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Developed unique way to fingerprint oil and assess how it changes over time
Years after the 2010 Deepwater Horizon Oil spill, oil continues to wash ashore as oil-soaked "sand patties," persists in salt marshes abutting the Gulf of Mexico, and questions remain about how much oil has been deposited on the seafloor.
Researchers used comprehensive two-dimensional gas chromatography (GCxGC) in their oil spill forensics to measure levels of degradation in biomarkers. THe biomarkers here are shown inside the dotted line.
Credit: Christoph Aeppli, Bigelow Laboratory for Ocean Sciences
Scientists from Woods Hole Oceanographic Institution and Bigelow Laboratory for Ocean Sciences have developed a unique way to fingerprint oil, even after most of it has degraded, and to assess how it changes over time. Researchers refined methods typically used to identify the source of oil spills and adapted them for application on a longer time frame to successfully identify Macondo Well oil, years after the spill.
"We were looking at two questions: how could we identify the oil on shore, now four years after the spill, and how the oil from the spill was weathering over time," explained Christoph Aeppli, Senior Research Scientist at Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine, and lead author of the study reported in Environmental Science & Technology. Aeppli worked with his then-colleagues at Woods Hole Oceanographic Institution, and University of California, Santa Barbara on the investigation and report.
Researchers used comprehensive two-dimensional gas chromatography (GCxGC) in their oil spill forensics to measure levels of degradation in biomarkers. Biomarkers are molecular fossils. Each reservoir has specific amounts of different biomarkers, so oil biomarkers serve as identifiers much like human fingerprints.
Biomarkers are usually recalcitrant in reservoirs, but when exposed for a long time to the environment, some are altered due to natural processes. Oil consists of tens of thousands of compounds, and many of them can be degraded by bacteria or broken down by sunlight. This research was designed to determine the resiliency of specific biomarkers and to see how they held up when exposed to environmental conditions on shore.
"We found that some biomarkers—homohopanes and triaromoatic steroids (TAS), specifically – degraded within a few years following the Deepwater Horizon spill," said Chris Reddy, a scientist at Woods Hole Oceanographic Institution and co-author of the paper. "These biomarkers are not as resilient as once thought and they may provide a future window into determining how much, and how quickly, these oil components may linger in the environment when exposed to air, sunlight, and the elements."
Researchers sought to determine the specific source of the biomarkers degradation. Through analysis of oil-soaked "sand patties" collected along the Gulf shore over a 28-month period, they found that most biomarker compounds were recalcitrant and could be used to identify DWH oil. Some biomarkers, however, degraded. "This knowledge is helping us improve our oil spill forensics. It is providing a foundation for better, longer-term identification techniques that account for exposure of oil to wind, waves, sunlight, and microbial degradation over long times," added Aeppli.
Aeppli, Reddy and colleague Dave Valentine from UC Santa Barbara will apply this new oil fingerprinting technique to process tens of thousands of samples collected shortly after the DWH spill.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment. For more information, please visit http://www.whoi.edu.
Bigelow Laboratory for Ocean Sciences conducts research ranging from microbial oceanography to large-scale ocean processes that affect the global environment. Recognized as a leader in Maine's emerging innovation economy, the Laboratory's research, education, and technology transfer programs are spurring significant economic growth in the state.
Darlene Crist | Eurek Alert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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13.07.2018 | Life Sciences | <urn:uuid:7941e82a-dc05-4667-8a12-84a7f7b3e864> | 3.546875 | 1,541 | Content Listing | Science & Tech. | 32.903338 | 95,537,943 |
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Chimp genome released
© BioMed Central Ltd 2003
Published: 15 December 2003
A first draft of the chimpanzee genome sequence has been completed, US researchers announced Wednesday (December 10). Investigators, funded by the National Human Genome Research Institute (NHGRI), also aligned the chimp sequence with the human sequence to facilitate comparisons.
All data from the draft sequence, which covered most of the chimp's 3.1 billion bases, has been made publicly available. Scientists in the United States, Europe, and Japan will now begin analyzing that data and comparing it to the human sequence in hopes of finding clues to genome evolution, disease genes, and regulation. Comparing humans' sequence to that of our closest relative also may help researchers start to address an age-old question: "Everybody sort of wonders what makes us human," Kerstin Lindblad-Toh, codirector of the Genome Sequence and Analysis Program at the Massachusetts Institute of Technology's (MIT's) Center for Genome Research, told us.
"This is a notification more to the scientific community than to the public that the sequence is done, the assembly is done, it's out there," Richard Wilson, director of the Genome Sequencing Center at Washington University in St. Louis, told us. "And that there are a couple of really good computational tools that you can use to start getting into that sequence and start finding your favorite human gene in the chimp." The sequencing effort, which cost approximately $20 million, was undertaken by sequencing centers at Washington University and the Eli and Edythe L. Broad Institute of MIT.
According to white papers written by University of Washington scientists Maynard Olson, Robert Waterston and others, the sequencing project's rationales included identifying sites of sequence differences between the chimp and human; investigating the genomic basis of differences in chimp and human gene expression that have been measured with microarrays; comparing physiology, anatomy, and pathology, such as different rates of epithelial cancers and the progression of HIV to AIDS; and conducting evolutionary and population genetic studies to compare, for instance, regions of rapid evolution and differences in polymorphism rate.
Some scientists have already begun to analyze and compare chimp and human genomes and make assertions about human evolution. In a separate work published in Science on Friday (December 12), scientists at Celera Diagnostics report their own comparison of regions of the human and chimp genomes, concluding the processes like hearing and olfaction evolved at a relatively fast rate in humans.
"In general you'd expect evolution to work at the level of the gene," senior author Michele Cargill of Celera told us. "But for a few of these categories, it seems to be acting on the class of gene."
Researchers used polymerase chain reaction primers to show positive selection in humans for 1600 coding sequences of the approximately 20,000 genes analyzed. They found that human genes involved in olfaction, hearing, amino acid catabolism, and other processes had more genes than expected undergoing positive selection. In the case of hearing, for example, this positive selection may suggest that humans evolved to have different sensitivities to different frequencies of sound that are important for developing speech and understanding language. Having the chimp genome sequence in hand will now enable researchers to extend their chimp-human comparisons to potentially important noncoding sequences, which comprise about 98% of the chimp genome.
Started in January of this year, the NHGRI-funded genome sequencing of the chimp has fourfold coverage, meaning each base has been sequenced an average of four times. The human genome has 10-fold coverage, and the mouse genome about sevenfold.
The completed human sequence provided a sort of reference to expedite the assembly. According to Wilson, the chimp sequencing, despite employing fewer sequencing centers, was completed at least twice as fast as the generation of the human draft done in 1998, 1999, and 2000. "With chimp and human, we're looking for the differences. And with mouse and human, we were looking for the similarities," said Lindblad-Toh.
The chimp genome's similarity to the human's, however, may make it a less useful tool for disease gene finding than the genome of a more distant relative. "Every gene has its best model organism," Wilson said. "For some disease genes, the chimp's going to tell you a lot. For others it won't tell you much because it's too close to the human."
There are currently no plans for an additional draft of the chimp genome, though Wilson and Waterston advocate doing additional sequencing to fill in the gaps and get better coverage, improve accuracy, and better understand the level of variation.
- Chimp genome assembled by sequencing centers, National Human Genome Research Institute news release, December 10, 2003., [http://www.nhgri.nih.gov/11509418]
- Ensembl Chimpanzee Genome Server, [http://pre.ensembl.org/Pan_troglodytes/]
- Sequencing the chimpanzee genome, [http://www.genome.gov/Pages/Research/Sequencing/SeqProposals/ChimpGenome2.pdf]
- Science, [http://www.sciencemag.org/content/current/] | <urn:uuid:05c4228a-e803-4e6b-9408-2c6616084b30> | 2.734375 | 1,110 | News Article | Science & Tech. | 30.743242 | 95,537,954 |
Changes in leaching, availability, bioaccumulation, and vertical distribution of lead (Pb) in soil 20 years after the cessation of shooting activity were studied by comparing three pine forest sites in southern Finland: an active shooting range, an abandoned shooting range, and a noncontaminated control site. At both shooting ranges, shooting activity had lasted for 20 years, but it had taken place 20 years earlier at the abandoned range. Up to 4 kg m(-2) of Pb pellets had accumulated in the soil at both shooting ranges, and extremely high Pb concentrations, reaching 50,000 mg kg(-1) , were detected in the organic soil layer. Elevated Pb concentrations were also found in leachate waters and in the biota. Concentrations of Pb in the top organic soil layer and in some of the biota were lower at the abandoned shooting range, which can be taken as a sign of starting recovery of the forest ecosystem. However, the concentration of water-extractable Pb had not decreased in the topsoil, possibly indicating the release of Pb from decaying litter. Deeper in the organic soil layer, weathering of Pb pellets enhanced Pb availability and leaching, indicating an increased risk of groundwater contamination over time at shooting sites located above aquifers.
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It's Saturday morning. I've got a need to send a command to the spacecraft I work on, but here I sit at home, unshowered and in a robe, listening to my children make a lot of noise in the other room. But this isn't a problem, you see, because we live in the 21st century. Here's how it works:
-- The spacecraft sends data from Mars, which currently is 11 minutes and 44 seconds away from Earth when traveling at the speed of light. This is how long the data takes to reach the giant, 70-meter wide antenna in the desert up in Goldstone, California.
-- The antenna receives the data and it is converted into bits (ones and zeroes) to be sent across dedicated "telephone" lines between the antenna and where I work.
-- Where I work has machines that receive the data and process it into meaningful information, where it makes it available via a broadcast.
-- I have logged in via the internet, to have this data sent to my home from where I work using my DSL line.
-- My laptop is connected to my DSL via a wireless modem, and the data flows across that connection to my display.
This data contains information regarding the spacecraft. Where are the solar arrays pointed? How much power is available from the solar panels? How much processing time is being used on the onboard computer? What are the temperatures on the electronics boxes? What instruments are collecting data at this time? How much data is back-logged, needing to be sent to Earth? What commands are currently being issued by the spacecraft? Over 10,000 points of information about the spacecraft are transmitted from Mars within mere seconds. At best, the spacecraft can transmit data at a rate of over 6 million bits per second -- depending on the distance between Mars and Earth (right now they're pretty close together).
So, here I sit, in my home, unshowered and in a robe, while data is being transmitted directly from Mars into my home. I looked at this data a moment ago and concluded that all is well, so I called somebody at work and gave them a "go" for sending the command to the spacecraft. It's on it's way to Mars right now. And I know this is true as I sit in my home, unshowered and in a robe.
Isn't modern technology wonderful?
Winning teams sleep well.
11 hours ago | <urn:uuid:d6253d43-f192-4592-9b89-605552d3f89d> | 2.796875 | 500 | Personal Blog | Science & Tech. | 60.808381 | 95,537,964 |
In physics, an orbit is the path that an object makes around another object while under the influence of a source of centripetal force. Most common use of orbit indicates that of a celestial body revolving around a star or planet under the influence of gravity. When more than one body is orbiting a central body, interaction among the orbiting bodies also exists, which may cause changes of their orbits. While planets in the Solar System form a stable state over the major part of the history of the Solar System, smaller objects such as asteroids and comets keep changing their orbits and eventually will be cast out of the Solar System or will collide with other bodies. Orbits in celestial bodies inspired scientists to derive electron orbitals bound to an atom, and others to believe it as a manifestation of God's eternal principles of creation.
Orbits were first analyzed mathematically by Johannes Kepler who formulated his results in his three laws of planetary motion based on Tycho Brahe's observational data. First, he found that the orbits of the planets in our solar system are elliptical, not circular (or epicyclic), as had previously been believed based on Ptolemy's view, and that the sun is not located at the center of the orbits, but rather at one focus. Second, he found that the orbital speed of each planet is not constant, as had previously been thought, but rather that the speed of the planet depends on the planet's distance from the sun. And third, Kepler found a universal relationship between the orbital properties of all the planets orbiting the sun. For each planet, the cube of the planet's distance from the sun, measured in astronomical units (AU), is equal to the square of the planet's orbital period, measured in Earth years. Jupiter, for example, is approximately 5.2 AU from the sun and its orbital period is 11.86 Earth years. So 5.2 cubed equals 11.86 squared, as predicted.
Isaac Newton demonstrated that Kepler's laws were derivable from his theory of gravitation and that, in general, the orbits of bodies responding to the force of gravity were conic sections. Newton showed that a pair of bodies follow orbits of dimensions that are in inverse proportion to their masses about their common center of mass. Where one body is much more massive than the other, it is a convenient approximation to take the center of mass as coinciding with the center of the more massive body.
Within a planetary system, planets, dwarf planets, asteroids (a.k.a. minor planets), comets, interplanetary dusts, and space debris orbit the central star in elliptical orbits. A comet in a parabolic or hyperbolic orbit about a central star is not gravitationally bound to the star and therefore is not considered part of the star's planetary system. To date, no comet has been observed in our solar system with a distinctly hyperbolic orbit. Bodies which are gravitationally bound to one of the planets in a planetary system, either natural or artificial satellites, follow orbits about that planet.
Owing to mutual gravitational perturbations, the eccentricities of the orbits of the planets in our solar system vary over time. Mercury, the smallest planet in the Solar System, has the most eccentric orbit. At the present epoch, Mars has the next largest eccentricity while the smallest eccentricities are those of the orbits of Venus and Neptune.
As two objects orbit each other, the periapsis is that point at which the two objects are closest to each other and the apoapsis is that point at which they are the farthest from each other.
In the elliptical orbit, the center of mass of the orbiting-orbited system will sit at one focus of both orbits, with nothing present at the other focus. As a planet approaches periapsis, the planet will increase in velocity. As a planet approaches apoapsis, the planet will decrease in velocity.
There are a few common ways of understanding orbits.
As an illustration of an orbit around a planet, the much-used cannon model may prove useful (see image below). Imagine a cannon sitting on top of a tall mountain, which fires a cannonball horizontally. The mountain needs to be very tall, so that the cannon will be above the Earth's atmosphere and we can ignore the effects of air friction on the cannon ball.
If the cannon fires its ball with a low initial velocity, the trajectory of the ball curves downwards and hits the ground (A). As the firing velocity is increased, the cannonball hits the ground farther (B) away from the cannon, because while the ball is still falling towards the ground, the ground is increasingly curving away from it (see first point, above). All these motions are actually "orbits" in a technical sense—they are describing a portion of an elliptical path around the center of gravity—but the orbits are of course interrupted by striking the earth.
If the cannonball is fired with sufficient velocity, the ground curves away from the ball at least as much as the ball falls—so the ball never strikes the ground. It is now in what could be called a non-interrupted, or circumnavigating, orbit. For any specific combination of height above the center of gravity, and mass of the object being fired, there is one specific firing velocity that produces a circular orbit, as shown in (C).
As the firing velocity is increased beyond this, a range of elliptical orbits are produced; one is shown in (D). If the initial firing is above the surface of the earth as shown, there will also be elliptical orbits at slower velocities; these will come closest to the earth opposite the firing the point.
At a faster velocity called escape velocity, again depending on the firing height and mass of the object, an infinite orbit such as (E) is produced—first a range of parabolic orbits, and at even faster velocities a range of hyperbolic orbits. In a practical sense, both of these infinite orbit types mean the object is "breaking free" of the planet's gravity, and "going off into space."
The velocity relationship of two objects with mass can thus be considered in four practical classes, with subtypes:
1. No orbit
2. Interrupted orbits
3. Circumnavigating orbits
4. Infinite orbits
For a system of only two bodies that are influenced only by their mutual gravity, their orbits can be exactly calculated by Newton's laws of motion and gravity, assuming the effect of general relativity is insignificant. Briefly, the sum of the forces will equal the mass times its acceleration. Gravity is proportional to mass (gravitational mass is equal to inertial mass), and falls off proportionally to the square of distance.
To calculate, it is convenient to describe the motion in a coordinate system that is centered on the heavier body, and we can say that the lighter body is in orbit around the heavier body.
An unmoving body that's far from a large object has more gravitational potential energy than one that's close, because it can fall farther.
With two bodies, an orbit is a conic section. The orbit can be open (so the object never returns) or closed (returning), depending on the total kinetic + potential energy of the system. In the case of an open orbit, the speed at any position of the orbit is at least the escape velocity for that position, in the case of a closed orbit, always less.
An open orbit has the shape of a hyperbola (when the velocity is greater than the escape velocity), or a parabola (when the velocity is exactly the escape velocity). The bodies approach each other for awhile, curve around each other around the time of their closest approach, and then separate again forever. This may be the case with some comets if they come from outside the solar system.
A closed orbit has the shape of an ellipse. In the special case that the orbiting body is always the same distance from the center, it is also the shape of a circle. Otherwise, the point where the orbiting body is closest to Earth is the perigee, called periapsis (less properly, "perifocus" or "pericentron") when the orbit is around a body other than Earth. The point where the satellite is farthest from Earth is called apogee, apoapsis, or sometimes apifocus or apocentron. A line drawn from periapsis to apoapsis is the line-of-apsides. This is the major axis of the ellipse, the line through its longest part.
Orbiting bodies in closed orbits repeat their path after a constant period of time. This motion is described by the empirical laws of Kepler, which can be mathematically derived from Newton's laws. These can be formulated as follows:
Except for special cases like Lagrangian points, no method is known to solve the equations of motion for a system with four or more bodies. The two-body solutions were published by Newton in Principia in 1687. In 1912, Karl Fritiof Sundman developed a converging infinite series that solves the 3-body problem, however it converges too slowly to be of much use.
Instead, orbits can be approximated with arbitrarily high accuracy. These approximations take two forms.
One form takes the pure elliptic motion as a basis, and adds perturbation terms to account for the gravitational influence of multiple bodies. This is convenient for calculating the positions of astronomical bodies. The equations of motion of the moon, planets and other bodies are known with great accuracy, and are used to generate tables for celestial navigation. Still there are secular phenomena that have to be dealt with by post-newtonian methods.
The differential equation form is used for scientific or mission-planning purposes. According to Newton's laws, the sum of all the forces will equal the mass times its acceleration (F = ma). Therefore accelerations can be expressed in terms of positions. The perturbation terms are much easier to describe in this form. Predicting subsequent positions and velocities from initial ones corresponds to solving an initial value problem. Numerical methods calculate the positions and velocities of the objects a tiny time in the future, then repeat this. However, tiny arithmetic errors from the limited accuracy of a computer's math accumulate, limiting the accuracy of this approach.
Differential simulations with large numbers of objects perform the calculations in a hierarchical pairwise fashion between centers of mass. Using this scheme, galaxies, star clusters and other large objects have been simulated.
If some part of a body's orbit enters an atmosphere, its orbit can decay because of drag. At each periapsis, the object scrapes the air, losing energy. Each time, the orbit grows less eccentric (more circular) because the object loses kinetic energy precisely when that energy is at its maximum. This is similar to the effect of slowing a pendulum at its lowest point; the highest point of the pendulum's swing becomes lower. With each successive slowing more of the orbit's path is affected by the atmosphere and the effect becomes more pronounced. Eventually, the effect becomes so great that the maximum kinetic energy is not enough to return the orbit above the limits of the atmospheric drag effect. When this happens the body will rapidly spiral down and intersect the central body.
The bounds of an atmosphere vary wildly. During solar maxima, the Earth's atmosphere causes drag up to a hundred kilometres higher than during solar minimums. Some satellites with long conductive tethers can also decay because of electromagnetic drag from the Earth's magnetic field. Basically, the wire cuts the magnetic field, and acts as a generator. The wire moves electrons from the near vacuum on one end to the near-vacuum on the other end. The orbital energy is converted to heat in the wire.
Orbits can be artificially influenced through the use of rocket motors which change the kinetic energy of the body at some point in its path. This is the conversion of chemical or electrical energy to kinetic energy. In this way, changes in the orbit shape or orientation can be facilitated. Another method of artificially influencing an orbit is through the use of solar sails or magnetic sails.
Orbital decay can also occur due to tidal forces for objects below the synchronous orbit for the body they are orbiting. The gravity of the orbiting object raises tidal bulges in the primary, and since below the synchronous orbit the orbiting object is moving faster than the body's surface the bulges lag a short angle behind it. The gravity of the bulges is slightly off of the primary-satellite axis and thus has a component along the satellite's motion. The near bulge slows the object more than the far bulge speeds it up, and as a result the orbit decays. Conversely, the gravity of the satellite on the bulges applies torque on the primary and speeds up its rotation. Artificial satellites are too small to have an appreciable tidal effect on the planets they orbit, but several moons in the solar system are undergoing orbital decay by this mechanism. Mars' innermost moon Phobos is a prime example, and is expected to either impact Mars' surface or break up into a ring within 50 million years.
Finally, orbits can decay or develop via the emission of heat absorbed from sunlight shone on the body. Depending on more detailed mechanism and condition, this effect is called as either Poynting-Robertson effect which is effective on dusts or Yarkovsky effect which is effective on small asteroids.
A synchronous orbit is an orbit in which an orbiting body (usually a satellite) has a period equal to the average rotational period of the body being orbited (usually a planet), and in the same direction of rotation as that body.
A satellite in a synchronous orbit that is both equatorial and circular will appear to be suspended motionless above a point on the orbited planet's equator. A synchronous orbit about the Earth that is circular and lies in the equatorial plane is called a geostationary orbit. If the orbit is inclined to the Earth's equator or is noncircular, it is called a geosynchronous orbit. The corresponding terms for synchronous orbits around the planet Mars are areostationary and areosynchronous orbits.
A body in a non-equatorial synchronous orbit will appear to oscillate north and south above a point on the planet's equator, while a body in an elliptical orbit (in the equatorial plane) will appear to oscillate east and west. The combination of these two motions produces a figure-eight pattern as seen from the orbited body, and it is called an "analemma."
Synchronous orbits are commonly employed by artificial satellites used for communication.
A geosynchronous orbit is an orbit around the Earth with an orbital period matching the Earth's sidereal rotation period. This synchronization means that for an observer at a fixed location on Earth, a satellite in a geosynchronous orbit returns to exactly the same place in the sky at exactly the same time each day. The special case of a geosynchronous orbit that is circular and directly above the equator is called a geostationary orbit.
A semisynchronous orbit has an orbital period of 0.5 sidereal days, i.e. 11 h 58 min. Relative to the Earth's surface it has twice this period. An example is the Molniya orbit.
Every geosynchronous orbit has a semi-major axis of 42,164 km (26,200 miles). When the orbit has a non-zero inclination or eccentricity, the ground track of a satellite in that orbit is a more or less distorted figure-eight, returning to the same places once per sidereal day.
A geostationary orbit (GEO) is a circular geosynchronous orbit directly above the Earth's equator—that is, at 0° inclination and zero orbital eccentricity. From the ground, a geostationary object appears motionless in the sky.
A satellite in this orbit appears stationary with respect to a fixed point on the rotating Earth. As a result, an antenna can point in a fixed direction and maintain a link with the satellite. It is therefore the orbit of most interest to operators of artificial satellites, including communication, television, and weather satellites.
Geostationary orbits can only be achieved very close to the ring 35,786 kilometers (km) (22,240 statute miles) above mean sea level. This altitude is significant because it produces an orbital period equal to the Earth's period of rotation, known as the sidereal day. In practice, this means that all geostationary satellites have to exist on this ring directly above the equator. Because the latitude is fixed at 0°, satellite locations may differ by longitude only.
A worldwide network of geostationary meteorological satellites is used to provide visible and infrared images of the Earth's surface and atmosphere. These satellite systems include:
Most commercial communications satellites and television satellites operate in geostationary orbits. (Russian television satellites have used elliptical Molniya and Tundra orbits due to the high latitudes of the receiving audience.) The first satellite placed into a geostationary orbit was Syncom-3, launched by a Delta-D rocket in 1964.
A perfect stable geostationary orbit is an ideal that can only be approximated. In practice, the satellite will drift out of this orbit because of perturbations such as the solar wind, solarradiation pressure, variations in the Earth's gravitational field, and the gravitational effect of the Moon and Sun. For this reason, the satellite is equipped with thrusters that correct for these effects and maintain the orbit in a process known as stationkeeping. The consumption of thruster propellant for station keeping places a limitation on the lifetime of the satellite.
At the end of their service life, the satellites in geostationary orbit are decommissioned. They may continue to be used in inclined orbits (where the orbital track appears to follow a figure-of-eight loop centered on the Equator) or be raised to a "graveyard" disposal orbit.
Synchronous orbits exist around all moons, planets, stars and black holes — unless they rotate so slowly that the orbit would be outside their Hill sphere. Most inner moons of planets have synchronous rotation, so their synchronous orbits are, in practice, limited to their leading and trailing Lagrange points. Objects with chaotic rotations (such as Hyperion) are also problematic, as their synchronous orbits keep changing unpredictably.
Elliptical orbits can be and are designed for communications satellites that keep the satellite within view of its assigned ground stations or receivers. A satellite in an elliptical geosynchronous orbit will appear to oscillate in the sky from the viewpoint of a ground station, tracing an analemma in the sky. Satellites in highly elliptical orbits must be tracked by steerable ground stations.
Theoretically an active geosynchronous orbit can be maintained if forces other than gravity are also used to maintain the orbit, such as a solar sail. Such a statite can be geosynchronous in an orbit different (higher, lower, more or less elliptical, or some other path) from the conic section orbit formed by a gravitational body. Such devices are still theoretical.
A further form of geosynchronous orbit is obtained by the theoretical space elevator in which one end of the structure is tethered to the ground, maintaining a longer orbital period than by gravity alone if under tension.
Other definitions of geosynchronous orbit
The following orbits are special orbits that are also used to categorize orbits:
The idea of a geosynchronous satellite for communication purposes was first published in 1928 by Herman Potočnik. The geostationary orbit was first popularized by science fiction author Arthur C. Clarke in 1945 as a useful orbit for communications satellites. For this reason, this orbit is sometimes referred to as the Clarke orbit. Similarly, the Clarke Belt is the part of space approximately 35,786 km above mean sea level in the plane of the equator where near-geostationary orbits may be achieved.
The first communications satellite placed in a geosynchronous orbit was Syncom 2, launched in 1963. Geosynchronous orbits have been in common use ever since, including satellite television.
Initially, geostationary satellite also carried cellphone calls but are no longer used so predominantly for voice communication, partly due to the inherent disconcerting delay in getting information to the satellite and back (it takes light or radio about a quarter of a second to make the round trip, thus two parties talking via satellite will perceive about a half second delay in round-trip response). Similarly, international Internet connectivity has shifted away from satellite links.
Nearly all populated land locations on the Earth now have terrestrial communications facilities (microwave, fiber-optic), even undersea, with more than sufficient capacity. Satellite telephony is now mainly limited to small, isolated locations that have no terrestrial facilities, such as Canada's arctic islands, Antarctica, the far reaches of Alaska and Greenland, and ships at sea.
When atomic structure was first probed experimentally early in the twentieth century, an early picture of the atom portrayed it as a miniature solar system bound by the Coulomb force rather than by gravity. This was inconsistent with electrodynamics and the model was progressively refined as quantum theory evolved, but there is a legacy of the picture in the term orbital for the wave function of an energetically bound electron state.
All links retrieved February 23, 2015.
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The history of this article since it was imported to New World Encyclopedia: | <urn:uuid:263c0760-8d2a-4746-a721-f65de13215d6> | 3.984375 | 4,595 | Knowledge Article | Science & Tech. | 35.105362 | 95,537,975 |
A View from Emerging Technology from the arXiv
Stars Could Have Wormholes at Their Cores, Say Astrophysicists
Far from being links between empty regions of space, wormholes could form shortcuts from one star to another.
Wormholes are shortcuts in spacetime, throat-like links between otherwise distant parts of the Universe. There’s no evidence that they exist but they do arise mathematically as stable solutions to the equations of relativity, just like other exotic objects such as black holes.
There’s good evidence that black holes exist so astrophysicists can’t simply dismiss the other solutions. In fact, they’ve devoted a good deal of time and effort to working out how wormholes might form, what they would look like and what might keep them open.
But in thinking about wormholes, they’ve tended to imagine them as empty tunnel-like superhighways between one region of empty space and another.
But Vladimir Dzhunushaliev at the Eurasian National University in Kazakhstan and a few pals have a different idea. They say there’s no reason why wormholes can’t be packed full of matter. And today they unveil the properties of such objects.
They begin by imagining an ordinary star or a neutron star with a wormhole at its heart. “For a distant observer, such a star would very much look like an ordinary star,” they say.
However, there would be some important differences. For a start, this star would have to have a twin at the other end of the wormhole. These stars would be like Siamese twins, joined at the hip by the most bizarre of connections.
These twins would also pulse in an unusual way. That’s because the exotic matter in the wormhole would be able to flow back and forth, like liquid in a u-tube, setting up a kind of resonance that makes the stars oscillate.
That could lead to the release of energy in all kinds of ways, creating ultra high energy cosmic rays, for example.
It also means there ought to be a way of distinguishing these Siamese twins from other stars. That’s harder than it sounds, however.
The detailed calculations need to work out what oscillations are possible need to take account of the singularities that exist where wormholes are concerned. That makes them fiendishly difficult and certainly beyond Dzhunushaliev and co for the moment.
So they make no specific predictions about how astronomers could hunt down these objects.
That leaves an interesting puzzle for others to tackle. If stars can exist with wormholes at their centre, we’d obviously like to know what they look like so we can see whether there are any nearby. Time to get calculating.
Ref: arxiv.org/abs/1102.4454: A Star Harbouring A Wormhole At Its Center
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:6190aa61-e996-46c7-a42a-02b31c290b87> | 3.46875 | 636 | Truncated | Science & Tech. | 51.496639 | 95,537,984 |
Hubble Astronomers Develop a New Use for a Century-Old Relativity Experiment to Measure a White Dwarf’s Mass
Astronomers have used the sharp vision of NASA’s Hubble Space Telescope to repeat a century-old test of Einstein’s general theory of relativity. The Hubble team measured the mass of a white dwarf, the burned-out remnant of a normal star, by seeing how much it deflects the light from a background star.
This observation represents the first time Hubble has witnessed this type of effect created by a star. The data provide a solid estimate of the white dwarf’s mass and yield insights into theories of the structure and composition of the burned-out star.
First proposed in 1915, Einstein’s general relativity theory describes how massive objects warp space, which we feel as gravity. The theory was experimentally verified four years later when a team led by British astronomer Sir Arthur Eddington measured how much the sun’s gravity deflected the image of a background star as its light grazed the sun during a solar eclipse, an effect called gravitational microlensing.
Astronomers can use this effect to see magnified images of distant galaxies or, at closer range, to measure tiny shifts in a star’s apparent position on the sky. Researchers had to wait a century, however, to build telescopes powerful enough to detect this gravitational warping phenomenon caused by a star outside our solar system. The amount of deflection is so small only the sharpness of Hubble could measure it.
Hubble observed the nearby white dwarf star Stein 2051B as it passed in front of a background star. During the close alignment, the white dwarf’s gravity bent the light from the distant star, making it appear offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a quarter from 1,500 miles away.
Using the deflection measurement, the Hubble astronomers calculated that the white dwarf’s mass is roughly 68 percent of the sun’s mass. This result matches theoretical predictions.
The technique opens a window on a new method to determine a star’s mass. Normally, if a star has a companion, astronomers can determine its mass by measuring the double-star system’s orbital motion. Although Stein 2051B has a companion, a bright red dwarf, astronomers cannot accurately measure its mass because the stars are too far apart. The stars are at least 5 billion miles apart – almost twice Pluto’s present distance from the sun.
“This microlensing method is a very independent and direct way to determine the mass of a star,” explained lead researcher Kailash Sahu of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “It’s like placing the star on a scale: the deflection is analogous to the movement of the needle on the scale.”
Sahu will present his team’s findings at 11:15 a.m. (EDT), June 7, at the American Astronomical Society meeting in Austin, Texas.
The Hubble analysis also helped the astronomers to independently verify the theory of how a white dwarf’s radius is determined by its mass, an idea first proposed in 1935 by Indian American astronomer Subrahmanyan Chandrasekhar. “Our measurement is a nice confirmation of white-dwarf theory, and it even tells us the internal composition of a white dwarf,” said team member Howard Bond of Pennsylvania State University in University Park.
Sahu’s team identified Stein 2051B and its background star after combing through data of more than 5,000 stars in a catalog of nearby stars that appear to move quickly across the sky. Stars with a higher apparent motion across the sky have a greater chance of passing in front of a distant background star, where the deflection of light can be measured.
After identifying Stein 2051B and mapping the background star field, the researchers used Hubble’s Wide Field Camera 3 to observe the white dwarf seven different times over a two-year period as it moved past the selected background star.
The Hubble observations were challenging and time-consuming. The research team had to analyze the white dwarf’s velocity and the direction it was moving in order to predict when it would arrive at a position to bend the starlight so the astronomers could observe the phenomenon with Hubble.
The astronomers also had to measure the tiny amount of deflected starlight. “Stein 2051B appears 400 times brighter than the distant background star,” said team member Jay Anderson of STScI, who led the analysis to precisely measure the positions of stars in the Hubble images. “So measuring the extremely small deflection is like trying to see a firefly move next to a light bulb. The movement of the insect is very small, and the glow of the light bulb makes it difficult to see the insect moving.” In fact, the slight movement is about 1,000 times smaller than the measurement made by Eddington in his 1919 experiment.
Stein 2051B is named for its discoverer, Dutch Roman Catholic priest and astronomer Johan Stein. It resides 17 light-years from Earth and is estimated to be about 2.7 billion years old. The background star is about 5,000 light-years away.
The researchers plan to use Hubble to conduct a similar microlensing study with Proxima Centauri, our solar system’s closest stellar neighbor.
The team’s result will appear in the journal Science on June 9. | <urn:uuid:dcf1a9a7-68e3-46b5-a620-f7e4150ac58c> | 3.96875 | 1,166 | News (Org.) | Science & Tech. | 45.412824 | 95,537,994 |
This article is introduces you with the Hibernate framework. You will learn the features and advantages of using Hibernate in your projects.
What is Hibernate Framework?
Hibernate is Java based open source project for persisting the Java objects (POJO's) into persistence store (e.g. database). It is one of the most used ORM tool in the software industry. ORM stands for Object Relational Mapping and it provides the API for saving the persistence objects to the data store. It also provides the API for performing insert, update, delete and query operations. Here there is not need to write the JDBC SQL statement and queries Hibernate Framework (ORM tool) automatically generates the necessary SQL statements and execute against database in runtime. It saves a lot of development time and increases the developers efficiency working on the project.
As mentioned above Hibernate Framework is free and open source framework which is distributed under the GNU Lesser General Public License. So, you can use Hibernate framework for free as well commercial application without paying any fee.
Hibernate framework supports OOP's principal and provides support for association, inheritance, polymorphism, composition and the collection framework. Developers can use all these principals of Java while working with the Hibernate framework.
Following diagram shows show you can use the Hibernate framework in your application:
From your Java application will call the Hibernate API and then Hibernate will perform the persistence acvities.
Features of Hibernate Framework:
Here is the important features and benefits of Hibernate:
More tutorials about Hibernate Introduction | <urn:uuid:d58053dc-9690-45bd-8c86-64bc87b6916b> | 2.9375 | 351 | Truncated | Software Dev. | 19.856521 | 95,538,002 |
Background and Aims Low-altitude mountains constitute important centres of diversity in landscapes with little topographic variation, such as the Southwest Australian Floristic Region (SWAFR). They also provide unique climatic and edaphic conditions that may allow them to function as refugia. We investigate whether the Porongurups (altitude 655 m) in the SWAFR will provide a refugium for the endemic Ornduffia calthifolia and O. marchantii under forecast climate change.
Methods We used species distribution modelling based on WorldClim climatic data, 30-m elevation data and a 2-m-resolution LiDAR-derived digital elevation model (DEM) to predict current and future distributions of the Ornduffia species at local and regional scales based on 605 field-based abundance estimates. Future distributions were forecast using RCP2.6 and RCP4.5 projections. To determine whether local edaphic and biotic factors impact these forecasts, we tested whether soil depth and vegetation height were significant predictors of abundance using generalized additive models (GAMs).
Key Results Species distribution modelling revealed the importance of elevation and topographic variables at the local scale for determining distributions of both species, which also preferred shadier locations and higher slopes. However, O. calthifolia occurred at higher (cooler) elevations with rugged, concave topography, while O. marchantii occurred in disturbed sites at lower locations with less rugged, convex topography. Under future climates both species are likely to severely contract under the milder RCP2.6 projection (approx. 2 °C of global warming), but are unlikely to persist if warming is more severe (RCP4.5). GAMs showed that soil depth and vegetation height are important predictors of O. calthifolia and O. marchantii distributions, respectively.
Conclusions The Porongurups constitute an important refugium for O. calthifolia and O. marchantii, but limits to this capacity may be reached if global warming exceeds 2 °C. This capacity is moderated at local scales by biotic and edaphic factors. | <urn:uuid:6c92d11f-104e-4986-b071-0859e8968f49> | 2.953125 | 449 | Academic Writing | Science & Tech. | 23.587868 | 95,538,059 |
BAMBERG — Since the beginning of February, a sixth-grade science project has been powering classrooms and children’s curiosity at Richard Carroll Elementary School.
Through a partnership between the school and utilities, students are getting a first-hand look at the power of solar energy.
“The way we use energy is going to play an extremely important role ... in meeting our state’s needs,” said Lonnie Carter, president and chief executive officer of Santee Cooper.
“This investment here at the Richard Carroll Elementary School as a green power solar school is part of that important future investment in renewable energy in our state. What this solar panel is doing is taking energy from the sun and transforming it into electricity in a form we can use,” he said.
The Bamberg Board of Public Works and Santee Cooper dedicated the school as the state’s 28th Green Power Solar School during a Friday ceremony.
The school has been equipped with a 2-kilowatt solar power system that is already producing electricity from the sun’s rays, providing students with a firsthand look at the opportunities and challenges of solar power.
Richard Carroll’s solar energy project has been in the works for three years, sixth-grade science teacher Bobbie Bunch said.
There was lot of paperwork, but it paid off in the end, according to Bunch.
The main concept she wanted kids to take away from the project is that energy is everywhere. It cannot be created or destroyed. It’s how things get moved around or transformed.
“It’s kind of a hard concept for the kids to wrap their minds around because you can’t really see it, feel it or touch it,” she said. “You can see it in action, but you can’t really touch it.”
Sixth-grader John Marshall said he learned about phototropism, where plants grow toward the sun so they can get as much energy as possible for photosynthesis.
That’s where the sun’s energy, water and carbon dioxide go into the plant and make sugar, he said.
The project was “pretty fun,” Marshall said.
A solar array panel was put in place last winter while students were out on break. It’s been collecting the sun’s energy and transforming it into useable electricity ever since.
“It traps the electricity, breaks up the electrons,” Bunch said. “The electrons flow into the building with the system we already have set up and it powers up everything we have in the building.”
The kids can go online and see how many kilowatts the array brings in per second, Bunch said.
The solar array was put into place by Santee Cooper and the Bamberg Department of Public Works at no expense to Bamberg District One.
“Solar energy is the future,” said Matt Medlin, chairman of the Bamberg Board of Public Works. “We can harness the sun’s energy.
“These kids have no idea about the power that lies at their fingertips.” | <urn:uuid:ead8c515-4b73-438e-bd89-31bcb934c67b> | 3.03125 | 662 | News Article | Science & Tech. | 58.140323 | 95,538,061 |
It’s amazing to think that just 100 years ago we believed the Milky Way was our entire universe. That was until Edwin Hubble—with the aid of a giant telescope at Mount Wilson in California—discovered other galaxies outside our own and revolutionised our understanding of the universe. Now a consortium of scientific institutions from Australia, Korea, Brazil and the United States are hoping to take us even further with the new Giant Magellan Telescope (GMT) that’s currently under construction in Chile.
Named after legendary Portuguese explorer Ferdinand Magellan (whose 1519-1522 expedition to the East Indies resulted in the first circumnavigation of the Earth), the GMT is spearheading a new wave of “super telescopes” that will revolutionise our perspective and understanding of the universe. It’s hoped this new giant telescope and others like it will help us to detect life on distant planets and see as far back as the Big Bang itself. How’s that for ambition?
The GMT project is currently under construction at Las Campanas Observatory in Chile’s Atacama Desert, having broken ground in November 2015. Its 8,500-foot altitude location is one of the driest places on Earth and is miles away from the smog and light pollution of big towns and cities, ensuring perfect observational conditions for more than 300 nights a year. First steps are to level a road to the observatory location and lay the foundations for the 1,100-ton telescope, with the project scheduled for completion sometime in 2021 at a cost of just over $1 billion. That’s a lot of green.
Of course, a giant telescope needs a giant lens. For the GMT, this will comprise seven enormous high-tech mirrors, each of which takes six years to build. With six 27-foot segments surrounding a central piece, the combined optical surface will come in at around 80 feet—more than twice the size of the 34-foot Great Canary Telescope in Spain (the current largest ground-based telescope in the world)—and will be around 10 times more powerful than the Hubble Space Telescope.
This incredible lens will collect light from the furthest edges of the universe and reflect it down through a series of mirrors to be captured by imaging cameras. From there, the concentrated light will be measured to determine how far away objects are and what they are made of. The accuracy required throughout this process is staggering; the GMT’s mirrors are curved to a precise shape and polished to within a wavelength of light (about one-millionth of an inch), and hundreds of actuators controlled by advanced computers will subtly adjust their shape to counteract atmospheric turbulence.
The GMT will be closely followed by the creatively-named Thirty Meter Telescope (98 feet) in Hawaii and the European Extremely Large Telescope (129 feet), which isn’t in Europe at all, but another Atacama Desert location. Together, they’ll help us examine distant galaxies and solar systems with unprecedented reach and clarity. We may finally discover evidence of life on distant planets, how the first galaxies were formed, what happened at the Big Bang, and what the fate of our universe will be. Huge questions, but can the GMT and other giant telescope projects deliver answers? We’ll just have to wait and see.
Q: Ever seen, or wanted to visit, one of these remote observatories? Tell us about it in the comments below.
Scientists Develop New Type of Cell That Could Revolutionize the Treatment of Heart Disease
THIS CONTENT WAS REPUBLISHED FROM AN EARLIER DATE.
Heart disease has consistently been one of the biggest killers of both men and women, with hundreds of thousands of families losing loved ones to the condition every year. But now a new study published in the journal Cell Stem Cell has identified a possible breakthrough in the treatment of heart disease, offering hope to anyone suffering from a dodgy ticker. The study was conducted by a team of researchers from the Gladstones Institutes, who have discovered a way to make a remarkable new type of cell that could help damaged hearts repair themselves.
Heart failure occurs when the heart is overworked or the supply of oxygen is too low. A sudden attack can cause the loss of huge amounts of important muscle cells known as cardiomyocytes (CMs). These CMs cannot regenerate by themselves, nor can they be replaced because transplanted heart cells tend not to survive in the patient’s body. As you can imagine, this makes the treatment of heart disease quite tricky; since heart cells can’t regenerate or be replaced, the damage is usually irreversible. “Scientists have tried for decades to treat heart failure by transplanting adult heart cells, but these cells cannot reproduce themselves, and so they do not survive in the damaged heart,” said Yu Zhang, MD, PhD, one of the lead authors of the study.
To overcome this dilemma, the team investigated the possibility of regenerating the heart using progenitors—stem cells that have already been programmed to develop into a specific type of cell. In this case, they targeted cardiovascular progenitor cells (CPCs), which are produced as the heart begins to form within the embryo. Using a revolutionary technique, the team were able to produce CPCs in the lab and halt their development so the cells remained effectively “frozen” until use. They called these lab-grown cells “induced expandable CPCs,” or ieCPCs.
Unlike adult heart cells, ieCPCs have the ability to replicate. If transplanted successfully, they could replace a patient’s damaged heart cells and possibly continue to self-repair. “Our generated ieCPCs can prolifically replicate and reliably mature into the three types of cells in the heart, which makes them a very promising potential treatment for heart failure,” said Zhang. To test this theory, the team injected some of the cells into a mouse that had suffered a heart attack. Remarkably, most of the cells transformed into functioning heart cells, generating new muscle tissue and blood vessels and improving the mouse’s overall heart function.
So what does all this mean for the treatment of heart disease? Well, it’s definitely big news. The cells used to treat the mouse were derived from skin cells, which means a patient’s own cells could potentially be used to treat their heart disease. The next step is to try and form human ieCPCs in the lab, and then follow up with human trials to see if the method is as effective. All going well, this could be a viable treatment for heart disease patients within the next few years.
Q: Is this the most important breakthrough yet in the field of heart disease research? Share your thoughts in the comments below.
Copyright 2016 David Carroll
How Li-Fi Technology Is Going to Change the Internet Game Forever
THIS CONTENT WAS REPUBLISHED FROM AN EARLIER DATE.
Are you sick of slow Internet connections and weak Wi-Fi signals? I know we’re talking First World problems here, but it still gets under my skin. Luckily, all that could be about to change soon, as there’s a new kid on the block. See, our old buddy Wi-Fi looks set to be surpassed by Li-Fi technology—a new method of data transmission that uses visible light communication instead of radio waves.
It’s been around for a while, and we already know the new tech can achieve staggering speeds of up to 224 Gbps in a laboratory setting. But now an Estonian startup called Velmenni has tested Li-Fi in an office environment, and they’ve managed a healthy 1 Gbps (about 100 times faster than current average Wi-Fi speeds). So we’re definitely getting closer to actually implementing Li-Fi technology in the real world, but what exactly is it? Let’s find out:
How Does Li-Fi Technology Work?
The term “Li-Fi” was first coined by its inventor Harald Haas, who unveiled the technology at a TED conference back in 2011. It’s basically a method of transmitting binary data across the visible light spectrum by quickly flicking a bulb on and off, just like Morse code. While that sounds like a recipe for blindness and seizures, the flickering happens so fast that it’s imperceptible to the human eye. It’s not a difficult technology to implement, either—with just a simple modification, virtually any bulb can be converted into a Li-Fi transmitter/receiver, from the lamp on your desk to the overhead light in a car or airplane.
How Is It Going to Change the Way We Connect?
Well, there’s the enormous jump in connection speeds for a start. But aside from that, Li-Fi technology offers a number of tangible benefits. It’s highly efficient, because we already use bulbs everywhere for the purposes of illumination. Piggybacking data over the same waves would reduce our energy costs right off the bat. It’s also highly secure, because light waves can’t penetrate walls. Then you have all the potential applications of the technology. Imagine cars that can transmit data back and forth to prevent accidents, or street lamps that function as free data access points. Pretty cool, no?
When Will We Get to Use It?
Given the successful field test in Estonia, it wouldn’t be unreasonable to expect to see Li-Fi making its way to our homes and workplaces within the next couple of years. But before you get too excited, you should know that Li-Fi technology has its limitations. For example, the fact that light waves can’t pass through walls is great for security, but it’s problematic from a practical standpoint. Also, Li-Fi sort of falls apart once you move outdoors because of pollution and interference from natural light sources.
In all likelihood, it will supplement Wi-Fi technology rather than replace it altogether (at least in the early stages of its rollout), so don’t throw away your existing router just yet. With that said, it’s definitely got some serious potential to revolutionise the Internet. But here’s the million-dollar question: does Li-Fi mean the end of that annoying “buffering” symbol? We’ll just have to wait and see.
Q: Any other tech developments you’re pumped about seeing? Tell us about them in the comments below.
David Carroll is a freelance writer, self-published author, and chief health-nut at thepaleotoolkit.com. Outside of work, he loves hurling (an amazing Irish sport), playing video games and hanging out with his dogs. Follow him on Twitter (@DavidAshCarroll) and Google+.
If climate change is real, then why is Antarctic ice cover growing?
The North Pole has been losing ice cover at an alarming rate in recent years as the Arctic region steadily warms up. For those not in denial about climate change, it’s a constant and potent reminder that something needs to be done, and done quickly. But if the planet really is getting warmer, how is it possible that Antarctic ice cover has not only remained stable, but actually grown in recent years? It’s a question that has proven difficult to answer and provided interesting fodder for the climate change debate, but now a team of researchers from NASA believe they may have put the issue to bed.
In a study published in the journal Remote Sensing of Environment, the authors show that the reason the Antarctic is not melting like the Arctic is due to differences in topography, climate and ocean levels between the two regions. “Our study provides strong evidence that the behavior of Antarctic sea ice is entirely consistent with the geophysical characteristics found in the southern polar region, which differ sharply from those present in the Arctic,” explained lead researcher Son Nghiem.
Every year, Antarctic ice expands and shrinks according to seasonal cycles in the Southern Hemisphere. The NASA team used satellite radar, sea temperature, ocean levels and other data to track this ice formation and identify any contributing factors. They found that as new ice forms in the Antarctic, it is pushed northwards by winds and forms a kind of “protective shield” around the continent. The winds continue to pack ice up against the shield, increasing its thickness up to 1,000 kilometers (620 miles) in parts. As the ice shield continues to drift away from the continent, it leaves behind an area of open water where new ice can form, protected from waves.
All of this occurs in a region where the sea surface temperature remains below freezing at -1 degrees celsius (30F). This “temperature boundary” is dictated by ocean currents which are particular to the surrounding area, and are influenced by sea floor creatures the researchers identified in their study. So far from being a paradox, the behaviour of the surrounding ocean and wind patterns influenced by the topography of the Antarctic create an environment that’s well-suited to the formation and persistence of ice. The same factors are not present in the Arctic, which leaves the region more vulnerable to the effects of global warming.
NASA’s study has given us the most cohesive explanation to date for the disparate behaviour of Arctic and Antarctic ice cover. The growth of sea ice in the southern region might appear to contradict everything we know about global warming, but in fact, it’s simply a product of differences in climate and topography between the two poles. Despite their obvious similarities, the Arctic and Antarctic are quite different. So if you encounter anyone who cites the ice cover paradox as evidence against climate change, point them to this study and explain they’re comparing apples and oranges.
Q: What’s the number one obstacle getting in the way of tackling climate change? Share your thoughts in the comments below.
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INDIANA U. (US) — The aggressive behavior of wild birds varies according to how their brains process testosterone, according to a new study.
An Indiana University biologist has shown that natural variation in measures of the brain’s ability to process steroid hormones predicts functional variation in aggressive behavior.
The team measured natural variation in aggressiveness toward the same sexes in male and female free-living dark-eyed juncos (Junco hyemalis) early in the breeding season. (Credit: Joel McGlothlin)
The new work led by Kimberly A. Rosvall, a postdoctoral fellow and assistant research scientist in the IU Bloomington College of Arts and Sciences’ department of biology, has found strong and significant relationships between aggressive behavior in free-living birds and the abundance of messenger RNA in behaviorally relevant brain areas for three major sex steroid processing molecules: androgen receptor, estrogen receptor, and aromatase.
“Individual variation is the raw material of evolution, and in this study we report that free-living birds vary in aggression and that more aggressive individuals express higher levels of genes related to testosterone processing in the brain,” she says.
“We’ve long hypothesized that the brain’s ability to process steroids may account for individual differences in hormone-mediated behaviors, but direct demonstrations are rare, particularly in unmanipulated or free-living animals.”
Rosvall says the study shows that aggression is strongly predicted by individual variation in gene expression of the molecules that initiate the genomic effects of testosterone. The new work appears June 6 in Proceedings of The Royal Society B.
The findings are among the first to show that individual variation in neural gene expression for three major sex steroid processing molecules predicts individual variation in aggressiveness in both sexes in nature—results that should have broad implications for understanding the mechanisms by which aggressive behavior may evolve.
“On the one hand, we have lots of evidence to suggest that testosterone is important in the evolution of all kinds of traits,” Rosvall notes. “On the other hand, we know that individual variation is a requirement for natural selection, but individual variation in testosterone does not always predict behavior. This conundrum has led to debate among researchers about how hormone-mediated traits evolve.”
To find such strong relationships between behavior and individual variation in the expression of genes related to hormone-processing is exciting because it tells scientists that evolution could shape behavior via changes in the expression of these genes, as well as via changes in testosterone levels themselves.
The team measured natural variation in aggressiveness toward the same sexes in male and female free-living dark-eyed juncos (Junco hyemalis) early in the breeding season. The dark-eyed junco is a North American sparrow that is well studied with respect to hormones, behavior, and sex differences.
By comparing individual differences in aggressiveness (flyovers or songs directed at intruders) to circulating levels of testosterone and to neural gene expression for the three major sex steroid processing molecules, the researchers were able to quantify measures of sensitivity to testosterone in socially relevant brain areas: the hypothalamus, the ventromedial telencephalon, and the right posterior telencephalon.
Their results suggest selection could shape the evolution of aggression through changes in the expression of androgen receptor, estrogen receptor, and aromatase in both males and females, to some degree independently of circulating levels of testosterone.
They found, for example, that males that sing more songs at an intruder have more mRNA for aromatase and estrogen receptor in the posterior telencephalon, and also that males and females that dive-bomb an intruder more frequently have more androgen receptor, estrogen receptor, and aromatase mRNA in brain tissues including the medial amygdala, an area of the brain that’s known to control aggression in rodents and other birds. mRNA are single-stranded copies of genes that are translated into protein molecules.
The work reveals there is ample variation in hormone signal and in gene expression on which selection may act to affect aggressiveness. It also establishes a prerequisite for the evolution of testosterone-mediated characteristics through changes in localized gene expression for the key molecules that process sex steroids, and suggests that trait evolution can occur with some degree of independence from circulating testosterone levels.
“Researchers have thought this was probably the case for about a hundred years, based on a lot of really important work that uses experimental manipulations like castration or hormone replacement,” Rosvall says. “But very few people have looked to see if individuals actually do vary in expression of these genes, and whether this individual variation means anything, in terms of an animal’s behavior. Our work shows that it does.”
The new insights into how neuroendocrine mechanisms of aggression may be modified as populations diverge into species also offer opportunities for future research, including trying to determine whether genes that are up- or down-regulated in response to environmental stimuli may be the same genes that contribute to the evolution of certain traits and characteristics.
Co-authors on the paper with Rosvall contributed from Indiana University, as well as University of California Los Angeles. The work was funded by the National Institutes of Health, the Indiana Academy of Sciences, and the National Science Foundation.
More news from Indiana University: http://newsinfo.iu.edu/ | <urn:uuid:70ad41ed-eee5-4f99-ae0e-5a485c335de8> | 3.3125 | 1,099 | News Article | Science & Tech. | 11.183249 | 95,538,074 |
This article is now available on fcole90.github.io
A scene from the movie A.I. Artificial Intelligence (2001) – © 2001 – Warner Brothers and Dreamworks LLC – All Rights Reserved
Contents at a glance:
- Real neural networks and Artificial Neural Networks
- The abilities and the limits of the current Artificial Neural Networks models
The neurons are the cells responsible for the transmission of the signal through the human nervous system. A single neuron cannot achieve much by itself, but groups of them can create highly complex networks, with billions of connections. Neural networks can be considered the analogue of what processors are for computers: a powerful calculation machine.
Scheme visualisation of a mulipolar neuron.
Artificial Neural Networks (ANN) are mathematical models which mimic the functioning of human neural networks, and it is thanks to them that today we are experiencing a new spring in the artificial intelligence research field. The artificial neuron is represented as simply as a summation unit, which makes a weighted sum of the inputs of its afferent neurons. The entity of its output is related to the value of the inputs sum and to the activation function.
An artificial neural network is an interconnected group of nodes, akin to the vast network of neurons in a brain. Here, each circular node represents an artificial neuron and an arrow represents a connection from the output of one neuron to the input of another. – Wikipedia
What makes neurons especially powerful, is their ability to learn. This has been discovered to be determined by the establishment, the strengthening or loosening of connections between neurons. In the model of artificial neural networks such a mechanism has been mimicked leveraging the values of the weights which represent the connections. As such, the lower (or higher) the value the loosen (or stronger) the connection will be.
The algorithm responsible for this learning operations, in the ANN, is the backpropagation. It’s a technique which uses derivatives to find the connection pattern which minimises the error given a certain task. It was discovered in the 80s, but only recently computers have become powerful enough to compute it in complex multilayered networks. This lead to the deep learning revolution that we are experiencing today, and to very complex artificial intelligences, which can beat the strongest human players at Go, drive cars and become everyone’s personal assistant.
However ANNs, as they’re currently modelled, require a very hard and long training before they can do all their marvelous things, which is the reason behind the immense growth of value of large collections of data, usually known as Big Data. This limits upset even one or the pioneers of the backpropagation algorithm, Geoffrey Hinton, who recently suggested to get rid of the current learning method, to try to discover something totally new. Clearly backpropagation cannot be trashed from one day to another, but the development of new means for modelling learning is a major interest of the artificial intelligence researchers.
The way to discover more powerful techniques to mimic learning is long and perilous but new discoveries in neuroscience may unravel and lead to new and unexpected fields. Studying the behaviour and inner working of the brain can open paths to new state of the art algorithms and techniques for machine learning. | <urn:uuid:4bc3146e-42fe-478f-ad13-77cb52c70d9e> | 3.671875 | 661 | Truncated | Science & Tech. | 34.055185 | 95,538,098 |
Zeeman-Doppler Imaging of active late-type stars
Stellar magnetic fields, as a crucial component of star formation and evolution, evade direct observation at least with current and near future instruments. However investigating whether magnetic fields are generated by a dynamo process or represent relics from the formation process, or whether they show a behavior similar to the sun or something very different, it is essential to investigate their structure and temporal evolution. Fortunately nature provides us with the possibility to indirectly observe surface topologies on distant stars by means of Doppler shift and polarization of light, though not without its challenges. Based on the mentioned effects, the so called Zeeman-Doppler Imaging technique is a powerful method to retrieve magnetic fields from rapid rotating stars based on measurements of spectropolarimetric observations in terms of Stokes profiles. In recent years, a large number of stellar magnetic field distributions could be reconstructed by Zeeman-Doppler Imaging (ZDI). However, the implementation of this method often relies on many approximations because, as an inversion method, it entails enormous computational requirements. | <urn:uuid:f1078edb-8230-4cba-891a-662446d4ea15> | 3.140625 | 223 | Knowledge Article | Science & Tech. | 2.434873 | 95,538,099 |
Nanotechnology is a branch of technology that deals with matter at a molecular scale. By manipulating the arrangement of atoms, it’s possible to change the nature of the material they compose. According to the latest Nanotech News, nanotechnology is being used to improve the performance of drones and UAVs, particularly in the field of agriculture.
Drones In Agriculture
Agricultural drones provide farmers with a bird’s-eye view of their crops, giving them valuable information they could not otherwise access. With infrared images, farmers can detect signs of disease in plants that they would not be able to see with their eyes alone. In addition, drones can do certain types of agricultural work, like spraying crops with fertilizers or pesticides. Advances in drone technology are thus helping farmers increase productivity and reduce their costs. Nanotechnology is making a difference in the following ways.
Under the best circumstances, agricultural drones don’t have a very long flight time. Most last only ten to fifteen minutes in the air. When a drone is carrying a liquid crop spray, the weight of the spray can shorten that time even further. However, the lighter the weight of the liquid it carries, the longer and farther a drone will be able to fly. With nanotechnology, scientists are developing more potent liquids, meaning that drones carry less of it and spray it in a finer mist.
Another factor in a drone’s flight time is its battery life. Standard batteries cannot keep a drone in the air very long, and having to recall drones frequently to change batteries is not the most efficient use of time. However, through nanotechnology, new graphene batteries are being developed that can increase performance by 50%. Even an extra 5 minutes on each flight can make a big difference over the course of a day’s work.
Stronger Drone Components
Drones have to be sturdy to withstand inevitable crashes and collisions. A new nanocoating can help protect drones not only from impact but also from weather by shielding it from moisture and insulating it against extremely hot or cold temperatures. Because the coating is no thicker than a molecule, it adds nothing to the weight of the drone. | <urn:uuid:9b4e2ec6-841f-4266-a4bc-521320ab57b2> | 3.9375 | 441 | Knowledge Article | Science & Tech. | 39.649217 | 95,538,122 |
Set nets appear to be scratching fewer Hector's Dolphins in Akaroa Harbour, and although that's good it makes it harder to gauge survival rates, researchers say.
Akaroa Marine reserve has been in place since 2014, which means fishing and the removal of any living or non-living marine resource is prohibited.
University of Otago's Marine Science Department student Lindsay Wickman said estimates showed about 10 percent had markings in the 1990s compared to estimates of 6.5 percent now.
She said dolphins could also get markings from other sources, such as sharks.
"It can be hard to delineate which is caused by which, but of all the types, set netting was the type that was restricted and could be contributing to fewer marks," she said.
Lindsay Wickman said while this was good news, it meant sample sizes could now be smaller.
"So everything we learn about the population comes from just this proportion of individuals that have these markings or nicks on their fins," she said.
"As our sample size becomes lower, it makes things like survival rate, which we use as an indicator of the health of the population less precise and harder to see if the population is increasing or decreasing," she said.
She said researchers use the dolphins who have distinct markings to monitor the species, rather than the more invasive method of tagging.
"It removes any impact that we as researchers might have on their behaviour, or even their survival rate, because what if we use tags which might make it more difficult to swim."
She said Hector's already tended to have less markings than other dolphin species.
"Bottlenose dolphins can have much higher mark rate, usually about 80 or 90 percent of the dolphins can be marked, that can make a big difference when trying to estimate population health," she said.
She said this could be related to Hector's dolphin's social behaviour, as bottlenose dolphins were more likely to have aggressive interactions with each other.
As technology improves, researchers might be able to find other ways of identifying dolphins, she said. | <urn:uuid:293936c7-06e0-4cd6-bb46-96ae7b519f93> | 3.375 | 423 | News Article | Science & Tech. | 44.57997 | 95,538,137 |
Sea salt aerosol (SSA) contains both inorganic salts and organic matter from the ocean. It is thought that the amount of organic matter transferred to SSA depends on microbiological activity. The organic matter in sea spray can contain dissolved organic matter or even microbes themselves, like bacteria and viruses.
Salt spray is largely responsible for corrosion of metallic objects near the coastline, as the salts accelerate the corrosion process in the presence of abundant atmospheric oxygen and moisture. Salts do not dissolve in air directly, but are suspended as fine particulates, or dissolved in microscopic airborne water droplets.
The salt spray test is the notable measure of material endurance, particularly if the material will be used outdoors and must perform in a mechanical load bearing or otherwise critical role. These results are often of great interest to the marine industries, whose products may suffer extreme acceleration of corrosion and subsequent failure due to the salt water environment.
- Lewis, Ernie; Schwartz, Stephen (2004). Sea Salt Aerosol Production: Mechanisms, Methods, Measurements, and Models. Washington, DC: American Geophysical Union. p. 413. ISBN 087590-417-3.
- Gantt, Brett; Meskhidze, Nicholas (2013). "The physical and chemical characteristics of marine primary organic aerosol: a review". Atmospheric Chemistry and Physics. 13 (8): 3979–3996. Bibcode:2013ACP....13.3979G. doi:10.5194/acp-13-3979-2013.
- O'Dowd, C.D.; Facchini, M.C.; Cavalli, F.; Ceburnis, D.; Mircea, M.; Decesari, S.; Fuzzi, S.; Yoon, Y.J.; Putaud, J.P. (2004). "Biogenically driven organic contribution to marine aerosol". Nature. 431 (7009): 676–680. Bibcode:2004Natur.431..676O. doi:10.1038/nature02959. PMID 15470425.
- Russell, L.M.; Hawkins, L.N.; Frossard, A.A.; Quinn, P.K.; Bates, T.S. (2010). "Carbohydrate-like composition of submicron atmospheric particles and their production from ocean bubble bursting". Proc. Natl. Acad. Sci. USA. 107 (15): 6652–6657. Bibcode:2010PNAS..107.6652R. doi:10.1073/pnas.0908905107. PMC . PMID 20080571.
- Blanchard, D.C.; Syzdek, L.D. (1972). "Concentration of Bacteria in Jet Drops from Bursting Bubbles". J. Geophys. Res. 77 (27): 5087. Bibcode:1972JGR....77.5087B. doi:10.1029/jc077i027p05087. | <urn:uuid:afbcb4c2-a5c5-41df-b897-54da9cfa7c79> | 3.09375 | 629 | Knowledge Article | Science & Tech. | 68.730604 | 95,538,140 |
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Extinction is a natural fact, and a lot of species have gone extinct in the past. You don’t see dinosaurs walking down your street today because they went extinct about 65 million years ago. Extinction is a natural process. But it is sometimes considered unnatural when humans cause extinction. Perhaps a species is overhunted like the dodo. Or maybe the forest that a certain kind of bird lives in is cut down and turned into farmland. If a species starts to decrease in number because of human action, some people get concerned. If their numbers get too low they might be considered to be in danger of extinction. When this happens the species is called an endangered species. If enough scientists agree, it is put on the endangered species list. To protect species on the endangered species list the government might make it illegal to hunt it, or turn a portion of the forest the species lives in into a national park to prevent it from being cut down.
Once a species is put on the endangered species list there are three ways for it to be removed from the list, or to be delisted. One way is for new information to be discovered which reveals that the species was never actually endangered to begin with. The second way is for the species to increase in numbers enough to be considered recovered, as was the case with the American bald eagle. Lastly, the species can be delisted because it's become extinct. The dusky seaside sparrow was not so lucky as the bald eagle. It was delisted when protection efforts failed and it became extinct. Since the Endangered Species Act was passed in 1973, the federal government has delisted 47 species.
The International Union for Conservation of Nature (IUCN) uses these categories for species status. Extinct (EX) - No individuals remaining. Extinct in the Wild (EW) - Known only to survive in captivity, or as a naturalized population outside its historic range. Critically Endangered (CR) - Extremely high risk of extinction in the wild. Endangered (EN) - High risk of extinction in the wild. Vulnerable (VU) - High risk of endangerment in the wild. Near Threatened (NT) - Likely to become endangered in the near future. Least Concern (LC) - Lowest risk. Does not qualify for a more at risk category. Widespread and abundant taxa are included in this category.
The International Union for the Conservation of Nature, or IUCN, keeps the most complete list of endangered species in the world. The IUCN list is called the Red List instead of the Red Book. It uses the chart above to tell how serious the threat of extinction is to each species on the list. The chart below tells how many of each kind of species are on the Red List.
Dr. Biology. (2011, January 28). What is an Endangered Species?. ASU - Ask A Biologist. Retrieved July 23, 2018 from https://askabiologist.asu.edu/endangered-species
Dr. Biology. "What is an Endangered Species?". ASU - Ask A Biologist. 28 January, 2011. https://askabiologist.asu.edu/endangered-species
Dr. Biology. "What is an Endangered Species?". ASU - Ask A Biologist. 28 Jan 2011. ASU - Ask A Biologist, Web. 23 Jul 2018. https://askabiologist.asu.edu/endangered-species
The Dusky Seaside Sparrow went extinct in 1987. | <urn:uuid:380b9ef2-76b8-4c47-95c3-5a48e0890beb> | 3.859375 | 747 | Knowledge Article | Science & Tech. | 57.983958 | 95,538,158 |
Atomic Structure of Surfaces with Adsorbates
In studies of clean surfaces, the presence of any foreign species is absolutely undesirable. However, a large number of investigations concern surfaces on which a controlled amount of certain foreign atoms or molecules are intentionally added. The foreign species can be added to the surface in different ways, including condensation from vapor phase (adsorption), segregation from the sample bulk, or diffusion along the surface. Taking into account that adsorption is the most widely used technique, the added species is conventionally called the adsorbate. The material of the host surface is called the substrate. In the present chapter, the atomic structure of clean surfaces with adsorbates is discussed. The consideration is limited to adsorbate layers with an effective coverage of up to one atomic layer. Thus, multilayer thin films are beyond the scope of the chapter. Already formed (in most cases, equilibrium) structures are treated, while the dynamic processes involved in their formation will be discussed elsewhere.
KeywordsSurface Phase Adsorbate Atom Substrate Atom Adsorbate Coverage Unit Mesh
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- 9.7.M. Nielsen, J.P. McTague, W. Ellenson: Adsorbed Layers of D 2 , H 2 , O 2 , and 3 He on Graphite Studied by Neutron Scattering. J. Physique 38, 10 (1977)Google Scholar
- 1.V.G. Lifshits, A.A. Saranin, A.V. Zotov: Surface Phases on Silicon (John Wiley, Chichester 1994) (structures occurring at the adsorbate-covered Si surfaces)Google Scholar
- 2.G.A. Somorjai: Introduction to Surface Chemistry and Catalysis (John Wiley, New York 1994) Chapter 2 (vast list of structures occurring at clean crystal surfaces with adsorbates in tabular form with brief comments)Google Scholar
- 3.National Institute of Standards and Technology (NIST) Surface Structure Database (SSD), Version 3.0 http://www.nist.gov/srd/nist42.htm. (powerful graphics of SSD allow detailed assessment of atomic-scale structures of surfaces)
- 4.H.P. Bonzel (Ed.): Physics of Covered Solid Surfaces. Landolt-Börnstein. Vol. III/42. (Springer, Berlin, Heidelberg, New York 2001) (structures occurring on adsorbate-covered metal and semiconductor surfaces)Google Scholar | <urn:uuid:e6d59e0f-8ce4-47ab-95d4-bb8508601a7f> | 2.59375 | 536 | Academic Writing | Science & Tech. | 45.008605 | 95,538,163 |
Studying living things can prove to be highly significant when evaluating contamination suffered by a specific environment. A research team from the University of the Basque Country (UPV/EHU), with Dr. Nestor Etxebarria as director, is involved in this monitoring of contaminants.
As Dr. Etxebarria explains, “it is known that ports are contaminated; what we are investigating is to what extent the contaminants therein reach aquatic organisms”. The project, Comprehensive evaluation of contamination in sediments at ports along the northern Spanish coast, using chemical, biochemical and ecotoxicological tools, is within the remit of the lines of research by the Analytical Research and Innovation (IBEA) research team led by Professor Juan Manuel Madariaga, and aided by doctors Alberto de Diego, Gorka Arana, Aresatz Usobiaga and Olatz Zuloaga.
Biomonitoring of metals and organic substances
Chemists at UPV/EHU, working together with a team of marine biologists from the University of Vigo and a similar team from AZTI-Tecnalia, have been analysing the harbours at this Galician city, as well as those in Bilbao and the port of Pasajes: their waters, the sediments and living creatures therein. They measure the concentration of contaminants and analyse the biological consequences that these cause in the aquatic organisms, using biomonitoring.
“We take mussels from clean waters and place them at points we wish to analyse in order to see how much and what kind of contamination is accumulated”, stated Dr Etxebarria. “The Galician biologists are in charge of studying the consequences of the contaminants on the mussels; we measure the concentration of the contaminants received by the mussels”, he added.
The object of the research is to answer questions such as: where is each kind of contamination located? What is the chemical origin of each? Of all the contaminants, the UPV/EHU team have only managed to analyse a few, amongst which is tributyltin (TBT) metal, used in the past for painting the hulls of vessels. “Today TBT is banned but it is highly durable and it can still be found in waters”, stated Dr Etxebarria. Organic substances have also been studied, such as polyaromatic carbohydrates (PAH) from ships fuel, the phtalates used in making plastics or the polychloride biphenyls (PCBs) derived from oils. “These last are similar to dioxines and in the past were used in very powerful transformers. They are also prohibited, but are still present in the water”, said Dr. Etxebarria.
Biological and chemical sampling
Each year Vigo, Bilbao and Pasajes are visited and simples are taken over two or three days. Five or six zones at each port are analysed, one of which is believed to be clean, i.e. as a control, and the other four or five contaminated. “We place 20 or 30 mussels mounted on plastic supports and inside gauzes, and submerge them at a depth of two metres”, explained Dr. Etxebarria, “after a certain period, we collect them for analysis of level and type of contamination accumulated”.
But using living beings to measure contamination also has its risks. “In some cases the contamination is high and the mussels can die”, states Dr Etxebarria. This is why the UPV/EHU team has created a new method for monitoring contaminants: “by using polymeric mountings, we simulate chemically what the mussels do, i.e. accumulate contaminants”. Moreover, in this way, it is possible to systemise the sampling.
Evaluation of the tools
The research led by Nestor Etxebarria is to finish in 2009, but they already have some provisional results. “The situation in the port of Bilbao is quite homogenous; we have taken samples in the areas of Getxo, Santurce and the exterior port (Bilbao, in the Basque Country) and the results are similar in each case. On the other hand, in Vigo (Galicia) we detected wide differences from one zone to another, for example between water near a shipyard and the open sea”, Dr Etxebarria said.
Apart from carrying out a diagnosis of port waters, another aim of the project is to evaluate the methodology and tools of the sampling. The European Directive on water obliges government bodies to monitor contaminants in all canals and along all coasts. “We wish to know if our methodology and the sampling tools that we have developed are useful for this purpose”, said Dr Etxebarria. “On the one hand, we have seen that zones supposedly clean are not as clean as we thought; it is necessary to redefine the selection of these clean zones. On the other, we are also perfecting the tool that chemically simulates the role of the mussels, in order to carry out even more precise sampling”, he concluded.
Garazi Andonegi | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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23.07.2018 | Life Sciences | <urn:uuid:2e6649ff-7742-4a1c-b982-e0e3f54e1fe9> | 2.671875 | 1,695 | Content Listing | Science & Tech. | 37.618944 | 95,538,165 |
Community Contributor | Jul 3, 2018 | 0
21 February 2014
The most prominent feature of this week’s daily synoptic charts is the strong cyclonic low-pressure core that develop in the Mozambican channel. The first gyration became discernible late last week. The depression grew in strength over the weekend and by Monday it was a marked tropical cyclone.
As the week progressed it slowly migrated south, and continued to intensify, so much so that by Wednesday it was given a name. Known as cyclone Guito, its core pressure on the ocean surface has dropped to 989 milliBar, indeed low enough to be classified as a tropical cyclone. Vertical velocity inside a low pressure core can be considerable and Guito is no exception. What it means is that it exerts an influence on weather patterns through all atmospheric layers, from the surface up to 50,000 feet, where it peters out and due to its rotation, spreads like an open umbrella influencing the weather for many thousands of kilometres away from the core. This is also the case with Guito. Despite being some 2000 km away from the Namibia Botswana border, it advected a massive amount of moisture over a very vast area of the southern African subcontinent. But, equally dominant, and persistent, is the ever-present high pressure cell over the south Atlantic ocean.
The approaching high opposed the Indian Ocean low leading to a so-called convergence line, i.e. where the two meet. This line is usually quite prominent and situated most often along a line more or less from Ruacana in the north west to Aroab in the south east, but it does move either west or east, depending on the dynamics between the opposing forces. The convergence line played a big part in this week’s rainfall which, for the greater part, remained west of the convergence line, following the western escarpment. The outcome was light rain from the Kunene region, across Erongo, the western half of Hardap, and the western half of Karas, then curving back over the Orange River valley with isolated showers up to the Kalahari. In the upper air however, were the telltale signs of another high pressure system, this time south east of South Africa. In the 2013 summer, this same high pressure cell exerted much influence in the alto levels, above 35,000 feet, over the western half of southern Africa. During the summer, the regular inflow of moisture from Angola and the DRC, was time and again depleted by the influence of this high pressure cell at the very high level. The result was the drought.
Now it has appeared again, but its core has shifted to a point south of Madagascar with the result that it is now depleting the moisture over the central plateau of southern Africa. The interplay between low and high pressure systems produced a week with much promise but very little actualisation. Rainfall was widespread, even down to the south western part of the Karas region, but it produces only isolated, brief falls, with very few readings above 5mm. PS. The Namibia Meteorological Service has become psychic, managing to publish the rainfall for the 20th, already on the 19th.
Conditions for the circulation of moisture over the western half of Namibia remain favourable but intensities will be scant. The Inter-Tropical Convergence Zone has moved further north by some 800 km and is now situated over central Angola from west to east. Chances of it approaching Namibia and entering our airspace are slim, but with the strong zonal flow east to west, i.e. from Mozambique to Angola, surface and middle layer airflow will continue to advect some moisture. Rainfall expectations for the whole country remain positive, but restrained. As the high pressure cell slips around the southern Cape, the wind will be southerly, then south easterly backing to east and eventually north to north westerly. This will help improve conditions for local rainfall, but do not expect fireworks. However, widespread rain is expected for most of next week for most of the country excepting the coastal plain. | <urn:uuid:514f9b47-440f-42ba-bb27-35bbcdecd6ad> | 3.015625 | 854 | News Article | Science & Tech. | 46.157693 | 95,538,194 |
In a week mostly dominated by NASA’s announcement of the discovery of organic molecules on Mars, some other important science stories may have slipped under the radar. In the Science Dispatches for the first week of June 2018; a possible breakthrough in the treatment of cancer, the self-consuming rocket and counting bees.
A look at a selection of the most important and interesting science stories from the first week of May 2018, including NASA’s INSIGHT probe’s mission to Mars, nuclear fusion for space exploration, photosynthetic sea-slugs and Stephen Hawking’s final research-paper.
In what represents a major breakthrough in infertility treatment, reproductive biologist Evelyn Telfer and colleagues at the University of Edinburgh have finally completed the development of a human egg outside the human body for the first time, it was announced in January. The development represents the first step it what may be a major victory for both infertile couples and women who have suffered illnesses such as cancer in prepubescence, looking to have children. | <urn:uuid:aab1fe48-4e4b-4c3a-9057-25312c7c2b73> | 2.53125 | 212 | Content Listing | Science & Tech. | 21.901558 | 95,538,195 |
src attribute can be applied to many elements like
<input>, etc. It can be used to specify the content of the frame with either absolute or relative URL. A URL that starts with the URL scheme and scheme specific part ( http:// , https:// , ftp:// , etc.) is an absolute URL, and the location of the resource can be resolved looking only at the url itself. A relative URL is in a sense incomplete: to resolve it, you need the scheme and hostname, and these are typically taken from the current context.
In general, it is considered best-practice to use relative URLs, so that your website will not be bound to the base URL of where it is currently deployed. Always use relative URLs (for local resources)!! Further reading here.
src = ""and
src = "#":
Let’s say the base url is : http://mysite.com/myapp/
src = ""-> Absolute url: http://mysite.com/myapp/ (This is using empty src where browsers still send calls to server and thus causing a page refresh)
src = "#"-> Absolute url: http://mysite.com/myapp/# (It could be used which forms a hash url and hash urls are not sent to server, note that it could cause the page to scroll to the top)
Most people use
src = "#""as a placeholder for links when they don’t want any resource to be loaded (probably load it dynamically later), and it avoids the unnecessary call to server.
For example, this line of code won’t display this YouTube video since it is a relative URL:
<iframe src = "youtube.com/embed/u0DLCyWrxDo"></iframe>
There are two ways to work this out:
src = "http://youtube.com/embed/u0DLCyWrxDo"writes an absolute URL and specifies an http:// scheme.
src = "//youtube.com/embed/u0DLCyWrxDo"writes a relative URL without a scheme, also called protocol-relative URL. In this way it requests within the same protocol as your current page.
targetattribute of an
<form>element, or the
formtargetattribute of an
Example demo with
<a>has to match the
Better to set the attribute
frameborderequal to “0” in order to hide the default black frame border.
When it contains a URL:
URLs are not restricted to Web (HTTP)-based documents, but can use any protocol supported by the browser. For example, file:, ftp:, and mailto: work in most browsers. When
hrefcontains a URL, it applies to similar rules with the
A typical relative url like
href="?name=jadesends a GET request to the server.
When it contains a URL frament:
A URL fragment is a name preceded by a hash mark (#), which specifies an internal target location (an
idof an HTML element) within the current document. Once again, it won’t send a GET request to the server.
This line of code will trigger an alert when you click the anchor.
We usually use
href='#'for the same purpose, but this causes the browser to jump to the top of the page, which may not be wanted. And we couldn’t simply leave the href blank, because href=” is a link back to the current page (ie. it causes a page refresh).
This attribute instructs browsers to download a URL instead of navigating to it, so the user will be prompted to save it as a local file. If the attribute has a value, it is used as the pre-filled file name in the Save prompt (the user can still change the file name if they want).
In HTTP response headers, if
The browser will download the file automatically without adding a
<a>. Otherwise, this attribute is demanded.
<a href="abc.txt" download="new.txt">download text file</a>
Specifies where to display the linked URL. It is a name of, or keyword for a browsing context: a tab, window, or
<iframe>(associated with its
nameattribute). The following keywords have special meanings:
- _self: Load the URL into the same browsing context as the current one. This is the default behavior.
- _blank: Load the URL into a new browsing context. This is usually a tab, but users can configure browsers to use new windows instead.
- _parent: Load the URL into the parent browsing context of the current one. If there is no parent, this behaves the same way as _self.
- _top: Load the URL into the top-level browsing context (that is, the “highest” browsing context that is an ancestor of the current one, and has no parent). If there is no parent, this behaves the same way as _self.
Defines where the data gets sent. Its value must be a valid URL. If this attribute isn’t provided, the data will be sent to the URL of the page containing the form.
Defines which HTTP method to send the data with (it can be “GET” or “POST”). Both
<form>have the same function as navigating to a specific page, however
<a>can only send GET request.
The GET method is used to ask the server for sending back a given resource: the GET request sends an empty body (POST can send with both the query strings and the entity body). Since the body is empty, if a form is sent using this method the data sent to the server is appended to the URL. You’ll see the URL like www.foo.com/?say=Hi&to=Mom appear in the browser address bar when you submit a form. The data is appended to the URL after a question mark (?) as a series of name/value pairs and each pair is separated by an ampersand (&).
When the value of the method attribute is post, enctype specifies the value of the Content-Type HTTP header included in the request generated when the form is submitted. This header is very important because it tells the server what kind of data is being sent.
application/x-www-form-urlencoded: The default value if the attribute is not specified. In human terms, this means: “This is the form data that has been encoded into URL parameters.” The syntax looks like
key1=val1&key2=val2&.... Consider the code below,
<form action="newform" method="post"> <input type="text" name="username"> <input type="password" name="password"> <input type="submit" value="Submit"> </form>
After submitting this form, the formdata would be something like:
multipart/form-data: The value used for an
<input>element with the type attribute set to “file”.
Every form must have a submit button in order to be submitted (there’s also implicit submission, see more in
<input>section). Submit Button (
<input>element) –> state (type=submit).
Similar rules with
<a>’s target attribute.
framename: The response is displayed in a named iframe.
type = "button"and
type = "submit":
If there’s only one
<button>in a form, it would automaticlly turn into a submit button which means
<button type="submit">; If you specify
<button type="button">explicitly then it would just be a simple push button (Note: IE7 has a bug where the type attribute of a
<button>defaults to button instead of submit. Therefore for IE7 compatibility you’ll need
<input type="button">is also a simple push button，only
<input type="submit">is a submit button.
Implicit submission of
<form>when pressing Enter Key:
Implicit submission is vital to assistive technologies and impaired users that cannot use a mouse at all. From the HTML5 specification:
“There are pages on the Web that are only usable if there is a way to implicitly submit forms, so user agents [browsers] are strongly encouraged to support this.”
There are two situations submitting a form in this way.
In a form with no submit buttons, implicit submission will be done if only one input is present. Therefore, pressing Enter in this textbox will submit the form:
<form action = "/abc"> <label for = "name">Name:</label> <input id = "name" name="username" type="text"> </form>
If the form has multiple input elements, the form can not be submitted automatically. Therefore, if you have a form with more than one input field, always include a submit button, then pressing Enter can still submit the form successfully.
For explicit prevention please read this article.
type = "checkbox":
<input type="checkbox">choose me, when clicking the text ‘choose me’, the checkbox will not be automatically checked. To prevent this problem, we should use
<input>at the same time:
<label for = >should match
<input id = >in order to associate the label with the input. For a more convenient way, there’s no need to assign an
forvalue, just put
<input>as a child element of the corresponding
valueattribute of checkbox inputs:
Represents the value of the checkbox. This is never seen on the client-side, but on the server this is the value given to the data submitted with the checkbox’s
Take the example above, for label ‘Bananas’, the input we’ve got has a name of fruit, and a value of banana. When the form is submitted, the data name/value pair will be
If the value attribute was omitted (like label ‘Clickable label’), the default value for the checkbox is on , so the submitted data in that case would be
clickable-label=on; if the checkbox is unchecked, the submitted data for that will remain empty.
Handling multiple checkboxes：
In real-world situations you’ll be likely to encounter multiple checkboxes. If they are completely unrelated, then you can just deal with them all separately, as shown above. However, if they’re all related, things are not quite so simple.
Also referring to last ‘fruit’ example, we’ve given each checkbox the same
name. If all three checkboxes are checked and then the form is submitted, you’ll get a string of name/value pairs submitted like this:
fruit=banana&fruit=orange&fruit=apple. When this data reaches the server-side, you should be able to capture it as an array of related values and deal with it appropriately.
type = "radio":
<input>elements of type
radioare generally used in radio groups—collections of radio buttons describing a set of related options. Only one radio button in a given group can be selected at the same time.
Represents a control that provides a menu of options (another way of making choices).
See the following example code and pay attention to the attributes of
disabled. We can also make multiple choices by adding the boolean
multiple attribute to
<select>, and hold the Ctrl, Command, or Shift keys while clicking to select or deselect multiple options.
It is used for displaying tabular data. You can think of it as a way to describe and display data that would make sense in spreadsheet software. Essentially: columns and rows.
We usually use the first row as the header of a table, which contains no data, just the titles of columns. We can do that with the
<thead>element, wrapped up a table row like
<tr><th>name</th><th>age</th></tr>, where ‘th’ stands fot tabular headers. When you use
<thead>, there must be no
<tr>that is a direct child of
Empty table head:
For all the actual table data cells, wrap all rows of data in
<td>elements are tabular data.
<th>elements are not necessarily limited to being within the
<thead>. They simply indicate header information. Certain columns (e.g. the first column) might also represent titles.
Empty table data:
Indicates the footer of the table. Like
<thead>, best for semantically indicating these are not data rows but ancillary information.
Defines a group of columns within a table. HTML has a method of defining styling information for an entire column of data all in one place — the
<colgroup>elements. The nth
<col>specifies the styles for the nth column in a table. Even if we do not want to style the first column, we still have to include a blank
<col>element — if we didn’t, the styling would just be applied to the first column also.
No matter where you place
<tfoot>inside a table using HTML, the browser would still render the table as the ‘heade-body-foot’ order. If you leave out
<tbody>element and only write
<td>, the browser will auto complete the
<tbody>when rendering it; if there’s no
<tfoot>, everything will be rendered according to the order written in HTML. | <urn:uuid:72fa98eb-caa9-4d36-9b00-97b01a1c5946> | 3.5 | 2,916 | Documentation | Software Dev. | 54.66649 | 95,538,205 |
A View from Emily Singer
How Fast Are We Mutating?
Different people may have different rates of mutation.
The ability to sequence the entire genomes–the sequence of almost every letter of an individual’s DNA–of parents and their children has for the first time allowed scientists to directly measure how fast our species is mutating. Preliminary studies are coming up with some surprising findings, including more variation than initially thought. A more accurate measure of the number of spontaneous genetic changes passed down from generation to generation will allow scientists to better estimate the timing of key events in our evolutionary history, as well as to evaluate whether some families are more likely to have children suffering from developmental disorders.
These mutations, thought to result from mistakes in DNA replication during the creation of sperm or eggs, are the basis for evolution. Some changes are benign, some are harmful–spontaneous mutations have been linked to autism and other developmental disorders–and some confer special advantages on their bearer. “Mutation is a good thing,” says Don Conrad, a researcher at the Wellcome Trust Sanger Institute, in the United Kingdom. “We need to be able to respond to changes in our environment.”
Last March, Leroy Hood and collaborators at the Institute for Systems Biology in Seattle, sequenced the complete genomes of a nuclear family of four, the first published example of a family having their genomes sequenced. By comparing the sequence of parents and offspring, researchers could calculate the rate of spontaneous mutations arising in the human genome from one generation to the next. The rate equates to about 70 mutations per child, lower than previous estimates.
Don Conrad has now followed up those estimates with his own analysis of family genomes, comparing mutation rates in two different nuclear families who were sequenced as part of the 1000 genomes project, an international collaboration to assess new sequencing technologies and examine genetic variability across different populations. Conrad’s study confirmed Hood’s figure, but it was also the first to separate out mutation rates from whole genome data based on gender. Previous indirect estimates suggest that the mutation rate is three to six times higher in men than women, a phenomena thought to be explained by the fact that sperm undergo many more cell divisions during development than do eggs. In preliminary findings presented last week at the Personal Genomes conference in Cold Spring Harbor, New York, he found that the father in a family from Utah had a mutation rate 11 times higher than the mother, higher than any previously reported figures. In the second family, from Africa, the maternal mutation rate was higher than the paternal one, which is contrary to the prevailing theory.
By simulating how mutation rates would vary had the parents in the two families switched partners, Conrad calculated that there could be as much as a tenfold difference in rates among individuals. He cautions that the work is based on data from just two families and needs to be replicated in larger samples. “I’ll be exited to see what people come up with over the next six months, as they analyze sequences of more families,” he says. One drawback in the study is that scientists don’t know what age the parents were when they had their children; older parents tend to have more mutations in their gametes. In addition, the sequencing used DNA derived from cells from each individual, rather than direct DNA samples, though Conrad says he controlled for any errors this might have introduced.
It’s not yet clear what determines an individual’s mutation rates, though genetics likely play a major role. A mutation in a DNA repair enzyme, for example, could increase error rates in the replication of a genome. Environmental factors are also a possibility, however, Conrad says that no one has yet identified specific culprits. X-rays and toxic chemicals affect DNA in so-called somatic cells, or adult tissue, rather than the germline cells that go on to form eggs and sperm. It’s also not yet clear what the consequences of a highly variable mutation rate would be, though it’s possible that families with higher rates would be more likely to have children with sporadic disease.
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:8804d676-6c88-4262-84ce-026c80eb2b23> | 3.3125 | 873 | Truncated | Science & Tech. | 28.596362 | 95,538,216 |
|CNIDARIA : CAPITATA : Tubulariidae||SEA ANEMONES AND HYDROIDS|
Description: The stem of this hydroid has a tough, yellowish coloured tegument. Usually the stems are clustered together and fuse with each other towards the base of the colony. The polyp colour is pale pink through to red, and consists of a central circlet of oral tentacles surrounded by paler but larger aboral tentacles. Gonothecae arise within this inner set of tentacles. Overall height 100-150mm, diameter of the polyp and tentacles about 15mm.
Habitat: A characteristic species of current swept bedrock and boulders, which may attach to other substrata such as kelp stipes.
Distribution: This species is common on all coasts of the British Isles.
Similar Species: Could be confused with Tubularia larynx.
Key Identification Features:
Distribution Map from NBN: Interactive map : National Biodiversity Network mapping facility, data for UK.
WoRMS: Species record : World Register of Marine Species.
|Picton, B.E. & Morrow, C.C. (2016). Tubularia indivisa Linnaeus, 1758. [In] Encyclopedia of Marine Life of Britain and Ireland. |
http://www.habitas.org.uk/marinelife/species.asp?item=D1440 Accessed on 2018-07-19
|Copyright © National Museums of Northern Ireland, 2002-2015| | <urn:uuid:b6df7e6e-da27-4f7b-a599-8c12e9c684bd> | 2.96875 | 318 | Knowledge Article | Science & Tech. | 45.029513 | 95,538,227 |
New study shakes up understanding of when continents connected
A long-standing fact widely accepted among the scientific community has been recently refuted, which now has major implications on our understanding of how Earth has evolved.
Until recently, most geologists had determined the land connecting North and South America, the Isthmus of Panama, had formed 3.5 million years ago. But new data shows that this geological event, which dramatically changed the world, occurred much earlier. In a comprehensive biological study, researchers have confirmed this new information by showing that plants and animals had been migrating between the continents nearly 30 million years earlier.
'This means the best-dated geological event we ever had is wrong,' said Prosanta Chakrabarty, LSU associate professor in the Department of Biological Sciences and Curator of Ichthyology at the LSU Museum of Natural Science. His research on the evolution of freshwater and marine organisms in Central America was part of the study with colleagues at the Smithsonian Tropical Research Institute, American Museum of Natural History and the University of Gothenburg, which included living and extinct mammals, birds, plants, fish and invertebrate animals published by the Proceedings of the National Academy of Sciences.
The researchers found large pulses of movement among these plants and animals between North and South America from 41 million, 23 million and eight million years ago. These coordinated spikes in migration imply that geological changes in Central America, such as landmass formation and new freshwater corridors, were aiding migration for many kinds of plants and animals.
'Before, South America was thought of as an island with no communication until 3.5 million years, so the only way to explain such high biodiversity was to say that it accumulated extremely fast. Now, with a longer history, we know that processes and patterns took a lot of time to form,' said Christine Bacon, lead author of the study and associate researcher at the University of Gothenburg. 'Our results change our understanding of the biodiversity and climate, both at the regional and global levels.'
Even after the reported geological closure, geminate marine species, those close relatives found on opposite sides of the narrow isthmus, also provide evidence that this landmass between North and South America is more like a sponge where organisms can periodically pass rather than a solid barrier. The current expansion of the Panama Canal has yielded new fossils that have informed these observations.
'Now we know that the closure of the Isthmus of Panama, which is supposed to be one of the biggest deals in geology, is just one part of a really complicated puzzle of how the continents came together,' Chakrabarty said.
He and colleagues at LSU mapped the evolution of two major families of fishes in Central America -- cichlids, which include many aquarium fish, and poeciliids, which include guppies and swordtails. They collected samples of fishes from every country in Central America and sequenced the DNA to determine the genetic relationship between species. Matching the skeletal structure of fish found in the fossil record, they calibrated the DNA-based evolutionary tree and determined the age of each species.
Because freshwater fish can only migrate when a new passage way opens to a river or lake, there must have been dry land with freshwater running through it, Chakrabarty said. Therefore, their arrival in Central America signifies early geological changes.
'The cool thing is there are so many freshwater fish species that are essentially stuck in one place until the land changes, so they can tell us about the history of the Earth,' he said.
The formation of the Isthmus of Panama had large-scale effects on the planet. It divided the Atlantic and Pacific oceans, thus changing sea levels and ocean currents. This affected global temperatures possibly causing periods of glaciation.
'The geology of this whole region is so complicated, and it's amazing to me that the biology can inform us of that,' he said.
Chakrabarty has been conducting research on Central American freshwater fish for about 15 years. He has received more than $1 million in National Science Foundation funding for this work. He and his lab have collected fish species from every country in Central America and have expanded the specimen collection at LSU to South America, the Greater Antilles and much of Asia. He is currently researching the evolution and migration of freshwater fish between South America, Central America and the Greater Antilles that may have began 50 to 60 million years ago.
Alison Satake | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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19.07.2018 | Life Sciences | <urn:uuid:1e206cd3-0cef-4067-ae6b-5b4b609bfa41> | 3.734375 | 1,542 | Content Listing | Science & Tech. | 35.87425 | 95,538,230 |
McGill University researchers have successfully amplified light with so-called "colloidal quantum dots," a technology that had been written off by many as a dead-end.
Over the last 15 years, repeated quantum dot research efforts failed to deliver on expected improvements in amplification, and many researchers started to believe that an unknown but insurmountable law of physics was blocking their path. Essentially, they said, quantum dots would simply never work well for one of their primary applications.
However, after extensive research, Professor Patanjali (Pat) Kambhampati and colleagues at McGill University's Department of Chemistry determined that colloidal quantum dots do indeed amplify light as promised. The earlier disappointments were due to accidental roadblocks, not by any fundamental law of physics, the researchers said. Their results were published in the March 2009 issue of Physical Review Letters.
Colloidal quantum dots can actually be painted directly on to surfaces, and this breakthrough has enormous potential significance for the future of laser technology, and by extension, for telecommunications, next-generation optical computing and an innumerable array of other applications.
Lasers – beams of high-powered coherent light – have applications in dozens of fields, most notably in telecommunications, where they are used to transmit voice and data over fibre-optic cables. Like sound, radio waves or electricity, laser signals gradually lose power over distance and must be passed through an amplifier to maintain signal strength. Until now, the best available amplification technology was the quantum well, a thin sheet made of semi-conductor material which confines electrons to a one-dimensional plane, and consequently amplifies light. Colloidal quantum dots perform a similar function, but in a three-dimensional box-like structure instead of a flat sheet.
"Everyone expected this little box to be significantly better than a thin sheet," Kambhampati said. "You'd require less electrical power, and you wouldn't need to use arrays of expensive cooling racks. The idea was to make the lasing process as cheap as possible. But the expected results were not really there. So people said 'let's forget about the quantum dot' and they tried rods or onion shapes. It became a game of making a whole soup of different shapes and hoping one of them would work.
"In our view," he continued, "no one had figured out how the simple, prototypical quantum dot actually worked. And if you don't know that, how are you going to rationally construct a device out of it?"
In the end, Kambhampati and his colleagues discovered that the major problem lay in the way researchers had been powering their quantum dot amplifiers.
"We discovered that there was nothing fundamentally wrong with the dots. If you weren't careful in your measurements, when powering the quantum dot, you would accidentally create a parasitic effect that would kill the amplification." he said. "Once we understood this, we were able to take a quantum dot that no one believed could amplify anything, and turned it into the most efficient amplifier ever measured, as far as I know."
ABOUT McGILL UNIVERSITY
McGill University, founded in Montreal, Que., in 1821, is Canada's leading post-secondary institution. It has two campuses, 11 faculties, 10 professional schools, 300 programs of study and more than 33,000 students. McGill attracts students from more than 160 countries around the world. Almost half of McGill students claim a first language other than English – including 6,000 francophones – with more than 6,200 international students making up almost 20 per cent of the student body.
Mark Shainblum | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
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20.07.2018 | Materials Sciences | <urn:uuid:84f9b4df-f639-48f3-855f-f22686a6e69b> | 3.9375 | 857 | Knowledge Article | Science & Tech. | 46.767896 | 95,538,245 |
Use the Home link to return to the home page. Do not use the back button.
Solar azimuth 80.5 degrees. Solar altitude 21.6 degrees. Observer Solar Time = 6.71 hours. Observer Hour Angle = -79.42 degrees.
Declination Angle = 21.11 degrees. Current EOT = -377 seconds.
1. Use the Home link to return to the home page. Do not use the back button.
2. Sunrise and sunset occur at a solar elevation of roughly -0.83 degrees. This accounts for refraction and the diameter of the solar disk.
3. No correction is applied for the observerís elevation or the elevation of the observerís horizon. These factors are highly dependent upon local terrain.
4. No correction is applied to solar altitude for refraction. Refraction is a little over half a degree at the horizon dropping to zero directly overhead.
5. Time Zone is the number of hours the local time zone is offset from UTC(GMT), negative to the west and positive to the east.
Standard times are EST=-5, CST=-6, MST=-7 and PST=-8.
Daylight times are EDT=-4, CDT=-5, MDT=-6 and PDT=-7.
6. EOT (Equation of Time) accounts for difference between the clock (mean time) and the position of the sun (solar time).
This variation is caused by the fact that the earth's orbit is elliptical and the earth is tilted on its axis.
7. At Solar Noon all of the following is true: The sun is at it's highest altitude for the day, the sun is due south (180 degrees),
solar time is 12:00 and the Hour Angle is zero.
You wish to know the sun position at 6:00 AM on 5/14/2007 at Ames, Iowa. Enter the Ames latitude and longitude in degrees (42.03 Lat, -93.62 Lon).
Ames is in the central time zone and on daylight savings time for the specified date so it's time zone is -5 hours.
Therefore enter the date 2007, 5, 14; the time 6, 0, 0; and the time zone -5. Then click Compute. | <urn:uuid:da1cf761-4bd1-4daa-9940-68d6efd2ad8e> | 3.203125 | 472 | Documentation | Science & Tech. | 82.154642 | 95,538,254 |
The research which I am currently doing as part of my research assistantship here at CU is to investigate the damping of gravitationally induced wakes in rings due to interparticle collisions. I am doing this work under the supervision of Glen Stewart. The study of wakes in rings was essentially born with the voyager flyby of Saturn. Before that time it was generally believed that the rings of Saturn were rather uniform. Close up images and ring occultations however, shows that this was definitely not the case. Instead there were many small details and structures in the rings. One of these was called the Encke gap. It was a thin region (approximately 325km across) in which there were no ring particles. Occultation data from the rings near the Encke gap showed that there were wakes, where the optical depth of the rings fluctuated in a wave like pattern that damped out farther from the gap.
By looking at these wakes people were able to determine that they most likely were formed by a small moon that had an orbit in the gap, and that it was due the presence of this moon that the gap itself existed. The moon was actually found on several voyager images and given the name Pan. To some this might sound like it should be the end of the story, but there are still many questions associated with the structure of these wakes.
In 1991 Glen published a paper in Icarus entitled "Nonlinear Satellite Wakes in Planetary Rings." In this paper he did a derivation of the structure of these wakes without collisional dampening using kinetic theory and working in guiding center coordinates. This paper has been the starting block for my own research in which I use Glen's analytic distribution of ring particles as an initial condition and simulate a statistical sampling of ring particles as they move down stream and calculate how they are effected by collisions.
The output from a number of these simulations can be found here.
To date I have developed a code that can find and process collisions for many thousands of particles (I have been using 100,000) on a single processor workstation fast enough to complete the integration of a full synodic period (~550 orbits) in well under a week of run time. There are two main reasons for this, but I can't put too much here yet. I do need to get some type of publication from this work.
Of course, this code only deals with collisions and because of how far from Saturn the Encke gap is located, gravitational interactions between the particles is also important. For this reason the next step in the evolution of this project is to add self-gravity to the simulations. It is quite possible that even if the wakes don't persist through a synodic period with only collisions they will with gravity.
Previous work by Salo has shows that at distances near that of the gap, that particles will form persistent clumps due simply to mutual gravitational attraction. However, the structures that he found are significantly smaller than the wakes caused by Pan though the scale of those structures might have been largely determined by the size of his simulation, as he readily points out.
Back to my Main Page.email@example.com | <urn:uuid:ed3dc272-ab46-40b4-808f-c504dfd4ea3c> | 2.625 | 640 | Personal Blog | Science & Tech. | 45.963826 | 95,538,258 |
Single branch of Xanthocyparis vietnamensis with two foliage types. Immature foliage on the left and mature foliage on the right.
Image courtesy of Daniel Harder, Arboretum at UCSC.
Type locality of Xanthocyparis vietnamensis within the limestone mountain system at Bat Dai Son, Ha Giang Province, Quan Ba District, Bat Dai Son Municipality within the Bat Dai Son Provincial Protected Area, Viet Nam.
Image courtesy of Daniel Harder, Arboretum at UCSC
An unusual conifer found in a remote area of northern Vietnam has been identified as a genus and species previously unknown to science. The limestone ridges where the tree grows are among the most botanically rich areas in Vietnam, said Daniel Harder, currently director of the University of California at Santa Cruz (UCSC) Arboretum and a co-discoverer of the new species. The discovery is published in the current issue of the journal Novon.
"Biologists don’t need to contemplate finding life on another planet to imagine making extraordinary discoveries; the fact is, most of the species living on our own planet are still unknown," says Norman Platnick, program director in the National Science Foundation’s (NSF) division of environmental biology, which funded the research. "That kind of basic, new knowledge about life, its interrelationships, and how it is distributed across the globe, often has enormous practical implications, guiding the search for new medicines, new pesticides, and even new ways to control alien, invasive species."
Harder spent several years in Vietnam, working to establish an on-going survey of Vietnamese plants organized by the Missouri Botanical Garden, which received the NSF funding that helped enable this research. During that time, he and his collaborators discovered more than 100 new species of plants. But the conifer now known as the golden Vietnamese cypress is by far the most remarkable of those discoveries, he said.
Cheryl Dybas | 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
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:417cdf4b-e8f7-4348-aafb-521976d30125> | 3.21875 | 999 | Content Listing | Science & Tech. | 34.466592 | 95,538,265 |
We humans love to build sandcastles, but we aren’t the only ones. Click “Read More” to see what other animals enjoy a good sandcastle, and do some underwater math!
We love learning new words here at Bedtime Math, and we just discovered a great one, “porcupette:” If you want to learn what this means, too, click “Read More” and do the porcupette math!
Our 8-legged friend the octopus is an animal that’s been around for nearly 300 million years. Maybe that’s why it’s become pretty smart for a slimy sea creature. Click “Read More” to find out multi-talented leggy creature, and do the octopus math!
Recently, a fisherman in China caught a 16-foot long whale shark in his fishing net, weighing more than 2 tonnes. It was so huge that he had to drape it over a truck to drive it to the fish market! Click “Read More” to get the numbers behind sharks, and do the math.
It’s exciting when anyone invents a machine that’s going to make our world better, like cleaning up garbage from our oceans. It’s even more exciting when that person is a 19-year-old kid. Click “Read More” to find out about this cool new invention and do the Ocean Cleanup math!
In places with lots of farms, it can be tricky to keep crops and farm animals safe from wild animals, while still letting those wild animals live. For once, we can solve both problems at the same time. Click “Read More” to see how poison apples are doing this – and do the math!
No matter how much you love pet fish, there’s a limit as to how many you can have. The rule is 1 gallon of water for every 1 inch of fish. So if you want more fish, you have to build a bigger fish tank, like this one guy did. Click “Read More” to see just how big this tank is and do the fishy math!
Sometimes cars just stop working right in the middle of the road. But it’s not often that they stop working for the reason that one woman’s car in New Mexico stopped. Click “Read More” to see what shock awaited her when she opened the hood – and do the math!
It’s fun to eat at a restaurant, since each person can choose anything he’d like from the menu. And that matters a lot if your dog is coming along, too. At some restaurants in the U.S., there’s no need to bring home a doggy bag for your pooch – they’re allowed to come with you. Click “Read More” to chew on some numbers behind these doggy dinner hot spots.
The bat is a strange, spooky animal. It looks like a mouse with spiky wings, and makes squeaky sounds to find the food it’s hunting down to eat. The biggest, most alarming crowd of these might be the Congress Avenue Bridge bats in Austin, Texas, with more than 1 1/2 million bats. Click “Read More” to find out what’s so good about these animals – and do the batty math! | <urn:uuid:d7d362c7-d012-48b9-979b-c805d314f81b> | 2.625 | 711 | Content Listing | Science & Tech. | 75.37874 | 95,538,270 |
Aboard the Shuttle Orbiter water is generated using a hydrogen-oxygen fuel cell which produces both electricity and very pure water. Water can also be produced by reduction of CO2 by hydrogen over a suitable catalyst. The Sabatier and Bosch processes are two Carbon Dioxide Reduction Systems which have been studied extensively. The Sabatier method has been selected for International Space Station (ISS). These three systems are presented below:
Current technology for the reduction of carbon dioxide to produce water aboard the International Space Station (ISS) is embodied in the Sabatier Reactor.
For each mole of carbon dioxide reduced, this system produces two moles of water and one mole of methane. The methane is vented to space. For this reason, only half of the hydrogen consumed in this reaction can be recovered by electrolysis. The Sabatier reaction utilizes an alumina supported ruthenium catalyst and, in comparison to the Bosch reaction, has the advantage of greater thermodynamic favorability and higher reaction rates.
The primary disadvantage of the Sabatier process is that twice as much hydrogen is consumed as can be recovered by the electrolysis of the produced water. This results in a substantial perturbation in the material balance for the production of oxygen from carbon dioxide. Using the Sabatier process either the hydrogen imbalance must be compensated for by resupply, or not all of the carbon dioxide can be processed.
The Bosch reaction produces only water and elemental carbon, allowing all of the hydrogen consumed to be recovered by electrolysis. This makes closure of the oxygen - carbon dioxide - water - oxygen loop possible.
The net reaction produces heat (2.3x103 J/g of carbon produced at 650C), and is the result of two successive reactions, one fast,
and a second rate controlling slow reaction.
The primary problems associated with the Bosch reactor are slow reaction rates and the generation of particulate carbon which fouls the catalyst surface and which plugs the catalyst bed. As shown below, the thermodynamics are also somewhat less favorable than those for the Sabatier Reaction.
Catalysts are critical to the Bosch process, due to the intrinsically slow kinetics. Iron, cobalt, and nickel catalyze the Bosch reaction. Minor additions of ruthenium significantly improve kinetics. The most commonly used catalyst is "steel wool" due to its relatively high exposed active surface. Significant surface reactions include the formation of carbide intermediates as well as oxide layers which poison catalytic activity. Typical reaction temperatures are in the range of 450 to 600C. Even at these relatively high temperatures single pass reduction efficiencies are typically below 10%, hence practical reactor designs require recycle operation. A more significant disadvantage is the inactivation of catalyst surfaces and the plugging of the reactor caused by a buildup of particulate carbon. While greater efficiencies in terms of material balances aboard spacecraft are possible using the Bosch reaction, much further development work will be required before the system is competitive with the Sabatier process from a practical standpoint.
Author: Tugrul Sezen BACK TO COURSE MAIN PAGE BACK
TO SPACE SETTLEMENT HOME PAGE
BACK TO COURSE MAIN PAGE
BACK TO SPACE SETTLEMENT HOME PAGE
Curator: Al Globus
NASA Responsible Official: Dr. Ruth Globus
If you find any errors on this page contact Al Globus.
This mirror of the NASA Ames Research Center Space Settlement web site is provided by: | <urn:uuid:21399635-b5c1-4f28-b35f-977f47303028> | 3.359375 | 713 | Knowledge Article | Science & Tech. | 22.538091 | 95,538,292 |
Data on the geomagnetic field in the Balkan region and state borders were regarded as confidential information for a long time. Unfortunately this meant that geomagnetic field information was confidential information. The Republic of Macedonia was in a complicated situation because geomagnetic investigations were carried out by experts from Belgrade, Serbia and Montenegro. When Macedonia became an independent country, a team of experts from the Faculty of Mining and Geology, Department for Geology and Geophysics in Stip and Faculty of Natural Sciences and Mathematics, Institute of Physics in Skopje, started activities to establish a Geomagnetic Observatory in Macedonia. In the last four years, with the help of Dr. Jean Rasson from Institut Royal Météorologique, Centre du Physique du Globe in Dourbes, Belgium, a network of 15 repeat stations for measurement of the geomagnetic field in the Republic of Macedonia was created. For the first time since independence, all elements of geomagnetic field were determined.
KeywordsConfidential Information State Border Magnetic Compass Backup Role Geomagnetic Observatory
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The findings by University College Dublin scientists published in the journal Biology Letters on 25 July 2012 suggest that rising soil temperatures due to climate change may be extending the geographical habitat range of the earthworm Prosellodrilus amplisetosus.
This is a P. amplisetosus in soil in the urban farm Dublin, Ireland.
Credit: Carol Melody, UCD
"Soil decomposer species including earthworms are frequently introduced into non-native soils by human activities like the transportation of nursery plants or live fish bait," says Dr Olaf Schmidt from the School of Agriculture and Food Science, and the Earth Institute, University College Dublin, one of the authors of the report.
"There have been a few recordings of the earthworm P. amplisetosus outside of its native range in the Aquitaine region of south-western France, but now we have discovered a successfully thriving population in Ireland, about 1,000 km north of its native habitat."
Urban farms have higher temperatures than rural farms so the scientists suggest that this may have helped P. amplisetosus to become established in this new location. The mean yearly air temperature in Aquitaine in south-western France is about 3 degrees higher than in Dublin, Ireland.
The finding brings to 27 the total number of known earthworm species living in Irish soils.
According to the scientists, the Mediterranean species of earthworm P. amplisetosus is not an invasive species in Ireland. It does not directly compete for resources with the other resident species.
"By comparing the chemical composition of the worms, we discovered that the newcomers feed on a portion of the soil that the other resident earthworms do not use," says Carol Melody, a PhD student at the School of Agriculture and Food Science, University College Dublin, who co-authored the research paper.
"P. amplisetosus is a soil decomposer that eats organic carbon in portions of the soil to which the resident worm species don't have access," she says.
"If other soil decomposers like P. amplisetosus start to expand their habitat ranges we could see increasing amounts of CO2 being released from the soil where previously this carbon had been locked up because it was inaccessible to native earthworm species," says Dr Schmidt.
A sample of the P. amplisetosus found thriving in Dublin, Ireland, has been deposited in the Natural History Museum in London to archive the scientific discovery and to make scientists in Britain aware of the southern vagrants.
Dominic Martella | EurekAlert!
O2 stable hydrogenases for applications
23.07.2018 | Max-Planck-Institut für Chemische Energiekonversion
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
23.07.2018 | Health and Medicine
23.07.2018 | Earth Sciences
23.07.2018 | Science Education | <urn:uuid:03819453-f776-4627-acc8-f43bd2d73e27> | 3.375 | 1,115 | Content Listing | Science & Tech. | 38.395299 | 95,538,303 |
Sherwood B. Idso, 2001. "Carbon-Dioxide-Induced Global Warming: A Skeptic’s View of Potential Climate Change", Geological Perspectives of Global Climate Change, Lee C. Gerhard, William E. Harrison, Bernold M. Hanson
Download citation file:
Over the course of the past two decades, I have analyzed a number of natural phenomena that reveal how earth’s near-surface air temperature responds to surface radiative perturbations. These studies all suggest that a 300 to 600 parts per million (ppm) doubling of the atmosphere’s carbon dioxide (CO2) concentration could raise the planet’s mean surface air temperature by only about 0.4°C. Even this modicum of warming may never be realized, however, for it could be negated by a number of planetary cooling forces that are intensified by warmer temperatures and by the strengthening of biological processes that are enhanced by the same rise in atmospheric CO2 concentration that drives the warming. Several of these cooling forces have individually been estimated to be of equivalent magnitude, but of opposite sign, to the typically predicted greenhouse effect of a doubling of the air’s CO2 content, which suggests to me that little net temperature change will ultimately result from the ongoing buildup of CO2 in earth’s atmosphere. Consequently, I am skeptical of the predictions of significant CO2-induced global warming that are being made by state-of-the-art climate models and believe that much more work on a wide variety of research fronts will be required to properly resolve the issue. | <urn:uuid:0a065be0-97d7-4fa3-8dcc-8e862ffb84f3> | 2.96875 | 325 | Academic Writing | Science & Tech. | 31.167987 | 95,538,316 |
Studying the benefits of pest control for kea
DOC scientists have published research in the NZ Journal of Ecology (June 2018) on the effects of aerial 1080 in protecting nesting kea from predators.
This research was carried out from 2009-2012 on the South Island West Coast. It measured the nesting success of kea and compared this before and after aerial 1080 treatment and with an area where there was no predator control.
The results showed that kea nests were nine times more likely to survive and successfully produce chicks after aerial 1080 predator control.
Research also shows there is a risk of losing some kea to 1080 poisoning but in most cases this risk is easily offset by the improved nesting success after predator control.
Our scientists calculate that overall, the kea population is better off after 1080 treatment than without it. If predators are not controlled after a beech mast or seeding event, high stoat levels wipe out most nests and kill adult birds too.
Research in Kahurangi National Park
DOC has monitored kea nesting success in Kahurangi National Park since 2009.
In the 2015 and 2016 kea breeding seasons, on average 50% of monitored nests produced young kea. This followed aerial 1080 predator control in 2014 and 2016.
This is a big improvement on previous years without predator control in Kahurangi. Between 2009 and 2014 only 2% of nests were successful in areas without predator control.
DOC has tracked a total of 71 kea through 8 aerial 1080 operations in Kahurangi National Park (2009-2016) at four different sites (Mt Arthur, Wangapeka, Anatoki, and Oparara) and two birds were poisoned. The loss of these birds is unfortunate but would have been easily offset by the much better nesting success of the kea population in the park after predator control.
View larger graph (SVG, 35K)
Other monitoring results | <urn:uuid:1d6c0be5-9f49-4557-b42f-9f6b42eb9904> | 3.203125 | 390 | Knowledge Article | Science & Tech. | 49.81871 | 95,538,318 |
The conference, which took place in conjunction with the official inauguration of ICSU’s Regional Office for Asia and the Pacific, addressed how science could be used to prevent natural and human-induced hazards from becoming catastrophic events. UNESCO, through its Regional Office for Science in Jakarta, and the Academy of Sciences of Malaysia co-sponsored the conference.
The number of recorded natural disasters has increased dramatically in recent times, from about 100 per decade in 1940 to nearly 2800 per decade in the 1990s. Unfortunately, the Asia-Pacific region is no stranger to such events -- an example being the Indian Ocean tsunami, which happened at the end of 2004. Other examples of recent disasters include the hurricanes Katrina and Wilma, the earthquake in Kashmir and landslides in the Philippines. Such disasters kill, injure or displace millions of people a year and cause hundreds of billions of dollars worth of damage.
Today’s conference ties in with the planning for a major new initiative on hazards that ICSU launched last year. This programme, which builds on work done by the international scientific community to date, plans to use science to prevent natural and man-made hazards from becoming catastrophic events. While we can’t stop flooding and earthquakes, we should be able to prevent these events from becoming economic and human disasters. But to do this, scientists and policy makers need to work together more closely.
For instance, policy makers must take more notice of scientific evidence that can help prevent natural hazards from causing widespread devastation. In turn, scientists need to find new ways of communicating their research so that policy makers better understand how to integrate it into their decision-making processes. Moreover, new research to find out more about why disasters are increasing, and which human activities could worsen or lessen their effect, is urgently required. Finally, the public also needs to be kept informed of any imminent hazards as well as any decisions taken by policy makers.
“In ten years, the result should be that fewer people die, fewer are adversely impacted and wiser investments are made,” said Gordon McBean, Chair in Policy for the Institute for Catastrophic Loss Reduction at the University of Western Ontario and Chair of the ICSU Scoping Group on Environmental Hazards and Disasters.
Speakers at today’s conference focused on hazards like extreme weather events, earthquake prediction, landslides and land fires, tsunami early warning systems and the effects of the 2004 tsunami on livelihoods in the Indian Ocean area. “This conference is the first activity organised by ICSU’s Regional Office for Asia and the Pacific,” explained Mohd Nordin Hasan, Director of the Regional Office. “It also marks the beginning of greater involvement of scientists from developing countries in setting the agenda and eventually engaging in international research on environmental hazards and disasters”
Belle Dumé | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:365334cc-31ff-4783-804f-38f072176717> | 3.515625 | 1,240 | Content Listing | Science & Tech. | 34.949753 | 95,538,325 |
IBM developerWorks: Inline assembly for x86 in Linux
Apr 01, 2001, 14:00 (2 Talkback[s])
(Other stories by Bharata B. Rao)
How to Help Your Business Become an AI Early Adopter
[ Thanks to Kellie
for this link. ]
"Bharata B. Rao offers a guide to the overall use and structure
of inline assembly for x86 on the Linux platform. He covers the
basics of inline assembly and its various usages, gives some basic
inline assembly coding guidelines, and explains the instances of
inline assembly code in the Linux kernel."
"If you're a Linux kernel developer, you probably find yourself
coding highly architecture-dependent functions or optimizing a code
path pretty often. And you probably do this by inserting assembly
language instructions into the middle of C statements (a method
otherwise known as inline assembly). Let's take a look at the
specific usage of inline assembly in Linux. (We'll limit our
discussion to the IA32 assembly.)"
"Let's first look at the basic assembler syntax used in Linux.
GCC, the GNU C Compiler for Linux, uses AT&T assembly syntax.
Some of the basic rules of this syntax are listed below. (The list
is by no means complete; I've included only those rules pertinent
to inline assembly.)" | <urn:uuid:abf9f31a-b951-4098-b82c-92d4145c97ac> | 2.921875 | 292 | Truncated | Software Dev. | 48.230275 | 95,538,343 |
Two scientists in the Laboratoire Écologie & Évolution (CNRS/Université Pierre et Marie Curie/École normale supérieure de Paris) have demonstrated the adaptive nature of the reproductive behavior of certain arthropods from one laying to another, in the same female.
Thomas Tully and Régis Ferrière, researchers in the Laboratoire Écologie & Évolution(1), studied populations of Collembola, one of the most ancient and abundant groups of arthropods on Earth.
They showed that over the course of evolution, some Collembola populations have acquired an extraordinary ability to adjust their reproductive behavior when faced with abrupt environmental or social change. From one laying to another, a female can adapt not only the number but the size of her eggs, so that the young will be more capable of surviving in their new environmental conditions.
In a food-rich environment, females will tend to lay a larger number of smaller eggs. In a highly competitive environment, where individuals are numerous but food is less abundant, the eggs will be fewer in number but larger, thus allowing larger newborns to survive better under these difficult conditions.
Such flexibility constitutes a major adaptation, but the scientists also noted that the most plastic lines of Collembola were also those that experienced the earliest mortality. In this species, two strategies coexist in nature: plastic reproduction at the cost of reduced longevity, or a longer life without any great capacity for reproductive adjustment.
Comparison of these two strategies, which diverged at an early stage in the evolutionary history of this species, suggests that accelerated aging could result not simply from more intense reproduction but also from a high level of plasticity and genetic potential for reproduction.
Julien Guillaume | alfa
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Materials Sciences
19.07.2018 | Earth Sciences
19.07.2018 | Life Sciences | <urn:uuid:683e38ac-c289-4625-831d-b5cac8c28b9a> | 3.4375 | 1,010 | Content Listing | Science & Tech. | 33.048614 | 95,538,361 |
Bismuth: the essentials
Bismuth atoms have 83 electrons and the shell structure is 126.96.36.199.18.5. The ground state electronic configuration of neutral bismuth is [Xe].4f14.5d10.6s2.6p3 and the term symbol of bismuth is 4S3/2.
Bismuth is a white, crystalline, brittle metal with a pinkish tinge. Bismuth is the most diamagnetic of all metals, and the thermal conductivity is lower than any metal, except mercury. It has a high electrical resistance, and has the highest Hall effect of any metal (that is, the greatest increase in electrical resistance when placed in a magnetic field).
Cartoon by Nick D Kim ([Science and Ink], used by permission).
Bismuth: physical properties
Bismuth: heat properties
- Melting point: 544.4 [271.3 °C (520.3 °F)] K
- Boiling point: 544.4 [271.3 °C (520.3 °F)] K
- Enthalpy of fusion: 20.5 kJ mol-1
Bismuth: atom sizes
- Atomic radius (empirical): 160 pm
- Molecular single bond covalent radius: 151 (coordination number 3) ppm
- van der Waals radius: [ 280 ] ppm
- Pauling electronegativity: 2.02 (Pauling units)
- Allred Rochow electronegativity: 1.67 (Pauling units)
- Mulliken-Jaffe electronegativity: 2.15 (20% s orbital)
Bismuth: orbital properties
- First ionisation energy: 702.95 kJ mol‑1
- Second ionisation energy: 1611.6 kJ mol‑1
- Third ionisation energy: 2466.5 kJ mol‑1
Bismuth: crystal structure
Bismuth: biological data
- Human abundance by weight: (no data) ppb by weight
Bismuth has no biological role. However it has been used for some time as a medicine (tripotassium dicitratobismuthate) for treatment of stomach upsets. In combination with antibiotics it is now used for treatment of some stomach ulcers. It is also to be found in haemorrhoid creams such as Anusol cream and Hemocaneas as bismuth oxide and in Anusol ointment as bismuth subgallate.
Reactions of bismuth as the element with air, water, halogens, acids, and bases where known.
Bismuth: binary compounds
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of bismuth where known.
Bismuth: compound properties
Bond strengths; lattice energies of bismuth halides, hydrides, oxides (where known); and reduction potentials where known.
Bismuth: historyBismuth was discovered by known since ancient times in unknown at not known. Origin of name: from the German word "bisemutum".
Isolation: it is not normally necessary to make bismuth in the laboratory as it is available commercially. Bismuth is found in nature largely as bismite (Bi2O3), bismuthinite (Bi2S3), and bismutite [(BiO)2CO3]. However it is generally made as a byproduct of copper, lead,tin, silver, gold, and zinc plants. The final step involves a reduction of the oxide by charcoal. | <urn:uuid:786bb8b6-6c97-4da3-aecd-bf63a3ad0d51> | 3.03125 | 784 | Knowledge Article | Science & Tech. | 54.798679 | 95,538,382 |
Carbon Sequestration in Reclaimed Mined Soils of Ohio Page: 3 of 15
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
This research project is aimed at assessing the soil organic carbon (SOC) sequestration potential
of reclaimed minesoils (RMS). The experimental sites, owned and maintained by the American
Electrical Power, are located in Guernsey, Morgan, Noble, and Muskingum Counties of Ohio.
These sites, characterized by age chronosequences, were reclaimed with and without topsoil
application and are under continuous grass or forest cover. Among the three sites chosen for this
study one was reclaimed in 1978 (Cumberland), one in 1987 (Switch Grass) and one site was
reclaimed in 1994 (Tilton's Run). All three sites were reclaimed with topsoil application and
were under continuous grass cover. Eighteen experimental plots were developed on each site.
Five fertilization treatments were applied in triplicate on each experimental site. During this
quarter, water infiltration tests were performed on the soil surface in the experimental plots. Soil
samples were analyzed for soil moisture characteristics. This report presents the data on
infiltration rates, volume of transport and storage pores, and available water capacity (AWC) of
soil. The infiltration rates after 5 min (is) showed high statistical variability (CV > 0.62) among
the three sites. Both steady state infiltration rate and cumulative infiltration showed moderate to
high variability (CV > 0.35). The mean values for the infiltration rate after 5 min, steady state
infiltration rate, and cumulative infiltration were higher for Switch Grass (2.93 +2.05 cm mini;
0.63 0.34 cm mini; 113.07 +39.37 cm) than for Tilton's Run (1.76 1.42 cm min~; 0.40 +0.18
cm mini; 73.68 25.94 cm), and lowest for Cumberland (0.63 +0.34 cm mini; 0.27 0.19 cm
mini; 57.89 +31.00 cm). The AWC for 0-15 cm soil was highest at Tilton's Run (4.21 +1.75 cm)
followed by Cumberland (3.83 +0.77 cm) and Switch Grass (3.31 +0.10 cm). In 15-30 cm depth
Switch Grass had higher AWC (3.15 +0.70 cm) than Tilton's Run (3.00 +0.43 cm) and
Cumberland (2.78 +0.34 cm). In 30-50 cm depth Tilton's Run had higher AWC (4.31 +1.25 cm)
Shukla, Lorenz and Lal- C-MASC Oct 05
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Shukla, M.K.; Lorenz, K. & Lal, R. Carbon Sequestration in Reclaimed Mined Soils of Ohio, report, October 1, 2005; United States. (digital.library.unt.edu/ark:/67531/metadc885921/m1/3/: accessed July 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department. | <urn:uuid:30741ab6-bd5f-4d76-8ac6-d3e5afaed149> | 2.53125 | 827 | Truncated | Science & Tech. | 69.73403 | 95,538,404 |
+44 1803 865913
Edited By: Freek D van der Meer and Steven M de Jong
425 pages, B/w photos, figs
Presents the concepts of imaging spectrometry by discussing the underlying physics and the analytical image processing techniques. The second part of the book presents in detail a wide variety of applications of these new techniques.
From the reviews: "Overall, this book is a valuable reference source. It is a good alternative to a general remote sensing textbook in the optical domain, because most of the underlying physical principles are given with sufficient detail to provide a good understanding of the applications and of the limitations of hyperspectral sensing. Overall it is a good quality work, with only a limited number of repetitions from one chapter to another, which is sometimes difficult to achieve in a multi-authored book." (GEOMATICA, 57:4, 2004)
Acknowledgements. About the Editors. Contributors. Introduction. Part I: Basic principles of imaging spectrometry. 1. Basic physics of spectrometry. 2. Imaging spectrometry: Basic analytical techniques. Part II: Prospective applications of imaging spectrometry. 3. Imaging spectrometry for surveying and modelling land degradation. 4. Field and imaging spectrometry for identification and mapping of expansive soils. 5. Imaging spectrometry and vegetation science. 6. Imaging spectrometry for agricultural applications. 7. Imaging spectrometry and geological applications. 8. Imaging spectrometry and petroleum geology. 9. Imaging spectrometry for urban applications. 10. Imaging spectrometry in the Thermal Infrared. 11. Imaging spectrometry of water. Acronyms. Index. References.
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The Ohlone tiger beetle was discovered in 1987 and is found in only five sites in Santa Cruz County, California. Tiger beetles are members of the ground beetle family and often have large bulging eyes, long, slender legs and large curved mandibles (jaws). Adults are bright metallic green in color with leathery forewings and small white spots, and they measure from 9.5 to 12.4 mm long. Their long, slender legs are coppery-green in color. These beetles only emerge for about two months each year (late January to early April).
This species prefers to hunt, breed, and dig burrows for their eggs in open grasslands or along open, single-track trails and dirt roads in coast terrace meadows that support native grasses. These trails are naturally created by passing cattle and other wildlife, hikers, and mountain bikers. As its name suggests, the Ohlone tiger beetle is a ferocious predator, preferring to lurk alongside trails to ambush unsuspecting insects and pounce on them along the path. They can also chase prey while in flight. They are active during the day and are able to run or take flight quickly to escape their own predators. Females bury their young (larvae) in moist dirt holes, measuring 4 to 6 mm. The larvae of tiger beetles are usually large-headed, hump-backed grubs that are ferocious predators like their parents, flipping backwards to capture prey insects that happen to cross their paths. Diet consists of ants, isopods, and possibly earthworms.
The most serious threats to this species include loss of habitat due to urban development and competition with invasive exotic species. Some non-native plants have taken a heavy toll on native biodiversity. This species is also at great risk of being trampled upon by recreational trail users such as mountain bikers, joggers, and bikers. To preserve their critical habitat and protect the species, each year, the trails are temporarily closed to all users when the beetles emerge in late January.
Copyright Notice: This article is licensed under the GNU Free
Documentation License. It uses material from the Wikipedia article "Ohlone tiger beetle".
Ohlone Tiger Beetle Facts Last Updated:
May 12, 2017
To Cite This Page:
Glenn, C. R. 2006. "Earth's Endangered Creatures - Ohlone Tiger Beetle Facts" (Online).
Accessed 7/23/2018 at http://earthsendangered.com/profile.asp?sp=907&ID=9.
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A digital scientific notation
Leibniz is an attempt to define a digital scientific notation, i.e. a formal language for writing down scientific models in terms of equations and algorithms. Such models can be published, cited, and discussed, in addition to being manipulated by software.
The best way to get an impression of what Leibniz is and what
you can do with it is to read the one-page introduction
"Leibniz by example".
Then you can move on to the other examples
and tothe manual. Readers interested
in the studying the implementation (which needs and will get
a serious cleanup) should start by looking at the file
an overview of the code structure.
Leibniz is named after Gottfried Wilhelm Leibniz, who made important contributions to science, mathematics, formal logic, and computation, topics that are all relevant to this project. He invented a widely used notation for calculus, laid the foundation of equational logic by his definition of equality, and anticipated formal logic with his "calculus ratiocinator".
In a word: experimental. The major milestone that the implementation has reached is to play its role of a digital scientific notation: Leibniz specifications are embedded into the plain text discourse written for human readers, just like traditional semi-formal mathematical notation. This matters because it eliminates an important source of mistakes: the translation from human-readable and peer-reviewed descriptions of models and methods into computer-readable code.
However, many features that I have planned for the language are still missing: built-in collection types (lists/arrays, sets, ...) interfaces to databases and external datasets, support for workflows. Although in principle today's Leibniz can be used for everything (given that it's Turing-complete), it is still insufficient to express many aspects of computational science in a sufficiently concise and convenient form.
Required software, installation
This first implementation of Leibniz is written in Racket, whose support for implementing languages and language extensions is particularly useful for this project. In addition to Racket itself, Leibniz depends on the following libraries:
To install Leibniz and its dependencies, first install the Racket system on your computer, and then type, in a terminal window:
raco pkg install git://github.com/khinsen/leibniz\?path=leibniz
To run the Leibniz test suite, type
raco test -c leibniz
You can then use Leibniz in two ways:
In Racket's IDE, called DrRacket. Any file starting with
is treated as a Leibniz document. Clicking on the Leibniz button creates a human-readable HTML version and a machine-readable XML version of the document, and opens the HTML file immediately in a browser for inspection.
Write your Leibniz documents using any text editor, and generate the HTML/XML files using the
leibnizcommand line utility. It is part of installation process, but the location where it ends up is very platform-dependent. The good news is that the precise location is indicated near the end of the installation process, so have a careful look at the log output of
raco pkg install ....
For more information, see the Leibniz manual:
In DrRacket, go to the "Help" menu and select "Racket Documentation". This will open the table of contents of the Racket documentation in a browser. Search for "Leibniz" and click the link.
From a terminal command line, run "raco docs leibniz"
I expect to properly document and release this code at some time, under a meaningful license. But for now, it is research code covered by the CRAPL license.
The following articles are helpful to understand the context in which Leibniz is developed:
My essay Scientific notations for the digital era explains the concept of digital scientific notations, in particular as opposed to scientific software.
I have written two short essays on related topics: Scientific communication in the digital age and Verifiable research: The missing link between replicability and reproducibility
Leibniz is based on equational logic and term rewriting. This seems an appropriate choice for scientific models that are traditionally written as mathematical equations. Algorithms are expressed by giving a direction to certain equations, indicating that the left-hand side is supposed to be replaced by the right-hand side in simplifying an expression. Term rewriting has been used for a long time in computer algebra, notably by Mathematica.
Leibniz differs from Mathematica and most other computer algebra systems in using an order-sorted term algebra, in which each term is assigned a sort, which is similar to what is called a type in programming languages. For a detailed discussion of order-sorted algebra, see
- Order-sorted algebra I: Equational deduction for multiple inheritance, overloading, exceptions and partial operations by J. A. Goguen and J. Meseguer
Term rewriting in order-sorted algebras has been implemented in the specification languages OBJ and its modern offshoot Maude. For readers familiar with these languages, a Leibniz "context" is roughly the same as an "object" in OBJ or a "functional module" in Maude. Reading the Maude documentation is currently the best preparation for understanding Leibniz.
However, Leibniz is much simpler than Maude, lacking both Maude's flexible syntax and its support for non-functional modules. This is due to a very different focus: Maude is a language for writing specifications for complex software, whereas Leibniz is a notation for scientific models. Scientific models are much simpler than most software, but they can be processed by a wide range of software. Leibniz must therefore be easy to implement in a wide range of software packages, whereas reimplementing Maude is of little interest, given that its source code is open.
Most branches of this repository contain experiments that test the utility and feasibility of ideas for improvements and new features. Each branch has a short note in this place that explains its reason for being. This branch (master) always contains the version currently considered most useful.
Note that all branches except master may be rebased, or modified in other ways. If you want to fork this repository, please don't rely on any branch other than master. | <urn:uuid:7da3b66a-73da-44c8-bc26-3b8959e4274d> | 3.25 | 1,362 | Documentation | Software Dev. | 33.236821 | 95,538,436 |
Concept: Yellowstone National Park
- Proceedings of the National Academy of Sciences of the United States of America
- Published over 1 year ago
The economic and ecological costs of wildfire in the United States have risen substantially in recent decades. Although climate change has likely enabled a portion of the increase in wildfire activity, the direct role of people in increasing wildfire activity has been largely overlooked. We evaluate over 1.5 million government records of wildfires that had to be extinguished or managed by state or federal agencies from 1992 to 2012, and examined geographic and seasonal extents of human-ignited wildfires relative to lightning-ignited wildfires. Humans have vastly expanded the spatial and seasonal “fire niche” in the coterminous United States, accounting for 84% of all wildfires and 44% of total area burned. During the 21-y time period, the human-caused fire season was three times longer than the lightning-caused fire season and added an average of 40,000 wildfires per year across the United States. Human-started wildfires disproportionally occurred where fuel moisture was higher than lightning-started fires, thereby helping expand the geographic and seasonal niche of wildfire. Human-started wildfires were dominant (>80% of ignitions) in over 5.1 million km(2), the vast majority of the United States, whereas lightning-started fires were dominant in only 0.7 million km(2), primarily in sparsely populated areas of the mountainous western United States. Ignitions caused by human activities are a substantial driver of overall fire risk to ecosystems and economies. Actions to raise awareness and increase management in regions prone to human-started wildfires should be a focus of United States policy to reduce fire risk and associated hazards.
Scientific management of wildlife requires confronting the complexities of natural and social systems. Uncertainty poses a central problem. Whereas the importance of considering uncertainty has been widely discussed, studies of the effects of unaddressed uncertainty on real management systems have been rare. We examined the effects of outcome uncertainty and components of biological uncertainty on hunt management performance, illustrated with grizzly bears (Ursus arctos horribilis) in British Columbia, Canada. We found that both forms of uncertainty can have serious impacts on management performance. Outcome uncertainty alone - discrepancy between expected and realized mortality levels - led to excess mortality in 19% of cases (population-years) examined. Accounting for uncertainty around estimated biological parameters (i.e., biological uncertainty) revealed that excess mortality might have occurred in up to 70% of cases. We offer a general method for identifying targets for exploited species that incorporates uncertainty and maintains the probability of exceeding mortality limits below specified thresholds. Setting targets in our focal system using this method at thresholds of 25% and 5% probability of overmortality would require average target mortality reductions of 47% and 81%, respectively. Application of our transparent and generalizable framework to this or other systems could improve management performance in the presence of uncertainty.
The effect of anthropogenic noise on terrestrial wildlife is a relatively new area of study with broad ranging management implications. Noise has been identified as a disturbance that has the potential to induce behavioral responses in animals similar to those associated with predation risk. This study investigated potential impacts of a variety of human activities and their associated noise on the behavior of elk (Cervus elaphus) and pronghorn (Antilocapra americana) along a transportation corridor in Grand Teton National Park.
Since 1980, bison have injured more pedestrian visitors to Yellowstone National Park (Yellowstone) than any other animal (1). After the occurrence of 33 bison-related injuries during 1983-1985 (range = 10-13/year), the park implemented successful outreach campaigns (1) to reduce the average number of injuries to 0.8/year (range = 0-2/year) during 2010-2014 (unpublished data, National Park Service, September 2015). During May-July 2015, five injuries associated with bison encounters occurred (Table). Case reports were reviewed to evaluate circumstances surrounding these injuries to inform prevention.
Tracking and preventing the spillover of disease from wildlife to livestock can be difficult when rare outbreaks occur across large landscapes. In these cases, broad scale ecological studies could help identify risk factors and patterns of risk to inform management and reduce incidence of disease. Between 2002 and 2014, 21 livestock herds in the Greater Yellowstone Area (GYA) were affected by brucellosis, a bacterial disease caused by Brucella abortus, while no affected herds were detected between 1990 and 2001. Using a Bayesian analysis, we examined several ecological covariates that may be associated with affected livestock herds across the region. We showed that livestock risk has been increasing over time and expanding outward from the historical nexus of brucellosis in wild elk on Wyoming’s feeding grounds where elk are supplementally fed during the winter. Although elk were the presumed source of cattle infections, occurrences of affected livestock herds were only weakly associated with the density of seropositive elk across the GYA. However, the shift in livestock risk did coincide with recent increases in brucellosis seroprevalence in unfed elk populations. As increasing brucellosis in unfed elk likely stemmed from high levels of the disease in fed elk, disease-related costs of feeding elk have probably been incurred across the entire GYA, rather than solely around the feeding grounds. Our results suggest that focused disease mitigation in areas where seroprevalence in unfed elk is high could reduce the spillover of brucellosis to livestock. We also highlight the need to better understand the epidemiology of spillover events with detailed histories of disease testing, calving, and movement of infected livestock. Finally, we recommend using case-control studies to investigate local factors important to livestock risk.
Birds in U.S. national parks find strong protection from many longstanding and pervasive threats, but remain highly exposed to effects of ongoing climate change. To understand how climate change is likely to alter bird communities in parks, we used species distribution models relating North American Breeding Bird Survey (summer) and Audubon Christmas Bird Count (winter) observations to climate data from the early 2000s and projected to 2041-2070 (hereafter, mid-century) under high and low greenhouse gas concentration trajectories, RCP8.5 and RCP2.6. We analyzed climate suitability projections over time for 513 species across 274 national parks, classifying them as improving, worsening, stable, potential colonization, and potential extirpation. U.S. national parks are projected to become increasingly important for birds in the coming decades as potential colonizations exceed extirpations in 62-100% of parks, with an average ratio of potential colonizations to extirpations of 4.1 in winter and 1.4 in summer under RCP8.5. Average species turnover is 23% in both summer and winter under RCP8.5. Species turnover (Bray-Curtis) and potential colonization and extirpation rates are positively correlated with latitude in the contiguous 48 states. Parks in the Midwest and Northeast are expected to see particularly high rates of change. All patterns are more extreme under RCP8.5 than under RCP2.6. Based on the ratio of potential colonization and extirpation, parks were classified into overall trend groups associated with specific climate-informed conservation strategies. Substantial change to bird and ecological communities is anticipated in coming decades, and current thinking suggests managing towards a forward-looking concept of ecological integrity that accepts change and novel ecological conditions, rather than focusing management goals exclusively on maintaining or restoring a static set of historical conditions.
Past research indicates that whitebark pine seeds are a critical food source for Threatened grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem (GYE). In recent decades, whitebark pine forests have declined markedly due to pine beetle infestation, invasive blister rust, and landscape-level fires. To date, no study has reliably estimated the contribution of whitebark pine seeds to the diets of grizzlies through time. We used stable isotope ratios (expressed as δ13C, δ15N, and δ34S values) measured in grizzly bear hair and their major food sources to estimate the diets of grizzlies sampled in Cooke City Basin, Montana. We found that stable isotope mixing models that included different combinations of stable isotope values for bears and their foods generated similar proportional dietary contributions. Estimates generated by our top model suggest that whitebark pine seeds (35±10%) and other plant foods (56±10%) were more important than meat (9±8%) to grizzly bears sampled in the study area. Stable isotope values measured in bear hair collected elsewhere in the GYE and North America support our conclusions about plant-based foraging. We recommend that researchers consider model selection when estimating the diets of animals using stable isotope mixing models. We also urge researchers to use the new statistical framework described here to estimate the dietary responses of grizzlies to declines in whitebark pine seeds and other important food sources through time in the GYE (e.g., cutthroat trout), as such information could be useful in predicting how the population will adapt to future environmental change.
Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (∼3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations.
We explored multiple linkages among grey wolves (Canis lupus), elk (Cervus elaphus), berry-producing shrubs and grizzly bears (Ursus arctos) in Yellowstone National Park. We hypothesized competition between elk and grizzly bears whereby, in the absence of wolves, increases in elk numbers would increase browsing on berry-producing shrubs and decrease fruit availability to grizzly bears. After wolves were reintroduced and with a reduced elk population, we hypothesized there would be an increase in the establishment of berry-producing shrubs, such as serviceberry (Amelanchier alnifolia), which is a major berry-producing plant. We also hypothesized that the percentage fruit in the grizzly bear diet would be greater after than before wolf reintroduction. We compared the frequency of fruit in grizzly bear scats to elk densities prior to wolf reintroduction during a time of increasing elk densities (1968-1987). For a period after wolf reintroduction, we calculated the percentage fruit in grizzly bear scat by month based on scats collected in 2007-2009 (n = 778 scats) and compared these results to scat data collected before wolf reintroduction. Additionally, we developed an age structure for serviceberry showing the origination year of stems in a northern range study area. We found that over a 19-year period, the percentage frequency of fruit in the grizzly diet (6231 scats) was inversely correlated (P < 0·001) with elk population size. The average percentage fruit in grizzly bear scats was higher after wolf reintroduction in July (0·3% vs. 5·9%) and August (7·8% vs. 14·6%) than before. All measured serviceberry stems accessible to ungulates originated since wolf reintroduction, while protected serviceberry growing in a nearby ungulate exclosure originated both before and after wolf reintroduction. Moreover, in recent years, browsing of serviceberry outside of the exclosure decreased while their heights increased. Overall, these results are consistent with a trophic cascade involving increased predation by wolves and other large carnivores on elk, a reduced and redistributed elk population, decreased herbivory and increased production of plant-based foods that may aid threatened grizzly bears.
- Proceedings of the National Academy of Sciences of the United States of America
- Published 4 months ago
The wildland-urban interface (WUI) is the area where houses and wildland vegetation meet or intermingle, and where wildfire problems are most pronounced. Here we report that the WUI in the United States grew rapidly from 1990 to 2010 in terms of both number of new houses (from 30.8 to 43.4 million; 41% growth) and land area (from 581,000 to 770,000 km2; 33% growth), making it the fastest-growing land use type in the conterminous United States. The vast majority of new WUI areas were the result of new housing (97%), not related to an increase in wildland vegetation. Within the perimeter of recent wildfires (1990-2015), there were 286,000 houses in 2010, compared with 177,000 in 1990. Furthermore, WUI growth often results in more wildfire ignitions, putting more lives and houses at risk. Wildfire problems will not abate if recent housing growth trends continue. | <urn:uuid:3b479b00-bfe3-49fe-8ab5-e9bc2a543860> | 3.296875 | 2,823 | Academic Writing | Science & Tech. | 23.972202 | 95,538,462 |
In mathematics, the Grothendieck group construction in abstract algebra constructs an abelian group from a commutative monoid M in the most universal way in the sense that any abelian group containing a homomorphic image of M will also contain a homomorphic image of the Grothendieck group of M. The Grothendieck group construction takes its name from the more general construction in category theory, introduced by Alexander Grothendieck in his fundamental work of the mid-1950s that resulted in the development of K-theory, which led to his proof of the Grothendieck–Riemann–Roch theorem. This article treats both constructions.
- 1 Grothendieck group of a commutative monoid
- 2 Grothendieck group and extensions
- 3 Grothendieck groups of exact categories
- 4 Grothendieck groups of triangulated categories
- 5 Further examples
- 6 References
Grothendieck group of a commutative monoid
Given a commutative monoid M, we want to construct "the most general" abelian group K that arises from M by introducing additive inverses. Such an abelian group K always exists; it is called the Grothendieck group of M. It is characterized by a certain universal property and can also be concretely constructed from M.
Let M be a commutative monoid. Its Grothendieck group K is an abelian group with the following universal property: There exists a monoid homomorphism
such that for any monoid homomorphism
from the commutative monoid M to an abelian group A, there is a unique group homomorphism
This expresses the fact that any abelian group A that contains a homomorphic image of M will also contain a homomorphic image of K, K being the "most general" abelian group containing a homomorphic image of M.
To construct the Grothendieck group K of a commutative monoid M, one forms the Cartesian product
(The two coordinates are meant to represent a positive part and a negative part: (m1, m2) is meant to correspond to the element m1 − m2 in K.)
Addition on M×M is defined coordinate-wise:
- (m1, m2) + (n1, n2) = (m1 + n1, m2 + n2).
Next we define an equivalence relation on M×M. We say that (m1, m2) is equivalent to (n1, n2) if, for some element k of M, m1 + n2 + k = m2 + n1 + k (the element k is necessary because the cancellation law does not hold in all monoids). The equivalence class of the element (m1, m2) is denoted by [(m1, m2)]. We define K to be the set of equivalence classes. Since the addition operation on M×M is compatible with our equivalence relation, we obtain an addition on K, and K becomes an abelian group. The identity element of K is [(0, 0)], and the inverse of [(m1, m2)] is [(m2, m1)]. The homomorphism i : M→K sends the element m to [(m, 0)].
Alternatively, the Grothendieck group K of M can also be constructed using generators and relations: denoting by (Z(M),+') the free abelian group generated by the set M, the Grothendieck group K is the quotient of Z(M) by the subgroup generated by . (Here +' and -' denote the addition and subtraction in the free abelian group Z(M) while + denotes the addition in the monoid M.) This construction has the advantage that it can be performed for any semigroup M and yields a group which satisfies the corresponding universal properties for semigroups, i.e. the "most general and smallest group containing a homomorphic image of M". This is known as the "group completion of a semigroup" or "group of fractions of a semigroup".
In the language of category theory, any universal construction gives rise to a functor; we thus obtain a functor from the category of commutative monoids to the category of abelian groups which sends the commutative monoid M to its Grothendieck group K. This functor is left adjoint to the forgetful functor from the category of abelian groups to the category of commutative monoids.
For a commutative monoid M, the map i : M→K is injective if and only if M has the cancellation property, and it is bijective if and only if M is already a group.
Examples: the integers, the Grothendieck group of a manifold and of a ring
The easiest example of a Grothendieck group is the construction of the integers Z from the natural numbers N. First one observes that the natural numbers (including 0) together with the usual addition indeed form a commutative monoid (N,+). Now when we use the Grothendieck group construction we obtain the formal differences between natural numbers as elements n - m and we have the equivalence relation
for all n ∈ N. This defines the integers Z. Indeed, this is the usual construction to obtain the integers from the natural numbers. See "Construction" under Integers for a more detailed explanation.
The Grothendieck group is the fundamental construction of K-theory. The group K0(M) of a compact manifold M is defined to be the Grothendieck group of the commutative monoid of all isomorphism classes of vector bundles of finite rank on M with the monoid operation given by direct sum. This gives a contravariant functor from manifolds to abelian groups. This functor is studied and extended in topological K-theory.
The zeroth algebraic K group K0(R) of a (not necessarily commutative) ring R is the Grothendieck group of the monoid consisting of isomorphism classes of finitely generated projective modules over R, with the monoid operation given by the direct sum. Then K0 is a covariant functor from rings to abelian groups.
The two previous examples are related: consider the case where R is the ring of complex-valued smooth functions on a compact manifold M. In this case the projective R-modules are dual to vector bundles over M (by the Serre-Swan theorem). Thus K0(R) and K0(M) are the same group.
Grothendieck group and extensions
Another construction that carries the name Grothendieck group is the following: Let R be a finite-dimensional algebra over some field k or more generally an artinian ring. Then define the Grothendieck group G0(R) as the abelian group generated by the set of isomorphism classes of finitely generated R-modules and the following relations: For every short exact sequence
of R-modules add the relation
Note that the proposed definition of Grothendieck group G0(R) is well-defined. Let R be an Artinian ring, and suppose and are isomorphic finitely generated R-modules. Then there exists the following short exact sequence
The exact sequence hence implies that . Since , it follows that . The proposed definition also implies that for any two finitely generated R-modules M and N, . This follows from the given split short exact sequence.
Let K be a field. Then the Grothendieck group is an abelian group generated by symbols for any finite dimensional K-vector space V. In fact, is isomorphic to whose generator is the element . Here, the symbol for a finite K-vector space V is defined as , the dimension of the vector space V. Suppose we have the following short exact sequence of K-vector spaces.
Since any short exact sequence of vector spaces splits, it holds that . In fact, for any two finite dimensional vector spaces V and W the following holds.
The above equality hence satisfies the condition of the symbol in the Grothendieck group.
Note that any two isomorphic finite dimensional K-vector space has the same dimension. Also, any two finite dimensional K-vector space V and W of same dimension are isomorphic to each other. In fact, every finite n-dimensional K-vector space V is isomorphic to . The observation from the previous paragraph hence proves the following equation.
Hence, every symbol is generated by the element with integer coefficients, which implies that G0(K) is isomorphic to with the generator .
More generally, let be the set of integers. The Grothendieck group is an abelian group generated by symbols for any finitely generated abelian groups A. We first note that any finite abelian group G satisfies that . The following short exact sequence holds, where the map is multiplication by n.
The exact sequence implies that , so every cyclic group has its symbol equal to 0. This in turn implies that every finite abelian group G satisfies by the Fundamental Theorem of Finite Abelian groups.
Observe that by the Fundamental Theorem of Finitely Generated Abelian Groups, every abelian group is isomorphic to a direct sum of a torsion subgroup and a torsion-free abelian group isomorphic to for some non-negative integer r. Note that the integer r is defined as the rank of the abelian group A. Define the symbol as . Then the Grothendieck group G0() is isomorphic to with generator . Indeed, the observation made from the previous paragraph shows that every abelian group A has its symbol the same to the symbol where . Furthermore, the rank of the abelian group satisfies the conditions of the symbol of the Grothendieck group. Suppose we have the following short exact sequence of abelian groups.
Then tensoring with the rational numbers implies the following equation.
Since the above is a short exact sequence of -vector spaces, the sequence splits. Therefore, we have the following equation.
On the other hand, we also have the following relation. For more information, see: Rank of Abelian Group.
Therefore, the following equation holds.
Hence we have shown that G0() is isomorphic to with generator .
Grothendieck group satisfies a universal property. We make a preliminary definition: A function χ from the set of isomorphism classes to an abelian group A is called additive if, for each exact sequence 0 → A → B → C → 0, we have . Then, for any additive function χ: R-mod → X, there is a unique group homomorphism f: G0(R) → X such that χ factors through f and the map that takes each object of to the element representing its isomorphism class in G0(R). Concretely this means that f satisfies the equation f([V]) = χ(V) for every finitely generated R-module V and f is the only group homomorphism that does that.
Examples of additive functions are the character function from representation theory: If R is a finite-dimensional k-algebra, then we can associate the character χV: R → k to every finite-dimensional R-module V: χV(x) is defined to be the trace of the k-linear map that is given by multiplication with the element x ∈ R on V.
By choosing a suitable basis and writing the corresponding matrices in block triangular form one easily sees that character functions are additive in the above sense. By the universal property this gives us a "universal character" such that χ([V]) = χV.
If k = C and R is the group ring C[G] of a finite group G then this character map even gives a natural isomorphism of G0(C[G]) and the character ring Ch(G). In the modular representation theory of finite groups k can be a field , the algebraic closure of the finite field with p elements. In this case the analogously defined map that associates to each k[G]-module its Brauer character is also a natural isomorphism onto the ring of Brauer characters. In this way Grothendieck groups show up in representation theory.
we have a canonical element
In fact the Grothendieck group was originally introduced for the study of Euler characteristics.
Grothendieck groups of exact categories
A common generalization of these two concepts is given by the Grothendieck group of an exact category . Simply put, an exact category is an additive category together with a class of distinguished short sequences A → B → C. The distinguished sequences are called "exact sequences", hence the name. The precise axioms for this distinguished class do not matter for the construction of the Grothendieck group.
The Grothendieck group is defined in the same way as before as the abelian group with one generator [M] for each (isomorphism class of) object(s) of the category and one relation
for each exact sequence
Alternatively one can define the Grothendieck group using a similar universal property: An abelian group G together with a mapping is called the Grothendieck group of iff every "additive" map from into an abelian group X ("additive" in the above sense, i.e. for every exact sequence we have ) factors uniquely through φ.
Every abelian category is an exact category if we just use the standard interpretation of "exact". This gives the notion of a Grothendieck group in the previous section if we choose -mod the category of finitely generated R-modules as . This is really abelian because R was assumed to be artinian and (hence noetherian) in the previous section.
On the other hand, every additive category is also exact if we declare those and only those sequences to be exact that have the form with the canonical inclusion and projection morphisms. This procedure produces the Grothendieck group of the commutative monoid in the first sense (here means the "set" [ignoring all foundational issues] of isomorphism classes in .)
Grothendieck groups of triangulated categories
Generalizing even further it is also possible to define the Grothendieck group for triangulated categories. The construction is essentially similar but uses the relations [X] - [Y] + [Z] = 0 whenever there is a distinguished triangle X → Y → Z → X.
- In the abelian category of finite-dimensional vector spaces over a field k, two vector spaces are isomorphic if and only if they have the same dimension. Thus, for a vector space V the class in . Moreover, for an exact sequence
- m = l + n, so
- Thus , the Grothendieck group is isomorphic to Z and is generated by [k]. Finally for a bounded complex of finite-dimensional vector spaces V*,
- where is the standard Euler characteristic defined by
- For a ringed space , one can consider the category of all locally free sheaves over X. K0(X) is then defined as the Grothendieck group of this exact category and again this gives a functor.
- For a ringed space , one can also define the category to be the category of all coherent sheaves on X. This includes the special case (if the ringed space is an affine scheme) of being the category of finitely generated modules over a noetherian ring R. In both cases is an abelian category and a fortiori an exact category so the construction above applies.
- In the case where R is a finite-dimensional algebra over some field, the Grothendieck groups G0(R) (defined via short exact sequences of finitely generated modules) and K0(R) (defined via direct sum of finitely generated projective modules) coincide. In fact, both groups are isomorphic to the free abelian group generated by the isomorphism classes of simple R-modules.
- There is another Grothendieck group G0 of a ring or a ringed space which is sometimes useful. The category in the case is chosen to be the category of all quasi-coherent sheaves on the ringed space which reduces to the category of all modules over some ring R in case of affine schemes. G0 is not a functor, but nevertheless it carries important information.
- Since the (bounded) derived category is triangulated, there is a Grothendieck group for derived categories too. This has applications in representation theory for example. For the unbounded category the Grothendieck group however vanishes. For a derived category of some complex finite-dimensional positively graded algebra there is a subcategory in the unbounded derived category containing the abelian category A of finite-dimensional graded modules whose Grothendieck group is the q-adic completion of the Grothendieck group of A.
- Michael F. Atiyah, K-Theory, (Notes taken by D.W.Anderson, Fall 1964), published in 1967, W.A. Benjamin Inc., New York.
- Achar, Pramod N.; Stroppel, Catharina (2013), "Completions of Grothendieck groups", Bulletin of the London Mathematical Society, 45 (1): 200–212, arXiv: , doi:10.1112/blms/bds079, MR 3033967.
- Hazewinkel, Michiel, ed. (2001) , "Grothendieck group", Encyclopedia of Mathematics, Springer Science+Business Media B.V. / Kluwer Academic Publishers, ISBN 978-1-55608-010-4
- "Grothendieck group". PlanetMath. | <urn:uuid:be42419c-1a1a-47cc-a6bc-111ebdeeeae0> | 2.703125 | 3,858 | Knowledge Article | Science & Tech. | 44.189917 | 95,538,470 |
Found this interesting post on the New Mars forums about nitrogen deposits on Mars:
You know, I've been wondering about this nitrogen thing for a while now. I'm not so sure atmospheric nitrogen is a prerequisite for a stable ecosystem. It would seem that once there is "fixed" nitrogen in a biological system (e.g. ammonia, nitrates, nitrites) there can exist a nitrogen cycle entirely decoupled from the atmosphere. See the EPA image below:
Through plant and animal decomposition and assimilation, the nitrogen can make a complete cycle and sustain a happy ecosystem. The only rub is that "denitrifying" bacteria, who live in anoxic conditions such as the soil and stagnant water, like to use nitrate instead of oxygen as their metabolic electron acceptor. This turns the fixed nitrogen into atmospheric N2, which is useless to all life except nitrogen fixing bacteria, who help return it to a biologically accessible form. There are also abiotic ways nitrogen is fixed, such as UV radiation, lightning, and volcanic activity.
In some sense the question comes down to this: Are we setting up our terraformed ecosystem using gaseous N2 or a fixed form like nitrates? Either will work. If we use gaseous N2 we need to make sure we have >5 mbar, and it will take a while for fixing bacteria to build up enough fixed nitrogen from this for an ecosystem to operate. On the other hand, if we initially introduce nitrates higher plants will be able to immediately use it as a nutritive resource. Again, we have the requirement that we have >5 mbar worth of nitrates so that when denitrifying bacteria start bleeding nitrogen off to the atmosphere there will be enough pressure for nitrogen fixing bacteria to reabsorb it.
There is a second reason nitrates are attractive: they probably already exist on Mars. Many people claim that this is speculation since we haven't observed any nitrates on Mars, but this is uncompelling. The truth is that: 1) nitrates are extremely hard to detect using spectrographic techniques, and 2) there is every reason to believe that nitrates would only exist in substantial quantities at depths of ~1 meter. An excellent paper by (Sutter et al. 2007) demonstrates this by using soil from the Atacama Desert, an oft used terrestrial Martian analog. The Atacama is hyperarid (50 times less water than Califronia's Death Valley), with heavy saline deposits, nearby volcanos, and has thin air and high UV due to its elevation. It also boasts the world's most incredible nitrate deposits: in many regions >7% of the soil is nitrate by weight (Prellwitz et al. 2006). However, as (Sutter et al. 2007) show, even in the areas with the most concentrated nitrate deposits we cannot discern them via spectrometry until they occupy ~1% of the soil by weight, and that doesn't happen until a depth of ~1 meter has been reached. Below this depth the nitrate fraction can quickly explode up to 30% of the soil's weight.
So the Atacama has huge nitrate deposits; why think that Mars does too? It is thought that Atacama's deposits are due largely to the volcanism of the surrounding area, which is estimated to have fixed 2800 megatons of nitrogen from the air (Oyarzun & Oyarzun 2007). Extrapolating this to the global volcanism of Mars using (Geeley & Schneid 1991), we would expect 180 million megatons, or 45 mbar worth of nitrogen to be fixed as nitrates and nitrites. In addition it has been experimentally demonstrated by (Segura et al. 2005) that UV radiation could have fixed almost 2 megatons of nitrogen every year on early Mars. Between the time of Mars formation 4.6 Gyr ago and the beginning of the Late Heavy Bombardment 4.0 Gyr ago, this mechanism could have fixed 250 mbar of nitrogen in the soil before impactors blew off much of Mars' atmosphere. This would also be before the Martian global magnetic field decayed and solar wind erosion began.
But did Mars even have this much nitrogen to start with? By analogy with Earth a planet of Mars' mass could have accumulated 120 mbar of N2 during formation, and by analogy with Venus it might have begun with 560 mbar. Even if Mars began with an extremely pessimistic 1 bar CO2, the ratio of C/N = 20 in comets and terrestrial planet atmospheres means it should have begun with at least 25 mbar N2. And since (Phillips et al. 2001) estimate a magmatic outgasing of 1.5 bar of CO2 during the formation of Tharsis, anywhere from 38 to 250 mbar N2 could have been added to the atmosphere later, based on possible magma N2 contents from (Segura et al. 2005).
Ok, Mars had the ability to fix large amounts of nitrogen in the past, as well as a significant inventory from which to fix it. So where is it? Well, nitrates are extremely soluble, meaning that during Mars' wet period(s) most of it would have quickly dissolved and been transported to the northern plains. As the water froze/evaporated the nitrates would have been deposited primarily in the Utopian basin, which seems to have originally been an impact crater the size of Hellas that's been filled in with sediment due to its watershed containing over 2/3 of the Martian surface (Bandert 2004). Other locations of heavy nitrate deposits might be the Acidalia, Amazonis, Argyre, Chryse, Echus, Hellas, and Isidis plains.
Interestingly, the crustal thickness at these locations is very thin, on the order of that found at Iceland or thinner, suggesting that the geothermal gradient there may be sufficient to support liquid water at relatively shallow depths. According to (Halevy et al. 2007) such sites could experience large carbonate deposit formation after the recession of Mars' acidic seas. I find it intriguing that large deposits of both nitrates and carbonates might be located in the same places, along with the geothermal means to decompose them directly into CO2, N2, and O2. Just drill down to ~650°C, pipe down your carbonates and nitrates with some sand, and you get all those nice atmospheric gases boiling out plus a "slag" of useful building materials like sodium silicate (water glass) and calcium silicate (the prime component of Portland cement). If you don't throw in the sand you can get sodium hydroxide (lye) and calcium oxide (lime), both of which are also very useful. This is all currently within our technological reach, and perhaps could be used to provide raw materials for early research facilities and colonies.
However, even if you could magically use all the geothermal heat flux of Mars (~4 terawatts) to decompose nitrates for 1000 years, you still wouldn't have 5 mbar N2. One could conceivably use nuclear or solar furnaces to decompose nitrates, but I'm not sure it's worth it when you can just spread the nitrates around like fertilizer, which is all it really is. Just let the ecosystem absorb it and redistribute it naturally.
Terrestrial analogs for interpretation of infrared spectra from the Martian surface and subsurface: Sulfate, nitrate, carbonate, and phyllosilicate-bearing Atacama Desert soils B Sutter, JB Dalton, SA Ewing, R Amundson, and CP McKay, Journal of Geophysical Research, Vol. 112, G04S10
Nitrate Concentrations in Atacama Desert soils and Their Implications for the Antiquity of the Atacama Desert. J Prellwitz, J Rech, G Michalski, B Buck, MS Howell, and A Brock, 18th World Conference of Soil Science, July 15, 2006 http://a-c-s.confex.com/crops/wc2006/te … P18247.HTM
Massive Volcanism in the Altiplano-Puna Volcanic Plateau and Formation of the Huge Atacama Desert Nitrate Deposits: A Case for Thermal and Electric Fixation of Atmospheric Nitrogen J Oyarzun & R Oyarzun, International Geology Review, Volume 49, Number 10 / October 2007
Magma Generation on Mars: Amounts, Rates, and Comparisons with Earth, Moon, and Venus R Geeley & BD Schneid, Science 15 November 1991: Vol. 254. no. 5034, pp. 996-998
Ancient Geodynamics and Global-Scale Hydrology on Mars RJ Phillips, MT Zuber, SC Solomon, MP Golombek, BM Jakosky, WB Banerdt, DE Smith, RME Williams, BM Hynek, O Aharonson, and SA Hauck II, Science, Vol 291, 30 March 2001
Implications of the Utopia gravity anomaly for the resurfacing of the northern plains of Mars WB Banerdt, Second Conference on Early Mars (2004)
A Sulfur Dioxide Climate Feedback on Early Mars I Halevy, MT Zuber, and DP Schrag, Science Vol 318, 1903, 21 December 2007
Background: 50g sample of Orbitec JSC-Mars-1A was frozen (-1°C) for around 48 hours, after the addition of 25g distilled H20.
Sample was frozen in a 118 mL (4 oz) food-safe plastic container.
Result: The sample tolerated up to 40 lbs resting weight, gently placed, for the duration of a 60-second trial. It seems like it could do twice that in weight, and also duration, but that's all I have here. I dropped it onto concrete from a height of ~60 inches (~152.4 cm). The sample did not break systemically, only slightly crumbling with the broken-off material weighing approximately 1.10g (wet/mostly frozen).
My intention is to smash it with a hammer, but I'm going to freeze a terran soil sample first as an analog.
Received about 2 lbs of regolith simulant yesterday. What do you think some of the preliminary experiments should be? | <urn:uuid:5ec08886-9bb5-486d-8e7c-8c012c8fa2b3> | 3.359375 | 2,156 | Comment Section | Science & Tech. | 48.553507 | 95,538,471 |
The summit crater of Hawaii's Kilauea Volcano has grown dramatically large since the latest eruption began in May, so large that it may be threatening a museum at Hawaii Volcanoes National Park.
The U.S. Geological Survey said in a Twitter post on Monday that a GPS station location in the Halemaumau Crater was knocked out of service after subsiding 310 feet as the subsidence continues to grow.
Since the eruption started on May 3, sending magma spewing out along fissures in the eastern Puna region of the island, the volcano's crater has been subsiding. That has caused near-daily earthquakes, rock falls and subsequent explosions at the summit.
"The current slumping and rocksliding is a response to magma draining from the former summit lava lake. However, we don't know if or when the lake might reappear," the agency said on Twitter.
The USGS said over the weekend that over 350 earthquakes greater than magnitude 2.5 were reported in a 24-hour peroid at the summit.
On Sunday, the USGS conducted a drone flight over the crater area, showing the dramatic changes as the lava has drained out. According to USGS, the deepest part of Halemaumau is now over 1,300 feet below the caldera floor.
"This thing is getting deeper and deeper as these explosions continue to happen," volcanologist and University of Hawaii at Manoa professor Mike Garcia told KHON, adding that he is not entirely sure what it means.
"You would have thought that whatever was going on initially, that magma would have drained out and gone down to east rift zone. That happened in the early days of May. Since that happened the explosions continued. Does that mean a deeper reservoir continues to drain?"
Garcia said it's hard to predict what will happen next because it's too dangerous to observe the volcano directly, but that new cracks are forming outwards from the old crater.
This is affecting nearby buildings, such as the Thomas A. Jaggar Museum at Hawaii Volcanoes National Park. Artifacts were being removed last week because park staff saw building cracks inside the museum, the Hawaii Tribune-Herald reported.
The building, which also houses the USGS Hawaiian Volcano Observatory, hasn't been structurally assessed. But there is concern that it could slide into the volcano's growing summit crater, park spokeswoman Jessica Ferracane told the paper.
"Every single day, we are sustaining damage from these ongoing earthquakes," Ferracane said. "The cracks and the fractures along the overlook of Jaggar go through rock walls down through the ground."
Even if the volcanology museum is spared from destruction, it might not be safe to reuse, Ferracane said.
"It's mildly possible it could be reused," Ferracane said. "I'm not sure if we want to reuse it because of the proximity to a very unstable cliff."
The Associated Press contributed to this report. | <urn:uuid:9bc4ba88-b69d-4ee4-91c1-b26fc4d29aef> | 3.046875 | 614 | News Article | Science & Tech. | 51.656286 | 95,538,481 |
In the past 100 years, 27 species of fish have died out in North America and four have become extinct. The U.S. government currently protects 149 fish species and subspecies and a total of 1,311 species under the U.S. Endangered Species Act.
"Endangered and threatened U.S. fish outnumber mammals, reptiles, birds, etcetera," said Bain. Since 1966 when the federal government started identifying threatened species, only 16, including the American alligator, American peregrine falcon and brown pelican, have recovered. "Recovery is very rare," said Bain, who has been monitoring the shortnose sturgeon's population since the mid-1990s and has access to data on the populations since the 1970s.
"The nature of this species, its habitat and evidence for a large and secure population are an example of successful protected species management," said Bain. "Scientists and legislators have called for changes in the U.S. Endangered Species Act; the act is being debated in Congress and has been characterized as failing to recover species."
However, he said, recovery of the shortnose sturgeon suggests the combination of species and habitat protection with patience can successfully recover threatened species, even next to one of the busiest cities in the world.
The study will appear in the Jan. 24 edition of PLoS ONE, an international, peer-reviewed, open-access, online publication from the Public Library of Science.
Press Relations Office | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
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Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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By Richard Schmude Jr.
Every novice astronomer - and lots of non-astronomers - could be conversant in seeing a "star" that indicates that characteristic regular slide around the starry history of the sky. synthetic satellites might be visible any evening, and a few as shiny because the planets. yet what percentage people can establish which satellites or spent release automobile casing we're seeing?
Artificial Satellites and the way to watch Them describes all of the diversified satellites that may be saw with no optical relief, together with after all the foreign area Station and the numerous secret agent satellites operated by way of diverse international locations. Richard Schmude seems at them intimately and describes how they are often saw via amateurs, the way to realize them, or even how one can are expecting their orbits.
Artificial satellites have replaced because the starting of the millenium. numerous extra international locations have introduced them. And novice astronomers have applied electronic cameras to be able to snapshot satellites to a solution of approximately 3 ft. This booklet describes how one can realize, notice, and photograph satellites. Examples of contemporary photos and the way they have been made are given. It additionally deals up to date descriptions of the numerous satellites which are orbiting the Earth and different celestial our bodies. Readers can find out how satellites impression our daily lives. in brief, Artificial Satellites and the way to watch Them is an in depth and updated evaluation of synthetic satellites and the way to check them within the evening sky.
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The Moderate Resolution Imaging Spectroradiometer instrument known as MODIS takes amazing visible and infrared images of tropical cyclones, among other things, and captured a good look into the eye of Bruce on Dec. 19 at 03:41 UTC.
NASA's Terra satellite passed over the center of Tropical Cyclone Bruce on Dec. 19 at 03:40 UTC and the MODIS instrument captured this image, clearly showing an eye.
Although Bruce's eye seemed to have some high clouds, the eye was still visible. Also visible by MODIS were thick bands of thunderstorms wrapping around the storm's northern quadrant. Convection (rising air that forms the thunderstorms that make up a tropical cyclone) was seen strengthening around the eyewall.
On December 19 at 1500 UTC, Tropical Cyclone Bruce's maximum sustained winds were near 90 knots/103.6 mph/166.7 kph. Bruce was centered near 12.7 south and 90.7 east, about 330 nautical miles/379.8 miles/611.1 km west of Cocos Island, Australia. It was moving to the west-southwest at 10 knots/11.5 mph/18.5 kph.
Bruce is moving along the northern edge of an elongated area of subtropical high pressure and is expected to continue moving to the west-southwest for another three days according to the Joint Typhoon Warning Center.
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Daily Archives: 24-October-2015
Navigators use the altitudes of solar system objects to assist them with determining their positions. The most commonly used solar system objects are the Sun, Moon, Venus, and Mars. There is a small error caused by the fact that navigators are making their sextant measurements from the surface of the ocean and not from the center of the Earth, which is the reference point used by nautical almanacs. Parallax has no practical significance when measuring the positions of stars because they are so far away relative to the radius of the Earth. Continue reading → | <urn:uuid:de598912-e26a-464d-b1dd-11f3301b5711> | 3.015625 | 305 | Content Listing | Science & Tech. | 39.569827 | 95,538,534 |
A Chemist’s Perspective on the Role of Phosphorus at the Origins of Life
Received: 28 June 2017 / Revised: 6 July 2017 / Accepted: 11 July 2017 / Published: 13 July 2017
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The central role that phosphates play in biological systems, suggests they also played an important role in the emergence of life on Earth. In recent years, numerous important advances have been made towards understanding the influence that phosphates may have had on prebiotic
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The central role that phosphates play in biological systems, suggests they also played an important role in the emergence of life on Earth. In recent years, numerous important advances have been made towards understanding the influence that phosphates may have had on prebiotic chemistry, and here, we highlight two important aspects of prebiotic phosphate chemistry. Firstly, we discuss prebiotic phosphorylation reactions; we specifically contrast aqueous electrophilic phosphorylation, and aqueous nucleophilic phosphorylation strategies, with dry-state phosphorylations that are mediated by dissociative phosphoryl-transfer. Secondly, we discuss the non-structural roles that phosphates can play in prebiotic chemistry. Here, we focus on the mechanisms by which phosphate has guided prebiotic reactivity through catalysis or buffering effects, to facilitating selective transformations in neutral water. Several prebiotic routes towards the synthesis of nucleotides, amino acids, and core metabolites, that have been facilitated or controlled by phosphate acting as a general acid–base catalyst, pH buffer, or a chemical buffer, are outlined. These facile and subtle mechanisms for incorporation and exploitation of phosphates to orchestrate selective, robust prebiotic chemistry, coupled with the central and universally conserved roles of phosphates in biochemistry, provide an increasingly clear message that understanding phosphate chemistry will be a key element in elucidating the origins of life on Earth. | <urn:uuid:3c136a6b-9cd2-4ca5-b241-875ada192ad3> | 2.59375 | 419 | Truncated | Science & Tech. | 14.700308 | 95,538,535 |
Land around powerlines could be boon to birds
CONCORD, N.H. (AP) - Transmission lines may be eyesores for most people but for songbirds, the forest around them might just be critical habitat.
A team of researchers want to see if these birds are populating land cleared along the route of a powerline - as well as areas that have been recently logged - in New Hampshire and Maine.
In other parts of the country, the shrubby habitat of these younger forests have been found to offer much-needed protection for the birds from predators, as well as a steady diet of insects and fruit.
This May 2016 photo provided by Matt Tarr shows a prairie warbler in southeastern New Hampshire. Scientists will be banding scores of song birds in 2017 like the prairie warbler to better understand how they are using forests in New Hampshire and Maine that have been changed either by transmission lines or logging. (Matt Tarr via AP)
One of the researchers says these habitats are "incredibly important" for the songbirds in those parts of northern New England.
"Our goal is to get a better understanding for how these habitats function in our landscape," said Matt Tarr, a wildlife specialist at the University of New Hampshire Cooperative Extension.
Tarr and his colleagues will catch the songbirds in mist nests starting later this month, band them and then track them over the next two years. They will be focused on 24 transmission line rights of way and 12 areas that been logged in southeastern New Hampshire and southern Maine.
Tarr said there are as many as 40 species of songbirds that nest in young forests and another group that nest in mature forests.
"However, there is growing evidence suggesting that after their birds finish their nesting and the young leave the nest, they leave mature forests and come into the young forest to complete their development."
The nearly $250,000 study is being funded by the federal Natural Resources Conservation Service as well as the National Fish and Wildlife Foundation's New England Forests and Rivers Fund. A contributor to the New England fund is the utility Eversource, which has proposed the Northern Pass energy transmission project that has sparked criticism from property owners, tourism officials and others.
Northern Pass entails building a 192-mile electricity transmission line from Pittsburg to Deerfield, New Hampshire, carrying enough Hydro-Quebec energy to southern New England markets to power about a 1.1 million homes.
Tarr said the study isn't about finding an upside to transmission lines but rather trying to determine how birds use the forests that emerge after a project is built.
"It helps us understand how transmission lines function in providing that habitat on the landscape," he said.
The information they get could be critical to policymakers as they work to create more young forests for birds as well as other species like cottontail rabbits in New England.
"Do they have positive effects or do they have negative effects?" he said. "We might find these rights of way aren't used as we think they are for mature forest birds. That would be important for us to know."
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A “meat shower” is exactly what it sounds like, but it turns out there’s a pretty simple, likely explanation for what caused it.
Image: Kristopher Volkman/Flickr
On a cool March day in Kentucky in 1876, hunks of meat rained down from the sky. The event was witnessed by a farm wife, whose yard was scattered with the chunks of flesh—enough to, as was described at the time, “fill a horse wagon full.”
“I have no idea what that means, but it was published in virtually all the accounts I've seen,” Kurt Gohde, a professor of art of Transylvania University in Lexington, Kentucky, and an expert on the meat showers, said on the latest episode of Motherboard podcast Science Solved It. “In 1876, if you said, ‘Oh it was a horse wagon full of meat,’ that was like saying now, ‘It's like a big gulp from McDonalds.’ So everybody knew exactly what that meant.”
Gohde became interested in the meat showers after moving to Kentucky and picking up a book about local weather phenomena. Shortly after, while going through the school’s archives to photograph old portraits, he stumbled across an old jar with a small chunk of flesh floating in amber liquid. Based on his knowledge of the event and the dating of the jar, he was able to determine that it was a sample of that very meat shower.
At the time of the meat rain, locals were puzzled about what could have caused it. They tried to determine what kind of meat it was, with guesses that ranged from mutton to bear meat, and some neighbors were even brave enough to eat it.
“So meat falls from the sky and apparently that was not alarming enough to them to not eat it,” Gohde said.
But even after tasting it, the townspeople of Olympia Springs, where the meat fell, couldn’t surmise how it happened. Samples, like the one sent to Transylvania University, were preserved and sent to scientists around the country but before they got a chance to present their hypotheses, everyone kind of lost interest. It wasn’t until Gohde discovered a long overlooked explanation from a scientist in Kentucky that we finally got the answer: vulture vomit.
“Meat is heavy,” explained Joe Walston, the Vice President for Field Programs at the Wildlife Conservation Society “If you want to take off quickly with a huge amount of weight, the first thing you're going to do is vomit.”
Vultures don’t typically vomit from feeling sick because their stomachs are super acidic, which allows them to digest all of the gross stuff they eat, like partially-decayed carcasses. But vultures tend to gorge themselves when they eat because they don’t know when they’ll get their next meal. This means they have to sit and digest for a while after feeding, but if something startles them and they need to get airborne quickly, they have been known to vomit to lighten the load—they’ll even vomit in the air as they’re taking off, if they have to.
Walston said the theory that a group of startled, recently-fed vultures vomited causing the meat showers was a highly plausible theory, and made sense with what we know about vultures. Gohde added that the state of the meat, and the kind of tissue found in it, would also make sense for a vulture’s diet.
“It's not all like it was run through a meat slicer, so it is different sizes, and it is torn pieces. That does make sense,” Gohde said. “And it also makes sense because the scientists who [later] looked at it under a microscope didn't venture any guess as to what animal it came from. But they noticed that there was cartilage and lung tissue.”
It sounds like something from a horror film, but the truth about this story is that the only horrifying thing is that a bunch of people most likely ate chunks of vulture vomit, trying to figure out what it was.
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posted by Shana
A 30.00mL sample of 0.150M KOH is titrated with 0.125M HClO4 solution. Calculate the pH after the following volumes of acid have been added: 30.0 mL, 35.0 mL, 36.0 mL, 37.0 mL, 40.0 mL
This is a strong acid/strong base titration so the pH at the equivalence point will be 7.00. The first thing to do is to calculate where the equivalence point is.The following will do that.
mL acid x M acid = mL base x M base
mL acid x 0.125 = 30.00 x 0.150
mL acid = ?
Then set up an ICE chart for each addition of acid to the base. We start with how many moles of KOH? That is M x L = 0.150 x 0.0300 = .0045
Additions of HClO4 are
30.00 x 0.125 = 0.00375
35.00 --- you can fill
36.00 --- you can fill
40.00 --- you can fill.
..........KOH + HClO4 ==>KClO4 + H2O
The ICE chart tells you what you have at this point in the titration which for 30.00 mL is a solution of KOH and KClO4 in a volume of 60.00 mL (30.00 acid _ 30.00 base).
M KOH = moles/L = 0.00075/0.0600 = 0.0125M KOH. Then pOH = ? and obtain pH from pH + pOH = pKw = 14.
Everything up to equilvanece point is done this way. The equivalence point, as I pointed out above has a pH of 7.00, and everything after the equivalence point done the same way EXCEPT you should note that for those points its the HClO4 in excess. Post your work if you get stuck.
I am doing similar homeowrk and I was wondering how you calculate the ph after the equivalence point? | <urn:uuid:78556f7b-cf5b-48ad-bebd-8a56e9a2e3bc> | 2.9375 | 454 | Q&A Forum | Science & Tech. | 112.190001 | 95,538,557 |
posted by Boris
A method for scrubbing CO2(g) from the air on a spacecraft is to allow CO2(g) to react with NaOH according
to the following (unbalanced reaction).
NaOH(s) + CO2(g) → Na2CO3(s) + H2O(l)
Use the appropriate thermodynamic tables to calculate the enthalpy, entropy and standard Gibbs free energy
at 298K. (For the solid sodium carbonate, you need to use the following data: Molar heat capacity at constant
pressure 112.3 J/(mol K), Standard molar entropy 135 J/(mol K), Standard molar enthalpy of formation -1130.7
Any help to figure this out would be great I don't even know where to start
The problem doesn't say so but implies you want the dH, dS, dG FOR THE REACTION.
1. You have the equation, balanced it.
2. dHrxn = (n*dHf products) - (n*dHf reactants)
3. dSrxn = (n*dSf procuts) - (n*dSf reactants)
4. Then dGrxn = dHrxn - TdSrxn. Substitute and solve for dG.
Post your work if you get stuck.
The dHf and dSf you will need for Na2CO3 is listed in the problem. I presume the others are listed in your text/notes. | <urn:uuid:aa85f502-090a-4d20-945c-15511ac979ad> | 2.984375 | 329 | Q&A Forum | Science & Tech. | 87.115175 | 95,538,558 |
NEWPORT, Ore. - An unusual combination of oceanic and atmospheric events may be to blame for a mysterious and sudden die-off of numerous crabs, fish and invertebrate animals off the central Oregon coast during the past two weeks.
Oregon State University researchers who are studying near-shore ecosystems say extremely low oxygen levels - especially in the lower water column - appear to be the culprit.
"Though we are just beginning to amass the evidence, it appears that there has been a confluence of events relating to coastal upwelling and wind patterns," said Jane Lubchenco, the Wayne and Gladys Valley Professor of Marine Biology at OSU. "There isn't any sign that this was the result of human activities. It appears to be a natural event, albeit an unusual one."
Scientists first began to suspect a problem in mid-July. Oregon Department of Fish and Wildlife staff members who were surveying the near-shore ocean off Cape Perpetua with a remotely operated vehicle were surprised to find no live fish swimming in an area that in previous years had been densely populated with rockfish. This time, they saw only dead sculpins and invertebrates on the ocean floor.
Calls to ODFW soon began coming in from crabbers, who were pulling up pots that were full of Dungeness crabs, other shellfish, octopus, other invertebrates and fish - and most of them were dead. Then small numbers of dead fish and other sea life began washing ashore near Seal Rock, between Newport and Waldport on the central Oregon coast.
"Some of the crabbers offered to set their pots in certain places and ways to help us learn more," said Dave Fox, marine habitat project leader with ODFW. "There has been a real cooperative effort between the crabbers and the scientists from OSU to help us determine what happened."
Initially, Fox said, the crabbers were concerned the deaths may have been caused by naturally occurring toxins. ODFW sent samples to the Oregon Department of Agriculture for testing, and those tests came back negative.
A team of scientists led by Jane Huyer from OSU's College of Oceanic and Atmospheric Sciences has been monitoring ocean conditions off Newport and off Heceta Head several years, and as part of their routine research measured seawater conditions in mid-July. Huyer reported that the water contained some of the lowest oxygen levels the researchers had ever seen near shore.
Huyer said there is always a large pool of very low oxygen water at depths 2,500 feet below the surface, but this does not normally affect marine life near the coast. Lubchenco is co-principal investigator for another ongoing research project called the Partnership for Interdisciplinary Studies of Coastal Oceans, or PISCO. Bruce Menge, also co-principal investigator for PISCO, and his team of field researchers recorded more of the same - dead wolf eels, Dungeness crabs and sculpins as well as smaller numbers of dead ling-cod and other rockfish at sites along the central coast.
Further water samples taken by PISCO scientists aboard the university's research ship, the R/V Elakha, provided evidence to explain the mysterious die-off. "What we found were surprisingly low levels of oxygen in the water column - as low as one or two milligrams per liter, which classified it as hypoxic," said Francis Chan, a post-doctoral researcher on the PISCO project. "That means it cannot sustain most marine life.
"It is almost an unprecedented event around here," he added. "We have a lot of researchers who have been studying this part of the coast for more than 25 years who have never seen such a situation."
Brian Grantham, a research associate in OSU's Department of Zoology, said the low oxygen levels may have been the result of strong upwelling and unusual atmospheric conditions. From spring through early fall, he said, upwelling brings colder, deeper and more oxygen-depleted water close to shore. There, the high-nutrient waters are exposed to sunlight and microscopic marine plants grow abundantly. As these decay and sink, they consume some of the remaining oxygen in the water.
When summer winds are weak, the surface waters are warm, and there is reduced mixing of oxygen from the surface to the bottom. This allows the low values of oxygen at the bottom to persist and intensify, in effect, smothering much of the sea life in the area.
"If this happens for a day or two, the fish and crabs probably survive," Grantham said. "But over a period of time, perhaps 3-5 days or longer, the oxygen deprivation becomes deadly. It seems to affect the animals that stay hunkered down in one spot, particularly sculpins, wolf eels, worms and young fish. The larger fish may have the ability to swim away and find patches of water that have more oxygen."
Lubchenco said the scientists are not yet sure how widespread the hypoxic zone is, the extent of the damage to sea life, or how long it will last. OSU researchers are planning to collect more samples and download data from PISCO's network of environmental monitoring stations during the next few days to determine if low oxygen levels are still present, and to identify the physical boundaries of the problem.
ODFW also plans to take out its ROV off Cape Perpetua beginning Aug. 24.
The researchers from OSU and ODFW both reported that the water in the hypoxic zone was murky and there was an odor in the air - "kind of a strong, low-tide smell you'd find in the bay," Fox said.
Oregon is not alone in facing unusual low-oxygen phenomena. The so-called "Dead Zone" in the Gulf of Mexico is experiencing widespread loss of marine life, though the problems there are caused by agricultural runoff via the Mississippi River, said Karina Nielsen, an OSU post-doctoral researcher with PISCO. A more relevant and naturally occurring hypoxic zone takes place off South Africa, she added.
"They have an upwelling system that is similar to that of Oregon, and almost every year for the past 10 years they have seen rock lobsters literally walk out of the water and onto the beach," Nielsen said. "They are desperately looking for oxygen."
The Oregon hypoxic zone is "an unusual event that appears to be naturally occurring," according to Lubchenco.
"This is exactly why the research we are doing on near-shore ecosystems is so critical - to better understand the mechanisms behind such events, and increase our ability to respond to them in the most appropriate manner," she said.
ODFW officials are interested in learning if hypoxia has affected other parts of the coast, Fox said. Crabbers and fishermen who encounter unusual numbers of dead marine life are asked to call 541-867-4741.
The Partnership for Interdisciplinary Studies of Coast Oceans is a five-year, $20 million project funded by the David and Lucile Packard Foundation. OSU is the lead institution for the study, which also includes Stanford University, the University of California at Santa Cruz, and the University of California at Santa Barbara.
Click photos to see a full-size version. Right click and save image to download.
Jane Lubchenco (OSU), 541-737-5337 | <urn:uuid:6b829fc6-3f4d-470b-92bd-0766cb3073a5> | 2.6875 | 1,536 | News (Org.) | Science & Tech. | 40.720343 | 95,538,567 |
Bildtext får vara max två rader text. Hela texten ska högerjusteras om den bara ska innehålla fotobyline! Photo: B. Christensen/Azote
science, policy and practice
IPBES is today an international science-policy platform analogous to the IPCC. Several centre researchers are involved in breaking new ground in how research on social-ecological systems is assessed and how knowledge from very different cultures is assimilated.
Over several years, Maria Schultz, Pernilla Malmer, and Maria Tengö, all part of the Stockholm Resilience Centre’s SwedBio programme, have worked closely with indigenous peoples and local community organisations to connect indigenous and local knowledge with scientific knowledge. They have also led the development of the Multiple Evidence Base approach, which helps connect knowledge system views from indigenous, local, and scientific knowledge systems in a transparent fashion. Its work has received significant attention in the science-policy-practice community.
In 2016, centre researcher Garry Peterson was one of the editors of the IPBES methodological assessment report on scenarios and models of biodiversity and ecosystem services. The 350-page report assessed what knowledge, tools and practices exist to explore possible futures for biodiversity and ecosystem services. It identified gaps in data, knowledge, methods, and tools, and provides guidance on how to address these gaps. Peterson led the assessment of models and scenarios of ecosystem services in this report.
During the fourth IPBES plenary meeting, which took place in February 2016 in Kuala Lumpur, Malaysia (main picture), a scoping report for a global biodiversity and ecosystem assessment was approved. It was developed by an expert group including SRC director Johan Rockström and Belinda Reyers, head of the GRAID programme. During the meeting in Kuala Lumpur, IPBES also hosted a two-day stakeholder meeting where indigenous peoples and local communities connected with other stakeholders, such as environmental organisations, scientific networks, businesses, and UN bodies (pictured below). The two-days were organised by IUCN and Future Earth and facilitated by Owen Gaffney from the Stockholm Resilience Centre and Australian researcher Simone Maynard.
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New book chapter looks into the economic, cultural and ecological reasons why some people leave the fisheries and aquaculture sector, and what could be done to reverse the trend | <urn:uuid:12771d02-0326-4a41-8edf-ead89f7c2ab1> | 2.5625 | 676 | Content Listing | Science & Tech. | 18.6896 | 95,538,569 |
Virginia Institute of Marine Science
Special report in applied marine science and ocean engineering ; no. 252.
More sediment, nutrients and pollutants are discharged into an estuary during a few days of flood inflow than during many months or years of average inflow (Meade, 1972; Schubel, 1977), but few observations document the sedimentary response of an estuary to high freshwater inflow. Such inflows are usually unexpected and estuarine water charact~ristics change too rapidly to permit systematic measurements. Moreover, the expenditure of effort and number of sampling vessels required on short notice is beyond the resources of a single research group or institute. Yet, freshwater inflow observations are a key to improving water quality; especially to ameliorate the effects of high turbidity, depleted oxygen and low salinity which can cause oyster motalities (Zaborski and Haven, 1980). Many si9nificant ecological effects are noted by Snedakar, et al., 1977. Exceptional sediment deposition shoals shipping channels, fills boat basins, and blanke~ts oyster grounds. Suspended sediments adsorb toxic contaminates, nutrients and organic matter, and thus can affect plant production and the distribution of shellfish, plants and other life.
The HIFLO experiment was planned to observe and evaluate the response of an estuary to high freshwater inflow and high influx of suspended sediment. Of special interest are the questions: How far seaward does the sediment load from an event go before settling to the bed? How do the hydrodynamic conditions for sediment transport change? What is the sequence of estuarine processes triggered by a river flood?
Co-published as Chesapeake Research Consortium publication ; no. 95.
Suspended sediments -- Virginia -- Rappahannock River Estuary;Sedimentation and deposition -- Virginia -- Rappahannock River Estuary;Sedimentation and deposition -- Virginia -- Rappahannock River Estuary;
Nichols, M. M., Cronin, L. E., Cronin, W. B., Gross, M. G., Nelson, B. W., Pierce, J. W., & Ulanowicz, R. E. (1981) Response to freshwater inflow in the Rappahannock Estuary, Virginia : Operation HIFLO '78. Special report in applied marine science and ocean engineering ; no. 252.. Virginia Institute of Marine Science, College of William and Mary. https://scholarworks.wm.edu/reports/722 | <urn:uuid:288bddc2-012b-4960-9f2e-4b4ae08c8bf4> | 3.109375 | 520 | Academic Writing | Science & Tech. | 33.738605 | 95,538,572 |
Why earthquakes occur
Why do earthquakes occur? And cause such havoc? The sudden release of energy does it, we are told. What form of energy is this, and why is it suddenly released?india Updated: Mar 14, 2003 11:58 IST
Why do earthquakes occur? The sudden release of energy does it, we are told. What form of energy is this, and why is it suddenly released?
The form of energy most commonly involved is the release of elastic strain energy. Though other forms of energy are also involved, eg gravitational potential, chemical reactions, or motion of bodies, elastic strain within the crust of the Earth is the only form of energy that is stored in sufficient quantity in the Earth to produce major earthquakes. As these happen within the earth’s crust, these are called tectonic quakes (from the Greek tektonikos – of a builder). Most seismologists agree with the theory of plate tectonics, which explains the process.
Plates move in relation to each other. However, this movement is not always similar. They can move towards each other, away from each other and also slide past each other. While the moving away of plates or sliding past each other does not cause stress to be accumulated, converging plates are the danger zone. This is because as they crash against each other and one subducts below the other, enormous pressure gets built up in the rock layers.
When earthquakes occur at the boundary of plates, they are called Interplate Earthquakes. Examples of these would include those in the Himalayan region, or the Pacific quakes. Those that occur away from plate boundaries are called Intraplate earthquakes.
Those that occur in the supposedly stable parts, also usually the oldest parts, of the continental crust are called Stable Continental Region Earthquakes. The Latur earthquake would fall in this category.
If you’ve felt a major quake, you would have noticed that there are vibrations even after the main quake. An earthquake, especially a major one, is rarely a single movement. Instead the main quake is followed, and occasionally even preceded by a series of smaller quakes. As in the case of the Bhuj quake, these aftershocks may felt up to even days after the main quake. | <urn:uuid:5300fdd3-cd28-4ddd-b19d-8a7128af276a> | 3.703125 | 465 | Knowledge Article | Science & Tech. | 47.32051 | 95,538,594 |
The study, published online in the journal Proceedings of the National Academy of Sciences, found that ocean acidification can degrade not only individual species, as past studies have shown, but entire ecosystems. This results in a homogenized marine community, dominated by fewer plants and animals.
"The background, low-grade stress caused by ocean acidification can cause a whole shift in the ecosystem so that everything is dominated by the same plants, which tend to be turf algae," said lead author Kristy Kroeker, a postdoctoral researcher at the Bodega Marine Laboratory at UC Davis.
"In most ecosystems, there are lots of different colorful patches of plants and animals -- of algae, of sponges, of anemones," Kroeker said. "With ocean acidification, you lose that patchiness. We call it a loss of functional diversity; everything looks the same."
In the waters surrounding Castello Aragonese, a 14th century castle off the coast of Italy, volcanic vents naturally release bubbles of carbon dioxide gas, creating different levels of acidity among the marine-animal and plant communities there. These gradients of acidity gave the scientists a glimpse of what a future marked by increasingly acidic ocean waters could look like, and how the creatures and plants living in those environments may react to it.
The researchers selected three reef zones--of low, high and extremely high acidity, representing world ocean conditions for the present day, 2100 and 2500, respectively. Then they removed animals and vegetation from the rocks there. Every few months for three years, Kroeker dived to the study plots to photograph them and watch how the plots in each zone recovered.
By examining how recovery differed among zones, the study found that acidic water reduced the number and variety of species. In the non-acidic plots, many different plants and animals, including turf algae, would colonize and grow. Calcareous species, such as sea urchins and snails, would then eat them, allowing for variety through time.
However, in both the high and extremely high acidic plots, fleshy turf algae increased steadily and overtook the zones, as the urchins and other grazers were either not present or did not graze on the algae while in these zones.
Calcareous grazers play key roles in maintaining the balance within marine ecosystems. They are also considered among the most vulnerable species to ocean acidification.
"Our research is showing that if the role of these grazers changes with ocean acidification, you might expect to see cascading effects of the whole ecosystem," Kroeker said. "If the pattern holds for other calcareous grazers, this has implications for other ecosystems, as well."
Co-authors in the study include Maria Cristina Gambi of the Stazione Zoologica Anton Dohrn in Naples, Italy, and Fiorenza Micheli of Stanford University.
The research was supported by a National Science Foundation Graduate Research Fellowship, a Stanford University Chambers Fellowship, a Pew Fellowship in Marine Conservation and the Stazione Zoologica Anton Dohrn.
The study, "Community dynamics and ecosystem simplification in a high-CO2 ocean," will be available at http://www.pnas.org.About UC Davis
Kat Kerlin, UC Davis News Service, (530) 752-7704, firstname.lastname@example.org
Kristy Kroeker | EurekAlert!
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
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Inside the comet 67P/Churyumov — Gerasimenko there are no large voids. The mission of “Rosetta” the European space Agency made measurements that clearly demonstrated and solved the old mystery. Comets are icy debris left over from the formation of the planets 4.6 billion years ago. Spacecraft have visited a total of eight comets, and through these missions we pulled a picture of the basic properties of these space-time capsules. On some questions the answers were found, others appeared.
Comets, as we know, consist of a mixture of ice and dust, and if there were compact, gravity superior to water. However, previous measurements have shown that some of them have very low density, much lower than water ice. Low density means that the comet must be extremely porous.
But what is this porosity: due to large voids in the subsurface of the comet, or due to a more homogeneous structure with low density? Continue reading
Among all the planets of the Solar system Jupiter occupies a special position. First, it is the largest planet in our Solar system. Secondly, it is the planet having the largest number of satellites (currently known 67). Thirdly, it is not just the heaviest planet in the Solar system, and planet, the mass of which in 2.47 times the mass of all other planets combined. Ganymede, one of Jupiter’s moons, is the largest natural satellite in the Solar system. In addition, the popularity of the planet gives a local landmark – the Great red spot (BKP), which is a mysterious storm, continuing on Jupiter for hundreds of years.
It should be noted that most of the news concerning Jupiter, deals either with his companions or with BCP. It’s safe to say that much more interest for scientists is the study of the satellites it than him. Of particular interest are the moons IO and Europe . IO has a huge number of active volcanoes, for which this satellite was the status of the most geologically active satellite in the Solar system. And the ice surface of Europa conceals a liquid ocean, which literally forces scientists to look for life on this satellite. In this category of our website you southeastasia with the latest news concerning Jupiter’s moons and, of course, himself. Continue reading
April 12, Russia celebrates cosmonautics Day. This holiday was established by the decree of the Presidium of the Supreme Soviet on 9 April 1962 in honor of the world’s first manned flight into space.
April 12, 1961 in earth orbit was launched the world’s first spaceship‑satellite “Vostok” with a man on Board. The launch of the first manned space craft was headed by Sergei Korolev, Anatoly Kirillov, Leonid Voskresenskiy.
Pilot‑cosmonaut of the ship was a Soviet citizen pilot major Yuri Gagarin. The start of the space multistage rocket was successful and after the set speed and separation from the last stage of the carrier rocket, the ship began a free flight on an orbit around the Earth.
After circling the globe, through 108 minutes after launch, was included braking propulsion system and the spacecraft‑the satellite began to descend from orbit to landing. In 10 hours 55 minutes Moscow time the astronaut landed in a given area of arable land in the Volga river near village of Smelovka in the Ternovsky district of the Saratov region. Continue reading | <urn:uuid:c718bac2-f0fc-4d71-ba4a-b485ca670862> | 2.8125 | 735 | Content Listing | Science & Tech. | 47.161628 | 95,538,603 |
An anonymous reader quotes a report from Space.com: Astronomers have traced a high-energy neutrino to its cosmic source for the first time ever, solving a century-old mystery in the process. Observations by the IceCube Neutrino Observatory at the South Pole and a host of other instruments allowed researchers to track one cosmic neutrino to a distant blazar, a huge elliptical galaxy with a fast-spinning supermassive black hole at its heart. And there’s more. Cosmic neutrinos go hand in hand with cosmic rays, highly energetic charged particles that slam into our planet continuously. So, the new find pegs blazars as accelerators of at least some of the fastest-moving cosmic rays as well. Astronomers have wondered about this since cosmic rays were first discovered, way back in 1912. But they’ve been thwarted by the particles’ charged nature, which dictates that cosmic rays get tugged this way and that by various objects as they zoom through space. Success finally came from using the straight-line journey of a fellow-traveler ghost particle.
On Sept. 22, 2017, [...] IceCube picked up another cosmic neutrino. It was extremely energetic, packing about 300 teraelectron volts — nearly 50 times greater than the energy of the protons cycling through Earth’s most powerful particle accelerator, the Large Hadron Collider. Within 1 minute of the detection, the facility sent out an automatic notification, alerting other astronomers to the find and relaying coordinates to the patch of sky that seemed to house the particle’s source. The community responded: Nearly 20 telescopes on the ground and in space scoured that patch across the electromagnetic spectrum, from low-energy radio waves to high-energy gamma-rays. The combined observations traced the neutrino’s origin to an already-known blazar called TXS 0506+056, which lies about 4 billion light-years from Earth. The IceCube team also went through its archival data and found more than a dozen other cosmic neutrinos that seemed to be coming from the same blazar. These additional particles were picked up by the detectors from late 2014 through early 2015. The findings are reported in two separate studies published in the journal Science.
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Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
From classical antiquity through the 19th century, science as a type of knowledge was more closely linked to philosophy. In the West, the term natural philosophy encompassed fields of study that are currently associated with disciplines such as classical physics, astronomy and medicine and was a precursor of modern natural sciences (life science and physical science). In the 17th and 18th centuries, scientists increasingly sought to formulate knowledge in terms of laws of nature. Over the centuries, the term science became associated with the scientific method, a systematic way of studying the natural world and particularly in the 19th century, multiple distinguishing characteristics of contemporary modern science began to take shape.
Modern science is typically divided into three major branches that consist of the natural sciences (e.g. biology, chemistry, physics), which study nature in the broadest sense; the social sciences (e.g. psychology, sociology, economics), which study individuals and societies; and the formal sciences (e.g. mathematics, logic, theoretical computer science), which study abstract concepts. There is disagreement, however, on the formal sciences being a science as they do not rely on empirical evidence. Disciplines that use science, such as engineering and medicine, are described as applied sciences.
Science is related to research and is commonly organized by academic and research institutions as well as government agencies and companies. The practical impact of scientific research has led to the emergence of science policies that seek to influence the scientific enterprise by prioritizing the development of commercial products, armaments, health care, and environmental protection.
(born February 9, 1963, New York
), is a physicist
at Columbia University
. His book The Elegant Universe: Superstrings, Dimensions, and the Quest for the Ultimate Theory
was a finalist for the Pulitzer Prize
in nonfiction, and winner of The Aventis Prizes for Science Books
. The Elegant Universe
was later made into a PBS
television special with Dr. Greene as the narrator. His second book, The Fabric of the Cosmos
(2004), is about space
, and the nature of the universe. Aspects covered in this book include non-local particle entanglement as he relates to special relativity
and basic explanations of string theory. It is an examination of the very nature of matter and reality, covering such topics as spacetime
, origins and unification, and including an exploration into reality and the imagination.
Did you know... | <urn:uuid:ff5c8992-e06f-49c0-9872-aa8a62dccebe> | 3.453125 | 531 | Knowledge Article | Science & Tech. | 26.018653 | 95,538,652 |
- Views 1753
The real time Samoa SST monitoring buoys whose temperature you see are probably SOUTH of Tutuila in the approaches to Pago Pago Harbor?
The hot water is NORTH of Tutuila, Upolu, and Savaii, and has intensified in recent weeks, but is being restrained by a marine thermal front just to the south of the Samoan Islands (West and East). If you’re lucky that front will move northward, but if it moves southward, be prepared for sudden change and bleaching.
On adaptation, we have known for a hundred years that there were coral populations acclimated to local higher temperatures, but that is not the same thing as adaptation to global warming. For example, the corals in the Persian Gulf, adapted to the highest temperatures of all, bleach at the same Hotspot intensity as elsewhere in the world, and in fact almost all of them have already died from repeated high temperature coral bleaching events. The Mariana Islands, which you mention below as a possible haven from bleaching, are far from that, and have also suffered repeated bleaching events.
As you point out, a great deal of publicity, and funding, has been given to those who are saying what people want to hear: “no problem, resilient corals will just adapt to global warming”. If corals were really adapting we would surely have seen a change in the thresholds since 1982? If thermal adaptation is really out there, it is still buried in the noise.
Time will tell if coral adaptation is actually happening, but so far I see no convincing evidence of any change in the HotSpot bleaching temperature-time thresholds that I worked out from satellite data in the 1980s, those thresholds still work just as well now to predict bleaching, and there has not been any noticeable change in them yet, although there are certainly less and less of the more sensitive corals around to bleach!
Claims have been made that corals in the northern third of the Great Barrier Reef in particular were already adapting their thresholds or were more resistant to high temperature bleaching. What we are hearing so far about the current bleaching event indicates severe coral mortality, more than 50%, has already happened, even though the mortality is not yet over, and this was only a mild bleaching event in term of the HotSpot intensity times duration. In fact the thermal stress in the GBR was much less than that suffered by most other areas being affected in this El Niño. If anything this extreme mortality response to so brief a stress seems to strongly suggest that either these corals are NOT more resistant as claimed, but if anything, more sensitive!
Time will also tell how the corals in many other places being affected, most not yet being reported, actually respond, because many if not most of those locations suffered greater thermal stress than the GBR did this year. We won’t know until the end of the year.
In our reviews of the global patterns of coral bleaching and HotSpots since 1982, specifically those in 1998, and the 1987 (2nd Global) Bleaching Event, Ray Hayes, Bert Williams, Don McAllister and I concluded this would happen again in the next major El Niño. Indeed, so had Peter Glynn back after the First Global Bleaching Event in 1982. We simply were lucky that the next El Niño, which should have come around 4 years later, took 18 long years to return! There’s no surprise in what is happening now, and coupled with global warming, this event could kill most of the world’s remaining corals this year. Time will tell.
The world has fooled itself that mass coral bleaching was “unexplained” for three decades after it was clear that coral reefs were the most vulnerable ecosystems to global warming, were already at their upper temperature limit, and could take no further warming. All the governments, funding agencies, and BINGOs (Big International NGO, like TNC) have wasted money on marine “protected” areas full of dying corals which were proclaimed to be “resilient” by their managers. Corals are dying just as fast in MPAs as outside them: In 60 years of diving all over the world I’ve never seen a marine protected area with more corals in it than if it had never been protected at all!
There has been ZERO funding to prepare for the severe bleaching events we knew would come by preparing with Biorock Coral Arks, shown in 1998 to have 1600% to 5000% higher coral survival from severe high temperature thermal stress than nearby corals, except in Indonesia and Panama, run without funding by community groups.
Hopefully at the end of this Global Bleaching Event (which is very far from the third!) we will learn the lessons we have repeatedly failed to learn from all the preceding ones! But unfortunately for many, if not most, places it will unfortunately be too late. | <urn:uuid:b66841a0-78d9-40bc-886e-45ac9cce49d6> | 2.65625 | 1,024 | Comment Section | Science & Tech. | 41.389325 | 95,538,653 |
These convulsions flung primordial material billions of miles from the hot, inner regions of the gas cloud that later collapsed to form the sun, out into the cold, nether regions of the solar system, where they became incorporated into an icy comet.
“If you take a gas of solar composition and let it cool down, the very first minerals to solidify are calcium and aluminum-rich,” said Steven Simon, Senior Research Associate in Geophysical Sciences at the University of Chicago. And comet Wild 2 does contain these and other minerals formed at high temperatures. “That’s an indication of transport from the inner solar system to the outer solar system, where comets are thought to have formed,” he said.
Simon presents his data in the November 2008 issue (expected to be published early next year) of Meteoritics and Planetary Science. His 11 co-authors include Lawrence Grossman, Professor in Geophysical Sciences at the University of Chicago.
Either turbulence within the nebula, or a phenomenon called bipolar outflow from the early sun could account for the long-distance transport of cometary material, according to Simon and his Meteoritics co-authors.
Bipolar outflow results when the rotating disks that surround developing new stars jet gas from their polar regions, which astronomers have observed telescopically. “That’s part of the so-called X-wind model, which is somewhat controversial,” Simon said.
The controversial aspect of the X-wind model is the claim that the process would produce the kind of granules that Simon and his colleagues have now identified in comet Wild 2. Another less likely possibility: The cometary material in question may have formed around another star of composition similar to the sun, then drifted into the outer reaches of the solar system. There it became incorporated into comet Wild 2.
The extraterrestrial dust particles that Simon and his colleagues examined were among thousands that NASA’s Stardust spacecraft collected from comet Wild 2 in January 2004. Two years later, Stardust became the first mission to return samples of a comet to Earth.
Simon, Grossman and collaborators identified all three particles described in the Meteoritics study as pieces of a shattered refractory inclusion, one of the most unusual and informative materials discovered in early analyses of the Wild 2 samples. Such inclusions, found in some meteorites, formed by condensation from the gas in the solar nebula at temperatures of more than 2,500 degrees Fahrenheit early in the history of the solar system.
The three particles were named Inti, Inti-B and Inti-C, after the Incan sun god. The original, unbroken particle would have measured no more than 30 microns across, much narrower than a human hair.
As Simon, Grossman and a team of colleagues reported in 2006, Inti contains a suite of minerals that likely were forged in fiery conditions found deep inside the cloud of gas and dust that formed the sun, Earth and the planets. And yet comets probably formed in the outer reaches of the solar system, far beyond Neptune.
Contributing to an array of scientific analyses in the Meteoritics article were co-authors David Joswiak, Donald Brownlee and Graciela Matrajt of the University of Washington; Hope Ishii, John Bradley, Miaofang Chi, Jerome Aléon, Stewart Fallon and Ian Hutcheon of Lawrence Livermore National Laboratory in California; and Kevin McKeegan of the University of California, Los Angeles.
Most of this team, including Simon and Grossman, were among the 75 co-authors who published the first analysis of the comet Wild 2 particles in the Dec. 15, 2006, issue of the journal Science. A striking aspect of the Science and Meteoritics studies is the similarity in chemical composition between the Wild 2 samples and particles from carbonaceous chondrite meteorites. These meteorites contain material that has been unaltered since the birth of the solar system 4.5 billion years ago.
Equally striking is the complete lack of any water-bearing minerals in the cometary grains. Carbonaceous chondrites are rich in hydrated silicates, clay-like minerals that emit water when heated, “but there’s no hydrated silicate in the comet sample,” Grossman said.Scientists organized the Stardust mission with the expectation that Wild 2’s samples would reveal a bonanza of exotic minerals, including debris from stars that had met their demise long before the birth of the sun. They may need to
rethink how comets formed, according to Grossman.
“Because they’re loaded with ices we’ve always thought that these are outer solar system objects,” he said. “But maybe cometary ices formed much closer in, after the inner part of the solar nebula cooled off, and incorporated the high-temperature stuff that formed earlier.”
The Stardust mission was scientifically important because comets are usually out of reach, Grossman said. And yet aside from the sun, they may be the most abundant material in the solar system. “There may be more stuff in the comets than in all the planets put together,” he said.
Steve Koppes | Newswise Science News
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Timing of arrival/emergence to the breeding grounds is under contrasting natural and sexual selection pressures. Because of differences in sex roles and physiology, the balance between these pressures on either sex may differ, leading to earlier male (protandry) or female (protogyny) arrival. We test several competing hypotheses for the evolution of protandry using migration data for 22 bird species, including for the first time several monochromatic ones where sexual selection is supposedly less intense. Across species, protandry positively covaried with sexual size dimorphism but not with dichromatism. Within species, there was weak evidence that males migrate earlier because, being larger, they are less susceptible to adverse conditions. Our results do not support the 'rank advantage' and the 'differential susceptibility' hypotheses, nor the 'mate opportunity' hypothesis, which predicts covariation of protandry with dichromatism. Conversely, they are compatible with 'mate choice' arguments, whereby females use condition-dependent arrival date to assess mate quality.
Mendeley saves you time finding and organizing research
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|Asp viper, V. aspis|
Vipera is a genus of venomous vipers. It has a very wide range, being found from North Africa to just within the Arctic Circle and from Great Britain to Pacific Asia. The name is possibly derived from the Latin words vivus and pario, meaning "alive" and "bear" or "bring forth"; likely a reference to the fact that most vipers bear live young. Currently, 23 species are recognized.
The members of this genus tend to be stout and small in size, the largest of them, V. ammodytes, can reach a maximum length of 95 cm and the smallest, V. monticola, reaches a maximum length of 40 cm.
The heads of the members of this genus are clearly separated from the body, they are triangular in shape and in most species are covered in small scales, although in some species, notably V. berus, have small plates on the top of their heads. These old world vipers tend to have a single nasal scale that may sometime be fused with a prenasal scale like in the case of V. albicornuta. Most species have large supraocular scales that tend to extend beyond the posterior margin of the eye. Some species also have some sort of horn on the head, either right behind the nasal scale, or behind the supraocular scales.
The color scheme and camouflage of the members of this genus vary widely, from a grayish ground color with dark brown transverse bands in the case of V. albizona to browner colors with grey transverse bands edged with black in the case of V. ammodytes.
They can be found all around the Old World, hence the common name of the genus, "Old World vipers". they can be found most notably in Europe, from Portugal to Turkey. They can also be found on some islands in the Mediterranean sea (Sicily, Elba and Montecristo), the United Kingdom. They can also be found in the Maghreb region of Africa with species living in Morocco (V. monticola) and northern parts of Algeria and Tunisia in the case of V. latastei. Many species can also be found in the Caucasus mountains, parts of Iraq, Jordan, Israel and Syria. Only one species (V. berus) discovered so far lives in East Asia, most notably North Korea, northern China and northern Mongolia.
Most species prefer cooler environments. Those found at lower latitudes tend to prefer higher altitudes and dryer, rocky habitats, while the species that occur at more northern latitudes prefer lower elevations and environments that have more vegetation and moisture.
Most Vipera species have venom that contains both neurotoxic and haemotoxic components. Bites vary widely in severity.
V. ammodytes is most likely the one with the most toxic venom. In a study solely involving mice, Brown (1973) shows that the LD50 is about 1.2/mg/kg through an IV, 1.5 mg/Kg when injected in the peritoneum (IP) and 2.0 mg/kg when administered subcutaneously.
V. berus venom is considered to be on the lower end of the scale when it comes to toxicity, (Minton, 1974) suggests that the LD50 values for mice are about 0.55 mg/kg IV, 0.80 mg/kg IP and 6.45 mg SC. Venom yield tends to be lower in this species with Minton citing 10–18 mg per bite in specimens 48–62 cm while Brown suggest only 6 mg for the same sized specimens.
However, bites from Vipera species are rarely as severe as those from larger Macrovipera or Daboia.
|Image||Species||Taxon author||Subsp.*||Common name||Geographic range|
|V. albicornuta||Nilson & Andrén, 1985||0||Iranian mountain viper||The Zanjan Valley and surrounding mountains in northwestern Iran.|
|V. albizona||Nilson, Andrén & Flärdh, 1990||0||Central Turkish mountain viper||Central Turkey.|
|V. ammodytes||(Linnaeus, 1758)||4||Horned viper||North-eastern Italy, southern Slovakia, western Hungary, Slovenia, Croatia, Bosnia-Herzegovina, Serbia, Montenegro, Albania, Republic of Macedonia, Greece (including Macedonia and Cyclades), Romania, Bulgaria, Turkey, Georgia and Syria.|
|V. aspisT||(Linnaeus, 1758)||4||Asp viper||France, Andorra, northeastern Spain, extreme southwestern Germany, Switzerland, Monaco, the islands of Elba and Montecristo, Sicily, Italy, San Marino and northwestern Slovenia.|
|V. barani||Böhme & Joger, 1984||0||Baran's adder||Northwestern Turkey.|
|V. berus||(Linnaeus, 1758)||2||Common European adder||From western Europe (Great Britain, Scandinavia, France) across central (Italy, Albania, Bulgaria and northern Greece) and eastern Europe to north of the Arctic Circle, and Russia to the Pacific Ocean, Sakhalin Island, North Korea, northern Mongolia and northern China.|
|V. bornmuelleri||F. Werner, 1898||0||Bornmuellers viper||Golan Heights, southern Lebanon and Syria.|
|V. bulgardaghica||Nilson & Andrén, 1985||0||Bulgardagh viper||The Bulgar Dagh (Bolkar Dagi) mountains, Nigde Province, south central Anatolia, Turkey.|
|V. darevskii||Vedmederja, Orlov & Tuniyev, 1986||0||Darevsky's viper||The southeastern Dzavachet Mountains in Armenia and adjacent areas in Georgia.|
|V. dinniki||Nikolsky, 1913||0||Dinnik's viper||Russia (Great Caucasus) and Georgia (high mountain basin of the Inguri River), eastward to Azerbaijan.|
|V. kaznakovi||Nikolsky, 1909||0||Caucasus viper||Northeastern Turkey, Georgia and Russia (eastern Black Sea coast.|
|V. latastei||Boscá, 1878||1||Lataste's viper||Extreme southwestern Europe (France, Portugal and Spain) and northwestern Africa (the Mediterranean region of Morocco, Algeria and Tunisia).|
|V. latifii||Mertens, Darevsky & Klemmer, 1967||0||Latifi's viper||Iran: upper Lar Valley in the Elburz Mountains.|
|V. lotievi||Nilson et al., 1995||0||Caucasian meadow viper||The higher range of the Big Caucasus: Russia, Georgia and Azerbaijan.|
|V. monticola||Saint-Girons, 1954||0||Atlas mountain viper||High Atlas Mountains, Morocco.|
|V. nikolskii||Vedmederja, Grubant & Rudajewa, 1986||0||Nikolsky's viper||Central Ukraine.|
|V. orlovi ||Tuniyev & Ostrovskikh, 2001||0||Orlov's viper||Western Caucasus.|
|V. palaestinae||F. Werner, 1938||0||Palestine viper||Syria, Jordan, Israel and Lebanon.|
|V. pontica||Billing, Nilson & Sattler, 1990||0||Pontic adder||Known only from the Coruh valley in Artvin Province, northeastern Turkey.|
|V. raddei||Boettger, 1890||0||Rock viper||Eastern Turkey, northwestern Iran, Armenia, Azerbaijan, and probably Iraq.|
|V. seoanei||Lataste, 1879||1||Baskian viper||Extreme southwestern France and the northern regions of Spain and Portugal.|
|V. ursinii||(Bonaparte, 1835)||0||Meadow viper||Southeastern France, eastern Austria (extinct), Hungary, central Italy, Croatia, Bosnia-Herzegovina, northern and northeastern Albania, Romania, northern Bulgaria, Greece, Turkey, northwestern Iran, Armenia, Azerbaijan, Georgia, Russia and across the Khazakstan, Kirgizia and eastern Uzbekistan steppes to China (Xinjiang).|
|V. wagneri||Nilson & Andrén, 1984||0||Ocellated mountain viper||The mountains of eastern Turkey and adjacent northwest Iran.|
|V. xanthina||(Gray, 1849)||0||Rock viper||Extreme northeastern Greece, the Greek islands of Symi, Kos, Kalimnos, Leros, Lipsos, Patmos, Samos, Chios and Lesbos, European Turkey, the western half of Anatolia (inland eastward to Kayseri), and islands (e.g. Chalki, Kastellórizon [Meis Adasi]) of the Turkish mainland shelf.|
* Not including the nominate subspecies. T: type species
- List of viperine species and subspecies
- Viperinae by common name
- Viperinae by taxonomic synonyms
- McDiarmid RW, Campbell JA, Touré TA. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, Volume 1. Washington, District of Columbia: Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
- Spawls S, Branch B. 1995. The Dangerous Snakes of Africa: Natural History, Species Directory, Venoms and Snakebite. Sanibel Island, Florida: Ralph Curtis Books/Dubai: Oriental Press. 192 pp. ISBN 0-88359-029-8.
- Mallow D, Ludwig D, Nilson G. 2003. True Vipers: Natural History and Toxinology of Old World Vipers. Malabar, Florida: Krieger Publishing Company. 359 pp. ISBN 0-89464-877-2.
- Gotch AF. 1986. Reptiles -- Their Latin Names Explained. Poole, UK: Blandford Press. 176 pp. ISBN 0-7137-1704-1.
- "Vipera". Integrated Taxonomic Information System. Retrieved 13 August 2006.
- Brown JH. 1973. Toxicology and Pharmacology of Venoms from Poisonous Snakes. Springfield, Illinois: Charles C. Thomas. 184 pp. LCCCN 73-229. ISBN 0-398-02808-7.
- Minton SA Jr. 1974. Venom Diseases. Springfield, Illinois: CC Thomas Publ. 256 pp. ISBN 978-0-398-03051-3.
- "Vipera orlovi ". The Reptile Database. www.reptile-database.org.
- Beolens B, Watkins M, Grayson M. 2011. The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. ISBN 978-1-4214-0135-5. (Vipera orlovi, pp. 196-197).
- Arnold EN, Burton JA. 1978. A Field Guide to the Reptiles and Amphibians of Britain and Europe. London: Collins. 272 pp. ISBN 0-00-219318-3. (Genus Vipera, pp. 211, 214.)
- Boulenger GA. 1896. Catalogue of the Snakes in the British Museum (Natural History). Volume II., Containing the...Viperidæ. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers.) xiv + 727 pp. + Plates I.- XXV. (Genus Vipera, pp. 471–472.)
- Laurenti JN. 1768. Specimen medicum, exhibens synopsin reptilium emendatam cum experimentis circa venena et antidota reptilium austriacorum. Vienna: "Joan. Thom. Nob. de Trattern". 214 pp. + Plates I.- V. (Genus Vipera, p. 99.)
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Vertical variation in the distribution of rocky shore assemblages is greater than horizontal variation, as shown by univariate and multivariate analysis performed with data obtained along 1000km of shoreline and covering from the upper supralittoral to the upper infralittoral zone (-1m). Consequently, vertical littoral zonation is a consistent pattern at a regional scale within the same biogeographical zone. While their distribution varies at the same shore height, marine species and assemblages from rocky shores show a specific vertical sequence known as zonation. A key question in ecology is how consistent is zonation along large spatial scales. The aim of this study is to show distribution patterns of littoral assemblages at a regional scale and to identify the most relevant abiotic factors associated to such patterns. The study is based on a detailed and extensive survey at a regional scale on a tideless rocky shore. Benthic macroflora and macrofauna of 750 relevés were described along the vertical axis of 143 transects distributed across the shoreline of Catalonia (NW Mediterranean). The Detrended Correspondence Analysis (DCA) first axis is highly related to the height on the shore: species, relevés, and assemblages grade from lower to upper height (infralittoral to supralittoral). As observed in nature, different assemblages co-occur at the same height at different sites, which is shown along DCA second axis. The abiotic variables that best explain the assemblage distribution patterns are: height (75% of the model inertia), longitude (14.6%), latitude (7.2%) and transect slope (2.9%). The Canonical Correspondence Analysis (CCA) first axis is related to height on the shore and explains four times more variance than CCA second axis, which is related to the horizontal gradient. Generalized Lineal Model (GLM) results show that height on the shore is the factor explaining most of the variance in species presence. Most studied species show distribution patterns related to latitude and longitude, but always in a much smaller proportion than to height. © 2014 The Authors.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:dabc2a4d-7a16-436a-982e-03d05bf57239> | 3 | 469 | Academic Writing | Science & Tech. | 24.550882 | 95,538,673 |
27 Sep 2017, 10:07 • c++, python • 808 views
The fixpoint operator (\(\mu\)) on functions provides a way of converting nonrecursive functions into recursive ones. Let's learn how to implement it in Python and C++.
26 Sep 2017, 09:20 • c++, algebraic types • 125 views
The recently released C++17 provides a new type,
std::variant, for implementing sum types. This post focusses on its basic use.
3 Oct 2017, 07:07 • c++, catamorphism • 2160 views
In functional programming, fixpoints of data types are used to define recursive types. Let’s see an example of how one can use this technique in C++.
15 Oct 2017, 17:02 • monads, c++ • 191 views • 1 comment
Implementing monads in C++ is a little tricky, since there are no higher-kinded types. We can however use template specialisation to achieve the same effect. | <urn:uuid:6ae177f1-99ed-4bf8-8c3f-1bc01caa5de3> | 2.5625 | 216 | Content Listing | Software Dev. | 68.345625 | 95,538,685 |
One of just three jaguars known to be living in the U.S. was recently killed by poachers. Experts identified the jaguar’s pelt in a recent photo and say it is Yo’oko, a male jaguar (Panthera onca) that was known to roam the Huachuca Mountains in southern Arizona, the Arizona Daily Star reported.
The rosette patterns on a jaguar’s pelt are unique to each individual, a trait that allowed officials with the Arizona Game and Fish Department to identify Yo’oko’s pelt in a photo sent to them from the Tucson-based Northern Jaguar Project. The endangered carnivore had been photographed near the Mexican border in Arizona several times in 2016 and 2017, according to the Center for Biological Diversity, a nonprofit organization focused on protecting endangered species.
It’s unclear when Yo’oko died or who killed him, but the Arizona Daily Star reported today (June 28) that he may have been killed by a mountain lion hunter. A local rancher, Carlos Robles Elias, told the Arizona Daily Star that he heard from a friend that the jaguar was trapped and killed six months ago somewhere in Sonora, Mexico, near the U.S. border. [Photos: Elusive Jaguars Take Center Stage]
It’s illegal to hunt or kill jaguars, which are an endangered species, and a jaguar may not have been what Yo’oko’s killer was after. Elias told the Arizona Daily Star that he suspects a hunter was hired to trap a mountain lion, which are legal to kill in Arizona, but caught Yo’oko instead. Ranchers in the area go after mountain lions and other predators that eat calves and threaten the ranchers’ livelihood, the Arizona Daily Star reported.
The Northern Jaguar Project, a nonprofit working to conserve jaguars, has declined to share the source of the pelt photo. The group doesn’t want to risk losing the trust of ranchers and farmers in the area, whose support the group depends on for conserving endangered native species like jaguars, the Arizona Daily Star reported.
Seven jaguars have been photographed in the U.S. in the past 20 years, although in the last three years, experts have spotted only three of the wild cats, according to the Center for Biological Diversity. However, jaguars once lived throughout the Southwest, from Louisiana to Southern California. Hunting and habitat loss over the past 150 years has decimated the population and jaguars have been listed as endangered by the U.S. Fish and Wildlife Service since 1972.
Original article on Live Science. | <urn:uuid:2d80def8-5526-48ea-bfdb-9b765b1c37fd> | 2.671875 | 559 | Truncated | Science & Tech. | 48.254356 | 95,538,688 |
AWI researchers model climate changes caused by the submersion of the Greenland-Scotland Ridge
The Arctic Ocean was once a gigantic freshwater lake. Only after the land bridge between Greenland and Scotland had submerged far enough did vast quantities of salt water pour in from the Atlantic. With the help of a climate model, researchers from the Alfred Wegener Institute have demonstrated how this process took place, allowing us for the first time to understand more accurately how Atlantic circulation, as we know it today came about. The results of the study have now been published in the journal Nature Communications.
Every year, ca. 3,300 cubic kilometres of fresh water flows into the Arctic Ocean. This is equivalent to ten percent of the total volume of water that all the world’s rivers transport to the oceans per year. In the warm and humid climate of the Eocene (ca. 56 to 34 million years ago), the inflow of freshwater was probably even greater.
However, in contrast to today, during that geological period there was no exchange of water with other oceans. The influx of saline Atlantic and Pacific water, which today finds its way into the Arctic Ocean from the Pacific via the Bering Strait and from the North Atlantic via the Greenland-Scotland Ridge, wasn’t possible – the region that is today completely submerged was above the sea at that time.
Only once the land bridge between Greenland and Scotland disappeared did the first ocean passages emerge, connecting the Arctic with the North Atlantic and making water exchange possible. Using a climate model, researchers from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have now successfully simulated the effect of this geological transformation on the climate.
In their simulations, they gradually submerged the land bridge to a depth of 200 metres. “In reality, this tectonic submersion process lasted several million years,” says Climate Scientist Michael Stärz, first author of the study. “Interestingly, the greatest changes in the circulation patterns and characteristics of the of the Arctic Ocean only occurred when the land bridge had reached a depth of over 50 metres below the surface.”
This threshold depth corresponds to the depth of the surface mixed layer, and determines where the relatively light Arctic surface water ends and the underlying layer of inflowing North Atlantic water begins. “Only when the oceanic ridge lies below the surface mixed layer can the heavier saline water of the North Atlantic flow into the Arctic with relatively little hindrance,” explains Stärz.
“Once the ocean passage between Greenland and Scotland had reached this critical depth, the saline Arctic Ocean as we know it today was created.” The formation of ocean passages plays a vital role in global climate history, as it leads to changes in heat transport in the ocean between the middle and polar latitudes.
The theory that the Arctic Basin was once isolated is supported by the discovery of freshwater algae fossils in Eocene deep-sea sediments that have been obtained during international drilling near the North Pole in 2004. What was once a land bridge now lies ca. 500 metres under the ocean and consists almost entirely of volcanic basalt. Iceland is the only section remaining above the surface.
Notes for Editors
Original publication in Nature Communications:
Michael Stärz, Wilfried Jokat, Gregor Knorr, Gerrit Lohmann: „Threshold in North Atlantic-Arctic Ocean circulation controlled by the subsidence of the Greenland-Scotland Ridge“ DOI: 10.1038/ncomms15681.
Printable images are available at: https://www.awi.de/nc/en/about-us/service/press/press-release/wie-der-arktische-...
Your contact person at the Dept. of Communications and Media Relations is Sebastian Grote, tel. +49 (0) 471 4831-2006 (e-mail: sebastian.grote(at)awi.de).
Your scientific contact person is Dr Gregor Knorr, tel. +49 (0) 471 4831-1769 (e-mail: gregor.knorr(at)awi.de).
The Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) conducts research in the Arctic, Antarctic and oceans of the high and mid-latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctica. The Alfred Wegener Institute is one of the 18 research centres of the Helmholtz Association, the largest scientific organisation in Germany.
Ralf Röchert | idw - Informationsdienst Wissenschaft
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:c9d322c7-1ac4-41d8-8458-6386fc54021c> | 3.484375 | 1,605 | Content Listing | Science & Tech. | 41.013769 | 95,538,693 |
Nearly half of the organic carbon stored in soil around the world is contained in Arctic permafrost, which has experienced rapid melting, and that organic material could be converted to greenhouse gases that would exacerbate global warming.
When permafrost thaws, microbial consumption of those carbon reserves produces carbon dioxide - much of which eventually winds up in the atmosphere, but scientists have been unsure of just how the system works.
A new study published this week in Nature Communications outlines the mechanisms and points to the importance of both sunlight and the right microbial community as keys to converting permafrost carbon to CO2. The research was supported by the U.S. National Science Foundation and the Department of Energy.
"We've long known that microbes convert the carbon into CO2, but previous attempts to replicate the Arctic system in laboratory settings have failed," noted Byron Crump, an Oregon State University biogeochemist and co-author on the study. "As it turns out, that is because the laboratory experiments did not include a very important element - sunlight.
"When the permafrost melts and stored carbon is released into streams and lakes in the Arctic, it gets exposed to sunlight, which enhances decay by some microbial communities, and destroys the activity for other communities. Different microbes react differently, but there are hundreds, even thousands of different microbes out there and it turns out that the microbes in soils are well-equipped to eat sunlight-exposed permafrost carbon."
The research team from Oregon State and the University of Michigan was able to identify compounds that the microbes prefer using high-resolution chemistry and genetic approaches. They found that sunlight makes permafrost soils tastier for microbes because it converts it to the same kinds of carbon they already like to eat - the carbon they are adapted to metabolize.
"The carbon we're talking about moves from the soil into rivers and lakes, where it is completely exposed to sunlight," Crump said. "There are no trees and no shade, and in the summer, there are 24 hours a day of sunlight. That makes sunlight potentially more important in converting carbon into CO2 in the Arctic than in a tropical forest, for example."
As the climate continues to warm, there are interesting ramifications for the Arctic, said Crump, who is a faculty member in OSU's College of Earth, Ocean, and Atmospheric Sciences.
"The long-term forecast for the Arctic tundra ecosystem is for the warming to lead to shrubs and bigger plants replacing the tundra, which will provide shade from the sunlight," Crump said. "That is considered a negative feedback. But there also is a positive feedback, in that seasons are projected to expand. Spring will arrive earlier, and fall will be later, and more water and carbon will enter lakes and streams with more rapid degradation of carbon.
"Which feedback will be stronger? No one can say for sure."
The stakes are high, Crump said. There is more carbon stored in the frozen permafrost than in the atmosphere. It has accumulated over millions of years by plants growing and dying, with a very slow decaying process because of the freezing weather.
"Some of the organic matter is less tasty to microbes than others," Crump said, "but bacterial communities are diverse, so there will be something out there that wants that energy and will use it."
Byron Crump | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:1ee693c8-cd97-4dd0-8353-9775bca50e59> | 4.25 | 1,319 | Content Listing | Science & Tech. | 40.398996 | 95,538,704 |
"C W" wrote in message
I am new to OOP. I'm a bit confused about the following code.
def __init__(self, time):
self.time = time
time = '6:30'
clock = Clock('5:30')
I set time to 6:30, but it's coming out to 5:30. I guess it's because I
passed in 5:30, so, it's replaced?
In print_time(), the variable 'time' is not the same as the variable
'time', a local variable, is set to '6:30'.
'self.time', an instance variable, is set to '5:30'.
You printed self.time, hence the result. | <urn:uuid:a4e21f49-fa10-458d-8b35-1e5396341179> | 2.6875 | 160 | Comment Section | Software Dev. | 93.3865 | 95,538,705 |
National Center for
3PMF: Crystal structure of Staphylococcal nuclease variant Delta+PHS V23A at cryogenic temperature
Proc. Natl. Acad. Sci. U. S. A. (2012) 109 p.6945-6950
It has been known for nearly 100 years that pressure unfolds proteins, yet the physical basis of this effect is not understood. Unfolding by pressure implies that the molar volume of the unfolded state of a protein is smaller than that of the folded state. This decrease in volume has been proposed to arise from differences between the density of bulk water and water associated with the protein, from pressure-dependent changes in the structure of bulk water, from the loss of internal cavities in the folded states of proteins, or from some combination of these three factors. Here, using 10 cavity-containing variants of staphylococcal nuclease, we demonstrate that pressure unfolds proteins primarily as a result of cavities that are present in the folded state and absent in the unfolded one. High-pressure NMR spectroscopy and simulations constrained by the NMR data were used to describe structural and energetic details of the folding landscape of staphylococcal nuclease that are usually inaccessible with existing experimental approaches using harsher denaturants. Besides solving a 100-year-old conundrum concerning the detailed structural origins of pressure unfolding of proteins, these studies illustrate the promise of pressure perturbation as a unique tool for examining the roles of packing, conformational fluctuations, and water penetration as determinants of solution properties of proteins, and for detecting folding intermediates and other structural details of protein-folding landscapes that are invisible to standard experimental approaches. | <urn:uuid:f74bac8c-1292-43b3-9793-200edb94fb8b> | 2.546875 | 348 | Knowledge Article | Science & Tech. | 26.185909 | 95,538,720 |
Hormone sensitive gene regulation in seasonal singing birds
Nature lovers are fascinated by the increasing number of singing birds when spring is approaching. Scientists also take advantage of this seasonal phenomenon because they are able to investigate the underlying mechanism, however the evolutionary and molecularbiological background is largely unknown.
A team of researchers from the Max Planck Institute for Ornithology in Seewiesen and from the Max Planck Institute for Molecular Genetics in Berlin have now identified the genome of the canary. With these data they were able to decipher the evolution of hormone-sensitive gene regulation in seasonal singing birds.
Canaries have been domesticated since the 15th century and are the descendants of the wild canary that lives on the Azores, Madeira and Canary Islands in the North Atlantic Ocean. Like their wild ancestors, domesticated canaries sing stereotyped songs under long-day (breeding) conditions and more variable songs under short-day (non-breeding) photoperiods.
The canary has become a preferred model to investigate the neurological changes affecting hormone-dependent song. This is because it has a pronounced reproductive season, with seasonal changes in song and steroid hormone concentrations, and a varying degree of brain plasticity between the breeding and the non-breeding season.
A team of researchers from the department of Behavioural Neurobiology around Manfred Gahr at the Max Planck Institute for Ornithology in Seewiesen and from the Sequencing Core Facility under guidance of Bernd Timmermann from the Max Planck Institute for Molecular Genetics in Berlin together with colleagues from Brazil and the UK now have studied how hormone-sensitive gene regulation has evolved in songbirds. The work resulted in the first high quality assembly and annotation of a female canary genome. In birds, females are the ‘heterogametic’ sex (ZW) and therefore the analysed genome sequence contained both types of sex chromosomes, says Heiner Kuhl from the Max Planck Institute for Molecular Genetics.
Whole genome alignments between the canary and already identified genomes throughout the bird taxa showed that on a global scale bird genomes are quite similar. However, differences appeared when comparisons were conducted on a finer scale. For example, at the level of the nucleotide there are considerable species differences, which can impact small genetic sequences, such as steroid hormone receptor binding sites. Such differences in these regions might lead to major differences in gene regulation, even between closely related species, says Carolina Frankl-Vilches from the Max Planck Institute for Ornithology.
Following this global analysis the scientists focused on gene networks that had three characteristics – were showing enrichment or under-representation in the expression profiles of the song control regions HVC and RA, showed seasonality, and were testosterone-sensitive. To verify whether the hormone-sensitive elements among these genes are specific for the canary, they also looked at the genes of the zebra finch because this species did not evolve hormone-sensitive song expression. Among all HVC expressed genes, including the seasonal and testosterone-induced gene pools, many were strictly canary-specific. These analyses reveal specific evolutionary changes in different parts of the song system that control seasonal singing behaviour.
Thus, in the canary, those genes that are sensitive for testosterone and estrogen, and are also involved in the rewiring of neurons, might be crucial for re-differentiation of the underlying neuronal substrate, such as HVC, leading to seasonal song patterning. The present study demonstrates the need for high-quality genome assembly to detect the evolution of genes in comparative studies, says the coordinator of the study, Manfred Gahr from the Max Planck Institute for Ornithology.
Carolina Frankl-Vilches, Heiner Kuhl, Martin Werber, Sven Klages, Martin Kerick, Antje Bakker, Edivaldo de Oliveira, Christina Reusch, Floriana Capuano, Jakob Vowinckel, Stefan Leitner, Markus Ralser, Bernd Timmermann, Manfred Gahr
Using the canary genome to decipher the evolution of hormone-sensitive gene regulation in seasonal singing birds
Genome Biology, 3 February 2015
Dr. Carolina Frankl-Vilches | Max Planck Institute for Ornithology, Seewiesen
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
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:aa773981-43d2-4ccf-9c1f-d0ea3919b886> | 3.640625 | 1,464 | Content Listing | Science & Tech. | 22.47822 | 95,538,734 |
posted by marie
1-What phase are daughter cells in as a result of mitosis?
2- During what phase of mitosis do centromeres divide and the chromosone-mes move toward their respective poles?
3- Wchich phase of mitosis is the last phase that chromatids are together?
4-What structure is produced when spindle fibers radiate from centrioles?
CAN you check my answer please? | <urn:uuid:fa455d55-65a0-442a-9816-7ff369655caf> | 3.015625 | 93 | Q&A Forum | Science & Tech. | 51.703143 | 95,538,735 |
The October 2014 issue of ESA Frontiers spotlights river management in the Anthropocene
Last spring, the Colorado River reached its delta for the first time in 16 years, flowing into Pacific Ocean at the Gulf of California after wetting 70 miles of long-dry channels through the Sonoran Desert.
Tides flow backwards up the dry channels of the Colorado River delta, as seen in an astronaut photo taken June 21, 2013. Prior to the construction of the Hoover Dam and other large water projects on the Colorado, the delta estuary supported a great diversity of species in 3,000 square miles (7,700 square kilometers) of braided channels and lagoons. Now, the riverbed often dries not far from the Arizona-Mexico border. In the spring of 2014, an experimental “pulse” of 105,000 acre-feet (130 million cubic meters) of water were released from the lowest dam on the river in an effort to recover some the lost services provided by the lower Colorado ecosystems. Credit, NASA.
The planned 8-week burst of water from Mexico’s Morelos Dam on the Arizona-Mexico border was the culmination of years of diplomatic negotiations between the United States and Mexico and campaigning from scientists and conservation organizations. Now ecologists wait to see how the short drink of water will affect the parched landscape.
This year’s spring pulse held less than 1 percent of the volume of the Colorado’s annual spring floods before the construction of ten major dams and diversions to municipalities, industry, and agriculture. A return of the lush Colorado delta of the 1920s will not be possible.
But there is hope that periodic flows will bring back willow, mesquite, and cottonwood trees, revive insects and dormant crustaceans, give respite to birds migrating on the Pacific Flyway, and ease strains on fisheries in the Sea of Cortez (Gulf of California).
Environmental flows for natural, hybrid, and novel riverine ecosystems in a changing world
There are two primary ways to achieve “environmental flows” of water necessary to sustain river ecosystems, write Mike Acreman, of the UK’s Centre for Ecology & Hydrology, and colleagues in a review published this month in Frontiers in Ecology and the Environment: controlled releases like the recent experiment on the Colorado that are designed with specific objectives for ecology and ecosystem services in mind and hands-off policies that minimize or reverse alterations to the natural flow of the river.
For rivers like the Colorado, already much altered and bearing heavy demands from many different user groups, a “designer” approach is more practical than attempting to return the river closer to its natural, pre-development state, say the authors. Designers work to create a functional ecosystem or support ecosystem services under current conditions, rather than recreate a historical ecosystem.
Achieving ecological objectives requires planning beyond minimum flows and indicator species to encompass seasonal floods and slack flows and a holistic look at the plants, fish, fungi, birds and other life inhabiting the river, its banks and its marshes. Managers must plan to turn on the taps when ecosystems can capitalize on the flow, lest water releases do more harm than good. Several decades of applied research guided the planning for the engineered “spring flood” on the lower Colorado this year, which was timed for the germination of native trees.
Rebirth of the Elwha River
For rivers with fewer economic and social demands, restoration guided by historical records of the natural dynamics of the river can be an effective restoration strategy, say Acreman and colleagues. To preserve species and get the maximum value from ecosystem services, river systems need to fluctuate in natural rhythms of volume, velocity, and timing ( to put it very simplistically).
At the end of the twentieth century, Washington State decided that the water of the Elwha River would be most valuable flowing freely through Olympic National Park to the Pacific at the Strait of Juan de Fuca, supporting salmon, trout, clams, and tourism. Habitat and eroded coastline are recovering at an astonishing pace only one year after the demolition of two dams freed the river, as Noreen Parks reports for her news story “Rebirth of the Elwha River” in ESA Frontier’s October Dispatches.
Rivers of the Anthropocene?
Outside protected wilderness, the Elwha’s story may be more of an anomaly than a blueprint for future river restoration projects. As non-native species, land development, and climate change remodel river ecosystems, it is no longer easy to define what is “natural” for river systems. But heavily used, regulated, and altered rivers have ecological value.
“The future of freshwater biodiversity is inextricably linked to land and water infrastructure management,” writes N LeRoy Poff of Colorado State University in his guest editorial for ESA Frontiers, in which he contemplates whether rivers have changed so much that we need to rethink some of our conceptions about restoration.
“We are rapidly entering an era where restoration interventions will be guided less by statistical deviations from historical reference conditions and more by “process-based” understanding of organism–environment relationships,” he writes.
Mike Acreman, Angela H Arthington, Matthew J Colloff, Carol Couch, Neville D Crossman, Fiona Dyer, Ian Overton, Carmel A Pollino, Michael J Stewardson, and William Young (2014). Environmental flows for natural, hybrid, and novel riverine ecosystems in a changing world. Frontiers in Ecology and the Environment 12: 466–473. http://dx.doi.org/10.1890/130134
Noreen Parks (2014). “Rebirth of the Elwha River.” Dispatches. Frontiers in Ecology and the Environment 12: 428–432. http://dx.doi.org/10.1890/1540-9295-12.8.428
N LeRoy Poff (2014). Rivers of the Anthropocene? Frontiers in Ecology and the Environment 12: 427–427.http://dx.doi.org/10.1890/1540-9295-12.8.427
ESA is the world’s largest community of professional ecologists and a trusted source of ecological knowledge, committed to advancing the understanding of life on Earth. The 10,000 member Society publishes six journals and broadly shares ecological information through policy and media outreach and education initiatives. The Society’s Annual Meeting attracts over 3,000 attendees and features the most recent advances in ecological science. Visit the ESA website at http://www.esa.org.
Liza Lester | Eurek Alert!
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....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
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Quasars are the brilliant beacons of light that are powered by black holes feasting on captured material, and in the process, heating some of the matter to millions of degrees. The brightest quasars reside in galaxies distorted by collisions with other galaxies. These encounters send lots of gas and dust into the gravitational whirlpool of hungry black holes.
THE HOMES OF QUASARS. The galaxies in these four images have so much dust surrounding them that the brilliant light from their quasars cannot be seen in these Hubble Space Telescope images. Quasars are the brilliant beacons of light that are powered by black holes feasting on captured material, and in the process, heating some of the matter to millions of degrees. The galaxies are part of a census of 30 quasar host galaxies conducted with two of NASA's premier observatories, the Hubble Space Telescope and Spitzer Space Telescope. They were found in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). The study shows that 26 of the host galaxies bear no tell-tale signs of collisions with neighbors, such as distorted shapes. The quasars found in normal-looking galaxies are fainter than those powered by collisions between galaxies, which send lots of gas and dust into the gravitational whirlpool of hungry black holes. The dimmer quasars are triggered by black holes snacking on such tasty treats as a batch of gas or the occasional small satellite galaxy. They are the most abundant type of quasar, according to the Hubble analysis. The images at top right, bottom left, and bottom right reveal three of the survey's normal-looking galaxies that host quasars. Only one galaxy in the sample, at top left, shows evidence of an interaction with another galaxy. The two white blobs are the cores from both galaxies. A streamer of material, colored brown and blue, also lies below the merging galaxies. The galaxies existed roughly 8 billion to 12 billion years ago, during a peak epoch of black-hole growth. The galaxies' masses are comparable to our Milky Way's. The blue patches are star-forming regions. The brown areas are either dust or old stars. The images were taken by Hubble's Wide Field Camera 3 between 2011 and 2012.
Now, however, astronomers are uncovering an underlying population of fainter quasars that thrive in normal-looking spiral galaxies. They are triggered by black holes snacking on such tasty treats as a batch of gas or the occasional small satellite galaxy.
A census of 30 quasar host galaxies conducted with two of NASA's premier observatories, the Hubble Space Telescope and Spitzer Space Telescope, has found that 26 of the host galaxies bear no tell-tale signs of collisions with neighbors, such as distorted shapes. Only one galaxy in the sample shows evidence of an interaction with another galaxy. The galaxies existed roughly 8 billion to 12 billion years ago, during a peak epoch of black-hole growth.
The study, led by Kevin Schawinski of Yale University, bolsters evidence that the growth of most massive black holes in the early universe was fueled by small, long-term events rather than dramatic short-term major mergers.
"Quasars that are products of galaxy collisions are very bright," Schawinski said. "The objects we looked at in this study are the more typical quasars. They're a lot less luminous. The brilliant quasars born of galaxy mergers get all the attention because they are so bright and their host galaxies are so messed up. But the typical bread-and-butter quasars are actually where most of the black-hole growth is happening. They are the norm, and they don't need the drama of a collision to shine."
Schawinski's science paper has been accepted for publication in a letter to the Monthly Notices of the Royal Astronomical Society.
For his analysis, Schawinski analyzed galaxies observed by the Spitzer and Hubble telescopes in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). He chose 30 dust-enshrouded galaxies that appeared extremely bright in infrared images taken by the Spitzer telescope, a sign that their resident black holes are feasting on infalling material. The dust is blocking the quasar's light at visible wavelengths. But infrared light pierces the dust, allowing Schawinski to study the galaxies' detailed structure. The masses of those galaxies are comparable to our Milky Way's.
Schawinski then studied the galaxies in near-infrared images taken by Hubble's Wide Field Camera 3. Hubble's sharp images allowed careful analysis of galaxy shapes, which would be significantly distorted if major galaxy mergers had taken place and were disrupting the structure. Instead, in all but one instance, the galaxies show no such disruption.
Whatever process is stoking the quasars, it's below the detection capability of even Hubble. "I think it's a combination of processes, such as random stirring of gas, supernovae blasts, swallowing of small bodies, and streams of gas and stars feeding material into the nucleus," Schawinski said.
A black hole doesn't need much gas to satisfy its hunger and turn on a quasar. "There's more than enough gas within a few light-years from the center of our Milky Way to turn it into a quasar," Schawinski explained. "It just doesn't happen. But it could happen if one of those small clouds of gas ran into the black hole. Random motions and stirrings inside the galaxy would channel gas into the black hole. Ten billion years ago, those random motions were more common and there was more gas to go around. Small galaxies also were more abundant and were swallowed up by larger galaxies."
The galaxies in Schawinski's study are prime targets for the James Webb Space Telescope, a large infrared observatory scheduled to launch later this decade. "To get to the heart of what kinds of events are powering the quasars in these galaxies, we need the Webb telescope. Hubble and Spitzer have been the trailblazers for finding them."
The team of astronomers in this study consists of K. Schawinski, B.D. Simmons, C.M. Urry, and E. Glikman (Yale University), and E. Treister (Universidad de Concepción, Chile).
For images and more information about this study, visit:
For more information about the Hubble Space Telescope, visit:
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.
Ray Villard | Newswise Science News
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
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Team work is just as important in your brain as it is on the playing field: A new study published online on April 19 by the Proceedings of the National Academy of Sciences reports that groups of brain cells can substantially improve their ability to discriminate between different orientations of simple visual patterns by synchronizing their electrical activity.
The paper, "Cooperative synchronized assemblies enhance orientation discrimination," by Vanderbilt professor of biomedical engineering A. B. Bonds with graduate students Jason Samonds and Heather A. Brown and research associate John D. Allison provides some of the first solid evidence that the exact timing of the tiny electrical spikes produced by neurons plays an important role in brain functioning. Since the discovery of alpha waves in 1929, experts have known that neurons in different parts of the brain periodically coordinate their activity with their neighbors. Despite a variety of theories, however, scientists have not been able to determine whether this "neuronal synchrony" has a functional role or if it is just a by-product of the brains electrical activity.
Until recently studies have focused on the firing rate of brain cells as the basic unit of information – the bits and bytes – used by our organic computer. The reason for this fixation was evidence that the firing rates of sensory neurons contain important information. For example, the higher the firing rate of the pain-sensing neurons in the back of your hand, the greater your brains perception of pain in that location.
David F. Salisbury | 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
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
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Dynamical Theory of Electron Diffraction (Two-Beam Approximation)
The main assumption in the kinematieal theory is that amplitudes of diffracted waves are negligible as compared to the amplitude of the incident electron wave. At the same time, electrons interact with matter much more strongly than X-rays. Therefore, multiple scattering effects appear in the crystal under certain conditions, so that amplitudes of diffracted waves might become comparable to the amplitude of the incident beam.
KeywordsWave Vector Dispersion Curve Dynamical Theory Diffract Wave Crystal Thickness
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Must see TV: take a peek inside Nanosys’ Silicon Valley Quantum Dot fab with NBC Learn & Dr. Paul Alivisatos (Berkeley)
Readers’ Note: Dr. Alivisatos (Berkeley) has been a pioneer of ‘nano-cystals’ and their potential applications. Most recently these ‘crystals’ or Quantum Dots have found their way into commercial application for Display Screens. However the much larger vision for QD’s has significant (“game changing”) implications for: Solar Energy, Bio-Medicine, Drug Theranostics & Delivery, Lighting and Hybrid-Materials (Coatings, Paints, Security Inks as examples). Enjoy the Video ~ Team GNT
Nanosys scientific co-founder and Director of the Lawerence Berkeley National Lab, Dr. Paul Alivisatos, takes NBC Learn on a tour of Nanosys’ Silicon Valley Quantum Dot manufacturing facility.
The section on Nanosys begins at 2:16 – enjoy!
Dr Alivisatos, who recently received the 2016 National Medal of Science, talks with NBC reporter Kate Snow about how this amazing nanotechnology that he helped pioneer is changing the way our TVs work today:
SNOW: When quantum dots of different sizes are grouped together by the billions, they produce vivid colors that have changed the way we look at display screens. The initial research, funded by the NSF, has found its way into many applications, including a nanotechnology company called Nanosys, which produces 25 tons of quantum dot materials every year, enough for approximately 6 million 60 inch TVs.
ALIVISATOS: What we have here is a plastic film that contains inside of it quantum dots, very tiny, tiny crystals made out of semiconductors. It actually contains two sizes of nanoparticle – a very small size that emits a green color and a slightly larger size that emits a red color of light.
SNOW: This film is embedded into tablets, televisions, and laptops to enhance their displays with brilliant color.
ALIVISATOS: One of the things that we’ve learned about vision is that we have receptors in our eyes for green, red and blue colors. And if we want a really high quality display, we need to match the light emission from our display to the receptors in our eyes. | <urn:uuid:6008101f-2435-4037-90e5-27d78b70388a> | 2.765625 | 493 | Truncated | Science & Tech. | 38.566522 | 95,538,806 |
- Frontier letter
- Open Access
Geophysical assessment of migration and storage conditions of fluids in subduction zones
© Pommier; licensee Springer. 2014
Received: 3 February 2014
Accepted: 14 May 2014
Published: 23 May 2014
By enhancing mass transfer and energy release, the cycle of volatiles and melt is a major component of subduction. Investigating this fluid cycle is therefore critical to understand the past and current activity of subduction zones. Fluids can significantly affect rock electrical conductivity and elastic parameters that are measured using electromagnetic and seismic methods, respectively. This letter emphasizes how these geophysical methods complement each other to provide information about the storage of fluids in subduction systems. By compiling electromagnetic and seismic results from various subduction zones, a possible correlation between electrical conductivity and seismic wave attenuation anomalies in the mantle wedge is observed, consistent with fluid accumulation. A possible relationship between geophysical properties and the slab age is also suggested, whereas no significant trend is observed between electrical conductivity or seismic wave attenuation and estimates of water flux in the mantle wedge. These field-based relationships require further constrains, emphasizing the need for new measurements in the laboratory.
The dynamics and time-evolution of subduction are driven by mechanical and chemical processes that influence buoyancy forces, slab motion, contrasting thermal fields, phase equilibria, and volatile transport. By enhancing mass transfer and energy release, the cycle of fluids in subduction zones is a critical component of slab recycling and continental building processes. A better understanding of the role of melt and volatiles in subduction zones is therefore key to improving our knowledge of the geodynamic processes at work. It can also help us better assess volcanic and earthquake hazards in these contexts.
The cycle of fluids is expected to differ significantly between subduction zones. For instance, varying temperatures cause dehydration reactions to occur at shallower depths in the slabs of warm subduction zones (e.g., Southwest Japan, Cascades) compared to slabs of cold subduction zones (e.g., Tonga, Java) (Peacock and Wang 1999). Fluid migration was found to be faster than subduction velocity in warm subduction systems (e.g., approximately 7 cm/year versus approximately 4 cm/year, respectively, in Southwest Japan, Kawano et al. 2011), suggesting a continuous hydration of the mantle wedge due to upward fluid migration along the subduction interface. In colder environments, comparable fluid and subduction velocities (e.g., approximately 10 cm/year in Northeast Japan, Kawano et al. 2011) imply that a non-negligible amount of water reaches the lower mantle and triggers melting, as evidenced by geochemical signatures of island arc magmas (e.g., Stolper and Newman 1994; Wallace 2005). Significant water contents in the mantle are suggested by modeling studies. For instance, van Keken et al. (2011) estimated that the global H2O flux to the deep mantle corresponds roughly to one ocean mass over the Earth's history.
Fluids influence electrical conductivity and seismic velocity in different ways (see Unsworth and Rondenay 2013). These physical properties are measured using electromagnetic and seismic methods, respectively, offering a unique way to map in situ fluid distributions in real time. When interpreted together with petrological results, geophysical data can be used to constrain fluid chemistry, temperature, fraction, and connectivity. Though some important findings have been obtained to relate electrical and seismic data to fluid distribution, thermal structure, and mineralogy (e.g., Kazatchenko et al. 2004; Hacker and Abers 2004; ten Grotenhuis et al. 2005), further work is required to understand the possible relationships between geophysical parameters sensitive to fluids and subduction dynamics.
This letter addresses how electromagnetic and seismic methods complement each other to help define the storage conditions of fluid processes in subduction. It aims to stimulate laboratory investigations that use a joint electrical-seismic approach and combine geophysical data with subduction settings.
Geophysical structure of subduction zones and fluid detection
Electrical conductivity structure of subduction zones
Location and average electrical conductivity (EC) of main conductors detected in electromagnetic studies of subduction zones
Forearc or trench-close conductor
Distance from trench (km)
Distance from trench (km)
1. Chile-Bolivia (19.5°S-21°S)
Brasse et al. (2002)
2. Chile-Bolivia (17°S-19°S)
Brasse and Eydam (2008)
3. Costa Rica
Worzewski et al. (2011)
Joedicke et al. (2006)
5. Philippine Sea
Shimakawa and Honkura (1991)
6. South Chile
Brasse et al.(2009)
7. Central Argentina
300 or less
Booker et al. (2004)
8. Cascadia, British Columbia
Soyer and Unsworth (2006)
9. Cascadia, Oregon
Evans et al. (2013)
Galanopoulos et al. (2005)
Matsuno et al. (2012)
Bertrand et al. (2012)
13. Kyushu, Japan
Ichiki et al. (2000)
14. Hokkaido, Japan
Ichiki et al. (2009)
15. North Honshu, Japan
Toh et al. (2006)
16. Central New Zealand
Wannamaker et al. (2009)
This synthetic model suggests that the contrast in electrical conductivity between stable hydrous minerals in the slab and the mantle can be less than 1 log unit. This observation is consistent with the results from magnetotelluric studies that can hardly distinguish the slab from the surrounding mantle and, therefore, often resort to seismic studies to locate the slab (Brasse and Eydam 2008; Naif et al.2013). Figure 1B also predicts that the electrical response of hydrous minerals (chlorite, amphibole) may be similar to that of partial melt at conditions relevant to subduction, therefore hampering the identification of a free fluid phase. Improving our understanding of fluid distribution in subduction zones requires the integration of results from electromagnetic surveys with those from petrology and seismology.
Input from seismic studies
Different seismic techniques are used to probe subduction zones (see Unsworth and Rondenay 2013). Among the different seismic observables, a reduction in seismic velocities and quality factor Q can be used to infer fluid-bearing regions at depth and define fluid pathways (e.g., Syracuse et al.2008; Rychert et al.2008). In particular, seismic wave attenuation (Q−1) and Poisson's ratio (Vp/Vs) are sensitive to the presence of fluid and high temperature (Takei 2002), and some models showed that seismic velocities can be related to the fluid content within the mantle wedge (e.g., Carlson and Miller 2003). Estimates of volume fraction of fluids have been proposed based on these seismic parameters, and further work is needed to place stronger quantitative constraints (Aizawa et al. 2008). Low seismic velocity zones are commonly detected at shallow depths in relatively warm subduction contexts (Hirose et al.2008) and at higher depths in the mantle wedge of cold subduction environments (Tsuji et al. 2008). Seismic attenuation can be caused by mechanisms that are not all related to the presence of fluid, such as grain defect microdynamics, viscosity, and scattering (e.g., Johnston et al.1979; Karato and Spetzler 1990). Therefore, the interpretation of seismic attenuation in terms of fluid requires its coupling with other fluid-dependent geophysical parameters.
Location, highest seismic wave attenuation values, and wave velocity ratios of mantle wedge seismic anomalies
Forearc or trench-close anomaly
f range (Hz)
f range (Hz)
Wiens et al. (2008)
3. NE Japan
4. Honshu, Japan
Tsumura et al. (2000)
Ko et al. (2012)
6. Central Java, Indonesia
Bohm et al. (2013)
7. North New Zealand
Eberhart-Phillips et al. (2008)
40 and 80-120
Chen and Clayton (2009)
9. Nicaragua-Costa Rica
10. Central Andes −21, −22.1°S
11. Central Andes −24.2°S
Schurr et al. (2003)
Stachnik et al. (2004)
The inversion of converted and scattered teleseismic waves method does not clearly identify the zones of fluid accumulation (e.g., Rondenay et al. 2010), but rather fronts of serpentinization (Bostock et al. 2002), whose location is consistent with thermal and petrological subduction models at shallow depth (<~70 km). Serpentinization of the slab and mantle wedge is ascribed to a series of dehydration reactions that lead to permanent changes in the mineralogy and represents a major component of the fluid cycle at shallow depth (e.g., Reynard 2013).
Beneath the Cascades (Figure 2B), several small low seismic velocity zones are present, but no pronounced low-velocity zone can be distinctly observed in the mantle wedge where partial melt is expected (Rondenay et al. 2008), whereas electrical data clearly identified conductive zones interpreted as fluid accumulation areas, noted as A, B, C (Figure 2C; Evans et al. 2013). Region A is consistent with the presence of fluids from slab dehydration at shallow depth, B with a zone of fluid accumulation possibly related to the volcanic plumbing system, and C is in agreement with the presence of deeper partial melting. These conductive anomalies correspond to zones of seismic velocity reduction in Figure 2B, but they could not be clearly identified on the seismic profile without additional constraints from the electromagnetic study.
Relating electrical and seismic parameters to map fluid distribution
Electrical conductivity-seismic velocity relationships in fluid-bearing materials
Attempts to relate electrical and seismic properties of fluid-bearing materials are scarce (Kazatchenko et al. 2004; Pommier and Garnero 2014). These petrophysical models are based on theoretical approaches and laboratory measurements and aim to improve the interpretation of geophysical data. Another approach would consist of exploring electrical conductivity-seismic velocity relationships by considering their values from field measurements.
with a correlation coefficient R of 0.78 for P waves and 0.96 for S waves. These relationships suggest that the higher the electrical conductivity of the anomaly, the higher its seismic attenuation, suggesting a plausible link in their cause.
Several and possibly combined causes can explain increases in electrical conductivity, Qp−1, and Qs−1. Because temperature affects both electrical and elastic parameters of fluid-bearing materials (e.g., Faul et al. 2004; ten Grotenhuis et al. 2005), thermal contrasts could explain the trend observed in Figure 3. For instance, the increase in EC between the Mariana electrical anomaly and the more conductive one in Honshu (difference of approximately 0.30 S/m, Table 1) can be explained by an increase from 1,200°C to 1,300°C, considering a hydrous basalt (6.3 wt.% H2O) as the fluid phase (Ni et al. 2011), a melt fraction of 5%, and using the Hashin-Shtrikman upper bound (Hashin and Shtrikman 1962). The difference in seismic wave attenuation (Qp−1 = 93 to 132 in Mariana, 150 in Honshu, Table 2) can be caused by a temperature change of 50°C (1,200°C to 1,250°C) or less on the corresponding frequency range according to the model by Faul et al. (2004) for a dunite containing 5% melt.
The geometry of the interconnected fluid phase in solid matrix can also explain the relationship between electrical conductivity and P wave and S wave attenuations. At defined fluid fraction, a change in fluid interconnectivity and geometry is likely to influence seismic velocities (S wave velocities more than P wave velocities, Watt et al. 1976), which will affect Poisson's ratio and increase seismic attenuation (e.g., Jackson et al. 2004). Fluid interconnectivity can also affect electrical conductivity significantly enough to explain the variations observed in Figure 3 (several tenths of S/m) (e.g., ten Grotenhuis et al. 2005). The spatial distribution of fluid can also be responsible for seismic and electrical anisotropy observed in the field (e.g., Kawakatsu et al. 2009; Caricchi et al. 2011), which is not considered in the present study.
Fluid composition affects electrical conductivity and may affect seismic velocities, though the effect of fluids (in particular, water) on seismic observables is poorly constrained and calibrated (Aizawa et al. 2008). The difference in electrical conductivity between the backarc anomaly in Honshu (>0.15 S/m) and in Mariana (approximately 0.01 S/m) (Table 1) is comparable to the conductivity increase caused by the addition of 7 wt.% H2O to a basalt at 1,200°C, using the conductivity model by Ni et al. (2011). This would be consistent with the fact that the Mariana slab may have released most of its aqueous fluids, whereas the younger Honshu slab can still be expelling them, enriching partial melt accumulation zones with aqueous phase and leading to higher conductivity values.
An increase in the fluid content increases electrical conductivity (e.g., Nesbitt 1993), increases seismic wave attenuation (e.g., Jackson et al. 2004), and decreases seismic velocities (e.g., Mainprice 1997). Laboratory studies showed that electrical conductivity is very sensitive to fluid fraction (e.g., Caricchi et al. 2011; Yoshino et al. 2012), suggesting that a small change in fluid fraction can explain the differences in electrical conductivity between the different anomalies plotted in Figure 3 (assuming a similar temperature).The relationship between electrical conductivity and seismic wave attenuation presented in Figure 3 suggests that the fluid conditions affect electrical conductivity and seismic wave attenuation in a similar manner, assuming that fluids are responsible for the electric and seismic signals. Further electrical and seismic investigations are needed to demonstrate if the slope (or intercept) of this empirical relationship depends on the amount of fluids and their storage conditions and therefore place quantitative constraints on the nature of zones of fluid accumulation.
Relating electrical conductivity and seismic velocities to subduction settings
Subduction settings can also be expressed through the slab thermal parameter (slab age × convergence speed) (Kirby et al. 1991). Its value is small for slow subduction of young lithosphere (e.g., Mexico, Cascades) and high for fast subduction of old lithosphere (e.g., Tonga, Java). No distinct relationship is observed between electrical conductivity of mantle wedge anomalies (forearc and backarc) and the slab thermal parameter. However, as underlined in Figure 4C, seismic wave attenuation tends to be higher for low slab thermal parameter values. This would be consistent with an abundant release of fluids related to the dehydration process of a young crust, whereas the fast subduction of an old lithosphere does not promote fluid accumulation, leading to low seismic attenuation.
Geophysical parameters and global slab water flux
Geochemical studies proposed to estimate the fluxes of fluids (particularly water) in subduction, and models have been developed to estimate the amount of water expelled under compaction at shallow depth, as well as the amount of water reaching the deep mantle (e.g., Carlson and Miller 2003; van Keken et al.2011).
Concluding remarks: potential for improving the understanding of subduction settings using a joint electrical-seismic approach
Although thermo-mechanical models of subduction do not necessarily agree on the time-evolution, they all point out extreme temperature gradients across the slab-mantle interface (e.g., Syracuse et al.2010). As underlined by Poli and Schmidt (2002), this suggests that a wide pressure-temperature-composition space has to be characterized to predict the evolution of subducting slabs. Because of the sensitivity of geophysical parameters to temperature and composition, electrical and seismic field studies, when combined with thermo-mechanical models, can be a useful tool to understand the pathways that led to the current state of a subduction system and may help define plausible scenarios for its evolution.
A few attempts combined the P-T paths of slabs from thermal models and phase equilibria on hydrous basalt or peridotite compositions (e.g., Poli and Schmidt 2002; Syracuse et al.2010). Recently, Unsworth and Rondenay (2013) compared possible P-T paths of the slab with seismic velocity attenuation for a basaltic melt after Hacker (2008), attempting to relate dynamic models of subduction to the seismic properties of melt. Our knowledge of subduction would benefit from further joint investigations that promote the interpretation of seismic velocity and electrical conductivity in terms of composition and subduction dynamics. The recent expansion of geophysical experiments such as the EarthScope USArray seismic-magnetotelluric network offers the potential to improve significantly the relationships between electrical and elastic parameters.
This manuscript benefitted from discussions with and informal reviews by Stéphane Rondenay and Ed Garnero. Discussions with Kurt Leinenweber were also appreciated. The author thanks two anonymous reviewers for their comments.
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Daily application of carbon dating
Keep in mind that during this process, not all of the mass is conserved.
Its consistent rate of decay allows the age of an object to be determined by the proportion of carbon-14 to other carbon isotopes. Carbon-14 is also used as a radioactive tracer for medical tests.Step into the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory on any given day, and you may see researchers tracking the dynamics of the Earth’s carbon cycle, searching for signatures of nuclear fuel reprocessing or determining the age of remains from the Chicago Police Department’s cold case files.These vastly different projects have one thing in common: They all use accelerators to measure levels of carbon-14 and other isotopes.This inconsistent amount of carbon-14 renders the test less accurate but opens up testing possibilities not available for older samples.For example, it is possible to determine the age of a person born after the 1940s using the carbon-14 content of teeth.Radioactive isotopes are used to determine the age of old artifacts, diagnose disease, and treat certain types of medical conditions.
In this lesson, we are going to take a closer look at each of these applications of nuclear chemistry. The answer is 'run on nuclear fusion.' Nuclear fusion occurs when two or more atoms fuse together to form a single, heavier atom.
Human remains, fossils and organic materials from archaeological sites are all dated using carbon-14.
Books, clothing and food remains are all archaeological artifacts that can be carbon dated.
Nuclear chemistry is a field of chemistry that deals with the use of radioactive isotopes and other nuclear reactions.
Nuclear reactions provide us with enormous amounts of energy.
In AMS, researchers direct a beam of cesium ions at a sample. | <urn:uuid:e465d978-3749-4d8f-b3ae-8a5c6ff65ff2> | 3.890625 | 372 | Knowledge Article | Science & Tech. | 37.148202 | 95,538,824 |
Above is a visual astronomy image of a fireball trail with some burning still visible from a meteor as it passed overhead in Chelyabinsk, Russia, on February 15, 2013.
Such meteors are within the size range for consideration in meteor astronomy.
From a radiation point of view many entities and objects can be or appear radiated from a source. They travel faster than a local environment or atmosphere and as such are perceived as traveling through. Size can range from electrons to galaxy clusters. Those radiated entities or objects from the size of a nucleus down to an electron are studied by the type of particles. Radiated electrons are studied with electron astronomy. Radiated nuclei are usually studied as cosmic ray astronomy. The larger entities and objects are here studied as meteor astronomy, where the term meteor is generalized with a theoretical definition to encompass these larger entities and objects.
For example, Jupiter is usually considered a gaseous giant planet in orbit around the Sun. But, it is also a large radiated object, a special object for study by meteor astronomy, that is now in an orbit around an apparently stationary object called the Sun. The Sun in turn is in an orbit around the center of the Milky Way galaxy. From this point of view the Sun can be studied with meteor astronomy as a radiated object.
- 1 Theoretical meteor astronomy
- 2 High-velocity galaxies
- 3 Hypervelocity stellar meteors
- 4 Emissions
- 5 Absorptions
- 6 Nebulas
- 7 Clouds
- 8 Aerometeors
- 9 Plasma meteors
- 10 Rains
- 11 Hydrometeors
- 12 Cryometeors
- 13 Lithometeors
- 14 X-rays
- 15 Ultraviolets
- 16 Opticals
- 17 Visuals
- 18 Atmospheres
- 19 Meteorites
- 20 Sun
- 21 Venus
- 22 Earth
- 23 Meteor showers
- 24 Jet streams
- 25 Meteoroids
- 26 Moon
- 27 Mars
- 28 Jupiter
- 29 Saturn
- 30 Uranus
- 31 Neptune
- 32 Volcanic bombs
- 33 Craters
- 34 Geophysics
- 35 Earth sciences
- 36 Hypotheses
- 37 See also
- 38 References
- 39 External links
Theoretical meteor astronomy
- any atmospheric phenomenon" or
- a fast moving streak of light in the night sky caused by the entry of extraterrestrial matter into the earth's atmosphere is called a meteor.
These were sometimes classified as aerial or airy meteors (winds), aqueous or watery meteors (hydrometeors: clouds, rain, snow, hail, dew, frost), luminous meteors (rainbows and aurora), and igneous or fiery meteors (lightning and shooting stars).
For this resource, an alternative theoretical definition to handle all sizes of radiated entities or objects is proposed.
Here's that theoretical definition:
Def. any natural object radiating through a portion or all of the Earth's or another natural, astronomical object's atmosphere is called a meteor.
These are usage notes:
- Such an object may be as small as an electron or much larger.
- Astronomical objects that are atoms, nuclei, or subatomic particles are part of cosmic-ray astronomy.
- Astronomical objects larger than atoms, nuclei, or subatomic particles that are fast-moving relative to perceived, almost motionless objects, radiating through another natural object's atmosphere or gaseous environment are also here referred to as meteors.
- These can be a high-velocity star moving through the interstellar medium or a larger object moving through an intergalactic medium.
- At the extreme a meteor can be a galaxy cluster moving relative to apparently stationary clusters in its neighborhood of the universe.
Here's another theoretical definition:
Def. an astronomy of meteors (as a form of radiation) is called meteor astronomy.
"The irregular galaxy NGC 1427A is a spectacular example of the resulting stellar rumble. Under the gravitational grasp of a large gang of galaxies, called the Fornax cluster, the small bluish galaxy is plunging headlong into the group at 600 kilometers per second or nearly 400 miles per second."
"Galaxy clusters, like the Fornax cluster, contain hundreds or even thousands of individual galaxies. Within the Fornax cluster, there is a considerable amount of gas lying between the galaxies. When the gas within NGC 1427A collides with the Fornax gas, it is compressed to the point that it starts to collapse under its own gravity. This leads to formation of the myriad of new stars seen across NGC 1427A, which give the galaxy an overall arrowhead shape that appears to point in the direction of the galaxy's high-velocity motion."
Hypervelocity stellar meteors
Def. a star moving faster than 65 km/s to 100 km/s relative to the average motion of the stars in the Sun's neighbourhood is called a high-velocity star.
Def. a high-velocity star moving through space with an abnormally high velocity relative to the surrounding interstellar medium is called a runaway star.
Def. a star whose elliptical orbit takes it well outside the plane of its galaxy at steep angles is called a halo star.
Def. the solid material thrown into the air by a volcanic eruption that settles on the surrounding areas is called tephra.
"[T]ephra, is a general term for fragments of volcanic rock and lava that are blasted into the air by volcanic explosions or carried upward in the volcanic plume by hot, hazardous gases. The larger fragments usually fall close to the volcano, but the finer particles can be advected quite some distance. ... [Fine ash] can contain rock, minerals, and volcanic glass fragments smaller than .1 inch in diameter, or slightly larger than the size of a pinhead."
"[T]he carbonaceous material [is] known from observation to dominate the terrestrial [micrometeorite (MM)] flux."
"Ureilites occur about half as often as eucrites (Krot et al. 2003), are relatively friable, have less a wide range of cosmic-ray exposure ages including two less than 1 Myr, and, like the dominant group of MM precursors, contain carbon."
"The Horsehead Nebula, a part of the optical nebula IC434 and also known as Barnard 33, was first recorded in 1888 on a photographic plate taken at the Harvard College Observatory. Its coincidental appearance as the profile of a horse's head and neck has led to its becoming one of the most familiar astronomical objects. It is, in fact, an extremely dense cloud projecting in front of the ionized gas that provides the pink glow so nicely revealed in this picture. We know this not only because the underside of the 'neck' is especially dark, but because it actually casts a shadow on the field to its east (below the 'muzzle')."
Def. a large white puffy cloud is called a cumulus cloud.
Def. a visible mass of
- water droplets suspended in the air ...
- steam ...
- smoke ...
- a group or swarm is called a cloud.
Def. a discrete unit of air, wind, or mist traveling or falling through or partially through an atmosphere is called an aerometeor.
Def. a wind whose direction and speed are determined by a balance of the horizontal pressure gradient force and the force due to the earth's rotation to the left in the northern hemisphere and to the right in the southern hemisphere is called a geostrophic wind.
Def. a warm dry wind blowing down the side of a mountain is called a foehn, or foehn wind, or chinook.
The chinook generally blows from the southwest, but its direction may be modified by topography. When it sets in after a spell of intense cold, the temperature may rise by 20–40°F in 15 minutes due to replacement of a cold air mass with a much warmer air mass in minutes.
"Wind shear is a change in wind direction, wind speed, or both, along a given direction in space (e.g., along a horizontal or vertical distance)."
Def. a strong, abrupt rush of wind is called a gust.
A coronal cloud is a cloud, or cloud-like, natural astronomical entity, composed of plasma and usually associated with a star or other astronomical object where the temperature is such that X-rays are emitted. While small coronal clouds are above the photosphere of many different visual spectral type stars, others occupy parts of the interstellar medium (ISM), extending sometimes millions of kilometers into space, or thousands of light-years, depending on the size of the associated object such as a galaxy.
"[A] medium-strength flare erupted from the sun on July 19, 2012. The blast also generated the enormous, shimmering plasma loops, which are an example of a phenomenon known as "coronal rain," agency officials said."
"Hot plasma in the corona cooled and condensed along strong magnetic fields in the region" slowly falling back to the solar surface as plasma "rain".
Def. liquid moisture that falls visibly in separate drops is called rain.
The Kerala red rain phenomenon was a blood rain (red rain) event that occurred from July 25 to September 23, 2001, when heavy downpours of red-coloured rain fell sporadically on the southern Indian state of Kerala, staining clothes pink. Yellow, green, and black rain was also reported. Colored rain was also reported in Kerala in 1896 and several times since, most recently in June 2012.
Red rains were also reported from November 15, 2012 to December 27, 2012 occasionally in eastern and north-central provinces of Sri Lanka, where scientists from the Sri Lanka Medical Research Institute (MRI) are investigating to ascertain their cause.
The colored rain of Kerala began falling on July 25, 2001, in the districts of Kottayam and Idukki in the southern part of the state. Yellow, green, and black rain was also reported. Many more occurrences of the red rain were reported over the following ten days, and then with diminishing frequency until late September.
According to locals, the first colored rain was preceded by a loud thunderclap and flash of light, and followed by groves of trees shedding shriveled grey "burnt" leaves. Shriveled leaves and the disappearance and sudden formation of wells were also reported around the same time in the area. It typically fell over small areas, no more than a few square kilometers in size, and was sometimes so localized that normal rain could be falling just a few meters away from the red rain. Red rainfalls typically lasted less than 20 minutes. Each milliliter of rain water contained about 9 million red particles, and each liter of rainwater contained approximately 100 milligrams of solids. Extrapolating these figures to the total amount of red rain estimated to have fallen, it was estimated that 50,000 kilograms (110,000 lb) of red particles had fallen on Kerala.
The brownish-red solid separated from the red rain consisted of about 90% round red particles and the balance consisted of debris. The particles in suspension in the rain water were responsible for the color of the rain, which at times was strongly colored red. A small percentage of particles were white or had light yellow, bluish gray and green tints. The particles were typically 4 to 10 µm across and spherical or oval. [Transmission electron microscope] Electron microscope images showed the particles as having a depressed center. At still higher magnification some particles showed internal structures.
In November 2001, commissioned by the Government of India's Department of Science & Technology, the Center for Earth Science Studies (CESS) and the Tropical Botanical Garden and Research Institute (TBGRI) issued a joint report which concluded that:
"The color was found to be due to the presence of a large amount of spores of a lichen-forming alga belonging to the genus Trentepohlia. Field verification showed that the region had plenty of such lichens. Samples of lichen taken from Changanacherry area, when cultured in an algal growth medium, also showed the presence of the same species of algae. Both samples (from rainwater and from trees) produced the same kind of algae, indicating that the spores seen in the rainwater most probably came from local sources."
Def. precipitation products of the condensation of atmospheric water vapour are called hydrometeors.
"Condensation or sublimation of atmospheric water vapor produces a hydrometeor. It forms in the free atmosphere, or at the earth's surface, and includes frozen water lifted by the wind. Hydrometeors which can cause a surface visibility reduction, generally fall into one of the following two categories:
- Precipitation. Precipitation includes all forms of water particles, both liquid and solid, which fall from the atmosphere and reach the ground; these include: liquid precipitation (drizzle and rain), freezing precipitation (freezing drizzle and freezing rain), and solid (frozen) precipitation (ice pellets, hail, snow, snow pellets, snow grains, and ice crystals).
- Suspended (Liquid or Solid) Water Particles. Liquid or solid water particles that form and remain suspended in the air (damp haze, cloud, fog, ice fog, and mist), as well as liquid or solid water particles that are lifted by the wind from the earth’s surface (drifting snow, blowing snow, blowing spray) cause restrictions to visibility. One of the more unusual causes of reduced visibility due to suspended water/ice particles is whiteout, while the most common cause is fog."
A megacryometeor is a very large chunk of ice sometimes called huge hailstones, but do not need to form in thunderstorms.
A megacryometeor is a very large chunk of ice which, despite sharing many textural, hydro-chemical and isotopic features detected in large hailstones, is formed under unusual atmospheric conditions which clearly differ from those of the cumulonimbus cloud scenario (i.e. clear-sky conditions). They are sometimes called huge hailstones, but do not need to form in thunderstorms. Jesus Martinez-Frias, a planetary geologist at the Center for Astrobiology in Madrid, pioneered research into megacryometeors in January 2000 after ice chunks weighing up to 6.6 pounds (3.0 kg) rained on Spain out of cloudless skies for ten days.
Def. pieces of ice falling as precipitation are called hail.
Def. a single ball of hail is called a hailstone.
Def. water ice crystals falling as light white flakes are called snow.
Def. a suspension of dry dust in the atmosphere is called a lithometeor.
"A lithometeor consists of solid particles suspended in the air or lifted by the wind from the ground."
"A lithometeor is the general term for particles suspended in a dry atmosphere; these include dry haze, smoke, dust, and sand."
"Dry haze is an accumulation of very fine dust or salt particles in the atmosphere; it does not block light, but instead causes light rays to scatter. Dry haze particles produce a bluish color when viewed against a dark background, but look yellowish when viewed against a lighter background. This light-scattering phenomenon (called Mie scattering) also causes the visual ranges within a uniformly dense layer of haze to vary depending on whether the observer is looking into the sun or away from it."
Heavy metal pollution may occur in lithometeors.
"The rise of airborne dust is constantly augmenting from the desert (Bilma) to the southern Sahelian stations (Niamey) where it has increased by a factor five. ... the Sahelian zone with airborne dust during the 80s ... All stations have recorded a general increase of wind velocity. The increase of lithometeors frequency as well as the wind velocity during the drought period is not explained by the aridification."
At right is the only available X-ray image, by the Chandra X-ray Observatory, of Mira A on the right and Mira B (left). "Mira A is losing gas rapidly from its upper atmosphere [apparently] via a stellar wind. [Mira B is asserted to be a white dwarf. In theory] Mira B exerts a gravitational tug that creates a gaseous bridge between the two stars. Gas from the wind and bridge accumulates in an accretion disk around Mira B and collisions between rapidly moving particles in the disk produce X-rays."
At left is a radiated object and its associated phenomena.
Ultra-violet studies of Mira by NASA's Galaxy Evolution Explorer (Galex) space telescope have revealed that it sheds a trail of material from the outer envelope, leaving a tail 13 light-years in length, formed over tens of thousands of years. It is thought that a hot bow-wave of compressed plasma/gas is the cause of the tail; the bow-wave is a result of the interaction of the stellar wind from Mira A with gas in interstellar space, through which Mira is moving at an extremely high speed of 130 kilometres/second (291,000 miles per hour). The tail consists of material stripped from the head of the bow-wave, which is also visible in ultra-violet observations. Mira's bow-shock will eventually evolve into a planetary nebula, the form of which will be considerably affected by the motion through the interstellar medium (ISM).
"A skydiver may have captured the first film ever of a meteorite plunging down at terminal velocity, also known as its “dark flight” stage."
"The footage was captured in 2012 by a helmet cam worn by Anders Helstrup as he and other members of the Oslo Parachute Club jumped from a small plane that took off from an airport in Hedmark, Norway."
“It can’t be anything else. The shape is typical of meteorites -- a fresh fracture surface on one side, while the other side is rounded.”
“It has never happened before that a meteorite has been filmed during dark flight; this is the first time in world history.”
"Having the rock in hand would certainly help. But despite triangulations and analyses, Helstrup and his recruits still haven’t found it."
The image at the top of the article shows "[t]he trail of a falling object ... seen above the Urals city of Chelyabinsk [on] February 15, 2013".
Meteors become visible between about 75 to 120 kilometers (34 - 70 miles) above the Earth. They disintegrate at altitudes of 50 to 95 kilometers (31-51 miles). Most meteors are observed at night, when darkness allows fainter objects to be recognized. Most meteors glow for about a second.
A fireball is a brighter-than-usual meteor. The International Astronomical Union defines a fireball as "a meteor brighter than any of the planets" (magnitude −4 or greater). The International Meteor Organization (an amateur organization that studies meteors) has a more rigid definition. It defines a fireball as a meteor that would have a magnitude of −3 or brighter if seen at zenith. This definition corrects for the greater distance between an observer and a meteor near the horizon. For example, a meteor of magnitude −1 at 5 degrees above the horizon would be classified as a fireball because if the observer had been directly below the meteor it would have appeared as magnitude −6. For 2011 there are 4589 fireballs records at the American Meteor Society.
Def. a fireball reaching magnitude −14 or brighter. is called a bolide.
Def. a fireball reaching an magnitude −17 or brighter is called a superbolide.
At right is a cell phone camera image of the green fireball over San Mateo, California, that left meteorite fragments. "The asteroid entered at a speed of 14 km/s, typical but on the slow side of other meteorite falls for which orbits were determined. ... The orbit in space is also rather typical: perihelion distance close to Earth's orbit (q = 0.987 AU) and a low-inclination orbit (about 5 degrees). ... 2012, October 17 - At 7:44:29 pm PDT this evening, a bright fireball was seen in the San Francisco Bay Area."
"The distribution of photographic meteors in iron, stony, and porous meteors is given in this paper". "[A]mong all the 217 meteors for which we know the beginning there are 70 iron meteors, i. e. about 32 p. c., and 147 stony meteors, i. e. 68 p. c." The meteor streams: Perseids, Geminids, Taurids, Lyrids, κ Cygnids and Virginids, are quite stony.
"The dominant group in all cases are stony meteors."
Some data suggest that Mira B is a normal main sequence star of spectral type K and roughly 0.7 solar masses, rather than a white dwarf as first envisioned.
Analysis in 2010 of rapid optical brightness variations has indicated that Mira B is in fact a white dwarf.
Atmospheric astronomy has three basic aspects: astronomy conducted through an atmosphere, astronomy of an atmosphere, and astronomy conducted using an atmosphere.
Gaseous objects have at least one chemical element or compound present in the gaseous state. These gaseous components make up at least 50 % of the detectable portion of the gaseous object. Atmospheric astronomy determines whether gaseous objects have layers or spherical portions predominantly composed of gas.
Within these spherical portions may occur various gaseous meteors such as clouds, winds, or streams.
Def. any or all of the forms of water particles, whether liquid or solid, that fall from the atmosphere are called precipitation.
Meteors typically occur in the mesosphere, and most range in altitude from 75 km to 100 km. Millions of meteors occur in the Earth's atmosphere every day.
Imaged at right is an igneous Martian shergottite meteorite. "The perimeter exhibits a fusion crust from the heat of entry into the Earth’s atmosphere. It is a fresh sample of NWA 6963, an igneous Martian shergottite meteorite found in September 2011 in Morocco. Meteorites are often labeled NWA for North West Africa, not because they land there more often, but because they are easy to spot as peculiar objects in the desert sands. From the geochemistry and presence of various isotopes, the origin and transit time is deduced. The 99 meteorites from Mars exhibit precise elemental and isotopic compositions similar to rocks and atmosphere gases analyzed by spacecraft on Mars, starting with the Viking lander in 1976. Compared to other meteorites, the Martians have younger formation ages, unique oxygen isotopic composition (consistent for Mars and not for Earth), and the presence of aqueous weathering products. A trapped gas analysis concluded that their origin was Mars quite recently, in the year 2000."
"The formation ages of meteorites often come from their cosmic-ray exposure (CRE), measured from the nuclear products of interactions of the meteorite in space with energetic cosmic ray particles. This one is particularly young, having crystallized only 180 million years ago, suggesting that volcanic activity was still present on Mars at that time. Volcanic flows are the youngest part of a planet, and this one happened to be hit by a meteor impact, ejecting" it from the youthful Mars.
"Sun-grazing comets almost never re-emerge, but their sublimative destruction near the sun has only recently been observed directly, while chromospheric impacts have not yet been seen, nor impact theory developed." "[N]uclei are ... destroyed by ablation or explosion ... in the chromosphere, producing flare-like events with cometary abundance spectra."
"The death of a comet at r ~ Rʘ has been seen directly only very recently (Schrijver et al 2011) using the SDO AIA XUV instrument. This recorded sublimative destruction of Comet C/2011 N3 as it crossed the solar disk very near periheloin q = 1.139Rʘ."
"The phenomenon of flare induced sunquakes - waves in the photosphere - discovered by Kosovichev and Zharkova (1998) and now widely studied (e.g. Kosovichev 2006) should also result from the momentum impulse delivered by a cometary impact."
"Coronal clouds, type IIIg, form in space above a spot area and rain streamers upon it."
The solar wind originates through the polar coronal holes.
In visual astronomy almost no variation or detail can be seen in the clouds. The surface is obscured by a thick blanket of clouds. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. It has thick clouds of sulfur dioxide. There are lower and middle cloud layers. The thick clouds consisting mainly of sulfur dioxide and sulfuric acid droplets. These clouds reflect and scatter about 90% of the sunlight that falls on them back into space, and prevent visual observation of the Venusian surface. The permanent cloud cover means that although Venus is closer than Earth to the Sun, the Venusian surface is not as well lit.
Strong 300 km/h winds at the cloud tops circle the planet about every four to five earth days. Venusian winds move at up to 60 times the speed of the planet's rotation, while Earth's fastest winds are only 10% to 20% rotation speed.
The Earth is home to showers, jet streams, and meteoroids.
Meteors may occur in showers, which arise when the Earth passes through a trail of debris left by a comet, or as "random" or "sporadic" meteors, not associated with a specific single cause. A number of specific meteors have been observed, largely by members of the public and largely by accident, but with enough detail that orbits of the meteoroids producing the meteors have been calculated. All of the orbits passed through the asteroid belt.
The Perseid meteor shower, usually the richest meteor shower of the year, peaks in August. Over the course of an hour, a person watching a clear sky from a dark location might see as many as 50-100 meteors. Most meteors are actually pieces of rock that have broken off a comet and continue to orbit the Sun. The Earth travels through the comet debris in its orbit. As the small pieces enter the Earth's atmosphere, friction causes them to burn up.
"The Orionid meteor shower [leftover bits of Halley's Comet] is scheduled to reach its maximum before sunrise on Sunday morning (Oct. 21 ). This will be an excellent year to look for the Orionids, since the moon will set around 11 p.m. local time on Saturday night (Oct. 20) and will not be a hindrance at all ... The orbit of Halley's Comet closely approaches the Earth's orbit at two places. One point is in the early part of May producing a meteor display known as the Eta Aquarids. The other point comes in the middle to latter part of October, producing the Orionids."
"At 66 kilometers (41 miles) per second, they appear as fast streaks, faster by a hair than their sisters, the Eta Aquarids of May. And like the Eta Aquarids, the brightest of family tend to leave long-lasting trains. Fireballs are possible three days after maximum."
"The Leonid meteor shower peaked early Saturday (Nov. 17 ), and some night sky watchers caught a great view. The Leonids are a yearly meteor display of shooting stars that appear to radiate out of the constellation Leo. They are created when Earth crosses the path of debris from the comet Tempel-Tuttle, which swings through the inner solar system every 33 years."
Def. any of the high-speed, high-altitude air currents that circle the Earth in a westerly direction is called a jet stream.
Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. The main jet streams are located near the tropopause, the transition between the troposphere (where temperature decreases with altitude) and the stratosphere (where temperature increases with altitude). The major jet streams on Earth are westerly winds (flowing west to east). Their paths typically have a meandering shape; jet streams may start, stop, split into two or more parts, combine into one stream, or flow in various directions including the opposite direction of most of the jet. The strongest jet streams are the polar jets, at around 7–12 km (23,000–39,000 ft) above sea level, and the higher and somewhat weaker subtropical jets at around 10–16 km (33,000–52,000 ft). The Northern Hemisphere and the Southern Hemisphere each have both a polar jet and a subtropical jet. The northern hemisphere polar jet flows over the middle to northern latitudes of North America, Europe, and Asia and their intervening oceans, while the southern hemisphere polar jet mostly circles Antarctica all year round.
Def. a relatively small (sand- to boulder-sized) fragment of debris in a solar system is called a meteoroid.
"As of 2011 the International Astronomical Union officially defines a meteoroid as a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom".
The visible path of a meteoroid that enters the Earth's atmosphere (or another body's) atmosphere is called a meteor, or colloquially a shooting star or falling star. If a meteoroid reaches the ground and survives impact, then it is called a meteorite.
Beech and Steel, writing in Quarterly Journal of the Royal Astronomical Society, proposed a new definition where a meteoroid is between 100 µm and 10 m across. Following the discovery and naming of asteroids below 10 m in size (e.g., 2008 TC3), Rubin and Grossman refined the Beech and Steel definition of meteoroid to objects between 10 µm and 1 m in diameter. The near-Earth object (NEO) definition includes larger objects, up to 50 m in diameter, in this category. Very small meteoroids are known as micrometeoroids (see also interplanetary dust).
The composition of meteoroids can be determined as they pass through Earth's atmosphere from their trajectories and the light spectra of the resulting meteor. Their effects on radio signals also give information, especially useful for daytime meteors which are otherwise very difficult to observe.
The light spectra, combined with trajectory and light curve measurements, have yielded various compositions and densities, ranging from fragile snowball-like objects with density about a quarter that of ice, to nickel-iron rich dense rocks.
In meteoroid ablation spheres from deep-sea sediments, "[t]he silicate spheres are the most dominant group."
From these trajectory measurements, meteoroids have been found to have many different orbits, some clustering in streams (see Meteor showers) often associated with a parent comet, others apparently sporadic. Debris from meteoroid streams may eventually be scattered into other orbits. ... Meteoroids travel around the Sun in a variety of orbits and at various velocities. The fastest ones move at about 26 miles per second (42 kilometers per second) through space in the vicinity of Earth's orbit. The Earth travels at about 18 miles per second (29 kilometers per second). Thus, when meteoroids meet the Earth's atmosphere head-on (which would only occur if the meteors were in a retrograde orbit), the combined speed may reach about 44 miles per second (71 kilometers per second). Meteoroids moving through the earth's orbital space average about 20 km/s.
Lunar origin is established by comparing the mineralogy, the chemical composition, and the isotopic composition between meteorites and samples from the Moon collected by Apollo missions.
Cosmic ray exposure history established with noble gas measurements have shown that all lunar meteorites were ejected from the Moon in the past 20 million years. Most left the Moon in the past 100,000 years.
All six of the Apollo missions on which samples were collected landed in the central nearside of the Moon, an area that has subsequently been shown to be geochemically anomalous by the Lunar Prospector mission. In contrast, the numerous lunar meteorites are [likely to be] random samples of the Moon and consequently provide a more representative sampling of the lunar surface than the Apollo samples. Half the lunar meteorites, for example, likely sample material from the farside of the Moon.
At top left is a NASA photograph showing the bright flash of light from a meteor impact that occurred on the Moon on March 17, 2013. According to NASA, a 0.3 m rock slammed into the lunar surface at 90,120 km/h, creating a fresh crater 20 m wide.
"The crash caused the biggest and brightest explosion scientists have seen since they started monitoring lunar meteorite strikes in 2005. ... The lunar blast was the equivalent of 5 tons of TNT going off".
"The flash was so bright it saturated the camera".
Martian meteors are thought to be from Mars because they have elemental and isotopic compositions that are similar to rocks and atmosphere gases analyzed by spacecraft on Mars.
At right is a Hubble Space Telescope image of a dust storm on Mars. The picture was snapped on October 28, 2005. The regional dust storm on Mars had "been growing and evolving over the past few weeks. The dust storm, which is nearly in the middle of the planet in this Hubble view is about 930 miles (1500 km) long measured diagonally, which is about the size of the states of Texas, Oklahoma, and New Mexico combined. No wonder amateur astronomers with even modest-sized telescopes have been able to keep an eye on this storm. The smallest resolvable features in the image (small craters and wind streaks) are the size of a large city, about 12 miles (20 km) across. The occurrence of the dust storm is in close proximity to the NASA Mars Exploration Rover Opportunity's landing site in Sinus Meridiani. Dust in the atmosphere could block some of the sunlight needed to keep the rover operating at full power. ... The large regional dust storm appears as the brighter, redder cloudy region in the middle of the planet's disk. This storm has been churning in the planet's equatorial regions for several weeks now, and it is likely responsible for the reddish, dusty haze and other dust clouds seen across this hemisphere of the planet in views from Hubble, ground based telescopes, and the NASA and ESA spacecraft studying Mars from orbit. Bluish water-ice clouds can also be seen along the limbs and in the north (winter) polar region at the top of the image."
At left is an image of a "newly formed impact crater, observed by HiRISE on Mars Reconnaissance Orbiter. The impact that formed the crater exposed the water ice beneath the surface. Some of the ice can be seen scattered at the adjascent area in the subimages. The blast zone (excavated dark material) is almost 800 meters (half a mile) across. The crater itself is just over 20 meters (66 feet) across".
"This crater is one of a special group that have excavated down to buried ice. This ice gets thrown out of the crater onto the surrounding terrain. Although buried ice is common over about half the Martian surface, we can only easily discover craters in dusty regions. The overlap between areas that both have buried ice and surface dust is unfortunately small. So even though we have discovered over 100 new impact craters we have only discovered 7 new craters that expose buried ice."
"When craters excavate this buried ice it tells us something about the extent and depth of buried ice on Mars (controlled by climate); this information is used by planetary scientists to figure out what the recent climate of Mars was like. It has also been a surprise that this ice is so clean. Scientists expected this buried ice to be a mixture of ice and dirt; instead this ice seems to have formed in pure lenses. Yet another surprise that Mars had in store for us!"
The ice (presumably water ice) is white in the image, but take note of the blue dust or regolith also exposed.
The second image at right is a subimage of the one at left. It is natural color and shows in better detail both the ice (white) and the blue material.
At second left is an image showing an impact crater on Planum Boreum, or the North Polar Cap, of Mars, as observed by HiRISE on Mars Reconnaissance Orbiter in natural color.
"Impact craters on the surface of Planum Boreum, popularly known as the north polar cap, are rare. This dearth of craters has lead scientists to suggest that these deposits may be geologically young (a few million years old), not having had much time to accumulate impact craters throughout their lifetime."
"It is also possible that impacts into ice do not retain their shape indefinitely, but instead that the ice relaxes (similar to glass in an old window), and the crater begins to disappear. This subimage shows an example of a rare, small crater ( approximately 115 meters, or 125 yards, in diameter). Scientists can count these shallow craters to attain an estimate of the age of the upper few meters of the Planum Boreum surface."
"The color in the enhanced-color example comes from the presence of dust and of ice of differing grain sizes. The blueish ice has a larger grain size than the ice that has collected in the crater. The reddish material is dust. The smooth area stretching to the upper right, away from the crater may be due to winds being channeled around the crater or to fine-grained ice and frost blowing out of the crater."
The third image at right shows a freshly formed impact crater that occurred on Mars between February 2005 and July 2005. Note the blue material expelled from the crater rock onto the nearby Martian landscape.
Jupiter has been called the Solar System's vacuum cleaner, because of its immense gravity well and location near the inner Solar System. It receives the most frequent comet impacts of the Solar System's planets.
A 1997 survey of historical astronomical drawings suggested that the astronomer [Giovanni Domenico Cassini] Cassini may have recorded an impact scar in 1690. The survey determined eight other candidate observations had low or no possibilities of an impact. A fireball was photographed by Voyager 1 during its Jupiter encounter in March 1979. During the period July 16, 1994, to July 22, 1994, over 20 fragments from the comet Shoemaker–Levy 9 (SL9, formally designated D/1993 F2) collided with Jupiter's southern hemisphere, providing the first direct observation of a collision between two Solar System objects. This impact provided useful data on the composition of Jupiter's atmosphere.
On July 19, 2009, an impact site was discovered at approximately 216 degrees longitude in System 2. This impact left behind a black spot in Jupiter's atmosphere, similar in size to Oval BA. Infrared observation showed a bright spot where the impact took place, meaning the impact warmed up the lower atmosphere in the area near Jupiter's south pole.
2010 Jupiter impact event: A fireball, smaller than the previous observed impacts, was detected on June 3, 2010, by Anthony Wesley, an amateur astronomer in Australia, and was later discovered to have been captured on video by another amateur astronomer in the Philippines. Yet another fireball was seen on August 20, 2010.
The second image at right shows the atmospheric impact sites for the Comet Shoemaker-Levy 9 fragments. Spectroscopic studies revealed absorption lines in the Jovian spectrum due to diatomic sulfur (S2) and carbon disulfide (CS2), the first detection of either in Jupiter, and only the second detection of S2 in any astronomical object. Other molecules detected included ammonia (NH3) and hydrogen sulfide (H2S). The amount of sulfur implied by the quantities of these compounds was much greater than the amount that would be expected in a small cometary nucleus, showing that material from within Jupiter was being revealed.
The upper clouds are composed of ammonia crystals.
In 1990, the Hubble Space Telescope imaged an enormous white cloud near Saturn's equator that was not present during the Voyager encounters and in 1994, another, smaller storm was observed. The 1990 storm was an example of a Great White Spot, a unique but short-lived phenomenon that occurs once every Saturnian year, roughly every 30 Earth years, around the time of the northern hemisphere's summer solstice. Previous Great White Spots were observed in 1876, 1903, 1933 and 1960, with the 1933 storm being the most famous. If the periodicity is maintained, another storm will occur in about 2020.
Wind speeds on Saturn can reach 1,800 km/h (1,100 mph) ... Voyager data indicate peak easterly winds of 500 m/s (1800 km/h).
Infrared imaging has shown that Saturn's south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System. Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, believed to be the warmest spot on Saturn.
Uranus has a complex, layered cloud structure, with methane thought to make up the uppermost layer of clouds. With a large telescope of 25 cm or wider, cloud patterns may be visible. When Voyager 2 flew by Uranus in 1986, it observed a total of ten cloud features across the entire planet. Besides the large-scale banded structure, Voyager 2 observed ten small bright clouds, most lying several degrees to the north from the collar.
In the 1990s, the number of the observed bright cloud features grew considerably partly because new high resolution imaging techniques became available. Most were found in the northern hemisphere as it started to become visible. An early explanation - that bright clouds are easier to identify in the dark part of the planet, whereas in the southern hemisphere the bright collar masks them - was shown to be incorrect: the actual number of features has indeed increased considerably. Nevertheless there are differences between the clouds of each hemisphere. The northern clouds are smaller, sharper and brighter. They appear to lie at a higher altitude. The lifetime of clouds spans several orders of magnitude. Some small clouds live for hours, while at least one southern cloud may have persisted since Voyager flyby. Recent observation also discovered that cloud features on Uranus have a lot in common with those on Neptune. For example, the dark spots common on Neptune had never been observed on Uranus before 2006, when the first such feature dubbed Uranus Dark Spot was imaged. The speculation is that Uranus is becoming more Neptune-like during its equinoctial season.
On August 23, 2006, researchers at the Space Science Institute (Boulder, CO) and the University of Wisconsin observed a dark spot on Uranus's surface, giving astronomers more insight into the planet's atmospheric activity.
The wind speeds on Uranus can reach 250 meters per second (900 km/h, 560 mph). The tracking of numerous cloud features allowed determination of zonal winds blowing in the upper troposphere of Uranus. At the equator winds are retrograde, which means that they blow in the reverse direction to the planetary rotation. Their speeds are from −100 to −50 m/s. Wind speeds increase with the distance from the equator, reaching zero values near ±20° latitude, where the troposphere's temperature minimum is located. Closer to the poles, the winds shift to a prograde direction, flowing with the planet's rotation. Windspeeds continue to increase reaching maxima at ±60° latitude before falling to zero at the poles. Windspeeds at −40° latitude range from 150 to 200 m/s. Since the collar obscures all clouds below that parallel, speeds between it and the southern pole are impossible to measure. In contrast, in the northern hemisphere maximum speeds as high as 240 m/s are observed near +50 degrees of latitude. ... Observations included record-breaking wind speeds of 229 m/s (824 km/h) and a persistent thunderstorm referred to as "Fourth of July fireworks".
At the time of the 1989 Voyager 2 flyby, the planet's southern hemisphere possessed a Great Dark Spot. In 1989, the Great Dark Spot, an anti-cyclonic storm system spanned 13000×6600 km, was discovered by NASA's Voyager 2 spacecraft. Some five years later, on 2 November 1994, the Hubble Space Telescope did not see the Great Dark Spot on the planet. Instead, a new storm similar to the Great Dark Spot was found in the planet's northern hemisphere.
The Scooter is another storm, a white cloud group farther south than the Great Dark Spot. Its nickname is due to the fact that when first detected in the months before the 1989 Voyager 2 encounter it moved faster than the Great Dark Spot. Subsequent images revealed even faster clouds.
The Small Dark Spot is a southern cyclonic storm, the second-most-intense storm observed during the 1989 encounter. It initially was completely dark, but as Voyager 2 approached the planet, a bright core developed and can be seen in most of the highest-resolution images.
The persistence of companion clouds shows that some former dark spots may continue to exist as cyclones even though they are no longer visible as a dark feature. Dark spots may dissipate when they migrate too close to the equator or possibly through some other unknown mechanism.
The upper-level clouds occur at pressures below one bar, where the temperature is suitable for methane to condense.
High-altitude clouds on Neptune have been observed casting shadows on the opaque cloud deck below. There are also high-altitude cloud bands that wrap around the planet at constant latitude. These circumferential bands have widths of 50–150 km and lie about 50–110 km above the cloud deck.
Because of seasonal changes, the cloud bands in the southern hemisphere of Neptune have been observed to increase in size and albedo. This trend was first seen in 1980 and is expected to last until about 2020. The long orbital period of Neptune results in seasons lasting forty years.
Neptune has the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 kilometres per hour (1,300 mph).
On Neptune winds reach speeds of almost 600 m/s—nearly attaining supersonic flow. More typically, by tracking the motion of persistent clouds, wind speeds have been shown to vary from 20 m/s in the easterly direction to 325 m/s westward. At the cloud tops, the prevailing winds range in speed from 400 m/s along the equator to 250 m/s at the poles. Most of the winds on Neptune move in a direction opposite the planet's rotation. The general pattern of winds showed prograde rotation at high latitudes vs. retrograde rotation at lower latitudes. The difference in flow direction is believed to be a "skin effect" and not due to any deeper atmospheric processes. At 70° S latitude, a high-speed jet travels at a speed of 300 m/s.
Def. "distinctively shaped [natural] projectiles ... which acquired their shape essentially before landing" are called bombs.
Def. a bomb "ejected from a volcanic vent" is called a volcanic bomb.
Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight.
The image at top right is an "[a]ccretionary lava ball [coming] to rest on the grass after rolling off the top of an ‘a‘a flow in Royal Gardens subdivision. Accretionary lava balls form as viscous lava is molded around a core of already solidified lava."
Volcanic bombs cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they do not have grains making them extrusive igneous rocks. Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight.
Volcanic bombs can be extremely large; the 1935 eruption of Mount Asama in Japan expelled bombs measuring 5–6 m in diameter up to 600 m from the vent. A large volcanic bomb is shown in the third image at right from Strohn, Germany.
Volcanic bombs are known to occasionally explode from internal gas pressure as they cool, but explosions are rare. Bomb explosions are most often observed in 'bread-crust' type bombs.
Ribbon or cylindrical bombs form from highly to moderately fluid magma, ejected as irregular strings and blobs. The strings break up into small segments which fall to the ground intact and look like ribbons. Hence, the name "ribbon bombs". These bombs are circular or flattened in cross section, are fluted along their length, and have tabular vesicles.
Spherical bombs also form from high to moderately fluid magma. In the case of spherical bombs, surface tension plays a major role in pulling the ejecta into spheres.
Spindle, fusiform, or almond/rotational bombs are formed by the same processes as spherical bombs, though the major difference being the partial nature of the spherical shape. Spinning during flight leaves these bombs looking elongated or almond shaped; the spinning theory behind these bombs' development has also given them the name 'fusiform bombs'. Spindle bombs are characterised by longitudinal fluting, one side slightly smoother and broader than the other. This smooth side represents the underside of the bomb as it fell through the air.
Cow pie bombs are formed when highly fluid magma falls from moderate height; so the bombs do not solidify before impact (they are still liquid when they strike the ground). They consequently flatten or splash and form irregular roundish disks, which resemble cow-dung.
Bread-crust bombs are formed if the outside of the lava bombs solidifies during their flights. They may develop cracked outer surfaces as the interiors continue to expand.
Cored bombs are bombs that have rinds of lava enclosing a core of previously consolidated lava. The core consists of accessory fragments of an earlier eruption, accidental fragments of country rock or, in rare cases, bits of lava formed earlier during the same eruption.
Def. a hemispherical pit, a basinlike opening or mouth about which a cone is often built up, any large roughly circular depression or hole is called a crater.
The image at right shows a chain of 13 craters (Enki Catena) on Ganymede measuring 161.3 km in length. The Enki craters formed across the sharp boundary between areas of bright terrain and dark terrain, delimited by a thin trough running diagonally across the center of this image. The ejecta deposit surrounding the craters appears very bright on the bright terrain. Even though all the craters formed nearly simultaneously, it is difficult to discern any ejecta deposit on the dark terrain.
Most meteoroids that cause meteors are about the size of a pebble.
Meteors have roughly a fifty percent chance of a daylight (or near daylight) collision with the Earth.
A relatively small percentage of meteoroids hit the Earth's atmosphere and then pass out again: these are termed Earth-grazing fireballs (for example The Great Daylight 1972 Fireball).
Terminal velocity of hail, or the speed at which hail is falling when it strikes the ground, varies by the diameter of the hail stones. A hail stone of 1 cm (0.39 in) in diameter falls at a rate of 9 metres per second (20 mph), while stones the size of 8 centimetres (3.1 in) in diameter fall at a rate of 48 metres per second (110 mph). Hail stone velocity is dependent on the size of the stone, friction with air it is falling through, the motion of wind it is falling through, collisions with raindrops or other hail stones, and melting as the stones fall through a warmer atmosphere.
Def. a particle classification system based on diameter is called the Wentworth scale.
Def. a particle less than 1 micron in diameter is called a colloid.
Def. a particle less than 3.9 microns in diameter is called a clay.
Def. a particle from 3.9 to 62.5 microns in diameter is called a silt.
Def. a particle less than 62.5 microns in diameter is called a mud.
Def. a particle from 62.5 microns to 2 mm in diameter is called a sand.
Def. a particle from 2 to 64 mm in diameter is called a gravel.
Def. a particle from 2 to 4 mm in diameter is called a granule.
Def.' a particle from 4 to 64 mm in diameter is called a pebble.
Def. a particle from 64 to 256 mm in diameter is called a cobble.
Def. a particle [or large piece of stone greater than 256 mm in diameter that can theoretically be moved if enough force is applied is called a boulder.
Rain is measured in units of length per unit time, typically in millimeters per hour, or in countries where imperial units are more common, inches per hour. The "length", or more accurately, "depth" being measured is the depth of rain water that would accumulate on a flat, horizontal and impermeable surface during a given amount of time, typically an hour. One millimeter of rainfall is the equivalent of one liter of water per square meter.
The standard way of measuring rainfall or snowfall is the standard rain gauge, which can be found in 100-mm (4-in) plastic and 200-mm (8-in) metal varieties. The inner cylinder is filled by 25 mm (0.98 in) of rain, with overflow flowing into the outer cylinder. Plastic gauges have markings on the inner cylinder down to 0.25 mm (0.0098 in) resolution, while metal gauges require use of a stick designed with the appropriate 0.25 mm (0.0098 in) markings. After the inner cylinder is filled, the amount inside it is discarded, then filled with the remaining rainfall in the outer cylinder until all the fluid in the outer cylinder is gone, adding to the overall total until the outer cylinder is empty.
Def. the study of the atmosphere and its phenomena, especially with weather and weather forecasting is called meteorology.
Def. the study of the theoretical effects of astronomical bodies and forces on the Earth’s atmosphere and on the atmosphere of other astronomical objects is called astrometeorology.
Def. a system of winds rotating around a center of low atmospheric pressure, the more or less violent small-scale circulations such as tornadoes, waterspouts, and dust devils is called a cyclone.
- Meteors range in size from that of small molecules to galaxy filaments.
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- Yahoo Advanced Web Search | <urn:uuid:2ce7b1ff-7628-4410-a1fe-441e3b164b1d> | 3.90625 | 17,969 | Knowledge Article | Science & Tech. | 65.151273 | 95,538,829 |
Chemical Sensors to Sniff out Diseases in Human Breath
News Feb 14, 2006
Researchers at University at Buffalo have announced that they are developing a rugged Breathalyzer-type device that, just like the nose of a human - or other mammal - will contain thousands of chemical sensors "trained" to recognize complex chemical patterns, some of which are known biomarkers for certain diseases.
"These volatile biomarkers are free for the asking and taking," said Frank V. Bright, Ph.D., UB Distinguished Professor in the Department of Chemistry in the College of Arts and Sciences, A. Conger Goodyear Professor of Chemistry and principal investigator.
"They emanate from us all of the time. They are large in volume, much safer to handle than biofluids and available through totally non-invasive means."
Called gaseous metabolites, these are the same odors that some animals use to identify their offspring, owners, mates, prey or competitors.
So far, multiple volatile chemicals have been detected by other scientists as biomarkers, correlating their presence and concentration with human diseases ranging from diabetes and AIDS to lung cancer and various mental illnesses.
While there are other electronic "noses" already on the market, they cannot correlate reliably their read-outs to a particular disease state, Bright said.
"The UB device will be unique because it will be designed to exploit, and in some ways mimic, the concepts of olfaction," he continued.
"Despite the fact that we might encounter numerous really smelly things in our lifetime, it is not as if there are billions of discrete sensors within our noses that nature designed a priori to respond selectively to every possible smelly odor."
"Rather, there are suites of receptors in our nasal passages and the collective response from all of these receptors to an odor or set of odors can be discriminated," he said.
In the same way, the UB device will contain individual chemical sensors, perhaps as many as a million, which collectively will produce a pattern revealing the chemical signature of a patient's breath, which may be related to a particular disease state.
That pattern will then be used to "train" neural networks, groups of connected artificial neurons capable of learning new information, to discriminate potentially between patients with specific diseases.
"The power of neural networks in this research is that they will pull out the important features and save them so that when they are exposed to a chemical pattern they have 'seen' before, the device will elicit the right response," said Albert H. Titus, Ph.D., assistant professor of electrical engineering in the UB School of Engineering and Applied Sciences and a co-investigator on the project.
He added that with neural network processing, the size of the sensor elements can stay very small, each measuring about 10 micrometers in size.
Titus is building complementary metal oxide semiconductor (CMOS) arrays that simultaneously will read the signals produced by each of the sensor elements.
"The issue with this application is can you come up with a unique ensemble of sensor elements that exhibit enough diversity to respond to a large variety of small, chemically similar species to give you a chance of realizing the chemical fidelity that you need?" asked Bright.
To achieve that fidelity, he said the chemical sensors will be made out of xerogels, porous glass-like materials that consist of nanoscopic pores, which can be tuned to recognize specific chemicals or classes of chemicals.
Bright explained that the envisioned device will work as follows: As the breath sample flows through the breath-testing device, the individual sensing elements will change their color or intensity; those changes will be detected by the CMOS array, producing electrical signals that then can be processed by the neural network.
"The Oishei Foundation's generosity will enable our team to have a prototype ready for clinical testing within a year," said Bright.
Mouse Study Suggests That Dietary Fat, Not Carbs, Drives ObesityNews
A mouse study that made over 100,000 measurements of body weight and fat has concluded that the sole driver of obesity in mice is increased dietary fat content.READ MORE
Peering Inside ProteinsNews
The proteins in our bodies are sophisticated structures that perform specific jobs to keep us functioning and healthy. Understanding how a protein is wired could help researchers develop ways to control its activity. A new technique lets researchers look into the atomic structures of proteins to see that wiring.READ MORE | <urn:uuid:bd253d3c-61dc-4f46-a333-69ee1df8fa23> | 2.53125 | 912 | News Article | Science & Tech. | 29.28449 | 95,538,836 |
is the number of moles of solute dissolved in one kilogram of solvent. Note: be careful not to confuse molality and molarity. Molality is represented by a small "m," whereas molarity is represented by an upper case "M."
the number of moles of a solute dissolved in a liter of solvent. Note: be careful not to confuse molality and molarity. Molality is represented by a small "m," whereas molarity is represented by an upper case "M."
is a unit that enables scientists to calculate the weight of any chemical substance, be it an element or a compound. Molar mass is the sum of all of the atomic masses in a formula. More information and molar mass calculator.
a complete chemical unit. While a molecule is often thought of as consisting of more than one atom, this is not always true. For instance, helium has only one atom per molecule. The oxygen molecule (O2) contains two atoms, as do chlorine (Cl2), hydrogen (H2) and nitrogen (N2). Some molecules are huge having a molecular weight in the millions. Macromolecules contain literally thousands of atoms. Some macromolecules must remain in tact in order to retain their chemical entity. These are usually proteins. Polymers are chains or networks of repeating sequences of chemical units known as molecules. Examples are polypropylene or cellulose. Molecules of polymers can be broken without destroying the chemical integrity.
Facilities for recycling municipal waste. There are dirty MRFs, which take all garbage as a collective and sort out the recycables at a central facility, and there are clean MRFs that require recycables to be separated out by the generator and are collected separately.
Includes non-hazardous non-liquid waste generated in households, commercial businesses, light industry and commercial establishments. The exact definition varies from one municipality to another.
Are modern waste incinerators that are highly regulated in terms of permissible emissions. They also produce energy either in the form of steam or electricity.
If you need to cite this page, you can copy this text:
Kenneth Barbalace. Chemistry & Environmental Dictionary - Molality - MWC. EnvironmentalChemistry.com. 1995 - 2018. Accessed on-line: 7/20/2018 | <urn:uuid:d93d09e0-f995-4f9b-b2bf-040b8c857bb9> | 3.375 | 477 | Structured Data | Science & Tech. | 29.714952 | 95,538,841 |
What is Style Guide Driven Development?
- Definition of Style Guide Driven Development
- Style Guide Documentation Examples
As its name indicates, Style Guide Driven Development is about driving the development of a system or application using a style guide. But not only that, it’s also about driving the DESIGN and about using a LIVING style guide: developing components and documenting them in a style guide.
Traditionally, when we think about front end implementation, we think about
Using Style Guide Driven Development, designers use a living style guide as the starting point for their designs. Living Style Guides (LSG) are living documents that are generated straight from the source code. In that way, the entire process from design to development centers around the style guide, keeping it consistent and up-to-date.
At Bitovi, designers and developers cover these areas of web design (design,
CSS implementation. And we use Living Style Guides to communicate our designs more efficiently and achieve a more polished product.
Here is a good example: When implementing the following toolbar, as a designer, we would first look at the style guide and bring in the styles that we will be using. We would also learn what design patterns are used currently and create my design based on them.
Then, after multiple iterations, when the design is ready to go and we are ready for implementation, we would create a new page in the application style guide. This would give us a blank slate to write the markup (in HTML) and the styles (in
sass depending on the project). But it would also give us a framework to work with, because the style guide is connected to the application style sheet. This means that the predefined styles that we used in the design mockups would be available to use in the implementation.
So we can quickly implement our own design, without worrying about messing up with the application (at least not yet!).
Then, we would document the different “cases” or “states” where this toolbar would be used. For instance, how the toolbar looks like when the user is logged out, vs when logged in. Or how the display of new features look in the toolbar.
Bitovi can help you build your app using this methodology. Let’s work together.
This type of documentation is very powerful, because on the one hand you don’t have to recreate each scenario in your app (which can be very time consuming). But also, having these scenarios side by side, allows us to change and try things when implementing and we can see right away the effect that they will have across the different use cases or states.
Now with this document in hand, your dev can move along and take care of wiring things up, scrambling APIs or whatever magic that they do!
That is the gist of what Style Guide Driven Development is. In the next lesson we will delve into Living Style Guides vs Traditional Style Guides.
Lesson: What is style guide driven development
First post and replies | Last post by Adriana De La Cuadra, 11 months ago | <urn:uuid:76a038f7-9923-4a9b-a951-c68a95ff873a> | 2.984375 | 637 | Product Page | Software Dev. | 45.085021 | 95,538,858 |
Applications of the Double Frequency Technique in Bubble Sizing and Pressure Measurements in Fluids
The detection and sizing of microbubbles in fluids has potential applications in industry and medicine. Non-invasive techniques using ultrasound appear attractive compared to optical techniques. Different methods employing ultrasound have been shown to be capable of detecting bubbles in fluids and of estimating their sizes. These include those using the Doppler effect (Nishi, 1972)1 , resonant scattering (Fairbanks and Scully, 1977)2 and second harmonic generation (Miller, 1981)3. There are some major drawbacks in these techniques. In the Doppler technique there is no way of distinguishing echoes from a cluster of small bubbles from those of a large bubble occupying the same volume. The Doppler technique is also incapable of detecting stationary bubbles, such as those trapped in tissues. The resonant scattering and the second harmonic generation techniques work on the basis of the fact that bubbles have a characteristic resonant frequency dependent on their sizes. In resonant scattering, however, it is found that larger bubbles give rise to a stronger echo than bubbles at resonance, giving rise to ambiguities which would make it difficult to measure the size distribution of bubbles covering a range of sizes. Both the resonant scattering and the second harmonic generation methods suffer from poor spatial resolution.
KeywordsResonant Frequency Harmonic Generation Bubble Size Double Frequency Large Bubble
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- 4.V.L. Newhouse and P.M. Shankar, J.A.S.A., Vol. 75, 1473–1477 (1984).Google Scholar | <urn:uuid:8276147b-8be6-428f-98b6-4ab822c0147e> | 3.265625 | 332 | Truncated | Science & Tech. | 39.082562 | 95,538,870 |
C Reference is a quick reference for the C programming language. If you are an experienced C programmer use it as a quick reference guide, or if you are a student or just learning C it can be a valuable tool to help the learning process. All of the data is contained within the application, no internet connection is required.
The C functions are separated into the following categories:
String Conversion Functions
Also included is a reference guide for
Each detail sheet contains Syntax, Description and Example sections. Sample code is supplied for each detail sheet. | <urn:uuid:e496563d-36bf-4a1c-8767-63ad4fab4f47> | 2.515625 | 110 | Product Page | Software Dev. | 41.94075 | 95,538,881 |
New study advances multimessenger astrophysics
A new simulation of supermassive black holes--the behemoths at the centers of galaxies--uses a realistic scenario to predict the light signals emitted in the surrounding gas before the masses collide, said Rochester Institute of Technology researchers.
Two supermassive black holes at the center of a large gas disk are on a collision course in a time sequence simulated by RIT scientists. An alternating flow of gas fills and depletes mini disks feeding the black holes, shown above. Characteristic light signals emitted in the gas could mark the location of the invisible masses. (Note: The dot at the center of the image is not part of the simulation.)
Credit: RIT Center for Computational Relativity and Gravitation
The RIT-led study represents the first step toward predicting the approaching merger of supermassive black holes using the two channels of information now available to scientists--the electromagnetic and the gravitational wave spectra--known as multimessenger astrophysics. The findings appear in the paper "Quasi-periodic Behavior of Mini-disks in Binary Black Holes Approaching Merger," published in the Astrophysical Journal Letters.
"We've performed the first simulation in which an accretion disk around a binary black hole feeds individual accretion disks, or mini-disks, around each black hole in general relativity and magnetohydrodynamics," said Dennis Bowen, lead author and postdoctoral researcher at RIT's Center for Computational Relativity and Gravitation.
Unlike their less massive cousins, first detected in 2016, supermassive black holes are fed by gas disks that surround them like doughnuts. The strong gravitational pull of the black holes that inspiral toward one another heats and disrupts the flow of gas from disk to black hole and emits periodic signals in the visible to X-ray portions of the electromagnetic spectrum.
"We have not yet seen two supermassive black holes get this close," Bowen said. "It provides the first hints of what these mergers will look like in a telescope. The filling and refilling of mini-disks affect the light signatures."
The simulation models supermassive black holes in a binary pair, each surrounded by its own gas disks. A much larger gas disk encircles the black holes and disproportionately feeds one mini-disk over another, leading to the filling-and-refilling cycle described in the paper.
"The evolution is long enough to study what the real science outcome would look like," said Manuela Campanelli, director of the Center for Computational Relativity and Gravitation and a co-author on the paper.
Binary supermassive black holes emit gravitational waves at lower frequencies than stellar-mass black holes. The ground-based Laser Interferometer Gravitational-wave Observatory, in 2016, detected the first gravitational waves from stellar mass black holes collisions with an instrument tuned to higher frequencies. LIGO's sensitivity is unable to observe the gravitational wave signals produced by supermassive black hole coalescence.
The launch of the space-based Laser Interferometer Space Antenna, or LISA, slated for the 2030s, will detect gravitational waves from colliding supermassive black holes in the cosmos. When operational in the 2020s, the ground-based Large Synoptic Survey Telescope, or LSST, under construction in Cerro Pachón, Chile, will produce the widest, deepest survey of light emissions in the universe. The pattern of signals predicted in the RIT study could guide scientists to orbiting pairs of supermassive black holes.
"In the era of multimessenger astrophysics, simulations such as this are necessary to make direct predictions of electromagnetic signals that will accompany gravitational waves," Bowen said. "This is the first step toward the ultimate goal of simulations capable of making direct predictions of the electromagnetic signal from binary black holes approaching merger."
Bowen and his collaborators combined simulations from RIT's Black Hole Lab computer clusters and the Blue Waters supercomputer at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, one of the largest supercomputers in the United States.
Astrophysicists from RIT, Johns Hopkins University and NASA Goddard Space Flight Center collaborated on the project. The publication is based on Bowen's Ph.D. dissertation at RIT and completes research begun by a co-author, Scott Noble, a former RIT post-doctoral researcher, now at NASA Goddard. Their research is part of a collaborative National Science Foundation-funded project led by Campanelli. Co-authors include Vassilios Mewes, RIT postdoctoral researcher; Miguel Zilhao, former RIT post-doctoral researcher, now at Universidade de Lisboa, in Portugal; and Julian Krolik, professor of physics and astronomy at Johns Hopkins University.
In an upcoming paper, the authors will explore further the correlation between gas flowing in and out of the accretion disks and fluctuating light emissions. They will present predictions of light signatures scientists can expect to see with advanced telescopes when looking for supermassive black holes approaching merger.
Susan Gawlowicz | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Stochastic Methods and Non-Fractal Applications
Our everyday environment abounds with examples of stochastic phenomena, objects or activities that are governed by probabilistic laws [COX65]. These range from observations evident to any observer, such as the number of people in a supermarket checkout queue or the time taken to drive to work on a particular day, to more latent situations, such as the energy levels of subatomic particles. Practitioners of statistics and operational research have, for decades, used computers to create models of such activity in order to gain useful insights into the behaviour of systems that depend on statistical or probabilistic laws. More recently, stochastic methods have been used to model certain natural phenomena in a visually convincing way. Images depicting simulations of the structures of, for example, plants [PRUS90] and other life forms [KAAN91], marble [PERL85], clouds [VOSS85], mountainous tenain [SAUP88] and the boundaries of cities [BATT91] have become familiar. Many researchers use standard “random number generators” to reproduce such effects; not all of them appreciate the implications of what they are doing. The purpose of this tutorial is to describe some of the underlying statistical theory and to show its application to a selection of techniques in computer graphics. The development will be explanatory rather than theoretically rigorous. The intention is to give end users an understanding of the methods they are using without converting them into statistical experts. Statistics is similar to many other technical subjects in that much of its mystique is concerned with its terminology. Many terms will be highlighted when introduced.
KeywordsComputer Graphic Cycle Length Random Number Generator Sample Space Stochastic Method
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- [BATT91]Batty, M., (1991) Cities as Fractals: Simulating Growth and Form, in Fractals and Chaos, Crilly, A J., R.A. Earnshaw, H. Jones (eds), Springer-Verlag, New York, N.Y.Google Scholar
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Application Security Testing: An Integral Part of DevOps
Many times in life one has to Excel 2 Win!
This tutorial presents a simple sample demonstrating how to get access to data copied from a Microsoft Excel Sheet and present the same in a DataGrid control within a Windows Form Application.
This is increasingly becoming quite a popular request amongst users because many have traditionally used Microsoft Excel as their primitive data store. Any automation effort will face requests from users to optionally allow them to copy the Excel data directly into the application using the neat old copy/paste sequence that they are so used to!
The sample is intended to serve as a good starting point to customize it to one's requirements.
To jump straight into action, here is a list of the typical sequence of action that needs to be carried out within the Windows Application, assuming the copied Excel data is being held in the Clipboard:
- Access & extract the Clipboard data
- Format the data into a DataGrid control bindable form
- Bind the data to the DataGrid control
Figure 1: Sample Data in an Excel Sheet
Well, there is still some work that needs to be done, but the good part is the effort is not more than 15 minutes of your time!
First, here is some information on the important .NET Framework Classes that we would befriend during the course of this sample:
- Clipboard: Nothing can be easier that this. .NET provides access to the Clipboard by using a Class, not surprisingly, called Clipboard. We would use the Clipboard Class to extract the data contained within it.
- IDataObject: This interface provides a format-independent mechanism for transferring data. We would use this interface to extract and store the Clipboard Excel data.
- DataFormats: This one provides light in the dark. The Class is composed of certain pre-defined format names of data that the Clipboard can hold, such as Comma Separated Values, Html, Bitmap, and so forth. We would use the Class to identify Excel data extracted in an IDataObject.
With friendly Classes in the pocket, let us start looking at the meaty part now.
Figure 2: The Sample Application User Interface
Access & Extract the Clipboard Data
Firstly, we need to peek into the Clipboard and extract its content into a container object. For this, we use the GetDataObject method of the Clipboard Class and contain it as an IDataObject.
Dim objPresumablyExcel As IDataObject = Clipboard.GetDataObject()
Next, we need to make a quick check whether the data is indeed Excel data. Excel data is represented as Comma Seperated Values in the Clipboard, with line breaks between two rows of data. Hence, we make use of the GetDataPresent method of the IDataObject by passing it the predefined format name CommaSeperatedValue of the DataFormats Class to do the verification.
If (objPresumablyExcel.GetDataPresent(DataFormats. _ CommaSeparatedValue)) Then ... ... ... End If
Format the Data into a DataGrid Control Bindable Form
The data is raw and we need to format it into a form or object that can be bound to a DataGrid control. The sample uses the DataTable object to bind to the DataGrid control.
Dim tblExcel2WinData As New DataTable
Now, there are many ways in which you can treat and format the data. For the purpose of the sample, we would first convert and cast the contents of the IDataObject into a Stream of data that will be contained in an object of the StreamReader Class.
Dim srReadExcel As New StreamReader(CType(objPresumablyExcel. _ GetData(DataFormats.CommaSeparatedValue), Stream))
The next task would be to read this stream of data one line at a time. A loop is the order of the day.
While (srReadExcel.Peek() > 0) ... ... ... End While
Within the loop, we need to start replicating the contents of the StreamReader object in a DataTable object. To achieve this, we first extract a row of data in the Stream Reader object into a String variable.
Dim sFormattedData As String sFormattedData = srReadExcel.ReadLine()
The String variable will now contain the column values for a row of Excel data separated by comma. We split this String variable into an array.
Dim arrSplitData As Array arrSplitData = sFormattedData.Split("")
The number of Array items is equivalent to the number of columns of data copied from the Excel Sheet. We prepare the DataTable to reflect the same number of columns.
If tblExcel2WinData.Columns.Count <= 0 Then For iLoopCounter = 0 To arrSplitData.GetUpperBound(0) tblExcel2WinData.Columns.Add() Next End If
Finally, we loop the array to add the contents of individual columns into a DataTable Row and add the Row to the DataTable.
Dim iLoopCounter As Integer Dim rowNew As DataRow rowNew = tblExcel2WinData.NewRow() For iLoopCounter = 0 To arrSplitData.GetUpperBound(0) rowNew(iLoopCounter) = arrSplitData.GetValue(iLoopCounter) Next tblExcel2WinData.Rows.Add(rowNew)
Bind the Data to the DataGrid Control
The copied Excel Sheet data is successfully replicated and contained in the DataTable object. All that remains to be done now is to bind the DataTable object to the DataGrid control.
dgrExcelContents.DataSource = tblExcel2WinData.DefaultView()
Figure 3: The Excel Sheet data in the DataGrid Control
And hey, presto, the Excel Sheet data magically appears in the DataGrid control! | <urn:uuid:fe7d90cf-fcbd-4520-a4d1-0ff8498802d0> | 2.515625 | 1,251 | Tutorial | Software Dev. | 47.238964 | 95,538,930 |
- Chemistry. an anode that is attached to a metal object subject to electrolysis and is decomposed instead of the object.
Origin of sacrificial anode
First recorded in 1975–80
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- metallurgy an electropositive metal, such as zinc, that protects a more important electronegative part by corroding when attacked by electrolytic action | <urn:uuid:03b8b144-b6bf-4ee2-900c-1627a5a58834> | 2.703125 | 102 | Structured Data | Science & Tech. | 13.46375 | 95,538,935 |
Date to unix timestamp
Friday , 20 July, 2018 07:46:13 | GMT (Time zone: UTC)
Unix timestamp to date
What is unix timestamp?
Unix timestamp is the number of seconds since january 1, 1970 00:00:00 GMT.
How do we get timestamp in PHP?
Using strtotime() function we can get unix timestamp. it is also very important to note that strtotime() requires a default timezone otherwise it will generate timestamp in server timezone which could be misleading.
PHP Code Example:How do we get readable date from timestamp?
We can use date() function to generate readable date.
PHP Code Example: | <urn:uuid:22fbfb5f-e90c-4bee-939d-a8faabab794b> | 2.640625 | 147 | Tutorial | Software Dev. | 53.982079 | 95,538,945 |
Linear Algebra Method in Combinatorics
- Linear Algebra Method in Combinatorics
- 2018-06-19 14:00-15:00
Georgia State University教授
Erdos-Ko-Rado theorem is a cornerstone of extremal set theory. In his seminal paper that determined the Shannon capacity of the pentagon, Lovasz gave a proof of the EKR theorem by using linear algebra. In this talk I will sketch this proof and other applications of linear algebra in Combinatorics, including a recent result of Hao Huang and the speaker. | <urn:uuid:01a38348-06f2-434e-a981-ce3996991edc> | 2.5625 | 125 | News (Org.) | Science & Tech. | 33.207778 | 95,538,948 |
|laziness, impatience, and hubris|
Re^3: Regular expressions across multiple linesby afoken (Abbot)
|on Apr 24, 2016 at 19:04 UTC||Need Help??|
Well, it may look so, but what really happens is different. See chomp:
This safer version of chop removes any trailing string that corresponds to the current value of $/ (also known as $INPUT_RECORD_SEPARATOR in the English module).
Note: Not a single word of the CR or LF control characters, the CR-LF pair, or NL (newline).
The input record separator $/ is documented, it defaults to an abstract "newline" character:
The input record separator, newline by default. This influences Perl's idea of what a "line" is. [...] See also Newlines in perlport.
Now, "newlines". Perl has inherited them from C, by using two modes for accessing files, text mode and binary mode. In text mode, the systems native line ending, whatever that may be, is translated from or to a logical newline, also known as "\n". In binary mode, file content is not modified during read or write. C has been defined in a way that the logical newline is identical with the native line ending on unix, LF. So, there is no difference between text mode and binary mode ON unix.
Quoting Newlines in perlport:
What happens here is that Perl has reasonable defaults for text handling, so it opens files (including STDIN, STDOUT, STDERR) in text mode by default, $/ defaults to a single logical newline ("\n"), and so native newline characters are translated before chomp just removed that "\n", on any platform.
When reading text files using a non-native line ending, things will usually go wrong:
Of course, it depends on the system you are using:
So, chomp is NOT cross-platform. It can handle input from native text files on all platform out of the box. But if you have to work with ASCII files with mixed line endings (CR, LF, CR-LF, LF-CR), chomp can't work reliably. This is not chomp's fault, neither is it perl's fault.
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-) | <urn:uuid:6725626a-96fd-4179-8787-b7ded9b54609> | 2.59375 | 514 | Comment Section | Software Dev. | 60.355299 | 95,538,976 |
Diphenylamine (DPA), sodium orthophenylphenate (SOPP), benomyl, and thiabendazole (TBZ) are frequently used to control the physical, chemical, and bacterial degradation of fruit during controlled-atmosphere storage. Once discharged to the environment, these chemicals may either be degraded or remain unaltered. Furthermore, the parent compounds and/or their metabolites may either remain at the initial point of release or be transported to other locations. In water, for example, chemicals may either stay in solution (in their original form and/or as derivatives), or they may be removed from solution by precipitation, by adsorption on suspended particles or bottom sediments, by uptake by biota, and/or by volatilization to the atmosphere.
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- Environmental transformations of DPA, SOPP, benomyl, and TBZ
Jasenka V. Zbozinek
- Springer New York
Fallstudie Überschwemmungskarten/© Thaut Images | Fotolia | <urn:uuid:d5d6ebdd-aabf-4b56-8acb-f17b3598ee6b> | 2.609375 | 243 | Knowledge Article | Science & Tech. | 2.083333 | 95,538,977 |
Though it has long been known by scientists that an ecosystem needs different kinds of plants and animals for optimal functioning, University of Georgia scientists have recently found that the genetic diversity of species within a habitat also affects ecosystem processes.
"It is not just the quantity of species diversity that matters, it is also the quality of genetic diversity," said lead author Mike Madritch, an ecology doctoral student at UGA. Madritch studied carbon and nitrogen fluxes during decomposition of leaf litter and found a significant link between nutrient output and the genetic variation of the leaves.
The study was co-authored with Mark Hunter, associate professor of ecology at UGA, and published this week in the Ecological Society of Americas journal, Ecology. The research was funded by the National Science Foundation and the Andrew W. Mellon Foundation.
Kim Carlyle | 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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20.07.2018 | Materials Sciences | <urn:uuid:f8a1b11c-d2b2-4d68-a271-b89b7b30e422> | 2.984375 | 768 | Content Listing | Science & Tech. | 35.067674 | 95,538,991 |