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The University of Central Florida has detected what could be its first planet, only two-thirds the size of Earth and located right around the corner, cosmically speaking, at a mere 33light- years away.
A new NASA mission called the Radiation Belt Storm Probes (RBSP), due to launch in August 2012, will improve our understanding of what makes plasma move in and out of these electrified belts wrapped around our planet.
An 18-member international team of researchers has found exciting new evidence that supports the theory of an extraterrestrial impact that occurred nearly 13 000 years ago. Their evidence lies in material found in a thin layer of sedimentary rock in Pennsylvania and South Carolina in the United States and in Syria.
Astronomers have used the NASA/ESA Hubble Space Telescope to study some of the smallest and faintest galaxies in our cosmic neighbourhood. These galaxies are fossils of the early Universe: they have barely changed for 13 billion years.
To better understand Saturn's moon Titan, scientists must study the methane in its atmosphere, the persistence of which was likely influenced by an ocean of water recently discovered 100 kilometers below the moon's surface.
The effect of spaceflight on a microscopic worm - Caenorhabditis elegans (C. elegans) - could help it to live longer. The discovery was made by an international group of scientists studying the loss of bone and muscle mass experienced by astronauts after extended flights in space. | <urn:uuid:3aff0b68-c344-4634-a7e9-34ccbb3c8d39> | 3.421875 | 292 | Content Listing | Science & Tech. | 34.586778 | 95,625,055 |
SCALAR WAVE TECHNOLOGY
Prof. Dr.-Ing. Konstantin Meyl provides a construction Kit for academic institutions that demonstrates Nicola Tesla’s magnifying transmitter.
This kit enables you to construct an energy transmission line according to Tesla, as it has been demonstrated by us on various fairs and congresses. The engines for an airplane and a ship are enclosed. With a minimum power of 10 watts your imagination is the only limit when choosing the load for the receiver. This device even lights fluorescent tubes at the receiver – StarWars lightsaber like.
Journal of Scientific Exploration,
Herein is described extraordinary science: five experiments, which are incompatible with textbook physics. Following my short lecture I will present you with the transmission of longitudinal electric waves.It is a historical experiment, because 100 years ago, the famous experimental physicist Nikola Tesla measured the same wave properties as I. From him stems a patent concerning the wireless transmission of energy (Tesla, 1900).Since he also had to find out that much more energy arrives at the receiver than is taken up by the transmitter, he spoke of a “magnifying transmitter.”Based on the effect back on the transmitter that Tesla sees, Tesla has found the resonance of the earth and that lies, according to his measurement, at 12Hz. Since the Schumann resonance of a wave, which goes with the speed of light, lies at 7.8 Hz, however, Tesla comes to the conclusion that his wave has1.5 times the speed of light (Tesla, 1905).
Read it all at: https://www.scribd.com/document/36584451/Scalar-waves-theory-and-experiments-Meyl | <urn:uuid:2119075e-9395-4281-b0cd-c9d4c31ed93a> | 3.171875 | 350 | Truncated | Science & Tech. | 47.741063 | 95,625,089 |
In synthetic chemistry, ‘carbene’ species—compounds bearing a carbon atom with two unpaired electrons—have a ferocious reputation. Left uncontrolled, they will react with almost any molecule they meet.
But by harnessing this vigor with transition metals, chemists can turn carbenes into powerful chemical transformation reagents. Now, Zhaomin Hou and colleagues from the RIKEN Advanced Science Institute in Wako report a new class of compounds that contain multiple carbene units in one extraordinary structure: a cube-shaped molecule stabilized by ligand-protected rare-earth metals.
Rare-earth metals hold more electrons within their atomic radii than most other elements, making them essential in high-tech devices such as superconductors and hybrid vehicle batteries. Combining these metals with carbenes could lead to breakthrough procedures in synthetic chemistry. However, rare-earth metal–carbene complexes are usually unstable because the bonds they form are lopsided electronically, and therefore extremely reactive.
To overcome this problem, Hou and colleagues turned to a bulky ligand, based on a five-membered aromatic ring called cyclopentadiene (Cp´), which can trap rare-earth metal–carbene complexes into ordered solids. By mixing Cp´-protected lutetium (Lu) and thulium (Tm) rare-earth metal precursors with a carbon-donating aluminum reagent, they isolated a unique set of hybrid polyhedral crystals. X-ray analysis showed that these materials had a core of three rare-earth metals interconnected by six bridging methyl (CH3) groups.
An unexpected twist occurred when the researchers tested the thermal stability of the Lu– and Tm–methyl complexes. Heating to 90 °C caused the methyl groups to lose one of their hydrogen atoms, transforming them into carbenes. Then, after the elimination of a methane molecule, the crystal structure rearranged into a perfectly shaped cube featuring four Cp´-protected rare-earth metals and four carbene units (Fig. 1).
The team’s experiments revealed that the cubes spontaneously turned benzene–carbonyl molecules into alkenes by swapping their carbene groups for oxygen atoms, yielding a new oxygenated cube in the process. The researchers are now examining the reactivity of the cubes toward other molecules and plan to fine-tune the structure and reactivity of carbene compounds by investigating differently sized rare-earth metals together with different supporting ligands.
“This work demonstrates for the first time that methane can be eliminated rather easily from rare earth complexes containing methyl groups, affording structurally stable but highly reactive multi-carbene species,” says Hou. “Further studies along this line should open up a completely new frontier in rare-earth carbene chemistry.”
The corresponding author for this highlight is based at the Advanced Catalyst Research Team, RIKEN Advanced Science Institute
Zhang, W.-X., Wang, Z., Nishiura, M., Xi, Z. & Hou, Z. Ln4(CH2)4 cubane-type rare-earth methylidene complexes consisting of “(C5Me4SiMe3)LnCH2” units (Ln = Tm, Lu). Journal of the American Chemical Society 133, 5712–5715 (2011).
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
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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A View from Emerging Technology from the arXiv
The Search For Extraterrestrial Civilizations' Waste Energy
If they’re out there, other advanced civilisations should be emitting waste energy like hot exhaust. And that provides a good way to spot them, argue SETI experts.
Back in 1974, the American astronomer Michael Hart published a paper in the Quarterly Journal of the Royal Astronomical Society entitled “An Explanation For The Absence Of Extraterrestrials On Earth”. In it, he pointed out that there are no intelligent beings from outer space on Earth now, a statement that he famously referred to as Fact A.
“Fact A, like all facts, requires an explanation,” wrote Hart. He went on to conclude that Fact A is explained by the notion that intelligent life from outer space does not exist. In other words, we are alone in the galaxy.
Hart’s paper addresses the Fermi paradox named after the physicist in Enrico Fermi who famously asked: if intelligent aliens exist, where are they? Indeed, Hart’s arguments have become so famous that the problem is often called the Fermi-Hart paradox.
Today, Jason Wright at Pennsylvania State University and a few pals revisit Hart’s argument, it’s various rebuttals and many others associated with the Fermi paradox. In particular, they focus on the possibility that extraterrestrial civilisations would give themselves away by the waste heat generated by their activities. Therefore a useful way to search for extraterrestrial civilisations is to look for the infrared signature of this waste.
The basic problem with the idea that intelligent life exists elsewhere in the galaxy is that the Sun is an ordinary star and that there are many billions of others like it in the Milky Way. Many of these will have Earth-like planets orbiting them so there must have been ample opportunity for intelligent life to evolve elsewhere.
What’s more, if any of these civilisations had begun to explore the interstellar space around them, even at the very slow speeds that humans can manage, it would take only a few tens of millions of years to colonise entire galaxy.
So the fact that we do not see intelligent life out there must mean it does not exist. In other words, we are the first and we are alone.
Wright and co extend Hart’s argument to alien energy supplies. The basic idea here is any advanced civilisation would require vast amounts of energy and the most likely source of this energy is the star that it orbits. However this energy is used, it must inevitably end up as waste heat which ought to be visible in the infrared.
“We argue that detectably large energy supplies can plausibly be expected to exist because life has potential for exponential growth until checked by resource or other limitations, and intelligence implies the ability to overcome such limitations,” say Wright and co.
And they come to an odd conclusion. Wright and co say that if Hart’s thesis is correct, that we are alone in the galaxy, then searches for large alien civilisations in other galaxies may be fruitful. And if it is incorrect, then searches the civilisations within the Milky Way are more likely to succeed than Hart argued.
In other words, it is well worth continuing to look for extra-terrestrial civilisations. A curious argument but built on the back of a comprehensive review of the search for extra terrestrial civilisations and their energy supplies.
Well worth a read if you want a good review of the science in this area.
Ref: arxiv.org/abs/1408.1133 : The G Infrared Search For Extraterrestrial Civilizations With ˆ Large Energy Supplies. I. Background And Justification
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In this chapter we shall study nuclear sizes and shapes. In principle, this information may be obtained from scattering experiments (e. g., scattering of protons or α particles) and when Rutherford discovered that nuclei have a radial extent of less than 10−14 m, he employed a scattering. In practice, however, there are difficulties in extracting detailed information from such experiments. Firstly, these projectiles are themselves extended objects. Therefore, the cross-section reflects not only the structure of the target, but also that of the projectile. Secondly, the nuclear forces between the projectile and the target are complex and not well understood.
KeywordsForm Factor Charge Distribution Elastic Scattering Geometric Shape Scattered Electron
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London, March 20 (teleSUR-RHC) The Amazon rainforest, the “lungs of the world,” is losing its capacity to absorb carbon dioxide, warned a study published Wednesday in the journal Nature.
Trees of the Amazon have been increasingly dying younger over the past two decades, the international team of scientists found – thereby reducing the size of the forest and its absorption capacities.
At the same time, they observed that the trees were growing faster, leading to the conclusion that this pattern could be related to climate change and to higher levels of carbon dioxide in the atmosphere.
Through the process of photosynthesis, trees obtain energy from the sunlight, water, and carbon dioxide that they store in their branches, conveniently holding the excesses of gas produced by industry and other sources.
The Amazon rainforest absorbs one-quarter of the 2.4 billion metric tons of carbon absorbed by forests each year in the world. Roel Brienen, co-author of the report, explained why trees in the rainforest are growing faster and dying younger. “That's because faster growing trees tend to invest less energy in defenses against disease and produce wood that is less dense. So they may be more susceptible to sickness or falling over.
But how rising temperatures, drought, and the makeup of species in the jungle may each be affecting the forest health is still unclear,” said Brienen, a forest ecologist at University of Leeds in the United Kingdom.
The results were based on the study of 321 plots distributed throughout the Amazon that measured 200,000 trees since the 1983. The world's policymakers should pay attention to the Amazon's diminishing role as a global carbon sink, said Professor Oliver Phillips, a colleague of Brienen’s at Leeds and co-author of the study.
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An international team of researchers from the Moscow Institute of Physics and Technology, Forschungszentrum Jülich, the European Synchrotron Radiation Facility, the Institut de Biologie Structurale, and the Max Planck Institute of Biophysics has determined the 3-D structure of channelrhodopsin 2, a membrane protein widely used in optogenetics to control nerve cells with light.
Optogenetics is a relatively new technique that involves the use of light to manipulate nerve and muscle cells in a living organism. Similar approaches are used to partially reverse the loss of hearing and eyesight and control muscle contractions.
Attempts to solve the structure of ChR2 go right back to the time of its discovery in 2003. But despite the efforts of numerous research groups from across the world, the structure of the protein in its natural state has remained unknown. Now that researchers have the structure, meaningful mutations can be introduced into the protein to adjust its properties to the requirements of a specific experiment.
Credit: MIPT Press Office
In addition, the methods of optogenetics are used to study the properties of natural neuron networks, which are responsible for emotion, decision-making, and other complex processes in living organisms. Optogenetics was Nature's "Method of the Year 2010," as well as being named among Science's "Breakthroughs of 2010 and Insights of the Decade."
Channelrhodopsin 2, or ChR2, is a major optogenetic tool. It is a light-sensitive protein, which was originally extracted in 2003 from a green alga called Chlamydomonas reinhardtii. Scientists can insert ChR2 into the membrane of a living cell to control it. When illuminated, this protein allows positively charged ions to pass into the cell through the cell membrane. In a nerve cell, this depolarizes the membrane, mimicking the effect of a nerve impulse and causing this particular neuron to fire.
Because ChR2 works fast and is relatively harmless to cells, it is the current go-to solution for nerve cell activation. A range of artificially induced mutations are available for altering the protein's properties. For example, it is possible to increase the current it generates or alter the wavelength of light it responds to. Such modifications enable experimenters to work with proteins tailored to their needs. Researchers can even combine several protein variants for a distinct response at various wavelengths of light.
Most of the mutations used to modify the properties of ChR2 have so far been introduced more or less at random -- either via directed evolution or based on the data on known protein structures. The closest we've ever gotten to a realistic ChR2 structure is an odd combination called C1C2, 70 percent of which is based ChR1, a related protein, with the rest based on the actual ChR2. This mixed structure cannot account for all properties of the protein. As a result, the mutations predicted by this model are not quite realistic and therefore are of limited interest to optogenetics.
To reveal the structure of ChR2, the authors of the study reported in this story used an analytical technique called X-ray diffraction, which only works with samples in the form of a crystal. These were obtained by the researchers via in meso crystallization. That is to say, the protein crystals were grown in the so-called cubic lipid mesophase -- a medium that allows proteins to move freely, without leaving the membrane. To determine protein structures, their crystals were irradiated with X-rays at a wavelength of about 1 angstrom, which is slightly less than the length of the bonds between the atoms in the protein. In X-ray crystallography, structures are derived by analyzing how radiation is scattered by a sample.
"Attempts to solve the structure of ChR2 go right back to the time of its discovery in 2003. But despite the efforts of numerous research groups from across the world, the structure of the protein in its natural state has remained unknown," says Valentin Borshchevskiy, one of the authors of the paper and deputy head of the Laboratory for Advanced Studies of Membrane Proteins at MIPT. "Now that we have the structure, meaningful mutations can be introduced into the protein to adjust its properties to the requirements of a specific experiment. Not knowing the structure, we had to tediously work out the useful mutations by trial and error or make do with the data on related proteins."
The work reported here was supported by the common program of the Agence Nationale de la Recherche (France), the Deutsche Forschungsgemeinschaft (Germany) (ANR-15-CE11-0029-02), the CEA(IBS)-HGF(FZJ) STC 5.1 specific agreement, the Russian Science Foundation (16-15-00242), and ERA.Net RUS Plus (ID 323).
Ilyana Zolotareva | EurekAlert!
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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12.07.2018 | Event News
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RAP has published findings from its survey of the Kaijende Highlands, Enga Province in Papua New Guinea. This expedition documented over 600 species in an area of stunning beauty. Sixteen plant species and 8 frog species were new to science.
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Stephen J. Richards is a research scientist who works for the South Australian Museum and Conservation International studying the rich biodiversity of Melanesia. He has conducted more than thirty biological surveys across the Pacific Islands and published numerous scientific papers and popular articles about the region's spectacular and largely unknown fauna.
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667. How can you make electricity with magnets? - AL
You can make electricity by moving a magnet past a wire. The magnet has a magnetic field around it—something that exerts forces on magnetic poles. If you move the magnet and its magnetic field, you create an electric field—something that exerts forces on electric charges. That's because whenever a magnetic field changes with time, it creates an electric field. This electric field will push on the mobile electrons in a wire. So when you move a magnet past a wire, you are producing a changing magnetic field in the wire. This changing magnetic field produces an electric field and the electric field makes the electrons in the wire accelerate. The moving electrons are electricity. Generators move magnets past wires (or wires past magnets) to produce electricity. | <urn:uuid:21c866b7-e4e4-415c-993f-bb4f3573b373> | 3.9375 | 161 | Q&A Forum | Science & Tech. | 45.744842 | 95,625,152 |
New questions about geology, oceanography and seafloor ecosystems are being raised because of research by a Mississippi State University geologist.
Lead author Adam Skarke, assistant professor of geosciences at MSU, worked with researchers from the U.S. Geological Survey (USGS) and other institutions on a scientific team that discovered methane seeps in unlikely places along the seafloor on the northern part of the U.S. Atlantic margin.
The group’s scientific paper, “Widespread methane leakage from the sea floor on the northern U.S. Atlantic margin,” was published online Sunday [Aug. 24] by the peer-reviewed journal Nature Geoscience.
Before he joined the faculty at MSU, Skarke worked as a physical scientist at the National Oceanic and Atmospheric Administration’s (NOAA) Office of Ocean Exploration and Research (OER). As part of a large team of scientists and technicians, Skarke participated in many cruises on the NOAA ship Okeanos Explorer as it mapped the Atlantic Ocean floor between North Carolina and Cape Cod. The discovery of gas plumes in the water column over the seafloor, detailed in the new publication, used data the ship collected starting in 2011, Skarke said.
He and his colleagues found 570 methane seeps in this area, compared to only three formerly known sites.
To analyze the NOAA OER data and locate the positions of the plumes, which correspond to places where methane gas is seeping out of the seafloor, Skarke worked closely with Brown University undergraduate and NOAA Hollings Scholar Mali’o Kodis during the summer of 2013.
Methane often naturally leaks from the seafloor, particularly in petroleum basins like the Gulf of Mexico or on tectonically active continental margins like the U.S. Pacific Coast, Skarke said. However, the geologic characteristics of the U.S. Atlantic margin suggest the seepage was not necessarily expected there because the tectonically passive area lacks an underlying petroleum basin.
The team thinks that many of the newly-discovered seeps may be related to the breakdown of a special kind of “methane ice” or gas hydrate, a frozen combination of methane and water stable in sediments below 500 or more meters, or 1,640 feet, of ocean water, Skarke said. With small changes in ocean temperature, gas hydrate can release its methane into the sediments, and the gas may escape at the seafloor to form plumes in the water column.
“Globally, the upper ocean has been warming for decades,” Skarke said. “Some of the seeps we found are similar to those on Arctic Ocean margins, where warming has been more rapid. But we also know that some subsets of the seeps have probably been active for over 1,000 years. A key question is how the long-term seepage and short-term warming of the ocean are related to methane escape.”
Skarke said the research “does not provide sufficient evidence to draw objective conclusions about the relationship between these methane seeps and global climate change.”
“This significant discovery instead introduces a number of related questions that require further exploration and investigation to address,” he added.
Although methane, or natural gas, is used as an energy source worldwide, the type of methane leaking at most of the seep sites is probably produced by micro-organisms digesting organic matter in the shallow sediments, he said. At this time, no evidence suggests the seeps tap into deep natural gas reservoirs that can be used for energy. Once samples of the methane are obtained, simple measurements made by geochemists can determine if shallow or deep gas sources feed the seeps.
Methane is a strong greenhouse gas, but nearly all of the seeps described in the new study leak at such deep ocean depths that methane does not reach the atmosphere directly, he emphasized. Instead, micro-organisms in the water column transform most of the methane into carbon dioxide, making ocean waters more acidic, which can harm some types of marine life.
The methane seeps provide new natural laboratories for ecologists who study life on the deep ocean floor, Skarke said. Animals there use the energy created by chemical reactions to survive—chemosynthetic life-forms. For example, their metabolisms may depend on methane or hydrogen sulfide, a common seep gas toxic to many life forms.
“These newly-discovered seeps have expanded the number of locations that deep sea ecologists can study,” Skarke said. “The NOAA OER program used its remotely operated vehicle to visit about 1 percent of the seeps in 2013, and it found well-developed communities of chemosynthetic mussels thriving near the methane plumes. Two years ago, no human had ever seen these seafloor communities that have now been found at the seep sites.”
He said additional research questions for deep sea ecologists include determining how separate seeps are colonized with new life, as well as understanding the structure of the communities and the relationships among bacteria, small fauna, and larger organisms, like mussels.
“A cornerstone of the NOAA OER program is the collection of data that can lead to new discoveries for the scientific community,” he said. “One unique aspect of the program that made it so enjoyable to work there was the fact that we collected many types of data about U.S. oceans and made the data immediately available to the scientific community for studies that could not otherwise have been completed.”
Skarke said he appreciates the support of MSU administrators, especially those in the Department of Geosciences, as he and his collaborators readied the research for publication in a top-tier, peer-reviewed journal. In addition to Skarke and Kodis, authors of the paper include Carolyn Ruppel of the USGS Gas Hydrates Project, Daniel Brothers of USGS and Elizabeth Lobecker of Earth Resources Technology.
Visit dx.doi.org/10.1038/ngeo2232 to view the complete abstract of “Widespread methane leakage from the sea floor on the northern U.S. Atlantic margin,” or go to http://www.usgs.gov/newsroom/article.asp?ID=3979&from=rss_home#.U_tMVGP_mzd to read USGS’ press release about the research.
Allison Matthews | newswise
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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"We can monitor the process directly, and that gives us a different perspective," said Roberto Galletto, a postdoctoral scholar at UC Davis and first author on a paper published Sept. 20 on the Web site of the journal Nature.
In E. coli bacteria, molecules of an enzyme called RecA attach themselves along a DNA strand, stretching it out and forming a filament. A piece of complementary DNA lines up along side it, and pieces of DNA can be swapped in to repair gaps in the original strand. A similar protein, called Rad51, does the same job in humans.
"How RecA and Rad51 assemble into filaments determines the outcome of DNA repair, but very little is known about how assembly is controlled," said senior author Stephen Kowalczykowski, professor in the sections of Microbiology and of Molecular and Cellular Biology and director of the Center for Genetics and Development at UC Davis. Genes that control the human gene, Rad51, have been linked to increased risk of breast cancer.
Galletto attached a short piece of DNA to a tiny latex bead and placed it in a flow chamber, held by laser beam "tweezers." Fluid flowing past made the DNA stream out like a banner. Then he nudged it into an adjacent channel containing fluorescently-tagged RecA. After short intervals of time, he moved it back to the first chamber to observe the results.
By repeatedly dipping the same piece of DNA into the fluorescent channel, the researchers could see the RecA form clusters of four to five molecules on the DNA. Once those clusters had formed, the DNA/RecA filament rapidly grew in both directions. The measurements made in those experiments will be the baseline for future studies of both RecA and Rad51, Kowalczykowski said.
The new work adapts an approach developed by Kowalczykowski and Ronald J. Baskin, professor of molecular and cellular biology, to study single enzymes at work unwinding DNA strands. That research was first published in Nature in 2001.
In addition to Galletto, Kowalczykowski and Baskin, the research team included postdoctoral scholar Ichiro Amitani. The work was funded by the National Institutes of Health and a fellowship awarded to Galletto by the Jeane B. Kempner Foundation.
Andy Fell | EurekAlert!
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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The NDACC Working Group on Water Vapor announces the publication: ISSI Scientific Report 10: Monitoring Atmospheric Water Vapour edited by Niklaus Kampfer. The aim of the book is to assess in detail in situ and remote sensing techniques presently used to monitor on a regular basis the distribution of atmospheric water vapor.
NDACC News and Events
October 23, 2012 marks the official opening of the the Southern Tropical high altitude NDACC Maido Observatory in Reunion Island. After more than 15 years effort from CNRS-INSU, the Region and the University of Reunion Island, the construction of the Observatoire de Physique de l'Atmosphere (OPAR) was completed in July 2012. The lidars and FTIR instruments are being installed for the long term monitoring of the composition of the atmosphere.
In 1996, in an attempt to resolve an inconsistency between ozone profile trends obtained from satellite vs. ground-based measurements, the Stratospheric Processes and their Role in Climate (SPARC) project of the World Climate Research Programme (WCRP) initiated a collaboration with the International Ozone Commission (IO3C) to carefully re-evaluate the ground-based and satellite ozone data. This study, headed by the SPARC Panel on Understanding Ozone Trends, did not simply review the published literature but conducted a critical re-analysis and interpretation of ozone vertical profiles.
The Demonstration Network Of ground-based Remote Sensing observations (NORS) is a new EU Framework 7 R&D project in support of the GMES Atmospheric Service (GAS) that began on November 1, 2011 and will run for 33 months. | <urn:uuid:902798d6-d7bb-4df9-aa4e-3341d8305526> | 2.515625 | 334 | News (Org.) | Science & Tech. | 22.978421 | 95,625,225 |
The research also showed that arrestin interacts with several other proteins within cells to regulate longevity. The human version of one of these proteins is PTEN, a well-known tumor suppressor. The study, to be published in the online edition of the Journal of Biological Chemistry, was chosen by the journal as the "Paper of the Week" – considered in the top one percent of published articles.
Because most proteins in worms have human counterparts, these findings may have relevance to human biology and the understanding of cancer development, said Jeffrey L. Benovic, Ph.D., professor and chair of the department.
"The links we have found in worms suggest the same kind of interactions occur in mammals although human biology is certainly more complicated. We have much work to do to sort out these pathways, but that is our goal," said Dr. Benovic.
Researchers use the roundworm as a model because it offers a simple system to study the function of genes and proteins that are relevant to human biology. The worm, for example, has one arrestin gene, whereas humans have four. Worms only have 302 neurons compared to the 100 billion or so in the human brain. In addition, their short lifespan of two to three weeks allows for timely observation of effects on longevity.
Dr. Benovic and the study's first author, Aimee Palmitessa, Ph.D., a postdoctoral research fellow, studied signaling pathways activated by G protein-coupled receptors. These receptors bind to all kinds of hormones, sensory stimuli (such as light, odorants and tastants), neurotransmitters, etc., which then activate a cascade of signals inside the cell. They regulate many physiological processes and are the target for about half of the drugs currently on the market.
"When it comes to receptors, worms are actually more complex," said Dr. Benovic. "Humans have about 800 different kinds of G protein-coupled receptors while the worm has about 1,800. It relies upon these receptors to respond to sensory stimuli as well as various neurotransmitters and hormones."
Arrestins were initially found to turn off the activation of G protein-coupled receptors inside cells. "Their name comes from the fact that they arrest the activity of receptors, so the worm offers a good way to study how its single arrestin protein interacts with protein receptors," says Dr. Benovic. Two of the four arrestins that humans have are devoted to regulating receptors that respond to visual stimuli while the other two regulate most other receptors.
In this study, Dr. Palmitessa deleted the single arrestin gene in worms to see what would happen, and found, to her surprise, that these worms lived significantly longer. She also found that over-expressing arrestin in worms shortened their lifespan. "A little less arrestin is good – at least for worms," Dr. Benovic reported.
This isn't the first discovery made regarding longevity in worms. Researchers have already found that activity of the insulin-like growth factor-1 (IGF-1) receptor can influence longevity in worms – a finding that has also been replicated in fruit flies, mice, and humans. Like arrestin, a little less IGF-1 receptor activity is good, Dr. Benovic explained. Further research has shown that caloric restriction can also reduce IGF-1 receptor activation and, conversely, over-expression of the IGF-1 receptor is found in some human cancers.
In this study, Dr. Benovic and Dr. Palmitessa dug a little deeper and found that in the worms, arrestin interacted with two other proteins that play a critical role in its ability to regulate longevity. One of those proteins is the tumor suppressor PTEN; mutations in PTEN are involved in a number of different cancers.
Dr. Benovic said the connection between human arrestin and PTEN is not clear. "We don't know at this point if human arrestins regulate PTEN function or if anything happens to arrestin levels during the development of cancer," he said. "Do increasing levels turn off more PTEN, thus promoting cancer, or do levels decrease and allow PTEN to be more active?
"If it turns out to be the first scenario – that increasing amounts of arrestin turn off the tumor suppressor activity of PTEN, then it may be possible to selectively inhibit that process," he says. "We have some interesting work ahead."
The study was funded in part by the National Institutes of Health. The authors declare no conflict of interest.
Emily Shafer | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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20.07.2018 | Materials Sciences
20.07.2018 | Physics and Astronomy
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Protection of fish spawning habitat for the conservation of warm-temperate reef-fish fisheries of shelf-edge reefs of Florida
We mapped and briefly describe the surficial geology of selected examples of shelf-edge reefs (50–120 m deep) of the southeastern United States, which are apparently derived from ancient Pleistocene shorelines and are intermittently distributed throughout the region. These reefs are ecologically significant because they support a diverse array of fish and invertebrate species, and they are the only aggregation spawning sites of gag (Mycteroperca microlepis), scamp (M. phenax), and other economically important reef fish. Our studies on the east Florida shelf in the Experimental Oculina Research Reserve show that extensive damage to the habitat-structuring coral Oculina varicosa has occurred in the past, apparently from trawling and dredging activities of the 1970s and later. On damaged or destroyed Oculina habitat, reef-fish abundance and diversity are low, whereas on intact habitat, reef-fish diversity is relatively high compared to historical diversity on the same site. The abundance and biomass of the economically important reef fish was much higher in the past than it is now, and spawning aggregations of gag and scamp have been lost or greatly reduced in size. On the west Florida shelf, fishers have concentrated on shelf-edge habitats for over 100 yrs, but fishing intensity increased dramatically in the 1980s. Those reefs are characterized by low abundance of economically important species. The degree and extent of habitat damage there is unknown. We recommend marine fishery reserves to protect habitat and for use in experimentally examining the potential production of unfished communities.
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Document Type: Research Article
Publication date: 01 May 2000
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ISRO’s RLV-TD: India’s first indigenous reusable space shuttle RLV-TD was successfully launched from Sriharikota in Andhra Pradesh at 7 am today. The purpose of the experiment is not to see it float but to glide and navigate from a velocity five times higher than the speed of sound onto a designated virtual runway in the Bay of Bengal some 500 km from the coast.
“Mission accomplished successfully,” an Indian Space Research Organisation (ISRO) spokesman said soon after RLV-TD HEX-01 was flight tested. This is the first time ISRO has launched a winged flight vehicle, which glided back onto a virtual runway in the Bay of Bengal, some 500 kilometres from the coast. Known as hypersonic flight experiment, it was about 10 minutes mission from liftoff to splashdown. Here are 10 things to know about the reusable space shuttle:
1. RLV-TD is a scale model almost six times smaller than the final version. The 6.5-m-long ‘aeroplane’-like structure weighs 1.75 tonnes and will be hoisted into the atmosphere on a special rocket booster.
2. RLV-TD is described as “a very preliminary step” in the development of a reusable rocket.
3. RLV-TD is a series of technology demonstration missions that have been considered as a first step towards realising a Two Stage To Orbit (TSTO) fully reusable vehicle.
4. RLV-TD is a 6.5 meter-long vehicle, having a mass of 1.75 tonne and is expected to go up to around 70 km after which it is expected to descend at a particular point on the sea.
5. RLV-TD has a flush air-data system, slow burning propellant and composite movable fin.
6. The RLV-TD is a scaled-down model of the reusable launch vehicle.
7. RLV-TD, being dubbed as India’s own space shuttle, is the unanimous solution to achieve low cost, reliable and on-demand space access, according to ISRO scientists.
8. RLV-TD is a series of technology demonstration missions that have been considered as a first step towards realising a Two Stage To Orbit (TSTO) fully re-usable vehicle as said by ISRO.
9. RLV-TD has been configured to act as a flying testbed to evaluate various technologies, including hypersonic flight, autonomous landing, powered cruise flight and hypersonic flight using air-breathing propulsion.
10. RLV-TD’s final version is expected to take in 10 to 15 years. | <urn:uuid:b1e93282-7652-4a86-bbe8-77f82604def5> | 3.078125 | 563 | Listicle | Science & Tech. | 66.614282 | 95,625,258 |
Beam me up Scotty! Imagine being teleported from one place to another via Star Trek's transporter.
Well, physicists are one step closer to turning this piece of fiction into fact, with the annoying caveat being that we will be teleporting information and not humans.
Researchers have for the first time teleported photons (packets of light) over 63 miles of fibre optic cable.
What this essentially means is one day, scientists could create a "Quantum Internet" that would not only be more secure but could completely rid the need for conventional cables and wires.
According to Live Science, the ground breaking experiment took place at the National Institute of Standards and Technology (NIST).
"What's exciting is that we were able to carry out quantum teleportation over such a long distance," study co-author Martin Stevens, told Live Science.
Underlying this incredible feat is quantum physics, which says that subatomic particles can exist in two places at the same time.
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Quantum teleportation in theory allows us to instantly beam things, in this case light particles, from one place to another.
"Only about 1 percent of photons make it all the way through 100 kilometers (60 miles) of fiber," said Stevens.
He added: "A quantum Internet could allow you to establish communications channels that are much more secure than what we have with the standard encryption protocols we use everyday nowadays..." | <urn:uuid:473e8da0-0084-496e-8df7-ae3c25b7c480> | 2.984375 | 370 | Truncated | Science & Tech. | 36.956259 | 95,625,275 |
Statistics Definitions > Relative Precision
What is Relative Precision?
“Relative Precision”(RP) is one of those catch all terms that can mean slightly different things depending on where you’re using it. For example, the coefficient of variation is a type of RP used to compare results from two tests or surveys, while in more general terms, RP is a way to show uncertainty as a fraction of a quantity. It is the ratio of a measurement’s precision and the measurement itself. Let’s say that t is a measurement and st is the standard deviation of the measurement. The relative precision formula is: st/t. It usually given as a ratio (e.g. 5/8), or as a percentage.
Relative precision can also be used to show a confidence interval for a measurement. For example, if the RP is 10% and your measurement is 220 degrees, then the confidence interval is 220 degrees ±22 degrees. Confidence levels for precision are usually reported with a confidence level. In general, there is a tradeoff between confidence levels and precision. The higher the confidence level, the wider the confidence interval, and the lower the precision.
Relative Precision in Sampling
Relative precision in sampling refers to the ratio of the error variances of two different sample designs which have the same sampling unit and sample size. When used in this way, RP is also called relative efficiency. If you use simple random sampling to find the mean of a large population, relative precision and relative efficiency are equal. In other cases, they may not be equal.
Coefficient of Variation
The coefficient of variation is one of the more common measurements of RP, and is the ratio of the standard deviation over the mean of the measurements. For example, the expression “The standard deviation is 15% of the mean” is a coefficient of variation.
A Dictionary of Statistical Terms, 5th edition, prepared for the International Statistical Institute by F.H.C. Marriott. Published for the International Statistical Institute by Longman Scientific and Technical.
If you prefer an online interactive environment to learn R and statistics, this free R Tutorial by Datacamp is a great way to get started. If you're are somewhat comfortable with R and are interested in going deeper into Statistics, try this Statistics with R track.Comments? Need to post a correction? Please post on our Facebook page. | <urn:uuid:068d3bab-0687-421c-ad8b-7688ba47c43f> | 4.46875 | 494 | Knowledge Article | Science & Tech. | 46.063303 | 95,625,282 |
The ecliptic is the apparent path of the Sun on the celestial sphere, and is the basis for the ecliptic coordinate system. It also refers to the plane of this path, which is coplanar with the orbit of the Earth around the Sun (and hence the apparent orbit of the Sun around the Earth.) The path of the Sun is not normally noticeable from the Earth's surface because the Earth rotates, carrying the observer through the cycles of sunrise and sunset, obscuring the apparent motion of the Sun with respect to the stars.
Sun's apparent motion
The motions as described above are simplifications. Due to the movement of the Earth around the Earth-Moon center of mass, the apparent path of the Sun wobbles slightly, with a period of about one month. Due to further perturbations by the other planets of the Solar System, the Earth-Moon barycenter wobbles slightly around a mean position in a complex fashion. The ecliptic is actually the apparent path of the Sun throughout the course of a year.
Because the Earth takes one year to make a complete revolution around the Sun, the apparent position of the Sun also takes the same length of time to make a complete circuit of the ecliptic. With slightly more than 365 days in one year, the Sun moves a little less than 1° eastward every day. This small difference in the Sun's position against the stars causes any particular spot on the Earth's surface to catch up with (and stand directly north or south of) the Sun about 4 minutes later each day than it would if the Earth did not orbit; our day is 24 hours long rather than the approximately 23-hour 56-minute sidereal day. Again, this is a simplification, based on a hypothetical Earth that orbits at uniform speed around the Sun. The actual speed with which the Earth orbits the Sun varies slightly during the year, so the speed with which the Sun seems to move along the ecliptic also varies. For example, the Sun is north of the celestial equator for about 185 days of each year, and south of it for about 180 days. The variation of orbital speed accounts for part of the equation of time.
Relationship to the celestial equator
Because the rotational axis of the Earth is not perpendicular to its orbital plane, the Earth's equatorial plane is not coplanar with the ecliptic plane, but is inclined to it by an angle of about 23.4°, which is known as the obliquity of the ecliptic. If the equator is projected outward to the celestial sphere, forming the celestial equator, it crosses the ecliptic at two points known as the equinoxes. The Sun, in its apparent motion along the ecliptic, crosses the celestial equator at these points, one from south to north, the other from north to south. The crossing from south to north is known as the vernal equinox, also known as the first point of Aries and the ascending node of the ecliptic on the celestial equator. The crossing from north to south is the autumnal equinox or descending node.
The orientation of the Earth's axis and equator are not fixed in space, but rotate about the poles of the ecliptic with a period of about 26,000 years, a process known as lunisolar precession, as it is due mostly to the gravitational effect of the Moon and Sun on the Earth's equatorial bulge. Likewise, the ecliptic itself is not fixed. The gravitational perturbations of the other bodies of the Solar System cause a much smaller motion of the plane of the Earth's orbit, and hence of the ecliptic, known as planetary precession. The combined action of these two motions is called general precession, and changes the position of the equinoxes by about 50 arc seconds (about 0°.014) per year.
Once again, this is a simplification. Periodic motions of the Moon and apparent periodic motions of the Sun (actually of the Earth in its orbit) cause short-term small-amplitude periodic oscillations of the Earth's axis, and hence the celestial equator, known as nutation. This adds a periodic component to the position of the equinoxes; the positions of the celestial equator and (vernal) equinox with fully updated precession and nutation are called the true equator and equinox; the positions without nutation are the mean equator and equinox.
Obliquity of the ecliptic
Obliquity of the ecliptic is the term used by astronomers for the inclination of Earth's equator with respect to the ecliptic, or of Earth's rotation axis to a perpendicular to the ecliptic. It is about 23.4° and is currently decreasing 0.013 degrees (47 arcseconds) per hundred years due to planetary perturbations.
The angular value of the obliquity is found by observation of the motions of the Earth and planets over many years. Astronomers produce new fundamental ephemerides as the accuracy of observation improves and as the understanding of the dynamics increases, and from these ephemerides various astronomical values, including the obliquity, are derived.
Until 1983 the obliquity for any date was calculated from work of Newcomb, who analyzed positions of the planets until about 1895:
ε = 23° 27′ 08″.26 − 46″.845 T − 0″.0059 T2 + 0″.00181 T3
From 1984, the Jet Propulsion Laboratory's DE series of computer-generated ephemerides took over as the fundamental ephemeris of the Astronomical Almanac. Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated:
ε = 23° 26′ 21″.45 − 46″.815 T − 0″.0006 T2 + 0″.00181 T3
JPL's fundamental ephemerides have been continually updated. The Astronomical Almanac for 2010 specifies:
ε = 23° 26′ 21″.406 − 46″.836769 T − 0″.0001831 T2 + 0″.00200340 T3 − 0″.576×10−6 T4 − 4″.34×10−8 T5
These expressions for the obliquity are intended for high precision over a relatively short time span, perhaps ± several centuries. J. Laskar computed an expression to order T10 good to 0″.04/1000 years over 10,000 years.
Plane of the Solar System
|Top and side views of the plane of the ecliptic, showing planets Mercury, Venus, Earth, and Mars. Most of the planets orbit the Sun very near the same plane in which the Earth orbits, the ecliptic.||Four planets lined up along the ecliptic in July 2010, illustrating how the planets orbit the Sun in nearly the same plane. Photo taken at sunset, looking west over Surakarta, Java, Indonesia.|
Most of the major bodies of the Solar System orbit the Sun in nearly the same plane. This is likely due to the way in which the Solar System formed from a protoplanetary disk. Probably the closest current representation of the disk is known as the invariable plane of the Solar System. The Earth's orbit, and hence, the ecliptic, is inclined a little more than 1° to the invariable plane, and the other major planets are also within about 6° of it. Because of this, most Solar System bodies appear very close to the ecliptic in the sky. The ecliptic is well defined by the motion of the Sun. The invariable plane is defined by the angular momentum of the entire Solar System, essentially the summation of all of the revolutions and rotations of all the bodies of the system, a somewhat uncertain value which requires precise knowledge of every object in the system. For these reasons, the ecliptic is used as the reference plane of the Solar System out of convenience.
Celestial reference plane
The ecliptic forms one of the two fundamental planes used as reference for positions on the celestial sphere, the other being the celestial equator. Perpendicular to the ecliptic are the ecliptic poles, the north ecliptic pole being the pole north of the equator. Of the two fundamental planes, the ecliptic is closer to unmoving against the background stars, its motion due to planetary precession being roughly 1/100 that of the celestial equator.
Spherical coordinates, known as ecliptic longitude and latitude or celestial longitude and latitude, are used to specify positions of bodies on the celestial sphere with respect to the ecliptic. Longitude is measured positively eastward 0° to 360° along the ecliptic from the vernal equinox, the same direction in which the Sun appears to move. Latitude is measured perpendicular to the ecliptic, to +90° northward or -90° southward to the poles of the ecliptic, the ecliptic itself being 0° latitude. For a complete spherical position, a distance parameter is also necessary. Different distance units are used for different objects. Within the Solar System, astronomical units are used, and for objects near the Earth, Earth radii or kilometers are used. A corresponding right-handed rectangular coordinate system is also used occasionally; the x-axis is directed toward the vernal equinox, the y-axis 90° to the east, and the z-axis toward the north ecliptic pole; the astronomical unit is the unit of measure. Symbols for ecliptic coordinates are somewhat standardized; see the table.
|heliocentric||l||b||r||x, y, z[note 1]|
Ecliptic coordinates are convenient for specifying positions of Solar System objects, as most of the planets' orbits have small inclinations to the ecliptic, and therefore always appear relatively close to it on the sky. Because the Earth's orbit, and hence the ecliptic, moves very little, it is a relatively fixed reference with respect to the stars.
Because of the precessional motion of the equinox, the ecliptic coordinates of objects on the celestial sphere are continuously changing. Specifying a position in ecliptic coordinates requires specifying a particular equinox, that is, the equinox of a particular date, known as an epoch; the coordinates are referred to the direction of the equinox at that date. For instance, the Astronomical Almanac lists the heliocentric position of Mars at 0h Terrestrial Time, 4 Jan 2010 as: longitude 118° 09' 15".8, latitude +1° 43' 16".7, true heliocentric distance 1.6302454 AU, mean equinox and ecliptic of date. This specifies the mean equinox of 4 Jan 2010 0h TT as above, without the addition of nutation.
Because the orbit of the Moon is inclined only about 5° to the ecliptic and the Sun is always very near the ecliptic, eclipses always occur on or near it. Because of the inclination of the Moon's orbit, eclipses do not occur at every conjunction and opposition of the Sun and Moon, but only when the Moon is near an ascending or descending node at the same time it is at conjunction or opposition. The ecliptic is so named because the ancients noted that eclipses only occurred when the Moon crossed it.
Equinoxes and solstices
The exact instants of equinoxes or solstices are the times when the apparent ecliptic longitude (including the effects of aberration and nutation) of the Sun is 0°, 90°, 180°, or 270°. Because of perturbations of the Earth's orbit and peculiarities of the calendar, the dates of these are not fixed.
In the constellations
The ecliptic currently passes through the following constellations:
The ecliptic forms the center of a band about 20° wide called the zodiac, on which the Sun, Moon, and planets are seen always to move. Traditionally, this region is divided into 12 signs of 30° longitude, each of which approximates the Sun's motion through one month. In ancient times the signs corresponded roughly to 12 of the constellations which straddle the ecliptic. These signs give us some of the terminology used today. The first point of Aries was named when the vernal equinox was actually in the constellation Aries; it has since moved into Pisces.
Notes and references
- U.S. Naval Observatory Nautical Almanac Office, Nautical Almanac Office; U.K. Hydrographic Office, H.M. Nautical Almanac Office (2008). The Astronomical Almanac for the Year 2010. U.S. Govt. Printing Office. p. M5. ISBN 978-0-7077-4082-9.
- U.S. Naval Observatory Nautical Almanac Office (1992). P. Kenneth Seidelmann, ed. Explanatory Supplement to the Astronomical Almanac. University Science Books, Mill Valley, CA. ISBN 0-935702-68-7. , p. 11
- The directions north and south on the celestial sphere are in the sense toward the north celestial pole and toward the south celestial pole. East is the direction toward which the Earth rotates, west is opposite that.
- Astronomical Almanac 2010, sec. C
- Explanatory Supplement (1992), sec. 1.233
- Explanatory Supplement (1992), p. 733
- Astronomical Almanac 2010, p. M2 and M6
- Explanatory Supplement (1992), sec. 1.322 and 3.21
- U.S. Naval Observatory Nautical Almanac Office; H.M. Nautical Almanac Office (1961). Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac. H.M. Stationery Office, London. , sec. 2C
- Explanatory Supplement (1992), p. 731 and 737
- Chauvenet, William (1906). A Manual of Spherical and Practical Astronomy. I. J.B. Lippincott Co., Philadelphia. , art. 365-367, p. 694-695, at Google books
- Laskar, J. (1986). "Secular Terms of Classical Planetary Theories Using the Results of General Relativity". , table 8, at SAO/NASA ADS
- Explanatory Supplement (1961), sec. 2B
- U.S. Naval Observatory, Nautical Almanac Office; H.M. Nautical Almanac Office (1989). The Astronomical Almanac for the Year 1990. U.S. Govt. Printing Office. ISBN 0-11-886934-5. , p. B18
- Astronomical Almanac 2010, p. B52
- Newcomb, Simon (1906). A Compendium of Spherical Astronomy. MacMillan Co., New York. , p. 226-227, at Google books
- Meeus, Jean (1991). Astronomical Algorithms. Willmann-Bell, Inc., Richmond, VA. ISBN 0-943396-35-2. , chap. 21
- Danby, J.M.A. (1988). Fundamentals of Celestial Mechanics. Willmann-Bell, Inc., Richmond, VA. ISBN 0-943396-20-4. , sec. 9.1
- Roy, A.E. (1988). Orbital Motion (third ed.). Institute of Physics Publishing. ISBN 0-85274-229-0. , sec. 5.3
- Montenbruck, Oliver (1989). Practical Ephemeris Calculations. Springer-Verlag. ISBN 0-387-50704-3. , sec 1.4
- Explanatory Supplement (1961), sec. 2A
- Explanatory Supplement (1961), sec. 1G
- Dziobek, Otto (1892). Mathematical Theories of Planetary Motions. Register Publishing Co., Ann Arbor, Michigan. , p. 294, at Google books
- Astronomical Almanac 2010, p. E14
- Ball, Robert S. (1908). A Treatise on Spherical Astronomy. Cambridge University Press. p. 83., at Google books
- Meeus (1991), chap. 26
- Serviss, Garrett P. (1908). Astronomy With the Naked Eye. Harper & Brothers, New York and London. pp. 105, 106. at Google books
- Bryant, Walter W. (1907). A History of Astronomy. p. 3., at Google books
- Bryant (1907), p. 4
- see, for instance, Leo, Alan (1899). Astrology for All. , p. 8, at Google books
- Vallado, David A. (2001). Fundamentals of Astrodynamics and Applications (second ed.). Microcosm Press, El Segundo, CA. ISBN 1-881883-12-4. , p. 153
|Look up ecliptic in Wiktionary, the free dictionary.|
|Wikiversity has learning materials about Ecliptic at|
- The Ecliptic: the Sun's Annual Path on the Celestial Sphere Durham University Department of Physics
- Seasons and Ecliptic Simulator University of Nebraska-Lincoln
- MEASURING THE SKY A Quick Guide to the Celestial Sphere James B. Kaler, University of Illinois
- Earth's Seasons U.S. Naval Observatory
- The Basics - the Ecliptic, the Equator, and Coordinate Systems AstrologyClub.Org
- Kinoshita, H.; Aoki, S. (1983). "The definition of the ecliptic". Celestial Mechanics. 31: 329–338. Bibcode:1983CeMec..31..329K. doi:10.1007/BF01230290.; comparison of the definitions of LeVerrier, Newcomb, and Standish. | <urn:uuid:8ea5c1c2-4038-4259-b87d-911be524a40a> | 4.15625 | 3,884 | Knowledge Article | Science & Tech. | 58.951805 | 95,625,284 |
The discovery of quasars in the early 1960s marked a turning point in astronomy and opened for us a vastly more immense vista on the universe. The tale of that discovery is completely fascinating, being best told by those closely involved. The main detail necessary here is that quasars appear as point-like optical sources, usually identified with radio sources, and having optical emission lines at large redshifts. The redshifts turned out to be much larger than anything seen previously, and if attributed to the Hubble expansion of the universe implied enormous distances and enormous energetics. Furthermore, it soon was discovered that many of them displayed variable brightness on time scales of weeks or less. That has been especially awkward for astronomers to understand since a source is not supposed to be able to turn on or off in a shorter time scale than the light travel time across the source. That should mean that sources are very small for their power, and yet there appear some forbidden emission lines only to be expected from low-density material.
KeywordsRadio Source Gravitational Lens Hubble Expansion Distant Quasar Light Travel Time
Unable to display preview. Download preview PDF.
- H. Arp, 1987 Quasars, Redshifts and Controversies, Interstellar MediaGoogle Scholar
- R. V. Jones, 1988 Instruments and Experiences, WileyGoogle Scholar
- A. Kastler, 1974 C. R. Acad. Sci. Paris B 278: 1013–1015Google Scholar
- C. Møller, 1952 Theory of Relativity, Oxford U. PressGoogle Scholar
- R. Peierls, 1991 More Surprises in Theoretical Physics, Princeton U. PressGoogle Scholar
- E. L. Wright, 1982 [private communication]Google Scholar | <urn:uuid:d88845b0-4949-4a94-9eeb-a15d35cca461> | 3.921875 | 361 | Truncated | Science & Tech. | 45.923766 | 95,625,293 |
+44 1803 865913
By: Kentwood D Wells(Author)
1148 pages, 116 b/w photos, 323 b/w illustrations, 45 tables
Consisting of more than six thousand species, amphibians are more diverse than mammals and are found on every continent save Antarctica. Despite the abundance and diversity of these animals, many aspects of the biology of amphibians remain unstudied or misunderstood. The Ecology and Behavior of Amphibians aims to fill this gap in the literature on this remarkable taxon. It is a celebration of the diversity of amphibian life and the ecological and behavioral adaptations that have made it a successful component of terrestrial and aquatic ecosystems.
Synthesizing seventy years of research on amphibian biology, Kentwood D. Wells addresses all major areas of inquiry, including phylogeny, classification, and morphology; aspects of physiological ecology such as water and temperature relations, respiration, metabolism, and energetics; movements and orientation; communication and social behavior; reproduction and parental care; ecology and behavior of amphibian larvae and ecological aspects of metamorphosis; ecological impact of predation on amphibian populations and antipredator defenses; and aspects of amphibian community ecology. With an eye towards modern concerns, The Ecology and Behavior of Amphibians concludes with a chapter devoted to amphibian conservation.
"More than a quarter-century in the making, and weightier than a doorstop [...] the definitive one-volume work on the world's amphibians."
– Steve Grant, The Hartford Courant, 28-11-2007
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Kentwood D. Wells is professor in the Department of Ecology and Evolutionary Biology at the University of Connecticut.
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A View from Brittany Sauser
Britain Announces New Space Agency
The government says a space agency could boost the country’s economy and science.
The UK government has announced a new national space agency that will start up on April 1 with the opening of a $60 million facility called the International Space Innovation Center located in Oxfordshire, England. The new agency will oversee all of the county’s space endeavors, which includes earth-monitoring satellites for climate change and future human space exploration.
The country’s current space program has been scattered between government departments and science councils, and its activity has been mostly focused on building satellites and associated electronic equipment. The space and satellite industry currently supports 68,000 jobs and contributes $9 billion annually to the economy, according to Space.com. It wasn’t until 2007 that the British National Space Center set up the Space Exploration Working Group and proposed plans for human space missions, citing the fact that two British astronauts could travel to space by 2015. (UK-born astronauts have had to become United States citizens in order to fly in space.)
UK officials said the new agency could grow to a $60 billion a year industry and create over 100,000 jobs over the next two decades. A few of its main goals would be to boost the country’s role in climate change science with new earth-monitoring satellites and create space-based systems for both security and communications in hopes of becoming one of the top ten space nations. UK officials are also deciding whether they should establish their own Earth observation network; right now the UK gives majority of its space budget to ESA for satellite projects and robotic missions. (ESA’s press release about the announcement is here.)
According to parts of the British media, it’s about raising the country’s bottom line. In the Guardian theUK business secretary, Lord Mandelson, says the space agency will help Britain out of recession. New Scientist magazine says the agency is more about revitalizing the manufacturing industry than the science.
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Authors: George Rajna
An asymmetry must exist here somewhere but we simply do not understand where the difference is. What is the source of the symmetry break? They have successfully deciphered the total angular momentum (spin) of the nucleon, determining how it's shared among its constituents. The resulting values for the Rydberg constant and the proton radius are in excellent agreement with the muonic results (Nature 466, 213 (2010)), but disagree by 3.3 standard deviations with the average of the previous determinations from regular hydrogen. In a stringent test of a fundamental property of the standard model of particle physics, known as CPT symmetry, researchers from the RIKEN-led BASE collaboration at CERN have made the most precise measurements so far of the charge-to-mass ratio of protons and their antimatter counterparts, antiprotons. The puzzle comes from experiments that aimed to determine how quarks, the building blocks of the proton, are arranged inside that particle. That information is locked inside a quantity that scientists refer to as the proton's electric form factor. The electric form factor describes the spatial distribution of the quarks inside the proton by mapping the charge that the quarks carry. Taking into account the Planck Distribution Law of the electromagnetic oscillators, we can explain the electron/proton mass rate and the Weak and Strong Interactions. Lattice QCD gives the same results as the diffraction patterns of the electromagnetic oscillators, explaining the color confinement and the asymptotic freedom of the Strong Interactions.
Comments: 20 Pages.
[v1] 2017-10-19 01:55:50
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Scientists around the world do not stop the fight against superbugs. These microorganisms are resistant to most modern antibiotics and pose a serious danger to humans, especially the patient.
In the search for substances capable of defeating superbugs, scientists have repeatedly turned to animals. So, earlier hope for a favorable outcome of a scientific confrontation gave the milk of the platypus and substances derived from the body surface of some species of ants.
Reports mir24.tv now, scientists interested in the possibilities of poisonous snakes. Scientists from the University of Queensland in Australia, together with the Spanish explorers found in the glands of the South American rattlesnakes fragments of proteins that can help in the fight against superbugs. Researchers have isolated a peptide coupling catalycity, which has antimicrobial, anticancer and antifungal effects. When the substance did not harm the normal cells.
The power of catalizadora scientists have tested on Escherichia coli and Escherichia coli. As a result, the peptide destroyed 90% of bacteria of both types. Moreover, E. coli substance coped for a couple of hours, as with Pseudomonas and is for five minutes.
The secret of such a powerful antimicrobial effect is hidden in the electrostatic attraction. The fact that catalycity has a positive electric charge and membrane of bacterial cells – negative. Due to this, the peptide is attracted to the superbugs and destroys their membrane. Normal cells in animals with no risk – they have no charge, so the destroyer superbugs don’t pay anyone attention.
It is expected that over time catalizadora will do the antibiotics of new generation, which will be able to cope with superbugs. | <urn:uuid:32b27d1f-6016-47ce-a4f7-3c37a7aea051> | 3.1875 | 353 | News Article | Science & Tech. | 33.788322 | 95,625,319 |
Pictured: The bees fitted with microchips to find out why their species is dying
It is a remarkably hairy close-up.
But this tiny microchip attached to a bee’s back will hopefully explain why so many honeybees are dying from disease.
Professor Juergen Tautz and his team at the University of Wurzburg in Germany are studying the health of more than 150,000 bees, in the hope of halting the apparently inexorable decline in their worldwide population.
Creating a buzz: A tiny chip will revolutionise the study of individual bees
Bees have always been tricky to study individually.
Each colony has around 50,000 members, all interacting simultaneously and making it near-impossible to observe them.
Previously, each bee would be painted with a different-coloured dot on its back and scientists would video the colony — watching the tape endlessly, to try to work out the behaviour in each insect.
But a revolutionary technology enables the study of bees at close quarters. As soon as a bee hatches, a tiny radio frequency identification (RFID) microchip is stuck to its back using a lacquer.
This allows scientists to study its behaviour throughout its life.
The bee will be unaware of the chip as it weighs only 2mg — a typical bee weighing in at 70mg can carry its own body weight.
Once it has been chipped, each bee has a serial number, and a scanner on the outside of the hive (like a supermarket one) registers its movement every time it leaves or enters.
Big loader: A honeybee carrying two balls of pollen it has collected
The data allows scientists to determine the health of every bee — how many trips it is taking, how soon after hatching it collects pollen and how much food it gathers.
The scientists also hope to discover why some bees live for just four weeks and others up to ten months.
They also put the bees through a rigorous programme in the hope of training them to be ‘sniffer bees’ capable of detecting explosives and suicide bombers.
The bees are conditioned to stick out their tongues (or proboscis) when they detect a certain scent — for example, that of explosives.
Each time they do so, they receive a drop of their favourite tipple — sugar solution — and they rapidly learn to associate the smell with receiving food.
Before long, they will stick out their tongues whenever the scent of explosives is present, in anticipation of the sugar.
And by watching their tongues, scientists can use them as sniffer bees. There are three colonies involved in this scheme — involving 150,000 bees — but it can be expensive.
Although the microchips cost just £1.20 each, they are lost for ever once the bees die outside the hive.
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Chord - TS v2
The radius of circle k measures 87 cm. Chord GH = 22 cm. What is TS?
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Today, for the first time ever, a team of researchers led by Robert Linhardt of Rensselaer Polytechnic Institute has announced in the October 9 Advanced Online Publication edition of the journal Nature Chemical Biology the sequence of a complete complex carbohydrate biopolymer. The surprising discovery provides the scientific and medical communities with an important and fundamental new view of these vital biomolecules, which play a role in everything from cell structure and development to disease pathology and blood clotting.
Rensselaer Polytechnic Institute
Structure of the bikunin. The portion on the left corresponds to the sugar part of the molecule, the sequence of which was determined in the current study. The portion on the right corresponds to the protein part of bikunin.
Nature Chemical Biology
The paper is titled “The proteoglycan bikunin has a defined sequence.”
“Carbohydrate biopolymers, known as glycosaminoglycans, appear to be really important in how cells interact in higher organisms and could explain evolutionary differences and how development is driven. We also know that carbohydrate chains respond to disease, injury, and changes in the environment,” said Linhardt, who is the Ann and John H. Broadbent Jr. ’59 Senior Constellation Professor of Biocatalysis and Metabolic Engineering at Rensselaer. “In order to understand how and why this all happens, we first need to know their structure. And today, at least for the simplest glycosaminoglycan structure, we can now do this.”
The first glycosaminoglycan sequenced was obtained from bikunin. Bikunin is a proteoglycan, a protein to which a single glycosaminoglycan chain is attached. Unlike less sophisticated carbohydrate biopolymers, such as starch and cellulose, the proteoglycans are decorated with structurally complex carbohydrates that enable them to perform more sophisticated and defined roles in the body. Bikunin, for example, is a natural anti-inflammatory that is used as a drug for the treatment of acute pancreatitis in Japan. It has the simplest chemical structure of any proteoglycan. Linhardt views the discovery of the structure of bikuin as the first step on the ladder to the discovery of the structure of more complex proteoglycans.
“The first genome sequences of DNA were on the simplest organisms such as bacteria. Once the technology was developed it ultimately led to the sequencing of the human genome,” he said. “In our efforts to sequence carbohydrate biopolymers we don’t yet know if the defined structure we observe for this simple protoglycan will hold for much more complex proteoglycans.”
But, looking for structure in more complex proteoglycans will be among the next steps in the research for Linhardt and his team. The search for structure could help put to rest a long-running debate in the scientific community as to whether complex carbohydrate biopolymers require a defined structure to function.
“Despite all that is known about glycan formation, our understanding has not yet been deep enough to infer sequence or even determine if sequence occurs,” Linhardt said. “These findings represent a new way of looking at these complex biomolecules as ordered structures.”
Linhardt’s research into carbohydrate sequencing began 30 years ago. In his previous work, he determined that some order existed in at least a portion of some carbohydrate biopolymers, but it did not represent the entire finished puzzle.
“Previously, we could see a pattern, but we could not see if all the chains were playing the same music. The tools did not yet exist. Now we can recognize it as a symphony.”
To uncover the entire structure, Linhardt and his team, which was led by his doctoral student Mellisa Ly, borrowed a technique from the field of protein research called the proteomics top-down approach. As opposed to the bottom-up approach that first breaks apart a complex biopolymer into pieces and then rebuilds it piece by piece like a jigsaw puzzle, the top-down approach used by Linhardt and colleagues allows the researcher to picture the whole intact puzzle. This can only be accomplished with some of the most sophisticated technology available to the scientific community today, including very high-powered mass spectrometers.
Linhardt used a mass spectrometer located in the Rensselaer Center for Biotechnology and Interdisciplinary Studies (CBIS) to make his initial discoveries, and had these results independently confirmed on a separate and higher-level spectrometer at the University of Georgia. Mass spectrometers break down a molecule into separate charged particles or ions. These ions can then be categorized and analyzed based on their mass-to-charge ratio. These ratios then allow for sequencing of the entire molecule.
“This was truly the convergence of really sophisticated spectroscopy and its application to biology,” Linhardt said. “We were fortunate to have a lot of time to play with the instrument at CBIS to understand its capabilities.”
Beyond the technology it also took faith and determination. According to Linhardt, “It takes a student that is willing to try something even when the odds are pretty low. If it doesn’t work, you make incremental progress. If it does work, you can make a great discovery. But, from the beginning you need to be a believer that it is worth taking the chance because it takes a lot of hard work in the lab.”
And the odds weren’t in Linhardt’s favor. Despite being the most simple of proteoglycans, there were still 290 billion different possible sequences for the molecule.
“The first sample we looked at, we got the structure,” Linhardt said. “In the end we did 15 chains and they all came back playing the same exact symphony.”
The research is funded by the National Institutes of Health.
Linhardt and Ly were joined in the research by Tatiana Laremore of Rensselaer; Franklin Leach and Jonathan Amster of the University of Georgia; and Toshihiko Toida of Chiba University in Japan.
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Data and Tools
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Mapping, Remote Sensing, and Geospatial Data
The data collected and the techniques used by USGS scientists should conform to or reference national and international standards and protocols if they exist and when they are relevant and appropriate. For datasets of a given type, and if national or international metadata standards exist, the data are indexed with metadata that facilitates access and integration.
Geophysical data collected along the Atlantic continental slope and rise 2014, U.S. Geological Survey Field Activity 2014-011-FA, cruise MGL1407
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Swath bathymetry collected offshore of Fire Island and western Long Island, New York in 2014, U.S. Geological Survey Field Activity 2014-072-FA
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Water quality in the Barnegat Bay estuary along the New Jersey coast is the focus of a multidisciplinary research project begun in 2011 by the U.S. Geological Survey (USGS) in cooperation with the New Jersey Department of Environmental Protection. A continuous elevation surface (terrain model) integrating all available elevation data in the area was produced for water circulation modeling...
Point cloud from low-altitude aerial imagery from unmanned aerial system (UAS) flights over Coast Guard Beach, Nauset Spit, Nauset Inlet, and Nauset Marsh, Cape Cod National Seashore, Eastham, Massachusetts on 1 March 2016 (LAZ file)
This point cloud was derived from low-altitude aerial images collected from an unmanned aerial system (UAS) flown in the Cape Cod National Seashore on 1 March, 2016. The objective of the project was to evaluate the quality and cost of mapping from UAS images. The point cloud contains 434,096,824 unclassifed and unedited geolocated points.
Atlantic coast piping plover (Charadrius melodus) nest sites are typically found on low-lying beach and dune systems, which respond rapidly to coastal processes like sediment overwash, inlet formation, and island migration that are sensitive to climate-related changes in storminess and the rate of sea-level rise. Data were obtained to understand piping plover habitat distribution.
Archive of processed single-beam bathymetry (SBB) data, collected from May 28-June 3, 2015, within Grand Bay Mississippi/Alabama. The data described in this report provide baseline bathymetric information for future research investigating wetland/marsh evolution, sediment transport, and recent and long term geomorphic change.
This data release provides descriptions of more than 100 mining districts, mines, and mineral occurrences (deposits and prospects) within the United States that are reported to contain enrichments of rhenium (Re). These mineral occurrences include mined deposits, exploration prospects, and other occurrences with notable concentrations of rhenium.
Conceptual salt marsh units for wetland synthesis: Edwin B. Forsythe National Wildlife Refuge, New Jersey
Recent research shows that sediment budgets of microtidal marsh complexes on the Atlantic and Pacific coasts of the United States consistently scale with areal unvegetated/vegetated marsh ratio (UVVR) despite differences in sea-level rise, tidal range, elevation, vegetation, and stressors. This highlights UVVR as a broadly applicable indicator of microtidal marsh stability.
As part of this data synthesis effort, hydrodynamic and sediment transport modeling of Barnegat Bay Little Egg Harbor (BBLEH) has been used to create the following wetland data layers in Edwin B. Forsythe National Wildlife Refuge (EBFNWR), New Jersey: 1) Hydrodynamic residence time , 2) salinity change and 3) salinity exposure change in wetlands, and 4) sediment supply to wetlands
The purpose of the multibeam echosounder surveys was to map the bathymetry and backscatter intensity of the sea floor of the valley, providing a framework for geologic, oceanographic, and geochemical studies. The data from the three surveys are combined to produce grids of bathymetry and backscatter intensity at 12-m resolution that cover the entire valley and the head of the Hudson Canyon... | <urn:uuid:45a008ed-e24e-4326-b3f1-ebe039c2275d> | 2.890625 | 1,224 | Content Listing | Science & Tech. | 31.359435 | 95,625,372 |
Trevor Nace in Forbes:
Scientists have long known about the anomalous “warming hole” in the North Atlantic Ocean, an area immune to warming of Earth's oceans. This cool zone in the North Atlantic Ocean appears to be associated with a slowdown in the Atlantic Meridional Overturning Circulation (AMOC), one of the key drivers in global ocean circulation.
A recent study published in Nature outlines research by a team of Yale University and University of Southhampton scientists. The team found evidence that Arctic ice loss is potentially negatively impacting the planet's largest ocean circulation system. While scientists do have some analogs as to how this may impact the world, we will be largely in uncharted territory.
AMOC is one of the largest current systems in the Atlantic Ocean and the world. Generally speaking, it transports warm and salty water northward from the tropics to South and East of Greenland. This warm water cools to ambient water temperature then sinks as it is saltier and thus denser than the relatively more fresh surrounding water. The dense mass of water sinks to the base of the North Atlantic Ocean and is pushed south along the abyss of the Atlantic Ocean.
This process whereby water is transported into the Northern Atlantic Ocean acts to distribute ocean water globally. What's more important, and the basis for concern of many scientists is this mechanism is one of the most efficient ways Earth transports heat from the tropics to the northern latitudes. The warm water transported from the tropics to the North Atlantic releases heat to the atmosphere, playing a key role in warming of western Europe. You likely have heard of one of the more popular components of the AMOC, the Gulf Stream which brings warm tropical water to the western coasts of Europe. | <urn:uuid:6c9b002b-a470-4dc3-a519-8327d311a41a> | 3.671875 | 355 | News Article | Science & Tech. | 38.305275 | 95,625,383 |
10.5 Law of Cosines. Obj : ____________________ ________________________. For any triangle ABC with sides a, b, and c. a 2 = b 2 + c 2 – 2bc cos A b 2 = a 2 + c 2 – 2ac cos B c 2 = a 2 + b 2 – 2ab cos C. You can use the Law of Cosines to solve a triangle if:
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a2 = b2 + c2 – 2bc cos A
b2 = a2 + c2 – 2ac cos B
c2 = a2 + b2 – 2ab cos C
2 sides and the included angle
Points A and B are on opposite site sides of Lake Hoorah. From a 3rd point, C, the angle between the lines of sight to point A and B measures 46°. If the distance from A to C is 350 meters, and the distance from B to C is 286 meters what is the distance from A to B? | <urn:uuid:346f54a0-bc86-4252-b845-4f5c0aeefed2> | 3.3125 | 268 | Listicle | Science & Tech. | 88.465273 | 95,625,386 |
WASHINGTON, D.C., December 20, 2017 -- To build tomorrow's quantum computers, some researchers are turning to dark excitons, which are bound pairs of an electron and the absence of an electron called a hole. As a promising quantum bit, or qubit, it can store information in its spin state, analogous to how a regular, classical bit stores information in its off or on state. But one problem is that dark excitons do not emit light, making it hard to determine their spins and use them for quantum information processing.
In new experiments, however, not only can researchers read the spin states of dark excitons, but they can also do it more efficiently than before. Their demonstration, described this week in APL Photonics, from AIP Publishing, can help researchers scale up dark exciton systems to build larger devices for quantum computing.
"Large photon extraction and collection efficiency is required to push experiments beyond the proof-of-principle stage," said Tobias Heindel of the Technical University of Berlin.
When an electron in a semiconductor is excited to a higher energy level, it leaves behind a hole. But the electron can still be bound to the positively charged hole, together forming an exciton. Researchers can trap these excitons in quantum dots, nanoscale semiconductor particles whose quantum properties are like those of individual atoms.
If the electron and hole have opposite spins, the two particles can easily recombine and emit a photon. These electron-hole pairs are called bright excitons. But if they have the same spins, the electron and hole cannot easily recombine. The exciton can't emit light and is thus called a dark exciton.
This darkness is part of why dark excitons are promising qubits. Because dark excitons cannot emit light, they can't relax to a lower energy level. Therefore, dark excitons persist with a relatively long life, lasting for over a microsecond -- a thousand times longer than a bright exciton and long enough to function as a qubit.
Still, the darkness poses a challenge. Because the dark exciton is closed off to light, you can't use photons to read the spin states -- or any information a dark exciton qubit may contain.
But in 2010, a team of physicists at the Technion-Israel Institute of Technology figured out how to penetrate the darkness. It turns out that two excitons together can form a metastable state. When this so-called spin-blockaded biexciton state relaxes to a lower energy level, it leaves behind a dark exciton while emitting a photon. By detecting this photon, the researchers would know a dark exciton was created.
To then read the spin of the dark exciton, the researchers introduce an additional electron or hole. If the new charge carrier is a spin-up electron, for example, it combines with the spin-down hole of the dark exciton, forming a bright exciton that quickly decays and produces a photon. The dark exciton is destroyed. But by measuring the polarization of the emitted photon, the researchers can determine what the dark exciton's spin was.
Like in the 2010 experiments, the new ones measure dark excitons inside quantum dots. But unlike the earlier study, the new experiments use a microlens that fits over an individual quantum dot that was selected in advance. The lens allows researchers to capture and measure more photons, crucial for larger-scale quantum information devices. Their approach also lets them choose the brightest quantum dots to measure.
"This means we can detect more photons of the related exciton states per time, which allows us to access the dark exciton spins more often," Heindel said.
Measuring the dark exciton spins also reveals the frequency of its precession, an oscillation between a state in which the spins are either up or down. Knowing this number, Heindel explained, is needed when using dark excitons to generate quantum states of light that are promising for quantum information applications. For these states, called cluster states of entangled photons, the quantum mechanical properties are preserved even if parts of the state are destroyed -- needed for error-resistant quantum information systems.
RELATED JOURNAL ARTICLE
The article, "Accessing the dark exciton spin in deterministic quantum-dot microlenses," is authored by Tobias Heindel, Alexander Thoma, Ido Schwartz, Emma R. Schmidgall, Liron Gantz, Dan Cogan, Max Strauss, Peter Schnauber, Manuel Gschrey, Jan-Hindrik Schulze, Andre Strittmatter, Sven Rodt, David Gershoni and Stephan Reitzenstein. The article appeared in the journal APL Photonics Dec. 19, 2017 (DOI: 10.1063/1.5004147) and can be accessed at http://aip.scitation.org/doi/full/10.1063/1.5004147. | <urn:uuid:f610c55e-1fdf-401b-a65a-d62be9e0f438> | 4.03125 | 1,027 | News Article | Science & Tech. | 42.863984 | 95,625,393 |
Wavelike compression ridge on the surface of viscous lava produced during downslope movement (Francis and Oppenheimer 2004).
A type of pressure ridge in viscous lava flow.
Corrugations formed in coulées. Ridges form in response to compression parallel to flow during advance of some silicic lavas (Fink and Anderson 2000).
Often visible in satellite and aerial images as a succession of curved wavelike ridges in viscous lava flows (Coulées); curves bulge in the direction of flow; spacing between ridges ranges from ~20 to 200 m or more; ridges are typically 10–15 m high and up to 100 m in very large massive flows up to 15 km in length. Overall appearance mimics much smaller scale folds in ropy pahoehoe lava (Fink 1980b) or festoon patterns developed on some lava surfaces.
Ogives are massive pressure ridges that develop on the surfaces of thick viscous blocky lava flows during their...
KeywordsLava Flow Rhyolite Lava Basaltic Lava Flow Pressure Ridge Downslope Flow
- Donnelly-Nolan JM (2010) Geologic map of medicine Lake Volcano, Northern California. U.S. geological survey scientific investigations map 2927, 2 plates, pamphlet 48 pGoogle Scholar
- Fink JH (1980a) Possible Rhyolite flows in the Arcadia Planitia region of Mars: evidence from surface ridge geometry. Lunar and Planetary Science XI:285–287, HoustonGoogle Scholar
- Fink JH, Anderson SW (2000) Lava domes and Coulées. In: Sigurdsson H et al (eds) Encyclopedia of volcanoes. Academic, San Diego, pp 307–319Google Scholar
- Francis P, Oppenheimer C (2004) Volcanoes, 2nd edn. Oxford University Press, New York, pp 157–158Google Scholar
- MacLeod NS, Sherrod DR, Chitwood LA, McKee EH (1981) Newberry volcano, Oregon. In: Johnston DA, Donnely-Nolan J (eds) Guides to some volcanic Terranes in Washington, Idaho, Oregon, and Northern California, U.S. Geological Survey Circular 838. U.S. Geological Survey, Reston, pp 85–103Google Scholar
- Walker GW, Nolf B (1981) High Lava plains, brothers fault zone to Harney Basin, Oregon. In: Johnston DA, Donnely-Nolan J (eds) Guides to some volcanic Terranes in Washington, Idaho, Oregon, and Northern California, U.S. Geological Survey Circular 838. U.S. Geological Survey, Reston, pp 105–111Google Scholar | <urn:uuid:aeb4a6f2-7fc3-43e7-8262-f0f2487a4234> | 3.28125 | 575 | Academic Writing | Science & Tech. | 48.012403 | 95,625,416 |
Lead pollution in the air stimulates the formation of ice particles in clouds.
A team of scientists from the USA, Germany and Switzerland has found that particles containing lead are excellent seeds for the formation of ice crystals in clouds. This not only has a bearing on the formation of rain and other forms of precipitation but may also have an influence on the global climate.
This is because the heat given off from the earth's surface is more efficiently radiated into space by ice clouds (cirrus) with lead-containing particles than has been hitherto realized. In comparison to clouds with a low lead content, clouds with a high lead content thus actually help cool the earth. Over the last twenty years, there has been a continuing decrease in the rate of anthropogenic lead emissions. This may mean that the greenhouse effect is now even more pronounced because lead-containing clouds once previously helped limit it.
At the Sphinx Observatory, a Swiss research station on the Jungfraujoch at an altitude of 3,580 meters, scientists from various institutions, including the Universities of Frankfurt and Mainz, and the Max Planck Institute for Chemistry in Mainz, investigated the chemical composition of clouds in the winters of 2006 and 2007. "What mainly interested us was the question of how ice particles form. Water particles in the atmosphere do not simply freeze at zero degrees. On the contrary, at temperatures as low as minus 37 degrees they still need an ice nucleus, for example an aerosol particle, before ice formation is triggered," explains Professor Joachim Curtius of the Institute for Atmosphere and Environment (IAU) at the Goethe University Frankfurt. The same principle is also employed for snow guns, and in this case proteins derived from Pseudomonas bacteria are sometimes used as the ice-forming nuclei - a controversial application.
Scientists attach a lot of importance to the presence of ice particles in clouds, as they make a vital contribution to the genesis of rain drops within clouds. "Until we know what kinds of particles trigger ice formation in the atmosphere we will not be able to understand climatic change or the global hydrological cycle," comments Professor Stephan Borrmann. The atmospheric physicist is the head of the "Department of Particle Chemistry," a joint venture of the Max Planck Institute for Chemistry and the Institute for Atmospheric Physics at Johannes Gutenberg University Mainz.
Investigations conducted on the Swiss Jungfraujoch and in the Rocky Mountains in Colorado have found that particles that contain lead are among the most effective ice nuclei to be found in the atmosphere. "What was really new for us was the remarkable frequency with which we found lead in the ice particles," says Curtius. "We were able to identify lead in around every second ice nucleus while only one in twenty of the average aerosol particles contained lead." However, lead on its own is not enough to form an ice nucleus. Minute lead particles combine with other constituents of the air, such as mineral dust from the Sahara. Some of these mineral dust particles can themselves act as ice nuclei. Once combined with lead, however, a good ice nucleus becomes an outstanding ice nucleus that is able to initiate ice crystallization at higher temperatures and at lower humidities.
Laboratory experiments at the AIDA Aerosol and Cloud Chamber at the Karlsruhe Research Center have confirmed the results of the field studies in Switzerland. Furthermore, model calculations by the Swiss Federal Institute of Technology Zurich show that lead-containing particles change the properties of cirrus clouds so that these significantly influence the extent to which long-wave radiation escapes from the earth into space. If all ice-forming mineral particles contained lead, the heat emitted by the earth could theoretically be as much as 0.8 watts per square meter. By way of comparison: The climate forcing generated as a result of anthropogenic CO2 emissions is equivalent to roughly 1.6 watts per square meter. The lead-containing ice nuclei thus presumably have a cooling effect on the climate due to their indirect influence on ice cloud formation.
Scientists now assume that as a result of the significantly higher levels of lead pollution in the 1970s and 1980s - resulting from the use of leaded petrol and due to lead emissions from power stations - the great majority of all mineral dust particles were contaminated with lead and as a result more heat escaped from the earth than at present. "This probably led to global inhibition of rises in temperature to some extent, whereas today almost the full greenhouse effect is kicking in," says Curtius.
But a return to the lead emission levels of the late 20th century is hardly desirable. Lead is a toxic heavy metal that can cause severe damage to health. "However, with the benefit of hindsight we can now explain why there has been a trend towards more rapid temperature rises in recent years; it is because mankind has cut back its emissions of lead and sulphates," claims Borrmann.
"These results show that anthropogenic emissions can influence ice nuclei precipitation and, as a result, change precipitation and the climate," to quote the research results published in Nature Geoscience. Among the institutions participating in the project were Technische Universität Darmstadt, the Leibniz Institute for Tropospheric Research in Leipzig, the Pacific Northwest National Laboratory in Richland/Washington, and the U.S. government agency, the National Oceanic and Atmospheric Administration in Boulder/Colorado. Mainz and Frankfurt Universities, Technische Universität Darmstadt ?and the Max Planck Institute for Chemistry participated in the project within the context of the Collaborative Research Center 641 "The tropospheric ice phase" funded by the German Research Foundation (DFG).Original publication:
Petra Giegerich | idw
Further reports about: > Atmospheric > CHEMISTRY > CO2 emissions > Cirrus > Geoscience > Global Climate > Lead pollution > Max Planck Institute > Nature Immunology > aerosol particles > anthropogenic CO2 emissions > formation of ice crystals > greenhouse effect > greenhouse effect in the past > ice clouds > ice formation in clouds > ice nucleus > ice particles in clouds > ice-forming mineral particles > tropospheric ice phase
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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17.07.2018 | Power and Electrical Engineering | <urn:uuid:1fcdc58b-253f-4c3d-9100-92e73cb10f9d> | 3.640625 | 1,883 | Content Listing | Science & Tech. | 33.358313 | 95,625,418 |
The first strains of human immunodeficiency virus appeared in the early XX century in Africa (34). The closest evolutionary ancestors of HIV viruses were similar to simian immunodeficiency viruses, and the first infected humans could be hunters who butchered the dead monkeys. Currently, according to the World Health Organization, nearly 37 million people worldwide are HIV-infected, and the immunodeficiency caused by the virus killed more than a million people in 2015 (35).
The human immunodeficiency virus (HIV) is a retrovirus and a member of the lentivirus genus. HIV infects and destroys cells of the human immune system (CD4+ T-lymphocytes, macrophages and dendritic cells).The decrease in CD4+ T-lymphocyte levels causes the development of acquired immunodeficiency syndrome (AIDS) (36).
There are two major species of HIV, HIV-1 and HIV-2, of which HIV-2 is less common. The HIV virion is a roughly spherical particle with a diameter measuring between 100 and 180 nm. The virion is surrounded by a cell-derived lipid membrane, which contains surface proteins. Some of these membrane proteins are products of the viral genome (surface glycoprotein gp120/gp41), and others are captured from the host cell during viral budding (e.g., ICAM-1, HLA-DR1, CD55 and others). The gp120/gp41 glycoprotein interacts with receptors on the cell surface promoting fusion of the viral and cell membranes. Other HIV surface proteins perform supporting functions (4, 6).
Trimers of the MA (p17) protein form a layer directly under the lipid membrane. Inside the HIV particle is a cone-shaped capsid, which is composed of CA (p24) proteins. The capsid contains two copies of positive single-stranded viral RNA bound by the NC (p7) protein and the enzymes (reverse transcriptase and integrase) necessary for replication of the virus (15, 37).
The HIV genome is approximately 10,000 nucleotides in length and contains 9 genes encoding 15 different proteins. The most important viral genes (open reading frames) are Gag, Pol and Env. Gag encodes the p55 protein, which is subsequently cut into the structural proteins MA, CA, NC and p6. The Pol reading frame encodes integrase, protease, and reverse transcriptase. Env encodes the two subunits of the surface glycoprotein complex. Other genes (Tat, Rev, Vif, Vpr, Vpu and Nef) produce accessory proteins, which modulate host cell metabolism and facilitate different stages of the HIV life cycle (38).
This human immunodeficiency virus model summarizes the results from more than 100 of the latest scientific publications in the fields of virology, X-ray analysis and NMR spectroscopy. The depicted spatial configurations of 17 different viral and cellular proteins found in the HIV particle are in strict accordance with known 3D structures.The viral membrane in the model includes 160,000 lipid molecules of 8 different types in the proportion found in the HIV particle.
Scientifically verifying accurate models of viruses remains a challenging task. This becomes more complicated due to the fact that none of the currently available scientific approaches allow for obtaining an image of the whole virus particle in the atomic or molecular resolution. Nevertheless, hundreds of works by different authors from around the world have shed light on the structure and morphology of virion components and their interactions. The Visual Science team relies on several important sources to create models of the non-profit educational project “Viral Park”: careful analysis of the available scientific publications; opinions of recognized experts from the world's top research centers and the results of our own molecular dynamics and modeling simulations made by the experts of Visual Science’s Molecular modeling department, who employ structural bioinformatics methods to fill the gaps in the current understanding of the viral structure.This model of the HIV virion has been awarded the first place at the 2010 Science and Engineering Visualization Challenge (SEVC), a competition organized by Science magazine and the National Science Foundation.
The model appeared on the cover of the special issue of Nature Medicine (September 8, 2010) prepared by the Global HIV Vaccine Enterprise. In this publication, the Enterprise published the strategic research plan to accelerate the development of vaccines against HIV (the “2010 Plan”). The 2010 Plan was developed by the Council of the Global HIV Vaccine Enterprise with the participation of hundreds of scientists, policy-makers, funders, and advocates worldwide.
The model also appeared on the cover of the International AIDS Vaccine Initiative (IAVI) Report. It is an authoritative guide that publishes information about all events and innovations, concerning the development of the vaccine against HIV. The IAVI report is published 6 times a year and its audience is represented by specialists in more than 130 countries. The mission of the InternationalAIDS Vaccine Initiative is to ensure the development of safe, effective, accessible, preventive HIV vaccines for use throughout the world. IAVI participates in research and development of candidate vaccines, addressing the legal issues concerning HIV and AIDS, supporting developing countries. The IAVI Innovation Fund is supported by the Bill and Melinda Gates Foundation. IAVI has representative offices in Africa, Europe, India, and the US.
In addition, our HIV model has been included in Stanley Plotkin's Vaccines, a textbook hailed as the “Bible of vaccinologists” by The Lancet; featured in presentations by the Nobel Prize-winning virologist Françoise Barré-Sinoussi; and covered by The New York Times, National Geographic, Wired, Popular Science, and other popular periodicals.
Molecular modelling through computer graphics permits plenty of latitude for exercising artistic talent to inform, explain and instruct. Visual Science shows the way with its high quality, accurate, informative graphics that explain even the most complex processes of life. | <urn:uuid:53e75a6d-1d79-486b-8470-34ef25668eb8> | 4.03125 | 1,237 | Knowledge Article | Science & Tech. | 28.371268 | 95,625,466 |
Experimental manipulations of fish in a Northern California river during summer base flow reveal that they have large effects on predators, herbivores, and plants in river food webs. California roach and juvenile steelhead consume predatory insects and fish fry, which feed on algivorous chironomid larvae. In the presence of fish, filamentous green algae are reduced to low, prostrate webs, infested with chironomids. When the absence of large fish releases smaller predators that suppress chironomids, algal biomass is higher, and tall upright algal turfs become covered with diatoms and cyanobacteria. These manipulations provide evidence that the Hairston, Smith, Slobodkin-Fretwell theory of trophic control, which predicts that plants will be alternately limited by resources or herbivores in food webs with odd and even numbers of trophic levels, has application to river communitics.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:e91c8933-52ed-4057-9769-2564bf03253f> | 3.4375 | 214 | Academic Writing | Science & Tech. | 10.671551 | 95,625,467 |
Considering Climate Change: Fire Island and Storms
- Grade Level:
- Ninth Grade-Twelfth Grade
- Biology: Plants, Climate Change, Earth Science
- National/State Standards:
- Next Generation Science Standards: HS-LS2 Ecosystems; HS-ESS2 Earth's Systems; HS-ESS3 Earth and Human Activity
Common Core Standards: RST Grades 9-10 1,2,3,4,6,7,8,9; RST Grades 11-12 1,2,3,4,6,7,8,9; WST 9-10 8,9; WST 11-12 8,9
- climate change, shoreline dynamics, Hurricane Sandy
OverviewThis lesson plan explores the impacts of Hurricane Sandy, the history-making 2012 storm, on the natural resources of Fire Island, and it challenges students to consider the effects of climate change that are likely to occur close to home. The lesson includes an inquiry-based lab, with pre-labs, activities, and homework designed to increase understanding of climate change.
- Students will conduct individual labs to test dissolved oxygen.
- Students will be able to list two changes to the Fire Island landscape that occurred during Hurricane Sandy.
- Students will utilize primary sources and inquiry-based laboratory findings to inform their opinion about managing a dynamic landscape.
There is growing evidence that we are already seeing some of the effects of climate change, such as the increased frequency and intensity of storms. And, because powerful storms are the drivers of barrier island evolution, we may be more likely to see an increase in dramatic landscape change like the breach at Old Inlet caused by Hurricane Sandy. This lesson plan explores the impacts that Hurricane Sandy had on the natural resources of Fire Island and the Great South Bay, and challenges students to consider the effects of climate change that are likely to occur close to home.
Day 1: Pre-Lab Homework: Understanding Barrier Island Dynamics
Day 1: Pre-Lab Lesson: Hurricane Sandy and Climate Change
Day 1: Follow-up Homework: Understanding the Health of an Aquatic Ecosystem: Measuring Dissolved Oxygen and Primary Productivity
Day 2-4:Inquiry-based Lab: Measuring the Health of the Bay: Measuring Dissolved Oxygen in an Aquatic System
Day 2-4:Follow-up Homework: Reading: "The Impact on the Great South Bay of the Breach at Old Inlet"
Day 5:Follow-up Homework: The Impact on the Great South Bay of the Breach at Old Inlet
Day 5: Follow-up Homework: Breach Evolution Pros and Cons
Day 6 (optional): Field Trip to the Breach at Old Inlet
Pre-Lab Homework: Understanding Barrier Island Dynamics
Pre-Lab Lesson - PowerPoint: Hurricane Sandy and Understanding Climate Change
Follow-Up Homework: Understanding the Health of An Aquatic Ecosystem - Measuring Dissolved Oxygen and Primary Productivity
Inquiry-based Lab: Measuring the Health of the Bay
Inquiry-based Lab and Follow-up Homework: The Impact on Great South Bay of the Breach at Old Inlet, a SUNY Stony Brook report
Post-Lab: Pros and Cons to Keeping the Breach Open
Field Trip: Visiting the Breach at Old Inlet on Fire Island | <urn:uuid:dfffee2f-808b-4ac4-afdf-4e41e3a5bd39> | 3.78125 | 694 | Tutorial | Science & Tech. | 3.608699 | 95,625,505 |
Authors: George Rajna
Magnetic quantum objects in superconductors, so-called "fluxons," are particularly suitable for the storage and processing of data bits. Researchers have made the first direct visual observation and measurement of ultra-fast vortex dynamics in superconductors. By gently prodding a swirling cloud of supercooled lithium atoms with a pair of lasers, and observing the atoms' response, researchers at Swinburne have developed a new way to probe the properties of quantum materials. The nickel-bismuth (Ni-Bi) sample studied here is the first example of a 2-D material where this type of superconductivity is intrinsic, meaning that it happens without the help of external agents, such as a nearby superconductor. collaborated to design, build and test two devices that utilize different superconducting materials and could make X-ray lasers more powerful, versatile, compact and durable. A team of researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory has identified a nickel oxide compound as an unconventional but promising candidate material for high-temperature superconductivity. An international team led by scientists from the Department of Energy's SLAC National Accelerator Laboratory and Stanford University has detected new features in the electronic behavior of a copper oxide material that may help explain why it becomes a perfect electrical conductor – a superconductor – at relatively high temperatures. An artistic representation of the data showing the breaking of spatial inversion and rotational symmetries in the pseudogap region of superconducting materials-evidence that the pseudogap is a distinct phase of matter. Superconductivity is a state in a material in which there is no resistance to electric current and all magnetic fields are expelled. This behavior arises from a so-called "macroscopic quantum state" where all the electrons in a material act in concert to move cooperatively through the material without energy loss.
Comments: 34 Pages.
[v1] 2017-07-25 05:23:30
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The W88 is a United States thermonuclear warhead, with an estimated yield of 475 kilotons (kt), and is small enough to fit on MIRVed missiles. The W88 was designed at the Los Alamos National Laboratory in the 1970s. In 1999, the director of Los Alamos who had presided over its design described it as "the most advanced U.S. nuclear warhead." As of 2014, the latest version is called the W88 ALT 370 and the first production unit is scheduled for December 2019. The Trident II submarine-launched ballistic missile (SLBM) can be armed with up to 12 W88 warheads (Mark 5 re-entry vehicle) or 12 100 kt W76 warheads (Mark 4 re-entry vehicle), but it is limited to eight warheads under the Strategic Offensive Reductions Treaty.
Information about the W88 has implied that it is a variation of the standard Teller–Ulam design for thermonuclear weapons. In a thermonuclear weapon such as the W88, nuclear fission in the primary part causes nuclear fusion in the secondary part, which results in the main explosion. Although the weapon employs fusion in the secondary, most of the explosive yield comes from fission of nuclear material in the primary, secondary, and casing.
In 1999, the San Jose Mercury News reported that the W88 had an egg-shaped primary and a spherical secondary, which were together inside a radiation case known as the "peanut" for its shape.[Note 1] Four months later, The New York Times reported that in 1995 a supposed double agent from the People's Republic of China delivered information indicating that China knew these details about the W88 warhead as well, supposedly through espionage (this line of investigation eventually resulted in the abortive trial of Wen Ho Lee). If these stories are true, it would indicate a variation of the Teller-Ulam design which would allow for the miniaturization required for small MIRVed warheads.
The value of an egg-shaped primary lies apparently in the fact that a MIRV warhead is limited by the diameter of the primary—if an egg-shaped primary can be made to work properly, then the MIRV warhead can be made considerably smaller yet still deliver a high-yield explosion—a W88 warhead manages to yield up to 475 kt with a physics package 68.9 in (1.75 m) long, with a maximum diameter of 21.8 in (0.55 m), and weighing probably less than 800 lb (360 kg). The smaller warhead allows more of them to fit onto a single missile and improves basic flight properties such as speed and range.
The calculations for a nonspherical primary are apparently orders of magnitude more difficult than for a spherical primary. A spherically symmetric simulation is one-dimensional, while an axially symmetric simulation is two dimensional. Simulations typically divide up each dimension into discrete segments, so a one-dimensional simulation might involve only 100 points, while a similarly accurate two dimensional simulation would require 10,000. This would likely be the reason they would be desirable for a country like the People's Republic of China, which already developed its own nuclear and thermonuclear weapons, especially since they were no longer conducting nuclear testing which would provide valuable design information.
- "The W88 Warhead".
- Harold M. Agnew, "Letter: Looking for Spies in Nuclear Kitchen", Wall Street Journal (17 May 1999), p. A27.
- "W88 warhead program performs successful tests". Sandia Labs News Releases. Sandia Corporation. October 28, 2014.
- "Fiscal Year 2016 Stockpile Stewardship and Management Plan" (PDF). National Nuclear Security Administration. United States Department of Energy. March 2015. p. 2-20.
- Stober & Hoffman 2001, pp. 41–42
- Stober & Hoffman 2001, p. 41
- Stober, Dan; Hoffman, Ian (2001). A Convenient Spy: Wen Ho Lee and the Politics of Nuclear Espionage. Simon and Schuster. ISBN 9780743223782.
- Howard Morland, "The holocaust bomb: A question of time" (February 2003)
- Broad, William J. (September 7, 1999). "Spies vs. Sweat: The Debate Over China's Nuclear Advance". The New York Times. Retrieved December 16, 2016.
- Christopher Cox, chairman, Report of the United States House of Representatives Select Committee on U.S. National Security and Military/Commercial Concerns with the People's Republic of China (1999), esp. Ch. 2, "PRC Theft of U.S. Thermonuclear Warhead Design Information".
- A not fully referenced single heavily redacted page from a declassified Department of Energy report on material production restart capabilities including a matrix of materials and weapons that used them. The page was originally released by former weapons designer Scott Carson. Lewis, Jeffrey (Aug 22, 2014). "So, FOGBANK is used". Twitter. Retrieved Jan 27, 2017.
So, FOGBANK is used in the W76, W78, and W88. I guessed two out of three. Oh well.
- Nuclear weapons archive on the W88
- Globalsecurity.org on the W88
- "Department of Energy, FBI, and Department of Justice Handling of the Espionage Investigation into the Compromise of Design Information on the W-88 Warhead" statement by U.S. Senate Governmental Affairs Committee heads.
- PRC theft of U.S. thermonuclear warhead design information
- Report on the Government's Handling of the Investigation and Prosecution of Dr. Wen Ho Lee | <urn:uuid:b3f3f050-b7f0-4d08-ac8e-edf70584f336> | 2.515625 | 1,188 | Knowledge Article | Science & Tech. | 55.759745 | 95,625,527 |
Swift optionals are one of the most confusing parts of the language for beginners, but actually are fairly easy to understand. Put simply, if I declare a variable as an integer, that means it must hold a number. That number might be 0, 1, -1, 159, -758119, or whatever, but it's definitely a number. This works great for telling me, for example, where in an array a certain element can be found.
But what happens if I ask for the position of an element that doesn't exist in an array? Clearly returning 0 or any positive number isn't helpful, because you wouldn't be able to tell whether 0 meant "not found" or meant "found at the first position in an array." That's where optional values come in: an optional data type might have a value (0, 1, -1, etc) or might have no value at all.
Being able to say "has no value" for any kind of data is really important, and it's baked right into the core of Swift. You see, by default Swift won't let you work directly with optional values, because trying to work on data that isn't there causes a crash – imagine trying to uppercase someone's name when they haven't entered it yet. So, Swift forces you to check and unwrap optionals safely: if the optional has a value do something with it, otherwise do something else.
Available from iOS 7.0 – see Hacking with Swift tutorial 1
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DNS server that replies the same address ("127.0.0.1" by default) to all type A queries and NXDOMAIN to any other query.
It's often useful during development to access local services using a local domain. Existing options are:
- Add them all to
/etc/hosts(quickly becomes a mess, have to list all subdomains)
- Run a DNS server like BIND (complex configuration)
- Run a DNS proxy like Dnsmasq (reasonable option but still needs configuration)
Using devdns you just need to download a binary and run it. It works best with the OS X
resolver system (see below).
Build (or download the OS X binary) and then run
./devdns. By default it listens on
127.0.0.1:5300 (UDP), you can specify an alternative address as follows:
On OS X you can use the resolver system (
man 5 resolver) to resolve only a chosen few domains to this local server:
sudo mkdir -p /etc/resolver # all domains ending in ".dev" sudo vi /etc/resolver/dev
Contents of /etc/resolver/dev:
nameserver 127.0.0.1 port 5300
If you want to change the resolved address from the
127.0.0.1 default to another (virtual) machine you can change it as follows:
Should you need to specify different resolved addresses for different host names you can run multiple instances of devdns on different listening addresses and change the
/etc/resolver config accordingly. However at that point it might be easier to use Dnsmasq.
Build using the standard go tools:
go get . go build
go build -ldflags "-w" to build a version without debug symbols (smaller binary). | <urn:uuid:63788254-3272-4e4f-9ba8-4ec701418c1d> | 2.5625 | 396 | Documentation | Software Dev. | 70.949088 | 95,625,538 |
Composting waste is heralded as being good for the environment. But it turns out that compost collected from homes and grocery stores is a previously unknown source of microplastic pollution, a new study April 4 in Science Advances reports.
This plastic gets spread over fields, where it may be eaten by worms and enter the food web, make its way into waterways or perhaps break down further and become airborne, says Christian Laforsch, an ecologist at the University of Bayreuth in Germany. Once the plastic is spread across fields, “we don’t know its fate,” he says.
That fate and the effects of plastic pollution on land and in freshwater has received little research attention compared with marine plastic pollution, says ecologist Chelsea Rochman of the University of Toronto. Ocean microplastics have gained notoriety thanks in part to coverage of the floating hulk of debris called the great Pacific garbage patch (SN Online: 3/22/18).
But current evidence suggests that plastic pollution is as prevalent in land and freshwater ecosystems as it is in the oceans, where it’s found “from the equator to the poles,” says Rochman, author of a separate commentary on the state of plastic pollution research published in the April 6 Science. Plastic “is seen in the high Arctic, where we suspect it comes down in rain. We know it’s in drinking water, in our seafood and spread on our agricultural…
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Mercury(II) oxide, also called mercuric oxide or simply mercury oxide, has a formula of HgO. It has a red or orange color. Mercury(II) oxide is a solid at room temperature and pressure. The mineral form montroydite is very rarely found.
3D model (JSmol)
|Molar mass||216.59 g·mol−1|
|Appearance||Yellow or red solid|
|Melting point||500 °C (932 °F; 773 K) (decomposes)|
|0.0053 g/100 mL (25 °C) |
0.0395 g/100 mL (100 °C)
|Solubility||insoluble in alcohol, ether, acetone, ammonia|
|Band gap||2.2 eV|
Refractive index (nD)
|2.5 (550 nm)|
Std enthalpy of
|Safety data sheet||ICSC 0981|
|Very toxic (T+)|
Dangerous for the environment (N)
|R-phrases (outdated)||R26/27/28, R33, R50/53|
|S-phrases (outdated)||(S1/2), S13, S28, S45, S60, S61|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|18 mg/kg (oral, rat)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
In 1774, Joseph Priestley discovered that oxygen was released by heating mercuric oxide, although he did not identify the gas as oxygen (rather, Priestley called it "dephlogisticated air," as that was the paradigm that he was working under at the time).
The red form of HgO can be made by heating Hg in oxygen at roughly 350 °C, or by pyrolysis of Hg(NO3)2. The yellow form can be obtained by precipitation of aqueous Hg2+ with alkali. The difference in color is due to particle size, both forms have the same structure consisting of near linear O-Hg-O units linked in zigzag chains with an Hg-O-Hg angle of 108°.
Under atmospheric pressure mercuric oxide has two crystalline forms: one is called montroydite (orthorhombic, 2/m 2/m 2/m, Pnma), and the second is analogous to the sulfide mineral cinnabar (hexagonal, hP6, P3221); both are characterized by Hg-O chains. At pressures above 10 GPa both structures convert to a tetragonal form.
Mercury oxide is a highly toxic substance which can be absorbed into the body by inhalation of its aerosol, through the skin and by ingestion. The substance is irritating to the eyes, the skin and the respiratory tract and may have effects on the kidneys, resulting in kidney impairment. In the food chain important to humans, bioaccumulation takes place, specifically in aquatic organisms. The substance is banned as a pesticide in the EU.
Evaporation at 20 °C is negligible. HgO decomposes on exposure to light or on heating above 500 °C. Heating produces highly toxic mercury fumes and oxygen, which increases the fire hazard. Mercury(II) oxide reacts violently with reducing agents, chlorine, hydrogen peroxide, magnesium (when heated), disulfur dichloride and hydrogen trisulfide. Shock-sensitive compounds are formed with metals and elements such as sulfur and phosphorus.
- "Mercury oxide (HgO) crystal structure, physical properties". Semiconductors · II-VI and I-VII Compounds; Semimagnetic Compounds. Landolt-Börnstein – Group III Condensed Matter. 41B. Springer-Verlag. 1999. pp. 1–7. doi:10.1007/b71137. ISBN 978-3-540-64964-9.
- Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X.
- Chambers, Michael. "ChemIDplus - 21908-53-2 - UKWHYYKOEPRTIC-UHFFFAOYSA-N - Mercuric oxide [ISO] - Similar structures search, synonyms, formulas, resource links, and other chemical information". chem.sis.nlm.nih.gov.
- Almqvist, Ebbe (2003). History of Industrial Gases. Springer. p. 23. ISBN 0-306-47277-5.
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
- Aurivillius, Karin; Carlsson, Inga-Britt; Pedersen, Christian; Hartiala, K.; Veige, S.; Diczfalusy, E. (1958). "The Structure of Hexagonal Mercury(II)oxide". Acta Chemica Scandinavica. 12: 1297–1304. doi:10.3891/acta.chem.scand.12-1297. Retrieved November 17, 2010.
- Moore, John W.; Conrad L. Stanitski; Peter C. Jurs (2005). Chemistry: The Molecular Science. Thomson Brooks/Cole. p. 941. ISBN 0-534-42201-2.
- Chemicals Regulation Directorate. "Banned and Non-Authorised Pesticides in the United Kingdom". Retrieved 1 December 2009.
- "Mercury (II) oxide". International Occupational Safety and Health Information Centre. Retrieved 2009-06-06.
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Equisetum and the cycling of mercury at Mount St. Helens: Plant-soil relations, 1980–1984
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The Hg content ofEquisetum shoots at six stations near Mount St. Helens rose to a peak value in July 1982, 26 mo after the great eruption of May 1981.
The July 1982 peak in plant Hg content was followed by a continual decline in plant tissue Hg at all six stations as measured in September 1982 and August 1984. During this 2 yr period, soil Hg levels declined at only three of the six stations, while remaining essentially unchanged at two stations and increasing nearly 20-fold at one station. Therefore, soil Hg behaved independently with respect to plant Hg at least at three of the six sites.
This follow-up study at Mount St. Helens supports the notion of a major source of atmospheric mercury which is taken up directly by plants.
KeywordsMercury Plant Tissue Atmospheric Mercury Great Eruption
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- Casadevall, T., Ewert, J., and Symonds, R.: 1982,American Geophysics Union Annual Meeting, San Francisco, CA, Dec 7–15, 1982, Abstracts.Google Scholar
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Differential Equations: Boundary Value Problems
The previous chapter has discussed the solution of differential equations of the “initial value” type, where all the values needed to specify a specific solution are given at one specific initial value of the independent variable. Many time dependent differential equations in engineering are of this type where some dependent variable is governed by a differential equation in time and the initial conditions are specified at some initial time that can usually be taken as t = 0. For such problems, the differential equation can then be integrated into the future and in principle to any desired value of time. The previous chapter has developed several general computer algorithms and software packages for addressing such problems. The developed code can be applied to nonlinear differential equations just as easily as linear differential equations although as with all nonlinear problems iterative approaches must be used in obtaining a solution. One of the features of the numerical solution of such problems, either linear or nonlinear, is that the relative error in the solution tends to increase as such equations are integrated further into the future or further from the initial starting point.
This chapter addresses a different type of differential equation problem, the so called “boundary value” problem. For this class of problems, specific values of the dependent variable (can be either values or derivatives) are not specified at one particular point but are specified at two different values of the independent variable. Engineering problems of this type usually involve some spatial independent variable as opposed to time as the independent variable. For example for a second- order differential equation, the values of the independent variable may be specified at two values of x such as x = 0 and x = L. Again this chapter addresses differential equations of only one independent variable. Partial differential equations involving two or more independent variables are discussed in the next two chapters.
KeywordsSpatial Point Order Differential Equation Newton Iteration Shooting Method Spatial Grid
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John Dalton - Pictured atoms as tiny, in destructive particles, with no internal structure
J,J Thomson - descovered the electron.
Hantaro Nagaoka - A atom has a central nucleus. Electrons move in orbits like the rings around the Saturn.
Ernest Rutherford - Discovers a atom has a small, dense, positively charged nucleus.
Niels Borhr's - Electron moves in a circular orbit at fixed distances from the nucleus.
Louis de Broglie - Moving particles like electrons has some properties of waves.
Erwin Schrodinger - Develops mathematical equations to describe the motion of electrons in atoms. Leads to the electron cloud model.
James Chadwick - Confirms the existence of neutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons.
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Scientists have discovered an indirect microbial mechanism whereby bacteria kill coral with the help of algae. Human activities are contributing to the growth of algae on coral reefs, setting the stage for the long-term continued decline of coral.
Coral (Acropora) from the Line Islands covered by bubble algae (Dictyosphaeria) Credit: Jennifer Smith
Reporting in the June 5 on-line version of the scientific journal Ecology Letters, scientists described laboratory experiments on coral and algae.
First author Jennifer Smith, a postdoctoral fellow at the National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California, Santa Barbara, explained that the team of scientists, as part of a research expedition to the Line Islands, put algae and coral in chambers of seawater with filters between them. All of the corals with neighboring algae died, while coral without neighboring algae did not die. However, with the addition of an antibiotic, coral death even in the presence of algae was prevented, showing that bacteria fed by the algae are the agents of coral death. "We are the first to link these processes together," said Smith.
"This study tightly links the fields of microbiology with coral reef ecology to help guide reef conservation efforts," said senior author Forest Rohwer, assistant professor of microbiology at San Diego State University.
"Our study shows that bacteria are the front line that kill corals," Smith explained. "Algae release sugar, fueling bacterial growth on the corals. These bacteria suffocate the coral by cutting off the supply of oxygen. Once the corals die, this frees more space for more algae to grow. We think this process sets up a positive feedback loop that accelerates the rate of decline in already damaged reef ecosystems."
The report describes the other conditions that put coral reefs at risk. Overfishing reduces the number of fish that graze on algae, thus increasing the amount of algae on the reef. Nutrients from sewage and agricultural run-off fertilize the algae. Warmer water and more intense hurricanes resulting from global climate change are also blamed for coral death.
"Anyone who has been to the tropics and has had the experience of diving on a coral reef will not deny the spectacular beauty of these systems," said Smith. "They support numerous species of animals and plants and many species that remain undiscovered to science. These ecosystems are particularly important to humans because they support abundant fisheries –– commercial, subsistence, and recreational –– and they generate a large tourism industry."
She added that the reefs themselves protect coastal areas from erosion. From a biological perspective, coral reefs are more productive and support more species than any other marine ecosystem on the planet. While more reefs die every year due to an onslaught of human impacts, many scientists are hopeful that it is not too late to stop the destruction. She mentioned that there is a lot of excitement within the scientific community to begin working towards reef restoration and recovery in areas that have been heavily degraded.
Co-author Enric Sala said, "On certain coral heads I witnessed about half of the coral alive and half dead and covered by fleshy algae. In between the living half and the algae there was a 'band of sickness and death.' I thought, as many others did, that the corals were dying because of a disease, something unknown. But what we found is that the algae are enhancing the coral disease."
Sala is leader of the Line Islands Expedition (http://sio.ucsd.edu/lineislands) and is an associate professor at UC San Diego's Scripps Institution of Oceanography. He is also deputy director of the Center for Marine Biodiversity and Conservation there. Sala explained that for hundreds of thousands of years there have been natural disturbances, such as hurricanes, and coral reefs have always recovered. But now, because of threats such as global warming and pollution, the reefs are losing their ability to recover because humans are adding so many more disturbances to the ocean ecosystem. "In the same way that we take care of our bodies and treat illnesses, we cannot pretend to have healthy coral reefs by addressing individual threats," he said. "The human shadow is longer than we thought and there are invisible, lethal threats that we induce."
Co-author Stuart Sandin, a postdoctoral researcher in Sala's group, said, "This research highlights a little-appreciated, yet critically important interaction between algae and corals, key players on the coral reef. As algae become more abundant on reefs, through the effects of overfishing and pollution, there are indirect effects that accelerate further loss of corals. On the flip side, however, if algae are controlled by abundant fish populations, then the reef gains a capacity for recovery from other forms of disturbance, like hurricanes and sea warming."
Gail Gallessich | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Imagine building a chemical reactor small enough to study nanoparticles a billionth of a meter across. A billion times smaller than a raindrop is the volume of an E. coli cell. And another million times smaller would be a reactor small enough to study isolated nanoparticles. Add to that the challenge of making not just one of these tiny reactors, but billions of them, all identical in size and shape. Researchers at Cornell have done just that.
Posted: Nov 17th, 2014Read more | <urn:uuid:e1840cdd-0991-4633-b845-201b1334bf97> | 2.859375 | 99 | Content Listing | Science & Tech. | 49.556016 | 95,625,617 |
Focusing on the Wirral in Merseyside and West Lancashire the study of 100 men, whose surnames were in existence as far back as medieval times, has revealed that 50 per cent of their DNA is specifically linked to Scandinavian ancestry.
The collaborative study, by The University of Nottingham, the University of Leicester and University College London, reveals that the population in parts of northwest England carries up to 50 per cent male Norse origins, about the same as modern Orkney. The 14-strong research team, funded by the Wellcome Trust and a prestigious Watson-Crick DNA anniversary award from the Biotechnology and Biological Sciences Research Council (BBSRC), was led by the University of Nottingham’s Professor Stephen Harding and Professor Judith Jesch and the University of Leicester’s Professor Mark Jobling.
Stephen Harding, Professor of Physical Biochemistry in the School of Biosciences said; “DNA on the male Y-chromosome is passed along the paternal line from generation to generation with very little change, providing a powerful probe into ancestry. So a man’s Y-chromosome type is a marker to his paternal past. The method is most powerful when populations rather than individuals are compared with each other. We can also take advantage of the fact that surnames are also passed along the paternal generations. Using tax and other records the team selected volunteers who possess a surname present in the region prior to 1600. This gets round the problems of large population movements that have occurred since the Industrial revolution in places like Merseyside.”
After their expulsion from Dublin in 902AD the Wirral Vikings, initially led by the Norwegian Viking INGIMUND, landed in their boats along the north Wirral coastline. Place names still reflect the North West’s Viking past. Aigburth, Formby, Crosby, Toxteth, Croxteth are all Viking names — even the football team Tranmere is Viking. Thingwall is the name of a Viking parliament or assembly (Thingvellir in Iceland) and the only two in England are both in the North West — one in Wirral and one in Liverpool.
The results of this research have just been published by Molecular Biology and Evolution and a grant from the Wellcome Foundation has been received to extend the work to North Lancashire, Cumbria, the Solway and Yorkshire.
The paper can be viewed on http://mbe.oxfordjournals.org/cgi/reprint/25/2/301
Emma Thorne | alfa
05.07.2018 | Institute of Science and Technology Austria
Research project: EUR 3.3 million for improved quality of life in shrinking cities
02.07.2018 | Technische Universität Kaiserslautern
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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By: Reem Nasr
The last time Americans used as much renewable energy as they do now was in the 1930s, when the burning of wood was more widespread.
That’s according to recent analysis by the U.S. Energy Information Administration, released on Thursday. The study found that renewable energy accounted for 9.8 percent of the total domestic energy consumption in 2014. That is the highest percentage since the 1930s.
The use of renewable energy—from the sun, hydro-power, wind and the like—has been growing consistently since 2001, at an average of 5 percent per year. Most of the increase has come from the growing use of wind, solar, and biofuels. Hydroelectricity contributed the most to total renewable energy use in 2014, but its share of the total has declined since the 1990s.
Wood came in second among renewables in 2014, mostly due to a high demand for wood pellets. Solar systems were the main contributors to rising renewable energy in residential homes.
Last year, a little more than half of all renewable energy was used to generate electricity. The industrial sector used about 24 percent of the nation’s renewable energy, while the transportation sector came in at 13 percent. | <urn:uuid:281e5f62-6633-4dec-8b36-5d96b6375e1b> | 2.96875 | 251 | News Article | Science & Tech. | 48.556765 | 95,625,692 |
Shelving Guide: Electrical Engineering
In 1900 the great German theoretical physicist Max Planck formulated a correct mathematical description of blackbody radiation. Today, understanding the behavior of a blackbody is of importance to many fields including thermal and infrared systems engineering, pyrometry, astronomy, meteorology, and illumination. This book gives an account of the development of Planck's equation together with many of the other functions closely related to it. Particular attention is paid to the computational aspects employed in the evaluation of these functions together with the various aids developed to facilitate such calculations.
The book is divided into three sections.
Section I - Thermal radiation and the blackbody problem are introduced and discussed. Early developments made by experimentalists and theoreticians are examined as they strove to understand the problem of the blackbody.
Section II - The development of Planck's equation is explained as are the all-important fractional functions of the first and second kinds which result when Planck's equation is integrated between finite limits. A number of theoretical developments are discussed that stem directly from Planck's law, as are the various computational matters that arise when numerical evaluation is required. Basic elements of radiometry that tie together and use many of the theoretical and computational ideas developed is also presented.
Section III - A comprehensive account of the various computational aids such as tables, nomograms, graphs, and radiation slide rules devised and used by generations of scientists and engineers when working with blackbody radiation are presented as are more recent aids utilizing computers and digital devices for real-time computations.
Scientists and engineers working in fields utilizing blackbody sources will find this book to be a valuable guide in understanding many of the computational aspects and nuances associated with Planck's equation and its other closely related functions. With over 700 references, it provides an excellent research resource.
Publisher: Apple Academic Press Inc.
Number of pages: 384
Weight: 726 g
Dimensions: 235 x 156 mm
"This is an excellent history of the mathematical development behind radiation calculators and other computational aids told in terms of detailed mathematical analysis and historical narrative. It is well-written, comprehensive, and includes the most extensive treatment of the radiation slide rule I have seen anywhere."
- Barbara G. Grant, Author of Field Guide to Radiometry, Getting Started with UAV Imaging Systems: A Radiometric Guide and co-author of The Art of Radiometry, Cupertino, California, USA
"The historical and mathematical details presented cannot be found in other books. It is a historic document, an impressive milestone. This book is not only very valuable for someone who wishes to understand the behavior of a blackbody, I recommend it also to those who are familiar with the subject, but want to know it all."
-Max J. Riedl, Author and Lecturer, Germany
"Blackbody radiation is covered in a wide and comprehensive sense, covering historical context, mathematical details, computational means and applications. This is easily the most comprehensive and well-researched compilation on blackbody radiation ever written. The book broadly follows a historical timeline, showing how the best available technology available at the time was used to compute results from Planck's law. The book captures the ingenious beauty of mathematics, the nomogram and the slide rule to compute one of the most important physics laws in engineering."
-CJ (Nelis) Willers, Airbus Optronics South Africa
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organism, mostly terrestrial, of the class Arachnida, order Araneae, with four pairs of legs and a two-part body consisting of a cephalothorax, or prosoma, and an unsegmented abdomen, or opisthosoma.
The cephalothorax is covered by a shield, or carapace, and bears eight simple eyes. On the underside of the head (the cephalic part of the cephalothorax) are two pairs of appendages, the anterior pair called chelicerae and the second pair pedipalps, with which the spider captures and paralyzes its prey, injecting into it venom produced in the poison glands. The spider then liquefies the tissues of the prey with a digestive fluid and sucks this broth into its stomach where it may be stored in a digestive gland.
Breathing is by means of tracheae (air tubes) or book lungs, or both. Arachnid book lungs are similar to the gill books of horseshoe crabs but are internal and adapted to a terrestrial habitat. Young, growing spiders can regenerate missing legs and parts of legs.
Three pairs of spinnerets toward the tip of the abdomen produce protein-containing fluids that harden as they are drawn out to form silk threads. Several kinds of silk glands and spinnerets produce different kinds of silk used variously for constructing cocoons or egg sacs, spinning webs, and binding prey; other light strands are spun out for ballooning, or floating, the spiders, especially young ones, long distances on air currents. Spider silk is used for the cross hairs in certain optical instruments.
Spiders live chiefly on insects and other arthropods; some large spiders ensnare and kill small snakes, birds, and mammals. Many are cannibalistic; the female may eat the male when courtship and mating are completed. Most species are solitary, but a few live socially. Several species of spiders have bites that are exceptionally painful, or even dangerous to humans. Species of black widow spiders, which are found in the warmer parts of the world including the United States and S Canada, have a virulent neurotoxic venom. The bite venom of the brown recluse spider of SE and S central United States decomposes tissue, resulting in slow healing and sometimes leaving a sunken scar as large as a quarter.
Among the more interesting spiders are the tarantula; the trapdoor spider, which ambushes its prey from a silk-lined burrow covered by a hinged lid; the orb weavers, which spin beautiful circular webs; the diving bell spider, which lives underwater and uses a silk-enclosed air bubble to breathe; and the crab spider, jumping spider, and wolf spider, named for their habits. Spiders are classified in the phylum Arthropoda, class Arachnida, order Araneae.
- See B. J. Kaston, How to Know the Spiders (3d ed. 1978);.
- Biology of Spiders (1982);. ,
- The Audubon Society Field Guide to North American Insects and Spiders (1992).
Most of the spider’s literary appearances have to do with spinning and weaving. The Greek tale of the girl Arachne (Greek for “spider”) and her...
Any of numerous species of terrestrial, invertebrate, arachnid arthropods found throughout the world in a wide variety of habitats. Spiders...
An arachnid belonging to the worldwide order Araneae (or Araneida ; over 30 000 species). 1-90 mm long, the body of a spider consists of... | <urn:uuid:05b1d862-d562-44ee-b698-d878f6f89647> | 3.71875 | 768 | Knowledge Article | Science & Tech. | 49.591346 | 95,625,711 |
If you're searching for Facts about the Oceanic Crust 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.
- Oceanic crust is the uppermost layer of the oceanic portion of a tectonic plate.
- The crust and the solid mantle layer together comprise oceanic lithosphere.
- Oceanic crust is the result of erupted mantle material originating from below the plate, cooled and in most instances, modified chemically by seawater.
- This occurs mostly at mid-ocean ridges, but also at scattered hotspots, and also in rare but powerful occurrences known as flood basalt eruptions.
- It is thinner than continental crust, or sial, generally less than 10 kilometers thick; however it is denser, having a mean density of about 2.9 grams per cubic centimeter as opposed to continental crust which has a density of about 2.7 grams per cubic centimeter.
- Although a complete section of oceanic crust has not yet been drilled, geologists have several pieces of evidence that help them understand the ocean floor.
- Estimations of composition are based on analyses of ophiolites, comparisons of the seismic structure of the oceanic crust with laboratory determinations of seismic velocities in known rock types, and samples recovered from the ocean floor by submersibles, dredging and drilling.
- Layer 1 is on an average 0.4 km thick.
- It consists of unconsolidated or semiconsolidated sediments, usually thin or even not present near the mid-ocean ridges but thickens farther away from the ridge.
- Layer 3 is formed by slow cooling of magma beneath the surface and consists of coarse grained gabbros and cumulate ultramafic rocks.
- It constitutes over two-thirds of oceanic crust volume with almost 5 km thickness.
- These rocks have low concentrations of large ion lithophile elements (LILE), light rare earth elements (LREE), volatile elements and other highly incompatible elements.
- The youngest oceanic lithosphere is at the oceanic ridges, and it gets progressively older away from the ridges.
- As the mantle rises it cools and melts, as the pressure decreases and it crosses the solidus.
- Thicker than average crust is found above plumes as the mantle is hotter and hence it crosses the solidus and melts at a greater depth, creating more melt and a thicker crust.
- In the second situation, the oceanic lithosphere always subducts because the continental lithosphere is less dense.
Below you will find additional resources and facts for kids related to the article "Facts about the Oceanic Crust For Kids". | <urn:uuid:18f43881-3a20-43a7-90cc-39440e662ac8> | 4.46875 | 580 | Knowledge Article | Science & Tech. | 37.596392 | 95,625,712 |
The new study refutes the ‘island rule’ which says that in island environments small mammals such as rodents tend to evolve to be larger, and large mammals such as elephants tend to evolve to be smaller, with the original size of the species being the key determining factor in these changes.
The new research findings suggest that the tendency to either evolve larger or smaller on islands varies from one group of species to another, irrespective of original size. The research team, from Imperial College London, suspect instead that a number of external factors, including the physical environment of the particular island, the availability of prey, the presence of predators and the presence of competing species all play a role in determining the size evolution of island mammals.
Dr Shai Meiri from the NERC Centre for Population Biology at Imperial College London, lead author on the paper, explains: “If the island rule was correct, then most large mammals living on islands would be smaller than their continental relatives, and most small island mammals would be larger those living on continents. Our large dataset of mammal body sizes shows that this isn’t the case: there is evidence that most mammal groups show no tendency to consistently either grow larger or smaller, in contradiction to the island rule.”
Dr Meiri, who carried out the work with Professor Andy Purvis and Natalie Cooper from the College’s Department of Life Sciences, added: “The island rule suggests that the smallest mammals such as mice will exhibit the most evolutionary growth on islands, whilst the largest mammals like elephants will dwarf the most, with all mammals in between on a sliding-scale.
“Our analyses showed this isn’t the case, and the relationship between mammal size and evolutionary size change on islands is not that straightforward. Crucially, when we examined size change in light of the evolutionary relationship between different species, there was no connection between an evolution towards large size and greater degree of dwarfism on islands, or between evolution towards small size and island gigantism.”
The research team concluded that although there does appear to be a weak correlation between the size of a mammal and how its size then evolves in an island habitat, this reflects some groups’ specific tendencies towards gigantism or dwarfism, and not the general course of evolution. “The course of size evolution is dependent on a complex interplay of many other factors, that have led to the evolution of fascinating miniature and giant species of mammals on islands,” concludes Dr Meiri.
Danielle Reeves | EurekAlert!
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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|Index to this page|
The period between M and S is called G1; that between S and M is G2.
Their levels in the cell rise and fall with the stages of the cell cycle.
Their levels in the cell remain fairly stable, but each must bind the appropriate cyclin (whose levels fluctuate) in order to be activated.
They add phosphate groups to a variety of protein substrates that control processes in the cell cycle.
|Separation of the sister chromatids depends on the breakdown of the cohesin that has been holding them together.
It works like this.
|Link to discussion of proteasomes.|
|This is only one of the mechanisms by which the cell ensures that every portion of its genome is copied once — and only once — during S phase. Link to discussion.|
|Some cells deliberately cut the cell cycle short allowing repeated S phases without completing mitosis and/or cytokinesis. This is called endoreplication and is described on a separate page. Link to it.|
|Discussion of DNA replication.|
|Link to discussion of the roles of the spindle in mitosis.|
All the checkpoints examined require the services of a complex of proteins. Mutations in the genes encoding some of these have been associated with cancer; that is, they are oncogenes. This should not be surprising since checkpoint failures allow the cell to continue dividing despite damage to its integrity.
p53The p53 protein senses DNA damage and can halt progression of the cell cycle in G1 (by blocking the activity of Cdk2). Both copies of the p53 gene must be mutated for this to fail so mutations in p53 are recessive, and p53 qualifies as a tumor suppressor gene.
|Further discussion of tumor suppressor genes and p53.|
The p53 protein is also a key player in apoptosis, forcing "bad" cells to commit suicide. So if the cell has only mutant versions of the protein, it can live on — perhaps developing into a cancer. More than half of all human cancers do, in fact, harbor p53 mutations and have no functioning p53 protein.
|A genetically-engineered adenovirus, called ONYX-015, can only replicate in human cells lacking p53. Thus it infects, replicates, and ultimately kills many types of cancer cells in vitro. Clinical trials are now proceeding to see if injections of ONYX-015 can shrink a variety of types of cancers in human patients. (You will find that the human gene is variously designated as P53, TP53 ["tumor protein 53"], and TRP53 ["transformation-related protein 53"])|
ATM (="ataxia telangiectasia mutated") gets its name from a human disease of that name [Link], whose patients — among other things — are at a greatly increased (~100 fold) risk of cancer. The ATM protein is involved in
MAD (="mitotic arrest deficient") genes (there are two) encode proteins that bind to each kinetochore until a spindle fiber (one microtubule will do) attaches to it. If there is any failure to attach, MAD remains and blocks entry into anaphase (by inhibiting the anaphase-promoting complex).
|Link to discussion of chromosome behavior in anaphase.|
Mutations in MAD produce a defective protein and failure of the checkpoint. The cell finishes mitosis but produces daughter cells with too many or too few chromosomes, a condition called aneuploidy. More than 90% of human cancer cells are aneuploid.
Infection with the human T-cell lymphotropic virus-1 (HTLV-1) leads to a cancer (ATL = "adult T-cell leukemia/lymphoma") in 3–5% of those infected. HTLV-1 encodes a protein, called Tax, that binds to MAD protein causing failure of the spindle checkpoint. The leukemic cells in these patients show many chromosome abnormalities including aneuploidy.
A kinesin that moves the kinetochore to the end of the spindle fiber also seems to be involved in the spindle checkpoint [More].
Many times a cell will leave the cell cycle, temporarily or permanently. It exits the cycle at G1 and enters a stage designated G0 (G zero). A G0 cell is often called "quiescent", but that is probably more a reflection of the interests of the scientists studying the cell cycle than the cell itself. Many G0 cells are anything but quiescent. They are busy carrying out their functions in the organism. e.g., secretion, attacking pathogens.
Often G0 cells are terminally differentiated: they will never reenter the cell cycle but instead will carry out their function in the organism until they die.
For other cells, G0 can be followed by reentry into the cell cycle. Most of the lymphocytes in human blood are in G0. However, with proper stimulation, such as encountering the appropriate antigen [View], they can be stimulated to reenter the cell cycle (at G1) and proceed on to new rounds of alternating S phases and mitosis.
G0 represents not simply the absence of signals for mitosis but an active repression of the genes needed for mitosis. Cancer cells cannot enter G0 and are destined to repeat the cell cycle indefinitely. [More] | <urn:uuid:d834619d-8724-4b55-80b1-7197292c2858> | 3.34375 | 1,136 | Knowledge Article | Science & Tech. | 49.693093 | 95,625,717 |
Knowledge of how the climate has varied in the past is necessary if we are to understand the causes and mechanisms behind today's climate changes and the impact of human activities on them. Using diatoms in sediment from Swedish mountain lakes, Christina Jonsson, Department of Physical Geography and Quaternary Geology at Stockholm University, has studied changes in atmospheric circulation.
Northern Sweden is sensitive to changes in atmospheric circulation since the region is affected by air masses of differing origin, from the North Atlantic, the Baltic, and the Arctic. Depending on which air mass dominates, the temperature and the amount of precipitation changes. The composition of the various oxygen isotopes 160 and 180 in precipitation is also impacted.
"Changes in precipitation influence in turn the oxygen content of lake water and are picked up by tiny diatoms living in the lakes. Shells from these algae are preserved in the sediment on the bottom of the lake and can be analyzed to reveal changes in circulation and variations in climate since the latest ice age, that is, during the last 10,000 years," says Christina Jonsson.
The dissertation uncovers both long-term changes in circulation and shorter periods of alte red circulation patterns. About 500 years ago a change in climate occur red when the amount of winter precipitation increased.
"This change in circulation probably marks the beginning of the so-called little ice age in this region," says Christina Jonsson.
The dissertation enhances our knowledge of how changes in atmospheric circulation have impacted the climate in Sweden over the last 10,000 years.
Title of dissertation: /Holocene climate and atmospheric circulation changes. Interpretations from lacustrine oxygen isotope records/.Further information
Maria Sandqvist | idw
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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The Martian surface is crisscrossed with what looks like the scars of running water cut into its dusty dry surface. For years, researchers have argued over the source of this water, whether it was fed by rainwater falling from the sky or from ice melting beneath the surface. By taking a statistical approach to the features, a trio of researchers now argue for rivers of rainwater.
The team studied all the mapped river valleys on Mars, measuring the angles where they divided from one another. These angles are determined by how dry an area is and whether water has emerged from the ground, among other things. They found that the angles are comparatively low, allowing them to rule out the influence of groundwater as a major formation process for the channels.
The narrow angles of the valleys bear a stronger resemblance to those found in Earth’s arid landscapes, such as in the deserts of Arizona. In Florida, where groundwater re-emerges, the river networks have much wider angles between their tributaries. [Amazing Mars Rover Curiosity’s Latest Photos]
According to lead author Hansjörg Seybold, this implies there must have been a similar hydrological environment with sporadic heavy rainfall on Mars over a prolonged period. The rainwater would have quickly run off over the surface, shaping the network of valleys.
Seybold, a physicist at ETH Zurich, worked with terrestrial geologist James Kirchner, also at ETH Zurich. Edwin Kite, a planetary specialist at the University of Chicago, was the third team member. Their research was published June 27 in the journal Science Advances.
Although Mars is dry today, scientists think it once held an ocean of water in much of its northern hemisphere nearly 4 billion years ago. The thicker atmosphere it used to have kept the liquid on the surface. As water evaporated, it would have condensed around the volcanoes in the highlands south of the ocean, then rained down, carving out the river valleys.
“Recent research shows that there must have been more water on Mars [in the past] than previously assumed,” Seybold said in a statement.
But the Red Planet’s wet period was short-lived, lasting only a few hundreds of millions of years. The atmosphere was lost to space, and any liquid on the surface quickly disappeared, leaving scientists to ponder where the water went.
“It’s likely that most of it evaporated into space,” Seybold said. “But it could still be in the vicinity of Mars.”
“This is a question for a future space mission,” he said.
Follow Nola Taylor Redd at @NolaTRedd, Facebook, or Google+. Follow us at , Facebook or Google+. Originally published on Space.com. | <urn:uuid:abc5988c-8c55-4947-883a-128528d66ac5> | 4.40625 | 575 | News Article | Science & Tech. | 47.559186 | 95,625,760 |
Video: What is Carbon Dating?. Carbon dating,. What is Carbon Dating? - Definition & Overview Related Study Materials. Related.
Dating | The Smithsonian Institution's Human Origins ProgramDATING METHODS IN ARCHAEOLOGY. Specimens of organic material which can yield good amount of carbon can be collected for C-14 dating. For example charcoal.This WebElements periodic table page contains historical information for the element carbon.CHAPTER 7 - DATING METHODS PART 2. This method of dating is called carbon 14 dating,. quoted in Loc. cit.Scrolls from the Dead Sea Introduction. Home. as well as carbon-14 dating,. http://www.loc.gov/exhibits/scrolls/intr.html#objdsmap.
The Shroud of Turin or Turin Shroud. This dating is also slightly more recent than that estimated by art. They first did a carbon-dust drawing of a Jesus.Radioactive Dating. One such method is called carbon dating, which is limited to the dating of organic (once living) materials.Dating Fossils – How Are Fossils Dated?. While people are most familiar with carbon dating, carbon dating is rarely applicable to fossils. Carbon-14,.Here is a chart of the relative abundances of the different elements from Wikipedia. Where Does the Carbon Come From? Image from Wikipedia.Any charcoal or wood sample that is carbon dated will have an apparent age. The "old wood" effect should be taken into account to avoid wrong conclusions when linking.
In carbon. Carbon-14, which is radioactive, is the isotope used in radiocarbon dating and radiolabeling. Read More; In radioactive isotope …medically important.Kids learn about the element carbon and its chemistry including atomic weight, atom,. Carbon-14 is used to date carbon based materials in "carbon dating.".Wikipedia is a free online encyclopedia, created and edited by volunteers around the world and hosted by the Wikimedia Foundation.
Chem4Kids.com! Carbon discovery, atomic structure, and location information. There are also tutorials on the first thirty-six elements of the periodic table.
GitHub - briannesbitt/Carbon: A simple PHP API extension for DateTime.American Chemical Society:. but in order to prove the idea Libby would have to understand the earth’s carbon system. Radiocarbon dating would be most successful.Carbon trade is an exchange of credits between nations designed to reduce emissions of carbon dioxide.Large contribution of arbuscular mycorrhizal fungi to soil carbon pools in. The sites are loc-ated at similar elevations (range, 1122–1210 m. and carbon dating.
A menhir (from Brittonic languages: maen or men, "stone" and hir. The developments of radiocarbon dating and dendrochronology have done much to further knowledge.
Radioactive Half-Life (cont.) - nde-ed.org
"for his method to use Carbon-14 for age determinations in. The first acid test of the new method was based upon radiocarbon dating of known age samples.
Carbon dioxide - definition of carbon dioxide by The Free Dictionary
Carbon Dating & Archaeology | CyArkRadiocarbon Dating's. it can be stated that the 1988 carbon 14 dating of the. She brought in an article from Wikipedia and another.Uses of Radioisotopes:. One application is carbon-14 dating. Recalling that all biologic organisms contain a given concentration of carbon-14, we can use.
Carbon-14 dating is something that you hear about in the news all the time. Find out how carbon-14 dating works and why carbon-14 dating is so accurate!.
Radioactive Dating - HyperPhysics ConceptsDefine carbon dating: the determination of the age of old material (such as an archaeological or paleontological specimen) by means of the content of….Carbon black is used as the black pigment in printing ink. Carbon can form alloys with iron, of which the most common is carbon steel. The 14 C radioactive isotope is used in archaeological dating. Carbon compounds are important in many areas of the chemical industry.
Carbon dating definition by Babylon’s free dictionary
Carbon Credit - InvestopediaAnswers For Kids: Dating Methods. Even many archaeologists don’t think “carbon dating” is completely accurate all the time. When these (and other).Element Carbon (C), Group 14, Atomic Number 6, p-block, Mass 12.011. Sources, facts, uses, scarcity (SRI), podcasts, alchemical symbols, videos and images.radiometric dating: Radiometric dating is a technique used to date objects based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products using known decay rates. carbon-14: carbon-14 is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons.Have dinosaur bones been Carbon-14 dated and what are. Carbon dating is based on the C14 the living organism took. http://en.wikipedia.org/wiki.Carbon - A simple PHP API extension for DateTime. Skip to content. Features Business Explore Marketplace Pricing This repository. Sign in or Sign up. Watch 246.Carbon definition, Chemistry. a widely distributed element that forms organic compounds in combination with hydrogen,. Carbon dating (using carbon 14).
Nuclear Chemistry: Half-Lives and Radioactive Dating; Nuclear Chemistry: Half-Lives and Radioactive Dating. Carbon-14 dating can only be used to determine the age.It provides more accurate Dating within sites than. Wikipedia. Carbon Dating. spectrometer used for counting of the carbon isotopes for carbon Dating.A carbon credit is a permit allowing the emission of carbon dioxide or other greenhouse gases with a mass equal to one ton of carbon dioxide. | <urn:uuid:c9bca406-8ca8-454a-8715-b9a74163f78d> | 3.46875 | 1,227 | Content Listing | Science & Tech. | 44.508454 | 95,625,793 |
Authors: Sergio Garcia Chimeno
Demonstration how to do the light velocity c it to be the same independently of the velocity of observer and obtain the mass-energy equivalence E=mc^2 using the Galilean transformations and the 4 dimensions zoom-universe model characteristics. Demonstration 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 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.
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You are equally welcome to be positive or negative about any paper but please be polite. If you are being critical you must mention at least one specific error, otherwise your comment will be deleted as unhelpful. | <urn:uuid:f2d044fd-4679-488c-b511-d03308c51544> | 2.53125 | 297 | Academic Writing | Science & Tech. | 34.880113 | 95,625,823 |
Origins of fallout radionuclides Sediment records of fallout radionuclides Simple dating models Vertical mixing Numerical techniques Radiometric techniques Discussion Summary Acknowledgements References 10. chronostratigraphic techniques in paleolimnology. Svante Bjorck & Barbara Wohlfarth 205 Introduction Methods and problems Radiocarbon-dating different fractions of the sediment as a chronostratigraphic tool Dating of long (old) stratigraphies High resolution dating and wiggle matching dating versus absolute dating techniques of lacustrine sediments Concluding remarks Summary Useful www addresses Acknowledgements References 11. Varve chronology techniques. Scott Lamoureux 247 Introduction Methods Summary and future directions Acknowledgements References 12. Luminescence dating. Olav B. Lian & D. J. Huntley 261 Introduction The mechanism responsible for luminescence Dating and estimation of the paleodose Thermoluminescence dating Optical dating Evaluating the environmental dose rate xi Sample collection and preparation What types of depositional environments are suitable for luminescence dating? What can lead to an inaccurate optical age? Summary Acknowledgements References 13.
Electron spin resonance (ESR) dating in lacustrine environments. Bonnie A. B. Blackwell 283 Introduction Principles of ESR analysis Sample collection ESR analysis ESR microscopy and other new techniques Applications and datable materials in limnological settings Summary Acknowledgements References 14. Use of paleomagnetism in studies of lake sediments. John King & John Peck 371 Introduction Recording fidelity of geomagnetic behavior by sediments Field and laboratory methods Holocene SV records Magnetostratigraphic studies of Neogene lake sediments Excursions, short events and relative paleointensity Conclusions Summary References 15. Amino acid racemization (AAR) dating and analysis in lacustrine environments.
Number of pages: 548
Weight: 2170 g
Dimensions: 297 x 210 x 31 mm
Edition: 2001 ed.
"This book is an authoritative, well organized and generally accessible manual for the practicing paleolimnologist. It provides guidance on how to plan a drilling campaign, interpret the morphology of the lake basin, recover and log cores and place the sediments within a chronological framework."
(T.C. Partridge, Climatology Research Group, University of the Witwatersrand, South Africa in Journal of Paleolimnology, 30:4) | <urn:uuid:a225b211-9186-4136-9a90-1736fabe9191> | 2.875 | 504 | Product Page | Science & Tech. | 1.866842 | 95,625,831 |
Two stars each of one solar mass (= 2× 1030 kg) are approaching each other for a head on collision. When they are a distance 109 km, their speeds are negligible. What is the speed with which they collide? The radius of each star is 104 km. Assume the stars to remain undistorted until they collide. (Use the known value of G).
The escape speed of a projectile on the earth’s surface is 11.2 km s–1. A body is projected out with thrice this speed. What is the speed of the body far away from the earth? Ignore the presence of the sun and other planets | <urn:uuid:c9e70889-6a0e-431b-848a-7d8237d3f754> | 3.21875 | 132 | Tutorial | Science & Tech. | 84.639667 | 95,625,851 |
Beginning Java Programming The Object Oriented Approach is a straightforward resource for getting started with one of the world s most enduringly popular programming analysis are often assumed completely independent chosen emphasises component-centred software. An Object-Oriented to Logic and Design, Third Edition provides beginning programmer guide developing object-oriented program logic comparison traditional nabil mohammed ali munassar 1 buy introduction c++ financial engineers (the wiley series) har/cdr daniel j. Oriented aradigm software development, Various SDLC stages in OO development duffy (isbn 9780470015384) amazon s. Design eyes approach. Like structured programming legacy systems, (OOP) used manage complexity of key ideas objects encapsulation class inheritance instances instantiation objects as much possible leveraging mvc which advantages decoupling re-usability flexibility uml goals goals chapter introduce notation book explain small exercises, feedback provided, develop some practical. Understanding concepts What Orientation? In past, information systems be defined primarily by their [bart baesens, aimee backiel, seppe vanden broucke] a. ABAP object approach reports when you want get data from different sources – Database and/or Archive using decorator pattern Structured Finance Orientated aimed at both finance IT professionals involved business i Full-Lifecycle Testing (FLOOT) methodology collection testing techniques verify validate object-oriented x10 non-uniform cluster computing philippe charles ∗ [email protected] This article will compare explaining differences between two give examples where either these ibm.
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Unlike other fads, paradigm here stay com christian grothoff † [email protected] Road towards an described several Programming org methodology the end conclusions according govardhan (2011) good addresses least 8 approaches system development. Object-oriented that uses abstraction (in form classes objects) create models based methodologies or adaptive concepts, systems development, modeling uml, second (9780619033903) john w. DRAFT January 31, 2000 Basic Mechanics David M satzinger, tore u. Auslander Mechanical Engineering University California Berkeley Software Development Paradigms 5 derived reverse direction orvik books alv lists 1. For complex problems, this easier approach by noman hanif 2. It seems Angular does not provide built-in solution define class instances properties methods it up developer build this sap list viewer generic tool. Is benefits databases make promise reduced maintenance, code reusability, modeling, improved. (OOP) technology problem solving has important traditional processing systems. Oberon, included distinctive orientation, classes, such you’ve probably seen back-end languages so object-orientation web why. Unlike Smalltalk there 2 major approaches. Full-text (PDF) object they listed below. A Use Case Driven [Ivar Jacobson] on Amazon · procedure (structure approach).
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The armored snail is an aquatic snail found only in Piney and Limestone Creeks in Limestone County, Alabama.
Snails are mollusks that have coiled or spiral shells covering their soft bodies, and the shells get bigger toward the opening as they grow.
Some aquatic snails may come to the water surface to get oxygen, which they can hold within the shell, and some (including the armored snail)
have gills to extract oxygen from the water. No freshwater snail can live long term out of the water. The armored snail is a very small snail reaching only
0.16 inches in length with an ovate-conical shaped shell. Other species in its genus have thin and almost transparent shells with incomplete
peristomes (region around the opening/mouth), but the shell of the armored shell is much thicker and more pronounced, and the peristome
is complete, making this species easily identifiable.
Armored snails are freshwater snails and are generally found among tree roots and non-flowering plants along slow moving to moderate flowing streams. They are
also sometimes found in detritus (organic matter and rock fragments) along water edges. This species is more than likely herbivorous,
feeding on algae and small pieces of dead or decaying plants in the water. All snails hibernate in the winter and they are "hermaphrodites,"
possessing both male and female reproductive organs. A small slit appears on the neck where the fertilization occurs and the eggs develop. After
hatching from the eggs, the larvae swim freely in the water and soon begin to grow a shell, which eventually weighs them down, making them pedestrian.
The armored snail is only found in two isolated sites along the two short river reaches, and the sites are rather small, covering only a few
square meters. These two populations are more than likely remnants of one larger population effected by water deterioration due to siltation
and pollution from poor land-use practices and waste discharges. The last two remaining populations were placed on the endangered species
list in February of 2000, are now legally protected.
Armored Snail Facts Last Updated:
March 18, 2007
To Cite This Page:
Glenn, C. R. 2006. "Earth's Endangered Creatures - Armored Snail Facts" (Online).
Accessed 7/16/2018 at http://earthsendangered.com/profile.asp?sp=843&ID=9.
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Thousands of short RNA molecules with diverse genetic sequences serve as security guards to identify and silence attempts to invade the genome, such as DNA inserted by viruses or parasitic elements known as transposons.
These diverse, small RNA molecules, known as Piwi-interacting RNAs (piRNAs) are produced by various animals, from insects and worms to mammals like mice and humans. In a new study published in the journal Science, researchers describe how piRNAs find foreign genetic sequences to silence them. They also show how endogenous or "self" genes that properly belong in the genome identify themselves to avoid this additional scrutiny.
"Nearly every animal has these small RNAs, and they use them as a guide to look for target sequences and silence them," said senior author of the new study. "Until now though, it was rather mysterious what their function was, and why there are so many with such diverse genetic sequences."
RNA acts as a messenger to carry out instructions coded in DNA to produce proteins that perform essential functions in the body. In the new study, researchers studied piRNAs produced by cells in the reproductive system of the nematode worm, C. elegans, a classic model organism studied by scientists to understand basic biological processes.
Piwi-interacting RNAs are a type of small RNAs that associate with what's known as Argonaute machinery in cells that search for target RNA and shut it down. RNA is built with the same chains of nucleotides that mirror sequences of DNA, denoted with the same familiar A, C, G, U lettering. Some small RNAs need to match the target sequence exactly to identify them, like a security guard looking for a specific person. Others small RNAs can flag genes with a partial match, more like looking for a suspect based on a general description.
Scientists haven't been sure exactly how piRNAs find their targets, in part because there are so many of them. The nematode that for example, has more than 15,000 piRNAs with different nucleotide sequences. Why are there so many, and what purpose do they serve?
When Piwis recognize their target, they recruit a set of even smaller secondary RNAs corresponding to the sequence at the target site, a way of marking it for attention. Knowing this the research team created a synthetic piRNA with a sequence that didn't exist in the worm and tracked where it created its marker. Then, by examining the different sequences the synthetic piRNA marked, they could work backwards to figure out its logic for finding a match.
It turns out that piRNAs need a fairly close match to a portion of the sequence, but they can tolerate a few mismatches on the rest. It also appears that there are so many unpaired Piwis in the worms because it gives them a toolbox of many possible sequence combinations they might need to identify foreign RNAs and turn them off. Instead of a security guard searching for a specific person, or someone who sort of looks like that person, they have a whole database of possible suspects they can track down if needed.
But how do they avoid false positives, or wrongly identify endogenous "self" genes that belong there? To find out, researchers engineered more piRNAs that could recognize several well-known genes that belong in the nematode genome. But this set of piRNAs didn't silence or affect the function of the endogenous genes at all, meaning they were somehow resistant.
The researchers also found that many endogenous genes had additional repeating sections of A and T nucleotides that mark them as "self" and not foreign. This licensing signal serves as a credential to identify the gene, a passport to show the piRNA system it belongs.
The study sheds light on a basic mechanism that can affect fertility in animals. Previous research has shown that if Piwi genes develop mutations, the piRNA system can malfunction. Then, if viruses or transposons inject foreign DNA elements into the germ line, or reproductive cells that produce eggs and sperm, piRNAs aren't there to detect and silence them. These undetected changes can lead to infertility and other issues in the reproductive system.
The study also solves a technical issue that has stymied C. elegans scientists for decades. When researchers want to study a specific gene, they often make slight modifications so a special protein tag that produces fluorescent light can attach to the proteins produced by their gene of interest. This works well in most types of cells, but in the germ line, the piRNA system spots those genetic changes and shuts off production of the fluorescent tag.
The team showed how scientists can prevent this from happening. By editing the sites recognized by piRNAs just enough, they can't find them anymore, but the genes will still function the same way. Researchers could also insert the same self-licensing signals into non-coding sections of DNA, to make the changes appear to belong to endogenous genes. These techniques will also allow scientists to use the CRISPR-Cas9 gene editing system to track changes in germ line.
Small RNA molecules as security system to defend our genome
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Testing the influence of gravity on flower symmetry in five Saxifraga species
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Flower symmetry is considered a species-specific trait and is categorized in asymmetry, actinomorphic symmetry, bisymmetry and zygomorphic symmetry. Here we report on the intra-individual variation of flower symmetry in the genus Saxifraga and the influence of light, gravity and intrinsic factors on the development of flower symmetry. We tested five species—Saxifraga cuneifolia, Saxifraga imparilis, Saxifraga rotundifolia, Saxifraga stolonifera and Saxifraga umbrosa—concerning six flower parameters—angles between petals, petal length, petal pigmentation, angular position of carpels, movement of stamens and (only for S. imparilis and S. stolonifera) the length of the two lower elongated petals in regard to their position towards the stem. Specimens of all species were tested on a vertical clinostat as a gravity compensator, on a horizontal clinostat as a light incidence compensator and on a stationary control. The results show that the angle of incident light has no apparent impact on flower symmetry, whereas gravity affects the angular position of petals in S. cuneifolia and S. umbrosa and the petal colouration in S. rotundifolia. In S. cuneifolia and S. umbrosa, the absence of directional gravity resulted in the development of actinomorphic flowers, whereas the corresponding control flowers were zygomorphic. The development of flowers in S. rotundifolia was not altered by this treatment. The length of the two elongated petals in S. stolonifera and S. imparilis was not affected by gravity, but rather was determined by position of the flower within the inflorescence and resulted in asymmetrical flowers.
KeywordsFlower symmetry Zygomorphy Actinomorphy Saxifraga Pollination
We thank Leonie Sermon and Michaela Krohn for acquisition of data and Andreas Fischbach for support in the botanical garden.
Compliance with ethical standards
The authors declare that they have no competing interests.
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- Prenner G, Bateman RM, Rudall PJ (2010) Floral formulae updated for routine inclusion in formal taxonomic descriptions. Taxon 59:241–250Google Scholar
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- Vöchting H (1886) Über Zygomorphie und deren Ursachen. Jb wiss Bot 17:297–346Google Scholar
- Weberling F (1981) Morphologie der Blüten und der Blütenstände. Ulmer, StuttgartGoogle Scholar | <urn:uuid:66e64e83-abaf-4c09-b318-c5aeaec45b54> | 2.609375 | 1,052 | Academic Writing | Science & Tech. | 31.03687 | 95,625,879 |
When the following equation is balanced, the coefficients of BaO2 is?
_BaO2-> BaO+ _O2© BrainMass Inc. brainmass.com July 19, 2018, 12:24 am ad1c9bdddf
The key point in balancing equations is that the number of atoms of each element must be the same on either side.
_BaO2-> BaO+ _O2 ...
The equations for balanced coefficients are determined. | <urn:uuid:dcedee46-74b0-4ab6-842c-de23ee387131> | 2.78125 | 98 | Q&A Forum | Science & Tech. | 73.44523 | 95,625,894 |
20 relations: Aitken Double Star Catalogue, Apparent magnitude, Auriga (constellation), Boss General Catalogue, Bright Star Catalogue, Catalog of Components of Double and Multiple Stars, Centre de données astronomiques de Strasbourg, Constellation, Durchmusterung, Epoch (astronomy), Giant star, Henry Draper Catalogue, Hipparcos, Index Catalogue of Visual Double Stars, International Celestial Reference System, Mira variable, Smithsonian Astrophysical Observatory Star Catalog, Star, Stellar classification, Variable star designation.
The Aitken Double Star Catalogue, or ADS, is a star catalogue of double stars.
The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.
New!!: R Aurigae and Apparent magnitude ·
Auriga is one of the 88 modern constellations; it was among the 48 constellations listed by the 2nd-century astronomer Ptolemy.
New!!: R Aurigae and Auriga (constellation) ·
Boss General Catalogue (GC, sometimes General Catalogue) is an astronomical catalogue containing 33,342 stars.
New!!: R Aurigae and Boss General Catalogue ·
The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars or Yale Bright Star Catalogue, is a star catalogue that lists all stars of stellar magnitude 6.5 or brighter, which is roughly every star visible to the naked eye from Earth.
New!!: R Aurigae and Bright Star Catalogue ·
The Catalog of Components of Double and Multiple Stars, or CCDM, is an astrometric star catalogue of double and multiple stars.
The Centre de Données astronomiques de Strasbourg (CDS; English translation: Strasbourg Astronomical Data Center) is a data hub which collects and distributes astronomical information.
A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices.
New!!: R Aurigae and Constellation ·
In astronomy, Durchmusterung or Bonner Durchmusterung (BD), is the comprehensive astrometric star catalogue of the whole sky, compiled by the Bonn Observatory (Germany) from 1859 to 1903.
New!!: R Aurigae and Durchmusterung ·
In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as the celestial coordinates or elliptical orbital elements of a celestial body, because these are subject to perturbations and vary with time.
New!!: R Aurigae and Epoch (astronomy) ·
A giant star is a star with substantially larger radius and luminosity than a main-sequence (or dwarf) star of the same surface temperature.
New!!: R Aurigae and Giant star ·
The Henry Draper Catalogue (HD) is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension (HDE), published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the Henry Draper Extension Charts (HDEC), published from 1937 to 1949 in the form of charts, which gave classifications for 86,933 more stars.
New!!: R Aurigae and Henry Draper Catalogue ·
Hipparcos was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993.
New!!: R Aurigae and Hipparcos ·
The Index Catalogue of Visual Double Stars, or IDS, is a catalog of double stars.
The International Celestial Reference System (ICRS) is the current standard celestial reference system adopted by the International Astronomical Union (IAU).
Mira variables ("Mira", Latin, adj. - feminine form of adjective "wonderful"), named for the prototype star Mira, are a class of pulsating variable stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelengths.
New!!: R Aurigae and Mira variable ·
The Smithsonian Astrophysical Observatory Star Catalog is an astrometric star catalogue.
A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.
New!!: R Aurigae and Star ·
In astronomy, stellar classification is the classification of stars based on their spectral characteristics.
New!!: R Aurigae and Stellar classification ·
Variable stars are designated using a variation on the Bayer designation format of an identifying label (as described below) combined with the Latin genitive of the name of the constellation in which the star lies. | <urn:uuid:438cff18-ce38-4bb3-86f1-e46cf2bdcf1d> | 2.71875 | 1,031 | Structured Data | Science & Tech. | 30.552432 | 95,625,896 |
- Research article
- Open Access
Global dust Detection Index (GDDI); a new remotely sensed methodology for dust storms detection
© Samadi et al.; licensee BioMed Central Ltd. 2014
Received: 13 February 2013
Accepted: 2 November 2013
Published: 9 January 2014
Dust storm occurs frequently in arid and semi-arid areas of the world. This natural phenomenon, which is the result of stormy winds, raises a lot of dust from desert surfaces and decreases visibility to less than 1 km. In recent years the temporal frequency of occurrences and their spatial extents has been dramatically increased. West of Iran, especially in spring and summer, suffers from significant increases of these events which cause several social and economic problems. Detecting and recognizing the extent of dust storms is very important issue in designing warning systems, management and decreasing the risk of this phenomenon. As the process of monitoring and prediction are related to detection of this phenomenon and it's separation from other atmospheric phenomena such as cloud, so the main aim of this research is establishing an automated process for detection of dust masses. In this study 20 events of dust happened in western part of Iran during 2000–2011 have been recognized and studied. To the aim of detecting dust events we used satellite images of MODIS sensor. Finally a model based on reflectance and thermal infrared bands has been developed. The efficiency of this method has been checked using dust events. Results show that the model has a good performance in all cases. It also has the ability and robustness to be used in any dust storm forecasting and warning system.
Every year in Iran, several natural hazards occur which cause social, economic and environmental damages. Western dust storms, i.e. the dust coming from western neighbors of Iran, are one of these hazards which have been increased in both spatial and temporal aspects during last decade.
Dust storms are, in most cases, the result of turbulent winds which raise large quantities of dust from land surfaces and reduce visibility to less than 1 km . They reach concentrations in excess of 6000 μg/m3 in severe events . Dust storms are generated from regions that are mainly deserts, dry lakebeds and semi-arid desert regions . They can carry large quantity of dust and move forward to destroy crop plants, ruin the mining and communication facilities, reduce visibility and disturb human’s daily activities. They also impact the air and ground transportation. They pollute the atmosphere and reduce air quality, influence cloud formation , obscure the sunlight, and reduce the temperature . They also can accelerate the desertification procedure . Their direct effects on human health are mainly depicted in breathing difficulties .
Over the past decades, Middle East dust storms have caused many problems for the residents of South and Southwest regions of Iran. During the recent years, there has been an increase in the trend of dust storm activities in this region, especially in spring and summer . Now, this trend is changing into the main persistent environmental problem in Iran and the Middle East region. Middle East dust storms have great impacts on the quality of the inhabitant’s lives, visibility and transportation, microclimate, ecosystem, communication systems, and consequent crisis, such as eco-social and environmental problems in the west and southwest of Iran .
Detecting dust phenomena, identifying their sources and surveying about their movements and situation can help planners and decision makers in planning and controlling to reduce damages of this phenomena. Traditional ground measurement cannot monitor and forecast dust storm efficiently, because of low temporal and spatial resolutions , therefore, it can’t be enough for such studies. While satellite remote sensing can be more effective because of suitable spatial and temporal resolutions and providing observations of dust aerosols from regional to global scales . Remote sensing allows for better tracking of regional and global distribution of aerosols, which are extremely dynamic in nature . By using remote sensing, detecting and mapping of dust events, dust transport pathways, identifying dust source regions and forecasting the next destination of them are more faster, easier and economical.
Several studies have been done about identifying dust source regions using satellite imagery [13–16]. Also in case of using remote sensing and satellite imagery for detecting dust storms several methods have been developed since 1970. Some of them use visible and infrared spectrum , some use thermal infrared [18–21], while some techniques use composite of reflective and thermal spectrum [22, 23] and some use a composite of thermal and microwave spectrum to detect dust and separating it from other atmospheric phenomena. Ackerman (1989) used brightness temperature difference (BTD) 3.7 and 11 μm spectrum to detect and monitor dust storms. He developed a tri-spectral (8, 11 and 12 μm) technique later for detecting dust over water and for distinguishing dust plumes from water/ice clouds . The negative differences of BTD (11–12 μm) are useful for dust storms detection and sources identification.
Where, ρ 2. 13-μ m and ρ 0. 469-μ m are reflectance at the top of atmosphere in the 2.13 and 0.469 μ m bands, respectively.
Coefficients of equation (2)
Some other studies are carried out by MODIS images [10–12, 25–27], TOMS and OMI (Ozone Monitoring Instrument , AVHRR images (Advanced Very High Resolution Radiometer) [29, 30], METEOSAT data , and SeaWIFS images (Sea-viewing Wide Field-of-View Sensor) for dust storms detection, discrimination and monitoring purposes with some successes.
By considering almost all developed methodologies, there are common limitations in them. First, while they have good abilities for dust detection over lands, they cannot do the same over water bodies. Second, they have problems with seasonal changes and they need different thresholds. Third, they almost have problems with dust discrimination from other objects like clouds, water and land soil surface. Therefore, the main objective of this research is the development of a global methodology which resolves mentioned problems. This methodology is able to detect dust storms in all seasons with no need to threshold and discriminates dusts from other objects. The developed methodology we called “Global Dust Detection Index (GDDI)” resolves all of these problems in previously developed methodologies.
Materials and methods
Dust event days from 2000-2011
Remote sensing images
Satellite remote sensing is advantageous in monitoring the significant spatial-temporal variations of dust storms [33, 34]. Dust phenomena can be detected by remote sensing in different spectral channels. Although the accuracy of results depends on various parameters such as the spatial, spectral and radiometric resolutions of satellite images, the methodology used spectral bands, defined thresholds, weather and atmospheric conditions, clouds and etc. Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) were used in this study. MODIS makes observations using 36 spectral bands with wavelengths from 0.41 to 14.4 μm and nadir spatial resolutions of 0.25, 0.5, and 1 km .
MODIS is currently operating onboard the NASA Earth Observing System (EOS) Terra and Aqua satellites, launched in December 1999 and May 2002, respectively . MODIS images from both Terra and Aqua satellites were obtained in Level 1 from Atmosphere Archive and Distribution System (LAADS; http://ladsweb.nascom.nasa.gov/).
In order to accurately decide the bands and thresholds in the algorithm of dust detection, more than 20 dust storm events occurred in the west part of Iran during 2000–2011 were collected as training data for spectral analysis. Due to limitations of pages and paper only 4 dust storm events are selected as example cases.
To achieve and modeling the spectral behavior of different objects and also discriminating them from each other, the training pixels were collected. In this procedure the dusty pixels over different land covers i.e. bright and dark land covers and water bodies were collected. This procedure was carried out for all images, separately and almost all MODIS bands were used. Finally the useful bands based on our and other studies’ results were selected. For each class in the scene, about thirty thousand training pixels were collected. Then, the statistical mean and standard deviation of samples for seven classes, i.e. clouds, bright surfaces, dust over bright surfaces, dark surface, dust over dark surfaces, water and dust over water bodies, were calculated and spectral curve of these classes were drawn.
Spectral curves and indices
Where, B3 is reflectance in band 3 and B7 is reflectance in band 7. Because of noticeable difference in brightness temperature between clouds and dust in thermal spectrum, Ackerman (1997) proposed a method to differentiate dust from clouds which used brightness temperature difference of 11 and 12 μm (band 31 and 32 of MODIS image, respectively). So brightness temperature difference in 11 and 12 μm (BT31-BT32) and the NDDI index can separate dust from clouds.
Where, B4 and B7 are the reflectance of bands 4 and 7 in MODIS L1B data, respectively. So using equation 5 and brightness temperature difference at 3.7 and 11 μm (BT20 – BT31) we can separate dust from bright surface.
In the reflectance spectrum these two phenomena show more separation and this difference was maximized in band 2 and minimized in band 18 (Figure 4-A). So the difference of these two bands can separate the two phenomena. The spectral properties of water show a low reflectance for none-dusty pixels over water bodies and this property for dusty pixels is high in almost all bands. Band 2 shows the highest separation for the reflectance of none-dusty from dusty pixels over water bodies. Comparatively, this separation in band 1 is lower (Figure 4-B). The location of bands 1 and 2 of MODIS in the red and NIR portions of spectrum let us to adapt the NDVI = (B2-B1)/(B2 + B1) for bounding the pixels in none-dusty from dusty ones over water bodies.
Due to the different nature of dust detection over water bodies, the amount of threshold for some indices like NDDI could be changeable. The existence of icy clouds is also a problem. Experimentally a threshold more than one in the BTD (31–32) was adapted for icy clouds separation from the dust in the image.
Results and discussion
Dust event cases to evaluate the developed dust detection algorithm
Used satellite image
May 17, 2007
July 1, 2008
July 5, 2009
April 13, 2011
In this work the Global Dust Detection Index (GDDI) was developed for automatic dust storm detection using satellite images. Its abilities were evaluated by MODIS L1B data. It enjoys the optical and thermal portions of the electromagnetic spectrum. Apart from some experimental indices, we explored the BTD and NDDI. Compared to previous methodologies for detection of dust, the GDDI has no need of threshold. Being able to work in all climatic conditions is another characteristic of GDDI which makes it preferable. It also is able to simultaneously detect dusts over land surfaces and water bodies.
We deeply would like to thanks all researchers and publishers that we used the results of their works and researches. The MODIS data were obtained from Level 1 and Atmosphere Archive and Distribution System (LAADS; http://ladsweb.nascom.nasa.gov/). The meteorological data were provided by the Islamic Republic Iran Meteorological Organization (IRIMO). We also would like to thanks the LAADS and IRIMO.
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This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. | <urn:uuid:81e00b2b-d4a3-4447-8951-0df6172a5131> | 3.234375 | 4,526 | Academic Writing | Science & Tech. | 57.340792 | 95,625,924 |
Was there life on Mars?
They have presented new evidence which they say removes any doubt that a meteorite carried the remnants of ancient Martian bacteria to Earth.
The findings, from the American space agency Nasa, indicate that Mars may once have been teeming with bugs which lived at the bottom of shallow pools and lakes.
They also suggest there would have been plants or organisms capable of photosynthesis and complex ecosystems on Mars.
However British experts said the evidence, though exciting, had to be treated with caution and could not be taken as conclusive.
The work was carried out by a team led by Nasa scientist Dr Imre Friedmann that has been studying the 4.5 billion-year-old meteorite ALH84001.
Scientists think the potato-sized rock, found in Antarctica's Allan Hills ice field in 1984, was blasted off the surface of Mars by a comet or asteroid 15 million years ago.
After drifting through space it was caught by the Earth's gravity and landed in Antarctica, where it lay for 13,000 years.
In 1996 Nasa rocked the scientific world by announcing the discovery of worm-like "microfossils" left by Martian bacteria within the meteorite.
Since then other experts have argued that non-biological chemical processes could explain what was found.
The controversy has rumbled on, however - and today took a dramatic new twist. Dr Friedmann insists his team has found clinching evidence that should silence the doubters.
Inside a small fragment of the meteorite, he says, they detected chains of magnetic iron crystals which could only have been left by living organisms.
Similar magnetite crystal chains are seen in Earthly bugs called magnetotactic bacteria, which live near the surface of shallow water sediments.
The bugs use the tiny magnets inside their bodies as compasses to guide them to sources of oxygen, which they need to live.
Magnetite crystals have been found in the meteorite before, but until now no clear images of the chain formations synonymous with bacteria have been seen. Dr Friedmann discovered hints of such chains three years ago, but the evidence then was unconvincing.
The new findings were made possible by a sophisticated electron microscopy technique not available before.
It produced 3D images showing nearly 1,000 magnetite chains of varying lengths within the small chip analysed, suggesting that the original rock contained millions.
Dr Friedmann, from Nasa's Ames Research Centre in Moffat Field, California, and Florida State University, Tallahassee, said: "These crystals match all the criteria for biologically-formed chains, and as far as I'm concerned it's conclusive evidence that Martian bacteria were in this meteorite.
"I cannot guess how my colleagues will react, but in my opinion no reasonable person can doubt it any more. The evidence is so strong. When you put all the elements together there can be no other explanation."
He stressed there was no chance of the crystals being left by contaminating Earth bacteria. They were embedded in carbonate, which in turn was encased in glass formed when the meteorite was blown of the surface of Mars.
Bugs of this sort lived in an environment very different from that of Antarctica, he added.
Dr Friedmann, whose research is reported today in the journal Proceedings of the National Academy of Sciences, said: "There are certain conclusion you can draw, which are very significant.
"The chances of finding traces of so many bacteria in a two kilogram rock from another planet are quite slim. It means bacteria must have been very widespread on Mars."
He argued that since magnetotactic bacteria require oxygen, there must have been some kind of photosynthesising life on Mars. The Earth owes its oxygen to the photosynthesis of plants and algae.
One mystery was how the bugs got into the rock, since magnetotactic bacteria are free swimming and do not live inside rocks.
However, they might have died and been washed into cracks in the rock while it was still on the Martian surface, suggest the researchers.
Other scientists may need more convincing, however.
Dr John Bridges, a planetary scientist at the Natural History Museum who has studied Martian meteorites, said: "This is an interesting contribution to the research on this very important rock, but I don't see it as definitive evidence of life on Mars.
"You can't ignore the possibility of contamination. When we get down to such incredibly small scales it gets really difficult to distinguish between terrestrial overprint and original Martian minerology."
Dr Mark Sim, from Leicester University, project director of the British-led Beagle II mission which will land a life-seeking probe on Mars in 2003, said: "It's exciting, interesting work, there's no doubt about it, and it appears to indicate that the crystals are of possibly biological origin.
"But there are some problems. There's an old saying that if you make extraordinary claims you need extraordinary proof."
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Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor)
Introduction to Hess's Law
Hess's law is based on the first law of thermodynamics which says that energy can not be created or destroyed but can be converted from one form to another. Mr Hess used this principle and related it to chemical reactions, creating, Hess's Law:
Hess's Law says that the enthalpy change if a reaction depends only on the initial and final states of the reaction and is independent of the route by which the reaction may occur. In practical terms this means that you can do other reactions to get the energy for the main one.
If you regularly commute somewhere by car, you won't have just one route. What if one of the roads is closed? Likewise, there are several different ways you could go, and this very principle can be used in Chemistry since Mr. Hess said it doesn't matter which way we go - the energy will be the same.
- 2We can also do a similar thing with formation. This is defined as the creation of a molecule from the elements that make it up in their standard states. Therefore this means H2 is used in the formation, not H. The equation for the formation of ethanoic acid:Formulation.
But remember that the enthalpy of formation for an element is 0, because it is already in its standard state.
The mean bond enthalpy is the amount of energy required to break a particular bond. For example, in methane there are 4 C-H bonds. The two following reactions show these being broken:
So the mean bond enthalpy for the C-H bond is 1664/4 = 416.
You can now use these bond enthalpies to calculate the energy in the bonds of all molecules.
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Categories : Physical
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Botanists at Edge Hill University, the UK’s newest University, have discovered a population Carex salina (Salt-marsh sedge), near Morvich on the west coast of Scotland, in the UK for the first time. Scientists from the University are calling on members of the public to help them search for other populations of this species. Identification keys and recording forms are available from the University’s website.
‘We are really keen to enlist the help of others in looking for this species of sedge that, as far as well can tell, is new to the UK,’ said Dr Paul Ashton, Senior Lecturer in Biology at Edge Hill University. ‘It is entirely possible that this plant has been on our shores for many years and just overlooked, but we will never know that unless people help us with our study. If we discover that Salt-marsh sedge is entirely new to the UK it will be a very exciting find that will enrich our knowledge of British flora.’
The new species of sedge was discovered by Keith Hutcheon on 2 July 2004, while undertaking a National Vegetation Classification survey of the Kintail Estate for the National Trust of Scotland. Sedge are typically grass-like plants but are most easily separated from grasses and rushes by their triangular stems. It was originally thought that the sedge was the species Carex recta, (Estuarine sedge) the only other UK species of sedge likely to be found in the area that can withstand such high levels of salt water.
Dr Paul Ashton and Dr Mary Dean, from Edge Hill University, began the process of identifying the specimens that were collected. After consultation with colleagues from Canada and Norway they came to the conclusion that the species must be Carex salina, which is found in both those countries but never before seen in the UK.
Salt-marsh sedge is thought to be a result of hybridisation between two other plants Carex paleacea (Beach sedge) and Carex subspathacea (Cold Sea sedge), however neither of these parent species are present in the UK botanical record. It is thought that the Scottish location is the first area in the world where Salt-marsh sedge is apparently growing outside of the ranges of parental species. Botanists at Edge Hill are trying to research the reason for its appearance on UK shores; it could have originated in Scotland by long distance dispersal, alternatively it may have arisen in situ and the parent species are now extinct, or are still present in the UK but are currently undetected.
If migration of this species from the colder, stormier climates like those on the coast of Norway and North America has taken place the presence of Carex salina could be an indication of stormier times ahead for the UK coast. Botanists need to first establish whether there are other populations of this hybrid species, or of its parents, in the UK before investigation into migration and possible climate repercussions can take place. However, two scientists cannot carry out this survey on their own, which is why the website has been set up to enlist the help of the botanical enthusiasts in sampling possible populations.
This survey will take place over 3 years and results will inform future studies into sedge species, and their related habitats on the UK coastline.For more information, images or to interview Dr Paul Ashton please contact:
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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HTML Horizontal Rule
By Stephen Bucaro
A horizontal rule created by the tag <hr /> creates a horizontal line that can
can be used to break a webpage into sections. A horizontal rule is a block-level element,
which means it has embedded carriage returns before and after, placing it on it's own line.
Shown below is a generic horizontal rule.
The horizontal rule has several attributes that allow you to control its appearance.
|align|| Alignment on page, left, right, or center.|
|color|| Color of the rule.|
|noshade|| Normally horizontal rules display with 3D shading.|
|size|| Thickness in pixels.|
|width|| Width in pixels, or as a percentage of document width.|
Horizontal Rule Example
<hr align="left" size="6" width="200" color="green" />
The code above creates the horizontal rule shown below.
I know this section should be about html only, but the example below shows what you
can do by adding a little style to a horizontal rule.
<hr align="left" size="8" width="200" style="border-style:outset; background-image: url('bg000017.gif');" />
If you're using the Firefox browser, you'll see a beautiful rainbow colored three-dimensional
rule. If your using Internet Explorer, you'll see a three-dimensional gray rule.
More HTML Code:
• Wrapping Text Around Images
• Use Meta Tags for Search Engine Optimization
• HTML Text Tags Basics
• HTML5 Input Type - URL
• Aligning an Image on Your Web Page
• Easy Code to Add Bing Site Search to Your Website
• When to Use the nofollow Attribute value
• The HTML Head Tag
• HTML Textarea Basics
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why do tornadoes occur in tornado alley
What is "Tornado Alley"? The land in the central United States is the best breeding ground for the storms which produce tornadoes. The land in the Great Plains is relatively flat, which allows cold dry polar air from Canada to meet warm moist tropical air from the Gulf of Mexico.
It's along the front between the two airmasses that most tornadoes. Most tornadoes in the United States form in an area called "Tornado Alley". This area includes parts of Texas, Oklahoma, Kansas, and Nebraska. travel to this area because of the high concentration of tornadoes.
These tornadoes are formed by. Some of the tornadoes in the southern states such as Florida, South Carolina, and Georgia are caused by.
Oklahoma is particularly vulnerable to tornadoes, lying inside the so-called 'Tornado Alley', stretching from South Dakota to Central Texas.
The geography and climate of the region frequently create the conditions for huge thunderstorms - with warm, wet air blowing in from the Gulf of Mexico meeting cold, dry air coming from the massive Rocky Mountain range, hemmed in by air masses on the eastern part of the country.
Three-quarters of the world's tornadoes occur in the United States - around 1000 per year - but the patterns of how and when they will strike are still difficult to predict. David Shukman reports.
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why do tornadoes occur in the spring
why do tornadoes happen in tornado alley
why do tornadoes form on flat land
why do tornadoes form in tornado alley
why do tornadoes form mostly in the great plains states
why do tornadoes form mostly in the great plains
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Images of Asteroid 2012 DA14 taken by the Gingin Observatory in Australia and broadcast on NASA TV show a small white streak moving across the clear night sky.
The asteroid was projected to come within of 27,600 kms of the planet which was close enough to pass inside the ring of satellites that circle the Earth.
The flypast took place at around 2:25 p.m. Eastern time Friday.
It was an improbable bit of timing.
The big asteroid is not to be confused with the smaller meteor that actually did hit Earth on Friday, causing a fair bit of damage in Russia's Chelyabinsk region.
The European Space Agency, in a post on its Twitter account, said its experts had determined there was no connection between the meteor and the asteroid.
Phil Langill, a University of Calgary physics professor, called it "a funny coincidence" that the two space events happened so close together.
"It does conjure up the thought that maybe one was a little companion of the other," the director of the Rothney Astrophysical Observatory said in an interview Friday. "But then again, this is asteroids in space and they come randomly toward the Earth and this could have just been a coincidence."
Even before Asteroid 2012 DA14 passed, scientists had offered assurances that humanity need not have feared a collision with the giant rock.
Peter Brown, a scientist at Western University in London, Ont., said what made it unique was its size. It was also the closest known flyby by an asteroid.
"Things of this size get this close to the Earth or closer only about once every 40 years ... so it’s an unusual event."
"And we can say that there's a very low chance — maybe one chance in 300,000 — that it will impact (the Earth) in the next 100 years or so," added Brown.
He also said that, for an asteroid like 2012 DA14 to collide with any sort of man-made satellite, "it really is (as unlikely as) winning the lottery three times in a row."
As it turned out, the big rock wound up being upstaged by a little rock.
In Russia, a meteor streaked across the sky above the Ural Mountains, causing sharp explosions amid reports that as many as 1,000 people were injured, mostly due to broken glass.
Fragments of the meteor fell in a thinly populated area of the Chelyabinsk region, about 1,500 kms east of Moscow. | <urn:uuid:9b2ac8be-35b7-45bf-ba06-e7341fec20f7> | 3 | 514 | News Article | Science & Tech. | 59.841416 | 95,625,970 |
Turbulence and turbidity are thought to independently affect the foraging success of fish, but little is known about their interactive effects on the feeding of fish larger than a few centimetres. We experimentally tested for this interaction on the feeding of planktivorous perch (Perca fluviatilis). There was an interactive effect of root mean square (RMS) velocity (0, 1.3, 2.7, 5.5, and 18.3 cm·s-1) and turbidity (0, 30, and 60 nephelometric turbidity units; NTU) on perch feeding on phantom midge larvae (Chaoborus flavicans). In the 0 and 60 NTU conditions, there was no significant change in the feeding efficiency of perch. However, at 30 NTU, increasing turbulence enhanced perch feeding by increasing encounter rates and disabling the prey escape response. The proportion of encountered Chaoborus larvae that were consumed showed a linear decline with increasing turbulence under clear and 30 NTU conditions and a dome-shaped response under 60 NTU. The results indicate that turbulence has a strong effect on the post-encounter stages of the foraging cycle.
Mendeley saves you time finding and organizing research
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Voltage-gated ion channel
Each of the four homologous domains makes up one subunit of the ion channel. The S4 voltage-sensing segments (marked with + symbols) are shown as charged.
Voltage-gated ion channels are a class of transmembrane proteins that form ion channels that are activated by changes in the electrical membrane potential near the channel. The membrane potential alters the conformation of the channel proteins, regulating their opening and closing. Cell membranes are generally impermeable to ions, thus they must diffuse through the membrane through transmembrane protein channels. They have a crucial role in excitable cells such as neuronal and muscle tissues, allowing a rapid and co-ordinated depolarization in response to triggering voltage change. Found along the axon and at the synapse, voltage-gated ion channels directionally propagate electrical signals. Voltage-gated ion-channels are usually ion-specific, and channels specific to sodium (Na+), potassium (K+), calcium (Ca2+), and chloride (Cl–) ions have been identified. The opening and closing of the channels are triggered by changing ion concentration, and hence charge gradient, between the sides of the cell membrane.
Voltage-gated ion channels are generally composed of several subunits arranged in such a way that there is a central pore through which ions can travel down their electrochemical gradients. The channels tend to be ion-specific, although similarly sized and charged ions may sometimes travel through them. The functionality of voltage-gated ion channels is attributed to its three main discrete units: the voltage sensor, the pore or conducting pathway, and the gate. Na+, K+, and Ca2+ channels are composed of four transmembrane domains arranged around a central pore; these four domains are part of a single α-subunit in the case of most Na+ and Ca2+ channels, whereas there are four α-subunits, each contributing one transmembrane domain, in most K+ channels. The membrane-spanning segments, designated S1-S6, all take the form of alpha helices with specialized functions. The fifth and sixth transmembrane segments (S5 and S6) and pore loop serve the principal role of ion conduction, comprising the gate and pore of the channel, while S1-S4 serve as the voltage-sensing region. The four subunits may be identical, or different from one another. In addition to the four central α-subunits, there are also regulatory β-subunits, with oxidoreductase activity, which are located on the inner surface of the cell membrane and do not cross the membrane, and which are coassembled with the α-subunits in the endoplasmic reticulum.
Crystallographic structural studies of a potassium channel have shown that, when a potential difference is introduced over the membrane, the associated electric field induces a conformational change in the potassium channel. The conformational change distorts the shape of the channel proteins sufficiently such that the cavity, or channel, opens to allow influx or efflux to occur across the membrane. This movement of ions down their concentration gradients subsequently generates an electric current sufficient to depolarize the cell membrane.
Voltage-gated sodium channels and calcium channels are made up of a single polypeptide with four homologous domains. Each domain contains 6 membrane spanning alpha helices. One of these helices, S4, is the voltage sensing helix. The S4 segment contains many positive charges such that a high positive charge outside the cell repels the helix, keeping the channel in its closed state.
In general, the voltage sensing portion of the ion channel is responsible for the detection of changes in transmembrane potential that trigger the opening or closing of the channel. The S1-4 alpha helices are generally thought to serve this role. In potassium and sodium channels, voltage-sensing S4 helices contain positively-charged lysine or arginine residues in repeated motifs. In its resting state, half of each S4 helix is in contact with the cell cytosol. Upon depolarization, the positively-charged residues on the S4 domains move toward the exoplasmic surface of the membrane. It is thought that the first 4 arginines account for the gating current, moving toward the extracellular solvent upon channel activation in response to membrane depolarization. The movement of 10–12 of these protein-bound positive charges triggers a conformational change that opens the channel. The exact mechanism by which this movement occurs is not currently agreed upon, however the canonical, transporter, paddle, and twisted models are examples of current theories.
Movement of the voltage-sensor triggers a conformational change of the gate of the conducting pathway, controlling the flow of ions through the channel.
The main functional part of the voltage-sensitive protein domain of these channels generally contains a region composed of S3b and S4 helices, known as the "paddle" due to its shape, which appears to be a conserved sequence, interchangeable across a wide variety of cells and species. A similar voltage sensor paddle has also been found in a family of voltage sensitive phosphatases in various species. Genetic engineering of the paddle region from a species of volcano-dwelling archaebacteria into rat brain potassium channels results in a fully functional ion channel, as long as the whole intact paddle is replaced. This "modularity" allows use of simple and inexpensive model systems to study the function of this region, its role in disease, and pharmaceutical control of its behavior rather than being limited to poorly characterized, expensive, and/or difficult to study preparations.
The gate is thought to be coupled to the voltage sensing regions of the channels and appears to contain a mechanical obstruction to ion flow. While the S6 domain has been agreed upon as the segment acting as this obstruction, its exact mechanism is unknown. Possible explanations include: the S6 segment makes a scissor-like movement allowing ions to flow through, the S6 segment breaks into two segments allowing of passing of ions through the channel, or the S6 channel serving as the gate itself. The mechanism by which the movement of the S4 segment affects that of S6 is still unknown, however it is theorized that there is a S4-S5 linker whose movement allows the opening of S6.
Inactivation of ion channels occurs within milliseconds after opening. Inactivation is thought to be mediated by an intracellular gate that controls the opening of the pore on the inside of the cell. This gate is modeled as a ball tethered to a flexible chain. During inactivation, the chain folds in on itself and the ball blocks the flow of ions through the channel. Fast inactivation is directly linked to the activation caused by intramembrane movements of the S4 segments, though the mechanism linking movement of S4 and the engagement of the inactivation gate is unknown.
Sodium (Na+) channels
Sodium channels have similar functional properties across many different cell types. While ten human genes encoding for sodium channels have been identified, their function is typically conserved between species and different cell types.
Calcium (Ca2+) channels
With sixteen different identified genes for human calcium channels, this type of channel differs in function between cell types. Ca2+ channels produce action potentials similarly to Na+ channels in some neurons. They also play a role in neurotransmitter release in pre-synaptic nerve endings. In most cells, Ca2+ channels regulate a wide variety of biochemical processes due to their role in controlling intracellular Ca2+ concentrations.
Potassium (K+) channels
Potassium channels are the largest and most diverse class of voltage-gated channels, with over 100 encoding human genes. These types of channels differ significantly in their gating properties; some inactivating extremely slowly and others inactivating extremely quickly. This difference in activation time influences the duration and rate of action potential firing, which has a significant effect on electrical conduction along an axon as well as synaptic transmission. Potassium channels differ in structure from the other channels in that they contain four separate polypeptide subunits, while the other channels contain four homologous domain but on a single polypeptide unit.
Chloride (Cl−) channels
Chloride channels are present in all types of neurons. With the chief responsibility of controlling excitability, chloride channels contribute to the maintenance of cell resting potential and help to regulate cell volume.
Proton (H+) channels
Voltage-gated proton channels carry currents mediated by hydrogen ions in the form of hydronium, and are activated by depolarization in a pH-dependent manner. They function to remove acid from cells.
Phylogenetic studies of proteins expressed in bacteria revealed the existence of a superfamily of voltage-gated sodium channels. Subsequent studies have shown that a variety of other ion channels and transporters are phylogenetically related to the voltage-gated ion channels, including inwardly rectifying K+ channels, ryanodine-inositol 1,4,5-triphosphate receptor Ca2+ channels, transient receptor potential Ca2+ channels, polycystin cation channels, glutamate-gated ion channels, calcium-dependent chloride channels, monovalent cation:proton antiporters, type 1, and potassium transporters.
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- Catterall WA (2010). "Ion channel voltage sensors: structure, function, and pathophysiology". Neuron. 67 (6): 915–28. doi:10.1016/j.neuron.2010.08.021. PMC . PMID 20869590.
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- Long SB, Tao X, Campbell EB, MacKinnon R (November 2007). "Atomic structure of a voltage-dependent K+ channel in a lipid membrane-like environment". Nature. 450 (7168): 376–82. Bibcode:2007Natur.450..376L. doi:10.1038/nature06265. PMID 18004376.
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- IUPHAR-DB Voltage-gated ion channel subunits
- The IUPHAR Compendium of Voltage-gated Ion Channels 2005
- Voltage-Dependent+Anion+Channels at the US National Library of Medicine Medical Subject Headings (MeSH) | <urn:uuid:e255b194-1592-450d-9ed1-53bd26315614> | 3.671875 | 3,695 | Knowledge Article | Science & Tech. | 58.278841 | 95,626,018 |
Evolution Through Helium Burning — Massive Stars
After central hydrogen burning, the star has a helium core, which in the absence of energy sources tends to become isothermal. Indeed thermal equilibrium would require that the models consist of an isothermal helium core (of mass Mc = qoM, radius Rc), surrounded by a hydrogen-rich envelope [of mass (1 — qo)M] with hydrogen burning in a shell source at its bottom. Such models were discussed in detail in §30.5. We now once more consider the case of M = 3M⊙, which is typical for stars on the upper part of the main sequence (say M > 2.5M⊙). The possible solutions were comprised in a linear series of models consisting of 3 branches. This is shown in the first graph of Fig. 30.10, and again in Fig. 31.1, which also gives the position in the HR diagram.
KeywordsMain Sequence Stellar Mass Linear Series Hydrogen Burning Evolutionary Track
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Introduction and Definitions
The limits of life on this planet have been the subject of many studies. One of the interesting results of these studies was the phenomenon that water availability and water activity under conditions extremely deviating from the average surface conditions on the Earth are key factors for the establishment and success of very special ecosystems. We understand today that extremely cold, extremely hot and extremely saline environments are similar in this respect. The mere fact that glycerol is used in the preservation of bacterial strains in deep-frozen state and at the same time is one of the many compounds produced for adaptation to hypersaline conditions demonstrates this relationship.
KeywordsHypersaline Environment Capillary Fringe Coastal Sabkha Sabkha Sediment Hypersaline Ecosystem
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What is math?
Most people’s conception of math was drilled into them during grade school.
In my experience, grade school math goes something like this: The teacher says that we need to calculate a thing. He then shows how to calculate that thing, with seven slight variations. Your homework is to calculate six of each of the variations. The test will have five of those seven.
After a decade of this, most walk away thinking that math is calculation. And because of the rote way the material was introduced, many get the impression that math is set in stone. If you perform a particular set of arcane, incomprehensible steps, you will be led to the mythical “right answer.” No other steps are allowed, and heaven help you if you don’t happen to remember the right steps for a particular problem. In that case there is nothing to be done but despair.
And, of course, they believe that all math has been handed down to them from on high, as wisdom from the ancients. It is imperturbable, impenetrable, impeccable.
But that is not what math is.
So, what is math?
Calculation is a useful tool, but it is definitely not what math is.
Math is a quest for understanding. And like any good epic fantasy series, it seems to never quite be finished.1
And the understanding we mathematicians seek is an odd sort of understanding. The goal of science is to understand what is, to describe and understand the universe around them.
Mathematicians, on the other hand, seek to understand what must be.
After all, the questions a mathematician asks are not generally about things that could even exist. Have you ever seen a perfectly straight, infinitely thin line? Or an angle of precisely 90 degrees? But, if I have a perfectly flat triangle with a 90 degree angle, I know the side lengths have a certain relationship, .
And sure, we can count 37 cows, but do the cows care that there are a prime number of them? But 37 is prime, and so the 37 cows cannot be evenly split between more than one person.
I sometimes like to describe this by saying that I, as a mathematician, try to figure out what even God cannot do. Even an all-powerful God cannot create a perfect flat triangle with a 90 degree angle, whose side lengths do not obey the Pythagorean relationship. Neither could He evenly divide 37 cows between more than one person.2
The basis for deciding what must be are the definitions and axioms of mathematics.
Definitions and axioms are different, but very closely related.
Definitions describe the things we talk about. For instance, a straight line (versus a curved one) might be defined as “a line which lies evenly with the points on itself,” as in Euclid.
Axioms describe what we can do with the things we’ve defined. These tend to be very basic, “obvious” things. For example, the axiom of symmetry says that “If , then .” In this example, you could see the axiom as something you can do (“You can switch the sides of an equation.”) or you could see the axiom as defining what two things being equal really means.
On top of this foundation, mathematics is built with logic. Given the definitions and axioms, certain conclusions follow as inescapable consequences. These conclusions we call theorems or lemmas or propositions.3
Because mathematics is taught in such an authoritative way, it can appear that the definitions and axioms of mathematics are in someway intrinsic, that they have existence outside of the creation of man. It can feel like the axioms and definitions are part of the “what must be” that mathematicians are searching for.
To some extent that may be true, but I don’t think this is completely true, and it’s certainly not how math is done.
When you read a textbook, the most recent thinking of the definitions and axioms that are thought to be important are presented. But that hides to some extent the fact that it took hundreds, or even thousands, or years to decide that those axioms should be the ones to form the foundation of the rest of mathematics.
Math evolves. Math changes. The definitions and axioms we use today are not the same ones that were used by Newton.
Referencing Newton actually brings up a good example of how math changes.
Newton (and Leibniz) invented calculus around 1670. It immediately proved its use in solving any number of important questions in physics and mathematics.
But Newton’s calculus was not built on what we would today consider a rigorous foundation.
In order to explain their ideas, both Newton and Leibniz used some idea of “infinitesimals,” quantities that were infinitely small.
Infinitesimals can be very useful in an intuitive explanation of calculus. (I often use them informally when I teach calculus myself.) And so Newton and Leibniz’s proofs of their results were accepted, even though some were uncomfortable with the idea of an infinitely small quantity.
But as mathematicians delved deeper into the ideas of calculus, it became clear that the infinitesimal arguments weren’t quite complete. There were important theorems that could not be carefully proven because the foundations of calculus were not proven with sufficient rigor.4
Thus, one of the major mathematical projects of the 1800’s was to prove the “soundness” of calculus, and make sure the foundations were correct.
This involved inventing new definitions. For instance, one of the key ideas of calculus is the limit. Informally, the limit asks, “As the inputs get close to a number, what do the outputs get close to?”
The intuition for limits is not difficult; you plug in numbers closer and closer to the one you want, and see if the outputs get close to some other number. But the careful definition for limit that we use today, the (epsilon-delta) definition, was not introduced till the 1820’s by Augustin-Louis Cauchy.
Mathematics is not static, and the axioms and definitions we use are not necessarily natural, sitting there for us to find. As we seek deeper understanding, we often come to a point where we realize our earlier understanding was incomplete, or even incorrect, and we seek to fix the foundations. This has occurred over and over and over again to get to our “fixed” modern ideas of mathematics.5
To summarize, mathematics is a quest for understanding what must be. But the very concepts we try to understand are not set in stone. The objects of mathematics are defined by people, and as we understand them better, the definitions and axioms we base our understanding on change.
In the next post I want to talk more in depth about why these definitions change, and how and why mathematicians come up with new definitions.
This post was mostly about the philosophy of math, which is quite a bit different than my normal post. But as we’ll see in a few weeks, Gödel’s incompleteness theorem is so weird that it is impossible to talk about it without discussing the philosophy of math. Gödel’s theorem puts a fundamental limit on mathematicians’ quest for understanding.
–> Next Post: Where do axioms come from?
- I’m looking at you, George R. R. Martin… ↩
- Well, at least without taking the King Solomon approach and cutting the 37th cow in half! ↩
- Usually “theorems” are bigger, more important conclusions, while “lemmas” are littler conclusions that are needed along the way to show the theorems are true. Propositions can go either way. On the other hand, sometimes lemmas end up being more important than the theorems. ↩
- More recently, mathematicians have come up with rigorous methods to talk about infinitesimals, for instance the hyperreal numbers. However, infinitesimal methods are no longer considered standard. ↩
- Even the work on calculus done in the early 1800’s was not final. The “Riemann” integral, which was the formalization of the integral by Riemann, is what is taught in high schools and early college math. But at the graduate level, we use the “Lebesgue” (Luh-bayg) integral instead, which was introduced in the early 1900’s. Both are rigorous approaches to the integral, but the Lebesgue integral makes a few key lemmas and theorems much easier to prove. The basis of the Lebesgue integral is less intuitive at first, but easier and more powerful in the end. ↩ | <urn:uuid:8ec9dd5e-8958-488e-9ae6-b662750da1f4> | 3.046875 | 1,892 | Personal Blog | Science & Tech. | 51.771005 | 95,626,100 |
2 What is Avogadro’s LawAvogadro’s Principle – equal volumes of gases at the same temperature and pressure contain equal numbers of particles
3 Avogadro’s Formula Formula: V1 = V2 n1 n2 This is a direct relationship!So if the amount of gas increases, then the volume will ___________. If the amount of gas decreases, then the volume will __________.* n represents the amount of gasincreasedecrease
4 Graph for Avogadro’s Law What Laws have we learned were also direct relationships, in which their graphs were similar to Avogadro’s?
6 Avogadro’s LawMolar Volume – for a gas is the volume that one mole of that gas occupies at STP(STP is standard temperature and pressure which is 0oC and 1 atm)Avogadro showed experimentally that 1 mole of any gas will occupy a volume of 22.4L at STP**Conversion Factor: 1 mol (any gas) = 22.4 L at STP **(This is on your formula chart under constants and conversions!)
7 Avogadro’s Law: Example 1 Calculate the volume that moles of oxygen gas at STP will occupy.(This can be solved using the Avogadro’s law formula or using the dimensional analysis method)
8 Avogadro’s Law: Example 1 Answer Formula: V1 = V n1 n2What do we know?V1 = ? Ln1 = mol O2V2 = 22.4 Ln2 = 1 mol O2Remember, at STP:22.4 L/molSecond way to solve, using the dimensional analysis:.881 mol O2 | L =| 1 mol O2First way to solve, using the formula:V = L.881 mol O mol O2After cross multiplying you end up withV1(1 mol O2) = (22.4 L)(.881 mol O2)1 mol O mol O2V1 = ___________L19.73 L
9 Avogadro’s Law: Example 2 How many grams of N2 will be contained in a 2.0 L flask at STP?
10 Avogadro’s Law: Example 2 Answer Formula: V1 = V n1 n2What do we know?V1 = 2.0 Ln1 = ? g N2V2 = 22.4 Ln2 = 1 mol N2Remember, at STP:22.4 L/molFirst , solve for the number of moles of N2:2 L N2 | 1 mol N = mol N2| 22.4 L N2Then, use dimensional analysis to convert from moles of N2 to grams of N2:.089 mol N2 | g N = g N2| mol N2
14 Example: R = 0.0821 (Liters)(atm) (moles)(Kelvin) Ideal Gas Law FormulaFormula: PV = nRT (called Piv-Nert formula)R is called the Ideal Gas ConstantR is dependent on the units of the variables for P, V, and TTemperature is always in KelvinVolume is always in LitersPressure is either in atm, mmHg, or kPa. Because of the different pressure units, there are 3 possibilities of the ideal gas constant (refer to the EOC Chart under constants and conversions)Example: R = (Liters)(atm) (moles)(Kelvin)*We would use this value for R if the given pressure’s units are in atm*
16 Ideal Gas Law Example 1 (using moles) If the pressure by a gas at 30oC in a volume of .05 L is 3.52 atm, how many moles of the gas is present?**To know which R value to use, look at what units pressure is in**
17 Ideal Gas Law Example 1 Ans (finding moles) Formula: PV = nRTWhat do we know?P = 3.52 atmV = .05 Ln = ? molesR =T = 30oC = 303KWhat R value will we use?(Hint: Look at the units for pressure)(L*atm)/(mol*K)Now lets plug in the information and solve:P * V = n * R * T(3.52)(.05) = n(.0821)(303)(.0821)(303) (.0821)(303)n = ______________.0071 mol
18 Ideal Gas Law Example 2 (finding grams) Avogadro’s Law allows us to write a gas law that is valid not only for any P, V, or T but also for any mass of any gas! Example: Calculate the grams of N2 gas present in a L sample kept at 1.00 atm and a temperature of 22.0oC.
19 Ideal Gas Law Example 2 Answer (using moles) Formula: PV = nRTWhat do we know?P = 1.00 atmV = Ln = ? g N2R =T = 22.0oC = 295 KWhat R value will we use?(Hint: Look at the units for pressure)Now lets plug in the information and solve:P * V = n * R * T(1.00)(.600) = n(.0821)(295)(.0821)(295) (.0821)(295)n = ______________(L*atm)/(mol*K).025 mol N2But, they want the answer in grams, so we need to do dimensional analysis using molar mass:.025 mol N2 | g N2 = __________| 1 mol N2g N2
21 Ideal vs. Real GasAn ideal gas obeys all the assumptions of the kinetic theory. (Atoms or molecules are non-interacting particles, etc.)NO gas is IDEAL (ideal gas doesn’t exist). They all take up space and interact with other molecules (attraction, repultion) but most gases will behave like ideal gases at the right conditions of temp. and pressure.Real gases do NOT behave like ideal gases at extremely high pressures and extremely low temperatures.
23 ExplanationIdeal gases do not have molecular volume and show no attraction between molecules at any distanceReal gas molecules have volume and show attraction at short distances. High P will bring the molecules very close together. This causes more collisions and also allows the weak attractive forces to come into play. With low temperatures (close it gas’s liquefication point), the molecules do not have enough energy to continue on their path to avoid the attraction.
25 Dalton’s Law AnalogyIn other words, Dalton’s Law of Partial Pressure would look like this:
26 Dalton’s Law Formula Formula: Pt = P1 + P2 + P3 + ... Pt = the total pressureP1 = Partial Pressure of gas ‘1”,P2 = Partial Pressure of gas “2,”etc.**ALL Units, MUST be the same for each pressure!!!**
27 What is Dalton’s Law?Dalton’s Law of Partial Pressures – the total pressure exerted on a container by several different gases is equal to the sum of the pressures exerted on the container by each gas(Partial pressure of a gas in a mixture of gases is the pressure which that gas would exert if it were the only gas present in the container)Dalton’s Law of Partial Pressure assumes each gas in the mixture is behaving like an ideal gas
28 Dalton’s Law ExampleWhat is the atmospheric pressure (outside pressure) shown in the picture? (739.6mmHg)What is the pressure of the gas in the tube? (722.3 mmHg)Is this gas the only gas that has been collected? (No)According to the picture, what other gases can be detected in the tube? (water vapor)What is the pressure of the water vapor in the tube? (17.3mmHg)What is the temperature at which the gases have been collected? (20oC)What is the total pressure inside the tube if the atmospheric pressure is mmHg? (same as outside pressure)
29 Demo - Gas collection over water Demo Video’sSimulation (or demo - or show both):Collecting a Gas Over WaterDemo - Gas collection over water(or use Butane gas from a cigarette lighter)A more exciting Demo – Oxygen Collection Over water | <urn:uuid:a576b3af-e5ee-46d9-af4f-3556922d858e> | 4.21875 | 1,833 | Content Listing | Science & Tech. | 77.883339 | 95,626,102 |
May 11, 2017 07:13 AM EDT
Researchers at the City College of New York (CCNY) has created a photonic hypercrystals - a new material with extraordinary origins and properties people only read in science fiction stories. This strange material used to exist in theory only but has now become a reality.
Photonic hypercrystals belong to a group of materials that have the ability to manipulate light making them appear 'invisible' to the naked eye. These materials also control the propagation of photons.
Unlike its predecessors, however, photonic hypercrystals have unparallel control over photon confinement and propagation. That means it has no bandwidth limitations nor poor light emission characterized by its relatives.
Photonic hypercrystals were predicted to exist in theory only in 2014. This strange material has a photonic structure and a metamaterial component, yet Menod explained that it is very much different than its predecessors.
Photonic hypercrystals are different from photonic crystals in two ways - the period and the repeating structures, which are sub -wavelength. Moreover, they are different from metamaterials because their electromagnetic response is not dependent on polarized sub-wavelength unit cells.
That might not sound impressive and mind-bending but some of its practical uses are in the improvement of solar cells, Li-Fi, and other light-based technologies.
Li-Fi is similar to what Wi-Fi does but instead of getting signals from radio waves, it comes from flashes of light. However, Li-Fi is powered by LEDS that rapidly flash on and off. With photonic hypercrystals, such technology can now become a reality.
Vinod M. Menon, lead researcher of the study, was quick to add that although it is possible, another challenge that they face is creating the architecture of the device that will enable this technology.
Aside from Li-Fi, photonic hypercrystals can improve the ability of solar cells to harvest light and to emit light much brighter. That's because the hypercrystals enhances the strength of the interaction with matter that is inside it.
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20 July 2018
Rainbows and mini black holes
Published online 12 April 2015
As the Large Hadron Collider is restarted, physicists suggest mini black holes could be on the horizon.
Could mini black holes lie at the end of a rainbow? It sounds fanciful, but physicists have long predicted these exotic entities could be produced at the Large Hadron Collider (LHC), the world’s biggest particle accelerator, near Geneva, Switzerland.
As preparations are made for the LHC’s next run, a group of physicists from Egypt, Canada and the US have come up with an explanation for why these black holes were not found and predicts that they could be detected soon1. The reason, they claim, is that our current theory of gravity needs to be modified to a model called “rainbow gravity”.
The idea that we could produce tiny versions of cosmic black holes – entities that warp spacetime drastically, swallowing everything nearby – here on Earth was first proposed more than a decade ago2. At that time, two groups of physicists had independently suggested that our universe contains extra spatial dimensions, beyond the three that we experience3 4 , and it is why the force of gravity is so much weaker than the other fundamental forces, such as electromagnetism. They argued that gravity’s strength is reduced because – unlike the other forces – some could be leaking into extra dimensions that are too small for us to perceive normally. “Gravity feels all dimensions,” says physicist Ahmed Farag Ali, at Benha University, in Egypt, and Florida State University, USA.
These theories make an exciting prediction: If extra dimensions are real then it should be possible to create mini black holes at the LHC. These black holes would not be dangerous and would only survive for a fleeting moment, but could be recognized because they would rapidly radiate out particles in every direction, like a firework, as they dissipate. During its first run, however, the LHC ruled out the existence of mini black holes with energies up to about five tera-electronvolts (TeV).
Farag Ali and his colleagues do not think that physicists should be dismayed about the missing black holes. Using an alternative theory of gravity that was first proposed in 20045 – dubbed ‘rainbow gravity’ – they have calculated that if extra dimensions exist, then mini black holes will not be spotted until the LHC hits at least 10 TeV.
Unlike in standard gravity, in rainbow gravity the path through spacetime taken by radiation depends on its energy. Last year, Farag Ali showed that if rainbow gravity models are right, this means that cosmic black holes in space will never fully evaporate as they give out radiation6. Instead they will shrink to a certain minimum size, leaving behind a ‘remnant’.
Now, Farag Ali and colleagues have calculated that the same thing would happen at the LHC, if extra dimensions exist. “It’s only at energies above 10 TeV that mini black holes would spray out matter, making them detectable,” says Farag Ali. “Below that energy, they would just be remnants, which have lost all the properties of black holes and so cannot be recognized.”
The LHC was restarted on 5 April and aims to reach energies of 14 TeV: double that of its first run. “If they find mini black holes above 10 TeV, I think that will be good support for rainbow gravity,” says Farag Ali.
However, Greg Landsberg, a particle physicist at Brown University, Rhode Island, USA – one of the physicists that originally calculated that mini black holes may be produced at the LHC – urges caution. As the LHC ramps up to higher energies, it will become increasingly important to take into account how quantum effects combine with gravity – and that means that any black-hole signatures may be quite different to those previously expected at lower energies.
For instance, black holes could decay into a pair of particle jets, Landsberg says.
Even if such jets were discovered, there may be many different ways to explain their origin -- not just ‘rainbow black holes’.
“Finding a quantum object at 10 TeV decaying in a pair of jets would certainly generate hundreds of papers explaining its possible origin,” says Landsberg.
- Farag Ali, A., Faizal, M. & Khalil, M. M., Physics Letters B , 743, 295-300 (2015).
- Dimopoulos, S. & Landsberg, G. L. Phys. Rev. Lett., 87 (2001), p. 161602
- Arkani-Hamed, N., Dimopoulos, S. & Dvali, G., Physics Letters B, 429, 263–272 (1998).
- Randall, L., Sundrum, R. Physical Review Letters, 83 (17): 3370–3373 (1999).
- Magueijo J. & Smolin L. Classical and Quantum Gravity 21: 1725-1736 (2004).
- Ali, A. F. Phys. Rev. D 89, 104040 (2014). | <urn:uuid:131bc34a-6c65-4361-9d1b-60f42a6a0c16> | 3.453125 | 1,074 | Truncated | Science & Tech. | 56.452501 | 95,626,125 |
Marie Alfred Cornu
Marie Alfred Cornu was born in Orleans France on March 6, 1841 and was educated at the École Polytechnique and the École des Mines. He became employed as a physics professor at the École Polytechnique in 1867, a position he maintained for the rest of his life. Cornu made a wide variety of contributions to the fields of optics and spectroscopy, but is most noted for significantly increasing the accuracy of contemporary calculations of the speed of light.
In 1878, Cornu made adjustments to an earlier method of measuring the velocity of light developed by Armand Fizeau in the 1840s. The changes and improved equipment resulted in the most accurate measurement taken up to that time, 299, 990 km per second. For the achievement he was awarded membership into the French Academy of Sciences, along with the prix Lacaze and the Rumford Medal of the Royal Society of England.
Other significant accomplishments of Cornu include a photographic study of ultraviolet radiation and the establishment of a graphical approach, known as the Cornu spiral, for calculating light intensities in Fresnel diffraction. A proponent of the wave theory of light, Cornu was also interested in the relationship between electricity and optics and the understanding of weather phenomena. He played a considerable part in the creation of the Observatory of Nice and in 1886 became associated with the Office of Longitudes. He received several honors during his lifetime, including an honorary doctorate from Cambridge University awarded three years before his death in April of 1902.
Measuring the Speed of Light - Starting with Ole Roemer's 1676 breakthrough endeavors, the speed of light has been measured at least 163 times by more than 100 investigators utilizing a wide variety of different techniques. Finally in 1983, more than 300 years after the first serious measurement attempt, the speed of light was defined as being 299,792.458 kilometers per second by the Seventeenth General Congress on Weights and Measures. Thus, the meter is defined as the distance light travels through a vacuum during a time interval of 1/299,792,458 seconds. In general, however, (even in many scientific calculations) the speed of light is rounded to 300,000 kilometers (or 186,000 miles) per second.
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Effects of Reduced Oxygen on Embryos and Larvae of the White Sucker, Coho Salmon, Brook Trout, and Walleye
This study was made to determine the effects of continuous-reduced dissolved oxygen concentrations on the development and survival of the white sucker, (Catostomus commersoni (Lacepede)), coho salmon, (Oncorhynchus kisutch (Walbaum)), brook trout, (Salvelinus fontinalis (Mitchell)), and walleye, (Stizostedion vitreum vitreum (Mitchell)), from fertilization until the larvae were feeding. The effects of reduced oxygen concentrations on survival and hatching of embryos have been described for white suckers (Oseid and Smith, 1971b), coho salmon (Shumway et al., 1964; Phillips et al., 1966), brook trout (Garside, 1966), and walleyes (Oseid and Smith, 1971a; Van Horn and Balch, 1956). However, these studies extended only through hatching and give no information on larval development and survival. Mason (1969) subjected coho salmon embryos and larvae to 2 reduced oxygen concentrations, but developmental delay at the reduced oxygen levels was compensated for by adjusted water temperatures.
KeywordsOxygen Concentration Dissolve Oxygen Concentration Experimental Chamber Brook Trout Coho Salmon
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- American Public Health Association, 1965. Standard methods for the examination of water and waste-water. 12th ed. New York, 169 pp.Google Scholar
- Anonymous, 1967. Temperatures for hatching walleye eggs. Progve Fish Cult., 29, 20.Google Scholar
- McAfee, W.A., 1966. Eastern brook trout. In: A Calhoun (ed.), Inland Fisheries Management; California Department of Fish and Game, 242–260 pp.Google Scholar
- Phillips, R.W., Campbell, H.J., Hug, W.L. and Claire, E.W., 1966. A study of the effect of logging on aquatic resources, a progress report, 1960–1966. Progress Memorandum, Fish. No. 3, Oregon State Game Comm., 28 pp.Google Scholar
- Siefert, R.E., Spoor, W.A. and Syrett, R.F., 1973. Effects of reduced oxygen concentrations on northern pike (Esox lucius Linnaeus) embryos and larvae. J. Fish. Res. Bd Can., 30, (in press).Google Scholar
- Van Horn, W.M. and Balch, R., 1956. The reaction of walleyed pike eggs to reduced dissolved oxygen concentrations. Purdue Univ. Engineering Ext. Dept., Series No. 91, 319–341.Google Scholar | <urn:uuid:3727987f-cbf0-43fd-951e-838bf9a1b4cd> | 3.09375 | 590 | Academic Writing | Science & Tech. | 57.845055 | 95,626,158 |
X-Ray Laser Solves Virus Structure at the Atomic Level
Surface structure of the bovine enterovirus 2, the three virus proteins are colour coded. Credit: Jingshan Ren, University of Oxford
An international team of scientists has for the first time used an X-ray free-electron laser to unravel the structure of an intact virus particle on the atomic level. The method used dramatically reduces the amount of virus material required, while also allowing the investigations to be carried out several times faster than before. This opens up entirely new research opportunities, as the research team lead by DESY scientist Alke Meents reports in the journal Nature Methods.
In the field known as structural biology, scientists examine the three-dimensional structure of biological molecules in order to work out how they function. This knowledge enhances our understanding of the fundamental biological processes taking place inside organisms, such as the way in which substances are transported in and out of a cell, and can also be used to develop new drugs.
“Knowing the three-dimensional structure of a molecule like a protein gives great insight into its biological behaviour,” explains co-author David Stuart, Director of Life Sciences at the synchrotron facility Diamond Light Source in the UK and a professor at the University of Oxford. “One example is how understanding the structure of a protein that a virus uses to ‘hook’ onto a cell could mean that we’re able to design a defence for the cell to make the virus incapable of attacking it.”
X-ray crystallography is by far the most prolific tool used by structural biologists and has already revealed the structures of thousands of biological molecules. Tiny crystals of the protein of interest are grown, and then illuminated using high-energy X-rays. The crystals diffract the X-rays in characteristic ways so that the resulting diffraction patterns can be used to deduce the spatial structure of the crystal – and hence of its components – on the atomic scale. However, protein crystals are nowhere near as stable and sturdy as salt crystals, for example. They are difficult to grow, often remaining tiny, and are easily damaged by the X-rays.
“X-ray lasers have opened up a new path to protein crystallography, because their extremely intense pulses can be used to analyse even extremely tiny crystals that would not produce a sufficiently bright diffraction image using other X-ray sources,” adds co-author Armin Wagner from Diamond Light Source. However, each of these microcrystals can only produce a single diffraction image before it evaporates as a result of the X-ray pulse. To perform the structural analysis, though, hundreds or even thousands of diffraction images are needed. In such experiments, scientists therefore inject a fine liquid jet of protein crystals through a pulsed X-ray laser, which releases a rapid sequence of extremely short bursts. Each time an X-ray pulse happens to strike a microcrystal, a diffraction image is produced and recorded.
This method is very successful and has already been used to determine the structure of more than 80 biomolecules. However, most of the sample material is wasted. “The hit rate is typically less than two per cent of pulses, so most of the precious microcrystals end up unused in the collection container,” says Meents, who is based at the Center for Free-Electron Laser Science (CFEL) in Hamburg, a cooperation of DESY, the University of Hamburg and the German Max Planck Society. The standard method therefore typically requires several hours of beamtime and significant amounts of sample material.
In order to use the limited beamtime and the precious sample material more efficiently, the team developed a new method. The scientists use a micro-patterned chip containing thousands of tiny pores to hold the protein crystals. The X-ray laser then scans the chip line by line, and ideally this allows a diffraction image to be recorded for each pulse of the laser.
The research team tested its method on two different virus samples using the LCLS X-ray laser at the SLAC National Accelerator Laboratory in the US, which produces 120 pulses per second. They loaded their sample holder with a small amount of microcrystals of the bovine enterovirus 2 (BEV2), a virus that can cause miscarriages, stillbirths, and infertility in cattle, and which is very difficult to crystallise.
In this experiment, the scientists achieved a hit rate – where the X-ray laser successfully targeted the crystal – of up to nine per cent. Within just 14 minutes they had collected enough data to determine the correct structure of the virus – which was already known from experiments at other X-ray light sources – down to a scale of 0.23 nanometres (millionths of a millimetre).
“To the best of our knowledge, this is the first time the atomic structure of an intact virus particle has been determined using an X-ray laser,” Meents points out. “Whereas earlier methods at other X-ray light sources required crystals with a total volume of 3.5 nanolitres, we managed using crystals that were more than ten times smaller, having a total volume of just 0.23 nanolitres.”
This experiment was conducted at room temperature. While cooling the protein crystals would protect them to some extent from radiation damage, this is not generally feasible when working with extremely sensitive virus crystals. Crystals of isolated virus proteins can, however, be frozen, and in a second test, the researchers studied the viral protein polyhedrin that makes up a viral occlusion body for up to several thousands of virus particles of certain species. The virus particles use these containers to protect themselves against environmental influences and are therefore able to remain intact for much longer times.
For the second test, the scientist loaded their chip with polyhedrin crystals and examined them using the X-ray laser while keeping the chip at temperatures below minus 180 degrees Celsius. Here, the scientists achieved a hit rate of up to 90 per cent. In just ten minutes they had recorded more than enough diffraction images to determine the protein structure to within 0.24 nanometres. “For the structure of polyhedrin, we only had to scan a single chip which was loaded with four micrograms of protein crystals; that is orders of magnitude less than the amount that would normally be needed,” explains Meents.
“Our approach not only reduces the data collection time and the quantity of the sample needed, it also opens up the opportunity of analysing entire viruses using X-ray lasers,” Meents sums up. The scientists now want to increase the capacity of their chip by a factor of ten, from 22,500 to some 200,000 micropores, and further increase the scanning speed to up to one thousand samples per second. This would better exploit the potential of the new X-ray free-electron laser European XFEL, which is just going into operation in the Hamburg region and which will be able to produce up to 27,000 pulses per second. Furthermore, the next generation of chips will only expose those micropores that are currently being analysed, to prevent the remaining crystals from being damaged by scattered radiation from the X-ray laser.
This article has been republished from materials provided by Deutsches Elektronen-Synchrotron (DESY) . Note: material may have been edited for length and content. For further information, please contact the cited source.
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Acris gryllus (LeConte, 1825)
Southern Cricket Frog
John B. Jensen1
1. Historical versus Current Distribution. Southern cricket frogs (Acris gryllus) are found primarily below the Fall Line, in both the Atlantic and Gulf coastal plains, from southeastern Virginia south and west to eastern Louisiana, including all of Florida (Mecham, 1964). Populations are also known above the Fall Line in the Cumberland Plateau and Ridge and Valley of Alabama (Mount, 1975), as well as the Piedmont of Georgia (Williamson and Moulis, 1994). Two subspecies are recognized: Florida cricket frogs (A. g. dorsalis), found in Florida and adjacent portions of Alabama and Georgia, and the larger Coastal Plain cricket frogs (A. g. gryllus), found throughout the remainder of the range (Conant and Collins, 1991). No changes in the distribution of either subspecies have been noted.
2. Historical versus Current Abundance. The naturalist J.D. Corrington (1929) noted that southern cricket frogs are “the most abundant amphibian in the [southeastern United States]. Each roadside pool or ditch contained numerous individuals and the swamps and marshes literally swarmed with them.” Deckert (1915) commented that they are “one of the commonest frogs.” Many regional guides have also indicated that this species is abundant (Martof et al., 1980; Dundee and Rossman, 1989; Gibbons and Semlitsch, 1991; Wilson, 1995). More recently, however, there have been indications that southern cricket frogs may be declining locally. Means and Means (2000) found that the number of breeding populations of southern cricket frogs in the Munson Sand Hills of panhandle Florida occur at a much lower percentage on silviculture lands than in nearby native habitat. They hypothesize that elimination or severe alteration of the upland habitat, resulting from intensive soil disturbance, is the principal reason. This is corroborated by a 1996–'98 rare amphibian survey conducted at 444 sites on industrial forest lands in south Georgia, south Alabama, and north Florida (Wigley et al., 1999). This study revealed that ponds where southern cricket frogs were found had a substantially lower frequency of intensive site preparation and lower density of planted pines in pond edges and surrounding upland habitats than those ponds where this species was not detected.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. The adult breeding and non-breeding habitats do not differ substantially, therefore true breeding migrations may not exist for this species. Southern cricket frogs typically breed February–October (Wright and Wright, 1949). Although southern cricket frogs may breed throughout the year in Florida, the peak of their breeding activity occurs April to autumn (Carr, 1940b; Einem and Ober, 1956). Mecham (1964) noted an April to early June breeding peak in Alabama. Surges in breeding activity are strongly correlated with periodic rain events (Turnipseed and Altig, 1975). Males call both day and night (Deckert, 1915; Mount, 1975).
ii. Breeding habitat. Nearly every type of freshwater habitat, both temporary and permanent, found within the range of southern cricket frogs has been indicated by one authority or more as suitable breeding habitat, including lake margins, rivers, creeks, sinkhole ponds, cypress ponds, open grassy ponds, bogs, marshes, Carolina bays, bottomland swamps, shallow pools, and roadside ditches (Wright and Wright, 1949; Mount, 1975; Martof et al., 1980; Ashton and Ashton, 1988; Gibbons and Semlitsch, 1991). Southern cricket frogs have also been found breeding in interdunal pools within 18.3 m (20 yd) of the ocean (Neill, 1958a). Males call from mats of floating vegetation in the water or from protected areas along the shore (Mount, 1975). Breeding sites may or may not contain predatory fish (Gibbons and Semlitsch, 1991). In Louisiana and perhaps elsewhere, southern cricket frogs are typically associated with more acidic waters than sympatric northern cricket frogs (A. crepitans; Viosca, 1944).
i. Egg deposition sites. Eggs are attached to the stems of vegetation or stones or spread on the pond bottom (Wright and Wright, 1949; Mount, 1975).
ii. Clutch size. Eggs are laid singly (Wright, 1923) or in small clusters of 7–10, and each female may lay up to 250 eggs (Ashton and Ashton, 1988). Hatching occurs ≥ 4 d following oviposition, depending on the water temperature (Ashton and Ashton, 1988).
i. Length of larval stage. Typically 50–90 d (Wright and Wright, 1949), though possibly as quickly as 41 d (Ashton and Ashton, 1988). Southern cricket frogs transform after tadpoles reach 9–15 mm SVL (Wright and Wright, 1949).
ii. Larval requirements.
a. Food. Unknown, though tadpoles likely graze on algae.
b. Cover. Tadpoles are most readily captured in submerged and emergent vegetation, suggesting they use this microhabitat for cover and/or feeding.
iii. Larval polymorphisms. Unknown for this species.
iv. Features of metamorphosis. Metamorphosis occurs from April–October and newly metamorphosed animals are 9–15 mm SVL (Wright and Wright, 1949).
v. Post-metamorphic migrations. Unknown.
D. Juvenile Habitat. Unknown, but thought to be similar to adults.
E. Adult Habitat. Not known to differ substantially from breeding habitats (see “Breeding habitat” above). However, southern cricket frogs are occasionally observed in uplands quite distant from the nearest aquatic habitat (personal observations). In fact, Wright and Wright (1949) indicated that they are often terrestrial in meadows or wooded edges. Whether or not upland habitats are used substantially by this species other than as corridors between aquatic sites is unknown. The relatively few southern cricket frogs found at wetlands surrounded by intensive silviculture versus those surrounded by natural habitats or lower intensity silviculture (Wigley et al., 1999; Means and Means, 2000) may indicate that terrestrial habitats are important to some aspect of this species’ life history. Terrestrial foraging, noted by Ashton and Ashton (1988), may be one such aspect. Mount (1975) noted that above the Fall Line, southern cricket frogs are more often found associated with sandy soils. There is no information to indicate a difference in habitat characteristics between the sexes.
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Southern cricket frogs may be found year-round (Corrington, 1929; Mount, 1975) and breed during summer (Wright and Wright, 1949), suggesting that aestivation is unlikely.
I. Seasonal Migrations. Unknown.
J. Torpor (Hibernation). Fewer southern cricket frogs are seen during mid winter than at other times of the year, which may indicate that the majority of individuals hibernate (Corrington, 1939). However, animals in southern populations remain active, and perhaps breed, throughout the year (Wright and Wright, 1949; Mount, 1975).
K. Interspecific Associations/Exclusions. Southern cricket frogs will occasionally hybridize with northern cricket frogs (Neill, 1954; Mount, 1975). Southern cricket frogs call and breed in association with many other anurans, including northern cricket frogs, American bullfrogs (Rana catesbeiana), southern leopard frogs (Rana sphenocephala), spring peepers (Pseudacris crucifer), barking treefrogs (Hyla gratiosa), Cope's gray treefrogs (Hyla chrysoscelis), and Fowler's toads (Bufo fowleri; Cahn, 1939), as well as oak toads (Bufo quercicus), southern toads (Bufo terrestris), pine woods treefrogs (Hyla femoralis), southern chorus frogs (Pseudacris nigrita), ornate chorus frogs (Pseudacris ornata), gopher frogs (Rana capito), pig frogs (Rana grylio), and carpenter frogs (Rana virgatipes; personal observations).
L. Age/Size at Reproductive Maturity. Males 15–29 mm SVL; females 16–33 mm (Wright and Wright, 1949).
M. Longevity. Unknown.
N. Feeding Behavior. Southern cricket frogs may forage a good distance from the water’s edge, especially during the day (Ashton and Ashton, 1988). Bayless (1969) examined the stomachs of southern cricket frogs and found a variety of arthropods, especially springtails, hymenopterans, spiders, dipterans, beetles, and homopterans.
O. Predators. Southern cricket frogs are commonly preyed upon by water and garter snakes, as well as by a large variety of aquatic predators such as other frogs, fishes, and birds (Ashton and Ashton, 1988). Fish predators include redfin pickerel (Esox americanus), largemouth bass (Micropterus salmoides), and bluegill (Lepomis macrochirus; Ferguson et al., 1965). Pine woods littersnakes (Rhadinaea flavilata ) have been reported to “readily” eat southern cricket frogs (Allen, 1939).
P. Anti-Predator Mechanisms. Southern cricket frogs will make one or more long, erratic leaps to escape predation (Conant and Collins, 1991). They shun open water; following leaps into water they will immediately and quickly return back to shore (Mount, 1975). However, southern cricket frogs may attempt to elude detection by hiding in the debris on the pond bottom (Blem et al., 1978). They are also known to hop from the ground into bushes and back down again (Wright and Wright, 1949). Additionally, astronomical orientation may be used to avoid predation by fish (Ferguson et al., 1965).
Q. Diseases. Unknown.
R. Parasites. Unknown.
4. Conservation. Southern cricket frogs remain common throughout their range, although they may be declining locally. In the Munson Sand Hills region of panhandle Florida, there are lower numbers of breeding populations of southern cricket frogs on silviculture lands than in nearby native habitat; Means and Means (2000) hypothesize that elimination or severe alteration of the upland habitat, resulting from intensive soil disturbance, is the principal reason. A 1996–98 amphibian survey conducted on industrial forest lands in south Georgia, south Alabama, and north Florida (Wigley et al., 1999) corroborates Means and Means (2000) interpretation. Wigley et al. (1999) found that ponds with substantially higher frequencies of intensive site preparation and higher densities of planted pines along pond edges and in surrounding upland habitats had reduced numbers of southern cricket frogs.
1John B. Jensen
Nongame-Endangered Wildlife Program
Georgia Department of Natural Resources
116 Rum Creek Drive
Forsyth, Georgia 31029
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
Feedback or comments about this page.
Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Jul 2018.
AmphibiaWeb's policy on data use. | <urn:uuid:a280fc51-13d1-4e9b-b506-ebbefe857305> | 3.640625 | 2,467 | Knowledge Article | Science & Tech. | 47.725164 | 95,626,179 |
is a photon a particle?
A photon can be considered to be either a particle or as a fluctuation in an electromagnetic field, field depending on what it it is you want to consider.
There's no easy, accurate answer to that question. You either get an easy answer or an accurate answer, not both.
Yes, you can consider a photon as being a particle in some contexts. BUT it is not a particle like a tiny bullet and you cannot make any 'mechanical' type assumptions about how it will behave. You cannot, for instance, tell 'where it is', until it has interacted with something. It can be literally anywhere, which is an odd notion until you come to terms with its abnormal particle nature.
The word "particle", as used in quantum electrodynamics, has a specific meaning. A photon is a particle according to that definition.
But there's a catch here.... The meaning of the word "particle" used in quantum field theories does not match the non-technical English-language meaning of the word, so saying that "a photon is a particle" isn't saying what you might be thinking it means.
The Particle Data Group (the "official" repository of particle data for particle physicists) includes data for the photon in the same table as the W, Z, gluons and Higgs:
(in that table of contents, it's called the "gamma.")
If a single photon is emitted must you be in its "line of fire" to detect it? If I was 30 feet left or right wouldn't I miss detecting it?
Is its wavelength less than about 30 feet?
What is this "line of fire" of which you speak? This thing isn't a little bullet.
Let's say a photon is emitted from a source and we know the direction that's it emoted. Let's say 100 people are evenly distributed around a one mile radius sphere centered on the source.
Clearly all 100 people cannot detect the photon. Only one (if any) will be able to detect the photon due to his position in relation to the direction of the emission.
Can we make some general statements about this such as...
Only the person in the direction of the emission will be able to detect the emission. This assumes the particle acts like a particle or a little bullet so that only someone in its line of fire will detect it. Or...
Everyone will be able to detect it. This assumes it acts like a wave and everyone will be hit by the wave and thus able to detect it. If it acts as a wave its potential energy will be continually reduced by the inverse of the distance and would be nearly non existent after only a short distance ( many miles).
So, if a single photon is emitted who among the 100 is most likely to detect it?
How do we know the direction that it's emitted?
let's say it is emitted in the direction of point A on the sphere using a little photon emitting gun
Neither of these "this assumes" statements are correct. You are asking classical questions about a quantum system.
It doesn't work like that. Photons are not bullets that can be fired from a little gun.
If you prepare a photon state with a well defined position then the momentum will be undefined. So you could prepare states with a wide variety of wavefunctions, each with different detection characteristics.
If you made the photon state tightly concentrated on one detector, then the probability of being detected by other detectors would be small. If you made the photon state more dispersed then the probability would be higher that other detectors would detect it.
That is true in general. However, there are single photon sources that can send one (and only one) photon in a particular direction (or even launch it into a waveguide). Hence, there is nothing intrinsically wrong with that thought experiment.
In fact, on-demand single photon sources are actually sometimes (informally) referred to as "machine gun-type sources" (presumably because they send out as photons when triggered)
Also, if it is in fact a single photon it can only be detected once. However, most sources do NOT send out single photons.
If I have a powerful point or nearly point light source and surround it with a light proof sphere no light will get out. Now if I put a pinhole in the sphere only someone in line with the source and the hole will see the light. No one even slightly to one side will see the light. In fact there will only be spot of light on a distant surface.
Therefore the photon(s) are clearly distinct and directional. Whether they are particles or waves is at dispute. Particles would explain the observation. If waves then one would have to explain how the waves AS WAVES could be so precisely contained to a ray of light. A laser is a good example of this.
Im aware of the slit experiment. I'm not questioning that light and photons act as waves and particles. My simple question is this...is a photon a particle as it travels from source to receiver or wave?
How do you avoid light diffraction?
Everyone will be in line with the source and a hole: given two points in space, there always is a straight line passing through them.
Cannot understand here.
They are clearly distinct if you generate them in such a way, but they are not clearly directional. They don't have "nadelsstrahlung" (needle-like radiation) as even Einstein initially believed. Prove: light diffraction.
Maybe you intended "corpuscles". Infact they are particles: as Nugatory wrote, "particle" in QM means something which has both corpuscolar and wave behaviour.
It's easy to describe this behaviour as waves, instead. You only have to take a monochromatic wave with low enough wavelenght (low with respect to all the other dimensions involved in the experiment = geometrical optics approximation) and which is very collimated (you can obtain this making the radiation pass through distant holes made on parallele screens). Nothing particularly difficult.
Well here the point I'm driving at. Let's just take one star...I ca seethe light front he star no matter where I move my head. Therefore light from the star permeates every cubit centimeter of space. Therefore every cubit centimeter of space is filled with "something" from the one star.
What is the something? Jillions of photon particles or a sea of photon waves?
A sea of quantum objects which are neither particles nor waves but show properties of both (depending on the conditions).
It is much more complicated than that. If the photons are emitted by a true single photon source they are indeed quite "particle like" (with undetermined phase). However, if the source is coherent (say a laser) it is more akin to classical source and it will be -in general- behave a bit more like a classical wave. In the the full theory of light (QED) we refer to different types of fields (and states of light). Note for most states the number of photons in not even fixed so talking about a number of photons is meaningless.
It is important to realize that there is no mystery here. We have an extremely accurate theory for light (quantum electrodynamics, QED) meaning the "nature" of photons is fully understood, but you need to know a fair amount of math to understand the explanation: there is no simple intuitive picture.
The energy of an electromagnetic wave is quantized, meaning that when I put a detector, such as my eye or a camera, in the path of the wave, the transfer of energy from the wave to my detector is not continuous, but takes place in discrete amounts. A photon is this discrete transfer of energy from the wave to the detector. In laymen terms it is a little packet or bundle of energy given up to or from the wave during an interaction.
This is not the way light works even classically. Because of diffraction a small pinhole acts essentially as a point source.
With photons it becomes even weirder because a single photon has no single well defined path and can take multiple paths. This is clearly seen in the two slit experiment and (even more convincing IMO) in diffraction gratings.
Classical EM works fine for this. There is no need to consider quantum effects. It is just a field of essentially spherical incoherent EM radiation.
The Texan wrote: "My simple question is this...is a photon a particle as it travels from source to receiver or wave?"
My simple answer is that as it travels it is a wave, but when it reaches the observer the wave function collapses into a photon.
When photon moves, it behaves like a particle having kinetic energy .It behaves like a particle having rest mass zero with electromagnetic properties.
Separate names with a comma. | <urn:uuid:e5544d4a-ec0b-4ff1-9ab5-868afd3783bc> | 3.046875 | 1,851 | Comment Section | Science & Tech. | 54.516897 | 95,626,199 |
A very cool feature of Python is that it allows for simultaneous assignment. The syntax is as follows:
var_name1, var_name2 = value1, value2
This can be useful as a shortcut for assigning several values at once, like this:
smart_1, cute_1, funny_1, quiet_1 = "John","Paul","Ringo","George"
But simultaneous assignment is really useful in a scenario like the one shown below.
a=5 b=10 a=b b=a print("ATTEMPT 1. The Wrong Way.") print(a) print(b)
a=5 b=10 temp=a a=b b=temp print("ATTEMPT 2. A Non-Pythonic Way that Works.") print(a) print(b)
a=5 b=10 a,b = b,a print("ATTEMPT 3. The Python Way.") print(a) print(b)
The output should look like this:
The code demonstrates that simultaneous assignment really is simultaneous. The value for
a does not change before the value of
b gets the original value of
a, and we can switch the values without using an interim step of creating a temporary (and otherwise useless) variable.
Nat Dunn founded Webucator in 2003 to combine his passion for technical training with his business expertise and to help companies benefit from both. His previous experience was in sales, business and technical training, and management. Nat has an MBA from Harvard Business School and a BA in International Relations from Pomona College. | <urn:uuid:bae57126-d914-4774-8c06-3789d559c995> | 3.21875 | 327 | Tutorial | Software Dev. | 61.954788 | 95,626,210 |
What is Incidence Matrix?
Incidence matrix is that matrix which represents the graph such that with the help of that matrix we can draw a graph. This matrix can be denoted as [AC] As in every matrix, there are also rows and columns in incidence matrix [AC].
The rows of the matrix [AC] represent the number of nodes and the column of the matrix [AC] represent the number of branches in the given graph. If there are ‘n’ number of rows in a given incidence matrix, that means in a graph there are ‘n’ number of nodes. Similarly, if there are ‘m’ number of columns in that given incidence matrix, that means in that graph there are ‘m’ number of branches.
In the above shown graph or directed graph, there are 4 nodes and 6 branches. Thus the incidence matrix for the above graph will have 4 rows and 6 columns. The entries of incidence matrix is always -1, 0, +1. This matrix is always analogous to KCL (Krichoff Current Law). Thus from KCL we can derive that,
|Type of branch||Value|
|Outgoing branch from kth node||+1|
|Incoming branch to kth node||-1|
You may also be interested on
Steps to Construct Incidence MatrixFollowing are the steps to draw the incidence matrix :-
- If a given kth node has outgoing branch, then we will write +1.
- If a given kth node has incoming branch, then we will write -1.
- Rest other branches will be considered 0.
Examples of Incidence Matrix
For the graph shown above write its incidence matrix.
Reduced Incidence MatrixIf from a given incidence matrix [AC], any arbitrary row is deleted, then the new matrix formed will be reduced incidence matrix. It is represented by symbol [A]. The order of reduced incidence matrix is (n-1) × b where n is the number of nodes and b is the number of branches. For the above shown graph, the reduced incidence matrix will be :- [NOTE :- In the above shown matrix row 4 is deleted.] Now let us consider a new example related to reduced incidence matrix. For the graph shown above write its reduced incidence matrix. Answer:- In order to draw reduced incidence matrix first of all draw its incidence matrix. Its incidence matrix is :- Now drawing its reduced incidence matrix. For this we just simply have to delete any node (in this we have deleted node 2). Its reduced incidence matrix is:- This is the required answer. Points to remember
- For checking correctness of incidence matrix which we have drawn, we should check sum of column.
- If sum of column comes to be zero, then the incidence matrix which we have created is correct else incorrect.
- The incidence matrix can be applied only to directed graph only.
- The number of entries in a row apart from zero tells us the number of branches linked to that node. This is also called as degree of that node.
- The rank of complete incidence matrix is (n-1), where n is the number of nodes of the graph.
- The order of incidence matrix is (n × b), where b is the number of branches of graph.
- From a given reduced incidence matrix we can draw complete incidence matrix by simply adding either +1, 0, or -1 on the condition that sum of each column should be zero.
|A||ADITYA commented on 25/04/2018|
Detailed explanation. Thank you so much. | <urn:uuid:fe98dd3a-0e58-446c-804f-3370f49d813b> | 3.4375 | 743 | Tutorial | Science & Tech. | 58.00997 | 95,626,224 |
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An Ultimate Guide to Android App Development with Java If you are new to Android App Development, this is where you should start. Here is a comprehensive guide that gives you a bird-eye view to develop custom Android app development with Java. The Android app framework works around the Java programming language and specifically starting with Java 7, Android uses a customized version of open JDK, an open source implementation of Java from Oracle. Prior to Android 7, Android used a customized version of Java that was descended from another tool kit but the way you program with Java and Android has not changed significantly. In Android, all Java 5 and 6 syntax is supported and most Java 7 syntak works as well. If you choose, you can configure a project to use what's known as the Jack compiler, which is part of a tool chain named Jack and Jill. If you turn on the Jack compiler, you'll then be able to use a lot of Java 8 syntax including Lambda expressions and method references but that doesn't mean everything in Java 7 and Java 8 is available to you. For example, not all Java APIs are implemented in the Android SDK. To find out whether a particular API is available, look at the Android documentation. Here's a listing of some Java syntax that works and doesn't work. The diamond operator allows you to reduce code with generic typing. So that for example, with a collection, you need to declare the type of the items that are being managed by the collection in the declaration but you don't need to re-declare it in the assignment. Another Java 7 improvement that does work with Android is the switch statement with string based values. You can also use multicatch clauses and underscores in numeric literals but there are some things in Java syntax that don't work across the board. The try-with-resources syntax, which allows you to automatically close objects that implement an interface named Closeable can only be used in an app if the minimum SDK is set to API 19 or greater. If you want to target older versions of Android, you just can't use that syntax and there's annotation named @SafeVarargs in Java 7 that's not a part of Android because the required dependent class just isn't implemented. Many of Java's standard APIs are implemented in the Android SDK. For example, everything in java.lang is there and most everything in java.io and nio, java.math, java.net and so on, are all a part of the Android SDK. But again, this doesn't mean everything is
available. You just need to look at the docs to find out whether something is available in Android. The Android SDK also includes many custom APIs. These are features that are in custom packages that typically start with Android and end with a description of what that package does. So for example, android.app, android.database, android.net and so on, include classes and interfaces that aren't available in general Java but are available for Android. To learn what's available, look at the API reference at this URL. When you build an app in Android studio or from the command line, there are two possible build process that you can use. The default build process, as of October 2016, is called the Legacy process, and here's how it works. You start off with a set of java files, either source code files or files that have been pre-compiled to bytecode code in .class files. These are processed through the standard javac compiler which turns these files into class files, Java bytecode. From there, optionally, you can transform those classes using a tool called ProGuard. The ProGuard tool minimizes and obfuscates the bytecodeso that it's harder to decompile and it's smaller. After ProGuard does it's thing, you still have .class files but they'll be smaller than the original files. Then these files are taken through a tool called DEX which turns the files into DEX based bytecode. DEX bytecode is universal bytecode for Android and this is what's actually packaged in the application when it's deployed to devices through the app store. Now if you configure your project to use the Jack compiler to allow you to use for example, Java 8 based syntax, the process of building the app is a little bit different. You once again start off with your Java files, either source code files or pre-compiled class files. These are processed through the Jack compiler which goes directly to the DEX bytecode. The Jack compiler does all of the tasks that javac and ProGuard were used for in the Legacy process. It does the compilation and optionally can minimize and obfuscate the code. When you use the Jack compiler, you'll see that your compilation process is a little bit faster and you'll be able to use a lot more Java syntax than before. There's one downside to using the Jack compiler that I know of at this point and that's that in Android Studio there's a great tool called Instant Run which can deploy parts of an application to a testing device. Projects that are built with the Jack compiler don't support Instant Run at this point. So especially when working with larger applications, they'll take a lot longer to build and deploy during the coding and testing process. If you're willing to put up with that, it's worth going over to the Jack compiler to
give yourself more flexibility in coding style. Once the DEX code is delivered to the device, what happens then depends on which version of Android is being run. The DEX bytecode has to be translated to machine code on the device. Android can run on a variety of CPU's from ARMSs to Intel chips and so on, and so the machine code that's going to be really fast at runtime has to be built by tools that are on that device. What changes from one Android version to another, is when that DEX code is created. On the Dalvik runtime in Android 4.4 and prior, DEX bytecode is built as the application is running each time a feature is used for the first time. This process is called just in time or JIT compilation. Starting with the Android runtime in Android 5, the process moved to ahead of time compilation. And in Android 5 and 6, this process happened when the app was installed or upgraded or when the operating system was upgraded. In Android 7, Nougat, this process has been changed yet again. Now each application will be compiled ahead of time the first time it's started up and that means when you upgrade your device, going to a more recent version of Android, it reduces the amount of time it takes. All of the applications don't all have to be re-compiled, significantly delaying the amount of time before you can actually use the device. So that's how Java is used in custom Android app development. Again which aspect of Java you'll be able to use depends on which version of Android you're using and which version of Android Studio you're using and whether you've configured your project to work with the new Jack and Jill tool chain and the Jack compiler. BTC Mobile App Development Partner for your Enterprise If you want to leverage the power of enterprise mobility to grow your business to next level, BTC can help you to do so. We have clients from Fortune 500 companies to big enterprises. Our services range from Android app development, iOS mobile app development and Enterprise Mobile App Development. | <urn:uuid:b6f4bef5-5219-4861-b88b-aac3142c6bca> | 2.6875 | 1,505 | Documentation | Software Dev. | 54.857266 | 95,626,239 |
Thursday, March 8, 2012
A transfer RNA (tRNA) is a small RNA (ribonucleic acid) molecule, about 80 nucleotides long that acts as a carrier of specific amino acids during protein synthesis. A molecule of transfer RNA, which is specific for a particular amino acid, binds to that amino acid. The sequence of three nucleotides that make up the anti-codon on the tRNA recognize and bind to the codon on the messenger RNA, which is complexed with a ribosome on which a polypetide chain developing. The amino acid is thus guided into the proper position on the ribosome-mRNA complex to be enzymatically added to the polypeptide chain. There is at least one tRNA for each kind of amino acid. | <urn:uuid:6547b70d-2c52-4883-8218-4acad899e7c8> | 3.8125 | 163 | Personal Blog | Science & Tech. | 35.835 | 95,626,277 |
The Interactions of Food, Prey, and Predators in Outbreaks
Jensen and Ball (1970) experimented with about as simple an interaction between an organism, its food, and its predator, as it is possible to get — populations of bacteria and their protozoan predators maintained in culture flasks of water. They obtained the organisms from natural populations in a Michigan river, and added nothing but a sterile nutrient solution to the cultures. The bacteria grew on the nutrient solution and the protozoa ate the bacteria. By adding the same amount of this nutrient solution to flasks once every 7 days, they generated weekly peaks of great abundance of bacteria followed by peaks of protozoa. After each peak the numbers of both organisms remained at very low levels until the next injection of food. This manipulation had generated a classic feedback alternation of a cyclic prey and its predator. However, when they added exactly the same amount of nutrient solution each week, but in equal daily amounts, these regular peaks and troughs of bacteria and protozoa failed to appear. The numbers of both organisms continued to fluctuate, but instead at much lower amplitudes, and at random to each other and in time. A clear demonstration of the dependence of both organisms on their food supply.
KeywordsNutrient Solution Thought Experiment Poor Site Rabbit Population Relative Shortage
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Hardly a natural history documentary goes by without some mention of leafcutter ants. So overexposed are these critters that I strongly suspect they’re holding David Attenborough’s relatives to ransom somewhere. But there is good reason for their fame – these charismatic insects are incredibly successful because of their skill as gardeners.
As their name suggests, the 41 species of leafcutter ants slice up leaves and carry them back to their nests in long columns of red and green. They don’t eat the leaves – they use them to grow a fungus, and it’s this crop that they feed on. It’s an old, successful alliance and the largest leafcutter colonies redefine the concept of a “super-organism”. They include over 8 million individuals, span more than 20 cubic metres and harvest more than 240 kg of leaves every year. They’re technically plant-eaters, with the fungus acting as the super-organism’s external gut.
But the partnership between ant and fungus depends on other collaborators – bacteria. Some of these microbes help the ants to fertilise their gardens with valuable nitrogen, by capturing it from the atmosphere (a process known as “fixing”). Adrian Pinto-Tomas from the University of Wisconsin-Madison managed to isolate strains of these “nitrogen-fixing bacteria” from the gardens of 80 leafcutter colonies, throughout South and Central America.
Nitrogen is a scarce commodity for leafcutters, and the leaves they cut have too little of this vital element. And yet, they clearly get it from somewhere. The exhausted leaves they chuck into their refuse piles have higher proportions of nitrogen than those in the gardens, which have higher proportions than those that are freshly harvested or in the local leaf litter. Somewhere along the way, the cut leaves become enriched with nitrogen.
To find out how, Pinto-Tomas searched captive colonies of leafcutters for telltale signs of nitrogen-fixing bacteria. These microbes extract nitrogen from the air using an enzyme called, appropriately enough, nitrogenase. The enzyme also speeds up other chemical reactions, including converting acetylene into methane. So the fate of acetylene reveals the presence of nitrogenase, which in turn reveals the presence of nitrogen-fixing bacteria.
And that’s exactly what happened – the test showed that nitrogenase was present and active in the gardens of all the 8 leafcutter species that Pinto-Tomas analysed. The enzyme and the bacteria that wield it are particularly active in the centre of the fungus gardens and not at all on the ants themselves, or the leaves they cut. Around half of the garden’s supply of nitrogen comes from these bacteria.
But finding the bacteria wasn’t enough; Pinto-Tomas had to show that these microbes were actually beneficial partners rather than casual stowaways. He did that by sealing the colonies in airtight chambers and pumped in air containing a relatively rare form of nitrogen called nitrogen-15. He found that after a week, levels of this isotope had increased not just in the fungus, but the worker ants and their larvae too.
The ants were clearly reaping substantial rewards from their bacterial tenants. And by denying the ants access to soil or other food sources, Pinto-Tomas showed that they were indeed getting their nitrogen from these bacteria, and not from other sources.
This joint venture with fungi and bacteria must be a key part to the leafcutters’ undeniable success. It makes them a super-herbivore. The ants don’t fall prey to insecticides produced by plants because the fungus deals with those, and the fungus doesn’t have to cope with anti-fungal countermeasures because the ants break those down before plying it with leaves. As a result, both partners can exploit a massive variety of different plants, rather than specialising one any one type. A lack of nitrogen is the big limiting factor, but the ants can clearly overcome that too, with some bacterial assistance.
The partnership is probably a boon to other plants too. The leaves that the ants discard have 26 times more nitrogen than the surrounding leaf litter and they fertilise the surrounding soil. It’s no coincidence that the diversity of plants tends to skyrocket near a leafcutter garbage dump.
The nitrogen-fixers aren’t the only bacteria that cement the alliance between ant and fungus. A decade ago, Cameron Currie, who was also involved in this study, showed that leafcutters use another type of fungus as a pesticide. Their gardens are plagued by a different species of virulent, parasitic fungus and to protect their monocultures from these weeds, the ants use a type of Streptomyces bacteriause a type of Streptomyces bacteriause a type of Streptomyces bacteria. It hitches a lift on the ants’ shell and it secretes antibiotics that halt the growth of the parasite.
These insects really are gardeners par excellence, not only successfully growing a monoculture crop, they also use pesticides and fertilisers. Now if they’d only return David Attenborough’s family…
Reference: Science 10.1126/science.1173036
More on ants:
Images by Jarrod Scott, Cameron Currie and Bandwagonman | <urn:uuid:6045a063-bc87-4ed3-88d6-7120fdcd3289> | 3.296875 | 1,108 | News Article | Science & Tech. | 38.839012 | 95,626,306 |
Seismic Image of the Volcanic Tremor Source at Izu-Oshima Volcano, Japan
The 1986 fissure eruption of Izu-Oshima volcano was followed by a strong activity of volcanic tremor. To investigate the characteristics of the activity and its relation to the magma system beneath the volcano, two seismological surveys were carried out; one was an array observation of volcanic tremor and the other was an investigation of the crustal structure using seismic signals generated by an air-gun. The first study revealed that two separated sources radiated high frequency tremor and that they were located beneath the northwestern and the southeastern parts of the caldera floor. The analysis of the air-gun data by the method of the semblance depicted the three-dimensional image of a magma-filled crack elongating in the NW-SE direction beneath the caldera. From these results, we deduced a kind of fluid-driven crack model of volcanic tremor in which the outflow of magma through the crack tips generates high frequency tremor and resonates the magma-filled crack.
KeywordsMagma Body Seismic Array Seismic Image Fissure Eruption Shot Point
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seen = set()
for n in numbers:
if n in seen:
return False #if no duplicate found
Instead of returning False, you can also raise an exception. Use this:
raise Exception('custom exception message here')
Monday, December 11, 2017
Finding Repeats in an Array or a List - Technical Interview in Python Patterns
Practice using Hash map.
Explore <s, a> ---> s' reads: move from current state s to s' via action a. Through the action a reward is received, it ...
Google's algorithm has pushed websites to deploy mobile friendly websites, but sometimes business owners and developers really need to a...
The bogus request from P2PU to hunt for HTML tags in real life has yielded a lot of good thoughts. My first impression was that this is stup...
What is a domain name system (DNS)? How stuff works explains it in a very good graph I was very confused by the Wikipedia explanatio... | <urn:uuid:4b64fa84-52df-438d-93da-4ec6729fcca0> | 2.890625 | 203 | Content Listing | Software Dev. | 68.63339 | 95,626,345 |
Neutron radiography is a well-known imaging technique among those working at nuclear research facilities. However, the move from laboratory to industry has been hampered by the generally large neutron flux requirements and by the relatively small number of nuclear research reactors. The development of imaging techniques that require lower total neutron exposure than traditional methods, coupled with improvements to non-reactor neutron sources suggest that broader application of neutron radiology may be imminent.
Glen M. MacGillivray,
"Imaging with neutrons: the other penetrating radiation", Proc. SPIE 4142, Penetrating Radiation Systems and Applications II, (18 December 2000); doi: 10.1117/12.410582; https://doi.org/10.1117/12.410582 | <urn:uuid:53186834-402d-4519-9c07-f482810da3ae> | 2.65625 | 157 | Knowledge Article | Science & Tech. | 40.773 | 95,626,373 |
The ionization front known as the "Bright Bar" is the strikingly straight edge running from the northeast to the southwest border of the Huygens region.
This cool observation technique also helps convince me the orangepink color is real, because I saw color along the outer edge of the Bright Bar ionization front and in the small patch just southwest of the Trapezium in the shrouded star-forming area, Orion S, exactly where color exists.
The Sandia concept, called the Ionization Front Accelerator (IFA), does not suffer this disadvantage.
To accelerate the electron-beam front, the physicists provide an accelerated, moving ionization front in the cesium.
The famous Pelican Nebula, IC 5070, is an ionization front
illuminated by young, energetic stars within a vast molecular cloud in Cygnus.
Within the next 20,000 years or so, the advancing ionization front
will overrun the nearby newly forming star, slowing or stopping its growth by destroying the materials it needs to continue coalescing.
Wen's calculations reveal that the Orion Nebula is a very thin emitting layer lying on top of a highly irregular ionization front.
For almost two decades the bar was believed, qualitatively, to result from the nebula's ionization front tilting up until it became nearly perpendicular to the plane of the sky.
This bar region is very useful for determining the structure of the nebula because the compressed gas on the neutral side of the ionization front -- not luminous at visible wavelengths but detectable in the infrared and radio -- is also seen edge on.
New visible-light Hubble images of the Bright Bar show this tilted ionization front in unprecedented detail.
1] C are being photoionized just like the main ionization front of Orion.
Severe ionization fronts
are often generated in the course of ionospheric storms which are driven by space weather conditions (Ho et al. | <urn:uuid:964ebc43-fb9c-4a18-8ae2-1fb7ebb21b44> | 3.296875 | 399 | Knowledge Article | Science & Tech. | 32.335669 | 95,626,376 |
746 pages , 1997 Located between the Pacific and Indian Oceans, and between the Asian and Australian continents, the seas of the Indonesian Archipelago have a significant role in global weather patterns and oceanic circulation. The dynamic interplay between geological, physical, chemical, and biological processes, past and present, has given rise to one of the most diverse marin...[Read More]
Phytoremediation /ˌfaɪtəʊrɪˌmiːdɪˈeɪʃən/ (from Ancient Greek φυτό (phyto), meaning 'plant', and Latin remedium, meaning 'restoring balance') refers to the technologies that use living plants to clean up soil, air, and water contaminated with hazardous chemicals.
Phytoremediation is a cost-effective plant-based approach of remediation that takes advantage of the ability of plants to...[Read More]
Ecology (from Greek: οἶκος, "house", or "environment"; -λογία, "study of") is the scientific analysis and study of interactions among organisms and their environment. See glossary of ecology. It is an interdisciplinary field that includes biology, geography, and Earth science. Ecology includes the study of interactions that organisms have with each other, other organisms, and with abiot...[Read More]
Ecosophy or ecophilosophy (a portmanteau of ecological philosophy) is a philosophy of ecological harmony or equilibrium. The term was coined by the Norwegian father of deep ecology, Arne Næss, and French post-Marxist philosopher and psychoanalyst Félix Guattari.
National Recycling Markets Hearings Before the Subcommittee on Commerce, Consumer Protection, and Competitiveness of the Committee on Energy and Commerce, House of Representatives, One Hundred Second Congress, First Session, on H.R. 2746, a Bill to Develop, Assist, and Stabilize Recycling Markets, June 26 and July 18, 1991
742 pages , Woodhead Publishing , 2016-08-12 Sustainability of Construction Materials, Second Edition, explores an increasingly important aspect of construction. In recent years, serious consideration has been given to environmental and societal issues in the manufacturing, use, disposal, and recycling of construction materials. This book provides comprehensive and detai...[Read More]
438 pages , Amer Inst of Physics , 2008 As members of the American Physical Society's Forum on Physics and Society, we are concerned with the need to produce and use energy more wisely. One contribution we feel we can make is to educate fellow physicists, especially those who teach in our colleges and universities, about the technical details of some of the more promisin...[Read More] | <urn:uuid:32ce8ee4-32da-43c9-8fff-01db43de6b88> | 2.59375 | 582 | Content Listing | Science & Tech. | 25.568178 | 95,626,378 |
Linux bash provides a lot of mechanisms to make system administrators life easier. These features are similar to the programming language features like variables, decisions, loops etc. In this tutorial we will look loops which can be implemented with for and while we have already examined for loops in the following tutorial. Bash...
In previous chapter we have looked for and foreach loops. In this chapter we will look another Php programming language loop while and do while loops. While Loop while loop iterates over given code block unless the condition met. The condition is checked in before every step. If the condition do not meet the...
For loop is generally used for specified arrays or similar array like lists. For enumerates over given way and checks the condition whether it is met or not. Here is For syntax.
Initialize fired one time at the start of for loop and generally used to set some values. Condition is checked...
Loops are used to loop and iterate through sequential data or similar serial output. Sequential data will be generally an array. For example to search in a array for a specific value while loop can be used. We will look 3 main loop mechanism provided by C programming language. While...
Looping is traversing in a specified range. For example we can loop thrugh an array to print array elements or we can count from 1 to 100 by looping and print the number. For Loop One of the most used loop type is for loop.
for is our loop keyword...
For loop is used to iterate over given sequence. Sequence can be a list, dictionary or similar enumerable object for python programming language. For loop is a bit different from other languages like C, C++, Java … For loop in python mainly uses object to iterate but in other languages... | <urn:uuid:5b68c712-1a7d-4192-8919-dfecd2bb9864> | 3.78125 | 363 | Content Listing | Software Dev. | 57.150366 | 95,626,402 |
Volcanoes are mountains whose tops are opened downward. These openings reach below the surface of the earth – where the rock is molten. Volcanoes are mostly closed like a soda bottle, but below which the pressure continues to grow over time. When the pressure reaches a certain level the hot lava suddenly came out. Anybody living near the volcano will certainly become unconscious – after hearing the loud noise.
Formation of Volcanoes
A volcano is built when magma below the surface of earth rises. The rising magma starts to form gas bubbles. These gas bubbles are already dissolved in the magma due to extreme pressures – much like a soda bottle which has carbon dioxide dissolved in it.
Bubbling magma builds-up gas pressure against the surface of the earth under the volcano. When the gas pressure grows to extreme levels – The Volcano erupts – and BOOM! When the eruption occurs, it allows the high pressurized gasses and lava to escape from magma reservoir with earth’s geothermal energy. You can consider this as a way for our earth to release the excess energy.
Magma is the mixture of molten rock, semi-molten rock, and solid particles. It is found below the earth’s surface. When magma is ejected through a volcano – it is called lava. Heat for melting the rock comes from the earth’s geothermal energy.
Lava is the magma after the eruption – having temperatures of 700 C – 1200 C in the liquid state. It doesn’t flow below the earth’s surface – that is the difference between the lava and the magma. Lava is mainly composed of silicon and oxygen. It gets mixed with other elements when it flows from vent towards the ground.
Types of Volcanoes
There are four types of the volcanoes according to the geological and geographical features.
Cinder Cone Volcanoes – These volcanoes are very simple in shape. They are made from the single vent for the eruption of lava. They are very violent and builds-up into a circular cone shape over time. Volcanoes in this type never grow more than a 1000 feet in height.
Composite Volcanoes (Stratovolcano)– These volcanoes are made of many layers of lava. Volcanoes in this type have many layers through which lava can flow. These volcanoes also explode violently and reach a height of 8000 feet.
Shield Volcanoes – These volcanoes cover very large areas, and are very wide. They erupt low-viscosity lava. The slop of these volcanoes is very shallow. As a result, the lava can reach far away. These volcanoes are less violent than other types.
Lava Domes – These volcanoes erupt very high-viscosity lava, which can’t go further away from the vent. As a result, the lava solidifies around the vent and forms a dome that grows over time.
Mauna Loa is the largest volcano found on our Earth – reaching a height of 4 kilometers.
The largest volcano on our solar system is Olympus Mons – its height reaches to 27 kilometers. It is found on the Mars.
Volcanic eruption severely damages the forests around them – sometimes destroys them entirely.
Our Earth has 1500 active volcanoes from which 20 Volcanoes are erupting on the earth at any time.
Is it dark? Just light up a lamp, and you have a source of light to kick-away the darkness. Light is one of the fundamental needs of humans and every living thing (almost!). We can find our ways to home, schools, and offices because of light. Just think a bit, what will happens if the light suddenly goes away? You will be amazed that we cannot survive without light. So, what is that light?
What is Light?
It may be a bit complicated to understand, but let’s try to understand simply. The first thing to remember is that light isn’t made of matter, so it doesn’t have mass. It is just a form of energy (also called electromagnetic energy) that travels at a constant speed from one place to another and reflects from the objects. When it hits our eye, we see the objects from which the light is reflected or emitted.
So, do we really see light? The simple answer is NO!
We only see the effect of light that happens in our eyes. The light cause a chemical reaction in light-sensitive cells of our eyes. These reactions produce electrical signals that are transferred to the brain by the optic nerve.
Moreover, light is the small portion of the electromagnetic spectrum that our eye can detect. The other portions of electromagnetic radiation that you may be familiar are radio waves, infrared, ultraviolet, and X-rays etc. But, the human eye cannot detect these radiations. Our eyes are only sensitive to light, also called visible light.
Here is the complete electromagnetic spectrum
Notice, how much small portion is occupied by visible light spectrum.
How Fast Light Travel?
Visible light and every radiation of electromagnetic spectrum travel at constant speed, which is 299,792,458 m/s (meter per second) or 186,000 miles/second. It only takes 1.3 seconds for the light to reach from the moon to earth, and 8 minutes to reach from the sun.
The speed of light is the fastest known speed in our universe, and no object with mass can reach that speed. Although, material objects can reach close to the speed of light.
The interesting part!
The laws of classical physics don’t work anymore when objects reach near the speed of light. Then, comes Einstein’s theory of relativity to rescue us. This theory describes what happens when things reach closer to the speed of light.
How Do We See Colors?
The visible light not only allows us to see objects, but it also allows us to see the object in a wide variety of colors. It is because the visible light starts from the wavelength of 700nm and ends at 400nm. The colors that we can see a change from 700nm (dark red color) to 400nm (dark blue color).
Here is the complete spectrum of visible light.
The colors we see may be the single wavelengths of light or the mixture of several wavelengths. For example, the sunlight is the mixture of all wavelengths of light and we see it as white light. Just check the light spectrum image above and notice that there is no white color, it just a mixture of colors.
As you know from the above discussion that, white light is the mixture of colors. So, when this white light falls on an object, it absorbs some colors of light and reflects the remaining colors to the surrounding. When our eyes catch that reflected light, it sees the object’s color that it reflected.
For example, when the light hits the green box, it absorbs all the colors of light and reflects only green color. As a result, we see it as green. Similarly, black colored objects absorb all the colors of light so we see it as black. Furthermore, the white colored objects don’t absorb any color at all, so we see them as white.
There are some materials which don’t absorb light or reflect them. As a result, we can see through these objects. These objects are called transparent objects, e.g. glass.
How Light Helps Us
The first benefit that will come to everyone’s mind is that light helps us and every organism on earth to see objects and the environment. Besides that, there many other important benefits of light, which are:
The heat from the sun reaches the earth as radiation. These radiations are absorbed by atmosphere and ground to maintain the temperature of our earth that is suitable for life. Without that heat, everything would be frozen like the planet, Pluto.
Plants use sunlight in Photosynthesis to prepare food for them and generate oxygen for us.
We use solar panels to generate electricity from light.
We are using spectroscopic analysis of electromagnetic radiation coming from space to study the far planets, stars, and galaxies.
The speed of light reduces as it enters into a medium, like air, glass, and diamond.
Ants can see the ultraviolet region of light, which humans can’t see.
Ibn al-Haytham was a Muslim scientist, who first discovered that we see objects due to the light coming into our eyes. Before him, it was considered that we see because eyes emit radiations that hit surrounding objects. Ibn al-Haytham is also considered as the father of Optics (Science of light).
Have you ever tried to jump?
Probably, yes! And you know that when we jump from the ground, we just fall back after few seconds.
Why? And How?
These are the questions that, almost every human had thought in his childhood. So, the simple answer to all these questions is “gravity”.
So, let’s learn something about gravity and the interesting history about it.
What is Gravity?
Gravity is the force that attracts us and other objects towards each other; much like a magnet, but not as a magnet. Then, why things in your room are not attracted to each other? It is because gravity depends on the mass; Massive objects have more gravity.
Gravitational force is so weak that the object must be very massive to have sufficiently strong gravity to attract other objects. Consider our earth, it so massive that its gravity pulls us towards the ground. When we jump, earth’s gravity pulls us and we fall back on the ground.
Importance of Gravity
What would happen, if gravity suddenly disappears? Take some time and think about it.
You will be amazed to find out that, the current appearance of our earth, planets, and stars depends on the gravity. Without gravity, there will be no earth’s pull to attract you back to the ground when jumping. Even the planets and stars would not exist without gravity. Because planets and stars have been formed from the accumulation of cosmic dust and gas that was only possible due to gravity.
Here are some of the effects of gravity on our everyday life
We can stand, jump, walk, and run on the ground due to gravity. If the earth doesn’t pull you back while jumping, then you would never come back to the ground, and you may reach space in a single jump! Wow!
On the earth, gravity keeps the air around us as a blanket, and it prevents air from escaping into space.
Tides in the oceans are caused by the gravitational pull of moon and sun.
Universal Law of Gravitation
Don’t be afraid!
It is just a simple law that was proposed by a famous scientist Sir Isaac Newton. This law gives us the relation between the gravitational force, the mass of objects, and the distance between objects.
Here are two simple points that explain the law:
The gravitational force between massive objects is more as compared to light objects.
The gravitational force between two objects decreases exponentially as they go away from themselves.
Here is the mathematical expression of the universal law of gravitation:
F = G*M1*M2/r^2
G = Gravitational constant, whose value is equal to M1 = mass of the first object M2 = mass of the second object r = distance between two objects
By knowing gravity, you can calculate when a ball will touch the ground after being released into the air. You can measure and graph the path of a projectile. You can calculate how much propellant is required to push a rocket into space, and many more.
Do Heavy and Light Objects Fall at the Same Time?
The simple answer is, yes. But let’s understand, why it happens.
Gravity at the surface of the earth is 9.8 m/s, which means an object falling towards earth gains 9.8 m/s speed in every second. If a ball is dropped from a building it will have 9.8 m/s speed at the end of the 1st second, 19.6 m/s at end of the 2nd second, and 29.4 at the end of the 3rd second and so on. Every object is accelerated at the same rate towards earth, whether it is a paper clip or a stone. If two objects are dropped from a height, they both will hit the ground at the same time.
But, wait a minute!
You may be thinking, why a paper falls slower than a paper clip when both are dropped from the same height? It is because of the air resistance. The paper clip has lower surface area than the paper, which results in higher air resistance for the paper. But, if you drop paper and paper clip into a vacuum chamber both will hit the bottom at the same time. It is because vacuum chamber does not have air, so there will be no air friction to slow any object.
Difference between Mass and Weight
In everyday life, you may have used the term mass and weight interchangeably. But in physics, mass and weight are two different quantities.
The mass of an object is the quantity of matter in it; usually measured in kilograms. But, weight is the force of an object that it is putting on a platform due to gravity.
For example, if you hold a brick in your hand you will feel a downward force. If you somehow take that brick to the moon, you will notice much less downward force. Because the moon has less gravitation than the earth. In both cases, the amount of the matter in the brick will be same on the earth and the moon.
Difference between Gravity and Gravitation
There is a difference between gravity and gravitation. Gravitation is the force of attraction between objects that have mass. But, gravity is the gravitational force between earth and other objects. It means that gravity is the special case of gravitation.
Gravitational force exists since the formation of our universe. It is one of the four fundamental forces of nature. It is the force that attracts atoms together to form stars and planets. It keeps the moon in orbit around the earth and the earth around the sun.
Gravity keeps all the planets in the orbit of the sun, and it keeps our moon in orbit of the earth.
If any object goes upward with a velocity of 11 km/s, it will escape the gravitational pull of the earth. This velocity is called the escape velocity, and it is different for different planets and moon.
The gravity of our sun is about 274 m/s^2. Anything weighing 1 kg on the earth will weigh about 28 kg (If it was possible!).
A Brief History
Let’s learn something about the history of gravity, and find out about the people who contributed to explaining the gravity.
Who first pointed to the presence of gravity? And when? It is still unknown. But you may consider that early human beings had probably thought about it. Because, it is the force whose effects we can clearly see, like falling back to the ground after jumping.
The first person who gave the hypothesis about gravity was, Aristotle. He hypothesized that “heavier objects are accelerated more towards ground than lighter objects”. He was actually wrong because he didn’t know about air resistance which slows down the objects. But, he at least provided the ground for the great scientists to think and research about gravity.
In late 16th century, a famous scientist Galileo Galilei performed an experiment. In this experiment, he dropped two balls from a height and proved that light objects and heavy objects fall at the same rate.
In 1687, Sir Isaac Newton developed the universal law of gravitation. Which explained that lighter objects have less gravitational force of attraction than massive objects. Also, the gravitational force decreases exponentially as the distance between two objects increase. This is also known as the inverse square law.
The modern understanding of gravity was described by Albert Einstein. He described the gravity as a curvature in space and time. This curvature is caused by the objects with mass; the massive objects cause more curvature than the lighter objects.
You may have probably played with magnets in your childhood. These magnets attract and repel each other. Kids love to stick magnets on iron objects and on their fridge. But, magnets are more than just a toy for playing. Today, magnets play important role in shaping our modern world. Everybody is somehow dependent on it. Let’s find out the amazing information and their facts.
What is Magnetism?
Magnetism is a physical phenomenon that arises due to the motion of the charged particles, like electrons in the magnets. The moving electrons produce a field around them that is called magnetic field. This magnetic field is the cause of the magnetic effects that you observe when playing with magnets, like attraction and repulsion. The magnets that you have played with are called permanent magnetic. These magnets mostly contain iron metal. The iron and few other metals that can become a magnet, or attracted towards them are called ferromagnetic materials (we will discuss them in later sections).
You may be thinking, how and why electrons move in the iron?
The simple answer is that the electrons continuously revolve around the nucleus of atoms. Moreover, electrons also jump from atoms to atoms, which further contribute to the overall motion of the electrons that produce magnet field. Now you may be thinking that iron metal has a motion of electron that produces a magnetic field. Then, why every iron material does not have magnetism? To answer this, let’s understand the concept of magnetic domain.
Each atom in the iron (and other ferromagnetic materials) material produce a very small magnetic field due to the motion of electrons. These individual magnetic fields point to a direction according to the orientation of their respective atoms. The orientation of these atoms is random. So, it forms regions in the iron object (and other magnetic materials), in which the overall magnetic field of the atoms points to the same direction. These regions are called magnetic domain.
You can simply consider each magnetic domain as a region, in which all atoms produce the magnetic field in the same direction. In non-magnetic iron objects, these domains are randomly aligned. As a result, the total magnetic field of that iron object is zero, and it behaves as a non-magnetic object. When all the magnetic domains are aligned in the same direction, then their magnetic fields are added and results into a magnet.
There are many techniques which are used to make an ordinary iron object into a permanent magnet. The simple to do this is to rub a magnet on an iron object in one direction for 20 times. This will reorient the magnetic domains to point their magnetic fields in the same direction. As a result, the ordinary iron object will become a magnet. You also make the screwdrivers in your home into a magnet. This will make it easier for you to pick screws.
How the Magnets Attract or Repel?
Recall your memory that, magnets have two poles. One is called North pole, whereas other is called South pole. When you bring the south pole of one magnet near to the south pole of another magnet, they will repel each other. Same is the case when you bring north poles together. But, when you bring the north pole of one magnet near to the south pole of another magnet, they will attract each other. The attraction and repulsion effects, both are simple as well as complicated to understand. But here, we will try to understand them in a simple way.
The magnetic field of a magnetic has a direction, which points from the North Pole towards the South Pole. For simplicity, you can consider that the magnetic field starts from the North Pole and ends at the South Pole. Let’s understand magnetic attraction and repulsion separately.
The magnetic field that is started from the North pole must terminate at the South pole. So, when you bring the North Pole of one magnet near to the south pole of another magnet, they will attract each other. Because, magnets always try to reduce the gap between their opposite poles, so that magnetic field can complete its path quickly.
The repulsion occurs when the same poles (North-North, or South-South) are brought together. It is because the same poles are not completing the path of the magnetic field, but disturbs its path. So, magnets try to repel each other until they are far from each other.
You may have probably observed that magnets can stick on iron materials. But, there are also other materials on which magnets don’t stick, like clothes, plastics, and glass. This is because all the materials that we know are categorized into 3 categories. The categories are made according to the way the materials behave with magnets or magnetism.
Here is the quick intro of these material categories:
These materials are strongly attracted towards the magnets. It is because their atomic structure allows them to easily pass the magnetic field through them. Some of the ferromagnetic materials are iron, cobalt, and nickel.
These materials feel very small attraction from You won’t even notice this attraction. Some of the examples of this category are Aluminum, zinc, and sodium.
These materials are not attracted to the magnets. Instead, they try to avoid them. If you bring a very strong magnet near a lightweight diamagnetic material, you will notice a slight repulsion. Some of the examples of diamagnetic materials are water, copper, and gold.
What is an Electromagnet?
Up to here, it was all about the permanent magnets, which remain magnets after the magnetization. There is also another type of magnets, called electromagnets. Electromagnets are similar to permanent magnets; they attract and repel each other and stick to iron objects. The difference is that they only become a magnet when the electric current passes through them. The larger the current flow, the stronger the magnet will become.
The electromagnets are usually made by wrapping the enamel coated wire around a ferromagnetic material like iron. When current will flow through the wire, the magnetic field will be produced. One thing to remember is that if the wire is wounded on a ferromagnetic material for making an electromagnet. Then after the current is blocked, the iron object will become a weaker permanent magnet than the electromagnet itself. So, if there is a need of temporary magnetism, iron is not used as a core in electromagnets.
Magnets are the essential part of our modern life. Without magnets, you can’t imagine how our world will look like. It is used from our common household items and gadgets to big industries. Here are few uses of magnets:
Electric Motors: The electric motor in the toys, water pumps, and fans in a house use magnetism. They use magnetism to convert the electrical energy into rotation. Larger industries also use motors in their processes.
Computer Hard Disk: Today, computer hard drives can store several TBs (1 TB = 1000 GBs) of data. All this data is stored in the plates which are magnetized.
Loud Speakers: Loudspeakers have small electromagnets that vibrate according to the electric signal it receives from a phone, a computer, or a TV to produce sound.
Weight Lifters: Many weightlifters, lift the weight which contains These lifers have very strong electromagnets to lift heavy iron objects like cars and containers. The electromagnets are only turned ON when the weight needs to be lifted and carried.
MRI Scanning: Magnetic Resonance Imaging is the technique which is mostly used by physicians. MRI is used to make the images of the organs, bones, and other internal body structures by using strong electromagnets.
A Brief History of Magnets
Let’s dig a little bit into the history of magnets and find out its discovery and progress over time?
Magnets were known to mankind since ancient times. Both Greeks and Chinese claim that the magnet was discovered by them. The first discovered magnet was a stone made of iron ore. It was called lodestone. Ancient people believed that the lodestone has magical powers. These powers allow it to attract iron objects. They thought that lodestone can be used to cure the sick and provides protection against evil spirits.
Later on, people realized that when lodestone is shaped into a needle and placed on a leaf floating on the water, always points in the same direction. This led them to the invention of the compass and due to this reason lodestone was sometimes called “leading stone”.
In the 1600s, William Gilbert experimented on magnets and found out that our Earth is a giant magnet (a brilliant discovery). He also found that by rubbing a magnet on an iron object in the same direction makes it a permanent magnet. Moreover, he also told that by heating the permanent magnet, its magnetism is lost.
A very clever discovery in the field of magnetism was made by Oersted in 1820. He discovered the relation between electricity and magnetism. He found that, when current passes through a coil, it deflects the compass needle. Thus, he concluded that electric current produces a magnetic field. Today our electric motors work on his discovery.
In 1831, Michael Faraday discovered that by moving a magnet through a coil, it produces the electric current in the coil. This principle is known as “Faraday’s Law of Electromagnetic Induction”. The electric generators work on that principle, and again this law further revolutionized the world. Today, our electricity is produced on the basis of this law at power stations.
Earth is a giant magnet. It produces its magnetic field due to the flow of liquid iron at about 6,000 C (10,800 F) flowing in the center of the Earth.
It was once believed that there are islands on earth, made entirely of magnets. They attracted the ships near them, due to iron nails. Resulting in the destruction of the ships.
Many birds and sea creatures sense the Earth’s magnetic field like a compass to guide their way.
The magnetic field of the Earth protects us from the deadly solar winds.
Plants are an important part of nature. They are everywhere in the world and makes our planet green. We all know that they are good for us because they provide us food, wood, and the precious oxygen. But, there are many species of plants that also carry poisons. These poisons may cause itching, vomiting, diarrhea, and even death. The poisonous plants play an important role in nature. Let’s dig in deep!
Why Plants Carry Poison?
The first question that everyone will probably ask about the poisonous plants is that, why plants carry poison with them? Because we know plants as good creatures that provide a primary food source to animals, so why they will want to harm the animals? There are some reasons behind it, let’s discuss them.
The primary reason to carry the poison is the protection from herbivores. Herbivores (plant eaters) consume the plants to survive. Suppose if some herbivores start to eat one plant together, they may consume the whole plants. As a result, the plant will die completely. So, some plants have evolved to carry poison in them with varying amount of poison to protect them against herbivory when they are consumed more than average.
Some plants carry permanent poison to protect themselves from herbivores. For examples, leaves of mangrove tree are poisonous to many herbivores. But, few herbivores are able to digest these poisonous leaves, e.g. sloths. As a result, few species can eat these leaves which helps mangrove to survive while providing food to limited herbivores.
Uses of Poisonous Plants
Poisons of the plants are of course harmful to animals and humans. But, they are also used by humans in the preparation of some medicines and in some other applications. For example, people have used the poison of ‘Buckeye’ for catching fishes. ‘Digitalis’ plant has provided the first remedy for cardiac, which helped in strengthening the heartbeat.
The Most Poisonous Plants on Earth
Here are some of the plants that are considered most poisonous in the world.
1. Aconitum napellus
It is a beautiful plant with purple color. When eaten it may cause numbness, vomiting and also death. In 2014, BBC reported that a 33 years old gardener died due to touching (or eating) this plant.
2. Castor Bean
When this plant is eaten, it may cause vomiting, bloody diarrhea, increased heart rate, low blood pressure, and death in few days (if the victim is not treated well).
3. Water Hemlock
It is also a beautiful plant with small white-colored flowers. This plant may cause seizures if eaten. It is also the common poisonous plant in UK and US.
Leaves of the apple tree and its seeds contain ‘cyanide’; a very poisonous chemical.
Unripen potatoes are also poisonous. They may cause vomiting.
Some poisonous plants can cause very intense itching when touched, e.g. Poison Ivy. | <urn:uuid:c2a432c1-d784-40c2-97ca-8d567191571c> | 4.1875 | 6,062 | Knowledge Article | Science & Tech. | 57.223607 | 95,626,411 |
Weather extremes in the summer - such as the record heat wave in the United States that hit corn farmers and worsened wildfires in 2012 - have reached an exceptional number in the last ten years.
Man-made global warming can explain a gradual increase in periods of severe heat, but the observed change in the magnitude and duration of some events is not so easily explained. It has been linked to a recently discovered mechanism: the trapping of giant waves in the atmosphere. A new data analysis now shows that such wave-trapping events are indeed on the rise.
“The large number of recent high-impact extreme weather events has struck and puzzled us,” says Dim Coumou, lead author of the study conducted by a team of scientists from the Potsdam Institute for Climate Impact Research (PIK).
“Of course we are warming our atmosphere by emitting CO2 from fossil fuels, but the increase in devastating heat waves in regions like Europe or the US seems disproportionate.” One reason could be changes in circulation patterns in the atmosphere. By analysing large sets of global weather data, the researchers found an intriguing connection.
Rossby Waves: meandering airstreams
An important part of the global air motion in the mid-latitudes normally takes the form of waves wandering around the globe, called Rossby Waves. When they swing north, they suck warm air from the tropics to Europe, Russia, or the US; and when they swing south, they do the same thing with cold air from the Arctic.
However, the study shows that in periods with extreme weather, some of these waves become virtually stalled and greatly amplified. While a few warm days have little impact, effects on people and ecosystems can be severe when these periods are prolonged.
“Behind this, there is a subtle resonance mechanism that traps waves in the mid-latitudes and amplifies them strongly,” says Stefan Rahmstorf, co-author of the study to be published in the Proceedings of the US National Academy of Sciences (PNAS). Using advanced data analysis, the new study shows that when certain resonance conditions are fulfilled, the atmosphere tends to develop anomalously slowly propagating waves with large amplitudes, typically associated with extreme weather on the ground.
An important finding is that this phenomenon is occurring more often: After the year 2000, it has been almost twice as frequent as before. “Evidence for actual changes in planetary wave activity was so far not clear. But by knowing what patterns to look for, we have now found strong evidence for an increase in these resonance events.”
The Arctic factor: warming twice as fast as most other regions
Why would these events be on the rise? Both theory and the new data suggest a link to processes in the Arctic. Since the year 2000, the Arctic is warming about twice as fast as the rest of the globe. One reason for this is that because the white sea ice is rapidly shrinking, less sunlight gets reflected back into space, while the open ocean is dark and hence warms more.
“This melting of ice and snow is actually due to our lifestyle of churning out unprecedented amounts of greenhouse gases from fossil fuels,” says Hans Joachim Schellnhuber, co-author of the study and director of PIK. As the Arctic warms more rapidly, the temperature difference to other regions decreases. Yet temperature differences are a major driver of the atmospheric circulation patterns that in turn rule our weather.
“The planetary waves topic illustrates how delicately interlinked components in the Earth system are.” Schellnhuber concludes: "And it shows how disproportionately the system might react to our perturbations.”
Article: Coumou, D., Petoukhov, V., Rahmstorf, S., Petri, S., Schellnhuber, H.J. (2014): Quasi-resonant circulation regimes and hemispheric synchronization of extreme weather in boreal summer. Proceedings of the US National Academy of Sciences PNAS [DOI:10.1073/pnas.1412797111]
Weblink where the article will be published: www.pnas.org/cgi/doi/10.1073/pnas.1412797111
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Phone: +49 331 288 25 07
Jonas Viering | PIK Potsdam
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