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Sapphire is a node.js application framework, specifically designed for the creation of Single Page Applications (SPA). These applications have a number of special considerations over more traditional web applications, for example, hot loading of parts of the application when they are needed, construction of the application from multiple sources, AJAX service functions to perform backend actions and retrieve updated data, and a front end API that ties it all together.
For full documentation of Sapphire, check out the Sapphire Site.
Quick Install Guide
npm install -g sapphire-express cd project sapphire install npm install
Creating a project
sapphire app test
here #windows . here #osx or linux node server
What's going on here?
When Sapphire is installed globally, it creates a command line interface that can be used to create skeletons for a number of Sapphire specific features. The two options used here are install and app. The first creates a sapphire installation in the current directory. This will install the default sapphire server.js file, a config directory with default confiuration files and a package.json file with the required npm packages. It also creates a batch or shell script called here that can be used to setup the necessary environment variables to point Sapphire at the configuration files.
The second option, app, creates a basic application. In this case, we are creating the application "test". The application isn't very exciting, but it's a place to start.
For a more indepth look at Sapphire, checkout the the Sapphire Site. | <urn:uuid:f17b7243-f33b-455c-ac61-d74cfdcbca40> | 2.578125 | 319 | Product Page | Software Dev. | 40.251941 | 95,538,999 |
Crater Outflow (Venus)
Reference work entry
A crater outflow is a relatively thin (sometimes radar transparent) and often lobate lava-like flow feature associated with an impact crater on Venus. A crater outflow is typically asymmetrically distributed around a crater.
Crater outflows are clearly distinguished from ballistic ejecta. Many of them have an often lobate, radar-bright, lava-like deposit originating within the continuous ejecta blanket and flow for up to several crater diameters along topographic gradients but in some cases, initially uphill (downrange from the crater). They often have fluvial-like morphologies and sinuous channels originating on, cutting through, and continuing away from fluidized ejecta blankets (Johnson and Gaddis 1996; Komatsu et al. 1991). The...
- Duval DM, Wood CA (1992) Impact crater flows on Venus: morphological evidence for complex ejection dynamics. Lunar Planet Sci Conf XXIII:321, HoustonGoogle Scholar
- Herrick RR, Sharpton VL, Malin MC, Lyons SN, Feely K (1997) Morphology and morphometry of impact craters. In: Bougher SW, Hunten DM, Phillips RJ (eds) Venus II. University of Arizona Press, pp 1015–1046. Database available online: http://www.lpi.usra.edu/resources/vc/
- Komatsu G, Kargel JS, Baker VR, Lewis JS, Strom RG (1991) Fluidized impact ejecta and associated impact melt channels on Venus. Lunar Planet Sci Conf 22:741Google Scholar
© Springer Science+Business Media New York 2015 | <urn:uuid:bb470613-d532-49f6-9ab8-670e96d92a1a> | 2.78125 | 347 | Academic Writing | Science & Tech. | 40.784069 | 95,539,039 |
The total number of procedures performed went down from 2015 by 5% to 3.94 million procedures. This included 4,932 procedures on 3,530 dogs, 3,569 procedures on 2,440 primates. 3.87 million animals were used overall.
Of the 1.91 million genetically altered animals created or bred, nearly all were mice (86% or 1.65 million procedures). Creation of many different strains of animals with genetic mutations to single genes is the main reason for such high numbers; as they need to be bred in large numbers to maintain the desired mutation. The number of genetically altered animals used in experiments has also continued to rise over the past 10 years, with another 1% increase from 2015 (720,000 procedures) to 2016 (729,000 procedures).
GM animals are defined as those with genetic characteristics that have been altered using genetic engineering and HM animals are those possessing one or more genes that have undergone mutation either naturally or deliberately induced and that are known to be harmful to the animal.
The main reason for such large numbers is the creation of many different animal strains with very specific and targeted genetic mutations to single genes. Such specifically altered animals (mainly mice) would require a large number of additional identical animals to be bred in order to maintain the desired mutation within that particular strain.
Between 2007 and 2016, the total number of procedures increased by 23% (735,000 procedures). The creation/breeding of genetically altered animals primarily accounted for this rise (745,000 procedures), while the number of experimental procedures decreased by 9,400 procedures.
Of the 2.02 million experimental procedures completed in 2016, the majority involved mice, 60% (1.22 million procedures); fish, 14% (287,000 procedures); rats, 12% (239,000 procedures) and birds; 7% (150,000 procedures). Experimental procedures involving specially protected species (i.e. horses, donkeys, dogs, cats, and non-human primates) accounted for 0.9% (18,000) of procedures in 2016.
Of note is the fact that the severity assessments for 2.02 million experimental procedures (not including breeding) completed in 2016 show a rise in the number of procedures assessed as moderate or severe. In total, 35% of all procedures were assessed as moderate or severe compared with 30% in 2015. The number of procedures assessed as mild went down from 51% to 46%.
For the full report on the statistics on animal use in scientific research visit the National Statistics page for Annual statistics relating to scientific procedures performed on living animals in accordance with Animals (Scientific Procedures) Act 1986 on the GOV.UK website.
Animal Free Research UK is showing how research that helps us fundamentally understand human biology and disease can and should take place without the need to use any animals. | <urn:uuid:a4092f82-6f83-45bd-8089-254e8763fe09> | 3.046875 | 575 | Knowledge Article | Science & Tech. | 43.556129 | 95,539,042 |
There are high costs and high risks associated with the consequences of space weather events, as insurance companies recognise.
Intense space weather events are triggered by the explosive release of energy stored in the Sun’s magnetic field.
A strong burst of electromagnetic energy reaches the Earth with the potential to disrupt many of our fundamental services, such as satellite and aviation operations, navigation, and electricity power grids. Telecommunications and information technology are likewise vulnerable to space weather.
Research by the Radio and Space Plasma Physics Group in the University of Leicester’s Department of Physics and Astronomy helps our understanding of coupling processes between the solar wind and the Earth’s magnetosphere by allowing the observation of the consequences of space weather with an unprecedented resolution.
Postgraduate researcher James Borderick explained: “We introduce the importance of utilising ground-based measurements of the near space environment in conjunction with spacecraft observations and then proceed to explain the direct influences of space weather on our own technological systems.
“Utilising our new radar modes and an international array of ground-based and space-based instruments, we are ever increasing our understanding of the countless phenomena associated with the solar-terrestrial interaction.”
“One day this may lead us to the accurate predictions of the occurrence and consequences of phenomena such as Coronal Mass Ejections (CMEs), and perhaps an active defence.”
The use of ground-based radars for observations of ionospheric and magnetospheric dynamics is well established. The Super Dual Auroral Radar Network (SuperDARN) consists of networks of High-Frequency radars surrounding the northern and southern poles, which have yielded extensive data on our near space environment.
A new “double pulse” pulse sequence has been implemented on the Radio Space Plasma Physics Group’s Co-operative UK Twin Located Auroral Sounding System (CUTLASS) radars. CUTLASS forms part of SuperDARN.
The new sounding mode enhances the temporal resolution of observations of plasma irregularities within the ionosphere. It increases the cadence of pulse transmissions within the same transmission time as the standard SuperDARN-operating mode.
As an undergraduate physicist at the University of Leicester, he was awarded both the Philips and Departmental Prizes in Physics and achieved the highest mark of all 4th year undergraduates in his final year. Between his penultimate and final years, he obtained a position on the prestigious SURE research programme where he conducted a preliminary investigation on the coupling processes between the Solar Wind and the Earth’s magnetic field. He has just recently presented his Double Pulse findings at the SuperDARN Conference of 2008 in New South Wales, Australia. In the future, he hopes to continue in academia, forwarding science and simultaneously enthusing the next generation of scientists.
The research is being presented to the public at the University of Leicester on Thursday 26th June. The Festival of Postgraduate Research introduces employers and the public to the next generation of innovators and cutting-edge researchers, and gives postgraduate researchers the opportunity to explain the real world implications of their research to a wide ranging audience.
More information about the Festival of Postgraduate Research is available at: www.le.ac.uk/gradschool/festival
Ather Mirza | alfa
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
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18.07.2018 | Materials Sciences | <urn:uuid:a1ade669-d78c-497f-a447-a321b1ce6219> | 3.109375 | 1,317 | Content Listing | Science & Tech. | 30.346104 | 95,539,056 |
what is the big idea of energy? To A. Einstein, it was that Energy and Mass are equivalent, and that the sum total of both, with a factor called entropy, is constant in the universe. what is the big idea of energy i need help on finding
what is the big idea of energy? The big idea for me is that mass and energy is one in the same, that each can be converted to the other. For some others, the big idea is that Entropy is created from useful energy, and in natural processes,
iron+sulphur together are a mixture of small grains yellow and dark grey.Its chemical symbol is 'Fe + S'.When it reacts with oxygen they create a new chemical substance; Iron Sulphide. What do you put for 'explain the reaction using …
Hi Im in year 7 and to get a level 6 we have to explain the big idea of energy. Our project is about the reation of iron and sulphur to make iron sulphide. We have been told to explain using the big idea of energy. pls help me asap!!!! | <urn:uuid:15905a1a-a7b8-423c-a969-c7b3fc02337f> | 3.046875 | 227 | Q&A Forum | Science & Tech. | 68.713516 | 95,539,057 |
Astronomers were able to see, for the first time, the light of a star different from the sun, deformed by the gravitational force of a nearby object
Astrophysicists have been able to confirm , thanks to the Hubble Space Telescope, a corollary of Albert Einstein ‘s theory of general relativity enunciated more than a century ago, which was thought to be impossible to obtain direct observation in distant stars .
These astronomers were able to see, for the first time, the light of a star different from the sun, deformed by the gravitational force of an object passing by.
This phenomenon, called “gravitational lens effect”, opens a new window on the history and evolution of galaxies such as ours, the Milky Way, according to the scientists, whose observations were published Wednesday.
“Einstein would be proud,” said Terry Oswalt, a professor of physics at the University of Aeronautics at Embry Riddle in Maryland,” and one of its key forecasts has successfully passed a rigorous test of observation.
The effect of gravitational lens was first observed in 1919 when, during a total eclipse, the light the sun deformed and took the form of a circle.
“When an object passes exactly between us and a star, this lens effect forms a perfect circle of light called the Einstein ring,” explained Professor Oswalt.
This observation was then the first convincing proof of Albert Einstein’s theory of general relativity, according to which gravity is fundamental force acting on space and time.
However, Einstein considered that this effect was impossible to observe in other stars since they were too far from each other.
In an article published in 1936 in the same journal Science, the German physicist wrote “that for this reason (the distance between stars) there was no hope of being able to see this phenomenon directly.”
Einstein then could not anticipate the appearance of the Hubble telescope in 2009, which revolutionized astronomy by allowing observation of stars and galaxies far away.
With the help of Hubble , the team led by Kailash Sahu of Baltimore’s Space Telescope Science Institute observed the light of a distant star diverted by a white dwarf, “Stein 2051-B” .
A white dwarf is a star that has exhausted its hydrogen but is still massive despite its small size.
A new tool
At least 97% of the stars that exist and have existed in our galaxy, including the sun, are or will become white dwarfs, which tells us both about our future and our past, experts say.
The amplitude of the deviation of light from a star depends directly on the mass and gravity exerted by the white dwarf.
The mass of Stein 2051-B represents about two-thirds of the mass of the sun.
During this last observation, Professor Sahu and his team realized that the star and the dwarf Stein 2051-B were not fully aligned, which explained that the Einstein circle formed by the deviated light was asymmetric, Mass of the white dwarf.
For Professor Oswalt, this observation is important because “it seeks a new tool to determine the mass of celestial objects, difficult to calculate otherwise.”
This research “also solves an ancient mystery about the mass and composition of the white dwarf Stein 2051-B,” he says.
Oswalt added that “Professor Sahu’s team also confirmed the findings of Indian astrophysicist Subrahmanyan Chandrasekhar, Nobel Prize for Physics in 1983, for his theory on the relationship between mass and radius of white dwarfs.”
Thanks to this gravitational lens effect, astronomers were able to announce in 2016 to have observed for the first time four simultaneous images of a very distant supernova.
In the case of this supernova, an end-of-life star that exploded more than 9 billion years ago, the mass of surrounding galaxies had strongly deformed space- time and diverted light. | <urn:uuid:0f7d0e33-57d3-4a4a-a900-db2ed62ca67d> | 3.921875 | 826 | News Article | Science & Tech. | 33.589003 | 95,539,074 |
The photosynthetic water-splitting reaction catalysed by the oxygen-evolving center (OEC) in the photosystem II of plants releases protons, electrons and dioxygen, which is one of the most important processes for energy and material conversions on Earth. OEC is a Mn4Ca-cluster and cycles through five different states (Sn, n = 0–4), wherein S0 is the most reduced state, S1 is the dark stable state and S2, S3 and S4 are intermediate states. OEC rapidly releases O2 in the S4 state, then returns to the S0 state. The detailed structure of the OEC in the S1 state was reported by Umena et al. in 2011 and improved by Suga et al. in 2015 . These reports from Shen's group have revealed that OEC is composed of an asymmetric Mn4CaO5-cluster coordinated by four water molecules, one imidazole and six carboxylate groups from protein side chains (Fig. 1). Determination of the accurate structure of the OEC in the S1 state [1,2] is a breakthrough in the field of photosynthesis. However, because of the complexities of the large protein environment and the dynamic changes of the OEC during the water-splitting reaction, it is a great challenge to reveal its detailed reaction mechanism. Figure 1. View largeDownload slide Structures of OEC in the S1 and S3 states. Figure 1. View largeDownload slide Structures of OEC in the S1 and S3 states. Recently, Shen's group reached a new milestone . They reported the structure of the S3 intermediate state OEC by using time-resolved serial femtosecond X-ray crystallography with an X-ray free electron laser , which, for the first time, identified the formation of the O–O bond between the ‘famous’ μ4-O5 and a newly inserted oxygen atom (O6) with a length of 1.5 Å (Fig. 1). The O=O bond formation is key to understanding the mechanism of the photosynthetic water-splitting reaction, which has attracted the extensive attention of various spectroscopic and theoretical studies during the last several decades . A recent breakthrough from Shen's group has provided unambiguous evidence for the crucial O–O bond formation ; meanwhile, new questions arise for future studies. For example, how is the O6 atom inserted into the OEC? What are the functional roles of the four water molecules coordinated to the OEC, and what is the real function of the μ2-O4 atom? Finally, what is the structure of the OEC in the S4 state? According to the binding mode of the O–O bond in the S3 state, the release of O2 in the S4 state would produce four reactive sites, namely three 5-coordinated manganese (i.e. Mn1, Mn3, Mn4) and one 6-coordinated calcium. Based on our knowledge from an artificial Mn4CaO4-cluster , significant structural rearrangements would occur to accommodate the newly formed Mn4CaO4-cluster. In summary, the previous outstanding achievements by Shen's group revealed the accurate structures of the OEC in the S1 state [1,2], which was already considered to be a breakthrough in photosynthesis. The recent finding on the mechanism of O–O bond formation is a new milestone for photosynthetic research. These achievements have contributed to enhancing our knowledge on photosynthetic oxygen evolution tremendously, and will significantly promote the development of the new generation of man-made OEC for water-splitting reactions in artificial photosynthesis, aiming to produce clean and renewable fuels from sunlight and water. REFERENCES 1. Umena Y , Kawakami K , Shen JR et al. Nature 2011 ; 473 : 55 – 60 . CrossRef Search ADS PubMed 2. Suga M , Akita F , Hirata K et al. Nature 2015 ; 517 : 99 – 103 . CrossRef Search ADS PubMed 3. Suga M , Akita F , Sugahara M et al. Nature 2017 ; 543 : 131 – 5 . CrossRef Search ADS PubMed 4. Perez-Navarro M , Neese F , Lubitz W et al. Curr Opin Chem Biol 2016 ; 31 : 113 – 9 . CrossRef Search ADS PubMed 5. Zhang C , Chen C , Dong H et al. Science 2015 ; 348 : 690 – 3 . CrossRef Search ADS PubMed © The Author(s) 2017. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. All rights reserved. For permissions, please e-mail: email@example.com
National Science Review – Oxford University Press
Published: Aug 2, 2017
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Structure of Molecular Machine for Targeted Viral DNA Destruction Determined
News Aug 08, 2014
With a featured publication in the Aug. 7 issue of Science, Montana State University researchers have made a significant contribution to the understanding of a new field of DNA research, with the acronym CRISPR, that holds enormous promise for fighting infectious diseases and genetic disorders.
“We generally think of bacteria as making us sick, but rarely do we consider what happens when the bacteria themselves get sick. Viruses that infect bacteria are the most abundant biological agents on the planet, outnumbering their bacterial hosts 10 to 1,” said Blake Wiedenheft, senior author of the paper and assistant professor in MSU’s Department of Microbiology and Immunology.
“Bacteria have evolved sophisticated immune systems to fend off viruses. We now have a precise molecular blueprint of a surveillance machine that is critical for viral defense,” Wiedenheft said.
These immune systems rely on a repetitive piece of DNA in the bacterial genome called a CRISPR. CRISPR is an acronym that stands for Clustered Regularly Interspaced Short Palindromic Repeats. These repetitive elements maintain a molecular memory of viral infection by inserting short segments of invading viral DNA into the DNA of the “defending” bacteria. This information is then used to guide the bacteria’s immune system to destroy the invading viral DNA.
The molecular blueprint of the surveillance complex was determined by a team of scientists in Wiedenheft’s lab at MSU using a technique called X-ray crystallography. Ryan Jackson, a postdoctoral fellow in the Wiedenheft lab, collected X-ray diffraction data from synchrotron radiation sources located in Chicago, Berkeley, and Stanford.
“Interpreting these X-ray diffraction patterns is a complex mathematical problem and Ryan is one of a few people in the world capable of interpreting this data,” Wiedenheft said.
To help determine the structure, Wiedenheft sent Jackson to Duke University for a biannual meeting on X-ray crystallography. At the meeting, Jackson sat between “two of the greatest minds in the field of X-ray crystallography”– Randy Read from the University of Cambridge and Thomas Terwilliger from Los Alamos National Lab -- whose expertise facilitated the computational analysis of the data, which was critical for determining the structure.
“The structure of this biological machine is conceptually similar to an engineer’s blueprint, and it explains how each of the parts in this complex assemble into a functional complex that efficiently identifies viral DNA when it enters the cell,” Wiedenheft said. “This surveillance machine consists of 12 different parts and each part of the machine has a distinct job. If we’re missing one part of the machine, it doesn’t work.”
Understanding how these machines work is leading to unanticipated new innovations in medicine and biotechnology and agriculture. These CRISPR-associated machines are programmable nucleases (molecular scissors) that are now being exploited for precisely altering the DNA sequence of almost any cell type of interest.
“In nature, these immune systems evolved to protect bacteria from viruses, but we are now repurposing these systems to cut viral DNA out of human cells infected with HIV. You can think of this as a form of DNA surgery. Therapies that were unimaginable may be possible in the future,” Wiedenheft said.
“We know the genetic basis for many plant, animal, and human diseases, and these CRISRP-associated nucleases are now being used in research settings to surgically remove or repair defective genes,” Wiedenheft said. "This technology is revolutionizing how molecular genetics is done and MSU has a large group of researchers that are at the cutting edge of this technological development.”
Natural Product Could Lead to New Class of Commercial HerbicideNews
By looking for microorganism's protective shield, specifically the genes that can make it, a team discovered a new and potentially highly effective type of weed killer. This finding could lead to the first new class of commercial herbicides in more than 30 years.READ MORE | <urn:uuid:e2f988cb-7de1-4ff5-8b2a-d4c6ae04d4a8> | 3.140625 | 891 | News Article | Science & Tech. | 23.473837 | 95,539,119 |
Since the completion of the human genome an important goal has been to elucidate the function of the now known proteins: a new molecular method enables the investigation of the function for thousands of proteins in parallel. Applying this new method, an international team of researchers with leading participation of the Technical University of Munich (TUM) was able to identify hundreds of previously unknown interactions among proteins.
The human genome and those of most common crops have been decoded for many years. Soon it will be possible to sequence your personal genome for less than 1000 Euros. At yet, there is a well-kept secret: for thousands of the roughly 20,000 – 30,000 proteins encoded in the genome it is not clear what they do in the body, which function they have.
This makes it difficult to interpret many upcoming data and understand the underlying molecular processes – and this is the case in diverse fields such as medical research, plant research or the development of alternative energy sources.
The function of a protein is a composite of many different aspects: with which proteins does it work together? How are its functions regulated and which processes are affected by it? Even for the reference plant thale cress (Arabidopsis thaliana) the function for about 10,000 proteins remains enigmatic. Filling this knowledge gap will take a long time using current methodologies. Elucidating these molecular functions is therefore of preeminent importance.
Microarrays enable the Investigations of Thousands of Proteins
Protein microarrays allow the investigation of thousands of proteins in a single experiment. Microarrays are only a few centimeters in size and host thousands of individual test spots on very small space. To produce standard protein microarrays small amounts of proteins are printed to a glass slide and chemically fixed in each spot where they are then available for experiments.
However, this approach requires the prior production and purification of thousands of proteins, which is time consuming and expensive. Together these costs have prevented the widespread use of protein microarrays despite their enormous potential.
The research group of Pascal Falter-Braun of the Chair of Plant Systems Biology at TUM together with colleagues from the USA and Japan now achieved a possibly decisive breakthrough: DNA, which is much easier and cheaper to produce, is printed instead of proteins and the protein arrays are subsequently ‘developed’. DNA contains the information that specifies the shape of proteins. After printing the DNA on the array the latter is submerged in a reaction mixture that synthesizes the proteins specified by the printed DNA. A chemical anchor that is attached to the glass surface rapidly and tightly captures the so developed proteins, which are then available for functional studies.
The method is called ‘nucleic acid programmable protein array’ which, in conjunction with the employed capture agent, is abbreviated Halo-NAPPA. By using the new capture chemistry the researchers were able to increase the density of the arrays such that it is now possible to accommodate all proteins encoded in a genome on just a few arrays. The scientists could demonstrate the potential of the protein arrays in the context of plant hormone signaling pathways, which, for example, mediate responses to drought stress or against pathogens.
1000 novel Protein-Protein Interactions discovered
For the study now published in PNAS interactions of 38 of some of the most important transcription factor proteins of thale cress were investigated. Transcription factors determine which genes are active at what time and in which conditions and consequently have a critical role in organisms. The transcription factors themselves can be activated or inactivated by interacting with other proteins – in the present study nearly 1000 new interactions for the investigated transcription factors were detected using the protein microarrays. “Many of the now observed interactions have never been documented. They will help us to understand how biological systems and the underlying molecular networks function”, says Falter-Braun.
Proteins in plants and in man do not act in isolation but have mutual regulatory relationships and act together in complex networks – the research focus of the TUM team around Falter-Braun. In all organisms proteins have key roles and execute nearly all biological processes. “Possibly, the new method is a milestone towards understanding which proteins interact with which other proteins or other molecules in cells. Because it is cheaper and simpler a wider range of researchers can now work with these protein arrays to investigate protein functions” says Falter-Braun.
The scientist is convinced that the new method will also help to accelerate research in the research on renewable energies and the understanding of diseases.
Junshi Yazakia, Mary Gallia, Alice Y. Kima, Kazumasa Nitob, Fernando Alemand, Katherine N. Changb, Anne-Ruxandra Carvunise, Rosa Quana, Hien Nguyena, Liang Songb, José M. Alvarezh, Shao-shan Carol Huangb, Huaming Chena, Niroshan Ramachandrani, Stefan Altmannj, Rodrigo A. Gutiérrezh, David E. Hille, Julian I. Schroederd, Joanne Choryb, Joshua LaBaerl, Marc Vidale, Pascal Braunj and Joseph R. Eckera: Mapping transcription factor interactome networks using HaloTag protein arrays, PNAS June 2016.
Dr. Pascal Falter-Braun
Technical University of Munich
Chair of Plant Systems Biology
85354 Freising, Germany
Phone: 08161 /71 5645
Dr. Ulrich Marsch | Technische Universität München
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:32651c5c-7e17-4ab8-b2c4-3c59755e73cb> | 3.703125 | 1,782 | Content Listing | Science & Tech. | 35.545514 | 95,539,155 |
Using the statements, can you work out how many of each type of rabbit there are in these pens?
There are 78 prisoners in a square cell block of twelve cells. The clever prison warder arranged them so there were 25 along each wall of the prison block. How did he do it?
This task, written for the National Young Mathematicians' Award 2016, invites you to explore the different combinations of scores that you might get on these dart boards.
Exactly 195 digits have been used to number the pages in a book. How many pages does the book have?
A group of children are using measuring cylinders but they lose the labels. Can you help relabel them?
Are these domino games fair? Can you explain why or why not?
This problem is based on the story of the Pied Piper of Hamelin. Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!
This magic square has operations written in it, to make it into a maze. Start wherever you like, go through every cell and go out a total of 15!
What is the sum of all the three digit whole numbers?
What do you notice about the date 03.06.09? Or 08.01.09? This challenge invites you to investigate some interesting dates yourself.
This task, written for the National Young Mathematicians' Award 2016, focuses on 'open squares'. What would the next five open squares look like?
The clockmaker's wife cut up his birthday cake to look like a clock face. Can you work out who received each piece?
Add the sum of the squares of four numbers between 10 and 20 to the sum of the squares of three numbers less than 6 to make the square of another, larger, number.
The Scot, John Napier, invented these strips about 400 years ago to help calculate multiplication and division. Can you work out how to use Napier's bones to find the answer to these multiplications?
Find out what a Deca Tree is and then work out how many leaves there will be after the woodcutter has cut off a trunk, a branch, a twig and a leaf.
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 put plus signs in so this is true? 1 2 3 4 5 6 7 8 9 = 99 How many ways can you do it?
Look carefully at the numbers. What do you notice? Can you make another square using the numbers 1 to 16, that displays the same properties?
Use your logical-thinking skills to deduce how much Dan's crisps and ice-cream cost altogether.
A game for 2 people. Use your skills of addition, subtraction, multiplication and division to blast the asteroids.
Fill in the missing numbers so that adding each pair of corner numbers gives you the number between them (in the box).
Arrange eight of the numbers between 1 and 9 in the Polo Square below so that each side adds to the same total.
Arrange three 1s, three 2s and three 3s in this square so that every row, column and diagonal adds to the same total.
There are 44 people coming to a dinner party. There are 15 square tables that seat 4 people. Find a way to seat the 44 people using all 15 tables, with no empty places.
Zumf makes spectacles for the residents of the planet Zargon, who have either 3 eyes or 4 eyes. How many lenses will Zumf need to make all the different orders for 9 families?
Fill in the numbers to make the sum of each row, column and diagonal equal to 34. For an extra challenge try the huge American Flag magic square.
What do the digits in the number fifteen add up to? How many other numbers have digits with the same total but no zeros?
There were chews for 2p, mini eggs for 3p, Chocko bars for 5p and lollypops for 7p in the sweet shop. What could each of the children buy with their money?
Can you arrange 5 different digits (from 0 - 9) in the cross in the way described?
Investigate the different distances of these car journeys and find out how long they take.
There are over sixty different ways of making 24 by adding, subtracting, multiplying and dividing all four numbers 4, 6, 6 and 8 (using each number only once). How many can you find?
Cherri, Saxon, Mel and Paul are friends. They are all different ages. Can you find out the age of each friend using the information?
Using 3 rods of integer lengths, none longer than 10 units and not using any rod more than once, you can measure all the lengths in whole units from 1 to 10 units. How many ways can you do this?
This challenge focuses on finding the sum and difference of pairs of two-digit numbers.
Find the sum and difference between a pair of two-digit numbers. Now find the sum and difference between the sum and difference! What happens?
This task follows on from Build it Up and takes the ideas into three dimensions!
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?
This dice train has been made using specific rules. How many different trains can you make?
Suppose there is a train with 24 carriages which are going to be put together to make up some new trains. Can you find all the ways that this can be done?
Place the digits 1 to 9 into the circles so that each side of the triangle adds to the same total.
If each of these three shapes has a value, can you find the totals of the combinations? Perhaps you can use the shapes to make the given totals?
You have 5 darts and your target score is 44. How many different ways could you score 44?
You have two egg timers. One takes 4 minutes exactly to empty and the other takes 7 minutes. What times in whole minutes can you measure and how?
This activity is best done with a whole class or in a large group. Can you match the cards? What happens when you add pairs of the numbers together?
There is a clock-face where the numbers have become all mixed up. Can you find out where all the numbers have got to from these ten statements?
Can you find which shapes you need to put into the grid to make the totals at the end of each row and the bottom of each column?
There are 4 jugs which hold 9 litres, 7 litres, 4 litres and 2 litres. Find a way to pour 9 litres of drink from one jug to another until you are left with exactly 3 litres in three of the jugs.
Winifred Wytsh bought a box each of jelly babies, milk jelly bears, yellow jelly bees and jelly belly beans. In how many different ways could she make a jolly jelly feast with 32 legs?
Sam got into an elevator. He went down five floors, up six floors, down seven floors, then got out on the second floor. On what floor did he get on?
These two group activities use mathematical reasoning - one is numerical, one geometric. | <urn:uuid:426b6731-02f0-438b-b05c-521c57a8bb3c> | 3.9375 | 1,528 | Content Listing | Science & Tech. | 74.551302 | 95,539,168 |
On Sat, 24 Feb 2018 00:03:06 +1100, Chris Angelico wrote:
>> Is numpy a general purpose C library that can also be called from any
>> language that can use a C API? Or is it specific to Python?
> No, it's a general purpose FORTRAN library that can also be called from
> any language that can use a generic C, FORTRAN, COBOL, etc API.
Numpy itself is a collection of Python interfaces to a number of C and
Fortran libraries. You can't generally call numpy from other languages --
you can't even call numpy from other Python implementations, unless they
support calling C/Fortran. Jython, for example, can't do it without help:
and while PyPy can call numpy, doing so is slow, and there's a custom
fork of numpy specially for PyPy:
Remember that numpy show cases the exact reason Python was invented: to
act as an easy to use "glue language" to join together efficient and
useful, but not so easy to use, libraries written in C and Fortran.
Jython was invented to support Java libraries, and IronPython to make it
easy to integrate with the Dot-Net ecosystem. | <urn:uuid:be3ba787-c8d1-4916-b385-d68de9fac8e1> | 2.640625 | 270 | Comment Section | Software Dev. | 46.57201 | 95,539,185 |
Land degradation is one of the causes of desertification of drylands in the Mediterranean. UAVs can be used to monitor and document the various variables that cause desertification in drylands, including overgrazing, aridity, vegetation loss, etc. This paper examines the use of UAVs and accompanying sensors to monitor overgrazing, vegetation stress and aridity in the study area. UAV images can be used to generate digital elevation models (DEMs) to examine the changes in microtopography as well as ortho-photos were used to detect changes in vegetation patterns. The combined data of the digital elevation models and the orthophotos can be used to identify the mechanisms for desertification in the study area.
Kyriacos Themistocleous, "The use of UAVs for monitoring land degradation," Proc. SPIE 10428, Earth Resources and Environmental Remote Sensing/GIS Applications VIII, 104280E (Presented at SPIE Remote Sensing: September 12, 2017; Published: 5 October 2017); https://doi.org/10.1117/12.2279512.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the conference proceedings. They include the speaker's narration along with a video recording of the presentation slides and animations. Many conference presentations also include full-text papers. Search and browse our growing collection of more than 12,000 conference presentations, including many plenary and keynote presentations. | <urn:uuid:ebea8a02-4820-4219-8f29-9c71b8539781> | 3.109375 | 308 | Truncated | Science & Tech. | 23.15 | 95,539,188 |
Sunday, September 08, 2013
GlobAlbedo Project Mapping Changes In Earth’s Reflectivity
The amount of sunlight being absorbed or reflected by Earth is one of the driving forces for weather and climate. Satellites are providing this information with unprecedented accuracy.
The reflecting power of a surface is known as ‘albedo’. Bright snow and ice have a high albedo, meaning they reflect solar radiation back into space, while green areas like forests and fields have a much lower albedo.
The lower the albedo, the more energy from the Sun is absorbed.
Changes in Earth’s surfaces can therefore affect how much of the Sun’s energy is absorbed – such as a decrease in snow cover or an increase in the area used for agriculture. If the amount of energy absorbed changes, this has an effect on Earth’s energy budget and ultimately affects our weather and climate.
To help scientists build better simulations of weather and climate, ESA’s GlobAlbedo project is using satellite data to map changes in Earth’s reflectivity.
Led by University College London, the team used readings from the Envisat and Spot-Vegetation satellites to produce global surface albedo maps from 1998 to 2011. The maps, available for free online, provide the most accurate measure of Earth’s reflectivity to date.
“GlobAlbedo is the first gap-free, 1 km-resolution map of Earth’s land surface with an uncertainty estimate for every pixel. This could only have been produced from satellite data,” said Professor Jan-Peter Muller of University College London, leader of the GlobAlbedo project.
By combining data from different satellite sensors, scientists have maximized the coverage and created a time series that can be extended to include historical as well as future satellite measurements.
The maps have proven useful to a variety of users, including the UK Met Office. Scientists there have been using them to update the land surface albedo information in the Met Office’s operational Global Atmosphere weather model, resulting in more accurate weather predictions and climate forecasts.
“Tests show that they help to give more accurate temperature forecasts over the United States and Asia, especially in summer,” said Dr Malcolm Brooks from the Met Office. “We expect to be producing operational forecasts using these data in the spring of 2014.” Read More | <urn:uuid:7eb25588-ff9a-442e-8a00-c2f2efe1f4f5> | 4.15625 | 505 | News (Org.) | Science & Tech. | 27.765799 | 95,539,190 |
A new national plant translocation database could be on the horizon, after researchers gathered to map out the sources of existing translocation data at
a recent workshop.
“The number of translocations on record came as a bit of a surprise – I didn’t think there would be so many,” says Dr David Coates from WA’s Department of Parks and Wildlife, who leads the TSR Hub’s Threatened plant reintroduction and relocation project.
“After sending out a preliminary spreadsheet, we received records of approximately 230 plant translocations. Some of these may be duplicates, but we suspect that the number may double as we work through the grey literature.”
According to the preliminary tally, up to half of the plant translocations have taken place in Western Australia.
Dr Coates, who is based at the West Australian Department of Parks and Wildlife says the uncertainty surrounding the true number of translocations and varying degrees of data quality highlights the need for a co-ordinated national database.
“There’s a lot of data to manage and a lot of organisations working on translocation projects including government departments, NGO’s and community groups. The data these organisations collect can vary in terms of scale and quality, so we need to determine what’s readily available, as well as the data-fields we would like to see included in future projects.”
Workshop participants also spent some time reviewing the criteria for measuring translocation success.
“There are a number of stages or levels that might indicate success – establishment, flowering and seeding but the ultimate measure remains a viable self-sustaining population. That is difficult to determine without high-quality data,” says Dr Coates.
“We can use molecular markers to compare the genetic diversity of translocated and source populations. Accurate data allows us to analyse population viability, observe population trends and model them.”
Plans for a new edition of the Guidelines for Translocation of Threatened Plants in Australia, in collaboration with the Australian Network for Plant Conservation Inc, were also discussed.
“The existing Guidelines have covered the most important topics very well, but we would like to update some of the existing examples and provide new case studies.”
Image: banksia fuscobractea by Andrew Crawford from WA's Department of Parks and Wildlife
Most people know that cats kill many birds and mammals, but they also have impacts on less charismatic species.
Australian cats are killing about 650 million reptiles per year, according to new research published in the journal Wildlife Research.
You have to be pretty lucky to make a living by combining your passion and interests, and that’s exactly how Dr Daniel White feels about his current state of affairs. Dan began his career studying genes, and has since applied his science to saving species. Here he describes how.
The TSR Hub recognises that outcomes for threatened species will be improved by increasing Indigenous involvement in their management. In response to this, the Hub is guided by an Indigenous Reference Group and has a number of projects across Australia that are collaborating with Indigenous groups on threatened species research on their country.
A new contagious fungal plant disease has entered Australia, myrtle rust. It’s highly mobile, can reproduce rapidly and is infecting many species across a broad geographic range. Containment and eradication responses have so far been unsuccessful.
Australia is losing large old hollow-bearing trees in our mountain ash forests due to logging, fires and climate change. A team at the Australian National University have been investigating the importance of these trees, the implications of their loss and things we can do to ensure we have enough mountain giants for the future. | <urn:uuid:24eeebef-60b8-49d1-ac71-47b64558effe> | 3.34375 | 765 | News (Org.) | Science & Tech. | 30.577564 | 95,539,193 |
New technologies have a way of generating new kinds of garbage which, in hindsight, often turn out to be harder to dispose of than most people dared imagine. The maxim holds true for automobiles and plastic bottles, and lately the embattled nuclear industry has provided vet another example.
The problem of what to do with nuclear waste—especially the most lethally radioactive “high level” waste that comes from spent reactor fuel—has troubled the Federal Government for 30 years. Nuclear weapons programs, for example, have left legacy of 79 million gallons of radioactive liquid and solid waste. More than 400 thousand gallons has leaked from storage tanks at the Government's Hanford Reservation in Washington State since 1958.
The leakage, from tanks once expected to hold up for 500 years, permanently contaminated the surrounding soil, but caused no injuries and showed no indication of seeping down to the water table or the Columbia River nearby. Although the corroding tanks now seem under control, the leakage has raised questions about the ability of human institutions to guard such dangerous materials literally for millenia.
In recent months, new difficulties have escalated the waste problem—how to dispose of the used fuel from commercial nuclear power plants. Failure to resolve these new questions could, within a year, result in temporary shutdowns for as many as 14 of the nation's 56 operable nuclear power plants. Moreover, the waste debate has also intensified a debate over the future of the Government's multi‐billion dollar project to develop a commercial breeder reactor.
The nuclear waste cycle, and the industry's difficulties, begin when a utility removes spent fuel from a reactor's core. Months of immersion bring little outward change in the appearance of the long, thin fuel rods, which are metal tubes filled with hard black pellets of uranium oxide.Continue reading the main story
However, when a heavy crane lowers the spent fuel into a concrete storage basin filled with cooling water, the old rods emit a striking, sapphire‐blue light. The light comes from intense radioactive decay of the accumulated products of nuclear fission, some of which, like cesium and strontium, remain lethal for tens of thousands of years.
The spent fuel also contains leftover uranium and, as a by‐product, plutonium. From the beginning the nuclear age, in the 1940's, Government and industry have assumed that they could reclaim this useful uranium and plutonium as fuel; indeed, this is what the breeder reactor is all about—it is designed to make more fuel than it consumes, converting uranium into plutonium.
Thus fuel reprocessing has been a key part of the grand design for a nuclear economy. And it is this process that has now fallen on hard times.
Reprocessing plants seem a combination of a sewage plant and Fort Knox. Behind massive concrete walls (for shielding), remotely controlled equipment chops up the spent fuel, dissolves it in acid, and chemically extracts uranium and plutonium, leaving a residual soup of liquid radioactive waste. It is this hot leftover “soup” that must be isolated from the earth's biosphere for centuries.
Private companies, have built only three such plants in the United States. One, near Buffalo, was shut down in 1972 for remodeling and because of repeated mishaps that overexposed employes to fission products. This plant is not scheduled to reopen until 1979. A second plant, built near Chicago by General Electric at a cost of $64‐million; proved a technological flop, and may simply be abandoned. The third plant is being built in South Carolina, but it alone is not large enough to handle all the spent fuel coming from the nation's nuclear power plants.
Amid these difficulties, there is growing skepticism in Congress that plutonium, an extremely toxic metal that also lends itself to weapons, can in fact be recycled safely and economically. The Nuclear Regulatory Commission proposed last week to hold up the licensing of plutonium recycling facilities until 1978, at least, pending further study of environmental and safeguard problems.
Spent fuel is piling up at utilities and non‐working reprocessing plants, and storage space is running short. Once its storage space is filled a reactor would have to shut down. Fourteen reactors may be affected this year, and 28 more in 1976.
Some experts think storage space can be expanded cheaply and safely simply by putting more fuel in existing storage basins than is currently allowed. But environmental groups are likely to raise legal challenges on safety grounds.
Last month, under pressure from the Environmental Protection Agency and nuclear critics, the Energy Research and Development Agency began anew the long and muddled search for a way to store highlevel wastes. The agency said it was shelving indefinitely its plan to build a $55‐million concrete warehouse for waste called the Retrievable Surface Storage Facility. Instead, the agency will accelerate development of a “pilot” storage vault to be excavated in a salt bed 3,500 feet beneath the desert in southeastern New Mexico.
Many geologists have long favored salt‐bed storage in principle, and so has the Environmental Protection Agency. But the last time the Government picked an experimental site—near Lyons, Kans., in the late 1950's—it turned out to be politically unpopular and geologically unsuitable, and was abandoned.
William D. Rowe, the environmental agency's chief of radiation programs, wrote recently that the failure to settle on an ultimate method of disposal “places nuclear energy in a rather unfavorable light.” And Mr. Rowe added that the agency considers waste disposal to be “the major unresolved problem involving nuclear fission as an electrical energy source.”
The Growing Skepticism
Atomic Weapons Alone Have Left 79 Million Gallons of Liquid ‘Garbage’Continue reading the main story | <urn:uuid:6ba2fe86-8037-4a86-8cb1-a19a0a76ecc8> | 3.40625 | 1,172 | Truncated | Science & Tech. | 35.288025 | 95,539,198 |
The desire to detect possible variations of the total solar irradiance (TSI), the total amount of power supplied to the Earth from the Sun by radiative means, has been a goal for more than a century. Interest in this quantity arose from a realization that it is a determining factor of the Earth’s climate. At any time in the Earth’s history the atmospheric composition and the distribution of oceans and land masses combine with the solar irradiance to determine the radiative balance, and hence the climate, of the Earth’s biosphere.
KeywordsSolar Cycle Solar Irradiance Total Solar Irradiance Solar Maximum Mission Total Solar Irradiance Monitor
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The largest ever study of bird genetics has not only shaken up but completely redrawn the avian evolutionary tree. The study challenges current classifications, alters our understanding of avian evolution, and provides a valuable resource for phylogenetic and comparative studies in birds.
Birds are among the most studied and loved animals, and much of what we know about animal biology – from natural history to ecology, speciation, reproduction, etc. – is based on birds. Nevertheless, the avian tree-of-life has remained controversial and elusive – until now.
For more than five years, the Early Bird Assembling the Tree-of-Life Research Project, centered at The Field Museum, has been examining DNA from all major living groups of birds. Thus far, scientists have built and analyzed a dataset of more than 32 kilobases of nuclear DNA sequences from 19 different locations on the DNA of each of 169 bird species. The results of this massive research, which is equivalent to a small genome project, will be published in Science on June 27, 2008.
"Our study and the remarkable new understanding of the evolutionary relationships of birds that it affords was possible only because of the technological advances of the last few years that have enabled us to sample larger portions of genomes," said Shannon Hackett, one of three lead authors and associate curator of birds at The Field Museum. "Our study yielded robust results and illustrates the power of collecting genome-scale data to reconstruct difficult evolutionary trees."
The results of the study are so broad that the scientific names of dozens of birds will have to be changed, and biology textbooks and birdwatchers' field guides will have to be revised. For example, we now know that:
Birds adapted to the diverse environments several distinct times because many birds that now live on water (such as flamingos, tropicbirds and grebes) did not evolve from a different waterbird group, and many birds that now live on land (such as turacos, doves, sandgrouse and cuckoos) did not evolve from a different landbird group.
Similarly, distinctive lifestyles (such as nocturnal, raptorial and pelagic, i.e., living on the ocean or open seas) evolved several times. For example, contrary to conventional thinking, colorful, daytime hummingbirds evolved from drab nocturnal nightjars; falcons are not closely related to hawks and eagles; and tropicbirds (white, swift-flying ocean birds) are not closely related to pelicans and other waterbirds.
Shorebirds are not a basal evolutionary group, which refutes the widely held view that shorebirds gave rise to all modern birds.
"With this study, we learned two major things," said Sushma Reddy, another lead author and Bucksbaum Postdoctoral Fellow at The Field Museum. "First, appearances can be deceiving. Birds that look or act similar are not necessarily related. Second, much of bird classification and conventional wisdom on the evolutionary relationships of birds is wrong."
The evolution of birds has been notoriously difficult to determine. This is probably because modern birds arose relatively quickly (within a few million years) during an explosive radiation that occurred sometime between 65 million and 100 million years ago. The result of this rapid divergence early in the evolutionary history of birds is the fact that many groups of similar-looking birds (for example, owls, parrots and doves) have few, if any, living intermediary forms linking them to other well-defined groups of birds. This makes it very difficult to determine how some of these groups are evolutionarily related.
Many previous studies of avian evolution yielded conflicting results. This new study, however, is more robust because of the use of large amounts of sequence data from across the genome. The Early Bird group sequenced approximately 32 kilobases of aligned data per species, which is about five times more nuclear data than any previous study. Furthermore, the data were analyzed using several different methods and programs.
"Unlike other studies, we consistently found several well-supported, deep divisions within Neoaves (a basal division of birds that includes 95% of all living birds), and this signal was persistent across analyses," said Rebecca Kimball, the third lead author of the study and [associate professor of zoology] at the University of Florida, Gainesville.
The other co-authors of this study include scientists from the University of California, Berkeley; Smithsonian Institution; Stellenbosch University (South Africa); University of Maryland; Louisiana State University; Wayne State University; and the University of New Mexico. More than half of the people who worked on or trained in this project were women.
At The Field Museum, much of the DNA sequencing and analysis was conducted in the Pritzker Laboratory for Molecular Systematics and Evolution. The lab was established in 1974 for genetic research and to study and help preserve the world's biodiversity. Since 2000, over 190 scientists from 29 countries have trained in the lab. Today, there are more than 60 active projects in the Pritzker Lab, examining everything from sharks to plants to lichens, and from owls to flamingos.
Just last month, The Field Museum opened the Daniel F. and Ada L. Rice DNA Discovery Center, which puts a public face on the Pritzker Lab. The center opens up a working state-of-the-art laboratory to Museum visitors, who will be able to observe researchers extracting, sequencing, and analyzing DNA for several projects, including the Early Bird research. In addition, they will be able to speak with scientists at set times as they work.
In addition to the viewing area, the 1,850-square-foot DNA Discovery Center includes videos, hands-on interactives, and informative displays. The exhibition is intended for adults and students in junior high school and above. Located on the mezzanine overlooking Stanley Field Hall, the DNA Discovery Center is free with general admission.
There are an estimated 82 million birdwatchers in the United States alone, making it the country's second (to gardening) most popular hobby. Therefore, interest in the results of the Early Bird research project will be far reaching.
"We now have a robust evolutionary tree from which to study the evolution of birds and all their interesting features that have fascinated so many scientists and amateurs for centuries," Reddy said. "Birds exhibit substantial diversity (largest of the tetrapod groups), and using this 'family tree' we can begin to understand how this diversity originated as well as how different bird groups are interrelated."
Greg Borzo | EurekAlert!
O2 stable hydrogenases for applications
23.07.2018 | Max-Planck-Institut für Chemische Energiekonversion
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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23.07.2018 | Science Education | <urn:uuid:d873603c-3347-47d4-829d-bf84d59f4a89> | 4.03125 | 1,935 | Content Listing | Science & Tech. | 34.533768 | 95,539,215 |
A new study suggests that symbiotic relationships between trees and the mycorrhyzae that grow in their roots may not be as mutually beneficial as previously thought.
The so-called symbiotic relationship between trees and the fungus that grow on their roots may actually work more like a capitalist market relationship between buyers and sellers, according to the new study published in the journal New Phytologist.
Recent experiments in the forests of Sweden had brought into a question a long-held theory of biology: that the fungi or mycorrhizae that grow on tree roots work with trees in a symbiotic relationship that is beneficial for both the fungi and the trees, providing needed nutrients to both parties. These fungi, including many edible mushrooms, are particularly common in boreal forests with scarce nutrients. But in contrast to the current paradigm, the new research shows that they may be the cause rather than the cure for the nutrient scarcity.
In the recent experiments, researchers found that rather than alleviating nutrient limitations in soil, the root fungi maintain that limitation, by transferring less nitrogen to the trees when nutrients are scarce than when they are abundant in the soil.
The new study, led by IIASA Ecosystems Services and Management researcher Oskar Franklin in collaboration with the Swedish University of Agricultural Sciences, used a theoretical model to explain the new experimental findings, by simulating the interaction between individual fungus and plant. It suggests that since each organism competes with others in trading nutrients such as carbon and nitrogen, the system as a whole may function more like a capitalistic market economy than a cooperative symbiotic relationship. The competition among trees makes them export excessive amounts of carbon to the fungi, which seize a lot of soil nutrients.
“The new theory pictures a more business-like relationship among multiple buyers and sellers connected in a network. Having multiple symbiotic trading-partners generates competition among both the fungi and the plants, where each individual trades carbon for nutrients or vice versa to maximize profits, not unlike a capitalistic market economy,” says Franklin.
“Although doing business with fungi is a good deal from each tree’s own point of view it traps the whole forest in nutrient limitation,” he says.
Understanding boreal forest nutrient cycles is incredibly important for modeling climate change, because it influences how much carbon dioxide these regions can absorb, as well as how they are influenced by the increasing concentrations of greenhouse gases in the atmosphere. Franklin says, “This syndrome is aggravated by rising CO2. As more carbon becomes available to the trees, the limitation of nitrogen generated by mycorrhizae becomes even more important, possibly eliminating or even reversing the expected CO2 fertilization effect in boreal forest.”
Franklin O, Näsholm T, Högberg P, Högberg MN. 2014. Forests trapped in nitrogen limitation: an ecological market perspective on ectomycorrhizal symbiosis. New Phytologist. DOI: 10.1111/nph.12840
Näsholm T, Högberg P, Franklin O, Metcalfe D, Keel SG, Campbell C, Hurry V, Linder S, Högberg MN. 2013. Are ectomycorrhizal fungi alleviating or aggravating nitrogen limitation of tree growth in boreal forests? New Phytologist 198(1): 214-221.
For more information please contact:
Ecosystems Services and Management
Tel: +43(0) 2236 807 251
IIASA Press Office
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Katherine Leitzell | idw - Informationsdienst Wissenschaft
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...
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17.07.2018 | Power and Electrical Engineering | <urn:uuid:f57b3a9f-9bb5-4676-ab61-f4bd74c8b59a> | 3.140625 | 1,521 | Content Listing | Science & Tech. | 38.117386 | 95,539,234 |
3 Ways to Calculate Acceleration - wikiHow
How to Calculate Acceleration. Three Methods:Calculating Average Acceleration from Two Velocities Calculating Acceleration from a Force Check Your Understanding Community Q&A.
What is Acceleration? How is It Calculated? Find Out Now
F = Mass (m) x Acceleration Due to Gravity (g). Since Earth is not a perfect sphere, the mass exerted by it is not exactly same on all points of its surface.
What is the formula to calculate vertical acceleration? How... - Quora
Related QuestionsMore Answers Below. How do I find the vertical acceleration? How is the quantity effect calculated?
Acceleration Calculator - Omni - How to find acceleration?
Acceleration calculator works from two different angles - either velocity difference over a period of time or net force vs mass.
Define acceleration. Objectives Know what acceleration is and how...
Outcomes (5) Define acceleration and state how it can be calculated. (6) Calculate acceleration from practical observations. (7) Analyse the factors which will affect acceleration. Key terms: acceleration, speed, time, force.
How to find the acceleration? What is the formula for calculating the...
From the course of physics it is known: Acceleration of a body with its equally accelerated motion is a quantity equal to the ratio of the change in speed to the time interval for which this change occurred.
A Guide on How to Calculate Acceleration: Average and Instantaneous
Below, I will discuss how to calculate acceleration for two cases: average and instantaneous accelerations.
How To Calculate The Acceleration - The Science
Instruction how to calculate acceleration. Step 1: It shows the increase in body acceleration speed per unit time. As speed, and it may be constant and variable depending on the type of motion.
How to Calculate Acceleration With Friction - Sciencing
The formula is acceleration (a) equals friction (F) divided by its mass (m) or a = F ÷ m as per Newton's second law. How to Calculate Friction Force. Force is a vector quantity, which means you must consider the direction in which it acts.
How Do You Calculate Acceleration? - Reference.com
What Is a Change in Velocity Called? How Do You Calculate the Max Height Equation? When Velocity Is Positive and Acceleration Is Zero, What Happens to an Object's Motion?
How is acceleration due to gravity calculated? - Socratic
In this answer I'll keep it short by just explaining how we can calculate acceleration due to gravity on the surface of the earth (I am just assuming earth because you didnt mention the planet and everyone is only curious about earth ) So here we go
Solved: 1. How Will You Calculate The Linear Acceleration ...
4. For this experiment, if you plot torque versus angular acceleration, what is the slope of the data? A.the force acting on the system.
BBC - GCSE Bitesize: Forces and acceleration calculations
The same force could accelerate a 1kg mass by 50m/s2 or a 100kg mass by 0.5m/s2. Putting it simply, we can say that it takes more force to accelerate a larger mass.
How Fast is Earth Moving? Speed and Acceleration to Calculate...
What is Earth's speed and acceleration, when rotation, orbit of the sun, and the solar system's orbit of the Milky Way are calculated?
How to calculate Acceleration and... - ExplainingMaths.com
Example Question about how to calculate Acceleration and Deceleration. On your IGCSE GCSE Maths exam you will probably be asked to calculate either the acceleration or deceleration of a moving object.
Physics Equations Page - What it is and when to use it...
It can be used to calculate an object's displacement using initial velocity, constant acceleration, and time. This is often times used to calculate how far an object moves vertically under the influence of gravity (agravity = g = 9.81 m/s2).
How to calculate force, acceleration, and mass!! by hannah craven...
What was the measurement of the force it was pushed? What is force,acceleration, and mass? A force is simply a push or pull.
Magnitude of Acceleration - What is Magnitude of Acceleration
But, while calculating the magnitude, we are least bothered about the direction of the acceleration. In the case of circular motion, the direction is limited to two.
How to calculate spectral acceleration (design acceleration)...
The accuracy in determination of PSA is very important in calculating the final shear load. Could you explain how to estimate such value for a given site? How to calculate spectral acceleration (design acceleration) for the each type of site class?.
How to calculate acceleration on a distance time... - The Student Room
Part a) Use the distance time graph to determine the speed of the object at a time of 4s - which it irked outs I be 4ms-1 Part b) literally all it says is "calculate the acceleration".
How do you calculate the Acceleration due to gravity?
acceleration equation Difference between positive and negative acceleration Examples of negative acceleration Formula for average acceleration Uniform acceleration in physics what is negative acceleration? what is positive acceleration?
Force, Mass, Acceleration and How to Understand... - Owlcation
Definitions of force, mass, velocity, acceleration, weight. Vector diagrams. Newton's three laws of motion and how an object behaves when a force is applied.
How to calculate depreciation on computer hardware... - TechRepublic
How else are you going to know when it is time to purchase new equipment? This cheat sheet explains what computer hardware depreciation is, how it works, and how to apply it in your business.
How to Use an iPhone and Physics to Measure the Height of... - WIRED
Now I will show you how to measure distance using the accelerometer, just like I said I would at the end of that post.
How can I determine my local values of gravitational acceleration and...
To calculate a pressure value using a liquid column - for example a mercury barometer - or a pressure balance it is necessary to know the gravitational acceleration at the
How To Calculate Displacement
Before learning to calculate displacement, let us define displacement and learn what is position vector and how to write it. Definition of Displacement.
We are looking for acceleration and to calculate the acceleration, we must divide the change in velocity(i.e., 40 m/s) by the amount of time
What is acceleration? - How do we describe changes in velocity?
Acceleration describes how velocity changes. Any change in velocity, including speeding up, slowing down, or turning, creates acceleration.
Calculating Acceleration · Remember the relationship between acceleration, velocity and time interval
What is Gravity--How is it Calculated? What is Weight?
In the example above, the force of gravity acting on the person is 6.20 x 102 N. What is the process for calculating the weight of the person in pounds using 1N:2.2 x 10-2lb.
Earthquake Hazards 201 - Technical Q&A
I am trying to calculate the ground motion effect for a certain location in California. I obtained the design spectrum acceleration from your site, but I would like to identify the soil type of this location - how can I get that? What is a distance metric?
Acceleration - Unit Converter & Calculator
On this page. Metric. British (Imperial) and U.S. System. Gravity / Free Fall. Vehicle Acceleration. Navigate units. Find a unit.
At the bottom of the hill, her velocity will be greater than it was at the top. You can calculate her average acceleration down the hill if you know her starting and ending velocities and how long it
How to Calculate Resultant Velocity - Synonym - Find Acceleration
One basic idea is the concept of speed and how it changes. Calculating the speed of an object can be a simple process if a few basic rules are kept in mind.
The lab will show how graphs of displacement versus time and velocity versus time can be used to find acceleration. Materials: Hot Wheels car, 1m inclined plane, 2 notebooks, meter stick, stopwatch.
Forward Acceleration - Calculating speed from acceleration
The acceleration can be measured by calculating the slope of the line, rise over run, which happens to be 1/1 or simply 1. This is calculated by figuring how far up (rise) the line goes for a certain distance over (run). We could also have take the entire graph and said that the slope is 10/10, a fraction that...
(a) If the distance X is 10 cm, calculate, for the bob, (i) the periodic time (ii) the initial acceleration of the bob (iii)the subsequent maximum speed of the bob.
this problem is of *A brief description and diagram of important patterns pointing out trends or. interest and what the equipment and how it was used inconsistencies.
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2. How is mass related to inertia? 3. What is the net force and how is it determined? Figure 2.4: The net force acting on a box. being pushed.
Force and Acceleration
Quantify how much change there was in the class average accelerations by calculating the percentage difference between the highest and lowest class average values. (We cannot calculate percentage error in this situation, as we do not know the theoretical values.)
Part II: Essential Topics in Physics. Chapter 7 Acceleration, Mass, and Energy. Overview. Ballistics.
Instantaneous Speed Tutorial - what is it, and how to calculate it
However if you have a situation where the acceleration is constant, and you know what the starting velocity is, you can use arithmetics to calculate the instantaneous speed at any given time.
calculated - Перевод на русский - примеры... - Reverso Context
is the mean acceleration, in metres per second squared (m/s2), which shall be calculated by the equation: среднее ускорение, в метрах в секунду в квадрате (м/с2), рассчитываемое по уравнению
Calculating acceleration by numerical differentiation in Python
I think the first derivative gives me the speed and the second derivative gives me the acceleration. I'm interested in calculating the acceleration using numerical differentiation. How can this be done in python?
Calculating the estimated print time of an already sliced file
If someone can find out how the acceleration settings are calculated by the printer and what G-code command can be used to get the acceleration settings out of the printer, I would be really interested in knowing more about this.
How to calculate a logical curve along a set of values? - QuestionFocus
...and the rate of increase in value accelerates the further up you go, but there is no simple formula for calculating this rate of acceleration.
How Do You Calculate The Average Speed?
The speed is constant, so it was correctly used to calculate the times, and then Calculating average formula & practice problems video your calculator. | <urn:uuid:ad9297a9-cac1-40ec-bb98-92df6cb4a1ff> | 4.09375 | 2,417 | Q&A Forum | Science & Tech. | 44.149602 | 95,539,238 |
A View from Emerging Technology from the arXiv
Best of 2011: Billion-Ton Comet May Have Missed Earth by a Few Hundred Kilometers in 1883
In October, a reanalysis of historical observations suggested that Earth narrowly avoided an extinction event just over a hundred years ago
On 12th and 13th August 1883, an astronomer at a small observatory in Zacatecas in Mexico made an extraordinary observation. José Bonilla counted some 450 objects, each surrounded by a kind of mist, passing across the face of the Sun.
Bonilla published his account of this event in a French journal called L’Astronomie in 1886. Unable to account for the phenomenon, the editor of the journal suggested, rather incredulously, that it must have been caused by birds, insects or dust passing front of the Bonilla’s telescope. (Since then, others have adopted Bonilla’s observations as the first evidence of UFOs.)
Today, Hector Manterola at the National Autonomous University of Mexico in Mexico City, and a couple of pals, give a different interpretation. They think that Bonilla must have been seeing fragments of a comet that had recently broken up. This explains the ‘misty’ appearance of the pieces and why they were so close together.
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:3c2b83b7-710e-441f-9613-cb360ee0b933> | 3.5 | 295 | Truncated | Science & Tech. | 35.886427 | 95,539,254 |
Uniquely preserved pollen was extracted from intestines of fossil insects from the Lower Permian of the Urals. A species of Hypoperlidae, an extinct family ancestral to bark-lice, bugs and plant-hoppers, and two species of Grylloblatida, a predominantly Permian group with a few extant representatives related to stoneflies, contain protosaccate taeniate grains of several pollen genera well known as dispersed microfossils and occasionally found in sporangia of conifers, peltasperms and glossopterids. This is so far the earliest direct evidence of pollinivory, a major factor of plant-insect coevolution. The partly digested pollen grains reveal infratectal reticulum and other structural details of evolutionary significance. It is suggested that the peculiar taeniate pollen of worldwide distribution in the Permian might simultaneously evolve in several groups of Paleozoic seed plants in relation to pollinivory that, by altering the micropyle load and thereby the pollen/ovule ratio, could also affect ovuliferous structures. Thus pollinivory might impel rapid diversification of gymnosperms in the Permian. The pollinivorous Hypoperlidae, which have evolved in the direction of ovulivory, might initiate insect pollination in the process.
Mendeley saves you time finding and organizing research
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You are here: Home Environment Climate Change 2012 – The Sixth Most Severe Drought in United States History 2012 – The Sixth Most Severe Drought in United States History The current drought is the sixth most severe drought in the United States. The drought is affecting vegetation, including crops. by Heather Carr July 18, 2012, 2:46 am 6 Comments The current drought is the sixth most severe drought in the United States. The drought is affecting vegetation, including crops. The map above shows “vegetation anomaly” for Jun 25-Jul 10, 2012, compared with the same dates between 2002 and 2012. The darker the brown, the less vegetation coverage compared to prior years. Green areas indicate lusher vegetation. The central part of the United States has been the hardest hit. Crop yields are expected to be lower this year than last. A warm spring prompted many farmers to plant earlier and more than usual. Now many crops look like they will be a loss. The USDA fast track drought designations are helping to make aid available to those farmers who stand to lose because of this drought. The current drought is a result of several weather patterns coming together to push the jet stream further north this year, taking with it the rain that crops need. Vegetation anomaly map courtesy of NASA’s Earth Observatory See more Previous article FDA Bans BPA in Sippy Cups and Baby Bottles Next article Why are my cucumbers falling off of the vine? 6 Pings & Trackbacks Pingback:2012: 6th Most Severe Drought in US History | Planetsave Pingback:Climate Change Deniers are Almost Extinct - Page 10 - US Message Board - Political Discussion Forum Pingback:How Much Water is Your Home Wasting? Pingback:Drought Increases Runoff Pollution Pingback:Massive Dust Storm Moves Through Colorado and Kansas • Insteading Pingback:How Much Water is Your Home Wasting? • Insteading Leave a Reply Cancel reply Your email address will not be published. Required fields are marked *Comment Name * Email * Website Save my name, email, and website in this browser for the next time I comment. Upload a photo / attachment to this comment (PNG, JPG, GIF - 6 MB Max File Size): (Allowed file types: jpg, gif, png, maximum file size: 6MB. | <urn:uuid:ece37713-0fac-4b01-9f36-aa9c2bcc35ad> | 2.8125 | 479 | Truncated | Science & Tech. | 51.915577 | 95,539,275 |
If Brazil gets a climate protocol, like the Kyoto Protocol for the rich countries, it will be possible to create an incentive for the country to reduce the deforestation of the Amazon region. The Kyoto Protocol targets a reduction of emissions of carbon dioxide and greenhouse gases.
In a new study, Martin Persson, in collaboration with Christian Azar, at the Section for Physical Resource Theory, Chalmers University of Technology in Sweden, has examined how to deal with emissions of carbon dioxide from deforestation in the Amazon in a future international climate agreement, after Kyoto.
“An international climate agreement can create pressure to reduce deforestation in the Amazon region, but it is important that emissions from deforestation be included in a way that does not undermine work to reduce emissions in the energy sector,” says Martin Persson.
Jorun Fahle | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:2dd4e799-334f-41e0-849d-13c9ee7e17d4> | 2.765625 | 765 | Content Listing | Science & Tech. | 33.160294 | 95,539,278 |
Service Oriented Integration
Service-oriented Integration (SOI) – a logical extension of functional integration – is where the applications integrate by using service interactions in an SOA environment. Service are provided by source application (service provider) and consumed by target applications (service consumers). Typically, SOI is implemented as systems that consume and provide XML-based Web services.
SOI addresses the issues of integrating heterogeneous and inflexible systems while overcoming the difficulties of functional Integration in terms of location and technology of the function. For example, functionality in a mainframe can be exposed as a web service implemented using a .Net framework.
In SOI, the service defines a contract – such as the technology, communications protocols, and message definitions – that all service consumers must conform to in order to communicate with the service. SOI enables loose coupling, thereby bringing flexibility and interoperability to newer heights – to the extent that the service provider as well as consumers need not be fixed – and the change in the service provider can be transparent to the service consumers.
In spite of its various benefits, Web Services using XML is not a panacea for all integration scenarios – as it involves considerable effort (for implementation) and overhead (during runtime). For example, usage of XML while providing maximum level of data independence does have a performance overhead due to transformations required.
Let us look at the W3 Definition of Web Services – “Web services architecture is an interoperability architecture that provides a standard means of interoperating between different software applications, running on a variety of platforms and/or frameworks”.
Web Service and XML make the most sense in case of Integration between Unknowns, applications running in heterogeneous environment, and applications that change frequently.
If the organization has application predominantly running on a single platform and hence do not have the complexities associated with integration between disparate platforms – which is chiefly addressed by SOI, using SOI makes most sense for integration with external world – web portals, other web sites etc. – where the flexibility and interoperability is most required.
If SOI is considered for integration of applications internal to the organization – as they provide the maximum flexibility and interoperability, use of Enterprise Service Bus concept and use of commercial tools is strongly recommended.
For basic information on SOA, Web Services and ESB, refer to earlier blogs https://itknowledgeexchange.techtarget.com/enterprise-IT-tech-trends/essentials-of-soa-web-services-and-esb-in-the-integration-context-part-i/. | <urn:uuid:05fea787-138f-4a21-8164-97f4f47fa375> | 2.78125 | 527 | Knowledge Article | Software Dev. | 6.30333 | 95,539,290 |
A computer reconstruction of Haliestes (artificially colored, above), and a modern sea spider, Nymphon (bleached, below), which is about 50% larger, and with longer legs.
Volcanic ash that encased and preserved sea life in the Silurian age 425 million years ago near Herefordshire, UK has yielded fossils of an ancient sea spider, or pycnogonid, one of the most unusual types of arthropod in the seas today.
Sea spiders are soft-bodied arthropods, found widely in modern oceans. For two-centuries there has been a controversy about the relationship of sea spiders to land spiders, scorpions, ticks and mites because of their unique body form. Sea spiders have a long proboscis and unusual limb structures used in mating and carrying brooding embryos. The fossil record of their relationship is sparse because of their delicate nature.
"This is the earliest adult fossil example, and it is preserved in extraordinary detail," said author Derek Briggs, professor of geology and geophysics, and Director of the Yale Institute of Biospheric Studies. "Volcanic ash that trapped ancient sea life in this location rapidly encased the creatures making a concrete-like cast of the bodies. The cavity later filled in with carbonate solids so we have a fossil record to study now."
Janet Rettig Emanuel | 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:fe09264e-f63c-4b6d-8dcb-19f3e0a70a40> | 3.59375 | 872 | Content Listing | Science & Tech. | 36.892064 | 95,539,295 |
If a brand new item must be produced ahead of the copying can manifest, the duplicate constructor is employed (Observe: this features passing or returning objects by benefit). If a whole new item doesn't have to be established prior to the copying can manifest, the assignment operator is employed. Overloading the assignment operatorThis purpose fin
which make using quite possibly the most error-vulnerable attributes of C++ redundant, so that they can be banned (inside our set of rules).They are meant to make code more simple and a lot more suitable/safer than most present C++ code, with out lack of effectiveness.You may order online homework on our Internet site and forget about all issues. E
(Easy) An assignment operator ought to return T& to permit chaining, not options like const T& which interfere with composability and putting objects in containers. Usually a constructor establishes an invariant and often acquires methods required for an object to be used (that happen to be then generally launched by a destructor).
(Very simple) An assignment operator really should return T& to empower chaining, not options like const T& which interfere with composability and Placing objects in containers.This simple guideline illustrates a subtle difficulty and demonstrates modern uses of inheritance and object-oriented structure principles.A examination must validate that t
What we need to do to help make this functionality would be to url The 2 into a true system. We don't have To accomplish this our selfs, we can just instruct gcc to make it happen for us:I would like server plan utilizing sockets(tcp connection) for several customer for just a Home windows. Anyone please give an answer or notionE mail Me : Use this | <urn:uuid:2ad36985-5c21-4e1d-947e-e8a025538b59> | 2.859375 | 348 | Tutorial | Software Dev. | 30.288597 | 95,539,303 |
10 Emerging Trends That Prove the World is Actually Getting Better
Nov 07, 2016 17:42
Society as a whole has progressed at an extremely fast rate in the last 100 years. So much so that we've actually made more progress in science and technology in the last 10 years alone. From raising life expectancy and reducing infant mortality, to improving literacy rates and information access, to also decreasing the percentage worldwide in extreme poverty, the world does indeed look like it is getting to a better place.
Here are some of the emerging trends that are also contributing to more good news than the usual bad we see on mainstream media.
10. 3D printing
It started out as science fiction on Star Trek, but has now become one step closer to revolutionizing how we produce, and unleash inventions and applications. While it’s been around for a while already, 3-D printing has only very recently become more affordable.
The possible applications for it also seem endless for now. From pushing out models and prototypes at a faster pace, it can also, very rudimentary print edible food too. For example, astronauts on the International Space Station may soon be able to eat some 3D printed pizza.
On top of that, scientists are also working on being able to produce living organs from 3D printing, which will no doubt be one of the biggest medical advances in the years to come. Imagine being able to print an organ instead of waiting for one on the donor’s list. This could change the medical landscape for good.
9. Supercomputers will make science and technology progress faster
With every turn of a yearly quarter, we are greeted with some new discovery and invention that could have the possibility of changing our lives. The pace of innovation seems to be speeding up compared to what we’ve seen in the past 20 years and it will only be getting faster from this point onwards.
The effect of such, can be seen with the introduction of supercomputers, crunching and processing more data for a desired result faster than what we could possibly have done in the past. Futurists like Ray Kurzweil even predict that a personal computer may be able to match the human brain capability by 2020.
It’s not surprising that it might be happening already. In very recent news, Google’s AI just beat one of the top players for a game of Go. If supercomputers can calculate thousands of permutations in a game, imagine what more can be done for science! The Go board game champion eventually bested Google’s AI after losing a couple of rounds before that.
For now, science is dishing out more definite research of the things we didn’t know for sure before, and technology is paving the way for it. From gene research to slow down aging to other kinds of incredible medical advances, we’re at the cusp of a better world for sure.
8. We may one day be able to travel without accidents happening
Self driving cars may just be around the corner. Or at least, until Google figures out how not to cause one after their most recent and only crash.
Nevertheless, the idea of self-driving cars would primarily be to reduce the amount of human error. Nothing can be perfect or faultless, which is why the auto industry is still, we’re guessing, hard at work figuring out how to bring this to market and comply with changing laws to accommodate such a paradigm shift in how we travel daily.
Many automakers are already experimenting with introductory features from self-parking to taking control of your vehicle for you on a highway. And as our technology continues to progress, we see companies adding more like collision avoidance to headlights and even tires that are smart enough to communicate road and weather conditions to the car.
Regardless, the tech is here, and we’re probably very close to perfecting it, and with any luck and hope, accidents on the road could be a thing of the past, or reduced to the most minimal of accounts.
7. The Ozone layer is slowly recovering
Thanks to the ban on CFC and the reduction of carbon footprint, the world's efforts are slowly starting to pay off. Over 300 scientists found that the ozone layer is on its track to recovery in the next few decades. Scientists predict that our naturally-made protective layer should recover in a couple of decades. .
The hole that was discovered some 40 years ago has been discovered to be repairing itself. If this keeps up, we could very well see an avoidable decrease in sun-related skin cancers. More importantly, the hole over the arctic is slowly closing up. Still, we face a real risk of rising sea levels as the ice in the arctic continue to melt an alarming rate.
We need the ozone layer. Desperately too. And even as the hole closes up, scientists say that we can expect temperatures to rise by 3 degrees Celsius on average still. The biggest threat is coming from warming seas for now, and even though the global rise has come to a plateau, we shouldn’t be resting on our laurels yet.
At the very least and as a first step to recovery, we’ll probably see the ozone layer’s hole fully closed by the end of the century.
6. We may be able to one day mine asteroids, thus saving the world.
Natural resource is finite. And to risk sounding like Superman’s birth planet’s history, many projects are now underway with the idea of mining an asteroid for what’s needed.
The first project of its kind is notably from the company called Planetary Resources. The objective is simple. Land an asteroid-mining robot on one and bring it back home for use on Earth. The idea sounds incredibly ambitious, and it may also answer some of our pressing questions of life elsewhere in the universe.
The idea isn’t far fetched either, as many agencies and companies are being set up to do this. According to its president and chief engineer, space mining could be reality by 2025. The goal is to first transform asteroid water into rocket fuel to further space exploration and then, eventually harvest valuable and useful metals from the space rocks.
But weirdly enough, the race to space mining could potentially set off a Star War. Though, I think we’ll only cross that bridge when we get there. For now, we might have to gamble on its resources to help the rest of humanity.
5. Bill Gates might actually make his poo-water thing work.
Many of Bill Gates’ interesting feats have been done outside of Microsoft. He’s now more concerned in making the world, literally a better place. One of his highlight projects from 2015 was the showcase technology that turns pee into water.
Clean water is a luxury most of us take for granted. And that’s because we’re not living in an area where it doesn’t exist. For certain parts of the world, this problem isn’t just affecting how dehydrated a person can be, but also, the many other problems that come from bad and dirty water. Chief example of this would be water-borne diseases.
If successfully implemented, Bill Gates’ poo water could do many things, and one of its primary goal is extending human life expectancy for people with no access to clean water. According to news and research, 1-10 suffer and perish from water-borne diseases.
Bill may not have the persona of Tony Stark, but he’s got the will and brains to get it done. He’s also working on multiple ideas on how to make the world a better place. You can check out his blog for more information on other projects.
4. We are very very close to beating HIV
Our battle with HIV seems to be one of the longest ones we’ve had for decades. It almost feels as if we’re not really making any progress since there’s no “cure” per se. However, that could not be any more false, but the answer is more complicated.
From stem cell treatment to new drugs, medical advances have been more effective than before, notably in keeping it at bay and in some instances curing it too. Antiretroviral drugs have shown positive results in certain cases of removing the virus if administered at an extremely early stage.
HIV is incredibly complex and stubborn. It evolves faster than most of the other viruses and for that reason, it’s able to escape total annihilation. Future and experimental treatments target the broad properties of the virus making it harder for HIV to change or escape. If we are able to keep it in its unevolved stage, we might be able to laser in with the kill.
While the answer isn’t definite for the time being, scientists are working on multiple models to tackle the problem. We’re almost there, and it’s only a matter of time before we unlock its secrets completely.
3. Companies are reducing their carbon footprint
The cost of business can be high, but in this day and age, companies are finding more efficient and cheaper ways to produce the same quality stuff whilst leaving a smaller carbon footprint.
LEGO, is searching for a sustainable material to substitute its plastic bricks to dramatically reduce (LINK 26) its environmental impact seeing in just 2014 the company produce 60 billion of them. Levi’s is looking to reduce the amount of water that it takes in the manufacturing process of their jeans. Microsoft and Facebook are both using alternative methods to power and cool their datacenters.
Still, the global greenhouse gas emissions are on a high but very much lower compared (LINK 30) to the past decade. As countries like China reduce its coal dependence, we can expect some good changes to happen, albeit at a slow pace.
A more concerted effort in this aspect will have significant positive consequences. One that’s worth looking at from both a business and environmental point of view.
2. Brain signals can control stuff
Imagine being able to use your mind to control your limbs. Scientists are making breakthroughs like this by translating brain signals into commanding lines for prosthetic parts. Its potential stretches beyond helping amputees and the unfortunate. Further progress may open the doors to helping people walk again.
Projects like these aren’t just making life better, but it’ll also help us understand the complexity of our brains and the possibility of discovering all its secrets. If being able to control limbs and exosuits sounds impressive, how about using your brainwaves to control a robot too?
Thought-controlled robotics work by recognizing which brain signals do what, and then telling machines to do just that when these signals are detected. Scientists don’t need to understand how the brain was creating those signals. They only needed to recognize its patterns and make machines do that too.
The applications of this seem endless. From limbs to machines, to even a car that is controlled by your thoughts.
1. Miracle material stops bleeding fast
A huge percentage of deaths are potentially survivable - if only they did not bleed out. A 17-year-old teenager invented a way to stop all it. The concept of his product is basically a gel that holds the wound together, and a binding agent that repairs the tissue.
Joe Landolina's biotech company may play a role in saving more lives in the future than we possibly could in the past with their product VeTiGel. It works by first creating a mesh around the wound to stitch it up, and uses fibrin to as a bonding agent to clot the blood and heal the wound at the same time.
That’s not all either. A new Israeli bandage is now being used as a treatment to stop a deadly hemorrhage without having the need to apply pressure.
Both approaches can help not just in emergency situations but also during surgery if and when bleeding goes out of control.
If you are looking forward to rank your website on top, you might have asked SEO experts a common question – how much time does it take to reach the top rank on Google? The answer is complicated and can never be definite. Read more
It is, without doubt, evident that SEO has had a massive impact in the internet world today, so much that emerging website owners are already informed on techniques like keyword SERP tracking to give the ultimate SEO value to their site. Additionally, useful tools have come up, such as the social network checker that allows web owners, bloggers, small business owners as well as large enterprises check whether the content they share on social media have an impact on their overall digital marketing strategy, and it is affecting the overall ranking of their sites. Read more
Demand for 3D printing has exploded in recent years with hundreds of new 3D printer producers being developed to help meet this huge growth in demand. So, who are the new trailblazers in the industry? We take a look at the top five manufacturers of 3D printers, who are set to shape the industry with new products and innovations. Read more | <urn:uuid:399741e1-0935-4115-aa9e-528a413d9100> | 2.5625 | 2,700 | Listicle | Science & Tech. | 53.190198 | 95,539,382 |
Importance of terrestrially-derived, particulate phosphorus to phosphorus dynamics in a west coast estuary
- R. M. Chambers, J. W. Fourqurean, J. T. Hollibaugh, S. M. Vink
- Estuaries SCOPUS
- Coastal and Estuarine Research Federation in 1995
- Cited Count
- Springer JSTOR
Allochthonous inputs of suspended particulate matter from freshwater environments to estuaries influence nutrient cycling and ecosystem metabolism. Contributions of different biogeochemical reactions to phosphorus dynamics in Tomales Bay, California, were determined by measuring dissolved inorganic phosphorus exchange between water and suspended particulate matter in response to changes in salinity, pH, and sediment redox. In serum bottle incubations of suspended particulate matter collected from the major tributary to the bay, dissolved inorganic phosphorus release increased with salinity during the initial 8 h; between 1–3 d, however, rates of release were similar among treatments of 0 psu, 16 psu, 24 psu, and 32 psu. Release was variable over the pH range 4–8.5, but dissolved inorganic phosphorus releases from sediments incubated for 24 h at the pH of fresh water (7.3) and seawater (8.1) were similarly small. Under oxidizing conditions, dissolved inorganic phosphorus release was small or dissolved inorganic phosphorus was taken up by particulate matter with total P content <50 μmoles P g−1; release was greater from suspended particulate matter with total phosphorus content >50 μmoles P g−1. In contrast, under reducing conditions maintained by addition of free sulfide (HS−), dissolved inorganic phosphorus was released from particles at all concentrations of total phosphorus in suspended particulate matter, presumably from the reduction of iron oxides. Since extrapolated dissolved inorganic phosphorus release from this abiotic source can account for only 12.5% of the total dissolved inorganic phosphorus flux from Tomales Bay sediments, we conclude most release from particles is due to organic matter oxidation that occurs after estuarine deposition. The abiotic, sedimentary flux of dissolved inorganic phosphorus, however, could contribute up to 30% of the observed net export of dissolved inorganic phosphorus from the entire estuary.
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We're about to build our first webpage: a homepage for your blog! But first, let's learn a little bit about Django URLs.
What is a URL?
A URL is simply a web address. You can see a URL every time you visit a website – it is visible in your browser's address bar. (Yes!
127.0.0.1:8000 is a URL! And
https://djangogirls.org is also a URL.)
Every page on the Internet needs its own URL. This way your application knows what it should show to a user who opens that URL. In Django, we use something called
URLconf (URL configuration). URLconf is a set of patterns that Django will try to match the requested URL to find the correct view.
How do URLs work in Django?
Let's open up the
mysite/urls.py file in your code editor of choice and see what it looks like:
"""mysite URL Configuration [...] """ from django.urls import path, include from django.contrib import admin urlpatterns = [ path('admin/', admin.site.urls), ]
As you can see, Django has already put something here for us.
Lines between triple quotes (
""") are called docstrings – you can write them at the top of a file, class or method to describe what it does. They won't be run by Python.
The admin URL, which you visited in the previous chapter, is already here:
This line means that for every URL that starts with
admin/, Django will find a corresponding view. In this case, we're including a lot of admin URLs so it isn't all packed into this small file – it's more readable and cleaner.
Your first Django URL!
Time to create our first URL! We want 'http://127.0.0.1:8000/' to be the home page of our blog and to display a list of posts.
We also want to keep the
mysite/urls.py file clean, so we will import URLs from our
blog application to the main
Go ahead, add a line that will import
blog.urls. Note that we are using the
include function here so you will need to add that import.
mysite/urls.py file should now look like this:
from django.urls import path, include from django.contrib import admin urlpatterns = [ path('admin/', admin.site.urls), path('', include('blog.urls')), ]
Django will now redirect everything that comes into 'http://127.0.0.1:8000/' to
blog.urls and looks for further instructions there.
Create a new empty file named
urls.py in the
blog directory. All right! Add these first two lines:
from django.urls import path from . import views
Here we're importing Django's function
url and all of our
views from the
blog application. (We don't have any yet, but we will get to that in a minute!)
After that, we can add our first URL pattern:
urlpatterns = [ path('', views.post_list, name='post_list'), ]
As you can see, we're now assigning a
post_list to the root URL. This URL pattern will match an empty string and the Django URL resolver will ignore the domain name (i.e., http://127.0.0.1:8000/) that prefixes the full url path. This pattern will tell Django that
views.post_list is the right place to go if someone enters your website at the 'http://127.0.0.1:8000/' address.
The last part,
name='post_list', is the name of the URL that will be used to identify the view. This can be the same as the name of the view but it can also be something completely different. We will be using the named URLs later in the project, so it is important to name each URL in the app. We should also try to keep the names of URLs unique and easy to remember.
If you try to visit http://127.0.0.1:8000/ now, then you'll find some sort of 'web page not available' message. This is because the server (remember typing
runserver?) is no longer running. Take a look at your server console window to find out why.
Your console is showing an error, but don't worry – it's actually pretty useful: It's telling you that there is no attribute 'post_list'. That's the name of the view that Django is trying to find and use, but we haven't created it yet. At this stage, your
/admin/ will also not work. No worries – we will get there.
If you want to know more about Django URLconfs, look at the official documentation: https://docs.djangoproject.com/en/2.0/topics/http/urls/ | <urn:uuid:8d4e3da2-252c-472f-8682-abb043e517c5> | 3.234375 | 1,076 | Tutorial | Software Dev. | 83.044989 | 95,539,399 |
Millions of years ago, a pair of exploding stars showered our planet with radioactive fallout. Had those supernovae popped off a bit closer to home, Earth's biosphere would have been toast. But even at a distance of 300 light years, the stellar events might have had an impact on the evolution of life here. A supernova remnant. Image: NASA
The idea that astrophysical phenomena, including black hole x-ray flares and supernovae, can shake up life on Earth enough to direct evolution has been around for a while. And when a crop of scientific studies published in Nature and Science this past April presented evidence for two nearby back-to-back supernovae toward the end of the Pliocene, scientists immediately began discussing potential impacts on Earth's climate and biology.
Now, the hypothesis that there were impacts has gotten a boost from a computer modelling study, which estimates how much additional radiation life on Earth was dosed with following the cosmic fireworks. To cut to the chase, the radiation load for terrestrial and shallow marine life would have roughly tripled for thousands of years after each event, thanks to a 20-fold increase in the number of high-energy muon particles striking the ground.
This was a bit of a surprise. "I was expecting there to be very little effect at all," said University of Kansas physicist Adrian Melott, who co-authored the study appearing this week in The Astrophysical Journal Letters.
Melott is not a biologist, but he doesn't seem to mind a bit of wild speculation where supernovae are concerned. Regarding the new finding, he says the extra radiation at ground level might have been enough to increase the rate of DNA mutation, which in turn could have briefly sped-up evolution. (Evolution can't occur unless DNA is mutating, a process that typically happens very, very slowly.)
The study further suggests that high-energy cosmic radiation could have increased the ionisation, or electric charge, of the troposphere, resulting in more cloud-to-ground lightning strikes. Whether tropospheric ionisation had an additional climatic or ecological impact remains an open question.
It's by no means a silver bullet for the argument that supernovae have impacted evolution — just another shred of evidence that the history of life on Earth was a rocky roller coaster. Really, it's a miracle we're here at all. | <urn:uuid:7ae952db-83df-47ed-a403-b3b8d7129292> | 3.84375 | 486 | News Article | Science & Tech. | 36.946374 | 95,539,426 |
Each of our Solar System's outer gaseous planets hosts a system of multiple satellites, and these objects include Jupiter's volcanic Io and Europa with its believed subsurface ocean, as well as Titan with its dense and organic-rich atmosphere at Saturn. While individual satellite properties vary, the systems all share a striking similarity: the total mass of each satellite system compared to the mass of its host planet is very nearly a constant ratio, roughly 1:10,000.
Research by scientists at Southwest Research Institute, published in the June 15 issue of Nature, proposes an explanation as to why the gaseous planets display this consistency, and why the satellites of gas planets are so much smaller compared to their planet than the principal satellites of solid planets.
Jupiter's four Galilean satellites are each roughly similar in size, while Saturn has one large satellite together with numerous much smaller satellites. Even so, the total mass in both satellite systems is about a hundredth of one percent (0.0001) of the respective planet's mass. The Uranian satellite system structure is similar to that of Jupiter, and it also exhibits the same mass ratio. In contrast, the large satellites of solid planets contain much larger fractions of their planet's masses, with the Moon containing 1 percent (0.01) of the Earth's mass, and Pluto's satellite, Charon, containing more than 10 percent (0.1) of its mass.
Why do the gas planets, each with unique formation histories of their own, have satellite systems containing a consistent fraction of each planet's mass, and why is this fraction so small compared to solid planet satellites? Dr. Robin Canup and Dr. William Ward of the SwRI Space Studies Department propose that it was the presence of gas, primarily hydrogen, during the formation of these satellites that limited their growth and selected for a common satellite system mass fraction.
As the gas planets formed, they accumulated hydrogen gas and solids such as rock and ice. The final stage of a gas planet's formation is believed to involve an inflow of both gas and solids from solar orbit into planetary orbit, producing a disk of gas and solids orbiting the planet in its equatorial plane. It is within that disk that the satellites are believed to have formed.
Canup and Ward considered that a growing satellite's gravity induces spiral waves in a surrounding gas disk, and that gravitational interactions between these waves and the satellite cause the satellite's orbit to contract. This effect becomes stronger as a satellite grows, so that the bigger a satellite gets, the faster its orbit spirals inward toward the planet. The team proposes that the balance of two processes -- the ongoing inflow of material to the satellites during their growth and the loss of satellites to collision with the planet -- implies a maximum size for a gas planet satellite consistent with observations.
Using both numerical simulations and analytical estimates of the growth and loss of satellites, the team shows that multiple generations of satellites were likely, with today's satellites being the last surviving generation that formed as the planet's growth ceased and the gas disk dissipated. Canup and Ward demonstrate that during multiple cycles of satellite growth and loss, the fraction of the planet's mass contained in its satellites at any given time maintains a value not very different from 0.0001 across a wide range of model parameter choices.
The team's direct simulations are also the first to produce satellite systems similar to those of Jupiter, Saturn and Uranus in terms of number of satellites, their largest masses and the spacings of the large satellite orbits.
"We believe our results present a strong case that the satellite systems of Jupiter and Saturn formed within disks produced as the planet itself was in its final growth stages," says Canup. "However, the origin of the Uranian satellite system remains more uncertain, and the likelihood of our results being applicable to that planet depends on how Uranus achieved its nearly 98-degree axial tilt, which is a topic of active study."
For extrasolar systems, this research suggests that the largest satellites of a Jupiter-mass planet would be Moon-to-Mars sized, so that Jovian-sized exoplanets would not be expected to host satellites as large as the Earth. This is relevant to the potential habitability of satellites in extrasolar systems.
The NASA Planetary Geology and Geophysics and Outer Planets Research programs funded this research. The article, "A common mass scaling for satellite systems of gaseous planets," by Canup and Ward, appears in the June 15 issue of Nature.
Source: Southwest Research Institute
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Anthropogenic noise is a burgeoning issue for national parks. Acoustical monitorng has revealed chronic noise exposure even in remote wilderness sites. Increased noise levels significantly reduce the distance and area over which acoustic signals can be sensed by an animal receiver. A borad range of research findings indicates the potential severity of this threat to diverse taxa, and recent studies document substantial changes in behavior, breeding success, density and community structure in response to noise. Ansalysis of these data make a compelling case for systemic efforts to preserve acoustic environments throughout the National Park System.
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DescriptionDiscover new and emerging applications of polymer nanofibers alongside the basic underlying science and technology. With discussions exploring such practical applications as filters, fabrics, sensors, catalysts, scaffolding, drug delivery, and wound dressings, the book provides polymer scientists and engineers with a comprehensive, practical ""how-to"" reference. Moreover, the author offers an expert assessment of polymer nanofibers' near-term potential for commercialization. Among the highlights of coverage is the book's presentation of the science and technology of electrospinning, including practical information on how to electrospin different polymer systems.
1.1 Historical Background.
1.2 Basic Experimental Approach.
1.3 Description of Electrostatic Spinning.
1.4 Nanofiber Applications Areas.
2 Introduction to Polymer Solutions.
2.1 Average Molecular Weight.
2.2 Selecting Solvents: Solubility Parameter.
2.3 Thermodynamic Criterion for Solubility.
2.4 Macromolecular Models.
2.5 Viscosity of Dilute Polymer Solutions.
2.6 Concentrated Polymer Solutions.
3 Electrospinning Basics.
3.1 Molecular Weight Effects 56
3.2 Electrical Charge.
3.3 Bead Formation in Electrospinning.
3.4 Introduction to Electrospinning Practice.
4 Factors Affecting Nanofiber Quality.
4.1 The Polymer Solution.
4.4 Applied Potential.
4.5 Feed Rate.
4.6 Capillary Tip.
4.7 Gap Distance.
4.8 Relative Importance of Variables.
4.9 Examples of Reported Data.
5 Characterization of Nanofibers and Mats.
5.1 Mat Porosity and Pore Size Distribution.
5.2 Nanofiber Diameters and Pore Sizes by Microscopy.
5.3 Mechanical Properties of Mats.
5.4 Single-Fiber Characterization.
5.5 Nanofiber Crystallinity.
6 Composite Nanofibers.
6.1 Carbon Nanotubes in Nanofibers.
6.2 Metal–Nanofiber Composites.
6.3 Polymer–Clay Composites.
6.4 Decorated or Exocomposite Nanofibers.
7 Biomedical Applications of Nanofibers.
7.1 Drug Delivery Applications.
7.2 Scaffolding Applications of Nanofibers.
7.2.1 Natural Biopolymers.
7.3 Other Applications.
7.4 Future Directions.
8 Applications of Nanofiber Mats.
8.1 Introduction to Air Filtration.
8.2 Nanofiber Sensors.
8.3 Inorganic Nanofibers.
9 Recent Developments in Electrospinning.
9.1 Nanofibers with Surface Porosity.
9.2 Core–Shell Nanofibers.
9.3 Highly Aligned Nanofiber Mats.
9.4 Mixed Polymer Nanofibers and Nanofiber Mats.
9.5 Crosslinked Nanofibers.
Appendix I. Electrospun Polymers Used in Tissues Engineering and biomedical Applications.
Appendix II: Summary Table of Electrospun Polymer Nanofibers. | <urn:uuid:60b98ad6-d2cc-4c0d-968b-72d04b7af51d> | 2.625 | 700 | Content Listing | Science & Tech. | 35.927822 | 95,539,450 |
Hyperbolic Sets, Symbolic Dynamics, and Strange Attractors
The solutions of ordinary differential equations can have an erratic time dependence which appears in some ways to be random. We have seen several such examples in Chapter 2. The present chapter is devoted to a discussion of simple, geometrically defined systems in which such chaotic motion occurs. We shall describe both the irregular character of individual solutions and the complicated geometric structures associated with their limiting behavior. The principal technique which we use is called symbolic dynamics and the general approach to the questions we adopt is referred to as dynamical systems theory. We shall not develop this theory systematically but will state some of its major results and provide a brief guide to its literature. Our strategy in solving specific problems will generally involve the use of numerical or perturbation methods, such as those of Chapter 4, to establish the existence of interesting geometrical structure in appropriate Poincaré maps, followed by the use of the methods of this chapter.
KeywordsUnstable Manifold Hausdorff Dimension Stable Manifold Strange Attractor Symbolic Dynamics
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+44 1803 865913
By: H Denny, J Treweek, B Wood and Michael Gillman
173 pages, Col figs
This book looks at three topics in environmental science: Grasslands discusses the importance of grasslands and introduces the different types. It considers the pressures on grassland ecosystems and looks at various approaches to conservation, management and restoration. Tropical Forests takes a look inside tropical forests, at their structure, biodiversity and the interactions that take place within them. It concludes with a section which discusses the future of these forests. Biological Conservation discusses how science can help identify and quantify conservation problems and suggests possible solutions to these problems. Throughout the book there are questions and activities for the reader to engage with. Answers and explanations are provided at the end of each section.
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An electric potential (also called the electric field potential, potential drop or the electrostatic potential) is the amount of work needed to move a unit positive charge from a reference point to a specific point inside the field without producing any acceleration. Typically, the reference point is Earth or a point at Infinity, although any point beyond the influence of the electric field charge can be used.
According to classical electrostatics, electric potential is a scalar quantity denoted by V or occasionally φ, equal to the electric potential energy of any charged particle at any location (measured in joules) divided by the charge of that particle (measured in coulombs). By dividing out the charge on the particle a quotient is obtained that is a property of the electric field itself.
This value can be calculated in either a static (time-invariant) or a dynamic (varying with time) electric field at a specific time in units of joules per coulomb (J C−1), or volts (V). The electric potential at infinity is assumed to be zero.
A generalized electric scalar potential is also used in electrodynamics when time-varying electromagnetic fields are present, but this can not be so simply calculated. The electric potential and the magnetic vector potential together form a four vector, so that the two kinds of potential are mixed under Lorentz transformations. Work done by external force in bringing a unit positive charge from any point 'P' to point 'R' is Vp-Vr = (Up-Ur)/q .
Classical mechanics explores concepts such as force, energy, potential etc. Force and potential energy are directly related. A net force acting on any object will cause it to accelerate. As an object moves in the direction in which the force accelerates it, its potential energy decreases: the gravitational potential energy of a cannonball at the top of a hill is greater than at the base of the hill. As it rolls downhill its potential energy decreases, being translated to motion, kinetic energy.
It is possible to define the potential of certain force fields so that the potential energy of an object in that field depends only on the position of the object with respect to the field. Two such force fields are the gravitational field and an electric field (in the absence of time-varying magnetic fields). Such fields must affect objects due to the intrinsic properties of the object (e.g., mass or charge) and the position of the object.
Objects may possess a property known as electric charge and an electric field exerts a force on charged objects. If the charged object has a positive charge the force will be in the direction of the electric field vector at that point while if the charge is negative the force will be in the opposite direction. The magnitude of the force is given by the quantity of the charge multiplied by the magnitude of the electric field vector.
where C is an arbitrary path connecting the point with zero potential to r. When the curl ∇ × E is zero, the line integral above does not depend on the specific path C chosen but only on its endpoints. In this case, the electric field is conservative and determined by the gradient of the potential:
The potential energy and hence also the electric potential is only defined up to an additive constant: one must arbitrarily choose a position where the potential energy and the electric potential are zero.
These equations cannot be used if the curl ∇ × E ≠ 0, i.e., in the case of a nonconservative electric field (caused by a changing magnetic field; see Maxwell's equations). The generalization of electric potential to this case is described below.
Electric potential due to a point charge
The electric potential arising from a point charge Q, at a distance r from the charge is observed to be
where ε0 is the permittivity of vacuum. This is known as the Coulomb potential.
The electric potential due to a system of point charges is equal to the sum of the point charges' individual potentials. This fact simplifies calculations significantly, since addition of potential (scalar) fields is much easier than addition of the electric (vector) fields.
The equation given above for the electric potential (and all the equations used here) are in the forms required by SI units. In some other (less common) systems of units, such as CGS-Gaussian, many of these equations would be altered.
Generalization to electrodynamics
When time-varying magnetic fields are present (which is true whenever there are time-varying electric fields and vice versa), it is not possible to describe the electric field simply in terms of a scalar potential V because the electric field is no longer conservative: is path-dependent because (Faraday's law of induction).
Instead, one can still define a scalar potential by also including the magnetic vector potential A. In particular, A is defined to satisfy:
where B is the magnetic field. Because the divergence of the magnetic field is always zero due to the absence of magnetic monopoles, such an A can always be found. Given this, the quantity
is a conservative field by Faraday's law and one can therefore write
where V is the scalar potential defined by the conservative field F.
The electrostatic potential is simply the special case of this definition where A is time-invariant. On the other hand, for time-varying fields,
The SI derived unit of electric potential is the volt (in honor of Alessandro Volta), which is why a difference in electric potential between two points is known as voltage. Older units are rarely used today. Variants of the centimeter gram second system of units included a number of different units for electric potential, including the abvolt and the statvolt.
Galvani potential versus electrochemical potential
Inside metals (and other solids and liquids), the energy of an electron is affected not only by the electric potential, but also by the specific atomic environment that it is in. When a voltmeter is connected between two different types of metal, it measures not the electric potential difference, but instead the potential difference corrected for the different atomic environments. The quantity measured by a voltmeter is called electrochemical potential or fermi level, while the pure unadjusted electric potential V is sometimes called Galvani potential . The terms "voltage" and "electric potential" are a bit ambiguous in that, in practice, they can refer to either of these in different contexts.
- Absolute electrode potential
- Electrochemical potential
- Electrode potential
- Gluon field
- Liénard–Wiechert potential
- Mathematical descriptions of the electromagnetic field
- Voltage, or (electric) potential difference
- Politzer P, Truhlar DG (1981). Chemical Applications of Atomic and Molecular Electrostatic Potentials: Reactivity, Structure, Scattering, and Energetics of Organic, Inorganic, and Biological Systems. Boston, MA: Springer US. ISBN 978-1-4757-9634-6.
- Sen K, Murray JS (1996). Molecular Electrostatic Potentials: Concepts and Applications. Amsterdam: Elsevier. ISBN 978-0-444-82353-3.
- Griffiths DJ (1998). Introduction to Electrodynamics (3rd. ed.). Prentice Hall. ISBN 0-13-805326-X.
- Jackson JD (1999). Classical Electrodynamics (3rd. ed.). USA: John Wiley & Sons, Inc. ISBN 978-0-471-30932-1.
- Wangsness RK (1986). Electromagnetic Fields (2nd., Revised, illustrated ed.). Wiley. ISBN 978-0-471-81186-2.
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News from Mathnasium of Pasadena
How Geometry Explains the Phases of the Moon
Sep 27, 2017
As you’ve probably noticed, the Moon doesn’t always look the same. In fact, the Moon goes through a “moonthly” cycle lasting about 29.5 days (yes, that’s where the word “month” comes from). This cycle takes the Moon through its full range of phases and eventually leaves it back in the phase it started in.
As you’ve probably also noticed, the Moon is occasionally visible during the day. In fact, if you’re paying attention, you may have noticed that it’s visible during the day a lot. But it’s also sometimes only visible during the night. And if you are really paying attention, you may have noticed that there’s a relationship between when the Moon is visible during the day or night and its phase.
What’s behind this relationship? What determines what time of day the Moon is visible? And what causes the Moon to change phases in the first place? The answer is math—and, in particular, geometry.
How does it work? Let's find out.
It's getting warm outside ... Come in to Mathnasium and let's learn math!
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Marshall Fundamental’s 8th-grade Math Field Day team won the top team trophy in the 2017 LA...
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The technology took a long time to acquire, required step by step planning and increased social interaction across the generations. This led to the human brain developing new abilities.
200 000 years ago, small groups of people wandered across Africa, looking like us anatomically but not thinking the way we do today. Studies of fossils and the rate of mutations in DNA show that the human species to which we all belong – Homo sapiens sapiens – has existed for 200 000 years.
But the archaeological research of recent years has shown that, even though the most ancient traces of modern humans are 200 000 years old, the development of modern cognitive behaviour is probably much younger. For about 100 000 years, there were people who looked like us, but who acted on the basis of cognitive structures in which we would only partially recognise ourselves and which we do not define today as modern behaviour.
It is precisely that period of transformation that the researchers at Lund University in Sweden have studied. In the next issue of the well renowned Journal of Human Evolution, they present their new findings on the early modern humans that existed in what is now South Africa, approximately 80 000 years ago.
The findings show that people at that time used advanced technology for the production of spearheads and that the complicated crafting process developed the working memory and social life of humans.
“When the technology was passed from one generation to the next, from adults to children, it became part of a cultural learning process which created a socially more advanced society than before. This affected the development of the human brain and cognitive ability”, says Anders Högberg, PhD.
The technology led to increased social interaction within and across the generations. This happened because the crafting of stone spearheads took a long time to learn and required a lot of knowledge, both theoretical and practical. Producing a stone spearhead also required the ability to plan in several stages. This social learning contributed to the subsequent development of early modern humans’ cognitive ability to express symbolism and abstract thoughts through their material culture, for example in the form of decorated objects.
“The excavations have been carried out in a small cave; the location we have studied is called Hollow Rock Shelter and lies 250 km north of Cape Town. We are cooperating with the University of Cape Town and the research we have just published is part of a larger research project on this location”, says Professor Lars Larsson.The article is entitled Lithic technology and behavioural modernity: New results from the Still Bay site, Hollow Rock Shelter, Western Cape Province, South Africa.
http://authors.elsevier.com/offprints/YJHEV1563/70884d412686a738f8080c0e473c6c11For more information, please contact:
Megan Grindlay | idw
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
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NASA's Aqua satellite passed over Typhoon Ma-on early on July 19, at 0347 UTC (11:47 p.m. EDT on July 18) and imagery from the Atmospheric Infrared Sounder (AIRS) instrument showed a large area of very cold cloud top temperatures from strong thunderstorms to the east and south of the center. As Ma-on moved near the island of Shikoku today, infrared satellite data showed the cloud tops warmed (dropped in height). That's because Ma-on was interacting with the land and wind shear increased, weakening the strength of convection (that builds the thunderstorms).
The TRMM satellite captured the rainfall rates occurring within Typhoon Ma-on (before it weakened) on July 19. The red areas are heavy rainfall, falling at a rate of 2 inches (50 mm) per hour. The yellow and green areas indicate moderate rainfall between .78 to 1.57 inches (20-40 mm) per hour. Credit: NASA/SSAI, Hal Pierce
At 1500 UTC (11 a.m. EDT) on July 19, Typhoon Ma-on's maximum sustained winds were near 55 knots. Tropical storm-force winds extended out to 140 miles from the storm's center. Ma-on was moving to the northeast near 10 knots. It was about 300 miles west-southwest of Yokosuka, Japan near 33.3 North and 134.2 East. At that time, it was brushing the island of Shikoku's southern coast near Muroto Point. Shikoku one of four islands in the four main islands of Japan, and is the smallest. It is located south of Honshu.
Ma-on is expected to continue weakening and is now expected to recurve to the east-southeast and head back to sea sometime on July 20.
Rob Gutro | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
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New postcranial skeleton of ancient dolphin Albertocetus meffordum found in South Carolina
A partial skeleton from an Oligocene dolphin species was found in South Carolina, according to a study published November 8, 2017 in the open-access journal PLOS ONE by Robert Boessenecker from the College of Charleston, South Carolina, USA, and Erum Ahmed and Jonathan Geisler from the New York Institute of Technology, New York, USA.
Previous research has shed light on the early evolutionary history of toothed whales, and particularly xenorophid dolphins – the earliest group of echolocating dolphins. Since the archaeological record for Xenorophidae is very limited, prior studies have focused on the crania or earbones of xenorophid dolphins.
The authors of the present study report five new specimens of xenorophid dolphins from North and South Carolina. Four of the specimens belonged to the xenorophid Albertocetus meffordorum, and one contained a partial skeleton including ribs, vertebrae, and chevrons as well as a partial skull and mandible. Since these specimens were collected from formations dating to the Oligocene (33.9 million to 23 million years before the present), this finding extends the known evolutionary history for this group.
The researchers studied the internal anatomy of the Albertocetus cranium using CT scan data, revealing that its brain was quite large in size, the largest yet for an early Oligocene toothed whale. Brain anatomy was further intermediate between modern cetaceans (such as dolphins, whales, and porpoises) and terrestrial even-toed hoofed animals (such as pigs, deer, and sheep). The partial vertebral column indicates that Albertocetus retained a similar shape and moved similarly to its archaeocete ancestors that lived 40 to 35 million years ago. Vertebrae from the tail indicate that Albertocetus had tail flukes like modern dolphins, but not a caudal peduncle – a narrow tail stock seen in all modern whales and dolphins.
The authors suggest that further collecting efforts in North and South Carolina might yield additional cetaceans that are contemporary with the specimens described in this study, and would continue to piece together the evolutionary history of this species.
The lead author Robert Boessenecker says, "Fossils like these new specimens of Albertocetus are critical windows into the earliest evolution of modern whales, and shed light on the split between baleen whales and echolocating whales about 30-35 million years ago."
In your coverage please use this URL to provide access to the freely available article in PLOS ONE: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0186476
Citation: Boessenecker RW, Ahmed E, Geisler JH (2017) New records of the dolphin Albertocetus meffordorum (Odontoceti: Xenorophidae) from the lower Oligocene of South Carolina: Encephalization, sensory anatomy, postcranial morphology, and ontogeny of early odontocetes. PLoS ONE 12(11): e0186476. https://doi.org/10.1371/journal.pone.0186476
Funding: This work was supported by National Science Foundation DEB 0640361 JHG and National Science Foundation EAR 1349607 JHG. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
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Gaussian process(Redirected from Gaussian processes)
In probability theory and statistics, a Gaussian process is a stochastic process (a collection of random variables indexed by time or space), such that every finite collection of those random variables has a multivariate normal distribution, i.e. every finite linear combination of them is normally distributed. The distribution of a Gaussian process is the joint distribution of all those (infinitely many) random variables, and as such, it is a distribution over functions with a continuous domain, e.g. time or space.
A machine-learning algorithm that involves a Gaussian process uses lazy learning and a measure of the similarity between points (the kernel function) to predict the value for an unseen point from training data. The prediction is not just an estimate for that point, but also has uncertainty information—it is a one-dimensional Gaussian distribution (which is the marginal distribution at that point).
For some kernel functions, matrix algebra can be used to calculate the predictions using the technique of kriging. When a parameterised kernel is used, optimisation software is typically used to fit a Gaussian process model.
The concept of Gaussian processes is named after Carl Friedrich Gauss because it is based on the notion of the Gaussian distribution (normal distribution). Gaussian processes can be seen as an infinite-dimensional generalization of multivariate normal distributions.
Gaussian processes are useful in statistical modelling, benefiting from properties inherited from the normal. For example, if a random process is modelled as a Gaussian process, the distributions of various derived quantities can be obtained explicitly. Such quantities include the average value of the process over a range of times and the error in estimating the average using sample values at a small set of times.
is a multivariate Gaussian random variable. That is the same as saying every linear combination of has a univariate normal (or Gaussian) distribution. Using characteristic functions of random variables, the Gaussian property can be formulated as follows: is Gaussian if and only if, for every finite set of indices , there are real-valued , with such that the following equality holds for all
where denotes the imaginary unit .
A key fact of Gaussian processes is that they can be completely defined by their second-order statistics. Thus, if a Gaussian process is assumed to have mean zero, defining the covariance function completely defines the process' behaviour. Importantly the non-negative definiteness of this function enables its spectral decomposition using the Karhunen–Loève expansion. Basic aspects that can be defined through the covariance function are the process' stationarity, isotropy, smoothness and periodicity.
Stationarity refers to the process' behaviour regarding the separation of any two points x and x' . If the process is stationary, it depends on their separation, x − x', while if non-stationary it depends on the actual position of the points x and x'. For example, the special case of an Ornstein–Uhlenbeck process, a Brownian motion process, is stationary.
If the process depends only on |x − x'|, the Euclidean distance (not the direction) between x and x', then the process is considered isotropic. A process that is concurrently stationary and isotropic is considered to be homogeneous; in practice these properties reflect the differences (or rather the lack of them) in the behaviour of the process given the location of the observer.
Ultimately Gaussian processes translate as taking priors on functions and the smoothness of these priors can be induced by the covariance function. If we expect that for "near-by" input points x and x' their corresponding output points y and y' to be "near-by" also, then the assumption of continuity is present. If we wish to allow for significant displacement then we might choose a rougher covariance function. Extreme examples of the behaviour is the Ornstein–Uhlenbeck covariance function and the squared exponential where the former is never differentiable and the latter infinitely differentiable.
Periodicity refers to inducing periodic patterns within the behaviour of the process. Formally, this is achieved by mapping the input x to a two dimensional vector u(x) = (cos(x), sin(x)).
Usual covariance functionsEdit
There are a number of common covariance functions:
- Constant :
- Gaussian noise:
- Squared exponential:
- Rational quadratic:
Here . The parameter ℓ is the characteristic length-scale of the process (practically, "how close" two points and have to be to influence each other significantly), δ is the Kronecker delta and σ the standard deviation of the noise fluctuations. Moreover, is the modified Bessel function of order and is the gamma function evaluated at . Importantly, a complicated covariance function can be defined as a linear combination of other simpler covariance functions in order to incorporate different insights about the data-set at hand.
Clearly, the inferential results are dependent on the values of the hyperparameters θ (e.g. ℓ and σ) defining the model's behaviour. A popular choice for θ is to provide maximum a posteriori (MAP) estimates of it with some chosen prior. If the prior is very near uniform, this is the same as maximizing the marginal likelihood of the process; the marginalization being done over the observed process values . This approach is also known as maximum likelihood II, evidence maximization, or empirical Bayes.
Brownian motion as the integral of Gaussian processesEdit
The fractional Brownian motion is a Gaussian process whose covariance function is a generalisation of that of the Wiener process.
A Gaussian process can be used as a prior probability distribution over functions in Bayesian inference. Given any set of N points in the desired domain of your functions, take a multivariate Gaussian whose covariance matrix parameter is the Gram matrix of your N points with some desired kernel, and sample from that Gaussian.
Inference of continuous values with a Gaussian process prior is known as Gaussian process regression, or kriging; extending Gaussian process regression to multiple target variables is known as cokriging. Gaussian processes are thus useful as a powerful non-linear multivariate interpolation tool. Gaussian process regression can be further extended to address learning tasks in both supervised (e.g. probabilistic classification) and unsupervised (e.g. manifold learning) learning frameworks.
Gaussian processes can also be used in the context of mixture of experts models, for example. The underlying rationale of such a learning framework consists in the assumption that a given mapping cannot be well captured by a single Gaussian process model. Instead, the observation space is divided into subsets, each of which is characterized by a different mapping function; each of these is learned via a different Gaussian process component in the postulated mixture.
Gaussian process prediction, or krigingEdit
When concerned with a general Gaussian process regression problem (kriging), it is assumed that for a Gaussian process f observed at coordinates x, the vector of values is just one sample from a multivariate Gaussian distribution of dimension equal to number of observed coordinates |x|. Therefore, under the assumption of a zero-mean distribution, , where is the covariance matrix between all possible pairs for a given set of hyperparameters θ. As such the log marginal likelihood is:
and maximizing this marginal likelihood towards θ provides the complete specification of the Gaussian process f. One can briefly note at this point that the first term corresponds to a penalty term for a model's failure to fit observed values and the second term to a penalty term that increases proportionally to a model's complexity. Having specified θ making predictions about unobserved values at coordinates x* is then only a matter of drawing samples from the predictive distribution where the posterior mean estimate A is defined as
and the posterior variance estimate B is defined as:
where is the covariance between the new coordinate of estimation x* and all other observed coordinates x for a given hyperparameter vector θ, and are defined as before and is the variance at point x* as dictated by θ. It is important to note that practically the posterior mean estimate (the "point estimate") is just a linear combination of the observations ; in a similar manner the variance of is actually independent of the observations . A known bottleneck in Gaussian process prediction is that the computational complexity of prediction is cubic in the number of points |x| and as such can become unfeasible for larger data sets. Works on sparse Gaussian processes, that usually are based on the idea of building a representative set for the given process f, try to circumvent this issue.
- "Platypus Innovation: A Simple Intro to Gaussian Processes (a great data modelling tool)".
- MacKay, David, J.C. (2003). Information Theory, Inference, and Learning Algorithms (PDF). Cambridge University Press. p. 540. ISBN 9780521642989.
The probability distribution of a function is a Gaussian processes if for any finite selection of points , the density is a Gaussian
- Dudley, R.M. (1989). Real Analysis and Probability. Wadsworth and Brooks/Cole.
- Bishop, C.M. (2006). Pattern Recognition and Machine Learning. Springer. ISBN 0-387-31073-8.
- Barber, David (2012). Bayesian Reasoning and Machine Learning. Cambridge University Press. ISBN 978-0-521-51814-7.
- Rasmussen, C.E.; Williams, C.K.I (2006). Gaussian Processes for Machine Learning. MIT Press. ISBN 0-262-18253-X.
- Grimmett, Geoffrey; David Stirzaker (2001). Probability and Random Processes. Oxford University Press. ISBN 0198572220.
- Seeger, Matthias (2004). "Gaussian Processes for Machine Learning". International Journal of Neural Systems. 14 (2): 69–104. doi:10.1142/s0129065704001899.
- The documentation for scikit-learn also has similar examples.
- Liu, W.; Principe, J.C.; Haykin, S. (2010). Kernel Adaptive Filtering: A Comprehensive Introduction. John Wiley. ISBN 0-470-44753-2.
- Stein, M.L. (1999). Interpolation of Spatial Data: Some Theory for Kriging. Springer.
- Emmanouil A. Platanios and Sotirios P. Chatzis, “Gaussian Process-Mixture Conditional Heteroscedasticity,” IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 36, no. 5, pp. 888–900, May 2014.
- Sotirios P. Chatzis, “A Latent Variable Gaussian Process Model with Pitman-Yor Process Priors for Multiclass Classification,” Neurocomputing, vol. 120, pp. 482–489, Nov. 2013.
- Smola, A.J.; Schoellkopf, B. (2000). "Sparse greedy matrix approximation for machine learning". Proceedings of the Seventeenth International Conference on Machine Learning: 911–918.
- Csato, L.; Opper, M. (2002). "Sparse on-line Gaussian processes". Neural Computation. 14 (3): 641–668. doi:10.1162/089976602317250933.
- The Gaussian Processes Web Site, including the text of Rasmussen and Williams' Gaussian Processes for Machine Learning
- A gentle introduction to Gaussian processes
- A Review of Gaussian Random Fields and Correlation Functions
- STK: a Small (Matlab/Octave) Toolbox for Kriging and GP modeling
- Kriging module in UQLab framework (Matlab)
- Matlab/Octave function for stationary Gaussian fields
- Yelp MOE – A black box optimization engine using Gaussian process learning
- ooDACE – A flexible object-oriented Kriging matlab toolbox.
- GPstuff – Gaussian process toolbox for Matlab and Octave
- GPy – A Gaussian processes framework in Python
- Interactive Gaussian process regression demo
- Basic Gaussian process library written in C++11
- scikit-learn – A machine learning library for Python which includes Gaussian process regression and classification
- - The Kriging toolKit (KriKit) is developed at the Institute of Bio- and Geosciences 1 (IBG-1) of Forschungszentrum Jülich (FZJ) | <urn:uuid:4b03182b-4179-4f33-9c95-991adb1ce718> | 3.34375 | 2,694 | Knowledge Article | Science & Tech. | 39.570047 | 95,539,545 |
Fossils of tiny ball-like creatures from around 600 million years ago are reported
- September 29, 2014
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New-found fossils of strange, tiny ball-like creatures from around 600 million years ago are reported in the research journal Nature this week.
Understanding creatures from this early time has been difficult as they are very different from anything alive today. The newfound fossils are no exception. They seem to represent a lineage that became an evolutionary dead end-they are not ancestors of living animals, according to the authors of the new study.
The fossils, from an area in southern China called the Ediacaran Doushantuo Formation, date back to just before a burst of animal diversity known as the Cambrian explosion, according to the researchers. Life had not yet emerged from the oceans. Yet this “pre-Cambrian era,” with hard-to-find fossils, represents almost 90 percent of the history of life on Earth.
The new specimens, slightly under a millimeter wide, are thought to offer a window onto the early evolution of complex multiple-celled organisms.
Many fossils from the region in China seem defy attempts to categorize them. For example, Megasphaera-another ball-like microfossil made up of one or more cells in a thick envelope-has been thought to represent various groups, including bacteria, algae or early animal embryos.
The new “microfossils” from the Doushantuo Formation show clear signs of traits characteristic of animals, said the authors, Shuhai Xiao of Virginia Tech university and colleagues. These characteristics include cell differentiation; separation of reproductive cells; and “programmed” cell death, a system used to clear out no-longer-useful cells.
The evidence indicates the fossils, dubbed Megaclonophycus, probably aren't bacteria, the authors said, calling for further investigation into where the minuscule creatures sit on the “family tree” of life.
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Volume 18 Issue 9
The UK has recently taken steps to protect the oceans from further pollution, and these steps involve tiny pieces of plastic called “microbeads.” If you have been in the cosmetics aisle at Target or your local grocery stores in the last year, you have run into these small but very impactful pieces of plastic. They are the shiny flecks in exfoliating scrubs and other gel products. But they are also in other places, including cleaning products and synthetic clothing.
The problem with microbeads exists just in what might seem to make them unimportant: their size. Imagine you have just taken a shower, and the shampoo and body wash that you use just happens to contain these tiny, probably meaningless microbeads. You turn the shower off, and the remnants of your soaps wash down the drain, microbeads and all. This water eventually finds itself at a wastewater treatment plant, so the microbeads should be taken care of here. Right? Wrong. Microbeads are so small that they cannot be filtered: they slip through the cracks. And these cracks lead to local waterways, the rivers you drive along on your way to work, which lead to the oceans. And the microbeads begin to build up in the ocean, tiny pieces of plastic unable to be broken down.
But how much impact can these microbeads really have? According to a report conducted in 2016 by the Environmental Audit Committee of the British House of Commons, just one shower can involve over 100,000 microbeads down the drain. Multiply 100,000 by the number of people in the world and you will get a gigantic number. Furthermore, this results in an enormous amount of plastic entering our oceans every single day. And for what reason? So that our shampoos are more aesthetically appealing?
The massive amount of microbeads building up in the oceans have deadly effects on marine life. When microbeads make their journey from the shampoo bottle to the ocean, they tend to absorb chemicals along the way. These chemicals could be anything from motor oil to industrial chemicals that have found their way into local waterways. So, when a fish ingests a microbead, it is ingesting any number of chemicals. Not only is this bad news for the fish, but it is also bad news for any other living thing connected to that fish through their ecosystems. In short, microbeads are killing an unknown amount of marine life.
The good news is that the UK has decided to join a (hopefully) growing list of countries that have decided to outlaw microbeads. The United States passed the Microbeads-Free Waters Act of 2015, which outlawed microbeads beginning in July 2017, and Canada and New Zealand imposed bans which are beginning this year. Microbeads are still alive and well, but more countries in the European Union are starting to join in the outlawing. Moreover, eight million tons of plastic may be entering the oceans every year, but, perhaps, these new laws will start to really make a difference in that number.
Shoe, Des. “The U.K. Has Banned Microbeads, Why?” New York Times. New York Times. 9 January 2018. Web. 11 February 2018. | <urn:uuid:5a313748-7d70-4251-8bc2-82311103d224> | 3.65625 | 689 | Nonfiction Writing | Science & Tech. | 58.409962 | 95,539,552 |
- Open Access
MicroRNA, sex determination and floral meristem determinacy in maize
© BioMed Central Ltd 2008
Published: 30 January 2008
Sex determination in the flowers of maize involves the abortion of stamen or pistil development. Recent work investigating genes that control this process reveals that a microRNA is involved in both the sex determination of the male inflorescence and its growth pattern.
The decision to develop as a male or female is fundamental to most life forms. In animals the genetic and environmental signals that influence this decision are diverse and the subject of intense study, yet this question has received relatively little attention in plants. Why the difference? While unisexuality is common in animals, it is not so common in flowering plants. The model plant Arabidopsis thaliana, for example, has perfect (bisexual) flowers with pollen-producing stamens and ovule-producing pistils wrapped in whorls of petals and sepals. While we have a clear understanding of how the identity of floral organs is controlled in Arabidopsis, this plant is of limited value for understanding how plant species have attained unisexuality. For the most part, flowering plants with bisexual flowers have collectively evolved a multitude of additional and interesting mechanisms to avoid self-fertilization, which most animal species avoid by making sure that each individual is unisexual and populations have equal proportions of males and females.
Of those flowering plant species that do produce unisexual flowers, some are dioecious, having strictly male or female flowers and unisexual individuals, whereas others are monoecious and produce both unisexual male and female flowers but on the same plant. Maize (Zea mays) is a monoecious plant that produces imperfect (unisexual) male flowers, or florets, in the tassel and imperfect female florets in the ear. In maize, imperfect florets arise by the arrest of stamen development in female flowers and by the abortion of pistil primordials in the male, suggesting that sex determination is not a problem of floral-organ identity, but rather a matter of what regulates the arrest of stamen or pistil development in the ear and tassel florets, respectively. In maize, the application of the plant hormone gibberellin (GA) to tassels feminizes the tassel, whereas depletion of endogenous GA masculinizes ear florets , indicating that stamen and pistil development are under hormonal control. Given the rich history of maize genetics and the agronomic importance of its seeds, maize is an excellent and important system for understanding how unisexuality can evolve in flowering plants.
The architecture of the maize tassel is fairly complex (Figure 1a), even though the hundreds of individual tassel florets are extremely reduced in size and simple in structure, as illustrated in Figure 1b. Each male floret consists of two bracts (the lemma and palea), two minute scales called lodicules, and three stamens. Florets are organized into units, called spikelets, with each spikelet enclosed by two bracts called glumes. In maize, each male spikelet contains two florets, while those in the ear contain one. The spikelets are collectively organized into units called spikes, with many spikes collectively making up the tassel. The organization of spike, spikelets and florets is engineered by the inflorescence apical meristem, which contains the population of stem cells that deliver new daughter cells to the growing plant. As the spike inflorescence develops, the inflorescence meristem continuously forms new branch derivatives that initiate spikelet pair meristems; after branching, each spikelet pair meristem undergoes a transition to produce two spikelet meristems; each spikelet meristem then undergoes a transition to produce two floret meristems that initiate the organs of the floret. Eventually, all meristems terminate, the florets mature, open and shed their pollen.
The tassels of mutant ts4 plants differ from wild type in several ways (see Figure 1a): they have feminized florets, show increased spikelet branching and typically produce more than two florets per spikelet. The increase in branching and floret number reflects an inability of the meristems to switch from an indeterminate to a determinate state as the tassel develops. Thus, in addition to promoting male development, the wild-type ts4 gene functions to impose determinacy on the spikelet and spikelet pair meristems.
To understand how these tasselseed genes control sex determination in the male floret, Chuck and colleagues cloned the ts4 gene and discovered that it is a member of the miR172 family of microRNAs (miRNAs) that is known to regulate the APETALA2 (AP2) family of transcription factors [4, 5]. As it turns out, the same authors had previously shown that the maize indeterminate spikelet1 (ids1) gene encodes an AP2-like gene . Like ts4 tassels, ids1 tassels produce additional florets; however, ids1 florets in the tassel are not feminized like the ts4 florets.
How ids1 affects branching and meristem transitions is not clear, although some clues are provided by the characterization of ap2 mutations in Arabidopsis. In Arabidopsis, ectopic expression of a mutant form of ap2 altered in its miRNA172-binding site leads to several floral defects, including the loss of floral determinacy . This phenotype mimics the agamous (ag) phenotype, consistent with the function of AG as necessary for carpel initiation . Chuck et al. propose that a similar relationship between ids1 and an AG-like gene could occur in maize. By reducing AG expression in the floret, the prolonged expression of ids1 would prevent the differentiation of stem cells in the meristem, thus allowing the spikelet meristem to form additional floret meristems. This and other hypotheses remain to be tested.
From an evolutionary perspective, it will be interesting to see if the mechanism of sex determination in maize that is defined by ts4 and ids1 is common to other monoecious or dioecious species of plants, including the homosporous ferns, which determine their sexual phenotype during the gametophytic phase of growth and where meristem development and sex determination go hand-in-hand . Given that monoecy has evolved multiple times in different angiosperm lineages, and dioecy often follows , the study of Chuck et al. provides new tools to understand how widespread this mechanism of sex determination is.
- Nickerson NH: Sustained treatment with gibberellin acid of five different kinds of maize. Ann Mo Bot Gard. 1959, 46: 19-37. 10.2307/2394566.View ArticleGoogle Scholar
- Veit B, Schmidt RJ, Hake S, Yanofsky MF: Maize floral development: new genes and old mutants. Plant Cell. 1993, 5: 1205-1215. 10.1105/tpc.5.10.1205.PubMedPubMed CentralView ArticleGoogle Scholar
- Chuck G, Meeley R, Irish E, Sakai H, Hake S: The maize tasselseed4 microRNA controls sex determination and meristem cell fate by targeting Tasselseed6/indeterminate spikelet1. Nat Genet. 2007, 39: 1517-1521. 10.1038/ng.2007.20.PubMedView ArticleGoogle Scholar
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- Chen X: A microRNA as a translational repressor of APETALA2 in Arabidopsis flower development. Science. 2004, 303: 2022-2025. 10.1126/science.1088060.PubMedView ArticleGoogle Scholar
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- Irish EE: Experimental analysis of tassel development in the maize mutant tassel seed 6. Plant Physiol. 1997, 114: 817-825.PubMedPubMed CentralGoogle Scholar
- Lohmann JU, Weigel D: Building beauty: the genetic control of floral patterning. Dev Cell. 2002, 2: 135-142. 10.1016/S1534-5807(02)00122-3.PubMedView ArticleGoogle Scholar
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- Geber MA, Dawson TE, Delph LF: Gender and Sexual Dimorphism in Flowering Plants. 1999, Berlin: SpringerView ArticleGoogle Scholar | <urn:uuid:190a6c5f-8164-4d11-b832-d7f369ed4aa5> | 2.765625 | 1,988 | Academic Writing | Science & Tech. | 36.55277 | 95,539,566 |
Publisher: Wikibooks 2010
An introduction to the chemical world is set forth in this text. The units of study: Properties of Matter; Atomic Structure; Compounds and Bonding; Chemical Reactions; Aqueous Solutions; Phases of Matter; Chemical Equilibria; Chemical Kinetics; Thermodynamics; Chemistries of Various Elements.
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by Edward W. Pitzer - Bookboon
A brief introduction to the fundamentals of chemistry. The textbook is designed to introduce chemistry to students who will take only one chemistry course in their academic career. Certain chemistry topics are covered in a generalized manner.
by Craig Jensen, Etsuo Akiba, Hai-Wen Li (eds.) - MDPI AG
The reversible elimination of hydrogen from metal hydrides serves as the basis for unique methods of energy transformation. This technology has found widespread practical utilization in applications such as hydrogen compressors, storage, batteries.
by Thomas Eisner, Jerrold Meinwald - National Academies Press
This book highlights selected research areas that are contributing to advancement of chemical ecology. Leading experts review the chemistry of insect defense; phyletic dmoninance; social regulation; eavesdropping, alarm and deceit; and reproduction.
by Soren Prip Beier - BookBoon
Membrane processes are key unit operations in almost all parts of the chemical, biochemical, and pharmaceutical downstream processing. In this book, microfiltration, ultrafiltration, nanofiltration, and reverse osmosis are introduced. | <urn:uuid:1a65d62a-6315-4c63-af50-d6ae0acd6292> | 3.03125 | 325 | Content Listing | Science & Tech. | 12.624669 | 95,539,572 |
Many molecular materials, be they hydrogen for fuel cells or drugs, can be stored in metal-organic frameworks (MOFs).
This would even be possible for metal nano particles for catalysis, were there not one little hindrance: if the void spaces in the MOF are too large, a second embedded framework system automatically develops during the synthesis process. This "uncontrolled proliferation" leads to a significant reduction in the size of the voids.
A team of chemical scientists at the Ruhr-University in Bochum, working under the auspices of Prof. Christof Wöll and Prof. Roland A. Fischer have now managed to solve this major problem by developing an alternative preparation process. They do not allow the entire metal-organic framework to develop in one single step, but grow it layer-by-layer on an "intelligent" organic surface. This enables the formation of voids that are large enough for metal particles. The scientists have documented their results in the current edition of NATURE Materials.
Void spaces are too small for metals
The highly porous MOFs usually reveal two different types of structural elements. Transverse bars comprised of organic molecules are connected by inorganic coupling units containing metal ions. Mixing these reactants and heating leads to self-organized formation of MOFs. These metal-organic frameworks are of global interest because they can be loaded with the most diverse of materials. Prof. Wöll explained that the spectrum ranges from the storage of liquid hydrogen in the tank of a car all the way to a storage site for drugs. These "porous" materials are also of interest for heterogeneous catalysis. For this purpose, metal particles are embedded in the pores - this does, however, necessitate relatively large void spaces. Prof. Fischer pointed out that this has been a fundamental problem in the synthesis of MOFs to date. If the pores are too large, numerous instances of the MOF lattice develop simultaneously, forming an interlaced network of numerous structures. This in turn leads to reduction in the size of the individual voids within the frameworks.
Layer-by-layer production of larger frameworks
The scientists at the Departments of Physical Chemistry (Wöll) and Inorganic Chemistry (Fischer) at the Ruhr-University in Bonn (RUB) can now bypass this interpenetration problem. They developed a new synthesis procedure, described as liquid phase epitaxy, which differs from the usual synthesis (i.e. mixing all the reactants in solution and subsequent heating thereof). Intelligent surfaces coated with substrates are alternately dipped into pots each of which contains only one type of MOF structural element. The organic surfaces ensure that only one structural alternative of the MOF develops, thus avoiding interpenetration and yielding the desired large void spaces. Prof. Wöll is pleased to announce that it is thus now possible to produce materials with significantly larger pores than had been the case to date. Currently the scientists are trying to store metal clusters in the spacious voids. These in turn could be used for heterogeneous catalysis and sensorics.
The scientists produce the intelligent surfaces that ensure that exactly the desired MOFs develop by self-assembly: simply dipping metal substrates into solutions of so-called organothiols (sulphurous organic molecules) yields a high-quality organic coating. The sulphur atoms bind tightly to the metal substrate, thus acting as anchors for the organic molecules, yielding self-assembled monolayers (SAMs). The growth of the frameworks on the surface of the SAMs can then be controlled by the particular choice of the organothiol. It is even possible to "dictate" their orientation by using "tailor-made" SAMs
Osama Shekhah, Hui Wang, Markos Paradinas, Carmen Ocal, Björn Schüpbach, Andreas Terfort, Denise Zacher, Roland A. Fischer, and Christof Wöll: Controlling Interpenetration in Metal-Organic Frameworks by Liquid Phase Epitaxy. In: Nature Materials, 3.5.2009, DOI: 10.1038/NMAT2445
Prof. Christof Wöll, Department of Physical Chemistry I at the Ruhr-University Bochum, D-44780 Bochum, Germany, Tel: +49 (0) 234/32-25529, Fax: +49 (0) 234/32-14182, E-Mail: email@example.com, Faculty-Homepage: http://www.pc.rub.de
Dr. Josef König | idw
Further reports about: > CHEMISTRY > Large void storage volume > MOF > Metal-Organic Frameworks > heterogeneous catalysis > intelligent substrates > metal nano particles for catalysis > molecular-organic frameworks > organic molecule > organic molecules > organic surface > sulphur atoms > uncontrolled proliferation
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...
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17.07.2018 | Power and Electrical Engineering | <urn:uuid:8869526e-1e2f-475e-8d27-f46cff8e328d> | 3.359375 | 1,687 | Content Listing | Science & Tech. | 36.579782 | 95,539,583 |
Climate change due to human activities is predicted to change many aspects of the environment, from atmospheric carbon dioxide to temperature and rainfall1. Modellers are confident in the projected temperature increases, but the predictions about rainfall are much less certain. Changes in rainfall patterns will impact on many aspects of ecosystems, including how nutrients move.
Associate Professor Sally Power studies how these nutrient cycles are being affected by human-induced changes in the environment. She took up a position two years ago at the Hawkesbury Institute of the Environment, University of Western Sydney after completing her studies and working at the Imperial College in London. She previously completed a post-doctoral position at La Trobe University, Melbourne and loved Australia, so now she’s here permanently. Associate Professor Power is passionate about the understanding the interactive impact of multiple climate drivers on ecosystems.
At a recent seminar at Macquarie University Associate Professor Power spoke about three projects she is involved with at the moment:
- Drought and diversity in the UK (DIRECT)
- Rainfall extremes (DRI-grass)
- Elevated CO2 impacts on forest nutrient cycling (EucFACE)
The DIRECT project (Diversity, Rainfall and Elemental Cycling in a Terrestrial Ecosystem) aims to answer questions about how grassland ecosystems will respond to predicted rainfall changes and whether biodiversity will buffer these effects of a rainfall pattern change2. To test these ideas the research team constructed an array of grassland plots with a range of plants functional groups – perennials, caespitose grasses and annual plants (Figure 1)3.
Figure 1. Plant traits selection for the DIRECT experiment
Image: Grantham Institute, Imperial College London (4).
Rainfall predicted for the year 2100 (down 30% in summer, up 15% in winter) was applied to these plots to see how different vegetation communities might respond to rainfall changes2. Key ecosystem processes (such as respiration rate and nutrient cycling) were faster when there were a range of perennial plants present. Process rates in vegetation plots dominated by annual plants or caespitose grasses were not strongly affected by changes in rainfall2. This research showed that plant functional groups are important for maintaining grassland ecosystem function and they need to be considered in future management plans2.
In addition, the researchers used different plots in the same area and changed the rainfall pattern to see if drought and deluge impact differently on the grassland ecosystem. The rainfall treatments used were5:
- Current levels;
- Prolonged drought – 30% drop in rainfall; and
- Reduced frequency – same amount of rain, concentrated into heavier falls less frequently.
The key findings were that changing the frequency of rainfall affected the number of species, especially the perennial species5. Surprisingly the number of species was not affected by the change in the total amount of rain (prolonged drought). The reduced rainfall frequency also lead to an increase in respiration and the grassland ecosystem switched from being a net carbon sink to net carbon source (from overall absorbing carbon to overall emitting carbon; Figure 2)5. The results of this experiment suggest that grassland ecosystems are relatively resistant to predicted rainfall changes5.
Figure 2. Change from carbon sink to carbon source for each rainfall treatment (A = ambient; PD = prolonged drought; RF = reduced frequency; adapted from image presented by Associate Professor Power)
Associate Professor Power is also in the preliminary stages of some large scale experiments in western Sydney. The first of these experiments is DRI-grass (Drought & Root Herbivore Interactions in a Grassland Ecosystem). This study asks whether Australian grassland ecosystems have stronger responses to the amount or frequency of rain and whether these responses are affected by root herbivores6. Associate Professor Power emphasised that root herbivores are very abundant and their weight can exceed the weight of the sheep in a hectare7. Root herbivores can respond directly and indirectly to changes in rainfall patterns and can make it harder for plants to cope with climate change impacts8.
The research team has set up five different rainfall treatments: +50% rain; -50% rain; 3 week rainfall cycle with the same total amount of rain; summer drought; and the ambient conditions (Figure 3). The rainfall treatments only began in June 2013 and the root herbivores are not yet in place. So far the researchers have observed there are lower species abundances under drought conditions and an increase in summer rain has led to the dominance of African lovegrass.
Figure 3. Rainfall shelters for the DRI-grass experiment in the foothills
of the Blue Mountains (Image: The Hermon Slade Foundation; 6)
The second project in western Sydney is being conducted in the EucFACE facility (Eucalyptus Free Air CO2 Enrichment)9 located in an intact Cumberland Plain Woodland ecosystem. Associate Professor Power and her team are looking at how elevated CO2 increases rates of nutrient cycling in the ecosystem. So far they have noticed there is an increase in available phosphorus, but no change in the amount of available nitrogen in elevated CO2 conditions.
Once the data is collected from these long term experiments, Associate Professor Power aims to understand some of the impacts of climate change on grassland ecosystems and make recommendations about how these systems should be managed to mitigate these impacts.
- IPCC (2013). Summary for Policymakers. In: Climate Change 2013: The Physical Science Basis. Working Group I Contribution to the IPCC Fifth Assessment Report. Cambridge University Press, Cambridge.
- Fry EL, Manning P, Allen DGP, Hurst A, Everwand G, Rimmler M & Power SA (2013). Plant Functional Group Composition Modifies the Effects of Precipitation Change on Grassland Ecosystem Function. PLoS ONE, 8(2): e57027. doi: 10.1371/journal.pone.0057027.
- Fry EL, Power SA & Manning P (2014b). Trait-based classification and manipulation of plant functional groups for biodiversity-ecosystem function experiments. Journal of Vegetation Science, 25, 248–261. doi: 10.1111/jvs.12068.
- Fry E, Hurst A, Everwand G, Rimmler M, Manning P & Power S (2009). Poster: “Diversity, Rainfall and Elemental Cycling in a Terrestrial ecosystem, (DIRECT)” presented at Committee for Atmospheric Pollution Effects Research AGM. https://workspace.imperial.ac.uk/climatechange/public/pdfs/CAPER_poster.pdf, accessed 25 May 2014.
- Fry EL, Manning P & Power SA (2014a). Ecosystem functions are resistant to extreme changes to rainfall regimes in a mesotrophic grassland. Plant Soil, doi: 10.1007/s11104-014-2137-2.
- The Hermon Slade Foundation (2014). Drought, deluge and diversity decline – How do root herbivores affect grassland resilience to predicted changes in rainfall patterns? http://www.hermonslade.org.au/projects/HSF_13_12/hsf_13_12.html, accessed 25 May 2014.
- Britton E (1978). A revision of the Australian chafers (Coleoptera: Scarabaeidae: Melolonthinae) Vol. 2. Tribe Melolonthini. Australian Journal of Zoology, 26, 1–150, Supplementary Series.
- Bardgett RD & Wardle DA (2003). Herbivore-mediated linkages between aboveground and belowground communities. Ecology, 84, 2258-2268. doi: 10.1890/02-0274.
- Hawkesbury Institute of the Environment (2014). EucFACE, http://www.uws.edu.au/hie/facilities/face, accessed 25 May 2014. | <urn:uuid:02103a36-c23e-4455-a623-f198994a4bd2> | 3.390625 | 1,638 | About (Org.) | Science & Tech. | 39.570114 | 95,539,591 |
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Tracking of a Fluorescent Dye in a Freshwater Lake with an Unmanned Surface Vehicle and an Unmanned Aircraft System
Schmale, David G.
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Recent catastrophic events in our oceans, including the spill of toxic oil from the explosion of the Deepwater Horizon drilling rig and the rapid dispersion of radioactive particulates from the meltdown of the Fukushima Daiichi nuclear plant, underscore the need for new tools and technologies to rapidly respond to hazardous agents. Our understanding of the movement and aerosolization of hazardous agents from natural aquatic systems can be expanded upon and used in prevention and tracking. New technologies with coordinated unmanned robotic systems could lead to faster identification and mitigation of hazardous agents in lakes, rivers, and oceans. In this study, we released a fluorescent dye (fluorescein) into a freshwater lake from an anchored floating platform. A fluorometer (fluorescence sensor) was mounted underneath an unmanned surface vehicle (USV, unmanned boat) and was used to detect and track the released dye in situ in real-time. An unmanned aircraft system (UAS) was used to visualize the dye and direct the USV to sample different areas of the dye plume. Image processing tools were used to map concentration profiles of the dye plume from aerial images acquired from the UAS, and these were associated with concentration measurements collected from the sensors onboard the USV. The results of this project have the potential to transform monitoring strategies for hazardous agents, enabling timely and accurate exposure assessment and response in affected areas. Fast response is essential in reacting to the introduction of hazardous agents, in order to quickly predict and contain their spread. | <urn:uuid:d43c593d-663b-42e2-b33c-be0643bbe668> | 3.078125 | 359 | Academic Writing | Science & Tech. | 21.859842 | 95,539,596 |
In quantum mechanics, an atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus. The term atomic orbital may also refer to the physical region or space where the electron can be calculated to be present, as defined by the particular mathematical form of the orbital.
Each orbital in an atom is characterized by a unique set of values of the three quantum numbers n, ℓ, and m, which respectively correspond to the electron's energy, angular momentum, and an angular momentum vector component (the magnetic quantum number). Each such orbital can be occupied by a maximum of two electrons, each with its own spin quantum number s. The simple names s orbital, p orbital, d orbital and f orbital refer to orbitals with angular momentum quantum number ℓ = 0, 1, 2 and 3 respectively. These names, together with the value of n, are used to describe the electron configurations of atoms. They are derived from the description by early spectroscopists of certain series of alkali metal spectroscopic lines as sharp, principal, diffuse, and fundamental. Orbitals for ℓ > 3 continue alphabetically, omitting j (g, h, i, k, …) because some languages do not distinguish between the letters "i" and "j".
Atomic orbitals are the basic building blocks of the atomic orbital model (alternatively known as the electron cloud or wave mechanics model), a modern framework for visualizing the submicroscopic behavior of electrons in matter. In this model the electron cloud of a multi-electron atom may be seen as being built up (in approximation) in an electron configuration that is a product of simpler hydrogen-like atomic orbitals. The repeating periodicity of the blocks of 2, 6, 10, and 14 elements within sections of the periodic table arises naturally from the total number of electrons that occupy a complete set of s, p, d and f atomic orbitals, respectively, although for higher values of the quantum number n, particularly when the atom in question bears a positive charge, the energies of certain sub-shells become very similar and so the order in which they are said to be populated by electrons (e.g. Cr = [Ar]4s13d5 and Cr2+ = [Ar]3d4) can only be rationalized somewhat arbitrarily.
- 1 Electron properties
- 2 History
- 3 Orbital names
- 4 Hydrogen-like orbitals
- 5 Quantum numbers
- 6 Shapes of orbitals
- 7 Orbital energy
- 8 Electron placement and the periodic table
- 9 Transitions between orbitals
- 10 See also
- 11 References
- 12 Further reading
- 13 External links
With the development of quantum mechanics and experimental findings (such as the two slit diffraction of electrons), it was found that the orbiting electrons around a nucleus could not be fully described as particles, but needed to be explained by the wave-particle duality. In this sense, the electrons have the following properties:
- The electrons do not orbit the nucleus in the manner of a planet orbiting the sun, but instead exist as standing waves. Thus the lowest possible energy an electron can take is similar to the fundamental frequency of a wave on a string. Higher energy states are similar to harmonics of that fundamental frequency.
- The electrons are never in a single point location, although the probability of interacting with the electron at a single point can be found from the wave function of the electron. The charge on the electron acts like it is smeared out in space in a continuous distribution, proportional at any point to the squared magnitude of the electron's wave function.
- The number of electrons orbiting the nucleus can only be an integer.
- Electrons jump between orbitals like particles. For example, if a single photon strikes the electrons, only a single electron changes states in response to the photon.
- The electrons retain particle-like properties such as: each wave state has the same electrical charge as its electron particle. Each wave state has a single discrete spin (spin up or spin down) depending on its superposition.
Thus, despite the popular analogy to planets revolving around the Sun, electrons cannot be described simply as solid particles. In addition, atomic orbitals do not closely resemble a planet's elliptical path in ordinary atoms. A more accurate analogy might be that of a large and often oddly shaped "atmosphere" (the electron), distributed around a relatively tiny planet (the atomic nucleus). Atomic orbitals exactly describe the shape of this "atmosphere" only when a single electron is present in an atom. When more electrons are added to a single atom, the additional electrons tend to more evenly fill in a volume of space around the nucleus so that the resulting collection (sometimes termed the atom's "electron cloud") tends toward a generally spherical zone of probability describing the electron's location, because of the uncertainty principle.
Formal quantum mechanical definition
Atomic orbitals may be defined more precisely in formal quantum mechanical language. Specifically, in quantum mechanics, the state of an atom, i.e., an eigenstate of the atomic Hamiltonian, is approximated by an expansion (see configuration interaction expansion and basis set) into linear combinations of anti-symmetrized products (Slater determinants) of one-electron functions. The spatial components of these one-electron functions are called atomic orbitals. (When one considers also their spin component, one speaks of atomic spin orbitals.) A state is actually a function of the coordinates of all the electrons, so that their motion is correlated, but this is often approximated by this independent-particle model of products of single electron wave functions. (The London dispersion force, for example, depends on the correlations of the motion of the electrons.)
In atomic physics, the atomic spectral lines correspond to transitions (quantum leaps) between quantum states of an atom. These states are labeled by a set of quantum numbers summarized in the term symbol and usually associated with particular electron configurations, i.e., by occupation schemes of atomic orbitals (for example, 1s2 2s2 2p6 for the ground state of neon—term symbol: 1S0).
This notation means that the corresponding Slater determinants have a clear higher weight in the configuration interaction expansion. The atomic orbital concept is therefore a key concept for visualizing the excitation process associated with a given transition. For example, one can say for a given transition that it corresponds to the excitation of an electron from an occupied orbital to a given unoccupied orbital. Nevertheless, one has to keep in mind that electrons are fermions ruled by the Pauli exclusion principle and cannot be distinguished from the other electrons in the atom. Moreover, it sometimes happens that the configuration interaction expansion converges very slowly and that one cannot speak about simple one-determinant wave function at all. This is the case when electron correlation is large.
Fundamentally, an atomic orbital is a one-electron wave function, even though most electrons do not exist in one-electron atoms, and so the one-electron view is an approximation. When thinking about orbitals, we are often given an orbital visualization heavily influenced by the Hartree–Fock approximation, which is one way to reduce the complexities of molecular orbital theory.
Types of orbitals
Atomic orbitals can be the hydrogen-like "orbitals" which are exact solutions to the Schrödinger equation for a hydrogen-like "atom" (i.e., an atom with one electron). Alternatively, atomic orbitals refer to functions that depend on the coordinates of one electron (i.e., orbitals) but are used as starting points for approximating wave functions that depend on the simultaneous coordinates of all the electrons in an atom or molecule. The coordinate systems chosen for atomic orbitals are usually spherical coordinates (r, θ, φ) in atoms and cartesians (x, y, z) in polyatomic molecules. The advantage of spherical coordinates (for atoms) is that an orbital wave function is a product of three factors each dependent on a single coordinate: ψ(r, θ, φ) = R(r) Θ(θ) Φ(φ). The angular factors of atomic orbitals Θ(θ) Φ(φ) generate s, p, d, etc. functions as real combinations of spherical harmonics Yℓm(θ, φ) (where ℓ and m are quantum numbers). There are typically three mathematical forms for the radial functions R(r) which can be chosen as a starting point for the calculation of the properties of atoms and molecules with many electrons:
- The hydrogen-like atomic orbitals are derived from the exact solution of the Schrödinger Equation for one electron and a nucleus, for a hydrogen-like atom. The part of the function that depends on the distance r from the nucleus has nodes (radial nodes) and decays as e−(constant × distance).
- The Slater-type orbital (STO) is a form without radial nodes but decays from the nucleus as does the hydrogen-like orbital.
- The form of the Gaussian type orbital (Gaussians) has no radial nodes and decays as .
Although hydrogen-like orbitals are still used as pedagogical tools, the advent of computers has made STOs preferable for atoms and diatomic molecules since combinations of STOs can replace the nodes in hydrogen-like atomic orbital. Gaussians are typically used in molecules with three or more atoms. Although not as accurate by themselves as STOs, combinations of many Gaussians can attain the accuracy of hydrogen-like orbitals.
The term "orbital" was coined by Robert Mulliken in 1932 as an abbreviation for one-electron orbital wave function. However, the idea that electrons might revolve around a compact nucleus with definite angular momentum was convincingly argued at least 19 years earlier by Niels Bohr, and the Japanese physicist Hantaro Nagaoka published an orbit-based hypothesis for electronic behavior as early as 1904. Explaining the behavior of these electron "orbits" was one of the driving forces behind the development of quantum mechanics.
With J. J. Thomson's discovery of the electron in 1897, it became clear that atoms were not the smallest building blocks of nature, but were rather composite particles. The newly discovered structure within atoms tempted many to imagine how the atom's constituent parts might interact with each other. Thomson theorized that multiple electrons revolved in orbit-like rings within a positively charged jelly-like substance, and between the electron's discovery and 1909, this "plum pudding model" was the most widely accepted explanation of atomic structure.
Shortly after Thomson's discovery, Hantaro Nagaoka predicted a different model for electronic structure. Unlike the plum pudding model, the positive charge in Nagaoka's "Saturnian Model" was concentrated into a central core, pulling the electrons into circular orbits reminiscent of Saturn's rings. Few people took notice of Nagaoka's work at the time, and Nagaoka himself recognized a fundamental defect in the theory even at its conception, namely that a classical charged object cannot sustain orbital motion because it is accelerating and therefore loses energy due to electromagnetic radiation. Nevertheless, the Saturnian model turned out to have more in common with modern theory than any of its contemporaries.
In 1909, Ernest Rutherford discovered that the bulk of the atomic mass was tightly condensed into a nucleus, which was also found to be positively charged. It became clear from his analysis in 1911 that the plum pudding model could not explain atomic structure. In 1913 as Rutherford's post-doctoral student, Niels Bohr proposed a new model of the atom, wherein electrons orbited the nucleus with classical periods, but were only permitted to have discrete values of angular momentum, quantized in units h/2π. This constraint automatically permitted only certain values of electron energies. The Bohr model of the atom fixed the problem of energy loss from radiation from a ground state (by declaring that there was no state below this), and more importantly explained the origin of spectral lines.
After Bohr's use of Einstein's explanation of the photoelectric effect to relate energy levels in atoms with the wavelength of emitted light, the connection between the structure of electrons in atoms and the emission and absorption spectra of atoms became an increasingly useful tool in the understanding of electrons in atoms. The most prominent feature of emission and absorption spectra (known experimentally since the middle of the 19th century), was that these atomic spectra contained discrete lines. The significance of the Bohr model was that it related the lines in emission and absorption spectra to the energy differences between the orbits that electrons could take around an atom. This was, however, not achieved by Bohr through giving the electrons some kind of wave-like properties, since the idea that electrons could behave as matter waves was not suggested until eleven years later. Still, the Bohr model's use of quantized angular momenta and therefore quantized energy levels was a significant step towards the understanding of electrons in atoms, and also a significant step towards the development of quantum mechanics in suggesting that quantized restraints must account for all discontinuous energy levels and spectra in atoms.
With de Broglie's suggestion of the existence of electron matter waves in 1924, and for a short time before the full 1926 Schrödinger equation treatment of hydrogen-like atom, a Bohr electron "wavelength" could be seen to be a function of its momentum, and thus a Bohr orbiting electron was seen to orbit in a circle at a multiple of its half-wavelength (this physically incorrect Bohr model is still often taught to beginning students). The Bohr model for a short time could be seen as a classical model with an additional constraint provided by the 'wavelength' argument. However, this period was immediately superseded by the full three-dimensional wave mechanics of 1926. In our current understanding of physics, the Bohr model is called a semi-classical model because of its quantization of angular momentum, not primarily because of its relationship with electron wavelength, which appeared in hindsight a dozen years after the Bohr model was proposed.
The Bohr model was able to explain the emission and absorption spectra of hydrogen. The energies of electrons in the n = 1, 2, 3, etc. states in the Bohr model match those of current physics. However, this did not explain similarities between different atoms, as expressed by the periodic table, such as the fact that helium (two electrons), neon (10 electrons), and argon (18 electrons) exhibit similar chemical inertness. Modern quantum mechanics explains this in terms of electron shells and subshells which can each hold a number of electrons determined by the Pauli exclusion principle. Thus the n = 1 state can hold one or two electrons, while the n = 2 state can hold up to eight electrons in 2s and 2p subshells. In helium, all n = 1 states are fully occupied; the same for n = 1 and n = 2 in neon. In argon the 3s and 3p subshells are similarly fully occupied by eight electrons; quantum mechanics also allows a 3d subshell but this is at higher energy than the 3s and 3p in argon (contrary to the situation in the hydrogen atom) and remains empty.
Modern conceptions and connections to the Heisenberg uncertainty principle
Immediately after Heisenberg discovered his uncertainty principle, Bohr noted that the existence of any sort of wave packet implies uncertainty in the wave frequency and wavelength, since a spread of frequencies is needed to create the packet itself. In quantum mechanics, where all particle momenta are associated with waves, it is the formation of such a wave packet which localizes the wave, and thus the particle, in space. In states where a quantum mechanical particle is bound, it must be localized as a wave packet, and the existence of the packet and its minimum size implies a spread and minimal value in particle wavelength, and thus also momentum and energy. In quantum mechanics, as a particle is localized to a smaller region in space, the associated compressed wave packet requires a larger and larger range of momenta, and thus larger kinetic energy. Thus the binding energy to contain or trap a particle in a smaller region of space increases without bound as the region of space grows smaller. Particles cannot be restricted to a geometric point in space, since this would require an infinite particle momentum.
In chemistry, Schrödinger, Pauling, Mulliken and others noted that the consequence of Heisenberg's relation was that the electron, as a wave packet, could not be considered to have an exact location in its orbital. Max Born suggested that the electron's position needed to be described by a probability distribution which was connected with finding the electron at some point in the wave-function which described its associated wave packet. The new quantum mechanics did not give exact results, but only the probabilities for the occurrence of a variety of possible such results. Heisenberg held that the path of a moving particle has no meaning if we cannot observe it, as we cannot with electrons in an atom.
In the quantum picture of Heisenberg, Schrödinger and others, the Bohr atom number n for each orbital became known as an n-sphere in a three dimensional atom and was pictured as the mean energy of the probability cloud of the electron's wave packet which surrounded the atom.
Orbitals are given names are usually given in the form:
where X is the energy level corresponding to the principal quantum number n, type is a lower-case letter denoting the shape or subshell of the orbital and it corresponds to the angular quantum number ℓ, and y is the number of electrons in that orbital.
For example, the orbital 1s2 (pronounced as the individual numbers and letters: "one ess two") has two electrons and is the lowest energy level (n = 1) and has an angular quantum number of ℓ = 0.
There is also another, less common system still used in X-ray science known as X-ray notation, which is a continuation of the notations used before orbital theory was well understood. In this system, the principal quantum number is given a letter associated with it. For n = 1, 2, 3, 4, 5, …, the letters associated with those numbers are K, L, M, N, O, … respectively.
The simplest atomic orbitals are those that are calculated for systems with a single electron, such as the hydrogen atom. An atom of any other element ionized down to a single electron is very similar to hydrogen, and the orbitals take the same form. In the Schrödinger equation for this system of one negative and one positive particle, the atomic orbitals are the eigenstates of the Hamiltonian operator for the energy. They can be obtained analytically, meaning that the resulting orbitals are products of a polynomial series, and exponential and trigonometric functions. (see hydrogen atom).
For atoms with two or more electrons, the governing equations can only be solved with the use of methods of iterative approximation. Orbitals of multi-electron atoms are qualitatively similar to those of hydrogen, and in the simplest models, they are taken to have the same form. For more rigorous and precise analysis, numerical approximations must be used.
A given (hydrogen-like) atomic orbital is identified by unique values of three quantum numbers: n, ℓ, and mℓ. The rules restricting the values of the quantum numbers, and their energies (see below), explain the electron configuration of the atoms and the periodic table.
The stationary states (quantum states) of the hydrogen-like atoms are its atomic orbitals.[clarification needed] However, in general, an electron's behavior is not fully described by a single orbital. Electron states are best represented by time-depending "mixtures" (linear combinations) of multiple orbitals. See Linear combination of atomic orbitals molecular orbital method.
The quantum number n first appeared in the Bohr model where it determines the radius of each circular electron orbit. In modern quantum mechanics however, n determines the mean distance of the electron from the nucleus; all electrons with the same value of n lie at the same average distance. For this reason, orbitals with the same value of n are said to comprise a "shell". Orbitals with the same value of n and also the same value of ℓ are even more closely related, and are said to comprise a "subshell".
Because of the quantum mechanical nature of the electrons around a nucleus, atomic orbitals can be uniquely defined by a set of integers known as quantum numbers. These quantum numbers only occur in certain combinations of values, and their physical interpretation changes depending on whether real or complex versions of the atomic orbitals are employed.
In physics, the most common orbital descriptions are based on the solutions to the hydrogen atom, where orbitals are given by the product between a radial function and a pure spherical harmonic. The quantum numbers, together with the rules governing their possible values, are as follows:
The principal quantum number n describes the energy of the electron and is always a positive integer. In fact, it can be any positive integer, but for reasons discussed below, large numbers are seldom encountered. Each atom has, in general, many orbitals associated with each value of n; these orbitals together are sometimes called electron shells.
The azimuthal quantum number ℓ describes the orbital angular momentum of each electron and is a non-negative integer. Within a shell where n is some integer n0, ℓ ranges across all (integer) values satisfying the relation . For instance, the n = 1 shell has only orbitals with , and the n = 2 shell has only orbitals with , and . The set of orbitals associated with a particular value of ℓ are sometimes collectively called a subshell.
The magnetic quantum number, , describes the magnetic moment of an electron in an arbitrary direction, and is also always an integer. Within a subshell where is some integer , ranges thus: .
The above results may be summarized in the following table. Each cell represents a subshell, and lists the values of available in that subshell. Empty cells represent subshells that do not exist.
|ℓ = 0||ℓ = 1||ℓ = 2||ℓ = 3||ℓ = 4||…|
|n = 1|
|n = 2||0||−1, 0, 1|
|n = 3||0||−1, 0, 1||−2, −1, 0, 1, 2|
|n = 4||0||−1, 0, 1||−2, −1, 0, 1, 2||−3, −2, −1, 0, 1, 2, 3|
|n = 5||0||−1, 0, 1||−2, −1, 0, 1, 2||−3, −2, −1, 0, 1, 2, 3||−4, −3, −2, −1, 0, 1, 2, 3, 4|
Subshells are usually identified by their - and -values. is represented by its numerical value, but is represented by a letter as follows: 0 is represented by 's', 1 by 'p', 2 by 'd', 3 by 'f', and 4 by 'g'. For instance, one may speak of the subshell with and as a '2s subshell'.
Each electron also has a spin quantum number, s, which describes the spin of each electron (spin up or spin down). The number s can be +1/ or −1/.
The Pauli exclusion principle states that no two electrons in an atom can have the same values of all four quantum numbers. If there are two electrons in an orbital with given values for three quantum numbers, (n, l, m), these two electrons must differ in their spin.
The above conventions imply a preferred axis (for example, the z direction in Cartesian coordinates), and they also imply a preferred direction along this preferred axis. Otherwise there would be no sense in distinguishing m = +1 from m = −1. As such, the model is most useful when applied to physical systems that share these symmetries. The Stern–Gerlach experiment — where an atom is exposed to a magnetic field — provides one such example.
An atom that is embedded in a crystalline solid feels multiple preferred axes, but often no preferred direction. Instead of building atomic orbitals out of the product of radial functions and a single spherical harmonic, linear combinations of spherical harmonics are typically used, designed so that the imaginary part of the spherical harmonics cancel out. These real orbitals are the building blocks most commonly shown in orbital visualizations.
In the real hydrogen-like orbitals, for example, n and ℓ have the same interpretation and significance as their complex counterparts, but m is no longer a good quantum number (though its absolute value is). The orbitals are given new names based on their shape with respect to a standardized Cartesian basis. The real hydrogen-like p orbitals are given by the following
where p0 = Rn 1 Y1 0, p1 = Rn 1 Y1 1, and p−1 = Rn 1 Y1 −1, are the complex orbitals corresponding to ℓ = 1.
The equations for the px and py orbitals depend on the phase convention used for the spherical harmonics. The above equations suppose that the spherical harmonics are defined by . However some quantum physicists include a phase factor (-1)m in these definitions, which has the effect of relating the px orbital to a difference of spherical harmonics and the py orbital to the corresponding sum. (For more detail, see Spherical harmonics#Conventions).
Shapes of orbitals
Simple pictures showing orbital shapes are intended to describe the angular forms of regions in space where the electrons occupying the orbital are likely to be found. The diagrams cannot show the entire region where an electron can be found, since according to quantum mechanics there is a non-zero probability of finding the electron (almost) anywhere in space. Instead the diagrams are approximate representations of boundary or contour surfaces where the probability density | ψ(r, θ, φ) |2 has a constant value, chosen so that there is a certain probability (for example 90%) of finding the electron within the contour. Although | ψ |2 as the square of an absolute value is everywhere non-negative, the sign of the wave function ψ(r, θ, φ) is often indicated in each subregion of the orbital picture.
Sometimes the ψ function will be graphed to show its phases, rather than the | ψ(r, θ, φ) |2 which shows probability density but has no phases (which have been lost in the process of taking the absolute value, since ψ(r, θ, φ) is a complex number). | ψ(r, θ, φ) |2 orbital graphs tend to have less spherical, thinner lobes than ψ(r, θ, φ) graphs, but have the same number of lobes in the same places, and otherwise are recognizable. This article, in order to show wave function phases, shows mostly ψ(r, θ, φ) graphs.
The lobes can be viewed as standing wave interference patterns between the two counter rotating, ring resonant travelling wave "m" and "−m" modes, with the projection of the orbital onto the xy plane having a resonant "m" wavelengths around the circumference. Though rarely depicted the travelling wave solutions can be viewed as rotating banded tori, with the bands representing phase information. For each m there are two standing wave solutions ⟨m⟩+⟨−m⟩ and ⟨m⟩−⟨−m⟩. For the case where m = 0 the orbital is vertical, counter rotating information is unknown, and the orbital is z-axis symmetric. For the case where ℓ = 0 there are no counter rotating modes. There are only radial modes and the shape is spherically symmetric. For any given n, the smaller ℓ is, the more radial nodes there are. Loosely speaking n is energy, ℓ is analogous to eccentricity, and m is orientation. In the classical case, a ring resonant travelling wave, for example in a circular transmission line, unless actively forced, will spontaneously decay into a ring resonant standing wave because reflections will build up over time at even the smallest imperfection or discontinuity.
Generally speaking, the number n determines the size and energy of the orbital for a given nucleus: as n increases, the size of the orbital increases. When comparing different elements, the higher nuclear charge Z of heavier elements causes their orbitals to contract by comparison to lighter ones, so that the overall size of the whole atom remains very roughly constant, even as the number of electrons in heavier elements (higher Z) increases.
Also in general terms, ℓ determines an orbital's shape, and mℓ its orientation. However, since some orbitals are described by equations in complex numbers, the shape sometimes depends on mℓ also. Together, the whole set of orbitals for a given ℓ and n fill space as symmetrically as possible, though with increasingly complex sets of lobes and nodes.
The single s-orbitals () are shaped like spheres. For n = 1 it is roughly a solid ball (it is most dense at the center and fades exponentially outwardly), but for n = 2 or more, each single s-orbital is composed of spherically symmetric surfaces which are nested shells (i.e., the "wave-structure" is radial, following a sinusoidal radial component as well). See illustration of a cross-section of these nested shells, at right. The s-orbitals for all n numbers are the only orbitals with an anti-node (a region of high wave function density) at the center of the nucleus. All other orbitals (p, d, f, etc.) have angular momentum, and thus avoid the nucleus (having a wave node at the nucleus). Recently, there has been an effort to experimentally image the 1s and 2p orbitials in a SrTiO3 crystal using scanning transmission electron microscopy with energy dispersive x-ray spectroscopy. Because the imaging was conducted using an electron beam, Coulombic beam-orbital interaction that is often termed as the impact parameter effect is included in the final outcome (see the figure at right).
The shapes of p, d and f-orbitals are described verbally here and shown graphically in the Orbitals table below. The three p-orbitals for n = 2 have the form of two ellipsoids with a point of tangency at the nucleus (the two-lobed shape is sometimes referred to as a "dumbbell"—there are two lobes pointing in opposite directions from each other). The three p-orbitals in each shell are oriented at right angles to each other, as determined by their respective linear combination of values of mℓ. The overall result is a lobe pointing along each direction of the primary axes.
Four of the five d-orbitals for n = 3 look similar, each with four pear-shaped lobes, each lobe tangent at right angles to two others, and the centers of all four lying in one plane. Three of these planes are the xy-, xz-, and yz-planes—the lobes are between the pairs of primary axes—and the fourth has the centres along the x and y axes themselves. The fifth and final d-orbital consists of three regions of high probability density: a torus with two pear-shaped regions placed symmetrically on its z axis. The overall total of 18 directional lobes point in every primary axis direction and between every pair.
There are seven f-orbitals, each with shapes more complex than those of the d-orbitals.
Additionally, as is the case with the s orbitals, individual p, d, f and g orbitals with n values higher than the lowest possible value, exhibit an additional radial node structure which is reminiscent of harmonic waves of the same type, as compared with the lowest (or fundamental) mode of the wave. As with s orbitals, this phenomenon provides p, d, f, and g orbitals at the next higher possible value of n (for example, 3p orbitals vs. the fundamental 2p), an additional node in each lobe. Still higher values of n further increase the number of radial nodes, for each type of orbital.
The shapes of atomic orbitals in one-electron atom are related to 3-dimensional spherical harmonics. These shapes are not unique, and any linear combination is valid, like a transformation to cubic harmonics, in fact it is possible to generate sets where all the d's are the same shape, just like the px, py, and pz are the same shape.
Although individual orbitals are most often shown independent of each other, the orbitals coexist around the nucleus at the same time.
This table shows all orbital configurations for the real hydrogen-like wave functions up to 7s, and therefore covers the simple electronic configuration for all elements in the periodic table up to radium. "ψ" graphs are shown with − and + wave function phases shown in two different colors (arbitrarily red and blue). The pz orbital is the same as the p0 orbital, but the px and py are formed by taking linear combinations of the p+1 and p−1 orbitals (which is why they are listed under the m = ±1 label). Also, the p+1 and p−1 are not the same shape as the p0, since they are pure spherical harmonics.
Qualitative understanding of shapes
The shapes of atomic orbitals can be qualitatively understood by considering the analogous case of standing waves on a circular drum. To see the analogy, the mean vibrational displacement of each bit of drum membrane from the equilibrium point over many cycles (a measure of average drum membrane velocity and momentum at that point) must be considered relative to that point's distance from the center of the drum head. If this displacement is taken as being analogous to the probability of finding an electron at a given distance from the nucleus, then it will be seen that the many modes of the vibrating disk form patterns that trace the various shapes of atomic orbitals. The basic reason for this correspondence lies in the fact that the distribution of kinetic energy and momentum in a matter-wave is predictive of where the particle associated with the wave will be. That is, the probability of finding an electron at a given place is also a function of the electron's average momentum at that point, since high electron momentum at a given position tends to "localize" the electron in that position, via the properties of electron wave-packets (see the Heisenberg uncertainty principle for details of the mechanism).
This relationship means that certain key features can be observed in both drum membrane modes and atomic orbitals. For example, in all of the modes analogous to s orbitals (the top row in the animated illustration below), it can be seen that the very center of the drum membrane vibrates most strongly, corresponding to the antinode in all s orbitals in an atom. This antinode means the electron is most likely to be at the physical position of the nucleus (which it passes straight through without scattering or striking it), since it is moving (on average) most rapidly at that point, giving it maximal momentum.
A mental "planetary orbit" picture closest to the behavior of electrons in s orbitals, all of which have no angular momentum, might perhaps be that of a Keplerian orbit with the orbital eccentricity of 1 but a finite major axis, not physically possible (because particles were to collide), but can be imagined as a limit of orbits with equal major axes but increasing eccentricity.
Below, a number of drum membrane vibration modes and the respective wave functions of the hydrogen atom are shown. A correspondence can be considered where the wave functions of a vibrating drum head are for a two-coordinate system ψ(r, θ) and the wave functions for a vibrating sphere are three-coordinate ψ(r, θ, φ).
None of the other sets of modes in a drum membrane have a central antinode, and in all of them the center of the drum does not move. These correspond to a node at the nucleus for all non-s orbitals in an atom. These orbitals all have some angular momentum, and in the planetary model, they correspond to particles in orbit with eccentricity less than 1.0, so that they do not pass straight through the center of the primary body, but keep somewhat away from it.
In addition, the drum modes analogous to p and d modes in an atom show spatial irregularity along the different radial directions from the center of the drum, whereas all of the modes analogous to s modes are perfectly symmetrical in radial direction. The non radial-symmetry properties of non-s orbitals are necessary to localize a particle with angular momentum and a wave nature in an orbital where it must tend to stay away from the central attraction force, since any particle localized at the point of central attraction could have no angular momentum. For these modes, waves in the drum head tend to avoid the central point. Such features again emphasize that the shapes of atomic orbitals are a direct consequence of the wave nature of electrons.
In atoms with a single electron (hydrogen-like atoms), the energy of an orbital (and, consequently, of any electrons in the orbital) is determined exclusively by . The orbital has the lowest possible energy in the atom. Each successively higher value of has a higher level of energy, but the difference decreases as increases. For high , the level of energy becomes so high that the electron can easily escape from the atom. In single electron atoms, all levels with different within a given are (to a good approximation) degenerate, and have the same energy. This approximation is broken to a slight extent by the effect of the magnetic field of the nucleus, and by quantum electrodynamics effects. The latter induce tiny binding energy differences especially for s electrons that go nearer the nucleus, since these feel a very slightly different nuclear charge, even in one-electron atoms; see Lamb shift.
In atoms with multiple electrons, the energy of an electron depends not only on the intrinsic properties of its orbital, but also on its interactions with the other electrons. These interactions depend on the detail of its spatial probability distribution, and so the energy levels of orbitals depend not only on but also on . Higher values of are associated with higher values of energy; for instance, the 2p state is higher than the 2s state. When , the increase in energy of the orbital becomes so large as to push the energy of orbital above the energy of the s-orbital in the next higher shell; when the energy is pushed into the shell two steps higher. The filling of the 3d orbitals does not occur until the 4s orbitals have been filled.
The increase in energy for subshells of increasing angular momentum in larger atoms is due to electron–electron interaction effects, and it is specifically related to the ability of low angular momentum electrons to penetrate more effectively toward the nucleus, where they are subject to less screening from the charge of intervening electrons. Thus, in atoms of higher atomic number, the of electrons becomes more and more of a determining factor in their energy, and the principal quantum numbers of electrons becomes less and less important in their energy placement.
The energy sequence of the first 35 subshells (e.g., 1s, 2p, 3d, etc.) is given in the following table. Each cell represents a subshell with and given by its row and column indices, respectively. The number in the cell is the subshell's position in the sequence. For a linear listing of the subshells in terms of increasing energies in multielectron atoms, see the section below.
Note: empty cells indicate non-existent sublevels, while numbers in italics indicate sublevels that could (potentially) exist, but which do not hold electrons in any element currently known.
Electron placement and the periodic table
Several rules govern the placement of electrons in orbitals (electron configuration). The first dictates that no two electrons in an atom may have the same set of values of quantum numbers (this is the Pauli exclusion principle). These quantum numbers include the three that define orbitals, as well as s, or spin quantum number. Thus, two electrons may occupy a single orbital, so long as they have different values of s. However, only two electrons, because of their spin, can be associated with each orbital.
Additionally, an electron always tends to fall to the lowest possible energy state. It is possible for it to occupy any orbital so long as it does not violate the Pauli exclusion principle, but if lower-energy orbitals are available, this condition is unstable. The electron will eventually lose energy (by releasing a photon) and drop into the lower orbital. Thus, electrons fill orbitals in the order specified by the energy sequence given above.
This behavior is responsible for the structure of the periodic table. The table may be divided into several rows (called 'periods'), numbered starting with 1 at the top. The presently known elements occupy seven periods. If a certain period has number i, it consists of elements whose outermost electrons fall in the ith shell. Niels Bohr was the first to propose (1923) that the periodicity in the properties of the elements might be explained by the periodic filling of the electron energy levels, resulting in the electronic structure of the atom.
The periodic table may also be divided into several numbered rectangular 'blocks'. The elements belonging to a given block have this common feature: their highest-energy electrons all belong to the same ℓ-state (but the n associated with that ℓ-state depends upon the period). For instance, the leftmost two columns constitute the 's-block'. The outermost electrons of Li and Be respectively belong to the 2s subshell, and those of Na and Mg to the 3s subshell.
The following is the order for filling the "subshell" orbitals, which also gives the order of the "blocks" in the periodic table:
- 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
The "periodic" nature of the filling of orbitals, as well as emergence of the s, p, d and f "blocks", is more obvious if this order of filling is given in matrix form, with increasing principal quantum numbers starting the new rows ("periods") in the matrix. Then, each subshell (composed of the first two quantum numbers) is repeated as many times as required for each pair of electrons it may contain. The result is a compressed periodic table, with each entry representing two successive elements:
1s 2s 2p 2p 2p 3s 3p 3p 3p 4s 3d 3d 3d 3d 3d 4p 4p 4p 5s 4d 4d 4d 4d 4d 5p 5p 5p 6s 4f 4f 4f 4f 4f 4f 4f 5d 5d 5d 5d 5d 6p 6p 6p 7s 5f 5f 5f 5f 5f 5f 5f 6d 6d 6d 6d 6d 7p 7p 7p
Although this is the general order of orbital filling according to the Madelung rule, there are exceptions, and the actual electronic energies of each element are also dependent upon additional details of the atoms (see Electron configuration#Atoms: Aufbau principle and Madelung rule).
The number of electrons in an electrically neutral atom increases with the atomic number. The electrons in the outermost shell, or valence electrons, tend to be responsible for an element's chemical behavior. Elements that contain the same number of valence electrons can be grouped together and display similar chemical properties.
For elements with high atomic number Z, the effects of relativity become more pronounced, and especially so for s electrons, which move at relativistic velocities as they penetrate the screening electrons near the core of high-Z atoms. This relativistic increase in momentum for high speed electrons causes a corresponding decrease in wavelength and contraction of 6s orbitals relative to 5d orbitals (by comparison to corresponding s and d electrons in lighter elements in the same column of the periodic table); this results in 6s valence electrons becoming lowered in energy.
Examples of significant physical outcomes of this effect include the lowered melting temperature of mercury (which results from 6s electrons not being available for metal bonding) and the golden color of gold and caesium.
In the Bohr Model, an n = 1 electron has a velocity given by , where Z is the atomic number, is the fine-structure constant, and c is the speed of light. In non-relativistic quantum mechanics, therefore, any atom with an atomic number greater than 137 would require its 1s electrons to be traveling faster than the speed of light. Even in the Dirac equation, which accounts for relativistic effects, the wave function of the electron for atoms with Z > 137 is oscillatory and unbounded. The significance of element 137, also known as untriseptium, was first pointed out by the physicist Richard Feynman. Element 137 is sometimes informally called feynmanium (symbol Fy). However, Feynman's approximation fails to predict the exact critical value of Z due to the non-point-charge nature of the nucleus and very small orbital radius of inner electrons, resulting in a potential seen by inner electrons which is effectively less than Z. The critical Z value which makes the atom unstable with regard to high-field breakdown of the vacuum and production of electron-positron pairs, does not occur until Z is about 173. These conditions are not seen except transiently in collisions of very heavy nuclei such as lead or uranium in accelerators, where such electron-positron production from these effects has been claimed to be observed. See Extension of the periodic table beyond the seventh period.
There are no nodes in relativistic orbital densities, although individual components of the wave function will have nodes.
Transitions between orbitals
Bound quantum states have discrete energy levels. When applied to atomic orbitals, this means that the energy differences between states are also discrete. A transition between these states (i.e., an electron absorbing or emitting a photon) can thus only happen if the photon has an energy corresponding with the exact energy difference between said states.
Consider two states of the hydrogen atom:
State 1) n = 1, ℓ = 0, mℓ = 0 and s = +1/
State 2) n = 2, ℓ = 0, mℓ = 0 and s = +1/
By quantum theory, state 1 has a fixed energy of E1, and state 2 has a fixed energy of E2. Now, what would happen if an electron in state 1 were to move to state 2? For this to happen, the electron would need to gain an energy of exactly E2 − E1. If the electron receives energy that is less than or greater than this value, it cannot jump from state 1 to state 2. Now, suppose we irradiate the atom with a broad-spectrum of light. Photons that reach the atom that have an energy of exactly E2 − E1 will be absorbed by the electron in state 1, and that electron will jump to state 2. However, photons that are greater or lower in energy cannot be absorbed by the electron, because the electron can only jump to one of the orbitals, it cannot jump to a state between orbitals. The result is that only photons of a specific frequency will be absorbed by the atom. This creates a line in the spectrum, known as an absorption line, which corresponds to the energy difference between states 1 and 2.
The atomic orbital model thus predicts line spectra, which are observed experimentally. This is one of the main validations of the atomic orbital model.
The atomic orbital model is nevertheless an approximation to the full quantum theory, which only recognizes many electron states. The predictions of line spectra are qualitatively useful but are not quantitatively accurate for atoms and ions other than those containing only one electron.
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|Wikiquote has quotations related to: Atomic orbital|
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|Wikimedia Commons has media related to Atomic orbitals.|
- Guide to atomic orbitals
- Covalent Bonds and Molecular Structure
- Animation of the time evolution of an hydrogenic orbital
- The Orbitron, a visualization of all common and uncommon atomic orbitals, from 1s to 7g
- Grand table Still images of many orbitals | <urn:uuid:211d0aec-1b8a-4d46-baa9-c19dc6a4e60e> | 3.84375 | 12,274 | Knowledge Article | Science & Tech. | 49.748206 | 95,539,608 |
Monarch butterflies may warrant U.S. Endangered Species Act protection because of farm-related habitat loss blamed for sharp declines in cross-country migrations of the orange-and-black insects, the U.S. Fish and Wildlife Service said on Monday.
Monarch populations are estimated to have fallen by as much as 90 percent during the past two decades because of destruction of milkweed plants they depend on to lay their eggs and nourish hatching larvae, according to the Xerces Society for Invertebrate Conservation.
The loss of the plant is tied to factors such as increased cultivation of crops genetically engineered to withstand herbicides that kill native vegetation, including milkweed, the conservation group says.
Monarchs, unique among butterflies for the regularity and breadth of their annual migration, are also threatened by widespread pesticide use and logging of mountain forests in central Mexico and coastal California where some of them winter, said biologist Karen Oberhauser at the University of Minnesota.
The Fish and Wildlife Service said on Monday a petition requesting federal protections for monarchs – filed by the Xerces Society and others – “presents substantial information indicating that listing may be warranted.”
The agency’s initial review will take about a year to complete.
The butterflies, revered for their delicate beauty after emerging from a jade green chrysalis ornamented by gold stitching, are roughly divided into two populations in the United States according to their fall migration patterns.
Monarchs from east of the Continental Divide wing across 3,000 miles to Mexico, while those from west of the Divide in Rocky Mountain states like Idaho make a relatively shorter journey to California.
An estimated 1 billion monarchs migrated to Mexico in 1996 compared with just 35 million last year, according to Marcus Kronforst, a University of Chicago ecologist who has studied monarchs.
Monarch populations are tracked by an extensive network of professional and citizen scientists who make up part of the butterfly’s vast and loyal following.
“Almost every person I’ve talked to about monarchs has expressed a deep love and admiration for them that was often formed in childhood,” said Beth Waterbury, regional wildlife biologist for the Idaho Department of Fish and Game.
The monarchs’ navigation remains mysterious. While they are known to orient themselves by the sun’s position, and by the Earth’s magnetic field on cloudy days, it is unclear how new generations find their way to wintering sites they have never seen, Oberhauser said.
(Reporting by Laura Zuckerman in Salmon, Idaho; Editing by Steve Gorman and Peter Cooney) | <urn:uuid:bd1c02b2-a161-4486-855c-e9c1e11e0b53> | 3.40625 | 539 | Truncated | Science & Tech. | 25.761531 | 95,539,653 |
Almost all theories of fundamental interactions are nowadays based on the gauge concept. Starting with the historical example of quantum electrodynamics, we have been led to the successful unified gauge theory of weak and electromagnetic interactions, and finally to a non abelian gauge theory of strong interactions with the notion of permanently confined quarks. The. early theoretical work on gauge theories was devoted to proofs of renormalizability, investigation of short distance behaviour, the discovery of asymptotic freedom, etc . . , aspects which were accessible to tools extrapolated from renormalised perturbation theory. The second phase of the subject is concerned with the problem of quark confinement which necessitates a non-perturbative understanding of gauge theories. This phase has so far been marked by the introduc tion of ideas from geometry, topology and statistical mechanics in particular the theory of phase transitions. The 1979 Cargese Institute on "Recent Developments on Gauge Theories" was devoted to a thorough discussion of these non-perturbative, global aspects of non-abelian gauge theories. In the lectures and seminars reproduced in this volume the reader wilf find detailed reports on most of the important developments of recent times on non perturbative gauge fields by some of the leading experts and innovators in this field. Aside from lectures on gauge fields proper, there were lectures on gauge field concepts in condensed matter physics and lectures by mathematicians on global aspects of the calculus of variations, its relation to geometry and topology, and related topics.
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To read on e-ink devices like the Sony eReader or Barnes & Noble Nook, you'll need to download a file and transfer it to your device. Please follow the detailed Help center instructions to transfer the files to supported eReaders. | <urn:uuid:8db758a9-4e17-4a3b-afc4-f60654144d49> | 2.625 | 382 | Product Page | Science & Tech. | 22.647698 | 95,539,691 |
|Think about Loose Coupling|
Re: Closure - Perl Perspectiveby tobyink (Abbot)
|on Oct 17, 2014 at 09:13 UTC||Need Help??|
A closure is a subroutine that makes use of a lexical variable defined outside the subroutine. For example:
The foo() sub is said to be a "closure", and the $foo variable has be "closed over".
When most people talk about closures though, they are usually referring to anonymous functions rather than named ones like above. Something like:
In fact, people often use the word "closures" to refer to anonymous functions even if the function doesn't close over any variables!
This is probably due to the fact that in most programming languages (including Perl) there's no syntactic difference between defining an anonymous sub that closes over a variable verses one that does not. They are implemented subtly differently internally though as can be seen by this example:
You'll notice that the three non-closure coderefs share a reference address. This is an optimization that Perl does. (I have at least twice had to work around this optimization by defining a dummy variable and closing over it. But then again, I do a lot of weird stuff in Perl. Most people probably never need to care about this difference.)
Anyway, coming back to Data::Form::Validator - it does accept coderefs as arguments in some places. Whether those coderefs are technically closures (i.e. they close over external variables), it probably doesn't care. | <urn:uuid:ba7ece1f-6263-464b-923e-5a97b4eef63f> | 3.078125 | 323 | Comment Section | Software Dev. | 44.693135 | 95,539,759 |
We haven’t made it look pretty, since we’re only going to use it for demonstration purposes.We have assigned it the name “Registration Form”, and then have put the following labels and input fields in an unordered list: user id, password, name, address, zip code, e-mail and about.Let’s start with building a registration form with multiple input fields, so that we can have something more concrete to work on.Create an HTML file named This is the whole HTML code for the registration form.
In the below demo the regular expression looks for one or more uppercase or lowercase letters within the character class [A-Za-z], followed with an end of a line anchor $ Some undesired spaces and dashes from the user input can be removed by using the string object replace() method.
The regular expression is used to find the characters and then replace them with empty spaces.
Now we can go on and validate the information we get from these inputs.
to avoid any erroneous data to be inserted into the database. So let us learn some basics because I have written this article only focusing on beginners and students. Example I hope you now understand the basics of validation in Java Script, now let us create the one sample web application that demonstrates how to do validation. | <urn:uuid:1655fa92-f003-4b21-9ff0-a3d91d5b8011> | 2.703125 | 274 | Tutorial | Software Dev. | 42.771221 | 95,539,779 |
|http://www.fishbase.org/Summary/speciesSummary.php?genusname=Pleuronectes&speciesname=platessa ---> http://www.fishbase.org/summary/Pleuronectes-platessa.html|
Add your observation in
Common name (e.g. trout)
Genus + Species (e.g. Gadus morhua)
Actinopterygii (ray-finned fishes) >
(Righteye flounders) > Pleuronectinae
Greek, pleura = side, ribe + Greek, nekton = swimmer (Ref.
. More on author:
Environment / Climate / Range
Marine; brackish; demersal; oceanodromous (Ref.
); depth range 0 - 200 m (Ref.
), usually 10 - 50 m (Ref.
). Temperate; 2°C - 15°C (Ref.
); 72°N - 36°N, 54°W - 45°E
Northern Sea. Reports from the Mediterranean Sea appear to be misidentifications of
. It may have been present in some areas of the Mediterranean in the past, as a result of climatic changes related to the ice age, but at present times seem to be absent (Ref.
Length at first maturity / Size / Weight / Age
, range 24 - 42 cm
Max length : 100.0 cm SL male/unsexed; (Ref.
); common length : 40.0 cm TL male/unsexed; (Ref.
); max. published weight: 7.0 kg (Ref.
); max. reported age: 50 years (Ref.
: 48 - 59. Smooth with small scales. Bony ridge behind the eyes. Upper side brown or greenish brown with irregularly distributed bright red or orange spots. The underside is white. Lateral line straight, slightly curved above pectoral fin. Dorsal fin reaching eye. More than 30 vertebrae.
Adults live on mixed bottoms, the older the deeper the occurrence; small individuals are usually seen on bathing beaches (Ref.
). Occurs on mud and sand bottom from a few meters down to about 100 m, at sea, estuaries and rarely entering freshwaters (Ref.
). Reported as resident intertidal species with homing behavior (Ref.
). Feed mainly on thin-shelled mollusks and polychaetes. Batch spawner (Ref.
). The most important flatfish for fisheries in Europe. Utilized fresh and frozen; eaten steamed, fried, boiled, microwaved and baked (Ref.
). Active at night in the very shallow water while day time is spent buried in the sand. Stationary for long periods, tagging experiments have shown that their spawning migrations can be long. Changes in the environmental conditions have been disadvantageous. Populations in Kattegat and Danish belts decreased in 1980's and early 1990's due to discharge of nutritive salts. Wadden sea is still an excellent nursery ground (Ref.35388).
Adult spawn when the temperature is around 6 °C (Ref.
Cooper, J.A. and F. Chapleau
, 1998. Monophyly and intrarelationships of the family Pleuronectidae (Pleuronectiformes), with a revised classification. Fish. Bull. 96(4):686-726. (Ref.
IUCN Red List Status (Ref.
Least Concern (LC)
Threat to humans
Fisheries: highly commercial; aquaculture: commercial; gamefish: yes; aquarium: public aquariums
; publication :
) | FIRMS
Sea Around Us
Stamps, Coins Misc.
Check for Aquarium maintenance
Check for Species Fact Sheets
Check for Aquaculture Fact Sheets
Websites from users
Catalog of Fishes
| IGFA World Record |
Otolith Atlas of Taiwan Fishes
| Reef Life Survey |
Tree of Life
) | World Records Freshwater Fishing |
Estimates of some properties based on models
Preferred temperature (Ref.
): 6.8 - 12.4, mean 10.2 (based on 658 cells).
Phylogenetic diversity index (Ref.
= 0.6250 [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00776 (0.00691 - 0.00872), b=3.06 (3.02 - 3.10), in cm Total Length, based on LWR estimates for this species (Ref.
Trophic Level (Ref.
): 3.2 ±0.50 se; Based on food items.
): Medium, minimum population doubling time 1.4 - 4.4 years (K=0.06-0.34; tm=2-6; tmax=30; Fec=50,000).
Prior r = 0.39, 2 SD range = 0.2 - 0.77, log(r) = -0.94, SD log(r) = 0.34, Based on: 4 M, 15 K, 42 tgen, 3 tmax, 26 Fec records
): High to very high vulnerability (71 of 100) .
Price category (Ref.
Luna, Susan M.
Capuli, Estelita Emily
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Total processing time for the page : 0.2369 seconds | <urn:uuid:36bd1190-4518-4447-b1c2-7b828137db1b> | 2.734375 | 1,263 | Knowledge Article | Science & Tech. | 74.908155 | 95,539,783 |
Biostratigraphy of the Equatorial North Pacific DOMES Sites A, B, and C
Radiolarians from box cores and gravity cores indicate that Quaternary sediment covers the sea floor at DOMES Sites A, B, and C; however, at Sites A and B dissolution-resistant, reworked Tertiary species (predominantly middle and late Eocene and early Miocene) generally outnumber the fragile Quaternary forms. In contrast, at Site C an early Miocene calcareous nannofossil flora underlies the Quaternary layer in three cores, and specimens of different ages are not mixed; barren sediment generally underlies the Quaternary in the remainder of cores from Site C. The abundant admixture of Tertiary radiolarians in Quaternary sediment at Sites A and B is most likely caused by an increase ill bottom current activity during the Pleistocene, resulting in several cycles of erosion and redeposition of Tertiary sediment. This physical process of erosion, aided by selective dissolution of fragile radiolarians, explains the dominance of dissolution-resistant forms in the mixtures.
KeywordsMiddle Eocene Quaternary Sediment Late Eocene Manganese Nodule Calcareous Nannoplankton
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Radionuclide Transport in a Dolomite Aquifer
The most probable paths for radionuclide transport between the biosphere and the proposed bedded salt repository (WIPP) in southeastern New Mexico are through dolomite formations which are the only currently water-bearing units overlying the repository horizon. This paper describes some of the experimental work performed to determine the potential for radionuclide migration in these formations. Included are the results of radionuclide sorption studies on natural dolomites (Magenta and Culebra) and on synthetic dolomite (proto-dolomite). Sorption on natural dolomites was evaluated with respect to core sample location, ground water composition, nuclide concentration and water volume to rock mass ratios used in making the measurements. The results show that a discrete value such as a distribution coefficient (Kd) assigned to a given radionuclide does not accurately describe its interactions with site specific geological formation.
KeywordsSorption Coefficient Radionuclide Transport Dolomite Formation Radionuclide Migration American Nuclear Society
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- 10.A. W. Lynch and R. G. Dosch, “Migration of Cesium in Dolomite from the Los Medanos Area in Southeastern New Mexico,” 1979 Annual Meeting of the American Nuclear Society, Atlanta, Georgia, June 3–8 (1979).Google Scholar | <urn:uuid:45013b9f-6117-47de-b2f0-1926fd2bda69> | 2.71875 | 749 | Truncated | Science & Tech. | 52.261413 | 95,539,788 |
Researcher Daniel Gustafsson has studied chewing lice on sandpipers around the world and investigated how host birds' migration patterns affect louse distribution and reationships.
With no wings and very small eyes, chewing lice are, by and large, helpless away from their host.
Daniel Gustafsson has studied species of chewing lice that live on the birds' wings and compared them with species that live on their body feathers.
"Given that chewing lice are almost totally dependent on direct contact between two birds to spread, lice that sit on birds' wings should find it easier to use occasional contact between two hosts to spread than those that sit closer to birds' bodies," Daniel Gustafsson says.Unexpected results
"This is surprising as body lice should be more limited to one particular species of bird," Daniel Gustafsson says. "The real opportunities for spreading should be between parents and their offspring in the nest, or between adult birds during mating."
Genetic and morphological data from two different genera show complicated patterns.
"Wing lice from small bird host species are found on more host species than those that parasitize larger bird host species," Daniel Gustafsson says.Genetically almost identical
"Sandpipers are incredibly mobile," Daniel Gustafsson says. "They breed around the Polar Circle but fly to the tropics during the Arctic winter, following specific migration routes known as flyways."
He has studied sandpipers in Sweden, Japan, Australia, and Canada.
When sandpipers migrate, they do so in enormous flocks, often tens of thousands strong and containing several different species. These winter flocks should offer excellent opportunities for the lice to spread as the birds often stand in tight groups at high tide and at night.
"But it would appear that several factors other than geography play a role, including the size of the host bird," Daniel Gustafsson explains. "Specific rest and wintering environments probably play a role, too, as some of the host birds that generally winter in fresh water localities carry species of wing lice that differ from those that live on bird species that are mainly found on the seashore."Common on mammals
Other chewing lice have been seen to switch between host ducks by walking on the water surface.
Chewing lice are common in birds and most groups of mammals. There are two species that live on humans: pubic lice and head lice.
The thesis has been successfully defended.Bibliographic data:
Colorectal cancer risk factors decrypted
13.07.2018 | Max-Planck-Institut für Stoffwechselforschung
Algae Have Land Genes
13.07.2018 | Julius-Maximilians-Universität Würzburg
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences | <urn:uuid:f2d6a49e-f261-4827-addf-87525422fb7d> | 4 | 1,159 | Content Listing | Science & Tech. | 42.73664 | 95,539,809 |
||This book is a text which applies to students and professors of physics. Because it offers a broad view on laser physics and presents most recent results on the dynamics of laser light, such as self-pulsing and chaos, it will be of interest also to scientists and engineers engaged in laser research or development. This text starts at a rather elementary level and will smoothly lead the reader into the more difficult problems of laser physics, including the basic features of the coherence and noise properties of laser light.
In the introductory chapters, typical experimental set-ups and laser materials will be discussed, but the main part of this book will be devoted to a theoretical treatment of a great variety of laser processes. The laser, or the optical maser, as it was originally called, is one of the most important inventions of this century and has found a great number of important applications in physics, chemistry, medicine, engineering, telecommunications, and other fields. It bears great promises for further applications, e.g. in computers. But also from the point of view of basic research, a study of the physical processes which produce the unique properties of laser light are equally fascinating. The laser is a beautiful example of a system far from thermal equilibrium which can achieve a macroscopically ordered state through "self-organization". It was the first example for a nonequili-brium phase transition, and its study eventually gave birth to synergetics, a new interdisciplinary field of research.
I got involved in laser physics at a rather early stage and under most fortunate circumstances. In 1960 I was working as visiting scientist at the Bell Telephone Laboratories, Murray Hill. There I soon learned that these laboratories were searching for a revolutionary new light source. Two years earlier, in 1958, this source had been proposed by Schawlow and Townes, who derived in particular the laser condition and thus demonstrated the feasibility of this new device. At Bell Telephone Laboratories I soon got involved in a theoretical study of the laser processes and continued it at Stuttgart University. I developed a laser theory whose basic features I published in 1962 and which I then applied to various concrete problems, | <urn:uuid:c64bba21-4745-44d6-a8ef-ae2784ae7e01> | 2.765625 | 435 | Product Page | Science & Tech. | 30.73388 | 95,539,811 |
All submissions for this problem are available.
2 Milkmen Aditya and Rahul were doing very good business in their village as partners and had many milk containers of the following sizes.
The codes for each of the sizes are given in the braces they are supposed to be entered in the input as specified in INPUT section.
Can (CN) 10 gallons Pail (PL) 2 gallons Gallon (G) Quart (Q) 1/4 gallon Pint (PN) 1/8 gallon Cup (CP) 1/16 gallon
Now Rohan who lives in the same village took up a assignment to know in how many ways can the milkmen store X gallons of milk using any combination of these containers. For instance, the milkmen can store one Quart four ways:
1: 1 quart 2: 2 pints 3: 1 pint + 2 cups 4: 4 cups
One gallon can be stored 26 different ways.
In all data, X is a positive integer number and 1 <= X gallons <= 50. Rohans program must compute the number of combinations for each separate input value in less than ten seconds (which means that your program might run as long as 10*n seconds for n input values).
Your program should read values from the file first the Quantity and then followed by the code for each of the sizes as specified above in the second line (and compute and print the number of combinations) until encountering a value of #.
Your output should give the number of ways specified for the input.
A example is given below:
Sample Input 1 G # Sample Output 26
|Time Limit:||15 sec|
|Source Limit:||50000 Bytes|
|Languages:||C, CPP14, JAVA, PYTH, PYTH 3.5, PYPY, CS2, PAS fpc, PAS gpc, RUBY, PHP, GO, NODEJS, HASK, rust, SCALA, swift, D, PERL, FORT, WSPC, ADA, CAML, ICK, BF, ASM, CLPS, PRLG, ICON, SCM qobi, PIKE, ST, NICE, LUA, BASH, NEM, LISP sbcl, LISP clisp, SCM guile, JS, kotlin, PERL6, TEXT, SCM chicken, CLOJ, COB, FS|
Fetching successful submissions
If you are still having problems, see a sample solution here. | <urn:uuid:8e80cfee-3da8-45bf-ab47-a8deee69891b> | 2.796875 | 531 | Tutorial | Software Dev. | 62.49639 | 95,539,839 |
A Look at Clouds from All Sides Now
By Marcia Goodrich | Published
Clouds play a crucial part in regulating climate, but precious little is actually known about clouds’ inner workings and their role on Earth. A group of Michigan Technological University scientists hopes to change that, thanks to a $1.4 million grant from the National Science Foundation.
The grant provides the lion’s share of the funding for a chamber that will allow researchers to study cloud processes under realistic temperatures, pressures, and humidity levels, mimicking conditions from sea level to the lower levels of the stratosphere, where jet planes fly.
The chamber, to be located in the Great Lakes Research Center, won’t be built until later in 2011, but lead investigator Raymond Shaw expects it will be in the shape of a cylinder, two meters in diameter and one meter high. “With a volume of pi, we have taken to calling it the pi can,” says Shaw, a professor of physics.
One thing that makes the pi can special will be its ability to recreate something that all air travelers are familiar with: turbulence. “We will be able to cool the top surface of the chamber and heat the bottom, so air plumes are constantly rising and falling, mixing and stirring, creating a fluctuating, but well characterized, environment for cloud formation,” Shaw says.
Clouds are much more important than most people give them credit for, he says. “If you imagine looking at the Earth from outer space, what you see is really only a little bit of earth. You actually see a lot more clouds and oceans. We call it Planet Earth, but it’s really Planet Cloud.”
Clouds cool the world by reflecting sunlight; they also warm it by keeping warmth from radiating into outer space. Yet clouds are hard to quantify. Small and scattered, each one is made of countless tiny droplets that freeze in strange ways, at temperatures well below the textbook 0 degrees Celcius. How bright clouds are, and how much moisture they may contain, are variables to consider. “We want to better understand clouds so we can understand their importance to climate,” Shaw says. “We also hope to address some very immediate, practical questions, like ‘Is it going to rain on my picnic Friday?’”
In addition, the chamber will help advance research in a variety of related areas. Lynn Mazzoleni, an assistant professor of chemistry, will use the chamber to study atmospheric pollutants and particulates, called aerosols, which undergo chemical changes when they enter clouds’ watery environment.
Shaw expects that the chamber will attract scientists from all over the world. “It’s a major research instrumentation program,” he says. “The real scientific work will come after the chamber is built and proven. We hope this can become a research destination.”
In addition to Shaw and Mazzoleni, other investigators on the project are physics faculty members Will Cantrell and Claudio Mazzoleni. Simon Carn and Bill Rose, of geological and mining engineering and sciences, and Paul Doskey and Judith Perlinger, of civil and environmental engineering, are also contributing to the project. Joerg Schumacher from Technische Universitaet Ilmenau, an expert in computational studies of turbulence, is a member of the proposal team.
Michigan Tech’s Departments of Physics and Chemistry; the Earth, Planetary and Space Sciences Institu the College of Sciences and Arts; and the Office of the Vice President for Research provided support and an additional $600,000 to fund the cloud chamber project.
Michigan Technological University is a public research university, home to more than 7,000 students from 54 countries. Founded in 1885, the University offers more than 120 undergraduate and graduate degree programs in science and technology, engineering, forestry, business and economics, health professions, humanities, mathematics, and social sciences. Our campus in Michigan’s Upper Peninsula overlooks the Keweenaw Waterway and is just a few miles from Lake Superior. | <urn:uuid:a7917249-7a64-4ea1-9d30-e8dde75aadae> | 3.796875 | 850 | News (Org.) | Science & Tech. | 40.309892 | 95,539,848 |
Washington: A team of researchers have demonstrated that frozen water in the form of snow or frost can melt to form debris flows on sunward-facing slopes of sand dunes in the Alaskan arctic at air temperatures significantly below the melting point of water.
The debris flows consist of sand mixed with liquid water, which cascade down steep slopes.
Southwest Research Institute (SwRI) scientists made their observations at the Great Kobuk Sand Dunes, in Kobuk Valley National Park, Alaska.
This site serves as an Earth-based cold-climate "analog" to dunes on Mars. Debris flows formed on days when air temperatures measured continuously by the team remained below the melting point of water.
Very few minutes of above-freezing ground surface temperatures are needed to locally melt frozen water and mobilize sand down steep slopes.
The scientists hypothesize that fresh patches of wind-deposited dark sand on bright white snow caused local hot spots to form where solar radiation was absorbed by the sand and conducted into the underlying snow.
This enabled meltwater to briefly form and sand to be mobilized despite subfreezing local air temperatures. A similar mechanism may be responsible for triggering debris flows on frozen Martian sand dunes.
The Alaskan debris flows formed at ground temperatures that may correspond to those occurring locally and seasonally on the surface of Mars, said hydrogeologist Dr. Cynthia Dinwiddie, a principal engineer in SwRI`s Geosciences and Engineering Division.
The Alaskan debris flows are morphologically similar to small, defrosting-related "dark dune spot" seepage flows that seasonally form in late winter on frost-covered Martian sand dunes. | <urn:uuid:bf29db72-d378-4836-9760-c603808fe6a8> | 3.578125 | 350 | News Article | Science & Tech. | 30.720044 | 95,539,850 |
Join GitHub today
GitHub is home to over 28 million developers working together to host and review code, manage projects, and build software together.Sign up
Creating Rule Generators
Clone this wiki locally
You can create a rule generator by creating a class called
RuleGenerator which inherits from
core.generator.AbstractRuleGenerator class. This class should implement two essential methods:
- public RuleGenerator(SLDescription sl, ElapsedCpuTimer time): This is the constructor of the rule generator.
- public String generateRules(SLDescription sl, ElapsedCpuTimer time): This function is responsible returning the interaction rules and termination rules.
All functions are provided with the same two objects:
- Sprite Level Description (SLDescription) object: is a description object that provides the user with functions to retrieve information about the current level and the associated sprites. It provides the user with function to test rules and termination conditions. Follow this link for more information about SLDescription.
- Elapsed Cpu Timer (ElapsedCpuTimer) object: is a timer object that provides the amount allowed for this function.
generateRules function should return a 2 arrays of string. The first is an array of the interaction rules in the generated game. The second is an array of the termination conditions in the generated game.
The next pages shows sample of rule generators: | <urn:uuid:ec0b4963-cc68-46a6-9291-2f0ec80d787c> | 2.8125 | 289 | Documentation | Software Dev. | 21.961833 | 95,539,873 |
Species Detail - Eurasian Curlew (Numenius arquata) - Species information displayed is based on all datasets.
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
Protected Species: Wildlife Acts || Protected Species: EU Birds Directive || Protected Species: EU Birds Directive >> Annex II, Section II Bird Species || Threatened Species: Birds of Conservation Concern || Threatened Species: Birds of Conservation Concern >> Birds of Conservation Concern - Red List
1 January (recorded in 2003)
31 December (recorded in 2010)
National Biodiversity Data Centre, Ireland, Eurasian Curlew (Numenius arquata), accessed 21 July 2018, <https://maps.biodiversityireland.ie/Species/10039> | <urn:uuid:044d8549-3ab1-4a67-9ba7-50e9ea77ca41> | 2.75 | 198 | Structured Data | Science & Tech. | 22.723622 | 95,539,877 |
Atomic and Elementary Particle Physics
The field theory of matter developed in this book reveals that there are only correlated spin-1 /2 matter field components that comprise any complex system of matter. The ‘photon’ and the ‘neutrino’ are not elementary particle fields. Rather, they are virtual fields that couple matter to effect their mutual interaction. The bound electron—proton coupled with the long range electromagnetic force (with the virtual photon) is called hydrogen. The bound electron-proton, coupled with the short range electromagnetic force (with the virtual neutrino) is called neutron. These two types of electromagnetic force follow from the factorization of the electromagnetic field theory into a scalar and a pseudoscalar part, which may be identified, respectively, with the standard and the weak electromagnetic interactions. Such a factorization follows from the rejection of reflection symmetry in the electromagnetic (and all other) interactions in nature, in accordance with the underlying symmetry groups of the theory of relativity — the Poincaré group for special relativity and the Einstein group for general relativity.
KeywordsMatter Field Charged Pion Elementary Matter Neutral Pion Lamb Shift
Unable to display preview. Download preview PDF. | <urn:uuid:a332e322-ff25-4ba5-b120-4325d342c89c> | 3.578125 | 251 | Truncated | Science & Tech. | 19.132778 | 95,539,880 |
EVOLUTION. Natural Selection. Mechanism for evolution Differential survival and reproduction of chance inherited variants, depending on environmental conditions. EVOLUTION by Natural Selection.
Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment
Where is the Proof?
Their existence confirms that species are not fixed but can evolve into other species over time.
ARM = carrying
Front Leg = walking
Front Flipper = swimming
Radius & Ulna
Lizard Tortoise Pig Human | <urn:uuid:a2560cbd-364b-4dcf-97fc-ec40ad259863> | 2.90625 | 108 | Structured Data | Science & Tech. | 1.2595 | 95,539,891 |
The simplest device to measure interaction of a sample with light is the absorbance spectrophotometer. Monochromatic light is passed through the sample (or, in some cases, reflected from it). If absorption occurs, the light intensity that arrives at a detector is lower than what would arrive in the absence of the sample.
Monochromatic Light Isosbestic Point High Optical Quality Absorbance Spectrophotometer Hyperchromic Effect
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
This is a preview of subscription content, log in to check access. | <urn:uuid:00f02e1d-99f8-4f95-b3b2-43867b7f1ac4> | 2.84375 | 135 | Truncated | Science & Tech. | 28.925404 | 95,539,907 |
Since 2013, I've seen anywhere between 2 and 71 at some point in January, often with 30-40 degree (or greater) swings from one day to the next. December and February are similar.
On the other hand, July has seen far more consistency with temperatures only ranging between 51 and 94 for extremes and generally remaining between 60 and 90. June and August are similar.
So, why is the middle of Summer more consistent than the middle of Winter?
U.S. & Caribbean Weather Discussions and Severe Weather Events
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Users browsing this forum: No registered users and 13 guests | <urn:uuid:68fcb625-0262-4f0f-867f-adeca800aa97> | 2.90625 | 143 | Comment Section | Science & Tech. | 58.885946 | 95,539,921 |
By “voxel-based sphere” I mean a sphere made up of cubes. Sorry if that is not the correct terminology. Imagine a sphere made out of legos. Except each voxel is a cube (unlike most legos). Determining the voxel distribution to make the sphere I suppose would involve calculating the x/y/z of a position on the sphere and then ‘snapping’ it to the nearest multiple of the voxel width/height.
Here’s a calculator that can generate one:
And here is an image of one (cross sectioned):
Given the diameter of this voxel sphere (in number of voxels, e.g. ’20 voxels in diameter’), how can I calculate:
Is there a formula possible here? 🙂 | <urn:uuid:f1d0ff43-d660-4076-a517-f8d4c7955821> | 3.0625 | 176 | Personal Blog | Science & Tech. | 52.089914 | 95,539,931 |
One of Nasa’s most important spacecraft is running out of fuel and has been forced to nap.
The Kepler Space Telescope has spent the last decade scouring the sky for other Earths, hunting for planets elsewhere in the universe that might contain life. As part of that mission, it has found a whole host of exciting planets, many of which look like our own and are exciting candidates for life.
But that mission could soon come to a close, as the spacecraft’s fuel runs out and engineers send it into a hibernation state.
That nap will last until early August, when it will wake back up and engineers attempt to get hold of the data it collected before it was powered down. If that is successful and there is enough fuel, Kepler will begin new observations – but it is possible that it will not be able to continue.
For now, engineer’s highest priority is to get the existing science data back down to Earth. To do that, the onboard antenna must be pointing down to Earth, and engineers will focus on making sure that happens if it can reawaken from its power down.
Kepler has been searching for planets outside our solar system for nearly a decade, after being launched in 2009. Considered the pioneer of planet hunting, it’s discovered nearly 3,000 confirmed worlds and as many potential candidates.
Kepler has run into a whole range of other problems before, and had been initially scheduled for a much shorter mission. It has shown surprised its engineers in getting around many of those issues.
But it will not be able to come back from an empty fuel tank. If there is not enough power to wake it back up, the spacecraft will die. | <urn:uuid:e625d21b-8ee3-4c1b-9089-531cca375811> | 3.375 | 349 | News Article | Science & Tech. | 55.411591 | 95,539,935 |
"For this particular study aircraft-based Doppler radar information was ingested into the system," said Fuqing Zhang, professor of meteorology, Penn State. "Our predictions were comparable to or better than those made by operational global models."
Zhang and Erin B. Munsell, graduate student in meteorology, used The Pennsylvania State University real-time convection-permitting hurricane analysis and forecasting system (WRF-EnKF) to analyze Hurricane Sandy. While Sandy made landfall on the New Jersey coast on the evening of Oct. 29, 2012, the analysis and forecast system began tracking on Oct. 21 and the Doppler radar data analyzed covers Oct. 26 through 28.
The researchers compared The WRF-EnKF predictions to the National Oceanic and Atmospheric Administration's Global Forecast System (GFS) and the European Centre for Medium-Range Weather Forecasts (ECMWF). Besides the ability to effectively assimilate real-time Doppler radar information, the WRF-EnKF model also includes high-resolution cloud-permitting grids, which allow for the existence of individual clouds in the model.
"Our model predicted storm paths with 100 km -- 50 mile -- accuracy four to five days ahead of landfall for Hurricane Sandy," said Zhang. "We also had accurate predictions of Sandy's intensity."
The WRF-EnKF model also runs 60 storm predictions simultaneously as an ensemble, each with slightly differing initial conditions. The program runs on NOAA's dedicated computer, and the analysis was done on the Texas Advanced Computing Center computer because of the enormity of data collected.
To analyze the Hurricane Sandy forecast data, the researchers divided the 60 runs into groups -- good, fair and poor. This approach was able to isolate uncertainties in the model initial conditions, which are most prevalent on Oct. 26, when 10 of the predictions suggested that Sandy would not make landfall at all. By looking at this portion of the model, Zhang suggests that the errors occur because of differences in the initial steering level winds in the tropics that Sandy was embedded in, instead of a mid-latitude trough -- an area of relatively low atmospheric pressure -- ahead of Sandy's path.
"Though the mid-latitude system does not strongly influence the final position of Sandy, differences in the timing and location of its interactions with Sandy lead to considerable differences in rainfall forecasts, especially with respect to heavy precipitation over land," the researchers report in a recent issue of the Journal of Advances in Modeling Earth Systems.
By two days before landfall, the WRF-EnKF model was accurately predicting the hurricane's path with landfall in southern New Jersey, while the GFS model predicted a more northern landfall in New York and Connecticut, and the ECMWF model forecast landfall in northern New Jersey.
Hurricane Sandy is a good storm to analyze because its path was unusual among Atlantic tropical storms, which do not usually turn northwest into the mid-Atlantic or New England. While all three models did a fairly good job at predicting aspects of this hurricane, the WRF-EnKF model was very promising in predicting path, intensity and rainfall.
NOAA is currently evaluating the use of the WRF-EnKF system in storm prediction, and other researchers are using it to predict storm surge and risk analysis.
The National Science Foundation, National Oceanic and Atmospheric Administration, NASA and the Office of Naval Research supported this work. Yonghui Weng, a research associate in Zhang's group, performed the real-time WRF-EnKF runs.
A'ndrea Elyse Messer | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Power and Electrical Engineering
17.07.2018 | Life Sciences
16.07.2018 | Physics and Astronomy | <urn:uuid:ac4bb7f4-2d65-4516-b515-7f5aba8962ff> | 2.640625 | 1,371 | Content Listing | Science & Tech. | 37.361674 | 95,539,943 |
There are twice as many emperor penguins in Antarctica than was previously thought, according to a new study released today by an international team of researchers using high-resolution satellite mapping technology. This first-ever count of an entire species from space provides an important benchmark for monitoring the impact of environmental change on the population of this iconic bird.
Scientists from the University of Minnesota Polar Geospatial Center co-authored the research with partners from the British Antarctic Survey. The research is published today in the journal PLoS ONE. In the journal, the scientists describe how they used Very High Resolution (VHR) satellite images to estimate the number of penguins at each colony around the coastline of Antarctica. Using a technique known as pan-sharpening to increase the resolution of the satellite imagery, the science teams were able to differentiate between birds, ice, shadow and penguin poo (guano).
They then used ground counts and aerial photography to calibrate the analysis. These birds breed in areas that are very difficult to study because they are remote and often inaccessible with temperatures as low as -58°F (-50°C).
Lead author and geographer Peter Fretwell at the British Antarctic Survey (BAS), which is funded by the UK's Natural Environment Research Council, said the research findings are groundbreaking.
"We are delighted to be able to locate and identify such a large number of emperor penguins," Fretwell said. "We counted 595,000 birds, which is almost double the previous estimates of 270,000 to 350,000 birds. This is the first comprehensive census of a species taken from space."
On the ice, emperor penguins with their black and white plumage stand out against the snow and colonies are clearly visible on satellite imagery. This allowed the team to analyze 44 emperor penguin colonies around the coast of Antarctica, with seven previously unknown.
"The methods we used are an enormous step forward in Antarctic ecology because we can conduct research safely and efficiently with little environmental impact, and determine estimates of an entire penguin population," said co-author Michelle LaRue from the University of Minnesota Polar Geospatial Center, which is funded by the U.S. National Science Foundation and is part of the university's College of Science and Engineering.
"The implications of this study are far-reaching," LaRue added. "We now have a cost-effective way to apply our methods to other poorly-understood species in the Antarctic, to strengthen on-going field research, and to provide accurate information for international conservation efforts."
BAS biologist Phil Trathan and co-author of the study noted the impact this research could have on the changing environment.
"Current research suggests that emperor penguin colonies will be seriously affected by climate change," Trathan said. "An accurate continent-wide census that can be easily repeated on a regular basis will help us monitor more accurately the impacts of future change on this iconic species."
Scientists are concerned that in some regions of Antarctica, earlier spring warming is leading to loss of sea ice habitat for emperor penguins, making their northerly colonies more vulnerable to further climate change.
"Whilst current research leads us to expect important declines in the number of emperor penguins over the next century, the effects of warming around Antarctica are regional and uneven," Trathan said. "In the future we anticipate that the more southerly colonies should remain, making these important sites for further research and protection."
This research is a collaboration between British Antarctic Survey, University of Minnesota/National Science Foundation, Scripps Institution of Oceanography and the Australian Antarctic Division.
To read the entire research paper in the PLoS ONE journal, visit http://z.umn.edu/penguin12.
Watch a video of Michelle LaRue discussing the research: http://www.nsf.gov/news/news_videos.jsp?cntn_id=123854&media_id=72238&org=NSF
Michelle LaRue bio: http://www.agic.umn.edu/people/larue
U of M Polar Geospatial Center: http://www.agic.umn.edu/
Feature story: 'The emperor's new close-up': http://www1.umn.edu/news/features/2012/UR_CONTENT_381718.html
Department of Earth Sciences: http://www.geo.umn.edu/
Department of Fisheries, Wildlife and Conservation Biology: http://fwcb.cfans.umn.edu/
Matt Hodson | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
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See attached file.© BrainMass Inc. brainmass.com July 19, 2018, 6:02 am ad1c9bdddf
The function f(v) is the number of particles with velocities within a volume d^3v in velocity space. The constant A is a normalization constant. The formula is valid when the gas is in thermal equilibrium. Maxwell was the first to test this formula experimentally. He let a gas stream out of a container into a vacuum for a short time. The gas molecules then moved toward a very fast rotating disk. Molecules with different speeds would hit the disk at different positions. The disk is made out of a material that will cause the molecules hitting it to stick to the disk causing it to discolor. By investigating the disk one can then deduce the speed distribution.
a) The average of v_x is zero due to the symmetry of the speed distribution as a function of v_x.
b) The average of |v_x| can be computed as follows. We first normalize f(v) such that it gives the probability density for the speed:
f(v) = [m/(2 pi k T)]^(3/2) exp[-m v^2/(2 k T)] (1)
The integral of f(v)d^3 v is thus ...
A detailed solution is given. | <urn:uuid:3d5db62d-6d6b-429d-ae9b-ee9cc7e4f34b> | 3.765625 | 289 | Academic Writing | Science & Tech. | 76.95619 | 95,539,965 |
The issue of the effects of the space environment on spacecraft needs to be understood for the long term exposure of structures in space. In order to better understand the effect of these hostile phenomena on spacecraft, several types of studies are worth performing in order to simulate at some level the effect of the environment. For example the effect of protons and electrons impacting structural materials are easily simulated through experiments using the Van de Graff and Pelletron accelerators currently housed at MSFC. Proton fluxes with energies of 700 KeV - 2.5 MeV can be generated and used to impinge on sample targets to determine the effects of the particles. Also the Environmental Effects Facility at MSFC has the capability to generate electron beams with energies from 700 KeV to 2.5 MeV. These facilities will be used in this research to simulate space environmental effects from energetic particles. Ultraviolet radiation, particularly less than 400 nm wavelength, is less well characterized at this time. The Environmental Effects Facility has a vacuum system dedicated to studying the effects of ultraviolet radiation on specific surface materials. This particular system was assembled in a previous study in order to perform a variety of experiments on materials proposed for the Space Station. That system has continued to function as planned and has been used in carrying out portions of the proposed study. | <urn:uuid:87249492-1460-42b9-b823-37244803826a> | 3.34375 | 260 | Knowledge Article | Science & Tech. | 29.348386 | 95,539,977 |
Science, Natural Phenomena & Medicine
Tuesday, November 27, 2012
Part of the Virgo Cluster, the
is a line of galaxies located about 72 million light years away. It was discovered by
Armenian astronomer Benik Jegischewitsch Markarjan in the 1970s. | <urn:uuid:43584c64-ec31-4d61-8e05-38904c34fe95> | 2.859375 | 62 | Personal Blog | Science & Tech. | 31.707895 | 95,539,978 |
Nuclear fission is the process of splitting atoms larger than iron, such as Uranium or Plutonium into two smaller atoms with the release of huge amount of energy and neutrons. Nuclear fission is discovered first. …
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Controlled nuclear fission is used to generate electricity and uncontrolled nuclear fission is used to make nuclear weapons, such as atomic bombs and hydrogen bombs. Nuclear fission also produces a large amount of nuclear wastes. “In nuclear weapons, fission and fusion of certain slightly radioactive materials release energy in a huge explosion” (Medalia, 2004, p. 1).
“The element uranium is the main fuel used to undergo nuclear fission to produce energy since it has many favorable properties. Uranium nuclei can be easily split by shooting neutrons at them. Also, once a uranium nucleus is split, multiple neutrons are released which are used to split other uranium nuclei. This phenomenon is known as a chain reaction.
Nuclear fusion is the process of joining two atoms smaller than iron such as hydrogen or helium to produce heavier atoms and that large amount of energy is produced in this reaction, which is much more than the energy produced by nuclear fission. Nuclear fusion is the main source of energy in the universe because all the stars including the sun produce energy by nuclear fusion. Other than nuclear fission, man has not yet discovered a method to control nuclear fusion, and nuclear fusion is not used to generate electricity. Scientists are working hard to discover a method to control nuclear fusion so that it can be used to generate electricity. Nuclear fusion is only used in hydrogen bomb which is the deadliest weapon humanity has ever seen. The temperature required to start a nuclear fusion is so large that it is provided by the explosion of an atom bomb.
Benefits of Nuclear Energy: The largest advantage of nuclear power is that it does not emit any harmful gases to the atmosphere like carbon dioxide, sulphur dioxide, or nitrogen dioxide, that is, no green house gasses like carbon dioxide is emitted to the atmosphere, and so using nuclear fuel can reduce global warming. As nitrogen dioxide and sulphur dioxide are not emitted, acid rains can also be reduced. The only emission from nuclear reactors is water vapor. Hence nuclear energy is known as clean energy. “It is difficult to explain to a non-specialist (though it is actually true) that the nuclear reactor of a nuclear power station is nothing like an atomic bomb, that the power station burning coal or oil offers much greater danger and harm to the environment as well as a biological threat to people than does a nuclear station or breeder reactor of the same capacity rating” (Sakharov, 1978, p. 12). “Although the initial cost of building nuclear plants is high, the running costs are relatively low. One reason the costs are low is that nuclear plants need only a small amount of uranium to produce a lot of energy. In fact, if the cost of uranium is doubled, costs would only be increased by 7%. 1 truck of uranium produces as much energy as 1000 trucks of coal!” (Advantages of Nuclear Power, 2012). Efficiency: Another major advantage of nucl
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By the law of conservation of energy, one type of energy can be converted to the other (TutorVista.com). Every type of energy can be converted to the other. Thermal, solar, wind, hydrodynamic, geothermal and other types of renewable energy sources can be utilized to generate electrical power.
The cost of nuclear electricity has come down in the recent past and the impediments to the expansion of nuclear energy at this point are mainly restricted to problems that arise out of the ignorance of people regarding the processes that are associated with nuclear energy and the accidents that happen as a result of instances of human negligence.
These events have unfortunately created misconceptions about nuclear power, which highlight more on perceived disadvantages than its benefits. This paper is a critical examination of nuclear energy focusing on its advantages and disadvantages in relation to other sources of energy.
The search of alternate energy source is revolving around solar energy and nuclear energy. Even though solar energy is renewable in nature, feasible technologies to convert it into useful energy forms are still not developed properly. On the other hand, the technology for the exploitation of nuclear energy is well developed.
All scientists agree today that this increased concentration of greenhouse gases is responsible for climatic change, change that is perhaps natural, but is certainly accelerated by human activity. These discharges are caused mainly by transport vehicles. However, the use of fossil fuels in the generation of electricity is also contributing to the worsening situation.
According to the report scientists discovered that splitting of certain heavy atoms could result in production of enormous amount of energy. This fundamental process is the heartbeat of all the nuclear processes taking place in today’s world. Over the history, this form of energy production has served for various purposes and applications.
These countries are France, Japan, and the United States. This is despite the fact that there are 439 nuclear reactors for power generation scattered across 31 countries. Statistics have shown that this
When the atoms are merged or split in a set process of chemical reactions, nuclear energy is created (Kate 2002). When the nucleuses of an atom are split it is called fission but when they are merged it is called
Fission is basically separating an atom into two atoms and the energy produced during the separation is transformed in massive energy. The current issue of global warming has led to the popularity of nuclear energy since its mitigation is
4 Pages(1000 words)Essay
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Molar absorptivity, also known as the molar extinction coefficient, measures how well a chemical species absorbs a given wavelength of light. It is commonly used in chemistry and should not be confused with the extinction coefficient, which is used more often in physics. The standard units for molar absorptivity are square meters per mole, but it is usually expressed as square centimeters per mole.
Define the variables to calculate the molar absorptivity. The absorbance (A) is the amount of light within a given wavelength that is absorbed by the solution. The concentration (c) of the absorbing species is the amount of absorbing species per unit volume. The path length (l) is the distance light travels through the solution. Molar absorptivity is represented by "e."
Apply Beer-Lambert Law
Use Beer-Lambert Law to calculate the molar absorptivity of a single absorbing species. The equation is A = ecl, so the equation for molar absorptivity is e = A ÷ cl.
Calculate Total Absorbance
Calculate the total absorbance of a solution that contains more than one absorbing species. Expand the Beer-Lambert law to A = (e1c1 + e2c2 + ...)l, where "ei" is the molar absorptivity of species "i," and "ci" is the concentration of species "i" in the solution.
Calculate Molar Absorptivity
Calculate the molar absorptivity from the absorption cross-section and Avogadro's Number (approximately 6.022 x 10^23); d = (2.303 ÷ N)e, where "d" is the absorption cross section and "N" is Avogadro's Number. Therefore, d = (2.303 ÷ (6.022 x 10^23))e = 3.82 x 10^(-21)e, so e = (2.62 x 10^20)d.
Predict Molar Absorptivity of Light
Predict the molar absorptivity of light at 280 nm by a protein. The molar absorptivity under these conditions depends on the number of aromatic residues the protein has, especially tryptophan. | <urn:uuid:7e5b66c2-a898-4acf-bbc7-91e300cfa783> | 4.09375 | 476 | Tutorial | Science & Tech. | 53.253992 | 95,540,021 |
Create a column as cursor in sql pdf ‘blob’ in a table. Read the content of the file.
Save in ‘blob’ type column in a table or store them in a folder and establish the pointer to link them in the database. To retrieve the file from the database, SELECT query is executed and ID of the file is passed as an argument. It uses MS- SQL as the query language. Use of keyword WITH ENCRYPTION. Create a Store Procedure with Encryption. Please forward this error screen to sharedip-10718057119. This article has multiple issues.
Unsourced material may be challenged and removed. SQL functionality with each successive release of the Oracle Database. SQL units such as procedures, functions, packages, types, and triggers, which are stored in the database for reuse by applications that use any of the Oracle Database programmatic interfaces. SQL also resembles Pascal in several aspects.
Such objects can also persist as column values in Oracle database tables. SQLite API by including a version of SQLite in Berkeley DB. SQL code on Berkeley DB. One can use control statements like decision making, iterative control if only SQL is to be used. SQL is basically a procedural language, which provides functionality of decision making, iteration and many more features like other procedural programming languages. | <urn:uuid:bdd37200-0272-4fc9-bc2c-3b6ed19cdd78> | 2.828125 | 273 | Truncated | Software Dev. | 40.857435 | 95,540,075 |
Bats on the brink: A search for the grey long-eared bat
One of the UK's rarest mammals, the grey long-eared bat, is in danger of disappearing from the country, according to research.
A four-year study by scientists from the University of Bristol estimated that there were just 1,000 of the bats left - all confined to southern England.
BBC science reporter Victoria Gill went in search of the bats at a secret location in Devon - one of just ten known maternal roosts.
Dr Orly Razgour, who led the research and was the guide on this bat safari, says the bats' foraging habitat needs to be protected if the species is to survive in this country.
The Bat Conservation Trust has published the findings in a new conservation management plan.
05 Aug 2013 | <urn:uuid:8c6ea50a-5941-4bde-b0fb-f74e28642d25> | 3.140625 | 169 | Truncated | Science & Tech. | 56.059353 | 95,540,088 |
Learn how aspnet core implements dependency injection and how to use it. Note this hands on lab assumes you have basic knowledge of aspnet mvc and aspnet mvc 4 filters if you have not used aspnet mvc 4 filters before we rec. Dependency injection in net presents core di patterns in plain c so youll fully understand how di works covers integration with standard microsoft . What is dependency injection dependency injection di is a pattern that can help developers decouple the different pieces of their applications it provides a . Take advantage of dependency injection in aspnet core to plug in components and improve code maintenance and testability
How it works:
1. Register Trial Account.
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July 22, 2018
Conservation Effects Assessment Project (CEAP)
Assessments in CEAP are carried out at national, regional and watershed scales on cropland, grazing lands, wetlands and for wildlife. The three principal components of CEAP—the national assessments, the watershed assessment studies, and the bibliographies and literature reviews— contribute to building the science base for conservation. That process includes research, modeling, assessment, monitoring and data collection, outreach, and extension education. Focus is being given to translating CEAP science into practice.
A CEAP-Wildlife Conservation study published in December 2017 looked at how “Small Forest Openings Support Shrubland Birds and Native Bees in the Northeast.”[i] While the study was conducted in the heavily forested area of western Massachusetts, there are findings that can apply to other locations in the east, such as the mid-south area. Here is a summary:
• Once prevalent on the landscape, early successional habitats are now rare in the northeastern United States. As a result, populations of many wildlife species that rely on these habitats (dominated by shrubs, young trees, grasses, and forbs) have declined.
• Group selection timber harvest can be used to create small forest openings (typically <1 hectare) and has the potential to provide needed shrub land habitats within the parceled forests.
• Use of small forest openings by shrub land bird and bee communities was assessed across a range of forest opening sizes and configurations to develop guidelines for optimizing the value of small forest openings to these high-priority wildlife resources.
• Minimum-area requirements for black-and-white warbler, common yellowthroat, chestnut-sided warbler, eastern towhee, and gray catbird were at most 0.23 ha, while indigo buntings and prairie warblers required larger openings (minimum-area requirements of 0.56 and 1.11 hectare, respectively). Prairie warblers were more likely to be found in openings closer to large patches of habitat, such as power line corridors (>50 m wide) even if those openings were relatively small in size.
• Despite their inability to support all shrub land bird species in the region, small forest openings can
provide habitat for several species of conservation concern if proper attention is given to promoting suitable microhabitat, patch, and landscape characteristics.
• Bee abundance and diversity were significantly higher in forest openings than in mature forest. Individual opening size did not affect bee abundance or diversity; however, bees were more abundant and diverse in openings and adjacent mature forest when there was more early successional habitat in the surrounding landscape. Bee abundance and diversity in forest openings tended to decrease with vegetation height and increase with a metric representing floral richness and abundance. In adjacent mature forests, eusocial, soft-wood-nesting, and small bees exhibited the opposite pattern, increasing with the succession of openings and decreasing with greater floral richness abundance within openings.
• Results suggest that the creation of small forest openings may help to promote bees both in openings and adjacent mature forest, with certain guilds benefitting more than others.
One study on wildlife, specifically Bobwhite Quail and grassland birds, would be of specific interest to field trailers. The study considered states in the south and mid-south and found that in “over 14 states, breeding Bobwhite densities were 70-75% greater around CP33 buffered fields than around unbuffered crop fields. Fall Bobwhite covey densities were 50-110% greater around CP33 fields than around unbuffered crop fields. Several upland songbirds (e.g., dickcissel, field sparrow) responded strongly to CP33 in the landscape. Findings illustrate the wildlife value of field borders and other buffer practices implemented through EQIP, WHIP, and other conservation programs.”
“Buffers can be established around field edges on any cropland. Buffers can be planted along one or more sides of a field, however establishing a buffer around the entire field should be considered and is highly encouraged. CP33 is considered year-round habitat, and as such, should be considered ‘hands off’ from any farming operations.”
Read general information about Habitat Buffers for Upland Birds at: https://www.fsa.usda.gov/Assets/USDA-FSA-Public/usdafiles/FactSheets/2015/CRPProgramsandInitiatives/Practice_CP33_Habitat_Buffers_for_Upland_Birds.pdf
For further information on CRP buffers, especially for Bobwhite Quail habitat establishment, read “Habitat Buffers for Upland Birds Program Sheet” at: https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1119726.pdf
Read more of the studies conducted by CEAP on topics related to Wildlife, Cropland, Wetlands, Grazing Lands, and Watershed Assessments at: https://www.nrcs.usda.gov/wps/portal/nrcs/main/national/technical/nra/ceap/ and at http://ceap-nrcs.opendata.arcgis.com/
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Sat watching the bumble bees and a curious fly . #bumblebee #pollen #fly #flowers #insects #photography #canon
bumblebees are large, fuzzy insects with short, stubby wings. they are larger than honeybees, but they don't produce as much honey. however, they are very important pollinators. without them, food wouldn't grow.
two-thirds of the world's crop species depend on animals to transfer pollen between male and female flower parts, according to ecologist rachel winfree, an assistant professor in the department of entomology at rutgers university. many animals are pollinators — including birds, bats and butterflies — but "there's no question that bees are the most important in most ecosystems," she said in a 2009 article in national wildlife magazine.
while other animals pollinate, bumblebees are particularly good at it. their wings beat 130 times or more per second, according to the national wildlife federation, and the beating combined with their large bodies vibrates flowers until they release pollen, which is called buzz pollination. buzz pollination helps plants produce more fruit.
there are over 255 species of bumblebees, according to the integrated taxonomic information system(itis), so bumblebees can be many sizes. the largest is the queen of the bombus dahlbomii, which can grow up to 1.6 inches (4 centimeters) long. this is three to four times longer than the american bumblebee, according to scientific american.
it has often been said that bumblebees defy aerodynamics and should not be able to fly. however, a recent study resolved the enigma and showed how the tiny wings keep the bee in the air. the study, published in the journal proceedings of the national academy of sciences in 2005, used high-speed photography to show that bumblebees flap their wings back and forth rather than up and down.
the wing sweeping is a bit like a partial spin of a "somewhat crappy" helicopter propeller, researcher michael dickinson, a professor of biology and insect flight expert at the university of washington, told live science in a 2011 article. however, the angle to the wing also creates vortices in the air — like small hurricanes. | <urn:uuid:191997b9-a8dd-4c2c-90d6-e29e8c9a00b4> | 4.0625 | 471 | Knowledge Article | Science & Tech. | 40.807672 | 95,540,135 |
A View from Emerging Technology from the arXiv
How Flake-Handling Trick Will Enable Graphene’s Next Revolution
The ability to stack graphene sheets on top of each other should make possible an entirely new class of devices that exploit previously inaccessible physics, say researchers
In recent months, a new sense of excitement has spread through the graphene research community. These guys are no longer focused on what they can do with single layers of carbon chickenwire. Instead they have a more ambitious plan.
The new goal is to take single layers of high quality graphene and pile them on top of each other to create what physicists call van der Waals heterostructures, layer cakes of carbon crystals each just a single atom thick that promise to behave in entirely new ways. The hope is that this will open the way to undreamt of applications in superconductivity, semiconductor physics and so on.
But there is a problem. Creating layer cakes of crystalline sheets is fraught with difficulty, so research groups around the world are racing to find better ways of doing it.
Today Xu-Dong Chen and a few buddies at Nankai University in China say they have developed a new and easier way to do it that opens up the possibility of exploring the potential of these devices in much greater detail.
Ideally, physicists would simply grow one layer of graphene on top of another but nobody has worked out how to do this, particularly when they want to orient each layer’s crystal structure in different directions. What’s more, graphene grown in this way is of much lower quality than the stuff they can get by cleaving single layers from a bigger lumps.
This cleaving process creates flakes of high-quality graphene sheets but it also introduces other problems. Nobody has cracked the problem of how to carve these flakes into the required shapes and then to pick them up individually and place them in the required spot.
Hard though it is to credit, the standard technique for gathering high quality graphene is to pick up the flakes using little more than Scotch tape. That sounds better suited to removing fluff from a dinner suit then creating electronic devices of the future.
And indeed it is fraught with problems. The main one is that Scotch tape picks up everything it comes into contact with. So as well as the desired flake, this process also brings a whole load of unwanted flakes too and these can end up contaminating the environment or device into which they are placed.
Xu-Dong and co have a more advanced approach that targets specific flakes of graphene, carves them into any desired shape and then picks them up individually so that they can be transferred and placed in a new environment.
The process is relatively straightforward. It begins by identifying the graphene flake to be removed and then carving it into shape with a laser.
The next step is to cover the entire substrate, including all the unwanted graphene flakes, with photoresist and then use the laser to expose the photoresist above the patterned graphene to light. The exposed photoresist is then dissolved to reveal the graphene below.
The final step is to pick up the exposed graphene using the ordinary Scotch tape technique. Since all the unwanted graphene flakes are covered by undissolved photoresist, this only transfers the desired graphene sheet.
Xu-Dong and co have tested their idea by creating a number of graphene patterns and transferring them to other environments. For example, they placed a square sheet of graphene onto a microcavity to create a molecular sieve. They also fabricated graphene ribbons of various widths and thicknesses and transferred them without distortion or fracture. They even use the technique to place graphene structures on top of gold electrodes, an important step in device manufacture.
This new-found ability to selectively transfer sheets of graphene cleanly and accurately is an important enabling step towards creating van der Waals heterostructures. To date, the best attempts have created structures of up to 6 layers but of course physicists want more. This new technique may well give them that.
There are limitations, of course. The new technique requires the hands-on involvement of a researcher at every stage. So it is clearly unsuited to mass production. But that matters little at this stage when physicists are merely attempting to understand the properties and capabilities of this new class of device. The problems of mass production can safely be saved for later.
The promise is huge. Physicists have known for some time now that graphene has extraordinary electronic and mechanical properties. They’ve now spent a decade or so getting to grips with this.
The big question now is what becomes possible when these monolayers are stacked. For example, physicists know that high-temperature superconductivity comes about because of the way that layers of copper oxides are stacked and that the temperature at which superconductivity kicks in is particularly sensitive to the distance between each layer. However the mechanisms involved are unknown.
Graphene is itself a reasonable superconductor so an interesting question is whether its superconducting temperature could be raised by stacking graphene sheets in certain ways or by alternating the sheets with other materials.
It’s this kind of thinking that raises the tantalising prospect that van der Waals heterostructures will be able to exploit previously inaccessible physics.
And that is just the beginning. Physicists are intensely interested in the growing number of other two-dimensional crystals that have been discovered in recent years. These include hexagonal boron nitride, molybdenum disulphide, tungsten diselenide and so on. Just what could be possible with pancakes structures created with these materials is an exciting question to ponder.
And with techniques like this, we may not have long to find out.
Ref: arxiv.org/abs/1308.5514: The Selective Transfer Of Patterned Graphene
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Macro Definition & Call
It has been aforementioned that a macro consists of a name, a set of formal parameters, and a body of codes.
A macro can be defined by enclosing a set of statements between a macro header and a macro end statement.
The formal structure of a macro includes the following features:
Macro prototype statement: Specifies the name of the macro and name and type of formal parameters.
Model statements: Specify the statements in the body of the macro from which assembly language statements are to be generated during expansion.
Macro preprocessor statement: Specifies the statement used for performing the auxiliary function during macro expansion A macro prototype statement can be written as follows: <name_of_macro> [<formal parameter spec> [,…]]
where [<formal parameter spec> [,…]] defines the parameter name and its kind, which are of the following form:
- A macro can be called by writing the name of the macro in the mnemonic field of the assembly language. The syntax of a typical macro call can be of the following form:
<name_of_macro> [<actual_parameter_spec> [,…]]
- The MACRO directive in the mnemonic field specifies the start of the macro definition and it should compulsorily have the macro name in the label field.
- Also, The MEND directive specifies the end of the macro definition.
- Moreover, The statements between MACRO and MEND directives define the body (model statements) of the macro and can appear in the expanded code.
INCR&MEM_VAL, &INC_VAL, ®
INCR A, B
- A macro call in a program leads to macro expansion. To expand a macro, the name of the macro placed in the operation field, and no special directives are necessary. During macro expansion, the macro name statement in the program is replaced by the sequence of assembly statements. So, Let us consider the following example:
INCR A, B, AREG
- Also, The preceding example uses a statement that calls the macro. The assembly code sequence INCR A,B, AREG is an example of the macro call, with A and B being the actual parameters of the macro.
- While passing over the assembly program, the assembler recognizes INCR as the name of the macro, expands the macro, and places a copy of the macro definition (along with the parameter substitutions). The expanded code for the code is as below.
+ MOVER REG A
+ ADDREG B
+ MOVEM REG A
- Moreover, The statements marked with a ‘+’ sign in the preceding label field denote the expanded code and differentiate them from the original statements of the program. | <urn:uuid:64f94948-35de-49bb-ac81-6f082b607a0b> | 3.765625 | 577 | Documentation | Software Dev. | 27.823048 | 95,540,151 |
This thesis aims to resolve some open questions about sonic boom, and particularly secondary sonic boom, which arises from long-range propagation in a non-uniform atmosphere. We begin with an introduction to sonic boom modelling and outline the current state of research. We then proceed to review standard results of gas dynamics and we prove a new theorem, similar to Kelvin's circulation theorem, but valid in the presence of shocks. We then present the definitions used in sonic boom theory, in the framework of linear acoustics for stationary and for moving non-uniform media. We present the wavefront patterns and ray patterns for a series of analytical examples for propagation from steadily moving supersonic point sources in stratified media. These examples elucidate many aspects of the long-range propagation of sound and in particular of secondary sonic boom. The formation of `fold caustics' of boomrays is a key feature. The focusing of linear waves and weak shock waves is compared. Next, in order to address the consistent approximation of sonic boom amplitudes, we consider steady motion of supersonic thin aerofoils and slender axisymmetric bodies in a uniform medium, and we use the method of matched asymptotic expansions (MAE) to give a consistent derivation of Whitham's model for nonlinear effects in primary boom analysis. Since for secondary boom, as for primary, the inclusion of nonlinearities is essential for a correct estimation of the amplitudes, we then study the paradigm problem of a thin aerofoil moving steadily in a weakly stratified medium with a horizontal wind. We again use MAE to calculate approximations of the Euler equations; this results in an inhomogeneous kinematic wave equation. Returning to the linear acoustics framework, for a point source that accelerates and decelerates through the sound speed in a uniform medium we calculate the wavefield in the `time-domain'. Certain other motions of interest are also illustrated. In the accelerating and in the manoeuvring motions fold caustics that are essentially the same as those from steady motions in stratified atmospheres again arise. We also manage to pinpoint a scenario where a `cusp caustic' of boomrays forms instead. For the accelerating motions the asymptotic analysis of the wavefield reveals the formation of singularities which are incompatible with linear theory; this suggests the re-introduction of nonlinear effects. However, it is a formidable task to solve such a nonlinear problem in two or three dimensions, so we solve a related one-dimensional problem instead. Its solution possesses an unexpectedly rich structure that changes as the strength of nonlinearity varies. In all cases however we find that the singularities of the linear problem are regularised by the nonlinearity.
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Choose a citation style from the tabs below | <urn:uuid:c06c58e1-8c58-425c-a71c-032d061d3947> | 2.703125 | 591 | Academic Writing | Science & Tech. | 20.870045 | 95,540,167 |
Fundamental Theorems about Holomorphic Functions
Having led to the Cauchy integral formula and the Cauchy-Taylor representation theorem, the theory of integration in the complex plane will temporarily pass off of center-stage. The power of the two mentioned results has already become clear but this chapter will offer further convincing examples of this power. First off, in section 1 we prove and discuss the Identity Theorem, which makes a statement about the “cohesion among the values taken on by a holomorphic function.” In the second section we illuminate the holomorphy concept from a variety of angles. In the third, the Cauchy estimates are discussed. As applications of them we get, among other things, Liouville’s theorem and, in section 4, the convergence theorems of Weierstrass. The Open Mapping Theorem and the Maximum Principle are proved in section 5.
KeywordsPower Series Maximum Principle Holomorphic Function Entire Function Convergence Theorem
Unable to display preview. Download preview PDF. | <urn:uuid:526a0a63-0529-4496-96a6-a00fbe7135c3> | 3.0625 | 216 | Truncated | Science & Tech. | 31.972436 | 95,540,227 |
Papilio aegeus aegeus Donovan
Interesting aspects: One of the larger butterflies to occur in Australia, and the largest to be found in South Australia. It has quickly adapted to the introduced Citrus trees in Australia and can now be found in many areas where these trees are cultivated.
It has a reasonably fast and direct flapping flight in open areas, although the flight of the female is normally more subdued and slow as it goes about its business of egg laying. The butterflies always seem to be in flight, but are usually approachable, if only for a brief moment. Both sexes are often seen nectaring at flowers, particularly lantana, when they can be easily approached. The large size of this butterfly can sometimes bring out phobias in people so inflicted.
Larval food-host: Native and introduced Rutaceae. Native hosts include Citrus(Eremocitrus) glauca (desert lime),**Eriostemon spp (wax flower), **Geijera spp including G. parviflora (wilga), **Philotheca spp (wax flower) incl. **P. myoporoides (native daphne), **Phebalium spp, **Zieria spp. Introduced and preferred hosts include cultivated *Citrus spp, *Citrus(Fortunella) spp (kumquat), *Citrus(Poncirus) trifoliata (wild orange), *Choisya ternata (Mexican orange-blossom). The butterfly prefers the tropical and subtropical plant species of the above plant groups, and in South Australia it has not been noted to utilise any of the locally occurring temperate species, including Citrus(Eremocitrus) glauca and Geijera parviflora. Larvae in captivity can sometimes be transferred to other swallowtail hostplants like *Apium graveolens (celery), *Daucus carota (carrot), *Petroselinum crispum (parsley) (Apiaceae), Owenia sp (emu apple) (Meliaceae), *Capparis nobilis (caper bush) (Capparaceae), and *Cinnamomum camphora (camphor laurel) (Lauraceae). The females will not normally lay eggs on these latter plants. The larvae prefer to eat the young leaves of the hostplant, but larger larvae will eat the older leaves.
Eggs: Eggs hatch in a week.
Larvae: The first four instars are the bird-dropping stage. The fifth and final instar is a green camouflage stage.
All larvae stages feed exposed on the hostplant. When disturbed, the larvae can evert a reddish orange coloured, fleshy bifid osmeterium from behind the head that emits a distinct citrus-like pungent odoriferous secretion, smelling like rotting oranges on the ground beneath an orange tree. This secretion acts as a deterrent to both vertebrate (birds, lizards and mice) and invertebrate (ants, spiders and wasps) predators. It is more effective if the chemical can be deposited on the predator, hence the larvae will attempt to throw their heads (and osmeterium) either backwards or sideways if a predator attacks from the rear or side. The secretion is usually composed of a butyric acid compound having irritant properties. The osmeterium is present in all stages of the larvae, and is found in all the Papilionidae group of butterflies. In other species the osmeterium can have a different colour such as green, blue or black.
Pupae: Pupal stage about 17 days (2-3 weeks)
Flight period in S.A.: The butterfly is seen all year round in the humid tropics and subtropics of eastern Australia. During seasons with abnormal humidity it will move south during summer and autumn, occasionally reaching South Australia and Victoria. Most of the South Australian records are from the big invasion of subtropical butterflies that occurred during the summer of 1973-1974. Interestingly, there were no recordings for the butterfly in S.A, during the recent drought breaking big rains of the 2010-2011 flight season.
Distribution: Normally a humid tropical and subtropical eastern states butterfly with vagrant tendencies. Within South Australia the butterfly has been sporadically documented from the southeastern portion of the state. A small breeding colony was once semi-established at Whyalla but due to the destructive behaviour of its large larvae on garden Citrus this colony was short lived. Another breeding colony was reported from Waikerie in the Riverland during the mid 1970's but it is not known if it still exists. Breeding records from the eastern states suggest this butterfly would be unable to establish permanently south of about the Waikerie latitude.
Interested public now have access to live eggs and pupae reared in the heated butterfly houses of the eastern states, and so it is likely additional random recordings will continue to occur in future years.
Habitat: It prefers moist woodland and forest areas. Potential native and introduced hostplants occur throughout the state, but the butterfly and its early stages require warm humid and sheltered conditions to survive.
Conservation Status in S.A.: A vagrant.
Threats: It is considered a minor pest in the Citrus orchards occurring in the eastern states and is sometimes sprayed. However, it is unlikely to survive long in any commercial Citrus orchard due to the persistent spray activity that occurs in these orchards. Its larvae are large and are capable of damaging the younger foliage of its hostplant, although usually the larvae numbers are kept low by natural predators.
Conservation Strategy: None required. If you are lucky enough to have the butterfly established in your area then nurture it, as it is a large spectacular butterfly.
Author: R. GRUND, © copyright 17 January 2000, all rights
Last update 29 April 2002. | <urn:uuid:b80c9d04-780f-4961-9b29-558dfbb3cee7> | 2.703125 | 1,262 | Knowledge Article | Science & Tech. | 38.03356 | 95,540,260 |
module [switches] [sub-command [sub-command-args]]
module is a user interface to the Modules package. The Modules package provides for the dynamic modification of the user’s environment via modulefiles.
Each modulefile contains the information needed to configure the shell for an application. Once the Modules package is initialized, the environment can be modified on a per-module basis using the module command which interprets modulefiles. Typically modulefiles instruct the module command to alter or set shell environment variables such as PATH, MANPATH, etc. Modulefiles may be shared by many users on a system and users may have their own set to supplement or replace the shared modulefiles.
The modulefiles are added to and removed from the current environment by the user. The environment changes contained in a modulefile can be summarized through the module command as well. If no arguments are given, a summary of the module usage and sub-commands are shown.
The action for the module command to take is described by the sub-command and its associated arguments.
The Modules package and the module command are initialized when a shell-specific initialization script is sourced into the shell. The script creates the module command as either an alias or function and creates Modules environment variables.
The module alias or function executes the modulecmd.tcl program located in /usr/share/Modules/libexec and has the shell evaluate the command’s output. The first argument to modulecmd.tcl specifies the type of shell.
The initialization scripts are kept in /usr/share/Modules/init/<shell> where <shell> is the name of the sourcing shell. For example, a C Shell user sources the /usr/share/Modules/init/csh script. The sh, csh, tcsh, bash, ksh, zsh and fish shells are supported by modulecmd.tcl. In addition, python, perl, ruby, tcl, cmake, r and lisp “shells” are supported which writes the environment changes to stdout as python, perl, ruby, tcl, lisp, r or cmake code.
Initialization may also be performed by calling the autoinit sub-command of the modulecmd.tcl program. Evaluation into the shell of the result of this command defines the module alias or function.
Examples of initialization¶
C Shell initialization (and derivatives):
source /usr/share/Modules/init/csh module load modulefile modulefile ...
Bourne Shell (sh) (and derivatives):
. /usr/share/Modules/init/sh module load modulefile modulefile ...
require "/usr/share/Modules/init/perl.pm"; &module('load', 'modulefile', 'modulefile', '...');
import os exec(open('/usr/share/Modules/init/python.py').read()) module('load, 'modulefile', 'modulefile', '...')
Bourne Shell (sh) (and derivatives) with autoinit sub-command:
eval "`/usr/share/Modules/libexec/modulecmd.tcl sh autoinit`"
Upon invocation modulecmd.tcl sources if it exists a site-specific configuration script located in /usr/share/Modules/etc/siteconfig.tcl. This Tcl script enables to supersede any global variable or procedure definition of modulecmd.tcl.
Afterward, modulecmd.tcl sources rc files which contain global, user and modulefile specific setups. These files are interpreted as modulefiles. See modulefile for detailed information.
Upon invocation of modulecmd.tcl module run-command files are sourced in the following order:
- Global RC file as specified by $MODULERCFILE or /usr/share/Modules/etc/rc. If $MODULERCFILE points to a directory, the modulerc file in this directory is used as global RC file.
- User specific module RC file $HOME/.modulerc
- All .modulerc and .version files found during modulefile seeking.
Command line switches¶
The module command accepts command line switches as its first parameter. These may be used to control output format of all information displayed and the module behavior in case of locating and interpreting modulefiles.
All switches may be entered either in short or long notation. The following switches are accepted:
Give some helpful usage information, and terminates the command.
Lists the current version of the module command. The command then terminates without further processing.
Debug mode. Causes module to print debugging messages about its progress.
Pipe all message output into less (or if set, $MODULES_PAGER) if error output stream is a terminal. See also MODULES_PAGER section.
Do not pipe message output into a pager.
Display avail, list and savelist output in short format.
Display avail, list and savelist output in long format.
On avail sub-command, display only the default version of each module name. Default version is either the explicitly set default version or the highest numerically sorted modulefile if no default version set (see Locating Modulefiles section in the modulefile man page).
On avail sub-command, display only the highest numerically sorted version of each module name (see Locating Modulefiles section in the modulefile man page).
Print the usage of each sub-command. If an argument is given, print the Module-specific help information for the modulefile.
Load modulefile into the shell environment.
Remove modulefile from the shell environment.
swap [modulefile1] modulefile2
switch [modulefile1] modulefile2
Switch loaded modulefile1 with modulefile2. If modulefile1 is not specified, then it is assumed to be the currently loaded module with the same root name as modulefile2.
Display information about one or more modulefiles. The display sub-command will list the full path of the modulefile and the environment changes the modulefile will make if loaded. (Note: It will not display any environment changes found within conditional statements.)
List loaded modules.
avail [-d|-L] [-t|-l] [path…]
List all available modulefiles in the current MODULEPATH. All directories in the MODULEPATH are recursively searched for files containing the modulefile magic cookie. If an argument is given, then each directory in the MODULEPATH is searched for modulefiles whose pathname, symbolic version-name or alias match the argument. Argument may contain wildcard characters. Multiple versions of an application can be supported by creating a subdirectory for the application containing modulefiles for each version.
Symbolic version-names and aliases found in the search are displayed in the result of this sub-command. Symbolic version-names are displayed next to the modulefile they are assigned to within parenthesis. Aliases are listed in the MODULEPATH section where they have been defined. To distinguish aliases from modulefiles a @ symbol is added within parenthesis next to their name. Aliases defined through a global or user specific module RC file are listed under the global/user modulerc section.
List all available symbolic version-names and aliases in the current MODULEPATH. All directories in the MODULEPATH are recursively searched in the same manner than for the avail sub-command. Only the symbolic version-names and aliases found in the search are displayed.
use [-a|–append] directory…
Prepend one or more directories to the MODULEPATH environment variable. The –append flag will append the directory to MODULEPATH.
Reference counter environment variable MODULEPATH_modshare is also set to increase the number of times directory has been added to MODULEPATH.
Remove one or more directories from the MODULEPATH environment variable if reference counter of these directories is equal to 1 or unknown.
Reference counter of directory in MODULEPATH denotes the number of times directory has been enabled. When attempting to remove directory from MODULEPATH, reference counter variable MODULEPATH_modshare is checked and directory is removed only if its relative counter is equal to 1 or not defined. Elsewhere directory is kept and reference counter is decreased by 1.
Unload then load all loaded modulefiles.
Unload all loaded modulefiles.
Execute modulefile into the shell environment. modulefile must be specified with a fully qualified path. Once executed modulefile is not marked loaded in shell environment which differ from load sub-command.
Display the information set up by the module-whatis commands inside the specified modulefiles. These specified modulefiles may be expressed using wildcard characters. If no modulefile is specified, all module-whatis lines will be shown.
Seeks through the module-whatis informations of all modulefiles for the specified string. All module-whatis informations matching the string will be displayed. string may contain wildcard characters.
Execute and display results of the Module-specific tests for the modulefile.
Record the currently set MODULEPATH directory list and the currently loaded modulefiles in a collection file under the user’s collection directory $HOME/.module. If collection name is not specified, then it is assumed to be the default collection. If collection is a fully qualified path, it is saved at this location rather than under the user’s collection directory.
If MODULES_COLLECTION_TARGET is set, a suffix equivalent to the value of this variable will be appended to the collection file name.
By default, if loaded modulefile corresponds to the default module version, the bare module name is recorded. If MODULES_COLLECTION_PIN_VERSION is set to 1, module version is always recorded even if it is the default version.
Restore the environment state as defined in collection. If collection name is not specified, then it is assumed to be the default collection. If collection is a fully qualified path, it is restored from this location rather than from a file under the user’s collection directory. If MODULES_COLLECTION_TARGET is set, a suffix equivalent to the value of this variable is appended to the collection file name to restore.
When restoring a collection, the currently set MODULEPATH directory list and the currently loaded modulefiles are unused and unloaded then used and loaded to exactly match the MODULEPATH and loaded modulefiles lists saved in this collection file. The order of the paths and modulefiles set in collection is preserved when restoring. It means that currently loaded modules are unloaded to get the same LOADEDMODULES root than collection and currently used module paths are unused to get the same MODULEPATH root. Then missing module paths are used and missing modulefiles are loaded.
Delete the collection file under the user’s collection directory. If collection name is not specified, then it is assumed to be the default collection. If MODULES_COLLECTION_TARGET is set, a suffix equivalent to the value of this variable will be appended to the collection file name.
Display the content of collection. If collection name is not specified, then it is assumed to be the default collection. If collection is a fully qualified path, this location is displayed rather than a collection file under the user’s collection directory. If MODULES_COLLECTION_TARGET is set, a suffix equivalent to the value of this variable will be appended to the collection file name.
List collections that are currently saved under the user’s collection directory. If MODULES_COLLECTION_TARGET is set, only collections matching the target suffix will be displayed.
Add modulefile to the shell’s initialization file in the user’s home directory. The startup files checked (in order) are:
C Shell.modules, .cshrc, .csh_variables and .login
TENEX C Shell.modules, .tcshrc, .cshrc, .csh_variables and .login
Bourne and Korn Shells.modules, .profile
GNU Bourne Again Shell.modules, .bash_profile, .bash_login, .profile and .bashrc
Z Shell.modules, .zshrc, .zshenv and .zlogin
Friendly Interactive Shell.modules, .config/fish/config.fish
If a module load line is found in any of these files, the modulefiles are appended to any existing list of modulefiles. The module load line must be located in at least one of the files listed above for any of the init sub-commands to work properly. If the module load line is found in multiple shell initialization files, all of the lines are changed.
Does the same as initadd but prepends the given modules to the beginning of the list.
Remove modulefile from the shell’s initialization files.
initswitch modulefile1 modulefile2
Switch modulefile1 with modulefile2 in the shell’s initialization files.
List all of the modulefiles loaded from the shell’s initialization file.
Clear all of the modulefiles from the shell’s initialization files.
Print path to modulefile.
Print path of available modulefiles matching argument.
append-path [-d C|–delim C|–delim=C] [–duplicates] variable value…
Append value to environment variable. The variable is a colon, or delimiter, separated list. See append-path in the modulefile man page for further explanation.
prepend-path [-d C|–delim C|–delim=C] [–duplicates] variable value…
Prepend value to environment variable. The variable is a colon, or delimiter, separated list. See prepend-path in the modulefile man page for further explanation.
remove-path [-d C|–delim C|–delim=C] [–index] variable value…
Remove value from the colon, or delimiter, separated list in environment variable. See remove-path in the modulefile man page for further explanation.
Returns a true value if any of the listed modulefiles has been loaded or if any modulefile is loaded in case no argument is provided. Returns a false value elsewhere. See is-loaded in the modulefile man page for further explanation.
Returns a true value if any of the listed collections exists or if any collection exists in case no argument is provided. Returns a false value elsewhere. See is-saved in the modulefile man page for further explanation.
Returns a true value if any of the listed directories has been enabled in MODULEPATH or if any directory is enabled in case no argument is provided. Returns a false value elsewhere. See is-used in the modulefile man page for further explanation.
Returns a true value if any of the listed modulefiles exists in enabled MODULEPATH. Returns a false value elsewhere. See is-avail in the modulefile man page for further explanation.
Returns the names of currently loaded modules matching passed modulefile. Returns an empty string if passed modulefile does not match any loaded modules. See module-info loaded in the modulefile man page for further explanation.
modulefiles are written in the Tool Command Language (Tcl) and are interpreted by modulecmd.tcl. modulefiles can use conditional statements. Thus the effect a modulefile will have on the environment may change depending upon the current state of the environment.
Environment variables are unset when unloading a modulefile. Thus, it is possible to load a modulefile and then unload it without having the environment variables return to their prior state.
Collections describe a sequence of module use then module load commands that are interpreted by modulecmd.tcl to set the user environment as described by this sequence. When a collection is activated, with the restore sub-command, module paths and loaded modules are unused or unloaded if they are not part or if they are not ordered the same way as in the collection.
Collections are generated by the save sub-command that dumps the current user environment state in terms of module paths and loaded modules. By default collections are saved under the $HOME/.module directory.
Collections may be valid for a given target if they are suffixed. In this case these collections can only be restored if their suffix correspond to the current value of the MODULES_COLLECTION_TARGET environment variable (see the dedicated section of this topic below).
The module command exits with 0 if its execution succeed. Elsewhere 1 is returned.
A colon separated list of all loaded modulefiles.
The path that the module command searches when looking for modulefiles. Typically, it is set to the master modulefiles directory, /usr/share/Modules/modulefiles, by the initialization script. MODULEPATH can be set using module use or by the module initialization script to search group or personal modulefile directories before or after the master modulefile directory.
Path elements registered in the MODULEPATH environment variable may contain reference to environment variables which are converted to their corresponding value by module command each time it looks at the MODULEPATH value. If an environment variable referred in a path element is not defined, its reference is converted to an empty string.
The location of the master Modules package file directory containing module command initialization scripts, the executable program modulecmd.tcl, and a directory containing a collection of master modulefiles.
The location of the active module command script.
If set to 1, register exact version number of modulefiles when saving a collection. Elsewhere modulefile version number is omitted if it corresponds to the implicit or explicitly set default version.
The collection target that determines what collections are valid thus reachable on the current system.
Collection directory may sometimes be shared on multiple machines which may use different modules setup. For instance modules users may access with the same HOME directory multiple systems using different OS versions. When it happens a collection made on machine 1 may be erroneous on machine 2.
When a target is set, only the collections made for that target are available to the restore, savelist, saveshow and saverm sub-commands. Saving collection registers the target footprint by suffixing the collection filename with
.$MODULES_COLLECTION_TARGET. Collection target is not involved when collection is specified as file path on the saveshow, restore and save sub-commands.
For example, the MODULES_COLLECTION_TARGET variable may be set with results from commands like lsb_release, hostname, dnsdomainname, etc.
Text viewer for use to paginate message output if error output stream is attached to a terminal. The value of this variable is composed of a pager command name or path eventually followed by command-line options.
Paging command and options are defined for Modules in the following order of preference: MODULES_PAGER environment variable, then the default set in modulecmd.tcl script configuration. Which means MODULES_PAGER overrides default configuration.
If MODULES_PAGER variable is set to an empty string or to the value cat, pager will not be launched.
Value to set to environment variable <VAR> for modulecmd.tcl run-time execution if <VAR> is referred in MODULES_RUN_QUARANTINE.
A space separated list of environment variable names that should be passed indirectly to modulecmd.tcl to protect its run-time environment from side-effect coming from their current definition.
Each variable found in MODULES_RUN_QUARANTINE will have its value emptied or set to the value of the corresponding MODULES_RUNENV_<VAR> variable when defining modulecmd.tcl run-time environment.
Original values of these environment variables set in quarantine are passed to modulecmd.tcl via <VAR>_modquar variables.
If set to 1, disable any xtrace or verbose debugging property set on current shell session for the duration of either the module command or the module shell initialization script. Only applies to Bourne Shell (sh) and its derivatives.
If set to 1 prior to Modules package initialization, enable Modules compatibility version (3.2 release branch) rather main version at initialization scripts running time. Modules package compatibility version should be installed along with main version for this environment variable to have any effect.
A colon separated list of the full pathname for all loaded modulefiles.
Value of environment variable <VAR> passed to modulecmd.tcl in order to restore <VAR> to this value once started.
Reference counter variable for path-like variable <VAR>. A colon separated list containing pairs of elements. A pair is formed by a path element followed its usage counter which represents the number of times this path has been enabled in variable <VAR>. A colon separates the two parts of the pair.
The MODULESHOME directory.
The system-wide modules rc file. The location of this file can be changed using the MODULERCFILE environment variable as described above.
The user specific modules rc file.
The user specific collection directory.
The directory for system-wide modulefiles. The location of the directory can be changed using the MODULEPATH environment variable as described above.
The modulefile interpreter that gets executed upon each invocation of module.
The Modules package initialization file sourced into the user’s environment. | <urn:uuid:710f2104-4f00-4b9f-9d1c-ab7bd13e6b72> | 3.28125 | 4,502 | Documentation | Software Dev. | 29.084538 | 95,540,275 |
Until a few decades ago, there were only nine planets known to mankind existing in the solar system. The existence of other planets orbiting around other stars could only be hypothesized and no one could definitively answer the question if they really existed out there.
Today, with Pluto being excluded from the list of true planets, only eight planets have been accounted for in our solar system. But more than 3500 distant exoplanets have been discovered so far and this number continues to grow rapidly. Some really strange worlds can be found among them.
Kepler-78b: Something that does not exist
The main thing worth knowing about this planet is that it should not even exist. At least modern ideas about the origins and laws of evolution of planets do not imply this. The planet Kepler-78b is located too close, only 900 thousand kilometers, to its host star Kepler-78 (exoplanets are often referred to by the names of stars they orbit and adding letters which correspond to the order in which they were discovered in the vicinity of the star, or their distance from the star). For comparison, our red-hot Mercury is at the distance of at least 46 million kilometers from the sun.
Theoretically, at the time of the planet’s formation, the young star had to be somewhat larger. Could it be the case that Kepler-78b originated from … inside the star? This is, of course, impossible. Most likely, the planet had moved closer to its start later, but how and why it had happened still remains completely incomprehensible.
By itself, the planet Kepler-78b is slightly larger in size compared to Earth, but due to unusual conditions of its host star, planet’s environment is different from that of Earth. Surface temperature is in the range of sizzling 2400° C. But this should not last for long as the nearby star is gradually pulling the planet in, and will completely swallow it in a matter of 2-3 billion years.
WASP-12b: Non-spherical planet
While Kepler-78b may remain in existence for some time, the planet WASP-12b is already experiencing its death. Nowadays, it is pulled apart by its star’s attraction forces, all to the delight of astronomers who are able to observe this cruel but fascinating process in real time. Some of the matter from the WASP-12b surface is already absorbed by the star, and the planet itself is severely deformed, so that its shape resembles not quite a spherical soccer ball, but rather an elongated rugby ball. It has about 10 million years to continue its existence; it is unlikely that it will be more than that.
Located 800 light-years away from Earth, WASP-12b belongs to the class of exoplanets called “hot Jupiters”, enormous gas giants which resemble well-known planet Jupiter. It is 40% larger and it rotates around its sun at a much closer distance: a year lasts a little longer than 24 hours on Earth.
TrES-2b: The world of darkness
Dark Planet TrES-2b reflects almost no light. If we were able to travel to this planet located 750 light-years away from Earth in the Draco constellation, we would be able to see a huge, jet-black ball of gas with some light shades of dark red. This world resembles hell. The temperature here is about 1000°C, and superheated gas is dimly lit with a dark red glow.
Astronomers are aware of other similar dark planets, which are able to reflect at least 10% of incident radiation of the parent star. TrES-2b reflects less than 1%, it is the darkest planet known to us. The planet’s secret still remains unclear. Perhaps it consists mainly of sodium or potassium, chemical elements which perfectly absorb radiation and this could be one of the explanations.
V 391: Vital force
No, it is not about life on this planet, which cannot exist here. It is about the planet’s surprising and amazing strength and ability to prolong its existence. The parent star of V391 planet, beta Pegasus is in the last phase of its evolution, which our sun may get to only in 5 billion years from now. At this stage, the star managed to swell enormously, turning into a red giant, but then began a reverse process of compression. V391 happened to be too close to the star, only 1.7 times farther away than we are from our own Sun. As some day it may be when our planet will be absorbed by the swollen sun, the planet ended up inside outer layers of its aged star. However, to the surprise of scientists, the planet miraculously survived this process.
HD 189773b: Rain of glass
Located only 63 light years away, HD 189773b became the first planet for which we were able to observe and detect its true colors. It is almost the same blue in color as our beloved Earth, unfortunately, this is where the similarity ends.
HD 189773b is a gas giant, with surface temperatures up to 1000°C. Combined with tremendous pressure, it creates a bizarre environment where in the planet’s atmosphere silicon particles are transformed into liquid glass, which falls back on the surface as rain. These rains of glass spread violent hurricanes, which reach 7 thousand km/h in their speed.
55 Cancri e: A diamond of trillion carats
Only twice as big as our planet, 55 Cancri e is eight times heavier than and twice as dense as Earth. The planet is orbiting its star at a close range, so to orbit the distance around the star only takes 18 Earth’s hours. The planet is located at a distance of 40 light-years away from Earth, near a star which is much more carbon-rich than our own Sun.
It is possible that 55 Cancri e consists of pure carbon, which under high pressure conditions and at extremely high (2700°C) temperatures must exist in the form of a pure diamond.
PSR B1620-26b: Methuselah
The oldest known planet, PSR B1620-26b was nicknamed after a biblical character Methuselah for its long existence. The planet’s age is estimated to be 12.7 billion years. Back then, even the Milky Way was still in the early stages of its development, and neither Earth nor Sun existed.
Methuselah revolves around a binary star system located at a distance of 12400 light-years from Earth. Moreover, both ancient stars have long been “dead”, one of them turned into a pulsar, and the other has become a white dwarf.
TrES- 4: Loose Giant
1400 light years from us, in the constellation of Hercules, there is a planet called TrES-4, the largest of all planets known to date. Its size is more than 1.7 times greater than that of Jupiter, the true giant in the solar system, and has density which makes its composition somewhat perplexing. The planet’s average density is comparable to the density of a bottle cork, it could easily float on the ocean surface, if we could find a huge ocean of suitable size for it to float in.
TrES- 4 is only 7.2 million kilometers away from its host star and can make a complete revolution around the star in three Earth’s days. Because of this proximity to the star, the planet’s temperatures reach almost 1300°C.
Gliese 436 b: The Hot ice planet
This planet is covered with hot ice, not the type of ice we are accustomed to. Located in the Leo constellation, only 30 light-years away, Gliese 436 b is heated to 300°C, but the massive size comparable to that of Neptune creates enormous pressure on its surface, causing surface water of the planet to remain in the form of ice, despite of extremely high temperatures. At the same time, the outer layers of overheated Gliese 436 b evaporate, resulting in a cloud of steam enveloping the planet.
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Increased loads of land-based pollutants through river plumes are a major threat to the coastal water quality, ecosystems and sanitary heath. Identifying the coastal areas impacted by potentially polluted freshwaters is necessary to inform management policies and prevent degradation of the coastal environment. This study presents the first monitoring of the Adour River turbid plume (south-eastern Bay of Biscay, France) using multi-annual MODIS data. Satellite data are processed using a regional algorithm that allows quantifying and mapping suspended matter in coastal waters. The results are used to investigate the spatial and temporal variability of the Adour River turbid plume and to identify the risk of exposure of coastal ecosystems to the turbid plume waters. Changes in river plume orientation and spatial extent as well as suspended matter discharged through the river are correlated to the main hydro-climatic forcings acting in the south-eastern Bay of Biscay. The Adour River turbid plume is shown to be a highly reactive system mainly controlled by the river discharge rates and modulated by the wind changes. Despite the relatively small size of the Adour River, the Adour River turbid plume can have a non-negligible impact on the water quality of the southern Bay of Biscay and the MSM and associated contaminants/nutrients transported within the Adour turbid river plume have the potential to be disseminated far away along the northern shoreline or offshore. The main areas of influence of the river plume are defined over multi-annual (3 years) and seasonal periods. The results presented in this study show the potential of 250-m MODIS images to monitor small river plumes systems and support management and assessment of the water quality in the south-eastern Bay of Biscay. © 2013 Elsevier Ltd.
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By adding ultraviolet light to a model prebiotic reaction, researchers from the Georgia Institute of Technology and the University of Roma, “La Sapienza”, have discovered a route by which the missing guanine could have been formed. They also found that the RNA bases may have been easier to form than previously thought -- suggesting that starting life on Earth might not have been so difficult after all.
The findings are reported June 14, 2010 in the journal ChemBioChem. This collaborative work is supported by the National Science Foundation (NSF), the National Aeronautics and Space Administration, and the European Space Agency. The NSF funding is provided through the Center for Chemical Evolution at Georgia Tech.
Understanding how life emerged is one of the greatest scientific challenges. There is considerable evidence that the evolution of life passed through an early stage in which RNA played a more central role, before DNA and protein enzymes appeared.
Recent efforts to understand the prebiotic formation of the building blocks of RNA have focused on the chemical formamide (H2NCOH) as a potential starting material to create the RNA bases because it contains the four required elements -- carbon, hydrogen, oxygen and nitrogen -- and because of its stability, reactivity and low volatility compared to water. Previous reports have shown that these nucleic acid components -- with the exception of guanine -- can be synthesized by heating formamide to 160 degrees Celsius in the presence of mineral catalysts.
In their ChemBioChem paper, the researchers show for the first time that guanine can be produced by subjecting a solution of formamide to ultraviolet radiation during heating. The trace gaunine yield was greatly enhanced when minerals and photons were used together. In addition, production of adenine and a related molecule called hypoxanthine increased when ultraviolet light was added to the heating process -- a 15-fold increase was seen in adenine yield.
“These results potentially relax some of the requirements and reactions necessary to get life started, because formamide molecules would not have had to be in contact with a particular type of rock when heated on the prebiotic Earth, if the formamide was exposed to direct sunlight during heating,” said Nicholas Hud, a professor in the Georgia Tech School of Chemistry and Biochemistry.
The study demonstrated that guanine, adenine and hypoxanthine can be produced at lower temperatures than previously reported, even in the absence of minerals, as long as photons are added.
“For these experiments we built a very simple reaction chamber with an inexpensive 254-nanometer photon source to simulate conditions that could have been present on early Earth,” explained Thomas Orlando, also a professor in Georgia Tech’s School of Chemistry and Biochemistry. “We didn’t need extremely sophisticated experimental systems or expensive lasers; however, we did use sophisticated mass spectrometers to analyze the resulting complex chemical mixtures.”
The Hud and Orlando laboratories conducted experiments by heating formamide to 130 degrees Celsius -- 30 degrees cooler than previous experiments -- and shining ultraviolet light onto it.
“Our work has allowed us to consider a different type of ‘primordial soup’ than what has previously been considered possible starting conditions for life,” said Orlando. “Our model prebiotic reaction is attractive because most aspects of the process were likely to occur on the early Earth and it reduces chemical constraints.”
The authors suggest that aqueous pools containing small amounts of formamide may have existed on the early Earth. During hot and dry periods, water evaporation could have given rise to concentrated solutions of formamide and exposed mineral surfaces coated with formamide.
By conducting additional experiments at 100 degrees Celsius with solutions of formamide and water, the researchers confirmed that this “drying pool” model could give rise to solutions of formamide capable of producing the compounds found in their earlier experiments.
“While there is still a lot of chemistry required for us to better understand the formation of biological molecules needed for life, these one-pot reactions that occur due to the synergy of thermal and photochemical processes tell us that the chemical and environmental requirements to produce life are probably less restrictive than we once thought,” added Hud.
Sapienza University professor of molecular biology Ernesto Di Mauro, and Georgia Tech chemistry graduate students Hannah Barks and Ragan Buckley and research scientist Gregory Grieves also contributed to this work.
This project is supported by the National Science Foundation (NSF) (Award No. CHE-0739189) and the National Aeronautics and Space Administration (NASA) (Award Nos. NNG05GP20G and NNX08AO14G). The content is solely the responsibility of the principal investigator and does not necessarily represent the official view of the NSF or NASA.
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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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Clamshell-Shaped Protein Puts the 'Jump' in 'Jumping Genes'
News Aug 21, 2015
The clamshell shape, they say, has never before been seen in a protein but connects nicely with its function: that of bending a segment of DNA into a 180-degree U-turn.
The finding, they say, advances the scientific understanding of how DNA segments get moved around among bacteria, often bringing with them genes that confer toxicity or antibiotic resistance.
The protein, called IstB, is genetically similar to a whole family of related proteins found in bacteria, plants and animals, so the Johns Hopkins team says it was surprised to learn that its structure and function are not so similar to those of its family members. “What we learned is that IstB showcases the ability of natural selection to find new uses for class of enzyme that’s been around a very long time,” says James Berger, Ph.D., professor of biophysics and biophysical chemistry at the Johns Hopkins University School of Medicine.
At the heart of the research, Berger says, is a piece of DNA, called IS21, which is a type of transposon, or jumping gene. These segments of DNA hold the blueprint for making proteins that can cut and otherwise manipulate DNA to leave one spot in a genome and land elsewhere.
On its own, Berger points out, a jumping gene is neither helpful nor harmful but can become so if, for example, it inserts itself into and disrupts a normally functional gene. “Or it could take a nearby gene with it when it jumps,” he adds. “That gene will then be in new surroundings and under new control, which could be helpful or harmful to an organism depending on the gene’s function.”
Berger says he and postdoctoral fellow Ernesto Arias-Palomo, Ph.D., were aware that IS21 is found in some disease-causing bacteria, like plague’s Yersinia pestis, and close to genes that make those bacteria toxic to people. “That made us suspect it might play a role in moving those genes around, which can ultimately cause the transfer of harmful genes to previously harmless bacteria,” he says.
To examine the idea, the team focused on IstB, one of the two proteins IS21 encodes. The other encoded protein is IstA, which cuts and pastes the IS21 transposon. IstB is its helper protein.
The team knew based on IstB’s genetic sequence that it contains a “reactor” site that extracts the energy found in certain chemical molecules and uses it to alter DNA. But how it works and how it collaborates with IstA was a mystery.
Using X-rays and beams of electrons to probe IstB’s structure and function, the researchers found that IstB is made of 10 smaller units, which are organized into two parallel horseshoes of five units each. Double strands of DNA fit in between.
“What we saw is that IstB can take a straight piece of DNA and bend it 180 degrees, or take a bent piece of DNA and hold it in that position,” says Berger. “That primes the DNA for the insertion of a transposon.
Biochemical tests further showed that IstA recognizes the bent DNA bound by IstB and kicks off the IstB, probably to make the DNA accessible for the cuts it will make, explains Berger.
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Washington: A US government report has confirmed that 2016 topped 2015 as the hottest year globally in 137 years of record keeping.
“Most indicators of climate change (in 2016) continued to follow trends of a warming world,” the US National Oceanic and Atmospheric Administration (NOAA) said on Thursday. “Several, including land and ocean temperatures, sea level and greenhouse gas concentrations in the atmosphere broke records set just one year prior,” it said.
The State of the Climate report, a sort of annual check-up for the planet, was compiled by NOAA researchers and had contributions from over 450 scientists from nearly 60 countries. According to the report, the 2016 average global carbon dioxide concentration was 402.9 parts per million (ppm), an increase of 3.5 ppm compared with 2015 and the largest annual increase observed in the 58-year record, it said.
Global surface temperature was also the highest on record. “Aided in part by the strong El Nino early in the year, the 2016 combined global land and ocean surface temperature was record-high for a third consecutive year,” it said. “The increase in temperature ranged from 0.45-0.56 degrees Celsius above the 1981-2010 average.”
Meanwhile, average sea surface temperature in 2016 was the highest on record, 0.36-0.41 degrees Celsius higher than the 1981-2010 average and surpassing the previous mark set in 2015 by 0.01-0.03 degrees Celsius. In addition, the global average sea level rose to a new record high in 2016, and, according to the new report, was about 3.25 inches (82 mm) higher than that observed in 1993, when satellite record-keeping for sea level began. | <urn:uuid:c0722b82-dd25-468a-9a43-7193939f8505> | 3.25 | 361 | News Article | Science & Tech. | 62.665677 | 95,540,309 |
Conservation of angular momentum is a fundamental property of nature, one that astronomers use to detect the presence of satellites circling distant planets. In 1927, it was proposed that this principle should apply to chemical reactions, but a clear demonstration has never been achieved.
In the current issue of Science, MSU chemist Jim McCusker demonstrates for the first time the effect is real and also suggests how scientists could use it to control and predict chemical reaction pathways in general.
"The idea has floated around for decades and has been implicitly invoked in a variety of contexts, but no one had ever come up with a chemical system that could demonstrate whether or not the underlying concept was valid," McCusker said. "Our result not only validates the idea, but it really allows us to start thinking about chemical reactions from an entirely different perspective."
The experiment involved the preparation of two closely related molecules that were specifically designed to undergo a chemical reaction known as fluorescence resonance energy transfer, or FRET. Upon absorption of light, the system is predisposed to transfer that energy from one part of the molecule to another.
McCusker's team changed the identity of one of the atoms in the molecule from chromium to cobalt. This altered the molecule's properties and shut down the reaction. The absence of any detectable energy transfer in the cobalt-containing compound confirmed the hypothesis.
"What we have successfully conducted is a proof-of-principle experiment," McCusker said. "One can easily imagine employing these ideas to other chemical processes, and we're actually exploring some of these avenues in my group right now."
The researchers believe their results could impact a variety of fields including molecular electronics, biology and energy science through the development of new types of chemical reactions.
Dong Guo, a postdoctoral researcher, and Troy Knight, former graduate student and now research scientist at Dow Chemical, were part of McCusker's team. Funding was provided by the National Science Foundation.
Michigan State University has been working to advance the common good in uncommon ways for more than 150 years. One of the top research universities in the world, MSU focuses its vast resources on creating solutions to some of the world's most pressing challenges, while providing life-changing opportunities to a diverse and inclusive academic community through more than 200 programs of study in 17 degree-granting colleges.
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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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Top: The periodic tabwe of de chemicaw ewements.|
Bewow: Exampwes of certain chemicaw ewements. From weft to right: hydrogen, barium, copper, uranium, bromine, and hewium.
A chemicaw ewement is a species of atoms having de same number of protons in deir atomic nucwei (dat is, de same atomic number, or Z). 118 ewements are identified, of which de first 94 occur naturawwy on Earf wif de remaining 24 being syndetic ewements. There are 80 ewements dat have at weast one stabwe isotope and 38 dat have excwusivewy radionucwides, which decay over time into oder ewements. Iron is de most abundant ewement (by mass) making up Earf, whiwe oxygen is de most common ewement in de Earf's crust.
Chemicaw ewements constitute aww of de ordinary matter of de universe. However astronomicaw observations suggest dat ordinary observabwe matter makes up onwy about 15% of de matter in de universe: de remainder is dark matter; de composition of dis is unknown, but it is not composed of chemicaw ewements. The two wightest ewements, hydrogen and hewium, were mostwy formed in de Big Bang and are de most common ewements in de universe. The next dree ewements (widium, berywwium and boron) were formed mostwy by cosmic ray spawwation, and are dus rarer dan heavier ewements. Formation of ewements wif from 6 to 26 protons occurred and continues to occur in main seqwence stars via stewwar nucweosyndesis. The high abundance of oxygen, siwicon, and iron on Earf refwects deir common production in such stars. Ewements wif greater dan 26 protons are formed by supernova nucweosyndesis in supernovae, which, when dey expwode, bwast dese ewements as supernova remnants far into space, where dey may become incorporated into pwanets when dey are formed.
The term "ewement" is used for atoms wif a given number of protons (regardwess of wheder or not dey are ionized or chemicawwy bonded, e.g. hydrogen in water) as weww as for a pure chemicaw substance consisting of a singwe ewement (e.g. hydrogen gas). For de second meaning, de terms "ewementary substance" and "simpwe substance" have been suggested, but dey have not gained much acceptance in Engwish chemicaw witerature, whereas in some oder wanguages deir eqwivawent is widewy used (e.g. French corps simpwe, Russian простое вещество). A singwe ewement can form muwtipwe substances differing in deir structure; dey are cawwed awwotropes of de ewement.
When different ewements are chemicawwy combined, wif de atoms hewd togeder by chemicaw bonds, dey form chemicaw compounds. Onwy a minority of ewements are found uncombined as rewativewy pure mineraws. Among de more common of such native ewements are copper, siwver, gowd, carbon (as coaw, graphite, or diamonds), and suwfur. Aww but a few of de most inert ewements, such as nobwe gases and nobwe metaws, are usuawwy found on Earf in chemicawwy combined form, as chemicaw compounds. Whiwe about 32 of de chemicaw ewements occur on Earf in native uncombined forms, most of dese occur as mixtures. For exampwe, atmospheric air is primariwy a mixture of nitrogen, oxygen, and argon, and native sowid ewements occur in awwoys, such as dat of iron and nickew.
The history of de discovery and use of de ewements began wif primitive human societies dat found native ewements wike carbon, suwfur, copper and gowd. Later civiwizations extracted ewementaw copper, tin, wead and iron from deir ores by smewting, using charcoaw. Awchemists and chemists subseqwentwy identified many more; aww of de naturawwy occurring ewements were known by 1950.
The properties of de chemicaw ewements are summarized in de periodic tabwe, which organizes de ewements by increasing atomic number into rows ("periods") in which de cowumns ("groups") share recurring ("periodic") physicaw and chemicaw properties. Save for unstabwe radioactive ewements wif short hawf-wives, aww of de ewements are avaiwabwe industriawwy, most of dem in wow degrees of impurities.
- 1 Description
- 1.1 Atomic number
- 1.2 Isotopes
- 1.3 Isotopic mass and atomic mass
- 1.4 Chemicawwy pure and isotopicawwy pure
- 1.5 Awwotropes
- 1.6 Properties
- 1.7 The periodic tabwe
- 2 Nomencwature and symbows
- 3 Origin of de ewements
- 4 Abundance
- 5 History
- 6 List of de 118 known chemicaw ewements
- 7 See awso
- 8 References
- 9 Furder reading
- 10 Externaw winks
The wightest chemicaw ewements are hydrogen and hewium, bof created by Big Bang nucweosyndesis during de first 20 minutes of de universe in a ratio of around 3:1 by mass (or 12:1 by number of atoms), awong wif tiny traces of de next two ewements, widium and berywwium. Awmost aww oder ewements found in nature were made by various naturaw medods of nucweosyndesis. On Earf, smaww amounts of new atoms are naturawwy produced in nucweogenic reactions, or in cosmogenic processes, such as cosmic ray spawwation. New atoms are awso naturawwy produced on Earf as radiogenic daughter isotopes of ongoing radioactive decay processes such as awpha decay, beta decay, spontaneous fission, cwuster decay, and oder rarer modes of decay.
Of de 94 naturawwy occurring ewements, dose wif atomic numbers 1 drough 82 each have at weast one stabwe isotope (except for technetium, ewement 43 and promedium, ewement 61, which have no stabwe isotopes). Isotopes considered stabwe are dose for which no radioactive decay has yet been observed. Ewements wif atomic numbers 83 drough 94 are unstabwe to de point dat radioactive decay of aww isotopes can be detected. Some of dese ewements, notabwy bismuf (atomic number 83), dorium (atomic number 90), and uranium (atomic number 92), have one or more isotopes wif hawf-wives wong enough to survive as remnants of de expwosive stewwar nucweosyndesis dat produced de heavy metaws before de formation of our Sowar System. At over 1.9×1019 years, over a biwwion times wonger dan de current estimated age of de universe, bismuf-209 (atomic number 83) has de wongest known awpha decay hawf-wife of any naturawwy occurring ewement, and is awmost awways considered on par wif de 80 stabwe ewements. The very heaviest ewements (dose beyond pwutonium, ewement 94) undergo radioactive decay wif hawf-wives so short dat dey are not found in nature and must be syndesized.
As of 2010, dere are 118 known ewements (in dis context, "known" means observed weww enough, even from just a few decay products, to have been differentiated from oder ewements). Of dese 118 ewements, 94 occur naturawwy on Earf. Six of dese occur in extreme trace qwantities: technetium, atomic number 43; promedium, number 61; astatine, number 85; francium, number 87; neptunium, number 93; and pwutonium, number 94. These 94 ewements have been detected in de universe at warge, in de spectra of stars and awso supernovae, where short-wived radioactive ewements are newwy being made. The first 94 ewements have been detected directwy on Earf as primordiaw nucwides present from de formation of de sowar system, or as naturawwy occurring fission or transmutation products of uranium and dorium.
The remaining 24 heavier ewements, not found today eider on Earf or in astronomicaw spectra, have been produced artificiawwy: dese are aww radioactive, wif very short hawf-wives; if any atoms of dese ewements were present at de formation of Earf, dey are extremewy wikewy, to de point of certainty, to have awready decayed, and if present in novae, have been in qwantities too smaww to have been noted. Technetium was de first purportedwy non-naturawwy occurring ewement syndesized, in 1937, awdough trace amounts of technetium have since been found in nature (and awso de ewement may have been discovered naturawwy in 1925). This pattern of artificiaw production and water naturaw discovery has been repeated wif severaw oder radioactive naturawwy occurring rare ewements.
List of de ewements are avaiwabwe by name, atomic number, density, mewting point, boiwing point and by symbow, as weww as ionization energies of de ewements. The nucwides of stabwe and radioactive ewements are awso avaiwabwe as a wist of nucwides, sorted by wengf of hawf-wife for dose dat are unstabwe. One of de most convenient, and certainwy de most traditionaw presentation of de ewements, is in de form of de periodic tabwe, which groups togeder ewements wif simiwar chemicaw properties (and usuawwy awso simiwar ewectronic structures).
The atomic number of an ewement is eqwaw to de number of protons in each atom, and defines de ewement. For exampwe, aww carbon atoms contain 6 protons in deir atomic nucweus; so de atomic number of carbon is 6. Carbon atoms may have different numbers of neutrons; atoms of de same ewement having different numbers of neutrons are known as isotopes of de ewement.
The number of protons in de atomic nucweus awso determines its ewectric charge, which in turn determines de number of ewectrons of de atom in its non-ionized state. The ewectrons are pwaced into atomic orbitaws dat determine de atom's various chemicaw properties. The number of neutrons in a nucweus usuawwy has very wittwe effect on an ewement's chemicaw properties (except in de case of hydrogen and deuterium). Thus, aww carbon isotopes have nearwy identicaw chemicaw properties because dey aww have six protons and six ewectrons, even dough carbon atoms may, for exampwe, have 6 or 8 neutrons. That is why de atomic number, rader dan mass number or atomic weight, is considered de identifying characteristic of a chemicaw ewement.
The symbow for atomic number is Z.
Isotopes are atoms of de same ewement (dat is, wif de same number of protons in deir atomic nucweus), but having different numbers of neutrons. Thus, for exampwe, dere are dree main isotopes of carbon, uh-hah-hah-hah. Aww carbon atoms have 6 protons in de nucweus, but dey can have eider 6, 7, or 8 neutrons. Since de mass numbers of dese are 12, 13 and 14 respectivewy, de dree isotopes of carbon are known as carbon-12, carbon-13, and carbon-14, often abbreviated to 12C, 13C, and 14C. Carbon in everyday wife and in chemistry is a mixture of 12C (about 98.9%), 13C (about 1.1%) and about 1 atom per triwwion of 14C.
Most (66 of 94) naturawwy occurring ewements have more dan one stabwe isotope. Except for de isotopes of hydrogen (which differ greatwy from each oder in rewative mass—enough to cause chemicaw effects), de isotopes of a given ewement are chemicawwy nearwy indistinguishabwe.
Aww of de ewements have some isotopes dat are radioactive (radioisotopes), awdough not aww of dese radioisotopes occur naturawwy. The radioisotopes typicawwy decay into oder ewements upon radiating an awpha or beta particwe. If an ewement has isotopes dat are not radioactive, dese are termed "stabwe" isotopes. Aww of de known stabwe isotopes occur naturawwy (see primordiaw isotope). The many radioisotopes dat are not found in nature have been characterized after being artificiawwy made. Certain ewements have no stabwe isotopes and are composed onwy of radioactive isotopes: specificawwy de ewements widout any stabwe isotopes are technetium (atomic number 43), promedium (atomic number 61), and aww observed ewements wif atomic numbers greater dan 82.
Of de 80 ewements wif at weast one stabwe isotope, 26 have onwy one singwe stabwe isotope. The mean number of stabwe isotopes for de 80 stabwe ewements is 3.1 stabwe isotopes per ewement. The wargest number of stabwe isotopes dat occur for a singwe ewement is 10 (for tin, ewement 50).
Isotopic mass and atomic mass
The mass number of an ewement, A, is de number of nucweons (protons and neutrons) in de atomic nucweus. Different isotopes of a given ewement are distinguished by deir mass numbers, which are conventionawwy written as a superscript on de weft hand side of de atomic symbow (e.g. 238U). The mass number is awways a whowe number and has units of "nucweons". For exampwe, magnesium-24 (24 is de mass number) is an atom wif 24 nucweons (12 protons and 12 neutrons).
Whereas de mass number simpwy counts de totaw number of neutrons and protons and is dus a naturaw (or whowe) number, de atomic mass of a singwe atom is a reaw number giving de mass of a particuwar isotope (or "nucwide") of de ewement, expressed in atomic mass units (symbow: u). In generaw, de mass number of a given nucwide differs in vawue swightwy from its atomic mass, since de mass of each proton and neutron is not exactwy 1 u; since de ewectrons contribute a wesser share to de atomic mass as neutron number exceeds proton number; and (finawwy) because of de nucwear binding energy. For exampwe, de atomic mass of chworine-35 to five significant digits is 34.969 u and dat of chworine-37 is 36.966 u. However, de atomic mass in u of each isotope is qwite cwose to its simpwe mass number (awways widin 1%). The onwy isotope whose atomic mass is exactwy a naturaw number is 12C, which by definition has a mass of exactwy 12, because u is defined as 1/12 of de mass of a free neutraw carbon-12 atom in de ground state.
The standard atomic weight (commonwy cawwed "atomic weight") of an ewement is de average of de atomic masses of aww de chemicaw ewement's isotopes as found in a particuwar environment, weighted by isotopic abundance, rewative to de atomic mass unit. This number may be a fraction dat is not cwose to a whowe number. For exampwe, de rewative atomic mass of chworine is 35.453 u, which differs greatwy from a whowe number as it is an average of about 76% chworine-35 and 24% chworine-37. Whenever a rewative atomic mass vawue differs by more dan 1% from a whowe number, it is due to dis averaging effect, as significant amounts of more dan one isotope are naturawwy present in a sampwe of dat ewement.
Chemicawwy pure and isotopicawwy pure
Chemists and nucwear scientists have different definitions of a pure ewement. In chemistry, a pure ewement means a substance whose atoms aww (or in practice awmost aww) have de same atomic number, or number of protons. Nucwear scientists, however, define a pure ewement as one dat consists of onwy one stabwe isotope.
For exampwe, a copper wire is 99.99% chemicawwy pure if 99.99% of its atoms are copper, wif 29 protons each. However it is not isotopicawwy pure since ordinary copper consists of two stabwe isotopes, 69% 63Cu and 31% 65Cu, wif different numbers of neutrons. However, a pure gowd ingot wouwd be bof chemicawwy and isotopicawwy pure, since ordinary gowd consists onwy of one isotope, 197Au.
Atoms of chemicawwy pure ewements may bond to each oder chemicawwy in more dan one way, awwowing de pure ewement to exist in muwtipwe chemicaw structures (spatiaw arrangements of atoms), known as awwotropes, which differ in deir properties. For exampwe, carbon can be found as diamond, which has a tetrahedraw structure around each carbon atom; graphite, which has wayers of carbon atoms wif a hexagonaw structure stacked on top of each oder; graphene, which is a singwe wayer of graphite dat is very strong; fuwwerenes, which have nearwy sphericaw shapes; and carbon nanotubes, which are tubes wif a hexagonaw structure (even dese may differ from each oder in ewectricaw properties). The abiwity of an ewement to exist in one of many structuraw forms is known as 'awwotropy'.
The standard state, awso known as reference state, of an ewement is defined as its dermodynamicawwy most stabwe state at a pressure of 1 bar and a given temperature (typicawwy at 298.15 K). In dermochemistry, an ewement is defined to have an endawpy of formation of zero in its standard state. For exampwe, de reference state for carbon is graphite, because de structure of graphite is more stabwe dan dat of de oder awwotropes.
Severaw kinds of descriptive categorizations can be appwied broadwy to de ewements, incwuding consideration of deir generaw physicaw and chemicaw properties, deir states of matter under famiwiar conditions, deir mewting and boiwing points, deir densities, deir crystaw structures as sowids, and deir origins.
Severaw terms are commonwy used to characterize de generaw physicaw and chemicaw properties of de chemicaw ewements. A first distinction is between metaws, which readiwy conduct ewectricity, nonmetaws, which do not, and a smaww group, (de metawwoids), having intermediate properties and often behaving as semiconductors.
A more refined cwassification is often shown in cowored presentations of de periodic tabwe. This system restricts de terms "metaw" and "nonmetaw" to onwy certain of de more broadwy defined metaws and nonmetaws, adding additionaw terms for certain sets of de more broadwy viewed metaws and nonmetaws. The version of dis cwassification used in de periodic tabwes presented here incwudes: actinides, awkawi metaws, awkawine earf metaws, hawogens, wandanides, transition metaws, post-transition metaws, metawwoids, reactive nonmetaws, and nobwe gases. In dis system, de awkawi metaws, awkawine earf metaws, and transition metaws, as weww as de wandanides and de actinides, are speciaw groups of de metaws viewed in a broader sense. Simiwarwy, de reactive nonmetaws and de nobwe gases are nonmetaws viewed in de broader sense. In some presentations, de hawogens are not distinguished, wif astatine identified as a metawwoid and de oders identified as nonmetaws.
States of matter
Anoder commonwy used basic distinction among de ewements is deir state of matter (phase), wheder sowid, wiqwid, or gas, at a sewected standard temperature and pressure (STP). Most of de ewements are sowids at conventionaw temperatures and atmospheric pressure, whiwe severaw are gases. Onwy bromine and mercury are wiqwids at 0 degrees Cewsius (32 degrees Fahrenheit) and normaw atmospheric pressure; caesium and gawwium are sowids at dat temperature, but mewt at 28.4 °C (83.2 °F) and 29.8 °C (85.6 °F), respectivewy.
Mewting and boiwing points
Mewting and boiwing points, typicawwy expressed in degrees Cewsius at a pressure of one atmosphere, are commonwy used in characterizing de various ewements. Whiwe known for most ewements, eider or bof of dese measurements is stiww undetermined for some of de radioactive ewements avaiwabwe in onwy tiny qwantities. Since hewium remains a wiqwid even at absowute zero at atmospheric pressure, it has onwy a boiwing point, and not a mewting point, in conventionaw presentations.
The density at a sewected standard temperature and pressure (STP) is freqwentwy used in characterizing de ewements. Density is often expressed in grams per cubic centimeter (g/cm3). Since severaw ewements are gases at commonwy encountered temperatures, deir densities are usuawwy stated for deir gaseous forms; when wiqwefied or sowidified, de gaseous ewements have densities simiwar to dose of de oder ewements.
When an ewement has awwotropes wif different densities, one representative awwotrope is typicawwy sewected in summary presentations, whiwe densities for each awwotrope can be stated where more detaiw is provided. For exampwe, de dree famiwiar awwotropes of carbon (amorphous carbon, graphite, and diamond) have densities of 1.8–2.1, 2.267, and 3.515 g/cm3, respectivewy.
The ewements studied to date as sowid sampwes have eight kinds of crystaw structures: cubic, body-centered cubic, face-centered cubic, hexagonaw, monocwinic, ordorhombic, rhombohedraw, and tetragonaw. For some of de syndeticawwy produced transuranic ewements, avaiwabwe sampwes have been too smaww to determine crystaw structures.
Occurrence and origin on Earf
Chemicaw ewements may awso be categorized by deir origin on Earf, wif de first 94 considered naturawwy occurring, whiwe dose wif atomic numbers beyond 94 have onwy been produced artificiawwy as de syndetic products of man-made nucwear reactions.
Of de 94 naturawwy occurring ewements, 83 are considered primordiaw and eider stabwe or weakwy radioactive. The remaining 11 naturawwy occurring ewements possess hawf wives too short for dem to have been present at de beginning of de Sowar System, and are derefore considered transient ewements. Of dese 11 transient ewements, 5 (powonium, radon, radium, actinium, and protactinium) are rewativewy common decay products of dorium and uranium. The remaining 6 transient ewements (technetium, promedium, astatine, francium, neptunium, and pwutonium) occur onwy rarewy, as products of rare decay modes or nucwear reaction processes invowving uranium or oder heavy ewements.
Ewements wif atomic numbers 1 drough 40 are aww stabwe, whiwe dose wif atomic numbers 41 drough 82 (except technetium and promedium) are metastabwe. The hawf-wives of dese metastabwe "deoreticaw radionucwides" are so wong (at weast 100 miwwion times wonger dan de estimated age of de universe) dat deir radioactive decay has yet to be detected by experiment. Ewements wif atomic numbers 83 drough 94 are unstabwe to de point dat deir radioactive decay can be detected. Three of dese ewements, bismuf (ewement 83), dorium (ewement 90), and uranium (ewement 92) have one or more isotopes wif hawf-wives wong enough to survive as remnants of de expwosive stewwar nucweosyndesis dat produced de heavy ewements before de formation of our sowar system. For exampwe, at over 1.9×1019 years, over a biwwion times wonger dan de current estimated age of de universe, bismuf-209 has de wongest known awpha decay hawf-wife of any naturawwy occurring ewement. The very heaviest 24 ewements (dose beyond pwutonium, ewement 94) undergo radioactive decay wif short hawf-wives and cannot be produced as daughters of wonger-wived ewements, and dus dey do not occur in nature at aww.
The periodic tabwe
The properties of de chemicaw ewements are often summarized using de periodic tabwe, which powerfuwwy and ewegantwy organizes de ewements by increasing atomic number into rows ("periods") in which de cowumns ("groups") share recurring ("periodic") physicaw and chemicaw properties. The current standard tabwe contains 118 confirmed ewements as of 10 Apriw 2010.
Awdough earwier precursors to dis presentation exist, its invention is generawwy credited to de Russian chemist Dmitri Mendeweev in 1869, who intended de tabwe to iwwustrate recurring trends in de properties of de ewements. The wayout of de tabwe has been refined and extended over time as new ewements have been discovered and new deoreticaw modews have been devewoped to expwain chemicaw behavior.
Use of de periodic tabwe is now ubiqwitous widin de academic discipwine of chemistry, providing an extremewy usefuw framework to cwassify, systematize and compare aww de many different forms of chemicaw behavior. The tabwe has awso found wide appwication in physics, geowogy, biowogy, materiaws science, engineering, agricuwture, medicine, nutrition, environmentaw heawf, and astronomy. Its principwes are especiawwy important in chemicaw engineering.
Nomencwature and symbows
The known ewements have atomic numbers from 1 drough 118, conventionawwy presented as Arabic numeraws. Since de ewements can be uniqwewy seqwenced by atomic number, conventionawwy from wowest to highest (as in a periodic tabwe), sets of ewements are sometimes specified by such notation as "drough", "beyond", or "from ... drough", as in "drough iron", "beyond uranium", or "from wandanum drough wutetium". The terms "wight" and "heavy" are sometimes awso used informawwy to indicate rewative atomic numbers (not densities), as in "wighter dan carbon" or "heavier dan wead", awdough technicawwy de weight or mass of atoms of an ewement (deir atomic weights or atomic masses) do not awways increase monotonicawwy wif deir atomic numbers.
The naming of various substances now known as ewements precedes de atomic deory of matter, as names were given wocawwy by various cuwtures to various mineraws, metaws, compounds, awwoys, mixtures, and oder materiaws, awdough at de time it was not known which chemicaws were ewements and which compounds. As dey were identified as ewements, de existing names for ancientwy-known ewements (e.g., gowd, mercury, iron) were kept in most countries. Nationaw differences emerged over de names of ewements eider for convenience, winguistic niceties, or nationawism. For a few iwwustrative exampwes: German speakers use "Wasserstoff" (water substance) for "hydrogen", "Sauerstoff" (acid substance) for "oxygen" and "Stickstoff" (smodering substance) for "nitrogen", whiwe Engwish and some romance wanguages use "sodium" for "natrium" and "potassium" for "kawium", and de French, Itawians, Greeks, Portuguese and Powes prefer "azote/azot/azoto" (from roots meaning "no wife") for "nitrogen".
For purposes of internationaw communication and trade, de officiaw names of de chemicaw ewements bof ancient and more recentwy recognized are decided by de Internationaw Union of Pure and Appwied Chemistry (IUPAC), which has decided on a sort of internationaw Engwish wanguage, drawing on traditionaw Engwish names even when an ewement's chemicaw symbow is based on a Latin or oder traditionaw word, for exampwe adopting "gowd" rader dan "aurum" as de name for de 79f ewement (Au). IUPAC prefers de British spewwings "awuminium" and "caesium" over de U.S. spewwings "awuminum" and "cesium", and de U.S. "suwfur" over de British "suwphur". However, ewements dat are practicaw to seww in buwk in many countries often stiww have wocawwy used nationaw names, and countries whose nationaw wanguage does not use de Latin awphabet are wikewy to use de IUPAC ewement names.
According to IUPAC, chemicaw ewements are not proper nouns in Engwish; conseqwentwy, de fuww name of an ewement is not routinewy capitawized in Engwish, even if derived from a proper noun, as in cawifornium and einsteinium. Isotope names of chemicaw ewements are awso uncapitawized if written out, e.g., carbon-12 or uranium-235. Chemicaw ewement symbows (such as Cf for cawifornium and Es for einsteinium), are awways capitawized (see bewow).
In de second hawf of de twentief century, physics waboratories became abwe to produce nucwei of chemicaw ewements wif hawf-wives too short for an appreciabwe amount of dem to exist at any time. These are awso named by IUPAC, which generawwy adopts de name chosen by de discoverer. This practice can wead to de controversiaw qwestion of which research group actuawwy discovered an ewement, a qwestion dat dewayed de naming of ewements wif atomic number of 104 and higher for a considerabwe amount of time. (See ewement naming controversy).
Precursors of such controversies invowved de nationawistic namings of ewements in de wate 19f century. For exampwe, wutetium was named in reference to Paris, France. The Germans were rewuctant to rewinqwish naming rights to de French, often cawwing it cassiopeium. Simiwarwy, de British discoverer of niobium originawwy named it cowumbium, in reference to de New Worwd. It was used extensivewy as such by American pubwications prior to de internationaw standardization (in 1950).
Specific chemicaw ewements
Before chemistry became a science, awchemists had designed arcane symbows for bof metaws and common compounds. These were however used as abbreviations in diagrams or procedures; dere was no concept of atoms combining to form mowecuwes. Wif his advances in de atomic deory of matter, John Dawton devised his own simpwer symbows, based on circwes, to depict mowecuwes.
The current system of chemicaw notation was invented by Berzewius. In dis typographicaw system, chemicaw symbows are not mere abbreviations—dough each consists of wetters of de Latin awphabet. They are intended as universaw symbows for peopwe of aww wanguages and awphabets.
The first of dese symbows were intended to be fuwwy universaw. Since Latin was de common wanguage of science at dat time, dey were abbreviations based on de Latin names of metaws. Cu comes from Cuprum, Fe comes from Ferrum, Ag from Argentum. The symbows were not fowwowed by a period (fuww stop) as wif abbreviations. Later chemicaw ewements were awso assigned uniqwe chemicaw symbows, based on de name of de ewement, but not necessariwy in Engwish. For exampwe, sodium has de chemicaw symbow 'Na' after de Latin natrium. The same appwies to "W" (wowfram) for tungsten, "Fe" (ferrum) for iron, "Hg" (hydrargyrum) for mercury, "Sn" (stannum) for tin, "K" (kawium) for potassium, "Au" (aurum) for gowd, "Ag" (argentum) for siwver, "Pb" (pwumbum) for wead, "Cu" (cuprum) for copper, and "Sb" (stibium) for antimony.
Chemicaw symbows are understood internationawwy when ewement names might reqwire transwation, uh-hah-hah-hah. There have sometimes been differences in de past. For exampwe, Germans in de past have used "J" (for de awternate name Jod) for iodine, but now use "I" and "Iod".
The first wetter of a chemicaw symbow is awways capitawized, as in de preceding exampwes, and de subseqwent wetters, if any, are awways wower case (smaww wetters). Thus, de symbows for cawifornium and einsteinium are Cf and Es.
Generaw chemicaw symbows
There are awso symbows in chemicaw eqwations for groups of chemicaw ewements, for exampwe in comparative formuwas. These are often a singwe capitaw wetter, and de wetters are reserved and not used for names of specific ewements. For exampwe, an "X" indicates a variabwe group (usuawwy a hawogen) in a cwass of compounds, whiwe "R" is a radicaw, meaning a compound structure such as a hydrocarbon chain, uh-hah-hah-hah. The wetter "Q" is reserved for "heat" in a chemicaw reaction, uh-hah-hah-hah. "Y" is awso often used as a generaw chemicaw symbow, awdough it is awso de symbow of yttrium. "Z" is awso freqwentwy used as a generaw variabwe group. "E" is used in organic chemistry to denote an ewectron-widdrawing group or an ewectrophiwe; simiwarwy "Nu" denotes a nucweophiwe. "L" is used to represent a generaw wigand in inorganic and organometawwic chemistry. "M" is awso often used in pwace of a generaw metaw.
At weast two additionaw, two-wetter generic chemicaw symbows are awso in informaw usage, "Ln" for any wandanide ewement and "An" for any actinide ewement. "Rg" was formerwy used for any rare gas ewement, but de group of rare gases has now been renamed nobwe gases and de symbow "Rg" has now been assigned to de ewement roentgenium.
Isotopes are distinguished by de atomic mass number (totaw protons and neutrons) for a particuwar isotope of an ewement, wif dis number combined wif de pertinent ewement's symbow. IUPAC prefers dat isotope symbows be written in superscript notation when practicaw, for exampwe 12C and 235U. However, oder notations, such as carbon-12 and uranium-235, or C-12 and U-235, are awso used.
As a speciaw case, de dree naturawwy occurring isotopes of de ewement hydrogen are often specified as H for 1H (protium), D for 2H (deuterium), and T for 3H (tritium). This convention is easier to use in chemicaw eqwations, repwacing de need to write out de mass number for each atom. For exampwe, de formuwa for heavy water may be written D2O instead of 2H2O.
Origin of de ewements
Onwy about 4% of de totaw mass of de universe is made of atoms or ions, and dus represented by chemicaw ewements. This fraction is about 15% of de totaw matter, wif de remainder of de matter (85%) being dark matter. The nature of dark matter is unknown, but it is not composed of atoms of chemicaw ewements because it contains no protons, neutrons, or ewectrons. (The remaining non-matter part of de mass of de universe is composed of de even more mysterious dark energy).
The universe's 94 naturawwy occurring chemicaw ewements are dought to have been produced by at weast four cosmic processes. Most of de hydrogen and hewium in de universe was produced primordiawwy in de first few minutes of de Big Bang. Three recurrentwy occurring water processes are dought to have produced de remaining ewements. Stewwar nucweosyndesis, an ongoing process, produces aww ewements from carbon drough iron in atomic number, but wittwe widium, berywwium, or boron. Ewements heavier in atomic number dan iron, as heavy as uranium and pwutonium, are produced by expwosive nucweosyndesis in supernovas and oder catacwysmic cosmic events. Cosmic ray spawwation (fragmentation) of carbon, nitrogen, and oxygen is important to de production of widium, berywwium and boron, uh-hah-hah-hah.
During de earwy phases of de Big Bang, nucweosyndesis of hydrogen nucwei resuwted in de production of hydrogen-1 (protium, 1H) and hewium-4 (4He), as weww as a smawwer amount of deuterium (2H) and very minuscuwe amounts (on de order of 10−10) of widium and berywwium. Even smawwer amounts of boron may have been produced in de Big Bang, since it has been observed in some very owd stars, whiwe carbon has not. It is generawwy agreed dat no heavier ewements dan boron were produced in de Big Bang. As a resuwt, de primordiaw abundance of atoms (or ions) consisted of roughwy 75% 1H, 25% 4He, and 0.01% deuterium, wif onwy tiny traces of widium, berywwium, and perhaps boron, uh-hah-hah-hah. Subseqwent enrichment of gawactic hawos occurred due to stewwar nucweosyndesis and supernova nucweosyndesis. However, de ewement abundance in intergawactic space can stiww cwosewy resembwe primordiaw conditions, unwess it has been enriched by some means.
On Earf (and ewsewhere), trace amounts of various ewements continue to be produced from oder ewements as products of nucwear transmutation processes. These incwude some produced by cosmic rays or oder nucwear reactions (see cosmogenic and nucweogenic nucwides), and oders produced as decay products of wong-wived primordiaw nucwides. For exampwe, trace (but detectabwe) amounts of carbon-14 (14C) are continuawwy produced in de atmosphere by cosmic rays impacting nitrogen atoms, and argon-40 (40Ar) is continuawwy produced by de decay of primordiawwy occurring but unstabwe potassium-40 (40K). Awso, dree primordiawwy occurring but radioactive actinides, dorium, uranium, and pwutonium, decay drough a series of recurrentwy produced but unstabwe radioactive ewements such as radium and radon, which are transientwy present in any sampwe of dese metaws or deir ores or compounds. Three oder radioactive ewements, technetium, promedium, and neptunium, occur onwy incidentawwy in naturaw materiaws, produced as individuaw atoms by nucwear fission of de nucwei of various heavy ewements or in oder rare nucwear processes.
The fowwowing graph (note wog scawe) shows de abundance of ewements in our Sowar System. The tabwe shows de twewve most common ewements in our gawaxy (estimated spectroscopicawwy), as measured in parts per miwwion, by mass. Nearby gawaxies dat have evowved awong simiwar wines have a corresponding enrichment of ewements heavier dan hydrogen and hewium. The more distant gawaxies are being viewed as dey appeared in de past, so deir abundances of ewements appear cwoser to de primordiaw mixture. As physicaw waws and processes appear common droughout de visibwe universe, however, scientist expect dat dese gawaxies evowved ewements in simiwar abundance.
The abundance of ewements in de Sowar System is in keeping wif deir origin from nucweosyndesis in de Big Bang and a number of progenitor supernova stars. Very abundant hydrogen and hewium are products of de Big Bang, but de next dree ewements are rare since dey had wittwe time to form in de Big Bang and are not made in stars (dey are, however, produced in smaww qwantities by de breakup of heavier ewements in interstewwar dust, as a resuwt of impact by cosmic rays). Beginning wif carbon, ewements are produced in stars by buiwdup from awpha particwes (hewium nucwei), resuwting in an awternatingwy warger abundance of ewements wif even atomic numbers (dese are awso more stabwe). In generaw, such ewements up to iron are made in warge stars in de process of becoming supernovas. Iron-56 is particuwarwy common, since it is de most stabwe ewement dat can easiwy be made from awpha particwes (being a product of decay of radioactive nickew-56, uwtimatewy made from 14 hewium nucwei). Ewements heavier dan iron are made in energy-absorbing processes in warge stars, and deir abundance in de universe (and on Earf) generawwy decreases wif deir atomic number.
The abundance of de chemicaw ewements on Earf varies from air to crust to ocean, and in various types of wife. The abundance of ewements in Earf's crust differs from dat in de Sowar system (as seen in de Sun and heavy pwanets wike Jupiter) mainwy in sewective woss of de very wightest ewements (hydrogen and hewium) and awso vowatiwe neon, carbon (as hydrocarbons), nitrogen and suwfur, as a resuwt of sowar heating in de earwy formation of de sowar system. Oxygen, de most abundant Earf ewement by mass, is retained on Earf by combination wif siwicon, uh-hah-hah-hah. Awuminum at 8% by mass is more common in de Earf's crust dan in de universe and sowar system, but de composition of de far more buwky mantwe, which has magnesium and iron in pwace of awuminum (which occurs dere onwy at 2% of mass) more cwosewy mirrors de ewementaw composition of de sowar system, save for de noted woss of vowatiwe ewements to space, and woss of iron which has migrated to de Earf's core.
The composition of de human body, by contrast, more cwosewy fowwows de composition of seawater—save dat de human body has additionaw stores of carbon and nitrogen necessary to form de proteins and nucweic acids, togeder wif phosphorus in de nucweic acids and energy transfer mowecuwe adenosine triphosphate (ATP) dat occurs in de cewws of aww wiving organisms. Certain kinds of organisms reqwire particuwar additionaw ewements, for exampwe de magnesium in chworophyww in green pwants, de cawcium in mowwusc shewws, or de iron in de hemogwobin in vertebrate animaws' red bwood cewws.
|Ewements in our gawaxy||Parts per miwwion|
Deemed essentiaw trace ewement by U.S., not by European Union
Suggested function from deprivation effects or active metabowic handwing, but no cwearwy-identified biochemicaw function in humans
Limited circumstantiaw evidence for trace benefits or biowogicaw action in mammaws
No evidence for biowogicaw action in mammaws, but essentiaw in some wower organisms.
(In de case of wandanum, de definition of an essentiaw nutrient as being indispensabwe and irrepwaceabwe is not compwetewy appwicabwe due to de extreme simiwarity of de wandanides. Thus Ce, Pr, and Nd may be substituted for La widout iww effects for organisms using La, and de smawwer Sm, Eu, and Gd may awso be simiwarwy substituted but cause swower growf.)
The concept of an "ewement" as an undivisibwe substance has devewoped drough dree major historicaw phases: Cwassicaw definitions (such as dose of de ancient Greeks), chemicaw definitions, and atomic definitions.
Ancient phiwosophy posited a set of cwassicaw ewements to expwain observed patterns in nature. These ewements originawwy referred to earf, water, air and fire rader dan de chemicaw ewements of modern science.
The term 'ewements' (stoicheia) was first used by de Greek phiwosopher Pwato in about 360 BCE in his diawogue Timaeus, which incwudes a discussion of de composition of inorganic and organic bodies and is a specuwative treatise on chemistry. Pwato bewieved de ewements introduced a century earwier by Empedocwes were composed of smaww powyhedraw forms: tetrahedron (fire), octahedron (air), icosahedron (water), and cube (earf).
Ewement – one of dose bodies into which oder bodies can decompose, and dat itsewf is not capabwe of being divided into oder.
In 1661, Robert Boywe proposed his deory of corpuscuwarism which favoured de anawysis of matter as constituted by irreducibwe units of matter (atoms) and, choosing to side wif neider Aristotwe's view of de four ewements nor Paracewsus' view of dree fundamentaw ewements, weft open de qwestion of de number of ewements. The first modern wist of chemicaw ewements was given in Antoine Lavoisier's 1789 Ewements of Chemistry, which contained dirty-dree ewements, incwuding wight and caworic. By 1818, Jöns Jakob Berzewius had determined atomic weights for forty-five of de forty-nine den-accepted ewements. Dmitri Mendeweev had sixty-six ewements in his periodic tabwe of 1869.
From Boywe untiw de earwy 20f century, an ewement was defined as a pure substance dat couwd not be decomposed into any simpwer substance. Put anoder way, a chemicaw ewement cannot be transformed into oder chemicaw ewements by chemicaw processes. Ewements during dis time were generawwy distinguished by deir atomic weights, a property measurabwe wif fair accuracy by avaiwabwe anawyticaw techniqwes.
The 1913 discovery by Engwish physicist Henry Mosewey dat de nucwear charge is de physicaw basis for an atom's atomic number, furder refined when de nature of protons and neutrons became appreciated, eventuawwy wed to de current definition of an ewement based on atomic number (number of protons per atomic nucweus). The use of atomic numbers, rader dan atomic weights, to distinguish ewements has greater predictive vawue (since dese numbers are integers), and awso resowves some ambiguities in de chemistry-based view due to varying properties of isotopes and awwotropes widin de same ewement. Currentwy, IUPAC defines an ewement to exist if it has isotopes wif a wifetime wonger dan de 10−14 seconds it takes de nucweus to form an ewectronic cwoud.
By 1914, seventy-two ewements were known, aww naturawwy occurring. The remaining naturawwy occurring ewements were discovered or isowated in subseqwent decades, and various additionaw ewements have awso been produced syndeticawwy, wif much of dat work pioneered by Gwenn T. Seaborg. In 1955, ewement 101 was discovered and named mendewevium in honor of D.I. Mendeweev, de first to arrange de ewements in a periodic manner. Most recentwy, de syndesis of ewement 118 was reported in October 2006, and de syndesis of ewement 117 was reported in Apriw 2010.
Discovery and recognition of various ewements
Ten materiaws famiwiar to various prehistoric cuwtures are now known to be chemicaw ewements: Carbon, copper, gowd, iron, wead, mercury, siwver, suwfur, tin, and zinc. Three additionaw materiaws now accepted as ewements, arsenic, antimony, and bismuf, were recognized as distinct substances prior to 1500 AD. Phosphorus, cobawt, and pwatinum were isowated before 1750.
Most of de remaining naturawwy occurring chemicaw ewements were identified and characterized by 1900, incwuding:
- Such now-famiwiar industriaw materiaws as awuminium, siwicon, nickew, chromium, magnesium, and tungsten
- Reactive metaws such as widium, sodium, potassium, and cawcium
- The hawogens fwuorine, chworine, bromine, and iodine
- Gases such as hydrogen, oxygen, nitrogen, hewium, argon, and neon
- Most of de rare-earf ewements, incwuding cerium, wandanum, gadowinium, and neodymium.
- The more common radioactive ewements, incwuding uranium, dorium, radium, and radon
Ewements isowated or produced since 1900 incwude:
- The dree remaining undiscovered reguwarwy occurring stabwe naturaw ewements: hafnium, wutetium, and rhenium
- Pwutonium, which was first produced syndeticawwy in 1940 by Gwenn T. Seaborg, but is now awso known from a few wong-persisting naturaw occurrences
- The dree incidentawwy occurring naturaw ewements (neptunium, promedium, and technetium), which were aww first produced syndeticawwy but water discovered in trace amounts in certain geowogicaw sampwes
- Three scarce decay products of uranium or dorium, (astatine, francium, and protactinium), and
- Various syndetic transuranic ewements, beginning wif americium and curium
Recentwy discovered ewements
The first transuranium ewement (ewement wif atomic number greater dan 92) discovered was neptunium in 1940. Since 1999 cwaims for de discovery of new ewements have been considered by de IUPAC/IUPAP Joint Working Party. As of January 2016, aww 118 ewements have been confirmed as discovered by IUPAC. The discovery of ewement 112 was acknowwedged in 2009, and de name copernicium and de atomic symbow Cn were suggested for it. The name and symbow were officiawwy endorsed by IUPAC on 19 February 2010. The heaviest ewement dat is bewieved to have been syndesized to date is ewement 118, oganesson, on 9 October 2006, by de Fwerov Laboratory of Nucwear Reactions in Dubna, Russia. Tennessine, ewement 117 was de watest ewement cwaimed to be discovered, in 2009. On 28 November 2016, scientists at de IUPAC officiawwy recognized de names for four of de newest chemicaw ewements, wif atomic numbers 113, 115, 117, and 118.
List of de 118 known chemicaw ewements
The fowwowing sortabwe tabwe shows de 118 known chemicaw ewements.
- Atomic number, name, and symbow aww serve independentwy as uniqwe identifiers.
- Names are dose accepted by IUPAC; provisionaw names for recentwy produced ewements not yet formawwy named are in parendeses.
- Group, period, and bwock refer to an ewement's position in de periodic tabwe. Group numbers here show de currentwy accepted numbering; for owder awternate numberings, see Group (periodic tabwe).
- State of matter (sowid, wiqwid, or gas) appwies at standard temperature and pressure conditions (STP).
- Occurrence, as indicated by a footnote adjacent to de ewement's name, distinguishes naturawwy occurring ewements, categorized as eider primordiaw or transient (from decay), and additionaw syndetic ewements dat have been produced technowogicawwy, but are not known to occur naturawwy.
- Cowor specifies an ewement's properties using de broad categories commonwy presented in periodic tabwes: Actinide, awkawi metaw, awkawine earf metaw, wandanide, post-transition metaw, metawwoid, nobwe gas, powyatomic or diatomic nonmetaw, and transition metaw.
|List of chemicaw ewements|
|Z[I]||Symbow||Ewement||Origin of name||Group||Period||Atomic weight (u (±))||Density (g/)||Mewt (K) ||Boiw (K)||C[I] (J/)||χ[I]||Abundance in Earf's crust[II] (mg/)|
|1||H||Hydrogen||composed of de Greek ewements hydro- and -gen meaning 'water-forming'||1||1||1.008[III][IV][V][VI]||0.00008988||14.01||20.28||14.304||2.20||1400|
|2||He||Hewium||de Greek hewios, 'sun'||18||1||4.002602(2)[III][V]||0.0001785||—[VII]||4.22||5.193||–||0.008|
|3||Li||Lidium||de Greek widos, 'stone'||1||2||6.94[III][IV][V][VIII][VI]||0.534||453.69||1560||3.582||0.98||20|
|4||Be||Berywwium||beryw, a mineraw||2||2||9.0121831(5)||1.85||1560||2742||1.825||1.57||2.8|
|5||B||Boron||borax, a mineraw||13||2||10.81[III][IV][V][VI]||2.34||2349||4200||1.026||2.04||10|
|6||C||Carbon||de Latin carbo, 'coaw'||14||2||12.011[III][V][VI]||2.267||3800||4300||0.709||2.55||200|
|7||N||Nitrogen||de Greek nitron and '-gen' meaning 'niter-forming'||15||2||14.007[III][V][VI]||0.0012506||63.15||77.36||1.04||3.04||19|
|8||O||Oxygen||from de Greek oxy-, bof 'sharp' and 'acid', and -gen, meaning 'acid-forming'||16||2||15.999[III][V][VI]||0.001429||54.36||90.20||0.918||3.44||461000|
|9||F||Fwuorine||de Latin fwuere, 'to fwow'||17||2||18.998403163(6)||0.001696||53.53||85.03||0.824||3.98||585|
|10||Ne||Neon||de Greek neos, meaning 'new'||18||2||20.1797(6)[III][IV]||0.0008999||24.56||27.07||1.03||–||0.005|
|11||Na||Sodium||de Engwish word soda (natrium in Latin)||1||3||22.98976928(2)||0.971||370.87||1156||1.228||0.93||23600|
|12||Mg||Magnesium||Magnesia, a district of Eastern Thessawy in Greece||2||3||24.305[VI]||1.738||923||1363||1.023||1.31||23300|
|13||Aw||Awuminium||from awumina, a compound (originawwy awumium)||13||3||26.9815385(7)||2.698||933.47||2792||0.897||1.61||82300|
|14||Si||Siwicon||from de Latin siwex, 'fwint' (originawwy siwicium)||14||3||28.085[V][VI]||2.3296||1687||3538||0.705||1.9||282000|
|15||P||Phosphorus||de Greek phoosphoros, 'carrying wight'||15||3||30.973761998(5)||1.82||317.30||550||0.769||2.19||1050|
|16||S||Suwfur||de Latin suwphur, 'fire and brimstone'||16||3||32.06[III][V][VI]||2.067||388.36||717.87||0.71||2.58||350|
|17||Cw||Chworine||de Greek chworos, 'greenish yewwow'||17||3||35.45[III][IV][V][VI]||0.003214||171.6||239.11||0.479||3.16||145|
|18||Ar||Argon||de Greek argos, 'idwe'||18||3||39.948(1)[III][V]||0.0017837||83.80||87.30||0.52||–||3.5|
|19||K||Potassium||New Latin potassa, 'potash' (kawium in Latin)||1||4||39.0983(1)||0.862||336.53||1032||0.757||0.82||20900|
|20||Ca||Cawcium||de Latin cawx, 'wime'||2||4||40.078(4)[III]||1.54||1115||1757||0.647||1||41500|
|21||Sc||Scandium||Scandia, de Latin name for Scandinavia||3||4||44.955908(5)||2.989||1814||3109||0.568||1.36||22|
|22||Ti||Titanium||Titans, de sons of de Earf goddess of Greek mydowogy||4||4||47.867(1)||4.54||1941||3560||0.523||1.54||5650|
|23||V||Vanadium||Vanadis, an Owd Norse name for de Scandinavian goddess Freyja||5||4||50.9415(1)||6.11||2183||3680||0.489||1.63||120|
|24||Cr||Chromium||de Greek chroma, 'cowor'||6||4||51.9961(6)||7.15||2180||2944||0.449||1.66||102|
|25||Mn||Manganese||corrupted from magnesia negra, see Magnesium||7||4||54.938044(3)||7.44||1519||2334||0.479||1.55||950|
|26||Fe||Iron||Engwish word (ferrum in Latin)||8||4||55.845(2)||7.874||1811||3134||0.449||1.83||56300|
|27||Co||Cobawt||de German word Kobowd, 'gobwin'||9||4||58.933194(4)||8.86||1768||3200||0.421||1.88||25|
|28||Ni||Nickew||from a mischievous sprite of German miner mydowogy, Nickew||10||4||58.6934(4)||8.912||1728||3186||0.444||1.91||84|
|29||Cu||Copper||Engwish word (Latin cuprum)||11||4||63.546(3)[V]||8.96||1357.77||2835||0.385||1.9||60|
|30||Zn||Zinc||German word Zinke (prong, toof)||12||4||65.38(2)||7.134||692.88||1180||0.388||1.65||70|
|31||Ga||Gawwium||Gawwia, de Latin name for France||13||4||69.723(1)||5.907||302.9146||2673||0.371||1.81||19|
|32||Ge||Germanium||Germania, de Latin name for Germany||14||4||72.630(8)||5.323||1211.40||3106||0.32||2.01||1.5|
|33||As||Arsenic||Engwish word (Latin arsenicum)||15||4||74.921595(6)||5.776||1090 [IX]||887||0.329||2.18||1.8|
|34||Se||Sewenium||de Greek sewene, 'moon'||16||4||78.971(8)[V]||4.809||453||958||0.321||2.55||0.05|
|35||Br||Bromine||de Greek bromos, 'stench'||17||4||79.904[VI]||3.122||265.8||332.0||0.474||2.96||2.4|
|36||Kr||Krypton||de Greek kryptos, 'hidden'||18||4||83.798(2)[III][IV]||0.003733||115.79||119.93||0.248||3||1×10−4|
|37||Rb||Rubidium||de Latin rubidus, 'deep red'||1||5||85.4678(3)[III]||1.532||312.46||961||0.363||0.82||90|
|38||Sr||Strontium||Strontian, a smaww town in Scotwand||2||5||87.62(1)[III][V]||2.64||1050||1655||0.301||0.95||370|
|40||Zr||Zirconium||Persian Zargun, 'gowd-cowored'; German Zirkoon, 'jargoon'||4||5||91.224(2)[III]||6.506||2128||4682||0.278||1.33||165|
|41||Nb||Niobium||Niobe, daughter of king Tantawus from Greek mydowogy||5||5||92.90637(2)||8.57||2750||5017||0.265||1.6||20|
|42||Mo||Mowybdenum||de Greek mowybdos meaning 'wead'||6||5||95.95(1)[III]||10.22||2896||4912||0.251||2.16||1.2|
|43||Tc||Technetium||de Greek tekhnètos meaning 'artificiaw'||7||5||[X]||11.5||2430||4538||–||1.9||~ 3×10−9[XI]|
|44||Ru||Rudenium||Rudenia, de New Latin name for Russia||8||5||101.07(2)[III]||12.37||2607||4423||0.238||2.2||0.001|
|45||Rh||Rhodium||de Greek rhodos, meaning 'rose cowoured'||9||5||102.90550(2)||12.41||2237||3968||0.243||2.28||0.001|
|46||Pd||Pawwadium||de den recentwy discovered asteroid Pawwas, considered a pwanet at de time||10||5||106.42(1)[III]||12.02||1828.05||3236||0.244||2.2||0.015|
|47||Ag||Siwver||Engwish word (argentum in Latin)||11||5||107.8682(2)[III]||10.501||1234.93||2435||0.235||1.93||0.075|
|48||Cd||Cadmium||de New Latin cadmia, from King Kadmos||12||5||112.414(4)[III]||8.69||594.22||1040||0.232||1.69||0.159|
|50||Sn||Tin||Engwish word (stannum in Latin)||14||5||118.710(7)[III]||7.287||505.08||2875||0.228||1.96||2.3|
|51||Sb||Antimony||uncertain: perhaps from de Greek anti, 'against', and monos, 'awone', or de Owd French antimoine, 'Monk's bane' (stibium in Latin)||15||5||121.760(1)[III]||6.685||903.78||1860||0.207||2.05||0.2|
|52||Te||Tewwurium||Latin tewwus, 'earf'||16||5||127.60(3)[III]||6.232||722.66||1261||0.202||2.1||0.001|
|53||I||Iodine||French iode (after de Greek ioeides, 'viowet')||17||5||126.90447(3)||4.93||386.85||457.4||0.214||2.66||0.45|
|54||Xe||Xenon||de Greek xenos, 'strange'||18||5||131.293(6)[III][IV]||0.005887||161.4||165.03||0.158||2.6||3×10−5|
|55||Cs||Caesium||de Latin caesius, 'sky bwue'||1||6||132.90545196(6)||1.873||301.59||944||0.242||0.79||3|
|56||Ba||Barium||de Greek barys, 'heavy'||2||6||137.327(7)||3.594||1000||2170||0.204||0.89||425|
|57||La||Landanum||de Greek wandanein, 'to wie hidden'||3||6||138.90547(7)[III]||6.145||1193||3737||0.195||1.1||39|
|58||Ce||Cerium||de den recentwy discovered asteroid Ceres, considered a pwanet at de time||6||140.116(1)[III]||6.77||1068||3716||0.192||1.12||66.5|
|59||Pr||Praseodymium||de Greek praseios didymos meaning 'green twin'||6||140.90766(2)||6.773||1208||3793||0.193||1.13||9.2|
|60||Nd||Neodymium||de Greek neos didymos meaning 'new twin'||6||144.242(3)[III]||7.007||1297||3347||0.19||1.14||41.5|
|61||Pm||Promedium||Promedeus of Greek mydowogy who stowe fire from de Gods and gave it to humans||6||[X]||7.26||1315||3273||–||1.13||2×10−19[XI]|
|62||Sm||Samarium||Samarskite, de name of de mineraw from which it was first isowated||6||150.36(2)[III]||7.52||1345||2067||0.197||1.17||7.05|
|64||Gd||Gadowinium||Johan Gadowin, chemist, physicist and minerawogist||6||157.25(3)[III]||7.895||1585||3546||0.236||1.2||6.2|
|66||Dy||Dysprosium||de Greek dysprositos, 'hard to get'||6||162.500(1)[III]||8.55||1680||2840||0.17||1.22||5.2|
|67||Ho||Howmium||Howmia, de New Latin name for Stockhowm||6||164.93033(2)||8.795||1734||2993||0.165||1.23||1.3|
|69||Tm||Thuwium||Thuwe, de ancient name for Scandinavia||6||168.93422(2)||9.321||1818||2223||0.16||1.25||0.52|
|71||Lu||Lutetium||Lutetia, de Latin name for Paris||6||174.9668(1)[III]||9.84||1925||3675||0.154||1.27||0.8|
|72||Hf||Hafnium||Hafnia, de New Latin name for Copenhagen||4||6||178.49(2)||13.31||2506||4876||0.144||1.3||3|
|73||Ta||Tantawum||King Tantawus, fader of Niobe from Greek mydowogy||5||6||180.94788(2)||16.654||3290||5731||0.14||1.5||2|
|74||W||Tungsten||de Swedish tung sten, 'heavy stone' (W is wowfram, de owd name of de tungsten mineraw wowframite)||6||6||183.84(1)||19.25||3695||5828||0.132||2.36||1.3|
|75||Re||Rhenium||Rhenus, de Latin name for de river Rhine||7||6||186.207(1)||21.02||3459||5869||0.137||1.9||7×10−4|
|76||Os||Osmium||de Greek osmè, meaning 'smeww'||8||6||190.23(3)[III]||22.61||3306||5285||0.13||2.2||0.002|
|77||Ir||Iridium||Iris, de Greek goddess of de rainbow||9||6||192.217(3)||22.56||2719||4701||0.131||2.2||0.001|
|78||Pt||Pwatinum||de Spanish pwatina, meaning 'wittwe siwver'||10||6||195.084(9)||21.46||2041.4||4098||0.133||2.28||0.005|
|79||Au||Gowd||Engwish word (aurum in Latin)||11||6||196.966569(5)||19.282||1337.33||3129||0.129||2.54||0.004|
|80||Hg||Mercury||de New Latin name mercurius, named after de Roman god (Hg from former name hydrargyrum, from Greek hydr-, 'water', and argyros, 'siwver')||12||6||200.592(3)||13.5336||234.43||629.88||0.14||2||0.085|
|81||Tw||Thawwium||de Greek dawwos, 'green twig'||13||6||204.38[VI]||11.85||577||1746||0.129||1.62||0.85|
|82||Pb||Lead||Engwish word (pwumbum in Latin)||14||6||207.2(1)[III][V]||11.342||600.61||2022||0.129||1.87||14|
|83||Bi||Bismuf||Uncertain, possibwy Arabic or German||15||6||208.98040(1)[X]||9.807||544.7||1837||0.122||2.02||0.009|
|84||Po||Powonium||Named after de home country of Marie Curie (Powonia, Latin for Powand), who is awso de discoverer of Radium||16||6||[X]||9.32||527||1235||–||2.0||2×10−10[XI]|
|85||At||Astatine||de Greek astatos, 'unstabwe'||17||6||[X]||7||575||610||–||2.2||3×10−20[XI]|
|86||Rn||Radon||From radium, as it was first detected as an emission from radium during radioactive decay||18||6||[X]||0.00973||202||211.3||0.094||2.2||4×10−13[XI]|
|87||Fr||Francium||Francia, de New Latin name for France||1||7||[X]||1.87||300||950||–||0.7||~ 1×10−18[XI]|
|88||Ra||Radium||de Latin radius, 'ray'||2||7||[X]||5.5||973||2010||0.094||0.9||9×10−7[XI]|
|89||Ac||Actinium||de Greek aktis, 'ray'||3||7||[X]||10.07||1323||3471||0.12||1.1||5.5×10−10[XI]|
|90||Th||Thorium||Thor, de Scandinavian god of dunder||7||232.0377(4)[X][III]||11.72||2115||5061||0.113||1.3||9.6|
|91||Pa||Protactinium||de Greek protos, 'first', and actinium, which is produced drough de radioactive decay of protactinium||7||231.03588(2)[X]||15.37||1841||4300||–||1.5||1.4×10−6[XI]|
|92||U||Uranium||Uranus, de sevenf pwanet in de Sowar System||7||238.02891(3)[X]||18.95||1405.3||4404||0.116||1.38||2.7|
|93||Np||Neptunium||Neptune, de eighf pwanet in de Sowar System||7||[X]||20.45||917||4273||–||1.36||≤ 3×10−12[XI]|
|94||Pu||Pwutonium||Pwuto, a dwarf pwanet in de Sowar System (den considered de ninf pwanet)||7||[X]||19.84||912.5||3501||–||1.28||≤ 3×10−11[XI]|
|95||Am||Americium||The Americas, as de ewement was first syndesized on de continent, by anawogy wif europium||7||[X]||13.69||1449||2880||–||1.13||0[XII]|
|96||Cm||Curium||Pierre Curie, a physicist, and Marie Curie, a physicist and chemist, named after great scientists by anawogy wif gadowinium||7||[X]||13.51||1613||3383||–||1.28||0[XII]|
|97||Bk||Berkewium||Berkewey, Cawifornia, where de ewement was first syndesized, by anawogy wif terbium||7||[X]||14.79||1259||2900||–||1.3||0[XII]|
|98||Cf||Cawifornium||Cawifornia, where de ewement was first syndesized||7||[X]||15.1||1173||(1743)[XIII]||–||1.3||0[XII]|
|99||Es||Einsteinium||Awbert Einstein, physicist||7||[X]||8.84||1133||(1269)[XIII]||–||1.3||0[XII]|
|100||Fm||Fermium||Enrico Fermi, physicist||7||[X]||(9.7)[XIII]||(1125)[XIII]||–||–||1.3||0[XII]|
|101||Md||Mendewevium||Dmitri Mendeweev, chemist and inventor||7||[X]||(10.3)[XIII]||(1100)[XIII]||–||–||1.3||0[XII]|
|102||No||Nobewium||Awfred Nobew, chemist, engineer, inventor of dynamite||7||[X]||(9.9)[XIII]||(1100)[XIII]||–||–||1.3||0[XII]|
|103||Lr||Lawrencium||Ernest O. Lawrence, physicist||7||[X]||(15.6)[XIII]||(1900)[XIII]||–||–||1.3||0[XII]|
|104||Rf||Ruderfordium||Ernest Ruderford, chemist and physicist||4||7||[X]||(23.2)[XIII]||(2400)[XIII]||(5800)[XIII]||–||–||0[XII]|
|106||Sg||Seaborgium||Gwenn T. Seaborg, scientist||6||7||[X]||(35.0)[XIII]||–||–||–||–||0[XII]|
|107||Bh||Bohrium||Niews Bohr, physicist||7||7||[X]||(37.1)[XIII]||–||–||–||–||0[XII]|
|108||Hs||Hassium||Hesse, Germany, where de ewement was first syndesized||8||7||[X]||(40.7)[XIII]||–||–||–||–||0[XII]|
|109||Mt||Meitnerium||Lise Meitner, physicist||9||7||[X]||(37.4)[XIII]||–||–||–||–||0[XII]|
|110||Ds||Darmstadtium||Darmstadt, Germany, where de ewement was first syndesized||10||7||[X]||(34.8)[XIII]||–||–||–||–||0[XII]|
|111||Rg||Roentgenium||Wiwhewm Conrad Röntgen, physicist||11||7||[X]||(28.7)[XIII]||–||–||–||–||0[XII]|
|112||Cn||Copernicium||Nicowaus Copernicus, astronomer||12||7||[X]||(23.7)[XIII]||–||~357[XIV]||–||–||0[XII]|
|113||Nh||Nihonium||de Japanese name for Japan, Nihon, where de ewement was first syndesized||13||7||[X]||(16)[XIII]||(700)[XIII]||(1400)[XIII]||–||–||0[XII]|
|114||Fw||Fwerovium||Fwerov Laboratory of Nucwear Reactions, part of JINR where de ewement was syndesized; itsewf named for Georgy Fwyorov, physicist||14||7||[X]||(14)[XIII]||–||~210||–||–||0[XII]|
|115||Mc||Moscovium||Moscow Obwast, Russia, where de ewement was first syndesized||15||7||[X]||(13.5)[XIII]||(700)[XIII]||(1400)[XIII]||–||–||0[XII]|
|116||Lv||Livermorium||Lawrence Livermore Nationaw Laboratory (in Livermore, Cawifornia) which cowwaborated wif JINR on its syndesis||16||7||[X]||(12.9)[XIII]||(709)[XIII]||(1085)[XIII]||–||–||0[XII]|
|117||Ts||Tennessine||Tennessee, United States||17||7||[X]||(7.2)[XIII]||(723)[XIII]||(883)[XIII]||–||–||0[XII]|
|118||Og||Oganesson||Yuri Oganessian, physicist||18||7||[X]||(5.0)[XIII][XV]||–||(350)[XIII]||–||–||0[XII]|
- Chemicaw database
- Discovery of de chemicaw ewements
- Ewement cowwecting
- Fictionaw ewement
- Gowdschmidt cwassification
- Iswand of stabiwity
- List of chemicaw ewements
- List of nucwides
- List of de ewements' densities
- Periodic Systems of Smaww Mowecuwes
- Prices of ewements and deir compounds
- Systematic ewement name
- Tabwe of nucwides
- Timewine of chemicaw ewement discoveries
- The Mystery of Matter: Search for de Ewements (PBS fiwm)
- Atomas, a game about combining ewements
- IUPAC (ed.). "chemicaw ewement". Internationaw Union of Pure and Appwied Chemistry. doi:10.1351/gowdbook.C01022.
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- See de timewine on p.10 in Oganessian, Yu. Ts.; Utyonkov, V.; Lobanov, Yu.; Abduwwin, F.; Powyakov, A.; Sagaidak, R.; Shirokovsky, I.; Tsyganov, Yu.; et aw. (2006). "Evidence for Dark Matter" (PDF). Physicaw Review C. 74 (4): 044602. Bibcode:2006PhRvC..74d4602O. doi:10.1103/PhysRevC.74.044602.
- wbw.gov (2005). "The Universe Adventure Hydrogen and Hewium". Lawrence Berkewey Nationaw Laboratory U.S. Department of Energy. Archived from de originaw on 21 September 2013.
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- foodiww.edu (18 October 2006). "How Stars Make Energy and New Ewements" (PDF). Foodiww Cowwege.
- Dumé, B. (23 Apriw 2003). "Bismuf breaks hawf-wife record for awpha decay". Physicsworwd.com. Bristow, Engwand: Institute of Physics. Retrieved 14 Juwy 2015.
- de Marciwwac, P.; Coron, N.; Dambier, G.; Lebwanc, J.; Moawic, J-P (2003). "Experimentaw detection of awpha-particwes from de radioactive decay of naturaw bismuf". Nature. 422 (6934): 876–8. Bibcode:2003Natur.422..876D. doi:10.1038/nature01541. PMID 12712201.
- Sanderson, K. (17 October 2006). "Heaviest ewement made – again". News@nature. Nature News. doi:10.1038/news061016-4.
- Schewe, P.; Stein, B. (17 October 2000). "Ewements 116 and 118 Are Discovered". Physics News Update. American Institute of Physics. Archived from de originaw on 1 January 2012. Retrieved 19 October 2006.
- United States Environmentaw Protection Agency. "Technetium-99". epa.gov. Retrieved 26 February 2013.
- Harvard–Smidsonian Center for Astrophysics. "ORIGIN OF HEAVY ELEMENTS". cfa.harvard.edu. Retrieved 26 February 2013.
- "ATOMIC NUMBER AND MASS NUMBERS". ndt-ed.org. Retrieved 17 February 2013.
- periodic.wanw.gov. "PERIODIC TABLE OF ELEMENTS: LANL Carbon". Los Awamos Nationaw Laboratory.
- Katsuya Yamada. "Atomic mass, isotopes, and mass number" (PDF). Los Angewes Pierce Cowwege. Archived from de originaw (PDF) on 11 January 2014.
- "Pure ewement". European Nucwear Society.
- Meija, J.; et aw. (2016). "Atomic weights of de ewements 2013 (IUPAC Technicaw Report)". Pure and Appwied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
- IUPAC 2016, Tabwe 2, 3 combined; uncertainty removed.
- Wiwford, J. N. (14 January 1992). "Hubbwe Observations Bring Some Surprises". The New York Times.
- Wright, E. L. (12 September 2004). "Big Bang Nucweosyndesis". UCLA, Division of Astronomy. Retrieved 22 February 2007.
- Wawwerstein, George; Iben, Icko; Parker, Peter; Boesgaard, Ann; Hawe, Gerawd; Champagne, Ardur; Barnes, Charwes; Käppewer, Franz; et aw. (1999). "Syndesis of de ewements in stars: forty years of progress" (PDF). Reviews of Modern Physics. 69 (4): 995–1084. Bibcode:1997RvMP...69..995W. doi:10.1103/RevModPhys.69.995. Archived from de originaw (PDF) on 28 September 2006.
- Earnshaw, A.; Greenwood, N. (1997). Chemistry of de Ewements (2nd ed.). Butterworf-Heinemann.
- Crosweww, K. (1996). Awchemy of de Heavens. Anchor. ISBN 0-385-47214-5.
- Pwato (2008) [c. 360 BC]. Timaeus. Forgotten Books. p. 45. ISBN 978-1-60620-018-6.
- Hiwwar, M. (2004). "The Probwem of de Souw in Aristotwe's De anima". NASA/WMAP. Archived from de originaw on 9 September 2006. Retrieved 10 August 2006.
- Partington, J. R. (1937). A Short History of Chemistry. New York: Dover Pubwications. ISBN 0-486-65977-1.
- Boywe, R. (1661). The Scepticaw Chymist. London, uh-hah-hah-hah. ISBN 0-922802-90-4.
- Lavoisier, A. L. (1790). Ewements of chemistry transwated by Robert Kerr. Edinburgh. pp. 175–6. ISBN 978-0-415-17914-0.
- Transactinide-2. www.kernchemie.de
- Carey, G. W. (1914). The Chemistry of Human Life. Los Angewes. ISBN 0-7661-2840-7.
- Gwanz, J. (6 Apriw 2010). "Scientists Discover Heavy New Ewement". The New York Times.
- "IUPAC Announces Start of de Name Approvaw Process for de Ewement of Atomic Number 112" (PDF). IUPAC. 20 Juwy 2009. Retrieved 27 August 2009.
- "IUPAC (Internationaw Union of Pure and Appwied Chemistry): Ewement 112 is Named Copernicium". IUPAC. 20 February 2010. Archived from de originaw on 24 February 2010.
- Oganessian, Yu. Ts.; Utyonkov, V.; Lobanov, Yu.; Abduwwin, F.; Powyakov, A.; Sagaidak, R.; Shirokovsky, I.; Tsyganov, Yu.; et aw. (2006). "Evidence for Dark Matter" (PDF). Physicaw Review C. 74 (4): 044602. Bibcode:2006PhRvC..74d4602O. doi:10.1103/PhysRevC.74.044602.
- Greiner, W. "Recommendations" (PDF). 31st meeting, PAC for Nucwear Physics. Joint Institute for Nucwear Research. Archived from de originaw (PDF) on 14 Apriw 2010.
- Staff (30 November 2016). "IUPAC Announces de Names of de Ewements 113, 115, 117, and 118". IUPAC. Retrieved 1 December 2016.
- St. Fweur, Nichowas (1 December 2016). "Four New Names Officiawwy Added to de Periodic Tabwe of Ewements". The New York Times. Retrieved 1 December 2016.
- "Periodic Tabwe – Royaw Society of Chemistry". www.rsc.org.
- "Onwine Etymowogy Dictionary". etymonwine.com.
- Wieser, Michaew E.; et aw. (2013). "Atomic weights of de ewements 2011 (IUPAC Technicaw Report)". Pure Appw. Chem. IUPAC. 85 (5): 1047–1078. doi:10.1351/PAC-REP-13-03-02. (for standard atomic weights of ewements)
- Sonzogni, Awejandro. "Interactive Chart of Nucwides". Nationaw Nucwear Data Center: Brookhaven Nationaw Laboratory. Retrieved 2008-06-06. (for atomic weights of ewements wif atomic numbers 103–118)
- Howman, S. W.; Lawrence, R. R.; Barr, L. (1 January 1895). "Mewting Points of Awuminum, Siwver, Gowd, Copper, and Pwatinum". Proceedings of de American Academy of Arts and Sciences. 31: 218–233. doi:10.2307/20020628. JSTOR 20020628.
|Wikimedia Commons has media rewated to Chemicaw ewements.|
- Baww, P. (2004). The Ewements: A Very Short Introduction. Oxford University Press. ISBN 0-19-284099-1.
- Emswey, J. (2003). Nature's Buiwding Bwocks: An A-Z Guide to de Ewements. Oxford University Press. ISBN 0-19-850340-7.
- Gray, T. (2009). The Ewements: A Visuaw Expworation of Every Known Atom in de Universe. Bwack Dog & Levendaw Pubwishers Inc. ISBN 1-57912-814-9.
- Scerri, E. R. (2007). The Periodic Tabwe, Its Story and Its Significance. Oxford University Press.
- Stradern, P. (2000). Mendeweyev's Dream: The Quest for de Ewements. Hamish Hamiwton Ltd. ISBN 0-241-14065-X.
- Kean, Sam (2011). The Disappearing Spoon: And Oder True Tawes of Madness, Love, and de History of de Worwd from de Periodic Tabwe of de Ewements. Back Bay Books.
- Compiwed by A. D. McNaught and A. Wiwkinson, uh-hah-hah-hah. (1997). Bwackweww Scientific Pubwications, Oxford, ed. Compendium of Chemicaw Terminowogy, 2nd ed. (de "Gowd Book"). doi:10.1351/gowdbook. ISBN 0-9678550-9-8.
- XML on-wine corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiwed by A. Jenkins. | <urn:uuid:31da8b13-d413-4c97-8323-f1740fd93135> | 3.171875 | 22,383 | Knowledge Article | Science & Tech. | 66.857542 | 95,540,324 |
A Web view is a package of Web pages, style sheets, icons, and banners that represent a complete Web site. Web views can contain special Java Web Components (JWC) that add Orchestrator functions to the pages of the Web views. For example, you can add components that allow users to run workflows from a browser.
Orchestrator Web views update content dynamically without obliging users to reload complete pages. Orchestrator provides a library of Tapestry Framework 4.0 components to help you build customized Web views to access Orchestrator functions from a Web browser. Tapestry components provide access to objects in the Orchestrator server, such as the workflows in the library and the virtual machines in the inventory. You can also insert Dojo 0.4.1 components into Web views.
Orchestrator provides a Web view template that you can use as the basis for developing Web views. The Web view template contains skeleton HTML pages and Web view components that you can extend and adapt. You can also export existing Web views to use as templates that you can adapt to create new Web views.
You typically create or modify the pages of a Web view externally by using Web design tools. Creating or modifying Web pages independently of Orchestrator allows you to separate the Web design process from the process of developing Orchestrator Web view components. You import the Web view pages and components into the Orchestrator server and complete the process of creating the Web view in the Orchestrator client.
Developing Orchestrator Web views can require knowledge of some or all of the following Web development technologies and standards. For documentation about the different technologies, consult the Web sites of the organizations that maintain the standards.
Cascading stylesheets (CSS). See http://www.w3.org/Style/CSS/.
Ajax platform. See http://www.ajax.org/.
Dojo toolkit. See http://www.dojotoolkit.org/.
Java programming language. See http://www.oracle.com/technetwork/java/index.html.
Java Web Components (JWC) from the Tapestry Framework. See http://tapestry.apache.org/.
Object-Graph Navigation Language (OGNL). See http://www.opensymphony.com/ognl/.
Third-party URLs are subject to changes beyond the ability of VMware to control. If you find a URL in VMware documentation that is out of date, notify VMware at firstname.lastname@example.org. You might be able to locate a third-party document by searching from the third-party home page. | <urn:uuid:5df6b934-406b-4811-b299-a50261183eb3> | 2.734375 | 549 | Documentation | Software Dev. | 55.489542 | 95,540,330 |
The planet's travels profoundly influenced the solar system, changing the nature of the asteroid belt and making Mars smaller than it should have been. These details are based on a new model of the early solar system developed by an international team that includes NASA's Goddard Space Flight Center in Greenbelt, Md. The work is being reported in a Nature paper posted on June 5, 2011.
Not long after Jupiter formed, it got pulled slowly toward the sun, carried on currents of swirling gas. Saturn also got pulled in, and when the two giant planets came close enough to each other, their fates became linked. Their sun-bound death spiral came to a halt when Jupiter was about where Mars is now; then the pair turned and moved away from the sun. The researchers who developed this model of the early solar system call it the "Grand Tack," a reference to the sailing maneuver. Credit: NASA Goddard Space Flight Center
"We refer to Jupiter's path as the Grand Tack, because the big theme in this work is Jupiter migrating toward the sun and then stopping, turning around, and migrating back outward," says the paper's first author, Kevin Walsh of the Southwest Research Institute in Boulder, Colo. "This change in direction is like the course that a sailboat takes when it tacks around a buoy."
According to the new model, Jupiter formed in a region of space about three-and-a-half times as far from the sun as Earth is (3.5 astronomical units). Because a huge amount of gas still swirled around the sun back then, the giant planet got caught in the currents of flowing gas and started to get pulled toward the sun. Jupiter spiraled slowly inward until it settled at a distance of about 1.5 astronomical units—about where Mars is now. (Mars was not there yet.)
"We theorize that Jupiter stopped migrating toward the sun because of Saturn," says Avi Mandell, a planetary scientist at NASA Goddard and a co-author on the paper. The other co-authors are Alessandro Morbidelli at the Observatoire de la Cote d'Azur in Nice, France; Sean Raymond at the Observatoire de Bordeaux in France; and David O'Brien at the Planetary Science Institute in Tucson, Ariz.
Like Jupiter, Saturn got drawn toward the sun shortly after it formed, and the model holds that once the two massive planets came close enough to each other, their fates became permanently linked. Gradually, all the gas in between the two planets got expelled, bringing their sun-bound death spiral to a halt and eventually reversing the direction of their motion. The two planets journeyed outward together until Jupiter reached its current position at 5.2 astronomical units and Saturn came to rest at about 7 astronomical units. (Later, other forces pushed Saturn out to 9.5 astronomical units, where it is today.)
The effects of these movements, which took hundreds of thousands to millions of years, were extraordinary.
"Jupiter migrating in and then all the way back out again can solve the long-standing mystery of why the asteroid belt is made up of both dry, rocky objects and icy objects," Mandell says.
Astronomers think that the asteroid belt exists because Jupiter's gravity prevented the rocky material there from coming together to form a planet; instead, the zone remained a loose collection of objects. Some scientists previously considered the possibility that Jupiter could have moved close to the sun at some point, but this presented a major problem: Jupiter was expected to scatter the material in the asteroid belt so much that the belt would no longer exist.
"For a long time, that idea limited what we imagined Jupiter could have done," Walsh notes.
Rather than having Jupiter destroy the asteroid belt as it moved toward the sun, the Grand Tack model has Jupiter perturbing the objects and pushing the whole zone farther out. "Jupiter's migration process was slow," explains Mandell, "so when it neared the asteroid belt, it was not a violent collision but more of a do-si-do, with Jupiter deflecting the objects and essentially switching places with the asteroid belt."
In the same way, as Jupiter moved away from the sun, the planet nudged the asteroid belt back inward and into its familiar location between the modern orbits of Mars and Jupiter. And because Jupiter traveled much farther out than it had been before, it reached the region of space where icy objects are found. The massive planet deflected some of these icy objects toward the sun and into the asteroid belt.
"The end result is that the asteroid belt has rocky objects from the inner solar system and icy objects from the outer solar system," says Walsh. "Our model puts the right material in the right places, for what we see in the asteroid belt today."
Poor Little Mars
The time that Jupiter spent in the inner solar system had another major effect: its presence made Mars smaller than it otherwise would have been. "Why Mars is so small has been the unsolvable problem in the formation of our solar system," says Mandell. "It was the team's initial motivation for developing a new model of the formation of the solar system."
Because Mars formed farther out than Venus and Earth, it had more raw materials to draw on and should be larger than Venus and Earth. Instead, it's smaller. "For planetary scientists, this never made sense," Mandell adds.
But if, as the Grand Tack model suggests, Jupiter spent some time parked in the inner solar system, it would have scattered some material available for making planets. Much of the material past about 1 astronomical unit would have been dispersed, leaving poor Mars out at 1.5 astronomical units with slim pickings. Earth and Venus, however, would have formed in the region richest in planet-making material.
"With the Grand Tack model, we actually set out to explain the formation of a small Mars, and in doing so, we had to account for the asteroid belt," says Walsh. "To our surprise, the model's explanation of the asteroid belt became one of the nicest results and helps us understand that region better than we did before."
Another bonus is that the new model puts Jupiter, Saturn, and the other giant planets in positions that fit very well with the "Nice model," a relatively new theory that explains the movements of these large planets later in the solar system's history.
The Grand Tack also makes our solar system very much like the other planetary systems that have been found so far. In many of those cases, enormous gas-giant planets called "hot Jupiters" sit extremely close to their host stars, much closer than Mercury is to the sun. For planetary scientists, this newfound likeness is comforting.
"Knowing that our own planets moved around a lot in the past makes our solar system much more like our neighbors than we previously thought," says Walsh. "We're not an outlier anymore."
Liz Zubritsky | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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1. The expanding universe of microRNAs
MicroRNAs (miRNAs) are short RNA molecules encoded by plant and animal genomes that have garnered significant interest for their ability to regulate gene expression. A number of miRNAs have been discovered in recent years, however it is likely that many miRNAs have gone undetected. Two papers published in Genome Research utilize the twelve fly genomes to identify novel miRNAs, further refine the set of known miRNAs, and investigate the biology and origins of miRNA genes.
In a study led by Dr. David Bartel, a combination of computational methods and high-throughput sequencing techniques identified new miRNAs conserved across the Drosophila species. “The new fly genomes enabled us to predict new miRNAs, 20 of which we experimentally confirmed, and the genome alignments enabled us to more accurately predict the evolutionarily conserved targets of these and other miRNAs,” explains Bartel.
While computational methods are important for identifying novel miRNAs, large-scale sequencing of small RNAs indicates that many miRNAs continue to evade prediction. “Most of the 59 novel miRNAs that we found were not predicted by us or by others,” describes Bartel. “This illustrates the advantages of high-throughput sequencing of small RNAs, and the limitations of comparative sequence analysis for miRNA gene identification.”
In a related paper, a study led by Dr. Manolis Kellis utilized the twelve Drosophila genomes to computationally predict and experimentally validate novel miRNAs by defining the structural and evolutionary properties of known miRNAs. Classification of newly identified miRNAs has revealed greater diversity in the regulation gene expression by miRNAs, with increased potential for combinatorial regulation, and provided new insights on miRNA biogenesis and function. “We learned that both arms of a miRNA hairpin can produce functional miRNAs, which sometimes work cooperatively to target a common pathway,” explains Kellis.
The combination of comparative and experimental analyses by both groups also provided novel evidence for emergent gene function, deriving from the portion of the miRNA hairpin previously believed to be discarded, and the strand of the DNA previously not thought to produce a miRNA.
David Bartel, Ph.D., Whitehead Institute/MIT/HHMI, Cambridge, MA, USA firstname.lastname@example.org, +1-617-258-5287 or
Eric Lai, Ph.D., Sloan-Kettering Institute, New York, NY, USA email@example.com, +1-212-639-5578 or
J. Graham Ruby, Whitehead Institute/MIT/HHMI, Cambridge, MA, USA firstname.lastname@example.org, +1-617-324-1651Reference:
Manolis Kellis, Ph.D., MIT/Broad Institute, Cambridge, MA, USA email@example.com, +1-617-253-2419 or
Alexander Stark, Ph.D., MIT/Broad Institute, Cambridge, MA, USA firstname.lastname@example.org, +1-617-253-6079Reference:
2. Revisiting D. melanogaster
Drosophila melanogaster is one of the most intensely studied model organisms in biology. Numerous studies over the years have defined nearly 14,000 protein-coding genes by experimental and computational methods, however these methods are likely to have produced erroneous annotations or may be missing other annotations. In order to assess the D. melanogaster protein-coding gene catalog, a group of researchers led by Dr. Manolis Kellis identified evolutionarily signatures of protein-coding genes by comparative analysis of the twelve fly genomes. This strategy was then applied to evaluation of the current catalog and identification of genes that have escaped annotation.
The study led to the discovery of hundreds of new genes, refined existing genes, and concluded that greater than 10% of the protein-coding gene annotations requires refinement.
Additionally, the work revealed abundant unusual gene structures. “We have learned that many brain-expressed proteins may be undergoing post-transcriptional changes by stop-codon read-through,” explains Kellis. “We found 149 genes for which a conserved stop codon is followed by strong evidence of protein-coding selection for up to hundreds of amino acids, suggesting a new mechanism for post-transcriptional regulation in animal genomes.” The researchers also report additional widespread evidence suggesting several diverse mechanisms of post-transcriptional regulation for protein-coding genes.
Manolis Kellis, Ph.D., MIT/Broad Institute, Cambridge, MA, USA email@example.com, +1-617-262-6121Reference:
3. Keeping genes in order
In humans and other vertebrate genomes, long-range regulatory DNA sequences known as highly conserved noncoding elements (HCNEs) have been found to cluster around genes involved in developmental processes, forming genomic regulatory blocks (GRBs). The GRBs are conserved in vertebrates, maintaining the order, or microsynteny, of associated genes on the chromosome. In this study, researchers utilize mosquito genome sequences and sequences available from the twelve fly genome project to investigate the microsynteny underlying GRBs across a wider range of evolution than previously possible.
“By using insect (Drosophila and mosquito) genome comparisons, we show that long-range regulation of developmental genes by arrays of highly conserved regulatory elements is an ancient feature that has shaped the evolution of metazoan genomes,” says Dr. Boris Lenhard, senior investigator of the study.
“Additionally, we present genome-wide evidence that the responsiveness of genes to long-range regulation is partially determined by the type of their core promoter,” explains Lenhard, addressing the issue of how some genes that are conserved in GRBs are not regulated by HCNEs.
Boris Lenhard, Ph.D., University of Bergen, Bergen, Norway firstname.lastname@example.org, +47-555-84362Reference:
4. Tracing the origins of relocated genes
Investigations into the evolution of genomes have revealed significant upheaval in genome organization: insertions, deletions, rearrangement or duplication of large regions, and even duplication of entire genomes. In addition, individual genes have undergone genomic relocation. Sequencing of the twelve Drosophila genomes now allows deeper investigations into single gene relocation and its origins.
“The availability of twelve fly genomes provides a unique opportunity to investigate fine-scale events, such as relocation of individual genes, using whole genome comparative analysis across various levels of evolutionary divergence,” explains primary author Arjun Bhutkar. Bhutkar and colleagues identify and characterize positionally relocated genes (PRGs) in the Drosophila genus, and provide evidence for two distinct origins of PRGs: transposition of genes at the level of DNA, and retrotransposition of RNAs into the genome.
The researchers extended their study to comparisons of Drosophila and other insect genomes. “Such analyses demonstrate the role of PRGs in evolutionary chromosomal organization,” says Bhutkar, as this study highlights the role of PRGs in creation of genomic diversity.
Arjun Bhutkar, Harvard University, Cambridge, MA, USA/Boston University, Boston, MA, USA email@example.com, +1-617- 495-2906 or
William M. Gelbart, Ph.D., Harvard University, Cambridge, MA, USA firstname.lastname@example.org, +1-617-495-2906Reference:
Please direct requests for pre-print copies of the manuscripts to Peggy Calicchia, the Editorial Secretary for Genome Research (email@example.com; +1-516-422-4012). In addition to the five articles highlighted above, the following will also appear in the issue:
5. Heger, A. and Ponting, C. 2007. Evolutionary rate analyses of orthologues and paralogues from twelve Drosophila Genomes. Genome Res. doi:10.1101/gr.6249707
6. Villasante, A. et al. 2007. Drosophila telomeric retrotransposons derived from an ancestral element that was recruited to replace telomerase. Genome Res. doi:10.1101/gr.6365107
7. Stage, D.E. and Eickbush, T.H. 2007. Sequence variation within the rRNA gene loci of twelve Drosophila species. Genome Res. doi:10.1101/gr.6376807
8. Stark, A. et al. 2007. Reliable prediction of regulator targets using 12 Drosophila genomes. Genome Res. doi:10.1101/gr.7090407
9. Rasmussen, M.D. and Kellis, M. 2007. Accurate gene-tree reconstruction by learning gene- and species-specific substitution rates across multiple complete genomes. Genome Res. doi:10.1101/gr.7105007
Scientists uncover the role of a protein in production & survival of myelin-forming cells
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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.
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An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism. The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 reaction. In most organic elimination reactions, at least one hydrogen is organic reaction mechanism pdf to form the double bond: the unsaturation of the molecule increases.
It is also possible that a molecule undergoes reductive elimination, by which the valence of an atom in the molecule decreases by two, though this is more common in inorganic chemistry. During the 1920s, Sir Christopher Ingold proposed a model to explain a peculiar type of chemical reaction: the E2 mechanism. E2 is a single step elimination, with a single transition state. It is typically undergone by primary substituted alkyl halides, but is possible with some secondary alkyl halides and other compounds. E2 typically uses a strong base.
It must be strong enough to remove a weakly acidic hydrogen. In order for the pi bond to be created, the hybridization of carbons needs to be lowered from sp3 to sp2. An example of this type of reaction in scheme 1 is the reaction of isobutylbromide with potassium ethoxide in ethanol. E1 is a model to explain a particular type of chemical elimination reaction.
E1 stands for unimolecular elimination and has the following specificities. It is a two-step process of elimination: ionization and deprotonation. Ionization: the carbon-halogen bond breaks to give a carbocation intermediate. E1 typically takes place with tertiary alkyl halides, but is possible with some secondary alkyl halides. The reaction rate is influenced only by the concentration of the alkyl halide because carbocation formation is the slowest step, aka the rate-determining step. E1 reactions are in competition with SN1 reactions because they share a common carbocationic intermediate.
Only reaction product A results from antiperiplanar elimination. The presence of product B is an indication that an E1 mechanism is occurring. An example in scheme 2 is the reaction of tert-butylbromide with potassium ethoxide in ethanol. E1 eliminations happen with highly substituted alkyl halides for two main reasons. Highly substituted carbocations are more stable than methyl or primary substituted cations. Such stability gives time for the two-step E1 mechanism to occur.
If SN1 and E1 pathways are competing, the E1 pathway can be favored by increasing the heat. The reaction rate is influenced by the reactivity of halogens, iodide and bromide being favored. Fluoride is not a good leaving group, so eliminations with fluoride as the leaving group have slower rates than other halogens. Pyrolysis of Aryl Sulfonate Esters in the Absence of Solvent: E1 or E2?
A Puzzle for the Organic Laboratory”. Deuterium Kinetic Isotope Effects in Gas-Phase SN2 and E2 Reactions: Comparison of Experiment and Theory”. This page was last edited on 25 October 2017, at 03:34. Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. Simple functional groups can be arranged in order of increasing oxidation state. Many reactions classified as reductions also appear in other classes. For instance conversion of the ketone to an alcohol by lithium aluminium hydride can be considered a reduction but the hydride is also a good nucleophile in nucleophilic substitution.
In disproportionation reactions the reactant is both oxidised and reduced in the same chemical reaction forming two separate compounds. Asymmetric catalytic reductions and asymmetric catalytic oxidations are important in asymmetric synthesis. Most oxidations are conducted with air or oxygen. These oxidation include routes to chemical compounds, remediation of pollutants, and combustion. Reductions that do not fit in any reduction reaction mechanism and in which just the change in oxidation state is reflected include the Wolff-Kishner reaction.
Link Archived 2008-05-15 at the Wayback Machine. This page was last edited on 6 March 2018, at 09:54. The true key to successful mastery of alkene reactions lies in practice practice practice. However, when you have a homework assignment, quiz,exam around the corner, it helps to have a reaction summary guide for quick reference. That’s why I created this alkene reaction overview.
For in-depth learning of alkene reactions watch my Tutorial Videos or visit my Reaction Library. See the detailed video explaining this cheat sheet linked on the bottom of this page. 18 Alkene Reaction Shortcuts in 15 Minutes The video below is a walk-through of the above cheat sheet explaining the reaction tricks and shortcuts. Tomorrow is my hydrocarbon test and I wonder 2 complete my whole revision within just 15-20 mins by using ur orgo cheat sheets and shortcut videos. Glad to hear I’ve helped you, Anshul! Just perfect for Late Revision notes!
Have you seen this tutorial for Aromaticity? Is the oxidative cleavage on your cheat sheet correct? I am struggling so bad in ochem, is there any way you can help me or give me tips? Exam was Monday but rained out in Houston. | <urn:uuid:6e408384-146c-46c0-99fe-84c5b29a21d4> | 3.5625 | 1,117 | Knowledge Article | Science & Tech. | 35.528182 | 95,540,354 |
Because most proteins are very large, complex molecules made up of hundreds or thousands of amino acids, they usually must be cut up into more manageable pieces for analysis. Today, this most commonly is done by using special enzymes called “proteases” that sever the chains at well-known locations. The protease trypsin, for example, cuts proteins at the locations of the amino acids lysine and arginine. Analyzing the residual fragments can identify the original protein. But enzymes are notoriously fussy, demanding fairly tight control of temperature and acidity, and the enzymatic cutting process can be time-consuming, from a matter of hours to days.
Illustration of the cleavage of proteins near a titanium dioxide surface: when illuminated with ultraviolet light, hydroxyl radicals are formed in water near the semiconductor's surface and cut proteins at the location of the amino acid proline. Credit: NIST
For a “radically” different approach, the NIST group turned to a semiconductor material, titanium dioxide. Titanium dioxide is a photocatalyst—when exposed to ultraviolet light its surface becomes highly oxidizing, converting nearby water molecules into hydroxyl radicals, a short-lived, highly reactive chemical species.** In the NIST experiments, titanium dioxide coatings were applied to a variety of typical microanalysis devices, including microfluidic channels and silica beads in a microflow reactor. Shining a strong UV light on the area, in the presence of a protein solution, creates a small “cleavage zone” of hydroxyl radicals that rapidly cut nearby proteins at the locations of the amino acid proline.
Although development work remains to be done, according to the researchers, the NIST photocatalysis technique offers several advantages over conventional enzyme cleavage of proteins. It’s not particularly sensitive to temperature or acidity, and needs no additional reagents other than dissolved oxygen in the solution. It’s a simple arrangement, easy to incorporate into a wide range of instruments and devices, and titanium dioxide, an inorganic material, will last virtually forever in a broad range of conditions—enzymes have to be treated carefully and stored in temperature-controlled environments. The target amino acid, proline, is relatively sparse in most proteins, but it’s found at key locations, such as sharp turns in the molecule, that aid analysis. And it’s fast—in trials with the protein angiotensin I, the team obtained detectable cleavage patterns in as little as 10 seconds.
Michael Baum | EurekAlert!
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For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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.
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In findings they believe are fundamentally important to both biology and medicine, chemists at the University of North Carolina at Chapel Hill have shown experimentally for the first time that proteins can behave differently inside cells than when taken out of those cells and studied in test tubes.
"For 40 years, we thought we could learn most everything about proteins by studying them in water, but this work shows we are missing important observations by looking at them just in water or other solutions," said Dr. Gary Pielak, professor of chemistry and lead author of the study. "Our work demonstrates that we need to study them under the conditions they are found in inside the cell."
The research is relevant to medicine because the protein is related to proteins associated with Parkinsons and Alzheimers diseases and cancer, the scientists say.
David Williamson | EurekAlert!
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
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Plant mothers talk to their embryos via the hormone auxin
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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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