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8 May , 2018 by Matt Williams
A new study by an international team of scientists ventures that the Earth has had several moons in the past, all of which crashed to Earth over time.
Astronomy, Space Exploration
7 May , 2018 by Matt Williams
According to a new study, one of the greatest health risks posed by missions to the Moon could be the health effects of breathing lunar dust.
Colonization, esa, Geology
15 Mar , 2018 by Matt Williams
A team that participated in the ESA’s Pangaea-X program recently produced the largest 3D image of a cave system in Spain, and the technology could be used to map out lava tubes on the Moon and Mars too
4 Jan , 2018 by Matt Williams
As it makes its way towards the asteroid Bennu, the OSIRIS-REx mission continues to provide us with breathtaking images of our planet.
Astronomy, Extrasolar Planets, Kepler Mission
25 Oct , 2017 by Matt Williams
A new study by an astrophysicists from the Max Planck Institute for Solar System Research shows that the first exomoon ever discovered could actually be a gas giant moon!
22 Aug , 2017 by Matt Williams
A new study of the “Rusty Rocks” returned by the Apollo 16 mission suggest that the Moon’s interior is very dry, contrary to what recent studies have claimed
10 Aug , 2017 by Matt Williams
A new study by researchers from MIT has cast doubt on when the Moon lost its magnetic field, indicating that it lasted for another 1 billion years
25 Jul , 2017 by Matt Williams
A new study by a team from Brown University has revealed evidence of widespread water on the lunar surface, which could also point towards water in the interior.
Astronomy, Guide to Space
10 Jul , 2017 by Matt Williams
A single day on the Moon lasts the equivalent of 29.5 Earth days, which is the result of its tidally-locked orbit with Earth, and Earth’s orbit around the Sun.
5 Jul , 2017 by Matt Williams
A team of MIT graduate students was recently honored by NASA’s RASC-AL competition for their MARINA space habitat design
Space stories from across the internet, sent to you by email. | <urn:uuid:ab2b869e-4dba-4272-bc1a-6794820a7bc8> | 3.453125 | 472 | Content Listing | Science & Tech. | 35.75471 | 95,508,457 |
The Fourier transform plays an important role in science and technology The one-dimensional Fourier transform F, for instance, connects a time signal f(t) with its complex spectral function A(v) which gives information about the frequency content of the signal.
KeywordsSpatial Frequency Amplitude Spectrum Circular Aperture Halftone Image Fourier Plane
Unable to display preview. Download preview PDF.
- 9.1M. Born, E. Wolf: Principles of Optics (Pergamon, Oxford 1980)Google Scholar
- 9.2J. W. Goodman: Introduction to Fourier Optics (McGraw-Hill, New York 1968)Google Scholar | <urn:uuid:c4052aa2-0573-40e6-8c86-dc213f42a71b> | 3.140625 | 140 | Truncated | Science & Tech. | 52.133678 | 95,508,473 |
Integration of Transcendental Functions
Having developped the required machinery in the previous chapters, we can now describe the integration algorithm. In this chapter, we define formally the integration problem in an algebraic setting, prove the main theorem of symbolic integration (Liouville’s Theorem), and describe the main part of the integration algorithm.
KeywordsElementary Function Algebraic Closure Integration Algorithm Transcendental Function Logarithmic Derivative
Unable to display preview. Download preview PDF. | <urn:uuid:244a5f0f-426c-433c-87f8-b8dc7b265bc9> | 2.578125 | 107 | Truncated | Science & Tech. | 0.508859 | 95,508,474 |
184.108.40.206. Late Holocene Neoglacial Fluctuations
Records for the last 4,500 years generally indicate that temperatures were lower than the Holocene thermal maximum. A general cooling, known as the Iron Age neoglaciation, occurred between 2,500 and 4,500 years ago. A moderate climate amelioration followed near the dawn of the Roman Empire, before a return to cooler climates during the second half of the first millennia A.D. (the Dark Ages). Thence followed the Medieval optimum (1100 to 1300 A.D.), in which European temperatures reached some of the warmest levels for the last 4,000 years. | <urn:uuid:d56ea802-ad5a-445e-8693-ff480cfdee50> | 3.140625 | 138 | Knowledge Article | Science & Tech. | 59.246539 | 95,508,527 |
12 July 2018
Tiny molecular sensor within cells
Published online 30 November 2016
A group of researchers have come up with a way to assemble a protein sensor inside plant cells to detect previously unclear chemical signalling.
A team of researchers devised a tiny sensor that operates within the plant cell to detect, for the first time, an important class of plant signalling molecules1.
Strigolactones are a group of compounds, closely related in chemical structure, that plant cells use to regulate various aspects of growth and development and are involved in symbiosis with root fungi, but are also used by weeds to recognize host roots incidentally leading to crop yield losses.
When strigolactones are sensed by the cell, a signalling cascade is initiated which culminates in the degradation of a specific target protein called SMLX, as a part of the response process. But the details of how strigolactones signal different responses remain obscure.
Capitalizing on this knowledge, a team of researchers from Germany and Saudi Arabia designed a sensor based on SMLX degradation to better understand strigolactone signalling.
Their sensor is a protein molecule containing SMLX fused to a light-emitting protein called firefly luciferase. This fusion protein is in turn connected via a peptide that cleaves itself in cells to another light-emitting protein called REN luciferase, which emits at a different wavelength. This way, the measured firefly luciferase light signal which drops upon SMLX destruction can be normalized to the unaffected REN luciferase signal for the purpose of monitoring SMLX degradation.
The team encoded this design in the form of DNA, which they could inject into immature plant cells, where the cells’ protein expression machinery would then translate it to assemble the protein sensor.
The team showed that, as expected, cells exposed to strigolactones showed a decrease in the light signal from the firefly luciferase. They went on to demonstrate that by using different mutant backgrounds for candidate members of strigolactone signalling pathways and monitoring SMLX degradation, that new strigolactone-specific receptors in the cell can be identified to better understand this process.
- Samodelov, S. L. et al. StrigoQuant: a genetically encoded biosensor for quantifying strigolactone activity and specificity. Sci. Adv. 2, e1601266 (2016). | <urn:uuid:65f41ac2-edfd-43f2-9d51-ca2e0ac9b342> | 3.359375 | 499 | Truncated | Science & Tech. | 27.791091 | 95,508,539 |
Potential Indirect Effects of Humans on Water Quality
News Oct 16, 2015
A recently published study shows that a newly studied class of water contaminants that is known to be toxic and hormone disrupting to marine animals is present likely due in part to indirect effects of human activity. The contaminants are more prevalent in populated areas in the San Francisco Bay, suggesting that human impacts on nutrient input or other changes in water quality may enhance natural production.
The study by an international team of researchers was led by the University of Minnesota. Collaborators on the project include the San Francisco Estuary Institute, Science Museum of Minnesota’s St. Croix Watershed Research Station, ETH Zurich, and Pace Analytical.
The contaminants studied are hydroxylated polybrominated diphenyl ethers (OH-BDEs) and are found around the world from the U.S. to Sweden to China. Recent evidence shows that the production of OH-BDEs occurs naturally from marine bacteria and algae. Levels of these chemicals have been increasing over time and have been detected in Baltic salmon, polar bears, bald eagles and human plasma. Previous studies have shown disruption of thyroid function and neurological development due to OH-BDEs.
“Even though OH-BDEs are produced naturally, it shows that natural does not equal safe,” said lead researcher William Arnold, a professor in the University of Minnesota Department of Civil, Environmental and Geo- Engineering. “We need to find out why they are increasing.”
The researchers looked at whether there might be a tie to flame retardants used extensively since the 1970s called polybrominated diphenyl ethers (PBDEs). Manufacturing facilities, sewage/wastewater, and precipitation are all known sources of PBDE pollution. Researchers also analyzed the popular antibacterial agent triclosan, which is chemically similar to OH-TriBDE. Because the onset of production of triclosan and PBDEs followed a similar timeline, the researchers hypothesized that the study would indicate common human-related pollution as the cause of OH-BDEs.
From 2012-14, the researchers analyzed surface sediment and sediment cores in the San Francisco Bay, Point Reyes National Seashore and Minnesota lakes to determine a possible source for the increasing OH-BDEs. They found higher concentrations in San Francisco Bay compared to Point Reyes National Seashore, a marine system with limited human impact. They found no OH-BDEs in the freshwater lakes of Minnesota.
The findings suggest that higher nutrients and water temperatures in the urban area of San Francisco Bay may influence microbial activity and increase OH-BDE levels. Small amounts of OH-BDEs were detected in the less populated Point Reyes National Seashore area, which accounted for a normal level of natural production.
“We were surprised to find no OH-BDEs in the freshwater of Minnesota because flame retardants are used in Minnesota. This showed us that this is likely not the cause of OH-BDEs,” Arnold said. “But that’s not the end of the story. There were still more OH-BDEs in the populated areas of San Francisco Bay, which highlights the complicated nature of human activity and how it affects our aquatic systems.”
Getting to Know the Microbes that Drive Climate ChangeNews
A new understanding of the microbes and viruses in the thawing permafrost in Sweden may help scientists better predict the pace of climate change.READ MORE
Perinatal Exposure to Phthalates Results in Lower Number of Neurons and Synapses in the Medial Prefrontal CortexNews
Phthalates - chemicals used in plastics belonging to the same class as Bisphenol A (BPA) - can potentially interfere with hormones important for the developing brain.READ MORE
‘Nitrogen Footprint’ Tool Offers Guide to Pollution ReductionNews
Researchers have helped create the first tool to calculate the ‘nitrogen footprint’ of an organisation. The tool will provide a guide to sustainability and pollution reduction for daily activities such as food consumption, travel and energy use.READ MORE | <urn:uuid:500f6426-3964-4c09-a073-f6bf16f09fcd> | 2.796875 | 855 | Content Listing | Science & Tech. | 25.295302 | 95,508,544 |
Roy J. MEYERS
Science & Mechanics ( January, year unknown, ca. 1930 )
Compressed Air Motor Runs Car
Either the era of "free air" is about to come to an end, or the cost of motoring is about to be reduced to practically nothing. In an amazing demonstration conducted recently in Los Angeles a standard automobile chasis, powered with a newly-developed compressed air motor, whizzed around the city streets at not one cent of cost to the driver for fuel.
The engine, which is the result of six years of research by Roy J. Meyers, resembled in general appearance a radial airplane motor. It is mounted in an upright position in the same space occupied by a gasoline motor in standard cars.
A side view of the compressed air car, showing the four fuel tanks which will drive the car 500 miles at a speed of 35 miles per hour. The engine requires no cooling system, no ignition system, no carburetor, or the hundreds of moving parts included in a standard gasoline engine.
A front view, showing how the compressed air engine is mounted. An electric heater, operated by a batter and generator, heats the air until it attains a pressure of 200 lbs. As the warm air goes through the engine and is cooled, it is recovered and drawn into a compressing chamber, where is is heated again and returned to the tank.
Your Support Maintains this Service --
The Rex Research Civilization Kit
... It's Your Best Bet & Investment in Sustainable Humanity on Earth ...
Ensure & Enhance Your Survival & Genome Transmission ...
Everything @ rexresearch.com on a Data DVD ! | <urn:uuid:cadbc024-9ade-449f-8a61-2fdcb2bce8cf> | 3.0625 | 339 | Knowledge Article | Science & Tech. | 56.74668 | 95,508,550 |
In combinatorics, an expander graph is a sparse graph that has strong connectivity properties, quantified using vertex, edge or spectral expansion as described below. Expander constructions have spawned research in pure and applied mathematics, with several applications to complexity theory, design of robust computer networks, and the theory of error-correcting codes.
- 1 Definitions
- 2 Relationships between different expansion properties
- 3 Constructions
- 4 Applications and useful properties
- 5 See also
- 6 Notes
- 7 References
- 8 External links
Intuitively, an expander is a finite, undirected multigraph in which every subset of the vertices that is not "too large" has a "large" boundary. Different formalisations of these notions give rise to different notions of expanders: edge expanders, vertex expanders, and spectral expanders, as defined below.
A disconnected graph is not an expander, since the boundary of a connected component is empty. Every connected graph is an expander; however, different connected graphs have different expansion parameters. The complete graph has the best expansion property, but it has largest possible degree. Informally, a graph is a good expander if it has low degree and high expansion parameters.
The edge expansion (also isoperimetric number or Cheeger constant) h(G) of a graph G on n vertices is defined as
In the equation, the minimum is over all nonempty sets S of at most n/2 vertices and ∂S is the edge boundary of S, i.e., the set of edges with exactly one endpoint in S.
The vertex isoperimetric number (also vertex expansion or magnification) of a graph G is defined as
where is the outer boundary of S, i.e., the set of vertices in with at least one neighbor in S. In a variant of this definition (called unique neighbor expansion) is replaced by the set of vertices in V with exactly one neighbor in S.
The vertex isoperimetric number of a graph G is defined as
where is the inner boundary of S, i.e., the set of vertices in S with at least one neighbor in .
When G is d-regular, a linear algebraic definition of expansion is possible based on the eigenvalues of the adjacency matrix A = A(G) of G, where is the number of edges between vertices i and j. Because A is symmetric, the spectral theorem implies that A has n real-valued eigenvalues . It is known that all these eigenvalues are in [−d, d].
Because G is regular, the uniform distribution with for all i = 1, ..., n is the stationary distribution of G. That is, we have Au = du, and u is an eigenvector of A with eigenvalue λ1 = d, where d is the degree of the vertices of G. The spectral gap of G is defined to be d − λ2, and it measures the spectral expansion of the graph G.
It is known that λn = −d if and only if G is bipartite. In many contexts, for example in the expander mixing lemma, a bound on λ2 is not enough, but indeed it is necessary to bound the absolute value of all the eigenvalues away from d:
Since this is the largest eigenvalue corresponding to an eigenvector orthogonal to u, it can be equivalently defined using the Rayleigh quotient:
is the 2-norm of the vector .
The normalized versions of these definitions are also widely used and more convenient in stating some results. Here one considers the matrix , which is the Markov transition matrix of the graph G. Its eigenvalues are between −1 and 1. For not necessarily regular graphs, the spectrum of a graph can be defined similarly using the eigenvalues of the Laplacian matrix. For directed graphs, one considers the singular values of the adjacency matrix A, which are equal to the roots of the eigenvalues of the symmetric matrix ATA.
Relationships between different expansion properties
The expansion parameters defined above are related to each other. In particular, for any d-regular graph G,
Consequently, for constant degree graphs, vertex and edge expansion are qualitatively the same.
When G is d-regular, there is a relationship between the isoperimetric constant h(G) and the gap d − λ2 in the spectrum of the adjacency operator of G. By standard spectral graph theory, the trivial eigenvalue of the adjacency operator of a d-regular graph is λ1=d and the first non-trivial eigenvalue is λ2. If G is connected, then λ2 < d. An inequality due to Dodziuk and independently Alon and Milman states that
Similar connections between vertex isoperimetric numbers and the spectral gap have also been studied:
Asymptotically speaking, the quantities , , and are all bounded above by the spectral gap .
There are three general strategies for constructing families of expander graphs. The first strategy is algebraic and group-theoretic, the second strategy is analytic and uses additive combinatorics, and the third strategy is combinatorial and uses the zig-zag and related graph products. Noga Alon showed that certain graphs constructed from finite geometries are the sparsest examples of highly expanding graphs.
Algebraic constructions based on Cayley graphs are known for various variants of expander graphs. The following construction is due to Margulis and has been analysed by Gabber and Galil. For every natural number n, one considers the graph Gn with the vertex set , where : For every vertex , its eight adjacent vertices are
Then the following holds:
Theorem. For all n, the graph Gn has second-largest eigenvalue .
By a theorem of Alon and Boppana, all large enough d-regular graphs satisfy , where λ is the second largest eigenvalue in absolute value. Ramanujan graphs are d-regular graphs for which this bound is tight. That is, they satisfy . Hence Ramanujan graphs have an asymptotically smallest possible λ. They are also excellent spectral expanders.
Lubotzky, Phillips, and Sarnak (1988), Margulis (1988), and Morgenstern (1994) show how Ramanujan graphs can be constructed explicitly. By a theorem of Friedman (2003), random d-regular graphs on n vertices are almost Ramanujan, that is, they satisfy
with probability as n tends to infinity.
Applications and useful properties
The original motivation for expanders is to build economical robust networks (phone or computer): an expander with bounded valence is precisely an asymptotic robust graph with the number of edges growing linearly with size (number of vertices), for all subsets.
Expander graphs have found extensive applications in computer science, in designing algorithms, error correcting codes, extractors, pseudorandom generators, sorting networks (Ajtai, Komlós & Szemerédi (1983)) and robust computer networks. They have also been used in proofs of many important results in computational complexity theory, such as SL = L (Reingold (2008)) and the PCP theorem (Dinur (2007)). In cryptography, expander graphs are used to construct hash functions.
The following are some properties of expander graphs that have proven useful in many areas.
Expander mixing lemma
The expander mixing lemma states that, for any two subsets of the vertices S, T ⊆ V, the number of edges between S and T is approximately what you would expect in a random d-regular graph. The approximation is better the smaller is. In a random d-regular graph, as well as in an Erdős–Rényi random graph with edge probability d/n, we expect edges between S and T.
More formally, let E(S, T) denote the number of edges between S and T. If the two sets are not disjoint, edges in their intersection are counted twice, that is,
Then the expander mixing lemma says that the following inequality holds:
where λ is the absolute value of the normalized second largest eigenvalue.
Expander walk sampling
The Chernoff bound states that, when sampling many independent samples from a random variables in the range [−1, 1], with high probability the average of our samples is close to the expectation of the random variable. The expander walk sampling lemma, due to Ajtai, Komlós & Szemerédi (1987) and Gillman (1998), states that this also holds true when sampling from a walk on an expander graph. This is particularly useful in the theory of derandomization, since sampling according to an expander walk uses many fewer random bits than sampling independently.
Expander property of the braingraphs
Using the magnetic resonance imaging (MRI) data of the NIH-funded large Human Connectome Project, it was shown by Szalkai et al. that the graph, describing the anatomical brain connections between up to 1015 cerebral areas, is a significantly better expander in women than in men.
- Hoory, Linial & Widgerson (2006)
- Definition 2.1 in Hoory, Linial & Widgerson (2006)
- Bobkov, Houdré & Tetali (2000)
- Alon & Capalbo (2002)
- cf. Section 2.3 in Hoory, Linial & Widgerson (2006)
- This definition of the spectral gap is from Section 2.3 in Hoory, Linial & Widgerson (2006)
- Dodziuk 1984.
- Alon & Spencer 2011.
- Theorem 2.4 in Hoory, Linial & Widgerson (2006)
- See Theorem 1 and p.156, l.1 in Bobkov, Houdré & Tetali (2000). Note that λ2 there corresponds to 2(d − λ2) of the current article (see p.153, l.5)
- see, e.g., Yehudayoff (2012)
- Alon, Noga (1986). "Eigenvalues, geometric expanders, sorting in rounds, and ramsey theory". Combinatorica. 6: 207–219. doi:10.1007/BF02579382.
- see, e.g., p.9 of Goldreich (2011)
- Theorem 2.7 of Hoory, Linial & Widgerson (2006)
- Definition 5.11 of Hoory, Linial & Widgerson (2006)
- Theorem 5.12 of Hoory, Linial & Widgerson (2006)
- Theorem 7.10 of Hoory, Linial & Widgerson (2006)
- Szalkai, Balazs; Varga, Balint; Grolmusz, Vince (2015). "Graph Theoretical Analysis Reveals: Women's Brains Are Better Connected than Men's". PLoS ONE. 10 (7): e0130045. doi:10.1371/journal.pone.0130045. PMC . PMID 26132764.
- Szalkai, Balázs; Varga, Bálint; Grolmusz, Vince (2017). "Brain size bias compensated graph-theoretical parameters are also better in women's structural connectomes". Brain Imaging and Behavior. doi:10.1007/s11682-017-9720-0. ISSN 1931-7565. PMID 28447246.
Textbooks and surveys
- Alon, N.; Spencer, Joel H. (2011). "9.2. Eigenvalues and Expanders". The Probabilistic Method (3rd ed.). John Wiley & Sons.
- Chung, Fan R. K. (1997), Spectral Graph Theory, CBMS Regional Conference Series in Mathematics, 92, American Mathematical Society, ISBN 0-8218-0315-8
- Davidoff, Guiliana; Sarnak, Peter; Valette, Alain (2003), Elementary number theory, group theory and Ramanujan graphs, LMS student texts, 55, Cambridge University Press, ISBN 0-521-53143-8
- Hoory, Shlomo; Linial, Nathan; Widgerson, Avi (2006), "Expander graphs and their applications" (PDF), Bulletin (New Series) of the American Mathematical Society, 43 (4): 439–561, doi:10.1090/S0273-0979-06-01126-8
- Krebs, Mike; Shaheen, Anthony (2011), Expander families and Cayley graphs: A beginner's guide, Oxford University Press, ISBN 0-19-976711-4
- Ajtai, M.; Komlós, J.; Szemerédi, E. (1983), "An O(n log n) sorting network", Proceedings of the 15th Annual ACM Symposium on Theory of Computing, pp. 1–9, doi:10.1145/800061.808726, ISBN 0-89791-099-0
- Ajtai, M.; Komlós, J.; Szemerédi, E. (1987), "Deterministic simulation in LOGSPACE", Proceedings of the 19th Annual ACM Symposium on Theory of Computing, ACM, pp. 132–140, doi:10.1145/28395.28410, ISBN 0-89791-221-7
- Alon, N.; Capalbo, M. (2002), "Explicit unique-neighbor expanders", The 43rd Annual IEEE Symposium on Foundations of Computer Science, 2002. Proceedings, p. 73, doi:10.1109/SFCS.2002.1181884, ISBN 0-7695-1822-2
- Bobkov, S.; Houdré, C.; Tetali, P. (2000), "λ∞, vertex isoperimetry and concentration", Combinatorica, 20 (2): 153–172, doi:10.1007/s004930070018.
- Dinur, Irit (2007), "The PCP theorem by gap amplification" (PDF), Journal of the ACM, 54 (3): 12–es, doi:10.1145/1236457.1236459.
- Dodziuk, Jozef (1984), "Difference equations, isoperimetric inequality and transience of certain random walks", Trans. Amer. Math. Soc., 284 (2): 787––794, doi:10.2307/1999107.
- Gillman, D. (1998), "A Chernoff Bound for Random Walks on Expander Graphs", SIAM Journal on Computing, Society for Industrial and Applied Mathematics, 27 (4,): 1203–1220, doi:10.1137/S0097539794268765
- Goldreich, Oded (2011), "Basic Facts about Expander Graphs" (PDF), Studies in Complexity and Cryptography: 451–464, doi:10.1007/978-3-642-22670-0_30
- Reingold, Omer (2008), "Undirected connectivity in log-space", Journal of the ACM, 55 (4): Article 17, 24 pages, doi:10.1145/1391289.1391291
- Yehudayoff, Amir (2012), "Proving expansion in three steps", ACM SIGACT News, 43 (3): 67–84, doi:10.1145/2421096.2421115 | <urn:uuid:e288174a-bf8a-4af2-a2ac-ac52a2a369f2> | 2.96875 | 3,374 | Knowledge Article | Science & Tech. | 61.178953 | 95,508,556 |
Paris (AFP) – A food shortage likely caused by climate change is shrinking a South Antarctic fur seal colony and changing the profile of its surviving members, researchers said Wednesday.
South Georgia island’s Antarctic fur seal pups have a lower average birth weight, and there are fewer breeding adults — who hold out longer to reproduce than in the past, according to study results published in the journal Nature.
Only the biggest animals survive to adulthood and reproduce.
These are classic symptoms of long-term food stress, and emerged at the same time that availability of Antarctic krill, small crustaceans which are a fur seal staple, dwindled.
The authors linked this, in turn, to higher sea and air temperatures in the region, and a decline in sea ice.
“Climate change has reduced prey availability and caused a significant decline in seal birth weight,” they wrote.
“We detected a 24-percent decline in the number of breeding females over the past 27 years.”
Prior to this new decline, Antarctic fur seals bounced back from being hunted for their pelt to near extinction in the nineteenth century.
Another common feature of the breeding female seals was high “heterozygosity” — that is the level of diversity in the genes they obtained from their parents.
The characteristic is linked to Darwin’s natural selection theory, as a heterozygous group of individuals carries a wider variety of genes that may allow adaptation to a changing environment through evolution in the future.
Evolution happens when natural selection leads to an increase in the frequency of one or more favourable gene variants in a population.
The team found that, counter-intuitively, evidence of natural selection for heterozygosity was not translating into an evolutionary benefit for the Georgia Island seal population.
Only individual genes can be passed on to offspring, not the complete code and not the trait of heterozygosity itself.
This means that many pups are born to “survival fit” mothers who are not “fit” themselves, and won’t make it to adulthood.
Giant tabular icebergs surrounded by ice floe drift in Vincennes Bay in the Australian Antarctic Territory on January 11, 2008
© AFP/File Torsten Blackwood
“The clock is effectively being reset with each generation,” study co-author Joseph Hoffman of the University of Bielefeld’s Department of Animal Behaviour told AFP by email.
As local food availability has been progressively falling over time, fewer and fewer pups are surviving until breeding age and the population is in decline.
The authors said the findings were important for anticipating how the entire South Georgia ecosystem may react to climate change — including albatrosses, penguins, whales and fish that also hunt krill.
The study results were based on data collected from 1982 to 2012 from individual seals, including their genetics, as well as environmental and climate statistics.
In a comment on the study, zoologists Tim Coulson and Sonya Clegg said it remained to be established whether the seals were unusual in their response to climate change, or whether this was typical.
“Either way, it may be much harder to arrest the ongoing decline in fur seals in the 21st century than it was in the 20th.” | <urn:uuid:04125a05-c7a8-4662-bf49-c928eb7656e7> | 3.515625 | 681 | News Article | Science & Tech. | 29.200393 | 95,508,575 |
|Scope: Global & Europe|
|Scientific Name:||Salmo labrax Pallas, 1814|
|Taxonomic Notes:||Genetic data show that resident trouts from the northern Black Sea basin represent a lineage very different from those of the Atlantic, Mediterranean and Caspian basins, but there is no published morphological comparison. Presently, a single species of Salmo is recognized in the northern Black Sea basin (in addition to the extinct S. schiefermuelleri). A population from upper Vardar (Lipkovska) is tentatively referred to S. labrax; it is superficially distinguished from all Balkan species by its very slightly emarginate caudal. In upper Danube, S. trutta is present and hybrid populations are or might be present in lower Danube, Dniestr, Dniepr and Don.|
|Red List Category & Criteria:||Least Concern (Regional assessment) ver 3.1|
|Reviewer(s):||Kottelat, M. & Smith, K.|
Because the species has been impacted by the construction of dams (mostly more than three generations ago), it has now stabilised at a lower level and, therefore, does not qualify for the threatened or Near Threatened category. The anadromous ecotype is very rare in Europe now. Because of dams, most returning adults are unable to reach spawning sites. The resident populations are less impacted by the dams.
European Union 27 = LC. Same rationale as above.
Rivers draining to northern Black Sea. Lipkovska stream in upper Vardar drainage (Macedonia). Anatolian populations have recently been show to be two distinct species, Salmo coruhensis and S. rizeensis, reducing the distribution area of the species.
Native:Austria; Belarus; Bosnia and Herzegovina; Bulgaria; Croatia; Czech Republic; Georgia; Hungary; Macedonia, the former Yugoslav Republic of; Moldova; Montenegro; Poland; Romania; Russian Federation; Serbia; Slovakia; Slovenia; Ukraine
|Current Population Trend:||Unknown|
|Habitat and Ecology:||Habitat: |
At sea, along coasts at depths of up to 50 m. Migrates to hill streams. Resident part of populations in streams and uppermost reaches with fast current, cold clear water and stone or gravel bottom. Spawns in upper reaches with fast current.
Anadromous, lacustrine and resident ecotypes. Spawns in October-January. Parrs spend 2-4 years in rivers and streams, then smoltify and migrate to sea or mature in freshwater. Spends 2-4 years at sea. Anadromous individuals return to rivers in April-May and again in October-November. Eggs hatch in 6-8 weeks. Parrs and resident adults feed on a wide variety of aquatic and terrestrial invertebrates. Anadromous and large lacustrine individuals feed mainly on fish and large crustaceans. Anadromous individuals feed while in rivers.
|Movement patterns:||Full Migrant|
|Use and Trade:||It is harvested for human consumption, and for sport fishing.|
|Major Threat(s):||The anadromous ecotype is very rare in Europe. Because of damming, most returning adults are unable to reach spawning sites. The resident populations are less impacted by the dams.|
|Conservation Actions:||No information available.|
|Citation:||Freyhof, J. 2011. Salmo labrax. The IUCN Red List of Threatened Species 2011: e.T135658A4172650.Downloaded on 22 July 2018.|
|Feedback:||If you see any errors or have any questions or suggestions on what is shown on this page, please provide us with feedback so that we can correct or extend the information provided| | <urn:uuid:99224769-511a-4228-92a7-c67af6d9d4cd> | 2.6875 | 825 | Knowledge Article | Science & Tech. | 39.158917 | 95,508,595 |
A dangerous volcano could be about to erupt – for first time since 1728.
Alarming signs are starting to appear at the summit of one of Iceland’s most dangerous volcanoes.
A 72-foot (22-meter) depression in the snow at the of the Oraefajokull volcano is the only visible sign of an seismic activity.Teenager and restaurant at war after he pays for most of $45 dinner with quarters
It has been dormant since its last eruption in 1727-1728, though a recent increase in activity and geothermal water leakage that has scientists very worried.
With the snow hole on Iceland’s highest peak deepening 18 inches (45 centimeters) each day, authorities have raised the volcano’s alert safety code to yellow.
Experts at Iceland’s Meteorological Office have detected 160 earthquakes in the region in the past week alone as they step up their monitoring of the volcano.
The earthquakes are on the small side, but the number is exceptionally high.
‘Oraefajokull is one of the most dangerous volcanos in Iceland. It’s a volcano for which we need to be very careful,’ said Sara Barsotti, Coordinator for Volcanic Hazards at the Icelandic Meteorological Office.Gay woman barred from having LSBNSNLV personalized licence plate
What worries scientists the most is the devastating potential impact of an eruption at Oraefajokull.
Located in southeast Iceland about 320 kilometers (200 miles) from the capital, Reykjavik, the volcano lies under the Vatnajokull glacier, the largest glacier in Europe.
Its 1362 eruption was the most explosive since the island was populated, even more explosive that the eruption of Italy’s Mount Vesuvius in 79 A.D. that destroyed the city of Pompei.
There is also a lack of historical data that could help scientists predict the volcano’s behavior.Thai boys stuck in cave gave the cutest answers during press conference
‘It’s not one of the best-known volcanos,’ Barsotti said. ‘One of the most dangerous things is to have volcanos for which we know that there is potential for big eruptions but with not that much historical data.’
Iceland is home to 32 active volcanic sites, and its history is punctuated with eruptions, some of them catastrophic.
The 1783 eruption of Laki spewed a toxic cloud over Europe, killing tens of thousands of people and sparking famine when crops died.
Some historians cite it as a contributing factor to the French Revolution. | <urn:uuid:fbf22a43-113a-4343-8759-2845dae35fac> | 3.34375 | 545 | News Article | Science & Tech. | 42.292 | 95,508,663 |
A Non-Destructive Technique for the On-Line Quality Control of Green and Baked Anodes †
AbstractCarbon anodes play an important role in the electrolytic production of aluminum. They have a significant economic and environmental impact. Carbon anodes are made of dry aggregates, composed of petroleum coke, recycled rejects, and butts, bound by coal tar pitch. Due to several factors, defects (cracks/pores) appear in anodes during the fabrication process, affecting their quality. It is thus essential to control the quality of anodes before their use in the electrolysis cell. Current practice for the quality evaluation (visual inspection, core analysis) gives limited information. As an alternative to this practice, electrical resistivity measurements can be used. Electrical resistivity is one of the key indicators for anode quality and its homogeneity. A simple and non-destructive method has been developed for the specific electrical resistivity measurement of anodes (SERMA) for on-line control of anode quality. Various tests have been carried out at both lab scale and industrial scale. In this study, the electrical resistivity distributions in the lab-scale anodes were measured and compared with those of the tomography analysis. The method is able to detect defective anodes even before the baking process. View Full-Text
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Benzaoui, A.; Kocaefe, D.; Bhattacharyay, D.; Kocaefe, Y. A Non-Destructive Technique for the On-Line Quality Control of Green and Baked Anodes †. Metals 2017, 7, 128.
Benzaoui A, Kocaefe D, Bhattacharyay D, Kocaefe Y. A Non-Destructive Technique for the On-Line Quality Control of Green and Baked Anodes †. Metals. 2017; 7(4):128.Chicago/Turabian Style
Benzaoui, Abderrahmane; Kocaefe, Duygu; Bhattacharyay, Dipankar; Kocaefe, Yasar. 2017. "A Non-Destructive Technique for the On-Line Quality Control of Green and Baked Anodes †." Metals 7, no. 4: 128.
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here. | <urn:uuid:1a96c826-13bb-4e97-b1a2-0f44518e9513> | 2.671875 | 504 | Truncated | Science & Tech. | 31.661709 | 95,508,675 |
“Controlling the anomalous and topological Hall effects by applying an electric field could lead to new types of memory and logic devices
Two magnetic phenomena that could be harnessed for memory or logic applications can be controlled by simply applying an electric field to suitably designed structures, RIKEN researchers have shown1.
The Hall effect was discovered in 1879 by Edwin Hall, who realized that applying a magnetic field at right angles to an electric current causes the flowing electrons to veer in the direction perpendicular to both the applied magnetic field and the current, creating a voltage in that direction.
In ferromagnetic materials, the Hall effect can occur even without applying a magnetic field; in this case, it is called the anomalous Hall effect. Furthermore, in certain materials, local magnetic moments arrange themselves into stable vortex-like configurations known as skyrmions, and the fictitious magnetic field produced by the skyrmions gives rise to an analogous phenomenon known as the topological Hall effect. Both the anomalous and topological Hall effects arise due to the strong coupling between the spin and orbital angular momenta of electrons in some materials.
Inspired by the recent observation of the topological Hall effect in structures consisting of SrRuO3 and SrIrO3, Jobu Matsuno from the RIKEN Center for Emergent Matter Science and his co-workers explored the effect of applying an electric field in heterostructures composed of these materials.
“Despite the scientific importance of the anomalous and topological Hall effects, it has not been possible to control them so far,” says Matsuno. “They are both transport properties that are electrically accessible inside devices.”
The team fabricated three heterostructures that had strontium titanate (SrTiO3) as a substrate: in one, a non-magnetic SrIrO3 layer was capped with ferromagnetic SrRuO3; in the second, the two materials were inverted; and in the third, SrIrO3 was not used.
The researchers then applied a voltage perpendicular to the layers in each heterostructure. In the first one, the voltage clearly influenced both the anomalous and topological Hall effects (Fig. 1), whereas no such effect was observed in the other two heterostructures.
The origin of this electric-field modulation has not yet been clarified, but Matsuno and co-workers have some ideas. “We strongly believe that the strong spin−orbit coupling of electrons in iridium plays a significant role,” says Matsuno.
The researchers think it will be possible to control other magnetic properties, such as the magnetic anisotropy or the magnetic domain wall motion, by inserting thin layers of materials with strong spin−orbit coupling between a ferromagnetic layer and a gate dielectric. These phenomena could then potentially be used in a range of devices.” | <urn:uuid:3ac527f6-c384-4765-9b2e-dfe01b36ae80> | 3.484375 | 598 | News Article | Science & Tech. | 20.210083 | 95,508,678 |
NASA's Curiosity rover has found new science "results" on Mars and the agency will disclose the findings at a press conference that starts at 11.30 pm India time on 7 June.
NASA earlier this week announced that the Curiosity rover had started analysing drilled samples on Mars in one of its onboard labs for the first time in more than a year.
It had to stop analysing samples on the Red Planet after a mechanical problem took the rover drill offline in December 2016.
It successfully tested a new drilling method in May on the Red Planet, making a 50-millimetre deep hole in a target called "Duluth".
Launched in 2011, Curiosity was designed to assess whether Mars ever had an environment able to support small life forms called microbes.
NASA has not yet provided clues on what the new results are about, but it said that during the event, NASA scientists will have chats with the the public and media on the findings.
The public can send questions on social media and the event will air live on NASA Television and the agency's website. Interested people will also be able to watch it on several social media platforms including Facebook Live, YouTube and Twitter/Periscope.
The findings will also be published in the journal Science. | <urn:uuid:a3670bb2-cfd6-4587-8575-37c54f848eff> | 2.6875 | 256 | News Article | Science & Tech. | 49.401021 | 95,508,680 |
The spacecraft will zip within 142 miles of the planet's surface at more than 100,000 miles per hour on Sept. 29, taking high-resolution color images of the surface terrain. MESSENGER also will be making ultraviolet and visible light measurements of the harsh planet's surface, its tenuous atmosphere and a comet-tailed gas cloud 25,000 thousand miles long that trails behind the planet.
MESSENGER is carrying seven instruments -- a camera, a magnetometer, an altimeter and four spectrometers -- and includes CU-Boulder's Mercury Atmospheric and Surface Composition Spectrometer, or MASCS. Despite the spacecraft's eye-popping speed, rapid rotation maneuvers during the flyby will allow the MASCS instrument to "stare" at a handful of selected targets such as surface craters as the spacecraft passes overhead, said CU-Boulder Senior Research Associate William McClintock.
"We will be pointing at each individual target from several different angles during the flyby, which will allow us to collect more data," said McClintock of CU-Boulder's Laboratory for Atmospheric and Space Physics and a MESSENGER mission co-investigator who led the development of the MASCS instrument. The MASCS team is particularly interested in unusual surface deposits spotted by the camera during Messenger's previous flybys, McClintock said.
"One of the big questions planetary scientist have is how much iron there is on Mercury's surface," said McClintock. "We hope to pinpoint the iron, determine what chemical form it is in and how it is bound up on the planet's surface." Iron, which dominates Mercury's core, is responsible for maintaining the planet's magnetic field.
The dynamic magnetic field of Mercury absorbs and stores energy from the powerful solar wind, periodically "snapping like a rubber band" and driving charged particles into the planet's surface, said McClintock. The collisions cause atoms of sodium, potassium and calcium -- and likely iron, silicon and aluminum -- to be ejected into the planet's wispy atmosphere, he said.
Some of the atoms are then accelerated by solar radiation pressure into the gigantic gas cloud tail, while other drift back down to the planet's surface, only to be lofted once again into the exosphere, where they make their way into gaseous tail, he said.
McClintock said that after the third and final flyby, the researchers will have collected about the same amount of data as they will gather during a single orbit around Mercury. Once MESSENGER settles into a yearlong pattern of twice-a-day orbits around Mercury in 2011, analyzing the massive streams of images and data "will be like drinking from a fire hose," said McClintock.
Dozens of CU-Boulder undergraduate students at LASP will become more and more involved in data analysis during the next several years as information and images pour back to Earth from MESSENGER said Mark Lankton, the LASP program manager for the MASCS instrument. The information will be streamed to LASP's Space Technology Building in the CU-Research Park.
"The hands-on space education and training opportunities offered to students at LASP in science, engineering and mission operations is available at few other places in the world," said LASP Director Daniel Baker, a co-investigator on the MESSENGER mission. "CU-Boulder undergraduates and graduate students are involved in virtually all of our space efforts, from designing and building flight instruments to controlling satellites from campus, which makes for a profound educational experience."
The 4.9 billion-mile-journey to Mercury requires MESSENGER to make more than 15 loops around the sun to guide it closer to Mercury's orbit. The craft is equipped with a large sunshade made from a heat-resistant ceramic fabric to protect it from the sun.
"During this third encounter, the MESSENGER camera will again image areas never before seen at close range, and we will obtain color images of other regions at resolutions superior to those of previous observations," said MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington.
LASP also has a spectrometer riding on NASA's Cassini spacecraft that is now touring the Saturn system, a dust detector aboard the New Horizons spacecraft making its way to Pluto, and is leading a $485 million orbiting space mission slated for launch by NASA in 2013 to probe the past climate of Mars. CU-Boulder is the only research institution in the world to have designed and built space instruments for NASA that have been launched to every planet in the solar system.
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
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19.07.2018 | Life Sciences | <urn:uuid:c712a62a-b3d6-498e-a8fd-73a05bf57ea8> | 3.328125 | 1,587 | Content Listing | Science & Tech. | 38.642572 | 95,508,681 |
Oceanic anoxic events (OAEs) record profound changes in the climatic and paleoceanographic state of the planet and represent major disturbances in the global carbon cycle. OAEs that manifestly caused major chemical change in the Mesozoic Ocean include those of the early Toarcian (Posidonienschiefer event, T-OAE, ∼183 Ma), early Aptian (Selli event, OAE 1a, ∼120 Ma), early Albian (Paquier event, OAE 1b, ∼111 Ma), and Cenomanian–Turonian (Bonarelli event, C/T OAE, OAE 2, ∼93 Ma). Currently available data suggest that the major forcing function behind OAEs was an abrupt rise in temperature, induced by rapid influx of CO2 into the atmosphere from volcanogenic and/or methanogenic sources. Global warming was accompanied by an accelerated hydrological cycle, increased continental weathering, enhanced nutrient discharge to oceans and lakes, intensified upwelling, and an increase in organic productivity. An increase in continental weathering is typically recorded by transient increases in the seawater values of 87Sr/86Sr and 187Os/188Os ratios acting against, in the case of the Cenomanian-Turonian and early Aptian OAEs, a longer-term trend to less radiogenic values. This latter trend indicates that hydrothermally and volcanically sourced nutrients may also have stimulated local increases in organic productivity. Increased flux of organic matter favored intense oxygen demand in the water column, as well as increased rates of marine and lacustrine carbon burial. Particularly in those restricted oceans and seaways where density stratification was favored by paleogeography and significant fluvial input, conditions could readily evolve from poorly oxygenated to anoxic and ultimately euxinic (i.e., sulfidic), this latter state being geochemically the most significant. The progressive evolution in redox conditions through phases of denitrification/anammox, through to sulfate reduction accompanied by water column precipitation of pyrite framboids, resulted in fractionation of many isotope systems (e.g., N, S, Fe, Mo, and U) and mobilization and incorporation of certain trace elements into carbonates (Mn), sulfides, and organic matter. Sequestration of CO2 in organic-rich black shales and by reaction with silicate rocks exposed on continents would ultimately restore climatic equilibrium but at the expense of massive chemical change in the oceans and over time scales of tens to hundreds of thousands of years.
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While modelling studies suggest that mesoscale eddies strengthen the subduction of mode waters, this eddy effect has never been observed in the field. Here we report results from a field campaign from March 2014 that captured the eddy effects on mode-water subduction south of the Kuroshio Extension east of Japan. The experiment deployed 17 Argo floats in an anticyclonic eddy (AC) with enhanced daily sampling. Analysis of over 3,000 hydrographic profiles following the AC reveals that potential vorticity and apparent oxygen utilization distributions are asymmetric outside the AC core, with enhanced subduction near the southeastern rim of the AC. There, the southward eddy flow advects newly ventilated mode water from the north into the main thermocline. Our results show that subduction by eddy lateral advection is comparable in magnitude to that by the mean flow—an effect that needs to be better represented in climate models.
A universal feature of the global subtropical gyres is the presence of mode water, a thick layer of water with homogeneous properties within the main thermocline1,2 (Supplementary Note 1). Mode water is important in the climate system as ‘memories’ of climate variability3 and by ‘breathing in’ anthropogenic carbon dioxide4,5. Current climate models suffer large biases in representing mode-water subduction6,7. Mode-water subduction takes place near the western boundary current extensions with high eddy activities8,9. Previous studies propose the poor representation of mesoscale eddy effects as the major cause of the biases7,10. Results from eddy-resolving models suggest that mesoscale eddy contribution to the mode-water subduction is on the same order of magnitude as that by the mean flow11,12,13.
Physical processes by which mesoscale eddies affect subduction remain unclear, and are challenging to observe in the field. ACs have been observed to trap mode water while migrating equatorwards14,15,16,17; however, previous data did not resolve eddies to provide a quantitative estimate of eddy subduction and transport. The transport due to eddy-trapping is much weaker in the meridional than the zonal direction18, given the predominant westward propagation of mesoscale eddies19. In addition to the eddy-trapping transport, we propose a larger, complementary eddy lateral advective effect. Specifically, in the North Pacific, the southward eddy flow on the eastern rim of the AC advects south the dense, winter deep-mixed layer water from the north across large-scale density gradient into the permanent thermocline7. The cross-frontal eddy advection leads to an equatorward ‘bolus’ transport20 of the newly ventilated mode water. Although this eddy-advective effect on mode-water subduction has been suggested from eddy-resolving model simulations7,13, it has never been verified in field observations.
The present study investigates this eddy lateral advective effect on subduction and transport of the North Pacific subtropical mode water (STMW) through a targeted field experiment: the Pacific Mode-Water Ventilation Experiment (P-MoVE; ref. 21) that made the first direct observations of eddy subduction processes in the western North Pacific. We deploy 17 Argo-profiling floats with enhanced daily sampling in an AC south of the Kuroshio Extension (KE) in late March 2014 (See Methods). On the basis of more than 3,000 hydrographic Argo profiles following the AC, we find that the southward eddy flow transports relatively low potential vorticity (PV) and apparent oxygen utilization (AOU) from the northern winter deep-mixed layer into the permanent thermocline, suggesting a ‘sweet spot’ of subduction outside the eddy core on the southeastern rim of the AC. Together with results from the eddy-resolving model, we quantify that the southward eddy PV flux in the study region is comparable in magnitude to that by the mean flow, with the lateral advection dominating over the eddy-trapping effect. We conclude that the eddy lateral advection plays a key role in ventilating the interior of the upper ocean and increasing the net subduction of mode water.
Observing eddy-induced subduction and transport
During the P-MoVE cruise, 17 Argo-profiling floats with enhanced daily sampling were deployed in an AC in the STMW-formation region in late March 2014 (Methods; Fig. 1a). The AC trajectory (red line in Fig. 1a) is determined by tracking the time-varying AC centre from satellite altimetry analysis, cross-checked against the geometry of velocity streamlines around the sea-level anomaly (SLA) maximum. Several Argo floats followed the westward-migrating AC through summer until the eddy disintegrated on encountering the Izu Ridge in late September (Fig. 1b). The floats provide more than 3,000 hydrographic profiles that offered an unprecedented detailed view of STMW subduction and dissipation. This section reports results from the field campaign.
We use an eddy-following coordinate system—(Δx, Δy) for the relative position of the Argo floats to the AC centre—to construct the composite AC fields based on the data of the 17 Argo-profiling floats (Methods). Figure 2a–i shows in raw data dots the mixed layer depth, AOU and PV around the AC on the core density surface of STMW (25.3σθ) for March to August. Here PV is calculated as , where ρ is potential density, f is the Coriolis parameter and ρ0 is a reference density (1024, kg m−3). Oxygen sensors have been deployed on the 17 Argo floats, and AOU is defined as the difference between the saturated and observed dissolved oxygen (DO) concentrations22. Similar patterns are obtained when the Argo data are interpolated on a 0.1 × 0.1 grid (Supplementary Fig. 1). During March–June, the data display east–west asymmetries (Fig. 2 and Supplementary Fig. 1), with larger mixed layer depth and lower values of PV and AOU in the southeast than in the northwest part of the AC (Supplementary Fig. 2a–c).We compare the vertical sections along the southeast and northwest tracks of the AC for PV (Fig. 3) and AOU (Fig. 4). The PV and AOU in the STMW layer show asymmetry between the southeast and northwest rims of the AC. Along the southeastern track of the AC, the STMW is ventilated and renewed with lowest PV (<1.5 × 10−10 m−1 s−1) and AOU (<25 ml kg−1) during March–April (Figs 3a,b and 4a). After earlier April, the STMW pycnostad loses contact with the atmosphere, but the PV (AOU) lower than 1.5 × 10−10 m−1 s−1 (25 ml kg−1) persists until June (Figs 3e and 4c), implying the eddy southward advection of low PV and AOU from the northern STMW-formation region. By contrast, on the northwest rim of the AC (Figs 3c,d,f and 4b,d), the PV and AOU in STMW are much higher (PV>1.5 × 10−10 m−1 s−1; AOU>35 ml kg−1). No ventilation occurs there, and the STMW pycnostad is sheltered from the surface even in March.
The subduction of low PV and AOU only happens on the southeast rim of the AC. There, the southward eddy flow carries low PV water from the deep-mixed layer into the permanent thermocline, suggesting a ‘sweet spot’ of subduction by eddies (Figs 2a,g, 3a,b and 4a and Supplementary Fig. 1a,g). Owing to the southward intrusion of the deep-mixed layer and the thick mode-water layer underneath, the vertical density gradient is low on the eastern rim of the AC (Supplementary Fig. 3). In May–June, the STMW is capped by the seasonal thermocline that forms under surface warming (Fig. 3e). The southward advection of low PV and AOU (Figs 2e,h, 3e and 4c) by the eddy flow from the STMW-formation region in the north continues as the large-scale, meridional PV gradient remains strong (green dot line in Fig. 2j). From late June to August, by contrast, the newly formed STMW in the north erodes steadily as the seasonal thermocline develops, weakening the background meridional PV gradient (red dash line in Fig. 2j). The southward advection of STMW on the eastern rim of the AC weakens and eventually ceases (Fig. 2f,i).
Thus, our field observations have captured eddy effects on STMW subduction and ventilation. The PV asymmetry between the southeast and northwest rims of the AC (Figs 2g,h, 3e,f and Supplementary Fig. 2a–c) is a result of eddy advection across the background PV gradient. By advecting south the denser low PV water from the winter deep-mixed layer, the southward eddy flow acts to ventilate the interior of the upper ocean.
Data model comparison
Does the current eddy-resolving model faithfully represent the observed eddy-advective effect on STMW subduction? To address this question, we deploy synthetic Argo floats in the Ocean General Circulation Model (OGCM) for the Earth Simulator (OFES) model, and use the ‘offline particle-tracking method’ to track the floats. The Methods section (Track ACs in the model) describes how we deploy synthetic Argo floats in the eddy-resolving model OFES to mimic the sampling in the field. We tracked 14 ACs located in the study region (140°E–150°E, 28°–33°N) in late March. On the basis of the samples taken by the synthetic Argo floats, we construct the composite AC fields in OFES, and compare with observations.
We find that the eddy-resolving model successfully captures the eddy-advective effect. The east–west asymmetry in PV during March–April is confirmed in the OFES composites (Fig. 2k,l). As in observations, low (high) values of PV are found in the southeast (northwest) part of the AC (Supplementary Fig. 2d). The sampling of the east–west PV asymmetry can be improved by a more widely spread Argo array for the first few days; however, such an array is unstable on the outer rim of the eddy. In the model, the synthetic Argo floats away from the AC core cannot follow the AC movement and leave the AC soon.
Figure 5 provides a closer look into the eddy-advective effect in both the model and observations. PV is nearly homogeneous inside the AC core that traps winter deep-mixed layer water from the AC origin, but is asymmetric outside the AC core between the west and east rims where the outer ring of the eddy stirs the ambient fluid. There, the southward (northward) eddy flow advects relatively low (high) PV into (from) the permanent thermocline (Figs 3a–d and 5a,b,d,e,g,h), with a net effect to strengthen the ventilation of the interior ocean. The majority of the eddy PV flux occurs outside the eddy core as detailed in the next section.
We chose an AC from the model that has the eddy PV flux close to that of the AC in the field to compare the zonal asymmetry of PV () and tangential velocity () in Fig. 5. In OFES, the east–west PV asymmetry is sharper and the scatters of PV from the composite mean are narrower (Fig. 5e) than those in our observations (Fig. 5b), possibly because of insufficient horizontal dissipation23.
For comparison with the observed AC that trapped low PV water in the eddy centre (Fig. 2g–i), Fig. 2k,l shows results for ‘mode-water-trapping’ ACs in the OFES model. Not all ACs trap low PV in their eddy centres (Supplementary Fig. 4a,b). However, both types of ACs show east–west PV asymmetry in the study region during March–April, illustrating the eddy lateral advective effect. Furthermore, cyclonic eddies (CCs) near the STMW ventilation region show similar eddy lateral advective effects (Supplementary Fig. 4c). The east–west PV asymmetry is comparable in magnitude between the two types of ACs and CCs (Supplementary Fig. 4d).
Estimate the eddy-induced PV transport
On the basis of the Argo sampling, we estimate the time-averaged PV flux by a single AC during March and April on the core density surface of STMW, including the eddy-trapping and lateral advective transports (Table 1). The relationship between the eddy PV flux and the mode-water subduction rate is discussed in Methods. The Methods section (Estimate the time-averaged PV transport by a single AC) also describes in detail how we integrate the spatially and temporally varying Argo samples for the time-averaged eddy PV flux by individual ACs. We compare the estimates between the model and observations, and with the exact calculation from full model data (Fig. 5 and Table 1). The Argo sampling errors are less than 10%.
We compare the eddy-trapping and the eddy-advective PV transport based on the observed AC and the mode-water-trapping ACs we tracked in the model (Table 1). The net eddy-advective transport is large around the rim of the AC (1<|Δx|<2), but it is almost zero within the eddy core ((|Δx|<1), where the PV is well mixed and PV asymmetry is weak (Fig. 5c,f,i). The zonally integrated eddy PV flux by the observed AC with a normalized eddy radius is estimated at 8.24±0.82 × 10−12 s−2 because of lateral advection, and 0.73±0.07 × 10−12 s−2 because of the eddy-trapping effect. The eddy-trapping transport is smaller by one order of magnitude than the eddy lateral advective transport (Fig. 5c and Table 1). This result is confirmed by analysis of 14 ACs from the eddy-resolving model (Fig. 5i and Table 1).
The eddy lateral advective transport is comparable in magnitude to that by the mean flow. Directly calculated from OFES, the zonal-integrated PV transport on the core density surface of STMW across 30°N (140–150°E) by the mean flow is at 2.92 × 10−6 m s−2, while the eddy-induced PV transport is at 2.88 × 10−6 m s−2. Typically, there are 2.26 AC–CC pairs passing this section with an averaged eddy radius of 98.67 km. If we assume that eddy transport is symmetric between ACs and CCs, the equivalent PV flux by one single eddy (AC or CC) with a normalized eddy radius would be 6.45 × 10−12 s−2. This is in broad agreement with the estimate by the synthetic Argo data in the model (7.09±0.71 × 10−12 s−2). These results support the importance of the eddy lateral advection for STMW subduction.
We address the estimate errors associated with limited Argo samples by comparing the exact eddy PV transport based on the full model data with the estimates based on the synthetic Argo samples. We find that the sampling of 17 Argo profiles per day captures the sub-eddy-scale east–west PV asymmetry and the time-averaged meridional eddy PV transport during March and April (green and yellow lines in Fig. 5d–i). The error caused by the Argo sampling is less than 10%, compared with perfect sampling in the model (Supplementary Fig. 5). This lends some credibility to the estimates from our Argo observations. Although 17 Argo floats could not fully resolve the instantaneous eddy PV flux that varies in space and time (as indicated by scatters from the composite mean in Fig. 5), our enhanced daily sampling enables a time-averaged estimate with errors less than 10%.
Quantitatively, our observations of one single eddy captured eddy-advective effects in the fields but only allow for order of magnitude estimates of these effects. Our estimate of the eddy PV flux is subject to several sources of uncertainty due to the limited sample size (only one AC observed in the field) and spatiotemporal variability among mesoscale eddies. These uncertainties are difficult to quantify at the current stage. The eddy PV fluxes, especially the long-term mean, need to be better quantified in the future with more observations.
Variations in mixing with the AC
The isopycnal PV is well mixed within the AC core but displays a strong asymmetry outside the core in the east–west direction (Fig. 5). The enhanced temporal and vertical sampling of our Argo observations allows us to examine the difference in vertical mixing between inside and outside the AC core (Figs 2i and 6). As the season progresses, the low PV trapped in the AC core seems less dissipated than that in the surroundings (Fig. 2i), perhaps because the PV barrier reduces lateral mixing18. In many of our Argo profiles for March–May, the STMW displays a ‘multicore structure’24,25, with more than one PV minima in the vertical (Fig. 6c) both in and outside the AC core. Remarkably, the PV minima prefer to form at discrete densities of 25.0, 25.2 and 25.4σθ (Fig. 6a,b). In summer, pycnostads with multiple PV minima in STMW become rare outside the AC and gradually mixed into one single broad dense core (Fig. 6b,e). In the AC core, by contrast, the multicore structure of STMW persists even in summer (Fig. 6a,d), indicating a weak vertical mixing there. The summer histogram retains the characteristic tri-modal structure in the AC core, while it transforms into a smooth distribution outside that shifts towards higher density due to the seasonal erosion of the light STMW.
Our enhanced vertical sampling yielded a large number of high-resolution profiles that enables studying the seasonal evolution of the STMW multicore structure for the first time. Such studies will shed light on how the multicore structure forms and why it persists for a longer time inside the AC core.
We have observed the eddy-advective effect on mode-water subduction using a specially designed eddy-resolving array of 17 Argo-profiling floats deployed in an AC in the mode-water formation region. Our analysis of over 3,000 hydrographic profiles reveals that the PV and AOU are asymmetric about the AC centre, a structure indicative of lateral advection by the eddy. We further estimated that the southward eddy PV flux in the study region is comparable in magnitude with that by the mean flow, with the lateral advection dominating over the eddy-trapping effect. More eddy-resolving observations are needed to improve the estimates of long-term mean eddy fluxes. We found that the eddy lateral advection has significant seasonal variations, being strongest in winter and gradually weakening after June. The seasonal variations are closely related to the strength of the background PV gradient that forms between the newly ventilated STMW to the north and the old STMW to the south. As the seasonal thermocline develops, the background meridional PV gradient weakens, and the southward PV advection eventually ceases.
The maximum eddy subduction takes place around the eastern rim of the AC (1<Δx<2; Figs 2g and 5). There, the subducted fluids may escape from the eddy into the interior ocean. Indeed, some of the floats left the eddy and moved southwards from the eastern rim of the AC (Fig. 1b). Besides, PV is not conservative along a trajectory of eddy flow as clear in the east–west asymmetry in Fig. 2g because of dissipation (for example, submesoscale processes). Thus, the eddy lateral advection causes a net PV flux to ventilate the interior of the upper ocean and to increase the net subduction of mode water. As long as meridional background PV gradients are maintained, the eddy advection is active, even if a fluid particle released in early winter circulates around the eddy and re-enters the mixed layer before the winter ends. This is different from Stommel’s Ekman demon26.
While eddy tracer fluxes have been estimated with satellite altimetry and surface drifters27,28,29,30,31, previous studies mainly focused on the sea surface. Recent studies32,33 using subsurface Argo data investigated an important but different eddy effect of mixing high PV from polewards of the KE (a damping effect on mode-water formation). Our field campaign targets at the subduction process south of the KE. Our subsurface data resolve the AC in a statistical sense, permitting observational estimates of eddy subduction effects in the region for the first time.
Eddy advection significantly affects the subduction and transport of STMW. In coarse-resolution climate models (Fig. 7a), the subduction of low PV water is confined to a narrow point, and the southward transport of low PV is along the mean streamline (Fig. 7a), indicating the dominance of the mean flow advection. By contrast, in gridded Argo observations, STMW subducts into the thermocline in a broad region of the winter deep-mixed layer (Fig. 7b). After subduction, the PV minimum is trapped near the outcrop within a narrow band. The width of the low PV band is ∼200–300 km, corresponding to the length scale of mesoscale eddies. Even within the climatological low PV band, ∼49% of historical Argo profiles do not contain STMW (Fig. 7c,d and Supplementary Fig. 6), another fact that underlines the importance of eddies for the subduction and transport of STMW.
A popular parameterization of geostrophic eddies widely used in climate models is the Gent and McWilliams scheme34,35. Coupled Model Intercomparison Project Phase 5 (CMIP5)-class models typically use Gent and McWilliams diffusion coefficients less than 1,000 m2 s−1 (refs 36, 37). The values seem to be too small. Our Argo observations imply an eddy diffusivity on the order of (104 m2 s−1) in the study region (see Methods). This is consistent with several recent modelling studies that have advocated increasing the near-surface diffusivity to several thousand m2 s−1, but with a regional structure that peaks at O (104 m2 s−1) in the most energetic area of the ocean10.
The value of our study is in the field campaign that was designed to test the hypothesis that the lateral advection by eddies enhances mode-water subduction. To our knowledge, it is the first time that this eddy effect has been detected in the field. We have successfully deployed an eddy-resolving array of 17 Argo floats inside an AC. Setting the parking depth at 500 dbar helped to keep many Argo floats trapped within the eddy, and the enhanced daily sampling yielded enough data for eddy-resolving composites. Reduced temporal sampling sharply reduces the number of profiles on the AC rim, deteriorating the representation of the sub-eddy-scale east–west asymmetry in PV structure (Supplementary Fig. 7). The enhanced vertical sampling, on the other hand, enables a large-scale study of seasonal evolution of the STMW multicore structure, a project that is underway. Additional eddy-resolving field experiments are necessary to better quantify the large-scale effects of mesoscale eddies.
The KE is the window where the winter-mixed layer ventilates the main thermocline of the North Pacific to the south. The ventilation makes the KE an important carbon sink38,39,40. Results from our field campaign call for improved representation of eddy effects on the subduction and transport of STMW to achieve more realistic simulations of the regional biogeochemical cycle and reliable projections of its change.
The field experiment
To investigate the eddy effect on subduction and transport of the STMW, the P-MoVE cruise deployed 17 Argo-profiling floats (World Meteorological Organization IDs 2901550–2901566) inside an AC. We considered ACs located west of 150°E (A and B in Supplementary Fig. 8) in late March 2014 for deployment. Since the AC A was close to the Izu Ridge, it might dissipate over the rough topography. Thus, we chose the AC B near 147.5°E, 29.5°N, which is a typical eddy with a radius of 71.5 km and rotational speed of 29 cm s−1 (Supplementary Fig. 9).
The P-MoVE was conducted on the Research Vessel (R/V) Dongfanghong 2 from 17 March to 23 April 2014. During the cruise, the target AC position was identified in advance from the near-real-time SLA field and communicated to the vessel each day. Conductivity, temperature, and depth (CTD), expendable bathythermograph (XBT) and shipboard acoustic Doppler current Profiler measurements (Supplementary Fig. 10a) were first conducted around the target AC to identify the AC centre before deploying the Argo-profiling floats. A significant difference in the vertical temperature profiles existed between the western (black line in Supplementary Fig. 10b) and eastern (red line in Supplementary Fig. 10b) sides of the AC. Vertical temperature gradient was much weaker on the eastern side of the AC, suggesting fresh STMW formation there. Seventeen Argo floats were deployed on 27 March 2014 inside the AC (see deployment locations in Supplementary Fig. 10c). We deployed the Argo floats with an emphasis on the southeast part of the AC.
To keep the floats trapped in the migrating AC, we set the parking depth at 500 dbar. The floats dive to 1,000 dbar from the parking depth before the ascent, during which they conduct temperature, salinity and DO measurements. Each float makes observations daily as it rises from 1,000 dbar to near the sea surface, with a 2-dbar sampling interval above 600 m and 10 dbar below it. Compared with the conventional Argo sampling intervals of 10 days and 10 dbar, our enhanced time sampling proves crucial for our Argo array to maintain eddy-resolving capability, while the enhanced vertical sampling is instrumental in identifying reduced mixing of mode water within the AC core as detailed in Results.
To complement the P-MoVE Argo data, we include the following data: the historical ungridded raw data of Argo in the domain of interest (15–45°N, 120°–180°E) from 2004 to 2014, the daily SLA data from AVISO41 on a horizontal grid of 1/3°, the eddy-tracking data set of Chelton et al.19 and the daily outputs from OFES with a horizontal grid of 1/10° (ref. 42). All the Argo data passed the Argo real-time quality control, and those flagged as bad are eliminated. For the comparison of observational and simulated quantities, we use the gridded monthly Roemmich–Gilson Argo Climatology43, the mean dynamical topography from the CNES-CLS09 product44 and a randomly selected climate model—HadGEM2-CC from CMIP5 under the historical scenario.
Composite AC fields
On the basis of the daily SLA data from AVISO and the hydrographic profiles of the 17 Argo-profiling floats, we construct composites referenced to the AC centre (the red line in Fig. 1a or the black line in Fig. 1b). An eddy-following coordinate system (Δx, Δy) is used for the relative position of the Argo floats to the AC centre. The each-day AC centre is first identified based on the geometry of velocity streamlines around the SLA maximum. We interpolate each T–S and oxygen profile vertically on 1-dbar intervals using the Akima spline. Argo DO profile data are checked with shipboard CTDO and DO in the water samples at the time of launch (not shown here). Argo DO measurements failed the global range test after August 2014. The DO data after that are excluded.
Track ACs in the model
On the basis of the daily outputs of OFES, we use the ‘offline particle-tracking’ method to deploy synthetic Argo floats to track ACs in the model. We choose 14 ACs located within 140°E–150°E, 28°–33°N in March for 1994–2007. Seventeen synthetic Argo floats were deployed for each AC, and the deployment locations are similar as in Supplementary Fig. 10c. In line with the parking depth of 500 m, the synthetic Argo float’s movement was determined by the model’s daily velocity at 500 m. We record the float trajectory every day and take a vertical profile. Since the target AC is a ‘mode-water eddy’ where low PV water is trapped in the AC centre, we only track ACs with a low PV core in the model for one-to-one data-model comparison.
Estimate the time-averaged PV transport by a single AC
We define the time-averaged meridional PV (q) transport on the core density surface of STMW, 25.3σθ, across a zonal section (−2<x<2; the unit is the normalized distance from the eddy centre to the outer boundary of the eddy core) that the AC occupies as:
where the bracket denotes zonal integration and the over bar denotes time mean. Note that equation (1) is under the eddy-following coordinate system. We can divide v (the meridional flow speed) and q into the climatological zonal average and the deviation from the climatological zonal average, and . Then, the time mean meridional PV transport is . We further define the eddy-induced velocity as:
where is the relative velocity to the moving frame and Cy is the AC propagation velocity. For the ‘mode-water-trapping’ AC (Fig. 5), Cy is constant but is wholly antisymmetric about the AC centre, while is well mixed within the eddy core (|Δx|<1) but antisymmetric around the rim of the AC (1<|Δx|<2). Thus, and . The total meridional transport can be decomposited as follows:
Here the eddy effects are divided into two parts: the Eddy-trapping effect and the non-eddy-trapping lateral advective effect .
Using equation (3), we estimate the time-averaged eddy PV flux for March–April based on the Argo sampling. We first calculate () directly for each Argo sample (−0.5<y<0.5), and then obtain the time mean per Δx=0.1 bin (solid green line in Fig. 5), and finally integrate zonally for the total eddy PV flux by one AC (Table 1).
This estimate (here after ) contains errors due to limited Argo sampling. To quantify the error, we compare the estimate to the exact calculation () from the full model data. For the full model data, we first calculate the instantaneous () for each grid point around the AC, and then integrate temporally and zonally. We calculate the estimate error, , for each AC we tracked in OFES and find that the error due to limited Argo sampling is less than 10% (Supplementary Fig. 5). Including the ±10% error due to limited Argo sampling, we add a value range for the estimate of the eddy PV flux in Table 1.
Relation between eddy PV flux and subduction rate
The meridional PV flux (T) on the core density surface of STMW is the product of velocity (v) and PV (q),
and the time mean PV flux is
The time mean PV transport can be rewritten as a ‘transport velocity’ after dividing by the mean PV,
where the eddy-induced velocity in equations (6) is , known as the ‘bolus velocity’20.
Following Marshall11, the water mass subduction rate () in an eddying ocean can be described in terms of transport velocities
where [, ] is the transport velocity at the base of the mixed layer, z=−h. In particular, the subduction by mesoscale eddies is
From equations (6) and (7), we obtain the relation between the subduction rate and PV flux that transports low PV water from mixed layer into the permanent thermocline:
The comparison between the mean and the eddy PV flux in the present study reflects the relative contribution of the mean and the eddy flow to the subduction rate by lateral induction.
Estimate the eddy diffusivity coefficients
where κ is the eddy diffusivity. Here we use equation (10) to diagnose κ.
The averaged eddy PV flux for the target AC is estimated at 8.24±0.82 × 10−12 s−2 (Table 1). This calculation for zonal integration is within [−2R, 2R], where R is the eddy radius. As the target AC is a typical eddy in the study region (Supplementary Fig. 9), we extend the estimate to a broad region by considering the frequency of eddy occurrence
where α is the frequency of the eddy occurrence in the study region (135–175°E, 28–32°N). Here α is defined as:
where T is the total length of observations, Llon and Llot are the zonal and meridional distances of the study region, respectively, N is the total number of mesoscale eddies (both ACs and CCs, if we assume that eddy PV transport is symmetric between them), 4R represents the extent for integration for Jobs and Teddy is the averaged lifetime of mesoscale eddies.
On the basis of the eddy-tracking data set of Chelton et al.19 for 1992–2012, in the study region (135–175°E, 28–32°N), the total number of mesoscale eddies N=1,147 (eddies near the boundaries are excluded), the average eddy radius R=89.5 km and the averaged lifetime of mesoscale eddies Teddy=11 weeks. Together with the length of observations T=1,095 weeks, and the zonal and meridional distances of the study region Llon=3,849.3 km and Llat=444.5 km, respectively, α is estimated as 86.3%. We obtain a long-term mean eddy PV flux in the study region, J=7.11±0.71 × 10−12 s−2.
The corresponding mean PV gradient is estimated to be −1.64 × 10−16 m−2 s−1 based on the Roemmich–Gilson Argo climatology (blue line in Fig. 2j). Correspondingly, the eddy diffusivity is in the range of (4.34±0.43) × 104 m2 s−1. Our Argo observations imply an eddy diffusivity on the order of 104 m2 s−1 in the study region.
How to cite this article: Xu, L. et al. Observing mesoscale eddy effects on mode-water subduction and transport in the North Pacific. Nat. Commun. 7:10505 doi: 10.1038/ncomms10505 (2016).
We wish to thank the captain and crew of the ‘R/V Dongfanghong 2’ for conducting the P-MoVE and the reviewers for their constructive comments. This work was supported by the National Basic Research Program of China (2012CB955602), the Natural Science Foundation of China (41490643, 41476002, 41490641, 41506010, 41176006 and 41221063), the China Postdoctoral Science Foundation-funded project, the Fundamental Research Funds for the Central Universities (201503029) and the US National Science Foundation.
Supplementary Figures 1-10, Supplementary Note 1 and Supplementary References. | <urn:uuid:9dcbd704-3332-460e-a0c8-feffa38b4e60> | 2.59375 | 7,965 | Truncated | Science & Tech. | 53.797991 | 95,508,718 |
Coronal holes are areas on the sun's corona that are darker, lower-density, and (relatively) colder than the rest of the plasma on the surface of our nearest star. They're the source of the kind of solar wind gusts that carry solar particles out to our magnetosphere and beyond, causing auroras (and, less awesomely, geomagnetic storms) here on Earth.
When coronal holes are captured in extreme ultraviolet light images, they reveal themselves as dark spots that appear, to human eyes, to be plasma voids.
Well, last week -- between May 28 and 31 -- one of those coronal holes rotated toward Earth. It was a big one: "one of the largest," NASA says, "we have seen in a year or more." And the Solar Dynamics Observatory's Atmospheric Imaging Assembly, fortunately, got a shot of the thing. Above, via a combination of three wavelengths of UV light, is an image of the hole. It's pretty gorgeous, as holes go.
Beyond the photo, though, what effects will the coronal hole's rotation Earth-ward have on those of us living on Earth? Not much, for better or for worse. The solar wind streams that coronal holes can cause generally take two to three days to travel to our planet, so we've likely already experienced the anticlimactic effects of this particular hole. And while coronal holes are more likely to affect Earth after they've rotated more than halfway around the visible hemisphere of the sun -- which was the case with this guy -- the most this one would have done, astronomers say, was to generate some aurora. A pretty harmless effect from, you know, a GIANT HOLE IN THE SUN.
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Use technology to fix climate change
There are people who believe in climate change and there are those who don't.
Even more controversial, is the cause of climate change.
Some put the blame on the actions of humans. Others say it is a natural process.
Once the debate became political all reason fled the scene. It is virtually impossible to have a sensible debate about climate change.
Even scientists, who are supposed to be objective, find that their opinions on climate change might influence whether their research is funded.
This is hardly a situation that is conducive to reasoned debate and scientific research.
Let's look at some facts.
It is clear that the Earth's climate is changing. Graphs of global temperature show a slow steady rise since the start of the industrial revolution. These temperature curves mirror the energy use by our civilization. This is a fact that has been independently verified by several different and unrelated means of determining global temperatures over long periods of time.
Now, one of the first lessons that scientists learn is that just two bits of data -- in this case, our emissions of carbon dioxide (CO2) and temperature increase -- appear to have a correlation, does not mean that one causes the other.
In the absence of more data, it would be just as easy to say that rising temperatures cause increased CO2 emissions. That conclusion is patent nonsense, but the data could be twisted to support it.
What you need to do is to find a mechanism that could cause temperatures to rise because of increased CO2 emissions. Scientists have found such a mechanism in something called the greenhouse effect. In a greenhouse, visible and ultra-violet light stream through the glass windows and heat the plants and floor. These heat photons, called infra-red, cannot escape through the glass so the interior heat just builds.
In a similar way, certain gases, such as CO2 and methane, act like the greenhouse glass, allowing high-energy light through but block the escape of heat causing the Earth's temperature to rise.
Sounds like case closed, doesn't it?
Not so fast.
The Earth's climate is far more complex than a simple greenhouse.
We have frozen but dry poles and, at the equator, hot humid tropics.
We have an atmospheric circulation system that transports heat around the globe. And we have oceans that are tremendous heat reservoirs that hold onto heat and also move it around. Europe would be much colder if not for the Gulf Steam current, for instance.
There are many things about how the Earth's climate works that we still don't understand. Further, we are hampered because we do not have a temperature sensor network at every spot on the globe. One of the characteristics of weather systems is that they are tremendously sensitive to initial conditions and a small error in measurement in one part of the world could mean big differences in predictions only a few days ahead. That is why weather forecasts are inaccurate if you go more than a week or so into the future.
Now the politics gets worse.
We have learned that the Earth's temperature is increasing. We have a mechanism that would appear to support a suggested cause, but we are unclear on many details of how our climate actually works, but we are reasonably certain that anthropogenic (caused by people) climate change is real.
Now, what do we do about it?
Some people in the Green movement would have us all go back to the Middle Ages where we all grew our own food and the most advanced technology was that of the iron forge in the village blacksmith's shop. They say we should all use less energy and take less from the environment. These are not necessarily bad goals, however, as a practical proposition, they are not going to happen.
I believe the answer is not less technology, but vastly more technology.
We can reduce our carbon footprint by using new technologies that are starting to mature, such as wind and solar for energy generation. Electric vehicles are a key component in this strategy. Our homes are one of the biggest contributors of greenhouse gases and more efficient heating and cooling systems would tremendously help. Also, believe it or not, if we all adopted a vegetarian diet, we would not have millions of cows emitting methane, a gas that is about 30 times more effective as a greenhouse gas than CO2.
Interestingly, I don't see a lot of people suggesting vegetarianism to combat global warming.
One of the big opportunities to reduce our CO2 is something called carbon sequestration. In this process, we take carbon dioxide from the air and put it underground, either as a liquid, or in compound with other chemicals that hold the CO2 and prevent it from being released in the air. Perhaps the best example of this is limestone, which is basically calcium carbonate. which can hold a lot of carbon out of the atmosphere.
Unfortunately, there is much nonsense written about climate change. For instance, Canada contributes about two per cent of global CO2 emissions. If you shut down Canada's entire economy and strip the land of everything but rocks, you would have a reduction of greenhouse gas that a country, such as China, could replace in a couple of months.
Climate change is happening.
We can argue about the causes and the solutions, but it is important that such discussions be based on solid scientific evidence that is not tainted by politics.
Tim Philp has enjoyed science since he was old enough to read. Having worked in technical fields all his life, he shares his love of science with readers weekly. He can be reached by e-mail at: email@example.com or via snail mail c/o The Expositor.
Brantford Expositor 2018 © | <urn:uuid:88a87d00-a120-48a3-a570-44ead5e9f39f> | 3.15625 | 1,164 | Personal Blog | Science & Tech. | 48.007992 | 95,508,750 |
1. On the basis of electronegativity, list the following in order of increasing bond polarity: H-F, H-Cl, H-Br, H-I.
2. Draw the lewis structure and indicate the direction of the bond dipole for C-F and Si-S.
3. Which of the following species is smaller: I or I-? why?
4. What simple ion is formed from the element with Z=89?
5. On the basis of electron configurations, predict the formula of the Type I ionic compound formed from the elements Z=49 and Z=51.
6. What is(are) the noble gas(es) that has (have) the same electron configuration as each of the ions in the compound formed from Z=31 and Z=16
7. Why are the valence electrons of an atom the only electrons likely to be involved in bonding to other atoms.
8. Draw the Lewis structure for the compound formed from elements Z=6 and Z=16.
9. Draw the Lewis structure for the following compound: GeBr4.
10. Draw the Lewis structure for the PO4-3 ion, indicating any resonance forms.
11. Draw the Lewis structure for the hydrogen sulfate ion, indicating any resonance forms.
12. Using VSEPR theory, predict the molecular structure of PbCl4 and H2Te.© BrainMass Inc. brainmass.com July 17, 2018, 3:39 pm ad1c9bdddf
The solution provides detailed explanations for various atomic theory and bonding related questions. Diagrams and formulas are also included. | <urn:uuid:b8eaf7c1-179e-4935-9f74-a312c5ec2a13> | 4.0625 | 344 | Tutorial | Science & Tech. | 75.573046 | 95,508,771 |
Meteorites that had fallen from an asteroid impact that lit up the skies over California and Nevada in April are showing scientists just how complex an asteroid surface can be.
These are some of the 77 fragments of the Sutter’s Mill meteorite fall that were collected in April 2012.
Credit: NASA/E. James
A new study published in Science this week by an international team of researchers describes the speedy recovery of the meteorites and reports that this space rock is an unusual example from a rare group known as carbonaceous chondrites, which contain some of the oldest material in the solar system.
The study of these meteorites and others like them could hold answers to unsolved mysteries about the origin of life on Earth as they contain molecules such as water and amino acids.
"We found that this meteorite is a 'breccia,' a mixture of different rocks that accumulated at the surface of a larger asteroid, and those surfaces can be more diverse than we thought before," said co-author Denton Ebel, chair of the Division of Physical Sciences at the American Museum of Natural History.
About eight months ago, several Doppler weather radars detected a hail of rocks following a fireball traveling at a record-breaking 28.6 kilometers per second (about 64,000 miles per hour) over the Sierra Nevada in northern California. An immediate search-and-recover mission, led by NASA Ames Research Center, the SETI Institute, and the University of California, Davis, resulted in the retrieval of 77 meteorites. The fragments, which were in pristine shape despite entering the atmosphere at a speed twice as fast as a typical meteorite fall, were collectively called the Sutter's Mill meteorite after the nearby historical site that started the California Gold Rush.
"From the loud sonic boom, we quickly realized that this was an asteroid several meters in size, the biggest object to hit over land since the impact of asteroid 2008 TC3 in the north of Sudan in 2008," said lead author and meteor astronomer Peter Jenniskens of NASA Ames and SETI. "That asteroid proved to be a mixed bag of different types of meteorites, and we realized it would be very interesting to find out how diverse the Sutter's Mill meteorites were."
Several fragments were sent to laboratories around the world for simultaneous analysis of the meteorite's mineralogy and structure. The Sutter's Mill meteorite was classified as a CM chondrite, C standing for carbonaceous—high in carbon content—and M standing for the group's type specimen, the Mighei meteorite that fell in Ukraine in the late 1800s.
Ebel received five Sutter's Mill meteorites to study using x-ray computed tomography (CT), an imaging technique that takes pictures of the inside of a specimen without destroying it. The Museum's scanner takes more than 1,000 x-ray images of the object as it rotates inside of the machine. The data collected from these x-rays are then converted by computers to form a 3-D image of the specimen's interior, one slice at a time, to understand the components of the meteorite.
"In the same way that medical tomography, called CAT scanning, is used to image the interior of the human body, CT scanning in a research laboratory allows us to obtain images of the interiors of solid objects, but with a much higher resolution," Ebel said. "This is a fundamentally important tool not just for looking at rocks but for curating them and figuring out whether anything interesting is inside."
CT scans at the Museum, and at the University of California, Davis in an effort led by cosmochemist Qing-Zhu Yin, revealed that no two Sutter's Mill meteorites are the same. The meteorites contained angular pieces of different composition and density. They showed diversity on millimeter scale.
"This was the first time that a CM chondrite was found to be clearly a breccia," Yin said. "The rocky fragments came together following impacts on the parent asteroid, which implies that this meteorite originated from near its surface."
Analyses performed using different techniques at other institutions were in agreement: the mineralogy and other geochemical features of these fragments are unexpectedly diverse and complex. This suggests that the surface of the asteroid that spawned the CM chondrites, their "parent body," is more complex than previously thought.
"This meteorite is special because it records many collisional processes and mixing that we, oddly, don't see very often," Ebel said. "Maybe the real question is 'why don't we see more of this?' It could be that most of the samples we've worked with in the past didn't hold up very well as they entered the atmosphere. Or that we're just seeing a small segment of what's really out there because we don't have meteorite records of what fell to the Earth thousands or millions of years ago. We still have a lot of work to do to figure out what's really going on in the asteroid belt."
Kendra Snyder | EurekAlert!
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For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
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posted by pooja
1state relative mass and charge of an electron
2 an atom of an element X may be written as 4X^9 (a)What does the figure 9 indicate? (b)what is the number of protons in an atom X? (c)what is the number of electrons in an atoms X? (d)what does the number 4 indicate?
3 describe the rutherfords nuclear madel of an atom
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Numerous strategies have been developed over the years to deal with the difficulties involved in the development of large-scale software architectures. Object-oriented programming and several architecture description languages (ADLs) are examples of such strategies. In recent years, component-based software engineering (CBSE) has been emerging as an approach to software construction in which pre-manufactured software "components" with well-defined interfaces are designed and implemented, and subsequently incorporated into larger software systems. Increasing popularity of CBSE is related to recent advances in two areas:
Although there are many (informal) definitions of software components, there seems to be agreement that software components are software "units" which "enable practical reuse of software and amortization of investments over multiple applications" [C. Szyperski, "Software Components", 2nd ed.]. Software components, as opposed to other units of reuse, such as source code libraries, designs, and architectures, are executable units of independent production, acquisition and deployment that interact to form a functioning system. Insistence on independence and executable form is essential to allow for multiple vendors and robust integration [C. Szyperski].
Systems composed of software components are called component-based systems. The requirement for independence and executable form rules out many software abstractions, such as type declarations, C macros, C++ templates, or Smalltalk blocks. Other abstractions, such as procedurs, classes or modules, or even entire applications, can form components as long as they are in executable form that remains composable.
Selection and evaluation of components are critical to CBSE [A.W. Brown, Foundations for Component-Based Software Engineering]. Component selection can be based on component compatibility; two components are compatible if any sequence of operations requested by one of the interacting components can be satisfied by the other components. Component compatibility can be analyzed at the level of component interfaces (i.e., the internal structure of the component can be abstracted), and Petri nets can be used to model sequences of (requested and provided) operations at the interface level. In this sense, Petri net models can be considered parts of component specifications.
Specific projects in this area include:
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* The Small Comets Frequently Asked Questions List *
Version 3.0 April 9, 1999
On this page we answer the most commonly asked questions about small comets. This FAQ will be regularly updated. More information on the small comets is available in the original discovery papers and the Replies to Comments that appeared in Geophysical Research Letters, and in The Big Splash by Louis A. Frank with Patrick Huyghe, published in 1990 by Birch Lane Press.
What is the difference between these small comets and the large comets like Hale-Bopp and Halley's?
The small comets are a million times smaller than these more famous comets. The small comets also contain little dust and lack the iron and other metals necessary to make them glow brightly and produce a tail like the larger comets. But what they have in common--and the reason they were dubbed "small comets" in the first place--is that they are both largely made of water.
Why haven't the space shuttle and our satellites been hit by these small comets?
In low Earth orbit, where the space shuttle flies, astronauts can expect to run into the cometary water clouds from the small comets once in every 200 orbits. At the shuttle's altitude a small comet has already disintegrated in a cloud; it is no longer a solid object and the collision with a cloud is benign. So the astronauts have probably flown through these things and not known it. But at high altitudes, an impact of a spacecraft with a small comet would be disastrous. Since these comets are small and the collision frequency is low, an average-sized spacecraft would only be struck once in every 50,000 years or so. This means that one spacecraft in every thousand will be struck in high Earth orbit every 50 years. Has it happened yet? No one knows. But some spacecraft have been lost and no one knows why.
Why hasn't the Spacewatch Telescope seen the small comets?
It has. In 1988, Clayne Yeates, the late Jet Propulsion Laboratory physicist and science manager for the Galileo project, used the Spacewatch Telescope in a "skeet shooting" mode to obtain some stunning optical images of very faint streaks from the small comets. The objects he photographed had the same motion in orbit, the same speed, and were about the size, darkness, and frequency as the atmospheric holes themselves, or could be deduced from the known characteristics of atmospheric holes. [ L.A. Frank, J.B. Sigwarth, and C.M. Yeates, "A Search for Small Solar-System Bodies Near the Earth Using a Ground-Based Telescope: Technique and Observations," Astronomy & Astrophysics, 228, 522, February 1990.]
How long have the small comets been bombarding the Earth?
We do not know. But if the present influx of small comets is assumed to
be true for the past 4.5 billion years as well, then the small comets may
be responsible for all the water in the oceans and in our atmosphere.
In the spring of 1999 some scientists concluded that the Earth's water probably did not come from comets. So how could the small comets be responsible for the water in the Earth's oceans?
The possibility that the water in our oceans is due to an influx of large comets during the early history of our planet has been quite popular among many scientists until recently. But things have changed now that we can remotely determine the amount of deuterium, or heavy hydrogen, in these well-known large comets. These remarkable measurements have shown that the fraction of deuterium relative to that for hydrogen in the large comets is inconsistently high relative to that in our oceans. That is, the large comets cannot be the source of our oceans because this hydrogen "fingerprint" does not match. And because some scientists view the small comets as simply miniature versions of the large comets , they have concluded that the hydrogen fingerprint of the small comets is similarly inconsistent as the source of water in our oceans. But this conclusion is not necessarily correct because the small comets have already been shown to be much different in composition than the large comets. Measurements by the Polar spacecraft have shown that there is little dust and sodium in the small comets compared to the large comets. Thus the contents of the small comets greatly differ from those of large comets and there is no reason to conclude that the hydrogen fingerprints of these two classes of solar system objects are the same. Tom Donahue, a well-known atmospheric scientist at the University of Michigan, has proposed that the question of origins of our oceans can be resolved by measurements of the hydrogen fingerprint in the upper atmosphere because some of the contents of the small comets are continually deposited there. This is a difficult measurement but it would be decisive in establishing the small comets as the source of the ocean's waters. To date such an instrument has not been proposed for launching on a small rocket or for remote sensing from an orbiting spacecraft.
How do we know that these objects are depositing water in our atmosphere?
This startling conclusion comes from trying to account for the presence in the images of the "atmospheric holes," those dark spots where the ultraviolet dayglow has been absorbed over areas of 50 to 100 km in diameter. This is a large area and requires a lot of material. For the wavelength range viewed by the Polar and Dynamics Explorer cameras, water is the only common gaseous substance in the solar system that can efficiently absorb the dayglow along the line-of-sight of the cameras. No one has ever offered an alternative mechanism or substance. The absorption cross section of the water molecule is large and very well known. The total water cloud mass is still large, in the range of 20 to 40 tons. In addition, one of the Polar cameras for visible wavelengths was used to independently verify that the objects contained large amounts of water by viewing the intensities of OH radical emissions at 308.5 nm, which is the standard proxy for water in the studies of large comets. The OH is produced by the dissociation of water molecules in the sun's light and the OH radical fluoresces very brightly in the sunlight. This finding is a great achievement and is beyond the capabilities of any other camera flown to date. There is a large amount of water in these cometary gas clouds. The final closure was provided by the remarkable fact that the frequency of the OH trails is very similar to the occurrence frequency of atmospheric holes.
Why do the small comets break up and turn into clouds of water vapor?
The small comets are giant, loosely packed "snowballs" with some kind of thin shell, made perhaps of carbon, that holds them together as they travel through interstellar space. But as they approach the electrically charged Earth, the electrostatic stress on these objects causes them to break up at an altitude of about 800 miles above Earth. Rapid electrostatic erosion appears to be the mechanism responsible for stripping the thin protective mantle from the water-snow core of a small comet. By the time the fragments of the comet have descended to about 600 miles, the "snowball" fragments have been vaporized by the Sun's rays.
How much water do the small comets add to the Earth's surface?
At a rate of one 20-to-40 ton comet every three seconds, this influx of
small comets into the atmosphere would add about one inch of water to the
Earth's surface every 20,000 years or so. The implications of this added
water for long range global climate, global warming, and pollution
mitigation will need to be examined by the experts in those fields.
Is there any geological evidence to support the need for such an "outside" source of water as the small comets?
There is indeed. In 1999, David Deming, a geologist at the University of Oklahoma, published a refereed paper [Palaeo, 146, 33-51, 1999] which has attracted the attention of many scientists. His work points out that recent investigations of the movement of oceanic continental plates into the mantle, known as subduction, show that the loss rates for the water on this planet are very large as the plates carry the water deep below the surface. So unless there is an influx of water to our planet on time scales much shorter than its age of 4 billion years or so, our planet would be presently "dry as a bone." Remarkably the necessary influx of water from interplanetary space agrees quite well with what the small comets are calculated to be bringing to the Earth.
The amount of water added to the atmosphere by the small comets seems to conflict with well-established evidence that the stratosphere is extremely dry. How can you explain this?
The influx of water into the stratosphere from the small comets is insufficient to provide a "wet" stratosphere. The problems lie in the lower thermosphere and upper mesosphere. Simple models of water transport by eddy diffusion could not support the cometary water influxes if the upper boundary were taken above these regions. But the small comet's momentum carries the water into the mesosphere and thus provides a low percentage of water vapor in the atmosphere. This effect could accommodate the cometary water influx into the atmosphere without exceeding the known densities. To date no one to my knowledge has used such a source term in the standard atmospheric models. Below the mesopause at about 50 miles there is a general pattern of atmospheric circulation that extends into the troposphere. The cometary water would be carried in this circulation pattern. The stratosphere is dry because the "cold finger" near the tropopause precipitates the water into the troposphere. This cometary "rainfall" is insignificant relative to the rest of the water being transported at these altitudes.
Are noctilucent clouds produced by small comets?
The influx of small comets into Earth's atmosphere may help explain the source of water needed to form noctilucent clouds. These strange and quite beautiful clouds can be seen over the polar regions during the summer months. They are thin clouds, wavy or banded, colored silver or bluish white. They form at an altitude of about 55 miles, in the coldest part of the upper atmosphere, a relatively unexplored boundary known as the mesopause. No other cloud occurs so high in the sky. They are called noctilucent clouds because they can only be seen against a dark sky when illuminated by the setting sun. These clouds require considerably more water vapor than can be expected at that altitude from ocean evaporation. No one thoroughly understands why these clouds exist. But rocket-borne experiments sent up by aeronomers--those who explore the upper atmosphere--to probe these clouds have shown that the clouds are composed of ice crystals formed around meteoric dust particles--a finding that suggests small comets might indeed be responsible.
Do the small comets also impact the Moon? If so, where are these impacts and why don't we see dust clouds on the moon when the comets hit? Why didn't the Apollo seismometers record their impacts? Where is all the water on the Moon?
If you remember that the small comets are like fluffy snowballs--not rocks--the Moon does not present a problem to the existence of small comets. It's the difference between throwing a rock at your car and a snowball; one will leave a permanent mark, the other will not. Because the Moon is one thirteenth as large as the Earth it should receive about thirteen times fewer objects than the Earth. But the seismometers that were set up on the Moon during the Apollo missions recorded only about 2,000 events a year. How to account for this apparent discrepancy? The small comets do impact the Moon, but the seismometers were calibrated by looking at the seismic signature of everything from nuclear explosions to bullets shot into loose sand. No one ever worked out what effect a large snowball would have on the lunar surface. The small comets that strike the Moon will not make impact craters;they probably kick up some lunar dust and produce strange glows, and indeed these kinds of anomalous events have been reported by lunar observers for centuries. It is the seismometers' lack of sensitivity to the impact of small comets that accounts for the discrepancy in the low number of large objects detected on the Moon relative to the number of such objects that are seen falling into Earth's atmosphere. But if small comets strike the Moon, where is all the water then? The lunar gravity is such that practically all the water vapor from the impact of small comets simply flies off, though some of the water molecules may wander around and eventually condense in the crevices near the poles--exactly where it has been reported of late.
Can the small comets help resolve the long standing controversy about the difference in impact rates on the Moon and into the Earth's atmosphere?
Yes, there is a well known discrepancy between the number of objects of a given mass which are impacting Earth's atmosphere as inferred from fireballs in the atmosphere and the number of objects of similar mass as detected by the Apollo seismic network. Even taking in account the fact that the Moon is smaller than the Earth, the number of objects impacting the Moon has been found to be considerably less than those in our atmosphere. This major discrepancy has never been resolved, but the flux of small comets provides the solution to this problem. Because there is no dust in these small comets, their glow in the atmosphere must be estimated from the heat they produce when they hit the atmosphere at supersonic speeds. We have roughly estimated the visual magnitudes of the impacting small comets and find them to be in the range of -2 to -4. Remember, of course, that solar radiation is not available on the nightside of Earth to produce a large water vapor cloud as it does on the dayside where the atmospheric holes are observed. The number of fireballs in Earth's atmosphere with a visual magnitude of -2 is in the range of about 10,000 to 100,000 for each 24 hour period, according to D.W. McKinley, in Meteor Science and Engineering (McGraw Hill, 1961). And so the small comets do help explain the difference in the number of observed impacts on the Moon and in the Earth's atmosphere.
If the small comets are hitting Earth and the Moon, shouldn't they also be impacting the other planets in the solar system?
They do. But few small comets will survive inside the Earth's orbit because they will be destroyed by the Sun's heat. So there will be no small comets for Mercury, and maybe just a few for Venus. But the rest of the planets and their moons do get pelted by the small comets. While Earth gets about 10 million smallcomets a year, Mars receives less than a million and a half, Jupiter gets 16 billion,Saturn gets 4 billion, Uranus gets 260 million, Neptune gets 300 million, and Pluto only about 500 thousand a year. If the ice is not visible on the surface, as is it for many planetary moons, then the water and ice from the small comets probably lies beneath the planet's surface.
Where do the small comets come from?
The small comets do not come from the Oort cloud located far beyond the orbits of the planets, but from an inner belt of cometary material beginning just beyond the orbit of Neptune. To explain the constant bombardment of the Earth by small comets, a large, dark, as-yet-undiscovered planet must be regularly passing through the outer part of this comet belt where the small comets are thought to be located. The eccentric orbit of this dark planet is speculated to cross the comet belt once every 26 million years or so, sending swarms of small comets streaming into the inner solar system and toward the Earth itself.
Are all the small comets the same size? Is there any variation in their flux at the Earth?
The size of the "small comets" no doubt varies somewhat. Most
are thought to be in the 20-40 ton range, but there will also be some
even smaller comets--and some occasional larger ones. Some of these
larger ones may be responsible for such things as anomalous ice falls
that have been reported in the literature. And just as there are
variations in the sizes of these objects, there have probably also been
peaks and valleys in the influx of small comets on Earth over time.
Is there a seasonal variation in the observed influx of small comets?
Three sets of data for the period November through January point to a very pronounced seasonal variation. Recent data from the Polar spacecraft show that the influx of small comets into the Earth's atmosphere is 10 times greater in early November than in mid-January, when the small comet rate diminishes dramatically. This is the same seasonal variation discovered in the 1980s in images from a different camera aboard a different spacecraft, Dynamics Explorer-1, which traveled a different orbit than the Polar spacecraft. The oldest data set showing the influx of small comets into the Earth's atmosphere dates back to 1955. Using forward scatter radar, two Canadian scientists, E. L. Vogan and L. L. Campbell, found exactly the same seasonal variation, a November high and January low, in their non-shower, or sporadic, radar meteor rate. Why the atmospheric hole rate should correlate so well with the meteor rate measured by forward scatter radar is no mystery. After all, small comets are just a part of the meteoric dust and debris that orbits the Sun and falls into the Earth's atmosphere on a daily basis. Because the weakly bound small comets and mantle debris are expected to produce ionization at higher altitudes than stony or iron meteoroids, forward scatter radar--which is much more sensitive to ionization at higher altitudes than backscatter radar--is ideally suited to record the infall of small comets. (Backscatter radar events, on the other hand, are dominated by the infall of iron and stony meteoroids.)
Why is there a period in January when the small comets don't seem to be running into us?
The seasonal variations of the small comet fluxes are due to events in the distant disk of comets which lies generally parallel to the orbital planes of the planets, including that of Earth. Passing stars or a rogue dark orbiting planet cause local disturbances in the distant disk of comets which send some of them into the inner solar system. The position of a given disturbance would provide a corresponding stream of small comets at a particular position of the Earth's orbit around the Sun, that is, at a given time in the year. During the course of a year our planet will intercept the composite of these showers which accounts for the features in the atmospheric hole rates. For example, the minimum during January would correspond to a position in the distant comet disk for which there was no local disturbance. In future years, telescopes should be able to determine the orbits of the small comets and hence the general location of the corresponding disturbances in the enormous comet disk which lies beyond the planets.
Is there a daily variation in the observed influx of small comets?
Yes, there is. The maximum rate of atmospheric holes is observed from about 10 a.m. to 11 a.m. This maximum is two to three times greater than the event rate at 6 p.m. There is a good reason for this. First consider a uniform stream of small comets directed parallel to the Earth's orbital motion and travelling 10 km/s relative to Earth. Of course, the small comets are all influenced by the Earth's gravitational field when they are close to our planet. In the evening the small comet trajectories are more-or-less parallel to the gravitational force. The comets speed up but they are not deflected very much as they plunge toward the atmosphere. On the other hand, trajectories passing over noon are directed almost perpendicular to the gravitational field and they will be significantly bent toward the atmosphere and thus "gravitationally focused." So the impacts on the dayside atmosphere, including the effects of gravitational focusing, will be confined to local times at the equator extending from local evening at 6 p.m. to about 10 a.m. In the absence of gravitational focusing this impact zone is confined to local times at 6 p.m. to local noon. Then realize that for the trajectories of the small comets just above Earth's atmosphere the path length, and hence the duration, of a given atmospheric hole is substantially longer for the comet trajectories which graze the atmosphere at late morning hours relative to the direct plunging of the evening cometary water clouds. What this means then is that the late morning comets have a higher probability of being recorded by the camera. The small comets also have a range of perihelia, although not as far in as the orbit of Venus, and a limited range of inclinations, which will act to widen the maximum in the late local morning hours. This daily variation in the small comet influx is a fundamental feature associated with the fact that the comets are moving in a stream past the Earth. If the small comets were moving in random directions relative to Earth, there would be no such daily variation.
Can the small comets be seen by the naked eye?
You cannot see an intact small comet with the naked eye, but if you have a lot of patience--and a little luck--you might be able to see a small comet immediately after it breaks apart in the atmosphere. To see the flash produced by the disruption of a small comet you must stand out on a clear dark night, looking up at a 40 degree angle, until you see a short streak that quickly snuffs out. It will be about the brightness of Venus for about two seconds before it vanishes. But you will have to be out there for a hundred hours or so to see one. A hundred hours of clear night viewing does not happen often in the average lifetime.
How can amateur astronomers spot the small comets?
Amateur astronomers whose telescopes have mirrors or lenses measuring 12
inches or larger should be able to sight the small comets before they
disrupt in the atmosphere. During the course of a day there are two
times for observation, each about one or two hours long. One ends about
45 minutes before sunrise; the other begins about 45 minutes after
sunset. The small comets will be seen at a distance about 4,000-7,200 km
(2,500 to 4,500 miles) from the observer, so the telescope should be
pointed in such a way that it is looking for them at these distances,
just outside the Earth's shadow. Inside the shadow the objects are not
illuminated by the Sun and are invisible. Every hour or so a small,
quite dim object will slowly move across your view, as long as your field
of view is about four times the size of the Moon. The object will move at
a distance equal to the Moon's diameter every five seconds or so. (For
more details, see How to Search for Small
Comets.) Several amateur astronomers have reported seeing such
Do the small comets contain organic material that may be responsible for seeding life on Earth?
The small comets may contain organic materials, though this is only
speculation at the moment. If they do, they would seem to be ideal
vehicles for carrying organics safely through the atmosphere; they do not
burn up the way meteors do, and their icy interiors may protect the
organics just long enough to slip safety to Earth on a cushion of water
Could the water vapor from the small comets account for the "fireflies" that John Glenn and other astronauts saw on the early orbital missions?
No. By the time of Scott Carpenter's flight three months later, NASA had determined that those brilliant little specks floating around outside the spacecraft were caused by tiny ice crystals fluttering out from beneath the rippled heat shingles of the Mercury capsules.
How do the new results from NASA's Polar satellite confirm the original Dynamics Explorer images from a decade ago showing "holes" in the atmosphere?
There is no question that the Polar images confirm the previous Dynamics Explorer observations of atmospheric holes. This includes the dimensions of the holes, their frequency of appearance over the sunlit atmosphere, and their east-to-west motion across the sunlit atmosphere. The Polar detections are approximately several thousand per day and, accounting for viewing and image accumulation times, give a global rate in the range of 5 to 20 per minute. The database consists of 50,000 to 100,000 direct detections per month as clusters of darkened pixels. In many cases the holes are detected in consecutive frames, most are moving from east to west, and the effects of the camera platform motion (double vision) are present when the instrument computers do not compensate for this latter effect. The verification of the existence of atmospheric holes is completely secure.
The spectacular small comet streak acquired on Sept. 26, 1996 at UT 2228 and shown on the "front page" of the small comet site is obviously a processed image. What does the original "raw" Earth camera image look like?
The Near Real Time images available on our Visible Imaging System web site as "Current Image" or "Past Current Images" are actually a "stack" of five consecutive "raw" images all with some cosmetic processing to remove cosmic ray hits, nightglow backgrounds, flat-field optical normalizing, distortion removal, etc. These same corrections have been applied to the "streak" image in question. On the right is the "raw" streak image of Sept. 26, 1996.
How are the altitudes of the small comet trails in the Polar images calculated?
The approximate altitudes of the trails are determined by the apparent lengths of the trails between shutter closings of the camera and the fact that the apparent speed of the objects is about 10 km/s. Generally, the shorter the trail, then the greater distance between the trail and the Polar spacecraft.
Do you maintain a catalog of small comet sightings by the Polar cameras?
Yes, we do. The Catalog of Atmospheric Holes associated with the impact of small comets into Earth's atmosphere is is available for each day of the year starting April 20, 1997. In addition, the current image from the Polar spacecraft is available live.
Now that the existence of the small comets has been confirmed by the Polar spacecraft, what's next?
What we have to do now is go up there and meet the small comets at 600 miles out. Polar sees these objects with great resolution but from a great distance. Now we have to get up close and see these objects in detail. And that's just what a group of us--Sigwarth and myself, along with some of my former critics, including Thomas Donahue and Michael Combi at the University of Michigan; Paul Feldman at John Hopkins University; Robert Meier, George Carruthers and Charles Brown at the Naval Research Laboratory; and Ralph Bohlin at the Space Telescope Science Institute--have proposed. This proposed spacecraft is the first step in doing more sophisticated studies on these objects. Its two imagers will not only be more powerful and sensitive than those on Polar, but they will be able to look at the emissions coming from these objects. We are going to be looking for carbon, oxygen and simple organic gases. Maybe later we will be able to send a major mission after these objects and bring back samples.
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Human Family Tree Mapped Out in new Detail by Stanford Genetic Sequencing Effort
News Feb 25, 2008
Stanford University researchers have created the highest resolution map of human genetic diversity to date, providing insight into how groups of people throughout the world are related and adding weight to previous theories that humans originated from Africa.
The researchers surveyed 650,000 genetic locations in people from 51 populations to derive the map, providing data that will become a valuable tool in the search for disease-related genes. The work is published in the Feb. 22 issue of Science.
Marcus Feldman, PhD, professor of biological sciences, who has spent decades studying human genetic diversity, along with co-author Luca Cavalli-Sforza, PhD, professor emeritus of genetics, said the work expands upon many of their earlier ideas. “This is the definitive study to show variation within populations,” Feldman said.
The data groups people according to their similarities at 650,000 DNA locations. At each location, a person has one of the four DNA letters: an A, T, C or G. All those who have a G at a specific location would be grouped together, and so on. Although many genetic researchers over the years have clamored for exactly this kind of extensive sequencing effort, few labs have had the resources to tackle it.
The Stanford group was uniquely suited to the project because of the technical capabilities of the Stanford Human Genome Center, which also played a role in sequencing the human genome.
“This data shows that all humans are related in complex ways,” said co-author Gregory Barsh, MD, PhD, professor of genetics. “Many of what we’d call populations are really mixtures of people.”
The data also hold some new information. A group of people in Siberia share some genetic similarities and, by inference, ancestry with people indigenous to South America. Feldman said this data makes sense based on previous theories about human migration from Siberia across the Bering bridge to the Americas.
In addition to seeing which groups are related, the data give researchers the ability to track human migration. Anthropologists had previously thought humans originated in sub-Saharan Africa and left to colonize the rest of the world in several waves. This theory, known as “Out of Africa,” was supported by some previous genetic studies but wasn’t universally accepted.
This new data bolsters the Out-of-Africa model, showing that populations have less genetic diversity the farther that population is from Africa. This result is expected if the adventurous people leaving Africa represented only a small portion of the overall diversity of the population. This small group would establish new, less diverse populations elsewhere in the world.
Perhaps even more important than what the researchers found is what others may be able to learn from the data in the future. The researchers made their data publicly available as soon as they completed the analysis.
Although that gave competing groups a head start on projects of their own, senior author Richard Myers, PhD, professor of genetics, said it was the right thing to do. The only stipulation was that other groups allow the Stanford team to publish the first paper using the data, following the precedent set by the public effort to sequence the human genome.
“Like the human genome project, this will enable people to learn important new things about human history and disease,” Myers said. Co-author Hua Tang, PhD, assistant professor of genetics, said the work should help propel researchers toward personalized treatments for genetic diseases, such as cancers.
One place where the data will be useful is in the hunt for disease-related genes, said Devin Absher, PhD, senior scientist at the Stanford Human Genome Center where the experiments were performed and much of the analysis took place. Absher and Jun Li, PhD, senior scientist, are co-first authors of the paper.
When looking for disease genes, researchers compare groups of people with and without a given disease and look for genetic differences. Some of those differences may be attributable to the subjects’ genetic heritage rather than the disease itself. The data from the Stanford study should help researchers identify which variations are due to genetic heritage, helping them to focus on variations associated with the disease.
The data also confirm earlier work that the vast majority of genetic variation occurs within populations rather than between populations. “Most of the DNA variation we see has nothing to do with what the people who use the term ‘race’ usually mean,” Feldman said.
The DNA for this work comes from the Human Genome Diversity Panel, a collection initiated by Cavalli-Sforza in a collaboration with the Centre Etude Polymorphism Humain in Paris. Working with bioethicists to ensure samples were collected properly, anthropologists from around the world started sending blood to this collection in the 1990s.
The 51 populations used in the Stanford study were chosen mostly on the basis of where anthropologists were able to get samples. Feldman and Cavalli-Sforza hope to one day have access to samples from additional populations, which will add to what’s known about the genetic diversity and relatedness of the world’s populations.
DNA from the HGDP is freely available. In fact, a paper published in Nature on Feb. 21 from a group led by Noah Rosenberg, PhD, assistant professor of genetics at the University of Michigan and former graduate student of Feldman’s, looks at the same samples and reaches many of the same conclusions as the Stanford study.
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A new device developed by Wyss Institute reseachers safely traps delicate sea creatures inside a folding polyhedral enclosure and lets them go without harm using a novel, origami-inspired design. The ultimate aim is to allow the sea creatures to be (gently) analyzed in high detail.READ MORE
International Conference on Neurooncology and Neurosurgery
Sep 17 - Sep 18, 2018 | <urn:uuid:734ea0b2-e75a-4a81-931a-0606f2858922> | 3.03125 | 1,370 | Content Listing | Science & Tech. | 31.648221 | 95,508,938 |
The study of the mathematical dynamical systems presented in the previous chapters advanced our understanding of the dynamics of nonlinear deterministic systems. We now know that random-looking behavior can arise from simple nonlinear systems. Such dynamics, now termed chaotic dynamics, exhibit complicated strange attractors that are fractal sets with positive Lyapunov exponents. We also learned how the dynamic behavior of a system can change via bifurcations, and how period doubling, intermittency, and crisis can take a system from a periodic to a nonperiodic evolution.
KeywordsMutual Information Lyapunov Exponent Correlation Dimension Embedding Dimension Capacity Dimension
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Forces with magnitudes F1 = 42N and F2 = 35N act at a common point and make an angle of 77°12'. How big is their resultant?
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In point O acts three orthogonal forces: F1 = 20 N, F2 = 7 N and F3 = 19 N. Determine the resultant of F and the angles between F and forces F1, F2 and F3.
- Trapezoid MO
The rectangular trapezoid ABCD with right angle at point B, |AC| = 12, |CD| = 8, diagonals are perpendicular to each other. Calculate the perimeter and area of the trapezoid.
Determine the dimensions of the cuboid, if diagonal long 31 dm has angle with one edge 61° and with other edge 52°.
Determine angles of the right triangle with the hypotenuse c and legs a, b, if: ?
Calculate volume and surface area of the cone with diameter of the base d = 15 cm and side of cone with the base has angle 52°.
- Rotation of the Earth
Calculate the circumferential speed of the Earth's surface at a latitude of 61°. Consider a globe with a radius of 6378 km.
Determine the dimensions of cuboid a, b, c; if diagonal d=9 dm has angle with edge a α=55° and has angle with edge b β=58°
- Regular 5-gon
Calculate area of the regular pentagon with side 7 cm.
Triangle KLM is given by plane coordinates of vertices: K[-4, -18] L[-13, 15] M[-1, 8]. Calculate its area and itsinterior angles.
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In right triangle is: ? Determine the value of s and c: ? ?
- Triangle SAS
Calculate area and perimeter of the triangle, if the two sides are 51 cm and 110 cm long and angle them clamped is 130°.
- Angle between vectors
Find the angle between the given vectors to the nearest tenth of a degree. u = (-22, 11) and v = (16, 20)
Mast has 13 m long shadow on a slope rising from the mast foot in the direction of the shadow angle at angle 15°. Determine the height of the mast, if the sun above the horizon is at angle 33°.
Steeple seen from the road at an angle of 75°. When we zoom out to 25 meters, it is seen at an angle of 20°. What is high?
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The volume of the rotation of the cone is 472 cm3 and angle between the side of the cone and base angle is 70°. Calculate lateral surface area of this cone.
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Calculate the angle between these two lines: ? ?
Calculate the area of regular pentagon, which diagonal is u=17. | <urn:uuid:90165423-b3f9-49ca-b18c-76953de335f6> | 3.90625 | 687 | Tutorial | Science & Tech. | 76.405979 | 95,508,952 |
The Heartland Inventory and Monitoring Network began vegetation inventory and monitoring of four permanent sampling sites in the park’s restored tallgrass prairie and savanna in 2008. This augmented ongoing vegetation monitoring at the park by assessing changes specifically in the prairie/savanna community. The Network quantified species composition, structure and diversity in the prairie/savanna community before and after prescribed burns. Monitoring occurred in May of 2008, 2009 and 2011.
Plant Community Monitoring at Wilson’s Creek National Battlefield
Boundless prairie and majestic oak savannas characterized the landscape that early settlers found in this area of the Midwest. Experts estimate that only about 2% of original tallgrass prairie remains and less than 1% of the savanna remains. The NPS has been restoring prairies and savannas in places where they complement the history of the site. By undertaking a long-term plant monitoring program, the network establishes status and tracks trends in the plant community conditions.
Park management activities have occurred in the areas encompassing all four monitoring sites during the sample period. Most notable, prescribed fires were initiated in November 2008 and August 2010. In addition to prescribed fires, the areas around three sites were mowed in April 2011. This management activity results in short-term responses of the community that will eventually produce long-term outcomes. No trends were detected in vegetation community composition or structure at the end of the sample period. More data will be required to determine long-term conditions. Additionally scientists found that: 1. Of the 140 species observed during the sample period, 110 were native species. 2. Foliar cover of Chinese bushclover (Lespedeza cuneata), an invasive plant targeted for control by the park, increased between 2008 and 2011 in all but a single monitoring site.
Visit the Heartland Inventory & Monitoring Network website for more information about who we are and what we do.
Back to Wilson's Creek Nature. | <urn:uuid:1dd2b6c1-0c13-4d3b-b513-da643c83f266> | 2.828125 | 397 | Knowledge Article | Science & Tech. | 32.039139 | 95,508,966 |
VHIL researcher Kathryn Segovia says people have real, emotional reactions to virtual reality. Virtual environments could be used to help with a person's fear of heights, or help someone with an eating disorder. CNN SciTechBlog »,View PDF
Written by VHIL
- We Are VR: Will virtual reality make you virtuous?, PRX Big Picture Science
- Experiencing nature: Embodying animals in immersive virtual environments increases inclusion of nature in self and involvement with nature
- Experience on Demand: What Virtual Reality Is, How It Works, and What It Can Do
- The effects of virtual human’s spatial and behavioral coherence with physical objects on social presence in AR
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How Climate Influenced Fresh Water during Last Ice Age
News Jun 01, 2015
Usually increases in methane levels are linked to warming in the Northern Hemisphere, but scientists have identified rapid increases in methane during particularly cold intervals.
These findings are important, researchers say, because they identify a critical piece of evidence for how the Earth responds to changes in climate.
"Essentially what happened was that the cold water influx altered the rainfall patterns at the middle of the globe," said Rachael Rhodes, a research associate in the College of Earth, Ocean, and Atmospheric Sciences at Oregon State Univ. and lead author on the study, which was funded by the National Science Foundation. "The band of tropical rainfall, which includes the monsoons, shifts to the north and south through the year.
"Our data suggest that when the icebergs entered the North Atlantic causing exceptional cooling, the rainfall belt was condensed into the Southern Hemisphere, causing tropical wetland expansion and abrupt spikes in atmospheric methane," she added.
During the last ice age, much of North America was covered by a giant ice sheet that many scientists believe underwent several catastrophic collapses, causing huge icebergs to enter the North Atlantic—phenomena known as Heinrich events. And though they have known about them for some time, it hasn't been clear just when they took place and how long they lasted.
Rhodes and her colleagues examined evidence from the highly detailed West Antarctic Ice Sheet Divide ice core. They used a new analytical method perfected in collaboration with Joe McConnell at the Desert Research Institute in Reno, Nevada, to make extremely detailed measurements of the air trapped in the ice.
"Using this new method, we were able to develop a nearly 60,000-year, ultra-high-resolution record of methane much more efficiently and inexpensively than in past ice core studies, while simultaneously measuring a broad range of other chemical parameters on the same small sample of ice," McConnell noted.
Utilizing the high resolution of the measurements, the team was able to detect methane fingerprints from the Southern Hemisphere that don't match temperature records from Greenland ice cores.
"The cooling caused by the iceberg influx was regional but the impact on climate was much broader," said Edward Brook, an internationally recognized paleoclimatologist from Oregon State Univ. and co-author on the study. "The iceberg surges push the rain belts, or the tropical climate system, to the south and the impact on climate can be rather significant."
Concentrating monsoon seasons into a smaller geographic area "intensifies the rainfall and lengthens the wet season," Rhodes said.
"It is a great example of how inter-connected things are when it comes to climate," she pointed out. "This shows the link between polar areas and the tropics, and these changes can happen very rapidly. Climate models suggest only a decade passed between the iceberg intrusion and a resulting impact in the tropics."
The study found that the climate effects from the Heinrich events lasted between 740 and 1,520 years.
Getting to Know the Microbes that Drive Climate ChangeNews
A new understanding of the microbes and viruses in the thawing permafrost in Sweden may help scientists better predict the pace of climate change.READ MORE
Perinatal Exposure to Phthalates Results in Lower Number of Neurons and Synapses in the Medial Prefrontal CortexNews
Phthalates - chemicals used in plastics belonging to the same class as Bisphenol A (BPA) - can potentially interfere with hormones important for the developing brain.READ MORE
Rocky Planet Neighbour Looks Familiar, but is Not Earth's TwinNews
Last autumn, the world was excited by the discovery of an exoplanet called Ross 128 b, which is just 11 light years away from Earth. New work has for the first time determined detailed chemical abundances of the planet’s host star, Ross 128.READ MORE | <urn:uuid:00fc7f7b-160c-4ab5-ae49-ed41d7a4bbb9> | 3.9375 | 801 | News Article | Science & Tech. | 29.278231 | 95,509,027 |
A team of experts has refuted previous findings published last summer stating that Pfiesteria is not toxic to fish or humans. When they cultured the same strain of P. shumwayae studied by the dissenting scientists, it produced a toxin that killed fish within minutes.
Dr. JoAnn Burkholder, director of North Carolina State Universitys Center for Applied Aquatic Ecology, presented the results of the new study Tuesday at the 10th International Conference on Harmful Algae in St. Petersburg, Fla. The findings are significant because they reconfirm a decade of research showing that Pfiesteria is a dangerous toxic organism.
Last summers papers had been critical of work by Burkholder and other scientists who discovered Pfiesteria and described its life cycle and toxic impacts on fish and mammals. However, the dissenting scientists work was based primarily on research with one strain. In the new study three laboratories, assisted in toxin analysis by a fourth "blind" lab, have shown that this allegedly nontoxic strain does produce toxin after all. Burkholder said that their teams results differed because they grew the culture under conditions that allowed it to express toxicity.
Dr. JoAnn Burkholder | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
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Interpretation of groundwater ages Most groundwaters are mixtures of water with different ages because of the nature of flow in porous media.The age distribution depends on the hydrogeologic attributes of the aquifer concerned, as well as characteristics of the sampling point such as bore depth and screen length.In our tritium measurement, water samples of 0.5-3.0litres (or even less) are generally used for the He that has been generated from a certain amount of water and is finally determined using a helium mass spectrometer.This method is the most sensitive one that can be used to detect low-level tritium concentrations of environmental waters.Water in rain, oceans, lakes, streams and glacial ice pick up these tracers through contact with the atmosphere.
Tritium is also produced in nuclear reactions, hence there was a large peak in atmospheric tritium concentration in the 1960s and early 1970s is due to nuclear weapons testing.
In contrast to other noble gas mass spectrometric laboratories, we have developed and applied a novel helium isotope dilution technique, which has significantly improved the accuracy of our tritium measurements.
The method consists of four major steps: (1) a water sample is first distilled; (2) then the distilled water sample is loaded into a metal container (0.1–7.0litres) and the dissolved gases including helium are removed from the water by vacuum pumping; (3) the sample is stored for a few weeks or months so that He atoms are produced from tritium decay; and (4) the helium fraction that comes from the decay of the tritium is admitted into the noble gas mass spectrometer and then the abundance of the helium isotopes is measured simultaneously.
The tritium concentration of a sample can be calculated from the measured ), tse and tem are the times elapsed from sampling to extraction and from extraction to measurement, respectively, m and Δm are the masses of the sample and the vaporised water during the degassing step, and α=1.15 is the ratio of the tritium concentration in the liquid phase and the water vapour.
Please contact us to discuss your needs before sending your samples to our lab. | <urn:uuid:8d4830d2-f1b7-415f-8cc7-0526c5445dda> | 3.703125 | 473 | Knowledge Article | Science & Tech. | 38.655 | 95,509,065 |
Avian brains get the study they deserve and are found to be equal in ability to mammalian brains, reports Sandra Blakeslee . (New York Times)
"New Caledonian crows create more complex tools with their beaks and feet. They trim and sculpture twigs to fashion hooks for fetching food. They make spears out of barbed leaves, probing under leaf detritus for prey.
"In a laboratory, when a crow named Betty was given metal wires of various lengths and a four-inch vertical pipe with food at the bottom, she chose a four-inch wire, made a hook and retrieved the food.
"Apes and corvids are highly social. One explanation for intelligence is that it evolved to process and use social information - who is allied with whom, who is related to whom and how to use this information for deception. They also remember.
"Clark nutcrackers can hide up to 30,000 seeds and recover them up to six months later.
"Nutcrackers also hide and steal. If they see another bird watching them as they cache food, they return later, alone, to hide the food again. Some scientists believe this shows a rudimentary theory of mind - understanding that another bird has intentions and beliefs.
"Magpies, at an earlier age than any other creature tested, develop an understanding of the fact that when an object disappears behind a curtain, it has not vanished.
"At a university campus in Japan, carrion crows line up patiently at the curb waiting for a traffic light to turn red. When cars stop, they hop into the crosswalk, place walnuts from nearby trees onto the road and hop back to the curb. After the light changes and cars run over the nuts, the crows wait until it is safe and hop back out for the food.
"Pigeons can memorize up to 725 different visual patterns, and are capable of what looks like deception. Pigeons will pretend to have found a food source, lead other birds to it and then sneak back to the true source.
"Parrots, some researchers report, can converse with humans, invent syntax and teach other parrots what they know. Researchers have claimed that Alex, an African gray, can grasp important aspects of number, color concepts, the difference between presence and absence, and physical properties of objects like their shapes and materials. He can sound out letters the same way a child does."
Sherman Alexie cancels book tour for memoir about his mother.
Why is Ben Murphy so happy? Because for once in his life, he's on time. He beat Roger Davis, Steve Kanaly and the moderator to the pan...
Last night I read Julian Barnes' The Sense of an Ending . Yes, the night before it went up against Donald Ray Pollock's The Devil Al...
When I finished Kevin Brockmeier's A Brief History of the Dead last spring I immediately did a search to see if the Coca-Cola Corp. had... | <urn:uuid:82eb8586-7f3b-424f-84fa-f1d3158972ae> | 3.359375 | 617 | Content Listing | Science & Tech. | 61.663222 | 95,509,089 |
Background: Why PyViz? ¶
Many of the activities of a data scientist or analyst require visualization, but it can be difficult to assemble a set of tools that cover all of the tasks involved. Initial exploration needs to be in a flexible, open-ended environment where it is simple to try out and test hypotheses. Once key aspects of the data have been identified, the analyst might prepare a specific image or figure to share with colleagues or a wider audience. Or, they might need to set up an interactive way to share a set of data that would be unwieldy as a fixed figure, using interactive controls to let others explore the effects of certain variables. Eventually, for particularly important data or use cases, the analyst might get involved in a long-term project to develop a full-featured web application or dashboard to deploy, allowing decision makers to interact directly with live data streams to make operational decisions.
With Python, initial exploration is typically in a Jupyter notebook, using tools like Matplotlib and Bokeh to develop static or interactive plots. These tools support a simple syntax for making certain kinds of plots, but showing more complex relationships in data can quickly turn into a major software development exercise, making it difficult to achieve understanding during exploration. Simple apps can be built using ipywidgets to control these visualizations, but the resulting combinations end up being tightly coupled to the notebook environment, unable to migrate into a standalone server context with an application that can be shared more widely. Bokeh includes widgets that can work in both notebook and server environments, but these can be difficult to work with for initial exploration. Bokeh and Matplotlib both also have limitations on how much data they can handle, in part because Bokeh requires the data to be put into the web browser’s limited memory space.
To address these issues, we have developed a set of open-source Python to streamline the process of working with small and large datasets (from a few points to billions) in a web browser, whether doing exploratory analysis, making simple widget-based tools, or building full-featured dashboards. The libraries in this ecosystem include:
- HoloViews : Declarative objects for instantly visualizable data, building Bokeh plots from convenient high-level specifications
- GeoViews : Visualizable geographic data that that can be mixed and matched with HoloViews objects
- Datashader : Rasterizing huge datasets quickly as fixed-size images
- Param : Declaring user-relevant parameters, making it simple to work with widgets inside and outside of a notebook context
These projects can be used separately or together in a wide variety of different configurations to address different needs. For instance, if we focus on the needs of a data scientist/analyst who wants to understand the properties of their data, we can compare that to the approach suggested for a software developer wanting to build a highly custom software application for data of different sizes:
Here Datashader is used to make large datasets practical by rendering images outside the browser, either directly for a programmer or via a convenient high-level interface using HoloViews, and the results can be embedded in interactive Bokeh plots if desired, either as a static HTML plot, in a Jupyter notebook, or as a standaline application.
Behind the scenes, these tools rely on a wide range of other open-source libraries for their implementation, including:
- Pandas : Convenient computation on columnar datasets (used by HoloViews and datashader)
- Xarray : Convenient computations on multidimensional array datasets (used by HoloViews and Datashader)
- Dask : Efficient out-of-core/distributed computation on massive datasets (used by Datashader)
- Numba : Accelerated machine code for inner loops (used by Datashader)
- Fastparquet : Efficient storage for columnar data
- Cartopy : Support for geographical data (using a wide range of other libraries)
To give you an idea what sort of functionality is possible with these tools, you can check out some of these links first if you wish:
Getting started ¶
First, you should browse through the already-run versions of the PyViz tutorials to see what they cover and how it all works. But everything on this website is a Jupyter Notebook that you can run yourself, once you follow the installation instructions, so the next step is to try it all out and have fun exploring it! | <urn:uuid:3a21ed99-401c-49c8-bc7c-510bf00db88e> | 2.59375 | 935 | About (Org.) | Software Dev. | 1.506278 | 95,509,090 |
A buffer solution is made of 0.100 M HOCl and 0.250 M NaOCl. What is the pH of the resulting solution when a 15.0-mL portion of 0.200 M HCl is added to 100.0 mL of the buffer?© BrainMass Inc. brainmass.com July 16, 2018, 12:33 am ad1c9bdddf
You need the buffers mathematical equation, and to be able to identify each speices.
Ka = [H+] x (A-/HA)
Ka is the Ka of the acid HA
[H+] is your pH term (your answer in most cases)
A- is the conjugate species of the acid HA
HA is the acid that we have the Ka value for...
Setting up the BUFFER equation...
Ka = [H+] x 0.250/0.100
From this we can find the pH before the ...
The solution explains the steps necessary to find the pH of a buffer solution after some HCl is added in almost 300 words. | <urn:uuid:5529b007-c430-44ba-be84-c72a8c8e647c> | 3.203125 | 223 | Q&A Forum | Science & Tech. | 103.621928 | 95,509,111 |
Engineers at Duke University have found that buckyballs hinder the ability of bacteria and other microorganisms to accumulate on the membranes used to filter water in treatment plants. This attribute leads the researchers to believe that coating pipes and membranes with these nanoparticles may prove to be an effective strategy for addressing one of the major problems and costs of treating water.
A buckyball, or C60, is one shape within the family of tiny carbon shapes known as fullerenes. They are named after Richard Buckminster Fuller, the inventor of the geodesic dome, since their shape resembles his famous structure.
"Biofouling is viewed as one of the biggest costs associated with membrane-based water treatment systems," said Claudia Gunsch, assistant professor of civil engineering at Duke's Pratt School of Engineering and senior member of the research team. "These membranes have very small pores, so they can get stopped up quickly. If we could increase the time between membrane replacements by 50 percent, for example, that would be a huge cost savings."
According to Chae, the addition of buckyballs to treatment membranes had a two-fold effect. First, treated membranes showed less bacterial attachment than non-treated membranes. After three days, the membranes treated with buckyballs had on average 20 colony forming units, the method by which bacterial colonies are counted.
"In contrast, the number of bacterial colonies on the untreated membrane was too numerous to count," Chae said.
Chae also found that the presence of the buckyballs inhibited respiration, or the ability of the bacteria to use oxygen to fuel its activities.
"As the concentration of buckyballs increased, so did the inhibition of respiration," Chae said. "This respiratory inhibition and anti-attachment suggests that this nanoparticle may be useful as an anti-fouling agent to prevent the biofouling of membranes or other surfaces."
Gunsch said the mechanisms involved are not well-understood.
Both Gunsch and Chae believe that since buckyballs are one of the most widely used nanoparticles, additional research is needed to determine if they have any detrimental effects on the environment or to humans. This is one of many issues being studied at Duke's Center for Environmental Implications of Nanotechnology.
"We need to figure out how resistant these coatings will be to long-term use," Gunsch said. "If they can indeed prevent fouling, they will last longer. If they slough off over time, we need to know what the effects will be."
The current experiments in the laboratory were conducted with Escherichia coli K12, a strain of the bacteria that is widely used in laboratory experiments.
"We focused on a quite specific microorganism, so the next stage of our research will to see if these nanoparticles will have the same effects on bacteria commonly found in the environment or those in mixed microbial communities," Chae said. "We also plan to build a small-scale version of a treatment plant in the lab to conduct these tests."
Richard Merritt | EurekAlert!
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
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Each year, naturalists across the U.S. go to war with invasive plants. Take lesser celandine, for instance. The delicate yellow petals, which emerge in early spring, belie a resounding—and frustrating—toughness. The plant beats native wildflowers to bloom, and usurps their habitats in the process. As of April 2016, it’s been detected in 25 states; a model from the Animal and Plant Health Inspection Service at the USDA estimated that up to 79 percent of land in the U.S. could be hospitable to an infestation.
A naturalist in Washington, D.C., recently told National Geographic about how the weed has choked out nearly 200 acres of the city’s Rock Creek Park. “People say, ‘Why don’t you dig it up?’” he said. “I could dig this up for a thousand years and you would not see anywhere near the end of it.”
Invasive species are tricky to eradicate. A recent piece in Smithsonian described how some land managers in Maryland are resorting to flame throwers to scorch the unwelcome and aggressive guests—including lesser celandine—into oblivion. Removing the weeds by hand can have a counterproductive effect by broadcasting portions of the entangled root system to a new location.
Removal is tough, but it matters. As native plants’ numbers dwindle, so do the populations of native pollinators that survive on them. In turn, that shrinking cohort struggles to pollinate crops and sustain habitats.
Native plants are struggling across the country. In Chicago, for instance, land-use change has altered or destroyed a significant share of these habitats, says Rachel Goad, the manager of the Plants of Concern program at the Chicago Botanic Garden. At one point, she says, Illinois was 60 percent tall grass prairie; today, less than 0.01 percent of that ecosystem remains. That means that there’s not much space for prairie species, and invasive ones encroach on them, too.
Maintaining existing open space isn’t necessarily a cure-all, either. “Sometimes you preserve kind of a postage stamp that’s surrounded on all sides by roads, parking lots, and housing developments, and it can change the way water moves through the site, and the nutrients really considerably,” says Goad.
In response to these threats, cities across the U.S. are launching campaigns designed to nurture native plants. Last month, the Washington, D.C., Department of Energy & Environment debuted an initiative to hand out 8,000 packets of native seeds, each containing enough to cover about 50 square feet. At subway stations throughout the District, commuters could grab a seed mixture including native wildflowers such as wild senna, purple coneflower, and butterfly milkweed. Julia Robey Christian, the public information officer for the DOEE, tells CityLab that this effort sprung out of the District’s focus on rehabilitating local meadows. The giveaway, she says, aims to “raise public awareness of the importance of pollinators and meadow habitat in the District and to provide opportunities for residents to engage with our surrounding natural environment.”
How do people respond to the threats posed by invasive species? That’s the question that the Human Dimensions Research Unit—a cohort within the Department of Natural Resources at Cornell University—aims to clarify. The team collects information about perceptions and behaviors surrounding management of natural resources. Last year, they circulated surveys around New York state. On those surveys, home gardeners indicated that they were willing to tweak their behaviors to look out for native plants: More than 53 percent of respondents said they’d be “very willing” to change their behavior if they learned they were contributing to spreading invasive species; less than 1 percent wouldn’t entertain the idea. More than half of the subjects had already combated invasive species in their own gardens, and nearly one-third researched plants prior to planting with an eye towards replacing invasive species with native or noninvasive ones.
Still, only about 30 percent of gardeners said they were very concerned about invasive species. Bruce Lauber, a senior research associate in the HRDU and co-author of the report, speculates that this discrepancy might have something to do with ideas about what constitutes the “wild” world. “When you’re involved in an activity on your property (like gardening) you may not expect to be in a ‘natural’ habitat in the same way that you would if you were off fishing in a lake or stream or camping in the woods,” he tells CityLab.
Overall, though, since many respondents were already aware of invasive species and receptive to changing their behavior, the authors concluded that outreach initiatives might be most useful if they focused on behaviors that are “easier and less costly to carry out.” Lauber is encouraged by public interventions such as handing out native seeds. These initiatives “certainly fit the description of the kind of intervention we were suggesting—[they] give people a low-cost, low-effort way to try planting native species,” he says.
Urbanites who don’t own their property might not be able to sow a native garden. Instead, Goad suggests adding elbow grease to the cause through volunteering. Local organizations often recruit volunteers to help remove invasive species, plant natives into an area that’s being restored, or work as citizen scientists to collect data on at-risk species. “People can learn about their native ecosystems, wherever they live, and how to support them,” she says.
And even on a municipal scale—as construction uproots native plants—there’s hope for re-establishing habitats. Once lost, native plants aren’t necessarily gone forever. In The Atlantic, Nate Berg recently wrote about reimagining a road that fractured a decommissioned army base (now park land) in San Francisco. Green-roofed tunnels will encase the newly subterranean road, granting the Presidio 14 more usable acres—and space to expand the populations of native grasses, shrubs, and succulents. Berg reported that more than 50 species were being collected and cultivated for landscaping, which is expected to be fully installed by 2018. In Washington, D.C., Christian adds, the DOEE is also partnering with the Department of Transportation and Department of Public Works to install meadow habitats along roadways and in medians.
Despite their crucial role in urban ecosystems, says Goad, “I think plants often get overlooked.” She believes the solution is, in part, reminding people of the extent to which they live alongside the natural world, not separate from it. “To whatever degree we can remove this hard barrier between nature and where people live, will be so beneficial to native plants and wildlife.”
This article appears courtesy of CityLab.
We want to hear what you think. Submit a letter to the editor or write to firstname.lastname@example.org. | <urn:uuid:8c8992ee-28c8-4b8f-9b77-47cbf4437e25> | 3.4375 | 1,477 | Truncated | Science & Tech. | 44.500173 | 95,509,159 |
The birds sing distinctly different songs today than did their ancestors 30 years ago – changes passed along generation to generation, according to a new study of more than three decades' worth of sparrow recordings by University of Guelph researchers.
Integrative biology professors Ryan Norris and Amy Newman, along with researchers at Bowdoin College and Williams College in the U.S., analyzed the songs of male Savannah sparrows (Passerculus sandwichiensis) recorded over three decades, and found that the songs had changed distinctly from 1980 to 2011.
“The change is the result of cultural transmission of different song elements through many generations,” said Norris.
He said the change in tune resembles variations in word choice and language among humans.
“If you listen to how people used to talk in the 1890s and how we talk today, you would notice major differences, and this is the result of shifts in culture or the popularity of certain forms,” he said. “The change in sparrow songs over time has occurred much the same way.”
The sparrows, which live on Kent Island, N.B., in the Bay of Fundy, can generally sing only one song type with several parts. Male sparrows learn that song early in their first year and continue to sing the same tune for the rest of their lives.
“Young male sparrows learn their songs from the birds around them,” said Norris. “It may be their fathers, or it could be other older male birds that live nearby.”
Each male sparrow has its own unique sound, added Newman.
“While the island’s sparrows all sing a characteristic ‘Savannah sparrow song,’ with the same verses and sound similar, there are distinct differences between each bird,” she said. “Essentially, it is like karaoke versions of popular songs. It is the rise and fall in popular cover versions that has changed over time.”
The researchers found that each song generally has three primary elements. The first identifies the bird as a Savannah sparrow, the second indicates which individual is singing, and the third component is used by females to assess males.
Using sonograms recorded from singing males each breeding season, the researchers determined that, although the introductory notes had stayed generally consistent for the last 30 years, the sparrows had added a series of clicks to the middle of their songs. The birds had also changed the ending trill: once long and high-frequency, it is now shorter and low-frequency.
“We found that the ending trill of the song has become shorter, likely because female sparrows preferred this, because males with shorter trills had higher reproductive success,” Norris said.
Kent Island has been home to the Bowdoin Scientific Station since it was donated by J. Sterling Rockefeller in 1932, and the birds have been recorded since the 1980s. Individual birds are also monitored throughout their lifetime.
“We know the identity and history of every single sparrow in the study population,” said Norris, who has led the project with Newman since 2009. “To have 30 years of recordings is very rare, and it was definitely surprising to see such drastic changes.”
Their study appears in the January 2013 issue of Animal Behaviour.For more information:
Ryan Norris | 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...
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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- An automated spectroradiometer for global and diffuse irradiance has been designed.
- The spectrometer has been thoroughly characterized.
- Agreement of simultaneous measurements with a BSRN station is good.
- Measured spectra were used for inversion of atmospheric radiative transfer model 6S.
- Column water vapor, ozone, and aerosol optical depth can be retrieved from inversion.
An automated hyperspectral radiometer for the measurement of global and diffuse sky irradiance, SkySpec, has been designed for providing the SMEAR-Estonia research station with spectrally-resolved solar radiation data. The spectroradiometer has been carefully studied in the optical radiometry laboratory of Tartu Observatory, Estonia. Recorded signals are corrected for spectral stray light as well as for changes in dark signal and spectroradiometer spectral responsivity due to temperature effects. Comparisons with measurements of shortwave radiation fluxes made at the Baseline Surface Radiation Network (BSRN) station at Tõravere, Estonia, and with fluxes simulated using the atmospheric radiative transfer model 6S and Aerosol Robotic Network (AERONET) data showed that the spectroradiometer is a reliable instrument that provides accurate estimates of integrated fluxes and of their spectral distribution. The recorded spectra can be used to estimate the amount of atmospheric constituents such as aerosol and column water vapor, which are needed for the atmospheric correction of spectral satellite images.
Journal: Journal of Quantitative Spectroscopy and Radiative Transfer - Volume 204, January 2018, Pages 272-280 | <urn:uuid:2c2a619c-d5ea-4620-b6b0-40084fe655d2> | 2.75 | 457 | Truncated | Science & Tech. | 16.105024 | 95,509,218 |
A fabulous sunset at Drake Bay near Corcovado national park, Costa Rica. See other beautiful phenomena from the Costa Rica.
Sea turtles are amongst the most fascinating animals on Earth because of the way they have adapted their bodies in order to survive life in harsh, saltwater environments. These various species of sea turtles are distinguishable by appearance, lifestyle and other unique characteristics. Unfortunately, most of the species have been overexploited and now face endangerment in the same habitats that once allowed their populations to thrive. Conservation efforts have been improved over the years, but more drastic measures need to be encouraged if the sea turtles’ future is to be secured.
Turtles and tortoises belong to the order Testudinata, which is divided into two suborders. These suborders, Cryptodira (hidden-necked turtles) and Pleurodira (side-necked turtles), are comprised of about 250 species. Sea turtles belong to the Cryptodirans suborder, consisting of species living throughout the tropical and temperate oceans of the world and most types living on land or in lakes and rivers. (Cogger 108). More specifically, sea turtles are separated into the family Cheloniidae (Loggerhead turtles, Flatback turtles, Green turtles, Hawksbill turtles, Kemp’s ridley and Olive ridley) and the family Dermochelyidae (Leatherback turtle) (Alderton, 175). These seven species of sea turtles reached their peak during the Jurassic and Cretaceous periods, 200 to 65 million years ago (Zweifel 114).
Sea turtles’ anatomical features began evolving about 150 million years ago, when some turtles moved from living on land to living in the sea (Lehrer 92). This unique evolution required the animal to make the necessary adaptations to life in an aquatic, saltwater environment. One change involved the limbs becoming paddle-shaped, in order to push itself through the water. This necessary movement also requires that the forelimbs be more powerfully developed than the hind, a distinction with most other turtles. Since the limbs have evolved to benefit them in the water, this is the only group that must drag its body when on land to lay eggs (Lehrer 93). Another majr evolutionary change took place internally with the lacrymal gland, located in the eye. The high levels of salt in the new aquatic environment caused stress on the kidneys of sea turtles. This adaptation to the environment allows the reptiles to take saltwater into their bodies and then excrete the salts through the lacrymal gland. This conversion from saltwater to freshwater keeps the internal organs from failing and prevents the sea turtle from becoming dehydrated (Alderton 40).
I chose to focus my paper on the Atlantic or Kemp’s ridley (Lepidochelys kempii) species because it is the most critically endangered marine chelonian and predominantly positioned in our Tropical Marine Ecology course’s area of study. This chelonian was named after Richard M. Kemp, a fisherman who located the species in Florida (http://turtles.org/ridleyd.htm). The Kemp’s ridley sea turtle is found mainly in the Gulf of Mexico and surrounding warm Atlantic waters. Occasionally, in the summer and fall seasons, the turtles will migrate up to New England via the Gulf Stream (Conant 76). This sea turtle may have become isolated in this area as a result of the Panamanian land-bridge closure four million years ago (Alderton 116). Kemp’s ridleys are carnivorous animals because the mainstays in their diet include crabs, lobster, snails, jellyfish, shrimp and clams.
Many physical characteristics help to distinguish the Kemp’s ridley species from all other sea turtles. First, it averages 23 to 27.5 inches, distinctively making it the smallest sea turtle. The size of the sea turtle caused it to receive the nickname “Bastard turtle” because of the belief that it is a hybrid between Loggerhead turtles and Green turtles (Conant 77). Even though Kemp’s ridley is the smallest sea turtle, it has an unusually large head. The head contains a recognizable “beak” that is used to catch and separate hard-shelled prey (http://www.cresli.org). Kemp’s ridley is also the only sea turtle with an almost circular carapace (upper part of the shell) because it is almost as wide as it is long (Conant 77). This carapace will change from a gray-black color at birth to a lighter gray-olive color at maturity. The plastron (lower part of the shell) will develop from gray-black to a cream-white color (http://turtles.org/ridleyd.htm).
After mating offshore, female sea turtles leave their aquatic environment in order to lay their eggs, while males remain in the ocean their entire lives. These females always return to the same beach for nesting. Extensive research has been done to try to determine if the sea turtles will only lay eggs at the beach in which they were born. It is believed that newly hatched sea turtles will eat some sand to imprint the smell and taste, allowing it to find the same beach in the years to come (Cogger 115).
The Kemp’s ridley has numerous unique characteristics relating to its nesting habits. First, this species only utilizes one nesting beach, Tamaulipas, Mexico, which is located on the eastern coast. This adds to its vulnerability of extinction because hunters can easily determine when and where the eggs are laid (Zweifel 114). The Kemp’s ridley females usually nest three times from April through July, with a 10 to 28 day resting period in between. The nesting process, which averages the laying of 110 eggs, may take place in a range from every year to every three years (http://dep.state.ct.us). Contrasting it from all other sea turtles, the Kemp’s ridley is a diurnal nester, as opposed to a nocturnal nester, which means they lay their eggs during the daylight hours. In order to elude predators and have a higher chance for survival, the nesting procedure must be done in a swift manner, causing the turtles to frantically dig and crawl atop each other. The Kemp’s ridleys collectively come ashore for the arribada, or “arrival”. In 1947, this communal nesting used to reach numbers of 42,000 at one time. Recently, with the decreasing population, the arribadas have reached levels as low as 400 females per season (http://www.nmfs.noaa.gov). The small size and light weight is an advantage of the Kemp’s ridley sea turtles. This allows for a smaller track to be left in the sand, which can lead predators to the nesting site. Sea turtles also prefer to nest when winds are strong, so that their track and scent is dispersed, further helping to conceal the nesting location (Alderton 119).
On December 2, 1970, the Kemp’s ridley was placed on the endangered list, a condition that has since remained unchanged. The endangerment is further evident because the overall population is believed to be less than 5,000, even though Kemp’s ridleys have received protection in Mexico since the 1960’s (Alderton 119). Predators are the main cause of this drastic reduction in population. Humans are their largest predator, but other animals such as coyotes, wild dogs and feral hogs also place a high risk on the Kemp’s ridleys’ survival. Collecting the eggs, fishing, killing the mature turtles for meat and directly taking them for indigenous use are a few of the ways that human involvement in the oceanic world has impaired the population (http://www.nmfs.noaa.gov). Even though these examples have led to a dramatic reduction, the shrimp trawlers have made an even greater impact. Before regulations were placed on shrimping, each year an estimated 500 to 5,000 Kemp’s ridleys found themselves caught in trawls, crab traps and gill nets, where they would later drown. The mortality is much higher for Kemp’s ridleys than other sea turtles because they feed mainly on the crustaceans being caught, as opposed to other turtles that favor marine vegetation (Alderton 120). It seems that a slow recovery is on its way due to stricter regulations in regards to shrimp trawlers. Turtle Excluder Devices (TEDs) must now be used in order to reduce the number of turtles that are trapped and drown, by recognizing objects larger than shrimp in the net. The shrimp fleets have been drastically reduced and the near shore water off of Tamaulipas, Mexico is closed during the nesting season, although it is loosely enforced (http://www.nmfs.noaa.gov).
Human population growth and coastal development are yet additional risks to Kemp’s ridleys. As the Mexican population grows and more people desire to live in areas close to the beach, the single nesting site of the Kemp’s ridley is becoming increasingly threatened. Kemp’s ridleys are also threatened by marine pollution, debris and dredging. These threats are still linked to humans because they are direct results of human actions. The nesting area and the two main feeding sites are in locations of high-density offshore oil extraction. Oil exploration and production leave Kemp’s ridleys at an elevated level of vulnerability to oil spills. Debris floating in the Gulf of Mexico, such as hooks, cans, cellophane or rope, can easily be ingested or cause entanglement of the sea turtles. The dredging operations may directly kill Kemp’s ridleys or cause degradation of their habitat. The channeling that is a result of the dredging leads to decreased water quality and altered current flow, which will change the migratory habits of the turtles (http://www.nmfs.noaa.gov). These examples are not the only causes of concern for Kemp’s ridleys, but they are the threats that pose the greatest problem with decreasing population numbers.
Luckily, conservation efforts have become more apparent in recent years and in some areas are proving to be beneficial. The Caribbean Conservation Corporation is the oldest sea turtle conservation organization in the world. It runs many tracking programs and focuses on the education, research and passing of conservation actions in order to increase sea turtle population (http://www.cccturtle.org/). One such effort is the Recovery Plan for U.S. Population of Kemp's Ridley Sea Turtle by the U.S Fish and Wildlife Service and National Marine Fisheries Service in 1992. The goal of this plan is to move Kemp’s ridleys from the endangered list to the threatened list (http://turtles.org/ridleyd.htm).
In 1947, research shows that there were 162,400 mature Kemp’s ridleys. Less than 30 years later, in 1974, the same study shows that the population level had dropped to 4,872 (http://www.seaturtle.org/). Currently, numbers are hard to determine, but it is estimated that less than 5,000 Kemp’s ridleys remain (Alderton 119). Hopefully, since hundreds of programs and projects have been enacted over the years, each one will make a small difference and together progress will be achieved. Individually we can all make a difference through actions such as donations, letters to government officials regarding conservation efforts, promoting the usage of TED’s and respecting the Kemp’s ridleys’ habitat. If humans want to be able to study and experience the unique aspects of Kemp’s ridleys, we must make an extreme effort in the near future to protect the remaining sea turtles, so their populations can once again flourish.
Alderton, David (1988) Turtles & Tortoises of the World, Facts on File Publications, New York. Pg. 40, 115-122, 175.
Caribbean Conservation Corportaion. http://www.cccturtle.org/. World Wide Web.
Cogger, Harold (1998) Encyclopedia of Reptiles & Amphibians; Second Edition, Academic Press, San Diego. Pg. 108-117.
Conant, Roger and Joseph T. Collins (1991) Peterson Field Guide; Reptiles and Amphibians of Eastern & Central North America; Third Edition, Houghton Mifflin Company, Boston. Pg.75-78.
Connecticut Department of Environmental Protection. http://dep.state.ct.us/burnatr/wildlife/factshts/krsturt.htm. World Wide Web.
Kemp’s Ridley. http://turtles.org/ridleyd.htm. World Wide Web.
Kemp’s Ridley Sea Turtle. http://www.cresli.org/cresli/turtles/kemprid.html. World Wide Web.
Lehrer, John (1993) The World of Turtles and Tortoises, Tetra Press, New York. Pg.92-101.
Office of Protected Resources. http://www.nmfs.noaa.gov/prot_res/species/turtles/kemps.html. World Wide Web.
Sea Turtles. http://www.seaturtle.org/. World Wide Web.
Zweifel, Richard (1992) Reptiles & Amphibians, Smithmark Publishers, New York. Pg. 114-117.
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Hebrew University researchers surveyed a 5,000 km long strip of the sea and measured the calcification rates of coral reefs and open sea plankton over the whole Red Sea area
Following a 5,000 km long ocean survey, research published in the Proceedings of the National Academy of Sciences presents a new way to measure how the acidification of water is affecting marine ecosystems over an entire oceanic basin.
Figure 1: An aerial photo of a coral reef. Researchers developed a new tool to quantify the effect of ocean acidification on calcifying organisms. (Photo: Boaz Lazar, Hebrew University)
As a result of man-made emissions, the content of CO2 in the atmosphere and oceans has increased dramatically during recent decades. In the ocean, the accumulating CO2 is gradually acidifying the surface waters, making it harder for shelled organisms like corals (Figure 1) and certain open sea plankton to build their calcium carbonate skeletons.
Since this process impacts the functioning of many marine ecosystems, it has been intensively studied in recent years. However, getting an accurate measure is complicated because the effect of ocean acidification on the rates of calcium produced by marine organisms is highly variable and species specific.
Since scientists tend to use local and site-specific field measurements, treating reef environments and open sea environments separately, their measurements reflect the local response of individual organisms to elevated CO2 levels, and not the overall picture.
To get a clearer picture of how ocean acidification is affecting large marine areas, a group of Israeli researchers studied a 5,000 km long strip of ocean (Figure 2), from Eilat to the Seychelles crossing the Red Sea, the Gulf of Aden and the Western Indian Ocean.
The group was led by Profs. Boaz Lazar and Jonathan Erez and the Ph.D. student Zvi Steiner, together with Prof. Amitai Katz, all from the Fredy and Nadine Herrmann Institute of Earth Sciences at the Hebrew University of Jerusalem, together with Prof. Aldo Shemesh and Dr. Ruth Yam of the Weizmann Institute of Science.
The researchers developed a new method to simultaneously assess the overall calcification rates of coral reefs and pelagic (open sea) plankton over a whole oceanic basin, based on variations in surface water chemistry. These variations result from the tendency of organisms that precipitate calcium carbonate skeletons to replace some of the calcium in their skeletons with other elements (e.g. the element strontium).
These replacements depend on growth conditions and are typical for each group of organisms. Owing to this characteristic, corals produce calcium carbonate with a different chemistry than calcareous (composed largely of calcium carbonate) plankton, and their overall effect alters the chemistry of the ocean water. This is the first study that demonstrates the feasibility of quantifying this type of information on an oceanic basin scale.
The group estimated that pelagic plankton precipitate 80% of the Red Sea calcium carbonate, and coral reefs precipitate about 20%. This data is a crucial milestone if we wish to track the effect of anthropogenic activity originating from human actions, since it is not possible to quantify change without having objective baseline conditions.
Monitoring the variations in coral and plankton growth rates every few years can provide essential information regarding rates of environmental change in tropical and subtropical seas like the Red Sea, Caribbean and South China Sea.
The research was published in PNAS (Proceedings of the National Academy of Sciences of the United States of America) as ”Basin scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean”. The research was supported by the Israel Science Foundation, the Bill and Melinda Gates Foundation and the Israeli Ministry of Science and Technology.
For information or interviews, contact:
Hebrew University Foreign Press Liaison
02-5882844 / +972-54-8820860
Dov Smith | Hebrew University
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
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Nasa to shoot lasers at space junk around Earth to prevent collisions with satellites
- Nasa fears ‘Kessler Syndrome’, where there is too much space junk for it to be safe to fly out, leaving us trapped on Earth
Nasa is considering using lasers to deflect space junk around Earth and stop it colliding with satellites.
Lasers similar to those used for welding in car factories would be fired through telescopes to ‘nudge’ piles of rubbish left in orbit.
The gentle movement would stop them from taking out communications satellites or hitting the International Space Station.
Crowded: An artist's impression of space junk in low-Earth orbit. Nasa is considering using lasers to deflect the debris and stop it colliding with satellites
The process could also avoid what is known as ‘Kessler Syndrome’, where there is too much space junk flying around Earth for it to be safe to fly out, leaving us trapped on our own planet.
Such a situation has been predicted by Nasa for more than 30 years and a string of recent near-misses have added urgency to the need to find a solution.
Now a team led by Nasa space scientist James Mason have claimed that gently moving junk off course could be the answer.
The theory is that the photons in laser beams carry a tiny amount of momentum in them which, under the right circumstances, could nudge an object in space and slow it down by 0.04 inches per second.
By firing a laser at a piece of junk for a few hours it should be possible to alter it’s course by 650ft per day.
WHAT IS SPACE JUNK?
Since the first object, Sputnik One, was launched into space 53 years ago, mankind has created a swarm of perhaps tens of millions of items of debris.
The rubbish circling the planet comes from old rockets, abandoned satellites and missile shrapnel.
It is estimated that there are 370,000 pieces of space junk floating in Earth's orbit.
The picture above shows a ball of twisted metal, thought to be fallen space junk, on a farm in Queensland, Australia, in 2008.
While that won’t be enough to knock it out of orbit, it could be sufficient to avoid a collision with a space station or satellite.
The theory marks a change in approach from previous research which looked into using expensive military Star Wars-style lasers to destroy space junk.
The new project uses equipment that is available for just $800,000 (£500,000) with the final bill coming to just tens of millions of dollars.
Existing telescopes could even be modified, bringing the cost down further.
Nudging would also be more accurate and it is thought the process could divert up to half of all space junk.
Some 20,000 pieces of rubbish are
currently being monitored in low-Earth orbit, the majority of which are
discarded bits of spacecraft or debris from collisions.
Serious accidents in recent years included the 2009 smash between the Iridium 33 satellite and the Kosmos 2251 satellite.
The communications vessels collided at more than 3,000m per second - the first major smash between two operational satellites in Earth orbit.
Nasa engineer Creon Levit said it was imperative that something was done about space junk.
‘There’s not a lot of argument that this is going to screw us if we don’t do something’ he told Wired.
‘Right now it’s at the tipping point … and it just keeps getting worse.’
The new paper was submitted to the journal Advances in Space Research.
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- Zoom, the new social video challenge putting kids and pets at risk | <urn:uuid:67399833-132d-4211-b912-b808189f9bee> | 3.328125 | 939 | News Article | Science & Tech. | 48.718862 | 95,509,233 |
If you were a geologist, how would you go about studying regional metamorphosis?© BrainMass Inc. brainmass.com July 18, 2018, 3:18 am ad1c9bdddf
Please see response attached for best formatting, which is also presented below. I hope this helps and take care.
Metamorphic rock is a type of rock that forms as a result of an existing rock remelting as the result of extreme heat or pressure. Often metamorphic rocks retain some characteristics of the parent rock from which it is derived. There are two types of metamorphosis that rocks can undergo, contact metamorphosis and regional metamorphosis. Regional metamorphosis occurs when large pockets of molten rock rise to up in the crust, in a similar manner that hot air rises. As a result, the rocks that lie over this hot pocket of magma is partially melted and transformed in a wide geographic area. http://www.maroon.com/bigbend/met/index.html
SEE ATTACHED RESPONSE FOR DIAGRAM
The rest of this response is according to Monroe and Wicander (1995), which is referenced below:
Most metamorphic rocks result from regional metamorphism, which occurs in large areas and usually caused by tremendous temperatures, pressures, and deformities within deeper portions of the Earth's crust. Geologists study regional metamorphosis by identifying the gradiation in metamorphism (along convergent plate margins) through identifying the metamorphic minerals that are present. Certain metamorphic minerals are associated with different heat and pressures, and thus ...
From the perspective of a geologist, this solution explains how to study regional metamorphosis. | <urn:uuid:84021577-e293-42b8-92ed-e33347d99943> | 3.859375 | 353 | Q&A Forum | Science & Tech. | 40.184537 | 95,509,235 |
A joint study published in Cell by the teams headed by Miquel Coll at the Institute for Research in Biomedicine (IRB Barcelona) and the Institute of Molecular Biology of CSIC, both in Barcelona, and Dolf Weijers at the University of Wageningen, in the Netherlands, unravels the mystery behind how the plant hormones called auxins activate multiple vital plant functions through various gene transcription factors.
This shows the atomic structure of an ARF/DNA complex. Auxins control the growth and development of plants through ARF
Credit: (Author: R. Boer, IRB/CSIC)
At the molecular level, the hormone serves to unblock a transcription factor, a DNA-binding protein, which in turn activates or represses a specific group of genes. Some plants have more than 20 distinct auxin-regulated transcription factors. They are called ARFs (Auxin Response Factors) and control the expression of numerous plant genes in function of the task to be undertaken, that is to say, cell growth, flowering, root initiation, leaf growth etc.
Using the Synchrotron Alba, near Barcelona, and the European Synchrotron Radiation Facility, in Grenoble, Dr. Miquel Coll, a structural biologist and his team analyzed the DNA binding mode used by various ARFs. For this purpose, the scientists prepared crystals of complexes of DNA and ARF proteins obtained by Dolf Weijers team in Wageningen, and then shot the crystals with high intensity X-rays in the synchrotron to resolve their atomic structure. The resolution of five 3D structures has revealed why a given transcription factor is capable of activating a single set of genes, while other ARFs that are very similar with only slight differences trigger a distinct set.
"Each ARF recognizes and adapts to a particular DNA sequence through two binding arms or motifs that are barrel-shaped, and this adaptation differs for each ARF," explains Roeland Boer, postdoctoral researcher in Miquel Coll's group at IRB Barcelona, and one of the first authors of the study.
The ARF binding mode to DNA has never been described in bacteria or animals. "It appears to be exclusive to plants, but we cannot rule out that it is present in other kingdoms. Our finding is highly relevant because we have revealed the ultimate effect of a hormone that controls plant development on DNA, that is to say, on genes." says Miquel Coll.
Cell (2014) http://dx.doi.org/10.1016/j.cell.2013.12.027More information: Sònia Armengou. Oficina de prensa.Institut de Recerca Biomèdica (IRB). 93 403 72 55/ 618 294 070
Sònia Armengou | 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:2d83c601-6e9e-4cb9-a8bd-233e5a2d640c> | 3.125 | 1,257 | Content Listing | Science & Tech. | 44.937803 | 95,509,244 |
Abrasion in action.
Mechanical weathering is a term geologists use to describe the group of natural forces that act on larger rocks to break them down into smaller ones. Here are some examples of how mechanical weathering works.
When water freezes, it expands. So when water gets trapped in the pores and crevices of a rock then freezes, it can push the rock apart, causing it to break. Some minerals, like calcium carbonate, can have a similar effect.
Growing bacteria, plant and tree roots can destroy a rock by working their way down into its nooks and crannies, forcing the rock apart and causing it to break into smaller pieces.
In areas where the temperature fluctuates dramatically, rock can expand and contract over a very short period of time, weakening it and causing breaks.
Rocks formed under the Earth’s surface are subjected to tremendous pressure. As those rocks are moved toward the Earth’s surface, pressure is released and the rock expands, which can lead to fracturing.
The movements of water and wind can expose rocks to friction and abrasion from other rocks, particles and surfaces, causing them to break apart. | <urn:uuid:83d66f9d-260a-4c81-83fb-24f5a391b091> | 4.4375 | 242 | Knowledge Article | Science & Tech. | 49.881136 | 95,509,259 |
Topics in Group Theory
In this final chapter we extend our knowledge of group theory. Among other aspects of finite groups, we investigate permutation groups and obtain two results of cardinal importance in the theory of finite groups. In the first of these, we establish the structure of Abelian groups and, in the second, we establish the existence of the so-called ‘Sylow p-subgroups’ of a finite group.
KeywordsAbelian Group Normal Subgroup Finite Group Cyclic Group Symmetric Group
Unable to display preview. Download preview PDF. | <urn:uuid:445d6ece-d9ba-48d6-985f-508c1235c3e6> | 3.125 | 119 | Truncated | Science & Tech. | 42.802581 | 95,509,268 |
Scientists discover structure within the Sun's atmosphere Engadget - July 20, 2018
By taking these advanced steps, the team was able to determine that the Sun's outer corona does indeed have a physical structure
Giant Waves Nearly Half a Million Miles Across Seen on the Sun for the First Time Live Science - May 22, 2018
Huge, slow-moving waves that drive Earth's weather and shape the swirls in Jupiter's atmosphere also exist on the sun, new research reveals. Called Rossby waves or planetary waves, the large-scale waves occur in all rotating fluids, but now they've been identified on the sun.
What will happen when our sun dies? Science Daily - May 7, 2018
Scientists agree the sun will die in approximately 10 billion years, but they weren't sure what would happen next... until now. A team of international astronomers predict it will turn into a massive ring of luminous, interstellar gas and dust, known as a planetary nebula. A planetary nebula marks the end of 90% of all stars active lives and traces the star's transition from a red giant to a degenerate white dwarf. But, for years, scientists weren't sure if the sun in our galaxy would follow the same fate: it was thought to have too low mass to create a visible planetary nebula.
Waves similar to those controlling weather on Earth have now been found on the Sun PhysOrg - May 7, 2018
A team of scientists has discovered new waves of vorticity on the Sun. These Rossby waves propagate in the direction opposite to rotation, have lifetimes of several months, and maximum amplitudes at the Sun's equator. For forty years scientists had speculated about the existence of such waves on the Sun, which should be present in every rotating fluid system. Now, they have been unambiguously detected and characterized for the first time. The solar Rossby waves are close relatives of the Rossby waves known to occur in the Earth's atmosphere and oceans.
The amazing moment the sun stamps out its own eruption: NASA footage captures magnetic forces as they shred dense solar material and cause it to collapse Daily Mail - August 13, 2017
Spectacular footage of what first appeared to be a solar eruption, but then turned out to be something else, has given scientists insight into the sun's magnetic landscape. On September 30, 2014, a suite of NASA instruments spotted what appeared to be a solar eruption - but soon after, a serpentine structure known as a filament rose from the surface and collapsed, being shredded to pieces by invisible magnetic forces. A study on the phenomenon revealed it was caused by a filament pushing up against a complex magnetic structure 'like two igloos smashed against each other,' which then ate away at the filament and caused chips of solar material to spray.
NASA watches the Sun put a stop to its own eruption PhysOrg - August 13, 2017
On Sept. 30, 2014, multiple NASA observatories watched what appeared to be the beginnings of a solar eruption. A filament - a serpentine structure consisting of dense solar material and often associated with solar eruptions - rose from the surface, gaining energy and speed as it soared. But instead of erupting from the Sun, the filament collapsed, shredded to pieces by invisible magnetic forces. Because scientists had so many instruments observing the event, they were able to track the entire event from beginning to end, and explain for the first time how the Sun's magnetic landscape terminated a solar eruption.
Sun experiences seasonal changes, new research finds PhysOrg - April 7, 2015
The Sun undergoes a type of seasonal variability with its activity waxing and waning over the course of nearly two years, according to a new study by a team of researchers led by the National Center for Atmospheric Research (NCAR). This behavior affects the peaks and valleys in the approximately 11-year solar cycle, sometimes amplifying and sometimes weakening the solar storms that can buffet Earth's atmosphere. The quasi-annual variations appear to be driven by changes in the bands of strong magnetic fields in each solar hemisphere. These bands also help shape the approximately 11-year solar cycle that is part of a longer cycle that lasts about 22 years.
Current Solar Activity - NOAA
CRYSTALINKS HOME PAGE
PSYCHIC READING WITH ELLIE
2012 THE ALCHEMY OF TIME | <urn:uuid:eb34a614-74e0-44d1-8d9c-215451a42fbd> | 3.34375 | 884 | Content Listing | Science & Tech. | 38.121996 | 95,509,288 |
In this section, we are going to describe the text tag. The text tag is a generic tag that is used to render a I18n text message. Follow one of the three steps:
1. Keep the message to be displayed in a resource bundle with the same name as the action that it is associated with ie. create a properties file in the same package as your Java class with the same name as your class, but with .properties extension.
2. If the property file does-not work or the message is not found in the resource bundle, then the body of the tag will be used as default message.
3. If there is no body, then the name of the message will be used.
Add the following code snippet into the struts.xml file.
|<action name="textTag" class="net.roseindia.textTag">
Create an action class as shown below:
Create a property file in the same package where your
Java program file (textTag.java)
is saved with the name as package.properties.
webname1 = http://www.RoseIndia.net
webname2 = http://www.javajazzup.com
webname3 = http://www.newstrackindia.com
Now create a jsp page to see the working of the
The first three tags
<s:text name="webname1">,<s:text name="webname2">
and <s:text name="webname3"> uses the package.properties
file to display the text message.
The next tag
<s:text name="empname">Vinod, Amit, Sushil, .......</s:text>
uses the body of the tag as a default message.
The last tag
does not have access to the package.properties
files nor does it have a body so it uses name of the message to display.
Output of the textTag.jsp: | <urn:uuid:821525b9-2dbf-4d07-baf5-c294b9248809> | 3.09375 | 416 | Tutorial | Software Dev. | 73.13004 | 95,509,293 |
Scientists at the University of Reading are leading a consortium (universities of Reading, Cardiff and Southampton, and the Natural History Museum) that is developing a "virtual laboratory" to help researchers around the world make sense of the mass of diverse, incomplete and often incompatible databases available on different species, according to an article published in the July edition of BBSRC business.
One species covered by the scientists is the yellow-flowered Spanish Broom which is now well established by roadsides in the UK, but it has also travelled to Latin America and South Africa. The “virtual laboratory” will help scientists around the world better understand whether this present distribution represents the natural spread of the species to fill its bioclimatic envelope, or if it is simply the work of Spanish or British colonialists transferring a favourite plant. Researchers will also be able to investigate how distributions of species will be affected by the predicted climate change scenarios.
BiodiversityWorld is one of BBSRC’’s Government-funded e-Science GRID pilot projects - it will use the GRID to provide a distributed computing environment able to collate data from around the world and to use an array of biodiversity modelling and analytical tools. As a virtual laboratory it will also provide a collaborative environment in which research groups and resource providers can work together.
Dr Neil Caithness | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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:18a8522d-8a42-4b03-aa12-c00d816d31aa> | 3.078125 | 875 | Content Listing | Science & Tech. | 32.73581 | 95,509,305 |
The Japan Agency for Marine-Earth Science and Technology (Jamstec) recently released incredible footage (filmed on May 18, 2017) which captured a snailfish in the Mariana Trench at a depth of 8,178 meters - considered to be the deepest point ever for filming fish on camera.
The footage was taken using 4K ultrahigh resolution cameras, mounted on an unmanned hadal lander, which was operated by the agency’s deep-sea research vessel Kairei.
The Chinese Academy of Sciences announced last April that they have recorded a fish at a depth of 8,152 meters in the same trench on the territory of Guam, thus setting a world record for filming a fish at an accurately measured depth.
“We hope we can shed more light on the deep-sea ecology and the depth limit for fish to inhabit,” said senior Jamstec researcher Kazumasa Oguri.
According to the agency, after the observation equipment was placed on the northern slope of the trench, the cameras caught amphipods consuming mackerel placed on the lander as bait to attract deep-ocean creatures. The type of snailfish filmed, possibly a Mariana snailfish, is believed to visit the trench to feed on amphipods. In footage shot on a different day at a depth of 7,498 meters, the same type of snailfish was observed eating the amphipods.
According to recent studies, the hypothetical depth limit for fish habitation is 8,200 meters because they are unable to control osmotic pressure below that level. (source: japantimes.co.jp)
Credit to 'Japan Agency for Marine-Earth Science and Technology'. | <urn:uuid:7642d800-512e-483a-9c71-9a78ff492fcf> | 2.90625 | 349 | News Article | Science & Tech. | 39.67486 | 95,509,307 |
Structures, Unions, Enumerations and Typedefs
This chapter examines structures, unions, enumerations and typedefs which allow a programmer to create new data types. The ability to create new types is an important and very powerful feature of C++ and releases a programmer from being restricted to the integral types offered by the language. Structures enable a programmer to form a collection of similar or different data types into a single user-defined data type, unlike arrays, which are collections of a single data type. The data members of a structure are, by default, publicly accessible. User-defined structures integrate exactly into the language. In other words, there is a single syntax for the definition and manipulation of objects of both integral C++ and user-defined types.
KeywordsFunction Argument Member Function Float Mass Void Main Const Point
Unable to display preview. Download preview PDF. | <urn:uuid:68382d47-3044-40f8-a917-d630e1a845fe> | 3.28125 | 181 | Truncated | Software Dev. | 23.789173 | 95,509,317 |
Normally muscles contract in order to support the body, but in a rare condition known as cataplexy the body's muscles "fall asleep" and become involuntarily paralyzed. Cataplexy is incapacitating because it leaves the affected individual awake, but either fully or partially paralyzed. It is one of the bizarre symptoms of the sleep disorder called narcolepsy.
"Cataplexy is characterized by muscle paralysis during cognitive awareness, but we didn't understand how this happened until now, said John Peever of the University of Toronto's Department of Cell & Systems Biology. "We have shown that the neuro-degeneration of the brain cells that synthesize the chemical hypocretin causes the noradrenaline system to malfunction. When the norandrenaline system stops working properly, it fails to keep the motor and cognitive systems coupled. This results in cataplexy – the muscles fall asleep but the brain stays awake."
Peever and Christian Burgess, also of Cell & Systems Biology used hypocretin-knockout mice (mice that experience cataplexy), to demonstate that a dysfunctional relationship between the noradrenaline system and the hypocretin-producing system is behind cataplexy. The research was recently published in the journal Current Biology in September.
The scientists first established that mice experienced sudden loss of muscle tone during cataplectic episodes. They then administered drugs to systematically inhibit or activate a particular subset of adrenergic receptors, the targets of noradrenaline. They were able to reduce the incidence of cataplexy by 90 per cent by activating noradrenaline receptors. In contrast, they found that inhibiting the same receptors increased the incidence of cataplexy by 92 per cent. Their next step was to successfully link how these changes affect the brain cells that directly control muscles.
They found that noradrenaline is responsible for keeping the brain cells (motoneurons) and muscles active. But during cataplexy when muscle tone falls, noradrenaline levels disappear. This forces the muscle to relax and causes paralysis during cataplexy. Peever and Burgess found that restoring noradrenaline pre-empted cataplexy, confirming that the noradrenaline system plays a key role.
Kim Luke | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:b61bb56f-5370-45ce-a1c3-06054385150b> | 3.359375 | 1,055 | Content Listing | Science & Tech. | 28.48846 | 95,509,320 |
Scientists have known for years that the energy cost of walking and running is related primarily to the work done by muscles to lift and move the limbs.
But how much energy does it actually take to get around? Does having longer legs really make a difference?
Herman Pontzer, Ph.D., assistant professor of physical anthropology in Arts & Sciences, has developed a mathematical model for calculating energy costs for two and four-legged animals. His research was published in a recent issue of The Journal of Experimental Biology.
"All things being equal, leg length is one of the major determinants of cost," says Pontzer, "If two animals are identical except for leg length, the animal with longer legs is more efficient."
The fossil record shows that two million years ago, there was a big increase in leg length in early humans. Pontzer suggests that one reason for this increase could have been the energy saved by having longer legs. "If you greatly increase the distance that you travel each day, then you'd expect evolution to act on walking efficiency," he says. "That way, the energy you save on travel can be spent instead on survival and reproduction."
Pontzer's LiMB model is an equation that predicts walking and running. Importantly, the model predicts that the rate of force generation — and therefore the rate of energy use — is related to limb length. Longer legs mean less force production and lower energy cost.
To test his equation, Pontzer put people, goats and dogs on a treadmill in his lab, and measured how much oxygen each used during walking and running at various speeds.
He found that the LiMB model explained more of a variation in locomotor cost than other predictors, including contact time and body mass, showing that it worked for animals with four legs as well as two.
Herman Pontzer | EurekAlert!
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Transportation and Logistics
16.07.2018 | Agricultural and Forestry Science | <urn:uuid:59c4c524-9713-49f3-a5df-a96bcf9cc10c> | 4 | 1,031 | Content Listing | Science & Tech. | 43.535699 | 95,509,336 |
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Salis is an artificial life simulation, based on Tom Ray's Tierra.
nino - Apr 12 2018 09:13 AM
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Posted 26 April 2017 - 02:32 PM
What does it really mean by "escaping" in a string ?
The escape-sequence replacements are −
\n is replaced by the newline character
\r is replaced by the carriage-return character
\t is replaced by the tab character
\$ is replaced by the dollar sign itself ($)
\" is replaced by a single double-quote (")
\\ is replaced by a single backslash (\)
Does it mean "translate"/"convert"/"substitute" or does it mean "ignore this single quote and don't take it as the ending single quote" ? I thought the former but some google result links mention the latter but mostly Googling brings irrelevant results. Brings up links related to mysqli_real_escape_string. | <urn:uuid:b21d1d51-8b2c-410a-a290-9dcca2a6dd7b> | 2.734375 | 249 | Comment Section | Software Dev. | 48.232707 | 95,509,339 |
A decade ago, a British philosopher put forth the notion that the universe we live in might in fact be a computer simulation run by our descendants. While that seems far-fetched, perhaps even incomprehensible, a team of physicists at the University of Washington has come up with a potential test to see if the idea holds water.
A North Carolina State University researcher has taken a "snapshot" of the way particles combine to form carbon-12, the element that makes all life on Earth possible. And the picture looks like a bent arm.
The breakthrough technology allows the integration of different optical components side-by-side with electrical circuits on a single silicon chip using, for the first time, sub-100nm semiconductor technology.
Engineers at the California Institute of Technology (Caltech) have created a device that can focus light into a point just a few nanometers across - an achievement they say may lead to next-generation applications in computing, communications, and imaging. | <urn:uuid:6a55223d-231b-4da0-ab24-ddda79857ac5> | 2.953125 | 196 | News Article | Science & Tech. | 24.07433 | 95,509,361 |
+44 1803 865913
Leaf beetles are one of the largest groups of beetles, with tens of thousands of species worldwide and around 280 in Britain. They belong mainly to the family Chrysomelidae, but also to two small closely related families, the Megalopodidae and Orsodacnidae. Leaf Beetles provides a comprehensive overview with detailed and accessible coverage of the natural history, ecology and biology of leaf beetles.
Topics cover the life history of leaf beetles, biology, their environment, natural enemies and interactions with humans. There is a thorough discussion about identification of British species, including detail on the juvenile stages (eggs, larvae, pupae) and a concise key to adults. A chapter is dedicated to study techniques and materials. Leaf Beetles is illustrated throughout with colour photographs and line drawings.
Leaf beetles is a vital resource for entomology students and educators, naturalists, nature conservationists, those involved in agriculture, horticulture and the management of stored produce.
2. Life history
3. Leaf beetles in their environment
4. Natural enemies of leaf beetles
5. Distribution and abundance
6. Identification of adults of British and Irish leaf beetles
7. Study techniques and materials
8. Useful addresses and links
9. References and further reading
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Dave Hubble is a freelance ecologist. He is the organiser of the UK's Chrysomelidae Recording Scheme and recently wrote the AIDGAP key to UK species. He also teaches Environmental Science at the Open University.
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Quenda poo critical to saving threatened tuart trees
Successful urban-dwellers they may be, but new research has found that quendas, also known as southern brown bandicoots, are critical to maintaining the health of Australian forests.
SOMETIMES MISTAKEN for big rats, quendas (Isoodon obesulus) – more commonly known as southern brown bandicoots – are successful urban-dwellers, often caught sipping from dog bowls or hiding under houses.
Found across Western Australia, South Australia and parts of Tasmania, their populations have persisted making them the only digging mammals that have managed to survive rapid overdevelopment of their habitats.
But they weren’t always city-slickers. New research has revealed the critical role they play in the ecosystem of Australian forests, specifically, the symbiotic relationship they have with the critically endangered tuart tree (Eucalyptus gomphocephala).
According to experts from Murdoch University, trees like tuart have suffered from the impacts of changing climate. Many of the forest trees are susceptible to insect infestations and fungal diseases. It’s estimated that over 500 ha of tuart woodland in Perth collapsed between 2010 and 2011.
The tuart trees rely on a type of fungi known as ‘ectomycorrhizal’, which helps the trees grow and survive adverse conditions. And now, by growing tuart seedlings in soil and mixing it with quenda scat, researchers found that the humble bandicoot is the critical link between the tuart trees and the fungi.
“We found that spores of fungi from the quenda poo can successfully germinate and colonise the roots of tuart seedlings after passage through the quenda gut,” Edith Cowan University fungal ecologist Anna Hopkins and Murdoch University quenda expert Natasha Tay told Australian Geographic.
“What this study shows, for the first time, is how quenda are a key linking element between the fungi and the tuart, helping disperse viable fungal spores throughout the landscape in their poo, and are thus critical to maintaining healthy tuart forests.”
Anna added that it’s not just the spreading of fungal spores that makes quendas important – it’s also their digging that mixes soil layers, helping with water infiltration and nutrient cycling.
Unfortunately, while quendas are better adapted to urban life than other animals, they still face a number of threats. “The clearing of habitat for urban expansion is the biggest threat to quendas. Not only do they lose suitable habitat, but it also brings quenda into closer contact with roads and predation by feral or pet animals,” said Natasha.
And a decline in their populations, as this new research shows, will have wider impacts for Australian forests. “I hope that this study will help people to understand just how interconnected our ecosystems are. The ectomycorrhizal fungi, the quenda and the tuart all rely on each other to survive and create healthy forests,” Anna said. | <urn:uuid:bc8589a3-6205-43ce-b6da-bbe773ea184f> | 3.59375 | 641 | News Article | Science & Tech. | 33.659577 | 95,509,367 |
In ecology, species homogeneity is a lack of biodiversity. Species richness is the fundamental unit in which to assess the homogeneity of an environment. Therefore, any reduction in species richness, especially endemic species, could be argued as advocating the production of a homogenous environment.
Homogeneity in agriculture and forestry; in particular, industrial agriculture and forestry use a limited number of species. About 7,000 plants (2.6% of all plant species) have been collected or cultivated for human consumption. Of these, a mere 200 have been domesticated and only a dozen contribute about 75% of the global intake of plant-derived calories.
95% of world consumption of protein derives from a few domesticated species, i.e. poultry, cattle and pigs. There are about 1,000 commercial fish species, but in aquaculture fewer than 10 species dominate global production. Human food production therefore rests on the tips of pyramids of biodiversity, leaving the majority of species not utilised and not domesticated.
Species naturally migrate and expand their ranges, utilising new habitats and resources, e.g. the cattle egret. These natural invasions, an incursion in the absence of anthropogenic influences, occur "when an intervening barrier is removed, or through the development of biotic or abiotic transportation mechanisms, able to overcome the barrier in question". Introductions, or human-mediated invasions, have in the last century become more frequent. It is estimated that on an average day more than 3,000 species alone are in transit aboard ocean-going vessels.
- Using species richness as the unit for which to assess global homogeneity, it appears that anthropogenic assistance in alien species establishment has done much to reduce the number of endemic species, especially on remote islands. Some 'species-poor' habitats may, however, benefit in diversity if an invader can occupy an empty niche. Arguably, that environment becomes more diverse, equally it has also "become more similar to the rest of the world", though ecological interactions between the invaders and the natives are likely to be unique. Indeed, many species are so well naturalised that they are considered native, yet they were originally introduced; with the best examples probably being the Roman and Norman introduction of the hare and the rabbit respectively to Britain.
- Introduction of non-endemic species and subsequent eradication of species can happen remarkably fast; evolutionary tempo is, however, slow and "succession of rapid change [will] result in a great impoverishment". That impoverishment will indeed equate in a world that is more similar, as there will simply be less species to formulate difference.
- ^ Luc Hens and Emmanuel K. Boon Causes of Biodiversity Loss: a Human Ecological Analysis, MultiCiencia. Human Ecology Department, Belgium.
- ^ "Food Security and Biodiversity. Biodiversity in Development" (PDF). Archived from the original (PDF) on 12 June 2007. Retrieved 17 November 2009.
- ^ Drake, J.A., Mooney, H.A., Castri, F.di., Groves, R.H., Kruger, F.J., Rejmánek, M. and Williamson, M. (1989). Biological Invasions: A Global Perspective, SCOPE 37. John Wiley and Sons. ISBN 0-471-92085-1
- ^ Carlton, J (1996). "Pattern, process, and prediction in marine invasion ecology". Biological Conservation. 78: 97. doi:10.1016/0006-3207(96)00020-1.
- ^ Cariton, J. T.; Geller, J. B. (1993). "Ecological Roulette: the Global Transport of Nonindigenous Marine Organisms". Science. 261 (5117): 78–82. doi:10.1126/science.261.5117.78. PMID 17750551.
- ^ Lövei, G.L. (1997). "Global Change Through Invasion". Nature. 388 (6643): 627–628. doi:10.1038/41665.
- ^ Rees, P. A. (2001). "Is there a legal obligation to reintroduce animal species into their former habitats?". Oryx. 35: 216. doi:10.1046/j.1365-3008.2001.00178.x.
- ^ Preston (1962). "The Canonical Distribution of Commonness and Rarity: Part II". Ecology. 43 (3): 410. doi:10.2307/1933371. JSTOR 1933371.
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How to Use the DateTime Class in PHP
One of the things most developers face is dealing with time calculations and logging. In this lesson we play around with the DateTime class and see how useful it can be.
We start off with a simple example where we set the $date variable to today's date (Line 3).
We then format the date into the Year-month-day format.
<?php $date = new DateTime('today'); echo $date->format('Y-m-d'); // based on today's date the output will be 2016-01-11
The nice thing about the DateTime class is that we can also do things like this:
<?php $date = new DateTime('next Friday'); echo $date->format('Y-m-d'); // based on today's date the output will be 2016-01-15
<?php $date = new DateTime('11th January 1870'); echo $date->format('l'); // output will be: Tuesday
We can also perform calculations. We have already used this function in this tutorial.
<?php $date1 = new DateTime('11th January 1870'); $date2 = new DateTime('27-12-2032'); $difference = $date1->diff($date2); echo $difference->format('%R%a days'); // output will be +59520 days
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PHP for Beginners
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The rewind statement will position an external file connected for sequential access at the very first record in that file.
rewind (unit, iostat, err)
The unit specifier must be an integer unit number that corresponds a file that was linked to the program earlier using the open command. It lets the computer know which file needs to be rewound (marker of current position set to the beginning of the file).
The iostat= specifier is purely optional. If used, it needs an integer variable placed after the equals sign. The compiler will then assign either a value of zero to the integer variable denoting no error occurred when rewinding the file or a positive value if an error occurred. The type of error that occurs will dictate exactly what positive value is assigned to the integer variable. Interpretation of the meaning of non-zero value is system dependent.
This is another purely optional specifier for the rewind statement. It provides statement label to branch to if an error occurs while rewinding the file.
One instance in which this statement is useful is when a file is read to get the number of lines that are contained within it before any data is read from the file. For instance if the following read was done to find the number of lines contained within the file,
100 read(37,*,end=101) dummy ldata = ldata + 1 Go to 100 101 continue
It would leave the position marker at the end of the file. Before actual data values could be read, the rewind command would have to issued as follows.
lecture twenty two
examples: log_plot.f and noadv.f
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Formal group law
In mathematics, a formal group law is (roughly speaking) a formal power series behaving as if it were the product of a Lie group. They were introduced by S. Bochner (1946). The term formal group sometimes means the same as formal group law, and sometimes means one of several generalizations. Formal groups are intermediate between Lie groups (or algebraic groups) and Lie algebras. They are used in algebraic number theory and algebraic topology.
A one-dimensional formal group law over a commutative ring R is a power series F(x,y) with coefficients in R, such that
- F(x,y) = x + y + terms of higher degree
- F(x, F(y,z)) = F(F(x,y), z) (associativity).
The simplest example is the additive formal group law F(x, y) = x + y. The idea of the definition is that F should be something like the formal power series expansion of the product of a Lie group, where we choose coordinates so that the identity of the Lie group is the origin.
More generally, an n-dimensional formal group law is a collection of n power series Fi(x1, x2, ..., xn, y1, y2, ..., yn) in 2n variables, such that
- F(x,y) = x + y + terms of higher degree
- F(x, F(y,z)) = F(F(x,y), z)
where we write F for (F1, ..., Fn), x for (x1,..., xn), and so on.
The formal group law is called commutative if F(x,y) = F(y,x).
- Prop. If R is -torsion free then any one-dimensional formal group law over R is commutative.
- Proof. The torsion freeness gives us the exponential and logarithm which allows us to write F as F(x,y) = exp(log(x) + log(y)).
There is no need for an axiom analogous to the existence of an inverse for groups, as this turns out to follow automatically from the definition of a formal group law. In other words we can always find a (unique) power series G such that F(x,G(x)) = 0.
A homomorphism from a formal group law F of dimension m to a formal group law G of dimension n is a collection f of n power series in m variables, such that
- G(f(x), f(y)) = f(F(x, y)).
A homomorphism with an inverse is called an isomorphism, and is called a strict isomorphism if in addition f(x)= x + terms of higher degree. Two formal group laws with an isomorphism between them are essentially the same; they differ only by a "change of coordinates".
- The additive formal group law is given by
- The multiplicative formal group law is given by
This rule can be understood as follows. The product G in the (multiplicative group of the) ring R is given by G(a,b) = ab. If we "change coordinates" to make 0 the identity by putting a = 1 + x, b = 1 + y, and G = 1 + F, then we find that F(x, y) = x + y + xy. Over the rational numbers, there is an isomorphism from the additive formal group law to the multiplicative one, given by exp(x) − 1. Over general commutative rings R there is no such homomorphism as defining it requires non-integral rational numbers, and the additive and multiplicative formal groups are usually not isomorphic.
- More generally, we can construct a formal group law of dimension n from any algebraic group or Lie group of dimension n, by taking coordinates at the identity and writing down the formal power series expansion of the product map. The additive and multiplicative formal group laws are obtained in this way from the additive and multiplicative algebraic groups. Another important special case of this is the formal group (law) of an elliptic curve (or abelian variety).
- F(x,y) = (x + y)/(1 + xy) is a formal group law coming from the addition formula for the hyperbolic tangent function: tanh(x + y) = F(tanh(x), tanh(y)), and is also the formula for addition of velocities in special relativity (with the speed of light equal to 1).
- is a formal group law over Z[1/2] found by Euler, in the form of the addition formula for an elliptic integral (Strickland):
Any n-dimensional formal group law gives an n dimensional Lie algebra over the ring R, defined in terms of the quadratic part F2 of the formal group law.
- [x,y] = F2(x,y) − F2(y,x)
The natural functor from Lie groups or algebraic groups to Lie algebras can be factorized into a functor from Lie groups to formal group laws, followed by taking the Lie algebra of the formal group:
- Lie groups → Formal group laws → Lie algebras
Over fields of characteristic 0, formal group laws are essentially the same as finite-dimensional Lie algebras: more precisely, the functor from finite-dimensional formal group laws to finite-dimensional Lie algebras is an equivalence of categories. Over fields of non-zero characteristic, formal group laws are not equivalent to Lie algebras. In fact, in this case it is well known that passing from an algebraic group to its Lie algebra often throws away too much information, but passing instead to the formal group law often keeps enough information. So in some sense formal group laws are the "right" substitute for Lie algebras in characteristic p > 0.
The logarithm of a commutative formal group law
If F is a commutative n-dimensional formal group law over a commutative Q-algebra R, then it is strictly isomorphic to the additive formal group law. In other words, there is a strict isomorphism f from the additive formal group to F, called the logarithm of F, so that
- f(F(x,y)) = f(x) + f(y)
- The logarithm of F(x, y) = x + y is f(x) = x.
- The logarithm of F(x, y) = x + y + xy is f(x) = log(1 + x), because log(1 + x + y + xy) = log(1 + x) + log(1 + y).
If R does not contain the rationals, a map f can be constructed by extension of scalars to R⊗Q, but this will send everything to zero if R has positive characteristic. Formal group laws over a ring R are often constructed by writing down their logarithm as a power series with coefficients in R⊗Q, and then proving that the coefficients of the corresponding formal group over R⊗Q actually lie in R. When working in positive characteristic, one typically replaces R with a mixed characteristic ring that has a surjection to R, such as the ring W(R) of Witt vectors, and reduces to R at the end.
The formal group ring of a formal group law
The formal group ring of a formal group law is a cocommutative Hopf algebra analogous to the group ring of a group and to the universal enveloping algebra of a Lie algebra, both of which are also cocommutative Hopf algebras. In general cocommutative Hopf algebras behave very much like groups.
For simplicity we describe the 1-dimensional case; the higher-dimensional case is similar except that notation becomes messier.
Suppose that F is a (1-dimensional) formal group law over R. Its formal group ring (also called its hyperalgebra or its covariant bialgebra) is a cocommutative Hopf algebra H constructed as follows.
- As an R-module, H is free with a basis 1 = D(0), D(1), D(2), ...
- The coproduct Δ is given by ΔD(n) = ∑D(i) ⊗ D(n−i) (so the dual of this coalgebra is just the ring of formal power series).
- The counit η is given by the coefficient of D(0).
- The identity is 1 = D(0).
- The antipode S takes D(n) to (−1)nD(n).
- The coefficient of D(1) in the product D(i)D(j) is the coefficient of xiyj in F(x, y).
Conversely, given a Hopf algebra whose coalgebra structure is given above, we can recover a formal group law F from it. So 1-dimensional formal group laws are essentially the same as Hopf algebras whose coalgebra structure is given above.
Formal group laws as functors
Given an n-dimensional formal group law F over R and a commutative R-algebra S, we can form a group F(S) whose underlying set is Nn where N is the set of nilpotent elements of S. The product is given by using F to multiply elements of Nn; the point is that all the formal power series now converge because they are being applied to nilpotent elements, so there are only a finite number of nonzero terms. This makes F into a functor from commutative R-algebras S to groups.
We can extend the definition of F(S) to some topological R-algebras. In particular, if S is an inverse limit of discrete R algebras, we can define F(S) to be the inverse limit of the corresponding groups. For example, this allows us to define F(Zp) with values in the p-adic numbers.
The group-valued functor of F can also be described using the formal group ring H of F. For simplicity we will assume that F is 1-dimensional; the general case is similar. For any cocommutative Hopf algebra, an element g is called group-like if Δg = g ⊗ g and εg = 1, and the group-like elements form a group under multiplication. In the case of the Hopf algebra of a formal group law over a ring, the group like elements are exactly those of the form
- D(0) + D(1)x + D(2)x2 + ...
for nilpotent elements x. In particular we can identify the group-like elements of H⊗S with the nilpotent elements of S, and the group structure on the group-like elements of H⊗S is then identified with the group structure on F(S).
The height of a formal group law
Suppose that f is a homomorphism between one dimensional formal group laws over a field of characteristic p > 0. Then f is either zero, or the first nonzero term in its power series expansion is for some non-negative integer h, called the height of the homomorphism f. The height of the zero homomorphism is defined to be ∞.
The height of a one dimensional formal group law over a field of characteristic p > 0 is defined to be the height of its multiplication by p map.
Two one dimensional formal group laws over an algebraically closed field of characteristic p > 0 are isomorphic if and only if they have the same height, and the height can be any positive integer or ∞.
- The additive formal group law F(x, y) = x + y has height ∞, as its pth power map is 0.
- The multiplicative formal group law F(x, y) = x + y + xy has height 1, as its pth power map is (1 + x)p − 1 = xp.
- The formal group law of an elliptic curve has height either one or two, depending on whether the curve is ordinary or supersingular. Supersingularity can be detected by the vanishing of the Eisenstein series .
There is a universal commutative one-dimensional formal group law over a universal commutative ring defined as follows. We let
- F(x, y)
- x + y + Σci,j xiyj
and we define the universal ring R to be the commutative ring generated by the elements ci,j, with the relations that are forced by the associativity and commutativity laws for formal group laws. More or less by definition, the ring R has the following universal property:
- For any commutative ring S, one-dimensional formal group laws over S correspond to ring homomorphisms from R to S.
The commutative ring R constructed above is known as Lazard's universal ring. At first sight it seems to be incredibly complicated: the relations between its generators are very messy. However Lazard proved that it has a very simple structure: it is just a polynomial ring (over the integers) on generators of degrees 2, 4, 6, ... (where ci,j has degree 2(i + j − 1)). Daniel Quillen proved that the coefficient ring of complex cobordism is naturally isomorphic as a graded ring to Lazard's universal ring, explaining the unusual grading.
- If is a functor from Artin algebras to groups which is left exact, then it is representable (G is the functor of points of a formal group. (left exactness of a functor is equivalent to commuting with finite projective limits).
- If is a group scheme then , the formal completion of G at the identity, has the structure of a formal group.
- A smooth group scheme is isomorphic to . Some people call a formal group scheme smooth if the converse holds.
- formal smoothness asserts the existence of lifts of deformations and can apply to formal schemes that are larger than points. A smooth formal group scheme is a special case of a formal group scheme.
- Given a smooth formal group, one can construct a formal group law and a field by choosing a uniformizing set of sections.
- The (non-strict) isomorphisms between formal group laws induced by change of parameters make up the elements of the group of coordinate changes on the formal group.
Formal groups and formal group laws can also be defined over arbitrary schemes, rather than just over commutative rings or fields, and families can be classified by maps from the base to a parametrizing object.
The moduli space of formal group laws is a disjoint union of infinite-dimensional affine spaces, whose components are parametrized by dimension, and whose points are parametrized by admissible coefficients of the power series F. The corresponding moduli stack of smooth formal groups is a quotient of this space by a canonical action of the infinite-dimensional groupoid of coordinate changes.
Over an algebraically closed field, the substack of one dimensional formal groups is either a point (in characteristic zero) or an infinite chain of stacky points parametrizing heights. In characteristic zero, the closure of each point contains all points of greater height. This difference gives formal groups a rich geometric theory in positive and mixed characteristic, with connections to the Steenrod algebra, p-divisible groups, Dieudonné theory, and Galois representations. For example, the Serre-Tate theorem implies that the deformations of a group scheme are strongly controlled by those of its formal group, especially in the case of supersingular abelian varieties. For supersingular elliptic curves, this control is complete, and this is quite different from the characteristic zero situation where the formal group has no deformations.
A formal group is sometimes defined as a cocommutative Hopf algebra (usually with some extra conditions added, such as being pointed or connected). This is more or less dual to the notion above. In the smooth case, choosing coordinates is equivalent to taking a distinguished basis of the formal group ring.
Some authors use the term formal group to mean formal group law.
Lubin–Tate formal group laws
We let Zp be the ring of p-adic integers. The Lubin–Tate formal group law is the unique (1-dimensional) formal group law F such that e(x) = px + xp is an endomorphism of F, in other words
More generally we can allow e to be any power series such that e(x) = px + higher-degree terms and e(x) = xp mod p. All the group laws for different choices of e satisfying these conditions are strictly isomorphic.
For each element a in Zp there is a unique endomorphism f of the Lubin–Tate formal group law such that f(x) = ax + higher-degree terms. This gives an action of the ring Zp on the Lubin–Tate formal group law.
This construction was introduced by Lubin & Tate (1965), in a successful effort to isolate the local field part of the classical theory of complex multiplication of elliptic functions. It is also a major ingredient in some approaches to local class field theory.
- Underwood, Robert G. (2011). An introduction to Hopf algebras. Berlin: Springer-Verlag. p. 121. ISBN 978-0-387-72765-3. Zbl 1234.16022.
- Manin, Yu. I.; Panchishkin, A. A. (2007). Introduction to Modern Number Theory. Encyclopaedia of Mathematical Sciences. 49 (Second ed.). p. 168. ISBN 978-3-540-20364-3. ISSN 0938-0396. Zbl 1079.11002.
- Koch, Helmut (1997). Algebraic Number Theory. Encycl. Math. Sci. 62 (2nd printing of 1st ed.). Springer-Verlag. pp. 62–63. ISBN 3-540-63003-1. Zbl 0819.11044.
- e.g. Serre, Jean-Pierre (1967). "Local class field theory". In Cassels, J.W.S.; Fröhlich, Albrecht. Algebraic Number Theory. Academic Press. pp. 128–161. Zbl 0153.07403.Hazewinkel, Michiel (1975). "Local class field theory is easy". Advances in Math. 18 (2): 148–181. doi:10.1016/0001-8708(75)90156-5. Zbl 0312.12022.Iwasawa, Kenkichi (1986). Local class field theory. Oxford Mathematical Monographs. The Clarendon Press Oxford University Press. ISBN 978-0-19-504030-2. MR 0863740. Zbl 0604.12014.
- Adams, J. Frank (1974), Stable homotopy and generalised homology, University of Chicago Press, ISBN 978-0-226-00524-9
- Bochner, Salomon (1946), "Formal Lie groups", Annals of Mathematics, Second Series, 47: 192–201, doi:10.2307/1969242, ISSN 0003-486X, JSTOR 1969242, MR 0015397
- M. Demazure, Lectures on p-divisible groups Lecture Notes in Mathematics, 1972. ISBN 0-387-06092-8
- Fröhlich, A. (1968), Formal groups, Lecture Notes in Mathematics, 74, Berlin, New York: Springer-Verlag, doi:10.1007/BFb0074373, MR 0242837
- P. Gabriel, Étude infinitésimale des schémas en groupes SGA 3 Exp. VIIB
- Formal Groups and Applications (Pure and Applied Math 78) Michiel Hazewinkel Publisher: Academic Pr (June 1978) ISBN 0-12-335150-2
- Lazard, Michel (1975), Commutative formal groups, Lecture Notes in Mathematics, 443, Berlin, New York: Springer-Verlag, doi:10.1007/BFb0070554, ISBN 978-3-540-07145-7, MR 0393050
- Lubin, Jonathan; Tate, John (1965), "Formal complex multiplication in local fields", Annals of Mathematics, Second Series, 81: 380–387, doi:10.2307/1970622, ISSN 0003-486X, JSTOR 1970622, MR 0172878, Zbl 0128.26501
- Neukirch, Jürgen (1999). Algebraic Number Theory. Grundlehren der mathematischen Wissenschaften. 322. Berlin: Springer-Verlag. ISBN 978-3-540-65399-8. MR 1697859. Zbl 0956.11021.
- Strickland, N. "Formal groups" (PDF).
- Zarkhin, Yu.G. (2001) , "F/f040820", in Hazewinkel, Michiel, Encyclopedia of Mathematics, Springer Science+Business Media B.V. / Kluwer Academic Publishers, ISBN 978-1-55608-010-4 | <urn:uuid:29df963e-6a8b-4ef4-b3ff-ed00d5222a98> | 3.1875 | 4,632 | Knowledge Article | Science & Tech. | 68.205821 | 95,509,433 |
Max Planck researchers show that Manduca sexta moths acquired the highest energy gain when they visited flowers that matched the length of their proboscis. The moths were supported in their choice of the best-fitting nectar sources by an innate preference for the scent of matching flowers.
That the morphology of many pollinators corresponds strikingly to the shape of the flowers they pollinate was observed more than 150 years ago by Charles Darwin. He described this perfect mutual adaptation of flowers and pollinators as the result of a co-evolutionary process.
A hawk moth (Manduca sexta) uses its eight-centimeter-long proboscis to drink nectar from a flower of Nicotiana alata.
Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, have now provided further proof of the famous naturalist’s theory. They were able to show that Manduca sexta moths acquired the highest energy gain when they visited flowers that matched the length of their proboscis.
The moths were supported in their choice of the best-fitting nectar sources by an innate preference for the scent of matching flowers. The results of this study have been published in the journal Nature Communications (Nature Communications, May 2016, doi: 10.1038/NCOMMS11644).
Flower-pollinator systems as a result of mutual adaptation
Charles Darwin, the founder of the theory of evolution, was an astute observer of nature. His extraordinary understanding of natural history laid the foundation of his theory about the origin of species. In 1862, he published a book about orchids and their pollinators in which he described the orchid Angraecum sesquipedale, which was cultivated in England but originated from Madagascar.
Because of the flower’s morphology, Darwin hypothesized that there must be a pollinator in the plant’s native habitat with an extraordinarily long proboscis enabling the nectar in the flower to be reached. In 1903, more than 20 years after Darwin’s death, such a pollinator was in fact discovered: the hawk moth Xanthopan morganii, which received the subspecies name praedicta (the predicted) in honor of Darwin’s hypothesis. This moth has a proboscis which is more than 22 centimeters long.
Biologists use the term “pollination syndrome” when they explain the amazing diversity of flowering plants and pollinators which has emerged as a result of co-evolution. A flower-pollinator system can be highly specialized. Both partners benefit from the relationship: The plant increases the likelihood it will transfer pollen to flowers of conspecifics and not waste it on other species. Specialized pollinators, on the other hand, have an advantage over competing generalist pollinators, which are also foraging for nectar, because their proboscis is better adapted. The disadvantages of such specialization are that the reproductive success of the highly specialized plant wanes when its pollinator is absent, and the survival rate of the pollinator decreases in the absence of the plant as well.
Darwin’s observations inspired Markus Knaden, who heads the studies with Manduca sexta hawk moths in the Department of Evolutionary Neuroethology, and his colleagues. They hypothesized that there must be a flower which fits this pollinator perfectly, although the moth is a generalist and visits a broad range of flowering plants. The tobacco hawk moths are larger than usual moths; when they hover in front of a flower in order to drink nectar they must beat their wings more than 30 times a second, an activity which looks exhausting and requires a lot of energy. The high energy loss makes the right selection of flowers extremely important: the moths cannot afford to waste energy on flowers whose nectar they cannot reach.
Energy balance after visiting a flower
In order to test their hypothesis, the scientists first developed a small wind tunnel which they used to determine the energy loss of moths during the flight. The loss was determined by measuring the carbon dioxide the moths were breathing out. (The amount of carbon dioxide exhaled is directly related to the energy moths consume when foraging for nectar.) In addition, the researchers used gas-chromatographic and mass-spectrometric analyses to calculate the concentrations of single sugars in the nectar of the flower species used in the experiments and thus to determine each flower’s calorie content.
Altogether, seven tobacco species of the genus Nicotiana were tested. These Nicotiana flowers differed greatly in the lengths of their corollas; in centimeters, these ranged from less than 1.5 (Nicotiana rustica), to over 3 (Nicotiana attenuata), to 7.5 (Nicotiana alata) and to more than 11 (Nicotiana longiflora). “Although we had originally expected that the longer flowers which contain more nectar would also be more attractive in terms of energy gain, we found that essentially all flowers in our test provided the same amount of calories. While the longer flowers had more nectar, the nectar of shorter flowers was more concentrated. The nectar provided could not be the reason why visiting some flowers was more profitable than visiting others,” explains Alexander Haverkamp, a doctoral student who is the first author of the study.
From their measurements and calculations, the scientists were able to deduct the energy balance: the net-energy gain which resulted from balancing the energy gain per flower visit against the energy spent on hovering in front of a flower. Energy loss can be measured in the form of carbon dioxide, whereas energy gain is measured as the calories acquired from nectar uptake.
3-D tracking in the wind tunnel
Are moths able to assess the expected net-energy gain of a flower from a distance? To answer this question, the researchers designed a three-dimensional tracking system specially developed for the wind tunnels and consisting of multiple cameras which can record the movements of single moths. The flight of each moth was recorded in the dark for four minutes and then evaluated. For the first time, scientists were able to measure and visualize where in the wind tunnel odor molecules (here, the scents of the flowers) were present and at what concentrations. This new technology made it possible to correlate the presence of an odor with the behavior of a moth, especially when the moth first came into contact with this odor.
All moths in the experiments were encountering the scent of flowers for the first time; therefore, their responses to the odors and the preferences they revealed had to be innate. Hungry moths showed the strongest response to the flower of Nicotiana alata. The odor of this flower was especially attractive. Moths which encountered this odor plume immediately navigated towards it. Moreover, the moths were easily able to reach the nectar of these flowers with their probosces.
Therefore, only visits to N. alata flowers resulted in a positive net-energy gain. When visiting other Nicotiana flowers, hawk moths spent excessive amounts of energy, because they had difficulty drinking nectar from flower corollas which were too short or too long. “We showed that Darwin's prediction that each flower has a pollinator with a proboscis fitting into the flower, in Manduca not only resulted in a very long tongue, but also in a preference for the odor of the fitting flower. And that this co-evolution is beneficial for the moth, as the moth gets the best energy gain from fitting flowers,” Knaden concluded.
The pollination syndrome is important for the survival of many plants. In the course of evolution, mutual adaptations have resulted in the emergence of many species as well as in highly specialized flower-pollinator interactions. “Each pollinating species is important for the biological diversity on our planet. If one of the two partners becomes rare or extinct, this may have fatal consequences,” Haverkamp points out. Without pollinators, many flowers could no longer produce fruits. This would affect not only crop yield but the variety of food available for all humans. [AO]
Haverkamp, A., Bing, J., Badeke, E., Hansson, B. S., Knaden, M. (2016). Innate olfactory preferences for flowers matching proboscis length ensure optimal energy gain in a hawkmoth. Nature Communications. DOI: 10.1038/NCOMMS11644
Dr. Markus Knaden, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, Tel. +49 3641 57-1421, E-Mail firstname.lastname@example.org
Contact and Picture Requests:
Angela Overmeyer, M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail email@example.com
Download of images and movies: http://www.ice.mpg.de/ext/downloads2016.html
http://www.ice.mpg.de/ext/1280.html?&L=0 Scent guides hawk moths to the best-fitting flowers
http://www.ice.mpg.de/ext/downloads2016.html?&L=0 Download of photos and videos
http://www.ice.mpg.de/ext/evolutionary-neuroethology.html Department of Evolutionary Neuroethology
Angela Overmeyer | Max-Planck-Institut für chemische Ökologie
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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20.07.2018 | Materials Sciences | <urn:uuid:ef124579-8ab8-4ab5-8710-b544fe8142de> | 3.890625 | 2,588 | Content Listing | Science & Tech. | 41.797811 | 95,509,436 |
The Copenhagen Diagnosis updates the last IPCC report. Most of the news isn’t encouraging:
Global ice-sheets are melting at an increased rate; Arctic sea-ice is disappearing much faster than recently projected, and future sea-level rise is now expected to be much higher than previously forecast, according to a new global scientific synthesis prepared by some of the world’s top climate scientists.
In a special report called ‘The Copenhagen Diagnosis’, the 26 researchers, most of whom are authors of published IPCC reports, conclude that several important aspects of climate change are occurring at the high end or even beyond the expectations of only a few years ago.
The report also notes that global warming continues to track early IPCC projections based on greenhouse gas increases. Without significant mitigation, the report says global mean warming could reach as high as 7 degrees Celsius by 2100. | <urn:uuid:03288027-f05a-4f75-aefe-cc3eef9d95ca> | 2.953125 | 177 | News Article | Science & Tech. | 30.455865 | 95,509,441 |
Hydrogen (H), a colourless, odourless, tasteless, flammable gaseous substance that is the simplest member of the family of chemical elements. The hydrogen atom has a nucleus consisting of a proton bearing one unit of positive electrical charge; an electron, bearing one unit of negative electrical charge, is also associated with this nucleus. Under ordinary conditions, hydrogen gas is a loose aggregation of hydrogen molecules, each consisting of a pair of atoms, a diatomic molecule, H2. The earliest known important chemical property of hydrogen is that it burns with oxygen to form water, H2O; indeed, the name hydrogen is derived from Greek words meaning “maker of water.”
Although hydrogen is the most abundant element in the universe (three times as abundant as helium, the next most widely occurring element), it makes up only about 0.14 percent of Earth’s crust by weight. It occurs, however, in vast quantities as part of the water in oceans, ice packs, rivers, lakes, and the atmosphere. As part of innumerable carbon compounds, hydrogen is present in all animal and vegetable tissue and in petroleum. Even though it is often said that there are more known compounds of carbon than of any other element, the fact is that, since hydrogen is contained in almost all carbon compounds and also forms a multitude of compounds with all other elements (except some of the noble gases), it is possible that hydrogen compounds are more numerous.
Elementary hydrogen finds its principal industrial application in the manufacture of ammonia (a compound of hydrogen and nitrogen, NH3) and in the hydrogenation of carbon monoxide and organic compounds.
Hydrogen has three known isotopes. The mass numbers of hydrogen’s isotopes are 1, 2, and 3, the most abundant being the mass 1 isotope generally called hydrogen (symbol H, or 1H) but also known as protium. The mass 2 isotope, which has a nucleus of one proton and one neutron and has been named deuterium, or heavy hydrogen (symbol D, or 2H), constitutes 0.0156 percent of the ordinary mixture of hydrogen. Tritium (symbol T, or 3H), with one proton and two neutrons in each nucleus, is the mass 3 isotope and constitutes about 10−15 to 10−16 percent of hydrogen. The practice of giving distinct names to the hydrogen isotopes is justified by the fact that there are significant differences in their properties.
Paracelsus, physician and alchemist, in the 16th century unknowingly experimented with hydrogen when he found that a flammable gas was evolved when a metal was dissolved in acid. The gas, however, was confused with other flammable gases, such as hydrocarbons and carbon monoxide. In 1766 Henry Cavendish, English chemist and physicist, showed that hydrogen, then called flammable air, phlogiston, or the flammable principle, was distinct from other combustible gases because of its density and the amount of it that evolved from a given amount of acid and metal. In 1781 Cavendish confirmed previous observations that water was formed when hydrogen was burned, and Antoine-Laurent Lavoisier, the father of modern chemistry, coined the French word hydrogène from which the English form is derived. In 1929 Karl Friedrich Bonhoeffer, a German physical chemist, and Paul Harteck, an Austrian chemist, on the basis of earlier theoretical work, showed that ordinary hydrogen is a mixture of two kinds of molecules, ortho-hydrogen and para-hydrogen. Because of the simple structure of hydrogen, its properties can be theoretically calculated relatively easily. Hence hydrogen is often used as a theoretical model for more complex atoms, and the results are applied qualitatively to other atoms.
Also important for steelmaking is the absorption and removal of the two gases hydrogen and nitrogen. Hydrogen can enter liquid steel from moist air, damp refractories, and wet flux and alloy additions. It causes brittleness of solidified steel—especially in large pieces, such…
Physical and chemical properties
The Table lists the important properties of molecular hydrogen, H2. The extremely low melting and boiling points result from weak forces of attraction between the molecules. The existence of these weak intermolecular forces is also revealed by the fact that, when hydrogen gas expands from high to low pressure at room temperature, its temperature rises, whereas the temperature of most other gases falls. According to thermodynamic principles, this implies that repulsive forces exceed attractive forces between hydrogen molecules at room temperature—otherwise, the expansion would cool the hydrogen. In fact, at −68.6° C attractive forces predominate, and hydrogen, therefore, cools upon being allowed to expand below that temperature. The cooling effect becomes so pronounced at temperatures below that of liquid nitrogen (−196° C) that the effect is utilized to achieve the liquefaction temperature of hydrogen gas itself.
|Some properties of normal hydrogen and deuterium|
|ionization potential||13.595 electron volts||13.600 electron volts|
|electron affinity||0.7542 electron volts||0.754 electron volts|
|nuclear magnetic moment (nuclear magnetons)||2.7927||0.8574|
|nuclear quadrupole moment||0||2.77(10−27) square centimetres|
|bond distance||0.7416 angstrom||0.7416 angstrom|
|dissociation energy (25 degrees C)||104.19 kilocalories per mole||105.97 kilocalories per mole|
|ionization potential||15.427 electron volts||15.457 electron volts|
|density of solid||0.08671 gram per cubic centimetre||0.1967 gram per cubic centimetre|
|melting point||−259.20 degrees Celsius||−254.43 degrees Celsius|
|heat of fusion||28 calories per mole||47 calories per mole|
|density of liquid||0.07099
|boiling point||−252.77 degrees Celsius||−249.49 degrees Celsius|
|heat of vaporization||216 calories per mole||293 calories per mole|
|critical temperature||−240.0 degrees Celsius||−243.8 degrees Celsius|
|critical pressure||13.0 atmospheres||16.4 atmospheres|
|critical density||0.0310 gram per cubic centimetre||0.0668 gram per cubic centimetre|
|heat of combustion to water (g)||−57.796 kilocalories per mole||−59.564 kilocalories per mole|
Hydrogen is transparent to visible light, to infrared light, and to ultraviolet light to wavelengths below 1800 Å. Because its molecular weight is lower than that of any other gas, its molecules have a velocity higher than those of any other gas at a given temperature and it diffuses faster than any other gas. Consequently, kinetic energy is distributed faster through hydrogen than through any other gas; it has, for example, the greatest heat conductivity.
A molecule of hydrogen is the simplest possible molecule. It consists of two protons and two electrons held together by electrostatic forces. Like atomic hydrogen, the assemblage can exist in a number of energy levels.
Ortho-hydrogen and para-hydrogen
Two types of molecular hydrogen (ortho and para) are known. These differ in the magnetic interactions of the protons due to the spinning motions of the protons. In ortho-hydrogen, the spins of both protons are aligned in the same direction—that is, they are parallel. In para-hydrogen, the spins are aligned in opposite directions and are therefore antiparallel. The relationship of spin alignments determines the magnetic properties of the atoms. Normally, transformations of one type into the other (i.e., conversions between ortho and para molecules) do not occur and ortho-hydrogen and para-hydrogen can be regarded as two distinct modifications of hydrogen. The two forms may, however, interconvert under certain conditions. Equilibrium between the two forms can be established in several ways. One of these is by the introduction of catalysts (such as activated charcoal or various paramagnetic substances); another method is to apply an electrical discharge to the gas or to heat it to a high temperature.
The concentration of para-hydrogen in a mixture that has achieved equilibrium between the two forms depends on the temperature as shown by the following figures:
Essentially pure para-hydrogen can be produced by bringing the mixture into contact with charcoal at the temperature of liquid hydrogen; this converts all the ortho-hydrogen into para-hydrogen. The ortho-hydrogen, on the other hand, cannot be prepared directly from the mixture because the concentration of para-hydrogen is never less than 25 percent.
The two forms of hydrogen have slightly different physical properties. The melting point of para-hydrogen is 0.10° lower than that of a 3:1 mixture of ortho-hydrogen and para-hydrogen. At −252.77° C the pressure exerted by the vapour over liquid para-hydrogen is 1.035 atmospheres (one atmosphere is the pressure of the atmosphere at sea level under standard conditions, equal to about 14.69 pounds per square inch), compared with 1.000 atmosphere for the vapour pressure of the 3:1 ortho–para mixture. As a result of the different vapour pressures of para-hydrogen and ortho-hydrogen, these forms of hydrogen can be separated by low-temperature gas chromatography, an analytical process that separates different atomic and molecular species on the basis of their differing volatilities. | <urn:uuid:845f02f9-ee66-42d6-9228-1822fe25f3a5> | 3.9375 | 2,024 | Knowledge Article | Science & Tech. | 37.81953 | 95,509,463 |
Why 8 Endangered Rhinos Died in Mission to Save Them
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06 July 2018, 09:14 | Edward Lowe
A northern white female rhinoceros named Najin at Ol Pejeta Conservancy in Kenya in 2015
Researchers from Italy say they have created the first-ever hybrid rhino embryo produced outside the womb, following the death of the last male rhino of the species.
Over the past two decades, attempts at establishing a sustainable northern white rhino population - including natural breeding programs as well as artificial insemination - have been unsuccessful, according to Jan Stejskal, director of communication and global projects at the Dvůr Králové Zoo in the Czech Republic, who was involved in the study. Writing in the journal Nature Communications, researchers said they've succeeded in creating embryos using frozen northern white rhino sperm and eggs from a southern white rhinoFatu, one of the only two female northern white rhinos left in the world, walks in the pen where she is kept for observation, at the Ol Pejeta Conservancy in Laikipia county in Kenya on March 2. They are both protected by armed guards round the clock.
Hope is carrying the hope to prevent the extinction of the Northern White Rhino. "Our goal is that we have, in three years, the first northern white rhino calf born", Hildebrandt told NPR. Instead, they suggested, work should focus on saving other endangered rhino species that can still be found in the wild. In a dish, the scientists used northern white rhinoceros sperm to fertilize the southern white rhinoceros eggs, producing hybrid embryos. There are 21,000 SWRs and they can be used as surrogates. "The northern white rhino didn't fail in evolution", he said. Eggs and sperm from northern white rhino are in short supply, due to the rarity of the subspecies. Scientists hopes their breakthrough technique will lead to the re-establishment of a viable NWR breeding population.
What they want to do is turn these embryonic stem cells into eggs and sperm using stem cell technology. Several embryos are now cryopreserved for future transfer into surrogate mothers to carry a pregnancy to term.
According to the researchers, only four embryos have survived to the blastocyst stage.
If successful, this could see a calf born within three years in Kenya - and even more at Longleat Safari Park in Wiltshire.
It was the eggs that were more hard to collect. Professor Renfree says the key to the project was new technology developed by Professor Thomas Hildebrandt, who's based at the Leibniz-Institut in Berlin, that for the first time allowed collection of eggs from the ovaries of rhinoceroses. All conservation efforts to save this species have been foiled by human activities such as poaching, civil war and habitat loss.
"Our results are solid, reproducible and very promising".
This lab achievement is a very early step towards the much longer-term goal of resurrecting a population of full-blooded northern white rhinos, said Jan Stejskal, director of worldwide projects at the Dvur Kralove Zoo in the Czech Republic and an author of the paper, in a press briefing on Tuesday.
The project team is hopeful of getting permission to take eggs from the last two female NWRs from the Kenyan authorities. But it is a tedious and risky procedure which requires a long device to be inserted in the rectum while the rhinos must be put under anesthetic for two hours.
"We are very afraid that during this procedure can happen something unpredictable". "We should come at it with everything we've got", Roth said.
IVF techniques have not been a big success. "These techniques have the potential to help the other endangered rhino species, including the Sumatran rhino and the Indian rhino and and other large mammals such as the Gaur, a large Asian cow that is also at risk of extinction". They are the black-footed ferret, the giant panda and the Asian elephant. Some experts have criticised the effort however, saying it comes too late.
Pakistan ex-PM Nawaz Sharif given 10-year jail term
The former prime minister has described the corruption charges against him and his family as being politically motivated. Sharif's daughter, Maryam, widely seen as his chosen political heir, was sentenced to seven years in prison.
Anthony Bourdain Was Worth a Lot Less Than Thought
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Woman live tweets budding romance, sends Twitter into frenzy
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DNA tests being used to reunite children with parents
The goal is to weed out bogus claims by people who aren't related to the children but are trying to get a hold of them anyway. HHS has always been charged with caring for unaccompanied minors crossing the border, thousands of children every year.
Trump's scandal-hit environment chief Pruitt resigns
For additional commentary on Pruitt and Wheeler, listen to this recent episode of GTM's newest podcast Political Climate . President Donald Trump's tweet on Thursday that EPA chief Scott Pruitt resigned may have prompted some to celebrate.
Followers of Japanese cult leader also executed
He pleaded not guilty and never testified, but muttered and made incoherent remarks in court during the eight years of his trial. In 2016, police in Russian Federation conducted a number of raids on suspected cult members in Moscow and St Petersburg. | <urn:uuid:c1b54e10-4b35-4590-9891-6806ac054ba1> | 3.453125 | 1,274 | News Article | Science & Tech. | 41.589411 | 95,509,470 |
The main reason for the existence of climatic regions on our planet is the tilting of the Earth's vertical axes and the elliptic rotation of the Earth around the sun. This causes the amount of incoming solar radiation to vary throughout a year. As a result we have four seasons each lasting around 90 days.
As said, the orbit of the Earth around the sun is not a perfect circle, this too is causing variations in the seasons and weather. It is more like an elliptical and during January the Earth is closest to the sun (perihelion). And even this ellipse is also not stable causing more changes in the incoming solar radiation (insolation).
Also variations in the output of the sun's energy will too have an effect on our climate in the long term.
In this text, and the next article, we will delve a bit deeper to understand the result of all these variables and we will see the effects on our climate realizing that climate science can never be settled as we learn more and more each day.
Before we start, lets establish one thing: the climate on this planet has never been stable and never will. It changes daily, weekly and so on. At the moment we are living between two ice ages in what is called an interglacial warm period (Holocene) and we are nearing the end of it, so enjoy while it lasts. It could change within a short period of time dropping us into a new Ice Age.
Some are afraid that the Earth warms a couple of degrees, but the real danger is cooling. A warmer atmosphere can hold more CO2 which is used by plant life and this results in more food for humans. This is good!
There has, in 4.5 billion years of the Earth’s existence, always been climate changes. There have been ice ages, magnetic reversals, volcanic activity, tsunamis, earthquakes and a host of other natural events.
Climate changes are mainly caused by the following phenomena: astronomic, atmospheric and tectonic influences. Variations in the orbit around and output of the sun and the constant moving of the tectonic plates all have an influence on our climate.
And we see the results of those changes when we drill out cores of ice from permanent glaciers to examine them. See image on top of the page from the Vostok ice core.
The axial tilt of the Earth varies between 22,1 ° and 24,5 ° (its 23,5 ° at the moment) in a period of 41000 years. Also, due to precession the tilt moves around the real vertical axes. This is caused by the gravitational pull of the moon and the sun (both equal) and takes some 26000 years.
The elliptical orbit of the Earth around the sun is also influenced by the gravitational pull from planets as Jupiter and Saturn with a cycle between 95000 and 125000 years. This eccentricity would not exist if Earth was the only planet orbiting the sun. This yearly orbit also has a precession effect (apostle precession) with a cycle of around 23000 years. The orbit of the Earth also moves up and down (inclination) with a period of 70000 years and variations of the invariable plane cause cycles of 100000 years, very similar to the Ice Age period.
All these variations in the movement of planet Earth are called Milankovitch cycles as theorized by Milutin Milankovitch in his study of the ice ages and variations of the Earth's orbit with effect on climate changes. Where he found some remarkable coincidences!
More on this subject in the next off-site article from WUWT: The effects of irregularities in the Earth’s orbit .
The Earth's climate warms and cools by a number of different cycles, causing variation in the amount of insolation received. The result is that Earth receives a varying amount of heat (energy) and the average temperature will either drop or rise as a result of these cycles and the climate will either be cool or be warmer.
In the Middle Ages there was a warming period (MWP) where the average temperature was higher than today, even with a 35 % lower CO2 level. So there it is: CO2 has nothing to with warming!
We all remember the paintings in the galleries from the Middle Ages, they show us that the Earth was in a cooler period between about 1400 AD and 1850 AD. Even in this short period the temperature fluctuated again caused by a 40 year cycle. This "Little Ice Age" was known for short growing seasons with a drier climate and cold winters as can be seen on some of the Medieval paintings.
The drop in global temperatures was only a modest 2 °C, and the effects of this global cooling cycle were felt more in the higher latitudes, closer to the poles. Move the mouse over the image to see global temperatures 10000 years into the past.
The climate on Earth has been warming up since the last Ice Age (Pleistocene), some 18000 years ago. In fact, every 100000 years the climate warms up and we are now almost at the end of the current warm and cozy interglacial period and probably heading for a new Ice Age. See the next image for a temperature vs CO2 overview since 10700 before present.
At the moment we are in an interglacial period, in between two ice ages. Enjoy while it lasts as human kind prospers only while its warm! More detailed information in the next off-site link from WUWT about the paleo climate . | <urn:uuid:67660717-69cb-454d-af46-48d9dafdb2ba> | 3.84375 | 1,146 | Knowledge Article | Science & Tech. | 54.598507 | 95,509,475 |
Researchers find that the average latitude where tropical cyclones achieve maximum intensity has been shifting poleward since 1980
Over the past 30 years, the location where tropical cyclones reach maximum intensity has been shifting toward the poles in both the northern and southern hemispheres at a rate of about 35 miles, or one-half a degree of latitude, per decade according to a new study, The Poleward Migration of the Location of Tropical Cyclone Maximum Intensity, published tomorrow in Nature.
As tropical cyclones move into higher latitudes, some regions closer to the equator may experience reduced risk, while coastal populations and infrastructure poleward of the tropics may experience increased risk. With their devastating winds and flooding, tropical cyclones can especially endanger coastal cities not adequately prepared for them. Additionally, regions in the tropics that depend on cyclones' rainfall to help replenish water resources may be at risk for lower water availability as the storms migrate away from them.
The amount of poleward migration varies by region. The greatest migration is found in the northern and southern Pacific and South Indian Oceans, but there is no evidence that the peak intensity of Atlantic hurricanes has migrated poleward in the past 30 years.
By using the locations where tropical cyclones reach their maximum intensity, the scientists have high confidence in their results.
"Historical intensity estimates can be very inconsistent over time, but the location where a tropical cyclone reaches its maximum intensity is a more reliable value and less likely to be influenced by data discrepancies or uncertainties," said Jim Kossin, the paper's lead author, who is a scientist with NOAA's National Climatic Data Center currently stationed at the NOAA Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin–Madison.
Consistent with this poleward shift, many other studies are showing an expansion of the tropics over the same period since 1980.
"The rate at which tropical cyclones are moving toward the poles is consistent with the observed rates of tropical expansion," explains Kossin. "The expansion of the tropics appears to be influencing the environmental factors that control tropical cyclone formation and intensification, which is apparently driving their migration toward the poles."
The expansion of the tropics has been observed independently from the poleward migration of tropical cyclones, but both phenomena show similar variability and trends, strengthening the idea that the two phenomena are linked. Scientists have attributed the expansion of the tropics in part to human-caused increases of greenhouse gases, stratospheric ozone depletion, and increases in atmospheric pollution.
However, determining whether the poleward shift of tropical cyclone maximum intensity can be linked to human activity will require more and longer-term investigations.
"Now that we see this clear trend, it is crucial that we understand what has caused it - so we can understand what is likely to occur in the years and decades to come," says Gabriel Vecchi, scientist at NOAA's Geophysical Fluid Dynamics Laboratory and coauthor of the study.
NOAA's mission is to understand and predict changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us on Facebook, Twitter, Instagram and our other social media channels.
Monica Allen | Eurek Alert!
New research calculates capacity of North American forests to sequester carbon
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Scientists discover Earth's youngest banded iron formation in western China
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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A single, ghostly subatomic particle that traveled some 4 billion light-years before reaching Earth has helped astronomers pinpoint a likely source of high-energy cosmic rays for the first time. Subsequent observations with the National Science...
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Melissa Hoffman tells us about the new techniques astronomers have developed to locate some of the youngest planets in our galaxy.
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Astronomers have given one of Einstein’s predictions on gravity its most stringent test yet. By precisely tracking the meanderings of three stars in a single system – two white dwarf stars and one ultra-dense neutron star – the researchers...
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Two independent teams of astronomers have uncovered convincing evidence that three young planets are in orbit around an infant star known as HD 163296. Using a new planet-finding strategy, the astronomers identified three discrete disturbances in a...
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GALAXY 13.28 BILLION LIGHT-YEARS AWAY SHOWS SURPRISING SIGNS OF CHEMICAL MATURITY
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A micelle (//) or micella (//) (plural micelles or micellae, respectively) is an aggregate (or supramolecular assembly) of surfactant molecules dispersed in a liquid colloid. A typical micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle centre. This phase is caused by the packing behavior of single-tail lipids in a bilayer. The difficulty filling all the volume of the interior of a bilayer, while accommodating the area per head group forced on the molecule by the hydration of the lipid head group, leads to the formation of the micelle. This type of micelle is known as a normal-phase micelle (oil-in-water micelle). Inverse micelles have the head groups at the centre with the tails extending out (water-in-oil micelle). Micelles are approximately spherical in shape. Other phases, including shapes such as ellipsoids, cylinders, and bilayers, are also possible. The shape and size of a micelle are a function of the molecular geometry of its surfactant molecules and solution conditions such as surfactant concentration, temperature, pH, and ionic strength. The process of forming micelles is known as micellisation and forms part of the phase behaviour of many lipids according to their polymorphism.
The ability of a soapy solution to act as a detergent has been recognized for centuries. However, it was only at the beginning of the twentieth century that the constitution of such solutions was scientifically studied. Pioneering work in this area was carried out by James William McBain at the University of Bristol. As early as 1913, he postulated the existence of "colloidal ions" to explain the good electrolytic conductivity of sodium palmitate solutions. These highly mobile, spontaneously formed clusters came to be called micelles, a term borrowed from biology and popularized by G.S. Hartley in his classic book Paraffin Chain Salts: A Study in Micelle Formation.
Individual surfactant molecules that are in the system but are not part of a micelle are called "monomers". Micelles represent a molecular assembly, in which the individual components are thermodynamically in equilibrium with monomers of the same species in the surrounding medium. In water, the hydrophilic "heads" of surfactant molecules are always in contact with the solvent, regardless of whether the surfactants exist as monomers or as part of a micelle. However, the lipophilic "tails" of surfactant molecules have less contact with water when they are part of a micelle—this being the basis for the energetic drive for micelle formation. In a micelle, the hydrophobic tails of several surfactant molecules assemble into an oil-like core, the most stable form of which having no contact with water. By contrast, surfactant monomers are surrounded by water molecules that create a "cage" or solvation shell connected by hydrogen bonds. This water cage is similar to a clathrate and has an ice-like crystal structure and can be characterized according to the hydrophobic effect. The extent of lipid solubility is determined by the unfavorable entropy contribution due to the ordering of the water structure according to the hydrophobic effect.
Micelles composed of ionic surfactants have an electrostatic attraction to the ions that surround them in solution, the latter known as counterions. Although the closest counterions partially mask a charged micelle (by up to 92%), the effects of micelle charge affect the structure of the surrounding solvent at appreciable distances from the micelle. Ionic micelles influence many properties of the mixture, including its electrical conductivity. Adding salts to a colloid containing micelles can decrease the strength of electrostatic interactions and lead to the formation of larger ionic micelles. This is more accurately seen from the point of view of an effective charge in hydration of the system.
Energy of formation
Micelles form only when the concentration of surfactant is greater than the critical micelle concentration (CMC), and the temperature of the system is greater than the critical micelle temperature, or Krafft temperature. The formation of micelles can be understood using thermodynamics: Micelles can form spontaneously because of a balance between entropy and enthalpy. In water, the hydrophobic effect is the driving force for micelle formation, despite the fact that assembling surfactant molecules is unfavorable in terms of both enthalpy and entropy of the system. At very low concentrations of the surfactant, only monomers are present in solution. As the concentration of the surfactant is increased, a point is reached at which the unfavorable entropy contribution, from clustering the hydrophobic tails of the molecules, is overcome by a gain in entropy due to release of the solvation shells around the surfactant tails. At this point, the lipid tails of a part of the surfactants must be segregated from the water. Hence, they start to form micelles. In broad terms, above the CMC, the loss of entropy due to assembly of the surfactant molecules is less than the gain in entropy by setting free the water molecules that were "trapped" in the solvation shells of the surfactant monomers. Also important are enthalpic considerations, such as the electrostatic interactions that occur between the charged parts of surfactants.
Micelle packing parameter
The micelle packing parameter equation is utilized to help "predict molecular self-assembly in surfactant solutions":
where is the surfactant tail volume, is the tail length, and is the equilibrium area per molecule at the aggregate surface.
Block copolymer micelles
The concept of micelles was introduced to describe the core-corona aggregates of small surfactant molecules, however it has also extended to describe aggregates of amphiphilic block copolymers in selective solvents. It is important to know the difference between these two systems. The major difference between these two types of aggregates is in the size of their building blocks. Surfactant molecules have a molecular weight which is generally of a few hundreds of grams per mole while block copolymers are generally one or two orders of magnitude larger. Moreover, thanks to the larger hydrophilic and hydrophobic parts, block copolymers can have a much more pronounced amphiphilic nature when compared to surfactant molecules.
Because of these differences in the building blocks, some block copolymer micelles behave like surfactant ones, while others don't. It is necessary therefore to make a distinction between the two situations. The former ones will belong to the dynamic micelles while the latter will be called kinetically frozen micelles.
Certain amphiphilic block copolymer micelles display a similar behavior as surfactant micelles. These are generally called dynamic micelles and are characterized by the same relaxation processes assigned to surfactant exchange and micelle scission/recombination. Although the relaxation processes are the same between the two types of micelles, the kinetics of unimer exchange are very different. While in surfactant systems the unimers leave and join the micelles through a diffusion-controlled process, for copolymers the entry rate constant is slower than a diffusion controlled process. The rate of this process was found to be a decreasing power-law of the degree of polymerization of the hydrophobic block to the power 2/3. This difference is due to the coiling of the hydrophobic block of a copolymer exiting the core of a micelle.
Block copolymers which form dynamic micelles are some of the tri-block Poloxamers under the right conditions.
Kinetically frozen micelles
When block copolymer micelles don't display the characteristic relaxation processes of surfactant micelles, these are called kinetically frozen micelles. These can be achieved in two ways: when the unimers forming the micelles are not soluble in the solvent of the micelle solution, or if the core forming blocks are glassy at the temperature in which the micelles are found. Kinetically frozen micelles are formed when either of these conditions is met. A special example in which both of these conditions are valid is that of polystyrene-b-poly(ethylene oxide). This block copolymer is characterized by the high hydrophobicity of the core forming block, PS, which causes the unimers to be insoluble in water. Moreover, PS has a high glass transition temperature which is, depending on the molecular weight, higher than room temperature. Thanks to these two characteristics, a water solution of PS-PEO micelles of sufficiently high molecular weight can be considered kinetically frozen. This means that none of the relaxation processes, which would drive the micelle solution towards thermodynamic equilibrium, are possible. Pioneering work on these micelles was done by Adi Eisenberg. It was also shown how the lack of relaxation processes allowed great freedom in the possible morphologies formed. Moreover, the stability against dilution and vast range of morphologies of kinetically frozen micelles make them particularly interesting, for example, for the development of long circulating drug delivery nanoparticles.
In a non-polar solvent, it is the exposure of the hydrophilic head groups to the surrounding solvent that is energetically unfavourable, giving rise to a water-in-oil system. In this case, the hydrophilic groups are sequestered in the micelle core and the hydrophobic groups extend away from the center. These inverse micelles are proportionally less likely to form on increasing headgroup charge, since hydrophilic sequestration would create highly unfavorable electrostatic interactions.
Supermicelle is a hierarchical micelle structure (supramolecular assembly) where individual components are also micelles. Supermicelles are formed via bottom-up chemical approaches, such as self-assembly of long cylindrical micelles into radial cross-, star- or dandelion-like patterns in a specially selected solvent; solid nanoparticles may be added to the solution to act as nucleation centers and form the central core of the supermicelle. The stems of the primary cylindrical micelles are composed of various block copolymers connected by strong covalent bonds; within the supermicelle structure they are loosely held together by hydrogen bonds, electrostatic or solvophobic interactions.
When surfactants are present above the critical micelle concentration (CMC), they can act as emulsifiers that will allow a compound that is normally insoluble (in the solvent being used) to dissolve. This occurs because the insoluble species can be incorporated into the micelle core, which is itself solubilized in the bulk solvent by virtue of the head groups' favorable interactions with solvent species. The most common example of this phenomenon is detergents, which clean poorly soluble lipophilic material (such as oils and waxes) that cannot be removed by water alone. Detergents clean also by lowering the surface tension of water, making it easier to remove material from a surface. The emulsifying property of surfactants is also the basis for emulsion polymerization.
Micelle formation is essential for the absorption of fat-soluble vitamins and complicated lipids within the human body. Bile salts formed in the liver and secreted by the gall bladder allow micelles of fatty acids to form. This allows the absorption of complicated lipids (e.g., lecithin) and lipid-soluble vitamins (A, D, E, and K) within the micelle by the small intestine.
- Lipid bilayer
- Micellar liquid chromatography
- Micellar solutions
- Vesicle (biology)
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- Chen, Xi; An, Yingli; Zhao, Dongyun; He, Zhenping; Zhang, Yan; Cheng, Jing; Shi, Linqi (August 2008). "Core−Shell−Corona Au−Micelle Composites with a Tunable Smart Hybrid Shell". Langmuir. 24 (15): 8198–8204. doi:10.1021/la800244g. PMID 18576675. | <urn:uuid:a9e09172-b9ac-45a3-9481-117389f368d8> | 3.71875 | 3,970 | Knowledge Article | Science & Tech. | 42.014559 | 95,509,483 |
I thought it would output false true.But it gave true true.how?
(i==j)---------I and j are references having same value but different object references.Then how come it will produce true.Please explain it for me.
Post by:Ryan McGuire
, Ranch Hand
The problem isn't with your understanding of == and equals(); it's a question of what you're printing out.
So let's say i and j are two different objects. That means that the condition in your first if would be false. Therefore you print the boolean value of i!=j, as opposed to the String "i!=j". Since i is NOT == j, the expression i!=j is true. That's what gets printed: "true".
You can collapse that first if/else with its two println() statements into just a single...
You have a similar problem with the second if. Let's say i="Ryan" and j="Shiva". The expression in the if will be false, so it goes to the else part. There it prints out the value of the expression !i.equals(j). Since i.equals(j) is false, NOT i.equals(j) is true. So "true" gets printed.
Just replace that whole if/then with...
[ March 29, 2006: Message edited by: Ryan McGuire ]
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SafeClimate, a project of the Sustainable Enterprise Program at World Resources Institute, provides the tools, information, and connections to help you take positive action in your home, organization, and local community.
Why SafeClimate was Established
Human activity is greatly increasing the concentration of greenhouse gases in the Earth's atmosphere, which is triggering climate change (global warming). The potential implications are truly daunting: more frequent and severe storms, greater numbers of droughts and decreased crop yields, increased episodes of air pollution and related human health problems, spread of pests and pathogens, rising sea levels and coastal land loss, and adverse impacts on forests, coral reefs, and other ecosystems.
In response to these threats, the majority of Americans (according to recent Newsweek and Wirthlin Group surveys) have expressed their willingness to take individual action in order to reduce the negative impact we are having on the Earth's climate. In spite of this need, there currently exist few readily available means for such concerned citizens and organizations to learn about, and take concrete steps to reduce, their climate impact. SafeClimate.net has been established to address this need by engaging, informing and empowering individuals and organizations to easily and swiftly act on their desire to help protect the Earth's climate and, in doing so, safeguard biodiversity.
SafeClimate.net makes the climate change issue tangible for visitors by allowing them to calculate their own personal greenhouse gas emissions "footprint" and then take specific actions to reduce this impact. SafeClimate's objectives are to:
- Educate citizens on climate change and to the fact that there are easy actions they can take right now on an individual and organizational level to help with this serious threat
- Facilitate individual actions that when combined will go a long way to protect our climate and reduce species loss
- Strengthen the market for climate friendly products and services
- Present legislators and business leaders with compelling evidence that ordinary citizens consider climate protection an important priority
- Demonstrate the use of the Internet as a potent tool for empowering citizens to address local and global environmental challenges
- Showcase individuals, organizations, and companies that pledge to reduce their carbon emissions and the actions they take.
World Resources Institute
WRI is an environmental think tank that goes beyond research to create practical ways to protect the Earth and improve people's lives. WRI's mission is to move human society to live in ways that protect the Earth's environment for current and future generations.
WRI's goals are to:
- Reverse the rapid degradation of ecosystems, assuring their capacity to provide the goods and services on which human well-being depends.
- Halt the changes to the Earth's climate caused by human activity.
- Catalyze the adoption of policies and practices that expand prosperity while reducing the use of materials and generation of wastes.
- Guarantee people's access to information and decisions regarding natural resources and environment.
WRI's Climate Commitment: In May 1999, WRI made a significant public statement, pledging to achieve zero net carbon emissions by 2005 or sooner. This is one the first commitments of this magnitude and time frame undertaken by a public or private institution. WRI's effort to reduce its greenhouse gas emissions to zero presents a unique opportunity to facilitate similar efforts by other organizations and businesses and to demonstrate the technical and economic feasibility of achieving such a commitment. In order to meet its own climate pledge WRI has developed robust measurement guidelines and analytical tools, as well as gaining experience with the full range of practical emissions reduction opportunities. This expertise and easy-to-use toolkit will be shared, as it becomes available, through SafeClimate.net with other organizations interested in taking the climate pledge. For more information about WRI's climate pledge please contact: firstname.lastname@example.org.
Thanks to the knowledge and experience of Conservation International (CI), WRI has recently expanded sections of Safeclimate.net with more information on the importance of making climate solutions biodiversity friendly. We are very grateful to CI for all of their expertise and financial support provided through the Center for Environmental Leadership in Business. For more information on CI, please visit www.conservation.org. For more information on the Center for Environmental Leadership in Business please visit www.celb.org. | <urn:uuid:ddc71d63-dea0-4cc7-83d7-40ad8f7c5d6c> | 3.078125 | 861 | About (Org.) | Science & Tech. | 19.129867 | 95,509,563 |
Gutter on Right Side of Page.When the object is serialized out as xml, its qualified name is w:rtlGutter.
Assembly: DocumentFormat.OpenXml (in DocumentFormat.OpenXml.dll)
'Declaration Public Class GutterOnRight _ Inherits OnOffType 'Usage Dim instance As GutterOnRight
public class GutterOnRight : OnOffType
[ISO/IEC 29500-1 1st Edition]
17.6.16 rtlGutter (Gutter on Right Side of Page)
This element specifies that the page gutter shall be placed on the right side of the page for this section only. The page gutter defines the amount of extra space added to the specified margin, above any existing margin values. [Note: This setting is typically used when a document is being created for binding, in order to ensure that the resulting margins are present after the binding gutter is consumed by the printed matter binding. end note]
If the gutter is set to the side of the page by the omission of the gutterAtTop element (§188.8.131.52), then each section's gutter is placed at the left by default, unless that default is overridden by the rtlGutter element.
[Example: Consider a document with three sections, with gutter properties defined as follows:
<w:p> <w:pPr> <w:sectPr> <w:pgMar w:gutter="1440" …/> … </w:sectPr> </w:pPr> </w:p> … <w:p> <w:pPr> <w:sectPr> <w:pgMar w:gutter="1440" …/> <w:rtlGutter w:val="0" /> … </w:sectPr> </w:pPr> </w:p> … <w:p> <w:pPr> <w:sectPr> <w:pgMar w:gutter="1440" …/> <w:rtlGutter /> … </w:sectPr> </w:pPr> </w:p>
The first and second sections both place the gutter on the left side, the first by omission of the rtlGutter attribute, and the second by explicitly turning it off. The third section, however, moves the gutter to the right side via the use of the rtlGutter attribute. end example]
If the gutterAtTop element (§184.108.40.206) is specified and true, then each section's gutter is at the top and this setting is ignored.
sectPr (§17.6.17); sectPr (§17.6.18); sectPr (§17.6.19)
This element’s content model is defined by the common boolean property definition in §17.17.4.
© ISO/IEC29500: 2008.
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe. | <urn:uuid:dbc175a1-9214-432b-80ad-aa9408a1fb52> | 2.75 | 662 | Documentation | Software Dev. | 77.287164 | 95,509,565 |
Cyclodextrins (CDs) are compounds formed from five or more units of glucose linked by α-1,4 glycosidic bonds. The most common CDs have six (α-CD), seven (β-CD) and eight (γ-CD) glucose units forming the cone shaped structure, that is able to accommodate hydrophobic molecules within is interior, the diameter of which is approximately 5.2 A° (α-CD), 6.6 A° (β-CD), and 8.4 A° (γ-CD) . Externally, the structure is sufficiently hydrophilic to make CDs water soluble. These cyclic glucose polymers are used in the pharmaceutical, cosmetic and food industries.
Citation: Blanco KC, dos Santos FJ, Bernardi NS, Júnior MJ, Monti R, et al. (2013) Reuse of Cyclodextrin Glycosyltransferase through Immobilization on Magnetic Carriers. Enz Eng 2:111. | <urn:uuid:0a163055-5751-401e-80c3-f39063c65a4a> | 2.921875 | 210 | Knowledge Article | Science & Tech. | 61.4947 | 95,509,568 |
GCOS Implementation Plan review.
19 August 2016
The Global Climate Observing System (GCOS) programme is conducting an open consultation on how best to perform, coordinate and deliver atmospheric, oceanic and terrestrial observations to report on the state of the Earth´s climate; as well as adaptation to and mitigation of climate change. GCOS is a co-sponsored programme by WMO, IOC-UNESCO, ICSU and UNEP. GCOS serves as the climate observation component of the Global Earth Observation System of Systems (GEOSS).
Earth observations are required to meet the needs of the United Nations Framework Convention on Climate Change (UNFCCC), adaptation services and climate science, as well as climate observations for the Rio Conventions, the Sustainable Development Goals, the Ramsar Convention and the Sendai Framework for Disaster Risk Reduction.
The GCOS Programme has prepared a new implementation plan in consultation with the global climate scientific and observing community which will be submitted to the UNFCCC for its Conference of Parties (COP 22) meeting which starts on 7 November 2016, in Marrakech, Morocco.
GCOS published its first Implementation Plan in 2004 and updated it in 2010. Previous GCOS implementation plans have guided major investments in observational systems, such as satellite systems and international cooperation on ocean systems.
This 2016 plan is a new plan taking into account the latest developments in Earth observations and climate policy. The next update is due in five years, with a new plan due in 10 years.
The public review of the new GCOS Implementation Plan is open from Monday 25 July to Monday 5 September. All reviewers contributing comments will be credited in the final report.
Blog post: Earth Observations for Urban Resilience: Takeaways from ICLEI’s 2018 Resilient Cities Congress
Blog post: World Day to Combat Desertification and Drought 2018 – GEO Land Degradation Neutrality Activity | <urn:uuid:564378d8-a758-4370-89c3-b32e7d735021> | 2.796875 | 389 | News (Org.) | Science & Tech. | 28.898 | 95,509,581 |
Species Detail - Wood Sandpiper (Tringa glareola) - 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).
Protected Species: Wildlife Acts || Protected Species: EU Birds Directive || Protected Species: EU Birds Directive >> Annex I Bird Species || Threatened Species: Birds of Conservation Concern || Threatened Species: Birds of Conservation Concern >> Birds of Conservation Concern - Amber List
25 May (recorded in 2013)
10 September (recorded in 2011)
National Biodiversity Data Centre, Ireland, Wood Sandpiper (Tringa glareola), accessed 20 July 2018, <https://maps.biodiversityireland.ie/Species/10063> | <urn:uuid:026cb5dd-b192-49ca-800f-4d275ecd76de> | 2.890625 | 191 | Structured Data | Science & Tech. | 26.374055 | 95,509,603 |
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Pass the Dramamine: World's largest wave recorded
The World Meteorological Organization officially announced it's largest wave ever recorded. Alyse Barker (@IamAlyseBarker) has the story. Buzz60
Pass the Dramamine.
Though it happened three years ago, the world's biggest wave, a 62-foot-tall monstrosity in the North Atlantic, has just been certified by the World Meteorological Organization (WMO).
“This is the first time we have ever measured a wave of 19 meters (62 feet). It is a remarkable record,” said WMO Assistant Secretary-General Wenjian Zhang.
The wave beat the previous record of 59.96 feet, which was also set in the North Atlantic back in 2007.
The wave was recorded by an automated buoy on Feb 4, 2013, in the North Atlantic ocean between Iceland and the U.K. It followed the passage of a strong cold front, which produced winds of up to 50.4 mph over the area.
The WMO Commission for Climatology’s Extremes Evaluation Committee classified it as “the highest significant wave height as measured by a buoy.”
Wave height is defined as the distance from the crest of one wave to the bottom of the next. The term “significant wave height” means the average of the highest one-third of waves as measured by an instrument.
What about rogue waves? And isn't it likely there have been bigger, unmeasured waves? "There have been many less reliable estimates of rogue waves from other platforms, and from satellite radar," said wave expert Val Swail from Environment Canada.
"These are generally unverifiable, since there is no ground truth for the satellite, and the others tend to be from pitching and rolling platforms such as ships," he added.
The world's highest waves typically occur in the North Atlantic during ferocious winter storms, according to the WMO. | <urn:uuid:91e596a4-dd43-4048-b816-db92f8e9ef44> | 3.171875 | 424 | Truncated | Science & Tech. | 49.54425 | 95,509,621 |
Parallel programming deals with multi-processing and multi-threading. With the advent of multi-core computers, parallel programming has become essential. In this chapter we discuss the POSIX threading library (pthread). User annotated compiler supported parallelism with OpenMP is described with the help of examples in Section 12.2. The new features of OpenMP version 3.0 (task computing) is presented with the help of examples in Section 22.214.171.124. In addition to multi-threading, parallel computing has been successfully deployed on cluster grids (called the Beowulf class). The most common API used in cluster computing is MPI (message passing interface) which is discussed in this chapter. In addition to these well established parallel programming systems, the rapid rise of many-core and other forms of parallelism has also created new systems which have had less exposure. In particular the Intel Thread Building Block library, and GPGPU computing with NVIDIA CUDA and OpenCL are described.
KeywordsApplication Program Interface Message Passing Interface Code Block Static Schedule OpenMP Directive
Unable to display preview. Download preview PDF. | <urn:uuid:dd5491cf-5ba1-4774-aed0-9e5a5a5d4498> | 3.28125 | 231 | Truncated | Software Dev. | 40.409773 | 95,509,658 |
Flexibility may be a crucial advantage in the defence against pathogens
When a foreign substance invades a body, the body produces antibodies that recognise and fight the intruder by means of antibodies that bind to a specific portion of the intruder - the antigen. Memory cells are then formed in the course of the defence reaction.
These cells make sure that the body can respond more quickly and more strongly to any recurring attack of the same pathogen. According to a study just published in "Science" by scientists of the Whitehead Institute for Biomedical Research, Cambridge, USA, and the Helmholtz Centre for Infection Research (HZI) in Braunschweig, Germany, the common notion, i.e. that the body produces antibodies with a perfectly fitting key-lock design for a specific antigen exclusively, is not true.
Antibodies are produced by a certain type of white blood cells called B-cells or B-leukocytes which patrol our lymph nodes in search of pathogens every day. When a B-cell binds to an antigen by means of its receptor, the B-cell either produces a reasonably well-fitting antibody directly or it gets involved in the formation of a germinal centre. Germinal centres are antibody training sites:
The B-cells proliferate in them, diversify their antibodies through mutation and optimise them through selection. "In the course of time, the affinity of the antibodies for the antigens increases. Basically, only the most effective antibodies persist. This evolutionary process is called affinity maturation," says Michael Meyer-Hermann, who is the director of the "System Immunology" department at the HZI.
Meyer-Hermann and his colleague, Gabriel Victora, from the Whitehead Institute for Biomedical Research aimed to test this theory in the scope of a project funded by the Human Frontiers Science Program in order to find out more about the process of affinity maturation. For this purpose, the researchers combined single-cell sequencing with brainbow experiments, a technique that is common in brain and developmental research. In this technique, mother cells are stained with random fluorescent proteins, which they then pass on to their daughter cells.
"This allows us to recognise exactly which lineage the cells have come from, and which founder cells dominate the germinal centre," says Meyer-Hermann. "According to what was known, we presumed that only a few cells established the germinal centre and that the strong selection pressure would lead to uni-coloured germinal centres."
The results of the sequencing were astounding: "According to common belief, there are on the order of three to five founder cells per germinal centre. We just showed that the number is closer to 100," says Meyer-Hermann. The brainbow experiments showed that the germinal centres do not become as uni-coloured as expected. While some centres turned uni-coloured in the course of the antibody selection process, there were others which consisted of different colours even after a long period of time.
This means that there is not one definite dominant antibody, but that many different antibodies coexist.
Perhaps it is not always of advantage to adapt perfectly to a pathogen. After all, the pathogens keep developing too. "The more specific the antibodies are, the more difficult it may be for them to respond to mutations in the pathogens," says Meyer-Hermann. "Accordingly, a certain degree of variability and flexibility could be crucial for keeping up with the constantly changing pathogens."
In the long term, these insights might help in the development of new vaccines, since antibodies are the fundamental basis of vaccines. "Once we know what affects the ratio of dominant-clone versus diverse germinal centres, we can specifically adapt the diversity of the induced antibodies to the mutation rate of the pathogen in the vaccination protocols we use," says Meyer-Hermann.
Susanne Thiele | Helmholtz-Zentrum für Infektionsforschung
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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Basic Principles of Carbon Dating. Radiocarbon, or carbon 14, is an isotope of the element carbon that is unstable and weakly radioactive. Carbon Dating Standards.. we can do no more than guess.". wrote that were it not for radiocarbon dating, "we would still be foundering in a sea of. "for his method to use Carbon-14.Carbon-14 dating—explained in everyday terms. and all radiocarbon dating is made with this in mind. How do we know what the ratio was before then,.The element carbon is not found in a pure form in the human body, but rather in compounds within the body. What Does Carbon Do for Human Bodies? by Glenn Singer.
The method - radiocarbon WEB-info
Is it a problem with radiometric dating that carbon 14 is found in materials dated to millions of years old?. Or do we need another dating method all together?.Experts can compare the ratio of carbon 12 to carbon 14 in dead material to the ratio when the organism was. We can use a formula for carbon 14 dating to find the.B.C.'s tax, implemented in 2008, covers most types of fuel use and carbon emissions. It started out low. B.C.'s example shows that we can do that,.
Carbon-14 dating: Carbon-14 dating. Carbon-14 is continually formed in nature by the interaction of neutrons with nitrogen-14 in the. so that we can fully.
Dating Fossils – How Are Fossils Dated? - FossilEra.comIf the radioactive element carbon-14 breaks down quickly—within a few thousand years—why do we still find it in. Doesn’t Carbon Dating Disprove the.Carbon-14-dated dinosaur bones are less than 40,000 years old. carbon-14 dating dinosaur bones carbon dated dinosaur fossils date. dinosaur bones. We then.Discussion on the inaccuracies found using the Carbon-14 dating method,. We will deal with carbon dating first and. unlike carbon dating, mostly use the.What cant be dated using carbon 14?. though, to use carbon-1 … 4 dating if there are remnants of organic matter that was trapped under a lava flow.Dinosaur bones do not have carbon-14. the past 100,000 years has been obtained from many other methods besides radiometric dating. We have already mentioned.
DeYoung goes on to explain the carbon dating technique using accelerator mass spectrometry, or AMS. This. So how do we defeat the young earth arguments?.
Half-life and carbon dating (video) | Nuclei | Khan AcademyThe technique used is called carbon dating, and in this lesson we will learn what this is and. What is Carbon Dating? - Definition. What is Carbon Dating?.Carbon - Real-life applications. We have stated that carbon forms tetravalent bonds,. Radiocarbon dating is used to date the age of charcoal,.Dating Fossils – How Are Fossils Dated? So, how do we know how old a fossil is?. While people are most familiar with carbon dating,.
Radiocarbon Dating of Dinosaur Fossils. but those dates were not arrived at by use of carbon-14 dating methods. or do we deny the evidence because of our biases?.How is carbon dating done?. how do we know how much carbon 14 we started with? That's actually kind of cool. It's a semi-long story, so bear with me.
Radioactive dating - Australian Museum
10 Methods Scientists Use to Date Things | Mental FlossIn the movies, scientists use “carbon dating” to determine the age of ancient artifacts and dinosaur bones. But what is the real science behind carbon.
Carbon dating, rate of decay, how far can we. much carbon-14 it had to begin with. To do that we need. any radiological dating systems we currently use.
For radiocarbon dating to be possible,. Because the carbon present in a plant comes from the atmosphere in. in a sample we can then calculate the age of the.DATING METHODS IN ARCHAEOLOGY. when we do not have written records. While collecting samples for radio carbon dating we should take utmost care,. | <urn:uuid:0344254e-374d-4ed4-86ac-47d7c355369d> | 3.546875 | 886 | Content Listing | Science & Tech. | 65.990266 | 95,509,664 |
August 27, 2012
According to this article, it's possible.
http://www.mnn.com/earth-matters/space/ ... ew-quantum
Bryan Nelson Sun, Jun 02 2013 at 4:16 PM
According to Albert Einstein's theory of general relativity, black holes are uninhabitable chasms of spacetime that end in a "singularity," or a mass of infinite density. It's a place so bleak that even the laws of physics break down there. But what if black holes aren't so forbidding? What if they are instead some kind of intergalactic stargate, or maybe even a passageway into a whole other universe?
It may sound like the premise for a clever science-fiction movie, but new calculations by quantum physicists now suggest that the stargate idea might actually be the better theory. According to the startling new results, black holes do not culminate in a singularity. Rather, they represent "portals to other universes," reports New Scientist.
This new theory is based on a concept known as 'loop quantum gravity' (or LQG). It was first formulated as a way of merging standard quantum mechanics and standard general relativity, in order to remedy incompatibilities between the two fields. Basically, LQG proposes that spacetime is granular, or atomic, in nature; It is made up of miniscule, indivisible chunks about the same size as the Planck length — which roughly amounts to 10-35 meters in size.
The modern definition of ‘racist’ is someone who’s winning an argument with a liberal.
June 23, 2013
Einstein's theory never stated that black holes were portals to other universes. It wasn't until theorists applied Loop Quantum Gravity to the theory of general relativity that they theorize that black holes could possibly be a gateway.
I remember reading an article how a team of scientists are creating a satellite to create a black hole (small, obviously), and use it to harness the energy to power space travel because of the energy that black holes emit. If that's the case, I wouldn't think black holes are gateways.
http://www.dailygalaxy.com/my_weblog/20 ... hips-.html
Dr. Michio Kaku explained how worm holes would be the way to travel between universes, or to travel across our own universe faster than the speed of light (not that we would be going faster than the speed of light, but we'd be taking an extreme shortcut), which I think some people mistake one for the other.
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Salamanders may be surprisingly resistant to climate change
The Appalachian Mountains are a global hotspot for salamanders, and ten percent of the world’s salamander species reside in the Southern Appalachian region.
But climate change could make the region inhospitable for salamanders by 2080, leading to an increased risk of extinction for the amphibians and decreasing the rich biodiversity of the area.
However, a new study found that salamander resilience and adaptability, also known as plasticity, has been underestimated by previous research.
The study was conducted by researchers from Clemson University and published in the journal Science Advances.
Salamanders have a great ability to adapt to their environment which led Eric Riddell and Michael Sears, the study’s lead authors, to conclude that salamander plasticity will reduce potential extinction risk up to 72 percent.
Unlike previous studies, the researchers took into account salamander plasticity and how salamanders respond and adapt to stressful temperatures.
“This is one of the first papers that has exclusively looked at plasticity in this sense,” said Sears. “We’re telling you that our new predictions are nowhere near as dire as earlier predictions. In this part of the world, this is a particularly big deal. We can now say more accurately what might occur if climatic conditions continue to deteriorate.”
Sears and Riddell searched for salamanders in North Carolina and estimated the amphibian rough biomass in the area.
The exact number of salamanders in the Appalachian is not known, but in just one square mile of forest, its estimated that you could find a combined salamander biomass of 2500 to 5000 pounds.
Because salamanders are mostly nocturnal many people are probably unaware of just the sheer amount of lizard-like amphibians in the area.
Understanding the threats that climate change poses to salamanders and their habitats is important not just because of the risk of biodiversity loss, but also because of the crucial role that salamanders play in the local ecosystem.
Some salamanders are lungless and absorb oxygen through their moist skin.
This is why previous estimates were concerned about the potential risks of climate change as warmer temperatures would increase aridity in the area making it harder for certain salamanders to absorb the oxygen they need.
However, due to how long salamanders have been in the area, Sears and Riddell feel that their resilience has been largely underestimated and that when temperatures inevitably increase, salamanders will adapt.
David Wake, a curator of the Museum of Vertebrate Zoology at the University of California, Berkeley who was not involved in the study, agreed with Sears and Riddell’s theory of salamander plasticity.
“During the past 2 million years, the southern Appalachians have experienced some dramatic incidents of climate change,” said Wake. “So, how did the salamanders handle it? And how will they handle the accelerated climate change that most scientists accept as a near certainty? In short, they are able to adjust their physiology much more than we previously thought, and this perhaps accounts for much of their ability to deal with climate change – not by running away, but by using their abilities to adjust through time.” | <urn:uuid:d58547d1-dbb0-4c61-9cf2-8d000287727e> | 3.5 | 684 | News Article | Science & Tech. | 26.008706 | 95,509,693 |
+44 1803 865913
By: Michael A Rex and Ron J Etter
354 pages, Col & b/w figs
Frigid, dark, and energy-deprived, the deep sea was long considered hostile to life. However, new sampling technologies and intense international research efforts in recent decades have revealed a remarkably rich fauna and an astonishing variety of novel habitats. These recent discoveries have changed the way we look at global biodiversity.
In "Deep-Sea Biodiversity," Michael Rex and Ron Etter present the first synthesis of patterns and causes of biodiversity in organisms that dwell in the vast sediment ecosystem that blankets the ocean floor. They provide the most comprehensive analysis to date of geographic variation in benthic animal abundance and biomass. The authors document geographic patterns of deep-sea species diversity and integrate potential ecological causes across scales of time and space. They also review the most recent molecular population genetic evidence to describe how and where evolutionary processes have generated the unique deep-sea fauna.
"Deep-Sea Biodiversity" offers a new understanding of marine biodiversity that will be of general interest to ecologists and is crucial to responsible exploitation of natural resources at the deep-sea floor.
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Basically what i have so far is that I have extracted a string from a file and converted it into a date using DateFormat or so I think. I want to do some calculations with this date object, e.g subtract this date from current date and multiply by 24 to give me a float object which i can use for further calculations.
Many Thanks in Anticipation.
Originally posted by Jim Yingst:
You can also use Date's getTime() method to get the number of milliseconds elapsed since Jan 1, 1970 (GMT). From this you can calculate a lot of things, probably more easily than using Celandar. However some calculations are eaiser with Calendar - esp anything that depends on how many days there are in a given month. Generally, I'd try using getTime() first, and then use Calendar methods only if I have to.
That was my first thought, but depending on how far forward or back you want to calculate, you will have to account for leap seconds and such. I'm assuming GregorianCalendar handles leap time for you. Basically, it depends on what kind of calculations you need to do.
[ January 21, 2003: Message edited by: Jason Menard ]
Practically speaking, for most applications this is probably a non-issue. Astronomers and people doing celestial navigation may disagree. But for the rest of us, the worst-case scenario I can imagine is something like this: imagine you're looking for the number of days between two Dates, and you use code like this:
The problem would be if there have been any negative leap seconds introduced between d1 and d2, and the difference is one or more seconds less than some integer multiple of 24*60*60*1000. In this case integer division will round the result towards zero, yielding a difference in days which is 1 less than the expected ("correct") answer. In practice I don't see how this could happen, since all leap seconds so far (and all expected in the forseeable future) are positive, reflecting additional seconds inserted into the day, not removed from it. But if we want to be safe, modify the code a bit:
This forces the division to be done with doubles rather than longs, and rounds the result to the closest integer, rather than rounding towards zero. Which should be more than sufficient to cover up any annoying leap second errors.
[ January 21, 2003: Message edited by: Jim Yingst ]
Since being a new comer to JAVA, I am in process of transformation at the moment.
What I understand is that I can use the gettime() method from Date object to miillisecond for two dates and then use them for calculation , Can I use settime() to set the date object to my desired dates.
Is is also possible to have two GeorgianCalendar object set to my given dates, could I use them for doing the subtraction. e.g. with the code below
GregorianCalendar beginCalendar = new GregorianCalendar();
GregorianCalendar endCalendar = new GregorianCalendar();
endCalendar.setTime(new Date()); //I want to use current date for this one
long res = endCalendar - beginCalendar // if this does work will it give me answer seconds or days System.out.println("Difference in days: " + res);
Don't count your weasels before they've popped. And now for a mulberry bush related tiny ad:
Rocket Oven Kickstarter - from the trailbosshttps://coderanch.com/t/695773/Rocket-Oven-Kickstarter-trailboss | <urn:uuid:d14d1980-120e-4db7-881c-4de35c7b5eee> | 2.71875 | 759 | Comment Section | Software Dev. | 47.429507 | 95,509,705 |
This program illustrates the quantum states of a one-dimensional infinite square well with a symmetric constant-energy step perturbation. The perturbed eigenfunctions are calculated, both ground and several excited states, as well as the expansion coefficients in terms of the unperturbed eigenfunctions. A challenge section asks the user to answer various questions regarding mixing coefficients and the results of the perturbation.
This simulation is part of a collection of animations/simulations for the teaching of concepts in quantum mechanics.
Kohnle, A. (2014, September 1). QuVis: Symmetric Perturbation. Retrieved July 20, 2018, from https://www.st-andrews.ac.uk/physics/quvis/simulations_html5/sims/SymmetricPerturbation/SymmetricPerturbation.html
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Arctic Ocean 2018 is an ambitious expedition to the Arctic that aims to establish an in situ laboratory alongside one of the Arctic’s multi-year ice floes. Departing from Longyearbyen, Svalbard, the icebreaker Oden will make a quick transit north from Fram Strait into the pack ice, looking for a large, persistent ice floe on which to build an experimental camp.
The ship will drift with this ice floe for about five weeks. During that time scientists from fourteen different research projects will collaborate on-board to collect measurements and samples and from the ocean and ice as well as the air. The samples will help to better understand the important role of clouds in the Arctic climate system as well as the role of microbes in the process of cloud formation. Researchers will take detailed observations from the ocean surface through the troposphere, especially targeting the surface energy balance and the vertical structure of the lower troposphere, including clouds, will explore sources of aerosols in the upper ocean, as well as sea ice biology and chemistry.
The expedition is a collaboration between the Arctic Climate Across Scales project (ACAS), a YOPP-endorsed project, funded by the Knut and Alice Wallenberg Foundation, and co-funded by INTAROS; together with collaborators from Leeds University (UK) funded by the Natural Environment Research Council (NERC) and Stockholm University, funded by the Swedish Research Council. Other participants are funded by the US’ National Science Foundation.
This expedition will run from July 31 to September 24, 2018. For more information on the expedition, visit the Arctic Ocean 2018 site.
You can check out all the INTAROS observing sites in this interactive map.
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As kids most of us have played with magnets with great curiosity. When we bring close two opposite ends of magnets we can see that they attract each other but when we bring the same ends closer they repel each other. This phenomenon is used by modern technology and it has always puzzled people.
Magnetism can explain the reasons behind this strange attraction and repulsion that acts between two poles. The attraction or repulsion force that acts between two magnets or a magnet and a neutral object is called magnetism. A magnet has the power to attract other objects made of nickel, iron, steel and cobalt. It does so by the magnetic field around it.
Every magnet has two poles – North Pole and South Pole. Earth has its own magnetic field and if a magnet is hung from a point to rotate freely its one end will point towards north and the other towards south. The magnetic force is a result of the electrons that are loose and move freely inside the magnets. At one end of the magnet there is a density of negatively charge ions and at another there is a dearth of negatively charged ions. When the opposite poles are brought close they attract each other because one of the poles is negatively charged and the other pole is positively charged.
The purpose that drives the magnetic force is to make successful exchange of electrons possible and bring the poles to a neutral state. The same poles repel each other because they are both negatively or positively charged. The same poles cannot exchange electrons and become neutral. This is the same reason why magnets attract neutral objects like iron or nickel towards them. Every object ultimately wants to lose the charge and become stable and neutral.
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Thanks! It helped me a lot and The language skills are excellent.
My relatives always say that I am killing my time here at net, but I
There should be more articles and videos about this social issues, so
Thanks alot im now more aware about it!
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Posted on 16/01/2017 by Frédéric Dalleau
Before doing linux kernel development, I started by typing
make in a kernel tree. After booting, I always had some non working peripherals. So my second step was to use a distribution specific build procedure. For example, the Ubuntu kernel build instructions can be found at https://wiki.ubuntu.com/KernelTeam/GitKernelBuild. It works, and one can easily build a kernel and install it, with all peripheral working. But this method will quickly reach its limitations to write new kernel code. On a decent computer (i7 5600U), the build/test cycle lasts about 30 minutes. It is possible to build only the needed module and
insmod/rmmod, but in case of a crash followed by a rebooting, the developer loses its work environment.
The next step is to run the kernel inside a virtual machine.
VirtualBox is well known, very user friendly and supports a large amount of different OSes. Installation of a VirtualBox will be under the hour mark. But rebuilding the Ubuntu kernel is still a 30 minute cycle. Additionnaly exchanging files between Virtualbox and the host will involve some kind of networking or file sharing that have to be setup. For kernel development, Virtualbox Guest additions have to be rebuilt often when the kernel is updated.
Qemu is another virtual machine. A complete distro can be installed into it. But it has a very interesting option: -kernel. With that option, QEMU will boot the kernel binary provided as argument. Ubuntu users can try :
$ sudo qemu-system-x86_64 -kernel /boot/vmlinuz-`uname -r`
This will boot your kernel within QEMU, but an error occurs immedialy: There is no filesystem to boot. Also, since
/boot is readable only by root, sudo permission is required. This is not needed with a user built kernel.
debootstrap allows to install a debian distribution in a directory. Before going too fast, if your file system is mounted with the nodev option, it won’t be possible to create device nodes. Instead, we will mount a qemu image file on a directory and use debootstrap in the mount point we created as in the following:
IMG=qemu-image.img DIR=mount-point.dir qemu-img create $IMG 1g mkfs.ext2 $IMG mkdir $DIR sudo mount -o loop $IMG $DIR sudo debootstrap --arch amd64 jessie $DIR sudo umount $DIR rmdir $DIR
The target rootfs is a matter of taste. For learning purposes, using busybox would be very interesting too. But for development purposes, having all the debian development tools in the rootfs is very useful.
Boot as follow:
$ sudo qemu-system-x86_64 -kernel /boot/vmlinuz-`uname -r`\ -hda qemu-image.img\ -append "root=/dev/sda single"
To silence the warning about raw format, replace “-hda qemu-image.img” with “-drive file=qemu-image.img,index=0,media=disk,format=raw”
Boot as a single user to change root password and create a user.
Now it is time to build your own kernel. There exist a make kvmconfig option that tunes an existing configuration and makes it usable from QEMU. However, it will not create a .config file from scratch. So we will start from generic config file and kvmify it. It is still possible to build a dedicated config file that will allow for shorter build time, but that would require several iterations.
git clone --depth=1 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cd linux make x86_64_defconfig make kvmconfig make -j 8
Use the resulting file in the command line below. We can drop sudo.
$ qemu-system-x86_64 -kernel arch/x86/boot/bzImage -hda qemu-image.img -append "root=/dev/sda"
KVM accelerates x86 virtualization in QEMU. It will only accelerate x86 platforms. It is as simple as adding a command line option.
$ qemu-system-x86_64 -kernel bzImage -hda qemu-image.img -append "root=/dev/sda" --enable-kvm
Now your debootstrap image boots in less than two seconds. This can be checked in dmesg. Before –enable-kvm, systemd is started 5.9 seconds after boot. After enabling, systemd is started after 1.7 seconds. A more than 3 times shorter boot time. And it just can’t be compared to ubuntu. Note that we don’t have a full user interface up, so we cannot compare apple with peaches.
Initially, QEMU displays its own screen in a dedicated window. For a terminal use case, this is not really pratical as it gets into the ALT tab list, the keyboard and mouse capture are not suitable for this use either. Copying and pasting also aren’t very practical. It is much more convenient to remove the graphic interface and instruct the kernel to write to ttyS0 that qemu redirect to the terminal in –nographic mode.
$ qemu-system-x86_64 -kernel bzImage -append "root=/dev/sda console=ttyS0" -hda qemu-image.img --enable-kvm --nographic
halt in qemu will stop the kernel, but the qemu process would continue running on the host and would have to be killed. The proper command to terminate the virtual machine is :
$ shutdown -h now
A second part to this post is planned, stay tuned!
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An asteroid zoomed by Earth on Tuesday night at 6:05 p.m. EDT at almost 126,000 miles outside our atmosphere, according to NBC News.
That distance is almost half the amount of miles from the Earth to the moon and will be the closest approach of an asteroid to Earth in almost 300 years, according to EarthSky.org.
The asteroid known as 2010 WC9 was flying at almost 29,000 miles per hour as it passed Earth with a diameter of 60 to 134 meters (200 to 400 feet) which is as "big across as a city block," according to asteroid expert Dr. Erin Ryan from NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The asteroid was still too small to be seen with just the naked eye during the close call, but Northholt Branch Observatories, an astronomy group based in London, live-streamed a telescopic view of the celestial being zooming by on its Facebook page in the days before Tuesday.
"At no time will it be visible to the eye as it sweeps past Earth," notes Earth Sky. "It might get as bright as magnitude +11, which would make it bright enough to be seen in amateur telescopes pointed at the correct location and time"
Dr. Paul Chodas, director of the Center for Near-Earth Object Studies at the NASA Jet Propulsion Laboratory in Pasadena, California, said astronomers associated with the NASA-funded Cataline Sky Survey first spotted 2010 WC9 in 2010.
Scientists quickly determined the asteroid posed no threat to Earth, according to Dr. Chodas who said, "We knew enough not to be worried."
Ryan said if an asteroid the size of WC9 were to strike the earth, it could create a small crater and shatter windows and glass for miles nearby.
A similar event happened in 2013 after a meteor exploded over Chelyabinsk, Russia.
But some asteroids aren't just rocks, they also contain types of metal, which if one the size of WC9 that contained metal hit Earth, Ryan said, "you'd get a crater about as big as Meteor Crater."
Meteor Crater is almost 4,000 feet in diameter and 600 feet deep around 19 miles outside Winslow, Arizona, also known as the Barringer Crater in honor of the Daniel Barringer who was the first scientist to note the crater it could have been created by meteorite impact.
It's often considered the best-preserved meteorite crater on earth and was declared a National Natural Landmark in 1967 by the U.S. government.
Astronomers said there was no need to be concerned about the potential of an asteroid striking earth.
Dr. Chodas said an asteroid of that size typically collides with Earth once every 6,000 years.
Dr. Amy Mainzer, another asteroid expert at the Jet Propulsion Laboratory, told NBC News last year, “There are no objects that have been identified that are known to be on a collision course with Earth.”
-WN.com, Maureen Foody
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We are developing simulation models for the Tasman and Golden Bays area to test what is likely to happen to marine ecosystems under different scenarios. This enables managers, Māori and other stakeholders to explore ‘What if?’ questions, and consider the implications of potential management decisions.
Project leader: Ian Tuck, NIWA
What happens in Tasman and Golden Bays if…?
We are developing simulation models for the Tasman and Golden Bays area to test what is likely to happen to marine ecosystems under different scenarios. This enables managers, Māori and other stakeholders to explore ‘what if?’ questions, and consider the implications of potential management decisions.
We have developed and validated an ecosystem model using the Atlantis framework. The Atlantis model is a computer representation of the bays that can be used to mimic and help understand dynamics and flow-on effects. It includes everything in the ecosystem from sunlight and nutrients through to top predators and fisheries. This allows us to test different management or environmental scenarios to understand effects on the whole ecosystem. This Atlantis model is ready to use, so we are now developing appropriate scenarios to investigate.
These scenarios are being informed by consultation (through workshops) with Regional Councils, Māori, managers, and a range of stakeholders, to get an understanding of their concerns for the region’s marine environment, and the types of scenarios they would like to investigate.
We are also developing other food web and sizebased ecosystem models, and investigating ways to test and compare them to determine which are most appropriate and useful, and the level of complexity needed to answer different sorts of questions.
This work is linked with the Participatory tools project, which will use the models to determine the trade-offs that will result from different decisions.
Latest news and updates
Improving marine management is critical to New Zealand's future health and wealth, but research in isolation is not enough. Excellent engagement with, and participation from, all users and sectors of society is essential.
We therefore invite comment on our draft strategy for Phase II (2019–2024). This strategy has been co-developed with Māori and stakeholders.
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During excavations in the open lignite-mining pit Na Duong in Vietnam, a joint team from the University of Tübingen and the Senckenberg Center for Human Evolution and Palaeoenvironment Tübingen discovered the world’s oldest bighead carp. With a length of only 5 centimeters, Planktophaga minuta is also the smallest known fossil representative of this East Asian group. Modern bighead carp are among the largest members of the carp family, reaching a length of up to 1.5 meters and a weight of 50 kilograms.
Since 2008, an international research team led by Prof. Dr. Madelaine Böhme from the Senckenberg Center for Human Evolution and Palaeoenvironment (HEP) of the University of Tübingen has been studying prehistoric ecosystems and fossils in Vietnam.
In the course of this research the scientists discovered approximately 37 million-year-old sediments from Lake RhinChua, dating to the late Eocene. These freshwater sediments contained a wealth of fossilized animals and plants; hence, Lake RhinChua is also referred to as the “Asian Messel” by the researchers.
During their studies the team discovered teeth belonging to an entirely new genus and species of fish: The oldest known bighead carp, Planktophaga minuta, is a representative of the “East Asian group of Leuciscinae.”
With a length of ca. 5 centimeters it is the smallest fossil representative of this East Asian group, and a mere dwarf compared to its modern living relatives. Modern bighead carp are among the largest members of the carp family. They grow up to a length of 1.5 meters and can weigh in at 50 kilograms.
Planktophaga minuta and its relatives
Besides Planktophaga minuta (which translates to small plankton eater), an additional six species of carp have been discovered in Lake RhinChua. All of them have living relatives that are still found today in China’s Pearl and Yangtze River system. This is proof that the roots of the modern freshwater fish fauna in Southeast Asia reach far into the past.
Bighead carp in exile
Originally, the bighead carp was native to the larger rivers and stagnant water bodies of southern China. During the 1960s, bighead carp were introduced in Europe, including Germany, as a means to control aquatic plants. Only later did researchers discover that the bighead carp failed to “fulfill this task,” since they mainly feed on animal plankton. In Europe, introduced bighead carp can be found in ponds, lakes and occasionally in streams and rivers.
Böhme, M. et al.; Na Duong (northern Vietnam) – an exceptional window into Eocene ecosystems from Southeast Asia, ZittelianaA 53, 120 A 5 (2014).
Prof. Dr. Madeleine Böhme
Department of Geosciences
Senckenberg Center for Human Evolution and Palaeoenvironment
(currently away on expedition)
Senckenberg Gesellschaft für Naturforschung
Phone 069- 7542 1444
University of Tübingen
Phone 07071 – 29-76789
Dr. Sören Dürr | Senckenberg
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Carbon Pools and Fluxes as an Indicator of Riparian Restoration
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Riparian forests are integral components of the landscape. The inherent biogeochemical processes that occur in such forests provide numerous benefits to wildlife and society. Maintaining good water quality is a major benefit from riparian forests and therefore, the maintenance, creation, or restoration of riparian forests is indispensable. This study was designed to broaden current knowledge of the complex, interrelated biogeochemical processes and determine indices for riparian forest restoration based on the various carbon pools/fluxes that may represent restoration success. This study was implemented on the Savannah River Site, an Environmental Research Park, where several riparian forests are recovering from thermal disturbances. The streams in these forests were subjected to thermal discharges that increased flows and resulted in removal of soil and a decline in the amount of woody vegetation. Two of these riparian forests are at different ages post-disturbance and represent different stages of recovery, which provides an exceptional opportunity to study successional processes in riparian forests and enhance restoration efforts. Linear transects perpendicular to the main stream channels were established in 2 recovering riparian forests of different ages (two areas in Pen Branch ~ 8 years post-disturbance; Fourmile Branch ~ 12 years post disturbance) and an undisturbed (thermally) more mature riparian forest (Meyerâ s Branch ~ 60 years). Along these transects quantitative data were obtained on above and belowground carbon pools and fluxes. Carbon pools exhibited a close correlation with riparian forest development. Biomass and carbon pools increased with increasing riparian forest stand age. The importance of the herbaceous carbon pool declined relative to the total above ground biomass, and the root carbon pool increased with forest age/succession. In general, net primary production (NPP) in young riparian forests (~8-10 years) rapidly approached and even exceeded NPP of more mature riparian forests. Once the herbaceous stage of succession was surpassed, the litterfall component of NPP plays a greater role riparian forests. As a woody overstory became established (after ~ 8-10 years), annual litterfall rates as a function of NPP were independent of forest age. Establishment of woody species occurred ~8 to 10 years after thermal disturbance and litterfall amount in young riparian forests rapidly became comparable to mature riparian forests. Lateral litter movement from the riparian forest toward the stream was less than the amount of litter (carbon pool) deposited from upstream into the riparian forest during a flood event. Overall lateral litter movement supplied less energy to the stream system than vertical inputs. A decline in riparian forest floor biomass was observed with increasing riparian forest development. However, a difference in foliar forest floor percent carbon lended itself to a minimal increase in the forest floor carbon pool with increasing riparian forest age. Woody debris in riparian forests comprised a relatively small carbon pool compared to tree and soil carbon pools. The species composition of litter appeared to be more of an overriding factor influencing decomposition rates than forest age. The influence of litter quality was evident in the decomposition rates of the different litter composites used in this study. In all 4 sites the litter composite from the mature riparian forest decomposed significantly more than the litter composites from the younger riparian forests. The fairly rapid decomposition of red maple (Acer rubrum L.), which was one of the main components in the mature riparian forest litter composite, influenced the greater decomposition rate. The litter composites from the younger riparian forests were similar and both included more decomposition resistant litter types, specifically waxmyrtle (Myrica cerifera L.) and alder (Alnus serrulata (Ait.) Willd.). Decomposition rates did not differ between the individual successional stages. Riparian forests are intimately associated with their hydroperiod. During flood events the riparian forest receives inputs of organic matter and sediment, and the amount of deposition may decrease along a distance gradient from the main stream channel. The differential amount of inputs could affect forest productivity. However, in these riparian forests, a distance gradient effect was not observed. Trends in herbaceous biomass were evident along a microtopographic moisture gradient. The ridge and swale microtopography prevalent in the younger riparian forests counteracted a distance from the stream channel gradient effect across the riparian forest. This study provided knowledge of how carbon pools and fluxes change with riparian forest recovery from disturbance as well as through different seral stages. Implementing the findings of this study will enhance restoration evaluation efforts to ensure that these areas continue to provide the numerous benefits gleamed from them.
- Doctoral Dissertations | <urn:uuid:b06114f8-0d10-4c60-ae9c-a7ef9343177d> | 3.234375 | 998 | Academic Writing | Science & Tech. | 17.607158 | 95,509,809 |
What is Cap?
Cap meaning (also called “Lid”) A layer of relatively warm air aloft, usually several thousand feet above the ground, which suppresses or delays the development of thunderstorms. Air parcels rising into this layer become cooler than the surrounding air, which inhibits their ability to rise further and produce thunderstorms. As such, the cap often prevents or delays thunderstorm development even in the presence of extreme instability. However, if the cap is removed or weakened, then explosive thunderstorm development can occur.
The cap is an important ingredient in most severe thunderstorm episodes, as it serves to separate warm, moist air below and cooler, drier air above. With the cap in place, air below it can continue to warm and/or moisten, thus increasing the amount of potential instability. Or, air above it can cool, which also increases potential instability. But without a cap, either process (warming/moistening at low levels or cooling aloft) results in a faster release of available instability – often before instability levels become large enough to support severe weather development.
reference: National Weather Service Glossary | <urn:uuid:42283245-a730-41e1-a5b6-12cc29b39f7f> | 4.1875 | 232 | Knowledge Article | Science & Tech. | 23.445 | 95,509,817 |
General: Species in this genus do not have pigmented eyes. Multiple species of Munidopsis have been identified along the Pacific coast; these may not be distinguishable on video.
Habitat description: Benthic, mostly soft sediment.
Consulting taxonomist: Mary Wicksten, Professor, Texas A&M University, College Station, Texas.
ReferencesEncyclopedia of Life
Tree of Life
World Register of Marine Species
National Center for Biotechnology Information
Jones, W.J. and E. Macpherson (2007). Molecular phylogeny of the East Pacific squat lobsters of the genus Munidopsis (Decapoda: Galatheidae) with the descriptions of seven new species. Journal of Crustacean Biology. 27: 477-50.
Citation: Munidopsis (unknown) Deep-Sea Guide (DSG) at http://dsg/mbari.org/dsg/view/concept/Munidopsis. Monterey Bay Aquarium Research Institute (MBARI). Consulted on 2018-07-20. | <urn:uuid:9c4a97dc-9130-4dcf-81a3-c2071b1bbe99> | 2.765625 | 223 | Knowledge Article | Science & Tech. | 34.02014 | 95,509,829 |
Skip to Content
Scientists at Massey University have been involved in calculating the structure of oganesson, a relatively new element which has proved elusive to study.
First synthesised as a single atom in 2002 at the Joint Institute for Nuclear Research (JINR) in Russia, oganesson is the only noble gas which doesn’t naturally occur and must be synthesised in experiments. It is also one of only two elements to be named after a living scientist, nuclear physicist Yuri Oganessian.
However, studying one of the heaviest elements with the highest atomic number to ever be synthesised (118), is no easy task. Oganesson is radioactive and extremely unstable with a half-life of less than a millisecond, making it impossible to examine by chemical methods. This means computing its electronic structure is the next best thing, which is in itself a formidable task.
Massey’s Distinguished Professor Peter Schwerdtfeger of the New Zealand Institute for Advanced Study, together with nuclear physicist Witold Nazarewicz of Michigan State University in the United States and their respective teams, were able to make these calculations.
Professor Schwerdtfeger says, “Calculations are the only way to get at its behaviour with the tools that we currently have, and they have certainly provided some interesting findings.”
The work suggests that oganesson electrons aren’t confined to distinct orbitals and are distributed evenly.
“On paper, we thought that it would have the same rare gas structure as the others in this family. In our calculations however, we predict that oganesson more or less loses its shell structure and become a smear of electrons.”
Additionally, it was thought to be a gas under normal conditions, but is now predicted to be a solid according to newest research from the Massey group.
“Oganesson is quite different to the other rare gas atoms, as its shells are barely visible in an electron localisation function plot and has been smeared to near-invisibility,” he adds. “Oganesson comes quite close to the limiting case of a Fermi gas.”
The team also calculated the structure of protons and neutrons inside the nucleus, which indicated a smeared-out structure for the neutrons as well. The protons however retain some shell-like ordering.
Created: 20/10/2017 | Last updated: 19/10/2017
Page authorised by Corporate Communications Director
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A recent study published by a team of international scientists analysed the Fermi Paradox and why we are seemingly alone in the universe.
The so-called Fermi Paradox addresses the imbalance between the probability of alien life in space and the lack of evidence for its existence.
And scientists now think there is a 30 percent chance we are alone in our home galaxy the Milky Way.
The study, titled “Dissolving the Fermi Paradox”, claims extraterrestrial life in space could be less advanced than on Earth or simply no longer exist.
Dr Anders Sandberg, Oxford University, told Universe Today: “One can answer the Fermi Paradox by saying intelligence is very rare, but then it needs to be tremendously rare.
“Another possibility is that intelligence doesn’t last very long, but it is enough that one civilisation survives for it to become visible.
“Attempts at explaining it by having all intelligence acting in the same way – staying quiet, avoiding contact with us, transcending – fail since they require every individual belonging to every society in every civilisation to behave in the same way, the strongest sociological claim ever.
“Claiming long-range settlement or communication are impossible requires assuming a surprisingly low technology ceiling.
“Whatever the answer is, it more or less has to be strange.”
The famous Drake Equation proposed by astronomer Frank Drake in the 1960s purports the sheer size of the cosmos should yield a great number of alien civilisations.
The mathematical equation factors in star formation rates, the number of hospitable planets and how far communicate signals need to travel through space among others things.
But Dr Sandberg and his colleagues Eric Drexler and Toby Ord broke the equation down to incorporate new elements, such as the chemical origins of life, which complicated the matter.
The scientists argued the equation is full of uncertainties and is “open to bias”.
Dr Sandberg said: “Many parameters are very uncertain given current knowledge.
“While we have learned a lot more about the astrophysical ones since Drake and Sagan in the 1960s, we are still very uncertain about the probability of life and intelligence.
“When people discuss the equation it is not uncommon to hear them say something like: ‘this parameter is uncertain, but let’s make a guess and remember that it is a guess’, finally reaching a result that they admit is based on guesses.
“But this result will be stated as single number, and that anchors us to an apparently exact estimate – when it should have a proper uncertainty range.” | <urn:uuid:17c5e291-6132-4a90-9fc2-8d255662af47> | 3.75 | 542 | News Article | Science & Tech. | 27.665672 | 95,509,850 |
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Ice exists in water, in air, in earth and in living organisms. The purpose of this book is to describe in mathematical, physical and biological terms, the growth and decay of ice, on a scale ranging from molecular to macroscopic. Consideration of the growth of ice in each of the above contexts provides a clearer understanding of the processes involved and results in a comprehensive overview not available elsewhere. This book will be of particular use to any graduate student, scientist or engineer requiring an introduction and reference for ice-related projects: theoretical or experimental; in the laboratory or the field.
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Wolf-Rayet Stars as IMF Probes
Wolf-Rayet stars are the evolved descendents of massive stars. Their extraordinary properties make them useful tracers of the stellar initial mass function (IMF) in a young stellar population. I discuss how the interpretation of spectral diagnostics are complicated by the interplay of stellar, nebular, and dust properties. There is mounting observational evidence for spatial inhomogeneities in the gas and dust distribution. The interplay of these inhomogeneities can significantly alter frequently used star-formation and IMF indicators. Specific examples presented in this contribution are the starburst galaxies NGC 1614, NGC 2798, and NGC 3125.
KeywordsMassive Star Equivalent Width Stellar Wind Initial Mass Function Starburst Galaxy
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Today, loading a web page on a big website usually involves a database query -- to retrieve the latest contributions to a discussion you're participating in, a list of news stories related to the one you're reading, links targeted to your geographic location, or the like.
But database queries are time consuming, so many websites store -- or "cache" -- the results of common queries on web servers for faster delivery.
If a site user changes a value in the database, however, the cache needs to be updated, too. The complex task of analyzing a website's code to identify which operations necessitate updates to which cached values generally falls to the web programmer. Missing one such operation can result in an unusable site.
This week, at the Association for Computing Machinery's Symposium on Principles of Programming Languages, researchers from MIT's Computer Science and Artificial Intelligence Laboratory presented a new system that automatically handles caching of database queries for web applications written in the web-programming language Ur/Web.
Although a website may be fielding many requests in parallel -- sending different users different cached data, or even data cached on different servers -- the system guarantees that, to the user, every transaction will look exactly as it would if requests were handled in sequence. So a user won't, for instance, click on a link showing that tickets to an event are available, only to find that they've been snatched up when it comes time to pay.
In experiments involving two websites that had been built using Ur/Web, the new system's automatic caching offered twofold and 30-fold speedups.
"Most very popular websites backed by databases don't actually ask the database over and over again for each request," says Adam Chlipala, an associate professor of electrical engineering and computer science at MIT and senior author on the conference paper. "They notice that, 'Oh, I seem to have asked this question quite recently, and I saved the result, so I'll just pull that out of memory.'"
"But the tricky part here is that you have to realize when you make changes to the database that some of your saved answers are no longer necessarily correct, and you have to do what's called 'invalidating' them. And in the mainstream way of implementing this, the programmer needs to manually add invalidation logic. For every line of code that changes the database, the programmer has to sit down and think, 'Okay, for every other line of code that reads the database and saves the result in a cache, which ones of those are going to be broken by the change I just made?'"
Chlipala is joined on the paper by Ziv Scully, a graduate student in computer science at Carnegie Mellon University, who worked in Chlipala's lab as an MIT undergraduate.
The new compiler begins by analyzing the Ur/Web code and determining what data to cache and how to organize it. For instance, if certain types of queries are almost always performed in conjunction with each other, Ur/Web will cache the associated data in a single table. The compiler also decides whether to cache raw data, HTML code, or, if the program structure permits it, entire webpages.
Then the compiler goes through the code and compares every operation that updates a value in the database with every operation that queries the database, to determine which cached values need to be invalidated when, and it adds the appropriate cache-invalidation commands in the appropriate places.
Like many programming languages, Ur/Web has an associated "runtime," a small program that runs in the background to manage the execution of applications written in the language. Chlipala and Scully also updated the Ur/Web runtime to monitor the frequency with which cached database queries are reused. Any that prove superfluous are deleted, which improves the system's efficiency.
In addition to testing the system on two full websites, Chlipala and Scully also tested it on a handful of smaller programs, also written in Ur/Web, which are part of a standard set of benchmarks used to compare different Web development frameworks. On those, the new system offered speedups of between twofold and fivefold.
They did not, however, compare sites developed using their system to sites that use hand-coded caching because, as Chlipala explains, "Ur/Web's so much faster than everything else."
"Even if it turns out that someone could put in the extra work and get a tripling of the throughput, our argument is that it's a pretty good deal to get a doubling of your throughput with no extra work," he adds.
Written by Larry Hardesty, MIT News Office
PAPER: A program optimization for automatic database result caching http://adam.
ARCHIVE: Crash-tolerant data storage http://news.
ARCHIVE: Taking the grunt work out of Web developmenthttp://news.
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Various types of sediments and rocks were analyzed for the relationship between hydraulic conductivity (K) and scale of measurement No variations of K with scale were observed for homogeneous media such as quartz-arenites (quartz sandstones). However, hydraulic conductivity increased with scale of measurement in heterogeneous media. The scaling behavior can be described with the equation K = c (V)m, where c is a parameter characteristic of the geological medium that relates to geological variables such as average pore size and pore interconnectivity in porous media, and probably fracture opening and fracture interconnectivity in fractured media. V is the volume of tested material (used as scale measure), and m is the exponent of the relationship (slope of the line on a log-log plot). The value of the exponent depends on the type or types of flow present. Porous flow media have an exponent of 0.5, multiple flow media an exponent between 0.5 and 1.0, and fracture and conduit flow controlled media an exponent of about 1.0. The more dominant fracture/conduit flow is relative to porous flow, the closer the exponent is to 1.0. K increases with scale up to a rock volume after which the aquifer approaches the properties of an equivalent homogeneous medium and K remains constant with scale. This volume (upper bound of the relationship) is related to the degree of heterogeneity in a medium. It is at a much larger scale in karstic media (if encountered at all) than in nonkarstic and more homogeneous media. Both confined and unconfined aquifers exhibit a similar scale dependence.
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An ability to predict weld microstructure is critical for introduction of new materials, as well as, optimization of existing materials. Complexity of weld microstructure evolution is related to inter- action of phase stability, multicomponent diffusion, steep temperature gradients and morpho- logical instabilities during rapid heating and cooling. In the past two decades, computational thermodynamic and kinetic models have been developed to predict these interactions in wide range of alloys. In the first section, a brief introduction of thermodynamic and kinetic models is given. Models for free energy of solid solution and compound phases, as a function of composition and temperature, are discussed. The underlying assumptions of kinetic models, including local equilibrium at the interface and conditions, are highlighted. In the second section, adoption of these models for predicting weld microstructure evolutions is demonstrated with practical examples from structural alloys. The examples focus on the phase transformations that may occur in liquid state (e.g. inclusion formation), during solidification (e.g. solidification range, phase selection, and segregation) and during solid-state transformations (e.g. growth and dissolution of second phases). In the third section, challenges and opportunities facing widespread use of these tools, as well as, validation using high-resolution and in-situ characterization tools are highlighted.
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