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A part of the Strait of Juan de Fuca, which separates Washington state from Canada's British Columbia, is a potential "hot spot" for toxic harmful algal blooms affecting the Washington and British Columbia coasts.
Marine scientists found that under certain conditions, toxic algal cells from an offshore "initiation site" break off and are transported to nearshore areas, where they may trigger harmful algal blooms that ultimately force the closure of Washington state shellfish beds along beaches.
"Knowing more about these blooms is critical for protecting human and ecosystem health," said David Garrison, director of the National Science Foundation (NSF)'s Biological Oceanography Program, which co-funded the research. "This research is a very successful step toward addressing harmful algal blooms in the U.S."
The study, conducted by a team of scientists from NOAA's Fisheries Service, San Francisco State University and the universities of Washington, Maine and Western Ontario, is part of the interagency Ecology and Oceanography of Harmful Algal Blooms Pacific Northwest Program.
"Understanding how and where harmful algal blooms originate will help provide early warnings to protect human health and reduce the impact of biotoxins on coastal shellfisheries," said Vera Trainer, lead author of a paper published in the January issue of the journal Limnology & Oceanography, and a scientist at the NOAA Fisheries Northwest Fisheries Science Center in Seattle.
Scientists noted that the Juan de Fuca eddy, a circular water mass rotating some 30 miles off the northern coast of Washington at the mouth of the Juan de Fuca Strait, frequently contained significant populations of the microscopic toxic alga, Pseudo-nitzschia.
Over the course of the five-year study, the researchers took thousands of measurements at sea and conducted experiments onboard research vessels and in their laboratories. They hoped to better understand the factors that initiate and sustain the growth of this toxic alga, and to determine why it produces a deadly biotoxin.
This naturally-produced biotoxin, domoic acid, can accumulate in shellfish, crabs and some fish.
By attacking the nervous system it can cause adverse health effects or death in birds, marine mammals and humans who consume affected marine species. Fishing communities may suffer severe economic losses as a result of closures of recreational, subsistence and commercial harvesting, and lost tourism.
The Limnology & Oceanography paper is titled "Variability of Pseudo-nitzschia and domoic acid in the Juan de Fuca eddy region and its adjacent shelves."
Source: National Science Foundation
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Bipolar flows — or jet sources — are abundant in the Universe. They first made their appearance in the early 1960s, as (1) extended, extragalactic radio sources, of sizes between ≳ 102pc and ≲ Mpc, powered by quasars. Miniature copies of them were discovered less than 20 years later, mostly at optical and infrared frequencies, powered by (2) young binary neutron stars (like SS 433) and BHCs, (3) very young ordinary stars (pre-T-Tauri stars, YSOs), and probably even (4) forming binary white dwarfs, at the centers of planetary nebulae. The stellar-mass ones also tend to be called micro quasars. The jet family therefore consists of 4 distinct classes; see Fig. 11.1, Plate 10, and the cover picture.
KeywordsAccretion Disk Active Galactic Nucleus Lorentz Factor Planetary Nebula Central Engine
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Odorant receptors of recent insects evolved long after insects migrated from water to land.
An insect’s sense of smell is vital to its survival. Only if it can trace even tiny amounts of odor molecules is it is able to find food sources, communicate with conspecifics, or avoid enemies.
According to scientists at the Max Planck Institute for Chemical Ecology, many proteins involved in the highly sensitive odor perception of insects emerged rather late in the evolutionary process.
The very complex olfactory system of modern insects is therefore not an adaptation to a terrestrial environment when ancient insects migrated from water to land, but rather an adaptation that appeared when insects developed the ability to fly. The results were published in the Open Access Journal eLife (eLife, March 26, 2014, doi: 10.7554/elife.02115)
Many insect species employ three families of receptor proteins in order to perceive thousands of different environmental odors. Among them are the olfactory receptors. They form a functional complex with another protein, the so-called olfactory receptor co-receptor, which enables insects to smell the tiniest amounts of odor molecules in their environment very rapidly.
Crustaceans and insects share a common ancestor. Since crustaceans do not have olfactory receptors, previously scientists assumed that these receptors evolved as an adaptation of prehistoric insects to a terrestrial life. This hypothesis is also based on the assumption that for the ancestors of recent insects, the ability to detect odor molecules in the air rather than dissolved in water was of vital importance.
Early research on insect olfactory receptors focused entirely on insects with wings. Ewald Große-Wilde and Bill S. Hansson and their colleagues from the Max Planck Institute for Chemical Ecology in Jena, Germany, have now taken a closer look at the olfactory system of wingless insects, which − in evolutionary terms − are older than winged insects: the jumping bristletail Lepismachilis y-signata and the firebrat Thermobia domestica, which are both wingless, as well as the leaf insect Phyllium siccifolium, which is winged and was used as a control. As all three studied insect species emerged at different times in insect evolution, the scientists wanted to track the historical development of olfactory receptors.
Christine Mißbach, first author of the study, analyzed the active genes in the insect antennae where the olfactory receptors are located and describes her discovery this way: “Astonishingly, the firebrat, which is more closely related to flying insects, employs several co-receptors, while the odorant receptors themselves are absent.”
However, the researchers did not find any evidence for an olfactory system which is based on odorant receptors in the most basal insect, the jumping bristletail.
“According to these findings, the receptor family which is important for olfaction in recent insects evolved long after the migration of insects from water to land,” Ewald Große-Wilde summarizes. The researchers are convinced that the main olfactory receptors evolved independently of the co-receptor long after insects had adapted to terrestrial life. They hope that further analyses will reveal why some insect species have only co-receptors, no main receptors, and also clarify the function these co-receptors have on their own. [AO]
Missbach, C., Dweck, H., Vogel, H., Vilcinskas, A., Stensmyr, M. C., Hansson, B. S., Grosse-Wilde, E. (2014). Evolution of insect olfactory receptors. eLife, doi:10.7554/elife.02115.
Dr. Ewald Große-Wilde, Max Planck Institute for Chemical Ecology, 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, email@example.com
Download of high-resolution images via http://www.ice.mpg.de/ext/735.html
Angela Overmeyer | Max-Planck-Institut
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
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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.
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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.
"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.
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Seasonal wetlands on the Lake Wales Ridge, Florida: does a relict seed bank persist despite long term disturbance?
- 355 Downloads
Wetlands maintain biodiversity and provide numerous ecosystem services, so the pressure to perform successful restoration consequently is high. However, restoration projects rarely include an in-depth assessment of wetland potential for recovery, and restoration techniques may not be tailored to site-specific concerns. This study examined the seed bank of disturbed wetlands slotted for hydrologic, but not vegetation, restoration to determine if a seed bank comparable to that of nearby undisturbed wetlands persisted despite long-term anthropogenic disturbance. We compared the aboveground vegetation and seed bank compositions under drained, drawdown, and flooded conditions between undisturbed and historically ditched (“disturbed”) wetlands. Disturbed and undisturbed wetlands shared fewer than 30 % of total aboveground species. While undisturbed wetlands were dominated by graminoids, disturbed wetlands had greater cover of forbs. The seed banks of disturbed wetlands had high species diversity, but their composition was dissimilar to that of nearby undisturbed wetlands. In total, the seed banks of both disturbance histories germinated 56 species; drained conditions had the fewest germinants while flooded conditions had the most. Germinant richness was significantly affected by disturbance, moisture, and their interaction; evenness was significantly affected by moisture, and Shannon diversity by disturbance. Because the seed bank of disturbed wetlands included many fast-growing wetland plants, passive vegetation restoration and active hydrologic restoration may result in wetlands overgrown with weedy species and with fewer conservative wetland plants. An understanding of the capacity for seed banks to re-vegetate wetlands post-restoration and approximate undisturbed wetlands is crucial to the overall success of restoration projects.
KeywordsSeed bank Indicator species analysis Florida Panicum abscissum
We would like to thank Archbold Biological Station for opportunity and funds to conduct this research. We would especially like to acknowledge Carl Weekley and the other members of Archbold Biological Station’s Plant Ecology Program, who provided countless days of scientific support throughout this study. Additionally, we would like to thank Carl Weekley, Richard Marinos, Betsie Rothermel, and an anonymous reviewer for reviewing this manuscript.
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A uranate is a ternary oxide involving the element uranium in one of the oxidation states +4, +5 or +6. A typical chemical formula is MxUyOz, where M represents a cation. The uranium atom in uranates(VI) has two short collinear U–O bonds and either four or six more next nearest oxygen atoms. The structures are infinite lattice structures with the uranium atoms linked by bridging oxygen atoms. "Ammonium diuranate" is an intermediate in the production of uranium oxide nuclear fuels.
A method of general applicability involves combining two oxides in a high temperature reaction. For example,
- Na2O + UO3 → Na2UO4
Another method is the thermal decomposition of a complex, such as an acetate complex. For example, microcrystalline barium diuranate, BaU2O7 was made by thermal decomposition of barium uranyl acetate at 900 °C.
- Ba[UO2(ac)3]2 → BaU2O7 + ... (ac=CH3CO2−)
Uranates are insoluble in water and other solvents, so pure samples can only be obtained by careful control of reaction conditions.
Naturally occurring uranates are rare and always occur as secondary minerals. Examples include curite, becquerelite and soddyite named after prominent radiochemists Pierre Curie and Marie Curie, Henri Becquerel and Frederick Soddy, respectively. Uranates can be prepared by adding alkali to an aqueous solution of a uranyl salt. However, the composition of the precipitate that forms is variable and depends on the chemical and physical conditions used.
All uranates(VI) are mixed oxides, that is, compounds made up of metal(s), uranium and oxygen atoms. No uranium oxyanion, such as [UO4]2− or [U2O7]2−, is known. Instead, all uranate structures are based on UOn polyhedra sharing oxygen atoms in an infinite lattice. The structures of uranates(VI) are unlike the structure of any mixed oxide of elements other than actinide elements. A particular feature is the presence of linear O-U-O moieties, which resemble the uranyl ion, UO22+. However, the U-O bond length varies from 167 pm, which is similar to the bond length of the uranyl ion, up to about 208 pm in the related compound α-UO3, so it is debatable as to whether these compounds all contain the uranyl ion. There are two principal types of uranate which are defined by the number of nearest-neighbour oxygen atoms in addition to the "uranyl" oxygens.
In one group, including M2UO4 (M=Li, Na, K) and MUO4 (M=Ca, Sr) there are six additional oxygen atoms. Taking calcium uranate, CaUO4, as an example, the six oxygen atoms are arranged as a flattened octahedron, flattened along the 3-fold symmetry axis of the octahedron which also runs through the O-U-O axis (local point group D3d at the uranium atom). Each of these oxygen atoms is shared between three uranium atoms, which accounts for the stoichiometry, U + 2×O + 6×1/3 O = UO4. The structure has been described as a hexagonal layer structure. It can also viewed as a distorted fluorite structure in which two U-O distances have decreased and the other six have increased.
In the other group, exemplified by barium uranate, BaUO4, there are four additional oxygen atoms. These four oxygens lie in a plane and each is shared between two uranium atoms, which accounts for the stoichiometry, U + 2×O + 4×1/2 O = UO4. The structure may called a tetragonal layer structure.
Magnesium uranate, MgUO4, has a quite different structure. Distorted UO6 octahedra are linked into infinite chains; the "uranyl" U-O bond length is 192 pm, not much shorter than the other U-O bond length of 218 pm.
A number of so-called diuranates are known. They fall into two categories, compounds of exact composition, synthesized by combination of metal oxides or thermal decomposition of salts of uranyl complexes and substances of approximate composition, found in yellowcake. The name refers only to the empirical formula, MxU2O7; the structures are completely different from ions such as the dichromate ion. For example, in barium diuranate, BaU2O7, UO6 octahedral units are joined by sharing edges, forming infinite chains in the directions of the crystallographic a and b directions.
Uranates with more complicated empirical formulas are known. Essentially these arise when the cation:uranium ratio is different from 2:1 (monovalent cations) or 1:1 (divalent cations). Charge-balance constrains the number of oxygen atoms to be equal to half the sum of charges of the cations and uranyl groups. For example, with the cation K+, compounds with K:U ratios of 2, 1 and 0.5 were found, corresponding to empirical formulas K2UO4, KUO3 and K2U4O13. The uranate structures in these compounds differ in the way the UOx structural units are linked together.
Halo-uranates are compounds in which one oxygen atom is replaced by two halogen atoms. For example, CaU2O6F2 is described as an "isotype" of the oxide U3O8. In the structure of the oxyfluoride, UO2F2, there is the same hexagonal layer structure as in CaUO4. Other anions, such as nitrate, can also be present in uranates.
Properties and uses
When the alkali used is ammonia, so-called ammonium diuranate, known in the industry as ADU, is the main constituent of yellowcake. The exact composition of the precipitate depends to some extent on the conditions and anions that are present and the formula (NH4)2U2O7, is only an approximation. The precipitates obtained on addition of ammonia to uranyl nitrate solution under different conditions of temperature and final pH, when dried, were considered as loosely bound compounds with an ammonia/uranium ratio of 0.37 containing varying amounts of water and ammonium nitrate. In other studies it was found to approximate to the gross formulas 3UO3·NH3·5H2O, The asymmetric stretching frequency of the uranyl ion was found to decrease with increasing NH4+ content. This decrease is continuous and no band splitting was observed, indicating that the ammonium uranate system is homogeneous and continuous.
ADU is an intermediate in the production of uranium oxides to be used as nuclear fuel; it is converted directly into an oxide by heating. βUO3 is produced at about 350 °C and U3O8 is obtained at higher temperatures. When the alkali used is sodium hydroxide, so-called sodium diuranate, SDU, is produced. This can also be converted into an oxide. Another choice of alkali is magnesium oxide, making magnesium diuranate, known as MDU.
Oxides and uranates of uranium(VI) have been used in the past as yellow ceramic glazes as in Fiesta and to make yellow-green uranium glass. Both of these applications are abandoned due to concern regarding radioactivity of the uranium. Uranates are important in radioactive waste management.
Three series of uranates(V) have been characterized. Compounds with the formula MIUO3 have a perovskite structure. Compounds MI3UO4 have a defect rock-salt structure. MI7UO6 structures are based on a hexagonally close-packed array of oxygen atoms. In all cases the uranium is at the centre of an octahedron of oxygen atoms. Few other compounds of uranium(V) are stable.
Barium uranate, BaUO3, is made from barium oxide and uranium dioxide in an atmosphere that contains absolutely no oxygen. It has a cubic crystal structure (space group Pm3m). An extensive series of non-stoichiometric mixed oxides exists. The UO2/PuO2 system is important in the fuel of fast breeder reactors. Cerium uranium blue, of variable formula CexU1–xO2, has a structure similar to the fluorite structure.
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Burns, C. J.; Neu, M.P.; Boukhalfa, H.; Gutowski, K. E.; Bridges, N. J.; Roger, R. D. (2004). "Chapter 3.3, The Actinides". Comprehensive Coordination Chemistry II. Elsevier. pp. 189–345. doi:10.1016/B0-08-043748-6/02001-6. ISBN 0-08-043748-6. | <urn:uuid:96900136-1f3a-49d4-b4ae-3699cde8c0c8> | 3.765625 | 3,090 | Knowledge Article | Science & Tech. | 64.178303 | 95,586,649 |
+44 1803 865913
Edited By: Christian Koeberl and Herbert Henkel
552 pages, 187 illustrations
This volume is the 8th in a series of impact books resulting from the activities of the scientific program "Response of the Earth System to Impact Processes" (IMPACT), by the European Science Foundation. The book resulted from an international meeting at Mora, Sweden, which was held as part of the IMPACT program. The papers cover various structural geologic, geochemical, and geophysical topics on research of asteroid impact structures on Earth and Mars.
From the reviews of the first edition: "This book presents a wide-ranging view of some of the latest research into impacts and some useful reviews. ! The book is richly illustrated throughout with pertinent photographs, maps, diagrams and graphs. ! All of the articles are clearly written, contain good overviews of the related research literature and extensive and useful bibliographies. They will be of great value to research workers and graduate students. ! It should attract a wide readership from among impact researchers worldwide ! ." (Chris Hayward, Geological Magazine, Vol. 143, 2006)
From the contents: Impact Tectonics ? General Aspects.- Structural and Tectonic Aspects of Impact Craters.- Impact Studies by Numerical and Experimental Methods.- Economic Aspects of Impact Structures.
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A simple page can be coded using HTML but it requires a command to run this page on the internet. The coding of command is written either in client side, or in server side or in both scripts. Usually a user interface program is scripted in the client side scripting where the user action is essential like button clicks, performing client oriented task etc. The client side coding is also used for creating dynamic web pages, which contents change frequently. Client-side script executes locally in the browser, which provides the user with a lively and responsive interface.
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When any command or request is sent to the web server, the server sent the necessary file to the user’s server on which they reside. The user's web browser executes the script then displays the document with visible output from the script. | <urn:uuid:c9ff706a-4e32-4e9d-898d-3bc3c827be46> | 3.375 | 215 | Documentation | Software Dev. | 47.09968 | 95,586,663 |
French geologist Alexandre-Emile Béguyer de Chancourtois listed the elements on paper tape and wound them, spiral like, around a cylinder. Certain ‘threes’ of elements with similar properties came together down the cylinder. He called his model the ‘telluric screw’.
English chemist John Newlands noticed that, if the elements were arranged in order of atomic weight, there was a periodic similarity every 8 elements. He proposed his ‘law of octaves’ on this.
Russian chemist Dmitri Mendeleev produced a periodic table based on atomic weights but arranged ‘periodically’. Elements with similar properties appeared under each other. Gaps were left for yet to be discovered elements.
Lothar Meyer complied a periodic table of 56 elements based on a regular repeating pattern of physical properties such as molar volume. Once again, the elements were arranged in order of increasing atomic weights.
William Ramsay discovered the noble gases and realised that they represented a new group in the periodic table.
Henry Moseley determined the atomic number of each of the known elements. He realised that, if the elements were arranged in order of increasing atomic number rather than atomic weight, they gave a better fit within the ‘periodic table’.
Glenn Seaborg artificially produced heavy mass elements such as neptunium. These new elements were part of a new block of the periodic table called ‘actinides’. | <urn:uuid:28fe0cf6-4eab-4864-acbd-cb86974b0dc5> | 4.125 | 307 | Knowledge Article | Science & Tech. | 30.823788 | 95,586,672 |
We use dibutyl phosphate to simulate the behavior of the phosphate group in DNA towards the attack of low energy electrons. We find that the compound undergoes effective dissociative electron attachment within a low energy resonant feature at 1 eV and a further resonance peaking at 8 eV. The dissociative electron attachment (DEA) reactions are associated with the direct cleavage of the C-O and the P-O bond but also the excision of the PO-, PO3-, H2PO3- units. For the phosphate group coupled in the DNA network these reactions represent single strand breaks. We hence propose that the most direct mechanism of single strand breaks occurring in DNA at subexcitation energies (< 4 eV) is due to DEA directly to the phosphate group.
Mendeley saves you time finding and organizing research
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10 February 2006
10 February 2006
Scientists at the National Institute of Standards and Technology (NIST) have created polymer nanotubes that are unusually long (about 1 centimetre) as well as stable enough to maintain their shape indefinitely.
Described in a new paper in Proceedings of the National Academy of Sciences,* the NIST nanotubes may have biotechnology applications as channels for tiny volumes of chemicals in nanofluidic reactor devices, for example, or as the “world’s smallest hypodermic needles” for injecting molecules one at a time.
Carbon nanotubes are of keen interest in nanotechnology research, especially for making ultrastrong fibres and other structures. Nanotubes made from other materials are used for transport in biochemical applications, but are typically fragile and usually collapse within a few hours. The NIST team developed processes for extending the shelf life of polymer nanotubes—considered essential for commercial applications—and forming sturdy nanotube network structures.
First the researchers made tiny, fluid-filled spherical containers with bi-layer membranes consisting of polymers with one end that likes water and one end that does not. (These fluid-filled containers are a spin-off of liposomes, artificial cells with fatty membranes used in cosmetics and for drug delivery.) The researchers made the membranes stretchy by adding a soap-like fluid to change the polymer membranes’ mechanical properties. Then they used “optical tweezers” (highly focused infrared lasers) or tiny droppers called micropipettes to pull on the elastic membranes to form long, double-walled tubes that are less than 100 nanometres in diameter.
A chemical was added to break bonds between atoms in one section of the polymers and induce new bonds to form between the two different sections, forming a rigid “cross-linked” membrane. The nanotubes are then snipped free from the parent cell with an “optical scalpel” (highly focused ultraviolet laser pulse). The nanotubes maintain their shape even after several weeks of storage, and can be removed from the liquid solution and placed on a dry surface or in a different container. The optical tweezers can be used to custom build nanotube network structures. The work was supported in part by the Office of Naval Research.
*J.E. Reiner, J.M. Wells, R.B. Kishore, C. Pfefferkorn, and K. Helmerson. 2006. Stable and robust polymer nanotubes stretched from polymersomes. Proceedings of the National Academy of Sciences. Published online Jan. 23, 2006.
ThermHex Waben and EconCore will exhibit at the IAA Commercial Vehicles exhibition in Hannover, Germany, on 20-27 September 2018.
Technical Fibre Products (TFP) will exhibit nonwovens for use in surface finishing, imparting EMI shielding or fire protection, and other transport applications, at the JEC Conference on The Future of Composites in Transportation, taking place in Chicago, US, on 27-28 June.
TRB Lightweight Structures has developed a carbon fibre reinforced plastic (CFRP) sandwich panel door leaf using a bio-based resin and a 100% recycled foam core. | <urn:uuid:601d6570-76ef-4028-a5d3-af919a86d427> | 3.78125 | 686 | News Article | Science & Tech. | 33.198871 | 95,586,717 |
Q. An n-type silicon sample with Nd=10^16cm-3 is steadily illuminated such that g'=10^21cm-s^-1. If tn0=tp0=10^-6s, calculate the position of the quasi-Fermi levels for electrons and holes with respect to the intrinsic level (assume that ni=1.5x10^10cm^-3).© BrainMass Inc. brainmass.com July 16, 2018, 4:28 pm ad1c9bdddf
Please see attached for solution.
The excess carrier concentration due to steady light illumination is:
dn = dp = gtn (no trapping) ...
The solution clearly explains how to obtain the quasi Fermi level given the data in the question using relevant theory. | <urn:uuid:6ca80d65-bd44-4831-9819-b8c174195ab1> | 2.53125 | 170 | Q&A Forum | Science & Tech. | 84.623182 | 95,586,735 |
- PANEL 2
A BUCKET OF MUD
To explore the microscopic (very small) fauna of the estuary we employed
an environmental research company, Ecowise Consultants, to carry out a
study of the animals who live in the mud. This layer contains many species
that live on the bacteria and algae and other even smaller creatures that
live in their thousands, even millions, here and in water bodies fresh
and salty. Most of the microinvertebrates here are roughly about the size
of a pinhead. All the animals you see here were basically scooped up in
a bucket of mud.
The people pictured in this panel are Denise and Katherine from Ecowise
Consultants collecting mud to be analysed in the laboratory.
on the image to find out more about each of the animals in this panel. | <urn:uuid:5c149910-ace3-4303-ba06-087ab8fbaf73> | 3.234375 | 177 | Knowledge Article | Science & Tech. | 36.762901 | 95,586,744 |
Why is this renowned scientific magazine so enthusiastic about the work of the Würzburg chemists? This is because stable triple bonds have already been realized for almost all chemical elements in the world that theoretically allow a connection of this nature to be established between them - with the exception of boron and oxygen.
Admittedly, triple bonds between boron and oxygen had already been created in the laboratory, but until now this had only been achieved under extreme conditions: the temperatures had to be well below freezing point for this to happen and both elements have to be present as gases - and in the end the triple bond had no enduring stability.
Triple bond stable at room temperature
It is a very different story for Würzburg's chemistry professor Holger Braunschweig and his colleagues Achim Schneider and Dr. Krzysztof Radacki. They have produced, purified, and characterized a stable boron-oxygen triple bond at room temperature in commonly used solvents.
In its purest form, their product exists as a colorless powder. It can withstand temperatures of up to 100 degrees Celsius for many hours. It is not affected by either daylight or UV radiation. Holger Braunschweig concludes: "For the first time ever, science has at its disposal a stable molecule in which a triple bond has been realized between oxygen and boron."
Exciting prospect for basic research
What use will this have? There are no foreseeable applications for the molecule in everyday life as yet. But this newly created boron-oxygen triple bond is an exciting prospect for basic research.
Reactivity studies have already been conducted on the new molecule at Würzburg's Institute of Inorganic Chemistry. The researchers have joined other elements directly to the triple bond and also separated them from it further. How can the molecule be modified? What can be added to it? These questions will also set the agenda for the work that the scientists wish to pursue next.
Holger Braunschweig: recognized boron expert
Holger Braunschweig is a recognized expert in the chemistry of the element boron. His work in this area has recently been acknowledged by the German Research Foundation (DFG): in 2009, he was awarded the Leibniz Prize, which comes with 2.5 million euros in funding and has the reputation of being a kind of "German Nobel Prize".
Boron - a unique element
What is so special about boron? For chemists, this element represents a challenge: it is electron deficient and in a sense craves these particles. It can only satisfy this craving by forming compounds with other elements. "The compounds that boron creates are highly unusual," explains the professor. A leading textbook on inorganic chemistry even devotes a full chapter to this unique element - this alone is indicative of its special status.
Oxoboryl Complexes: Boron-Oxygen Triple Bonds Stabilized in the Coordination Sphere of Platinum, Holger Braunschweig, Krzysztof Radacki, and Achim Schneider, Science 16 April 2010 328: 345-347, DOI: 10.1126/science.1186028
Prof. Dr. Holger Braunschweig, Institute of Inorganic Chemistry, University of Würzburg, phone +49 (0)931 31-85260, email@example.com
Robert Emmerich | idw
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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5 May , 2015 by Fraser Cain
Evolution explains how life adapts and evolves over eons. But how did life originate? Chemists Miller and Urey put the raw chemicals of life into a solution, applied an electric charge, and created amino acids – the building blocks of life.
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As modern cosmologists rely more and more on the ominous "dark matter" to explain otherwise inexplicable observations, much effort has gone into the detection of this mysterious substance in the last two decades, yet no direct proof could be found that it actually exists.
Even if it does exist, dark matter would be unable to reconcile all the current discrepancies between actual measurements and predictions based on theoretical models. Hence the number of physicists questioning the existence of dark matter has been increasing for some time now. Competing theories of gravitation have already been developed which are independent of this construction. Their only problem is that they conflict with Newton's theory of gravitation.
"Maybe Newton was indeed wrong", declares Professor Dr. Pavel Kroupa of Bonn University´s Argelander-Institut für Astronomie (AIfA). "Although his theory does, in fact, describe the everyday effects of gravity on Earth, things we can see and measure, it is conceivable that we have completely failed to comprehend the actual physics underlying the force of gravity".
This is a problematical hypothesis that has nevertheless gained increasing ground in recent years, especially in Europe. Two new studies could well lend further support to it. In these studies, Professor Kroupa and his former colleague Dr. Manuel Metz, working in collaboration with Professor Dr. Gerhard Hensler and Dr. Christian Theis from the University of Vienna, and Dr. Helmut Jerjen from the Australian National University, Canberra, have examined so-called "satellite galaxies".
This term is used for dwarf galaxy companions of the Milky Way, some of which contain only a few thousand stars. According to the best cosmological models, they exist presumably in hundreds around most of the major galaxies. Up to now, however, only 30 such satellites have been observed around the Milky Way, a discrepancy in numbers which is commonly attributed to the fact that the light emitted from the majority of satellite galaxies is so faint they remain invisible.
A detailed study of these stellar agglomerates has revealed some astonishing phenomena: "First of all, there is something unusual about their distribution", Professor Kroupa explains, "the satellites should be uniformly arranged around their mother galaxy, but this is not what we found". More precisely, all classical satellites of the Milky Way – the eleven brightest dwarf galaxies – lie more or less in the same plane, they are forming some sort of a disc in the sky. The research team has also been able to show that most of these satellite galaxies rotate in the same direction around the Milky Way – like the planets revolve around the Sun.
Contradiction upon Contradiction
The physicists do belief that this phenomenon can only be explained if the satellites were created a long time ago through collisions between younger galaxies. "The fragments produced by such an event can form rotating dwarf galaxies", explains Dr. Metz, who has recently moved across to the Deutsches Zentrum für Luft- und Raumfahrt (German Aero-space Center). But there is an interesting catch to this crash theory, "theoretical calculations tell us that the satellites created cannot contain any dark matter". This assumption, however, stands in contradiction to another observation. "The stars in the satellites we have observed are moving much faster than predicted by the Gravitational Law. If classical physics holds this can only be attributed to the presence of dark matter", Manuel Metz states.
Or one must assume that some basic fundamental principles of physics have hitherto been incorrectly understood. "The only solution would be to reject Newton´s classical theory of gravitation", says Pavel Kroupa. "We probably live in a non-Newton universe. If this is true, then our observations could be explained without dark matter". Such approaches are finding support amongst other research teams in Europe, too.
It would not be the first time that Newton's theory of gravitation had to be modified over the past hundred years. This became necessary in three special cases: when high velocities are involved (through the Special Theory of Relativity), in the proximity of large masses (through the theory of General Relativity), and on sub-atomic scales (through quantum mechanics). The deviations detected in the satellite galaxy data support the hypothesis that in space where extremely weak accelerations predominate, a "modified Newton dynamic" must be adopted. This conclusion has far-reaching consequences for fundamental physics in general, and also for cosmological theories. ¬¬Famous astrophysicist Bob Sanders from the University of Groningen declares: "The authors of this paper make a strong argument. Their result is entirely consistent with the expectations of modified Newtonian dynamics (MOND), but completely opposite to the predictions of the dark matter hypothesis. Rarely is an observational test so definite."
Metz, Manuel; Kroupa, Pavel; Theis, Christian; Hensler, Gerhard; Jerjen, Helmut: Did the Milky Way dwarf satellites enter the halo as a group? (The Astrophysical Journal 2009; doi: 10.1088/0004-637X/697/1/269)
Metz, Manuel; Kroupa, Pavel; Jerjen, Helmut: Discs of Satellites: the new dwarf spheroidals (Monthly Notices of the Royal Astronomical Society 2009; doi: 10.1111/j.1365-2966.2009.14489.x)Contact:
Dr. Pavel Kroupa | EurekAlert!
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Multiplication(Redirected from Implied multiplication)
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Multiplication (often denoted by the cross symbol "×", by a point "⋅", by juxtaposition, or, on computers, by an asterisk "∗") is one of the four elementary mathematical operations of arithmetic; with the others being addition, subtraction and division.
The multiplication of whole numbers may be thought as a repeated addition; that is, the multiplication of two numbers is equivalent to adding as many copies of one of them, the multiplicand, as the value of the other one, the multiplier. Normally, the multiplier is written first and multiplicand second (though this can vary by language).
For example, 4 multiplied by 3 (often written as and spoken as "3 times 4") can be calculated by adding 3 copies of 4 together:
Here 3 and 4 are the factors and 12 is the product.
Thus the designation of multiplier and multiplicand does not affect the result of the multiplication.
Multiplication can also be visualized as counting objects arranged in a rectangle (for whole numbers) or as finding the area of a rectangle whose sides have given lengths. The area of a rectangle does not depend on which side is measured first, which illustrates the commutative property. The product of two measurements is a new type of measurement, for instance multiplying the lengths of the two sides of a rectangle gives its area, this is the subject of dimensional analysis.
The inverse operation of multiplication is division. For example, since 4 multiplied by 3 equals 12, then 12 divided by 3 equals 4. Multiplication by 3, followed by division by 3, yields the original number (since the division of a number other than 0 by itself equals 1).
Multiplication is also defined for other types of numbers, such as complex numbers, and more abstract constructs, like matrices. For these more abstract constructs, the order that the operands are multiplied sometimes does matter. A listing of the many different kinds of products that are used in mathematics is given in the product (mathematics) page.
Notation and terminologyEdit
- (verbally, "two times three equals six")
The sign is encoded in Unicode at U+00D7 × MULTIPLICATION SIGN (HTML
There are other mathematical notations for multiplication:
- The middle dot notation, encoded in Unicode as U+22C5 ⋅ dot operator, is standard in the United States, the United Kingdom, and other countries where the period is used as a decimal point. When the dot operator character is not accessible, the interpunct (·) is used. In other countries that use a comma as a decimal mark, either the period or a middle dot is used for multiplication.
- In algebra, multiplication involving variables is often written as a juxtaposition (e.g., xy for x times y or 5x for five times x), also called implied multiplication. The notation can also be used for quantities that are surrounded by parentheses (e.g., 5(2) or (5)(2) for five times two). This implicit usage of multiplication can cause ambiguity when the concatenated variables happen to match the name of another variable, when a variable name in front of a parenthesis can be confused with a function name, or in the correct determination of the order of operations.
- In matrix multiplication, there is a distinction between the cross and the dot symbols. The cross symbol generally denotes the taking a cross product of two vectors, yielding a vector as the result, while the dot denotes taking the dot product of two vectors, resulting in a scalar.
In computer programming, the asterisk (as in
5*2) is still the most common notation. This is due to the fact that most computers historically were limited to small character sets (such as ASCII and EBCDIC) that lacked a multiplication sign (such as
×), while the asterisk appeared on every keyboard. This usage originated in the FORTRAN programming language.
The numbers to be multiplied are generally called the "factors". The number to be multiplied is called the "multiplicand", while the number of times the multiplicand is to be multiplied comes from the "multiplier". Usually the multiplier is placed first and the multiplicand is placed second, however sometimes the first factor is the multiplicand and the second the multiplier. Additionally, there are some sources in which the term "multiplicand" is regarded as a synonym for "factor". In algebra, a number that is the multiplier of a variable or expression (e.g., the 3 in 3xy2) is called a coefficient.
The common methods for multiplying numbers using pencil and paper require a multiplication table of memorized or consulted products of small numbers (typically any two numbers from 0 to 9), however one method, the peasant multiplication algorithm, does not.
Multiplying numbers to more than a couple of decimal places by hand is tedious and error prone. Common logarithms were invented to simplify such calculations. The slide rule allowed numbers to be quickly multiplied to about three places of accuracy. Beginning in the early 20th century, mechanical calculators, such as the Marchant, automated multiplication of up to 10 digit numbers. Modern electronic computers and calculators have greatly reduced the need for multiplication by hand.
The Egyptian method of multiplication of integers and fractions, documented in the Ahmes Papyrus, was by successive additions and doubling. For instance, to find the product of 13 and 21 one had to double 21 three times, obtaining 2 × 21 = 42, 4 × 21 = 2 × 42 = 84, 8 × 21 = 2 × 84 = 168. The full product could then be found by adding the appropriate terms found in the doubling sequence:
- 13 × 21 = (1 + 4 + 8) × 21 = (1 × 21) + (4 × 21) + (8 × 21) = 21 + 84 + 168 = 273.
The Babylonians used a sexagesimal positional number system, analogous to the modern day decimal system. Thus, Babylonian multiplication was very similar to modern decimal multiplication. Because of the relative difficulty of remembering 60 × 60 different products, Babylonian mathematicians employed multiplication tables. These tables consisted of a list of the first twenty multiples of a certain principal number n: n, 2n, ..., 20n; followed by the multiples of 10n: 30n 40n, and 50n. Then to compute any sexagesimal product, say 53n, one only needed to add 50n and 3n computed from the table.
In the mathematical text Zhoubi Suanjing, dated prior to 300 BC, and the Nine Chapters on the Mathematical Art, multiplication calculations were written out in words, although the early Chinese mathematicians employed Rod calculus involving place value addition, subtraction, multiplication and division. These place value decimal arithmetic algorithms were introduced by Al Khwarizmi to Arab countries in the early 9th century.
The modern method of multiplication based on the Hindu–Arabic numeral system was first described by Brahmagupta. Brahmagupta gave rules for addition, subtraction, multiplication and division. Henry Burchard Fine, then professor of Mathematics at Princeton University, wrote the following:
- The Indians are the inventors not only of the positional decimal system itself, but of most of the processes involved in elementary reckoning with the system. Addition and subtraction they performed quite as they are performed nowadays; multiplication they effected in many ways, ours among them, but division they did cumbrously.
Grid method multiplication or the box method, is used in primary schools in England and Wales & in some areas of the United States to help teach an understanding of how multiple digit multiplication works. An example of multiplying 34 by 13 would be to lay the numbers out in a grid like:
30 4 10 300 40 3 90 12
and then add the entries.
The classical method of multiplying two n-digit numbers requires n2 simple multiplications. Multiplication algorithms have been designed that reduce the computation time considerably when multiplying large numbers. In particular for very large numbers, methods based on the discrete Fourier transform can reduce the number of simple multiplications to the order of n log(n) log log(n).
Products of measurementsEdit
One can only meaningfully add or subtract quantities of the same type but can multiply or divide quantities of different types. Four bags with three marbles each can be thought of as:
- [4 bags] × [3 marbles per bag] = 12 marbles.
When two measurements are multiplied together the product is of a type depending on the types of the measurements. The general theory is given by dimensional analysis. This analysis is routinely applied in physics but has also found applications in finance.
A common example is multiplying speed by time gives distance, so
- 50 kilometers per hour × 3 hours = 150 kilometers.
Products of sequencesEdit
Capital Pi notationEdit
The product of a sequence of terms can be written with the product symbol, which derives from the capital letter Π (Pi) in the Greek alphabet. Unicode position U+220F (∏) contains a glyph for denoting such a product, distinct from U+03A0 (Π), the letter. The meaning of this notation is given by:
The subscript gives the symbol for a dummy variable (i in this case), called the "index of multiplication" together with its lower bound (1), whereas the superscript (here 4) gives its upper bound. The lower and upper bound are expressions denoting integers. The factors of the product are obtained by taking the expression following the product operator, with successive integer values substituted for the index of multiplication, starting from the lower bound and incremented by 1 up to and including the upper bound. So, for example:
More generally, the notation is defined as
where m and n are integers or expressions that evaluate to integers. In case m = n, the value of the product is the same as that of the single factor xm. If m > n, the product is the empty product, with the value 1.
One may also consider products of infinitely many terms; these are called infinite products. Notationally, we would replace n above by the lemniscate ∞. The product of such a series is defined as the limit of the product of the first n terms, as n grows without bound. That is, by definition,
One can similarly replace m with negative infinity, and define:
provided both limits exist.
- Commutative property
- The order in which two numbers are multiplied does not matter:
- Associative property
- Expressions solely involving multiplication or addition are invariant with respect to order of operations:
- Distributive property
- Holds with respect to multiplication over addition. This identity is of prime importance in simplifying algebraic expressions:
- Identity element
- The multiplicative identity is 1; anything multiplied by 1 is itself. This feature of 1 is known as the identity property:
- Property of 0
- Any number multiplied by 0 is 0. This is known as the zero property of multiplication:
- –1 times –1 is 1.
- Order preservation
- Multiplication by a positive number preserves order:
- For a > 0, if b > c then ab > ac.
- Multiplication by a negative number reverses order:
- For a < 0, if b > c then ab < ac.
- The complex numbers do not have an ordering.
In the book Arithmetices principia, nova methodo exposita, Giuseppe Peano proposed axioms for arithmetic based on his axioms for natural numbers. Peano arithmetic has two axioms for multiplication:
Here S(y) represents the successor of y, or the natural number that follows y. The various properties like associativity can be proved from these and the other axioms of Peano arithmetic including induction. For instance S(0), denoted by 1, is a multiplicative identity because
The axioms for integers typically define them as equivalence classes of ordered pairs of natural numbers. The model is based on treating (x,y) as equivalent to x − y when x and y are treated as integers. Thus both (0,1) and (1,2) are equivalent to −1. The multiplication axiom for integers defined this way is
The rule that −1 × −1 = 1 can then be deduced from
Multiplication with set theoryEdit
The product of non-negative integers can be defined with set theory using cardinal numbers or the Peano axioms. See below how to extend this to multiplying arbitrary integers, and then arbitrary rational numbers. The product of real numbers is defined in terms of products of rational numbers, see construction of the real numbers.
Multiplication in group theoryEdit
There are many sets that, under the operation of multiplication, satisfy the axioms that define group structure. These axioms are closure, associativity, and the inclusion of an identity element and inverses.
A simple example is the set of non-zero rational numbers. Here we have identity 1, as opposed to groups under addition where the identity is typically 0. Note that with the rationals, we must exclude zero because, under multiplication, it does not have an inverse: there is no rational number that can be multiplied by zero to result in 1. In this example we have an abelian group, but that is not always the case.
To see this, look at the set of invertible square matrices of a given dimension, over a given field. Now it is straightforward to verify closure, associativity, and inclusion of identity (the identity matrix) and inverses. However, matrix multiplication is not commutative, therefore this group is nonabelian.
Another fact of note is that the integers under multiplication is not a group, even if we exclude zero. This is easily seen by the nonexistence of an inverse for all elements other than 1 and −1.
Multiplication in group theory is typically notated either by a dot, or by juxtaposition (the omission of an operation symbol between elements). So multiplying element a by element b could be notated a b or ab. When referring to a group via the indication of the set and operation, the dot is used, e.g., our first example could be indicated by
Multiplication of different kinds of numbersEdit
Numbers can count (3 apples), order (the 3rd apple), or measure (3.5 feet high); as the history of mathematics has progressed from counting on our fingers to modelling quantum mechanics, multiplication has been generalized to more complicated and abstract types of numbers, and to things that are not numbers (such as matrices) or do not look much like numbers (such as quaternions).
- is the sum of N copies of M when N and M are positive whole numbers. This gives the number of things in an array N wide and M high. Generalization to negative numbers can be done by
- The same sign rules apply to rational and real numbers.
- Rational numbers
- Generalization to fractions is by multiplying the numerators and denominators respectively: . This gives the area of a rectangle high and wide, and is the same as the number of things in an array when the rational numbers happen to be whole numbers.
- Real numbers
- Real numbers and their products can be defined in terms of sequences of rational numbers.
- Complex numbers
- Considering complex numbers and as ordered pairs of real numbers and , the product is . This is the same as for reals, , when the imaginary parts and are zero.
- Equivalently, denoting as , we have
- Further generalizations
- See Multiplication in group theory, above, and Multiplicative group, which for example includes matrix multiplication. A very general, and abstract, concept of multiplication is as the "multiplicatively denoted" (second) binary operation in a ring. An example of a ring that is not any of the above number systems is a polynomial ring (you can add and multiply polynomials, but polynomials are not numbers in any usual sense.)
- Often division, , is the same as multiplication by an inverse, . Multiplication for some types of "numbers" may have corresponding division, without inverses; in an integral domain x may have no inverse " " but may be defined. In a division ring there are inverses, but may be ambiguous in non-commutative rings since need not be the same as .
When multiplication is repeated, the resulting operation is known as exponentiation. For instance, the product of three factors of two (2×2×2) is "two raised to the third power", and is denoted by 23, a two with a superscript three. In this example, the number two is the base, and three is the exponent. In general, the exponent (or superscript) indicates how many times the base appears in the expression, so that the expression
indicates that n copies of the base a are to be multiplied together. This notation can be used whenever multiplication is known to be power associative.
- Devlin, Keith (January 2011). "What Exactly is Multiplication?". Mathematical Association of America. Retrieved May 14, 2017.
With multiplication you have a multiplicand (written second) multiplied by a multiplier (written first)
- "小学校の掛け算の授業では、順序に意味があるらしい。" [In elementary school multiplication lessons, the order would appear to be meaningful] (in Japanese). September 30, 2009. Retrieved May 14, 2017.
- Khan Academy (2015-08-14), Intro to multiplication | Multiplication and division | Arithmetic | Khan Academy, retrieved 2017-03-07
- Khan Academy (2012-09-06), Why aren't we using the multiplication sign? | Introduction to algebra | Algebra I | Khan Academy, retrieved 2017-03-07
- Announcing the TI Programmable 88! (PDF). Texas Instruments. 1982. Archived (PDF) from the original on 2017-08-03. Retrieved 2017-08-03.
- Crewton Ramone. "Multiplicand and Multiplier". Crewton Ramone's House of Math. Retrieved 10 November 2015..
- "Google book search". Google Book Search.
- Fine, Henry B. (1907). The Number System of Algebra – Treated Theoretically and Historically (PDF) (2nd ed.). p. 90.
- "Peano arithmetic". PlanetMath. | <urn:uuid:0ec87e4d-909e-48ea-b534-622c3df483ac> | 4.21875 | 3,947 | Knowledge Article | Science & Tech. | 40.093688 | 95,586,813 |
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How is energy created? How does it work? How do we measure it? Find out with Eyewitness Energy and learn all about the ways that we power our world. From muscle energy and photosynthesis to fossil fuels, discover ways energy is created naturally and by using scientific machinery. Eyewitness reference books are now more interactive and colourful, with new infographics, statistics, facts and timelines, plus a giant pull-out wall chart, so you'll be an expert on energy in no time. Great for projects or just for fun, learn everything you need to know about energy with Eyewitness. | <urn:uuid:a01a3419-72e3-427a-b7e9-3304a9184fb8> | 2.859375 | 126 | Product Page | Science & Tech. | 50.215588 | 95,586,814 |
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Periglacial and paraglacial environments, located outside ice sheet margins but responding to similar climate forcings, are key to identifying climate change effects upon the Earth system. These environments are relicts of cold Earth processes and so are most sensitive to global warming. Changes in the distribution and thickness of permafrost in continental interiors have implications for ecosystem and landscape stability. Periglacial Alpine environments are experiencing increased rockfall and mass movement, leading to rock glacier instability and sediment release to downstream rivers. In turn, these landscape effects impact on natural hazards and human activities in these sensitive and geologically transient environments.
Papers in this volume explore some of these interrelated issues in field studies from Europe, North America and Asia. The volume will be of interest to geomorphologists, modellers, environmental managers, planners and engineers working on landscape, climate and environmental change in periglacial and paraglacial areas.
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Artist's concept of the Akatsuki spacecraft in orbit around Venus
|Mission type||Venus orbiter|
JAXA Special Site
|Mission duration||~2 years (science phase)
elapsed: 8 years, 1 month and 26 days
|Launch mass||517.6 kg (1,141 lb)|
|Power||>700 watts at 0.7 AU|
|Start of mission|
|Launch date||20 May 2010, 21:58:22UTC|
|Launch site||Tanegashima Yoshinobu 1|
|Period||15 days; to be adjusted to 9 days in March 2016|
|Flyby of Venus (failed insertion)|
|Closest approach||6 December 2010, 23:49:00 UTC|
|Orbital insertion||7 December 2015|
Akatsuki (あかつき, 暁?, "Dawn"), also known as the Venus Climate Orbiter (VCO) and Planet-C, is a Japanese (JAXA) space probe tasked to study the atmosphere of Venus. It was launched aboard an H-IIA 202 rocket on 20 May 2010, and failed to enter orbit around Venus on 6 December 2010. After the craft orbited the Sun for five years, engineers placed it into an alternative elliptical Venusian orbit on 7 December 2015 by firing its attitude control thrusters for 20 minutes. By using five different cameras, Akatsuki will study the stratification of the atmosphere, atmospheric dynamics, and cloud physics.
Akatsuki is a Japanese space mission to the planet Venus. Planned observations include cloud and surface imaging from an orbit around the planet with an infrared camera, which are aimed at investigation of the complex Venusian meteorology. Other experiments are designed to confirm the presence of lightning and to determine whether volcanism occurs currently on Venus. In most planets, the atmosphere circulates much slower than the rotation speed of the planet. However, on Venus, while the planet rotates at 6 km/h at the equator, the atmosphere spins around the planet at 300 km/h.
Akatsuki is Japan's first planetary exploration mission since the failed Mars orbiter Nozomi probe which was launched in 1998. Akatsuki was originally intended to conduct scientific research for two or more years from an elliptical orbit around Venus ranging from 300 to 80,000 km (190 to 49,710 mi) in altitude, but its alternate orbit, yet to be characterized, had to be highly elliptical. The budget for this mission is ¥14.6 billion (US$174 million) for the satellite and ¥9.8 billion (US$116 million) for the launch.
The main bus is a 1.45 × 1.04 × 1.44 m (4.8 × 3.4 × 4.7 ft) box with two solar arrays, each with an area of about 1.4 m2 (15 sq ft). The solar arrays provide over 700 W of power in Venus orbit. The total mass of the spacecraft at launch was 517.6 kg (1,141 lb). The mass of the science payload is 34 kg (75 lb).
Propulsion is provided by a 500-newton (110 lbf) bi-propellant, hydrazine-dinitrogen tetroxide orbital maneuvering engine and twelve mono-propellant hydrazine reaction control thrusters, eight with 23 N (5.2 lbf) of thrust and four with 3 N (0.67 lbf). It is the first spacecraft to use a ceramic (silicon nitride) retrofire thruster. The total propellant mass at launch was 196.3 kg (433 lb).
Communication is via an 8 GHz, 20-watt X-band transponder using the 1.6 m (5 ft 3 in) high-gain antenna. The high-gain antenna is flat to prevent heat from building up in it. Akatsuki also has a pair of medium-gain horn antennas mounted on turntables and two low-gain antennas for command uplink. The medium-gain horn antennas are used for housekeeping data downlink when the high-gain antenna is not facing Earth.
- the Lightning and Airglow Camera (LAC) will look for lightning in the visible wavelengths of 552 to 777 nanometers
- the ultraviolet imager (UVI) will study the distribution of specific atmospheric gases such as sulfur dioxide in ultraviolet wavelengths (293–365 nm)
- the longwave infrared camera (LIR) will study the structure of high-altitude clouds at a wavelength where they emit heat (10 μm)
- the 1 μm camera (IR1) will image heat radiation emitted from Venus's surface rocks (0.90–1.01 μm) and will help researchers to spot active volcanoes, if they exist
- the 2 μm camera (IR2) will detect heat radiation emitted from the lower reaches of the atmosphere (1.65–2.32 μm)
- the Ultra-Stable Oscillator (USO) for high precision measurement of distance and communication
A public relations campaign was held between October 2009 and January 2010 by the Planetary Society and JAXA, to allow individuals to send their name and a message aboard Akatsuki. Names and messages were printed in fine letters on an aluminium plate and placed aboard Akatsuki. 260,214 people submitted names and messages for the mission. Around 90 aluminum plates were created for the spacecraft, including three aluminium plates in which the images of the Vocaloid Hatsune Miku and her super deformed figure Hachune Miku were printed.
Akatsuki left the Sagamihara Campus on 17 March 2010, and arrived at the Tanegashima Space Center's Spacecraft Test and Assembly Building 2 on 19 March. On 4 May, Akatsuki was encapsulated inside the large payload fairing of the H-IIA rocket that launched the spacecraft, along with the IKAROS solar sail, on a 6-month journey to Venus. On 9 May, the payload fairing was transported to the Tanegashima Space Center's Vehicle Assembly Building, where the fairing was mated to the H-IIA launch vehicle itself.
Orbit insertion failure
Akatsuki was planned to initiate orbit insertion operations by igniting the orbital maneuvering engine at 23:49:00 on 6 December 2010 UTC. The burn was supposed to continue for twelve minutes, to an initial orbit of 180,000 to 200,000 km (110,000 to 120,000 mi) apoapsis / 550 km (340 mi) periapsis / four days orbital period around Venus.
The orbit insertion maneuver was confirmed to have started on time, but after the expected blackout due to occultation by Venus, the communication with the probe did not recover as planned. The probe was found to be in safe-hold mode, spin-stabilized state with ten minutes per rotation. Due to the low communication speed through the low-gain antenna, it took a while to determine the state of the probe. JAXA stated on 8 December that the probe's orbital insertion maneuver had failed. At a press conference on 10 December, officials reported that Akatsuki's engines fired for less than three minutes, far short of what was required to enter into Venus orbit. Further research found that the likely reason for the probe malfunction was salt deposits jamming the valve between the helium pressurization tank and the fuel tank. As a result, engine combustion became oxidizer-rich, with resulting high combustion temperatures damaging the combustion chamber throat and nozzle. A similar vapor leakage problem destroyed the NASA Mars Observer probe in 1993.
JAXA developed plans to attempt another orbital insertion burn when the probe returned to Venus in December 2015. This required placing the probe into "hibernation" or safe mode to prolong its life beyond the original 4.5-year design. JAXA expressed some confidence in keeping the probe operational, pointing to reduced battery wear, since the probe was then orbiting the Sun instead of its intended Venusian orbit.
Telemetry data from the original failure suggested that the throat of its main engine, the orbit maneuver engine (OME) was still largely intact, and trial jet thrusts of the probe's onboard OME were performed twice, on 7 and 14 September 2011. However, the thrust was only about 40 newtons (9.0 lbf), which was 10% of expectations. Following these tests, it was determined that insufficient specific impulse would be available for orbital maneuvering by the OME. It was concluded that the remaining combustion chamber throat was completely destroyed by transient ignition of the engine. As a result, the selected strategy was to use four hydrazine attitude control thrusters, also called reaction control system (RCS), to drive the probe into orbit around Venus. Because the RCS thrusters do not need oxidiser, the remaining 65 kg of oxidiser (MON) was vented overboard in October 2011 to lighten the spacecraft.
Three peri-Venus orbital maneuvers were executed on 1 November, 10 and 21 November 2011 using the RCS thrusters. A total delta-v of 243.8 m/s was imparted to the spacecraft. Because the RCS thrusters' specific impulse is low compared to the specific impulse of the OME, the previously planned insertion into low Venusian orbit became impossible. Instead, the new plan was to place the probe in a highly elliptical orbit with an apoapsis of a hundred thousand kilometers and a periapsis of a few thousand kilometers from Venus. Engineers planned for the alternate orbit to be prograde (in the direction of the atmospheric super-rotation) and lie in the orbital plane of Venus. The method and orbit were announced by JAXA in February 2015, with an orbit insertion date of 7 December 2015. The probe reached its most distant point from Venus on 3 October 2013 and had been approaching the planet since then.
After performing the last of a series of four trajectory correction maneuvers between 17 July and 11 September 2015, the probe was established on a rendezvous trajectory with Venus. The rendezvous occurred on 7 December 2015, when Akatsuki successfully entered Venus orbit after a 20-minute burn with 4 thrusters that were not rated for such a hefty propulsive maneuver. Instead of taking about 30 hours to complete an orbit around Venus—as was originally planned—Akatsuki will complete one orbit every nine days after an adjustment in March 2016.
After JAXA engineers measured and calculated its orbit following the December 7 operation, JAXA announced on December 9 that Akatsuki had successfully entered the intended elliptical orbit, as far as 440,000 km (270,000 mi) from Venus, and as close as 400 km (250 mi) from Venus's surface with an orbital period of 13 days and 14 hours. A follow-up thruster burn scheduled for 26 March 2016, will lower Akatsuki's peak altitude of its orbit to about 330,000 km (210,000 mi) and shorten its orbital period from 13 to 9 days. The 2-year science phase will start after the March 2016 orbit adjustment.
Having flown as close as 0.6 AU from the Sun, the gradual deterioration of heat insulation blankets was noticed, but the deterioration rate slowed in 2015 and the spacecraft survived the orbit transfer. It was unknown whether the cameras and related electronics aboard sustained damage, as temperatures within the spacecraft rose 30 to 40 °C above design parameters. Two days after orbit injection, controllers had verified the function of three of its cameras (UVI, LIR, IR1) and were planning verification of the other 3 scientific instruments (IR2, LAC, USO) in the next few days.
- Ikaros, solar sail demonstrator, launched along with Akatsuki
- Nozomi (probe), 1998 Mars mission (did not enter orbit)
- Sakigake, Japan's first interplanetary probe, 1985
- Suisei (probe)
- Venus probes
- Takeshi, Oshima; Tokuhito, Sasaki. "Development of the Venus Climate Orbiter PLANET-C (AKATSUKI)". NEC Technical Journal. 6 (1): 47–51.
- Stephen Clark (20 May 2010). "H-2A Launch Report – Mission Status Center". Spaceflight Now. Archived from the original on 20 May 2010. Retrieved 20 May 2010.
- "Japanese probe fires thrusters in second bid to enter Venus orbit". The Japan Times. 7 December 2015. Retrieved 7 December 2015.
- Szondy, David. "Akatsuki probe enters orbit around Venus". Retrieved 7 December 2015.
- Clark, Stephan. "Japanese probe fires rockets to steer into orbit at Venus". Retrieved 7 December 2015.
- Chris Bergin (20 May 2010). "AXA H-IIA carrying Akatsuki and IKAROS launches at second attempt". NASASpaceFlight. Retrieved 19 November 2010.
- Limaye, Sanjay. "Live from Sagamihara: Akatsuki Orbit Insertion – Second Try". Retrieved 7 December 2015.
- Wenz, John (21 September 2015). "Japan's Long Lost Venus Probe May Boom Back to Life". Popular Mechanics. Retrieved 14 October 2015.
- Nakamura, N.; et al. (May 2011). "Overview of Venus orbiter, Akatsuki". Earth, Planets and Space. 63 (5): 443–457. ISSN 1880-5981. doi:10.5047/eps.2011.02.009.
- "Exploring the Venusian Atmosphere – AKATSUKI/PLANET-C". Akatsuki Special Site. Retrieved 5 December 2015.
- "AKATSUKI orbit control at perihelion". JAXA. 1 November 2011. Retrieved 3 December 2011.
- Staff writers (8 December 2010). "Japan probe shoots past Venus, may meet again in six years". Spacedaily.com. Retrieved 3 December 2011.
- "Mission overview". PLANET-C Team/JAXA. Retrieved 3 December 2011.
- "Akatsuki (Venus Climate Orbiter / Planet-C)". The Planetary Society. Retrieved 19 November 2010.
- Nakamura, Masato; Imamura, Takeshi; Ueno, Munetaka; et al. "Planet-C: Venus Climate Orbiter mission of Japan" (pdf). Planetary and Space Science. 55 (12): 1831–1842. Bibcode:2007P&SS...55.1831N. doi:10.1016/j.pss.2007.01.009.
- "Messages From Earth: Send your Message to Venus on Akatsuki". The Planetary Society. 2010. Archived from the original on 7 April 2010. Retrieved 2 April 2010.
- "We will deliver your message to the bright star Venus – Akatsuki Message Campaign". JAXA. Retrieved 19 November 2010.
- "AKATSUKI Message Campaign". JAXA. 2010. Retrieved 2 April 2010.
- 金星へ届け！ 県民が寄せ書き [Hoping that It Will Reach Venus! Residents of The Prefecture Write Something Together] (in Japanese). Oita Godo Shimbum. 17 May 2010. Retrieved 20 July 2010.
- "打ち上げを目前に控えた「あかつき」と「IKAROS」の機体が公開" [The Airframes of "Akatsuki" And "IKAROS" just before Those Launch Are Opened]. Mycom Journal (in Japanese). Mainichi Communications. 12 March 2010. Retrieved 20 July 2010.
- "Venus Climate Orbiter "AKATSUKI" (PLANET_C): Topics". JAXA. 1 November 2011. Retrieved 3 December 2011.
- "Launch of Venus probe Akatsuki postponed due to bad weather". Japan Today. 18 May 2010. Retrieved 19 November 2010.
- 来月７日に金星周回軌道へ＝あかつき、エンジン噴射−７年前は火星で失敗・宇宙機構. Jiji.com (in Japanese). Jiji Press. 18 November 2010. Retrieved 5 December 2010.
- 金星探査機「あかつき」の状況について [About the State of Venus Probe Akatsuki] (PDF) (in Japanese). 7 December 2010. Retrieved 7 December 2010.
- JAXA's press briefing, 22:00, 7 December 2010 JST
- "Japan's Venus Probe Fails to Enter Orbit". ABC News. Retrieved 8 December 2010.
- "Akatsuki Mission statement". The Planetary Society. Retrieved 8 December 2010.
- David Cyranoski (14 December 2010). "Venus miss is a setback for Japanese programme". Nature. Retrieved 21 December 2010.
- Nakamura, M.; Kawakatsu, Y.; Hirose, C.; Imamura, T.; Ishii, N.; Abe, T.; Yamazaki, A.; Yamada, M.; Ogohara, K.; Uemizu, K.; Fukuhara, T.; Ohtsuki, S.; Satoh, T.; Suzuki, M.; Ueno, M.; Nakatsuka, J.; Iwagami, N.; Taguchi, M.; Watanabe, S.; Takahashi, Y.; Hashimoto, G. L.; Yamamoto, H. (2014). "Return to Venus of the Japanese Venus Climate Orbiter AKATSUKI". Acta Astronautica. 93: 384–389. Bibcode:2014AcAau..93..384N. doi:10.1016/j.actaastro.2013.07.027.
- "Japanese Venus Probe Misses Orbit". Aviation Week & Space Technology.
- "Japanese craft to get second chance after missing Venus in 2010".
- 「あかつき」の旅 (2013年特別公開向け資料) (PDF) (in Japanese). PLANET-C Team/JAXA. 26 August 2013. Retrieved 8 June 2014.
- "AKATSUKI: Orbit successfully controlled". PLANET-C Team/JAXA. 5 August 2015. Retrieved 10 September 2015.
- "Venus Climate Orbiter "AKATSUKI" Inserted Into Venus' Orbit". JAXA. December 9, 2015.
- "AKATSUKI heading to Venus again". PLANET-C Team/JAXA. 9 January 2015. Retrieved 17 March 2015.
- "AKATSUKI successfully inserted into Venus' orbit". JAXA. 9 December 2015. Retrieved 2015-12-13.
|Wikimedia Commons has media related to Akatsuki (spacecraft).|
- JAXA Akatsuki Planet-C page
- JAXA Akatsuki Special Site
- Akatsuki on Twitter
- Exploring the Venusian Atmosphere – AKATSUKI/PLANET-C – Video
- Launch Report of the H-IIA Launch Vehicle No. 17 with the Venus Climate Orbiter "Akatsuki" (Planet-C) – Video
- Planet-C page (Solar Terrestrial Physics Group)
- Detailed Space Review article about Akatsuki and its recovery
- Presentation about Planet-C from the VEXAG meeting in November 2005 (PDF, 2.7 MB)
- Vieru, Tudor. "JAXA Gets Ready to Launch Venus Probe". Softpedia. Archived from the original on 23 March 2010. Retrieved 30 March 2010.
- Venus Climate Orbiter "AKATSUKI" (PDF, 1.72 Mb) | <urn:uuid:0d0b4788-4d41-4fe9-abcd-c6c1b95ea1e7> | 3.34375 | 4,176 | Knowledge Article | Science & Tech. | 60.820476 | 95,586,847 |
Next-generation gravitational wave detector in space will complement LIGO on Earth
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A string of detections -- four more binary black holes and a pair of neutron stars -- soon followed the Sept. 14, 2015, observation.
This is a visualization of the gravitational wave emission from a pair of orbiting compact objects. The upcoming space-based gravitational wave observatory LISA will be able to observe hundreds of such binary star systems in the Milky Way galaxy, including approximately 50 binaries found in globular clusters, reports a new Northwestern University study.These binary sources would contain all combinations of black hole, neutron star and white dwarf components.
Now, another detector is being built to crack this window wider open. This next-generation observatory, called LISA, is expected to be in space in 2034, and it will be sensitive to gravitational waves of a lower frequency than those detected by the Earth-bound Laser Interferometer Gravitational-Wave Observatory (LIGO).
A new Northwestern University study predicts dozens of binaries (pairs of orbiting compact objects) in the globular clusters of the Milky Way will be detectable by LISA (Laser Interferometer Space Antenna). These binary sources would contain all combinations of black hole, neutron star and white dwarf components. Binaries formed from these star-dense clusters will have many different features from those binaries that formed in isolation, far from other stars.
The study is the first to use realistic globular cluster models to make detailed predictions of LISA sources. "LISA Sources in Milky-Way Globular Clusters" was published today, May 11, by the journal Physical Review Letters.
"LISA is sensitive to Milky Way systems and will expand the breadth of the gravitational wave spectrum, allowing us to explore different types of objects that aren't observable with LIGO," said Kyle Kremer, the paper's first author, a Ph.D. student in physics and astronomy in Northwestern's Weinberg College of Arts and Sciences and a member of a computational astrophysics research collaboration based in Northwestern's Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).
In the Milky Way, 150 globular clusters have been observed so far. The Northwestern research team predicts one out of every three clusters will produce a LISA source. The study also predicts that approximately eight black hole binaries will be detectable by LISA in our neighboring galaxy of Andromeda and another 80 in nearby Virgo.
Before the first detection of gravitational waves by LIGO, as the twin detectors were being built in the United States, astrophysicists around the world worked for decades on theoretical predictions of what astrophysical phenomena LIGO would observe. That is what the Northwestern theoretical astrophysicists are doing in this new study, but this time for LISA, which is being built by the European Space Agency with contributions from NASA.
"We do our computer simulations and analysis at the same time our colleagues are bending metal and building spaceships, so that when LISA finally flies, we're all ready at the same time," said Shane L. Larson, associate director of CIERA and an author of the study. "This study is helping us understand what science is going to be contained in the LISA data."
A globular cluster is a spherical structure of hundreds of thousands to millions of stars, gravitationally bound together. The clusters are some of the oldest populations of stars in the galaxy and are efficient factories of compact object binaries.
The Northwestern research team had numerous advantages in conducting this study. Over the past two decades, Frederic A. Rasio and his group have developed a powerful computational tool -- one of the best in the world -- to realistically model globular clusters. Rasio, the Joseph Cummings Professor in Northwestern's department of physics and astronomy, is the senior author of the study.
The researchers used more than a hundred fully evolved globular cluster models with properties similar to those of the observed globular clusters in the Milky Way. The models, which were all created at CIERA, were run on Quest, Northwestern's supercomputer cluster. This powerful resource can evolve the full 12 billion years of a globular cluster's life in a matter of days.
NASA (ATP grant NNX14AP92G) and the National Science Foundation (grant AST-1716762) supported the research.
Other authors of the paper include Sourav Chatterjee and Katelyn Breivik, both of Northwestern and CIERA, and Carl L. Rodriguez, of the MIT-Kavli Institute for Astrophysics and Space Research.
Megan Fellman | EurekAlert!
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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16.07.2018 | Physics and Astronomy
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16.07.2018 | Earth Sciences | <urn:uuid:d4198999-50a9-4445-91a6-b53eb3776f1d> | 3.53125 | 1,615 | Content Listing | Science & Tech. | 35.11814 | 95,586,851 |
The Many Faces of Transport
Nature exhibits a bewildering variety of different transport phenomena. We all are aware that walking from one place to another demands the use of muscular strength to realize the activity. It requires an effort to perform the motion. This simple example shows that transport is related to energy conversion. We must convert potential energy into kinetic energy. However, this is not the whole story. We must also overcome friction during the walk in order to sustain the motion. These two aspects will play a crucial role in identifying motion as transport. In general we could say that motion in a physical system is a transport phenomenon, if the motion is correlated with dissipation. Dissipation is conversion of energy into chaotic motion or heat. The motion of the planets around the sun is usually not considered as transport, because there is no accompanying, or negligible, friction. Other examples of transport are the flow of water through a narrow tube, where friction is caused by the wall of the tube on the water flow: the transport of electrons in semiconductors, where dissipation or friction is caused by collisions of electrons on impurities, lattice defects and lattice vibrations, and possible other mechanisms. The latter example is already somewhat more subtle, because in a perfect lattice there will be no frictional forces, at least at zero temperature.
KeywordsChaotic Motion Quantum Transport Perturbative Approach Gate Leakage Mesoscopic System
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arstechnica looks at Breakthrough Starshot, the goal to send a spaceship to the nearest star at 20% the speed of light. While this would mean visiting another solar system — we could visit Alpha Centauri in 20 years — travelling at those speeds means that impact with a stray atom or — worse — a dust particle, would have some catastrophic consequences.
Dust presents a somewhat different problem. Small dust particles will essentially act like a simultaneous bombardment by a lot of gas atoms. That's because the energy binding things together in a dust particle is tiny compared to the energy of the collision itself, and the dust is largely composed of heavier atoms. But a sufficiently large dust particle will create a collision energetic enough to destroy a craft. And "sufficiently large" isn't very big; the authors estimate that it only has to be 15 micrometers across to kill off the craft. Fortunately, dust particles this size are rare, and the authors calculate the odds of running into one at 1050 to one against.
Overall, the authors find the effect of gas to be minor and only likely to cause damage down to a depth of 0.1 millimeters. Dust, however, is a different story. It will evaporate about 1.5 millimeters off the surface of the spacecraft, and melting will happen at depths of up to 10 millimeters. When every gram counts, this could be significant.
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Nestled inside this constantly changing magnetic bubble lies a donut of charged particles generally aligned with Earth’s equator. Known as the ring current, its waxing and waning is a crucial part of the space weather surrounding our planet, able to induce magnetic fluctuations on the ground as well as to transmit disruptive surface charges onto spacecraft.
Since 2008, NASA’s two TWINS spacecraft have been providing a sterescopic view of the ring current -- a hula hoop of charged particles that encircles Earth. Credit: J. Goldstein/SWRI
On June 15, 2008, a new set of instruments began stereoscopic imaging of this mysterious region. Called Two Wide-angle Imaging Neutral-atom Spectrometers or TWINS, these satellites orbit in widely separated planes to provide the first and only stereo view of the ring current. TWINS maps the energetic neutral atoms that shoot away from the ring current when created by ion collisions.
In five years of operation, the TWINS maps have provided three-dimensional images and global characterization of this region. The observatories track how the magnetosphere responds to space weather storms, characterize global information such as temperature and shape of various structures within the magnetosphere, and improve models of the magnetosphere that can be used to simulate a vast array of events.
“With two satellites, with two sets of simultaneous images we can see things that are entirely new,” said Mei-Ching Fok, the project scientist for TWINS at NASA’s Goddard Space Flight Center in Greenbelt, Md. “This is the first ever stereoscopic energetic neutral atom mission, and it’s changed the way we understand the ring current.”
Each spacecraft is in a highly elliptical orbit called a Molniya orbit, during which the spacecraft spend most of their time around 20,000 miles above Earth, where they get a great view of the magnetosphere. Initially launched for a two-year mission, TWINS was formally extended in 2010 for three more years, with another multi-year extension pending. Over that time, TWINS has worked hand in hand with other NASA missions that provide information about Earth’s magnetosphere.
“We’ve done some fantastic new research in the last five years,” said David McComas, the principal investigator for TWINS at the Southwest Research Institute in San Antonio, Texas. “As a mission of opportunity, it is a very inexpensive mission and it continues to return incredible science.”
TWINS science is based on two instruments that can track neutral atoms. The first is a neutral atom imager that records the atoms that naturally stream away when a neutral atom collides with an ion. This allows the instrument to map the original ions from far away – as if it could see atoms the way we see light – instead of only collecting data from the areas of space it passes through.
“Over the course of the last 20 years a completely new technique evolved so we can observe charged particles, such as those in the ring current, remotely,” said McComas. “The charged particles sometimes collide with a slow-moving neutral particle, in this case from a population of neutrals from Earth’s highly extended atmosphere, the geocorona.”
When this happens, an electron hops from the slow neutral atom to the fast ion, so now the former becomes charged, and the latter neutral. That new neutral speeds off in a straight direction, unfazed by the magnetic field lines around Earth that guide and control the motion of charged particles. TWINS collects such fast neutral particles and from that data scientists can work backward to map out the location and movement of the original ions.
The other instrument on TWINS is a Lyman alpha detector, which can measure the density of hydrogen from afar, and in this case observes the hydrogen cloud around Earth, the geocorona.
Most importantly, these instruments exist on both of the TWINS spacecraft. Much of the successful research in the last five years relies on the ability to watch these neutrals from two viewpoints, allowing scientists to analyze not only speed and number of particles, but also to determine the angles at which the particles left their original collisions. The stereo vision contributed to the detailed perspectives on how the magnetosphere reacts to space weather storms: both those due to the impact of a coronal mass ejection that traveled from the sun toward Earth and due to an incoming twist in the solar wind known as a co-rotating interaction region. TWINS has also revealed that the pitch angle at which the ions travel around Earth is different on each side of the planet. Such information helps scientists determine whether the ions are more likely to escape from the ring current out into space or to ultimately funnel down toward Earth.
“TWINS is a stereo mission, providing the first observations of the neutral atoms from two vantage points, but two spacecraft give us another advantage,” said Natalia Buzulukova, a magnetospheric scientist at Goddard who works with TWINS data. “Two spacecraft provide continuous coverage of the ring current, as one set of instruments always has a view.”
Because the spacecraft orbits are not in sync they provide stereoscopic imaging for a few hours each day, but there is always at least one spacecraft keeping tabs on how events are unfolding. Prior to TWINS, a spacecraft might see a tantalizing process taking place in the ring current for only a short while before its orbit took it out of view. The event might well have finished before the spacecraft came back around for its second look.
Such continuity has proved useful to determine what governs whether particles in the ring current will precipitate downward toward Earth as well as to provide a global temperature map of the magnetic tail trailing behind Earth, the magnetotail. Such a map had only ever previously been inferred from models and statistical analysis, never from a comprehensive data set of what was actually observed.
The Lyman-alpha instrument has been used in two ways. For one thing, it quantifies the geocorona in order to better understand how it affects the collisions in the ring current. It also has taught us more about the geocorona itself. Previously, researchers believed it to be a fairly simple sphere around Earth. The two TWINS instruments have shown how asymmetric it is, changing with the solar cycle, seasons, and even the hours of the day.
A final important feature of this fire hose of TWINS data is how much it helps improve computer simulations of the ring current and the rest of the magnetosphere. With accurate computer models, scientists can better predict how the magnetosphere will react to any given space weather event.
“We get two really unique things with two spacecraft: stereo imaging and continuous coverage. Together the observations we get are fantastic,” said McComas. “It’s an incredibly powerful combination of tools.”
TWINS is an Explorer Mission of Opportunity. Southwest Research Institute leads TWINS with teams of national and international partners. Goddard manages the Explorers Program for NASA's Science Mission Directorate in Washington, D.C.For more information about TWINS science and mission, visit:
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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...
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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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- Static debugging focuses on semantic analysis.
- In a certain program, suppose there are two variables: var1 and var2. The type of var1 is an integer, and the type of var2 is a float. Now, the program assigns the value of var2 to var1; then, there a possibility that it may not get correctly assigned to the variable due to truncation. This type of analysis falls under static debugging.
- Static debugging detects errors before the actual execution.
- Static code analysis may include detection of the following situations:
Dereferencing of variable before assigning a value to it
Truncation of value due to the wrong assignment
Redeclaration of variables
Presence of unreachable code
- Dynamic analysis is carried out during program execution. An interactive debugging system provides programmers with facilities that aid in testing and debugging programs interactively. A dynamic debugging system should provide the following facilities:
- Execution sequencing: It is nothing but observation and control of the flow of program execution. For example, the program may halted after a fixed number of instructions executed.
- Breakpoints: Breakpoints specify the position within a program till which the program gets executed without disturbance. Once the control reaches such a position, it allows the user to verify the contents of variables declared in the program.
- Conditional expressions: A debugger can include statements in a program to ensure that certain conditions reached in the program. These statements, known as assertions, can use to check whether some pre-condition or post-condition has met in the program during execution.
- Tracing monitors step by step the execution of all executable statements present in a program. The other name for this process is “step into”. Another possible variation is “step over” debugging that can execute at the level of procedure or function. This can implemented by adding a breakpoint at the last executable statement in a program.
- Traceback: This gives a user the chance to trace back over the functions, and the traceback utility uses stack data structure. Traceback utility should show the path by which the current state in the program reached.
- Program-display capabilities: While debugging in progress, the program being debugged must made visible on the screen along with the line numbers.
- Multilingual capability: The debugging system must also consider the language in which the debugging done. Generally, different programming languages involve different user environments and applications systems.
- Optimization: Sometimes, to make a program efficient, programmers may use an optimized code. Debugging of such statements can be tricky. However, to simplify the debugging process, a debugger may use an optimizing compiler that deals with the following issues:
Removing invariant expressions from a loop
Merging similar loops
Eliminating unnecessary statements
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By: Hem Sagar Baral and Carol Inskipp
242 pages, colour photos, distribution maps
Nepal's birdlife is among the richest in Asia, particularly considering the small size of the country. In total, 862 species have been recorded so far, including nearly 600 breeding species and 31 globally threatened species.
This book provides an overview of diversity of bird life in different agro-ecological and climatic zones of Nepal. Current status, threat and consequences are identified and conservation needs are recommended. The book also highlights 27 critical biological sites for bird and biodiversity conservation in Nepal. Thirteen out of 27 critical sites are within the protected area system, meaning they are relatively safer, and the rest are spread in and around wetlands, woodlots, river valleys and watersheds. In addition, five potentially important areas have also been identified which provide conservationists additional opportunities for timely action to protect Nepal's avifaunal diversity.
This IBA inventory fills the gap on national biodiversity inventory and helps government fulfill its obligations towards the CBD. It is hoped that the book will provide guidance to decision makers and planners to geographically focus financial and human resources, and avoid negative impact in land-use and development planning.
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L-A-Omega is the mathematical expression for collection of light within an optical system as it depends upon radiance, space, and angle.
The symbolic expression for L-A-Omega is Φ=LAΩ.
In which: Φ is the optical flow (photons per second, watts, or lumens); L is the radiance of an object (flow per area-and-angle); A is the area of the object; and Ω is the solid-angle of collection. The radiance L is constant throughout an optical system. The space-angle product AΩ also remains constant throughout an optical system unless an evanescent field is created. The space-angle product may be redistributed between an object and its image for maximum delivery of light into a detector of limited area.
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Through the use of an automated, underwater cell analyzer developed at the Woods Hole Oceanographic Institution (WHOI), researchers and coastal managers were recently able to detect a bloom of harmful marine algae in the Gulf of Mexico and prevent human consumption of tainted shellfish.
Shellfish beds in parts of Texas have been closed for a month, though they are expected to re-open in the next few days.
Working with Rob Olson and Heidi Sosik—plankton biologists and instrument developers at WHOI—biological oceanographer Lisa Campbell of Texas A&M University used their “Imaging FlowCytobot” instrument to detect a substantial increase in the abundance of the algae Dinophysis acuminata in the waters of Port Aransas, Texas.
Dinophysis acuminata produces okadaic acid, a toxin that accumulates in shellfish tissues and can cause diarrhetic shellfish poisoning (DSP) in humans. DSP is not life-threatening, but symptoms include nausea, cramping, vomiting, and diarrhea. Cooking does not destroy the toxin in the shellfish.
The Imaging FlowCytobot, which is automated and submersible, counts microscopic plants in the water and photographs them. The images and data are relayed back to a shore-based laboratory, where specially developed software automatically classifies the plankton into taxonomic groups.
“It is very satisfying to find that a technology we developed as a research tool can be so effective for protecting human health,” said Olson, who has worked with Sosik for several years to prototype and modify flow cytometers, which are more typically used in many biological and medical laboratories.
“We designed the Imaging FlowCytobot for continuous monitoring of a wide range of plankton, and that turns out to be just what was needed to detect a harmful algal bloom that no one expected."
The discovery of the Dinophysis bloom came while the researchers were actually looking for something else. Campbell, Olson, Sosik, and colleagues deployed the instrument in the fall of 2007 at the University of Texas Marine Sciences Institute laboratory in the Mission Bay Aransas National Estuarine Research Reserve.
Their principal goal was to observe Karenia brevis, another toxic alga that blooms periodically in the Gulf and can lead to neurotoxic shellfish poisoning. The research team would like to observe the next K. brevis bloom before it happens; such blooms are most common and most extreme in the Gulf of Mexico in the late summer and fall.
The team is also working to catalog the types and relative abundances of marine plants in the area throughout the year.
In mid-February 2008, Campbell reviewed plankton images collected by the Imaging FlowCytobot and detected a substantial increase in the abundance of the dinoflagellate Dinophysis, which occurs naturally in ocean waters worldwide but not usually in harmful quantities.
“We have never before observed a bloom of Dinophysis acuminata at such levels in the Gulf of Mexico,” Campbell said.
After reporting the increase to fellow researchers in coastal Texas, Campbell and colleagues collected water samples to confirm that algal toxins were present in the water.
Other researchers collected oyster samples and sent them for toxin analysis at a U.S. Food and Drug Administration laboratory.
On March 8, the Texas Department of State Health Services closed Aransas, Corpus Christi, and Copano bays to shellfish harvesting and recalled Texas oysters, clams, and mussels that had been sold between March 1-7.
A week later, six other bays and estuaries along the coast were closed. As of April 11, most shellfishing areas had been re-opened, and the Aransas, Copano, and Corpus Christi were expected to re-open in a matter of days.
The bloom and subsequent warnings occurred just days before the Fulton Oysterfest, a major shellfish festival in the region. At last report, no shellfish-related human illnesses have been reported in Texas this spring.
“This is exactly what an early warning system should be,” said Campbell. “It should detect a bloom before people get sick. So often, we don’t figure out that there is a bloom until people are ill, which is too late. The Imaging FlowCytobot has proven itself effective for providing an early warning.”
“With time, we have come to see that the instrument has obvious practical uses,” added Sosik. “It now appears ready to make the transition from basic research tool to operative tool."
Funding for Campbell’s monitoring program and construction of the instrument was provided by the National Oceanic and Atmospheric Administration’s Cooperative Institute for Coastal and Estuarine Environmental Technology (CICEET).
Funding for instrument development and earlier prototypes of the FlowCytobot and the Imaging Flow Cytobot was provided by WHOI—through its Ocean Life Institute, Coastal Ocean Institute, Bigelow Chair, and Access to the Sea Fund—and by the National Science Foundation.
The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans' role in the changing global environment.
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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....
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Markov chain Monte Carlo
In statistics, Markov chain Monte Carlo (MCMC) methods comprise a class of algorithms for sampling from a probability distribution. By constructing a Markov chain that has the desired distribution as its equilibrium distribution, one can obtain a sample of the desired distribution by observing the chain after a number of steps. The more steps there are, the more closely the distribution of the sample matches the actual desired distribution.
Random-walk Monte Carlo methods make up a large subclass of Markov chain Monte Carlo methods.
- 1 Application domains
- 2 Classification
- 3 Convergence
- 4 Software
- 5 See also
- 6 References
- 7 Sources
- 8 Further reading
- 9 External links
Markov chain Monte Carlo methods are primarily used for calculating numerical approximations of multi-dimensional integrals, for example in Bayesian statistics, computational physics, computational biology and computational linguistics.
In Bayesian statistics, the recent development of Markov chain Monte Carlo methods has been a key step in making it possible to compute large hierarchical models that require integrations over hundreds or even thousands of unknown parameters.
In rare event sampling, they are also used for generating samples that gradually populate the rare failure region.
Random walk Monte Carlo methods
When a Markov chain Monte Carlo method is used for approximating a multi-dimensional integral, an ensemble of "walkers" move around randomly. At each point where a walker steps, the integrand value at that point is counted towards the integral. The walker then may make a number of tentative steps around the area, looking for a place with a reasonably high contribution to the integral to move into next.
Random walk Monte Carlo methods are a kind of random simulation or Monte Carlo method. However, whereas the random samples of the integrand used in a conventional Monte Carlo integration are statistically independent, those used in Markov chain Monte Carlo methods are correlated. A Markov chain is constructed in such a way as to have the integrand as its equilibrium distribution.
Examples of random walk Monte Carlo methods include the following:
- Metropolis–Hastings algorithm: This method generates a random walk using a proposal density and a method for rejecting some of the proposed moves.
- Gibbs sampling: This method requires all the conditional distributions of the target distribution to be sampled exactly. When drawing from the full-conditional distributions is not straightforward other samplers-within-Gibbs are used (e.g., see ). Gibbs sampling is popular partly because it does not require any 'tuning'.
- Slice sampling: This method depends on the principle that one can sample from a distribution by sampling uniformly from the region under the plot of its density function. It alternates uniform sampling in the vertical direction with uniform sampling from the horizontal 'slice' defined by the current vertical position.
- Multiple-try Metropolis: This method is a variation of the Metropolis–Hastings algorithm that allows multiple trials at each point. By making it possible to take larger steps at each iteration, it helps address the curse of dimensionality.
- Reversible-jump: This method is a variant of the Metropolis–Hastings algorithm that allows proposals that change the dimensionality of the space. Markov chain Monte Carlo methods that change dimensionality have long been used in statistical physics applications, where for some problems a distribution that is a grand canonical ensemble is used (e.g., when the number of molecules in a box is variable). But the reversible-jump variant is useful when doing Markov chain Monte Carlo or Gibbs sampling over nonparametric Bayesian models such as those involving the Dirichlet process or Chinese restaurant process, where the number of mixing components/clusters/etc. is automatically inferred from the data.
Other Markov chain Monte Carlo methods
Training-based Markov chain Monte Carlo
Unlike most of the current Markov chain Monte Carlo methods that ignore the previous trials, using a new algorithm the Markov chain Monte Carlo algorithm is able to use the previous steps and generate the next candidate. This training-based algorithm is able to speed-up the Markov chain Monte Carlo algorithm by an order of magnitude.
Interacting Markov chain Monte Carlo methodologies are a class of mean field particle methods for obtaining random samples from a sequence of probability distributions with an increasing level of sampling complexity. These probabilistic models include path space state models with increasing time horizon, posterior distributions w.r.t. sequence of partial observations, increasing constraint level sets for conditional distributions, decreasing temperature schedules associated with some Boltzmann-Gibbs distributions, and many others. In principle, any Markov chain Monte Carlo sampler can be turned into an interacting Markov chain Monte Carlo sampler. These interacting Markov chain Monte Carlo samplers can be interpreted as a way to run in parallel a sequence of Markov chain Monte Carlo samplers. For instance, interacting simulated annealing algorithms are based on independent Metropolis-Hastings moves interacting sequentially with a selection-resampling type mechanism. In contrast to traditional Markov chain Monte Carlo methods, the precision parameter of this class of interacting Markov chain Monte Carlo samplers is only related to the number of interacting Markov chain Monte Carlo samplers. These advanced particle methodologies belong to the class of Feynman-Kac particle models, also called Sequential Monte Carlo or particle filter methods in Bayesian inference and signal processing communities. Interacting Markov chain Monte Carlo methods can also be interpreted as a mutation-selection genetic particle algorithm with Markov chain Monte Carlo mutations.
Markov Chain quasi-Monte Carlo (MCQMC) The advantage of low-discrepancy sequences in lieu of random numbers for simple independent Monte Carlo sampling is well known. This procedure, known as Quasi-Monte Carlo method (QMC), yields an integration error that decays at a superior rate to that obtained by IID sampling, by the Koksma-Hlawka inequality. Empirically it allows the reduction of both estimation error and convergence time by an order of magnitude.
More sophisticated methods use various ways of reducing the correlation between successive samples. These algorithms may be harder to implement, but they usually exhibit faster convergence (i.e. fewer steps for an accurate result).
Examples of non-random walk Markov chain Monte Carlo methods include the following:
- Hybrid Monte Carlo (HMC): Tries to avoid random walk behaviour by introducing an auxiliary momentum vector and implementing Hamiltonian dynamics, so the potential energy function is the target density. The momentum samples are discarded after sampling. The end result of Hybrid Monte Carlo is that proposals move across the sample space in larger steps; they are therefore less correlated and converge to the target distribution more rapidly.
- Some variations on slice sampling also avoid random walks.
- Langevin Markov chain Monte Carlo and other methods that rely on the gradient (and possibly second derivative) of the log posterior avoid random walks by making proposals that are more likely to be in the direction of higher probability density.
Usually it is not hard to construct a Markov chain with the desired properties. The more difficult problem is to determine how many steps are needed to converge to the stationary distribution within an acceptable error. A good chain will have rapid mixing: the stationary distribution is reached quickly starting from an arbitrary position. A standard empirical method to assess convergence is to run several independent simulated Markov chains and check that the ratio of inter-chain to intra-chain variances for all the parameters sampled is close to 1.
Typically, Markov chain Monte Carlo sampling can only approximate the target distribution, as there is always some residual effect of the starting position. More sophisticated Markov chain Monte Carlo-based algorithms such as coupling from the past can produce exact samples, at the cost of additional computation and an unbounded (though finite in expectation) running time.
Many random walk Monte Carlo methods move around the equilibrium distribution in relatively small steps, with no tendency for the steps to proceed in the same direction. These methods are easy to implement and analyze, but unfortunately it can take a long time for the walker to explore all of the space. The walker will often double back and cover ground already covered.
Several software programs provide MCMC sampling capabilities, for example:
- MCL - a cluster algorithm for graphs, by Stijn van Dongen
- HipMCL - Parallelized MCL algorithm using HighPerformance Computing
- BUGS / WinBUGS
- R (programming language) with the packages adaptMCMC, atmcmc, BRugs, mcmc, MCMCpack, ramcmc, rjags, etc.
- Software for Flexible Bayesian Modeling and Markov Chain Sampling, by Radford Neal.
- emcee (MIT licensed pure-Python implementation of Goodman & Weare's Affine Invariant Markov chain Monte Carlo Ensemble sampler)
- Gupta, Ankur; Rawlings, James B. (April 2014). "Comparison of Parameter Estimation Methods in Stochastic Chemical Kinetic Models: Examples in Systems Biology". AIChE Journal. 60 (4): 1253–1268. doi:10.1002/aic.14409. PMC . PMID 27429455.
- See Gill 2008.
- See Robert & Casella 2004.
- Banerjee, Sudipto; Carlin, Bradley P.; Gelfand, Alan P. Hierarchical Modeling and Analysis for Spatial Data (Second ed.). CRC Press. p. xix. ISBN 978-1-4398-1917-3.
- Gilks, W. R.; Wild, P. (1992-01-01). "Adaptive Rejection Sampling for Gibbs Sampling". Journal of the Royal Statistical Society. Series C (Applied Statistics). 41 (2): 337–348. doi:10.2307/2347565. JSTOR 2347565.
- Gilks, W. R.; Best, N. G.; Tan, K. K. C. (1995-01-01). "Adaptive Rejection Metropolis Sampling within Gibbs Sampling". Journal of the Royal Statistical Society. Series C (Applied Statistics). 44 (4): 455–472. doi:10.2307/2986138. JSTOR 2986138.
- Martino, L.; Read, J.; Luengo, D. (2015-06-01). "Independent Doubly Adaptive Rejection Metropolis Sampling Within Gibbs Sampling". IEEE Transactions on Signal Processing. 63 (12): 3123–3138. arXiv: . Bibcode:2015ITSP...63.3123M. doi:10.1109/TSP.2015.2420537. ISSN 1053-587X.
- Liu, Jun S.; Liang, Faming; Wong, Wing Hung (2000-03-01). "The Multiple-Try Method and Local Optimization in Metropolis Sampling". Journal of the American Statistical Association. 95 (449): 121–134. doi:10.1080/01621459.2000.10473908. ISSN 0162-1459.
- Martino, Luca; Read, Jesse (2013-07-11). "On the flexibility of the design of multiple try Metropolis schemes". Computational Statistics. 28 (6): 2797–2823. arXiv: . doi:10.1007/s00180-013-0429-2. ISSN 0943-4062.
- See Green 1995.
- Tahmasebi, Pejman; Javadpour, Farzam; Sahimi, Muhammad (August 2016). "Stochastic shale permeability matching: Three-dimensional characterization and modeling". International Journal of Coal Geology. 165: 231–242. doi:10.1016/j.coal.2016.08.024.
- Del Moral, Pierre (2013). Mean field simulation for Monte Carlo integration. Chapman & Hall/CRC Press. p. 626.
Monographs on Statistics & Applied Probability
- Del Moral, Pierre (2004). Feynman-Kac formulae. Genealogical and interacting particle approximations. Springer. p. 575.
Series: Probability and Applications
- Del Moral, Pierre; Miclo, Laurent (2000). Branching and Interacting Particle Systems Approximations of Feynman-Kac Formulae with Applications to Non-Linear Filtering (PDF). Lecture Notes in Mathematics. 1729. pp. 1–145. doi:10.1007/bfb0103798.
- Del Moral, Pierre (2006). "Sequential Monte Carlo samplers - P. Del Moral - A. Doucet - A. Jasra - 2006 - Journal of the Royal Statistical Society: Series B (Statistical Methodology) - Wiley Online Library". Journal of the Royal Statistical Society. Series B (Statistical Methodology). 68: 411–436. arXiv: . doi:10.1111/j.1467-9868.2006.00553.x. Retrieved 2015-06-11.
- Chen, S., Josef Dick, and Art B. Owen. "Consistency of Markov chain quasi-Monte Carlo on continuous state spaces." The Annals of Statistics 39.2 (2011): 673-701.
- Tribble, Seth D. Markov chain Monte Carlo algorithms using completely uniformly distributed driving sequences. Diss. Stanford University, 2007.
- Papageorgiou, Anargyros, and J. F. Traub. "Beating Monte Carlo." Risk 9.6 (1996): 63-65.
- Sobol, Ilya M (1998). "On quasi-monte carlo integrations". Mathematics and Computers in Simulation. 47 (2): 103–112. doi:10.1016/s0378-4754(98)00096-2.
- See Neal 2003.
- See Stramer 1999.
- Gelman, A.; Rubin, D.B. (1992). "Inference from iterative simulation using multiple sequences (with discussion)". Statistical Science. 7: 457–511. Bibcode:1992StaSc...7..457G. doi:10.1214/ss/1177011136.
- Cowles, M.K.; Carlin, B.P. (1996). "Markov chain Monte Carlo convergence diagnostics: a comparative review". Journal of the American Statistical Association. 91: 883–904. doi:10.1080/01621459.1996.10476956.
- Enright, AJ; Van Dongen, S; Ouzounis, CA (1 April 2002). "An efficient algorithm for large-scale detection of protein families". Nucleic Acids Research. 30 (7): 1575–84. PMID 11917018.
- Azad, A; Pavlopoulos, GA; Ouzounis, CA; Kyrpides, NC; Buluç, A (6 April 2018). "HipMCL: a high-performance parallel implementation of the Markov clustering algorithm for large-scale networks". Nucleic Acids Research. 46 (6): e33. doi:10.1093/nar/gkx1313. PMID 29315405.
- Christophe Andrieu, Nando De Freitas, Arnaud Doucet and Michael I. Jordan An Introduction to MCMC for Machine Learning, 2003
- Asmussen, Søren; Glynn, Peter W. (2007). Stochastic Simulation: Algorithms and Analysis. Stochastic Modelling and Applied Probability. 57. Springer.
- Atzberger, P. "An Introduction to Monte-Carlo Methods" (PDF).
- Berg, Bernd A. (2004). Markov Chain Monte Carlo Simulations and Their Statistical Analysis. World Scientific.
- Bolstad, William M. (2010). Understanding Computational Bayesian Statistics. Wiley. ISBN 0-470-04609-0.
- Casella, George; George, Edward I. (1992). "Explaining the Gibbs sampler". The American Statistician. 46: 167–174. doi:10.2307/2685208. (Basic summary and many references.)
- Gelfand, A.E.; Smith, A.F.M. (1990). "Sampling-Based Approaches to Calculating Marginal Densities". Journal of the American Statistical Association. 85: 398–409. doi:10.1080/01621459.1990.10476213.
- Gelman, Andrew; Carlin, John B.; Stern, Hal S.; Rubin, Donald B. (1995). Bayesian Data Analysis (1st ed.). Chapman and Hall. (See Chapter 11.)
- Geman, S.; Geman, D. (1984). "Stochastic Relaxation, Gibbs Distributions, and the Bayesian Restoration of Images". IEEE Transactions on Pattern Analysis and Machine Intelligence. 6: 721–741.
- Gilks, W.R.; Richardson, S.; Spiegelhalter, D.J. (1996). Markov Chain Monte Carlo in Practice. Chapman and Hall/CRC.
- Gill, Jeff (2008). Bayesian methods: a social and behavioral sciences approach (2nd ed.). Chapman and Hall/CRC. ISBN 1-58488-562-9.
- Green, P.J. (1995). "Reversible-jump Markov chain Monte Carlo computation and Bayesian model determination". Biometrika. 82 (4): 711–732. doi:10.1093/biomet/82.4.711.
- Neal, Radford M. (2003). "Slice Sampling". Annals of Statistics. 31 (3): 705–767. doi:10.1214/aos/1056562461. JSTOR 3448413.
- Neal, Radford M. (1993). "Probabilistic Inference Using Markov Chain Monte Carlo Methods".
- Robert, Christian P.; Casella, G. (2004). Monte Carlo Statistical Methods (2nd ed.). Springer. ISBN 0-387-21239-6.
- Rubinstein, R.Y.; Kroese, D.P. (2007). Simulation and the Monte Carlo Method (2nd ed.). Wiley. ISBN 978-0-470-17794-5.
- Smith, R.L. (1984). "Efficient Monte Carlo Procedures for Generating Points Uniformly Distributed Over Bounded Regions". Operations Research. 32: 1296–1308. doi:10.1287/opre.32.6.1296.
- Spall, J.C. (April 2003). "Estimation via Markov Chain Monte Carlo". IEEE Control Systems Magazine. 23 (2): 34–45. doi:10.1109/mcs.2003.1188770.
- Stramer, O.; Tweedie, R. (1999). "Langevin-Type Models II: Self-Targeting Candidates for MCMC Algorithms". Methodology and Computing in Applied Probability. 1 (3): 307–328. doi:10.1023/A:1010090512027.
- Diaconis, Persi (April 2009). "The Markov chain Monte Carlo revolution" (PDF). Bull. Amer. Math. Soc. 46 (2): 179–205. doi:10.1090/s0273-0979-08-01238-x. S 0273-0979(08)01238-X.
- Press, W.H.; Teukolsky, S.A.; Vetterling, W.T.; Flannery, B.P. (2007), "Section 15.8. Markov Chain Monte Carlo", Numerical Recipes: The Art of Scientific Computing (3rd ed.), Cambridge University Press, ISBN 978-0-521-88068-8
- Richey, Matthew (May 2010). "The Evolution of Markov Chain Monte Carlo Methods" (PDF). The American Mathematical Monthly. 117 (5): 383–413. doi:10.4169/000298910x485923.
- MCMC sampling and other methods in a basic overview, by Alexander Mantzaris (original link - now broken)
- PyMC - Python module implementing Bayesian statistical models and fitting algorithms, including Markov chain Monte Carlo.
- IA2RMS is a Matlab code of the Independent Doubly Adaptive Rejection Metropolis Sampling method for drawing from the full-conditional densities within a Gibbs sampler.
- Cite error: The named reference
:0was invoked but never defined (see the help page). | <urn:uuid:17f07e78-b53a-49de-82ce-5e7cf6aa4c89> | 3.390625 | 4,385 | Knowledge Article | Science & Tech. | 57.588604 | 95,587,045 |
The researchers analysed narrow, down-slope trending surface features on Mars that are darker than their surroundings, called Recurring Slope Lineae, or RSL. The feature would generally form during the warm seasons and gradually flows to downhill and eventually dry out during winter.
So, the streaks behave like tumbling sand grains, not like flowing water.
RSL are mostly found on steep rocky slopes in the dark regions of Mars, such as the southern mid-latitudes, Valles Marineris near the equator and in Acidalia Planitia on the northern plains.
Ambulance crew gives terminally ill patient a side trip to the beach
This is the poignant moment a crew of paramedics in Australia made a dying patient's wish come true by letting her see a beach one last time.
The researchers discovered these after observations using the Mars Reconnaissance Orbiter's High-Resolution Imaging Science Experiment (HiRISE) camera.
A new study suggests that dark streaks on Mars are signs of flowing sand - not water.
The team found that RSL occur on slopes steeper than 27 degrees, and the flow ends on reaching an "angle of repose" where dry sand accumulates and forms a lump, something which is commonly seen on dunes on Earth. "This new understanding of RSL supports other evidence that shows that Mars today is very dry". Liquid water would have readily extended to less steep slopes.
Cowboys suffer more misery with home defeat to Chargers
Rivers completed a pass to running back Austin Ekeler, but Cowboys cornerback Jourdan Lewis stopped Ekeler after a 12-yard gain. King had a 90-yard interception return for a touchdown in the fourth quarter along with three tackles and a passed defensed.
Monday's news throws cold water on 2015 research that indicated these recurring slope lines were signs of water now on Mars. Another report published in 2016 create doubts about the possibilities of underground water at RSL sites. It could be limited to traces of dissolved moisture from the atmosphere and thin films of water.
However, RSL remain puzzling. Seasonal changes in hydration of salt-containing grains might result in some trigger mechanism for RSL grainflows, such as expansion, contraction, or release of some water. If atmospheric water vapour is a trigger, then a question is why the RSL appear on some slopes but not others.
Scientists, however, are optimistic about the RSL as a unique feature of Mars. That's bad news in the hunt for microbes, unfortunately. "Remote sensing at different times of day could provide important clues".
Ready! Shoppers Hits Stores Early on Thanksgiving
Dave Hannon and his family also ate early to go shopping for clothes on Thursday. Once they're in - along with dozens of others - it's just their first store. | <urn:uuid:90b661ca-0200-41eb-bf75-6323bcff0b9a> | 3.5625 | 576 | News Article | Science & Tech. | 47.741844 | 95,587,072 |
about this item
The branch of physics which studies the behavior and flow of fluids is known as fluid mechanics. As a subject, fluid mechanics is mainly divided into two branches, fluid statics and fluid dynamics. Fluid statics studies fluids when they are at rest and fluid dynamics studies them in motion. Fluid mechanics is applied in a number of fields like mechanical engineering, chemical engineering, biology and astrophysics. This book unravels the recent studies in the field of fluid mechanics. It studies, analyses and upholds the pillars of fluid mechanics and its utmost significance in modern times. It is an essential guide for both academicians and those who wish to pursue this discipline further.
Number of Pages: 244
Publisher: Ingram Pub Services
Street Date: May 30, 2018
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Astronomers Discover First Interstellar Object Oumuamua
Written by: Tanya Patel - November 21, 2017
The first interstellar object was spotted racing through our Solar System. Astronomers caught sight of the object last month which has an unusual elongated cigar shape. The astronomers observing the object have also noticed it is red in color meaning its been in space for a long time.
Lead author at University of Hawaii’s Institute of Astronomy, Karen Meech said, “What we found was a rapidly rotating object, at least the size of a football field.”
The mysterious object known as A/2017U1 was caught on a sophisticated telescope system by researchers at the University of Hawaii. The object has been socially named Oumuamua meaning, “messenger sent from the distant past to reach out to us.”
Associate Administrator at NASA’s Science Mission Directorate, Thomas Zurbuchen said, “For decades we’ve theorized that such interstellar objects are out there, and now for the first time we have direct evidence they exist.” Zurbuchen further explained interstellar objects are vital to gain information about the formation of other Solar Systems.
Oumuamua is 400 meters in diameter and instantly stood out for scientists because of its size. Unlike any other asteriod or comet, Oumuamua will provide crucial information about the Solar System it comes from.
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Go out, grab a piece and bring it home.
Planets that formed over 10 billion years ago are about 5 billion light years from us, meaning that if we could somehow study planets that far away (we can’t) the light reaching us from there would have taken 5 billion years to reach us. Therefore, we’d be seeing what the planet looked like 5 billion... Continue Reading →
I don’t see either as being dependent on the other. In other words, you can believe in God and not in extraterrestrial life. Many religious people do in fact hold that view. On the other hand, you can believe in extraterrestrial life and not believe in God. I know many people who hold that view.... Continue Reading →
Transmissions from Mars to Earth and visa versa happen at the speed of light. However, Mars is sometimes near Earth and sometimes on the other side of the sun. Therefore, depending on where Mars is in relation to Earth in our orbit around the sun, transmission times change from 4 minutes to 24 minutes. If... Continue Reading →
When you look into a telescope at the galaxies and stars you are looking back in time, because it took time for the light of those objects to reach you. If it took 13 billion years to get you then you'd be seeing light that originated 13 billion years ago. If you could see clearly,... Continue Reading →
We have no proof life exists anywhere in the universe other than Earth. Given a planet with the right conditions, life can spring from matter and eventually evolve into something greater is the wet dream of science, but still an unproven theory.
Proxima Centauri, is our nearest star, about 4 light years away. A light year is the distance light travels in one year, or 9,460,730,472,581 kilometers. That's 9.46 trillion kilometers, or about 5.88 trillion miles. The fastest space ship we ever built was the Juno spacecraft, which in 2016 broke all speed records in space with a... Continue Reading →
In 2035, to be precise. It's a Thursday. It looks something like this and is about the size of the Empire State Building. If it does hit us it's going to destroy a lot of things on the planet, but not kill us completely. It's not an extinction event, just a big bad event. Bennu... Continue Reading →
Answer by Award-Winning Scifi Author C Stuart Hardwick "We” have. You presumably missed the memo. The far side of the moon was first photographed by Luna 3 in 1959. The above is a recent image captured by NASA’s LRO. If you are asking why we can only see the near side from Earth, that’s because the... Continue Reading → | <urn:uuid:2be70763-0f3a-4ed1-8f2e-1e6d6567053a> | 2.9375 | 571 | Content Listing | Science & Tech. | 74.459019 | 95,587,097 |
Recently, this crucial α-preformation probability was empirically deduced and exhibits a new feature that had been inferred to some extent by Professor REN Zhongzhou and his group from Department of Physics, Nanjing University. This work, titled "Model-independent trend of α-preformation probability", was published in SCIENCE CHINA Physics, Mechanics & Astronomy 2013, Vol. 56(8).
Pá values for the Po and Rn isotopic chains obtained from various models, including the present and previous results of the present group. A similar variation in all curves is clearly displayed.
Credit: ©Science China Press
Dating back to the end of the 19th century, nuclear physics established itself as a field of science with the discovery of radioactivity. Since those years, α decay has always been considered the eminent topic in nuclear physics. In particular, as the dominant decay mode of superheavy nuclei, it is currently the only useful tool in the identification of any new heavy element and its isotopes.
Theoretically, the decay process is usually imagined in the Gamow picture as a preformed α cluster tunneling through the α-daughter potential barrier. Without doubt, the α-preformation probability is critical in view of nuclear structure. Nevertheless, detailed studies of this quantity provide results that remain ambiguous, despite extensive experimental investigations.
In the present work, the authors proposed an empirical formula that for the first time directly deduces the preformation factor of the αparticle from the experimental data. The α-preformation factors of 171 even-even nuclei were initially obtained that strongly confirmed the key role played by the shell effect in the formation of the α cluster during decay. The study was also extended to include heavier cluster emissions with satisfactory results. These in turn prove to a certain degree that the present analysis of the α-preformation factor is reasonable and reliable.
Interestingly, a new feature of the α-preformation probability (Pα) became evident in a further study. From a different perspective, the α-preformation probabilities for a given isotopic chain extracted from different theoretical analyses were found to have quite similar behavior when comparing the present results with other studies. Across the various studies, the relative trend in the α-preformation probabilities for an isotopic chain were actually model-independent, although the deduced values of the α-preformation factor based on the respective model differ from each other (see Figure 1). The inference is that these studies are consistent with each other despite the different theoretical models, and the present study can be taken as a certain proof of reliability of the previous theoretical results.
This study gives valuable information on the preformation probability of emitted particles in α-decay, and the new model-independent feature has been identified in detail. The researchers hope that the present investigation can be extended to a broader range of nuclei, and be used to provide clues for their follow-up work on nuclear structure.
This research was supported by the National Natural Science Foundation of China (Grant Nos. 11035001, 10975072, 10735010 and 11120101005), the National Major State Basic Research and Development of China (Grant Nos. 2010CB327803 and 2013CB834400), the Knowledge Innovative Program of the Chinese Academy of Sciences (Grant No. KJCX2-SW-N02), the Research Fund of Doctoral Point (RFDP) (Grant No. 20100091110028), the Project Funded by the Priority Academic Programme Development of Jiangsu Higher Education Institutions (PAPD), the Research and Innovation Project for College Postgraduate of Jiangsu Province (Grant No. CXZZ12¬_0031) and the Science and Technology Development Fund of Macau (Grant No. 068/2011/A).
See the article: QIAN Y B, REN Z Z*. Model-independent trend of α-preformation probability. SCIENCE CHINA Physics, Mechanics & Astronomy, 2013, 56(8):1520-1524.
Science China Press Co., Ltd. (SCP) is a scientific journal publishing company of the Chinese Academy of Sciences (CAS). For 50 years, SCP takes its mission to present to the world the best achievements by Chinese scientists on various fields of natural sciences researches.
REN ZhongZhou | EurekAlert!
First evidence on the source of extragalactic particles
13.07.2018 | Technische Universität München
Simpler interferometer can fine tune even the quickest pulses of light
12.07.2018 | University of Rochester
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
13.07.2018 | Life Sciences | <urn:uuid:f3ab85ac-a9e1-45cf-a480-d791f355c995> | 2.609375 | 1,523 | Content Listing | Science & Tech. | 37.849167 | 95,587,100 |
A) The kind of number you describe is a perfect number. Note that the number itself is not included in the sum. The first three perfect numbers are 6, 28 and 496. Factors of 28 are 1, 2, 4, 7, and 14 (sum = 28). Factors of 496 are 1, 2, 4, 8, 16, 31, 62, 124 and 248 (sum = 496). These were known in the time of Pythagoras, about 500bc. Mathematicians have always been fascinated by patterns in number. Pupils can enter their own voyage of discovery. Euclid, around 300bc, had a method for working them out, and it is suggested that the Egyptians, too, probably knew about them.
First you need to work out 2 to various powers: (20 =1), (21 = 2), (22 = 4), (23 = 8); (20 + 21 + 22 +23 = 16); (25 = 32). The "power" tells us how many times to multiply the number by itself. So 24 = 2 X 2 X 2 X 2 = 16.
Euclid's method involves taking consecutive powers of 2 and adding them together (another way of looking at this is to double each number and add then add it) until you reach a prime number. Then multiply the prime by the last value of the power sequence. This is illustrated in the table below.
There are of course "amicable", "sociable", and many other kinds of numbers - another adventure!
Finding the perfect numbers is a way of practising other parts of maths - eg factors and number powers, and, without using a calculator, multiplication and simple addition.
For an extension of this work visit http:home1.pacific.net.sgnovelwayMEW2lesson1.html
For an historical perspective
For an algebraic definition http:mathworld.wolfram.comPerfectNumber.htm
Q) I work as part of a team in educational publishing. I visited the tax website the other day and found that on the section were you fill in to pay your tax there is both Pounds and a p sign, when you have paid, just Pounds remains. Should both be used or only one? This has always confused me.
A) I checked the website and found there are boxes beside where you enter the amounts. They are there for direction only, not as a mathematical notation.
When writing a sum of money, either the Pounds sign should be used or the 'p' sign, as these determine the units you are using. For example, pound;3.45 is correct as is pound;345p, whereas pound;3.45p is incorrect.
Confusion sometimes occurs for those who used the old Pounds s d before we decimalised our monetary system. In the old system, if I wanted to write, for example, pound;1.76 or 176p (new pence) I would write each unit (Pounds s d), to give about pound;1 15s 2d.
This poem was inspired by a dance course in Bristol.
Today on a visit to St Paul's I met a girl who puts up walls A defence against failure
"My name is Hannah"
then her offhand manner
"I'm really not interested!"
The dance timetables are organised
then Hannah's tutors are surprised
"I don't understand time"
"Look there's a clock face there"
they point, she doesn't care
Because it's maths
"There is just a chance If you learnt through dance
It might make sense".
Almost with a sigh
She'll give it a try.
It might help.
Through kinaesthetic creation
Now there's a lady in town
and her defences are down | <urn:uuid:4658277d-cfec-497b-843d-cecb74b0eaef> | 2.828125 | 793 | Q&A Forum | Science & Tech. | 75.415 | 95,587,105 |
It’s all go in summer for Greenland’s glaciers13 July 2018
It’s all go in summer for Greenland’s glaciers13 July 2018 The Copernicus Sentinel-1 mission has revealed that, on average, Greenland’s glaciers are now flowing more slowly into the Arctic Ocean. While glacial flow may have slowed overall, in summer glaciers flow 25% faster than they do in the winter.
Copernicus 20 years on21 June 2018
Copernicus 20 years on21 June 2018 This week marks 20 years since the manifesto was signed that gave rise to Europe’s Copernicus environmental programme. With seven Sentinel satellites already in orbit delivering terabytes of data every day, Copernicus is the biggest provider of Earth...
Antarctica hikes up sea level13 June 2018
Antarctica hikes up sea level13 June 2018 In a major collaborative effort, scientists from around the world have used information from satellites to reveal that ice melting in Antarctica has not only raised sea levels by 7.6 mm since 1992, but, critically, almost half of this rise has occurre... | <urn:uuid:4fd7fb1c-69fc-4674-baaf-642757846608> | 2.890625 | 229 | Content Listing | Science & Tech. | 49.41654 | 95,587,115 |
Plants, algae, and cyanobacteria (blue-green algae) are masters of everything to do with solar energy because they are able to almost completely transform captured sunlight into chemical energy.
This is in part because the electrons set free by the photons are transported out of the “light receptor” 1:1 to be used as the driving force for chemical reactions. Japanese researchers have now developed a new process to capture light energy with nearly equal efficiency.
As they report in the journal Angewandte Chemie, they “plug” a molecular “wire” directly into a biological photosynthetic system to efficiently conduct the free electrons to a gold electrode.
The efficiency of photovoltaic energy conversion is of critical significance for the practical application of solar installations. Theoretically, every photon absorbed should release one electron. Whereas modern solar cells are far from achieving high efficiency, natural photosynthetic systems achieve nearly 100 % quantum yield. To improve the efficiency of synthetic systems, experiments were attempted in which biological light-capturing units were deposited onto electrodes as thin films. However, the transfer of electrons from the light-capturing layer into the circuit in this type of system is so inefficient that most of the electrons don’t even make it to the target electrode.
The secret to the success of natural photosystems is the perfect fit of the individual components. The molecules fit precisely together like plugs and sockets and can pass electrons on directly and nearly without loss. The new approach taken by the Japanese researchers cleverly connects photosystem I (PSI) from the blue-green algae Thermosynechococcus elongatus with a synthetic apparatus. An important component of the electron transmission sequence of PSI is vitamin K1. The researchers removed the vitamin K1 from the PSI protein complex and replaced it with a synthetic analogue. This consists of three parts: 1) The same molecular “plug” with which vitamin K1 is bound to the protein complex (napthoquinone group) is used to “plug in” the synthetic binding component to PSI; 2) a molecular “wire” (hydrocarbon chain) with the same length as in vitamin K1 ensures that the binding component protrudes from the protein complex; and 3) at the other end of the wire is an additional “plug” (viologen group) that anchors the ensemble to a specially coated gold electrode. Electrons released by irradiation of PSI and transmitted along the wire are very efficiently transmitted to the gold electrode by the viologen group.
It may be possible to use this new strategy to integrate other biocomponents into synthetic systems.
Author: Nao Terasaki, National Institute of Advanced Industrial Science and Technology, Tosu (Japan), mailto:email@example.com
Title: Plugging a Molecular Wire into Photosystem I: Reconstitution of the Photoelectric Conversion System on a Gold Electrode
Angewandte Chemie International Edition 2009, 48, No. 9, 1585–1587, doi: 10.1002/anie.200805748
Nao Terasaki | Angewandte Chemie
Further reports about: > Angewandte Chemie > Molecular Target > Molecular Wires > PSI > Thermosynechococcus elongatus > artificial photosystem > biocomponents > biological photosynthetic system > blue-green algae > chemical energy > chemical reaction > cyanobacteria > electron transmission > light receptor > solar energy
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
16.07.2018 | Earth Sciences | <urn:uuid:e70d39f7-c8b8-4741-9987-85bb7a497061> | 3.765625 | 1,380 | Content Listing | Science & Tech. | 30.277109 | 95,587,116 |
You must have stumbled upon the news of SpaceX landing their Falcon 9 rocket booster on a barge in the middle of the ocean. Well guess what, landing rockets is the next big thing, and SpaceX is the pioneer.
What SpaceX did yesterday was launch the payload into space with the Dragon rocket, and then brought back the Falcon 9 rocket booster on earth so that it can be reused in a future mission. Unsurprisingly, it took SpaceX five tries to nail this landing. The previous landings ended up in explosions and toppling. This one though was spot on, and almost revolutionary for the company and for the world.
So what's the big deal with landing rocket boosters? Until now, boosters were essentially "use and throw" carriers of payload. They were huge monetary investments that were being hauled and destroyed in space. Bringing them back would greatly reduce the cost of sending stuff into space and also save gallons of fuel. It would also reduce the time and money spent in building new rocket booster for every space mission. Landing boosters could actually catalyse space exploration.
But of course, landing a tube filled with explosive fuel upright and in a controlled manner is a big technological challenge. These rocket boosters can be extremely dangerous if they ‘fall’ on earth. In fact, landing on earth doesn’t make sense at all, since rockets have a curved trajectory: once the payload is released into space, the rocket is usually above the ocean. Using fuel again to thrust the booster back towards land isn’t technically viable. Rather, using the remaining fuel to perform a controlled landing on the ocean makes a lot of sense. That’s the idea behind SpaceX’s landing on a barge.
SpaceX had previously performed a successful landing on land directly, but for the first time, it has successfully completed landing in the ocean. Of course, the internet reacted in awe and excitement, with thousands of retweets and likes. The topic was trending throughout the world for a few hours.
This landing will be the first step in making space travel and exploration more accessible, economical and environmentally friendly. Elon Musk is proving to be a revolutionary figure with his success with Tesla and now SpaceX, and I wish him best of luck for his future advancements. Of course, congratulations to SpaceX for making history! | <urn:uuid:c6513e49-8048-4a30-92f7-de5bf4ed60a1> | 2.921875 | 469 | Personal Blog | Science & Tech. | 52.04965 | 95,587,125 |
University of Utah scientists have shown how evolution works by reversing the process, reconstructing a 530-million-year-old gene by combining key portions of two modern mouse genes that descended from the archaic gene.
"It provides further evidence at the molecular level of how evolution has occurred and is occurring, and thus makes the process less mysterious," says Mario Capecchi, distinguished professor and co-chairman of human genetics at the University of Utah School of Medicine and an investigator with the Howard Hughes Medical Institute.
"We've shown some of the elements involved in the process of evolution by reversing this process and reconstructing a gene that later became two genes," he adds.
The study by Capecchi and postdoctoral fellow Petr Tvrdik was set for publication Monday, Aug. 7 in the August 2006 issue of the journal Developmental Cell.
The process of one gene splitting into multiple genes, which then mutate, "has occurred many times in evolution, but no one has put it back together again," Tvrdik says. "We are first to reconstruct an ancient gene. … We have proven that from two specialized modern genes, we can reconstruct the ancient gene they split off from. It illuminates the mechanisms and processes that evolution uses, and tells us more about how Mother Nature engineers life."
The ability to reconstruct an ancient gene from descendant genes also raises the possibility of a new type of gene therapy, in which a portion of a related gene could be inserted into a disease-causing mutant gene to restore its normal function and cure the disease, Capecchi and Tvrdik say.
Genes that Divided are Now Reunited
The study involved what are known as Hox genes, which are like orchestra conductors directing the actions of other genes during development of an animal embryo.
Until sometime between 530 million and 480 million years ago, early animals had 13 Hox genes. Then, in jawed fish – the last common ancestors of modern vertebrate animals – each Hox gene had split into four, so 13 became 52. Later, duplicate Hox genes either mutated in a way that proved useful, or vanished because they were redundant, so today in humans and other mammals there are 39 instead of 52 Hox genes.
The study focused on two modern Hox genes:
-- The Hoxa1 gene, which helps control how an embryo's brain stem develops and is compartmentalized into seven sections called rhombomeres. When Hoxa1 is disabled or "knocked out" in an embryonic mouse, the embryo dies shortly after birth because the brain stem is malformed, including the part necessary for breathing. (About 20 people with the same defect have been found among Apache and Navajo Indians in Arizona and in families in Turkey and Saudi Arabia. Their brain stem defects result in problems with breathing, hearing, balance and con-trol of the eyeballs.)
-- The Hoxb1 gene, which orders the formation of particular nerve cells in rhombomere 4 – nerves that ultimately control facial expressions in animals. When a mouse is born with a disabled Hoxb1 gene, it suffers facial paralysis, and is unable to blink its eyes, wiggle its whiskers or pull back its ears.
Tvrdik and Capecchi say that by combining critical portions of Hoxa1 and Hoxb1, they effectively recreated a gene with the function that the original Hox1 performed more than 530 million years ago.
The result: A mouse with a disabled Hoxb1 gene still was able to move eyelids, whiskers and ears because the reconstructed gene made up for the loss of Hoxb1.
How the Study was Conducted
Evolution proceeds as cells divide and each gene within them duplicates. Having two identical genes allows one to keep doing its normal job and the other can change, or mutate. Most mutations are for the worse and disappear. Others persist because they perform a new job that holds some advantage for allowing an organism to adapt. The quadrupling of Hox (and also other genes) a half-billion years ago provided animals with an advantage "because they had more genes to use for specialized jobs," including adapting to environmental changes, Tvrdik says.
Each gene is made of DNA. Some of the gene's DNA carries a code or blueprint that makes a protein to carry out some specific function in an organism. Some genetic mutations change this "coding region" and thus change the protein a gene makes.
Other mutations change other parts of the gene, known as "regulatory sequences," which decide when and where the gene and its protein act in an organism's body.
Because the gene's regulatory sequences can be 10 to 100 times larger than the gene's coding region, mutations are more likely there.
A key question was whether the Hoxa1 and Hoxb1 genes are different because their protein-coding regions have changed or their regulatory sequences have changed. So the scientists switched the two genes' coding regions. Each gene then produced the other gene's protein. Mice born with the switched genes were essentially normal.
That means the coding regions were interchangeable, and that evolution has changed each gene's regulatory sequence, not the protein-making coding region.
Next, Tvrdik and Capecchi took a small portion of the regulatory sequence from gene Hoxb1 (which controls facial expressions) and put it into Hoxa1, (which allows mice to breathe and survive after birth). And they disabled the remainder of Hoxb1.
Mice suffered facial paralysis when they were born with disabled Hoxb1 and without a portion of that gene inserted into the Hoxa1 gene. In response to a puff of air in the face, they couldn't blink their eyes, wiggle their whiskers and fold back their ears.
But when a portion of the Hoxb1 regulatory sequence was inserted into Hoxa1, the new gene performed the jobs of both genes. Mice born with the combined gene still were able to breathe and survive thanks to the Hoxa1 gene, and they could move their facial muscles, thanks to the small bit of the Hoxb1's regulatory sequence.
Capecchi says that by combining parts of both Hoxa1 and Hoxb1, he and Tvrdik reversed evolution.
"What we have done is essentially go back in time to when Hox1 did what Hoxa1 and Hoxb1 do today," he says. "It gives a real example of how evolution works because we can reverse it."
The hybrid Hoxa1-Hoxb1 gene is not fully identical to the half-billion-year-old Hox1 because it lacks Hoxc1 and Hoxd1. But Hoxc1 vanished during evolution because it was redundant, and Hoxd1 plays a minor role. So the combined Hoxa1-Hoxb1 gene performs essentially all the functions of the ancient gene, Capecchi says.
A New Approach to Gene Therapy?
Capecchi says scientists hypothesized that when a gene duplicates into identical genes, mutations can occur so the once-identical duplicates evolve to split the original job – a process is called subfunctionalization.
"We are giving an example of how it actually happened – what elements are involved and how you initially separate the functions, and how can you reconstruct the [ancient] gene to put the functions back again," Capecchi says.
The study raises the prospect of a new approach to gene therapy, Tvrdik says.
If a gene duplicated into two and they evolved separate functions in the body – for example, one gene works in the liver and the other in the brain – then "if the brain version of the gene becomes mutated or deleted [to cause a disease] and its gene replacement is difficult or impractical, then our work shows that the 'liver copy' potentially could be recruited to do the brain functions," Tvrdik says.
In other words, regulatory elements from the brain gene might be inserted into the liver gene to reconstruct a gene similar to the normal brain gene.
Capecchi speculated on a possible example: a form of inherited anemia named beta-thalassemia, which occurs when a mutant beta hemoglobin gene results in faulty production of hemoglobin. The new study suggests it might be possible to use regulatory sequences from the faulty gene to activate a similar gene, essentially creating an embryonic or juvenile beta hemoglobin gene that could make hemoglobin normally during adult life.
Lee Siegel | 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:d518c694-1e1b-49f7-b585-9fc46a5bcdd9> | 3.84375 | 2,447 | Content Listing | Science & Tech. | 39.898116 | 95,587,136 |
The universe is always expanding and astronomers have to try for years to estimate the Hubble constant. This is a unit of measurement that presents the rate at which the universe is expanding. Nonetheless, until now the values calculated were quite different.
Scientists were not able to measure exactly how fast the universe is expanding, but this might change. Discovering the rate at which the universe is expanding could offer plenty of answers about the origins of the universe and the future of cosmos.
A new way to measure the Hubble constant was discovered, and this time it might be more accurate than ever: gravitational waves. These are emitted by rare systems such as a black hole neutron star binary and the pairing of a black hole and neutron star.
“Black hole-neutron star binaries are very complicated systems, which we know very little about. If we detect one, the prize is that they can potentially give a dramatic contribution to our understanding of the universe,” explained says Salvatore Vitale, assistant professor of physics at MIT and lead author of the paper.
NASA’s Hubble Space Telescope and the European Space Agency’s Planck satellite were used for two measurements of the Hubble constant. However, new methods are used for Hubble estimates. Scientists use LIGO, the Laser Interferometer Gravitational-Wave Observatory, which is used in order to detect gravitational waves.
“Gravitational waves provide a very direct and easy way of measuring the distances of their sources. What we detect with LIGO is a direct imprint of the distance to the source, without any extra analysis,” Vitale explained. Back in 2017 LIGO and Virgo, its Italian counterpart managed to detect a pair of colliding neutron stars for the first time. There were plenty of gravitational waves released by the collision.
Brad is a former Senior Fellow at the Schuster Institute for Investigative Journalism at Brandeis University, is an award-winning travel, culture, and parenting writer. His writing has appeared in many of the Canada’s most respected and credible publications, including the Toronto Star, CBC News and on the cover of Smithsonian Magazine. A meticulous researcher who’s not afraid to be controversial, he is nationally known as a journalist who opens people’s eyes to the realities behind accepted practices in the care of children. Brad is a contributing journalist to Advocator.ca | <urn:uuid:c115dd72-b4ab-4139-bcd1-7ecaf4ae21e8> | 3.578125 | 485 | News Article | Science & Tech. | 29.745212 | 95,587,138 |
- Astronomy & Space Science
- Astronomical instruments
- LIGO (Laser Interferometer Gravitational-wave Observatory)
LIGO (Laser Interferometer Gravitational-wave Observatory)
Fritschel, Peter K. Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts.
Last reviewed:February 2017
Show previous versions
- LIGO (Laser Interferometer Gravitational-wave Observatory), published June 2014:Download PDF Get Adobe Acrobat Reader
- Operating principles
- Siting and status
- Links to Primary Literature
- Additional Readings
A physics research facility developed to detect cosmic gravitational waves and to measure these waves for scientific research. It consists of two installations in the continental United States, located in the states of Washington and Louisiana, which are operated in unison as a single observatory. Funded by the National Science Foundation (NSF), LIGO was originally designed and constructed by a team of scientists from the California Institute of Technology and the Massachusetts Institute of Technology, and by industrial contractors. Construction of the facilities was completed in 1999, and since then two generations of detectors have been installed and operated in LIGO. The first generation of detectors operated from 2001 to 2010, though no detections of gravitational waves were made. The second generation, known as Advanced LIGO, began operating in 2015, and made the first direct detection of gravitational waves in September 2015. LIGO is the leading member in a developing global network of gravitational-wave observatories.
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In 2003 and 2004, Dr Newton-Fisher studied a community of eight adult male and 21 adult female East African chimpanzees in Budongo Forest, Uganda. He observed that the females were subject to frequent aggression by adult males that was at times severe. However, between October and December 2003, he observed females retaliating in direct response to this aggression.
In almost half of his observed retaliations, the females formed coalitions of two to six members and retaliated with vocalisations, threatening gestures, and direct pursuit. Females were also witnessed physically attacking males that were aggressive to other females, and on several occasions were seen to solicit the support they then received.
Until Dr Newton-Fisher’s study, there have been no reports of female cooperative retaliation to such aggression from the wild despite more than four decades of detailed behavioural study across a number of populations and its occurrence among captive female chimpanzees.
Dr Newton-Fisher said, ‘Female wild chimpanzees form coalitions as a strategy to counter male aggression. This strategy may reduce the incidence, severity or effectiveness of male aggression. Why they do this is still unclear but the levels and forms of cooperative retaliation that I observed among the chimpanzees in Budongo Forest may be because these females tend to be more gregarious than in other populations of East African chimpanzees, as other work studying the same population has suggested.
‘Also, the absence of similar reports from wild populations suggests that females may be able to form coalitions only under appropriate conditions – such as ecology, demography or local tradition. If groups of females are able to spend time together because of the way food is distributed in the habitat, then they are ‘on-hand’ to provide support and form coalitions. Whether they do this simply because they are present when another female is threatened by a male, or because they have previously formed a supportive relationship, are questions for future research.’
Dr Newton-Fisher’s report is published in the International Journal of Primatology.
Gary Hughes | alfa
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
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Nb3Ge and Nb3Sn Films Prepared by High-Rate Magnetron Sputtering
During the past several years, considerable effort has been put into the fabrication of A15 superconductors, with particular emphasis on Nb3Sn and Nb3Ge. Nb3Ge probably cannot be produced by bulk fabrication or diffusion processes, which are successful with Nb3Sn, due to the metastable nature of the high critical temperature A15 phase, and thus must be “frozen in” at high temperatures by methods such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or low-energy sputtering. The latter technique has produced Nb3Ge films with the highest critical temperature, T c , and best self-field critical current density, J c . A variation on the low-energy sputtering technique is discussed, wherein a magnetic field in the vicinity of the sputtering target alters the plasma characteristics in such a way that deposition rates are enhanced (up to 1 µm/min) at very low operating voltages (≤400V dc). Then sputter deposition is competitive with CVD. This technique is capable of producing very high quality Nb3Sn films and Nb3Ge films with T c ≥21.5 K. By suitable adjustment of the sputtering parameters, it is possible to alter the microstructure and surface characteristics. The effect of controlled amounts of oxygen in the sputtering gas on the T c of Nb3Ge is described.
KeywordsSticking Coefficient High Critical Temperature Chemical Vapor Deposition Film Transition Temperature Width Versus Potential Drop
external magnetic field
upper critical field
self-field critical current density
partial pressure of oxygen
critical temperature, onset of superconductivity
sputtering gas temperature
transition temperature width
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Carbon offsetting initiatives could be improved with new insights into the make-up of tropical forests.
Amazon rainforest survey could improve carbon offset schemes
Researchers from the Universities of Leeds and Edinburgh studying the Amazon Basin have revealed unprecedented detail of the size, age and species of trees across the region by comparing satellite maps with hundreds of field plots.
The findings will enable researchers to assess more accurately the amount of carbon each tree can store. This is a key factor in carbon offset schemes, in which trees are given a cash value according to their carbon content, and credits can be traded in exchange for preserving trees.
Existing satellite maps of the area have estimated trees carbon content based largely on their height, but have not accounted for large regional variations in their shape and density.
Researchers say their findings could help quantify the amount of carbon available to trade in areas of forest. This could help administer carbon offsetting more accurately, and improve understanding of how much carbon is stored in the worlds forests, which informs climate change forecasts.
Professor Oliver Phillips from the University of Leeds School of Geography, who co-led the study, said: Satellites cant see species, but species really matter for carbon. This is the big challenge for the next generation of satellite and field scientists. New satellites will be launched soon that will be more sensitive to forest structure and biomass, but we must ensure we have sufficient ecological ground data to correctly interpret and use them.
Scientists studied a database of thousands of tree species, taken from more than 400 hectare-sized plots across the nine countries of the Amazon Basin Brazil, Bolivia, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname and Venezuela. The survey was developed as part of a sister project, known as RAINFOR, involving more than 200 researchers across the region.
Their research found that forests in the basins north-east on average stored twice as much carbon as those in the south-west, as a result of soil, climate and species variation. The north-east has slow-growing, dense-wooded species, while the south-west is dominated by light-wooded trees with faster turnover. In these naturally dynamic, light-wooded forests the species simply cant store as much carbon.
Tree species and dynamics are mostly controlled by soil conditions, largely unseen from above, according to Dr Carlos Quesada, RAINFOR soil scientist at the National Amazon Research Institution in Manaus, Brazil. The younger, shallow soils of the western Amazon tend to restrict root growth a case of live fast, die young.
Dr Ed Mitchard, lead author from the University of Edinburghs School of GeoSciences, said: Developing our understanding of this aspect of forests, in the Amazon and elsewhere, could be hugely important for our climate.
The study, funded by the Natural Environment Research Council, was published in Global Ecology and Biogeography.
For further information
Please contact the University of Leeds press office, 0113 343 4031 or email email@example.com | <urn:uuid:c9bb2bef-97c1-458f-baa6-766f9cc2affe> | 3.421875 | 626 | News Article | Science & Tech. | 30.952963 | 95,587,182 |
Propagation of Electromagnetic Waves Through the Atmosphere
The transmittance of the atmosphere is usually described by the quotient of incident radiant power divided by transmitted radiant power. It is a measure of the attenuation and extinction of wave propagation. The transmittance is a function of numerous variables: wavelength, distance, temperature, barometric pressure, gaseous mixture, rain, snow, dust, aerosols, bacteria and, in more detail, the size of particles of all these constituents. The limitations of atmospheric transmittance are given by the scattering and absorption of the emitted radiation. Scattering by air molecules (Rayleigh Scattering) and scattering by larger aerosol particles (Mie scattering) can be distinguished. Absorption in several spectral regions is mainly caused by water vapour, carbon dioxide and ozone. Figure 5.1 depicts the transmittance of atmosphere as a function of wavelength for a part of the visible and near-infrared (NIR) spectrum under specific conditions. The figure shows that only a limited part of the NIR spectrum is suitable for EDM.
KeywordsRefractive Index Water Vapour Pressure Endpoint Measurement Velocity Correction Wave Path
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‘We got some absolutely amazing footage from 7700 metres. More fish than we or anyone in the world would ever have thought possible at these depths,’ says project leader Dr Alan Jamieson of the University of Aberdeen’s Oceanlab, on board the Japanese research ship the Hakuho-Maru.
‘It’s incredible. These videos vastly exceed all our expectations from this research. We thought the deepest fishes would be motionless, solitary, fragile individuals eking out an existence in a food-sparse environment,’ says Professor Monty Priede, director of Oceanlab.
‘But these fish aren’t loners. The images show groups that are sociable and active – possibly even families – feeding on little shrimp, yet living in one of the most extreme environments on Earth.’
‘All we’ve seen before of life at this depth have been shrivelled specimens in museums. Now we have an impression of how they move and what they do. Having seen them moving so fast, snailfish seems a complete misnomer,’ he added.
Although some species of snailfish live in shallow water and even rock pools, the hadal snailfish are found exclusively below 6000 metres. Here they have to contend with total darkness, near freezing temperatures and immense water pressure – at this depth the pressure is 8,000 tonnes per square metre, equivalent to that of 1600 elephants standing on the roof of a Mini car. They feed on the thousands of tiny shrimp-like creatures that scavenge the carcasses of dead fish and detritus reaching the ocean floor.
Hadal snailfish live only in trenches around the Pacific Ocean, with different species confined to each region: the Chile and Peru trenches off South America, the Kermadec and Tonga trenches situated between Samoa and New Zealand in the South Pacific, and trenches of the North-West Pacific including the Japan trench, which Priede’s team is currently investigating.
The work is part of Oceanlab’s HADEEP project – a collaborative research programme with the University of Tokyo – devised by Priede to investigate life in the hadal region of the ocean, which is anything below 6000 metres down. The expedition, funded by the Natural Environment Research Council and the Nippon Foundation in Japan, started on 24 September and ended yesterday, 6 October.
The deep-sea equipment needed to survive the extreme pressure at these depths was designed and built by the Oceanlab team specifically for this mission. The submersible camera platforms, or ‘landers’, take five hours to reach the depths of the trenches and remain on the seafloor for two days before the signal is given for them to surface.
The team has been keeping an expedition blog, exclusive to Planet Earth online www.planetearth.nerc.ac.uk, a daily news site from the Natural Environment Research Council. The magazine website, which was launched last week, includes video footage and photographs of the expedition as well as blogs, podcasts, features and news.
Marion O'Sullivan | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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A team led by the University College London (UCL) test-fired the projectiles in Wales, recording a peak of 20,000 gee upon impact (where humans can survive up to 10 gee). Penetrators, which can carry data-collecting systems and sensors, are being developed as an alternative to manned space flight for the future exploration of moons in our solar system.
The team, led by Professor Alan Smith from UCL’s Mullard Space Science Laboratory, the University of Surrey, Birkbeck College, Imperial College, the Open University and QinetiQ ran the first three test firings of the high speed penetrators at QinetiQ’s long test track in Pendine, South Wales in May 2008. The projectiles were secured to a rocket sledge and fired along a rail track.
The penetrators, which contained a data- and sample-collecting system, a variety of sensors, accelerometers, a seismometer and a mass spectrometer (for analysis) hit a sand target at around 700 miles per hour. The electronics remained fully operational during impact, recording the deceleration in minute detail which peaked at about 20,000 gee (20,000 times the acceleration due to gravity, where humans can only survive around 10 gee).
Penetrator technology is being developed for future space exploration, to pierce the surface of planetary bodies such as our moon and the icy moons of Jupiter and Saturn. Penetrators offer a low cost approach to planetary exploration, but the enormous impact forces have meant that scientists have so far been reluctant to trust them.
Professor Smith said: “Prior to this trial, we had to rely on computer modelling and analysis. As far as we can tell the trial has been enormously successful, with all aspects of the electronics working correctly during and after the impact. I congratulate the team on this really impressive achievement – to get everything right first time is wonderful, and a tribute to British technology and innovation.”
The impact trial is part of a series of technical developments and studies in preparation for future planetary space missions. These include the proposed UK MoonLITE mission to the Moon which is hoped to be launched in 2013, and possible missions to moons of the outer planets – Europa, Ganymede, Enceladous and Titan. The trials were funded by the Science and Technology Facilities Council as part of MSSL’s Rolling Grant.
Professor Smith leads the UK penetrator consortium which is a grouping of British universities (UCL, University of Surrey, Birkbeck College, Imperial College, Leicester University and Open University) and UK industries (Astrium, QinetiQ and Surrey Satellite Technology Ltd).
Stuart Miller | alfa
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
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Texas A&M AgriLife scientists are working to better understand the ecology and taxonomy of Texas freshwater mussels. These mussels play critically important roles in freshwater ecosystems and have beneficial impacts on human health, making them a high priority for conservation. Fifteen species have previously been classified as "threatened," and now one--the Texas hornshell mussel--is officially listed as "endangered."
Texas freshwater mussel research
Freshwater mussels have the some of the highest rates of extinction of all freshwater organisms in the world. In Texas, 15 species are listed as state threatened, while 12 are pending review for federal listing under the Endangered Species Act.
Freshwater mussels play important roles in ecosystem maintenance through nutrient cycling, stabilizing stream-bed substrates and increasing habitat diversity. Population declines can have significant impacts to an ecosystem’s structure and function.
In Texas, the lack of basic biological information on freshwater mussels, such as life history, taxonomy, reproductive biology and habitat, use limits conservation and recovery efforts. Since 2011, NRI’s freshwater mussel research program has provided information on mussel taxonomy, population distribution and ranges, and other science-based knowledge and solutions for state and federal natural resource agencies.
The centerpiece of our program is a 2,000-square-foot wet lab located at the Texas A&M AgriLife Research and Extension Center in Dallas. Current research efforts include studies on:
- mussel reproductive biology,
- thermal and salinity tolerances, and
- molecular analyses to name a few.
Current research efforts include studies on mussel reproductive biology, thermal and salinity tolerances, and molecular analyses, to name a few. Data from these projects will help inform listing efforts, protect rare mussel species and promote aquatic ecosystem conservation.
As a research scientist for the Texas A&M Natural Resources Institute sin, Dr. Charles Randklev works on issues related to freshwater mussel conservation. His research expertise is unionid ecology with research interests …
Dr. Kentaro Inoue is an assistant research scientist at the Texas A&M Natural Resources Institute. Kentaro is an evolutionary and conservation biologist with a passion for freshwater molluscs (mussels and snails) and crus…
Misidentification of sex for Lampsilis teres, Yellow Sandshell, and its implications for mussel conservation and wildlife management
Megan C. Hess, Kentaro Inoue, Eric T. Tsakiris, Michael Hart, Jennifer Morton, Jack Dudding, Clinton R. Robertson, Charles R. Randklev
Prioritizing sites for conservation based on similarity to historical baselines and feasibility of protection
Traci Popejoy, Charles R. Randklev, Thomas M. Neeson, and Caryn C. Vaughn
Molecular and morphometric analyses reveal cryptic diversity within freshwater mussels (Bivalvia: Unionidae) of the western Gulf coastal drainages of the USA
Anna M Pieri, Kentaro Inoue, Nathan Johnson, Chase Smith, John Harris, Clinton R. Robertson, Charles Randklev
Novel technique to identify large river host fish for freshwater mussel propagation and conservation
Michael A. Hart, Wendell R. Haag, Robert Bringolf, James A. Stoeckel
An interpretive framework for assessing freshwater mussel taxonomic abundances in zooarchaeological faunas
T. Popejoy, S. Wolverton, L. Nagaoka, C.R. Randklev
Conservation implications of late Holocene freshwater mussel remains of the Leon River in central Texas
T. Popejoy, C.R. Randklev, S. Wolverton, L. Nagaoka
Structural Changes in Freshwater Mussel (Bivalvia: Unionidae) Assemblages Downstream of Lake Somerville, Texas
E.T. Tsakiris, C.R. Randklev
Generic reclassification and species boundaries in the rediscovered freshwater mussel ‘Quadrula’ mitchelli (Simpson in Dall, 1896)
J. M. Pfeiffer,N. A. Johnson. C. R. Randklev, R. G. Howells, J. D. Williams
Land use relationships for a rare freshwater mussel species (Family: Unionidae) endemic to central Texas
C. R. Randklev, H-H Wang, J. E. Groce, W. E. Grant, S. Robertson, N. Wilkins
Distribution of extant populations of Quadrula mitchelli (false spike)
C.R. Randklev, E.T. Tsakiris, R.G. Howells, J. Groce, M.S. Johnson, J. Bergmann, C. Robertson, A. Blair, B. Littrell, and N. Johnson
New distributional records for four rare freshwater mussel species (Family: Unionidae) in southwestern Louisiana
C.R. Randklev, J. Skorupski, B.J. Lundeen, and E.T. Tsakiris
Is False Spike, Quadrula mitchelli (Bivalvia: Unionidae), extinct? First account of a very-recently deceased individual in over thirty years
C.R. Randklev, E.T. Tsakiris, M.S. Johnson, J. Skorupski, L.E. Burlakova , J. Groce, and N. Wilkins
Status of the freshwater mussel (Unionidae) communities of the mainstem of the Leon River, Texas
C.R. Randklev, M.S. Johnson, E.T. Tsakiris, J. Groce, N. Wilkins
New and confirmed fish hosts for the threatened freshwater mussel Lampsilis bracteata
M.S. Johnson, P.D. Caccavale, C.R. Randklev, and J.R. Gibson
Taxonomic Status of Pigtoe Unionids in Texas
R. G. Howells, C. R. Randklev, N. B. Ford
First account of a living population of False Spike, Quadrula mitchelli (Bivalvia: Unionidae), in the Guadalupe River, Texas
C.R. Randklev, M.S. Johnson, E.T. Tsakiris, S. Rogers-Oetker, K.J. Roe, S. McMurray, C. Robertson, J. Groce, N. Wilkins
Mantle flap variation in Texas Fatmucket (Lampsilis bracteata)
R.G. Howells, C.R. Randklev, M.S. Johnson
Status of Freshwater Mussels in Texas
K. Winemiller, N. K. Lujan, R. N. Wilkins, R. T. Snelgrove, A. M. Dube, K. L. Skow, A. G. Snelgrove
Jennifer Morton hovers methodically over a row of clear, water-filled containers on a tight-spaced industrial shelving system. She plucks a mollusk from one of the containers, observing the specimen as part of a study on freshwater mussel tolerances.
Megan Hess, an assistant researcher looking into declining mussel populations, was recognized this past week for her ongoing work to determine the ratio of male to female freshwater mussels among certain critically imperiled species.
Though zebra mussels in Texas give mussels a bad name, other freshwater mussels are welcomed and needed in Texas waters.
Invasive zebra mussels, first confirmed in Texas in 2009, are causing major economic and environmental damages to Texas reservoirs. But unionid mussels, a family of freshwater mussels, are important indicators of water quality and stream health and play an important role in freshwater ecosystems, according to Dr. Charles Randklev, research scientist for the Texas A&M Institute of Renewable Natural Resources (IRNR).
It's not every day we have picture perfect proof to back some of our wildlife research predation theories. Looks like we've been dealt a different hand in luck lately. | <urn:uuid:27becd50-4e73-47ed-aa5f-6f37e8677b1a> | 3.28125 | 1,723 | About (Org.) | Science & Tech. | 45.636135 | 95,587,211 |
Scientists have found another space oddity 400 light-years from Earth: a binary star with three misaligned planet-forming discs.
The record breaking system was the most luminous Gamma-ray binary system to be detected.
If a star dies in a vacuum, and no galaxy is around to see it, did it ever truly live? Astronomers can start asking some pretty existential questions, after discovering that three massive stars went supernova while drifting in the vast darkness between galaxies - lonely deaths hundreds of light-years away from any known system.
NASA's Fermi Gama-ray Space Telescope recently identified an "exceptional" binary system that not only contains a rapidly spinning neutron star called a pulsar, but also a relatively small yellow star. Interestingly, close examination revealed that this second star serves much like a dance partner for the pulsar, causing it to exhibit some unusual behavior.
Astronomers stumbled upon an "upside-down planet" that offers a new method for studying binary star systems. | <urn:uuid:96e00652-c23d-4e2e-91d9-baf4005711ee> | 3.59375 | 206 | Content Listing | Science & Tech. | 30.089571 | 95,587,216 |
Respect Wildlife by Leaving Animals Alone
The term wildlife refers to the animals of this earth that are not the property of human beings and are not under direct human dominion and control....
"The term wildlife refers to all various kinds of non domesticated organisms, plants and animals. These animals are animals that have adapted to the life in the wild (nature) without the help of humans. W...[Read More]
418 pages , Elsevier , 2014-03-14 This book derives from a workshop held in Sweden to examine the environmental implications of the dramatic increase in carbon dioxide levels in the atmosphere in the last 50 years and to find ways of mitigating greenhouse gas emissions. This multi-disciplinary approach makes it essential reading not only for chemists but for all engineer...[Read More] | <urn:uuid:9886ebfe-8509-4eaa-a3d6-caa5705c7c7f> | 2.671875 | 159 | Content Listing | Science & Tech. | 51.422198 | 95,587,221 |
Optimize Memory Access to Increase Your Coding Performance
Optimize Memory Access to Increase Your Coding Performance
Learn about common memory coding problems as well as best practices and tips to help you increase your code performance.
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While CPUs have become blindingly fast in the past 20 years, memory access times have remained relatively constant. To get the most performance out of coding, serious programmers must not only choose the best algorithms but also need to design for highly efficient memory access. Although compilers have improved in recent years, they are unable to detect and remap most memory related coding oversights that could be avoided. For this reason, avoiding pitfalls associated with memory access requires careful analysis.
In this article, some common memory coding problems will be briefly described together with some best practices tips that can increase code performance. Many of the issues have to do with understanding virtual memory concepts, such as the difference between stack and heap memory, as well as understanding more subtle interactions of program execution with the cache hierarchy.
Memory Available to Executing Thread
Two high-level virtual memory concepts for program execution are the stack and heap. The stack refers to that memory allocated to an executing thread and consists of local variables, addresses for executing functions, and other process information. Each thread has its own stack. The heap is dynamically allocated memory; it is referred to as the free store and is a shared memory pool accessible by all executing threads. Memory on the stack is much faster to access because variables are arranged in a contiguous LIFO, while the memory on the "heap" is relatively slower since it is created randomly across RAM in blocks, requiring more complex and multithreading-safe management.
Variables stored on the stack are static variables, such as fixed sized arrays (e.g. A) that are not able to grow in size during thread execution. Once these variables on the stack go out of scope, or a running function completes, they go out of scope and are removed from the stack. Dynamically variables created on the "heap" with "new" in C++ or "malloc ()" in C, will remain on the heap until manually deallocated in the program code using one of the built in keywords like free, delete, or delete.
For the purpose of coding, the stack is faster because the access pattern is contiguous and consists of incrementing or decrementing a pointer, thereby making allocation and deallocation trivial. Also, the stack efficiently reuses bytes that are directly mapped to the cache. A disadvantage of the stack is that variables cannot be resized during execution and upon many recursive calls, the stack memory quickly fills up, potentially producing stack overflow. In contrast, the variables created at runtime on the heap, which is available to all threads, will have relatively slower access due to several factors associated with virtual memory management. Also, because the heap is a global resource, multithreaded synchronization overhead degrades access time. A common technique is to create large blocks of heap and dole these out to arrays when needed, essentially creating a local memory manager.
In the next section, more details of the cache hierarchy and best practices of memory allocation are described.
The Memory Hierarchy and Performance
At the heart of virtual memory management is the need to coordinate blocks and pages of memory across the memory hierarchy of modern computer architectures. This is difficult because both access times and size vary considerably down the hierarchy . The L1 cache can be accessed within 1-5 cycles and have sizes of ~32-64K, while L2 cache consumes 5-20 cycles upon access, with larger sizes of ~128-512K. These on-chip caches are considerably faster than main memory, or RAM, requiring more than 40-100 cycles.
Thus, significant performance degradation arises from non-optimal use of the cache hierarchy. Problems associated with reading and writing to and from the caches can be summarized as the 3 C's of cache inefficiency:
- Compulsory misses: the first time a page is loaded will produce unavoidable misses.
- Capacity misses: this occurs when all the active data cannot fit into the available cache space; this will cause reloading of cache pages.
- Conflict misses: when data is mapped to same cache lines, it can result in cache thrashing.
Since inefficient cache utilization results in lower performance, coding practices must be cache-aware to improve program execution efficiency. While modern compilers can optimize code in many ways, they are unable to fix some of the most blatant problems that can occur in memory access. The good news is that there are common practices that can help avoid such case.
Practical Coding Tips
A useful mnemonic for remembering the class of methods that are used to improve memory access performance is given by the 3 R's , as follows:
- Rearrange (code, data): Change layout to increase spatial locality.
- Reduce (size, number of cache lines read): Smaller/smarter formats, compression.
- Reuse (cache lines): Increase temporal (and spatial) locality.
Rearranging code and data refer to a set of techniques that optimize the mapping to the cache pages. Two examples are memory access order and memory alignment. To avoid cache thrashing, arrays should be scanned in increasing order, while multidimensional arrays should use the rightmost index for the innermost loops (e.g. for i to size; for j to size; A[j][i] ).
Memory alignment refers to arranging similarly-typed fields together in a structure with the most restrictively aligned types first. Compilers use an alignment criterion for fundamental types, thereby creating memory blocks that are certain multiples of memory. For maximum efficiency and avoid adding padding between objects, it is best practice to arrange types in objects from largest to smallest.
Another rearrangement in code is called hot/cold splitting, where locality of reference is obtained by splitting data structures into frequently used and infrequently used segments and allocating all the "frequently used" stuff together.
Reduce and reuse refer to techniques that minimize memory operations with temporal locality that reduce cache fetches. This is accomplished by reuse of data still in the cache by merging loops that use the same data.
The art of writing cache-aware code requires careful analysis of code with memory profiling tools. While there are many more memory optimization techniques, the general techniques described in this short article would go a long way to increase execution performance of many programs.
For more information on code performance improvements, see C++ code performance and C optimization.
C. Ericson. Real-time collision detection. Morgan-Kaufmann, 2005.
ISBN:1558607323. (Chapter on memory optimization)
Hennessy, J. L., and Patterson, D. A. Computer Architecture: A Quantitative
Approach, second ed. Morgan Kaufmann, 1996.
D.N. Truong, F. Bodin and A. Seznec, "Improving cache behavior of dynamically allocated data structures," Proceedings. 1998 International Conference on Parallel Architectures and Compilation Techniques (Cat. No.98EX192), Paris, 1998, pp. 322-329. doi: 10.1109/PACT.1998.727268
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NASA scientists have definitively detected the chemical acrylonitrile in the atmosphere of Saturn's moon Titan, a place that has long intrigued scientists investigating the chemical precursors of life.
On Earth, acrylonitrile, also known as vinyl cyanide, is useful in the manufacture of plastics. Under the harsh conditions of Saturn's largest moon, this chemical is thought to be capable of forming stable, flexible structures similar to cell membranes. Other researchers have previously suggested that acrylonitrile is an ingredient of Titan's atmosphere, but they did not report an unambiguous detection of the chemical in the smorgasbord of organic, or carbon-rich, molecules found there.
NASA Goddard scientists have made an exciting discovery on Saturn's largest moon, Titan. The team has definitively detected the molecule Acrylonitrile in Titan's atmosphere - a finding that has astrobiological relevance. NASA scientist Maureen Palmer narrates this video about the definitive detection of Acrylonitrile on Titan.
Credit: NASA's Goddard Space Flight Center
Now, NASA researchers have identified the chemical fingerprint of acrylonitrile in Titan data collected by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. The team found large quantities of the chemical on Titan, most likely in the stratosphere -- the hazy part of the atmosphere that gives this moon its brownish-orange color.
"We found convincing evidence that acrylonitrile is present in Titan's atmosphere, and we think a significant supply of this raw material reaches the surface," said Maureen Palmer, a researcher with the Goddard Center for Astrobiology at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of a July 28, 2017, paper in Science Advances.
The cells of Earth's plants and animals would not hold up well on Titan, where surface temperatures average minus 290 degrees Fahrenheit (minus 179 degrees Celsius), and lakes brim with liquid methane.
In 2015, university scientists tackled the question of whether any organic molecules likely to be on Titan could, under such inhospitable conditions, form structures similar to the lipid bilayers of living cells on Earth. Thin and flexible, the lipid bilayer is the main component of the cell membrane, which separates the inside of a cell from the outside world. This team identified acrylonitrile as the best candidate.
Those researchers proposed that acrylonitrile molecules could come together as a sheet of material similar to a cell membrane. The sheet could form a hollow, microscopic sphere that they dubbed an "azotosome." This sphere could serve as a tiny storage and transport container, much like the spheres that lipid bilayers can form.
"The ability to form a stable membrane to separate the internal environment from the external one is important because it provides a means to contain chemicals long enough to allow them to interact," said Michael Mumma, director of the Goddard Center for Astrobiology, which is funded by the NASA Astrobiology Institute. "If membrane-like structures could be formed by vinyl cyanide, it would be an important step on the pathway to life on Saturn's moon Titan."
The Goddard team determined that acrylonitrile is plentiful in Titan's atmosphere, present at concentrations up to 2.8 parts per billion. The chemical is probably most abundant in the stratosphere, at altitudes of at least 125 miles (200 kilometers). Eventually, acrylonitrile makes its way to the cold lower atmosphere, where it condenses and rains out onto the surface.
The researchers calculated how much material could be deposited in Ligeia Mare, Titan's second-largest lake, which occupies roughly the same surface area as Earth's Lake Huron and Lake Michigan together. Over the lifetime of Titan, the team estimated, Ligeia Mare could have accumulated enough acrylonitrile to form about 10 million azotosomes in every milliliter, or quarter-teaspoon, of liquid. That's compared to roughly a million bacteria per milliliter of coastal ocean water on Earth.
The key to detecting Titan's acrylonitrile was to combine 11 high-resolution data sets from ALMA. The team retrieved them from an archive of observations originally intended to calibrate the amount of light being received by the telescope array.
In the combined data set, Palmer and her colleagues identified three spectral lines that match the acrylonitrile fingerprint. This finding comes a decade after other researchers inferred the presence of acrylonitrile from observations made by the mass spectrometer on NASA's Cassini spacecraft.
"The detection of this elusive, astrobiologically relevant chemical is exciting for scientists who are eager to determine if life could develop on icy worlds such as Titan," said Goddard scientist Martin Cordiner, senior author on the paper. "This finding adds an important piece to our understanding of the chemical complexity of the solar system."
ALMA, an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere, the U.S. National Science Foundation and the National Institutes of Natural Sciences of Japan in cooperation with the Republic of Chile.
Elizabeth Zubritsky | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | 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...
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It is indeed a mystery why birds and (so far as we know) other
archosaurs have never evolved viviparity. Does this reflect a true
historical constraint, or is it just chance that living birds and
crocs don't include viviparous taxa? John Bois wrote...
> I forget who it was who claimed that the lack of
> viviparity in birds _needed_ an explanation; that the inability to
> provide a plausible hypothesis for this phenomenon was an
> embarrassement for evolutionary theory.
There is a lengthy and highly informative paper by Blackburn and
Evans (1986) on this very subject. They review all proposed reasons
for the lack of viviparity in birds (the most popular of which - one
of which has been used for turtles (by Samuel Tarsitano) as well -
include the embryonic calcium budget and the avian air-sac system)
and conclude that birds could not have evolved viviparity.
Embarrassingly, I forget exactly _why_ they conclude this. The paper
was in _American Naturalist_.
At times it has been suggested that various dinosaurs - viz.,
sauropods and pachycephalosaurs - may have been viviparous. Both
Phillip Currie and Alan Feduccia have speculated that
hesperornithiforms may have been viviparous. None of these
suggestions are compelling, and they are discordant with some data.
"She doesn't want it""Munch munch munch"
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
Burnaby Road email: email@example.com
Portsmouth UK tel: 01703 446718
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Instead of creating quantum computers based on qubits that can each adopt only two possible options, scientists have now developed a microchip that can generate “qudits” that can each assume 10 or more states, potentially opening up a new way to creating incredibly powerful quantum computers, a new study finds.
- Google’s Quantum Computing Plans Threatened by IBM Curveball Digest Article
- Cloud Quantum Computing Calculates Nuclear Binding Energy Digest Article
- Blind Quantum Computing for Everyone Digest Article
- Big Step Forward For Quantum Computing Digest Article
- Securing Tomorrow’s Information Through Post-Quantum Cryptography Digest Article | <urn:uuid:66a0dca9-893e-48aa-b479-ec495164603c> | 3.03125 | 128 | Content Listing | Science & Tech. | -57.008947 | 95,587,256 |
We are now in a position to see how the Mandelbrot set is defined. Let be some arbitrarily chosen complex number. Whatever this complex number is, it will be represented as some point on the Argand plane. Now consider the mapping whereby is replaced by a new complex number, given by
where с is another fixed (i.e. given) complex number. The number will be represented by some new point in the Argand plane. For example, if happened to be given as the number , then would be mapped according to
so that, in particular, 3 would be replaced by
and would be replaced by
When such numbers get complicated, the calculations are best carried out by an electronic computer.
Now, whatever с may be, the particular number 0 is replaced, under this scheme, by the actual given number . What about itself? This must be replaced by the number Suppose we continue this process and apply the replacement to the number ; then we obtain
Let us iterate the replacement again, applying it next to the above number to obtain
and then again to this number, and so on. We obtain a sequence of complex numbers, starting with 0:
Now if we do this with certain choices of the given complex number c, the sequence of numbers that we get in this way never wanders very far from the origin in the Argand plane; more precisely, the sequence remains bounded for such choices of с which is to say that every member of the sequence lies within some fixed circle centred at the origin (see Fig. 1). A good example where this occurs is the case , since
Fig. 1. A sequence of points in the Argand plane is bounded if there is some fixed circle that contains all the points. (This particular iteration starts with zero and has ).
in this case, every member of the sequence is in fact 0. Another example of bounded behaviour occurs with , for then the sequence is: ; and yet another example occurs with , the sequence being . However, for various other complex numbers с the sequence wanders farther and farther from the origin to indefinite distance; i.e. the sequence is unbounded, and cannot be contained within any fixed circle. An example of this latter behaviour occurs when , for then the sequence is ; this also happens when , the sequence being ; and also when , the sequence being
The Mandelbrot set, that is to say, the black region of our world of Tor'Bled-Nam, is precisely that region of the Argand plane consisting of points for which the sequence remains bounded. The white region consists of thoses points с for which the sequence is unbounded. The detailed pictures that we saw earlier were all drawn from the outputs of computers. The computer would systematically run through possible choices of the complex number c, where for each choice of с it would work out the sequence and decide, according to some appropriate criterion, whether the sequence is remaining bounded or not. If it is bounded, then the computer would arrange that a black spot appear on the screen at the point corresponding to с. If it is unbounded, then the computer would arrange for a white spot. Eventually, for every pixel in the range under consideration, the decision would be made by the computer as to whether the point would be coloured white or black.
The complexity of the Mandelbrot set is very remarkable, particularly in view of the fact that the definition of this set is, as mathematical definitions go, a strikingly simple one. It is also the case that the general structure of this set is not very sensitive to the precise algebraic form of the mapping that we have chosen. Many other iterated complex mappings (e.g. ) will give extraordinarily similar structures (provided that we choose an appropriate number to start with – perhaps not 0, but a number whose value is characterized by a clear mathematical rule for each appropriate choice of mapping). There is, indeed, a kind of universal or absolute character to these 'Mandelbrot' structures, with regard to iterated complex maps. The study of such structures is a subject on its own, within mathematics, which is referred to as complex dynamical systems.Главная Страница | <urn:uuid:56c3d2a2-574b-4efa-9aca-0715ed129e20> | 3.578125 | 876 | Academic Writing | Science & Tech. | 47.595209 | 95,587,259 |
An important breakthrough has been made in determining the forces responsible for the evolution of populations in nature. By studying wild populations of grayling (a close relative of salmon), Mikko Koskinen and Craig Primmer at the University of Helsinki and Thrond Haugen at the University of Oslo found that natural selection, a force suggested by Charles Darwin in `The Origin of Species`, was responsible for up-to 90% of grayling evolution.
In their study, published in Nature on October 24, the team stated that their findings were in fact the reverse of what many people expected: As the grayling originated from a common source only about a century ago and were very small in number, a random process known as genetic drift was expected to be the driving evolutionary force. However, by comparing the evolution of important biological features of the fish (such as growth rate) with the evolution of sections of DNA not affected by natural selection, the team found that natural selection was in fact much more important than genetic drift. This finding agrees with the hotly debated view of a British geneticist Sir Ronald Fisher, one of the founders of the field of population genetics.
Minna Meriläinen | alfa
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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.
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Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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3 months ago by Aliki Westrate and Kate Boersen
The research ship JOIDES resolution is undertaking scientific drilling research from March-May 2018 offshore of the North Island’s East Coast to learn more about the processes that drive large earthquakes and tsunami.
We are aware that some people are concerned about the drilling and coring research that is being undertaken and its purpose. The specific region being studied in this expedition is already known to have no potential as a gas hydrate resource, which is part of the reason drilling can proceed safely.
New Zealand’s participation in this expedition and in the International Ocean Discovery Programme is supported by Government scientific research funds.
We believe the more we understand about what causes these natural hazards to happen, the better we can be prepared.
29/04/18: 80 million years ago the Hikurangi Plateau was part of a super-plateau, formed north of NZ. Furthermore, it's unusually thick, and huge - 3 x bigger than the North Island. Read more here.
25/04/18: Back to the seamount! At one of our last sites on #Exp375 we are collecting core samples from the top of an extinct underwater volcano, Turanganui Knoll. To find out why and check out our interactive map.
19/04/18: Success - both observatories are installed! NZ's new under-sea quake lab now in action. Read more here.
16/04/18: The re-entry funnel to Site U1519 splashed into the moonpool today. It was lowered 1003m to the sea floor, about 33km east of Gisborne, NZ. In the coming days, we'll lower the 2nd observatory down through this funnel to sit 280m below the seabed. It will record pressure and temperature changes in the slow slip earthquake zone over time. Combined with our first observatory, both will give new insights into slow slip events at the subduction zone, and their relationship to larger magnitude earthquakes.
15/04/18: Our #EXP375 observatory blends ancient mariner's knowledge with high-tech design - watch Patrick explain how he learnt the 'lost art' of rope splicing to ensure the instruments inside the observatory didn't break or corrode. Watch here.
14/04/18: The casing is going in for NZ's 2nd subseafloor observatory 50km east of Gisborne.
13/04/18: Check out this new animation from #EXP375. It's of NZ's first sub-seafloor observatory ('Te Matakite') being installed in the Hikurangi Subduction Zone to record slow-slip earthquakes for the next 5 years. It is one of the most complex of its kind and in deep water a true engineering/science feat...the crew breathed a big sigh of relief once it was installed successfully!
11/04/18: You know it's rough when the doctor goes to bed after his shift and leaves the seasick pills out to help ourselves to! We're taking refuge in the Bay of Plenty for a few days before it calms down enough to install our 2nd observatory. The acronym they use is WOW - 'waiting on weather'.
10/04/18: We're transiting north to the Bay of Plenty to miss the worst of this incoming storm - a small hiatus to coring and installing observatories - but a good move I think. 4m and building out here....
10/04/18: Are seamounts part of the slow slip puzzle? We hope that coring right beside one on #EXP375 might answer that. To find out more about possible links between slow slip events and seamounts. Read more here.
09/04/18: We're deep in the Hikurangi Subduction Zone at our 2nd site U1520, 90km from the coast and in 3522m of water. The core has been so variable and interesting here - read more
06/04/18: We're halfway through #EXP375 already!
04/04/18: Success! NZ's first subseafloor observatory has been installed in the Hikurangi subduction zone to measure earthquakes in the years to come. It has been challenging but the #EXP375 team is thrilled. Read more here
02/04/18: Part 2 of #EXP375's series on NZ's first sub-seafloor observatory: how it fits in the global picture and what information it may give us to better understand earthquakes in the Hikurangi Subduction Zone. Read more here.
01/04/18: Expedition 375 Co-chief Scientists Laura Wallace and Demian Saffer and Core-log-seismic Integration Specialist Phil Barnes discuss slow slip events at the Hikurangi Subduction Margin and the goals of this expedition, which are to core at four sites beneath the seafloor and install the first two long-term monitoring observatories off the coast of New Zealand. Read more here.
30/03/18: Perfect day for a visit from NIWA's Tangaroa science vessel. The Tangaroa is here collecting OBS's (ocean bottom seismometers) which had been used over summer for the Hikurangi Subduction Zone seismic surveying work.
27/03/18: Read the first of our blogs on 'Te Matakite', the sub-seafloor observatory we are halfway through installing.Its aim is to tell us more about subduction zones and their earthquake and tsunami potential.
25/03/18: There's some artists among the #EXP375 science crew, and some, shall we say.. 'emerging' artists...These styrofoam cups went down with our underwater camera in the first stage of the 'Te Matakite' borehole observatory yesterday to be shrunk by the deep ocean pressure. When we pull them back up later they'll be about 10% of their original size.
24/03/18: Stage 1 complete! At 4am this morning our JR #EXP375 crew lowered the ACORK down 2700m to the re-entry platform. Our observatory is called TE MATAKITE (to see into the future).
It will be our eyes and ears down in the Hikurangi Subduction Zone, giving us so much insight into slow slip events and earthquakes here.
21/03/18: Sneak peak at the spacey looking funnel of the first sub-seafloor observatory we are preparing to install (weather permitting!). It's a bit like putting a satellite into space but this will sit 2.7km down on the seabed. The #EXP375CORK instruments will be carefully lowered through and below it into the frontal thrust #HikurangiSZ area experiencing slow slip earthquakes - 450m below the seabed...
17/03/18: Watch our #EXP375 video showing the #IODP drilling operation. Here they pull up the drill pipe & core liner, cut the core samples into 1.5m sections on the "catwalk", label them and then sample & describe. You can read more here.
16/03/18: Showing the next generation the JOIDES Resolution and its capabilities is so rewarding - Gisborne students Matthew Proffit and Travis Mitchell came on a #EXP375 ship tour after winning a NZ competition - they've named our first CORK observatory 'Te Matakite' - 'To see into the future'. Very apt! We hope to install it into the Hikurangi Subduction Zone next week, to be our eyes and ears down there for up to a decade....
15/03/18: Reaching our first site above the frontal thrust of the Hikurangi subduction zone and we're starting to drill - it's an ambitious and challenging project. Follow the #EXP375 ship's log here.
14/03/18: We're excited to reach Site 1 at the frontal thrust (aka hanging wall) of the Hikurangi subduction zone. And it's all hands on the catwalk when the very first core sample for #EXP375 is pulled up from 2700m below...read more here.
13/03/18: #EXP375 is making good progress up the east coast of NZ, although the swell is keeping things interesting for many of us. We are due to reach site 1 later today, then the work really begins.
12/03/18: It was great to have a look around at all the different parts of the ship today - it's an amazing vessel - part industrial drill rig, part floating science lab. Read the trip blog here.
11/03/18: #EXP375 is off! We had a great 2 day port call in Timaru and a beautiful sunrise as we left. Let's hope Tangaroa (god of the sea) remains calm on our journey up the east coast of NZ to Gisborne. Cyclone Hola? Read the trip blog here.
10/03/18: Day 2 in port and we're seeing the CORK observatories for the first time - it's like Raiders of the lost ark meets Journey to the centre of the earth...They have taken 3 years to make and will sit in the fault for up to a decade | <urn:uuid:587090c8-2178-42ba-9d50-e06e6aa0c3b6> | 3.359375 | 1,950 | News (Org.) | Science & Tech. | 69.283647 | 95,587,297 |
What do smoke rings, tornadoes and the Great Red Spot of Jupiter have in common?
This is a view from above of the growing and spiraling wave field emitted by a geophysical vortex due to the radiative instability. The black circle represents a boundary of the vortex core.
Credit: J. Park/Ecole Polytechnique-CNRS
They are all examples of vortices, regions within a fluid (liquid, gas or plasma) where the flow spins around an imaginary straight or curved axis. Understanding how geophysical (natural world) vortices behave can be critical for tasks such as weather forecasting and environmental pollution monitoring.
In a new paper in the journal Physics of Fluids, researchers Junho Park and Paul Billant of the CNRS Laboratoire d'Hydrodynamique in France describe their study of one such geophysical vortex behavior, radiative instability, and how it is affected by two factors, density stratification and background rotation.
Radiative instability is a phenomenon that alters the behavior of fluid flows and can deform a vortex. The "radiative" tag refers to the fact that it is an instability caused by the radiation of waves outward from a vortex.
"These waves can exist as soon as there is a density stratification -- a variation of densities -- throughout the vertical column of the vortex," Park said. "In this study, we have considered how background rotation -- in this case, the rotation of the Earth -- impacts them."
Examples of density stratification in nature, Park explained, include the decrease in air density as one moves higher in the atmosphere or the increase in water density due to salinity and temperature with increasing ocean depth. "So, the waves in our mathematical model are somewhat analogous to waves on the ocean surface," he said. "Likewise, the impact from background rotation on our modeled waves serves as an equal for the impact of the Coriolis force caused by the Earth's rotation."
"What we learned from our models is that strong background rotation suppresses the radiative instability, a characteristic that had been expected but whose dynamics had never been studied precisely," Park said. "We've now developed a sophisticated mathematical means to explain this phenomenon, and that's important to being better able to study and understand the behavior of geophysical vortices such as hurricanes and ocean currents."
Park said that he and Billant next plan to study instability behaviors in vortices with non-columnar shapes. "For example," he said, "there are pancake-shaped flows called Mediterranean eddies, or meddies, that would be worth studying since we know they affect the mixing of the components that make up the ocean ecosystem."
The article, "Instabilities and waves on a columnar vortex in a strongly-stratified and rotating fluid" by Junho Park and Paul Billant appears in the journal Physics of Fluids. See: http://dx.doi.org/10.1063/1.4816512
ABOUT THE JOURNAL
Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex or multiphase fluids. See: http://pof.aip.org
Jason Socrates Bardi | EurekAlert!
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
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Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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posted by Amanda
a solution is made by combining 10.0 ml of 17.5 M acetic acid with 5.54 g of sodium acetate and diluting to a total volume of 1.50 L.
a)calculate the pH of the solution.
b) how many grams and milliliters of 14.6 M potassium hydroxide needs to be added so pH=pKa?
c)what is the pH of the solution when 100ml of a 2.25 M HCL is added to the original buffer solution?
Tell me what you don't understand about this. The Henderson-Hasselbalch equation will do all of these. An ICE chart will help with b and c. | <urn:uuid:e7522d30-22ae-442f-aee8-c7a1d24de7c4> | 2.921875 | 149 | Q&A Forum | Science & Tech. | 92.990083 | 95,587,336 |
Basic Honeybee Biology. And other stuff. Placing Bees in the Animal Kingdom. Species ‘Apis’ A. dorsada – Asian, Large, Single Comb, Outside Dwelling A. floria – Asian, Small, Single Comb, Outside Dwelling A. cerina – Asian, Small, Parallel Comb, Cavity Dwelling
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
And other stuff
Apis cerana is the natural host to the mite Varroa jacobsoni and the parasite Nosema ceranae, both serious pests of the Western honey bee. Having coevolved with these parasites, A. cerana exhibits more careful grooming than A. mellifera, and thus has an effective defense mechanism against Varroa that keeps the mite from devastating colonies
The Worker (female bee) does all the work of the colony. A colony may have up to 60,000 workers.
The Queen (fully fertile female) specializes in producing eggs. She will lay one egg per minute, day and night, for a total of 1500 in a 24-hour period and 200,000 in a year.
The Drone (male bee) may number up to 500 in a colony in Spring and Summer. Their ONLY purpose is to fly from the hive and mate in the air with queens from other colonies.
A worker egg hatches after 3 days into a larva.
Nurse bees feed it royal jelly at first, then pollen & honey for 6 days.
It then becomes an inactive pupa.
The Worker Bee
Workers do everything but lay eggs and mate.
They build the comb from wax extruded from glands under their abdomen. They clean, defend, and repair the hive. They feed the larva, the queen, and the drones. They gather nectar, pollen, water, and propolis. They ventilate, cool & heat the hive.The Worker Bee
Feeding a female larva Royal Jelly for the entire larval stage.
The nurse bees feed the larva a diet of only royal jelly made from a gland on their heads.
In only 16 days a new queen emerges. She seeks out and destroys any rival queens, because there can be only one queen per colony.The Queen
She produces chemical scents which regulate hive activity.The Queen
This is necessary since worker bees only live 6 weeks in the summertime; and a colony needs to have 40 to 50 thousand bees at its peak.
She is cared for by the worker bees. This queen has been marked with a red dot for easy identification.The Queen
They have large eyes and wings and no stinger.
Their sole purpose is to mate with a queen from any hive, thereby transferring the genetic traits of their mother.
They die upon mating, or are expelled from the hive as winter approaches.The Drones | <urn:uuid:d18cdbed-d039-4b39-961b-15a3e2acec4c> | 3.65625 | 645 | Knowledge Article | Science & Tech. | 59.613547 | 95,587,338 |
Saturday, June 9, 2012
Darwin in the genome
(I am posting a press release from McGill related to a paper that has just officially come out.)
A current controversy raging in evolutionary biology is whether adaptation to new environments is the result of many genes, each of relatively small effect, or just a few genes of large effect. A new study published in Molecular Ecology strongly supports the first "many-small" hypothesis. McGill University professor Andrew Hendry, from the Department of Biology and the Redpath Museum, and evolutionary geneticists at Basel University in Switzerland, studied how threespine stickleback fish adapted to lake and stream environments in British Columbia, Canada.
The authors used cutting-edge genomic methods to test for genetic differences at thousands of positions ("loci") scattered across the stickleback genome. Very large genetic differences between lake and stream stickleback were discovered at more than a dozen of these loci, which is considerably more than expected under the alternative "few-large" hypothesis.
By examining four independently evolved lake-stream population pairs, the researchers were further able to show that increasing divergence between the populations involved genetic differences that were larger and present at more and more loci.
As these results were obtained using new high-resolution genetic methods, it is conceivable that previous perceptions of adaptation as being a genetically simple process are simply the result of a bias resulting from previous lower-resolution genomic methods.
"I suspect that as more and more studies use these methods, the tide of opinion will swerve strongly to the view that adaptation is a complex process that involves many genes spread across diverse places in the genome," says Prof. Hendry.
Roesti, M., A.P. Hendry, W. Salzburger, and D. Berner. 2012. Genome divergence during evolutionary diversification revealed in replicate lake-stream stickleback population pairs. Molecular Ecology 21:2852-2862. [Cover Article]. Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2012.05509.x/abstract
A News and Views about the article:
Nosil, P., and J.L. Feder. 2012. Widespread yet heterogeneous genomic divergence. Molecular Ecology 21:2829-2832. [Perspective]. Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2012.05580.x/abstract
Another paper employing SNP genome scans in lake-stream stickleback:
Deagle, B.C., F.C. Jones, Y.F. Chan, D.M. Absher, D.M. Kingsley, and T.E. Reimchen. 2012. Population genomics of parallel phenotypic evolution in stickleback across stream-lake ecological transitions. Proceedings of the Royal Society B. Biological Sciences 279 1732 1277-1286. Link: http://rspb.royalsocietypublishing.org/content/279/1732/1277.abstract?sid=cc0e3784-2fc0-41ea-ac1d-a5dd3919d5fd
As I sit here in an airport lounge en route to yet another far-flung destination, it seems appropriate to finally write a long-planned blo...
[ This post is from Gregor Rolshausen , I am just putting it up. –B. ] Arguably, among the most interesting shifts in evolutionary thinki...
(Genders match the original.) The Gandalf Extremely wise – if sometimes inscrutably so – and able to solve your biggest problems, th...
As an editor, reviewer, supervisor, committee member, and colleague, I have read countless papers and proposals and have seen similarly co... | <urn:uuid:77fb1fdb-3cc4-46c6-97cd-d430bda77a95> | 2.9375 | 810 | Personal Blog | Science & Tech. | 47.975758 | 95,587,375 |
+44 1803 865913
By: S Shultz, A Dunham, K Root, S Soucy, S Carroll and L Ginzburg
216 pages, illustrations, tables, includes CD-ROM
Real problems are explored using RAMAS Ecolab 2.0 software and sample files - all provided. The lab manual contains background information, exercises and suggestions for additional work.
Biodiversity - the diversity of life; recovery of the Blue Whale - measuring population growth; competition among Osprey - limits to population growth; wood storks and honeyeaters - estimating population parameters; Grizzly Bears - problems of small populations; Giant Pandas - small populations and endangered species; Hector's dolphins and the Redcockaded Woodpecker - conserving dwindling populations; African market hunting and Tuna exploitation - maintaining sustainable levels; the African White Rhino - too many for their own good?; the Wild Ass and the Black-footed Ferret - reintroduction of endangered species; park size and species diversity - lessons from islands; rescuing the spotted owl - conserving species in multiple populations; biodiversity's biggest threat - human population growth; the case of Patrick's Marsh Wren - making decisions to protect species; using RAMAS Ecolab - installation; uninstalling RAMAS Ecolab395; running the programs.
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On behalf of Parque Nacional Nahuel Huapi I would like to thank NHBS. The book will be very useful for my students.
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Type Function Object File Library io.* Return value none Revision 2018.3334 Keywords close, files See also io.open()
Closes the open file (file is returned from io.open()).
Note that files are automatically closed when their handles are garbage collected, but that takes an unpredictable amount of time to happen.
-- Path for the file local path = system.pathForFile( "myfile.txt", system.DocumentsDirectory ) -- Open the file handle local file, errorString = io.open( path, "r" ) if not file then -- Error occurred; output the cause print( "File error: " .. errorString ) else -- Read data from file local contents = file:read( "*a" ) -- Output the file contents print( "Contents of " .. path .. "\n" .. contents ) -- Close the file handle file:close() end file = nil | <urn:uuid:71470852-d77d-4f66-b790-673945447722> | 3.078125 | 187 | Documentation | Software Dev. | 49.326648 | 95,587,420 |
Why Do We Know So Little About One of the Most Abundant Animals on the Planet?
Krill are ecologically and economically important, yet they have long been misunderstood and misrepresented
Adapted excerpt from The Curious Life of Krill
What are krill? Ask the average person on the street to describe a krill, and the most frequent response is a blank look. On rare occasions the response is “krill are the tiny shrimp-like crustaceans that whales feed on.” Many imagine that krill are microscopic, like water fleas or phytoplankton. Few appreciate their real size, which is far from microscopic. If all the animal inhabitants of the ocean from the largest whale to the most minuscule invertebrate are lined up based on size or weight, krill fall in the middle of the pack. Next to their seafaring brethren, they are average in size — not large but not microscopic. Not even tiny.
photo by Stephen Nicol
Antarctic krill, one of 85 krill species, were first noticed by whalers in the Southern Ocean. The bellies of the giant whales they hunted were filled almost exclusively with what whalers variously described as shrimps, squillae, animalcules, and insects. Krill had identity issues from the start. Whalers had known of the existence of krill from their observations in the North Atlantic, where several species are abundant and were frequently sighted on the feeding grounds of the great whales.
The word krill is understood to mean “young fish” in Norwegian, but I was informed by a Norwegian colleague that the term is actually an onomatopoeia, a word formed to replicate the sound of millions of krill pattering on the water as they jumped clear of the surface — behavior I had witnessed firsthand in the Bay of Fundy. This surface swarming behavior, exhibited by many species of krill, was another indication of their existence. Since krill are generally only found deep in offshore waters, they are usually seen only by fishermen and whalers and others who venture far from land.
Krill go by many names in the languages of maritime nations. Gaelic fishermen knew them as suil dhu, which means “black eyes.” In Japan they are known as esada or okiami, and fishermen in the English-speaking world often refer to them as red bait. But most people have no need of a word for animals they never see and rarely hear of.
In the language of science, however, krill belong to the taxonomic order of Euphausiids, and several of their 85 species are abundant in oceanic and some coastal areas around the world. Not surprisingly, Antarctic krill, first scientifically described in 1855, are found in the waters around the frozen continent. It is, without doubt, the most abundant, ecologically and economically important, and best-studied Euphausiid species. From here on, I will use the term krill to refer to Antarctic krill.
Krill are mostly transparent, when alive, with splashes of contrasting red and green, large spherical black eyes, and an elongated, streamlined shape that tapers to a pointed feathery tail. The green comes from the algae they eat and the red from special pigmentation spots that can expand and contract, making their shells a lighter or darker shade of red. When viewed en masse krill can turn the ocean blood-red.
All species of krill also have electric-blue light-emitting organs that dot the body, providing a spectacular light show, particularly when freshly collected. The overall effect is startling, and those who see living krill for the first time are often struck by their translucent beauty. When viewed closely, they are undoubtedly crustaceans, distant cousins to the prawns and shrimps that are so familiar in the displays in fish markets.
The Australian Antarctic Division in Tasmania established a research aquarium especially for the study of Antarctic krill. The aquarium quickly became a favorite of tour groups who grew to appreciate the beauty of free-swimming krill, including visitors as diverse as schoolchildren, politicians, and wildlife celebrities, such as David Attenborough and Jacques Cousteau. This was often the first time they had seen living krill. Inevitably, comments began with, “I didn’t realize they were so big!” This has led to my lifetime quest: to quash the misconception that krill are microscopic organisms. Adult Antarctic krill can reach a length of over six centimeters (roughly two and a half inches) and can weigh up to two grams (0,07 ounces).
Photo Dr David Demer, NOAA/NMFS/SWFSC/AMLR.
Over the years, frustrated by constant references to the microscopic size of krill, I made what many have considered an unwise decision. I had a krill tattooed on my left arm as a handy illustration of the appearance and actual size of krill that I could flourish when needed. That was the theory anyway. Unfortunately, my tattoo artist, though undoubtedly talented, was unable to render my favorite crustacean at the requisite size, and he took a few liberties with its anatomy too. As a result, when I roll up my left sleeve I display a rather terrifying lobster-like creature about twice the size of a krill while declaring “krill look something like this. They are quite a bit smaller but are definitely not microscopic!” Not quite what I had in mind, but it’s still a guaranteed conversation starter.
Living krill are hard to find, and good images of live krill are scarce. An Internet search for krill more often than not turns up images of withered brown specimens practically reeking of formalin through the computer screen. Even worse, many depict species of other crustaceans that are mistakenly labeled as krill. I was once handed a brochure about the need to conserve and protect krill, but the sponsoring conservation organization had used a cover photograph of a swarm of squat lobsters, which have only a passing resemblance to krill. It is difficult to convince the public to conserve a species you can’t correctly identify.
Krill are certainly crustaceans with a shrimplike appearance. They are differentiated from actual common shrimps and prawns in that they don’t perch on the seafloor, but rather swim in the open ocean for their entire life—a pelagic, or “free-swimming,” lifestyle. To swim constantly requires enormous inputs of energy as krill are heavier than seawater. This apparent drawback has not impeded krill from an evolutionary perspective, and they are among the planet’s most successful inhabitants by any measure.
Krill also differ from other crustaceans in subtle ways, most of which could be spotted only by ardent crustacean scientists. For example, their gills are found outside their carapace (the largest part of the shell that covers their head and bodily organs). Sensory organs are strategically located on the front end of the body and consist of two pairs of antennae and large eyes. Krill also possess ten pairs of feathery feeding limbs, which they use to comb the water in a not-very- discriminating search for food particles, living and dead, animal and plant. This makes them highly versatile omnivores with a constant supply of food that allows them to swim, grow, and reproduce. Their tail is their powerhouse, almost pure muscle, which activates their five pairs of swimming legs to propel them forward, and it provides thrust for rapid backward escapes, often referred to as lobstering.
Krill rarely swim alone; they are most often found in swarms or schools containing astronomical numbers of companions, which, as anyone who comes from a large family can attest to, has both costs and benefits. Because they are average-sized, abundant, and aggregated, krill are a premium food source for organisms higher up the food chain. Entire marine ecosystems depend on krill to eat the truly tiny organisms, and in turn to provide themselves as concentrated protein for bigger animals. Krill swarms can be so extensive and visually striking that they can be seen from space.
It is difficult for krill scientists like me to avoid superlatives when describing Antarctic krill, because they are truly among the world’s most astonishing animals. Krill possess distinctive features that truly set them apart from the humdrum life in the oceans. Here are seven remarkable attributes of krill.
Krill are possibly the most abundant animal on the planet. It is a bold assertion that Antarctic krill could be the world’s most abundant multicelled animal (metazoan), and I should clarify that (1) I refer to Antarctic krill as a single species, not a general group, such as ants or beetles; (2) I use biomass as the unit of measure, meaning the number of individuals of a species multiplied by their average weight; and (3) I make the (rather shaky) assumption that we can accurately quantify the biomass of any species.
With those caveats in mind, an analysis by the World Wildlife Fund in 2011 suggested that cattle have a biomass of 520 million metric tons, human biomass is around 350 million metric tons, and krill are a rather distant third, with 150 million metric tons. A more recent assessment of krill biomass has put the figure at around 400 million metric tons, so krill are still in the running for global biomass domination. Without a doubt, however, krill have the greatest biomass of any marine metazoan. Because the oceans occupy seventy percent of the area of our planet, this fact alone makes them globally important.
photo courtesy by NOAA NMFS SWFSC Antarctic Marine Living Resources (AMLR) Program
Krill inhabit an entire ocean. Estimates of the area of the Southern Ocean inhabited by krill range from 19 to 32 million square kilometers (7,336,000 to 12,355,000 square miles), which is 10 percent of the planet’s ocean area, or roughly four times the land area of Australia. It is now apparent that Antarctic krill can also be found in all water depths — from the surface to the sea floor at 4,500 meters below. Living in this immense volume of water has extreme implications for krill, ranging from how they maintain connectivity between widely distant populations, to what physiological processes they require to cope with the daily pressure changes at different depths.
Krill form some of the largest aggregations of animal life. Krill live in three-dimensional swarms, or schools, that can stretch for 20 kilometers and contain as many as three million metric tons of animals (roughly 30 trillion individuals). Not surprisingly, such swarms have been described as the largest aggregation of animal life on Earth by the arbiter of all big things — Guinness World Records. These vast dynamic clouds of krill are difficult to envision, though the film Happy Feet 2 did a wonderful job of portraying what a krill swarm might look like, even if the constituent members of these swarms were slightly modified in the animation. The aggregating habit, the density of the swarms, and their sheer size make krill ecologically critical and economically important.
Krill are much bigger than people think. As I have already mentioned, krill, with a length of 6 centimeters (roughly 2.5 inches), are far from being microscopic. Krill size has a number of consequences for their visibility as prey and how they are valued by humans. Conservation efforts have historically enjoyed more success for large animals, such as whales, elephants, and tuna; interest in saving species wanes for those on the smaller end of the spectrum. Thus depicting a small animal as being smaller than it actually is compounds the problem.
Krill have a unique biology. Recent studies have revealed that the krill genome (the amount of genetic information in each cell) is roughly 12 times the size of the human genome. We are not yet sure what the implications are, but it is an astonishing fact on its own. Krill can grow rapidly when food is abundant and shrink when food is in short supply. This is not simply a krill weight-loss exercise; krill grow and shrink by molting their shells every month or so, and when starved they must downsize with each molt. This trait complicates attempts to determine their age. We know from keeping krill in aquaria that they are long-lived, with life spans exceeding those of many of their predators. This means that at any point in time the population of krill is the product of many seasons, not just one or two, a discovery that has revolutionized the science of krill ecology and the management of its fishery.
Krill are a delicious, nutritious food source. The largest animals that have ever lived on our planet are blue whales, and the largest population of these giants used to feed exclusively in the Southern Ocean on one single food item: Antarctic krill. The population of blue whales was estimated at over 100,000 individuals before commercial whaling reduced their numbers by 99 percent in the early 1900s.
Blue whales feed in Antarctic waters for only six months of the year; the other six months they migrate thousands of kilometers north to breed, during which time it is believed that they do not feed at all. How do they manage this? The answer must surely be in the abundance of krill and its nutritional value. Other baleen whale species, such as fin whales (the second-largest animal to have lived on Earth), humpback whales, and uncounted numbers of minke whales, all follow the same pattern of feeding in Antarctic waters and migration northward in winter.
In addition, krill are a prized food source for tens of millions of penguins, flying seabirds, seals, fish, and squid. How could this ecosystem, this single krill species, have supported such a massive level of predation?
Antarctic krill have been the target of the largest fishery in the Southern Ocean for the past 40 years. Few people are aware that there are several active fisheries operating in the Antarctic region. The largest of these fisheries is for krill. After Antarctic seals and whales had been hunted to near extinction, the fishing industry turned its attention to krill. But after 40 years of development, the industry still struggles to produce marketable krill products that justify the massive expense of fishing in the Southern Ocean. The fishery’s slow development has allowed conservation efforts to expand, but the enigmatic nature of krill makes even their conservation difficult.
We know that krill are ecologically and economically important. We also acknowledge that they are fascinating, beautiful creatures in their own right. So why have they been misunderstood and misrepresented for so long? Living at the far end of the world under a layer of seawater and ice proved a reasonable strategy for krill to keep a low profile for several millennia. However, once humans found the whale-rich Southern Ocean they began rendering it considerably less whale-rich, and they also began noticing the rather shy but utterly essential food of the giants — krill.
We humans have a tendency to see a resource and immediately assess whether we could use it to allow us to access a higher standard of living. This happened to krill in the 1960s, and since then considerable effort has been expended on catching krill and trying to commercially exploit krill as a resource, but this exercise has not been particularly successful, and as a species it has remained off the wider public’s radar — until now.
Krill are at a crossroads. As the Southern Ocean changes and opens to more human exploration and use, krill are once more under scrutiny for their economic possibilities. Krill oil is now widely available in drug stores and supermarkets, and questions are being asked about the nature of krill and the sustainability of the fishery.
This is an adapted excerpt from The Curious Life of Krill by Stephen Nicol. Copyright @ 2018 by the author. Reproduced by permission of Island Press, Washington, D.C.
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An AC circuit is an alternating current circuit. Instead of a constant voltage supplied by a battery, the voltage oscillates in a sine wave patter varying with time.
V = V_0sin(wt)
V_0 is the maximum voltage
W is the angular frequency
t is time
The first alternator to produce alternating current was a dynamo electric generator based on Michael Faraday’s principles. It was constructed by the French instrument maker Hippolyte Pixii in 1832. The earliest recorded practical application of alternating current is Guillaume Duchenne, inventor and developer of electrotherapy. In 1855, it was announced that AC currents were superior to direct current for electrotherapeutic triggering of muscle contractions.
AV voltage may be increased or decreased with a transformer; use of a higher voltage leads to significantly more efficient transmissions of power. The power losses in a conductor are a product of the square of the current and the resistance of the conductor.
P_L = I^2R
The power transmitted is equal to the product of the current and the voltage
P_t = IV
Therefore the same amount of power can be transmitted with a lower current by increasing the voltage.
© BrainMass Inc. brainmass.com July 23, 2018, 7:55 am ad1c9bdddf | <urn:uuid:7ea1274b-c730-4ca5-85a9-86a68bf4256f> | 3.90625 | 277 | Knowledge Article | Science & Tech. | 39.061455 | 95,587,427 |
What are the physics behind the beautiful game?
Spoiler: It is BIG.
Our panelists go head to head and a lifesize (knitted) gut is passed round the studio.
How can spotting X rays from exploding stars help identify skin cancers?
How an ancient Babylonian tablet has finally given up its 3,700-year-old mysteries.
How a mathematical search theory can be used to hunt for sunken ships on the bottom of the ocean.
Making waves in the lab to better understand mixing in the ocean.
Is maths our best bet to communicate with aliens?
How mathematicians use evolution to find the best solution to a problem.
We explain what game theory is and do a little experiment of our own...
From hexagonal honeycombs to counting to four, bees love maths!
If you fill out Drake's equation, life beyond Earth is highly probable...
Is the golden ratio really represented all throughout nature?
Surprisingly, scientists are using GCSE maths to figure out where the stars are in our galaxy...
Why is there no Nobel Prize for Maths and what happens when you finally achieve your life's goal?
A look back at one of the world's greatest mathematicians.
A team have created a new form of personalised medicine, which could mean
correct doses of drugs for transplant...
One way to create artificial intelligence is to copy the brain...
...and it's hiding in plain site. But where?
Do men really have more partners than women, and why are we
having less sex than ever?
Time seems to have a clear and irreversible direction; physics doesn't recognise this though. This problem has...
Believe it or not, a chocolate fountain can help answer important maths conundrums...
Tomorrow's Engineers Week aims to inspire the next generation of engineers.
Symmetry underpins much of modern physics and maths but what exactly | <urn:uuid:a4983fc9-9746-4cc6-bc7f-f67a1ebf1f41> | 2.828125 | 393 | Content Listing | Science & Tech. | 63.295655 | 95,587,433 |
Weighing the risks of plutonium power
Threat to public called virtually nil, despite concerns voiced by some anti-nuclear critics
Close-up observations of Pluto would be impossible without the use of generators that rely on cancer-causing plutonium to produce electricity and heat for New Horizons' instrumentation.
Pluto is much too far from the sun to rely on power modules that convert sunlight into electricity.
The spacecraft will carry 24 pounds of non-weapons-grade plutonium, which could pose a cancer threat if dispersed into Earth's atmosphere.
A dispersal could be triggered by a rocket explosion during ascent or a failure in which the spacecraft plummeted back to Earth.
New Horizons' plutonium has been encased in fire-resistant ceramic and enclosed in iridium and graphite jackets designed to prevent dispersal even in the event of an explosion.
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Still, said Bruce Gagnon, coordinator for the Maine-based Global Network Against Weapons and Nuclear Power in Space, which held a launch-site protest last weekend, "Space technology can and does fail. ... When you add plutonium to the equation, you are asking for trouble."
NASA's risk analysis places the odds of any kind of radioactive release during such flights at one in 350 launches.
A NASA study of one worst-case scenario placed the probability of a radiation release from a New Horizons crash within the 62-square-mile launch zone at one in 1.4 million. The odds of the crash itself were estimated at between one in 10,000 and one in a million. The risk of any one person developing cancer as a result of the exposure ranged from one in a million to one in 2 billion, according to the environmental impact statement.
A space agency-led response team that includes representatives of Homeland Security, the Federal Emergency Management Agency and state and local organizations will be assembled in Florida during New Horizons' launch period to respond to any accident.
Responders have been trained to protect the public from exposure, measure radiation levels and locate and recover radioactive materials, said NASA's Dwayne Brown.
The United States has launched plutonium generators on 25 missions dating to 1961, including Cassini, the spacecraft now orbiting Saturn.
Three early missions encountered difficulties.
A plutonium generator burned up in Earth's atmosphere after the 1964 launch failure of a navigation satellite. A generator was recovered intact after a 1968 launch failure of a weather satellite.
NASA's Apollo moon missions also carried the devices to power lunar experiments. When the Apollo 13 crew limped back to Earth in 1970 following a spacecraft explosion en route to the moon, the lunar lander and its radioactive cargo plunged deep into the Pacific Ocean. | <urn:uuid:5969f037-10e6-4922-b32b-e25cdf0483b9> | 2.890625 | 766 | Truncated | Science & Tech. | 36.635397 | 95,587,458 |
ELECTRICITY. Electric Charge. Atoms are made up of 3 particles Neutrons have a neutral charge. Protons have a positive charge. Electrons have a negative charge. An atom is electrically neutral if the number of electrons EQUALS the number of protons
And likes repel
These fields can push or pull over distances
Conductors= materials which allow excess electrons to easily move through them.
Examples : metals, water
The Earth also functions as a conductor.
Insulator= a material that doesn’t allow electrons
to move through it easily
Examples : plastic around wires, wood doors, fiberglass, rubbers
Notice what the handles are made of. Why?
Large static discharge
Air masses move and swirl
Negative charge induces a + charge
on ground (repel e-)
Bottom accumulates enough -
Positive charges are attracted
Electrons in cloud attracted
Electric charges move through air collide with atoms/molecules
Collisions cause atoms/molecules to emit light
in the air
Produce great amounts of heat
Powerful sound waves
Connection (conductor) will transfer any excess electric charge
“Grounding” – the act of making a connection for an electric charge to go to the Earth
Longer, thin wires have MORE resistance than short, thick wires
Potential Energy (height)
The potential difference (voltage) is 1.5 V.
To Lower Energy
cause the light bulb to stop glowing?
It is the only switch in series to both the battery and light.
A. 0.22 amp
B. 4.5 amps
C. 11.0 amps
D. 18.0 amps
V = I R so,
9V = I x 2 ohms or 4.5 amps
1729 A.D. Stephen Gray classifies materials as either conductors or insulators
He saw that the fibers on the string were standing up and also received a shock from the key when he touched it. | <urn:uuid:bbe828a0-2970-44be-8adf-cca3c5efa004> | 3.890625 | 422 | Structured Data | Science & Tech. | 56.78595 | 95,587,493 |
- Open Access
The giant eyes of giant squid are indeed unexpectedly large, but not if used for spotting sperm whales
© Nilsson et al.; licensee BioMed Central Ltd. 2013
Received: 10 July 2013
Accepted: 3 September 2013
Published: 8 September 2013
We recently reported (Curr Biol 22:683–688, 2012) that the eyes of giant and colossal squid can grow to three times the diameter of the eyes of any other animal, including large fishes and whales. As an explanation to this extreme absolute eye size, we developed a theory for visual performance in aquatic habitats, leading to the conclusion that the huge eyes of giant and colossal squid are uniquely suited for detection of sperm whales, which are important squid-predators in the depths where these squid live. A paper in this journal by Schmitz et al. (BMC Evol Biol 13:45, 2013) refutes our conclusions on the basis of two claims: (1) using allometric data they argue that the eyes of giant and colossal squid are not unexpectedly large for the size of the squid, and (2) a revision of the values used for modelling indicates that large eyes are not better for detection of approaching sperm whales than they are for any other task.
Results and conclusions
We agree with Schmitz et al. that their revised values for intensity and abundance of planktonic bioluminescence may be more realistic, or at least more appropriately conservative, but argue that their conclusions are incorrect because they have not considered some of the main arguments put forward in our paper. We also present new modelling to demonstrate that our conclusions remain robust, even with the revised input values suggested by Schmitz et al.
Information from allometry versus functional theory
Schmitz et al. explicitly assume that eyes are “expected” to scale allometrically with body size. But there is no known biological reason why eye size and body size should scale according to a power law with a constant exponent over several orders of magnitude. The purpose of allometry is to describe scaling relationships, not to explain them. In contrast, our paper is based on functional arguments, and reveals a law of diminishing returns, which renders it less rewarding to continue increasing the eye size the larger an eye becomes. This law of diminishing returns is caused by absorption and scattering of light in water, and is highly relevant for eye sizes that range from a few cm to the huge eyes of giant squid.
As an example, at 300 m depth, dark objects can be seen at a 6.5% longer range if the diameter of a 1 mm eye is increased by 10%, but if the eye is already 10 mm in diameter, a 10% further increase in diameter will only generate a 4% longer visual range, and for a 100 mm eye, a 10% size increase improves the visual range only by a modest 2.5%. The eyes of giant and colossal squid grow to almost 3 times this diameter, even though this provides a relatively small improvement in visual range. These theoretical findings strongly suggest that eyes of very large animals should be relatively smaller, given that the energetic cost of eyes scales linearly with body mass.
Schmitz et al. found that the eye size of adult giant squid is on or above the linear regression line on a log-log plot representing the scaling relationship for 87 smaller squid species. Because the exponent of the power law is below 1, allometry does indeed reveal a general tendency for larger squid to have relatively smaller eyes, as predicted by our law of diminishing returns. A striking feature of their results is the huge variation, which, for any given body size, allows a more than 6-fold difference in eye diameter within the standard deviation. This large variation undoubtedly reflects major differences in the visual ecology of different squid species, and speaks against the conclusion of Schmitz et al. that eye size is developmentally constrained in squid.
The unique visual task for giant squid
Our modelling of monitored water volume revealed that detection of very large extended objects provides much better performance returns than detection of smaller objects or point sources. Because giant and colossal squid live at depths where there is practically no daylight, the only large visible objects would be other animals triggering planktonic bioluminescence as they move through the water. The phenomenon is well known for revealing moving objects in the sea . Because the performance return for increasing the eye size beyond that of the largest fish eyes (9–10 cm) and up to that of giant and colossal squid (27 cm) is much better for large than for small objects, we concluded that spotting the diffuse planktonic glow from their main predator, the sperm whale, offers a plausible and unique advantage that may have generated selection favouring huge eyes in giant and colossal squid.
Revised values for modelling
Schmitz et al. do not refute our theoretical reasoning for the unique advantage of giant eyes, but they argue that the values we used for modelling of triggered plankton bioluminescence were overestimates. With their alternative estimates of bioluminescent flash intensity and distance between luminous plankton, Schmitz et al. found that our equations no longer revealed any unique advantage for large eyes in detection of very large objects. But they did not take account of the fact that our equations were formulated such that they make a significant underestimate of the number of planktonic organisms that are triggered by moving targets.
The equations consider only a single layer of planktonic organisms within a circle inscribed within the target boundaries. In reality, the planktonic organisms that will be triggered to emit light are not restricted to a single layer, but involve the whole volume of water displaced by the moving target. For the prey of an approaching sperm whale, we can assume that at least the water displaced by the front 5 m of the whale’s linear length (to its widest point) will be in view. A conservative estimate of the displaced water volume seen by the prey would be a cylinder with a diameter of 2 m and a length of 5 m. If we use the revised value from Schmitz et al. of 0.55 m for the nearest neighbour distance between luminous plankton, the displaced water volume in view will contain an average of 66 luminous plankton (for the relation between density and nearest neighbour distance in 3D see , and for the 2D case, see ). In the calculations of Schmitz et al. the equivalent number is only 2.6 luminous plankton triggered by a 2 m target.
If we take the displaced water volume into account in the calculations of visual performance of very large eyes (Figure 1), even the revised lower values of plankton abundance and bioluminescent flash intensity suggested by Schmitz et al. reverses their conclusion and thus supports our original findings . Consequently, the assertions of Schmitz et al. are insupportable and our suggestion that the huge eyes of giant squid are uniquely suited for detecting sperm whales remains intact.
- Schmitz L, Motani R, Oufiero CE, Martin CH, McGee MD, Gamarra AR, Lee JJ, Wainwright PC: Allometry indicates that giant eyes of giant squid are not exceptional. BMC Evol Biol. 2013, 13: 45-10.1186/1471-2148-13-45.PubMed CentralPubMedView ArticleGoogle Scholar
- Nilsson D-E, Warrant EJ, Johnsen S, Hanlon R, Shashar N: A Unique Advantage for Giant Eyes in Giant Squid. Curr Biol. 2012, 22: 683-688. 10.1016/j.cub.2012.02.031.PubMedView ArticleGoogle Scholar
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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. | <urn:uuid:6d246b5d-fd86-485e-b393-31ac9c144371> | 3 | 1,857 | Truncated | Science & Tech. | 49.919915 | 95,587,506 |
The Lake-Induced Convection Experiment provided special field data during a westerly flow cold air outbreak (CAO) on 13 January 1998, which has afforded the opportunity to examine in detail an evolving convective boundary layer. Vertical cross sections prepared from these data, extending from upstream over Wisconsin out across Lake Michigan, show the modifying effects of land-water contrast on boundary layer mixing, entrainment, heating, and moisture flux. Through this analysis, an interesting case of lake-effect airmass modification was discovered. The data show atypical differing heights in vertical mixing of heat and moisture, as well as offshore downwelling and subsidence effects in the atmosphere. Analvsis shows evidence of a new observational feature, the moisture internal boundary layer (MIBL) that accords well with the often recognized thermal internal boundary layer (TIBL). The "interfacial" layer over the lake is also found to be unusually thick and moist, due in part to the upstream conditions over Wisconsin as well as the effectiveness of vertical mixing of moist plumes over the lake (also seen in the aircraft datasets presented). Results show that the atmosphere can be much more effective in the vertical mixing of moisture than heat or momentum (which mixed the same), and thus represents a significant departure from the classical bottom-up and top-down mixing formulation. Four scales of coherent structures (CSs) with differing spatial and temporal dimensions have been identified. The CSs grow in a building block fashion with buoyancy as the dominating physical mechanism for organizing the convection (even in the presence of substantial wind shear). Characteristic turbulence statistics from aircraft measurements show evidence of these multiple scales of CSs, ranging from the smallest (microscale) in the cloud-free path region near the Wisconsin shore, to the largest (mesoscale) in the snow-filled boundary layer near the Michigan shore. A large eddy simulation (LES) model has also been employed to study the effects of buoyancy and shear on the convective structures in lake-effect boundary layers. The model simulation results have been divided into two parts: 1) the general relationship of surface heat flux versus wind shear, which shows the interplay and dominance of these two competing forcing mechanisms for establishing convection patterns and geometry (i.e., rolls versus cells), and 2) a case study simulation of convection analogous to the CSs seen in the CFP region for the 13 January 1998 CAO event. Model simulations also show, under proper conditions of surface heating and wind shear, the simultaneous occurrence of differing scales of CSs and at different heights, including both cells and rolls and their coexisting patterns (based on the interplay between the effects of buoyancy and shear).
Mendeley saves you time finding and organizing research
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Chimpanzees seem to be able to tell when others hold mistaken beliefs. We all know that the way someone sees the world, and the way it really is, aren’t always the same. The ability to recognize that someone’s beliefs may differ from reality has long been seen as unique to humans.
But new research on chimpanzees, bonobos and orangutans suggests our primate relatives may also be able to tell when something is just in your head.
The study is from researchers at Duke University, Kyoto University and the Max Planck Institute for Evolutionary Anthropology.
They Know When You’re Stupid
The capacity to tell when others hold mistaken beliefs is seen as a key milestone in human cognitive development. Humans develop this awareness in early childhood, usually before the age of five. It marks the beginning of a young child’s ability to fully comprehend the thoughts and emotions of others — what psychologists call theory of mind.
Such skills are essential for getting along with other people and predicting what they might do. They also underlie our ability to trick people into believing something that isn’t true. An inability to infer what others are thinking or feeling is considered an early sign of autism.
“This cognitive ability is at the heart of so many human social skills,” said Christopher Krupenye of Duke, who led the study along with comparative psychologist Fumihiro Kano of Kyoto University.
Apes can read minds too…
Over the years, studies have shown that apes are remarkably skilled at understanding what others want, what others might know based on what they can see and hear, and other mental states. But when it comes to understanding what someone else is thinking even when those thoughts are false, apes have consistently failed the test until now.
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More formally, two sets of points are called congruent if, and only if, one can be transformed into the other by an isometry, i.e., a combination of rigid motions, namely a translation, a rotation, and a reflection. This means that either object can be repositioned and reflected (but not resized) so as to coincide precisely with the other object. So two distinct plane figures on a piece of paper are congruent if we can cut them out and then match them up completely. Turning the paper over is permitted.
In elementary geometry the word congruent is often used as follows. The word equal is often used in place of congruent for these objects.
- Two line segments are congruent if they have the same length.
- Two angles are congruent if they have the same measure.
- Two circles are congruent if they have the same diameter.
In this sense, two plane figures are congruent implies that their corresponding characteristics are "congruent" or "equal" including not just their corresponding sides and angles, but also their corresponding diagonals, perimeters and areas.
The related concept of similarity applies if the objects have the same shape but do not necessarily have the same size. (Most definitions consider congruence to be a form of similarity, although a minority require that the objects have different sizes in order to qualify as similar.)
Determining congruence of polygons
For two polygons to be congruent, they must have an equal number of sides (and hence an equal number—the same number—of vertices). Two polygons with n sides are congruent if and only if they each have numerically identical sequences (even if clockwise for one polygon and counterclockwise for the other) side-angle-side-angle-... for n sides and n angles.
Congruence of polygons can be established graphically as follows:
- First, match and label the corresponding vertices of the two figures.
- Second, draw a vector from one of the vertices of the one of the figures to the corresponding vertex of the other figure. Translate the first figure by this vector so that these two vertices match.
- Third, rotate the translated figure about the matched vertex until one pair of corresponding sides matches.
- Fourth, reflect the rotated figure about this matched side until the figures match.
If at any time the step cannot be completed, the polygons are not congruent.
Congruence of triangles
If triangle ABC is congruent to triangle DEF, the relationship can be written mathematically as:
In many cases it is sufficient to establish the equality of three corresponding parts and use one of the following results to deduce the congruence of the two triangles.
Sufficient evidence for congruence between two triangles in Euclidean space can be shown through the following comparisons:
- SAS (Side-Angle-Side): If two pairs of sides of two triangles are equal in length, and the included angles are equal in measurement, then the triangles are congruent.
- SSS (Side-Side-Side): If three pairs of sides of two triangles are equal in length, then the triangles are congruent.
- ASA (Angle-Side-Angle): If two pairs of angles of two triangles are equal in measurement, and the included sides are equal in length, then the triangles are congruent.
The ASA Postulate was contributed by Thales of Miletus (Greek). In most systems of axioms, the three criteria – SAS, SSS and ASA – are established as theorems. In the School Mathematics Study Group system SAS is taken as one (#15) of 22 postulates.
- AAS (Angle-Angle-Side): If two pairs of angles of two triangles are equal in measurement, and a pair of corresponding non-included sides are equal in length, then the triangles are congruent. AAS is equivalent to an ASA condition, by the fact that if any two angles are given, so is the third angle, since their sum should be 180°. ASA and AAS are sometimes combined into a single condition, AAcorrS – any two angles and a corresponding side.
- RHS (Right-angle-Hypotenuse-Side), also known as HL (Hypotenuse-Leg): If two right-angled triangles have their hypotenuses equal in length, and a pair of shorter sides are equal in length, then the triangles are congruent.
The SSA condition (Side-Side-Angle) which specifies two sides and a non-included angle (also known as ASS, or Angle-Side-Side) does not by itself prove congruence. In order to show congruence, additional information is required such as the measure of the corresponding angles and in some cases the lengths of the two pairs of corresponding sides. There are a few possible cases:
If two triangles satisfy the SSA condition and the length of the side opposite the angle is greater than or equal to the length of the adjacent side (SSA, or long side-short side-angle), then the two triangles are congruent. The opposite side is sometimes longer when the corresponding angles are acute, but it is always longer when the corresponding angles are right or obtuse. Where the angle is a right angle, also known as the Hypotenuse-Leg (HL) postulate or the Right-angle-Hypotenuse-Side (RHS) condition, the third side can be calculated using the Pythagorean Theorem thus allowing the SSS postulate to be applied.
If two triangles satisfy the SSA condition and the corresponding angles are acute and the length of the side opposite the angle is equal to the length of the adjacent side multiplied by the sine of the angle, then the two triangles are congruent.
If two triangles satisfy the SSA condition and the corresponding angles are acute and the length of the side opposite the angle is greater than the length of the adjacent side multiplied by the sine of the angle (but less than the length of the adjacent side), then the two triangles cannot be shown to be congruent. This is the ambiguous case and two different triangles can be formed from the given information, but further information distinguishing them can lead to a proof of congruence.
In Euclidean geometry, AAA (Angle-Angle-Angle) (or just AA, since in Euclidean geometry the angles of a triangle add up to 180°) does not provide information regarding the size of the two triangles and hence proves only similarity and not congruence in Euclidean space.
Definition of congruence in analytic geometry
In a Euclidean system, congruence is fundamental; it is the counterpart of equality for numbers. In analytic geometry, congruence may be defined intuitively thus: two mappings of figures onto one Cartesian coordinate system are congruent if and only if, for any two points in the first mapping, the Euclidean distance between them is equal to the Euclidean distance between the corresponding points in the second mapping.
A more formal definition states that two subsets A and B of Euclidean space Rn are called congruent if there exists an isometry f : Rn → Rn (an element of the Euclidean group E(n)) with f(A) = B. Congruence is an equivalence relation.
Congruent conic sections
Two conic sections are congruent if their eccentricities and one other distinct parameter characterizing them are equal. Their eccentricities establish their shapes, equality of which is sufficient to establish similarity, and the second parameter then establishes size. Since two circles, parabolas, or rectangular hyperbolas always have the same eccentricity (specifically 0 in the case of circles, 1 in the case of parabolas, and in the case of rectangular hyperbolas), two circles, parabolas, or rectangular hyperbolas need to have only one other common parameter value, establishing their size, for them to be congruent.
For two polyhedra with the same number E of edges, the same number of faces, and the same number of sides on corresponding faces, there exists a set of at most E measurements that can establish whether or not the polyhedra are congruent. For cubes, which have 12 edges, only 9 measurements are necessary.
Congruent triangles on a sphere
As with plane triangles, on a sphere two triangles sharing the same sequence of angle-side-angle (ASA) are necessarily congruent (that is, they have three identical sides and three identical angles). This can be seen as follows: One can situate one of the vertices with a given angle at the south pole and run the side with given length up the prime meridian. Knowing both angles at either end of the segment of fixed length ensures that the other two sides emanate with a uniquely determined trajectory, and thus will meet each other at a uniquely determined point; thus ASA is valid.
The congruence theorems side-angle-side (SAS) and side-side-side (SSS) also hold on a sphere; in addition, if two spherical triangles have an identical angle-angle-angle (AAA) sequence, they are congruent (unlike for plane triangles).
The plane-triangle congruence theorem angle-angle-side (AAS) does not hold for spherical triangles. As in plane geometry, side-side-angle (SSA) does not imply congruence.
A symbol commonly used for congruence is an equals symbol with a tilde above it, ≅, corresponding to the Unicode character 'approximately equal to' (U+2245). In the UK, the three-bar equal sign ≡ (U+2261) is sometimes used.
- Clapham, C.; Nicholson, J. (2009). "Oxford Concise Dictionary of Mathematics, Congruent Figures" (PDF). Addison-Wesley. p. 167. Archived from the original on 29 October 2013. Retrieved 2 June 2017.
- "Congruence". Math Open Reference. 2009. Retrieved 2 June 2017.
- Parr, H. E. (1970). Revision Course in School mathematics. Mathematics Textbooks Second Edition. G Bell and Sons Ltd. ISBN 0-7135-1717-4.
- Cornel, Antonio (2002). Geometry for Secondary Schools. Mathematics Textbooks Second Edition. Bookmark Inc. ISBN 971-569-441-1.
- Alexander Borisov, Mark Dickinson, and Stuart Hastings, "A congruence problem for polyhedra", American Mathematical Monthly 117, March 2010, pp. 232-249.
- Alexa Creech, "A congruence problem" http://184.108.40.206/teaching/projects/creech_final.pdf Archived November 11, 2013, at the Wayback Machine.
- Michael Bolin, "Exploration of Spherical Geometry", September 9, 2003, pp.6-7. http://math.iit.edu/~mccomic/420/notes/Bolin_spherical.pdf
- Hollyer, L., http://www.uh.edu/~hollyer/Module6/m6ppt/sld089.htm | <urn:uuid:45532c2a-f7ca-4a93-aab0-6ebb1549a034> | 4.4375 | 2,403 | Knowledge Article | Science & Tech. | 44.576565 | 95,587,538 |
Does the world we live in exist? Scientists say no – at least not until it’s measured anyway, and this would pertain to small scale. For Australian scientists, recreating experiments confirmed quantum physics’ predictions. The existence of reality is questionable.
If this sounds complex, not to worry. This experiment poses one simple question: Since some elementary particles act as a particle or a wave, then when is this classification decided? This question pushes us to understand how reality is established.
Most people assume that objects such as electrons or photons either wave-like or particle-like just because that’s the way it is. They think that measurements aren’t necessary to come to either conclusion. Quantum theory disagrees and suggests that conclusions can only be made by measurements taken at the end of the object’s journey.
Andrew Truscott of the Australian National University said:
“Reality doesn’t exist unless you look at it, and measurements mean everything.”
The experiment in question is the John Wheeler’s Delayed Choice experiment, first suggested in 1978. This experiment was ahead of its time, and not until 40 years later, utilized to its full potential. Using helium atoms scattered by laser light, scientists set out to measure the journey of objects in our reality.
Roman Khakimov, a Ph.D. student working on the experiment, said:
“Light is more like a wave, so we use atoms, which are more complex. Atoms have mass and interact with electric fields.”
Scientists placed a number of atoms in a suspended state, known as the Bose-Einstein condensate. After capture, all but one of the atoms were ejected. This atom was then placed within a pair of laser beams, to scatter the path of the object, creating a “grating” pattern. The process is similar to how light is scattered when falling upon a grating. After the atom passed through the first grating, a second grating was dropped, intersecting the paths, which added destructive or constructive interference.
This result is an action pointed toward a wave, which can travel both paths. If the second grating is not added, the atom travels only one path, which points toward particle. This suggests that the atom doesn’t know its nature until it passes through a second grating.
“These experiments prove that particle-like or wave-like existence is only possible when measured at the end of the journey. There is no travel from point A to point B. It’s not that simple.”
Using these theories, we are able to develop lasers, LEDS and computer chips. This may sound strange, but it’s just a part of a quantum theory that governs the small world. Until now, these pure experiments weren’t possible. Now, these demonstrations confirm these ideas work.
Latest posts by Sherrie (see all)
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- 8 Signs You May Have Clairvoyant Abilities and How to Develop Them - July 19, 2018
- Knowing The 7 Stages of Grief Will Help You Survive Loss, Break-up, and Trauma - July 18, 2018
- 14 Signs of Stress and Non-Obvious Psychological Causes of It - July 14, 2018
- Teen Angst: 7 Signs Your Teen Is Suffering and How to Help Them - July 11, 2018 | <urn:uuid:ea7a9b8f-cb87-473b-9877-52ffdfb70bd4> | 3.78125 | 726 | Personal Blog | Science & Tech. | 54.401662 | 95,587,656 |
Come to our PaleoTime-BE International Fossil Show in Wijgmaal (BE), on November 11 2018!
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How do fossils form?
When an organism dies and is buried by sediments, there is a chance that it may be preserved as a fossil. In most cases, this does not happen, and the remains will be eaten by natural scavengers and decay processes. However, due to specific environmental factors such as rapid burial or in extremely low oxygen conditions, the natural scavengers cannot reach the remains and an organism can be preserved as a fossil. Due to the forming of new layers of sediment on top, the pressure increases in the layer in which the organism or the residues are burried. This starts the fossilization processes, by which the original organic material is replaced by mineral components: the remains are 'fossilized'. When, in the course of time by tectonic movements and erosion these layers emerge on the surface, the fossil can be discovered and excavated.
In these arid conditions the chance of fossilisation is limited, unless the remains are burried very fast
Good conditions for fossilization are very rare, and usually disruption of the remains occurs to some extent, so especially the hard parts of organisms (shell, bones and teeth) are preserved. Since sedimentation is more common in river and marine environments, fossils of aquatic organisms are much more numerous than fossils of land organisms. The latter are mainly found in deposits of catastrophic events such as volcanic eruptions, landslides or floods. The best preserved fossils occur where a quickly burial of the remains with fine-grained sediments is followed by very low oxygen levels. In such conditions, normal decay processes have no chance and even soft tissues can be preserved, sometimes to the finest details.
Nonetheless, much of the eventual preservation still depends on the chemical composition of the deposits in which the fossil remains are embedded. Within the deposits, the fossil can be partly converted into other minerals by the influence of chemical processes. In that case, the internal structure of the fossil remains well preserved. It is also possible that the original fossil completely dissolves after deposition. The remaining cavity can then later be filled by other minerals, but again you will only find a "print". The internal structure of the fossil will be lost. Even after the fossilization the fossil may be damaged or get dissolved, for example by percolation of water through the rock, or by differential weathering processes when the fossil is close to the Earth's surface. The latter you can often observe in the field yourself. When a fossil-bearing layer is exposed by natural erosion, fossils that are several feet deeper in the layer are sometimes better preserved than those located on or near the weathering plane.
Deposits with a very special fossil content are known in science as Lagerstätten. There is a distinction between the so-called 'Konservat-lagerstätten" in which the fossils are preserved in an exceptional way, and 'Konzentrat-Lägerstatten', in which excessive amounts or concentrations of fossils are found. These lagerstätten are without exception of great scientific significance. Konservat-lagerstätten are often the result of very specific chemical conditions, in which the fossils have been through a conversion to phosphate, silica and pyrite, like carbon film, or like imprint in another medium (e.g. microbial mats on the sea floor).
Do you have additional information for this article? Please contact the Fossiel.net Team. | <urn:uuid:4fe54056-75a1-4021-8713-7759d763d508> | 4.40625 | 755 | Knowledge Article | Science & Tech. | 35.738105 | 95,587,702 |
Distributions which are approximately normal are frequently encountered, e.g. most sets of random errors follow the normal distribution.
The normal distribution is important as a ‘limiting distribution’, i.e. it can be used as an approximation to other distributions (see sections 8.7 and 8.8).
The normal distribution is easy to use.
It has been shown that the results obtained by assuming a non-normal population to be normally distributed are reasonably accurate when the departure from normality is not too severe.
The central limit theorem shows that the means of samples of size n from any population are approximately normally distributed. The approximation improves as n gets bigger.
KeywordsNormal Distribution Poisson Distribution Binomial Distribution Normal Approximation Normal Curve
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> I found some strange behaviour in the hash function.
> When applied to numbers, it works ok, but when applied
> to strings, it leads to a huge number of collisions.
> # uniq hashed values, using 50000 different numbers: 50000
> # uniq hashed values, using 50000 different strings: 10271
> # ==========================================================
You are right. This is not optimal. Thanks for the hint!
The reason is the initSeed()/initSeedE_E function in
It uses numbers directly, and the names (which are techincally also
numbers) in case of symbols. But for symbols these numbers have less
entropy, as they are not as denseley packed bit patterns like pure
numbers (basically what Oskar Wieland points out in his reply).
initSeed() should be improved, by doing more than simply adding up the
32-bit or 64-bit "digits", at least in case of symbols. Any proposals? | <urn:uuid:58ed6a06-a3a0-45cd-bbf2-c86828d29b2f> | 2.671875 | 219 | Comment Section | Software Dev. | 59.383333 | 95,587,725 |
Views of the Solar System
by Calvin J. Hamilton
Views of the Solar System presents a vivid multimedia adventure unfolding the splendor of the Sun, planets, moons, comets, asteroids, and more. Discover the latest scientific information, or study the history of space exploration, rocketry, early astronauts, space missions, spacecraft through a vast archive of photographs, scientific facts, text, graphics and videos.
Home page url
Download or read it online for free here:
by Elbert A. King - Lunar and Planetary Institute
The excitement of the Apollo program was that it accomplished a bold leap from the surface of the Earth to the Moon. The deed challenged our technology and engineering skill. Preparations are being made now for another and even more daring leap.
by James Schombert - University of Oregon
The purpose of this course is to educate you on the basic science behind our exploration of the Solar System so you may make informed choices as future/current voters on issues of our environment and the future of science in this country.
by Jonathan P. Williams, Lucas A. Cieza - arXiv
Flattened disks of cool dust and gas are found around almost all low mass stars shortly after their birth. This review addresses observations of the outer parts of protoplanetary disks with a focus on recent infrared and (sub-)millimeter results.
by George F. Chambers - S. S. McClure Co.
The book presents in a readable, yet soundly scientific, language a popular account of eclipses of the Sun and Moon, and very briefly of certain kindred astronomical phenomena similar to those which operate in connection with eclipses. | <urn:uuid:a9a8d741-71f6-42d3-8fcc-2fa3b15ae03c> | 3.140625 | 340 | Content Listing | Science & Tech. | 42.061283 | 95,587,726 |
In part one of this three-part series on deep testing complex systems, I covered the practical aspects of deep testing and demonstrated how to test difficult areas of code, such as the user interface, networking, and asynchronous code.
- The Challenges Behind Multi-Cloud Management
- Red Hat cloud a road map to government cloud computing based on openness, portability, and choice
- Agile Desktop Infrastructures: You CAN Have It All
- Developing a User-Centric Secure Mobile Strategy: It's in Reach
In this article, I discuss some techniques and utilities I have used to successfully test complex systems in C++. In the final article next week, I'll discuss similar complex testing for Python (with Swig C++/Python bindings) and high-volume, highly available C#/.NET Web services.
Obstacles to Testing Complex C++ Code
C++ arguably poses the most difficult challenges for testing among the major industrial-strength programming languages and environments. There are several challenges to deal with: Build speed is slow; the language uses weak types; and C++ programmers love twisting code or template-based designs to extract every last bit of performance. Let's look at how these factors affect testing complex code.
Slow Build Speeds
C++ projects (especially cross-platform projects) are often built as one big monolith. They can comprise large numbers of static project libraries along with many more third-party libraries that are all linked together to generate the final executable (often, several executables).
The result of this monolithic construction is less than stellar dependency management. I've seen several large C++ codebases where every merge was a project in itself involving a dedicated build engineer to convene multiple developers to help resolve conflicts and build the software, sometimes requiring multiple building passes to combat cyclic dependencies. Add the tools used to build many cross-platform C++ projects (such as make) and you get a picture of slow, very complex builds.
The impact of this on testing is profound. When simply building the software is such a chore, the tendency is to minimize the number of artifacts you generate. This leads to one of several unpleasant choices:
- No tests just build the software and play with it; trust your QA team to find all the bugs.
- Add some test support to the main software with compile-time or runtime switches.
- One big test executable (or test framework) that links against all the dependencies and contains all the tests.
- Many small test executables, each linked against its dependencies.
Option #1 is an obvious no-go from serious testing point of view (but very common in practice).
Option #2 is cumbersome. It doesn't let you to perform isolated testing and complicates the final product with testing code and dependencies.
Option #3 requires a slow build of the huge test executable whenever you make a small change (either to the code under test or to the test itself).
Option #4 requires a lot of tinkering around. It's pretty good when you work on an isolated bug or feature and has to build just one small test executable, but when you want to run a suite of regression tests, you will have to wait a long time for the build because each and every small executable will have to link against all its dependencies, which will duplicate a lot of effort (especially for common libraries used by every test executable).
The Quest for Performance
C++ was designed for raw performance. You pay only for what you use. It is compatible with C, which started as a glorified assembly language. In later years, C++ became a multi-paradigm language supporting procedural, object-oriented, and generic programming styles, while still maintaining its C compatibility and performance. However, this led to a programming language that is an order of magnitude more difficult to learn and practice than other mainstream languages. In its glory days (early '90s), C++ was used for everything, especially on Windows. You wrote your number-crunching code and your user interface and your networking code in C++, and that was that. The rise of the Web and Java changed everything. Suddenly, the programming language of your project wasn't a given and you could even mix and match programming languages in the same project. Later, hardware got faster, other languages got better (C#, Python), and Web applications where developed in every possible language except C++ (anyone remember ATL server?). That relegated C++ to the engine to do what it does best fast processing. C++ programmers (unless they are polyglot and dabble in other languages) justifiably focus more than anything on generating fast and tight code. Many great C++ developers formed their habits before automated unit testing and the agile movement made it to the big stage. Also, because performance is very often a system-wide property and not just the sum of the performance of the various components, its pursuit leads to a dependence on the usefulness of unit testing.
Very Weak Type System
C++ is a statically typed language, but its type system is very weak. You can freely cast any pointer to any other pointer using
reinterpret_cast. It can perform implicit casts/coercions/promotions on your behalf in certain situations. In addition, it has the legacy C preprocessor that allows inventing private sub-languages in a non-typesafe way. Add to that powerful templates with no constraints. Because all these features are heavily used in industrial strength programs, you end up with a combustible concoction that is pretty difficult to reason through and to feel secure that you have covered in your tests all the ways the code can misbehave. | <urn:uuid:3995555e-4e05-4367-904f-cd711cf0437b> | 2.546875 | 1,164 | Personal Blog | Software Dev. | 39.028769 | 95,587,734 |
Humans need plants to survive, and plants need soil. But what happens when human, geological and climatic activity alters soil composition and structure and diminishes the amount of fertile land available?
Erosion and weathering can hinder the soil's ability to maintain a nutritional balance -- a process crucial to maintaining life around the globe.
"Our sustenance is all based on the soil, and yet we lose soil every day to erosion," said Susan Brantley, a professor of geosciences at Pennsylvania State University. "It's important for us to understand how the soil is formed in the first place."
Brantley's research was featured today at the Goldschmidt Conference hosted by the University of Tennessee, Knoxville, and Oak Ridge National Laboratory.
A worldwide network of field research sites takes an interdisciplinary approach to studying Earth's "critical zone," the multi-layered region from groundwater to vegetation canopy. Understanding how the soil interacts with its environment and changes over both a short-term and geological time scale offers insight into the potential renewability of soil.
Funding for United States observatories in this "Critical Zone Exploration Network" is granted by the National Science Foundation. Brantley was a pioneer in setting up the network and conducts research at one of the first observatories to receive a grant, the Susquehanna Shale Hills observatory in Pennsylvania.
Here, Brantley and her team are investigating why the soil contains an unusually high amount of manganese. Using data gathered from other critical zone observatories across the states, she and her colleagues are discovering a correlation between nearby industrial facilities and this excess manganese in the soil.
The Goldschmidt Conference, held the week of June 13-18, brings together thousands of geochemists from around the world to discuss new scientific discoveries regarding the Earth, energy and the environment.
Whitney Holmes | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Günter Von Kiedrowski, of Ruhr Universität Bochum in Germany, described the new and emerging science of complex systems chemistry. The field takes the opposite approach from that of the genomics pioneer Craig Venter, who wants to build a minimal living cell.
"Venter wants to see what is left if you knock out everything but what is needed to survive," says Von Kiedrowski. "We want to look at how you get to that from the bottom up. Darwin's tree of life must have roots, and it is our mission to find them."
Complex systems chemistry uses computer models to simulate combinations of reactions, involving membrane forming reactions, self-replicating nucleic acids and metabolic energy-producing reactions. Then it examines how these systems develop in time and space.
Breaking the symmetry
One promising area is the discovery of reaction systems that lead to the spontaneues generation of chiral asymmetry. It is a universal property of life that compounds such as amino acids and sugars exist exclusively in a one-handed form although both forms are equally likely from an energetic point of view. It is quite difficult to achieve this asymmetry in non-living chemical reactions. Chemistry tends to create equal proportions of the different forms, which behave like objects and their mirror images. "The recipe for asymmetry is the co-occurence of positive and negative feedback loops within such systems," says Von Kiedrowski.Complex systems chemistry cannot tell the story of life entirely. "We are in the same position as the physicists trying to understand the origin of the universe," says Von Kiedrowski. "We will not know exactly how life began, because we do not know the precise conditions at the time, but we can get a good model of how it could have happened with this approach."
Clues from Mars
Understanding the context of early life from the evidence on Earth is difficult. Because the Earth's crust is so active, there is very little surface rock remaining from the time when life originated, before 3.5 billion years ago. "There are only two places on Earth where rocks formed at that time are relatively well preserved," says Tanja Zegers, a geoscientist from Utrecht University in the Netherlands. These are at Pilbara in Australia and Kaapvaal in South Africa.
The pillow basalts at Pilbara provide strong evidence that there was liquid water on Earth at that time, because their shape could only have developed underwater. Liquid water is crucial for life. But, says Zegers, understanding the origin of life from this evidence is a bit like trying to piece together western civilisation from Asterix and Obelix cartoons.
On Mars, by contrast, about 50% of the surface is from before 3.7 billion years ago, so there is a lot more to work with. "Mars may be our best bet to find out about life's origins on Earth," says Zegers.
At the time life was evolving on Earth, it seems there was liquid water on Mars too, and a similar environment in many respects. The oldest areas on Mars have hydrated minerals, like clays, which contain water within the mineral structure. They also show signs of surface flows like river networks. But about 3.8 billion years ago, the Martian atmosphere declined and the planet went into a deep freeze. Now, atmospheric pressure on Mars is too low for water to exist as a liquid at all.
Understand habitability on Mars and early Earth requires focused geological research. Several missions to Mars, to map the planet and eventually bring back samples, are ongoing and planned by the European Space Agency (ESA) and NASA in the coming years.
But Zegers argues that, in Europe, Mars research is not well co-ordinated. There is no organisation responsible for managing and disseminating the scientific and survey data resulting from European Mars missions, and the scientific community using the data is not fully involved in the early stages of mission-planning.
"Mars science is key to addressing some of the most fundamental scientific questions we have," says Zegers. "We need a European programme for missions to Mars, and a European planetary information programme."
This research was presented at the "Complex Systems: Water and Life" Frontiers of Science conference, organized by European Science Foundation and COST, 29-31 October, Taormina, Sicily.
Thomas Lau | alfa
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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12.07.2018 | Event News
03.07.2018 | Event News
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20.07.2018 | Information Technology
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Prospects for lensed supernovae behind galaxy clusters with the James Webb Space TelescopeTanja Petrushevska
, 2018, objavljeni povzetek znanstvenega prispevka na konferenci
Opis: Galaxies, and clusters of galaxies, can act as gravitational lenses and magnify the light of
objects behind them. The effect enables observations of very distant supernovae, that
otherwise would be too faint to be detected by existing telescopes, and allows studies of
the frequency and properties of these rare phenomena when the universe was young.
Under the right circumstances, multiple images of the lensed supernovae can be
observed, and due to the variable nature of the objects, the difference between the arrival
times of the images can be measured. Since the images have taken different paths
through space before reaching us, the time-differences are sensitive to the expansion rate
of the universe. One class of supernovae, Type Ia, are of particular interest to detect. Their
well known brightness can be used to determine the magnification, which can be used to
understand the lensing systems. I will also report our discovery of the first resolved
multiply-imaged gravitationally lensed supernova Type Ia. I will also show the expectations
of search campaigns that can be conducted with future facilities, such as the James Webb
Space Telescope (JWST) or the Wide-Field Infrared Survey Telescope (WFIRST).
Ključne besede: Strong lensing, Hubble constant, measuring expansion history with time delays, lensed supernovae
Objavljeno: 09.07.2018; Ogledov: 76; Prenosov: 3
Polno besedilo (4,14 MB)
Searching for supernovae in the multiply-imaged galaxies behind the gravitational telescope A370Tanja Petrushevska
, Ariel Goobar
, D. J. Lagattuta
, R. Amanullah
, Laura Hangard
, S. Fabbro
, C. Lindman
, K. Paech
, J. Richard
, J.P. Kneib
, 2017, izvirni znanstveni članek
Opis: Aims. Strong lensing by massive galaxy clusters can provide magnification of the flux and even multiple images of the galaxies that lie behind them. This phenomenon facilitates observations of high-redshift supernovae (SNe) that would otherwise remain undetected. Type Ia supernovae (SNe Ia) detections are of particular interest because of their standard brightness, since they can be used to improve either cluster lensing models or cosmological parameter measurements.
Methods. We present a ground-based, near-infrared search for lensed SNe behind the galaxy cluster Abell 370. Our survey was based on 15 epochs of J-band observations with the HAWK-I instrument on the Very Large Telescope (VLT). We use Hubble Space Telescope (HST) photometry to infer the global properties of the multiply-imaged galaxies. Using a recently published lensing model of Abell 370, we also present the predicted magnifications and time delays between the images.
Results. In our survey, we did not discover any live SNe from the 13 lensed galaxies with 47 multiple images behind Abell 370. This is consistent with the expectation of 0.09 ± 0.02 SNe calculated based on the measured star formation rate. We compare the expectations of discovering strongly lensed SNe in our survey and that performed with HST during the Hubble Frontier Fields (HFF) programme. We also show the expectations of search campaigns that can be conducted with future facilities, such as the James Webb Space Telescope (JWST) or the Wide-Field Infrared Survey Telescope (WFIRST). We show that the NIRCam instrument aboard the JWST will be sensitive to most SN multiple images in the strongly lensed galaxies and thus will be able to measure their time delays if observations are scheduled accordingly.
Ključne besede: gravitational lensing: strong / supernovae: general / galaxies: clusters: individual: A 370
Objavljeno: 28.06.2018; Ogledov: 134; Prenosov: 4
Polno besedilo (4,14 MB)
Nebesa pod Triglavom - samo s sodobnimi Gabrščki, Bevki in PoberajiZoran Božič
, druga izvedena dela
Opis: Razmislek o koreninah slovenske državnosti, o odporu pred prvo svetovno vojno, v času fašizma in med drugo svetovno vojno. Napotek za sodobne voditelje naroda.
Ključne besede: dan državnosti, Solkan, Andrej Gabršček, France Bevk, Vladimir Poberaj, domoljubje, Avstro-Ogrska, Bohinjska železnica, Umirajoči bog Triglav, staroverci, fašizem, druga svetovna vojna, nemško taborišče, narodnoosvobodilna borba
Objavljeno: 26.06.2018; Ogledov: 108; Prenosov: 0
Polno besedilo (206,67 KB) | <urn:uuid:28446491-cd62-48d7-94a0-bce4c583359d> | 3.046875 | 1,204 | Content Listing | Science & Tech. | 29.850349 | 95,587,758 |
It is not always easy to distinguish between images and mirror images of molecules, but this knowledge is important when one image of a molecule is a drug and the mirror image is toxic. One new approach to this may be chiral recognition in the gas phase.
This involves using synchrotron radiation (highly energetic photons from a particle accelerator) to eject electrons from the molecules and analyzing their trajectories. In the journal Angewandte Chemie, German researchers have now demonstrated that such experiments also work with a compact laser system.
The trick is to replace the individual high-energy photon with three laser photons that excite the molecule through intermediate levels until it releases an electron (this method is known as REMPI, Resonance-Enhanced Multi-Photon Ionization). “It is thus possible to eject electrons with less energetic but more intense light,” explains Thomas Baumert of the University of Kassel.
For the measurements, the light must be circularly polarized. What does this mean? “Ordinary” light consists of waves that oscillate in all spatial directions perpendicular to their direction of travel. If light is linearly polarized, the light waves oscillate exclusively in one plane. When light is circularly polarized, the light wave oscillates in a helical form, because its amplitude describes a circle around the axis of travel – either to the right or the left.
Molecules in the gas phase are randomly oriented and thus encounter the laser light from all possible angles; the ejected electrons also fly off in every possible direction as they leave the molecule. By using both a special configuration for measurement and special calculation processes, the team is able to determine the distribution of the angles of the electrons’ flight paths. In the case of linearly polarized light, the distribution is symmetrical.
“However, when the electrons are ejected by circularly polarized light, we find a distinct asymmetry to the angles at which the free electrons are found in relation to the laser beam,” reports Baumert. “This asymmetry is inverted if left circularly polarized light is used instead of right, an effect known as photoelectron circular dichroism. We observe the same effect when we keep the circular polarization the same but change from the “right handed” to the “left handed” structure of the chiral molecule being observed.”
The researchers were able to demonstrate this with the chiral compounds camphor and fenchone.
“This circular dichroism effect has previously only been observed with synchrotron radiation. In contrast, our procedure uses a compact laser system, so that this method is not limited to basic laboratory research but, because of the magnitude of the observed effects, may also find its way into analysis,” according to Baumert.About the Author
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201109035
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
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The term biodiversity refers to the variety of all forms of life such as plants, animals, and microorganisms in an ecosystem. In its commitment to being a biodiverse campus, UIC will take steps to protect and support health and diversity of ecosystems on campus.
For many city dwellers, exposure to urban parks and other green spaces will provide most of their encounters with the outside world. Such experiences can have a lifelong impact on awareness and concerns about environmental issues. An institution as large as UIC has the potential to educate and inspire students, faculty, staff, and neighbors through its thoughtful and sustainable approach to increasing biodiversity in its open spaces. In addition to their educational benefits, biodiverse spaces increase the attractiveness of the campus, thus playing an important role in recruiting students and employees.
UIC will create a resilient campus landscape supportive of a variety of life, such as plants, animals, and people.
4A. Promote Consumption of Local Food on Campus – Explore contracting options with local and regional food vendors and opportunities for on-site food production. | <urn:uuid:40e9de3d-9a8a-431d-9a74-87f52dcee552> | 2.953125 | 213 | About (Org.) | Science & Tech. | 28.492016 | 95,587,777 |
Using the zebrafish, a model organism widely used in genetic studies, researchers have found that when it comes to social interactions with other fish, individual zebrafish learn to prefer one fish color pattern over another according to their early experience with these patterns. The work extends the utility of zebrafish to studies of behavior and evolution and is reported by University of Texas researchers Raymond E. Engeszer, Dr. David M. Parichy, and Dr. Michael J. Ryan.
Social behavior has long been of interest to biologists and psychologists alike. The studies reported this week suggest that the extensive knowledge of zebrafish genetics will afford researchers an opportunity to see how genes, development, and environment lead to behaviors that mediate social interactions.
The investigators examined the way fish choose their consorts during the formation of loose social aggregates, called shoals, and they exploited the developmental genetic resources of this biomedical model organism to manipulate the appearance of the fish. Fish were chosen to have drastically different color patterns, either blue and gold stripes or an absence of stripes and a uniform mother-of-pearl color. This difference was the result of a single DNA base change in the fishs genome. To determine whether genes or the environment determine individuals preferences, the investigators raised subject fish either with other fish of their own color or with fish of the alternate color. When subject fish were later allowed to choose which color of fish to associate with, they greatly preferred whichever color pattern they had been raised with, irrespective of their own color. This learned social preference could have enormous impacts on the survival and reproductive success of individual fish. This work represents a first step in using the zebrafish and the tools of developmental genetics to investigate long-standing questions concerning the impact of behavior on evolution.
Heidi Hardman | 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.
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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.
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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A study published in the journal Science Advances shows that the American Southwest and Central Plains could be on course for super-droughts the like of which they have not witnessed in over a 1,000 years. The researchers' empirical drought-reconstruction models project significantly drier conditions in the later half of the 21st century compared to the 20th century and earlier paleoclimatic intervals.
Study reveals unprecedented US drought risk
Resource / Study reveals unprecedented US drought risk
By Futures Centre / 13 Feb 2015
What might the implications of this be? What related resources have you seen?
Sensemaking / Nespresso France leads companies tracking sustainable actions on blockchain
Sensemaking / With Paris ratified, will the UK pick up its game on climate change? | <urn:uuid:e4ebdc0b-3656-4bfc-b5b5-5d3c621aaaa2> | 3.15625 | 156 | Truncated | Science & Tech. | 33.015 | 95,587,816 |
The object, known as an evaporating gas globule, or EGG, has the same mass as the sun and appears to be evolving in a violent environment much like the one believed to have produced Earth’s sun, said researcher Jeffrey Linsky of JILA, a joint institute of CU-Boulder and the National Institute of Standards and Technology. Located in a region called the Pillars of Creation in the Eagle Nebula roughly 7,000 light-years from Earth, the object -- dubbed E42 -- is thought to be in the earliest stage astronomers have ever detected a star like the sun, said Linsky.
A new image of the Pillars of Creation, consisting of a Hubble Space Telescope image overlaid with Chandra X-ray data, was released Feb.15 by the Chandra X-ray Observatory Center in Cambridge, Mass. The image, which shows red, green and blue dots representing low-, medium- and high-energy X-rays, indicates there are relatively few X-ray sources in the pillars and suggests the Eagle Nebula is past its star-forming prime, said Linsky.
Linsky and colleagues from West Chester University in Pennsylvania, the University of Exeter in England and the University of Arizona analyzed visual and infrared emissions from the pillars to identify E42, the sun-like proto-star. E42 is located in the left pillar on the right edge of a node jutting out to the right about two-thirds of the way down the pillar.
“We think this is a very, very early version of our own sun,” said Linsky.
E42 is one of 73 EGGs discovered in the Pillars of Creation in 1996 with the Hubble Space Telescope by Arizona State University astronomer Jeff Hester and his team. While 11 of the EGGs have been determined to contain infant stellar objects, only four are massive enough to form a star. Of those, E42 is the only one that has a sun-sized mass, said Linsky.
“The four proto-stars that we have identified on the edges of the pillars are probably the youngest stars ever imaged by astronomers,” Linsky said.
While Linsky and his team used Chandra to zero in on more than 1,100 hotter, more mature stars in the Eagle Nebula, neither E42 nor the other three EGGs believed massive enough to form stars were observed to be emitting any X-rays, he said. “The results indicate young, evolving stars like E42 have not yet developed the magnetic structures needed to produce X-rays,” he said.
Earth’s sun is thought to have formed some 5 billion years ago after clouds of dust and gas were seared by ultraviolet radiation and pounded by shockwaves from one or more supernovae explosions, Linsky said. “The sun was likely born in a region like the Pillars of Creation because the chemical abundances in the solar system indicate that a supernova occurred nearby and contributed its heavy elements to the gas of which the sun and the planets formed.”
A January 2007 study by an astronomy team from France suggested the pillars were toppled some 6,000 years ago by a nearby supernova explosion, as evidenced by a glowing cloud of scorched dust adjacent to the pillars. Since the pillars are roughly 7,000 light years away, the French team contends they will still be visible from Earth as “ghost images” for another thousand years or so.
“My guess is that the shock wave from the supernova may have been far enough away so that E42 and some of the other stars may have survived,” said Linsky. “But I guess we will have to wait another thousand years or so to get the answer.”
Jeffrey Linsky | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences | <urn:uuid:5c107219-2b6a-4382-8147-ec87931bcfab> | 3.453125 | 1,419 | Content Listing | Science & Tech. | 46.106259 | 95,587,837 |
Ocean acidification and its effects on coral reef growth
Aptly named "Rainforests of the Sea", tropical coral reefs are one of the most biodiverse ecosystems on the planet. Much like how trees of a forest provide shelter for plants and animals living within, corals reefs provide food and shelter for millions of species ranging from microscopic bacteria to predatory sharks. Not only do coral reefs harbor vast ecological wealth, but they also provide us with ecosystem services valued at over $300 billion each year by supporting tourism, fishing, and protecting our coastlines by absorbing wave energy.
Unfortunately, coral reef health is in decline worldwide (read also the Break: The silent battle of young corals against ocean acidification). Reefs are currently challenged by a variety of threats ranging from local factors like pollution and overfishing to global-scale issues like climate change and ocean acidification. Ocean acidification threatens many marine organisms, particularly calcifiers like oysters, crabs, and corals - this is because changing seawater chemistry interferes with calcification, the process by which organisms build protective shells or skeletons. Coral reefs are widely regarded as one of the most vulnerable ecosystems to ocean acidification, in part because the very architecture of the ecosystem relies on calcifying organisms. Through calcification many corals build the spectacular, beautiful, and protective calcium carbonate skeletons that form reefs. Without coral calcification, there are no reefs, and without reefs, there is no food or shelter for the millions of associated species.
Much of the attention surrounding coral reefs and ocean acidification has focused on future implications - what does ocean acidification mean for the future of coral reefs? Will changing seawater chemistry cause reefs to stop growing altogether? These are important questions that are being addressed through ongoing laboratory and field studies. However, the chemistry of the oceans has already changed. Since the pre-industrial revolution (circa 1880), the oceans have absorbed ~25% of the extra carbon dioxide humans injected into the atmosphere, causing the acidity of the oceans to increase by ~30%. The motivating question for our study was to understand whether these changes in seawater chemistry that have already occurred are having measurable impacts on coral reefs - in other words, is ocean acidification already impairing coral reef growth?
To understand whether ocean acidification is already impairing coral reef growth, we restored the seawater chemistry of a natural coral reef to pre-industrial conditions. After effectively reversing ocean acidification we measured the effects this had on coral reef calcification. While studies have addressed this question in the laboratory using individual species or small groups of organisms, this was the first seawater chemistry manipulation experiment of a coral reef in the natural environment. As you might imagine, manipulating the chemistry of seawater flowing over a coral reef is not an easy task. This was an engineering scale problem that involved altering the chemistry of over 200 tons of seawater while accounting for dilution, hydrodynamics (flow and circulation), and many other factors. Understanding how to do this correctly took years! Using a 15,000 liter reservoir, we added sodium hydroxide, which lowers water acidity, to the seawater flowing over a coral reef, to restore seawater chemistry closer to pre-industrial conditions. After allowing this experimental seawater to flow over the reef for approximately one hour, we checked if temporarily reversing ocean acidification increased coral reef calcification. We repeated our experiment fifteen times over the course of several weeks.
We found that when seawater chemistry was restored closer to pre-industrial conditions, corals grew more quickly. These results provided the first strong evidence that ocean acidification is already slowing coral reef growth. This approach of manipulating seawater chemistry to mitigate ocean acidification has been indicated as a geoengineering technique to save coral reefs from global change. Our results suggest that, when implemented on small scales, this approach might temporarily increase reef calcification, thereby mitigating ocean acidification in the short-term. However, scaling this approach over long periods of time and over the geographic scales necessary is technically infeasible. The Great Barrier Reef, for example, extends over 2,000 km! The only long-term solution to mitigating ocean acidification and securing the health of coral reef ecosystems is to drastically cut carbon emissions. We hope our findings will draw attention to the issue that ocean acidification is not just a concern for the future, but that it's already impairing valuable marine ecosystems, emphasizing the need to act quickly and responsibly to preserve the future of coral reefs.
Albright R, Caldeira L, Hosfelt J et al. Reversal of ocean acidification enhances net coral reef calcification. Nature. 2016;531(7594):362-365. doi:10.1038/nature17155.
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Earthquakes 'contribute to global warming by releasing greenhouse gas from the ocean floor'
- Scientists find methane released into North Arabian Sea by 1945 earthquake
- More than seven million cubic metres of methane was released by quake
- Discovery shows natural source of greenhouse gas emissions, they claim
Earthquakes may contribute to global warming by releasing greenhouse gas from the ocean floor, a study suggests.
Scientists uncovered evidence that a large earthquake in 1945 released more than seven million cubic metres of methane into the North Arabian Sea.
The discovery exposes a natural source of greenhouse gas emissions that has not been considered before, they claim.
Scientists have found evidence that a 1945 earthquakes released more than seven million cubic metres of methane into the North Arabian Sea
As a greenhouse gas, methane is 20 times more potent than carbon dioxide, but less abundant in the atmosphere.
Enormous quantities of methane are locked in icy structures called hydrates on the floors of the continental shelves surrounding the Earth's land masses.
An estimated 1,000 to 5,000 gigatonnes of carbon is trapped in methane hydrates - more than the total amount released by burning fossil fuels each year.
Analysis of sediment cores taken from the North Arabian Sea in 2007 revealed chemical signs of large-scale methane release.
A search of historical records showed that a magnitude 8.1 earthquake had occurred nearby in 1945.
'Based on several indicators, we postulated that the earthquake led to a fracturing of the sediments, releasing the gas that had been trapped below,' said lead scientist Dr David Fischer, from the University of Bremen in Germany.
The study, published in Nature Geoscience, could show that earthquakes contribute to global warming
A conservative estimate indicated that roughly 7.4 million cubic metres of methane had escaped, said the researchers writing in the journal Nature Geoscience.
'There are probably even more sites in the area that had been affected by the earthquake,' Dr Fischer added.
Methane hydrates have been suggested as a promising energy source, but mining them is expensive and risky.
The hydrates help to stabilise the ocean floor, and there is a chance that disturbing them will trigger land slips and tsunamis.
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A U-shaped optical fiber sensing system designed to measure the refractive index of liquid had been
proposed. The sensing mechanism of U-shaped optical fiber was discussed. A general single-mode
fiber was bent into U-shaped and partially cladding of U-shaped fiber was corroded by HF acid buffer
solution. Powers of different diameters of U-shaped fibers had been measured by many experiments.
The results showed that the diameter of U-shaped fiber cladding 40 μm and the diameter of U-shaped
was 1 cm were suitable to measure liquid refractive index. Then, this U-shaped optical fiber was
immersed in liquid, such as pure water, ethanol, acetone and isopropanol, respectively. The evanescent
field of the U-shaped fiber should be modulated by the liquid. The optical signal in the U-shaped fiber
was measured with the optical spectrum analyzers(OSA). Finally, the experimental results were
analyzed, and the spectra in the air was selected as a reference. The relative intensity was obtained for
the different liquid. These results showed that the relative intensity of the liquid had a good linear
relationship. This sensing device could accurately demarcate refractive index of liquid. It is simple, low
cost, and it can also be applied in measuring the level of liquid. | <urn:uuid:3ccf6cc4-08e2-4aeb-983b-9c19ed60b048> | 3.078125 | 284 | Academic Writing | Science & Tech. | 33.453447 | 95,587,856 |
New ink Sampling Technique Taking a Bite of out Time
News Jul 18, 2007
Researchers at the Midwest Forensics Resource Center at Iowa State University are building a library of ink profiles to help forensic scientists identify inks on fraudulent documents and other evidence.
MFRC scientists will pair mass spectrometry with a new sampling technique called Direct Analysis in Real Time (DART) to reveal the chemical makeup of ink faster and in greater detail than ever before.
DART mass spectrometry analyzes ink by creating a stream of warm gas containing excited-state helium atoms or nitrogen molecules in the DART source. The gas stream is pointed at an ink sample, and the gas and excited-state species evaporate and ionize molecules from the sample. A mass spectrometer measures the production of ions to create mass spectrum data for each ink sample tested.
In contrast to other types of ink analysis, like liquid chromatography, which require cutting a small sample from a questioned document, DART mass spectrometry is able to test documents without physically or visually altering them. The questioned document is open to the environment, and all sizes of materials may be tested in their original form.
According to Roger Jones, U.S Department of Energy’s Ames Laboratory associate chemist, “The great thing about the DART system is that it can sample the ink straight off the paper. You don’t have to extract a sample first. Before DART, we had to cut a little bit of sample out and dissolve it in solvent for analysis. So, now we can look at the document without visibly altering it, which is good for forensic science. We don’t destroy the evidence.”
Eliminating the sampling extraction process saves busy forensic scientists time. Jones said that benefit alone would have been enough to consider the DART method a success.
“We would have been satisfied with the mass spectra looking basically like the spectra obtained by the old extraction mass spectrometry methods, because the DART system still gets around damaging the sample and reduces the work involved in analysis,” said Jones, “Time constraints are the major complaint of every forensic scientist. Their caseloads are so large that they just don’t have the time to do traditional ink analysis.”
But, on top of saving time and preserving evidence, the DART method also yields rich data about ink samples than previous sampling methods. Initial tests of the DART system indicate that the mass spectra reveal more components of the ink than conventional mass spectra. Using DART, forensic scientists may be able to differentiate between inks like never before.
Jones and John McClelland, Ames Laboratory senior physicist and DART project leader, plan a three-phase project. Currently in the first phase, they are experimenting to determine the best way to analyze inks and build the library.
The library of ink mass spectra will be produced in the second phase of the project. Researchers will use samples from the U.S. Secret Service International Ink Library to create a comprehensive, vetted, and computer searchable library of mass spectra of the more than 8,000 inks the Secret Service has compiled.
The third phase of the project will focus on creating computer software used to store and access the mass spectra library.
“Commercial mass spectrometry software available today is all based on the old style of mass spectrometry. We get a different type of data from DART. So, the assumptions used in existing software for searching and matching mass spectra do not work the best for DART,” said Jones.
Deep-Sea Conditions Impact Oil DegradationNews
Degradation rates of oil were slower in the dark and cold waters of the depths of the Gulf of Mexico than at surface conditions, according to an international team of geoscientists trying to understand where the oil went during the Deepwater Horizon oil spill.READ MORE
Lake gives Clues to Earth's Ancient AtmosphereNews
A sample of ancient oxygen, teased out of a 1.4 billion-year-old evaporative lake deposit in Ontario, provides fresh evidence of what the Earth’s atmosphere and biosphere were like during the interval leading up to the emergence of animal life.READ MORE | <urn:uuid:76b2d149-d2bf-403d-8766-6862a1d3091f> | 2.875 | 879 | News Article | Science & Tech. | 38.287644 | 95,587,857 |
Washington-based Agni Energy, spearheaded by 25-year-old Demitri Hopkins, says its ‘beam-target’ blueprint will focus and control the elements required to achieve nuclear fusion more efficiently than previous designs – with a company spokesman hailing it as “a paradigm shift in power”.
The Sun, like other stars, is a natural fusion reactor, and efforts to replicate the processes which drive it have been ongoing for decades, with nuclear fusion long regarded as the “Holy Grail of energy production”.
Such reactors would involve the fusing together of two lighter atomic nuclei to form a heavier nucleus, releasing energy in the process.
Unlike nuclear fission, which is the method by which energy is generated by conventional nuclear power stations, fusion produces little nuclear waste, and releases three to four times more energy.
Agni’s plans attempt to incorporate the best elements from previous ideas by utilising a method by which a beam of ions is focused on to a solid fuel target using both electric fields and magnetic fields.
The design means that the ion beam has a short path to its target and does not need to be controlled for long before fusion happens.
The energy released can then be used to generate electrical power.
Agni’s spokesman said: “AGNI is expected to achieve 16 million times the efficiency of coal, 10 times the efficiency of nuclear fission, produce no waste and zero emissions.”
If ultimately successful, Agni’s method would be a massive breakthrough which could render conventional nuclear power stations and fossil fuels obsolete.
However, plenty of others have hailed breakthroughs in the past which have come to nothing.
In 1989, US scientists Martin Fleischmann and Stanley Pons claimed to have developed a way of generating nuclear fusion at room temperature, a process they referred to as “cold fusion”.
However, they were unable to replicate their findings, with the American Physical Society eventually concluding that it was an example of “pathological science”, whereby people are tricked into false results by subjective effects.
Nevertheless, the race to build a fusion reactor is hotting up, with numerous companies now devoting resources towards developing a successful method.
Experts predict it will become a reality within 30 years – and much quicker than that if Agni’s efforts prove successful. | <urn:uuid:de5ec684-927e-447c-a485-d1b0f4629658> | 3.15625 | 487 | News Article | Science & Tech. | 28.582381 | 95,587,863 |
+44 1803 865913
By: JE Simpson
240 pages, Illus
The sea breeze affects our lives in many ways; it controls our local weather, not only on the coast but also in many districts inland. Air pollution and smog, also the distribution of airborne insect pests and the spread of pollen are all controlled by the sea breeze. In the world of sport it is important to glider pilots, sailors and surfers, and balloonists. In the book we see how radar, lidar and satellite photography have helped to forecast and map sea breezes and the all-important 'sea-breeze front'. The book ends with a description of laboratory experiments mostly carried out by the author and his co-workers, and a simple summary of theoretical models.
The book will be welcomed by those researching in the subject but will also be valuable to the general reader who is interested in local weather and the natural environment.
'Simpson's crisp written style and unparalleled knowledge of all aspects of sea breezes enables us to see the atmosphere with new eyes.' New Scientist 'The book is very well finished. Its coverage, written style and good use of illustrative material make it appealing to both the non-specialist meteorologist and the lay reader.' Quarterly Journal of the Royal Meteorological Society 'The book has no competitors. It may be recommended to both the general reader and the professional meteorologist with an interest in, or problem related to, sea breeze.' Deborah J. Abbs, World Meteorological Organization Bulletin
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Authors: Pawan Kumar Bishwakarma
A regular polygon is a planar geometrical structure with all sides of equal length and all angles of equal magnitude. The ratio of perimeter of any regular polygon to the length of its longest diagonal is a constant term and the ratio converges to the value of as the number of sides of the polygon increases. The result has been shown to be valid by actually calculating the ratio for each polygon by using corresponding formula and geometrical reasoning. A computational calculation of the ratio has also been presented to validate the convergence. The values have been calculated up to 30 significant digits.
Comments: 16 Pages.
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[v2] 2018-01-06 02:31:12
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2018 Watershed Report CardMar 23, 2018
- 2018 Watershed Report Card
A Watershed Report Card for the region, released today by the North Bay-Mattawa Conservation Authority, tells us that overall, we're in good shape with room for improvement in a few subwatersheds. (View here)
While grades varied throughout the 20 subwatersheds that fall within NBMCA's jurisdiction, overall groundwater quality, stream water quality and forest conditions scored an "A". Wetland cover ranked a "B" and lake quality ranked a "B+".
"Overall the watershed is in good shape based on the data currently available. These key environmental indicators are helping NBMCA and our partners target our watershed management programs, focus and refine our monitoring efforts, and measure environmental change," said Brian Tayler, NBMCA's CAO.
The scores were calculated in each category based on guidelines produced, reviewed and updated every five years by a committee comprised of Ontario's conservation authorities, Conservation Ontario and some provincial representatives from the Ministry of the Environment and Climate Change.
Nitrate, nitrite and chloride concentrations were measured at least twice in wells located in four subwatersheds to determine the groundwater grade. Very low concentrations, indicative of high water quality, were measured at all the wells.
Water quality grades in streams were based on total phosphorus (TP) concentration measured regularly at one or more sites in 10 subwatersheds. The overall grade of "A" represents a weighted average. While five of the measured subwatersheds were good or excellent, four scored a "C".
Phosphorus levels in 11 area lakes were good or excellent with the exception of Wasi Lake where phosphorus levels resulted in a "Fair" ranking.
Improved accuracy in data and mapping provided a more accurate measurement of wetlands and forest conditions for the 2018 report card, resulting in a number of subwatershed grade improvements.
NBMCA's watershed scored an "A" in forest conditions, with 84 per cent of the land covered in forest.
The grades typically decline around urban areas because of reduced natural vegetation and increased paved surfaces.
There are 27 000 hectares of wetlands within our watershed area, covering about 10% of the land. Wetland area in the subwatersheds range from a high of 36% in Jessups Creek subwatershed to a low of 5% in the Mattawa River subwatershed. High forest cover generally accounts for the subwatersheds with lower wetland cover scores.
To learn more about the ecosystem health of the North Bay-Mattawa watershed and what individuals can do to help improve grades, the report card can be viewed here
For more information about Conservation Ontario's watershed check-up initiative and the health of watersheds throughout the province, visit www.watershedcheckup.ca. | <urn:uuid:771a3a25-4d0d-4bfe-9ac3-0b8bc8050d14> | 2.90625 | 578 | News (Org.) | Science & Tech. | 26.87102 | 95,587,883 |
This page uses content from Wikipedia and is licensed under CC BY-SA.
An endolith is an organism (archaeon, bacterium, fungus, lichen, algae or amoeba) that lives inside rock, coral, animal shells, or in the pores between mineral grains of a rock. Many are extremophiles, living in places previously thought inhospitable to life. They are of particular interest to astrobiologists, who theorize that endolithic environments on Mars and other planets constitute potential refugia for extraterrestrial microbial communities.
The term "endolith", which defines an organism that colonizes the interior of any kind of rock, has been further classified into three subclasses:
Endoliths have been found in rock down to a depth of 3 kilometres (1.9 mi), though it is unknown if that is their limit (due to the cost involved in digging so deep). The main threat to their survival seems not to result from the pressure at such depth, but from the increased temperature. Judging from hyperthermophile organisms, the temperature limit is at about 120 °C (Strain 121 can reproduce at 121 °C), which limits the possible depth to 4-4.5 km below the continental crust, and 7 or 7.5 km below the ocean floor. Endolithic organisms have also been found in surface rocks in regions of low humidity (hypolith) and low temperature (psychrophile), including the Dry Valleys and permafrost of Antarctica, the Alps, and the Rocky Mountains.
Endoliths can survive by feeding on traces of iron, potassium, or sulfur. (See lithotroph.) Whether they metabolize these directly from the surrounding rock, or rather excrete an acid to dissolve them first, remains to be seen. The Ocean Drilling Program found microscopic trails in basalt from the Atlantic, Indian, and Pacific oceans that contain DNA. Photosynthetic endoliths have also been discovered.
As water and nutrients are rather sparse in the environment of the endolith, they have a very slow reproduction cycle. Early data suggests that some only engage in cell division once every hundred years. In August 2013 researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old and reproducing only once every 10,000 years. Most of their energy is spent repairing cell damage caused by cosmic rays or racemization, and very little is available for reproduction or growth. It is thought that they weather long ice ages in this fashion, emerging when the temperature in the area warms.
As most endoliths are autotrophs, they can generate organic compounds essential for their survival on their own from inorganic matter. Some endoliths have specialized in feeding on their autotroph relatives. The micro-biotope where these different endolithic species live together has been called a Subsurface Lithotrophic Microbial Ecosystem (SLiME).
Only limited research has been done concerning the distribution of marine endolithic fungi and its diversity even though there is a probability that endolithic fungi could perhaps play an important role in the health of coral reefs.
Endolithic fungi have been discovered in shells as early as the year 1889 by Edouard Bornet and Charles Flahault. These two French phycologists specifically provided descriptions for two fungi: Ostracoblabe implexis and Lithopythium gangliiforme. Discovery of endolithic fungi, such as Dodgella priscus and Conchyliastrum, has also been made in the beach sand of Australia by George Zembrowski. Findings have also been made in coral reefs and have been found to be, at times, beneficial to their coral hosts.
In the wake of worldwide coral bleaching, studies have suggested that the endolithic algae located in the skeleton of the coral may be aiding the survival of coral species by providing an alternative source of energy. Although the role that endolithic Fungi play is important in coral reefs, it is often overlooked because much research is focused on the effects of coral bleaching as well as the relationships between coelenterate and endosymbiotic symbiodinia.
According to a study done by Astrid Gunther endoliths were also found in the island of Cozumel (Mexico). The endoliths found there not only included algae and fungi but also included cyanobacteria, sponges as well as many other microborers.
Until the 1990s phototrophic endoliths were thought as somewhat benign but since then evidence has surfaced that phototrophic endoliths (primarily cyanobacteria) have infested 50 to 80% of midshore populations of the mussel species Perna perna located in South Africa.The infestation of Phototrophic endoliths resulted in lethal and sub-lethal effects such as the decrease in strength of the mussel shells. Although the rate of thickening of the shells were faster in more infested areas it is not rapid enough to combat the degradation of the mussel shells.
Evidence of endolithic fungi were discovered within dinosaur eggshell found in central China. They were characterized as being “needle-like, ribbon-like, and silk-like."
Fungus is seldom fossilized and even when it is preserved it can be difficult to distinguish endolithic hyphae from endolithic cyanobacteria and algae. Endolithic microbes can, however, be distinguished based on their distribution, ecology, and morphology. According to a 2008 study, the endolithic fungi that formed on the eggshells would have resulted in the abnormal incubation of the eggs and may have contributed to the mass extinction of these dinosaurs. It may also have led to the preservation of dinosaur eggs, including some that contained embryos. | <urn:uuid:d58c710a-d0d4-410a-ade8-c71e71ccae67> | 4.34375 | 1,185 | Knowledge Article | Science & Tech. | 29.056897 | 95,587,904 |
Windows and solar panels in the future could be made from one of the best - and cheapest - construction materials known: wood. Researchers have developed a new transparent wood material that's suitable for mass production.
Over millennia, bacteria have evolved a variety of specialized mechanisms to move themselves through their particular environments. In two recent studies researchers used a state-of-the-art imaging technique to capture, for the first time, three-dimensional views of this tiny complicated machinery in bacteria.
High-tech metal alloys are widely used in important materials such as the cladding that protects the fuel inside a nuclear reactor. But even the best alloys degrade over time. Now, researchers has found a way of greatly reducing the damaging effects these metals suffer from exposure to hydrogen.
The worries that even nanotechnology proponents had in the early 2000s about possible health and environmental risks - and their impact on investor and consumer confidence - seem to have evaporated. So what's changed?
Researchers have found that quantum effects are the reason that hydrogen sulphide - which has the distinct smell of rotten eggs- behaves as a superconductor at record-breaking temperatures, which may aid in the search for room temperature superconductors.
Researchers have developed a piezo-optomechanical circuit that converts signals among optical, acoustic and radio waves. A system based on this design could move and store information in next-generation computers.
Researchers have shown that a law of physics having to do with electron transport at nanoscale can also be analogously applied to the ion transport. This discovery provides insight into a key aspect of how ion channels function within our living cells. | <urn:uuid:979c3676-e215-4326-84ad-2ab65df00d9e> | 2.65625 | 333 | Content Listing | Science & Tech. | 28.576569 | 95,587,919 |
Researchers have identified some of the underlying physics that may explain how insects can so quickly recover from a stall in midflight -- unlike conventional fixed wing aircraft, where a stalled state often leads to a crash landing.
The left image represents a non-rotating wing in the presence of incident flow; it exhibits a stalled state. The right image, taken shortly after the onset of rotation (at 36 degrees), shows a stable, lift-generating flow structure.
Credit: Matthew Bross
The analysis, in which the researchers studied the flow around a rotating model wing, improves the understanding of how insects fly and informs the design of small flying robots built for intelligence gathering, surveillance, search-and-rescue, and other purposes. The work is described in the journal Physics of Fluids.
An insect such as a fruit fly hovers in the air by flapping its wings -- a complex motion akin to the freestyle stroke in swimming. The wing rotates in a single plane, and by varying the angle between the plane and its body, the insect can fly forward from a hovering position.
To simulate the basics of this action, Matthew Bross and colleagues at Lehigh University in Bethlehem, PA, studied how water flows around a rotating model wing consisting of a rectangular piece of acrylic that is twice as long as it is wide. The rotation axis is off to the side of the wing and parallel to its width, so that it rotates like half of an airplane propeller. To simulate forward motion -- a scenario in which the insect is accelerating or climbing -- the researchers pumped water in the direction perpendicular to the plane of rotation.
"We were able to identify the development of flow structure over an insect-scaled wing over a range of forward flight velocities," Bross explained. The researchers made detailed three-dimensional computer visualizations of the flow around the wing, finding that a leading-edge vortex -- a feature crucial for providing lift -- almost immediately appears once the wing starts to rotate after a stalled state.
The article, "Flow structure on a rotating wing: effect of steady incident flow," by Matthew Bross, Cem Alper Ozen and Donald Rockwell appears in the journal Physics of Fluids. See: http://dx.doi.org/10.1063/1.4816632
ABOUT THE JOURNAL
Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex or multiphase fluids. See: http://pof.aip.org
Jason Socrates Bardi | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | 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...
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17.07.2018 | Power and Electrical Engineering | <urn:uuid:78fc0477-f33d-4828-86a5-e52333ad58a0> | 3.71875 | 1,175 | Content Listing | Science & Tech. | 42.070844 | 95,587,934 |
May 05, 2017 AM EDT One doesn't necessarily need to know where Eta Aquarii is, meteors leave a persistent trail which all point back to Eta Aquarii's direction.
Apr 07, 2017 AM EDT The Earth-like planter, GJ 1132b was discovered using the GROND imager telescope at the European Southern Observatory in Chile.
Dec 23, 2016 AM EST A planet-eating star has been found 300 light years away.
Dec 20, 2016 AM EST NASA has released a video showing how carbon dioxide spreads on the Earth's atmosphere.
Jan 20, 2014 AM EST The bacteria found in mud along the banks of a remote salt lake near Yosemite National Park, breathe toxic metal like antimony and arsenic instead of oxygen, according to a University of Georgia ...
Dec 07, 2013 AM EST Rising ocean acidification is threatening the survival of copepods, the tiny crustaceans, according to an expedition to the Arctic, which was a part of the Catlin Arctic Survey.
Oct 08, 2013 AM EDT In attempt to determine the conditions that give rise to clouds in the Red Planet’s atmosphere, researchers at Massachusetts Institute of Technology (MIT) established Mars-like conditions within a ...
Jun 23, 2018 AM EDTWhat if you can control robots with a simple flick of a finger? A team of experts is trying to make that a reality through this latest experiment.
Jun 16, 2018 AM EDTScientists from the Boston University School of Medicine looked into the effects of flavored e-cigarettes to the lining of blood vessels. Here are ...
May 31, 2018 AM EDTLendingTree outs its study that identifies places in the United States with the most student debt. Here's the complete list. | <urn:uuid:2d1030e0-a79c-41e4-83d7-079bbfa1f31a> | 2.75 | 357 | Content Listing | Science & Tech. | 59.770263 | 95,587,937 |
Scientists from the Lomonosov Moscow State University have studied DNA packaging methods in the cell nucleus
Scientists from the Lomonosov Moscow State University in collaboration with their colleagues from the USA have conducted a research on DNA packaging in the cell nucleus and its alteration in the process of DNA replication. DNA packaging is supposed to have strong influence on genes' activity. It's also one of the mechanisms of epigenetic control of gene expression.
Igor Kireev, Doctor of Biological Sciences, who is the Chief of Department of electron microscopy at the Belozersky Institute of Physico-Chemical Biology and one of the article authors, says: "Although all the cells in a given organism possesse similar genetic information, not all genes operate in a particular cell type. In fact, the set of active genes determines the cell fate. There are some cellular mechanisms assisting the cell to remember, which genes should be activated and which should not. This is the epigenetic control or, in other words, cell memory, that determines what the cell is and due to which genes it has been formed in such a way. We were interested in so called high levels of chromosome structural organization, which are formed through a series of consecutive phases in DNA packaging."
DNA exists in a cell as a complex of proteins -- chromatin. Initial stages of chromatin compaction are studied quite well. These are nucleosomes, protein globules, each is around 10 nanometers long and consisting of 8 histone protein molecules, around which DNA is wrapped. Then a chain of nucleosomes is packed in a way that we don't know yet, resulting in thicker fibrils and chromonemata. At the end we get a very high degree of compaction. So, the length of a most densely compacted mitotic chromosome is 20 000 times smaller than the length of DNA, which is packed inside it.
Replication is the process of copying DNA molecule and transcription is the process of RNA synthesis, both using DNA as a template. It was traditionally assumed high compaction of DNA in chromatin to be a hindrance for these template-based synthesis processes and should be disassembled on a scale of quite large chromatin domains. It was fairly difficult to identify these domains and analyze their structural organization at high spatial resolution without disturbing their natural structure.
Igor Kireev comments: "We've offered a method of labeling chromatin domains based on differences in replication timing of active and inactive gene loci. While actively transcribed chromosome regions - so called euchromatin - replicate at the very beginning of synthetic phase of cell cycle, inactive "silent" heterochromatin replicates during its second half. Our technique has allowed to perform nondestructive detection of these two fractions of chromatin at electron microscopy level. It's based on combination of new-synthesized DNA labeling using click-chemistry methods with subsequent detection of reaction products by correlative siperresolution optical microscopy and immunoelectron microscopy. In other words, we can see one and the same molecule in this cell both in optical and electron microscopes."
Application of this approach has given two surprising observations. First of all, "working" chromatin, contrary to traditional ideas, maintains quite high level of packaging, as it's represented by highly structured chromatin fibrils of lhigher order - chromonemata. Secondly, it's turned out that DNA in chromonema structure possesses high degree of structural flexibility, what means that it's able to sort of flow from one section of chromonema fiber to the neighboring one. However, the general dense structure of chromonema doesn't change. These observations don't fit the existing theories of chromosome spatial organization, however, at the same time allow to offer new hypotheses concerning mechanisms of epigenetic information transfer in the process of cell division.
Igor Kireev continues: "We've made an assumption, that newly-synthetized DNA in chromatin structures isn't fixed but could move inside them, interacting with that DNAsegments, which hasn't doubled yet and "remembers everything". Moreover, this DNA contains necessary molecular components for recovery of lost epigenetic information".
Another result, mentioned in the article, which has been published in Current Biology, lies in the fact that genome structural organization doesn't have strict hierarchy. There are, of course, some gradual levels of DNA organization. It was thought earlier that there should be a strictly ordered system, which uniquely leads to chromosome formation. But now it's turned out that everything could be organized in a different way - there are some building principles, but within specified chromatin frameworks DNA has some freedom and flexibility.
Igor Kireev shares future plans: "Further research development includes, first of all, transition to analysis of individual chromosome loci. We are going to label them both on optical and electron microscopic levels with the help of TALE technology. And, secondly, further research will tackle with elaboration of even more native methods of in vivo labeling, which are compatible with such advanced technologies, as cryo-electron microscopy".
Scientists hope to approach closely to DNA spatial organization, applying direct methods of visualization of chromatin packaging ways with high resolution. As far as practical part is concerned, the researches will help to clarify structural aspects of epigenetic control of gene expression and, probably, offer some ways of its regulation. This will contribute to elaboration of more effective approaches to therapeutic intervention, for instance, to fight cancer or ageing, where epigenetic component plays an important role.
Vladimir Koryagin | EurekAlert!
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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100 amps of electricity crackle in a vacuum chamber, creating a
spark that transforms carbon vapor into tiny structures. Depending
on the conditions, these structures can be shaped like little,
60-atom soccer balls, or like rolled-up tubes of atoms, arranged
in a chicken-wire pattern, with rounded ends. These tiny, carbon
nanotubes, discovered by Sumio Iijima at NEC labs in 1991, have
amazing properties. They are 100 times stronger than steel, but
weigh only one-sixth as much. They are incredibly resilient
under physical stress; even when kinked to a 120-degree angle,
they will bounce back to their original form, undamaged. And
they can carry electrical current at levels that would vaporize
ordinary copper wires.
Learn more about carbon nanotubes from the many resources on this site, listed below. More information on Carbon nanotubes can be found here.
how to combine the negative capacitance model with the carbon nano tube transistor model in verilog a file?
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Is there an analytical model for cnt based organic solar cells?
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I looking for any information about chirality of Double-wall Nanotube?
I looking for any information about chirality of Double Wall CNT?
Cap interaction between 2 nanotubes facing each other
Closed | Responses: 1
Is it possible to use nanomaterials simulation tool kit to compute the potential energy minima between the two capped nanotube facing each other?
Does the mechanical properties of carbon nanotubes depend on length
How we can use CNT as a channel in FETs?.
What is the difference b/w nano particles and nano objects?
how to compute the potential relief of DWNT
which tool is to be used if i want to compute the potential relief of an double wall nanotube? whats the difference between molecular dynamics simulation and ab initio calculation.
Is it possible to do some simulation with boron nitride nanotube? I just saw with CNT but looking with BNNT
How to simulate carbon nanotubes for single and multi walled for thermal conductivity
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is there any tool to simulate the thermal conductivity for single walled and multiwalled carbon nanotubes
Carbon nanotube structure model?
Dear fellow members, is there a carbon nanotube model here of a few nanometers I could get in either XYZ or preferably PDB file, minimized?
how to obtain http proxy:port to launch carbon nanotube interconnect analyser
multiple tube CNFET
Sir I am wishing to design multiple tube CNFET, but I cann’t choose the tool suitable for it. Please inform me which should be preferred
The electrical field from the gate of CNFET can not affect the transistor.
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I tried to fabricate the Carbon nanotube field effect transistor (CNFET) for around half a year, however, none of them is working till now. The main problem was the source to... | <urn:uuid:400a1277-33c8-47a4-804f-89e66509346f> | 3.40625 | 704 | Q&A Forum | Science & Tech. | 39.815968 | 95,587,950 |
Enjoy some of the extensive magazine, newspaper and web-based coverage of our work through the years.
Enjoy a sampling of print media featuring Dr. Nichols' efforts collected on ISSU.
The eastern section of the spiraling mass, between Hawaii and California, is estimated to be around twice the size of Texas (some estimates peg the entire mass at twice the size of the continental United States), and is having ecosystem-wide impacts, according to a recent studypublished in Biology Letters.
Miriam Goldstein, a graduate student researcher at Scripps Institution of Oceanography at the University of California, San Diego, and the lead author of the study, told Truthout that by adding this amount of plastic to the oceans, humans could be causing large-scale change to the ocean’s ecological system.
“We found eggs on the pieces of plastic, and these were sea skater [insect] eggs,” Goldstein said. “Sea skaters naturally occur in the gyre and are known to lay their eggs on floating objects. So we found that the amount of eggs being laid had increased with the amount of plastic.”
Goldstein says that, although the study’s findings clearly raise immediate concerns, the most serious consequences may be ones we can’t yet foresee. “Our work shows there could be potential effects to the ocean ecosystem that we can’t expect or predict,” she said. “There are five subtropical gyres, one in each ocean basin, and they are natural currents. They are vast areas of the oceans; together they comprise the majority of the area of the oceans. So altering them on a large scale could have unexpected results on all kinds of things.”
The study shows how an increase in pollution, in this case an immense amount of plastic, may have dire consequences for animals across the entire marine food web.
This Scripps study follows a report by colleagues at the institution that showed that 9 percent of the fish collected during the trip to study the gyre had plastic waste in their stomachs.
Published in Marine Ecology Progress Series, that study estimated that fish at intermediate ocean depths in the North Pacific Ocean could be ingesting plastic at the staggering rate of 12,000 to 24,000 tons per year.
Dr. Wallace J. Nichols, a research associate at the California Academy of Sciences, told Truthout he finds plastic on every beach he visits across the globe, and added, “Probably every sea turtle on the planet interacts with plastic at some point in its life.”
Jo Royle, a UK-based trans-ocean skipper and ocean advocate, has seen the same.
“For 13 years I’ve been crossing oceans,” she told Truthout. “I’ve seen plastic on the coastline of Antarctica, and over the years we’ve noticed plastic becoming more of an issue on remote islands. Over the last seven years we’ve seen it increase dramatically. I can’t remember the last time I’ve been on a beach and not seen plastic.”
Biological oceanographer Dr. Debora Iglesias-Rodriguez, with the National Oceanography Centre at Britain’s University of Southampton, is concerned that ocean pollution isn’t viewed as a pressing issue – despite the fact that it is accelerating.
“Marine pollution is a big issue,” she told Truthout. “There is this idea that oceans have unlimited inertia, but nanoparticles of plastic getting into marine animals and the food chain are affecting fish fertility rates, and this affects food security and coastal populations. Pollution is having a huge impact on the oceans, and is urgent and needs to be dealt with.”
Nichols concurs, adding that, when it comes to the oceans, we are now seeing the cautionary predictions of previous decades coming true.
“From a climate change/fisheries/pollution/habitat destruction point of view, our nightmare is here; it’s the world we live in,” Nichols said. “You see evidence of the impact of climate change on the oceans everywhere now. The collapsing fisheries, the changes in the Arctic and the hardship communities that live there are having to face, the frequency and intensity of storms – everything we imagined 30 to 40 years ago when the environmental movement was born, we’re dealing with those now…. The toxins in our bodies, food web, and in the marine mammals, it’s all there.”
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