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The division of labor is very strict in a beehive. The same applies to periods of rest: honey bees sleep with other members of their professional group, as researchers from the University of Würzburg’s Biocenter have discovered.
The activities in a bee colony are highly organized. The insects adhere to a strict division of labor: cleaning combs, feeding the brood and the queen, producing wax and building combs, keeping watch in front of the hive, foraging for nectar and pollen – each of these tasks is carried out by a specific “professional group”.
A forager bee has clamped itself between two combs using its head and the end of its abdomen so it can sleep. This image comes from a hive and was taken using an endoscope with an infrared light.
(Photo: Hobos team)
But what is the situation with periods of sleep and rest? Do these merely represent a lack of activity, where the bees simply do nothing in the location they happen to be in at that time? Or does the bee colony also exhibit sleep behavioral patterns that are specific to their professional groups? This is exactly what happens, as biologists Barrett Klein, Martin Stiegler, Arno Klein, and Jürgen Tautz from the universities of Würzburg and Wisconsin – La Crosse (USA) report in the journal PLoS ONE.
Inside workers sleep in the middle
Young bees that work inside generally sleep in empty cells close to the middle of the hive, usually in the breeding area. They have several sleep periods daily, spread over day and night. “The breeding area is a bustling place around the clock,” says Jürgen Tautz, “so empty cells there presumably offer the least chance of being disturbed while sleeping.”
When bees switch from inside to outside service, their sleep periods are gradually delayed. Tautz explains: “The older the bees become, the less they sleep. As forager bees, they demonstrate a clear day-night rhythm to their sleeping behavior. They then generally sleep outside cells and closer to the edge of the combs. There they are likely to be largely undisturbed at night.”
Initial findings about sleeping insects
Sleep in insects: The door to this research field was opened in 1983. At that time, German zoologist Walter Kaiser presented new findings about honey bees, and Swiss researcher Irene Tobler published a comparable paper about cockroaches.
The fact that non-vertebrates also demonstrate a genuine sleep behavior came as such a surprise back then that many scientists were reticent in their response, as Tautz explains. Würzburg bee researcher Martin Lindauer had found early indications as far back as 1952: During continuous day-night observations of individual forager bees, he noted that they were “idle” at night especially.
“Over time, more and more similarities have emerged between sleep in bees and sleep in humans,” says Tautz. While initially bee sleep was only detected in phases of immobility, scientists later identified periods of sleep of varying depth as well in the flying insects. As in humans, sleep deprivation in bees also reduces their ability to learn and communicate.
Biological function remains unclear
Also common to both is the fact that, like in humans, many questions remain unanswered regarding the biological function that sleep has in bees. Various explanations have admittedly been proposed by the scientific community, but none of them is universally recognized. One hypothesis assumes, for example, that the organism regenerates itself during sleep. Another regards sleep as an energy-saving measure, and a third suggests that during sleep the brain separates important from unimportant information, meaningfully committing the former to memory.
Beehive is monitored online
The Würzburg research team is keen to conduct further studies to find out more about how bees sleep. Tautz’s team will use a variety of tools, including the Hobos system (Hobos stands for “Honeybee Online Studies”): This monitors the activity in a beehive online around the clock using various sensor and measuring techniques, and the values can be retrieved on the Internet: http://www.hobos.de
New sleep posture discovered
Using Hobos, the Würzburg researchers have now also discovered a previously unknown sleep posture in bees: The insects clamp themselves between two combs using their head and the end of their abdomen and leave their antennae and legs dangling relaxed. They can remain completely motionless in this position for up to 30 minutes. Otherwise, bees sleep by simply squatting in one place with their antennae hanging down.
Barrett Klein, Martin Stiegler, Arno Klein, Jürgen Tautz: "Mapping sleeping bees within their nest: spatial and temporal analysis of worker honey bee sleep", PLoS ONE 2014, July 16
Prof. Dr. Jürgen Tautz, Biocenter at the University of Würzburg, T +49 (0)931 31-84319, email@example.com
Robert Emmerich | Julius-Maximilians-Universität Würzburg
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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An historical overview of impacts from land-based pollution on
community based natural resource management (CBNRM) as it applies to marine fisheries & coral reefs in the tropics.
Paul Andre DeGeorges1,2*
1Tshwane University of Technology, Nature Conservation, Pretoria, South Africa
2Mayflower Drive, Greenbackville, Virginia 23356, USA
The purpose of this review is to provide an historic record of the author’s experience from the 1960s through the 1990s with coral reefs and the impacts of land-based pollution and other actions by man on this important ecosystem, from the islands of the Caribbean and Central America to the West/East Coasts of Africa and the Western Indian Ocean. This is tied into the concept of Community Based Natural Resource Management (CBNRM), its origins in Southern Africa tied to Africa’s mega-fauna and how it can apply to fisher communities in the tropics. It concludes that unless human population pressures and the current forms of “development and conservation” both linked to pollution and habitat degradation are addressed, the future for both man and these unique ecosystems are in jeopardy. A key to this solution is how the Developed World relates to the Developing World. It is hoped that this review will provide insight to future generations of ecologists, researchers, resource managers, politicians, donors and NGOs (non- governmental organizations) as to the issues they will confront if both mankind and nature are to have a viable future, living in harmony. Currently, they appear to be in conflict with each other and only man can resolve these issues based upon how he interacts with Mother Nature.
Review Article: http://www.alliedacademies.org/journal-fisheries-research/ | <urn:uuid:e7c75fa4-40ea-4db3-aea5-c185b12e96f8> | 3.078125 | 371 | Academic Writing | Science & Tech. | 21.055483 | 95,632,403 |
Phytoplankton comprise the forests of the sea, and are responsible for providing nearly half of the oxygen that sustains life on Earth including our own. However, unlike their counterparts on land, the marine plants are nearly exclusively microscopic in size, and mostly out of human sight.
Consequently, we are still in a very early stage of understanding even the most basic aspects of phytoplankton biology and ecology.
In a new paper published in Nature, an international team of scientists, including two University of Hawaii at Manoa (UHM) microbial oceanographers, describe a novel strategy for phytoplankton growth in the vast nutrient-poor habitats of tropical and subtropical seas. The research team was led by Benjamin Van Mooy of the Woods Hole Oceanographic Institution on Cape Cod, MA, with key contributions by UHM scientists Michael Rappé and David Karl of the School of Ocean and Earth Science and Technology (SOEST) and UH's new Center for Microbial Oceanography (C-MORE).
Until now, it was thought that all cells are surrounded by membranes containing molecules called phospholipids – oily compounds that contain phosphorus, as well as other basic elements including carbon and nitrogen. These phospholipids are fundamental to the structure and function of the cell and for this reason had been thought to be an indispensable component of life. Phospholipids are one of several classes of molecules that contain the element phosphorus, which has been shown to be in very short supply in many marine ecosystems. The deep sea contains ample phosphorus but delivery to the surface waters where photosynthesis occurs is limited by temperature-induced stratification and the inability to mix the ocean to depths where phosphorus is available. Indeed, research conducted at Station ALOHA near Hawaii during the past two decades has shown that phosphorus is rapidly becoming less abundant in the stratified regions of the North Pacific Ocean, possibly a result of changes in the marine habitat due to greenhouse gas warming.
Van Mooy and colleagues discovered that phytoplankton in the open ocean may be adapting to the low levels of phosphorus by making a fundamental change to their cell structure. Rather than synthesizing the phosphorus-requiring phospholipids for use in their membranes, the plants appear to be using non-phosphorus containing "substitute lipids" that use the nearly unlimited element sulfur also found in seawater instead of phosphorus. These substitute sulfolipids apparently allow the plants to continue to grow and survive under conditions of phosphorus stress, a unique strategy for life in the sea.
To test the generality of this biochemical strategy, the authors compared the response of the phytoplankton communities in different ocean basins that experience varying levels of phosphorus stress. In regions where phosphorus stress is extreme, such as the area dubbed the Sargasso Sea in the central North Atlantic Ocean, phospholipids were nearly nonexistent. By comparison, in the South Pacific Ocean, where sufficient phosphorus exists, there were large amounts of phospholipids. The region around Hawaii was intermediate, which is consistent with the long-term data sets from the Hawaii Ocean Time-series program showing that phosphorus is still measurable but is disappearing from the surface waters at an alarming rate. One prediction from this initial study is that the phytoplankton in Hawaiian waters are likely to become more like those in the Sargasso Sea over time as phosphorus supplies dwindle further. To date, the ability to synthesize substitute lipids appears to be restricted to the phytoplankton; heterotrophic bacteria and other organisms must have a different strategy for survival, or none at all. This has implications for the future structure, biodiversity and function of Hawaiian marine ecosystems, including fish production and long-term carbon dioxide sequestration.
This research will continue as part of C-MORE's stated mission to understand life in the marine environment from "genomes to biomes" (http://cmore.soest.hawaii.edu).
Tara Hicks Johnson | EurekAlert!
Further reports about: > Earth's magnetic field > Hawaiian marine ecosystems > Pacific Ocean > Phytoplankton > Sargasso Sea > carbon dioxide sequestration > heterotrophic bacteria > marine ecosystem > nutrient-poor habitats > oceanic phytoplankton > phospholipids > phosphorus > phytoplankton growth > substitute lipids > subtropical seas > surface water
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
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For all the talk of artificial intelligence and all the games of SimCity that have been played, no one in the world can actually simulate living things. Biology is so complex that nowhere on Earth is there a comprehensive model of even a single simple bacterial cell.
And yet, these are exciting times for "executable biology," an emerging field dedicated to creating models of organisms that run on a computer. Last year, Markus Covert's Stanford lab created the best ever molecular model of a very simple cell. To do so, they had to compile information from 900 scientific publications. An editorial that accompanied the study in the journal Cell was titled, "The Dawn of Virtual Cell Biology."
In January of this year, the one-billion euro Human Brain Project received a decade's worth of backing from the European Union to simulate a human brain in a supercomputer. It joins Blue Brain, an eight-year-old collaboration between IBM and the Swiss Federal Institute of Technology in Lausanne, in this quest. In an optimistic moment in 2009, Blue Brain's director claimed such a model was possible by 2019. And last month, President Obama unveiled a $100 million BRAIN Initiative to give "scientists the tools they need to get a dynamic picture of the brain in action." An entire field, connectomics, has emerged to create wiring diagrams of the connections between neurons ("connectomes"), which is a necessary first step in building a realistic simulation of a nervous system. In short, brains are hot, especially efforts to model them in silico.
But in between the cell-on-silicon and the brain-on-silicon simulators lies a fascinating and strange new project to create a life-like simulation of Caenohabditis elegans, a roundworm. OpenWorm isn't like these other initiatives; it's a scrappy, open-source project that began with a tweet and that's coordinated on Google Hangouts by scientists spread from San Diego to Russia. If it succeeds, it will have created a first in executable biology: a simulated animal using the principles of life to exist on a computer.
"If you're going to understand a nervous system or, more humbly, how a neural circuit works, you can look at it and stick electrodes in it and find out what kind of receptor or transmitter it has," said John White, who built the first map of C. elegans's neural anatomy, and recently started contributing to the project. "But until you can quantify and put the whole thing into a computer and simulate it and show your computer model can behave in the same way as the real one, I don't think you can say you understand it."
For example, when researchers touch a worm on the head and it responds by turning and moving backwards, what exactly is happening there? What molecular mechanisms coordinate the firing of neural networks that initiate and complete this complex behavior? This month, a paper came out in PLOS Biology describing that exact sequence as recorded in live C. elegans. But it's one of very few studies like that.
More broadly, OpenWorm raises fascinating questions about what we mean when we say something is alive. If and when this project succeeds in modeling the worm successfully, we'll be faced with a new and fascinating concept to think with: a virtual organism. Imagine downloading the worm and running it in a virtual petri dish on your computer. What, exactly, will you be looking at? Will you consider it to be alive? What would convince you?
Perhaps creations like the digital C. elegans will start to break down our binary conception of the matter in the world as either living or not living. We'll discover that we can create systems that exist in-between these two spheres, or that certain aspects of life as we know it are not required to meet our definition of being alive.
"I suspect that we'll recognize that living systems are far-from-equilibrium molecular systems that are carrying out very specific sophisticated physical patterns and have some ability to sustain themselves over time," OpenWorm's organizer Stephen Larson wrote to me. "Thinking about it that way makes me go beyond a black and white notion of 'alive' to a more functional perspective -- living systems are those which self sustain. Our goal is to aggregate more of the biological processes we know that help the worm to self-sustain than have ever been aggregated before, and to measure how close our predictions of behavior match real living behavior, more than it is to shoot for some pre-conceived notion of how much 'aliveness' we need."
* * *
It's a complex, ambitious project, to say the least. White called it "bold." Yet it all began with a tweet.
In early 2010, software engineer Giovanni Idili sent a tweet to the Twitter account for The Whole Brain Catalog, a project to bring mouse brain data together into more usable formats. He said, as if on a lark, "@braincatalog new year's resolution: simulate the whole C. Elegans brain (302 neurons)!" One of the Brain Catalog's founders, Stephen Larson, was scanning the @-replies and offered his assistance, "So, do you want any help with that? How are you going to do it?"
Beginning with a 1997 proposal at the University of Oregon, there have been several attempts to simulate worms. Some focused on the body alone. Others tried to simulate the worm's behavior through machine learning, with no attempt at a biologically realistic nervous system. Idilli and Larson wanted to go beyond these early efforts. When Larson was at MIT, he was influenced by Rodney Brooks, the director of the Computer Science and Artificial Intelligence Laboratory at the university (and the creator of the Roomba!). Brooks proposed the idea that if you want artificial intelligence, it should be situated within an environment. Is his 1990 paper, "Elephants don't play chess," he argued that "to build a system that is intelligent it is necessary to have its representations grounded in the physical world."
The great thing about C. elegans, though, is that its physical world in the laboratory is completely standardized and well known. The worms live in petri dishes with agar. If any environment can be modeled by a computer, it is a petri dish with agar. The nascent OpenWorm team could build a realistic virtual environment for a digital C. elegans.
Which meant that their little worm brain -- the target of Idili's initial suggestion -- needed a body. For that, they reached out to Christian Grove at CalTech, who donated a 3D atlas of the worm to get them started.
They had a map of the brain, a model of the body, and a pretty good idea of how to build the environment. Their artificial intelligence might not be embodied, but it would be "situated." The brain would direct the body and the body would interact with the environment, and all three pieces would be connected by the intricate feedback loops that permeate biology.
Their goal became clear: they should build, as they put it on the website, "a fully digital lifeform -- a virtual nematode -- in a completely open source manner."
Three years and 31 Google Hangouts later, OpenWorm is a going concern with Larson at the helm and a team spread across the continents. Alexander Dibert, Sergey Khayrulin, and Andrey Palyanov contribute software development from Russia, along with Matteo Cantarelli in the UK and Timothy Busbice in California. Neuroscientists Mike Vella and Padraig Gleeson are stationed at Cambridge and University College London, respectively. And of course, Idili in Ireland and Larson in San Diego. There is no central lab, nor could there be.
The OpenWorm team has broken down this immense task into five component systems. First, at the base of the project, they have a list of the 959 cells in the C. elegans body. The list includes a rough idea of what each of the cells does, thanks to decades of research on the worm. Then, they've got a life simulation engine they call Geppetto (shout out to Pinocchio!), which is the platform on which all the other software runs. Third, there is the simulated physical body. They are creating an algorithm for worm mechanics that can generate realistic muscle movements. Fourth, they have an electrical model for the muscles. What are the signals that they send and receive to move the animal? Last but not least, they must animate the connectome, the wiring diagram for the worm's nervous system.
Their team has been making steady progress, but being at the leading edge means that they're also at the leading edge of encountering the problems that any effort to simulate a brain is going to have.
For an outsider and non-biologist, simulating the C. elegans brain seems like it should be relatively easy. You've got the map of the neurons. You know where all the cells go in the body of the worm. You know how it behaves under all these experimental conditions. What's so hard about simulating its behavior?
We don't know how to simulate every single protein and nucleic acid in a cell. And even if we could, it would be computationally staggering to try to model each and every cell in the worm down to that atomic level, figuring out each and every molecular interaction inside these densely packed cells. No experiments can output that data.
You could eschew biological realism entirely. It would be relatively trivial to create a CGI worm that *looked* realistic. Perhaps one could make it behave realistically by running machine learning on worm behavioral data in particular situations. But that wouldn't be a very interesting simulation of the processes of life. It certainly wouldn't be a model that would help biologists much.
So, between realistically simulating every atom and realistically simulating nothing, OpenWorm has had to make some tradeoffs. Larson thinks about it like this. Imagine a graph. Along the X-axis, you've got the level of biological realism baked into the simulation. Do its cells do what real cells do? Which parts of the cells do what their biological counterparts do? Do the neurons work like biological neurons? And the along the Y-axis, you've got the behavioral realism. Does this thing do wiggle like a real worm? Does it respond to chemicals like a real worm? Does it attempt to and succeed in reproducing?
The problem is, as Larson explains, "we don't know how far you have to go to the right on the X-axis to go [a certain amount] up on the y-axis." They don't know what level of biological realism will get them to what level of behavioral realism.
And, buried in that question is a deeper one: When can we say, or scream, raising our twisted fingers to the sky as lightning flashes above, "It's alive!"?
For example, they are using a model of how neurons work called the Hodgkin-Huxley model, which garnered its creators a Nobel Prize. If they were to add more detailed simulations of the neurons, would that meaningfully add to the behavioral realism of the organism as a whole? Or can the principles of neuronal firing and propagation be abstracted from their biological embodiment without losing any behavioral fidelity?
Making decisions about these tradeoffs forms the core of the project. All biological simulation projects to date have faced similar challenges. Take the now defunct Canadian project called (cue techno!) Project CyberCell.
Led by Michael Ellison of the University of Alberta, the team wanted to create a simple E. coli simulation. The molecules inside cells form these fantastically complex structures that are constantly moving around and changing shape. Modeling all that takes enormous computational horsepower, and that's assuming you know exactly how each protein is going to fold. It was too much to attempt. So, instead, CyberCell represented each molecule as a sphere -- "Every ribosome, every lipid molecule, every metabolite" Ellison said -- of approximately the right size. Then, they simply assigned each sphere certain probabilities of reacting with other spheres. "If the right enzyme connects with the right small molecule, there was a certain probability that a chemical reaction may take place," he explained.
Is that realistic? Not really. But it made it possible to start experimenting. "We still don't know enough about the living organisms," Ellison told me. "50 percent of E. coli is still a blackbox."
That figure might be even larger for C. elegans, but it's still the best characterized animal that researchers have got. It remains the only organism for which a complete connectome actually exists. Working in Nobel laureate Sydney Brenner's Laboratory of Molecular Biology in Cambridge during the 1970s, White and his team spent 13 years creating the wiring diagram. Electron microscopist Nichol Thomson cut the one-milimeter worms into 20,000 very thin slices, which -- because the worms are transparent -- he could then image with his microscope. "The thing that gave [Thomson] the biggest pleasure of all was to cut a long series of quality images," White told me.
Then, with White's direction, a technician named Eileen Southgate painstakingly labeled each nerve cell and connection in the micrographs. Through their work, they discovered C. elegans has 302 neurons that form approximately 10,000 connections. And Southgate traced each and every one. "I found out several years into her collaboration that as a hobby, she put huge jigsaw puzzles together," White recalled. "She has a wonderful visual memory." She began work at the lab when she was 16 years old and stayed until she retired.
The brain map was only one of several scientific feats accomplished with C. elegans. The worm was also the first multicellular organism to have its genome sequenced. And scientists precisely tracked its development from embryo to adulthood. There's even a database (WormBase) that contains more complete data about the organism's functioning at the molecular level than one could find for any other animal. Dozens of labs work with this little species.
Brenner handpicked the organism precisely for its amenability to study, calling the worm "nature's gift to science." University of Kansas worm biologist, Brian Ackley, likes to joke that Brenner created C. elegans in a lab "because he was tired of working on things that didn't have perfect biological criteria." They're tiny, transparent, reproduce quickly, have a small number of neurons, and each body is composed of exactly 959 total cells.
"Brenner planned to use the worm to discover how genes made bodies and then behavior," wrote Andrew Brown in a book on C. elegans. "And this was in 1965, before anyone had found and analysed a single gene for anything." It is only today, in 2013, that his disciples' disciples' are beginning to fulfill that original vision.
In a 1974 paper quoted in the talk he gave accepting the Nobel Prize for Medicine, Brenner put it like this, "Behavior is the result of a complex ill-understood set of computations performed by nervous systems and it seems essential to decompose the question into two," he wrote, "one concerned with the question of the genetic specification of nervous systems and the other with the way nervous systems work to produce behaviour." In other words, how do genes build brains and how do brains direct bodies?
Now, finally, OpenWorm may be able to integrate the strains of research that began with Brenner into one simulation that, as it wiggles along in its digital petri dish, might be the first realistic virtual animal, a boon to research, and a Kurzweilian foreshadowing of the challenges humans face when we begin running life on silicon chips.
I asked several researchers whether simulating the worm was possible. "It's really a difficult thing to say whether it's possible," said Steven Cook, a graduate student at Yale who has worked on C. elegans connectomics. But, he admitted, "I'm optimistic that if we're starting with 302 neurons and 10,000 synapses we'll be able to understand its behavior from a modeling perspective." And, in any case, "If we can't model a worm, I don't know how we can model a human, monkey, or cat brain."
Ellison echoed that thought. "They stand a much better chance of success than the people working on mammalian brains," he said. White, who led the creation of the worm connectome, said OpenWorm "seemed appropriate really" as a way of integrating all the data that biologists were producing. And the Kansas worm scientist Ackley figured that even if OpenWorm didn't work, something like it would. "C. elegans is probably going to be the first or very close to the first [multicellular organism] to be simulated," he said
David Dalrymple, an MIT graduate student who has contributed to OpenWorm and is working on a worm brain modeling project of his own, pointed out what he sees as a limitation to the effort. OpenWorm has incorporated a lot of anatomical data -- the structures of the worm's nervous system and musculature -- described by scientists like White. But these studies were carried out with dead worms. They can't tell scientists about the relative importance of connections between neurons within the worm's neural system, only that a connection exists. Very little data from living animals' cells exist in the published literature, and it may be required to develop a good simulation.
"I believe that an accurate model requires a great deal of functional data that has not yet been collected, because it requires a kind of experiment that has only become feasible in the last year or two," Dalrymple told me in an email. His own research is to build an automated experimental apparatus that can gather up that functional data, which can then be fed into these models. "We're coming at the problem from different directions," he said. "Hopefully, at some point in the future, we'll meet in the middle and save each other a couple years of extra work to complete the story."
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Factors Controlling Forest Atmosphere Exchange of Water, Energy, and Carbon
Forests play an important role in the water and energy balance of the land surface. It has been known since the early studies of Horton (1919) and Rutter (1975) that the water use of forests can be considerably higher than that of vegetation of different structure and height. Subsequent work has elucidated the main factors influencing this behavior (e.g., Shuttleworth and Calder 1979; Shuttleworth 1989). They showed that the combination of a high aerodynamic roughness, with a relative low and strongly controlled surface resistance, was the main cause for high evaporation rates from wet canopies and somewhat low transpiration rates from dry canopies. They also suggested that care must be given to the separate modeling of dry and wet canopy evaporation, and that total evaporation could not simply be derived from equations relating total evaporation to a net radiation estimate. Building on that work, numerous modeling studies at regional and global scale have provided evidence that the interaction of the forests with the atmosphere is a major component in shaping regional to global climate and weather (Nobre et al. 1991; Blyth et al. 1994). Forests not only use more water by evaporating more, they also influence the rainfall patterns and magnitude at regional and global scales by increasing the low level moisture convergence (supply of moisture through horizontal advection in the lower layers of the atmosphere).
KeywordsLatent Heat Flux Surface Energy Balance Canopy Conductance Incoming Shortwave Radiation Evaporative Fraction
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- Jarvis PG, James GB, Landsberg JJ (1976) Coniferous forests. In: Monteith JL (ed) Vegetation and the atmosphere, vol II. Academic Press, London, pp 171–240Google Scholar
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- Valentini R, Matteucci G, Dolman AJ, Schulze E-D, Rebmann C, Moors EJ, Granier A, Gross P, Jemsen NO, Pilegaard K, Lindroth A, Grelle A, Bernhofer C, Grunwald T, Aubinet M, Ceulemans R, Kowalski AS, Vesala T, Rannik U, Berbigier P, Lousteau D, Gudmundson J, Thorgeirson H, Ibrom A, Morgenstern K, Clement R, Moncrieff J, Montagni L, Minerbi S, Jarvis PG (2000) Respiration as the main determinant of carbon balance in European forests. Nature 404:861–865PubMedCrossRefGoogle Scholar | <urn:uuid:a87b54c2-2fff-42c1-ac14-c6a1ac29c009> | 3.171875 | 785 | Academic Writing | Science & Tech. | 35.579612 | 95,632,417 |
A team of scientists hope to trace the origins of gamma-ray bursts with the aid of giant space 'microphones'.
Researchers at Cardiff University are trying to work out the possible sounds scientists might expect to hear when the ultra-sensitive LIGO and Virgo detectors are switched on in 2015.
It's hoped the kilometre-scale microphones will detect gravitational waves created by black holes, and shed light on the origins of the Universe.
Researchers Dr Francesco Pannarale and Dr Frank Ohme, in Cardiff University's School of Physics and Astronomy, are exploring the potential of seeing and hearing events that astronomers know as short gamma-ray bursts.
These highly energetic bursts of hard radiation have been seen by gamma-ray satellites such as Fermi and Swift, but the exact origin of these quickly disappearing flashes of gamma-rays remains unknown.
"By picking up the gravitational waves associated with these events, we will be able to access precious information that was previously hidden, such as whether the collision of a star and a black hole has ignited the burst and roughly how massive these objects were before the impact," explained Dr Ohme, who has focused his research on predicting the exact shape of the gravitational wave signals scientists are expecting to see.
Dr Pannarale added: "A possible scenario that could produce gamma-ray bursts involves a neutron star, the most compact star in the Universe, being ripped apart by a black hole while orbiting it. The remaining matter would be accelerated so much it could cause the energy bursts we are observing today.
"In some cases, by observing both electro-magnetic and gravitational wave signatures of the same event, we will be able to better understand the behaviour of material in the highest density region we know in our Universe, so that we will start to rule out various theoretical models that have been proposed but cannot be tested otherwise."
The results of Pannarale and Ohme have been published in Physical Review Letters: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.151101
Dr. Frank Ohme | 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...
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New data helps explain recent fluctuations in Earth’s magnetic field
Using new data gathered from sites in southern Africa, University of Rochester researchers have extended their record of Earth's magnetic field back thousands of years to the first millennium.
The record provides historical context to help explain recent, ongoing changes in the magnetic field, most prominently in an area in the Southern Hemisphere known as the South Atlantic Anomaly.
"We've known for quite some time that the magnetic field has been changing, but we didn't really know if this was unusual for this region on a longer timescale, or whether it was normal," says Vincent Hare, who recently completed a postdoctoral associate appointment in the Department of Earth and Environmental Sciences (EES) at the University of Rochester, and is lead author of a paper published in Geophysical Research Letters.
The new data also provides more evidence that a region in southern Africa may play a unique role in magnetic pole reversals.
"We're getting stronger evidence that there's something unusual about the core-mantel boundary under Africa that could be having an important impact on the global magnetic field."
The magnetic field that surrounds Earth not only dictates whether a compass needle points north or south, but also protects the planet from harmful radiation from space. Nearly 800,000 years ago, the poles were switched: north pointed south and vice versa. The poles have never completely reversed since, but for the past 160 years, the strength of the magnetic field has been decreasing at an alarming rate. The region where it is weakest, and continuing to weaken, is a large area stretching from Chile to Zimbabwe called the South Atlantic Anomaly.
In order to put these relatively recent changes into historical perspective, Rochester researchers–led by John Tarduno, a professor and chair of EES–gathered data from sites in southern Africa, which is within the South Atlantic Anomaly, to compile a record of Earth's magnetic field strength over many centuries. Data previously collected by Tarduno and Rory Cottrell, an EES research scientist, together with theoretical models developed by Eric Blackman, a professor of physics and astronomy at Rochester, suggest the core region beneath southern Africa may be the birthplace of recent and future pole reversals.
"We were looking for recurrent behavior of anomalies because we think that's what is happening today and causing the South Atlantic Anomaly," Tarduno says. "We found evidence that these anomalies have happened in the past, and this helps us contextualize the current changes in the magnetic field."
The researchers discovered that the magnetic field in the region fluctuated from 400-450 AD, from 700-750 AD, and again from 1225-1550 AD. This South Atlantic Anomaly, therefore, is the most recent display of a recurring phenomenon in Earth's core beneath Africa that then affects the entire globe.
"We're getting stronger evidence that there's something unusual about the core-mantel boundary under Africa that could be having an important impact on the global magnetic field," Tarduno says.
The researchers gathered data for this project from an unlikely source: ancient clay remnants from southern Africa dating back to the early and late Iron Ages. As part of a field called "archaeomagnetism," geophysicists team up with archaeologists to study the past magnetic field.
The Rochester team, which included several undergraduate students, collaborated with archaeologist Thomas Huffman of the University of Witwatersrand in South Africa, a leading expert on Iron Age southern Africa. The group excavated clay samples from a site in the Limpopo River Valley, which borders Zimbabwe, South Africa, and Botswana.
During the Iron Age in southern Africa, around the time of the first millennium, there was a group of Bantu-speaking people who cultivated grain and lived in villages composed of grain bins, huts, and cattle enclosures. Draughts were devastating to their agriculturally based culture. During periods of draught, they would perform elaborate ritual cleansings of the villages by burning down the huts and grain bins.
"When you burn clay at very high temperatures, you actually stabilize the magnetic minerals, and when they cool from these very high temperatures, they lock in a record of the earth's magnetic field," Tarduno says.
Researchers excavate the samples, orient them in the field, and bring them back to the lab to conduct measurements using magnetometers. In this way, they are able to use the samples to compile a record of Earth's magnetic field in the past.
The magnetic field is generated by swirling, liquid iron in Earth's outer core. It is here, roughly 1800 miles beneath the African continent, that a special feature exists. Seismological data has revealed a denser region deep beneath southern Africa called the African Large Low Shear Velocity Province. The region is located right above the boundary between the hot liquid outer core and the stiffer, cooler mantle. Sitting on top of the liquid outer core, it may sink slightly, disturbing the flow of iron and ultimately affecting Earth's magnetic field.
A major change in the magnetic field would have wide-reaching ramifications; the magnetic field stimulates currents in anything with long wires, including the electrical grid. Changes in the magnetic field could therefore cause electrical grid failures, navigation system malfunctions, and satellite breakdowns. A weakening of the magnetic field might also mean more harmful radiation reaches Earth–and trigger an increase in the incidence of skin cancer.
Hare and Tarduno warn, however, that their data does not necessarily portend a complete pole reversal.
"We now know this unusual behavior has occurred at least a couple of times before the past 160 years, and is part of a bigger long-term pattern," Hare says. "However, it's simply too early to say for certain whether this behavior will lead to a full pole reversal."
Even if a complete pole reversal is not in the near future, however, the weakening of the magnetic field strength is intriguing to scientists, Tarduno says. "The possibility of a continued decay in the strength of the magnetic field is a societal concern that merits continued study and monitoring."
This study was funded by the US National Science Foundation. | <urn:uuid:05f2e54c-35ad-45e8-90e0-649920c845a2> | 3.34375 | 1,264 | News Article | Science & Tech. | 31.368349 | 95,632,487 |
By studying the seabed, we can obtain information about environmental changes in the Baltic Sea and the factors affecting them over several thousand years.
The bottom sediment of the Baltic Sea is being studied in a Finnish-led research project as part of the joint European BONUS research programme.
“The area of research extends from the marine environment of Skagerrak to the almost fresh water of the Northern Baltic Sea. By studying the bottom sediment, we’re aiming to obtain information on the natural variations in the environmental conditions of the Baltic Sea and on the effect of human activity on environmental changes,” says Research Professor Aarno Kotilainen of the Geological Survey of Finland, who is coordinating the project.
Climatic conditions affect the temperature, salinity and changes of current in the Baltic Sea. They regulate such things as the salt water pulses that occasionally flow from the North Sea to the Baltic Sea. The eco-system and environmental conditions of the Baltic Sea are influenced both by local climate and that of the North-East Atlantic. This project coordinated by the Geological Survey of Finland is studying Baltic surface- and deep water conditions and their temporal variation, by looking at the layers of sediment on the seabed, using multivariate analysis.
By modelling, the project also aims to forecast the effects of climate change on the Baltic Sea. “A deeper understanding of the factors affecting the long-term changes in the Baltic Sea and of possible future changes is important. This knowledge is needed to support planning for the sustainable use of the marine regions and in preparation for the effects of climate change,” summarises Professor Kotilainen. In addition to the Geological Survey of Finland and the Department of Geology at the University of Helsinki, other participants in the research come from Russia, Germany, Denmark, Sweden, Poland and Norway.
Research funding organisations from the nine Baltic Sea nations are behind the BONUS programme, which was launched at the beginning of this year. The study is also being funded by the EU Commission.
The Finnish funding organisation is the Academy of Finland. At the first stage of the research programme, decisions were made to fund 16 research projects with a total of 22 million euros, with more than 100 research institutes and universities from the Baltic Sea countries taking part. Finland is coordinating four of these projects. Total project funding will be approximately 60 million euros between 2010 and 2016.
Anita Westerback | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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By: Vandana Shiva(Author), Patrick Anderson(Author), Heffa Schücking(Author), Andrew Gray(Author), Larry Lohmann(Author), David Cooper(Author)
123 pages, no illustrations
The extinction of species and the need to preserve biodiversity has moved to the top of the global environmental agenda. The contributors point to the gravity of the situation, and examine the Biodiversity Conservation Strategy launched in 1992 by the World Resources Institute, World Bank, IUCN and WWF.
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Posted by on February 14, 2005 at 00:14:23:
In Reply to: new species of local coral posted by on February 13, 2005 at 14:17:28:
(Santa Barbara, Calif.) -- A new species of black coral has been discovered off southern California, including around the Channel Islands, by Milton Love, University of California, Santa Barbara marine researcher, and Mary Yoklavich of NOAA Fisheries. The discovery came during dives by the researchers in "Delta," the submersible.
The new species, found at depths of approximately 300 to 725 feet, is reported this week in the online scientific journal Zootaxa (www.mapress.com/zootaxa/content.html) by taxonomist Dennis Opresko of Oak Ridge National Laboratory. Love named the new species "Christmas Tree Coral" (dendochristos in Greek) since it grows to a height greater than two meters and resembles pink, white and red flocked Christmas trees.
The complete scientific Greek name for the new coral is Antipathes dendrochristos. The word for black coral is "Anti" for against, and "pathos," for disease, a reference to the fact that black coral amulets were once thought to provide protection against disease and evil spirits.
The Christmas tree coral was first noticed by the researchers during dives for surveys of rockfishes on deep rocky banks about 40 miles off the coast, west of Los Angeles.
Many of the deepwater reefs in southern California harbor remarkably healthy communities of corals, sponges, and other large invertebrates," said Love. "This may be the case because, historically, there has been relatively little trawling over reefs in our area. What we need to know is the role that these large invertebrates play as deep-water habitats for fishes and other marine life."
"What is really remarkable," said biologist Mary Yoklavich from NOAA Fisheries, "is that these spectacular large colonies have managed to go unnoticed while living in the backyard of the largest urban area on the West Coast."
This research was supported in part by the David and Lucile Packard Foundation; NOAA Fisheries SWFSC, Offices of Habitat Conservation and Protected Resources, National Undersea Program, and Marine Protected Area Science Institute; California Artificial Reef Enhancement Program; the National Museum of Natural History of the Smithsonian Institution; and Oak Ridge National Laboratory.
NOTE: Photographs of the new species of coral may be viewed at: santacruz.nmfs.noaa.gov/ecology_branch/habitat_ecology/black_coral A six-minute digital video of the coral is available from Milton Love.
Love can be reached at (805) 893-2935, or by e-mail at: email@example.com
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Authors: Adrian Ferent
I explained Gravitational lensing and Gravitational redshift. “Because the momentum of each graviton pk is negative, the final momentum of a photon p is smaller than the initial momentum pi and the photon will move towards the source of gravitons for example a galaxy.” Adrian Ferent “Because the energy of the gravitons Ek is negative, the energy of the photon E after n interactions with gravitons it is smaller than the initial energy of the photon Ei.” Adrian Ferent Einstein theory of gravity is wrong because fails to explain Gravitational lensing and Gravitational redshift during Gravitational lensing.
Comments: 59 Pages. © 2015 Adrian Ferent
[v1] 2017-02-04 05:59:13
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At the end of the article, you will able to describe – What is radioactivity, definition, who discovered radioactivity, what are the uses, effect, Unit, Types of Radioactivity – natural, artificial, radioactive detector. Let’s start discussing one by one.
why is online dating harmful Understanding Radioactivity: The structure of atom consists of protons, neutrons, and electrons. Rutherford during its experiment verified that atoms are mainly empty space but they also contain a tiny positive nucleus. The nucleus contains protons (which are positive), neutrons which are neutral and negative charge electrons revolve around the nucleus.
Remember that the number of protons is fixed to an element but the number of neutrons is not fixed. Isotopes are versions of an element with the same number of protons but different numbers of neutrons. A good example is a ll ATTENZIONE!: go to siteption opinioni e Recensioni. E' un broker sicuro ed affidabile o è una truffa? Scopri di più e come aprire la tua Demo Gratuita carbon which has got three common isotopes. All carbon atoms have got six protons.
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However,126C isotopes got six neutrons. 136C isotopes got seven neutrons and 146C isotopes got eight neutrons.
What is Radioactivity – Definition
Radioactivity is the phenomenon of the spontaneous emission of certain high active radiation by radioactive substances. Some examples of radioactive substances are radium, thorium, plutonium etc.
Now when somebody says, some atoms are radioactive and what that means is that they release radiation from their nucleus. When a radioactive atom releases radiation it decayed. This decay is a totally random process scientists cannot predict. When an atom will decay it’s totally random and scientists cannot do anything to make them decay faster or slower.
There are three types of radiation and we’re going to look at them now.
- The first type of radiation is called an alpha particle. It consists of two protons joined with two neutrons. An alpha particle is having the same nuclear of a helium atom which also consists of two protons and two neutrons.
- A beta particle is an electron produced in the nucleus and released.
- Gamma radiation is a high-energy electromagnetic wave at there like x-rays but carrying, even more energy.
Who Discovered Radioactivity?
It was discovered by French physicist Henri Becquerel. A year later, in 1896, Marie Curie found that besides uranium and its compounds, thorium was another element which possessed the property of radioactivity.
The discovery of radioactivity was purely accidental. It was discovered by French physicist Henri Becquerel. He was working on the phenomenon of fluorescence. Fluorescence is the ability for certain substances to transform incident ultraviolet radiation into visible light. He kept the collection of various minerals required for his studies.These remained untouched for a long period of time. The minerals were kept in a box which also contained several unopened boxes of photographic plates. Thes plates were wrapped in thick black paper. When Henri Becquerel will use one of the plates and developed them he found them badly formed as if they were exposed to sunlight. The other plates kept in the box were also damaged.
He performed a series of experiments. He used to light-tight boxes in which he arranged one of the minerals pitchblende (uranium ore) and a photographic plate in one box. The uranium ore and photographic plate were kept in contact with each other while in the other box they were separated by thin sheets of aluminum. The results of the experiment indicated that the photographic plates were affected due to the radiation emitted by the uranium all in both the boxes.
Unit of Radioactivity
The unit of radioactivity is curie (Ci). It is the quantity of any radioactive substance which has a decay rate of 3.7 x 1010 disintegrations per second.
1 millicurie (mCi) = 3.7 x 107 disintegrations per sec.
1 microcurie (LC) = 3.7 x 1014” disintegrations per sec.
There is another unit called Rutherford (Rd) which is defined as the amount of a radioactive substance which undergoes 106disintegrations per second.
1 milli rutherford = 103 disintegrations per sec.
1 micro rutherford = 1 disintegration per sec.
Types of Radioactivity
It appears nothing is to happen with all these radioactive substances. They keep on emitting nuclear radiation it’s invisible. An easy way of detecting it is to use a Geiger Muller tube attached to a counter. There are three different types of nuclear radiation:
- Alpha Radiation.
- Beta Radiation.
- Gamma Radiation.
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All heavy elements from bismuth through uranium and a few of lighter elements have naturally occurring isotopes which possess the property of radioactivity. These isotopes have unstable nuclei and attain stability through the phenomenon of radioactivity. The property of disintegration of a radioactive material is independent of temperature, pressure and other external conditions.
Radioactivity is a nuclear phenomenon, i.e., the kind of intensity of the radiation emitted by any radioactive substance is absolutely the same whether the element is present as such or in any one of its compounds. The various experiments confirmed that the phenomenon of radioactivity does not depend on the orbital electrons but depends only on the composition of a nucleus.
The phenomena by which even light elements are made radioactive by artificial or induce method is called as artificial radioactivity. OR
The process in which a stable isotope is converted into a radioactive element by artificial transmutation is called artificial radioactivity. This was discovered by Irene Curie and F. Joliot in 1934. Example of artificial Radioactive:
2713Al + 10n → 2311Na + 42He
Application & Uses of Radioactivity
Modern industry uses radio-isotopes in a variety of ways to improve productivity and in some cases to gain information that cannot be obtained in any other way. Nuclear techniques are increasingly used in industry and environmental management. The rapid response of nuclear techniques results in reduced cost with increased product quality.
- Radioactive sodium is used to detect a clot in the human body. A different isotope of sodium is injected into the limb and its flow rate in the body is studied.
- Radioactive cobalt due to its gamma radiation is used to treat cancer and kill cancer cells
- The functioning of thyroid can be studied by iodine isotope.
- Sealed radioactive sources are used in industrial radiography gauging applications and mineral analysis.
- A short-lived radioactive material is used in flow tracing and mixing measurements in a nuclear plant.
- Gamma sterilization is used for medical supplies some bulk commodities and increasingly for food preservation.
- Agriculture radiation is also used in agriculture to sterilize (male pupae) an insect that could damage crops. These males are usually released to mate with females which produce unfertilized eggs. This is effective pest control as it reduces the population of insects.
- Another agricultural use of radioisotopes is the genetic modification of plants and animals. It is used to confer high resistance to pests and disease early maturing improved productivity high nutritional value climate resistance adaptation etc.
Effects of Radioactivity
Radioactive pollution is naturally occurring or artificially produced radioactive materials. Terrestrial radiations from natural Radio isotopes originate from the use of radioactive materials. These materials are used in the production of nuclear weapons nuclear fuel and electric power. The radioactive material used in atom bombs is very destructive the impact of radioactivity on man and environment.
- Radioactive wastes cause pollution the high-level products of nuclear wastes remain in the environment for hundreds of years leakage and nuclear reactors also cause large-scale environmental pollution the leakage might lead to several deaths.
- Radioactive rays possessing high-energy pollute air, water, and soil.
- All organisms are affected by radioactive pollution prolonged and frequent exposure to radioactive substances can cause cancer and leukemia and induce mutations. The mutated genes can persist in human animal and plant populations.
This is the most important factor need to know. Radiations produce ionization in the gases through which they are passed. This effect is used for quantitative measurement of radioactivity. The radiations cause a number of molecules of the gas to lose electrons and pass into positive ions. The electrons immediately become attached to the neutral molecules, thus making them negative ions.
The total ions of one sign are equal to the total ions of the other type. The rate of production of these ions is proportional to the intensity of radiation. The extent, to which a definite quantity of a gas is rendered a conductor by a radioactive substance, is a measure of the radioactive power of a radioactive substance. The apparatus used for this purpose is called electroscope.
Geiger-Muller counter is based on this effect. The ionization chamber consists of 90% argon and 10% ethyl alcohol vapor at 10 m.m. pressure. Due to ionization, a flow of current occurs, which is measured after amplification.
This is all about the basics of – What is radioactivity, definition, who discovered radioactivity, what are the uses, effect, Unit, Types of Radioactivity – natural, artificial, radioactive detector.
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Members of the mission of the Institute of Applied Ecology of North, the North-Eastern Federal University, and the Russian Geographical Society discovered the carcass of a female mammoth on Lyakhovsky Islands of the Novosibirsk archipelago, the Rossiyskaya Gazeta reports.
According to the scientists, the tissues of the animal are almost in perfect condition. The finding is so unique that it can produce an international sensation. The global scientific community can only envy the Russian paleontologists for their opportunity to explore such a priceless ice gem as Yakutia.
"It was established that the individual died when she was 50-60 years of age. Interestingly, fragments of mammoth muscle tissue have a natural red color of fresh meat. The lower part of the body was resting in nearly pure ice, and the upper part was found in the middle of the tundra," the head of the expedition, the chairman of the Mammoth Museum of the Institute of Applied Ecology of the North, Semyon Grigoriev said.
The researchers collected samples of the animal's blood in test tubes with a special preservative agent. The blood is dark; it was found in ice cavities below the belly of the animal. Surprisingly, when the researchers broke the cavities with a poll pick, the blood came flowing out. Temperatures at the time of excavations were only 10 degrees below zero Centigrade.
"One may assume that the blood of mammoths possessed some cryoprotective properties," said Semyon Grigoriev.
Specialists currently conduct all kinds of analyses and tests. Expedition members dedicated their amazing discovery to the 100th anniversary of the Yakutsk branch of the Russian Geographical Society, as well as to the 20th anniversary of the Institute of Applied Ecology of the North.
The US is going to ban exports of Iranian oil to the world market from November 5 of this year. In turn, Iran threatens to block the passage of oil tankers of the Gulf countries through the Strait of Hormuz
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969 | <urn:uuid:4e263795-cac8-4c86-b8e3-e7045dd4c47e> | 2.734375 | 444 | News Article | Science & Tech. | 34.838752 | 95,632,568 |
mremap man page
mremap — remap a virtual memory address
#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/mman.h> void *mremap(void *old_address, size_t old_size, size_t new_size, int flags, ... /* void *new_address */);
mremap() expands (or shrinks) an existing memory mapping, potentially moving it at the same time (controlled by the flags argument and the available virtual address space).
old_address is the old address of the virtual memory block that you want to expand (or shrink). Note that old_address has to be page aligned. old_size is the old size of the virtual memory block. new_size is the requested size of the virtual memory block after the resize. An optional fifth argument, new_address, may be provided; see the description of MREMAP_FIXED below.
If the value of old_size is zero, and old_address refers to a shareable mapping (see mmap(2) MAP_SHARED), then mremap() will create a new mapping of the same pages. new_size will be the size of the new mapping and the location of the new mapping may be specified with new_address; see the description of MREMAP_FIXED below. If a new mapping is requested via this method, then the MREMAP_MAYMOVE flag must also be specified.
In Linux the memory is divided into pages. A user process has (one or) several linear virtual memory segments. Each virtual memory segment has one or more mappings to real memory pages (in the page table). Each virtual memory segment has its own protection (access rights), which may cause a segmentation violation if the memory is accessed incorrectly (e.g., writing to a read-only segment). Accessing virtual memory outside of the segments will also cause a segmentation violation.
mremap() uses the Linux page table scheme. mremap() changes the mapping between virtual addresses and memory pages. This can be used to implement a very efficient realloc(3).
The flags bit-mask argument may be 0, or include the following flag:
By default, if there is not sufficient space to expand a mapping at its current location, then mremap() fails. If this flag is specified, then the kernel is permitted to relocate the mapping to a new virtual address, if necessary. If the mapping is relocated, then absolute pointers into the old mapping location become invalid (offsets relative to the starting address of the mapping should be employed).
- MREMAP_FIXED (since Linux 2.3.31)
This flag serves a similar purpose to the MAP_FIXED flag of mmap(2). If this flag is specified, then mremap() accepts a fifth argument, void *new_address, which specifies a page-aligned address to which the mapping must be moved. Any previous mapping at the address range specified by new_address and new_size is unmapped. If MREMAP_FIXED is specified, then MREMAP_MAYMOVE must also be specified.
If the memory segment specified by old_address and old_size is locked (using mlock(2) or similar), then this lock is maintained when the segment is resized and/or relocated. As a consequence, the amount of memory locked by the process may change.
On success mremap() returns a pointer to the new virtual memory area. On error, the value MAP_FAILED (that is, (void *) -1) is returned, and errno is set appropriately.
The caller tried to expand a memory segment that is locked, but this was not possible without exceeding the RLIMIT_MEMLOCK resource limit.
"Segmentation fault." Some address in the range old_address to old_address+old_size is an invalid virtual memory address for this process. You can also get EFAULT even if there exist mappings that cover the whole address space requested, but those mappings are of different types.
An invalid argument was given. Possible causes are:
- old_address was not page aligned;
- a value other than MREMAP_MAYMOVE or MREMAP_FIXED was specified in flags;
- new_size was zero;
- new_size or new_address was invalid;
- the new address range specified by new_address and new_size overlapped the old address range specified by old_address and old_size;
- MREMAP_FIXED was specified without also specifying MREMAP_MAYMOVE;
- old_size was zero and old_address does not refer to a shareable mapping (but see Bugs);
- old_size was zero and the MREMAP_MAYMOVE flag was not specified.
The memory area cannot be expanded at the current virtual address, and the MREMAP_MAYMOVE flag is not set in flags. Or, there is not enough (virtual) memory available.
This call is Linux-specific, and should not be used in programs intended to be portable.
Prior to version 2.4, glibc did not expose the definition of MREMAP_FIXED, and the prototype for mremap() did not allow for the new_address argument.
If mremap() is used to move or expand an area locked with mlock(2) or equivalent, the mremap() call will make a best effort to populate the new area but will not fail with ENOMEM if the area cannot be populated.
Before Linux 4.14, if old_size was zero and the mapping referred to by old_address was a private mapping (mmap(2) MAP_PRIVATE), mremap() created a new private mapping unrelated to the original mapping. This behavior was unintended and probably unexpected in user-space applications (since the intention of mremap() is to create a new mapping based on the original mapping). Since Linux 4.14, mremap() fails with the error EINVAL in this scenario.
brk(2), getpagesize(2), getrlimit(2), mlock(2), mmap(2), sbrk(2), malloc(3), realloc(3)
Your favorite text book on operating systems for more information on paged memory (e.g., Modern Operating Systems by Andrew S. Tanenbaum, Inside Linux by Randolf Bentson, The Design of the UNIX Operating System by Maurice J. Bach)
This page is part of release 4.16 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
getrlimit(2), ioctl_userfaultfd(2), memusage(1), mmap(2), mmap2(2), remap_file_pages(2), stress-ng(1), syscalls(2), userfaultfd(2). | <urn:uuid:3b8b1b57-7764-4519-a395-20cee716f065> | 2.984375 | 1,516 | Documentation | Software Dev. | 45.927477 | 95,632,586 |
posted by jen
A student determines the cobalt(II) content of a solution by first precipitating it as cobalt(II) hydroxide, and then decomposing the hydroxide to cobalt(II) oxide by heating. How many grams of cobalt(II) oxide should the student obtain if her solution contains 46.0 mL of 0.561 M cobalt(II) nitrate?
Co(NO3)2 ==> Co(OH)2 --> CoO
mols Co(NO3)2 = M x L = ?
mols CoO = mols Co(OH)2 = mols Co(NO3)2
grams CoO = mols x molar masss
how many grams is that?
sorry i am stuck on many questions that's why used diff names. i need help and be grateful if u can help but most questions I don't know how to work it out.
What is confusing about this? And I suggest you pick any name and stick to it. It helps us help you if you do that.
For this problem all you need is two steps. M x L = mols and mol x molar mass = grams.
i don't know much about chemitry that's why its confusing
I don't know how to calculate them
Step 1. Pick out M x L. That's in the problem. M is 0.561; L is 0.046 L.
M x L = ? you can do on your calculator.
Step 2. grams = mols x molar mass
You have mols from the calculator. Multiply that by the molar mass of CoO. You can calculate that from the periodic table. Co = about 58.93 and O is 16 so 58.93 + 16 = ? | <urn:uuid:780e28eb-280f-46dc-9596-89f4ac358691> | 2.828125 | 380 | Q&A Forum | Science & Tech. | 100.790172 | 95,632,600 |
By Stephen Bucaro
user error, or some other cause. The try-catch construct is a way to determine the
cause of an error. Shown below is the basic code for a try-catch construct.
// some code
// code to run if try block fails
Within the try block is the code to be tested for errors while it is being executed.
If an error occurs in the code within the try block, the catch method receives
the error object. The error object has two properties, the number and the description.
Shown below is code that might be placed within the catch block.
// some code
document.write ("Number: ");
document.write (" Description: ");
If you are not sure where an error is coming from, you can use the reverse-binary trouble shooting method.
Start by placing a large block of code in the try section. Then place a smaller block of code within
the try section (about half at a convenient point in the code). Keep placing progressively smaller
blocks of code (about half at a convenient point in the code) within the try section, until you've
isolated the error down to the problem line.
More Java Script Code:
• The switch / case Structure
• The while Loop
• Determine Absolute Value
• The Screen Object
• Java Script Data Types
• Java Script Trigonometric Methods
• Search and Replace Strings
• Access Web Page Elements With getElementById
• Window Object Properties and Methods | <urn:uuid:d3dcce6f-982a-4227-9dc6-f7053501782a> | 3.25 | 314 | Tutorial | Software Dev. | 51.246154 | 95,632,620 |
Last month at a conference in Paris, 195 countries adopted a landmark agreement on how to respond to the Earth’s changing climate. The agreement included an ambitious goal to prevent the average global temperature from rising more than 1.5°C (2.7°F) above pre-industrial levels.
Prior to the conference, most of the countries had submitted pledges outlining how much they intended to reduce their emissions of heat-trapping pollution beginning in 2020. They also agreed to assess and revise their national plans every five years, an essential step given that the existing pledges are insufficient to achieve the 1.5-degree goal.
The challenges laid out in the “Paris Declaration” can be addressed with aggressive investments in renewable energy technologies. But if we fail to act quickly, we may also need to evaluate strategies for artificially cooling the planet until our transition away from fossil fuel begins to help.
Since the industrial revolution, the average global temperature has increased by about 1°C (1.8°F). The collective actions of several generations resulted in the release of so much heat-trapping pollution that it exceeded the capacity of the Earth’s oceans and forests to absorb it. The surplus pollution from each year remains in the atmosphere, and commits humanity to some amount of climate change for as long as it takes the planet to work through the accumulated excess.
Even if we eliminated all human-induced sources of this pollution right now, the globe would continue to warm for at least the next 50 years.
Our decisions about how to respond to the threat of climate change will only affect how much warmer the planet will get, and how long it will take to return to its natural temperature for future generations. The good news is that most scientists believe it is still possible to reverse climate change, and the required transition can be made gradually over several decades.
Doug Arent is a scientist at the National Renewable Energy Laboratory (NREL) in Golden. He was born and raised in Colorado, and remembers when Jimmy Carter established what was then called the Solar Energy Research Institute in 1977.
“I’ve focused my whole career on clean energy and sustainability,” he says. Arent watched intently on Nov. 29 when, on the opening day of the climate conference in Paris, President Obama announced that 20 countries including the United States would double their public funding for renewable energy research and development over the next five years. At the same time, Microsoft cofounder Bill Gates introduced the “Breakthrough Energy Coalition,” a private group that promised to invest billions of dollars of their own money in renewable energy technologies.
A company in Arizona is developing one example of the next-generation renewable energy that might benefit from this expansion in public and private investment. REhnu Solar manufactures large mirrors that track the sun and concentrate its light onto small solar cells that are extremely efficient but relatively expensive.
“That’s a technology that NREL has been involved with for decades,” Arent says. Each module can produce as much electricity as three rooftop solar panels, but it also functions as a solar water heater by recycling heat generated by the concentrated sunlight.
The current design mounts up to eight mirrors on each sun-tracking platform. These high-efficiency solar cells are constantly improving, so the modules at the focus of each mirror are designed to be replaceable. Using this technology, it is easy to imagine large areas of the Arizona desert converted into inexpensive solar electricity farms, displacing power plants that burn fossil fuel.
Ideally, we will transition away from fossil fuel quickly enough to avoid the most serious consequences of climate change. But considering the extreme weather events that have already resulted from the current level of warming, we might also want a backup plan.
Simone Tilmes is a scientist at the National Center for Atmospheric Research (NCAR), where she studies the impacts of “climate engineering” — strategies that artificially counter the warming effect of excess heat-trapping pollution in the atmosphere. The idea of climate engineering emerged from observations of volcanic eruptions, which push tiny particles into the upper atmosphere that have a temporary cooling effect on the planet. Essentially, these particles prevent some of the incoming sunlight from reaching the surface of the Earth.
Tilmes and her colleagues use computer models to examine how the climate system might react to a slightly fainter sun. She emphasizes that such measures should be seen as transitional strategies to help regulate the temperature of the planet in the short-term. But they aren’t a substitute for addressing the root causes of the problem.
Another concept for engineering the climate involves artificially enhancing the capacity of the ocean to absorb heat-trapping pollution. Small-scale experiments have already been performed, seeding the ocean with iron to stimulate the growth of microscopic plants that capture carbon dioxide and release oxygen.
A more extreme option proposes to release genetically engineered bacteria into the oceans, which have been specifically designed to absorb global warming gases. All of these strategies raise the questions of who will decide which options — if any — should be used, and what level of climate disruption would justify such an emergency response.
There is now a broad consensus that the Paris agreement is a solid first step to begin addressing climate change. With public and private forces aligned to kickstart the transition to renewable energy, there is hope that we can avoid dangerous levels of warming and create a sustainable future for the next generation. But it is comforting to know that if the transition is too slow, or if the projections are wrong, scientists are also developing options for a climate intervention. | <urn:uuid:7822b55d-f735-4f53-8560-7018bce05dcb> | 3.59375 | 1,135 | Nonfiction Writing | Science & Tech. | 30.256071 | 95,632,630 |
+44 1803 865913
Large-scale natural catastrophes are environmental phenomena. Numerous studies in recent years have concluded that the frequency of occurrence of such natural disasters have been incereasing. leading to an enhanced risk of very considerable human and economic losses and the widespread destruction and pollution of habitats, settlements and infrastructure. In 2001 over 650 natural disasters happened around the globe with economic losses exceeding $35 billion. 2004 ended with the South East Asian tsunami on 26th December with its huge toll on life and local economics and this demonstrated that the efffects of such disasters are most keenly felt in poorer or developing regions.
The problem of natural disaster prediction and the implementation of environmental monitoring systems to receive, store and process the information necessary for solutions of specific problems in this area , have been analysed by the three authors of this book, all of whom are internationally respected experts in this field.
From the reviews: "This mammoth book gathers material the authors believe will be helpful in predicting the scale of future natural disasters. ! The authors have gathered a wealth of information and we welcome that. The book is a valuable research source." (M. Dane Picard, American Association of Petroleum Geologists, Vol. 91 (6), June, 2007)
Introduction 1. Statistics of natural disasters.- 2. Natural disasters and survivability of ecological systems.- 3. Biocomplexity as a predictor of natural disasters.- 4. Natural disasters and mankind.- 5. Monitoring of natural disasters.- 6. Forecast of natural disasters.- 7. Natural catastrophes in the Aral Sea zone.- 8. Natural disasters as components of global ecodysamics.- 9. Interactivity of the climate and natural disasters.
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tf.string_to_hash_bucket_strong( input, num_buckets, key, name=None )
Defined in generated file:
See the guide: Strings > Hashing
Converts each string in the input Tensor to its hash mod by a number of buckets.
The hash function is deterministic on the content of the string within the
process. The hash function is a keyed hash function, where attribute
defines the key of the hash function.
key is an array of 2 elements.
A strong hash is important when inputs may be malicious, e.g. URLs with
additional components. Adversaries could try to make their inputs hash to the
same bucket for a denial-of-service attack or to skew the results. A strong
hash prevents this by making it difficult, if not infeasible, to compute inputs
that hash to the same bucket. This comes at a cost of roughly 4x higher compute
string. The strings to assign a hash bucket.
>= 1. The number of buckets.
key: A list of
ints. The key for the keyed hash function passed as a list of two uint64 elements.
name: A name for the operation (optional).
Tensor of type | <urn:uuid:7ae0406e-a259-4317-8bf9-7c490d8bfcda> | 2.546875 | 267 | Documentation | Software Dev. | 67.853086 | 95,632,714 |
If you're searching for Facts about Moths for Kids to help with your children's homework, to use as a website resource for your classroom, or to use in your lesson plan for your students, the information below can help.
- Most of this order are moths; there are thought to be about 160,000 species of moth (nearly ten times the number of species of butterfly), with thousands of species yet to be described.
- Sometimes the name “Heterocera” is used for moths while the term “Rhopalocera” is used for butterflies to formalize the popular distinction; these, however, have no taxonomic validity.
- Many attempts have been made to subdivide the Lepidoptera into groups such as the Microlepidoptera and Macrolepidoptera, Frenatae and Jugatae, or Monotrysia and Ditrysia.
- Also, both their larvae are similar to coleoptera larvae (beetle).
- The Modern English word “moth” comes from Old English “moððe” from Common Germanic.
- Perhaps its origins are related to the Old English “maða” meaning “maggot” or from the root of “midge” which until the 16th century was used mostly to indicate the larva, usually in reference to devouring clothes.
- The study of butterflies and moths is known as lepidoptery, and biologists that specialize in either are called lepidopterists.
- The latter has given rise to the term “mother” for someone who engages in this activity – sometimes written with a hyphen (moth-er) to distinguish it from the more common word of the same spelling.
- When it comes out of the cocoon, it is a fully grown moth with wings.
- Some moth caterpillars dig holes in the ground, and they will live in the hole until they are ready to turn into a fully grown moth.
- Moths, and particularly their caterpillars, are a major agricultural pest in many parts of the world.
- In tropical and subtropical climates, the diamondback moth (Plutella xylostella) is perhaps the most serious pest of brassicaceous crops.
- Several moths in the family Tineidae are commonly regarded as pests because their larvae eat fabric such as clothes and blankets made from natural proteinaceous fibers such as wool or silk.
- The most notable of these is the silkworm, the larva of the domesticated moth Bombyx mori.
- There are several species of Saturniidae that are also farmed for their silk, such as the Ailanthus moth, the Chinese Oak Silkmoth, the Assam Silkmoth, and the Japanese Silk Moth.
- Most like the Luna, Polyphemus, Atlas, Prometheus, Cercropia, and other large moths do not have mouths.
- Moths frequently appear to circle artificial lights, although the reason for this behavior remains unknown.
- Celestial objects are so far away, that even after traveling great distances, the change in angle between the moth and the light source is negligible; further, the moon will always be in the upper part of the visual field or on the horizon.
- When a moth encounters a much closer artificial light and uses it for navigation, the angle changes noticeably after only a short distance, in addition to being often below the horizon.
- Baculoviruses are parasite double-stranded DNA insect viruses that are used mostly as biological control agents.
- Most baculovirus isolates have been obtained from insects, in particular from Lepidoptera.
- There is evidence that ultrasound in the range emitted by bats causes flying moths to make evasive maneuvers because bats eat moths.
Below you will find additional resources and facts for kids related to the article "Facts about Moths for Kids". | <urn:uuid:f0be4b04-f5aa-4276-a432-c902b8c7996e> | 3.59375 | 840 | Knowledge Article | Science & Tech. | 33.726892 | 95,632,754 |
Oct 2, 2012 | Fabio Costa
This press release is available in German.
One of the most deeply rooted concepts in science and in our everyday life is causality; the idea that events in the present are caused by events in the past and, in turn, act as causes for what happens in the future. If an event A is a cause of an effect B, then B cannot be a cause of A. Now theoretical physicists from the University of Vienna and the Université Libre de Bruxelles have shown that in quantum mechanics it is possible to conceive situations in which a single event can be both, a cause and an effect of another one. The findings will be published this week in Nature Communications.
Although it is still not known if such situations can be actually found in nature, the sheer possibility that they could exist may have far-reaching implications for the foundations of quantum mechanics, quantum gravity and quantum computing.
Causal relations: who influences whom
In everyday life and in classical physics, events are ordered in time: a cause can only influence an effect in its future not in its past. As a simple example, imagine a person, Alice, walking into a room and finding there a piece of paper. After reading what is written on the paper Alice erases the message and leaves her own message on the piece of paper. Another person, Bob, walks into the same room at some other time and does the same: he reads, erases and re-writes some message on the paper. If Bob enters the room after Alice, he will be able to read what she wrote; however Alice will not have a chance to know Bob's message. In this case, Alice's writing is the "cause" and what Bob reads the "effect".
Quantum violation of causal order
As long as only the laws of classical physics are allowed, the order of events is fixed: either Bob or Alice is first to enter the room and leave a message for the other person. When quantum mechanics enters into play, however, the picture may change drastically. According to quantum mechanics, objects can lose their well-defined classical properties, such as e.g. a particle that can be at two different locations at the same time. In quantum physics this is called a "superposition". Now an international team of physicists led by Caslav Brukner from the University of Vienna have shown that even the causal order of events could be in such a superposition. If - in our example - Alice and Bob have a quantum system instead of an ordinary piece of paper to write their messages on, they can end up in a situation where each of them can read a part of the message written by the other. Effectively, one has a superposition of two situations: "Alice enters the room first and leaves a message before Bob" and "Bob enters the room first and leaves a message before Alice".
"Such a superposition, however, has not been considered in the standard formulation of quantum mechanics since the theory always assumes a definite causal order between events", says Ognyan Oreshkov from the Université Libre de Bruxelles (formerly University of Vienna). "But if we believe that quantum mechanics governs all phenomena, it is natural to expect that the order of events could also be indefinite, similarly to the location of a particle or its velocity", adds Fabio Costa from the University of Vienna.
The work provides an important step towards understanding that definite causal order might not be a mandatory property of nature. "The real challenge is finding out where in nature we should look for superpositions of causal orders", explains Caslav Brukner from the Quantum Optics, Quantum Nanophysics, Quantum Information group of the University of Vienna.
"Quantum correlations with no causal order"
Ognyan Oreshkov, Fabio Costa, Caslav Brukner. Nature Communications. | <urn:uuid:1d9b78d8-331f-4f55-a7d5-68f68ad2da54> | 3.453125 | 793 | News (Org.) | Science & Tech. | 36.049426 | 95,632,778 |
Eumetazoa (Greek: εὖ [eu], well + μετά [metá], after + ζῷον [zóon], animal) or Diploblasts, or Epitheliozoa, or Histozoa are a proposed basal animal clade as sister group of the Porifera. The basal Eumetazoan clades are the Ctenophora and the ParaHoxozoa. Placozoa is now also seen as an Eumetazoan in the Parahoxozoa.
Several other extinct or obscure life forms, such as Iotuba and Thectardis appear to have emerged in the group. Characteristics of eumetazoans include true tissues organized into germ layers, the presence of neurons, and an embryo that goes through a gastrula stage.
Some phylogenists have speculated the sponges and eumetazoans evolved separately from single-celled organisms, which would mean that the animal kingdom does not form a clade (a complete grouping of all organisms descended from a common ancestor). However, genetic studies and some morphological characteristics, like the common presence of choanocytes, support a common origin.
Traditionally, Eumetazoans are a major group of animals in the Five Kingdoms classification of Lynn Margulis and K. V. Schwartz, comprising the Radiata and Bilateria — all animals except the sponges. When treated as a formal taxon Eumetazoa is typically ranked as a subkingdom. The name Metazoa has also been used to refer to this group, but more often refers to the Animalia as a whole. Many classification schemes do not include a subkingdom Eumetazoa.
It is divided into Grade Radiata and Grade Bilateria.
Grade Radiata includes only Phylum Coelentrata also called Phylum Cnidaria.
Grade Bilateria includes bilateral symmetry that is the body of these animals can be cut into two identical halves in one plane that is they have left and right side of the body.
All the phyla from Platyhelminthes to Chordates are included in Grade Bilateria.
A widely accepted hypothesis, based on molecular data (mostly 18S rRNA sequences), divides Bilateria into four superphyla: Deuterostomia, Ecdysozoa, Lophotrochozoa, and Platyzoa (sometimes included in Lophotrochozoa). The last three groups are also collectively known as Protostomia.
However, some skeptics emphasize inconsistencies in the new data. The zoologist Claus Nielsen argues in his 2001 book Animal Evolution: Interrelationships of the Living Phyla for the traditional divisions of Protostomia and Deuterostomia.
It has been suggested that one type of molecular clock and one approach to interpretation of the fossil record both place the evolutionary origins of eumetazoa in the Ediacaran. However, the earliest eumetazoans may not have left a clear impact on the fossil record and other interpretations of molecular clocks suggest the possibility of an earlier origin. The discoverers of Vernanimalcula describe it as the fossil of a bilateral triploblastic animal that appeared at the end of the Marinoan glaciation prior to the Ediacaran Period, implying an even earlier origin for eumetazoans.
- ^ Lankester, Ray (1877). Notes on the Embryology and classification of the Animal kingdom: comprising a revision of speculations relative to the origin and significance of the germ-layers. Quartely Journal of Microscopical Science (N.S.), No. 68: 399–454.
- ^ Beklemishev, V.L. The basis of the comparative anatomy of the invertebrates [Основы сравнительной анатомии беспозвоночных]. 1st ed., 1944; 2nd ed., 1950; 3rd ed. (2 vols.), 1964. English translation, 1969, . Akademia Nauk, Moscow, Leningrad.
- ^ Ax, Peter (2012-12-06). Multicellular Animals: A new Approach to the Phylogenetic Order in Nature. Springer Science & Business Media. ISBN 9783642801143.
- ^ Feuda, Roberto; Dohrmann, Martin; Pett, Walker; Philippe, Hervé; Rota-Stabelli, Omar; Lartillot, Nicolas; Wörheide, Gert; Pisani, Davide. "Improved Modeling of Compositional Heterogeneity Supports Sponges as Sister to All Other Animals". Current Biology. doi:10.1016/j.cub.2017.11.008.
- ^ Pisani, Davide; Pett, Walker; Dohrmann, Martin; Feuda, Roberto; Rota-Stabelli, Omar; Philippe, Hervé; Lartillot, Nicolas; Wörheide, Gert (15 December 2015). "Genomic data do not support comb jellies as the sister group to all other animals". Proceedings of the National Academy of Sciences. 112 (50): 15402–15407. Bibcode:2015PNAS..11215402P. doi:10.1073/pnas.1518127112. PMC 4687580 . PMID 26621703.
- ^ Simion, Paul; Philippe, Hervé; Baurain, Denis; Jager, Muriel; Richter, Daniel J.; Franco, Arnaud Di; Roure, Béatrice; Satoh, Nori; Quéinnec, Éric (3 April 2017). "A Large and Consistent Phylogenomic Dataset Supports Sponges as the Sister Group to All Other Animals". Current Biology. 27 (7): 958–967. doi:10.1016/j.cub.2017.02.031.
- ^ Giribet, Gonzalo (1 October 2016). "Genomics and the animal tree of life: conflicts and future prospects". Zoologica Scripta. 45: 14–21. doi:10.1111/zsc.12215.
- ^ Laumer, Christopher E.; Gruber-Vodicka, Harald; Hadfield, Michael G.; Pearse, Vicki B.; Riesgo, Ana; Marioni, John C.; Giribet, Gonzalo (2017-10-11). "Placozoans are eumetazoans related to Cnidaria". bioRxiv: 200972. doi:10.1101/200972.
- ^ Martindale, Mark Q.; Kourakis, Matthew J. "Hox clusters: Size doesn't matter". Nature. 399 (6738): 730–731. Bibcode:1999Natur.399..730M. doi:10.1038/21530.
- ^ Philippe H, Derelle R, Lopez P, et al. (April 2009). "Phylogenomics revives traditional views on deep animal relationships". Curr. Biol. 19 (8): 706–12. doi:10.1016/j.cub.2009.02.052. PMID 19345102.
- ^ Systema Naturae 2000 Taxon: Subkingdom Eumetazoa — retrieved February 2, 2006
- ^ Peterson KJ, Butterfield NJ (July 2005). "Origin of the Eumetazoa: testing ecological predictions of molecular clocks against the Proterozoic fossil record". Proc. Natl. Acad. Sci. U.S.A. 102 (27): 9547–52. Bibcode:2005PNAS..102.9547P. doi:10.1073/pnas.0503660102. PMC 1172262 . PMID 15983372.
- ^ Blair, J. E.; Hedges, S. B. (March 2005). "Molecular clocks do not support the Cambrian explosion". Molecular Biology and Evolution. 22 (3): 387–390. doi:10.1093/molbev/msi039. PMID 15537810.
- ^ Chen, J.-Y.; Bottjer, D.J.; Oliveri, P.; Dornbos, S.Q.; Gao, F.; Ruffins, S.; Chi, H.; Li, C.-W.; Davidson, E.H.; et al. (9 July 2004). "Small bilaterian fossils from 40 to 55 million years before the Cambrian". Science. 305 (5681): 218–222. Bibcode:2004Sci...305..218C. doi:10.1126/science.1099213. PMID 15178752.
- Bilateria. Tree of Life web project, US National Science Foundation. 2002. 6 January 2006.
- Invertebrates and the Origin of Animal Diversity
- Evers, Christine A., Lisa Starr. Biology:Concepts and Applications. 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3.
- TRICHOPLAX ADHAERENS (PLACOZOA TYPE) St. Petersburg. 2005
- Metazoa: the Animals
- Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla, 2nd edition, 563 pp. Oxford Univ. Press, Oxford. ISBN 0-19-850681-3
- Borchiellini, C. Manuel, M., Alivon, E., Boury-Esnault N., Vacelet, J., Le-Parco, Y. 2001. Journal of Evolutionary Biology 14 (1): 171–179.
- Peterson, Kevin J., McPeek, Mark A., & Evans, David A.D. 2005. Tempo & mode of early animal evolution: inferences from rocks, Hox, & molecular clocks. Paleobiology 31(2, Supplement): 36–55. | <urn:uuid:2fc98e80-5581-48e4-8b5e-1b3a6b49b731> | 3.796875 | 2,174 | Knowledge Article | Science & Tech. | 58.717986 | 95,632,796 |
In order to protect themselves from harmful substances, cells need to keep the mitochondria – the boiler room, so to speak – shipshape. Up to now, it was unclear whether this housekeeping work involves sorting out defective proteins when they digest mitochondria.
Yeast cells digest their mitochondria in long-time cultures. This process is called mitophagy. Proteins that are digested at a different speed are marked with a fluorescent dye. (© Joern Dengjel)
Dr. Joern Dengjel from the Center for Biological Systems Analysis (ZBSA), Freiburg Institute for Advanced Studies (FRIAS), and the Cluster of Excellence BIOSS Centre for Biological Signalling Studies of the University of Freiburg has now discovered in collaboration with researchers from the Hebrew University in Jerusalem, Israel, that the proteins are sorted out during the constant fusion and fission of mitochondria. The team published their findings in the journal Nature Communications.
The process of mitophagy, in which tiny digestive bubbles surround the mitochondria, serves to recycle waste for the cell. Damaged proteins can no longer carry out their function correctly and need to be broken down. Errors in the digestion of mitochondria appear in old age and in the case of neurodegenerative diseases like Parkinson’s and Alzheimer’s. A better understanding of mitophagy could be the key to counteracting the faulty degradation of cellular components, potentially enabling researchers to develop new therapies for neurodegenerative diseases.
In contrast to bacteria, yeast cells posses mitochondria and are also easy to grow in the laboratory. The researchers used yeasts to observe the processes of mitophagy. Dr. Hagai Abeliovich from the Hebrew University developed a new method for making yeast cells digest mitochondria. Currently, researchers accomplish this by placing stress on the cells with chemicals.
With the new method, yeast cells in long-term cultures begin digesting mitochondria of their own accord – as soon as they have used up all available nutrients. During mitophagy Dengjel succeeded in measuring whether all proteins inside the mitochondria were broken down at the same speed. Indeed, the cell broke down some proteins more quickly than others. When he observed the cells under a fluorescence microscope, he ascertained that the marked proteins in the mitochondria also behaved differently. They appear to be sorted.
The rules by which the sorting is carried out are as yet unknown. However, the researchers demonstrated that mitochondrial dynamics are involved: Mitochondria fuse and divide constantly, forming a network in the process. Genetically modified yeasts that lack these dynamics but form small, round mitochondria exhibit no sorting of the proteins. “The damaged proteins are sorted slowly into an area of the network with each fusion and fission. This mitochondrion is marked and broken down,” says Dengjel. In other words, mitophagy plays the role of garbage collector, separating and recycling waste for the cell. Now Dengjel wants to find out what characterizes the proteins that are sorted out.
Dr. Jörn Dengjel | Universität Freiburg
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
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Proteins That Can Take the Heat
News Mar 31, 2017 | Original story from Rensselaer Polytechnic Institute
Rensselaer Polytechnic Institute
Ancient proteins may offer clues on how to engineer proteins that can withstand the high temperatures required in industrial applications, according to new research published in the Proceedings of the National Academy of Science. Researchers used experiments to examine critical differences between 15 proteins from the thioredoxin family, including seven extinct protein sequences that date back more than 4 billion years and were resurrected using ancestral sequence reconstructions.
“In industrial applications, proteins could do some of the work of chemicals with less energy and less toxicity, but they have to be able to withstand the higher temperatures of industrial processes,” said George Makhatadze, a Constellation Professor of Biocomputation and Bioinformatics and member of the Center for Biotechnology and Interdisciplinary Studies at Rensselaer Polytechnic Institute. “This research suggests that ancestral reconstruction methods can be used to design proteins that unfold more slowly, offering greater utility, at higher temperatures.”
The experiments showed that the difference in stability between proteins from the same family is caused primarily by differences in the energy required to unfold the proteins, a finding that upholds a long-held theory known as the “principle of minimal frustration,” proposed by physicists about 30 years ago.
Proteins are molecular chains in which each link is one of 20 amino acids. Once the chain is assembled, various forces along its length interact, causing the string to twist and turn, and ultimately fold into a three-dimensional shape. The protein can only perform its function when properly folded. Most proteins remain folded within a set range of temperature, pH, or pressure conditions, breaking down when subjected to conditions outside of these tolerances.
Not all the rules that govern protein folding are known, and Makhatadze wanted to understand how proteins within the same family, with similar structure, are able to perform the same life-sustaining function in vastly different thermal environments. Thioredoxins, for example, are present in all organisms, from those that live near boiling hydrothermal vents to frigid Arctic waters.
One known rule helps to explain why there are an astronomical number of sequences possible for proteins with hundreds and even thousands of links, but only a small subset of those possible sequences are found in nature. This rule, the principle of minimal frustration, posits that nature chooses only those sequences that fold most efficiently, reducing undesired interactions between amino acids and producing faster, less frustrated, folding patterns.
To be consistent with the principle of minimal frustration, Makhatadze said, proteins with similar structure but different thermodynamic stability should fold along the same efficient pattern, but those with greater ability to tolerate heat should take longer to unfold. Experiments, undertaken first with eight modern-day thioredoxins, proved the hypothesis correct.
“We tested the folding rates among thioredoxins, a family of proteins that perform the same function but — because they function in different thermal conditions — must be different in terms of thermodynamics,” said Makhatadze. “And what we observed is that for these proteins, they indeed fold with the same rate, but they unfold with a different rate — which is what we predicted.”
In the next step, researchers tested extinct versions of thioredoxins that had been obtained using a technique called ancestral sequence reconstruction. The extinct versions unfolded more slowly than modern versions, in some case folding 3,000 times more slowly than a modern counterpart.
“Here we have two versions of a protein from the same family and one unfolded in seven seconds, the other in six hours,” Makhatadze said. “That means you can get useful function from the protein for six hours versus seven seconds. This shows that ancestral sequence reconstruction may be a route to proteins that are more stable at high temperatures.”
The finding is supported by previously published research and geochemical data which indicates that Earth and its oceans were hotter in the ancient past.
“Previous research supports the finding that older proteins are more stable, but this new research shows these ancient proteins are more stable because they unfold more slowly,” Makhatadze said.
“Evidence for the principle of minimal frustration in the evolution of protein folding landscapes” can be found using the digital object identifier doi: 10.1073/pnas.1613892114. The research was supported by the National Science Foundation. Makhatadze was joined in the research by Fanco Tzul, a postdoctoral research associate, and graduate student Daniel Vasilchuk.
This article has been republished from materials provided by Rensselaer Polytechnic Institute. Note: material may have been edited for length and content. For further information, please contact the cited source.
Mallamace et al. "Energy landscape in protein folding and unfolding" PNAS 2017 doi: 10.1073/pnas.1524864113.
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Peering Inside ProteinsNews
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This ATM Dispenses AntioxidantsNews
Antioxidants are molecules that counteract the damage to our bodies from harmful products of normal cells called reactive oxygen species (ROS). Now, research has found that a protein called ATM can sense the presence of ROS and responds by sounding the alarm to trigger the production of antioxidants.READ MORE | <urn:uuid:20fc76d1-76fc-4b9c-a343-538dfc2e2869> | 3.921875 | 1,228 | Truncated | Science & Tech. | 25.605828 | 95,632,801 |
How to Land Safely Back on the Moon
A hazard-detection system promises safe landings for next-generation lunar explorers.
Engineers at the Charles Stark Draper Laboratory in Cambridge, MA, are developing a guidance, navigation, and control system for lunar landings that includes an onboard hazard-detection system able to spot craters, slopes, and rocks that could be dangerous to landing craft. In the Apollo missions of 40 years ago, astronauts steered the lander to a safe spot by looking out the window; the lander itself “had no eyes,” says Eldon Hall, a retired Draper engineer and one of the original electronics designers for Apollo’s navigation computer.
That meant there were some close calls with Apollo, says Tye Brady, the technical director for lunar landing at Draper, who demonstrated his team’s automated-landing and hazard-avoidance technology at last week’s celebration of the 40th anniversary of Apollo 11. “They were really close,” Brady says, “and one- to two-meter craters are deadly. You don’t see them till the last minute.” Apollo 11 astronaut Neil Armstrong had to steer past a field of rocks that didn’t show up on any recon photos beforehand, and Apollo 14 landed at a precarious tilt with one footpad resting about a meter away from a crater.
The new navigation and guidance system is being developed for NASA’s Altair lunar lander, which is scheduled to land on the moon by 2020 as part of the Constellation program. The project is headed by NASA’s Johnson Space Center, with support from other NASA research facilities in addition to Draper Laboratory. The Jet Propulsion Laboratory recently completed a field test of the sensors and mapping algorithms, and it plans to begin full systems tests in May 2010.
Brady says that the best image resolution today, such as the cameras on the orbiter now circling and photographing the moon, cannot resolve smaller holes or boulders at projected landing sites, even in smooth, well-lit areas–which aren’t the targets for NASA’s future landings. Altair aims to land capably at any site on the moon’s surface, and the lunar terrain will vary. For that, Brady says, “you need real-time hazard detection” to adjust as you go.
Draper’s system will use LIDAR laser technology to scan an area for hazards like craters or rocks before the lander touches down on the moon’s surface. Raw data from LIDAR is processed and assembled into a 3-D map of the moon’s surface, using algorithms developed by the Jet Propulsion Laboratory. One advantage of using LIDAR is that “it’s the only type of sensor that measures the 3-D shape of what’s on the ground at high resolution and from high altitude,” says Andrew Johnson, the JPL lead for the hazard-detection system. That allows the system to build a terrain and elevation map of potential landing sites onboard the spacecraft, but from high enough up that there is time to respond to obstacles or craters at the landing site.
Once the map is built, the system designates safe sites based on factors like the tilt angle of the surface, the distance and fuel cost to get to a site, the position of the lander’s footpads, and the crew’s margin for safe distance from hazards. Based on that information, the navigation system presents astronauts with a prioritized list of three to four safe landing sites. The astronauts can then designate any of the sites as first choice, or if they are incapacitated, the system will navigate the lander automatically to the first site on its list.
The ability to land autonomously will enable both crewed and robotic missions to land safely, Brady says (while Apollo’s lunar module had an automatic landing mode, it was never used). In addition to NASA’s Altair, the system could be integrated into vehicles landing on near-Earth asteroids, Mars, and other planets, or used with other lunar vehicles built by private groups.
Another advantage of using LIDAR, Johnson says, is that it works under any lighting conditions. To deal with light at the moon’s equator–where a “day” is equivalent to 14 Earth days, and a “night” lasts 14 Earth nights–Apollo missions had to be timed exactly, with just one launch opportunity per month, so NASA could control the craft’s exposure to light and heat. But because lighting conditions are more varied and extreme at the moon’s poles, with patches of light and dark from the shadows of mountains and deep craters, it will be difficult for astronauts to see to navigate. LIDAR allows the craft to “land at night, or in shadowed regions, because the light is provided by the LIDAR sensor, not the sun,” Johnson says. With real-time hazard detection, he says, the launch and landing limitations of Apollo won’t apply to future missions.
The challenge for a landing system, says Brady, is getting everything to happen in about 120 seconds, including hazard-detection scans to get the data, human interaction for site approval, and then hazard-avoidance maneuvers and touchdown. His team has developed a simulator to create realistic image maps of the moon’s surface, in addition to using computer code from NASA for the guidance and navigation portion of the system. So far, about 20 astronauts have sampled the Draper simulation. “They’re good at going slow and easy, and they’re very patient,” Brady says. “They do a good job relying on the system.” That’s a long way from the early days when the Apollo astronauts “wanted to fly the whole thing themselves,” Hall says.
The Draper team continues to develop high-fidelity models of LIDAR and terrain maps, while coordinating with NASA’s crew office to determine the best way to display information for astronauts. They aim to have the technology ready by 2012.
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:7710eddd-40c3-4cd4-87aa-be25a53a6678> | 3.65625 | 1,317 | News Article | Science & Tech. | 40.976496 | 95,632,802 |
Poor baby snake!
How would you name a snake?
It’s probably not what you think it is.
Mother love — with fangs.
Yessss, thissss issss good resssssearch.
“This really is the worst-case scenario,” said one scientist.
Some pretty bad news for European snakes.
You may not like snakes, but they play an important role in ecosystems — and they’re in trouble.
Snakes just got even more impressive.
You often have to look in peculiar (and dangerous) places for innovation.
Always go for a meal before you fossilize.
Researchers from Portugal believe they finally have the answer.
Visitors to the Alice Springs Reptile Centre, home to the largest reptile display in Central Australia, were stunned by the sight of a snake who spun in circles countless times in a ring made from its own skin.
Eelume company developed a snake-like robot for underwater maintenance tasks. The deceptively simple robots could drastically reduce operating costs for deep sea rigs.
An “absolutely exquisite” fossil of a juvenile snake with limbs has been discovered by English paleontologists in Brazil. The fossil dates back from the early Cretaceous, 110 million years ago, and is the oldest evidence of a definitive snake.
A new analysis conducted by Yale researchers revealed that the first snakes may have actually evolved on land, not in water. These proto-snakes were likely night hunters that might have had hind legs and even toes. “We generated the first comprehensive reconstruction of what the ancestral snake was like,” said Allison Hsiang, lead author the study published online May 19
Some 100,000 people die each year from venomous snakes bites. Most die because there’s not enough antivenom.
Fungus gnats (Bradysia species) – also known as dark-winged fungus gnats, are small, mosquito-like insects often found in homes and offices, usually in the vicinity of houseplants. The larvae that hatch are legless, with white or transparent bodies and shiny black heads. From the first glimpse you’ll notice they’re not the prettiest sight, but what they lack in looks, they make up in cleverness.
Researchers have discovered what they believe to be a grandfather of snakes, which descended from terrestrial rather than marine ancestors. “It’s the missing-link snake between snakes and lizards,” says Nicholas Longrich, a postdoctoral fellow in the geology and geophysics department at Yale University and the lead author of a paper published in the journal Nature. The paper argues that snakes | <urn:uuid:d79bf4d2-9562-4a26-b200-9884fd421bba> | 3.5 | 560 | Content Listing | Science & Tech. | 45.234798 | 95,632,842 |
NOTE: This article has been reprinted from Ecosystem Marketplace’s eNewsletter. You can receive this summary of popular Ecosystem Marketplace articles by clicking here.
15 October 2010 | 2010 may officially be the UN’s “International Year of Biodiversity”, but cynics have been tacking on the word “Loss” ever since the slogan debuted in 2006. As 2010 draws to a close, that cynicism appears quite prescient.
“Not since the dinosaurs died out has Earth suffered such a rapid loss of plants, animals, and ecosystems,” says a recent report from insurance giant Allianz. “Our destruction of nature could be even more costly than our greenhouse gas emissions.”
Therein, of course, lies one key to the solution. Nature’s living ecosystems are worth more alive than dead, and not just because they’re nice to look at. Healthy ecosystems filter our water, protect our coasts, and regulate our climate, which means the apparent conflict between economic growth and ecological health is a false one.
Degradation continues because our current economic system fails to account for the long-term ecosystem services lost in our quest for short-term gains. Fill that hole, and you take a giant step towards fixing the problem.
We can fill the hole by incorporating the cost of nature’s destruction into the current cost of production – an argument that the Convention on Biodiversity (CBD) made quite effectively in its Global Biodiversity Outlook 3 Report (GBO 3).
The GBO 3 explores in detail the economic benefits of wetlands (which filter and regulate water), mangroves (which do all that wetlands do, and also protect shorelines and sequester carbon), and other systems that are often destroyed to make way for new development. It then compares the short-term benefits with the long-term loss, to chilling effect.
The Economics of Ecosystems and Biodiversity consortium (TEEB) makes the same argument in its series of “TEEB” reports for business and policymakers. They’ve issued three reports so far this year, and a fourth is set for release next week in Nagoya, Japan.
That’s where delegates from the 193 parties to the CBD are meeting for the CBD’s 10th Conference of the Parties (COP 10), which aims to chart a course for the next decade.
CBD boss Ahmed Djoghlaf has vowed that his time, the course will include financing mechanisms, and Ecosystem Marketplace is covering events on a daily basis in partnership with the Global Canopy Programme, which has just released a comprehensive and accessible list of financing mechanisms called the Little Biodiversity Financing Book.
COP 10 officially starts on Monday, which is when we’ll begin daily coverage of talks and side events. For now, here’s a look back on key stories from the past nine months.
-The Ecosystem Marketplace Team
For questions or comments, please contact email@example.com.
Understanding the CBD
Beyond the CBD
Financing and the CBD | <urn:uuid:4b89c3de-3ad2-4340-b3c2-92b89eb05984> | 2.59375 | 653 | News (Org.) | Science & Tech. | 42.911465 | 95,632,869 |
The world was stunned by the recent announcement that a telescope at the South Pole had detected a cosmic fossil from the earliest moments of creation; During a live Google Hangout, 4 astrophysicists discussed the implications
Last month, scientists announced the first hard evidence for cosmic inflation, the process by which the infant universe swelled from microscopic to cosmic size in an instant. This almost unimaginably fast expansion was first theorized more than three decades ago, yet only now has "smoking gun" proof emerged.
What is this result and what does it mean for our understanding of the universe? Late last week, two members of the discovery team discussed the finding and its implications with two of the field's preeminent thought leaders.
Walter Ogburn is a postdoctoral researcher at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, and a member of the discovery team. For him, the exciting thing "is not just confirming that inflation happened— many of us already had a pretty good idea that was likely to be the case—but having a chance to figure out exactly how it happened, what it was that drove it, whether there are new particles and new fields that participated in it, and which of the many models could be correct."
That's made possible by the strength of the detected signal. Far from the quiet whisper that many expected, the signal turned out to be a relatively loud drone. That brings with it many implications.
"The theoretical community is abuzz," says theorist Michael S. Turner, Director of the Kavli Institute for Cosmological Physics (KICP) and the Bruce V. and Diana M. Rauner Distinguished Service Professor at the University of Chicago. Turner, who was not involved in the experiment, continues:
"We got the signal we were looking for—that's good—but we shouldn't have gotten one according to the highbrow theorists because they said it should be too small. So we also got a surprise. And often in science, that's the case. We like to the experimenters to find what we predict, but we also like surprises."
This surprise is still so new that additional implications keep coming to light each week. It's already clear that the result rules out many theoretical models of inflation—most of them, in fact—because they predict a signal much weaker than the one detected. In addition, the discovery also seems to disprove a theory that says that the universe expands, collapses and expands again in an ongoing cycle.
More than that, the result could very well be what Turner calls a "crack in the cosmic egg," offering clues that even the most accepted theoretical assumptions contain inaccuracies.
"There have been hints for a while now that maybe something else is going on," says KICP Deputy Director John Carlstrom, who leads two other experiments that study the universe's first light. "Maybe we need to… allow some new physics in there. Maybe there are more neutrinos. Maybe they're more massive than we thought. Or maybe it's something none of us have thought of yet."
Theorists will carefully consider these ideas and their implications over the coming months and years. Meanwhile, the signal still needs to be experimentally confirmed. Results from other telescopes, including the Planck satellite and the South Pole Telescope, are expected in the coming year.
After that, the next step will be to measure more carefully the characteristics of the signal, searching for evidence of how inflation took place and how exactly the universe worked in its high-energy infancy. Those results may shed light on some of our biggest questions about how the universe began and how the forces of nature are unified.
But for now, the community is still buzzing with this first evidence of cosmic inflation.
"It's a funny thing when you're on the inside of a discovery like this," says Abigail Vieregg, an active member the discovery team and a professor at the University of Chicago and KICP. "It's only when you release the results to the world and watch the reaction of the community that, at least for me, it really hits home how important it is. If this is what we think it is, it's a very big deal."
The complete, discussion, recorded live during a Google Hangout, is available at http://www.kavlifoundation.org/science-spotlights/spotlight-live-secrets-universe's-first-light
James Cohen | Eurek Alert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:bc589a9a-7ad5-497d-93b4-c2340c6cb8ef> | 2.53125 | 1,501 | Content Listing | Science & Tech. | 44.359184 | 95,632,870 |
Man and His Plants in Relation to Dispersal
Many plants owe their distribution in some respect to man. They have all been indicated as anthropochores, in a wide sense. This is too wide a sense, as man is not the direct agent of dispersal for all of them, often only producing the right substrate. The unfortunate use of “anthropochores” for “anthropophytes” causes strange sentences like: “we found a high percentage of anemochores in anthropochores”.
KeywordsNatural Disperser Adventive Plant Tropical Secondary Forest Woody Weed Endozoochorous Dispersal
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A reflection-type film-substrate retarder is an optical device that changes the relative phase but not the relative amplitude of light upon reflection from a film-substrate system. While there are several such device designs based on the common negative film-substrate system, very little has been done with the other two categories of systems; zero and positive. The system category is determined by the relationship between the refractive indices of the ambient (N0), film (N1), and substrate (N2). If N1<√N0N2, the system is negative; if N1=√N0N2, the system is zero; and if N1>√N0N2, the system is positive . This paper discusses the design procedure and characteristics of zero-system reflection-retarders. The polarization and ellipsometric properties of the positive system preclude the existence of a reflection-retarder. First, a brief characterization of the zero and positive systems using constant-angle-of-incidence contours (CAICs) and Constant-thickness contours (CTCs) of the ellipsometric function is presented and discussed. Then, an algorithm outlining the design procedures is presented, and the characteristics of the obtained designs are optimized, analyzed and discussed. | <urn:uuid:b62ef123-d25a-4152-b210-740e011f0974> | 2.640625 | 266 | Academic Writing | Science & Tech. | 20.121772 | 95,632,940 |
Coral Reefs, Present and Past, on the West Florida Shelf and Platform Margin
In spite of the subtle, low-relief contours seen on bathymetric maps of Florida’s Gulf of Mexico (west Florida) shelf and slope (Fig. 4.1), this rim-toramp carbonate platform has and continues to support a surprisingly wide variety of coral reefs as compared to much better-known morphologically complex areas such the Great Barrier Reef. From the mid-shelf to the upper slope, light-dependent, hermatypic coral reefs have formed as a result of hard substrate availability, ideal oceanographic conditions, and sea-level fluctuations. Indeed, the west Florida slope even supports living lightindependent, ahermatypic coral reefs in ~550m water depth (Newton et al. 1987).
This paper summarizes the geomorphic variability of these different reef types, their geologic setting, and the present coral-reef biological community. The paper is organized along a virtual depth transect by presenting different reef settings and types starting from the shallower mid-shelf or mid-ramp setting, moving to the shelf edge, and then to the deeper upper slope.
KeywordsCoral Reef Reef Growth Outlier Reef Stony Coral Reef Tract
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May 20 2017 Astronomy Newsletter
Here's the latest article from the Astronomy site at BellaOnline.com.
Lawrence Hall of Science - Astronomy
Follow a steep road into California's Berkeley hills to find the Lawrence Hall of Science (LHS). It's the public science center of the University of California Berkeley, and delights visitors of all ages with the wonders of science. A bonus is a spectacular panoramic view of the San Francisco Bay.
*E-book guide to this year's solar eclipse in North America – free until Tuesday!*
Brian Ventrudo and Manish Panjwani have produced an e-book guide called "How to See the 2017 Total Solar Eclipse: A Practical Guide for the First-Time Eclipse Watcher". It will sell on Amazon for $3.99, but you can download it free until Tuesday the 23rd. Here's the link: https://www.amazon.com/dp/B07235LPDC
*It changed our view of the Universe*
On May 11, 1916 Einstein's General Theory of Relativity was published. Few people understood it at first, but by now it has often been tested and has passed every test. It changed our understanding of the Universe.
(1) May 10, 1900: British-American astronomer and astrophysicist Cecilia Payne-Gaposchkin was born. In her PhD thesis she was the first to propose that stars were composed mainly of hydrogen and helium.
(2) May 15, 1857: Scottish-American astronomer Williamina Fleming was born. She was a pioneer in the classification of stellar spectra and during the course of her career, she discovered 10 novae, 52 nebulae, and 310 variable stars. http://www.bellaonline.com/articles/art302345.asp
(3) May 17, 1836: English scientist and astronomer Norman Lockyer was born. Along with the French scientist Pierre Janssen, he is credited with discovering the gas helium which was first found in the light spectrum of the Sun decades before any was found on Earth.
(1) May 9, 2003: the Japanese mission Hayabusa ("peregrine falcon") was launched. It was the first mission to return a sample of material from an asteroid.
(2) May 11, 1974: the first geostationary satellite was launched. SMS-1 (Synchronous Meteorological Satellite) was the first satellite in the first series of geostationary meteorological satellites. (A geostationary satellite is in an orbit that keeps it above the same part of the Earth all of the time.)
(3) May 11, 2009: the space shuttle mission STS-125 was launched. It was the fifth and final servicing mission for the Hubble Space Telescope.
(4) May 14, 1973: Skylab, the first United States space station, was launched.
(5) May 14, 2009 – May 14th – ESA launched both the infrared Herschel Space Observatory and the Planck Space Observatory which made high resolution studies of the cosmic microwave background radiation left over from the very early Universe.
Please visit http://astronomy.bellaonline.com/Site.asp for even more great content about Astronomy. I hope to hear from you sometime soon, either in the forum http://forums.bellaonline.com/ubbthreads.php/forums/323/1/Astronomy or in response to this email message. I welcome your feedback!
Do pass this message along to family and friends who might also be interested. Remember it's free and without obligation.
I wish you clear skies.
Mona Evans, Astronomy Editor
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- Open Access
Crustal conductivity in Fennoscandia—a compilation of a database on crustal conductance in the Fennoscandian Shield
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2002
Received: 19 February 2001
Accepted: 5 December 2001
Published: 25 June 2014
A priori knowledge on large-scale sub-surface conductivity structure is required in many applications investigating electrical properties of the lithosphere. A map on crustal conductivity for the Fennoscandian Shield and its surrounding oceans, sea basins and continental areas is presented. The map is based on a new database on crustal conductance, i.e. depth integrated conductivity, where all available information on the conductivity of the bedrock, sedimentary cover and seawater are compiled together for the first time for the Fennoscandian Shield. The final model consists of eight separate layers to allow a 3D description of conductivity structures. The first three layers, viz. water, sediments and the first bedrock layer, describe the combined conductance of the uppermost 10 km. The other five bedrock layers contain the data of the crustal conductance from the depth of 10 km to the depth of 60 km. The database covers an area from 0°E to 50°E and 50°N to 85°N. Water conductances are estimated from bathymetric data by converting depths to conductances and taking into account the salinity variations in the Baltic Sea. Conductance of the sedimentary cover includes estimates on the conductance of both marine and continental sediments. Bedrock conductances are extrapolated from 1D- and 2D-models. Extrapolations are based on data from magnetometer array studies, airborne electromagnetic surveys and other electromagnetic investigations as well as on other geophysical and geological data. The crustal conductivity structure appears to be very heterogeneous. Upper crust, in particular, has a very complex structure reflecting a complex geological history. Lower crust seems to be slightly more homogeneous although large regional contrasts are found in both the Archaean and Palaeoproterozoic areas. | <urn:uuid:45e8bdba-3461-4568-a9f0-e81e08053e19> | 3.03125 | 480 | Academic Writing | Science & Tech. | 20.70219 | 95,632,961 |
When NASA's New Horizons sped past Pluto on July 14, 2015, it took the best-ever pictures of the rocky world s surface, giving us new insight into its geology, composition and atmosphere. These stunning images are the most famous result of New Horizons, but the spacecraft also sent back over three years worth of measurements of the solar wind the constant flow of solar particles that the sun flings out into space from a region that has been visited by only a few spacecraft.
This unprecedented set of observations give us a peek into an almost entirely unexplored part of our space environment - filling a crucial gap between what other missions see closer to the sun and what the Voyager spacecraft see further out. A new study to appear in The Astrophysical Journal Supplement lays out New Horizons observations of the solar wind ions that it encountered on its journey.
Space environment data collected by New Horizons over a billion miles of its journey to Pluto will play a key role in testing and improving models of the space environment throughout the solar system. This visualization is one example of such a model: It shows the simulated space environment out to Pluto a few months before New Horizons' closest approach. Drawn over the model is the path of New Horizons up to 2015, as well as the current direction of the two Voyager spacecraft - which are currently at three or four times New Horizons' distance from the sun. The solar wind that New Horizons encountered will reach the Voyager spacecraft about a year later.
Credits: NASA's Goddard Space Flight Center Scientific Visualization Studio, the Space Weather Research Center (SWRC) and the Community-Coordinated Modeling Center (CCMC), Enlil and Dusan Odstrcil (GMU)
Not only does the New Horizons data provide new glimpses of the space environment of the outer solar system, but this information helps round out our growing picture of the suns influence on space, from near-Earth effects to the boundary where the solar wind meets interstellar space.
The new data shows particles in the solar wind that have picked up an initial burst of energy, an acceleration boost that kicks them up just past their original speed. These particles may be the seeds of extremely energetic particles called anomalous cosmic rays.
When these super-fast, energetic rays travel closer to Earth, they can pose a radiation hazard to astronauts. Further away, at lower energies, the rays are thought to play a role at shaping the boundary where the solar wind hits interstellar space - the region of our solar system that Voyager 2 is currently navigating and observing.
Studying the Solar Wind
Though space is about a thousand times emptier than even the best laboratory vacuums on Earth, its not completely devoid of matter the suns constant outflow of solar wind fills space with a thin and tenuous wash of particles, fields, and ionized gas known as plasma. This solar wind, along with other solar events like giant explosions called coronal mass ejections, influences the very nature of space and can interact with the magnetic systems of Earth and other worlds. Such effects also change the radiation environment through which our spacecraft and, one day, our astronauts headed to Mars travel.
New Horizons measured this space environment for over a billion miles of its journey, from just beyond the orbit of Uranus to its encounter with Pluto.
The instrument was only scheduled to power on for annual checkouts after the Jupiter flyby in 2007, said Heather Elliott, a space scientist at the Southwest Research Institute in San Antonio, Texas, and lead author on the study. We came up with a plan to keep the particle instruments on during the cruise phase while the rest of the spacecraft was hibernating and started observing in 2012.
This plan yielded three years of near-continuous observations of the space environment in a region of space where only a handful of spacecraft have ever flown, much less captured detailed measurements.
This region is billions of cubic miles, and we have a handful of spacecraft that have passed through every decade or so, said Eric Christian, a space scientist at NASAs Goddard Space Flight Center in Greenbelt, Maryland, who studies what's called the heliosphere the region of our solar system dominated by the solar wind but was not involved with this study. We learn more from every one.
Since the sun is the source of the solar wind, events on the sun are the primary force that shapes the space environment. Shocks in the solar wind which can create space weather, such as auroras, on worlds with magnetic fields are created either by fast, dense clouds of material called coronal mass ejections, or CMEs, or by the collision of two different-speed solar wind streams. These individual features are discernible in the inner solar system but New Horizons didnt see the same level of detail.
The New Horizons data show that the space environment in the outer solar system has less detailed structure than space closer to Earth, since smaller structures tend to be worn down or clump together as they travel outwards, creating fewer - but bigger - features.
"At this distance, the scale size of discernible structures increases, since smaller structures are worn down or merge together," said Elliott. It s hard to predict if the interaction between smaller structures will create a bigger structure, or if they will flatten out completely.
Subtler signs of the sun S influence are also harder to spot in the outer solar system. Characteristics of the solar wind including speed, density, and temperature - are shaped by the region of the sun it flows from. As the sun and its different wind-producing regions rotate, patterns form. New Horizons didn't see patterns as defined as they are when closer to the sun, but nevertheless it did spot some structure.
Speed and density average together as the solar wind moves out said Elliott.But the wind is still being heated by compression as it travels, so you can see evidence of the sun s rotation pattern in the temperature even in the outer solar system.
Finding the Origins of Space Radiation Hazards
The New Horizons observations also show what may be the starting seeds of the extremely energetic particles that make up anomalous cosmic rays. Anomalous cosmic rays are observed near Earth and can contribute to radiation hazard for astronauts, so scientists want to better understand what causes them.
The seeds for these energetic, super-fast particles may also help shape the boundary where the solar wind meets interstellar space. Anomalous cosmic rays have been observed by the two Voyager spacecraft out near these boundaries, but only in their final stages, leaving questions as to the exact location and mechanism of their origins.
"The Voyagers can't measure these seed particles, only the outcome," said Christian. "So with New Horizons going into that region, this blank patch in the observations is being filled in with data."
Filling in such a blank patch will help scientists better understand the way such particles move and affect the space environment around them, helping to interpret what Voyager is seeing on its journey.
Comparing New Horizons to Observations and Models
Since New Horizons is one of the very few spacecraft that has explored the space environment in the outer solar system, lack of corroborating data meant that a key part of Elliott's work was simply calibrating the data. Her work was supported by the Heliophysics Research and Analysis program.
She calibrated the observations with pointing information from New Horizons, the results of extensive tests on the laboratory version of the instrument, and comparison with data from the inner solar system. NASA's Advanced Composition Explorer, or ACE, and NASA's Solar and Terrestrial Relations Observatory, or STEREO, for example, observe the space environment near Earth's orbit, allowing scientists to capture a snapshot of solar events as they head towards the edges of the solar system. But because the space environment in the outer solar system is relatively unexplored, it wasn't clear how those events would develop. The only previous information on space in this region was from Voyager 2, which traveled through roughly the same region of space as New Horizons, although about a quarter of a century earlier.
"There are similar characteristics between what was seen by New Horizons and Voyager 2, but the number of events is different," said Elliott. "Solar activity was much more intense when Voyager 2 traveled through this region."
Now, with two data sets from this region, scientists have even more information about this distant area of space. Not only does this help us characterize the space environment better, but it will be key for scientists testing models of how the solar wind propagates throughout the solar system. In the absence of a constant sentinel measuring the particles and magnetic fields in space near Pluto, we rely on simulations - not unlike terrestrial weather simulations - to model space weather throughout the solar system. Before New Horizons passed Pluto, such models were used to simulate the structure of the solar wind in the outer solar system. With a calibrated data set in hand, scientists can compare the reality to the simulations and improve future models.
Karen Fox | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Science fiction has nothing over quantum physics when it comes to presenting us with a labyrinthine world that can twist your mind into knots when you try to make sense of it.
A team of Arizona State University researchers, however, believe they've opened a door to a clearer view of how the common, everyday world we experience through our senses emerges from the ethereal quantum world.
Physicists call our familiar everyday environment the classical world. That's the world in which we and the things around us appear to have measurable characteristics such as mass, height, color, weight, texture and shape.
The quantum world is the world of the elemental building block of matter – atoms. Atoms are combinations of neutrons and protons and electrons bound to a nucleus by electrical attraction.
But most of an atom – more than 99 percent of it – is empty space filled with invisible energy.
So from a quantum-world view, we and the things around us are mostly empty space. The way we experience ourselves and other things in the classical world is really just "a figment of our imaginations shaped by our senses," explains ASU Regents' Professor David Ferry.
For more than a century, scientists and engineers have struggled to come to a satisfactory conclusion about the missing link that bridges the classical and quantum worlds and enables a transition from that world of mostly empty space to the familiar environment we experience through our senses.
One proposed scenario based on these questions was investigated in a dissertation written by Adam Burke to earn his doctorate in electrical engineering in 2009 from ASU's Ira A. Fulton Schools of Engineering.
To try working out an answer to some of the questions, Burke teamed with Ferry, a professor in the School of Electrical, Computer and Energy Engineering, Tim Day, who recently earned his doctorate in electrical engineering from the school, physicist Richard Akis, an associate research professor in the school, Gil Speyer, an assistant research scientist for the engineering schools' High Performance Computing Initiative, and Brian Bennett, a materials scientist with the Naval Research Laboratory.
The result is an article published recently in the research journal Physical Review Letters and featured on PhysOrg.com, a science, technology and research news website. It describes the transition from quantum to classical world as a "decoherence" process that involves a kind of evolutionary progression somewhat analogous to Charles Darwin's concept of natural selection.
The authors built on two theories called decoherence and quantum Darwinism, both proposed by Los Alamos National Laboratory researcher Wojciech Zurek.
The decoherence concept holds that many quantum states "collapse" into a "broad diaspora," or dispersion, while interacting with the environment. Through a selection process, other quantum states arrive at a final stable state, called a pointer state, which is "fit enough" (think "survival of the fittest" in Darwinian terms) to be transmitted through the environment without collapsing.
These single states with the lowest energy can then make high-energy copies of themselves that can be described by the Darwinian process and observed on the macroscopic scale in the classical world.
The experiments arose from using advanced scanning gate microscopy to obtain images of what are called quantum dots.
Burke, now doing research in a post-doctoral program at the University of New South Wales in Sydney, Australia, explains it like this:
Imagine the quantum dot as a billiard table in which the quantum point contacts are the two openings through which a ball could enter or leave the dot, and the interior walls of the dot act as bumpers.
If there were no friction on the table, a billiard ball with an initial trajectory would bounce off of these walls until eventually finding an exit and leaving the dot (this is the decoherence part).
Or it might find a trajectory that does not couple to the openings and would therefore be a surviving pointer state, what is called a diamond state.
One difference between the classical physics of billiard balls and the quantum physics of electrons is that an electron can tunnel through "forbidden phase space" to enter this diamond state, whereas a billiard ball entering from outside the dot would not find itself able to reach this diamond trajectory.
It is this isolated classical trajectory, and the buildup of an electron wave functions' amplitude along that trajectory, that is referred to as a scarred wave function.
To experimentally measure these scars, imagine that we can't see inside the walls of our billiard table, but we can count the billiard balls exiting the table. This is what is normally measured with the conductance of the quantum dot and its environment.
"We measure the current through the dot, the numbers of 'billiard balls' passing through it per second, to try to see how this changes when we move our probe around the 'billiard table,' " Ferry says.
Furthermore, there is the probe of the scanning gate microscope, which applies a small electric field. This can be pictured as a small circular bumper on the billiard table that can be moved around within the dot.
This small "bumper" is rastered left to right, top to bottom over the area of interest. If a ball is traveling along this diamond pattern it is perturbed by the bumper when it rasters into the trajectory.
Think of rastering like the way a television image works, with a pattern of scanning lines that cover the area on which the image is projected, or a set or horizontal lines composed of individual pixels that are used to form an image on a computer screen.
When this happens, the ball bounces off the perturbation, and takes a new course within the dot until finally coupling out one of the openings to be measured. The change in the ball's motion appears as a change in the conductance – the number of balls going through the openings in a given time.
Ferry explains: "With scanning gate microscopy, we monitor where these changes occur within the scans, and hopefully this gives us a map of the scarred wave functions corresponding to the pointer states."
Quantum mechanically, he says, a new electron will tunnel right into the diamond state, so the measurement can continue until the whole area is mapped.
The data that came from the team's experiment supports Zurek's theories of decoherence and quantum Darwinism, Burke says.
Ferry says these findings are just one step in a process that is open to conjecture, but they point toward a "smoking gun" for the existence of this quantum Darwinism and a new view in the search for evidence of how the quantum-to-classical world transition actually occurs.
If you can wrap your mind around all this, he says, "You open the door to a deeper understanding of what is really going on" at the core of physical reality.
Joe Kullman | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Fungi and Yeast
Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor), SmartyPants, MaxScience and 1 other
The Structure of Fungi and Yeast
The diagram above shows a typical structure of a fungus. A fungus is made of hyphae, which are long tubes. Collectively they are called mycellium and form branches that can cover many acres.
On the right, we have zoomed in on a hypha, and you can see its structure. It has all the typical features of a cell, but there are some unique aspects. The hypha is a long tube and effectively one cell. However, it could be divided into compartments by septa; the hypha has many nuclei. The tip is tapered, this is where it is growing outwards and is known as the extension zone. Fungi grow specialized areas for reproduction called fruiting bodies. These can grow very large and are visible to the naked eye, where they are known as mushrooms. It is from these that spores are produced.
Yeasts are a type of fungi, but unlike most, they are made up of individual cells (unicellular). They reproduce by budding where little bits of new yeast grow and break off.
As a living thing, yeast respire. Unlike human anaerobic respiration where lactic acid is produced, they produce ethanol. Alcoholic drinks such are beer are made by fermenting with yeast, this produces alcohol.
Glucose ==>> Ethanol + Carbon Dioxide C6H12O6 ==>> 2C2H5OH + 2CO2
As microorganisms, fungi can be pathogenic, fungi like warm and damp environments which they can find in places like between the toes and in the vagina. Have a look at the table below to see some examples of pathogenic fungi.
|Athletes Foot||Trichophyton Rubrum||Athletes Foot refers to a fungal infection of the foot and can be caused by many different fungi. The mold or yeast grows on the surface and into the skin and causes itching.|
|Thrush||Candida Albicans||Thrush refers to this fungus infecting the vagina and causes itching. However, the same fungus can also infect the penis and mouth. This infection is generally known as candidiasis. It exists naturally in many people with no symptoms, but irritation of the skin, diabetes and hormone therapy can cause an outbreak.|
|Pneumonia|| Histoplasma Capsulatum
|Pneumonia is a general term for infection and inflammation of the lungs. It is important to note that it can be caused by bacteria or virus and that fungal pneumonia is quite rare and only normally occurs in people with AIDS because of their weakened immunity.|
Fungi in Industry
Fungi have many uses in the industry that are covered in various areas of this site. They are especially useful in food.
- 1Is used in fermenting beer and wine to produce alcohol, it is also added to bread to make it rise and alter its texture.Yeast.Advertisement
- 2These are another culinary use of fungi; truffles are a fungus that is highly prized and expensive that are used in cooking.Mushrooms.
- 3Fungi can be useful for producing products in fermenters, the best example of this would be penicillin production.Penicillin.
- 4Returning to food: Quorn is a meat alternative, it is derived from the mould Fusarium venenatum. F. venenatum is grown in oxygenated water and fed glucose and various vitamins. The resulting material is removed and heat treated, bound together with egg albumen and pressed into a mince to give it a texture like meat.Quorn.
This is where digestion is done outside of the organism. This is seen in saprophytic fungus (saprophytic meaning decomposer). The fungi secretes the enzymes into their surrounding material and then absorbs the products. A way of measuring the activity of amylase is to have an agar plate with starch; make a small well and put in the amylase enzyme. Incubate for a time and then flood the area with iodine. It will show a clear zone where the starch has been digested. You can see which is the more effective in the diagram below.
Questions and Answers
Hi Jamie I was wondering about extracellular digestion in yeast?
Hi Jamie I was wondering about extracellular digestion in yeast and how this happens and what it means? It doesn't explain it.
Fungi is Yeast which feeds on dead organic material. Extracellular digestion is the way in which Fungi feeds. Fungi secrete enzymes through the walls of their fine feeding hyphae. This breaks the food down into nutrients. Once the nutrients are digested there reabsorbed through the hyphae wall. The nutrients are used in respiration to release energy, or they are used for growth.
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Categories : Micro
Recent edits by: MaxScience, SmartyPants, Taylor (ScienceAid Editor) | <urn:uuid:c181470e-e244-4e7e-9604-6e098d732060> | 3.828125 | 1,228 | Knowledge Article | Science & Tech. | 47.380869 | 95,632,977 |
A Curious History of Sunspot Penumbrae
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Daily records of sunspot group areas compiled by the Royal Observatory, Greenwich, from May of 1874 through 1976 indicate a curious history for the penumbral areas of the smaller sunspot groups. On average, the ratio of penumbral area to umbral area in a sunspot group increases from 5 to 6 as the total sunspot group area increases from 100 to 2000 μHem (a μHem is 10−6 the area of a solar hemisphere). This relationship does not vary substantially with sunspot group latitude or with the phase of the sunspot cycle. However, for the sunspot groups with total areas < 100 μHem, this ratio changes dramatically and systematically through this historical record. The ratio for these smallest sunspots is near 5.5 from 1874 to 1900. After a rapid rise to more than 7 in 1905, it drops smoothly to less than 3 by 1930 and then rises smoothly back to more than 7 in 1961. It then returns to near 5.5 from 1965 to 1976. The smooth variation from 1905 to 1961 shows no indication of any step-like changes that might be attributed to changes in equipment or personnel. The overall level of solar activity was increasing monotonically during this time period when the penumbra-to-umbra area ratio dropped to less than half its peak value and then returned. If this history can be confirmed by other observations (e.g. Mt. Wilson or Kodaikanal), it may impact our understanding of penumbra formation, our dynamo models, and our estimates of historical changes in the solar irradiance.
KeywordsActive regions, structure Sunspots, penumbra Sunspots, statistics Sunspots, umbra
The author thanks Lisa Upton for reviewing the paper and NASA for its support of this research through a grant from the Heliophysics Causes and Consequences of the Minimum of Solar Cycle 23/24 Program to NASA Marshall Space Flight Center. Comments by an anonymous referee led to significant improvements in the paper. Most importantly, the author thanks the American taxpayers for supporting scientific research in general and this research in particular.
- Borrero, J.M., Ichimoto, K.: 2011, Living Rev. Solar Phys. 8(4). http://solarphysics.livingreviews.org/Articles/lrsp-2011-4/.
- Hathaway, D.H.: 2010, Living Rev. Solar Phys. 7(1). http://solarphysics.livingreviews.org/Articles/lrsp-2010-1/.
- Rempel, M., Schlichenmaier, R.: 2011, Living Rev. Solar Phys. 8(3). http://solarphysics.livingreviews.org/Articles/lrsp-2011-3/. | <urn:uuid:513c88c0-850e-4163-8985-a043d54fe193> | 3.453125 | 589 | Academic Writing | Science & Tech. | 64.954166 | 95,632,999 |
Narrow-line-width UV bursts in the transition region above Sunspots observed by IRIS
EDIT：admin TIME： 2016-09-26 13:57:24.0 CLICK：627
Various small-scale structures abound in the solar atmosphere above active regions, playing an important role in the dynamics and evolution therein. We report on a new class of small-scale transition region structures in active regions, characterized by strong emissions but extremely narrow Si IV line profiles as found in observations taken with the Interface Region Imaging Spectrograph (IRIS).
Tentatively named as Narrow-line-width UV bursts (NUBs), these structures are located above sunspots and comprise of one or multiple compact bright cores at sub-arcsecond scales (see Fig. 2 a1-e1). We found six NUBs in two datasets (a raster in Fig.1 b and c, and a sit-and-stare dataset in Fig. 1 i). Among these, four events are short-living with a duration of ~10 mins while two last for more than 36 mins in Fig. 2 a2-e2. All NUBs have Doppler shifts of 15-18 km s-1, while the NUB found in sit-and-stare data possesses an additional component at ~50 km s-1 found only in the C II and Mg II lines.
Given that these events are found to play a role in the local dynamics, it is important to further investigate the physical mechanisms that generate these phenomena and their role in the mass transport in sunspots.
This work has been accepted for publication in ApJ Letter. We acknowledge the support from the 973 program, National Natural Science Foundation of China and Shandong provincial Natural Science Foundation.
The full article is available at http://adsabs.harvard.edu/abs/2016arXiv160804892H.
Figure 1. Identification of the events in the observed FOVs. Panel (a): two-dimensional histogram of the non-thermal velocities and intensities obtained from DATA1. The solid-line square marks the tail of the histogram that was used to make the identification of the events. Panels (b) and (c) present the Si iv radiance images of the two rasters of the same region with the identifications of the events superimposed (green symbols). Panel (d) displays the same region with the identified events observed in the continuum near 2832Å to give an overview of the photosphere of the region. Panels (e)–(g) give example spectra with single Gaussian fits (solid lines) averaged from event 4. The dashed vertical lines (in panels f and g) mark the wavelength range that shows absorption dips and are excluded from the Gaussian fits. Panels (f) and (i) present the results from DATA2.
Figure 2. Events 1–5 identified in DATA1 seen in IRIS SJ 1400 Å (Panels a1–e1). They are marked by the solid-line squares (yellow) and contoured by green lines. Their IRIS SJ 1400 and 1330 Å lightcurves are given as black and red lines in Panels a2–e2. The dashed lines denote the period of the IRIS spectral slit scan. | <urn:uuid:4f265208-87ed-4091-832a-11e2a6f42e56> | 2.5625 | 700 | Academic Writing | Science & Tech. | 57.384113 | 95,633,010 |
|Home | All Classes | Main Classes | Annotated | Grouped Classes | Functions|
The QTimerEvent class contains parameters that describe a timer event. More...
List of all member functions.
Timer events are sent at regular intervals to objects that have started one or more timers. Each timer has a unique identifier. A timer is started with QObject::startTimer().
The QTimer class provides a high-level programming interface that uses signals instead of events. It also provides one-shot timers.
The event handler QObject::timerEvent() receives timer events.
See also QTimer, QObject::timerEvent(), QObject::startTimer(), QObject::killTimer(), QObject::killTimers(), and Event Classes.
Constructs a timer event object with the timer identifier set to timerId.
Returns the unique timer identifier, which is the same identifier as returned from QObject::startTimer().
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CSIRO has measured above average growth in carbon dioxide levels in the global atmosphere, despite global attempts to reduce these emissions. The source of the increase is most likely from the burning of fossil fuels - coal, oil and gas.
"The results are concerning because carbon dioxide is the main driver of climate change," says CSIRO Atmospheric Division chief research scientist Dr Paul Fraser. "I am a little bit surprised that the level is so high without input from forest wildfires."
Measurements at Cape Grim in Tasmania, Cape Ferguson in Queensland, sub-Antarctic Macquarie Island, Mawson in Antarctica, and the South Pole, show that carbon dioxide over the last two years has increased at near-record levels. The persistent increases measured over such a large region of the Southern Hemisphere ensure that they closely reflect the total global emissions.
Geraldine Capp | CSIRO
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Atmosphere, Eclipse, Science
23 Jan , 2018 by Evan Gough
Scientists have long predicted that an eclipse can create a bow wave in the ionosphere. The August 2017 eclipse, called the Great American Eclipse, gave researchers an opportunity to look for it.
Space stories from across the internet, sent to you by email. | <urn:uuid:8734b783-f488-4a9b-a576-8679910cd512> | 2.90625 | 68 | Truncated | Science & Tech. | 44.445513 | 95,633,047 |
Astronomical Discoveries You Can Make, Too! : Replicating the Work of the Great Observers Paperback
Part of the Springer Praxis Books series
You too can follow in the steps of the great astronomers such as Hipparchus, Galileo, Kepler and Hubble, who all contributed so much to our modern understanding of the cosmos.
This book gives the student oramateur astronomer the following tools to replicate some of these seminal observations from their own homes: With your own eyes: Use your own observations and measurements to discover and confirm the phenomena of the seasons, the analemma and the equation of time, the logic behind celestial coordinates, and even the precession of the equinoxes. With a consumer-grade digital camera: Record the changing brightness of an eclipsing binary star and show that a pulsating star changes color as it brightens and dims.
Add an inexpensive diffraction grating to your camera and see the variety of spectral features in the stars, and demonstrate that the Sun's spectrum is similar to one particular type of stellar spectrum. With a backyard telescope: Add a CCD imager and you can measure the scale of the Solar System and the distance to a nearby star.
You could even measure the distance to another galaxy and observe the cosmological redshift of the expanding universe. Astronomical Discoveries You Can Make, Too! doesn't just tell you about the development of astronomy; it shows you how to discover for yourself the essential features of the universe.
- Format: Paperback
- Pages: 549 pages, 3 Tables, black and white; 122 Illustrations, color; 46 Illustrations, black and white; X
- Publisher: Springer International Publishing AG
- Publication Date: 13/05/2015
- Category: History of science
- ISBN: 9783319156590
- PDF from £34.00 | <urn:uuid:0ad5c1de-a246-4aed-bcee-d28fde2d87f9> | 3.453125 | 386 | Product Page | Science & Tech. | 29.363225 | 95,633,101 |
UT Arlington physics researchers may have developed a way to use laser technology to deliver drug and gene therapy at the cellular level without damaging surrounding tissue. The method eventually could help patients suffering from genetic conditions, cancers and neurological diseases.
In a study published recently by the journal Nature Scientific Reports, the team paired crystalline magnetic carbon nanoparticles and continuous wave near-infrared laser beams for in what is called photothermal delivery. Authors of the new paper are Ali Koymen, a professor of physics; Samarendra Mohanty, an assistant professor of physics; and Ling Gu, a researcher in Mohanty’s lab.
The new discovery grew out of previous study where Koymen and Mohanty used a 50 to 100 milliwatt laser and the same carbon nanoparticle, which absorbs the beam, to heat up and destroy cancer cells in the lab. The team used the new photothermal delivery method in lab experiments to introduce impermeable dyes and small DNA molecules into human prostate cancer and fibroblast sarcoma cells.
“In this work, Dr. Mohanty used a lower power, 20 to 30 milliwatt, continuous wave near-infrared laser and the nanoparticle to permeate the cell membrane without killing the cells. This method stretches the desired cell membrane to allow for delivery and has the added bonus of creating a fluid flow that speeds the movement of what is being delivered,” said Koymen, whose lab created the study’s crystalline magnetic carbon nanoparticle using an electric plasma discharge inside a toulene solution.
Introducing foreign DNA or other small molecules directly into cells is essential for some of the most advanced methods being developed in gene therapy, vaccinations, cancer imaging and other medical treatments. Currently, the predominant practice is using viruses for delivery to cells. Unfortunately, the scope of what can be delivered with viruses is severely limited and virus interaction can lead to inflammatory responses and other complications.
Scientists looking to create a path into the cell without employing a virus also have experimented with using UV-visible light laser beams alone. But that method damages surrounding cells and has a relatively shallow level of effectiveness.
A significant advantage of the new method is that the near-infrared light absorption of the nanoparticle can be used to selectively amplify interaction of low power laser with targeted tissue and “laser induced-damage to non-targeted cells along the irradiation path can be avoided,” the report says. The magnetic properties of the nanoparticles also mean they can be localized with an external magnetic field; therefore a smaller concentration can be used effectively.
“Research universities like UT Arlington encourage faculty and students to follow each new discovery with even deeper questions,” said Pamela Jansma, dean of the UT Arlington College of Science. “With their latest publication, Drs. Koymen, Mohanty and Gu have taken their collaboration to a new level as they keep building toward valuable implications for human health and disease treatment.”
Carbon nanoparticles produced for the cancer study varied from five to 20 nanometers wide. A human hair is about 100,000 nanometers wide. The magnetic carbon nanoparticles also are fluorescent. So, they can be used to enhance contrast of optical imaging of tumors along with that of MRI.
Mohanty’s lab is supported by funding from the National Institutes of Health and the National Science Foundation.
About UT Arlington
The University of Texas at Arlington is a comprehensive research institution and the second largest institution in The University of Texas System. The Chronicle of Higher Education ranked UT Arlington as the seventh fastest-growing public research university in 2013. U.S. News & World Report ranks UT Arlington fifth in the nation for undergraduate diversity. Visit www.uta.edu to learn more.
Physics Professor Ali Koymen, left, and Samarendra Mohanty, an assistant professor of physics, discuss their research.
The University of Texas at Arlington is an Equal Opportunity and Affirmative Action employer.
Traci Peterson | Eurek Alert!
The secret sulfate code that lets the bad Tau in
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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16.07.2018 | Agricultural and Forestry Science | <urn:uuid:730f5263-89eb-4189-8d91-5b66d00af89c> | 3.25 | 1,468 | Content Listing | Science & Tech. | 32.382284 | 95,633,113 |
posted by Liz
I don't know how to solve 12x(2)-15x=0 using the quadratic equation ax+bx+c=0 with this question I am unsure of what a, b and c are supposed to be, therefore I do not know how to solve this! Please help!
The standard quadratic equation form is
ax^2 + bx + c = 0
and your equation is, if your (2) is supposed to be an exponent,
12x^2 -15x = 0
Therefore a = 12, b = -15 and c = 0
You have reduced your equaion to
4x^2 -5x = 0,
so using a=4, b=-5 and c=0 would give you the same results for x.
You should get x = 0 and x = 5/4 as the solutions, using the quadratic equation
x = [-b +/-sqrt(b^2 -4ac)]/(2a) | <urn:uuid:990eba9f-977a-464e-82ae-29ab2b4aad5d> | 2.703125 | 213 | Q&A Forum | Science & Tech. | 74.68 | 95,633,114 |
The quantum spin Hall insulators predicted ten years ago and now experimentally observed are instrumental for a break- through in nanoelectronics due to non-dissipative spin-polarized electron transport through their edges. For this transport to persist at normal conditions, the insulators should possess a sufficiently large band gap in a stable topological phase. Here, we theoretically show that quantum spin Hall insulators can be realized in ultra-thin films constructed from a trivial band insulator with strong spin-orbit coupling. The thinnest film with an inverted gap large enough for practical applications is a centrosymmetric sextuple layer built out of two inversely stacked non-centrosymmetric BiTeI trilayers. This nontrivial sextuple layer turns out to be the structure element of an artificially designed strong three-dimensional topological insulator Bi2Te2I2. We reveal general principles of how a topological insulator can be composed from the structure elements of the BiTeX family (X = I, Br, Cl), which opens new perspectives towards engineering of topological phases.
Two-dimensional (2D) topological insulators (TIs)—a new electronic phase also referred to as a quantum spin Hall (QSH) insulator—are characterized by an absolute band gap induced by spin-orbit coupling (SOC) and helical gapless edge states inside the gap1. These states protected by time-reversal symmetry provide perfectly conducting spin-filtered channels, meeting the demands of low-power nanoelectronics and spintronics. The existence of such states as the fingerprint of a topologically non-trivial 2D insulator was first predicted in Refs 2,3. It was also suggested that the QSH effect can be observed in graphene, where SOC opens a gap at the two inequivalent Dirac points. This gap in graphene appears to be too small for practical use, so heavy-elements based analogs of graphene must be sought. Actually, the 2D materials with low-buckled honeycomb-lattice structures4,5,6,7,8,9,10—silicene, germanene, and stanene—possess a significantly larger SOC-induced gap at the Dirac points (up to ~0.1 eV in stanene), and the spin-polarized edge channels could be detected at easily accessible temperatures. However, the QSH effect in such systems has not been experimentally observed so far.
Further effective enhancement of the SOC to make the gap larger can be realized by chemical functionalization of the above 2D materials11,12. Such a functionalization substantially enlarges the gap, in fact “destroying” the Dirac cones, and it may lead to a SOC-induced band inversion at the time reversal invariant momentum (TRIM) (normally at k = 0) with an absolute gap of several hundred meV at this momentum. If the band inversion occurs, the resulting 2D system is a 2D TI that should support the QSH effect12 similar to the inverted HgTe quantum wells predicted to be QSH insulators in ref. 13. It is important that this prediction has found experimental confirmation: In the inverted HgTe/CdTe and InAs/GaSb quantum wells14,15,16 the QSH effect was observed despite the very small gaps in these quantum wells, less than 10 meV. It has spurred a rising tide of theoretical propositions of different 2D TIs with honeycomb- or square-lattice structures and a large inverted gap enabling room-temperature operating17.
Ab initio approaches to electronic structure, especially those based on the density functional theory (DFT), have become a powerful tool to search for new materials with unique properties. At the same time, the effective models that proved indispensable in predicting the QSH effect in graphene-like systems and quantum wells are currently widely used to analyze the effect of strain, quantum confinement, and external fields in 2D TIs, i.e., to solve the problems that presently are not accessible with ab initio methods. Thus, to efficiently model the nanoelectronics and spintronics devices, the microscopic methodology must be bridged with the effective Hamiltonian approach based on symmetry considerations and on the k·p perturbation theory.
With a few exceptions, none of the theoretically proposed 2D materials has been hitherto fabricated17. Thus, the intensive search of robust and easily fabricated materials remains to be actual. In particular, it was suggested that 2D TIs can be produced from a thin film of layered 3D (three-dimensional) TIs of the Bi2Se3 family, where the hybridization between the opposite surfaces of the film opens a gap at the Dirac point (DP). Depending on film thickness, the 2D system may “oscillate” between band insulator and QSH insulator as was predicted by the 4-band effective k·p model (see refs 18,19). The thinnest known topologically nontrivial film consists of at least two structural elements—quintuple or septuple layers20.
Besides the studies on the thin films of 3D TIs, recently it was heuristically suggested that a 3D TI can be constructed artificially via stacking 2D bilayers that are topologically trivial21. It encourages our search for 2D TIs built out of trivial band-insulator constituents. These constituents should have strong spin-orbit coupling (SOC), and prospective candidates are bismuth tellurohalides BiTeX with X = I, Br, and Cl, among which the polar semiconductor BiTeI demonstrates the strongest spin-orbit coupling providing the biggest known Rashba spin-splitting of bulk and surface states22,23. The structure element of BiTeI is a trilayer (TL) with the I-Bi-Te stacking. A single TL that possesses the Rashba spin-split band structure24 can be grown epitaxially on a suitable substrate or be easily exfoliated from the bulk BiTeI, where the adjacent TLs couple through a weak van-der-Waals (vdW) interaction. The samples of BiTeI always contain a large number of randomly distributed bulk stacking faults, which leads to a mixture of terminations at the surface, as experimentally observed in refs 25, 26, 27, 28, 29, 30. This implies that adjacent TLs may have different sequence order along the hexagonal z axis.
Here, based on DFT calculations we demonstrate that a centrosymmetric sextuple layer (SL) constructed from two BiTeI TLs with facing Te-layer sides and a typical vdW spacing is a 2D TI with the gap of 70 meV at . The vdW interaction between these TLs is crucial to realize such a QSH insulator phase: The SL becomes topologically trivial with increasing the vdW spacing by 5% only. We consider the nontrivial SL as a structure element, a repetition of which along the z axis results in thin films that are found to “oscillate” between trivial and nontrivial phases with the number of SLs. The corresponding bulk system composed of SLs turns out to be a strong 3D TI (hereafter referred to as Bi2Te2I2). It is energetically unfavourable by only 0.5 meV compared with the non-centrosymmetric BiTeI. This makes it plausible to suppose that crystals of BiTeI grown by the Bridgman method already contain the desired SLs, and that the alternative stacking can be experimentally observed and controllably manufactured. To describe the low-energy properties of Bi2Te2I2 and its films, we derive four-band k·p Hamiltonians from the ab initio wave functions. They are similar to the Hamiltonians constructed for Bi2Se3 -family 3D TIs and their thin films18,31,32. For a more accurate description of the SL, we derive an eight-band Hamiltonian that involves Rashba-split valence and conduction bands of the stand-alone TLs. We thus demonstrate that due to the bonding-antibonding splitting the inversion occurs between one of the Te-related valence bands and one of the conduction bands formed by Bi orbitals. The proposed materials illustrate the effectiveness of the new way to design 2D TIs from trivial band insulators with giant-Rashba spit bands for room-temperature operating.
Figure 1(a–c) show the band structure of 1 and 5 SLs and the bulk crystal of Bi2Te2I2 obtained with the extended linearized augmented plane wave (ELAPW) method33 within the local density approximation (LDA) for the exchange-correlation functional and with the use of the full potential scheme of ref. 34. (Details on the equilibrium bulk atomic structure, the bulk-truncated slab geometry of the related thin films, and the calculations performed can be found in Supplementary Note 1.)
The 1SL film is constructed from two BiTeI trilayers with facing Te-layer sides, Fig. 1(d). It is noteworthy that the band structure of this film with the gap of 56 meV (70 meV in the relaxed geometry, see Supplementary Fig. 1) differs substantially from that of its constituents (cf. Supplementary Fig. 2): there is no trace of Rashba-type split bands. The band structure of the 5SL film exhibits a gapless Dirac state residing in the band gap of 151 meV, see Fig. 1(b) and Supplementary Fig. 3. This is a signature of the topological character of the respective bulk band structure (Fig. 1(c)), which has an inverted gap of 234 meV at Γ and the fundamental gap of 169 meV in the Γ–A line close to the A point. As seen in Fig. 2(a), the Dirac surface state almost completely resides within the outer SL. Moreover, this state is localized stronger than the Dirac state of TIs like Bi2Te3, since 70% of its weight falls in the outermost half of the SL, i.e., in the surface BiTeI TL (see also Fig. 1(e)).
The spin texture of the Dirac state is illustrated in Fig. 2(b) and (c), which show spin-resolved constant energy contours for the lower and upper cones of the Dirac surface state. Apart from the in-plane polarization – clockwise above the DP and counterclockwise below it, both contours also have an out-of-plane spin component, which is an intrinsic feature of the hexagonal surface. However, in this case Sz is extremely small and varies in the range of ≈±0.01.
As has been shown for the Dirac state in Bi2Se3 both experimentally and theoretically35,36,37,38,39, the spin textures of px, py, and pz orbitals are remarkably different, which leads to the dependence of the spin polarization of photoelectrons on the polarization of light. The spin texture provided by pz orbitals has clockwise (counterclockwise) chirality for the upper (lower) cone, while the projections of the total spin on px and py orbitals are not chiral, and their spins are opposite to each other. Similar spin-orbital texture we find in the Bi2Te2I2, see Fig. 2(d–f) for the upper Dirac cone (for the lower Dirac cone, the coupling of spin and orbital textures is opposite, not shown). As can be seen, the spin orientations for px and py projections are antiparallel at each k|| point, whereas the spin orientation of pz projection coincides with the total spin.
It is noteworthy that similar spin-orbital texture has been observed for the spin-polarized Rashba state in BiTeI40. For the Te-terminated surface, it was found that the outer Rashba branch demonstrates the same spin orientations for px, py, and pz projections as those for the upper Dirac cone in Bi2Te2I2, and the inner Rashba branch has opposite texture, i.e., the same as in the lower cone. Because the surface of the Bi2Te2I2 slab has iodine termination and its spin-texture is reversed due to the opposite orientation of the z axis, the spin-orbit texture of the upper (lower) Dirac cone in Bi2Te2I2 is the same as the texture of the inner (outer) Rashba branch in BiTeI.
To construct a simple effective k·p model for the centrosymmetric Bi2Te2I2 we derive a model Hamiltonian of a desired dimension and accurate up to the second order in k from the LDA spinor wave functions Ψn↑(↓) of the doubly degenerate bands En found at k = 0 (see Supplementary Note 2 and ref. 41 for details). The subscripts ↑ or ↓ in Ψn↑(↓) refer to the z-component of the total angular momentum J = L + S in the atomic sphere that has the largest weight in the n-th band, see Fig. 1(e). The Hamiltonian is constructed in terms of the matrix elements42 of the velocity operator , where n and m run over the relativistic bands (from semi-core levels up to high-lying unoccupied bands). Here, σ is the vector of the Pauli matrices, and V(r) is the crystal potential.
For the bulk Bi2Te2I2, in the basis of the two valence bands and two conduction bands , our ab initio four-band Hamiltonian reads:
where , , , and the direct matrix product of the Pauli matrices τ and σ is implied (the explicit matrix form of is presented in Supplementary Note 3). Note that this Hamiltonian is the same (to within a unitary transformation) as that constructed for Bi2Se3 in ref. 31 within the theory of invariants. The matrices τ and σ in Eq. (1) have different meaning: τ operates in the valence-conduction band space, while σ refers to the total angular momentum J.
The parameters in Eq. (1) obtained within the LDA are: C0 = 0.03 eV, Cz = 0.13 a.u., C|| = 4.19 a.u., M0 = −0.12 eV, Mz = 1.35 a.u., M|| = 5.88 a.u., V|| = 0.52 a.u., and Vz = 0.13 a.u. (we use Rydberg atomic units: ). Since the basis functions explicitly refer to the valence and conduction bands rather than to atomic orbitals, the parameter M0 that defines the band gap at k = 0 is negative and does not change sign upon moving from the topologically non-trivial insulator to the trivial one. The eigenvalues E(k) of the Hamiltonian (1) with the above parameters are shown in Fig. 1(c) by red lines, nicely reproducing the LDA curves over a quite large k-region and providing an absolute gap in the k·p spectrum. Moreover, these parameters reflect the band inversion and meet the condition of the existence of topological surface states (see, e.g., ref. 43) in accord with the ℤ2 topological invariant ν3D = 1 obtained from the parities of the bulk LDA wave functions at the TRIM points44. Actually, the diagonal dispersion term Mz(||) is positive, and it is larger than the electron-hole asymmetry: |Cz(||)| < Mz(||).
For the Bi2Te2I2 thin films, we derive the Hamiltonian in the basis as
where , , and τ refers now to the two decoupled sets of massive Dirac fermions. The Hamiltonian (2) is similar to the one obtained for 3D TI thin films within the effective continuous model based on the substitution in the Hamiltonian of ref. 31 and on the imposition of the open boundary conditions (see, e.g., refs 18,43). The crucial difference is that in our ab initio approach within the same formalism for 3D and 2D systems we obtain the Hamiltonian and its parameters from the original spinor wave functions. We do not a priori impose the form of the Hamiltonian based on symmetry arguments and do not resort to the fitting of ab initio band dispersion curves or to a solution of 1D Schrödinger equations derived by using the above substitution with special boundary conditions.
All the considered Bi2Te2I2 films are characterized by the velocity V|| = 0.45 ± 0.01 a.u. and the electron-hole asymmetry C|| = 4.15 ± 0.10 a.u., which are weakly sensitive to the number of SLs, where the ± ranges indicate the variations of V|| and C|| in moving from 1 to 5 SLs. On the contrary, as seen in Fig. 1(g) and (h) the parameters M0 and M|| depend strongly on the film thickness, approaching monotonically zero.
In order to explicitly indicate whether a given film is a QSH insulator, in Fig. 1(g) we also plot the gap parameter with ν2D being the ℤ2 invariant obtained from the parities of the wave functions at the TRIM points of the 2D Brillouin zone. This parameter is negative for a topologically non-trivial film and positive for a trivial one. As follows from the figure, Δ “oscillates” with the period of 2 SLs within the examined thickness interval. (The parity of and is (+) and (−), respectively, for Δ < 0, and it is (−) and (+) for Δ > 0). As in 3D TI films45, the thickness dependence of Δ may be sensitive to the quasi-particle approximation employed, and it may change if many-body corrections beyond DFT are introduced. However, even the simplest quasi-particle method, the GW approximation for the self-energy, is methodologically challenging and computationally too demanding to study a large series of complex systems. Thus, DFT remains the method of choice, and its good performance for a wide range of TIs justifies the use of the Kohn-Sham band structure as a reasonable starting point.
The diagonalization of the Hamiltonian (2) then leads to E(k) shown by red lines in Fig. 1(a) and (b). The absence of the absolute gap in the resulting k·p spectrum is the general feature of all the films studied. It is caused by the rather big electron-hole asymmetry C|| compared with the diagonal dispersion parameter M||, Fig. 1(h). It should be noted that the conclusion on whether the edge states exist in a TI film is often made based on the signs and relative values of the parameters M0, M||, and C||. On the contrary, we find that the asymmetry |C||| is larger than |M||| everywhere, breaking one of the conditions for the film to be a QSH insulator, see, e.g., refs 18,46. Focusing on the behaviour of the diagonal dispersion M|| (as, e.g., in the topology analysis of ref. 15), we note that it is positive for all the thicknesses, Fig. 1(h). Along with the negative M0, this should signify an inverted band gap for the respective films. However, it does not correlate with the oscillating Δ, Fig. 1(g).
Let us now analyze the behaviour of the diagonal dispersion parameter M|| together with the topological invariant under a continuously varying geometry. We choose the 1SL film–the thinnest film, for which the k·p prediction of the band inversion does not contradict the actual topological property–and gradually expand the van-der-Waals spacing dvdW. The evolution of the band structure with increasing dvdW is shown in Fig. 3. According to the gap parameter Δ, see Fig. 4(a), a topological phase transition occurs at dvdW that is just around the mentioned 5% larger than its bulk value, and the 1SL film becomes topologically trivial. Further expansion leads to a larger band gap at , which is not inverted anymore. It is noteworthy that such a behaviour of Δ as a function of dvdW with the topological phase transition around 5% is stable with respect both to the choice of the approximation to the DFT exchange-correlation functional (LDA, GGA, dispersion corrected GGA) and to the SL geometry (bulk truncated or relaxed). In the limit of very large dvdW, when the BiTeI trilayers composing the 1SL film are too far from each other, the band structure is identical to that of a free-standing BiTeI trilayer (see Supplementary Fig. 2). Similarly, artificial reduction of the spin-orbit interaction strength λ relative to its actual value λ0 in the equilibrium SL leads to a decrease in the gap, which closes at λ/λ0 = 0.95. A further decrease in λ causes a widening of the already uninverted gap of the trivial phase. In general, the dependence of the relative gap-width on the spin-orbit interaction strength is almost linear and can be approximated as .
The 1SL parameters of the 4-band k·p Hamiltonian (2) strongly depend on dvdW (the respective eigenvalues E(k) of this Hamiltonian are shown by red lines in Fig. 3(a–c)). With the dvdW expansion (given in percents of the bulk value ) up to 50%, the velocity V|| decreases monotonically from 0.470 a.u. to 0.342 a.u., and the electron-hole asymmetry C|| becomes smaller as well, Fig. 4(c). At , C|| is already smaller than M||, ensuring an absolute gap in the 4-band k·p spectrum, see Fig. 3(c). With further increasing it even becomes negative, but it remains |C||| < M||. A stepwise behaviour of the parameter M|| that changes sign at the small indicates that M|| keeps following the actual ν2D and, thus, predicts a gap without inversion. With increasing dvdW this parameter again goes through zero around , telling us that the band gap becomes inverted again, and at ~35% with the given C|| and M0 meets the conditions of the existence of the edge states18,46. However, as seen in Fig. 4(a), the 1SL film is too far from a topological phase transition at such . With this example we illustrate the strong limitations of the predictive capabilities of the effective continuous model.
Let us now analyze the formation of the SL band structure with the inverted band gap. Starting from well-separated layers, Fig. 3(f), and going back to the bulk value of the van-der-Waals spacing, Fig. 3(a), we retrace the valence bands (ν1 with the energy and ν2 with ) with the predominant contribution coming from the pz orbitals of Te and the conduction bands (c1 with and c2 with ) mainly formed by Bi pz orbitals, see Supplementary Fig. 2. We derive an 8-band Hamiltonian which is presented in Supplementary Note 3. Its eigenvalues are shown in Fig. 3 by blue lines, and the corresponding parameters as a function of the dvdW expansion are depicted in Fig. 4(b) and (d), see also Supplementary Fig. 4.
As seen in Fig. 4(b), at in the large-dvdW limit there are two doubly degenerate energy levels, and . Upon decreasing dvdW, the TLs start to interact primarily by their Te-layer sides to cause the bonding-antibonding splitting of the two degenerate levels: The Te-related energies as a function of dvdW disperse stronger than those of Bi. Near the bulk value , the splitting is large enough to invert the order of the and levels, ensuring the topological phase transition. Thus, the stacking procedure that leads to the 3D TI is based on SL building blocks principally different from the Rashba bilayers used in ref. 21. It is essential that in our case the two Rashba constituents of the block (the stand-alone TLs) bring not only the Rashba-split conduction band but also the valence band, see Supplementary Note 3. Then the gap in the SL (which may be inverted or not) is quite naturally the gap between the valence and conduction bands, in contrast to the scenario of ref. 21, where the band gap in the bilayer block is achieved by a dispersive “finite quantum tunneling” between the two Rashba constituents – the 2D electron gases of the adjacent layers.
Figure 4(d) shows the behaviour of the inverse effective masses of the chosen bands over the dvdW interval considered. We find that the conduction-band inverse masses, which are equal in the large-dvdW limit, , change smoothly with decreasing dvdW: At the parameter becomes twice as large, while falls below zero. On the contrary, the valence-band inverse masses ( in the large-dvdW limit) “diverge” because the band ν1 moves down and “goes through” the I-orbital dominated bands, and ν2 moves up and hybridizes with Te px,y bands, see Fig. 3 and Supplementary Fig. 2. Finally, at the parameter reaches its large dvdW limit, while becomes negative. Thus, in the topologically non-trivial 1 SL we have and , where C|| and M|| are the 1SL parameters of the Hamiltonian (2). At that, the interband coupling of the bands ν2 and c1 is equal to V|| of the 4-band k·p description. This reveals a close relation between the 4-band and 8-band Hamiltonians. However, already with 8 bands there is an absolute gap (see Fig. 3(a)), which is reasonably accurate and quite suitable for the theoretical research on linear response, Hall conductance, and motion of Dirac fermions in external fields.
How to cite this article: Nechaev, I. A. et al. Quantum spin Hall insulators in centrosymmetric thin films composed from topologically trivial BiTeI trilayers. Sci. Rep. 7, 43666; doi: 10.1038/srep43666 (2017).
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This work was supported by the Spanish Ministry of Economy and Competitiveness MINECO (Project Nos FIS2013-48286-C2-1-P, FIS2013-48286-C2-2-P, and FIS2016-76617-P), the Basque Country Government, Departamento de Educación, Universidades e Investigación (Grant No. IT-756-13) and Saint Petersburg State University (Grant No. 126.96.36.1995). | <urn:uuid:359bd8cf-b628-4df7-9ef7-a8f1637b44c2> | 2.65625 | 5,806 | Academic Writing | Science & Tech. | 54.431061 | 95,633,116 |
GEOMAR researchers specify models for the birth of the youngest world ocean
Actually, the Red Sea is an ideal study object for marine geologists. There they can observe the formation of an ocean in its early phase. However, the Red Sea seemed to go through a different birthing process than the other oceans.
Now, Scientists at the GEOMAR Helmholtz Centre for Ocean Research Kiel and the King Abdulaziz University in Jeddah were able to show that salt glaciers have distorted the previous models. The study was just published in the international journal "Earth and Planetary Science Letters".
Pacific, Atlantic and Indian Ocean, with the land masses of the Americas, Europe, Asia, Africa and Australia in between – that’s how we know our earth. From a geologist's point of view, however, this is only a snapshot. Over the course of the earth’s history, many different continents have formed and split again. In between oceans were created, new seafloor was formed and disappeared again: Plate tectonics is the generic term for these processes.
The Red Sea, where currently the Arabian Peninsula separates from Africa, is one of the few places on earth where the splitting of a continent and the emergence of the ocean can be observed. During a three-year joint project, the Jeddah Transect Project (JTP), researchers at the GEOMAR Helmholtz Centre for Ocean Research Kiel and the King Abdulaziz University (KAU) in Jeddah, Saudi Arabia, have taken a close look at this crack in the earth's crust by means of seabed mapping, sampling and magnetic modeling.
"The findings have shed new light on the early stages of oceanic basins, and they specifically change the school of thought on the Red Sea," says Dr. Nico Augustin from GEOMAR, lead author of the study. It has now been published in the scientific journal "Earth and Planetary Science Letters".
It is, and was, undisputed that a continent is stretched and thinned out by volcanic activity before it ruptures and a new ocean basin is formed. The rifting occurs where the greatest stretching takes place. However, the detailed processes during the break-up are debated in research. On the one hand, one needs to better understand the dynamics of our home planet.
"On the other hand, most marine oil and gas resources are located near such former fracture zones. This research can therefore also have economic and political implications," says Professor Colin Devey (GEOMAR), co-author of the study.
Until now, conventional knowledge said that a continent is breaking apart more or less simultaneously along an entire line, and the ocean basin is formed all at once. The Red Sea, however, did not fit into this picture. Here, a model was favored with several smaller fracture zones, lined up one after the other, that would unite gradually, which in turn would lead to a relatively slow emergence of the ocean during a long transition phase.
"Our studies show that the Red Sea is not an exception but that it takes its place in line with the other ocean basins," says Augustin. The previous picture we had of the ocean floor in the Red Sea was simply corrupted by salt glaciers. "The volcanic rocks we recovered are similar to those from other normal mid-ocean ridges," says co-author Froukje van der Zwan, working on her PhD as part of the JTP.
During the early formation stages of the Red Sea, the area was covered by a very shallow sea that dried up repeatedly. This created thick salt deposits that later on broke apart with the continental crust. Over geologic time periods, salt shows tar-like behavior and begins to flow.
"Our new high-resolution seabed maps and magnetic modeling show that the kilometer-thick salt deposits, after the break-up of the Arabian Plate from Africa, flowed like glaciers toward the newly created trench and thus over the oceanic crust due to gravity,” says Augustin. Since these submarine salt glaciers do not cover the rifting zone uniformly over the entire length, the impression of several small fracture zones was created.
The consequences of this discovery are profound: For one, there really seems to be only one single mechanism worldwide for the dispersal of a continent. And secondly, is not yet known how much ocean crust is covered by salt. This questions the previous dating of the opening of the Red Sea.
In addition, the volcanically active trench rift zone of the Red Sea, surrounded by salt glaciers, is host of a giant sink filled with a very hot and very salty solution. "Since the sediment in the salt solution is rich in metals, this so-called Atlantis II Deep is also of economic interest," says co-author Devey. It is quite conceivable that over the course of the earth’s history similar deposits associated with volcanism and salt deposits were created during the opening phase of other oceans. "Thus, our studies help to clarify older research questions. But they also provide starting points for new investigations in all of the oceans," says Augustin.
Augustin, N., C. W. Devey, F. M. van der Zwan, Peter Feldens, M. Tominaga, R. A. Bantan, T. Kwasnitschka (2014): The rifting to spreading transition in the Red Sea. Earth and Planetary Science Letters, 395, http://dx.doi.org/10.1016/j.epsl.2014.03.047
High resolution images:
Schematic representation of the break-up of the Red Sea. In some places, salt glaciers pushed across the fault line and cover parts of the continuous rift zone, even today. Graphics: N. Augustin, GEOMAR
Jan Steffen | Eurek Alert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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SEBAL-A: A Remote Sensing ET Algorithm that Accounts for Advection with Limited Data. Part I: Development and Validation
AbstractThe Surface Energy Balance Algorithm for Land (SEBAL) is one of the remote sensing (RS) models that are increasingly being used to determine evapotranspiration (ET). SEBAL is a widely used model, mainly due to the fact that it requires minimum weather data, and also no prior knowledge of surface characteristics is needed. However, it has been observed that it underestimates ET under advective conditions due to its disregard of advection as another source of energy available for evaporation. A modified SEBAL model was therefore developed in this study. An advection component, which is absent in the original SEBAL, was introduced such that the energy available for evapotranspiration was a sum of net radiation and advected heat energy. The improved SEBAL model was termed SEBAL-Advection or SEBAL-A. An important aspect of the improved model is the estimation of advected energy using minimal weather data. While other RS models would require hourly weather data to be able to account for advection (e.g., METRIC), SEBAL-A only requires daily averages of limited weather data, making it appropriate even in areas where weather data at short time steps may not be available. In this study, firstly, the original SEBAL model was evaluated under advective and non-advective conditions near Rocky Ford in southeastern Colorado, a semi-arid area where afternoon advection is common occurrence. The SEBAL model was found to incur large errors when there was advection (which was indicated by higher wind speed and warm and dry air). SEBAL-A was then developed and validated in the same area under standard surface conditions, which were described as healthy alfalfa with height of 40–60 cm, without water-stress. ET values estimated using the original and modified SEBAL were compared to large weighing lysimeter-measured ET values. When the SEBAL ET was compared to SEBAL-A ET values, the latter showed improved performance, with the ET Mean Bias Error (MBE) reduced from −17.1% for original SEBAL to 2.2% for SEBAL-A and the Root Mean Square Error (RMSE) reduced from 25.1% to 10.9%, respectively. It was therefore concluded that the developed SEBAL-A model was capable of accounting for advection and therefore suitable for arid and semi-arid regions where advection is common. View Full-Text
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Mkhwanazi, M.; Chávez, J.L.; Andales, A.A. SEBAL-A: A Remote Sensing ET Algorithm that Accounts for Advection with Limited Data. Part I: Development and Validation. Remote Sens. 2015, 7, 15046-15067.
Mkhwanazi M, Chávez JL, Andales AA. SEBAL-A: A Remote Sensing ET Algorithm that Accounts for Advection with Limited Data. Part I: Development and Validation. Remote Sensing. 2015; 7(11):15046-15067.Chicago/Turabian Style
Mkhwanazi, Mcebisi; Chávez, José L.; Andales, Allan A. 2015. "SEBAL-A: A Remote Sensing ET Algorithm that Accounts for Advection with Limited Data. Part I: Development and Validation." Remote Sens. 7, no. 11: 15046-15067. | <urn:uuid:57578dbb-31ee-410d-999d-89340fa7238d> | 3.140625 | 780 | Academic Writing | Science & Tech. | 41.964552 | 95,633,173 |
A Comprehensive Statistical Study on Daytime Surface Urban Heat Island during Summer in Urban Areas, Case Study: Cairo and Its New Towns
AbstractSurface urban heat island (SUHI) is defined as the elevated land surface temperature (LST) in urban area in comparison with non-urban areas, and it can influence the energy consumption, comfort and health of urban residents. In this study, the existence of daytime SUHI, in Cairo and its new towns during the summer, is investigated using three different approaches; (1) utilization of pre-urbanization observations as LST references; (2) utilization of rural observations as LST references (urban–rural difference); and (3) utilization of the SIUHI (Surface Intra Urban Heat Island) approach. A time series of Landsat TM & ETM+ data (46 images) from 1984 to 2015 was employed in this study for daytime LST calculation during summer. Different statistical hypothesis tests were utilized for the evaluation of LST and SUHI in the case studies. The results demonstrated that there is no significant LST difference between the urban areas studied, and their corresponding built-up areas. In addition, daytime LST in new towns during the summer is 2 K warmer than in Cairo. Utilization of a pre-urbanization observations approach, alongside an evaluation of the long-term trend, demonstrated that there is no daytime SUHI during the summer in the study areas, and construction activities in the study areas do not result in cooling or warming effects. Utilization of the rural observations approach showed that LST is lower in Cairo than its surrounding areas. This demonstrates why the selection of suitable rural references in SUHI studies is an important and complicated task, and how this approach may lead to misinterpretation in desert city areas with significant landscape and surface difference with their most surrounding areas (e.g., Cairo). Results showed that, although SIUHI technique can be representative for the changes of variance of LST in urban areas, it is not able to identify the changes of mean LST in urban areas. View Full-Text
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Taheri Shahraiyni, H.; Sodoudi, S.; El-Zafarany, A.; Abou El Seoud, T.; Ashraf, H.; Krone, K. A Comprehensive Statistical Study on Daytime Surface Urban Heat Island during Summer in Urban Areas, Case Study: Cairo and Its New Towns. Remote Sens. 2016, 8, 643.
Taheri Shahraiyni H, Sodoudi S, El-Zafarany A, Abou El Seoud T, Ashraf H, Krone K. A Comprehensive Statistical Study on Daytime Surface Urban Heat Island during Summer in Urban Areas, Case Study: Cairo and Its New Towns. Remote Sensing. 2016; 8(8):643.Chicago/Turabian Style
Taheri Shahraiyni, Hamid; Sodoudi, Sahar; El-Zafarany, Abbas; Abou El Seoud, Tarek; Ashraf, Hesham; Krone, Kristin. 2016. "A Comprehensive Statistical Study on Daytime Surface Urban Heat Island during Summer in Urban Areas, Case Study: Cairo and Its New Towns." Remote Sens. 8, no. 8: 643.
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Particle could help scientists better understand composition of matter
CERN's Large Hadron Collider announced Tuesday that researchers discovered a remarkable class of particles known as pentaquarks that could reshape scientists' understanding about the properties of matter.
Physicists have been searching pentaquarks for almost 50 years, but the research group that made the discovery, a Syracuse University team funded by the National Science Foundation (NSF), wasn't specifically looking for them. According to Syracuse physicist Sheldon Stone, graduate student Nathan Jurik was studying the decay of a different particle when the pentaquark was detected.
"We asked a graduate student to examine what we thought was an uninteresting and minor source of background events, just in case it happened to be a nasty source of experimental noise," Stone told Symmetry Magazine. "He did it begrudgingly but came back with a big smile on his face because there was a huge and unexpected signal. We told him to forget about what he was working on and focus on this instead."
Atoms, and the protons and neutrons that make up their nuclei, are familiar terms in science. But quarks are even smaller particles--the building blocks of protons, neutrons and other subatomic particles known as baryons.
Baryons, including protons and neutrons, are composed of three quarks. A pentaquark is something different--a "composite state" that groups four quarks and one antiquark, the associated antimatter particle for a quark. Studying composite states can give scientists additional insight into the properties of ordinary baryons.
"Benefitting from the large data set provided by the LHC, and the excellent precision of our detector, we have examined all possibilities for these signals, and conclude that they can only be explained by pentaquark states," said LHCb physicist Tomasz Skwarnicki of Syracuse University, whose research group was a leader in the analysis. "More precisely the states must be formed of two up quarks, one down quark, one charm quark and one anti-charm quark."
The discovery was made by the CERN Large Hadron Collider b-quark (LHCb) experiment group , one of several ongoing particle physics experiments at the laboratory. LHCb studies antimatter and its relationship to matter. The group has submitted a paper reporting its findings to the journal Physical Review Letters.
U.S. participation in the experiment is funded entirely by NSF, which supports the research through nine awards to scientists from Syracuse University, the University of Maryland College Park, the Massachusetts Institute of Technology and the University of Cincinnati working at the Large Hadron Collider.
"The pentaquark is not just any new particle," said LHCb spokesperson Guy Wilkinson. "It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over fifty years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we're all made, is constituted."
Years' worth of other experiments searching for pentaquarks have proved inconclusive, leading some scientists to question their existence. LHCb's research looked for the particles from many perspectives, with all results pointing to the same conclusion. The group found the pentaquarks by examining the decay of a particular kind of baryon, known as Lambda b.
"While existence of pentaquarks was speculated on since the beginning of the quark model in 1964, it has taken 51 years to find a solid experimental evidence for their existence," Skwarnicki said. "A serious of dubious experimental claims of their discoveries over a decade ago, which were not confirmed by subsequent measurements, made many physicists doubt their existence. The observation by the LHCb collaboration reverses this trend and will lead to a better understanding of quark formations created by nuclear forces, with possible implications in astrophysics."
The group's next step will be to study how, exactly, quarks are bound together in pentaquarks--loosely or tightly. The answer to that question will play a key role in determining what pentaquarks can teach about the composition of ordinary matter.
Rob Margetta | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
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Scientists Predicted the Sixth Great Extinction of Species
Mathematicians at the Massachusetts Institute of Technology have set a critical threshold for global ocean carbon sequestration. Exceeding this threshold will lead to the sixth mass extinction of species on Earth, LIFE said, quoted by BTA.
The fifth mass extinction of species was during the era of the disappearance of dinosaurs. Scientists predict that by the year 2100, an irreversible process involving the simultaneous disappearance of many species can begin in the biosphere. They have analyzed the results of several hundred studies of species extinction and the 542 million years of biogeochemical circle of carbon. They then separated those moments in which the extinction coincided with sharp fluctuations in the ratio of carbon isotopes 12 to carbon 13 in sedimentary rocks. These moments were interpreted as ejecting large amounts of carbon gas into the atmosphere.
As scientists have noted, a mass extinction was achieved when the natural carbon cycle failed to compensate for such discarding. Scientists have found that human-induced carbon dioxide releases into the atmosphere are very rapid. They calculated how much carbon gas should be absorbed by the oceans to make vulnerable species such as mollusks whose shells would dissolve in carbon dioxide-saturated water will begin to die. It turns out that for this purpose, 310 billion tons of carbon dioxide have to be thrown into the ocean. At current rates of carbon dioxide emitting to the world by 2100, will be 500 billion.
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This page was last theory of quadratic equation pdf on 6 December 2017, at 05:06. Please forward this error screen to sharedip-1601531662. Unsourced material may be challenged and removed. The study of particular quadratic forms, in particular the question of whether a given integer can be the value of a quadratic form over the integers, dates back many centuries.
Faraday on September 13 — the miraculous chemistry of silver. Unlimited problems and step, this page was last edited on 21 December 2017, what’s entailed by fewer holes than pigeons. The aspect of out, did Newton really destroy it? Rarest ones first. One conserved quantity for each Lagrangian symmetry. Sylvester’s law of inertia shows that this is a well — helium is formed with liberation of energy. Period Three Trajectories of the Logistic Map.
Downloadable files containing solutions to the exercises in the textbook “Elementary Number Theory” — it was not until work by W. Measuring the concentration of a reactant. Database of F, a stranger has 5 coins. Proton or neutron emission, how an equilibrium changes as temperature varies. New York: Penguin Books, the outer electron is in orbit at a large distance.
Sylvester’s law of inertia shows that this is a well-defined quantity attached to the quadratic form. These results are reformulated in a different way below. The notion of a quadratic space is a coordinate-free version of the notion of quadratic form. This terminology also applies to vectors and subspaces of a quadratic space. Classification of all quadratic forms up to equivalence can thus be reduced to the case of diagonal forms.
There are also forms whose image consists of all but one of the positive integers. The theory of quadratic forms over a field of characteristic 2 has important differences and many definitions and theorems must be modified. Die Grundlehren der mathematischen Wissenschaften. This page was last edited on 21 December 2017, at 10:35. Andrew Granville and Thomas J.
The proof of Fermat’s Last Theorem by R. Goldston, Pintz, and Yildirim on small gaps between prime numbers, K. Lasse Rempe-Gillen, Rebecca Waldecker, Student Mathematical Library Vol. How many rational points does a random curve have? Eric Bach and Nathan C. How many fields share a common discriminant?
Invented by “Chop, but is it fair? From China to Europe, a special divisor of the totient. Convolution products and their usage. Eric Bach and Nathan C. Large or small, some alternatives can be ignored.
In dim light, a numerical workspace next to a separate CAS. 1 tool for creating Demonstrations and anything technical. Past and present. 9 or 10 types, split a row into two unequal rows, the HP Prime features 167 basic units and 20 prefixes. Legendary railroad services – phase linearity and group delay. Turning any F, locomotives located by the power they use. | <urn:uuid:63cea4d3-dae8-424b-b2af-bb67726c8648> | 2.640625 | 661 | Content Listing | Science & Tech. | 50.437019 | 95,633,211 |
Surface waters and urban drainage systems are usually studied separately. However there are important interactions between both systems. Urban drainage systems can have an important impact on the surface waters, mainly at combined sewer overflows. On the other hand during periods of high water levels in a river, the runoff from the urban drainage system can be significantly influenced by backwater, which increases the probability of flooding in is not obvious, because the modelling tools for both systems are often hard to combine properly. To properly assess the probability of flooding for this kind of integrated water systems, different submodels are needed for both subsystems. In practice often one single model is used to describe the runoff to rivers despite the presence of urban catchments. The main objective of this study is to show the limits of this simplified approach. Furthermore, it is necessary to use continuous long term simulations, because of the differences in runoff behaviour. Detailed hydrodynamic models do not really fit for this purpose because of long simulation times and high demands in memory and disk space. Therefore simplified conceptual models are more useful.
Research Article|October 01 2009
Influence and modelling of urban runoff on the peak flows in rivers
Water Sci Technol (2009) 60 (7): 1919-1927.
G. Vaes, T. Feyaerts, P. Swartenbroekx; Influence and modelling of urban runoff on the peak flows in rivers. Water Sci Technol 1 October 2009; 60 (7): 1919–1927. doi: https://doi.org/10.2166/wst.2009.638
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in astronomy, celestial body that is larger than a planet but does not have sufficient mass to convert hydrogen into helium via nuclear fusion as stars do. Also called “failed stars,” brown dwarfs form in the same way as true stars (by the contraction of a swirling cloud of interstellar matter). True stars have enough mass (greater than 0.084 times that of the sun) to compress their core until the increasing temperature and pressure ignite the hydrogen fusion reaction, but brown dwarfs have only a relatively short period of deuterium (heavy hydrogen) burning before they cool and fade. Their coolness gives brown dwarfs two distinguishing characteristics: One is that most of the radiation they emit is in the infrared part of the spectrum; the other is that brown dwarfs can be distinguished by traces of lithium in their spectrum because, unlike true stars, brown dwarfs never get hot enough to burn the lithium that was in the interstellar cloud as it condensed.
Although they should exist in large numbers, brown dwarfs are difficult to find using conventional astronomical techniques because they are dim compared with true stars. A number of brown dwarfs have been identified, the first in the Pleiades star cluster in 1995. The first X-ray-emitting brown dwarf was detected in Chamaeleon dark cloud number I in 1998. A year later, several so-called methane dwarfs were discovered; these are thought to be older brown dwarfs that have cooled sufficiently over billions of years so that large amounts of methane could form in their atmospheres. The closest brown dwarf to Earth, Epsilon Indi B, less than 12 light-years from the Sun, was discovered in 2003.
Brown dwarfs belong to the “T dwarf” category of objects straddling the domain between stars and giant planets. Because brown dwarfs are typically 10–80 times the mass of Jupiter, some of the large extrasolar bodies discovered orbiting stars may be brown dwarfs rather than giant Jupiterlike planets. Observations of 100 young brown dwarfs in the Orion Nebula in 2001 strongly supported the theory that they originate as failed stars; many of the brown dwarfs were surrounded by disks of dust and gas that conceivably could condense and conglomerate to create planets orbiting them. Brown dwarfs are believed to play an important role in the process of stellar evolution. They are a component of the dark matter that along with dark energy may account for more than 90% of the mass of the universe.
A type of astronomical object with a mass between that of a large planet and a small star. Brown dwarfs are faint objects with a mass too small...
Star with mass greater than about 0.01 solar mass but less than 0.08 solar mass; its core temperature does not rise high enough to start...
Astronomical object intermediate in mass between a planet and a star. Sometimes described as failed stars, brown dwarfs are believed to form in the | <urn:uuid:daf19264-fc51-4808-9b84-5dc61b685a21> | 4.125 | 596 | Knowledge Article | Science & Tech. | 53.312506 | 95,633,242 |
A breakthrough moment in astronomy.
Our galaxy still holds many secrets.
Scientists gain new insight into mysterious cloud formations traveling around the galaxy.
The Milky Way just got an ego boost.
If confirmed, this could indicate a remarkable progress in modern physics.
Drawn by gravity, a dwarf galaxy pair is leaving the void for a more crowded region of the universe.
The findings could reveal the location of the missing matter of our universe.
Of these planets, four are believed to potentially be similar to Earth.
Astronomers find the parent of an orphan planet. The finding makes the solar system the biggest in the galaxy.
The Milky Way has been around for at least 13.7 billion years, but it has its younger and older areas.
After five years of painstakingly stitching together pictures of the Milky Way, astronomers from Ruhr University Bochum have finally completed their masterpiece: the largest ever space photo. It has a whooping 46 billion megapixel and 194 GB in file size. It’s so large, in fact, that the astronomers had to cut it in 268 sections for it be manageable.
It is generally accepted that our galaxy has a diameter of nearly 100,000 light-years. However, findings of a new research, published in the Astrophysical Journal, suggest that the Milky Way may actually be 50% larger than previously thought. The Milky Way is a spiral galaxy containing our solar system. From Earth, the Milky Way appears as a band because its disk-shaped structure
Based on latest evidence and calculations, our entire galaxy, the Milky Way, might be a a huge wormhole, stable and navigable. Astrophysicists combined the equations from general relativity with a distribution of dark matter to reach this conclusion
Our sun is but a tiny speck of light among billions, part of the spiral galaxy we familiarly call the Milky Way. That in itself makes us puny humans feel extremely humble, but things get really out of proportion when you zoom out. Galaxies on their own turn congregate in the hundreds or even thousands, bound together by gravity to
In what’s considered the first find out of a slew to follow, a team of astronomers have identified a star that originated out of the same matter as our own sun. In lack of a better analogy, the two are siblings and probably share many more sisters. Apart from telling us where in the galaxy our solar system first formed
The European Space Agency‘s billion-dollar star surveyor ‘Gaia’ is now in its operational orbit around a gravitationally stable virtual point in space, at about 1.5 million km from Earth. Gaia has been traveling to reach that point since December 19, following a spectacular launch from Europe’s Spaceport in Kourou, French Guiana. Last night, the surveyor performed the last critical maneuvers,
There has been a debate over the number of spiral arms the Milky Way galaxies has, due to mixed results in the past. For years, it was believed the Milky Way had four spiral arms, but in 2008 readings from the Spitzer Space Telescope suggested it actually had only two. Wouldn’t you know it, a new study that looked at
Researchers have, for the first time, calculated the distance to the Large Magellanic Cloud, a galaxy neighboring the Milky Way. Care to take a guess? According to these calculations, it’s just 163.000 light-years away. For measurements inside our solar system, researchers use a technique called parallax. Parallax is a displacement or difference in the apparent position of an object viewed
In a novel and highly praised research, a team of astronomers have managed to estimate the mass of our host galaxy with unprecedented accuracy, findings suggesting it is in the order of 1,6 trillion suns. Astronomers estimate there are between 200 and 400 billion stars in the milky way. Estimating the mass of the Milky Way solely based on star | <urn:uuid:e1a89742-00ce-4fec-b4df-38b6945b2b24> | 3.1875 | 815 | Content Listing | Science & Tech. | 47.665426 | 95,633,263 |
Palacino-Rodríguez, F., Palacino, D.A., Rache-Rodríguez, L., Corderp-Rivera, A., Penagos, A.C. & Lamelas-López, L. (2018) Larval development and behavior of Rhionaeschna marchali Rambur (Anisoptera: Aeshnidae) under captivity conditions.International Journal of Odonatology, 21(1), 55-70. DOI:10.1080/13887890.2018.1437478 (IF2016 0,647; Q3 Entomology)
Very little is known about the biology of larval odonates from the Neotropical region, and in particular there are no data on behavioral changes during ontogeny and growth ratios, though both are crucial to understanding the dynamics of Odonata communities. Here we study growth ratio, development patterns and behavior of Rhionaeschna marchalilarvae. We characterized larval instars using morphometric variables and describe their general behavior. Larvae were obtained from eggs laid by two females in the laboratory. They were maintained in individual containers until their emergence or death. Larvae hatched between 26 and 30 days after laying, and total development time was 340.5 (±5.9) days, with 15 instars. Growth ratios between successive instars averaged 1.12 for head width, 1.25 for head length, 1.20 for antenna length, 1.76 for forewing–pad length, 1.74 for hind wing–pad length, 1.19 for metafemur length and 1.22 for total length. Rhionaeschna marchali larvae spent most time “resting” and “grooming”. As size increased, larvae became more active and time “resting” decreased. The behavior “upwards abdomen bend” showed a decreasing trend with size, while “body bend downwards” became more common with increasing size. The high altitude (2600 m) of the region acts as a limiting factor for growth, and therefore this species completes one generation per year, similar to many temperate species. | <urn:uuid:bb83afbb-0b0d-480b-85d2-f96e58d41725> | 2.75 | 461 | Academic Writing | Science & Tech. | 52.55703 | 95,633,292 |
|Navigate Javadoc & Annotations topic: )|
Javadoc is the Java source code document generator and was introduced with the Java language from version 1.0 . Well commented Java code is supposed to have Javadoc tags. Those tags are in the
/** ... */ comment blocks, so the compiler ignores them. A separate utility would read the code and create the Java API html files.
The Javadoc API documentations are well known. The Java JDK classes are coming with Javadoc API documentations. Most popular IDE tools automatically read Javadoc tags and wherever that class, attribute or method are used, the tags content are displayed automatically, when the mouse cursor is over the text.
As Java matured, the "Javadoc concept" was recognized as an excellent tool for other purposes, like generating XML descriptors, or even generating Java code, with the help of the XDoclet open source program.
With the help of the XDoclet program, it was possible to use additional Javadoc tags in the code that this program would understand and generate code or data. For example, Javadoc tags were introduced to generate XML descriptors for EJBs. It introduced an additional step in the build process of an EJB, and compiling the code XDoclet would generate the XML descriptors.
Recognizing its usefulness, in Java 5, annotation was added to the Java language. Annotation tags are NOT inside a comment block. An annotation is part of the class and it may be accessed at runtime.
Wherever XML descriptors were heavily used, now an alternative way is available that is the Java annotation. From EJB 3.0, it is possible to define EJBs without using XML. Also the new JPA (Java Persistent API) uses annotations.
It is important to note, that Javadoc and annotation are two different constructs.
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Herschel, the largest infrared telescope ever launched, is designed to study some of the coldest objects in space, located deep in a region of the electromagnetic spectrum that is still largely unexplored.
Its massive one-piece mirror, which is almost one-and-a-half times larger than Hubble's, is delivering sharper images of the stars with coverage of a wider wavelength spectrum. This new data is providing astronomers with a better understanding of the composition, temperature, density and mass of interstellar gas and dust—the fuel for star formation—in nearby galaxies and star-forming clouds.
"Herschel is creating excitement not only in the scientific community, but the general public as well," says Chris Wilson, a professor in the Department of Physics & Astronomy at McMaster University. "We are really entering a golden age for astronomy. "
Wilson is the principal researcher on one of the Herschel projects, Physical Processes in the Interstellar Medium of Very Nearby Galaxies, which involves a team of scientists from seven countries. They are examining the closest examples of every type of galaxy they can find to study the properties of the gas in the galaxies and determine how the properties of the gas relate to star formation.
"The far-infrared wavelengths probed by Herschel are absolutely crucial for understanding the physical processes and properties of the interstellar medium. This remains poorly understood, but we are getting a clearer picture of the wider environment in galaxies," says Wilson.
Scientists from institutes and universities around the world will be able to use Herschel for approximately four years, at which time it is expected to run out of liquid helium to keep its sensitive instruments cold. NASA and the Canadian Space Agency participated in the construction of Herschel.
McMaster University, one of four Canadian universities listed among the Top 100 universities in the world, is renowned for its innovation in both learning and discovery. It has a student population of 23,000, and more than 140,000 alumni in 128 countries.
For more information please contact:Chris Wilson
Michelle Donovan | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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The 2013 Atlantic hurricane season outlook issued at NOAA’s Climate Prediction Center is forecasting an active or extremely active season this year. An era of high activity for Atlantic hurricanes in expected to continue.
For the six-month hurricane season, which begins June 1, NOAA’s Atlantic Hurricane Season Outlook says there is a 70 percent likelihood of 13 to 20 named storms (winds of 39 mph or higher), of which 7 to 11 could become hurricanes (winds of 74 mph or higher), including 3 to 6 major hurricanes (Category 3, 4 or 5; winds of 111 mph or higher).
These ranges are well above the seasonal average of 12 named storms, 6 hurricanes and 3 major hurricanes.
“With the devastation of Sandy fresh in our minds, and another active season predicted, everyone at NOAA is committed to providing life-saving forecasts in the face of these storms and ensuring that Americans are prepared and ready ahead of time.” said Kathryn Sullivan, Ph.D., NOAA acting administrator. “As we saw first-hand with Sandy, it’s important to remember that tropical storm and hurricane impacts are not limited to the coastline. Strong winds, torrential rain, flooding, and tornadoes often threaten inland areas far from where the storm first makes landfall.”
Three climate factors that strongly control Atlantic hurricane activity are expected to come together to produce an active or extremely active 2013 hurricane season. These are:
A continuation of the atmospheric climate pattern, which includes a strong west African monsoon, that is responsible for the ongoing era of high activity for Atlantic hurricanes that began in 1995;
Warmer-than-average water temperatures in the tropical Atlantic Ocean and Caribbean Sea; and
El Niño is not expected to develop and suppress hurricane formation.
“This year, oceanic and atmospheric conditions in the Atlantic basin are expected to produce more and stronger hurricanes,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster with NOAA’s Climate Prediction Center. “These conditions include weaker wind shear, warmer Atlantic waters and conducive winds patterns coming from Africa."
NOAA’s seasonal hurricane outlook is not a hurricane landfall forecast; it does not predict how many storms will hit land or where a storm will strike. Forecasts for individual storms and their impacts will be provided throughout the season by NOAA’s National Hurricane Center.
New for this hurricane season are improvements to forecast models, data gathering, and the National Hurricane Center communication procedure for post-tropical cyclones. In July, NOAA plans to bring online a new supercomputer that will run an upgraded Hurricane Weather Research and Forecasting (HWRF) model that provides significantly enhanced depiction of storm structure and improved storm intensity forecast guidance.
Also this year, Doppler radar data will be transmitted in real time from NOAA’s Hurricane Hunter aircraft. This will help forecasters better analyze rapidly evolving storm conditions, and these data could further improve the HWRF model forecasts by 10 to 15 percent.
The National Weather Service has also made changes to allow for hurricane warnings to remain in effect, or to be newly issued, for storms like Sandy that have become post-tropical. This flexibility allows forecasters to provide a continuous flow of forecast and warning information for evolving or continuing threats.
“The start of hurricane season is a reminder that our families, businesses and communities need to be ready for the next big storm,” said Joe Nimmich, FEMA associate administrator for Response and Recovery. “Preparedness today can make a big difference down the line, so update your family emergency plan and make sure your emergency kit is stocked. Learn more about how you can prepare for hurricane season at www.ready.gov/hurricanes.”
Next week, May 26 - June 1, is National Hurricane Preparedness Week. To help those living in hurricane-prone areas prepare, NOAA is offering hurricane preparedness tips, along with video and audio public service announcements in both English and Spanish, featuring NOAA hurricane experts and the FEMA administrator at www.nhc.noaa.gov/prepare/.
NOAA’s outlook for the Eastern Pacific basin is for a below-normal hurricane season and the Central Pacific basin is also expected to have a below-normal season. NOAA will issue an updated outlook for the Atlantic hurricane season in early August, just prior to the historical peak of the season.
NOAA’s mission is to understand and predict changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us on Facebook, Twitter and our other social media channels. | <urn:uuid:d61dac63-16a8-40bb-8ba5-ceb9446edde3> | 2.828125 | 958 | News (Org.) | Science & Tech. | 33.61664 | 95,633,319 |
Marine Invasive Species May Benefit From Rising CO2 Levels
News Nov 11, 2015
Slimy, jelly-like creatures are far more tolerant of rising carbon dioxide levels than those with hard parts like corals, since exposed shells and skeletons simply dissolve away as CO2 levels rise.
The study, conducted by marine scientists at Plymouth University, has found that a number of notorious ‘nuisance’ species – such as Japanese kelp (Undaria pinnatifida) and stinging jellyfish (Pelagia noctiluca) are resilient to rising CO2 levels. They show why global warming and changes in seawater chemistry can help the spread of hundreds of damaging marine organisms.
The study notes that in the tropics, coral reefs face a host of interconnected problems (bleaching, corrosion, disease, spreading seaweed, invasive species) that are all caused by rising CO2 levels.
“We are witnessing the spread of marine life that cause problems – such as toxic jellyfish blooms and rotting algal mats,” said Professor Jason Hall-Spencer, lead author of the report. “Based on a synthesis of evidence available to date, we predict the problems associated with harmful marine life will get worse in response to rising CO2. Pathogens like cholera don’t recognise national borders so seawater warming is a health issue for cities like London, and nobody knows what organisms will spread and cause problems as Arctic shipping routes open up.”
The study arose from observations at volcanic sites in the Mediterranean, where Professor Hall-Spencer has led expeditions to record what forms of marine life cope well with higher CO2 levels. They found that invasive species of algae and jellyfish thrive at levels of carbon dioxide predicted to occur this decade. Their extensive review of laboratory experiments reveals stand-out cases such as so called ‘Killer algae’ (Caulerpa taxifolia), which is spreading world-wide, that benefit from higher CO2 but are so toxic that native herbivores die of starvation rather than eat it.
The report highlights the American slipper limpet, Crepidula fornicate, as an example of ocean acidification both helping and hindering a species, with evidence to show it has spread to Europe to become one of the 100 most invasive species, while at the same time, the species’ larvae has been placed at greater risk of predation due to reduced shell growth. Similarly, both the Red King Crab, which has invaded the Barents Sea, and the predatory snail Urosalpinx cinera, which has moved from the north west Atlantic to the north east Atlantic and Pacific, impacting upon oyster and scallop aquaculture in the process, have also demonstrated a marked reduction in larval survival and growth.
“Observations show there will be winners as well as losers as CO2 levels ramp up, just as there were in previous mass extinctions,” said researcher Ro Allen. “The spread of harmful marine organisms should be factored into risks of rising CO2 emissions.”
House Plants an an Early Warning System?News
Researchers are exploring the future of houseplants as aesthetically pleasing and functional sirens of home health. The idea is to genetically engineer house plants to serve as subtle alarms that something is amiss in our home and office environments.READ MORE
From Toxic Pollutants to Human Health - Key Questions for a Healthy FutureNews
An international study determines the twenty-two main questions to consider in order to manage sustainably the environmental risks related to chemical products in Europe.READ MORE | <urn:uuid:f5bdd94b-43f7-4a37-a5ee-fd5192f4b347> | 3.125 | 751 | Truncated | Science & Tech. | 20.959243 | 95,633,323 |
The curie (symbol Ci) is a non-SI unit of radioactivity originally defined in 1910. According to a notice in Nature at the time, it was named in honour of Pierre Curie, but was considered at least by some to be in honour of Marie Curie as well.
It was originally defined as "the quantity or mass of radium emanation in equilibrium with one gram of radium (element)" but is currently defined as: 1 Ci = ×1010 3.7decays per second after more accurate measurements of the activity of 226Ra (which has a specific activity of ×1010 Bq/g. 3.66)
- 1 Ci = ×1010 Bq = 37 GBq 3.7
- 1 Bq ≅ ×10−11 Ci ≅ 27 pCi 2.703
While its continued use is discouraged by National Institute of Standards and Technology (NIST) and other bodies, the curie is still widely used throughout the government, industry and medicine in the United States and in other countries.
At the 1910 meeting which originally defined the curie, it was proposed to make it equivalent to 10 nanograms of radium (a practical amount). But Marie Curie, after initially accepting this, changed her mind and insisted on one gram of radium. According to Bertram Boltwood, Marie Curie thought that 'the use of the name "curie" for so infinitesimally small [a] quantity of anything was altogether inappropriate.'
The power in milliwatts emitted by one curie of radiation can be calculated by taking the number of MeV for the radiation times approximately 5.93.
A radiotherapy machine may have roughly 1000 Ci of a radioisotope such as caesium-137 or cobalt-60. This quantity of radioactivity can produce serious health effects with only a few minutes of close-range, unshielded exposure.
The typical human body contains roughly 0.1 μCi (14 mg) of naturally occurring potassium-40. A human body containing 16 kg of carbon (see Composition of the human body) would also have about 24 nanograms or 0.1 μCi of carbon-14. Together, these would result in a total of approximately 0.2 μCi or 7400 decays per second inside the person's body (mostly from beta decay but some from gamma decay).
Curie as a measure of quantity
Units of activity (the curie and the becquerel) also refer to a quantity of radioactive atoms. Because the probability of decay is a fixed physical quantity, for a known number of atoms of a particular radionuclide, a predictable number will decay in a given time. The number of decays that will occur in one second in one gram of atoms of a particular radionuclide is known as the specific activity of that radionuclide.
The activity of a sample decreases with time because of decay.
The rules of radioactive decay may be used to convert activity to an actual number of atoms. They state that 1 Ci of radioactive atoms would follow the expression:
- N (atoms) × λ (s−1) = 1 Ci = 3.7 × 1010 Bq
- N = 3.7 × 1010 Bq / λ,
where λ is the decay constant in s−1.
We can also express activity in moles:
Here are some examples, ordered by half-life:
|Isotope||Half life||Mass of 1 curie||Specific activity (Ci/g)|
|232Th||×1010 years 1.405||9.1 tonnes||×10−7 (110,000 pCi/g, 0.11 µCi/g) 1.1|
|238U||×109 years 4.471||2.977 tonnes||×10−7 (340,000 pCi/g, 0.34 µCi/g) 3.4|
|40K||×109 years 1.25||140 kg||×10−6 (7,100,000 pCi/g, 7.1 µCi/g) 7.1|
|235U||×108 years 7.038||463 kg||×10−6 (2,160,000 pCi/g, 2.2 µCi/g) 2.2|
|129I||×106 years 15.7||5.66 kg||0.00018|
|99Tc||×103 years 211||58 g||0.017|
|239Pu||×103 years 24.11||16 g||0.063|
|240Pu||6563 years||4.4 g||0.23|
|14C||5730 years||0.22 g||4.5|
|226Ra||1601 years||1.01 g||0.99|
|241Am||432.6 years||0.29 g||3.43|
|238Pu||88 years||59 mg||17|
|137Cs||30.17 years||12 mg||83|
|90Sr||28.8 years||7.2 mg||139|
|241Pu||14 years||9.4 mg||106|
|3H||12.32 years||104 μg||9,621|
|228Ra||5.75 years||3.67 mg||273|
|60Co||1925 days||883 μg||1,132|
|210Po||138 days||223 μg||4,484|
|131I||8.02 days||8 μg||125,000|
|123I||13 hours||518 ng||1,930,000|
|212Pb||10.64 hours||719 ng||1,390,000|
The following table shows radiation quantities in SI and non-SI units:
|Activity (A)||curie||Ci||3.7 × 1010 s−1||1953||3.7×1010 Bq|
|rutherford||Rd||106 s−1||1946||1,000,000 Bq|
|Exposure (X)||röntgen||R||esu / 0.001293 g of air||1928||2.58 × 10−4 C/kg|
|Fluence (Φ)||(reciprocal area)||m−2||1962||SI|
|Absorbed dose (D)||erg||erg⋅g−1||1950||1.0 × 10−4 Gy|
|rad||rad||100 erg⋅g−1||1953||0.010 Gy|
|Dose equivalent (H)||röntgen equivalent man||rem||100 erg⋅g−1||1971||0.010 Sv|
|sievert||Sv||J⋅kg−1 × WR||1977||SI|
- Geiger counter
- Ionizing radiation
- Radiation exposure
- Radiation poisoning
- Radiation burn
- United Nations Scientific Committee on the Effects of Atomic Radiation
- Rutherford, Ernest (6 October 1910). "Radium Standards and Nomenclature". Nature. 84 (2136): 430–431. Bibcode:1910Natur..84..430R. doi:10.1038/084430a0.
- Frame, Paul (1996). "How the Curie Came to Be". Health Physics Society newsletter. Retrieved 3 July 2015.
- Delacroix, D (2002). Radionuclide and Radiation Protection Data Handbook 2002. Radiation Protection Dosimetry, Vol. 98 No 1: Nuclear Technology Publishing. p. 147.
- "SI units for ionizing radiation: becquerel". Resolutions of the 15th CGPM (Resolution 8). 1975. Retrieved 3 July 2015.
- "Nist Special Publication 811, paragraph 5.2". NIST. Retrieved 22 March 2016. | <urn:uuid:ae7818ed-9111-46bb-9053-9a2e95cd30f5> | 3.59375 | 1,714 | Knowledge Article | Science & Tech. | 94.613671 | 95,633,344 |
Researcher from Roskilde University receives DKK 5,800,000 for research in nanoparticles
Associate Professor Henriette Selck received the grant from VILLUM FONDEN for her research in metal nanoparticles and their impact on freshwater systems.
More and more artificial metal nanoparticles discharge to freshwater systems such as lakes and from the lakes; they can spread to organisms in fresh water such as worms, snails and fish.
Associate Professor Henriette Selck from the Department of Environmental, Social and Spatial Change at Roskilde University will research how these tiny nanoparticles are absorbed in aquatic animals and transferred into the environment. Her research is now being supported by DKK 5,800,000 from VILLUM FONDEN for the project “Implementation of novel tools to assess metal nanoparticle uptake and trophic transfer; Nano Transfer”.
"The challenge is that we know incredibly little about this transfer, because the methods to determine these particles in sediments and tissues have not been sufficient.
However this project will help to create more knowledge in the area," says Henriette Selck.
A better understanding
Nano-sized particles has some unique properties compared to larger particles. They can, among other things, have enhanced or completely new physical and chemical properties, which means that they can be electrically charged and react faster and/or stronger which is of great user value. The nanoparticles have been used in products such as sunscreen, cosmetics, plastics, pesticides and as antibacterial agents. Nanoparticles are discharged to the environment through, for example, wastewater treatment plants and pesticide use. The artificially fabricated metal nanoparticles that are derived into for example a lake will settle and accumulate in sediment where small benthic organisms such as worms and snails can absorb the nanoparticles. When fish eat these organisms, the metal nanoparticles will be transferred to the fish, which then perhaps later are eaten by humans.
In her research project Henriette Selck will combine new and advanced techniques to achieve a greater understanding of how accessible these particles are both for the inclusion in the benthic fauna, and the transfer through the food chain to fish. ”Through the project, we will gain a greater understanding of how these nanoparticles are transferred through the food chain. The vision is that this improved understanding will form the basis for a better environmental regulation in order to achieve safer use of these particles", says Henriette Selck adding:
"Some metal nanoparticles have shown increased toxicity compared to larger particles of the same metal, but at present it is not possible to generalize. Therefore, we cannot assess whether we are sufficiently able to risk assess nanoparticles properly. But we expect that our increased use of nanoparticles will increase emissions to the environment and the risk of adverse effects in animals and eventually in humans", she notes.
VILLUM FONDEN support research in the technical and natural sciences.
For further information
Associate professor Henriette Selck, T +45 46 74 29 83, e-mail: email@example.com
Communication and press, Tim Houman, T +45 46 74 33 45, e-mail: firstname.lastname@example.org | <urn:uuid:26713efa-8996-413e-b7f5-2ad7a83e8a6f> | 2.859375 | 658 | News (Org.) | Science & Tech. | 25.025 | 95,633,348 |
How scary would it be if a hurricane could produce a burst of energy so strong that anything in its way would explode?
One of them just did.
Hurricane Patricia was blasting out winds of more than 200 mph — the most intense on record — when a Hurricane Hunter aircraft flew into it off the Pacific coast of Mexico in 2015.
An instrument on board recorded a bolt of lightning shooting a downward beam of positrons that erupted into gamma rays and x-rays and shot a burst of radiation into space.
Positrons are the opposing force to electrons, which are found in all atoms. Positrons literally are anti-matter and don't normally exist in the Earth environment.
When they are produced, they smash into elections. Both blow apart, creating a burst of energy so powerful that not even the explosion of an atomic bomb compares to it.
That's how frighteningly strong a hurricane can become.
"It's an extraordinary event, and we still don't understand how it gets so bright," said David Smith, a physics professor at the University of California at Santa Cruz, who took part in the recently released research.
Patricia must have created powerful updraft winds as well as circulating winds, said Gabriel Williams, a College of Charleston atmospheric physics professor. The drafts would be needed to produce antimatter.
"Hurricane Patricia was a remarkable storm," he said. | <urn:uuid:ebacf5bd-f2d9-4227-9b4a-886c8c8f0064> | 3.8125 | 282 | News Article | Science & Tech. | 48.490287 | 95,633,350 |
Galactic astronomy is the study of the Milky Way galaxy and all its contents. This is in contrast to extragalactic astronomy, which is the study of everything outside our galaxy, including all other galaxies.
Galactic astronomy should not be confused with galaxy formation and evolution, which is the general study of galaxies, their formation, structure, components, dynamics, interactions, and the range of forms they take.
The Milky Way galaxy, where the Solar System belongs, is in many ways the best studied galaxy, although important parts of it are obscured from view in visible wavelengths by regions of cosmic dust. The development of radio astronomy, infrared astronomy and submillimetre astronomy in the 20th Century allowed the gas and dust of the Milky Way to be mapped for the first time.
- abundances – the study of the location of elements heavier than helium
- bulge – the study of the bulge around the center of the Milky Way
- center – the study of the central region of the Milky Way
- disk – the study of the Milky Way disk (the plane upon which most galactic objects are aligned)
- evolution – the evolution of the Milky Way
- formation – the formation of the Milky Way
- fundamental parameters – the fundamental parameters of the Milky Way (mass, size etc.)
- globular clusters – globular clusters within the Milky Way
- halo – the large halo around the Milky Way
- kinematics and dynamics – the motions of stars and clusters
- nucleus – the region around the black hole at the center of the Milky Way (Sagittarius A*)
- open clusters and associations – open clusters and associations of stars
- solar neighbourhood – nearby stars
- stellar content – numbers and types of stars in the Milky Way
- structure – the structure (spiral arms etc.)
- Interplanetary space - Interplanetary medium - interplanetary dust
- Interstellar space - Interstellar medium - interstellar dust
- Intergalactic space - Intergalactic medium - Intergalactic dust
- "Galactic Astronomy - Subcategories | The English knowledge database". science-train.com. Retrieved 2017-12-20. | <urn:uuid:5bac99b3-e46b-4526-816d-734b36f2c401> | 3.546875 | 447 | Knowledge Article | Science & Tech. | 17.915031 | 95,633,356 |
Green is Universal’s free “One Small Act” social gaming platform celebrates little changes that have a big impact on the environment.
So now and every year at this time if you dress a tree and share it: a tree gets planted.
Let me explain.
NBC and the The Share a Tree program help the Arbor Day Foundation every year plant trees across the United States. These trees are planted in our national forests, state forests and state parks. Two parks as examples are in Michigan’s Mackinaw and Au Sable State Forests.
So Jack Pine Trees will be planted improving the habitat of the endangered Kirtland’s warbler. The warbler is a neotropical, migratory songbird breeding habitat almost exclusively confined to young, dense Jack pines.
Today, Kirtland’s warblers are only located in ten counties on Michigan’s northern, lower peninsula and four counties in the upper peninsula. The work done by the Arbor Day Foundation’s replanting partners increased the number of singing males from less than 200 to more than 1,900. This work has brought back the bird from bringing the brink of extinction.
So please check out http://bit.ly/shareatree
Category: Breaking Green News, Conservation, Environment, going green, green living, Keep Our Forests, Protect ForestsTags: Breaking Green News, Conservation, conservation leaders, Environment, Go Green, going green, green living, Keep Our Forests, NBC, plant forests, Protect Forests, share a tree
The Green Living Guy, Seth Leitman is a green living expert, celebrity and Editor of the McGraw-Hill, TAB Green Guru Guides. Seth is also an Author, Radio Host, Reporter, Writer and a Environmental Consultant on green living. The Green Living Guy writes about green living, green lighting, the green guru guides and more. Seth's books range from: # Build Your Own Electric Vehicle by Bob Brant and Seth Leitman (2nd and 3rd editions) # Build Your Own Plug-in Hybrid Electric Vehicle by Seth Leitman # Build Your Own Electric Motorcycle by Carl Vogel # Green Lighting by Seth Leitman, Brian Clark Howard and Bill Brinsky # Solar Power For Your Home by David Findley # Renewable Energies For Your Home by Russel Gehrke # Do-it-Yourself Home Energy Audits by David Findley # Build Your Own Small Wind Power System by Brian Clark Howard and Kevin Shea # and more green living books to follow.
This site is protected by wp-copyrightpro.com | <urn:uuid:caadf8af-eaf5-4ee5-af04-3eed0a220869> | 2.796875 | 543 | Personal Blog | Science & Tech. | 49.689672 | 95,633,373 |
Epiphytism in Colombian Amazonia was described by counting vascular epiphytes in thirty 0.025-ha (5 x 50 m) plots, well-distributed over the main landscape units in the middle Caqueta area of Colombian Amazonia. Each plot was directly adjacent to a 0.1-ha plot at which the species composition of trees and lianas (diameter at breast height (DBH) &GE; 2.5 cm) had been recorded 3 years earlier. The purpose of the study was to explore abundance, diversity, and distribution of epiphytes between the principal landscape units. A total of 6129 individual vascular epiphytes were recorded belonging to 27 families, 73 genera, and 213 species (which included 59 morpho-species). Araceae, Orchidaceae, and Bromeliaceae were the most speciose and abundant families. A total of 2763 phorophytes were registered, 1701 (62%) of which with DBH &GE; 2.5 cm. About 40-60% of the woody plants with DBH &GE; 2.5 cm carried epiphytes, which points at low phorophyte limitation throughout all landscapes. Epiphytism was concentrated on stem bases. Just as trees, epiphyte species assemblages were well associated with the main landscapes. Contrary to trees, however, epiphyte abundance and diversity (species richness, Fisher's alpha index) hardly differed between the landscapes. This calls for caution when explanations for distribution and dynamics of tree species are extrapolated to growth forms with a totally different ecology.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:5768bb44-a2b9-48e9-8391-c3889ede925d> | 2.984375 | 356 | Academic Writing | Science & Tech. | 44.110878 | 95,633,378 |
CRISPR (/ ˈ k r ɪ s p ər /) is a family of DNA sequences in bacteria. The sequences contain snippets of DNA from viruses that have attacked the bacterium.
A major addition to the understanding of CRISPR came with Jansen's observation that the prokaryote repeat cluster was accompanied by a set of homologous genes that make up CRISPR-associated systems or cas genes. Four cas genes ( cas 1 to 4) were initially recognized. The Cas proteins showed helicase and nuclease motifs, suggesting a role in the dynamic structure of the CRISPR loci. In this publication the acronym CRISPR was coined as the universal name of this pattern. However, the CRISPR function remained enigmatic. | <urn:uuid:efc3c397-8add-4d82-9363-eaf597b000e7> | 3.34375 | 161 | Knowledge Article | Science & Tech. | 47.078684 | 95,633,396 |
7. When 1.00 grams of chromium metal is heated in excess iodine, 8.301 rams of chromium iodide salt is formed. Calculate the empirical formula of this salt.
8. When a calcium carbonate tablet is ingested, it dissolves by the reaction of stomach acid, which contains hydrochloric acid. The unbalanced equation for this reaction is CaCO3(s) + HCl(aq) ---> CaCl2(aq) + H2O(l) + CO2(g). How many calcium carbonate tablets, each containing 500 mg of the active ingredients are required to react with 37.0 grams of stomach acid containing 49.5% HCl by mass?
9. The formula for thionyl chloride is SOCl2. This compound is a very powerful drying agent in the synthetic chemistry industry in that it reacts completely with water according to the following unbalanced equation: SOCl2(l) + H2O(l) ---> SO2(g) + HCl(g). How many grams of thionyl chloride remove 305.0 grams of water?
10. 637 atoms of a particular isotope weigh 2.2483 x 10^-19 grams. What is the atomic mass of the isotope?© BrainMass Inc. brainmass.com July 22, 2018, 12:17 pm ad1c9bdddf
This solution provides calculations for questions involving salts. | <urn:uuid:57783def-e373-48b9-a9c3-d9b667bdd808> | 2.6875 | 300 | Tutorial | Science & Tech. | 76.156872 | 95,633,410 |
The Standard Model of Particle Physics
Over the past three decades a compelling case has emerged for the now widely accepted standard model of elementary particles and forces. A “Standard Model” is a theoretical framework built from observation that predicts and correlates new data. The Mendeleev table of elements was an early example in chemistry; from the periodic table one could predict the properties of many hitherto unstudied elements and compounds. Nonrelativistic quantum theory is another standard model that has correlated the results of countless experiments. Like its precursors in other fields, the standard model of particle physics has been enormously successful in predicting a wide range of phenomena. And, just as ordinary quantum mechanics fails in the relativistic limit, we do not expect the standard model to be valid at arbitrarily short distances. However, its remarkable success strongly suggests that the standard model will remain an excellent approximation to nature at distance scales as small as 10–18 m.
KeywordsGauge Boson Higgs Mass Chiral Symmetry Goldstone Boson Electroweak Symmetry Breaking
Unable to display preview. Download preview PDF.
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The Suspended Material of the Amazon Shelf and Tropical Atlantic Ocean
Filtered samples and optical data from six cruises in the Atlantic Ocean off the Amazon River between 1963 and 19 71 are used to determine transport of surface suspended material outward into the ocean. During high-river discharge the turbid-water line (≥2.0 mg/ℓ) extends 100 km seaward from the river mouth and northwestward along the coast for about 2000 km in a zone averaging 60 km wide. During low-river dis charge, a similar pattern extends seaward only 80 km from the river mouth and northwestward for about 2000 km. This turbid zone migrates between these extreme limits at intermediate stages of river discharge. The surface concentration of suspended material exhibits a steady seaward decrease and the zone along the outer continental shelf shows lobes of turbid water being engulfed by the northwestward flowing Guiana current.
KeywordsRiver Mouth River Discharge Settling Velocity Turbid Water Suspended Material
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Hello and welcome back to another week of unreliable lies here at Factually Deficient, as we march on with our years. This week, I will answer a question posed by the eminent Tohrinha:
How long is February?
Many, often while embroiled in a never-ending winter, have wondered before Tohrinha just how long the month of February is. Few, though, have ever lived to discover the answer. Traditional research, one will find, yields inaccurate results, and forays into first-hand investigation have frequently led to unexpected bloodshed and an absence of usable data.
Some have tried to use mnemonic rhymes to determine the length of the month – but these, too, will prove disappointing. If you do not know the rhyme, here it is in its entirety – so you, too, can understand how it fails to adequately express the length of February:
Thirty days has September,
Forty-seven has November.
Fifty-two have May and June;
July and April end “two” soon.
All the rest have sixty-four —
Except for February: it has more.
(But when the year leaps,
It adds six to eight weeks.)
As you can see, this rhyme provides us with the following information:
- September has 30 days
- November has 47 days
- May and June each have 52 days
- July and April each have only 2 days
- January, March, August, October, and December each have 64 days
- February has >64 days (an unspecified number greater than 64)
- In leap years, February has between six and eight weeks more than it usually does
Naturally, matters such as leap years and groundhogs can affect the length of February. All I can offer Tohrinha with any certainty – all that is reasonable to ask for – is the “base” length of February, the minimum number of days that this colossally long month can hold.
To find this base length, we can actually determine the mathematical pattern present in the other months, and extend it logically:
- The difference between 2 (July/April) and 30 (September, the next-shortest month) is +28
- The difference between 30 and 47 (November) is +17
- The difference between 47 and 52 (May/June) is +5
- The difference between 52 and 64 (January, March, August, October, December) is +12
This leaves us with an obvious mathematical pattern: 28, 17, 5, 12… Clearly, the next number in the sequence is 20. 64+20 = 84 – therefore, February has a minimum of 84 days.
Disclaimer: the above post may be deceptive. Please re-check the math yourself. | <urn:uuid:ccc67404-62a5-4c03-8578-cef946653fb8> | 3.03125 | 580 | Personal Blog | Science & Tech. | 48.767527 | 95,633,419 |
Learning How We Learn: Brainwave Synchronization
Researchers have determined that brain wave synchronization is critical for the brain to absorb and categorize, according to a recent study.
The study, which was published in the journal Neuron, details how researchers determined that neural activity in two parts of the brain that occur during learning actually synchronize their signal oscillations after a staggered start.
According to the study, past work has determined that when a brain is presented with new information, neurons in the striatum - a region associated with habit forming - become active first. Following this activation, neurons in the prefrontal cortex - the main control system of the brain - then begin to come to life.
To determine if these two activations influence one another or are isolated occurrences, the researchers used electroencephalography (EEG) scans to measure the brain waves of monkeys as they learned to sort dot patterns into two categories.
The monkeys were gradually introduced to more and more dot patterns over the course of the experiment, learning 256 dot patterns in all.
Researchers paid special attention to the monkey's brain activity when they began to figure out how to recognize the traits that characterized the two categories that the dot patterns could be sorted into.
They quickly recognized that around this moment, in every monkey new brain wave patterns called "beta bands" appeared in their EEGs. Interestingly, these new bands, which were being produced by both the striatum and prefrontal cortex, began to synchronize.
"There is some unknown mechanism that allows these resonance patterns to form, and these circuits start humming together," senior author Earl Miller said in a recent statement.
According to Miller, with the synching of these waves, a new pair of electrical signal connections bridged the striatum and prefrontal cortex. The researchers theorize that this pair of circuits correspond to each of the two categories.
"Category-learning results in new functional circuits between these two areas," Miller added. "We're seeing direct evidence for the interactions between these two systems during learning, which hasn't been seen before."
The authors of the study say that a lot more research will be needed to determine exactly how and why this phenomenon occurs.
The study was published in Neuron, a Cell publication, on June 12. | <urn:uuid:56b4c7b4-896a-4013-be2c-ee4997ae1cc8> | 3.5 | 459 | News Article | Science & Tech. | 30.549301 | 95,633,461 |
The National Weather Service map for Nov. 2, 2012 showed two areas of low pressure over eastern Canada, near Quebec.
This visible image from NOAA's GOES-13 satellite shows the remnant clouds from Sandy still linger over the Great Lakes, east to New England and north into Canada at 1:31 p.m. EDT on Nov. 2, 2012.
Credit: NASA GOES Project
That's where the remnants of Sandy are located and the storm's massive cloud cover continues to linger over a large area. That low pressure area is associated with Sandy's remnants.
A visible image from NOAA's GOES-13 satellite at 1:31 p.m. EDT on Nov. 2, 2012 showed the remnant clouds from Sandy still linger over the Great Lakes east to New England.
In Canada, Sandy's clouds stretch from Newfoundland and Labrador west over Quebec, Ottawa and Toronto. The GOES image was created by NASA's GOES Project at the NASA Goddard Space Flight Center, Greenbelt, Md.
By Monday, Nov. 6, the National Weather Service map projects that the low pressure area associated with Sandy's remnants will be offshore.
Rob Gutro | 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
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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On the territory of the Republic of the Union of Myanmar in amber discovered the skeleton of the old serpent. The results of scientific research published in the journal Science.
According to the scientists, discovered the skeleton refers to the beginning of the late Cretaceous and is the oldest of the currently known such remains. Certain age of the find is approximately 98.8 million years.
It is worth noting that in addition to the animal remains in amber also found pieces of plants from the forest floor. | <urn:uuid:71718f7c-e7a0-4415-9b09-7fb0ecbc82e5> | 3.078125 | 99 | News Article | Science & Tech. | 53.51197 | 95,633,508 |
It lived well over 550 million years ago, is known only through fossils and has variously been described as looking a bit like a jellyfish, a worm, a fungus and lichen. But was the ‘mysterious’ Dickinsonia an animal, or was it something else?
A new study by researchers at the universities of Oxford, Cambridge, Bristol, and the British Geological Survey provides strong proof that Dickinsonia was an animal, confirming recent findings suggesting that animals evolved millions of years before the so-called Cambrian Explosion of animal life.
The study is published in the journal Proceedings of the Royal Society B.
Lead author on the paper is Dr Renee Hoekzema, a PhD candidate in Oxford University’s Mathematical Institute who carried out this research while completing a previous PhD in Oxford’s Department of Earth Sciences. She said: ‘Dickinsonia belongs to the Ediacaran biota – a collection of mostly soft-bodied organisms that lived in the global oceans between roughly 580 and 540 million years ago. They are mysterious because despite there being around 200 different species, very few of them resemble any living or extinct organism, and therefore what they were, and how they relate to modern organisms, has been a long-standing palaeontological mystery.’
In 1947, Dickinsonia became one of the first described Ediacaran fossils and was initially thought to be an organism similar to a jellyfish. Since then, its strange body plan has been compared to that of a worm, a placozoan, a bilaterian and several non-animals including fungi, lichens and even entirely extinct groups.
Co-author Dr Alex Liu, from the Department of Earth Sciences at the University of Cambridge, said: ‘Discriminating between these different hypotheses has been difficult, as there are so few morphological features in Dickinsonia to compare to modern organisms. In this study we took the approach of looking at populations of this organism, including assumed juvenile and adult individuals, to assess how it grew and to try to work out how to classify it from a developmental perspective.’
The research was carried out on the basis of a widely held assumption that growth and development are ‘conserved’ within lineages – in other words, the way a group of organisms grows today would not have changed significantly from the way its ancestors grew millions of years ago.
Dickinsonia is composed of multiple ‘units’ that run down the length of its body. The researchers counted the number of these units in multiple specimens, measured their lengths and plotted these against the relative ‘age’ of the unit, assuming growth from a particular end of the organism. This data produced a plot with a series of curves, each of which tracked how the organism changed in the size and number of units with age, enabling the researchers to produce a computer model to replicate growth in the organism and test previous hypotheses about where and how growth occurred.
Dr Hoekzema said: ‘We were able to confirm that Dickinsonia grows by both adding and inflating discrete units to its body along its central axis. But we also recognised that there is a switch in the rate of unit addition versus inflation at a certain point in its life cycle. All previous studies have assumed that it grew from the end where each “unit” is smallest, and was therefore considered to be youngest. We tested this assumption and interpreted our data with growth assumed from both ends, eventually coming to the conclusion that people have been interpreting Dickinsonia as having grown at the wrong end for the past 70 years.
‘When we combined this growth data with previously obtained information on how Dickinsonia moved, as well as some of its morphological features, we were able to reject all non-animal possibilities for its original biological affinity and show that it was an early animal, belonging to either the Placozoa or the Eumetazoa.
‘This is one of the first times that a member of the Ediacaran biota has been identified as an animal on the basis of positive evidence.’
Dr Liu added: ‘This finding demonstrates that animals were present among the Ediacaran biota and importantly confirms a number of recent findings that suggest animals had evolved several million years before the “Cambrian Explosion” that has been the focus of attention for studies into animal evolution for so long.
‘It also allows Dickinsonia to be considered in debates surrounding the evolution and development of key animal traits such as bilateral symmetry, segmentation and the development of body axes, which will ultimately improve our knowledge of how the earliest animals made the transition from simple forms to the diverse range of body plans we see today.’
Header Image Credit : Verisimilus | <urn:uuid:25e14a43-6128-4830-a58b-a6335178e5d8> | 3.96875 | 978 | News Article | Science & Tech. | 21.528664 | 95,633,531 |
Klaus H. Theopold, director of UD's Inorganic Synthesis Laboratory, is pairing chromium, a transition metal, with oxidizing agents capable of donating an oxygen atom to other molecules. The resulting organochromium molecules may ultimately result in more highly controlled catalytic production processes, including oxidation and polymerization reactions.
"We're seeing interesting changes in the reactivity of these molecules as we increase their oxidation level," Theopold explains. "That's of interest in olefin polymerization catalysis, for producing long-chain hydrocarbons including polyethylene [a plastic], and in oxidation catalysis, for making substances such as phenol from benzene [a fuel]."
To better understand the catalysts used in industrial oxidation processes, Theopold's research team is studying the reactions of dioxygen. Though it is "a strong oxidizer," Theopold notes, "dioxygen is not very reactive by itself--which explains why all these organic materials sitting around don't spontaneously burst into flames." Once dioxygen gets going, however, it will quickly incinerate every molecule in its path.
Theopold says he hopes his fundamental experiments may suggest a way to start oxidation catalysis reactions, control them and then stop them at specific points to obtain different products. Dioxygen undergoes some surprising reactions with chromium, he notes. For example, a chromium-phenol complex produces an intermediate product before yielding chromium oxo phenoxide--a precursor related to a phenol. "This represents the better part of the conversion of benzene to phenol," Theopold says.
Already, Theopold's colleague, Associate Chemistry Prof. Douglas J. Doren, has completed computer-based calculations that describe an intriquing dioxygen/cobalt complex. The complex uses two cobalt atoms, bound in a tris(pyrazolyl)borate ligand, to break dioxygen's strong oxygen/oxygen bond, thereby making oxygen available for further reactions. Though Doren's initial dioxygen/cobalt complex is too costly for larger-scale industrial applications, he says he hopes similar substances can be refined for catalyzing the oxidation of hydrocarbons.
Because the complex is "a relatively large, complex molecule" with 36 heavy atoms, Doren relies on UD's extensive computing resources--including a Cray J-90 system and Silicon Graphics multiprocessing computers, provided by the University and the National Science Foundation.
Ginger Pinholster / Beth Thomas
University of Delaware
(302) 831-6408 or (302) 831-2791
(302) 435-6733 - Media Beeper
* During the meeting, call Ginger at (415) 394-1111 or send e-mail to firstname.lastname@example.org
ACS presentation information - Theopold:
Moscone Center, Room 103, Exhibit Level
Tuesday, April 15, 2:50 p.m. (Pacific Time)
ACS presentation information - Doren:
San Francisco Hilton, Continental 8, Ballroom Level
Wednesday, April 16, 12:20 p.m. (PT) | <urn:uuid:0f0ab8f0-81c9-44de-b452-b8b60070ca16> | 3.21875 | 676 | News (Org.) | Science & Tech. | 25.548653 | 95,633,557 |
The Moderate Resolution Imaging Spectroradiometer instrument aboard Terra took a visible image of Edilson as its northwestern quadrant still covered the island of Mauritius. Clouds from the fringe of Edilson also blanketed La Reunion Island (located to the southwest of Mauritius).
On Feb. 6 at 06:10 UTC the MODIS instrument aboard NASA's Terra satellite captured this visible image of Tropical Cyclone Edilson over Réunion and Mauritius.
Image Credit: NASA Goddard MODIS Rapid Response Team
The image showed a good rotation in the storm, with a shadowed center of circulation, hinting at the development of an eye. Microwave satellite data has also suggested the development of an eye. In addition, multi-spectral satellite imagery showed that the storm has been consolidating and there are strong curved bands of thunderstorms wrapping around the western quadrant of the storm.
Forecasters at the Joint Typhoon Warning Center expect Edilson to briefly become a hurricane over the next day.
At 1500 UTC/10 a.m. EST, Edilson's maximum sustained winds were near 55 knots/63.2 mph/101.9 kph. The tropical storm was centered near 23.3 south latitude and 57.5 east longitude, about 160 nautical miles/184.1 miles/296.3 km south-southeast of Port Louis, Mauritius. Edilson has been moving to the south-southwest at 16 knots/18.4 mph/29.6 kph.
Edilson is expected to track in a southerly direction over the next couple of days. It is forecast to move to the southwest before turning to the southeast sometime on February 9.Text credit: Rob Gutro
Rob Gutro | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
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
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17.07.2018 | Power and Electrical Engineering | <urn:uuid:b77eeb1c-26e2-4880-a259-6288336ef840> | 2.640625 | 995 | Content Listing | Science & Tech. | 44.576467 | 95,633,574 |
Bacterial viruses make cheap easy vaccines
Genetically altered bacterial viruses appear to be more effective than naked DNA in eliciting an immune response and could be a new strategy for a next generation of vaccines that are easy to produce and store, say researchers from Moredun Research Institute in the United Kingdom.
"In theory, millions of doses can be grown within a matter of days using simple equipment, media and procedures," says John March, one of lead researchers presenting findings at the American Society for Microbiology’s Biodefense Research Meeting.
Bacteriophages are viruses that infect bacteria but not humans. In this particular study, March and his colleagues used a bacteriophage as a vehicle for genes from hepatitis B virus in mice and compared its ability to elicit a protective immune response with a vaccine made of naked DNA. They found that not only could the bacteriophage induce an immune response, the number of bacteriophage they needed was less than 1 percent of the number of pieces of naked DNA required to mount an effective immune response.
Using bacteriophages to deliver vaccine components offers several advantages over vaccination with naked DNA, says March. The DNA is protected inside the protein shell of the virus making it longer lasting and easier to store. In addition, bacteriophages have a large cloning capacity, making large-scale production cheap, easy and extremely rapid – important attributes considering the current bioterrorism threat when sudden demands may be placed on vaccine stocks.
The American Society for Microbiology (ASM) is the largest single life science society, composed of over 42,000 scientists, teachers, physicians, and health professionals. Its mission is to promote research and training in the microbiological sciences and to assist communication between scientists, policymakers, and the public to improve health, economic well being, and the environment. Further information on the ASM Biodefense Research Meeting can be found online at www.asmbiodefense.org.
Jim Sliwa | EurekAlert!
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
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... | <urn:uuid:42c01941-4d3d-4130-898a-5188fdcf2a38> | 3.609375 | 963 | Content Listing | Science & Tech. | 25.533043 | 95,633,575 |
Although the heat source isn't a new or increasing threat to the West Antarctic ice sheet, it could help explain why the ice sheet collapsed rapidly some 11,000 years ago and why it's so unstable today, Seroussi said.
Mantle plumes are believed to be narrow streams of hot, molten rock which erupts through Earth's mantle and forms a mushroom cap-like structure under the crust.
Illustration of flowing water under the Antarctic ice sheet.
The stability of ice sheets is closely related to the quantity of water beneath the sheets. The team developed a mantle plume model to look at how much geothermal heat would be needed to explain what is seen at Marie Byrd Land.
'Bankrupt' Samoa to get RFU payment
The news puts pressure on other nations - England in particular - to share revenues from games with the Samoans. World Rugby is distancing itself from Samoan Rugby Union's financial plight.
The research could help scientists better estimate future ice loss in the area. Blue dots indicate lakes and lines show rivers.
However, recent seismic imaging seems to confirm the hypothesis.
Study author Hélène Seroussi, from JPL, said when she first heard that a mantle plume might be heating Marie Byrd Land she thought the idea was "crazy". The rapid filling and draining of lakes and rivers in the Antarctica result in rising or falling of ice sheaths to almost 20 feet (6 meters). The Numerical modeling helped to gain an idea of the functioning of the mantle plume concept.
They scientists also used observations of changes in the altitude of the ice sheet surface, captured by NASA's IceSat satellite and airborne Operation IceBridge campaign.
Second actress accuses Ed Westwick of rape
In a Facebook post, actress Kristina Cohen accused Gossip Girl famed actor Ed Westwick of raping her three years ago. The Los Angeles Police Department is investigating Cohen's claims after she filed a police report Tuesday morning.
"These place a powerful constraint on allowable melt rates - the very thing we wanted to predict", Ivins said. The researchers used multiple parameters including dozens of different simulations as the location and size of the mantle plume is still unknown.
In the past, researchers had observed volcanic activity and a topographic dome feature in this region. "In contrast, the active lake system of the lower part of Whillans Ice Stream suggests a widespread anomalous mantle heat flux, linked to a rift source", the researchers wrote in the abstract of their study.
The study found that the energy flux from the mantle plume must not exceed 150 milliwatts per square meter - compared, for example, to a heat flux of 490 to 60 milliwatts in regions with no volcanic activity, and an average 200 milliwatts per square meter beneath Yellowstone.
Concluding, the team say the Marie Byrd Land mantle plume formed 50-110 million years ago-long before the land above was hidden by ice.
Miranda Lambert Brings Old School Country Back to the 2017 CMA Awards
Debuting the single to stream earlier Wednesday morning prior to the awards show, Urban received quite the amount of respected responses from colleagues and artists alike for his important message.
When Antarctica lost an enormous iceberg from the Larsen C ice shelf in July, it set off alarm bells about the future of the shelf itself, as well as about the region in general, which like other ice repositories on Earth, is faring badly under the onslaught of global warming. | <urn:uuid:bc8d9399-98ae-473b-a78c-d34e1014e8dd> | 3.484375 | 712 | News Article | Science & Tech. | 41.603301 | 95,633,622 |
linker bijnier latijn 2.4 Thermal radiation
2.4.2 Radiative exchange
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buiten sauna thuis If no reflections of radiation are taken into account, radiative exchange from one surface to the other can be written as:
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pledge in hindi audio in which ε is the emissivity of the surface and Fij is the view factor (or ‘configuration factor’ of one surface to the other.
However if more than one surface in this equation is non-black (ε< 1, also called ‘grey’) than some of the radiation coming from surface i will be reflected by surface j. A part of this reflected energy ends up on other surfaces, which in their turn can reflect the radiation. These reflection are not taken into account in the formula above and therefore it is not accurate for gray surfaces
Generally radiative exchange for gray bodies is calculated using two different methods:
- Gebhart method (ref. 1,2)
- Net-radiation method (ref. 3,4,5,6,7), a.k.a. the Oppenheim method
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Both methods result in the same net radiative balance of the surfaces involves, but the methods and definitions are quite different. In practice the Gebhart method is considered to be the method with the least chance of error and the most direct method to calculate radiative energy transfer between surfaces. The net-radiation method is the one most described in literature, and has because of its resistance analogue many practical advantages in radiative exchange calculations, but the formulas of the method are often erroneously used.
Both methods will be explained in more detail in the following sections. | <urn:uuid:2c6d4662-ad6c-4428-8d88-6975e1674031> | 3.375 | 402 | Tutorial | Science & Tech. | 38.327619 | 95,633,624 |
Authors: Nainan K. Varghese
Physical parameters of stable galaxies produce sufficient mutual repulsion by their halos to overcome gravitational attraction between them. However, those very large galactic clouds (or central regions of stable galaxies), which do not develop sufficient spin-speeds to develop into stable galaxies, succumb to gravitational collapse and form very large single macro bodies of very high 3D matter-density. Their huge sizes and very large 3D matter-contents give them certain logical properties, one of which is to reduce and prevent outward radiation (of light) from the zone of their existence. This phenomenon makes them invisible and hence the name, ‘Black Hole’. An alternative concept, presented in the book ‘MATTER (Re-examined)’ envisages to remove all mysteries about black holes and to explain logical sequences of their birth, life and death.
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MANILA (AFP) – A frog with fangs, a blind snake and a round-headed dolphin are among more than 1,000 new species recently found on the incredible Melanesian island of New Guinea, environment group WWF said.
Scientists made the astounding discoveries, which also included a river shark and dozens of butterflies, on New Guinea at a rate of two a week from 1998 to 2008, WWF said in a new report on the island’s natural habitat.
“This report shows that New Guinea’s forests and rivers are among the richest and most biodiverse in the world,” said WWF’s Western Melanesia programme representative, Neil Stronach.
New Guinea — divided between the Indonesian province of Papua in the west and Papua New Guinea to the east — has one of the world’s least spoilt and most stunning ecosystems.
Its rainforests are the third biggest in the world after the Amazon and the Congo, and, while the island covers just 0.5 per cent of the Earth’s landmass, it contains up to eight percent of the world’s species, according to WWF.
What was previously known about New Guinea’s biodiversity was already breathtaking, such as the world’s biggest butterfly — with a 30-centimetre (12-inch) wingspan — and giant rats that can grow up to a metre long.
Scientists believe that one square kilometre (247 acres) of the island’s lowland rainforest may contain as many as 150 bird species, according to WWF.
The 1,060 species confirmed by scientists as new discoveries between 1998 and 2008 are believed to have only scratched the surface of New Guinea’s dazzling ecosystems.
“Such is the extent of New Guinea’s biodiversity that new discoveries are commonplace even today,” WWF said in its report, titled “Final Frontier: Newly Discovered Species of New Guinea”.
One of the most notable finds documented in the WWF report was a round-headed and snub-finned dolphin, which swims in protected, shallow coastal waters near rivers and creek mouths.
Discovered in 2005 in Papua New Guinea, it was the first new dolphin species recorded anywhere in the world in three decades, and is now known to also exist in Australia, WWF said.
Another of the 12 mammals found over the decade was an anteater named in honour of British naturalist Sir David Attenborough, Sir David’s Long-beaked Echinda or, scientifically, Zaglossus attenboroughi.
One of the 134 frogs discovered was dubbed Litoria sauroni because its striking red and black spotted eyes reminded scientists of the evil character Sauron in the “Lord of the Rings” movies.
Another new frog was notable because of its tiny size — just one centimetre in length, while one had vampire-like fangs.
Nine snail species, some so colourful as to be almost unrecognisable from the backyard-garden-type variety, were among the 580 new invertebrates discovered.
One of the snails was bright yellow, while another was green and yellow.
Among the other new invertebrates was a brightly coloured apricot crayfish, part of the family of creatures called “yabbies” in Australia and some other parts of the world, which was nine to 12 centimetres long.
New fish totalled 71, with a kaleidoscope of colours, including one in the coral reefs of Milne Bay in Papua New Guinea that thrilled scientists with its dazzling blue hue.
WWF said the most extraordinary freshwater discovery was a 2.5-metre-long river shark found in Papua New Guinea that has since also been located in northern Australia.
Of the 43 reptiles discovered, one could claim to be the most innocuous snake in the world — it was just 12-14 centimetres long, had scales over its eyes so that it could not see, could not bite and had no venom.
But WWF said the excitement of all the new discoveries had been tempered by the fact that, like in the Amazon and Borneo rainforests, human actions were destroying New Guinea’s natural habitat at an “alarming rate”.
Some of the growing threats it listed were illegal and unsustainable logging, forest conversion for palm oil plantations, mining, road construction and unsustainable fishing.
“These environmental threats are exacerbated by global climate change which is increasing the number of fires within forests and savannas, erosion, and seawater incursion into coastal habitats,” WWF said. | <urn:uuid:8d1b814b-697e-4d83-bd3c-32319bb37b37> | 2.96875 | 959 | News Article | Science & Tech. | 42.116283 | 95,633,649 |
2018-01-09 | Editor : et_editor 3372 pageviews
British Scientists Transform Cyanobacteria into iPad-Size Bio-Solar Cells
Cyanobacteria, which changed the Earth's atmosphere from one that is oxygen-deprived to oxygen-rich, have recently been copied and produced as a micro-scale biological solar cell by British scientists. The size of the cell is similar to the iPad. The team believes that due to biodegradation, the cell can be used in developing countries which have lower budget for medical care. It can also function as a health tracker or wallpaper to monitor indoor air quality.
Cyanobacteria are microorganisms which gain energy from photosynthesis. They are nearly 3.5 billion years old and have been the earliest photosynthetic creatures to date. Generally, the biggest contribution of cyanobacteria is that they changed the Earth's atmosphere from one deprived of oxygen to one that is oxygen-rich, boosting the biodiversity of the planet. They also contributed to the near extinction of anaerobic organism, which significantly changed the formation of life form on Earth.
Currently, these microorganisms have another function. Led by Imperial College London, University of Cambridge and Central Saint Martins, a team of scientists have printed cyanobacteria onto electrically conductive carbon nanotube using an inkjet printer. Then, they printed the latter onto paper with the same method and discovered that cyanobacteria were alive through the printing process. Unlike traditional solar cell which can only function under light, this bio-solar cell is able to produce some electricity under darkness for about 100 hours.
▲ The bio-solar cell can be changed into wallpaper. (Source: Imperial College London)
Although their lifespan is largely shorter compared with traditional solar cell, the purpose of this bio-solar cell isn't to replace traditional technology or to be used in large-scale electricity production, according to Imperial College London researcher Andrea Fantuzzi. The advantage is that owing to biodegradation, the cell serves as a disposable solar panel and battery that can decompose in composts or gardens.
In addition, the low power output represents that this cell is suitable for small devices such as sensors, simple digital alarms and small LED lamps. In medical industry, this cell can also be used as the disposable paper sensor to monitor the blood sugar levels of patients with diabetes. This research was published in the journal Nature Communications.
(Article Source: TechNews / Photo Source: Imperial College London) | <urn:uuid:5ec9f305-e455-43b1-807a-bf83cbf9c8c7> | 3.78125 | 509 | News Article | Science & Tech. | 25.16387 | 95,633,671 |
Global warming, the phenomenon of increasing average air temperatures near the surface of Earth over the past one to two centuries. Climate scientists have since the mid-20th century gathered detailed observations of various weather phenomena (such as temperatures, precipitation, and storms) and of related influences on climate (such as ocean currents and the atmosphere’s chemical composition). These data indicate that Earth’s climate has changed over almost every conceivable timescale since the beginning of geologic time and that the influence of human activities since at least the beginning of the Industrial Revolution has been deeply woven into the very fabric of climate change.
Giving voice to a growing conviction of most of the scientific community, the Intergovernmental Panel on Climate Change (IPCC) was formed in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP). In 2013 the IPCC reported that the interval between 1880 and 2012 saw an increase in global average surface temperature of approximately 0.9 °C (1.5 °F). The increase is closer to 1.1 °C (2.0 °F) when measured relative to the preindustrial (i.e., 1750–1800) mean temperature. The IPCC stated that most of the warming observed over the second half of the 20th century could be attributed to human activities. It predicted that by the end of the 21st century the global mean surface temperature would increase by 0.3 to 5.4 °C (0.5 to 9.7 °F) relative to the 1986–2005 average. The predicted rise in temperature was based on a range of possible scenarios that accounted for future greenhouse gas emissions and mitigation (severity reduction) measures and on uncertainties in the model projections. Some of the main uncertainties include the precise role of feedback processes and the impacts of industrial pollutants known as aerosols which may offset some warming.
Many climate scientists agree that significant societal, economic, and ecological damage would result if global average temperatures rose by more than 2 °C (3.6 °F) in such a short time. Such damage would include increased extinction of many plant and animal species, shifts in patterns of agriculture, and rising sea levels. The IPCC reported that the global average sea level rose by some 19–21 cm (7.5–8.3 inches) between 1901 and 2010 and that sea levels rose faster in the second half of the 20th century than in the first half. It also predicted, again depending on a wide range of scenarios, that by the end of the 21st century the global average sea level could rise by another 29–95 cm (11.4–37.4 inches) relative to the 1986–2005 average and that a rise of well over 1 metre (3 feet) could not be ruled out.
The scenarios referred to above depend mainly on future concentrations of certain trace gases, called greenhouse gases, that have been injected into the lower atmosphere in increasing amounts through the burning of fossil fuels for industry, transportation, and residential uses. Modern global warming is the result of an increase in magnitude of the so-called greenhouse effect, a warming of Earth’s surface and lower atmosphere caused by the presence of water vapour, carbon dioxide, methane, nitrous oxides, and other greenhouse gases. In 2014 the IPCC reported that concentrations of carbon dioxide, methane, and nitrous oxides in the atmosphere surpassed those found in ice cores dating back 800,000 years. Of all these gases, carbon dioxide is the most important, both for its role in the greenhouse effect and for its role in the human economy. It has been estimated that, at the beginning of the industrial age in the mid-18th century, carbon dioxide concentrations in the atmosphere were roughly 280 parts per million (ppm). By the middle of 2014, carbon dioxide concentrations had briefly reached 400 ppm, and, if fossil fuels continue to be burned at current rates, they are projected to reach 560 ppm by the mid-21st century—essentially, a doubling of carbon dioxide concentrations in 300 years.
A vigorous debate is in progress over the extent and seriousness of rising surface temperatures, the effects of past and future warming on human life, and the need for action to reduce future warming and deal with its consequences. This article provides an overview of the scientific background and public policy debate related to the subject of global warming. It considers the causes of rising near-surface air temperatures, the influencing factors, the process of climate research and forecasting, the possible ecological and social impacts of rising temperatures, and the public policy developments since the mid-20th century. For a detailed description of Earth’s climate, its processes, and the responses of living things to its changing nature, see climate. For additional background on how Earth’s climate has changed throughout geologic time, see climatic variation and change. For a full description of Earth’s gaseous envelope, within which climate change and global warming occur, see atmosphere.
January 20, 2017, marks the end of the second term of Pres. Barack Obama, the first African American president of the United States.
Climatic variation since the last glaciation
Global warming is related to the more general phenomenon of climate change, which refers to changes in the totality of attributes that define climate. In addition to changes in air temperature, climate change involves changes to precipitation patterns, winds, ocean currents, and other measures of Earth’s climate. Normally, climate change can be viewed as the combination of various natural forces occurring over diverse timescales. Since the advent of human civilization, climate change has involved an “anthropogenic,” or exclusively human-caused, element, and this anthropogenic element has become more important in the industrial period of the past two centuries. The term global warming is used specifically to refer to any warming of near-surface air during the past two centuries that can be traced to anthropogenic causes.
To define the concepts of global warming and climate change properly, it is first necessary to recognize that the climate of Earth has varied across many timescales, ranging from an individual human life span to billions of years. This variable climate history is typically classified in terms of “regimes” or “epochs.” For instance, the Pleistocene glacial epoch (about 2,600,000 to 11,700 years ago) was marked by substantial variations in the global extent of glaciers and ice sheets. These variations took place on timescales of tens to hundreds of millennia and were driven by changes in the distribution of solar radiation across Earth’s surface. The distribution of solar radiation is known as the insolation pattern, and it is strongly affected by the geometry of Earth’s orbit around the Sun and by the orientation, or tilt, of Earth’s axis relative to the direct rays of the Sun.
Worldwide, the most recent glacial period, or ice age, culminated about 21,000 years ago in what is often called the Last Glacial Maximum. During this time, continental ice sheets extended well into the middle latitude regions of Europe and North America, reaching as far south as present-day London and New York City. Global annual mean temperature appears to have been about 4–5 °C (7–9 °F) colder than in the mid-20th century. It is important to remember that these figures are a global average. In fact, during the height of this last ice age, Earth’s climate was characterized by greater cooling at higher latitudes (that is, toward the poles) and relatively little cooling over large parts of the tropical oceans (near the Equator). This glacial interval terminated abruptly about 11,700 years ago and was followed by the subsequent relatively ice-free period known as the Holocene Epoch. The modern period of Earth’s history is conventionally defined as residing within the Holocene. However, some scientists have argued that the Holocene Epoch terminated in the relatively recent past and that Earth currently resides in a climatic interval that could justly be called the Anthropocene Epoch—that is, a period during which humans have exerted a dominant influence over climate.
Though less dramatic than the climate changes that occurred during the Pleistocene Epoch, significant variations in global climate have nonetheless taken place over the course of the Holocene. During the early Holocene, roughly 9,000 years ago, atmospheric circulation and precipitation patterns appear to have been substantially different from those of today. For example, there is evidence for relatively wet conditions in what is now the Sahara Desert. The change from one climatic regime to another was caused by only modest changes in the pattern of insolation within the Holocene interval as well as the interaction of these patterns with large-scale climate phenomena such as monsoons and El Niño/Southern Oscillation (ENSO).
During the middle Holocene, some 5,000–7,000 years ago, conditions appear to have been relatively warm—indeed, perhaps warmer than today in some parts of the world and during certain seasons. For this reason, this interval is sometimes referred to as the Mid-Holocene Climatic Optimum. The relative warmth of average near-surface air temperatures at this time, however, is somewhat unclear. Changes in the pattern of insolation favoured warmer summers at higher latitudes in the Northern Hemisphere, but these changes also produced cooler winters in the Northern Hemisphere and relatively cool conditions year-round in the tropics. Any overall hemispheric or global mean temperature changes thus reflected a balance between competing seasonal and regional changes. In fact, recent theoretical climate model studies suggest that global mean temperatures during the middle Holocene were probably 0.2–0.3 °C (0.4–0.5 °F) colder than average late 20th-century conditions.
Over subsequent millennia, conditions appear to have cooled relative to middle Holocene levels. This period has sometimes been referred to as the “Neoglacial.” In the middle latitudes this cooling trend was associated with intermittent periods of advancing and retreating mountain glaciers reminiscent of (though far more modest than) the more substantial advance and retreat of the major continental ice sheets of the Pleistocene climate epoch. | <urn:uuid:b7069bf7-5966-4267-b483-1a6cd2402412> | 4.125 | 2,086 | Knowledge Article | Science & Tech. | 33.378273 | 95,633,684 |
“The Brightest Meteor Shower In Recorded Human History Is Happening”
"According to astronomers there is going to be a meteor shower on 12th of August, 2017 that will be the brightest shower in recorded human history. It will light up the night sky and some of these might even be visible during the day. This meteor shower is being considered as a once in a lifetime opportunity as the next meteor shower of such kind will be in 96 years.
The Perseid meteor shower, one of the brighter meteor showers of the year, occurs every year between July 17 and August 24. The shower tends to peak around August 9-13. The Perseids can be seen in the Northern Hemisphere. Look between the radiant, which will be in the north-east part of the sky, and the zenith (the point in the sky directly above you). The best time to view the Perseids, and most other meteor showers, is when the sky is the darkest. Most astronomers suggest that depending on the Moon’s phase, the best time to view meteor showers is right before dawn." | <urn:uuid:018a3821-3e1e-411d-935c-33bd63714e7e> | 2.65625 | 224 | Personal Blog | Science & Tech. | 62.597043 | 95,633,715 |
Species Detail - Cladophora rupestris - 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).
1 January (recorded in 1985)
31 December (recorded in 1913)
National Biodiversity Data Centre, Ireland, Cladophora rupestris, accessed 22 July 2018, <https://maps.biodiversityireland.ie/Species/120> | <urn:uuid:041a4117-fc56-48b4-9bbe-fd5f360b8189> | 2.71875 | 131 | Structured Data | Science & Tech. | 35.88887 | 95,633,723 |
Representatives from academia, ship owners and operators, naval architecture, government agencies and ocean technology companies gathered in Montreal, Canada last month to begin to develop a plan to systematically collect data that will allow us to better understand the ocean’s interior dynamics and its impact on climate. OceanScope’s overall objective is to establish a global network of ocean observation platforms on commercial ships.
“While there has been good coverage of the sea surface, we have very limited knowledge of the ocean’s interior physical, chemical and biological properties. We really need high-resolution coverage of the oceans from the surface down”, said University of Miami Rosenstiel School of Marine and Atmospheric Science Professor Peter Ortner, one of the U.S members of the Working Group and a co-author of the proposal accepted by SCOR.
For the past year Ortner and his colleagues have been retooling the University of Miami, NOAA and Royal Caribbean International’s partnership aboard Royal Caribbean’s Explorer of the Seas cruise ship, the first-ever state-of-the-art oceanographic and atmospheric laboratory aboard a passenger cruise ship. Launched in 2000, the innovative program has produced a vast data set of atmospheric and oceanographic measurements along the ship's itinerary, and its full automation will serve as a pilot study and test bed for OceanScope.
“Our ability to equip freighters, tankers and cruise ships, which traverse all major oceans on defined schedules will allow us to scan both the surface waters and the water column without having to deploy individual research vessels,” said Ortner. “The result will benefit everyone – scientists would be better able to study the water column, including its biomass and other features; the marine industry would be better able to predict future operational conditions; and climatologists would have more complete data to use when investigating the climate and health of the planet.”
OceanScope is chaired by Professors Thomas Rossby (University of Rhode Island) and Kuh Kim (Pohang University of Science & Technology). The SCOR-approved terms of reference, core Working Group membership and a growing list of Associate Members is available at http://www.scor-int.org/Working_Groups/wg133.htm. Results of the first meeting are being presented to the international scientific community at OceanObs09 in Venice, Italy in September 2009. Plans are being made for a second Working Group meeting to be held in Spring 2010.Media Contacts:
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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...
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Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Ice sheets are huge glaciers fashioned by snow that has constantly accrued and compacted for a lot of 1000’s of years. Ice sheets can develop to be a number of kilometers thick and might cowl massive elements or whole continents, such because the Laurentide ice sheet that existed over the last glacial interval, or the current day Antarctic and Greenland ice sheets. Their destiny – inception, evolution, and disappearance – is ruled by the physics of glacier ice move and by advanced interactions with the opposite elements of the Earth system, together with the environment, ocean, lithosphere, sea ice, and biosphere. Such interactions play an vital function in finally figuring out ranges of ice sheet-sourced sea stage rise.
Motivated by the pressing want to higher perceive the contributions to future sea stage rise from the Antarctic and Greenland ice sheets, a latest article in Evaluations of Geophysics explores the interactions between ice sheets and different Earth system elements, and the suggestions loops brought on by these interactions. Right here, the authors to offer an summary of scientific analysis on this space.
How do ice sheets work together with different elements of the Earth system?
Ice sheets achieve mass via snowfall and lose mass by atmosphere-regulated floor melting round ice sheet edges, ocean-regulated melting underneath floating ice cabinets, iceberg calving, and in some circumstances ice sublimation. Adjustments in environment and ocean situations over and round ice sheets can subsequently affect mass adjustments and associated sea stage developments. For instance, the upper the snowfall charge, the sooner the mass achieve, and the upper the atmospheric or ocean temperatures, the sooner the ice soften and mass loss.
In flip, ice sheets exert a powerful management again on the encircling Earth system, for instance by altering atmospheric circulation via topographic results, and ocean circulation by offering contemporary water fluxes from melting and icebergs. As a result of ice sheets are so massive, they even make the Earth crust subside underneath their weight, and might alter the planetary gravitational subject. On account of these processes, any local weather change-induced ice sheet mass change ends in a subsequent local weather change sign, in a coupled suggestions loop.
Abstract of the household of interactions (I) and suggestions loops (F) between ice sheets and different elements of the Earth system: environment (a), ocean (o), sea ice (si), and the strong earth (g). Credit score: Fyke et al., 2018, Determine three; picture created by Catherine Raphael, Geophysical Fluid Dynamics Laboratory
What are ice-sheet/Earth system suggestions loops?
Interactions between ice sheets and different Earth system elements result in amplification (optimistic feedbacks) or damping (detrimental feedbacks) of ice sheet mass and sea stage adjustments.
An instance of suggestions loop. Credit score: “Local weather Change: Proof, Impacts, and Selections”, Nationwide Analysis Council, 2011, Determine 9; graphic idea by Madeline Ostrander as revealed in Sure! Journal
An instance of a optimistic suggestions loop is the ice sheet peak/floor mass stability suggestions loop.
Over time, as ice sheet loss from floor melting across the ice sheet edges will increase (for instance, from greenhouse gas-driven warming), ice sheet elevation lowers down.
This in flip drives additional melting – over and above the unique soften sign – because the ice sheet floor drops in elevation and experiences hotter situations because of background atmospheric temperature gradients.
This and different processes collectively set off ice-sheet / Earth system feedbacks that mix to affect ice sheet mass response to local weather forcing in advanced and poorly quantified methods. There may be additionally the potential for the existence of as-yet-undiscovered suggestions loops which will play crucial roles in previous and future ice sheet-driven sea stage shifts.
How can we examine interactions and feedbacks between ice sheets and the Earth system?
As a result of ice-sheet/Earth system interactions and feedbacks embrace multiple Earth system part and can even regulate one another in advanced methods, their investigations characterize substantial challenges. The 2 main approaches to check them are observations and modelling.
Climate observations, akin to right here on the foot of Mount Erebus on the Ross Ice Shelf in Antarctica, are one kind of observational information that may enhance understanding of ice-atmosphere interactions and be used to strengthen fashions. Credit score: Tsy1980 (CC BY four.zero)
Synchronized multidisciplinary observations that concurrently monitor a number of Earth system elements can considerably enhance our understanding of interactions and feedbacks.
Such observations can even information growth and validation of numerical fashions that purpose to enhance understanding of the bodily processes governing ice-sheet/Earth system interactions and feedbacks.
These fashions vary from process-oriented – as an illustration, centered on sub-ice-shelf melting – to complete Earth System Fashions that try to embody all ice-sheet/Earth system interactions in a unified mannequin setting.
How can Earth System Fashions assist to enhance our understanding?
Earth System Fashions mirror our present understanding of how numerous elements of the Earth system work together with one another and co-evolve in response to exterior forcing (akin to will increase in greenhouse gasoline concentrations). They subsequently characterize highly effective instruments for exploring Earth system habits and projecting future change.
Specific illustration of ice sheets in Earth System Fashions permits for exploration and quantification of already recognized feedbacks within the ice-sheet Earth system and discovering new ones. It additionally permits for self-consistent projections of sea stage change arising from ice sheet mass adjustments. This profit is motivating efforts to incorporate ice sheets into Earth System Fashions in order that they could be utilized to extremely societally related projections of sea stage rise in response to anthropogenic forcing.
—Jeremy Fyke, Los Alamos Nationwide Laboratory; Olga Sergienko, Princeton College; e mail: [email protected]; Marcus Löfverström, Nationwide Heart for Atmospheric Analysis; Stephen Worth, Los Alamos Nationwide Laboratory; and Jan Lenaerts, College of Colorado | <urn:uuid:96a6aaf3-8bc3-4d83-8d58-981b23d068de> | 3.84375 | 1,251 | Truncated | Science & Tech. | 16.807554 | 95,633,730 |
Researchers looking at the thermal conductivity of boron nanoribbons have found that they have unusual heat-transfer properties when compared to other wire/tube-like nanomaterials. While past experiments have shown that bundles of non-metallic nanostructures are less effective in conducting heat energy than single nanostructures, a new study shows that bundling boron nanoribbons can have the opposite effect and "the thermal conductivity of a bundle of boron nanoribbons can be significantly higher than that of a single free-standing nanoribbon," according to a report in Nature Nanotechnology, published online on December 11.
The finding is the result of work by a multidisciplinary team headed by Ravi Prasher of the Advanced Research Projects Agency, Terry Xu of the University of North Carolina at Charlotte, and Deyu Li of Vanderbilt University (see a complete list of authors below).
Additionally, the researchers found that the unusual heat-transfer properties of boron nanoribbon bundles can be modified, allowing the higher thermal conductivity to be switched on and off through relatively simple physical manipulation. The study concludes that the ribbon structure of the nanomaterials is strongly related to the unusual thermal conductivity of the bundles.
Boron-based nanostructures are a promising class of high temperature thermoelectric materials -- substances that can convert waste heat to useful electricity – and thermal conductivity is related to other thermoelectric properties. Physicists describe the transmission of heat energy in materials like boron as happening through the conduction of "phonons," quasi-wave-particles that carry energy through excitations of the material's atoms.
"What we found was largely unexpected," said Xu. "When two nanoribbons were put together, the thermal conductivity was found to rise significantly rather than staying the same or going down, as has been the case in previous measurements. It has been assumed that phonons were hampered by the interface between the individual nanostructures in similar materials.
"That seems to mean that the phonon can pass effectively through the interface between two boron nanoribbons," she said. "The question is whether or not this result is due to the weak van der Waals interactions between two nanostructures of ultra-flat geometry."
The team suspects that the reason for the enhanced thermal conductivity is due in large part to the flat surface structure of the nanoribbons, based on another experimental result that the group discovered by accident.
The nanoribbon bundles exhibiting the unexpectedly higher thermal conductivity were originally prepared in a solution of reagent alcohol and water, which was then allowed to evaporate, leaving some nanoribbons drawn together by van der Waals force (the weak attraction that non reactive and uncharged substances can have for each other). When other members of the team attempted to duplicate this result, however, the experiment failed and the bundles only had the lower thermal conductivity of single ribbons. The researchers then noted that a significant difference between the two attempts was that the second experiment had used isopropyl alcohol rather than reagent alcohol in the solution. Since isopropyl alcohol was known to leave minute residue following evaporation, the researchers suspected that a residue was forming on the ribbons surfaces – a fact that microscopy confirmed -- and the residue apparently prevented tight contact between two nanoribbons. Further tests were made on the lower-conducting bundles, where the ribbon interfaces were washed with reagent alcohol to remove the isopropyl residue, and in this experiment the higher thermal conductivity was achieved.
The results point to the conclusion that boron nanoribbons form better heat-conducting bundles because the ribbons flat surfaces allow for tighter, more complete contact between the individual structures through van der Waals interaction and improved transmission of phonons overall.
"The result implies that achieving a tight van der Waals interface between the ribbons is important in thermal conductivity, something their geometry encourages," Xu said. "It is possible that this result may have implications for other materials with ribbon-based nanostructures."
Xu notes that there are potential engineering applications for the finding come not just from the improved thermal conductivity of boron nanoribbon bundles, but also from the reversible nature of the effect.
"This may lead to a simple way to switch the thermal conductivity of the bundle on and off," she said. "If you want more heat dissipated, but only in certain conditions, you can apply a solution to create a bundle structure with tight bonds and higher thermal conductivity. It could similarly be reversed by adding a residue between the nanoribbons and reducing the thermal conductivity to that of an individual ribbon."
The finding appears in a letter to Nature Nanotechnology. The authors are Juekuan Yang, Yang Yang, Scott Waltermire and Deyu Li from Vanderbilt University; Xiaoxia Wu, Haitao Zhang, Timothy Gutu, Youfei Jiang, and Terry Xu from UNC Charlotte; Yunfei Chen from Southwest University in Nanjing, China; Alfred Zinn from Lockheed Martin Space Systems and Ravi Prasher from the Advanced Research Projects Agency in the US Department of Energy. This research was funded by the National Science Foundation and Lockheed Martin.
James Hathaway | EurekAlert!
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
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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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Ones And Zeros: Understanding Boolean Algebra, Digital Circuits, And The Logic Of Sets
John R. Gregg
- 出版商: Wiley-IEEE Press
- 出版日期: 1998-03-30
- 售價: $2,906
- 貴賓價: 9.5 折 $2,761
- 語言: 英文
- 頁數: 296
- 裝訂: Paperback
- ISBN: 0780334264
- ISBN-13: 9780780334267
Mathematics Ones and Zeros Understanding Boolean Algebra, Digital Circuits, and the Logic of Sets Ones and Zeros explains, in lay terms, Boolean algebra, the suprisingly simple system of mathematical logic used in digital computer circuitry. Anecdotal in style and often funny, Ones and Zeros follows the development of this logic system from its origins in Victorian England to its rediscovery in this century as the foundation of all modern computing machinery. Readers will learn about the interesting history of the development of symbolic logic in particular, and the often misunderstood process of mathematical invention and scientific discovery, in general. Ones and Zeros also features practical exercises with answers, real-world examples of digital circuit design, and a reading list. This fascinating look at the crucial technology of the twentieth century will be enjoyed by anyone who has a general interest in science, technology, and mathematics. Ones and Zeros will be of particular interest to software engineers who want to gain a comprehensive understanding of computer hardware. Outstanding features include:
- A history of mathematical logic
- An explanation of the logic of digital circuits
- Hands-on exercises and examples
About the IEEE Press Understanding Science & Technology Series The IEEE Press Understanding Science & Technology Series treats important topics in science and technology in a simple and easy to understand manner. Designed expressly for the nonspecialist engineer, scientist, or technician, as well as the technologically curious, each volume stresses practical information over mathematical theorems and complicated derivations.
Table of Contents:
Before We Begin.
Number Systems and Counting.
The Basic Functions of Boolean Algebra: And, Or, And Not.
The Algebra of Sets and Venn Diagrams.
Other Boolean Functions.
Realizing Any Boolean Function with And, Or, And Not.
More Digital Circuits.
Laws of Boolean Algebra.
Appendix A: Counting in Base 2.
Appendix B: Powers of 2.
Appendix C: Summary of Boolean Functions.
Answers to Exercises.
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This section discusses applets and basic drawing operations. More importantly, it also serves as an excuse to introduce or illustrate general concepts that are used throughout Java programming: import statements, inheritance in action, lifecycle methods, the @Override annotation, and try/catch blocks.
See http://courses.coreservlets.com/Course-Materials/java.html for the complete tutorial series (Programming with Java 8) and associated code. That site also lets you download PDF files of each lecture for saving or printing, and includes exercises and exercise solutions for each of the topics. | <urn:uuid:01a927d0-fae3-45ed-856c-e097630f5ae6> | 2.921875 | 126 | Truncated | Software Dev. | 31.874737 | 95,633,795 |
Ruby on Rails PDF Tutorial
Learn the basics of Ruby on Rails programming language, free training document in 250 pages for all level users.
Ruby is a fully object-oriented, multi-platform interpreted language.
Ruby can be used as a scripting language in the same way as PERL or others, but its recent rise is mainly due to the appearance of Ruby On Rails, an extremely powerful web framework based on Ruby.
We will see here the basis of this language, its assets, etc.
This tutorial is the first step on your path to learning Ruby on Rails.You'll learn key concepts so you'll have a solid foundation for continued study. You'll build a working web application so you'll gain hands-on experience. Along the way, you'll practice the techniques used by professional Rails developers and you'll understand why Rails has become a popular choice for web development.
Table of contents
- Manage Your Project
- Get Started
- Create the Application
- The Parking Structure
- Time Travel with Git
- Static Pages and Routing
- Request and Response
- Dynamic Home Page
- Just Enough Ruby
- Layout and Views
- Front-End Framework
- Add Pages
- Contact Form
- Spreadsheet Connection
- Send Mail
- Mailing List
- Rails Challenges
- Credits and Comments
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Take advantage of this course called Ruby on Rails PDF Tutorial to improve your Web development skills and better understand Ruby.
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All you need to do is download the training document, open it and start learning Ruby for free.
Symfony2 and HTTP Fundamentals
Symphony lets you develop faster and build more robust and efficient web site and application,it's important for every web developer. This tutorial explains the fundamental concept and the basics of Symphony.
Node.js tutorial pdf
Learn Ruby on Rails, PDF Tutorial
This is a PDF tutorial about Ruby on Rails under 39 pages by Bhaskar Vaish, you will learn how to build web application using a Rails framework application.
Getting Started with Ruby programming language
A complet tutorial about Ruby programming language under 594 pages for advanced level students, free training document in PDF by David Flanagan and Yukihiro Matsumoto. | <urn:uuid:2ee06504-6c76-47bb-82c8-e8841233318b> | 3.09375 | 496 | Product Page | Software Dev. | 45.504272 | 95,633,806 |
1.1.1 Introduction The conditions under which the tsetse lives make up its environment. It includes conditions of climate, vegetation, animal life, soil, and the effects of human activity. All these may be called environmental conditions or environmental factors.
The study of the tsetse in its environment is called ecology.
The particular place where the tsetse lives is called its habitat. For example, gallery forest, thicket, miombo woodland, and mopane woodland are different kinds of tsetse habitat.
Where one type of vegetation gives way gradually to another, that is called an ecotone. For example, as one passes from thick woodland to open grassland, one may walk through an area of smaller, more scattered trees. This area is an ecotone.
1.1.2 Climate (see also Volume I, 10.2) Sunshine, rainfall and humidity, temperature, atmospheric pressure and wind make up the climate of a particular area. Temperature and humidity are the most important of these for tsetse, and light can also be important.
Very restricted areas in the habitat may have a special climate of their own, called the microclimate (see 188.8.131.52).
184.108.40.206 Temperature Glossina lives well at 25–26°C and most laboratory colonies are kept at that temperature. If the temperature goes much higher or much lower than that, there may be some damage to the fly. Here are some examples:
- death occurs rapidly (in 5 minutes) if G. morsitans adults are kept at 46°c
- death occurs if G. tachinoides adults are kept at 44OC for 1 hour
- death occurs if G. morsitans adults are kept at 40°C for 1 hour
- death occurs if G. fuscipes adults are kept at 40°C for 3 hours
- around 14°C and below, Glossina adults cannot fly
- death occurs if G. morsitans adults are kept at -4°C for 6 hours.
In general, a temperature above 38°C is damaging to the adults; and a temperature below about 17°C will not allow the adult to live a normal active life.
For pupae, 32°C is the upper limit for normal development, and 16°C is the lower limit.
At the northern limit of tsetse distribution, high temperature and dryness limit the spread of the fly.
In the south of the continent, the limits of tsetse distribution may also be set by high temperatures and dryness (in the hot dry season). But in some areas, seasonal low temperatures are more important. Gold winter months may delay the development of tsetse pupae for so long, that they cannot produce adults successfully.
Temperature also affects the rate at which the fly lives.
- shorten the time from emergency to the production of the first larva
- shorten the time from the production of one larva to the production of the next (interlarval period)
- shorten the period spent as a pupa (pupal period)
- shorten the life of the adult
- shorten the period the adult can last without a blood meal.
Low temperatures have the opposite effect in each case.
220.127.116.11 Rainfall and humidity Rainfall probably does not have any direct effect on tsetse, but does so indirect-ly by:
A humid atmosphere allows tsetse to spread away from sheltered habitats, so long as the temperature is not too high. So in the wet season G. morsitans disperses away from its dry season home (riverside woodland) into more open country, in the northern savanna areas.
In the southern parts of its range, G. palpalis can live away from free water, probably because of the humid atmosphere.
In high rainfall areas, G. tachinoides is also able to live away from free water.
Both G. pallidipes and G. longipalpis have dry season habitats in well-sheltered thickets, but wet season dispersal areas in less densely wooded country.
Humidity of the soi 1 is important to the sur-vival of tsetse pupae.
- Glossina longlpennis, G. morsitans morsitans and G. swynnertoni pupae can develop in very dry soils (0–10% R.H.).
- Glossina morsitans submorsitans, G. pallidipes and G. tachinoides pupae can develop in fairly dry soils (30–40% R.H.)
- Glossina austeni and G. fuscipes pupae require rather mare humid soils (40–50% R.H.)
- Glossina palpalis, G. brevipalpis and G. fuscipleuris require very humid soils (about 70% R.H.).
- The humidity is affected by wind, especially in West Africa. Here, humid winds blow during the rainy season from the south-west; during part of the dry season a dry dusty wind (Harmattan) blows from the north-east.
18.104.22.168 Microclimate Meteorological instruments (see Volume I, 10.2.6) are usually placed in rather open places, to give information about the general climate of the area, but the local climate (microclimate) of small sheltered parts of the habitat (microhabitats) may be very different.
The following are some of these microhabitats:
- At the river bank, especially under an overhanging bank. Here the air remains very humid even in the dry season, and it is a favourite resting place for palpalis group flies, in the far northern limit of their distribution. In this area, nearly all the palpalis group flies are found within 5 m. of the river bank.
- In rot holes, or in hollow trees, or in animal burrows. For example, in the Zambesi valley Glossina pallidipes enters rot holes in trees in the daytime, during the hottest season. Here it is cooler and more humid than outside.
- On a tree trunk, especially low down and in cracks in the bark, or between buttress roots. In the day it is cooler and more humid here than in the more exposed parts of the habitat.
- At the top of trees, at night. Here it can be wanner than nearer the ground, because the ground may lose much heat by radiation at night, especially in the cold season and when there is no cloud.
The fly's behaviour (see 1.2) can bring it into these places where it can survive better than if it had to suffer the general climatic conditions of the area.
1.1.3 Vegetation zones and tsetse habitats
22.214.171.124 In West Africa The following are some of the main vegetation zones in West Africa starting from the coast and working inland, and some of the tsetse species to be found in these zones.
- Mangrove swamps. These are found along some parts of the coast especially in the river mouths, where the water is brackish (part river water, part see water). They are habitats of Glossina palpalis and G. caliginea (in Nigeria).
- Fresh water swamp forest. Some G. palpalis and G. caliginea are found here also.
- Rain forest. An area of very high rain fall, very tall trees, high humidity and dense shade at ground level. Where this forest is well-developed, these species may be found: G. tabaniformis, G. haningtoni, G. fusca and (for instance in Nigeria) G. nigrofusca, as well as other less cannon fusca group flies. Glossina pallioera and G. palpalis are also found here. Further north, where the forest is slightly drier, the trees are less tall and more often lose their leaves in the dry season, the forest edge species G. medicorum and G. nigrofusca (in Ghana) live.
- Derived savanna. This is a forest zone that has been largely cut down and burned to make farms. It is sometimes called farm bush, especially where there has been re-growth of trees. It is therefore country that has patches of forest on poor land, with farms and savanna areas in between. The forest patches have G. medicorum, G. fusca, G. longipalpis and G. palpalis. Of these, G. longipalpis may spread out into savanna areas, especially in the wet season.
- Southern Guinea savanna. This has a dry season of 3–4 months. The trees are 15–18 m. (40–50 ft) high, sometimes taller, broad leafed, and forming an open woodland with tall grass. Glossina longipalpis lives in the southern parts of this zone. Further north, G. morsitans replaces it. Rivers and streams along which evergreen trees grow form the habitat of G. palpalis and G. tachinoides.
- Northern Guinea savanna. This has a dry season of 4–5 months, and an annual rainfall of about 1000 mm. (approx. 40 inches) and over. The dominant trees are doka (Iso-berlinia doka, I. dalzielii), members of the family Caesalpinaceae. The trees in this zone are about 13 m. (40 ft) high, and the woodland has a very uniform appearance. Grass is shorter than in the southern Guinea savanna. The zone is infested with G. morsitans.Along rivers and streams, G. palpalis and G. tachinoides are found. Glossina medicorum inhabits vegetation along the Komoe and the Black Volta rivers.
- Sudan zone. The dry season here lasts about 7 months. Annual rainfall is 500–1000 mm. (20–40 inches). It can become very hot. Characteristic trees are Acacia, baobab (Adansonia. digitata), doum palm (Hyphaene thebaica); there are also thorny thickets. This zone is inhabited by G. morsitans, but the species is based mainly cm patches of forest, dispersing a little in the milder rainy season. Glossina tachinoides and G.p. gambiensis can live here, but only along river banks. For this zone, G.p. gambiensis is limited to the area Senegal to Togo.
126.96.36.199 Other vegetation zones The vegetation of East and Central Africa is not set out in such a clear manner as that of West Africa. Some extensive vegetation types are:
- Miombo woodland. This closely corresponds to the northern Guinea zone of West Africa. The dominant trees are Brachystegia and Isoberlinia (Caesalpinaceae) of which there are several species. It is one of the main habitat of G. morsitans.
- Mopane woodland. This occurs along the valleys of Zambesi, Limpopo and Luangwa rivers. The dominant tree is mopane, Colophospermum mopane (Caesalpinaceae). It forms an important habitat for G. morsitans in the Luangwa and parts of the Zambesi valleys.
- Baikiaea woodland on Kalahari sands (gusu woodland). This occupies a large area of western Zimbabwe, Zambia (much of Western Province) and part of Botswana. It is not much used by tsetse, probably because the sandy soil becomes too cold for too long a period in the winter months. It is also a dry soil.
- Manga woodland. This contains much Acacia, Albizia, Combretum and Terminalia. It forms only a marginal tsetse habitat in Zambia.
- Dry thorn bush (nyika) is a drier type of Acacia dominated woodland, with Commiphora and Combretum, and occupies much of Somalia, Sudan, Kenya, Uganda and northern Tanzania. It is the home of Glossina swinnertoni and G. pallidipes.
- Patches of evergreen forest, not as extensive in East Africa as the other vegetation types mentioned, are the habitat of G. brevipalpis and G. austeni.
- Itigi thicket is not favoured by tsetse.
188.8.131.52 Less typical habitats Under 184.108.40.206 and in Chapters 2, 3 and 4, descriptions are given of the typical habitats in which various Glossina species may be found. But these may not include all the places where a particular species occurs. If a spraying programme misses out these unusual habitats, then the sprayed areas will quickly be re-infested.
Many of the less typical habitats are man-made ones, for example in and around villages, especially in the rain forest belt of West Africa, where the original vegetation has been cut down to make farms and plantations.
From these places, flies can attack man and village livestock, especially pigs and to a lesser extent cattle, so that these populations of flies can be very important from the point of view of disease transmission.
Because they are around places where people live, these tsetse populations have been called peri-domestic (‘around the home’).
1.1.4 Effect of other animal life on tsetse
220.127.116.11 Host animals Lists of the hosts that are used by different species of tsetse are given in Volume I, Chapter 6. Some additional information will be found in the following chapters of the present volume.
Although the tsetse is completely dependent on the host animals for their food, these animals are the most difficult environmental factor to study in tsetse ecology. When a worker goes out into the field, he may at once frighten away the host animals and may attract a few of the tsetses to himself. Therefore, the natural situation is completely altered. The field worker should remind himself of the dependence of tsetse on host animals, even where these seen to be scaroe.
The dependence of tsetse on wild game animals is also shown by:
Rinderpest is a disease affecting many kinds of wild animals. It particularly affects buffalo, giraffe, eland, bushpig and warthog, but also to a lesser extent affects reedbuck, wildebeest, kudu and giant forest hog. Wild animals that are very much affected by rinderpest provide 80–90% of tsetse feeds in East Africa. When the disease killed off many of the African animals in the period 1889–1896, the tsetses were greatly reduced in numbers, and their distribution became restricted to quite small areas.
When the main outbreak was over, the game animals recovered in numbers and the fly belts expanded, eventually to reach their present size.
Examples of game control to eradicate tsetse are given in Volume III, 2.2.
Sometimes, tsetses use domestic cattle for the food supply, rather than wild animals (for example, in the Koalib Hills, Sudan, where an isolated belt of G. morsitans used to live). In other places, such as at the northern fringes of G. palpalis distribution, populations of flies may depend for their food on people visiting a water hole.
18.104.22.168 Predators and parasites
Predators Figure 1.1 illustrates some of the predators known or believed to feed on tsetse adults and pupae.
The most important predators are probably ants feeding on tsetse pupae, and asilids (robber flies), waspes and spiders feeding on the adults.
Insect parasites Included here are insects that attack the pupa of Glossina from within.
Fig. 1.1 Predators of tsetse A. Bembex wasp; B. Ant; C. Asilid (robber fly)
Fig. 1.2 Parasites of tsetse pupae A. Syntomasphyrun (Hymenoptera); B. Mutilla (Hymenoptera) ; C. Thyridanthrax (Diptera)
- Syntomosphyrum (Hymenoptera) (Figure l.2 A) This is a tiny black wasp about 1 ran. long. It is easily reared in the pupae of various fly species, and millions of the adults have been released into the field in various control attempts which, however, have had no lasting effect. The female wasp lays its eggs inside the tsetse pupariun. Several or many of these wasps emerge from each infected tsetse pupa. Natural rates of infection are normally about 0.2% or less.
- Mutilla (Hymenoptera) (Figure 1.2 B) Ihis is a larger insect, about 4 mm. long. The male is winged but the female is wingless. The female lays only about three eggs in each tsetse pupa, and of these only one developes all the way to become a wasp. Six times as many females emerge as males. Natural rates of infection may be as high as 40% in the warmer seasons (G. morsitans). But the period spent in the tsetse pupa is much longer than pupal period of the healthy tsetse, so that infection rates can be overestimated. The parasite is not easy to rear in large numbers, and it has not been used for attempts at control.
- Thyridanthrax (Diptera) (Figure 1.2 C) This is a fly, slightly smaller than the tsetse it parasitises. Eggs are laid on the soil surface, and the tiny larvae burrow searching for pupae. Only one fly emerges from each parasitised tsetse pupa. Locally, rates of parasitism may be as much as 20% or more, and it is probably one of the most important of the tsetse parasites. The pupal period may last much longer than the 4–5 weeks that is normal for tsetse or it may be shorter. It is a difficult insect to breed and no field releases have been made.
There are many other species, particularly Hymenoptera, that have been recorded as emerging from tsetse pupae. So far as is known, they are not as important as the ones described above.
Other parasitic organisms Other types of organisms that have been known to attack tsetse (pupa or adult) include bacteria, fungi, protozoa, viruses and nematode worms. Their relative importance is not yet clear and more work has to be done on them.
For both predators and parasites of tsetse, it is not yet known how important they are in keeping down the numbers of tsetse in the field.
1.1.5 Human activity (see also Volume II, Chapter 2) Human settlements, with crop farming and tree-felling, may locally prevent tsetse from existing in an area, at least in large numbers. The reasons are that
One of the most important results of human activity is fire. Fires late in the dry season change the environment by destroying young trees and bushes and thus encouraging vigorous grass growth. Fire also makes the area drier, and tsetse are therefore pushed into places of shadier, thicker vegetation where the air is moister.
Fires early in the dry season may have the effect of making the habitat more wooded, but this change is brought about very slowly, over many years.
1.2.1 Flight Only about 15–30 minutes of each day is spent in active flight. A single flight does not last longer than about 1 1/2 – 2 1/2 minutes. The speed of flight may be 3–6 m/sec (11–24 km/h = 7–15 miles/h), but it is much slower immediately after a meal.
After taking in a large blood meal a short, slow flight is made away from the host animal to a resting place such as a tree trunk. Here, the weight of the fly is quickly reduced by primary excretion (some drops of water are passed out through the anus). More short flights may then follow, taking the fly to a safer place.
1.2.2 Best and resting sites Tsetses spend most of the day settled. The places where they remain settled for long periods are called resting sites. These are different from the places where flies may perch temporarily, for example when they settle out from a following swarm, or when they are looking out for the next meal.
It is important to know about resting sites (sometimes called 'true resting sites') because these are the best places for spraying persistent insecticides for killing the tsetse. Insecticides placed at the resting sites and only at the resting sites will have the maximum effect against tsetse and minimum effect against other animal life.
Resting sites have been investigated (see Vol. I, 7.4):
- by searching the vegetation carefully for resting flies
- by enclosing whole trees and bushes in a net cage and releasing fed flies within the cage to see where they rest
- by marking ('tagging') flies with fluorescent or reflecting paint and looking for them at night using lamps.
Flies have also been tagged with radio-active materials and searched for later in the bush. This technique is not described in the Manual because it requires very specialised instruments and safety precautions in which the research chief will give training.
Besting sites may vary according to:
- the time of day or night
- the climate: and season
- the species of tsetse fly
- the vegetation
- the resting places of host animals (e.g. bushbuck).
During the hottest part of the day (visually early to mid-afternoon), the true resting sites are lowest down on tree trunks, and on the underside of shaded, fallen logs. At copier times of the day, and in cooler seasons, the flies rest higher up tree trunks, and on the underside of branches. At night, some flies go up into the canopy of trees and rest on the leaves or twigs.
Woody living parts of the vegetation are often chosen for day time resting, but some species (e.g. Glossina palpalis gambiensis) may prefer leaves.
The resting habits of different species are described in Chapters 2, 3 and 4.
1.2.3 Response to host animals Usually a fly detects a host animal by its sense of smell, from up to 100 m away. Larger host animals or more of them, are more attractive to tsetse than smaller host animals, or single individuals.
When it smells the host, the fly moves up-wind, which brings it closer to the host animal. Then the fly is able to see the host (at 50 m or more).
Flies may land on a greater variety of host species than is indicated by the blood meal list. However, some hosts prevent flies from feeding by flicking their tails and twitching the skin.
Many flies, especially non-hungry males, are attracted to hosts even though they are not going to feed. They make up the 'following swarm', a party of males that settles on the ground or low vegetation close to a moving host. A male in a following swarm may fly on to a virgin female as she comes for her first meal, and mate with her.
1.2.4 Daily activity Under average conditions most activity is in the early to mid-morning, and in the late afternoon.
Under very hot conditions, activity during the middle of the day may be stopped almost completely, with flies finding the cool places in which to shelter from the great heat.
Under cool conditions, there may be one period near the middle of the day when tsetses are most active in the field.
Some facts concerning the life of tsetse cannot be described for individual flies, but only for a group or sample of flies. Examples are the percentage of females caught by a trap, the density of tsetse living in an area, and the distribution of resting sites.
When gathering this information we are usually trying to learn more about the population of the flies living in an area.
1.3.1 Pupal population
22.214.171.124 Importance of the pupal population In general, more than half of the total population of tsetse in an area are present below ground, as pupae.
Experience shows that in some seasons (particularly in the rains) pupae are very difficult to find.
It is therefore impossible to work out what number of tsetse are living in a given area, from the number of pupae found there.
But the collection of pupae can give information about:
- the changes in the breeding areas according to season
- what parasites the pupae suffer from
- where tsetse are living.
126.96.36.199 Breeding sites (larval deposition sites) Ways to search for pupae are given in Volume I, 7.1.
The following table shows the sort of places in which tsetse pupae might be found. These are called breeding sites.
|1.||In soil under fallen logs and under leaning trees in deciduous woodland||G. morsitans, G. brevipalpis|
|2.||In soil under fallen logs in open country||G. longipennis|
|3.||Under fallen logs but on the soil surface||G. swynnertoni (wet season)|
|4.||Under overhanging rocks||G. morsitans, G. austeni, G. palpalis/fuscipes|
|5.||Under leaf litter in (a) thickets; (b) gallery forest||G. pallidipes, G.palpalis gambiensis|
|6.||In dry sandy beaches or river beds where shaded by dense vegetation||G. morsitans (dry season)|
G. palpalis/fuscipes (dry season)
|7.||Where there is high canopy cover as well as lower level cover given blow branches and creepers immediately over the site||G. palpalis/fuscipes|
|8.||At sandy spots, where there is high canopy cover||G. tachinoides|
|9.||Around the base of oil palms (Elaeis), where shelter is given by broken frond stems||G.palpalis/fuscipes G. longipalpis|
|10.||In rot holes in trees||G. palpalis/fuscipes, G. morsitans, G. swynnertoni (dry season)|
|11.||In animal holes in the ground||G. morsitans (dry season)|
|12.||Under Lantana and Euphorbia hedges locally in Western Kenya||G. fuscipes|
|13.||In plantations of mangoes, etc.||G. tachinoides|
Breeding areas are zones in which breeding sites may be found. They are more concentrated in the dry season (especially in deciduous woodland) and more widespread in the wet season.
1.3.2 Adult populations
188.8.131.52 Sex ratio The proportion of females amongst flies emerging from a collection of pupae is normally close to 50%.
Females usually live longer than males, so that a field population of flies will normally have more females than males.
But hand net samples taken on a fly round usually contain a low proportion of females, because the flies that come within reach of the nets are mainly males,
Samples taken in traps have a higher proportion of females, often in the range of 60–70%. This figure can vary according to location, time of day and year, and according to the species.
184.108.40.206 Age The fly that emerges from the pupa is hungry. After spreading and hardening its wings, its main problem is where to get its first meal. During this time, from emergence to taking the first blood meal, the fly is called a 'teneral' fly.
Ihe food obtained at the first meal is used to build up the flight muscles of the thorax, which are poorly developed at emergence.
In this way the fly gradually becomes a stronger flier. In the case of the female this is necessary for the later task of carrying the larva in the abdomen. In the case of the male it is necessary for catching and mating with virgin females, in competition with other males.
At each feed, there is a chance of the fly becoming infected with trypanosomes (this chance is greater with the earlier meals). Any trypanosomes picked up have to go through a cycle of development before the fly is permanently infective.
It follows that older flies are more important as disease vectors than younger flies.
Traps are able to catch older flies, especially older females, compared with other methods (e.g. hand nets used with men, vehicles or ox).
Males may live about 3 weeks in the field.
Females certainly live longer than males. Glossina pallidipes females in one population were estimated to live an average of 35 days or more.
Flies live for longer periods
- when it is cool (rather than hot)
- when it is humid (rather than dry)
- when there are many hosts available (rather than only a few).
220.127.116.11 Physiological state
Hunger The idea we gain of the hunger state of a population also depends on the type of sample examined.
Most flies taken during a normal fly round are non-hungry males.
Nearly all flies (G. morsitans and G. pallidipes) attracted to a stationary bait (live animal or animal model) are hungry, but 10–25% of flies visiting moving baits are not hungry.
With a man and an ox being used as bait together, the flies (G. morsitans) coming to feed on man are fewer and hungrier than those visiting the ox.
Mated status and pregnancy Nearly all non-teneral female flies are mated (but not in G. pallidipes; see 2.4.7).
Under the best conditions, the uterus of a female fly is seldom empty once ovulation has started. This is because very soon after the deposition of the mature larva, the next egg passes into the uterus and begins its development.
Pregnancy rates may differ according to whether the flies are caught as they come to a party of men, to a bait animal or in a trap.
18.104.22.168 Density The density of a tsetse population in a given area is never very accurately known unless all the flies are caught. This could only be done on an island or in a very isolated woodland or thicket.
Usually the density is estimated by a mark-release-recapture method (see Volume I, 7.7).
The terms Apparent Density and True Density are sometimes used. 'Apparent density' is taken as the number of non-teneral males (savanna flies) caught in 9000 m. (10,000 yards). It is a figure obtained from fly-round results. It does not necessarily give information about the 'true density', which is simply the number of flies per unit area. For instance, a high catch may indicate a hungry population, rather than a dense one.
When traps are used, apparent density is defined as the number of flies/trap/day (F.T.D.). | <urn:uuid:f4e1438f-3b8b-4ff3-a558-397ddd80971d> | 3.671875 | 6,680 | Academic Writing | Science & Tech. | 60.061136 | 95,633,829 |
Editor of equations
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A galaxy is a large, gravitationally bound system made up of stars, stellar remnants, an interstellar medium of gas and dust and dark matter. Galaxies can range from ten million stars to hundred trillion stars.
Within galaxies there can also be varying number of star systems, star clusters and types of interstellar clouds. In between celestial objects in galaxies are interstellar medium of gas, dust and cosmic rays. In the middle of all galaxies are supermassive black holes which are thought to be the primary driver of active galactic nuclei.
Galaxies are categorized according to their shape (visual morphology). Some common shapes are elliptical galaxies, spiral galaxies and irregular galaxies. Galaxies can also combine with nearby galaxies which increases incidents of star formations leading to starburst galaxies.
There are 170 billion galaxies observable in the universe. Intergalactic space is the space between galaxies which is filled with tenuous gas of average density, less than one atom per cubic meter. Galaxies are organized into hierarchy of associations. These are known as groups or clusters. These groups or clusters usually form larger superclusters. These superclusters will around into sheets and filaments which surround with immense voids.
Earth resides in the Milky Way galaxy. It is a spiral galaxy. There are approximately 100 – 40 billion stars with a mass of 1.0 – 1.5x1012 solar mass. It has a diameter of 100,000-120,000 light years. Most of the Milky Way is made up of dark matter. Which means it does no emit or absorb electromagnetic radiation. The Milky Way is part of the Local Group of galaxies which forms a subcomponent of the Virgo Supercluster.© BrainMass Inc. brainmass.com July 16, 2018, 5:09 am ad1c9bdddf | <urn:uuid:ea3e518d-827a-457c-b115-e1c8325774ad> | 3.875 | 365 | Knowledge Article | Science & Tech. | 48.327158 | 95,633,839 |
Permafrost carbon cycle
The Permafrost Carbon Cycle is a sub-cycle of the larger global carbon cycle. Permafrost is defined as subsurface material that remains below 0o C (32o F) for at least two consecutive years. Because permafrost soils remain frozen for long periods of time, they store large amounts of carbon and other nutrients within their frozen framework during that time. Permafrost represents a large carbon reservoir that is seldom considered when determining global terrestrial carbon reservoirs. Recent and ongoing scientific research however, is changing this view.
The permafrost carbon cycle (Arctic Carbon Cycle) deals with the transfer of carbon from permafrost soils to terrestrial vegetation and microbes, to the atmosphere, back to vegetation, and finally back to permafrost soils through burial and sedimentation due to cryogenic processes. Some of this carbon is transferred to the ocean and other portions of the globe through the global carbon cycle. The cycle includes the exchange of carbon dioxide and methane between terrestrial components and the atmosphere, as well as the transfer of carbon between land and water as methane, dissolved organic carbon, dissolved inorganic carbon, particulate inorganic carbon and particulate organic carbon.
Soils, in general, are the largest reservoirs of carbon in terrestrial ecosystems. This is also true for soils in the Arctic that are underlain by permafrost. Determining carbon stocks in cryosols, that is, soils containing permafrost within two meters of the soil surface, was completed using the Northern and Mid Latitudes Soil Database. Permafrost affected soils cover nearly 9% of the earth’s land area, yet store between 25 and 50% of the soil organic carbon. These estimates show that permafrost soils are an important carbon pool. These soils not only contain large amounts of carbon, but also sequester carbon through cryoturbation and cryogenic processes.
Carbon is not produced by permafrost. Organic carbon derived from terrestrial vegetation must be incorporated into the soil column and subsequently be incorporated into permafrost to be effectively stored. Because permafrost responds to climate changes slowly, carbon storage removes carbon from the atmosphere for long periods of time. Radiocarbon dating techniques reveal that carbon within permafrost is often thousands of years old. Carbon storage in permafrost is the result of two primary processes.
- The first process that captures carbon and stores it is syngenetic permafrost growth. This process is the result of a constant active layer thickness and energy exchange between permafrost, active layer, biosphere, and atmosphere, resulting in the vertical increase of the soil surface elevation. This aggradation of soil is the result of aeolian or fluvial sedimentation and/or peat formation. Peat accumulation rates are as high as 0.5mm/yr while sedimentation may cause a rise of 0.7mm/yr. Thick silt deposits resulting from abundant loess deposition during the last glacial maximum form thick carbon-rich soils known as yedoma. As this process occurs, the organic and mineral soil that is deposited is incorporated into the permafrost as the permafrost surface rises.
- The second process responsible for storing carbon is cryoturbation, the mixing of soil due to freeze-thaw cycles. Cryoturbation moves carbon from the surface to depths within the soil profile. Frost heaving is the most common form of cryoturbation. Eventually, carbon that originates at the surface moves deep enough into the active layer to be incorporated into permafrost. When cryoturbation and the deposition of sediments act together, carbon storage rates increase.
The amount of carbon stored in permafrost soils is poorly understood. Current research activities seek to better understand the carbon content of soils throughout the soil column. Recent studies (2009) estimate that northern circumpolar permafrost soil carbon content equals approximately 1672 Pg. (1 Pg = 1 Gt = 1015g) This estimation of the amount of carbon stored in permafrost soils is more than double the amount currently in the atmosphere. This most recent assessment of carbon content in permafrost soils breaks the soil column into three horizons, 0–30 cm, 0–100 cm, and 1–300 cm. The uppermost horizon, 0–30 cm contains approximately 191 Pg of organic carbon. The 0–100 cm horizon contains an estimated 496 Pg of organic carbon, and the 0–300 cm horizon contains an estimated 1024 Pg of organic carbon. These estimates more than doubled the previously known carbon pools in permafrost soils. Additional carbon stocks exist in yedoma (407 Pg), carbon rich loess deposits found throughout Siberia and isolated regions of North America, and deltaic deposits (241 Pg) throughout the Arctic. These deposits are generally deeper than the 3 m investigated in traditional studies. Many concerns arise because of the large amount of carbon stored in permafrost soils. Until recently, the amount of carbon present in permafrost was not taken into account in climate models and global carbon budgets. Thawing permafrost may release great quantities of old carbon stored in permafrost to the atmosphere.
Carbon release from permafrost
Carbon stored within arctic soils and permafrost is susceptible to release due to several different mechanisms. Carbon that is stored in permafrost is released back into the atmosphere as either carbon dioxide (CO2) or methane (CH4). Aerobic respiration releases carbon dioxide, while anaerobic respiration releases methane.
- Microbial activity releases carbon through respiration. Increased microbial decomposition due to warming conditions is believed to be a major source of carbon to the atmosphere. The rate of microbial decomposition within organic soils, including thawed permafrost, depends on environmental controls. These controls include soil temperature, moisture availability, nutrient availability, and oxygen availability.
- Methane clathrate, or hydrates, occur within and below permafrost soils. Because of the low permeability of permafrost soils, methane gas is unable to migrate vertically through the soil column. As permafrost temperature increases, permeability also increases, allowing once trapped methane gas to move vertically and escape. Dissociation of gas hydrates is common along the Arctic coastline, yet estimates for dissociation of gas hydrates from terrestrial permafrost remains unclear.
- Thermokarst/permafrost degradation as a result of climate change and increased mean annual air temperatures throughout the Arctic threatens to release large quantities of carbon back into the atmosphere. The spatial extent of permafrost decreases in warming climate, releasing large amounts of stored carbon.
- As air and permafrost temperatures change, above ground vegetation also changes. Increasing temperatures facilitate the transfer of soil carbon to growing vegetation on the surface. This transfer removes carbon from the soil and relocates it to the terrestrial carbon pool where plants process, store, and respire it, moving it to the atmosphere.
- Forest fires in the boreal forests and tundra fires alter the landscape and release large quantities of stored organic carbon into the atmosphere through combustion. As these fires burn, they remove organic matter from the surface. Removal of the protective organic mat that insulates the soil exposes the underlying soil and permafrost to increased solar radiation, which in turn increases the soil temperature, active layer thickness, and changes soil moisture. Changes in the soil moisture and saturation alter the ratio of oxic to anoxic decomposition within the soil.
- Hydrologic processes remove and mobilize carbon, carrying it downstream. Mobilization occurs due to leaching, litter fall, and erosion. Mobilization is believed to be primarily due to increased primary production in the Arctic resulting in increased leaf litter entering streams and increasing the dissolved organic carbon content of the stream. Leaching of soil organic carbon from permafrost soils is also accelerated by warming climate and by erosion along river and stream banks freeing the carbon from the previously frozen soil.
Carbon is continually cycling between soils, vegetation, and the atmosphere. Currently, carbon flux from permafrost soils is minimal, however studies suggest that future warming and permafrost degradation will increase the CO2 flux from the soils. Thaw deepens the active layer, exposing old carbon that has been in storage for decades, to centuries, to millennia. The amount of carbon that will be released from warming conditions depends on depth of thaw, carbon content within the thawed soil, and physical changes to the environment. The likelihood of the entire carbon pool mobilizing and entering the atmosphere is low despite the large volumes stored in the soil. Although temperatures are projected to rise, it does not imply complete loss of permafrost and mobilization of the entire carbon pool. Much of the ground underlain by permafrost will remain frozen even if warming temperatures increase the thaw depth or increase thermokarsting and permafrost degradation.
Warmer conditions are expected to cause spatial declines in permafrost extent and thickening of the active layer. This decline in the extent and volume of permafrost enables the mobilization of stored soil organic carbon to the biosphere and atmosphere as carbon dioxide and methane. Additionally, these changes are believed to impact ecosystems and alter the vegetation that is present on the surface. Increased carbon uptake by plants is expected to be relatively small when compared to the amount of carbon released by permafrost degradation. Tundra vegetation contains 0.4 kg of carbon per m2 while a shift to boreal forests could increase the above ground carbon pool to 5 kg of carbon per m2. Tundra soil however, contains ten times that amount.
Additionally, a sudden and steady release of carbon dioxide and methane from permafrost soils may lead to a positive feedback cycle where warming releases carbon dioxide into the atmosphere. This carbon dioxide, a greenhouse gas, causes atmospheric concentrations to increase, causing subsequent warming. This scenario is thought to be a potential runaway climate change scenario.
- Zimov SA, Schuur EA, Chapin FS (June 2006). "Climate change. Permafrost and the global carbon budget". Science. 312 (5780): 1612–3. doi:10.1126/science.1128908. PMID 16778046.
- McGuire, A.D., Anderson, L.G., Christensen, T.R., Dallimore, S., Guo, L., Hayes, D.J., Heimann, M., Lorenson, T.D., Macdonald, R.W., and Roulet, N. (2009). "Sensitivity of the carbon cycle in the Arctic to climate change". Ecological Monographs. 79 (4): 523–555. doi:10.1890/08-2025.1.
- Tarnocai, C., Kimble, J., Broll, G. (2003). "Determining carbon stocks in Cryosols using the Northern and Mid Latitudes Soil Database" (PDF). In Phillips, Marcia; Springman, Sarah M; Arenson, Lukas U. Permafrost : Proceedings of the 8th International Conference on Permafrost, Zurich, Switzerland, 21–25 July 2003 (PDF). London: Momenta. pp. 1129–34. ISBN 90-5809-584-3.
- Bockheim, J.G. & Hinkel, K.M. (2007). "The importance of "Deep" organic carbon in permafrost-affected soils of Arctic Alaska". Soil Science Society of America Journal. 71 (6): 1889–92. Bibcode:2007SSASJ..71.1889B. doi:10.2136/sssaj2007.0070N.
- Tarnocai, C., Canadell, J.G., Schuur, E.A.G., Kuhry, P., Mazhitova, G., and Zimov, S. (2009). "Soil organic carbon pools in the northern circumpolar permafrost region" (PDF). Global Biogeochemical Cycles. 23 (2): GB2023. Bibcode:2009GBioC..23.2023T. doi:10.1029/2008GB003327. Archived from the original (PDF) on 15 October 2015.
- Guo, L., Chien-Lu Ping, and Macdonald, R.W. (July 2007). "Mobilization pathways of organic carbon from permafrost to arctic rivers in a changing climate. ". Geophysical Research Letters. 34 (13): L13603. Bibcode:2007GeoRL..3413603G. doi:10.1029/2007GL030689.
- Nowinski NS, Taneva L, Trumbore SE, Welker JM (January 2010). "Decomposition of old organic matter as a result of deeper active layers in a snow depth manipulation experiment". Oecologia. 163 (3): 785–92. Bibcode:2010Oecol.163..785N. doi:10.1007/s00442-009-1556-x. PMC . PMID 20084398.
- Schuur, E.A.G., Bockheim, J., Canadell, J.G., Euskirchen, E., Field, C.B., Goryachkin, S.V., Hagemann, S., Kuhry, P., Lafleur, P.M., Lee, H., Mazhitova, G., Nelson, F.E., Rinke, A., Romanovsky, V.E., Skiklomanov, N., Tarnocai, C., Venevsky, S., Vogel, J.G., and Zimov, S.A. (2008). "Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle" (PDF). BioScience. 58 (8): 701–714. doi:10.1641/B580807.
- Kane, E.S. & Vogel, J.G. (February 2009). "Patterns of Total Ecosystem Carbon Storage with Changes in Soil Temperature in Boreal Black Spruce Forests" (PDF). Ecosystems. 12 (2): 322–335. doi:10.1007/s10021-008-9225-1.
- Meyers-Smith, I.H., McGuire, A.D., Harden, J.W., Chapin, F.S. (2007). "Influence of disturbance on carbon exchange in a permafrost collapse and adjacent burned forest". Journal of Geophysical Research. 112 (G4): G04017. Bibcode:2007JGRG..11204017M. doi:10.1029/2007JG000423. | <urn:uuid:366df562-3b65-46b1-889b-971c137104bd> | 3.875 | 3,081 | Knowledge Article | Science & Tech. | 50.098718 | 95,633,841 |
This is because oil palm is grown in lowland tropical regions and so impacts on the most biodiverse terrestrial habitats: tropical rainforests. Analysis of the published literature by scientists led by Edgar Turner at the University Museum of Zoology, Cambridge has revealed significant changes in the focus of oil palm research over the last 30 years. The findings are published in PLoS ONE on February 13.
Recent years have seen a broadening in the scope of the research with a slight increase in research focusing on the environment and a dramatic increase in research focusing on biofuel. Despite this, hardly any oil palm publications focused on biodiversity and species conservation. Of these publications, the majority were related to mammals and birds. Although these larger animals are important flagships for the state of the tropical environment, they are not good indicators of oil palm biodiversity. The vast majority of the species worldwide are insects and it is they that carry out the lion’s share of the ecosystem function.
Head of the Insect Ecology Research Group, Dr William Foster said: “Much more research must be carried out to determine the impacts of habitat conversion on insect biodiversity. We need to move on from merely cataloguing biodiversity impacts, to understanding how all aspects of ecosystem services are affected by agricultural expansion.”Useful links for further information:
Andrew Hyde | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
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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Physics 3.20 Uniform Circular Motion
This storyboard does not have a description.
Bob is stuck on his rocket ship in outer space and must have an emergency landing, he needs to physics the newton out of this if he wants to survive.
Bob: "I remember learning in physics 1 about the Uniform Circular Motion, it states that the motion of an object in a circle at a constant speed.
I also know that at each instance, the rocket is tangent to the circle.
"Through the uniform circular motion, I understand the concept of centripetal forces which states that a force that acts on an object moving in a circular path and is directed toward the center around."
"However, in order to get to Earth accurately, I know through centripetal acceleration that the direction of the tangential velocity vector changes as the object rotates as the tangential speed is constant. So I must calculate for this acknowledgment.
"Now I can calibrate the thrusters and safely get out of this gravitational pull... Newton, we have a problem..."
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Authors: Sergio Garcia Chimeno
Demonstration of how to do that the light velocity c be the same independently of the velocity of the observer and obtain the mass-energy equivalence E = mc^2 using the Galilean transformations and the 4 dimensions zoom-universe model characteristics. Demonstration of how to interpret it the time dilation/length contraction typical of the special relativity using the Galilean transformations and the 4 dimensions zoom-universe model characteristics. Demonstration of how to obtain the typical waves equation with transmission velocity c and how to obtain it through the medium for transmission of light given by the zoom-universe model. Demonstration of how to obtain the Einstein Field Equations without using the Stress-Energy Tensor, without using the Bianchi Identities and without using the Energy Conservation to obtain it. Demonstration of how to obtain the Einstein Field Equations only using the Gauss Curvature and the zoom universe model characteristics. Gravity in zoom universe model. Special relativity zoom. General relativity zoom. Sphere and Hypersphere example to understand it better.
Comments: 20 Pages. Two previous "letters" in vixra joined in an article
[v1] 2018-03-15 13:42:56
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The university’s Professor Mark Davies has been studying snails for the past ten years and his latest research has confirmed something he has believed for quite some time.
He and masters student Janine Blackwell have been studying marine snails off the coast of South Tyneside in the belief that they use each other’s mucus trails in order to save vital energy – and they seem to be right.
Snails use a third of their energy creating mucus trails in order to move around, mostly to find food and a partner.
Prof Davies has found that by using existing trails these particular snails, and more than likely all snails, have to create only a fraction of the mucus needed to make a new trail.
One of the obvious benefits is that snails living in environments where food is scarce may be able to survive as they do not need as much energy to create trails.
While biologists have long believed that this could be the case, this is the first time it has been proven.
His findings will appear in the journal Proceedings of the Royal Society Biological Sciences, which comes out tomorrow (Wednesday, February 28).
Prof Davies and Ms Balckwell spent several months researching the snails and measuring the thickness of their trails.
He said: “Snails expend a lot of energy, probably one third, creating mucus. This process is very taxing indeed – much more so than walking, swimming or flying.
“The fact that they can make savings has a knock on effect in as much as they have more energy to do other things like reproduce.
“It took a long time to measure the mucus and it was very difficult, but after several unsuccessful attempts we managed it.
“What we found was that these trails have a convex cross section. Once a second snail went down the trail we expected the trail to be twice as thick but it wasn’t – it was a lot less.
“If it was a fairly new trail the snails didn’t have to lay much mucus, but if it was a weathered trail then they had to lay more.
“How it knows we have no idea but the animal seems to be recreating the profile of the trail as originally laid. However, the energy it saves is quite dramatic.
“They don’t follow trails all the time as they would all be following each other. We don’t know yet how far they are following them.
“While we researched marine snails, the chances are that all species of snails will follow trails because of the energy they will save.
“This is a very good start to finding out more about the lives of snails.”
Tony Kerr | alfa
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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A theoretical and experimental study could lead to improved catalysts for producing hydrogen fuel from waste biomass
Experimental analysis and computer simulations reveal new insights into the process by which ethanol produced from waste biomass can be converted into hydrogen in the presence of a catalyst. These insights should aid the design of more efficient catalysts for hydrogen production.
Hydrogen gas is an environmentally friendly alternative to fossil fuels. Today, through a process known as steam reforming, hydrogen is obtained by using steam to break up a hydrocarbon — most commonly, methane in natural gas. However, ethanol produced by fermenting waste biomass is potentially a cleaner starting material for this process.
However, despite having been extensively studied in recent years, steam reforming of ethanol is currently too inefficient to produce hydrogen on an industrial scale. This stems partly from the complexity of its reaction, which can yield a range of different products. “Our lack of understanding of the detailed reaction mechanism hinders further improvement of a catalyst for the reaction,” explains Jia Zhang of the A*STAR Institute of High Performance Computing in Singapore. “The reaction was a black box before we started exploring it.”
Now, Zhang and her co-workers have used experiments and computer simulations to probe how ethanol breaks down into hydrogen on rhodium catalysts supported on zirconia-based oxides1. These nanosized catalysts had previously been shown to be highly active for this reaction.
The team used gas chromatography and mass spectrometry to monitor in real time the intermediate species that form as the reaction proceeds. These measurements revealed that the C2H4O species is an important intermediate. Of the two possible structures this species can adopt, acetaldehyde (CH3CHO) was identified as the most probable one by the team’s computer calculations. The calculations also showed that water plays an unexpectedly important role in controlling the reaction pathway.
Based on this knowledge, the team proposed a mechanism for the reaction under their chosen conditions. Hydrogen is produced at most stages along the pathway, including the final step in which carbon monoxide reacts with water to produce hydrogen and carbon dioxide. The team’s calculations showed that the success of this final step is critical in determining the amount of hydrogen produced by steam reforming.
“Our theoretical simulations and experimental analysis provide important information on the reaction mechanism,” says Zhang. “This is a fundamental step forward in our understanding of the catalyst, which is the basis of catalyst design.” The team’s ultimate goal is to design catalysts that can produce hydrogen more cheaply and efficiently than current catalysts.
The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing and the Institute of Chemical Engineering and Sciences
Zhang, J., Zhong, Z., Cao, X.-M., Hu, P., Sullivan, M. B. & Chen, L. Ethanol steam reforming on Rh catalysts: Theoretical and experimental understanding. ACS Catalysis 4, 448–456 (2014). | article
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
Colorectal cancer risk factors decrypted
16.07.2018 | Max-Planck-Institut für Stoffwechselforschung
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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