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The genome that feeds the world
© BioMed Central Ltd 2002
Published: 5 April 2002
Rice is one of the most highly consumed cereals in the world and is the staple diet of over half the world's population. In the April 5 Science, two independent groups report the first draft sequences of the rice genome. Stephen Goff and researchers at Syngenta's Torrey Mesa Research Institute (TMRI) in California, carried out whole-genome shotgun sequencing of the Oryza sativa L. Ssp. japonica subspecies (Science 2002, 296:92-100), while scientists in China, at the Beijing Genomics Institute (BGI), chose the widely cultivated Oryza sativa L. Ssp. Indica (Science 2002, 296:79-92).
The availability of data from two subspecies will provide ample material for comparative genomics. The first observation is the differences in reported size: the BGI group report a genome that is 10% bigger (at 466 Mb) than the TMRI sequence (420 Mb); both are relatively small for a grass genome. It remains to be determined whether this difference is due to subspecies differences related to repeat sequences, or technical differences in the assembly and annotation strategies. The Syngenta draft sequence (referred to as Syd) covers 93% of the genome and has a GC content of 44%. The BGI sequence has similar coverage (92%) and a predicted misassembly error rate of 1.1%; the Chinese group document a gradient of GC content in rice coding sequences. Repetitive DNA accounts for 42-45% of the rice genomes including MITEs (miniature inverted-repeat transposable elements) and retrotransposons.
Both groups provide estimates of the number of genes (from 32,000 to 55,000), reiterating what we have already learnt about the discrepancy between apparent organismal complexity and total gene number (humans are estimated to have around 35,000 genes and Arabidopsis around 25,000); the mean gene size is 4.5 kb. The numbers may represent an over-estimation and reflect the difficulty in predicting genes.
Both groups report extensive comparison with the other published plant genome, that of the dicot weed Arabidopsis thaliana, which is 3.7 times smaller. Most (80-85%) Arabidopsis genes have a rice homolog, and about a third of these appear to be specific to plants; about half of the predicted rice genes have no Arabidopsis homolog. Over-represented plant gene classes include RING-finger proteins and F-box-domain proteins that play roles in protein turnover and degradation.
Analysis of the synteny between the rice and Arabidopsis genomes provides insights into the evolution of monocots and dicots. Certain classes of disease resistance R genes appear to have evolved since the divergence of the two types of plant. Rice and Arabidopsishave homologous genes implicated in flowering and development, although the conservation of these genetic networks merits further investigation. A quarter of rice genes may be involved in metabolism, with much apparent gene redundancy.
The two draft rice genome sequences will serve as an important platform for cereal genomics. Completion of the sequence and improvements in annotation will lead to crop improvements that should help to feed the world.
- Science, [http://www.sciencemag.org]
- Syngenta, [http://www.syngenta.com]
- Torrey Mesa Research Institute, [http://www.tmri.org]
- Genome Database of Chinese super hybrid rice, [http://btn.genomics.org.cn/rice]
- Plant sequence completed, [http://www.genomebiology.com/spotlights/articles/SpotlightCompiler.asp?xml=20001214-2.xml] | <urn:uuid:43042ba1-bb6a-476a-a8be-f680f527927a> | 3.015625 | 801 | Truncated | Science & Tech. | 43.652712 | 95,622,426 |
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Unformatted text preview: Physics 227N/232N Quiz 4 - February 28, 2013 5-7. Name‘ - _ Group: __qO/— l I will uphold the Honor Code: \ql. Capacitance
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One of the world's deadliest mosquitoes sustains its taste for human blood thanks in part to a genetic tweak that makes it more sensitive to human odor, according to new research.
Researchers report in the journal Nature that the yellow fever mosquito contains a version of an odor-detecting gene in its antennae that is highly attuned to sulcatone, a compound prevalent in human odor. The researchers found that the gene, AaegOr4, is more abundant and more sensitive in the human-preferring "domestic" form of the yellow fever mosquito than in its ancestral "forest" form that prefers the blood of non-human animals.
Researchers report that the yellow fever mosquito sustains its taste for human blood thanks in part to a genetic tweak that makes it more sensitive to human odor. The human-preferring 'domestic' form of the mosquito (right) contains a version of the odor-detecting gene AaegOr4 in its antennae that is highly attuned to sulcatone, a compound prevalent in human odor. The researchers found that this gene is more abundant and more sensitive in the domestic form than in its ancestral 'forest' form (left), which prefers the blood of non-human animals.
Credit: Carolyn McBride, Department of Ecology and Evolutionary Biology and the Princeton Neuroscience Institute
The research provides a rare glimpse at the genetic changes that cause behaviors to evolve, explained first author Carolyn "Lindy" McBride, an assistant professor in Princeton University's Department of Ecology and Evolutionary Biology and the Princeton Neuroscience Institute who conducted the work as a postdoctoral researcher at the Rockefeller University. Uncovering the genetic basis of changes in behavior can help us understand the neural pathways that carry out that behavior, McBride said.
The research also could help in developing better ways to stem the yellow fever mosquito's appetite for humans, McBride said. The yellow fever mosquito is found in tropical and subtropical areas worldwide and is the principal carrier of yellow fever, the measles-like dengue fever, and the painful infection known as chikungunya.
Yellow fever annually kills tens of thousands of people worldwide, primarily in Africa, while dengue fever infects hundreds of millions. The research also suggests a possible genetic root for human preference in other mosquitoes, such as malaria mosquitoes, although that species is genetically very different from the yellow fever mosquito.
"The more we know about the genes and compounds that help mosquitoes target us, the better chance we have of manipulating their response to our odor" McBride said, adding that scent is not the only driver of mosquito behavior, but it is a predominant factor.
The researchers first conducted a three-part series of experiments to establish the domestic yellow fever mosquito's preference for human scent. Forest and domestic mosquitoes were put into a large cage and allowed to bite either a guinea pig or a researcher's arm.
Then the mosquitoes were allowed to choose between streams of air that had passed over a guinea pig or human arm. Finally, to rule out general mosquito attractants such as exhaled carbon dioxide, mosquitoes were allowed to choose between the scent of nylon sleeves that had been in contact with a human or a guinea pig.
In all three cases, the domestic form of the yellow fever mosquito showed a strong preference for human scent, while the forest form primarily chose the guinea pig. Although domestic mosquitoes would sometimes go for the guinea pig, it happened very rarely, McBride said.
McBride and colleagues then decided to look for differences in the mosquitoes' antennae, which are equivalent to a human's nose. They interbred domestic and forest mosquitoes, then interbred their offspring to create a second hybrid generation. The genomes of these second-generation hybrids were so completely reshuffled that when the researchers compared the antennae of the human- and guinea pig-preferring individuals they expected to see only genetic differences linked directly to behavior, McBride said.
The researchers found 14 genes that differed between human- and guinea pig-preferring hybrids -- two of them were the odorant receptors Or4 and Or103. Choosing to follow up on Or4, the researchers implanted the gene into fruit-fly neurons. They found that the neurons exhibited a burst of activity when exposed to sulcatone, but no change when exposed to guinea pig odors. McBride plans to further study Or103 and other genes that could be linked to host preference at Princeton.
This work provides insight into how the domestic form of the yellow fever mosquito evolved from its animal-loving ancestor into a human-biting specialist, McBride said. "At least one of the things that happened is a retuning of the ways odors are detected by the antennae," she said. "We don't yet know whether there are also differences in how odor information is interpreted by the brain."
The paper, "Evolution of mosquito preference for humans linked to an odorant receptor," was published by Nature Nov. 13, 2014.
This work was supported in part by the National Institutes of Health (NIDCD grant no. DC012069; NIAID grant no. HHSN272200900039C; and NCATS CTSA award no. 5UL1TR000043); the Swedish Research Council and the Swedish University of Agricultural Science's Insect Chemical Ecology, Ethology and Evolution initiative; and the Howard Hughes Medical Institute.
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8. Radius of Curvature
By M. Bourne
We can draw a circle that closely fits nearby points on a local section of a curve, as follows.
Application of Radius of Curvature
When engineers design train tracks, they need to ensure the curvature of the track will be safe and provide a comfortable ride for the given speed of the trains. [Image source].
We say the curve and the circle osculate (which means "to kiss"), since the 2 curves have the same tangent and curvature at the point where they meet.
The radius of curvature of the curve at a particular point is defined as the radius of the approximating circle. This radius changes as we move along the curve.
How do we find this changing radius of curvature?
The formula for the radius of curvature at any point x for the curve y = f(x) is given by:
`text(Radius of curvature)` `=([1+((dy)/(dx))^2]^(3//2))/(|(d^2y)/(dx^2)|)`
The curvature of a given curve at a particular point is the curvature of the approximating circle at that point.
The curvature depends on the radius - the smaller the radius, the greater the curvature (approaching a point at the extreme) and the larger the radius, the smaller the curvature. (A very large approximating circle means the curve is almost a straight line at that point.)
The radius of curvature R is simply the reciprocal of the curvature, K. That is,
`R = 1/K`
So we'll proceed to find the curvature first, then the radius will just be the reciprocal of that curvature.
Let P and `P_1` be 2 points on a curve, "very close" together, as shown.
`Delta s` is the length of the arc `PP_1`.
`Delta theta` is the angle turned by the tangent line as it moves from P to `P_1`.
The curvature of the arc from P to `P_1` is given by
`(Delta theta)/(Delta s)`
Now, the curvature K at point P is given by:
`K=lim_(Delta theta->0)(Delta theta)/(Delta s) = (d theta)/(ds)`
We now need to find `(d theta)/(ds)` and we use the Chain Rule: ` (d theta)/(ds) = (d theta)/(dx)dx/(ds)`
Note that `tan\ theta=dy/dx`, so `theta=arctan(dy/dx)`
Returning to our formula, ` (d theta)/(dx)= d/(dx)arctan ((dy)/(dx))`
In the Differentiation of Transcendental Functions chapter we'll learn the derivative of `y=arctan\ u`, where `u=f(x)`, is given by `(dy)/(dx)=((du)/(dx))/(1+u^2)`
With `u= arctan ((dy)/(dx))` we differentiate as follows:
` (d theta)/(dx)= d/(dx)arctan ((dy)/(dx))`
We also need `dx/(ds)`, which is given by:
Putting it all together gives us the formula for curvature, `K`:
`K= (d theta)/(ds)=((d^2y)/(dx^2))/[1+(dy/dx)^2]^(3/2)`
Now the radius of curvature is just the reciprocal of this expression, that is:
Of course, the radius needs to be positive, so we take the absolute value of the denominator (bottom) of the fraction.
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Find the radius of curvature for the cubic
y = 2x3 − x + 3
at the point x = 1.
First, let's draw the graph and see what the question means.
y = 2x3 − x + 3
I have used equal scaling along the 2 axes (so that later, when I draw the circle, it will not have an elliptical shape).
Now, to find the radius of curvature, we need:
So now we are ready to substitute into the formula to give us the radius at any point x:
Now to find the radius of curvature at the required point x = 1, we substitute:
To show what we have done, let's look at the graph of the curve (blue) with the approximating circle (dark red) overlaid. The circle is a good approximation for the curve at (1, 4).
We can show that the center of the approximating circle is `(−9.8, 6.17)`.
How did I find that center?
We know the length of the radius shown in the diagram (`11.05` units).
We know 1 point on that radius line, `(1,4)`, and we need to find the one at the other end, the center. Let's call it (x1, y1).
We're going to set up 2 equations using these 2 unknowns.
We know that
So the slope of the tangent at `x = 1` is
6(1)2 − 1 = 5.
Now, the slope of the normal (the line at right angles to the tangent at the point of contact) is −1/5. (See Tangents and Normals.)
So we can use the formula y − y1 = m(x − x1) and the known slope `-1/5` and point `(1, 4)` to find the equation of the line containing the radius as follows:
y − 4 = (−1/5) (x − 1), which gives:`y = −x/5 + 21/5`
The unknown point (x1, y1) lies on this line, so we can say
Next, we use the distance formula:
We know the distance r (since it is the radius), and one of our points is (1,4), and using our expression connecting x1 and y1, we can solve these simultaneously as:
This is one equation in one unknown, which after some algebra gives us
x1 = − 9.833 (and another positive solution which doesn't apply here)
Substituting this back into `y_1=-(x_1)/5+21/5` gives
y1 = 6.167
So the center of the circle is `(−9.8, 6.17)`.
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In the following interactive graph you can explore what "changing radius of curvature" means.
Slowly drag the point "P" around the curve to see the changing radius of curvature (segment CP). It works best if you use a left-right motion - don't worry about following the up-down of the graph.
You'll notice at the point of inflexion there is interesting behavior. The circle changes from being below the curve to above (when moving left to right). When we are right on the point of inflexion, what does the circle become?
[This example was supplied by a reader.]
We have a curve which is defined by data points and we don't know the function for this data. How can we find the radius of curvature?
We take any 3 data points to illustrate ways of solving this. I chose the points (1, 1), (2, 3) and (3,8).
We'll do this in 3 different ways, just for fun (and for learning about how different math approaches can be used)!
Method 1: Approximation Using a Parabolic Fit and Calculus Methods
The graph connecting the generic data points `(1, 1)`, `(2, 3)` and `(3, 8)` is as follows.
One way of finding the radius of curvature is to find the (unique) parabola passing through these 3 points. Parabolas are excellent for approximating curves in a local region. (See more on Parabolas.)
We proceed as follows. In general, a parabola has the form:
y = ax2 + bx + c
Substituting our given points (1, 1), (2, 3) and (3, 8) into the general form of the parabola gives us 3 equations in 3 unknowns:
1 = a + b + c
3 = 4a + 2b + c
8 = 9a + 3b + c
Solving this set of 3 simultaneous equations gives us:
a = 1.5
b = −2.5
c = 2
So the parabola passing through the points `(1, 1), (2, 3)` and `(3, 8)` is
y = 1.5x2 − 2.5x + 2
We see this parabola passes through each of the 3 points:
Using this as our function (which we can only do in this local region for the original data points), we apply the formula for the radius of curvature:
`text(Radius of curvature)` `=([1+((dy)/(dx))^2]^(3//2))/|(d^2y)/(dx^2)|`
We need to find the first and second derivatives and evaluate them at the center point `(2, 3)`.
At `x = 2` (the middle of our 3 points), `dy/dx = 3.5`
Now for the second derivative:
So the radius of curvature at the middle point (2, 3) is:
So we've found a parabola that approximates our function for the local area near our data points. Then we found the radius of curvature - that is, the radius of a circle that "fits" our curve near our data points.
Here are the 3 data points, the parabola we found, and the circle indicating the curvature for the given 3 points. It has radius `16.08`.
Method 2: Using Linear Approximations and Calculus Methods
We can approximate the value of `(dy)/(dx)` at the middle point `(2,3)` of our 3 points as follows.
The slope of the line joining `(1, 1)` and `(2, 3)` is given by:
The slope of the line joining `(2, 3)` and `(3,8)` is given by:
We "average" these slopes to find a crude value for `(dy)/(dx)`:
Now for the slope of the slope (i.e. the second derivative). We find the change in slope m divided by the change in x for the interval x = 1.5 to x = 2.5 (which are the mid-points of our 2 lines joining the 3 given points):
`"Slope of slope"=(Deltam)/(Deltax)=(5-2)/1` `=3~~(d^2y)/(dx^2)`
Interestingly, these approximate values are exactly the same as our parabola approximation above.
Substituting into our radius of curvature formula, we obtain the same value as for Method 1:
Checking our answer, we can see that the (dark red) approximating circle (center D, with radius `16.08`) passes quite closely through our data points. It may be possible to improve on this by taking weighted averages to get more appropriate values for the first and second derivatives.
Of course, my reader would need to do the same process for every set of 3 adjacent data points. He was writing a computer program to do this, so it would not be so tedious.
Easy to understand math videos:
Method 3: Finding the Radius of the Circle through our 3 Points
This is an exact method for finding the required radius of curvature. We'll actually find the equation of the circle passing through the 3 points.
In general, the x-value for the center of the circle passing through 3 points A (x1, y1), B (x2, y2), C (x3, y3), joined by lines with slopes m1 and m2 is given by:
(The above formula is based on finding the intersection of the perpendicular bisectors of the 2 lines joining the 3 points, as follows.)
So for our given data points, we have:
(We found the values for m1 and m2 in Method 2, above.)
Now to find the y-value for center of the circle. The formula for the first perpendicular bisector is given by:
`y_("Perp")` `=- 1/m_1(x-(x_1+x_2)/2)+(y_1+y_2)/2`
So for our data points, we can obtain the y-value for the center of the circle by substituting the known values, as follows:
`y_c` `=-1/2(-10.833-(1+2)/2)+(1+3)/2` `=8.1665`
So the center of the circle passing through the points `(1, 1), (2, 3)` and `(3, 8)` is given by `(-10.83, 8.17)`.
Finally, we can find the radius by simply finding the distance between the center of the circle and any one of the points on the circle. I have chosen `(1,1)`:
`text(Radius) = sqrt((x_2-x_1)^2+(y_2-y_1)^2`
[See more on Distance Formula.]
So the radius of curvature for the 3 points `(1, 1), (2, 3)` and `(3, 8)` is `13.83`, when finding the actual circle passing through the 3 points.
Our answer is slightly different to the answers obtained by using a parabolic model and linear approximations. | <urn:uuid:34bc627e-b9e3-427d-a6c3-04fbb2cda885> | 4.40625 | 3,056 | Tutorial | Science & Tech. | 75.92692 | 95,622,457 |
An Introduction to Atmospheric Radiation
This Second Edition of An Introduction to Atmospheric Radiation has been extensively revised to address the fundamental study and quantitative measurement of the interactions of solar and terrestrial radiation with molecules, aerosols, and cloud particles in planetary atmospheres. It contains 70% new material, much of it stemming from the investigation of the atmospheric greenhouse effects of external radiative perturbations in climate systems, and the development of methodologies for inferring atmospheric and surface parameters by means of remote sensing. Liou's comprehensive treatment of the fundamentals of atmospheric radiation was developed for students, academics, and researchers in atmospheric sciences, remote sensing, and climate modeling.
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Darwinists have called it one of “nature’s worst designs,” “obviously a ridiculous detour,” asserting that “no engineer would ever make a mistake like that.”
The giraffe is one of those all-star icons of evolution, familiar from textbook covers, that falls apart on closer inspection.
Darwin thought everything evolved from a simple cell by mindless chance processes. The animals don’t know that.
Charles Darwin famously offered a suggestion as to how his theory could be falsified.
German geneticist Wolf-Ekkehard Lönnig Tackles Giraffe Evolution Last year, German geneticist Wolf-Ekkehard Lönnig critiqued evolutionary accounts of the infamously complex long neck of the giraffe. He recounts how various Darwinists had claimed things like “the evolution of the long-necked giraffe can be reconstructed through fossils,” but Lönnig concluded that “the fossil evidence for the gradual […] | <urn:uuid:9cc526be-1818-41ce-8ed0-09ad466b2ff7> | 2.53125 | 214 | Content Listing | Science & Tech. | 27.06951 | 95,622,481 |
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Transport mechanism of suspended matter above the shelf slope at the mouth of Tokyo Bay
Transport mechanism of suspended matter above the shelf slope is investigated with the use of the moorings of time-series sediment trap, current meter and nephelometer at three stations at the mouth of Tokyo Bay, Japan during 21 to 25 August 1993. Tidal pump mechanism is effective for the transport of suspended matter at the shelf edge, but the boring-like flood tidal current resuspends the settled suspended matter, on the bottom of shelf slope and the resuspended matter is resulted to be moved upslope in one tidal cycle at 10 m above the bottom of shelf slope.
KeywordsJapan Transport Mechanism Tidal Cycle Suspended Matter Sediment Trap
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Schmidt, a UIC associate professor of biological sciences, determined paternity of 29 frozen embryos saved from a female whale shark caught off the coast of Taiwan in 1995. The embryos, studied in collaboration with Professor Shoou-Jeng Joung at the National Taiwan Ocean University, are extremely rare.
The pregnant shark carried a surprisingly large number of embryos -- 304 -- still in the uterus and representing a spectrum of age and development stages ranging from being still egg-encased to developed, near-term animals.
Schmidt and her colleagues spent several years developing DNA genetic markers to study whale sharks, initially for population genetics, but in this study the tool was used to determine paternity.
Shark reproduction is still an emerging science, but what is known suggests that most broods are sired by more than one male. That is not what Schmidt found with this particular female whale shark.
"These differently aged embryos -- itself unusual across animal species -- had the same father," Schmidt said. "We have to be very cautious in drawing conclusions from a single litter, but the data suggest female whale sharks store sperm after a single mating event, and subsequently fertilize their own eggs as they are produced."
If the finding can be supported from analysis of other whale shark litters, Schmidt said, "it would suggest that there is no whale shark breeding ground where large numbers of animals meet to mate, but rather that mating occurs as an isolated event."
Follow-up studies may be serendipity. International protocols protect whale sharks from capture, few are housed in aquariums, and those that are are usually less than 25 years old and not yet sexually mature. Scientists typically study whale sharks at seasonal feeding grounds, but those animals are usually juveniles not mature enough to breed. Rarely are adult females observed in the wild.
"Protections for whale sharks have increased in many parts of the world, yet shark numbers seem to be declining, and the average size is getting smaller," said Mark Meekan, principal research scientist with the Australian Institute of Marine Sciences.
"This is a classic sign of overfishing, where larger, more valuable animals are selectively removed," he said. "Targeted fishing of breeding-age animals in a late-maturing species can be devastating for its survival."
The findings are reported in the journal Endangered Species Research, published online Aug. 4. Other authors include Meekan; Joung and Chien-Chi Chen of the National Taiwan Ocean University; Saad I. Sheikh, formerly of UIC; and Bradley Norman of ECOCEAN Inc.
The work was funded by a grant from Project Aware.
EDITORS: Photos to accompany this story are available at http://newsphoto.lib.uic.edu/v/whale_shark/
Paul Francuch | Newswise Science News
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
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Life Sciences
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TeachMeFinance.com - explain Polar Jet Stream
Polar Jet Stream The term 'Polar Jet Stream' as it applies to the area of the weather can be defined as ' Used interchangably with Polar Jet; a jet stream marked by a concentration of isotherms and strong vertical shear, this jet is the boundary between the polar air and the subtropical air. It often divides into two branches, the north and the south, and marks the high speed core of the prevailing westerlies. It is associated with the location and motion of the high and low pressure areas of the middle latitudes, and therefore, is variable in position, elevation, and wind speed. Its position tends to migrate south in the Northern Hemispheric winter and north in the summer, and its core winds increase during the winter and become less strong in the summer'.
About the author
Copyright © 2005-2011 by Mark McCracken, All Rights Reserved. TeachMeFinance.com is an informational website, and should not be used as a substitute for professional medical, legal or financial advice. Information presented at TeachMeFinance.com is provided on an "AS-IS" basis. Please read the disclaimer for details. | <urn:uuid:4768d2bd-08bf-4bef-bd22-cc1e0a5d17e9> | 2.921875 | 252 | Knowledge Article | Science & Tech. | 46.818971 | 95,622,527 |
"The second law of thermodynamics states that the entropy of an isolated system never decreases due to the fact that isolated systems spontaneously evolve towards thermodynamic equilibrium"¹. Thermodynamic equilibrium is the state of maximum entropy.
The second law of thermodynamics can be understood and explained using the underlying quantum statistical mechanics with the assumption of low-entropy initial conditions in the distance past. In statistical mechanics, entropy is the measure of the number of microscopic configurations corresponding to a macroscopic state.
The second law of thermodynamics has been expressed in many ways. The following at the most predominantly used.
Heat can never pass from a colder to a warmer body without some other change.
It is impossible to cool matter in a system below the temperature of the coolest of the surround objects
Principle of Caratheodory
In every neighborhood of any state S of an adiabatically isolated system there are states inaccessible from S.
1. Planck, Max. "Vom Relativen Zum Absoluten."Die Naturwissenschaften 13.3 (1925): 463-64. Print.© BrainMass Inc. brainmass.com July 19, 2018, 8:00 am ad1c9bdddf | <urn:uuid:ca77d102-100d-448d-bc7e-018922e69364> | 3.40625 | 257 | Knowledge Article | Science & Tech. | 35.500879 | 95,622,529 |
Authors: Nainan K. Varghese
Abstract: By simple mechanics, it is impossible for a free macro body to orbit around another moving macro body, in any type of closed geometrical path. However, while considering two-body problems, relative parameters of macro bodies are considered with one of them steady in space. This simple method of mathematical analysis can give accurate prediction of their future relative parameters. Orbital path of a planetary body appears around its static central body. Circular/elliptical orbits around a static central body, being an imaginary figure, has no value other than to indicate relative positions of concerned macro bodies. All macro bodies, in nature, are moving. In cases of moving central bodies (real situations) or when there are more than two macro bodies in a system, relative considerations cannot describe their orbital paths. Due to phenomenal success of solution to two-body problem by relative considerations, a firm but erroneous belief has established that all planetary bodies move around their central bodies. Adamant belief in imaginary circular/elliptical orbital path is carried forward to three-body system to create an imaginary but unsolvable problem. Three-body problem (as considered today with respect to planetary motions) is unsolvable because real and imaginary situations are mixed in it. It is nothing but a deception from reality, adopted to create a baseless mystery.
Comments: 8 Pages. Published in General Science Journal
Unique-IP document downloads: 200 times
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You are equally welcome to be positive or negative about any paper but please be polite. If you are being critical you must mention at least one specific error, otherwise your comment will be deleted as unhelpful. | <urn:uuid:bf4647ca-66b1-4619-9392-e3c5f8939844> | 2.859375 | 434 | Academic Writing | Science & Tech. | 24.348729 | 95,622,544 |
BAS Marine Ecologist, University College Cork, UK
*Corresponding author: Barnes DKA, BAS Marine Ecologist, University College Cork, Republic of Ireland, Europe, British Antarctic Survey, NERC, Madingley Road, Cambridge, CB24 9PE, UK, Email: email@example.com
Submission: February 03, 2018; Published: March 19, 2018
ISSN: 2578-0336 Volume1 Issue5
Carbon-capture and storage (CCS) is expensive but as commercialization is proving problematic and economic estimates of climate change costs escalate, non-mainstream alternatives should be discussed. We present a thought experiment based on potential for increased carbon capture on polar continental shelves. West Antarctic, and probably Arctic, continental shelves are sites of significant negative feedbacks on climate change through benthos carbon accumulation. At South Georgia, moraines on the margins of the continental shelf (bulldozed there by past glaciations) show much more biological richness and activity than the typical mud covering ~88% of the shelf. We estimate that most carbon accumulation, and ultimately sequestration, occurs at these moraines (12% of shelf). Seabed CCS by benthos could increase 400% if it was all rubble. We think this could be achieved with minimal environmental impacts but at current CCS values it would take 10,000 years (Antarctic) and 1000 years (Arctic) to recoup transport costs.
Keywords: Carbon immobilization; benthos; South georgia; CO2; Antarctica | <urn:uuid:e3ed8ad2-9405-4999-a0d3-1627345dc76b> | 2.8125 | 327 | Academic Writing | Science & Tech. | 16.785111 | 95,622,579 |
GPS, Radiodating, and Plate Tectonics
The second article by @Joel_Duff to read shows how GPS (which gives us position on the earth), radiodating of ancient rocks (to get their age) work together to show us that the earth looks old. The key forumula is the same we used to date DNA (Heliocentric Certainty Against a Bottleneck of Two?):
Distance equals the product of time and rate. Remember now that the continents were all once joined into a single super continent, Pangea, and then slowly drifted appart. YEC’s agree with this, but think it happened much quicker, in the lifetime of Peleg (https://answersingenesis.org/geology/plate-tectonics/did-the-continents-split-apart-in-the-days-of-peleg/)
We can measure the distance between continents (D), and the time that separated using radiodating (T). Those two numbers give us a way to measure how quickly they are moving (R). Now, with GPS, we have an independent way to measure the rate (R). The rate measured by these two approaches matches really well, even though they use different assumptions.
This is just another example of why we say that the earth look old. There is no reason for these estimates to line up unless the continents really did split apart a long time by a process that we still see unfolding right now. Otherwise, this is just an amazing coincidence. The earth really does appear old. | <urn:uuid:8cd8f979-5d85-4ce7-964d-2016c650c0ce> | 3.5625 | 326 | Comment Section | Science & Tech. | 52.406923 | 95,622,589 |
July 28 2010 Astronomy Newsletter
Some readers have asked for help in learning what's in the night sky, so that's my theme for this week.
Here are two new articles from the Astronomy site at BellaOnline.com.
Absolute Beginners - Start Skywatching
You'd like to know the night sky? But you haven't a got a telescope, live in a city, don't know any constellations or can't tell a star from a planet? Time to give up? Absolutely not. Time to read on and look up.
Absolute Beginners - The Summer Sky
Warm summer nights are a great time to study the sky. Here is a guide to the main summer constellations. You can see all of these things without a telescope, so head outside and look up.
You can see the loveliest sight in the sky around half an hour after sunset, so you don't even have to stay up late to look. Look to the western sky to see a very bright Venus with Saturn and Mercury close together and to the upper left of Venus. By the end of the week they'll all be close together and they'll stay that way into the first half of August.
Note: If you live at higher latitudes, e.g., the UK and much of Canada, you may find that Mars and Saturn are lost in the twilight, but you should still be able to see a bright Venus.
By the way, if you live in the USA and would like to find an astronomy club near you, this page should be able to help: http://nightsky.jpl.nasa.gov/club-map.cfm
(1) The first successful picture of a total solar eclipse was taken 159 years today on July 28,1951. The observer Berkowski (first name unknown) took it at the Royal Observatory in what was Koningsberg, Prussia (now Kalingrad, in Russia).
(2) People have been complaining about traffic for years. Is there anywhere completely free from traffic? At one time we could safely have said the Moon would be, but Saturday July 31st is the fortieth anniversary of the first vehicle being driven on the Moon. Astronauts Dave Scott and Jim Irwin drove the Lunar Roving Vehicle.
This picture from Nasa Images shows Dave Scott in the vehicle.
(3) Maria Mitchell, first professor of astronomy of Vassar College and second woman to be credited with the discovery of a comet, was born on August 1, 1818.
Wishing you clear skies.
Please visit astronomy.bellaonline.com for even more great content about Astronomy.
To participate in online discussions, this site has a community forum all about Astronomy located here -
I hope to hear from you sometime soon, either in the forum or in response to this email message. I welcome your feedback!
Do pass this message along to family and friends who might also be interested. Remember it's free and without obligation.
Mona Evans, Astronomy Editor
One of hundreds of sites at BellaOnline.com
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Master List of BellaOnline Newsletters | <urn:uuid:b872dff0-8bc5-4d02-be7f-b3d1b372e9ad> | 2.96875 | 664 | Personal Blog | Science & Tech. | 61.134749 | 95,622,602 |
We already know that large-scale wind and solar are becoming competitive without subsidies in some parts of the world, even while fossil fuels remain hooked on government support.
Now, as reported by TV network YLE, a team of researchers at Finnish universities has shown that a rapid transition to wind and solar in the next five to ten years offers the cheapest, most cost effective option for meeting China's growing energy demand:
The Finnish researchers are confident that renewable energy sources like solar and wind power will become the cheapest form of energy production in Asia within the next ten years. What is more, energy produced in this way provides the added benefits of being inexpensive, emission-free and promoting self-sufficiency. Professor of solar energy Christian Breyer from the Lappeenranta University says the project’s large-scale simulation of functioning renewable energy networks is the first of its kind.
What's particularly interesting about this research is not just that individual renewable energy projects might be cost competitive in the very near future, but also that—to quote Professor Breyer—a "network fully based on renewable energy is possible in Northeast Asia."
The idea of meeting our entire energy demand from renewable sources has, until recently, been seen as a pipe dream. Yet with entire cities signing up to go 100% renewable, and with renewable energy costs tumbling, energy storage becoming mainstream, and energy demand falling in many parts of the world even as economies grow, a truly low carbon economy is beginning to feel a whole lot more feasible.
Ten years from now, we may look at the historic China US climate pledge and laugh at its lack of ambition.
I surely hope so.
And so, most likely, does anyone who has to breathe Beijing's poisonous air. | <urn:uuid:92f9c357-6952-41ef-9037-d0c634ad5068> | 2.84375 | 355 | Nonfiction Writing | Science & Tech. | 26.311139 | 95,622,630 |
We could better understand how earthquakes work thanks to new nanoscale research which studies the relationships between water, friction and mineral chemistry.
This was completed by scientists at the University of Illinois, who used microscopic friction measurements to find that some rocks can dissolve and may cause faults to slip.
It's thought that the study, published in the journal Nature Communications, could lead to a better understanding of earthquake dynamics.
As part of the research, the scientists closely examined how water and calcite (a mineral that is very common in the Earth's crust) interact at various pressures and groundwater compositions to influence frictional forces along faults.
"Water is everywhere in these systems," said civil and environmental engineering professor, Rosa Espinosa-Marzal, who was a co-author on the study. "There is water on the surface of minerals and in the pore spaces between mineral grains in rocks. This is especially true with calcite-containing rocks because of water's affinity to the mineral."
The study focuses on calcite-rich rocks in the presence of naturally occurring salty groundwater, or brine, along fault surfaces. The rock surfaces that slide past each other along faults are not smooth. The researchers zoomed in on the naturally occurring tiny imperfections or unevenness on rocks' surfaces, called asperities, at which friction and wear originate when the two surfaces slide past each other.
"The chemical and physical properties of faulted rocks and mechanical conditions in these systems are variable and complex, making it difficult to take every detail into account when trying to answer these types of questions," added Espinosa-Marzal.
"So, to help understand water's role in fault dynamics, we looked at a scaled-down, simplified model by examining single asperities on individual calcite crystals."
For the experiments, the team submerged calcite crystals in brine solutions at various concentrations and subjected them to different pressures to simulate a natural fault setting. Once the crystals were in equilibrium with the solution, they used an atomic force microscope to drag a tiny arm with a silicon tip across the crystal to measure changes in friction.
The researchers found what they expected: As the pressure applied on the crystals increased, it became more difficult to drag the tip across the crystal's surface. However, when they increased pressure to a certain point and the tip was moved slowly enough, the tip began to slide more easily across the crystal.
This told them that something had happened to the tiny asperity under higher pressures that caused a decrease in friction. The atomic force microscope also allows them to image the crystal surface, and see that the groove increased in size, confirming that the calcite had dissolved under pressure.
While Espinosa-Marzal said that this shows that such studies warrant serious consideration in future work, she admitted that there are still many more questions related to the research that need to be answered..
"Our research also suggests that it might be possible to mitigate earthquake risk by purposely changing brine compositions in areas that contain calcite-rich rocks. This consideration could be beneficial in areas where fracking is taking place, but this concept requires much more careful investigation," she added.
The site is perfectly situated for launching small satellites into orbit
Delegates at the ESOF 2018 conference were warned that their perceptions of the digital age were coloured by private industry
Concept vehicle uses gas turbine technology to generate electricity
Fresh from the notes of Ming-Chi Kuo of TF International Securities | <urn:uuid:2a4ae703-d54b-4fa4-999f-bf1c23163b1e> | 4.09375 | 708 | News Article | Science & Tech. | 22.503689 | 95,622,631 |
Plans to drill deep beneath the frozen wastes of the Antarctic, to investigate subglacial lakes where ancient life is thought to exist, may have to be reviewed following a discovery by a British team led by UCL (University College London) scientists at the Natural Environment Research Council (NERC)Centre for Polar Observation and Modelling (CPOM).
In a Letter to Nature they report that rivers the size of the Thames have been discovered which are moving water hundreds of miles under the ice. The finding challenges the widely held assumption that the lakes evolved in isolated conditions for several millions years and thus may support microbial life that has evolved independently. It has been suggested that if microbes exist in the lakes, they could function in the same way as those in the subsurface ocean of Jupiters moon Europa or within subsurface water pockets on Mars.
Professor Duncan Wingham, of UCL, Director of CPOM and who led the team, says: "Previously, it was thought water moves underneath the ice by very slow seepage. But this new data shows that, every so often, the lakes beneath the ice pop off like champagne corks, releasing floods that travel very long distances.
Judith Moore | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:87c17326-9092-47e3-9f6b-af7c7ba287c0> | 3.734375 | 882 | Content Listing | Science & Tech. | 38.402395 | 95,622,643 |
1. a metal sphere has a charge of +8.0 micro C. What is the charge after 6.0 x 10^13 electrons have been placed on it?
2. Two Charge attract each other with force of 1.5N. What will be the force if the distance is reduced to one ninth of it original value.© BrainMass Inc. brainmass.com July 18, 2018, 10:17 am ad1c9bdddf
1. The charge carried by each electron is -1.6x10^(-19) C. ...
The solution calculates the charges and the forces for two questions regarding charges and a metal sphere. | <urn:uuid:d8fa6b26-eda5-4624-9098-bffa0366c4fb> | 3.578125 | 136 | Q&A Forum | Science & Tech. | 96.552917 | 95,622,648 |
Question 8 load handel for i=1:73113 noise(i)=cos(100*i*0.1); end x=y+noise'; sound(x)
Noise in communication systems: probability and random signals I = imread('peppers.png'); imshow(I); noise = 1*randn(size(I)); Noisy = imadd(I,im2uint8(noise)); imshow(Noisy);
Noise in communication systems: probability and random signals Noise is a random signal. By this we mean that we cannot predict its value. We can only make statements about the probability of it taking a particular value, or range of values.
The Probability density function (pdf) p(x) of a random signal, or random variable x is defined to be the probability that the random variable x takes a value between x 0 and x 0 + x. We write this as follows: p(x 0 ) x =P(x 0 <x< x 0 + x)
The probability that the random variable will take a value lying between x 1 and x 2 is then the integral of the pdf over the interval [x 1 x 2 ]:
From the rules of integration: P(x_1<x<x_2)=P(x_2)-P(x_1)
Continuous distribution. An example of a continuous distribution is the Normal, or Gaussian distribution: where m=, is the mean and standard variation value of p(x). The constant term ensures that the distribution is normalized.
Continuous distribution. This expression is important as many actually occurring noise source can be described by it, i.e. white noise or coloured noise.
How would this be used? If we want to know the probability of, say, the noise signal, n(t), having the value [-v_1, v_1], we would evaluate: P(v_1)-P(-v_1)
The distribution function P(x) is usually written in terms of as a function of the error function erf(x). The complementary error function erfc is defined by erfc(x)=1- erf(x)
Discrete distribution. Probability density functions need not be continuous. If a random variable can only take discrete value, its PDF takes the forms of lines. An example of a discrete distribution is the Poisson distribution
We cannot predicate value a random variable may take on a particular occasion. We can introduce measures that summarise what we expect to happen on average. The two most important measures are the mean (or expectation )and the standard deviation. The mean of a random variable x is defined to be
In the examples above we have assumed that the mean of the Gaussian distribution to be 0, the mean of the Poisson distribution is found to be. The mean of a distribution is, in common sense, the average value.
The variance is defined to be The square root of the variance is called standard deviation.
The standard deviation is a measure of the spread of the probability distribution around the mean. A small standard deviation means the distribution are close to the mean. A large value indicates a wide range of possible outcomes. The Gaussian distribution contains the standard deviation within its definition.
In many cases the noise present in communication signals can be modelled as a zero-mean, Gaussian random variable. This means that its amplitude at a particular time has a PDF given by Eq. above. The statement that noise is zero mean says that, on average, the noise signal takes the values zero.
We have already seen that the signal to noise ratio is an important quantity in determining the performance of a communication channel. The noise power referred to in the definition is the mean noise power. It can therefore be rewritten as SNR= 10 log 10 ( S / 2 )
If only thermal noise is considered, we have =kT m B where T is the Boltzman's constant (k=1.38 x 10 -23 J/K) T m is the temperature and B is the receiver bandwidth.
Correlation or covariance Cov(X,Y) = E(X-EX)(Y-EY) correlation is normalized covariance Positive correlation Negative correlation No correlation
Stochastic process A stochastic process is a collection of random variables x(t), for each fixed t, it is a random variable For example, when x(t) is a Gaussian variable, it is called a Gaussian process A special Gaussian process is called
white noise n(t) White noise is a random process with a flat power spectrum. In other words, the signal contains equal power within a fixed bandwidth at any center frequency. White noise draws its name from white light in which the power spectral density of the light is distributed over the visible band in such a way that the eye's three color receptors are approximately equally stimulated.
White noise vs. colour noise The most noisy noise is a white noise since its autocorrelation is zero, i.e. corr(n(t), n(s))=0 when t > s Otherwise, we called it colour noise since we can predict some outcome of n(t), given n(s)
load handel plot(y) size(y) x=randn(73113,1); plot(abs(fft(z))) z=y+.1*x; plot(abs(fft(z))) hold on plot(abs(fft(y)),'r') plot(abs(fft(.1*x)),'g') | <urn:uuid:9732dff6-3acb-4a83-b3d4-b7bdd5b2e83c> | 3.5625 | 1,161 | Truncated | Science & Tech. | 58.477663 | 95,622,655 |
How can the Universe be studied? There is no way to affect a research object of infinite dimensions. It means that the research can only be carried out via observations, employing all methods available. To this end scientists have been inventing more and more powerful telescopes which would enable them to examine closely remote spots of the Universe and to hear a `voice` of the sky at all available bandwidths. The scientists are planning to dispatch to space a cryogen submillimetric telescope called `Submillimetron`, which is supposed to play the role of a supersensitive `ear`. Hopefully, this device will provide astronomers with the first map of the Universe radiation at a 3 THz waveband. It is worth noting that the wavelength of this bandwidth makes tenth parts of a millimetre, it means that the bandwidth is at the boundary between infrared rays and microwave frequency. The stars are almost invisible at submillimetric waves and do not prevent the scientists from seeing remote Galaxies.
The Galaxies are so far away, that the time period required for their radiation to reach the Earth is close to the age of the Universe. By now the scientists have found only a few such remote Galaxies with the help of optic telescopes, while `Submillimetron` will find about a million of such objects, this invention will reveal an almost unexplored world. A team of the experienced scientists from Sweden, Finland and Russia are developing the unique device. The Russian party is represented by Academician N. Kardashev, who is heading the research activities of the project, the following entities being involved in the project implementation: Centre of Astronomy and Space, (Physical Institute of the Academy of Sciences), Institute of Physical Problems (Russian Academy of Sciences), Institute of Radio Engineering and Electronics (Russian Academy of Sciences) as well as Space Rockets Corporation `Energy`, which is in charge of the telescope delivery to the space station.
It is impossible to perceive THz-radiation on the Earth - it is overlapped by the infrared radiation. That is why the telescope is to be transported to space `to listen to the stars` without disturbances, although even in space the telescope will have to be screened -from the solar and earth radiation in this case.
Olga Maksimenko | alphagalileo
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine | <urn:uuid:b90fecc8-8e38-4170-be16-5eb4fc01b0da> | 3.765625 | 1,103 | Content Listing | Science & Tech. | 37.649686 | 95,622,658 |
Can radiocarbon dating date
By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
A common misconception about radiocarbon dating is that it gives a precise date---3577 B. In actual practice radiocarbon dating can only give a range of dates for a given sample---3650 to 3410 B.
C., for example---the true date lying somewhere in that range.
We will deal with carbon dating first and then with the other dating methods.
Carbon has unique properties that are essential for life on Earth. | <urn:uuid:aa009f6f-6896-488c-b979-3c66a0465474> | 3.71875 | 163 | Knowledge Article | Science & Tech. | 55.495103 | 95,622,693 |
The findings come as an increasing number of studies – of both lab animals and humans – are revealing that some synthetic chemicals in household products can cause health problems by interfering with normal hormone action.
Called endocrine disruptors, or endocrine disrupting substances (EDS), such chemicals have been linked in animal studies to a variety of problems, including cancer, reproductive failure and developmental anomalies.
This is the first endocrine study to investigate the hormone effects of the antibacterial compound triclocarban (also known as TCC or 3,4,4'-trichlorocarbanilide), which is widely used in household and personal care products including bar soaps, body washes, cleansing lotions, wipes and detergents. Triclocarban-containing products have been marketed broadly in the United States and Europe for more than 45 years; an estimated 1 million pounds of triclocarban are imported annually for the U.S. market.
The researchers found two key effects: In human cells in the laboratory, triclocarban increased gene expression that is normally regulated by testosterone. And when male rats were fed triclocarban, testosterone-dependent organs such as the prostate gland grew abnormally large.
Also, the authors said their discovery that triclocarban increased hormone effects was new. All previous studies of endocrine disruptors had found that they generally act by blocking or decreasing hormone effects.
“This finding may eventually lead to an explanation for some rises in some previously described reproductive problems that have been difficult to understand,” said one author, Bill Lasley, a UC Davis expert on reproductive toxicology and professor emeritus of veterinary medicine. More analyses of antibacterials and endocrine effects are planned, he said.
Consumers should not take this study as guidance on whether to use triclocarban-containing products, Lasley said. “Our mothers taught us to wash our hands well before the advent of antimicrobial soaps, and that practice alone prevents the spread of disease.”
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:e0c96a1a-53cb-480d-a2d7-0bb19fb4b30b> | 3.09375 | 1,002 | Content Listing | Science & Tech. | 30.720588 | 95,622,702 |
Type Function Library io.* Return value String, Number, or
Revision 2018.3333 Keywords io, read, file See also io.open() io.input()
Reads the file set by io.input(), according to the given formats which specify what to read. For each format, the function returns a string or a number with the characters read, or
nil if it cannot read data with the specified format. When called without formats, it uses a default format that reads the entire next line (
If you are reading data from a file,
file:read() should be used instead of
io.read( [fmt1] [, fmt2] [, ...] )
"*l"— Reads the next line (skipping the end of line), returning
nilon end of file (EOF). This is the default format.
"*n"— Reads a number; this is the only format that returns a number instead of a string.
"*a"— Reads the whole file, starting at the current position. On end of file, it returns the empty string.
nilon end of file. If this number is
0, it reads nothing and returns an empty string, or
nilon end of file. | <urn:uuid:2aadc1fd-4803-40e6-9d97-48935a34bc13> | 3.859375 | 262 | Documentation | Software Dev. | 77.026991 | 95,622,710 |
Biology Question #2572
stephanie, a 13 year old female from windsor asks on February 13, 2005,
Why can't spruce trees compete with maple trees in more southern forests? What advantages do the maple trees have?
viewed 14211 times
answered on February 19, 2005
The answer is surface area. The bigger the leaves the more energy can be captured from sunlight and used to help the tree grow. The maple tree has large flat leaves that do this very effeciently while the spruce has needles with a smaller area, so they cannot grow as quickly or survive as well in lower light areas as the maple. The problem is that large leaves are not good in the winter since they would dry out quickly once the tree freezes and then would die. To get around this problem the maple looses its leaves each winter. The spruce has a different solution - it has leaves with a small surface area and a waxy coating that stops them form drying out when frozen. The problem for the maple is that it takes a certain amount of time to grow the leaves in the spring which results in lost growing time compared to the spruce. In southern areas the lost growing time is more than made up for by the larger leaves... but in the north where the growing season is shor! ter the advantage goes to the spruce with its year round needles.
Add to or comment on this answer using the form below.
Note: All submissions are moderated prior to posting.
If you found this answer useful, please consider making a small donation to science.ca. | <urn:uuid:0d0bfdf4-8559-485e-853d-6d8d1e46cead> | 3.765625 | 326 | Q&A Forum | Science & Tech. | 66.645758 | 95,622,716 |
Projectional Editing: The Future of Programming
Projectional Editing: The Future of Programming
Learn about the Projectional Editor technology for programming, how it's being used to create domain-specific languages, and more.
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We have been taught for many years how programming should be done. Have you ever stopped for a second and questioned whether perhaps there is a better way?
In the beginning, programming was done in absolute binary. For years this was the only way to do it. It was only later that the Symbolic Optimal Assembly Program (SOAP) was introduced. For old developers, using assembly was “sissy stuff” and a real programmer would not waste machine capacity on doing the assembly.
Developers had an easier way to code right in the front of their eyes, but a lot of them still refused to see it.
It was a similar story in 1957 when John Backus and his team created Fortran. The community was again skeptical that this new method could outperform assembly. Old generations stuck to their old ways.
Looking back now, it seems like the decision to change technology should have been clear, but at the time it was not. Nowadays, more and more developers are receptive to new technologies, but it is hard to change the fundamental principles with which programmers were taught.
Now, we again have a unique technology before us called Projectional Editing. Projectional Editing is not a new technology; back in 2008, Martin Fowler was already talking about it. JetBrains MPS is already using this technology for its language workbench to create domain-specific languages.
A projectional editor allows the user to efficiently edit the abstract syntax tree (AST) representation of the code. It can mimic the behavior of a text editor for textual notations, a diagram editor for graphical languages, a tabular editor for editing tables, and so on. The user interacts with the code through intuitive on-screen visuals.
In parser-based approaches, users use text editors to enter character sequences that represent programs. A parser then checks the program for syntactic correctness and constructs an abstract syntax tree (AST) from the character sequence. The AST contains all the semantic information expressed by the program, i.e. keywords, and the purely syntactic aspects are then committed.
In projectional editors, the process happens the other way around: as a user edits the program, the AST is modified directly. This is similar to the Model-view-controller (MVC) pattern where every editing action triggers a change in the AST.
When editing a UML diagram, for example, users don't draw pixels onto a canvas for an "image parser" to read the drawing, parse it, and then create the AST. That would be way too limiting to what you can draw so that the engine would understand. Rather, the editor creates an instance of a Class as you drag a class from the palette to the canvas. A projection engine then renders the diagram, in this case drawing a rectangle for the class. You can then re-arrange visual elements on the screen without changing the meaning of your diagram.
This approach can be generalized to also work with text editors. Every program element is stored as a node with a unique ID (UID) in the AST. References are based on actual pointers (references to UIDs). The AST is actually an ASG, (an abstract syntax graph), from the start, because cross-references are first-class rather than being resolved after parsing. The program is then persisted to disk as XML, but this process is transparent to the user.
Avoiding the parser provides users with two more benefits:
Detaching the notation from the persistence format of the code enables multiple notations to be defined for a single language. The users can then interact with the code through one notation, and use another notation to debug, review code, or resolve merge conflicts.
Languages can be modularized, and users can then combine languages that they want to use in their programs. The projectional editor easily resolves any ambiguities in language definitions.
As part of the new IT industry generation, we have to question the status quo and dogmas established by the old generations. We should not settle for less, we need to be our own critics on everything from UI element to fundamental statements of programming. Projectional Editing is here and we can either choose to ignore it or seize it for all its worth.
If you are still curious about Projectional Editing you can join the JetBrains MPS webinar which will take place September 19, 4:00 PM - 5:00 PM CEST. Register here.
Opinions expressed by DZone contributors are their own. | <urn:uuid:daa3f38c-d489-4de0-9e7d-73b3248cc956> | 3.015625 | 1,014 | Truncated | Software Dev. | 45.667802 | 95,622,746 |
I’ve started with Ideals in ring theory but still not comfortable with the analogy it has with normal subgroups in group theory.Like we can visualize normal subgroups as
Is there some good intutive way to visualize Ideals to see the analogy?
These two pictures give a reasonable description of how cosets work, but they are not really suitable for explaining why normal subgroups and ideals are “analogous.”
These two diagrams say, in effect, “$G$ can be split up into chunks (cosets) and $gH$ is basically $H$ translated by $g$. These two translations are different in general, but when $H$ is normal, multiplying on the left and the right unambiguously translate $H$ to $gH=Hg$.”
But that is basically where the usefulness of looking at the internal structure of cosets ends. The fruitful path is to then ask “Is there some obvious structure that makes the set of cosets more than a set? Can I make it into a group or a ring?”
For groups, the obvious candidate for $aH\cdot bH$ is $abH$. But as you probably know, this isn’t well defined unless $H$ is normal in $G$.
If $R$ is a ring and $I$ is an ideal, then not only do we need $I$ to be a normal subgroup of $(R,+)$, so that $(a+R)+(b+R)=a+b+R$ is well defined, we also need $(a+r)(b+R)=ab+R$ to be well defined. It turns out that the absorption properties of ideals are exactly saying that this multiplication is well defined, so that the set of cosets becomes a ring.
Once you make the set of cosets into a group (or a ring) then you can talk about the homomorphism $G\to G/H$ and $R\to R/I$, and see that $H$ is the kernel of the first homomorphism, and $I$ is the kernel of the second homomorphism. This gives an equivalent way of looking at normal subgroups and ring ideals: they are precisely the kernels of homomorphisms. This viewpoint is probably the most unifying of the two ideas (and indeed many more.)
Later on, conditions on the quotient $G/H$ (or $R/I$) can circle back to be conditions on $H$ and $I$. When learning about the two concepts in general for the first time, though, it makes more sense to focus on what these two definitions mean for the quotient, and not for the internal structure of each coset. | <urn:uuid:45e6a96e-58df-4917-af40-a4a91129fc06> | 2.796875 | 577 | Personal Blog | Science & Tech. | 61.410404 | 95,622,753 |
Advanced Assembler Directives
- The syntax of this directive is
ORIGIN <address specification>
where <address specification> is an <operand specification> or <constant>.
- This directive instructs the assembler to put the address given by <address specification> in the location counter.
- The ORIGIN statement is useful when the target program does not consist of a single contiguous area of memory.
- The ability to use an <operand specification> in the ORIGIN statement provides the ability to change the address in the location counter in a relative rather than absolute manner.
- The EQU directive has the syntax
<symbol> EQU <address specification>
where <address specification> is either a <constant> or <symbolic name> ±
- The EQU statement simply associates the name <symbol> with the address specified by <address specification>. However, the address in the location counter is not affected.
- The LT0RG directive, which stands for ‘origin for literals’, allows a programmer to specify where literals should be placed.
- The assembler uses the following scheme for placement of literals: When the use of a literal is seen in a statement, the assembler enters it into a literal pool unless a matching literal already exists in the pool.
- At every LTORG statement, as also at the END statement, the assembler allocates memory to the literals of the literal pool and clears the literal pool.
- This way, a literal pool would contain all literals used in the program since the start of the program or since the previous LTORG statement.
- Thus, all references to literals are forward references by definition.
- If a program does not use an LTORG statement, the assembler would enter all literals used in the program into a single pool and allocate memory to them when it encounters the END statement.
ORIGIN [ Advanced Assembler Directives ]
- Statement number 18 of the above program viz. ORIGIN LOOP + 2 puts the address 204 in the location counter because symbol LOOP is associated with the address 202. The next statement MULT CREG, B gave the address 204.
- On encountering the statement BACK EQU LOOP, the assembler associates the symbol BACK with the address of LOOP i.e. with 202.
LTORG [ Advanced Assembler Directives ]
- In assembly program, the literals =’5′ and =’1′ added to the literal pool in Statements 2 and 6, respectively. The first LTORG statement (Statement 13) allocates the addresses 211 and 212 to the values ‘5’ and ‘1’. A new literal pool now started. The value T is put into this pool in Statement 15. This value allocated the address 219 while processing the END statement. The literal =’1′ used in Statement 15 therefore refers to location 219 of the second pool of literals rather than location 212 of the first pool. | <urn:uuid:6b18e824-e7ec-40e2-9292-707e64e055e7> | 3.796875 | 632 | Documentation | Software Dev. | 38.46516 | 95,622,759 |
Artist’s impression of NASA’s Solar Probe Plus spacecraft on approach to the sun. Set to launch in 2018, Solar Probe Plus will orbit the sun 24 times, closing in with the help of seven Venus flybys. The spacecraft will carry 10 science instruments specifically designed to solve two key puzzles of solar physics: why the sun’s outer atmosphere is so much hotter than the sun’s visible surface, and what accelerates the solar wind that affects Earth and our solar system. The Johns Hopkins University Applied Physics Laboratory manages the Solar Probe Plus mission for NASA and leads the spacecraft fabrication, integration and testing effort.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory
Solar Probe Plus Moves into Advanced Development
Solar Probe Plus — NASA’s ambitious mission to fly through and examine the sun’s atmosphere — has reached a key stage of development.
Solar Probe Plus will begin advanced design, development and testing — a step NASA designates as Phase C — following a successful design review in which an independent assessment board deemed that the mission team, led by the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., was ready to move ahead with full-scale spacecraft fabrication, assembly, integration and testing.
Technicians at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., prepare an engineering model of the Solar Probe Plus Thermal Protection System, or TPS, for vibration tests in October 2013. The main feature of the TPS is an 8-foot-diameter, 4.5-inch-thick, carbon-carbon, carbon foam shield that will sit atop the Solar Probe Plus spacecraft body. The system will protect Solar Probe Plus from temperatures exceeding 2,500 degrees Fahrenheit and impacts from hypervelocity dust particles as it flies through the sun’s outer atmosphere. The vibration tests simulate the shaking the spacecraft will undergo during launch; Solar Probe Plus is scheduled to launch in 2018.
Credit: Johns Hopkins University Applied Physics Laboratory
“Solar Probe Plus will fly closer to the sun than any spacecraft before it — almost 10 times closer to the sun than the planet Mercury — and this presents unprecedented technical challenges,” says Andrew Driesman, Solar Probe Plus project manager at APL. “Whether it was devising ways for a spacecraft to survive so close to the sun, or to collect data in such an extreme environment, the concept of an operational solar probe had challenged engineers and scientists for decades, and now we’re another step closer to making it happen.”
Set to launch in 2018, Solar Probe Plus will orbit the sun 24 times, closing in with the help of seven Venus flybys. At its closest passes the probe will speed 118 miles per second through the sun’s outer atmosphere, or corona, coming about 3.8 million miles (about 6.2 million kilometers) from the surface to explore a region — and face hazards — no other spacecraft has encountered. Solar Probe Plus will carry 10 science instruments specifically designed to help solve two key puzzles of solar physics: why the sun’s outer atmosphere is so much hotter than the sun’s visible surface, and what accelerates the solar wind that affects Earth and our solar system.
“The answers to these questions can be obtained only through in-situ measurements of the solar wind down in the corona,” says APL’s Nicky Fox, Solar Probe Plus project scientist. “Solar Probe Plus gets close enough to provide the missing links, with the right complement of instruments to make the measurements. For the first time, we will be able to go up and touch our star.”
APL, which manages the mission and leads the spacecraft fabrication and integration effort, has made significant progress on several enabling technologies, such as the carbon-carbon composite heat shield that will protect Solar Probe Plus from temperatures exceeding 2,500 degrees Fahrenheit and impacts from hypervelocity dust particles. Engineers have also built and tested a liquid-cooling system to keep the spacecraft’s solar arrays at safe operating temperature throughout the voyage, and spacecraft parts are undergoing high-velocity dust tests that simulate flights through swarms of high-energy particles near the sun.
“Solar Probe Plus is a pathfinder for voyages to other stars and will explore one of the last unexplored regions of the solar system, the solar corona, where space weather is born,” says Lika Guhathakurta, Solar Probe Plus program scientist at NASA Headquarters in Washington.
The Solar Probe Plus team includes engineers, scientists, technicians and other experts from government, academia and industry. The mission is part of NASA’s Living With a Star program, designed to learn more about the sun and its effects on planetary systems and human activities. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the program for the Science Mission Directorate at NASA Headquarters.
Quelle: The Johns Hopkins University Applied Physics Laboratory LLC.
NASA Gives Green Light for Johns Hopkins APL to Begin Building Solar Probe Plus Spacecraft
Artist rendering of Solar Probe Plus, solar panels folded into the shadows of its protective shield, as it gathers data on its approach to the sun.
NASA’s Solar Probe Plus mission — which will fly closer to the sun than any spacecraft has before — reached a major milestone last month when it successfully completed its Critical Design Review, or CDR.
An independent NASA review board met at the Johns Hopkins University Applied Physics Laboratory, or APL, in Laurel, Maryland, March 16-20, 2015, to review all aspects of the mission plan. APL has designed and will build and operate the spacecraft for NASA. The CDR certifies that the Solar Probe Plus mission design is at an advanced stage and that fabrication, assembly, integration and testing of the many elements of the mission may proceed.
Solar Probe Plus is scheduled to launch aboard a United Launch Alliance Delta 4-Heavy rocket with an upper stage from Cape Canaveral Air Force Station, Florida. The launch window opens for 20 days starting on July 31, 2018. Over 24 orbits, the mission will use seven flybys of Venus to reduce its distance from the sun. The closest three will be just 3.8 million miles from the surface of the star.
Scientists have long wanted to send a probe through the sun’s outer atmosphere, or corona, to better understand the solar wind and the material it carries into our solar system. The primary science goals for the Solar Probe Plus mission are to trace the flow of energy and understand the heating of the solar corona and to explore the physical mechanisms that accelerate the solar wind and energetic particles.
To meet those objectives, Solar Probe Plus will carry four instrument suites into the corona and study the solar wind and energetic particles as they blast off the surface of the star. These instruments will study magnetic fields, plasma, and energetic particles, and will image the solar wind. The instruments are: the Fields Experiment from the University of California Space Sciences Laboratory, Berkeley, California; the Integrated Science Investigation of the Sun from the Southwest Research Institute, San Antonio; the Solar Wind Electrons Alphas and Protons Investigation from the Smithsonian Astrophysical Observatory, Cambridge, Massachusetts; and the Wide Field Imager for Solar Probe Plus from the Naval Research Laboratory, Washington, D.C.
The spacecraft and instruments will be protected from the sun’s heat by a 4.5-inch-thick carbon-composite shield. During the closest passes around the sun, temperatures outside the spacecraft will reach nearly 2,500 degrees Fahrenheit.
Solar Probe Plus is part of NASA’s Living With a Star Program to explore aspects of the connected sun–Earth system that directly affect life and society. LWS is managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland, for NASA’s Science Mission Directorate in Washington.
Solar Probe Plus Mission Moves Closer to 'Touching the Sun' in 2024
Artist’s conception of the Solar Probe Plus spacecraft near the Sun. Image Credit: NASA/JHUAPL
The Solar System is a busy place, with spacecraft currently visiting most of the planets as well as some dwarf planets and comets. Akatsuki is at Venus, several rovers and orbiters are at Mars, the Juno spacecraft just reached Jupiter, Cassini is still orbiting Saturn, Dawn is still at Ceres, and Rosetta continues to study the comet 67P. Mercury, Uranus, Neptune, and Pluto have all been visited by previous missions as well. But there is one other place in the Solar System which will also be explored more closely in the near future: the Sun.
The Sun may seem like an unlikely place to want to send a probe since you can only get so close before being fried to dust. NASA wants to do just that, however, with a new mission called Solar Probe Plus. The mission, which will be the first to “touch” the Sun’s outer atmosphere, is now on track for a planned launch in the summer of 2018, with a first close approach in 2024.
The mission has just passed a critical development milestone, with a successful NASA management review on July 7. It is now moving into the system assembly, integration, test, and launch stage, known as Phase D, which continues until launch.
“Reaching this stage means a lot to the team and our stakeholders,” said Andy Driesman, Solar Probe Plus project manager at the Johns Hopkins Applied Physics Laboratory (JHUAPL), which manages the mission for NASA and is building the spacecraft. “It shows we’ve designed a spacecraft, instruments and a mission that can address the engineering challenges associated with the harsh solar environment, and send back the data that scientists have sought for decades. It’s humbling to see designs and ideas start to become a spacecraft.”
The Solar Probe Plus under construction at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. Photo Credit: NASA/JHUAPL
Illustration of the Solar Probe Plus spacecraft. Image Credit: JHUAPL
The spacecraft itself will be about 8 feet (2.4 meters) in diameter and weigh 1,350 pounds (612 kilograms).
SPP won’t get too close, but it will pass several times through the Sun’s outer atmosphere, the corona, during a period of 24 orbits, to collect data. With each pass, it will move a bit closer to the Sun. At its closest, during three orbits, it will pass within 3.9 million miles (6.3 million kilometers) of the Sun’s surface, which is about seven times closer than any previous spacecraft has been, including ones at Mercury. The solar energy at that distance will be immense, about 500 times more than spacecraft tend to have to deal with at Earth’s distance from the Sun. Mercury, by comparison, is 35.98 million miles (57.9 million kilometers) from the Sun. A 4.5-inch (11.4-centimeter) thick carbon-composite shield will protect the probe’s instruments from temperatures reaching nearly 2,500 degrees Fahrenheit (1,371 degrees Celsius). The previous record holder was the Helios 2 spacecraft, which passed about 27 million miles (44 million kilometers) from the Sun in April 1976.
The main objectives of the mission include obtaining new data on solar activity to help to better forecast space-weather events like solar flares which can directly impact Earth and orbiting satellites, trace the flow of energy from the Sun, better understand how the Sun’s outer atmosphere is heated, and explore the physical mechanisms which accelerate the solar wind. The solar wind is the continuous stream of charged and energetic particles flowing out from the Sun, which can affect spacecraft.
Four different instrument suites on SPP will study the Sun’s magnetic fields, plasma, energetic particles, and solar wind. Five different science investigations include:
Solar Wind Electrons Alphas and Protons Investigation, which will specifically count the most abundant particles in the solar wind—electrons, protons, and helium ions—and measure their properties. The investigation also is designed to catch some of the particles in a special cup (known as a Faraday cup) for direct analysis. Principal Investigator: Justin C. Kasper, Smithsonian Astrophysical Observatory, Cambridge, Mass.
The Wide-field Imager, a telescope that will make 3-D images of the Sun’s corona, or atmosphere. The experiment actually will see the solar wind and provide 3-D images of clouds and shocks as they approach and pass the spacecraft. This investigation complements instruments on the spacecraft providing direct measurements by imaging the plasma the other instruments sample. Principal Investigator: Russell Howard, Naval Research Laboratory, Wash.
The Fields Experiment, which will make direct measurements of electric and magnetic fields, radio emissions, and shock waves that course through the Sun’s atmospheric plasma. The experiment also serves as a giant dust detector, registering voltage signatures when specks of space dust hit the spacecraft’s antenna. Principal Investigator: Stuart Bale, University of California Space Sciences Laboratory, Berkeley, Calif.
The Integrated Science Investigation of the Sun, which consists of two instruments that will take an inventory of elements in the Sun’s atmosphere using a mass spectrometer to weigh and sort ions in the vicinity of the spacecraft. Principal Investigator: David McComas, Southwest Research Institute, San Antonio.
Heliospheric Origins with Solar Probe Plus Principal Investigator Marco Velli, of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., is the mission’s observatory scientist, responsible for serving as a senior scientist on the science working group. He will provide an independent assessment of scientific performance and act as a community advocate for the mission.
A few “fun facts” about the mission include:
Solar Probe Plus will orbit the Sun 24 times, gradually “walking in” toward the Sun with each pass. The closest points of each orbit come well within orbit of Mercury, the closest planet to the Sun.
On the final three orbits, Solar Probe Plus will fly to within 8.5 solar radii of the Sun’s “surface” 8.5 solar radii is 8.5 times the radius of the Sun, or about 3.7 million miles. That is about seven times closer than the current record-holder for a close solar pass, the Helios spacecraft.
At closest approach, Solar Probe Plus will be hurtling around the Sun at approximately 450,000 miles (739,000 kilometers) per hour! That’s fast enough to get from Philadelphia to Washington, D.C., in one second.
Solar Probe Plus will pass Venus less than two months after launch and will be collecting science data at its first solar pass just one month later.
At closest approach to the Sun, while the front of Solar Probe Plus’ solar shield faces temperatures approaching 2,500 degrees Fahrenheit (or about 1,400 degrees Celsius), the spacecraft’s payload will be near room temperature.
The mission was first approved back in April 2015, after completing a Critical Design Review (CDR).
“The completion of CDR is a testament to the focused, diligent work of APL, NASA, the instrument teams and our industry partners,” said Driesman. “We’re excited to continue working on a difficult mission that’s been more than 50 years in the making, one that is now achievable thanks to advances in technology, materials and design.”
Solar Probe Plus will make several close flybys of Venus during its mission. Image Credit: JHU/APL
Solar Probe Plus is scheduled to launch aboard a United Launch Alliance Delta 4-Heavy rocket with an upper stage from Cape Canaveral Air Force Station in Florida, with a launch window opening for 20 days starting on July 31, 2018. The mission timeline, in brief:
Launch – July 31, 2018
Venus flyby #1 – Sept. 27, 2018
Venus flyby #2 – Dec. 21, 2019
Venus flyby #3 – July 5, 2020
Venus flyby #4 – Feb. 15, 2021
Venus flyby #5 – Oct. 10, 2021
Venus flyby #6 – Aug. 15, 2023
Venus flyby #7 – Oct. 31, 2024
First close approach – Dec. 19, 2024
Solar Probe Plus has actually been in a concept stage for the past 50 years, with various previous designs; the current design is based on a proposal from 2005, in a study performed at the Johns Hopkins University Applied Physics Laboratory (JHUAPL). The original design would have used nuclear power (an RTG engine), but that was replaced with the newer design, without the RTG and for less cost. The new design is actually capable of providing more science than before as well. Solar Probe Plus is the keystone of the Living With a Star (LWS) program.
Understanding how the Sun behaves is of course important since it can directly affect life on Earth. Our Sun is a relatively stable star, but changes in solar energy output, such as during massive solar flares, can still have an impact. The data gathered should also help scientists better understand other stars as well, especially ones which are similar to our Sun, and how this may affect the potential habitability of some exoplanets. | <urn:uuid:c03d2ca3-c98d-461f-a5a0-0acb1c615a23> | 3.5 | 3,605 | News (Org.) | Science & Tech. | 44.517716 | 95,622,763 |
Findings reported this week reveal how an evolutionary innovation involving the sharing of genes between two ant species has given rise to a deep-seated dependency between them for the survival of both species populations. The new work illustrates how genetic exchange through interbreeding between two species can give rise to a system of interdependence at a high level of biological organization--in this case, the production of worker ants for both species.
Millions of years before the first modern humans evolved, ants were practicing many of the social innovations we consider to be our own: division of labor, agriculture, and even slavery. Indeed, these traits have been taken to their extreme in many ant species, such as the case of slavemaker ants, which have become so specialized for raiding food from the colonies of other ants that they can no longer feed themselves or raise their younger siblings. Recent work on ants suggests that we may need to add genetic engineering to the list of innovations ants have evolved to employ. In two species of harvester ants, populations have been discovered in which queens mate with males of another species to produce genetically novel hybrid workers. In a new study, Dr. Sara Helms Cahan and colleagues demonstrate that both of the species involved have effectively given up the ability to produce pure-species workers in favor of the hybrids, thereby becoming completely dependent on one another for survival.
Female ants are generally found in two forms: reproductive queens and sterile workers. The role, or caste, of an individual is determined for life at a certain stage in her development. In virtually all ant species, it is the environment in which a female is raised, rather than a genetic predisposition, that determines which caste she will adopt. However, in two harvester ant populations in southern New Mexico, queens and workers from the same colonies are genetically very different; in both species at the site, only the queens are genetically derived from a pure species-specific lineage, whereas all the workers are hybrids that possess a combination of genes from the two species in a single individual. It is not currently known whether the ants benefit from having hybrids do the work, but, as is evident from the researchers own attempts at selective breeding and genetic engineering, combining genomes is an easy way to produce novel characteristics that may be highly advantageous for growth, environmental tolerance, or disease resistance. Regardless of the specific advantages, however, it is clear that these ants have committed themselves to the hybrid workforce strategy. When the researchers prevented queens from mating with males of the other species, very few succeeded in making any workers at all, a handicap that would lead to certain population failure in the field. The new findings suggest that specialization involving reliance on interspecific hybrid workers has left these species unable to survive independently of one another.
Heidi Hardman | EurekAlert!
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:317b2e19-bb2b-4aa3-a13b-693b4cfbe11c> | 3.796875 | 1,227 | Content Listing | Science & Tech. | 34.632899 | 95,622,764 |
Greenhouse Gases Observing Satellite
Planned: 5 years |
Elapsed: 9 years, 5 months, 25 days
|Launch mass||1,750 kilograms (3,860 lb)|
|Start of mission|
|Launch date||23 January 2009, 03:54UTC|
|Launch site||Tanegashima Yoshinobu 1|
|Perigee||674 kilometres (419 mi)|
|Apogee||676 kilometres (420 mi)|
|Epoch||25 January 2015, 03:12:11 UTC|
|Wavelengths||12900 - 13200 cm−1 / 5800 - 6400 cm−1 / 4800 - 5200 cm−1 / 700 - 1800 cm−1 (FTS)|
|Resolution||0.2 cm−1 (FTS)|
TANSO-FTS - Infrared Fourier Transform Spectrometer|
TANSO-CAI - Thermal and Near-Infrared Sensor
The Greenhouse Gases Observing Satellite (GOSat), also known as Ibuki (Japanese: いぶき Hepburn: Ibuki, meaning "breath"), is an Earth observation satellite and the world's first satellite dedicated to greenhouse-gas-monitoring. It measures the densities of carbon dioxide and methane from 56,000 locations on the Earth's atmosphere. The GOSAT was developed by the Japan Aerospace Exploration Agency (JAXA) and launched on 23 January 2009, from the Tanegashima Space Center. Japan's Ministry of the Environment, and the National Institute for Environmental Studies (NIES) use the data to track gases causing the greenhouse effect, and share the data with NASA and other international scientific organizations.
GOSAT was launched along with seven other piggyback probes using the H-IIA, Japan's primary large-scale expendable launch system, at 3:54 am on 23 January 2009 UTC on Tanegashima, a small island in southern Japan, after a two-day delay due to unfavourable weather. At approximately 16 minutes after liftoff, the separation of Ibuki from the launch rocket was confirmed.
According to JAXA, the Ibuki satellite is equipped with a greenhouse gas observation sensor (TANSO-FTS) and a cloud/aerosol sensor (TANSO-CAI) that supplements TANSO-FTS. The greenhouse gas observation sensor of Ibuki observes a wide range of wavelengths (near-infrared region–thermal infrared region) within the infrared band to enhance observation accuracy. The satellite uses a spectrometer to measure different elements and compounds based on their response to certain types of light. This technology allows the satellite to measure "the concentration of greenhouse gases in the atmosphere at a super-high resolution."
- "Outlines of GOSAT and TANSO Sensor" (PDF). Retrieved 26 January 2009.
- "Orbit Insertion of the Greenhouse Gases Observing Satellite "IBUKI" (GOSAT)" (PDF) (Press release). JAXA. Retrieved 26 January 2009.
- "GOSAT (IBUKI) Satellite details 2009-002A NORAD 33492". N2YO.com. 25 January 2015. Retrieved 25 January 2015.
- "'IBUKI' Chosen as Nickname of the Greenhouse Gases Observing Satellite (GOSAT)" (Press release). JAXA. 15 October 2008. Retrieved 29 May 2009.
- "Japan launches rocket with greenhouse-gas probe". The Associated Press. 23 January 2009. Retrieved 23 January 2009.
- Fujioka, Chisa (23 January 2009). "Japan launches satellite to monitor greenhouse gases". Reuters. Retrieved 23 January 2009.
- "Greenhouse gases Observing SATellite "IBUKI"(GOSAT)". Japan Aerospace Exploration Agency. Retrieved 23 January 2009.
- Gerein, Keith (21 January 2009). "Alta. scientists to track greenhouse gases from space". Calgary Herald. Archived from the original on 31 January 2009. Retrieved 24 January 2009. | <urn:uuid:46cb4f8b-466c-4d16-909a-d117a13af9c7> | 3.34375 | 856 | Knowledge Article | Science & Tech. | 47.854217 | 95,622,789 |
A New Technique of Tollmien-Schlichting Wave Cancellation in a Sound-Exposed Boundary Layer
It is well know that sound can reduce the laminar portion of a boundary layer. Sound reflects from a wing surface and generates unstable waves (Tollmien-Schlichting waves) which undergo linear amplification and non-linear interactions, and eventually lead to turbulence. Acoustic disturbances excite T.-S. waves via scattering by longitudinal inhomogeneities in the boundary layer, such as in the vicinity of the wing leading edge or because of unevenness on the wing surface. Unstable wave generation near the leading edge of a wing was investigated experimentally by Shapiro (1977). The generation over unevenness was investigated experimentally by Aizin & Polyakov (1984) and theoretically by Ruban (1984) and Goldstein (1985). Of course the second mechanism of unstable wave generation may be removed by smoothing the wing surface, but the leading edge inhomogeneity is not removable. The methods of boundary layer flow laminarization proposed here are based upon mutual cancellation of T.-S. waves excited near the leading edge and over artificial unevenness. Such cancellation is achieved by a special choice of unevenness. The paper is devoted to mathematical justification of such methods.
KeywordsBoundary Layer Boundary Layer Flow Laminar Boundary Layer Wing Surface Unstable Wave
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- Aizin, L.B. and Polyakov, N.F. 1979 Acoustic generation of Tollmien Schlichting waves over local unevenness of surface immersed in stream. Preprint 17, Akad. Nauk SSSR, Siberian Div. Inst. Theor. Appl. Mech, Novosibirsk.Google Scholar
- Kosorygin, V.S. and Polyakov, N.F. 1990 The autodestruction of unstable waves in laminar boundary layer flow, Preprint 11, Akad. Nauk SSSR, Siberian Div. Inst. Theor. Appl. Mech, Novosibirsk.Google Scholar
- Manuilovich, S.V. 1990 On the possibility of cancellation of Tollmien-Schlichting waves by sound, Dokl. Akad. Nauk SSSR, 313, 280–282.Google Scholar
- Ruban, A.I. 1984, On the generation of Tollmien-Schlichting waves by sound, Izv. Akad. Nauk SSSR, Mekh, Zhidk. Gaza, 5, 44–52.Google Scholar
- Shapiro, P.J. 1977 The influence of sound upon laminar boundary layer instability, MIT Acoustic and Vibration Lab Rep 83458–83560-1. Google Scholar | <urn:uuid:5aa71ef9-0a41-407a-ad72-27984864bc6e> | 2.953125 | 581 | Academic Writing | Science & Tech. | 47.82512 | 95,622,791 |
- Open Access
Flexibility of foraging strategies of the great skua Stercorarius skua breeding in the largest colony in the Barents Sea region
© The Author(s). 2018
Received: 8 November 2017
Accepted: 15 March 2018
Published: 23 March 2018
Foraging strategies of seabird species often vary considerably between and within individuals. This variability is influenced by a multitude of factors including age, sex, stage of annual life cycle, reproductive status, individual specialization and environmental conditions.
Using GPS-loggers, we investigated factors affecting foraging flight characteristics (total duration, maximal range, total distance covered) of great skuas Stercorarius skua of known sex breeding on Bjørnøya, Svalbard, the largest colony in the Barents Sea region. We examined influence of sex (females are larger than males), phase of breeding (incubation, chick-rearing), reproductive status (breeders, failed breeders) and bird ID (they are known for individual foraging specialization). Our analyses revealed that only bird ID affected foraging flight characteristics significantly, indicating a high degree of plasticity regardless of sex, reproductive status or phase of breeding. We recognized three main groups of individuals: 1) those preying mainly on other seabirds in the breeding colonies (6%), 2) those foraging at sea (76%) and kleptoparasiting other seabirds and/or foraging on fish and/or offal discarded by fishing vessels, and 3) those alternating between preying on other seabirds in breeding colonies and foraging at sea (18%). Despite marked size sexual dimorphism, we found no apparent sex differences in flight characteristics. Birds after egg- or chick-loss and thus not constrained as central foragers did not modify their foraging flights.
Great skuas breeding on Bjørnøya displayed a high degree of plasticity regardless of sex, reproductive status or phase of breeding. We recognized groups of individuals regularly preying in the seabird colonies, foraging at sea, and alternating between both strategies. This suggests foraging specialization of some individuals.
Foraging strategies of seabird species often vary considerably between and within individuals. This variability results from targeting usually widely-dispersed, spatiotemporally patchy prey and the influence of a multitude of other factors including age, sex, stage of annual life cycle, reproductive status, individual specialization and environmental conditions. These factors have major implications for our understanding of seabird ecology, because they affect the use of resources, level of intra-specific competition and niche partitioning .
Sexual differences in foraging behaviour are apparent in many seabirds. This may reflect habitat specialization and/or sex-specific nutrient requirements [2–4] and reduces competition between males and females. Sexual size dimorphism is thought to play a functional role in flight performance and is used to explain differences in the at-sea distribution of male and female seabirds . Partial or complete sexual foraging segregation has been reported in several seabird groups including both sexually dimorphic and monomorphic species (e.g. [6, 7]). Sexual segregation in foraging may be especially expressed in years of greater environmental stochasticity, when food availability is reduced .
Age may affect foraging strategy considerably, and immature birds avoid competition with adults by feeding in suboptimal habitats which increases their foraging time (e.g. [9–11]). Younger or less experienced breeders may forage less efficiently and/or at a lower trophic level, which may be reflected in reduced breeding performance compared to older birds [9, 12–14]. Immatures may be far more exploratory and lack route or foraging site fidelity compared to adult breeders . Inferior foraging success in younger individuals reflects their poorer skills in identifying, catching or handling prey or in selecting suitable locations, and weaker motor control or physiological fitness .
Within a single breeding season, seabirds may adopt a temporally flexible foraging strategy to satisfy different energy and time demands of incubation and chick-rearing and both their own energetic requirements and those of their offspring. The changing degree of central-place constraint in successive phases of the breeding and seasonal changes in prey availability may affect distribution, activity patterns or diet of seabirds [4, 15, 16]. Foraging strategies may also vary within a single breeding season as a response to fluctuations in prey availability that is driven by prey biology, environmental conditions and/or prey depletion near the colony due to intense foraging (“Storer-Ashmole’s halo” [17–20]). Moreover, some species (albatrosses, petrels, little auk Alle alle) adopt an unimodal foraging strategy during incubation (trip of similar duration) and bimodal strategy during chick-rearing, alternating short trips to nearby locations to collect food for chicks, and long trips to further location mainly for self-feeding (e.g. [21–24]).
One of the less studied factors affecting foraging strategy is reproductive status. Failed breeders often continue to associate with the colony, operating as central-place foragers but expand their foraging areas . They may be partially or completely segregated from breeders, probably to avoid competition .
Many marine birds and mammals show individual feeding specializations in terms of distribution, behaviour, diet or other aspects of resource acquisition that remain after accounting for the group effects of sex, age, breeding stage and status [26, 27]. Individual specialization may be expressed in fidelity to feeding sites, consistency in foraging trip characteristics, diving patterns and other at-sea activity, habitat use, specific prey items or trophic level in the short or long term . Foraging specializations are probably learned during individual exploratory behaviours early in life, which then become canalized with age and experience [28, 29].
In this study, we investigated foraging flights of great skuas Stercorarius skua breeding on Bjørnøya (Svalbard), one of the northernmost breeding areas within this species’ range . The great skua is a dietary generalist exploiting a wide range of prey. It searches for and catches food exclusively on the wing, mainly by splash-diving onto surface fish shoals. It may also kleptoparasitise and prey on seabirds or forage on discards from fishing vessels [31, 32]. The great skua is an important predator of seabirds during the breeding season taking eggs, chicks and adult birds. Dietary specialization of great skua pairs and colonies has been documented in several studies [5, 33–36]. Remains of seabirds (mainly black-legged kittiwakes Rissa tridactyla and northern fulmars Fulmarus glacialis) and fish were found in 98 and 38% of pellets of great skuas breeding on Bjørnøya in 2008–2009. Considerable fractions (33 and 61% in 2008 and 2009, respectively) of pairs breeding there showed dietary specialization on seabirds (≥70% pellets contained only seabird remains) . The great skua breeds mainly colonially on flat or gently sloping ground. The female lays 1–2 eggs that are incubated for 26–32 days by both sexes, although mainly by the female. The semi-altricial chicks stay in the nest area for 40–51 days after hatching. The chicks are guarded mainly by the female and fed by both parents . The great skua and other skuas (Stercorariinae), like other birds with a raptorial lifestyle, display sexual size dimorphism with females being larger than males .
Despite extensive studies on the great skua foraging and breeding ecology (e.g. [35, 38, 39]), foraging flights during the chick-rearing period have been studied so far only in Shetland and St. Kilda, Outer Hebrides .
Because of various time budgets of incubating and chick-rearing individuals, birds during incubation would have longer foraging flights than during chick-rearing given the necessity of adults to feed chicks in regular intervals;
Due to various time budgets and duties, failed breeders free of central place forager constraint would have longer foraging flights to more distant areas enabling them to feed beyond the cost-effective flight distance to the colony;
Regardless of breeding status and phase of the breeding period and considering sexual size dimorphism, larger females will perform flights of longer duration and range compared to smaller males;
Individual great skuas that specialized in foraging on local resources (other seabirds on the same island) would perform shorter trips characterized by high repeatability in utilisation densities.
To characterize foraging flights of great skuas, we used global positioning system (GPS) loggers (Harrier, Skua and Uria models, Ecotone, Sopot, Poland) recording time, position and momentary speed. We deployed 21 loggers on one pair member from 21 nests. We captured the birds on nests during the incubation period in June 2014 in the colony in Flakmyrvatna area in NW part of the island. The study area contained 107 breeding pairs. The logger weight (including attachment, Harrier: 19.1–19.3 g; Skua: 26.3 g; Uria: 11.2 g) was equivalent to 1.2–1.5% (Harrier, N = 14 individuals), 1.7–2.1% (Skua, N = 4) and 0.7–0.9% (Uria, N = 3) of the bird’s body mass. The lightest logger type (Uria) was attached to the tail feathers. Other types of loggers were attached with full harness (12 Harriers, 4 Skuas) or with a loop around head and tail (2 Harriers). The GPS-loggers used a bidirectional radio link with base stations installed in the colony, allowing remote data download. To save battery life, the base station automatically switched off the loggers while they were within the download range of the base station. The loggers restarted to record positions when birds left the base station signal range. Sampling interval was set to 15 min; however, when the battery voltage was low, the interval increased to 60 min. The field-tested accuracy of the GPS receiver was ±10 m for 95% of positions. We analysed only records with sampling rates of up to 30 min. Within longer intervals between recorded positions, birds may have had time to return to the colony and start a new trip.
We sexed the studied birds molecularly based on DNA extracted from blood following a modified protocol of . We amplified CHD genes from extracted DNA by PCR using primers 2550F and 2718R . Analyses were carried out at the Norwegian University of Science and Technology, Trondheim.
Trips characteristics of GPS-equipped great skuas breeding on Bjørnøya
No of flights of GPS-tracked birds
No of birds
6 M 11F
To monitor the status of GPS-logger equipped individuals and their nests, we controlled the nest content 4–10 d days after the logger deployment. We found that all studied great skuas failed breeding. Among the 21 nests, 53% failed at the incubation stage. In the remaining 47%, at least one chick hatched but all died after 1 to 17 days. Similar breeding failure was recorded in the whole colony area, where no birds were caught. No chicks reached the age of 20 days in 107 nests monitored. We do not know the precise reason of this failure, but we observed frequent conspecific predation which can be related to unfavourable feeding conditions (HS – unpubl. data).
Based on the geographical positions recorded by the GPS-loggers, we analysed the following foraging flights characteristics: (1) maximum range of flights – distance from the colony to the distal point reached on each foraging trip; (2) the total distance covered (km) as the sum of the distances (km) between all GPS positions along each individual’s track; in the case of incomplete trips (i.e. without the first or last position), the missing part was estimated based on distance of the first/the last position nearest to the colony; (3) total trip duration, defined as the time between departure and return to colony; in the case of the incomplete trips, the lacking part was estimated based on the momentary speed and distance of the first/the last position nearest to the colony. To characterize the whole area utilized by studied individuals, we calculated minimal convex polygon (MCP).
Considering the sample size for particular studied features (sex, reproductive status, phase of breeding), we were able to perform analyses including sex and ID of birds for the incubation periods for 17 individuals. For nine individuals, we compared flight characteristics during incubation before and after eggs loss. For one male and one female, we were able to compare flight characteristics during incubation, chick-rearing and after chick loss.
To characterize flights of males and females during the incubation period, we used Conditional Inference Tree (CIT). This is a non-parametric class of regression tree, examining the relationship between multiple explanatory variables and a single response variable using a recursive binary-partitioning process. Model outputs produce an ‘inverted tree’, in which the root at the top contains all observations, which is divided into two branches at the node. The aim of splitting the data at each step is to establish groups that had a between-variation as large, and within-variations as small, as possible. The node provides information about the explanatory variable name and its probability value. Branches are further split into two subsequent nodes and so on. . CIT uses a machine learning algorithm to determine when splitting is no longer valid using statistically-determined stopping criterion, an a priori p value . CIT is robust to typical regression problems such as over-fitting, collinearity, and bias with regard to the types of explanatory variables used [47, 48]. We conducted CIT analyses in R software using party package . We checked significance of nodes in CIT analyses using structural change test implemented in strucchange package in R .
For data from the incubation period with satisfactory sample size, we calculated utilization distributions (UD, a probability distribution constructed from data providing the location of an individual in space at different points in time) for home ranges (95% kernel density) and core ranges (50% kernel density) of males and females in Geospatial Modelling Environment (GME) ver. 0.7.4.0 software (www.spatialecology.com/gme/) using kde function using plugin bandwidth selection. To investigate overlap between utilization distributions (i.e. 95 and 50% kernel density isopleth) of males and females during the incubation period before egg loss, individuals before and after egg loss, and individuals during incubation and chick-rearing periods, we used adehabitat package in R with algorithm BA, i.e. the Bhattacharyya’s affinity, a statistical measure of affinity between two populations. It ranges from zero (no overlap) to 1 (identical UDs) . To measure individual consistency in UD between particular trips, we calculated the mean Bhattacharyya’s affinity of all pairwise combinations of the recorded trips and then calculated the mean value for particular individuals.
To estimate how many flights were to seabird colonies at the south end of Bjørnøya, we counted all flights within a 1 km buffer around the seabird cliff. We mapped data from the GPS loggers, performed spatial analyses and produced all figures with maps using ArcMap/ArcGIS 10.3.1 (Environmental Systems Research Institute, Redlands, CA, USA).
Trips characteristics of GPS-equipped great skuas breeding on Bjørnøya
Total flight duration [h]
Maximal range [km]
Total distance covered [km]
Factors affecting foraging flights characteristics during incubation
In the case of maximal range of foraging flights, bird ID characterized the best observed variability. Two main nodes were recognized: 106.6 km (node 2 represented by 12 individuals) and 212.4 km (node 3 represented by 5 individuals) (Fig. 2b).
CIT results indicated that bird ID best characterized total distance covered. Two main nodes: 246.8 km (node 2 represented by 12 individuals) and 613.8 km (node 3 represented by 5 individuals) (Fig. 2c) were recognized.
In the case of maximal convex polygon of all recorded GPS positions, bird ID characterized the best observed variability with two main nodes: 81.4 km2 (node 2 represented by 13 individuals) and 2085.1 km2 (node 3 represented by 4 individuals) (Fig. 2d).
Factors affecting foraging flights of birds that lost eggs
In the case of maximal range of foraging flights, bird ID and sex characterized the best observed variability. Two main nodes were recognized: node 2 represented by 6 individuals and characterized by more distant flights (mean 174.3 km) and node 3. The latter node represented by 3 individuals was split by sex. Females were characterised by higher maximal range of foraging flights (mean 96.4 km) compared to the male (58.4 km) (Fig. 3c, 4b).
In the case of CIT total distance covered during foraging flights, bird ID and sex characterized the best observed variability. Two main nodes were recognized: 518.8 km (node 2 represented by 6 individuals) and node 3 represented by 3 individuals. The latter node was split by sex. Females were characterised by higher total distance covered during foraging flights (mean 230.8 km) compared to the male (154.1 km) (Fig. 4c).
In the case of maximal convex polygon of all recorded GPS positions, bird ID characterized the best observed variability. Two main nodes were recognized: 2207.7 km2 (node 2 represented by 5 individuals) and 262.9 km2 (node 3 represented by 4 individuals) (Fig. 4d).
In the case of nine incubating individuals that lost eggs, the 95% utilisation distributions showed a Bhattacharyya’s affinity (BA) of 0.74 between the phases before and after egg loss. In the case of core range, the BA value was lower - 0.36.
Factors affecting foraging fights of individuals that lost chicks
We found that in the case of two individuals tracked throughout incubation (INC) and chick-rearing (BCD – before chick death, ACD - after chick death), the 95% utilisation distributions showed Bhattacharyya’s affinities (BA) of 0.71 between INC and BCD, 0.56 between INC and ACD, and 0.36 between BCD and ACD. In the case of core range, the BA values were 0.30 between INC and BCD, 0.25 between INC and ACD, and 0.14 between BCD and ACD.
The consistency of utilisation density of particular flights (i.e. mean BA values per individual) ranged from 0.36 to 0.79 in the case of home range (HR, 95% kernel density) and from 0.06 to 0.32 in the case of core range (CR, 50% kernel density) (Table 1). The trips of HAR 30 were characterized by the highest consistency (the highest values of mean Bhattacharyya’s affinity) of both HR and CR. Almost half (47%) of the studied great skuas had mean BA values for HR higher than average value for all individuals. In the case of CR, only 29% individuals were characterized by BA values higher than average value.
Our study revealed that individual specialization had the greatest effect on foraging flights of great skuas breeding on Bjørnøya. Three main strategies were identified: foraging on other seabirds, foraging at sea and a generalist strategy mixing the two. Similarly, great skuas from Unst, Shetland exhibited dietary specialization: a small proportion fed almost exclusively upon seabirds, a small proportion fed as generalists and most feed on fishery discards . Also the southern hemisphere species, the brown skua Stercorarius antarcticus lonnbergi breeding on King George Island (Maritime Antarctica) adopted three main strategies; foraging in a penguin colony, in a storm-petrel colony and at sea . Individual specialization may have a selective advantage where resources are to some extent predictable. The specialist foraging preference is probably passed to offspring through learning as they need to develop particular skills to successfully pursue different foraging modes including kleptoparasitism, predation of selected prey species or scavenging [1, 35, 54].
The study from Unst, Shetland revealed that great skuas specialized in seabird predation were able to spend less time foraging than individuals feeding predominantly on fish in the open sea . In concordance with this, the total trip duration of the female from Bjørnøya that specialized in foraging in the seabird colonies (median 2.1 h) was similar to the mean values 1.1–3.0 h reported for the radio-tracked seabird specialists from Shetland . The proportion of great skuas foraging mostly in seabird colonies in our study (5.8%) was lower than the frequency of seabird specialists calculated based on pellet composition analyses performed in the same colony, i.e. 33% in 2008 and 62% in 2009 . It is, however, possible that great skuas also killed seabirds at sea, not only in the colonies.
Comparison of frequencies of foraging flight ranges of GPS logger equipped great skuas breeding on Bjørnøya (this study) and on the Foula, Shetland, UK
Distance from colony
< 20 km
The mean foraging trip duration in our study (5.2 h) was similar to 4.95 h reported for great skuas from Unst, Shetland that specialized in feeding on fish . However, the minimum convex polygons of great skuas breeding on Unst (mean values 1.0–14.4 km2) were considerably smaller than those in our study (median values 29.4–4629.7 km2). This may be explained by the higher proportion of individuals specialized as local seabird predators on Unst (20%) than on Bjørnøya (6%) ). Moreover, some pairs of great skuas on Unst defended feeding territories within a section of seabird colony and thereby diminished considerably their minimum convex polygon.
The majority of the individuals studied on Bjørnøya flew out to sea, over the shallow shelf area and along the shelf break slope (Fig. 1). The Svalbard Bank, with a minimum depth of less than 40 m is considered as the most productive area in the Barents Sea with primary production about 2–3 times higher than in the adjacent, deeper waters . The shelf break zone is also a good foraging habitat for zooplanktivorous and piscivorous fish and birds including black-legged kittiwakes, Brünnich’s guillemots, common guillemots and little auks [43, 57–59]. It is thus possible that the studied great skuas may kleptoparasite or/and prey on seabirds foraging there or returning to the colony. A great skua dietary study from Bjørnøya from 2008 to 2009 revealed that most of fish otoliths found in pellets originated from Gadiformes fish . Most of the species within this group are mid-water or bottom dwelling species and thus probably only available as discards from fishing vessels . This source of food is a locally important diet component of the great skua breeding in the Outer Hebrides or Shetland . The fishing activity in the Barents Sea in 2014 included areas around Bjørnøya , but the level of discards is unknown . It has been reported, however, that discards of Atlantic cod Gadus morhua from the Norwegian shrimp fishery in the Barents Sea consists mainly of 1- and 2-year-olds (i.e. with mean body length 10.4 and 18.4 cm, respectively ) and thus optimal food for great skuas. Great skuas from Bjørnøya may also prey directly on pelagic fish, such as the capelin Mallotus villosus during foraging flights at sea by dipping or surface-seizing. This is supported by an observation of adult and chick regurgitates consisting of capelin remains (H. Strøm unpubl. data), although it is also possible that these remains originated from kleptoparasitism. In Shetland, great skua diet composition varied among the colonies and was dependent on the colony size. The majority of individuals from large colonies fed on fish, including discards, and only a small proportion specialised in killing seabirds . With regard to the size and the rapid growth of the Bjørnøya population, it is likely that they have adapted to feed on widely abundant fish such as capelin or fish discarded from fisheries.
Almost half of the studied birds were consistent in their home range areas (mean values of BA higher than the average) suggesting frequent foraging in the same areas during consecutive flights. This would be expected of individuals repeatedly visiting seabird colonies or those exploring areas characterized by similar oceanographic features as fronts in the shelf break zone providing opportunity to find their own fish or kleptoparasitise other seabirds gathered there to forage. Individuals alternating between flights to sea and to the seabirds colonies had lower repeatability of utilisation densities values than the average for all individuals studied.
That neither sex nor phase of reproduction of the studied birds affected foraging flight characteristics significantly was unexpected. This may be interpreted as high inter-individual variability in foraging being more important than other sources of variability. The only sex difference in total trip duration found was in the small subgroup of birds (three individuals) during incubation but, in this case, sex effect was also a proxy for bird ID. Our result corroborates a study of great skuas and other skuas (Stercorariinae) that found no support for the theory that sexual dimorphism evolved as a result of specialized roles during breeding (smaller males with lower wing loading foraging more efficiently due to greater agility) .
Surprisingly, after losing eggs or chicks, individuals freed of the restraint of central-place foraging did not modify their flights characteristic as did failed breeding northern giant petrels Macronectes halli and southern giant petrels M. giganteus . Using similar home ranges before and after egg loss may indicate foraging site fidelity by the Bjørnøya birds. It suggests that feeding grounds utilized by the studied great skuas were at least good enough for self-maintenance.
We are aware of possible limitations of our study. Firstly, we did not know the age of the studied individuals. It has been reported that time spent foraging to provide food for chicks increases with age of great skua parents breeding in Shetland . Secondly, the 2014 breeding season was a complete failure for great skuas from Bjørnøya with no chicks reaching an age beyond 20 days. Furthermore, there was a 26% reduction in the number of breeding pairs (to 107 nests in the whole monitoring area) compared to 2013 (HS, pers. obs.). We suppose that the breeding failure may have been the result of high conspecific predation rate driven by suboptimal feeding conditions on foraging grounds. In 2014, the stock of the only semi-pelagic or pelagic gadoid fish, the polar cod Boreogadus saida, which could have been preyed directly by great skuas or indirectly by kleptoparasiting other seabirds (this fish is frequently preyed by Brünnich’s guillemots and black-legged kittiwakes breeding on or sampled around Bjørnøya [57, 68]), was reduced and its distribution shifted northeastwards, beyond the Barents Sea shelf . The capelin stock at the time of the study was also significantly reduced [62, 69] thereby possibly influencing great skuas directly or/and indirectly. In years when capelin is scarce, the piscivorous guillemots breeding on Bjørnøya may rely more on euphausiids for food . In such years, the kleptoparasitic behaviour of great skuas may be less energetically profitable than in years with a higher contribution of fat-rich fish in their diets. In this context, foraging flights characteristics may also have been different than in other seasons. Finally, logger deployment might be considered as a cause of the breeding failure but this was unlikely due to the overall breeding failure recorded throughout the colony. Moreover, other studies of great skuas fitted with GPS devices revealed that foraging flights characteristics and territory attendance rates were similar to those of control individuals .
The characteristics of great skua foraging flights on Bjørnøya during a poor breeding season were individual rather than a response to sex or breeding status (after or before egg or chick loss). Almost half of the studied birds were consistent in their home range areas during consecutive flights suggesting foraging specialization. Some individuals fed regularly in the seabird colonies at the southern part of the island, some foraged at sea in areas with oceanographic features as fronts providing opportunity to kleptoparasiting or even direct hunting for fish, and some birds used both foraging strategies.
Our study demonstrates the effectiveness of GPS-tracking as a tool for investigating foraging specialization of great skuas. Future studies could usefully apply the same approach, ideally supported by diet composition estimation (e.g. stable isotope ratios, pellet composition), to investigate consistency and flexibility in the foraging strategies.
We thank Elínborg Sædís Pálsdóttir and Magdalena Hadwiczak for assistance in the field. We appreciate the improvements of our English as suggested by Rob Barrett.
The study was supported by funds from Poland through University of Gdańsk, and from Norway through the SEAPOP program (http://seapop.no/), and the Norwegian Polar Institute.
Availability of data and materials
The datasets used and/or analysed during the current study are available from the corresponding author on request.
DJ drafted the manuscript, performed statistical analyses and discussed the concept of the study. LMI collected data in the field, prepared GPS data, and discussed the concept of the study. HS facilitated access to the studied area, managed the project, collected data, discussed the concept of the study. HHH collected data in the field. LS managed and developed the concept of the study. All authors read and approved the final manuscript.
The study was conducted with permission of the Governor of Svalbard and Norwegian Animal Research Authority.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. 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.
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How? Read on….
How To Define Website Development
Web development often refers to development of websites that are hosted over the internet and involves building and maintaining these pages.
The entire process includes many aspects such as web design, content development and network security. Depending on the size of the site and company, the process can involve anywhere from one person to hundreds of people who work on the project of developing a site.
The process of web development can be broken down into even smaller components. These include hand-coding pages often with the help of a text editor, using different programs to build a web page, or maintaining a blog or webpage.
While knowing the basics of web envelopment are important, there are other functions of the process that are just as vital.
What Does a Front End Web Developer Do?
It’s the job of Front End Developers to create and implement the familiar layouts of our favorite publications and sites. While this is the simple definition , it is a bit more complicated.
Front end development involves how the web page design looks and how it is formatted. Think of a web site as layers and you get the picture. It involves how the site is structured, its design and how one maneuvers through the site.
This involves coding HTML, Java Script, CSS code and formatting pictures through GIF or JPEG format, Their job involves almost every aspect of what it take to make a web page and site functional for users including the layout, navigation and internal links within the site.
What Does a Web Developer Do?
These employees go beyond the front end developer and handle all aspects of a web site. Other titles they go by can include ‘web designers’ or ‘webmasters’. Their job is to design and maintain the entire website, including the design and development of the site.
They create these web pages by considering their client’s targeted goal and audience. They then investigate different designs and figure out which works best for their client’s needs.
In addition, they maintain the technical aspects of web sites and monitor site traffic. They also track the site’s traffic and keep track of the site’s page load speed.
Another important aspect of a web developer’s job is helping to create and maintain e-commerce websites.
What Does a Web Development Company Do?
Web development companies deal with all aspects of developing and maintain a web site.
Although most companies offer a broad and full range of services, many specialize in one specific type of design or serve a particular industry.
Some companies offer their services only to large corporations while others choose one niche such as medical . Some companies specialize in one particular language or coding while others offers all and use multiple website content management programs such as Word Press, Joomla or Drupal.
Different tasks taken on by a web development company includes the following:
- Initial client consultation to garner the needs of a client and what their web site should look like and what its purpose is.
- Web engineering or maneuvering the world wide web and the development and operation of the web and web pages.
- Web design or creating a web page using coding and formatting.
- Developing content for clients.
- Providing web server services and overseeing network security configuration
What is Full Stack Web Development?
Full stack web development covers almost all aspects of web development and the web developer’s job. Full-stack development involves the broader aspects of web development including software development. Often they have a more in depth expertise in the role of soft ware and web development. A full-stack developer would also be proficient in multiple areas at once such as:
- Hosting environment, server, and network capabilities.
- Databases referred to as relational and correlational.
- How to interact with Application Programming Interfaces (APIs) and the external world.
- Correlation between user interface and user experience
- All aspects of quality assurance
- Web site and program security.
- In depth understanding of customer and business needs.
Summary: Our Online World and Web Development
Web developers and the companies they work for have helped create the online world we have all become accustomed to.
As the internet continues to grow and change, web development continues to be vital to make best use of the latest capabilities (including the latest features for your own business website).
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Determination of the Effective Surface of a Spent Spacecraft to Take into Account the Influence of Light Pressure on its Motion
A method for determining the effective surface area of a spent satellite depending on its spatial orientation is suggested on the example of the GLONASS spacecraft (SC). To determine the effective area, a point-set model is considered. The satellite is represented as a set of points uniformly distributed over the SC surface. Then longitude and latitude angles are varied in the system of coordinates rigidly affixed to the SC, and the point set is projected onto the image plane. The contour of the projected set is determined, and its area is calculated. As a result, an approximate dependence of the effective satellite area on two orientation angles is obtained.
Keywordsartificial Earth satellite spent spacecraft light pressure effective spacecraft surface GLONASS
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- 4.A. G. Aleksandrova, I. N. Chuvashov, and T. V. Bordovitsyna, in: Proc. of the IXth All-Russian Scient. Conf. “Fundamental and Applied Problems of Modern Mechanics,” Tomsk (2016), pp. 328–330.Google Scholar
- 5.A. G. Aleksandrova and I. N. Chuvashov, in: Proc. of the IXth All-Russian Scient. Conf. “Fundamental and Applied Problems of Modern Mechanics,” Tomsk (2016), pp. 331–333.Google Scholar
- 6.R. Webster and M. A. Oliver, Geostatistics for Environmental Scientists, John Wiley & Sons Ltd. (2007).Google Scholar | <urn:uuid:b12eb9de-64d8-4ca0-8d45-6c9fe62e014a> | 2.859375 | 352 | Academic Writing | Science & Tech. | 50.785268 | 95,622,877 |
Black holes make for a perplexing subject matter, don’t you think! Questioning reality and the physical form take us further into these enigmas, shedding light on new ideas.
The magic of black holes
So, what’s the big deal anyway? What is so interesting about this subject?
Black holes are interesting due to the power of their gravitational pull. This grip warps time and space within a ‘deep well’. Anything, passing close, will be absorbed, never to return.
It is a common assumption that black holes have a ‘back door’, so to speak. This is what Hawking said, anyway. This back door is simply an exit from reality which leads to the existence where time and the laws of nature are different from what we understand. It’s a mystery, what stands on the other side, and the world’s greatest scientists never tire of pondering the meaning of it all. Hawking also wanted to understand what happens right outside the black hole, this side of the ‘back door’. Following laws of physics, borrowed from Albert Einstein and Paul Dirac, Hawking came upon something shocking. Black holes didn’t just pull in materials, they also emit radiation.
A recent paper presents a new idea on the black hole subject, revealing what exactly will happen if you touch a black hole. This theory suggests there is no back door to the universe – black holes are impenetrable fuzzballs.
Professor of physics at Ohio State University and author of the paper, Samir Mathur, says when you near the fuzzball, you will be destroyed. A fuzzball is a fuzzy area of space, unlike recent beliefs of the black hole being smooth. Oddly enough, you will not die but become a holographic copy of yourself. This copy will be embedded upon the fuzzball’s surface.
This theory was first introduced in 2003 and brought excitement to the scientific community. Finally, a solution to a certain paradox could be explained. This was a paradox discovered by Steven Hawking over 40 years ago.
Mathur’s calculations paved the way for 15 years of maturing his argument. His latest paper suggests:
‘Black holes, as a holographic copy, are exactly how scientists should be thinking about black holes being fuzzballs-this brings understanding to the black hole’s behavior.”
The fundamental laws of physics state that nothing in the universe can be completely destroyed. Almost 30 years later, Hawking has failed to provide a solution to the paradox while Mathur may be onto something. Unlike Hawking believes that black holes absorb and completely destroy materials, Mathur believes that materials are absorbed but remain on the surface of the ‘fuzzball’.
Mathur told Business Insider:
“Material which is absorbed as a hologram is transformed, not really destroyed – there is also no exact copy, because of the universe’s reputation for imperfection.”
The String theory
Mathur can also explain his idea mathematically using the string theory. The string theory is the idea that particles are made of string that interact to create all things in the universe.
Although the string has never been observed, it offers solutions to scientific mysteries like quantum gravity the unified theory of everything. Mathur says that black holes are fuzzballs made of masses of string, which make this theory fit perfectly into the string theory.
Contested once more
Some scientists partially agree with Mathur, the difference lying with the notion of survival after being absorbed by the black hole. In 2012, a group of physicists, at the University of California, stated that you would not survive at all if pulled into the black hole and favored a term ‘firewall’. So, we are torn between fuzzball and firewall, it seems.
“The only way to conduct an experiment to test each theory would be to create tiny black holes in a particle accelerator. Although this is questionable as well.”
Many scientists support Mathur’s ideas, and only time will tell the truth of fuzzballs. As for rivaling theories, they will hold fast until proven otherwise. Aren’t black holes interesting? I think so.
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Geometrical Optics Multiple Choice Questions 22 PDF Download
Practice geometrical optics MCQs, grade 10 physics test 22 for online courses learning and test prep, spherical mirrors multiple choice questions and answers. Spherical mirrors revision test includes physics worksheets to learn.
Physics multiple choice questions (MCQ) on object 20 cm tall is located 14 cm from a concave mirror having focal length 20 cm. height of object is with options 32.5 cm, 35.6 cm, 50.8 cm and 66.7 cm, spherical mirrors quiz for competitive exam prep, viva interview questions with answers key. Free physics study guide to learn spherical mirrors quiz to attempt multiple choice questions based test.
MCQs on Geometrical Optics Quiz PDF Download Worksheets 22
MCQ. An object 20 cm tall is located 14 cm from a concave mirror having focal length 20 cm. The height of the object is
- 35.6 cm
- 32.5 cm
- 50.8 cm
- 66.7 cm
MCQ. The angle of incidence 45° is greater than critical angle of the glass which is
MCQ. Lenses form images through
MCQ. A smooth surface of silver reflects rays of light in
- many directions
- one direction
- two directions
- no direction
MCQ. If the power of a convex lens is 5D then at what distance the object should be placed from the lens so that its real and 2 times larger image is formed?
- 30 cm
- 20 cm
- 15 cm
- 25 cm | <urn:uuid:77bd4350-0894-415b-ade0-0ec6ae954c0c> | 3.15625 | 331 | Tutorial | Science & Tech. | 85.985071 | 95,622,892 |
[This post is part of my activities as M.Sc. Software Engineering student in University of Amsterdam]
Software testing is an important process during software development. Software developers and testers spend a lot of time and effort to create effective test cases and integrate the testing process in their workflow inside an organization. Although software testing is a great investment for the software’s quality and software’s life, creating test cases manually is a very time-consuming, high-cost and, most importantly, an error prone process. Since this is a common and considerable problem, there has been researched and developed methods that can automate the test generation and make the testing process effortless and reliable. Those methods can reduce the time and cost and increase the quality of the test cases set. A solution for automated software tests generation is given from the Search Based Software Testing which uses optimization algorithms, like genetic algorithms, simulated annealing, swarm optimization and more, to achieve the tests cases generation.
The term Search Based Software Engineering has been coined by Harman and Jones in 2001 , and is considered as an optimization discipline for software engineering. SBSE has applications on many software engineering areas such as Requirements engineering, Software metrics, Software project management, Automated Software Repair (automated bug fixes) and Software Testing. The first publication on Search-Based Software Testing was in 1976, from Webb Miller and David Spooner . That work concerned test data generation which included a ‘cost-function’ (also called fitness function for meta-heuristics) for running a simple optimization process. It was a notable contribution to the area since it was different from the existing static methods of that time. The basic idea of the search based test data generation approach is that the set of possible inputs to the program forms a search space and the test adequacy criterion is coded as a fitness function . Furthermore, the test in this situation is transformed into an optimization problem. The test object searches for test data that fulfils the respective test aim in the search space .
The simplest implementation of an optimization algorithm is a random search. This method is very poor on finding solution, especially when those solutions are widely spread to the search space . A solution is provided from optimization algorithms and meta-heuristics which “guide” the solutions into the search space by using fitness functions which calculate the quality of the generated solutions . A simple optimization algorithms is the Hill-Climbing. In that algorithm a solution starts at a random point and the points that are close to the current point are evaluated for their “quality” (fitness). If a better solution is found, then the algorithm moves to that point and the process is repeated until the best solution is found. The problem with this method is that when a space doesn’t offer a better solution then there may be a ‘local minima’ of that space. An alternative to simple Hill Climbing is Simulated Annealing. Search by Simulated Annealing is similar to Hill Climbing, except movement around the search space is less restricted and therefore it provides the avoidance of local minimas by introducing a “jumping around” of the solution.
Although meta-heuristic methods like Hill-Climbing work for simple optimizations, software is a non-linear problem and the conversion of test aim to optimization problems mostly leads to complex, discontinuous, and non-linear search spaces. Evolutionary Algorithms have proved a very powerful optimization algorithm for software testing. An important contribution was from Xanthakis et al who applied Genetic Algorithms to the problem . Introducing genetic algorithms to such a problem helped a lot by expanding the search space and providing a form of ‘global’ search, sampling many points in the search space at once. Therefore, Evolutionary Testing implemented as a subfield of the SBT to apply genetic algorithms into the SBST problem.
Search-based optimization can be applied to many areas of testing, more specifically it requires the testing goal to be defined numerically. Therefore search based software testing is considered as a very good solution and many authors are trying to adapt that method . The first application area of the SBT, taken from Miller and Spooner approach is in the Structural Testing (White-Box). It is considered the most applicable and most researched area . In Structural Testing the fitness functions are for path coverage, branch coverage, data flow coverage and more. The program that is under testing performs a code tracing process (Dynamic Structural Test) and is executed with inputs suggested by the meta-heuristic algorithm. The code instrumentation helps with the presence of loops and complex logic which makes it difficult to be analysed statically. The path that has been taken during the execution is compared with some structure of interest for which coverage is attempted to be found .
Another application area of SBT is the Temporal Testing in which the purpose is to find the Best Case Execution Time (BCET) and the Worst Case Execution Time (WCET). This is very helpful for safety critical systems and embedded / real time systems. From reports, search based testing has good results in those kind of tests , . The fitness function in this situation is the execution time of the software and it can be found by running it with some inputs. The genetic algorithm generates inputs and rates their quality through the fitness function. In the case of the BCET the search tries to find the minimum execution time, while in the case of WCET the search tries to find the longer execution time.
Although Functional Testing (Black-Box) has not that many publications , it is considered as an evolving area while many search techniques can be applied to this kind of testing including simulated annealing, genetic algorithms and particle swarm optimization. Particle swarm optimization is a “population based stochastic search technique” that is inspired by social metaphors of behavior and swarm theory. Functional testing describes the logical behaviour of a system. The fitness function rates the solutions based on how close they are to satisfying the conjuncts to each route. The solution generated tries to optimize this distance to the minimum .
Finally SBT can also be applied on the Gray-Box Testing area which combines both structural and functional information. This area includes the following applied methods. Assertion Testing, is a method where the search tries to find test cases that violate assertion conditions which are inserted in the code by the developers. Another is the Exception Condition Testing in which the meta-heuristics search for inputs and test the run-time errors handling in the code (exceptions). The are many future references that can be applied in this kind of testing therefore it is considered as a growing area .
Although the Search Based Software Engineering is not widely applied in the software industry, the Search Based Software Testing, as a sub-field, has been developed a lot all over the years with considerable contributions from both the academic and industry (mostly from embedded and real time systems) world. As it can be seen SBT can be applied on many areas including many kinds of testing and produce impressive results. In conclusion, the are many references and prospects of future work on this field that can help the software developers, testers and most importantly the manually testing process which is slow and painful for many organizations.
Mark Harman, “The Current State and Future of SBSE”, Future of Software Engineering
(FOSE’07), IEEE Computer Society, 2007.
Stefan Mairhofer, Robert Feldt, Richard Torkar, “Search-based Software Testing and Test Data Generation for a Dynamic Programming Language”, (GECCO’11), ACM, 2011.
Phil McMinn, Search-Based Software Testing: Past, Present and Future, 4th International Workshop on Search-Based Software Testing Berlin Germany, March 2011
W. Miller and D. Spooner, “Automatic generation of floating point test data,” IEEE Transactions on Software Engineering, vol. 2, no. 3, 1976.
M. Harman and J. Clark, “Metrics are fitness functions too,” in International Software Metrics Symposium (METRICS 2004). IEEE Computer Society, 2004.
P. Maragathavalli, Search based software test data generation using evolutionary computation, International Journal of Computer Science & Information Technology (IJCSIT), Vol 3, No 1, Feb 2011.
S. Xanthakis, C. Ellis, C. Skourlas, A. Le Gall, S. Katsikas, and K. Karapoulios, “Application of genetic algorithms to software testing (Application des algorithmes genetiques au test des logiciels),” in 5th International Conference on Software Engineering and its Applications, Toulouse, France, 1992
P. Puschner and R. Nossal, “Testing the results of static worst-case execution-time analysis” Computer Society Press, 1998.
J. Wegener, H. Sthamer, B. F. Jones, and D. E. Eyres, “Testing real-time systems using genetic algorithms” Software Quality Journal, vol. 6, no. 2, 1997.
Raluca Lefticaru, Florentin Ipate, Functional Search-based Testing from State Machines, IEEE Computer Society, 2008.
Phil McMinn, Search-based Software Test Data Generation: A Survey, Software Testing Verification and Reliability 14(2), 2004. | <urn:uuid:21cf92f4-0f25-4a6a-97fa-db7ce6d5fd95> | 2.6875 | 1,943 | Personal Blog | Software Dev. | 35.748889 | 95,622,898 |
Species Detail - Northern Spinach (Eulithis populata) - Species information displayed is based on all datasets.
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
insect - moth
19 May (recorded in 1957)
14 November (recorded in 1982)
National Biodiversity Data Centre, Ireland, Northern Spinach (Eulithis populata), accessed 18 July 2018, <https://maps.biodiversityireland.ie/Species/78730> | <urn:uuid:422d0c33-6c7c-4793-85be-e0e2e02bbcbe> | 2.515625 | 142 | Structured Data | Science & Tech. | 37.074 | 95,622,900 |
Rocket launches from Poker Flat Research Range
FOR IMMEDIATE RELEASE: Feb. 20, 2012
CONTACT: Geophysical Institute science writer Ned Rozell, 907-474-7468, email@example.com
Fairbanks, Alaska—On Saturday, Feb. 18 at 8:41 p.m. Alaska time, scientists launched a NASA sounding rocket from Poker Flat Research Range into a brilliant aurora display. The rocket mission, designed to gather information on space weather conditions that affect satellite communications, was a success.
“It was a terrific aurora, the rocket worked great, the instruments worked great and the supporting radar (at Poker Flat) worked wonderfully,” said Steve Powell of Cornell University, the principal investigator for the launch. “We achieved all of our objectives. We’re ecstatic over the results and our graduate students can’t wait to sink their teeth into the data.”
After monitoring satellites earlier Saturday that showed an abundance of charged particles coming from the sun and streaming toward Earth’s magnetic field, members of the rocket team, which included University of Alaska Fairbanks researchers and personnel from NASA’s Wallops Flight Facility in Virginia, were prepared for a night of vigorous aurora. With clear skies at Poker Flat and also at the villages of Fort Yukon and Venetie, where they had narrow-field cameras aimed toward the sky, the scientists opened their launch window at 8 p.m. They watched the aurora dance directly overhead at Poker Flat, waited until the aurora was perfect over Fort Yukon and then launched the two-stage rocket.
In the 10 minutes, 25 seconds it took for the rocket to arc to a high point 200 miles above Venetie to the payload’s landing in northern Alaska, a complicated array of antennas deployed, and the rocket both gathered and then transmitted an immense amount of information back to Poker Flat.
“We got a CD of data in our pockets the same night,” Powell said. Graduate students at Cornell University, the University of New Hampshire, Dartmouth College and the University of Oslo will use the data as part of their doctoral studies. Their goal is to better model Earth’s upper atmosphere and discover more about how space weather affects satellite communications we use every day.
The launch is the first and final one from Poker Flat Research Range this spring. Technicians from the range are today searching for the two rocket motors used to propel the mission. A few days after its launch, Powell was at Poker Flat marveling how the launch went.
“So many things have to come together to have a mission success, and we had them all Saturday night.”
Poker Flat Research Range is the largest land-based sounding rocket range in the world and is located 30 miles north of Fairbanks on the Steese Highway. The UAF Geophysical Institute operates the range under contract to NASA. More than 300 major scientific sounding rockets have launched from the facility since it was founded in 1969.
ADDITIONAL CONTACTS: Steve Powell, Cornell University, 607-227-8421.
Poker Flat Research Range: 907-455-2110.
PHOTO CAPTION/CREDIT: A NASA sounding rocket with instruments aboard to collect data on space weather launches from Poker Flat Research Range, 30 miles north of Fairbanks, on February 18, 2012 at 8:41 p.m.
Photo by C. Heinselman. | <urn:uuid:4727e822-9c42-485c-944d-a3cd76842758> | 2.9375 | 719 | News (Org.) | Science & Tech. | 49.526696 | 95,622,903 |
Harvard scientists are helping to paint the fullest picture yet of how a handful of factors, particularly world-wide increases in atmospheric carbon dioxide, combined to end the last ice age approximately 20,000 to 10,000 years ago.
As described in a paper published April 5 in Nature, researchers compiled ice and sedimentary core samples collected from dozens of locations around the world, and found evidence that while changes in Earth's orbit may have touched off a warming trend, increases in CO2 played a far more important role in pushing the planet out of the ice age.
"Orbital changes are the pacemaker. They're the trigger, but they don't get you too far," lead author Jeremy Shakun, a visiting postdoctoral fellow in Earth and Planetary Science Shakun, said. "Our study shows that CO2 was a much more important factor, and was really driving worldwide warming during the last deglaciation."
Though scientists have known for many years, based on studies of Antarctic ice cores, that deglaciations over the last million years and spikes in CO2 were connected, establishing a clear cause-and-effect relationship between CO2 and global warming from the geologic record has remained difficult, Shakun said. In fact, when studied closely, the ice-core data indicate that CO2 levels rose after temperatures were already on the increase, a finding that has often been used by global warming skeptics to bolster claims that greenhouse gases do not contribute to climate change.
Many climate scientists have addressed the criticism and shown that the lag between temperature and CO2 increases means that greenhouse gases were an amplifier, rather than trigger, of past climate change, but Shakun and his colleagues saw a larger problem – while CO2 measurements taken from air bubbles in the ice cores reflect levels throughout the global atmosphere, temperatures recorded in the ice only reflect local Antarctic conditions.
To get a more accurate picture of the relationship between global temperature and CO2, they synthesized dozens of core samples – 80 in all – collected from around the world.
"We have ice cores from Greenland, people have cored the sea floor all around the world, they've cored lakes on the continents, and they have worked out temperature histories for all these sites," Shakun said. "Putting all of these records together into a reconstruction of global temperature shows a beautiful correlation with rising CO2 at the end of the ice age. Even more interesting, while CO2 trails Antarctic warming, it actually precedes global temperature change, which is what you would expect if CO2 is causing the warming.
"The previous science clearly said that CO2 had something to do with warming," Shakun added. "It has gone up and down in tandem with the ice ages, so it is clearly involved. If it was an amplifier, the question was how big of an amplifier? Does it explain a lot of climate change, or was it a small piece, and other factors were more important? I think this research really points a strong finger at the idea that CO2 was a major player."
Armed with that evidence, Shakun and colleagues were able to sketch out how a series of factors aligned that eventually led to a worldwide warming trend and the end of the ice age.
Most scientists now believe, Shakun said, that the first domino wasn't an increase in greenhouse gases, but a gradual change in Earth's orbit. That orbital change resulted in more sunlight hitting the northern hemisphere. As the ice sheets over North America and Europe melted, millions of gallons of fresh water flooded into the North Atlantic and disruped the cyclical flow of ocean currents.
"Ocean circulation works like a global conveyor belt," Shakun said. "The reason it's important for climate is because it's moving heat around. If you look at it today, the northern hemisphere is on average, a couple degrees warmer than the south, and that's partly because the ocean is pulling heat northward as it flows across the equator in the Atlantic.
"But if you turn the conveyor belt off, it's going to warm the south because you're no longer stealing that heat away. Warming the southern hemisphere, in turn, shifts the winds and melts back sea ice that had formed a cap, trapping carbon in the deep ocean."
As more and more CO2 enters the atmosphere, Shakun said, the global warming trend continues, "and pretty soon you're headed out of an ice age."
While the research strengthens the link between CO2 and the Ice Ages, Shakun believes it also reinforces the importance of addressing CO2-driven climate change in our own time.
"I don't think this tells us anything fundamentally new about global warming," Shakun said. "Most scientists are not in doubt about the human-enhanced greenhouse effect – there are nearly a dozen strong pieces of evidence that it is affecting global climate. This is just one more log on the fire that confirms it."
Shakun's research was supported by a National Oceanic and Atmospheric Administration Climate and Global Change Fellowship and by the National Science Foundation, and conducted using resources at the Oak Ridge National Laboratory.
Peter Reuell | EurekAlert!
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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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Listen to the Betty Boops of the insect world as they "boop oop a doop" in the hive.
And I thought the squeaks of a baby sloth were cute? Well, they are ... but they've got some tough competition from a very surprising source: Whooping honeybees.
So it isn't new news that honeybees make a vibrational pulse to communicate. Sam Wong writes in New Scientist that while scientists have known about this signaling since the 1950s, they first speculated that it indicated a request for food. "Later, it was shown that the signal was produced when one bee tried to inhibit another from performing a waggle dance," Wong writes, "a behaviour that tells other bees where to forage." It was later interpreted as a warning signal.
But new research has an update to those theories: The vibrational pulse – AKA the cute whoop – could actually be an expression of surprise.
While inaudible to our feeble human ears, with the aid of accelerometers embedded in the honeycomb, researcher Martin Bencsik and his team from the UK's Nottingham Trent University were able to record the vibrations from within the hive. Over the course of a year, they discovered that the signal was significantly more frequent than previously thought. “There’s no way a bee was trying to inhibit another one that frequently, and there’s no way a bee would request food that frequently” says Bencsik.
With these recordings, they were also able to determine that the whoops occurred mostly in the evening – which isn't prime waggle-dance time. Even more enlightening, a soft knock on the hive wall elited a collective whoop from hundreds of bees all at the same time. Sounds like surprise to me. Upon viewing the hive action with inner-hive cameras, they found that the signal often occurred when one bee bumped into another
“We suggest that, in the majority of instances, it is bees being startled that produce the signal,” says Bencsik. The team propose that instead of the “stop” signal, it should be called the “whooping” signal.
See the full research here; and enjoy some bees a-whooping in the video below. | <urn:uuid:fc00b972-b1ea-477f-9eea-c8cbc79d41d7> | 3.015625 | 470 | News Article | Science & Tech. | 52.407393 | 95,622,906 |
People staying in tune with the news about renewable energy will be well aware how solar energy in the last decade has been a cycle of ups and downs. However, it appears this year marks the best year for solar energy so far. How did this happen?
China is on its way to become the first "Green Superpower" through building the world's largest solar farm in the western province of Qinghai.
France has just become the site of the world's first solar-paneled roadway. Wattway deployed on the streets of Tourouvre-au-Perche a massive 1,000-meter long solar-paneled roadway. The roadway is part of the company's 1,000-kilometer goal.
Everybody is well aware that the nuclear accident in Chernobyl is the worst nuclear accident in modern history. It directly caused the deaths of 50 people, with an additional 4,000 fatalities that were caused by exposure to radiation.
Solar power has become cheaper than coal in some parts of the world. And statistics show that in less than a decade, it will be the lowest-cost option almost anywhere in the globe.
France has just opened what it says is the world's first solar panel road in a Normandy village. The road is a whopping 1km route in the small village of Tourouvre-au-Perche covered with 2,800sqm of electricity-generating panels.
Scientists revealed that the outer five percent of the Sun's layer is spinning slower than the rest of the mass.
A new company from Hungary is reinventing urban and road planning by installing solar panels made from recycled plastics on sidewalks to collect both solar and kinetic energy.
Engineers from the University of California, Irvine have successfully implemented a new technique capable of converting and using the excess energy from solar panels or wind farms.
The government of Myanmar is planning to provide electricity to thousands of villages through off-grid solar energy.
Official photos from NASA seem to confirm that alien spacecrafts are circling the sun to harvest solar energy
Engineers from the University of New South Wales have managed to add to the growing benefits of using perovskite solar cells. Aside from being flexible, easily manufactured and cheap, they have now broke a world efficiency record.
India will be home to the world's largest solar power plant. This means India is set to be the third biggest solar market as early as 2017.
With the goal of India to replace coal with cheaper solar power by 2020, the South Asian country has recently unveiled the world's largest solar power plant, making it the world's third largest solar power market next year.
Solar cells made of tin can potentially be more adaptable and simpler to produce than the current technology used in solar power cells today. This appears to be proven in a paper that tries to find alternative solutions to lead perovskites. | <urn:uuid:9d2f7421-e402-4040-9345-19c84864270e> | 3.1875 | 578 | Content Listing | Science & Tech. | 48.441492 | 95,622,921 |
- This Annex defines facilities for supporting the implementation of
distributed systems using multiple partitions working cooperatively as part
of a single Ada program.
- A distributed system is an interconnection of one or more processing
nodes (a system resource that has both computational and storage
capabilities), and zero or more storage nodes (a system resource that has
only storage capabilities, with the storage addressable by one or more
- A distributed program comprises one or more partitions that execute
independently (except when they communicate) in a distributed system.
- The process of mapping the partitions of a program to the nodes in a
distributed system is called configuring the partitions of the program.
- The implementation shall provide means for explicitly assigning library
units to a partition and for the configuring and execution of a program
consisting of multiple partitions on a distributed system; the means are
- An implementation may require that the set of processing nodes of a
distributed system be homogeneous.
(1) The partitions comprising a program may be executed on differently
configured distributed systems or on a non-distributed system without
requiring recompilation. A distributed program may be partitioned
differently from the same set of library units without recompilation.
The resulting execution is semantically equivalent.
(2) A distributed program retains the same type safety as the equivalent
single partition program.
Clauses and Subclauses
- Categorization of Library Units -- TOC
- Shared Passive Library Units
- Remote Types Library Units
- Remote Call Interface Library Units
- Consistency of a Distributed System
- Remote Subprogram Calls -- TOC
- Pragma Asynchronous
- Example of Use of a Remote Access-to-Class-Wide Type
- Partition Communication Subsystem
-- Email comments, additions, corrections, gripes, kudos, etc. to:
Page last generated: 95-03-12 | <urn:uuid:925d872c-b0d7-4195-9cbb-6874c75349f0> | 2.5625 | 405 | Documentation | Software Dev. | -5.049355 | 95,622,949 |
Newton’s method for finding roots:
In optimization we are essentially finding roots of derivative.
We are approximating function using Taylor series. We are finding minimum of this approximated function. This root will be our new guess. This perspective is used in derivation.
Andrew N.G Lecture
| Gradient Descent
|| Slightly more complex (Requires computing and inverting hessian)
| Needs choice of learning rate alpha
|| No parameters (third point in image is optional )
| Needs more iteration
|| Needs fewer iteration
| Each iteration is cheaper O(n) where n is no of features
|| Each iteration is costly. Hessian is (n+1) * (n+1). Inverting matrix is roughly O(n^3)
| Use when no of features are less (n<1000)
|| Use when (n > 10,000)
Motivation behind these notes is that geometry helps in providing intuitive derivation to machine learning models and optimization scenarios !
Line in 2D resembles plane in 3D, not the line in 3D.
Concept of distance is essentially projection, It can be either sine (Cross product) or cosine (Dot product)
Formula for multivariate gaussian distribution
Formula of univariate gaussian distribution
- There is normality constant in both equations
- Σ being a positive definite ensure quadratic bowl is downwards
- σ2 also being positive ensure that parabola is downwards
On Covariance Matrix
Definition of covariance between two vectors:
When we have more than two variable we present them in matrix form. So covariance matrix will look like
- Formula of multivariate gaussian distribution demands Σ to be singular and symmetric positive semidefinite, which in terms means sigma will be symmetric positive semidefinite.
- For some data above demands might not meet
Following derivations are available at :
- We can prove that when covariance matrix is diagonal (i.e there is variables are independent) multivariate gaussian distribution is simply multiplication of single gaussian distribution of each variable.
- It was derived that shape of isocontours (figure 1) is elliptical and axis length is proportional to individual variance of that variable
- Above is true even when covariance matrix is not diagonal and for dimension n>2 (ellipsoids)
Linear Transformation Interpretation
This was proved in two steps :
Step-1 : Factorizing covariance matrix
Step-2 : Change of variables, which we apply to density function
p(X, Y) is joint distribution
p(X/Y) is conditional distribution
p(X) is marginal distribution (Y is marginalized out).
You can not get conditional distribution from joint distribution with just by integration. There is no such relationship.
There are just two rules for probability. Sum rule and product rules. And then there is Bayes theorem.
We might want to look at a table like below and calculate joint and conditional distribution and marginalized out one of the variable.
Further reading : | <urn:uuid:4fdf591c-49f6-4f86-8c16-5fdd6e872198> | 2.78125 | 651 | Personal Blog | Science & Tech. | 27.108661 | 95,622,964 |
The NOAA Collection within the Bridge Ocean Science Education Resource Center is a selection of exemplary NOAA resources that have been reviewed by educators and selected as particularly well-suited for educational purposes.
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Find NOAA education resources on the Bridge by entering a search term in the box to the right (grade level is optional). Or, navigate through the resources using the menu on the left.
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National Oceanic and Atmospheric Administration A one stop site for information concerning everything oceans and atmosphere. Obtain the latest weather reports, marine forecasts, tidal information, hurricane information, resource-related news, even space weather forecasts. Other featured topics include climate, research, charting and navigation, and habitat management. Additional features include photo and video galleries, satellite imagery, funding information, and the newly-introduced NOAA Storm Tracker. Fisheries section features information on marine mammals, sea turtles, and aquaculture. | <urn:uuid:930ba76f-ee2f-4281-ba83-564298f50377> | 2.578125 | 185 | Content Listing | Science & Tech. | 1.708851 | 95,622,991 |
A photonic crystal is a periodic optical nanostructure that affects the motion of photons in much the same way that ionic lattices affect electrons in solids. Photonic crystals occur in nature in the form of structural coloration and animal reflectors, and, in different forms, promise to be useful in a range of applications.
In 1887 the English physicist Lord Rayleigh experimented with periodic multi-layer dielectric stacks, showing they had a photonic band-gap in one dimension. Research interest grew with work in 1987 by Eli Yablonovitch and Sajeev John on periodic optical structures with more than one dimension—now called photonic crystals.
Photonic crystals can be fabricated for one, two, or three dimensions. One-dimensional photonic crystals can be made of layers deposited or stuck together. Two-dimensional ones can be made by photolithography, or by drilling holes in a suitable substrate. Fabrication methods for three-dimensional ones include drilling under different angles, stacking multiple 2-D layers on top of each other, direct laser writing, or, for example, instigating self-assembly of spheres in a matrix and dissolving the spheres.
Photonic crystals can, in principle, find uses wherever light must be manipulated. Existing applications include thin-film optics with coatings for lenses. Two-dimensional photonic-crystal fibers are used in nonlinear devices and to guide exotic wavelengths. Three-dimensional crystals may one day be used in optical computers. Three-dimensional photonic crystals could lead to more efficient photovoltaic cells as a source of power for electronics, thus cutting down the need for an electrical input for power.
Photonic crystals are composed of periodic dielectric, metallo-dielectric—or even superconductor microstructures or nanostructures that affect electromagnetic wave propagation in the same way that the periodic potential in a semiconductor crystal affects electron motion by defining allowed and forbidden electronic energy bands. Photonic crystals contain regularly repeating regions of high and low dielectric constant. Photons (behaving as waves) either propagate through this structure or not, depending on their wavelength. Wavelengths that propagate are called modes, and groups of allowed modes form bands. Disallowed bands of wavelengths are called photonic band gaps. This gives rise to distinct optical phenomena, such as inhibition of spontaneous emission, high-reflecting omni-directional mirrors, and low-loss-waveguiding. Intuitively, the bandgap of photonic crystals can be understood to arise from the destructive interference of multiple reflections of light propagating in the crystal at the interfaces of the high- and low- dielectric constant regions, akin to the bandgaps of electrons in solids.
The periodicity of the photonic crystal structure must be around half the wavelength of the electromagnetic waves to be diffracted. This is ~350 nm (blue) to ~650 nm (red) for photonic crystals that operate in the visible part of the spectrum—or even less, depending on average index of refraction. The repeating regions of high and low dielectric constant must, therefore, be fabricated at this scale, which is difficult.
Photonic crystals have been studied in one form or another since 1887, but no one used the term photonic crystal until over 100 years later—after Eli Yablonovitch and Sajeev John published two milestone papers on photonic crystals in 1987. The early history is well documented in the form of a story when it was identified as one of the landmark developments in physics by the American Physical Society.
Before 1987, one-dimensional photonic crystals in the form of periodic multi-layer dielectric stacks (such as the Bragg mirror) were studied extensively. Lord Rayleigh started their study in 1887, by showing that such systems have a one-dimensional photonic band-gap, a spectral range of large reflectivity, known as a stop-band. Today, such structures are used in a diverse range of applications—from reflective coatings to enhancing LED efficiency to highly reflective mirrors in certain laser cavities (see, for example, VCSEL). A detailed theoretical study of one-dimensional optical structures was performed by Vladimir P. Bykov, who was the first to investigate the effect of a photonic band-gap on the spontaneous emission from atoms and molecules embedded within the photonic structure. Bykov also speculated as to what could happen if two- or three-dimensional periodic optical structures were used. The concept of three-dimensional photonic crystals was then discussed by Ohtaka in 1979, who also developed a formalism for the calculation of the photonic band structure. However, these ideas did not take off until after the publication of two milestone papers in 1987 by Yablonovitch and John. Both these papers concerned high-dimensional periodic optical structures, i.e., photonic crystals. Yablonovitch's main goal was to engineer photonic density of states to control the spontaneous emission of materials embedded in the photonic crystal. John's idea was to use photonic crystals to affect localisation and control of light.
After 1987, the number of research papers concerning photonic crystals began to grow exponentially. However, due to the difficulty of fabricating these structures at optical scales (see Fabrication challenges), early studies were either theoretical or in the microwave regime, where photonic crystals can be built on the more accessible centimetre scale. (This fact is due to a property of the electromagnetic fields known as scale invariance. In essence, electromagnetic fields, as the solutions to Maxwell's equations, have no natural length scale—so solutions for centimetre scale structure at microwave frequencies are the same as for nanometre scale structures at optical frequencies.)
By 1991, Yablonovitch had demonstrated the first three-dimensional photonic band-gap in the microwave regime. The structure that Yablonvitch was able to produce involved drilling an array of holes in a transparent material, where the holes of each layer form an inverse diamond structure – today it is known as Yablonovite.
In 1996, Thomas Krauss demonstrated a two-dimensional photonic crystal at optical wavelengths. This opened the way to fabricate photonic crystals in semiconductor materials by borrowing methods from the semiconductor industry.
Today, such techniques use photonic crystal slabs, which are two dimensional photonic crystals "etched" into slabs of semiconductor. Total internal reflection confines light to the slab, and allows photonic crystal effects, such as engineering photonic dispersion in the slab. Researchers around the world are looking for ways to use photonic crystal slabs in integrated computer chips, to improve optical processing of communications—both on-chip and between chips.
Such techniques have yet to mature into commercial applications, but two-dimensional photonic crystals are commercially used in photonic crystal fibres (otherwise known as holey fibres, because of the air holes that run through them). Photonic crystal fibres were first developed by Philip Russell in 1998, and can be designed to possess enhanced properties over (normal) optical fibres.
Study has proceeded more slowly in three-dimensional than in two-dimensional photonic crystals. This is because of more difficult fabrication. Three-dimensional photonic crystal fabrication had no inheritable semiconductor industry techniques to draw on. Attempts have been made, however, to adapt some of the same techniques, and quite advanced examples have been demonstrated, for example in the construction of "woodpile" structures constructed on a planar layer-by-layer basis. Another strand of research has tried to construct three-dimensional photonic structures from self-assembly—essentially letting a mixture of dielectric nano-spheres settle from solution into three-dimensionally periodic structures that have photonic band-gaps. Vasily Astratov's group from the Ioffe Institute realized in 1995 that natural and synthetic opals are photonic crystals with an incomplete bandgap. The first demonstration of an "inverse opal" structure with a complete photonic bandgap came in 2000, from researchers at the University of Toronto, Canada. The ever-expanding field of biomimetics—the study of natural structures to better understand and use them in design—is also helping researchers in photonic crystals. For example, in 2006 a naturally occurring photonic crystal was discovered in the scales of a Brazilian beetle. Analogously, in 2012 a diamond crystal structure was found in a weevil and a gyroid-type architecture in a butterfly.
The fabrication method depends on the number of dimensions that the photonic bandgap must exist in.
One-dimensional photonic crystalsEdit
In a one-dimensional photonic crystal, layers of different dielectric constant may be deposited or adhered together to form a band gap in a single direction. A Bragg grating is an example of this type of photonic crystal. One-dimensional photonic crystals can be either isotropic or anisotropic, with the latter having potential use as an optical switch.
Recently, researchers fabricated a graphene-based Bragg grating (one-dimensional photonic crystal) and demonstrated that it supports excitation of surface electromagnetic waves in the periodic structure by using 633 nm He-Ne laser as the light source. Besides, a novel type of one-dimensional graphene-dielectric photonic crystal has also been proposed. This structure can act as a far-IR filter and can support low-loss surface plasmons for waveguide and sensing applications.
Two-dimensional photonic crystalsEdit
In two dimensions, holes may be drilled in a substrate that is transparent to the wavelength of radiation that the bandgap is designed to block. Triangular and square lattices of holes have been successfully employed.
The Holey fiber or photonic crystal fiber can be made by taking cylindrical rods of glass in hexagonal lattice, and then heating and stretching them, the triangle-like airgaps between the glass rods become the holes that confine the modes.
Three-dimensional photonic crystalsEdit
There are several structure types that have been constructed:
- Spheres in a diamond lattice
- The woodpile structure – "rods" are repeatedly etched with beam lithography, filled in, and covered with a layer of new material. As the process repeats, the channels etched in each layer are perpendicular to the layer below, and parallel to and out of phase with the channels two layers below. The process repeats until the structure is of the desired height. The fill-in material is then dissolved using an agent that dissolves the fill-in material but not the deposition material. It is generally hard to introduce defects into this structure.
- Inverse opals or Inverse Colloidal Crystals-Spheres (such as polystyrene or silicon dioxide) can be allowed to deposit into a cubic close packed lattice suspended in a solvent. Then a hardener is introduced that makes a transparent solid out of the volume occupied by the solvent. The spheres are then dissolved with an acid such as Hydrochloric acid. The colloids can be either spherical or nonspherical.
- A stack of two-dimensional crystals – This is a more general class of photonic crystals than Yablonovite, but the original implementation of Yablonovite was created using this method.
- "The photonic crystal beam splitter that we made is a fundamental optical component used to control polarized light," explains Dr Mark Turner from Swinburne University. "Specifically what makes our device unique is its ability to directly work with circular polarization at a microscopic scale."
- Circular polarization uses 3D laser nanotechnology to exploit circular polarization to build a microscopic prism that contains in excess of 750,000 polymer nanorods. Light focused on this beam splitter penetrates or is reflected, depending on polarization.
Higher-dimensional photonic crystal fabrication faces two major challenges:
- Making them with enough precision to prevent scattering losses blurring the crystal properties
- Designing processes that can robustly mass-produce the crystals
One promising fabrication method for two-dimensionally periodic photonic crystals is a photonic-crystal fiber, such as a holey fiber. Using fiber draw techniques developed for communications fiber it meets these two requirements, and photonic crystal fibres are commercially available. Another promising method for developing two-dimensional photonic crystals is the so-called photonic crystal slab. These structures consist of a slab of material—such as silicon—that can be patterned using techniques from the semiconductor industry. Such chips offer the potential to combine photonic processing with electronic processing on a single chip.
For three dimensional photonic crystals, various techniques have been used—including photolithography and etching techniques similar to those used for integrated circuits. Some of these techniques are already commercially available. To avoid the complex machinery of nanotechnological methods, some alternate approaches involve growing photonic crystals from colloidal crystals as self-assembled structures.
Mass-scale 3D photonic crystal films and fibres can now be produced using a shear-assembly technique that stacks 200–300 nm colloidal polymer spheres into perfect films of fcc lattice. Because the particles have a softer transparent rubber coating, the films can be stretched and molded, tuning the photonic bandgaps and producing striking structural color effects.
Computing photonic band structureEdit
The photonic band gap (PBG) is essentially the gap between the air-line and the dielectric-line in the dispersion relation of the PBG system. To design photonic crystal systems, it is essential to engineer the location and size of the bandgap by computational modeling using any of the following methods:
- Plane wave expansion method
- Finite element method
- Finite difference time domain method
- Order-n spectral method
- KKR method
- Bloch wave – MoM method
- Construction of the Band Diagram
Essentially, these methods solve for the frequencies (normal modes) of the photonic crystal for each value of the propagation direction given by the wave vector, or vice versa. The various lines in the band structure, correspond to the different cases of n, the band index. For an introduction to photonic band structure, see Joannopoulos.
The plane wave expansion method can be used to calculate the band structure using an eigen formulation of the Maxwell's equations, and thus solving for the eigen frequencies for each of the propagation directions, of the wave vectors. It directly solves for the dispersion diagram. Electric field strength values can also be calculated over the spatial domain of the problem using the eigen vectors of the same problem. For the picture shown to the right, corresponds to the band-structure of a 1D distributed Bragg reflector (DBR) with air-core interleaved with a dielectric material of relative permittivity 12.25, and a lattice period to air-core thickness ratio (d/a) of 0.8, is solved using 101 planewaves over the first irreducible Brillouin zone.
To speed calculation of the frequency band structure, the Reduced Bloch Mode Expansion (RBME) method can be used. The RBME method applies "on top" of any of the primary expansion methods mentioned above. For large unit cell models, the RBME method can reduce time for computing the band structure by up to two orders of magnitude.
Photonic crystals are attractive optical materials for controlling and manipulating light flow. One dimensional photonic crystals are already in widespread use, in the form of thin-film optics, with applications from low and high reflection coatings on lenses and mirrors to colour changing paints and inks. Higher-dimensional photonic crystals are of great interest for both fundamental and applied research, and the two dimensional ones are beginning to find commercial applications.
The first commercial products involving two-dimensionally periodic photonic crystals are already available in the form of photonic-crystal fibers, which use a microscale structure to confine light with radically different characteristics compared to conventional optical fiber for applications in nonlinear devices and guiding exotic wavelengths. The three-dimensional counterparts are still far from commercialization but may offer additional features such as optical nonlinearity required for the operation of optical transistors used in optical computers, when some technological aspects such as manufacturability and principal difficulties such as disorder are under control.
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- http://ab-initio.mit.edu/book/photonic-crystals-book.pdf[full citation needed]
- Hosein, I. D; Ghebrebrhan, M; Joannopoulos, J. D; Liddell, C. M (2010). "Dimer Shape Anisotropy: A Nonspherical Colloidal Approach to Omnidirectonal Photonic Band Gaps". Langmuir. 26 (3): 2151–9. doi:10.1021/la902609s. PMID 19863061.
- Hosein, Ian D; Lee, Stephanie H; Liddell, Chekesha M (2010). "Dimer-Based Three-Dimensional Photonic Crystals". Advanced Functional Materials. 20 (18): 3085–91. doi:10.1002/adfm.201000134.
- Hosein, Ian D; John, Bettina S; Lee, Stephanie H; Escobedo, Fernando A; Liddell, Chekesha M (2009). "Rotator and crystalline films viaself-assembly of short-bond-length colloidal dimers". J. Mater. Chem. 19 (3): 344–9. doi:10.1039/B818613H.
- "Optical computing gets a lift on butterfly wings". www.gizmag.com.
- Turner, Mark D; Saba, Matthias; Zhang, Qiming; Cumming, Benjamin P; Schröder-Turk, Gerd E; Gu, Min (2013). "Miniature chiral beamsplitter based on gyroid photonic crystals". Nature Photonics. 7 (10): 801. Bibcode:2013NaPho...7..801T. doi:10.1038/nphoton.2013.233.
- Ang, Angeleene S; Sukhov, Sergey V; Dogariu, Aristide; Shalin, Alexander S (2017). "Scattering Forces within a Left-Handed Photonic Crystal". Scientific Reports. 7: 41014. Bibcode:2017NatSR...741014A. doi:10.1038/srep41014. PMC . PMID 28112217.
- Ordejón, Pablo (1998). "Order-N tight-binding methods for electronic-structure and molecular dynamics". Computational Materials Science. 12 (3): 157–91. doi:10.1016/S0927-0256(98)00027-5.
- Richard M Martin, Linear Scaling 'Order-N' Methods in Electronic Structure Theory
- "EM21 - EM Lab". emlab.utep.edu.
- John D Joannopoulos; Johnson SG; Winn JN; Meade RD (2008), "Photonic Crystals: Molding the Flow of Light", Photonic Crystals: Molding the Flow of Light (2nd ed.), Princeton NJ: Princeton University Press, Bibcode:2008pcmf.book.....J, ISBN 978-0-691-12456-8[page needed]
- Hussein, M. I (2009). "Reduced Bloch mode expansion for periodic media band structure calculations". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 465 (2109): 2825–48. arXiv: . Bibcode:2009RSPSA.465.2825H. doi:10.1098/rspa.2008.0471. JSTOR 30243411. | <urn:uuid:ec0005b0-9aa1-47f7-8c50-42664d84bb4d> | 3.703125 | 6,169 | Knowledge Article | Science & Tech. | 51.146836 | 95,622,996 |
About this book
This book is an introduction to the theory of Hilbert space, a fundamental tool for non-relativistic quantum mechanics. Linear, topological, metric, and normed spaces are all addressed in detail, in a rigorous but reader-friendly fashion. The rationale for an introduction to the theory of Hilbert space, rather than a detailed study of Hilbert space theory itself, resides in the very high mathematical difficulty of even the simplest physical case. Within an ordinary graduate course in physics there is insufficient time to cover the theory of Hilbert spaces and operators, as well as distribution theory, with sufficient mathematical rigor. Compromises must be found between full rigor and practical use of the instruments. The book is based on the author's lessons on functional analysis for graduate students in physics. It will equip the reader to approach Hilbert space and, subsequently, rigged Hilbert space, with a more practical attitude.
With respect to the original lectures, the mathematical flavor in all subjects has been enriched. Moreover, a brief introduction to topological groups has been added in addition to exercises and solved problems throughout the text. With these improvements, the book can be used in upper undergraduate and lower graduate courses, both in Physics and in Mathematics.
- DOI https://doi.org/10.1007/978-3-319-03713-4
- Copyright Information Springer International Publishing Switzerland 2015
- Publisher Name Springer, Cham
- eBook Packages Physics and Astronomy
- Print ISBN 978-3-319-03712-7
- Online ISBN 978-3-319-03713-4
- Series Print ISSN 2198-7882
- Series Online ISSN 2198-7890
- Buy this book on publisher's site | <urn:uuid:7e864588-1156-4c75-b925-329349a80e0b> | 2.84375 | 358 | Product Page | Science & Tech. | 37.717036 | 95,623,035 |
This image of Tassiusaq Fjord on the west coast of Greenland shows a moraine -- a pile of boulders and other debris pushed up by a glacier which has long since retreated inland. Scientists at Ohio State University and their colleagues will use plant material found in moraines to gauge the flow and retreat of glaciers on the island. A new study using data from NASA’s Landsat 7 and Terra satellites has shown that the nearby Jakobshavn Glacier is flowing faster than before, and it is retreating rapidly from the Greenland coastline. Data for this image came from Terra’s Advanced Spaceborne Thermal Emission and Reflection Radiometer instrument. Image created by Catherine Tremper, courtesy of Ohio State University.
One of the world’s fastest-moving glaciers is speeding up and retreating rapidly, a recent study has revealed.
The finding has surprised scientists, because while the margins of the Jakobshavn (pronounced "yah-cub-SAH-ven") Glacier had been slowly retreating from the southwest coast of Greenland since before 1900, this retreat appeared to have stopped by the early 1990s when the first accurate measurements were made. Now the glacier is accelerating.
The glacier, one of the major drainage outlets of Greenland’s interior ice sheet, is thinning more than four times faster than it had for most of the 20th Century. Accompanying this thinning is a substantial increase in ice speed.
Pam Frost Gorder | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences | <urn:uuid:0246ed91-ca04-4759-9bee-9f5808e11815> | 4.0625 | 943 | Content Listing | Science & Tech. | 42.30661 | 95,623,038 |
Researchers have developed powerful new techniques to see in unprecedented detail how blood-forming cells develop in zebrafish. The scientists have used this system to transplant blood cells with fluorescent "tags" so they can observe how the cells restore the blood system in mutant zebrafish that do not have any red blood cells.
The techniques may be helpful in learning how bone marrow transplants reconstitute the immune systems of patients whose immune cells have been destroyed by chemotherapy during cancer treatment.
The researchers, led by Howard Hughes Medical Institute investigator Leonard Zon, published their studies November 9, 2003, in Nature Immunology. Zon and colleagues from Childrens Hospital Boston collaborated on the studies with researchers from the University of California at Los Angeles.
Jim Keeley | EurekAlert!
Colorectal cancer risk factors decrypted
13.07.2018 | Max-Planck-Institut für Stoffwechselforschung
Algae Have Land Genes
13.07.2018 | Julius-Maximilians-Universität Würzburg
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
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Chlorocypha schmidti Pinhey, 1967
Type locality: Mt Hoyo, Bunia, Ituri, DRC
Male belongs to several species with (a) head all black or with yellowish, brown or green spots, but no blue markings; (b) at least mid and hind tibiae with anterior white streaks; (c) Abd all red, sometimes gradually becoming yellow towards end. Identified by combination of (1) found only at streams in E DRC; (2) relatively large, Hw 22-25 mm; (3) head and thorax entirely black at maturity; (4) S2 all black, at most with almost indiscernible red central spots, S3 laterally black extending onto dorsum especially at segment base, and S4-5 with small (sub)apical black markings. [Adapted from Dijkstra & Clausnitzer 2014]
Not known, but probably (headwater) streams shaded by forest. Probably often with submerged roots, dead trunks or branches and/or coarse detritus. From 800 to 1400 m above sea level.
Abdomen (dorsal view)
Map citation: Clausnitzer, V., K.-D.B. Dijkstra, R. Koch, J.-P. Boudot, W.R.T. Darwall, J. Kipping, B. Samraoui, M.J. Samways, J.P. Simaika & F. Suhling, 2012. Focus on African Freshwaters: hotspots of dragonfly diversity and conservation concern. Frontiers in Ecology and the Environment 10: 129-134.
- Pinhey, E. C. G. (1967). African Chlorocyphidae (Odonata). Journal Entomological Society Southern Africa, 29, 161-197. [PDF file]
Citation: Dijkstra, K.-D.B (editor). African Dragonflies and Damselflies Online. http://addo.adu.org.za/ [2018-07-17]. | <urn:uuid:9c8aab95-c164-4839-9441-3967d782ef3a> | 2.71875 | 433 | Knowledge Article | Science & Tech. | 75.226847 | 95,623,080 |
Tuesday, July 17, 2018
Science and Technology Research News
Tag: Twin Otter
Laser Mapping Project Shows Effects of Physical Changes in Antarctica’s Dry...
August 8, 2017
Researchers funded by the National Science Foundation (NSF) have publicly released high-resolution maps of Antarctica's McMurdo Dry Valleys, a globally unique polar desert. The high-resolution...
The Science and Technology Behind Tomorrow's Innovations
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AbstractTo study desertification processes relating to soil erosion, a climatological and altitudinal gradient from south to north was selected in Crete (Greece) and four locations were selected along the gradient. At the locations precipitation ranged from 1400 mm/year at the highest location to 400 mm/year at the lowest. All locations are affected by the actual land use: intensive grazing, small controlled fires, and abandoned agricultural terraces. Representative soil profiles were described in the field and analyzed in the laboratory, and rainfall simulation experiments in the field measured soil erosion over different soil surfaces and land uses. Data on physical and chemical properties were obtained from the soil profiles and soil hydrology, and erosion data were obtained from the rainfall simulation experiments. Soil aggregation was studied with samples taken from the soil in the rainfall simulation plots and special attention being paid to the aggregate size distribution and the water-stable microaggregation. The interaction between climatological conditions and land use seems to be the main factor controlling soil erosion. This paper describes how the expected erosion along the gradient (from the most humid to the driest site) can be affected and disturbed by specific processes derived from land use.
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- Properties and Erosional Response of Soils in a Degraded Ecosystem in Crete (Greece)
A. C. Imeson
J. M. Schoorl
I. R. Tiemessen
- Springer Netherlands
Fallstudie Überschwemmungskarten/© Thaut Images | Fotolia | <urn:uuid:3d89059e-9385-4720-8383-a50cf28737bc> | 3.171875 | 331 | Academic Writing | Science & Tech. | 23.751271 | 95,623,119 |
NOTE: Most of the High Level Science Products are unavailable while unscheduled maintenance is being performed. They will be incrementally restored over the course of this week. We apologize for any inconvenience.
Analysis of Individual Copernicus Scans of a Star
One the useful aspects of the Copernicus archive is that it can be used in searches for spectral variability of bright stars. Using gamma Cas as an example, let's say we want to check the results of <Slettebak and Snow (1978)> who reported the amazing development of emission in the UV resonance lines of Si IV and Mg II in just a few minutes. The feature was not present in the first spectral line Copernicus scanned, yet it was found to develop over the time it took the scan to reach the second (bluer) line in each doublet. Do we believe this? To check out this claim, we can access and compare individual Copernicus scans from the original study.
This can be done in a variety ways, either interactively on Copernicus Web pages, or using the IDL-based FITS readers mrdfits or ifitsrd (IRAF/STSDAS tasks do not yet read most Copernicus FITS files because these files generally contain variable array lengths. The IDL-based routine fxbread also works, but only on one file row (scan) per read. It is impractical to use it for reading many rows). It is usually convenient to determine first the scan numbers needed, e.g. by inputting the observing times into the Copernicus search page.
One should recall that Copernicus scans are stored in 5- or 6-row groups. This is because Copernicus observations were made with simultaneous U1 (U2, U3) and V1 (V2, V3) tubes. U3 and/or V3 were used to monitor particle backgrounds empirically. An alternate tube (e.g. U2 for U1, V2 for V1, or vice versa) was employed to shield the tube used for data collection from scattered light. Data for each of these tubes was recorded as a separate binary row (scan). Additionally, the tback field in each data scan is a modeled radiation background spectrum. This background can be subtracted from the tcounts array to produce a "net" spectrum.
The first step is to determine the object number of interest. A single FITS file for the object contains all the observations done by Copernicus. This file contains a 3-digit number corresponding to the object name for the mission. (This number is given by the star_num field.) To do this, go to the <complete target list> page. For gamma Cas, one finds the filename c084.pep, so the object number is 084.
Next one should determine the range of scan numbers. This can be best learned from the search Web page under "Co-added Scans" by putting in the starname, wavelength limits, and rage of observation dates. For our present query, enter "gamma Cas," "1380," "1415," and "27 Jan 1977 .. 29 Jan 1977), respectively, and run the search. One record is returned with the scan range 1974--2273. We may now download the software and work on it with our favorite IDL-based FITS reader.
The REC_* keywords indicate only the time for a reference position in that Copernicus orbit during which observations were made, not the exact observation time (the difference between these times may be up to one orbital period of about 96 minutes). A conveninent way of getting the correct time of observation is to download the program coptime from the ftp area ) (<ftp://archive.stsci.edu/pub/copernicus>) and use it for the scan(s) of interest to determine these times. This is shown for scans 1974-2273 as follows:
i = indgen(300) +1974
The output provides a listing of start and end times which are accurate to about 1s.
Here are three examples of reading in scans 1974-2273 in mrdfits or ifitsrd. Of the two routines, mrdfits reads in multiple file rows much faster, but ifitsrd permits an alternative to IDL structures and working with selected data fields. (For a primer on IDL structures, click <here.>)
Example 1, with mrdfits (structure only):
p = mrdfits('c084.pep',1,h,range=[1973,2272])
(Note the 0-based indexing.)
i = indgen(300) + 1974
The array i contains the indices corresponding to the 300 scans of potential interest. The array h contains keywords unique to the object gamma Cas and is the header of the primary array record (which contains only this header, no data). The parameter e is the keyword header for each of the 40 data fields and includes the field name for each. The parameter p is the data structure containing the observations. The IDL keyword /struc specifies the data are to be packed into an IDL structure, while /sil suppresses a summary of the data contents to the screen. In this case, /nvla is critical for Copernicus files because it suppresses an optional keyword array which would attempt to report the number of elements in the variable length arrays. For Copernicus data this value, the number of wavelength points scanned, often varies from observation to observation. If /nvla is not specified, the run of ifitsrd will abort if the number of array elements in successive scans differs from the first scan read.
An alternative way of examining the data structure contents is to type:
By either printing out of the keywords in the string array e or by this "help" command one obtains the field-name convention needed to work with data fields.
Let's suppose we want work with the following fields: rec_num, tube_name, nnn (array length), yr_obs, day_obs, hr_obs, min_obs, tlambda (wavelength array), tcounts (raw counts), tback (background). These are, respectively field numbers 3, 14, 15, 16, 17, 18, 19, 36, 37, 39), which we will designate as variables with the letter f. In the call to ifitsrd, we use the keyword efld to list these field numbers corresponding to the extracted data fields, as follows:
i = indgen(300) + 1974
At this point it's a good idea to check on the wavelength direction of the scan, e.g. by printing out the first and last wavelength element. These elements are numbered in the sense they were observed, with the first element (either shortest or longest wavelength) being the one first recorded in time.
From coptime and the Slettebak and Snow paper, we find that the observations of interest are scans 2144 (Si IV doublet) and 2145 (Mg II) doublet. These are monitored by the U2 and V2 tubes, respectively. We may compare these, for example, to the immediately preceding observations, 2139 and 2140, by printing or plotting them out. Note here that all arrays are padded to 176 elements (except for arrays already containing 176 scanned elements). Thus, generally we must first determine the number of actual (nonzero) data points; for these two pairs of observations these array lengths are 148, 176, respectively. Finally, we plot out the arrays of interest. For example:
plot,a(170).tlambda(0:147),a(170).tcounts(0:147) - a(170).tback(0:147)
and so forth.
Do you see the published variations? | <urn:uuid:cb4d2b68-993a-4b39-90a1-f6ce25771bef> | 3.078125 | 1,633 | Tutorial | Science & Tech. | 57.747693 | 95,623,121 |
The star, known as EV Lacertae, isn’t much to write home about. It’s a run-of-the-mill red dwarf, by far the most common type of star in the universe. It shines with only one percent of the Sun’s light, and contains only a third of the Sun’s mass. At a distance of only 16 light-years, EV Lacertae is one of our closest stellar neighbors. But with its feeble light output, its faint magnitude-10 glow is far below naked-eye visibility.
"Here’s a small, cool star that shot off a monster flare. This star has a record of producing flares, but this one takes the cake," says Rachel Osten, a Hubble Fellow at the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Md. "Flares like this would deplete the atmospheres of life-bearing planets, sterilizing their surfaces."
The flare was first seen by the Russian-built Konus instrument on NASA’s Wind satellite in the early morning hours of April 25. Swift’s X-ray Telescope caught the flare less than two minutes later, and quickly slewed to point toward EV Lacertae. When Swift tried to observe the star with its Ultraviolet/Optical Telescope, the flare was so bright that the instrument shut itself down for safety reasons. The star remained bright in X-rays for 8 hours before settling back to normal.
EV Lacertae can be likened to an unruly child that throws frequent temper tantrums. The star is relatively young, with an estimated age of a few hundred million years. The star rotates once every four days, which is much faster than the sun, which rotates once every four weeks. EV Lacertae’s fast rotation generates strong localized magnetic fields, making it more than 100 times as magnetically powerful as the Sun’s field. The energy stored in its magnetic field powers these giant flares.
EV Lacertae’s constellation, Lacerta, is visible in the spring for only a few hours each night in the Northern Hemisphere. But if the star had been more easily visible, the flare probably would have been bright enough that the star could have been seen with the naked eye for one to two hours.
The flare’s incredible brightness enabled Swift to make detailed measurements. "This gives us a golden opportunity to study a stellar flare on a second-by-second basis to see how it evolved," says Stephen Drake of NASA Goddard.
Since EV Lacertae is 15 times younger than our Sun, it gives us a window into our solar system’s early history. Younger stars rotate faster and generate more powerful flares, so in its first billion years the sun must have let loose millions of energetic flares that would have profoundly affected Earth and the other planets.
Flares release energy across the electromagnetic spectrum, but the extremely high gas temperatures produced by flares can only be studied with high-energy telescopes like those on Swift. Swift's wide field and rapid repointing capabilities, designed to study gamma-ray bursts, make it ideal for studying stellar flares. Most other X-ray observatories have studied this star and others like it, but they have to be extremely lucky to catch and study powerful flares due to their much smaller fields of view.
Says Eric Feigelson of Penn State University in University Park, Pa., "I find it remarkable that a satellite designed to detect the explosive birth of black holes in distant galaxies can also detect explosions on stars in the immediate neighborhood of our Sun."
Robert Naeye | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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:0eee9bca-0564-442f-aeb3-809464bf4d80> | 3.765625 | 1,331 | Content Listing | Science & Tech. | 46.657885 | 95,623,144 |
“Central America is a major, emerging “hot spot” in the tropics where climate change impacts on the environment will be pronounced, and the loss of species associated with climate has already been identified,” says doctoral candidate Ambarish Karmalkar of the UMass Amherst Climate System Research Center.
He recently attended the first conference organized in Costa Rica to study this issue. “We have completed a regional climate model showing that many areas of Costa Rica will become warmer and drier as climate change accelerates, and these changes will be amplified at higher elevations.”
Additional members of the research team include Raymond Bradley, a professor of geosciences at UMass Amherst, and Henry Diaz of the National Oceanic and Atmospheric Administration.
According to Karmalkar, Costa Rica has a unique geography that supports a stunning array of plants, animals and insects. The land begins at sea level on both the western Pacific coast and the eastern Caribbean coast, rising to over 3,000 meters above sea level in the central mountain range. As the land rises, differences in temperature and precipitation caused by elevation create an array of distinct ecosystems stacked on top of each other, each one housing a unique biological community.
Above 1,000 meters, rising air creates a continual cloud layer that constantly bathes the vegetation in horizontal precipitation, allowing plants and animals to survive the dry season from December to April. These cloud forests are essential to maintaining freshwater resources in Costa Rica, and the height at which the clouds develop is a critical factor for these ecosystems. Since they are highly dependant on temperature and precipitation, these ecosystems are particularly vulnerable to climate change.
To predict the effects of climate change, a regional modeling system capable of accommodating the complex topography of Central America was chosen. After validating the computer model using rainfall and temperature data collected in Central America between 1961 and 1990, the team looked at what would happen if carbon dioxide in the atmosphere doubled. The results of this medium-to-high scenario, called the A2 scenario in reports issued by the Intergovernmental Panel on Climate Change, were striking.
“If carbon dioxide levels double, this region will not only experience an increase in temperature of more than three Kelvins, but all future temperatures will likely be higher than the complete range of present-day temperatures,” says Karmalkar. “In addition, the model simulation indicates that high elevation Pacific slopes and the Caribbean lowlands will receive up to 30 percent less precipitation. Simulations also indicate an overall increase in the height of the cloud base of up to 300 meters.”
According to Karmalkar, as temperatures rise, various ecosystems will try to migrate to where they are comfortable, moving in an upslope direction in this case. As they migrate, plants and animals will disturb other species, and eventually run out of space as they reach the top of the mountains. The result may be a loss of many species that can’t survive the new conditions.
“After the extinction of the golden toad sometime between 1987 and 1989, corresponding with a warm event in the Pacific Ocean, scientists began relating climate change to the loss of biodiversity in Costa Rica,” says Karmalkar. “Since then, the Monteverde Institute has been documenting biological changes that could be related to climate change.”
Karmalkar plans to study the entire region of Central America, determining large climate dynamics of the region and how that will change in the future. “Central America has a unique annual cycle of precipitation, with a midsummer drought that occurs during July and August,” says Karmalkar. “Knowing how climate change will affect this cycle will be important for agriculture, which is an integral part of the economy of the region.”
Ambarish Karmalkar | 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
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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Astronomers used Chandra to observe a neutron star, known as RX J0822-4300, over a period of about five years. During that span, three Chandra observations clearly show the neutron star moving away from the center of the Puppis A supernova remnant. This remnant is the stellar debris field created during the same explosion in which the neutron star was formed about 3700 years ago.
By combining how far it has moved across the sky with its distance from Earth, astronomers determined the neutron star is moving at over 3 million miles per hour. At this rate, RX J0822-4300 is destined to escape from the Milky Way after millions of years, even though it has only traveled about 20 light years so far.
"This star is moving at 3 million miles an hour, but it's so far away that the apparent motion we see in five years is less than the height of the numerals in the date on a penny, seen from the length of a football field," said Frank Winkler of Middlebury College in Vermont. "It's remarkable, and a real testament to the power of Chandra, that such a tiny motion can be measured."
"Just after it was born, this neutron star got a one-way ticket out of the Galaxy," said co-author Robert Petre of NASA's Goddard Space Flight Center in Greenbelt, Md. "Astronomers have seen other stars being flung out of the Milky Way, but few as fast as this."
So-called hypervelocity stars have been previously discovered shooting out of the Milky Way with speeds around one million miles per hour. One key difference between RX J0822-4300 and these other reported galactic escapees is the source of their speed. The hypervelocity stars are thought to have been ejected by interactions with the supermassive black hole in the Galaxy's center.
This neutron star, by contrast, was flung into motion by the supernova that created Puppis A. The data suggest the explosion was lop-sided, kicking the neutron star in one direction and the debris from the explosion in the other.
The supernova was precipitated when the core of a massive star imploded to form a neutron star. Computer simulations show that the infall of the outer layers of the star onto a neutron star releases an enormous amount of energy. As this energy propagates outward, it can reverse the infall and eject the outer layers of the star at speeds of millions of miles per hour. Due to the complexity of the flow, the ejection is not symmetric, leading to a rocket effect that propels the neutron star in the opposite direction.
The breakneck speed of the Puppis A neutron star, plus an apparent lack of pulsations from it, is not easily explained by even the most sophisticated supernova explosion models.
"The puzzle about this cosmic cannonball is how nature can make such a powerful cannon," said Winkler. "The high speed might be explained by an unusually energetic explosion, but the models are complicated and hard to apply to real explosions."
Megan Watzke | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
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The term pedotransfer function was coined by Johan Bouma as translating data we have into what we need. The most readily available data come from soil survey, such as field morphology, soil texture, structure and pH. Pedotransfer functions add value to this basic information by translating them into estimates of other more laborious and expensively determined soil properties. These functions fill the gap between the available soil data and the properties which are more useful or required for a particular model or quality assessment. Pedotransfer functions utilize various regression analysis and data mining techniques to extract rules associating basic soil properties with more difficult to measure properties.
Although not formally recognized and named until 1989, the concept of the pedotransfer function has long been applied to estimate soil properties that are difficult to determine. Many soil science agencies have their own (unofficial) rule of thumb for estimating difficult-to-measure soil properties. Probably because of the particular difficulty, cost of measurement, and availability of large databases, the most comprehensive research in developing PTFs has been for the estimation of water retention curve and hydraulic conductivity.
The first PTF came from the study of Lyman Briggs and McLane (1907). They determined the wilting coefficient, which is defined as percentage water content of a soil when the plants growing in that soil are first reduced to a wilted condition from which they cannot recover in an approximately saturated atmosphere without the addition of water to the soil, as a function of particle-size:
With the introduction of the field capacity (FC) and permanent wilting point (PWP) concepts by Frank Veihmeyer and Arthur Hendricksen (1927), research during the period 1950-1980 attempted to correlate particle-size distribution, bulk density and organic matter content with water content at field capacity (FC), permanent wilting point (PWP), and available water capacity (AWC).
In the 1960s various papers dealt with the estimation of FC, PWP, and AWC, notably in a series of papers by Salter and Williams (1965 etc.). They explored relationships between texture classes and available water capacity, which are now known as class PTFs. They also developed functions relating the particle-size distribution to AWC, now known as continuous PTFs. They asserted that their functions could predict AWC to a mean accuracy of 16%.
In the 1970s more comprehensive research using large databases was developed. A particularly good example is the study by Hall et al. (1977) from soil in England and Wales; they established field capacity, permanent wilting point, available water content, and air capacity as a function of textural class, and as well as deriving continuous functions estimating these soil-water properties. In the USA, Gupta and Larson (1979) developed 12 functions relating particle-size distribution and organic matter content to water content at potentials ranging from -4 kPa to -1500 kPa.
With the flourishing development of models describing soil hydraulic properties and computer modelling of soil-water and solute transport, the need for hydraulic properties as inputs to these models became more evident. Clapp and Hornberger (1978) derived average values for the parameters of a power-function water retention curve, sorptivity and saturated hydraulic conductivity for different texture classes. In probably the first research of its kind, Bloemen (1977) derived empirical equations relating parameters of the Brooks and Corey hydraulic model to particle-size distribution.
Jurgen Lamp and Kneib (1981) from Germany introduced the term pedofunction, while Bouma and van Lanen (1986) used the term transfer function. To avoid confusion with the term transfer function used in soil physics and in many other disciplines, Johan Bouma (1989) later called it pedotransfer function. (A personal anecdote hinted that Arnold Bregt from Wageningen University suggested this term).
Since then, the development of hydraulic PTFs has become a boom research topic, first in the US and Europe, South America, Australia and all over the world.
Although most PTFs have been developed to predict soil hydraulic properties, they are not restricted to hydraulic properties. PTFs for estimating soil physical, mechanical, chemical and biological properties have also been developed.
There are several available programs that aid determining hydraulic properties of soils using pedotransfer functions, among them are
- SOILPAR – By Acutis and Donatelli
- ROSETTA – By Schaap et al. of the USDA, uses artificial neural networks
Soil inference systems
McBratney et al. (2002) introduced the concept of a soil inference system, SINFERS, where pedotransfer functions are the knowledge rules for soil inference engines. A soil inference system takes measurements with a given level of certainty (source) and by means of logically linked pedotransfer functions (organiser) infers data that is not known with minimal inaccuracy (predictor).
- Bouma, J. (1989). "Using soil survey data for quantitative land evaluation". Advances in Soil Science. 9: 177–213.
- Acutis, M., and Donatelli, M. (2003). "SOILPAR 2.00: software to estimate soil hydrological parameters and functions". European Journal of Agronomy. 18 (3–4): 373–377. doi:10.1016/S1161-0301(02)00128-4.
- Schapp, M.G., Leij, F.J., and van Genuchten, M.Th. (2001). "rosetta: A computer program for estimating soil hydraulic parameters with hierarchical pedotransfer functions". Journal of Hydrology. 251 (3): 163–176. doi:10.1016/S0022-1694(01)00466-8.
- Minasny, Budiman (2007). "Predicting soil properties". Jurnal Ilmu Tanah dan Lingkungan. 7 (1): 54–67. | <urn:uuid:cc984220-4b89-443c-a951-1c76acb6046e> | 3.4375 | 1,245 | Knowledge Article | Science & Tech. | 38.557578 | 95,623,169 |
Monodromy and normal forms
We discuss the history of the monodromy theorem, starting from Weierstraß, and the concept of a monodromy group. From this viewpoint we compare then the Weierstraß, the Legendre and other normal forms for elliptic curves, explaining their geometric meaning and distinguishing them by their stabilizer in ℙSL(2, ℤ) and their monodromy. Then we focus on the birth of the concept of the Jacobian variety, and the geometrization of the theory of Abelian functions and integrals. We end illustrating the methods of complex analysis in the simplest issue, the difference equation f(z) = g(z + 1) - g(z) on ℂ.
KeywordsNormal Form Analytic Continuation Meromorphic Function Elliptic Curve Elliptic Curf
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(Washington, DC)—We know poisonous snakes are dangerous, but what exactly makes venom so powerful? Evolutionary biology tells us why venom is useful for snakes, but chemistry tells us how venom works. This week, Reactions sheds some light on the proteins in venom, as well as its potential medical uses. Check it out here: https:/
The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 158,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
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Acoustic resonance is the tendency of an acoustic system to absorb more energy when it is forced or driven at a frequency that is the same as one of its own natural frequencies of vibrations. Acoustic resonance is sometimes used to narrow mechanical resonance to the frequency range of human hearing. Since acoustics is defined in general terms concerning vibrational waves in matter, acoustic resonance can occur at frequencies outside the range of human hearing.
An acoustically resonant object usually has more than one resonance frequency. This is especially true at harmonics of the strongest resonance. The object will easily vibrate at these frequencies and vibrate less strongly at other frequencies. It can pick out its resonance frequency from a complex excitation such as an impulse or a wideband noise excitation; it is filtering out all frequencies other than its resonance.
Acoustical resonance is important for instrument builders. Most instruments used resonators, such as, the strings and body of a guitar, the length of tube in a flute, and the shape of a drum membrane. It is also important in hearing.© BrainMass Inc. brainmass.com July 20, 2018, 1:15 am ad1c9bdddf | <urn:uuid:7277212f-6e0c-4066-8436-6169d5c121c4> | 4.21875 | 242 | Knowledge Article | Science & Tech. | 33.291875 | 95,623,234 |
Facebook volunteers and work-at-home moms might be making city planning decisions, thanks to AI research conducted by MIT scientists. Researchers from MIT’s media lab have been feeding computers a steady stream of data for the last four years to build an AI capable of determining why some cities grow and others decay.
The data the researchers are using has been compiled from people, regular Joes and Janes, who choose between two randomly selected pictures to determine which one seems less dangerous or more appealing. Currently it’s all common-sense driven: most of us would agree a typically beautiful environment will foster growth better than a landscape of derelict buildings.
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Finally, with enough data, the AI has been returning results — which have been compared with human responses to the same image pairings. The researchers ‘proofed’ their data by comparing responses from Amazon Mechanical Turk workers. According to MIT the robots got it right a little more than 70% of the time, which was better than expected. In the future MIT researchers plan on increasing the number of people contributing data, going so far as to say they may need to advertise on Facebook to draw more participants.
At first-glance it doesn’t sound very impressive – they’re just feeding data into an algorithm by hand based on thousands of different human interpretations. People decide which Google Map image in a pair looks like a nicer neighborhood, scientists determine if the machine agrees, and vice-versa.
The ultimate goal is for us to glean insight into our problems by learning what the machines can teach us about ourselves. Professor César Hidalgo, the director of the Collective Learning group at the MIT Media Lab, told Co.Design:
I do hope that this research starts helping us understand how the urban environment affects people and how it’s affected by people so that when we do policy in the context of urban planning, we have a more scientific understanding of the effect different designs have in the behaviors of the populations that use them
Until the machines learn to define beauty for themselves – which is a scary thought – we’ll need to explain to them why one city’s streets are lined with despair and another shows the promise of growth and renewal. Once AI is up to speed, however, we’ll be able to start saving dying communities with machine-learning. Computers can draw exponentially more patterned-based conclusions than humans.
The better we can understand an issue, the more connections we can determine — and the better our solutions will be. Thanks to MIT we may be on the verge of solving decades-old urban rejuvenation problems. | <urn:uuid:52891a98-9c71-42fc-b0f9-866ed2b15ff1> | 3.25 | 556 | News Article | Science & Tech. | 41.222867 | 95,623,238 |
Now showing items 11-13 of 13
Small-scale species richness in forest canopy gaps: the role of niche limitation versus the size of the species pool
(Opulus Press, 1998-06)
The form of the relationship between local species richness and the number of species in the surrounding region can be used as a test between competing theories of community structure. For 32 canopy gaps in New Zealand ...
Tree regeneration in a New Zealand rain forest influenced by disturbance and drainage interactions
(Opulus Press, 2005-08)
Question: Does canopy tree regeneration response to different large disturbances vary with soil drainage? Location: Old-growth conifer (Dacrydium and Dacrycarpus), angiosperm (Nothofagus and Weinmannia) rain forest, Mount ...
Leaf damage does not affect leaf loss or chlorophyll content in the New Zealand pepper tree, kawakawa (Macropiper excelsum)
(New Zealand Ecological Society, 2000)
Kawakawa (Macropiper excelsum) is an understorey, forest tree which sustains conspicuous and substantial herbivory from the larvae of a geometrid moth, Cleora scriptaria. This study examined the relationship between leaf ... | <urn:uuid:682b7369-cf15-4fe3-98aa-d1a8198e5cd2> | 2.609375 | 256 | Content Listing | Science & Tech. | 35.510714 | 95,623,243 |
The Unruly Galaxy
Published on February 6, 2016 by Jacqueline Taylor
A side-portrait of LO95 0313-192. Credit: ESA/Hubble & NASA; acknowledgement, Judy Schmidt
Breaking astronomers’ standards one billion light years away is an unusual and oddly named galaxy, whose abnormalities have raised important questions about jet propulsion in the cosmos. Like our own galaxy the Milky Way, LO95 0313-192 is classified as a spiral galaxy. The name describes the appearance of arms swirling outwards from the center. Characteristically they contain lots of dust and gas, which make them prime areas for star formation. However, unlike the billions of other spiral galaxies, LO95 0313-192 also has giant jets of subatomic particles spewing from its center into space. These superheated outbursts are much more common in another type of galaxy called elliptical (also named for its shape), or in galaxies merging together. These jets are propelled by gravitational energy generated by the supermassive black hole at the galaxy’s core, and can travel at nearly the speed of light. It is unknown how these huge radio-emitting jet propulsions are formed, but scientists are hopeful that observing 0313-192 will lead to answers. In its wake, three more oddly behaving spiral galaxies have been discovered. Investigation is under way to reevaluate galaxy classification, jet propulsion science, and perhaps even how galaxies were formed in the Early Universe. | <urn:uuid:dce795e4-3ad5-40c4-8df0-7b1dd851a0a7> | 3.71875 | 296 | News (Org.) | Science & Tech. | 29.804109 | 95,623,258 |
Although numerous studies concerning the Holocene climate of the southern Iberian Peninsula were accomplished within the last few decades, the climate history of this region is still poorly understood. Various studies deal with a combination of proxies, which are neither easy to compare nor is their connection easy to explain, e.g., due to spatial patterns and time transgression. Within this study, the suitability of the lacustrine sediments from the Laguna Salada (Andalucía region, southern Spain) as a paleoclimate archive is investigated. The lake sediments were evaluated using a multi-proxy approach including sedimentological, mineralogical, geochemical and biological analyses. The sediments reflect the evolution of the lake from pre-Medieval times onwards and Characeae as well as Ostracod analyses give an indication of paleosalinity. Moreover does the geochemical composition provide profound information concerning changes of elemental and mineralogical composition. Nevertheless, a robust, high-resolution chronology could not be achieved owed to the scarcity of material available for radiocarbon dating and contamination problems. Furthermore, poor preservation of pollen restricted the reconstruction of vegetation history, which could have complemented important information concerning climatic changes and human activity.
https://www.sciencedirect.com/science/article/pii/S1040618216312988 Accessed 14 times | Last updated 18.05.2018
Schröder, T., van 't Hoff, J., Ortiz, J., de Torrez Perez-Hidalgo, T., Lopez-Salez, J., Melles, M., Holzhausen, A., Wennrich, V., Viehberg, F., Reicherter, K. (2017): Shallow hypersaline lakes as paleoclimate archives: A case study from the Laguna Salada Malaga province, southern Spain. – In: Quaternary International, DOI: 10.1016/j.quaint.2017.08.006
|Authors||Schröder, Tabea and van 't Hoff, Jasmijn and Ortiz, Jose Eugenio and de Torrez Perez-Hidalgo, Trinidad J. and Lopez-Salez, Jose Antonio and Melles, Martin and Holzhausen, Anja and Wennrich, Volker and Viehberg, Finn and Reicherter, Klaus|
|Title||Shallow hypersaline lakes as paleoclimate archives: A case study from the Laguna Salada Malaga province, southern Spain| | <urn:uuid:1d4cc297-4546-48d8-ac3d-af201a908947> | 2.828125 | 519 | Truncated | Science & Tech. | 27.116487 | 95,623,268 |
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However, more dedicated effort needs to be taken up in this regard.
The Giant Panda is a peaceful creature (WWF, 2015). The black and white fur of the animal is its distinctive feature of the animal and the animal is adored worldwide and in China. The animal belongs to the kingdom Animalia, Phylum Chordata, Class Mammalia, Order Carnivora, family Ursidae. Panda is the rarest among the bear family with only around 1600 species left worldwide. The Panda is considered as an endangered species. Adult panda can grow to more than 4 feet in height. The Panda eats 26 to 84 pounds of bamboo every day and in order to eat these large amounts of bamboo the Panda has large wrists. A new born Panda is of the size of a stick of butter but the adult panda is of the size of 330 pounds (IUCN, 2015). The panda grows at a rapid pace because the new born panda is 1/900tth of the size of an adult panda. Giant pandas are found in the temperate montane forests. The bamboo stands in these forests are dense and grow at an altitude of 12200-4100m (more often 1,500-300 m). The density of population in a particular region depends on the density of bamboo in a particular region and hill slope (Smithsonian national zoological park, 2015). Giant pandas generally stick to a place and prefer not to hibernate but in winter they descend down the hill slopes to warmer regions. The Animal’s primary habitat is China’s Yangtze basin. China’s main staple food is bamboo that is found widely in the region (Defenders of wildlife, 2015). The region is the economic and geographic heart of the region.
Pandas spend a lot of time eating and most of the food that they eat is Bamboo. Almost 55% of their day time is spent on eating. They use over 60 species of bamboo as their food. However out of the 60 species of bamboo only 35 species comprise their main food. The pandas use different species of bamboo as food in different seasons. Previously it was
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The devastating changes can be observed in erratic climate changes across the globe resulting in global warming and increase in climate related natural disasters like tsunami, flash floods, forest fires, tornadoes etc. The energy related requirements of human race have been met through exploitation of natural resources which have become sparse that are having massive adverse impact on the population at large.
Biodiversity Conservation Name Course: Instructor: Date: Abstract Biodiversity refers to the variety and assortment of various life forms in the environment. This includes the variety of plants and animals in various ecosystems including marine ecosystems, forest ecosystems as well as grasslands.
In a vastly deteriorating environment and with numerous species nearing extinction, federal law, institutions and individuals feel the responsibility of conserving the environment for future generations. One example of collaboration between the above mentioned members of community is conservation easement.
Environment is the conditions or the surroundings through which a human being, plant or animal operates. It involves the air, the waters, the soil, forests, etc. The environment is beneficial because it is a habitat to living things, source of food for animals, source of medicine and provides beautiful scenery during man’s relaxation.
Numerous Americans began to invest in stocks, and as stock value increased, more and more Americans became well-off. However, when the Wall Street stock market collapsed in 1929 the ‘golden age’ abruptly came to an end (Sanders 5). The U.S. was on the verge of falling into the Great Depression that was to endure for an entire decade.
It is during this century that many literary works focused on the relationship between man and the environment, leading to the emergence of the conservation movement, which is a political environmental and economic group that emerged with the sole objective of pushing for the protection of nature (Wilder, 53).
The direct benefits of this are reduced energy costs, improved environmental value and economic security for both individuals and countries. Industrial and commercial users would benefit through cost reduction
An important fact to note about Australia is that its Great Barrier Reef accounts for 10% of all reefs across the universe. Actually, it is one of the main reasons foreign tourists and locals alike flock the location in a bid to witness its magnificence. A
Harp seals are semi-aquatic animal marine mammals that spend most of their time in sea. The animal is sociable and lives peacefully with other seals. They give birth to single pups having white coats at birth time. Human beings hunt
In this lab investigation of whether the energy is conserved for different systems was performed. Three mechanical systems were used together with computer LoggerPro software Mechanical systems used were, a swinging pendulum,
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Follow explanation. LCDs are better.
It seems that LCD TV’s are environmentally friendly if you want good quality and low energy consumption.
Plasma: This particular TV display is probably the worst eco-friendly option to choose. While the picture is sharp and clear, “producing that perfect image requires a high resolution, and the higher the resolution, the more bandwidth—the rate at which data is transferred—the set needs,” according to GetDirectTV. Also, with any television, size matters. The bigger the set, the more energy and light it will take to illuminate the screen.
LCD: These sets seem to be somewhere in between Plasma and LED choices. While the technology of an LCD TV uses about a third of the energy consumption than Plasma, they still don’t quite beat the innovative technology of an LED TV.
One of the best tips for choosing a more environmentally-friendly television is to look at the Energy-Star rating that can be found on each TV display. And of course, as stated earlier, size does matter! Regardless of what kind of television you choose, the size will make the biggest impact. Remember, the bigger the size, the more energy consumption it requires. Not to say you have to sacrifice size or quality, but the amount of energy consumption is something to keep in mind.
Seasons do not greatly affect underground water sources.
Underground springs that bring melted snow water underground to a surface source are cold even in the middle of summer. The ground insulates the water that entered the aquifer at cold high altitudes keeping it cold regardless of air temperatures.
Underground springs, known as hot springs, get their heat by contact with the heated magma underneath the earth's surface. This hot springs will be close to boiling hot even in the middle of winter when there is snow on the ground.
The temperature of underground water sources depends on the source of the water not the air temperatures.
Biomass, geothermal, wind, tidal, solar, and hydroelectric
Biomass energy : The dilemma is "Food for people or food for energy?". It is good if a country can provide land for biomass production and does not encounter food deficiency.
Geothermal energy: In some areas the geothermal gradient is sufficient enough to exploit to generate electricity. Disadvantage of it is that geothermal liquids contain many different types of minerals and elements. When they are allowed to flow free, they might pollute the environment (for example in Aydin Buharkent Turkey).
Wind energy: When wind is in sufficient velocity, people want to benefit from it by using wind turbines. The disadvantages of it can be listed as: some birds and bats as well as bees die when this turbines are operated, a certain amount of land (a quarter US acre for example) is necessary to erect wind turbines (wind power company has to cut down trees and clear the area), noise pollution, etc.
Tidal power : During high-tide event store sea water and then when it is low-tide people can produce electric by operating specific turbines. The disadvantages of it are that not everywhere you can see this activity, some fish species might be affected, you disturb some coastal areas, etc.
Solar power: PV technology depends on sunshine. Under sunny conditions, mild (in terms of wind) conditions and less dusty (particulate matter) circumstances, photovoltaics can provide electricity. You need free land to build PV arrays. Some people argue that some birds and other avians are negatively affected by such structures.
Hydroelectric (dams): Water is cycled in nature. When you build a dam on suitable places on a river, you can store water and produce electricity by operating turbines. There are some disadvantages of such structures. First, stagnant water bodies do not oxygenate (aerate) easily compared to that in streams (rivers). Therefore, they are delicate to pollution. Moreover, some migrating fish species could not move towards upstream. They are badly affected. Finally, such large dams slow down the rotational velocity of the earth.
There are many issues related to renewable energy indeed. I was warned that I have provided a long answer. So far, that is it.
The process of photosynthesis removes Carbon dioxide from the atmosphere and turns the Carbon into Carbohydrates such as sugar starches, and cellulose.
The process of photosynthesis uses Carbon Dioxide as a reactant removing the Carbon Dioxide from the atmosphere. The reduction of Carbon Dioxide from the atmosphere helps to reduce global warming.
During the Mesozoic Era there were high levels of Carbon Dioxide that resulted in high levels of photosynthesis. The era of high carbon dioxide is also known as the Carboniferous Era. The High levels of Carbon Dioxide created large amounts of plant growth that created the coal deposits.
High levels of photosynthesis take large amounts of Carbon Dioxide out of the atmosphere to create sugars and starches used for plant growth.
Tropical forests are widely considered to have the greatest species diversity of the terrestrial biomes and the tundra biome has the least.
As temperature and precipitation decrease, biodiversity generally decreases.
High species diversity :
Tropical forests are widely considered to have the greatest species diversity of the terrestrial biomes but diversity is also high in the temperate deciduous biome and
Low species diversity :
The tundra biome has the least biodiversity, but the northern coniferous biome also has low species diversity. Generally speaking, desert biomes have low species diversity, but pockets of localized high biodiversity do exist. You can read more about exceptions [here] (http://www.conservationmagazine.org/2015/03/deserts-teem-with-biodiversity-if-you-know-where-to-look/) and here.
You can read more about diversity in different terrestrial biomes here.
You can find global biodiversity maps for amphibians, mammals, and birds here. The map below is of amphibian species diversity.
Use these controls to find questions to answer | <urn:uuid:f5abe5d8-9f4e-4b18-8baa-63b85bbcfcdb> | 3.03125 | 1,292 | Q&A Forum | Science & Tech. | 38.697689 | 95,623,283 |
North-south asymmetry in small and large sunspot group activity and violation of even-odd solar cycle rule
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According to Gnevyshev-Ohl (G-O) rule an odd-numbered cycle is stronger than its preceding even-numbered cycle. In the modern time the cycle pair (22, 23) violated this rule. By using the combined Greenwich Photoheliographic Results (GPR) and Solar Optical Observing Network (SOON) sunspot group data during the period 1874–2015, and Debrecen Photoheliographic Data (DPD) of sunspot groups during the period 1974–2015, here we have found that the solar cycle pair (22, 23) violated the G-O rule because, besides during cycle 23 a large deficiency of small sunspot groups in both the northern and the southern hemispheres, during cycle 22 a large abundance of small sunspot groups in the southern hemisphere. In the case of large and small sunspot groups the cycle pair (22, 23) violated the G-O rule in the northern and southern hemispheres, respectively, suggesting the north-south asymmetry in solar activity has a significant contribution in the violation of G-O rule. The amplitude of solar cycle 24 is smaller than that of solar cycle 23. However, Coronal Mass Ejections (CMEs) rate in the rising phases of the cycles 23 and 24 are almost same (even slightly large in cycle 24). From both the SOON and the DPD sunspot group data here we have also found that on the average the ratio of the number (counts) of large sunspot groups to the number of small sunspot groups is larger in the rising phase of cycle 24 than that in the corresponding phase of cycle 23. We suggest this could be a potential reason for the aforesaid discrepancy in the CME rates during the rising phases of cycles 23 and 24. These results have significant implication on solar cycle mechanism.
KeywordsSun: dynamo Sun: surface magnetism Sun: activity Sun: sunspots
The author thanks the anonymous referee for useful comments and suggestions.
- Gnevyshev, M.N., Ohl, A.I.: Astron. Ž. 25, 18 (1948) Google Scholar | <urn:uuid:a590c408-af81-4614-befc-57703d598c31> | 2.875 | 473 | Academic Writing | Science & Tech. | 49.991669 | 95,623,292 |
A comparison of crystals of calcium sulfate dihydrate grown in two different gel media, sodium silicate gel and bentonite clay gel, shows that the two media affect crystal habit and surface topography differently. Those crystals grown in silica gel at 40°C and pH 7.5 consist of elongated prisms, exhibit relatively smooth crystal faces, and are often twinned. Crystals grown in bentonite gel at the same temperature and similar pH tend to be tabular, exhibit a wide variety of kinks, steps, and pits on their surfaces, and are never twinned under our experimental conditions. A comparison of the bentonite-grown crystals with those commonly found in nature shows that bentonite resembles natural sediments in its effects on growth habit of gypsum. © 1974.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:01deb441-e40d-4844-8173-2c34d2c886a9> | 2.984375 | 180 | Academic Writing | Science & Tech. | 30.553927 | 95,623,295 |
New technology developed by bioengineers at the University of California, Berkeley, promises to make a workhorse lab tool cheaper, more portable and many times faster by accelerating the heating and cooling of genetic samples with the switch of a light.
This turbocharged thermal cycling, described in a paper to be published Friday, July 31, in the journal Light: Science & Application, greatly expands the clinical and research applications of the polymerase chain reaction (PCR) test, with results coming in minutes instead of an hour or more.
This is an artist's rendering of photonic PCR on a chip using light to rapidly heat and cool electrons at the surface of a thin film of gold. This method yields gene amplification results in mere minutes, and promises to transform point-of-care diagnostics in fields as diverse as medicine, food security and evolutionary biology.
Image courtesy of Luke Lee's BioPOETS lab
The PCR test, which amplifies a single copy of a DNA sequence to produce thousands to millions of copies, has become vital in genomics applications, ranging from cloning research to forensic analysis to paternity tests. PCR is used in the early diagnosis of hereditary and infectious diseases, and for analysis of ancient DNA samples of mummies and mammoths.
The huge impact of the PCR test in modern science was recognized in 1993 with a Nobel Prize in Chemistry for its inventors, Kary Mullis and Michael Smith.
Using light-emitting diodes, or LEDs, the UC Berkeley researchers were able to heat electrons at the interface of thin films of gold and a DNA solution. They clocked the speed of heating the solution at around 55 degrees Fahrenheit per second. The rate of cooling was equally impressive, coming in at about 43.9 degrees per second.
"PCR is powerful, and it is widely used in many fields, but existing PCR systems are relatively slow," said study senior author Luke Lee, a professor of bioengineering. "It is usually done in a lab because the conventional heater used for this test requires a lot of power and is expensive. Because it takes an hour or longer to complete each test, it is not practical for use for point-of-care diagnostics. Our system can generate results within minutes."
The slowdown in conventional PCR tests comes from the time it takes to heat and cool the DNA solution. The PCR test requires repeated temperature changes - an average of 30 thermal cycles at three different temperatures - to amplify the genetic sequence, a process that involves breaking up the double-stranded DNA and binding the single strand with a matching primer. With each heating-cooling cycle, the amount of the DNA sample is doubled.
To pick up the pace of this thermal cycling, Lee and his team of researchers took advantage of plasmonics, or the interaction between light and free electrons on a metal's surface. When exposed to light, the free electrons get excited and begin to oscillate, generating heat. Once the light is off, the oscillations and the heating stop.
Gold, it turns out, is a popular metal for this plasmonic photothermal heating because it is so efficient at absorbing light. It has the added benefit of being inert to biological systems, so it can be used in biomedical applications.
For their experiments, the researchers used thin films of gold that were 120 nanometers thick, or about the width of a rabies virus. The gold was deposited onto a plastic chip with microfluidic wells to hold the PCR mixture with the DNA sample.
The light source was an array of off-the-shelf LEDs positioned beneath the PCR wells. The peak wavelength of the blue LED light was 450 nanometers, tuned to get the most efficient light-to-heat conversion.
The researchers were able to cycle from 131 degrees to 203 degrees Fahrenheit 30 times in less than five minutes.
They tested the ability of the photonic PCR system to amplify a sample of DNA, and found that the results compared well with conventional PCR tests.
"This photonic PCR system is fast, sensitive and low-cost," said Lee, who is also co-director of the Berkeley Sensor and Actuator Center. "It can be integrated into an ultrafast genomic diagnostic chip, which we are developing for practical use in the field. Because this technology yields point-of-care results, we can use this in a wide range of settings, from rural Africa to a hospital ER."
The study lead author is Jun Ho Son, a UC Berkeley postdoctoral researcher in Lee's lab.
The Bill and Melinda Gates Foundation and the National Research Foundation of Korea helped support this research.
Sarah Yang | EurekAlert!
Lateral gene transfer enables chemical protection of beetles against antagonistic fungi
18.07.2018 | Johannes Gutenberg-Universität Mainz
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:806cafa2-91c5-489b-b109-dd9171456e4c> | 3.59375 | 1,619 | Content Listing | Science & Tech. | 43.909288 | 95,623,320 |
THE HIDDEN SCENTS OF SUMMER
Using pheromones to attract a mate.
A number of other British butterflies have similar sex scales. In some species they are woven into the patchwork of scales that cover the entire surface of the wing, while in others, like the silver-washed fritillary, there are very obvious concentrated androconial patches. Look out for the dark smudges on the forewing of the male gatekeeper, the thick bold lines on the wings of members of the skipper family ( pictured), and the dark suffusion on the wings of the male grayling – another butterfly famous for its dance. | <urn:uuid:c9ff6e3d-9f19-4a5f-a32b-479b800f366d> | 2.71875 | 133 | Truncated | Science & Tech. | 35.586477 | 95,623,338 |
The surface wave magnitude () scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements in Rayleigh surface waves that travel primarily along the uppermost layers of the Earth. It is currently used in People's Republic of China as a national standard (GB 17740-1999) for categorising earthquakes.
Surface wave magnitude was initially developed in 1950s by the same researchers who developed the local magnitude scale ML in order to improve resolution on larger earthquakes:
The successful development of the local-magnitude scale encouraged Gutenberg and Richter to develop magnitude scales based on teleseismic observations of earthquakes. Two scales were developed, one based on surface waves, , and one on body waves, .
Surface waves with a period near 20 s generally produce the largest amplitudes on a standard long-period seismograph, and so the amplitude of these waves is used to determine , using an equation similar to that used for .
— William L. Ellsworth, The San Andreas Fault System, California (USGS Professional Paper 1515), 1990–1991
Recorded magnitudes of earthquakes during that time, commonly attributed to Richter, could be either or .
The formula to calculate surface wave magnitude is:
where A is the maximum particle displacement in surface waves (vector sum of the two horizontal displacements) in μm, T is the corresponding period in s, Δ is the epicentral distance in °, and
According to GB 17740-1999, the two horizontal displacements must be measured at the same time or within 1/8 of a period; if the two displacements have different periods, weighed sum must be used:
where AN is the north-south displacement in μm, AE is the east-west displacement in μm, TN is the period corresponding to AN in s, and TE is the period corresponding to AE in s.
Vladimír Tobyáš and Reinhard Mittag proposed to relate surface wave magnitude to local magnitude scale ML, using
Other formulas include three revised formulae proposed by CHEN Junjie et al.:
Notes and references
- ^ a b XU Shaokui, LU Yuanzhong, GUO Lucan, CHEN Shanpei, XU Zhonghuai, XIAO Chengye, FENG Yijun (许绍燮、陆远忠、郭履灿、陈培善、许忠淮、肖承邺、冯义钧) (1999-04-26). "Specifications on Seismic Magnitudes (地震震级的规定)" (in Chinese). General Administration of Quality Supervision, Inspection, and Quarantine of P.R.C. Retrieved 2008-09-14.
- ^ William L. Ellsworth (1991). "SURFACE-WAVE MAGNITUDE (MS) AND BODY-WAVE MAGNITUDE (mb)". USGS. Retrieved 2008-09-14.
- ^ Vladimír Tobyáš and Reinhard Mittag (1991-02-06). "Local magnitude, surface wave magnitude and seismic energy". Studia Geophysica et Geodaetica. Retrieved 2008-09-14.
- ^ CHEN Junjie, CHI Tianfeng, WANG Junliang, CHI Zhencai (陈俊杰, 迟天峰, 王军亮, 迟振才) (2002-01-01). "Study of Surface Wave Magnitude in China (中国面波震级研究)" (in Chinese). Journal of Seismological Research (《地震研究》). Retrieved 2008-09-14. | <urn:uuid:c4e02fd5-4d5b-4050-9b00-c384396c0574> | 3.953125 | 848 | Knowledge Article | Science & Tech. | 45.995435 | 95,623,343 |
- Open Access
Rolling Pampas agroecosystem: which landscape attributes are relevant for determining bird distributions?
© Weyland et al.; licensee Springer. 2014
Received: 1 August 2013
Accepted: 6 December 2013
Published: 26 March 2014
Agricultural intensification is among the main factors affecting biodiversity. The Rolling Pampas of Argentina have undergone through a process of landscape transformation and agricultural intensification that altered avian diversity patterns. Grassland area loss is argued to be the main reason for grassland bird species declines, but there is a lack of studies that compare cropland vs. pastures including other landscape features as determinants of species richness and distribution. Also, it is needed to understand how these relations are modified at different spatial scales. In this study, we explored how species are associated to different landscape attributes and elements like land use, roadside vegetation, trees, homesteads, and water bodies. Our aim was to explore how bird species are associated to the new elements of the Pampas agroecosystem at different spatial scales to reveal which are important for avian management.
We ran field surveys covering a range of land use and landscape complexity, defined by the variety of component features. We performed canonical correspondence and diversity partition analyses to determine the association of species with land use, landscape complexity, and particular anthropogenic elements. Our results show that land use type is an important driver of bird species distributions, but it is also controlled by the presence of trees, houses, and water bodies that provide nesting and food resources. Simple landscapes have higher species turnover rates (beta diversity) than complex ones with similar gamma diversity, demonstrating that the effect of landscape simplification on bird diversity differs across spatial scales, leading to different possible management and conservation strategies.
New approaches are needed to manage agroecosystems for avian conservation. We need to take pragmatic approaches, and in highly disturbed ecosystems, anthropic elements have to be included as constituent parts of the system.
Loss of biodiversity in agroecosystems is a global concern since the last decades (Chapin et al. 2000). Land cover change and landscape simplification as consequences of land use intensification are factors identified as responsible for biodiversity loss (Benton et al. 2003; Tscharntke et al. 2005). Agroecosystems, however, can harbor a noteworthy biodiversity if properly managed (Pimentel et al. 1992). For that reason, we need to develop management plans aiming at obtaining agricultural production and at the same time minimizing its negative effects on biodiversity.
Landscape transformation by agriculturization leads to the creation of novel ecosystems, where new combinations of species and abiotic conditions are set (Hobbs et al. 2006). The Pampas grasslands of Argentina is one of the regions where agriculturization dramatically changed the landscape during the last two centuries (Ghersa and León 2001). This process lead to the reduction of grassland area and the introduction of the common elements of an agroecosystem: a network of roads and their roadsides, urbanization, and alteration of the presence and nature of water bodies (ponds, ditches, etc.). A conspicuous change was caused by the introduction of trees. Trees were introduced by European settlers to provide shade and delimitate the properties. Nowadays, many species have naturalized and invaded roadsides and riversides (Ghersa et al. 2002). In abandoned houses, secondary succession produces small (<5 ha) woodlots with a noticeable tree species richness (Chaneton et al. 2012).
Agriculturization of the Pampas affected biodiversity patterns across taxa (Suárez et al. 2000; Medan et al. 2011). In the case of birds, loss of grassland area is one of the main factors for the decline in species richness and abundance (Filloy and Bellocq 2007; Schrag et al. 2009; Cerezo et al. 2011; Azpiroz et al. 2012). The range of some species, like pampas meadowlark (Sturnella defillipii Bonaparte, 1850), white and black monjita (Xolmis dominicanus Vieillot, 1823), and pipits (Anthus spp. Vieillot, 1818), was reduced leading them to levels of conservation concern or regional extinction (Collar and Wege 1995; Krapovickas and Di Giacomo 1998; Gabelli et al. 2004).
Other attributes and elements of the agroecosystem, such as urbanization, artificial water bodies, and trees, also affected bird diversity, though their influence was less explored. Urbanization, as in other parts of the world, impoverished and homogenized bird fauna (Leveau and Leveau 2005; Faggi et al. 2006; Garaffa et al. 2009). Natural and artificial water bodies provide refuge for many species of birds (Shnack et al. 2000). Tree invasion in roadsides and riversides, on the other hand, negatively affected grassland species, but at the same time favored a group of species that colonized from surrounding regions, like Swainson’s hawk (Buteo swainsoni Bonaparte, 1838), picazuro pigeon (Patagioenas picazuro Temminck, 1813), flickers (Colaptes spp. Vieillot, 1818), and great kiskadee (Pitangus sulphuratus Linnaeus, 1766) (Comparatore et al. 1996; Codesido et al. 2011). Most of these species were already common species with no conservation concern.
Land use type (cropland vs. pasture) has received more attention than the other attributes and elements of the agroecosystem in relation toward its effect on biodiversity of the Pampas. Moreover, studies that evaluate the relative importance of the different landscape attributes to guide management plans for biodiversity conservation are still lacking. Previous studies showed that the landscape complexity rendered by particular configurations of trees, water bodies, and homesteads provides conditions for greater bird diversity, and may be more important than land use type (Weyland et al. 2012). Landscape complexity can not only contribute to species richness but also change the species distribution as the resource supply changes, particularly nesting and food. Furthermore, the effect of landscape complexity on biodiversity may differ across spatial scales (Flohre et al. 2011). Poggio et al. (2010), for example, found that more complex agricultural landscapes did not increase alpha (local) diversity of weeds in fencerows, but it increased gamma (regional) diversity through species turnover (beta diversity). It has been demonstrated for other taxa as well that biodiversity patterns at the local scale do not extrapolate to the regional scale (Gering et al. 2003; Fleishman et al. 2003). This leads to different patterns of species richness and composition depending upon the scale of landscape simplification considered. For this reason, finding how landscape attributes at different spatial scales affect bird distributions is important when discussing management plans to favor biodiversity (Tscharntke et al. 2005).
In this study, we explored how bird species are associated to the new attributes of the Rolling Pampas agroecosystem (agricultural land use, trees, homesteads) at local and landscape scales to reveal which are important for avian conservation and management. We hypothesize that (1) bird species distributions will be determined by the landscape elements that provide food and nesting resources, and (2) species assemblages will vary with landscape complexity depending upon the spatial scale.
Landscape classification and data collection
We characterized agricultural landscape at two spatial scales: facet and local. A facet is a combination of different ecotopes (being these the smaller holistic unit of land) (Zonneveld 1989). For the facet scale, we divided the study area with a grid of 8 × 8 km cells (hereafter, facets) (n = 364). In our study region, a 64-km2 area approximates the facet scale, comprising several farms and different land use type units (ecotopes in our case). We measured landscape attributes in each facet using supervised classified Landsat TM images of two cropping years (2006 and 2008, Figure 1c). This classification identifies seven land use types: water, lowlands, pastures, maize, soybean, wheat, and urban. ‘Lowlands’ and ‘pastures’ are differentiated by their topographic position in the landscape. Lowlands are temporally flooded natural grasslands that are found alongside rivers and streams in low positions. Pastures are sown pastures or semi-natural grasslands in higher positions. We randomly selected 39 facets in which we placed sampling points 1 km apart to ensure independence and avoid double counting (Ralph et al. 1995) (3 to 8 points per facet, n = 237) along secondary dirt roads (Figure 1b). In the facets selected, we also mapped tree lines and woodlots using Google Earth® images, because the supervised classification of Landsat images did not identify woody vegetation as a distinct land cover type.
Each point was visited once during the bird reproductive season of two consecutive years (2007 and 2008) to carry out field surveys. Bird surveys were carried out using the point count method (Ralph et al. 1995). Surveys were done in the first hours after sunrise (6:00 to 10:30 a.m.) in good weather conditions, and all birds seen or heard during 5 min in the 350-m radius were counted. This radius was determined based on the field observer’s ability to detect individuals and identify the species (G. Rocha, personal communication). At each point, we also measured landscape variables in the 350-m radius (hereafter, local scale) by visual inspection: cover area for each land use type, roadside vegetation condition (spontaneous, grazed, sprayed, cultivated, stubble, ploughed, ditch), and presence of trees (woodlots, tree lines, scattered trees), water bodies, and inhabited houses.
To determine the association of bird species to landscape attributes, we ran canonical correspondence analyses (CCA). We ran CCAs with variables at local and facet scales using presence/absence data of birds. We removed species that were detected in two or less sites, as the distribution of rare species in the environmental gradient cannot be adequately estimated with CCA (Batista 1991). That way, we kept 77 species for the analyses (Additional file 1: Table S1). The patterns for the rest of the species are discussed not statistically in the corresponding section.
Interset correlations of variables with axes of CCAs at local and facet scales
Trees (woodlots and tree lines)a
Bare soil cover
Tree lines lengtha
Number of tree linesa
Number of woodlandsa
where A is observed abundance in the sampling point.
We performed Monte Carlo randomization tests with 100 runs to evaluate the statistical significance of all ordinations.
We performed a diversity partition analysis to determine the species turnover among sites of different landscape complexities (used here indistinctly from heterogeneity). We built a fuzzy logic model to calculate a complexity index based on a combination of six attributes and elements: cover type richness, roadside vegetation complexity, trees as woodlots and tree lines, and presence of scattered trees, houses, and water bodies. The complexity of the landscape increases as more different elements and cover types are present. Using expert knowledge and adjusting the model with empirical data on bird species richness, we combined the six input variables through logic rules to get a complexity index ranging from 0 to 1 (see more details in Weyland et al. 2012). We then divided this local scale landscape complexity gradient in ten levels. The levels of highest landscape complexity had too few points, so we pooled them in a single level (0.8 to 1). We calculated gamma and mean alpha bird diversities for the sampling points in each complexity level. Gamma diversity was calculated as the total number of species of all the points in a given level of landscape complexity. As the number of points was unbalanced, we used a non-parametric species richness estimator (Chao2; Chao and Shen 2004) using SPADE software (Chao and Shen 2010). Beta diversity (species turnover) was calculated as the difference between gamma and mean alpha diversities in each complexity level (Lande 1996). We regressed gamma and mean alpha diversities against landscape complexity to determine whether there are differences in species turnover rates in landscapes with different complexities.
We ran a multi-response permutation procedure (MRPP) and indicator species analysis to determine whether there are differences in the composition of species assemblages in each landscape complexity level and which species determine these differences. For the diversity partition and indicator species analyses, we used all species identified.
As points sampled in two seasons are not independent, we pooled data of both survey years. We summed up bird presence/absence data, and we averaged environmental variables. Thus, the total point used in all analyses was 237. This data pooling was done for CCA, but not for indicator species and biodiversity partition analyses for which the data of each year was studied separately to avoid spurious relations between bird diversity and landscape complexity.
We recorded a total of 107 bird species, which represents approximately 40% of cited species for the region (Additional file 1: Table S1) (Narosky and DiGiacomo 1993). Only one, Polystictus pectoralis (Vieillot, 1817), a grassland species, is considered of conservation concern due to habitat loss (Collar and Wege 1995). It was found in very few sites and was not included for the CCA analyses.
Interset correlations of variables with axes of CCAs at local scale, considering trophic group abundance
Trees (woodlots and tree lines)
Bare soil cover
Our results show that anthropic elements of the landscape as well as land use are important for determining bird distributions and species richness. Furthermore, spatial scale alters the outcome of different landscape configurations on bird assemblage composition, regarding species identity as well as their feeding habits. These are important results to consider when designing management plans as we will discuss in this section.
In the Rolling Pampas agroecosystems, land use type is important for determining bird species distributions, but at the local scale, trees, homesteads, water bodies, and wetland vegetation are of equal importance. Based on our results and those of the previous studies, we conclude that the presence of these elements increases the landscape’s capacity for sustaining higher species richness levels (Shnack et al. 2000; Codesido and Bilenca 2011; Weyland et al. 2012), but it is also evident that bird species populations are distributed according to which elements are present. Trees and homesteads favored a group of exotic species to the Pampas, which migrated from the Espinal xerophytic forests and the Delta forests surrounding the region and are now commonly found, such as Mimus saturninus (Lichtenstein, 1823), P. sulphuratus, and Turdus rufiventris Vieillot, 1818. There was an expected association of grassland bird species to pasture cover in the landscape due to its physiognomic similarity to natural grasslands, but a large group of these species was related to annual crop cover (e.g., Nothura maculosa (Temminck, 1815), Rhynchotus rufescens (Temminck, 1815), Athene cunicularia (Molina, 1782), Ammodramus humeralis (Bosc, 1792), and Sturnella superciliaris (Bonaparte, 1851)). Apparently, annual crops are also sustaining some grassland species. It is possible that, under the current no-tillage annual cropping systems in the study area, wheat may offer environmental conditions that are more suitable for grassland birds than pastures because these are usually heavily grazed and disturbed by cattle, increasing the risk of predation and trampling (Cozzani and Zalba 2009). In fact, studies in the region demonstrate that only tall grass pastures support higher species richness, particularly of grassland species (Isacch and Martínez 2001; Filloy and Bellocq 2007; Codesido et al. 2011). Therefore, conditions generated by management of pastures seem to be more important than land use type per se for determining species distributions.
The provision of nesting resources seems to be an important factor for determining species distributions in the study area. In the Pampas, recent studies show that nest site availability is one of the main constraints that may also explain the rarity of some species inhabiting the region (Codesido et al. 2012). The extent and intensity of human alteration of the Rolling Pampas grasslands caused that only species with broad habitat requirements prevail. Indeed, the species that were dropped from our analyses for their low constancy values are those with more specific habitat requirements (like wetland or woodland specialists). Some of them are species of the Espinal and Delta ecoregions, near the limits of their distribution area (like Geothlypis aequinoctialis and Myiodynastes maculatus). These species not only may have low representation in the avifauna but also may have been subsampled in our surveys. Among the less represented species, we also found some grassland specialists (e.g., Embernagra platensis (Gmelin, 1789), Circus buffoni (Gmelin, 1788), Anthus correndera Vieillot, 1818, P. pectoralis, and Cistothorus platensis (Latham, 1790)), showing that these species where in fact the most affected by landscape transformation in the Pampas. In fact, we could not detect many other grassland species of conservation concern like S. defillipii or X. dominicanus (Vieillot, 1823), most probably due to range contraction and local extinctions. Most of the other species identified and included in our analyses are considered habitat generalists (Codesido et al. 20112012). Their association with environmental variables is generally weak, and this may explain why ordinations, although significant, explain a very low proportion of total variance.
It is argued that agricultural intensification may also deplete bird food supplies, thus determining the distribution of species in the landscape (Weibull and Östman 2003; Codesido et al. 2008; Gavier-Pizarro et al. 2012). Also, because feeding habit is one of the most important ecosystem functions of birds in productive systems (Sekercioglu et al. 2004), studies usually evaluate how landscape characteristics influence the distribution of species according to this trait (see, e.g., Gavier-Pizarro et al. 2012; Apellaniz et al. 2012). Our results show that landscape attributes are important for determining feeding group distributions only at the local scale. Insectivorous and carnivorous species were associated to pastures, water bodies, and soybean crops. Cattle and dung piles attract insects thus favoring insectivorous species. Soybean crops were recently sown when we carried out our surveys. The low vegetation cover may facilitate prey detection for carnivorous species (Leveau and Leveau 2002; Whittingham and Devereux 2008).
The information on how landscape attributes determine the distribution of bird species according to their ecological traits suggests directions to manage species abundance in the region. Not only land use should be considered for management but other landscape elements as well. Our results show that at the local scale, trees are among the most important elements for determining bird species distributions. Studies in the region demonstrate that some of the species favored are crop pests (like Myiopsitta monachus (Boddaert, 1783) or P. picazuro) (Codesido and Bilenca 2011), although our results show that these species are only slightly associated to trees. Differences in the structure or tree species composition of woodlands could explain the differences in their effect on bird distribution. New studies should evaluate what attributes of tree vegetation could be managed to locally exclude crop pest species while conserving the rest.
Other landscape features like water bodies or naturally vegetated roadsides could be managed as well to provide nesting resources to marsh and grassland species, respectively. Our study revealed no effect of roadside vegetation on species distributions, though many other studies demonstrated that they could be suitable places in agroecosystems both for nesting and foraging (Leveau and Leveau 2004; Vickery et al. 2009; Di Giácomo and López de Casenave 2010). We found roadside vegetation complexity was important only for granivorous species. In Pampas agroecosystems, where most grasslands were removed, this landscape feature may become an important source of weed seeds for birds. Roadsides constitute the last grassland relicts, and they are being removed for cropping (Burkart et al. 2011); thus, there is an urgent need to put into practice protection policies of these environments.
The diversity partition analysis showed that simple landscapes have similar gamma diversity as complex landscapes, but higher beta diversity. This means that, in Rolling Pampas agroecosystems, landscape simplification reduces species richness at local scales, but the sum of all types of simple landscapes covers all environmental conditions, thus sustaining the same number and identity of species as complex landscapes at broad spatial scale. The indicator species analysis showed that only a few of the remaining species in the Rolling Pampas are dependent on complex landscapes, while most of them need only the presence of specific landscape elements to cover their needs. Even the indicator species are somehow generalists as revealed by their low indicator values. These results were contrary to our expectations, but they agree with studies evaluating agricultural intensification in European agroecosystems (Flohre et al. 2011). A few elements may have a strong influence on simple landscapes functional differentiation, as each element provides resources for a limited group of species while excluding the rest. For example, as defined in this study, a simple landscape may have a pond but not trees. Thus, it sustains wetland bird species, but not species that nest in trees. This landscape may be complemented by another without water bodies but with trees. As a result, the complete set of species is maintained regionally though locally excluded.
These results have important implications for the interpretation of processes in agroecosystems and management plans. It is imperative to make explicit the spatial scale at which landscape simplification is evaluated. As our results suggest, simplification of agricultural landscapes at local scales may not have a severe impact on bird assemblages as long as the landscape still sustains a large pool of species enabling bird assembling through mass effects, i.e., the occurrence of species outside their core habitats (Schmida and Wilson 1985). That way, species conservation at regional scales is ensured even when local exclusions may occur. Even though, the accretion of local species richness could be hindered by at least two threats: (1) the spatial configuration does not allow site colonization of species from the regional pool, thus population persistence is not ensured, and (2) landscape simplification leads to the same type of landscapes at the local and, in turn, at the regional scale. This unwanted outcome may actually be the case in the Pampas agroecosystem as there is a trend towards agricultural intensification with soybean monoculture (Aizen et al. 2009; Vega et al. 2009). It is nonetheless worth noting that it would be equally detrimental if simplification was driven by the expansion of any other crop monoculture or the removal of landscape elements that provide for functional heterogeneity in the current Rolling Pampas agroecosystem. It is of fundamental importance, then, to maintain and generate landscape heterogeneity for providing suitable conditions for biodiversity.
Anthropic transformation of ecosystems generates new environmental conditions where the distribution and abundance of biotic elements are altered (Hobbs et al. 2006). In these cases, the management of landscapes to return them to original conditions may not be possible (Seastedt et al. 2008). For this reason, the dichotomy between natural and anthropic landscapes is not useful for conservation and management purposes. Rather, we need to incorporate all features present in the landscape, particularly those that are manageable, whether or not they are of natural or anthropic origin. This may apply to different agroecosystems in the world, but in the case of the Rolling Pampa, this situation is quite evident. In the present, the potential vegetation of the Pampas is a grassland dominated by exotic species, or even a woodland (Burkart et al. 2005; Tognetti et al. 2010). Although trees are exotic, their complete removal is highly improbable due to the cultural attachment to this type of vegetation. The same applies to other anthropic features of the landscape like human settlements and crops. Still, with few exceptions, most studies in the Pampas focus on land use type disregarding other landscape attributes and features that may be of equal importance in determining biodiversity. We do not advocate for planting trees in the Pampas or otherwise promote anthropic landscape change. We argue that conservation efforts need to take a pragmatic approach, and in highly disturbed ecosystems, anthropic elements have to be included as constituent parts of the system. As long as this necessity is incorporated in research and management, more effective biodiversity conservation plans will be developed.
FW was financed by a fellowship of the CONICET and the FONCYT. The ECOS-SECYT A07B04 grant permitted the exchanges between France and Argentina. The final stay in France of FW was made possible through a grant from the French Embassy and the Ministry of Education of Argentina. G. Rocha and P. Moreyra assisted in bird field surveys. Satellite images where provided by the Laboratory of Regional Analysis and Teledetection (LART-FAUBA). S Perelman and A Cerezo gave useful statistical advices.
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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. | <urn:uuid:6fae1d4e-1e67-4457-97c4-d663e75785df> | 3.46875 | 10,022 | Academic Writing | Science & Tech. | 41.645144 | 95,623,352 |
To determine whether genetic constraints on adaptive evolution were operating in a laboratory population of a flour beetle, Tribolium castaneum, we first estimated the direct selection acting on each of several body size traits. Strong selection in males for an increase in pupal weight and a decrease in the ratio of adult to pupal weight occurred. In addition, a non-significant trend for a decrease in adult width was found. No significant selection on females was detected, although there were trends toward an increase in pupal weight and a decrease in adult width. These estimates were then combined with estimates of the genetic variances and covariances of the traits to predict the multivariate response to selection, that is, the evolutionary change in the traits across one generation. These projections showed only a small predicted change in male pupal weight in spite of the strong selection on pupal weight, and a relatively large predicted increase in width in spite of the possible negative direct selection on this trait. Both of these results were due in part to the positive genetic covariance between pupal weight and width, and they therefore suggest the possibility of genetic constraints on adaptive evolution of these traits.
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Introductory Remarks on Remote Sensing
The increased potentialities of the remote sensing techniques—in particular the new methods outside the visible part of the electromagnetic spectrum—and the growing experience in a variety of civil applications during the last decade demonstrated new ways to the solutions of many problems of the natural sciences and opened a broader view on the relations between various large scale natural phenomena. But the potential utilization of the remote sensing technology to many public services and managements, which is not yet fully realized, may be expected to bring even more important achievements during the next decades by the qualitative and quantitative improvement of the remotely sensed information and due to the increased effectiveness of their procurement. This can be achieved by the possibilities of quick, small to medium scale (e.g. ground-based or airborne) but detailed, multi-sensor observation of special features within small areas or by less detailed, large to global scale (space borne) but repetitive and synoptic surveying.
KeywordsRemote Sensing Synthetic Aperture Radar Microwave Radiometer Introductory Remark Synoptic Surveying
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The results of a new study suggest that rising temperatures are leaving a mark on the world. According to a report published in the current issue of the journal Science, the first flowering of plants in Britain has changed by as much as 55 days over the past few decades in response to warmer weather. The results, the scientists say, are the "strongest biological signal yet of climatic change."
Alastair Fitter of the University of York and his father, naturalist Richard Fitter, analyzed 47 years of data that the senior Fitter collected from a single location in England. They determined that, on average, the first flowering for 385 plant species in the past decade occurred 4.5 days earlier than it did between 1954 and 1990. For 16 percent of the species, the date of the first bloom advanced by 15 days and one particularly affected plant, the white dead nettle, bloomed 55 days earlier than it had three decades ago. Since the 1960s, the mean temperatures for January, February and March--important months for spring flowering plants--have increased by 1.8 degrees Fahrenheit. If global temperatures continue to increase (some predictions for future warming are more than six degrees Fahrenheit), more dramatic changes could lie ahead.
The earlier bloom affects more than just the date when a garden will burst into color, the scientists report. Because some species are changing but others are not, plants may be forced into competition with unfamiliar foes. Moreover, the development of new hybrid species could be curtailed. The violet species Viola odorata and Viola hirta, for example, used to flower simultaneously. But because the former now flowers a month sooner than the latter, they are less likely to hybridize in the future. The authors conclude that the changes they have recorded, together with alterations to species’ geographical range that often accompany climate change, will have "profound ecosystem and evolutionary consequences."
Sarah Graham | Scientific American
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NMR spectra — especially 2D spectra — contain a wealth of information. It is important, therefore, to be certain of the relative value of each single piece of information. There are “soft” clues or hints that can only be evaluated through experience and a knowledge of analogous findings, i.e., on the basic of empirical evidence. A typical example is the evaluation of the chemical shifts (δ) of an atom by taking into account the nature of its neighboring atoms. Such hints should, whenever possible, be verified by experimental results. Information from characteristic S ranges are more reliable. For instance, it is clear that a 13C signal with δ = 210 corresponds to a carbonyl carbon and that this carbon cannot be a member of a carboxyl function. Many 1H, 1H and 13C, 1H coupling constants belong to the same category.
KeywordsCross Peak Cosy Spectrum Signal Splitting Signal Assignment Methine Carbon
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Ordered Join Geometries
In this chapter, as in the previous one, a new postulate is introduced. The postulate is equivalent to the familiar Euclidean property of linear order: If three distinct points are collinear, then one of the three is between the other two. Join geometries which satisfy the new postulate are called ordered join geometries or ordered geometries. Ordered geometries are exchange geometries studied in the last chapter, but the results there will not be used in the present investigation. A flood of results is produced. First come formulas for lines, rays and segments, expressing how they are divided into subrays and subsegments by their points. Next come many properties of polytopes familiar in Euclidean geometry and easily accessible to intuition. Then follow properties of convex sets, less familiar in classical geometry but no less important, the theorems of Radon, Helly and Caratheodory and related results. These flow from a sharpened expansion formula for the linear hull of a finite set mediated by a new type of dependence of points. This new type of dependence is defined in terms of the convex hull operation and is called convex dependence. It implies linear dependence in any join geometry and is equivalent to linear dependence in an ordered geometry. Finally, separation of linear spaces by linear subspaces is studied, and results familiar in Euclidean geometry are obtained for ordered geometries.
KeywordsLinear Space Distinct Point Common Point Euclidean Geometry Cardinal Number
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posted by Amy
Consider the reaction in aqueous solution:
6 HCl + 2 KMnO4 + 5 H2O2 ---> 5 O2 + 2 MnCl2 + 2 KCl + 8 H2O
1.) Write the total ionic equation.
2.) Write the net ionic equation.
3.) For each species (molecule or ion) in the net ionic equation, assign oxidation numbers to H, O, and Mn.
Instead of making this a question on a year of chemistry, tell us what you don't understand about this. It's just too long to type a bunch of stuff you already know. | <urn:uuid:f53c563c-b770-4949-a500-e8ba466b8dd4> | 3.78125 | 137 | Q&A Forum | Science & Tech. | 89.080204 | 95,623,423 |
Answers from the Whooping Crane Expert
Included in this Message:
Answers from the Whooping Crane Expert
Special thanks to ornithologist Laura Erickson for providing her time and expertise in responding to your questions below.
Q: Where in the continental US was the last place that the whooping cranes were known to nest?
A: They were last known to breed in the US in Louisiana, around White Lake in the southwestern part of the state. These birds were non-migratory. That Louisiana population was reduced from 13 to 6 birds following a hurricane in August 1940, and the last individual was taken into captivity in March 1950.
Q: There were only five cranes that hatched in the year 2001. What if they don't find a whooping crane mate in their Eastern flock, but instead try to mate with the more abundant Sandhill Cranes?
A: Like humans, Whooping Cranes don’t have to find a mate that is exactly the same age. But, also like humans, Whooping Cranes are only willing and able to mate with their own species. In the case of Whooping Cranes, they recognize their species by how their parents looked, especially keying in on their parents’ faces. These captive birds recognize the Whooping Crane “puppets” as their parents, and great care went into making the faces look EXACTLY like real Whooping Cranes.
In the 1970s, in one experiment, Whooping Crane eggs were hatched and reared by Sandhill Cranes. The Sandhill Cranes made fine parents, but these baby Whooping Cranes, when grown, ignored each other and only wanted to mate with Sandhill Cranes. Of course, every Sandhill Crane had also been raised by Sandhill Cranes, so they wanted nothing to do with Whoopers. That’s why that program was completely unsuccessful.
From: Deephaven, Minnesota
A: The “ultra babies” follow what they think are their parents—the puppets. When the puppets are on board the trike, the babies follow them.
Q: When will the four year old cranes lay eggs?
A: Two pairs of these cranes laid their first egg this year! Unfortunately, being very inexperienced, they accidentally broke the eggs. That happens to completely wild Whooping Cranes, too. They have their greatest breeding success after a few years of practice.
A: The very first ultralight-led migration of birds was by William Lishman, assisted by naturalist William Carrick, using an ultralight aircraft to lead a flock of 12 Canada geese on local flights. Even from the start this wasn't a single person effort! They recognized the potential for this technique to work for cranes, but as with most hugely important projects, it took a whole team of experts, from scientists and veterinarians who understood how to rear baby Whooping Cranes to the pilots and support team who work so hard every single day far away from their homes to make this project work year after year after year, to the people who help raise the money and get public support, like the wonderful Heather Ray (who shares so much Whooping Crane information with Journey North readers!) to make this kind of project a success. WCEP, the Whooping Crane Eastern Partnership, is truly a team, and would be weaker without all the team members supporting each other and working together.
Q: How much do the cranes eat before they migrate?
A: Before they migrate, the “Ultra-Cranes” are still growing and building their muscles, and eating as much as they can. This is also true of wild first-year Whooping Cranes. The simplest answer to your question is, as much as they can find!
Q: Can the cranes swim in deep water?
A: Babies could swim in deep water if they had to for short distances. Swimming is most common in chicks and involves floating and leg-paddling. But far away from shore, they could get waterlogged or chilled, and would have no way of getting out again. Fortunately, because they stay so close to their parents, they do not find themselves in that awkward situation!
Adult Whooping Cranes are not able to dive, and can not take off from deep water, so they stick to water not much deeper than their legs are long.
Annika, Danielle, and Caitie:
A: That’s a good question—will you remember to look back
in 8 years to see if I am right? Right now the Wood Buffalo/ Aransas
flock has 215 birds. I’m hoping that flock is at least up to 250
by 2013, but it’s a little scary because people are going to have
to start conserving water to ensure that the blue crab populations in
Texas stay healthy. The Florida non-migratory flock has 66 birds now,
including 5 babies. I hope they’re up to at least 80 birds by 2013,
but again, the birds there have problems with bobcats and bobcats might
be getting pretty good at catching them. The WCEP flock is up to 45 this
year, including 13 young birds.
Dominick and Charlie
A: When fully fueled, these ultralights can fly between 200 and 300 miles. That’s much farther than a Whooping Crane can fly using the flapping flight they need during ultralight migration. Cranes can go farther when they can ride on thermals, which is why the spring return migration is so much faster than the first fall migration.
A: Before the cranes take off in the morning, everyone needs to know where they’re going to stop that night. There needs to be enough space for a pen, and the team needs to know that any people around will stay away, not letting the cranes hear human voices or see people. When the birds take off in the morning, the support team heads out, too, straight for the place the cranes are expected to come down to. Very rarely, the cranes are flying so well near the end of their journey that they can skip a stop. One of the pilots can radio the team to let them know they have to go one more stop.
Q: What drives the crane to fly through the night?
A: Usually cranes don’t fly through the night. They may do this when in an unfamiliar place, when they find themselves over inappropriate habitat late in the day, or when they’re in a familiar place and know there will be a good place to land if they keep going.
Q: How do they navigate on cloudy days and nights?
A: When following the ultralight, Whooping Cranes don’t navigate—they just follow. On their return flight, they have an internal compass that probably depends on the position of the sun in the sky, and they also use landmarks. When on their own, they tend to do most of their migration flights on days when there are thermals to help them conserve energy, so they don’t need to worry about navigating when the sky is overcast—those are the days when there are no thermals. On the rare occasions when they fly at night, how do they know where they’re going? We don’t know for certain.
was chosen for the wintering habitat in part because the Chassahowitzka
National Wildlife Refuge is secluded, away
traffic and large enough to provide fine winter habitat. Wisconsin was
chosen for the same reason—the Necedah National Wildlife Refuge
is big and has an abundance of food and natural habitat.
Q: What drove 412 to fly three more hours at night?
A: 412 is a unique bird! From the start he’s been an unusually strong flier, and on day 48 last fall, he dropped away just 10 miles from the destination. By himself, he flew 80 miles south, then 80 miles north, landing 8 miles east of the morning's departure site at the Hiwassee State Wildlife Refuge! No one knows why he decided to fly at night one day, but he was the first of the 2004 whoopers to arrive back at Necedah—he must have a pretty good sense of direction!
A: The cranes in the WCEP flock wander a bit—some have been seen briefly in Minnesota, and in Wisconsin. Sometimes they fly off the refuge and explore other areas a bit. And last year some ended up in Michigan for the summer.
Q: Do they migrate to the same place year after year?
A: The Aransas/ Wood Buffalo flock is very consistent. Cranes learn their migration routes from their parents (or from their puppet parents!) Once in a while, some birds will get lost or for some reason or another turn up in different places. Humans will have to intervene when the situation is dangerous for the birds, but otherwise some birds may find themselves settling in new places over the years. If the species truly recovers, one day they may be nesting over a large part of the continent, as they did before the 1800s.
A: Cranes don’t typically use the stars for navigating. Birds that do memorize the one star that NEVER moves—Polaris. They migrate away from it in fall, and toward it in spring.
James, Ranan, Andrew, Connor, Clay
A: The WCEP team chose Florida because the Chassahowitzka met their needs as a good place for wintering cranes.
Q: Why do the birds go to Wisconsin and not the northeast?
A: Because that’s where they were raised.
Q: Why do the cranes migrate at all?
A: Because the ground and water freeze in winter over their summering range. They’d starve if they didn’t move. One natural flock in Louisiana didn’t migrate, because food was available year-round. And the introduced Kissimmee flock is also non-migratory.
Q: Why don't they stay in Florida?
A: Because their puppet parents taught them to migrate. The Kissimmee flock wasn’t raised to follow adult cranes or an ultralight, and they don’t migrate.
Stella, Jenna, Sarah
A: When cranes dance with their mates, it gets their hearts beating faster for a little while, and stirs feelings deep inside that stir up their hormones—special chemicals in their blood that get their bodies ready for breeding.
A: For the same reason that people get lost, or wander from their group. Cranes, like us and like all birds, have individual differences, and also on such a long journey, wind, rain, unexpected frights like predators, and other odd things can happen that make a bird suddenly take flight, or suddenly have to land. Last year the winds led one group to the eastern shore of Lake Michigan, and the birds didn’t want to cross the water, nor did they know how to fly north or south to go around the lake at first.
How to Use FAQ's About Journey North Species
Since 1995, experts have contributed answers to students' questions about each Journey North species. These questions and answers are archived in our FAQ's (Frequently Asked Questions) section. You can use today's Answers from the Expert above, along with those from previous years, in the activities suggested in the lesson, "FAQ's About Journey North Species" | <urn:uuid:8beb3a86-2bf2-4fca-84bb-a8a812968482> | 2.984375 | 2,407 | Q&A Forum | Science & Tech. | 60.983533 | 95,623,455 |
Physicists have devised a method for creating a special quantum entangled state. This state enables producing a high-precision ruler capable of measuring large distances to an accuracy of billionths of a metre.
Researchers have devised and demonstrated a novel approach to nanoactuation that relies on magnetomechanics instead of the conventional electromechanics utilized in micro and nanoactuated mechanical systems.
To study brain cell's operation and test the effect of medication on individual cells, the conventional Petri dish with flat electrodes is not sufficient. For truly realistic studies, cells have to flourish within three-dimensional surroundings.
Researchers have discovered a new phosphor that could make next-generation fluorescent and LED lighting even cheaper and more efficient. The team used highly luminescent clusters of silver atoms and the porous framework of minerals known as zeolites.
Gemeinsam mit Wissenschaftlern von zehn Partnerinstitutionen aus 5 EU Laendern setzen Radiologen des Uniklinikums Jena ihre Forschungsarbeit an multifunktionellen magnetischen Nanopartikeln fort, die zur Detektion und Bekaempfung von Krebs eingesetzt werden sollen.
Previous attempts to grow germanene show that these attractive properties seem to vanish when it is grown on a metal surface: a good conductor of current. To prevent this, scientists chose the semiconductor MoS2 as the substrate material.
While this nanotechnology could significantly enhance our food, it also raises big questions about safety. We only have to look at the strong reaction against genetically modified foods to see how important this issue is. How can we ensure that nanotechnology in food will be different? | <urn:uuid:4ab99079-e6cb-4736-87cb-29d8b939edf7> | 3.046875 | 362 | Content Listing | Science & Tech. | 18.454169 | 95,623,503 |
How do astronomers determine planets orbit?
For a long time astronomers thought that the planets orbited in a perfect circular shape but Johannes Kepler revealed that their path were not perfect circle. Most planetary orbits are nearly circular but when Kelper carefully observed and calculated he had established that they are not all perfectly circular. From Kepler’s work which was published between 1609 and 1619, he has improved the heliocentric theory of Nicolaus Copernicus, explaining how the planets speed varies. The planets orbit in an oval shape called ellipse with having the sun be in the middle of it all. Nearly all the planets orbit in the same direction which is counter clockwise except for Venus, Uranus and Pluto, astronomers believe this happens because of the sun’s strong pull of those planets.
With the earth being the third planet from the sun with a radius of 6370 kilometers which is 100 times smaller then the suns radius and the distance of 149 million kilometers away. The earth orbits around the sun once per year with the orbit being slightly elliptical in shape, the orbit defines a plane containing the sun. Since the earth orbits around the sun in a elliptical shape, the earth becomes closes to the sun calling it perihelion which happened during the month of January and the earth being the farthest away from the sun during the month of July called aphelion. The earth takes 23.439 hours to completely rotate on its own axis and take nearly 365.266 days to complete an orbit around the sun which is one calendar year.
In conclusion I really enjoyed learning about the planets in orbit. My questions that I have from after doing this project is how do planets in other galaxies orbit? It is the same orbit path as our galaxies?
http://nineplanets.org/overview.html, https://www.space.com/37054-we-dont-planet-different-orbit-types.html, http://funnel.sfsu.edu/courses/gm310/handouts/orbit_facts.html, https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion
How I figured out how to use what equations was mostly guess and check, but I did go off of the equations for like linear and quadratic. I found the most challenging thing was to make it look like ourselves. Jayna helped me a lot and we shared equations for different parts of the face. The assignment helped me realize what each equation is for and what kind of lines it makes.
For my peer teach Clare and I did field hockey, we had two P.E. classes to teach the class the basic rule, skills and drills to field hockey . We both had made daily plans for what we were going off of during the class which made it seem more organized and efficient. We would take turns to talk to the class and demonstrate. I think through out my peer teach I spoke loud, clearly and made the instructions easy to understand. I enjoyed doing my peer teach and I have realized that I like teaching things that I love.
For this activity we cut up an orange to make two hemispheres and took all of the orange out from the centre and traced the circumference of the orange on to a piece of paper as many times as you can. After we ripped apart the peel of the orange. we filled the circles that we have drawn with the ripped pieces of orange to make 4 full circles of peel. I learnt that the formula of a sphere is 4 x pi x r^2
My Estimate on how much water the Barrier contains behind in the lake is about 3/4 of the water in Garibaldi lake which is about 4,500,000,000 cubic meters since the volume is 6,099,609,059 cubic meters.
If the Berrier faulted, what do you think would happen. It would wipe out a lot. The weight of the water after the berrier would be broken would be 2,766,764.519 pounds per cubic meter, which could kill someone 35,000 times.
I would think that since the lake is 258.7 meters deep so if the berrier were to break i would imagine that only 3/4 of the water out.
This week it is Random Act of Caring week, and I chose a RAC to demonstrate throughout the week. I chose to do something for a close friend.
I met this girl at the beginning of the year and since then we have grown closer and closer everyday. I know in the past she has had struggles with friends and so i am so glad that she has found my friends and i. On Friday as couple of friends and i went to Dairy Queen but she could not come since she is working so hard on the backstage stuff of the school musical. I felt bad that we went and she was stuck at school so i decided that i would get her something and bring it back to her. i decided to get her a cookie ice cream cake and run it back to school with a bunch of spoons so we could give it to her and we could all enjoy it together.
What did you notice about the people who benefited from the RAC?
Since she has had a long day at school you could tell that she was grateful that we came back for her and she was vary surprised that we brought her a cake to all share.
What did you notice about yourself?
I notice that i could not take the smile i had on my face away. i knew that she was not expecting it so it felt good to see her face light up and make her day better. i also realized that even something small can make all the different to others. She was with others doing the lighting and they joined with eating that cake to and you could tell that they were grateful to have some ice cream in them as well.
How did performing a RAC contribute to your personal awareness and responsibility?
Performing the RAC helped me to be aware that even something small for someone can do all the difference. i realized that i should do more little things for people because it makes them feel good as well it makes me feel good.
Did you enjoy this RAC? Would you do it again? Would you change it, if so, how?
I really enjoyed doing this RAC and i would for sure do it again. It is going to be my goal to do more RAC and to do it in different ways, like making new friends, helping someone with something and so many other ways.
How did it contribute to your leadership skills?
Doing RAC contributes to my leadership skills by becoming a leader and stepping out side of my comfort zone. It has improved my view on being supportive and making peoples life and days better. | <urn:uuid:12d4ae7a-511e-4d78-b651-33c6eed720cf> | 3.90625 | 1,398 | Personal Blog | Science & Tech. | 68.590516 | 95,623,527 |
Scaling law of average failure rate and steady-state rate in rocks
- 177 Downloads
The evolution properties in the steady stage of a rock specimen are reflective of the damage or weakening growth within and thus are used to determine whether an unstable transition occurs. In this paper, we report the experimental results for rock (granite and marble) specimens tested at room temperature and room humidity under three typical loading modes: quasi-static monotonic loading, brittle creep, and brittle creep relaxation. Deformed rock specimens in current experiments exhibit an apparent steady stage characterized by a nearly constant evolution rate, which dominates the lifetime of the rock specimens. The average failure rate presents a common power–law relationship with the evolution rate in the steady stage, although the exponent is different for different loading modes. The results indicate that a lower ratio of the slope of the secondary stage with respect to the average rate of the entire lifetime implies a more brittle failure.
KeywordsSteady stage time-to-failure failure mode rock
This work is supported by National Natural Science Foundation of China (Grant 11672258), National Basic Research Program of China (Grant 2013CB834100) and Natural Science Foundation of Hebei Province (Grant D2015203398). We acknowledge useful comments of two anonymous reviewers.
- Amitrano, D., Grasso, J. R., & Senfaute, G. (2005). Seismic precursory patterns before a cliff collapse and critical point phenomena. Geophysical Research Letters, 32(5), L08314. doi: 10.1029/2004GL022270.
- Amitrano, D., & Helmstetter, A. (2006). Brittle creep, damage and time to failure in rocks. Journal of Geophysical Research, 111, 1–17, B11201. doi: 10.1029/2005JB004252.
- Andrade E. N. da C. (1910). On the viscous flow in metals and allied phenomena. Proceedings of the Royal Society of London. Series A, 84, 1.Google Scholar
- Atkinson, B., Meredith, P. (1987) The theory of subcritical crack growth with applications to minerals and rocks. In: Fracture mechanics of rocks (pp. 111–166). New York: Academic Press.Google Scholar
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- Jeager, J. C., Cook, N. G. W., & Zimmerman, R. (2007). Fundamentals of rock mechanics (4th ed.). London: Wiley-Blackwell.Google Scholar
- Lockner, D. A., & Byerlee, J. D. (1980). Development of fracture planes during creep in granite. In H. R. Hardy, F. W. Leiton, (Eds.) Proceedings of 2nd conference on acoustic emission/microseismic activity in geological structures and materials (pp 11–25). Clausthal-Zellerfeld, Germany: Trans Tech Publications.Google Scholar
- Omori, F. (1894). On the aftershocks of eathquakes. Journal of the College of Science, Imperial University of Tokyo, 7, 111–120.Google Scholar
- Perfettin, H., & Avouac, J. P. (2004). Postseismic relaxation driven by brittle creep: A possible mechanism to reconcile geodetic measurements and the decay rate of aftershocks, application to the Chi-Chi earthquake, Taiwan. Journal of Geophysical Research, 109, B02304. doi: 10.1029/2003JB002488.Google Scholar
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- Utsu, T. (1961). Statistical study on the occurrence of aftershocks. Geophysical Magazine, 30, 521–605.Google Scholar | <urn:uuid:266df83d-31a8-483b-99d8-b3a8e8ef8270> | 2.53125 | 1,132 | Academic Writing | Science & Tech. | 60.739598 | 95,623,536 |
C++/WinRT is an entirely standard modern C++17 language projection for Windows Runtime (WinRT) APIs, implemented as a header-file-based library, and designed to provide you with first-class access to the modern Windows API. With C++/WinRT, you can author and consume Windows Runtime APIs using any standards-compliant C++17 compiler. The Windows SDK includes C++/WinRT; it was introduced in version 10.0.17134.0 (Windows 10, version 1803).
C++/WinRT is for any developer interested in writing beautiful and fast code for Windows. Here's why.
The case for C++/WinRT
The C++ programming language is used both in the enterprise and independent software vendor (ISV) segments for applications where high levels of correctness, quality, and performance are valued. For example: systems programming; resource-constrained embedded and mobile systems; games and graphics; device drivers; and industrial, scientific, and medical applications, to name but some.
From a language point of view, C++ has always been about authoring and consuming abstractions that are both type-rich and lightweight. But the language has changed radically since the raw pointers, raw loops, and painstaking memory allocation and releasing of C++98. Modern C++ (from C++11 onward) is about clear expression of ideas, simplicity, readability, and a much lower likelihood of introducing bugs.
You use standard C++ data types, algorithms, and keywords when you use C++/WinRT. The projection does have its own custom data types, but in most cases you don't need to learn them because they provide appropriate conversions to and from standard types. That way, you can continue to use the standard C++ language features that you're accustomed to using, and the source code that you already have. C++/WinRT makes it extremely easy to call Windows Runtime APIs in any C++ application, from Win32 to UWP.
C++/WinRT performs better and produces smaller binaries than any other language option for the Windows Runtime. It even outperforms handwritten code using the ABI interfaces directly. That's because the abstractions use modern C++ idioms that the Visual C++ compiler is designed to optimize. This includes magic statics, empty base classes, strlen elision, as well as many newer optimizations in the latest version of Visual C++ targeted specifically at improving the performance of C++/WinRT.
|Introduction to C++/WinRT||An introduction to C++/WinRT—a standard C++ language projection for Windows Runtime APIs.|
|Get started with C++/WinRT||To get you up to speed with using C++/WinRT, this topic walks through a simple code example.|
|Frequently-asked questions||Answers to questions that you're likely to have about authoring and consuming Windows Runtime APIs with C++/WinRT.|
|Troubleshooting||The table of troubleshooting symptoms and remedies in this topic may be helpful to you whether you're cutting new code or porting an existing app.|
|Photo Editor C++/WinRT sample application||Photo Editor is a UWP sample application that showcases development with the C++/WinRT language projection. The sample application allows you to retrieve photos from the Pictures library, and then edit the selected image with assorted photo effects.|
|String handling||With C++/WinRT, you can call Windows Runtime APIs using standard C++ wide string types, or you can use the winrt::hstring type.|
|Standard C++ data types and C++/WinRT||With C++/WinRT, you can call Windows Runtime APIs using Standard C++ data types.|
|Boxing and unboxing scalar values to IInspectable||A scalar value needs to be wrapped inside a reference class object before being passed to a function that expects IInspectable. That wrapping process is known as boxing the value.|
|Consume APIs with C++/WinRT||This topic shows how to consume C++/WinRT APIs, whether they're implemented by Windows, a third-party component vendor, or by yourself.|
|Author APIs with C++/WinRT||This topic shows how to author C++/WinRT APIs by using the winrt::implements base struct, either directly or indirectly.|
|Error handling with C++/WinRT||This topic discusses strategies for handling errors when programming with C++/WinRT.|
|Handle events by using delegates||This topic shows how to register and revoke event-handling delegates using C++/WinRT.|
|Author events||This topic demonstrates how to author a Windows Runtime Component containing a runtime class that raises events. It also demonstrates an app that consumes the component and handles the events.|
|Concurrency and asynchronous operations||This topic shows the ways in which you can both create and consume Windows Runtime asynchronous objects with C++/WinRT.|
|XAML controls; bind to a C++/WinRT property||A property that can be effectively bound to a XAML control is known as an observable property. This topic shows how to implement and consume an observable property, and how to bind a XAML control to it.|
|XAML items controls; bind to a C++/WinRT collection||A collection that can be effectively bound to a XAML items control is known as an observable collection. This topic shows how to implement and consume an observable collection, and how to bind a XAML items control to it.|
|Interop between C++/WinRT and C++/CX||This topic shows two helper functions that can be used to convert between C++/CX and C++/WinRT objects.|
|Move to C++/WinRT from C++/CX||This topic shows how to port C++/CX code to its equivalent in C++/WinRT.|
|Interop between C++/WinRT and the ABI||This topic shows how to convert between application binary interface (ABI) and C++/WinRT objects.|
|Move to C++/WinRT from WRL||This topic shows how to port Windows Runtime C++ Template Library (WRL) code to its equivalent in C++/WinRT.|
|Weak references||C++/WinRT weak reference support is pay-for-play, in that it doesn't cost you anything unless your object is queried for IWeakReferenceSource.|
|Agile objects||An agile object is one that can be accessed from any thread. Your C++/WinRT types are agile by default, but you can opt out.| | <urn:uuid:ad1b5009-cb62-4185-8ef7-065efefdf672> | 2.859375 | 1,413 | Documentation | Software Dev. | 48.858005 | 95,623,555 |
WPF DataGrid (.NET 4) can be difficult to understand if you aren't used to thinking about objects and collections. This easy to follow introduction explains where the rows and columns have gone.
The big problem with most of the explanations of how the DataGrid and the examples that you will find is that they try to be realistic. They generally work with a database or some complex structured object and then explain a complicated set of steps but might be close to what you would really use the DataGrid for but they give little idea how it works. It can be difficult to separate the details that apply to the DataGrid generally and the technology it is being used with specifically.
This gives rise to questions, especially from programmers who have used other data grids, such as:
- "Where are the rows?"
- "How do I access a particular cell?"
- "How do I add another column?"
and so on.
The biggest mystery to the WPF DataGrid beginner is:
- "Where have all the rows gone?"
This article will show you exactly where they are and how the DataGrid works.
Look no binding!
Start a new Visual Studio/Express 2010 WPF project and place a DataGrid and a Button on the page.
The first problem we have to answer is where does the DataGrid get its data from? The standard answer is to use data binding and unless you understand how all this works it great detail it can obscure the simplicity of the mechanism. So while it might not be the commonest way of working let's start with a simple non-bound example.
The DataGrid will display any collection that implements IEnumerable and this means most of the collection classes that are supplied as part of the framework. When you create a DataGrid you get an empty collection object which you can access via the Items property. The Items property is read only as its purpose is to return a reference to the collection. You can however add objects to the collection using its Add method. For example:
If you try this out what you will see is a grid with some horizontal lines drawn. The lines clearly correspond to the two rows that you have just added but there is no sign of any data.
Whenever you see a grid with blank rows like this you can conclude that you have successfully given the grid some data to display but you so far have failed to set up the columns. In particular, you have failed to bind any columns to any of the data.
To see the data in the collection that we have set up we have to add some columns to the DataGrid's Columns collection. Columns do the work of actually displaying data and a DataGrid without any columns is a fairly useless object.
There are currently four types of column:
|DataGridTextColumn||displays text data|
|DataGridCheckBoxColumn||displays boolean data|
There is also the DataGridTemplateColumn which is completely customisable and will display any data for which there is a suitable display control.
The details of how some of these columns work is complicated - especially so the DataGridTemplateColumn - but the basic DataGridTextColumn is easy enough to use and given most simple data can be converted to text it is also very useful.
Let's add a DataGridTextColumn to the current example:
Following this addition the DataGrid now shows two rows and a single column - but still no data.
Each of the objects that make up the Items collection roughly speaking provides the data for a row of the grid. How does a column work out how to get the data it has to display from each object? The answer is that you have to setup a binding between it and the objects of the collection.
Usually each column is bound to a property of each object so that each column shows different data - but a column can be bound directly to the object. In this case the binding defaults to calling the object's ToString method to retrieve the display data. This can be useful during debugging and general development just to check that you have the correct collection associated with the grid.
In the case of our simple example it is enough to get the data displayed:
Columns).Binding = new Binding(".");
Notice that you have to cast the column to a DataGridTextColumn because the base class doesn't support a Binding property. This is one good reason for keeping a reference to any columns that you are setting up in code. That is:
DataGridTextColumn col1 =
col1.Binding = new Binding(".");
The binding "." simply means the root of the bound object, i.e. the entire object, and this means that the binding engine will call the object's ToString method. SInce the objects in the collection are Strings this displays their value as required and at last the DataGrid displays the data:
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Patrick Gatlin says his work measuring the height and width of raindrops using ground instruments provides an accuracy baseline that is then scaled up to ground radar and then to satellite measurements.
He is co-author of a paper on the topic (Tokay, Ali, Walter A. Petersen, Patrick Gatlin, Matthew Wingo, 2013: Comparison of Raindrop Size Distribution Measurements by Collocated Disdrometers. J. Atmos. Oceanic Technol., 30, 1672–1690; http://dx.doi.org/10.1175/JTECH-D-12-00163.1).
“That’s really the whole purpose of measuring raindrops, is for remote sensing purposes,” Gatlin says. Scaling up accuracy from a small sensor on the ground to large sections of the Earth being observed from space requires very accurately calibrated instruments. “Our ability to correctly depict rainfall using a sensor in space is closely tied to knowing how precipitation varies, right down to the individual raindrop and snowflake size.”
Perfecting ground-level instrument observations, enlarging those to encompass ground-based radar and then going even larger to develop accurate satellite measuring instruments is the best way to reduce error as the area under observation increases. “Before we invest in all this satellite instrumentation,” Gatlin says, “let’s make sure we’ve got it right.”
A coming big step in scaling up precipitation forecasting is NASA’s planned launch of its Global Precipitation Measurement (GPM) satellite toward the end of February. UAH is a mission contractor, headed at the university by Dr. Larry Carey, an associate professor of atmospheric science, and involving UAH Earth System Science Center research scientist Matt Wingo, who is working with NASA at their flight facility in Wallops Island, Va.
“UAH designed the platform for some of the ground-based instruments that will validate the information from the satellite,” says Gatlin.
Carrying an advanced radar/radiometer system to measure precipitation from space, the GPM is the core of what will be a global network of measuring satellites that will provide next-generation global observations of rain and snow. It will serve as a reference standard to unify precipitation measurements from a constellation of research and operational satellites.
Through improved measurements of precipitation globally, the GPM mission will help to advance understanding of Earth's water and energy cycle, improve forecasting of extreme events that cause natural hazards and disasters, and extend current capabilities in using accurate and timely precipitation information.
In his own research, Gatlin has ranged from Iowa and Oklahoma to Canada, Finland, Italy and France. Rather than raindrops, the Canadian research was designed to collect snowflake images in order to improve the accuracy of measuring devices for snowfall.
In each locale, an integrated network of ground-level measuring devices have been deployed, like the Parsivel2, a disdrometer that measures the particle size and velocity of raindrops falling through a laser. Also in use are two-dimensional video disdrometers, which use two video angles to create 2-D pictures that enable determination of raindrop shapes. A video disdrometer on loan from frequent research collaborator Colorado State University is located on the UAH campus behind Cramer Hall.
During a field study, the instruments on the ground take measurements while a plane flies through the clouds to collect actual raindrop information and another flies high above the clouds with remote sensing equipment to mimic satellite radar detection. Results from all the measurement methods are compared.
Enhanced satellite-based precipitation measurements will improve both rainfall and snowfall predictions on a global scale, Gatlin says. “We’ll be measuring rain and snow in some areas where we’ve never measured it before.” The ability to better measure raindrop size also can have impact on severe weather forecasting, as small raindrops lead to higher evaporation rates that have been correlated with larger and more forceful microbursts by UAH’s Dr. Kevin Knupp and others.
Gatlin is about to finish up a global study focusing just on very large raindrops 5 millimeters in size and larger. These drops are difficult to capture in the small measuring area afforded by measuring instruments, and so their observation is rare. Gatlin says out of 224 million drops he has researched, only 8,000 have been 5 mm or larger.
“Even though large raindrops can have the greatest impact on radar measurements, we don’t have a good idea of their concentration,” he says. “What I’ve been doing is bringing together all the raindrop data bases that have collected various types of rainfall data using the same techniques.”
Interestingly, while Sumatra holds the honor of having the greatest number of large drops overall, the largest drop collected in his study fell through a measuring device at the UAH campus. It measured 9.1 mm and was formed in a hailstorm when a falling piece of hail melted before landing.
Patrick Gatlin | Newswise
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Researchers of the Luxembourg Centre for Systems Biomedicine (LCSB) of the University of Luxembourg have discovered with the help of computer models how gut bacteria respond to changes in their environment – such as a decrease in oxygen levels or nutrient availability.
Microorganisms that normally compete or overthrow one another can switch to a cooperative lifestyle when their living conditions change: They even start producing substances to make life easier for the other species, helping them to survive. The entire microbial community then stabilises – and together adapts successfully to the new situation.
The researchers working with Prof. Dr. Ines Thiele, head of the LCSB Group “Molecular Systems Physiology” published their results in the journal “Applied and Environmental Microbiology” (DOI: 10.1128/AEM.00101-15).
The human gut is home to thousands of bacterial species, most of which have never been described in science. This ecosystem is a complex living community: The microorganisms live side-by-side, compete for nutrients, overthrow one another or even benefit off each other.
It is the aim of Almut Heinken, research associate in Ines Thiele’s workgroup, to understand these interactions more completely: “For my thesis, I worked with data from literature and modelled on the computer how certain bacterial species respond to one another when the living conditions in their environment change,” the scientist says. “Such models are a common method for making better predictions about the interactions of bacteria. We developed the method further and applied it for the first time to gut bacteria. With eleven species, we were able to calculate how they behave pairwise in the presence of human small intestinal cells.”
Almut Heinken discovered some surprising types of behaviour in these studies: “Bacteria that are otherwise very dominant and overthrow other species suddenly enter a symbiosis with those same species if, for example, the oxygen content in the environment drops. They emit substances that make it easier for otherwise outcompeted species to survive. And they, too, receive substances they wouldn’t get enough of under the unfavourable living conditions.” Heinken has calculated such symbiotic behaviour for the bacterial species Lactobacillus plantarum, for example.
This turnaround in metabolism is vital for the bacterial community to continue functioning within the different sections of the gut: For example, the oxygen content varies in different places along the small intestine. There is more oxygen on the walls than in the centre, and more at the start of the small intestine than at its end. “By the bacteria mutually supporting one another when they find themselves in a low-oxygen environment, the bacterial community remains functional as a whole – and so the digestion as well,” Almut Heinken explains. The nutrient supply and the presence of sloughed intestinal cells also undergo great spatial variance, and have an influence on the symbiotic behaviour of the bacteria.
The LCSB researchers are interested above all in the importance of these bacterial interactions in relation to diseases, as Ines Thiele explains: “We know that diet and digestion can have an influence on the onset of diseases. This relates not only to the gastrointestinal tract, but also to other areas, such as the nervous system and its diseases, such as Parkinson’s disease.”
The scientists’ long-term goal is therefore to understand the ecosystem of the gut in minutest detail. Accordingly, they are continually adding more bacterial species to their computer models. “If we manage to correlate certain responses of the bacterial community with the outbreak of diseases, then we will gain a powerful lever,” Thiele says: “We would thereby create the opportunity to influence the disease preventatively or therapeutically by diet or by tweaking the gut flora using probiotics.”
Contact: firstname.lastname@example.org; T. + 352 46 66 44 6423
Britta Schlüter | idw - Informationsdienst Wissenschaft
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A UWM professor recently helped DOE do just that by analyzing the DNA of a bacterium that can break down cellulose, the major structural component of plants that is also found in forestry by-products (including paper) and waste feedstocks.
Mark McBride, a professor of biological sciences, worked with DOE’s Joint Genome Institute and scientists at Los Alamos National Laboratory to examine the genes of Cytophaga hutchinsonii that are responsible for the organism’s ability to digest cellulose – the first step in the carbohydrate’s conversion into ethanol.
Sequencing the genome of C. hutchinsonii provides what McBride calls a “parts list” for the microbe, allowing scientists to explore how bacteria use these parts to build and run their key functions – some of which have potential uses in bioenergy.
The genome has revealed surprises, he says.
“Microorganisms typically require two kinds of enzymes to efficiently break down cellulose,” he says. “One type cuts the long carbohydrate molecule through the middle, while another chews small pieces from the ends.”
Not so with C. hutchinsonii. Although it efficiently digests cellulose, in DNA analysis it appears to be lacking one of the usual enzymes, suggesting that it may use either a novel strategy or novel enzymes.
The information McBride reports could help DOE devise mixtures of microorganisms or enzymes that will more efficiently convert cellulose into glucose, and finally into ethanol.
McBride’s interest in C. hutchinsonii goes beyond its possible value in bioenergy.
What really intrigues him is that it’s a “gliding bacterium,” able to crawl rapidly over surfaces by an unknown mechanism, which is the main subject of McBride’s research with another glider called Flavobacterium johnsoniae. The two microbes are not closely related.
“You are more closely related to a fruit fly than these two organisms are to each other,” he says.
However, from analysis of genes from the two bacteria, McBride suspects that they use the same basic machinery to move.
And there may be another connection. F. johnsoniae doesn’t eat cellulose, but it is able to digest a similar carbohydrate polymer, chitin. Like cellulose, chitin, which is found in the hard shells of lobsters and insects, is also difficult to break down.
McBride hypothesizes that digestion of cellulose and chitin may also be linked to cell movement, or motility.
“Loss of motility results in loss of ability to digest chitin,” he says. “This suggests that motility and digestion of some carbohydrate polymers may be connected in both gliding microbes.”
McBride and his students have used F. johnsoniae to study the motility of gliding bacteria for more than a decade. They cloned “mutants” of F. johnsoniae that are unable to move, and then attempted to “repair” them by inserting certain pieces of DNA.
In this way, they have uncovered nearly all the genetic components that propel the cells. It has been a long process. A decade ago, his lab had found one protein involved. He now knows of 24, and he doesn’t expect to find many more.
Until recently, McBride was not able to image the bacteria closely enough to see the structures involved in movement. Instead, he bonded latex spheres to the surface of F. johnsoniae cells and observed that they moved in all directions around the cell’s perimeter.
“The cell wall appears to have a series of moving conveyer belts,” he says.
He also has learned that some of the motility proteins (“parts”) act at the surface of the cell, and he thinks some are involved in forming nearly invisible filaments around the perimeter of the cell.
These filaments were recently imaged in collaboration with Sriram Subramaniam and Jun Liu at the National Institutes of Health by cryo-electron tomography.
“The filaments may be the cell’s ‘tires,’ and there are different kinds,” McBride says. “They are designed to help the organism move over a variety of surfaces, like an all-terrain vehicle.”
Besides providing movement, McBride says the filaments also may be needed to move the cellulose and chitin molecules to certain sites where they can be digested or taken into the cell.
McBride hopes the complete genome for C. hutchinsonii will yield other clues to the interconnections among gliding bacteria. He is now collaborating with DOE to sequence the entire genome of F. johnsoniae, which will allow a full comparison of the genes of the two microorganisms.
Mark McBride | EurekAlert!
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Cadherin prevents cortical deformation
Scientists from the Mechanobiology Institute, Singapore (MBI) at the National University of Singapore (NUS) have discovered that cadherin clusters, which are well known for forming junctions between cells, also play a role in stabilising the cell cortex. The study was published in the scientific journal Current Biology on 15 December 2016.
Figure: Surface and equatorial plane views of the C. elegans embryo. Non-junctional and non-adhesive HMR-1 clusters (green dots) are visible on the surface of a single cell and also on both cells following cell division. A belt of HMR-1 forming cell-cell junctions is observed between the 2 daughter cells (white-green line).
Credit: Mechanobiology Institute, National University of Singapore
A new role for cadherin
Multicellular life depends on the ability of cells to adhere to one another. This takes place through cell-cell junctions, protein complexes that physically connect cells together. At the core of cell-cell junctions is the protein cadherin, which spans across the cell membrane, sticking out of the cell to connect to cadherins on neighbouring cells. Cadherin also attaches to the internal cell cortex, a dense layer of proteins underneath the cell membrane which has two major components: the filament-forming protein actin that provides structural stability, and the motor protein myosin that enables dynamic movement of the cortex depending on the needs of the cell. This physical bridge between cells enables the transmission of both mechanical and biochemical signals across multicellular tissues.
However, scientists have observed clusters of cadherin on the cell surface which are not involved in cell-cell junctions. While it has been speculated that these non-junctional and non-adhesive cadherin clusters are being kept in reserve in order to strengthen or create new cell-cell junctions, the actual function of these clusters remained unknown.
With their expertise in cell adhesion and developmental biology, Principal Investigator Assistant Professor Ronen Zaidel-Bar and Research Fellow Dr Anup Padmanabhan of MBI used embryos from the nematode C. elegans to probe the function of these non-junctional cadherin clusters. After tagging the worm equivalent of cadherin, a protein named HMR-1, with a fluorescent marker, they were able to follow its location and movement by live imaging.
Focusing their investigation on the zygote, the single fertilised egg cell that develops into an embryo, they discovered that HMR-1 formed non-junctional, non-adhesive clusters similar to cadherin. Even though these non-junctional HMR-1 clusters did not form connections outside of the cell, they still remained internally associated with actin filaments of the cell cortex, but not the myosin motor proteins. In fact, the presence of non-junctional HMR-1 clusters prevents cortical accumulation of myosin and decreases the contractile activity of proteins that drive cortical movement.
In order to determine whether non-junctional HMR-1 affected cytokinesis - the physical process by which the cell cortex rotates and contracts to divide the cell into two - the scientists genetically altered the level of HMR-1. Reducing the amount of HMR-1 resulted in faster cytokinesis while increasing HMR-1 levels slowed it down, demonstrating that these non-junctional clusters have a key function in regulating movement of the cell cortex. Analysis of cortical dynamics during cell division revealed that HMR-1 clusters attached to the actin filaments effectively provided drag against cytoskeleton movement, by acting as structural anchors lodged in the cell membrane. The importance of this anchoring in maintaining cell integrity became clear following extended observation of embryos with reduced levels of HMR-1, which were vulnerable to cortical splitting, where a segment of cortex tears away from the cell membrane.
In essence, the non-junctional HMR-1 clusters can be thought of as cellular staples that help secure the cortex to the cell surface. The friction from the clusters stabilises the cortex and slows down cortical flow, preventing dramatic cortical deformation, while allowing enough cortical movement for fundamental processes like cytokinesis.
This new discovery means that scientists must re-evaluate their understanding of cadherin. The importance of non-junctional cadherin in stabilising the cell cortex must now be considered along with the classical function of cadherin in maintaining cell-cell junctions. This fresh perspective may unlock new avenues of investigation regarding the role of cadherin in health and disease.
Amal Naquiah | EurekAlert!
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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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|Scanning tunneling microscopy|
- 1 Characteristic X-ray Spectroscopy
- 2 X-ray emission spectroscopy
- 3 Other types of X-ray spectroscopy
- 4 See also
- 5 References
Characteristic X-ray Spectroscopy
When an electron from the inner shell of an atom is excited by the energy of a photon, it moves to a higher energy level. When it returns to the low energy level, the energy which it previously gained by the excitation is emitted as a photon which has a wavelength that is characteristic for the element (there could be several characteristic wavelengths per element). Analysis of the X-ray emission spectrum produces qualitative results about the elemental composition of the specimen. Comparison of the specimen's spectrum with the spectra of samples of known composition produces quantitative results (after some mathematical corrections for absorption, fluorescence and atomic number). Atoms can be excited by a high-energy beam of charged particles such as electrons (in an electron microscope for example), protons (see PIXE) or a beam of X-rays (see X-ray fluorescence, or XRF). These methods enable elements from the entire periodic table to be analysed, with the exception of H, He and Li. In electron microscopy an electron beam excites X-rays; there are two main techniques for analysis of spectra of characteristic X-ray radiation: energy-dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS).
Energy-dispersive X-ray spectroscopy
In an energy-dispersive X-ray spectrometer, a semiconductor detector measures energy of incoming photons. To maintain detector integrity and resolution it should be cooled with liquid nitrogen or by Peltier cooling. EDS is widely employed in electron microscopes (where not spectroscopy but imaging is a main task) and in cheaper and/or portable XRF units.
Wavelength dispersive X-ray spectroscopy
In a wavelength dispersive X-ray spectrometer the single crystal diffracts the photons (Bragg's law) which are collected by a detector. Without any motion there will be just one wavelength detected. By moving crystal and detector, a wide region of spectrum is observed (to collect all parts of spectrum three of four different single crystals may be needed). In contrast to EDS, WDS method is a method of sequential spectrum acquisition. While WDS is slower than EDS and more sensitive to positioning specimen in the spectrometer, it has superior spectral resolution and sensitivity. WDS is widely used in microprobes (where X-ray microanalysis is the main task) and in XRF; it is widely used in the field of x ray diffraction to calculate various data such as interplanar spacing and wavelength of the incident x ray using Bragg's law.
X-ray emission spectroscopy
The father-and-son scientific team of William Lawrence Bragg and William Henry Bragg, who were 1915 Nobel Prize Winners, were the original pioneers in developing X-ray emission spectroscopy. Jointly they measured the X-ray wavelengths of many elements to high precision, using high-energy electrons as excitation source. The cathode ray tube or an x-ray tube was the method used to pass electrons through a crystal of numerous elements. They also painstakingly produced numerous diamond-ruled glass diffraction gratings for their spectrometers. The law of diffraction of a crystal is called Bragg's law in their honor.
Intense and wavelength-tunable X-rays are now typically generated with synchrotrons. In a material, the X-rays may suffer an energy loss compared to the incoming beam. This energy loss of the re-emerging beam reflects an internal excitation of the atomic system, an X-ray analogue to the well-known Raman spectroscopy that is widely used in the optical region.
In the X-ray region there is sufficient energy to probe changes in the electronic state (transitions between orbitals; this is in contrast with the optical region, where the energy loss is often due to changes in the state of the rotational or vibrational degrees of freedom). For instance, in the ultra soft X-ray region (below about 1 keV), crystal field excitations give rise to the energy loss.
The photon-in-photon-out process may be thought of as a scattering event. When the x-ray energy corresponds to the binding energy of a core-level electron, this scattering process is resonantly enhanced by many orders of magnitude. This type of X-ray emission spectroscopy is often referred to as resonant inelastic X-ray scattering (RIXS).
Due to the wide separation of orbital energies of the core levels, it is possible to select a certain atom of interest. The small spatial extent of core level orbitals forces the RIXS process to reflect the electronic structure in close vicinity of the chosen atom. Thus, RIXS experiments give valuable information about the local electronic structure of complex systems, and theoretical calculations are relatively simple to perform.
There exist several efficient designs for analyzing an X-ray emission spectrum in the ultra soft X-ray region. The figure of merit for such instruments is the spectral throughput, i.e. the product of detected intensity and spectral resolving power. Usually, it is possible to change these parameters within a certain range while keeping their product constant...
Usually X-ray diffraction in spectrometers is achieved on crystals, but in Grating spectrometers, the X-rays emerging from a sample must pass a source-defining slit, then optical elements (mirrors and/or gratings) disperse them by diffraction according to their wavelength and, finally, a detector is placed at their focal points.
Spherical grating mounts
Henry Augustus Rowland (1848–1901) devised an instrument that allowed the use of a single optical element that combines diffraction and focusing: a spherical grating. Reflectivity of X-rays is low, regardless of the used material and therefore, grazing incidence upon the grating is necessary. X-ray beams impinging on a smooth surface at a few degrees glancing angle of incidence undergo external total reflection which is taken advantage of to enhance the instrumental efficiency substantially.
Denoted by R the radius of a spherical grating. Imagine a circle with half the radius R tangent to the center of the grating surface. This small circle is called the Rowland circle. If the entrance slit is anywhere on this circle, then a beam passing the slit and striking the grating will be split into a specularly reflected beam, and beams of all diffraction orders, that come into focus at certain points on the same circle.
Plane grating mounts
Similar to optical spectrometers, a plane grating spectrometer first needs optics that turns the divergent rays emitted by the x-ray source into a parallel beam. This may be achieved by using a parabolic mirror. The parallel rays emerging from this mirror strike a plane grating (with constant groove distance) at the same angle and are diffracted according to their wavelength. A second parabolic mirror then collects the diffracted rays at a certain angle and creates an image on a detector. A spectrum within a certain wavelength range can be recorded simultaneously by using a two-dimensional position-sensitive detector such as a microchannel photomultiplier plate or an X-ray sensitive CCD chip (film plates are also possible to use).
Instead of using the concept of multiple beam interference that gratings produce, the two rays may simply interfere. By recording the intensity of two such co-linearly at some fixed point and changing their relative phase one obtains an intensity spectrum as a function of path length difference. One can show that this is equivalent to a Fourier transformed spectrum as a function of frequency. The highest recordable frequency of such a spectrum is dependent on the minimum step size chosen in the scan and the frequency resolution (i.e. how well a certain wave can be defined in terms of its frequency) depends on the maximum path length difference achieved. The latter feature allows a much more compact design for achieving high resolution than for a grating spectrometer because x-ray wavelengths are small compared to attainable path length differences.
Early history of X-ray Spectroscopy in the U.S.
Philips Gloeilampen Fabrieken, headquartered in Eindhoven in the Netherlands, got its start as a manufacturer of light bulbs, but quickly evolved until it is now one of the leading manufacturers of electrical apparatus, electronics, and related products including X-ray equipment. It also has had one of the world's largest R&D labs. In 1940, the Netherlands was overrun by Hitler’s Germany. The company was able to transfer a substantial sum of money to a company that it set up as an R&D laboratory in an estate in Irvington on the Hudson in NY. As an extension to their work on light bulbs, the Dutch company had developed a line of X-ray tubes for medical applications that were powered by transformers. These X-ray tubes could also be used in scientific X-ray instrumentations, but there was very little commercial demand for the latter. As a result, management decided to try to develop this market and they set up development groups in their research labs in both Holland and the U.S.
They hired Dr. Ira Duffendack, a professor at University of Michigan and a world expert on infrared research to head the lab and to hire a staff. In 1951 he hired Dr. David Miller as Assistant Director of Research. Dr. Miller had done research on X-ray instrumentation at Washington University in St. Louis. Dr. Duffendack also hired Dr. Bill Parish, a well known researcher in X-ray diffraction, to head up the section of the lab on X-ray instrumental development. X-ray diffraction units were widely used in academic research departments to do crystal analysis. An essential component of a diffraction unit was a very accurate angle measuring device known as a goniometer. Such units were not commercially available, so each investigator had do try to make their own. Dr Parrish decided this would be a good device to use to generate an instrumental market, so his group designed and learned how to manufacture a goniometer. This market developed quickly and, with the readily available tubes and power supplies, a complete diffraction unit was made available and was successfully marketed.
The U.S. management did not want the laboratory to be converted to a manufacturing unit so it decided to set up a commercial unit to further develop the X-ray instrumentation market. In 1953 Norelco Electronics was established in Mount Vernon, NY, dedicated to the sale and support of X-ray instrumentation. It included a sales staff, a manufacturing group, an engineering department and an applications lab. Dr. Miller was transferred from the lab to head up the engineering department. The sales staff sponsored three schools a year, one in Mount Vernon, one in Denver, and one in San Francisco. The week-long school curricula reviewed the basics of X-ray instrumentation and the specific application of Norelco products. The faculty were members of the engineering department and academic consultants. The schools were well attended by academic and industrial R&D scientists. The engineering department was also a new product development group. It added an X-ray spectrograph to the product line very quickly and contributed other related products for the next 8 years.
The applications lab was an essential sales tool. When the spectrograph was introduced as a quick and accurate analytical chemistry device, it met with widespread skepticism. All research facilities had a chemistry department and analytical analysis was done by “wet chemistry” methods. The idea of doing this analysis by physics instrumentation was considered suspect. To overcome this bias, the salesman would ask a prospective customer for a task the customer was doing by “wet methods”. The task would be given to the applications lab and they would demonstrate how accurately and quickly it could be done using the X-ray units. This proved to be a very strong sales tool, particularly when the results were published in the Norelco Reporter, a technical journal issued monthly by the company with wide distribution to commercial and academic institutions.
An X-ray spectrograph consists of a high voltage power supply (50 kV or 100 kV), a broad band X-ray tube, usually with a tungsten anode and a beryllium window, a specimen holder, an analyzing crystal, a goniometer, and an X-ray detector device. These are arranged as shown in Fig. 1.
The continuous X-spectrum emitted from the tube irradiates the specimen and excites the characteristic spectral X-ray lines in the specimen. Each of the 92 elements emits a characteristic spectrum. Unlike the optical spectrum, the X-ray spectrum is quite simple. The strongest line, usually the Kalpha line, but sometimes the Lalpha line, suffices to identify the element. The existence of a particular line betrays the existence of an element, and the intensity is proportional to the amount of the particular element in the specimen. The characteristic lines are reflected from a crystal, the analyzer, under an angle that is given by the Bragg condition. The crystal samples all the diffraction angles theta by rotation, while the detector rotates over the corresponding angle 2-theta. With a sensitive detector, the X-ray photons are counted individually. By stepping the detectors along the angle, and leaving it in position for a known time, the number of counts at each angular position gives the line intensity. These counts may be plotted on a curve by an appropriate display unit. The characteristic X-rays come out at specific angles, and since the angular position for every X-ray spectral line is known and recorded, it is easy to find the sample's composition.
A chart for a scan of a Molybdenum specimen is shown in Fig. 2. The tall peak on the left side is the characteristic alpha line at a two theta of 12 degrees. Second and third order lines also appear.
Since the alpha line is often the only line of interest in many industrial applications, the final device in the Norelco X- ray spectrographic instrument line was the Autrometer. This device could be programmed to automatically read at any desired two theta angle for any desired time interval.
Soon after the Autrometer was introduced, Philips decided to stop marketing X-ray instruments developed in both the U.S. and Europe and settled on offering only the Eindhoven line of instruments.
In 1961, during the development of the Autrometer, Norelco was given a sub-contract from the Jet Propulsion Lab. The Lab was working on the instrument package for the Surveyor spaceship. The composition of the moon’s surface was of major interest and the use of an X-ray detection instrument was viewed as a possible solution. Working with a power limit of 30 watts was very challenging, but a device was delivered but it wasn’t used. Later NASA developments did lead to an X-ray spectrographic unit that did make the desired moon soil analysis.
The Norelco efforts faded but the use of X-ray spectroscopy in units known as XRF instruments continued to grow. With a boost from NASA, units were finally reduced to handheld size and are seeing widespread use. Units are available from Bruker, Thermo Scientific, Elvatech Ltd. and SPECTRA.
In recent years, major advances took place at the University of Washington at the hands of Dr. Oliver R. Hoidn who came up with a disposable x-ray camera based on mass produced complementary metal-oxide-semiconductor sensors and single-board computers. The outcome of this innovation was published in 2015 in the Review of Scientific Instruments.
Other types of X-ray spectroscopy
- "x ray spectroscopy" (PDF).
- THE CATHODE RAY TUBE IN X-RAY SPECTROSCOPY AND QUANTITATIVE ANALYSIS, Gorton R. Fonda and George B. Collins, Journal of the American Chemical Society, Vol. 53: Issue. 1: Pages. 113-125, Publication Date: January 1931 | <urn:uuid:5ddd1a8e-7d50-4abf-a941-4bf6e1a78ff1> | 3.546875 | 3,429 | Knowledge Article | Science & Tech. | 39.108151 | 95,623,637 |
The Nature of Mechanical Devices in Biological Systems
A mechanical device must have moving parts. Even the simplest lever turns about a fulcrum. A biological system clearly directs stress and strain so that action and information are transmitted in a deliberate spatial pattern. The question arises as to how this can be done at the molecular level. The available motions which must be built into a molecular machine are known to be side-chain motions (vibrations or rotations), segment motions (vibrations, rotations or lateral translations) domain motions (vibrations, rotations or lateral translations) and whole molecule movements. We know that the polymers involved are proteins, polysaccharides and polynucleotides. I have been concerned with the first two only. I shall describe some observations and views.
KeywordsMechanical Device Phosphoglycerate Kinase Molecular Machine Lateral Translation Domain Motion
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Castoreum, the dried scent glands of the Canadian beaver, was once one of the most valuable scent components derived from animals.
Castoreum contains a complex mixture of substances, including a number of compounds known as nupharamine alkaloids. Many of these have been structurally characterized. Researchers working with Horst Kunz at the University of Mainz (Germany) have now, as they report in the journal Angewandte Chemie, determined the stereochemistry (precise spatial structure) of another castoreum component by using a total synthesis. A total synthesis is the complete chemical synthesis of a complex organic natural substance from simple, easily attainable starting materials.
Beavers use their fat- and pheromone-containing gland secretions to groom their fur and to mark their territory. In the past, the resin-like content of the dried glands was used as medicine to treat various complaints, such as cramps, “hysteria”, and nervousness. In antiquity it was even used to treat epilepsy. Castoreum’s effectiveness can be explained by the salicylic acid it contains—aspirin is also based on this substance. Castoreum was once in such demand that the beaver was threatened with extinction. Today, there are special beaver farms where the beavers rub their secretions off onto special collection containers. In addition, castoreum is now only used for homeopathic remedies and in some perfumes.
The team from Mainz undertook the synthesis of a minor component (5-(3’-furyl)-8-methylindolizidine), which makes up less than 0.0002% of castoreum. In principle, the structure of this nupharamine is known. It has an indolizidine skeleton (a special ring system made of one six-membered and two five-membered rings). However, one detail has remained unknown: the stereochemistry at one of the carbon atoms of the six-membered ring. The four bonds of a carbon atom point toward the corners of a tetrahedron. If there are four different bonding partners, there are two possible spatial arrangements possible, which are mirror images of each other. This type of carbon center is called “chiral”.
One of the two possible versions of the nupharamine, the cis-trans form, has previously been produced enantioselectively. The German team has now achieved the enantioselective total synthesis of both versions—the all cis form for the first time. To do this they used a carbohydrate as a chiral auxiliary. This is a molecule that is attached to a starting material in order to shield one side of the molecule in subsequent reaction steps so that only the desired stereochemical form of the product is formed.
Spectroscopic and mass-spectrometric analyses of both synthetic products and the nupharamine isolated from natural castoreum showed that the all-cis form is identical to the natural product.
Angewandte Chemie International Edition, doi: 10.1002/anie.200805606
Further reports about: > Angewandte Chemie > Canadian beaver > Castoreum > Epilepsy > beaver > chemist > cramps > enantiomerically pure nupharamine alkaloids > fat- and pheromone-containing gland secretions > hysteria > mass-spectrometric analyses > methylindolizidine > nervousness > nupharamine alkaloids
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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19.07.2018 | Life Sciences | <urn:uuid:250ad86f-2663-4a43-8c49-3cff6020e7f6> | 3.421875 | 1,367 | Content Listing | Science & Tech. | 34.366583 | 95,623,679 |
Unless it does more, the United States probably will fall short of goals set under last year's Paris agreement to dramatically reduce emissions of heat-trapping gases, according to a new study.
The U.S. pledged to reduce its greenhouse gas emissions in 2025 by 26 to 28 percent below 2005 levels. But taking into account current efforts by state and local governments, the nation will only reach about four-fifths of that goal, according to a study in Monday's Nature Climate Change.
Looking at all types of greenhouse gases from energy and other sources— carbon dioxide, methane, nitrous oxide, and various fluorocarbons— two scientists at the U.S. Department of Energy's Lawrence Berkeley National Lab figure the U.S. will have to cut about 1,660 million tons of annual emissions. But current, proposed and even less concrete policies would only reduce about 1,330 million tons, leaving a gap around 330 million tons, they calculated.
The statistics have large margins of errors of plus or minus of hundreds of million tons.
"We can't get there with our current set of policies," said study lead author Jeffrey Greenblatt, a senior scientist at the national lab. "We would fall short of the target if there is no further action."
That doesn't mean that the U.S. can't reach its goal, it's just it has to do more and it can, Greenblatt said. He said he was optimistic that with more action the U.S. could come close to the 26 percent goal, if not achieve it.
The biggest reduction that Greenblatt and his colleague Max Wei calculate would come from the Obama administration's clean power plan that would cut carbon pollution from power plants, mostly coal. But that plan is on hold in the courts. If it doesn't go into effect, it will be even harder for the U.S. to reach its Paris goal, Greenblatt said. It's also a policy that Republicans, including Donald Trump, have vowed to repeal if they win.
Greenblatt and Wei have counted on gains from that policy, but it's still not enough.
So how could the U.S. get to its goal? Greenblatt and Wei briefly looked at a dozen possible ways, but none of them individually would bring huge reductions.
"I think it's going to be a variety of smallish efforts to get there," Greenblatt said.
By looking at sectors besides energy, and at all greenhouse gases—not just carbon dioxide, which has fallen dramatically because of a switch from coal power to natural gas for electricity, mostly because of lower gas prices—Greenblatt's reaches conclusions that are less optimistic than some advanced by others.
Six outside experts said the study's conclusions are both correct and not surprising.
Even if the courts uphold the Obama power plan, the delay makes it more difficult to cut carbon pollution in time, said MIT management professor John Sterman, who also founded a program that models climate emissions and goals. And the low cost of gasoline is prompting more driving, making it harder to reduce pollution.
"The U.S., states and cities will need to adopt more ambitious policies and soon to be able to fulfill our commitment under the Paris agreement," Sterman wrote in an email. But he said what is even more important is that the Paris deal "is not strong enough."
"To avoid the worst consequences of climate change, the U.S. and an all nations must cut emissions sooner and by more than called for under the Paris agreement," Sterman wrote. "There's simply no time to lose."
Nigel Purvis, a top environmental diplomat in the Bill Clinton and George W. Bush administrations and president of the non-governmental organization Climate Advisers , said that's why the U.S. goals are ambitious: "We didn't know how to get to the moon when JFK declared the moonshot but we worked hard, innovated and succeeded. The next administration will need to do the same to make sure the United States meets its climate goals."
Explore further: New ideas needed to meet California's 2050 greenhouse gas targets, study reports
Nature Climate Change, nature.com/articles/doi:10.1038/nclimate3125 | <urn:uuid:6ddad7e1-7ba3-4c20-84ac-327f9207d182> | 3.390625 | 873 | News Article | Science & Tech. | 61.588544 | 95,623,691 |
Introduction: Send Email Using Python!
In this beginner tutorial I will show you how to use Python programming language to write a simple command line app for sending emails via Gmail!
You will only need 11 lines of code!
Step 1: Download Python
Download Python 3.6.0 from https://www.python.org/downloads/
Step 2: Install Python & Add to Path
Open up the python installer you just downloads.
Click install, but make sure to check the checkboxes that say "Add Python to PATH" and "Install Pip"
Step 3: Install SMTPLib
- Open up your computer's command prompt.
On my Windows PC, this is done by going to Start, then typing in "CMD", clicking the "CMD" app to open it up.
2. In the command prompt, type in:
pip install smtplib
Then hit enter.
It will then install the library needed to connect Gmail to Python.
Step 4: Configure Gmail
- While logged into your gmail at gmail.com, go to https://myaccount.google.com/security
- Scroll down to the part that says "Allow less secure apps"
- Turn ON "allow less secure apps".
If you don't want to make your main gmail less secure, or if you don't already have gmail, then sign up for a new gmail solely for this purpose.
Step 5: Download the Python Script
Download the attached gmailpython.py file to a location on your computer that is easy to remember.
Or, simply copy the identical code below and paste it into your favorite text editor, then save it as "gmailpython.py" with UTF-8 encoding:
import smtplib gmailaddress = input("what is your gmail address? \n ") gmailpassword = input("what is the password for that email address? \n ") mailto = input("what email address do you want to send your message to? \n ") msg = input("What is your message? \n ") mailServer = smtplib.SMTP('smtp.gmail.com' , 587) mailServer.starttls() mailServer.login(gmailaddress , gmailpassword) mailServer.sendmail(gmailaddress, mailto , msg) print(" \n Sent!") mailServer.quit()
Step 6: Run the Script!
Open up command prompt the same way you did earlier.
type in cd ____
with the path to gmailpython.py replacing the blank line.
For example, on my laptop the command is
Hit enter, then type in
And hit enter again.
The command line app will now load, and it will prompt you for the your login details, your message, and who you want to send the message to!
Step 7: How It Works
That line above loads to smtplib library, which adds gmail integration to python.
gmailaddress = input("what is your gmail address? \n ") gmailpassword = input("what is the password for that email address? \n ") mailto = input("what email address do you want to send your message to? \n ") msg = input("What is your message? \n ")
These lines display a prompt for input, and store your answers in variables named "gmailaddress", "gmailpassword", "mailto", and "msg". Think of variables as nicknames for your input.
The "/n" tells the script to display a new line before the next command.
mailServer = smtplib.SMTP('smtp.gmail.com' , 587) mailServer.starttls()
The part above sets up the connection to the gmail mail server.
mailServer.login(gmailaddress , gmailpassword)
That part logs Python in to your Gmail account, taking the info from the variables that store your previous answers.
mailServer.sendmail(gmailaddress, mailto , msg)
That part sends the email message using the info from the variables that store your info.
print(" \n Sent!")
That part replies "Sent!" in the command line so you can know the code made it to that point.
Note: In Python 2.7, you don't need the parentheses around the quotes. We are using Python 3.6, which does require parentheses.
The final part quits the connection to the mail server.
Step 8: That's All!
I hope this was interesting and educational to you.
GaneshL6 made it! | <urn:uuid:33681cee-160c-4fc4-90dc-ef6ff780f68c> | 3.15625 | 981 | Tutorial | Software Dev. | 77.56288 | 95,623,705 |
A draft analysis of three UN scientific reports regarding global warming has concluded that by the year 2050, greenhouse gas emissions must be drastically reduced in order to avoid climate catastrophe.
The report suggests that reduction targets need to be set at between 40% and 70% lower than 2010 levels in order to avoid long lasting global warming damage.
Initially seen by Reuters, the report, published by the UN’s Intergovernmental Panel on Climate Change (IPCC), comes ahead of a climate change summit in Paris next year. Attending members of over 200 countries will be expected to sign an agreement that must lead to the relevant reductions.
According to the draft, which is due for publication in Copenhagen on November 2nd, “Deep cuts in greenhouse gas emissions to limit warming to 2C […] remain possible, yet will entail substantial technological, economic, institutional, and behavioural challenges.”
These cuts will primarily come from reductions in fossil fuel burning, which will require the tripling of investment and development in renewable energies like wind and solar, and nuclear power, the report said.
Global warming has already caused damage on all seven continents, according to the IPCC, who say there is a 95% chance that the warming has been caused by human activity.
“Human influence on the climate system is clear, and is estimated to have been the dominant cause of the warming observed since 1950,” the draft said.
Climate change has caused more extremes, in both heat and rainfall, harming food production and causing droughts which has affected crop yields. Unchecked climate change has consequently damaged economic growth, which has indirectly increased poverty rates – causing greater global conflict.
Cuts to fossil fuel emissions would affect the GDP of countries, but global GDP would be effected by a drop of just 0.06% per year from 2014, the report states.
The report was finished earlier this year in June, but has been continuously edited by researchers, “undergoing thorough revision”, said an IPCC spokesperson. It will be completed when a final draft is signed off by governments this month.
Photo source: ramzi hashisho via freeimages
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Common name: Rio Grande Chub
available through www.itis.gov
Identification: Woodling (1985); Sublette et al. (1990); Page and Burr (1991).
Size: 18 cm.
Native Range: Upper Rio Grande and Pecos River systems, Colorado and New Mexico; isolated population in Davis Mountains (Pecos River system), Texas (Page and Burr 1991).
Puerto Rico &
Interactive maps: Point Distribution Maps
Native range data for this species provided in part by NatureServe
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Gila pandora are found here.
Table last updated 5/25/2018
† Populations may not be currently present.
Means of Introduction: Unknown.
Status: Reported from New Mexico from an area thought to be outside its native range.
Impact of Introduction: Unknown.
Revision Date: 6/26/2000
Peer Review Date: 4/1/2016
Fuller, P., 2018, Gila pandora (Cope, 1872): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=541, Revision Date: 6/26/2000, Peer Review Date: 4/1/2016, Access Date: 7/15/2018
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information. | <urn:uuid:00ee06d8-917f-4170-a68e-ae7776eb3b65> | 2.875 | 422 | Structured Data | Science & Tech. | 52.251429 | 95,623,733 |
Measurement of Ambient Concentration and Surface Fluxes of O3, SO2 NOx and TSP in Uludag National Park
Uludag station is situated in the northwest part of the Turkey at longitude 40° 101 N, and latitude 20° 081 E (Fig. 9.7.1). The station is operated by the Middle East Technical University and Uludag University. Based on the fact that fluctuation of ambient concentration results in the changes in the vertical fluxes, first ambient concentration data were obtained. Starting in March 1993, measurements of O3, NOx, SO2 and TSP concentration at ground level have been made continuously. Meteorological parameters wind direction, wind speed, temperature and humidity were also measured continuously. Hard winter conditions at the Uludag mountain site (average snow-fall is about 1.5m) resulted in some technical problems with the instruments, which in turn resulted in some gaps in the data.
KeywordsDiurnal Variation Vertical Flux Photochemical Production Trace Substance Wind Sector
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- 1.N.A. Kelly, G.T., Wolf and A.M. Ferman, Atmos. Environ., 15 (1984) 561.Google Scholar
- 5.S.G. Tuncel, A. Baykal, G. Tuncel and U. Özer, Measurement of NOx, SO2, SPM and O3 at a High Altitude Station in Northwestern Turkey, Israel J. Chem., 34 (1995), 403.Google Scholar
- 6.NAPAP, The National Acid Precipitation assessment Program III, (1987), 4, Atmospheric Processes.Google Scholar | <urn:uuid:b05523a3-9dce-44fc-bf37-f9179b9170cd> | 2.5625 | 355 | Academic Writing | Science & Tech. | 57.859198 | 95,623,735 |
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A Comparison of Simulated and Field-Derived Leaf Area Index (LAI) and Canopy Height Values from Four Forest Complexes in the Southeastern USA
Iiames, J., E. Cooter, D. Schwede, AND J. Williams. A Comparison of Simulated and Field-Derived Leaf Area Index (LAI) and Canopy Height Values from Four Forest Complexes in the Southeastern USA. Forests. MDPI AG, Basel, Switzerland, 9(1):26, (2018).
Vegetative leaf area is a critical input to models that simulate human and ecosystem exposure to atmospheric pollutants. Leaf area index (LAI) can be measured in the field or numerically simulated, but all contain some inherent uncertainty that is passed to the exposure assessments that use them. LAI estimates for minimally managed or natural forest stands can be particularly difficult to develop as a result of interspecies competition, age and spatial distribution. Satellite-based LAI estimates hold promise for retrospective analyses, but we must continue to rely on numerical models for alternative management analysis. Our objective for this study is to calculate and validate LAI estimates generated from the USDA Environmental Policy Impact Climate (EPIC) model (a widely used, field-scale, biogeochemical model) on four forest complexes spanning three physiographic provinces in Virginia and North Carolina. Measurements of forest composition (species and number), LAI, tree diameter, basal area, and canopy height were recorded at each site during the 2002 field season. Calibrated EPIC results show stand-level temporally resolved LAI estimates with R2 values ranging from 0.69 to 0.96, and stand maximum height estimates within 20% of observation. This relatively high level of performance is attributable to EPIC’s approach to the characterization of forest stand biogeochemical budgets, stand history, interspecies competition and species-specific response to local weather conditions. We close by illustrating the extension of this site-level approach to scales that could support regional air quality model simulations
Open access article published in the journal, Forests.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
EXPOSURE METHODS & MEASUREMENT DIVISION | <urn:uuid:3ba91f51-9ac3-439d-97c2-1355493ca4f5> | 2.671875 | 517 | Academic Writing | Science & Tech. | 17.977563 | 95,623,762 |
Data Used in the Book
Hydrologic data discussed in this book include flow, rainfall, temperature, tree-ring data and Palmer’s Drought Severity Index (PDSI) Series. Flow data are obtained from the United States Geological Survey (USGS, 1992) and Earth Info (1993) data bases. Both rainfall and temperature data are obtained as two different sets. One set is obtained from the Historical Climatology Network (HCN) database (Nelson and Boden, 1993) for individual stations. Another set is obtained from the National Climatic Data Center (NCDC) database (NCDC, 1991) for state divisions. Precipitation and temperature data are also taken from Earth Info (1993) database. Tree-ring data are obtained from the National Oceanic and Atmospheric Administration database (NOAA, 1997). The PDSI data are obtained from National Climatic Data Center, NOAA.
KeywordsNational Climatic Data Multiple Segment Earth Info Synthetic Series Flow Time Series
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As Star Wars: The Force Awakens breaks box office records worldwide, Jessica Rowbury discusses whether photonics technologies could ever be used to build a real-life lightsaber
The lightsaber, or laser sword, was first introduced to cinema goers in 1977 in Star Wars Episode IV: A New Hope as the weapon used by the Jedi and the Sith.
Although fictional, few can deny that the lightsaber is an ingenious invention. It is compact and lightweight, yet can cut through virtually anything – from metal to human flesh. On screen, lightsabers appear as glowing blades that can deflect blaster bolts and that do not pass through one another during battles.
So, with the technological advances seen in photonics, would it ever be possible to create a real-life lightsaber?
The obvious choice for building a laser sword would be to use a laser, particularly as manufacturers have been striving towards more efficient and compact machines in recent years.
One clear issue with using lasers is that, because photons are considered to be massless and incapable of interacting with each other, the beams would not clash against one another like in the Star Wars battle scenes. ‘Light doesn’t like to interact with itself, so two beams of light would actually pass through each other – which wouldn’t be very useful in a fight,’ explained physics researcher Martin Ringbauer at the University of Queensland, Australia, in a recent announcement.
However, there has been research suggesting that photons can in fact interact, and even be joined, with one another. In September, scientists from the National Institute of Standards and Technology (NIST) in the United States took a step towards building objects out of photons.
Their work builds on research from 2013, which saw Harvard and MIT scientists create photonic molecules that the team said could behave like lightsabers, with the photons pushing and deflecting each other but staying linked.
To do this, the MIT/Harvard researchers pumped rubidium atoms into a vacuum chamber, and then cooled the vacuum to a few degrees above absolute zero. Weak laser light was then shone through the rubidium-filled vacuum; as individual photons travelled through the medium, they lost energy to the rubidium atoms, slowing them down. When the researchers used the laser to fire two photons, instead of one, they found that the photons became a two-photon molecule by the time it left the medium.
By tweaking a few parameters of MIT/Harvard’s binding process, NIST scientists demonstrated that photons could travel side by side, a specific distance from each other; the arrangement is similar to the way that two hydrogen atoms sit next to each other in a hydrogen molecule.
‘We’re learning how to build complex states of light that, in turn, can be built into more complex objects. This is the first time anyone has shown how to bind two photons a finite distance apart,’ NIST’s Alexey Gorshkov said.
So, if it is possible to build a molecule of light, why not a sword?
Although the research seems to be moving in the right direction, the challenges associated with integrating a laser into a handheld weapon are numerous.
Firstly, a laser has no fixed length. One solution could be to place a small mirror at the tip of the blade, but ‘can you imagine how embarrassing it would be to show up in the battlefield with a lightsaber surrounded by a whole supporting structure for a tiny mirror at its end? Apart from being really fragile, such a blade wouldn’t be able to hurt anyone,’ wrote Gianluca Sarri, lecturer at the Queen’s University Belfast, Ireland, in an article for The Conversation.
But even if a beam of light could be controlled, the next problem is generating enough energy in the small hilt of a lightsaber to power a laser.
Thanks to better cooling techniques, safety, and improved efficiency, industrial laser systems can now reach power levels of more than 100kW. However, the power supply for these lasers is huge and would certainly not fit in the tiny hilt of a lightsaber.
In addition, just thinking about the cooling mechanism that would be needed to prevent the hilt from melting into the holder’s hand is enough to give any laser supplier a headache.
Clearly, none of these characteristics describe a lightsaber; therefore it is very unlikely that laser swords will be seen in gift shops anytime soon.
However, an alternative technology could be plasma. This material is created through a process called ionisation, whereby a gas’s atoms are stripped of its electrons, causing the plasma to glow. A neon light is an example of plasma – it consists of a tube filled with neon gas in a plasma state.
Hot plasmas emit different colours depending on the gas they consist of. This characteristic could thus be used to create the different lightsabers seen in the Star Wars films; chlorine plasma, which emits green light, could yield the green weapons used by the Jedi, while the red lightsabers of the Sith could be created using helium, which emits in the red-to-violet region of the spectrum.
And because plasma conducts electricity, it can transport large electrical currents to the target material, causing it to heat up and melt. As stated in Sarri's article, in theory, a small but powerful power supply integrated into the hilt could be attached to a long, tiny filament that carries the electrical discharge and circulates gas around it. When the electrical current is turned on, the filament would become incandescent and the gas around it would turn into colourful, glowing plasma.
Don Lincoln, senior scientist from the United States’ Fermi National Accelerator Laboratory, calculated the energy a lightsaber would need to melt a blast door, which he described in an article on Space.com. Lincoln watched a sequence from Star Wars Episode I: The Phantom Menace showing Qui-Gon Jinn cutting through a heavy blast door – so, by assuming that the door was made of steel, and measuring the time it took, he estimated that 20MW of power would be required. This is enough power to run 14,000 average American houses.
Clearly, a power source of that density is beyond current technology. In addition, those sorts of temperatures would not only melt the door, but the Jedi’s hands. ‘So some sort of force field must keep in the heat,’ Lincoln said in the article. But ‘the blades appear to be using optical wavelengths, so the force field must contain infrared radiation, but let visible light through,’ he added.
‘Such technical investigations lead inevitably to invocations of unknown technologies. But, once you've done that, it is easy to simply say that the lightsaber consists of some kind of concentrated energy stored in a force field,’ Lincoln wrote.
So, how likely is it that a real-life lightsaber will ever be built? Although it seems obvious that they won’t be found in shops in time for next Christmas, the answer seems more complex than a simple ‘no’. | <urn:uuid:8ac0a9ad-0d8d-443d-af01-cbf5118c80cb> | 3.46875 | 1,458 | Truncated | Science & Tech. | 42.524629 | 95,623,768 |