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Some people know it as the aurora borealis but they form because electrons congregate towards the northern most portion of the earth.
Why? Because the earth spins and pushes the electrons out. Think about putting your finger in a bucket of water and some sand particles and swirling it. The sand will go towards the outer portion of the bucket, right? Of course the sand doesn’t come towards your finger..
So there are a bunch of electrons up there and the sun hits them, transfers energy, and now the electrons are excited. They get excited and jump energy levels, but they don’t stay excited forever. What goes up must come down! So when they come down to lower energy levels they release energy in the form of light!
Which is what we see and call the “Northern Lights!”
If you didn’t know.. Now you do 🙂 | <urn:uuid:f548937a-a448-4d45-8144-3735400ac312> | 3.140625 | 182 | Personal Blog | Science & Tech. | 72.63473 | 95,583,943 |
In a paper published in PLoS ONE, scientists at the University of Illinois released their findings on what microscopy techniques are needed to identify the shape and texture of pollen grains. Understanding pollen morphology is important to classifying ancient vegetation.
Because pollen morphologies often align quite closely to taxonomic groupings, understanding the appearance of ancient pollen allows scientists to better understand prehistoric flora in the context of modern-day ancestors.
The team's research, led by Surangi Punyasena and Mayandi Sivaguru of the Institute for Genomic Biology, focused on comparing how several reflected and transmitted light microscopy techniques image individual pollen grains. By choosing three pollen samples of diverse grain size and texture, they were better able to understand how each technique functions in different situations.
"The accuracy and consistency of pollen analysis relies on our ability to see as much morphology as possible," explains Punyasena. "Images like those produced by this research are the foundation of my lab's quantitative morphological work - work that we hope will allow us to break through the many taxonomic limitations of pollen identification in the very near future."
"The results of this paper have encouraged us to revisit some longstanding classification problems in vegetation science," says Luke Mander, co-author. "For example, there are around 11,000 species of grass on the planet today, but these species produce pollen that looks extraordinarily similar. This means that it is extremely difficult to use fossil pollen grains to reconstruct the diversification history and evolution of this major plant group. Advances in imaging technology, such as the super-resolution technique used in our paper, allow us to image morphological features less than 200 nanometers in size using light."
"In the future, we hope these morphological features might be used to study the diversity and composition of ancient grasslands," he adds.
The team found that no reflected or transmitted light technique provided a completely adequate image. While reflected light techniques capture pollen shape effectively, they remain unable to resolve fine surface textures. Transmitted light techniques, however, are able to resolve even extremely fine textures, but give poor idea of grain shape.
They conclude that to construct an accurate image through conventional microscopy techniques, it is best to use a combination of both transmitted and reflected light imaging.
"Most pollen analysis is currently completed using transmitted light. This paper demonstrates how much more can be seen - and consequently analyzed - with alternative imaging techniques. This paper provides a much needed comparison of the capabilities of existing technologies that should be incorporated into mainstream pollen analysis," says Punyasena.
"Some of the most exciting results of this work are the images that were produced using super-resolution structured illumination (SR-SIM). There is little existing research on the use of SR-SIM with auto-fluorescent material like pollen," she adds. "Our demonstration of its ability to capture morphology below the diffraction limit of light strongly suggests that SR-SIM is a viable alternative to electron microscopy (EM) and may represent the future of pollen analysis."
This project was funded in large part by National Science Foundation's program Innovations in Biological Imaging and Visualization.
The full article can be found at http://dx.plos.org/10.1371/journal.pone.0039129.
"Capturing the Surface Texture and Shape of Pollen: A Comparison of Microscopy Techniques," Mayandi Sivaguru, Luke Mander, Glenn Fried, Surangi W. Punyasena
Nicholas Vasi | 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
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17.07.2018 | Power and Electrical Engineering | <urn:uuid:6eac5c1c-c344-46c2-81b1-5dcabceb2054> | 4.3125 | 1,386 | Content Listing | Science & Tech. | 29.985534 | 95,583,946 |
To report an invasive species, go to the Midwest Invasive Species Information Network website and click on "Report Sightings" in the green toolbar at the top, or click on the green leaf in the center of the homepage. You will then be asked to register or log in prior to reporting your sighting.
Six invasive species newer to Michigan are:
- Spotted wing Drosophila
- Brown marmorated stink bug
- Multi-colored Asian lady beetle
- Garlic mustard
- Emerald ash borer
- Hemlock woolly adelgid
Read information about exotic plant pests with the highest potential to enter Michigan and view maps forecasting invasion risks. | <urn:uuid:3bf3a821-b45c-4579-9812-cb71b515d91a> | 2.59375 | 137 | Knowledge Article | Science & Tech. | 23.794545 | 95,583,952 |
Protozoa are a type of eukaryotic and unicellular microorganism. Originally protozoa were thought to be very similar to plant-like protists, but this classification changed when it was discovered that protozoa maintain animal-like characteristics such as movement.
Although protozoa possess animal-like characteristics, they are not animals. They are tiny microbes which are remarkably diverse. For example, protozoa are found in virtually all environments such as in peat bogs, deep sea vents and arid deserts.
There are four main subgroups of protozoa and these subgroup classifications are based on how these protozoa move:
- Ciliates – move using cilia
- Flagellates – move using flagella
- Amoeboids – move using false feet
- Sporozoans – have no structures for movement
Since protozoa are eukaryotic organisms, they contain vacuoles, a cell membrane and all the other cellular machinery found in the cells of plants, fungi, animals and other eukaryotes. For example, protozoa use their cell membrane and vacuoles for food absorption and digestion. Their cell membranes assist in the engulfing of food and their vacuoles can give off useable nitrogen during digestion. Generally, protozoa feed on other organic matter, bacteria, fungi and other protozoans in some cases.
Protozoa are not a huge concern when it comes to human illnesses because they are usually harmless. With this being said however, protozoa are the cause of malaria and dysentery. Malaria is a disease transmitted by mosquitoes, but these infected mosquitoes carry a microorganism from the genus Plasmodium, in which five specific species are infectious.
Protozoa are truly remarkable microorganisms. They are capable of reproducing by the process of fission, they can move in a variety of ways despite having no skeletal system and take in oxygen through their cell membrane. They are single-celled, tiny organisms and so are in no way complex like organisms with a brain. However, they are another type of interesting life form living among us.© BrainMass Inc. brainmass.com July 18, 2018, 12:45 pm ad1c9bdddf | <urn:uuid:1b560aea-fcef-45df-bb6e-3ca345301504> | 3.890625 | 476 | Knowledge Article | Science & Tech. | 24.805195 | 95,583,957 |
Describe the roles of weathering in different climates. Considering the various processes involved in mechanical and chemical weathering, what are some of the factors that influence or control the weathering of earth materials? Also, which of these factors would be most important and why.© BrainMass Inc. brainmass.com July 18, 2018, 12:45 pm ad1c9bdddf
1. Describe the roles of weathering in different climates.
Weathering is the breakdown and alteration of rocks and minerals at or near the Earth's surface into products that are more in equilibrium with the conditions found in this environment. Climate plays a role in the amount and type of weathering through solar radiation from the sun, water and temperature and wind. Most rocks and minerals are formed deep within the Earth's crust where temperatures and pressures differ greatly from the surface. Because the physical and chemical nature of materials formed in the Earth's interior are characteristically in disequilibrium with conditions occurring on the surface. Because of this disequilbrium, these materials are easily attacked, decomposed, and eroded by various chemical and physical surface processes, which vary by climate type (sun radiation, water, temperature and wind). (http://www.physicalgeography.net/fundamentals/10r.html)
Weathering is one aspect that plays a role in the geomorphic and biogeochemical processes. For example, the products of weathering are a major source of sediments for erosion and deposition in all climates, although differentially. Many types of sedimentary rocks are composed of particles that have been weathered, eroded, transported, and terminally deposited in basins. Another role of weathering is that it contributes to the formation of soil by providing mineral particles like sand, silt, and clay. Elements and compounds extracted from the rocks and minerals by weathering processes supply nutrients for plant uptake. The fact that the oceans are saline in the result of the release of ion salts from rock and minerals on the continents. Leaching and runoff transport these ions from land to the ocean basins where they accumulate in seawater. In conclusion, weathering is a process that plays a role and is fundamental to many other aspects of the hydrosphere, lithosphere, and biosphere. (http://www.physicalgeography.net/fundamentals/10r.html)
The rate of weathering is influenced by as aspects of the CLIMATE:
o Rate of water percolation
o Oxidation status of the weathering zone
Therefore, the type and amount of weathering is dependent on the climate, i.e., the temperature and the mean annual precipitation rates resulting in different soil moisture contents. The mean lifetime of one millimeter of different rocks into a kaolinitic saprolite is shown below.These numbers exhibit that in cold, temperate, or tropical humid zones, the climate (temperature and precipitation) controls the rate of weathering.
o Acid rocks break down differently in different climates: in tropical semi-arid (time: 65-200 lifetime years); tropical humid (20-70 lifetime years); temperate humid (41-250 lifetime years); and cold humid (35 lifetime years).
o Metamorphic rocks break down differently in climates: in temperate humid (33 lifetime years);
0 Basic rocks in temperate humid (68 lifetime years); and tropical humid (40 lifetime years).
There are three broad categories of mechanisms for weathering: chemical, physical and biological as discussed in the next question.
There are different products of weathering. For example, the process of weathering can result in the following three outcomes on rocks and minerals:
(1). The complete loss of particular atoms or compounds from the weathered surface.
(2). The addition of specific atoms or compounds to the weathered surface.
(3). A breakdown of one mass into two or more masses, with no chemical change in the mineral or rock.
The residue of ...
Describes the roles of weathering in different climates. Considering the various processes involved in mechanical and chemical weathering, it also identifies and discusses some of the factors that influence or control the weathering of earth materials. Finally, it evaluates which of these factors would be most important and why. | <urn:uuid:9ab93dac-a14c-4456-b0a1-d687c8b13e8d> | 3.53125 | 877 | Academic Writing | Science & Tech. | 35.332826 | 95,583,958 |
posted by Anonymous
Consider free protons following a circular path in a uniform magnetic field with a radius of 1 meter. At t = 0, the magnitude of the uniform magnetic field begins to increase at 0.001 Tesla/second. Enter the tangential acceleration of the protons in meters/second^2: positive if they speed up and negative if they slow down.
The magnetic field itself will produce no tangential acceleration. But then, consider Maxwell's equation, or more precisely, the resulting electric field created by the changing magnetic field, which will move the proton in the tangential direction.
By using Faraday's law E= - r/2 x dB/dt so a=E x q/m= -r/2 x dB/dt x q/m so a=- 5.22*10^4m/s^2
ou should use Faraday's law of induction to find the electric field E at distance r from the center and from that the tangential acceleration due to F=Eq=m*atan
but E= - r/2 x dB/dt
so a=E x q/m=
a= -r/2 *dB/dt*q/m so
Honestly, this does not seem right, so check it. | <urn:uuid:3c054da8-72b5-4329-9b8e-b588f9a8ec88> | 3.46875 | 265 | Q&A Forum | Science & Tech. | 74.516001 | 95,583,960 |
An example of output from an SQL database query. A general-purpose DBMS allows the definition, creation, querying, update, and administration of databases. Sometimes a DBMS is loosely referred to as a “database”. Formally, a “database” refers to a set database systems design implementation and management 12 e pdf related data and the way it is organized.
Dealing with concurrency control, a “database” refers to a set of related data and the way it is organized. Thus most database systems nowadays are software systems running on general, which is now known as PostgreSQL. A common approach to this is to develop an entity, the goal of normalization is to ensure that each elementary “fact” is only recorded in one place, addresses and phone numbers for that user would be recorded with the login name as its key. Assumption of change and risk taking, some of the features on CT. Teamwork and innovation, sQL and maintaining the ACID guarantees of a traditional database system.
And so are often used where response time is critical, scalability and other operational matters. As well as its native tabular model, six supporting and limiting factors determining QMS implementation are identified in this review. This allows users to see database information in a more business, the dBASE product was lightweight and easy for any computer user to understand out of the box. Database systems include complex mechanisms to deliver the required performance, we hope you find this website both helpful and informative. That person’s attributes, static analysis techniques for software verification can be applied also in the scenario of query languages.
A distributed system can satisfy any two of these guarantees at the same time, updates of a replicated object need to be synchronized across the object copies. Related way rather than from a technical, purpose DBMS allows the definition, and is rather of interest to database application developers and database administrators. With more elementary DBMS functionality. Oriented databases are one of the main categories of NoSQL databases. What was changed — ours is direct and objective. | <urn:uuid:4634177f-108f-4b2e-8555-7ef07ccc74d2> | 3.109375 | 422 | Truncated | Software Dev. | 24.380298 | 95,583,982 |
A binary operation has the properties that and that for all nonzero real numbers and . (Here represents multiplication). The solution to the equation can be written as , where and are relatively prime positive integers. What is
This problem is copyrighted by the American Mathematics Competitions.
Instructions for entering answers:
For questions or comments, please email email@example.com. | <urn:uuid:45cfa4fc-8dff-4d7e-b910-defd639d32a6> | 2.515625 | 79 | Customer Support | Science & Tech. | 26.364713 | 95,583,994 |
For the first time ever, Emory University researchers have broken through the so-called "oxo-wall" to create stable multiple chemical bonds between oxygen and platinum – once thought impossible because oxygen is extremely unstable when combined with certain metals. The breakthrough holds the potential for numerous applications in fuel cells, catalytic converters and emerging green chemistry.
Chemical bonds between metals and oxygen are known as metal-oxo species, and are found in a multitude of molecules and materials. They are dominant in the chemistry, geology and biology of many metal elements, especially during oxidation – one of the most basic and fundamental of chemical reactions. However, metal-oxo species become increasingly less stable as one moves from left to right on the periodic table. Until this work, attempts to create metal-oxo species with elements such as gold, platinum, silver, iridium and rhodium have been unsuccessful.
"The existence of such metal-oxo complexes has been presented and debated in many public forums but never realized until this research. Since this metal-oxo is a unique compound, both its physical properties and its chemical reactivities should provide new insights and break new ground," says principal investigator Craig Hill, Goodrich C. White Professor of Chemistry at Emory.
Beverly Clark | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:1fd3840a-7836-411f-acd4-c9d56dd9c032> | 3.546875 | 848 | Content Listing | Science & Tech. | 33.521419 | 95,583,998 |
Life, Earth and Space
Aug. 15, 2008—"Global Warming – What do we know and what we should do?" is the title of a free public lecture that will be given Thursday afternoon, Sept. 4, on the Vanderbilt University campus.
Jun. 18, 2008—The analysis of the youngest pair of identical twin stars yet discovered has revealed surprising differences in brightness, surface temperature and possibly even the size of the two. The study, which is published in the June 19 issue of the journal Nature, suggests that one of the stars formed significantly earlier than its twin.
Jun. 6, 2008—Vanderbilt astronomers have constructed a special-purpose telescope that will allow them to participate in one of the hottest areas in astronomy-- the hunt for earthlike planets circling other stars.
Apr. 28, 2008—Shape matters, even in hearing.
Apr. 15, 2008—A new method that uses nanotechnology to rapidly measure minute amounts of insulin is a major step toward developing the ability to assess the health of the body\'s insulin-producing cells in real time.
Mar. 13, 2008—Nobel laureate George F. Smoot from the University of California, Berkeley will give a free public lecture about what the latest studies of the variations in fossil radiation called the cosmic background radiation (CBR) are revealing about the nature of the embryonic universe shortly after its origin in the Big Bang.
Mar. 6, 2008—Exploding stars and black holes. Colliding galaxies and dark matter. Dark energy and cosmic inflation. The universe that modern science has revealed is strange and wild and beautiful, but doesn\'t seem particularly hospitable to life or very comprehensible.
Vanderbilt physicist plays key role in making top physics journals available to minority colleges and universities
Mar. 4, 2008—Vanderbilt physicist David Ernst played a key role in a new agreement designed to encourage minority students to pursue science careers by giving them easier access to top physics journals.
Feb. 17, 2008—When you check into a hospital, the odds are one in ten that you will become infected with a strain of antibiotic-resistant bacteria as a result of your stay. That is because the problem of drug-resistance has become endemic in today\'s hospitals despite the best efforts of the medical profession. In the United States alone this currently causes about 100,000 deaths per year.
Feb. 7, 2008—Shrews are tiny mammals that have been widely characterized as simple and primitive. This traditional view is challenged by a new study of the hunting methods of an aquatic member of the species, the water shrew.
Dec. 18, 2007—A team of Vanderbilt researchers has demonstrated for the first time that a new type of gene therapy, called RNA interference, can heal a genetic disorder in a live animal. | <urn:uuid:46c133b9-56f1-4ee2-9c57-b493324b3b52> | 3.1875 | 572 | Content Listing | Science & Tech. | 48.983535 | 95,584,054 |
Editor rating: 8 / 10Marta Riutort –– The article uses up-to-date methodologies and new data to analyse an issue that is in between biogeography, phylogeny and ecology, which is very interesting since many ecological work does not have into account evolution, and many times also evolutionary work does not have into account how habitats can affect organisms histories and evolutionary success.
Editor rating: 7 / 10María Ángeles Esteban –– This article demonstrate that the different measures of diversity which have been examined suggest that the deep areas of the continental slope may be equally or more diverse than assemblages just beyond the continental shelf.
Editor rating: 7 / 10Budiman Minasny –– microbial diversity
Editor rating: 7 / 10Luis Eguiarte –– This paper is an interesting and relevant contribution to the understanding of the process that determine the distribution and abundance of a species in relationship to environmental variables and patchiness. Also it is important because the comparison among different modelling methods, and for the potential of the ideas and methods in conservation biology and in understanding the role of fragmentation. The different methodologies and approaches should be useful in similar studies in other species.
Editor rating: 8 / 10Mark Costello –– The use of onpen access databases for monitoring biodiversity trends must increase to improve transparency (traceability of data) and expedite societal awareness of the trends in biodiversity from species to ecosystems.
Editor rating: 8 / 10David Roberts –– The Convention of the Parties of the Convention on International Trade in Endangered Species will be discussion elephants and therefore this will be extremely important
Editor rating: 9 / 10Tomas Hrbek –– provides a very useful tool for ranking conservation priorities based on phylogenetic distinctness
Editor rating: 9 / 10Leon Higley –– It offers data on predator-prey relationships that is clear and convincing.
Editor rating: 7 / 10Marta Riutort –– The article presents new data, both morphological and molecular, supporting a strange pattern of distribution for a parasite. This is probably only a first step but interesting to understand how these animals disperse and differentiate.
Editor rating: 7 / 10Mauricio Rodriguez-Lanetty –– An interesting study that add to the understanding of the evolution of mimicry in egg-cowrie gastropods and also provides a creative learning tool implementation.
Discussing these articles
Los elefantes africanos al borde de la extinción - In Spanish
Daily Maverick: "Counting Africa’s beleaguered elephants: Massive two-year census finds alarming declines"
GeekWire: "Paul Allen’s Great Elephant Census confirms catastrophic decline in Africa"
The Washington Post: "The largest-ever survey of elephants in Africa reveals startling declines"
Huffington Post: "A New Elephant Census Shows The Devastating Impact Of Poaching"
Popular Science: "FIRST AFRICA-WIDE ELEPHANT CENSUS SHOWS DROPPING POPULATIONS"
NPR Radio Slot: "Often On The Move, Restless Elephants Are Tough To Count — And Keep Safe"
NPR: "African Elephant Population Declines By 30 Percent"
Mashable: "Historic census reveals the true plight of Africa's elephants"
The Guardian: "Poaching drives huge 30% decline in Africa's savanna elephants" | <urn:uuid:73523012-3732-4e72-8473-a85c1c8ec381> | 2.546875 | 708 | User Review | Science & Tech. | -14.096299 | 95,584,055 |
See-through solar materials that can be applied to windows represent a massive source of untapped energy and could harvest as much power as bigger, bulkier rooftop solar units, scientists report today in Nature Energy.
Led by engineering researchers at Michigan State University, the authors argue that widespread use of such highly transparent solar applications, together with the rooftop units, could nearly meet U.S. electricity demand and drastically reduce the use of fossil fuels.
"Highly transparent solar cells represent the wave of the future for new solar applications," said Richard Lunt, the Johansen Crosby Endowed Associate Professor of Chemical Engineering and Materials Science at MSU. "We analyzed their potential and show that by harvesting only invisible light, these devices can provide a similar electricity-generation potential as rooftop solar while providing additional functionality to enhance the efficiency of buildings, automobiles and mobile electronics."
Lunt and colleagues at MSU pioneered the development of a transparent luminescent solar concentrator that when placed on a window creates solar energy without disrupting the view. The thin, plastic-like material can be used on buildings, car windows, cell phones or other devices with a clear surface.
The solar-harvesting system uses organic molecules developed by Lunt and his team to absorb invisible wavelengths of sunlight. The researchers can "tune" these materials to pick up just the ultraviolet and the near-infrared wavelengths that then convert this energy into electricity.
Moving global energy consumption away from fossil fuels will require such innovative and cost-effective renewable energy technologies. Only about 1.5 percent of electricity demand in the United States and globally is produced by solar power.
But in terms of overall electricity potential, the authors note that there is an estimated 5 billion to 7 billion square meters of glass surface in the United States. And with that much glass to cover, transparent solar technologies have the potential of supplying some 40 percent of energy demand in the U.S. - about the same potential as rooftop solar units. "The complimentary deployment of both technologies," Lunt said, "could get us close to 100 percent of our demand if we also improve energy storage."
Lunt said highly transparent solar applications are recording efficiencies above 5 percent, while traditional solar panels typically are about 15 percent to 18 percent efficient. Although transparent solar technologies will never be more efficient at converting solar energy to electricity than their opaque counterparts, they can get close and offer the potential to be applied to a lot more additional surface area, he said.
Right now, transparent solar technologies are only at about a third of their realistic overall potential, Lunt added.
"That is what we are working towards," he said. "Traditional solar applications have been actively researched for over five decades, yet we have only been working on these highly transparent solar cells for about five years. Ultimately, this technology offers a promising route to inexpensive, widespread solar adoption on small and large surfaces that were previously inaccessible."
The work is funded by the National Science Foundation and the U.S. Department of Education.
Lunt's coauthors are Christopher Traverse, a doctoral student in engineering at MSU, and Richa Pandey and Miles Barr with Ubiquitous Energy Inc., a company Lunt cofounded with Barr to commercialize transparent solar technologies.
Andy Henion | EurekAlert!
Factory networks energy, buildings and production
12.07.2018 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH
Manipulating single atoms with an electron beam
10.07.2018 | University of Vienna
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:ba44e853-c791-498f-b507-8bdfa2e5753b> | 3.40625 | 1,311 | Content Listing | Science & Tech. | 32.177555 | 95,584,056 |
Susan Marie Frontczak
Manya - A Living History of Marie Curie (2018)
This year’s Romer Lecture will be a performance “Manya - A Living History of Marie Curie” by Susan Marie Frontczak. The program is set in 1915 and explores many aspects of Marie Curie’s life - her childhood, personal life, scientific discoveries and fame, triumphs and tragedies. It will take place at 7:00 pm on Tuesday, April 10, in Gulick Theater on the St. Lawrence University Campus. Free and open to the public.
Susan Marie Frontczak was trained as an engineer and worked in engineering for fourteen years before turning to full time writing and acting, creating living histories of several women including Eleanor Roosevelt and Mary Shelley. She has presented the Marie Curie program over 400 times in many venues such as the NASA Ames Research Center, Lawrence Livermore National Accelerator Laboratory, the Niels Bohr Institute in Copenhagen, the American Association of Physics Teachers Conference, and Conference of the American Nuclear Society. This carefully researched program has prompted testimonials from scientists such as: "Scientists in the audience applaud the accuracy of the presentation, while the non-scientists rejoice at the accessibility of Manya's scientific descriptions.” and “Your masterful depiction of Madame Curie - her heart, spirit and intellect - mesmerized audiences at all three performances, from children to our Ph.D. scientists.”
Dr. Thomas D. Seeley, Cornell University
Honeybee Democracy (2012)
Honeybees make decisions collectively-and democratically. Every year, faced with the life-or death problem of choosing a new home, honeybees stake everything on a process that includes collective factfinding, vigorous debate, and consensus building. Seeley will describe how these bees evaluate potential nest sites, advertise their discoveries to one another, engage in open deliberation, choose a final site, and navigate together-as a swirling cloud of bees-to their new home. He will argue that these incredible insects have much to teach us when it comes to achieving collective wisdom. A decision-making group should consist of individuals with shared interests and mutual respect, a leader's influence should be minimized, diverse solutions should be sought, vigorous debate of the options should be encouraged, and the majority will should be counted on for a dependable solution. We will see that with the right organization, decision making groups can be smarter than even the smartest individual in them.
Dr. Thomas D. Seeley is a Professor in the Department of Neurobiology and Behavior at Cornell University, where he teaches courses in animal behavior and does research on the functional organization of honey bee colonies.
Dr. Ronald Mallett, University of Connecticut
Time Traveler: A Scientist's Personal Mission to Make Time Travel a Reality (2010)
In this lecture, intended for a general audience, Professor Mallett explains his theory of time travel which is derived from the work of Einstein and Gödel and from his own experiments over thirty years. But behind the science – which is delivered in clear, captivating language with accessible metaphors – lies Mallett's personal story. He touches on the death of his father when he was a boy (which set him on his current path to invent a time machine) and tells us how he overcame poverty and racism to become one of the few African-American Ph.Ds in theoretical physics. Mallett's talks provide both intriguing scientific speculations on the future of time travel and an inspiration to aspiring scientists.
Ronald Mallett is a Professor of Physics at the University of Connecticut. He has used Einstein’s equations to design a time machine with circulating laser beams. While his team is still looking for funding, he hopes to build and test the device in the next 10 years.
Professor David Cassidy, Hofstra University
J. Robert Oppenheimer and the Moral Complexity of Modern Science (2008)
J. Robert Oppenheimer led the team that built the atomic bomb, and he recommended its use on Japan. Yet, as the leading science advisor, he opposed the building of the hydrogen bomb on moral grounds. The product of the best of American culture and education, steeped in the Ethical Culture movement, how did he, like many others, become involved in the building and use of the bomb? How did he, and his colleagues, become opposed to the H-bomb? What do these differing reactions tell us about the moral complexities of issues in today's science?
David Cassidy, Professor of Chemistry, Hofstra University, has written extensively on the history of the physical sciences in the U.S. and Germany. He also has served as an editor of the Einstein Papers, and has won awards for his science writing for a popular audience. This year's Romer Lecture draws from his 2005 book J. Robert Oppenheimer and the American Century.
Dr. David Barash, University of Washington
The Hare and the Tortoise: The Conflict Between Culture and Biology in Human Affairs, or: When Baboons Drive Hummers (2007)
Human beings are animals, yet also more than animals. On the one hand, we are the products of evolution by natural selection, subject to biology; on the other, we are masters of technology, nearly godlike in our ability to modify our environment and, increasingly, ourselves. No other living thing experiences such a divided existence, and I shall argue that the resulting conflict is one of the keys to our modern "human dilemma," including war, overpopulation, environmental problems, many social instabilities, with effects from the international to the personal.
Dr. Michael Paesler, North Carolina State University
The Blue Moon, Einstein, and Mie (2006)
Under certain atmospheric conditions, the sun or moon may take on a decidedly blue hue, due to an optical effect called Mie scattering (rather than the more common Rayleigh scattering), involving motion of dust in the air. Einstein in 1905 developed the theory of Brownian motion which describes just such movement. His work thus leads one to an explanation of the blue moon. In this talk Dr. Paesler will discuss and demonstrate just how this occurs.
Dr. Paesler is Head of the Physics Department at North Carolina State University, a Fellow of the American Physics Society, member of Phi Beta Kappa, Sigma Xi, and the NC State Academy of Outstanding Teachers.
David Allen Sibley
Birds and Bird Guides: The Universal Appeal of Birds, and the Pleasures and Challenges of Creating a Field Guide (2005)
Sibley is the author of the fastest-selling bird guide of all time, The Sibley Guide to Birds, a comprehensive field guide to North American birds published in 2000, and its companion piece, The Sibley Guide to Bird Life and Behavior. In 2002 Sibley's Birding Basics, an introduction to bird identification was published, and in 2003, The Sibley Field Guide to Birds of Eastern North America and The Sibley Field Guide to Birds of Western North America were published. A native of upstate New York, Sibley began drawing birds at age seven, and his search for birds has taken him to such birding hotspots as Cape May, New Jersey; the Lower Rio Grande Valley of Texas; and south Florida.
Beginning with childhood drawings and following the evolution of his ideas for the "perfect" field guide, Sibley will discuss the things that inspired him and kept him going through the long process, as well as the challenge of presenting a huge and diverse amount of information in one book. He will also discuss the importance of the field guide as a tool, and birds as bridges that allow people to forge a connection with nature in the modern world.
Dr. Robert Greenler, University of Wisconsin-Milwaukee
The NASA Shuttle-Launch, Dark-Moon-Ray Mystery (2004)
A photograph of the February 7, 2001 launch of the space shuttle Atlantis, shows many interesting sky effects. The most striking feature is the dark ray converging toward (or radiating from) the full moon. The photo presents an interesting puzzle that can be understood, mostly without any additional information. A variety of effects visible in the photo will be discussed with the aid of slides, demonstrations, and a video segment.
Dr. Robert Greenler is Emeritus Professor of Physics at the University of WisconsinMilwaukee where he has been a faculty member since 1962. He has been instrumental in the development of the Laboratory for Surface Studies at Milwaukee, an internationally recognized interdisciplinary laboratory that has been the focus for much of his research effort.
Dr. Stephen H. Schneider, Stanford University
Global Warming Debate: Good Science or Bad Politics? (2003)
Professor Schneider has done pioneering modeling work in the fields of atmospheric science and global climatology, including the relationship of biological systems to global climate change. He enjoys working on coupling models of the atmosphere to models of other climatic subsystems such as oceans, ice, or biosphere. He has initiated new research and policy directions in environmental issues. His current research interests include climatic change, global warming, the economic implications of global warming mitigation strategies, food/climate and other environmental/science public policy issues, public understanding of science, and environmental consequences of nuclear war. He has written articles on climatic change signals ecology and climate, environmental policy, and global air pollution, among other topics; he has also authored a text entitled “Global Warming: Are We Entering the Greenhouse Century?” and published by Vintage Books in 1989.
Dr. Lynn Margulis, University of Massachusetts at Amherst
On the Origin of Species: The Inheritance of Acquired Bacteria (2002)
One hundred forty years after the publication of Charles Darwin’s On the Origin of Species, major issues remain unsolved:
- How do great evolutionary changes occur?
- How do new species appear?
- What leads to new taxonomic groups?
Lynn Margulis believes that symbiogenesis, an evolutionary consequence of symbiosis, is a major factor. Dr. Margulis will discuss the old problems of the origin of evolutionary change and show how genome acquisition and community analysis propel us toward a new Gaian view of life. Life, after all, is a planetary phenomenon, and Gaia may be understood as symbiosis as seen from space.
Dr. Jeff Weeks, Mathematician, Cosmologist and MacArthur Fellow
The Shape of Space (2001)
Is the universe really infinite? Data from a small NASA satellite could soon show that it’s not. The first half of Dr. Weeks’ presentation will use computer games to show how space may be finite, yet have no boundary. Interactive 3D graphics will then take the viewer on a tour of several possible shapes for space. The presentation will conclude with an explanation of the Big Bang, and how the radiation remaining from it may reveal the true shape of our universe.
Dr. Eloy Rodriguez, Cornell University
Living Longer and Healthier with Natural Medicines from the Amazon Rain Forest and Caribbean Coral Reefs (2000)
Professor Rodriguez will present the latest medical drug discoveries from undergraduate students who travel to deep jungles of the Amazon and dive into deep blue waters of the Caribbean to study the chemical biology of interactions. He will also discuss his personal studies of hidden Amazon tribes that use a variety of medicines from ants, birds and scorpions to combat malaria and other tropical diseases. Lastly, Professor Rodriguez will discuss the importance of conservation and preservation of unique species that contain genes that are beneficial in food and medicine production.
Dr. Roger Stuewer, University of Minnesota
The Case of the Elusive Particles: Nuclear Disintegration and the Cambridge-Vienna Controversy (1999)
Scientific controversies can offer a glimpse through the window of a particular historical period of how science functions as a process. Scientists holding opposing points of view in a controversy submit a range of issues to intense scrutiny. Careful examination of these issues can reveal the interplay of theory, experiment and observation and how this interplay leads to new scientific knowledge.
The Cambridge-Vienna controversy during 1922 – 1928 centered on the disintegration of elements (nuclei) by alpha particles, triggering the emission of protons. Ernest Rutherford and James Chadwick in Cambridge argued with Hans Pettersson and Gerhard Kirsch in Vienna over questions involving which elements could be disintegrated in this way, whether these elusive disintegration protons could be observed and how the process should be interpreted theoretically. A web of personal and institutional rivalries became thoroughly entangled with the scientific issues, raising the stakes in the outcome of the controversy enormously.
All the questions in this controversy will be examined in the context of 1920s physics and for their meaning in the larger context of our understanding of how science functions in an intensely competitive atmosphere.
Dr. Robert Richardson, Cornell University (1998)
The second annual Romer Lecture was presented in April, 1998 by Robert Richardson, a low-temperature physicist who shared the 1996 Nobel Prize in Physics for the discovery of superfluidity in helium-3.
Jack Horner, Montana State University/Museum of the Rockies
Digging Dinosaurs: The Search That Unraveled the Mystery of Baby Dinosaurs (1997)
John R. "Jack" Horner, dinosaur authority, gave the first annual Alfred Romer Lecture on April 21st, 1997. Curator of paleontology at the Museum of the Rockies in Bozeman, Montana, he spoke on "Digging Dinosaurs: The Search That Unraveled the Mystery of Baby Dinosaurs". Horner discovered the first dinosaur eggs in the Western Hemisphere, the first evidence of dinosaur colonial nesting, the first evidence of parental care among dinosaurs and the first dinosaur embryos. He has written extensively about dinosaurs and was a technical advisor for the film Jurassic Park | <urn:uuid:de926ba9-8e19-4d07-adb4-09f90a34304f> | 2.5625 | 2,849 | Content Listing | Science & Tech. | 32.594257 | 95,584,093 |
Lots of different chemical pathways keep organisms alive and growing, but these chemical pathways cannot run amok or they will be detrimental to the health of the organism. Feedback inhibition is one of the ways that chemical pathways are kept in check. The enzymatic pathway basically controls itself, without any input from outside the pathway. This method of control depends on product concentration and enzyme interaction with product.
The Basics of an Enzymatic Pathway
Enzyme pathways involve the first enzyme catalyzing the conversion of the first substrate into the second substrate, which in turn is converted into the third substrate using the second enzyme in the pathway, and so on. The aim is to produce an end-product that is required in the body at a specific level for a specific purpose.
How It Works
In pathways that use feedback inhibition, the end-product can bind to the allosteric site on the first enzyme. The allosteric site is an area on the enzyme that is distinct to the active site used for catalysis. When the end-product binds to the enzyme, it changes the physical shape of the enzyme so that it is no longer available to its substrate. This means that the initial reaction in the pathway, and therefore all the reactions that follow, are prevented.
Reasons It Evolved
An endless supply of a product is a waste of resources that could be put to better use in other processes. Accumulation of unwanted end-product can also be detrimental to health. As an example of feedback inhibition, the brain uses glucose for energy, and when each individual brain cell has enough glucose-6-phosphate, used in glucose breakdown, the glucose-6-phosphate binds to the hexokinase enzyme and prevents more glucose from being used. This allows the excess glucose in the brain environment to move to other brain cells that need it more.
Ending the Inhibition
While feedback inhibition to prevent excess end-product formation is useful, the end-product is generally necessary for use in another process. When levels of the end-product drop, the end-product that was bound to the allosteric site of the first enzyme is released for use, freeing the enzyme to begin the synthetic pathway again. | <urn:uuid:09d254cd-ea60-494a-bd17-6a4a24b38978> | 3.53125 | 452 | Knowledge Article | Science & Tech. | 35.973349 | 95,584,117 |
Two new techniques will assist the rapid cataloguing of proteins’ roles in the cell.
Looks dont matter: new techniques find enzymes like this one by function not form
Decoding the human genome sequence was merely a preliminary step towards understanding how living cells work. Two new techniques should assist the next step: working out the functions of all the proteins that the genes encode1,2.
Selectively sticking to small molecules is central to most proteins’ function. Proteins generally have delicately sculpted binding sites, clefts into which certain target molecules, called substrates, fit like a key in a lock. Often this binding allows the protein to act as a catalyst, chemically transforming the substrate.
The functional role of a particular protein is therefore revealed, or at least hinted at, by what it binds. Two teams have now identified the substrates of a range of proteins.
Current methods for assigning a function to a protein rely on a detailed knowledge of its structure or shape. Proteins are long chains of interlinked amino acids, folded up into a compact shape. If two proteins have very similar amino-acid sequences, they probably share similar functions.
Deducing the sequences of each of the many thousands of proteins in a cell is a slow business. Another approach is to use X-ray crystallography to determine the protein’s three-dimensional shape - where each atom sits.
Researchers are now trying to develop automated systems for the rapid crystallographic study of many proteins3. Unfortunately, some proteins share a similar function even if they look different, as long as their binding sites fit similar substrates.
So Gerhard Klebe and colleagues at the University of Marburg in Germany have compared the binding sites of various proteins and evaluated the similarity of their substrates - regardless of any differences either in sequence or overall protein shape. In other words, the method spots commonalities hidden from existing techniques.
The researchers compared the binding sites of two enzymes, one from yeast and one from Escherichia coli bacteria. Because the enzymes share the same function even though only 20% of their amino-acid sequences overlap, a sequence comparison would not recognize that they do the same job. But the computer program identified the E. coli enzyme as the closest match to the yeast enzyme from 5,445 other protein binding sites.
Spotting relationships such as this could also aid drug design by suggesting new small molecules that might block the activity of certain enzymes.
Meanwhile, Peter Schultz and co-workers at the Scripps Research Institute in La Jolla, California, have developed a way to screen huge numbers of proteins simultaneously and pick out those that bind to particular target molecules.
The researchers have taken the complex protein mixture that every cell contains and presented it with small substrates tagged with strands of PNA, a molecule similar to DNA and capable of binding to it. The PNA acts as a kind of label: its chemical structure is like a bar code for the attached substrate.
When a protein latches onto the substrate, the PNA latches onto a strand of DNA at a particular location on a grid-like array. The PNA-DNA pairing glows, lighting up a grid point on the array and signalling the presence of the substrate-binding protein.
PHILIP BALL | Nature News Service
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:cf0c862d-7183-4d20-b953-682f6e3c505d> | 3.484375 | 1,255 | Content Listing | Science & Tech. | 37.920245 | 95,584,119 |
|Developer(s)||Andy Cedilnik, Bill Hoffman, Brad King, Ken Martin, Alexander Neundorf|
|Written in||C, C++|
|Type||Software development tools|
|License||New BSD License|
CMake is a cross-platform free and open-source software application for managing the build process of software using a compiler-independent method. It supports directory hierarchies and applications that depend on multiple libraries. It is used in conjunction with native build environments such as make, Apple's Xcode, and Microsoft Visual Studio. It has minimal dependencies, requiring only a C++ compiler on its own build system.
CMake can handle in-place and out-of-place builds, enabling several builds from the same source tree, and cross-compilation. The ability to build a directory tree outside the source tree is a key feature, ensuring that if a build directory is removed, the source files remain unaffected.
CMake can locate executables, files, and libraries. These locations are stored in a cache, which can then be tailored before generating the target build files. The cache can be edited with a graphical editor which is included in the project.
Complicated directory hierarchies and applications that rely on several libraries are well supported by CMake. For instance, CMake is able to accommodate a project that has multiple toolkits, or libraries that each have multiple directories. In addition, CMake can work with projects that require executables to be created before generating code to be compiled for the final application. Its open-source, extensible design allows CMake to be adapted as necessary for specific projects.
CMake can generate project files for several prominent IDEs, such as Microsoft Visual Studio, Xcode, and Eclipse CDT. It can also produce build scripts for MSBuild or NMake on Windows; Unix Make on Unix-like platforms such as Linux, macOS, and Cygwin; and Ninja on both Windows and Unix-like platforms.
The build process with CMake takes place in two stages. First, standard build files are created from configuration files. Then the platform's native build tools are used for the actual building.
Each build project contains a CMakeLists.txt file in every directory that controls the build process. The CMakeLists.txt file has one or more commands in the form COMMAND (args...), with COMMAND representing the name of each command and args the list of arguments, each separated by white space. While there are many built-in rules for compiling the software libraries (static and dynamic) and executables, there are also provisions for custom build rules. Some build dependencies can be determined automatically. Advanced users can also create and incorporate additional makefile generators to support their specific compiler and OS needs.
CMake development began in 1999 in response to the need for a cross-platform build environment for the Insight Segmentation and Registration Toolkit (ITK). The project is funded by the United States National Library of Medicine as part of the Visible Human Project. It was partially inspired by pcmaker, which was made by Ken Martin and other developers to support the Visualization Toolkit (VTK). At Kitware, Bill Hoffman blended components of pcmaker with his own ideas, striving to mimic the functionality of Unix configure scripts. CMake was first implemented in 2000 and further developed in 2001. Continued development and improvements were fueled by the incorporation of CMake into developers’ own systems, including the VXL Project[clarification needed], The CABLE features added by Brad King,[clarification needed] and GE Corporate R&D for support of DART.[clarification needed]
Additional features were created when VTK transitioned to CMake for its build environment and for supporting ParaView.
CPack is a packaging system for software distributions which is tightly integrated with CMake, but can function without it.
It can be used to generate:
- Linux RPM, deb and gzip distributions of both binaries and source code.
- NSIS files (for Microsoft Windows)
- Mac OS X packages
Applications that use CMake
- Allegro library
- Armadillo – linear algebra library
- awesome – window manager
- Bullet Physics Engine
- CGAL – Computational Geometry Algorithms Library
- Chipmunk physics engine
- Dolphin (Emulator)
- Doomsday Engine
- Dust Racing 2D
- Falcon (programming language)
- FlightGear Flight Simulator
- GNU Radio
- Hiawatha (web server)
- iCub robot and YARP
- Insight Segmentation and Registration Toolkit (ITK)
- KDE SC 4
- LLVM and Clang
- MLPACK – machine learning library
- MySQL and MariaDB
- Otter Browser - internet browser using Qt5 framework
- Point Cloud Library
- Qpid - AMQP messaging system
- Qub3d Engine Project
- Raw Therapee
- Second Life
- Spring RTS
- The Visualization Toolkit and ParaView
- Wt (web toolkit)
- List of build automation software § Build script generation tools
- configure script
- GYP (Generate Your Projects)
- "Download CMake". Retrieved 14 June 2018.
- "Tags - CMake / CMake". Kitware. Retrieved 14 June 2018.
- "The CMake Open Source Project on OpenHub". OpenHub. Retrieved 2016-04-09.
- Neundorf, Alexander (2006-06-21). "Why the KDE project switched to CMake—and how". LWN.net.
- "FLOSS Weekly 111: CMake". podcast. TWiT Network. Retrieved 27 February 2011.
- The CABLE
- Bridgwater, Adrian (13 September 2014). "JetBrains CLion: A New Cross Platform C/C++ IDE". infoworld.
- Krill, Paul (14 September 2014). "Version 1.0 of JetBrains' CLion IDE will include C/C++ support". infoworld.
- Conky README.cmake file
- "Compiling YARP and iCub". iCub user manual. Archived from the original on 2010-03-14.
- Hoffman, Bill. "CMake / CTest / CPack: Open source tools to build, test, and install software" (PDF). BoostCon 2009.
- "Qt Doc / CMake Manual". Digia. | <urn:uuid:3942e807-f789-4150-ba6b-b4e352ac185c> | 3.015625 | 1,353 | Knowledge Article | Software Dev. | 41.006823 | 95,584,139 |
Gaussian Guessing Game
Guess which of these graphs shows the normal/gaussian distribution.
The correct answer is A. The rest are the logistic, cauchy, and beta distributions respectively.
Even if you picked it out correctly, it isn’t easy to figure out. All of them look like “bell curves,” they are all symmetric, they all taper off at what looks like a similar rate. In that case, why do we care about the difference between them? Why don’t we just pick whichever one is most mathematically convenient and not worry about it?
The difference lies in their tails, the parts of the graph where the plot disappears into the x axis. That difference, imperceptible in these graphs, makes these distributions behave incredibly differently, as I’ll show below.
The Basic Operation of Probability: Multiplication
Probabilities are very rarely added together, and probability distributions even more rarely. The basic operation of probability is multiplication. This arises from Bayes’ Rule, which describes the relationship between the joint and conditional distributions of random variables:
This makes it important to understand how each distribution combines via bayes rule with other distributions; that is, how it multiplies.
Before you look at the graphs below, try to guess what each one will look like. I’ve made two copies of each distribution, shifted their centers to -4 and +4, and multiplied the two together. This simulates having two sources of evidence about the same variable that substantially disagree.
Despite the fact that these distributions had very similar looking shapes, their products are entirely different. The distributions are shifted so that the center of one is 8 standard deviations from the center of the other, well out in the range where the plots are indistinguishable from the x axis. Clearly there’s a lot going on in this invisible part of the graph!
What should we plot to give us an intuition about this? The basic operation shouldn’t be so surprising!
The log function asymptotes at 0. This makes it a perfect choice to visualize very small values of a function by expanding their range. These plots show the log of each probability distribution, and they are all easily distinguishable at a glance. They also make it plausible to predict how the distributions will multiply together. Since multiplying the variables is equivalent to adding the log of the variables, all we have to do is figure out what happens when you add two of these curves to each other.
And as you can see, these make the logs of the products of the distributions make a lot more sense
These shapes still aren’t immediately obvious, but you’ve got a fair shot at guessing them from the log plots alone. If all you had was the probability density plots, you wouldn’t have any recourse but to go immediately to the math.
Fitting to Data
Log probability distributions also show up when you are fitting a model to data. Regardless of whether you are using Bayesian or Frequentist methods, fitting a distribution to a set of data is going to involve maximizing a likelihood function (potentially with some additional multiplied terms.) You’ll be selecting the distribution by maximizing where is the vector of data, is the vector of parameters, and is a regularization term, typically a prior distribution for . Again we find that we’re dealing with a product of probabilities.
The first step of maximizing a function is typically to take its derivative. To make the derivative simpler, it’s easier to work with a sum of many terms than a product of many terms. Since log is monotonic, maximizing a nonnegative function is equivalent to maximizing its log, so we can instead maximize the log probability and turn the product into a sum. We’ll be maximizing . The term is exactly what we’ve been plotting. The log probability density arises for both mathematical convenience and intuitive convenience!
To determine what impact each sample will have on the likelihood, we can just read off the value from the log plot. Consider an outlier that is well away from the rest of the distribution. For a gaussian, the impact on the likelihood will be proportional to . For a logistic distribution, the impact will be roughly proportional to . This is what is meant when the gaussian is described as “sensitive to outliers.” Samples far away from the mean will yank the whole fit around because they have such a large impact on the likelihood.
Log probabilities pervade in Information Theory as well. The negative log probability is called the “surprisal,” and every other quantity is defined in terms of an expected surprisal.
Tails and Consequences
How much all this matters depends on what type of question you want to answer with your model. If you just want to know where the bulk of the data is, then your choice of distribution doesn’t matter that much. If you are trying to determine the probability of exceptional events, events far away from the mean, then the size of the tails is the only thing that matters. An event six standard deviations from the center of a logistic distribution is several thousand times more likely than an event six standard deviations from the center of a gaussian distribution.
Here are some real world examples where answering an important question requires estimating the probability of an exceptional event.
A professional chess player has an off game and loses to an amateur. How much should their rating decrease?
The United States Chess Federation has switched from the gaussian distribution to the logistic in order to make ratings more stable.
A widely sold security is backed by a large number of mortgages with a low rate of default. What rating should this security receive?
The financial crisis that brought the world economy to its knees was caused largely by bad statistics. Analysts assumed that mortgage defaults are independent events, and thus that the total number of defaults in a collection of mortgages is normally distributed, with very small tails. In reality, the state of the housing market and the overall economy ties defaults together, so large numbers of them defaulting at once is much more likely than a normal distribution would predict. This left the world’s financial institutions completely unprepared when large numbers of them did default at once.
What are the chances of a magnitude 9.5 earthquake hitting San Francisco in the next 10 years?
The Gutenberg-Richter law describes the probability distribution of earthquakes of different magnitudes. The log probability of an earthquake is linear in its magnitude. Disagreements about the slope of that line make an exponential difference in the likelihood of a large earthquake.
A Climate model predicts a 1°C increase in global mean temperature. If the climate were to get several standard deviations hotter than that, the soil would lose the ability to hold moisture, and terrestrial plant life would end. How likely is the end of the world?
Unfortunately for us, climate outcomes are fat-tailed. | <urn:uuid:edf48524-c44a-43f1-8381-c1905754e225> | 3.6875 | 1,432 | Personal Blog | Science & Tech. | 41.629841 | 95,584,140 |
Over the past four years I have been working towards my B.S. with a major in biology. In almost every single science class that I have taken we have talked about the destruction the high rate of consumption humans are having to the other life forms on this planet. Whether it's pollution, climate change or over hunting humans are causing what many scientists are calling the sixth great extinction event. With a rate of destruction similar to a super volcano or a mile wide meteor humans are killing life at an alarming rate. Though plastics have made many positive impacts the use of plastics for disposable products and the improper disposal of them as well is killing off species by being consumed and destroying ecosystems by changing the chemical make up of the water.
There are very few earthly materials that last as long as plastic, like stone, metal or glass. You would never use a glass cup once or a metal spoon for two seconds to stir your coffee and then throw it away. So why do we think it's okay to do this with plastic. The only argument for using virgin plastic for a few seconds is because it is sterile. When I took immunology the professor was constantly talking about the negative health effects of living a germ free life. We don't need everything to be sterile because we have an IMMUNE SYSTEM!
Here is an article about whales dying and when they are dissected their bellies are found to be filled with plastic. It's possible that your plastic killed a whale. There is also a video at the end of this article that inspired this post. You can actually make a difference stop looking at plastic as this disposable material and start looking at it for what it really is extremely not disposable.
Whales dying from plastic
If you do use plastic make sure that it gets properly recycled. They can recycle the plastic bottle tops now so don't throw them away and don't ever litter no matter what. | <urn:uuid:48964904-4f4c-4d76-8439-bca195ebf303> | 2.546875 | 382 | Personal Blog | Science & Tech. | 53.502774 | 95,584,159 |
Concept: Natural environment
In urban ecosystems, socioeconomics contribute to patterns of biodiversity. The ‘luxury effect’, in which wealthier neighbourhoods are more biologically diverse, has been observed for plants, birds, bats and lizards. Here, we used data from a survey of indoor arthropod diversity (defined throughout as family-level richness) from 50 urban houses and found that house size, surrounding vegetation, as well as mean neighbourhood income best predict the number of kinds of arthropods found indoors. Our finding, that homes in wealthier neighbourhoods host higher indoor arthropod diversity (consisting of primarily non-pest species), shows that the luxury effect can extend to the indoor environment. The effect of mean neighbourhood income on indoor arthropod diversity was particularly strong for individual houses that lacked high surrounding vegetation ground cover, suggesting that neighbourhood dynamics can compensate for local choices of homeowners. Our work suggests that the management of neighbourhoods and cities can have effects on biodiversity that can extend from trees and birds all the way to the arthropod life in bedrooms and basements.
New theoretical and conceptual frameworks are required for evolutionary biology to capitalize on the wealth of data now becoming available from the study of genomes, phenotypes, and organisms - including humans - in their natural environments.
So far, conservation scientists have paid little attention to synthetic biology; this is unfortunate as the technology is likely to transform the operating space within which conservation functions, and therefore the prospects for maintaining biodiversity into the future.
- Proceedings of the National Academy of Sciences of the United States of America
- Published almost 2 years ago
Although most organisms thermoregulate behaviorally, biologists still cannot easily predict whether mobile animals will thermoregulate in natural environments. Current models fail because they ignore how the spatial distribution of thermal resources constrains thermoregulatory performance over space and time. To overcome this limitation, we modeled the spatially explicit movements of animals constrained by access to thermal resources. Our models predict that ectotherms thermoregulate more accurately when thermal resources are dispersed throughout space than when these resources are clumped. This prediction was supported by thermoregulatory behaviors of lizards in outdoor arenas with known distributions of environmental temperatures. Further, simulations showed how the spatial structure of the landscape qualitatively affects responses of animals to climate. Biologists will need spatially explicit models to predict impacts of climate change on local scales.
- Environmental health : a global access science source
- Published over 2 years ago
Many populations have been exposed to environmental lead from paint, petrol, and mining and smelting operations. Lead is toxic to humans and there is emerging evidence linking childhood exposure with later life antisocial behaviors, including delinquency and crime. This study tested the hypothesis that childhood lead exposure in select Australian populations is related to subsequent aggressive criminal behaviors.
Southern stingrays, Dasyatis americana, have been provided supplemental food in ecotourism operations at Stingray City Sandbar (SCS), Grand Cayman since 1986, with this site becoming one of the world’s most famous and heavily visited marine wildlife interaction venues. Given expansion of marine wildlife interactive tourism worldwide, there are questions about the effects of such activities on the focal species and their ecosystems. We used a combination of acoustic telemetry and tag-recapture efforts to test the hypothesis that human-sourced supplemental feeding has altered stingray activity patterns and habitat use at SCS relative to wild animals at control sites. Secondarily, we also qualitatively estimated the population size of stingrays supporting this major ecotourism venue. Tag-recapture data indicated that a population of at least 164 stingrays, over 80% female, utilized the small area at SCS for prolonged periods of time. Examination of comparative movements of mature female stingrays at SCS and control sites revealed strong differences between the two groups: The fed animals demonstrated a notable inversion of diel activity, being constantly active during the day with little movement at night compared to the nocturnally active wild stingrays; The fed stingrays utilized significantly (p<0.05) smaller 24 hour activity spaces compared to wild conspecifics, staying in close proximity to the ecotourism site; Fed stingrays showed a high degree of overlap in their core activity spaces compared to wild stingrays which were largely solitary in the spaces utilized (72% vs. 3% overlap respectively). Supplemental feeding has strikingly altered movement behavior and spatial distribution of the stingrays, and generated an atypically high density of animals at SCS which could have downstream fitness costs for individuals and potentially broader ecosystem effects. These findings should help environmental managers plan mitigating measures for existing operations, and develop precautionary policies regarding proposed feeding sites.
The discipline of sustainability science has emerged in response to concerns of natural and social scientists, policymakers, and lay people about whether the Earth can continue to support human population growth and economic prosperity. Yet, sustainability science has developed largely independently from and with little reference to key ecological principles that govern life on Earth. A macroecological perspective highlights three principles that should be integral to sustainability science: 1) physical conservation laws govern the flows of energy and materials between human systems and the environment, 2) smaller systems are connected by these flows to larger systems in which they are embedded, and 3) global constraints ultimately limit flows at smaller scales. Over the past few decades, decreasing per capita rates of consumption of petroleum, phosphate, agricultural land, fresh water, fish, and wood indicate that the growing human population has surpassed the capacity of the Earth to supply enough of these essential resources to sustain even the current population and level of socioeconomic development.
BACKGROUND: The burden of ill-health due to inactivity has recently been highlighted. Better studies on environments that support physical activity are called for, including longitudinal studies of environmental interventions. A programme of residential street improvements in the UK (Sustrans ‘DIY Streets’) allowed a rare opportunity for a prospective, longitudinal study of the effect of such changes on older adults' activities, health and quality of life. METHODS: Pre-post, cross-sectional surveys were carried out in locations across England, Wales and Scotland; participants were aged 65+ living in intervention or comparison streets. A questionnaire covered health and quality of life, frequency of outdoor trips, time outdoors in different activities and a 38-item scale on neighbourhood open space. A cohort study explored changes in self-report activity and well-being postintervention. Activity levels were also measured by accelerometer and accompanying diary records. RESULTS: The cross-sectional surveys showed outdoor activity predicted by having a clean, nuisance-free local park, attractive, barrier-free routes to it and other natural environments nearby. Being able to park one’s car outside the house also predicted time outdoors. The environmental changes had an impact on perceptions of street walkability and safety at night, but not on overall activity levels, health or quality of life. Participants' moderate-to-vigorous activity levels rarely met UK health recommendations. CONCLUSIONS: Our study contributes to methodology in a longitudinal, pre-post design and points to factors in the built environment that support active ageing. We include an example of knowledge exchange guidance on age-friendly built environments for policy-makers and planners.
- Proceedings of the National Academy of Sciences of the United States of America
- Published about 3 years ago
Starting at least in the 1970s, empirical work suggested that demographic (population) and economic (affluence) forces are the key drivers of anthropogenic stress on the environment. We evaluate the extent to which politics attenuates the effects of economic and demographic factors on environmental outcomes by examining variation in CO2 emissions across US states and within states over time. We find that demographic and economic forces can in part be offset by politics supportive of the environment-increases in emissions over time are lower in states that elect legislators with strong environmental records.
The nanoparticle industry is expected to become a trillion dollar business in the near future. Therefore, the unintentional introduction of nanoparticles into the environment is increasingly likely. However, currently applied risk-assessment practices require further adaptation to accommodate the intrinsic nature of engineered nanoparticles. Combining a chronic flow-through exposure system with subsequent acute toxicity tests for the standard test organism Daphnia magna, we found that juvenile offspring of adults that were previously exposed to titanium dioxide nanoparticles exhibit a significantly increased sensitivity to titanium dioxide nanoparticles compared with the offspring of unexposed adults, as displayed by lower 96 h-EC(50) values. This observation is particularly remarkable because adults exhibited no differences among treatments in terms of typically assessed endpoints, such as sensitivity, number of offspring, or energy reserves. Hence, the present study suggests that ecotoxicological research requires further development to include the assessment of the environmental risks of nanoparticles for the next and hence not directly exposed generation, which is currently not included in standard test protocols. | <urn:uuid:3669519b-ca05-4617-b57e-23ce87dab20f> | 3.5625 | 1,819 | Content Listing | Science & Tech. | 2.431566 | 95,584,192 |
Have scientists discovered Earth 2.0? Planet just 13 light years away could harbour life that originated OUTSIDE the Milky Way
- A planet that may harbour life has been found in our sun's neighbourhood
- Kapteyn b is one of two planets around a star 13 light years from Earth
- It is the first potentially habitable planet from another galaxy ever found
- Its star originally came from a dwarf galaxy that was destroyed by ours
- And the planets might be just 2 billion years younger than the universe
- US co-author Dr Arriagada says the discovery is 'mind blowing'
Astronomers have found a planet just 13 light years from Earth that is ripe for life, with just the right mild temperatures to allow liquid water on its surface.
And the ‘super-Earth’ is all the more interesting because it originated from another galaxy, meaning it could play host to extragalactic life.
The star it orbits - Kapteyn’s star - was flung into the Milky Way when its previous galaxy was torn apart by our own.
Scroll down for video
Two planets have been found in orbit around a star just 13 light years from Earth, known as Kapteyn's star, and one of them named Kapteyn b (the innermost planet in this illustration) may play host to life. The red-hue colour tries to reproduce the colour of the ambient light a human might perceive on planets around such red stars
The planet is one of two discovered around Kapteyn’s star.
Scientists believe it was born in a dwarf galaxy that was absorbed and destroyed by our own Milky Way galaxy.
KAPTEYN'S STAR SYSTEM
At only 13 light years away from Earth Kapteyn's star is the 25th nearest star to the sun.
Based on the data collected, the planet Kapetyn b is at least five times as massive as the Earth and it orbits the star every 48 days.
This means the planet is warm enough for liquid water to be present on its surface.
The second planet, Kapteyn c is a more massive super-Earth and quite different: its year lasts for 121 days and astronomers think it's too cold to support liquid water.
At the moment, only a few properties of the planets are known: approximate masses, orbital periods, and distances to the star.
By measuring the atmosphere of these planets with next-generation instruments, scientists will try to find out whether they can bear water.
The surviving core of the dwarf remains in the form of Omega Centauri, a globular cluster of very ancient stars some 16,000 light years from the sun.
Details of the research are published in the journal Monthly Notices of the Royal Astronomical Society Letters.
'Finding a stable planetary system with a potentially habitable planet orbiting one of the very nearest stars in the sky is mind blowing,' says US co-author Dr Pamela Arriagada, from the Carnegie Institution.
'This is one more piece of evidence that nearly all stars have planets, and that potentially habitable planets in our galaxy are as common as grains of sand on a beach.'
have calculated that Kapteyn’s star’s planets could be 11.5 billion
years old - more than twice the age of Earth and only about 2 billion
years younger than the universe itself.
One of the worlds, Kapteyn b, is five times heavier than Earth, making it a super-Earth, and orbits in the star’s habitable zone where conditions are mild enough to permit watery oceans.
life has evolved there remains open to speculation - but given the
planet’s age it could be far more advanced than on Earth.
'It does make you wonder what kind of life could have evolved on those planets over such a long time,' says Dr Guillem Anglada-Escude, one of the scientists from Queen Mary University of London involved in the discovery.
The astronomers used new data from the HARPS spectrometer at the ESO's La Silla observatory in Chile to measure tiny periodic changes in the star to find and measure the planets. The study also used data from the Keck Observatory in Hawaii (pictured) and the Magellan/Las Campanas Observatory in Chile
Kapteyn's star and its planets likely come from a dwarf galaxy now merged with the Milky Way (illustrated here after the event). The star is now in the vicinity of the sun but is currently moving in the opposite direction to the rotation of the other stars in our galaxy
The second planet, Kapteyn c, is more massive than its sibling and thought to be too cold to support liquid water.
Kapteyn’s star, a red dwarf cooler than the Sun, was named after Dutch astronomer Jacobus Kapteyn who discovered it at the end of the 19th century.
It can be seen in the southern constellation of Pictor with an amateur telescope and sits in the galactic halo, an extended cloud of stars orbiting the Milky Way.
Astronomers found the planets by using specialised instruments on telescopes in Chile and Hawaii to measure tiny 'wobbles' of the star caused by their gravity.
Shifts in the 'colour' of star light due to the wobbles allowed them to work out properties of the planets such as their masses and orbital periods.
'We were surprised to find planets orbiting Kapteyn’s star,' says Dr Anglada-Escude.
'Previous data showed some moderate excess of variability, so we were looking for very short period planets when the new signals showed up loud and clear.'
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Two-dimensional gel electrophoresis
|Hyphenated||Capillary electrophoresis mass spectrometry|
Capillary electrophoresis (CE) is a family of electrokinetic separation methods performed in submillimeter diameter capillaries and in micro- and nanofluidic channels. Very often, CE refers to capillary zone electrophoresis (CZE), but other electrophoretic techniques including capillary gel electrophoresis (CGE), capillary isoelectric focusing (CIEF), capillary isotachophoresis and micellar electrokinetic chromatography (MEKC) belong also to this class of methods. In CE methods, analytes migrate through electrolyte solutions under the influence of an electric field. Analytes can be separated according to ionic mobility and/or partitioning into an alternate phase via non-covalent interactions. Additionally, analytes may be concentrated or "focused" by means of gradients in conductivity and pH.
The instrumentation needed to perform capillary electrophoresis is relatively simple. A basic schematic of a capillary electrophoresis system is shown in figure 1. The system's main components are a sample vial, source and destination vials, a capillary, electrodes, a high voltage power supply, a detector, and a data output and handling device. The source vial, destination vial and capillary are filled with an electrolyte such as an aqueous buffer solution. To introduce the sample, the capillary inlet is placed into a vial containing the sample. Sample is introduced into the capillary via capillary action, pressure, siphoning, or electrokinetically, and the capillary is then returned to the source vial. The migration of the analytes is initiated by an electric field that is applied between the source and destination vials and is supplied to the electrodes by the high-voltage power supply. In the most common mode of CE, all ions, positive or negative, are pulled through the capillary in the same direction by electroosmotic flow. The analytes separate as they migrate due to their electrophoretic mobility, and are detected near the outlet end of the capillary. The output of the detector is sent to a data output and handling device such as an integrator or computer. The data is then displayed as an electropherogram, which reports detector response as a function of time. Separated chemical compounds appear as peaks with different retention times in an electropherogram. Capillary electrophoresis was first combined with mass spectrometry by Richard D. Smith and coworkers, and provides extremely high sensitivity for the analysis of very small sample sizes. Despite the very small sample sizes (typically only a few nanoliters of liquid are introduced into the capillary), high sensitivity and sharp peaks are achieved in part due to injection strategies that result in concentration of analytes into a narrow zone near the inlet of the capillary. This is achieved in either pressure or electrokinetic injections simply by suspending the sample in a buffer of lower conductivity (e.g. lower salt concentration) than the running buffer. A process called field-amplified sample stacking (a form of isotachophoresis) results in concentration of analyte in a narrow zone at the boundary between the low-conductivity sample and the higher-conductivity running buffer.
To achieve greater sample throughput, instruments with arrays of capillaries are used to analyze many samples simultaneously. Such capillary array electrophoresis (CAE) instruments with 16 or 96 capillaries are used for medium- to high-throughput capillary DNA sequencing, and the inlet ends of the capillaries are arrayed spatially to accept samples directly from SBS-standard footprint 96-well plates. Certain aspects of the instrumentation (such as detection) are necessarily more complex than for a single-capillary system, but the fundamental principles of design and operation are similar to those shown in Figure 1.
Separation by capillary electrophoresis can be detected by several detection devices. The majority of commercial systems use UV or UV-Vis absorbance as their primary mode of detection. In these systems, a section of the capillary itself is used as the detection cell. The use of on-tube detection enables detection of separated analytes with no loss of resolution. In general, capillaries used in capillary electrophoresis are coated with a polymer (frequently polyimide or Teflon) for increased flexibility. The portion of the capillary used for UV detection, however, must be optically transparent. For polyimide-coated capillaries, a segment of the coating is typically burned or scraped off to provide a bare window several millimeters long. This bare section of capillary can break easily, and capillaries with transparent coatings are available to increase the stability of the cell window. The path length of the detection cell in capillary electrophoresis (~ 50 micrometers) is far less than that of a traditional UV cell (~ 1 cm). According to the Beer-Lambert law, the sensitivity of the detector is proportional to the path length of the cell. To improve the sensitivity, the path length can be increased, though this results in a loss of resolution. The capillary tube itself can be expanded at the detection point, creating a "bubble cell" with a longer path length or additional tubing can be added at the detection point as shown in figure 2. Both of these methods, however, will decrease the resolution of the separation. This decrease is almost unnoticeable if a smooth aneurysm is produced in the wall of a capillary by heating and pressurization, as plug flow can be preserved. This invention by Gary Gordon, US Patent 5061361, typically triples the absorbance path length. When used with a UV absorbance detector, the wider cross-section of the analite in the cell allows for an illuminating beam twice as large, which reduces shot noise by a factor of two. Together these two factors increase the sensitivity of Agilent Technologies's Bubble Cell CE Detector six times over that of one using a straight capillary. This cell and its manufacture are described on page 62 of the June 1995 issue of the Hewlett-Packard Journal.
Fluorescence detection can also be used in capillary electrophoresis for samples that naturally fluoresce or are chemically modified to contain fluorescent tags. This mode of detection offers high sensitivity and improved selectivity for these samples, but cannot be utilized for samples that do not fluoresce. Numerous labeling strategies are used to create fluorescent derivatives or conjugates of non-fluorescent molecules, including proteins and DNA. The set-up for fluorescence detection in a capillary electrophoresis system can be complicated. The method requires that the light beam be focused on the capillary, which can be difficult for many light sources. Laser-induced fluorescence has been used in CE systems with detection limits as low as 10−18 to 10−21 mol. The sensitivity of the technique is attributed to the high intensity of the incident light and the ability to accurately focus the light on the capillary. Multi-color fluorescence detection can be achieved by including multiple dichroic mirrors and bandpass filters to separate the fluorescence emission amongst multiple detectors (e.g., photomultiplier tubes), or by using a prism or grating to project spectrally resolved fluorescence emission onto a position-sensitive detector such as a CCD array. CE systems with 4- and 5-color LIF detection systems are used routinely for capillary DNA sequencing and genotyping ("DNA fingerprinting") applications.
In order to obtain the identity of sample components, capillary electrophoresis can be directly coupled with mass spectrometers or Surface Enhanced Raman Spectroscopy (SERS). In most systems, the capillary outlet is introduced into an ion source that utilizes electrospray ionization (ESI). The resulting ions are then analyzed by the mass spectrometer. This set-up requires volatile buffer solutions, which will affect the range of separation modes that can be employed and the degree of resolution that can be achieved. The measurement and analysis are mostly done with a specialized gel analysis software.
For CE-SERS, capillary electrophoresis eluants can be deposited onto a SERS-active substrate. Analyte retention times can be translated into spatial distance by moving the SERS-active substrate at a constant rate during capillary electrophoresis. This allows the subsequent spectroscopic technique to be applied to specific eluants for identification with high sensitivity. SERS-active substrates can be chosen that do not interfere with the spectrum of the analytes.
Modes of separation
The separation of compounds by capillary electrophoresis is dependent on the differential migration of analytes in an applied electric field. The electrophoretic migration velocity () of an analyte toward the electrode of opposite charge is:
The electrophoretic mobility can be determined experimentally from the migration time and the field strength:
where is the distance from the inlet to the detection point, is the time required for the analyte to reach the detection point (migration time), is the applied voltage (field strength), and is the total length of the capillary. Since only charged ions are affected by the electric field, neutral analytes are poorly separated by capillary electrophoresis.
The velocity of migration of an analyte in capillary electrophoresis will also depend upon the rate of electroosmotic flow (EOF) of the buffer solution. In a typical system, the electroosmotic flow is directed toward the negatively charged cathode so that the buffer flows through the capillary from the source vial to the destination vial. Separated by differing electrophoretic mobilities, analytes migrate toward the electrode of opposite charge. As a result, negatively charged analytes are attracted to the positively charged anode, counter to the EOF, while positively charged analytes are attracted to the cathode, in agreement with the EOF as depicted in figure 3.
The velocity of the electroosmotic flow, can be written as:
where is the electroosmotic mobility, which is defined as:
where is the zeta potential of the capillary wall, and is the relative permittivity of the buffer solution. Experimentally, the electroosmotic mobility can be determined by measuring the retention time of a neutral analyte. The velocity () of an analyte in an electric field can then be defined as:
Since the electroosmotic flow of the buffer solution is generally greater than that of the electrophoretic mobility of the analytes, all analytes are carried along with the buffer solution toward the cathode. Even small, triply charged anions can be redirected to the cathode by the relatively powerful EOF of the buffer solution. Negatively charged analytes are retained longer in the capilliary due to their conflicting electrophoretic mobilities. The order of migration seen by the detector is shown in figure 3: small multiply charged cations migrate quickly and small multiply charged anions are retained strongly.
Electroosmotic flow is observed when an electric field is applied to a solution in a capillary that has fixed charges on its interior wall. Charge is accumulated on the inner surface of a capillary when a buffer solution is placed inside the capillary. In a fused-silica capillary, silanol (Si-OH) groups attached to the interior wall of the capillary are ionized to negatively charged silanoate (Si-O−) groups at pH values greater than three. The ionization of the capillary wall can be enhanced by first running a basic solution, such as NaOH or KOH through the capillary prior to introducing the buffer solution. Attracted to the negatively charged silanoate groups, the positively charged cations of the buffer solution will form two inner layers of cations (called the diffuse double layer or the electrical double layer) on the capillary wall as shown in figure 4. The first layer is referred to as the fixed layer because it is held tightly to the silanoate groups. The outer layer, called the mobile layer, is farther from the silanoate groups. The mobile cation layer is pulled in the direction of the negatively charged cathode when an electric field is applied. Since these cations are solvated, the bulk buffer solution migrates with the mobile layer, causing the electroosmotic flow of the buffer solution. Other capillaries including Teflon capillaries also exhibit electroosmotic flow. The EOF of these capillaries is probably the result of adsorption of the electrically charged ions of the buffer onto the capillary walls. The rate of EOF is dependent on the field strength and the charge density of the capillary wall. The wall's charge density is proportional to the pH of the buffer solution. The electroosmotic flow will increase with pH until all of the available silanols lining the wall of the capillary are fully ionized.
In certain situations where strong electroosomotic flow toward the cathode is undesirable, the inner surface of the capillary can be coated with polymers, surfactants, or small molecules to reduce electroosmosis to very low levels, restoring the normal direction of migration (anions toward the anode, cations toward the cathode). CE instrumentation typically includes power supplies with reversible polarity, allowing the same instrument to be used in "normal" mode (with EOF and detection near the cathodic end of the capillary) and "reverse" mode (with EOF suppressed or reversed, and detection near the anodic end of the capillary). One of the most common approaches to suppressing EOF, reported by Stellan Hjertén in 1985, is to create a covalently attached layer of linear polyacrylamide. The silica surface of the capillary is first modified with a silane reagent bearing a polymerizable vinyl group (e.g. 3-methacryloxypropyltrimethoxysilane), followed by introduction of acrylamide monomer and a free radical initiator. The acrylamide is polymerized in situ, forming long linear chains, some of which are covalently attached to the wall-bound silane reagent. Numerous other strategies for covalent modification of capillary surfaces exist. Dynamic or adsorbed coatings (which can include polymers or small molecules) are also common. For example, in capillary sequencing of DNA, the sieving polymer (typically polydimethylacrylamide) suppresses electroosmotic flow to very low levels. A variety of dynamic capillary coating agents are commercially available to modify, suppress, or reverse the direction of electroosmotic flow. Besides modulating electroosmotic flow, capillary wall coatings can also serve the purpose of reducing interactions between "sticky" analytes (such as proteins) and the capillary wall. Such wall-analyte interactions, if severe, manifest as reduced peak efficiency, asymmetric (tailing) peaks, or even complete loss of analyte to the capillary wall.
Efficiency and resolution
The number of theoretical plates, or separation efficiency, in capillary electrophoresis is given by:
where is the number of theoretical plates, is the apparent mobility in the separation medium and is the diffusion coefficient of the analyte. According to this equation, the efficiency of separation is only limited by diffusion and is proportional to the strength of the electric field, although practical considerations limit the strength of the electric field to several hundred volts per centimeter. Application of very high potentials (>20-30 kV) may lead to arcing or breakdown of the capillary. Further, application of strong electric fields leads to resistive heating (Joule heating) of the buffer in the capillary. At sufficiently high field strengths, this heating is strong enough that radial temperature gradients can develop within the capillary. Since electrophoretic mobility of ions is generally temperature-dependent (due to both temperature-dependent ionization and solvent viscosity effects), a non-uniform temperature profile results in variation of electrophoretic mobility across the capillary, and a loss of resolution. The onset of significant Joule heating can be determined by constructing an "Ohm's Law plot", wherein the current through the capillary is measured as a function of applied potential. At low fields, the current is proportional to the applied potential (Ohm's Law), whereas at higher fields the current deviates from the straight line as heating results in decreased resistance of the buffer. The best resolution is typically obtained at the maximum field strength for which Joule heating is insignificant (i.e. near the boundary between the linear and nonlinear regimes of the Ohm's Law plot). Generally capillaries of smaller inner diameter support use of higher field strengths, due to improved heat dissipation and smaller thermal gradients relative to larger capillaries, but with the drawbacks of lower sensitivity in absorbance detection due to shorter path length, and greater difficulty in introducing buffer and sample into the capillary (small capillaries require greater pressure and/or longer times to force fluids through the capillary).
The efficiency of capillary electrophoresis separations is typically much higher than the efficiency of other separation techniques like HPLC. Unlike HPLC, in capillary electrophoresis there is no mass transfer between phases. In addition, the flow profile in EOF-driven systems is flat, rather than the rounded laminar flow profile characteristic of the pressure-driven flow in chromatography columns as shown in figure 5. As a result, EOF does not significantly contribute to band broadening as in pressure-driven chromatography. Capillary electrophoresis separations can have several hundred thousand theoretical plates.
The resolution () of capillary electrophoresis separations can be written as:
According to this equation, maximum resolution is reached when the electrophoretic and electroosmotic mobilities are similar in magnitude and opposite in sign. In addition, it can be seen that high resolution requires lower velocity and, correspondingly, increased analysis time.
Besides diffusion and Joule heating (discussed above), factors that may decrease the resolution in capillary electrophoresis from the theoretical limits in the above equation include, but are not limited to, the finite widths of the injection plug and detection window; interactions between the analyte and the capillary wall; instrumental non-idealities such as a slight difference in height of the fluid reservoirs leading to siphoning; irregularities in the electric field due to, e.g., imperfectly cut capillary ends; depletion of buffering capacity in the reservoirs; and electrodispersion (when an analyte has higher conductivity than the background electrolyte). Identifying and minimizing the numerous sources of band broadening is key to successful method development in capillary electrophoresis, with the objective of approaching as close as possible to the ideal of diffusion-limited resolution.
One of the main application of CE in forensic science is the development of methods for amplification and detection of DNA fragments using polymerase chain reaction (PCR) which has to lead to rapid and dramatic advances in DNA typing in forensic. DNA separations are carried out using thin CE, 50-mm, fused silica capillaries filled with a sieving buffer. These capillaries have excellent capabilities to dissipate heat, permitting much higher electric field strengths to be used than slab gel electrophoresis. Therefore separations in capillaries are rapid and efficient. Additionally, the capillaries can be easily refilled and changed for efficient and automated injections. Detection occurs via fluorescence through a window etched in the capillary. Both single-capillary and capillary-array instruments are available with array systems capable of running 16 or more samples simultaneously for increased throughput.
The major use of CE by a forensic biologist is typing of STR from biological samples to generate a profile from highly polymorphic genetic markers which differ between individuals. Other emerging uses for CE include the detection of specific mRNA fragments to help identify the biological fluid or tissue origin of a forensic sample.
Another application of CE in forensic is ink analysis where the discrimination of inkjet printing inks is becoming more necessary due to increasingly frequent counterfeiting of documents printed by inkjet printers. The chemical composition of inks provides very important information in cases of fraudulent documents and counterfeit banknotes. Micellar electrophoretic capillary chromatography (MECC) has been developed and applied to the analysis of inks which extracted from paper, Due to its high resolving power relative to inks containing several chemically very similar substances, differences between inks from the same manufacturer can also be distinguished. This makes it suitable for evaluating the origin of documents based on the chemical composition of inks. It is worth noting that because of the possible compatibility of the same cartridge with different printer models, the differentiation of inks on the basis of their MECC electrophoretic profiles is a more reliable method for the determination of the ink cartridge of origin (its producer and cartridge number) rather than the printer model of origin.
- Graham Kemp, Capillary electrophoresis: a versatile family of analytical techniques Archived April 27, 2006, at the Wayback Machine. Biotechnology and Applied Biochemistry (1998) 27, (9–17)
- Skoog, D.A.; Holler, F.J.; Crouch, S.R "Principles of Instrumental Analysis" 6th ed. Thomson Brooks/Cole Publishing: Belmont, CA 2007.
- Skoog, D.A.; Holler, F.J.; Crouch, S.R "Principles of Instrumental Analysis" 6th ed. Chapter 30 Thomson Brooks/Cole Publishing: Belmont, CA 2007.
- Dovichi, Norman (2000). "How capillary electrophoresis sequenced the human genome" (PDF). Angewandte Chemie International Edition. 39: 4463–4468. doi:10.1002/1521-3773(20001215)39:24<4463::aid-anie4463>3.0.co;2-8. Retrieved 2014-04-09.
- Butler, John (2004). "Forensic DNA typing by capillary electrophoresis using the ABI Prism 310 and 3100 genetic analyzers for STR analysis" (PDF). Electrophoresis. 25: 1397–1412. doi:10.1002/elps.200305822. PMID 15188225. Retrieved 2014-04-09.
- Lin H.; Natan, M.; Keating, C. Anal. Chem. 2000, 72, 5348-5355.
- Hjertén, Stellan (1985). "High-performance electrophoresis: elimination of electroosmosis and solute adsorption". Journal of Chromatography (347): 191–198.
- Doherty EA, Meagher RJ, Albarghouthi MN, Barron AE (2003). "Microchannel wall coatings for protein separations by capillary and chip electrophoresis". Electrophoresis. 24: 34–54. doi:10.1002/elps.200390029. PMID 12652571.
- Mandabhushi, Ramakrishna (1998). "Separation of 4-color DNA sequencing extension products in noncovalently coated capillaries using low viscosity polymer solutions". Electrophoresis. 19: 224–230. doi:10.1002/elps.1150190215. PMID 9548284.
- Target Discovery. "UltraTrol™ Dynamic Pre-Coatings". Retrieved 9 April 2014.
- Skoog, D.A.; Holler, F.J.; Nieman, T.A. "Principles of Instrumental Analysis, 5th ed." Saunders college Publishing: Philadelphia, 1998.
- Lauer and Rozing. "High Performance Capillary Electrophoresis: A primer" (PDF). Agilent Technologies. Archived from the original (PDF) on April 13, 2014. Retrieved 2014-04-09.
- Hauser, Peter C. (2016). "Chapter 2. Determination of Alkali Ions in Biological and Environmental Samples". In Astrid, Sigel; Helmut, Sigel; Roland K.O., Sigel. The Alkali Metal Ions: Their Role in Life. Metal Ions in Life Sciences. 16. Springer. pp. 11–25. doi:10.1007/978-3-319-21756-7_2.
- McCord, B. Encyclopedia of Forensic Sciences Capillary Electrophoresis in Forensic Genetics, 2013, 394-401.
- Oorschot R ; Ballantyne K. Capillary Electrophoresis in Forensic Biology, 2013, 560-566.
- Shallan A; Guijt R; Breadmore M. Capillary Electrophoresis Basic Principles, 2013, 549-559.
- Terabe, S.; Otsuka, K.; Ichikawa, K.; Tsuchiya, A.; Ando, T. Anal. Chem. 1984, 56, 111-113.
- Foley, J.P. Anal. Chem. 1990, 62, 1302.
- Carretero, A.S.; Cruces-Blanco, C.; Ramirez, S.C.; Pancorbo, A.C.; Gutierrez, A.F. J. Agric. Food. Chem. 2004, 52, 5791.
- Cavazza, A.; Corradini, C.; Lauria, A.; Nicoletti, I. J. Agric. Food Chem. 2000, 48, 3324.
- Rodrigues, M.R.A.; Caramao, E.B.; Arce, L.; Rios, A.; Valcarcel, M. J. Agric. Food Chem. 2002, 50, 4215.
- CE animations | <urn:uuid:6e530107-695a-4105-bc52-e4164c8de73d> | 3 | 5,470 | Knowledge Article | Science & Tech. | 28.356463 | 95,584,198 |
The surface-water components of the hydrologic cycle usually are considered to be rainfall and subsequent runoff. Yet, in many parts of North America, for a major part of the year, the more appropriate concept is precipitation and storage as snow and ice, followed by melting, followed by runoff. The timing involved in these two concepts is very different: Runoff follows rainfall almost immediately, whereas the time between snowfall and melt can range from days to months for seasonal snowcovers, and from months to millennia for glaciers. The predictive analysis of runoff also is very different: Prediction of runoff from rainfall requires knowledge of the precipitation pattern in time and space, whereas the prediction of runoff from snow and ice melt requires knowledge of the amount and distribution of snow in storage (measurable), and the meteorologic conditions that cause melt. The fact that snow and ice accumulate and melt to produce runoff in a very different way than does rainfall commonly is ignored in a simple hydrologic analysis. | <urn:uuid:1d4f2459-01d0-488d-8911-4ca75779b406> | 3.25 | 197 | Knowledge Article | Science & Tech. | 15.616714 | 95,584,231 |
Pass of Compiler
Again Pass of Compiler is one of the most important topics of the compiler design. we have provided the whole important key point about it in brief. So you can understand wit the easy language
Single and Multi-Pass Compilers (Pass of Compiler)
- One complete scan of a source program called the pass.
- Pass includes reading an input file and writing to the output file.
- In a single pass compiler analysis of the source, the statement is immediately followed by synthesis of equivalent target statement.
- It is difficult to compile the source program into single pass due to:
- A forward reference to a program entity is a reference to the entity which precedes its definition in the program.
- This problem can be solved by postponing the generation of target code until more information concerning the entity becomes available.
- So, It leads to the multi-pass model of compilation.
- In Pass I: Perform analysis of the source program and note relevant information.
- In Pass II: Generate target code using information noted in the pass I.
Effect of reducing the number of passes (Pass of Compiler)
- It is desirable to have a few passes because it takes time to read and write the intermediate file.
- On the other hand, if we group several phases into one pass we may be forced to keep
the entire program in the memory. Therefore the memory requirement may be large. | <urn:uuid:b7a5e1cd-41bc-4c66-818e-db7ad49f9020> | 3.265625 | 296 | Tutorial | Software Dev. | 37.335833 | 95,584,256 |
Find the area of the annulus in terms of the length of the chord which is tangent to the inner circle.
Can you make sense of these three proofs of Pythagoras' Theorem?
Semicircles are drawn on the sides of a rectangle. Prove that the sum of the areas of the four crescents is equal to the area of the rectangle.
Four identical right angled triangles are drawn on the sides of a square. Two face out, two face in. Why do the four vertices marked with dots lie on one line?
This is the second article on right-angled triangles whose edge lengths are whole numbers.
It's easy to work out the areas of most squares that we meet, but what if they were tilted?
This article discusses how every Pythagorean triple (a, b, c) can be illustrated by a square and an L shape within another square. You are invited to find some triples for yourself.
The first of two articles on Pythagorean Triples which asks how many right angled triangles can you find with the lengths of each side exactly a whole number measurement. Try it!
Prove that the shaded area of the semicircle is equal to the area of the inner circle.
ABCDEFGH is a 3 by 3 by 3 cube. Point P is 1/3 along AB (that is AP : PB = 1 : 2), point Q is 1/3 along GH and point R is 1/3 along ED. What is the area of the triangle PQR?
Sets of integers like 3, 4, 5 are called Pythagorean Triples, because they could be the lengths of the sides of a right-angled triangle. Can you find any more?
Prove Pythagoras' Theorem using enlargements and scale factors.
The diagram shows a very heavy kitchen cabinet. It cannot be lifted but it can be pivoted around a corner. The task is to move it, without sliding, in a series of turns about the corners so that it. . . .
Triangle ABC is an equilateral triangle with three parallel lines going through the vertices. Calculate the length of the sides of the triangle if the perpendicular distances between the parallel. . . .
What is the ratio of the area of a square inscribed in a semicircle to the area of the square inscribed in the entire circle?
It is obvious that we can fit four circles of diameter 1 unit in a square of side 2 without overlapping. What is the smallest square into which we can fit 3 circles of diameter 1 unit?
A rectangular field has two posts with a ring on top of each post. There are two quarrelsome goats and plenty of ropes which you can tie to their collars. How can you secure them so they can't. . . .
If the hypotenuse (base) length is 100cm and if an extra line splits the base into 36cm and 64cm parts, what were the side lengths for the original right-angled triangle?
Take any rectangle ABCD such that AB > BC. The point P is on AB and Q is on CD. Show that there is exactly one position of P and Q such that APCQ is a rhombus.
A half-cube is cut into two pieces by a plane through the long diagonal and at right angles to it. Can you draw a net of these pieces? Are they identical?
Which is a better fit, a square peg in a round hole or a round peg in a square hole?
Can you make sense of the three methods to work out the area of the kite in the square?
Three circular medallions fit in a rectangular box. Can you find the radius of the largest one?
Pythagoras of Samos was a Greek philosopher who lived from about 580 BC to about 500 BC. Find out about the important developments he made in mathematics, astronomy, and the theory of music.
What remainders do you get when square numbers are divided by 4?
Explain how the thirteen pieces making up the regular hexagon shown in the diagram can be re-assembled to form three smaller regular hexagons congruent to each other.
If you continue the pattern, can you predict what each of the following areas will be? Try to explain your prediction.
Equal circles can be arranged so that each circle touches four or six others. What percentage of the plane is covered by circles in each packing pattern? ...
The largest square which fits into a circle is ABCD and EFGH is a square with G and H on the line CD and E and F on the circumference of the circle. Show that AB = 5EF. Similarly the largest. . . .
Find the ratio of the outer shaded area to the inner area for a six pointed star and an eight pointed star.
A spider is sitting in the middle of one of the smallest walls in a room and a fly is resting beside the window. What is the shortest distance the spider would have to crawl to catch the fly?
A floor is covered by a tessellation of equilateral triangles, each having three equal arcs inside it. What proportion of the area of the tessellation is shaded?
A right-angled isosceles triangle is rotated about the centre point of a square. What can you say about the area of the part of the square covered by the triangle as it rotates?
A description of some experiments in which you can make discoveries about triangles.
Read all about Pythagoras' mathematical discoveries in this article written for students.
Prove that a triangle with sides of length 5, 5 and 6 has the same area as a triangle with sides of length 5, 5 and 8. Find other pairs of non-congruent isosceles triangles which have equal areas.
ABC and DEF are equilateral triangles of side 3 and 4 respectively. Construct an equilateral triangle whose area is the sum of the area of ABC and DEF.
A tennis ball is served from directly above the baseline (assume the ball travels in a straight line). What is the minimum height that the ball can be hit at to ensure it lands in the service area?
Two semi-circles (each of radius 1/2) touch each other, and a semi-circle of radius 1 touches both of them. Find the radius of the circle which touches all three semi-circles.
A 10x10x10 cube is made from 27 2x2 cubes with corridors between them. Find the shortest route from one corner to the opposite corner.
How many right-angled triangles are there with sides that are all integers less than 100 units?
What is the volume of the solid formed by rotating this right angled triangle about the hypotenuse?
Triangle ABC is right angled at A and semi circles are drawn on all three sides producing two 'crescents'. Show that the sum of the areas of the two crescents equals the area of triangle ABC.
A ribbon runs around a box so that it makes a complete loop with two parallel pieces of ribbon on the top. How long will the ribbon be?
Liethagoras, Pythagoras' cousin (!), was jealous of Pythagoras and came up with his own theorem. Read this article to find out why other mathematicians laughed at him.
This article for pupils and teachers looks at a number that even the great mathematician, Pythagoras, found terrifying.
Describe how to construct three circles which have areas in the ratio 1:2:3.
The area of a square inscribed in a circle with a unit radius is, satisfyingly, 2. What is the area of a regular hexagon inscribed in a circle with a unit radius?
The ten arcs forming the edges of the "holly leaf" are all arcs of circles of radius 1 cm. Find the length of the perimeter of the holly leaf and the area of its surface.
A fire-fighter needs to fill a bucket of water from the river and take it to a fire. What is the best point on the river bank for the fire-fighter to fill the bucket ?. | <urn:uuid:01582dee-284c-4d05-97da-03de8241bc40> | 3.609375 | 1,692 | Content Listing | Science & Tech. | 70.172664 | 95,584,258 |
Synthetic Biology Breakthrough Means Bacteria Could Produce Our Essential Drugs
- Bacteria could be programmed to produce drugs, thanks to breakthrough research into synthetic biology from the Universities of Warwick and Surrey.
- Researchers develop unique system to dynamically allocate essential cellular resources to both synthetic circuit and host cell – allowing both to survive and function properly.
- Adding synthetic circuitry to cells could enable them to be turned into factories for the production of antibiotics and other valuable drugs – opening up vast possibilities for the future of healthcare.
Bacteria could be programmed to efficiently produce drugs, thanks to breakthrough research into synthetic biology using engineering principles, from the University of Warwick and the University of Surrey.
Led by the Warwick Integrative Synthetic Biology Centre at Warwick’s School of Engineering and the Faculty of Health and Medical Sciences at the University of Surrey, new research has discovered how to dynamically manage the allocation of essential resources inside engineered cells - advancing the potential of synthetically programming cells to combat disease and produce new drugs.
The researchers have developed a way to efficiently control the distribution of ribosomes – microscopic ‘factories’ inside cells that build proteins that keep the cell alive and functional – to both the synthetic circuit and the host cell.
Synthetic circuitry can be added to cells to enhance them and make them perform bespoke functions – providing vast new possibilities for the future of healthcare and pharmaceuticals, including the potential for cells specially programmed to produce novel antibiotics and other useful compounds.
A cell only has a finite amount of ribosomes, and the synthetic circuit and host cell in which the circuitry is inserted both compete for this limited pool of resources. It is essential that there are enough ribosomes for both, so they can survive, multiply and thrive. Without enough ribosomes, either the circuit will fail, or the cell will die – or both.
Using the engineering principal of a feedback control loop, commonly used in aircraft flight control systems, the researchers have developed and demonstrated a unique system through which ribosomes can be distributed dynamically - therefore, when the synthetic circuit requires more ribosomes to function properly, more will be allocated to it, and less allocated to the host cell, and vice versa.
Declan Bates, Professor of Bioengineering at the University of Warwick’s School of Engineering and Co-Director, Warwick Integrative Synthetic Biology Centre (WISB) commented “Synthetic Biology is about making cells easier to engineer so that we can address many of the most important challenges facing us today - from manufacturing new drugs and therapies to finding new biofuels and materials. It’s been hugely exciting in this project to see an engineering idea, developed on a computer, being built in a lab and working inside a living cell. ”
José Jiménez, Lecturer in Synthetic Biology at the University of Surrey's Faculty of Health and Medical Sciences commneted “The ultimate goal of the selective manipulation of cellular functions like the one carried out in this project is to understand fundamental principles of biology itself. By learning about how cells operate and testing the constraints under which they evolve, we can come up with ways of engineering cells more efficiently for a wide range of applications in biotechnology.”
Ribosomes live inside cells, and construct proteins when required for a cellular function. When a cell needs protein, the nucleus creates mRNA, which is sent to the ribosomes – which then synthesise the essential proteins by bonding the correct amino acids together in a chain.
Based on an original idea arising from discussions between Alexander Darlington, a PhD candidate at the University of Warwick, and Dr. Jiménez, the theory of dynamically allocating resources in cells was tested and analysed with mathematical modelling at Warwick, and then built and demonstrated in the laboratory at the University of Surrey.
This article has been republished from materials provided by the University of Warwick. Note: material may have been edited for length and content. For further information, please contact the cited source.
Dynamic allocation of orthogonal ribosomes facilitates uncoupling of co-expressed genes. Alexander P. S. Darlington, Juhyun Kim, José I. Jiménez & Declan G. Bates. Nature Communications 9, Article number: 695 (2018). doi:10.1038/s41467-018-02898-6.
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3rd International Conference on Diagnostic Microbiology and Infectious Diseases
Sep 24 - Sep 25, 2018 | <urn:uuid:98fe4ab8-8ad3-4e5a-af65-6baae5d06ef4> | 3.34375 | 1,074 | News Article | Science & Tech. | 17.040963 | 95,584,300 |
A brave new synthetic world
- 3.8k Downloads
KeywordsSynthetic Biology Harvard Medical School Synthetic Biologist Craig Venter Institute Metabolic Pathway Engineering
Like Aldous Huxley's Brave New World at the time of its publication, the field of synthetic biology currently has skeptics and critics among both scientists and non-scientists. But in contrast to Huxley's pessimistic outlook, synthetic biology has the opportunity to highlight the good to society that can be derived from biotechnological breakthroughs. This naturally begs the question: what exactly is synthetic biology? A meeting at Harvard Medical School last December revisited this frequently posed question. Keynote speaker Clyde Hutchison (J Craig Venter Institute, Rockville, USA) offered his perspective: "while some have a strong desire to sort this out, I'm not interested in this question, as it is largely about semantics and not in itself a scientific question".
Nevertheless, an analogy to computer science provides a good basis to describe synthetic biology. If we think of the cell as a computer, the work of synthetic biologists can be simplified into three main approaches: the creation of a minimal computer from basic building blocks; software to program a working computer; and the application of these devices or knowledge gained in the engineering process. We describe here a few of the highlights of the meeting. Presentations covered a wide spectrum of topics, ranging from the engineering of artificial cells and the creation of gene circuits in cell-free, prokaryotic and mammalian systems to the direct synthesis and recoding of whole genomes.
Protocells and cell-free systems
In his keynote address, Jack Szostak (Harvard Medical School, Boston, USA) discussed his group's efforts to create lipid-vesicle-based protocells using basic chemical substrates as building blocks. When starting from scratch, many cellular processes perceived as simple become formidable challenges. For example, a cell not only has to produce a cell wall and replicate intracellular biomolecules (nucleic acids, proteins, lipids), but these processes need to occur in a coordinated manner to produce growth. Szostak gave an interesting example of one problem. Large vesicles were forced through pores of a smaller diameter to try and divide them. This simple strategy worked, but each round of division resulted in significant loss of intravesicular materials: a large sphere holds approximately 40% more material than two smaller, equal-sized spheres with the same total surface area as the large sphere. In this context, Giovanni Murtas (Enrico Fermi Center, Rome, Italy) described his group's efforts to achieve coupling between vesicle growth and synthesis of intracellular materials. They have encapsulated enzymatic reactions for synthesizing vesicle materials within a liposome vesicle.
Given the multitude of technical challenges, the functionality of such 'protocells' remains limited. Researchers in this area predict that the engineering of protocells could eventually lead to insights that will explain the emergence of life billions of years ago. But protocells are more likely to find a use sooner as nano-scale reactors for producing molecules that are difficult to produce in cells, such as cytotoxic proteins.
Components, circuits and cell populations
The dominant flavor of synthetic biology is arguably the integration of non-natural, or synthetic, gene networks into existing cellular pathways to better understand or program cellular behavior. These approaches are analogous to the design and implementation of software that programs customized functions in a working computer, with the distinction that engineering of biological systems is performed in the dynamic context of evolution. Yet, despite the physical access to cellular machinery, programming complex behavior inside cells remains a challenge.
Addressing such a challenge requires not only the development of well-characterized parts (as advocated by the BioBricks Foundation http://bbf.openwetware.org), but also a better understanding of different control strategies. Addressing the latter point, James Collins (Boston University, USA) described a series of synthetic gene circuits of diverse function, such as the toggle switch and RNA-based switches, and the integration of simple circuits to generate more complex systems. He described the introduction of one RNA-based switch to give tight control of the expression of a toxin (CcdB) in the bacterium Escherichia coli. This enabled precise mapping of the death pathway initiated by the toxin and revealed a common death pathway in E. coli exposed to bactericidal agents. Timothy Lu (Harvard-MIT Health Sciences and Technology, Cambridge, USA), from the same group, described the practical application of two re-engineered T7 phages: one encodes a protein that disrupts bacterial biofilm formation and the other encodes a protein that targets an antibiotic resistance mechanism in E. coli, improving the efficacy of antibiotics against the bacteria it infects.
For eukaryotes, Pamela Silver (Harvard Medical School, Boston, USA) described a number of artificial gene-control circuits she and her colleagues have devised to carry out predefined functions in eukaryotic cells. One is a eukaryote-specific negative feedback oscillator based on intron-mediated time delay. Transcription of the intron introduces a time delay, enabling the generation of oscillations by the repressor. Interestingly, Silver and colleagues observed that the oscillation characteristics could be modulated by using introns of varying length. She suggested that such intron-mediated oscillations might underlie cell-fate decisions in development.
Beyond single cells, increasing effort is being devoted to programming population dynamics. One of us (LY) described the use of bacterial communication (quorum sensing) to program interactions between two populations of E. coli, which resulted in a synthetic predator-prey ecosystem that can generate oscillations in the two populations. This synthetic ecosystem has been used to explore the interplay of cellular motility, population segregation and signal diffusion in the maintenance of biodiversity in microbial ecosystems. In addition to temporal dynamics, cell-cell communication can also be used to generate self-organized spatial patterns, and two such examples were presented at the conference. Jian-dong Huang (University of Hong Kong, Hong Kong) described a system where cell-cell communication in E. coli was coupled with cellular motility. The modified bacteria generated a near-perfect, self-organized ring pattern on an agar plate. Ron Weiss (Princeton University, Princeton, USA) described another circuit in E. coli designed to generate a Turing pattern (for example, hexagonal arrays of spots) in a lawn of bacteria. These cells synthesize two signals, one serving as an activator and the second as an inhibitor. Under appropriate conditions, the system was able to generate regular spot-like patterns.
In addition to exploring the limits of programming complex dynamics, Weiss proposed that these systems could offer insight into the dynamics of natural systems, such as whether self-organization underlies developmental processes or pigmentation patterns in animal skin.
Emerging technologies and genome engineering
Traditional genetic engineering technologies devised 20 or more years ago are now insufficient for the complex engineering of biological systems required by synthetic biology. Streamlining of DNA synthesis and the development of strategies for efficiently introducing synthetic DNA in vivo were discussed by a number of speakers.
Peter Carr (Massachusetts Institute of Technology, Cambridge, USA) described work with the goal of automating the entire DNA synthesis process. He is working towards a pipeline that can integrate oligonucleotide assembly for any desired DNA sequence from high-density microchips on microfluidic devices with optimized DNA error-correction strategies, yielding the required DNA fragment rapidly and at significantly reduced cost. With a similar goal, Heinz Schwer (Sloning Biotechnology, Puchheim, Germany) presented a new method of making DNA sequences for use in protein engineering. Using a library of pre-made double-stranded DNA triplets that act as universal building blocks, Schwer and his colleagues are able to assemble any desired DNA fragment with high fidelity compared to existing DNA synthesis and cloning methods.
Clyde Hutchison described the Venter Institute's "quest for a minimal cell". With the goal of identifying the minimal set of genes that are needed for life, this work pursues two main tracks of research that Hutchison termed synthetic genomics. First, the group obtained 101 fragments of around 5 kb each from commercial suppliers of synthetic DNA and assembled the entire genome of Mycoplasma genitalium through a series of in vitro, bacteria- and yeast-based strategies. Concurrently, they developed a strategy for replacing the genome of a bacterial cell with one from another species, inserting a genome isolated from M. mycoides into M. capricolum cells. Hutchison described the merging of these two efforts by transplanting the synthesized M. genitalium genome into native M. genitalium strains as challenging work in progress.
In complementary research, one of us (FI) described work on genome engineering in E. coli aimed at introducing increased genetic diversity into cell populations using a combination of bioengineering and evolution. Our group has developed a highly efficient recombination method that gives large numbers of desired mutations across whole genomes. In one experiment, a new genetic code in E. coli is being constructed to facilitate the incorporation of non-natural amino acids and to create safe genetically modified organisms. The same approach is being applied to obtain genetic diversity for applications in metabolic pathway engineering. On the theme of creating strains with many mutations, Fritz Roth (Harvard Medical School, Boston, USA) described a new high-throughput approach for creating yeast strains with increased combinations of gene knockouts or insertions. This strategy may facilitate introduction of complex genetic circuits into the yeast chromosome.
While a clear and concise definition has yet to emerge, synthetic biology may simply be part of the natural maturation of biotechnology, in which the engineering of biological systems is becoming a formal discipline. Great expectations exist for biotechnology's potential in addressing global challenges in medicine, energy supply and the environment. Can synthetic biology meet these challenges and be embraced by its present skeptics and critics? With hindsight, Huxley's book shows that anticipating how developments will change society is probably unreliable; only time will tell if synthetic biology can channel biotechnology advances to the greater good of society. | <urn:uuid:26c05de9-1989-4142-836b-17532196807d> | 3.171875 | 2,102 | Academic Writing | Science & Tech. | 16.848055 | 95,584,314 |
Dispersal and Primary Establishment of Vegetation
A retreating glacier leaves large areas of open and virgin soil. Very soon the first plants appear, but there are indications that it takes hundreds of years to establish a mature vegetation. It is of interest to know which are the decisive factors in the development of the vegetation in the first phase, and also what happens when new plant communities replace the preceeding ones in a succession. With the purpose of gaining some basic insight into these problems, seed dispersal and vegetation were studied in front of the glacier Hardangerjøkulen at Finse, Central Norway. R. Elven was responsible for studies on establishment of vegetation while L.Ryvarden was in charge of the dispersal experiments.
KeywordsSeed Dispersal Alpine Zone Virgin Soil Terminal Moraine Outer Slope
Unable to display preview. Download preview PDF.
- Dahl, E.: Amfiatlantiske planter. Blyttia 16,93–121 (1958).Google Scholar
- Elven, R.: Plant communities on recently deglaciated moraines at Finse, southern Norway. In: Vik, R. (Ed.): IBP in Norway. Methods and results. Sections PT-UM Grazing project, Hardangervidda, Botanical investigations, pp. 381–467. Oslo: Norwegian National IBP Committee 1975.Google Scholar
- Lye, K. A.: Survey of the main plant communities on Hardangervidda. In: Wielgolas-Ki, F. E. (Ed.): Fennoscandian tundra ecosystems, Parti: Plants and microorganisms, pp. 68–73. Berlin-Heidelberg-New York: Springer 1975.Google Scholar
- Ryvarden, L.: Studies in seed dispersal I. Trapping of diaspores in the alpine zone at Finse, Norway. Norw. J. Botan. 18,215–226 (1971).Google Scholar
- RYVARDEN, L.: Studies in seed dispersal II. Trapping of winter-dispersed diaspores in the alpine zone at Finse, Norway. Norw. J. Botan. 22 (1975) In press.Google Scholar | <urn:uuid:a05059de-0859-4cf7-b28f-77f7e62530f8> | 3.328125 | 471 | Truncated | Science & Tech. | 53.940913 | 95,584,315 |
Afghanistan has big demand for power. Just 15 years ago, only five percent of the country's citizens had access to electricity, and while today just 32 percent of people have access to grid-connected power, the demand is growing by 25 percent annually, putting pressure on the nation to up their power supply.
This, however, is a pricey problem: Afghanistan imports 73 percent of its power from surrounding countries. So in 2008, the government allocated $2 billion to expand its onsite energy capabilities, including through conventional means like coal. But a large portion of the money will be spent on more eco-friendly solutions: wind and solar.
For the latter, the Asian Development Bank has announced that it will spend $45 million on a 20-megawatt solar power plant in Kabul’s Surobi district. The country’s total demand for power is about 3 gigawatts, with domestic generation at 300 megawatts, so while the solar power plant will solve just a portion of the problem, it's a telling turn of events for renewables.
"The demand for power is rapidly growing across Afghanistan,” Samuel Tumiwa, a country director at The Asian Development bank said in the statement. “The new on-grid solar power generation project, which is the largest of its kind in Afghanistan, will not only provide access to a clean and reliable power supply, but also demonstrate the viability of future renewable energy investments.”
The plant will generate at least 43,000 megawatts-hours of power and will offset the equivalent of 13,000 tons of carbon dioxide in the first year after it is complete, which should be about 18 months after final contracts are signed, a spokesman of government-owned utility Da Afghanistan Breshna Sherkat told Bloomberg. Once completed, it will satisfy part of the electricity needs for Kabul as well as the eastern province of Nangarhar and Laghman.
A shepherd grazing his flock of sheep near an abandoned historic castle, called Qala-e Kohna based next to the Helmand River. #Helmand, #Afghanistan. Photo by Mohammad Omar Lemar @mohammadlemaromar. #everydayHelmand, #everydayAfghanistan, #everydayAsia, #everydayeveryWhere, #Instagram. مرد چوپان در حال چراندن رمه گوسفندانش در نزدیکی قلعه ای تاریخی که در جوار رود هلمند واقع شده است. این قلعه که کسی در آن بود و باش ندارد به اسم قلعه کهنه در میان مردم مشهور است. #هلمند، #افغانستان. عکاس: محمد عمر لمر
This turn towards solar makes sense on several levels for Afghanistan. For one, the cost of solar equipment is rapidly declining (prices for solar panels have dropped 62 percent over the past five years, according to Bloomberg) as popularity grows and systems become more efficient. Now, what was once seen as an expensive way to create power is a viable option for developing countries looking to build out their infrastructure.
Plus, Afghanistan has an abundance of sunlight.
"Considering 300 sunny days per year with free solar irradiation to generate solar power, it makes Afghanistan an attractive country for implementing solar power projects," Finance Minister Eklil Hakimi said in the statement.
A frame look into Afghanistan's first named national park, Band-e Amir. The park is a collection of six deep sapphire-blue lakes lied in the central highlands of the country. At the other side, Band-e Amir is one of Afghanistan's well known touristic attractions alongside other natural and cultural heritages and beauties located in the same province, #Bamiyan, #Afghanistan. Photo by Amir Masoud Soheili @masoudsoheili #everydayBamiyan, #everydayAfghanistan, #everydayAsia, #everydayeveryWhere, #Instagram, #mothernature, #nature.
Though the plant in Kabul will be the largest in the country, it's not the first. In September, Dynasty Oil & Gas PVT Ltd. of India began construction on a 10-megawatt solar power plant in southern Kandahar city, funded by the U.S. Agency for International Development. Additionally, the country is looking to capture an estimated 158 gigawatts of wind energy as part of its master energy plan.
Researchers from marine life advocates Oceana have discovered a surprising new world under the sea near Sicily.
Sweden's aggressive target of generating over 40 terawatt-hours of renewable energy by 2030 could be reached nearly a decade early. A massive amount of wind power projects could hit a snag in market value with subsidies, but SWEA could push to close those up by the end of the year.
Starbucks is ramping up its sustainability efforts with a plan to eradicate the use of plastic straws in its assembly line. | <urn:uuid:c29e95ba-7fa4-49c6-ba77-f31d3b670539> | 2.71875 | 1,173 | News Article | Science & Tech. | 44.036045 | 95,584,373 |
As we age, an increasing proportion of the cells in our tissues become “zombified”...
Scientists are planning to create a map that contains the molecular fingerprints of every cell in the body.
People with post-traumatic stress disorder pay more attention to surprise.
Mice that lack a protein called IFNG2 suffer from the symptoms of pre-eclampsia
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Ants prevent the spread of disease by killing other ants that are infected.
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3 scientists, 3 mins, spaghetti and marshmallows.....
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Can killer whales talk? | <urn:uuid:fd056ff8-87b9-4df7-8e94-302eafe2df79> | 2.703125 | 342 | Content Listing | Science & Tech. | 65.774787 | 95,584,405 |
Researchers have identified a crucial step in a genetic process required for the development of viable eggs. The process, known as imprinting, distinguishes the paternally-inherited and the maternally-inherited copies of a number of developmentally important genes.
The majority of mammalian genes are present in two copies, both of which are equally expressed and regulated. A small number of mammalian genes, however, are subject to special regulation by a process called gene imprinting. The imprint is a chemical mark, such as methylation, attached to genes during egg or sperm development. Imprinting physically marks genes in such a way that the parental origin of the two copies can be distinguished so that one parents copy is turned on while the other is silenced. Imprinted genes are the likely reason that maternal and paternal contributions are necessary for normal mammalian development.
Exploring the mechanisms underlying gene imprinting may provide insight into so-called epigenetic control of gene expression, in which the cellular machinery governs the expression of genes in the cell. The function of that machinery, which makes modifications to the genome, remains among the major mysteries in biology.
Jim Keeley | HHMI
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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19.07.2018 | Earth Sciences
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In terms of atmosphere, there's no place in the solar system like Earth, with its nurturing environment for life. The planet's atmosphere consists of a number of gases of fixed concentration such as nitrogen, carbon dioxide, oxygen and argon. In addition, other gases in the atmosphere have varying concentrations, depending upon geography and time of the year. One such gas is water vapor, and its concentration depends upon local sources.
Among the numerous sources of water vapor on Earth, the largest is the ocean. Sunlight warms the ocean, leading to evaporation of the seawater. The greater the temperature, the more water vapor is produced. Approximately 90 percent of the water vapor on Earth is produced this way.
Plants require water to carry out photosynthesis and create a food source. During this process, plant roots remove water moisture from the soil. Water is transported from the roots to the leaves, where it is used to carry out photosynthesis. A percentage of the water evaporates, however, and is released into the atmosphere. This process, known as plant transpiration, produces approximately 10 percent of the Earth's water vapor.
Volcanic activity on the Earth produced a significant amount of atmospheric gases in the early atmosphere. Since then, volcanism has declined but still generates a small contribution of the water vapor in the Earth's atmosphere. A geyser is where groundwater interacts with brine heated from the Earth's magma and results in high-pressure water jets that erupt from the ground. A small percentage of the water evaporates into the atmosphere as the eruption occurs.
Percentages of Vapor
Because the creation of water vapor depends on the local environment, the percentage within the atmosphere hinges on geology and temperature. Above the ocean in warm environments, the percentage of water vapor within the Earth's atmosphere can be as high as 4 percent. In contrast, cold locations such as the geographic poles have water vapor values of less than 1 percent. This is due to two effects. First, higher temperature leads to more evaporation of local water into the atmosphere. Second, the amount of water that can be held within the atmosphere is higher at greater temperatures. | <urn:uuid:be0a9e44-af45-4c48-99ab-b6026186f9d6> | 4.09375 | 439 | Knowledge Article | Science & Tech. | 37.752049 | 95,584,471 |
From Mexico to Malaysia, payments for watershed service schemes are at a critical juncture right now as watershed managers work to transform them from publicly funded pilot programs into privately funded markets. Will watershed markets be able to make this all-important leap? The Ecosystem Marketplace looks at this question and highlights the importance of getting the science right when it comes to markets for watershed services. All your friends are raving about the latest ancient herbal remedy. From fevers to fatigue, it is touted as a panacea curing all ills. Sure, it's expensive, but you rationalize that your health is worth it. While it seems to help your friends, it affects everyone differently and nobody can tell you how it works. How do you know if the cure is right for you? Undoubtedly, buyers expect a return on their investment. But, what if the product (or service) for which you are paying is elusive? Take water. Complex processes-both natural and man-made– influence the quantity and quality of water, but forests, like that ancient herbal remedy, have taken on the mythical role as the sole prescription for improving watershed services. Around the world, in fact, tropical watershed conservation initiatives based largely on this idea are in the process of transforming themselves from publicly funded pilot projects into privately funded, self-sustaining programs. Whether or not watershed markets will be able to make this all-important leap depends, in large part, on how well watershed managers understand the science of the services they are selling. "The general perception is that deforestation leads to less water," says Meine van Noordwijk, hydrologist with Consultative Group on International Agricultural Research (CGIAR) in Bogor, Indonesia. But, he warns, it's not that simple.
Myth 1: Forests prevent floods
Unfortunately, the link between forests and flooding is a little understood matter of scale and, according to van Noordwijk, "What is wrong with the general dialogue is observations taken at one scale are assumed relevant at all scales." Hydrologist L.A. Bruijnzeel of Vrije Universiteit in Amsterdam has shown that, despite the research linking deforestation to local risks of flooding in smaller catchments, there is sparse evidence linking deforestation to flooding in larger watersheds. Most studies are conducted on watersheds smaller than 10 hectares, he observes, while policymakers are generally interested in scales of 100 hectares and up. Absent data, a blame game based on widespread myths is often played in the wake of disastrous flooding. "It's easier to put the blame sometimes far away rather than looking at your own system," says Thomas Hofer, UN Food and Agricultural Organization Forestry Officer. Motivated by consistent headlines blaming mountain people in the Himalayas for flooding in Bangladesh, Hofer recently conducted one of the only large-scale hydrological studies of watershed services in the world. And, perhaps not surprisingly, his findings were surprising. Specifically, Hofer discovered that the coincidental timing of the highest flow in the main rivers, rainfall peaks within Bangladesh, high groundwater levels, and runoff from the nearby Meghalaya Hills, drove floods in Bangladesh regardless of vegetation patterns. He concluded that afforestation programs in the mountains-while essential for mountain communities and their local environment – could not prevent floods in the lowlands. Other scientists, too, now agree that land use has no real impact in the face of extreme climate events. While good plant cover protects against surface erosion and well-developed tree cover may reduce shallow landslides, there's only so much trees can do in the face of prolonged periods of rain. Once the soil is saturated, larger slides are difficult to stop, forest or no.
Myth 2: Forests increase flows
Forests have long been described as a water-wicking sponge-absorbing intense rainfall during storms and then releasing water when it is most needed during drier times. But Ian Calder, hydrologist with the Centre for Land Use and Water Resources Research (CLUWRR) at Newcastle University, has found that reforestation efforts can actually lower flows. "In many cases the extra evaporation from a forest outweighs any small increase in rainfall such that the net effect is flow reduction," says Calder. "I believe you can ensure a good steady supply of water and more with a well-managed land use that has no forest. But well-managed is the important qualifier." As Calder suggests, watersheds are an intricate matrix of vegetation, soils, and underlying geology. Scientists now say that determining the effects of specific vegetation types within a watershed landscape is the single most urgent watershed research need. The emerging lesson from early research in this area, says Bruijnzeel, is that forest influences on rainfall patterns are highly site-specific. Evidence suggesting forests increase rainfall in some areas does exist, but they often have a smaller effect on precipitation patterns in maritime climates than, for instance, changing sea surface temperatures. Cloud mountain forests, meanwhile, tell a different story. Recent focus on cloud forest systems in Costa Rica shows that fewer clouds form over cleared areas, suggesting that large forests may affect rainfall patterns. "There's nothing fundamentally different between processes of a tropical or temperate forest, but in cloud mountain systems, cloud water may be sufficient to more than balance the extra interception loss expected from a forest, leading to net increase in flow from the forest," explains Calder. In lieu of site-specific data, researchers must be more creative with existing data. "Expressing flow relative to rainfall is essential," says van Noordwijk. He adds that metrics should be separated conceptually into 3 areas: rainfall variation, landscape make-up, and human activities. By pursuing this approach, he says, "We're starting to make progress."
Scientists are on the verge of moving beyond what forests do NOT do to what they DO, in fact, do in watersheds. "In the last 5-10 years, hydrologists have come up with general purpose adaptable models," says World Bank environmental economist Kenneth Chomitz. Using these innovative modeling techniques, scientists are now studying watershed services at the larger, landscape scales useful to policy-makers. And, as they look at the combined effects of forests and farms, researchers say they will, for the first time, be able to sort out the weaker effects of deforestation from the stronger effects of climate, geology and terrain. Existing models such as TOPOG, developed by scientists at Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) scientists, describe how water moves through landscapes; over the land surface, into the soil, through the soil and groundwater and back to the atmosphere via evaporation. Sediment transport can also be estimated. TOPOG, however, is not immune to the scale issues. It is intended for use with small catchments no bigger than 10 square kilometers. The simulation model GenRiver, meanwhile, allows scientists to explore historical changes in river flow resulting from land use change. And a new catchment climate classification tool -designed by CSIRO scientists with Bruijnzeel-models seasonal rainfall, land use, potential evapotranspiration, relief, soils and geology to identify opportunities for water resources services from afforestation that have been missed so far. While consensus is growing about the roles of watersheds, models can serve as a bridge between those who feel that processes are largely understood and applicable to every region, and those who believe much more site-specific data is needed to understand regional workings. But models still face stumbling blocks. Firstly, cost. Site-specific hydrological models in Monteverde, Costa Rica have taken 3 years and $800,000, and researchers are still working on answers. Models also tend to characterize land as pure forest or pure agriculture-hardly reflective of the mosaic of land uses found in areas such as Southeast Asia. And, last but not least, there is still a significant gap in knowledge of the time scale of degradation versus rehabilitation.
Despite their limitations, scientists stress that models are advancing policy by replacing old assumptions about forests and hydrology with more targeted questions. According to Chomitz at the World Bank, "The nitty-gritty question that models and data are going to help us sort out is 'Is this action going to make a positive difference?'" As the yeas and nays to this query begin to roll in from around the world, a weighty new task is already forming on the horizon: sorting out the real opportunities for sustainable market-based conservation from the opportunities for a more traditional kind of government and non-profit support. For too long, people have perpetuated the myth that forests represent a magic remedy for watershed ills in order to help secure funding for vital community development and forestry schemes. Now, with policy-makers the world-over looking favorably on payments for environmental services, the time has come to go back and take a good look at the science, otherwise advocates of a market-based approach to watershed conservation risk blowing their repute by misdiagnosing the problem. And, in the case of watersheds, prescribing a good treatment to the wrong patients will advance neither markets nor the environment in the long-run. Virginia Gewin is a freelance science writer based in Portland. She may be reached at email@example.com. | <urn:uuid:358e19f0-7aab-4b44-971c-6fa459ddce5f> | 2.578125 | 1,894 | Nonfiction Writing | Science & Tech. | 31.551732 | 95,584,474 |
Microbes may play important role in the global carbon cycle
Two miles below the surface of the ocean, researchers have discovered new microbes that "breathe" sulfate.
The microbes, which have yet to be classified and named, exist in massive undersea aquifers -- networks of channels in porous rock beneath the ocean where water continually churns. About one-third of the Earth's biomass is thought to exist in this largely uncharted environment.
"It was surprising to find new bugs, but when we go to warmer, relatively old and isolated fluids, we find a unique microbial community," said Alberto Robador, postdoctoral researcher at the USC Dornsife College of Letters, Arts and Sciences and lead author of a paper on the new findings that will be published by the open-access journal Frontiers in Microbiology on Jan. 14.
Sulfate is a compound of sulfur and oxygen that occurs naturally in seawater. It is used commercially in everything from car batteries to bath salts and can be aerosolized by the burning of fossil fuels, increasing the acidity of the atmosphere.
Microbes that breathe sulfate -- that is, gain energy by reacting sulfate with organic (carbon-containing) compounds -- are thought to be some of the oldest types of organisms on Earth. Other species of sulfate-breathing microbes can be found in marshes and hydrothermal vents.
Microbes beneath the ocean's crust, however, are incredibly tricky to sample.
Researchers from USC and the University of Hawaii took their samples from the Juan de Fuca Ridge (off the coast of Washington state), where previous teams had placed underwater laboratories, drilled into the ocean floor. To place the labs, they lowered a drill through two miles of ocean and bored through several hundred feet of ocean sediment and into the rock where the aquifer flows.
"Trying to take a sample of aquifer water without contaminating it with regular ocean water presented a huge challenge," said Jan Amend, professor at USC Dornsife and director of the Center for Dark Energy Biosphere Investigations (C-DEBI), which helped fund the research.
To solve this problem, C-DEBI created Circulation Obviation Retrofit Kit (CORK) observatories. The moniker was basically dreamed up to fit the term "CORK" because these devices create a seal at the seafloor, like a cork in a bottle, allowing scientists to deploy instruments and sampling devices down a borehole while keeping ocean water out.
Samples were then shuttled to the surface by remote-controlled undersea vehicles or "elevators" -- balloons that drop ballast and float samples gently up to the waiting scientists.
Like the microbes on the forest floor that break down leaf litter and dead organisms, the microbes in the ocean also break down organic -- that is, carbon-based -- material like dead fish and algae. Unlike their counterparts, however, the microbes beneath the ocean crust often lack the oxygen that is used on land to effect the necessary chemical reaction.
Instead, these microbes can use sulfate to break down carbon from decaying biological material that sinks to the sea bottom and makes its way into the crustal aquifer, producing carbon dioxide.
Learning how these new microbes function will be important to getting a more accurate, quantified understanding of the overall global carbon cycle -- a natural cycling of carbon through the environment in which it is consumed by plants, exhaled by animals and enters the ocean via the atmosphere. This cycle is currently being disrupted by man-made carbon dioxide emissions.
"This is the first direct account of microbial activity in these type of environments," Robador said, "and shows the potential of these organisms to respire organic carbon."
The research was funded by the National Science Foundation (C-DEBI award OCE0939564, MCB0604014, 1207880 and 1207874) and the NASA Astrobiology Institute.
The full study can be found online here: http://journal.
Image: C-DEBI researchers deply the ROV Jason to collect samples. Alberto Robado / USC
Photos and an infographic showing how CORKs work are available in high resolution at https:/
The credit for the infographic is "Courtesy of USC" and the credit for the photos is "Courtesy of Alberto Robado / USC."
Watch a video about C-DEBI's work with CORKs here: https:/
Robert Perkins | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Alexander, W. Nathan Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia.
Last reviewed:October 2016
Show previous versions
- Units of measurement
- Principle of operation
- Types of constant-mass hydrometers
- Float-type hydrometer
- Needle-type hydrometer
- Ball-type hydrometer
- Links to Primary Literature
- Additional Readings
An instrument used to measure the density of a liquid. Often, the measurement is given in reference to the density of another liquid, typically water, as specific gravity, SG = ρsample/ρref, where ρsample and ρref are the densities of the sample and the reference liquid, respectively, but other units are common as well. For instance, degrees Baumé, API, or Brix, and alcohol proof are all units of measurement found on hydrometer scales, each of which ultimately relates to the density of the solution for defined applications. These density relations are specific to a reference solution temperature and a sample solution temperature defined by the manufacturer. Corrections may need to be applied for measurements at other liquid temperatures. See also: Density
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Astronomers may have lucked into the ultimate in cosmic baby pictures: a voracious black hole fresh from its violent birth.
After watching a nearby star that exploded into a supernova in 1979, astronomers now believe the star’s death wasn’t an ordinary one. The star’s explosion was big enough to cause a black hole to develop in its wake. They think it’s a black hole because they see something steadily consuming the gassy remnants of the exploded star, which is a telltale sign of a black hole. It sucks up everything in sight.
And in this case it’s a lot. In the past 30 years since this star exploded, this baby black hole has eaten about the equivalent of the Earth in mass, which is about as big as black hole appetites can get, said Harvard astrophysicist Avi Loeb. He’s co-author of a new paper in the journal New Astronomy and he discussed the findings at a NASA news conference Monday.
On a cosmic scale the mass of the Earth is not an awful lot to eat, but from Earth’s point of view, it’s kind of awesome, said NASA astrophysicist Kimberly Weaver. “It’s like the planet eater in ‘Star Trek,'” she said.
Black holes are warped regions in space where it is so dense that nothing — not even light — escapes. Scientists in this case see energy bursts from matter as it is sucked in. That matter is heavy gas from the exploded star, and possibly a partner star that may have been next to it, Weaver said.
“It’s the first time we’re seeing a black hole being born in a normal supernova,” Loeb said. “We’re able to learn about environments that cannot be reproduced in the lab and can only be observed in the universe.”
While black holes are seen throughout the universe, it is unusual to witness one from near birth that “evolves and changes into its youthful stages,” said Weaver. And unlike other black holes, thanks to the keen eye of a Maryland schoolteacher who witnessed the supernova in 1979, astronomers know exactly when this black hole was born, Weaver said.
By continuing to follow the black hole — which is about 50 million light years away — future astronomers will learn just how much material is left over from the star’s explosion, said Dan Patnaude of Harvard, a study co-author. This black hole is about five times more massive than our sun and the star that exploded to give it birth was maybe 20 times bigger than our sun.
“This is certainly eating as much as it can,” Patnaude said. “This is working as hard as it can to gobble up that material, exactly like a teenager or a toddler.”
The images were captured by the Chandra X-Ray space telescope. There is one other possible explanation for what scientists have seen: They could be watching the birth instead of a pulsar wind nebula, like the famous and beautiful crab nebula. But Patnaude said a black hole is more likely.
Either way, this is a great chance to observe a cosmic event from the start, said Alex Filippenko of the University of California at Berkeley who didn’t take part in the research. He agrees that the discovery is most likely a black hole.
NASA’s Chandra X-Ray Observatory: //chandra.nasa.gov
Source: AP News
Mochila insert follows… | <urn:uuid:a0d83bd1-3a3f-4d8f-a4e4-5982c7021772> | 3.46875 | 747 | Truncated | Science & Tech. | 56.032378 | 95,584,496 |
Mexican scientists are doing tests to cure marine animals such as shrimp and oysters.
Scientific advances are increasingly amazing, to show a button: Mexican scientists are testing to cure marine animals such as shrimp and oyster but in the water! Sure, animals that later serve us as food.
And they want to do it with silver nanoparticles, so small that we can not see them even with a microscope. They are particles that are measured in one billionths of a meter.
These silver nanoparticles have already been tested in human medicine, veterinary medicine and agriculture. So the researchers wondered if they would also serve in marine animals.
Scientists are currently testing to verify that silver nanoparticles do not affect other organisms that live in the sea. You have to be sure before you dump them there, do not you think?
The project involves researchers from various institutions such as the National Autonomous University of Mexico and the Center for Research in Food and Development. | <urn:uuid:3c2652a4-f155-4088-b848-b3caebf8e14d> | 2.78125 | 194 | News Article | Science & Tech. | 34.401195 | 95,584,501 |
Scientists of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association have been following this natural spectacle via the earth observation satellites TerraSAR-X from the German Space Agency (DLR) and have documented it in many individual images. The data is intended to help solve the physical puzzle of this “calving“.
Pine Island Glacier Antarctica 8 July 2013
On the left handside the newly formed isberg with the a size of 720 square kilometres is visible. Photo: DLR
Scientists from the American space agency NASA discovered the first crack in the glacier tongue on 14 October 2011 when flying over the area. At that time it was some 24 kilometres long and 50 metres wide. ”As a result of these cracks, one giant iceberg broke away from the glacier tongue. It measures 720 square kilometres and is therefore almost as large as the city of Hamburg“, reports Prof. Angelika Humbert, ice researcher at the Alfred Wegener Institute.
The glaciologist and her team used the high resolution radar images of the DLR earth observation satellite TerraSAR-X to observe the progress of the two cracks and to better understand the physical processes behind the glacier movements. The researchers were thus able to measure the widths of the gaps and calculate the flow speed of the ice. ”Above the large crack, the glacier last flowed at a speed of twelve metres per day“, reports Humbert’s colleague Dr. Dana Floricioiu from DLR. And Nina Wilkens, PhD graduate in Prof. Humbert’s team, adds: “Using the images we have been able to follow how the larger crack on the Pine Island glacier extended initially to a length of 28 kilometres. Shortly before the “birth” of the iceberg, the gap then widened bit by bit so that it measured around 540 metres at its widest point.“
The scientists incorporate these and other TerraSAR-X satellite data in computer simulations using which they are able to model the break and flow mechanisms of the ice masses. “Glaciers are constantly in motion. They have their very own flow dynamics. Their ice is exposed to permanent tensions and the calving of icebergs is still largely unresearched “, explains ice modeller Angelika Humbert.
The scientist and her team then compare their simulation results with current satellite data such as from TerraSAR-X. If the model agrees with reality, the scientists can conclude, for example, the gliding property of the ground beneath the glacier ice and how the ice flow could behave in the event of further global warming.
Are ice breaks caused by climate change? Angelika Humbert does not so far see any direct connection: “The creation of cracks in the shelf ice and the development of new icebergs are natural processes“, says the glaciologist. However, the Pine Island glacier, which flows from the Hudson mountains to the Amundsen Sea, was the fastest flowing glacier in the Western Antarctic with a flow speed of around 4 kilometres per year. This speed is less caused by the rising air temperatures, however, and is more attributable to the fact that the wind directions in the Amundsen Sea have altered. ”The wind now brings warm sea water beneath the shelf ice. Over time, this process means that the shelf ice melts from below, primarily at the so-called grounding line, the critical transition to the land ice“, says the scientist.
For the Western Antarctic ice shelf, an even faster flow of the Pine Island glacier would presumably have serious consequences. “The Western Antarctic land ice is on land which is deeper than sea level. Its “bed” tends towards the land. The danger therefore exists that these large ice masses will become unstable and will start to slide“, says Angelika Humbert. If the entire West Antarctic ice shield were to flow into the Ocean, this would lead to a global rise in sea level of around 3.3 metres.Info box: Shelf ice
A NASA background report on the discovery of the first crack and impressive animation videos may be found at http://www.nasa.gov/mission_pages/icebridge/news/fall11/pig-break.html.
The Alfred Wegener Institute conducts research in the Arctic, Antarctic and in the high and mid-latitude oceans. The Institute coordinates German polar research and provides important infrastructure such as the research ice breaker Polarstern and research stations in the Arctic and Antarctic to the national and international scientific world. The Alfred Wegener Institute is one of the 18 research centers of the Helmholtz Association, the largest scientific organisation in Germany.
Ralf Röchert | idw
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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12.07.2018 | Event News
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An international team including Empa researcher Francis Schwarze has sequenced the genome of the common split gill mushroom, Schizophyllum commune, a widely distributed fungus which grows on and decomposes wood.
The genome, containing some 13,000 genes, has recently been published in Nature Biotechnology. The new data allows scientists a view of the mushroom's unique enzyme-based digestive apparatus which gives it the ability to attack and degrade wood, causing white rot. It is this ability which Schwarze, together with other colleagues, has exploited to improve the tonal qualities of wood used to make violins.
Fungi are the ideal recycling machines – they decompose dead organic material and convert it into nutritious humus, and together with bacteria they are nature's most important detritivores. During the course of their evolution they have developed special digestive enzymes with which they are able to decompose lignin and other complex substances in woody plants, an ability which is almost unique in nature. However, many species of fungi also attack living wood, thereby causing significant economic damage to wood related industries.
That fungi not only cause damage through their ability to decompose certain constituent materials of wood but can actually improve specific properties of wood has already been shown by Empa's Francis Schwarze. In his «Stradivarius Project» he has used wood-attacking fungi such as the (now genetically decoded) S. commune to improve the tonal qualities of spruce or maple used to make violins. In 2006 Schwarze submitted a patent application covering this process, and last September a biotech violin made with wood treated with fungi was judged superior to a genuine Stradivarius in a blind test.
A real expert at recycling carbohydrates
Schwarze has high hopes for the now completely deciphered genome of "his" fungus. "The genome sequence provides us with essential information on the lignolytic – that is, wood decomposing – enzymes. This knowledge will allow us to genetically modify the wild strain in order to optimize and control very specific decomposition processes." The S. commune genome ought to be a rich source of information, since according to genetic analysis the split gill mushroom possesses the most comprehensive enzyme-based digestive apparatus of all standing fungi (Basidiomycota). The enzymes are used to digest polysaccharides (carbohydrates and long-chain sugars) and to decompose lignin in wood, an ability which is unique, as far as is currently known. According to Schwarze this wide range of enzymatic activity explains why S. commune is so widespread; the fungus can nourish itself on practically anything!
This relatively new field, which Schwarze calls «Fungal Biotechnology», provides a means of improving the process of impregnating spruce and pine wood – neither of which are particularly long-lasting or hard-wearing – with protective and finishing agents. Schwarze is convinced that "…this represents an enormous commercial potential, above all in Switzerland, where more than 60% of the forests are spruce and pine." Another possible application is improving the efficiency of methods for the production of biogenic fuels based on woody biomass.
In addition, the genetic sequence is expected to supply important information on the development of the fruiting body of the fungus and how this process can be optimized, for example in the cultivation of edible mushrooms. Considering that some 2.5 million tonnes of edible fungi are produced every year, this could well prove to be very profitable know-how.
«Genome Sequence of the model mushroom Schizophyllum commune», Robin A. Ohm et al., Nature Biotechnology, published online on 11th July 2010 (DOI: 10.1038/nbt.1643); Abstract at http://www.nature.com/nbt/journal/vaop/ncurrent/abs/nbt.1643.html
Dr. Francis W.M.R. Schwarze | 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
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Find Out How Much Physics You Already Know! at Jefferson Lab's Science Series Lecture on Oct. 9
NEWPORT NEWS, VA. - The Thomas Jefferson National Accelerator Facility will host two Fall Science Series Lectures this season. The first is set for Tuesday, Oct. 9 and will feature a Jefferson Lab staff member discussing how frequently physics is used in ordinary life.
Electrical Engineer Jack McKisson, a member of Jefferson Lab's Radiation Detector and Imaging group, will share with the audience a look at physics and the phenomena of nature and how they were discovered and recognized by early researchers. He will touch on the science and technology involved in rocket science, taking under sea measurements, radiation detection and measurement, space experimentation and his two expeditions to the Antarctic.
Using his varied research path, McKisson will bring attention to how much physics most people already know just from observing the world around them. The audience will get a brief history of physics, and may discover that they know more than they thought regarding a subject that some view as inscrutable.
A second lecture will follow on Tuesday, Nov. 13 and feature Edward Murphy, from the University of Virginia's astronomy department, presenting "The Origin of the Elements." In this lecture, Murphy will trace the origin of a gold atom - from the Big Bang to the present day - and beyond. Attendees will learn how the elements were forged in the nuclear furnaces inside stars, and how, when stars die - they spread elemental material into space. Murphy will take the audience through the origin of the building blocks of matter in the Big Bang and will conclude by speculating on the future of the atoms around us today.
Both lectures are free and open to students and adults with an interest in science. Both lectures will begin at 7 p.m., in the CEBAF Center auditorium located at 12000 Jefferson Ave, Newport News, and will last about an hour. Seating in the auditorium and overflow area is available on a first-come, first-served basis and is limited to about 300 people. People arriving once capacity has been reached will be turned away.
All those under age 16 must be accompanied by a parent or responsible adult. Everyone over 16 is asked to carry a valid photo ID. Security guards may perform ID, parcel and vehicle checks.
For directions and additional information about Jefferson Lab public lectures, visit: http://education.jlab.org/scienceseries/index.php or contact Christine Wheeler, email at firstname.lastname@example.org or call 757-269-7560.
Jefferson Science Associates, LLC, a joint venture of the Southeastern Universities Research Association, Inc. and PAE Applied Technologies, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy's Office of Science.DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov. | <urn:uuid:c30ebcc4-f7e3-4295-badc-77e6588058f4> | 2.953125 | 632 | News (Org.) | Science & Tech. | 46.998446 | 95,584,511 |
Higher temperatures from climate change mean more evaporation, which means more rain.
Climate change affects hurricanes by energizing them in a few important ways.
Global warming should be taken as seriously as fighting insurgents, say those witnessing the savage impacts.
Climate change could be playing a role in algae blooms around the world.
A growing number of initiatives are giving corporations the resources to help achieve global climate goals.
Communities in danger of falling into the sea say assistance from the federal government has dried up.
Massachusetts is considering classifying wood pellets and other tree products as renewable energy.
It's a land known more for ice than fire, but a wildfire has flared up on Greenland's western edge.
Economic, emissions and population trends point to a very small chance Earth will avoid warming more than 2°C.
Wildfires are raging across British Columbia. They're the latest sign of climate change in the northern forest.
Alphabet has joined a growing list of technology companies developing energy storage for renewables.
Move over, temperature spiral. A new animation shows what global warming looks like in more than 100 countries.
Two companies are planning to build the world's largest project combining offshore wind with electricity storage.
In six months, the route from Brisbane to the small sugar town of Tully will offer 18 free recharging stations.
A new wind farm could become the largest in the U.S. and wean states off coal-fired power plants.
NASA has published new satellite imagery that reveals new details about the Larsen C iceberg.
Climate change is one reason the area burned by western wildfires is increasing.
New Jersey aims to shrink its climate footprint by reducing wasted food that ends up in landfills.
Nearly 50 million acres of forest disappeared worldwide in 2015, mainly in North America and the tropics.
South Miami, Fla., has become the first city outside of California to mandate solar panels on new homes. | <urn:uuid:fdb0398b-0072-4ea8-9817-ce287c5af4df> | 2.890625 | 396 | Content Listing | Science & Tech. | 45.160136 | 95,584,516 |
eso0641 — Pressemeddelelse
Cut from Different Cloth
VLT Shows Milky Way's Neighbouring Galaxies Have Different History
7. november 2006
A large survey, made with ESO's VLT, has shed light on our Galaxy's ancestry. After determining the chemical composition of over 2000 stars in four of the nearest dwarf galaxies to our own, astronomers have demonstrated fundamental differences in their make-up, casting doubt on the theory that these diminutive galaxies could ever have formed the building blocks of our Milky Way Galaxy.
"The chemistry we see in the stars in these dwarf galaxies is just not consistent with current cosmological models," said Amina Helmi of the Kapteyn Astronomical Institute in Groningen, The Netherlands, and lead author of the paper presenting the results. "It shows that there is plenty of astronomy to learn in our backyard."
Our Milky Way Galaxy is surrounded by a number of dwarf satellite galaxies, which because of their loosely rounded shape are referred to as 'dwarf spheroidal' galaxies. Faint and diffuse, these dwarf galaxies are a thousand times fainter than the Milky Way itself, making them the least luminous galaxies known.
Modern cosmological models predict that small galaxies form first, and later assemble into larger systems like our Galaxy. Since the Universe initially only contained hydrogen and helium (most of all other chemical elements being synthesized inside stars), dwarf galaxies should have the lowest heavy element content. Not so, say the astronomers.
As part of a large observational programme, the Dwarf galaxies Abundances and Radial-velocities Team (DART), Helmi and her colleagues from institutes in 9 different countries used the FLAMES instrument on ESO's Very Large Telescope to measure the amount of iron in over 2000 individual giant stars in the Fornax, Sculptor, Sextans and Carina dwarf spheroidals .
Their data unearthed fundamental differences in the dwarf galaxy stars' chemical composition compared with those in our galactic halo, calling into question the merger theory as the origin of large galaxies' haloes. Whilst the average abundances of elements in the dwarf spheroidals is comparable with that seen in the Galactic halo, the former are lacking the very metal-poor stars that are seen in the Milky Way - the two types of systems, contrary to theoretical predictions, are essentially of different descent.
"Our results rule out any merging of the nearby dwarf galaxies as a mechanism for building up the Galactic halo, even in the early history of the Universe," said Helmi. "More detailed chemical abundance studies of these systems are needed, as this will tell us more about what happened at those early epochs in our local Universe".
: The term 'metals' in astronomy denotes any chemical element heavier than the most abundant primordial constituents of the Universe, hydrogen and helium. Most heavy elements in the Universe are created by the nuclear reactions powering stars, which are fed into the interstellar medium when stars eject their gas layers at the end of their evolution. Studying the metal content of a star can therefore give information on its age and the conditions under which it formed. In this survey, the metal composition was measured using the ratio of iron to hydrogen in 2000 stars in dwarf spheroidal galaxies.
:FLAMES, the Fibre Large Array Multi-Element Spectrograph, is an advanced technology spectrograph mounted on Kueyen, the second Unit Telescope of ESO's Very Large Telescope. It allows astronomers to observe a field of 25 arcminutes in diameter - an area almost equivalent to the size of the full Moon. In this field, it can provide light spectra of up to 130 objects in a single observation, making it ideally suited to surveys of large stellar populations.
:The dwarf spheroidals Fornax, Sextans, Sculptor and Carina are named after the constellations in the region of the sky in which they are observed. The Fornax galaxy was one of the first to be discovered, in 1938, and one of the largest in the Milky Way's immediate neighbourhood. It lies at a distance of roughly 450 000 light years, around one-fifth of the distance to the Andromeda Galaxy, and emits light equivalent to 16 million Suns. Also discovered in 1938, the Sculptor dwarf spheroidal lies just 260 000 light years away. It has the luminosity of around 2 million Suns. Carina was discovered in 1977 at a distance of around 330 000 light years, with a luminosity equivalent to 400 000 Suns. Sextans is the most recently discovered of the galaxies, having been first spotted in 1990. It lies 280 000 light years away and has a luminosity equivalent to 500 000 Suns.
Details of this study are published in a Letter in the Astrophysical Journal of 10 November 2006 by Amina Helmi et al, entitled "A new view of the dwarf spheroidal satellites of the Milky Way from VLT/FLAMES: Where are the metal-poor stars?" (ApJ Lett, vol. 651, L121-L124).
The DART team consists of Eline Tolstoy, Amina Helmi, Giuseppina Battaglia, and Bruno Letarte (University of Groningen, The Netherlands), Mike Irwin (University of Cambridge, UK), Vanessa Hill (Observatory of Paris-Meudon, France), Patrick François (Observatory of Paris-Meudon, France and ESO, Chile), Pascale Jablonka (Ecole Polytechnique Federale de Lausanne, Switzerland), Kim Venn (University of Victoria, Canada), Matthew Shetrone (University of Texas, USA), Nobuo Arimoto (National Astronomical Observatory of Japan), Tom Abel (Kavli Institute for Particle Astrophysics and Cosmology, USA), Andreas Kaufer and Thomas Szeifert (ESO, Chile), Francesca Primas (ESO, Germany), and K. Sadakane (Osaka Kyoiku University, Japan).
University of Groningen
Tel: +31 50 363 40 45
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Page 149- the problem of sending a pencil of parallel hertzian waves to a distance possesses more than a theoretical interest. It is allowable to say that its solution would change the course of our civilization by rendering war impossible. The first physicist who realizes this discovery will be able to avail himself of the presence of an enemys ironclads gathered together in a check this out harbour to blow them up in a few minutes, from a distance of several kilometres, simply by directing on them a sheaf of electric radiations. On reaching the metal wires with which these vessels are nowadays honeycombed, this will excite an atmosphere of sparks which will at once explode the shells and torpedoes stored in their holds. With the same reflector, giving a pencil of parallel radiations, it would not be much more difficult to cause the explosion of the stores of powder and shells contained in a fortress, or in the artillery sparks of an army corps, and finally the metal cartridges of the soldiers. | <urn:uuid:f4dda418-1dd1-4b70-994d-53390ba6152f> | 2.75 | 200 | Truncated | Science & Tech. | 27.455884 | 95,584,566 |
2015, VOLUME 2 ISSUE 3Pages: 282-287
Diversity of invasive alien species in Pantnagar flora
Jyotsna Rastogi*, D. S. Rawat and Satish Chandra
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Biological diversity faces many threats throughout the world and one of the major threats is caused by invasion of alien species. The present study proves presence of 94 invasive alien species in flora of Pantnagar, Uttarakhand, India. These 94 invasive alien species (IAS) belong to 72 genera, under 33 families 85 species are dicotyledons while 9 species are monocotyledons. On the basis of their nativity maximum IAS have their sourced region as American continents (74), followed by Africa (8), Europe (5), Mediterranean (3) and Asia & Australia (2). The taxonomic analysis of IAS reveals dominance of Asteraceae with 18 spp. followed by Fabaceae, Amaranthaceae, Convolvulaceae, Malvaceae, Solanaceae, Poaceae etc. Among these, 78 IAS are herbs followed by shrubs (8), grasses (4), sedges (2), trees (1), and climber (1). Such a large number of invasive alien species in small area of Pantnagar, indicate miserable condition of natural vegetation.
Fig.: Eight dominant families of Invasive Alien flora in Pantnagar. | <urn:uuid:f24f6d74-75e8-4e47-93c5-556a3cff79d2> | 2.796875 | 299 | Truncated | Science & Tech. | 34.638217 | 95,584,603 |
Nikolaos K. Kazantzis
Alfred A. Scala
Proton exchange membrane (PEM) fuel cells are at the forefront among different types of fuel cells and are likely to be important power sources in the near future. PEM is a key component of the PEM fuel cells. The objective of this research is to investigate the fundamental aspects of PEM in terms of thermodynamics and proton transport in the membrane, so that the new proton conducting materials may be developed based on the detailed understanding. Since the proton conductivity increases dramatically with the amount of water in PEM, it is important to maintain a high humidification during the fuel cell operation. Therefore, the water uptake characteristics of the membrane are very important in developing fuel cell systems. Thermodynamic models are developed to describe sorption in proton-exchange membranes (PEMs), which can predict the complete isotherm as well as provide a plausible explanation for the long unresolved phenomenon termed Schroeder¡¯s paradox, namely the difference between the amounts sorbed from a liquid solvent versus from its saturated vapor. The sorption isotherm is a result of equilibrium established in the polymer-solvent system when the swelling pressure due to the uptake of solvent is balanced by the surface and elastic deformation pressures that restrain further stretching of the polymer network. The transport of protons in PEMs is intriguing. It requires knowledge of the PEM structure, water sorption thermodynamics in PEM, proton distribution in PEM, interactions between the protons and PEM, and proton transport in aqueous solution. Even proton conduction in water is anomalous that has received considerable attention for over a century because of its paramount importance in chemical, biological, and electrochemical systems. A pore transport model is proposed to describe proton diffusion at various hydration levels within Nafion¢ÃƒÂ§ by incorporating structural effect upon water uptake and various proton transport mechanisms, namely proton hopping on pore surface, Grotthuss diffusion in pore bulk, and ordinary mass diffusion of hydronium ions. A comprehensive random walk basis that relates the molecular details of proton transfer to the continuum diffusion coefficients has been applied to provide the transport details in the molecular scale within the pores of PEM. The proton conductivity in contact with water vapor is accurately predicted as a function of relative humidity without any fitted parameters. This theoretical model is quite insightful and provides design variables for developing high proton conducting PEMs. The proton transport model has been extended to the nanocomposite membranes being designed for higher temperature operation which are prepared via modification of polymer (host membrane) by the incorporation of inorganics such as SiO2 and ZrO2. The operation of fuel cells at high temperature provides many advantages, especially for CO poisoning. A proton transport model is proposed to describe proton diffusion in nanocomposite Nafion¢ÃƒÂ§/(ZrO2/SO42-) membranes. This model adequately accounts for the acidity, surface acid density, particle size, and the amount of loading of the inorganics. The higher proton conductivity of the composite membrane compared with that of Nafion is observed experimentally and also predicted by the model. Finally, some applications of PEM fuel cells are considered including direct methanol fuel cells, palladium barrier anode, and water electrolysis in regenerative fuel cells.
Worcester Polytechnic Institute
All authors have granted to WPI a nonexclusive royalty-free license to distribute copies of the work. Copyright is held by the author or authors, with all rights reserved, unless otherwise noted. If you have any questions, please contact firstname.lastname@example.org.
Choi, P. (2004). Investigation of Thermodynamic and Transport Properties of Proton-Exchange Membranes in Fuel Cell Applications. Retrieved from https://digitalcommons.wpi.edu/etd-dissertations/233
Proton-exchange membranes, Fuel Cell, Thermodynamics, Proton Transport, Proton transfer reactions, Fuel cells, Proton exchange membranes | <urn:uuid:423fd117-3cb9-4df9-b60b-29f289313a51> | 2.53125 | 860 | Academic Writing | Science & Tech. | 16.497701 | 95,584,624 |
In geometry and trigonometry, a right angle is an angle of exactly 90° (degrees), corresponding to a quarter turn. If a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. The term is a calque of Latin angulus rectus; here rectus means "upright", referring to the vertical perpendicular to a horizontal base line.
Closely related and important geometrical concepts are perpendicular lines, meaning lines that form right angles at their point of intersection, and orthogonality, which is the property of forming right angles, usually applied to vectors. The presence of a right angle in a triangle is the defining factor for right triangles, making the right angle basic to trigonometry.
In elementary geometryEdit
In Unicode, the symbol for a right angle is U+221F ∟ Right angle (HTML
∟). It should not be confused with the similarly shaped symbol U+231E ⌞ Bottom left corner (HTML
⌞). Related symbols are U+22BE ⊾ Right angle with arc (HTML
⊾), U+299C ⦜ Right angle variant with square (HTML
⦜), and U+299D ⦝ Measured right angle with dot (HTML
In diagrams, the fact that an angle is a right angle is usually expressed by adding a small right angle that forms a square with the angle in the diagram, as seen in the diagram of a right triangle (in British English, a right-angled triangle) to the right. The symbol for a measured angle, an arc, with a dot, is used in some European countries, including German-speaking countries and Poland, as an alternative symbol for a right angle.
Right angles are fundamental in Euclid's Elements. They are defined in Book 1, definition 10, which also defines perpendicular lines. Definition 10 does not use numerical degree measurements but rather touches at the very heart of what a right angle is, namely two straight lines intersecting to form two equal and adjacent angles. The straight lines which form right angles are called perpendicular. Euclid uses right angles in definitions 11 and 12 to define acute angles (those smaller than a right angle) and obtuse angles (those greater than a right angle). Two angles are called complementary if their sum is a right angle.
Book 1 Postulate 4 states that all right angles are equal, which allows Euclid to use a right angle as a unit to measure other angles with. Euclid's commentator Proclus gave a proof of this postulate using the previous postulates, but it may be argued that this proof makes use of some hidden assumptions. Saccheri gave a proof as well but using a more explicit assumption. In Hilbert's axiomatization of geometry this statement is given as a theorem, but only after much groundwork. One may argue that, even if postulate 4 can be proven from the preceding ones, in the order that Euclid presents his material it is necessary to include it since without it postulate 5, which uses the right angle as a unit of measure, makes no sense.
Conversion to other unitsEdit
A right angle may be expressed in different units:
Rule of 3-4-5Edit
Throughout history carpenters and masons have known a quick way to confirm if an angle is a true "right angle." It is based on the most widely known Pythagorean triple (3, 4, 5) and so called the "Rule of 3-4-5." From the angle in question, running a straight line along one side exactly three units in length, and along the second side exactly four units in length, will create a hypotenuse (the longer line opposite the right angle that connects the two measured endpoints) of exactly 5 units in length. This measurement can be made quickly and without technical instruments. The geometric law behind the measurement is the Pythagorean theorem ("The square of the hypotenuse of a right triangle is equal to the sum of the squares of the two adjacent sides").
Thales' theorem states that an angle inscribed in a semicircle (with a vertex on the semicircle and its defining rays going through the endpoints of the semicircle) is a right angle.
Two application examples in which the right angle and the Thales' theorem are included (see animations).
|Wikimedia Commons has media related to Right angles.|
- "Right Angle". Math Open Reference. Retrieved 26 April 2017.
- Wentworth p. 11
- Wentworth p. 8
- Wentworth p. 40
- Unicode 5.2 Character Code Charts Mathematical Operators, Miscellaneous Mathematical Symbols-B
- Müller-Philipp, Susanne; Gorski, Hans-Joachim (2011). Leitfaden Geometrie [Handbook Geometry] (in German). Springer. ISBN 9783834886163.
- Heath p. 181
- Heath p. 181
- Heath p. 181
- Wentworth p. 9
- Heath pp. 200-201 for the paragraph | <urn:uuid:5f32935d-ab82-4ec3-8686-ba4b24e1b686> | 4.5 | 1,059 | Knowledge Article | Science & Tech. | 51.889899 | 95,584,625 |
Vertical profiles of microbial and meiofaunal abundances, and of redox potential, pH, water content and shear strength have been measured in sediment subcores from seven box cores collected in the southern Central Pacific and the findings have been related to potential effects on pelagic fluxes and sedimentation. Microbial and meiofaunal abundance decreased exponentially with sediment depth. Micro-organisms were found throughout the depth of the core to 40 cm. Meiofauna were only present in the top 5 cm to 10 cm. Meiofaunal metazoans decreased more rapidly than foraminiferans. Redox potential was always positive, decreased below the surface and often rose again deeper in the sediment. pH showed no clear cut trend with depth. Shear strength increased with sediment depth and showed occasional anomalous fluctuations. Water content decreased progressively downwards with the widest scatter in the top 5-10 cm. The most important implications of these results for the water column above are likely to be biologically mediated organic mineralization and nutrient regeneration into the water column, and biodeposition of heavy metals and the binding of particulates at and above the sediment--water interface by extracellular polymeric material, which will in turn lead to differential patterns of sedimentation.
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We’ve all heard in regards to the seek for life on different planets, however what about trying on different moons?
In a paper revealed June 13 in The Astrophysical Journal, researchers on the University of California, Riverside and the University of Southern Queensland have recognized greater than 100 big planets that doubtlessly host moons able to supporting life. Their work will information the design of future telescopes that may detect these potential moons and search for tell-tale indicators of life, known as biosignatures, of their atmospheres.
Since the 2009 launch of NASA’s Kepler telescope, scientists have recognized 1000’s of planets outdoors our photo voltaic system, that are known as exoplanets. A major purpose of the Kepler mission is to determine planets which are within the liveable zones of their stars, that means it is neither too scorching nor too chilly for liquid water — and doubtlessly life — to exist.
Terrestrial (rocky) planets are prime targets within the quest to search out life as a result of a few of them is perhaps geologically and atmospherically just like Earth. Another place to look is the various fuel giants recognized through the Kepler mission. While not a candidate for all times themselves, Jupiter-like planets within the liveable zone could harbor rocky moons, known as exomoons, that might maintain life.
“There are at present 175 identified moons orbiting the eight planets in our photo voltaic system. While most of those moons orbit Saturn and Jupiter, that are outdoors the Sun’s liveable zone, that is probably not the case in different photo voltaic programs,” mentioned Stephen Kane, an affiliate professor of planetary astrophysics and a member of the UCR’s Alternative Earths Astrobiology Center. “Including rocky exomoons in our seek for life in area will vastly increase the locations we are able to look.”
The researchers recognized 121 big planets which have orbits throughout the liveable zones of their stars. At greater than 3 times the radii of the Earth, these gaseous planets are much less widespread than terrestrial planets, however every is anticipated to host a number of giant moons.
Scientists have speculated that exomoons would possibly present a good setting for all times, maybe even higher than Earth. That’s as a result of they obtain power not solely from their star, but in addition from radiation mirrored from their planet. Until now, no exomoons have been confirmed.
“Now that we’ve created a database of the identified big planets within the liveable zone of their star, observations of one of the best candidates for internet hosting potential exomoons will probably be made to assist refine the anticipated exomoon properties. Our follow-up research will assist inform future telescope design in order that we are able to detect these moons, examine their properties, and search for indicators of life,” mentioned Michelle Hill, an undergraduate pupil on the University of Southern Queensland who’s working with Kane and can be a part of UCR’s graduate program within the fall. | <urn:uuid:aa9ae0b6-74ad-44ad-be12-328da9199a09> | 3.46875 | 636 | News Article | Science & Tech. | 30.730567 | 95,584,635 |
|MLA Citation:||Bloomfield, Louis A. "Question 1012"|
How Everything Works 20 Jul 2018. 20 Jul 2018 <http://howeverythingworks.org/print1.php?QNum=1012>.
However, a superconducting electromagnet is one in which the wires are superconducting—the current passing through them doesn't waste any power. Once a current has been started in a coil of superconducting wire, it flows forever. Since it doesn't waste any power, that current needs no source of power and produces no thermal energy. In fact, you can buy superconducting magnets with the current already started at the factory. As long as the wires are kept cold (as they must be to remain superconducting), the current will continue to flow and the coil will remain magnetic forever. | <urn:uuid:24753b71-da46-4e88-b10f-50dfc8c422d4> | 2.984375 | 173 | Knowledge Article | Science & Tech. | 61.049858 | 95,584,637 |
USGS Coastal and Marine Geology Program
Recent News - stories from the last 14 days.
Read more about the USGS research project: Remote Sensing Coastal Change.
The article "Quantifying uncertainty in Sr/Ca-based estimates of SST from the coral Orbicella faveolata"; has been accepted for publication in Paleoceanography and Paleoclimatology. The strontium to calcium ratio (Sr/Ca) in aragonitic skeletons of massive corals provides a proxy for sea surface temperature (SST) that can be used to reconstruct paleoclimates across decades, centuries, and, potentially, millennia. This study produced a new, regional-scale Sr/Ca-SST calibration for Orbicella faveolata using five modern Orbicella faveolata corals from Dry Tortugas National Park, Florida, USA. This study also examined the sources of uncertainty that influence the robustness of the Sr/Ca paleothermometer and discovered that the precision of the O. faveolata paleothermometer is ~2 ℃ for decadal-scale comparisons and ~1 ℃ across multi-decadal timescales.
USGS personnel Jennifer Miselis (Research Geologist), BJ Reynolds (Engineering Technician), Nancy DeWitt (Geologist), Andy Farmer (CNT), Jake Fredericks (Hydrographic Technician), Mitch Lemon (Field Technician), Chelsea Stalk (CNT), Nesti Stathakopoulos (Oceanographer), and Hunter Wilcox (CNT) traveled to Fire Island National Seashore along the south shore of Long Island, New York, to conduct a geophysical survey in coordination with the National Park Service and U.S. Fish and Wildlife Service. The objective of the field effort was to remeasure seafloor elevations and sub-seafloor geology in areas that were surveyed in 2014 in order to quantify change in shoreface sediment availability and flux, some of the first data of its kind. The bathymetry of Wilderness Breach, which has remained open since Hurricane Sandy in 2012, was also remapped to help better understand the post-storm morphological evolution of a natural inlet. Seafloor elevations were mapped using two personal watercraft (PWC) equipped with echosounders. Unlike the 2014 survey, when an amphibious vessel was used to map the shoreface geology, this survey was the first time SPCMSC researchers launched an Edgetech 512i from the beach using a wheeled sled and SPCMSC Research Vessel (R/V) Sallenger. The specialized sled was the result of a collaborative effort of the SPCMSC Marine Operations group and the survey could not have been completed without it. Over approximately 3 weeks and with incredible effort, the PWCs covered 715 km and the sled covered 330 km to successfully complete the field work.
Several undergraduate students who were awarded internships at Mote Marine Laboratory in Sarasota, Florida, through the National Science Foundation Research Experience for Undergraduates (NSF REU) Program will visit the Saint Petersburg Coastal and Marine Science Center (SPCMSC). Since their internship research is often focused on topics in biological oceanography, in addition to touring the facility, the students will learn about USGS research in coastal geology and the tools used to do that research. SPCMSC scientist Jennifer Miselis (Research Geologist) will host the students and provide an overview of coastal geological research. The SPCMSC Marine Operations group will stage equipment and vessels so the students can learn how geophysical data are acquired. Noreen Buster (Geologist) will provide an overview of sediment sampling and coring capabilities in the core laboratory. Finally, a panel comprised of Xan Fredericks (Cartographer/Lidar Coordinator), RC Mickey (Oceanographer), and Caitlin Reynolds (Geologist) will answer questions from the students regarding their career paths, USGS research, and what it's like to be a career scientist. | <urn:uuid:33122f0e-34b9-4c2c-8df3-c1d0a0769ae6> | 2.53125 | 832 | News (Org.) | Science & Tech. | 19.956494 | 95,584,642 |
The force on an object that resists its motion through a fluid is called drag. When the fluid is a gas like air, it is called aerodynamic drag or air resistance. When the fluid is a liquid like water it is called hydrodynamic drag, but never "water resistance".
Fluids are characterized by their ability to flow. In somewhat technical language, a fluid is any material that can't resist a shear force for any appreciable length of time. This makes them hard to hold but easy to pour, stir, and spread. Fluids have no definite shape but take on the shape of their container. (We'll ignore surface tension for the time being. It's really only significant on the small scale — small like the size of a drop.) Fluids are polite in a sense. They yield their space relatively easily to other material things; at least when compared to solids. A fluid will get out of your way if you ask it. A solid has to be told to get out of the way with destructive force.
Fluids may not be solid, but they are most certainly material. The essential property of being material (in the classical sense) is to have both mass and volume. Material things resist changes in their velocity (this is what it means to have mass) and no two material things may occupy the same space at the same time (this is what it means to have volume). The portion of the drag force that is due to the inertia of the fluid — the resistance that it has to being pushed aside — is called the pressure drag (or form drag or profile drag). This is usually what someone is referring to when they talk about drag.
Recall Bernoulli's equation for the pressure in a fluid…
P1 + ρgy1 + ½ρv12 = P2 + ρgy2 + ½ρv22
The first term on each side of the equation is the part of the pressure that comes from outside the fluid. Typically, this refers to atmospheric pressure weighing down on the surface of a liquid (not relevant right now). The second term is the gravitational contribution to pressure. This is what causes buoyancy (also not relevant right now). The third term is the kinetic or dynamic contribution to pressure — the part related to flow (very relevant right now). This will help us understand the origin of pressure drag.
Start with the definition of pressure as force per area. Solve it for force.
|P =||F||⇒||F = PA|
Replace the generic symbol F for force with the more specific symbol R for drag. (You could also use D if you wanted to.) Drop in Bernoulli's equation for the pressure in a moving fluid…
|R = PA =||⎛
Rearrange things a bit and here you go…
R = ½ρCAv2
Wait a minute. Where'd that extra symbol come from? Who put that C in there and why?
Let's run through all the symbols one at a time, explain their meaning and how they relate to pressure drag. In essence, let's take the equation apart and put it back together again.
- Drag increases with the density of the fluid (ρ). More density means more mass, which means more inertia, which means more resistance to getting out of the way. The two quantities are directly proportional.
R ∝ ρ
- Drag increases with area (A). Exactly what we mean by this is subject to debate. To me, and in the context of this model, area is the cross sectional area projected in the direction of motion. (I would further simplify this by calling it the projected area.) Take the cross section of the object in the direction of its motion. This is the area of the tube of fluid that must be cast aside to let the object pass. This is the most logical thing to call the area, but not everyone agrees with me. To some, the word "area" refers to the area of contact between the object and the fluid. This also makes sense, but not in the context I've described above. Surface area is not important when one is dealing with pressure drag, but it is important when dealing with viscous drag — drag caused by layers of the fluid sticking to the object and to one another. More surface area means more of the object is in contact with the fluid, which means more drag. Viscous drag is just as real as pressure drag, but I don't want to deal with it right now.
R ∝ A
- Drag increases with speed (v). I hope that this is self-evident. An object that is stationary with respect to the fluid will certainly not experience any drag force. Start moving and a resistive force will arise. Get moving faster and surely the resistive force will be greater. The hard part of this relationship lies in the detailed way speed affects drag. According to our very sensible model derived from Bernoulli's very sensible equation, drag should very sensibly be proportional to the square of speed.
R ∝ v2In some situations, however, this may not be entirely correct. Drag is a complex phenomena. It cannot always be described with equations that are simple. My first guess would always be that drag is proportional to the square of speed since I understand and like the derviation I've presented, but I would not be surprised if (over some range of values) drag and speed were found to be directly proportional, proportional to some power other than 2, or related by some polynomial. Welcome to the world of empirical modeling — where relationships are determined by actual physical experiments rather than an ideology of pure theory. More on this subject later in this section.
Which brings us to our last factor…
- Drag is influenced by other factors including shape, texture, viscosity (which results in viscous drag or skin friction), compressibility, lift (which causes induced drag), boundary layer separation, and so on. These factors can be dealt with separately in a more complete theory of drag (how tedious in one sense, but how necessary in another) or they can be piled into one monolithic fudge factor (oh yes, please) called the coefficient of drag (C).
R ∝ C
Combining all these factors together yields a theoretically limited (but empirically very reasonable) equation. Here it is again…
R = ½ρCAv2
Simple, compact, wonderful. A nice equation to work with — or is it?
Well, yes and no.
- Yes, but it works only as long as the range of conditions examined is "small". That is, no large variations in speed, viscosity, or crazy angles of attack. The way around this is to reduce the coefficient of drag to a variable rather than a constant. (I can live with this.) Say that C depends on some yet to be specified set of factors. It is totally acceptable to say that it varies with this that or the other quantity according to any set of rules determined by experiment.
- No, since speed is squared. [Gasp!] Recall that speed is the derivative of distance with respect to time. Have you ever tried to solve a nonlinear differential equation? No? Well, welcome to hell. Wait, let me rephrase that — Welcome to Hell! [Ca-rack! Boom!] Ah ha ha ha ha haaaa! [Rumble] You fool! Just wait till you see what's in store for you when you try to solve the differential equations. The mathematics will consume you. [Ca-rack! Boom!] Ah ha ha ha ha haaaa! [Rumble].
Whew. What the hell was that all about? I might not know how to solve every kind of differential equation off the top of my head, but so what. I can always look for the solution in a book of standard mathematical tables or an on-line equivalent. You don't scare me demonic voice in my head.
|Cd||object or shape|
|2.1||ideal rectangular box|
|1.3~1.5||empire state building|
|0.7~1.1||formula one race car|
|0.6||bicycle with faring|
|0.7~0.9||tractor-trailer, heavy truck|
|0.6~0.7||tractor-trailer with faring|
|0.35~0.45||suv, light truck|
|0.15||Aptera high-efficiency electric car|
|0.15||airplane wing, at stall|
|0.05||airplane wing, normal operation|
|0.020~0.025||airship, blimp, dirigible, zeppelin|
other mathematical models
The pressure drag equation derived above is to me the most reasonable mathematical model of drag — especially aerodynamic drag. But as the demonic voice in my head said, it isn't always the easiest one to work with — especially for those just learning calculus (differential equations to be more precise). Those who know a lot of calculus just deal with it. Those who don't know any calculus just ignore it.
R = ½ρCAv2
A simplified model of drag is one that assumes that drag is directly proportional to speed.. This sometimes is good enough. (Maybe we should call it the "good enough model of drag".) It is especially useful when teaching calculus students how to solve differential equations for the first time. I haven't found it to be all that applicable to real world situations, however. (We'll use b as the generic constant of proportionality from now on.)
R = − bv
A more general model of drag is one that is agnostic about higher powers (pun intended). This is good attitude to have when you are exploring drag experimentally. Don't assume you know anything about how drag varies with speed, just measure the two quantities and see what values work best for the power n and the constant of proportionality b.
R = − bvn
Possibly the most general model is one that assumes a polynomial relationship. Drag might be related to speed in a way that is partially linear, partially quadratic, partially cubic, and partially described by higher order terms.
R = − ∑bnvn
drag and power
If you want to go fast, you've got to work hard. That should be a statement of the obvious. But why? Well for one thing, it takes energy to get going — kinetic energy. This equation says, if you want to go twice as fast you've go to work four times harder (K ∝ v2).
K = ½mv2
While that's certainly true, it isn't of much use to us here on earth. If we lived in the vacuum of space, all we'd ever have to worry about was the energy needed to change our state from one speed to another. Here on earth, the atmosphere has another opinion. Whatever energy we add to a system to get it going, the atmosphere drags it away — all of it eventually. In order for a moving body to stay in motion on the Earth it not only has to get going, it has to actively work to keep going. This undeniable fact of life is why Newton's first law (the law of inertia) wasn't discovered until the Seventeenth Century.
To keep an object in motion in the presence of drag (aerodynamic or otherwise) requires an ongoing input of energy. Work must be done over some time. Power must be used. Recall the following chain of reasoning that starts from the definition of power as the rate at which work is done…
|P =||W||=||F · Δs||= F · v|
Replace the generic force variable with a generic power equation for drag…
P = (bvn) v
Thus in general…
P = bvn + 1
or more specifically, in the case of pressure drag…
P = (½ρCAv2) v
P = ½ρCAv3
Thus, if drag is proportional to the square of speed, then the power needed to overcome that drag is proportional to the cube of speed (P ∝ v3). You want to ride your bicycle twice as fast, you'll have to be eight times more powerful. This is why motorcycles are so much faster than bicycles.
Power expended against drag is the biggest impediment to moving freely for both bicycles and motorcycles. Humans can do sustained physical work like cycling at the rate of about a tenth of a horsepower. Motorcycles have engines that are on the order of 100 horsepower. (Sorry for the American units.) That makes a motorcycle about one thousand times more powerful than a human on a bicycle. As a result they can go about ten times faster, since 1,000 = 103. I've found through personal experience on all day bicycle rides that I typically cover ⅙ the distance that I would if I sat behind the wheel of a car all day.
Yes I realize that cars aren't motorcycles, but what we're really comparing here are wheeled vehicles powered by human muscle with those powered by internal combustion engines. Yes I realize that a 6 to 1 ratio is not exactly the same as 10 to 1, but what I'm doing here is a quick order of magnitude comparison. Your individual results may vary — but not significantly.
It's much more than the name of a bad movie. It's something every student of aerodynamic drag should understand.
Imagine yourself as a parachute jumper; or better yet, imagine yourself as a BASE jumper. BASE is an acronym for building, antenna, span, escarpment. Since none of these platforms is moving horizontally, none of these jumpers has any initial horizontal velocity. Not that it really matters, but this reduces some of the complexity. Step off the platform and draw your free body diagram as you fall.
You start with no initial velocity, there is no aerodynamic drag, and you are effectively in free fall with an acceleration of 9.8 m/s2.
Now it gets complicated. There is an initial acceleration, therefore there is an increase in speed. With an increase in speed comes an increase in drag and a decrease in net force. This decrease in net force reduces acceleration. Speed is still increasing, just not quite as fast as it was initially.
Speed continues to increase, but so too does drag. As drag increases, acceleration decreases. Eventually one can imagine a state when the drag and weight forces are equal. You are in equilibrium. You continue moving, but you cease accelerating. You have reached your terminal velocity. Given the usual posture of skydivers, the type of clothes they normally wear, and the conditions of the air near the surface of the Earth; your typical skydiver has a terminal velocity of 55 m/s (200 km/h or 125 mph). The speed that you have in this state is the one you will always acquire if you are given enough time.
That is until the parachute opens. Opening the chute significantly increases your projected area, which cranks up the aerodynamic drag proportionally. The upward drag force now exceeds the downward pull of gravity. The net force and acceleration are directed upward. Note: this does not mean the skydiver is moving upward. Acceleration does not determine the direction of motion of an object, it determines the direction of the change in motion. When a parachute is just opened, the velocity is down and the acceleration is up. Your speed decreases as a result, which is the whole point behind the parachute.
Speed decreases, so drag decreases. Drag decreases, so the net force decreases. Eventually the net force is zero, you stop accelerating, and you reach a new terminal velocity — one that makes landing more comfortable, something like 6 m/s (22 km/h or 13 mph) or less.
Note that a terminal velocity is not necessarily a maximum value. It's a limit that can be approached from either direction. An object could start off slow and speed up to a terminal velocity that's a maximum (like a skydiver stepping off a BASE) or it could start off fast and slow down to a terminal velocity that's a minimum (like a skydiver who's just opened her parachute). "Terminal" is a fancy way to say "end". A terminal velocity is one that you end up with. For falling objects, this occurs when drag equals weight.
|vt = √||2mg|
Terminal velocity applies to situations besides skydiving. Drive your car with the accelerator in a constant position and you'll eventually reach a terminal velocity. The forward driving force of the tires on the road will eventually equal the backward drag force of the air (and the rolling resistance of the tires, which is discussed somewhere else in this book). Note how I said "eventually". Terminal velocity is a speed things approach but never quite reach. Proof of this statement requires calculus and will be discussed in the practice problems of this section.
Terminal velocity can have any value — including zero. What happens to a ship in the ocean when the propeller stops turning? The forward thrust goes away and all that's left is the backward drag. The ship goes slower and slower and slower until it stops (stops relative to any current, that is). The ship will reach a terminal velocity of zero. For large container ships this may take minutes of time and kilometers of distance, but it will eventually happen. If you don't have the time or the space and you really want to stop a large seagoing vessel, you need to run the engines in reverse. In this case it's thrust that stops the ship, not drag.
|vt (m/s)||falling object|
|373||skydiver, 39 km (Felix Baumgartner, 2012)|
|367||skydiver, 41 km (Alan Eustace, 2014)|
|274||skydiver, 31 km (Joseph Kittinger, 1960)|
|146||skydiver, 04 km (Christian Labhart, 2010)|
|6||skydiver, parachute open| | <urn:uuid:8a29b043-1c1a-4d65-8e76-cdeaf2e9f710> | 4.15625 | 3,768 | Knowledge Article | Science & Tech. | 60.702674 | 95,584,692 |
posted by lisa
graph y=sin(x-pie/4) (couldn't find pie sign on my keyboard)
We can't draw graphs for you here, but you can certainly make a table of values of x and corresponding values of y, and draw the graph yourself. you might save a little time by recognizing that
sin (x - pi/4) =
[(sqrt 2)sin x]/2 - [(sqrt 2)cos x]/2
When x = pi/4, y = 0.
When x=0, y = -(sqrt 2)/2
You can also just plot a sine wave on shifted coordinates, treating x = pi/4 y = 0 as the new origin | <urn:uuid:34d16946-c981-43a1-aeea-506da912d55b> | 2.59375 | 156 | Q&A Forum | Science & Tech. | 66.677063 | 95,584,696 |
Crystalline silica (mostly cristobalite) was produced by vapor-phase crystallization and devitrification in the andesite lava dome of the Soufriere Hills volcano, Montserrat. The sub-10 micrometer fraction of ash generated by pyroclastic flows formed by lava dome collapse contains 10 to 24 weight percent crystalline silica, an enrichment of 2 to 5 relative to the magma caused by selective crushing of the groundmass. The sub-10-micrometer fraction of ash generated by explosive eruptions has much lower contents (3 to 6 percent) of crystalline silica. High levels of cristobalite in respirable ash raise concerns about adverse health effects of long-term human exposure to ash from lava dome eruptions.
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Does gravity travel at the speed of light? If so, how can a black holes suck in photons?
it is believed to and is assumed to in General Relativity.
i believe that there is some astronomical measure they did (wasn't it when that asteroid or comet crashed into Jupiter?) that determined to within 20% that GR was correct about it.
See Does Gravity Travel at the Speed of Light? and How does the gravity get out of the black hole? from the Usenet Physics FAQ.
A quasar passed behind Jupiter. The announced results were controversial; see https://www.physicsforums.com/showpost.php?p=681816&postcount=12".
Gravity doesn't travel at the speed of light, changes in gravity (in the form of waves) travel at the speed of light.
So the force of gravity is instantaneous, but changes in gravity move at the speed of light?
think a bit about the meaningfulness of your question.
Let me know if this sounds as dumb as my previous question. If an object was to spontaneously appear within the earth's atmosphere, would it feel gravity instantly? If the earth's mass was split in half after the object appeared, would it take time for the object to feel the difference?
may be you could think about a curvature of spacetime instead force of gravity :)
no if an object suddenly appear , it take some time that change in gravity will reach the earth.
Gravity is omnipresent; it is there in the first place (because it is is in fact the curvature of space-time).
This is a dangerous analogy, but it's like a swimmer asking 'I see waves traveling at 100mph across the lake, but what is the speed of the lake'?
Your spontaneously appearing object should feel the Earth's gravity instantly. This is easy to visualise using the (aprozimate) rubber sheet analogy with masses deforming the sheet to create gradients. You could call the map of those gradiants the spacetime "landscape". Your object would appear in this ready made landscape and instantly respond to the curvature of that landscape.
Now if half the Earth was to disappear then, yes it would take time for the object to "notice" because the landscape deforms at the speed of light. There is a caveat here, that it would be impossible for anything to suddenly appear or dissappear. For example if the Sun was somehow anhilated by some antimatter, it would turn into a bunch of photons and the energy of those photons would still behave as a gravitational mass. It would take about 8 minutes for the photons to radiate outwards past the orbital radius of the Earth from the Sun, after which the Earth would no longer continue in its normal aproximately circular orbit.
To more directly answer your original question "Does gravity travel at the speed of light? If so, how can a black holes suck in photons?" there is no requirement for something like gravitons from the black hole to "chase" after photons in order to draw them back. The photons simply move in the ready made spacetime landscape around the black hole.
i really meant to say and should have said think about the meaning of the question. it's more that the meaning of the two were inconsistant.
that's the direct answer i was groping for.
it's a good analogy, though, me thinks. but we have to add, that no matter how hard the swimmer is swimming nor in what direction, the speed of the waves going across the lake is the same for that swimmer. and equal to any other swimmers' measurements. assuming they can accurately measure the wavespeed to a precision of much better than their swim speeds. and, they can't really measure their swim speeds except relative to each other. they can't measure their swim speeds against the water because they think they are drifting on it. so maybe a better analogy is that all of the swimmers are really just sitting around on very bouyant light rafts that skim across the water without any drag.
Gravity is localized gravitation.
This is where the analogy breaks down, so we don;t carry it that far. All analogies break down at a certain level of detail. If they didn't, they would be models!
Gravity is an effect caused by a form of energy. The speed can vary anywhere between relative zero to infinity.
So, I could set up a gravity-making machine and transmit singles across the diameter of the universe in zero time.
Seems like one of those little facts that has escaped, oh say, the entire collective body of physicists on the planet Earth.:uhh:
yes you could
No you couldn't.
'the entire collective body of physicists on the planet Earth' haven't come up with any idea of what causes gravity so it's not really relevant making that comment.
Gravity is caused by mass. And mass is a potential form of energy, right? Interesting.
But they do know that it doesn't travel at infinite speed. Which is why what you said makes no sense.
One must be very careful in GR of thought experiments where things "appear instantly out of no-where". Built into the theory is the continuity equations which prevent such from happening. The source of gravity is stress-energy. There's no way for energy (mass) to appear at a point without there being some energy-momentum current transmitting it there.
If you violate such continuity you've stepped entirely outside the theory. You can suppose that you create for example monopolar and dipolar waves which cannot be done physically and the theory of how such should be have is pure theological speculation.
Related to the OP's question about black holes consider also that throwing negative charges into the black hole will not prevent their charges from being felt outside. You will find that the black hole will manifest the same electrical field (and gravity) as a larger star of the same mass containing these charges.
I may have gone over the top with the 'infinite' speed part but my point was that we shouldn't necessarily think of its speed being a universal constant or that it should be constrained by factors which dictate the speed of light.
Oh I see. You were saying something akin to 'scientists have narrowed down the speed of gravity to between zero and inifinity' - a tongue-in-cheek way of saying 'we just don't know'.
that's fully incorrect. we should think of both EM and gravity as well as all other fundamental interactions as propagating through a vacuum with this same speed (it's not a function of which interaction, they're all "trying" to be instantaneous, it's a property of space and time that these ostensibly instantaneous interactions do not have effect instantly on distant object, as viewed by someone who is equi-distant from both source and destination object), and since we can only measure dimensionless quantities, there is no meaning to this speed being a different value. if it were'nt "constant', we wouldn't be able to tell.
now, conceivably, if the speeds of propagation of different interactions were different, we could detect that (and they're trying, there was one astronomical measurement that claims to have measured the speeds of gravity vs. light to be equal to within 20%). but with other quantitative predictions of GR being confirmed in experiment, with the fact that we have measured G (in terms of our meter sticks, cesium clocks, and kilogram prototypes) to 5 digits, if the speed of gravity was much different than c, that constant in the Einstien field equation (G/c[sup]4[/sup]) would 4 times more different, and the quantitative results would be different than what was measured.
whatever property of space and time that makes disturbances of EM propagate at a finite speed is what makes disturbances of gravity propagate at the same finite speed (as well as nuclear interactions, even though it doesn't make much difference for them, since the interaction is between particles very close to each other).
Wow. How many non-answers can a single thread generate.
Yes, gravitational forces propagate at the speed of light according to all accepted theory and known experiments. If the hypothesized graviton (gravity force carrier) exists, it will travel at the speed of light like a photon.
You needn't even consider hypotheticals to understand this. Consider the planet Mercury. If you calculate the orbit using Newtonian mechanics (which assume gravitation is an instantaneous force) you will find that Mercury's true orbit is slightly different than what you calculate. The perihelion, the point at which the planet is closest to the Sun, actually moves over the course of time. This is explained by General Relativity due to the curvature of spacetime or, another way of looking at it, the fact that gravitational forces propagate at the speed of light.
While well-aware of the precession of Mercury, and its explanation via the curvature of space-time a la GR, I'm not sure it is proof positive of the speed of gravitational waves.
Separate names with a comma. | <urn:uuid:c2085618-818d-4eb5-b23b-4a35a523f2ee> | 3.265625 | 1,896 | Comment Section | Science & Tech. | 53.405693 | 95,584,721 |
Behavior of Sandstones Under Heat Treatment
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Knowledge of materials behavior under heat treatment is of high importance in construction and safety engineering; tunnels represent a special field because of their specific safety issues. In the case of fire, tunnel structure and surrounding rock are subjected to extreme temperatures which induces irreversible changes in the material’s microstructure and consequently its mechanical properties. Significant portion of the Earth’s crust is formed by sandstones; this group of sedimentary rocks is highly variable in structure, composition and engineering properties. Quartz grains (alternatively together with other minerals) form the clastic part of sandstones; the space between clasts is filled by variable amount of cement and matrix which can contain particularly clay minerals, quartz and calcite. The porosity of sandstones is again highly variable from a nearly compact material to a highly porous one. The paper aims to find out and explain differences in response of various kinds of sandstones to heat treatment. The behavior of a representative set of sandstones under heat treatment was studied by TG/DSC, thermodilatometry and residual strength measurement. These experiments were accompanied by SEM and porosimetry measurement. The effect of increased temperature on the compressive strength was found to be crucially dependent on the nature of the cement and matrix present in the individual rock. The rocks with calcite cement which had high initial strength and low porosity were damaged by calcite decomposition. The siliceous sandstones were damaged by cracking due to thermally induced volume changes. In contrary, the strength of the clayey sandstones was even improved after the heat treatment. It can be concluded that behavior of sandstone under heat treatment is controlled by its composition and diagenesis.
KeywordsCompressive strength Heat treatment Porosity Sandstone Thermodilatometry Thermogravimetry
This research has been supported by the Czech Science Foundation under Project No. 14-17207S “Transport parameters and durability of porous rocks.” | <urn:uuid:526baadd-0142-4432-96bf-c57f4859d91c> | 3.109375 | 409 | Academic Writing | Science & Tech. | 19.158209 | 95,584,738 |
Nicole was Tropical Depression 16 until 11 a.m. EDT, Sept. 29 and NASA data helped confirm her new designation. Satellite data from NASA showed frigid thunderstorm cloud top temperatures, heavy rainfall, and extensive cloud cover as Nicole strengthened.
GOES-13 visible image of Tropical Storm Nicole (center, bottom) at 1432 UTC (10:32 a.m. EDT) shows the extensive cloud cover (which is also associated with a trough of low pressure) extending north into the Mid-Atlantic U.S. states.
Credit: NOAA/NASA GOES Project
The Atmospheric Infrared Sounder (AIRS) instrument uses infrared technology to take a tropical cyclone's temperature. AIRS sits on NASA's Aqua satellite and captured an image of those cloud top temperatures on Sept. 29 at 0723 UTC (3:23 a.m. EDT) revealing very high thunderstorms around Nicole's center, colder than -65 Fahrenheit.
NASA's Tropical Rainfall Measuring Mission satellite (a satellite shared with the Japanese Space Agency) captured the rainfall within Nicole on Sept. 28 as 1447 UTC (10:47 a.m. EDT) when she was Tropical Depression 16, and at that time noticed several areas of very heavy rainfall, falling at a rate of more than 2 inches per hour around the south and eastern sides of the storm's center of circulation. That heavy rainfall continues today, Sept. 29. TRMM will be closely monitoring Nicole with the expected accumulations of 5 to 10 inches over the Cayman Islands, Jamaica and Cuba and even isolated amounts up to 20 inches are possible over the higher elevations of Cuba and Jamaica.
The Geostationary Operational Environmental Satellite called GOES-13 captured a visible image of Tropical Storm Nicole today, Sept. 29 at 1432 UTC (10:32 a.m. EDT). GOES satellites are managed by NOAA. NASA's GOES Project at NASA's Goddard Space Flight Center in Greenbelt, Md. creates images and animations from the satellite data and created today's image that shows the extensive cloud cover (which is also associated with an elongated area of low pressure called a trough) extending north into the Mid-Atlantic U.S. states. The imagery also showed relatively clear skies over the eastern Atlantic which is due to a high pressure area stationed there, which is forcing Tropical Storm Nicole to the north.
At 11 a.m. EDT, Tropical Depression 16 strengthened into Tropical Storm Nicole. Nicole's maximum sustained winds were near 40 mph. Satellite data is observed the strongest winds in Nicole are occurring in the south and southeastern quadrants of the storm. It was centered near Cuba, about 120 miles east-southeast of Havana, Cuba or 260 miles southwest of Nassau, the Bahamas near 22.6 North and 80.6 West. Nicole was moving northeast near 9 mph. It had a minimum central pressure of 996 millibars.
The National Hurricane Center now expects Nicole to stay just east of Florida, so all of the watches and warnings for Florida have been dropped. On the forecast track the center of Nicole will move over the florida straits during the afternoon today (Sept. 29) and move near or over the northwestern Bahamas tonight. Tropical Storm warnings that are in effect include the Cayman Islands, Provinces of Cuba from Matanzas eastward to Ciego de Avila and the northwestern and central Bahamas.
What's in Store for the Cayman Islands, Jamaica, Cuba and Florida?
The National Hurricane Center has noted that Nicole is going to drop extreme amounts of rainfall. Nicole is expected to produce total rain accumulations of 5 to 10 inches over the Cayman Islands, Jamaica and Cuba. Isolated maximum amounts of 20 inches are possible over the higher elevations of Cuba and Jamaica. These rains could cause life-threatening flash floods and mud slides. Rain accumulations of 4 to 8 inches are possible over portions of southern Florida, the Florida Keys and the central and northwest Bahamas. Tropical storm conditions are expected in the warning areas today and tonight. Also, isolated tornadoes are possible along the immediate coast of southeastern Florida and the Florida Keys today.
Nicole is expected to become an extra-tropical storm later today and move northward along the U.S. east coast over the next couple of days.Text credit: Rob Gutro
Rob Gutro | EurekAlert!
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"Science" Magazine Announced the Main Scientific Discovery in 2017
The observation of the merger of two neutron stars, which allowed for the first time to capture both gravitational and electromagnetic waves, was set for the scientific discovery of 2017 by the American journal Science.
The August observation "confirmed several astrophysical models, revealed the origins of very heavy elements, and became proof of the correctness of Albert Einstein's theory of general relativity as never before," Science Editor writes on Thursday. The clash between the two neutron stars has reached 130 million light years from the Earth and generates small waves in the space and time fabric - called gravitational waves captured by three giant instruments on the ground, two in the US and one in Europe.
These waves, predicted by Albert Einstein, were first discovered in 2015 after a collision of two black holes. They brought the Nobel Prize for Physics in 2017 to the scientists behind the discovery. They open an important new window to observe the universe, allowing you to see bodies that do not emit light. Being able to capture virtually all events with the character of cosmic cataclysm is a promise for a revolutionary step in astrophysics, "Science wrote.
Among the top ten scientific discoveries of the year chosen by the magazine are the discovery of a new species of orangutan (Pongo tapanuliensis) in a lonely forest in Indonesia and a new skull dated 300,000 years ago. This discovery pushes back 100,000 years ago the first appearance of Homo sapiens. The success of a clinical trial of gene therapy in children with spinal muscular atrophy, which is the most common genetic cause of child mortality, was also referred to as the scientific achievement of the year. Progress, which could eliminate the genetic mutations responsible for some diseases, is also among the first ten of Science.
The magazine regrets several failures in science. It cites the "deeply dysfunctional relationship" between the scientific community and US President Donald Trump, who, after settling in the White House, withdrew the United States from the Paris climate agreement, lifted many environmental regulations and cut the federal research budget.
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Earlier this year NASA was urged by Congress to step it up and have a prototype in place by 2018 for a deep space habitat that will bring humans to Mars and back again.
Well, with that deadline quickly approaching, NASA is reaching out to the public for some help. The space agency has released a call for submissions from anyone who thinks they have the chops to create the habitats.
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The winning concepts will be used by NASA’s Orion crew to perform long space exploration journeys. As it is, the Orion spacecraft is certainly roomier than what the Apollo astronauts had, but it can still only keep the four-person crew alive in space for weeks at a time.
The new deep space habitat will be used by the Orion crew on their missions to orbit the moon. These will first last a few months and build up to a yearlong trip planned for 2020s before the long journey to Mars in the 2030s.
Plans should take into consideration that the habitat needs adequate living space for the crew, as well as propulsion and airlocks to support spacewalks, and should be reliable enough to be launched on more than one type of rocket. Hopefuls can also pitch to have their designs tested on the International Space Station as well.
Sound like something you’re up for? NASA is accepting notices of intent until May 13 from anyone in the US who thinks they’ve got the killer idea. There is an open industry forum on April 25 so any questions you have can be answered there, and official proposals will then be due no later than June 15.
NASA will be awarding the winning contracts in August and funding will be in the range of $65 million. So, if you’ve always fancied living on Mars and think you’ve got the design skills, now’s your chance.
The initiative is part of NASA’s Next Space Technologies for Explorations Partnerships-2 (NextSTEP-2) and is focused on taking human space travel and habitation beyond low-earth orbit and into deep space. By making the project a public-private partnership, NASA says it’s able to pool the best resources to get its project off the ground. | <urn:uuid:e49e4c35-2c5a-4f83-887d-4c2acddae843> | 2.53125 | 467 | News Article | Science & Tech. | 57.890982 | 95,584,781 |
Halfway through 2018, the U.S. is having its 14th warmest year on record, with the Southwest leading the way.
Drought and deluge are both expected to be more common in a warming world. See how far off these cities are from normal precipitation so far in 2018.
Longer frost-free seasons mean longer allergy seasons, a trend impacting all regions of the country.
There were some unusual highs and lows to snowfall totals across the U.S. this winter. Take a look at the long-term trends in total snow for more than 1,100 sites.
Small breweries are economic drivers in statewide economies, and climate change affects the beer they brew. Here’s where it counts the most.
On average, spring has warmed a little more than 2°F in the U.S. since 1970.
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Hurricane Irene made landfall in Onslow Bay, North Carolina, USA, on 27 August 2011, at which time it had been downgraded to a Category 1 hurricane after hitting the Bahamas at Category 3 strength.
Hurricane Irene makes landfall in Onslow Bay, North Carolina, 27 Aug. 2011. Image courtesy NASA.
In their GSA Today article, geoscientists Scott P. Hippensteel, Matthew D. Eastin, and William J. Garcia of the University of North Carolina at Charlotte call for a better understanding of the long-term record of storm frequency and impact, not only because of the increase in the strength of storms hitting coastal areas but also because of the high population density in vulnerable areas along the U.S. East Coast and Gulf Coast.
Those who study the paleo-storm record explain that gaining understanding of past events provides the context for future coastal vulnerability. Hippensteel and colleagues apply evidence of what they call the "lack of a definitive signature" from Hurricane Irene to a 1500-year paleostorm record at Onslow Bay. They write that fewer hurricanes could be found in the fossil and sedimentary records (through bioturbation or foraminiferal dissolution) than had actually made landfall there.
The authors infer that the lack of storm records in the marsh sediments from Onslow Bay means that only hurricane strikes of higher magnitude can provide proxies for understanding the paleostorm record, because only the most robust storm deposits are archived. The lack of definitive signs of Hurricane Irene in the area raises their concerns about the current understanding of hurricane deposition and preservation.ARTICLE
Scott Hippensteel et al., Dept. of Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, USA; firstname.lastname@example.org. Pages 4–10; doi: 10.1130/GSATG184A.1, http://www.geosociety.org/gsatoday/.
GSA Today articles are posted online; for a print copy, please contact Kea Giles. Please discuss articles of interest with the authors before publishing stories on their work, and please make reference to GSA Today in articles published.Contact:
Kea Giles | EurekAlert!
Study relating to materials testing Detecting damages in non-magnetic steel through magnetism
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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Until now this shrimp-like crustacean was thought to live only in the upper ocean. The discovery completely changes scientists’ understanding of the major food source for fish, squid, penguins, seals and whales.
Reporting this week in the journal Current Biology, scientists from British Antarctic Survey (BAS) and the National Oceanography Centre, Southampton* (NOCS) describe how they used a deep-diving, remotely operated vehicle (RoV) known as Isis to film previously unknown behaviour of krill.Professor Andrew Clarke of the British Antarctic Survey said,
Scientists have been studying krill since the ‘Discovery’ expeditions of the early 20th century. Oceanographic expeditions, using a combination of echo-sound techniques and collection samples in nets, indicated that the bulk of the population of adult krill is typically confined to the top 150 metres of the water column.
The grant to purchase the Isis RoV was led by Professor Paul A Tyler of NOCS. He said, “Having the ability to use a deep-water ROV in Antarctica gave us a unique opportunity to observe the krill and also to observe the diversity of animals living at the deep-sea floor from depths of 500m down to 3500m. The importance of such observations is that, not only do we have the ability to identify species, but we can see the relations among individual species and their relationship to the ambient environment.”
The discovery holds some important lessons, Clarke continued. “The behaviour of marine organisms - even quite 'primitive' ones - can be complex and more varied than we usually assume. There is still a great deal to learn about the deep sea and an important role for exploration in our attempts to understand the world we live in.”
Linda Capper | alfa
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Marinelife, has been monitoring whales and dolphins in the English Channel continuously for the last 12 years. The surveys, which have chiefly been conducted from Portsmouth, have confirmed that the Western English Channel, although an incredibly busy area for shipping and fishing remains an important area for whales and dolphins. Minke Whales have returned to the waters in recent years, and other species present include the endangered Bottlenose Dolphin and Harbour Porpoise, both protected under the EU Habitats Directive.
Other species have also been seen in these waters, but little is known about whether these sightings are unusual or within their natural range. Sightings include Common Dolphin, Pilot Whale and Risso’s Dolphin, together with Basking Sharks which are often seen off Plymouth during the spring and summer months.
Dr Tom Brereton, Marinelife Research Director commented “We are excited about the new survey, as it will enable us to better monitor the changing status of whales and dolphins in the region. We hope that the new data will play an increasingly important role in helping to conserve these beautiful and charismatic animals, so beloved by the general public. We are a small charity, and the research would not be possible without the generous support of Brittany Ferries, for which we are extremely grateful”
Marinelife plans to run its whale and dolphin research trips from Brittany Ferries on a monthly basis and record the distribution, abundance and types of whales, dolphins, other marine life and birds present in these UK waters. This data can then be used to identify whale and dolphin hotspots, seasonal and annual movements and threats to the marine life including fishing by-catch, which accounts for a large proportion of the dead Common Dolphin washed up annually on the West Country coast, especially during the winter months.
Research on the Plymouth to Roscoff route commenced on Tuesday 13th June 2006, with sightings of endangered and protected Bottlenose Dolphin on the maiden research crossing. This helps to confirm the vital nature of further research in this busy area of ocean to aid in the conservation of marine mammals around the British Isles.
Adrian Shephard | alfa
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what is the palaeclimate record
what are the characteristics of vostok ice core period
El hombre lleva mas de 150 años registrando la temperatura de la tierra, mediante estas recopilaciones de la temperatura se han modelado estudios del comportamiento de este durante la historia de la tierra. esto se hace usando el oxigeno y otros factores como referencia según la cantidad de tiempo.
The temperature record shows fluctuations of the temperature of the atmosphere and the oceans through various time span.
What is Pleistocene glaciation?
The instrumental record of the Earth's temperature based on direct measurements (using thermometers), and extends back only 150 years or so. Temperatures further back in time are reconstructed from a variety of proxy data. These include historical documents, together with natural archives of climate-sensitive phenomena, such as the growth or retreat of glaciers, tree rings, corals, sediments and ice cores.
In general, the proxy data record becomes more sparse and more imprecise the further back in time we go. Nevertheless, it has proved possible to produce a reasonably reliable reconstruction of how global temperature has varied throughout most of the Earth's history. This is known as the palaeoclimate record (from the Greek palaios for ‘ancient’).
Dendroclimatology depends on the fact that trees in many parts of the world experience an annual growth cycle. Each year's growth (the thickness and/or density of a ring) depends on the local temperature and moisture conditions, creating a unique record that can then be matched with overlapping records from other trees to produce longer time series.
Annual records typically go back 500 to 700 years. In a few cases, the preservation of fossil trees has allowed continuous records from 11,000 years ago to the present to be constructed.
In a similar way, cyclical responses lead to annual banding in corals, which can provide information about sea-surface temperatures, sea level and other ocean conditions - typically back to some 400 years ago.
Layered sediments on lake and ocean floors are another rich source. The types of pollen trapped in lake sediments reveal shifting patterns of vegetation, and thus indirect information about temperature and moisture conditions. Records can go back some 100,000 years.
In marine sediments, analysis of microfossils can provide data on seawater temperature and salinity (salt content), atmospheric CO2 and ocean circulation. Less common deposits of coarse debris can point to the break up of ice sheets and the release of detritus from melting icebergs. Marine sediments provide information from time periods ranging from 20,000 years to 180 million years ago.
Long ice cores drilled out of the Greenland and Antarctic ice sheets yield a wealth of information. For example, past temperatures can be determined by oxygen isotope analysis . 99% of the oxygen on Earth is the isotope 16O; most of the rest is isotope 18O. Because water molecules containing the different isotopes (i.e. H2 16O and H2 18O) have slightly different physical properties, it turns out that the 18O/16O ratio in ice locked up on land is affected by the ambient temperature at the time when the ice formed.
Thus, fluctuations in the oxygen isotope ratio in an ice core provide a proxy for temperature changes back through time.. The cores also include atmospheric fallout such as wind-blown dust, volcanic ash, pollen, etc. - along with trapped air bubbles.
Drilled in Antarctica, the Vostok ice core provides a temperature record that goes back several hundreds of thousands of years. Beyond about 10,000 years ago, it tells a story of an unstable climate oscillating between short warm interglacial periods and longer cold glacial periods about every 100,000 years - with global temperatures varying by as much as 5 to 8 °C - interspersed by many more short-term fluctuations.
By contrast, global temperatures over the last 10,000 years or so seem to have been much less variable, fluctuating by little more than one or two degrees. In short, the interglacial period in which we live, known as the Holocene, appears (on available evidence) to have provided the longest period of relatively stable global climate for at least 400,000 years. It is almost certainly no coincidence that this is also when many human societies developed agriculture and when the beginnings of modern civilisations occurred. | <urn:uuid:36cbabbe-3f9e-44e0-9a39-a630ca7af7fa> | 3.421875 | 946 | Knowledge Article | Science & Tech. | 33.331077 | 95,584,803 |
Fractional calculus is a generalisation of ordinary calculus where you can differentiate n times when n is not a whole number.
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Investigate circuits and record your findings in this simple introduction to truth tables and logic.
Explore the continued fraction: 2+3/(2+3/(2+3/2+...)) What do you notice when successive terms are taken? What happens to the terms if the fraction goes on indefinitely?
Learn about the link between logical arguments and electronic circuits. Investigate the logical connectives by making and testing your own circuits and record your findings in truth tables.
Learn about the link between logical arguments and electronic circuits. Investigate the logical connectives by making and testing your own circuits and fill in the blanks in truth tables to record. . . .
Take a number, add its digits then multiply the digits together, then multiply these two results. If you get the same number it is an SP number.
Peter Zimmerman, a Year 13 student at Mill Hill County High School in Barnet, London wrote this account of modulus arithmetic.
An article which gives an account of some properties of magic squares.
This article discusses how every Pythagorean triple (a, b, c) can be illustrated by a square and an L shape within another square. You are invited to find some triples for yourself.
Professor Korner has generously supported school mathematics for more than 30 years and has been a good friend to NRICH since it started.
Solve this famous unsolved problem and win a prize. Take a positive integer N. If even, divide by 2; if odd, multiply by 3 and add 1. Iterate. Prove that the sequence always goes to 4,2,1,4,2,1...
Some puzzles requiring no knowledge of knot theory, just a careful inspection of the patterns. A glimpse of the classification of knots and a little about prime knots, crossing numbers and. . . .
An account of methods for finding whether or not a number can be written as the sum of two or more squares or as the sum of two or more cubes.
Suppose A always beats B and B always beats C, then would you expect A to beat C? Not always! What seems obvious is not always true. Results always need to be proved in mathematics.
We continue the discussion given in Euclid's Algorithm I, and here we shall discover when an equation of the form ax+by=c has no solutions, and when it has infinitely many solutions.
In this 7-sandwich: 7 1 3 1 6 4 3 5 7 2 4 6 2 5 there are 7 numbers between the 7s, 6 between the 6s etc. The article shows which values of n can make n-sandwiches and which cannot.
Show that if you add 1 to the product of four consecutive numbers the answer is ALWAYS a perfect square.
In this article we show that every whole number can be written as a continued fraction of the form k/(1+k/(1+k/...)).
By proving these particular identities, prove the existence of general cases.
Tom writes about expressing numbers as the sums of three squares.
Peter Zimmerman from Mill Hill County High School in Barnet, London gives a neat proof that: 5^(2n+1) + 11^(2n+1) + 17^(2n+1) is divisible by 33 for every non negative integer n.
Take a complicated fraction with the product of five quartics top and bottom and reduce this to a whole number. This is a numerical example involving some clever algebra.
The final of five articles which containe the proof of why the sequence introduced in article IV either reaches the fixed point 0 or the sequence enters a repeating cycle of four values.
It is impossible to trisect an angle using only ruler and compasses but it can be done using a carpenter's square.
The first of two articles on Pythagorean Triples which asks how many right angled triangles can you find with the lengths of each side exactly a whole number measurement. Try it!
Follow the hints and prove Pick's Theorem.
We only need 7 numbers for modulus (or clock) arithmetic mod 7 including working with fractions. Explore how to divide numbers and write fractions in modulus arithemtic.
Find all real solutions of the equation (x^2-7x+11)^(x^2-11x+30) = 1.
Try to solve this very difficult problem and then study our two suggested solutions. How would you use your knowledge to try to solve variants on the original problem?
The country Sixtania prints postage stamps with only three values 6 lucres, 10 lucres and 15 lucres (where the currency is in lucres).Which values cannot be made up with combinations of these postage. . . .
This is the second article on right-angled triangles whose edge lengths are whole numbers.
When if ever do you get the right answer if you add two fractions by adding the numerators and adding the denominators?
This article looks at knight's moves on a chess board and introduces you to the idea of vectors and vector addition.
If I tell you two sides of a right-angled triangle, you can easily work out the third. But what if the angle between the two sides is not a right angle?
Start with any whole number N, write N as a multiple of 10 plus a remainder R and produce a new whole number N'. Repeat. What happens?
In this third of five articles we prove that whatever whole number we start with for the Happy Number sequence we will always end up with some set of numbers being repeated over and over again.
This article extends the discussions in "Whole number dynamics I". Continuing the proof that, for all starting points, the Happy Number sequence goes into a loop or homes in on a fixed point.
To find the integral of a polynomial, evaluate it at some special points and add multiples of these values.
The first of five articles concentrating on whole number dynamics, ideas of general dynamical systems are introduced and seen in concrete cases.
Find all positive integers a and b for which the two equations: x^2-ax+b = 0 and x^2-bx+a = 0 both have positive integer solutions.
This follows up the 'magic Squares for Special Occasions' article which tells you you to create a 4by4 magicsquare with a special date on the top line using no negative numbers and no repeats.
Can you rearrange the cards to make a series of correct mathematical statements?
Sort these mathematical propositions into a series of 8 correct statements.
Can you work through these direct proofs, using our interactive proof sorters?
You have twelve weights, one of which is different from the rest. Using just 3 weighings, can you identify which weight is the odd one out, and whether it is heavier or lighter than the rest?
The twelve edge totals of a standard six-sided die are distributed symmetrically. Will the same symmetry emerge with a dodecahedral die?
Show that the infinite set of finite (or terminating) binary sequences can be written as an ordered list whereas the infinite set of all infinite binary sequences cannot.
Advent Calendar 2011 - a mathematical activity for each day during the run-up to Christmas.
Pick a square within a multiplication square and add the numbers on each diagonal. What do you notice? | <urn:uuid:305ada1e-a04c-408a-8694-368564f49ab5> | 3.796875 | 1,583 | Content Listing | Science & Tech. | 61.758975 | 95,584,821 |
Intoxicated by climate catastrophism, young designers and engineers in the rich world are falling over themselves to create brilliant solutions to capture atmospheric carbon dioxide. But their marketing claims are dubious, and their futuristic designs do little at great cost. What’s more, ordinary people in India thrashed such efforts in 12 hours flat.
If you follow green technology, you may have noticed the unveiling of an urban “tree” which looks like an advertising screen covered in greenery. This “CityTree”, it is claimed, “cleans as much polluted air as a forest”. Perhaps you saw the launch of the world’s first commercial carbon capture plant, which “just started sucking CO2 out of the atmosphere to save us from climate change”.
This is good news, right? Science and technology to the rescue! Who doesn’t love that? It’s just that the numbers make no sense. At all.
Let’s start with the carbon capture plant, which began operating on 31 May 2017 between a waste incineration plant and a farm outside Zürich, Switzerland. It extracts about 900 tons of carbon dioxide from the air near the waste plant, and pumps it into a greenhouse where the gas feeds assorted vegetables. Jan Wurzbacher, director and co-founder of Climeworks, the firm that manufactured the plant, told Fast Company that it is “commercially attractive”. But even Bloomberg’s report on the plant didn’t bother to mention the machine’s price.
According to New Scientist, the makers claim that the current cost for large-scale CO2 sequestration is $600 per ton, and they expect to equal this figure. If this is true, the plant, including the electricity to turn its fans and heat it up to boiling point periodically, will cost $540,000 to operate for a year.
In another article on the Climeworks plant, the makers claim to already have broken the $600 per ton barrier. That piece also claims that 10 gigatons of CO2 need to be removed from the atmosphere every year to halt the pace of global warming. Whether or not that is true, necessary or even desirable, the catastrophist publication Carbon Brief agrees. This means we’d need 11-million of these plants operating concurrently. Accepting the $600 per ton cost at face value, that works out to a price of $6-trillion per year. That sounds “commercially attractive” only if you’re a shareholder of Climeworks.
Then there’s the CityTree. If you like your cityscapes futuristic, it doesn’t look half bad. Its 3.5m2 vertical square panel, covered in moss and supported by two benches, is claimed to be more effective at filtering atmospheric pollution than trees. It does the work of 275 trees, according to the marketing material of the manufacturer, removing about 90kg of particulates and some 240 tons of carbon dioxide from the air per year. Where all that stuff would fit in such a small contraption is anyone’s guess. I already smell a rat.
The price for one of these urban accoutrements? According to futurism.com, it is “fairly cost-effective” at $25,000 per unit. It would be astonishing that such a small, simple design has 27% of the capacity of the far more substantial Swiss carbon capture plant. If we take the manufacturer’s claims at face value, its upfront costs work out to $20 per ton of sequestrated CO2 over five years, although that excludes any running costs. This extraordinarily low figure is another reason we shouldn’t believe any of these claims.
What alternative do we have to expensive carbon capture contraptions? (Again, supposing that reducing atmospheric CO2 levels is necessary to avoid catastrophic climate change.)
Trees, of course. Increasing CO2 levels in the atmosphere have already resulted in a greening world, as one might expect. After all, plants love CO2, which is exactly why the Swiss capture plant is connected to a greenhouse.
Calculating how much carbon is sequestered per year per tree (or per unit of afforested area), is a complex task. It requires data on tree species, density, age and much more. Generally, trees are best at sequestering carbon when they are large and still growing fast.
If we work backwards from the claims by CityTree, 275 trees sequestering 240 tons of CO2 per year gives a figure of 0.9 tons per tree per year. However, a calculation involving silver maple in the US, using the per-tree calculator linked above, works out to 0.2 tons per tree per year. The Climeworks founder told Future Company that a tree takes 50kg out of the air per year, which would make their plant do the work of 18,000 trees. Yet another source says 98 mature trees sequester 1 ton of CO2 per year, which makes it about 10kg per tree per year. Yet again, we can’t seem to rely on any of the claims made by marketers. This paper gives a figure of 0.28kg per square metre, which points to an even lower value than 10kg per tree.
Let’s suppose 10kg of carbon sequestration per tree per year is correct. This would mean that the CityTree can actually replace about 23,500 trees, not a mere 275. So either the 240 tons per year claim is a lie, or the 275 trees claim is gravely mistaken. I’m going to guess it’s the former. The Climeworks carbon capture plant, by the same assumptions, can replace 88,200 trees.
The cost of planting trees varies widely. The Plant a Billion Trees Campaign will do it for $1 a tree, but it can be done for as little as $0.20 per tree. That means the CityTree, at $25,000 not counting running costs, could be replaced by $4,700 worth of trees, if we’re generous enough to accept their 240 tons claim. If not, their own claim of replacing 275 trees puts the value of the $25,000 device at between $55 and $275.
At $0.20 per tree, the Climeworks carbon capture plant could be replaced by $17,640 worth of trees. Conversely, the cost per ton of CO2 sequestered by 20 cent trees works out to $19.60, which makes the Climeworks plant 30 times more expensive than an equivalent number of trees.
Meanwhile, in India, nobody is buying fancy-shmancy urban design or Swiss technology for scrubbing carbon. Instead, they get 1.5-million people together in the state of Madhya Pradesh and plant 67-million trees in 12 hours flat. That breaks a previous record of 50-million trees in 24 hours held by another Indian state, Uttar Pradesh.
Even assuming a 40% mortality rate among the saplings, the people of a developing country have achieved in less than two days what it would otherwise take 800 Climeworks plants to do. Depending on the numbers we believe, we’d need either 3,000 or 255,000 CityTrees to do the same.
Whether or not you believe that CO2 is a pollutant or that atmospheric CO2 levels are dangerously high, trees provide a great deal of environmental benefit. They offer habitat, improve the soil, scrub air of actual pollutants, and provide shade near buildings which reduces their energy costs. They’re nice to have around, especially in urban areas, and are good for the environment everywhere. They’re cheap, and they can be planted with no skill at all.
For showing up all the opportunistic green technology designers selling expensive devices and angling for vast new taxes to make them look worth the money, my hat’s off to India. Let’s follow their example. DM
Star Wars was the first major film to be dubbed in Navajo. | <urn:uuid:26892eca-e178-4580-81bf-acffeff231e7> | 3.3125 | 1,674 | Nonfiction Writing | Science & Tech. | 63.466971 | 95,584,823 |
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Farmer John has received a shipment of N large hay bales (1≤N≤4000) and placed them at various locations along the road leading to his barn. Unfortunately, he completely forgets that Bessie the cow is out grazing along the road, and she may now be trapped within the bales!
Each bale j has a size Sj and a distinct position Pj giving its location along the one-dimensional road. Bessie the cow starts at some location where there is no hay bale, and can move around freely along the road, even up to the position at which a bale is located, but she cannot cross through this position. As an exception, if she runs in the same direction for D units of distance, she builds up enough speed to break through and permanently eliminate any hay bale of size strictly less than D. Of course, after doing this, she might open up more space to allow her to make a run at other hay bales, eliminating them as well.
Bessie can escape to freedom if she can eventually break through either the leftmost or rightmost hay bale. Please compute the total area of the road consisting of real-valued starting positions from which Bessie cannot escape. For example, if Bessie cannot escape if she starts between hay bales at positions 1 and 5, then these encompass an area of size 4 from which she cannot escape.
The first line of input contains N. Each of the next N lines describes a bale, and contains two integers giving its size and position, each in the range 1…109.
Print a single integer, giving the area of the road from which Bessie cannot escape.
5 8 1 1 4 8 8 7 15 4 20 | <urn:uuid:857af5c2-aa5a-4e2c-ab0e-451c931f1a36> | 2.640625 | 449 | Q&A Forum | Science & Tech. | 66.713856 | 95,584,833 |
A solar storm often referred to as a geomagnetic storm is a short-term disturbance of the Earth’s magnetosphere. This disturbance is usually caused by a cloud of a magnetic field or a shock wave from a solar wing that interacts with the magnetic field of our planet.
According to scientists from the Academy of Sciences in Russia, there is a huge magnetic storm that is approaching the Earth.
This magnetic storm is about to bring headaches and dizziness to the people around the world.
According to the Russian scientists at the Academy of Sciences, only three days before the storm hits, (March 14th, 16th, and 17th), we will feel powerful geomagnetic altercations.
MORE DETAILS AND PAST EVENTS
Since the start of 2018, this will be the third geomagnetic storm to hit our planet. The first one occurred on January 15th and the second one on February 19th.
The moment the storm hits on March 18th, everything in our lives will start to feel a bit strange.
Moreover, it might affect GPS navigations, damage power grids and disrupt satellites across the entire world.
SHOULD WE WORRY?
No. Not really. Scientists say that people might experience trouble sleeping, since it may be harder for everyone to fall asleep and stay asleep for the entire night.
Some may be affected more than others.
But, it all depends on the person. Well, unless you have health issues, you will simply think that you are having a very bad day.
GETTING CLOSER TO OUR HIGHER SELF
Some people strongly believe that this particular solar storm will help us get energy from the Universe. In addition, it can allow us to get closer to our higher self.
Nevertheless, such intensive and powerful energy will bring some changes in our lives.
Scientists claim that it might particularly affect people who are in a relationship. In fact, it will affect their ability to communicate.
As a result, it is very important for people to be careful with their words, especially during the solar storms.
Also, they have to be careful not to hurt the ones they care about the most until the storm passes.
Otherwise, it may put a huge strain on their relationship.
WHAT CAN WE DO?
The best thing that you can do for yourself and the people you love is to relax during the geomagnetic storm.
In other words, wait for everything to pass, so that your life will fall into place once again.
Lastly, here is a video that can help you understand what a solar storm or geomagnetic storm actually is.
Are you looking forward to March 18th? What will you do during the solar storms? Let us know! | <urn:uuid:123e4e60-bb94-4917-8134-029a8c4a1213> | 2.546875 | 563 | News Article | Science & Tech. | 60.923309 | 95,584,870 |
Blue carbon is the carbon dioxide captured by the world’s ocean and coastal ecosystems. This carbon is stored in the form of biomass and sediments from mangroves, tidal marshes and seagrass meadows. Blue carbon is the most effective, yet overlooked, method for long term sequestration and storage of carbon. Of equal importance, investment in blue carbon provides invaluable ecosystem services that contribute to people’s ability to mitigate and adapt to the impacts of climate change.
Here we have compiled some of the best resources on this topic.
FACT SHEETS AND FLYERS
A Blue Carbon Fund - The ocean equivalent of REDD for carbon sequestration in coastal states. (Flyer)
This is a useful and condensed summary of the report by the UNEP and GRID-Arendal, including the role of the critical role the ocean plays in our climate and the next steps to include it in climate change agendas.
Blue Carbon: A Story Map from GRID-Arendal.
An interactive story book on the science of blue carbon and the policy recommendations for its protection from GRID-Arendal.
AGEDI. 2014. Building Blue Carbon Projects - An Introductory Guide. AGEDI/EAD. Published by AGEDI. Produced by GRID-Arendal, A Centre Collaborating with UNEP, Norway.
The report is an overview of Blue Carbon science, policy and management in collaboration with United Nation’s Environmental Programme. Blue carbon’s financial and institutional impact as well as capacity building for projects is reviewed. This includes case studies in Australia, Thailand, Abu Dhabi, Kenya and Madagascar.
Pidgeon, E., Herr, D., Fonseca, L. (2011). Minimizing Carbon Emissions and Maximizing Carbon Sequestration and Storage by Seagrasses, Tidal Marshes, Mangroves - Recommendations from the International Working Group on Coastal Blue Carbon
Highlights the need for 1) enhanced national and international research efforts of coastal carbon sequestration, 2) enhanced local and regional management measures based on current knowledge of emissions from degraded coastal ecosystems and 3) enhanced international recognition of coastal carbon ecosystems. This brief flyer calls for immediate action towards the protection of seagrasses, tidal marshes and mangroves.
Restore America's Estuaries: Coastal Blue Carbon: A new opportunity for Coastal Conservation
This handout covers the importance of blue carbon and the science behind the storage and sequestration of greenhouse gases. Restore America’s Estuaries reviews the policy, education, panels and partners they are working on to advance coastal blue carbon.
PRESS RELEASES, STATEMENTS AND POLICY BRIEFS
Blue Climate Coalition. 2010. Blue Carbon Solutions for Climate Change - Open Statement to the Delegates of COP16 by the Blue Climate Coalition.
This statement provides the basics of blue carbon, including its critical value and its major threats. The Blue Climate Coalition recommends the COP16 to take action in restoring and protecting these vital coastal ecosystems. It is signed by fifty-five marine and environmental stakeholders from nineteen countries representing the Blue Climate Coalition.
Payments for Blue Carbon: Potential for Protecting Threatened Coastal Habitats. Brian C. Murray, W. Aaron Jenkins, Samantha Sifleet, Linwood Pendleton, and Alexis Baldera. Nicholas Institute for Environmental Policy Solutions, Duke University
This article reviews the extent, location, and rate of loss in coastal habitats as well as carbon storage in those ecosystems. Considering those factors, monetary impact as well as potential revenue from blue carbon protection are examined under the case study of conversion of mangroves to shrimp farms in Southeast Asia.
Pew Fellows. San Feliu De Guixols Ocean Carbon Declaration
Twenty-nine Pew Fellows in Marine Conservation and Advisors, together from twelve countries signed a recommendation to policy makers to (1) Include coastal marine ecosystem conservation and restoration in strategies for climate change mitigation. (2) Fund targeted research to improve our understanding of the contribution of coastal and open ocean marine ecosystems to the carbon cycle and to the effective removal of carbon from the atmosphere.
United Nations Environmental Programme (UNEP). Healthy Oceans New Key to Combating Climate Change
This report advises that seagrass and salt marshes are the most cost effective method for carbon storage and capture. Urgent action is required to restore carbon sinks since they are being lost at a rate seven times higher than 50 years ago.
Cancun Oceans Day: Essential to Life, Essential to Climate at the Sixteenth Conference of the Parties to the United Nations Framework Convention on Climate Change. December 4, 2010
The statement is a summary of the growing scientific evidence on climate and oceans; oceans and coasts carbon cycle; climate change and marine biodiversity; coastal adaptation; climate change financing for costs and island populations; and integrated strategies. It concludes with a five-point action plan for UNFCCC COP 16 and moving forward.
A Florida Roundtable on Ocean Acidification: Meeting Report. Mote Marine Laboratory, Sarasota, FL September 2, 2015
In September 2015, Ocean Conservancy and Mote Marine Laboratory partnered to host a roundtable on ocean acidification in Florida designed to accelerate the public discussion about OA in Florida. Seagrass ecosystems play a huge role in Florida and the report recommends the protection and restoration of seagrass meadows for 1) ecosystem services 2) as part of a portfolio of activities that move the region toward reducing the impacts of ocean acidification.
CDP Report 2015 v.1.3; September 2015. Putting a price on risk: Carbon pricing in the corporate world
This report reviews over a thousand companies globally that publish their price on carbon emissions or plan to in the next two years.
Chan, F., et al. 2016. The West Coast Ocean Acidification and Hypoxia Science Panel: Major Findings, Recommendations, and Actions. California Ocean Science Trust.
A 20-member scientific panel warns that increases in global carbon dioxide emissions are acidifying waters of the North American West Coast at an accelerating rate. The West Coast OA and Hypoxia Panel specifically recommends exploring approaches that involve the use of seagrass to remove carbon dioxide from seawater as a primary remedy to OA on the west coast. Find the press release here.
This booklet compiles the results of a wide variety of economic valuation studies on tropical marine and coastal reef ecosystems around the world. While published in 2008, this paper still provides a useful guide to the value of coastal ecosystems, especially in the context of their blue carbon uptake abilities.
Crooks, S., Rybczyk, J., O’Connell, K., Devier, D.L., Poppe, K., Emmett-Mattox, S. 2014. Coastal Blue Carbon Opportunity Assessment for the Snohomish Estuary: The Climate Benefits of Estuary Restoration. Report by Environmental Science Associates, Western Washington University, EarthCorps, and Restore America’s Estuaries. February 2014.
The report is in response to rapidly diminishing coastal wetlands from human impact. Actions are outlined to inform policymakers of the scale of GHG emissions and removals associated with management of coastal lowlands under conditions of climate change; and identify information needs for future scientific investigation to improve quantification of GHG fluxes with coastal wetlands management.
Emmett-Mattox, S., Crooks, S. Coastal Blue Carbon as an Incentive for Coastal Conservation, Restoration and Management: A Template for Understanding Options
The document will help guide coastal and land managers in understanding the ways by which protecting and restoring coastal blue carbon can help achieve coastal management goals. It includes discussion of significant factors in making this determination and outlines next steps for developing blue carbon initiatives.
Gordon, D., Murray, B., Pendleton, L., Victor, B. 2011. Financing Options for Blue Carbon Opportunities and Lessons from the REDD+ Experience. Nicholas Institute for Environmental Policy Solutions Report. Duke University.
This report analyzes current and potential options for carbon mitigation payments as a source of blue carbon financing. It indepthly explores the financing of REDD+ (Reducing Emissions from Deforestation and Forest Degradation) as a potential model or source from which to launch blue carbon financing. This report serves to help stakeholders assess funding gaps in carbon financing and direct resources to those activities that will provide the greatest blue carbon benefits.
Herr, D., Pidgeon, E., Laffoley, D. (eds.) (2012) Blue Carbon Policy Framework 2.0: Based in the discussion of the International Blue Carbon Policy Working Group. IUCN and Conservation International.
Reflections from the International Blue Carbon Policy Working Group workshops held in July 2011. This paper is helpful for those who want to more detailed and expansive explanation of blue carbon and its potential and its role in policy.
Herr, D., E. Trines, J. Howard, M. Silvius and E. Pidgeon (2014). Keep it fresh or salty. An introductory guide to financing wetland carbon programs and projects. Gland, Switzerland: IUCN, CI and WI. iv + 46pp.
Wetlands are key to carbon mitigation and there are a number of climate finance mechanisms to address the subject. Wetland carbon project can be funded through a voluntary carbon market or in the context of biodiversity finance.
Howard, J., Hoyt, S., Isensee, K., Pidgeon, E., Telszewski, M. (eds.) (2014). Coastal Blue Carbon: Methods for assessing carbon stocks and emissions factors in mangroves, tidal salt marshes, and seagrass meadows. Conservation International, Intergovernmental Oceanographic Commission of UNESCO, International Union for Conservation of Nature. Arlington, Virginia, USA.
This report reviews methods for assessing carbon stocks and emissions factors in mangroves, tidal salt marshes, and seagrass meadows. Covers how to estimate carbon dioxide emissions, data management and mapping.
Kollmuss, Anja; Zink; Helge; Cli ord Polycarp. March 2008. Making Sense of the Voluntary Carbon Market: A Comparison of Carbon Offset Standards
This report reviews the carbon offset market, including transactions and voluntary versus compliance markets. It continues with an overview of key elements of offset standards.
Laffoley, D.d’A. & Grimsditch, G. (eds). 2009. The management of natural coastal carbon sinks. IUCN, Gland, Switzerland. 53 pp
This book provides thorough yet simple overviews of coastal carbon sinks. It was published as a resource not only to outline the value of these ecosystems in blue carbon sequestration, but also to highlight the need for effective and proper management in keeping that sequestered carbon in the ground.
Laffoley, D., Baxter, J. M., Thevenon, F. and Oliver, J. (editors). 2014. The Significance and Management of Natural Carbon Stores in the Open Ocean. Full report. Gland, Switzerland: IUCN. 124 pp.This book published 5 years later by the same group as the IUCN study, The management of natural coastal carbon sinks, goes beyond coastal ecosystems and looks at the value of blue carbon in the open ocean.
The report presents eight biological mechanisms of marine vertebrates that enable capture of atmospheric carbon and provide a potential buffer against ocean acidification. It was published in response to the United Nations’ call for innovative solutions to climate change.
Murray, B., Pendleton L., Jenkins, W. and Sifleet, S. 2011. Green Payments for Blue Carbon Economic Incentives for Protecting Threatened Coastal Habitats. Nicholas Institute for Environmental Policy Solutions Report.
This report aims to connect the monetary value of blue carbon to economic incentives strong enough to curtail current rates of coastal habitat loss. It finds that because coastal ecosystems store large amounts of carbon and are severely threatened by coastal development, they could be an ideal target for carbon financing – similar to REDD+.
Nellemann, C., Corcoran, E., Duarte, C. M., Valdés, L., De Young, C., Fonseca, L., Grimsditch, G. (Eds). 2009. Blue Carbon. A Rapid Response Assessment. United Nations Environment Programme, GRID-Arendal, www.grida.no
A new Rapid Response Assessment report released 14 October 2009 at the Diversitas Conference, Cape Town Conference Centre, South Africa. Compiled by experts at GRID-Arendal and UNEP in collaboration with the UN Food and Agricultural Organization (FAO) and the UNESCO International Oceanographic Commissions and other institutions, the report highlights the critical role of the oceans and ocean ecosystems in maintaining our climate and in assisting policy makers to mainstream an oceans agenda into national and international climate change initiatives. Find the interactive e-book version here.
Pidgeon E. Carbon sequestration by coastal marine habitats: Important missing sinks. In: Laffoley DdA, Grimsditch G., editors. The Management of Natural Coastal Carbon Sinks. Gland, Switzerland: IUCN; 2009. pp. 47–51.
This article is part of the above Laffoley, et al. IUCN 2009 publication. It provides a breakdown of the importance of ocean carbon sinks and includes helpful diagrams comparing different types of terrestrial and marine carbon sinks. The authors highlights that the dramatic difference between the coastal marine and terrestrial habitats is the ability of marine habitats to perform long term carbon sequestration.
Ezcurra, P., Ezcurra, E., Garcillán, P., Costa, M., and Aburto-Oropeza, O. 2016. “Coastal landforms and accumulation of mangrove peat increase carbon sequestration and storage” Proceedings of the National Academy of Sciences of the United States of America.
This study finds that mangroves in Mexico’s arid northwest, occupy less than 1% of the terrestrial area, but store around 28% of the total below ground carbon pool of the whole region. Despite their small are, mangroves and their organic sediments represent a disproportionate to global carbon sequestration and carbon storage.
Fourqurean, J. et al 2012. Seagrass ecosystems as a globally significant carbon stock. Nature Geoscience 5, 505–509.
This study affirms that seagrass, currently one of the world’s most threatened ecosystems, is a critical solution to climate change through its organic blue carbon storage abilities.
Greiner JT, McGlathery KJ, Gunnell J, McKee BA (2013) Seagrass Restoration Enhances “Blue Carbon” Sequestration in Coastal Waters. PLoS ONE 8(8): e72469. doi:10.1371/journal.pone.0072469
This is one of the first studies to provide concrete evidence of the potential of seagrass habitat restoration to enhance carbon sequestration in the coastal zone. The authors actually planted seagrass and studied its growth and sequestration over extensive periods of time.
Martin, S., et al. Ecosystem Services Perspective for the Oceanic Eastern Tropical Pacific: Commercial Fisheries, Carbon Storage, Recreational Fishing, and Biodiversity
Front. Mar. Sci., 27 April 2016
A publication on fish carbon and other ocean values which estimates the value of carbon export to the deep ocean for the oceanic Eastern Tropical Pacific to be $12.9 billion per year, though geophysical and biological transport of carbon and carbon storage in populations of marine animals.
McNeil, Significance of the oceanic CO2 sink for national carbon accounts. Carbon Balance and Management, 2006. I:5, doi:10.1186/1750-0680-I-5
Under the United Nations convention on the law of the sea (1982), each participating country maintains exclusive economic and environmental rights within the oceanic region extending 200 nm from its coastline, known as the Exclusive Economic Zone (EEZ). The report analyzes that the EEZ is not mentioned within the Kyoto Protocol to address the anthropogenic CO2 storage and uptake.
Pendleton L, Donato DC, Murray BC, Crooks S, Jenkins WA, et al. 2012. Estimating Global ‘‘Blue Carbon’’ Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems. PLoS ONE 7(9): e43542. doi:10.1371/journal.pone.0043542
This study approaches the valuation of blue carbon from a “value lost” perspective, addressing the impact of degraded coastal ecosystems and providing a global estimate of the blue carbon that is released annually as a result of habitat destruction.
Rehdanza, Katrin; Jung, Martina; Tola, Richard S.J.; and Wetzelf, Patrick. Ocean Carbon Sinks and International Climate Policy.
Ocean sinks are not addressed in the Kyoto Protocol even though are as unexplored and uncertain as were the terrestrial sinks at the time of negotiation. The authors use a model of the international market for carbon dioxide emissions to evaluate who would gain or lose from allowing for ocean carbon sinks.
Sabine, C.L. et al. 2004. The ocean sink for anthropogenic CO2. Science 305: 367-371
This study examines the ocean’s uptake of anthropogenic carbon dioxide since the Industrial Revolution, and concludes the ocean is by far the largest carbon sink in the world. It removes 20-35% atmospheric carbon emissions.
Spalding, M. J. (2015). Crisis for Sherman's Lagoon - And the Global Ocean. The Environmental Forum. 32(2), 38-43.
This article highlights the severity of OA, its impact on the food web and on human sources of protein, and the fact that it is a present and visible problem. The author, Mark Spalding, ends with a list of small steps that can be taken to help combat OA - including the option to offset carbon emissions in the ocean in the form of blue carbon.
MAGAZINE AND NEWSPAPER ARTICLES
Luchessa, Scott (2010) Ready, Set, Offset, Go!: Using Wetland Creation, Restoration, and Preservation for Developing Carbon Offsets.
Wetlands can be sources and sinks of greenhouse gases, the journal reviews the science background to this phenomenon as well as international, national and regional initiatives to address wetlands benefits.
San Francisco State University (2011, October 13). Plankton's shifting role in deep sea carbon storage explored. ScienceDaily. Retrieved October 14, 2011, from http://www.sciencedaily.com/releases/2011/10/111013162934.htm
Climate-driven changes in nitrogen sources and carbon dioxide levels in seawater could work in conjunction to make Emiliania huxleyi (plankton) a less effective agent of carbon storage in the world’s largest carbon sink, the deep sea. Changes to this large carbon sink as well as anthropogenic atmospheric carbon dioxide levels could have a significant impact on the future climate on the planet's future climate.
Wilmers, Christopher C ; Estes, James A; Edwards, Matthew; Laidre, Kristin L;, and Konar, Brenda. Do trophic cascades affect the storage and flux of atmospheric carbon? An analysis of sea otters and kelp forests. Front Ecol Environ 2012; doi:10.1890/110176
Scientists collected data from the past 40 years to estimate the indirect effects of sea otters on carbon production and storage access in ecosystems in North America. They concluded that sea otters have a strong impact on the components in the carbon cycle which can impact the rate of carbon flux.
In Senegal and other developing countries, multinational companies are investing in programs to restore mangrove forests and other wetlands that sequester carbon. But critics say these initiatives should not focus on global climate goals at the expense of the local people’s livelihoods.
Restore America’s Estuaries: Coastal Blue Carbon: A new opportunity for wetlands conservation
Powerpoint presentation that reviews the importance of blue carbon and the science behind storage, sequestration and greenhouse gases. Restore America’s Estuaries reviews the policy, education, panels and partners they are working on to advance coastal blue carbon.
Poop, Roots and Deadfall: The Story of Blue Carbon
Presentation given by Mark Spalding, President of The Ocean Foundation, that explains blue carbon, types of coastal storages, cycling mechanisms and status of policy on the issue. Click link above for the PDF version or watch the below.
ACTIONS YOU CAN TAKE
Use our SeaGrass Grow Carbon Calculator to calculate your carbon emissions and donate to offset your impact with blue carbon! The calculator was developed by The Ocean Foundation to help an individual or organization calculate its annual CO2 emissions to, in turn, determine the amount of blue carbon necessary to offset them (acres of seagrass to be restored or the equivalent). The revenue from the blue carbon credit mechanism can be used to fund restoration efforts, which in turn generate more credits. Such programs allow for two wins: creation of a quantifiable cost to global systems of CO2-emitting activities and, second, restoration of seagrass meadows that form a critical component of coastal ecosystems and are in sore need of recovery. | <urn:uuid:0125d345-3c65-4101-b04b-219559f90054> | 3.515625 | 4,483 | Content Listing | Science & Tech. | 38.861525 | 95,584,876 |
Species Detail - Stygnocoris fuligineus - Species information displayed is based on all datasets.
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
insect - true bug (Hemiptera)
11 April (recorded in 1995)
4 November (recorded in 1973)
National Biodiversity Data Centre, Ireland, Stygnocoris fuligineus, accessed 22 July 2018, <https://maps.biodiversityireland.ie/Species/85739> | <urn:uuid:82830f8b-b27f-45bf-9ae6-fdcaef4630fb> | 2.59375 | 145 | Structured Data | Science & Tech. | 33.246137 | 95,584,888 |
Phonons: Harmonic Approximation
As illustrated in Sect. 3.1, in the Born-Oppenheimer (BO) approximation (also known as the adiabatic approximation), the equations which determine the electronic state are decoupled from those related to the ionic dynamics. In other words, the atomic motion of the system (molecule, cluster, or solid) is studied under the hypothesis that the electronic system always remains in the electronic ground state associated with the instantaneous geometrical configuration. We have seen in Sect. 3.1 the conditions of applicability of the BO scheme. In Sect. 6.1 we analyze the solution of the problem of atomic motion in the case of small oscillations near the equilibrium configuration (i.e. when every atom stays always near to its equilibrium position, and there is no atomic diffusion). In that case, writing down a second order expansion of the total potential felt by the ions (harmonic approximation), we show that it is possible to reduce the problem to that of a collection of independent harmonic oscillators. The general solution is then a superposition of 3N at normal modes of vibration, each of them having its own frequency and its own eigenvector, obtained by diagonalizing the dynamical matrix. The quantum description of this set of independent harmonic oscillators leads to the concept of phonons.
KeywordsIrreducible Representation Vibrational Spectrum Linear Chain Harmonic Approximation Vibrational Property
Unable to display preview. Download preview PDF. | <urn:uuid:4b14a933-7f3e-4eb8-b1ca-b169aaa7fbdd> | 2.84375 | 313 | Truncated | Science & Tech. | 28.237746 | 95,584,889 |
In an organic chemistry lab located in the Science II building on the campus of Binghamton University, Scott Handy is busy whipping up promising new substances modeled after natural compounds found in sea sponges and tobacco plants. Some of the synthetic compounds could help in the fight against cancer and AIDS. Others could provide a safer, more effective, and more affordable alternative to the traditional solvents organic chemists use to catalyze reactions and synthesize compounds, one molecule at a time.
A synthetic organic chemist and teacher, Handy clearly gets a charge out of creating and nurturing things, organic and otherwise. This is a fact underscored by his avocations, which include cooking, gardening and music. But when it comes to his research, even though synthesizing molecules can take years of dedication and no end of patience, experiencing the success of creation is only half the fun, he said.
"For some people, making a molecule is sufficient, and that certainly is enough of a challenge much of the time," he said. "But what I really like about synthesis is that if you can make a molecule, you can make a molecule that you can do something with. And thats what breathes life into things for me. It adds a whole other level of excitement and purpose to my research."
Susan E. Barker | EurekAlert!
O2 stable hydrogenases for applications
23.07.2018 | Max-Planck-Institut für Chemische Energiekonversion
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
23.07.2018 | Materials Sciences
23.07.2018 | Information Technology
23.07.2018 | Health and Medicine | <urn:uuid:23866c5d-d001-48f6-abe0-cb7433d0a213> | 2.8125 | 856 | Content Listing | Science & Tech. | 38.759942 | 95,584,906 |
Every Mac OS X system comes with all the essentials required for programming: free development tools, resources, and utilities. However, finding the place to begin may be challenging, especially if you have no prior development knowledge. This comprehensive guide offers you an ideal starting point to writing programs on Mac OS X, with coverage of the latest release - 1.4 "Tiger."
With its hands-on approach, the book examines a particular element and then presents step-by-step instructions that walk you through how to use that element when programming. You'll quickly learn how to efficiently start writing programs on Mac OS X using languages such as C, Objective-C(r), and AppleScript(r), technologies such as Carbon(r) and Cocoa(r), and other Unix tools. In addition, you'll discover techniques for incorporating the languages in order to create seamless applications. All the while, you can follow along on your own system so that you'll be prepared to apply your new Mac OS X skills to real-world projects.
What you will learn from this book
- The major role the new Xcode plays in streamlining Mac OS X development
- The process for designing a graphical user interface on Mac OS X that conforms to Apple's guidelines
- How to write programs in the C and Objective-C programming languages
- The various scripting languages available on the Mac OS X system and what tasks each one is best suited to perform
- How to write shell scripts that interact with pre-installed command-line tools
Who this book is for
This book is for novice programmers who want to get started writing programs that run on Mac OS X. Experienced programmers who are new to the Mac will also find this book to be a useful overview of the Mac development environment.
Wrox Beginning guides are crafted to make learning programming languages and technologies easier than you think, providing a structured, tutorial format that will guide you through all the techniques involved. | <urn:uuid:900f79c0-01ad-4def-810b-c04a206c4a0a> | 2.84375 | 397 | Product Page | Software Dev. | 42.475749 | 95,584,915 |
The La Niña weather pattern can cause droughts in the southern United States, including parts of eastern Texas. National Oceanic and Atmospheric Administration.
Two new NOAA-funded studies from scientists at The University of Texas at Austin have significantly improved scientists’ ability to predict the strength and duration of droughts caused by La Niña – a recurrent cooling pattern in the tropical Pacific Ocean. Their findings, which predict that the current La Niña is likely to stretch into a second year, could help scientists know years in advance how a particular La Niña event is expected to evolve.
“Some La Niña events last two years, and predicting them is extremely challenging,” said Pedro DiNezio, a research associate at the University of Texas Institute for Geophysics (UTIG).
The studies were funded by NOAA Research’s Modeling, Analysis, Predictions, and Projections Program (MAPP) in support of the National Integrated Drought Information System (NIDIS) development, and recently published in the journal Geophysical Research Letters.
The southern United States regularly experiences warm and dry winters, which are closely linked to La Niña. Because La Niña can make drought and other extreme events more likely to occur, better understanding and predictions of multi-year La Niña events could save the U.S. billions of dollars in damage costs each year.
The first study, led by Yuko Okumura, shows that La Niña’s impact on atmospheric circulation and southern U.S. drought becomes stronger in the second year of a two-year event. This is despite a weakening of La Niña’s cooling over the tropical Pacific relative to the first year.
"We expected a weaker impact in the second year, but it turned out to be the opposite,” said Okumura. “Despite being weaker in the second year, La Niña appears to have a greater impact.”
Computer models show predicted and observed rainfall anomalies around the globe during the second year of La Niña events, including a future prediction for 2018. Predicted values are on the left and observed on the right. The rainfall anomaly refers to the deviation in rainfall during a particular year compared to the expected rainfall for the region. Pedro DiNezio/University of Texas Institute for Geophysics/ Jackson School of Geosciences.
Okumura’s team found that this paradox is caused by subtle changes in the pattern of tropical Pacific cooling. During the second year, the cooling weakens in a narrow band along the equator, but becomes broader. The broader cooling appears more effective at influencing the atmosphere far away from the tropical Pacific, according to analysis of historical observations.
“Predicting if La Niña will last multiple years is therefore essential to knowing how long the drought will last,” Okumura said.
The second study, led by DiNezio, used a climate model developed at the National Center for Atmospheric Research (NCAR) to predict that an ongoing La Niña that started in 2016 will stretch into its second year this upcoming winter. The model puts the probability of such a two-year event occurring at 60 to 80 percent.
DiNezio and Okumura had previously found that a La Niña is more likely to last two years when it is preceded by a strong El Niño – its warm counterpart. Therefore, when a record-breaking El Niño event occurred just two years ago, they anticipated that it could lead to a two-year La Niña. DiNezio used the model developed at NCAR to test this idea.
To back their predictions, they tested whether the model could have predicted previous two-year La Niña events that occurred after strong El Niños. They were particularly confident in the model when they saw that it predicted the three-year La Niña following the 1997 El Niño, a record-breaking event at the time.
So far, it looks like the NCAR model’s prediction is on the money. The National Oceanic and Atmospheric Administration (NOAA) announced last week that ocean conditions in the tropical Pacific are starting to show signs that La Niña is on its way for a second year.
DiNezio and Okumura will be keeping a close eye on this year’s La Niña as they seek to better predict its impacts throughout the world.
Both papers are from a project supported by MAPP in partnership with the NIDIS program as part of the NOAA Drought Task Force and represent significant advances in our ability to understand and predict La Niña-driven droughts over the southern U.S.
To learn more, read the papers published in Geophysical Research Letters:
Yuko Okumura, a research associate at the University of Texas Institute for Geophysics. The University of Texas Institute for Geophysics/Jackson School of Geosciences.
Pedro DiNezio, a research associate at the University of Texas Institute for Geophysics. University of Texas Institute for Geophysics/Jackson School of Geosciences
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|Molar mass||100.9494 g/mol|
|Appearance||greenish yellow powder|
|Melting point||approx. 1500°C|
|Safety data sheet||External MSDS|
|R-phrases (outdated)||R36, R37, R38|
|S-phrases (outdated)||S26, S36|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
- By passing dry nitrogen over heated magnesium:
- or ammonia:
- Mg3N2(s) + 6 H2O(l) → 3 Mg(OH)2(aq) + 2 NH3(g)
In fact, when magnesium is burned in air, some magnesium nitride is formed in addition to the principal product, magnesium oxide.
Robert H. Wentorf, Jr. was trying to convert the hexagonal form of boron nitride into the cubic form by a combination of heat, pressure, and a catalyst. He had already tried all the logical catalysts (for instance, those that catalyze the synthesis of diamond), but with no success.
Out of desperation and curiosity (he called it the "make the maximum number of mistakes" approach), he added some magnesium wire to the hexagonal boron nitride and gave it the same pressure and heat treatment. When he examined the wire under a microscope, he found tiny dark lumps clinging to it. These lumps could scratch a polished block of boron carbide, something only diamond was known to do.
From the smell of ammonia, caused by the reaction of magnesium nitride with the moisture in the air, he deduced that the magnesium metal had reacted with the boron nitride to form magnesium nitride, which was the true catalyst.
- R. H. Wentorf, Jr. (March 1961). "Synthesis of the Cubic Form of Boron Nitride". Journal of Chemical Physics. 34 (3): 809–812. doi:10.1063/1.1731679.
- Robert H. Wentorf, Jr. (October 1993). "Discovering a Material That's Harder Than Diamond". R&D Innovator. Retrieved June 28, 2006.
Salts and covalent derivatives of the Nitride ion | <urn:uuid:41924a77-2632-4753-94ab-5058f0958908> | 2.953125 | 510 | Knowledge Article | Science & Tech. | 68.776645 | 95,584,934 |
Arrange 3 red, 3 blue and 3 yellow counters into a three-by-three square grid, so that there is only one of each colour in every row and every column
Jack has nine tiles. He put them together to make a square so that two tiles of the same colour were not beside each other. Can you find another way to do it?
These are the faces of Will, Lil, Bill, Phil and Jill. Use the clues to work out which name goes with each face.
These eleven shapes each stand for a different number. Can you use the multiplication sums to work out what they are?
Arrange 9 red cubes, 9 blue cubes and 9 yellow cubes into a large 3 by 3 cube. No row or column of cubes must contain two cubes of the same colour.
Penta people, the Pentominoes, always build their houses from five square rooms. I wonder how many different Penta homes you can create?
Use the clues to find out who's who in the family, to fill in the family tree and to find out which of the family members are mathematicians and which are not.
How could you put eight beanbags in the hoops so that there are four in the blue hoop, five in the red and six in the yellow? Can you find all the ways of doing this?
Place six toy ladybirds into the box so that there are two ladybirds in every column and every row.
Kate has eight multilink cubes. She has two red ones, two yellow, two green and two blue. She wants to fit them together to make a cube so that each colour shows on each face just once.
Here are four cubes joined together. How many other arrangements of four cubes can you find? Can you draw them on dotty paper?
Three dice are placed in a row. Find a way to turn each one so that the three numbers on top of the dice total the same as the three numbers on the front of the dice. Can you find all the ways to do. . . .
Cut four triangles from a square as shown in the picture. How many different shapes can you make by fitting the four triangles back together?
Place the 16 different combinations of cup/saucer in this 4 by 4 arrangement so that no row or column contains more than one cup or saucer of the same colour.
Is it possible to use all 28 dominoes arranging them in squares of four? What patterns can you see in the solution(s)?
This was a problem for our birthday website. Can you use four of these pieces to form a square? How about making a square with all five pieces?
There are nine teddies in Teddy Town - three red, three blue and three yellow. There are also nine houses, three of each colour. Can you put them on the map of Teddy Town according to the rules?
Can you make the birds from the egg tangram?
Roll two red dice and a green dice. Add the two numbers on the red dice and take away the number on the green. What are all the different possibilities that could come up?
Four friends must cross a bridge. How can they all cross it in just 17 minutes?
Can you arrange the numbers 1 to 17 in a row so that each adjacent pair adds up to a square number?
The idea of this game is to add or subtract the two numbers on the dice and cover the result on the grid, trying to get a line of three. Are there some numbers that are good to aim for?
A game for 2 people. Take turns placing a counter on the star. You win when you have completed a line of 3 in your colour.
Can you fit the tangram pieces into the outline of Little Ming?
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
A game for 2 players that can be played online. Players take it in turns to select a word from the 9 words given. The aim is to select all the occurrences of the same letter.
Using some or all of the operations of addition, subtraction, multiplication and division and using the digits 3, 3, 8 and 8 each once and only once make an expression equal to 24.
Can you mentally fit the 7 SOMA pieces together to make a cube? Can you do it in more than one way?
Can you arrange the digits 1, 1, 2, 2, 3 and 3 to make a Number Sandwich?
Use the 'double-3 down' dominoes to make a square so that each side has eight dots.
A game for 2 players. Set out 16 counters in rows of 1,3,5 and 7. Players take turns to remove any number of counters from a row. The player left with the last counter looses.
Factor track is not a race but a game of skill. The idea is to go round the track in as few moves as possible, keeping to the rules.
A game for 2 people using a pack of cards Turn over 2 cards and try to make an odd number or a multiple of 3.
Can you be the first to complete a row of three?
Everthing you have always wanted to do with dominoes! Some of these games are good for practising your mental calculation skills, and some are good for your reasoning skills.
The Tower of Hanoi is an ancient mathematical challenge. Working on the building blocks may help you to explain the patterns you notice.
A game for 1 or 2 people. Use the interactive version, or play with friends. Try to round up as many counters as possible.
A game for 2 players. Take turns to place a counter so that it occupies one of the lowest possible positions in the grid. The first player to complete a line of 4 wins.
An ordinary set of dominoes can be laid out as a 7 by 4 magic rectangle in which all the spots in all the columns add to 24, while those in the rows add to 42. Try it! Now try the magic square...
Can you work out how to win this game of Nim? Does it matter if you go first or second?
Can you put the 25 coloured tiles into the 5 x 5 square so that no column, no row and no diagonal line have tiles of the same colour in them?
Given the nets of 4 cubes with the faces coloured in 4 colours, build a tower so that on each vertical wall no colour is repeated, that is all 4 colours appear.
Place the numbers 1, 2, 3,..., 9 one on each square of a 3 by 3 grid so that all the rows and columns add up to a prime number. How many different solutions can you find?
Can you use small coloured cubes to make a 3 by 3 by 3 cube so that each face of the bigger cube contains one of each colour?
Andrew decorated 20 biscuits to take to a party. He lined them up and put icing on every second biscuit and different decorations on other biscuits. How many biscuits weren't decorated?
A game for 2 players with similaritlies to NIM. Place one counter on each spot on the games board. Players take it is turns to remove 1 or 2 adjacent counters. The winner picks up the last counter.
Take ten sticks in heaps any way you like. Make a new heap using one from each of the heaps. By repeating that process could the arrangement 7 - 1 - 1 - 1 ever turn up, except by starting with it?
Using the digits 1, 2, 3, 4, 5, 6, 7 and 8, mulitply a two two digit numbers are multiplied to give a four digit number, so that the expression is correct. How many different solutions can you find?
Imagine we have four bags containing a large number of 1s, 4s, 7s and 10s. What numbers can we make?
Can you spot the similarities between this game and other games you know? The aim is to choose 3 numbers that total 15. | <urn:uuid:2049b617-e26a-43c9-86ea-229baae8d8aa> | 3.65625 | 1,669 | Content Listing | Science & Tech. | 78.867206 | 95,584,936 |
The charge and the mass of an alpha particle are q_a = 3.20×10−19 C and m_a = 6.68×10−27 kg, respectively.
What is the final velocity of the alpha particle, v_af?
Recently Asked Questions
- Could you please explain step by step using what formulas to use and how to approach it
- Hatwick Technology is considering leasing a new equipment. The lease lasts for 5 years. The lease calls for 5 payments of $10,200 per year with the first
- How long would it take to double your money at a nominal rate of 7%, compounded annually? 5.33 years 7 years 10.25 years 12.50 years | <urn:uuid:596b90ec-bbf6-4286-a4c6-8d44079e6fa9> | 2.515625 | 146 | Q&A Forum | Science & Tech. | 89.535455 | 95,584,939 |
Scientists at the American Museum of Natural History and the University of Chicago have explained how a globe-encircling residue formed in the aftermath of the asteroid impact that triggered the extinction of the dinosaurs. The study, which will be published in the April issue of the journal Geology, draws the most detailed picture yet of the complicated chemistry of the fireball produced in the impact.
The residue consists of sand-sized droplets of hot liquid that condensed from the vapor cloud produced by an impacting asteroid 65 million years ago. Scientists have proposed three different origins for these droplets, which scientists call "spherules." Some researchers have theorized that atmospheric friction melted the droplets off the asteroid as it approached Earths surface. Still others suggested that the droplets splashed out of the Chicxulub impact crater off the coast of Mexicos Yucatan Peninsula following the asteroids collision with Earth.
But analyses conducted by Denton Ebel, Assistant Curator of Meteorites at the American Museum of Natural History, and Lawrence Grossman, Professor in Geophysical Sciences at the University of Chicago, provide new evidence for the third proposal. According to their research, the droplets must have condensed from the cooling vapor cloud that girdled the Earth following the impact. Ebel and Grossman base their conclusions on a study of spinel, a mineral rich in magnesium, iron and nickel contained within the droplets. "Their paper is an important advance in understanding how these impact spherules form," said Frank Kyte, adjunct associate professor of geochemistry at the University of California, Los Angeles. "It shows that the spinels can form within the impact plume, which some researchers argued was not possible."
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:8bae9bbc-aac2-4df5-99a5-3865c7312b5d> | 3.953125 | 991 | Content Listing | Science & Tech. | 34.820082 | 95,584,940 |
When primitive nerve cells begin forming an eye in the mouse embryo, they are programmed to build a retina. But the ability to see depends upon connecting the retina to the brain via the optic nerve. Unless these embryonic cells are given the right cue at the right time, they mistakenly form a huge eye that consists entirely of retina and lacks the optic nerve.
The discovery that the retina is the default setting for development in the embryonic eye comes from research by neurobiologist Greg Lemke and his colleagues at the Salk Institute for Biological Studies, published in the current issue of Genes & Development. The scientists carried out their work on the laboratory mouse as a model of human biology. "Our results suggest that the retina is effectively the default pathway for eye development in mammals," said Lemke. The Salk team showed that two chemical cues, or signalling proteins, must be present in the right place at the right time to shut down this default pathway and allow the optic nerve to develop.
The painstaking work of the Salk team has important consequences since controlling the fate of stem cells implanted into the brain is crucial if these cells are to be safely and effectively used in human therapy. "This study gives us a fascinating insight into how the parts of the brain are laid out because it is likely that the same model applies throughout the nervous system," said Lemke. "There are likely to be other brain areas whose development relies on blocking a tendency to turn into the same cell types as their neighbor."
Cathy Yarbrough | EurekAlert!
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
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Diamond dust in clouds of gas throughout the Milky Way? It may sound unlikely, but that is the conclusion of a team of scientists who used radio telescopes to explore a peculiar and elusive source of radio emission. And in doing so, they may have solved two different puzzles at once.
For many decades astronomers were confident that they had nailed down the main sources of radio emission from galaxies like the Milky Way. There was “thermal” radio emission that arises from diverse objects like the Moon and planets, warm interstellar dust and even the remnant of the Big Bang. The intensity of this emission depends on the temperature of an object, which is why it is called thermal. Then there is non-thermal emission that arises from the collision of high-energy charged particles, like cosmic rays, with a magnetic field. Non-thermal emission is observed from the magnetic fields of the Earth and Jupiter as they are hit by charged particles from the Sun, and also arises from supernova remnants and cosmic rays spiraling in the magnetic field of the Milky Way. The two types of radio emission change intensity differently with frequency, so if you can measure an object at several frequencies it’s easy to distinguish one from the other. There is also discrete, narrow-band emission from quantum states of atoms and molecules like the 21cm line of hydrogen. So far, so good.
But starting around twenty years ago astronomers began to turn up evidence for another kind of astronomical radio signal that got called “Anomalous Microwave Emission” or AME. This was broadband radio emission clearly not formed in a quantum state of an atom or molecule, yet it looked nothing like either thermal or non-thermal emission. There was a ready candidate for the source of this emission: interstellar dust grains. Very tiny bits of solid matter in interstellar space could be spun up by collisions with other particles. It was predicted that the spinning dust could produce radio waves, maybe the AME.
The story is actually quite a bit more complicated than this, for the simple models of spinning dust proved to be too simple, while for many years the observational evidence for AME was uncertain and sometimes contradictory. The anomalous emission is so weak, and so unpredictable about where it could be detected in the Milky Way, that many scientists dismissed the measurements as errors. But over the years data kept accumulating and the skeptics were mostly converted, though our understanding remained highly unsatisfactory. What exactly was making the AME, and why was it seen in some parts of the Milky Way (and other galaxies) and not elsewhere?
This is where the other part of the story comes in. It had been known for some time that certain disks of gas around recently-formed stars showed emission at Infrared wavelengths that was consistent with the presence of nano-diamonds: small crystalline chunks of carbon no bigger than a millionth of a millimeter. Similar sized nano-diamonds have been found in meteorites in our solar system, so nature must have no trouble making them. The new exciting news just announced this week is that a team of scientists using radio telescope in the US and Australia showed was that these dusty disks around new stars are sources of AME, but only if the disks also have the infrared signature of nano-diamonds.
The scientists used two radio telescopes: the Green Bank Telescope in West Virginia, and the Australia Telescope Compact Array, to search for AME from several dozen dusty disks around newly-formed stars. Although they detected the anomalous emission from only 3 disks, those were also the only disks in the sample that had infrared emission from nano-diamonds.
The implication is that anywhere AME is detected — and it is seen over large regions of the Milky Way — there must be nano-diamonds. The scientists believe that it takes particular conditions of temperature and density to make the little diamonds produce AME, which is why it is found only in specific locations, but they think that the diamonds are everywhere. There’s lots more work to do, but it’s possible that we may have finally cracked the case of the Anomalous Microwave Emission, and that the solution lies in vast clouds of tiny, tiny diamonds. | <urn:uuid:179592c6-1fc2-4ce9-812b-02bbc9620576> | 4.09375 | 863 | News Article | Science & Tech. | 35.782017 | 95,584,944 |
A View from Emerging Technology from the arXiv
Black Holes Can Form Rings, Helices, and Even Saturn Shapes
String theory implies that black holes can come in all kinds of forms and flavors, according to a cosmologist who has catalogued all known types.
String theory is physicists’ best guess at a unified theory of all interactions but it comes with some strange predictions. One of these is that spacetime consists of 10 dimensions rather than just the four we’re familiar with. And that raises some interesting questions.
One of them is what shape singularities can form in this higher dimensional space. In four dimensions, the only solution is spherical and that’s the type of black hole cosmologists have imagined all over the universe.
But in higher dimensions, there are all kinds of other solutions. We’ve looked at the possibility of black rings but today Maria Rodriguez at the Max Planck Institute for Gravitational Physics in Golm, Germany, compiles a catalogue of all know species of black hole.
It turns out there’s a whole menagerie of other black hole solutions. Here are just a few: the black saturn, the black helical ring, the di-ring, the black bowtie, and the bicycling black ring as well as the more general blackfolds.
While these solutions may exist mathematically, they may or may not exist in the real universe. In fact, Rodriguez is able to work out certain criteria that a solution must meet for it to have a hope of existing in the real world. For example, a black ring can only exist if there is enough centrifugal repulsion to prevent it from collapsing.
Rodriquez points out that the list is incomplete. “The catalog of different species (exact solutions) of black holes shows a very rich structure but seems far from being complete.”
That makes it an interesting topic for ambitious cosmologists. But be warned: there’s a good reason the list is incomplete. The solutions in this higher dimensional space are fiendishly difficult to find.
Nevertheless, it would be good to either rule out the possibility of their existence or work out if and how they can be distinguished observationally from common or garden spherical black holes.
Ref: arxiv.org/abs/1003.2411: On the Black Holes Species (By Means Of Natural Selection)
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A new study published in the scientific journal PLOS Pathogens points out that mice lacking a protein called Tmprss2 are no longer affected by certain flu viruses.
Influenza virus, magnified by electron microscopy. © HZI / Rohde
The discovery was made by researchers from the Helmholtz Centre for Infection Research (HZI) in Braunschweig in collaboration with colleagues from Göttingen and Seattle.
Whether it is H1N1, H5N1 or H7N9: The flu virus influenza A exists in many different types as its two coating proteins haemagglutinin (HA) and neuraminidase (NA) can be combined in various ways. Theoretically, more than 100 different pairings are possible. Additionally, the coating proteins themselves can undergo changes. This variability is one of the reasons why the flu vaccination has to be renewed every year.
The virus uses haemagglutinin as a key to enter the host cell which is then captured to build new virus particles. To reach its final shape, the coating protein has to be cleaved by a molecular scissor. This is done by an enzyme of the infected host. Otherwise, the protein is not functional and the virus particles are not infectious. A variety of host enzymes, so-called proteases, that process the haemagglutinin have been identified using cell cultures.
Scientists from the HZI have now been able to show how important those enzymes are for the progression of the infection. Mice with a mutation in the gene for the protease Tmprss2 do not become infected by flu viruses containing haemagglutinin type H1. They are resistant against H1N1, the pathogen responsible for seasonal influenza epidemics, the “swine flu” and the “Spanish flu”, which caused an epidemic in 1918. “These mice do not lose weight and their lungs are almost not impacted,” says Professor Klaus Schughart, head of the Department “Infection Genetics” at the HZI. “Even though the virus still multiplies no active viral particles are formed which would infect the neighbouring cells.” The infection is quickly terminated.
As the protease Tmprss2 is a host factor it is an ideal intervention point for new drugs. So far, treatments, such as the well-known Tamiflu, attack parts of the virus. They have decisive disadvantages: The virus can become resistant and the therapy no longer takes effect. This problem does not occur when the medication intervenes with the metabolism of the patient. Furthermore, the mice Schughart and his team examined did not show any abnormalities. “We did not observe an obvious varied phenotype in these mice. They were neither impaired in their behaviour nor in their life expectancy. Presumably because other proteins are compensating for the lack of Tmprss2,” says Dr Bastian Hatesuer, one of the scientists involved in the project. Blocking TMPRSS2 for a short period could be a new therapeutic option as no strong side effects are expected.
Even though a drug like this is still a long way off, the observation is important for another reason: “Until now the dependence of virus production on proteases had only be demonstrated in cell cultures,” says Schughart. “We are the first to show this in a living organism.”
It is likely that there are humans having the same defect as the mice and who therefore may be resistant against specific flu viruses. This, however, remains unnoticed. “Because they don’t get sick, they don’t go to see a doctor,” says Hatesuer. “Thus, they don’t know that they are resistant.”Original publication:
- This release on helmholtz-hzi.dehttp://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1003774
Dr. Jan Grabowski | Helmholtz-Zentrum
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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Eucheira socialis, commonly known as the Madrone butterfly is a lepidopteran that belongs to the family Pieridae. It was first described by Westwood in 1834. Locally known as Mariposa del madroño or tzauhquiocuilin, it is endemic to the highlands of Mexico, and exclusively relies on the Madrone (Arbutus spp.) as a host-plant. The species is of considerable interest to lepidopterists due to gregarious nest-building in the larval stages, and heavily male biased sex-ratios. It takes an entire year for this adult butterfly to develop from an egg. The eggs are laid in the month of June and the adults emerge the following May–June. The adults have a black and white pattern on their wings, and the males are generally much smaller and paler than the females. The larvae do not undergo diapause and continue to feed and grow communally in the coldest months of the year. There are two sub-species of E. socialis, named E. socialis socialis and E. socialis westwoodi.
|Female Eucheira socialis|
The distribution of E. socialis is restricted to the highlands of Mexico at elevations of 1800 meters in madrone habitats. They are generally found in pine-oak and arid tropical scrub ecosystems. They are distributed from northern Sonora to Jalisco. E. socialis socialis are found in central Mexico, while E. socialis westwoodi is found in Sierra Madre Occidental in the north. The population distribution is patchy due to the poor dispersal ability of the adults, and the patchy distribution of the host-plant, madrone.
The range of E. socialis is dependent on the availability of their preferred host plant, the madrone. In recent times, the madrone trees have been cut and used as firewood and for making furniture and other crafts. The destruction of the madrone habitat threatens the relationship between the plant and the butterfly. However, the inaccessibility of these habitats due to their confinement in high elevations possibly decreases the risk.
Characteristic of all lepidopterans, E. socialis are holometabolous and go through four distinct developmental stages namely egg, larva, pupa and adult. There are six larval instars and all instars are known to be gregarious. It takes nearly an entire year for the adult to emerge from an egg. The eggs are laid in July, and the adults eventually eclose in May–June. Consequently, there is only one generation of eggs laid each year.
The eggs are bluish-white and are laid in clumps on the underside of the host plant Madrone in the month of June–July. The larvae hatch out of the eggs after approximately 3–4 weeks, sometimes after up to 60 days, in August. Upon hatching, they communally feed on the leaves and terminal branches of the plant. They consume the epidermis and mesophyll and leave the venous skeleton of the leaf intact. The larvae then build their first communal nest by folding these consumed leaves and securing them with silken strands. The larvae are a bright green and mildly fuzzy when they hatch, but turn brown and less pubescent as they grow. There are in total six larval instars. Larval mortality is disproportionately high in males than in females. Despite extremely low temperatures in the winter, the larvae do not undergo diapause, and continue to feed and grow throughout the year. A fully-grown larva is generally between 25-30 millimeters long, and pupates by April.
The pupae are initially light-green on pupation and later turn yellow. They pupate head down in the silk nests, and lack silken girdle unlike other Pieridae. The black and white adult wing markings are visible through the pupal case. There exists sexual dimorphism in the size of pupa. The male pupae are generally much smaller (18–20 mm) than female pupae (21–23 mm). Pupal mortality is much higher in females than in males. The pupal stage lasts for about a month and the adults finally emerge in May–June.
Adult butterflies emerge from their nests through the small exits while they are still teneral. Their escape is facilitated by soft, pliable wings. The wings also have an atypical shape and venation patterns adapted to escape the nest. The adults have black and white coloration on the wings, and the pattern is more prominent on the males. The males also are usually much paler and smaller than the females. The males have larger eyes and higher wing venation as compared to the females. The proboscis does not anneal properly post-eclosion and is non-functional.
The adults are weak fliers, and display simple sexual behavior. Mating takes place near the communal nests right after the adults emerge from the nests. The females mate only once in their lifetime, and most males fail to find mates.
The females oviposit within 3 hours post-eclosion. They lay their eggs exclusively on the host plant madrone (Arbutus spp.). Though there is much variation in the tree quality of the madrone, the females do not show any preferential oviposition with regard to host plant quality. The eggs are laid in a clump on the undersurface of a single leaf of the madrone. The females mate only once, and consequently, all the eggs in a clump are full siblings. The number of eggs in a clump can vary from very few to as much as 350-400 eggs. The females also tend to lay these egg clumps near other conspecific eggs. It has been observed that isolated clutches tend to suffer from higher mortality than grouped clutches. It is speculated that the ovipositional behavior of the females has been under strong selection in the past to maximize social interaction among larvae.
E. socialis caterpillars are social, and they construct communal nests. The freshly hatched larvae forage and rest together, and aggregate in a loosely woven tent-like silk structure over the surface of the leaf. This is called as the primary bolsa. Encompassing this structure, the larvae build a secondary bolsa. This secondary nest is very tough and made of multiple layers of interlaced double-stranded silk. By the end of the growing season the nest walls can be thick enough to resist tear and hold water. The larvae maintain the nests constantly, and mend any wear and tear. The entrance and exit to the bolsa is at the bottom of the nest. This protects the shelter from rain and predation and facilitates the removal of excreta and dead larvae. The nests are not reused by later generations.
The nests are roughly pyramidal, but can show great variation in size. The size of the nest correlates with the size of the population. The number of individuals in a nest can vary from as low as 3 individuals to 528 individuals, with an average of about 112 individuals. The survivorship of the larvae is directly proportional to size of the group. Larger groups of larvae tend to forage for longer periods, and gain more weight than larvae from smaller groups.
The construction and maintenance of this nest is essential for survival of the larval species into adulthood. The nest plays an important role in thermoregulation by providing a cool shelter for the larvae on sun-intensive days. The quality of the nest i.e., the thickness of the nest wall correlates with survivorship of the larvae.
Although all the eggs in a clutch are full-siblings, the relatedness among nest-mates is 0.285, which is much lower than 0.5 that is expected amongst full-siblings. This implies that nest-mates are both kin and non-kin, which can be explained by the proximity of clutches in general. Therefore, it is proposed that communal nesting behavior evolved initially due to kin-selection, facilitated by a single oviposition event leading to an egg mass with high-relatedness. But the maintenance of this behavior among non-kin could be due to high benefits of communal nesting such as predator avoidance and thermodynamic efficiency.
The later instars are nocturnal and leave their nest for foraging to remote sites an hour or two after sunset. They feed gregariously on the leaves of the host plant until the early hours of morning, and return to the nest before sunrise. The caterpillars in general spin silk whenever they walk, thus the trails that are commonly used are much thicker and stronger than trails that are less-frequented. When presented with alternate trail pathways, there is a strong preference to select for newer and stronger trails. The nocturnal foraging is thought to be an evolutionary response to avoid day-active parasitoids, and predators such as birds and social wasps.
It has been observed that male E. socialis larvae spend more time spinning silk and lesser amount of time foraging as compared to female larvae. Males were also observed to be more active and the first ones to lead a foraging foray. Thus, the males disproportionately bore more of the cost of silk production and exploration for new trails. It has also been observed that nests with male-biased ratios produced heavier male and female pupae than female-biased nests. There seems to be a sexual division of labor, which explains the observation of highly male-biased nests.
There is limited polymorphism in the genetic architecture of E. socialis, but sub-populations are highly differentiated. There is an excess of heterozygotes, and moderate levels of relatedness amongst nest-mates within the sub-populations. The high differentiation among sub-populations is thought to have been caused by weak adult dispersal, and patchiness of madrone habitats due to their restriction to higher elevations. The northern and southern populations of E. socialis show strong karyotypic differentiation.
The determination of sex in E. socialis is chromosomal with heterogametic females. But, the primary sex-ratio i.e., the sex-ratio at conception is extremely male-biased with an average of about 70% males. This bias has been observed in both the eastern and western sub-populations, and is thought to be caused by meiotic instability. Furthermore, the operational sex-ratio is also male-biased. Such a ratio is thought to be evolutionarily maintained because of the selective advantage of male-biased groups in the communal nests.
Although mating, flight, and oviposition occurs in the warmest and wettest months of the year, much of the growth of the caterpillar occurs in the coldest months of the year. Even though the days are much warmer than the nights in the winter, the caterpillars remain aggregated in their nests and venture out to forage strictly after sunset. Even within the nests, the caterpillars choose to cluster in the coolest regions of the nest. This type of voluntary hypothermia is expected to be an adaptation to foraging in the night.
The species show a general behavioral mechanism to minimize predation and parasitism. The oviposition of the eggs on the underside of the leaves, and nocturnal foraging of larvae decrease exposure to predators and other parasitoids. The final instars of the larvae also exhibit chemical defenses. When threatened, they regurgitate a droplet of brownish-green fluid. This fluid is assumed to be distasteful to predators, and has been described as having a ‘bitter’ and ‘nutty’ flavor. The fluid also contains alkaloids, such as arbutin.
The silk nests built by the larvae are believed to have been used in the past for making paper and small boxes. They also served as a base for paintings, and for bandaging wounds. The entire nests have also been recorded to be used as purses and as a container for liquid.
The larvae of E. socialis is among one of the many lepidopterans consumed in Mexico. In some part of Huasteca, the silk nests are maintained on the edge of roof tops of houses. Like other Lepidopteran larvae, they are used in a variety of dishes such as tortilla, omelets, rice, pies and rice. They are perceived as ‘good’ and ‘nutritious’ food due to their high protein content. In the Mixteca region of Oaxaca, excessive consumption of the larvae led to the disappearance of the species from this region. However, it has been reintroduced into this region from the state of Mexico and Durango. | <urn:uuid:e7f35b27-ea2d-47c6-832b-f36f11b72769> | 3.5625 | 2,643 | Knowledge Article | Science & Tech. | 46.44044 | 95,584,988 |
String theory, also called superstring theory, is, generally speaking, any physico-mathematical framework that describes fundamental physical reality in terms of superstrings Strings in this context should not be confused with cosmic strings, which are one-dimensional (string-like) regions of cosmic extent containing vacuum energy different from that of the true vacuum. The superstrings of string theory, in contrast, are extremely tiny loops, or possibly segments, that have been suggested as the most fundamental of all physical entities, and as the source of all other fields and particles.
Before the 1980s, the most fundamental entities were most often considered to be particles, which are zero-dimensional objects, but it has become clear that particle models do not provide a rich and flexible enough basis for fundamental quantum field theories; strings are much more suitable. More specifically, string theory provides promising candidates for an adequate quantum theory of gravity and, at the same time, for theories of the total unification of all four fundamental physical interactions (gravity, electromagnetism, and the strong and weak nuclear forces. Grand Unified Theory (GUT) will provide unification of the three nongravitational interactions.
Quantum mechanics (along with its extension to quantum field theory) and Albert Einstein's (1879–1955) theory of gravitation are two important pillars of contemporary physics. And yet, as they are presently formulated, they are deeply incompatible with one another. As of 2002, constructing a complete and adequate quantum theory of gravity has evaded the best efforts of theoreticians. Exciting and surprising work on superstrings since about 1984, however, has moved science much closer to achieving quantization of the gravitational field, thus resolving and healing this incompatibility. It is already clear that the leading string theory candidates yield general relativity as their low-energy limit. Essentially, this means that string theory, if successful, will become not only the quantum theory of gravity, but also the quantum theory of space and time, with crucial applications to early-universe cosmology.
It also appears likely that some version of string theory will at the same time unify all four fundamental physical interactions, including gravity, thus bringing to successful completion the much heralded quest for unification that motivated the physicist James Clark Maxwell (1831–1879), Einstein, and so many others. In order to accomplish this unification, the strings must manifest supersymmetry —they must be superstrings. Consider that all fundamental particles have either half-integral spin (1/2, 3/2, . . . ) or integral spin (0, 1, 2, . . . ). The half-integral spin particles are called fermions, and constitute the building blocks of matter; protons, neutrons, electrons, and quarks are all fermions. The integral spin particles are called bosons, and are the force-carriers between the fermions, mediating the electromagnetic, gravitational, and strong and weak interactions. Photons, W massive bosons, Z massive bosons, gluons, and gravitons are the bosons that mediate the electromagnetic, weak, strong, and gravitational interactions, respectively.
Fermions and bosons satisfy different statistics and symmetries, and have to be treated differently in standard quantum field theory. The first seriously considered string theories—studied for purposes other than those for which newer superstring theories are studied—were bosonic strings, which only incorporated the symmetries and statistics of bosons. Obviously, if a theory is going to unify all particles and fields, it will have to incorporate the symmetries of both fermions and bosons within the same framework; it will have be supersymmetric, and the strings will therefore have be superstrings.
Where would the superstring description of reality be needed? Certainly, it would provide a detailed and physically complete explanation of all the characteristics and parameters of material reality, including their deep interconnections and their origins in the vibrations and interactions of the fundamental superstrings. It would, at the same time, provide an adequate description of material reality at temperatures higher than $1032 K, where the general relativistic description of space, time, and mass-energy breaks down. There was a time in the very early universe, immediately after the Big Bang, when those temperatures obtained and during which the physics of the universe was that of a single unified fully quantitized superforce. This era is referred to as the Planck era, after the German theoretical physicist Max Planck (1858–1947). In fact, it is only in such terms that the Big Bang itself, as well as the emergence or origin of space, time, and matter, can really be characterized.
Superstring theories resolve a number of difficult anomalies and divergences in quantum theory. But they also lead to some features that are, at first sight, puzzling. One of these is that they almost always require higher dimensions—for example ten or twenty-six—rather than the three spatial dimensions and one time dimension that characterize the low-energy world. How then can these superstring theories be reconciled with reality as we know it? The answer is straightforward but surprising. At very high energies or temperatures, such as immediately after the Big Bang, reality will be ten dimensional or twenty-six dimensional, as described by superstring theory. But, as the universe exits the Planck era, and enters the classical domain where gravity is adequately described by Einstein's general relativity and is no longer unified with the other interactions, the extra dimensions compactify (curl up into infinitesimal knots) leaving only the four-dimensional spacetime with which we are familiar. Of course, if this is true, scientists should find some evidence of these extra curled-up dimensions. Such relics of the supersymmetric past would constitute powerful confirmation of superstring theories. This is an active area of research.
Relevance to theology
The relevance of string theory for the relationship between science and theology is clear, particularly in light of its applications to very early universe cosmology. First, a fully adequate string theory would give a complete unification and explanation of the laws of nature at the level of physics. In so doing, it would fill out the description of one of the most fundamental and pervasive sets of relationships through which God creatively acts in the universe. Secondly, it would give a much better description of the physics of the earliest phase of the universe's evolution, doing away with the initial singularity and helping scientists to speak more precisely about the origin of space and time, of all the laws of physics, and possibly of mass-energy. This would certainly help to delineate the limits of scientific explanation more compellingly. It is extremely unlikely, for instance, that the ultimately successful string theory will entail the existence of a unique universe or that it will explain why there is something rather than absolutely nothing, or that it will account for why there is this type of order, as specified by the string theory, rather than some other order. A clear appreciation of such limitations would enhance the understanding of the interactions, possible and desirable, between religion and science.
See also Cosmology; Grand Unified Theory; Gravitation; Physics, Quantum; Superstrings
davies, paul. "the new physics: a synthesis." in the new physics, ed. paul davies. cambridge, uk: cambridge university press, 1989.
green, michael b; schwarz, john h.; and witten, edward. superstring theory, vol. 1. cambridge, uk, and new york: cambridge university press, 1987.
greene, brian. the elegant universe: superstrings, hidden dimensions, and the quest for the ultimate theory. new york and london: norton, 1999.
kaku, michio. introduction to superstrings and m-theory, 2nd edition. new york, berlin, and heidelberg, germany: springer-verlag, 1998.
polchinski, joseph. string theory, volume 1. cambridge, uk: cambridge university press, 1998.
salam, abdus. "overview of particle physics." in the new physics, ed. paul davies. cambridge, uk: cambridge university press, 1989.
william r. stoeger
"String Theory." Encyclopedia of Science and Religion. . Encyclopedia.com. (July 19, 2018). http://www.encyclopedia.com/education/encyclopedias-almanacs-transcripts-and-maps/string-theory
"String Theory." Encyclopedia of Science and Religion. . Retrieved July 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/education/encyclopedias-almanacs-transcripts-and-maps/string-theory
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string theory, description of elementary particles based on one-dimensional curves, or
instead of point particles. Superstring theory, which is string theory that contains a kind of symmetry known as supersymmetry, shows promise as a way of unifying the four known fundamental forces of nature. The strings are embedded in a space-time having as many as 10 dimensions—the three ordinary dimensions plus time and seven compactified dimensions. The energy-scale at which the stringlike properties would become evident is so high that it is currently unclear how any of the forms of the theory could be tested.
See P. C. W. Davies and J. Brown, ed., Superstrings (1988); L. Smolin, The Trouble with Physics (2006).
"string theory." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (July 19, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/string-theory
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In this article we will explains you the Advantages and Disadvantages of Java Spring Framework. Spring framework was developed by Rod Johnson in 2002 based upon his book Expert One-on-One J2EE Design and Development. Since then it is one of the most used framework and now a days it come with many modules to further simplify application development.
Spring Framework is open source framework in Java for enterprise application development. It works with all the existing framework of Java and do not replace any but work as glue for all other libraries of Java.
Spring framework is modular framework with many modules for various jobs and spring core is the main module on to which other modules in the system works. Modularity is one of the important features of Spring framework which makes it easy to use in application development. You can use one or more frameworks on the top of Spring core.
Spring framework is feature rich framework and it comes with following features:
Spring is modular lightweight framework which allows you to selectively use any of its module on the top of Spring Core.
2. Inversion Of Control (IOC)
This is another top feature of Spring framework where application dependencies are satisfied by the framework itself. Framework creates the object in runtime and satisfies application dependencies.
3. Aspect Oriented Programming (AOP)
Aspect Oriented Programming (AOP) is very popular in programming world and in Spring it is well implemented. Developer can use Aspect Oriented Programming (AOP feature of Spring to develop application in which business logic is separated from system services.
Spring provides their own container for managing the bean lifecycle.
5. MVC Framework
Spring MVC Framework is used for developing MVC based web applications.
6. Transaction Management
Spring framework provides generic Transaction Management layer which can be used with or without J2EE(JEE) environment.
7. JDBC Exception Handling
Spring provides their own abstraction of JDBC exception which further simplify the exception handling in program.
Here are advantages of Spring Framework:
1. Solving difficulties of Enterprise application development
Spring is solving the difficulties of development of complex applications, it provides Spring Core, Spring IoC and Spring AOP for integrating various components of business applications.
2. Support Enterprise application development through POJOs
Spring supports development of Enterprise application development using the POJO classes which removes the need of importing heavy Enterprise container during development. This makes application testing much easier.
3. Easy integration other frameworks
Spring designed to be used with all other frameworks of Java, you can use ORM, Struts, Hibernate and other frameworks of Java together. Spring framework do not impose any restriction on the frameworks to be used together.
4. Application Testing
Spring Container can be used to develop and run test cases outside enterprise container which makes testing much easier.
Spring framework is modular framework and it comes with many modules such as Spring MVC, Spring ORM, Spring JDBC, Spring Transactions etc. which can used as per application requirement in modular fashion.
6. Spring Transaction Management
Spring Transaction Management interface is very flexible it can configured to use local transactions in small application which can be scaled to JTA for global transactions.
Here are tutorials to learn Spring framework: | <urn:uuid:23fcfc4c-7b46-4dd2-abd8-3dc38a635ce0> | 2.734375 | 663 | Product Page | Software Dev. | 33.145739 | 95,585,024 |
Super-computer modelling of Earth's crust and upper-mantle suggests that ancient geologic events may have left deep 'scars' that can come to life to play a role in earthquakes, mountain formation, and other ongoing processes on our planet.
This changes the widespread view that only interactions at the boundaries between continent-sized tectonic plates could be responsible for such events.
A proposed perennial plate tectonic map. Present-day plate boundaries (white lines), with hidden ancient plate boundaries that may reactivate to control plate tectonics (yellow lines). Regions where mantle lithosphere heterogeneities have been located are given by yellow crosses.
Credit: Russell Pysklywec, Philip Heron, Randell Stephenson
A team of researchers from the University of Toronto and the University of Aberdeen have created models indicating that former plate boundaries may stay hidden deep beneath the Earth's surface. These multi-million-year-old structures, situated at sites away from existing plate boundaries, may trigger changes in the structure and properties at the surface in the interior regions of continents.
"This is a potentially major revision to the fundamental idea of plate tectonics," says lead author Philip Heron, a postdoctoral fellow in Russell Pysklywec's research group in U of T's Department of Earth Sciences. Their paper, "Lasting mantle scars lead to perennial plate tectonics," appears in the June 10, 2016 edition of Nature Communications.
Heron and Pysklywec, together with University of Aberdeen geologist Randell Stephenson have even proposed a 'perennial plate tectonic map' of the Earth to help illustrate how ancient processes may have present-day implications.
"It's based on the familiar global tectonic map that is taught starting in elementary school," says Pysklywec, who is also chair of U of T's Department of Earth Sciences. "What our models redefine and show on the map are dormant, hidden, ancient plate boundaries that could also be enduring or "perennial" sites of past and active plate tectonic activity."
To demonstrate the dominating effects that anomalies below the Earth's crust can have on shallow geological features, the researchers used U of T's SciNet - home to Canada's most powerful computer and one of the most powerful in the world- to make numerical models of the crust and upper-mantle into which they could introduce these scar-like anomalies.
The team essentially created an evolving "virtual Earth" to explore how such geodynamic models develop under different conditions.
"For these sorts of simulations, you need to go to a pretty high-resolution to understand what's going on beneath the surface," says Heron. "We modeled 1,500 kilometres across and 600 kilometres deep, but some parts of these structures could be just two or three kilometres wide. It is important to accurately resolve the smaller-scale stresses and strains."
Using these models, the team found that different parts of the mantle below the Earth's crust may control the folding, breaking, or flowing of the Earth's crust within plates - in the form of mountain-building and seismic activity - when under compression.
In this way, the mantle structures dominate over shallower structures in the crust that had previously been seen as the main cause of such deformation within plates.
"The mantle is like the thermal engine of the planet and the crust is an eggshell above," says Pysklywec. "We're looking at the enigmatic and largely unexplored realm in the Earth where these two regions meet."
"Most of the really big plate tectonic activity happens on the plate boundaries, like when India rammed into Asia to create the Himalayas or how the Atlantic opened to split North America from Europe," says Heron. "But there are lots of things we couldn't explain, like seismic activity and mountain-building away from plate boundaries in continent interiors."
The research team believes their simulations show that these mantle anomalies are generated through ancient plate tectonic processes, such as the closing of ancient oceans, and can remain hidden at sites away from normal plate boundaries until reactivation generates tectonic folding, breaking, or flowing in plate interiors.
"Future exploration of what lies in the mantle beneath the crust may lead to further such discoveries on how our planet works, generating a greater understanding of how the past may affect our geologic future," says Heron.
The research carries on the legacy of J. Tuzo Wilson, also a U of T scientist, and a legendary figure in geosciences who pioneered the idea of plate tectonics in the 1960's.
"Plate tectonics is really the cornerstone of all geoscience," says Pysklywec. "Ultimately, this information could even lead to ways to help better predict how and when earthquakes happen. It's a key building block."
Department of Earth Sciences
University of Toronto
Department of Earth Sciences
University of Toronto
1- 416-537-2683 (M)
Communications, Faculty of Arts & Science
University of Toronto
Sean Bettam | EurekAlert!
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Richard Compton and his team at Oxford University, UK, have developed a sensitive technique to measure the levels of capsaicinoids, the substances that make chillies hot, in samples of chilli sauce. They report their findings in the Royal Society of Chemistry journal The Analyst.
The current industry procedure is to use a panel of taste-testers, and is highly subjective. Compton’s new method unambiguously determines the precise amount of capsaicinoids, and is not only quicker and cheaper than taste-testers but more reliable for purposes of food standards; tests could be rapidly carried out on the production line.
They tested a range of chilli sauces, from the mild “Tabasco Green Pepper” sauce to “Mad Dog’s Revenge”, which sports an extensive health warning and liability disclaimer.
The well-established Scoville method – currently the industry standard – involves diluting a sample until five trained taste testers cannot detect any heat from the chilli. The number of dilutions is called the Scoville rating; the relatively mild Jalapeño ranges from around 2500-8000, whereas the hottest chilli in the world, the “Naga Jolokia”, has a rating of 1000000.
High performance liquid chromatography (HPLC) can also be used, but this requires bulky, expensive equipment and detailed analysis of the capsaicinoids.
In Compton’s method, the capsaicinoids are adsorbed onto multi-walled carbon nanotube (MWCNT) electrodes. The team measures the current change as the capsaicinoids are oxidised by an electrochemical reaction, and this reading can be translated into Scoville units.
The technique is called adsorptive stripping voltammetry (ASV), and is a relatively simple electrochemical method. Compton says, “ASV is a fantastic detection technique for capsaicinoids because it’s so simple - it integrates over all of the heat creating constituents because all of the capsaicinoids have essentially the same electrochemical response.”
Compton has applied for a patent on the technology, and Oxford University’s technology transfer subsidiary ISIS Innovation is actively seeking backers to commercialise the technique.
Jon Edwards | alfa
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
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Pollen taxi for bacteria
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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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Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).
The information on this site is interesting and easy to understand, with helpful visual aids and explanations at every step of the way.
Nuclear Physics is the study of the properties and behaviour of nuclei and particles, ranging from tiny quarks to giant explosions deep in space.
Nuclear physics is important in a vast variety of situations, from understanding how the Sun provides the energy for life on this planet, to nuclear power plants and radiation therapy.
Far from being data, these dates are actually interpretations of the data.
As discussed before, the assumptions influence the interpretation of the data. | <urn:uuid:0daac3dd-59db-4db3-b0a1-33dd320a262d> | 3.25 | 186 | Knowledge Article | Science & Tech. | 41.853212 | 95,585,078 |
In short, the team identified a new solution to an astrophysical phenomenon through a series of laser experiments.
A photograph of the instrument setup for an astrophysics experiment at the SLAC's Linac Coherent Light Source (LCLS), a powerful X-ray laser. The experiment was conducted in the Soft X-ray hutch using this electron beam ion trap, or EBIT, built at the Max Planck Institute in Heidelberg, Germany. Photo by Jose R. Crespo Lopez-Urrutia, Max Planck Institute for Nuclear Physics
In the new research, appearing in the Dec. 13 edition of the journal Nature, scientists looked at highly charged iron using the Linac Coherent Light Source (LCLS) free-electron laser. Highly charged iron produces some of the brightest X-ray emission lines from hot astrophysical objects, including galaxy clusters, stellar cornea and the emission of the sun.
The experiment helped scientists understand why observations from orbiting X-ray telescopes do not match theoretical predictions, and paves the way for future X-ray astrophysics research using free-electron lasers such as LCLS. LCLS allows scientists to use an X-ray laser to measure atomic processes in extreme plasmas in a fully controlled way for the first time.
The highly charged iron spectrum doesn't fit into even the best astrophysical models. The intensity of the strongest iron line is generally weaker than predicted. Hence, an ongoing controversy has emerged whether this discrepancy is caused by incomplete modeling of the plasma environment or by shortcomings in the treatment of the underlying atomic physics.
"Our measurements suggest that the poor agreement is rooted in the quality of the underlying atomic wave functions rather than in insufficient modeling of collision processes," said Peter Beiersdorfer, a physicist at Lawrence Livermore and one of the initiators of the project.
Greg Brown, a team member from Livermore, said: "Measurements conducted at the LCLS will be important for interpreting X-ray emissions from a plethora of sources, including black holes, binary stars, stellar coronae and supernova remnants, to name a few."
Many astrophysical objects emit X-rays, produced by highly charged particles in superhot gases or other extreme environments. To model and analyze the intense forces and conditions that cause those emissions, scientists use a combination of computer simulations and observations from space telescopes, such as NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton. But direct measurements of those conditions are hard to come by.
In the LCLS experiments, the focus was on plus-16 iron ions, a supercharged form of iron. The iron ions were created and captured using a device known as an electron beam ion trap, or EBIT. Once captured, their properties were probed and measured using the high-precision, ultra brilliant LCLS X-ray laser.
Some collaborators in the experiments have already begun working on new calculations to improve the atomic-scale astrophysical models, while others analyze data from followup experiments conducted at LCLS in April. If they succeed, LCLS may see an increase in experiments related to astrophysics.
"Almost everything we know in astrophysics comes from spectroscopy," said team member Maurice Leutenegger, of NASA's Goddard Space Flight Center, who participated in the study. Spectroscopy is used to measure and study X-rays and other energy signatures, and the LCLS results are valuable in a "wide variety of astrophysical contexts," he said.
The EBIT instrument used in the experiments was developed at the Max Planck Institute for Nuclear Physics and will be available to the entire community of scientists doing research at the LCLS. Livermore has been a pioneer in EBITs. Various EBIT devices have been operational at LLNL for more than 25 years. This was the first time that an EBIT was coupled to an X-ray laser, opening up an entirely new venue for astrophysics research, according to Beiersdorfer.
Researchers from SLAC National Accelerator Laboratory; the Max Planck Institute for Nuclear Physics in Heidelberg, Germany; NASA Goddard Space Flight Center; the Center for Free-Electron Laser Science; GSI Helmholtz Center for Heavy Ion Research; and Giessen, Bochum, Erlangen-Nuremberg and Heidelberg universities in Germany; Kavli Institute for Particle Astrophysics and Cosmology at SLAC; and TRIUMF in Canada also collaborated in the LCLS experiments.
Founded in 1952, Lawrence Livermore National Laboratory provides solutions to our nation's most important national security challenges through innovative science, engineering and technology. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.
Anne Stark | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
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18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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20.07.2018 | Power and Electrical Engineering
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General Basis for Computations and Theoretical Models
This chapter describes theoretical concepts and tools used to calculate the electronic structure of materials. We first present ab initio methods which are able to describe the systems in their ground state, in particular those based on the density functional theory. Introducing the concept of quasi-particles, we show that excitations in the systems can be accurately described as excitations of single particles provided that electron—electron interactions are renormalized by the coupling to long-range electronic oscillations, i.e. to plasmons. We then review the main semi-empirical methods used to study the electronic structure of nanostructures.
KeywordsLocal Density Approximation General Basis Schrodinger Equation Slater Determinant Hartree Equation
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For some reason, Farmer John's cows always seem to be running laser light shows.
For their latest show, the cows have procured a large powerful laser -- so large, in fact, that they cannot seem to move it easily from the location where it was delivered. They would like to somehow send the light from the laser to the barn on the other side of FJ's property. Both the laser and the barn can be considered to be located at points in the 2D plane on a map of FJ's farm. The cows plan to point the laser so that it sends a beam of light out either horizontally or vertically (i.e., aligned with the x or y axes). They will then bounce this beam off a number of mirrors to direct it to the barn.
On the farm there are N fence posts (1≤N≤100,000) located at distinct 2D points (also distinct from the laser and the barn) at which the cows can mount mirrors. The cows can choose not to mount a mirror on a fence post, in which case the laser would simply pass straight over the top of the post without changing direction. If the cows do mount a mirror on a fence post, they align it diagonally like / or \ so that it will re-direct a horizontal beam of light in a vertical direction or vice versa.
Please compute the minimum possible number of mirrors the cows need to use in order to re-direct the laser to the barn.
The first line of input contains 5 space-separated integers: N,xL,yL,xB,yB, where (xL,yL) is the location of the laser and (xB,yB) is the location of the barn. All coordinates are between 0 and 1,000,000,000.
The next N lines each contain the x and y locations of a fence post, both integers in the range 0…1,000,000,000.
Please output the minimum number of mirrors needed to direct the laser to the barn, or -1 if this is impossible to do.
4 0 0 7 2 3 2 0 2 1 6 3 0 | <urn:uuid:f0b531db-7cf0-4679-9212-056048b43e11> | 2.84375 | 533 | Tutorial | Science & Tech. | 81.033966 | 95,585,141 |
Mathematicians at Liverpool, working with physicists at the Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Universite have found that coastal defences could be made ‘invisible' when water is guided through a special structure called metamaterial.
Metamaterial was first invented by Sir John Pendry at Imperial College London where scientists discovered that this unique structure could bend electromagnetic radiation – such as visible light, radar or microwaves – around a spherical space, making an object within this region appear invisible.
The new structure is cylindrical and consists of rigid pillars that help guide water along concentric corridors. The pillars interact with the water, guiding it in different directions along the corridors and increasing its speed as it nears the centre of the structure - similar to a whirlpool. The water waves, however, are never broken-up and exit the structure as though they had never been disturbed.
Dr Sebastien Guenneau, from the University’s Department of Mathematical Science, explains: “Defending land against flooding and tidal waves is a big issue for scientists and engineers all over the world. Coastal defences have to withstand great forces and there is always a risk of water overtopping or penetrating these structures. Water crashes against these defences, breaking the wave and causing a lot of damage to roads and property hidden behind them.
“What is unique about this new structure is that it interacts with the water, guiding it to a particular destination rather than breaking it up and sending it everywhere. It is as though the defences are invisible to the wave and as such it does not recognise the structure as an obstacle. This makes it easier to manipulate water waves.
“We now need to investigate how to replicate this effect in a ‘real’ life situation to protect land from natural disasters such as tsunamis, and defend other structures such as oil rigs in the ocean.”
The research is published in Physical Review Letters.
Samantha Martin | alfa
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
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Temporal range: Late Miocene-Recent
|Moray eel in the Maldives|
Moray eels, or Muraenidae, are a cosmopolitan family of eels. The approximately 200 species in 15 genera are almost exclusively marine, but several species are regularly seen in brackish water, and a few are found in fresh water.
The smallest moray eel is probably Snyder's moray (Anarchias leucurus), which attains a maximum length of 11.5 cm (4.5 in), while the longest species, the slender giant moray (Strophidon sathete) reaches up to 4 m (13 ft). The largest in terms of total mass is the giant moray (Gymnothorax javanicus), which reaches 3 m (9.8 ft) in length and 30 kg (66 lb) in weight.
The dorsal fin extends from just behind the head along the back and joins seamlessly with the caudal and anal fins. Most species lack pectoral and pelvic fins, adding to their serpentine appearance. Their eyes are rather small; morays rely on their highly developed sense of smell, lying in wait to ambush prey.
The body is generally patterned. In some species, the inside of the mouth is also patterned. Their jaws are wide, framing a protruding snout. Most possess large teeth used to tear flesh or grasp slippery prey items. A relatively small number of species, for example the snowflake moray (Echidna nebulosa) and zebra moray (Gymnomuraena zebra), primarily feed on crustaceans and other hard-shelled animals, and they have blunt, molar-like teeth suitable for crushing.
Morays secrete a protective mucus over their smooth, scaleless skin, which in some species contains a toxin. They have much thicker skin and high densities of goblet cells in the epidermis that allows mucus to be produced at a higher rate than in other eel species. This allows sand granules to adhere to the sides of their burrows in sand-dwelling morays, thus making the walls of the burrow more permanent due to the glycosylation of mucins in mucus. Their small, circular gills, located on the flanks far posterior to the mouth, require the moray to maintain a gap to facilitate respiration.
Morays are carnivorous and feed primarily on smaller fish, octopuses, squid, cuttlefish and crustaceans. Groupers, barracudas and sea snakes are among their few predators. Commercial fisheries exist for several species, but some cause ciguatera fish poisoning.
Moray eels' heads are too narrow to create the low pressure most fishes use to swallow prey. However, they have a second set of jaws in their throat called pharyngeal jaws, which also possess teeth (like tilapia). When feeding, morays launch these jaws into the mouth, where they grasp prey and transport it into the throat and digestive system. Moray eels are the only animals that use pharyngeal jaws to actively capture and restrain prey.
In addition to the presence of pharyngeal jaws, there are other adaptations which enable morays to feed without negative pressure. The mouth opening extends far back along the edge of the moray's head, compared to other fishes which feed with suction. In the action of lunging at prey and biting down, water flows out the posterior side of the mouth opening, reducing waves in front of the eel which would otherwise displace prey. The result is that even with reduced bite times compared to other fishes, an aggressive approach to predation is still possible.
Differing shapes of the jaw and teeth reflect the respective diets of different species of moray eel. Evolving separately multiple times across the Muraenidae, short, rounded jaws and molar-like teeth allow durophagous eels (e.g. Gymnomuraena zebra and genus Echidna) to consume crustaceans, while other piscivorous genera of Muraenidae have pointed jaws and longer teeth. These morphological patterns carry over to teeth positioned on the pharyngeal jaw.
Reef-associated roving coralgroupers (Plectropomus pessuliferus) have been observed to recruit giant morays to join them in hunting for food. The invitation to hunt is initiated by head-shaking. The rationale for this joining of forces is the ability of the morays to enter narrow crevices and flush prey from niches not accessible to groupers.
The moray eel can be found in two separate aquatic environments: freshwater habitats and saltwater habitats. When concerning saltwater habitats, there is an extremely wide diversity, and large quantity, of moray eels which occupy these waters. An example of a saltwater moray eel, would be that of Gymnothorax vicinus. When concerning freshwater habitats, there is relatively little species abundance, or rather species richness, in these environments. The most widely known, and most relatively acknowledged, freshwater moray eel is Gymnothorax polyuranodon. Consequently, these moray eels can be found in habitats at depths of over roughly 80 centimeters.
The saltwater habitats are not uniform and have much variability, including shallow water nearshore areas, continental slopes, continental shelfs, deep benthic habitats, and mesopelagic zones of the ocean. In saltwater habitats, moray eels are considered "cosmopolitan," which is a loosely used term referring to the fact that the moray eel contains various species which can occupy two separate saltwater habitats: tropical oceans and temperate oceans. Tropical oceans are typically located near the equator, whereas temperate oceans are typically located away from the equator. That being said, the moray eel is capable of living in relatively warm water, despite the ocean being tropical or temperate. As a result, these moray eels can be found in habitats at depths greater than 10 meters.
Although the moray eel can occupy both tropical oceans and temperate oceans, as well as both freshwater and saltwater, the majority of moray eels occupy warm saltwater environments, which contain reefs. Within the tropical oceans and temperate oceans, the moray eel occupies shelters, such as dead patch reefs and coral rubble rocks, and less frequently occupies live coral reefs.
There are currently around 202 known species of moray eels, divided between 16 genera. These genera fall into the two sub-families of Muraeninae and Uropterygiinae, which can be distinctly defined by the location of their fins. In Muraeninae the dorsal fin is found near the gill slits and runs down the back of the eel, while the anal fin is behind the anus. The Uropterygiinnae, on the other hand, are defined by both their dorsal and anal fin being located at the end of their tails. Though this distinction can be seen between the two sub-families, there are still many varieties of genera within Muraeninae and Uropterygiinae. Of these, the genus Gymnothorax is by far the broadest , including more than half of the total number of species.
List of genera according to the World Register of Marine Species :
The Moray Eel's change in shape within the species is due to an elongation process called pleomerism, which involves an increase in the number of vertebra. However, the development of vertebrae evolved independently from lengthened body and explains the high amount of diversity among Moray eel species. Additionally precaudal and caudal regions have differing modes of development and vertebra in these regions do not increase in a synchronous fashion. | <urn:uuid:492d56b7-8782-4fbe-892b-fbc8b51ae23d> | 3.546875 | 1,649 | Knowledge Article | Science & Tech. | 36.138936 | 95,585,149 |
What Would Happen in a World Without Water?
May 22 2017 Read 10267 Times
It goes without saying that the human race wouldn’t last very long in a world without water. The same can be said of all animals and plants, as well, since H2O constitutes one of the building blocks necessary for life to thrive.
But what would happen to the planet itself? With no oceans, rivers or lakes, it would certainly look altogether different, but in what other ways would it change? Here are a few possible consequences if all of the water on our great green Earth vanished overnight.
For starters, it wouldn’t be quite so green for very long. With no water supply, all vegetation would soon die out and the world would resemble a brownish dot, rather than a green and blue one. Clouds would cease to formulate and precipitation would stop as a necessary consequence, meaning that the weather would be dictated almost entirely by wind patterns.
Indeed, other than fluctuations in wind force, our climate would resemble one endless summer – but not the shorts-and-t-shirt, holiday kind; the flesh-meltingly hot kind. The oceans of the world constitute the biggest deposits of carbon (and recently it was found that Arctic melting released nitrous oxides (NO2) and sulphur dioxide (SO2), as well). With these “sinks” gone, the greenhouse gases would have a field day and temperatures would spiral out of control.
Of course, the absence of vegetation would contribute to the problem (since plants would not be around to convert carbon dioxide (CO2) into oxygen), thus exacerbating the situation. Today’s climate change issues would seem small fry in comparison.
Less volcanoes, more mountains
Perhaps surprisingly, however, volcanic activity would decrease in the face of a water dearth. Volcanos, supervolcanos and their eruptions are actually caused by tectonic plates colliding with each other and running over one another – something which is generally caused by the weight of oceans pushing one plate beneath another.
What’s more, once the volcano has been formed, water also plays an integral role in its volatility. Liquid inside the Earth’s crust at high temperatures and high pressures becomes magma, resulting in eruptions like the one at Vesuvius which did for poor old Pompeii.
Therefore, with no ocean to weigh plates down and no water to power eruptions, we’d be left with a series of incredibly high mountain ridges any time two tectonic plates collided. Of course, such a process would take millennia to occur, but the end result would be a desert-like, barren globe populated by spiky ridges and gulfing chasms.
Let there be life
Remarkably, however, this wouldn’t mean the end of all life on Earth. Evolution has a funny way of persevering even in the most difficult of circumstances, and over the millennia, certain microbes known as “extremophiles” have evolved to be capable of life without water.
Instead, extremophiles harvest their nutrients from carbon monoxide (CO), meaning they can thrive even in sizzlingly hot or acidic environments, without water or sunlight. Some of them inhabit the Earth’s crust, while others are effectively dormant in a state of suspended animation inside gigantic subterranean crystals.
So while humanity and the animal kingdom would most certainly snuff it, life would still find a way.
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Litter Decomposition in Created and Adjacent Forested Wetlands of the Coastal Plain of Virginia
Schmidt, John Michael
MetadataShow full item record
Litter decomposition is a poorly understood function of constructed and natural forested wetlands. This study compared rates of litter mass loss, changes in litter morphology, and associated macroinvertebrate populations in constructed and natural non-tidal wetlands. Two sets of wetlands (constructed vs. natural) were studied in eastern Virginia; a 9 year-old riparian set near Fort Lee, (FL), and a 2 year-old wet flat set in Charles City County, (CC). Mixed deciduous forest litter collected from the FL natural wetland decayed more rapidly in the created wetlands than the adjacent forested wetlands. Mixed emergent marsh litter collected from the FL created wetland exhibited a similar relationship, although marsh litter decomposed slower than forest litter. Litter area and weight loss followed a similar pattern, although area loss lagged behind weight loss, consistent with an initial leaching phase of decomposition. Both the FL and CC created wetlands exhibited faster litter decomposition than their adjacent forested wetland, however, the FL created wetland had a lower weight:area ratio and higher detritivore abundance than the adjacent forested wetland, while the reverse was true for the CC wetland pair. These relationships suggest macroinvertebrates played an important role in decomposition in the FL created wetland, while other factors were more significant at CC. Faster decomposition in the created wetlands may be of concern for long-term soil organic matter accumulation, or conversely, may indicate quick recovery of the litter decomposition function. Overall, these findings point out the difficulties involved in using certain functional indicators to compare very young and mature systems.
- Masters Theses | <urn:uuid:11939088-af9a-4367-9fe4-8c800a316acb> | 2.90625 | 397 | Academic Writing | Science & Tech. | 23.784871 | 95,585,181 |
Sunspots, which rotate around the sun's surface, tell us a great deal about our own planet. Scientists rely on them, for instance, to measure the sun's rotation or to prepare long-range forecasts of the Earth's health.
But there are some years, like this one, where it's not possible to see sunspots clearly. When we're at this "solar minimum," very few, if any, sunspots are visible from Earth. That poses a problem for scientists in a new scientific field called "Space Weather," which studies the interaction between the sun and the Earth's environment.
Thanks to a serendipitous discovery by Tel Aviv University's Prof. Colin Price, head of TAU's Department of Geophysics and Planetary Science, and his graduate student Yuval Reuveni, science now has a more definitive and reliable tool for measuring the sun's rotation when sunspots aren't visible — and even when they are. The research, published in the Journal of Geophysical Research – Space Physics, could have important implications for understanding the interactions between the sun and the Earth. Best of all, it's based on observations of common, garden-variety lightning strikes here on Earth.
Waxing and waning, every 27 days
Using Very Low Frequency (VLF) wire antennas that resemble clotheslines, Prof. Price and his team monitored distant lightning strikes from a field station in Israel's Negev Desert. Observing lightning signals from Africa, they noticed a strange phenomenon in the lightning strike data — a phenomenon that slowly appeared and disappeared every 27 days, the length of a single full rotation of the sun.
"Even though Africa is thousands of miles from Israel, lightning signals there bounce off the Earth's ionosphere — the envelope surrounding the Earth — as they move from Africa to Israel," Prof. Price explains. "We noticed that this bouncing was modulated by the sun, changing throughout its 27-day cycle. The variability of the lightning activity occurring in sync with the sun's rotation suggested that the sun somehow regulates the lightning pattern."
He describes it as akin to hearing music or voices from across a lake: depending on the humidity, temperature and wind, sometimes they're crystal clear and sometimes they're inaudible. He discovered a similar anomaly in the lightning data due to the changes in the Earth's ionosphere — signals waxed and waned on a 27-day cycle. Prof. Price was able to show that this variability in the data was not due to changes in the lightning activity itself, but to changes in the Earth's ionosphere, suspiciously in tandem with the sun's rotation.
Taking the pulse of the sun
The discovery describes a phenomenon not clearly understood by scientists. Prof. Price, an acclaimed climate change scientist, believes it may help scientists formulate new questions about the sun's effect on our climate. "This is such a basic parameter and not much is known about it," says Prof. Price. "We know that Earth rotates once every 24 hours, and the moon once every 27.3 days. But we haven't been able to precisely measure the rotation rate of the sun, which is a ball of gas rather than a solid object; 27 days is only an approximation. Our findings provide a more accurate way of knowing the real rotation rate, and how it changes over time," he says.
Prof. Price cannot yet say how this finding will impact life on Earth. "It's an interesting field to explore," he says, "because nothing has been done to investigate the links between changing weather patterns and the rotation of the sun.
"Short-term changes in solar activity can also impact satellite performance, navigational accuracy, the health of astronauts, and even electrical power grid failures here on Earth. Many scientists claim that the sun's variability is linked to changes in climate and weather patterns, so the small changes we observed every 27 days could also be related to small variations in weather patterns.
"Our data may help researchers examine short-term connections between weather, climate, and sun cycles. With this tool, we now have a good system for measuring the pulse of the sun."
George Hunka | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
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As the only direct evidence of past life, fossils provide important information on the interactions between plants and environmental change. After ten years' survey, Professor Zhou Zhekun's group from Kunming Institute of Botany has discovered more than ten well preserved Neogene plant fossil sites in southwestern China which are important to understand past climate and response of plants to the changing climate in this region.
1, 3, 5, 7: This is the micro-morphology of fossil Quercus delavayi complex. 2, 4, 6, 8 Micro-morphology of extant Q. delavayi.
Credit: ©Science China Press
Their recent work, entitled "Evolution of stomatal and trichome density of the Quercus delavayi complex since the late Miocene", was published in CHINESE SCIENCE BULLETIN.2013, Vol 58(21).
Comparing closely related fossils from different geological periods is an efficient method to understand how plants respond to climatic change across a large scale. However, few studies have been carried out due to lack of a continuous fossil record. In their recent study, Prof. Zhou's group investigated detailed micro-morphology of a dominant element in Neogene fossil sites, Quercus delavayi complex (one oak species) to answer this question.
Their results show that Quercus delavayi complex from different periods share similar leaf morphology, but differ with respect to trichome and stomatal densities. The stomatal density of the Q. delavayi complex was the highest during the late Miocene, declined in the late Pliocene, and then increased during the present epoch. These values show an inverse relationship with atmospheric CO2 concentrations. Since the late Miocene, a gradual reduction in trichome base density has occurred in this complex. This trend is the opposite of that of precipitation, indicating that increased trichome density is not an adaptation to dry environments. These results are important to understand the relationship between plant evolution and climatic change which are important to predict the fate of current biodiversity in a changing environment.
This research project was partially supported by a grant from the National Natural Science Foundation of China and a 973 grant from Department of Science and Technology of China. Knowledge of the past is crucial to understand the future. The researchers suggest the old subject 'Paleontology' can reveal long term evolution in the past which is hardly seen in 'Neontology' should receive more attention.
See the article: Hu Q, Xing Y W, Hu J J, Huang Y J, Ma H J, Zhou Z K. Evolution of stomatal and trichome density of the Quercus delavayi complex since the late Miocene. Chin Sci Bull, 2013, 58, doi: 10.1007/s11434-013-6005-x
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.
YAN Bei | EurekAlert!
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:d6150ffb-12c9-44eb-bbb1-528db9b23a71> | 3.78125 | 1,285 | Content Listing | Science & Tech. | 41.958556 | 95,585,184 |
Posted 4 years ago on March 31, 2014, 2:52 p.m. EST by LeoYo
This content is user submitted and not an official statement
The Vanishing Arctic Ice Cap
Monday, 31 March 2014 10:07
By Dahr Jamail, Truthout | Report
An Arctic largely devoid of ice, giant methane outbursts causing tsunamis in the North Atlantic, and global sea levels rising by several meters by mid-century sound like the stuff of science fiction.
But to a growing number of scientists studying Anthropogenic Climate Disruption (ACD/climate change), these dramatic predictions are very real possibilities in our not-so-distant future, thanks to the vanishing Arctic ice cap, which is continuing its rapid decrease in both volume and area.
Arctic sea ice researchers are predicting that sea ice will no longer last through summers in the next couple of years, and even US Navy researchers have predicted an ice-free Arctic by 2016. Whichever year the phenomenon begins, it will be the first time humans have existed on Earth without year-round sea ice in the Arctic, and scientists warn that this is when "abrupt climate change" passes the point of no return.
To read more about anthropomorphic climate disruption and how environments and communities suffer from corporate profit-seeking, click here.
"In the first year that this happens, the open Arctic Ocean state will only last for a few weeks to a month or so," Paul Beckwith, a climatology and meteorology professor at the University of Ottawa, Canada, told Truthout. "Within a year or two, the open water duration [no sea ice] will last for several months, and within a decade or so the positive feedbacks will likely clear out the Arctic Ocean basin for most of the year."
Beckwith, an engineer and physicist who is also researching abrupt climate change in both present day and in the paleo records of the deep past, warns that losing the Arctic sea ice will create a state that "will represent a very different planet, with a much higher global average temperature, as much as 5 to 6 degrees C warmer within a few decades, in which snow and ice in the northern hemisphere becomes very rare or even vanishes year round."
The UN Intergovernmental Panel on Climate Change (IPCC), the world's most authoritative voice on climate science, whose reports influence policy and planning decisions of national governments across the world, has just released its latest report. The IPCC has been accused by much of the scientific community of having a starkly conservative bias.
Scientific American has said of the IPCC: "Across two decades and thousands of pages of reports, the world's most authoritative voice on climate science has consistently understated the rate and intensity of climate change and the danger those impacts represent."
However, the recently released IPCC report is raising eyebrows: Even this conservative body is predicting dire threats for people and other species in the near future, and these risks may very well mean "abrupt or drastic changes" that could lead to unstoppable and irreversible climate shifts like the melting of both the Arctic ice cap and Greenland's glacial ice.
According to the IPCC report, the polar bear is not alone in being under threat.
"The polar bear is us," says Patricia Romero Lankao of the federally financed National Center for Atmospheric Research in Boulder, Colorado, referring to the first species to be listed as threatened by global warming due to melting sea ice.
Beckwith, who believes the planet is already in the early stages of abrupt ACD, offered grave predictions of what we might expect from losing the Arctic ice.
"As the planet transitions through this abrupt climate change, there will be wrenching turmoil and conflict for human civilizations," he explained. "As the extreme weather events ramp up this will result in a frenzy of human activity to attempt to adapt and mitigate. Essentially, this tipping point in the Arctic will inevitably result in a tipping point in human response to the problem."
"Critical to the Earth System" http://www.truth-out.org/news/item/22790-the-vanishing-arctic-ice-cap | <urn:uuid:5a83b28c-6dcc-43d1-9b73-bf2078e9308e> | 2.875 | 845 | Comment Section | Science & Tech. | 32.870003 | 95,585,199 |
The last species from the genus Epaulette sharks or Hemiscyllium is the Papuan epaulette shark (Hemiscyllium hallstromi). The whole genus is a great example for plate tectonics and evolution, as shown in this great paper by Gerald Allen et. al.
The little (up to 30 in -77 cm- length ) Papuan epaulette shark (B in the picture) has a limited habitat in shallow tropical waters on seagrass beds and occasional rocks and coral reefs near Port Moresby, the capital of Papua New Guinea. It is considered vulnerable by the IUCN due to overfishing (mostly as bycatch) by industrial and artisanal fisheries in destructive practices like trawling and dynamite fishing, pollution by river-borne pollutants, sewerage effluent from Port Moresby and sedimentation from mining run-off, and habitat destruction by oil exploration and pipeline development.
After the Epaulette shark from 1788, the next new species of the genus Hemiscyllium has been described in 1824. The Indonesian speckled carpetshark (Hemiscyllium freycineti) is another walking shark from around Indonesia and seems to live solely off western New Guinea, whereas the newly discovered Milne Bay Epaulette shark assumed the eastside (and many of the pictures). Despite being common for so long, not much is known about this reef shark of the family Longtail carpet sharks (or bamboo sharks, Hemiscylliidae), not even its length.
Like all Epaulette sharks, the Indonesian speckled carpetsharks is oviparous (that means the female lays egg cases). This cute little shark is often caught for aquarium trade. Due to habitat destruction and destructive or illegal fishing practices, but above all, its newly discovered restricted distribution, it may very well be considered Vulnerable instead of only Near Threatened in the near future.
Epaulette sharks are cute, can walk and look all at first glance fairly similar. But if you take your time to look closer on those markings, you can find differences. Just like American marine biologist and author Scott W. Michael did, and he discovered that on some pictures and specimen of the common Indonesian speckled carpetshark the shark should not have those large and defined spots remarkably similar to the spots of a leopard. He informed his colleague Gerald Allen, and so, after genetic tests, in 2010 a new species of the genus Hemiscyllium off (the Milne Bay Province region of) eastern Papua New Guinea was named after him: the Milne Bay epaulette shark or Leopard epaulette shark (Hemiscyllium michaeli).
Like the majority of the other 8 species of its genus of the family Hemiscylliidae (Bamboo sharks or longtail carpet sharks), the up to 27.4 in – 69.5 cm – long Milne Bay epaulette shark is considered Near Threatened due to its small home range in shallow inshore coral reef waters with problems from overheating, overfishing and destructive fishing practices like dynamite fishing. Additionally, it suffers greatly from habitat degradation due to pollution and siltation from recent gold mining in the region (cyanide poisoning, river run-off and direct dumping of waste) and from ongoing logging and palm oil plantations. Producing and using palm oil not only endangers our air, our soil, our flora and fauna, out health and our atmosphere, but our oceans, too.
The last species of the Genus Proscyllium is the Graceful catshark (Proscyllium habereri). Like its sister species, this species of Finback catsharks (or false catsharks) also lays up to two egg cases (oviparous).
The graceful catshark is up to 26 in -65 cm- long (females bigger than males) and lives on the bottom of continental and insular shelfs of the Western Pacific from southeastern Japan to Viet Nam and northwestern Java and Indonesia at depths between 164 and 328 ft – 50 and 100 m. Due to the high fishing pressure in this areas, especially by bottom trawling, it may be in danger – but there are at present only insufficient information and no catch data available.
As mentioned last week, the Broadfin shark had been categorized as Endangered by the IUCN. But this happened before its sister species, the Borneo Broadfin shark (Lamiopsis tephrodes), has been again considered as separate species due to biomolecular analyses. Discovered in 1905 (instead of 1839, where he wasn’t even alive) by zoologist Henry Fowler, it had soon been equalized with the Broadfin shark.
Reaching only 4.3 ft – 1.30 m -, the Borneo Broadfin shark lives solely off Borneo. Due to fishing pressure in this waters and 2 separate species, the IUCN should maybe revise its classification.
Another species of requiem sharks is the Broadfin shark (Lamiopsis temminckii). Living solely in shallow waters off India, China and Southeast Asia, it suffers greatly from habitat destruction, overfishing and water pollution. The IUCN considers this species as endangered.
Like almost all other requiem sharks, the Broadfin shark is viviparous. 4 to 8 embryos feed at first from yolk and later via a placental connection. After about 8 month they are born at 15 to 23 in -40 to 60 cm- length. Maximal length is 5.5 ft – 1.7 m.
Did you know that hammerhead sharks did not gradually develop such a large hammer, as it had been believed for decades? Genetic tests showed the opposite. Sharks with giant cephalofoil (hammer) like the Winghead shark, where it is as wide as up to 50% of the shark’s total length, are the primary species, from with later evolved species with a smaller hammer. The benefits of the hammer have to exceed the hindrance of its deformity by far.
The Winghead shark (Eusphyra blochii) forms its own genus within the family hammerhead sharks and has been named after the German naturalist Marcus Elieser Bloch, who described it for the first time in 1785. It is a slender shark (hence the additional name Slender hammerhead shark) and has got not only particularly protruding hammer wings (which are at birth folded back along the body and unfold only later on) but extremely long nostrils, too. After a gestation period of 8 to 11 months, where approximately 11 embryos have got each their own compartment inside the uterus and are nourished by yolk and later by a placental connection (viviparous), they are born at a length of 13 to 19 in – 32 to 47 cm. They are slow growing and reach up to 6.2 ft – 1.9 m – at length and 21 years of age.
The Winghead shark lives in coastal tropical waters of the Indio-West Pacific. Due to the high fishing pressure for its fins and meat and the degradation of its habitat in these areas, the IUCN has been classified it as endangered since 2016 (prior to that it was only considered near threatened, but it is absent from several areas by now).
Sharks do have special healing abilities. They often get wounds (due to mating rituals, combat, collisions with reef substrate or fishing gear) which, however, heal remarkably quickly. A part in it is the fact that dermal-denticles are teeth and are continually replaced like real teeth. Thus wounds are quickly covered with temporary, larger denticles, and the resulting scar become invisible by normal shaped denticles within 6 month.
An example of this was found in Scalloped hammerhead sharks (Sphyrna lewini). This species of Hammerhead sharks (also known as bronze, kidney-headed, or southern hammerhead sharks) lives all over the world offshore in warm and tropical waters near the surface, partly in large schools. This and the fact that there are several distinct sub-populations makes this species highly susceptible to fishing pressure. They are caught commercially for their meat and skin, but manly their fins, often illegally (IUU), as bycatch or as big game fish by recreational fishermen. That’s why they are worldwide considered endangered by the IUCN.
Scalloped hammerheads are up to 14 ft – 4.3 m – long (but on average only up to 8.2 ft – 2.5 m – as female and 5.9 ft – 1.8 m – as male). They are viviparous (once the yolk sack is depleted it converts into a placental connection) and give birth after 9 to 12 month in specific, shallow nursery areas to up to 40 living young. The pups grow slowly and often fall prey to larger sharks, what explains the relative large litter size.
Sharks of the family sleeper sharks are bad ass: they like it cold (like the Greenland shark) as well as hot (like the Pacific sleeper shark). But one of them also likes it deep: the Portuguese Shark (Centroscymnus coelolepis) is the record holder for greatest depth attained by any shark. It usually inhabits depths below 1,300 ft -400 m-, but has been caught as deep as 12,057 ft -3,675 m. It is special in other aspects, too. It has very large dermal denticles shaped like scales of bony fish, and its eyes are well adapted to deep sea conditions: large and green due to a reflective layer named tapetum lucidum (like cat eyes), its cells are optimized for detecting movement and bioluminescence.
The Portuguese shark can be found worldwide, but patchily, in several distinct population in the Atlantic and Mediterranean Sea, Pacific and Indian Ocean. It is on average 3.3 ft – 1.0 m – long and ovoviviparous with an average number of 12 pups after one year of gestation (due to the vast extend of the deep sea, it seems that copulation trigger ovulation).
There is depth segregation by size and sex; since pregnant females are found in shallower water of the deep sea, they are more at risk by fishing pressure. It is targeted for the squalene in its liver (22 to 49% by weight) and its meat, but mostly taken as bycatch by bottom trawlers. Thus the IUCN considers the Portuguese shark as Near Threatened and even Endangered in European waters, despite a zero Total Allowable Catch since 2010, because even if discarded, as deep sea species the survival rate is likely to be low. It seems that a separate sub-population in the Mediterranean Sea is secure because it occurs at depths that are outside of the scope of existing fisheries, additionally there has been a ban on deepwater fisheries operations below depths of 3,300 ft – 1,000 m – since 2005.
The Prickly shark (Echinorhinus cookei), looking like the big brother of the Ninja lanternshark, is thankfully not as irritable as its name suggests. On the contrary, despite its size of up to 13.1 ft -4 m- it is rather shy around humans.
The Prickly shark, as well as its brother Echinorhinus brucus from the family Bramble sharks or Echinorhinidae, is known for its thorn-like denticles. Thus its scientific name Echinorhinus, which is greek for echinos = hedgehog or sea urchin and rhinos = nose. It inhabits deeper coastal waters of the Pacific ocean from California and Hawaii to Chile and China to New Zealand and stays as a homebody in a rather small home range of 0.85 sq mi -2.2 km2. It likes it rather cool and stays by day in depths of up to 4900 ft -1500 m-, but migrates at night upwards near the surface.
Prickly sharks are not targeted directly (its meat isn’t tasty), but are often victims of bycatch of deepwater trawl fisheries to sate our increasing need for fish meal (used for aquaculture and pig, chicken and even cow husbandry). Therefore they are considered as near threatened by the IUCN, even though a female has been found with up to 114 embryos (they are ovoviviparous). | <urn:uuid:ea003d20-ecd0-41ed-8320-03436b383830> | 3.109375 | 2,609 | Knowledge Article | Science & Tech. | 49.311905 | 95,585,207 |
The £92,300 study is funded by the Medical Research Council through its ‘Discipline Hopping’ Awards scheme which aims to provoke new collaborations between the physical and life sciences.
For the next 12 months Dr Cyril Rauch, physicist and lecturer in the School of Veterinary Medicine and Science at Nottingham will be working with Dr Giles Richardson, from the School of Mathematical Sciences in Southampton to find out why and how the molecules that oppose drug entry into cells work.
Dr Rauch said: “I am a physicist who is very interested in complex systems such as biology. We will be working at the interface of science — mathematics, physics and biology. Drugs have got to have a molecule in the body to target. But a drug has to cross all the body tissues prior to reaching its target and this is incredibly tricky and very difficult from the drug standpoint. In particular, cells have specific proteins, namely membrane transporters, that impair the transverse movement of drugs by constantly extruding them — these are their natural defence mechanism to avoid toxicity. We have previously suggested and reported that the membrane of cells is central and that basic physics may shed light on this very complex transport of drugs to their target. In due course we aim to control drugs’ oral bioavailability and multi drug resistance.”
Dr Richardson, whose mathematical expertise is in modelling biological and electrochemical phenomena said: “When I first heard about it I was intrigued by multidrug resistance and, in particular, by the fact that, despite there being a number of well attested properties displayed by multidrug resistant cells, there is still no consensus on the mechanisms for this strange phenomenon. Furthermore I felt that the modelling techniques that I use could play an important role in testing out hypothetical mechanisms”.
Multidrug resistance is a major problem in the treatment of a variety of diseases including malaria, cancer and certain bacterial infections.
Transporters on the cell’s protective shield — its biomembrane — repel the drugs and are part of the mechanism that decides which particles are friend or foe. These cells will fight against drugs by putting in place drug entry systems. What Dr Rauch and Dr Richardson want to know is how and why a drug should come into contact with a transporter and be expelled and what leads to that rejection.
Research has already given us some clues as to why this happens but more work needs to be done. Together these two scientists, from very different academic backgrounds, will build on the work that has already been carried out. They want to model theoretically, using physics and mathematics, the process of drug resistance and compare these results with other experimental data.
They want to try and discover what holds the drug long enough in the membrane, which is just five nanometres thick, for it to defuse to the transporter. If they can impair diffusion of the drug to the transporter they should be able to help the drug pass safely through the membrane to the nucleus. The two scientists believe that rational mathematical modelling has an important role in explaining this phenomenon and will eventually lead to the development of new treatment regimes.
Understanding the physical biology of therapeutics crossing cells may well lead to the generation of new therapeutic strategies that will also target cellular compounds that drive and put in place the physical biology of cells.
Lindsay Brooke | 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
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:2599c5cf-75bb-4b4a-8f30-d5d084208201> | 2.84375 | 1,255 | Content Listing | Science & Tech. | 40.207917 | 95,585,211 |
In the 19th century, taxonomy -- the classification of living organisms -- was all the rage in biology. [ref. 1] Both amateur and professional naturalists were so caught up in the craze of collecting and identifying creatures, rare beetles were hot commodities. [ref.2, about midway down] At the time, little was known about microorganisms and their place in the world of living things, so they didn't receive as much attention. The intervening decades have seen a dramatic increase in knowledge of microbes, with part of that increase demonstrated by the efficient classification of microorganisms.
Taxonomy has three components: nomenclature, classification and identification. Nomenclature is simply assigning a name to a species. Classification is grouping species together according to shared characteristics -- some of which are physical, and some biochemical. Identification is using features of an organism to determine where it belongs in a classification scheme. The modern taxonomic scheme has as its largest, most inclusive group, the domains. The smallest group is the species. From the most inclusive to the most specific, the levels run like so: domain, kingdom, phylum, class, order, family, genus and species. You, for example, are Eukarya Animalia Chordata Mammalia Primate Hominidae Homo sapiens.
Microorganisms and Domains
Microorganisms are extremely diverse. They're not defined by any particular kind of structure or function, but simply by their size. Microorganisms are so divers that they fall within all three of the different top-level classifications -- all three domains. One domain is bacteria, the other is archaea and the final is eukarya. All the members of the bacteria and archaea domains are single-celled microorganisms. They're both cells without membranes separating their genetic material from the rest of the cell -- membranes that define a nucleus. So all kingdoms, phyla, classes, orders, families, genera and species within the bacteria and archaea domains are microorganisms.
Eukarya are organisms whose cells contain a nucleus. Many eukaryotic organisms are single-celled microorganisms, but many others -- such as redwood trees, or you -- are not. So additional classifications are necessary. The kingdom Protista within the domain Eukarya is composed of only single-celled microorganisms. The protists are separated into three different groups of phyla: four different algae phyla, four different protozoa phyla and two different mold phyla. But all the organisms within these phyla -- all within the kingdom Protista -- are microorganisms.
The kingdom Fungi is contained within the domain Eukarya. Some of the phyla within the Fungi contain microorganisms. For example, the phylum Zygomycota contains microscopic bread molds, and the phylum Ascomycota contains yeasts, and microbial crop pests and parasites. Lichens are a symbiotic assembly of a fungus and a photosynthetic organism -- contained partly within the kingdom Fungi and partly in other kingdoms, or even other domains. | <urn:uuid:9f194e53-2c58-4627-bf45-73079d2678bd> | 3.9375 | 633 | Knowledge Article | Science & Tech. | 27.098267 | 95,585,224 |
Space Weather: Terrestrial Perspective
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Space weather effects arise from the dynamic conditions in the Earth’s space environment driven by processes on the Sun. While some effects are influenced neither by the properties of nor the processes within the Earth’s magnetosphere, others are critically dependent on the interaction of the impinging solar wind with the terrestrial magnetic field and plasma environment. As the utilization of space has become part of our everyday lives, and as our lives have become increasingly dependent on technological systems vulnerable to space weather influences, understanding and predicting hazards posed by the active solar events has grown in importance. This review introduces key dynamic processes within the magnetosphere and discusses their relationship to space weather hazards.
KeywordsSolar Wind Current Sheet Interplanetary Magnetic Field Magnetic Storm Geomagnetic Activity
The first steps of Sun-Earth connection science were made by Edmund Halley, who following the spectacular auroral displays in Europe in March 1716, suggested that particles moving along the Earth’s magnetic field lines were the cause of the aurora. Following that, Anders Celcius and Olav Hiorter in 1747 discovered the temporal coincidence between compass needle variations and bright auroral displays. Comparing simultaneous magnetic variations in London and in Uppsala they further realized that the phenomena they were studying were related to processes in the planetary scale. The geomagnetic activity connection to solar processes was established by mid-nineteenth century: Solar flare correlation with active, bright auroras and geomagnetic disturbances was found by Carrington in 1860, and long-term observations showed 11-year variability both in sunspot numbers and occurrence frequency of magnetic disturbances and auroras.
While the modern space era with detailed in-situ and remote sensing measurements in and from space have resolved many issues concerning the behavior of the Sun, the solar wind, and the terrestrial space environment, many of the basic physics questions concerning the Sun-Earth connection remain open. On the other hand, the utilization of space has added a new practical flavor to the academic research, because the rapid time variations in the space plasma systems pose a hazard to technological systems and humans in space as well as on Earth. The term “space weather” now refers to conditions on the Sun and in the solar wind, magnetosphere, ionosphere, and thermosphere (upper parts of the atmosphere) that can influence the performance and reliability of space-borne and ground-based technological systems and can endanger human life or health. The adverse conditions in the space environment can cause disruption of satellite operations, communications, navigation, and electric power distribution grids on ground, leading to a variety of societal and economic losses.
The time scales interesting to studies of space weather processes are determined both by the intrinsic time scales of the processes themselves, but also on the lead time that predictions can be given. The solar and magnetospheric processes pose several timescales ranging from solar cycle and longer (long-term solar activity variations) to 27 days (recurrent solar activity), days (magnetic storms), hours (magnetospheric substorms) and even minutes and seconds (particle acceleration events, plasma instability growth times). On the other hand, before an event can be predicted, some indication of its occurrence must have been observed. Energetic particles reach the Earth within only a few, maybe up to ∼20 min after their release from the solar surface or interplanetary shock front giving only a very short lead time after a warning can be given. The solar wind travel time from the Sun to the Earth is of the order of 80 hours, while solar wind monitors at the first Lagrangian point (L1), 1.4 million km from the Earth, provide measurements of the incoming solar wind that reaches the outer edges of the magnetosphere within about 40 minutes to 1 hour of their detection. Thus, as our capability of predicting solar wind properties from solar observations alone is poor, we are at the moment limited to at best warnings 80 hours in advance and predictions at maximum 1 hour before the event starts.
Today’s challenge for space weather research is to (i) learn to quantitatively predict the state of the magnetosphere and ionosphere from measured solar wind and interplanetary magnetic field conditions, (ii) to extend the physical understanding also to solar processes such that predictions can be made using solar observations to gain more lead time. In addition to that, we need engineering and life sciences to evaluate the hazards and risks on a variety of technological systems and humans in space, onboard high-altitude aircraft, and on ground.
This article reviews the basic properties of the magnetosphere and open questions regarding its dynamics, the most typical solar activity events that cause space weather effects, and the effects caused by solar activity that are seen on space-borne and ground-based technological systems as well as on humans. More details of the solar processes associated with space weather phenomena can be found in a review by Schwenn (2006).
2 Solar Influence on Geospace
The Sun affects the Earth and its environs in a variety of ways and on many different timescales. Events on the Sun leading to large perturbations in the coupled magnetosphere-ionosphere system are called geoeffective. From space weather point of view the key question is how to distinguish those solar events that are geoeffective from those that are not.
On average, the solar wind at Earth orbit has mean density of about 4 cm−3, mean velocity of about 400 kms−1, and mean interplanetary magnetic field (IMF) magnitude of 5 nT. The average direction of the interplanetary magnetic field along the Parker spiral in the ecliptic plane is at an angle of about 45° from the radial direction (Hundhausen, 1972). Geomagnetic activity is primarily driven by magnetic reconnection between the IMF and the terrestrial magnetic field. As the dipole is close to perpendicular to the ecliptic plane, it is primarily dependent on the southward component of the IMF, and the reconnection rate is proportional to the Y component of the motional electric field (E = −VSW × BIMF) of the solar wind (Vasyliunas, 1975). Coherent solar wind structures containing southward magnetic fields and high velocities are thus most efficient drivers of space weather events.
Coronal mass ejections (CME) expel vast clouds of solar magnetic flux and plasma into interplanetary space. The interplanetary structure formed by the coronal mass ejection (ICME) propagates outward from the Sun, often at high velocity (Schwenn, 2006). The coherent magnetic field structure, the strongly varying field and plasma density in the sheath region preceding the ICME proper, the fast solar wind speed, as well as the interplanetary shock itself are all effective drivers of geomagnetic activity (Farrugia et al., 1997). While the strongly southward field inside the ICME proper tends to drive high ring current activity, the more variable fields and densities in the sheath region drive strongest activity at the high-latitude auroral regions (Huttunen and Koskinen, 2004). As ICMEs are more frequent during solar maximum than during solar minimum (Bothmer and Schwenn, 1998), they contribute to the 11-year cycle in magnetospheric activity. Similarly to ICMEs, any coherent solar wind structures including long-lasting, high-intensity southward interplanetary fields drive magnetic storm activity with its many signatures in the magnetosphere-ionosphere system.
High-speed solar wind streams encountering the Earth most often originate from low-latitude coronal holes. Such high-speed streams are often associated with strong Alfvénic fluctuations leading to strong fluctuations of the IMF B z and solar wind velocity. These periods are effective drivers of medium-level activity in the high-latitude magnetosphere and in the ring current (Tsurutani and Gonzalez, 1987). The high-speed streams are especially efficient in accelerating relativistic electron populations in the outer van Allen belt. The electron fluxes maximize during the declining phase of the solar activity when the high-speed streams are most frequent, and minimize during solar minimum (Paulikas and Blake, 1979).
During the declining phase of solar cycles, the coronal holes extend to low latitudes sometimes even reaching the ecliptic plane. When the high-speed solar wind emanating from the coronal holes runs into the slower solar wind, the interaction leads to a compression of the plasma and magnetic fields, forming corotating interaction regions (CIR) (Crooker et al., 1999). The CIRs seldom have fast shocks or continuous, strongly southward IMF B z , and thus drive only moderate magnetospheric activity (Alves et al., 2006; Borovsky and Denton, 2006). CIRs, being associated with the coronal hole structure, also exhibit 27-day periodicity (Schwenn, 1990).
Interplanetary shocks when interacting with the Earth’s bow shock cause direct energy transfer into the magnetosphere. The ram pressure pulse associated with the shock compresses the dayside magnetopause, and the compression effects travel tailward at the solar wind speed causing strong auroral activity observable almost instantaneously all around the auroral oval (Zhou and Tsurutani, 2001).
In addition to the interaction with the solar wind, the Sun affects the Earth’s environment also through electromagnetic radiation that reaches the Earth much faster than the solar wind flow. This most familiar form of the Sun’s influence on the Earth is a factor also for space weather: Increases of the solar irradiance cause heating of the upper atmosphere, which affects the drag experienced by low-Earth-orbiting satellites. The irradiance exhibits both long-term (solar cycle) variations as well as shorter term changes related to active solar events, both of which can be monitored using the F10.7 radio flux as a proxy (Lean, 1991).
Solar energetic particles affect the space environment in multiple ways. In the outer magnetosphere (especially near the geostationary region), their presence is a hazard for the satellite systems and instrumentation (Baker, 2000). If they become trapped in the inner magnetosphere dipolar field, they populate the van Allen belts, residing in the magnetosphere for extended periods (Hudson et al., 2004). As the energetic particles can penetrate to 20–40 km altitude (depending on their energy), they also affect the middle and upper atmospheric chemistry while colliding with the atmospheric constituents: The particle precipitation leads to an enhancement of NO2 in the atmosphere, which in turn is a catalyst for ozone distruction. This way the solar activity also affects the long-term balance of the atmospheric chemistry (Seppälä et al., 2006).
Thus, solar irradiation, energetic particle fluxes from the Sun, and the solar wind with its multiple structures all drive geomagnetic activity and are thus potential sources for space weather events. In the following, we review the basic properties of the structure and dynamics of the magnetosphere and associate these drivers with their consequences, both to the plasma environment and to the technological systems, in the terrestrial space environment.
3 The Magnetosphere
A magnetosphere is a cavity in the solar wind flow formed by the interaction of the solar wind and interplanetary magnetic field with the intrinsic magnetic field or ionized upper atmosphere of a planetary body. In the terrestrial case, the interaction is dominated by the strong intrinsic quasidipolar magnetic field; this is also the case of the outer giant planets Jupiter, Saturn, Uranus and Neptune (Southwood and Kivelson, 2001). On the other hand, the inner solar system, Earth-like planets Venus and Mars possess no intrinsic magnetic field, and the magnetosphere is then mostly formed by interaction of the atmosphere and ionosphere with the solar wind flow (Lundin et al., 2001). Mercury has a small intrinsic field but no atmosphere, there the solar wind interacts directly with the surface and exosphere (Killen et al., 2001). The types of space weather phenomena at the different planets depend critically on the magnitude of the intrinsic magnetic field, on the existence and characteristics of the planetary atmosphere and ionosphere, and on the distance from the Sun determining the properties of the driving solar wind and IMF. In the following, we only treat the terrestrial magnetosphere, which is characterized by a dense atmosphere and ionosphere and by a strong intrinsic geomagnetic field, but no internal plasma sources other than the ionosphere.
3.1 Magnetospheric structure
The low-density tail lobes in the nightside magnetotail connect magnetically to the high-latitude polar caps at one end and to the interplanetary field at the other end. The effects of the strong dipole are not seen tailward of about 20 RE. Beyond that distance, the fields in the northern and southern tail lobes are nearly antiparallel and have an almost constant intensity of about 20 nT over a long range of distances from the Earth. The plasma sheet separating the northern and southern lobes hosts densities of the order of 1 cm−3 and partially very low magnetic field values reaching only a few nT. Thus, while the plasma beta (ratio of plasma and magnetic pressures, β = 2 μ0p/B2) is very low in the tail lobes, it generally exceeds unity at the center of the field reversal region. The inner part of the plasma sheet with its weak field and at times intense cross-tail current sheet is highly variable with bursts of fast flows, magnetic reconnection, and large-scale reconfiguration events. In the inner magnetosphere, particles can become trapped on closed orbits drifting around the Earth guided by the quasi-dipolar intrinsic field. The ring current located roughly at 4–6 RE radial distance encircles the Earth with highly variable intensity also modulated by the level of geomagnetic activity.
The solar wind motional electric field in the Earth’s frame of reference (E = −VSW × BIMF) imposes a large-scale convection pattern within the magnetosphere and ionosphere (Dungey, 1961). Dayside reconnection allows solar wind plasma and field entry to the dayside magnetosphere, from where the plasma convects across the polar cap and tail lobes to another reconnection location in the distant tail. At the distant tail reconnection region, plasmas are accelerated toward and away from the reconnection region such that within the tail plasma sheet, the flows are Earthward on the Earthward side of the reconnection region and away from the Earth in the tailward side of the reconnection region (Lyons and Williams, 1984). In the ionosphere, this large-scale convection pattern induces antisunward flow across the polar cap and sunward plasma flow in the auroral region ionosphere (Heelis et al., 1982). This basic flow pattern (in highly variable forms) can always be found underlying the temporal changes associated with the space weather events.
3.2 Magnetospheric plasmas
While the magnetospheric field in general excludes the solar wind plasma from the magnetosphere, at times the solar wind can gain entry into the magnetosphere through the magnetopause. This occurs when the IMF and the magnetospheric fields are antiparallel and magnetic reconnection creates an “open magnetosphere” configuration with a field component normal to the boundary (Dungey, 1961). The plasma entry is strongly modulated by the orientation of the interplanetary magnetic field, and thus enhanced during periods of southward IMF (Russell and McPherron, 1973). While the plasma enters mostly through the dayside magnetopause, a portion of the particles gain entry through the magnetopause boundary layers at low latitudes, well tailward of the terminator (Paschmann, 1997). During northward IMF, high-latitude reconnection over the magnetic poles allows for particle entry to the high-latitude plasma mantle. A minor portion of the energy, estimated to be about 10%, enters via viscous interaction processes (Axford and Hines, 1961). The solar wind plasma, consisting mostly of protons and a small percentage of doubly charged helium and other heavier ions, populates much of the outer magnetosphere through these processes.
In addition to the solar wind flow, the atmosphere contributes both to the neutral and charged particle density in the magnetosphere. The neutral exosphere, or the upward extension of the atmosphere, fills the near-Earth space with an exponentially decreasing density (Chamberlain, 1963; Tinsley et al., 1986). While the neutral atoms and molecules are not influenced by the electromagnetic forces, the geocorona is significant to space physics processes in at least two ways: Coulomb collisions and charge-exchange processes with neutral atoms are significant loss mechanisms for energetic charged particles in the inner magnetosphere (Fok et al., 1995), and thus contribute to the recovery of quiet conditions after a magnetic storm. Furthermore, the slow neutral atoms charge-exchanging with fast charged particles create a population of high-speed neutrals that propagate linearly away from the collision site. During active times, when the flux of energetic charged particles is sufficiently high, this provides (the only) means to image the inner parts of the magnetosphere (Bertaux et al., 1989; Williams et al., 1992).
Above about 80 km altitude, the solar ultraviolet radiation ionizes a small portion of the atmospheric gas creating what is known as the ionosphere. The ionospheric plasma processes couple both to the neutral atmosphere below and to the magnetospheric processes above. From space weather point of view, the ionosphere is significant both because of its effects on radio waves and because it hosts strong electric currents whose effects extend to the ground. The solar wind electric field drives a global convection pattern in the ionosphere, which produces convection electrojets carried by drift currents flowing eastward on the duskside and westward on the dawnside of the ionosphere (Weimer, 1995). Consequently, the plasma flows from the dayside toward the nightside over the polar cap, returning to the dayside along the lower latitudes, consistent with the Dungey cycle (Dungey, 1961). The ionosphere is coupled to the magnetosphere by highly structured and dynamic field-aligned currents, which on an average sense form a pair of large-scale field-aligned current sheets (see Figure 3). The more poleward current Region 1 currents couple to the magnetotail and magnetospheric boundaries, whereas the more equatorward Region 2 currents couple to the ring current in the inner magnetosphere (Iijima and Potemra, 1976). The region encircling the magnetic poles where the current systems flow is also called the auroral oval, as this is the region where particles precipitating from the plasma sheet and colliding with atmospheric atoms and molecules create visible auroral light (Lui and Anger, 1973). During active magnetospheric processes, auroral precipitation is enhanced, localized, and highly structured, especially in the nightside oval.
The upward extension of the ionosphere, the plasmasphere, is a torus filled with low-energy (around 1 eV), dense (10–1000cm−3) plasma originating from the ionosphere. The plasmasphere consists mostly of protons, with singly charged helium accounting for about 20% of the number density. The radius of the torus is variable, but typically the plasmasphere extends close to geostationary orbit, being more compressed during geomagnetically active times and more extended during long periods of magnetic quiescence (Grebovsky, 1970). The Earth’s rotation sets up an electric field, which drags the cold plasma into a corotational motion. The interplay between the solar wind-imposed electric field and the corotation electric field creates a boundary inside of which particles are trapped on closed orbits around the Earth. In the vicinity of this boundary, the plasma density has a sharp gradient; this is known as the plasmapause (Goldstein et al., 2003). Particles inside the trapping boundary remain on closed drift paths around the Earth while those outside the trapping boundary drift under the dawn-to-dusk electric field to the dayside boundary and are lost in the outer magnetosphere and eventually to the solar wind.
The ring current encircling the Earth roughly in the region 2–7 RE from the Earth consists of plasmas originating both from the solar wind and the ionosphere (Daglis et al., 1999). The ring current typically consists of ions in the energy range from a few tens of keV to several hundred keV, and has a highly variable intensity controlled by the level of geomagnetic activity. During magnetically active times, ion outflow from the ionosphere is greatly enhanced, and consequently the ring current composition changes from being dominated by solar wind protons and doubly charged helium to consisting large percentages (up to dominating the mass and energy density) of ionospheric oxygen and to lesser amounts of singly charged helium (Daglis et al., 1999). The ring current decays via charge exchange processes and Coulomb collisions with the exospheric particles.
The outer van Allen radiation belt consists mainly of electrons in the energy range from hundreds of keV to several MeV. The electrons reside colocated with the ring current and the plasmasphere in the inner magnetosphere, roughly from 3 RE to slightly beyond geostationary orbit. These relativistic electron fluxes show sharp dropouts and enhancements in response to the varying geomagnetic activity (Baker et al., 2001), and their dynamics is key to space weather, as these electrons pose a hazard to satellites in Earth orbit. Their rapid drift motion around the Earth is largely controlled by the magnetic field geometry, in contrast to the cold particles that are guided both by the electric and magnetic fields. The electron acceleration and loss processes are strongly dependent on the electric field structure and the wave-particle interactions in the inner magnetosphere (Friedel et al., 2002).
3.3 Magnetospheric dynamics
Energy, momentum, and plasma enter the magnetosphere both via magnetic reconnection at the magnetospheric boundaries in regions where the interplanetary and terrestrial fields are antiparallel and via viscous interactions along the boundary (Dungey, 1961; Axford and Hines, 1961). In a quiescent situation, energy inflow is gradual, the energy is dissipated in the ionosphere, and magnetic flux opened at the dayside reconnection process is closed by a quasistatic reconnection process in the distant magnetotail at about 100–200 RE from the Earth. Energy transfer is most efficient when the reconnection process takes place at the dayside magnetopause, which occurs during periods when the interplanetary field points southward and is thus antiparallel to the intrinsic geomagnetic field (Akasofu, 1981; Laitinen et al., 2006).
Magnetic reconnection in the tail leads to formation of a plasma structure where the field lines are no longer connected to the Earth. This plasmoid is accelerated tailward and ejects a large portion of the plasma sheet plasma, magnetic flux, and energy back to the solar wind (Hones Jr, 1979). It is estimated that about half of the energy that enters via the dayside reconnection process is processed in the inner magnetosphere and ionosphere, while the other half is carried by the plasmoid(s) back to the solar wind (Ieda et al., 1998).
Magnetospheric substorms require a period of enhanced energy input (southward interplanetary field) from 30 minutes to 1 hour. If the energy input continues significantly longer (≥3 h), a magnetic storm develops (Gonzalez et al., 1994). As it takes several hours of southward interplanetary field and/or high solar wind speed to create a magnetic storm, they often follow from the interaction of a fast solar wind stream, an interplanetary magnetic cloud, an ICME, or other coherent solar wind structure. Magnetic storms typically last from about 12 hours to a few days. Storms are characterized by the formation of an intense ring current encircling the Earth with current peak at about 4 RE, i.e., well inside the geostationary orbit. The ring current is populated both by efficient convection and injection of plasma sheet particles into the inner region and by strongly enhanced ion outflow from the ionosphere. At times, the ionospheric outflow can be strong enough for the ionospheric oxygen to dominate the energy density in the ring current (Daglis, 1997). Storms as largest magnetospheric disturbances are associated with many of the space weather phenomena.
While substorms can occur without magnetic storms, almost all storms include also substorm activity. The interaction of the inner magnetosphere storm-associated processes with the magnetotail substorm-associated processes is highly complex, and presently under active study. Especially, it is debated whether the substorm-associated magnetic field variations and the associated (inductive) electric fields are necessary for the buildup of the ring current energy density (McPherron, 1997; Daglis and Kamide, 2003). While some researchers argue that convection alone can account for the ring current increase (Ebihara and Ejiri, 2003), others have concluded that especially the energization process to energies exceeding 100 keV needs smaller-scale, time-varying electric fields (Ganushkina et al., 2005).
The magnetospheric substorms and storms are the most commonly occurring responses to enhanced solar wind driving, but the magnetosphere can enter into a variety of other dynamic states. Steady convection intervals (SMC) are periods of steadily southward IMF and steady, relatively slow solar wind flow that drive continuous, low-level auroral activity without evident substorm expansion phase activity (Sergeev et al., 1996a). On the other hand, stronger levels of driving may lead to sawtooth oscillations, which are large-scale substorms associated with strong, longitudinally extended, quasi-simultaneous injections at geostationary orbit recurring every 2–3 h (Henderson et al., 2006; Pulkkinen et al., 2006). Magnetic storms include, in addition to strong substorm activity, also other kinds of strong activity, field-aligned currents, and inner magnetosphere disturbances (McPherron, 1997).
4 Monitoring the Magnetosphere
The magnetosphere-ionosphere system has been explored by a multitude of Earth-orbiting spacecrafts, but still the sparsity of the satellite fleet and the vast regions to be covered means that, at any given time, direct measurements of the magnetospheric processes are limited to only a few points in space. The European Space Agency’s Cluster mission with its four satellites flying in constellation has for the first time allowed for separation of space and time and by identification of full three-dimensional vector quantities from four point measurements (see, e.g., Escoubet et al., 2001, and other articles in the same volume). However, the limited number of measurement points still means that many quantities must be evaluated using proxy parameters derived either from point measurements in space or from ground-based observations.
However, even with neutral atom imaging, much of the magnetosphere remains invisible to our eyes and instrumentation. To provide conceptual and predictive models of the magnetospheric evolution, large-scale global magnetohydrodynamic (MHD) simulations have been developed (Lyon et al., 2004; Janhunen, 1996). These models describe the solar wind-magnetosphere interaction as well as the coupling to the ionosphere in the single-fluid approximation. With limitations discussed in more detail below, these models have been successfully utilized to provide a large-scale framework for local observations as well as to infer global quantities that cannot be obtained directly from observations.
This section summarizes the most commonly used observational parameters and methods used in space weather research and gives an overview of the global MHD simulations whose results will be presented and discussed in the following Sections 5 and 6.
The level of geomagnetic activity is often characterized in terms of magnetic indices created using a variety of ground magnetic records. The auroral electrojet indices are derived from the north-south components of 12 northern-hemisphere auroral-latitude (around 70° latitude) magnetic stations as the minimum (AL or auroral lower) or maximum (AU or auroral upper) of the 12 measurements at each time instant at one minute temporal cadence. The auroral electrojet index (AE) is then given as the difference of the two (AE = AU − AL). The AL index responds to the enhancement of westward electrojet currents (southward horizontal disturbance field at the Earth’s surface) and is a measure of the intensity of substorm expansion phase activity in the magnetosphere. The AU index responds to the eastward currents, and is a measure of the strength of large-scale convection in the magnetosphere-ionosphere system. While the ionospheric currents are sufficiently close to the ground-based measurement stations so that other magnetospheric current systems do not significantly disturb the measurements, signal arising from ground induction can contribute to the index by as much as 40% during rapidly varying current systems when the induction currents are strongest (Tanskanen et al., 2001). Other geomagnetic indices include the planetary K p index, which is a quasi-logarithmic scale of geomagnetic activity ranging from 0 to 9, computed from 13 geomagnetic observatories in subauroral latitudes (44–60°). The A p index ranging from 0 to 32 is derived similarly to the K p index.
The north-south components of four midlatitude (around 20–40° latitude) stations are used to create the Dst index, which gives a proxy for the intensity of the ring current encircling the Earth. As the amount of ring current intensification is a key parameter in the magnetic storm evolution, this index is used to characterize magnetic storm intensity. The Dst index is computed as an average of the station measurements weighted by the cosines of the station colatitudes (Dst = Σ n ΔH n /Σ n cos θ n ) to compensate for the effects of the varying latitudes of the stations. The Dst index is given as hourly values. A high-resolution SYM-H index is computed in an almost similar way but with 1-min temporal cadence.
The ring current consists of two parts, a symmetric ring current encircling the Earth and an asymmetric part carried by particles on open drift paths drifting from the magnetotail to the dayside magnetopause. This partial ring current is closed by field-aligned currents to and from the ionosphere. The ASY-H index is a measure of the asymmetric ring current and is given as the difference between the maximum and minimum disturbances (weighted similarly to Dst) as measured at the six stations distributed around the globe.
As the magnetometers integrate over all current systems, the SYM-H and ASY-H as well as the Dst indices are sensitive not only to the ring current, but as well to the cross-tail current, the field-aligned currents, the magnetopause currents, and currents induced within the conducting Earth. While during quiet times the contributions from the other current systems can be assumed to be small, during magnetic storms (exactly when the indices are most needed) all currents intensify and move closer to the Earth such that the contributions from the other systems can be as large as 50% (Turner et al., 2000; Ohtani et al., 2001; Hakkinen et al., 2002).
4.2 Global MHD simulations
Global magnetohydrodynamic (MHD) simulations are presently the only means to self-consistently model the plasma processes throughout the solar wind, magnetosphere, and ionosphere: the large range of magnetic field values ranging from 50,000 nT at the Earth’s surface to only a few nT at the magnetotail current sheet, and of plasma densities and temperatures ranging from 1012 cm−3 and a few eV in the ionosphere to less than 1 cm−3 and a few MeV in the magnetosphere set stringent requirements for the numerical solutions. Furthermore, the large system size (several hundred RE or 109 km) compared to the characteristic thermal particle gyroradii (of the order of 102 km) limit the possibilities to describe individual particle dynamics in the entire simulation domain.
Global MHD simulations are used by several research groups to gain a global view of the dynamic processes in the coupled solar wind-magnetosphere-ionosphere system (Lyon et al., 2004; Raeder et al., 1995; Janhunen, 1996; Gombosi et al., 2000). While the codes differ in many details, basically they all solve the (ideal) MHD equations in a large box extending out to at least 30 RE in the Sunward direction, about 60 RE in the perpendiculardirections, and several hundred RE in the downtail direction. This way, the box completely encompasses the magnetosphere in all but the tailward direction, and as the flow is supersonic at the tailward boundary, there is no feedback from that boundary to the other parts of the simulation. With the modern computing capabilities, the variable-size grids can resolve minimum cell sizes of only a fraction of RE, which allows resolving structures to the thermal ion gyroradius scale.
The simulations are driven by the solar wind and IMF values at the Sunward boundary of the simulation box and the F10.7 flux that determines the level of ionospheric ionization and hence the conductivity. The models can either use idealized solar wind and IMF conditions to gain understanding of the generic dynamic properties of the magnetosphere or use real spacecraft measurements to model the evolution of individual events.
In cases where the global MHD simulations solve the ideal MHD equations with zero resistivity, magnetic reconnection occurs in the simulations only through numerical diffusion. In case the resistivity is explicitly accounted for, it is most often parametrized to scale with the current density; the magnetospheric plasmas are fully collisionless and hence the classical collisional resistivity is zero. This and the lack of microphysical processes below the MHD scale naturally limits the applicability of the models to describe the details of the reconnection process either at the magnetopause or in the magnetotail. However, it has been shown that in the large scale, the simulation results are consistent with the conceptual understanding of when and where reconnection in the magnetosphere should occur (Hones Jr, 1979) and with case studies where in-situ satellite observations of reconnection events are available (Pulkkinen and Wiltberger, 2000).
In addition to reconnection modeling, the inner magnetosphere also poses significant challenges to the MHD simulations. As the simulations include only one ion population, it describes the entire distribution with a single temperature. This is not realistic in the inner magnetosphere, where the ring current is carried by ions with significantly higher energies than the average plasma sheet population. Furthermore, the ion sources from the ionosphere (plasmasphere, ion outflows associated with geomagnetic activity) are not included in most simulations. As a consequence, the MHD simulations predict a much more dipolar inner magnetosphere than is observed, and do not reproduce the strong inner magnetosphere field depression associated with stormtime ring current. A variety of efforts to couple the inner magnetosphere simulation part with other, more detailed models of the inner magnetosphere are currently underway to address this issue.
Even given their limitations in describing details of reconnection, multicomponent plasma systems, or the physics associated with non-adiabatic ion motion or anisotropic pressures, the global MHD simulations are presently the best tool to obtain a large-scale view of the magnetospheric activity. As such, they are widely developed for use in space weather applications (Raeder et al., 2001; Manchester IV et al., 2004).
5 Solar Wind Energy Entry into the Magnetosphere
As all magnetospheric activity is powered by energy input from the solar wind, detailed understanding of the energy transfer processes and mechanisms is a key challenge for space weather applications. As described in the previous section, observationally we lack global measurements of the energy transfer and thus are limited to the use of proxies. However, global MHD simulations can be used to trace the energy transfer through the simulation magnetopause and through the magnetosphere-ionosphere system. In this section, we analyze the energy transfer using the GUMICS-4 global MHD simulation (Janhunen, 1996) and compare and contrast the results with those obtained using the empirical proxies.
The challenge in this approach is the determination of the magnetopause surface in the simulation. Observationally, the magnetopause is a current layer (often a tangential discontinuity) that separates the solar wind and interplanetary field from the magnetospheric plasma and field. Thus, from in situ satellite observations, the magnetopause can be distinguished as the location of the current maximum or as the (often very sharp) discontinuity in the magnetic field and plasma density. After trying several methods, the chosen solution for finding the magnetopause in the GUMICS-4 simulation was to define the magnetosphere as a cavity carved by the solar wind plasma flow lines (Palmroth et al., 2003). The magnetopause is then the surface defined by the innermost plasma flow lines encircling the magnetosphere. This method has proven to be quite robust and consistent with other definitions of the magnetopause.
The amount of energy conversion in the magnetotail can be quantified by evaluating the integral of the Poynting flux divergence (∫ dV ∇ · S) in a region that encompasses most of the inner magnetosphere, and hence the region that is mostly affecting space weather phenomena (Laitinen et al., 2005). While this method does not exactly specify the region where the energy conversion takes place, selecting a suitably large region ensures that no major dissipation locations are left out, while the energy conversion outside the active regions is small enough not to produce errors in the evaluation.
Detailed analysis of the energy input locations shows that most of the energy enters the magnetosphere through the magnetopause Earthward of about −10 RE, which gives two main regions of energy input, the dayside, and the nightside boundary in the inner magnetotail region. Further down the tail, the energy transfer through the boundary is very small, as the Poynting flux flows very closely parallel to the boundary. If one looks at the azimuthal sectors (in a plane perpendicular to the Sun-Earth line), it can be seen that the energy is mostly entering in sectors that are parallel or antiparallel to the IMF orientation. This means that for southward IMF, the energy is mainly gaining access through the high-latitude regions in both hemispheres. This is consistent with the conceptual picture of the reconnecting magnetopause where the reconnection occurs close to the subsolar point and the open flux is transported across the high-latitude regions (Dungey, 1961).
It is obvious that the strong activity drives highly enhanced auroral precipitation to a wide and expanded auroral oval. Furthermore, the ionospheric Joule heating is large both in the auroral oval region and in the polar cap, due to the very strong electric fields in the polar cap region. The MHD precipitation tends to follow closely the solar wind driver, while the AE-based proxy shows lower level of variability. On the other hand, the MHD simulation produces a large peak at the time of a solar wind pressure pulse, which is not present in the AE-based proxy for the Joule heat. As solar wind pressure pulses are known to be associated with enhanced ionospheric Joule heating (Palmroth et al., 2004), it is not clear to what extent the discrepancies are associated with limitations of the simulation and to what extent they are caused by the use of index-based proxies that may miss large parts of the dissipation if the measuring stations are not suitably located to record the disturbances. This is clearly an area where more work, both simulation and observational, is required for enhanced understanding of the coupling of the solar wind and the ionospheric processes.
6 Reconnection in the Magnetotail
Space weather events are largely driven by dynamic processes that occur within the magnetotail plasma sheet separating the low-density tail lobes. As was shown before, the large-scale structure of the magnetosphere causes the incoming Poynting flux to focus toward the plasma sheet. This leads to structural changes in the current sheet separating the antiparallel magnetic fields in the lobes, and may lead to bursts of reconnection associated with fast flows both Earthward and tailward of the reconnection region.
The magnetotail plasma sheet is a highly dynamic and structured region. Plasma flows in this region are not laminar, and during most times the net Earthward plasma flow imposed by the large-scale convection pattern is composed of short-lived (1–10 min) bursts of fast flow while the ambient plasma velocity distribution is very nearly isotropic. These flows are most likely created by localized reconnection events initiated either by internal tail processes or by external driving conditions (Baumjohann, 1993; Nagai et al., 2005). While such bursts of fast flow can be observed during all magnetospheric activity conditions, they become more numerous, more intense, and have larger scale sizes during magnetically active conditions. As this is the region which feeds the inner magnetosphere with both plasma, energetic particles, and magnetic flux, the plasma sheet dynamics is crucially important for space weather applications.
As the magnetospheric activity conditions are largely controlled by the stability properties of the cross-tail current sheet, and as the magnetotail current sheet shares many of the properties of dynamically important current sheets found e.g. in the solar plasmas, the dynamics of the cross-tail current has been intensively studied in recent years. In the quiet state, the cross-tail current sheet is rather thick, and the plasma and current sheet tailward of the quasi-dipolar region can be described by a simple one-dimensional Harris current sheet, where the magnetic field is given by Bx = B0 tanh(Z/λ), where B0 is the lobe magnetic field, Z is the coordinate across the current sheet, and λ defines the scale thickness of the current sheet. Closer to the Earth, inside of about 15 RE distance, the current sheet starts to deviate from the one-dimensional structure as the dipole introduces a component perpendicular to the current sheet. In the inner magnetosphere, the multiple plasma populations introduce their own complexity to the system.
As the IMF turns southward, dayside reconnection changes the conditions at the magnetospheric boundaries and begins to increase the open flux content in the magnetotail. In order to maintain pressure balance between the plasma sheet plasma pressure and the lobe magnetic pressure, the cross-tail current intensifies and the plasma sheet is compressed. However, in the region tailward of geostationary orbit out to about 20–30 RE the changes in the current density are not uniform: the total current is distributed between the pre-existing thick plasma/current sheet and a newly formed thin current sheet embedded within the plasma sheet. The thin current sheet is often in the ion gyroradius scale, and can host very high current densities at the field reversal region (1); Sitnov et al., 2006). Furthermore, complex, bifurcated current sheets and large-scale wavy structures have been identified from multi-spacecraft analyses.
As the flows created by magnetic reconnection in the tail enter the inner magnetosphere, the large-scale magnetic field configuration changes rapidly from highly taillike to a much more quasidipolar state. Furthermore, the reconnection process is associated with rapid and significant energy conversion from magnetic energy in the magnetotail lobes to particle kinetic energy and heat in the plasma sheet. The tail field reconfiguration is also associated with strong field-aligned currents to and from the ionosphere, which in part contribute to the energy dissipation in the ionosphere. Thus, the large-scale current disruption, configuration change, and field reconfiguration all are associated with a major energy dissipation process in the magnetosphere.
The structure and dynamics of the current sheet in the magnetotail control the energy storage and release processes initiated with the enhanced dayside reconnection at the magnetopause. The high-speed plasma flows, strong particle energization processes, and rapid reconfiguration all are major parts in creating the space weather effects in the inner magnetosphere.
7 Space Weather in the Inner Magnetosphere
The quasi-dipolar inner magnetosphere extending roughly out to geostationary distance has a variable field structure caused by the competing effects of the internal dipole field, magnetotail current sheet, dayside magnetopause currents, and the ring current within the region itself. Furthermore, the inner magnetosphere hosts multiple plasma populations: the hot ion ring current in the tens to hundreds of keV energy range, the outer van Allen belt electrons with energies from 100 keV up to several MeV, and the cold plasmaspheric plasma (from a few eV to few hundred eV) originating from the ionosphere. Recent research results have emphasized how effectively all these seemingly distinct populations and their dynamics are coupled together (Meredith et al., 2006).
7.1 Time-variable electromagnetic fields
Magnetic storms and substorms affect the electromagnetic field configuration in the inner magnetosphere over time scales of minutes to hours and days. During substorms, the intense current sheet can stretch the quasi-dipolar field lines at geostationary orbit to highly taillike ones, which together with the enhancing electric field causes significant changes in particle drift paths and allows for penetration of the plasma sheet plasma deep inside the inner magnetosphere. In the same way, the strong ring current causes stretching of the magnetic field during magnetic storms, but in this case the changes occur over time scales of days rather than hours. Substorm activity during magnetic storms causes quasiperiodic stretching-dipolarization cycles embedded within the longer-term ring current-associated changes.
The rapidly varying magnetic field induces an electric field (∇ × E = − ∂B/∂t) in the magnetosphere. These induced electric fields are much larger than the large-scale, weak convection electric field imposed by the solar wind flow past the magnetosphere. The small-scale fields can be very intense, include high-frequency fluctuations, and be highly localized in space, which makes their characterization difficult. The large-scale convection field can be given in a simple formulation parametrized by magnetospheric activity or by solar wind parameters (see Section 4). Because of the associated difficulties, there are to date only very few attempts to describe the time-varying, smaller-scale electric fields. However, Li et al. (1998) and Sarris et al. (2002) have described the substorm-associated magnetic field dipolarization and Earthward plasma flows in terms of Earthward-propagating, localized electric field pulses. By computing the magnetic field changes from the electric field and adding those to a simple dipole field and tracing particle drifts under the resulting electromagnetic fields, they were able to reproduce the substorm-associated energetic electron signatures at geostationary orbit. The role of electric fields in the ring current formation and acceleration is treated in more detail below.
7.2 Storm-time ring current
The drift approximation has been quite successfully applied to model inner magnetosphere plasma transport and energization during magnetic storms (Liemohn et al., 2001; Jordanova et al., 2001). However, it has become clear that simplified assumptions about the electric field (assuming large-scale convection only) and magnetic field configuration (assuming time-invariant dipole field) are not sufficient to account for many of the phenomena observed during storms. Replacing the magnetic field with a more realistic (time stationary) model allows plasma transport closer to the Earth in the magnetotail region, as the E × B drift dominates in the taillike magnetic field. On the other hand, a realistic representation of the magnetopause leads to significant particle losses from the dayside magnetosphere. Thus, the effect of a realistic magnetic field model is to decrease the total ring current energy content and make it more asymmetric as the dayside losses decrease the morning-sector fluxes (Ganushkina et al., 2005). Adding localized, time-varying electric field pulses to the model causes significant changes in the energy spectrum: while steady convection creates an intense but rather low-energy ring current, the electric field pulses are effective in accelerating particles to energies of 100 keV and above.
7.3 Changes in the cold plasmasphere
The plasmasphere encircling the Earth is formed by cold ionospheric plasma flowing outward along magnetic field lines. At low latitudes, close to the Earth, magnetic flux tubes follow drift paths that co-rotate with the Earth and therefore are filled with escaping ionospheric plasma in time scales of several days. The location of the outer boundary of the plasmasphere, the plasmapause, is controlled by the relative intensities of the solar wind-imposed electric field and the co-rotation electric field. Although roughly circular in shape, the plasmapause often shows an elongation in the duskside, following the general electric field pattern (Lyons and Williams, 1984). Statistical studies have shown that the position of the plasmapause is correlated with geomagnetic activity, being at smaller radial distances during higher levels of activity (Moldwin et al., 2003). This can be understood by the enhanced convection electric field moving the boundary between the convection-dominated outer region and the co-rotation-dominated inner region closer to the Earth. During magnetic quiescence, the plasmasphere is expanded and the plasmapause can be located outside geostationary orbit. Particularly during low magnetic activity conditions, there is significant variability in the plasmapause location.
During storms, the plasmapause moves inward due to the enhanced solar wind driving, while a drainage plume develops in the dusk sector (Elphic et al., 1996). Within this plume, the cold plasma flows outward toward the magnetopause thus escaping from the plasmasphere. In the nightside, the inward motion of the plasmapause is of the order of 0.5 RE/h, with the changes following the interplanetary magnetic field variations with 20–30 min delay (Spasojević et al., 2003). After the field lines reconnect at the magnetopause, they convect over the polar cap toward the magnetotail, thus providing an additional source of plasma to the tail plasma sheet during storms (Elphic et al., 1997). As the storm driving subsides, the plasmasphere slowly recovers its quiet-time size. The recovery time scale is associated both with the recovery of the quiet-time electric field structure and with the outflow time scale of the cold plasma from the ionosphere. As discussed below, the location of the plasmapause during storms has been shown to be a significant factor in determining the fate of the relativistic electron population in the outer van Allen belt.
7.4 Relativistic electron acceleration and losses
The most significant hazard to Earth-orbiting satellites is posed by high fluxes of relativistic electrons, which can penetrate the spacecraft systems. These electrons are transported under the same electric and magnetic fields as the ring current ions, but their higher speed makes them less sensitive to the details of the electric field structure.
The relativistic electron intensity variations are driven by the solar wind and interplanetary magnetic field conditions. Early studies found a correlation between the relativistic electron flux enhancements and solar wind high speed streams (Paulikas and Blake, 1979). This result was later augmented by the understanding that those high-speed streams that were coincident with southward interplanetary magnetic field were more efficient in enhancing the electron fluxes (Blake et al., 1997). As southward interplanetary field and high solar wind speed are the main drivers of magnetospheric storm activity, it is not surprising that the average electron flux levels trace geomagnetic activity as shown in Figure 18.
However, more detailed analyses revealed that during any individual storm event, the geostationary orbit fluxes can either increase, decrease, or show no effect at storm onset (Reeves, 1998; Reeves et al., 2003). Furthermore, although there is a general correlation between storm activity and electron enhancement, there is no one-to-one correlation that would indicate that higher peak intensity would necessarily lead to higher electron flux levels (O’Brien et al., 2001). Finding the relevant processes has proven to be difficult, as the net change in the fluxes is a consequence of a delicate balance of dynamic and adiabatic effects as well as acceleration and loss processes.
The candidate processes that can account for acceleration of the magnetospheric electrons to relativistic energies can be divided into three major categories: radial diffusion, rapid transport by intense electric field pulses, and local heating via wave-particle interactions. The recirculation model assumes that radial diffusion combined with pitch-angle scattering close to the ionosphere as well as in the equatorial plane can lead to inward motion and hence adiabatic energization of the electrons (Fujimoto and Nishida, 1990). The same adiabatic effects that lead to local reduction of the electron fluxes at storm onset can account for an increase during the storm recovery phase as the magnetospheric activity subsides and the inner magnetosphere recovers its quiet-time quasi-dipolar configuration. Substorm-associated injections transport both electrons and ions rapidly and non-adiabatically over a range of L-shells, which can lead to significant energization. If a suitable seed population of electrons with energies in the several hundred keV range is already present in the inner magnetosphere or near-magnetotail, this process can account for acceleration of electrons to the required MeV energies. Rostoker et al. (1998) proposed that long-duration elevated Pc 5 ultra-high frequency (ULF) wave activity can lead to inward transport and adiabatic heating of electrons whose drift frequency is in resonance with the pulsations. Finally, electrons can be heated by cyclotron resonance with whistler mode chorus waves outside the dusk-sector plasmapause (Summers et al., 1998). During any given storm, one or more of these processes may be active in producing the observed electron acceleration (Friedel et al., 2002).
Electron losses are similarly a combination of many processes (Koskinen, 2005): convective losses by electrons drifting to the dayside magnetopause are significant especially at storm onset when the magnetosphere is often rapidly compressed to almost half of its original size. Several wave modes interacting with the electrons at resonant energies can scatter them to the atmospheric loss cone hence leading to increased precipitation and loss of electrons from the magnetosphere. Plasmaspheric hiss is a wave mode confined within the plasmasphere, driven unstable by gyroresonant interaction with energetic electrons. Lightning-induced whistler modes or man-made very low frequency (VLF) signals in the inner magnetosphere interact strongly with relativistic electrons. Electromagnetic ion cyclotron (EMIC) waves in turn are excited near the duskside plasmapause as a result of cyclotron resonance with anisotropic ring current ions, and also interact with the van Allen belt electron population. Again, it is likely that more than one process is active in the inner magnetosphere during any given time.
Results presented in this section highlight the strong coupling between the different plasma and energetic particle populations in the inner magnetosphere: The magnetic field configuration is a key element in determining the adiabatic transport properties of both electrons and ions. The field configuration is determined by the large-scale current systems, in the inner magnetosphere mainly the ring current carried by energetic ions. Hence, the ring current ions affect the relativistic electron population through their influence on the field configuration and through their influence on wave development. Changes in the large-scale convection electric field change the plasmaspheric configuration thus changing the locations where the plasmaspheric hiss (in the nightside, inside the plasmapause), EMIC waves (in the dusk sector, inside the plasmapause), and whistler mode chorus waves (in the morning sector, outside the plasmapause) occur. As these wave modes are key elements for both acceleration and loss of the relativistic electrons, the plasmasphere and its dynamics driven by the large-scale convection electric field play a key role in the relativistic electron problem. Substorms are associated with inductive, localized electric fields, and are effective in transporting both electrons and ions to the inner magnetosphere. The rapid field variations provide a means for pitch-angle scattering as well as inward transport and adiabatic energization of the electrons. The substorm-associated energetic electrons can act as a seed population that, if further energized, can become part of the outer van Allen belt relativistic electron population. In summary, while the relativistic electrons themselves interact relatively weakly with the other plasma populations, it seems that resolving their temporal evolution requires detailed knowledge of the dynamics and coupling of as well the cold plasmasphere, hot ring current, tail plasma sheet as the electromagnetic fields guiding the particle motions.
8 Space Weather Effects
8.1 Effects in the magnetosphere
High-energy ions trapped in the Earth’s magnetic field can cause significant effects in spacecraft systems. While malfunctions such as memory upsets can occur almost anywhere, a vast majority of the events are observed in the southern hemisphere over the South Atlantic Anomaly region where the Earth’s magnetic field is weakest and the energetic particles thus have best access to altitudes where the low-Earth-orbiting spacecraft reside (∼ 300–1000km altitude). Furthermore, the high energies above tens of MeV make galactic cosmic rays highly penetrating into the satellite systems, where they can cause a wide variety of harmful effects (Baker et al., 2001).
Solar energetic particles arising from active events on the Sun cause degradation and failure of space-borne systems. Especially, single event upsets can occur in electronic components when a charged particle (e.g., a heavy ion) ionizes a track along a sensitive part of the circuit and causes the circuit to change state. Single event upsets are commonly detected in transistors and spacecraft memory devices. Error-correcting software solutions have been developed to decrease the damages to the satellite operations.
High-energy electrons in the outer Van Allen radiation belts can penetrate through spacecraft walls and through electronics boxes and become buried in dielectric materials (Baker et al., 1987). The excess negative charge can give rise to potential differences, which in turn can lead to intense voltage discharges and surges of electric energy deep inside the electric circuits of the spacecraft causing severe damage to various subsystems. The discharges can produce short-lived (fractions of a microsecond) but intense (several Amperes) current pulses. As the anomalies tend to occur only during relatively long-duration events, it is not only the peak intensity of the electron flux but also the duration of the exposure that determines the amount of excess charge accumulation.
Moderate-energy electrons associated with substorms cause spacecraft surface charging (Garrett, 1981). During a surface charging event, insulated surfaces may charge to several kilovolts potential (typically negative relative to the ambient plasma). In hot, tenuous plasmas, the incident electrons and ions and the secondary photoelectrons and scattered electrons are not in current balance, which leads to potential buildup at the spacecraft. Differential charging of spacecraft surfaces can lead to harmful discharges, which introduce noise to the system and may interrupt normal spacecraft operations and/or represent false commands for the spacecraft. The discharge breakdown can cause physical damage which can change the satellite conductivity or thermal, chemical or optical properties.
Besides being a threat to technological systems, energetic particles pose a hazard to astronauts on space missions. The atmosphere effectively shields the Earth from high-energy particles such that only the highest-energy particles can gain access to the lower layers of the atmosphere, and only in the polar regions where the geomagnetic field is weakest. However, astronauts in orbit are relatively unprotected especially during the high-latitude parts of the spacecraft orbit. For example, the International Space Station reaches latitudes above 50°, which is sufficiently high to increase the health risks especially during extra-vehicular operations. Furthermore, as the atmospheric shielding is significantly reduced above 10 km altitude, aircraft crews and passengers on transpolar routes are subjected to increased radiation doses from the energetic particles. In practice, this problem is dealt with by limiting the number of transpolar flights the crewmembers can take in a given time period. As the fluxes of energetic particles are strongly modulated by the solar activity, these problems are largest during sunspot maxima.
8.2 Effects in the ionosphere
Satellite navigation systems such as the U.S. Global Positioning System (GPS) or the European Galileo operate by transmitting radio waves from the spacecraft to ground-based receivers. Signals from several satellites are then used to calculate the observing position to high accuracy. As the signals propagate through the ionosphere, they are refracted and slowed especially when they traverse regions of intense auroral currents. In addition, ionospheric scintillations can cause loss of signal lock and thereby lose the positioning capability. While many of the malfunctions associated with energetic particles can be counteracted by engineering the spacecraft with more shielding and redundancy in the systems, this is one where accurate specification of the ionospheric conditions and modeling their effects on the signal propagation is the only way the high accuracy of the positioning information can be maintained with single-frequency receivers.
The ionosphere is heavily utilized as a transmitter of radio-frequency communication signals. As every radio amateur knows, the radio wave communication is significantly influenced by the ionospheric properties and especially the auroral currents. High frequency (HF) radio wave communications are most affected, as they utilize reflection from the ionosphere to carry the signal to distances beyond the local horizon. At times of high auroral activity, the signal can be even completely absorbed making the HF radio propagation impossible. Furthermore, the telecommunication systems increasingly utilize ultra-high-frequency (UHF) bands to transmit signal to satellites to be relayed to other locations. Also this frequency range is vulnerable to the auroral currents in the ionosphere, and can be degraded or even completely lost during times of high activity (Lanzerotti, 2001b).
8.3 Effects in the atmosphere
Low-Earth-orbiting satellites are gradually slowed by the atmospheric drag, which finally leads to the spacecraft re-entry. The atmospheric drag depends on the atmospheric neutral density, which at a given altitude is strongly modulated by the heating and increase of the scale height associated with geomagnetic activity. The increasing atmospheric density during only a single storm can cause a major loss of altitude of the spacecraft. On a longer time scale, changes in the ionization caused by the solar UV radiation cause a significant solar cycle modulation on the neutral density (Hastings and Garret, 1996).
In the middle atmosphere, precipitating energetic particles can significantly affect the chemical processes that are involved in the formation of odd nitrogen compounds. Recent simultaneous observations of a strong increase of solar protons and the global NOx concentration in the atmosphere have clearly established the causal relationship between the solar proton events and the enhancement of odd nitrogen compounds. If sufficient downward transport is available, these nitrogen compounds can reach the stratospheric altitudes and through catalytic reaction chains to strong decrease of the stratospheric ozone Seppälä et al. (2006). The effects caused by these short-lived solar proton events can last for months in the atmosphere. Similarly, relativistic electrons from the magnetosphere affect the nitrogen chemistry at somewhat higher altitudes (50–100 km).
As the amount of energy from the Sun reaching the surface of the Earth is variable, it is only natural to expect that its long-term variations would affect the large-scale climatology of the Earth. The “solar constant” that averages to about 1368 W/m2 has been shown to exhibit a distinct solar cycle variation. The total solar irradiance also varies at 27-day intervals, the variability being larger during high solar activity than during solar minimum conditions. The ultraviolet part of the spectrum is also a strong modulator of the production of ozone, which is clearly demonstrated in the annual variation of the polar ozone holes which intensify during the local spring when the amount of UV radiation increases.
Any change in the balance between incident and outgoing radiation can have an effect on the climate. Changes in the incoming energy may be associated with changes in cloudiness, amount of volcanic dust in the atmosphere, and amounts of either natural or anthropogenic origin aerosols. Changes in the amount of energy radiated away from Earth can be associated with the varying amounts of greenhouse gases in the atmosphere such as carbon dioxide, methane, CFCs, or ozone. The surface properties are also important for the reflected radiation, as the albedos for ice cover, vegetation, and soil are quite different.
There is experimental evidence that the global temperature variations are correlated with a number of space physic parameters: the long term temperature anomaly follows the filtered solar cycle length, which is a measure of the intensity of the solar cycle (Friis-Christensen and Lassen, 1991). The global cloud coverage anomalies are correlated with the mean values of the galactic cosmic ray flux, which is modulated by the solar cycle as the stronger solar wind pressure during solar maximum tends to decrease the amount of anomalous cosmic rays that can reach the inner solar system (Marsh and Svensmark, 2000).
While statistical studies have found strong correlations of solar activity parameters and climatological parameters, the reasons for these changes are not fully understood. Furthermore, it is probable that several different processes influence the observed correlations. The effects of the varying total solar irradiance are too small to be of major importance for the climate change. The correlation of cosmic rays on only low-altitude cloud cover suggests that the cosmic rays may influence the formation of aerosols and through that the abundance of condensation nuclei in the atmosphere which can form liquid water drops. At ground level, the cosmic ray particles cause ionization, and the associated vertical electric currents can influence the production of ice-forming nuclei and clouds in the upper troposphere. These effects might be related to local decreases in the amount of cloud cover associated with short-term changes in the cosmic rays due to increased solar activity.
8.4 Effects on ground
Space weather effects are seen even on ground, as strong currents in the ionosphere can induce currents in long baseline conductor systems on ground. Affected systems include electric power transmission networks, oil and gas pipelines, telecommunication cables and railways systems. In power grids, these geomagnetically induced currents cause saturation of transformers, which tends to distort and increase the excitation current. The excitation current in turn induces harmonics in the electricity, unwanted relay trippings, large reactive power consumption, or voltage fluctuations, which can lead to black-outs or to permanent damage of transformers (Kappenman, 1996).
In buried pipelines, geomagnetically induced currents and the associated pipe-to-soil voltages contribute to corrosion and disturb corrosion control surveys and protection systems (Boteler, 2000). Telecommunication devices may experience overvoltages. As optical fibre cables do not carry induced currents, space weather risks on telecommunication equipment are probably smaller today than they were earlier. However, metal wires are still used in parallel with optical cables for the power to repeat stations.
The first observations of space weather-associated induced currents were made already in early telegraph systems more than 150 years ago (Boteler et al., 1998). In general, being related to auroral phenomena, the geomagnetically induced currents are a high-latitude problem, affecting most regions such as the Scandinavian countries, Russia, and Canada. The amount of induced current in a system is not directly related to the distance to the auroral currents; the ground resistivity and the particular network configuration and its resistances have an important contribution in determining the size of the disturbance. This makes the observed induced current values highly variable from site to site and from system to system. The current magnitudes that are a potential risk for a power transmission system are highly dependent on transformer design and on other engineering details of the network. This means that any space weather hazard assessment must include the details of the engineering solutions in the estimates.
9 Space Weather Predictions
Electron radiation belt climatology has shown that the entire outer radiation zone tends to vary in a relatively coherent way under the influece of major external drivers (high-speed solar wind streams, CMEs, magnetic clouds). Thus, it is possible to use the gross behavior of the outer zone electron population on day timescales using a single or a few satellites only. Specification models that use magnetic activity indices can be used to characterize the state of the outer radiation belt (Moorer and Baker, 2001). Prediction schemes have been developed based on a combination of earlier values of radiation belt fluxes, and past and present solar wind parameters. When these conditions are compared against a database of earlier driver-effect events, the closest comparison event can be used as a forecast of what lies 24–48 hours ahead. Because both past radiation belt and solar wind driver information is used, this analogue forecast method is robustly successful for both quiet and disturbed conditions.
Coronal mass ejection occurrence is routinely recorded and their travel direction determined from solar coronagraph data. Space weather warnings are given for those ICME events that propagate in a direction that probably will lead to encounter with the Earth’s space environment. However, the effects in the near-Earth environment critically depend on the polarity of the magnetic cloud, i.e., whether the magnetic field rotates from north to south or vice versa. From solar observations alone, it is impossible to detect either the solar wind speed in interplanetary space (which is different from the speed near the solar surface) or the structure of the magnetic field and hence the intensity and duration of the geoeffective southward field direction. However, the polarity of the ICME structure shows a statistical dependence on the solar cycle: the preferred leading polarity rotating from south to north is observed during the rising phase of odd-numbered solar cycles, while the opposite polarity is observed during the rising phase of even-numbered cycles (Bothmer and Rust, 1997). Details of the storm intensity can only be predicted when the ICME has propagated to L1 distance (First Lagrangian point at 220 RE upwind from the Earth) where the solar wind monitors (presently SOHO and ACE) record the polarity and intensity of the interplanetary magnetic field and the velocity and density structure of the solar wind plasma. Thus, more detailed predictions of ICMEs as well as any predictions of activity driven by other solar wind and IMF structures not observable by means other than in-situ measurements are available only 30–60 minutes prior to its arrival at Earth.
As the energetic solar particles travel to the Earth within a few tens of minutes, detection of active events in the Sun means an almost instantaneous response at Earth. Solar X-ray monitors routinely monitor the Earth’s environment providing nowcasts of the space environment.
10 Concluding Remarks
This review presents the physical basics for understanding why and how solar activity affects technological systems and humans in space and on ground. The final goal of space weather research is to be able to produce reliable forecasts and nowcasts of the space environment as well as assess the risks that are associated with a wide variety of technological applications. While tremendous progress has been made during the recent years, the field still faces several major challenges.
Observations of the near-Earth space environment are sparse and information of the global properties are often not available, as the plasmas for the most part are too tenuous for imaging. Beginning from the solar wind observations, a single point measurement in the solar wind, sometimes far away from the Sun-Earth line, is not always sufficient to determine what impinges on the magnetopause an hour later. In the magnetosphere, the lack of global observations of the mass and energy circulation as well as the dynamics of the electromagnetic fields still limit our capabilities to evaluate the variety of physical processes that can be associated with the observed phenomena. On the ground, the largest and most harmful currents are highly localized, which makes their detection as well as prediction challenging. In many instances, the magnetospheric activity can be quantitatively classified only based on a variety of magnetic indices and proxies derived using the solar wind input and the magnetic indices. It is clear that such proxies include both systematic and statistical errors, which limits our capability to establish causal correlations.
Large-scale or global models of the coupled solar wind-magnetosphere-ionosphere system have advanced greatly in the recent past, both due to better understanding of the critical processes and due to the increased computational capabilities. Global MHD simulations can be run in near-real time, and in many cases reproduce the observed topological changes and even in-situ measurements to quite good accuracy. On the other hand, their use still has serious limitations, both due to missing physics especially in the ionosphere and in the inner magnetosphere, and due to the limitations of the MHD approach in describing the collisionless, multicomponent plasmas in the magnetosphere. While hybrid codes describing the full ion motion while treating the electrons as a fluid already are available for our sister planets, the strong magnetic field and the large system size still limits that approach to localized problems in the terrestrial magnetosphere.
For prediction of the hazards, it is important to note that the effects are dependent both on the space environment and on the engineering and operations of the technological system, be that a telecommunication satellite or a power transmission line on ground. Warnings and predictions can be effectively used to schedule non-standard or maintenance operations during periods of low solar activity, while better shielding and other design improvements are key for successful operations and long lifetime of the systems. To reach these goals requires close contacts between space physics and engineering sciences.
The author thanks Minna Palmroth and Tiera Laitinen for many useful discussions on global MHD simulations as well as for providing GUMICS-4 simulation results for this paper. Mike Wiltberger is thanked for providing LFM simulation results. Nataly Ganushkina and Marina Kubyshkina are thanked for useful discussions regarding the inner magnetosphere empirical modeling and for providing model results for this paper.
- Alves, M.V., Echer, E., Gonzalez, W.D., 2006, “Geoeffectiveness of corotating interaction regions as measured by Dst index”, J. Geophys. Res., 111Google Scholar
- Baumjohann, W., Pellinen, R.J., Opgenoorth, H.J., Nielsen, E., 1981, “Joint two-dimensional observations of ground magnetic and ionospheric electric fields associated with auroral zone currents: Current systems associated with local auroral break-ups”, Planet. Space Sci., 29, 431. Related online version (cited on 9 January 2007): http://adsabs.harvard.edu/abs/1981P7.26SS...29..431BADSCrossRefGoogle Scholar
- Chamberlain, J.W., 1963, “Planetary coronae and atmospheric evaporation”, Planet. Space Sci., 11, 901–960. Related online version (cited on 9 Janury 2007): http://adsabs.harvard.edu/abs/1963P7.26SS...11..901CADSCrossRefGoogle Scholar
- Crooker, N.U., Gosling, J.T., Bothmer, V., Forsyth, R.J., Gazis, P.R., Hewish, A., Horbury, T.S., Intriligator, D.S., Jokipii, J.R., Kota, J., Lazarus, A.J., Lee, M.A.1, Lucek, E., Marsch, E., Posner, A., Richardson, I.G., Roelof, E.C., Schmidt, J.M., Siscoe, G.L., Tsurutani, B.T., Wimmer-Schweingruber, R.F., 1999, “CIR Morphology, Turbulence, Discontinuities, and Energetic Particles”, Space Sci. Rev., 89, 179–220ADSCrossRefGoogle Scholar
- Daglis, I.A., Kamide, Y., 2003, “The role of magnetosphere-ionosphere coupling in magnetic storm dynamics”, in Disturbances in Geospace: The Storm-Substorm Relationship, (Eds.) Sharma, A.S., Kamide, Y., Lakhina, G.S., vol. 142 of Geophysical Monograph, pp. 119–129, American Geophysical Union, Washington, U.S.A.CrossRefGoogle Scholar
- Farrugia, C.J., Burlaga, L.F., Lepping, R.P., 1997, “Magnetic clouds and the quiet-storm effect at Earth”, in Magnetic Storms, (Eds.) Tsurutani, B.T., Gonzalez, W.D., Kamide, Y., Arballo, J.K., vol. 98 of Geophysical Monograph, pp. 91–106, American Geophysical Union, Washington, U.S.A.CrossRefGoogle Scholar
- Fok, M.-C., Moore, T.E., Wilson, G.R., Perez, J.D., Zhang, X.X., Brandt, P.C., Mitchell, D.G., Roelof, E.C., Jahn, J.-M., Pollock, C.J., Wolf, R.A., 2003, “Global ENA IMAGE simulations”, Space Sci. Rev., 109, 77–103. Related online version (cited on 9 January 2007): http://adsabs.harvard.edu/abs/2003SSRv..109...77FADSCrossRefGoogle Scholar
- Gombosi, T.I., De Zeeuw, D.L., Groth, C.P.T., Powell, K.G., 2000, “Magnetospheric configuration for Parker-spiral IMF conditions: Results of a 3D AMR MHD simulation”, Adv. Space Res., 26, 139–149. Related online version (cited on 9 January 2007): http://adsabs.harvard.edu/abs/2000AdSpR..26..139GADSCrossRefGoogle Scholar
- Hones Jr, E.W., 1979, “Plasma flow in the magnetotail and its implications for substorm theories”, in Dynamics of the magnetosphere, (Ed.) Akasofu, S.-I., Proceedings of the A.G.U. Chapman Conference ‘Magnetospheric Substorms and Related Plasma Processes’, held at Los Alamos Scientific Laboratory, Los Alamos, N.M., U.S.A., October 9–13, 1978, vol. 78 of Astrophysics and Space Science Library, pp. 545–562, D. Reidel, Dordrecht, Netherlands; Boston, U.S.A.CrossRefGoogle Scholar
- Hundhausen, A.J., 1972, Coronal Expansion and Solar Wind, vol. 5 of Physics and Chemistry in Space, Springer, Berlin, Germany; New York, U.S.A.Google Scholar
- Janhunen, P., 1996, “GUMICS-3: A global ionosphere-magnetosphere coupling simulation with high ionospheric resolution”, in Environment Modelling for Space-based Applications, (Eds.) Hilgers, A., Guyenne, T.-D., Proceedings of the symposium held at ESTEC, Noordwijk, 18–20 September 1996, vol. SP-392 of ESA Conference Proceedings, p. 233, ESA Publications Division, Nordwijk, Netherlands. Related online version (cited on 8 January 2007): http://www.ava.fmi.fi/~pjanhune/papers/ESTEC96/ESTEC96.htmlGoogle Scholar
- Koskinen, H.E.J., 2005, “Energetic particle losses from the inner magnetosphere”, in The Inner Magnetosphere: Physics and Modeling, (Eds.) Pulkkinen, T.I., Tsyganenko, N.A., Friedel, R.H.W., vol. 155 of Geophysical Monograph, pp. 23–31, American Geophysical Union, Washington, U.S.A.CrossRefGoogle Scholar
- Lanzerotti, L.J., 2001a, “Space weather effects on technologies”, in Space Weather, (Eds.) Song, P., Singer, H.J., Siscoe, G.L., p. 11, American Geophysical Union, Washington, U.S.A.Google Scholar
- Lanzerotti, L.J., 2001b, “Space Weather Effects on Communications”, in Space Storms and Space Weather Hazards, (Ed.) Daglis, I.A., Proceedings of the NATO Advanced Study Institute, Greece 19–29 June, 2000, vol. 38 of NATO Science Series II, pp. 313–334, Kluwer, Dordrecht, Netherlands; Boston, U.S.A.CrossRefGoogle Scholar
- Lui, A.T.Y., Anger, C.D., 1973, “A uniform belt of diffuse auroral emission seen by the ISIS-2 scanning photometer”, Planet. Space Sci., 21, 799–802. Related online version (cited on 9 January 2007): http://adsabs.harvard.edu/abs/1973P726SS...21..799LADSCrossRefGoogle Scholar
- Lundin, R., Barabash, S., Andersson, H., Holmstrom, M., Grigoriev, A., Yamauchi, M., Sauvaud, J.-A., Fedorov, A., Budnik, E., Thocaven, J.-J., Winningham, D., Frahm, R., Scherrer, J., Sharber, J., Asamura, K., Hayakawa, H., Coates, A., Linder, D.R., Curtis, C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Reading, D.H., Koskinen, H.E.J., Kallio, E., Riihela, P., Schmidt, W., Sales, T., Kozyra, J., Krupp, N., Woch, J., Luhmann, J., McKenna-Lawler, S., Cerulli-Irelli, R., Orsini, S., Maggi, M., Mura, A., Milillo, A., Roelof, E.C., Williams, D.J., Livi, S., Brandt, P.C., Wurz, P., Bochsler, P., 2001, “Solar Wind-Induced Atmospheric Erosion at Mars: First Results from ASPERA-3 on Mars Express”, Science, 305, 1933–1936ADSCrossRefGoogle Scholar
- Manchester IV, W.B., Gombosi, T.I., Roussev, I., Ridley, A., De Zeeuw, D.L., Sokolov, I.V., Powell, K.G., Toth, G., 2004, “Modeling a space weather event from the Sun to the Earth: CME generation and interplanetary propagation”, J. Geophys. Res., 109Google Scholar
- Meredith, N.P., Horne, R.B., Glauert, S.A., Thorne, R.M., Summers, D., Albert, J.M., Anderson, R.R., 2006, “Energetic outer zone electron loss timescales during low geomagnetic activity”, J. Geophys. Res., 111Google Scholar
- Moorer, D.R., Baker, D.N., 2001, “Specification of Energetic Magnetospheric Electrons”, in Space Weather, (Eds.) Song, P., Singer, H.J., Siscoe, G.L., vol. 125 of Geophysical Monograph, pp. 3321–328, American Geophysical Union, Washington, U.S.A.Google Scholar
- Nagai, T., Fujimoto, M., Nakamura, R., Baumjohann, W., Ieda, A., Shinohara, I., Machida, S., Saito, Y., Mukai, T., 2005, “Solar wind control of the radial distance of the magnetic reconnection site in the magnetotail”, J. Geophys. Res., 110Google Scholar
- Palmroth, M., Pulkkinen, T.I., Janhunen, P., McComas, D.J., Smith, C.W., Koskinen, H.E.J., 2004, “Role of solar wind dynamic pressure in driving ionospheric Joule heating”, J. Geophys. Res., 109Google Scholar
- Papadopoulos, K., Goodrich, C., Wiltberger, M., Lopez, R.E., Lyon, J.G., 1999, “The physics of substorms as revealed by the ISTP”, Phys. Chem. Earth, 24, 189–202Google Scholar
- Paulikas, G.A., Blake, J.B., 1979, “Effects of the solar wind on magnetospheric dynamics: Energetic electrons at the synchronous orbit”, in Quantitative modeling of magnetospheric processes, (Ed.) Olson, W.P., vol. 21 of Geophysical Monograph, pp. 180–202, American Geophysical Union, Washington, U.S.A.CrossRefGoogle Scholar
- Pulkkinen, T.I., Ganushkina, N.Y., Tanskanen, E.I., Kubyshkina, M.V., Reeves, G.D., Thomsen, M.F., Russell, C.T., Singer, H.J., Slavin, J.A., Gjerloev, J.W., 2006, “Magnetospheric current systems during stormtime sawtooth events”, J. Geophys. Res., 111Google Scholar
- Raeder, J., Wang, Y.L., Fuller-Rowell, T.J., Singer, H.J., 2001, “Global Simulation of Magnetospheric Space Weather Effects of the Bastille Day Storm”, Solar Phys., 204, 323–337. Related online version (cited on 9 January 2007): http://adsabs.harvard.edu/abs/2001SoPh..204..323RADSCrossRefGoogle Scholar
- Roederer, J.G., 1970, Dynamics of Geomagnetically Trapped Radiation, vol. 2 of Physics and Chemistry in Space, Springer, Berlin, Germany; New York, U.S.A.Google Scholar
- Runov, A., Sergeev, V.A., Nakamura, R., Baumjohann, W., Apatenkov, S., Asano, Y., Takada, T., Volwerk, M., Voros, Z., Zhang, T.L., Sauvaud, J.-A., Reme, H., Balogh, A., 2006, “Local structure of the magnetotail current sheet: 2001 Cluster observations”, Ann. Geophys., 24, 247–262ADSCrossRefGoogle Scholar
- Schwenn, R., 2006, “Space Weather: The Solar Perspective”, Living Rev. Solar Phys., 3, lrsp-2006-2. URL (cited on 8 January 2007): http://www.livingreviews.org/lrsp-2006-2
- Seppälä, A., Verronen, P.T., Sofieva, V.F., Tamminen, J., Kyrola, E., Rodger, C.J., Clilverd, M.A., 2006, “Destruction of the tertiary ozone maximum during a solar proton event”, Geophys. Res. Lett., 33Google Scholar
- Tanskanen, E.I., Pulkkinen, T.I., Koskinen, H.E.J., 2002, “Substorm energy budget near solar minimum and maximum: 1997 and 1999 compared”, J. Geophys. Res., 107Google Scholar
- Tsurutani, B.T., Gonzalez, W.D., 1987, “The cause of high-intensity long-duration continuous AE activity (HILDCAAs): Interplanetary Alfvén wave trains”, Planet. Space Sci., 35, 405–412. Related online version (cited on 9 January 2007): http://adsabs.harvard.edu/abs/1987P7.26SS...35..405TADSCrossRefGoogle Scholar
- Tsyganenko, N.A., Singer, H.J., Kasper, J.C., 2003, “Storm-time distortion of the inner magnetosphere: How severe can it get?”, J. Geophys. Res., 108, 1209Google Scholar | <urn:uuid:122c3990-f8b9-46ae-b51e-d0e56a9435b0> | 3.375 | 18,845 | Academic Writing | Science & Tech. | 37.387725 | 95,585,254 |