 653 | Academic Writing | Science & Tech. | 38.587015 | 95,546,776 |
- Open Access
Olivine: a supergreen fuel
© Schuiling; licensee Springer. 2013
Received: 26 August 2013
Accepted: 26 August 2013
Published: 2 September 2013
The hydration and carbonation of olivine, the most common mineral on Earth, produce a large amount of heat. Unfortunately, the reaction is too slow for normal technological applications, but when thermally well isolated, most of this heat can be recovered, not only for space heating but even for the production of high-pressure steam. During the reaction, CO2 is sustainably sequestered. In this paper, a number of potential applications are described. Using the hydration and carbonation of olivine not only increases the energy production but also sequesters at the same time large volumes of CO2 that would otherwise be emitted, or would have to be removed by expensive technologies. The term “supergreen fuel” refers to the fact that this energy production is not associated with CO2 production, but quite the contrary, it even sequesters CO2 while producing energy.
By this and similar weathering reactions throughout the history of the Earth, CO2 was removed from the atmosphere. The resulting magnesium bicarbonate solutions are carried by rivers to the sea, where marine organisms (corals, shellfish, and plankton) convert them to carbonate rocks. This is the way by which 99.94% of all the CO2 that has leaked out of the planet has been sustainably captured in rocks . This has saved us from the fate of our sister planet Venus, where weathering is impossible because Venus has no liquid water. All the CO2 that was ever emitted by Venus has stayed in the atmosphere, leading to a CO2 pressure of 85 bars and a surface temperature of 460°C.
At present, the amount of CO2 produced by the burning of fossil fuels is so large that this weathering process cannot keep pace, so the CO2 content of the atmosphere is rising, causing probably a climate change and certainly an ocean acidification. Increasing the rate of weathering as well to reach a new balance is the straightforward answer to the problem of rising CO2 levels in the atmosphere .
Exergy production from carbonation and hydration
Thermodynamic properties of substances in the reaction
Molar weight (grams)
Standard enthalpy change of formation (kJ/mol)
CO2 (ideal gas)
The enthalpy of the reaction is −169.1 kJ/mol CO2 or 0.47 kJ/gram of the stoichiometric mixture. As long as the water stays in the liquid state, the changes in the enthalpy of reaction as a function of temperature are minimal. With an average value for the specific heat of a gram of the stoichiometric mixture of 1.6 J/g/K (value for basalt), the system, when perfectly isolated, would reach a temperature of 593 K when it starts at 298 K. If water would be available as steam at the site, a higher end temperature could be reached. No allowance is made for the contribution of the iron end-member in this calculation. The reaction is different (see ‘Methane production’ section) because during the transformation, the divalent iron oxidizes to magnetite.
How can this heat be used?
It should be stressed again that the reaction proceeds slowly at low temperatures, so it is imperative that the system should have a large volume and be isolated very well to make sure that the heat that is slowly produced is not conducted or radiated away. Rocks are excellent isolating systems, so in the examples that follow, thick layers of olivine-rich rocks will be used for thermal isolation. The applications can roughly be divided into methane production, space heating, and power production.
Part of the CO2 in the biogas is transformed into bicarbonate. The bicarbonate dissolves in the digestate, making the biogas richer.
The absolute amount of produced methane increases as a consequence of reaction (3).
The biodigester does not smell any more. This is also a consequence of the iron part of the olivine which reacts with the H2S and precipitates as iron sulfides.
So, adding olivine powder to the biodigesters produces a richer and cleaner biogas and captures CO2. Because the fayalite is part of the mixed crystal of olivine, it must weather exactly at the same slow rate as the magnesium end-member. The olivine reaction will not lead to any disruption of the digester system, and in the experiments, no heating effect has been observed.
Salts (not only NaCl but also potassium and magnesium salts) are often mined by solution mining. This way of mining leaves, in the end large subterranean solution, holes filled with brine. These holes must remain filled with saturated brine and permanently pressurized to avoid subsidence or even collapse of the cavity. As a first step, one must install two pipes into the brine, one to pump in olivine sand, the other to remove brine. At the end, the cavity is filled with olivine sand. It will probably require some mechanical way to spread the olivine evenly in the cavity. The remaining free volume for the brine shrinks when the cavity is filled with olivine, and the displaced brine can be recovered. The cavity filled with olivine with pore water of brine forms a well-isolated system, in which one can pump warm CO2 from a nearby power station. The reaction starts slowly, but as the temperature rises due to the exothermic reaction taking place, the reaction goes faster, and one can recover hot (saline) water with which a warm swimming pool can be filled, or hot fresh water if the water is passed through a heat exchanger in the cavity. This hot water can even be used for space heating. When the temperature becomes too low, the water is pumped back into the cavity. The reaction products (serpentine + magnesite) of the olivine take up a larger volume than the loose olivine sand, so the pores between the grains gradually close and form a rock. This new serpentine-magnesite rock can support the cavity, making permanent monitoring and pressurizing superfluous.
Greenhouses also require heating. In NE Greece, there are a number of geothermal wells used for heating greenhouses. The geothermal fluids here are rich in CO2, which is emitted to the atmosphere. If one covers the well head with a hill of olivine sand from the tailings of a nearby magnesite mine, this olivine will react with the hot geothermal fluid. The heat of this exothermal reaction is added to the geothermal heat, thus increasing the amount of heat available for the greenhouses, and the CO2 in the geothermal fluid is no longer emitted to the atmosphere but is sequestered by the olivine reaction and sustainably stored.
A potentially attractive application for tourists could be the following. In the sea around the island of Milos (and for a part on the island itself), large volumes of hot CO2 are bubbling from the floor of the shallow sea .
Until now, olivine was only considered as a means to sequester CO2 by its reaction with CO2 and water. This process is known as enhanced weathering. The fact that this reaction also produces a considerable amount of energy has not yet been considered, because this heat is released too slowly for use in conventional technologies. It, therefore, does not fit into any classical system of power production. Olivine can become a supergreen fuel, however, if one fulfills the required conditions of good thermal isolation and large size of the reactant volume.
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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. | <urn:uuid:a564a4f9-bb9b-4e96-826c-121ada877fff> | 3.546875 | 1,996 | Truncated | Science & Tech. | 43.958132 | 95,546,794 |
|Molecular biology is the study of development, structure and function of macromolecules vital for life. It deals with the molecular basis of biological activity and overlays genetics and biochemistry. It concerns about the various system of a cell and interaction among various biomolecules and covers a broad scope of problems related to molecular and cell biology. Innovations are new idea, device or process. Innovations are the application of better solutions that meet new requirements, in articulated needs or existing market needs. It is proficient through more effective products, processes, services, technologies, or new ideas that are readily available to markets, governments and society. Innovations are something original and novel, as a significant, new that breaks into the market or society. | <urn:uuid:76dd7b88-0e6a-45cb-aedc-bfb3650552e4> | 2.84375 | 150 | Knowledge Article | Science & Tech. | 13.185 | 95,546,798 |
Understanding Chemistry. Environmental Science 2010. PERIODIC TABLE. Living Matter made up of:. C = Carbon H = Hydrogen N = Nitrogen O = Oxygen P = Phosphorous S = Sulfur. Importance of pH=Homeostasis.
Environmental Science 2010
1. All living organisms require specific pH ranges in order for their cells to function properly.
2. pH – potential Hydrogen (H+) in water or whatever liquid is being measured.
3. In more everyday terms, pH is a unit of measure for determining if a liquid is acidic or basic (alkaline).
4. pH is measured on a scale of 0.0 to 14.0.
a. Numbers < 7.0 = acidic
b. Numbers > 7.0 = basic
c. A pH of 7.0 indicates a neutral liquid
a. Liquid with a pH of 6.0 = 10X more acidic than
pure water (pH=7.0).
b. Liquid with a pH of 5.0 =100 X(10x10)
more acidic than pure water.
c. Liquid with a pH of 8.0 is ten times more basic
than pure water.
d. Liquid with a pH of 9.0 is one hundred times more
basic than pure water. | <urn:uuid:5429b04a-b806-4b00-a061-5722bd3d4c99> | 3.671875 | 273 | Structured Data | Science & Tech. | 87.405 | 95,546,800 |
The journal Science devotes a full issue to the uncertain future of Earth’s forests.
Ze Doca, Brazil in Nov. 2014. Image: Mario Tama/Getty
Forests are ecological superheroes—they ventilate the planet, nurture the most biodiverse habitats on Earth, and regulate global climate and carbon cycles. From the poles to the equator, our survival is completely dependent on healthy woodlands.
But according to the latest issue of Science, which is devoted to forest health, every major forest biome is struggling. While each region suffers from unique pressures, the underlying thread that connects them all is undeniably human activity.
For example, the first of the special issue's studies, led by forest ecologist Sylvie Gauthier, outlined the threats faced by boreal forests, which represent the largest forest habitats on Earth. These high-latitude woodlands are primarily coniferous, made up of pines, spruces, and larches, and stretch from the expansive forests of Canada to the Russian taiga.
Gauthier and her colleagues note that boreal forests have been traditionally very resistant to environmental changes that would devastate other biomes. "The resilience of these systems is well illustrated in the boreal forest of eastern North America," noted the team, "where the regional tree species pool has remained mostly unchanged over the past 8,000 years despite large fluctuations in climate and regional disturbance regimes."
But the adaptive prowess of boreal forests can only be pushed so far, and industrial logging of these timber-rich woodlands is beginning to take its toll. Gauthier's team estimates that two thirds of the world's boreal forests are now subject to heavy resource extraction, which has resulted in widespread pollution, deforestation, wildfires, and a less genetically diverse tree population.
Compounding these issues is the projected effect of climate change on northern forests. "Over the course of the 21st century, the boreal biome is expected to experience the largest increase in temperatures of all forest biomes," the team said. "Warmer temperatures would [...] lift the climate barriers to population growth or range expansion of native or invasive forest pests, resulting in severe outbreaks."
"The health of the immense and seemingly timeless boreal forest is presently under threat, together with the vitality of many forest-based communities and economies," the researchers said.
Temperate forests aren't faring much better, according to another study from the issue written by US Geological Survey ecologists Constance Millar and Nathan Stephenson. Temperate forests are primarily composed of deciduous trees that shed their leaves seasonally, and are common in mid-latitude regions around the world.
As with boreal forests, climate change is the most devastating threat facing temperate woodlands, which are especially vulnerable to droughts and wildfires. Deciduous trees have evolved to withstand these pressures to a certain degree, but the authors pointed out that the steep upward trend of rising temperatures is ushering in "megadisturbances" that will not be so easy to brush off.
"For millennia, drought has been a key disturbance agent in temperate forests," Millar and Stephenson said. "Over the past few decades, however, rising global temperatures have contributed to droughts of a severity that is unprecedented in the last century or more."
"[E]xceptional droughts, directly and in combination with other disturbance factors, are pushing some temperate forests beyond thresholds of sustainability," the team concluded.
Forests that have been severely dehydrated by megadroughts suffer from water depletion, and they also turn into enormous tinder piles that can feed megafires. On top of that, temperate forests coincide with heavy population densities, so there a lot of anthropogenic stressors on them as well, like pollution, industrial development, and invasive species.
"[T]he actions we take now in temperate forests can ease and guide transitions, diminishing effects to forest ecosystems and human societies," Millar and Stephenson said.
Last but not least, researchers led by geography professor Simon Lewis assessed one of the most biodiverse habitats on the planet—the tropical forest, characterized by evergreen broadleaf trees.
While Lewis and his colleagues noted that climate change is a major risk for tropical forests, they concluded that this biome is much more threatened by direct anthropogenic contact.
Along those lines, the team outline the ecological disturbances induced by human settlements over the course of several millennia, beginning with extinctions of tropical megafauna and ending with "today's global integration, dominated by intensive permanent agriculture, industrial logging, and attendant fires and fragmentation."
"The 21st century will see large increases in demand for products from tropical lands," the authors wrote. "Thus, the greatest threats will likely continue to be conversion and degradation but will be increasingly combined with the impacts of rapid climatic changes."
So, to sum up: Every forest biome on Earth is actively dying right now, and if this course isn't corrected, the deterioration of these valuable ecosystems will accelerate over the coming decades.
Of course, in each of the studies, the authors pointed out numerous ways to slow the alarming decline of forests worldwide, such as stricter conservation policies, better forestry management, and a global framework for policing climate change. These kinds of actions "would lessen the unwelcome shocks that living in the Anthropocene will bring this century," as Lewis's team put it.
In other words, it is absolutely possible for humans to curb the damage to forests, or perhaps even reverse it in some places. Indeed, given that our own fate is inexorably tied to that of the world's forests, it seems suicidal to consider any other option.
But whether we can pull this kind of turnaround off depends almost entirely on the human capacity to plan for the long-term health of the planet. If humans intend to survive this anthropogenic age we brought to the planet, we will have to up our game. | <urn:uuid:bc9783ad-eb87-4ebb-8d2f-f407fc7527da> | 4.0625 | 1,216 | News Article | Science & Tech. | 25.540545 | 95,546,812 |
“If you thought before science was certain—well, that is just an error on your part.” Richard Feynman, The Character of Physical Law
By Robert Lee Hotz – The Wall Street Journal – November 12, 2012
Northward winds are driving the record growth of winter sea ice around Antarctica, which stands in contrast to the extensive melting of the Arctic sea ice in recent years, scientists reported Sunday.
Northward winds are driving the record growth of winter sea ice around Antarctica, which stands in contrast to the extensive melting of the Arctic sea ice in recent years. Robert Lee Hotz has details on Lunch Break. Photo: Getty Images.
Their new research, based on 19 years of daily ice-motion measurements recorded by four satellites of the U.S. Defense Meteorological Satellite Program, highlights how geography, weather and climate patterns are affecting the planet’s polar regions in different ways.
Their analysis documented for the first time that long-term changes in the drift of annual sea ice around Antarctica were strongly affected by winds. The area of ocean covered by sea ice grew markedly in regions where the prevailing winds spread out the loosely compacted ice floes, they reported. It shrank in areas where the wind blew the floating ice up against the shore.
The researchers at NASA’s Jet Propulsion Laboratory in California and the British Antarctic Survey reported their work Sunday in Nature Geoscience.
“We have evidence now that the wind is driving the ice cover,” said JPL senior research scientist Ron Kwok, who led the study. “The expansion and contraction of ice around the continent is largely explained by wind forces, which is very different in the Antarctic than in the Arctic.”
Broadly speaking, the Earth’s polar regions are mirror opposites.
The Arctic Ocean is largely landlocked, surrounded by North America, Greenland and Eurasia, which limits the amount of sea ice there could be no matter which way the wind is blowing. Earlier this year, scientists reported that the extent of summer sea ice in the Arctic was the lowest since 1979, when satellite monitoring there began.
By contrast, Antarctica—the world’s coldest and windiest continent—is covered by an ice cap two miles thick and surrounded by the Southern Ocean. The annual growth of sea ice around Antarctica is the largest seasonal event on the planet.
With the onset of the Southern Hemisphere winter in March, the ice expands at 22 square miles a minute. In 1992, the direction of the drifting sea ice changed, with the spread of the ice doubling in some regions, the satellite measurements showed. Earlier this year, Antarctica’s sea ice reached a record expanse of 7.49 million square miles, before the spring thaw began.
In a separate study made public last month, climate scientists at NASA’s Goddard Space Flight Center in Maryland reported that winter sea ice surrounding Antarctica has been increasing by about 6,600 square miles every year—an area larger than Connecticut—during the same decades that the Arctic summer sea ice has been shrinking.
The researchers didn’t identify what was driving wind patterns around Antarctica. Generally, the annual ozone hole over Antarctica has strongly affected wind circulation throughout the Southern Hemisphere, studies have shown. Wind patterns around Antarctica also are linked to larger climate cycles such as El Niño.
“The larger connection to global climate change and warming is more difficult to say,” Dr. Kwok said. “We don’t understand that yet.”
Write to Robert Lee Hotz at email@example.com | <urn:uuid:4a18212b-e855-44af-bad8-3877b154105c> | 2.734375 | 739 | News Article | Science & Tech. | 45.287844 | 95,546,814 |
They are the most diverse ecosystems on Earth, but recent research confirms how the tropical rainforests are even more important than previously thought. There is a clue in the name – for these ecosystems not only have a lot of rain falling upon them, but actually create it, and not only locally but pumping moisture into the atmosphere to fall thousands of miles from where they stand.
The rainforests are also keeping the planet cooler than it would otherwise be, through catching and holding billions of tonnes of carbon, including some of that being released from planes, cars and power stations. By taking carbon out of the atmosphere and holding it tight in plants and soils, the forests are helping the world to tackle climate change.
And as time has gone on we’ve come to appreciate how the incredibly rich mix of animals and plants found in the rainforests is of far more than scientific interest, and important to save for more than its own sake. For not only is the wildlife diversity a source of our food supply (rainforest species have given rise to many of our most valued foods – including chicken, chocolate, maize and potatoes), but also many medicines, as molecules created through natural selection have been harnessed for among other things treatments for heart disease, anti-cancer agents and powerful painkillers.
Adaptations created in the rainforest are also proving valuable in a whole host of engineering and design applications. The wings of rainforest butterflies have inspired more efficient solar panels, hummingbirds the means to create vivid colour without paint and kingfishers the design ideas to make faster and quieter trains. Ant colonies are being studied to reveal ways of optimising transport networks while other rainforest wildlife is inspiring innovations in optics, acoustics, sensors and the development of composite materials.
So it is that the forests are more than simply collections of trees, but rather webs of connections within which the trees are (to our eyes at least) the most obvious components. The rainforests are tapestries woven from threads of sunshine, water, air, nutrients, photosynthesis, colour, sound and genes, all united into the fabric of an inseparable whole. They are connected by mammalian nuts and bolts, the ecological glue of birds and the strings and struts of insect life; the pollen between the flowers make fruits that are moved by animals including elephants, tapirs, pigs and monkeys, seeding the huge trees that lock up the carbon and pump water into the atmosphere.
But despite our increased understanding as to the intricate complexity and incalculable value of the rainforests, we have not as yet managed to stop their destruction. Across Central and South America, Africa and those parts of Asia and the Pacific where rainforests remain, the pressures on them are as intense as ever. As the forests fall, so water security is being effected, climate changing emissions released, and at the same time one of the best means to removing carbon dioxide from the atmosphere wrecked, while the loss of the rainforests is perhaps the biggest single cause for the mass extinction of animals and plants that is now upon us.
The reasons for on-going forest loss are well documented. The cutting of valuable timber trees not only causes damage to the forest but often opens the access for small-scale farmers, who clear the forest completely to make way for their crops. More devastating still has been the large-scale conversion of forests to fields of soya, ranks of oil palms, open expanses of cattle pastures and plantations of pulpwood and rubber trees, all meeting rising global demand for food and resources.
The good news is that none of these pressures need necessarily lead to forest loss. We increasingly have the means to stop and reverse the destruction. Success is very often bound up with the welfare of local people, whether they be small farmers or the original forest inhabitants, meaning that forest conservation is often as much a social venture as much as it is an environmental one.
For example, in South America one successful conservation strategy has relied upon indigenous rainforest tribes gaining legal control of their ancestral forest homelands. Whereas many outsiders regard the rainforest as an economic resource to be liquidated for financial profit, the Indians regard the intact forest as their home and act to protect it.
In Brazil about 200,000 indigenous people are looking after a huge area that comprises about twenty-five per cent of the total remaining rainforests in the world. In Colombia rainforest Indians control an area larger than Great Britain. In the Asia Pacific region the largest areas of remaining forest are on the island of New Guinea, where the indigenous people have retained control of their forested territories.
Another strategy that can make a difference is the empowerment of small-holders. If the tens of millions of farmers working small plots of land at the edge of the forests can be assisted to make a decent living, then it is more likely that conservation of what remains can succeed. Some of the largest chocolate companies are for example funding social programmes geared toward the protection of forests through helping the farmers who supply their key ingredient to get more out of their land.
Farming based on agroforestry methods has particular potential to make a positive difference. Agroforestry mimics the structure of the rainforest with a variety of crops grown beneath a canopy of fruit, nut or timber trees. Bananas, vegetables and root crops can be combined in ways that conserve moisture and nutrients while minimising the risk of disease and pest infestation.
National parks and other protected areas also have an important role to play and in some regions (such as West Africa) contain most of the forest that is left. So long as they can be maintained in the face of rising demand for land from expanding local populations, then they will be vital for the conservation of countless species, as well as helping sustain regional rainfall.
When it comes to commodity crops like soya and palm oil, then there is potential to rehabilitate some of the vast areas of already degraded lands that exist across the tropics, thereby enabling more output without impinging on remaining areas of natural forest. Many of the world’s biggest consumer brands have adopted ‘zero deforestation’ policies, meaning that market demand for crops grown without forest clearance will in years ahead grow.
Conservationists are finding that the best way to maintain the forests is at the level of landscapes. By looking at the whole landscape it is more likely that sustainable farming, conservation and livelihoods can be achieved together, through the cooperation of local and national governments, local people, funding agencies and the companies buying the commodities needed to make consumer products.
All of this requires money of course, but fortunately multi-billion dollar pledges have during recent years been made by richer countries to help the developing rainforest nations with these kinds of integrated conservation approaches, often on the back of international agreements, such as the 2015 Paris Climate Change accord. There are also powerful new technology-based tools including Global Forest Watch, that enable near real time monitoring of the forests, so that anyone can see if pledges to protect the forests are being met.
Conserving and restoring the tropical rainforests could be the bargain of the 21st century, bringing dividends of benefit the whole world. The task at hand is considerable, but achievable, should we demand that action is taken by governments and large companies to conserve these irreplaceable systems, not least through helping the people who live in and around them.
- Can trees grow in space?
- What would happen if all the trees were cut down?
- Do trees reduce air pollution levels?
- Are rainforests being replanted?
- Is it more environmentally friendly to buy a fake Christmas tree, or a real one?
- How many trees does it take to produce oxygen for one person? | <urn:uuid:c9741e20-efb2-45bb-af8e-d105ab86ffa0> | 3.75 | 1,576 | Knowledge Article | Science & Tech. | 30.43841 | 95,546,828 |
45th Annual Meeting of the Division of Plasma Physics
The emerging field of high energy density physics has been described by a recent National Academy of Science report as the "X-games" of contemporary science. The term high energy density is used to describe matter with pressures more than 1 million times the pressure on the surface of the earth. While high energy density matter is extreme by terrestrial standards, it can be found throughout the universe in a number of astrophysical settings and can be made for short times and within small volumes in the laboratory. In an invited talk on Monday morning Mark Herrmann of DOE’s Lawrence Livermore National Laboratory will describe recent expaeriments that provide a new entry for the "X-games": the laser driven dynamic hohlraum.
The new entry, called a laser driven dynamic hohlraum, consists of a spherical, laser-driven implosion of a plastic shell filled with xenon. As this thin shell implodes it sweeps up the xenon and causes it to radiate x-rays. When enough radiating xenon has been swept up, the xenon begins to trap x-ray radiation on the inside, creating a time-evolving cavity of intense x-rays -- a dynamic hohlraum. With this technique, it may be possible to achieve very high energy densities on experiments at the National Ignition Facility, which began initial physics operations this year.
David Harris | American Physical Society
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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:41489cb0-db20-4fbb-9ed7-dba302a708e5> | 3.046875 | 937 | Content Listing | Science & Tech. | 38.288173 | 95,546,836 |
Astronomy for You, with Ms. K. Let’s begin with our very own star…. Fun Sun Facts: The sun is 4.6 billion years old (the life cycle of a star is about 10 billion years). So, how big is a billion???
Fun Sun Facts:
The sun is 4.6 billion years old (the life cycle of a star is about 10 billion years). So, how big is a billion???
Stars are hot (5,500°C at the surface, 15 million°C at its core) glowing balls made of about 92% hydrogen and 8% helium, held together by its own gravity. They glow through nuclear fusion.
Our star is 150 million km away and the light takes 8 minutes to reach Earth.
Over 1 million Earths could fit inside the Sun.
•There are over 100 billion galaxies (large collections of stars) in our known universe and an estimated 100 billion stars in our Milky Way galaxy.
•Two thirds of the galaxies are spirals like the Milky Way, the rest are elliptical or toothpick shapes.
•Scientists believe the universe is expanding from a single point in space since the Big Bang, 14 billion years ago.
•We cannot see 95% of the known universe… it is in the form of dark energy and dark matter!
The nearest large galaxy to our own and the farthest “naked eye” object that can be seen from Earth (though a very dark sky is necessary).
Black holes are not empty spaces in the Universe. A black hole is a great amount of matter packed into a very small area, which results in a gravitational field so strong that nothing -- not even light -- can escape.
There are many kinds of black holes…and astronomers are discovering more all the time, observing with x-ray and radio wave telescopes.
Outside of our solar system, over 1,700 planets have been indentified. Some of these are “M-class” or capable of sustaining earth-like life forms.
Our solar system has eight planets, since Pluto was declared a dwarf planet (since it obviously did not form in the original accretion disc of the solar system)
Want to know more?
Yes, we are looking! And volunteer scientists can use their home computers to create “super-computers” to crunch the data. There are many other important science missions as well. Solar system space is being explored by many unmanned spacecraft.
Comet Tempel 1, photo taken by a research orbiter 67 seconds after an impacter hit the surface.
Is it possible at all for humans to achieve warp drive, like you see in Star Trek? A 2009 page from NASA said scientists aren’t sure about that.
“We are at the point where we know what we do know and know what we don’t, but do not know for sure if faster than light travel is possible,” | <urn:uuid:597d8dcd-51a9-4fa4-8b9f-1492f0337a37> | 3.75 | 608 | Personal Blog | Science & Tech. | 69.633053 | 95,546,841 |
Genetic Diversity of the First Baltic Population of Rangia cuneata (Bivalvia: Mactridae)
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The genetic diversity of the first Baltic population of the bivalve mollusk Rangia cuneata (G.B. Sowerby I, 1831) is studied on the basis of mtDNA COI gene sequences. It is shown that a single population of this alien species with a high level of genetic diversity inhabits the whole Vistula Lagoon. It is assumed that common rangia penetrated to the Vistula Lagoon at the larval stage with ballast waters. The first European R. cuneata population from the North Sea is regarded as the most probable source of introduction. Information on the genetic diversity of population of introduced species may be useful for forecasting of further ways of dispersal of the species.
KeywordsRangia cuneata alien species mtDNA Baltic Sea
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probably a wrong question.
maybe better questions would be
What is the mass of the Greenland Ice Sheet?
How much energy is needed to melt that mass completely?
What is the make break point of melting vs accumulating more mass?
How much energy is being applied above the make break point to the Ice Sheet each year?
Something like that.
This small detail is interesting
When heat is added to water, its temperature increases. Specific heat is the measure of the amount of heat or energy required to raise the temperature of 1 gram of a material 1°C. The specific heat of water is 1 calorie per gram, or 4.18 joules per gram.
Even more heat must be added in order to melt ice and vaporize water. The amount of heat required to melt ice is called the latent heat of fusion; its value is 80 calories per gram.
so it is going to take a lot of energy to completely melt the Greenland Ice Sheet. | <urn:uuid:103a7a45-fb14-4ade-af2e-edb1e1d4657d> | 3.15625 | 198 | Q&A Forum | Science & Tech. | 66.818077 | 95,546,863 |
NIBs and XIBs are files that describe user interfaces, and are built using Interface Builder. In fact, the acronym "NIB" comes from "NeXTSTEP Interface Builder", and "XIB" from "Xcode Interface Builder". NIBs and XIBs are effectively the same thing: XIBs are newer and are used while you're developing, whereas NIBs are what get produced when you create a build.
In modern versions of iOS and macOS, NIBs and XIBs have effectively been replaced by storyboards, although you may still meet them if you work on older projects.
Available from iOS 7.0
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NOAA's GOES-15 satellite captured a very active Eastern Pacific ocean on Aug. 2 at 0900 UTC (5 a.m. EDT) with one hurricane and two developing tropical low pressure areas. System 91E is farthest west and approaching the Central Pacific, while Hurricane Gil and System 90E trail behind to the east. The GOES-15 infrared image was created at NASA's GOES Project at the NASA Goddard Space Flight Center, Greenbelt, Md.
NOAA's GOES-15 satellite captured a very active Eastern Pacific ocean on Aug. 2 at 0900 UTC (5 a.m. EDT) with one hurricane and two developing tropical low pressure areas.
Image Credit: NASA GOES Project
System 91E Headed into Central Pacific Ocean
The low pressure area called "System 91E" has developed about 1,260 miles east-southeast of Hilo, Hawaii. The National Hurricane Center in Miami, Fla. and the Central Pacific Hurricane Center or CPHC in Honolulu, Hawaii are monitoring System 91E and expect any development to be slow. Because System 91E is moving into the Central Pacific Ocean it will soon become the responsibility of the CPHC. Currently, System 91E has a low chance of becoming a tropical cyclone during the next 48 hours.
Hurricane Gil Sandwiched
Hurricane Gil is sandwiched between two low pressure areas: System 91E to the west and System 90E to Gil's east. Gil appears to be inhibiting System 90E's development, but that may change if Gil weakens or moves farther away from the low.
At 5 p.m. EDT on Aug. 2, Gil's maximum sustained winds were near 85 mph/140 kph. The National Hurricane Center expects little change in strength during the next two days.
Gil was centered near 14.6 north latitude and 127.3 west longitude, about 1,275 miles/2,050 km west-southeast of the southern tip of Baja California, Mexico. Gil is moving west at 13 mph/20 kph and this motion is expected to continue with some decrease in forward speed during the next two days. The estimated minimum central pressure is 985 millibars.
In the GOES-15 satellite imagery Gil appears less organized and the area of strongest convection (rising air that forms the thunderstorms that make up the tropical cyclone) has been shrinking. Precipitable water imagery shows that drier air is wrapping into the eastern side of the storm and is likely the cause of the diminished organization.
Over the weekend of Aug. 3 and 4, the NHC expects slow weakening when Gil moves over progressively cooler water and into an environment of slightly stronger wind shear.
System 90E Being Affected by Hurricane Gil
Low pressure area called "System 90E" is still chasing Hurricane Gil. Located east of Gil, it is located about 900 miles southwest of the southern tip of the Baja California Peninsula of Mexico. Gil is moving westward at about 10 to 15 mph.
System 90E is producing disorganized thunderstorms, but NHC noted that if Hurricane Gil weakens, System 90E get a chance to develop. Gil's close proximity to System 90E is adversely affecting the storm's ability to organize. System 90E was given a 30 percent or medium chance of becoming a tropical cyclone over the next two days, and a higher chance over the next 5 days.Rob Gutro
Rob Gutro | EurekAlert!
Further reports about: > Active Agents > Eastern Pacific Ocean > Goddard Space Flight Center > Greenbelt > Hurricane > Hurricane Center > Hurricane Gil > NASA > NHC > National Hurricane Center > Pacific Ocean > Pacific coral > Space > low pressure area > monitoring System 91E > tropical cyclone > tropical diseases > tropical low pressure
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[C11] Integer types allows three representations for signed integral types:
See §5 C Signed Integer Wording for full wording.
C++ goes further than C and only requires that "the representations of integral types shall define values by use of a pure binary numeration system". To the author’s knowledge no modern machine uses both C++ and a signed integer representation other than two’s complement (see §6 Survey of Signed Integer Representations). None of [MSVC], [GCC], and [LLVM] support other representations. This means that the C++ that is taught is effectively two’s complement, and the C++ that is written is two’s complement. It is extremely unlikely that there exist any significant codebase developed for two’s complement machines that would actually work when run on a non-two’s complement machine.
C and C++ as specified, however, are not two’s complement. Signed integers currently allow the existence of an extraordinary value which traps, extra padding bits, integral negative zero, and introduce undefined behavior and implementation-defined behavior for the sake of this extremely abstract machine.
Let’s stop pretending that the abstract machine should represent integers as signed magnitude or ones' complement. These theoretical implementations are a different programming language, not our real-world C++. Developers who require signed magnitude or ones' complement integers would be better served by a pure-library solution, and so would the rest of us.
This paper proposes the following:
Status-quo Signed integer arithmetic remains non-commutative in general (though some implementations may guarantee that it is).
boolis represented as
true. All other representations are undefined.
boolonly has value bits, no padding bits.
Change Signed integers are two’s complement.
Change If there are M value bits in the signed type and N in the unsigned type, then M = N-1 (whereas C says M ≤ N).
Status-quo If a signed operation would naturally produce a value that is not within the range of the result type, the behavior is undefined. The author had hoped to make this well-defined as wrapping (the operations produce the same value bits as for the corresponding unsigned type), but WG21 had strong resistance against this.
Change None of the integral types have extraordinary values.
Change C11 note 53 has wording aroung trap representations within padding bits, e.g. for parity bits. C++ has no such wording.
Change Conversion from signed to unsigned is always well-defined: the result is the unique value of the destination type that is congruent to the source integer modulo 2N.
Change Conversion from enumeration type to integral is the same as that of converting from the enumeration’s underlying type and then to the destination type, even if the original value cannot be represented by the specified type.
Status-quo Conversion from integral type to enumeration is unchanged: if the original value is not within the range of the enumeration values the behavior is undefined.
Change Left-shift on signed integer types produces the same results as left-shift on the corresponding unsigned integer type.
Change Right-shift is an arithmetic right shift which performs sign-extension.
Status-quo shift by larger-than or equal-to bit-width remains undefined.
constexprevaluation of signed integer arithmetic with undefined result is not a core constant expression.
Change the range of enumerations without a fixed underlying type is simplified because of two’s complement.
is_modulotype trait remains
falsefor signed integer types unless an implementation chooses to defined overflow as wrap.
booland signed integer types, in addition to unsigned integer types and others before.
Status-quo atomic operations on signed integer types continues not to have undefined behavior, and is still specified to wrap as two’s complement (the definition is clarified to act as-if casting to unsigned and back).
Change address [LWG3047] to remove undefined behavior in pre-increment atomic operations.
This proposal leaves C unchanged, it merely restricts further the subset of C which applies to C++. Aaron Ballman volunteered to present this paper and the corresponding [N2218] to WG14, in the hope that C will approve compatible changes. The WG14 feedback is summarized in §7 WG14 Feedback from the Brno Meeting.
A final argument to move to two’s complement is that few people spell "ones' complement" correctly according to Knuth [TAoCP]. Reducing the nerd-snipe potential inherent in C++ is a Good Thing™.
Detail-oriented readers and copy editors should notice the position of the apostrophe in terms like “two’s complement” and “ones’ complement”: A two’s complement number is complemented with respect to a single power of 2, while a ones’ complement number is complemented with respect to a long sequence of 1s. Indeed, there is also a “twos’ complement notation,” which has radix 3 and complementation with respect to (2 . . . 22)3.
2. Edit History
2.1. r1 → r2
Update with feedback from WG14, available in §7 WG14 Feedback from the Brno Meeting.
2.2. r0 → r1
This paper was presented in Jacksonville to:
A joint SG6 numerics and SG12 undefined behavior session
The Evolution Working Group
The following polls were taken, and corresponding modifications made to the paper. The main change between [P0907r0] and the subsequent revision is to maintain undefined behavior when signed integer overflow occurs, instead of defining wrapping behavior. This direction was motivated by:
Performance concerns, whereby defining the behavior prevents optimizers from assuming that overflow never occurs;
Implementation leeway for tools such as sanitizers;
Data from Google suggesting that over 90% of all overflow is a bug, and defining wrapping behavior would not have solved the bug.
It is expected that this paper have little to no effect on code generation from current compilers. Known codegen changes should have no performance implication, for example:
Older x86 vector instructions don’t support arithmetic right shift, and therefore must remain scalar instead of vectorizing to non-arithmetic right shift.
An implementation which implements left shift using a rotate now need to also mask.
2.2.1. SG6 / SG12
|Change anything with respect to signed integers.||2||10||5||1||0|
|Moving any change from this paper to IS’20 is blocked on synchronizing with WG14.||4||9||4||0||1|
|Change the default unsigned integral types' behavior.||0||0||1||8||9|
|Changes we make constrain extended integral types.||10||4||2||0||1|
|Allow extraordinary value for signed integral types.||2||2||9||2||3|
We decided to independently conside what the "privileged" syntax' behavior should be when going out of range for:
cast of enums
INT_MIN / -1
addition / subtraction / multiplication and
Multiple answer poll would you be OK with these being the standards-mandated behavior for the "privileged" syntax behavior of signed integral types when going out of range:
1—generate extraordinary value
5—Rust-style wrap or trap, maybe contract violation?
9—intermediate values are mathematical integers (e.g.
(int)a+(int)b > INT_MAXwould be OK)
|Cast to enums outside of the enum’s representable range should be defined instead of undefined behavior.||0||1||1||5||8|
|Cast from ||6||6||3||0||1|
|We want two’s complement representation for signed types, regardless of what WG14 decides.||7||4||2||0||3|
Multiple answer poll addition / subtraction / multiplication and
-INT_MIN overflow is currently undefined behavior, it should instead be:
6—wrap or trap
5—intermediate values are mathematical integers
14—status quo (remain undefined behavior)
Multiple answer poll to opt-in to the other behaviors (both for
unsigned) we can create library or language changes. What should we explore
separately from this paper?
3—generate extraordinary value
10—Rust-style wrap or trap, maybe contract violation?
9—intermediate values are mathematical integers (e.g.
(int)a+(int)b > INT_MAXwould be OK)
14—operations with a bool set when overflow has occurred
|Shifting out of range ||2||7||5||1||1|
|Left shift should be the same for ||6||5||5||0||1|
|Right shift on a signed integral type should be an arithmetic shift (which sign-extends).||9||4||3||1||0|
|In C ||1||0||2||3||12|
The Evolution Working Group took the following polls:
|Disallow extraordinary value (trapping / NaN) for signed integral types.||16||12||7||1||2|
|Does EWG want to move signed integers to two’s complement, as presented in the current paper (without extraordinary values)?||11||17||7||2||1|
|Move to Core.||7||8||12||8||4|
The resolution on disallowing extraordinary values overrides the lack of consensus for change from SG6 / SG12.
The decision to not forward to Core was mainly motivated on hearing back from WG14. WG14 met in Brno, discussed [N2218], and provided feedback detailed in §7 WG14 Feedback from the Brno Meeting. EWG will see the paper again in Rappersvil, and will likely forward to Core at that point in time given the outcome of the next-to-last poll.
3. Proposed Wording
Leave the note in Program execution [intro.execution] ❡8 as-is:
[Note: Operators can be regrouped according to the usual mathematical rules only where the operators really are associative or commutative. For example, in the following fragmentint a, b; /* ... */ a = a + 32760 + b + 5;
the expression statement behaves exactly the same asa = (((a + 32760) + b) + 5);
due to the associativity and precedence of these operators. Thus, the result of the sum
(a + 32760)is next added to
b, and that result is then added to 5 which results in the value assigned to
a. On a machine in which overflows produce an exception and in which the range of values representable by an
[-32768, +32767], the implementation cannot rewrite this expression asa = ((a + b) + 32765);
since if the values for
bwere, respectively, -32754 and -15, the sum
a + bwould produce an exception while the original expression would not; nor can the expression be rewritten either asa = ((a + 32765) + b);
ora = (a + (b + 32765));
since the values for
bmight have been, respectively, 4 and -8 or -17 and 12. However on a machine in which overflows do not produce an exception and in which the results of overflows are reversible, the above expression statement can be rewritten by the implementation in any of the above ways because the same result will occur. —end note]
Modify Fundamental types [basic.fundamental] ❡4 onwards:
Unsigned integers shall obey the laws of arithmetic modulo 2n where n is the number of bits in the value representation of that particular size of integer.
This implies that unsigned arithmetic does not overflow because a result that cannot be represented by the resulting unsigned integer type is reduced modulo the number that is one greater than the largest value that can be represented by the resulting unsigned integer type.
wchar_tis a distinct type whose values can represent distinct codes for all members of the largest extended character set specified among the supported locales. Type
wchar_tshall have the same size, signedness, and alignment requirements as one of the other integral types, called its underlying type. Types
char32_tdenote distinct types with the same size, signedness, and alignment as
uint_least32_t, respectively, in
<cstdint>, called the underlying types.
Values of type
false†. [Note: There are no
long booltypes or values. —end note] Values of type
boolparticipate in integral promotions.
† Using a
boolvalue in ways described by this International Standard as “undefined”, such as by examining the value of an uninitialized automatic object, might cause it to behave as if it is neither
We need to define the storage for
boolsince we define signed and unsigned below, and that excludes
bool. The definition I propose is more restrictive than what we had before because it only allows two values to be represented, and doesn’t allow padding bits. This guarantees that
boolis trivially-copyable, and gives it a unique object representation, which as far as I know all compilers already guaranteed.
wchar_t, and the signed and unsigned integer types are collectively called integral types. A synonym for integral type is integer type.
The representations of integral types shall define values by use of a pure binary numeration system‡. [Example: This document permits two’s complement, ones' complement and signed magnitude representations for integral types. —end example]
‡ A positional representation for integers that uses the binary digits 0 and 1, in which the values represented by successive bits are additive, begin with 1, and are multiplied by successive integral power of 2, except perhaps for the bit with the highest position. (Adapted from the American National Dictionary for Information Processing Systems.)
An intermediate revision of this paper stated "Value bits are store contiguously in memory" in an attempt to preserve different endiannesses, and otherwise restricts implementations to "sane" layout. However, that change wasn’t presented to EWG and received pushback on the SG6 reflector. Would this be a desirable addition, should it be in a separate paper, or does it overconstrain implementations?
note M = N-1, whereas C says M ≤ N. I derive this from "For each of the standard signed integer types, there exists a corresponding (but different) standard unsigned integer type [...] each of which occupies the same amount of storage".
In C11 implementation requirements call it the "extraordinary value" and refer to 126.96.36.199 which calls it "is a trap representation or a normal value". Furthermore, in note 53 there’s wording around extraordinary values being held in padding bits (not just as a value stolen from the value representation), and since C++ wording used to only talk about "binary representation" it’d rather be very clear about the absence of extraordinary values. It’s unclear whether SG6 / SG12 guidance explicitly wanted to disallow padding bits from being special and trapping. I propose disallowing it.
Modify Integral conversions [conv.integral] ❡1 onwards:
A prvalue of an integer type can be converted to a prvalue of another integer type. A prvalue of an unscoped enumeration type can be converted to a prvalue of an integer type.
If the destination type is unsigned, the resulting value is the least unsigned integer congruent to the source integer (modulo 2n where n is the number of bits used to represent the unsigned type). [Note: In a two’s complement representation, this conversion is conceptual and there is no change in the bit pattern (if there is no truncation). —end note] If the destination type is signed, the value is unchanged if it can be represented in the destination type; otherwise, the value is implementation-defined.
Modify Static cast [expr.static.cast] ❡9 onwards:
A value of a scoped enumeration type can be explicitly converted to an integral type
. When that type is cvA value of a scoped enumeration type can also be explicitly converted to a floating-point type; the result is the same as that of converting from the original value to the floating-point type.
bool, the resulting value is
falseif the original value is zero and
truefor all other values. For the remaining integral types, the value is unchanged if the original value can be represented by the specified type. Otherwise, the resulting value is unspecified.
the above change is for enumeration to integer, which SG6 did not object to changing as suggested. It states the conversion in terms of the updated [conv.integral] rules.
A value of integral or enumeration type can be explicitly converted to a complete enumeration type. If the enumeration type has a fixed underlying type, the value is first converted to that type by integral conversion, if necessary, and then to the enumeration type. If the enumeration type does not have a fixed underlying type, the value is unchanged if the original value is within the range of the enumeration values, and otherwise, the behavior is undefined. A value of floating-point type can also be explicitly converted to an enumeration type. The resulting value is the same as converting the original value to the underlying type of the enumeration, and subsequently to the enumeration type.
the above unmodified paragraph is for integer to enumeration which SG6 voted to leave undefined in poll "Cast to enums outside of the enum’s representable range should be defined instead of undefined behavior".
Modify Shift operators [expr.shift] ❡1 onwards:
The operands shall be of integral or unscoped enumeration type and integral promotions are performed. The type of the result is that of the promoted left operand. The behavior is undefined if the right operand is negative, or greater than or equal to the length in bits of the promoted left operand.
The value of
E1 << E2is
E2bit positions; vacated bits are zero-filled.
Ifvalue of the result is E1×2E2, reduced modulo
E1has an unsigned type, the
one more than the maximum value representable in the result type. Otherwise, if
E1has a signed type and non-negative value, and E1×2E2 is representable in the corresponding unsigned type of the result type, then that value, converted to the result type, is the resulting value; otherwise, the behavior is undefined.
updated to reflect poll "Left shift should be the same for signed and unsigned".
The value of
E1 >> E2is
Ifvalue of the result is
E1has an unsigned type or if
E1has a signed type and a non-negative value, the
the integral part of the quotient of
E1has a signed type and a negative value, the resulting value is implementation-defined.
Leave Constant expressions [expr.const] ❡2 as-is:
eis a core constant expression unless the evaluation of
e, following the rules of the abstract machine, would evaluate one of the following expressions:
an operation that would have undefined behavior as specified in Clause 4 through 19 of this document [Note: including, for example, signed integer overflow, certain pointer arithmetic, division by zero, or certain shift operations —end note]
Modify Enumeration declarations [dcl.enum] ❡8:
For an enumeration whose underlying type is fixed, the values of the enumeration are the values of the underlying type. Otherwise, for an enumeration where emin is the smallest enumerator and emax is the largest, the values of the enumeration are the values in the range bmin to bmax, defined as follows:
Let K be 1 for a two’s complement representation and 0 for a ones' complement or sign-magnitude representation.bmax is the smallest value greater than or equal to max(|emin| - K, |emax|) and equal to 2M-1, where M is a non-negative integer. bmin is zero if emin is non-negative and -(bmax+ K) otherwise. The size of the smallest bit-field large enough to hold all the values of the enumeration type is max(M,1) if bmin is zero and M+1 otherwise. It is possible to define an enumeration that has values not defined by any of its enumerators. If the enumerator-list is empty, the values of the enumeration are as if the enumeration had a single enumerator with value 0.
numeric_limits members [numeric.limits.members] ❡61 onwards as-is:
static constexpr bool is_modulo;
trueif the type is modulo. A type is modulo if, for any operation involving
*on values of that type whose result would fall outside the range
[min(), max()], the value returned differs from the true value by an integer multiple of
max() - min() + 1.
falsefor signed integer types unless an implementation, as an extension to this document, defines signed integer overflow to wrap. —end example]
Meaningful for all specializations.
Modify Type properties [meta.unary.prop] ❡9 as follows:
The predicate condition for a template specialization
has_unique_object_representations<T>shall be satisfied if and only if:
Tis trivially copyable, and
any two objects of type
Twith the same value have the same object representation, where two objects of array or non-union class type are considered to have the same value if their respective sequences of direct subobjects have the same values, and two objects of union type are considered to have the same value if they have the same active member and the corresponding members have the same value.
The set of scalar types for which this condition holds is implementation-defined. [Note: If a type has padding bits, the condition does not hold; otherwise, the condition holds true for unsigned integral types. —end note]
this was missing from P0907r0. Adding signed here seems like a no-brainer. GCC and LLVM currently return
bool(and it currently isn’t implemented in MSVC). Try it out.
Modify Class template
ratio [ratio.ratio] ❡1 as follows:
If the template argument
Dis zero or the absolute values of either of the template arguments
Dis not representable by type
intmax_t, the program is ill-formed. [Note: These rules ensure that infinite ratios are avoided and that for any negative input, there exists a representable value of its absolute value which is positive.
In a two’s complement representation, thisexcludes the most negative value. —end note]
Modify Specializations for integers [atomics.types.int] ❡7 and ❡8 as follows:
Remarks: For signed integer types,
arithmetic is defined to use two’s complement representation.There are no undefined results
the operations this applies to are add, or, and, sub, xor, and is only meaningful for add and sub.T operator op=(T operand) volatile noexcept; T operator op=(T operand) noexcept;
Effects: Equivalent to:
return fetch_key(operand) op operand;
there’s an outstanding defect report for this [LWG3047], whose resolution should be updated as above.
4. Out of Scope
This proposal focuses on the representation of signed integers, and on tightening the specification when that representation is constrained to two’s complement. It is out of scope for this proposal to deal with related issues which have more to them than simply the representation of signed integers.
A non-comprehensive list of items left purposefully out:
Left and right shift with a right-hand-side equal to or wider than the bit-width of the left-hand-side.
Integral division or modulo by zero.
Integral division or modulo of the signed minimum integral value for a particular integral type by minus one.
Overflow of pointer arithmetic.
Library solution for ones' complement integers.
Library solution for signed magnitude integers.
Library solution for two’s complement integers with trapping or undefined overflow semantics.
Language support for explicit signed overflow truncation such as Swift’s (
&*), or complementary trapping overflow operators.
Library or language support for saturating arithmetic.
Mechanism to let the compiler assume that integers, signed or unsigned, do not experience signed or unsigned wrapping for:
A specific integral variable.
All integral variables (à la
A specific loop’s induction variable.
Mechanism to have the compiler list places where it could benefit from knowing that overflow cannot occur (à la
Endianness of integral storage (or endianness in general).
Bits per bytes, though we all know there are eight.
These items could be tackled in separate proposals, unless the committee wants them tackled here. This paper expresses no preference in whether they should be addressed or how.
5. C Signed Integer Wording
The following is the wording on integers from the C11 Standard.
For unsigned integer types other than unsigned char, the bits of the object representation shall be divided into two groups: value bits and padding bits (there need not be any of the latter). If there are N value bits, each bit shall represent a different power of 2 between 1 and 2N−1, so that objects of that type shall be capable of representing values from 0 to 2N − 1 using a pure binary representation; this shall be known as the value representation. The values of any padding bits are unspecified.
For signed integer types, the bits of the object representation shall be divided into three groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
signed charshall not have any padding bits. There shall be exactly one sign bit. Each bit that is a value bit shall have the same value as the same bit in the object representation of the corresponding unsigned type (if there are M value bits in the signed type and N in the unsigned type, then M ≤ N). If the sign bit is zero, it shall not affect the resulting value. If the sign bit is one, the value shall be modified in one of the following ways:
the corresponding value with sign bit 0 is negated (sign and magnitude);
the sign bit has the value −(2M) (two’s complement);
the sign bit has the value −(2M − 1) (ones’ complement).
Which of these applies is implementation-defined, as is whether the value with sign bit 1 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones’ complement), is a trap representation or a normal value. In the case of sign and magnitude and ones’ complement, if this representation is a normal value it is called a negative zero.
If the implementation supports negative zeros, they shall be generated only by:
>>operators with operands that produce such a value;
%operators where one operand is a negative zero and the result is zero;
compound assignment operators based on the above cases.
It is unspecified whether these cases actually generate a negative zero or a normal zero, and whether a negative zero becomes a normal zero when stored in an object.
If the implementation does not support negative zeros, the behavior of the
>>operators with operands that would produce such a value is undefined.
The values of any padding bits are unspecified. A valid (non-trap) object representation of a signed integer type where the sign bit is zero is a valid object representation of the corresponding unsigned type, and shall represent the same value. For any integer type, the object representation where all the bits are zero shall be a representation of the value zero in that type.
The precision of an integer type is the number of bits it uses to represent values, excluding any sign and padding bits. The width of an integer type is the same but including any sign bit; thus for unsigned integer types the two values are the same, while for signed integer types the width is one greater than the precision.
6. Survey of Signed Integer Representations
Here is a non-comprehensive history of signed integer representations:
John von Neumann suggested use of two’s complement binary representation in his 1945 First Draft of a Report on the EDVAC proposal for an electronic stored-program digital computer.
The 1949 EDSAC, which was inspired by the First Draft, used two’s complement representation of binary numbers.
Early commercial two’s complement computers include the Digital Equipment Corporation PDP-5 and the 1963 PDP-6.
The System/360, introduced in 1964 by IBM, then the dominant player in the computer industry, made two’s complement the most widely used binary representation in the computer industry.
The first minicomputer, the PDP-8 introduced in 1965, uses two’s complement arithmetic as do the 1969 Data General Nova, the 1970 PDP-11.
Many early computers, including the CDC 6600, the LINC, the PDP-1, and the UNIVAC 1107.
Successors of the CDC 6600 continued to use ones' complement until the late 1980s.
Descendants of the UNIVAC 1107, the UNIVAC 1100/2200 series, continue to do so, although ClearPath machines are a common platform that implement either the 1100/2200 architecture (the ClearPath IX series) or the Burroughs large systems architecture (the ClearPath NX series). Everything is common except the actual CPUs, which are implemented as ASICs. In addition to the IX (1100/2200) CPUs and the NX (Burroughs large systems) CPU, the architecture had Xeon (and briefly Itanium) CPUs. Unisys' goal was to provide an orderly transition for their 1100/2200 customers to a more modern architecture.
The IBM 700/7000 series scientific machines use sign/magnitude notation, except for the index registers which are two’s complement.
Wikipedia offers more details and has comprehensive sources for the above.
Thomas Rodgers surveyed popular DSPs and found the following:
SHARC family ships a C++ compiler which supports C++11, and where signed integers are two’s complement.
Texas Instruments ships a C++ compiler which supports C++14, and where signed integers are two’s complement.
CML Microcircuits has fixed ASIC for radio processing, and doesn’t seem to support C++.
Synaptics (formerly Connexant) makes audio input subsystem for voice assistants. The DSP runs fixed far-field signal processing algorithms and has programmable functions which run on standard ARM controller, using Raspbian.
In short, the only machine the author could find using non-two’s complement are made by Unisys, and no counter-example was brought by any member of the C++ standards committee. Nowadays Unisys emulates their old architecture using x86 CPUs with attached FPGAs for customers who have legacy applications which they’ve been unable to migrate. These applications are unlikely to be well served by modern C++, signed integers are the least of their problem. Post-modern C++ should focus on serving its existing users well, and incoming users should be blissfully unaware of integer esoterica.
7. WG14 Feedback from the Brno Meeting
WG14 met in Brno to discuss [N2218]. The paper was received very positively, especially given that no one in the room knew of an extant architecture that was not two’s complement for which there was a reasonably modern C compiler. The closest anyone came was the Unisys ClearPath compiler documentation which says:
Two’s complement arithmetic is used on many platforms. On ClearPath MCP systems, arithmetic is performed on data in signed-magnitude form. This can cause discrepancies in algorithms that depend on the two’s complement representation.
However, this compiler documentation also says that they only target C90, and was last updated on 2017.
There was worry about the search on impacted architectures not having been exhaustive. Given that WG14 will ship the IS in 5 years, it was felt that making them aware now should give vendors plenty of time to bring up reasons why this change would be bad for them.
It was pointed out that C already has cases that require two’s complement.
It was noted that the existing implementation latitude is a burden for library developers because they have to consider test cases where integers are not two’s complement but they have no way to actually exercise any of those test cases.
The following straw poll was taken:
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Is the Carbon Plateau Over?
Dec 10 2017 Read 1322 Times
Over the past three years, carbon emissions across the world had largely stalled, fuelling hopes that peak emissions had been reached and that we may have some chance of avoiding a global temperature hike of 2°C as agreed upon at the Paris Climate Summit in 2015.
However, new research led by the Global Carbon Project reveals that emissions are set to jump up again in 2017, reaching a new record high and making it almost impossible to achieve the goals laid out at COP21. If the Earth’s temperature does rise by the projected 2°C, it could have catastrophic and irreversible consequences for humans, plants and animals all over the world.
Back on the increase
Previous research conducted by the Global Carbon Project had found that carbon emissions had reached a plateau between 2014 and 2016, though leading scientists had warned at the time that it was too early to tell whether they had peaked once and for all.
The new study confirms those fears, with CO2 emissions projected to rise by 2% in 2017, reaching a record high 41 gigatonnes. Again, the chief author of the report would not be drawn on whether this upward trend would continue beyond the coming year. “We can’t say what trajectory is going to be realised,” explains Corinne Le Quéré, director of Tyndall Centre for Climate Change Research in East Anglia.
However, Le Quéré was clear that something must be done now to avoid temperature increases surpassing the 2°C threshold; continue as we are, and we could even reach a hike of 3°C. That would be disastrous for the world’s fragile biosphere.
Oil and gas still going strong
While more stringent monitoring measures and a changing public opinion towards coal may indicate that this fossil fuel is on its way out, oil and gas are still growing at an alarming rate. Fossil fuels still account for the vast majority of emissions (37 gigatonnes this year, or 90% of the total emissions), while land clearing of forested areas (to make way for palm oil plantations and the suchlike) account for the rest.
Of course, the data from the Global Carbon Project doesn’t even consider other harmful greenhouse gases (GHGs). The methane emissions from agriculture and dairy farming, for example, are arguably more damaging than CO2, since although they persist in the atmosphere for less than time than carbon, they can trap up to 100 times more heat.
More effective measures needed
Critics claim that the biggest stumbling block to bringing down emissions at the moment is the absence of a clear, coherent policy from governments all over the world. The technology does exist to change our polluting ways; the impetus to do so is sadly lacking.
Although the EU does have a carbon trading scheme (which underwent significant changes earlier this year), it has come under heavy criticism for the unpredictability and low value of the price it engenders. This, speculators have said, does not encourage businesses to prioritise curbing their emissions.
In any case, action will be needed imminently if we are to avoid catastrophic consequences for the planet. “Once we get above about 2°C of warming relative to the pre-industrial – and we’re not that far away from it now – we see some of the worst and potentially irreversible changes in climate,” explains Michael Mann, a Penn State climatologist. “And they’re not just incremental. They’re not just a nuisance. We are talking about a fundamental threat to our way of life.”
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The team believes that the remarkable structure may be associated with the detection of predators, in particular birds. The Blue Morpho butterflies (Morpho peleides), native to Central and South America, are more famous for their amazing wing colouration and now turn out to have ears on their wings.
The simple ear sits at the base of the wing and looks like a sheet of stretched rubber. This oval-shaped tympanal membrane, with an unusual dome in the middle, is attached directly to sensory organs and is responsible for converting sound waves into signals that can be picked up by nerve cells.
Using a tiny laser beam, lead researcher Katie Lucas scanned the surface of the membrane while it was in action, and found that lower pitch sounds cause vibrations only in a part of the outer membrane while higher pitch sounds caused the entire membrane to vibrate.
The unusual structure and properties of the membrane mean that this butterfly ear may be able to distinguish between low and high pitch sounds, and measurements of nerve recordings suggested the butterfly is more sensitive to lower pitches. Butterfly hearing is unusually sensitive to low pitch sounds compared to other insects with similar ears.
The structure of the membrane could mean the butterfly can hear a greater range of pitches, which as Katie Lucas and her colleagues postulate, may enhance the abilities of these butterflies to listen for birds. The team suggest that sensitivity to lower pitch sounds may detect the beating of birds’ wings, while higher pitches may tune into birdsong.
The research was carried out by scientists working at the School of Biological Sciences, University of Bristol, University of Strathclyde and Carleton University, Ontario, Canada.
It was funded by a Journal of Experimental Biology Travelling Fellowship to Katie Lucas, the Canadian Foundation for Innovation, Ontario Innovation Trust, Natural Science and Engineering Research Council of Canada and the Biotechnology and Biological Sciences Research Council (BBSRC), UK.
Auditory mechanics and sensitivity in the tropical butterfly Morpho peleides (Pampilionoidea, Nymphalidae) by Kathleen M. Lucas, James F. C. Windmill, Daniel Robert and Jayne E. Yack The Journal of Experimental Biology
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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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Energy is expensive. Thanks to the laws of thermodynamics, it’s just not possible to get more energy out of a system than you put in. Thus, when it comes to generating power, you’ll always be stuck with a bad investment. However, there is a bit of a work around to this problem. See, if you can get someone or something else to supply the initial energy for you, then you can reap the rewards without having to worry about the cost. And while that may not sound very honest, it is in fact the basic idea behind solar power.
See, the sun does all the work, crushing hydrogen atoms together and flinging the resultant energy out into space. All we have to do is figure out a way to harness it when it reaches earth.
Of course, that’s not to say that harnessing solar energy is easy. In order for us to be able to convert it into useable electricity, humanity first had to discover the photoelectric effect. See, when sunlight hits an object, the energy that it carries has to go somewhere. Some of it is reflected, but the majority of the energy is bled off as heat. However, certain materials allow for a third option. Silicon, for example, is a semiconductor, which means that the electrons contained inside it tend to get excited and move around when exposed to direct sunlight. This is known as the photoelectric effect. These electrons generate an electrical current, which can be captured and utilized.
This was first discovered in 1876 by William Grylls Adams and Richard Day, but it wasn’t until 1953 that Calvin Fuller, Gerald Pearson, and Daryl Chapin developed an efficient enough solar cell to actually be able to run small electrical devices from the power it produced. Within a few years, solar power began to be heavily used by both American and Soviet space programs.
Today, solar power is viewed as one of the most promising alternate energy sources available. After all, sunlight is free and abundant all over the world, and will continue to be so until the sun burns itself out in a few billion years from now.
As such, the solar industry is booming. In 2012, the solar industry grew a whopping 76%, and now supplies the United States with 3,133 megawatts of clean energy. This is, in part, thanks to growing concern over the environmental damage caused by the processes used to generate conventional power, as well as issues regarding the lack of coal and fossil fuel renewability.
The people are becoming interested in solar power, and the industry is answering them with exciting advances. The production of new, less expensive crystalline silicon panels, as well as advances in paper-thin solar cells, is making the once expensive panel production process more and more affordable. At the same time, home automation companies, such as Vivint are offering rentable solar power systems, which allow consumers to save on energy costs without having to worry about installation or maintenance.
As for what we can expect in the future, well, there has been a great deal of talk surrounding the possibility of double-sided solar panels. When strategically placed (as in such a way that allows it to capture sunlight both in the morning as well as in the afternoon, or on reflective surfaces that can pick up extra light that is being bounced back), these panels could possibly double the energy output of traditional single-sided panels. And if the United States wants to meet all of its energy requirements, it’s going to need much more solar paneling to do so. Some have discussed the possibility of replacing asphalt with durable solar panels across the country, and there is even some interest in placing a solar ring around the moon’s equator to “beam” energy back to earth.
Solar power is probably the best chance we have at creating a sustainable, efficient, and clean energy source. However, we still have a long way to go before we can all get our electricity from the sun. Still, with current advances pointing us in ever more promising directions, we may someday be able to run all of our machinery and electronics with nothing more than a stray sunbeam.
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|MLA Citation:||Bloomfield, Louis A. "Question 1165"|
How Everything Works 22 Jul 2018. 22 Jul 2018 <http://howeverythingworks.org/print1.php?QNum=1165>.
However, there are several complications when using this technique to measure a person's temperature. First, anything that lies between the person and you, and that absorbs or emit thermal radiation, will affect your measurement. That's because some of the thermal radiation that appears to be coming from the person may be coming from those in between things. Fortunately, air is moderately transparent to thermal radiation but many other things aren't. In fact, to get an accurate reading of person's temperature, you'd have to cool the telescope and the light detector so that they don't add their own thermal radiation to what you observe. You'd also have to use a mirror telescope because glass optics absorb infrared light.
Second, the temperature that you observe will be that of the person's skin and not their inner core temperature. That's because the person's skin absorbs any infrared light from inside the person and it emits its own infrared light to the world around the person. You can't observe infrared light from inside the person because the person's skin blocks your view. All you see is their skin temperature. | <urn:uuid:6e8721e8-4085-4358-bd5b-18aca0e4c5ba> | 2.9375 | 266 | Knowledge Article | Science & Tech. | 59.056932 | 95,547,032 |
(Science Daily) In the search for extraterrestrial life, scientists have turned over all sorts of rocks.
by Staff Writer, March 30th, 2018
Mars, for example, has geological features that suggest it once had — and still has — subsurface liquid water, an almost sure prerequisite for life. Scientists have also eyed Saturn’s moons Titan and Enceladus as well as Jupiter’s moons Europa, Ganymede and Callisto as possible havens for life in the oceans under their icy crusts.
Now, however, scientists are dusting off an old idea that promises a new vista in the hunt for life beyond Earth: the clouds of Venus.
In a paper published online today (March 30, 2018) in the journal Astrobiology, an international team of researchers led by planetary scientist Sanjay Limaye of the University of Wisconsin-Madison’s Space Science and Engineering Center lays out a case for the atmosphere of Venus as a possible niche for extraterrestrial microbial life.
“Venus has had plenty of time to evolve life on its own,” explains Limaye, noting that some models suggest Venus once had a habitable climate with liquid water on its surface for as long as 2 billion years. “That’s much longer than is believed to have occurred on Mars.”
On Earth, terrestrial microorganisms — mostly bacteria — are capable of being swept into the atmosphere, where they have been found alive at altitudes as high as 41 kilometers (25 miles) by scientists using specially equipped balloons, according to study co-author David J. Smith of NASA’s Ames Research Center.
There is also a growing catalog of microbes known to inhabit incredibly harsh environments on our planet, including the hot springs of Yellowstone, deep ocean hydrothermal vents, the toxic sludge of polluted areas, and in acidic lakes worldwide.
“On Earth, we know that life can thrive in very acidic conditions, can feed on carbon dioxide, and produce sulfuric acid,” says Rakesh Mogul, a professor of biological chemistry at California State Polytechnic University, Pomona, and a co-author on the new paper. He notes that the cloudy, highly reflective and acidic atmosphere of Venus is composed mostly of carbon dioxide and water droplets containing sulfuric acid.
The habitability of Venus’ clouds was first raised in 1967 by noted biophysicist Harold Morowitz and famed astronomer Carl Sagan. Decades later, the planetary scientists David Grinspoon, Mark Bullock and their colleagues expanded on the idea.
Supporting the notion that Venus’ atmosphere could be a plausible niche for life, a series of space probes to the planet launched between 1962 and 1978 showed that the temperature and pressure conditions in the lower and middle portions of the Venusian atmosphere — altitudes between 40 and 60 kilometers (25-27 miles) — would not preclude microbial life. The surface conditions on the planet, however, are known to be inhospitable, with temperatures soaring above 450 degrees Celsius (860 degrees Fahrenheit).
Limaye, who conducts his research as a NASA participating scientist in the Japan Aerospace Exploration Agency’s Akatsuki mission to Venus, was eager to revisit the idea of exploring the planet’s atmosphere after a chance meeting at a teachers’ workshop with paper co-author Grzegorz S?owik of Poland’s University of Zielona Góra. Slowik made him aware of bacteria on Earth with light-absorbing properties similar to those of unidentified particles that make up unexplained dark patches observed in the clouds of Venus. Spectroscopic observations, particularly in the ultraviolet, show that the dark patches are composed of concentrated sulfuric acid and other unknown light-absorbing particles.
Those dark patches have been a mystery since they were first observed by ground-based telescopes nearly a century ago, says Limaye. They were studied in more detail by subsequent probes to the planet.
“Venus shows some episodic dark, sulfuric rich patches, with contrasts up to 30-40 percent in the ultraviolet, and muted in longer wavelengths. These patches persist for days, changing their shape and contrasts continuously and appear to be scale dependent,” says Limaye.
The particles that make up the dark patches have almost the same dimensions as some bacteria on Earth, although the instruments that have sampled Venus’ atmosphere to date are incapable of distinguishing between materials of an organic or inorganic nature.
The patches could be something akin to the algae blooms that occur routinely in the lakes and oceans of Earth, according to Limaye and Mogul — only these would need to be sustained in the Venusian atmosphere.
Limaye, who has spent his career studying planetary atmospheres, was further inspired to revisit the idea of microbial life in the clouds of Venus by a visit to Tso Kar, a high-altitude salt lake in northern India where he observed the powdery residue of sulfur-fixing bacteria concentrated on decaying grass at the edge of the lake being wafted into the atmosphere.
Limaye notes, however, that a part of the equation that isn’t known is when Venus’ liquid water evaporated — extensive lava flows in the last billion years likely have either destroyed or covered up the planet’s earlier terrestrial history.
In the hunt for extraterrestrial life, planetary atmospheres other than Earth’s remain largely unexplored.
One possibility for sampling the clouds of Venus, says Limaye, is on the drawing board: VAMP, or Venus Atmospheric Maneuverable Platform, a craft that flies like a plane but floats like a blimp and could stay aloft in the planet’s cloud layer for up to a year gathering data and samples.
Such a platform could include instruments like Raman Lidar, meteorological and chemical sensors, and spectrometers, says Limaye. It could also carry a type of microscope capable of identifying living microorganisms.
“To really know, we need to go there and sample the clouds,” says Mogul. “Venus could be an exciting new chapter in astrobiology exploration.”
The Wisconsin scientist and his colleagues remain hopeful that such a chapter can be opened as there are ongoing discussions about possible NASA participation in Russia’s Roscosmos Venera-D mission, now slated for the late 2020s. Current plans for Venera-D might include an orbiter, a lander and a NASA-contributed surface station and maneuverable aerial platform.
This research was supported by NASA grants NNX09AE85G and NNX16AC79G. The VAMP concept is under development by Northrop Grumman Corp.
- Sanjay S. Limaye, Rakesh Mogul, David J. Smith, Arif H. Ansari, Grzegorz P. Słowik, Parag Vaishampayan. Venus’ Spectral Signatures and the Potential for Life in the Clouds. Astrobiology, 2018; DOI: 10.1089/ast.2017.1783
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The bedrock below the West Antarctic ice sheet is rising much more rapidly than expected, revealing a very different Earth structure than previously believed. This discovery has important implications in understanding climate changes in Antarctica
An international team of researchers, with a new study published in Science with DTU Space as lead author, finds that the bedrock below the West Antarctic Ice Sheet is rising much more rapidly than expected, revealing a very different Earth structure than previously believed. This discovery has important implications in understanding the past, present and future climate changes in Antarctica.
A picture of Amundsen Sea Embayment in West Antarctica with the ice sliced to show the bedrock and the earth cut to show the crust (brown) the bottom of the lithosphere (red area) and the mantle (yellow). The color gradient indicate the temperature from hot (bright yellow) to relatively cool (dark red). In space we see three satellites flying, from the right, a GPS satellite, GOCE, which measures the static gravity, and Cryosat2, which measures the changes in ice thickness. The ice thickness and the bedrock data are from BEDMAP2, the mantle temperature and the crustal thickness is derived from GOCE (data from Folker Pappa).
Illustration credit: Planetary Visions/ESA Illustration text: VR. Barletta
The unexpectedly fast rate of the rising earth may increase the stability of the ice sheet against catastrophic collapse due to ice loss. At the same time the rapid rise, known as uplift, also affects gravity measurements. This implies that up to 10 percent more ice has melted off the West Antarctica Ice Sheet (WAIS) than previously assumed.
"The results of our work will provide a very important contribution in the understanding of dynamics of the Earth along with the ice melting processes in Antarctica," said leading author of this new study, postdoctoral researcher Valentina R. Barletta at DTU Space, the National Space Institute at the Technical University of Denmark.
The Amundsen Sea Embayment (ASE) in West Antarctica alone contributes to 25 percent of all water estimated from melting ice on our planet. To make numbers easier to understand, in one year ASE loses enough to cover an area the size of Denmark (43.000 square km) with a 2.8 meters high layer of ice. The same area (ASE) holds enough ice to potentially raise the global sea level by 1.2 meters or to cover an area the size of Denmark with 11 km of ice.
"The large amount of water stored in Antarctica has implications for the whole planet, but especially for northern Europe", said Barletta, "because of a combination of gravitational effects, surprisingly, the ice lost in Antarctica mostly raises the sea level here, in northern Europe. In contrast, the ice lost in Greenland has no effect here, but it raises the sea level in the southern hemisphere and further destabilizes the WAIS."
"The uplift velocity in ASE was measured at up to 41 millimeters per year, one of the fastest rates ever recorded in glaciated areas. In comparison, the GPS stations installed nearby the Greenland ice streams record up to 30 millimeters per year, but we know that it is caused by an immediate elastic rebound of the earth, acting like a spring" said Abbas Khan, one of the coauthors and associate professor at DTU Space.
Participating researchers led by scientists at the Ohio State University (OSU) installed a series of GPS stations on rock outcrops around the ASE to measure its rise in response to thinning ice. "The rapid rise of the bedrock in this part of Antarctica suggests that the geology underneath the ice is different from what scientists had previously believed. The rate of uplift we found is unusual and very surprising. It's a game changer," said Terry Wilson, one of the leaders of the study and professor emeritus of Earth Sciences at OSU.
Under the massive weight of ice the earth subsides. "When the ice melts and gets thinner, the earth readjusts, and rises immediately by a few millimeters, which depends on the ice lost," explains Valentina Barletta. "But the earth also acts a bit like a very hard memory-foam mattress. And it slowly keeps readjusting for several thousand years after the melting. In Scandinavia the bedrock is still rising about 10 millimeters per year because of the last ice age."
Scientists call this delayed readjustment Glacial Isostatic Adjustment (GIA), which can also be described as the Earth retaining memory of the ice lost in the past. How fast this readjustment takes place, depends on the properties of the mantle, the portion inside the earth between the crust and the core that is 2900 kilometers thick.
"Thanks to the satellite observations, we were able to estimate the current ice thinning in ASE, and conclude that the measured uplift rate is up to 4 times larger than expected based on the current ice melting rates", says Barletta. Therefore the new study focused on the delayed readjustment of the Earth.
Valentina R. Barletta has run thousands of GIA simulations using different possible combinations of Earth properties and ice loss scenarios and found that the only way to produce such high uplift is for the Earth mantle to be very fluid (technically low viscosity).
"Normally we would see significant uplift happen slowly over thousands of years after the ice age, but here we see it take place in centuries or even decades. This tells us that the mantle below is very fluid and moves quickly when the weight of the ice is taken off," said Barletta. And the uplift is getting faster. According to this new study, in 100 years, the uplift rates at the GPS sites will be 2.5 to 3.5 times more rapid than currently observed.
Among the direct consequences of this study there is a revised estimate of the ice loss in ASE. When a massive amount of the ice melts it reduces the local gravity and leaves fingerprints that can be measured by satellites and used to estimate the total mass lost. But the earth's readjustment also produces a gravity change that partially compensates for this loss and hides the ice signal. "Now we know that in ASE the earth readjusts so fast that 10 percent of the ice loss was hidden, but now we can fix that," said Barletta.
The fast earth response is potential good news for the future of the WAIS. In this area of Antarctica most of the ice is grounded below sea level, and therefore vulnerable to melting from below by ocean water flowing in underneath the ice sheet. Here the earth uplift works as a feedback that can slow down the ice retreat in different ways.
The uplift raises the so called 'pinning points' - elevated features that pin the ice sheet to the bedrock, preventing the retreat of the grounded ice. At the same time the uplift changes the inland slope of the ground that becomes more effective in holding the ice from sliding away. In addition, the massive amount of the ice lost reduces the local gravity and the gravitational pull on the water, resulting in a lower sea level at the adjacent Antarctic coast. This in turn reduces the buoyancy of the whole ice sheet, promoting the stability of the ice sheet.
Modeling studies have shown that bedrock uplift could theoretically protect WAIS from collapse, at least in case of moderate climate changes. But it was believed that the process would take too long to have practical effects.
The mantle that we discovered under ASE is more fluid and hotter, and therefore the earth uplifts faster than in the most optimistic hypotheses used in previous studies. "Under many realistic climate models, this should be enough to stabilize the ice sheet," Wilson said. But, if future global warming is too extreme, according to the scientists the WAIS will most likely still collapse regardless of stabilizing feedbacks.
"Apart from giving us a new picture of the earth dynamics in Antarctica, the new findings will push to improve ice models for WAIS to get a more precise picture of what will happen in the future" said Barletta. "They also tell that we clearly need to improve our knowledge of the Earth structure under the whole Antarctic continent. To do so we use GPS in the few areas where they can be installed, and elsewhere we use data from ESA's Earth Explorer GOCE and seismic tomography."
Valentina Barletta, DTU Space | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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12.07.2018 | Event News
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20.07.2018 | Materials Sciences | <urn:uuid:7d0dc116-5dee-4429-a112-2f6f4998e2ee> | 4.1875 | 2,310 | Content Listing | Science & Tech. | 42.361917 | 95,547,038 |
This exoplanet, known as Kepler-78b, orbits its star very closely every 8.5 hours, making it much too hot to support life. The results are being published in the journal Nature.
This Earth-sized planet was discovered using data from NASA’s Kepler Space Telescope, and confirmed and characterized with the W. M. Keck Observatory.
Every 8.5 hours the planet passes in front of its host star, blocking a small fraction of the starlight. These telltale dimmings were picked up by researchers analyzing the Kepler data.
The team led by Dr. Andrew Howard (Institute for Astronomy, University of Hawaii at Manoa) then measured the mass of the planet with the Keck Observatory on Mauna Kea, in Hawaii. Using the ten-meter Keck I telescope fitted with the HIRES instrument, the team employed the radial velocity method to measure how much an orbiting planet causes its star to wobble, to determine the planet’s mass. This is another excellent example of the synergy between the Kepler survey, which has identified more than 3,000 potential exoplanet candidates, and Keck Observatory, which plays a leading role in conducting precise Doppler measurements of the exoplanet candidates.
A handful of planets the size or mass of Earth have been discovered recently. This is the first one with both quantities measured. “When you have both the size and the mass of an object, you can calculate its density, and thereby determine its composition,” explained Howard.
With a radius about 1.2 times of Earth's and a mass equal to about 1.7 times Earth’s, Kepler-78b has a density the same as Earth’s, suggesting that it is also made primarily of rock and iron. Its star is slightly smaller and less massive than the sun and is located about 400 light-years from Earth in the constellation Cygnus.
Kepler-78b is a member of a new class of “ultrashort period” planets recently identified by the Kepler spacecraft. These newfound worlds all orbit their stars with orbital periods of less than 12 hours. They’re also small, about one-to-two times the size of Earth. Kepler-78b is the first planet in this new class to have its mass measured. It is a mystery how these planets formed and made it so close to their host stars (only 1 percent of the Earth-Sun separation in the case of Kepler-78b).
A companion study led by Dr. Francesco Pepe (University of Geneva, Switzerland) used the same Kepler data but independent radial velocity observations and is being published in the same issue.
The two studies found similar results. “The gold standard in science is having your findings reproduced by other researchers,” explained Howard. “In this case, we did not have to wait for this to happen.”
The other members of Howard’s team are Roberto Sanchis-Ojeda (MIT), who analyzed the transit data taken by the Kepler spacecraft to find the planet and calculate its size, Dr. Geoffrey Marcy (University of California, Berkeley), Dr. John Johnson (Harvard), Dr. Debra Fischer (Yale), Benjamin Fulton and Evan Sinukoff (UHM graduate students), and Dr. Jonathan Fortney (University of California, Santa Cruz).
HIRES (the High-Resolution Echelle Spectrometer) produces spectra of single objects at very high spectral resolution, yet covering a wide wavelength range. It does this by separating the light into many "stripes" of spectra stacked across a mosaic of three large CCD detectors. HIRES is famous for finding planets orbiting other stars. Astronomers also use HIRES to study distant galaxies and quasars, finding clues to the Big Bang.
The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectroscopy and world-leading laser guide star adaptive optics systems. The Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.Science Contact:
Steve Jefferson | Newswise
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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Programming for the Java Virtual Machine (Anglais) Broché – 22 juin 1999
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Description du produit
Quatrième de couverture
The core of Java technology, the Java virtual machine is an abstract computing machine that enables the Java platform to host applications on any computer or operating system without rewriting or recompiling. Anyone interested in designing a language or writing a compiler for the Java virtual machine must have an in-depth understanding of its binary class format and instruction set. If you are programming with the Java programming language, knowledge of the Java virtual machine will give you valuable insight into the Java platform's security capabilities and cross-platform portability. It will increase your understanding of the Java programming language, enabling you to improve the security and performance of your programs.
The author employs a tutorial approach that provides a detailed look into the central workings of the technology and teaches the reader how to write real programs for the Java virtual machine. He describes methods for becoming a better programmer through an advanced understanding of the Java virtual machine and Java technology. Programming for the Java Virtual Machine offers comprehensive coverage of all the major elements of the Java virtual machine--classes and objects, control instructions, debugging, class loaders, compiling the Java programming language, performance issues, security, and threads and synchronization. The book provides an introduction to the Java Virtual Machine Specification (JVMS), with a collection of topics that help programmers understand the Java virtual machine and the JVMS better. In addition, the book features implementations of Prolog and Scheme, a language that runs on top of the Java virtual machine, generating Java virtual machine code as it runs and using a Java virtual machine class loader to load the generated code into the system.
You will find detailed information on such topics as:
- The Java virtual machine verification algorithm
- How Java virtual machine security works, and what it can and can't do
- Using class loaders to incorporate code and dynamically generated code from the Internet, the Java Foundation Classes, database queries, and other languages
- The mechanics of compiling the Java programming language for the Java virtual machine
- Implementing other languages using the Java virtual machine, including Scheme, Prolog, Sather, Eiffel, and regular expressions
Numerous examples illustrate techniques and concepts, and exercises with solutions help you gain practical experience.
Biographie de l'auteur
Joshua Engel is a programmer, computer scientist, and acknowledged expert in the Java virtual machine. He is Chief Software Developer for Knowledge Bus, Inc. (www.knowledgebus.com) During his extensive programming career, he has worked with dozens of programming languages and even designed a few of his own.
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When we are used to be Java developers, it is enriching to go over the Java code lines and to know how those lines are interpreted.
This book explains in details how the Java instructions proceed. Besides it demystify the miracle of "write once, run anywhere" by explain the mechanism of the Java Virtual Machine.
I was not a Java expert when I began reading it; I could say that it helps me to understand the back office of my programs.
Commentaires client les plus utiles sur Amazon.com
Although the book can expand more on its scheme->java implementation, I find it a very good starting point for any serious work. I wholeheartedly recommend the book to anyone interested in java and its jvm.
The remainder of the book explores various areas such as verification, debugging, the class file format, security, and most importantly, compiling Java and other languages into JVM code. Mostly, this material is a tutorial introduction to information provided in the Java Virtual Machine Specification, but there is some original material in the chapters devoted to compiling Scheme and Prolog.
Be aware that this book contains numerous errors; you'll want to grab the errata list from the Addison-Wesley website.
1. Java Compiler - Compiles the java programs we write to byte-code in .Class format.
2. Java Virtual Machine (JVM) - Executes the byte-codes that is in .Class format.
This essentially means that the JVM only cares about the byte-codes, and not about the high-level language that was used to program it. As you can see, this seperation of concerns opens up a lot of possibilities like
1. You can write a java program and compile to byte-code
2. Directly write byte-codes
3. Write code in some asssembly language and assemble it to byte-codes
4. Write code in an interesting scripting language like Ruby or Python and compile it to byte-codes.
All paths lead to the same destination; JVM can run the resulting byte-codes. The possibilities are endless if you have this understanding. In fact, there are more than a 100 languages that compile to java byte codes at present.
In this book, the authors intention is to get you started with the JVM features and how you can write programs that can be executed by the JVM. In the process you will learn the following...
1. What is inside the class file: An assembly language called Oolong, whose mnemonics closely resemble the class file op-codes is used to explain this concept. The author has clearly done an excellent job in decoding the JVM spec for this purpose.
2. Class loading: Loading classes into class area, statics etc are well explained in this section.
3. Byte-Code verification: A very important topic that is addressed only at a shallow level here. This is acceptable, as the intention of this book is an introduction to get you started and not as a reference for the JVM.
4. Compilling other languages to byte-code: Languages like scheme and prolog are used as examples to show how to compile other languages to byte-codes
5. Security in the JVM
If you are one among those who want to learn JVM, but not patient enough to digest a spec, then this book is for you. But, if you are a determined person who wants the full details of the JVM, then you should be typing in "The Java(TM) Virtual Machine Specification (2nd Edition)" in the Amazon Search box.
Having said that, the section on verification is interesting and the book itself does spark the imagination of what is possible (and what is not) with JVM bytecode. | <urn:uuid:87a56ff6-03e4-4b58-a338-6e92fc941f73> | 2.8125 | 1,599 | Product Page | Software Dev. | 37.988113 | 95,547,062 |
Diverse migration helps birds cope with environmental change
Migratory birds that are 'set in their ways' could be more vulnerable to environmental impacts – according to new research from the University of East Anglia (UEA).
Many species of migratory birds are in decline as a result of human impacts such as climate change and habitat loss.
New research published today reveals why some species are more vulnerable than others.
It shows that species that migrate to a more diverse range of winter locations during their non-breeding season – such as White Storks, Marsh Harriers and Reed Warblers – are less likely to suffer population decline.
However species that tend to 'funnel' into smaller areas during the winter – such as Turtle Doves and Wood Warblers – have been more vulnerable to declining numbers, caused by human impacts.
Lead researcher Dr James Gilroy from UEA's School of Environmental Sciences said: "Birds are well-known for their remarkable long-distance migrations, often involving extreme feats of navigation and endurance. Unfortunately, many migratory birds are in decline, and there is an urgent need to understand what determines their vulnerability to human impacts.
"We wanted to know whether 'migratory diversity' – the variability of migratory behaviour within species – plays a role in determining their population trends."
The research team studied the migration patterns of 340 bird species in relation to their status across Europe over the last two decades (1990-2012).
Dr Gilroy said: "We found that the species which scatter across wider areas in the non-breeding season have been more resilient, whereas those that converge along narrower routes, and hence occupy smaller wintering areas, have been more likely to decline.
"This suggests that these species may be particularly vulnerable to impacts like habitat loss and hunting in their non-breeding ranges. Species that spread across wider wintering areas, by contrast, might have a greater chance of reaching safe habitats in at least some parts of their range."
The research team also found that species classed as 'partial migrants' – meaning that their populations include both migratory individuals and others that remain in the breeding area all year round – were less likely to decline than fully migratory species, or even those that are fully resident.
Dr Gilroy said: "Many species adopt this mixed migratory strategy, including familiar species like Blackbirds and Robins. It looks like it could make them more resilient to human impacts – even in comparison to species that don't migrate at all. Many fully resident species like Lesser-spotted Woodpeckers and Willow Tits have been showing worrying declines in recent years.
"Partially migratory species also showed a greater capacity to shift their spring arrival dates forwards in recent decades, relative to fully migratory species. This trend towards earlier spring arrival might help species adapt to climate change, by allowing them to commence breeding earlier in the year as spring temperatures rise."
Co-author Dr Aldina Franco, also from UEA's School of Environmental Sciences, said: "The fact that migratory birds are declining globally has been troubling both scientific and conservation communities.
"We hope that this research will help relevant authorities identify ways to protect the long-distance migratory species that occupy small wintering areas. These are more likely to suffer population declines and need specific conservation efforts. Species with low migratory dispersion for example would benefit from a focus on conservation within their winter locations."
This research was funded by the Natural Environment Research Council (NERC) and is part of a project to investigate the causes and consequences of partial migration on birds. A high quality video about the project is available here: https://vimeo.com/151900214
'Migratory diversity predicts population declines in birds' is published in the journal Ecology Letters on January 26, 2016. | <urn:uuid:9998e20c-d82a-4e53-939d-d2d7f9b8ea03> | 3.390625 | 780 | News Article | Science & Tech. | 25.425903 | 95,547,078 |
Professor Jian-Ren Shen is recognized for his pioneering research on clarifying the fundamental reaction mechanism that governs photosynthetic water splitting, a process with fundamental importance in understanding how oxygenic photosynthetic organisms, such as plants, use energy from sunlight, water, and CO2 to survive.
Structure of PS II dimer
“I first started research on photosynthetic proteins in the beginning of my doctorate project,” says Shen. “Our findings published in 2011 were based on x-ray diffraction experiments of large, high quality single crystal of so-called ‘photosystem II’ (PS II) at Japan’s SPring-8 synchrotron radiation facility at Harima. The ability to produce large sized, single crystals of PS II, an extremely large membrane-protein complex, was critical for determining the crystalline structure of this protein complex to a resolution of 1.9 Angstroms. These results are the culmination of 20 years of my life spent on the development and improvement of the process to produce such large crystals.”
Professor Shen’s initial research on photosynthesis was focused on clarifying the effects of air pollution on plants. The objectives of this research necessitated clarification of the fundamental mechanism underlying photosynthesis, which in turn required the production of a high quality crystal of PS II. “After many years of exhaustive experiments and uncountable failures, we eventually succeeded in producing large, ‘tofu-like’ single crystals of PS II with dimensions of 0.7 x 0.4 x 0.1 mm,” explains Shen. “This was a major breakthrough that led to the ultra-high resolution analysis of PS II.”
Recent reports on the crystallographic analysis of PS II can be traced back to the early 2000s but the results yielded only ‘fuzzy’ images because of imperfections in the samples. In contrast the 2011 findings by Shen and colleagues yielded unprecedented images of the core of the PS II protein, showing the existence of cubic-core of four manganese atoms, five oxygen atoms, and a calcium atom, which constitutes the heart of plant life (Science 2011, 334, 1630).
“This cubic structure of Mn4CaO5 acts as a catalyst for the water splitting reaction induced by sunlight,” explains Shen. “These results have many important practical applications including the possibility of synthesizing artificial catalyst to dissociate water into oxygen and hydrogen to produce electricity in fuel cells, for example.”
Indeed there is increasing interests in ‘artificial photosynthesis’ for the production of energy. But Professor Shen says that his group will focus on basic research on the reaction mechanism of PS II. “Our next goal is to clarify the so-called ‘intermediate structure’ of PS II,” says Shen. “To do so we require even higher resolution x-ray diffraction experiments at both space and time levels. We are planning to use the SACLA X-ray Free Electron Laser (XFEL) facility in SPring-8 to achieve this. This will enable us to look at the movement of atoms during photosynthesis.”
Professor Shen’s contributions to clarifying the mechanisms underlying photosynthesis have received many accolades including the ‘Breakthrough of the Year’ for 2011 by AAAS Science; the 2012 Asahi Prize; and the launch of the Okayama University Photosynthesis Research Center on 1 April 2013.Further information:
Journal information1. Yasufumi Umena (1), Keisuke Kawakami (2), Jian-Ren Shen (2) and Nobuo Kamiya (1), Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9 Å; Nature 473, 55–61, (2011).
2 Division of Bioscience, Graduate School of Natural Science and Technology/Faculty of Science; Okayama University, Okayama 700-8530, Japan.
The role of Sodium for the Enhancement of Solar Cells
17.07.2018 | Max-Planck-Institut für Eisenforschung GmbH
Behavior-influencing policies are critical for mass market success of low carbon vehicles
17.07.2018 | International Institute for Applied Systems Analysis (IIASA)
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:fcc12908-49ae-48a9-b870-763aaf22b923> | 3.046875 | 1,477 | Content Listing | Science & Tech. | 39.154001 | 95,547,080 |
Thanks to a lucky conjunction of two satellites, a ground-based array of all-sky cameras, and some spectacular aurora borealis, researchers have uncovered evidence for an unexpected role that electrons have in creating the dancing auroras. Though humans have been seeing auroras for thousands of years, we have only recently begun to understand what causes them.
In this study, published in the Journal of Geophysical Research, scientists compared ground-based videos of pulsating auroras--a certain type of aurora that appears as patches of brightness regularly flickering on and off--with satellite measurements of the numbers and energies of electrons raining down towards the surface from inside Earth's magnetic bubble, the magnetosphere.
This all-sky movie shows a time lapse of a pulsating aurora on Jan. 3, 2012. Scientists compared the video, taken in Poker Flat, Alaska, over the course of three minutes, with satellite measurements of the numbers and energies of electrons raining down from the magnetosphere to better understand how electrons transfer energy to the upper atmosphere and create the auroras. The black mark traces the satellite foot point -- the place where the satellite is magnetically connected to the aurora -- of the Defense Meteorological Satellite Program satellite.
The team found something unexpected: A drop in the number of low-energy electrons, long thought to have little or no effect, corresponds with especially fast changes in the shape and structure of pulsating auroras.
"Without the combination of ground and satellite measurements, we would not have been able to confirm that these events are connected," said Marilia Samara, a space physicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author on the study.
Pulsating auroras are so-called because their features shift and brighten in distinct patches, rather than elongated arcs across the sky like active auroras. However, their appearance isn't the only difference. Though all auroras are caused by energetic particles--typically electrons--speeding down into Earth's atmosphere and colliding brilliantly with the atoms and molecules in the air, the source of these electrons is different for pulsating auroras and active auroras.
Active auroras happen when a dense wave of solar material--such as a high-speed stream of solar wind or a large cloud that exploded off the sun called a coronal mass ejection--hits Earth's magnetic field, causing it to rattle.
This rattling releases electrons that have been trapped in the tail of that magnetic field, which stretches out away from the sun. Once released, these electrons go racing down towards the poles, then they interact with particles in Earth's upper atmosphere to create glowing lights that stretch across the sky in long ropes.
On the other hand, the electrons that set off pulsating auroras are sent spinning to the surface by complicated wave motions in the magnetosphere. These wave motions can happen at any time, not just when a wave of solar material rattles the magnetic field.
"The hemispheres are magnetically connected, meaning that any time there is pulsating aurora near the north pole, there is also pulsating aurora near the south pole," said Robert Michell, a space physicist at NASA Goddard and one of the study's authors. "Electrons are constantly pinging back and forth along this magnetic field line during an aurora event."
The electrons that travel between the hemispheres are not the original higher-energy electrons rocketing in from the magnetosphere. Instead, these are what's called low-energy secondary electrons, meaning that they are slower particles that have been kicked up out in all directions only after a collision from the first set of higher-energy electrons. When this happens, some of the secondary electrons shoot back upwards along the magnetic field line, zipping towards the opposite hemisphere.
When studying their pulsating aurora videos, researchers found that the most distinct change in the structure and shape of the aurora happened during times when far fewer of these secondary electrons were shooting in along hemispheric magnetic field lines.
"It turns out that secondary electrons could very well be a big piece of the puzzle to how, why, and when the energy that creates auroras is transferred to the upper atmosphere," said Samara.
However, most current simulations of how the aurora form don't take secondary electrons into account. This is because the energy of the individual particles is so much lower than the electrons coming directly from the magnetosphere, leading many to assume that their contribution to the glowing northern lights is negligible. However, their cumulative effect is likely much larger.
"We need targeted observations to figure out exactly how to incorporate these low-energy secondary electrons into our models," said Samara. "But it seems clear that they may very well end up playing a more important role than previously thought."
Measurements of the number and energies of electrons were made by two satellites that happened to be passing overhead during these pulsating aurora events: Reimei, a JAXA satellite tasked with studying auroras, and a satellite from the U.S. Department of Defense's Defense Meteorological Satellite Program. The ground-based all-sky cameras--used to study both auroras and meteors--are operated at Poker Flat Research Range in Fairbanks, Alaska and the European Incoherent Scatter Scientific Association Radar Facility in Tromsø, Norway.
Susan Hendrix | EurekAlert!
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
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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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Researchers create plastic solar cells using food addictive
Researchers from North Carolina State University and the Chinese Academy of Sciences have created environment-friendly plastic solar cells using a food addictive and it can be manufactured at room temperature.
wo of the key advantages are that these cells can be mass produced in the open air environment and that the process doesn’t pose health or environmental hazards, said Long Ye, post-doctoral research scholar in physics at NC State. Ye and his colleagues developed a semi-printed plastic solar cell that utilised o-methylanisole (o-MA) as the solvent. O-MA is a commonly used flavouring agent in foods and is non-toxic to humans. Plastic solar cells are popular because they are lightweight, flexible, transparent and inexpensive to manufacture. Unfortunately, the halogen-containing solvents used in their manufacture are an obstacle to large-scale commercialisation. These solvents are key to making sure that the solar cell’s morphology, or structure, maximises its energy efficiency. However, they are environmentally hazardous. | <urn:uuid:27881955-2220-4f1d-a959-a7069a1452ef> | 2.96875 | 218 | News Article | Science & Tech. | 17.918322 | 95,547,104 |
Can someone explain how this happens?
What is the temperature of the ice?
I am not sure, if that would be a part of the answer then please explain it.
Let me word it this way: if I were making an alcoholic drink and took ice out of my freezer, put a few cubes in the drink and stirred, what factors could cool the drink to below zero?
Second question (if the first doesn't already answer it): would the drink be able to drop below 0°C if the drink was initially at room temperature, and the ice was initially at 0°C?
I meant to mark this as high school competency.
What is the temperature of your freezer? If it is below 0°C, where would be the problem? You'll need a lot of ice, however.
The ice cools the drink; the drink warms the ice. The will meet at a temperature in the middle somewhere. Exactly where depends on the starting temperatures and the relative masses of ice and drink. Also there'll be heat coming in from the room, but we could do this experiment in a good thermos flask to minimse that.
If the temperatures meet in the middle somewhere, what must be true about the ice to make the drink end up below zero? Is this plausible for ice from a home freezer?
Google "freezing point depression."
Everything that has been said so far I understand already. So there's no secret here? It's simply that the ice has to be cold enough to cool the drink below 0°C before reaching the equilibrium temperature?
I had read that it had something to do with the process of ice melting making the ice itself colder?
Is the temperature of the mixture of ice and alcohol always going to meet between the initial temperatures of the alcohol and the ice? Or could the melting ice cooling itself cause the mixture to drop below the ice's initial temperature?
I don't think that's possible.
Regardless of the amount of ice and specific heat capacity of the ice, the equilibrium temperature(final temperature of both substances) reached will be between the initial temperature of the ice and initial temperature of the alcohol, but you could get the alcohol to reach a temperature very close to that of the ice.
As soon as the ice and alcohol reach the same temperature the heat exchange will stop. What you are suggesting seems to go against the laws of thermodynamics. Heat energy always moves towards the colder body. Therefore the alcohol would never get colder than the ice melting, never get colder than the initial ice's temperature. When ice starts melting at zero, it is gaining energy from the alcohol which must have temperatures greater than zero for this to happen, meanwhile it gets cooler but as it gets to zero the heat exchange will stop :)
Hope this helps
Yes and no...
By definition it's the warmest parts of the ice that are melting. The heat to do the actual solid-to-liquid change has to come from somewhere warmer, which has to be the liquid. Heat cannot come from the (colder) ice. So no part of the ice gets colder.
However, we just took away the warmest part of the ice and left the cooler parts. So the temperature of the remaining ice is lower than the temperature of the ice before the warmest part went away. This is a cheat, in a sense. It's analogous to this: the mean of -5, -4, -3, -2, -1, 0 is -2.5. The average of -5, -4, -3, -2, -1 is -3, which is lower. It's only lower because I took away the highest member, not because I lowered any values.
Pressure? Dry ice?
I repeat, and add emphasis,
Heat is given up by the solid phase (ice) in the process of dissolving/diluting alcohol.
Actually, that isn't true(you aren't the only one who said it...): they meet at the freezing temperature of the liquid, regardless of either's starting temperature.
So that means, counter-intuitively, that they can end up colder than either started.
So the only thing that matters here is the freezing temp of the drink (as long as you add enough ice to reach it).
This is exactly what I was trying to fish out. Can you give an "explain like I'm five" explanation on how this happens?
So - it takes energy to mix the water and the alcohol, which I forgot about. When the booze is at 0C then any further melting requires work from somewhere, which means that either the temperature must drop or the ice must stop melting. Obviously dilute booze is a higher entropy state than booze plus ice. So any local melting will end up being a one-way street, where a pure water-ice mixture would be two-way.
Is that about right? Or am I missing something again?
Not necessarily. Put a cube of ice from the freezer in liquid nitrogen. Do you expect the nitrogen to freeze?
It is an interesting situation if the two phases are not the same material. We can have several different options, if we neglect mixing of the substances:
If the freezing point of the liquid is below the freezing point of the solid:
- everything freezes, the final temperature is below the freezing point of the liquid
- nothing of the solid melts, some of the liquid freezes, the final temperature is the freezing point of the liquid.
- nothing melts, nothing freezes, the final temperature is between the freezing/melting points
- nothing freezes, something melts, the final temperature is at the melting point of the solid
- everything melts, the final temperature is above the melting point of the solid (typical result with alcoholic drinks and ice)
If the freezing point of the liquid is above the freezing point of the solid:
- everything freezes
- the liquid freezes completely, the solid partially melts, final temperature at solid melting temperature
- liquid freezes completely, solid melts completely, final temperature between freezing/melting points
- liquid freezes partially, solid melts completely, final temperature at liquid freezing point
- everything melts
It gets more complicated if the two substances mix, e. g. melting ice changes the freezing point of the alcoholic drink.
That can happen below 0, if the ice starts cold enough.
A five year-old doesn't have much chance here, but I'll try to be basic...
This isn't like mixing two liquids together - the concept of an equilibrium temperature somewhere in between doesn't apply. A liquid freezes or a solid melts at one and only one temperature (per a given substance and pressure). If you add heat to ice (put it in a warmer liquid) it will melt at its melting temperature, period. If you remove heat from water, it will freeze at its freezing temperature, period. If those are different temperatures, the lower temperature wins because while the ice can exist as ice at a lower temperature than its freezing point, you can't remove heat from a liquid (by making it melt ice) without dropping its temperature.
This may seem like a bit of a contradiction, but it is actually somewhat similar to the simpler case of a liquid at its boiling point. There is only one boiling point at a given pressure and no matter how much heat you add, that won't change. Conversely, if you lower the pressure above a liquid (say, put it in a vacuum chamber), it will start to boil and that will lower the temperature to get it to the new boiling point.
No, that isn't what I said and is a totally different and much simpler situation because the nitrogen is boiling, not freezing and the temperature is lower, not higher than the ice temp.
You drop ice in LN2, all you get is colder ice.
Iàm sorry, but I donàt see how that can be a general statement. What assumptions are you making here?
I'm pretty sure both of those are impossible (unstable). Could you please detail the conditions that could cause them?
If you have solid steel and liquid water, the steel stays solid and the water stays liquid. Nothing freezes. Nothing melts.
This thread is about a water/alcohol mixture (perhaps also with sugar) in ice. If there are more complicated/different situations that have different outcomes, I don't thing it is wise to muddle the thread with them, particularly when the OP specifically asked for simplicity.
No one's made ice cream?!!
Even then, I don't see why you say temperature is not a factor. If the initial temperature of the ice is low enough, you can end up with the liquid freezing completely and the final mixture ending up below the freezing point of the liquid.
For those that haven't, here's how you set it up:
Take a large bucket and put some very salty water in it.
Now you have extra-cold water.
Only if you have a really bad bartender.
[Edit] Actually, even with a really bad bartender, that would be very difficult to achieve.
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The True Nature Of Time – New Documentary 2015
Theories of science have ignored time… until now. A new idea reveals how it created the Universe – and you, writes Robert Matthews.
Time: it rules our lives, and we all wish we had more of it. Businesses make money out of it, and scientists can measure it with astonishing accuracy. Earlier this year, American researchers unveiled an atomic clock accurate to better than one second since the Big Bang 14 billion years ago.
But what, exactly, is time? Despite its familiarity, its ineffability has defied even the greatest thinkers. Over 1,600 years ago the philosopher Augustine of Hippo admitted defeat with words that still resonate: “If no-one asks me, I know what it is. If I wish to explain it to him who asks, I do not know.” Yet according to theoretical physicist Lee Smolin, the time has come to grapple with this ancient conundrum: “Understanding the nature of time is the single most important problem facing science,” he says.
As one of the founders of the Perimeter Institute for Theoretical Physics in Ontario, Canada, which specialises in tackling fundamental questions in physics, Professor Smolin has spent more time pondering deep questions than most. So why does he think the nature of time is so important? Because, says Smolin, it is central to the success of attempts to understand reality itself.
To most people, this may sound a bit overblown. Since reality in all its forms, from the Big Bang to the Sunday roast, depends on time, isn’t it obvious that we should take time seriously? And didn’t scientists sort out its mysteries centuries ago? | <urn:uuid:fcc110fd-63b8-4313-8c4d-b6f6ab4d76bd> | 2.78125 | 354 | Personal Blog | Science & Tech. | 48.466423 | 95,547,154 |
The car accelerates at rate 0.5m/s2. How long travels 400 meters and what will be its speed?
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Ball was fired at an angle of 35° at initial velocity 437 m/s. Determine the length of the litter. (g = 9.81 m/s2). | <urn:uuid:a1778329-07d5-42ff-8eac-fa3ac2011931> | 2.984375 | 879 | Tutorial | Science & Tech. | 79.842604 | 95,547,167 |
The schlieren method of measuring far-field focal spots offers many advantages at the Shenguang III laser facility such as low cost and automatic laser-path collimation. However, current methods of far-field focal spot measurement often suffer from low precision and efficiency when the final focal spot is merged manually, thereby reducing the accuracy of reconstruction. In this paper, we introduce an improved schlieren method to construct the high dynamic-range image of far-field focal spots and improve the reconstruction accuracy and efficiency. First, a detection method based on weak light beam sampling and magnification imaging was designed; images of the main and side lobes of the focused laser irradiance in the far field were obtained using two scientific CCD cameras. Second, using a self-correlation template matching algorithm, a circle the same size as the schlieren ball was dug from the main lobe cutting image and used to change the relative region of the main lobe cutting image within a 100×100 pixel region. The position that had the largest correlation coefficient between the side lobe cutting image and the main lobe cutting image when a circle was dug was identified as the best matching point. Finally, the least squares method was used to fit the center of the side lobe schlieren small ball, and the error was less than 1 pixel. The experimental results show that this method enables the accurate, high-dynamic-range measurement of a far-field focal spot and automatic image reconstruction. Because the best matching point is obtained through image processing rather than traditional reconstruction methods based on manual splicing, this method is less sensitive to the efficiency of focal-spot reconstruction and thus offers better experimental precision.
Citation: Wang Z, Hu B, Yin Q (2017) An improved schlieren method for measurement and automatic reconstruction of the far-field focal spot. PLoS ONE 12(2): e0171415. https://doi.org/10.1371/journal.pone.0171415
Editor: Giuseppe Chirico, Universita degli Studi di Milano-Bicocca, ITALY
Received: July 31, 2016; Accepted: January 20, 2017; Published: February 16, 2017
Copyright: © 2017 Wang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information file.
Funding: This study was supported by the National Natural Science Foundation of China (11327303, 61405244) and by the project titled “Research on underwater imaging technology based on compressive sensing via soft range gating and adaptive polarized light."
Competing interests: The authors have declared that no competing interests exist.
The output parameters of a large laser facility, including the distribution in the time domain, the distribution in the spatial domain, the distribution in the frequency domain, the temporal distribution of the wave parameters, and the distribution in the far field, which differ for different experimental requirements, are closely related to the input energy. As a result, the distribution in the far field prevents the entire focal spot from being measured during a shooting experiment when the laser energy is at approximately the 10 kJ level . The distribution in the far field plays a key role in the measurement of the far-field focal spot. There are two purposes of measuring the precise focal spot in a laser facility . The first purpose is to determine the influence of the optical components on the far-field focal spot under different input power conditions . The second purpose is to provide a basis for improving the quality of the optical components once the spatial distribution of the focal spot has been obtained . However, the size and shape of the focal spot can only be improved when the position of the optical element is adjusted or when the structure of the laser path is modified by the designer.
An integrated diagnostic system is a multifunctional laser parameter system whose main functions are running the device during emission; completing the precision diagnosis of laser beam energy, near-field, far-field, pulse waveform and spectrum parameters; and obtaining the device operating parameters comprehensively and accurately. The most important task of the integrated diagnosis system is to construct the high-dynamic-range image of the far-field focal spot . The high-dynamic-range measurement of the focal-spot distribution always poses a difficult problem in diagnosing the parameters of a large laser facility and represents the key technology that must be addressed for high-power physical experiments.
At present, many scholars have made many significant contributions to research on methods of measuring the distribution of a far-field focal spot; the main methods include the array camera method, the diffraction grating method and the schlieren method. In 2012, Reyad Mehfuz developed the array camera method to test a far-field focal spot based on images exposed for different times to reconstruct a high-dynamic-range image . However, because a physical experiment at a high-power laser facility is a high-throughput targeting experiment, it is difficult to achieve multiple exposures in such a targeting experiment with the high precision required to measure the laser intensity. HE Yuanxing et al proposed a far-field focal spot reconstruction method based on a diffraction grating . The far-field laser spot is divided into two spots when such a grating is used, and the side lobe is submerged in noise and cannot be measured; thus, the main lobe must be blocked to detect the side lobe spot. Because the side lobe and main lobe are captured by the same CCD and because the main lobe is sheltered by a small schlieren ball, there is a large effect on the side lobe data that makes it very difficult to separate the side lobe data from the main lobe data. Because the dynamic range of the far-field focal spot measured by an integrated diagnosis system is up to 1000:1, it is very difficult for a single detector to meet the requirements of such a high dynamic range. Because the energy during emission reaches up to 10 kJ, if there is no large attenuation in the laser paths, the CCD used for detection will be completely saturated. If the attenuation is too large, although the far-field focal spot can be tested, the signal bottom of the focal spot will be submerged in noise. In the last year, a considerable amount of work has been done regarding schlieren. The application of different schlieren methods has resulted in great progress in many fields. For example, rainbow schlieren deflectometry has been employed to record the projection data of the temperature gradient field in test cavities . Background-oriented schlieren (BOS) uses correlation techniques on a background dot pattern to characterize thermal flows with good spatial and temporal resolution . Laser schlieren deflectometry (LSD) has been successfully employed as a temperature measurement method to reveal heat convection . A non-scanning 3D-CT (Computer Tomography) technique using a multi-directional quantitative schlieren system with a flash light source was proposed for the instantaneous density distribution of unsteady premixed flames . Despite the latest development mentioned above, one of the most classical applications of the schlieren method is measuring the far-field distribution of a high-power laser ; in this method, the main lobe and side lobe are measured on two separate laser paths, the side lobe is sheltered using a small schlieren ball, the intensity of the main lobe is magnified a given number of times, and the main lobe and side lobe data are merged to obtain a high-dynamic-range far-field focal spot. The schlieren method was proposed for far-field focal spot measurement at the National Ignition Facility in America . Because of the great differences in light energy density between the main lobe and side lobe of the focal spot, there is considerable drift when the laser beam is transmitted long distances; thus, the image quality of the main lobe and side lobe images is poor, meaning that the reconstructed image cannot be stitched accurately. The schlieren method has also been adopted for far-field focal spot measurement at Shenguang III in China. However, the conventional method used to reconstruct the image of the far-field focal spot is stitched manually, even though the texture is very clear and the quality is very good , resulting in a very low experimental efficiency.
Many investigators have studied the schlieren reconstruction algorithm. Cheng et al. introduced a far-field measurement principle using the schlieren method , but their principle lacks a detailed reconstruction step or mathematical model and cannot obtain the reconstructed focal spot automatically.
As a result, we conclude that, to achieve a robust measurement of the far-field focal spot under conditions of high input energy, low experimental efficiency and low reconstruction accuracy should be avoided, and the manual reconstruction steps that have been widely used in previous experiments are no longer suitable. In this paper, an improved algorithm for far-field focal spot measurement and automatic reconstruction that achieves good performance in terms of accuracy and efficiency is proposed. The detailed steps of the proposed method are summarized as follows. First, a weak light beam sampling and magnification imaging detection method is designed, and the main lobe and side lobe beam spots are captured by two scientific CCD cameras. Second, using a self-correlation template matching algorithm , the position for which the largest correlation coefficient between the side lobe image and the main lobe image with a circle dug is identified as the best matching point, enabling the automatic reconstruction of the main lobe and side lobe into a mosaic image. Then, the weighted average method is used to fuse the splicing edge. Finally, the least squares method is used to fit the center of the side lobe schlieren small ball, with an error of less than 1 pixel. The method applied to obtain the reconstructed image in the splice region texture achieves excellent agreement, with a registration error of less than 1 pixel; it can not only obtain the complete far-field image but also meet the efficiency requirements for targeting experiments. It will be important and significant for the ability of integrated diagnostic systems to assimilate laser parameters accurately and completely.
The principle of the measurement of the far field
To evaluate the focusing performance of different shooting lenses in a 10 kJ-level laser facility , a weak laser is sampled first. The laser is transmitted together in the front beam and divided into two beams after high-ratio attenuations. The two beams are then captured by two CCD cameras. The principle of the optical system is shown in Fig 1. The beam transmitted in the front of the small vacuum target chamber is the sampling optical path, and the beam transmitted in the back of the target chamber is the diagnostic optical path. The converging laser beam is transmitted from the wedge shooting lens, reflected by two wedge mirrors, and transmitted into the small vacuum target chamber. The small target chamber center is regarded as a benchmark, and the position of the shooting lens can be moved forward or backward according to the different focal lengths to ensure that the metering spot is located in the small target chamber center, thus completing the sampling of the focal spot. Most of the energy across the first sampling mirror transmission is absorbed by the energy cutoff, and the reflected weak light is transmitted into the vacuum small target chamber; thus, a huge vacuum system is avoided, ensuring that assessing the focal spot will be convenient.
The beam emitted from the center of the small target chamber is collimated to a small-diameter parallel laser by the transmission system. The energy of the laser will be attenuated by a factor of approximately one million after the beam crosses the high-rate attenuator. The beam is divided into the main lobe optical path and the side lobe optical path by a beam splitter. In the side lobe optical path, the parallel beam is first converged by magnifying lens 1, and the focus is magnified by magnifying lens 2. The small schlieren ball is placed at the focal point of magnifying lens 1 to shelter the focal spot center of the main lobe, and thus, the image captured by the side lobe CCD contains most of the laser spot information surrounding the small schlieren ball. In the main lobe optical path, the beam is attenuated appropriately, and the image captured by the main lobe CCD contains the laser spot information without blocking. To ensure consistency of the main lobe and side lobe in terms of optical aberrations, the main lobe optical path is similar to the side lobe optical path. The parameters of the two optical paths must be consistent in terms of the number and thickness of the attenuation component; the only difference is in the attenuation rate of each component. Therefore, the different far-field focal spots can be measured only when the appropriate magnifying lens group is replaced according to the different input energy, and the requirements of the facility can be met under different experimental conditions.
The automatic collimation system can be divided into the collimation system of the small target chamber and the focal spot optical path. The purpose of the front collimation system is to converge the sampling beam to the simulated target point. The first purpose of the collimation system located in the front small target chamber is to capture the accurate far-field laser spot of the simulated target point by the main lobe and side lobe CCDs and obtain the correct distribution of the far-field focal spot. The second purpose of the collimation system is to calibrate the parameters of the schlieren method, including the magnification ratio k of the main lobe intensity, the magnification ratio b of the laser spot image, and the relative position between the laser spot of the main lobe and the laser spot of the side lobe .
The mathematical model of the schlieren method
The mathematical model of the schlieren method for measuring the far-field focal spot was proposed in the literature . The reconstructed image can be expressed as the following function: (1) where the main lobe image function is h1(x, y), the domain is (x, y) ∈ A, the side lobe image function is h2(x, y), and the domain is (x, y) ∈ B. With the side lobe image as a reference, the main lobe intensity lobe is magnified K times (K>1), the main lobe is magnified b times (b>1), and the main lobe image is filled into the side lobe schlieren ball area. A certain proportion of the overlap edge is occupied by the main lobe and side lobe image.
The data of region A are replaced by the main lobe spot and are magnified K times, the data of region B are replaced by the side lobe spot, and the data of region C are overlapped by the main lobe spot and the side lobe spot. Region C is the transition zone and is shown in Fig 2; region A is the smaller inner ring region, and region B is the larger outer ring region. Region C is a transitional region with a width of 10 pixels and is used to fuse the splicing boundary of the merged image by the weighted average method. The radius of the smaller circle is the radius of the small schlieren ball minus 5 pixels, and the radius of the larger circle is the radius of the small schlieren ball plus 5 pixels. d1 and d2 represent the relative proportions of the image belonging to the overlapping main lobe and side lobe regions, respectively, where d1 + d2 = 1, 0< d1<1 and 0< d2<1.
Region C is the region between the smaller and larger circles and is a transitional region with a width of 10 pixels.
To calibrate the intensity magnification ratio K of the main lobe and the magnification ratio b of the laser spot, we designed a new collimation telescope component (i.e., a telescope and a small ball, as shown in Fig 1) in the integrated diagnosis system. The steps to calibrate K and b are as follows.
- The small schlieren ball is moved out of the laser beam, and the collimation telescope is moved into the laser beam. The images of the small telescopic ball are captured by the side lobe and main lobe CCDs, and the center coordinates of the small telescopic ball are (A1X, A1Y) and (B1X, B1Y).
- The small schlieren ball is moved a tiny distance. The new center coordinates of the telescopic ball image reflected in the side lobe CCD and main lobe CCD are (A2X, A2Y) and (B2X, B2Y), respectively, and the magnification ratio of the main lobe CCD relative to the side lobe CCD is b, which is the ratio of the distance between (B1X, B1Y) and (B2X, B2Y) to the distance between (A1X, A1Y) and (A2X, A2Y).
- To calibrate the intensity magnification ratio K, a standard laser source is inserted into the position of the small telescopic ball and captures the main lobe and side lobe images more than 20 times. The average gray level of the side lobe image divided by that of the main lobe image is given by K.
The schlieren automatic reconstruction algorithm
In previous experiments, the common method used to obtain the reconstructed image has been manual splicing . The corresponding coordinates of the schlieren ball center in the main lobe image are the most important parameters and are found using the manual method through repeated experimentation. To achieve automatic reconstruction of the far-field focal spot, a new method based on a self-correlation template matching algorithm is proposed in this paper because the following characteristics between the main lobe and side lobe images are observed: 1) a circular schlieren ball can be found in the side lobe image center, and 2) if a circle with the same size as the schlieren ball is dug from the main lobe image, the main lobe and side lobe images have very similar characteristics. If the schlieren ball dug from the main lobe image is moved within a certain range, when the correlation coefficient between the main lobe and side lobe images is maximal—that is, the two images present maximal similarity—the corresponding coordinates of the schlieren ball center in the main lobe image is finally found. Only when the schlieren ball region of the side lobe image is replaced by the data dug from the main lobe image and magnified K times will it be possible to obtain the best reconstructed image.
In the search for the optimal splicing position, a self-correlation template matching algorithm based on self-correlation matching theory is used ; the correlation coefficient of the two images is calculated as shown in formula (2): (2) where f (x, y) represents the image of size m × n, w (x, y) represents the sub-images of size J× L, and x = 0,1,2,…, n-L, y = 0,1,2,…, m-J. In the automatic reconstruction algorithm provided in this paper, f (x, y) represents the side lobe image, w (x, y) represents the main lobe image from which a circle with the same size as the schlieren ball is dug, and the size of the two images is 300 × 300.
The schlieren automatic reconstruction algorithm contains several important steps: preprocessing, obtaining the schlieren ball center by circle fitting, searching for the best matching point of the schlieren ball center in the main lobe image, and merging the main lobe and side lobe images. Among these, the critical step is to search for the best matching point of the schlieren ball center in the main lobe image (S1 File). The automatic reconstruction algorithm for this step is described briefly as follows.
Algorithm 1 schlieren automatic reconstruction algorithm
Input: orgpb image, orgzb image
1 Obtain the center of gravity orgzb and radius of small schlieren ball in orgpb.
2 Obtain the cutpb image
3 for m = -50: 50–1
for l = -50: 50–1
Obtain a cutzb image
Dig a circle region from cutzb image
4 Obtain the best matching position
5 Merge the image with the best matching cutzb image and cutpb image
Output: The reconstructed image
where orgzb is the original main lobe image of size 512×512, orgpb is the original side lobe image of size 512×512, cutzb is the cutting main lobe image of size 300×300, and cutpb is the cutting side lobe image of size 300×300.
Before the image is reconstructed, the background must be subtracted from the original main lobe and side lobe images. Second, the image captured by the CCD must be clipped because two 14-bit scientific CCDs with a resolution of 1024 × 1024 are used in the ICF experiment, and the best match point is searched by an automatic algorithm. Another reason to clip the image is that the size of the image captured by the CCD is larger than the size of the laser spot such that the amount of computation will be reduced during the reconstruction process when the images are clipped. The size of the clipped image is 512×512. The clipped images of the main and side lobes are recorded as orgzb and orgpb, respectively, and the laser spot is located as close to the center of the image as possible, as illustrated in Fig 3.
Calculating the center of the schlieren ball in the side lobe image.
To calculate the center of the schlieren ball, the edge of the schlieren ball must first be obtained using the Sobel operator , and then, the least squares method can be used to fit a circle with high fitting precision. According to the literature , the circle fitting formula is (3) (4) where N is the total number of boundary points, (xi, yi) represents the boundary coordinates of the side lobe image, and r is the radius. (x0, y0) is the center of the schlieren ball; the center and radius of the schlieren ball in the side lobe image obtained from the circle fitting formula are (Opx, Opy) and okr, respectively, and the side lobe data within the radius of the schlieren ball are set to zero. The code for calculating the center and radius using the circle fitting method is described in the supplemental information file (S1 File). The steps used to calculate the schlieren ball center are as follows:
- The clipping side lobe image is processed by the mathematical morphology , the result of which is shown in Fig 4(a).
- The edge of the small ball is detected using the Sobel operator ; the circle contour is shown in Fig 4(b).
- The circle contour is used to fit the circle using formula (3), and the result is shown in Fig 4(c).
The search for the best matching point of the schlieren ball center in the main lobe image.
To greatly reduce the time consumption when finding the best matching point of the schlieren ball center in the main lobe image, the main lobe and side lobe image must be clipped a second time, and the two images, with a size of 300×300, are denoted as cutzb and cutpb (Fig 5).
(a) The cutpb image. (b) The cutzb image. (c) The best matching with the schlieren ball dug from the main lobe image. (d) Three-dimensional cutpb image. (e) Three-dimensional cutzb image. (f) Three-dimensional image of the best matching with the schlieren ball dug from the main lobe image.
The steps used to identify the best matching points are as follows:
- Obtain the center of gravity (Ozx, Ozy) of orgzb. Obtain the center (Opx, Opy) and radius okr of the small schlieren ball in orgpb using the circle fitting method.
- Obtain the cutpb image of size 300×300, where the cutpb image is cut from the orgpb image, with the center located at (Opx, Opy). The center of cutpb is (Cpx,Cpy), which is equal to (150, 150), as shown in Fig 5(a).
- Obtain a matrix Pcir with size of 300×300, which marks the region of the small schlieren ball of cutpb. Pcir (i,j) is set to 0 when (i,j) is located within the region of the small ball of cutpb; otherwise, Pcir(i,j) is set to 1.
- Obtain the cutzb image with size of 300×300. The cutzb image is cut from the orgzb image, with the center located at (Ozx+l, Ozy+m), where l and m are the relative coordinates referring to the center of the rectangle region with size of 100×100. The l value range is −50 ≤ l < 50, and the m value range is −50 ≤ m < 50.
The white rectangle shown in Fig 6(a) and 6(b) is the real region of cutzb, with a size of 300 × 300. A circle region is dug from the new cutzb image, and cutzb (i,j) is set to 0 when Pcir (i,j) is equal to 0.
(a) The clipped region of the second clipped main lobe image in cutzb. (b) Identification of the best matching position, for which the correlation coefficient between the side lobe image and the main lobe image with a circle dug is maximal.
When l and m are changed from -50 to 49, the correlation coefficient between cutzb and cutpb is calculated using formula (2). When the correlation coefficient is maximized, the corresponding coordinates of the best matching position in the orgzb image are (Ozx+l, Ozy+m), and the maximal correlation coefficient is 0.8446. Thus, the main lobe cutting image surrounded by the white rectangle shown in Fig 6(b) is the best matching image of cutzb according to m,l, which is the final cutting image with size 300×300 and is denoted by cutzb'. The coordinates of the small schlieren ball in cutzb’ are (cxzb,cyzb).
Between cutpb and all cutzb images for which (Ozx+m, Ozy+m) is regarded as the center of the 100×100 region, the three-dimensional diagram of the correlation coefficient is shown in Fig 7. The figure shows that the positions corresponding to the maximum correlation coefficients m and l are -16 and 1, respectively. The code of the schlieren automatic reconstruction algorithm is presented in the supplemental information file (S1 File).
The steps of the image merging process are as follows:
- Fill the small ball region of cutpb. The data of cutpb located within the region of the small ball are replaced by the data of cutzb’ when Pcir(i,j) is equal to 0 and are magnified K times. The notation is cutpb’.
- The region of cutpb in orgpb is replaced by the final data of cutpb’ when Pcir(i,j) is equal to 0; thus, the new orgpb is the final merged image. The notation is Imerge.
- Fuse the splicing boundary by the weighted average method.
Because the edge of the small schlieren image is irregular, the real merging radius is increased by 5 pixels with respect to okr to eliminate the splicing mark in the merged image. The direct merging result is shown in Fig 8(a), the merging result of boundary fusion is shown in Fig 8(b) . The final three-dimensional reconstructed image is shown in Fig 8(c).
Results and discussion
Analysis of the texture characteristics of the splicing region
To verify the merging performance of automatic reconstruction, the texture features of the splicing edge are first analyzed. Because the main lobe image is spliced in the side lobe image when obtaining the reconstructed image, the splicing ring is shown in Fig 9(a). The merged image of the inner ring is filled with main lobe image data, and the merged image of the outer ring is filled with side lobe image data. As shown in Fig 9(b), the texture of the six selected regions is consistent. Among them, the stitching error of region 1 in the left and right directions is less than one pixel, the stitching error of regions 2 and 3 in the up and down directions is less than one pixel, and the texture of regions 4–6 is completely consistent; thus, the stitching precision of the reconstruction meets the experimental requirements.
(a) The position of the splicing ring. (b) The mosaic feature area.
To verify the splicing accuracy of the reconstructed image, the correlation coefficient between the reconstructed image and the main lobe image is 0.997 when the magnification ratio of the main lobe intensity relative to the side lobe intensity K = 1; thus, the reconstruction algorithm can be considered to be true and reliable. The means of the reconstructed image and the main lobe image are 34.621 and 35.735, respectively, and the variances are 65.810 and 65.099, respectively, indicating great similarity between the reconstructed image and the main lobe image.
Improvement of the precision of the center of the small schlieren ball
To improve the precision of the center of the small schlieren ball, formula (3) is used to calculate the schlieren ball center by the fitting method, and the real center and radius are obtained by manual calibration. Experimental data from 5 groups were used to analyze the precision of the center of the small schlieren ball between the circle fitting and the gravity method. The error comparison between the real center and the center of the two algorithms is shown in Table 1. As shown in the table, the error between the center obtained using the circle fitting method and the real center is (0.3, 0.36) pixels, and the error between the center of gravity method and the real center is (1.7, 1.5) pixels, demonstrating that the circle fitting algorithm is better than the gravity method and that the side lobe image center provides greater accuracy. Thus, the authenticity of the reconstructed image can be guaranteed. However, the center and radius of the small schlieren ball can be calculated using the fitting method as long as the circular boundary points are circulated only once. The time complexity of the algorithm is O(n), the calculating time is 0.8 s, and the time consumption is reduced over the whole reconstruction process.
There is a certain deficiency in obtaining the center of the schlieren ball: the small schlieren ball is placed at a fixed position to block the main lobe spot center when capturing the side lobe image, but the schlieren ball cannot block the side lobe spot center in the actual experiment. Therefore, an automatic alignment system must be designed to improve the positioning accuracy of the schlieren ball such that a perfectly sheltered side lobe image will ultimately be obtained.
Analysis of the calculations of the corresponding coordinates of the schlieren ball center in the main lobe image
To ensure the precision of the schlieren reconstruction, the most important factor is to accurately calculate the corresponding coordinates of the center of the schlieren ball in the main lobe image. The general methods for calculating the corresponding coordinates of the schlieren ball center in the main lobe image are the center of gravity method , the geometrical center method , the calibration method , and the self-correlation matching method , among others. The reconstruction errors of these 4 algorithms are shown in Table 2. The theoretical values of the corresponding coordinates in the shooting experimental data are (249.38, 272.68). The errors between corresponding coordinates obtained using 4 algorithms and the theoretical values are analyzed as follows: The errors of the center of gravity method and the geometrical center method are maximal, namely, greater than 10 pixels in the vertical direction. The error of the calibration method is smaller, namely, more than one pixel. Finally, the error of the autocorrelation matching method is minimal, namely, less than 1 pixel.
By calculating the correlation coefficient between the reconstructed and main lobe images, the similarity of the two images is obtained to determine the acceptability of the reconstructed method. When K = 1, the corresponding coordinates of the schlieren ball center in the main lobe image are first obtained via the four methods and then by image reconstruction. Finally, the correlation coefficient between the reconstructed images and the main lobe image are calculated, obtaining 0.629, 0.615 0.806 and 0.994. The correlation coefficient obtained using the self-correlation matching method is 0.994, and thus, the accuracy of the reconstructed image will be approximately 99.4%. The automatic reconstruction algorithm based on the self-correlation matching method is consistent and reliable, and the accuracy of the reconstructed image is verified. The mean values of the reconstructed image and of the main lobe image are 34.621 and 35.735, respectively, and the variances are 65.810 and 65.099, respectively, indicating the great similarity of the two images.
In previous targeting experiments, when seeking the best matching point for the schlieren ball center in the main lobe image, the general methods applied have been the calibration method , the center of gravity method and the geometrical center method , all of which have obvious deficiencies. For the calibration method, because there is great vibration and atmospheric turbulence when conducting a shooting experiment, the experimental conditions of the light path between the shooting experiment and the calibration are completely different. If the splicing point obtained in the calibration laser path is replaced by the splicing points obtained in the shooting laser path, there will be large errors. For the center of gravity method and the geometrical center method, when the distribution of the main lobe is more asymmetric, there will be substantial error between the center of gravity and the best stitching point. The best matching point stitching algorithm, which is proposed in this paper, has the following advantages: 1) it can find the location of the stitching automatically, 2) the stitching error is greatly reduced, and 3) the mosaic trace of the stitching position is eliminated by the boundary fusion algorithm.
Because there is background noise in the actual images captured by the CCDs, background noise must be considered during the process of automatic reconstruction. Under the assumption that the noise distribution functions of the main lobe and side lobe CCDs are m1(x1i, y1i) and m2(x2j, y2j), respectively, the distribution function of the reconstructed focal spot is expressed as (5) where g is the fused image; f1 and f2 are the main lobe and side lobe images, respectively; i and j are the coordinates of the CCD images; and d1 and d2 are the relative image proportions of the main lobe and side lobe in the overlapping region . d1 varies gradually from 1 to 0 as d2 varies from 0 to 1: d1 + d2 = 1, 0< d1<1, and 0< d2<1.
In formula (5), we can see that the absolute value of the background noise is different in each region of the merged image. Even if the average value of the background noise is subtracted from the main lobe and side lobe images, the noise standard deviation in each region of the merged image is different. (6) where σm1 and σm2 are the noise standard deviations of the main lobe and side lobe CCDs and σ is the noise standard deviation of the reconstructed image. Because the gray level is obvious when the reconstructed image is merged directly, the fade in/fade out method is used to fuse the overlapping boundary [11,14]. The weighted value is calculated based on the distance between the current pixel coordinates and the boundary coordinates (the cross point of the splicing ring and the line, which connects the center of the splicing ring and the current pixel) .
Analysis of the dynamic range
The dynamic range [17,21] of the reconstructed image is relative to both the dynamic ranges of the two CCDs and the intensity attenuation ratio K (K>1) . For the same peak value of the main lobe CCD, a smaller value of K results in a lower dynamic range and a smoother fused boundary (see Fig 10(a)), whereas a larger value of K results in a larger dynamic range and a more obvious splicing mark at the boundary. The rougher the merged image is in the splicing region, the larger is the error of the merged region (see Fig 10(b)). When b = 1 and K = 1, the linear region of the two CCD images is completely overlapped. The main lobe image is consistent with the side lobe image in the absence of the small ball. The distribution of background noise in the merged image is equivalent in each region, and the reconstructed image is smoothest in the overlapping region. When K>1, the linear overlapping region will decrease with increasing K, and the dynamic range of the reconstructed image will increase. However, the linear overlapping region will move to the linear lower limit of the main lobe CCD, and thus, the error of the fused boundary will increase, and the merged image will become rougher.
The dynamic range is defined as the ratio of the maximum gray value of the reconstructed image to the minimum valid gray value signal of the side lobe image. 90DL is the defined value of the minimum signal side lobe image, which is the gray mean value of a circle with a radius within 5 pixels of 1.5 times the small ball radius. The experimental data for the 3 groups are shown in Table 3.
As shown in the table, the measurement of a high-dynamic-range laser focal spot is implemented in 3 groups of experimental data. The measured dynamic range is greater than 1000:1, but there are huge differences in the light intensity attenuation ratio K because of different numbers of bits characterizing the CCD. The light intensity attenuation ratio obtained in experiments 1 and 2 is 10 times the intensity attenuation ratio obtained in experiment 3 because the measurement of the high-dynamic-range laser focal spot is mainly limited by the dynamic range of the scientific CCD. When the 14-bit scientific CCD is used to measure the far-field focal spot, the maximum gray value is 4095, and the dynamic range is only 100:1. To measure the far-field spot for which the maximum gray level is one hundred thousand or hundreds of thousands, the main lobe intensity will be attenuated by a factor of 25–250. Therefore, if the laser intensity of the splicing main lobe is magnified 25–250 times, a serious distortion of the reconstructed image will occur. The experimental results show that, when the intensity of the main lobe is magnified 1–10 times, the distortion is minimal, and the splicing effect is optimal. When the 16-bit scientific CCD is used in the actual experiment to measure the far-field spot, the maximum gray value is 65535. If the far-field focal spot for which the maximum gray level is hundreds of thousands is measured, the attenuation of the main lobe spot will only be 1–10 times. Thus, the distortion of the reconstructed image is very slight, and the splicing effect is optimized. However, 16-bit scientific CCDs are imported, and thus, they are more expensive. If the target energy is high and the attenuation is improper, a 16-bit scientific CCD will be damaged, which results in a high experimental cost.
Although the measurement of the far-field focal spot with a high dynamic range can be completed using the schlieren method, there are 3 shortcomings of this paper. 1) There is a certain deviation between the actual experimental results and the original expectations, and there is a severe distortion of the reconstructed focal spot, mainly because the intensity of the main lobe laser is magnified hundreds of times when the emission energy is excessive. As a result, it cannot accurately reflect the true spot distribution. In addition, the splicing step of the edges is obvious, and it is very difficult to obtain a satisfactory stitching effect. Moreover, because the small schlieren ball cannot block the side lobe spot center correctly during emission of the high-power facility, the edge of the side lobe spot is saturated. Thus, it is very difficult to identify the best matching point using the automatic reconstruction algorithm, and automatic matching will fail. 2) The first shortcoming described above is that the laser path is collimated by a simulated laser, namely, a beam emitted from a low-energy laser source when the total laser path is collimated and is different from the targeting laser, which is emitted from a high-power laser source of approximately 10000 J. The main lobe and side lobe spots are captured by the integrated diagnostic system. However, the actual experimental situation is such that the energy of the simulated laser is minimal. The simulated laser cannot reach the position of the side lobe CCD and main lobe CCD; thus, it is necessary to insert a relay light source at the position of the small target chamber to complete the collimation of the small target chamber behind the laser path, which increases the complexity and time requirement of the optical collimation. The main explanation for this is a lack of understanding of the design complexity of the optical path. 3) The mathematical model cannot consider the effect of noise on the reconstructed image. The noises of the two CCDs are different; thus, formula (8) in the focal spot distribution function is improved, and the impact of noise is analyzed in detail.
Based on the research presented in this paper, an integrated diagnostic system was designed to capture the main and side lobes of a far-field focused laser spot. The automatic reconstruction of the far-field focal spot was achieved. The least squares method was used to fit the center of the side lobe schlieren small ball. The findings will have very important significance in obtaining integrated and precise laser parameters.
This paper presents an improved schlieren method for constructing high-dynamic-range images of far-field focal spots and improving the reconstruction accuracy and efficiency. The main lobe and side lobe beam spots are captured by two scientific-grade 14-bit CCD cameras at a 10 kJ-level laser facility, and the measurement of the far-field focal spot for a high-power laser facility is achieved using schlieren reconstruction. A self-correlation template matching algorithm is used to identify the optimal matching position and to reconstruct the focal spot by identifying the position with the largest correlation coefficient between the side lobe image and the main lobe image with a circle dug as the best matching position, thereby enabling the automatic splicing of the main lobe and side lobe images. In addition, the least squares method is used to fit the center of the side lobe schlieren small ball, and the error is less than 1 pixel. The experimental results show that the method can achieve an accurate, high-dynamic-range measurement of the far-field focal spot and automatic image reconstruction. The texture of the reconstructed image in the splicing region shows excellent agreement; not only is the stitching error reduced greatly, to less than one pixel, but the experimental efficiency for targeting experiments is also greatly improved.
S1 File. There are two important algorithms in the Supporting Information file: the first algorithm is “Calculating the center of the schlieren ball”, and the second algorithm is “Searching for the best matching point”, in which the code for the algorithms and a list of all variables used in the algorithm are provided.
- Conceptualization: ZZW BLH.
- Data curation: BLH.
- Formal analysis: QYY.
- Funding acquisition: BLH.
- Investigation: ZZW BLH QYY.
- Methodology: BLH QYY.
- Project administration: ZZW BLH QYY.
- Resources: ZZW BLH QYY.
- Software: ZZW.
- Supervision: ZZW.
- Validation: BLH.
- Visualization: QYY.
- Writing – original draft: ZZW BLH QYY.
- Writing – review & editing: BLH.
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X-ray Laser Measures Atomic-scale Details of How Ring-shaped Gas Molecule Breaks Open, Unravels
Scientists for the first time tracked ultrafast structural changes, captured in quadrillionths-of-a-second steps, as ring-shaped gas molecules burst open and unraveled. Ring-shaped molecules are abundant in biochemistry and also form the basis for many drug compounds. The study points the way to a wide range of real-time X-ray studies of gas-based chemical reactions that are vital to biological processes.
SLAC National Accelerator Laboratory
This illustration shows shape changes that occur in quadrillionths-of-a-second intervals in a ring-shaped molecule that was broken open by light. The molecular motion was measured using SLAC's Linac Coherent Light Source X-ray laser. The colored chart shows a theoretical model of molecular changes that syncs well with the actual results. The squares in the background represent panels in an LCLS X-ray detector.
Researchers working at the Department of Energy’s SLAC National Accelerator Laboratory compiled the full sequence of steps in this basic ring-opening reaction into computerized animations that provide a “molecular movie” of the structural changes.
Conducted at SLAC’s Linac Coherent Light Source, a DOE Office of Science User Facility, the pioneering study marks an important milestone in precisely tracking how gas-phase molecules transform during chemical reactions on the scale of femtoseconds. A femtosecond is a millionth of a billionth of a second.
“This fulfills a promise of LCLS: Before your eyes, a chemical reaction is occurring that has never been seen before in this way,” said Mike Minitti, a SLAC scientist who led the experiment in collaboration with Peter Weber at Brown University. The results are featured in the June 22 edition of Physical Review Letters.
“LCLS is a game-changer in giving us the ability to probe this and other reactions in record-fast timescales,” Minitti said, "down to the motion of individual atoms." The same method can be used to study more complex molecules and chemistry.
The free-floating molecules in a gas, when studied with the uniquely bright X-rays at LCLS, can provide a very clear view of structural changes because gas molecules are less likely to be tangled up with one another or otherwise obstructed, he added. “Until now, learning anything meaningful about such rapid molecular changes in a gas using other X-ray sources was very limited, at best.”
New Views of Chemistry in Action
The study focused on the gas form of 1,3-cyclohexadiene (CHD), a small, ring-shaped organic molecule derived from pine oil. Ring-shaped molecules play key roles in many biological and chemical processes that are driven by the formation and breaking of chemical bonds. The experiment tracked how the ringed molecule unfurls after a bond between two of its atoms is broken, transforming into a nearly linear molecule called hexatriene.
"There had been a long-standing question of how this molecule actually opens up," Minitti said. “The atoms can take different paths and directions. Tracking this ultimately shows how chemical reactions are truly progressing, and will likely lead to improvements in theories and models.”
The Making of a Molecular Movie
In the experiment, researchers excited CHD vapor with ultrafast ultraviolet laser pulses to begin the ring-opening reaction. Then they fired LCLS X-ray laser pulses at different time intervals to measure how the molecules changed their shape.
Researchers compiled and sorted over 100,000 strobe-like measurements of scattered X-rays. Then, they matched these measurements to computer simulations that show the most likely ways the molecule unravels in the first 200 quadrillionths of a second after it opens. The simulations, performed by team member Adam Kirrander at the University of Edinburgh, show the changing motion and position of its atoms.
Each interval in the animations represents 25 quadrillionths of a second -- about 1.3 trillion times faster than the typical 30-frames-per-second rate used to display TV shows.
“It is a remarkable achievement to watch molecular motions with such incredible time resolution,” Weber said.
A gas sample was considered ideal for this study because interference from any neighboring CHD molecules would be minimized, making it easier to identify and track the transformation of individual molecules. The LCLS X-ray pulses were like cue balls in a game of billiards, scattering off the electrons of the molecules and onto a position-sensitive detector that projected the locations of the atoms within the molecules.
A Successful Test Case for More Complex Studies
“This study can serve as a benchmark and springboard for larger molecules that can help us explore and understand even more complex and important chemistry,” Minitti said.
Additional contributors included scientists at Brown and Stanford universities in the U.S. and the University of Edinburgh in the U.K. The work was supported by the DOE Office of Basic Energy Sciences.
SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the U.S. Department of Energy Office of Science. To learn more, please visit www.slac.stanford.edu
SLAC National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
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World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
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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Biohabitats’ Leaf Litter
Vol. 3 Number 1
Thoughts on Wolf Reintroduction & Ecosystem Restoration
The wolf…the big bad wolf, has gone from being admired and even worshiped in ancient times to persecuted, poisoned, slaughtered and extirpated from most of the United States. Embedded into our nursery rhymes, folklore and psychic, the wolf is now teaching us valuable lessons about the roles top predators (keystone species) play in maintaining a healthy ecosystem. We now know that keystone species such as wolves, by virtue of the key roles they play in the overall structure and functioning of an ecosystem, are essential to its integrity. They play a critical role in defining the mosaic pattern of vegetation, energy and nutrient cycling and the life cycles of species associated with their habitats. If we are serious about conserving our natural heritage and restoring fully functioning ecosystems, then we must give careful consideration to keystone species. What better species to turn our attention to than the gray wolf (Canis lupus).
The gray wolf originally was found throughout the northern hemisphere in every habitat where large ungulates were found. From mid-Mexico and India to the North Pole, the wolf roamed areas as diverse as Israel and Greenland. As human settlements encroached on wolf habitat, encounters with wolves increased, especially with livestock. Firearms, poisons and traps were developed and used ruthlessly against wolves. In Eurasia, most wolves disappeared except in mountainous regions of Italy, northern Spain, Eastern Europe, as well as the northern parts of the former Soviet Union and the central plains and mountainous regions of Asia. In North America, wolf numbers declined until about the 1950’s. Populations survived in Canada and Alaska, but the only area within the 48 contiguous United States that held a viable population of wolves was northern Minnesota and nearby Isle Royale National Park in Lake Superior.
Recognizing the importance of wolves and their interaction with the landscape, countries throughout the world are finding ways to coexist with this keystone species. In Spain, wolves live in wheat and sunflower fields with human densities of up to 200 people per square kilometer. In Canada, Alaska, Scandinavia, the Mideast, and much of Asia, wolf numbers are stable or increasing. The World Wildlife Fund and the World Conservation Union (IUCN) took great interest in the wolf, and the animal was listed in IUCN’s Red Data Book of endangered species.
In the United States many programs are being employed to repatriate wolves to some of their historic ranges. One of the leading scientists engaged in wolf reintroduction in the United States, Ed Bangs, speaks with Leaf Litter on efforts to reestablish a viable wolf population to the Greater Yellowstone ecosystem. Ed shares his thoughts and observations on how the wolf has reinitiated ecosystem processes that have been missing for the past 70 years. Speaking of sharing thoughts, responses to our Leaf Litter survey on wolves drew an overwhelming response. Many of you were not shy in sharing your opinion on what appears to be a lively and still very contentious issue.
In your next encounter with a predatory keystone species (before you start running), take stock of the profound significance these creatures have on the landscape. And remember, it takes a full suite of species to make our ecosystems, and psyche whole.
– Keith Bowers, Principal
Further ReadingSustainability vs. Resiliency: Designing for a Trajectory of Change
Aloha: An unforgettable trip to the bathroom
Why do you feel ecological restoration is so important?
Election 2016: Down, but not out…
More From This AuthorThoughts on Agroecology
Thoughts on Giving Children the Gift of Nature
Thoughts on Soil
Thoughts on GIS
Thoughts on Earth Day | <urn:uuid:85c90251-6d3f-46dc-b045-d4ed9294a146> | 3.40625 | 781 | Personal Blog | Science & Tech. | 33.216973 | 95,547,205 |
At the southern end of Hawaii’s Big Island, I’m standing on a cliff and watching the newest part of the world being made. Half a mile away, a torrent of lava bursts through the basalt of the island’s edge and pours into the turquoise Pacific. The spout of liquid rock has been shooting into the water day and night for weeks, half-shrouded by a thick cloud of smoke and sulfur dioxide. When the lava hits the ocean’s surface, rocks swept up in the flow explode like fireworks, shooting sharp fragments through the air.
The waters of Hawaii are no stranger to volcanic eruptions; they are, after all, how the islands were formed and continue to be reshaped. But this is unique. At the end of December, 22 acres of the island dropped into the sea as lava from Kīlauea, one of the most active volcanoes in the world, surged through the brittle cliffs. The lava flow shifted from dozens of small leaks to one huge lava “fire hose.” Now thousands of gallons flow into one specific part of the ocean every day.
At first glance, the lava hose looks like a static orange-red column extending from the cliff to the sea—steady, stately. But when I peer closer, I can see the lava bubbling and hissing, the air around it writhing in the 2,000-degree heat. It seems like a Biblical torrent of brimstone, designed to wipe out life entirely and begin anew. What, I wondered, could possibly survive this?
The answer, for the most part, is nothing. “In the areas where lava is entering the sea, there is essentially no marine life, as the bottom is being constantly recreated by the new lava rock,” says Steven Dollar, a marine researcher at the University of Hawaii at Manoa. The waters around the flow are so blistering that not even microscopic plankton could survive in them. Furthermore, waters around an eruption can become so choked with pumice and ash that local fish, birds, marine mammals, and plants die.
But in this case, destruction isn’t as disastrous as it seems. In fact, in the right circumstances a massive eruption like this can give ecosystems a big boost. The changing conditions don’t just wreak havoc; they spur new life.
A few years ago, Eric Achterberg led a team of researchers to study the effects of ash fall from Iceland’s notorious Eyjafjallajökull eruption, whose cloud grounded air traffic around Europe for nearly a week in 2010. They found a significant uptick in iron in the Iceland Basin, which, under the right conditions, could have resulted in a major boom in phytoplankton—a critical part of larger ocean ecosystems because they form diets for marine animals from jellyfish to baleen whales. The plankton feed on iron-rich volcanic ash as well as other nutrients, like nitrates and phosphates. At the time of the eruption, there weren’t enough of these other nutrients in the water for phytoplankton to flourish, but if the eruption had occurred earlier in the year, when nitrates and phosphates were plentiful, Achterberg expects he would have seen major changes to growth.
Phytoplankton are scarcer in the waters of Hawaii than up north. Nutrients tend to fall into cooler waters—which, in Hawaii, rarely mix with the warmer layers of the ocean where phytoplankton live. The ocean’s layers are stratified based upon temperature, density, chemical properties, and other characteristics, divided into columns from the surface of the water to its depths, much like layers of the earth’s atmosphere. But Kīlauea’s lava flow could make nitrates and phosphates more widely available in Hawaii’s waters as the layers mix more than usual.
Last year, researchers found volcanic eruptions change surrounding ocean-water temperatures and stratification. Megumi Chikamoto, a visiting researcher at Utah State University and the lead author of the study, explains that major volcanic eruptions push a dense cloud of ash into the atmosphere, preventing the transmission of light—and lowering the atmospheric temperature around the eruption by as much as 1.5 degrees Celsius. This temperature change cools the ocean below the eruption as well, allowing nutrients in different water layers to blend more easily. Chikamoto found a 5 to 10 percent increase of biological diversity in Pacific waters around major eruptions.
Chikamoto cautions that such an effect is dependent on other oceanic patterns, like El Niño and La Niña, and points out that her research focused only on large eruptions that released a significant ash plume. But she would be curious, she says, to see how heat from the Kīlauea lava flow affects water temperature in the short term, especially in the area immediately around the ecosystem.
Jason Adolf, the chair of University of Hawaii-Hilo’s marine science department, is about to find out. He and his colleagues will soon begin studying the effects of all that heat, rock, and ash on the Big Island’s marine life. “I’m not necessarily expecting the see the warm-water plume devoid of life,” Adolf says. “We may see it enriched with life.”
An abundance of plankton would attract the other marine life—manta rays, whale sharks—that feed on the organisms. And the change in temperature can draw in marine animals for other reasons; although humpback whales only feed on Arctic krill and small fish, some scientists have reported seeing the whales swimming through the unusually warm columns of water around the Kīlauea coastline.
The lava hose could even be the tip of the iceberg; there may be lava flowing under the water as well. If that’s the case, the flow might mimic underwater volcanoes and hydrothermal vents that draw bustling marine ecosystems, from bacteria and barnacles to shrimp and crabs. These vents provide energy from a source other than the sun—a process called chemosynthesis. “Imagine photosynthesis without light,” Adolf says. “[The creatures] use the reduced chemicals, like hydrogen sulfide, as an energy source.” He would like to discover whether a similar process is happening with Kīlauea.
Although marine life often suffers in the immediate vicinity of an active flow, Adolf says he hasn’t heard of any cases of fish around the site being killed unexpectedly. “Anything that would be able to swim would be able to avoid it,” he points out. And while pumice and ash can restrict life after an eruption, such an event is usually temporary; ocean currents carry off sediment and marine populations usually rebound fairly quickly. Plus, Kīlauea has been erupting, on and off, since 1983. Destruction is nothing new.
Adolf is cautious about speculating on what his team’s research may reveal, but he is optimistic about the project. “My gut feeling about the lava entering the ocean is that it’s less of a harmful, threatening thing than it is a wonderful thing,” he says. “I see it as a story of one of Earth’s more fascinating turns, how life responds to this sort of event.”
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Microscopic examination of microbiotic soil crust shows that the profiles of soil with a dense cyanobacterial cover had two different layers: a surface thin layer composed of aeolian-born materials and an organic layer formed by filamentous cyanobacteria associated with sand particles. The results indicate that microbiotic cover is an important determinant of sand fixation in the Gurbantunggut Desert, northern part of Xinjiang, Northwestern China. Microscopic examination of microbiotic crusts in this study revealed an intricate network of filamentous cyanobacteria and exopolysaccharides, which binds and entraps sand grains and conglutinate fine particles with each other. Resistance to wind erosion paralleled the different disturbance levels on microbiotic soil crust. Sandy soil surface disturbances resulted in greatly decreased soil resistance to wind erosion. Maximum wind tunnel velocity in this test (25 m s- 1) did not lead to any wind erosion on the surface of undisturbed microbiotic soil crust, i.e. 100% covered by microbiotic soil crust. As for different disturbance levels, the highest threshold friction velocity was seen in the sand surface with 10% disturbance of microbiotic crust. The surface microbiotic soil crusts have great effects on wind erosion rates. Wind erosion rates for sandy soil with 0% crust cover was about 46, 21, 17 times the soil with 90% crust cover at wind velocities of 18, 22, 25 m s- 1, respectively. This study confirms that the planners and managers of nature reserves in this area should understand the important ecological roles of microbiotic crust in desert ecosystems. The reduction of trampling on the soil will eventually result in the re-establishment of biological crusts and their associated organisms, and ultimately lead to lower levels of wind erosion. Additionally, strategies should be developed to manage livestock and oil exploration in order to avoid concentrated zones of impact. © 2005 Elsevier B.V. All rights reserved.
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Proteins' Subtle "Backrub" Motion Could have Important Implications
News Feb 09, 2006
Biochemists have detected a subtle new gyration that protein molecules undergo in the intricate, squirming dance that influences their activity in the cell.
The researchers have also created a realistic geometrical model of the twisting "backrub" motion that could help scientists understand the basics of protein function and design proteins for medical use.
Also, they said, the backrub motion could have implications for understanding how proteins can accommodate locally to some mutations that occur during evolution, without altering their global structure or function.
Lead author on the paper was graduate student Ian Davis, and the other co-author was Bryan Arendall. The research was supported by the National Institutes of Health and a Howard Hughes Medical Institute predoctoral fellowship to Davis.
Proteins comprise strings of amino acids whose links form a "backbone." Each kind of amino acid sprouts a characteristic molecular "side chain," and together the backbone and side chains determine a protein's structure and function.
The Duke researchers suspected the presence of backrub motions for other reasons, but their reality could be conclusively shown only by studying proteins frozen in crystalline form for structural analysis by x-ray crystallography.
"We were pleased but surprised that these crystal structures at liquid nitrogen temperatures actually could show us something really interesting about dynamics," said Jane Richardson.
In the highest resolution such crystal structures, in which individual atoms are directly visible, it is quite common to see a side chain that "dances", or flips back and forth between two different conformations.
The researchers traced the consequences of this motion back into the backbone and deduced that the local backbone structure must twist slightly in a particular way to accommodate the larger side-chain movement.
According to Richardson, this motion, which they dubbed a "backrub", is a subtle, concerted shift of the two backbone units on either side of the dancing side chain.
"Nobody has described this particular kind of motion before," said Richardson. "And that's because it's down in the noise, in terms of what the backbone is doing."
"You have to get ultra-high-resolution, clean maps that really show you exactly where the side chain atoms are. And then you can work backwards to figure out what the backbone must have done." The researchers created a geometrical "backrub" software tool to model this motion.
"Investigators had theorized that the backbone moved, but it has been rather difficult to prove what's really going on," said Richardson.
"There have been other previous models, but these were not as successful as one would like, presumably because they were not based on the kind of empirical data that we've now developed."
To understand how frequently the backrub motion occurred in proteins, Davis undertook an analysis of crystallographic data on 19 proteins.
"We took nineteen of the highest-resolution structures available - the best data we could get our hands on," said Davis.
"We then went through each of those structures one residue at a time, looking for evidence of some sort of motion that extended beyond just a side chain spinning."
Davis distinguished backrub motions by detecting movement of the first side chain atom attached to the backbone - a shift that could only occur if the backbone had moved, said Davis.
In analyzing some 4,000 amino acid units, Davis found backrub motion for 3 percent of the total and 75 percent of all the local backbone shifts.
"We were expecting to see some examples of this motion, but we were very surprised that it was so dominant over any other very local backbone motions," he said.
The fact that the backbone motions are common in proteins frozen in crystals suggests that they are even more prevalent in proteins in the liquid environment of the cell, said Richardson.
"The backrub motions in these frozen crystals have to be a subset of what goes on in solution or in the body," she said. "It's got to be more common when you have more flexibility."
Such ubiquity means that the backrub model developed by the researchers could have useful applications, said Richardson.
"The backrub model can be used by people doing homology modeling, in which they are starting with a known protein structure and trying to model the structure of a protein with a related but different sequence," she said.
"One knows that the backbone will shift in such cases, but previous methods of modeling those shifts have usually produced results farther from reality rather than closer."
"We think our backrub shifts can help predict how, either in natural evolution or in protein engineering, the local structure would accommodate the substitution of an amino acid with a different shape or size of side chain," said Richardson.
Analytical Tool Predicts Disease-Causing GenesNews
Predicting genes that can cause disease due to the production of truncated or altered proteins that take on a new or different function, rather than those that lose their function, is now possible thanks to an international team of researchers that has developed a new analytical tool to effectively and efficiently predict such candidate genes.
Single Gene Change in Gut Bacteria Alters Host MetabolismNews
Scientists have found that deleting a single gene in a particular strain of gut bacteria causes changes in metabolism and reduced weight gain in mice. The research provides an important step towards understanding how the microbiome – the bacteria that live in our body – affects metabolism.READ MORE
Gotta Sample 'Em All! Underwater Pokéball Captures Ocean LifeNews
A new device developed by Wyss Institute reseachers safely traps delicate sea creatures inside a folding polyhedral enclosure and lets them go without harm using a novel, origami-inspired design. The ultimate aim is to allow the sea creatures to be (gently) analyzed in high detail.READ MORE | <urn:uuid:d3b3107d-3e55-4fce-9f0f-dde3635fe43a> | 2.953125 | 1,190 | News Article | Science & Tech. | 28.95016 | 95,547,224 |
doi:10.1038/nindia.2018.84 Published online 4 July 2018
Networks, characterised by numerous connections and interactions permeate every field of research from social to biological and economical to technical. In an increasingly interconnected world, an important challenge has been to unravel the architecture of complex, constantly developing networks.
A multi-disciplinary international team of scientists, including some from India, have now used tools from geometry to characterise the shape of real world networks1.
The researchers have employed classical concepts of geometry to study how different ‘curvatures’ compare when put to test on robust networks such as European road network or biological networks. Curvature is a key mathematical concept, and the Ricci curvature – developed by Italian mathematician Gregorio Ricci Curbastro around the turn of the 20th century – was an essential ingredient in Einstein's formulation of General Relativity and “a driving force in the advancement of this science”, says lead author of the study Areejit Samal from the Institute of Mathematical Sciences (IMSc) in Chennai.
"As part of ongoing work with the Max Planck partner group in mathematical biology, we are developing curvature measures to characterise the geometry (or shape) of networks,” Samal told Nature India.
Along with German geometer Jürgen Jost, Samal’s team has used geometrical concepts to study real social networks such as that of jazz musicians, e-mail communication between people and infrastructure networks such as the US power grid, even biological ones like the yeast-protein interaction network. "We have analysed 17 real world networks from different domains... the architecture of real networks deviates from model networks," Samal says.
The structure of networks can be described using a graph that has a number of nodes and edges. Samal says it will become extremely important in future to characterise the shape of networks employing such classical geometry concepts. Practically speaking, mathematicians can use underlying information on curvature of edges or connections to identify bottlenecks or vulnerabilities to make these networks more robust. The sign and magnitude of the network curvature can also be used to predict the expansion of a growing network, such as the world wide web, Samal explains.
"In India, a natural test ground for our models could be the Indian financial market data," Samal says adding he is discussing this prospect with a senior econophysicist at the Jawaharlal Nehru University in New Delhi.
1. Samal, A. et al. Comparative analysis of two discretizations of Ricci curvature for complex networks. Sci. Rep. 8, 8650 (2018) doi: 10.1038/s41598-018-27001-3 | <urn:uuid:c189a5f5-7386-44fd-a631-c76f5f632c36> | 3.484375 | 572 | Truncated | Science & Tech. | 32.180987 | 95,547,244 |
One of Albert Einstein's most famous theories just passed its most rigorous test yet thanks to a laboratory more than 4,200 light-years from Earth.
As outlined in his Theory of Relativity, Einstein's understanding of gravity predicts that all objects will fall at the same rate, independent of both composition and mass. Also called the "equivalence principle," it's a famous concept that was first explored in the early 17th century by Galileo and later expanded on by Johannes Kepler and Isaac Newton. In 1907, Einstein stood on the shoulders of these giants to formulate the math behind why and how the equivalence principle existed, using it to guide his development of general relativity.
As shown in this video from the Apollo 15 mission to the moon, even NASA astronauts tested the equivalence principle on the lunar surface.
Despite Einstein's theory of gravity passing countless tests in experiments on Earth and beyond, alternative theories were proposed arguing that objects with extreme density, such as collapsed neutron stars, would prove the exception.
In an effort to explore if the equivalence principle could pass its most extreme test yet, an international team of astronomers turned their attention to a star system discovered in 2012 and located some 4,200 light-years from Earth. Called PSR J0337+1715, it contains a neutron star in a 1.6-day orbit with a white dwarf star, and the pair in a 327-day orbit with another white dwarf further away.
The answer lies in density
So what makes this distant laboratory so special? As the researchers explain in a new paper published in the journal Nature, it all comes down to the difference in density between the neutron star and its neighboring white dwarf.
"This is a unique star system," Ryan Lynch of the Green Bank Observatory, and coauthor on the paper, said in a statement. "We don't know of any others quite like it. That makes it a one-of-a-kind laboratory for putting Einstein's theories to the test."
Neutron stars are the smallest and densest stars, the result of a once-massive star collapsing on itself. How dense? It's estimated a normal matchbox-sized object containing neutron-star material would weigh an astounding 3 billion tonnes. By comparison, white dwarfs, remnants of stars that have exhausted their fuel, are slightly less dense.
If the alternative theories were correct, the difference in densities between these two giant objects should cause one to fall faster towards the outer white dwarf they orbit.
Over the course of six years, researchers used the Green Bank Telescope in West Virginia to record radio waves issuing from the neutron star and track its position in proximity to the inner white dwarf. The work is so precise that, even from a distance of thousands of light-years, they can track the location of the neutron star to within a few hundred meters.
After more than 400 hours of observation, they concluded any difference in acceleration between the two objects was simply too small to detect.
"These observations have limited the difference to be less than 3 parts in a million," study participant Duncan Lorimer, West Virginia University professor of physics and astronomy, said in a release. "This groundbreaking result limits the room for any alternative theories of gravity and has improved upon the best previous tests by a factor of about ten."
So whether it's a hammer and a feather or a neutron star and a white dwarf, objects really do fall at the same rate regardless of composition or mass. Decades after his passing, Albert Einstein's theories continue to hold firm even into the farthest reaches of space. As Lorimer states, however, there's one force yet to explore where things could yet get interesting.
"We know that the theory will ultimately break down when trying to describe the singularities of black holes," he added, talking about the one-dimensional point within a black hole where the rules of physics as we know them don't apply. "However in the regime probed by these experiments, Einstein's theory reigns supreme." | <urn:uuid:b451e1d3-92b4-4d1f-ace5-f1a5f187f488> | 4.21875 | 816 | News Article | Science & Tech. | 43.690521 | 95,547,269 |
Mechanical diggers have been working to help a rare freshwater shellfish in its last remaining stronghold in Wales.
The freshwater pearl mussel, which was once common throughout Europe, has its last remaining “viable” population in Wales on the Afon Eden, near Trawsfynydd.
Now workers for Natural Resources Wales are excavating areas of land close to streams that feed into the Eden to improve water quality – critical for the pearl mussels’ survival.
They will create 11 settlement ponds to act as a natural filter for nutrients, pollutants and sediment before they reach the river.
Elain Gwilym, Project Officer at Natural Resources Wales said:
“After excavating we will be planting 10,000 plants which will act as filters and help the ponds blend in with the surrounding area.
“One of the reasons freshwater pearl mussels have declined so much is because they are very sensitive to changes in water quality.
“This work will help redress the balance on the Eden and improve the habitat of this critically endangered species.
“And the work has other benefits because improved water quality will also help the fish and other wildlife in the river, whilst the ponds will become home to frogs and small mammals like voles.”
Freshwater pearly live to be over 100 years old, making them one of the longest-lived invertebrates, and they can grow as large as your hand.
Pearls in Peril (PIP) is a Life+ Nature project with 22 partners working together to restore river habitats benefiting freshwater pearl mussel and salmonids in 21 Special Areas of Conservation (SAC) rivers across Britain.
In Wales the work is located within the Afon Eden catchment and led by Natural Resources Wales (NRW). Pearls in Peril (PIP) has a total budget of £3.5million. | <urn:uuid:7b3648f1-69c6-48fe-b0f1-bd3ecce3e888> | 3.125 | 387 | News (Org.) | Science & Tech. | 42.123037 | 95,547,275 |