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Metric conversion is a systematic approach to problem solving that uses conversion factors to move or convert from unit ot another.
Many problems in chemistry and health science requires a change of units.You make changes in units everyday. We use metric system which is a common method of measuring system , in 1960 scientists adopted a modification of metric system called International system of Units (SI), to provide uniformity for units used in sciences.
Measurement Metric SI
Length Meter (m) Meter (m)
Volume Liter (L) cubic meter (m^3)
Mass Gram (g) Kilogram (kg)
Time Second (s) Second (s)
Temperature celsius degree Kelvin
The special feature of the metric system of units is that a prefix can be attached to any unit to increase or decrease its size by some factor of 10. For exampl; the prefixes milli & micro are used to make smaller units.A table is attached here lists some of the metric prefixes, their symbols and their values.
Point to note: The relationship of a prefix to a unit can be expressed by replacing the prefix with its numerical value.For exampl: when the prefix kilo in kilometer is replaced with its value of 1000,we find a kilometer is equal to 1000 meters.
Equalities: The comparisons which show the relationship between two units that measure the same quantity.For exampl, in the equality 1m = 100 cm,each quantity describes the same lengthbut in different unit.
meter to cm
1 cm = 10^-2 m
perfix centi value of prefix centi
In the above example you can see a length equality.To write the equality between centimeter and meter , we used the value of prefix centi which is 10^-2 , so then we got the equality between cm and meter(m) that 1 cm = 10^2 x m or this can also be written as 1 m = 100 cm
Writing conversion factors; Conversion factors are the ratio of equivalents values can be generated from equivalence statement.
From the above example of equality the conversion factor can be either
1cm/10^-2m or 10^-2m/1cm
How we use the conversion factor to solve the problems of unit conversion
** given unit x Find unit/ given unit = Find unit
** Given unit x related unit/given unit x Find unit/related unit = Find unit
Arrange the conversion factor so that starting ( given ) units cancels, you can do this by arranging the conversion factors so that the starting units is on the bottom of the conversion factor.
You may find one step unit conversion or two step or chain unit conversions.
Systemetic approach :
Sort information from the problem:by identifying the given quantity and unit , the quantity and unit you want & any relationships implied in problem.
Design a strategy to solve the problem: Devise a conceptual plan.
Apply steps in conceptual plan: Check units properly and multiply terms accross the top & divide by each bottom term.
This should be more clear with these examples;
convert 1.76 yd to centimeter:-
sort info ; Given = 1.76 yd ( yards) & Find : length in cm
Strategy : conceptual plan yd ==> m ==> cm, equivalence : 1m = 1.094 yd , 1 cm = 10^-2 m
conversion factors : 1m / 1.094 yd or 1.094 yd/ 1m and 1cm/10^-2m or 10^-2m/1cm
Solution: Given unit x related unit/given unit x Find unit/related unit
so, we use the conversion factor in which we have given & related units at the bottom so that we can cancel the given & related units.
1.76 yd x 1m / 1.094 yd x 1cm/10^-2m = 160.8775 cm = 161 cm | <urn:uuid:3bfd88be-666f-4aa1-aa5c-c37ea6f72e66> | 4.3125 | 829 | Tutorial | Science & Tech. | 55.934065 | 95,602,630 |
The distribution and ecology of 24 species of Decapoda Reptantia in the estuarine part of the rivers Rhine, Meuse, and Scheldt, in the southwestern part of The Netherlands, is discussed. A few species are common offshore, but a larger number are abundant in the seaward reaches of the estuaries at salinities over 15% Cl'. Below this value, only Carcinus maenas is abundant down to salinities of about 5% Cl'. In still lower salinities the alien brackish-water species Rhithropanopeus harrisii and the similarly alien freshwater species Eriocheir sinensis occur. This two species apparently occupy niches that were empty before the present inhabitants were imported from abroad. pg 212-214 The Shore Crab is certainly the commonest crab of the Delta area. Offshore, however, this species soon becomes rare and has already vanished a few kilometres from the inlets of the estuaries, exactly as described by BROEKHUYSEN (1936) for the tidal channels of the Wadden Sea area. Therefore Carcinus maenas is a typical species of the estuarine environment. Here it occupies a fairly large number of habitats: it is found in the small creeks of salt marshes, all over the tidal flats, on the mussel- and oysterbeds in shallow water, along the artificial "rocky shores" of the dikes, in the deeper part of the main tidal channels, and in non-tidal brackish inland waters. This variation of habitats points to a certain euryhalinity, and this is confirmed by the horizontal distribution over the estuaries. It is difficult, however, to relate the distribution of Carcinus to the salinity distribution as the species shows migratory movements. In general the following picture can be sketched. In summer, Carcinus maenas does not reach the isohaline of 5.5 7, Cl' at high tide during low river discharge (Fig. 11 a and b). Moreover, large concentrations of the species were only noted in salinities of at least 10 7. Cl' (Fig. 11 b). According to POULSEN (1922, 1949) C. maenas was still found at salinities of about 47. Cl' in the Baltic. BROEKHUYSEN (1936) mentions a similar limit for the former Zuiderzee. It is, however, a common phenomenon that marine species are able to penetrate further into the stable brackish water of the Baltic than into the unstable brackish waters of estuaries (DEN HARTOG, 1964). In winter, when high river discharges prevail, Carcinus is pushed back over a large distance in seaward direction. For instance, no Carcinus can be caught in this period in the Haringvliet, or in the Krammer-Volkerak area. In brackish non-tidal waters Carcinus also occurs, though not abundantly. It was found in some canals connected with estuaries, where salinity is fairly high, and in the Veerse Meer, which lake has a salinity varying between about 9 and 117. Cl'. These lake specimens are apparently in a rather bad condition since they only make slow movements when caught, unlike the specimens from the tidal waters which are always very lively. Most remarkable, however, is the occurrence in the brackish non-tidal creek near Schelphock on the island of Schouwen. This large creek was closed off from the sea in 1953, after the flood disaster early in that year. Owing to seepage of salt water it remained brackish and the salinity fluctuated between about 10 7. Cl' and 15 %o Cl'. Carcinus must have been able to tolerate the low salinities accompanied by low temperatures in the winter months, and even to reproduce in this body of water. The lowest salinity measured in winter was 10. 79 7. Cl although the temperature of the water was not measured at the same time, it is estimated to have been about 2' to 3' C, and at least under 5' C. In the extremely cold winter of 1962-63, temperatures fell below 0' C; in this period the salinity was about 13 % Cl'. In the other brackish non-tidal inland waters Carcinus does not occur, at least not continually. More extreme salinity conditions are probably the reason for this absence. The migratory movements of Carcinus in both the horizontal and the vertical directions are well known (BROEKHUYSEN, 1936; EDWARDS, 1958; NAYLOR, 1962). As pointed out above, Carcinus shows migratory behaviour in the upper reaches of the estuaries of the Delta area under the influence of salinity conditions. There is also a vertical migration: in summer the adults of the species colonize the extensive tidal flats and leave these flats again in the autumn. It seems that horizontally the males do not migrate as far out to sea as do the females. When the lower values are omitted, the data in the tables given by BROEKHUYSEN (1936), point in this direction. We tested the hypothesis that males and females do not differ in the distance they migrate in a seaward direction, and hence, that the ratio between females and males does not differ along the main axis of an estuary. For this purpose we used material caught in the Grevelingen in May of 1967. It was found, however, that the proportion of males became significantly larger in an inshore direction (0.05 > P > 0.02). Such a difference in the month of May could, however, also be caused by a more rapid inshore migration of the males than of the females, when both have wintered at an equal distance offshore. Therefore, this hypothesis was tested again for samples caught in February 1969. Owing to technical difficulties, it was only possible to obtain samples of crabs from the central and inner parts of the Grevelingen, and from the outer and central parts of the Oosterschelde estuary, the boundaries being arbitrary. These samples were combined and a X'-test was applied to see whether the distribution of the crabs was the same for the 82 males and the 70 females catched. Males predominated in the inner parts, females in the outer parts, and this difference in distribution proved to be highly significant (P < 0.005). It may therefore be concluded that in the estuaries of the Delta area, female Shore Crabs move in winter further out to sea than the males. This brings the females into warmer as well as saltier water. It is, however, impossible to distinguish between the effects of these two factors. As according to BROEKHUYSEN (1936) there is no correlation between sex and salinity, this difference may be the result of temperature. According to BROEKHUYSEN (1936) there is also no correlation between size and salinity. During our investigations we got the impression that the average size of carapace of a sample of crabs declined with declining salinity, but there was no significant decrease in size along the main axis of an estuary, at least not at salinities over 10% Cl'. Carcinus maenas can be found on all types of substrate, with the possible exception of very soft muds.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:1894eefa-2247-4fef-b2b7-04f07b0b8e37> | 3.03125 | 1,578 | Academic Writing | Science & Tech. | 45.44357 | 95,602,636 |
Write a C# console application in which you declare an array of five integers and store five values in the array. Write a try block in which you place a loop that attempts to access each element of the array, incrementing a subscript from 0 to 10. Create a catch block that catches the eventual IndexOutOfRangeException; within the block, display "Now you've gone beyond the bounds of the array" on the screen.© BrainMass Inc. brainmass.com July 18, 2018, 6:50 am ad1c9bdddf
Please find below the solution. Kindly let me know if you have any confusion or any further questions on this.
Don't forget to leave a positive feedback along with a good rating and, restrict the postings to me in future if you like the work.
(Please use the code provided only ...
The solution contains a properly written program which displays how to catch an exception when code tries to access an invalid array item. The code included is very easy to understand and follows all the proper coding guidelines. | <urn:uuid:71d8282f-1b50-4edd-859a-d7513dc0f4e6> | 2.671875 | 215 | Tutorial | Software Dev. | 61.487546 | 95,602,643 |
A new discovery from the Brain Mind Institute of the EPFL (Ecole Polytechnique Fédérale de Lausanne) shows that the brain rewires itself following an experience. The research further shows that this process of creation, testing, and reconfiguring of brain circuits takes place on a scale of just hours, suggesting that the brain is evolving considerably even during the course of a single day.
Scientists know that the strength of the connections between neurons changes to shape memories. They also know that the developing brain has a high level of plasticity as neurons forge connections with other neurons. This new research, published in the August 7, 2006 early online edition of the Proceedings of the National Academy of Sciences, goes further, investigating how neurons choose their connections with neighboring neurons. Researchers Henry Markram and Jean-Vincent Le Bé found that connections between neurons switch rapidly on and off, leading to a form of adaptive rewiring in which the brain is engaged in a continuous process of changing, strengthening and pruning its circuitry.
Studying neuron clusters from the neocortex of neonatal rats, Markram and Le Bé found that instead of growing preferentially towards specific receivers, neurons actually have no particular affinity for any other neuron, but instead remain in a state of perpetual readiness to reconfigure circuits. They found that over the course of just a few hours, connections are formed and re-formed many times.
“The circuitry of the brain is like a social network where neurons are like people, directly linked to only a few other people,” explains Markram. “This finding indicates that the brain is constantly switching alliances and linking with new circles of “friends” to better process information.”
In their samples, the rewiring process was occurring continuously at a slow pace. By exciting the sample with glutamate, they found that the rate increased markedly. This suggests that with a strong new experience, the brain accelerates its reconfiguration process, allowing new connections to be made, tested, and strengthened, and weaker ones removed so that the brain is quickly better adapted to the new situation.
“This continual rewiring of the microcircuitry of the brain is like a Darwinian evolutionary process,” notes Markram, “where a new experience triggers a burst of new connections between neurons, and only the fittest connections survive.”
Markram emphasizes that these findings may have important implications for brain research, even at a practical level. “This discovery opens up a whole new frontier for researchers as we now try to understand the evolutionary process that sets the brain on a particular course. Perhaps it could even reveal ways to steer the brain around particular circuitry pathologies such as epilepsy.”
Mary Parlange | alfa
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
Biological signalling processes in intelligent materials
18.07.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau
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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03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Life Sciences
18.07.2018 | Information Technology | <urn:uuid:61fc6634-df8d-402d-9ce8-f0d856e4ac86> | 3.390625 | 1,205 | Content Listing | Science & Tech. | 37.493154 | 95,602,645 |
The results of the coming geomagnetic storm may be pleasant – auroras as far south as Illinois – or unpleasant, such as GPS and communications problems, according to Young.
The coronal mass ejection is expected to hit the Earth at about 1:30 a.m. Eastern time Thursday – with a margin of error of plus or minus seven hours.
The most recent updates suggest that the effects of the geomagnetic storm—imagine taking a bar magnet and waving it at the Earth—won’t be anything for most of us to worry about, so we can just comfortably hope that the northern lights will be visible as far south as Illinois. Last October a strong CME passed through, and the results were visible as far south as Arkansas. Someone in Martin, Michigan (not that much farther north than Chicago; it’s about on a parallel with the Wisconsin-Illinois border) captured a timelapse:
Here’s what it looks like IN SPACE… and it’s also a good explanation of the phenomenon. The blast wave rippling across the sun is spectacular:
This one doesn’t seem like it’ll cause much of a fuss, but in January Lee Billings compellingly outlined a worst-case scenario:
All this may seem like doomsaying, but the historic record suggests otherwise: The Halloween Storm, in fact, pales in comparison to several earlier events. In 1989, ground currents from a less intense geomagnetic storm knocked out a high-voltage transformer at a hydroelectric power plant Quebec, plunging the Canadian province into a prolonged 9-hour blackout on an icy winter night. A far more extreme geomagnetic storm washed over the Earth in May of 1921, its magnitude illustrated in world-girdling aurorae and in fires that broke out in telegraph offices, telephone stations, and railroad routing terminals — sites that sucked up geomagnetic currents traveling through nascent power grids. An even more extreme storm in September 1859 caused geomagnetic currents so strong that for days telegraph operators could disconnect their equipment from battery power and send messages solely via the “auroral current” induced in their transmission lines. The 1859 storm is known as the “Carrington Event,” after a British astronomer who witnessed an associated solar flare and connected it with the subsequent earthbound disturbances.
Geomagnetic storms, though, can have less benign impacts. On Aug. 4, 1972, a Bell Telephone line running from Chicago to San Francisco got knocked out. Bell Labs researchers wanted to find out why, and their findings led them right back to 1859 and the auroral current.
Louis Lanzerotti, now an engineering professor at the New Jersey Institute of Technology, went digging in the Bell Labs library for similar events and explanations. Along with field research, the history became the core of a new approach to building more robust electrical systems.
In other SPACE NEWS, the Tevatron is dead but its data lives on:
Physicists from the Fermi National Accelerator Laboratory in Batavia, Ill., say they have found a bump in their data that might be the long-sought Higgs boson, a hypothesized particle that is responsible for endowing other elementary particles with mass.
“Based on the current Tevatron data and results compiled through December 2011 by other experiments, this is the strongest hint of the existence of a Higgs boson,” said the report, which will be presented on Wednesday by Wade Fisher of Michigan State University to a physics conference in La Thuile, Italy.
It has led to a joke in physics circles now: The Higgs boson has not been discovered yet, but its mass is 125 billion electron volts.
6 days ago | <urn:uuid:4df3c551-93c4-4f5d-8b87-7c359dc7c583> | 3.046875 | 776 | News Article | Science & Tech. | 38.198297 | 95,602,653 |
Callables and Future
The FiutureTask is "A cancellable asynchronous computation. This class provides a base implementation of Future, with methods to start and cancel a computation, query to see if the computation is complete, and retrieve the result of the computation."
Callables are just like Runnables to define the smallest unit of work called tasks. The difference between Callable and Runnable is that Runnable cannot return any result whereas Callable can return result of type Future. Later we can get the data from this return value.
Once we submit the Callable task to the Executor, it does not block and returns immediately. We can determine if the task is finished or not by using the isDone api. Once isDone returns TRUE, we can access the result from the future which was returned from submitting the task to the executor using the future.get() API. However, we must remember that get API is blocking and hence if the task is not completed when the get has been called, it will block the thread.
Actually FutureTask is designed to be used through the ExecutorService interface and the classes that implement it. It is those classes that use FutureTask and fork the threads and create non-blocking Asynchronous background task. Executors typically manage a pool of threads so that we don't have to create threads manually. All the threads in a thread-pool can be reused.
The source code is a working example of the use of FutureTask alongwith Executor model of the Java Concurrency Framework. The basic motto of the Application is the following.
Suppose we need to do a very time consuming task at any time of an Application. Ay reading a big chunk of data from a huge database. So the basic idea is that whenever the application starts we spawn a background thread through the executor framework and delegate the task of reading data to that background thread. While reading of the data is going on, we continue with our other task in the application. The background thread collects the data and keep it in the future variable which is returned when we submit the task to the executor service. Any time of the application lifecycle we can know if the task is completed or not by calling the api isDone() on the future returned from submitting the task. Then in later time we can access the already fetched data by using the get() api on the future variable which was returned when the task was submitted to the executor framework. Not only that, when the task is going on in the background we can cancel it at anytime we want. | <urn:uuid:65851183-d6f3-47c1-bcd3-c264b070a864> | 3.0625 | 524 | Documentation | Software Dev. | 44.489859 | 95,602,657 |
Valley Network (Venus)
Integrated system of elongate depressions cut into topography on Venus.
A type of valley on Venus
Networks of valleys, commonly with integrated systems of tributaries (Baker et al. 1992). Unlike channels, valley networks’ boundaries may not be shaped by fluids (Baker et al. 1992, 1997) and valleys show no bedforms indicative of surface flows (Komatsu et al. 2001; as also defined for Mars, Mars Channel Working Group 1983).
Labyrinthic valley network (Fig. 1). This is the most common type observed on Venus. Valleys are several km wide and 100 s km long. They are found within or near tectonically deformed terrains or near volcanic landforms (coronae) (Komatsu et al. 1992, 1993, 2001). Their morphology suggests structural control. Widths and depths of valleys appear significantly...
KeywordsSurface Flow Surface Slope Subsurface Flow Main Valley Valley System
- Baker VR, Komatsu G, Parker TJ, Gulick VC (1997) Channels and valleys on Venus. In: Venus II. University of Arizona Book Press, Tucson, pp 757–793Google Scholar
- Gulick VC, Komatsu G, Baker VR (1992) Integrated valley systems on Venus: a comparative morphological study. LPSC XXIII, pp 467–468Google Scholar
- Komatsu G, Gluick VC, Kargel JS, Baker VR (1992) Venus lava sapping valleys. LPSC XXIII, pp 719–720Google Scholar | <urn:uuid:ff5d7d90-98f9-4745-85f2-91597106c7ad> | 3.046875 | 333 | Academic Writing | Science & Tech. | 59.007835 | 95,602,658 |
A team of Germans competing at the Google Lunar X-Prize has already laid out plans for their first mission. What exactly is it? They plan to send out two probes to the Moon, all in hopes of proving that the Apollo 17 mission was truly successful.
A new research has revealed that astronauts who stay for long periods of time in space suffer from a strange eye condition: deformed eyeballs. This mysterious condition could be detrimental to future space exploration.
Is the U.S. ready for a full-blown war in space? Experts say that the US Military considers the prospect and is gearing up for a potential space warfare by developing weapons that could only exist in science fiction dreams.
A new satellite, which will be set out to collect pertinent information regarding natural disasters all over Africa, will be launched within next year. It gains its popularity not only because it is the continent's first private space satellite, but it has also been conceptualized by a group of high school girls. Experts believe that now, more than ever, is the best time for Africa to finally join the space race.
The European Space Agency announced that Italian astronaut Paolo Nespoli will be launched to the International Space Station next year, through an official statement released on November 24. Nespoli will be launched on a Soyuz vehicle in May 2017 on a five-month mission, which is part of a barter agreement between NASA and Italy’s ASI space agency involving ESA astronauts, according to ESA.
After quitting the European Union, the British government has expressed its utmost support to the European Space Agency.
The future of space is looking brighter than ever for Europeans, as the European Space Agency (ESA) announces that nine of its missions will be extended until 2018 through an official statement.
Are humans doomed? Stephen Hawking, the renowned physicist, thinks so. Hawking said that humanity will only have 1,000 years left, with an impending asteroid collision possibly wiping out humans by 3016.
Dubbed as Cassini's Ring-Grazing Orbits, Cassini will dive through the outer edge of Saturn's rings 20 times, once every seven days, from November 30 to April 22 next year.
Pentagon expert calls for some form of rules and regulations to address the danger of collision among spacecraft and debris in orbit around space.
Vector Space Systems has successfully pooled $1.25 million additional funding for its 2017 small launch vehicle project, Vector-R. The investor the Space Angels Network.
NASA scientists discovered 19 heartbeat star systems with the use of the space agency’s Kepler Telescope.
The powerful asteroid that wiped off the dinosaurs on Earth 66 millions years ago caused the planet's surface to vaporize and act like a liquid, a new study reveals.
For years, humanity has been wondering if we're not alone in the whole universe. It's been a source of mystery and fascination for alien hunters, with hundreds of UFO sightings popping in different locations. But now, Ben Miller, TV host and a PhD holder in physics, says our first alien counter will happen soon. | <urn:uuid:ec0c0b9e-742d-4e63-823c-e9a29cc8ad16> | 2.625 | 628 | Content Listing | Science & Tech. | 48.336407 | 95,602,662 |
The tiny black hole resides in a Milky Way
Galaxy binary system known as XTE J1650-500,
named for its sky coordinates in the southern
constellation Ara. NASA's Rossi X-ray Timing
Explorer (RXTE) satellite discovered the system
in 2001. Astronomers realized soon after J1650's
discovery that it harbors a normal star and a
relatively lightweight black hole. But the black
hole’s mass had never been measured to high
Shaposhnikov and his Goddard colleague Lev
Titarchuk presented their results on Monday,
March 31, at the American Astronomical Society
High-Energy Astrophysics Division meeting in Los
Angeles, Calif. Titarchuk also works at George
Mason University in Fairfax, Va., and the US
Naval Research Laboratory in Washington, DC.
The method used by Shaposhnikov and Titarchuk
has been described in several papers in the
Astrophysical Journal. It uses a relationship
between black holes and the inner part of their
surrounding disks, where gas spirals inward
before making the fatal plunge. When the feeding
frenzy reaches a moderate rate, hot gas piles up
near the black hole and radiates a torrent of
X-rays. The X-ray intensity varies in a pattern
that repeats itself over a nearly regular
interval. This signal is called a quasi-periodic
oscillation, or QPO.
Astronomers have long suspected that a QPO's
frequency depends on the black hole's mass. In
1998, Titarchuk realized that the congestion
zone lies close in for small black holes, so the
QPO clock ticks quickly. As black holes increase
in mass, the congestion zone is pushed farther
out, so the QPO clock ticks slower and slower.
To measure the black hole masses, Shaposhnikov
and Titarchuk use archival data from RXTE, which
has made exquisitely precise measurements of QPO
frequencies in at least 15 black holes.
Last year, Shaposhnikov and Titarchuk applied
their QPO method to three black holes whose
masses had been measured by other techniques. In
their new paper, they extend their result to
seven other black holes, three of which have
well-determined masses. "In every case, our
measurement agrees with the other methods," says
Titarchuk. "We know our technique works because
it has passed every test with flying colors."
When Shaposhnikov and Titarchuk applied their
method to XTE J1650-500, they calculated a mass
of 3.8 Suns, with a margin of uncertainty of
only half a Sun. This value is well below the
previous black hole record holder with a
reliable mass measurement, GRO 1655-40, which
tips the scales at about 6.3 Suns.
Below some unknown critical threshold, a dying
star should produce a neutron star instead of a
black hole. Astronomers think the boundary
between black holes and neutron stars lies
somewhere between 1.7 and 2.7 solar masses.
Knowing this dividing line is important for
fundamental physics, because it will tell
scientists about the behavior of matter when it
is scrunched into conditions of extraordinarily
Despite the diminutive size of this new record
holder, future space travelers had better
beware. Smaller black holes like the one in
J1650 exert stronger tidal forces than the much
larger black holes found in the centers of
galaxies, which make the little guys more
dangerous to approach. "If you ventured too
close to J1650's black hole, its gravity would
tidally stretch your body into a strand of
spaghetti," says Shaposhnikov.
Shaposhnikov adds that RXTE is the only
instrument that can make the high-precision
timing observations necessary for this line of
research. "RXTE is absolutely crucial for these
black hole mass measurements," he says.
Adapted from materials provided by NASA/Goddard
Space Flight Center. | <urn:uuid:1e6da411-8d19-4620-ba9b-08c8e28ab572> | 3.484375 | 885 | Knowledge Article | Science & Tech. | 46.458183 | 95,602,668 |
American Journal of Modern Physics
Volume 6, Issue 6, November 2017, Pages: 122-126
Received: Aug. 12, 2017;
Accepted: Aug. 28, 2017;
Published: Sep. 21, 2017
Views 2574 Downloads 150
Hua Ma, The College of Science, Air Force University of Engineering, Xi’an, People’s Republic of China
It is a basic, ancient and mysterious issue: why our space is three dimensional? This issue is related to philosophy, mathematics, physics and even religion, and thus aroused great research interests. The author makes an in-depth analysis of the problem, and finally comes to a conclusion: For any vector space with symmetry, orthogonality, homogeneity and completeness, the space dimension must be three on condition that: the energy obeys the law of conservation, the dynamics law is governed by the covariance principle, and thus the cross-product must can be defined in the space. Our space just meets and requires the above constraints, so its dimension is three.
A Physical Explanation on Why Our Space Is Three Dimensional, American Journal of Modern Physics.
Vol. 6, No. 6,
2017, pp. 122-126.
Copyright © 2017 Authors retain the copyright of this article.
This article is an open access article distributed under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/
) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Rynasiewicz, Robert, "Newton's Views on Space, Time, and Motion", Stanford Encyclopedia of Philosophy (Stanford University).
Schutz, Bernard, Gravity from the Ground Up: An Introductory Guide to Gravity and General Relativity (Cambridge University Press, 2004).
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Danielson, Donald A, Vectors and Tensors in Engineering and Physics (Westview (Perseus), 2nd ed., 2003). | <urn:uuid:a3f2882c-861e-481a-a4ed-bf96850b11cb> | 2.9375 | 873 | Academic Writing | Science & Tech. | 56.463886 | 95,602,673 |
Decoding the essence of being – understanding the brain and all its connections, that is Connectomics. Scientists from the Max Planck Institutes for Medical Research in Heidelberg, of Neurobiology in Martinsried near Munich, and the Massachusetts Institute of Technology (MIT) now made an important step in this direction:
950 neurons in a block of mouse retina, reconstructed from serial block-face electron microscopy data by more than 200 undergraduate students. Spheres indicate the cell bodies (ganglion cells: blue, amacrine cells: green, bipolar cells: orange, photoreceptors: gray). “Skeleton” reconstructions of all neurons appear as web between the cell body layers. Black/white background shows the final connectivity matrix (the “connectome”) between the 950 neurons.
© Julia Kuhl, Winfried Denk; Helmstaedter et al., 2013; (c) Max Planck Institute for Medical Research, Heidelberg, Germany
950 neurons reconstructed in a block of mouse retina, imaged using serial block-face electron microscopy (gray images). Spheres indicate cell bodies (red, ganglion cells, green, amacrine cells).
© Fabian Isensee, Julia Kuhl; Helmstaedter et al., 2013; © Max Planck Institute for Medical Research, Heidelberg, Germany
After analyzing data for four years, aided by about 200 undergraduate students, the scientists created a precise diagram of all nerve cells and their connections in a piece of mouse retina. Although representing only a small fraction of the brain, this diagram already revealed a new cell type and circuit motifs that may help to understand the reactions of certain retinal cells.
The human brain contains about 100 billion nerve cells, each of which is in contact with thousands of other cells. Scientists have long speculated that the essence of our being, our emotions, thoughts and memories, are all based on those contacts. How can we decode the mysteries hidden in these connections? ”Even a tiny cube of brain tissue contains thousands of cells and many millions of connections“, says Moritz Helmstaedter, first author of the study now published in Nature. Helmstaedter now leads his own research group at the Max Planck Institute of Neurobiology in Martinsried.
Undeterred by those numbers, the neurobiologists accepted the challenge and now report a first step in this direction. Together with their American collaborators, the Max Planck researchers describe how they mapped all neurons and their connections in a piece of mouse retina.
Even though the cube of retina was only a tenth of a millimetre on a side, it contained around 1000 neurons and more than half a million contacts between them. “We needed about a month to acquire the data and four years to analyse them” says Helmstaedter. The reason for this long time is the extensive analysis needed to extract the wiring from electron-microscope images of brain tissue. Extremely thin neuronal processes needed to be followed over long distances, without missing any of the multitudes of connections between them. Current computer algorithms are very useful in this process but often not reliable enough. Humans are thus still needed to make the decision whether a neuronal “wire” branches or not. In the current study it took 20,000 hours alone to make those decisions. To analyse an entire mouse brain in this way would require several billion hours of human attention.
The retina does not merely transform images into electrical signals. It separates and filters the image information before transmitting it to the brain. The network of neurons in this small neurocomputer is accordingly complex. While mapping this network the scientists encountered a novel type of cell, belonging to the class of bipolar cells, but with an as yet unknown function. Motifs elsewhere in the connection diagram might explain why some of the retinal cells respond to a stimulus in the way they do. “These results show that we are on the right path, even though we analysed only about one tenth of a percent of the entire mouse retina”, says Helmstaedter. He is convinced, as are many other neurobiologists, that mapping and decoding the connectome will revolutionize brain research.
“Our goal is to map and understand the connectome of an entire mouse brain“, says Winfried Denk, who is currently in the process of moving his laboratory from the Heidelberg institute to Martinsried. How realistic is such an ambitious goal, given that the analysis of a miniscule piece of retina already took four years? The entire brain is 200,000 times larger, but Denk doesn’t seem too worried: ”I'm confident that we can scale up the automated imaging process, the serial-block face electron microscopy, that we used for the piece of retina in such a way that we can image an entire mouse brain. Yet we may end up imaging continuously for a year or two.“ However, Denk also concedes that there is currently no realistic way to analyse the data. ”Except, of course, someone gives us the tens of billions of dollars to pay for the necessary manpower.“
Helmstaedter has a different idea – he and his group are counting on help from the internet community: “We work on launching the online game Brainflight this year, which will allow internet users all over the world to fly along nerves cells while collecting points. Their choices of flight paths will help us to identify the real connections between neurons." Modern algorithms are often based on machine-learning and thus get better the more training data they are given. The brainflight-data will therefore also help with the development of enhanced data-analysis algorithms for the computer.
ContactDr. Moritz Helmstaedter
Dr. Moritz Helmstaedter | Max-Planck-Institute
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The Power of Networks Lets Scientists Unravel the Complex Control of Biological Processes
News Jun 18, 2007
Scientists at the Samuel Lunenfeld Research Institute of Mount Sinai Hospital (Canada), the European Molecular Biology Laboratory (Germany), and Massachusetts Institute of Technology (USA) have created a new computational method called NetworKIN.
The method uses biological networks to identify relationships between molecules. In a cover story featured in the 14 June 2007 edition of the journal Cell, the scientists report insights into the regulation of protein networks that will ultimately help to target human disease.
“Thousands of proteins can be changed (via phosphorylation) but until now, it has not been possible to know which protein has made the change,” states Dr. Tony Pawson, distinguished investigator at the Lunenfeld.
Proteins are the functional agents that carry out all processes in a cell. But they only rarely act alone. Instead they accomplish their effects as part of big networks. How proteins interact in these networks often depends on phosphorylation, the addition of a phosphate at specific sites on a protein. Kinases are proteins that bring about the phosphorylation of other proteins and in this way regulate all cellular processes.
“Our method works a bit like getting a recommendation from Amazon,” says Dr. Peer Bork, group leader at EMBL. “The fact that certain books have been bought by the same customers tells you that they have something in common. In the same way biological networks tell us about shared features between different proteins. These help us predicting which kinases are likely to act on them.”
“By getting a network-wide view, multiple aberrant genes of kinase-controlled processes are more easily targeted,” states Dr. Rune Linding, postdoctoral fellow, Samuel Lunenfeld Research Institute. “In the future, the treatment of complex human diseases will be treated by targeting multiple genes.” Complex diseases like cancer often contain defects in several processes controlled by kinases.
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In spectroscopy, a forbidden mechanism (forbidden transition or forbidden line) is a spectral line associated with absorption or emission of light by atomic nuclei, atoms, or molecules which undergo a transition that is not allowed by a particular selection rule but is allowed if the approximation associated with that rule is not made. For example, in a situation where, according to usual approximations (such as the electric-dipole approximation for the interaction with light), the process cannot happen, but at a higher level of approximation (e.g. magnetic dipole, or electric quadrupole) the process is allowed but at a much lower rate.
An example is phosphorescent glow in the dark materials, which absorb light and form an excited state whose decay involves a spin flip, and is therefore forbidden by electric dipole transitions. The result is emission of light slowly over minutes or hours.
Although the transitions are nominally forbidden, there is a small probability of their spontaneous occurrence, should an atomic nucleus, atom or molecule be raised to an excited state. More precisely, there is a certain probability that such an excited entity will make a forbidden transition to a lower energy state per unit time; by definition, this probability is much lower than that for any transition permitted or allowed by the selection rules. Therefore, if a state can de-excite via a permitted transition (or otherwise, e.g. via collisions) it will almost certainly do so before any transition occurs via a forbidden route. Nevertheless, most forbidden transitions are only relatively unlikely: states that can only decay in this way (so-called meta-stable states) usually have lifetimes on the order milliseconds to seconds, compared to less than a microsecond for decay via permitted transitions. In some radioactive decay systems, multiple levels of forbiddenness can stretch life times by many orders of magnitude for each additional unit by which the system changes beyond what is most allowed under the selection rules. Such excited states can last years, or even for many billions of years (too long to have been measured).
The most common mechanism for suppression of the rate of gamma decay of excited atomic nuclei, and thus make possible the existence of a metastable isomer for the nucleus, is lack of a decay route for the excited state that will change nuclear angular momentum (along any given direction) by the most common (allowed) amount of 1 quantum unit of spin angular momentum. Such a change is necessary to emit a gamma-ray photon, which has a spin of 1 unit in this system. Integral changes of 2, 3, 4, and more units in angular momentum are possible (the emitted photons carry off the additional angular momentum), but changes of more than 1 unit are known as forbidden transitions. Each degree of forbiddenness (additional unit of spin change larger than 1, that the emitted gamma ray must carry) inhibits decay rate by about 5 orders of magnitude. The highest known spin change of 8 units occurs in the decay of Ta-180m, which suppresses its decay by a factor of 1035 from that associated with 1 unit, so that instead of a natural gamma decay half life of 10−12 seconds, it has a half life of more than 1023 seconds, or at least 3 x 1015 years, and thus has yet to be observed to decay.
Although gamma decays with nuclear angular momentum changes of 2, 3, 4, etc., are forbidden, they are only relatively forbidden, and do proceed, but with a slower rate than the normal allowed change of 1 unit. However, gamma emission is absolutely forbidden when the nucleus begins in a zero-spin state, as such an emission would not conserve angular momentum. These transitions cannot occur by gamma decay, but must proceed by another route, such as beta decay in some cases, or internal conversion where beta decay is not favored.
Beta decays here are classified according to the L-value of the emitted radiation. Unlike gamma decays, beta decays may proceed from a nucleus with a spin of zero and even parity, to a nucleus also with a spin of zero and even parity (Fermi transition). This is possible because the electron and neutrino emitted may be of opposing spin (giving a radiation total angular momentum of zero), thus preserving angular momentum of the initial state even if the nucleus remains at spin-zero before and after emission. This type of emission is super-allowed meaning that it is the most rapid type of beta decay in nuclei that are susceptible to a change in proton/neutron ratios that accompanies a beta decay process.
The next possible total angular momentum of the electron and neutrino emitted in beta decay is a combined spin of 1 (electron and neutrino spinning in the same direction), and is allowed. This type of emission (Gamow-Teller transition) changes nuclear spin by a unit of 1 to compensate. States involving higher angular momenta of the emitted radiation (2, 3, 4, etc.) are forbidden, and are ranked in degree of forbiddenness by their increasing angular momentum.
Specifically, when L > 0, the decay is referred to as forbidden. Nuclear selection rules require L-values greater than two to be accompanied by changes in both nuclear spin (J) and parity (π). The selection rules for the Lth forbidden transitions are:
where Δπ = 1 or −1 corresponds to no parity change or parity change, respectively. As noted, the special case of a Fermi 0+ → 0+ transition (which in gamma decay is absolutely forbidden) is referred to as super-allowed for beta decay, and proceeds very quickly if beta decay is possible. The following table lists the ΔJ and Δπ values for the first few values of L:
|Superallowed||0+ → 0+||no|
|First forbidden||0, 1, 2||yes|
|Second forbidden||1, 2, 3||no|
|Third forbidden||2, 3, 4||yes|
As with gamma decay, each degree of increasing forbiddenness increases the half life of the beta decay process involved by a factor of about 4 to 5 orders of magnitude.
Double beta decay has been observed in the laboratory, e. g. in 82
. Geochemical experiments have also found this rare type of forbidden decay in several isotopes. with mean half lives over 1018 yr .
Forbidden transitions in rare earth atoms such as erbium and neodymium make them useful as dopants for solid-state lasing media. In such media, the atoms are held in a matrix which keeps them from de-exciting by collision, and the long half life of their excited states makes them easy to optically pump to create a large population of excited atoms. Neodymium doped glass derives its unusual coloration from forbidden f-f transitions within the neodymium atom, and is used in extremely high power solid state lasers. Bulk semiconductor transitions can also be forbidden by symmetry, which change the functional form of the absorption spectrum, as can be shown in a Tauc plot.
Forbidden emission lines have been observed in extremely low-density gases and plasmas, either in outer space or in the extreme upper atmosphere of the Earth. In space environments, densities may be only a few atoms per cubic centimetre, making atomic collisions unlikely. Under such conditions, once an atom or molecule has been excited for any reason into a meta-stable state, then it is almost certain to decay by emitting a forbidden-line photon. Since meta-stable states are rather common, forbidden transitions account for a significant percentage of the photons emitted by the ultra-low density gas in space. Forbidden transitions in highly charged ions resulting in the emission of visible, vacuum-ultraviolet, soft x-ray and x-ray photons are routinely observed in certain laboratory devices such as electron beam ion traps and ion storage rings, where in both cases residual gas densities are sufficiently low for forbidden line emission to occur before atoms are collisionally de-excited. Using laser spectroscopy techniques, forbidden transitions are used to stabilize atomic clocks and quantum clocks that have the highest accuracies currently available.
Forbidden lines of nitrogen ([N II] at 654.8 and 658.4 nm), sulfur ([S II] at 671.6 and 673.1 nm), and oxygen ([O II] at 372.7 nm, and [O III] at 495.9 and 500.7 nm) are commonly observed in astrophysical plasmas. These lines are important to the energy balance of planetary nebulae and H II regions. The forbidden 21-cm hydrogen line is particularly important for radio astronomy as it allows very cold neutral hydrogen gas to be seen. Also, the presence of [O I] and [S II] forbidden lines in the spectra of T-tauri stars implies low gas density.
Forbidden line transitions are noted by placing square brackets around the atomic or molecular species in question, e.g. [O III] or [S II]. | <urn:uuid:3ac1f152-f37b-43dc-87f8-a5b8187bda38> | 3.1875 | 1,852 | Knowledge Article | Science & Tech. | 36.23173 | 95,602,709 |
Particle in a box
In quantum mechanics, the particle in a box model (also known as the infinite potential well or the infinite square well) describes a particle free to move in a small space surrounded by impenetrable barriers. The model is mainly used as a hypothetical example to illustrate the differences between classical and quantum systems. In classical systems, for example, a ball trapped inside a large box, the particle can move at any speed within the box and it is no more likely to be found at one position than another. However, when the well becomes very narrow (on the scale of a few nanometres), quantum effects become important. The particle may only occupy certain positive energy levels. Likewise, it can never have zero energy, meaning that the particle can never "sit still". Additionally, it is more likely to be found at certain positions than at others, depending on its energy level. The particle may never be detected at certain positions, known as spatial nodes.
The particle in a box model is one of the very few problems in quantum mechanics which can be solved analytically, without approximations. Due to its simplicity, the model allows insight into quantum effects without the need for complicated mathematics. It serves as a simple illustration of how energy quantization (energy levels), which are found in more complicated quantum systems such as atoms and molecules, come about. It is one of the first quantum mechanics problems taught in undergraduate physics courses, and it is commonly used as an approximation for more complicated quantum systems.
The simplest form of the particle in a box model considers a one-dimensional system. Here, the particle may only move backwards and forwards along a straight line with impenetrable barriers at either end. The walls of a one-dimensional box may be visualised as regions of space with an infinitely large potential energy. Conversely, the interior of the box has a constant, zero potential energy. This means that no forces act upon the particle inside the box and it can move freely in that region. However, infinitely large forces repel the particle if it touches the walls of the box, preventing it from escaping. The potential energy in this model is given as
where L is the length of the box, xc is the location of the center of the box and x is the position of the particle within the box. Simple cases include the centered box (xc = 0 ) and the shifted box (xc = L/2 ).
Position wave functionEdit
In quantum mechanics, the wavefunction gives the most fundamental description of the behavior of a particle; the measurable properties of the particle (such as its position, momentum and energy) may all be derived from the wavefunction. The wavefunction can be found by solving the Schrödinger equation for the system
where and are arbitrary complex numbers. The frequency of the oscillations through space and time is given by the wavenumber and the angular frequency respectively. These are both related to the total energy of the particle by the expression
which is known as the dispersion relation for a free particle. Here one must notice that now, since the particle is not entirely free but under the influence of a potential (the potential V described above), the energy of the particle given above is not the same thing as where p is the momentum of the particle, and thus the wavenumber k above actually describes the energy states of the particle, not the momentum states (i.e. it turns out that the momentum of the particle is not given by ). In this sense, it is quite dangerous to call the number k a wavenumber, since it is not related to momentum like "wavenumber" usually is. The rationale for calling k the wavenumber is that it enumerates the number of crests that the wavefunction has inside the box, and in this sense it is a wavenumber. This discrepancy can be seen more clearly below, when we find out that the energy spectrum of the particle is discrete (only discrete values of energy are allowed) but the momentum spectrum is continuous (momentum can vary continuously) and in particular, the relation for the energy and momentum of the particle does not hold. As said above, the reason this relation between energy and momentum does not hold is that the particle is not free, but there is a potential V in the system, and the energy of the particle is , where T is the kinetic and V the potential energy.
The size (or amplitude) of the wavefunction at a given position is related to the probability of finding a particle there by . The wavefunction must therefore vanish everywhere beyond the edges of the box. Also, the amplitude of the wavefunction may not "jump" abruptly from one point to the next. These two conditions are only satisfied by wavefunctions with the form
where n is a positive integer (1,2,3,4...). For a shifted box (xc = L/2), the solution is particularly simple. The simplest solutions, or both yield the trivial wavefunction , which describes a particle that does not exist anywhere in the system. Negative values of are neglected, since they give wavefunctions identical to the positive solutions except for a physically unimportant sign change. Here one sees that only a discrete set of energy values and wavenumbers k are allowed for the particle. Usually in quantum mechanics it is also demanded that the derivative of the wavefunction in addition to the wavefunction itself be continuous; here this demand would lead to the only solution being the constant zero function, which is not what we desire, so we give up this demand (as this system with infinite potential can be regarded as a nonphysical abstract limiting case, we can treat it as such and "bend the rules"). Note that giving up this demand means that the wavefunction is not a differentiable function at the boundary of the box, and thus it can be said that the wavefunction does not solve the Schrödinger equation at the boundary points and (but does solve everywhere else).
Finally, the unknown constant may be found by normalizing the wavefunction so that the total probability density of finding the particle in the system is 1. It follows that
Thus, A may be any complex number with absolute value √; these different values of A yield the same physical state, so A = √ can be selected to simplify.
It is expected that the eigenvalues, i.e., the energy of the box should be the same regardless of its position in space, but changes. Notice that represents a phase shift in the wave function, This phase shift has no effect when solving the Schrödinger equation, and therefore does not affect the eigenvalue.
Momentum wave functionEdit
The momentum wavefunction is proportional to the Fourier transform of the position wavefunction. With (note that the parameter k describing the momentum wavefunction below is not exactly the special kn above, linked to the energy eigenvalues), the momentum wavefunction is given by
where since is the cardinal sine sinc function, sinc(x)=sin(x)/x. For the centered box (xc= 0), the solution is real and particularly simple, since the phase factor on the right reduces to unity. (With care, it can be written as an even function of p.)
It can be seen that the momentum spectrum in this wave packet is continuous, and one may conclude that for the energy state described by the wavenumber kn, the momentum can, when measured, also attain other values beyond .
Hence, it also appears that, since the energy is for the nth eigenstate, the relation does not strictly hold for the measured momentum p; the energy eigenstate is not a momentum eigenstate, and, in fact, not even a superposition of two momentum eigenstates, as one might be tempted to imagine from equation (1) above: peculiarly, it has no well-defined momentum before measurement!
Position and momentum probability distributionsEdit
In classical physics, the particle can be detected anywhere in the box with equal probability. In quantum mechanics, however, the probability density for finding a particle at a given position is derived from the wavefunction as For the particle in a box, the probability density for finding the particle at a given position depends upon its state, and is given by
Thus, for any value of n greater than one, there are regions within the box for which , indicating that spatial nodes exist at which the particle cannot be found.
In quantum mechanics, the average, or expectation value of the position of a particle is given by
For the steady state particle in a box, it can be shown that the average position is always , regardless of the state of the particle. For a superposition of states, the expectation value of the position will change based on the cross term which is proportional to .
The variance in the position is a measure of the uncertainty in position of the particle:
The probability density for finding a particle with a given momentum is derived from the wavefunction as . As with position, the probability density for finding the particle at a given momentum depends upon its state, and is given by
where, again, . The expectation value for the momentum is then calculated to be zero, and the variance in the momentum is calculated to be:
The uncertainties in position and momentum ( and ) are defined as being equal to the square root of their respective variances, so that:
This product increases with increasing n, having a minimum value for n=1. The value of this product for n=1 is about equal to 0.568 which obeys the Heisenberg uncertainty principle, which states that the product will be greater than or equal to
where x0 is an arbitrary reference length.
Another measure of uncertainty in momentum is the information entropy of the probability distribution Hp:
For , the sum of the position and momentum entropies yields:
which satisfies the quantum entropic uncertainty principle.
The energies which correspond with each of the permitted wavenumbers may be written as
The energy levels increase with , meaning that high energy levels are separated from each other by a greater amount than low energy levels are. The lowest possible energy for the particle (its zero-point energy) is found in state 1, which is given by
The particle, therefore, always has a positive energy. This contrasts with classical systems, where the particle can have zero energy by resting motionlessly. This can be explained in terms of the uncertainty principle, which states that the product of the uncertainties in the position and momentum of a particle is limited by
It can be shown that the uncertainty in the position of the particle is proportional to the width of the box. Thus, the uncertainty in momentum is roughly inversely proportional to the width of the box. The kinetic energy of a particle is given by , and hence the minimum kinetic energy of the particle in a box is inversely proportional to the mass and the square of the well width, in qualitative agreement with the calculation above.
If a particle is trapped in a two-dimensional box, it may freely move in the and -directions, between barriers separated by lengths and respectively. For a centered box, the position wave function may be written including the length of the box as . Using a similar approach to that of the one-dimensional box, it can be shown that the wavefunctions and energies for a centered box are given respectively by
where the two-dimensional wavevector is given by
For a three dimensional box, the solutions are
where the three-dimensional wavevector is given by:
In general for an n-dimensional box, the solutions are
The 1-dimensional momentum wave functions may likewise be represented by and the momentum wave function for an n-dimensional centered box is then:
An interesting feature of the above solutions is that when two or more of the lengths are the same (e.g. ), there are multiple wavefunctions corresponding to the same total energy. For example, the wavefunction with has the same energy as the wavefunction with . This situation is called degeneracy and for the case where exactly two degenerate wavefunctions have the same energy that energy level is said to be doubly degenerate. Degeneracy results from symmetry in the system. For the above case two of the lengths are equal so the system is symmetric with respect to a 90° rotation.
More complicated wall shapesEdit
The wavefunction for a quantum-mechanical particle in a box whose walls have arbitrary shape is given by the Helmholtz equation subject to the boundary condition that the wavefunction vanishes at the walls. These systems are studied in the field of quantum chaos for wall shapes whose corresponding dynamical billiard tables are non-integrable.
Because of its mathematical simplicity, the particle in a box model is used to find approximate solutions for more complex physical systems in which a particle is trapped in a narrow region of low electric potential between two high potential barriers. These quantum well systems are particularly important in optoelectronics, and are used in devices such as the quantum well laser, the quantum well infrared photodetector and the quantum-confined Stark effect modulator. It is also used to model a lattice in the Kronig-Penny model and for a finite metal with the free electron approximation.
Conjugated polyene systems can be modeled using particle in a box. The conjugated system of electrons can be modeled as a one dimensional box with length equal to the total bond distance from one terminus of the polyene to the other. In this case each pair of electrons in each π bond corresponds to one energy level. The energy difference between two energy levels, nf and ni is:
The difference between the ground state energy, n, and the first excited state, n+1, corresponds to the energy required to excite the system. This energy has a specific wavelength, and therefore color of light, related by:
A common example of this phenomenon is in β-carotene. β-carotene (C40H56) is a conjugated polyene with an orange color and a molecular length of approximately 3.8 nm (though its chain length is only approximately 2.4 nm). Due to β-carotene's high level of conjugation, electrons are dispersed throughout the length of the molecule, allowing one to model it as a one-dimensional particle in a box. β-carotene has 11 carbon-carbon double bonds in conjugation; each of those double bonds contains two π-electrons, therefore β-carotene has 22 π-electrons. With two electrons per energy level, β-carotene can be treated as a particle in a box at energy level n=11. Therefore, the minimum energy needed to excite an electron to the next energy level can be calculated, n=12, as follows (recalling that the mass of an electron is 9.109 × 10−31 kg):
This indicates that β-carotene primarily absorbs light in the infrared spectrum, therefore it would appear white to a human eye. However the observed wavelength is 450 nm, indicating that the particle in a box is not a perfect model for this system.
Quantum well laserEdit
The particle in a box model can be applied to quantum well lasers, which are laser diodes consisting of one semiconductor “well” material sandwiched between two other semiconductor layers of different material . Because the layers of this sandwich are very thin (the middle layer is typically about 100 Å thick), quantum confinement effects can be observed. The idea that quantum effects could be harnessed to create better laser diodes originated in the 1970s. The quantum well laser was patented in 1976 by R. Dingle and C. H. Henry
Specifically, the quantum well’s behavior can be represented by the particle in a finite well model. Two boundary conditions must be selected. The first is that the wave function must be continuous. Often, the second boundary condition is chosen to be the derivative of the wave function must be continuous across the boundary, but in the case of the quantum well the masses are different on either side of the boundary. Instead, the second boundary condition is chosen to conserve particle flux as , which is consistent with experiment. The solution to the finite well particle in a box must be solved numerically, resulting in wave functions that are sine functions inside the quantum well and exponentially decaying functions in the barriers. This quantization of the energy levels of the electrons allows a quantum well laser to emit light more efficiently than conventional semiconductor lasers.
Due to their small size, quantum dots do not showcase the bulk properties of the specified semi-conductor but rather show quantised energy states. This effect is known as the quantum confinement and has led to numerous applications of quantum dots such as the quantum well laser.
Researchers at Princeton University have recently built a quantum well laser which is no bigger than a grain of rice. The laser is powered by a single electron which passes through two quantum dots; a double quantum dot. The electron moves from a state of higher energy, to a state of lower energy whilst emitting photons in the microwave region. These photons bounce off mirrors to create a beam of light; the laser.
The quantum well laser is heavily based on the interaction between light and electrons. This relationship is a key component in quantum mechanical theories which include the De Broglie Wavelength and Particle in a box. The double quantum dot allows scientists to gain full control over the movement of an electron which consequently results in the production of a laser beam.
Quantum dots are extremely small semiconductors (on the scale of nanometers). They display quantum confinement in that the electrons cannot escape the “dot”, thus allowing particle-in-a-box approximations to be applied. Their behavior can be described by three-dimensional particle-in-a-box energy quantization equations.
The energy gap of a quantum dot is the energy gap between its valence and conduction bands. This energy gap is equal to the band gap of the bulk material plus the energy equation derived from particle-in-a-box, which gives the energy for electrons and holes. This can be seen in the following equation, where and are the effective masses of the electron and hole, is radius of the dot, and is Planck's constant:
Hence, the energy gap of the quantum dot is inversely proportional to the square of the “length of the box,” i.e. the radius of the quantum dot.
Manipulation of the band gap allows for the absorption and emission of specific wavelengths of light, as energy is inversely proportional to wavelength. The smaller the quantum dot, the larger the band gap and thus the shorter the wavelength absorbed.
Different semiconducting materials are used to synthesize quantum dots of different sizes and therefore emit different wavelengths of light. Materials that normally emit light in the visible region are often used and their sizes are fine-tuned so that certain colors are emitted. Typical substances used to synthesize quantum dots are cadmium (Cd) and selenium (Se). For example, when the electrons of two nanometer CdSe quantum dots relax after excitation, blue light is emitted. Similarly, red light is emitted in four nanometer CdSe quantum dots.
One function of quantum dots is their use in lymph node mapping, which is feasible due to their unique ability to emit light in the near infrared (NIR) region. Lymph node mapping allows surgeons to track if and where cancerous cells exist.
This section needs expansion. You can help by adding to it. (August 2013)
The probability density does not go to zero at the nodes if relativistic effects are taken into account via Dirac equation.
- History of Quantum Mechanics
- Finite potential well
- Delta function potential
- Gas in a box
- Particle in a ring
- Particle in a spherically symmetric potential
- Quantum harmonic oscillator
- Semicircle potential well
- Configuration integral (statistical mechanics)
- Configuration integral (statistical mechanics), 2008. this wiki site is down; see this article in the web archive on 2012 April 28.
- Davies, p.4
- Actually, any constant, finite potential can be specified within the box. This merely shifts the energies of the states by .
- Davies, p. 1
- Bransden and Joachain, p. 157
- Davies p. 5
- Bransden and Joachain, p.158
- Majernik, Vladimir; Richterek, Lukas (1997-12-01). "Entropic uncertainty relations for the infinite well". J. Phys A. 30 (4). Bibcode:1997JPhA...30L..49M. doi:10.1088/0305-4470/30/4/002. Retrieved 11 February 2016.
- Majernik, Vladimir; Majernikova, Eva (1998-12-01). "The momentum entropy of the infinite potential well". J. Phys A. 32 (11). Bibcode:1999JPhA...32.2207M. doi:10.1088/0305-4470/32/11/013. Retrieved 11 February 2016.
- Bransden and Joachain, p. 159
- Davies, p. 15
- Todd Wimpfheimer, A Particle in a Box Laboratory Experiment Using Everyday Compounds, Journal of Laboratory Chemical Education, Vol. 3 No. 2, 2015, pp. 19-21. doi:10.5923/j.jlce.20150302.01.
- Pubchem. "beta-carotene | C40H56 - PubChem". pubchem.ncbi.nlm.nih.gov. Retrieved 2016-11-10.
- Sathish, R. K.; Sidharthan, P. V.; Udayanandan, K. M. "Particle in a Box- A Treasure Island for Undergraduates".
- P.J. Mohr, B.N. Taylor, and D.B. Newell, "The 2014 CODATA Recommended Values of the Fundamental Physical Constants". This database was developed by J. Baker, M. Douma, and S. Kotochigova. Available: . National Institute of Standards and Technology, Gaithersburg, MD 20899.
- β-Carotene http://www.sigmaaldrich.com/catalog/product/aldrich/855553?lang=en®ion=us (accessed Nov 8, 2016).
- Zory, Peter (1993). Quantum Well Lasers. San Diego: Academic Press Unlimited.
- U.S. Patent #3,982,207, issued September 21, 1976, Inventors R. Dingle and C. H. Henry ,"Quantum Effects in Heterostructure Lasers", filed March 7, 1975.
- Miller, David (1995). Burstein, Elias; Weisbuch, Claude, eds. Confined Electrons and Photons: New Physics and Applications. New York: Plenum Press. pp. 675–702.
- Miessler, G. L. (2013). Inorganic chemistry (5 ed.). Boston: Pearson. pp. 235–236. ISBN 978-0321811059.
- Zandonella, Catherine. "Rice-sized laser, powered one electron at a time, bodes well for quantum computing". Princeton University. Princeton University. Retrieved 8 November 2016.
- Rice, C.V.; Griffin, G.A. (2008). "Simple Syntheses of CdSe Quantum Dots". Journal of Chemical Education. 85 (6): 842. Bibcode:2008JChEd..85..842R. doi:10.1021/ed085p842. Retrieved 5 November 2016.
- "Quantum Dots : a True "Particle in a Box" System". PhysicsOpenLab. 20 November 2015. Retrieved 5 November 2016.
- Overney, René M. "Quantum Confinement" (PDF). University of Washington. Retrieved 5 November 2016.
- Zahn, Dietrich R.T. "Surface and Interface Properties of Semiconductor Quantum Dots by Raman Spectroscopy" (PDF). Technische Universität Chemnitz. Retrieved 5 November 2016.
- Bentolila, Laurent A.; Ebenstein, Yuval (2009). "Quantum Dots for In Vivo Small-Animal Imaging". Journal of Nuclear Medicine. 50 (4): 493–496. doi:10.2967/jnumed.108.053561. Retrieved 5 November 2016.
- Alberto, P; Fiolhais, C; Gil, V M S (1996). "Relativistic particle in a box" (PDF). European Journal of Physics. 17: 19–24. Bibcode:1996EJPh...17...19A. doi:10.1088/0143-0807/17/1/004.
- Bransden, B. H.; Joachain, C. J. (2000). Quantum mechanics (2nd ed.). Essex: Pearson Education. ISBN 0-582-35691-1.
- Davies, John H. (2006). The Physics of Low-Dimensional Semiconductors: An Introduction (6th reprint ed.). Cambridge University Press. ISBN 0-521-48491-X.
- Griffiths, David J. (2004). Introduction to Quantum Mechanics (2nd ed.). Prentice Hall. ISBN 0-13-111892-7. | <urn:uuid:3d4f1dc8-68ad-408e-9720-da749a300727> | 3.78125 | 5,331 | Knowledge Article | Science & Tech. | 49.868291 | 95,602,744 |
Sidereal Time, Civil Time and Solar Time
Sidereal time is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time it is possible to easily point a telescope to the proper coordinates in the night sky.
- Introduction to Astronomy
- The Celestial Sphere - Right Ascension and Declination
- What is Angular Size?
- What is the Milky Way Galaxy?
- The Astronomical Magnitude Scale
- Sidereal Time, Civil Time and Solar Time
- Equinoxes and Solstices
- Parallax, Distance and Parsecs
- A Newbie's Guide to Distances in Space
- Luminosity and Flux of Stars
- Kepler's Laws of Planetary Motion
- What Are Lagrange Points?
- Glossary of Astronomy & Photographic Terms
- Astronomical Constants
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Civil time is based on the position of the Sun in the sky. The 24 hours on a clock represent an apparent solar day. The apparent solar day is the time between successive transits of the Sun across an observer's meridian.
Apparent solar time, as measured by clocks, is not a very accurate system for measuring actual solar time. This is because the Earth's orbit is elliptical and the Earth's rotation axis is inclined by 23.5° from the orbital plane. Using this system would require clocks to run faster on some days and slower on others. To get around this, civil time uses an average solar time, which means that a solar day is an average of 24 hours and this is constant throughout the year. The difference between average solar time and apparent solar time is called the equation of time and varies by up to 16.25 minutes throughout the year. This average time gives rise to the Greenwich Mean Time.
Sidereal Time for Astronomers
During the course of a year, the Sun appears to move around the sky along the ecliptic, and if we look at the night sky each month at midnight we will see that the constellations also appear to move around the sky (albeit much slower). Consequently, the time as measured by the distant stars and the solar time measured by the Sun cannot be equal.
Astronomers time is best measured with reference to the background stars and is referred to as sidereal time.
The normal definition of a sidereal day is "the time between successive transits of the First Point of Aries" whereas the mean solar day is defined as the average time between transits of the sun. The Earth has a normal rotation rate of 365 times per year, so we expect the sun to transit 365 times in the year, compared with 366 transits of our chosen star. The extra transit occurs after the final transit of the Sun. This accounts for the difference between solar time and sidereal time.
By dividing the "extra" day into 365 parts, we can calculate that a sidereal day is about 4 minutes shorter than a solar day. Consequently, stars appear to rise 4 minutes earlier each evening.
The zero point used for sidereal time is the transit of the First Point of Aries at Greenwich, England, also known as Greenwich Sidereal Time (GST). It is 0 hours at solar noon at the time of the March equinox (approximately March 21). It is also 0h at midnight at the time of the September equinox (approximately September 21) in Greenwich.
Greenwich Sidereal Time is the local sidereal time for observers at Greenwich. Observers at other longitudes will also have their own local sidereal time (LST). This is calculated from GST using the following formula.
Equation 14 - Local Sidereal Time
Where λ is the observer's longitude expressed in hours:minutes.
Assume Greenwich Sidereal time is 12:30. What is local sidereal time at an observatory located at +20° (or 20° E)?
Longitude needs to be converted into hours and minutes. Since 24h = 360°, 20° corresponds to:
Equation 15 - Calculate Local Sidereal Time
1.33 hours is the decimal form of 1h 20 minutes.
Equation 16 - Local Sidereal Time Calculation
Hour Angle, Sidereal Time and Right Ascension
The hour angle (HA) of a celestial body is defined in as the angle measured westwards in units of time along the celestial equator from the observer's meridian to the hour circle passing through the celestial body. It, therefore, represents the sidereal time that has elapsed since that object was on the meridian.
It follows directly from this definition that the LST is the hour angle of the First Point of Aries.
The following equations illustrate the relationships between Local Sidereal Time, Right Ascension and Hour Angle.
Equation 17 - Relationship between LST, HA and RA
Last updated on: Wednesday 17th January 2018
A look at the celestial sphere and how we locate objects using Right Ascension and Declination
Kepler's Laws of Planetary Motion are simple, yet govern the mechanics of planets, solar systems and even galaxies. | <urn:uuid:d671a625-1ab4-45e6-a723-c3860caad4a8> | 3.65625 | 1,074 | Knowledge Article | Science & Tech. | 44.841209 | 95,602,746 |
A-DNA and Z-DNA Atlases. Dave Ussery Comparative Microbial Genomics first lecture, 18 September, 2002. Outline. Helix family. A-DNA. A-DNA helix. A-DNA was the first DNA helix characterised by Rosalind Franklin in the early 1950’s. A-DNA helices
Comparative Microbial Genomics
first lecture, 18 September, 2002
Z-DNA was the first DNA helix to be crystallised
(in 1979), and came to the surprise of many biologists.
It is a thin, LEFT-HANDED helix, with 12 bp/turn,
and has a zig-zag backbone (hence its name). Certain
alternating pyrimidine/purine sequences
(e.g., CGCGCG) will form this helix.
Consider a stretch of purines (G or A, abbreviated R)
of length n:
What is the probability of finding this in a random DNA | <urn:uuid:f9037bba-7d96-43df-8401-7678605f9d5e> | 3.5625 | 215 | Knowledge Article | Science & Tech. | 63.530712 | 95,602,752 |
Materials Could Capture CO2 and Make It Useful
Novel molecular structures are a first step toward economical carbon capture at a wide scale.
A viable technology for economical carbon capture would be a huge step in reducing greenhouse gas emissions.
Although progress has been made in limiting carbon emissions in some countries, particularly in Europe and North America, it’s clear that finding ways to capture carbon dioxide from smokestacks—or from the atmosphere—is becoming increasingly imperative. Available systems dramatically increase the cost of electricity from plants equipped with the technology. And what to do with all that carbon dioxide after it’s separated remains problematic.
Now a team of scientists at Lawrence Berkeley National Laboratory and the University of California, Berkeley, have devised a method that uses super-porous molecular structures known as covalent organic frameworks, with catalysts to convert the carbon dioxide to carbon monoxide, which can be used in making a range of materials including fuels, plastics, and even pharmaceuticals.
The new materials, says Chris Chang, a chemist with Berkeley Lab’s Chemical Sciences Division and one of the co-leaders of the research team, are based on “a highly stable, porous structure that’s decorated with all of these catalysts.” Though it’s early stage research and nowhere near ready to scale up to power plant levels, it’s an important step toward finding practical ways to absorb and use carbon dioxide in both waste streams and the air.
First developed in the mid-2000s by Omar Yaghi, now a professor of chemistry at UC Berkeley and the co-director of the Kavli Energy NanoSciences Institute, covalent organic frameworks are intricate, highly porous crystals that have a range of potential applications in gas storage, photonics, and various chemical processes. They are especially valuable as carbon capture materials because they function in the presence of water, which means you can eliminate the toxic organic solvents that are used in other forms of carbon capture; you’re no longer “fixing one problem and creating another,” as Yaghi puts it.
Capturing the carbon is half of the solution; turning it into usable materials is the second half. “The challenge has always been, could you convert it into some starting material that can be used as feedstocks for useful chemicals?” says Yaghi. “This work is the first step toward that challenge.”
Work on carbon capture from the waste streams of power plants has stalled in recent years (see “What Carbon Capture Can’t Do”). Current approaches center on postcombustion capture, generally using amine-based solvents; precombustion methods, such as gasifying coal before burning it; and oxy-combustion, which burns coal in pure oxygen rather than air. All are effective, but they’re expensive and inefficient. And none will work for removing carbon from the atmosphere (see “Can Sucking CO2 Out of the Atmosphere Really Work?”).
Work on novel techniques, like the research of Yaghi and Chang and their team, could open up new avenues to make carbon capture more feasible. One limitation is that the catalysis requires energy: thus, the system to capture and convert carbon dioxide would itself consume electricity. Chang says one goal is to link devices for carbon capture and conversion with solar panels.
“Capturing carbon selectively is a daunting challenge,” says Yaghi. “And converting it into a useful material adds to that. Five years ago we couldn’t have said we could do it. Now I wouldn’t say we’ve solved it, but we’re now in a position to say that this is feasible.”
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FAU researchers gain new insights into the electrical charge of platinum particles
Whether it is in catalytic processes in the chemical industry, environmental catalysis, new types of solar cells or new electronic components, nanoparticles are everywhere in modern production and environmental technologies, where their unique properties ensure efficiency and save resources.
The special properties of nanoparticles often arise from a chemical interaction with the support material that they are placed on. Such interactions often change the electronic structure of the nanoparticle because electrical charge is exchanged between the particle and the support.
Working groups led by Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and the University of Barcelona have now succeeded in counting the number of elementary charges that are lost by a platinum nanoparticle when it is placed onto a typical oxide support. Their work brings the possibility of developing tailor-made nanoparticles a step closer.*
One of the main questions that nanoscience researchers have been discussing for some time now is how nanoparticles interact with the support that they are placed on.
It is now clear that various physical and chemical factors such as the electronic structure, the nanostructure and – crucially – their interaction with the support control the properties of nanoparticles.
Although this interaction – specifically the transfer of electrical charge – has already been observed to a great extent, previous studies have not investigated how much charge is transferred and whether there is a relationship between the transfer and the size of the nanoparticle.
In order to measure the electrical charge that is exchanged the international team of researchers from Germany, Spain, Italy and the Czech Republic led by Prof. Dr. Jörg Libuda, Professor of Physical Chemistry, and Prof. Dr. Konstantin Neyman, University of Barcelona, prepared an extremely clean and atomically well-defined oxide surface, onto which they placed platinum nanoparticles.
Using a highly sensitive detection method at Elettra Sincrotrone Trieste the researchers were able to quantify the effect for the first time. Looking at particles with various numbers of atoms, from several to many hundred, they counted the number of electrons transferred and showed that the effect is most pronounced for small nanoparticles with around 50 atoms.
The magnitude of the effect is surprisingly large: approximately every tenth metal atom loses an electron when the particle is in contact with the oxide. The researchers were also able to use theoretical methods to show how the effect can be controlled, allowing the chemical properties to be adapted to better suit their intended application.
This would allow valuable raw materials and energy to be used more efficiently in catalytic processes in the chemical industry, for example.
The project was funded in part by the EU and by FAU's Cluster of Excellence 'Engineering of Advanced Materials' (EAM). The researchers at EAM aim to bring together basic research in the natural sciences and applied research in engineering to investigate and develop new hierarchically structured materials with specific electronic, optical, catalytic and mechanical properties.
Prof. Dr. Jörg Libuda
Phone: +49 9131 8527308
Dr. Susanne Langer | idw - Informationsdienst Wissenschaft
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
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The researchers want to understand the phenomena behind the magnetic storms engulfing the earth capable of destroying satellites and capable of damaging radio communications on the earth’s surface. For such experiment, they will also have to track down the reasons behind the tropical storms that take place on the ground and do affect these magnetic storms which take place about 60 miles above the earth’s surface. One of the brand new mission of NASA involves doing precisely the job mentioned above. The purpose is known as the Ionospheric Connection Explorer (ICON).
The primary objective of this mission is to analyze the winds of the ionized atoms and to find out how do they react to the different atmospheric conditions, | <urn:uuid:f8fb6769-8415-4cbb-9336-121ac2373298> | 3.609375 | 138 | Truncated | Science & Tech. | 28.60563 | 95,602,777 |
- Open Access
A framework for incorporating evolutionary genomics into biodiversity conservation and management
© Hoffmann et al.; licensee BioMed Central. 2015
Received: 19 September 2014
Accepted: 17 December 2014
Published: 28 January 2015
Evolutionary adaptation drives biodiversity. So far, however, evolutionary thinking has had limited impact on plans to counter the effects of climate change on biodiversity and associated ecosystem services. This is despite habitat fragmentation diminishing the ability of populations to mount evolutionary responses, via reductions in population size, reductions in gene flow and reductions in the heterogeneity of environments that populations occupy. Research on evolutionary adaptation to other challenges has benefitted enormously in recent years from genomic tools, but these have so far only been applied to the climate change issue in a piecemeal manner. Here, we explore how new genomic knowledge might be combined with evolutionary thinking in a decision framework aimed at reducing the long-term impacts of climate change on biodiversity and ecosystem services. This framework highlights the need to rethink local conservation and management efforts in biodiversity conservation. We take a dynamic view of biodiversity based on the recognition of continuously evolving lineages, and we highlight when and where new genomic approaches are justified. In general, and despite challenges in developing genomic tools for non-model organisms, genomics can help management decide when resources should be redirected to increasing gene flow and hybridisation across climate zones and facilitating in situ evolutionary change in large heterogeneous areas. It can also help inform when conservation priorities need to shift from maintaining genetically distinct populations and species to supporting processes of evolutionary change. We illustrate our argument with particular reference to Australia’s biodiversity.
Climate change threats to biodiversity
The latest IPCC report provides a very clear picture about current and accelerating climate change. Even if CO2 emissions can be completely curtailed by 2050, it is likely that there will be a further rise in temperature of at least 2°C above the current level of almost 1°C. Given the political challenges associated with emission reductions, it is doubtful whether such a timeframe for emission reduction will be realised. Therefore, the world is more likely facing an increase in mean temperature of 3°C–6°C, approaching the extent of change experienced in the last glacial maximum, coupled with an increase in temperature extremes. In addition, there will be a gamut of associated changes including ocean acidification, increases in fire incidence and severity, storm activity, the length and intensity of drought and flood conditions, as well as changes in the salinity of coastal areas .
The distributions of many species are expected to shift markedly during this period. Climate niche modelling predicts that many areas currently occupied by species and communities will no longer be suitable for them . Similarly, areas suitable for alpine and sub-alpine vegetation and fauna in Europe are expected to decline by more than 90%, e.g. [3,4]. At the same time, changes can be idiosyncratic and some species are expected to benefit from the effects of climate change; groups of invasive species and even some native species are expected to benefit in this way [6,7].
Predictions based on species distribution models are relatively crude because they assume that current distributions are limited by climatic factors, whereas the climatic space a species can tolerate may be substantially greater than the area where it actually persist [8,9]. To resolve this issue, investigators have explored the limits of tolerance or growth of species [10-12] but controversy remains about the best approach and interpretations of patterns across different species. Tolerance limits often depend not only on the immediate conditions being experienced but also on those encountered during development and the rate at which stresses act, as well as a variety of other factors [13-15]. Species may respond via plasticity, altering growth rates, triggering phenological changes and increasing resistance to extremes, all in an adaptive direction . Behavioural adaptation might also allow species to find areas with suitable microclimates within their current distributions or to track their niches as they move across space [18-20].
Biotic factors introduce another level of uncertainty into predictions, particularly when they generate an additional source of environmental stress, such as the widespread impact of mountain pine beetles on pine tree mortality in North America . Perhaps the most important biotic factor is human population growth and the impacts of more than 7 billion people on a natural environment that is increasingly under stress . The negative impacts of human activities on biodiversity are well documented and range from direct effects triggering species extinctions through overexploitation to indirect effects through removal of habitat for agriculture or resource extraction .
It is already clear that large-scale changes to natural communities are occurring and will accelerate over the coming decades . Many (perhaps the majority of) species face local extinction in at least part of their native range. A few species will track climate successfully, others will benefit from vacant space created by departing species, tropical and subtropical species may invade higher latitudes, but many communities will be lost, e.g. [3,5,25]. All of these changes will take place within the context of increased landscape fragmentation due to ongoing vegetation clearing and increasing calls to manipulate the environment to safeguard agriculture and property such as through fire suppression. There will also be flow-on effects of these changes on ecosystem services provided by the natural environment, directly impacting on the ability of species, including our own, to access the resources needed for persistence [26,27].
Opportunities and constraints for evolutionary adaptation
Given the scale and timeframe of climate change effects, what is the likelihood that species and communities can respond through evolutionary changes? Major life forms have persisted and adapted across geological epochs despite temperature changes that exceed those predicted under anthropogenic climate change. Whilst speciation and evolutionary divergence have occurred over millions of years, current species and populations have persisted through the more recent climatic oscillations of the Pleistocene [28,29]. In addition to these past evolutionary changes over geological time frames, there is also a growing (albeit still small) number of cases of rapid and contemporary evolutionary changes in natural animal and plant populations [30,31] that allow us to track the direct and indirect effects of climate change. Examples include genetic changes in the body colour of owls in response to predation linked to changing snow covers , changes in allozyme frequencies and inversions that preserve functional sets of genes in Drosophila known to be sensitive to temperature changes , and adaptive changes in the flowering time of Brassicas in response to drought . However, not all populations are expected to successfully adapt through evolutionary change. This may reflect a lack of genetic variation in base populations , interactions among traits that constrain evolutionary responses in one direction [32,36], and other factors such as the reduced effectiveness of selection in the presence of the plastic responses of individual genotypes (i.e. the extent to which they can be modified by the environment). These types of factors may help account for cases where adaptive evolutionary changes have not occurred, but were expected, as in the case of breeding time in birds .
Both population size and patterns of gene flow have been dramatically affected by human activities. Environments have become increasingly fragmented, leading to increasing levels of genetic distinctness and a loss of accessible genetic variation, e.g. [45,46]. Threatened environments may represent a series of islands surrounded by hostile conditions for the species. At its most extreme, species might be confined to zoos or botanical collections, living in a highly defined set of environmental conditions, at a small effective population size, with only limited scope to recruit new genes even with coordinated programmes to exchange material; see .
From an evolutionary perspective, natural populations are therefore threatened by three forces that interact to produce a downward spiral of evolutionary potential (Figure 1): (i) a reduction in genetic variation as a consequence of decreases in population size affecting in situ evolution, (ii) a reduction in gene flow preventing an influx of genetic variants from other populations and (iii) a reduction in environmental heterogeneity that can lead to a decrease in adaptive capacity of the species as a whole. The likelihood that evolutionary rescue (involving forced introgression from other populations or (sub)species) might mitigate some of the threats imposed by environmental change remains unknown , although it will likely depend on the availability of genetic variation within the populations/species concerned.
Against this backdrop of gloomy projections, the current revolution in genomics and other -omics technologies is providing unprecedented insights into evolutionary processes and offers an opportunity to significantly improve conservation planning and management decisions. Researchers can now identify parts of the genome that have been or could be involved in adaptive shifts, via new or existing variants in situ, or through hybridisation. At a functional level, genomics approaches can also identify the networks of genes/proteins and their expression profiles required for key adaptations. Whilst once limited in application to model organisms, the technology is now increasingly applicable to non-model species despite ongoing challenges around annotation [49,50]. Below, we briefly outline the various methods for generating and analysing genomic data bearing on biodiversity conservation, their strengths and weaknesses, and then describe how genomic information can explicitly be incorporated into a decision-making framework for biodiversity conservation in the face of climate change.
Methods for generating genomic data
The advent of next-generation sequencing has enabled population genetic and microevolutionary studies on a genome-wide scale. From hundreds of millions of dollars for the first draft of the human genome in 2001, the sequencing required to assemble a reference genome for a species now costs just a few thousand dollars. Economical sample preparation strategies reviewed in [51-53] now enable high-throughput genomics studies even without a reference genome . “Home-brew” methods for sequencing library preparation [55,56] have reduced per-sample cost and prices of commercial kits have followed a similar downward trend. It is now realistic to carry out whole genome sequencing (WGS) of 30 individuals of an insect species with a small (250 Mb) genome, for less than US$4000.
Although multi-individual WGS provides the highest accuracy and power in population genomics, it can still present a significant financial challenge when multiple populations are under investigation. There are several economical alternatives to WGS. First, the recently developed reduced-representation sequencing (RRS), including genotyping-by-sequencing (GBS) and RADSeq [57-59] technologies, can overcome this problem by targeting a subset (approximately 1%) of the genome. These approaches typically involve restriction enzyme digestion of genomic DNA, sample barcoding by attaching unique oligo-nucleotide sequences identifying individuals and selection of a subset of genomic fragments, followed by sequencing of multiple samples in the same lane on an Illumina sequencing platform. They provide data on hundreds to tens of thousands of nucleotide polymorphisms. In some cases, they tag the majority of the genes in the genome and, importantly, reduce per-sample costs substantially. These approaches can be used to answer a wide variety of questions on population structure and phylogeography; see [51,53,57]. RRS strategies typically aim for up to 10× coverage per site, which generally allows for accurate identification of heterozygous sites. Dual-end barcode sets of 384 or more now exist for the identification of individuals, which makes large sample sizes economical. One limitation of RRS approaches is that loci can suffer from “allelic dropout” due to polymorphisms in restriction sites [60,61], which may lead to an overestimate of divergence.
A second alternative to individual-based WGS is combining individuals into a pool, as in Poolseq; see [51,62] (PPS). The Poolseq approach does not allow the data for different individuals to be separated post-sequencing, but it is highly cost-effective for assessing population structure , genetic distance [64-66] and genome-wide patterns of heterozygosity. As little as 1× coverage of each diploid individual’s genome is needed, further reducing cost. However, a lower level of coverage will not adequately represent the pool of individuals, especially when the pool is small to begin with, and can therefore produce misleading population parameter estimates; see [60,61,67]. Guidelines [51,60,61,67] and software packages such as ngsTools and npstat , which carry out likelihood-based estimation of allele frequencies, are now available to help tackle these challenges.
Another affordable strategy for population genomic studies is transcriptome sequencing (TS). This approach yields data on genes which are expressed at reasonable levels, representing perhaps 1%–10% of the genome. Variants can then be identified in the sequenced transcriptome. If coverage is deep enough, biases are addressed and appropriate experimental replicates are included; differences in gene expression can also be detected between samples . Transcriptome sequencing is usually performed at the individual level, but it is also possible to estimate allele frequencies from sequencing of pooled samples and to compare different lines and populations . Variant identification from transcriptome data can suffer the same biases from low coverage sequences as Poolseq experiments and can also suffer from allelic dropout when only certain alleles are expressed in individual samples.
Whatever the sequencing platform used, most population genomics studies to date have based their analyses on single nucleotide polymorphisms (SNPs)—single-base variants in either functional or neutral regions of the genome. Whilst SNPs are informative and relatively easy to identify, studies on model species have shown that insertion-deletion polymorphisms (indels) also play an important role in genome evolution and adaptation [73-76]. Identifying indels from high-throughput sequencing data remains a difficult bioinformatic problem , and identifying large indels in RRS data is especially difficult because only a small percentage of the genome is sequenced. Indels are not just important for their own sake: if small indels are misaligned, then SNPs may be misidentified in the region . A few programs like the GATK2 best-practice pipeline attempt to resolve this by a local refinement of read alignments, but this can still suffer from discordance . Chromosomal rearrangements and other forms of structural variation are also involved in adaptation (reviewed in ). Such variation is still difficult to identify using short-read technology, but improved methodologies are under development [79,80].
Applications of genomics data to relevant steps in the decision framework
How genomics can help inform decisions
Can species tolerate change in situ?
Determining if a species is currently experiencing stress which suggests it is approaching the limit of physiological tolerance
Screen biomarkers indicative of stress. See
[TS] with [IG]
Gene expression analyses to identify abundance of key gene transcripts
For many species, further research is required to identify biomarkers; however genomics could facilitate this process. A challenge is that biomarkers need to be diagnostic of stress and reproducible—particularly for gene expression markers
Testing whether a species has sufficient phenotypic plasticity to tolerate projected change
[TS] with [IG]
Gene expression analyses. Gene transcript abundance can be used as a surrogate for overarching phenotypic responses
Observing phenotypes will be more appropriate/cost-effective in some cases, but in other cases, gene expression could screen many phenotypes simultaneously at lower cost per sample. For the latter, links to phenotypic data are required
Assessing a species’ historical demography to see how it responded to past climate change
[WGS], [RRS], [DE] with [IG] or [WGS], [DE] with [PPS]
Bayesian skyline plots/coalescent simulations or likelihood-based diffusion modelling from SNP data
Genomics can provide a comprehensive assessment; however, a similar outcome might be achieved using non-genomic tools (e.g. SSRs), particularly where data sets are already available
Do populations have enough genetic diversity for an evolutionary response?
Determining whether the species or population is currently experiencing inbreeding, which can lead to loss of genetic diversity essential for evolution
Genome-wide sequencing allows accurate estimation of heterozygosity in individuals and populations. See
[WGS], [RRS], [DE], [TS] with [IG] or [WGS],[DE] with [PPS]
Estimate F-statistics and heterozygosity from SNP data
Non-genomic tools (e.g. SSRs) can be applied to estimate diversity, particularly where data sets are already available. However genomics offers better resolution and diversity estimation. The effects of different levels of diversity on adaptability needs to be established through phenotypic comparisons
Assess whether there is enough standing genetic diversity to provide opportunities to adapt
Accurately estimate the levels of genetic diversity in populations. See
Estimate heterozygosity, DNA sequence diversity estimates (pi, theta) from SNP or sequence data
Determining whether selection has acted on genetic variation in the species
Allele frequency spectrum tests (e.g. Tajima’s D), linkage disequilibrium, non-synonymous to synonymous polymorphism ratios (e.g. Kn/Ks) from sequence data
Is genetic diversity strongly distributed across populations?
Identification of centres of genetic diversity, or genetically distinct regions, for prioritised conservation
Examine patterns of population genetic structure to identify outlier populations. See
[WGS], [RRS], [DE], [TS] with [IG] or [WGS],[DE] with [PPS]
Estimation of population differentiation based on SNP data using classical F-statistics, PCA or MCMC and Bayesian derived estimates of admixture (e.g. STRUCTURE)
Non-genomic tools (e.g. SSRs) could be applied to assess population differentiation. However genomics offers better resolution and accuracy of diversity patterns, which may be important for detecting fine scale structure
Are some populations adapted to local climate?
Identifying whether populations show adaptation to local climate (or other environmental variables)
[WGS], [RRS], [DE], [TS] with [IG] or [WGS], [DE] with [PPS]
Population level or landscape genomics methods based on SNP data: outlier tests, relative rate tests, allelic association with environment and allelic association with adaptive traits. Computational modelling of genomic diversity evolution under environmental change
How to confidently link climate variables to local adaptation, and how to infer adaptive capacity from genomic data are currently pressing questions in population genomics. However these questions also apply to other genetic methods. Characterising the local climate experienced by a species is also a challenge, but microclimate modelling is improving rapidly. Phenotypic data is still essential to determine the extent of adaptation
How quickly can genetic adaptation occur?
Identify rates of genetic adaptation to environment by screening adaptive variation in natural populations experiencing environmental change, or through simulated or experimental evolution. See [96-98]
Is gene flow high enough? (or too high?)
Determining the extent of gene flow between existing populations to inform on dispersal capability and also potential for adaptive alleles to spread or be swamped
[WGS], [RRS], [DE], [TS] with [IG] or [WGS],[DE] with [PPS]
Coalescent genealogy sampling to generate Bayesian and maximum likelihood estimates of migration and gene flow (e.g. Lamarc, Migrate), or MCMC and Bayesian-derived estimates of admixture (e.g. STRUCTURE) based on SNP data. Genomics also has the power to identify recent migrants and so test the efficacy of movement pathways
Genomics can provide a more comprehensive assessment of gene flow compared to non-genomic tools (e.g. SSRs), particularly where rates of gene flow are low
Is a positive evolutionary response possible through natural hybridisation with sympatric species?
Determining whether hybridisation occurs in nature
[WGS], [RRS], [DE], [TS] with [IG] or [WGS],[DE] with [PPS]
Identify hybrid ancestry via comparison to known non-hybrids. Estimate migration and gene flow (e.g. Lamarc, Migrate) and admixture (e.g. STRUCTURE) between species. Admixture quantification also confirms F1 hybrid fecundity
Non-genomic tools are available for identifying hybrids; however genomics gives unprecedented power to detect even low levels of introgression, and to understand how patterns of introgression vary across the genome. Phenotypic data are essential to determine whether hybridisation is adaptive
Assess how quickly beneficial alleles can move into a population or species
[WGS], [RRS], [DE], [TS] with [IG] or [WGS],[DE] with [PPS]
Track distribution of species specific alleles in population with regard to null selection models. Transmission distortion in artificial F2 hybrids can indicate genetic incompatibilities
Can species migrate quickly enough?
Assess potential for migration into climatic refugia given ecological constraints and known rates of gene flow
Provide accurate estimates of gene flow (as described above). See
[WGS], [RRS], [DE], [TS] with [IG] or [WGS],[DE] with [PPS]
Genomic estimates of gene flow can be coupled with data on rates of dispersal or movement and habitat analysis (path analyses, resistance models) to predict viability of dispersal pathways
Genomics can provide a more comprehensive assessment of gene flow compared to non-genomic tools (e.g. SSRs), particularly where rates of gene flow are low
Significantly, none of these applications absolutely requires individual-based whole-genome sequencing. However, high-quality whole-genome sequencing may be a viable option for species with small genomes and will always provide the most complete data set. Another reason to consider whole-genome sequencing is to assemble a reference genome from one individual or line of the species in question. This can greatly aid in SNP calling, mapping the variants that are identified and associating phenotypes to particular regions, either in genetic crosses or population surveys, involving quantitative trait loci (QTL) mapping and genome-wide association studies (GWAS), respectively . A typical reference genome sequencing project aims for >30× coverage, which is now relatively affordable. Currently, the limiting factor in de novo genome sequencing is the bioinformatic expertise required to assemble and annotate genomes to a high quality. At a minimum, annotation involves predicting the location and structure of a gene [117,118]; functional annotation then involves predicting the function of an identified gene, generally by comparison to related annotated genomes . In the latter case, annotations remain challenging for non-model organisms , particularly when genome assemblies are of a low quality .
Sequencing costs may well continue to decrease in the near future with third-generation sequencing (single molecule sequencing), and innovations such as nanopore-enabled nucleic acid sequencing could further improve quality and reduce costs . With read lengths of 49 kb + projected by companies like Oxford Nanopore , it may soon become possible to sequence entire genomes of non-model organisms for less than a thousand (US) dollars. This, combined with re-usable sequencing chips and mini USB-powered sequencers, ensures an increasingly important role for sequencing technologies in population genetic and microevolutionary studies related to climate change adaptation.
A decision framework
Assessing environment suitability and persistence
Assessing the likelihood that environmental suitability will decline
Species distribution models, often also referred to as ecological niche models or bioclimatic envelope models, and methods of modelling community-level turnover such as generalised dissimilarity modelling are currently the main tools used to obtain spatially explicit predictions of habitat (environmental) suitability for species under climate change [25,124,125] (D1 in Figure 2). These approaches use associations between climate and species’ distributions to enable projections of future potential distributions under climate change scenarios. Whilst uses of such models have been criticised in the past, models that thoroughly account for algorithmic uncertainties, followed by careful interpretation of results, remain useful and widely used tools for forecasting impacts of climate change on large numbers of species .
Assessing whether species can tolerate change in situ
If a substantive risk that environmental suitability will decline under climate change has been identified, then the next step is to determine which species and communities should become the focus of ongoing management (D2 in Figure 2). Whilst many species are expected to be at risk from climate change, others may not be threatened because the projected change will fall within their tolerance limits. This section briefly discusses how genomic approaches might be used to determine the extent to which species will be able to tolerate climatic changes in situ, without the need for evolutionary responses and management intervention.
The first approach is to screen biomarkers that are consistently linked to levels of physiological stress to determine whether physiological limits are being approached or exceeded. Transcriptome sequencing can provide a signal of physiological stress in natural populations and wild-caught individuals [49,127], indicating a population that may not be functioning at its peak; for instance, transcriptomic stress profiling on several fish species has demonstrated a link between changes in the expression of particular genes and the physical condition of the fish [81,128]. One current challenge with this approach is that key biomarker genes have not yet been identified for many groups of organisms, although transcriptomic data for a range of species across various stresses are rapidly accumulating and generalities about useful markers may emerge. A subsequent challenge is to interpret quantitative transcript changes in terms of the critical physiological limits for the species in question .
A related approach is to use transcriptomic profiling to determine whether there is a capacity to mitigate the detrimental effects of environmental change via phenotypic plasticity. Just as some aspects of a transcriptomic profile may indicate a species approaching a physiological limit, so can other changes in the profile highlight an underlying capacity to tolerate change through the physiological plasticity of individual genotypes, even when phenotypic responses are not outwardly evident [82,130]. Given the importance of phenotypic plasticity as an adaptive mechanism for organisms facing climate change, such transcriptomic approaches could be used to investigate their capacity to respond physiologically without necessarily involving any evolutionary change. As above, such an approach is currently constrained by the very limited understanding of how gene expression changes link to fitness/performance under stressful conditions, but the situation is expected to improve given the current proliferation of transcriptomic studies. The approach is illustrated by a transcriptomic comparison of populations of the sparrow Zonotrichia capensis from altitudinal extremes of its range, carried out on both individuals sampled directly from the field and on those then transferred to a low altitude “common garden” environment . There was no difference between the transcriptomes of the two populations under the latter conditions whereas samples obtained directly from the field differed in their expression of nearly 200 genes, pointing to the involvement of plastic changes in gene expression profiles rather than evolved differences among the populations.
Genomics can provide insights into the way populations of a species may have responded to climate change in the past. Estimates of historical demographic change over recent or long time scales can be obtained from analyses of the scale and structure of sequence variation in extant populations [132,133]. The time course of changes in population size and structure obtained can then be used to link past population expansions and contractions to historical climate change, giving a clue as to the vulnerability of a species (based on both plastic and evolved responses) to future climate change.
Finally, phylogenetic and phylogenomic studies may provide insights into the capacity of species and lineages to tolerate contemporary climate change (Table 1). The well-supported, well-dated phylogenetic trees that can be produced with genomic data provide an opportunity to assess whether certain taxonomic groups are more vulnerable to climate change than others. The potential insights that might emerge from such studies are illustrated by traditional multi-locus phylogenetic (rather than phylogenomic) studies carried out to date. Thus a continent-wide avian phylogeny showed that European birds whose niches evolved more slowly in the past exhibited greater levels of demographic decline in the twentieth century, both at the individual species and the overall family level . Similarly, Crisp et al. used a phylogenetic framework to show that relatively few groups of southern hemisphere plants have speciated from the alpine biome to the sclerophyll biome, but many have speciated across sclerophyll/arid boundaries, suggesting that groups of alpine species are more at risk of extinction than sclerophyll species given an equivalent amount of climate change.
If a species is predicted to tolerate climatic changes and persist in situ, then no further action is required other than ongoing monitoring and assessment (action 1 in Figure 2). If, on the other hand, it is predicted that the species may not be able to persist in situ, then the next step in the decision framework is to identify whether there are any climatic refugia, internal to the species range, that might buffer it from change and facilitate persistence.
Identifying climate refugia within a species’ current range
Refugia are defined as habitats that species retreat to, persist in and potentially expand from under changing environmental conditions, and are usually places providing environmental heterogeneity and climatic stability as regional environments change . Genomic data can be used in combination with ecological data and species distribution models to identify places where populations of a species have persisted through periods of climatic instability and maintained genetic diversity (D3 in Figure 2). Such places become candidate refugia for the species under future climate change. Genetic signatures of refugia have often been detected using organelle markers [137,138], but as noted above, lineages that have undergone bottlenecks over relatively recent geological timescales (e.g. glacial cycles) can also be identified using high numbers of neutral loci, which can accurately reconstruct temporal changes in effective population size skyline plots . For example, in antbirds in the Brazilian Atlantic Forest, genetic studies showed that populations in areas with high last glacial maximum (LGM) stability exhibited long-term population growth, whilst populations in less climatically stable regions showed strong demographic fluctuations, supporting previously hypothesised refugial areas . Ongoing work incorporating these genomically estimated demographic effects of climatic changes with spatial modelling is likely to improve future estimations of extinction risk . Climate change in the last glacial maximum (approximately 21 kya) can also be used to project future refugia utilising spatial modelling approaches (see below). Once refugia have been identified, they should be secured from further threat (Action 2 in Figure 2).
Measuring genetic diversity across landscapes: landscape genomics and beyond
Do populations have enough genetic diversity for an evolutionary response?
Conservation geneticists working on threatened species and other key species maintaining ecosystem function have largely focussed on selectively neutral variation to this point, in part because of its ability to provide unbiased estimates of demographic factors like population size, random drift, mutation and migration. The level of neutral variation in threatened and non-threatened species can also provide an indirect but reasonable indication of adaptive diversity when this is dependent on factors like population size [142,143]. Adaptive variation is much more difficult to measure directly because it requires either linking variation in specific genes to adaptive responses or assessing the extent to which variation in traits under selection is genetically determined (heritability and evolvability). Therefore, overall genetic diversity has generally been taken as a reasonable proxy for the small fraction of the diversity that is functionally associated with higher adaptive potential under climate change. However, population and quantitative genomics also now offer some powerful new ways to probe for adaptive variation (D4 in Figure 2).
Population genomics can distinguish particular loci showing signatures of selection from the genomic background, identifying whether adaptive genetic variation is present in the organism. The data required usually involve genome-wide sequencing of multiple genomes from the species in question, although various sampling designs are appropriate depending on the precise nature of the organism and the question. For example, some sampling designs are better able to measure linkage disequilibrium than others, and some designs also allow timeframes for selection to be estimated. The bioinformatics approaches are well established and have been used successfully in many cases, e.g. [144-149]. A key finding of early studies has been that genomic landscapes appear as mosaics, with some regions providing signatures diagnostic of various forms of positive and balancing selection, and others comprised of apparently neutral or near-neutral diversity [150-152].
This population genomic approach does not itself elucidate the precise targets of selection (which may be in large tracts of the genome spanning coding or regulatory regions) or the specific nature of fitness differences. However, two major quantitative genomics techniques are available that enable genomic data to be linked to the phenotype. In both cases, data are required jointly on genomic and phenotypic variation, either from population samples (GWAS) or crossing experiments (for QTL mapping). A variety of experimental designs are used, mostly based on samples of individuals but in some cases on pooled samples, and either WGS or various RRS, DNA enrichment (DE) or other sequencing strategies can be deployed (Table 1). Issues including the level of linkage disequilibrium and population structure in field populations and ease of breeding and productivity in laboratory crosses will determine which approach is taken and the specifics of the design, but there is a large body of literature to guide such studies; see discussion and references in . Whilst laborious, these experiments are being used more frequently and becoming cheaper. Examples of climate-related phenotypes that have been mapped to particular genetic variants by these means include life history adaptations in various populations of Arabidopsis and Parus major and tolerance to desiccation resistance and thermal stress in Drosophila.
The welter of transcriptomic and other functional genomic studies now being conducted on a wide range of organisms is rapidly expanding our understanding of both the potential functions of particular sorts of genes and their networks of functional relationships . Comparative genomics is helping to identify syntenic blocks and gene families which have expanded or contracted in association with particular ecological niches or adaptations such as frugivory in bats and sensitivity of honeybees to insecticides . A rapidly increasing number of studies are using such approaches to provide functional links between components of the genome and climate-related phenotypes, e.g. [131,161]. We anticipate a time when the results of genome-wide scans of sequence variation will be interpretable in these specific ways.
When assessing changes in genetic variation, museum and herbarium specimens can provide access to temporal series of collections or other material that for various reasons cannot be obtained otherwise. The technology for retrieving data of usable quality from such specimens has improved substantially, e.g. , and it has already enabled several studies showing progressive changes in gene frequencies in various organisms over time frames out to about 100 years, e.g. [112,163]. This may provide unique clues about recent genetic changes, be they losses of genetic variation or of positive selective processes already underway. In either case, they will be important inputs into decisions about interventions such as conservation translocations, both within (reinforcement translocation) and external to (assisted colonisation) species’ current ranges (“Defining translocations” section, actions 4 and 6 in Figure 2) and enforced hybridisation (action 7 in Figure 2) discussed further below.
If a species is assessed as harbouring adequate levels of genetic variation, then no direct management actions should be automatically triggered, although ongoing monitoring of genetic diversity can ensure the levels remain sufficient for adaptive responses (action 1 in Figure 2). If some populations harbour more genetic diversity than others, then understanding how that diversity is distributed across the species’ range, and the extent to which some populations have adapted to local climatic conditions, may lead to specific management actions (action 3 in Figure 2).
Although genomics provides powerful ways of assessing adaptive and neutral genetic variation, links between the different types of genetic diversity and adaptive capacity can only ultimately be established through phenotypic association studies. Whilst the presence of genetic variation in loci generally, and in those likely to be involved in adaptive changes, can highlight the potential for evolution, it does not necessarily indicate the extent to which phenotypes in populations can be changed by selection.
Do some populations have high genetic diversity?
Understanding how overall genetic diversity is partitioned among populations across a species’ range is critical in predicting the adaptive capacity of the species (D5a and D5b in Figure 2, Table 1). Additionally, it informs about the potential for migration to facilitate persistence under climate change . The approaches described in the sections below allow the identification of species that harbour low diversity in some populations and “hotspots” of genetic diversity in others. The latter are obvious targets for conservation and useful source populations for reinforcement translocations (“Defining translocations” section). Low-diversity populations, however, may have low adaptive potential under climate change and may be targets for improving connectivity (see “Gene flow” below, Figure 2 D6) or reinforcement translocations (action 4 in Figure 2, “Defining translocations” section) to increase diversity. The various sequencing strategies outlined above for population and quantitative genomics within populations are also applicable to samples from different populations and, as illustrated below, have often revealed significant differences in divergence levels across the genome.
Are some populations already adapted to local climate?
Where populations differ in their allelic composition, tests for genetic divergence deviating from theoretical neutral expectations can be applied to detect local adaptation (D5b in Figure 2). Quantifying local adaptation is important because this can indicate whether populations already possess genetic variation that could allow persistence under climate change. Measures of population differentiation such as Wright’s F ST are commonly used as a metric for local adaptation in methods for detecting adaptive divergence that can include explicit assumptions about demographic history [164-166], although this approach can indicate an excessive number of apparently adaptive loci if assumptions about demography are incorrect . Similarly, tests for consistent differences in the frequencies of alleles between replicated pairs of populations such as the Cochran-Mantel-Haenszel (CMH) test can be used to identify locally adapted loci where population pairs are compared for a common selective constraint . Relative rate tests such as the McDonald-Kreitman (MK) test permit comparisons of diversity within populations to divergences between them (or from related species), where departure from theoretical ratios for neutral loci can imply local adaptation [168,169]. Software is becoming available to allow many of these well-known tests to be carried out on genome-scale data [170-172].
For widespread species whose geographic ranges encompass environmental gradients, the association of allelic variation among populations (or individuals) with environmental factors can also be an indicator of local adaptation, as long as neutral patterns of genetic variation are taken into account [147,173-175]. Several statistical approaches have been developed to test for such associations, many of which incorporate information on demographic history utilising general linear models , logistic regression , generalised estimating equations or other types of models [179-181]. Central to these analyses is that demographic history is explicitly accounted for, in order to avoid erroneous conclusions of adaptive divergence in allele frequencies . These approaches have identified genomic regions differentiated across climatic gradients, such as four regions repeatedly associated with minimum temperature in the alpine plant Arabis alpina and five regions associated with precipitation in the alpine plant Campanula barbata . However, isolating the specific environmental factor responsible for spatial genetic variation can still be challenging because different factors will often be spatially correlated.
The above approaches highlight ways to identify genomic regions that are involved either in historic adaptation to longstanding ecological gradients or adaptation to recent environmental change including from anthropogenic sources [93,183]. This can help distinguish populations that may be at risk due to a lack of adaptive diversity from those which already possess genetic variants that could allow persistence under climate change. However, unless the contribution of specific genes to the size of adaptive shifts is known and the nature of environmental variation linked to the genes has been clearly identified, these types of approaches cannot indicate the rate and extent of an adaptive response possible across a species’ range. As with the intra-population variation considered above, quantitative genomics is still needed, both to narrow down the genomic region specifically responsible for the adaptive phenotypic differences and to assess the size of phenotypic effects associated with particular regions.
Is gene flow high enough (or too high)?
If genetic variation has been identified in certain populations of a species that could help other populations adapt to climate change, then it is important to determine whether there is an appropriate level of gene flow between populations (D6 in Figure 2). Gene flow can aid adaptation by increasing genetic variation and/or by introducing better adapted genotypes. Interbreeding with divergent individuals migrating into a population can also generate entirely new genotypes that may be better suited to tolerating the novel conditions expected under climate change [184-186]. Whilst gene flow usually does improve adaptive capacity, high levels of gene flow can also result in a loss of local adaptation and reduction in population fitness , although empirical evidence for deleterious gene flow is still limited .
Natural or anthropogenic barriers as well as habitat fragmentation can disrupt gene flow by preventing the migration and dispersal of individuals. Topographically complex landscapes with sharp environmental gradients may drive local adaptation and produce regions containing genotypes adapted to different conditions. This in turn may lead to isolation by adaptation—i.e. the exclusion of immigrating individuals from the breeding pool due to higher fitness of local genotypes [188,189]. These landscape-scale processes can also lead to reproductive isolation—such as through mating or flowering phenology—resulting in little or no effective gene flow between geographically close populations [190-192].
Historical and contemporary gene flow between populations can be accurately estimated using genomic data. For example, high contemporary gene flow as well as local adaptation in red abalone has been identified utilising SNPs discovered through transcriptome sequencing , whilst historical gene flow between closely related species of Heliconius butterflies was identified using targeted enrichment sequencing . RAD sequencing has identified genetic isolation among populations of herring and speciation in cichlid fishes . Gene flow estimates utilising RAD-seq-derived SNPs detected inbreeding in wild harbour seals, suggesting isolation between natural seal populations . Some of these genomic studies on gene flow, e.g. [99,193] are pointing to highly heterogeneous rates of gene flow across the genome; intra-population and quantitative analyses as outlined in previous sections are then invaluable in ascertaining the adaptive significance of such heterogeneity.
If key populations have been shown to be isolated from adaptive variation, or from high overall variation located elsewhere in the species’ range, then the next decision is to determine whether migration pathways can be restored (D7 in Figure 2).
Genetic opportunities—managing for diversity and adaptive capacity
The previous part of the framework deals with the importance of genetic diversity to evolutionary responses to environmental change, how to infer adaptive capacity from measures of genetic diversity and the potential importance of gene flow. The next part considers the potential of more active interventions for species for which the actions outlined to this point are unlikely to be sufficient.
Can degraded landscapes be restored to enhance gene flow and adaptive shifts?
Landscape revegetation is a major programme of activity to address climate change worldwide [195,196]. The aim is generally to restore fragmented and degraded landscapes, thus enhancing the scope, quality and accessibility of key refuge areas for both key species and whole communities . However, little effort is currently invested in assessing the adaptive potential of the trees and shrubs that have been planted and hence the likelihood that they will persist under climate change. At present, most revegetation efforts revolve around the notion of local provenancing, where germplasm is collected from neighbouring areas on the assumption that it is adapted to local conditions. If there is strong local adaptation, then this approach will facilitate short-term establishment, but it may not be the best approach in the longer term, given changing environmental conditions. Compounding the issue, local provenancing often results in seed collections from small local populations that are genetically depauperate [198,199], leading to low genetic variation with inadequate potential for adaptive response to future changed conditions [200,201].
Examples of application of genomic approaches to conservation and revegetation of some Australian trees and shrubs
Grey box (Eucalyptus microcarpa)
The University of Melbourne, CSIRO
Part of threatened vegetation community
Landscape genomics, including effects of fragmentation, and gene trait association
1) Identification of adaptive variation can be applied to guide selection of climatically adapted material based on projected changes to niche envelopes
Yellow box (Eucalyptus melliodora)
Australian National University, CSIRO, Department of Parks and Wildlife
Part of threatened vegetation community
Landscape genomics and gene trait association
River red gum (Eucalyptus camaldulensis)
Not currently threatened, but at risk due to river regulation
Landscape genomics, landscape transcriptomics and gene trait association
2) Monitor standing diversity in selections to maintain adaptive potential
Ironbox (Eucalyptus tricarpa)
Department of Parks and Wildlife, CSIRO, Edith Cowan University, University of Tasmania
Important species in fragmented communities of south-eastern Australia
3) Guide selections with respect to neutral population structure and gene flow
York gum (Eucalyptus loxophleba)
Department of Parks and Wildlife, CSIRO, Edith Cowan University, Australian National University
Important species in fragmented communities of south-western WA (SWWA)
Landscape genomics and functional trait assessment across climate gradient
4) Screen existing plantings—locally sourced—to assess their resilience based on the above criteria
Gimlet (Eucalyptus salubris)
Department of Parks and Wildlife, CSIRO, Edith Cowan University, Australian National University
Dominant species in Great Western Woodlands of SWWA
Landscape genomics and functional trait assessment across climate gradient
Jarrah (Eucalyptus marginata)
Department of Parks and Wildlife, Australian National University, CSIRO
Dominant species in jarrah forest system in SWWA
Landscape genomics and functional trait assessment across climate gradient
Marri (Corymbia calophylla)
Department of Parks and Wildlife, University of Western Sydney
Major co-dominant species in forest and woodlands in SWWA
Landscape genomics and functional trait assessment across climate gradient
Swamp peppermint (Taxandria linearifolia)
Department of Parks and Wildlife, Warren Catchment Council
Patchy distribution in riparian vegetation along river systems in SWWA
Landscape genomics across river catchment and climate gradient
Native willow (Callistachus lanceolata)
Department of Parks and Wildlife, Warren Catchment Council
Patchy distribution in riparian vegetation along river systems in SWWA
Landscape genomics across river catchment and climate gradient
River-bank Astartea (Astartea leptophylla)
Department of Parks and Wildlife, Warren Catchment Council
Patchy distribution in riparian vegetation along river systems in SWWA
Landscape genomics across river catchment and climate gradient
Waratah (Telopea speciosissima)
University of Western Sydney, The Royal Botanic Gardens, Sydney
Patchy distribution along an environmental gradient from coastal area to inland areas
Common garden experiments, landscape genomics across climate gradients
Several provenancing strategies involving assisted gene flow have been suggested in the context of climate change. Predictive provenancing requires identification of the predicted climate at a certain point in the future and sourcing seed from sites where that climate currently occurs . Composite provenancing involves mixing seed collected from increasing distances away from the site to maximise genetic diversity and mimic natural gene flow . Admixture provenancing suggests collecting seed from a range of environments without regard to the local site conditions . Climate-adjusted provenancing involves sourcing seed from sites along the projected direction of climate change [202,207]. Climate-adjusted provenancing has the advantage of simultaneously mixing seed sources to increase genetic variation and recruiting from populations likely to be adapted to future climates without needing to target any particular population specifically. This approach is particularly suitable for species with long generation times, where the impacts of climate change will be felt within a generation, and maximising the adaptive diversity in the gene pool is essential to future population persistence.
Assisted migration approaches, such as the various provenancing strategies outlined above, may be critical to maintain ecosystems under climate change . However, it should also be noted that the genetic potential of seed sources is just one of the many issues that require management in revegetation programmes (e.g. soil symbionts, disease, weed risk), and there are decision frameworks available for managing these issues [199,208,209] that can be applied in a wider climatic context.
Potential for naturally occurring hybridisation and introgression
If no populations within a species harbour adequate genetic diversity, the next step is to consider whether ongoing evolutionary responses to climate change might be enhanced by naturally occurring hybridisation with closely related species (D8 in Figure 2). Hybridisation has been shown to play a role in moving adaptive gene sets between closely related species, and in such cases, it will alter predictions for future phylogenetic diversity as well as the adaptive capacity of species, e.g. [210-213]. If hybridisation is as common and evolutionarily significant in natural systems as many researchers now consider, it could help species modify their phenotypes rapidly enough to accommodate current rates of environmental change. In the past, statistical evidence for determining the extent of hybridisation in nature has been difficult to obtain because patterns of genetic variation caused by hybridisation look similar to the patterns of genetic variation caused by the incomplete sorting of alleles that can accompany species divergence [212,214,215]. However, analytical approaches that use genome sequence data for robust inferences of hybridisation have recently been developed [215-219], which should help to better understand the extent and adaptive significance of hybridisation in nature.
Importantly, next-generation sequencing (NGS) sequencing of species complexes is showing that adaptive differentiation and introgression do not necessarily involve much of the genome. With our own species, researchers estimate that whilst less than 7% of our genome is introgressed with the DNA of extinct hominid species, the captured DNA sequences have helped humans adapt to a variety of climates and resist pathogens [211,212,218]. Although “genomic extinction” resulting from hybridisation in nature has been suggested by some researchers to occur where endemic species are replaced by invasive species that acquire endemic adaptations , genetic rescue by interspecific hybridisation need not abolish local adaptations. The genetic basis for many of these is likely to be concentrated in islands of adaptive divergence, such as seen in Eurasian Ficedula flycatchers and Heliconius butterflies . In humans, recent evidence has emerged that there is strong selection against regions of introgressed genomes that are not advantageous, including selection against genes that reduce the fertility of hybrids .
Several studies are also now capitalising on inexpensive NGS-based transcriptome analyses to dissect hybridisation and the impact that introgression events have on ecological diversification and reproductive compatibility of plant species (e.g. Helianthus sunflowers , tomatoes , alpine cress and Senecio ). Biotic and abiotic stress response genes are commonly implicated in ecological diversification and adaptation. Whilst gene expression differences for such genes occur between parent species and hybrids, there is little evidence at this point for regulatory incompatibility between the respective genomes of closely related hybridising species. In an informative study, Moran and Fontdevilla followed up full genome sequencing of two hybridising Drosophila species with a QTL analysis of the (incomplete) post-zygotic reproductive barriers between them. They successfully mapped several loci contributing to those barriers and showed they acted cumulatively according to a polygenic threshold model. That is, sterility was more a function of the extent of genetic divergence of the parent species’ genomes than the action of major hybrid sterility genes. Such findings could have important implications for genetic rescue efforts that consider breeding between genetically isolated populations and species, e.g. [226-228], but many more studies will be needed before generalisations will emerge.
Do climate refugia outside species’ current ranges exist and can species reach them?
From an ecological perspective, climatic refugia are often defined as those areas where the projected future environment is most similar to the current environment of a species or community or where environmental and spatial heterogeneity maintains microclimatic variation as regional environments change (D9 and D10 in Figure 2). The premise is that such sites are likely to serve as important refugia for species that are unable to adapt to the novel conditions projected under climate change. Identification of refugia is modelled for individual species using species distribution models as discussed previously or continent-wide for functional groups of organisms using community modelling . Such refugia can be identified using a range of pattern- and process-based characteristics, including climate projection models, combined with information about current environmental attributes, to estimate the scale of change expected across the landscape and the overall similarity between areas of current and future landscape. For instance, Dunlop et al. modelled the scale of novel environments expected under climate change across the Australian continent, in order to estimate the areas likely to have the least amount of change from their current climate. These projections were then used to estimate how well current environments are represented in the National Reserve System of Australia under future environments and thus how well the reserve system protects biodiversity over the longer term. These methods estimate refugial areas that are inside as well as outside the current range of species, which are important to persistence as long as the species are able to disperse to them and there is vacant ecological space .
Definition of terms used in translocations
Human-mediated movement of living organisms or their genes from one area, with release in another. Translocation is an overarching term
Intentional movement and release of a living organism or its genes where the primary objective is a conservation benefit: this will usually comprise improving the conservation status of the focal species locally or globally and/or restoring natural ecosystem functions or processes. It can cover translocations either within or outside the species indigenous range
Any conservation translocation within indigenous range and comprises reinforcement and reintroduction
Part of population restoration. The intentional movement and release of an organism into an existing population of conspecifics. Reinforcement aims to enhance population viability, for instance by increasing population size, by increasing genetic diversity or by increasing the representation of specific demographic groups or stages
Part of population restoration. The intentional movement and release of an organism inside its indigenous range from which it has disappeared
Intentional movement and release of an organism outside its indigenous range. Consists of assisted colonisation and ecological replacement
Part of conservation introduction, involves intentional movement and release of an organism outside its indigenous range to avoid extinction of populations of the focal species
Part of conservation introduction involves intentional movement and release of an organism outside its indigenous range to perform a specific ecological function
Last ditch efforts for critical species
Can assisted colonisation, enforced hybridisation and ex situ conservation help?
This section considers interventions for threatened species or populations that have failed or are likely to fail to persist with the management options above and are at, or approaching, endangered or critically endangered status (D11, D12 and D13 in Figure 2). It deals first with translocations aimed at restoring levels of genetic diversity and adaptive capacity within a species’ range (reinforcement translocations) (“Defining translocations” section, action 4 in Figure 2). Weeks et al. define these types of translocations as genetic rescue (where the aim is to rescue populations from the genetic effects of inbreeding and associated loss of genetic diversity and inbreeding depression) or genetic restoration (where the aim is to restore levels of adaptive genetic diversity via ongoing translocations from the source population). Note that some of the provenancing strategies considered in the section on revegetation above also have elements of genetic rescue/restoration, the key difference being that the species in question for revegetation are not themselves endangered and the focus for conservation. This section then considers translocations aimed at hybridising evolutionary significant units [232,233] and sub- or sibling species (assisted colonisation) (action 7 in Figure 2). Finally it discusses the last resort option of ex situ conservation (e.g. captive breeding or seed nurseries), which Weeks et al. term genetic capture (action 8 in Figure 2).
Genetic rescue and genetic restoration are appropriate where a key population of a species or subspecies has fallen to such low numbers <1,000 [199,234] that the exposure of genetic load through inbreeding becomes a significant fitness issue (inbreeding depression) compounding the challenges of adapting to a changing environment. Both genetic rescue and genetic restoration involve the translocation of individuals from another, larger population of the species, usually aiming for up to 20% gene flow from the source population [199,235] and, in the case of genetic restoration, also aiming to continue gene flow through ongoing translocation at a rate of at least one effective migrant per generation, which is thought to be enough to reduce the disruptive effects of genetic drift . The goal is to reduce genetic load, inbreeding depression and the detrimental effects of genetic drift whilst also, as with genetic adaptation above, enhancing the prospects for successful adaptation to the changing environment by boosting genetic variation and the opportunities it provides for generating novel recombinants. Hedrick has shown that gene flow of up to 20% into a recipient population is not likely to swamp locally adapted alleles, particularly those under strong selection. Such genetic rescue/restoration has been successful in several recent cases, such as the Florida panthers, greater prairie chickens in North America, adders in Sweden, South Island robins in New Zealand and mountain pygmy possums in Australia [227,237,238]. However, as with translocations for genetic adaptation above, it is still contentious and has been underutilised as a tool in the conservation of endangered species.
Genetic rescue and restoration translocations have partly been underutilised due to concerns around preserving “unique” genetically distinct populations and avoiding outbreeding depression. But uniqueness in endangered populations and species is more likely to be a result of drift processes than mutation alone and the risk of outbreeding depression has clearly been overstated . At any rate, the markers generated using NGS technologies will be more informative than neutral markers (e.g. microsatellites) for differentiating between populations that are adaptively unique, compared with those populations that have lost variation through drift processes by identifying loci under selection . Similarly, NGS might give greater insight into the likelihood of inbreeding and outbreeding depression by assessing the number of genomic regions that are adaptively unique within source and recipient populations, and that decrease fitness, e.g. .
Concerns about conserving genetic integrity, and problems with outbreeding depression, become more pronounced when the only option available for genetic rescue involves translocating individuals from a different subspecies or species. However, the increasing pressure from climate change and other drivers of widespread environmental change mean that the potential risks of such genetic rescue are increasingly outweighed by the opportunity to rescue species or subspecies that would otherwise disappear altogether. Whilst it is generally only enacted when population sizes have fallen to a few individuals, there have been some significant successes with this strategy. The classic case of genetic rescue involved the Florida panther (Puma concolor coryi) where the introduction of eight female pumas from a different subspecies (Puma concolor stanleyana) from Texas restored depleted genetic diversity, reversed inbreeding depression and increased population size . Similarly, the Norfolk Island boobook owl, Ninox novaeseelandiae undulata, was reduced to a single female in 1986, and the deliberate introduction of two males of its nearest relative (the New Zealand boobook, N. n. novaeseelandiae) saved this subspecies from extinction, albeit in hybrid form . Clearly, there are instances when such radical translocations can save endangered species (or at least some of their genetic history), and more thought needs to be given as to how NGS technologies might better inform about when these instances will lead to success (e.g. by examining patterns of adaptive diversity, developing better estimates of divergence at adaptive loci, etc.). NGS monitoring in the first few generations after the initial hybridisation might also suggest possible further interventions to maximise adaptation.
Another last resort option for endangered species involves ex situ conservation. Genetic issues are critical in this option but genetic input into the management of captive breeding/seed nursery programmes has generally been based on relatively few neutral markers . As already noted, genomics can now provide much more comprehensive coverage of neutral markers and give new insights into important adaptive processes. The data quality can also be improved by having access to a reference genome from the target species (or related species) and, as already noted, the costs of this continue to decrease, making it a viable option for conservation programmes.
More specifically, NGS resequencing will permit genetic relatedness among individuals to be accurately estimated across the genome. This in turn will enable better decisions, both in captive breeding strategies and in the selection of individuals for release back into particular field populations . This increases the chances of avoiding inbreeding depression and perhaps even increasing adaptive variation both in captive and natural populations. The prospects of avoiding some of the specific deleterious fitness effects that have plagued ex situ captive breeding programmes [245,246] are also improved, for example, by ensuring maximum diversity is retained in key genomic regions related to disease resistance and by reducing the frequencies of alleles that have been associated with mating incompatibility or specific recessive conditions, either in the species under study or in others . Changes in gene frequencies over generations of captive breeding can also alert managers to avoid alleles that may be associated with adaptation to captivity and to compare the genetic composition to natural populations, either overall or in specific localities targeted for reintroductions . As knowledge of gene function improves, it may be possible to identify and select for alleles associated with particular environments (e.g. desiccation resistance, drought tolerance or phenology that may be required under future climate scenarios ).
However, it should be emphasised that decisions around assisted colonisation and ex situ conservation will involve many considerations unrelated to genetic variation and evolutionary capacity. These include factors like evaluating the impact of removing individuals from source populations as well as the impact of introductions on existing biota in target sites, assessing the likely costs of such translocations within the context of other demands on conservation budgets, and social or cultural aspects such as the value placed by the public on a threatened species.
Our framework highlights the potential of genomic studies to contribute to strategies for conserving biodiversity. Both population and quantitative genomics are crucial, aided by, but not dependent on, a good reference genome sequence. However, these genomic approaches do not provide a panacea for the problems in biodiversity conservation under climate change. Their value will be easier to realise in some decision areas than others.
Population genomic data can now be used in relatively straightforward experiments to assess genetic diversity within and between species, to map levels of genetic diversity across landscapes, and to understand the relative importance of neutral evolutionary processes like genetic drift and migration in driving population dynamics. They can also now be used to understand the extent to which genetic changes have occurred as a consequence of natural selection driving local adaptation and to make inferences about the relative importance of evolutionary adaptation versus neutral process in driving patterns of biodiversity across landscapes. As such, population genomic data can provide unprecedented insights into the extent and evolutionary consequences of naturally occurring hybridisation in nature, and to assess and monitor the outcomes of management decisions that involve translocations, and efforts to restore degraded landscapes and communities through revegetation programmes.
However, the key limitations with population genomic approaches are that they do not of themselves identify the precise genetic variants that causally underpin adaptive responses to climate change, nor do they tell us about the size of the adaptive differences mediated by variation in particular genomic regions. Quantitative genomics, combined with appropriate ecological and quantitative evolutionary work, can address both these issues, although it is challenging in such studies to define complex physiological traits that are relevant to the ecology of species. One major issue with QTL mapping (but not GWAS) is its absolute dependence on managed breeding programmes, which may be not be feasible or affordable in many cases. Where population and quantitative genomics approaches can be undertaken, it may be possible to identify and implement substantively more effective and efficient management strategies for biodiversity under climate change.
Zoos and other breeding establishments will be important resources for the genomics work required for threatened fauna, as they have unique capabilities in rearing and breeding animals and are increasingly concerned with conservation issues. One of their major contributions to date has been in restoration programmes, breeding captive populations of animals for eventual release into the wild. This exercise has often suffered from a low success rate, due to factors such as ongoing inbreeding, genetic adaptation to captivity at the expense of adaptation to wild conditions and so on [247,248]. Whilst avoiding inbreeding and the exposure of deleterious recessive conditions is already a major goal in their breeding programmes, genomic approaches together with evolutionary thinking could provide data which are both more comprehensive and more precise on this point. Zoos could also play a larger role in the future in the quantitative and population genetics needed for evaluating other key management options, such as translocations and hybridisation by, for example, testing the viability and various adaptively important phenotypes of F1 and F2 offspring generated from crosses between populations, subspecies and other taxa.
Herbarium collections, seed banks and botanic gardens could fulfil the same sorts of functions for plants. In addition, where seed material can be maintained across years, there is an opportunity to capture the genetic variation present at a particular point in time and preserve it for later re-establishment of populations [249,250]. Such a resource could provide a valuable source of genetic variation and capture novel genotypes across regions as plant populations adapt to changing environmental conditions .
Finally, once genomic approaches become routine components of conservation programmes and restoration efforts, novel ways of thinking about the role of evolution in management programmes to maintain biodiversity and ecosystem functions are likely to emerge. New examples of phenomena like incomplete allele sorting and islands of adaptive divergence during speciation, and various introgression scenarios following hybridisation, have already become evident from the application of genomics to a range of non-model species. New levels of understanding of climate change adaptation and the role of hybridisation in adaptive processes are likely to emerge from this work. This understanding in turn will suggest novel approaches to biodiversity conservation and the maintenance of ecosystem function under a rapidly changing climate.
This paper arose out of a workshop funded through the Office of the Chief Executive Science Team at CSIRO and the Science Industry Endowment Fund.
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This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. | <urn:uuid:00878986-d549-46cc-ad85-45827bf82d85> | 3.015625 | 28,234 | Truncated | Science & Tech. | 29.362257 | 95,602,832 |
Over one thousand miles wide and three thousand miles long, the Sargasso Sea occupies almost two thirds of the North Atlantic Ocean. Within the sea, circling ocean currents accumulate mats of Sargassum seaweed that shelter a surprising variety of fishes, snails, crabs, and other small animals.
A recent paper by MBARI researcher Crissy Huffard and others shows that in 2011 and 2012 this animal community was much less diverse than it was in the early 1970s, when the last detailed studies were completed in this region.
This study was based on field research led by MBARI Senior Scientist Ken Smith, using the Lone Ranger, a 78-meter (255-foot) research vessel owned and operated by the Schmidt Ocean Institute. During three cruises in 2011 and 2012, Smith’s team steamed across the Sargasso Sea and used dip nets to collect samples of Sargassum seaweed (and its associated animals) at six different locations. They then classified and counted all the animals at each site.
The researchers chose their sampling and counting methods carefully so that they could compare their results with previous surveys that had been conducted in 1972 and 1973 in the same general part of the Sargasso Sea. Amazingly, the researchers could find no other studies between 1973 and 2011 during which scientists had systematically counted the Sargassum animal communities in this area.
When the team analyzed the data from the recent cruises, they were surprised to find that animal communities in the Sargassum rafts were significantly less diverse than those observed in the 1970s. For example, 13 species of animals in several different groups (worms, nudibranchs, crustaceans, and sea spiders) were observed in the historical samples but were missing from the recent samples.
Unfortunately, the researchers did not have enough data to determine whether the differences they observed were the result of long-term shifts in ocean conditions in the Sargasso Sea or natural variations from place-to-place, month-to-month, or year-to-year.
The authors note that ocean conditions were much cooler than normal during February 2011 and that there were large differences in animal communities observed just six months apart, in August 2011 and February 2012. So it is possible that this area routinely sees large natural variations in the types of animals present. As Huffard put it, “If this is a long-term decline [in biodiversity], then it is a very significant one. But we don’t know if this is part of the natural variability in this community.”
Previous studies indicate that much of the seaweed that ends up in the Sargasso Sea originates in the Gulf of Mexico and is carried into the central Atlantic by the Gulf Stream and other currents. This suggests that, in addition to local ocean conditions, large-scale variations in ocean currents and conditions in the Gulf of Mexico could affect the animals in Sargassum communities.
To tease out these confounding variables, Smith and Huffard are hoping to conduct a series of follow-up expeditions to the Sargasso Sea. They plan to focus on the northern part of the Sargasso Sea, near Bermuda, where more detailed historical data are available. They are presently working on a proposal for a grant that would allow them to analyze satellite imagery and collect field samples twice a year for three years. The proposed study would show how much year-to-year variability is normal for this region.
At first glance, the animals that live in Sargassum rafts seem isolated from the rest of the world. But, like the seaweed they live in, these animal communities have many links to larger ocean food webs. For example, Sargassum animals provide essential food for sea birds, sea turtles, and bluefin tuna—all long-distance migrators. In fact, Sargassum rafts have been designated as “essential fish habitat” by the South Atlantic Fishery Management Council.
The world’s oceans are changing, with water temperatures and ocean acidity on the rise and oxygen concentrations on the decline. In the Sargasso Sea, as in many other locations, detecting the biological effects of these long-term trends is a formidable challenge because animal communities can vary dramatically over short time periods. This study shows that animal communities in the Sargasso Sea are definitely changing. The next step is to find out why.
For additional information or images relating to this news release, please contact:
Original journal article:
C.L. Huffard, S. von Thun, A.D. Sherman, K. Sealey and K.L. Smith, Jr. (2014) Pelagic Sargassum community change over a 40-year period: temporal and spatial variability. Marine Biology, doi10.1007/s00227-014-2539-y.
Kim Fulton-Bennett | Eurek Alert!
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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16.07.2018 | Earth Sciences | <urn:uuid:ddbaf696-6b1d-445c-8660-b96339dff454> | 3.671875 | 1,665 | Knowledge Article | Science & Tech. | 44.176736 | 95,602,839 |
The research team of Prof. Sonja Hofer at the Biozentrum, University of Basel, has discovered why our brain might be so good at perceiving edges and contours. Neurons that respond to different parts of elongated edges are connected and thus exchange information. This can make it easier for the brain to identify contours of objects. The results of the study are now published in the journal “Nature”.
Individual visual stimuli are not processed independently by our brain. Rather neurons exchange incoming information to form a coherent perceptual image from the myriad of visual details impinging on our eyes. How our visual perception arises from these interactions is still unclear.
This is partly due to the fact that we still know relatively little about the rules that determine which neurons in the brain are connected to each other, and what information they exchange. The research team of Prof. Sonja Hofer at the Biozentrum, University Basel studies neuronal networks in the brain. She has now investigated in the mouse model what information individual neurons in the visual cortex receive from other neurons about the wider visual field.
Neurons receive information from large parts of the visual field
The visual cortex, the largest part of the human brain, is responsible for analyzing information from the eyes and enables us to perceive the visual world. Different neurons in this brain area react to components of the visual scene at specific positions in our visual field.
Sonja Hofer and her team could show that individual neurons also receive extensive additional information from the remaining visual field. “This is not surprising, because how we perceive individual visual stimuli strongly depends on their surrounding visual environment”, Hofer explains. Individual parts of an image are, for instance, merged into lines, contours and objects.
Edges in our environment are mirrored in the brain
The new study shows that neurons are most likely to be connected if they react to edges that lie on a common axis. “Our visual environment contains many long lines and contours”, Sonja Hofer explains. “The structure of the world around us is therefore mirrored in the pattern of synapses in the brain”.
Hofer’s team believes that this specific brain connectivity might facilitate the perception of elongated lines and edges: neurons that react to different parts of such edges are connected, can increase each other’s activity and therefore boost the response that contributes to the perception of these visual features.
Our brain is so good at identifying contours and objects in images that it is sometimes deceived into seeing them even if they do not actually exist (such as the edges of the blue triangle in the foreground of the figure). Such optical illusions show how primed our brain is to detect lines and object contours”, says Hofer. “Our findings reveal a mechanism that can contribute to this skill”.
Florencia M. Iacaruso; Ioana T. Gasler; Sonja B. Hofer
Synaptic organization of visual space in primary visual cortex.
Nature (2017) | DOI:
Sonja B. Hofer, University of Basel, Biozentrum, Tel. +41 61 207 17 65, email: firstname.lastname@example.org
Heike Sacher, Biozentrum, Communications, Tel. +41 61 207 14 49, email: email@example.com
Heike Sacher | Universität Basel
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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12.07.2018 | Event News
03.07.2018 | Event News
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16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:3b19fb76-b313-48f2-9140-d09b03be2221> | 3.6875 | 1,363 | Content Listing | Science & Tech. | 41.160814 | 95,602,840 |
National Center for
4HUE: Structure Of 5-chlorouracil Modified G:u Base Pair
Nucleic Acids Res. (2013) 41 p.2689-2697
The thymine analog 5-chlorouridine, first reported in the 1950s as anti-tumor agent, is known as an effective mutagen, clastogen and toxicant as well as an effective inducer of sister-chromatid exchange. Recently, the first microorganism with a chemically different genome was reported; the selected Escherichia coli strain relies on the four building blocks 5-chloro-2'-deoxyuridine (ClU), A, C and G instead of the standard T, A, C, G alphabet [Marliere,P., Patrouix,J., Doring,V., Herdewijn,P., Tricot,S., Cruveiller,S., Bouzon,M. and Mutzel,R. (2011) Chemical evolution of a bacterium's genome. Angew. Chem. Int. Ed., 50, 7109-7114]. The residual fraction of T in the DNA of adapted bacteria was <2% and the switch from T to ClU was accompanied by a massive number of mutations, including >1500 A to G or G to A transitions in a culture. The former is most likely due to wobble base pairing between ClU and G, which may be more common for ClU than T. To identify potential changes in the geometries of base pairs and duplexes as a result of replacement of T by ClU, we determined four crystal structures of a B-form DNA dodecamer duplex containing ClU:A or ClU:G base pairs. The structures reveal nearly identical geometries of these pairs compared with T:A or T:G, respectively, and no consequences for stability and cleavage by an endonuclease (EcoRI). The lack of significant changes in the geometry of ClU:A and ClU:G base pairs relative to the corresponding native pairs is consistent with the sustained unlimited self-reproduction of E. coli strains with virtually complete T-->ClU genome substitution. | <urn:uuid:e4407671-7e54-4e78-90ac-3938a2ca7213> | 2.9375 | 457 | Academic Writing | Science & Tech. | 59.64587 | 95,602,841 |
A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the lower end of a tube or other surface boundary, producing a hanging drop called a pendant drop. Drops may also be formed by the condensation of a vapor or by atomization of a larger mass of liquid.
A simple way to form a drop is to allow liquid to flow slowly from the lower end of a vertical tube of small diameter. The surface tension of the liquid causes the liquid to hang from the tube, forming a pendant. When the drop exceeds a certain size it is no longer stable and detaches itself. The falling liquid is also a drop held together by surface tension.
Viscosity and pitch drop experiments
Some substances that appear to be solid, can be shown to instead be extremely viscous liquids, because they form drops and display droplet behavior. In the famous pitch drop experiments, pitch - a substance somewhat like solid bitumen - is shown to be a liquid in this way. Pitch in a funnel slowly forms droplets, each droplet taking about 10 years to form and break off.
Pendant drop test
In the pendant drop test, a drop of liquid is suspended from the end of a tube by surface tension. The force due to surface tension is proportional to the length of the boundary between the liquid and the tube, with the proportionality constant usually denoted . Since the length of this boundary is the circumference of the tube, the force due to surface tension is given by
where d is the tube diameter.
The mass m of the drop hanging from the end of the tube can be found by equating the force due to gravity () with the component of the surface tension in the vertical direction () giving the formula
where α is the angle of contact with the tube, and g is the acceleration due to gravity.
The limit of this formula, as α goes to 90°, gives the maximum weight of a pendant drop for a liquid with a given surface tension, .
This relationship is the basis of a convenient method of measuring surface tension, commonly used in the petroleum industry. More sophisticated methods are available to take account of the developing shape of the pendant as the drop grows. These methods are used if the surface tension is unknown.
Drop adhesion to a solid
The drop adhesion to a solid can be divided to two categories: lateral adhesion and normal adhesion. Lateral adhesion resembles friction (though tribologically lateral adhesion is a more accurate term) and refers to the force required to slide a drop on the surface, namely the force to detach the drop from its position on the surface only to translate it to another position on the surface. Normal adhesion is the adhesion required to detach a drop from the surface in the normal direction, namely the force to cause the drop to fly off from the surface. The measurement of both adhesion forms can be done with the Centrifugal Adhesion Balance (CAB). The CAB uses a combination of centrifugal and gravitational forces to obtain any ratio of lateral and normal forces. For example, it can apply a normal force at zero lateral force for the drop to fly off away from the surface in the normal direction or it can induce a lateral force at zero normal force (simulating zero gravity).
The term droplet is a diminutive form of 'drop' - and as a guide is typically used for liquid particles of less than 500 µm diameter. In spray application, droplets are usually described by their perceived size (i.e., diameter) whereas the dose (or number of infective particles in the case of biopesticides) is a function of their volume. This increases by a cubic function relative to diameter; thus a 50 µm droplet represents a dose in 65 pl and a 500 µm drop represents a dose in 65 nanolitres.
A droplet with a diameter of 3 mm has a terminal velocity of approximately 8 m/s. Drops smaller than 1 mm in diameter will attain 95% of their terminal velocity within 2 m. But above this size the distance to get to terminal velocity increases sharply. An example is a drop with a diameter of 2 mm that may achieve this at 5.6 m.
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The major source of sound when a droplet hits a liquid surface is the resonance of excited bubbles trapped underwater. These oscillating bubbles are responsible for most liquid sounds, such as running water or splashes, as they actually consist of many drop-liquid collisions.
"Dripping tap" noise prevention
In 2018, scientists confirmed that, by reducing the surface tension of a body of liquid, it was possible to reduce or prevent noise due to droplets falling into it. This would involve adding soap, detergent or a similar substance to water. The reduced surface tension reduces the noise from dripping.
The classic shape associated with a drop (with a pointy end in its upper side) comes from the observation of a droplet clinging to a surface. The shape of a drop falling through a gas is actually more or less spherical for drops less than 2mm in diameter. Larger drops tend to be flatter on the bottom part due to the pressure of the gas they move through. As a result, as drops get larger, a concave depression forms which leads to the eventual breakup of the drop.
Raindrop sizes typically range from 0.5 mm to 4 mm, with size distributions quickly decreasing past diameters larger than 2-2.5 mm.
Scientists traditionally thought that the variation in the size of raindrops was due to collisions on the way down to the ground. In 2009 French researchers succeeded in showing that the distribution of sizes is due to the drops' interaction with air, which deforms larger drops and causes them to fragment into smaller drops, effectively limiting the largest raindrops to about 6 mm diameter. However, drops up to 10 mm (equivalent in volume to a sphere of radius 4.5 mm) are theoretically stable and could be levitated in a wind tunnel. The largest recorded raindrop was 8.8 mm in diameter, located at the base of a cumulus congestus cloud in the vicinity of Kwajalein Atoll in July 1999. A raindrop of identical size was detected over northern Brazil in September 1995.
Standardized droplet sizes in medicine
In medicine, this property is used to create droppers and IV infusion sets which have a standardized diameter, in such a way that 1 millilitre is equivalent to 20 drops. When smaller amounts are necessary (such as paediatrics), microdroppers or paediatric infusion sets are used, in which 1 millilitre = 60 microdrops.
A drop of water hitting a wet metal surface and ejecting more droplets, which become water globules and skim across the surface of the water.
A drop of water on an Asteraceae
Rain droplets on Rose plant leaf
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- Prosperetti, Andrea; Oguz, Hasan N. (1993). "The impact of drops on liquid surfaces and the underwater noise of rain" (PDF). Annual Review of Fluid Mechanics. 25: 577–602. Bibcode:1993AnRFM..25..577P. doi:10.1146/annurev.fl.25.010193.003045. Retrieved 2006-12-09.
- Rankin, Ryan C. (June 2005). "Bubble Resonance". The Physics of Bubbles, Antibubbles, and all That. Retrieved 2006-12-09.
- Pruppacher, H. R.; Pitter, R. L. (1971). "A Semi-Empirical Determination of the Shape of Cloud and Rain Drops". Journal of the Atmospheric Sciences. 28: 86–94. Bibcode:1971JAtS...28...86P. doi:10.1175/1520-0469(1971)028<0086:ASEDOT>2.0.CO;2.
- "Water Drop Shape". Retrieved 2008-03-08.
- McFarquhar, Greg (2010). "Raindrop Size Distribution and Evolution". Geophysical Monograph Series. 191. Bibcode:2010GMS...191...49M. doi:10.1029/2010GM000971.
- Emmanuel Villermaux, Benjamin Bossa (September 2009). "Single-drop fragmentation distribution of raindrops" (PDF). Nature Physics. 5 (9): 697–702. Bibcode:2009NatPh...5..697V. doi:10.1038/NPHYS1340. Lay summary.
- Hobbs, Peter V.; Rangno, Arthur L. (July 2004). "Super-large raindrops". Geophysical Research Letters. 31. Bibcode:2004GeoRL..3113102H. doi:10.1029/2004GL020167.
|Wikimedia Commons has media related to Water droplets.| | <urn:uuid:dc9c0d17-3981-4ff9-b4c6-64107c509c60> | 4 | 2,094 | Knowledge Article | Science & Tech. | 66.249905 | 95,602,868 |
Although environmental managers are usually social scientists, there are numerous requirements within the management matrix that need the input of geologists. Because environmental management cuts across nearly all segments of human activities, it is vital that most societal segments be represented on decision-making bodies. Environmental management consists of deliberate planning and administrating policies that determine the status of the biosphere. It involves all levels of human endeavors, agencies, companies, and governments — local, regional, and national. Furthermore, because of the extreme complexity of environmental matters, and the different constituencies, involvement of many different disciplines is required, especially those in the social and natural sciences. Also, guidelines for management necessitate flexibility, because the ultimate objectives and how to reach them depend upon a variety of factors. For example, the strategies to be adopted may vary depending upon what is being managed; is it a process, a resource, a land parcel, or some other type of entity?
KeywordsGeologic Hazard Underground Space Federal Land Hazard Identification California Water
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In this chapter, you’ve learned about the fundamental concepts that power the Spring Framework. You saw how to bootstrap a Spring ApplicationContext, learned the basics of configuring bean dependencies in Spring XML configuration files, and developed an understanding of bean scopes and life cycles. The benefits of dependency injection are now clear. You can effectively delegate to the Spring container to manage and resolve your application dependencies, and doing so can help keep your application’s dependencies loosely coupled. Finally, you were given a glimpse into the power of managing orthogonal coding concerns with AOP. Throughout the rest of this book, we will build on the Spring concepts introduced in this chapter to define and implement an art gallery application.
KeywordsConfiguration File Business Logic Open Source Project Public Void Dependency Injection
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Lithium is going to be very important in the future of renewable energy. Storing energy from sustainable sources like wind and solar will likely be required due to the unreliability of nature and our need to stockpile energy. With demand soon to be on the rise, Stanford scientists have been studying a new source where deposits of lithium can be easily found.
At the moment, most of our lithium is imported from Australia and Chile. Here in the United States, most of the natural lithium comes from brine pools in Nevada. It’s certainly not enough to satisfy upcoming demand, but lake deposits in supervolcanoes from the state, along with places like Oregon and Wyoming, may be just as rich in lithium as these leading countries. In fact, one area studied was the McDermitt volcanic field located between the Nevada-Oregon border.
These volcanoes aren’t the normal cone-shaped versions. Instead, supervolcanoes are massive holes in the ground that have filled up with water to create a lake. Since they shoot much more magma than a normal volcano when erupting, the cone-shaped roof collapses. As the lake forms, lithium is generated and turns into hectorite clay.
Thomas Benson, a PhD graduate at Stanford that’s been working on the study since 2012, compares these findings to the Gold Rush of 1849, saying, “We’ve had a gold rush, so we know how, why and where gold occurs, but we never had a lithium rush. The demand for lithium has outpaced the scientific understanding of the resource, so it’s essential for the fundamental science behind these resources to catch up.”
However, not all supervolcanoes are equal, and Stanford researchers have been figuring out the best way to measure these deposits. Lithium can evaporate easily, making it more difficult to work with than other volcanic rocks. Instead of digging up these deposits, they’ve decided to test out crystals in the water that held magma.
Benson and his team was able to determine how much lithium was in the lake through this alternative method. That’s because another material in the magma, zirconium, correlates to lithium. Since zirconium isn’t as volatile, scientists can figure out how much lithium is in the area. If there’s a high concentration of zirconium, that means less lithium is available.
Standard volcanoes already provide geothermal energy, but Benson noted in the study that this has no impact with supervolcanoes. The latter aren’t active, which is needed for the geothermal method. This also makes the mining process in lithium deposits much safer.
While scientists are still figuring out how much lithium can be extracted from these sites, it gives us great potential to avoid a monopoly in the industry. According to Futurism, Benson believes that “[lithium] demand will grow to between 3 and 35 megaton” compared to the 32.5 kilotons currently used annually. Perhaps a modern-day gold rush is on the horizon with these lithium deposits.
These seven Etsy shops from around the world offer an impressive range of cruelty-free products you can feel good about putting on your face.
A new report shares why decentralized energy grids will power the homes of the future and make a major difference in the lives of those in developing countries currently with limited or zero access to electricity.
Starbucks and McDonalds are working together to rethink to-go cups and inviting others to join them in creating eco-friendly packaging in an effort to reduce waste and environmental impact.
A new report finds that meat and dairy producers are on track to surpass the oil industry's greenhouse gas emissions. | <urn:uuid:d01a93b5-8d06-4dbe-88c9-81495030d8d0> | 3.875 | 770 | News Article | Science & Tech. | 43.255752 | 95,602,905 |
PHP Form Validation
Form validation is very important when you are developing a website in PHP. PHP Form Validation provides you the facility to apply the validation on the forms so that only required data can be accepted by the client. Form Validation Using PHP provides the lot of attributes of functions to validate the form and also you can develop your own logic to validate the form. Form validation is important part of the any website. Form Validation Using PHP is very simple to apply. Eitworld.com provides the easy learning on PHPForm Validation tutorial in easy way.
- A form is used to create input spaces where a user can enter some data or information. This data is passed over sever and used for some relevant tasks.
- Creating a form means that you are allowing users to change the code of your php script to some extent. With the help of this form, hackers can easily get a hole to get the data of your script. Thus before the entered data is processed further, it must be validated that it doesn't contain any harmful content.
- Here is the basic trick of form validation where we will use three php functions-
c language features
- Simple and Easy to learn.
- Powerful and Efficient.
application of c language
C language is used to develop a simple program and as well as complex Application and System software also. Some of the applications of C language are given below:
- Operating system
- Modern Programs
- Compiler, Assembler and Interpreter
- Network Drivers
- Text Editors and Print Spoolers.
Overview of Compiler and Interpreters
Before talking about the Compiler and Interpreter we have to know some important points as given below:
- A program is a set of instructions used to perform a particular task.
- These programs are written in assembly language or high level language (English words),this written program is called as source program which cannot be understood by the computer. Computer can only understand the instructions available in the form of machine language as '0' and '1'.
- The source program is to be converted to the machine language that is known as object program.
- Source program is converted into object program with the help of interpreter or compiler which are explained here in detail:
- Compiler reads the entire source program and converts it into the object program.
- Compiler provides errors of entire program at once instead of providing them line by line. Only error free program can be executed.
- Compiler consumes less time for converting source program to object program.
- Compiler is preferred where length of the source program is very large.
- Interpreter reads only one line of source program at a time and converts it into the object code.
- Interpreter provides error line by line.
- Interpreter consumes more time for converting source program to object program than compiler. | <urn:uuid:9afd69b4-03b7-47eb-afb1-c435864e1671> | 2.90625 | 594 | Tutorial | Software Dev. | 41.05746 | 95,602,914 |
The text is on the classical doppler effect, the relativistic doppler effect, aberration, and the transverse doppler effect. It also discusses wave fronts, first-order and second order effect, light-time correction, Galilean transformation, and parallax.
Part of a larger set of Physics Notes by James B. Calvert, Professor Emeritus, University of Denver.
%0 Electronic Source %A Calvert, J. %D September 6, 2003 %T Doppler Effect %V 2018 %N 21 July 2018 %8 September 6, 2003 %9 text/html %U http://mysite.du.edu/~jcalvert/phys/doppler.htm
Disclaimer: ComPADRE offers citation styles as a guide only. We cannot offer interpretations about citations as this is an automated procedure. Please refer to the style manuals in the Citation Source Information area for clarifications. | <urn:uuid:6080b2bd-42d4-4a7f-acc8-ce2671eb0d2c> | 2.515625 | 194 | Structured Data | Science & Tech. | 50.358625 | 95,602,917 |
The breakthrough comes from expressing certain genes in algae that increase the amount of photosynthesis in the plant, which leads to more biomass.
Expressing genes means that the gene's function is turned on.
"The key to this (increase in biomass) is combination of two genes that increases the photosynthetic carbon conversion into organic matter by 50 percent over the wild type under carbon dioxide enrichment conditions," said Martin Spalding, professor in the Department of Genetics, Development, and Cell Biology and associate dean for research and graduate studies in the College of Liberal Arts and Sciences.
Carbon enrichment conditions are those in which the algae has enough carbon dioxide.
This patent-pending technology is available for licensing from the Iowa State University Research Foundation, which also provided technology development funds.
This opens up possibilities for more and better biofuel development, according to Spalding.
"There is no doubt in my mind that this brings us closer [to affordable, domestic biofuel]," said Spalding.
In nature, algae are limited from growing faster because they don't get enough carbon dioxide from the atmosphere, according to Spalding.
In environments that have relatively low levels of carbon dioxide (CO2), such as air in earth's atmosphere, two genes in algae, LCIA and LCIB, are expressed - or turned on - to help capture and then channel more carbon dioxide from the air into the cells to keep the algae alive and growing.
However, when algae are in environments with high carbon dioxide levels, such as in soil near plant roots that are expiring carbon dioxide, the two relevant genes shut down because the plant is getting enough carbon dioxide.
The process is similar to a car driving up a hill. The accelerator - these two genes - is pressed and the engine works hard to climb a hill. But when going down an incline, the driver often lets up on the accelerator since more gas isn't needed - the genes shut down.
The two genes are expressed - essentially keeping algae's foot on the gas - even when they are in a carbon dioxide-rich environment and don't need additional carbon dioxide.
Research by Spalding's group shows that algae can be made to produce biomass with the accelerator floored, even in conditions where it would normally just coast, Spalding said.
"Based on some prior research we had done, we expected to see an increase, probably in the 10 to 20 percent range" he said. "But we were surprised to see this big of an increase."
In experiments to get the algae type (Chlamydomonas reinhardtii) to produce more biomass, Spalding first expressed LCIA and LCIB separately. Each effort granted a significant 10 to 15 percent increase in biomass.
When the two genes were expressed together, Spalding was surprised to see the 50 to 80 percent biomass increase.
"Somehow these two genes are working together to increase the amount of carbon dioxide that's converted through photosynthesis into biomass by the algae under conditions where you would expect there would already be enough carbon dioxide," said Spalding.
The excess biomass naturally becomes starch through the photosynthesis process, and increases the biomass starch by around 80 percent.
By using some existing mutated genes, Spalding can instruct the algae to make oil instead of starch. This process requires more energy and the process results in around a 50 percent increase in oil biomass.
Spalding's research was funded in part by grants from the Department of Agriculture's National Institute of Food and Agriculture and the Department of Energy, Advanced Research Projects Agency - Energy.
Martin Spalding | 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:831dda6b-854e-4660-8b5f-7565bbf5abab> | 4.09375 | 1,327 | Content Listing | Science & Tech. | 39.263658 | 95,602,918 |
"Marsupial" is a set of protocols defined by the Ministry of Education of Catalonia in the context of the 1-to-1 program educat1x1 - eduCAT 2.0.
Marsupial has been also adopted as a main interoperability protocol in the Punto Neutro de Recursos Educativos Digitales platform, promoted by the Spanish Ministry of Education.
The target of Marsupial is to facilitate the communication between Virtual Learning Environments (VLE) and on-line commercial textbooks provided by publishers.
Marsupial has three main functions:
- To define an internal structure of digital textbooks, usually as a tree of chapters or topics, thus facilitating direct references from the VLE to specific contents of the book.
- To manage credentials and authentication of students on textbook's platforms, so after a single login into the VLE, students can work with their digital textbooks (even from different publishers) without having to log-in again into each platform.
- To report into the VLE the results of exercises and activities made by students in digital textbooks. This allows teachers to have the results of all exercises collected in a single place, thus facilitating a global assessment.
Marsupial is based on SOAP, and operates in the following format:
- Remote content: module for displaying external content. Uses web services to report results of exercises between textbook platforms and the VLE.
NOTE: Remote SCORM is no longer maintained and has been removed from the "master" branch since August 2014. ZIP files with older versions of this module are archived on "/files/historical"
##Components Marsupial has three main components:
|/docs||The documents containing the open specification|
|/moodle||The implementation of a “Marsupial” client for Moodle 2|
Release packages can be found on Relases Tab
Old historical ones have been moved to historical_files branch
###Marsupial Publisher Simulator
A minimalistic implementation of a publisher platform, called Marsupial Publisher Simulator (MPS). It implements all the server-side protocols and provides “example” books for testing
##Licensing Marsupial is open source software, licensed under the terms of the GNU General Public License v2.
RGrade was created by Text-La Galera to simplify and make more usable the Moodle Gradebook when dealing with digital textbooks in Remote Content. | <urn:uuid:77bbe06d-910b-49a3-a205-59d111e0b3f0> | 2.96875 | 506 | About (Org.) | Software Dev. | 19.809643 | 95,602,926 |
Around 540 million years ago there was a sudden diversification of species on earth. Within a short period of time, countless new species evolved almost simultaneously, becoming the predecessors of today's main animal groups. But what caused this rapid evolution? Palaeontologists around the world have been searching for the answer to this question for centuries.
Researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have now confirmed the existing theories that extreme niche formation and tectonic plate movements are responsible for the development of the wide variety of species. Their findings have recently been published in the renowned journal PNAS*.
451 million years ago, an event took place that had a major influence on the evolution of life on earth. This event was the Cambrian explosion, which took place at the beginning of the Cambrian Period over a – from a geological point of view – relatively short period of 5 to 10 million years and saw the evolution of all of the major modern animal groups.
To find out what caused this event, researchers from FAU's Geozentrum Nordbayern evaluated a large database of fossils from the Cambrian Period. They analysed the biological diversity of all known species from this period on a local, regional and global level with the aim of understanding the ecological principles that led to the Cambrian explosion.
The causes? Niche formation and plate tectonics
'We discovered that while the number of species within local ecosystems increased in the early Cambrian Period, this was not the main reason for the evolution of the variety of species on a global level,' says Lin Na from FAU's Chair of Palaeoenvironmental Studies. Instead, the different evolution of different populations was much more important.
This is because as species adapted more and more to their environment their ecological niches became more restricted. This meant that individual populations evolved into new species that were adapted to their environments. Carnivores played an important role in this, as Prof. Dr. Wolfgang Kießling, Chair of Palaeoenvironmental Studies, explains.
'Carnivores kept populations small, preventing too much competition for resources. At the same time, however, they forced species to develop new ways of avoiding being eaten and increasingly sophisticated methods of getting food.'
This biological arms race controlled the variety of species at a local and regional level. However, on a global level there was another factor driving the evolution of species forward: plate tectonics. At the beginning of the Cambrian Period, the supercontinent Pannotia broke apart. From then on, deep oceans separated parts of the land and the different sea creatures evolved separately.
'We saw a significant increase in provincialism. The species composition found in the continents' different old shelf seas became more and more different. This could be the main reason that the total number of species increased so considerably,' says Lin Na.
*Lin Na, Wolfgang Kießling: 'Diversity partitioning during the Cambrian radiation', Proceedings of the National Academy of Sciences (USA). doi: 10.1073/pnas.1424985112
Prof. Dr. Wolfgang Kießling
Phone: +49 9131 8526959
Dr. Susanne Langer | 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
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:6940be95-7a96-45d7-810d-dd7b16fffb95> | 4.3125 | 1,308 | Content Listing | Science & Tech. | 38.719261 | 95,602,986 |
Join Patrick Royal for an in-depth discussion in this video My solution: Image-comparison algorithms, part of Code Clinic: Java (2014).
-Due to the complexity of image analysis,…there are actually a large number of different…algorithms that are commonly used…to compare images.…These range from very simple algorithms…that just work with one pixel at a time,…to complex algorithms that analyze groups…of pixels to look for patterns and structures…that can be compared.…Although modern algorithms have not yet achieved…the proficiency of the human eye, they're…commonly used for facial recognition,…fingerprint analysis, and text digitization.…Fortunately, we don't need to design such…a complicated algorithm for this task.…
The main algorithm that I have used in my solution…is called the least absolute deviation algorithm.…This function, which is also commonly used…for linear regressions, calculates the difference…between two pixels by taking the absolute value…of the difference between their red, green,…and blue values.…The algorithm is outlined in my…compare subset class.…The input for this class consists of three integers.…Integers A and B denote the starting coordinates…
Patrick introduces challenges and provide an overview of his solutions in Java. Challenges include topics such as statistical analysis, searching directories for images, and accessing peripheral devices.
Visit other courses in the series to see how to solve the exact same challenges in languages like C#, C++, PHP, Python, and Ruby.
Skill Level Intermediate
Q: I am unable to access the Lake Pend Oreille data from outside the U.S.
A: A static copy of this data is provided here for lynda.com members outside of the U.S
Problem One: Exploring Lake Pend Oreille
Problem Two: Image Analysis
Problem Three: Eight Queens
Problem Four: Accessing Peripherals
Problem Five: Recursion and Directories
Problem Six: Building the Web
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Observation of the abyssal current in the West Mariana Basin
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In order to investigate long-term variations of deep sea currents and temperature in the western North Pacific, a direct current measurement was made at 12.5°N, 137°E from July 1985 to July 1986. The current meter was moored at a depth of about 4,000 m (bottom depth 4,604 m) in the West Mariana Basin, very close to the deep water passage to the North Pacific Basin. Throughout the observed period, the current flows southward with an average speed of 0.8 cm sec−1. There are significant variations of both currents and temperature within the period of 60 days. For the shorter time scales, in addition to the tidal oscillations with one day and half day periods, there is a notable spectral peak of the current with a clockwise rotation at a period of 2.2 days, which is slightly shorter than the local inertial period of 2.3 days.
The observed southward current seems to indicate that the deep sea water in the West Mariana Basin flows out through the sill which is deeper than 4,000 m and is located about 200 km southeast of the mooring point. A simple analysis of the linear plane wave indicates that the medium time-scale variation with a period of 60 days is associated with the barotropic Rossby wave whose wavelength is 390 km and whose trough direction is 30° clockwise from the north.
KeywordsRossby Wave Clockwise Rotation Pacific Basin Bottom Depth Water Passage
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- Andow, T. (1987): Year-to-year variation of oceanographic sub-surface section along the meridian of 137°E. Oceanogr. Mag.,37, 47–73.Google Scholar
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|The Twin Quasar Q0957+561|
The Twin Quasar QSO 0957+561, which lies 7.8 billion light-years from Earth, is seen right in the center of this picture.
|Observation data (Epoch J2000)|
|Right ascension||10h 01m 20.99s|
|Declination||+55° 53′ 56.5″|
|Distance||8,700,000,000 ly (2,400,000,000 pc)|
|Apparent dimensions (V)||6" distance|
|Apparent magnitude (V)||16.7|
|Twin Quasar, Double Quasar, Twin QSO, QSO 0957+561, Q0957+561, SBS 0957+561, TXS 0957+561, 8C 0958+561, PGC 2518326, A: USNO-A2 1425-7427021 B:USNO-A2 1425-7427023|
|See also: Quasar, List of quasars|
The Twin Quasar (also known as Twin QSO, Double Quasar, SBS 0957+561, TXS 0957+561, Q0957+561 or QSO 0957+561 A/B), was discovered in 1979 and was the first identified gravitationally lensed object. It is a quasar that appears as two images, a result from gravitational lensing caused by the galaxy YGKOW G1 that is located in the line of sight between Earth and the quasar.
QSO 0957+561 A (SBS 0957+561 A) and QSO 0957+561 B (SBS 0957+561 B) are the two components of a double-imaged quasar, meaning that an intervening mass concentration between Earth and the quasar bends light so that two images of the quasar appear in the sky. This is known as gravitational lensing, and is a consequence of Einsteinian warped space-time. The quasar lies at redshift z = 1.41 (8.7 billion ly), while the lensing galaxy lies at redshift z = 0.355 (3.7 billion ly). The lensing galaxy with apparent dimension of 0.42×0.22 arcminutes lies almost in line with the B image, lying 1 arcsecond off. The quasar lies 10 arcminutes north of NGC 3079, in the constellation Ursa Major. The astronomical data services SIMBAD and NASA/IPAC Extragalactic Database (NED) list several other names for this system.
The Twin Quasar's two images are separated by 6 arcseconds. Both images have an apparent magnitude of 17, with the A component having 16.7 and the B component having 16.5. There is a 417 ± 3 day time lag between the two images.
The quasars QSO 0957+561A/B were discovered in early 1979 by an Anglo-American team around Dennis Walsh, Robert Carswell and Ray Weyman, with the aid of the 2.1 m Telescope at Kitt Peak National Observatory in Arizona, United States. The team noticed that the two quasars were unusually close to each other, and that their redshift and visible light spectrum were surprisingly similar. They published their suggestion of "the possibility that they are two images of the same object formed by a gravitational lens".
The Twin Quasar was one of the first directly observable effects of gravitational lensing, which was described in 1936 by Albert Einstein as a consequence of his 1916 General Theory of Relativity, though in that 1936 paper he also predicted "Of course, there is no hope of observing this phenomenon directly."
Critics however identified a difference in appearance between the two quasars in radio frequency images. In mid 1979 a team led by David Roberts at the VLA (Very Large Array) near Socorro, New Mexico/USA discovered a relativistic jet emerging from quasar A with no corresponding equivalent in quasar B. Furthermore, the distance between the two images, 6 arcseconds, was too great to have been produced by the gravitational effect of the galaxy G1, a galaxy identified near quasar B.
Young et al. discovered that galaxy G1 is part of a galaxy cluster which increases the gravitational deflection and can explain the observed distance between the images. Finally, a team led by Marc V. Gorenstein observed essentially identical relativistic jets on very small scales from both A and B in 1983 using VLBI (Very Long Baseline Interferometry). The difference between the large-scale radio images is attributed to the special geometry needed for gravitational lensing, which is satisfied by the quasar but not by all of the extended jet emission seen by the VLA near image A.
30 years of observation made it clear that image A of the quasar reaches earth about 14 months earlier than the corresponding image B, resulting in a difference of path length of 1.1 ly.
In 1996, a team at Harvard-Smithsonian Center for Astrophysics led by Rudy E. Schild discovered an anomalous fluctuation in one image's lightcurve, which led to a controversial and unconfirmable theory that there is a planet approximately three Earth masses in size in the lensing galaxy. The results remain speculative because the chance alignment that led to its discovery will never happen again. If it could be confirmed, however, it would make it the most distant known planet, 4 billion ly away.
In 2006, R. E. Schild suggested that the accreting object at the heart of Q0957+561 is not a supermassive black hole, as is generally believed for all quasars, but a magnetospheric eternally collapsing object. Schild's team at the Harvard-Smithsonian Center for Astrophysics asserted that "this quasar appears to be dynamically dominated by a magnetic field internally anchored to its central, rotating supermassive compact object" (R. E. Schild).
- "Seeing double". ESA/Hubble Picture of the Week. Retrieved 20 January 2014.
- Kundic, T.; Turner, E.L.; Colley, W.N.; Gott, III; Rhoads, J.E. (1997). "A robust determination of the time delay in 0957+561A,B and a measurement of the global value of Hubble's constant". Astrophys. J. 482: 75–82. arXiv: . Bibcode:1997ApJ...482...75K. doi:10.1086/304147.
- Nomenclature of Celestial Objects (Result I)
- Nature 279, S.381-384: 0957 + 561 A, B: twin quasistellar objects or gravitational lens? D.Walsh, R.F.Carswell, R.J.Weymann 31 May 1979
- Einstein, Albert (1936). "Lens-like action of a star by the deviation of light in the gravitational field". Science. 84: 506–507. Bibcode:1936Sci....84..506E. doi:10.1126/science.84.2188.506. PMID 17769014.
- TIME (1 October 1979). "Science: The Mysterious Celestial Twins". Time. Retrieved 2011-01-31.
- Young, P.; Gunn, J.E.; Oke, J.B.; Westphal, J.A. & Kristian, J. (1980). "The double quasar Q0957 + 561 A, B - A gravitational lens image formed by a galaxy at Z = 0.39". Astrophysical Journal. 241: 507–520. Bibcode:1980ApJ...241..507Y. doi:10.1086/158365.
- M.V. Gorenstein; et al. (1984). "The milli-arcsecond images of Q0957 + 561". Astrophysical Journal. 287: 538–548. Bibcode:1984ApJ...287..538G. doi:10.1086/162712.
- "Quasare im Doppelpack" aus "Astro-Lexikon" Andreas Müller August 2007
- New Scientist (issue 2037), Do alien worlds throng faraway galaxy? Govert Schilling 6 July 1996
- "Research Sheds New Light On Quasars". SpaceDaily.com. 26 July 2006.
- Q0957+561: Die historisch erste Linse mit Quasar – The University of Cologne.
- Q0957+561 – CCD image based on 45-min total exposure – March 2007.
- Q0957+561 A,B. | <urn:uuid:63fad5f5-d9f7-4bad-afeb-e20753a2554e> | 3.015625 | 1,835 | Knowledge Article | Science & Tech. | 75.954333 | 95,603,009 |
The Use of SIMS for Semiconductor Processing Technology: The Influence of Oxygen at Depth Profiling
Secondary ion mass spectrometry (SIMS) is one of the most powerful characterization methods in semiconductor processing technology. In SIMS, the presence of oxygen has been found to influence the intensities of the secondary ions emitted by the material under study, and therefore it is important to take the effect of oxygen into consideration. The following experimental facts are known. 1) The intensity of the secondary ion emitted from the surface or the interface of multilayer samples increases abnormally in the presence of oxygen (oxide). 2) When O2 + or 0- is used as primary ion beam, it is difficult to determine fully the identity of the upper most surface layer (~200A), because the concentration of oxygen implanted in the surface increases continuously.
KeywordsEpitaxial Layer Transparent Conductive Film Hydrogenate Amorphous Silicon Silicon Film Hydrogenate Amorphous Silicon Film Hydrogenate
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The reappearance of long-forgotten habitats and the resurgence of species unseen for years may not be among the expected effects of a natural disaster.
Yet that's exactly what researchers found in a study of the sandy beaches of south central Chile, after an 8.8-magnitude earthquake and devastating tsunami in 2010.
Their study also revealed a preview of the problems wrought by sea level rise--a major symptom of climate change.
In a scientific first, researchers from Southern University of Chile and the University of California, Santa Barbara (UCSB) were able to document the before-and-after ecological impacts of such cataclysmic occurrences.
A paper appearing today in the journal PLoS ONE details the surprising results of their study, pointing to the potential effects of natural disasters on sandy beaches worldwide.
The study is said to be the first-ever quantification of earthquake and tsunami effects on sandy beach ecosystems along a tectonically active coastal zone.
"So often you think of earthquakes as causing total devastation, and adding a tsunami on top of that is a major catastrophe for coastal ecosystems," said Jenny Dugan, a biologist at UCSB.
"As expected, we saw high mortality of intertidal life on beaches and rocky shores, but the ecological recovery at some of our sandy beach sites was remarkable.
"Plants are coming back in places where there haven't been plants, as far as we know, for a very long time. The earthquake created sandy beach habitat where it had been lost. This is not the initial ecological response you might expect from a major earthquake and tsunami."
Their findings owe a debt to serendipity.
The researchers were knee-deep in a study supported by FONDECYT in Chile and the U.S. National Science Foundation's (NSF) Santa Barbara Coastal Long-Term Ecological Research (LTER) site of how sandy beaches in Santa Barbara and south central Chile respond, ecologically, to man-made armoring such as seawalls and rocky revetments.
By late January, 2010, they had surveyed nine beaches in Chile.
The earthquake hit in February.
Recognizing a unique opportunity, the scientists changed gears and within days were back on the beaches to reassess their study sites in the catastrophe's aftermath.
They've returned many times since, documenting the ecological recovery and long-term effects of the earthquake and tsunami on these coastlines, in both natural and human-altered settings.
"It was fortunate that these scientists had a research program in the right place--and at the right time--to allow them to determine the responses of coastal species to natural catastrophic events," said David Garrison, program director for NSF's coastal and ocean LTER sites.
The magnitude and direction of land-level change resulting from the earthquake and exacerbated by the tsunami brought great effects, namely the drowning, widening and flattening of beaches.
The drowned beach areas suffered mortality of intertidal life; the widened beaches quickly saw the return of biota that had vanished due to the effects of coastal armoring.
"With the study in California and Chile, we knew that building coastal defense structures, such as seawalls, decreases beach area, and that a seawall results in the decline of intertidal diversity," said lead paper author Eduardo Jaramillo of the Universidad Austral de Chile.
"But after the earthquake, where significant continental uplift occurred, the beach area that had been lost due to coastal armoring has now been restored," said Jaramillo. "And the re-colonization of the mobile beach fauna was underway just weeks afterward."
The findings show that the interactions of extreme events with armored beaches can produce surprising ecological outcomes. They also suggest that landscape alteration, including armoring, can leave lasting footprints in coastal ecosystems.
"When someone builds a seawall, beach habitat is covered up with the wall itself, and over time sand is lost in front of the wall until the beach eventually drowns," said Dugan.
"The semi-dry and damp sand zones of the upper and mid-intertidal are lost first, leaving only the wet lower beach zones. This causes the beach to lose diversity, including birds, and to lose ecological function."
Sandy beaches represent about 80 percent of the open coastlines globally, said Jaramillo.
"Beaches are very good barriers against sea level rise. They're important for recreation--and for conservation."Media Contacts
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New Biosensors for Managing Microbial ‘Workers’
News Aug 05, 2015
Super productive factories of the future could employ fleets of genetically engineered bacterial cells, such as common E. coli, to produce valuable chemical commodities in an environmentally friendly way. By leveraging their natural metabolic processes, bacteria could be re–programmed to convert readily available sources of natural energy into pharmaceuticals, plastics and fuel products.
"The basic idea is that we want to accelerate evolution to make awesome amounts of valuable chemicals," said Wyss Core Faculty member George Church, Ph.D., who is a pioneer in the converging fields of synthetic biology, metabolic engineering, and genetics. Church is the Robert Winthrop Professor of Genetics at Harvard Medical School and Professor of Health Sciences and Technology at Harvard and MIT.
Critical to this process of metabolically engineering microbes is the use of biosensors. Made of a biological component — such as a fluorescent protein — and a 'detector' that responds to the presence of a specific chemical, biosensors act as the switches and levers that turn programmed functions on and off inside the engineered cells. They also can be used to detect which microbial 'workers' are producing the most voluminous amounts of a desired chemical. In this way, they can be thought of as the medium for two–way communication between humans and cells.
But so far, scientists have only had access to a limited variety of biosensors that have little relevance to the bio–manufacturing of valuable chemicals. Now, Wyss Institute researchers led by Church have developed a new suite of such sensors that not only increase the number of cellular "switches and levers" that scientists can use for complex genetic re–programming, but also respond to valuable products such as renewable plastics or costly pharmaceuticals and give microbes a voice to report on their own efficiency in making these products.
"We can communicate with cells much more effectively, and vice versa," said the study’s first author Jameson Rogers, a graduate researcher at the Wyss Institute who is pursuing his Ph.D. in Engineering Sciences from Harvard University. "If we compared this to controlling a computer, it’s almost like we have only had the up and down arrows available to us, and now suddenly we have doubled our control capabilities by adding the left and right arrows as well."
The Wyss team aims to leverage the new biosensors to aid in its efforts to develop renewable chemical production strategies using genetically engineered microbes.
Linked to green fluorescent protein (GFP), the biosensors can be used to trigger individual cells to give off visible fluorescence in a rate directly proportional to how well they are able to produce a desired chemical commodity. Using the new biosensors, the most efficient microbial workers are easily identified so that they can serve as the predecessors for colonies of engineered bacteria that evolve to become more efficient at producing renewable chemicals with each subsequent generation. This drastically reduces the bottleneck of the design–build–test cycle, which has historically been caused by engineers having to sift through teeming bacteria colonies to find top producers.
The findings could also lead to new applications in environmental monitoring using genetically engineered microbes to issue warning signals in the presence of pollutants or toxins, and could unlock new fundamental insights into metabolic pathways.
"Our team is developing several different ways to make even more custom biosensors," said Church. "We’re trying to control biological processes and we need new ways to get our hands in at the molecular level — we’re now reaching in deeper than we’ve previously been able to, and we still have many interesting new approaches."
"With this work, George and his team are bringing us closer to a sustainable future in which we would rely on bio–manufacturing for the clean production of chemical and pharmaceutical commodities," said Wyss Institute Founding Director Donald E. Ingber, M.D., Ph.D.
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Plan to avert a real Armageddon: Scientists say nuclear bomb CAN save Earth from asteroid collision (and don't worry, there's no need to send Bruce Willis into orbit)
It sounds like a plot fit for a disaster movie - but this is real life.
Scientists say they have worked out a way to blast an asteroid into space dust using an atomic bomb.
The plan has potentially world-saving consequences should an asteroid emerge on a collision course with Earth.
And unlike the film Armageddon - where Bruce Willis and his crew of stars fly a space shuttle to an oncoming Asteroid to drill a warhead into its core - the nuclear payload could be delivered by rocket.
Using one of the world's most powerful supercomputers at Los Alamos National Laboratory, physicists have calculated the effect of a nuclear blast on an incoming space rock.
Although Nasa and other space agencies have mapped most nearby asteroids, the effect of one catching us by surprise would be catastrophic and, they believe, is worth preparing for.
Boom: This picture shows the effect that a one megaton nuclear blast would have on an incoming asteroid that threatened Earth
No need for heroics: A team would not need to fly to the asteroid to deliver the payload as in Bruce Willis film Armageddon, above
Robert Weaver, R&D scientist at Los Alamos, used Cielo, their newest Cray supercomputer, to simulate the effect of nuking an asteroid.
'If one of these objects is discovered at a short notice time, say a few months away, and is on an Earth crossing trajectory there could be potentially devastation on a world-wide scale,' he said.
Luckily, Mr Weaver's team believes asteroids are really conglomerates of rocks held together by the force of gravity and that one atomic blast could be enough to shatter them into harmless space dust.
The calculation uses an asteroid of the size and shape of the mapped Itokawa asteroid, which has 500m across by 250m wide and is thought to be composed of granite rocks.
'Devastation on a world-wide scale': Robert Weaver, R&D scientist at Los Alamos National Laboratory, run the calculations because of the catastrophic effect that the impact of an asteroid hitting could have
Mostly harmless: After the atomic blast, the asteroid is reduced to a cloud of space rubble
By placing a one megaton bomb on the side of Itokawa, the simulation shows how a shockwave will travel through the asteroid from the detonation point and shake it to harmless rubble.
'As the shock wave moves through, ultimately this one megaton blast will disrupt all the rocks in the rock pile of this asteroid and if this were an Earth-crossing asteroid it would fully mitigate the hazard posed by the initial asteroid itself,' Mr Weaver said.
It is only since Los Alamos got their hands on Cielo, which runs on 32,000 processors, giving it a remarkable 1.35 petaflop calculating capacity, that simulations of this complexity could be run.
Mr Weaver said: 'The calculations I'm running new on Cielo in 3D are state of the art calculations on 32,000 processors.
'This is mind boggling to me. We've never run on this many processors.'
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Chemistry Question #102
Kelly, a 10 year old male from the Internet asks on December 8, 1999,
Why does an ice cube melt faster in tap water than salt water?
viewed 27033 times
Lara Baxley, Bakersfield College, California
answered on December 8, 1999
An ice cube does melt much faster in tap water than in salt water. The reason has to do with different rates of conduction of heat from the surrounding water to the ice cube.
When an ordinary ice cube melts in a regular glass of water, you have to remember that cold water (like the water from the ice cube) is actually denser than warm water (like the surrounding water in the glass). This is because cold water molecules have less energy and are a tiny bit closer together than molecules in warmer water. So as the ice cube melts, the cold water coming from it sinks to the bottom of the glass and the warm water from the bottom comes up to take its place. The water in the glass is therefore constantly moving, warming the ice cube by something called 'convection currents.'
But salt water is much denser than tap water, warm or cold, because of the salt in it. So when you put a freshwater ice cube into a glass of salt water, the cold water coming from the melting ice cube doesn't sink at all. Instead, the dense salt water stays at the bottom of the glass and the cold less-dense fresh water floats on top. Without any convection currents to carry the cold water away from the ice cube, the ice cube sits in relatively cold water and melts much more slowly.
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Imagine we have four bags containing a large number of 1s, 4s, 7s and 10s. What numbers can we make?
Imagine we have four bags containing numbers from a sequence. What numbers can we make now?
List any 3 numbers. It is always possible to find a subset of adjacent numbers that add up to a multiple of 3. Can you explain why and prove it?
A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?
Find some examples of pairs of numbers such that their sum is a factor of their product. eg. 4 + 12 = 16 and 4 × 12 = 48 and 16 is a factor of 48.
Choose any 3 digits and make a 6 digit number by repeating the 3 digits in the same order (e.g. 594594). Explain why whatever digits you choose the number will always be divisible by 7, 11 and 13.
You can work out the number someone else is thinking of as follows. Ask a friend to think of any natural number less than 100. Then ask them to tell you the remainders when this number is divided by. . . .
Many numbers can be expressed as the sum of two or more consecutive integers. For example, 15=7+8 and 10=1+2+3+4. Can you say which numbers can be expressed in this way?
The Tower of Hanoi is an ancient mathematical challenge. Working on the building blocks may help you to explain the patterns you notice.
How many moves does it take to swap over some red and blue frogs? Do you have a method?
Four bags contain a large number of 1s, 3s, 5s and 7s. Pick any ten numbers from the bags above so that their total is 37.
A game for two people, or play online. Given a target number, say 23, and a range of numbers to choose from, say 1-4, players take it in turns to add to the running total to hit their target.
A country has decided to have just two different coins, 3z and 5z coins. Which totals can be made? Is there a largest total that cannot be made? How do you know?
Can you find an efficient method to work out how many handshakes there would be if hundreds of people met?
Charlie has made a Magic V. Can you use his example to make some more? And how about Magic Ls, Ns and Ws?
What size square corners should be cut from a square piece of paper to make a box with the largest possible volume?
How many pairs of numbers can you find that add up to a multiple of 11? Do you notice anything interesting about your results?
Can you explain the strategy for winning this game with any target?
When number pyramids have a sequence on the bottom layer, some interesting patterns emerge...
Imagine you have a large supply of 3kg and 8kg weights. How many of each weight would you need for the average (mean) of the weights to be 6kg? What other averages could you have?
Try entering different sets of numbers in the number pyramids. How does the total at the top change?
Polygons drawn on square dotty paper have dots on their perimeter (p) and often internal (i) ones as well. Find a relationship between p, i and the area of the polygons.
Start with two numbers and generate a sequence where the next number is the mean of the last two numbers...
It would be nice to have a strategy for disentangling any tangled ropes...
Can you tangle yourself up and reach any fraction?
Think of a number, add one, double it, take away 3, add the number you first thought of, add 7, divide by 3 and take away the number you first thought of. You should now be left with 2. How do I. . . .
What would you get if you continued this sequence of fraction sums? 1/2 + 2/1 = 2/3 + 3/2 = 3/4 + 4/3 =
Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?
We can show that (x + 1)² = x² + 2x + 1 by considering the area of an (x + 1) by (x + 1) square. Show in a similar way that (x + 2)² = x² + 4x + 4
Square numbers can be represented as the sum of consecutive odd numbers. What is the sum of 1 + 3 + ..... + 149 + 151 + 153?
Charlie and Abi put a counter on 42. They wondered if they could visit all the other numbers on their 1-100 board, moving the counter using just these two operations: x2 and -5. What do you think?
Choose four consecutive whole numbers. Multiply the first and last numbers together. Multiply the middle pair together. What do you notice?
Imagine a large cube made from small red cubes being dropped into a pot of yellow paint. How many of the small cubes will have yellow paint on their faces?
Spotting patterns can be an important first step - explaining why it is appropriate to generalise is the next step, and often the most interesting and important.
Rectangles are considered different if they vary in size or have different locations. How many different rectangles can be drawn on a chessboard?
A little bit of algebra explains this 'magic'. Ask a friend to pick 3 consecutive numbers and to tell you a multiple of 3. Then ask them to add the four numbers and multiply by 67, and to tell you. . . .
Caroline and James pick sets of five numbers. Charlie chooses three of them that add together to make a multiple of three. Can they stop him?
Pick the number of times a week that you eat chocolate. This number must be more than one but less than ten. Multiply this number by 2. Add 5 (for Sunday). Multiply by 50... Can you explain why it. . . .
What are the areas of these triangles? What do you notice? Can you generalise to other "families" of triangles?
Can you find sets of sloping lines that enclose a square?
In how many ways can you arrange three dice side by side on a surface so that the sum of the numbers on each of the four faces (top, bottom, front and back) is equal?
It starts quite simple but great opportunities for number discoveries and patterns!
Explore the effect of reflecting in two parallel mirror lines.
Can you describe this route to infinity? Where will the arrows take you next?
Explore the effect of reflecting in two intersecting mirror lines.
The number of plants in Mr McGregor's magic potting shed increases overnight. He'd like to put the same number of plants in each of his gardens, planting one garden each day. How can he do it?
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Explore the effect of combining enlargements.
Consider all two digit numbers (10, 11, . . . ,99). In writing down all these numbers, which digits occur least often, and which occur most often ? What about three digit numbers, four digit numbers. . . .
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Other rational expressions with the irrational function
1. If , we can use .
2. If , we can use .
3. If can be factored as , we can use .
4. If and can be factored as , we can use
Frequently occuring integrals of irrational functions are: , where and is possitive on an interval. We can exclude the case, that the polynomial has a double root.
Taking the factor (if ) or (if ) we reduce the integral to the form or , leading (by means of substitution) to the integrals:
or , respectively.
3. Integration of TRIGONOMETRIC functions
1. Given an integral , i.e. the integrand is a rational function in terms of and . By the substitution the integral is reduced to an integral of a rational function. If , then , , and .
2. If = , then .
3. If = - , then .
If =- , then .
4. , ò and ï – even non-negative integers, then , .
5. For integrals we use following formulas:
6. , then and .
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The future of technology – it’s a scary concept, isn’t it? The sheer speed at which technology is advancing can be a struggle to keep up with and it can be difficult to stop and truly think about what effect this could have on our daily lives in the future. But no technology is quite as daunting as that of Artificial Intelligence.
From the effects it can have on our tedious daily activities, to a level at which it could come to help us understand market psychology to advance our businesses, the possibilities for Artificial Intelligence truly are endless, and perhaps it’s that fear of the unknown that makes it so potentially daunting! To ease your minds on the idea of AI, we’ve pulled together just a few of the main ways that this fascinating technology could impact our daily lives in the future and just a few ways that it already is!
In a world where the population is multiplying faster than we can keep up with and the need for more and more food is constantly on the rise, it’s just our luck that food production is reaching a plateau. With the Food and Agriculture Organisation of the United Nations (FAO) estimating that the population of the earth could reach 9.7 billion by 2050, farmers are under mounting pressure to grow more and more crops, and it’s a struggle that they just aren’t winning. Could the solution to this issue lie with AI? Well, in a way it already is!
One of the most widely accessible methods that AI could and is becoming big in farming is through automated tools. Drones, driverless tractors, automated irrigation systems and even facial recognition for cattle – yes, cattle! – are just a few of the endless possibilities for automation in farming.
Drones, for example, are far more than tools used to take some of the most breathtaking photos and videos technology has ever seen. A drone could make highly efficient crop monitoring and analysis that much easier and with driverless tractors taking some of the load away from an already strained workforce, the two can go hand in hand in making an efficient growing and harvesting process.
Then comes facial recognition. As humorous as it might sound, facial recognition can track cattle and even provide some level of information about the state of an animal at any one time, helping a farmer make themselves and their resources available for a higher number of cattle, and therefore more food production as a whole.
The possibilities for Artificial Intelligence to add to and improve upon medicines are endless. There is no limit to what AI could potentially do for us as humans and our healthcare, from curing a common cold to detecting tumors before they can become dangerous. One notable project currently in development is between Intel and some of the healthcare’s industry leaders. By 2020, they aim to have created a one-day precision medicine for cancer patients that utilizes Artificial Intelligence to diagnose and personalize a treatment plan within 24 hours.
With high-performance computing systems, oncologists can use AI to compare patient’s test results with the ever-growing database of previous cases. As soon as a match is found, the physician can then use this to customize a treatment plan to the patient. Of course, this has its pitfalls and still relies on human interaction. But, the use of Artificial Intelligence in medicines and diagnosis can significantly cut out the time it may take to diagnose and treat an illness, and even improve the accuracy of the diagnosis too.
Artificial Intelligence in safety, especially where our online security is concerned, is invaluable. Digital technology is constantly changing and expanding, and with this comes with an increase in online attacks, and this is particularly rife when it comes to children. The creation, access, and sharing of abusive images of and to children is a horrifically growing epidemic, but Artificial Intelligence could prove to play a huge part in finding the solution to this issue.
Using AI within protective services can mean faster, more efficient tackling of suspicious and harmful content online. Efficiency is key as the volume of online attacks increases, and Artificial Intelligence could turn a 30-day process into only a day or two which – when children or vulnerable people are involved – is valuable time saved.
AI use in entertainment is perhaps the most widely visible way that this technology is affecting our daily lives. Never before have all kinds of entertainment been so accessible, interactive or customizable, and this can partially be put down to the developments in Artificial Intelligence.
Accessibility in entertainment as far as AI is concerned is something that is already well on its way to becoming accessible to the masses. Smart hubs have made it easier than ever before for users to interact with their entertainment systems, all through voice control.
From activation through to giving orders to change a song or turn down the TV, hubs like Amazon Echo and Google Home are allowing users to complete a range of different actions, all just by saying so as though they were talking to a significant other. These hubs are taking the market by storm, but they aren’t the only way that AI is affecting entertainment.
Machine learning is already making its way into entertainment, from gaming to movie trailers. The horror movie ‘Morgan’ by 20th Century Fox and IBM Research was given a trailer formed from AI. The ‘Watson’ platform – IBM’s creation – was taken to a film school where it was used to analyze hundreds of horror movie trailers. From this, they could learn just what elements kept viewers on the edges of their seats and enticed them to watch the movie. From here, the AI was fed the final cut of ‘Morgan’, where it then selected the 10 best moments in the movie to use for a human editor to then go through and create a trailer from.
Gaming is another market where AI truly thrives. With the sheer volume of games in today’s markets, engaging users in immersive experiences isn’t always as simple as a good storyline and amazing graphics. Artificial Intelligence has given game developers the technology they need to create character-based, interactive stories that will respond to a player’s actions and decision making processes for an entirely customized and personalized experience.
Even computer versions of chess and poker can benefit from Artificial Intelligence, giving you a better game that isn’t just a matter of chance and is instead something entirely interactive and personal to each player.
But Is It All Good?
Of course, with all of the talk of Artificial Intelligence and its benefits, there are risks that need to be considered. We’ve all seen the movies – Artificial Intelligence becomes too intelligent, and tries to destroy the human race so it can take over the world… or something to that effect.
Currently, Artificial Intelligence is too narrow for such a feat, in that it is usually developed to perform only a few simple tasks rather than have the overall intelligence to mimic that of us as humans. But the concern is, however, that developing a stronger, entirely autonomous Artificial Intelligence isn’t so much that they will take over the world, but rather that they just won’t have the same morals as a human will.
Even humans themselves have such a wide range of mixed morals and different personality types, so how can Artificial Intelligence truly reflect that? When given a goal, an AI will walk down any path it needs to get to that goal, and the real question lies in whether or not this could lead to destruction. After all, autonomous weapons are already well within sight.
Overall, however, it’s important to realize that Artificial Intelligence is already a part of our lives. Whether you play video games, own a smart hub or happen to be a fan of ‘Morgan’, AI is here and it’s a rapidly developing technology. From medicine to online safety, AI systems can provide us with countless solutions to problems that we as humans may not be able to provide and while that is a terrifying thought in itself, it’s also a fascinating one. We’re still decades away from a robot takeover, so why not enjoy the improvements to our lives that Artificial Intelligence can bring in the meantime?
Will is the Executive Managing Editor at Feedster. Will and his team from Content HOW work with venture capital, marketing co-ops, and companies to attract and gain qualified leads.
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Graphite - a new twist
published: Jan. 15, 2008, recorded: December 2007, views: 1532
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Carbon is an element that is unique in the variety, utility and individuality of its allotropes. Diamond and graphite each have several uniquely extreme properties that have been exploited in twentieth century science and technology. Against the curious landscape of the periodic table the discoveries of fullerenes (1985) and nanotubes (1991) stand out as substantial landmarks. Their beauty lies in creating isolatable molecular forms. In the somewhat messier world of crystal defects, similar topological concepts can be applied, leading to sheets which are buckled, folded, 'welded' together, or unified into one sheet. The description of these defects comes from the science of dislocations, and their structures can be deduced from first principles methods, such as density functional theory (DFT). A connector between sheets, similar to the ramp connecting the floors of a multistorey car park, is a prismatic screw dislocation dipole. A fold is a pile-up of basal dislocation dipoles. The identification and characterization of dislocations in graphite, gives insight into structures which have been overlooked in the science of graphite, especially radiation damage which occurs in reactor graphite subjected to energetic neutrons.
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Aristotle suggested that all natural objects could be distinguished in terms of a natural and characteristic activity. Can we apply this approach to an ecosystem? Do different elements of an ecosystem perform different functions within that system? Could you reason from such ecological facts to normative conclusions about what should be? Why or why not?
I need help understanding this. Can you also provide references. Thanks.© BrainMass Inc. brainmass.com July 20, 2018, 6:38 pm ad1c9bdddf
Attached also as HTML with functioning links.
The answer is both yes, and no. That s a given component of an ecosystem plays an integral role (or roles) with the matrix of all that is there. However, if we remove a "cog", often times other components will assume the function, absorb the need for the function, or preclude the need for that functional element.
Let us consider resource partioning in a tree. Often times various sorts of birds will lay claim to certain segments of a tree environment: the upper canopy, lower canopy, mid-interior, trunk area, etc. A prime example of this would be the classic finches in the Galapagos as detailed by Darwin There, a single species radiated and adapted to take advantage of various food sources, not JUST in the trees, but also on the ground, etc. If one of these were to suddenly go "poof" then the food source (bugs, seeds, whatever) would begin to increase until either: A) that food item exceeds its own level of sustainability ...
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Discovering an exoplanet isn’t what it used to be. Since the first detection of a planet around another star in 1995, astronomers have found thousands more, thanks in large part to the Kepler Space Telescope, which—truly an overachiever—has discovered nearly 5,000 potential worlds and verified about half of them. Even the discovery of the most exciting kind of exoplanet—an Earth-sized world orbiting inside a star’s habitable zone—has become routine: Kepler has confirmed the existence of more than 30 of them.
But that doesn’t mean the discoveries are boring.
A rocky planet similar in size and temperature to Earth is orbiting a nearby star called Ross 128, astronomers announced Wednesday. The star is a red dwarf, a type of star that is smaller and cooler than stars like our sun, located just 11 light-years from our solar system.
This makes the planet, which has been named Ross 128 b, the second-closest temperate, Earth-sized planet to our little corner of the universe. The closest is Proxima b, which resides four light-years away in the habitable zone of Proxima Centauri, our nearest star, and was discovered last year.
Ross 128 b was found by ESO’s High-Accuracy Radial-Velocity Planet Searcher (HARPS), an instrument located at the La Silla Observatory in Chile, and the discovery is described in a paper in Astronomy and Astrophysics. Astronomers at HARPS spent 10 years gathering and refining data, which included more than 160 measurements of Ross 128, before they found the signal that turned out to be an exoplanet, said Xavier Bonfils, the paper’s lead author, an astronomer at Institut de Planétologie et d’Astrophysique de Grenoble in France. “To detect such a small signal requires a lot of data,” Bonfils said.
Stars like Ross 128 move ever so slightly because of the gravitational tug of nearby objects. These tiny movements can be seen as changes in a star’s light spectrum; when the star moves toward an observer—in this case, the HARPS instrument—its light looks slightly bluer, and when it moves away, it turns redder. If these shifts occur in regular patterns, that means there’s an exoplanet lurking. Astronomers can analyze this information to determine some of the planet’s properties. Nicola Astudillo-Defru, an astronomer at the University of Geneva and Bonfils’s coauthor, said he reacted with “a big wow” when the data showed a rocky and temperate world. “I feel so excited that I mailed Xavier minutes later with a clear URGENT in the subject,” he said in an email.
Astronomers say Ross 128 b completes an orbit around its star every 9.9 days. They estimate the exoplanet has an equilibrium temperature somewhere between -60 degrees and 20 degrees Celsius (-76 degrees to 68 degrees Fahrenheit).
Astronomers don’t know whether Ross 128 b resides in its star system’s habitable zone, that sweet spot where temperatures are just right for liquid water to pool on the surface of a rocky world. But they’re still hopeful that it might be able to support life. Red dwarfs like Ross 128 are dimmer than sun-like stars, emitting infrared instead of visible light. So while Ross 128 orbits 20 times closer to its star than the Earth does to the sun, the exoplanet receives only 1.38 times more stellar radiation than Earth. Bonfils said Ross 128 is “quieter” than other red dwarfs, like Proxima Centauri, which can unleash flares that bathe orbiting planets in ultraviolet and X-ray radiation.
“Some even think that the atmosphere can erode, can evaporate, due to these activities,” Bonfils said. The quiet nature of Ross 128 may have created a comfortable cosmic environment for life on the exoplanet to take hold, despite its planet’s close proximity to the star.
Ross 128 popped into headlines in July of this year, when astronomers at the Arecibo Observatory in Puerto Rico said they had detected a mysterious radio transmission coming from the star for about 10 minutes in mid-May. Stars can emit electromagnetic radiation in the form of radio waves, but this signal was recorded at a frequency scientists hadn’t seen before in red dwarfs. Arecibo and other telescopes quickly trained their eyes on Ross 128 for more observations, but the transmission never appeared again. The astronomers entertained several possible explanations, including—much to the internet’s delight—extraterrestrials. They eventually said the signal probably came from one or more geostationary satellites. But the discovery of an Earth-sized exoplanet around the star could restart some of that conversation.
“We are considering additional follow-up in light of the new discovery at radio and optical wavelengths,” said Andrew Siemion, the director of the Berkeley SETI Research Center who runs the Breakthrough Listen Initiative, aimed at finding evidence of extraterrestrial civilizations. The Breakthrough Listen team helped Arecibo astronomers observe Ross 128 this spring. “Nearby exoplanets are particularly exciting from a SETI perspective as they permit us to search for and potentially detect much weaker signals than from more distant targets.”
While Ross 128 is, in cosmic terms, just down the street from us, it would take a spaceship traveling at the speed of light 11 years to reach it. Humans, at least the kind Earth has today, will never reach their stellar neighbor. But they can get a closer look. In the next decade, powerful telescopes like ESO’s Extremely Large Telescope will be able to sniff out the atmospheres of distant exoplanets like Ross 128 b for hints of biomarkers like oxygen. This technology will usher in a new era in the search for exoplanets, in which astronomers learn not only that more are out there—and certainly, more are—but discover what they’re truly made of. The detection of life-giving molecules in the atmosphere of a distant world will be a momentous occasion. Perhaps thousands of those discoveries, on many worlds, will follow. Perhaps someday, that will start to become routine, too.
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Introduction to JPA
Download free Introduction to JPA for Beginners, course tutorial, a PDF file created by Bruce Campbell.
The use for the persistence of mapping allows us to offer a higher level of abstraction than the simple use of JDBC: This mapping ensures the transformation of objects to the database and also the opposite that whether for readings or updates (creation, modification or deletion).
The Java Persistence API is based on the entities that are simple annotated POJOs and a manager of these entities (EntityManager) that provides functionality to manipulate (add, modify delete, search). The Manager is responsible for managing the state entities and their persistence in the database.
Table of contents
- Object Relational Mapping
- Introduction to JPA
- Entity Manager
- Persistence Context
- En4ty Relationships
- JPA and Spring
- Java Stack Config
- Native Query
- Criteria Query
The annotations @Entity (and all the other JPA annotations) can be replaced and / or Overloaded (XML files outweigh the annotations) by recorded information in an XML configuration file.
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All you need to do is download the training document, open it and start learning JPA for free.
This tutorial present an overview about Java programming and Applets including (applet execution,applets attributes,security,..).
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ADA course in PDF
Welcome to the Ada Programming tutorial in PDF, training document under 200 pages intended to beginners.
Java Persistence with JPA
This tutorial is a reference guide to provide a framework on how to work with JPA and help you to start your first JPA applications,free PDF training course material on 33 pages .
Getting Started with JPA
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About half of the Amazon rainforest is subject to seasonal droughts of 3 months or more. Despite this drought, several studies have shown that these forests, under a strongly seasonal climate, do not exhibit significant water stress during the dry season. In addition to deep soil water uptake, another contributing explanation for the absence of plant water stress during drought is the process of hydraulic redistribution; the nocturnal transfer of water by roots from moist to dry regions of the soil profile. Here, we present data on patterns of soil moisture and sap flow in roots of three dimorphic-rooted species in the Tapajós Forest, Amazônia, which demonstrate both upward (hydraulic lift) and downward hydraulic redistribution. We measured sap flow in lateral and tap roots of our three study species over a 2-year period using the heat ratio method, a sap-flow technique that allows bi-directional measurement of water flow. On certain nights during the dry season, reverse or acropetal flow (i.e.,in the direction of the soil) in the lateral roots and positive or basipetal sap flow (toward the plant) in the tap roots of Coussarea racemosa (caferana), Manilkara huberi (maçaranduba) and Protium robustum (breu) were observed, a pattern consistent with upward hydraulic redistribution (hydraulic lift). With the onset of heavy rains, this pattern reversed, with continuous night-time acropetal sap flow in the tap root and basipetal sap flow in lateral roots, indicating water movement from wet top soil to dry deeper soils (downward hydraulic redistribution). Both patterns were present in trees within a rainfall exclusion plot (Seca Floresta) and to a more limited extent in the control plot. Although hydraulic redistribution has traditionally been associated with arid or strongly seasonal environments, our findings now suggest that it is important in ameliorating water stress and improving rain infiltration in Amazonian rainforests. This has broad implications for understanding and modeling ecosystem process and forest function in this important biome.
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The history of humanity’s grand sweep around the world is recorded in our genes and genealogies, our art and artifacts, our literature and languages.
It’s also written in the legions of tiny mites that live, eat, crawl, and have sex on your face.
There are two species of mites that live on human faces. Both look like wall plugs with legs, although one (Demodex folliculorum) is longer and rounder of bottom than the other (Demodex brevis). “Demodex” means “the worm that bores into fat,” which gives you a clue about their lifestyles. They bury head-down into our hair follicles, slurping up the oils we secrete.
We know they become more common with age, and they seem to be on every adult face—your face, my face, even Scarlett Johansson’s face. They’ll have accompanied James Cameron to the bottom of the ocean and Neil Armstrong to the moon. They have lived with humans for most of our evolutionary history but they were only discovered in 1841. They are almost certainly the animals that we spend most time with, but they’re largely a mystery.
“It’s so shocking to imagine that we all have these animals living on our faces and we know so little about them,” says Michelle Trautwein at the California Academy of Sciences.
Her team, together with Michael Palopoli at Bowdoin College, have started to clarify our relationship with humanity’s actual best friends. The sampled mites from 70 American volunteers, either scraping the creatures up with a bobby pin, or simply pulling their DNA straight from swabbed foreheads. They sampled colleagues, friends, local students, or people who turned to “Meet Your Mites” face-sampling events. “A lot of diverse people come to our events,” says Trautwein.
That diversity was crucial. For the first time, Palopoli and Trautwein discovered that Demodex folliculorum comes in four distinct lineages, named A to D. Their proportions vary among people with different ancestries in ways that reflect humanity’s own history.
For example, our species originated in Africa, and people of African descent still have the greatest diversity of face mites, with representation from all four lineages. Other regions only have a fraction of this former diversity—people from Asian backgrounds mostly host mites from Groups B and D, while those of European ancestry are almost exclusively swarming in D. People of Latin American ancestry are exceptional in hosting mites from all four groups, but this might reflect the region’s history of colonialism, including the heavy historical influx of slaves from Africa.
These results make sense, but they’re also counter-intuitive. Remember that the volunteers aren’t people aren’t from all over the world; they’re all Americans with different ancestries. “The common sense idea would be that an African-American who had been here for generations would have picked up mites from people of European ancestry,” says Palopoli.
That wasn’t the case. Instead, “some of these people are maintaining mites for generations outside of their region of ancestry,” says Trautwein. Her team even sampled one volunteer who was born in Asia and had moved to the U.S. eight years before—and his face was full of the Group B mites that are common in Asia.
It might be that the mites simply don’t move very much. Indeed, one of the researchers—known in the paper solely as “host 206”—confirmed that mite populations are incredibly stable by sampling his or her own body for three years. Alternatively, it could be that different types of skin select for different lineages of mites, because of the qualities of their hair or oils. The environment might also be important. George Perry from Pennsylvania State University wonders if there’s only one mite lineage in Europe because others are sensitive to persistent outdoor cold.
It does seems that mites aren’t jumping from neighbor to neighbor, but can certainly jump from parent to child: When the team analyzed three families, they found that children share their parents’ mites. “We’re not sharing them in the subway but only among our close family,” says Trautwein. “That allows them to be a marker for human evolution.”
David Reed from the Florida Museum of Natural History, who has done similar studies on head lice, agrees. “This particular parasite has a few real strengths that makes it particularly good for studying human evolution,” he says. “It’s ubiquitous, it stays within individuals and family groups, and it’s been with us for a long time.”
For, perhaps, all the time. Trautwein and Palopoli estimated that the four mite lineages diverged from each other at least 200,000 years ago, in parallel with the rise of our own species or perhaps even earlier. “They’ve likely been with us through all of our history,” says Trautwein. But the exact timing of our partnership is hard to pin down, especially since we don’t know the closest living relative of our face mites. There are Demodex species that specialize on dogs, cats, goats, cows, but no one has sequenced the mites on chimp faces yet.
“Really, it seems like there’s an unending supply of good parasites to study but too few people doing the hard work of sampling them worldwide,” says Reed. Trautwein is on the case, teaming up with Rob Dunn from North Carolina State University to collect mites from people on seven continents. She also wants to compare mites in mixed-race couples and their children. “What’s shocking about the mites is that no one has done anything,” she says. “Anything we can think of, we can do.”
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While any software method of handling stacks can be implemented in hardware, the generally practiced hardware implementation is to reserve contiguous locations of memory with a stack pointer into that memory. Usually the pointer is a dedicated hardware register that can be incremented or decremented as required to push and pop elements. Sometimes a capability is provided to add an offset to the stack pointer to nondestructively access the first few elements of the stack without requiring successive pop operations. Often times the stack is resident in the same memory devices as the program. Sometimes, in the interest of increased efficiency, the stacks reside in their own memory devices. | <urn:uuid:053a946f-cb17-4525-ab8c-9205ead7bae9> | 2.6875 | 122 | Knowledge Article | Software Dev. | 16.284147 | 95,603,172 |
- Open Access
A fruitful outcome to the papaya genome project
© BioMed Central Ltd 2008
Published: 06 June 2008
The draft genome sequence of a transgenic virus-resistant papaya marks the first genome sequence of a commercially important transgenic crop plant.
In regard to genomics, the papaya is an ideal and interesting species to work with. It has a very small diploid genome of 372 Mb , slightly smaller than rice and six times smaller than maize . The papaya belongs to the order Brassicales, which includes the model plant Arabidopsis as well as the cabbage family; it shared a common ancestor with Arabidopsis approximately 72 million years ago . The papaya can also be easily transformed and has a generation time of 9-15 months. Also of interest is its primitive sex-chromosome system, which has interested evolutionary biologists for years .
The papaya genome was sequenced using a whole-genome shotgun approach by the traditional Sanger method to approximately 3x coverage . The majority of assembled contigs added up to about 271 Mb (73% of the genome) with scaffolds spanning 370 Mb. About 167 Mb of sequence (or 235 Mb of scaffolds) could be anchored to the integrated genetic and physical map of the papaya genome. More than half (52%) of the papaya genome comprises repetitive sequences, mainly long terminal repeat retrotransposons. Cytogenetic studies suggest that the genome is about 65-70% euchromatic and 35-30% heterochromatic. Various measures were used to assess the coverage of the draft genome, such as the percentage of unique genes (unigenes) and genetic markers matching the assembly. The authors estimate that approximately 90% of the euchromatin has been covered, containing 92.1% of the unigenes and 92.4% of the genetic markers.
Automated annotation of the genome combined with the genome coverage led the team to project a gene content of 24,746 genes. Compared with the other four sequenced plant genomes, this gene count is 11-20% less than that of Arabidopsis , 34% less than rice , 46% less than poplar and 19% less than grape .
The indication that papaya contains the smallest number of genes of any plant yet sequenced was investigated further. First, all inferred non-redundant protein sequences from the five sequenced plant genomes were collapsed into 39,709 similarity groups, or 'tribes'. Then the numbers of genes found in each tribe were compared between papaya and each of the other genomes. In the papaya-Arabidopsis comparison, for example, 3,595 tribes out of 6,726 contained the same number of genes. However, for the remaining tribes, Arabidopsis genes outnumbered papaya by two to one, and this trend was consistent with all the other plant genome sequences.
The team next asked what the minimum set of genes required for an angiosperm might be. By determining the genes shared across all the 39,709 tribes among the five sequenced genomes they estimated this minimum to be 13,311 genes. As papaya had the smallest numbers of genes over the most tribes, these data further supported the idea that it has the lowest gene count of any plant genome so far sequenced.
One possible explanation for the lower than expected number of genes is that the papaya genome did not undergo the two rounds of recent whole-genome duplication observed in Arabidopsis . Analysis of syntenic blocks between papaya and Arabidopsis revealed that for single papaya genes, Arabidopsis has two to four corresponding genes, but that each Arabidopsis gene only has one counterpart in papaya.
Interestingly, when syntenic blocks from the grape genome were included along with Arabidopsis in the analysis, Ming et al. detected a possible ancient whole-genome triplication that occurred before the divergence of the three species, but after the separation of the monocotyledons and dicotyledons. This triplication event was first proposed on the evidence of the grape genome sequence and is now supported by the papaya sequence.
Ming et al. categorized several important gene families essential for papaya fitness. One surprise is the extremely small number of disease-resistance genes of the nucleotide-binding site leucine-rich repeat (NBS-LRR) class. Arabidopsis has more than 200 NBS-LRR genes and rice more than 600 . In contrast, there are only 55 NBS-LRR genes in papaya, but they are clustered in a similar fashion to those in Arabidopsis and rice. This dearth of NBS-LRR genes might suggest that papaya has developed alternative strategies of host defense, such as the evolution of other classes of resistance genes (for example, tomato Cf-like genes , rice Xa-21 like receptor kinase or maize Hm1-like detoxin protein ) or even of nonhost resistance , in which all members of a plant species exhibit resistance to all members of a given pathogen species.
The papaya genome has a similar number of genes to Arabidopsis and poplar for cellulose biosynthesis, cell wall and lignin syntheses, and ethylene biosynthesis, but fewer genes involved in cell-wall degradation and in light-induced and circadian rhythms. On the other hand, papaya has more genes associated with starch metabolism and the development of volatiles.
The papaya genome sequence also sheds new light on the primitive XY sex-chromosome system, where the Y chromosome contains a male-specific region (MSY) approximately 8 Mb in length [8, 19]. Two scaffolds (totaling approximately 4.5 Mb) from the female papaya genome sequence determined by Ming et al. aligned to a bacterial artificial chromosome (BAC) physical map of the X chromosome. The female region contained 254 genes, of which 75% were supported by expressed sequence tags. In contrast, only four expressed genes have so far been found among seven completely sequenced BACs (totaling 1.2 Mb in length) in the MSY region . Using repeat data derived from the whole-genome sequence, Ming et al. were able to show that 85.6% of the 1.2 Mb MSY sequence is composed of repeats. Although complete sequence data are not yet available for the MSY from a male genome, the sequence generated from the female will provide essential comparative information to help unravel the mysteries of the evolution and function of sex chromosomes in plants.
An important point of the paper by Ming et al. is that the genome analyzed was from a transgenic inbred line. The PRSV coat protein transgene confers resistance to the virus and was introduced into papaya by particle bombardment. Particle bombardment can cause the construct to be fragmented, resulting in multiple integration events within the genome . The genome sequence enabled the identification of multiple integration sites, three of which occurred in nuclear genomic regions that contained AT-rich DNA fragments from the chloroplast genome. From a regulatory viewpoint, precise identification of the insertion sites of a transgene is required by many countries in order to obtain permission to grow or import transgenic food crops. Now that these integration sites have been determined, a major hurdle to the introduction of transgenic papaya in other countries has been removed.
In summary, a new and interesting plant genome sequence is now publicly available for interrogation. The papaya genome provides basic plant research with an exciting new tool to better understand angiosperm evolution and sex-chromosome biology. It also provides clues to the minimum set of genes that are needed to be a flowering plant. On the practical side, the papaya genome sequence has yielded a vast set of molecular genetic markers that can be used to create higher yielding, more nutritious and hardier papaya varieties.
It is safe to assume that the genomes of all the major food and fiber crops will be sequenced within the next five years. This is an important goal for both the plant genomics community and the wider world if we are to meet the food and energy security needs of the future. Sequencing the papaya genome illustrates just how much we do not know about plant genomes and how important it will be to generate reference genome sequences at key nodes on the tree of life. One argument has recently been made to sequence the genome of Amborella trichopoda, which lies at the base of angiosperm evolution . Whoever coined the phrase 'post-genomics' has jumped the gun. Plant genomics has just touched the surface of new biological discovery and practical solutions in support of the next green revolution.
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A View from Emerging Technology from the arXiv
The Dark Matter Data Bonanza
After years of skepticism over the existence of dark matter, a growing number of experiments are revealing that dark matter was there all along.
The universe is filled with mysterious invisible stuff that refuses to interact with light. It doesn’t reflect, emit or absorb light. But astronomers know it is there because of its gravitational effect on the visible stuff. They call it dark matter.
But there is a problem. If dark matter exists (and on this blog we’ve looked at a number of alternative ideas), there ought to be a lot of it out there. Astronomers estimate that 83 percent of the mass of the universe should take this form. The rest, a mere 17 percent, is visible.
So where is all this stuff? It should permeate the Solar System, the Earth and our environment. And yet when physicists look for it, they find zip.
At least, most physicists find nothing. For the last few years, one group of scientists have been shouting from the rooftops that they can see dark matter.
These guys have placed a giant lump of salt at the bottom of a mine in Italy. This lump is a 250 kg crystal of sodium iodide doped with thallium. The thinking is that a collision between an exotic particle and a nuclei in the crystal would generate a photon that can be picked up by sensitive light detectors nearby.
This experiment is called DAMA/LIBRA and its results are controversial. While particles of dark matter can certainly generate photons in the crystal, any other kind of particle can also generate light too. So the experiment also picks up cosmic radiation, thermal neutrons and background radioactivity. This makes the results extremely noisy.
There is a way to separate the dark matter signal from all this background, however. As the Sun moves through the galaxy, it must also be moving through a sea of dark matter. And as the Earth moves around the Sun, it will plough more quickly into the sea of dark matter at some times of the year and at other times more slowly.
So the dark matter signal ought to have an annual modulation.
This is exactly what the DAMA/LIBRA people say they can see. The dark matter signal peaks in May and then drops away. And this no weak tentative signal–the DAMA/LIBRA people say the statistical evidence is so clear that there is almost no possibility that they are mistaken.
But most astrophysicists have ignored and even ridiculed the DAMA/LIBRA result. The reason is that there are many other dark matter detectors at the bottom of other mines around the world that see nothing. Many of these are thought to be more reliable because they screen ought the background noise from cosmic radiation and so on.
They should only see the dark matter. But they don’t.
Or at least they didn’t. A few weeks ago, a team with a detector called CoGeNT at the bottom of a mine in Minnesota announced that it had gathered very similar evidence to the DAMA/LIBRA experiment. Their evidence of dark matter is not as statistically strong but it is modulated in exactly the same way, peaking in late April or early May.
Today, Dan Hooper at the Fermi National Accelerator Laboratory and Chris Kelso from the University of Chicago review the data from CoGenT and DAMA/LIBRA and say they are compatible with each other. “If the true phase peaks in early May, this would represent a modulation consistent with that reported by the DAMA/LIBRA collaboration,” they say.
That’s quite a statement given the scepticism that many researchers have showed towards the DAMA/LIBRA team.
But the evidence doesn’t stop there. Hooper and Kelso also say that the type of dark matter that these results imply is consistent with other indirect evidence of dark matter that other experiments have seen. Things like the spectrum of gamma rays observed by the Fermi Gamma Ray Space Telescope and the haze seen by the WMAP spacecraft, thought to be generated by electrons near the centre of the galaxy emitting photons.
And there is more to come. Hooper and Kelso say that another experiment is on the verge of publishing detailed results that back up the DAMA/LIBRA-CoGenT claims. “The CRESST collaboration has reported the observation of an excess of events roughly consistent with that anticipated from a CoGeNT-like dark matter particle.”
So the world of dark matter research has been turned on its head in just a few months.After years of negative reports, we suddenly have an avalanche of positive ones.
That makes it an interesting topic not just for physicists but also for psychologists studying group dynamics too. The process by which scientific ideas become scientific facts has always been murky and strange.
But the truth is that it is as a susceptible to human foibles as any other field of endeavour and so just as likely to experience fads and fashions and sudden changes in opinion. It’ll be interesting to see what historians of science make of this episode.
Ref: http://arxiv.org/abs/1106.1066: Implications of CoGeNT’s New Results For Dark Matter
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Birds and Climate Change
Impacts and Conservation Responses
- James W. Pearce-Higgins, British Trust for Ornithology, Norfolk
- Rhys E. Green, University of Cambridge
- Date Published: July 2014
- availability: Available
- format: Paperback
- isbn: 9780521132190
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From the red grouse to the Ethiopian bush-crow, bird populations around the world can provide us with vital insights into the effects of climate change on species and ecosystems. They are among the best studied and monitored of organisms, yet many are already under threat of extinction as a result of habitat loss, overexploitation and pollution. Providing a single source of information for students, scientists, practitioners and policy-makers, this book begins with a critical review of the existing impacts of climate change on birds, including changes in the timing of migration and breeding and effects on bird populations around the world. The second part considers how conservationists can assess potential future impacts, quantifying how extinction risk is linked to the magnitude of global change and synthesising the evidence in support of likely conservation responses. The final chapters assess the threats posed by efforts to reduce the magnitude of climate change.Read more
- A critical review of the impacts of climate change on birds, providing a single source of information for students, scientists, practitioners and policy-makers
- Presents new meta-analysis of the impacts of climate change and the evidence in support of likely conservation responses
- Draws upon examples of bird populations and communities around the world, presenting a valuable resource for people working in a range of environments
Reviews & endorsements
"Over twenty years ago, when I first became interested in the impacts of climate change on wild plants and animals, the literature was limited and the field wide open. Now it is very hard to keep up. This marvellous book is exactly what I need to feel on top of the subject once more, and needs to be read not just by ornithologists, but by all ecologists struggling to understand and predict the impacts of climate change on the living world. The authors are two world-leaders on the impacts of climate change on birds. The text summarises the effects of climate change that have already happened, seeks to predict what we can expect in the future, and considers what conservation biologists can do to mitigate its effects. The coverage is comprehensive, and skilfully distils a large and complicated literature into a compelling … narrative."
John Lawton, Chairman, Yorkshire Wildlife Trust and Vice-President, RSPBSee more reviews
"Climate change is emerging as the biggest threat to nature worldwide and one of the most challenging to understand and address. This book synthesises the state of knowledge on these issues for birds: the best-known wildlife group, and one that can provide insights and solutions for biodiversity more generally. The chapters go beyond the well-documented effects of climate change on phenology to consider the impacts on demography and distributions, and the knock-on effects for ecological communities. Most useful for the conservation community are the chapters synthesising approaches to safeguarding species and important sites under a changing climate, including consideration of the impacts of mitigation measures. Through combining an exhaustive review of the scientific literature, novel insights, helpful summaries, informative graphics and accessible language, this book will be the first one I turn to when wanting to find out more about climate change impacts on birds and the implications for conservation."
Stuart Butchart, Head of Science, BirdLife International
"Ongoing climate change has already had substantial impacts on the natural world. In birds, it affects the timing of their breeding and migrations, their numbers and distribution patterns. This book provides the most thorough and detailed review of this rapidly expanding research area yet published, and discusses various conservation measures that can be taken to mitigate the increasing impacts of climate change. This book provides not only a thorough review of the main known impacts of climate change on bird populations, but also fresh analyses of the wealth of data now available from around the world. It also provides detailed assessments of measures that might be taken to help birds through this period of dramatic environmental change. The authors ably synthesise known information regarding birds and climate change, undertake new analyses of the data, and assess the conservation measures that might be taken to minimise the effects on bird populations."
Ian Newton, Emeritus Fellow, Centre for Ecology and Hydrology
"The science is well-explained and if you want to understand how climate change is already affecting birds, and how it will in future, as well as how scientists study these matters, then [this] is a book for you."
Mark Avery, former Conservation Director, RSPB
"Pearce-Higgins and Green have produced one of the best written textbooks that I have ever encountered … an invaluable resource for both scientific and lay audiences on the observed and projected impacts of climate change on our avifauna, and how these impacts can be reduced by appropriate adaptation and mitigation. This excellent book is highly recommended."
British Trust for Ornithology (bto.org)
"Birds and Climate Change offers readers a thorough review of knowledge on the impacts of climate change on bird populations, distributions, and conservation, drawing on a wide range of historical and up-to-date sources … the book is an excellent source for all professional ornithologists and graduate students embarking on work in avian demography, distribution, communities, and conservation, particularly because future research needs are also well and logically developed. Overall, we found this book to be the most thorough and detailed review to date on the impacts of climate change on free-living species and, though focused exclusively on birds, [it] should be appealing to a wide range of readers, from amateurs to academics."
Journal of Field Ornithology
"This book would have made my life easier during graduate school. … even though many review articles and a handful of volumes have attempted to synthesize climate change impacts on birds, a comprehensive and up-to–date reference is needed. This book fills that niche. … The authors also expand on previous works by giving a much more comprehensive treatment of the critical issue of avian range shifts from climate change. They cover more new ground by reviewing the effects of mitigation strategies (e.g., wind energy and tidal and wave power development) on birds. Finally, the comprehensive explanation of predictive modeling methods, including bioclimatic, abundance, and population models, gives a useful introduction to all major methods currently being used to predict climate change impacts on birds. … Overall, I highly recommend this book to anyone with an interest in the effects of climate change on birds."
J. Berton C. Harris, New Biological Books
'This book, the culmination of six years of hard work, is a masterful review of the scientific evidence that birds remain our most important biological indicators of how species are responding to modern climate change. … In summary, Birds and Climate Change is a comprehensive and thoughtful review of the impacts of modern climate change on bird populations and is essential reading for undergraduate and graduate students, scientists, managers, and policymakers interested in ornithology and bird conservation.' Benjamin Zuckerberg, The Condor: Ornithological Applications
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- Date Published: July 2014
- format: Paperback
- isbn: 9780521132190
- length: 477 pages
- dimensions: 245 x 189 x 20 mm
- weight: 1.01kg
- contains: 154 b/w illus. 21 tables
- availability: Available
Table of Contents
Foreword Michael B. Usher
1. Birds and climate change
Part I. Impacts:
2. Altered timings
3. The impact of altered timings
4. Further mechanisms of population impacts
5. Effects of climate change on distributions and communities
Part II. Conservation Responses:
6. Using models to predict the effects of climate change on birds
7. Conservation in a changing climate
8. Effects of climate change mitigation on birds
9. Overall conclusions
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Understanding the evolution of such fast muscles has been difficult for researchers because slow movement of a swimbladder does not generate sound.
In a study published online Nov. 29 in the journal Frontiers in Zoology, Virginia Commonwealth University biologists, together with researchers Hin-Kiu Mok, Ph.D., at the National Sun Yat-sen University in Taiwan, and Eric Parmentier, Ph.D., at the Université de Liège in Belgium, have found that the pearl-perch belonging to the fish order Perciformes utilizes a hybrid system with characteristics of slow and fast systems. The findings suggest an intermediate condition in the evolution of superfast sonic muscles that drive swimbladder vibration directly. Perciforms are one of the largest orders of vertebrates.
"This work for the first time demonstrates an intermediate condition in the potential evolution of these superfast muscles," said investigator Michael Fine, Ph.D., professor of biology at VCU, who served as corresponding author for the study.
"It's sort of like finding a fossil whale with leg bones indicating affinity to a terrestrial vertebrate, or a dinosaur with feathers indicating potential steps in the evolution of reptiles into birds," he said.
According to Fine, a number of fish produce sounds by contracting superfast muscles that vibrate the swimbladder to produce aggressive and courtship calls. For example, in the oyster toadfish found on the east coast of the United States, swimbladder muscles routinely contract more than 200 times a second when a male is calling for a mate. Fine and his colleagues recently found a group of fishes that produce sound by using slow muscles to pull the swimbladder, which then snaps back - like a rubber band - to produce sound. In this case the pearl perch has a hybrid system that uses a slow system but actually pulls the swimbladder forward with a fast muscle. The fish has a tendon that gets stretched and causes the bladder to snap back, producing the loud part of the sound.
"What is special about this perciform is that its sound producing system appears to have intermediate characteristics between slow systems which are only known in ophidiiform fishes, and fast muscles present in different groups of fishes," he said.
The work was supported in part by a grant from the National Science Council of Taiwan and the F.R.S.-FNRS in Belgium.
About VCU and the VCU Medical Center: Virginia Commonwealth University is a major, urban public research university with national and international rankings in sponsored research. Located on two downtown campuses in Richmond, VCU enrolls more than 31,000 students in 216 certificate and degree programs in the arts, sciences and humanities. Sixty-nine of the programs are unique in Virginia, many of them crossing the disciplines of VCU's 13 schools and one college. MCV Hospitals and the health sciences schools of Virginia Commonwealth University compose the VCU Medical Center, one of the nation's leading academic medical centers. For more, see http://www.vcu.edu
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For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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When termites munch on wood, the small bits are delivered to feed a community of unique microbes living in their guts, and in a complex process involving multiple steps, these microbes turn the hard, fibrous material into a nutritious meal for the termite host.
One key step uses hydrogen to convert carbon dioxide into organic carbon—a process called acetogenesis—but little is known about which gut bacteria play specific roles in the process. Utilizing a variety of experimental techniques, researchers from the California Institute of Technology (Caltech) have now discovered a previously unidentified bacterium—living on the surface of a larger microorganism in the termite gut—that may be responsible for most gut acetogenesis.
"In the termite gut, you have several hundred different species of microbes that live within a millimeter of one another. We know certain microbes are present in the gut, and we know microbes are responsible for certain functions, but until now, we didn't have a good way of knowing which microbes are doing what," says Jared Leadbetter, professor of environmental microbiology at Caltech, in whose laboratory much of the research was performed. He is also an author of a paper about the work published the week of September 16 in the online issue of the Proceedings of the National Academy of Sciences (PNAS).
Acetogenesis is the production of acetate (a source of nutrition for termites) from the carbon dioxide and hydrogen generated by gut protozoa as they break down decaying wood. In their study of "who is doing what and where," Leadbetter and his colleagues searched the entire pool of termite gut microbes to identify specific genes from organisms responsible for acetogenesis.
The researchers began by sifting through the microbes' RNA—genetic information that can provide a snapshot of the genes active at a certain point in time. Using RNA from the total pool of termite gut microbes, they searched for actively transcribed formate dehydrogenase (FDH) genes, known to encode a protein necessary for acetogenesis. Next, using a method called multiplex microfluidic digital polymerase chain reaction (digital PCR), the researchers sequestered the previously unstudied individual microbes into tiny compartments to identify the actual microbial species carrying each of the FDH genes. Some of the FDH genes were found in types of bacteria known as spirochetes—a previously predicted source of acetogenesis. Yet it appeared that these spirochetes alone could not account for all of the acetate produced in the termite gut.
Initially, the Caltech researchers were unable to identify the microorganism expressing the single most active FDH gene in the gut. However, the first authors on the study, Adam Rosenthal, a postdoctoral scholar in biology at Caltech, and Xinning Zhang (PhD '10, Environmental Science and Engineering), noticed that this gene was more abundant in the portion of the gut extract containing wood chunks and larger microbes, like protozoans. After analyzing the chunkier gut extract, they discovered that the single most active FDH gene was encoded by a previously unstudied species from a group of microbes known as the deltaproteobacteria. This was the first evidence that a substantial amount of acetate in the gut may be produced by a non-spirochete.
Because the genes from this deltaproteobacterium were found in the chunky particulate matter of the termite gut, the researchers thought that perhaps the newly identified microbe attaches to the surface of one of the chunks. To test this hypothesis, the researchers used a color-coded visualization method called hybridization chain reaction-fluorescent in situ hybridization, or HCR-FISH.
The technique—developed in the laboratory of Niles Pierce, professor of applied and computational mathematics and bioengineering at Caltech, and a coauthor on the PNAS study—allowed the researchers to simultaneously "paint" cells expressing both the active FDH gene and a gene identifying the deltoproteobacterium with different fluorescent colors simultaneously. "The microfluidics experiment suggested that the two colors should be expressed in the same location and in the same tiny cell," Leadbetter says. And, indeed, they were. "Through this approach, we were able to actually see where the new deltaproteobacterium resided. As it turns out, the cells live on the surface of a very particular hydrogen-producing protozoan."
This association between the two organisms makes sense based on what is known about the complex food web of the termite gut, Leadbetter says. "Here you have a large eukaryotic single cell—a protozoan—which is making hydrogen as it degrades wood, and you have these much smaller hydrogen-consuming deltaproteobacteria attached to its surface," he says. "So, this new acetogenic bacterium is snuggled up to its source of hydrogen just as close as it can get."
This intimate relationship, Leadbetter says, might never have been discovered relying on phylogenetic inference—the standard method for matching a function to a specific organism. "Using phylogenetic inference, we say, 'We know a lot about this hypothetical organism's relatives, so without ever seeing the organism, we're going to make guesses about who it is related to," he says. "But with the techniques in this study, we found that our initial prediction was wrong. Importantly, we have been able to determine the specific organism responsible and a location of the mystery organism, both of which appear to be extremely important in the consumption of hydrogen and turning it into a product the insect can use." These results not only identify a new source for acetogenesis in the termite gut—they also reveal the limitations of making predictions based exclusively on phylogenetic relationships.
Other Caltech coauthors on the paper titled "Localizing transcripts to single cells suggests an important role of uncultured deltaproteobacteria in the termite gut hydrogen economy," are graduate student Kaitlyn S. Lucey (environmental science and engineering), Elizabeth A. Ottesen (PhD '08, biology), graduate student Vikas Trivedi (bioengineering), and research scientist Harry M. T. Choi (PhD '10, bioengineering). This work was funded by the U.S. Department of Energy, the National Science Foundation, the National Institutes of Health, the Programmable Molecular Technology Center within the Beckman Institute at Caltech, a Donna and Benjamin M. Rosen Center Bioengineering scholarship, and the Center for Environmental Microbial Interactions at Caltech.
Written by Jessica Stoller-ConradContact:
Deborah Williams-Hedges | 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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By S. Ketov
Read or Download Advances in Quantum Field Theory PDF
Best quantum theory books
NEW 2017 variation. What determines shades? what's movement? All colors in nature derive from the wonderful constitution consistent 1/137. 035 999 1. .. , the main well-known unexplained quantity in nature. What determines its worth? All movement in nature is defined both by means of quantum concept or via Einstein's common relativity, theories that contradict one another.
Die zweisemestrig aufgebaute Quantentheorie-Vorlesung bildet den Kern des Hauptstudiums jedes Physikstudierenden. Der hier vorliegende erste Band stellt zunächst die physikalischen Gründe für die Quantenphysik dar und entwickelt die Wellenmechanik sowohl für gebundene Zustände als auch für Streuprozesse.
This e-book is the 1st quantity of a two-volume paintings, that is a higher model of a preprint released in German. We search to infer the funda psychological thoughts of quantum mechanics completely from an outline of macroscopic units. The microscopic platforms similar to electrons, atoms, and so forth. needs to be detected at the foundation of the macroscopic habit of the units.
Generally, box idea is taught via canonical quantization with a heavy emphasis on excessive strength physics. even if, the thoughts of box concept are appropriate to boot and are broadly utilized in a variety of different parts of physics corresponding to consdensed topic, nuclear physics and statistical mechanics.
- Quantum Computation and Quantum Information: 10th Anniversary Edition
- Lectures on the Mathematics of Quantum Mechanics II: Selected Topics
- Path Integral Approach to Quantum Physics: An Introduction
- The undivided universe: an ontological interpretation of quantum theory
- Advanced Quantum Theory, Third Edition
Additional resources for Advances in Quantum Field Theory
Color online) Number of color space states that apply to each space-spin configuration of selected multi-parton states for two methods of enumerating the color basis states. The upper curves are counts of all color configurations with zero color projection. The lower curves are counts of global color singlets (adapted from Ref. (4)). 46 16 Advances in Quantum Field Theory Will-be-set-by-IN-TECH I would like to close by mentioning that we are extending the QED application in several directions. One specific goal is to include the capability for treating strong time-dependent laser pulses to address non-perturbative QED processes (35).
Quaglioni and P. Navrátil, Phys. Rev.
8. (Color online) Anomalous magnetic moment of the electron calculated in BLFQ compared to the Schwinger result (44). 11254. The horizontal axis is the square root of the reciprocal of Nmax . Symbols are for the BLFQ results. Squares: even Nmax /2; circles: odd Nmax /2. 1 MeV as indicated in the legend. The lines are linear extrapolations of BLFQ results based on all the points shown which span Nmax = 10 − 118 1 8π 2 What is not so apparent from a visual inspection of Fig. 8 is the fact that the extrapolated values come closer to the Schwinger result if one limits the linear fit to results for only the larger values of Nmax . | <urn:uuid:f149c97a-a993-4321-b4c5-274c81b51ea9> | 2.53125 | 751 | Product Page | Science & Tech. | 44.899584 | 95,603,267 |
Discussion about Galaxies, Work Placement Opportunities & Diversity in Science
Tag Archives | galaxy
So how is it possible to have atmospheres around rocky planets in the Trappist 1 system?
Story about galaxy cluster Abell 2052.
How did our galaxy grow from nothing to the hundreds of billions of stars we see today?
What happens during a galaxy merger event? Is dark matter involved?
Nowadays, outer part of our Galaxy spins faster. But back in the early Universe it would have rotated much more slowly.
Let’s have a tour of our universe and learn about the life and death in the universe
What is a supermassive star? How many are there in our galaxy? | <urn:uuid:769290a3-e9ac-460d-8d65-bf4ebcb2d277> | 2.546875 | 146 | Content Listing | Science & Tech. | 48.848633 | 95,603,287 |
Beams of monoenergetic positrons with energies of a few eV to many keV have been used in experiments in atomic physics, solid state physics and materials science. The production of positron beams from a new source, an electron linac, is described.
Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production efficiency, moderator geometry, beam spot size and other positron beam parameters have been determined for electrons with energies from 60 to 120 MeV. Low-energy positron beams-produced with a high-energy electron linac can be of much higher intensity than those beams currently derived from radioactive sources. These higher intensity beams will make possible positron experiments previously infeasible.
Lawrence Livermore National Laboratory Microchannel Plate Positron Beam Channel Electron Multiplier Slow Positron
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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London: Male birds displaying gorgeous plumes seem to positively affect brooding females of the same species, improving offspring growth.
Scientists made the discovery during a breeding experiment with Houbara bustards, a North African bird species with a very distinctive courtship behaviour.
Females observing such colourful males showing off in the experiment were more fertile and had a greater breeding success due to an increased allocation of testosterone into their eggs, prompting an increase in the growth rate of chicks.
The results showed that using artificial insemination without appropriate stimulation of breeding females probably has negative impacts on their breeding performance and can therefore even affect the survival of a species, says Adeline Loyau and Frederic Lacroix, who led the study.
Loyau of the Helmholtz Centre for Environmental Research (UFZ) (Germany) and the French CNRS station for experimental ecology and her colleague Lacroix from Emirates Centre for Wildlife Propagation (ECWP), confronted 90 brooding Houbara bustard females (Chlamydotis undulata undulata) with various individuals of the same species.
In the ECWP in Moroccan Missour, 30 female birds were visually confronted with either highly displaying male birds, poorly displaying male birds, or females.
During the experiment the female birds under investigation were artificially inseminated and kept isolated in aviaries five metres apart from birds of the same species in other aviaries.
That way the scientists were able to exclude any other factors from playing a role in the experiment other than that of visual stimulation.
"To my knowledge our study is the first example in species conservation of a successful manipulation of maternal allocation of resources through sensory stimulation," explains behavioural biologist Loyau.
"Our results show that it is possible to control maternal allocation of resources independent of the quality of male genes," said Loyau, according to a UFZ, ECWP release.
Male display courtship constitutes an effective signal thereby providing conservationists with a simple and inexpensive means. The results could therefore be very significant for the improvement of captive breeding programmes of other threatened bird species.
The Houbara bustard is a sandy-coloured resident of deserts, with its distribution ranging from North Africa to Mongolia. In the Arab world it is common prey for falcon hunting.
Both hunting and a loss of habitat have diminished Houbara bustard populations and in the meantime the species is classified as vulnerable.
These findings were published in the online edition of Proceedings of the Royal Society B. | <urn:uuid:e9c54e6c-3270-4f05-bda3-262d5ebd3ba3> | 3.1875 | 516 | News Article | Science & Tech. | 14.655768 | 95,603,317 |
In a study published in Nature Genetics, scientists from the RIKEN Center for Life Science Technologies in Japan, in collaboration with the RIKEN Center for Integrative Medical Sciences, the University of Copenhagen and the Joint Genome Institute (Walnut Creek, California) have discovered that "jumping DNA" known as retrotransposons—viral elements incorporated into the human genome—may play a key role in the maintenance of pluripotency, the ability of stem cells to differentiate into many different types of body cells.
This story is part of a fundamental rethinking taking place in genomic science. In 2009, members of the FANTOM Consortium project reported that an important fraction of mammalian transcriptomes—meaning the RNA transcribed from the genome—consists of transcripts derived from retrotransposon elements, vestiges of ancient retroviruses from the same family as HIV that have in the past been considered to only parasite the genome. However, the biological function of these "jumping DNA"–associated RNA transcripts remained unknown.
In the current study on embryonic stem (ES) cells and induced pluripotent stem (iPS) cells using four high-throughput methods including cap analysis gene expression (CAGE), the researchers found that thousands of transcripts in stem cells that have not yet been annotated are transcribed from retrotransposons, presumably to elicit nuclear functions.
These transcripts were found to be expressed in stem cells, but not differentiated cells. Importantly, the work showed that several of these transcripts are involved in the maintenance of pluripotency, since degrading several of them using RNA interference caused iPS cells to lose their pluripotency and differentiate.
These transcripts appear to have been recruited, surprisingly both in the human and mouse genome, where they are used to maintain the pluripotency of stem cells. Somehow, organisms including humans appear to have recruited viral elements into their genome in a way that helps to maintain the pluripotency of stem cells that allow them to regenerate. Why this is so remains a mystery for future investigation.
Although the results of the study cannot be put directly into application in regenerative medicine, knowing that retrotransposon elements are essential in the transcriptional control of iPS and ES cells is an essential clue for solving the puzzle of how to create better types of cells in future regenerative medicine studies.
"Our work has just begun to unravel the scale of unexpected functions carried out by retrotransposons and their derived transcripts in stem cell biology. We were extremely surprised to learn from our data that what was once considered genetic 'junk', namely ancient retroviruses that were thought to just parasite the genome, are in reality symbiotic elements that work closely with other genes to maintain iPS and ES cells in their undifferentiated state.
This is quite different from the image given by textbooks that these genomic elements are junk," explains Dr. Piero Carninci, senior investigator of the study.
The study was funded by a JSPS (Japan Society for Promotion of Science) grant for Next Generation World-Leading Researchers.
Jens Wilkinson | Eurek Alert!
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
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How to make interactive components
How do you make a website interactive? That’s one question that many beginners get stuck at. In this video, I walk you through you need to know to build an interactive website.
The first thing you want to ask yourself is this—what makes a website interactive? Does it become interactive if you can click on things, or does it become interactive if things start moving around?
For most people, the answer is both.
But technically, a website becomes interactive when it responds to a user in some way.
If you can click on a something and something happens, or you can type on a keyboard and something happens, or can say something, and something happens, your site is interactive.
How do you know when something happens?
Imagine you’re thirsty right now. You get up from your computer and grab a cup of water.
In this case, there is a cue. Because you’re thirsty, you go grab water.
- mouse events
- touch events
- keyboard events
- form events
- scroll events
You can find a complete list of events on MDN’s event reference, you’ll find a link below the video.
To act on the events, your program needs to be able to detect the event itself. To do so, you use an event listener.
To add an event listener, you first have to select an element, with querySelector. In this example here we have a button and we’re selecting the button with document.querySelector.
To add an event listener, you use the
addEventListener method that’s present on all HTML elements.
The first parameter you pass into
So back to event the event listener. In this case, we pass in click as the first parameter.
The second parameter is a function to execute when the event occurs.
Callbacks allow you to configure different actions to perform when an event occurs; you can do anything you want in the callback function, including changing the back ground color with
style property or adding a class with classList.
To create some sort of animation, you can use CSS Transitions, that’s the easiest way. If you’re watching from the future, you’ll see a link in the description below. If you’re watching it now, wait till next Wednesday and I’ll send you an article.
That’s a super basic intro of events and how to create interactive components. With this info, you can get a lot done, including creating a sidebar that stays outside of the screen.
One more thing before we end.
The listening element
We used the button variable directly in the function for now. This is okay when you’re starting out, but not okay when you create more complex code.
If you refactor, and shift the callback out of the element, it becomes hard for you to understand what
button refers to. Let’s call this callback
If you change the
button variable to something else down below, the
handleClick function breaks.
One way to get the button, which I call the listening element, is to use the
Another way of getting the listening element is through event object.
The event object is an argument that’s present on all event listeners. You can get the listening element through
Personally, I prefer use event.currentTarget because I prefer to use ES6 arrow functions whenever I can. ES6 arrow functions lets you write succinct code, but it doesn’t give you the same
this value as normal functions. You can find out more about
this in this article.
One funny thing is: if you
console.log(event), you’ll see that currentTarget is actually
null, I’m not sure why this happens though, because
event.currentTarget refers to the listening element itself.
If you know why, or if you’re interested in finding the answer, do it and let me know in the comments below.
That’s it for today, I hope you have learned something useful.
If you liked this video, be sure to hit the subscribe button below, and you’ll get a video from me every Friday.
What’s even better is go to my website at zellwk.com and subscribe there. If you do that, I’ll share one article and one video every week to help you get better with frontend development.
With that, I’m off for the week. Have a great weekend.
Thanks for reading. Did this article help you in any way? If I did, I hope you consider sharing it; you might just help someone who felt the same way you did before reading the article. Thank you. | <urn:uuid:ad50f2f3-3e59-49d7-b9b9-75d013e3a476> | 2.5625 | 1,005 | Personal Blog | Software Dev. | 62.097672 | 95,603,321 |
Add an Image to a Web Page
By Stephen Bucaro
The first version of HTML, suggested by Tim Berners-Lee back in 1990, didn't even have
a tag for images, it was designed for presenting formatted text. But adding an image to a webpage
makes it much more interesting. There are many different image file formats, each identified
by its file extension, and each with its advantages and disadvantages.
However the HTML code to add an image to a webpage is the same for all formats. To add
an image to a webpage, use the <img> tag. The basic code is shown below.
<img src="path/filename.ext" />
The img tag's src attribute defines the path to the image file. The difficulty some beginner's
have is getting this path right. If you don't get the path right, a box will appear where the
image should be, but no image. If you put the image file in the same folder as the html file
that you want it to appear on, you eliminate all confusion because you don't need a path, just
the image file name, as shown below.
<img src="mypicture.jpg" />
However, it's very common to keep all images in a special folder named, images. If that
folder is in the same folder as the html file that you want it to appear on, the path is just
the name of that folder, as shown below.
<img src="images/mypicture.jpg" />
However, many times, the images folder is at a higher level in the directory structure
than the the html file that you want it to appear on. In that case, you must tell the browser
to move up one level by using two dots (..), and then to look down by using a forward slash
(/). An example path for this is shown below.
<img src="../images/mypicture.jpg" />
Both of these examples use "relative" paths. In other words, they define the path to
the image file relative to the location of the html file that you want it to appear on. If
you don't want to fool around with relative paths, you can use an absolute path. An absolute
path contains the domain name and domain extension, as shown below.
<img src="http://www.domain.com/images/mypicture.jpg" />
How do you get the absolute path? If you can call up the image file in your browser and
display it by itself, you'll see the absolute path in the browser's address bar. All you need
to do is copy and paste this address into your image tag.
Another way to get an absolute path is if the image is displayed on another webpage.
Call up that webpage in your browser and right-click on the image. In the menu that appears
select "View Image Info" (if you're using Firefox) or "Properties" (if you're using Internet
Explorer). A dialog box will open displaying the absolute path to the image file.
Adding an image to a webpage makes it much more interesting. But for the image to appear,
you have to get its path right. Using the methods described here, you have no problem defining
the correct path.
More HTML Code:
• Code For a Basic 2-Column Fluid Webpage Layout
• HTML Editors
• How to Write and Run HTML
• HTML abbr and acronym Tag
• Make an HTML Element Editable
• The Font Tag
• Easy Form Design
• HTML Table Basics
• Keywords Meta Tag Generator
• Adding Space Around an Image | <urn:uuid:b9cc03b7-6ae2-4026-8a4a-85c69c6a8782> | 2.609375 | 765 | Tutorial | Software Dev. | 64.05467 | 95,603,323 |
Multiply-ionized atoms for clocks, qubits, and constants
The world is mostly neutral. That is, most of the atoms in our environment are electrically neutral. The number of electrons in the outer parts of atoms equals the number of protons at the centers of atoms. As one or more electrons are plucked away from the atoms, the remaining electrons feel a much stronger positive pull from the nucleus.
This enhanced pull, causing the atoms to shrink in size, ensures that those electrons are less vulnerable to the distractions of their environment, making them potentially valuable for next-generation atomic clocks, for quantum information schemes (where the loss of quantum coherence in qubits is a paramount danger), and for experiments trying to detect slight variations in the fine structure constant, the parameter that sets the overall strength of the electromagnetic force.
A new theoretical study conducted by JQI adjunct fellow Marianna Safronova and her colleagues from groups around the world (1) provides the best yet study of how highly charged ions could be used for atomic timekeeping and for processing quantum information. They identify 10 such ions---for instance, samarium-14+ and neodymium-10+---along with estimates of ion properties experimenters need to know before beginning their work, things such as the expected lifetimes and internal energy levels for the excited states of the ions.
WORKING WITH HIGHLY CHARGED IONS
Charged-up atoms are hard to produce and control. At one of the facilities dedicated to this purpose, the Electron Beam Ion Trap (EBIT) at the Lawrence Livermore National Lab, a beam of electrons intercepts a beam of atoms, ionizing the atoms at they go. In this way charge states all the way up to +92 (fully ionized uranium atoms) have been achieved. The trick is to store such charged ions and to cool them to low temperatures. In the kind of atomic environments typical of atomic clocks or quantum computers, low temperature means small ion motion, which makes for better spectroscopy.
Spectroscopy, the measurement of the energy of atomic transitions, is all important for the applications mentioned above---clocks, quantum computing, and testing the constants of nature. Currently the world's time standard is pegged to a particular microwave transition in cesium-133 atoms.. Even higher precision and better clocks will result from the use of transitions in the optical range.
One problem of working with highly charged ions is that the gaps in the energy levels are too great. This is because when you ionize an atom, its energy levels get further apart. The light emanating from transitions in these ions is at too great a frequency, often in the ultraviolet part of the electromagnetic spectrum. Precision control and manipulation of ions needed for clocks and quantum information is harder or presently impossible to do in that UV or even x-ray energy regime. So in choosing ion candidates, it is important to search for transitions in the optical or near-optical range.
Another criterion is that the ions should be able to attain semi-stable excited states. A third criterion is that the characteristic transition is not between the states from the same electronic configuration. Such transitions do not have enhanced sensitivity to the study whether the fine structure constant is changing over time.. A fourth criterion is that the final ionic state should not be a radioactive substance, thus reducing handling problems.
Safronova and her colleagues, using these criteria and a state-of-the-art methods that they developed to study atoms arrived at their list of ten worthy ion species. They publish their results in the 18 July 2014 issue of Physical Review Letters (2).
Not the least part of their achievement is the authors' specification of the frequencies to be expected from the critical transitions in the candidate ions. It's hard enough to calculate the transition energies of un-ionized atoms, but even harder with these particular highly charged ions. They calculated the frequencies for their select ions and then compared (where appropriate) with the values observed in the lab. The difference, generally less than 1%, should reassure experimenters that Safronova and her colleagues can accurately predict properties of ions where no experimental data are available. .
The use of highly charged ions might result in more accurate clocks since the atoms will be more immune from interference from nearby electric or magnetic fields. But aren't atomic clocks already good? They are. In January 2014, physicists at NIST-Boulder announced the creation of an atomic clock that sets records for accuracy and stability, at the 6 parts-per-10^-18 level. This clock uses strontium atoms, and the observed transition is reported to an astounding degree of explicitness. The energy corresponds to a wave with a frequency of 429,228,004,229, 870.0(1.1) Hz.
If, however, we could go just a bit further, to the level of 10^-19, then important physics tests might be possible, including the chance to determine whether the fine structure constant (denoted by the Greek letter alpha), is changing in time or space. Astronomical data has been interpreted by some to suggest that alpha is changing at a small level. At the finer level of precision offered by highly charged ions, terrestrial tests of alpha's constancy could be carried out.
Other potential uses for atomic clocks emerge in areas where high precision is critical: geodesy, hydrology, navigation, and even the deep tracking of spacecraft. Safronova singles out the potential for quantum computing: "The highly charge ions we recommend," she said, "present a completely unexplored resource for quantum information owing to their unique atomic properties and their potential for reducing the sensitivity to troubling decoherence effects."
(1) Safronova is an adjunct fellow of the Joint Quantum Institute (NIST/University of Maryland) and is also a professor at the University of Delaware. Her colleagues hail from Delaware, the University of New South Wales, the University of Nevada, the University of Notre Dame, the Petersburg Nuclear Physics Institute, and the St. Petersburg Electrotechnical University.
(2) "Highly charged ions for atomic clocks, quantum information, and search for alpha variation," M.S. Safronova, V.A. Dzuba, V.V. Flambaum, U.I. Safronova, S.G. Porsev, and M.G. Kozlov, Phys. Rev. Lett. 113, 030801 – Published 16 July 2014. DOI: http://dx.doi.org/10.1103/PhysRevLett.113.030801
Marianna Safronova, email@example.com
Phillip F. Schewe | Eurek Alert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
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18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:11e1f896-f4b6-4620-8fe1-9f94083d61e9> | 3.5625 | 2,023 | Content Listing | Science & Tech. | 43.211516 | 95,603,339 |
Sorting an Icon list
Icon's built-in ``
sort()'' function can be used to
order the elements of a list. The expression
sort ( L )returns a list with the same number of elements as L, except they are sorted. This makes sense only for certain types---integers, reals, and strings.
As an example, here is a program that writes the lines from its input in sorted order:
procedure main() lines := ; # Create an empty list while put ( lines, read ( ) ); # Store all lines every write ( ! sort ( lines ) ); # Sort and write endThe second line reads each input line and adds it to the list. In the third line, the expression ``
sort(lines)'' returns a list of the lines in sorted order; the ``
!'' operator generates the lines from the sorted list in order, and then they are written to the output.
John Shipman, email@example.com
Last updated: 1998/02/08 23:18:24 UT | <urn:uuid:aab21e53-4811-4f8e-b2c8-4b4b98aa26a7> | 2.875 | 221 | Documentation | Software Dev. | 63.298067 | 95,603,343 |
+44 1803 865913
The first contribution in this volume investigates mainly the province of Khentii, covering an area with dominating higher or lower mountain ranges and tablelands above 600 m.s.l. Thus the diatom flora was supposed to resemble alpine and northern regions of Europe rather than mediterranean - like or subtropical regions, which proved to be correct.
The 3487 micrographs reproduced in this book encompass approximately 615 taxa - without any attempt to approach completeness in this first volume of a treatise. 65 taxa (64 from Mongolia) are described as new to science, 33 other taxa (noted as (?nov.)spec.) will prove probably as new species after some more information, about 114 taxa could not be identified sufficiently as established taxa nor do they possess convincing characters to be distinguished from more or less similar taxa.
The second smaller monograph in this volume deals with Sichuania lacustris, a biraphid diatom possessing an unique frustules morphology, completely dissimilar to all established taxa from freshwater habitats.
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Is it possible for your brain to hurt if you think too much?
This is one of those questions that until you ask it, you take the ‘answer’ for granted. So, Why are Women (Generally) Smaller than Men?
We have probably all had this experience. We listen to a recording of ourselves talking and insist that the tape doesn’t sound at all like our voice – but everyone else insists it does. So, is there a medical explanation for this lack of self-perception?
Humans are a fickle lot. You only have to look at how public opinion seems to swing wildly from day to day. So, it might come as rather refreshing to hear how British biologist, Thomas Henry Huxley, 150 years go made a rather pithy observation called “The Four Stages of Public Opinion”.
Sometimes it’s good to questions the assumed orthodoxy that we all seem to absorb by gradual osmosis from the culture and society we live and are brought up in. How do we know that fingerprints ARE unique?
Should you discover that you have the ability to bend the upper half of your thumb until it makes a right-angle you might feel rather chuffed with yourself as you can then describe yourself as “double jointed” – surely that means you have two joints where most people have one ? NO, unfortunately not!
There’s a popular belief that’s been around for a while that playing calssical music to a baby and even an unborn child will make them smarter. This is otherwise known as “The Mozart Effect”. So, this rather begs the question …. “Is there any truth in this?” and if so “How much can a baby actually hear inside their Mother’s womb?”
The problem with dinosaurs is that they lived a very long time ago- between 250 million and 65 million years ago – and the vast majority of our knowledge of them is based on fossilized bones and skeletons, which are all that have survived the ravages of time. So can we tell if dinosaurs were warm or cold-blooded ?
Most of us will be familiar with the aches that seem to accompany the bouts of flu we sometimes contract, especially during the change of seasons. But why does our whole body ache, including bits that really shouldn’t like teeth & hair ?
Having a bath has uses aside from getting clean and reading a good book: it gives you an excuse to observe a bodily quirk that it would appear has been with us since Homo sapiens left the trees.
Urban Myth or Science Fact : Is it true that we typically only use 10% of our brain ?
The internet was clearly invented with the sole purpose of allowing the earth’s population to watch cute cat movies. So, in this article we add to that great body of information, we like to call “internet fluff”, with some rather erudite answers to some of those perplexing questions about our feline friends.
A valentine’s day conundrum for you : Why does an X stand for a kiss? and why do humans kiss anyway?
Of all the things that define us as humans there is surely one remarkable thing that marks us out from other life on earth – language and the ability to communicate via speech. But what is it in our genes that allows us to do this?
On the face of it there seems little hope of working out precisely how a 75ft long, 50 ton Brachiosaur fed itself. However it is possible to make a few guesstimates, by assuming the present laws of physics and chemistry applied 65 million years ago. | <urn:uuid:e6fe1096-4803-4632-b701-5fe2c62097ad> | 2.640625 | 767 | Content Listing | Science & Tech. | 58.603996 | 95,603,404 |
Source of Inorganic and Organic Nutrients and Interaction with Photons
Dissolved HS comprise incompletely oxidized carbon. Therefore, HS have the potential to act as substrates for oxidations. Thess processes can be carried out by light or by microorganisms under oxygenated conditions. Usually photooxidation precedes microbial usage. When light is absorbed by the HS, a series of physical and above all, physico-chemical processes such as photolysis occurs. These processes have direct and indirect effects on the biota of lakes and rivers, especially on the heterotrophs. The complexity of these photochemical processes are described and their ecological role understood incrementally. Our present knowledge still gives an incomplete picture, which will gradually be completed.
KeywordsPhotosynthetically Active Radiation Dissolve Organic Nitrogen Dissolve Organic Matter Organic Nutrient Quantitative Structure Property Relationship
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The Caucasus Pearl-Bordered Fritillary (Boloria euphrosyne dagestanica) is a butterfly in the Nymphalidae family. It is an insect.
The Caucasus Pearl-Bordered Fritillary is orange with black spots on the upperside of its wings. The underside of its wings has a row of silver-pearl markings along the edge. The caterpillars are black with white or yellow spines along their backs.
Its wingspan measures about 4 centimetres (1.5 inches).
The Caucasus Pearl-Bordered Fritillary is found in the Caucasus and Transcaucasia, in countries such as Georgia, Armenia, Azerbaijan, and southern Russia. It prefers grasslands and woodlands.
The female Caucasus Pearl-Bordered Fritillary lays eggs in leaf litter on the ground, or on leaves. The eggs are laid singly, not in a group or cluster. The eggs hatch after 10-14 days.
Caterpillars emerge from the eggs and begin feeding on plant leaves. The caterpillars moult (shed their skin) three times in 5-6 weeks, before hibernating in a chrysalis. The chrysalis stage lasts for 10-14 days before adult butterflies emerge.
Adult butterflies feed on the nectar of flowers.
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM | <urn:uuid:2b3c287f-96ec-4344-ae34-9ea0f0171ad5> | 3.140625 | 303 | Knowledge Article | Science & Tech. | 49.062029 | 95,603,441 |
+44 1803 865913
By: Patrick Moore
Do you want a practical guide to astronomy? Would you like to be able to observe and understand the sky at night? Teach Yourself Astronomy is a comprehensive and straightforward guide to the 'science of the sky'. Assuming no prior knowledge, this book will ensure you grasp the basics of this fascinating science. You will soon learn how to observe the sun, moon, planets and other bodies such as comets and, with the help of star charts, you will be able to impress with your knowledge of the sky at night.
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Type Number Object DisplayObject Library display.* Revision 2018.3332 Keywords y, position See also object.x
Specifies the y position (in local coordinates) of the object relative to its parent — specifically, the y position of the object's anchorY point relative to its parent. Changing this value will move the object in the y direction.
This cannot be used on a physical body during a collision event. However, your collision handler may set a flag or include a time delay via timer.performWithDelay() so that the action can occur in the next application cycle or later. See the Collision Detection guide for a complete list of which APIs and methods are subject to this rule.
local rect = display.newRect( 0, 0, 50, 50 ) rect:setFillColor( 1, 1, 1 ) rect.y = 100 | <urn:uuid:4a546bc0-ac5d-44c0-99d9-ac18958d4ade> | 3.125 | 177 | Documentation | Software Dev. | 56.545746 | 95,603,451 |
A metal is an element, compound or alloy that is a good conductor of both electricity and heat. They are generally shiny, malleable and ductile. Some elements and compounds are not classified as metals unless under high pressures when they begin to act as metals.
Metallic substances atoms are closely positioned to neighboring atoms in either two possible arrangements. The first arrangement is body-centered cubic. In this arrangement, each atom is positioned at the center of eight other atoms. The second arrangement is face-centered cubic. In this arrangement, each atom is positioned in the center of six others. These two different arrangements form crystal structures. Structures of metals can change depending on the temperature.
Atoms from metallic substances can lost their outer shell electrons. This results in a free flowing cloud of electrons within their otherwise solid arrangement. It provides the ability of metallic substances to easily transmit heat and electricity. The solid characteristic of metals during this flow of electrons occurring is produced by electrostatic interactions between each atom and the electron cloud. This is called metallic bonding.
Metals are inclined to form cations through electron loss reacting with oxygen in the air to form oxides over various timescales. Transition metals (iron, copper, zinc) are slower to oxidize because they form passivation layers of oxide that protects the interior. Other metals such as palladium, platinum and gold, do not react with the atmosphere at all. This is due to the barrier layer of oxide which is formed on the surface which is impenetrable by further oxygen molecules. This allows those metals to retain their shiny appearance and good conductivity.
Alloys are a mixture of two or more elements, which the main component is a metal. Often pure metals are either to soft, brittle or chemically reactive for practical use. Combining different ratios of metals makes alloys have the desirable properties of the pure metals. Common alloys will incorporate aluminium, titanium, copper and magnesium.© BrainMass Inc. brainmass.com July 21, 2018, 4:09 am ad1c9bdddf | <urn:uuid:ac60fc45-c1cd-41ed-bfe2-99476afbb91f> | 3.984375 | 418 | Knowledge Article | Science & Tech. | 34.269543 | 95,603,482 |
Oxytocin, the body’s natural love potion, helps couples fall in love, makes mothers bond with their babies, and encourages teams to work together. Now new research at Rockefeller University reveals a mechanism by which this prosocial hormone has its effect on interactions between the sexes, at least in certain situations. The key, it turns out, is a newly discovered class of brain cells.
“By identifying a new population of neurons activated by oxytocin, we have uncovered one way this chemical signal influences interactions between male and female mice,” says Nathaniel Heintz, James and Marilyn Simons Professor and head of the Laboratory of Molecular Biology.
The findings, published today in Cell (October 9), had their beginnings in a search for a new type of interneuron, a specialized neuron that relays messages to other neurons across relatively short distances. As part of her doctoral thesis, Miho Nakajima began creating profiles of the genes expressed in interneurons using a technique known as translating ribosome affinity purification (TRAP) previously developed by the Heintz lab and Paul Greengard’s Laboratory of Molecular and Cellular Neuroscience at Rockefeller. Within some profiles from the outer layer of the brain known as the cortex, she saw an intriguing protein: a receptor that responds to oxytocin.
“This raised the question: What is this small, scattered population of interneurons doing in response to this important signal, oxytocin?” Nakajima says. “Because oxytocin is most involved in social behaviors of females, we decided to focus our experiments on females.”
To determine how these neurons, dubbed oxytocin receptor interneurons or OxtrINs, affected behavior when activated by oxytocin, she silenced only this class of interneurons and, in separate experiments, blocked the receptor’s ability to detect oxytocin in some females. She then gave them a commonly used social behavior test: Given the choice between exploring a room with a male mouse or a room with an inanimate object – in this case a plastic Lego block – what would they do?
Generally, a female mouse will go for the non-stackable choice. Legos just aren’t that interesting to rodents. But Nakajima’s results were confusing: Sometimes the mice with the silenced OxtrINs showed an abnormally high interest in the Lego, and sometimes they responded normally.
This led her to suspect the influence of the female reproductive cycle. In another round of experiments, she recorded whether the female mice were in estrus, the sexually receptive phase, or diestrus, a period of sexual inactivity. Estrus, it turned out, was key. Female mice in this phase showed an unusual lack of interest in the males when their receptors were inactivated. They mostly just sniffed at the Lego. There was no effect on mice is diestrus, and there was no effect if the male love interest was replaced with a female. When Nakajima tried the same alteration in males, there was also no effect.
“In general, OxtrINs appear to sit silently when not exposed to oxytocin,” says Andreas Görlich, a postdoc in the lab who recorded the electrical activity of these neurons with and without the hormone. “The interesting part is that when exposed to oxytocin these neurons fire more frequently in female mice than they do in male mice, possibly reflecting the differences that showed up in the behavioral tests.”
“We don’t yet understand how, but we think oxytocin prompts mice in estrus to become interested in investigating their potential mates,” Nakajima says. “This suggests that the social computation going on in a female mouse’s brain differs depending on the stage of her reproductive cycle.”
Oxytocin has similar effects for humans as for mice, however, it is not yet clear if the hormone influences the human version of this mouse interaction, or if it works through a similar population of interneurons. The results do, however, help explain how humans, mice and other mammals respond to changing social situations, Heintz says.
“Oxytocin responses have been studied in many parts of the brain, and it is clear that it, or other hormones like it, can impact behavior in different ways, in different contexts and in response to different physiological cues,” he says. “In a general sense, this new research helps explain why social behavior depends on context as well as physiology.”
Zach Veilleux | newswise
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
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20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:25956627-376b-4bf0-8069-bcfc260bdaf0> | 3.015625 | 1,547 | Content Listing | Science & Tech. | 33.510437 | 95,603,485 |
The Morningstar device, which initially weighs 190 pounds, was able to reduce its weight by 7% during a steady-state situation and as much as 20% during transient operation. In our original paper, three or four approaches were identified to possibly explain this phenomenon including: conversion of angular momentum into linear momentum; Gravito- Electro-Magnetism (GEM) effects- a Poynting vector force induction based upon the roller design, and retarded potentials. In the latter, the ring component acts as a reflection plane for the roller electric and magnetic fields and if the time is retarded, it is possible that the image from one roller may attract the adjacent roller to create self-acceleration. Additional possible explanations were identified in the operation of this nonlinear device. This spectrum of additional feasibilities warrants further investigation to determine the physical motivation that can induce the observed weight changes. There is caution regarding these and additional explanations which should fall within supportable technical evidence. These additional efforts include: cogravitation, matter waves, gravitational wave effects and a conjecture about spacetime perturbation. | <urn:uuid:6afa5788-6ecf-4ca7-99dc-c909c284634b> | 3.03125 | 221 | Academic Writing | Science & Tech. | 5.492 | 95,603,494 |
Although they both seem to do the same thing, there is a subtle difference between them.
cout << endl : Inserts a new line and flushes the stream cout << "\n" : Only inserts a new line.
cout << endl;
can be said equivalent to
cout << ‘\n’ << flush;
As a conclusion, cout << “\n” seems performance wise better than cout << endl; unless flushing of stream is required.
This article is contributed by Akshat Saxena. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above
- Problem with scanf() when there is fgets()/gets()/scanf() after it
- How to use getline() in C++ when there are blank lines in input?
- Basic Input / Output in C++
- Clearing The Input Buffer In C/C++
- C/C++ Preprocessors
- Common Memory/Pointer Related bug in C Programs
- Format specifiers in C
- Implicit initialization of variables with 0 or 1 in C
- Lex program to take input from file and remove multiple spaces, lines and tabs
- Left Shift and Right Shift Operators in C/C++ | <urn:uuid:a86281fb-e92a-4e38-ab06-5e8f2480c887> | 4.03125 | 271 | Truncated | Software Dev. | 43.543419 | 95,603,500 |
OLYMPIA, Washington (Reuters) – A North American bumblebee species that all but vanished from about half of its natural range has re-emerged in Washington state, delighting scientists who voiced optimism the insect might eventually make a recovery in the Pacific Northwest.
Entomologists and bee enthusiasts in recent weeks have photographed several specimens of the long-absent western bumblebee – known to scientists as Bombus occidentalis – buzzing among flower blossoms in a suburban park north of Seattle.
“It’s a pretty big deal,” said Rich Hatfield, a biologist for the Oregon-based Xerces Society for Invertebrate Conservation, which documents and reports such findings.
“It gives us hope that we can do some conservation work, and perhaps the species has a chance at repopulating its range,” he told Reuters this week.
The multiple sightings, including observations of several queens, are evidence of western bumblebee colonies in the area, although it hardly proves the species has returned in force and or that it will thrive in the region, Hatfield said.
Last year, a single western bumblebee, recognized by its distinctive white-banded bottom, was discovered by an insect enthusiast in her mother’s garden in suburban Brier, Washington. It was the first sighting in Washington state west of the Cascades in well over a decade.
Her sighting was confirmed earlier this month as more than an isolated incident when Will Peterman, 42, a freelance writer-photographer and self-described “bee nerd” from Seattle, ventured into a park in Brier to capture his own shots of Bombus occidentalis foraging in blackberry bushes for nectar and pollen.
He returned on Sunday with a group of University of Washington entomologists to conduct a more thorough canvass of the park and surrounding areas. While the group failed to locate a nest – hives are dwellings for domesticated honeybees – they identified and photographed at least three queens.
Hatfield said the queen bees observed in the park would normally be expected to go into hibernation soon, then produce offspring next year.
The mood among the scientists accompanying him was “almost giddy,” Peterman said. “This is grounds for optimism in a story that has been really bleak.”
CAUSE OF POPULATION CRASH UNCLEAR
Bombus occidentalis is one of four wild North American bumblebee species whose populations began to plummet two decades ago, while honeybees – commercially bred for the most part – have undergone less precipitous declines, Hatfield said.
Scientists have cited a number of likely factors for bumblebee declines, including parasites, pesticides and habitat fragmentation.
Until the mid-1990s, the western bumblebee was among the most common bees in the Western United States and Canada, where it was valued as a key pollinator for tomatoes and cranberries.
It has since virtually disappeared from about half its historic range, a vast stretch of the West Coast from central California to southern British Columbia, although its population remains relatively robust in the Mountain West.
Scientists are not certain what caused North American bumblebee populations to crash.
But a leading theory advanced by Robbin Thorp, a retired entomology professor at the University of California at Davis, points to efforts to commercially cultivate colonies of western bumblebees in Europe starting in the mid-1990s.
American-bred western queens shipped to Europe likely were exposed there to a fungus that might have spread and devastated wild North American bumblebee populations when infected European-bred bees were transported back to the United States, Hatfield said.
The discovery of the bees near Seattle could mean a population resistant to the fungus has emerged, he said. The bees may also be part of a population never exposed to the fungus or that originated in a distant colony to the east.
(By Jonathan Kaminsky. Editing by Steve Gorman, Douglas Royalty and Peter Cooney) | <urn:uuid:1d92c8d7-0a4c-448c-966b-fdd767890339> | 2.578125 | 828 | News Article | Science & Tech. | 25.283808 | 95,603,546 |
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Scientists: 2015 was hottest on record
2015 was the hottest year on record...surpassing 2014. USA TODAY
Just as a big winter storm arrives across the Midwest and heads for the East Coast, the federal scientists report the Earth went through its hottest year on record in 2015.
Could snowballs in the U.S. Capitol building be far behind, with renewed political fights over coal and global warming?
The globally averaged temperature over land and ocean surfaces for 2015 was the highest among all years since record keeping began in 1880, the National Oceanic and Atmospheric Administration said.
During the final month, the December combined global land and ocean average surface temperature was the highest on record for any month in the 136-year record.
The record warmth was broadly spread around the world, the agency reported Thursday morning.
The heat was fueled by a powerful El Niño and global warming, officials said.
A separate analysis of data from NASA agreed with NOAA's findings, Gavin Schmidt, director of NASA's Goddard Institute for Space Studies, told USA TODAY. “2015 was remarkable even in the context of the larger, long-term warming trend,” he said.
According to NASA, most of the warming has happened in the last 35 years, and 15 of the 16 warmest years have occurred since 2001, the newspaper reported.
“The whole system is warming up, relentlessly,” Gerald A. Meehl, a scientist at the National Center for Atmospheric Research in Boulder, Colo., told The New York Times.
The previous year, 2014, was also a global record.
"It's getting to the point where breaking a record is the norm," Texas Tech climate scientist Katharine Hayhoe told The Associated Press. "It's almost unusual when we're not breaking a record."
More from the AP:
NOAA said 2015's temperature was 58.62 degrees Fahrenheit (14.79 degrees Celsius), passing 2014 by a record margin of 0.29 degrees. That's 1.62 degrees above the 20th-century average. NASA, which measures differently, said 2015 was 0.23 degrees warmer than the record set in 2014.
Because of the wide margin over 2014, NASA calculated that 2015 was a record with 94 percent certainty, about double the certainty it had last year when announcing 2014 as a record.
Measured another way over a shorter period of time, it was the third warmest year, NOAA said. The 2015 temperature for the lower troposphere, or roughly the lowest five miles of the atmosphere, was third highest since 1979, at 0.65°F (0.36°C) above the 1981–2010 average, as analyzed by the University of Alabama Huntsville.
Now, about that snow. Meteorologists are reporting that the same weather forces that have brought the eastern U.S. an unusually warm winter will also possibly fuel "a blizzard for the ages" on the East Coast and including Washington, D.C. Slate reports: "Climate change and El Niño have pushed water temperatures in the Atlantic to near record highs right now, which could offer something similar to the boost a land-falling hurricane sometimes gets when traversing the Gulf Stream—a rapidly strengthening storm, though with snow instead of rain."
A significant winter storm has been forecast for across southern Indiana and North Central Kentucky starting with ice Thursday evening, turning to snow on Friday.
Like I said, perfect timing.
Reach reporter James Bruggers at (502) 582-4645 and at email@example.com.
Dr. Harold Wanless, nicknamed Dr. Doom, believes the government has underestimated sea level rise. | <urn:uuid:3d35af54-4193-4241-8605-1867e54334eb> | 3.078125 | 775 | News Article | Science & Tech. | 60.610441 | 95,603,588 |
Introduction. By: Dana, Hala, Sohaila What are Glaciers ? Can a glacier melt until summer? ( how it melts) What is it Caused by ? . Glaciers !!!!. G laciers.
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(how it melts)
A glacier is a large body of ice. A glacier is located in cold places. A glacier is 30-40 meters thick . A glacier is made out of water, sediment, rock, and ice. A glacier can fill a whole valley.
If the weather is warm and dry it can cause the glacier to shrink. Sometimes glaciers are caused by global warming and this is what the human response have. When summer arrives the glacier doesn't melt.
Glaciers begin when snow remains in the same year area.
They are 2 main types of glaciers an alpine glacier and continental glacier.
When a glacier collects over many years the ice falls done. | <urn:uuid:ad6d3d1f-1c1a-4ed1-8ed7-f3364f315e6b> | 3.90625 | 252 | Truncated | Science & Tech. | 66.235521 | 95,603,600 |
He missed the 'glitzy Oscars for science,' but that’s OK with Bob McKeown. McKeown is the Governor's Distinguished CEBAF Professor in William & Mary’s physics department as well as deputy director for science at Jefferson Lab. He was a participant in two of five experiments that share the 2016 Breakthrough Prize in Fundamental Physics.
Tue, 11/17/2015 - 12:00pm
Wed, 08/12/2015 - 01:32pm
Amber Boehnlein can’t remember a time when she didn’t love science.
As a child, growing up in the small Ohio village of Germantown, Boehnlein (pronounced “Bane Line”) would often play math games with her grandmother. She taught herself how to code while in high school. When she went off to college, it was only natural that she chose to study physics.
Thu, 07/16/2015 - 10:00am
CERN, the European Organization for Nuclear Research, has announced that its LHCb experiment has discovered two possible pentaquark particles that haven't been seen before. If confirmed, these new particles will herald the discovery of a whole new class of particles.
Pentaquarks gained international attention in 2003, when evidence for a lighter cousin of the pentaquarks announced by CERN was thought to have been found by experimenters at SPring-8 in Japan, the Department of Energy's Thomas Jefferson National Accelerator Facility, the Alikhanov Institute for Theoretical and Experimental Physics (ITEP) in the Russian Federation and the ELectron Stretcher and Accelerator (ELSA) in Germany.
Wed, 05/20/2015 - 04:00pm
Fans of science and science fiction have been warned that mixing matter with anti-matter can yield explosive results. And that’s just what physicists were counting on, in hopes of blowing wide open a puzzle that has confounded them for the last decade.
The puzzle comes from experiments that aimed to determine how quarks, the building blocks of the proton, are arranged inside that particle. That information is locked inside a quantity that scientists refer to as the proton’s electric form factor. The electric form factor describes the spatial distribution of the quarks inside the proton by mapping the charge that the quarks carry.
Wed, 05/20/2015 - 02:05pm
For as long as Matthew Burton can remember, he has been into science. When asked how far back, he readily recalls trying to bend a laser with magnets for an elementary school science fair project.
The young researcher has always been excited by technology, and physics, he says, gave him a path into that.
After high school, he headed to James Madison University on a (science, technology, engineering and math) STEM scholarship to study fundamental physics, and then to The College of William and Mary for its Ph.D. physics program.
Mon, 04/06/2015 - 09:12am
Andrew “Drew” Weisenberger, head of the Experimental Nuclear Physics Division’s Radiation Detector and Imaging Group, recently accepted the additional role of Chief Technology Officer (CTO) for Jefferson Lab.
As part of the detector group, Weisenberger has spent years advancing research to improve particle detector technology and seeking ways that discoveries in his field can be applied outside of the lab’s basic research program. He is part of the team that worked on the components and technology that brought to life a breast-cancer diagnostic device – a molecular-imaging camera – now commercially produced and sold by Dilon Technologies that can detect the tiniest of breast cancer tumors. Today that camera is used in hospitals and medical diagnostic centers around the world.
Fri, 03/20/2015 - 02:50pm
In roughly six years, Jefferson Lab’s YouTube channel has attracted 100,000 subscribers and has been viewed more than 30 million times.
To celebrate this milestone, achieved on Feb. 8, Science Education posted an episode of Frostbite Theater, titled 100,000 Subscribers! (And some liquid nitrogen!).
To mark the event, Frostbite Theater hosts Steve Gagnon, Science Education administrator, and Joanna Griffin, Public Affairs graphic artist, froze a 100 Grand® candy bar.
Thu, 08/14/2014 - 02:46pm
Jefferson Lab Offers Science Enrichment Program for 5th, 6th & 8th Grade Teachers; Registration Deadline is Sept. 12
Mon, 12/09/2013 - 10:30am
Fifteen minutes seems like a lifetime to Paul Brindza. It's the average lifetime of a neutron, one of the many subatomic particles that scientists study at Jefferson Lab. While that may seem like a fleeting existence to us, the Hall C engineer says that it's more than enough time for the subatomic particles to do some real damage as they travel inside the hall.
Now, Brindza and his colleague Bert Metzger have devised a system of products to stop neutrons and other particles before they can inflict harm on sensitive scientific equipment and computers. Their patented and patent-pending products are currently being installed in Hall C.
Fri, 04/26/2013 - 12:00pm
Ordinarily, physicists generally think of protons and neutrons as each containing three “valence” quarks, i.e. quarks that determine the charge of the proton or neutron. When they visualize the structure, they usually imagine these three quarks to be more-or-less on equal footing. Even so, puzzling data from an experiment carried out 40 years ago was thought to suggest that two of the quarks cluster together into what is called a diquark. However, there has been very little experimental evidence since then to support this idea - perhaps until now.
Wed, 02/06/2013 - 11:00am
A committee appointed by the U.S. Department of Energy and National Science Foundation to review and recommend the future course of nuclear physics research in the United States has issued a report supporting the continued funding of the experimental program at the U.S. Department of Energy's Jefferson Lab.
Mon, 08/20/2012 - 12:00am
When Melanie Goff, president of a small, minority, women-owned business, needed to find new business prospects in the federal government, she turned to Freda Hopper. Hopper has been working with small businesses looking to get their foot in the door to federal contracting as a small business program manager since 1998, serving small businesses from her position at Oak Ridge Operations Office in Oak Ridge, Tennessee.
Mon, 08/06/2012 - 12:00am
Fri, 08/03/2012 - 12:00am
A 13,000 square-foot office suite in Oyster Point will likely be the first place in the world where boron nitride nanotubes — a high-tech product developed at Jefferson Lab — will be manufactured for commercial use, officials said. The nanotubes, first discovered in California in the 1990s, could be used in products as diverse as satellites, golf clubs and computer screens.
Thu, 08/02/2012 - 12:00am
Hendrik Schatz studies exploding stars — or more specifically, what connection exploding stars have to our planet’s existence and the existence of elements on Earth today.
He suspects that about 15 billion years ago, stars either exploded or collided, sending radioactive particles into the universe. Eventually, these radioactive particles became stable, clinging together to form Earth and many of the elements we use today, such as gold and uranium.
Thu, 07/19/2012 - 12:00am
An international workshop on neutrinos is bringing particle physicists from all over the globe to William & Mary.
NuFact 2012 will be held in Williamsburg July 23-28, jointly sponsored by William & Mary and Jefferson Lab. Jeff Nelson, the Cornelia B. Talbot Term Distinguished Associate Professor of Physics at William & Mary, is one of the organizers of the conference, along with fellow physicists Robert McKeown, Patricia Vahle and Michael Kordosky.
Wed, 07/18/2012 - 12:00am
Mon, 07/16/2012 - 12:00am
Fri, 06/29/2012 - 06:24pm
Fri, 06/15/2012 - 12:00am | <urn:uuid:262ab091-9378-4740-b66f-3e19ffdcd016> | 2.59375 | 1,757 | Content Listing | Science & Tech. | 48.937232 | 95,603,611 |
The greens and blues of the ocean color from NASA satellite data have provided new insights into how climate and ecosystem processes affect the growth cycles of phytoplankton—microscopic aquatic plants important for fish populations and Earth’s carbon cycle.
At the bottom of the ocean’s food chain, phytoplankton account for roughly half of the net photosynthesis on Earth. Their photosynthesis consumes carbon dioxide and plays a key role in transferring carbon from the atmosphere to the ocean. Unlike the plant ecosystems on land, the amount of phytoplankton in the ocean is always followed closely by the abundance of organisms that eat phytoplankton, creating a perpetual dance between predators and prey.
Phytoplankton bloom (green and blue swirls) near the Pribilof Islands off the coast of Alaska, in the Bering Sea. The turquoise waters are likely colored by a type of phytoplankton called coccolithophores. This Sept. 22, 2014, image was created with Landsat 8 data.
Image Credit: NASA's Goddard Space Flight Center, Norman Kuring; USGS
This new analysis shows how tiny imbalances in this predator-prey relationship, caused by environmental variability, give rise to massive phytoplankton blooms, having huge impacts on ocean productivity, fisheries and carbon cycling. The study was released Thursday, Sept. 25, in the journal Nature Climate Change.
“The continuous year-in and year-out measurements provided by NASA’s ocean color satellites have dramatically changed our understanding of phytoplankton dynamics on the Earth,” said Mike Behrenfeld, author of the study and phytoplankton ecologist at Oregon State University, Corvallis, Oregon. “What we now see is a closely linked system of phytoplankton cell division and consumption lying at the heart of the plant’s annual cycle.”
Behrenfeld calls this close predator-prey relationship the “Dance of the Plankton.” This view is different from previous perspectives that have simply focused on environmental resources used by phytoplankton to grow, such as nutrients and light. The new view is important because it reveals that tiny imbalances can greatly impact Earth’s ecology.
Over the past few years, Behrenfeld has collaborated with Emmanuel Boss at the University of Maine, Orono; David Siegel at the University of California, Santa Barbara; and Scott Doney at Woods Hole Oceanographic Institute, Woods Hole, Massachusetts, to develop a new theoretical framework for explaining phytoplankton blooms, which they call the “Disturbance-Recovery Hypothesis.” According to this view, blooms can be started by any process that disturbs the natural balance between phytoplankton and their predators.
A disturbance may involve deep mixing of the surface ocean by storms, bringing up deep ocean water along coasts (known as coastal upwelling), a river flowing into the ocean or even an intentional disturbance such as fertilizing ocean ecosystems with iron. The new study is focused on the second part of the hypothesis – how plankton ecosystems recover once they have been disturbed.
Behrenfeld explained that in ocean ecosystems, the activities of the phytoplankton are closely followed by the organisms that consume phytoplankton, in a sense, similar to two balls connected by a rubber band. If one ball is hit with a paddle, it will accelerate ahead of the other ball. Once the lead ball starts to slow down, the other ball will catch it, even if the lead ball is still moving forward.
“Basically, phytoplankton are rubber-banded to their predators,” Behrenfeld said. “As long as the phytoplankton are accelerating in their division rate, they’ll stay ahead. As soon as they slow down, the predators that have been increasing along with the phytoplankton will quickly catch up, stop the bloom by consuming the phytoplankton, and then begin decreasing the numbers of phytoplankton.”
Using data from NASA’s Moderate Resolution Imaging Spectrometer (MODIS), Behrenfeld shows how tight predator-prey relationships are a common feature of plankton ecosystems across the global ocean. Even in regions where phytoplankton blooms do occur, they result from only minor imbalances in this relationship. By focusing on the North Atlantic Ocean, where one of the largest phytoplankton blooms happens each year, the study shows how deeper winter mixing gives rise to larger phytoplankton stocks. This finding is important because it suggests that ocean warming over the coming century, which will decrease winter mixing, may significantly decrease peak phytoplankton stocks.
Behrenfeld also tracked the annual cycles of phytoplankton over a 10-year period in the North Atlantic using data from NASA’s Sea-viewing Wide Field-of-view Sensor (SeaWiFS). He showed for the first time how changes in phytoplankton populations over time are governed by periods of accelerating and decelerating division rates. This discovery finally connects the start of a phytoplankton bloom to its final climax, which may occur many months later.
“Understanding the plankton ecosystem and how it responds to variability is very important for preparing and looking forward to how Earth’s system changes,” said Behrenfeld. “The environmental conditions that start and then sustain phytoplankton blooms are, in many cases, the same environmental factors that are impacted by climate change.”
The next steps are to understand how species succession impacts bloom development and to learn how the carbon dioxide taken up by phytoplankton is processed within plankton ecosystems and then transferred and stored in the deep ocean. These advances are critical for understanding how changes in phytoplankton blooms translate to impacts on fisheries and climate. These challenging goals will require a greater integration of satellite, modeling and field studies.
“Current satellites, such as Terra and Aqua, monitor changes in phytoplankton abundance that continuously occur across the globe,” said Behrenfeld. These changes reflect complex biological and physical interactions within ocean ecosystems. Understanding how these interactions function in today’s ocean is essential to predicting how marine ecosystems will change in the future.” Future missions, such as the Pre-Aerosol, Clouds, and ocean Ecosystem (PACE) mission, will further elucidate the plankton dynamics and responses to climatic shifts in the ocean.
Patrick Lynch | Eurek Alert!
Abrupt cloud clearing events over southeast Atlantic Ocean are new piece in climate puzzle
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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23.07.2018 | Life Sciences | <urn:uuid:fdd2f695-e4f6-4b62-ab44-8b3c3b7e3da9> | 3.921875 | 1,994 | Content Listing | Science & Tech. | 32.065358 | 95,603,622 |
With 46 chromosomes and six feet of DNA to copy every time most human cells divide, its not surprising that gaps or breaks sometimes show up in the finished product – especially when the cell is under stress or dividing rapidly, as in cancer.
But what is surprising – according to Thomas Glover, Ph.D., a geneticist at the University of Michigan Medical School – is that the breaks dont always occur at random. They happen at a few specific locations on chromosomes, when cells are under stress, during the stages in the cell cycle where DNA is copied, or replicated, and the cell splits into two identical daughter cells.
Scientists call them fragile sites, but the reasons for their inherent instability have remained a mystery. Now Glover and colleagues at the U-M Medical School and the Howard Hughes Medical Institute have discovered that a protein called ATR protects fragile sites from breaking during DNA replication. Results of their research will be published in the Dec.13 issue of Cell.
Sally Pobojewski | 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....
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23.07.2018 | Life Sciences | <urn:uuid:5170dbeb-bcfe-4728-be04-8560c9759bd4> | 3.5625 | 790 | Content Listing | Science & Tech. | 40.746339 | 95,603,623 |
Could the common cold virus help to treat a deadly cancer?
How the parasite Toxoplasma gondii adapts its growth rate to its environment
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And why is salt a problem?
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The new blood test to detect heart attacks. Plus, what's the difference between a heart attack and cardiac arrest?
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Distant twin-sun 'Tatooine' solar system could have habitable moon, say astronomers
- Earth-like moon could orbit two suns of Kepler-16 system
- Habitable moon would be shrouded in CO2 or methane
- Team urges Nasa to look for 'extrasolar moon'
A group of astrophysicists from The University of Texas at Arlington suggests a habitable Earth-like planet could exist in a distant solar system found by Nasa’s Kepler space telescope.
Kepler-16 has two stars, like Star Wars’ fictional Tatooine. Kepler-16 System made headlines in September when researchers discovered Kepler-16b, a cold, gaseous planet orbiting both stars.
The UT Arlington team, have concluded that an Earth-type planet could exist in the system’s ‘habitable zone’ – as a moon orbiting Kepler-16b.
The Kepler-16 System made headlines in September when researchers discovered Kepler-16b, a cold, gaseous planet orbiting both stars. The team has concluded that an Earth-type planet could exist in the system¿s ¿habitable zone¿ ¿ as a moon orbiting Kepler-16b
To host life in that zone, a terrestrial planet orbiting the two stars
would need to have high levels of greenhouse gases in its atmosphere
such as carbon monoxide or methane, they said.
UT Arlington Department of Physics professor Zdzislaw Musielak said, ‘This is an assessment of the possibilities. We’re telling them where a planet has to be in the system to be habitable. We’re hoping they will look there.’
‘There is less light from the star, so the planet itself has to maintain more heat,’ said PhD student Billy Quarles, one of the co-authors on the paper.
Science fiction: The notion of a planet wth two suns may seem familiar - because Luke Skywalker lived on one in Star Wars
Kepler's mission is to scour our section of the Milky Way galaxy for Earth-like planets in the so-called 'habitable zone' that is not too close and not too far away from the stars they orbit.
The spacecraft does this by finding stars whose light periodically gets dimmer, which means there is a planet passing between the star and Kepler's instruments. This is known as a planetary transit.
If the notion of a planet with two suns was displayed in the earliest Star Wars film on the fictional planet Tatooine, home of Luke Skywalker.
Tatooine was a rocky, desert planet, but Kepler-16b is a cool gas giant, Boss and other researchers said.
Extraordinary: An artist's illustration of Kepler-16b, the first planet known to orbit two stars
Kepler-16b is similar to Saturn in
size and mass, a cold gas giant that orbits its two suns every 229 days
at a distance of 65 million miles (104.6 million km).
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Species Detail - Brünnich's Guillemot (Uria lomvia) - Species information displayed is based on all datasets.
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
8 August (recorded in 2006)
24 December (recorded in 1986)
National Biodiversity Data Centre, Ireland, Brünnich's Guillemot (Uria lomvia), accessed 16 July 2018, <https://maps.biodiversityireland.ie/Species/10183> | <urn:uuid:c006cc73-cd5f-47ea-a9a1-8c6c3762ee6d> | 2.703125 | 145 | Structured Data | Science & Tech. | 46.098 | 95,603,634 |
A comprehensive, 21-year analysis of the fastest-melting region of Antarctica has found that the melt rate of glaciers there has tripled during the last decade.
The glaciers in the Amundsen Sea Embayment in West Antarctica are hemorrhaging ice faster than any other part of Antarctica and are the most significant Antarctic contributors to sea level rise.
This study is the first to evaluate and reconcile observations from four different measurement techniques to produce an authoritative estimate of the amount and the rate of loss over the last two decades.
“The mass loss of these glaciers is increasing at an amazing rate,” said scientist Isabella Velicogna, jointly of the UC Irvine and NASA’s Jet Propulsion Laboratory. Velicogna is a coauthor of a paper on the results, which has been accepted for Dec. 5 publication in the journal Geophysical Research Letters.
Lead author Tyler Sutterley, a UCI doctoral candidate, and his team did the analysis to verify that the melting in this part of Antarctica is shifting into high gear.
“Previous studies had suggested that this region is starting to change very dramatically since the 1990s, and we wanted to see how all the different techniques compared,” Sutterley said. “The remarkable agreement among the techniques gave us confidence that we are getting this right.”
The researchers reconciled measurements of the mass balance of glaciers flowing into the Amundsen Sea Embayment. Mass balance is a measure of how much ice the glaciers gain and lose over time from accumulating or melting snow, discharges of ice as icebergs, and other causes. Measurements from all four techniques were available from 2003 to 2009. Combined, the four data sets span the years 1992 to 2013.
The glaciers in the embayment lost mass throughout the entire period. The researchers calculated two separate quantities: the total amount of loss, and the changes in the rate of loss.
The total amount of loss averaged 83 gigatons per year (91.5 billion U.S. tons). By comparison, Mt. Everest weighs about 161 gigatons, meaning the Antarctic glaciers lost a Mt.-Everest’s-worth amount of water weight every two years over the last 21 years.
The rate of loss accelerated an average of 6.1 gigatons (6.7 billion U.S. tons) per year since 1992.
From 2003 to 2009, when all four observational techniques overlapped, the melt rate increased an average of 16.3 gigatons per year — almost three times the rate of increase for the full 21-year period. The total amount of loss was close to the average at 84 gigatons.
The four sets of observations include NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites, laser altimetry from NASA’s Operation IceBridge airborne campaign and earlier ICESat satellite, radar altimetry from the European Space Agency’s Envisat satellite, and mass budget analyses using radars and the University of Utrecht’s Regional Atmospheric Climate Model.
The scientists noted that glacier and ice sheet behavior worldwide is by far the greatest uncertainty in predicting future sea level. “We have an excellent observing network now. It’s critical that we maintain this network to continue monitoring the changes,” Velicogna said, “because the changes are proceeding very fast.”
About the University of California, Irvine: Founded in 1965, UCI is the youngest member of the prestigious Association of American Universities. The campus has produced three Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UCI has more than 30,000 students and offers 192 degree programs. Located in one of the world’s safest and most economically vibrant communities, it’s Orange County’s second-largest employer, contributing $4.8 billion annually to the local economy.
Media access: Radio programs/stations may, for a fee, use an on-campus ISDN line to interview UC Irvine faculty and experts, subject to availability and university approval. For more UC Irvine news, visit news.uci.edu . Additional resources for journalists may be found at communications.uci.edu/for-journalists.
Janet Wilson | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences
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Morpho-sedimentary features and sediment dispersal systems of the southwest end of the Ryukyu Trench: a source-to-sink approach
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The southwestern Ryukyu Trench near Taiwan is an ideal place for source-to-sink studies because of the short sediment transport route between the terrestrial sediment source in Taiwan and the marine sink in the Ryukyu Trench. Bathymetric and seismic reflection data and core samples from the area around the southwestern Ryukyu Trench were used to identify features of the trench–arc system, including submarine canyons, the trench wedge, bathymetric ridges, and forearc basins, which together form two distinct sediment dispersal systems: a longitudinal (trench-parallel) system and a transverse (trench-normal) system. The longitudinal sediment dispersal system carries sediments eroded from the Taiwan orogenic belt eastward, primarily along the Hualien Canyon and a channel–terminal fan system at its mouth, and deposits them in the southwestern end of the Ryukyu Trench. The transverse sediment dispersal system carries sediments eroded from the Ryukyu Islands downslope and deposits them in the Hoping, Nanao, East Nanao, and Hateruma forearc basins, behind the barrier formed by the E–W-trending Yaeyama Ridge on the trench-slope break. The presence of pyrrhotite, a characteristic component of sediments sourced from Taiwan, in a seafloor sample from the Ryukyu Trench and its absence in a sample from the East Nanao forearc basin support the view that the southwestern Ryukyu Trench is longitudinally fed by sediment derived from Taiwan, whereas the trench-slope forearc basins receive sediment transported transversely downslope from the Ryukyu Islands.
The authors gratefully recognize the efforts of Captain Takafumi Aoki and the crew of R/V Kairei during the KR15-18 survey. The cruises YK15-01 and KR15-18 were supported by the research project for Compound Disaster Mitigation on the Great Earthquakes and Tsunamis Around the Nankai Trough Region of the Japanese Ministry of Education, Culture, Sports, Science and Technology, Japan. We thank the Ministry of Science and Technology, Taiwan, for permission to use bathymetric and seismic reflection data stored in the Ocean Data Bank, National Taiwan University, Taiwan. We are grateful to Prof. H.S. Yu for constructive comments on our interpretations of seismic reflection profiles. The article benefitted from helpful assessments by two reviewers.
Compliance with ethical standards
Conflict of interest
The authors declare that there is no conflict of interest with third parties.
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Vorticity annihilation and inviscid blocking in multibody flows
Many environmental and processing engineering flows consist of collections of fixed or moving bodies (such as buildings, plants, bubbles and droplets). These flows may be unbounded or bounded high Reynolds number flows through groups of bodies, such as crop ‘canopies’ or buildings in the atmospheric boundary layer, boiler tubes in a furnace, flows through moving objects such as icebergs in the ocean, or bubble swarms in pipes. Examples of buildings in the urban terrain are given in Chapters 2 and 8, while plant canopies are described in Chapters 4 and 6. For many problems, the goal is to model the impact of many bodies on the ambient flow. There is an intrinsic complexity to modelling the flow through and around a group of bodies and estimating the flow signature they generate. In many cases, the huge number of bodies and the range of geometrical lengthscales (eg. from leaf size, to tree size, up to a forest scale, for plant canopies) means that traditional computational models, where the whole flow domain is meshed and solved numerically, are not able to include all the geometrical aspects . As such, average descriptors, such as a distributed drag force introduced into
KeywordsDrag Force Void Fraction High Reynolds Number Plant Canopy Bubble Diameter
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Now, in a new study, scientists take a page from the social science handbook and use leading indicators of the environment to presage the potential collapse of ecosystems. The study, published today (Jan. 5) in the Proceedings of the National Academy of Sciences by two ecologists and an economist, suggests it may be possible to use nature’s leading indicators to avert environmental disaster.
Ecosystems worldwide — lakes, ocean fisheries, coral reefs, forests, wetlands and rangelands — are under constant and escalating pressure from humans and many are on the brink of collapse, according to Stephen R. Carpenter, a University of Wisconsin-Madison professor of zoology and an author of the new study.
“It’s a big problem because they are very hard to predict. It is hard to get a handle on statistically,” says Carpenter of what ecologists call “regime shift,” a disastrous change in the way an individual ecosystem functions. Such change can be dramatic, as in the collapse of the North Atlantic cod fishery or increasing desertification in Africa and the Middle East, and can have serious economic, political and social consequences.
Stephen R. Carpenter, 608-262-8690, firstname.lastname@example.org
The idea of using leading indicators in science is not new. Geologists use seismic indicators to try to predict earthquakes and physicians use measures of such things as cholesterol and blood pressure to try to predict patient health. But applying the same kind of monitoring and statistical tools to forecast the health of ecosystems and, ultimately, to prevent serious ecological harm is only now coming into play, says Carpenter.
In the new study, Carpenter, Reinette Biggs of Stockholm University and William A. Brock, an economist at UW-Madison, used northern Wisconsin’s sport fishery as a laboratory to see if leading indicators of ecological collapse can be detected far enough in advance to avert disaster.
“The answer is ‘yes’ if the policy interventions can be swift and ‘no’ if there are delays,” says Carpenter of the study’s results.
Northern Wisconsin has the largest concentration of freshwater lakes in the world, and the sport fishery is a critical economic engine for the region. The researchers looked at two major threats to the fishery: overfishing and habitat destruction caused by lake home-building and the loss of trees that would otherwise fall into the lake and provide habitat for sport fish.
“If you are a fish, woody habitat is perfect. It’s a place to hide and it has food. It’s like a room with a refrigerator,” says Carpenter. “But there is way less habitat in lakes with a lot of houses. We are particularly concerned about woody habitat loss.”
In both the case of habitat loss and the case of overfishing, indicators of potential harm to the fishery can be detected before a breakdown in the lake ecosystem occurs, Carpenter explains. “However, only in the case of overfishing can policy change fast enough to avert the damage. It is not possible to act fast enough to avert the damage from habitat destruction because it takes too long to grow the trees. In that case, you have to start over.”
The key to avoiding disaster, Carpenter argues, is monitoring: “We really need to be monitoring and analyzing the data from these ecosystems as a way to keep them healthy. Otherwise, by the time the problem surfaces it is too late.”
Carpenter says it is possible to sense impending ecosystem regime shifts by carefully monitoring the changing variables that are likely to damage an environment. For example, daily measuring of chlorophyll in a lake could reveal an impending transition to a state where water quality will decline to the point that plant and animal communities in the lake are at risk.
“The behavior of the system becomes extremely variable in the run up to change. You see a lot of variability, and right at the point of regime shift, it becomes very unstable,” Carpenter notes.
According to Carpenter, in addition to expanded monitoring and analysis of ecosystem data, averting regime shifts depends on effective policy. Enabling society to respond more rapidly to information about looming change, he says, is necessary to keep ecosystems producing the things people need.
Terry Devitt | Newswise Science News
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
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 | Life Sciences
18.07.2018 | Materials Sciences
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Photovoltaic cells “harvest” the photons in sunlight and convert solar energy into electrical energy.
When a solar cell absorbs light, the photons “excite” an electron, which becomes separated from the “positive hole” left behind in the atom. This charge separation is the crucial first step that captures the energy derived from the incident photon. The negative electron migrates to an electrode, and the hole attracts another electron from a neighbouring atom, effectively moving the hole which ultimately migrates to the other electrode. Thus the electrons and the holes are collected at different electrodes giving an electrical potential (voltage). This drives a flow of the electrons (current) round the outer circuit where they can do some work (e.g. light a bulb or turn a motor) before combining with the holes at the other electrode and returning the system to its starting point..
Crystalline silicon cells are solid-state devices which use a continuous lattice of silicon. When the electron is excited, it is easy to separate it from its positive hole because they're both spread out across the “infinite” lattice, so the electrostatic attraction they feel for each other is low.
In a dye-sensitised solar cell (DSSC), the electron and the hole are created in the same way, but they're very close together because they are confined to one small molecule, rather than spread out over a very large lattice. This means there is a strong negative-positive electrostatic attraction between them and they tend to stick together. The electron-hole pair is called an "exciton,” and to get the electrons to flow and produce an electrical current, they are pulled apart using an interface between dissimilar materials – a dye with TiO2 on one side and a redox electrolyte on the other side.
The major difference between DSSC and crystalline silicon cells is therefore that DSSC use molecules rather than an infinite lattice, and also have to use a different mechanism to separate electrons from their positive holes – a process described as "excitonic" because it deals with excitons or electron-hole pairs.
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Tumiskan bawang putih bawang merah n rempas tumis..... Then....tumiskan lada cili yang ditumbuk lumat.... Then....masukkan kari yang dah d...
Mo Salah Top Primier League Top Scorer So Far. He even Scores 4 goals against Watford. I am rooted for him and for Liverpool to keep giv...
Lelaki Malaysia Kahwin Pelakon Terkenal Thailand Aug 02, 2016 Oleh Ezaura Rafe. Sumber Fb Oh Media Seperti yang kita tahu pelakon ... | <urn:uuid:54005732-4534-4f12-a3a7-4447b5d27ebf> | 4.125 | 592 | Personal Blog | Science & Tech. | 43.243499 | 95,603,667 |
Origin of Complex Life
News May 11, 2015
A new Nature study this week provided the strongest evidence yet of this in its description of a new archaeon – found near an arctic hydrothermal vent - with genetic properties of both archaea and eukarya.
“The most surprising moment was when we were a couple of weeks into the project and were were looking at the first datasets that we retrieved from the sequencing center,” senior author Uppsala University microbiologist Thijs Ettema told Bioscience Technology. “We started finding all these 'eukaryotic-type' genes among these archaeal sequences. We very soon realized that this was either a very big and significant find, or some kind of weird artefact. After doing a whole array of checks in order to make sure that we could rule out the latter, we were sure: we found an archaeon that shared several genes uniquely with eukaryotes. When later this archaeon, which we then named Lokiarchaeon, turned out to form a sistergroup with eukaryotes in the Tree of Life, we were ecstatic!”
Until recent years, it has been believed that life at base is comprised of three distinct branches, all of which hailed, individually, from an unknown single ancestor: arachael and bacterial cells, simple cells that lacked nuclei, and complex eukaryotic cells containing nuclei, cytoskeletons, organelles. That three-tree system was proposed by University of Illinois microbiologist Carl Woese, who added a third branch—the archaeal branch—to the tree in 1977.
But at about the same time, a 1967 paper by University of Massachusetts biologist Lynn Margulis began catching on. That unusual paper proposed that humans’ mitochondria, the critical energy packs of our cells, are actually bacteria that were once engulfed by other cells. Genetic analyses backing this up, in addition to other genetic data finding similarities between the life branches, led to doubt the three branches rose independently of each other.
The Uppsala team’s new discovery of Lokiarchaea, which possesses many unique eukaryotic and archaeal qualities, offers what Embley called in a companion commentary “spectacular” evidence that the above independent evolution may indeed not have occurred.
Instead, chaotic, complex eukaryotes like us may have emerged out of a two-billion-year old sea of serene, simple life forms due to the unusual engulfing of a bacteria by an archaea, forming a creature rife with new possibilities.
The new paper identifies “archaeal forms that are much more closely related to the hypothetical archaeal ancestor of eukaryotes than any other currently known group of archaea,” said Koonin. “These findings clinch the case for the origin of eukaryotes from within the archaeal diversity, and point to specific part of the archaeal evolutionary tree where eukaryotes belong.”
Equally importantly, Koonin continued, are the group’s findings that, “Lokiarchaeota combine a number of ‘eukaryotic-like’ features that previously have been found scattered among different archaeal genomes. In particular, they encode components of the actin cytoskeleton, the ESCRT-III system for membrane remodeling, and the ubiquitin system. Taken together, these findings give credence to the evolutionary scenario in which the eukaryotes evolved from an archaeon with a complex cellular organization that might have been capable of engulfing bacteria.”
Embley said that, in terms of clarifying the origins of our mitochondria, “the new Archaea appear to have the potential for endocytosis and/or phagocytosis (cellular incorporation and/or ingestion). This could allow them to take up material from the environment. In some versions of endosymbiotic theory, the host for the mitochondrial endosymbiont uses phagocytosis to engulf the bacterium that became the endosymbiont, and eventually the mitochondrion.”
On the other hand, he noted: “There is no genetic evidence in the new paper that the new Archaea contain any genes from the mitochondrial endosymbiont, so they do not appear to have mitochondria.” But the newly discovered creature’s actin-like proteins may simply indicate, he said, that eukaryotes evolved phagocytosis before acquiring mitochondria.
Did the team prove we are descended from Lokiarchaea-like creatures? “I think that the phylogenetic analyses are carefully done and use state-of-the-art methods,” Embley said. “It is really hard to correctly infer events that may have occurred some two billion years ago. But taken together, the combination of the tree, and the enhanced number of eukaryotic-like proteins, are rather convincing for a close relationship between Lokiarchaea and eukaryotes. I am sure that the new data and analyses will be subjected to very close scrutiny by the community once it is published, and the robustness of the trees and the position of eukaryotes within them, will be carefully tested as part of that process.”
Big Data Study Targets Genomic Dark Matter from Ocean Floor to Gut FloraNews
An international team led by computational biologist Fran Supek at IRB Barcelona develop a machine learning method to predict unknown gene functions of microbes.The system examines and compares ‘big data’ available on the metagenomes of human and environmental microbiomes.READ MORE
Bioethics Council Rules Heritable Genome Editing "Ethically Acceptable" In Certain CircumstancesNews
A leading UK bioethics advisory body has weighed in on the debate around human genetic modification, concluding that heritable genome editing – modifying the DNA of an egg, sperm or embryo with changes that will be passed on to future generations – could be ‘morally permissible’ in humans, provided key ethical tests are met.
Getting to Know the Microbes that Drive Climate ChangeNews
A new understanding of the microbes and viruses in the thawing permafrost in Sweden may help scientists better predict the pace of climate change.READ MORE | <urn:uuid:78bf89d5-29bf-43fa-bbaa-0ef3ab954224> | 3.46875 | 1,320 | News Article | Science & Tech. | 17.179933 | 95,603,678 |
But a third option may have just become feasible. For a long time, people have dreamed about technology that would allow carbon to be pulled out of the air and stored in the ground or recycled into fuel. Now, a team of Harvard scientists is claiming they have a much cheaper way to do this.
The scientists, led by David Keith — who has also formed a company called Carbon Engineering to commercialise his invention — have been testing technology at a pilot facility in Canada for years. Their claim — which some other experts find believable — is that they can remove carbon dioxide from the atmosphere much more cheaply than previous approaches, with greater cost reductions still to come.
Direct air capture is a crucial piece of the puzzle in lowering carbon levels. There’s really no other way to get rid of the carbon that’s already in the atmosphere, other than waiting the decades or centuries it takes to go away on its own. This technology will help humanity go beyond simply avoiding further damage to the planet’s environment, and fix some of the damage we have already caused.
Also, direct air capture is a way to do deep decarbonisation without waiting for renewables to become dirt-cheap. On the margin, emissions reduction — through energy efficiency, reforestation and renewable energy — is still cheaper than pulling carbon out of the air. But deep decarbonisation — reducing emissions not by a small percent, but by large amounts — would still be extremely expensive, which is why no one is doing it yet.
However, unlike emissions reduction, direct air capture’s economic costs probably don’t balloon — building 100 carbon-capture facilities should be more or less 100 times as expensive as building one. The inventors of the new technique estimate that if costs continue to fall as they expect, they could capture all the carbon the world emits for only 5% of global economic output.
Those predictions are probably overly rosy. And 5% of global output is still trillions of dollars. A much more realistic scenario is for nations to use carbon removal as a supplement to renewable energy and energy efficiency. Even spending 1% of global GDP would require a huge commitment by many industrial nations; and developed countries would probably be asked to foot more of the bill, having already emitted a lot of carbon in the past. There will be many political sticking points.
But carbon capture is now at least moving out of the realm of science fiction and into the realm of the possible. Stopping climate change will still require a large, global, co-ordinated effort, combining carbon taxes (or similar policies, such as cap-and-trade), continued advances in renewable energy, and government-funded carbon capture. But thanks to the magic of human innovation, we will be able to save the planet while also preserving our modern industrial society and keeping the engine of economic growth humming. | <urn:uuid:8bbf569c-d584-410e-9984-760a7bf5b063> | 4.25 | 581 | Personal Blog | Science & Tech. | 36.396565 | 95,603,700 |
Code reuse can make coding simpler and more efficient for program development. esProc supports basic code reuse by loop, as well as the modular programming in which a subroutine an external cellset is called. Here we’ll explain how to call a subroutine and a cross-cellset program in esProc.
1. Subroutine call
2015-02-02 30 0
esProc has some special ways to produce more orderly and more readable code, among which long statements and computational sub-statements will be illustrated in this article.
1. Long statements
If a long expression cannot be fully displayed when written in a single cell, one can write it in multiple cells according to ...
2015-01-29 34 0
The strings in esProc sometimes include some special identifiers that may cause ambiguity about the expression. So does the names of fields in a table sequence sometimes. The following will teach you how to deal with them properly.
1. Special identifiers in strings
A string may include various signs, some of which coul...
2015-01-09 34 0
In esProc, the storage of cellset variables is ubiquitous. Cell values are convenient references during computation, but they could occupy too much memory. Data can be cleared from cells to reduce memory footprint after they accomplish their mission in computation. It should be particularly noted that, when the interme...
2015-01-05 25 0
In esProc, strings are not merely a data type; they can also be used as macros or string constants to construct expressions, or employed by eval() function to generate expressions dynamically as needed.
Macros in esProc refer to strings for composing expressions, only that these strings are usually generated d...
2014-12-26 32 0
In esProc Getting Started: Types of Cells, we learned that cells in esProc have many types, including constant cell, computational cell, executable cell and comment cell, and etc. The code blocks into which code is written in esProc also have the similar types: computational block, assignment block, executable block an...
2014-12-25 30 0 | <urn:uuid:c84fb697-35b1-4de2-a91e-42c0e668453d> | 2.65625 | 445 | Content Listing | Software Dev. | 58.487499 | 95,603,706 |
The team, funded by a National Science Foundation (NSF) grant, collected data Oct. 4 through Oct. 11 to document the impacts of the 8.1 earthquake and the ensuing tsunami that occurred on Sept. 29. They examined flow depths, run-up heights, inundation distances, sediment depositions and damage patterns at various scales.
“In addition to timing – the fact that the tsunami struck in the daylight morning hours when most people were on their way to work or school – tsunami education, awareness and evacuation exercises really contained the death toll,” noted Hermann Fritz, one of the principal investigators and an associate professor of civil and environmental engineering at the Georgia Institute of Technology. “The technical solution doesn’t always work for coastlines near the epicenter with less than 30 minutes between earthquake and onslaught of the tsunami. Earthquakes with durations of more than 30 seconds serve as a natural warning, resulting in a spontaneous self-evacuation.”
Nearly 190 people were killed in the tsunami, with the majority of deaths reported in Samoa, a country governing the western part of the Samoan Islands in the South Pacific Ocean. The two main islands of Samoa are Upolu and Savai’i. American Samoa, a territory of the United States southeast of Samoa, is comprised of main island Tutuila, the Manu’a Islands, Rose Atoll and Swains Island. The Samoan government estimates the total damage from the tsunami at $147 million.
The team’s survey circled all of the main Samoan islands and spanned 350 kilometers from Ofu in the east to Savai’i in the west. The researchers learned that the tsunami impact peaked at Poloa near Tutuila’s western tip and Lepa at Upola’s southeast coast. Maximum run-up heights reached 17 meters at Poloa, and inundation distances and damage were recorded at Pago Pago, more than 500 meters inland. The harbor at Pago Pago, well-protected from ordinary storm waves, is vulnerable to long-period tsunami waves.
In addition, researchers noticed a marked difference between the evacuation process in Samoa and American Samoa. While most villagers in Samoa knew to rapidly evacuate after experiencing an earthquake, only a month earlier they had been told that cars help with evacuations, a deadly directive since most roads run parallel to the beach.
“Many perished trapped inside cars waiting in congested small roads or in long lines behind vehicles stopped by landslides or debris on the road,” said Costas Synolakis, principal investigator and professor of civil engineering at University of Southern California. “I have been on more than 20 tsunami field surveys, and in many ways this was one of the most surprising in terms of how carnage varied over fairly short distances. This was also the first time we noted what we suspected: misinformation kills.”
Emile Okal, a seismologist and professor of earth and planetary sciences at Northwestern University, conducted approximately 120 interviews with tsunami survivors in 70 different locations around Tutuila and Upolu. He found that most people were educated about tsunamis and knew how to react because of community-based educational programs, not ancestral stories.
“The last significant tsunami in Samoa occurred in 1917 and was very similar in seismology to the Sept. 29 tsunami. Surprisingly, no one I interviewed said they knew of family members being in a similar situation,” Okal observed. “Since the 2004 Indian Ocean tsunami and the 2007 Solomon Islands tsunami, there has been a concerted effort on the part of the local government in American Samoa to post signs and conduct evacuation drills in some Samoan communities. Many villages were completely destroyed, so I am impressed that the death toll was not larger. The bottom line is education worked.”
While Synolakis agreed that the death toll was probably minimized due to educational efforts, he said there is still a lot of progress that can be made. While working in the field on Oct. 7, the team experienced a real tsunami warning and witnessed first-hand the tremendous confusion and disorganization that followed.
“Although there are warning signs along the beaches in American Samoa, there is no information about where the evacuation routes are,” he said. “It’s also just as important to let people know when it’s safe to come back as it is to warn them. We definitely have our work cut out for us.”
The collected field data serves as benchmarking and validation of numerical tsunami models with wide-ranging applications including forecasting, warning and sediment transport. The researchers will present their findings at special sessions at the American Geophysical Union Fall Meeting in San Francisco this December. Brief publications summarizing the immediate results will follow in research journals.
This survey was partially supported by the Pacific Earthquake Research Center (PEER).
Nancy Fullbright | Newswise Science News
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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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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Supercomputing simulations at the Department of Energy's Oak Ridge National Laboratory could change how researchers understand the internal motions of proteins that play functional, structural and regulatory roles in all living organisms. The team's results are featured in Nature Physics.
"Proteins have never been seen this way before," said coauthor Jeremy Smith, director of ORNL's Center for Molecular Biophysics and a Governor's Chair at the University of Tennessee (UT). "We used considerable computer power to provide a unified conceptual picture of the motions in proteins over a huge range of timescales, from the very shortest lengths of time at which atoms move (picoseconds) right up to the lifetimes of proteins in cells (roughly 1000 seconds). It changes what we think a protein fundamentally is."
This is an illustration of the structure of a phosphoglycerate kinase protein that was subjected to molecular dynamics simulations. The relative motions of the red and blue domains of the proteins are highly complex, and can be described in terms of motion of a configurational point on a rough energy landscape (illustrated). The transitions of the structure between energy minima on the landscape can be described in terms of a network (illustrated), which is found to be fractal (self-similar) on every timescale.
Credit: Thomas Splettstoesser; http://www.scistyle.com
Studying proteins--their structure and function--is essential to advancing understanding of biological systems relevant to different energy and medical sciences, from bioenergy research and subsurface biogeochemistry to drug design.
Results obtained by Smith's UT graduate student, Xiaohu Hu, revealed that the dynamics of single protein molecules are "self-similar" and out of equilibrium over an enormous range of timescales.
With the help of Titan-- the fastest supercomputer in the U.S., located at the DOE Office of Science's Oak Ridge Leadership Computing Facility--Smith's team developed a complete picture of protein dynamics, revealing that the structural fluctuations within any two identical protein molecules, even if coded from the same gene, turn out to be different.
"A gene is a code for a protein, producing different copies of the protein that should be the same, but the internal fluctuations of these individual protein molecules may never reach equilibrium, or converge," Smith said. "This is because the fluctuations themselves are continually aging and don't have enough time to settle down before the protein molecules are eaten up in the cell and replaced."
Understanding the out-of-equilibrium phenomenon has biological implications because the function of a protein depends on its motions. Two individual protein molecules, even though they come from the same gene, will not function precisely the same way within the cell.
"You may have, for example, two identical enzyme molecules that catalyze the same reaction," said Smith. "But due to the absence of equilibrium, the rate at which the catalysis happens will be slightly different for the two proteins. This affects the biological function of the protein."
The team also discovered that the dynamics of single protein molecules are self-similar, or fractal over the whole range of timescales. In other words, the motions in a single protein molecule look the same however long you look at them for, from picoseconds to hundreds of seconds.
"The motions in a protein, how the bits of the protein wiggle and jiggle relative to each other, resemble one another on all these timescales," Smith said. "We represent the shape of a protein as a point. If it changes its shape due to motions, it goes to a different point, and so on. We joined these points, drawing pictures, and we found that these pictures are the same when you look at them on whatever timescale, whether it's nanoseconds, microseconds, or milliseconds."
By building a more complete picture of protein dynamics, the team's research reveals that motions of a single protein molecule on very fast timescales resemble those that govern the protein's function.
To complete all of the simulations, the team combined the power of Titan with two other supercomputers--Anton, a specialty parallel computer built by D.E. Shaw Research, and Hopper, the National Energy Research Scientific Computing Center's Cray XE6 supercomputer located at Lawrence Berkeley National Laboratory.
"Titan was especially useful for us to get accurate statistics," Smith said. "It allowed us to do a lot of simulations in order to reduce the errors and get more confident results."
The title of the Nature Physics paper is "The Dynamics of Single Protein Molecules is Non-Equilibrium and Self-Similar Over Thirteen Decades in Time."
This research was supported by the DOE Office of Science through an Advanced Scientific Computing Research (ASCR) Leadership Computing Challenge (ALCC) allocation and funded in part by a DOE Experimental Program to Stimulate Competitive Research (EPSCoR) award. The Oak Ridge Leadership Computing Facility and National Energy Research Scientific Computing Center are DOE Office of Science User Facilities.
ORNL is managed by UT-Battelle for the Department of Energy's Office of Science. DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.
NOTE TO EDITORS: You may read other press releases from Oak Ridge National Laboratory or learn more about the lab at http://www.
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Morgan McCorkle | 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....
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03.07.2018 | Event News
23.07.2018 | Health and Medicine
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23.07.2018 | Science Education | <urn:uuid:75b4ae4a-e8e8-44c7-a1c7-b8e3ef8c4384> | 3.28125 | 1,745 | Content Listing | Science & Tech. | 35.887573 | 95,603,742 |
Discovering a new planet or having an extra-terrestrial object like an asteroid named after them perhaps tops the wishlist of many astronomy enthusiasts, including school students.
Over the past 6 years, several amateur astronomers and students from across the country have made discoveries facilitated by city-based organisation SPACE under its educational outreach programme, the All India Asteroid Search Campaign (AIASC).
Asteroids are large numbers of small rocky bodies orbiting the sun that range enormously in size and can be typically found between the orbits of Mars and Jupiter. Astronomers vie with one another to be the first to spot them.
Now, under its AIASC for 2016, SPACE, in collaboration with the International Astronomical Search Collaboration (IASC), conducted by Patrick Miller from Hardin Simmons University in the US is offering students from India a chance to add to NASA’s database of asteroids hurtling in space.
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90 teams, of 2 participants each per team, from across the country have been selected for the programme that begins on June 27 and is spread out over two phases till August 23.
The overall purpose of the Asteroid Grand Challenge (AGC), a large-scale effort under NASA, is to encourage students and citizen scientists to identify and document asteroids in earth’s environment in order to assess their threat to the planet and also study them.
“The experience was great and I got to learn a lot,” says Amanjot Singh, who was the first to discover an object from Asia in 2010, as a student in class XI. Singh says he was enthused by the experience and has now joined SPACE as an instructor.
Under AIASC programme students and amateur astronomers get an opportunity to explore and study astronomy in a hands-on and detailed approach. The campaign gives the participants access to astronomy images, as well as opportunities to interact with international scientists.
This year’s participants are set to be also recognised for their contributions in the form of ‘digital badges’, that they can showcase on various social media networks like Facebook, Twitter and LinkedIn.
“A concept borrowed from gaming, a digital badge is a validated display of achievement, skill, quality or interest and the completion of specific tasks will allow the participants to apply for the AGC recognised badge related to the specified criteria,” says Mila Mitra, Scientific Officer, SPACE.
Also, says, Mitra, images captured from the Pan-STARRS telescope in Hawaii will be sent to the participants to study and detect asteroids.
Participants in this year’s aestroid search campaign seem excited for what is in store in the next few months.
Sathya Hari, a student from DPS Gurgaon says, “This is a huge opportunity and I’m excited to be a part of it. In a workshop we were taught all about software Astrometrica.
“It was a very interactive workshop and I didn’t even have to revise when I got home. We were told that we would get the opportunity to track a lot of objects this time, it sounds very exciting” he says.
Other participants echo his enthusiasm.
Neelabh Singh from Amity International School found the workshop entertaining and informative and says he is excited to learn the asteroid-finding software.
“Everyone is excited to find an asteroid, even though it is difficult to find one. This is a good opportunity we have,” he says.
The feeling of discovering an object is “life-changing” according to Vikrant Narang, one of the first ‘discoverers’.
“It is no doubt, life-changing. The feeling of discovering something not known is incredible” he says.
It is this life-changing feeling that students want to experience, each hoping to carve themselves a little space in history. | <urn:uuid:99711de3-2965-406a-b0ad-c917a47222c3> | 3.125 | 866 | News Article | Science & Tech. | 32.863595 | 95,603,754 |
The UN General Assembly has taken a first step toward establishing a Global Pact for the Environment, in a move opposed by the United States, Russia, and a handful of other nations. The pact would be aimed at finding gaps in protection of the environment around the globe and taking steps to address them. By a 142-5 vote on May 10, the 193-member world body approved a resolution to start identifying those gaps in international environmental laws. Under the resolution, UN Secretary-General Antonio Guterres is asked to produce a report on environmental gaps for the next General Assembly session starting in September. It also establishes a working group to discuss possible options for addressing any gaps, with a view to making recommendations to the assembly in 2019. The proposal passed despite opposition from the United States, Russia, Turkey, Syria, and the Philippines, but it has been championed by French President Emmanuel Macron. It ultimately could lead to adoption of an … [Read more...] about UN Endorses Plan To Address Gaps In Protecting Global Environment
Gases contribute to global warming
According to an international study, the tourism sector accounts for 8% of all anthropogenic emissions of CO2, and its carbon footprint could increase significantly due to a lack of regulations. EURACTIV’s partner le Journal de l’environnement reports. With low-cost flights and long distance holidays at discounted prices, tourism has become an activity responsible for a high level of greenhouse gas emissions (GHG), a trend which will continue to increase in the coming years if the demand for tourism continues to grow. This is not the first time the carbon footprint of tourism is evaluated. In 2007, the World Tourism Organisation (UNWTO) estimated the volume of carbon dioxide emissions caused by tourism to be 5% of the global carbon footprint, the equivalent of 1.3 billion tonnes of CO2 per year. Carbon emissions only Manfred Lenzen, a physicist from the University of Sydney and one of the authors of the study, believes the evaluation of the previous study to be undervalued … [Read more...] about Tourism’s growing contribution to GHG emissions
by Press Association 04/03/2018, 2:13 pm FacebookTwitterWhatsAppEmail Send us a story Sign up to our Daily newsletter A fascinating video of ice being dropped 90 metres into an Antarctic glacier has been shared thousands of times on Twitter – and it’s sure to appeal to your inner child. Climate scientist Peter Neff dropped the ice into the deep borehole and posted the video – for which you’ll certainly want the sound on. “The resulting noise is so unexpected and fascinating,” Peter told the Press Association. “The holes are beautiful blue portals.” Those holes are from Taylor Glacier in the McMurdo Dry Valleys of Antarctica, where Peter and his team were drilling to recover ice cores and study the gases trapped inside. “Glacier ice traps ancient air, caught in the space between snowflakes as they are slowly compressed into ice,” Peter said. “You can nicely see this in the image I’ve included of … [Read more...] about This captivating video of ice dropping down a 90-metre hole needs to be watched with the sound on
In the fight against climate change, much of the focus rests on reducing our dependence on fossil fuels and developing alternative energy sources. However, the results of a new study suggest that far more attention should be paid to deforestation and how the land is used subsequently – the effects of which make a bigger contribution to climate change than previously thought. The research, conducted by Cornell University and published in the journal Environmental Research Letters,shows just how much this impact has been underestimated. Even if all fossil fuel emissions are eradicated, if current rates of deforestation in the tropics continue through to 2100 then there will still be a 1.5 degree Celsius increase in global temperature. Most scientists believe that a temperature increase of 1.5 degrees above pre-industrial levels will bring dangerous disruption to the world's climate. Indeed, many already think this target may be unattainable. "A lot of the emphasis of climate policy … [Read more...] about Deforestation has double the effect on global warming than previously thought
Mount Agung on the Indonesian island of Bali is on the verge of a full-scale eruption with huge quantities of ash and dust spewed into the atmosphere as local authorities attempt to evacuate more than 100,000 people from the danger zone. On Tuesday (28 November), the country's National Disaster Management Authority declared the highest level of alert for the volcano. The number of eruptions was increasing and a large explosion was possible, they warned. Although scientists are unable to predict exactly how events will play out, the current ejection of ash, lava and other materials is likely to continue for weeks. There is even a chance that the eruptions could affect the global climate. When volcanoes erupt they throw millions of tonnes of ash and dust particles, as well as gases, into the atmosphere. Larger particles fall to the surface fairly quickly but smaller particles can accumulate to such an extent that solar radiation is blocked, creating a cooling effect on the area below. … [Read more...] about Could Bali’s Mount Agung eruption affect global climate? | <urn:uuid:0b0f2472-bebd-4392-9579-cf7667efaa1d> | 3.03125 | 1,076 | Content Listing | Science & Tech. | 41.717689 | 95,603,756 |
Atom used in radiocarbon dating
Radiocarbon dating is a method of estimating the age of organic material.It was developed right after World War II by Willard F.The fraction of the radiation transmitted through the dead skin layer is estimated to be 0.11.Small amounts of carbon-14 are not easily detected by typical Geiger–Müller (G-M) detectors; it is estimated that G-M detectors will not normally detect contamination of less than about 100,000 disintegrations per minute (0.05 µCi).
Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples.This is called the half-life—the amount of time required for one-half of a given number of atoms to disintegrate. The plot of the number of tiles as a function of the number of turns looks like this: Again, I made radioactive spheres disappear when they decayed.This is fine, because when carbon-14 decays, it produces nitrogen-14. But you could imagine that if you knew that the sample started with 20 percent blue spheres and you knew their half-life, then you could determine the age by examining one frame from the animation.The older a sample is, the less (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by this process date to around 50,000 years ago, although special preparation methods occasionally permit accurate analysis of older samples.The idea behind radiocarbon dating is straightforward, but years of work were required to develop the technique to the point where accurate dates could be obtained. | <urn:uuid:220ad929-a521-4053-9562-e67ad3f7b61f> | 3.734375 | 362 | Knowledge Article | Science & Tech. | 43.289934 | 95,603,762 |
Scientists found some brain cells whose signals reflect our interpretation of an imageŚnot so much the image itself
- September 30, 2014
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Scientists have identified some brain cells whose signals reflect our interpretation of an image-not so much the image itself, a study has found.
The researchers presented volunteers with photographs that lent themselves to two interpretations: each photo was a cross between two Hollywood celebrities. Certain information-carrying brain cells, or neurons, were found to fire signals depending on which actor the volunteer took the image to represent.
The findings echo a strand of philosophical thought known as British Empiricism as well as the ideas of Aristotle, some 2,400 years ago, said Rodrigo Quian Quiroga, a collaborator in the study.
“As Aristotle put it, we create images of the external world and use these images rather than the sensory stimulus itself for our thoughts. These neurons encode exactly that,” said Quiroga, who is director of the Center for Systems Neuroscience and head of bioengineering at the University of Leicester, U.K.
Many neurons fire off electrical signals, called action potentials, in response to specific stimuli. Which stimuli provoke signals, and how, differs depending on the exact cell or brain area. From this kind of activity, neuroscientists can figure out which tasks a specific neuron is involved in-for example, recognizing specific types of objects or ideas.
In Quiroga's study, for example, a neuron that originally reacted only to Whoopi Goldberg images fired to a “morph image” between Goldberg and Bob Marley only when the subject identified the morphed image as Goldberg. That same neuron remained inactive when the subject said the very same image was Marley.
The researchers concluded that neurons fire in line with conscious recognition of images rather than the actual images seen. Furthermore, they said, in most cases the neuron's responses to morphed pictures were the same as when shown the pictures without morphing.
The study is published in the research journal Neuron.
“We are constantly bombarded with noisy and ambiguous sensory information,” Quiroga noted. “Our brain is constantly making decisions based on such limited data.”
Although brain cells certainly exist that respond to specific features of an image-down to precise lines and shadows-Quiroga said the study shows that some brain cells respond to more than just these parts, or even their sum total. They report our interpretation of the image.
The cells were identified in an area of the brain called the medial temporal lobe, deep behind the temples. These neurons may also “play a key role in the formation of memory,” Quiroga said.
“We indeed see the face of a friend rather than the combination of visual features that compose the person's face,” he argued. “The neurons we report in this article fire exactly to this.”
Source : http://www.world-science.net | <urn:uuid:c1902240-a56a-401e-bbbb-f14c6e164acb> | 2.671875 | 626 | News Article | Science & Tech. | 38.41575 | 95,603,771 |
In their recently published study the glaciologists and climatologists, headed by Prof. Georg Kaser and Dr. Ben Marzeion from the Institute of Geography of the University of Innsbruck, have demonstrated that the contribution potential of glaciers to the water supply of populated areas varies regionally.
The scientists gathered data on the amount of precipitation on certain glaciers and calculated when the water is discharged and available in populated areas. “There is a big difference in whether the water is discharged in an arid period or in a period, when there usually is a lot of precipitation, e.g. in monsoon regions in Asia,“ explains Ben Marzeion.
“And there are regions, for instance around the Aral Sea, where precipitation happens in the mountain regions in winter. The glacier melt water runoff in summer is vital for the population living in this area.“ The Innsbruck researchers modeled estimates that show human dependence on glacier melt in a certain region. They demonstrate that high-mountain communities are highly dependent on glacier melt water but the population density is usually relatively low in these regions. “The impact is a lot more dramatic in mid latitude river basins, where the population density is a lot higher and glacier melt still contributes to the available water reservoir to a large extent,“ the climatologists explain.
The incentive of the study was the widespread discussion about the impact of climate change on water availability in highly populated regions. “In the last few years numbers have been named that do not pass a closer examination,“ says glaciologist and climatologist Georg Kaser. “It is an exaggeration when it is claimed that the melting of glaciers endangers the water supply of 2 billion people.” With their study the Innsbruck scientists want to draw attention to the considerable regional differences regarding the problem of future water supply. “By all means, the expected climatic development may have detrimental effects for smaller high-mountain communities.“
The data for the study was obtained from the World Glacier Inventory, global temperature and precipitation data and the Global Digital Elevation Model. The researchers investigated the whole river basin region of certain glaciers in the Himalayas, the Andes, the Caucasus Mountains, Siberia, North America and New Zealand. “In principle, this is a simple research approach, which, nevertheless, provides us with important arguments for a more differentiated discussion in climate research,“ says Georg Kaser, who is pleased about the results of the study, which has been published in the renowned scientific journal Proceedings of the National Academy of Sciences (PNAS). “With regard to the next report issued by the Intergovernmental Panel on Climate Change (IPCC), our data can be seen as the basis for regionally more precise estimations and they show that the impact of the expected climate change may be higher in some regions than in others,” says Kaiser.
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
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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NAMEflock - apply or remove an advisory lock on an open file
SYNOPSIS#include <sys/file.h> int flock(int fd, int operation);
DESCRIPTIONApply or remove an advisory lock on the open file specified by fd. The argument operation is one of the following: LOCK_SH Place a shared lock. More than one process may hold a shared lock for a given file at a given time. LOCK_EX Place an exclusive lock. Only one process may hold an exclusive lock for a given file at a given time. LOCK_UN Remove an existing lock held by this process. A call to flock() may block if an incompatible lock is held by another process. To make a nonblocking request, include LOCK_NB (by ORing) with any of the above operations. A single file may not simultaneously have both shared and exclusive locks. Locks created by flock() are associated with an open file table entry. This means that duplicate file descriptors (created by, for example, fork(2) or dup(2)) refer to the same lock, and this lock may be modified or released using any of these descriptors. Furthermore, the lock is released either by an explicit LOCK_UN operation on any of these duplicate descriptors, or when all such descriptors have been closed. If a process uses open(2) (or similar) to obtain more than one descriptor for the same file, these descriptors are treated independently by flock(). An attempt to lock the file using one of these file descriptors may be denied by a lock that the calling process has already placed via another descriptor. A process may only hold one type of lock (shared or exclusive) on a file. Subsequent flock() calls on an already locked file will convert an existing lock to the new lock mode. Locks created by flock() are preserved across an execve(2). A shared or exclusive lock can be placed on a file regardless of the mode in which the file was opened.
RETURN VALUEOn success, zero is returned. On error, -1 is returned, and errno is set appropriately.
ERRORSEBADF fd is not an open file descriptor. EINTR While waiting to acquire a lock, the call was interrupted by delivery of a signal caught by a handler; see signal(7). EINVAL operation is invalid. ENOLCK The kernel ran out of memory for allocating lock records. EWOULDBLOCK The file is locked and the LOCK_NB flag was selected.
CONFORMING TO4.4BSD (the flock() call first appeared in 4.2BSD). A version of flock(), possibly implemented in terms of fcntl(2), appears on most Unix systems.
NOTESflock() does not lock files over NFS. Use fcntl(2) instead: that does work over NFS, given a sufficiently recent version of Linux and a server which supports locking. Since kernel 2.0, flock() is implemented as a system call in its own right rather than being emulated in the GNU C library as a call to fcntl(2). This yields true BSD semantics: there is no interaction between the types of lock placed by flock() and fcntl(2), and flock() does not detect deadlock. flock() places advisory locks only; given suitable permissions on a file, a process is free to ignore the use of flock() and perform I/O on the file. flock() and fcntl(2) locks have different semantics with respect to forked processes and dup(2). On systems that implement flock() using fcntl(2), the semantics of flock() will be different from those described in this manual page. Converting a lock (shared to exclusive, or vice versa) is not guaranteed to be atomic: the existing lock is first removed, and then a new lock is established. Between these two steps, a pending lock request by another process may be granted, with the result that the conversion either blocks, or fails if LOCK_NB was specified. (This is the original BSD behavior, and occurs on many other implementations.)
SEE ALSOclose(2), dup(2), execve(2), fcntl(2), fork(2), open(2), lockf(3) See also Documentation/filesystem/locks.txt in the kernel source (Documentation/locks.txt in older kernels).
COLOPHONThis page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at //www.kernel.org/doc/man-pages/. FLOCK(2) | <urn:uuid:be343724-131b-48b4-8d6c-79d7680329be> | 2.71875 | 985 | Documentation | Software Dev. | 57.959406 | 95,603,792 |