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The University of Akron Wayne College∞Physics and Astronomy
Faculty: Dr. Tim Vierheller
What is physics?
Physics (Greek phusis: nature) is the science of Nature in the broadest sense. Physicists study the behavior and interactions of matter and energy across space and time, which are referred to as physical phenomena. Theories of physics are generally expressed as mathematical relations. Well-established theories are often referred to as physical laws or laws of physics. | <urn:uuid:e1d37f09-6182-4cbf-ac0c-d62ef5ea1f31> | 2.6875 | 103 | About (Org.) | Science & Tech. | 26.444737 | 95,573,607 |
about this item
An essential resource for learning about general relativity and much more, from four leading experts
Important and useful to every student of relativity, this book is a unique collection of some 475 problems--with solutions--in the fields of special and general relativity, gravitation, relativistic astrophysics, and cosmology. The problems are expressed in broad physical terms to enhance their pertinence to readers with diverse backgrounds.
In their solutions, the authors have attempted to convey a mode of approach to these kinds of problems, revealing procedures that can reduce the labor of calculations while avoiding the pitfall of too much or too powerful formalism. Although well suited for individual use, the volume may also be used with one of the modem textbooks in general relativity. | <urn:uuid:5039fa17-1179-4ab7-b6fc-e77f7a30b2a7> | 2.921875 | 152 | Product Page | Science & Tech. | 10.737884 | 95,573,647 |
Devil is indeed in the data and it is especially true for climate science and impacts. Global historical data on periods that were warm and warmer than today can provide insight on what the Earth may be like in the future owing to global warming, shows a new study published in journal Nature Geoscience.
The new global assessment based on warm periods over the past 3.5 million years, stresses on the urgency of reducing CO2 emissions to avert major environmental damages. It reveals that even with the Paris Agreement’s global warming limit of 2°C above preindustrial levels, climate zones and ecosystems will shift pole ward or to higher altitudes. The rapid polar warming may release significant additional greenhouse gases, and sea levels will rise by several meters over several thousand years, warns the study underscoring the urgency of reducing carbon dioxide emissions soon to meet the Paris Agreements in this century and beyond.
Long-term impacts underestimated
The study led by Hubertus Fischer, Katrin Meissner and Alan Mix has been conducted with a group of at least 60 scientists from 17 countries. The members of PAGES, Warmer Worlds have compiled evidence from the past to review the response of different components of the Earth System (such as marine and terrestrial ecosystems, ice sheets, sea ice etc.) to warming in various regions of the globe similar to what is expected for a maximum 1.5-2°C global warming as agreed upon in the Paris Agreement.
After comparing observations from the past with simulated data, the report says the long-term impact of warming, especially on Polar Regions, has been underestimated. It warns that even a warming of 1.5 to 2 degrees Celsius above preindustrial levels will be sufficient to trigger substantial long-term melting of ice in Greenland and Antarctica and sea-level rise of more than 6 meters, which will last for thousands of years. Also, the rate of sea-level rise may increase in comparison with the last decades.
Alan Mix of Oregon State University noted the importance of this sea-level rise while saying, “We are already beginning to see the effects of rising sea level. This rise may become unstoppable for millennia, impacting much of the world’s population, infrastructure, and economic activity that are located near the shoreline.”
Study warns 78 Indian cities of flooding
Resonating with projections by Alan Mix on rising sea level is another study published in the latest issue of Geophysical Research Letters that warns urban areas in India of frequent flooding due to increase in short‐duration precipitation extremes. This study, based on precipitation data, has warned of frequent and extreme flooding in 78 out of 89 Indian cities, if the global mean temperature (GMT) increases from 1.5 to 2°C from the pre‐industrial level. This study jointly conducted by Haider Ali and Vimal Mishra at IIT-Gandhnagar provides new insights into storm water designs in the rapidly urbanizing India.
In this study, the IIT-Gandhinagar has used the precipitation data to project future of Indian cities and would help plan climate-resilient cities. A similar study released in March 2018 had projected that the frequency of severe heat waves in India will increase 30-fold by 2100 under a 2°C warming scenario.
116-year-old data calls for urgent measures
The historical data, which is 116 years old, released by the India Meteorological Department (IMD) in Jan 2017 revealed that 2016 was the warmest year for India. In fact, India’s top five warmest years since 1901 have been recorded only in the last 15 years, showed the data. Another study that calculated temperature rise in terms of change occurring from decade to decade, using information from two different datasets from 1951 to 2013 too confirmed a rapid rise in surface temperatures in the past 70 years.
It has been established that India is the most vulnerable country in the world in terms of facing extreme weather events and needs adaptive measures at the regional level. This shows that there is a need for regional and regular data on climate vulnerability. The last comprehensive assessment of climate impacts released by the government in 2010 too had stressed on data gaps and demanded regional level data on—climate, natural ecosystems, soils, water from different sources, agricultural productivity and inputs and socio-economic parameters among others.
Data gaps remain
Even after eight years, the ministry of environment and forests has not been successful in collating regional level data on climate vulnerable sectors. While, the statistics related to climate change, released three years ago provided national-level information on temperature and few extreme weather events, it provided generic data on – ocean, biodiversity, health, soil, land and agriculture. The Envi-Stats 2018 released in April this year does provide state-level historical data on extreme weather events till 2016, but this too does not have regional figures, even though the information on glaciers provided is very useful.
With advances in data sciences, the scientists–global and national–will continue to project the future of our climate, based on current, historical data and simulations based on them.
As India celebrates National Statistics Day on June 29 with the theme ‘Quality Assurance of Official Statistics’, it is important that the Ministry of Statistics and Programme Implementation takes the lead to develop a comprehensive single-stop data repository on regional (district level) climate vulnerability along with other ministries.
While, the regional data and mapping of climate impacts will be an important key for an effective regional-level climate-resilient planning. It will also help the country monitor its progress in meeting the global SDG 13 that demands urgent action to combat climate change and its impacts. | <urn:uuid:5046e231-31e6-4d78-a2ae-3fc9e028e872> | 3.78125 | 1,150 | News Article | Science & Tech. | 28.976671 | 95,573,673 |
El Nino is a giant swell of abnormally warm water in the Pacific Ocean develops and sets off a chain reaction of weather events around the world and this year the weather scientists are predicting 2014 to be a major El Nino year with the consequences, and benefits that it brings.
The European Centre for Medium-range Weather Forecasts (ECMWF) have predicted with 90% certainty that El Niño is on its way and its going to be big.
'The amount of warm water in the Pacific is now significant, perhaps the biggest since the 1997-98 event' said Tim Stockdale, principal scientist at ECMWF, referring to the last full EL Nino year that produced the hottest year on record at the time and major global impacts.
India is expected to be the first to suffer, with weaker monsoon rains effecting the crop growing season before sweeping eastwards towards the Philippines where residents are being urged to save water to reduce the possible impact of the drier weather.
In Malaysia, the national water authority is preparing for a dry spell and contemplating water rationing and major effects are expected in Australia where 2013 was already its hottest year on record and El Nino is threatening to turn the temperature up even further and bring severe droughts.
On the flip side, as dry arid air turns east, wet weather spreads West bringing relief to areas such as parched California which is in the midst of an extreme drought. El Nino's also have the effect of damping down hurricane activity on the Eastern side of the United States.
Heavier than usual rainfall also brings floods in South American countries such as Ecuador, Peru, Chile and Argentina but potential drought relief in arid Chile and Bolivia.
By virtue of being on the opposite side of the globe, Europe is the continent least affected but we can get some minor knock on effects over here.
Throwing in a natural phenomenon with global warming is not going to be pretty, experts believing that climate change is driving bigger El Nino events as the seas warm and Prof Michael Raupach, director of the Climate Change Institute at the Australian National University warns that 'El Nino can be the thing that pushes you over the edge. It will be in the years when you get a big El Nino when you feel the impact of climate change the most'. | <urn:uuid:61e3ae13-1f72-4476-b7a6-22b188f4a2bc> | 3.1875 | 473 | Personal Blog | Science & Tech. | 33.79211 | 95,573,690 |
please write the incorrect line correctly
or the missing line please
Copy and paste gone horribly wrong, I'm afraid. Had one been following the instructions and actually writing the code there is no possible way it would look like this, not even by mistake. This is a mash-up.
Admit it. Or not. Either way.
so what to do now please help
The first line is fine, it initializes a global variable. Immediately following you want to get the raw input. That will give you something for
original. Once confirmed as word characters with some length we store the first letter. Now we have enough to construct a new string, with
word being defined as the lower of original.
new_word = word + first + pyg
The only step remaining is to take a slice of new_word and copy it back into that variable.
but i am not able to do that
can you please write the whole code please
No. You post yours, first, so we can copy and test it. A picture will not do.
ok i will type mine>>>>>>>>
pyg = 'ay'
new_word =word + first + pyg
original = raw_input('Enter a word:')
if len(original) > 0 and original.isalpha():
any replies ?????
i have typed my code
please can you reply now i have written my code | <urn:uuid:26bfc886-7cf4-417f-bc0f-c8285874eeeb> | 3.453125 | 292 | Comment Section | Software Dev. | 65.018217 | 95,573,710 |
The hearing sensitivity improves considerably in this way. The anterior part of the swim bladder functions in specialized fish species similar to an ear drum. Up to now the effects of the different swim bladder morphologies have not been investigated in detail in cichlid fishes.
Steatocranus tinanti has a tiny reduced swim bladder. Credit: Friedrich Ladich
The behavioural biologists of the University of Vienna Tanja Schulz-Mirbach and Friedrich Ladich as well as Brian Metscher from the Department of Theoretical Biology of the University of Vienna studied the relationship between the shape of the swim bladder and its function. "These fish are perfect for such an investigation because this fish family possesses a large variety of swim bladders ranging from tiny reduced ones to large highly specialized swim bladders with extensions up to the inner ear", the bioacoustician Tanja Schulz-Mirbach explains.
Different swim bladders
Currently we know approximately 1,300 species of cichlid fishes, which live in various habitats."Using microtomographic methods in cooperation with Brian Metscher we could reconstruct swim bladder specializations in detail", Tanja Schulz-Mirbach says. Some cichlid species such as the bottom-living Steatocranus tinanti inhabit fast flowing waters in the Congo river basin and their swim bladders are widely reduced. Cichlids which live in rather calm waters possess large bladders which either lack a connection to the inner ear such as the jewel cichlid Hemichromis guttatus or which possess anterior extensions bringing the swim bladder close to the inner ears. The Malagasy species Paratilapia polleni has simple tube-like swim bladder extensions whereas the Indian cichlid Etroplus maculatus has more complex extensions consisting of a gas-filled tube and a tissue pad which touches the inner ear.
Biologists in the bioacoustic lab of Friedrich Ladich measured hearing by recording acoustically evoked potentials (similar to EEGs) from the head of animals non-invasively. "We could show that species having specialized swim bladders detect higher sound frequencies and lower sound levels than species having reduced swim bladders", Schulz-Mirbach explains. However, the jewel cichlid which has a large swim bladder but no connection to the inner ear is also able to detect frequencies up to 3 kHz but only at higher sound levels. "This means that the presence of anterior swim bladder extensions results in better hearing but the size of the swim bladder is also important", explains Schulz-Mirbach says. She will continue to investigate the importance of the habitat noise on the development of hearing and if swim bladder specializations affect inner ear anatomy.
"Relationship between swim bladder morphology and hearing abilities. A case study on Asian and African cichlids": Tanja Schulz-Mirbach, Brian Metscher, Friedrich Ladich (PLoS ONE 2012) DOI: http://dx.plos.org/10.1371/journal.pone.0042292
Contacts:Dr. Friedrich Ladich
Friedrich Ladich | EurekAlert!
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:ab7e7fc3-c7e8-4351-8fa2-bc458371f34c> | 3.484375 | 1,305 | Content Listing | Science & Tech. | 39.022893 | 95,573,744 |
First results from the analysis of eight 'hot Jupiter' exoplanets suggest that winds and clouds play an important role in the atmospheric make up of these exotic planets. Catherine Huitson of the University of Exeter will present the results at the National Astronomy Meeting in St Andrews on Friday 5 July.
This is an artist's impression of a hot Jupiter.
Credit: NASA, ESA, and G. Bacon (STScI)
Hot Jupiters are giant exoplanets, similar in size to Jupiter, that orbit so close to their stars that their atmospheres can reach temperatures of 1000-3000 degrees Celsius. Astronomers can detect which gases are present in their atmospheres by analysing the spectrum of starlight filtered through the planet's atmosphere when the planet passes in front of the star. Last year, a team led by the University of Exeter was awarded nearly 200 hours on the NASA/ESA Hubble Space Telescope to examine eight planets using this technique – the largest survey of its type to date.
"These hot Jupiter planets are expected to have a vastly different composition from planets in our own Solar System like Jupiter, where temperatures at the cloud tops are around -150 degrees Celsius. The first planet we measured is one of the hottest to be observed, with a temperature of over 2000 degrees. The early results of the survey are now in, and they present a diverse range of puzzling properties," said Huitson.
The first, very hot planet observed showed an unexpected absence of titanium oxide. Current 3D models of hot Jupiter atmospheres suggest that grains of this heavy molecule should be circulated by fast winds, allowing gaseous titanium oxide to reach the observable upper atmosphere. The non-detection of the gas suggests that either the winds are not as strong as expected or the molecule is forming much larger grains that are too heavy be lifted.
Huitson explained, "Titanium oxide is a solid on Earth, but we expect it to be present in the atmosphere of the hottest hot Jupiters because of the extreme temperatures. This molecule is important because it could trap atmospheric heat high up forming a stratosphere – the same role ozone plays on Earth. However, our results show that this molecule is not present in the upper atmosphere, meaning that we need to revise our understanding of how wind processes distribute materials."
The team also made a confirmed detection of water vapour in the atmosphere of two planets. Importantly, the water was found in the quantities predicted by theory, contrasting with previously observed planets.
"While our models tell us that water (as steam) should be present in hot Jupiter atmospheres, until now the molecule has only been seen in limited quantities and in fewer planets than expected," said Huitson.
"Seeing steam in two exoplanets is a great confirmation of current theory. Our new findings suggest that previous non-detections were caused by opaque, high-up clouds obscuring the parts of the atmosphere where steam is present."
The results presented at the National Astronomy Meeting represent initial findings and work by the team is still ongoing to analyse all the data from the eight-planet Hubble survey.
"A surprising diversity is emerging from the continuing observations among planets with similar temperatures, and the remaining results are sure to present even more surprises as we try to understand such extreme and unknown objects," said Huitson.
IMAGESFigure1: An artist's impression of the sort of a hot Jupiter (credit: NASA, ESA, and G. Bacon (STScI)).
http://www.spacetelescope.org/static/archives/images/screen/opo0707a.jpgFigure 2: Diagram showing the method used to detect atmospheric components (credit ESA/David Sing).
SCIENCE CONTACTSCatherine Huitson
Tel: +44 (0)1334 462231, +44 (0)1334 46 2232
NOTES FOR EDITORS
Bringing together more than 600 astronomers and space scientists, the RAS National Astronomy Meeting (NAM 2013) will take place from 1-5 July 2013 at the University of St Andrews, Scotland. The conference is held in conjunction with the UK Solar Physics (UKSP: http://www.uksolphys.org) and Magnetosphere Ionosphere Solar Terrestrial (MIST: http://www.mist.ac.uk) meetings. NAM 2013 is principally sponsored by the RAS, STFC and the University of St Andrews and will form part of the ongoing programme to celebrate the University's 600th anniversary.
Meeting arrangements and a full and up to date schedule of the scientific programme can be found on the official website at http://www.nam2013.co.uk
About the University of Exeter
The Sunday Times University of the Year 2012-13, the University of Exeter is a Russell Group university and in the top one percent of institutions globally. It combines world-class research with very high levels of student satisfaction. Exeter has over 18,000 students and is ranked 7th in The Sunday Times University Guide, 10th in The Complete University Guide, 10th in the UK in The Times Good University Guide 2012 and 12th in the Guardian University Guide 2014. In the 2008 Research Assessment Exercise (RAE) 90% of the University's research was rated as being at internationally recognised levels and 16 of its 31 subjects are ranked in the top 10, with 27 subjects ranked in the top 20.
The University has invested strategically to deliver more than £350 million worth of new facilities across its campuses in the last few years; including landmark new student services centres - the Forum in Exeter and The Exchange in Cornwall - and world-class new facilities for Biosciences, the Business School and the Environment and Sustainability Institute. It has plans for another £330 million of investment between now and 2016.
The Royal Astronomical Society (RAS: http://www.ras.org.uk, Twitter: @royalastrosoc), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.
The Science and Technology Facilities Council (STFC: http://www.stfc.ac.uk, Twitter: @stfc_matters) is keeping the UK at the forefront of international science and tackling some of the most significant challenges facing society such as meeting our future energy needs, monitoring and understanding climate change, and global security. The Council has a broad science portfolio and works with the academic and industrial communities to share its expertise in materials science, space and ground-based astronomy technologies, laser science, microelectronics, wafer scale manufacturing, particle and nuclear physics, alternative energy production, radio communications and radar. It enables UK researchers to access leading international science facilities for example in the area of astronomy, the European Southern Observatory.
Founded in the 15th century, St Andrews is Scotland's first university and the third oldest in the English speaking world. Teaching began in the community of St Andrews in 1410 and the University was formally constituted by the issue of Papal Bull in 1413. The University is now one of Europe's most research intensive seats of learning – over a quarter of its turnover comes from research grants and contracts. It is one of the top rated universities in Europe for research, teaching quality and student satisfaction and is consistently ranked among the UK's top five in leading independent league tables produced by The Times, The Guardian and the Sunday Times.
The University is currently celebrating its 600th anniversary and pursuing a £100 million fundraising campaign, launched by Patron and alumnus HRH Prince William Duke of Cambridge, including £4 million to fund the creation of an 'Other Worlds' Think Tank and Observatory. The new think tank and Observatory project will extend the University of St Andrews' flagship work on extra-solar planets, and provide a creative environment for problem-focused research, education and continuing public engagement.
Jo Bowler | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:d753e9d4-28a0-477f-8d81-d8e0e5d89d4c> | 3.46875 | 2,356 | Content Listing | Science & Tech. | 38.210411 | 95,573,745 |
James Clark, The George Washington University’s Ronald B. Weintraub Professor of Biology, and Xu Xing, of the Chinese Academy of Science’s Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, have discovered a unique beaked, plant-eating dinosaur in China.
This finding demonstrates that theropod, or bird-footed, dinosaurs were more ecologically diverse in the Jurassic period than previously thought and offers important new evidence about how the three-fingered hand of birds evolved from the hand of dinosaurs. The discovery is featured in this week’s edition of the journal Nature.
“This new animal is fascinating in and of itself, and when placed into an evolutionary context it offers intriguing evidence about how the hand of birds evolved,” said Dr. Clark. Clark’s graduate student, Jonah Choiniere, also was involved in analyzing the new animal.
Dr. Xu, said, “This discovery is truly exciting, as it changes what we thought we knew about the dinosaur hand. It also is amazing to bring conciliation between the data from million-year-old bones and molecules of living birds.”
Limusaurus inextricabilis (meaning "mire lizard who could not escape") was found in 159 million-year-old deposits located in the Junggar Basin of Xinjiang, northwestern China. The dinosaur earned its name from the way its skeletons were preserved, stacked on top of each other in fossilized mire pits that were the subject of a 2008 National Geographic film, “Dino Death Trap.” A close examination of the fossil shows that its upper and lower jaws were toothless, demonstrating that the dinosaur possessed a fully developed beak. Its lack of teeth, short arms without sharp claws and possession of gizzard stones suggest that it was a plant-eater, though it is related to carnivorous dinosaurs.
The newly discovered dinosaur’s hand is unusual and provides surprising new insights into a long-standing controversy over which fingers are present in living birds, which are theropod dinosaur descendants. The hands of theropod dinosaurs suggest that the outer two fingers were lost during the course of evolution and the inner three remained. Conversely, embryos of living birds suggest that birds have lost one finger from the outside and one from the inside of the hand. Unlike all other theropods, the hand of Limusaurus strongly reduced the first finger and increased the size of the second. Drs. Clark and Xu and their co-authors argue that Limusaurus’ hand represents a transitional condition in which the inner finger was lost and the other fingers took on the shape of the fingers next to them. The three fingers of most advanced theropods are the second, third and fourth fingers—the same ones indicated by bird embryos—contrary to the traditional interpretation that they were the first, second and third.
Limusaurus is the first ceratosaur known from East Asia and one of the most primitive members of the group. Ceratosaurs are a diverse group of theropods that often bear crests or horns on their heads, and many have unusual, knobby fingers lacking sharp claws.
The fossil beds in China that produced Limusaurus have previously yielded skeletons of a variety of dinosaurs and contemporary animals described by Drs. Clark and Xu and their colleagues. These include the oldest tyrannosaur, Guanlong wucaii; the oldest horned dinosaur, Yinlong downsi; a new stegosaur, Jiangjunosaurus junggarensis; and the running crocodile relative, Junggarsuchus sloani.
This research was funded in part by the National Geographic Society, the National Science Foundation Earth Science Division, the Chinese National Natural Science Foundation, the Jurassic Foundation and the Hilmar Sallee bequest.
Dr. Clark has spent the last 18 years searching the Gobi Desert for dinosaurs. In 1991, he helped organize the first American expedition to Mongolia with the American Museum of National History. For the past seven years, his field work with Dr. Xu has focused on dinosaurs from the middle of the Jurassic Period, in the far western reaches of the Gobi.
The article, "A Jurassic ceratosaur from China and its significance for theropod digit reduction and avian digital homologies" appears in the June 18 edition of Nature. Nature is a weekly international journal publishing peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions.
Located four blocks from the White House, The George Washington University was created by an Act of Congress in 1821. Today, GW is the largest institution of higher education in the nation's capital. The university offers comprehensive programs of undergraduate and graduate liberal arts study, as well as degree programs in medicine, public health, law, engineering, education, business, and international affairs. Each year, GW enrolls a diverse population of undergraduate, graduate, and professional students from all 50 states, the District of Columbia, and more than 130 countries.
For more news about The George Washington University, visit www.gwnewscenter.org.
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:6cb688ce-736f-47f6-993f-789e370f6e2b> | 3.578125 | 1,696 | Content Listing | Science & Tech. | 37.185142 | 95,573,758 |
Using massive clusters of galaxies as "cosmic telescopes," a research team led by a Johns Hopkins University astronomer has found what may be infant galaxies born in the first billion years after the beginning of the universe.
Figure 1. (Abell 2218) The figure shows a three color image of the massive cluster of galaxies Abell 2218 taken with the Advanced Camera for Surveys in the Hubble Space Telescope. The distance to the cluster is approximately 2.5 billion light years. The blue arcs are star-forming galaxies that are behind the cluster approximately half way across the Universe. This is a beautiful example of a "cosmic telescope". Credit: H. Ford (JHU), W. Zheng (JHU), L. Infante (PUC), V. Motta(PUC, JHU), M. Postman (STScI), G. Illingworth (UCSC), M. Jee (JHU), R. White (STScI), N. Benitez (IAA), T. Broadhurst (Tel-Aviv Univ.), and NASA
If these findings are confirmed, the extra magnification provided by these gargantuan natural telescopes will have given astronomers their best-ever view of galaxies as they formed in the early universe, more than 12 billion years ago, said Holland Ford, a professor in the Henry A. Rowland Department of Physics and Astronomy at the universitys Krieger School of Arts and Sciences. Ford is the head of the Hubble Space Telescopes Advanced Camera for Surveys Science Team, which also includes researchers from the Space Telescope Science Institute, PUC in Chile, and other universities around the world.
Ford announced the teams results this morning at the American Astronomical Society meeting in Calgary, Alberta, Canada. The teams spectroscopic observations were made possible, he said, by gravitational lensing, the bending of light caused by gravitys warping of space in the presence of such massive objects as clusters of galaxies.
Lisa DeNike | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:1524f3bf-f06d-4ec3-89ef-faf46ff305df> | 3.3125 | 1,051 | Content Listing | Science & Tech. | 42.284196 | 95,573,759 |
Name the three isotopes of the element whose atomic number is 1. (b) What collective name do we give to a mixture of these three isotopes when they are present in the same ratios as in the universe as a whole?© BrainMass Inc. brainmass.com July 20, 2018, 3:17 am ad1c9bdddf
Protium: this one has no neutrons in the nucleus
Deuterium: this one has one neutron in the nucleus ...
Isotopes of hydrogen, with atomic number of 1, is determined. There are three possible isotopes with different numbers of neutrons in the atomic shell. | <urn:uuid:fb8bbf78-01c4-4064-85b1-afdae3b4e23d> | 3.109375 | 132 | Q&A Forum | Science & Tech. | 58.533889 | 95,573,766 |
Life Out of Bounds
Bioinvasion in A Borderless WorldBook - 1998
Worldwatch Institute researcher Chris Bright explains why conservation biologists are raising the alarm about a global threat to biodiversity that is unfolding largely unnoticed -- bioinvasion, the spread of alien, "exotic" organisms.With the exception of a few spectacular invasions, like the zebra mussel's conquest of the Great Lakes, there has been little public recognition of the dangers posed by these invading species. But exotic species are injuring our biological wealth on virtually every level -- from the genetic (when exotics interbreed with native species) to the wholesale transformation of landscapes.Life Out of Bounds shows that this "biological pollution" is now beginning to corrode the world's economies as well. But the policy responses, on both the national and international levels, have usually been weak and uncoordinated. This book outlines the current scientific research on the threat, the social and economic implications if these invasions are allowed to continue unchecked, and steps that can be taken to contain the spread of exotic species.
Publisher: New York, NY : W.W. Norton, 1998
Characteristics: 288 p. | <urn:uuid:393a29c8-afbb-47a2-8ab9-1eb53cd0f379> | 2.96875 | 241 | Product Page | Science & Tech. | 30.677367 | 95,573,768 |
When he’s not busy living out at sea and working with some of the world’s deadliest sea creatures, Richard is a marine biology research fellow at James Cook University and an Emmy-award-winning cinematographer. He may be risking his life in the process, but the research done by Richard and the team at Biopixel informs conservation strategies that help to protect and conserve the Great Barrier Reef. From measuring the metabolic systems of sharks to projects that increase turtle nesting and hatchling success, Richard is out there on the Reef gaining knowledge through his work that is invaluable for conservation.
Tiger Shark Project
A big part of protecting our precious marine biodiversity is conserving migration patterns of marine animals like sharks, turtles and whales. One of these species is the magnificent tiger shark, Galeocerdo cuvier, an iconic species of the Great Barrier Reef and an important apex predator.
Threats to migration, and tiger sharks, include habitat loss/degradation, climate change, creation of barriers, over-fishing or over-exploitation, as well as lack of awareness and information about migration patterns and their importance. Further research is needed to understand what drives migration, location of key habitats, and identify the threats to migration.
Impact on the Reef
As apex predators, tiger sharks are essential to maintaining ecological balance in the ocean, and this filters right down to the corals which house their prey. Tiger sharks are the main species affected by the culling programs in Australia. Since 1993, between 175 and 400 tiger sharks are killed each year in the Queensland Shark Control Program. If we are going to develop new and effective methods for protecting people and sharks, we need to understand their movement behaviour and habitat use.
Action being taken
The project is currently expanding previous research at Raine Island, studying tiger sharks to include most of the Queensland coast from the Fraser Island in the south, up to the GBR Marine Park and the Torres Strait in the north. This newly expanded long-term project will continue to study tiger sharks using satellite and acoustic transmitters to find out more about their movement behaviour, habitat use and migration patterns. Expansion of the project has so far seen tiger sharks tagged with satellite and acoustic tags at Batt Reef off Cairns and Fraser Island.
- Gather data and build awareness of the importance of apex predators like the tiger shark for marine environments like the GBR
- Determine if tiger sharks migration/movement strategies are driven by diet and/or reproduction.
- Evaluate the effectiveness of conservation strategies for highly mobile species such as tiger sharks
With enough support, this project will:
- Funds are needed to increase sample size and locations we work in - the Qld coast is long and we need to target other areas apart from Batt and Raine.
- With enough support we can study tiger sharks along the entire Queensland coast
- Develop material for school education – visit schools
Carry your Cupby Take 3 for the SeaCitizens Goal: 2500
87341 days to go
Sponsor a COTS Diverby Association of Marine Park Tourism OperatorsDonations Goal: $2500
$247541 days to go
Marine Debris, Plastics, Emissions
Banish the bagby Boomerang BagsCitizens Goal: 2500
122441 days to go
Unite for the reef.
Together, we can ease the pressures that the reef faces - but we need your support to do it. Because it’s only when we’re united as Citizens, that our individual actions can come together to make a real, physical impact on the Great Barrier Reef. | <urn:uuid:ab98eddd-d66a-4f58-931f-c0f4df912f95> | 3.3125 | 748 | About (Org.) | Science & Tech. | 31.883505 | 95,573,780 |
Species Detail - Pacific Golden Plover (Pluvialis fulva) - 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).
Pacific Golden Plover
9 March (recorded in 1997)
19 October (recorded in 1991)
National Biodiversity Data Centre, Ireland, Pacific Golden Plover (Pluvialis fulva), accessed 21 July 2018, <https://maps.biodiversityireland.ie/Species/10847> | <urn:uuid:c4664b78-4e37-4ef6-bf4b-0594ed0d3d1a> | 2.84375 | 146 | Structured Data | Science & Tech. | 35.901 | 95,573,783 |
Introduction to GraphQL
Introduction to GraphQL
Learn about GraphQL, a platform that uses flexible syntax and systems that simply describe your data requirements and interactions.
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Creating a web application can seem like a complicated task depending on how many functions should be in it. In any situation, development requires lots of effort from developers — starting with architecture, then frontend and backend development, and then, of course, testing. Some may compare the process of application creation to an onion, which has lots of different layers. One of the layers that is really important is where you have to arrange a special inquiry tool.
Don’t know what it is?
Inquiry tools are the bridges that make it possible to get data from the backend. Seem clear and simple? The process of such tool-building can be really challenging, especially if you are a junior developer. For that purpose, various companies and organizations have created a lot of helpful platforms that make it easier to start and understand the development process. One of such platform is GraphQL. Despite its newness, many top development companies globally have used it a lot in their projects.
Surely, you want to know more, but let’s start with the basics.
What Is the Purpose of GraphQL?
GraphQL was created directly for different APIs. Its main purpose is to use flexible syntax and systems that simply describe the data requirements and interactions. Throughout its history, GraphQL became an example of properly functioning and reliable software, which could be used in a pretty simple way — even by junior-level programmers. Thanks to its features and opportunities, which have been implemented by the creators, GraphQL was able to replace other earlier customized tools, which have been designed for the same purpose. When we discuss the functions and aspects of GraphQL, it is essential to present those key opportunities.
GraphQL was based on the usage of different important functions. What are they?
- First of all, the essential primary function is schema. When you are using that tool, you get the opportunity to collect various inquiries in a proper way to avoid a mess. Even more, thanks to the simplicity, the entire process of collecting all needed inquiries became much faster and easier. So, there is no need, for now, to write a huge piece of code just to achieve an easy purpose.
- The second one is a function called query. That function operates with the inquiries on reading types with attributes. For any system operating with APIs, that function could play one of the most important roles. Thus, in order to make it much more straightforward, the creators replaced various functions and options with only one, which is also really useful if you have a bit of practice in this area.
- Mutation is another essential function focused on the inquiries of the type recording. It’s interesting to know that GraphQL is operated only through the usage of several function sets, and it is really better comparing to those systems that have been used previously.
- The attribute function makes it possible to launch a filtered and detailed search. It becomes valuable if you need a direct and certain response to a certain inquiry.
- The last two tools, type and field, were made regarding entity description and key characteristics of a type, respectively.
Advantages and Disadvantages of GraphQL
No one could argue that a tool is totally perfect. While you are thinking about starting to use GraphQL, it's good to learn the advantages and disadvantages of it.
What Are the Pros?
- Development time. As you may have already noticed, one of the main benefits of GraphQL is that you, as a potential user, can do some development things much more quickly. For example, instead of writing huge texts of code, it may be enough just to use one or two primary functions to achieve what you need.
- Opportunity to simply perform changes. The next pro is the high level of flexibility of your project. It is possible thanks to the simplicity of code writing. Even if you have a fully operational and finished program, you still have the opportunity to alter it in any way you need and want, making it more sophisticated — or, as a contrast, more simple and clear for those who are going to use your application. So, the flexibility of the code structure and entire system deserves the first place in the list of all of the benefits of that very system.
- Simple understanding. Another positive feature is the high level of organization within the system itself. You may remember that previously, we were talking about the type function. Thanks to this function, the searching process becomes elementary for any user. Due to the existence of such a tool, any person can get what they need without a mound of useless data and information. Thus, you may be able to evaluate the entire potential of GraphQL as a system for the usage of any person regardless of their qualification in a specific area.
- Documentation magic. Another benefit of GraphQL is a function of self-documentation, which allows you not to worry about the formalities. If you are using an older version of the software similar to GraphQL, it is possible to face useless and pretty complicated documentation within the code itself, which is not good if you are dealing with a big project and have to deal with other many essential aspects of it while setting the priorities wisely.
However, don’t forget about inconvenient features. You may think that they are not so valuable during the development process. But forewarned is forearmed.
What Are the Cons?
GraphQL suffers from a lack of a proper middleware structure. This could be solved by dividing it into different schemes. It is possible to make the API so that the functionality is grouped according to which middleware they need closed, but many schemes are not the best option.
Of course, the development process would not be stuck if your entire project is functions-compact. Keep in mind that you may have to deal with such an issue.
Another thing is the problem with bugs. We have to admit and keep in mind that during the development process, it will not be a surprise at all if you face several severe and harmful bugs that will make it impossible to properly regulate the API. Due to this, making backups becomes an essential task if you are interested in a good result and a fully functioning and well-regulated program. But who doesn't face this, right?
How to Use GraphQL
These steps will help you organize the right flow. Just follow them one by one.
Installation of GraphQL
Operating with this language, in theory, looks pretty simple. To install GraphQL, you may need only your brain, your hands, and a computer. The installation begins with a composer that is already really comprehensive. This means, that you do not need a tone of various additional extensions and programs to launch that machine. Installation can be launched only through one particular function:
composer.json. If you are going to use it with a connection to Laravel, going here is a good decision.
How to Create a Schema
As with the majority of things in GraphQL, the creation of a schema is simple. Schemas are useful if you have to include public endpoints into your project. Moreover, those that need identification may require a lot of your attention. So, in order to arrange a schema, you may need two basic tools: function and facade. Combining these tools, you may be able to operate with a finished version of a schema for your API without any problems and complications.
How to Create a Query
First of all, you have to arrange a type. After you create one, you must add it to a special files folder, which is config/graphql.php. After that, you may be sure that a half of the job is done and you need only to implement some final frames to get a proper result. After that step, you need to be really careful and find out the queries that have to return a particular type. Finally, you must add all that you have to the same folder config/graphql.php.
How to Arrange a Mutation
The creation of a mutation may be similar to the query creation. Lots of the operations within GraphQL tend to have similar algorithms, meaning that you just need to keep in mind how to use the basics and then later put more and more layers on your fundamental knowledge. Mutations accept arguments and then return certain types. For example, you may use it if you have an obligation to change your password. Now, you need to use the function, which is called resolve. That tool allows you to upgrade an existing model and then return it after the improvements. You may also use different validation rules. Yes, maybe it's going to be more complicated, but anyway, it is a kind of diversity. In the very end, when you already have a finished function, you have to add it to an already well-known folder, which is config/graphql.php.
How to Make a Flow
The flow is the most complex part of the usage of GraphQL due to the fact that you need to make a lot of movements here. So, first of all, you have to write the type for each of the objects. And for creation type, you need the finished model.
After its creation, you must define for which fields you need them and then deal with the method of returning them. After that, you have to register all of the types in the schema, as in the example above. But there is a pretty important feature that you have to keep in mind: if the object you are going to make is independent, you must write a query for it. Finally, after you have all of the needed elements, you have to design a mutation while using all of the components.
In this article, our team was doing our best to show how to operate with a query manager as widespread as GraphQL. Due to the fact that it is becoming more and more popular, lots of the businessmen and beginning programmers who are interested in the creation of their own applications start looking for the skilled experts who always are ready to help. Mostly, they face two options: choosing highly expensive IT companies or choosing freelancers, who are not always reliable.
Opinions expressed by DZone contributors are their own. | <urn:uuid:f9ceaebf-b256-402f-b306-4fc5ccbf0ca8> | 3.015625 | 2,162 | Truncated | Software Dev. | 50.456154 | 95,573,799 |
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These are the problems I'm having with the ground up hypothesis; assuming that
protobirds already had elongated feathers on their arms, what advantage would
this give a ground running predator? If they leapt into the air, these "wings"
would actually slow them down due to drag, making them more vulnerable to
predators. I think a more streamlined animal with powerful legs and no "wings"
at all would make more sense for a specialized "jumper" (kangaroo). Also, why
would they be leaping up into the air in the first place? To catch insects? No
animal that does this exists. If they evolved simple wings to provide lift
while running, wouldn't this actually reduce traction and in turn slow them
down and make them less stable? To me, an at least somewhat arboreal animal
that used it's elongated feathers or even protofeathers to parachute from an
elevated position makes more sense; I will not recite all the proposed stages
of flight that would gradually develop from that that point, because
others have already explained it better than I ever could.
Regarding potential arboreality in archaeopterx; I think one only needs to
look at the modern hoatzin chick
http://en.wikipedia.org/wiki/Image:Hoatzin_chick.jpg. Here is a fully modern
bird that, in the early stages of its life, has claws that are very similar to
those found on archaeopterx, which it uses purely for climbing. Now I know this
is probably the 10,000th time this has been brought up, but I think it's a
pretty damn good example of a modern flightless dinsoaur possibly reverting
back to its ancestral condition. Some claim archaeopteryx lacks adaptations for
arboreality, yet they had greatly elongated fingers that would have been good
for little else other than climbing, or swimming. Primitive bats had greatly
elongated fingers with claws on all five digits which they used for climbing as
well. Fossil bats make a good case for at least one group of flying animals
evolving from arboreal gliders.
There is a strong selective advantage for an arboreal animal to evolve some
sort of parachute or gliding system to prevent injury from falling or to
conserve energy by leaping from tree to tree instead climbing all the way down
and back up a tree trunk, or cliff face: this is made obvious by the large
number of arboreal creatures that have evolved in this way. On the other hand,
you do not see any primarily ground running, leaping animals evolving some sort
of simple gliding or flight system; the only animals that do anything like this
are birds, yet they already have a fully developed and highly sophisticated
flight mechanism. There are plenty of jumping, kangaroo like animals, yet none
of them have evolved wing membranes or any organ other than stronger legs (and
smaller arms) to increase airtime.
I know my earlier statements were pretty unscientific (if not downright
ignorant) but at least it got some people riled up and resulted in some very
informative, thought provoking responses.
I love this Mailing list =)
- From: jrc <email@example.com> | <urn:uuid:573b8a3c-87e5-4220-b805-8fc842ef3277> | 3.40625 | 728 | Comment Section | Science & Tech. | 41.773399 | 95,573,807 |
Why is Java called the ‘Platform Independent Programming Language’?
Platform independence means that execution of your program does not dependent on type of operating system(it could be any : Linux, windows, Mac ..etc). So compile code only once and run it on any System (In C/C++, we need to compile the code for every machine on which we run it). Java is both compiler(javac) and interpreter(jvm) based lauguage. Your java source code is first compiled into byte code using javac compiler. This byte code can be easily converted to equivalent machine code using JVM. JVM(Java Virtual Machine) is available in all operating systems we install. Hence, byte code generated by javac is universal and can be converted to machine code on any operating system, this is the reason why java is platform independent.
Explain Final keyword in java?
Final keyword in java is used to restrict usage of variable, class and method.
Variable: Value of Final variable is constant, you can not change it.
Method: you can’t override a Final method.
Class: you can’t inherit from Final class.
Refer this for details
When is the super keyword used?
super keyword is used to refer:
- immediate parent class constructor,
- immediate parent class variable,
- immediate parent class method.
Refer this for details.
What is the difference between StringBuffer and String?
String is an Immutable class, i.e. you can not modify its content once created. While StringBuffer is a mutable class, means you can change its content later. Whenever we alter content of String object, it creates a new string and refer to that,it does not modify the existing one. This is the reason that the performance with StringBuffer is better than with String.
Refer this for details.
Why multiple inheritance is not supported in java?
Java supports multiple inheritance but not through classes, it supports only through its interfaces. The reason for not supporting multiple inheritance is to avoid the conflict and complexity arises due to it and keep Java a Simple Object Oriented Language. If we recall this in C++, there is a special case of multiple inheritance (diamond problem) where you have a multiple inheritance with two classes which have methods in conflicts. So, Java developers decided to avoid such conflicts and didn’t allow multiple inheritance through classes at all.
Can a top level class be private or protected?
Top level classes in java can’t be private or protected, but inner classes in java can. The reason for not making a top level class as private is very obvious, because nobody can see a private class and thus they can not use it. Declaring a class as protected also doesn’t make any sense. The only difference between default visibility and protected visibility is that we can use it in any package by inheriting it. Since in java there is no such concept of package inheritance, defining a class as protected is no different from default.
What is the difference between ‘throw’ and ‘throws’ in Java Exception Handling?
Following are the differences between two:
- throw keyword is used to throw Exception from any method or static block whereas throws is used to indicate that which Exception can possibly be thrown by this method
- If any method throws checked Exception, then caller can either handle this exception(using try catch block )or can re throw it by declaring another ‘throws’ clause in method declaration.
- throw clause can be used in any part of code where you feel a specific exception needs to be thrown to the calling method
throw new Exception(“You have some exception”)
throw new IOException(“Connection failed!!”)
throws IOException, NullPointerException, ArithmeticException
What is finalize() method?
Unlike c++ , we don’t need to destroy objects explicitly in Java. ‘Garbage Collector‘ does that automatically for us. Garbage Collector checks if no references to an object exist, that object is assumed to be no longer required, and the memory occupied by the object can be freed. Sometimes an object can hold non-java resources such as file handle or database connection, then you want to make sure these resources are also released before object is destroyed. To perform such operation Java provide protected void finalize() in object class. You can override this method in your class and do the required tasks. Right before an object is freed, the java run time calls the finalize() method on that object. Refer this for more details.
Difference in Set and List interface?
Set and List both are child interface of Collection interface. There are following two main differences between them
- List can hold duplicate values but Set doesn’t allow this.
- In List interface data is present in the order you inserted but in the case of Set insertion order is not preserved.
What will happen if you put System.exit(0) on try or catch block? Will finally block execute?
By Calling System.exit(0) in try or catch block, we can skip the finally block. System.exit(int) method can throw a SecurityException. If Sysytem.exit(0) exits the JVM without throwing that exception then finally block will not execute. But, if System.exit(0) does throw security exception then finally block will be executed.
This article is compiled by Dharmesh Singh.
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- IdentityHashMap get() Method in Java | <urn:uuid:7fc5967e-444f-488e-bf82-2aebebccd0d5> | 3.46875 | 1,380 | Q&A Forum | Software Dev. | 42.201958 | 95,573,818 |
The mass of an electron appears prominently in many of the fundamental laws that govern the subatomic realm, yet direct measurement has been complicated by the particle’s scrawny mass. Now, a team of physicists has overcome this challenge to produce the most precise electron mass measurement ever made.
Instead of trying to measure the mass directly, the researchers bound a single electron to a bare carbon nucleus and placed the resulting atom in a uniform electromagnetic field called a Penning trap. Inside the trap, the atom began oscillating in circles with a steady frequency.
The team then shot the trapped atom with microwaves, causing the spin of the electron to flip up and down. By comparing the frequency of the atom's circular movements with the frequency of the spin-flipping microwaves, the team used quantum electrodynamics equations to derive the mass of the electron compared with a proton.
The team's new measurement is 13 times more precise than previous efforts, with an uncertainty of just 0.03 parts per billion, the researchers report online today in Nature. The group’s precise result will help physicists more accurately calculate the fine-structure constant, an important value in tests of the standard model of particle physics, which shapes our understanding of the basic building blocks of the universe. | <urn:uuid:a62f9a76-cf4a-4f09-b263-020787e7afc3> | 3.984375 | 260 | News Article | Science & Tech. | 33.410639 | 95,573,828 |
posted by Tong
Consider the following reaction in the solvent CCl4 in a 1-L flask:
What is the equilibrium moles of IBr, Br2 and I2 are 0.2, 0.1 and 0.1, calculate the equilibrium constant Kc.
I assume you mean the equilibrium mols are as given and you want to know Kc.
(IBr) = 0.2/1 L - 0.2M
(Br2) = 0.1/1) = 0.1M
(I2) = 0.1/1) = 0.1M
Then Kc = (Br2)*(I2)/(IBr)^2
Substitute and solve for Kc. | <urn:uuid:691d3d67-e0f0-4ee5-bf42-e13ee1cde798> | 2.609375 | 157 | Q&A Forum | Science & Tech. | 118.031299 | 95,573,829 |
34°C / 93°F
The measurements for the water temperature in Kálymnos are provided by the daily satellite readings provided by the NOAA. The temperatures given are the sea surface temperature (SST) which is most relevant to recreational users.
The graph below shows the range of monthly Kálymnos water temperature derived from many years of historical sea surface temperature data.
These average ocean temperatures for Kálymnos are calculated from several years of archived data.
Whilst sea temperatures for Kálymnos are as accurate as current data allows, there may be slight local and regional variations depending on conditions. Time of day and wind direction may have a temporary local effect as can water flows from neraby rivers. | <urn:uuid:ed6d9ea2-73b7-47ef-bfc9-0b1505f0919f> | 2.609375 | 151 | Knowledge Article | Science & Tech. | 23.846149 | 95,573,838 |
By Tobias Holck Colding, William P. Minicozzi II
Minimum surfaces date again to Euler and Lagrange and the start of the calculus of adaptations. a number of the innovations built have performed key roles in geometry and partial differential equations. Examples comprise monotonicity and tangent cone research originating within the regularity thought for minimum surfaces, estimates for nonlinear equations in keeping with the utmost precept bobbing up in Bernstein's classical paintings, or even Lebesgue's definition of the essential that he constructed in his thesis at the Plateau challenge for minimum surfaces. This booklet begins with the classical conception of minimum surfaces and finally ends up with present study themes. Of some of the methods of impending minimum surfaces (from advanced research, PDE, or geometric degree theory), the authors have selected to target the PDE features of the idea. The ebook additionally comprises the various functions of minimum surfaces to different fields together with low dimensional topology, normal relativity, and fabrics technology. the one necessities wanted for this booklet are a simple wisdom of Riemannian geometry and a few familiarity with the utmost precept
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This creation to the idea of advanced manifolds covers an important branches and techniques in complicated research of numerous variables whereas thoroughly fending off summary strategies regarding sheaves, coherence, and higher-dimensional cohomology. in simple terms common tools comparable to strength sequence, holomorphic vector bundles, and one-dimensional cocycles are used.
Advanced variables is an exact, based, and attractive topic. offered from the viewpoint of contemporary paintings within the box, this new ebook addresses complex issues in complicated research that verge on present components of analysis, together with invariant geometry, the Bergman metric, the automorphism teams of domains, harmonic degree, boundary regularity of conformal maps, the Poisson kernel, the Hilbert remodel, the boundary habit of harmonic and holomorphic features, the inhomogeneous Cauchy–Riemann equations, and the corona challenge.
"And what's the use," suggestion Alice, "of a booklet with no photos or conversations in it? " -Lewis Carroll This publication is written for modem undergraduate scholars - now not the perfect stu dents that arithmetic professors want for (and who sometimes grace our campuses), however the scholars like many the writer has taught: gifted yet ap preciating evaluate and reinforcement of prior direction paintings; keen to work flat out, yet difficult context and motivation for the math they're studying.
This booklet examines the interesting interface among differential geometry and continuum mechanics, now recognized as being of accelerating technological value. themes mentioned comprise isometric embeddings in differential geometry and the relation with microstructure in nonlinear elasticity, using manifolds within the description of microstructure in continuum mechanics, experimental dimension of microstructure, defects, dislocations, floor energies, and nematic liquid crystals.
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Additional info for A course in minimal surfaces
Shefel’ (1974) Shefel’ (1975)). If a Cl-smooth surface F is an affinely stable immersion in E3 of a metric of one of the classes Ki. K,, K,, then F is a normal surface of non-negative curvature, a saddle surface, or a normal developable surface, respectively. 4. Gauss’s Theorem. One of the basic relations between the intrinsic and extrinsic geometries of smooth surfaces in E3 is Gauss’s theorem, which says that the curvature of the intrinsic metric of a surface is equal to the area of its spherical image.
Z. 1 of Ch. 3). Hence it is easy to conclude that m+(v) is equal to the largest number of pairwise disjoint crusts that can be cut off by hyperplanes with normal directed towards the crust. The class of surfaces with p’ < co includes all convex and saddle surfaces. It is easy to see that the latter are characterized by the condition p+(F) = 0. Z. Z. Shefel’ (1975). If a surface F in E3 is not smooth, then the equality p’ = W+ may be violated independently of the degree of smoothness of the metric.
Burago (1984) to the case of non-regular surfaces. 3. Inequalities. An important property of the inequalities given below between the extrinsic and intrinsic characteristics of a surface is that they hold without any smoothness assumptions for all surfaces of the class under consideration, and hence they show that in the class @ the properties of the metric have an influence on the extrinsic geometry of a surface in E” for any II. D. Burago (1968b)). Let F be a compact surface in E” (closed or with boundary). | <urn:uuid:94f41f2c-2758-49a6-b59a-6e14f1defe5d> | 2.65625 | 1,058 | Content Listing | Science & Tech. | 27.296252 | 95,573,877 |
Saturn Video Clip
Watch a great and easy to understand video of Saturn for Children:
Picture of Saturn Video Contents
This short video shares some of the HD images NASA released about the massive storm on Saturn. Through this video, you will be able to see how a unique 6-sided jet stream called “the hexagon” is a wavy jet stream of winds with a rotating storm at the center.
Liked the Picture of Saturn video? Research much longer data regarding Saturn’s Hexagon.
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Declan, Tobin. " Saturn Space Video for Kids ." Easy Science for Kids, Jul 2018. Web. 20 Jul 2018. < http://easyscienceforkids.com/picture-of-saturn-for-kids-video/ >.
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Software development has lot of methodologies and standardized approaches to make the development process efficient such as object oriented programming, domain-driven design, test-driven design and behaviour driven design etc. Automation testing, since the very beginning, has been relatively new when it comes to processes and standards. But now it has gained lot of exposure in terms of standardization and has been under the process of continuous improvement and evolvement through design patterns. Automation testing is a process of developing software to test software. Hence, the test patterns are loosely similar to design patterns that are used in software development. Design patterns show how to design the test automation testware so that it will be efficient and easy to maintain. The most challenging part in test automation has always been the code maintenance. A lot of test automation projects have drowned or were scrapped due to the inability of the frameworks to cope up with the growing codebases. In order to keep the maintenance cost low, the automation engineers should strive to minimize the code that they reinvent or create from scratch by using existing functionality for common, generic, or repeated operations.
What are the types of Design Patterns in test automation?
1.Design Patterns in Test implementation
2. Architectural Design Patterns
Multi Layered Architecture
3.Functional Design Patterns
Page Object Design Pattern
What are the advantages of using Design Patterns?
The use of design patterns offers below advantages:
- Low maintenance effort and time
- Low maintenance cost
- Enhanced code reusability
- Enhanced reliability
- Structured codebase which is easy to fix and extend
- Improved communication
The design patterns contribute to a major chunk in defining the test automation best practices. The benefits of test automation cannot be reaped effectively without implementing the required design patterns specific to a test automation project.
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Density and Abundance of Secretive Marsh Birds in IowaWaterbirds
Publication VersionPublished Version
AbstractA decrease in wetland habitats throughout North America has caused a decline in populations of marsh birds. The objective of this study was to estimate population densities and abundances of secretive marsh birds in Iowa. Call-broadcast surveys were conducted in conjunction with distance sampling for eight species of marsh birds at wetlands in three regions of Iowa during 2009 and 2010. Regions were defined by observed microhabitat characteristics which also corresponded to physiographic regions. Region-specific density estimates were obtained using Program Distance for four species of marsh birds for which sufficient detections existed (Pied-billed Grebe [Podilymbus podiceps], Least Bittern [Ixobrychus exilis], Virginia Rail [Rallus limicola] and Sora [Porzana carolina]). The range of density estimates was 0.019 birds/ha (95% CI = 0.014-0.024) for Least Bittern to 0.12 birds/ha (95% CI = 0.11-0.14) for Pied-billed Grebe. Density estimates were highest in Region 2 for Pied-billed Grebe, Region 1 for Virginia Rail, and Region 3 for Sora. Least Bittern density was similar between Regions 1 and 2, but was 0.027 birds/ha lower in Region 3. The need to focus conservation efforts on areas of the state where large amounts of suitable habitat exist and marsh bird densities are highest is illustrated by the observed differences in species' densities across regions. Information on the current population status of marsh birds in Iowa and regions where conservation efforts can be directed are provided by these density estimates.
Copyright OwnerThe Waterbird Society
Citation InformationTyler Harms and Stephen J. Dinsmore. "Density and Abundance of Secretive Marsh Birds in Iowa" Waterbirds Vol. 35 Iss. 2 (2012) p. 208 - 216
Available at: http://works.bepress.com/tyler-harms/3/ | <urn:uuid:b8b53d0c-7b20-49aa-a845-42266112c961> | 2.9375 | 439 | Academic Writing | Science & Tech. | 43.589527 | 95,573,903 |
Researchers from the University of Zurich and the University Hospital Zurich have discovered the protein that enables natural embryonic stem cells to form all body cells. In the case of embryonic stem cells maintained in cell cultures, this allrounder potential is limited. Scientists want to use this knowledge to treat large bone fractures with stem cells.
Stem cells are considered biological allrounders because they have the potential to develop into the various body cell types. For the majority of stem cells, however, this designation is too far-reaching.
Adult stem cells, for example, can replace cells in their own tissue in case of injury, but a fat stem cell will never generate a nerve or liver cell. Scientists therefore distinguish between multipotent adult stem cells and the actual allrounders – the pluripotent embryonic stem cells.
Epigenetic marks determine potential for development
Differences exist even among the true allrounders, however. Embryonic stem cells that grow in laboratory cell cultures are in a different state than the pluripotent cells found inside the embryos in the first days of development. In a study in the journal Nature Cell Biology, researchers led by Paolo Cinelli of the University Hospital Zurich and Raffaella Santoro of the University of Zurich have now demonstrated the mechanism by which natural allrounders differ from embryonic stem cells in cultures.
At the center of their discovery is a protein called Pramel7 (for "preferentially expressed antigen in melanoma"-like 7) found in the cells of embryonic cell clusters that are just a few days old. This protein guarantees that the genetic material is freed from epigenetic marks consisting of chemical DNA tags in the form of methyl groups.
"The more methyl groups are removed, the more open the Book of Life becomes," Cinelli says. Since any cell of the human body can develop from an embryonic stem cell, all genes have to be freely accessible at the beginning. The more a cell develops or differentiates, the stronger its genetic material is methylated and "sealed closed" again. In a bone cell, for example, only those genes are active that the cell requires for its function, the biochemist explains.
Protein is responsible for perfect pluripotency
Despite its short action period of just a few days, Pramel7 seems to play a vital role: When the researchers headed up by Cinelli and Santoro switched off the gene for this protein using genetic tricks, development remained stuck in the embryonic cell cluster stage. In the cultivated stem cells, on the other hand, Pramel7 is rarely found. This circumstance could also explain why the genetic material of these cells contains more methyl groups than that of natural embryonic cells – the perfect allrounders, as Cinelli calls them.
Using the stem cell function to regenerate bone tissue
His interest in stem cells lies in the hope of one day being able to help people with complex bone fractures. "Bones are great at regenerating and they are the only tissue that does not build scars," Paolo Cinelli says. The bone stumps must be touching, however, in order to grow together. When a bone breaks in multiple places and even through the skin, for example, in a motorcycle accident, the sections of bone in between are often no longer usable. For such cases, a bone replacement is required. His team is studying carrier materials that they want to populate with the body's own stem cells in the future. "For this reason, we have to know how stem cells work," Cinelli adds.
Urs Graf, Elisa A. Casanova, Sarah Wyck, Damian Dalcher, Marco Gatti, Eva Vollenweider, Michal J. Okoniewski, Fabienne A.Weber, Sameera S. Patel, Marc W. Schmid, Jiwen Li, Jafar Sharif, Guido A. Wanner, Haruhiko Koseki, JieminWong, Pawel Pelczar, Lorenza Penengo, Raffaella Santoro and Paolo Cinelli. Pramel7 mediates ground-state pluripotency through proteasomal-epigenetic combined pathways. Nature Cell Biology. 12 June 2017; doi:10.1038/ncb3554
PD Paolo Cinelli, PhD
Clinic for Traumatology
University Hospital Zurich
Phone +41 44 255 36 78
Kurt Bodenmüller | Universität Zürich
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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|University of Toronto, Canada|
|Keynote: J Material Sci Eng|
|One specific type of corneal nano-nipple arrays found on many insect compound eyes are hexagonally arranged protrusions in the shape of inverted paraboloids. Prior studies have focused on the anti-reflection properties of the eyes due to the nano-nipple structure, which depends mainly on the shape of individual nipples. However, in the past, little attention was given to the details of the arrangement of nano-nipples, which was qualitatively described as consisting of multiple domains. In the current study, remarkable defect structures were found through structural analysis using crystallographic principles. The investigated species is the Mourning Cloak butterfly (Nymphalis antiopa), which is common in North America as well as Europe and Asia. On its corneas, nano-nipples are predominantly in 2-D hexagonal arrangement with an average diameter of 170 nm and an average lattice parameter of 205 nm. An eye with 2 mm in diameter has approximately 10,000 ommatidia and 140 million nipples. However, within the hexagonal structure, there are nipples that deviate from the regular arrangement by having different numbers of Nearest Neighbours (NN); instead of 6 NN required by hexagonal symmetry, about 10% of nano-nipples have 5 or 7 NN and are described as 5- and 7-fold coordination defects (disclinations), respectively. Since the 5- and 7-fold disclinations usually occur adjacent to each other, they are collectively referred to as 5-7 defects. An individual 5-7 defect pair affects the nipple structure in a similar fashion as a dislocation in 2-D crystals. Furthermore, the 5-7 defects are not arranged randomly; instead, they show a strong preference to align in rows to divide the domains of nano-nipples like grain boundaries between crystals. The distribution of the domain sizes is log-normal, and analysis of the orientations of nipple domains indicate no preferred orientation. This intriguing structure will be discussed in reference to protrusion formation theories by i) microvilli secretion and ii) reaction-diffusion controlled coating development, respectively. Finally, a comparison will be presented with similar structural defects found in man-made 2-D materials such as self-assembled monolayers or graphene.|
Uwe Erb received his PhD in Materials Science in 1980 from the University of Saarland (Germany). He currently is a Professor in Materials Science and Engineering at the University of Toronto. He is an Inventor on 18 patents related to the synthesis of nanostructured materials by electrochemical methods, and has authored about 250 scientific publications in the field of nanomaterials. He and his research team were the first to synthesize fully dense nanostructured materials in 1985, and developed numerous industrial applications for these materials with various companies. More recently, his research has been broadened to include bio-inspired nanostructures.
Email: [email protected]
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You may have heard the term perimeter before, in like a spy movie or something. What does it mean in geometry? Find out here! Subscribe: ...
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Learn how to find the area of a regular polygon using the formula A=1/2ap in this free math video tutorial by Mario's Math Tutoring. We go through two examples.
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By: Stephen Welton Taber
308 pages, B/w photos, illus, maps
Authoritative look at five economically important species: The red imported fire ant, the black imported fire ant, the tropical fire ant, the southern fire ant, and the golden fire ant. Begins with a general introduction and a history of their invasion of North America and continues with additional chapters on natural history, origin and evolution, animals that share the fire ants' nest, the mixed successes of chemical control, and natural enemies and the hopes for biocontrol. Also examined are the pros and cons of fire ants, their medical importance, and suggestions for future research. The appendices list all known fire ant species and explain how to prepare, preserve, and identify every known species occurring in the United States.
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The hydrogen line, 21-centimeter line or H I line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation is at the precise frequency of 1420405751.7667±0.0009 Hz, which is equivalent to the vacuum wavelength of 21.1061140542 cm in free space. This wavelength falls within the microwave region of the electromagnetic spectrum, and it is observed frequently in radio astronomy, since those radio waves can penetrate the large clouds of interstellar cosmic dust that are opaque to visible light.
The microwaves of the hydrogen line come from the atomic transition of an electron between the two hyperfine levels of the hydrogen 1s ground state that have an energy difference of ~ 5.87433 µeV. It is called the spin-flip transition. The frequency, ν, of the quanta that are emitted by this transition between two different energy levels is given by the Planck–Einstein relation E = hν. According to that relation, the photon energy of a 1,420,405,751.7667 Hz photon is ~ 5.87433 µeV. The constant of proportionality, h, is known as the Planck constant.
The ground state of neutral hydrogen consists of an electron bound to a proton. Both the electron and the proton have intrinsic magnetic dipole moments ascribed to their spin, whose interaction results in a slight increase in energy when the spins are parallel, and a decrease when antiparallel. The fact that only parallel and antiparallel states are allowed is a result of the quantum mechanical discretization of the total angular momentum of the system. When the spins are parallel, the magnetic dipole moments are antiparallel (because the electron and proton have opposite charge), thus one would expect this configuration to actually have lower energy just as two magnets will align so that the north pole of one is closest to the south pole of the other. This logic fails here because the wave functions of the electron and the proton overlap; that is, the electron is not spatially displaced from the proton, but encompasses it. The magnetic dipole moments are therefore best thought of as tiny current loops. As parallel currents attract, the parallel magnetic dipole moments (i.e., antiparallel spins) have lower energy. The transition has an energy difference of 5.87433 µeV that when applied in the Planck equation gives:
where h, is the Planck constant and c is the speed of light.
This transition is highly forbidden with an extremely small transition rate of 2.9×10−15 s−1, and a mean lifetime of the excited state of around 10 million years. A spontaneous occurrence of the transition is unlikely to be seen in a laboratory on Earth, but it can be artificially induced using a hydrogen maser. It is commonly observed in astronomical settings such as hydrogen clouds in our galaxy and others. Owing to its long lifetime, the line has an extremely small natural width, so most broadening is due to Doppler shifts caused by bulk motion or nonzero temperature of the emitting regions.
During the 1930s, it was noticed that there was a radio 'hiss' that varied on a daily cycle and appeared to be extraterrestrial in origin. After initial suggestions that this was due to the Sun, it was observed that the radio waves seemed to propagate from the centre of the Galaxy. These discoveries were published in 1940 and were noted by Jan Oort who knew that significant advances could be made in astronomy if there were emission lines in the radio part of the spectrum. He referred this to Hendrik van de Hulst who, in 1944, predicted that neutral hydrogen could produce radiation at a frequency of 1420.4058 MHz due to two closely spaced energy levels in the ground state of the hydrogen atom.
The 21 cm line (1420.4 MHz) was first detected in 1951 by Ewen and Purcell at Harvard University, and published after their data was corroborated by Dutch astronomers Muller and Oort, and by Christiansen and Hindman in Australia. After 1952 the first maps of the neutral hydrogen in the Galaxy were made, and revealed for the first time the spiral structure of the Milky Way.
The 21 cm spectral line appears within the radio spectrum (in the L band of the UHF band of the microwave window to be exact). Electromagnetic energy in this range can easily pass through the Earth's atmosphere and be observed from the Earth with little interference.
Assuming that the hydrogen atoms are uniformly distributed throughout the galaxy, each line of sight through the galaxy will reveal a hydrogen line. The only difference between each of these lines is the doppler shift that each of these lines has. Hence, one can calculate the relative speed of each arm of our galaxy. The rotation curve of our galaxy has been calculated using the 21 cm hydrogen line. It is then possible to use the plot of the rotation curve and the velocity to determine the distance to a certain point within the galaxy.
Hydrogen line observations have also been used indirectly to calculate the mass of galaxies, to put limits on any changes over time of the universal gravitational constant and to study the dynamics of individual galaxies.
The line is of great interest in big bang cosmology because it is the only known way to probe the "dark ages" from recombination to reionization. Including the redshift, this line will be observed at frequencies from 200 MHz to about 9 MHz on Earth. It potentially has two applications. First, by mapping the intensity of redshifted 21 centimeter radiation it can, in principle, provide a very precise picture of the matter power spectrum in the period after recombination. Second, it can provide a picture of how the universe was reionized, as neutral hydrogen which has been ionized by radiation from stars or quasars will appear as holes in the 21 cm background.
However, 21 cm observations are very difficult to make. Ground-based experiments to observe the faint signal are plagued by interference from television transmitters and the ionosphere, so they must be made from very secluded sites with care taken to eliminate interference. Space based experiments, even on the far side of the Moon (where they would be sheltered from interference from terrestrial radio signals), have been proposed to compensate for this. Little is known about other effects, such as synchrotron emission and free–free emission on the galaxy. Despite these problems, 21 cm observations, along with space-based gravity wave observations, are generally viewed as the next great frontier in observational cosmology, after the cosmic microwave background polarization.
The Pioneer plaque, attached to the Pioneer 10 and Pioneer 11 spacecraft, portrays the hyperfine transition of neutral hydrogen and used the wavelength as a standard scale of measurement. For example, the height of the woman in the image is displayed as eight times 21 cm, or 168 cm. Similarly the frequency of the hydrogen spin-flip transition was used for a unit of time in a map to Earth included on the Pioneer plaques and also the Voyager 1 and Voyager 2 probes. On this map, the position of the Sun is portrayed relative to 14 pulsars whose rotation period circa 1977 is given as a multiple of the frequency of the hydrogen spin-flip transition. It is theorized by the plaque's creators that an advanced civilization would then be able to use the locations of these pulsars to locate the Solar System at the time the spacecraft were launched.
The 21 cm hydrogen line is considered a favorable frequency by the SETI program in their search for signals from potential extraterrestrial civilizations. In 1959, Italian physicist Giuseppe Cocconi and American physicist Philip Morrison published "Searching for Interstellar Communications", a paper proposing the 21 cm hydrogen line and the potential of microwaves in the search for interstellar communications. According to George Basalla, the paper by Cocconi and Morrison "provided a reasonable theoretical basis" for the then nascent SETI program. Similarly, Pyotr Makovetsky proposed SETI use a frequency which is equal to either
Since π is an irrational number, such a frequency could not possibly be produced in a natural way as a harmonic, and would clearly signify its artificial origin. Such a signal would not be overwhelmed by the H I line itself, or by any of its harmonics. | <urn:uuid:e93b42f3-9fa3-4611-9973-074e977c6ce4> | 3.9375 | 1,706 | Knowledge Article | Science & Tech. | 39.39065 | 95,573,937 |
How close are we to photographing a Black Hole? November 23, 2017 What does a black hole look like? No one knows for sure. Artists make their images based on what physicists think they look like. Watch the video… But that could be about to change. [Youtube] By Agis F| 2017-11-23T10:32:52+00:00 Nov 23, 2017|Categories: Astronomy|Tags: Black Hole| Related Posts The History of Earth Jul 21, 2018 | 0 Comments Oldest Fossil of a Baby Snake found preserved in Amber Jul 20, 2018 | 0 Comments Listen to the mysterious Sounds of Saturn Jul 19, 2018 | 0 Comments Moon and Venus over Cannon Beach Jul 18, 2018 | 0 Comments Leave A Comment Cancel reply Comment Current [email protected] * Leave this field empty Notify me of follow-up comments by email. | <urn:uuid:c33e8862-cc83-4d90-b0de-abbe8e6e1b68> | 2.90625 | 180 | Truncated | Science & Tech. | 69.944167 | 95,573,940 |
Buildings destroyed by the 2011 Tohoku earthquake released thousands of tons of climate-warming and ozone-depleting chemicals into the atmosphere, according to a new study.
New research suggests that the thousands of buildings destroyed and damaged during the 9.0 magnitude earthquake and tsunami that struck Japan four years ago released 6,600 metric tons (7,275 U.S. tons) of gases stored in insulation, appliances and other equipment into the atmosphere.
Emissions of these chemicals, called halocarbons, increased by 21 percent to 91 percent over typical levels, according to the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.
The study is the first to look at how the Tohoku earthquake affected the release of halocarbons into the atmosphere and likely one of the first to examine emissions of these gases following a natural disaster, according to the study’s authors.
“What we found is a new mechanism of halocarbon emissions coming from the earthquake,” said Takuya Saito, a senior researcher at the National Institute for Environmental Studies in Tsukuba, Japan, and lead author of the new paper.
Halocarbons released as a result of the earthquake include chemicals that deplete the ozone layer and contribute to global warming – including some gases that are no longer used because of those harmful effects on the environment. These include chlorofluorocarbons like CFC-11, a powerful ozone-depleting chemical used in foam insulation until it was phased out in 1996, and hydrochlorofluorocarbons like HCFC-22, an ozone-depleting refrigerant that is also a powerful greenhouse gas and is in the process of being phased out of use. Among other halocarbons released by the earthquake were hydrofluorocarbons, or HFCs, and sulfur hexafluoride, both potent greenhouse gases.
The emissions of the six halocarbons released from Japan in 2011 are equivalent to the discharge of 1,300 metric tons (1,433 U.S. tons) of CFC-11 alone — equal to the amount of CFC-11s found in 2.9 million refrigerators manufactured before the chemical was banned. The total emissions of the six chemicals are also equivalent to the release of 19.2 million metric tons (21.2 million U.S. tons) of carbon dioxide into the atmosphere – an amount equal to about 10 percent of Japanese vehicle emissions in 2011, according to the study’s authors.
Saito and his colleagues decided to investigate halocarbon emissions and their relationship to the earthquake after ground-based air monitoring stations in Japan recorded surprising high levels of these chemicals. The stations are on Hateruma Island, east of Taiwan; Cape Ochiishi, on the east side of Hokkaido; and Ryori, north of Tokyo on Honshu.
The study’s authors combined these measurements with an atmospheric model and other mathematical methods to figure out that increased emissions from the earthquake were involved, how much of the emissions could be attributed to the disaster and how they compared to previous years.
They found that emissions of all six halocarbons were higher from March 2011 to February 2012, following the earthquake, than they were during the same time the year before the event and during the same period the year after it.
About 50 percent of the halocarbon emissions after the earthquake were of HCFC-22, likely due to damage to refrigerators and air conditioners. Emissions of the gas were 38 percent higher than the years before and after the earthquake. Emissions of CFC-11 were 72 percent higher than emissions before and after the earthquake, likely due to damage to insulation foams used in appliances and buildings, according to the study. Emissions of two types of HFCs — HFC-134a and HFC-32 — rose by 49 percent and 63 percent compared to the years before and after the disaster.
The new study also calculates the total impact of the increased emissions on ozone depletion and global warming. The earthquake-triggered surge of halocarbons increased ozone loss from Japanese emissions of those six gases by 38 percent* from March 2011 to February 2012 compared to the same time period in the years before and after the event. The amount of heat trapped in the atmosphere because of Japan’s emissions of those six gases rose 36 percent from March 2011 to February 2012 compared to earlier and later years because of the extra emissions from the earthquake, according to the new study.
Saito said the new study shows the importance of including the release of gases from natural disasters in emissions estimates. Although the global effect of one event is small — emissions associated with the Tohoku earthquake accounted for 4 percent or less of global emissions in 2011 — the cumulative effect could be larger, he said. Natural disasters accelerate the release of halocarbons and replacement of these gases could lead to the use of more halocarbons, according to the study.
National halocarbon emissions estimates by the Japanese government did not factor in the release of the chemicals due to the earthquake and are likely underestimating the amount of these substances in the atmosphere, according to Saito. Governments rely on inventories of chemicals and generic data about how they are used to estimate their amounts in the atmosphere – called a “bottom-up” approach” — whereas the new study uses actual measurements of the gases – called a “top-down” approach. “It is apparent that there are unreported emissions,” Saito said.
The new study shows that there could be a need to include the amount of halocarbons released by catastrophic events in emissions estimates, said Steve Montzka, a research chemist at the National Oceanic and Atmospheric Administration in Boulder, Colorado, who was not involved in the research. It also highlights the need for more measurements of halocarbons in the atmosphere, he added, rather than relying on bottom-up emissions estimates from inventories.
“Atmospheric scientists often say that relying solely on bottom-up inventories to tell you how greenhouse gas emissions change is like going on a diet without weighing yourself,” Montzka said.
*Note: This value has been corrected from the accepted manuscript posted online.
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“Extraordinary halocarbon emissions initiated by the 2011 Tohoku earthquake”
Takuya Saito: National Institute for Environmental Studies, Tsukuba, Japan;
Xuekun Fang: Norwegian Institute for Air Research, Kjeller, Norway; and State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China;
Andreas Stohl: Norwegian Institute for Air Research, Kjeller, Norway;
Yoko Yokouchi and Jiye Zeng: National Institute for Environmental Studies, Tsukuba, Japan;
Yukio Fukuyama: Japan Meteorological Agency, Tokyo, Japan;
Hitoshi Mukai: National Institute for Environmental Studies, Tsukuba, Japan.
Contact Information for the Authors:
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Xuekun Fang: firstname.lastname@example.org, +1 (617) 955-9144.
Andreas Stohl: email@example.com, +49-89-374-18029
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Nanci Bompey | American Geophysical Union
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23.07.2018 | Life Sciences | <urn:uuid:f7cd2b24-b5a2-4ba6-8553-73ec3c827b50> | 3.125 | 2,363 | Knowledge Article | Science & Tech. | 33.991196 | 95,573,941 |
A High Power, Frequency Tunable Colloidal Quantum Dot (CdSe/ZnS) Laser
AbstractTunable lasers are essential for medical, engineering and basic science research studies. Most conventional solid-state lasers are capable of producing a few million laser shots, but limited to specific wavelengths, which are bulky and very expensive. Dye lasers are continuously tunable, but exhibit very poor chemical stability. As new tunable, efficient lasers are always in demand, one such laser is designed with various sized CdSe/ZnS quantum dots. They were used as a colloid in tetrahydrofuran to produce a fluorescent broadband emission from 520 nm to 630 nm. The second (532 nm) and/or third harmonic (355 nm) of the Nd:YAG laser (10 ns, 10 Hz) were used together as the pump source. In this study, different sized quantum dots were independently optically pumped to produce amplified spontaneous emission (ASE) with 4 nm to 7 nm of full width at half-maximum (FWHM), when the pump power and focusing were carefully optimized. The beam was directional with a 7 mrad divergence. Subsequently, these quantum dots were combined together, and the solution was placed in a resonator cavity to obtain a laser with a spectral width of 1 nm and tunable from 510 to 630 nm, with a conversion efficiency of about 0.1%. View Full-Text
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Prasad, S.; AlHesseny, H.S.; AlSalhi, M.S.; Devaraj, D.; Masilamai, V. A High Power, Frequency Tunable Colloidal Quantum Dot (CdSe/ZnS) Laser. Nanomaterials 2017, 7, 29.
Prasad S, AlHesseny HS, AlSalhi MS, Devaraj D, Masilamai V. A High Power, Frequency Tunable Colloidal Quantum Dot (CdSe/ZnS) Laser. Nanomaterials. 2017; 7(2):29.Chicago/Turabian Style
Prasad, Saradh; AlHesseny, Hanan S.; AlSalhi, Mohamad S.; Devaraj, Durairaj; Masilamai, Vadivel. 2017. "A High Power, Frequency Tunable Colloidal Quantum Dot (CdSe/ZnS) Laser." Nanomaterials 7, no. 2: 29.
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here. | <urn:uuid:1955eec6-c591-4522-af6d-7dbfcc736c9f> | 2.515625 | 562 | Academic Writing | Science & Tech. | 54.925714 | 95,573,950 |
Just over a month ago, a short paper appeared in Nature Methods saying that the gene editing technique known as CRISPR-Cas9 has a big problem: it creates unexpected mutations all over the genome. This was startling news for a technique that has been hailed worldwide as a dramatic breakthrough, not only because it is the easiest gene-editing method yet invented, but also because it is (supposedly) very precise.
This new paper, by Kellie Schaefer and colleagues, found hundreds of mutations (in experimental mice) that weren't supposed to be there. The results contradicted earlier studies that showed CRISPR caused very few of these "off-target" mutations. One of the authors, Stephen Tsang, commented:
Not surprising, the resulting news headlines were gloomy. The stock in three companies trying to commercialize gene editing–Editas Medicine, Intellia Therapeutics and CRISPR Therapeutics–all fell sharply. (Interestingly, the stocks started falling on May 24, and bottomed out on May 31. The paper appeared online on May 30.) Scientists involved with these companies quickly responded, arguing that the study was flawed, but of course those scientists have a lot of money at stake.
Who was right? Well, a new paper by Caleb Lareau and colleagues, just released in the bioRxiv preprint repository, re-examines the same data and concludes that CRISPR is just fine. I've read both papers so you don't have to. Here's what seems to be going on.
The study by Schaefer et al. used CRISPR-Cas9 to create mutations in two mice (called F03 and F05), and then sequenced their genomes. They also sequenced the genome of a third mouse, called FVB. All three mice were supposed to be genetically identical.
Then they compared all three genomes to a "reference" mouse to find mutations. (Aside: this is something my own lab does all the time, so I know the techniques well.) They found over 1,500 mutations in each mouse (which wasn't surprising, because the reference mouse differs from their three lab animals), but they found hundreds more mutations in the two CRISPR-edited mice. That was the main surprise from Schaefer's paper, and it's the basis for their claim that CRISPR causes numerous off-target mutations.
I had a big problem with this claim even before reading Lareau's paper. Just TWO mice? That's a ridiculously tiny sample. But I digress.
Lareau et al. pointed out, correctly, that Schaefer's conclusion depends on the mice being genetically identical. But what if the two CRISPR mice (F03 and F05) were closer to each other than to the third mouse, FVB? (It's analogous to comparing two siblings with a first cousin, although these mice are much more inbred than any humans.) In that case, the result falls apart.
Fortunately, Schaefer et al. made all their data available (props to them for doing that), so Lareau could answer this question quite precisely.
It turns out that F03 and F05 are much closer to each other than either one is to FVB. Lareau discovered that the two CRISPR mice share thousands of mutations that FVB doesn't have.
What does this mean? Lareau and colleagues conclude that the "unexpected" mutations in the CRISPR-edited mice were already there before the experiment began, and were not caused by gene editing. As they put it:
...the CRISPR-treated embryos most likely already harbored these private SNPs and indels prior to nuclease treatment whereas the control mouse did not.
In other words, it seems highly unlikely that CRISPR gene editing caused hundreds of unexpected mutations in these mice.
Even though CRISPR is probably being overhyped right now, it is nonetheless genuinely exciting technology. Nature Methods was probably too eager to publish a controversial result, an all-too-common problem with big-name journals, and it seems to have done a poor job managing peer review. (Aside: I'd love to see what the reviewers said. Did they miss the obvious problems, or did the journal editors ignore the reviewers? I doubt we'll ever know.)
A final note: this kerfuffle illustrates the tremendous value of rapid publication through pre-print archives. Lareau et al.'s paper appeared a few days ago (July 5) on bioRxiv, along with all the data they used to support their arguments. We'll probably see a journal version too, but that will take months. Getting this paper out faster was a win for science.
(Postscript: Two of the authors on the bioRxiv paper have financial interests in CRISPR technology companies, which they disclosed in the paper. I have no financial interests in any of these companies.)
Steven Salzberg is the Bloomberg Distinguished Professor of Biomedical Engineering, Computer Science, and Biostatistics at Johns Hopkins University. | <urn:uuid:841c94ac-6741-4c85-87fa-53ef6d651ed9> | 3.09375 | 1,050 | Nonfiction Writing | Science & Tech. | 52.770736 | 95,573,956 |
The introduction of non-intrusive measurement techniques in wind tunnel experimentation has been a turning point in error free data acquisition. Laser velocimetry has been progressively implemented and utilized in various wind tunnels; e.g. subsonic, transonic, and supersonic. The success of the laser velocimeter technique is based on an accurate measurement of scattered light by seeding particles introduced into the flow stream in the wind tunnel. Therefore, application of appropriate seeding particles will affect, to a large extent the acquired data. The seeding material used depends on the type of experiment being run. Among the seeding material for subsonic tunnel are kerosene, Kaolin, and polystyrene. Polystyrene is known to be the best because of being solid particles, having high index of refraction, capable of being made both spherical and monodisperse. However for high temperature wind tunnel testing seeding material must have an additional characteristic that is high melting point. Typically metal oxide powders such as Al2O3 with melting point 3660 F are used. The metal oxides are, however polydispersed, have a high density, and a tendency to form large agglomerate that does not closely follow the flow velocity. The addition of flame phase silica to metal oxide helps to break up the agglomerates, yet still results in a narrow band of polydispersed seeding. The less desirable utility of metal oxide in high temperature wind tunnels necessitates the search for a better alternative particle seeding which this paper addresses. The Laser Velocimetry (LV) characteristic of polystyrene makes it a prime candidate as a base material in achieving the high temperature particle seeding inexpensively. While polystyrene monodisperse seeding particle reported has been successful in a subsonic wind tunnel, it lacks the high melting point and thus is not practically usable in a high temperature wind tunnel. It is well known that rise in melting point of polystyrene can be achieved by a cross-linking technique. Since polystyrene already possesses all the desired characteristics for LV, to circumvent the low melting point, a cross-linking technique was investigated. | <urn:uuid:2deef678-c63e-416d-b9c5-8a4203d7b7da> | 2.703125 | 448 | Truncated | Science & Tech. | 17.932976 | 95,574,005 |
High-level programming language
In computer science, a high-level programming language is a programming language with strong abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language elements, be easier to use, or may automate (or even hide entirely) significant areas of computing systems (e.g. memory management), making the process of developing a program simpler and more understandable than when using a lower-level language. The amount of abstraction provided defines how "high-level" a programming language is.
The first high-level programming language designed for computers was Plankalkül, created by Konrad Zuse. However, it was not implemented in his time, and his original contributions were largely isolated from other developments due to World War II, aside from the language's influence on the "Superplan" language by Heinz Rutishauser and also to some degree Algol. The first significantly widespread high-level language was Fortran, a machine-independent development of IBM's earlier Autocode systems. Algol, defined in 1958 and 1960 by committees of European and American computer scientists, introduced recursion as well as nested functions under lexical scope. It was also the first language with a clear distinction between value and name-parameters and their corresponding semantics. Algol also introduced several structured programming concepts, such as the while-do and if-then-else constructs and its syntax was the first to be described in formal notation – "Backus–Naur form" (BNF). During roughly the same period, Cobol introduced records (also called structs) and Lisp introduced a fully general lambda abstraction in a programming language for the first time.
"High-level language" refers to the higher level of abstraction from machine language. Rather than dealing with registers, memory addresses and call stacks, high-level languages deal with variables, arrays, objects, complex arithmetic or boolean expressions, subroutines and functions, loops, threads, locks, and other abstract computer science concepts, with a focus on usability over optimal program efficiency. Unlike low-level assembly languages, high-level languages have few, if any, language elements that translate directly into a machine's native opcodes. Other features, such as string handling routines, object-oriented language features, and file input/output, may also be present. One thing to note about high-level programming languages is that these languages allows the programmer to be detached and separated from the machine. That is, unlike low-level languages like assembly or machine language, high-level programming can amplify the programmer's instructions and trigger a lot of data movements in the background without their knowledge. The responsibility and power of executing instructions have been handed over to the machine from the programmer.
High-level languages intend to provide features which standardize common tasks, permit rich debugging, and maintain architectural agnosticism; while low-level languages often produce more efficient code through optimization for a specific system architecture. Abstraction penalty is the border that prevents high-level programming techniques from being applied in situations where computational limitations, standards conformance or physical constraints require access to low-level architectural resources (fi, response time(s), hardware integration). High-level programming exhibits features like more generic data structures/operations, run-time interpretation, and intermediate code files; which often result in execution of far more operations than necessary, higher memory consumption, and larger binary program size. For this reason, code which needs to run particularly quickly and efficiently may require the use of a lower-level language, even if a higher-level language would make the coding easier. In many cases, critical portions of a program mostly in a high-level language can be hand-coded in assembly language, leading to a much faster, more efficient, or simply reliably functioning optimised program.
However, with the growing complexity of modern microprocessor architectures, well-designed compilers for high-level languages frequently produce code comparable in efficiency to what most low-level programmers can produce by hand, and the higher abstraction may allow for more powerful techniques providing better overall results than their low-level counterparts in particular settings. High-level languages are designed independent of a specific computing system architecture. This facilitates executing a program written in such a language on any computing system with compatible support for the Interpreted or JIT program. High-level languages can be improved as their designers develop improvements. In other cases, new high-level languages evolve from one or more others with the goal of aggregating the most popular constructs with new or improved features. An example of this is Scala which maintains backward compatibility with Java which means that programs and libraries written in Java will continue to be usable even if a programming shop switches to Scala; this makes the transition easier and the lifespan of such high-level coding indefinite. In contrast, low-level programs rarely survive beyond the system architecture which they were written for without major revision. This is the engineering 'trade-off' for the 'Abstraction Penalty'.
The terms high-level and low-level are inherently relative. Some decades ago, the C language, and similar languages, were most often considered "high-level", as it supported concepts such as expression evaluation, parameterised recursive functions, and data types and structures, while assembly language was considered "low-level". Today, many programmers might refer to C as low-level, as it lacks a large runtime-system (no garbage collection, etc.), basically supports only scalar operations, and provides direct memory addressing. It, therefore, readily blends with assembly language and the machine level of CPUs and microcontrollers.
Assembly language may itself be regarded as a higher level (but often still one-to-one if used without macros) representation of machine code, as it supports concepts such as constants and (limited) expressions, sometimes even variables, procedures, and data structures. Machine code, in its turn, is inherently at a slightly higher level than the microcode or micro-operations used internally in many processors.
There are three general modes of execution for modern high-level languages:
- When code written in a language is interpreted, its syntax is read and then executed directly, with no compilation stage. A program called an interpreter reads each program statement, following the program flow, then decides what to do, and does it. A hybrid of an interpreter and a compiler will compile the statement into machine code and execute that; the machine code is then discarded, to be interpreted anew if the line is executed again. Interpreters are commonly the simplest implementations of the behavior of a language, compared to the other two variants listed here.
- When code written in a language is compiled, its syntax is transformed into an executable form before running. There are two types of compilation:
- Machine code generation
- Some compilers compile source code directly into machine code. This is the original mode of compilation, and languages that are directly and completely transformed to machine-native code in this way may be called "truly compiled" languages. See assembly language.
- Intermediate representations
- When code written in a language is compiled to an intermediate representation, that representation can be optimized or saved for later execution without the need to re-read the source file. When the intermediate representation is saved, it may be in a form such as byte code. The intermediate representation must then be interpreted or further compiled to execute it. Virtual machines that execute byte code directly or transform it further into machine code have blurred the once clear distinction between intermediate representations and truly compiled languages.
- Source-to-Source Translated or Trans-compiled
Note that languages are not strictly "interpreted" languages or "compiled" languages. Rather, implementations of language behavior use interpretation or compilation. For example, Algol 60 and Fortran have both been interpreted (even though they were more typically compiled). Similarly, Java shows the difficulty of trying to apply these labels to languages, rather than to implementations; Java is compiled to bytecode and the bytecode is subsequently executed by either interpretation (in a JVM) or compilation (typically with a just-in-time compiler such as HotSpot, again in a JVM). Moreover, compilation, trans-compiling, and interpretation are not strictly limited to just a description of the compiler artifact (binary executable or IL assembly).
High-level language computer architecture
Alternatively, it is possible for a high-level language to be directly implemented by a computer – the computer directly executes the HLL code. This is known as a high-level language computer architecture – the computer architecture itself is designed to be targeted by a specific high-level language. The Burroughs large systems were target machines for Algol 60, for example.
- Abstraction (computer science)
- Generational list of programming languages
- Low-level programming languages
- High-level assembler
- Very high-level programming languages
- Categorical list of programming languages
- HThreads - RD Glossary
- London, Keith (1968). "4, Programming". Introduction to Computers. 24 Russell Square London WC1: Faber and Faber Limited. p. 184. ISBN 0571085938.
The 'high' level programming languages are often called autocodes and the processor program, a compiler.
- London, Keith (1968). "4, Programming". Introduction to Computers. 24 Russell Square London WC1: Faber and Faber Limited. p. 186. ISBN 0571085938.
Two high level programming languages which can be used here as examples to illustrate the structure and purpose of autocodes are COBOL (Common Business Oriented Language) and FORTRAN (Formular Translation).
- Giloi, Wolfgang, K. (1997). "Konrad Zuse's Plankalkül: The First High-Level "non von Neumann" Programming Language". IEEE Annals of the History of Computing, vol. 19, no. 2, pp. 17–24, April–June, 1997. (abstract)
- Although it lacked a notion of reference-parameters, which could be a problem in some situations. Several successors, including AlgolW, Algol68, Simula, Pascal, Modula and Ada therefore included reference-parameters (The related C-language family instead allowed addresses as value-parameters).
- Surana P (2006). "Meta-Compilation of Language Abstractions" (PDF). Archived from the original (PDF) on 2015-02-17. Retrieved 2008-03-17.
- Kuketayev. "The Data Abstraction Penalty (DAP) Benchmark for Small Objects in Java". Retrieved 2008-03-17.
- Chatzigeorgiou; Stephanides (2002). "Evaluating Performance and Power Of Object-Oriented Vs. Procedural Programming Languages". In Blieberger; Strohmeier. Proceedings - 7th International Conference on Reliable Software Technologies - Ada-Europe'2002. Springer. p. 367.
- Manuel Carro; José F. Morales; Henk L. Muller; G. Puebla; M. Hermenegildo (2006). "High-level languages for small devices: a case study" (PDF). Proceedings of the 2006 international conference on Compilers, architecture and synthesis for embedded systems. ACM. | <urn:uuid:b27c3f44-63f1-4a5f-8c0c-9b7fb6a57e52> | 3.953125 | 2,346 | Knowledge Article | Software Dev. | 23.58167 | 95,574,039 |
The mystery of 506.5 nm feature of reflectance spectra of Vesta and Vestoids: Evidence for space weathering?
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Although asteroid 4 Vesta and Vestoids have been believed to be the source of a group of basaltic meteorites called HEDs, there have been detailed spectral analyses on the spectral redness and the 506.5 nm absorption band, suggesting controversy on their space weathering processes and origins. In order to evaluate a possibility that such an apparent inconsistency may be explained by the space weathering, the 506.5 nm spectral feature and reddening trend are examined for Vesta and Vestoids, HED meteorites, lunar soils, and laser irradiated pyroxene samples in this paper. Our results indicate that all fresh HED meteorites have the 506.5 nm band at different wavelengths according to their classes, lunar soils seem to lose the 506.5 nm band as they mature, and pulse laser irradiation on the pyroxene sample seems to reduce the 506.5 nm band. Therefore, absence of the 506.5 nm band on some Vestoids can be due to space weathering although the relationship between the visible redness and presence/absence of the 506.5 nm band of Vesta and Vestoids is inconsistent with the assumed HED-lunar space weathering trend based on the above laboratory results. Other possible explanations are that some Vestoids experienced shock heavy enough to erase the 506.5 nm band and that pyroxenes on some Vestoids are not similar to those in HED meteorites. Even if the latter case is true and some Vestoids are not made of HED materials, HED meteorites could still come from Vesta unless we assume all Vestoids have to be fragments of Vesta.
KeywordsSpace Weathering Pulse Laser Irradiation Lunar Soil Lunar Planet Lunar Sample
- Gaffey, M. J., The asteroid (4) Vesta: Rotational spectral variations, surface material heterogeneity, and implications for the origin of the basaltic achondrites, Lunar Planet. Sci., 14, 231–232, 1983 (abstract).Google Scholar
- Hiroi, T. and C. M. Pieters, Origin of Vestoids suggested from the space weathering trend in the visible reflectance spectra of HED meteorites and lunar soils, Antarct. Meteorite Res., 11, 163–170, 1998.Google Scholar
- Hiroi, T. and S. Sasaki, Importance of space weathering simulation products in compositional modeling of asteroids: 349 Dembowska and 446 Aeternitas as examples, Meteoritics and Planet. Sci., 2001 (accepted).Google Scholar
- Wasson, J. T., C. M. Pieters, A. V. Fisenko, L. F. Semjonova, and P. H. Warren, Simulation of space weathering of eucrites by laser impulse irradiation, Lunar Planet. Sci., 29, 1998 (abstract # 1940).Google Scholar
- Yamada, M., S. Sasaki, H. Nagahara, A. Fujiwara, S. Hasegawa, H. Yano, T. Hiroi, H. Ohashi, and H. Ohtake, Simulation of space weathering of Planet-forming materials: Nanosecond pulse laser irradiation and proton implantation on olivine and pyroxene samples, Earth Planets Space, 51, 1255–1265, 1999.CrossRefGoogle Scholar | <urn:uuid:e51bbff7-cd71-498e-b614-160065379d84> | 2.578125 | 741 | Academic Writing | Science & Tech. | 52.873019 | 95,574,041 |
Scientists discover how birds localize sound sources
Unlike mammals, birds have no external ears. The outer ears of mammals play an important function in that they help the animal identify sounds coming from different elevations. But birds are also able to perceive whether the source of a sound is above them, below them, or at the same level.
Now a research team from Technische Universität München (TUM) has discovered how birds are able to localize these sounds, namely by utilizing their entire head. Their findings were published recently in the PLOS ONE journal.
It is springtime, and two blackbirds are having a sing-off. They are both competing for the attentions of a female. But to pick a successful suitor, the female must first be able to find him.
“Because birds have no external ears, it has long been believed that they are unable to differentiate between sounds coming from different elevations,” explains Hans A. Schnyder from the TUM Chair of Zoology. “But a female blackbird should be able to locate her chosen mate even if the source of the serenade is above her.”
Mammals identify sound sources in the vertical plane using their external ears, which absorb, reflect or diffract the sound waves because of their special structure. Their sense of hearing uses this information to determine the elevation of the sound source. But how do birds perceive these differences?
The head does the work of external ears
By studying three avian species – crow, duck and chicken – Schnyder discovered that birds are also able to identify sounds from different elevation angles. It seems that their slightly oval-shaped head transforms sound waves in a similar way to external ears.
“We measured the volume of sounds coming from different angles of elevation at the birds’ eardrums,” relates Schnyder. All sounds originating from the same side as the ear were similarly loud, regardless of their elevation. The ear on the opposite side of the head registered different elevations much more accurately – in the form of different volume levels.
Different volume levels reveal sound sources
It all comes down to the shape of the avian head. Depending on where the sound waves hit the head, they are reflected, absorbed or diffracted. What the scientists discovered was that the head completely screens the sound coming from certain directions. Other sound waves pass through the head and trigger a response in the opposite ear.
The avian brain determines whether a sound is coming from above or below from the different sound volumes in both ears. “This is how birds identify where exactly a lateral sound is coming from – for example at eye height,” continues Schnyder. “The system is highly accurate: at the highest level, birds can identify lateral sounds at an angle of elevation from -30° to +30°.”
Interaction between hearing and sight improves orientation
Why have birds developed sound localization on the vertical plane? Most birds have eyes on the sides of their heads, giving them an almost 360° field of vision. Since they have also developed the special ability to process lateral sounds coming from different elevations, they combine information from their senses of hearing and vision to useful effect when it comes to evading predators.
A few birds of prey like the barn owl have developed a totally different strategy. This species hunts at night, and like humans its eyes are front-facing. The feather ruff on their face modifies sounds in a similar way to external ears. The owl hears sounds coming from in front of it better than the other bird species studied by Schnyder.
So there is a perfect interaction between the information they hear and the information they see - as earlier studies were able to demonstrate. “Our latest findings are pointing in the same direction: it seems that the combination of sight and hearing is an important principle in the evolution of animals,” concludes Schnyder.
The Avian Head Induces Cues for Sound Localization in Elevation; Hans A. Schnyder, Dieter Vanderelst, Sophia Bartenstein, Uwe Firzlaff and Harald Luksch; PLOS ONE, November 2014, DOI: 10.1371/journal.pone.0112178
Interview with Hans A. Schnyder: How birds do get by without external ears? (YouTube)
Pictures for download
Technische Universität München
Chair of Zoology
Hans A. Schnyder
phone: +49 8161 71-2806
Prof. Harald Luksch
phone: +49 8161 71-2801
Barbara Wankerl | EurekAlert!
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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18.07.2018 | Health and Medicine | <urn:uuid:b4781f67-e3a4-4aac-9dea-3c250abec9e9> | 4.40625 | 1,599 | Content Listing | Science & Tech. | 44.849786 | 95,574,076 |
Asteroids play the role of time capsules showing what molecules originally existed in our solar system, and may help explain how life started on Earth, a study suggests.
Finding complex molecules in asteroids provides the strongest evidence that such compounds were present on the Earth before life formed, said Nicholas Hud from Georgia Institute of Technology in the US.
Knowing what molecules were present helps establish the initial conditions that led to the formation of amino acids and related compounds that, in turn, came together to form peptides, small protein-like molecules that may have kicked off life on our planet.
"It's important for us to study materials from asteroids and meteorites, the smaller versions of asteroids that fall to Earth, to test the validity of our models for how molecules in them could have helped give rise to life.
"We also need to catalogue the molecules from asteroids and meteorites because there might be compounds there that we had not even considered important for starting life," he said.
NASA scientists have been analysing compounds found in asteroids and meteorites for decades, and their work provides a solid understanding for what might have been present when the Earth itself was formed, Hud said.
He believes there are many possible ways that the molecules of life could have formed. Life could have gotten started with molecules that are less sophisticated and less efficient than what we see today.
Like life itself, these molecules could have evolved over time. "What we find is that these compounds can form molecules that look a lot like modern peptides, except in the backbone that is holding the units together," said Hud.
"The overall structure can be very similar and would be easier to make, though it does not have the ability to fold into as complex structures as modern proteins.
"There is a tradeoff between the simplicity of forming these molecules and how close these molecules are to those found in contemporary life," said Hud. | <urn:uuid:55b319d7-d7c1-4566-a923-29e080e200b1> | 3.890625 | 383 | News Article | Science & Tech. | 28.295923 | 95,574,122 |
Producing a makefile for a C or C ++ program is tedious, especially because of the very special syntax of this file, which dates back to ancient computers.
One found now that it was more convenient to produce a CMake file from which a makefile file can be generated automatically. But that does not simplify the work and we see that there are hundreds of tutorials on the web to help build this new configuration file for generating configuration files.
To put it simply, I wrote No Make, a program that finds the dependencies of each source file by itself and compiles them, before generating the executable program.
No Make checks for each source file if there is an object file already generated or if the source is newer than the object file, and it compiles the source only in this case.
One can however with the option -a choose to regenerate the whole project. In both cases with one command:
nomake -a source
"source" is the name of the source code of the file containing the "main" function. The extension is optional. It must include the header files of the sources on which it depends, which themselves must also have #include for their dependencies. Another constraint is that all source files must have the same extension, ".c" or ".cpp".
No Make first builds a list of all the necessary files, based on the include commands, and compiles the sources starting with the ones with the least dependencies and ending with the one with the most.
To display the list of options, just type the name of the program:
The source code is included. License: Apache 2.0
Works with Visual C on Windows. | <urn:uuid:201dbf7b-c43a-42da-be6a-2de717a99a00> | 3.078125 | 340 | Documentation | Software Dev. | 49.87512 | 95,574,138 |
|Metamath Proof Explorer||
|Mirrors > Home > MPE Home > Th. List > ru||Structured version Unicode version|
|Description: Russell's Paradox.
Proposition 4.14 of [TakeutiZaring] p.
In the late 1800s, Frege's Axiom of (unrestricted) Comprehension, expressed in our notation as , asserted that any collection of sets is a set i.e. belongs to the universe of all sets. In particular, by substituting (the "Russell class") for , it asserted , meaning that the "collection of all sets which are not members of themselves" is a set. However, here we prove . This contradiction was discovered by Russell in 1901 (published in 1903), invalidating the Comprehension Axiom and leading to the collapse of Frege's system.
In 1908, Zermelo rectified this fatal flaw by replacing Comprehension with a weaker Subset (or Separation) Axiom ssex 4347 asserting that is a set only when it is smaller than some other set . However, Zermelo was then faced with a "chicken and egg" problem of how to show is a set, leading him to introduce the set-building axioms of Null Set 0ex 4339, Pairing prex 4406, Union uniex 4705, Power Set pwex 4382, and Infinity omex 7598 to give him some starting sets to work with (all of which, before Russell's Paradox, were immediate consequences of Frege's Comprehension). In 1922 Fraenkel strengthened the Subset Axiom with our present Replacement Axiom funimaex 5531 (whose modern formalization is due to Skolem, also in 1922). Thus, in a very real sense Russell's Paradox spawned the invention of ZF set theory and completely revised the foundations of mathematics!
Another mainstream formalization of set theory, devised by von Neumann, Bernays, and Goedel, uses class variables rather than set variables as its primitives. The axiom system NBG in [Mendelson] p. 225 is suitable for a Metamath encoding. NBG is a conservative extension of ZF in that it proves exactly the same theorems as ZF that are expressible in the language of ZF. An advantage of NBG is that it is finitely axiomatizable - the Axiom of Replacement can be broken down into a finite set of formulas that eliminate its wff metavariable. Finite axiomatizability is required by some proof languages (although not by Metamath). There is a stronger version of NBG called Morse-Kelley (axiom system MK in [Mendelson] p. 287).
Russell himself continued in a different direction, avoiding the paradox with his "theory of types." Quine extended Russell's ideas to formulate his New Foundations set theory (axiom system NF of [Quine] p. 331). In NF, the collection of all sets is a set, contradicting ZF and NBG set theories, and it has other bizarre consequences: when sets become too huge (beyond the size of those used in standard mathematics), the Axiom of Choice ac4 8355 and Cantor's Theorem canth 6539 are provably false! (See ncanth 6540 for some intuition behind the latter.) Recent results (as of 2014) seem to show that NF is equiconsistent to Z (ZF in which ax-sep 4330 replaces ax-rep 4320) with ax-sep 4330 restricted to only bounded quantifiers. NF is finitely axiomatizable and can be encoded in Metamath using the axioms from T. Hailperin, "A set of axioms for logic," J. Symb. Logic 9:1-19 (1944).
Under our ZF set theory, every set is a member of the Russell class by elirrv 7565 (derived from the Axiom of Regularity), so for us the Russell class equals the universe (theorem ruv 7568). See ruALT 7569 for an alternate proof of ru 3160 derived from that fact. (Contributed by NM, 7-Aug-1994.)
|1||pm5.19 350||. . . . . 6|
|2||eleq1 2496||. . . . . . . 8|
|3||df-nel 2602||. . . . . . . . 9|
|4||id 20||. . . . . . . . . . 11|
|5||4, 4||eleq12d 2504||. . . . . . . . . 10|
|6||5||notbid 286||. . . . . . . . 9|
|7||3, 6||syl5bb 249||. . . . . . . 8|
|8||2, 7||bibi12d 313||. . . . . . 7|
|9||8||spv 1965||. . . . . 6|
|10||1, 9||mto 169||. . . . 5|
|11||abeq2 2541||. . . . 5|
|12||10, 11||mtbir 291||. . . 4|
|13||12||nex 1564||. . 3|
|14||isset 2960||. . 3|
|15||13, 14||mtbir 291||. 2|
|Colors of variables: wff set class|
|Syntax hints: wn 3 wb 177 wal 1549 wex 1550 wceq 1652 wcel 1725 cab 2422 wnel 2600 cvv 2956|
|This theorem was proved from axioms: ax-1 5 ax-2 6 ax-3 7 ax-mp 8 ax-gen 1555 ax-5 1566 ax-17 1626 ax-9 1666 ax-8 1687 ax-6 1744 ax-7 1749 ax-11 1761 ax-12 1950 ax-ext 2417|
|This theorem depends on definitions: df-bi 178 df-an 361 df-tru 1328 df-ex 1551 df-nf 1554 df-sb 1659 df-clab 2423 df-cleq 2429 df-clel 2432 df-nel 2602 df-v 2958|
|Copyright terms: Public domain||W3C validator| | <urn:uuid:f5749c63-0d4a-4275-bfd2-bcdf8c1393ba> | 3.140625 | 1,373 | Documentation | Science & Tech. | 88.913365 | 95,574,161 |
|Holarchaea species from New Zealand, possibly Holarchaea novaeseelandiae|
Holarchaea is a spider genus with only two described species as of September 2016[update], although there may be undescribed species from New Zealand. It was formerly placed as the only genus in the family Holarchaeidae, but is now placed in Anapidae by the World Spider Catalog.
Distribution and habitat
Holarchaea species are known only from the forests of Tasmania and New Zealand, where they live in microhabitats with consistently high humidity.
Holarchaea Forster, 1955
- Holarchaea globosa (Hickman, 1981) – Tasmania
- Holarchaea novaeseelandiae (Forster, 1949) (type species) – New Zealand
- Forster, R. R. & N. I. Platnick (1984). A review of the archaeid spiders and their relatives, with notes on the limits of the superfamily Palpimanoidea (Arachnida, Araneae). Bull. Am. Mus. nat. Hist. 178:1-106. Abstract - PDF (60Mb)
- Meier J. & White J. (eds) (1995). Handbook of Clinical Toxicology of Animal Venoms and Poisons. Boca Raton: CRC Press.
|Wikispecies has information related to Holarchaea|
|This araneomorph spider -related article is a stub. You can help Wikipedia by expanding it.| | <urn:uuid:b947b9da-f0c4-4f4a-8259-19f5e6752ea8> | 2.59375 | 315 | Knowledge Article | Science & Tech. | 47.110721 | 95,574,163 |
'We're reminded what it's like to deal with the force of nature': From collecting molten lava in buckets to perching on crater edges, Scientists reveal the dangers of monitoring Hawaii's Kilauea volcano
- Scientists have been measuring the eruptions 24/7 since Kilauea first exploded more than two months ago
- They are a mix of USGS staff, University of Hawaii researchers and trained volunteers working six-to-eight-hour shifts in teams of two to five
- They avoid synthetics because they melt in the intense heat and wear gloves to protect their hands from sharp volcanic rock and glass, while helmets protect against falling lava and respirators ward off sulfur gases
Dressed in heavy cotton, a helmet and respirator, Jessica Ball worked the night shift monitoring 'fissure 8,' which has been spewing fountains of lava as high as a 15-story building from a slope on Hawaii's Kilauea volcano.
The lava poured into a channel oozing toward the Pacific Ocean several miles away.
In the eerie orange nightscape in the abandoned community of Leilani Estates, it looked like it was flowing toward the scientist, but that was an optical illusion, Ball said.
'The volcano is doing what it wants to. ... We're reminded what it's like to deal with the force of nature,' said Ball, a geologist with the U.S. Geological Survey.
Scroll down for video
A geologist is collecting sample of molten lava from 2011 Kamoamoa eruption, at Kilauea Volcano, Hawaii, U.S., March 6, 2011. Picture taken on March 6, 2011.
Scientists have been in the field measuring the eruptions 24 hours a day, seven days a week since Kilauea first exploded more than two months ago.
They are a mix of USGS staff, University of Hawaii researchers and trained volunteers working six-to-eight-hour shifts in teams of two to five.
They avoid synthetics because they melt in the intense heat and wear gloves to protect their hands from sharp volcanic rock and glass.
A USGS geologist making observations of the fissure 8 lava channel at sunset is pictured in this July 3, 2018 fisheye lens handout photograph near the Kilauea volcano eruption in Hawaii, U.S
Helmets protect against falling lava stones, and respirators ward off sulfur gases.
This is not a job for the faint hearted.
Geologists have died studying active volcanoes. David Alexander Johnston, a USGS volcanologist was killed by the 1980 eruption of Mount St. Helens in Washington state.
In 1991, American volcanologist Harry Glicken and his French colleagues Katia and Maurice Krafft were killed while conducting avalanche research on Mount Unzen in Japan.
Kelly Wooten, a geologist and volcanologist at Hawaiian Volcano Observatory (HVO) is downloading radiometer data on rim of Halema?Äòuma?Äòu Crater in Kilauea Volcano, Hawaii, U.S., December 19, 2008
Dr. Jessica Ball of USGS, a geologist and volcanologist who does research at the US Geological Survey and Dr. Rick Hazlett (R) of University of Hawai'i at Hilo, are measuring temperatures in a crack near fissure 10 in the Leilani Estates Subdivision in Hawaii, U.S., June 8, 2018.
July 7, 2018 - Hawaii, U.S. - For several years, a special ultraviolet camera has been located near Keanakako'i Crater at Kilauea's summit. The camera was capable of detecting SO2 gas coming from Halemaumau crater. This morning, the camera was removed because there is very little SO2 to measure these days at the summit. In addition, cracking near Keanakako'i Crater was making access difficult.
Ball, a graduate of the State University of New York at Buffalo, located in upstate New York near the Canadian border, compared Kilauea's eruptions to Niagara Falls.
'It gives you the same feeling of power and force,' she said.
Kilauea, which has been erupting almost continuously since 1983, is one of the world's most closely monitored volcanoes, largely from the now-abandoned Hawaiian Volcano Observatory at the summit.
But the latest eruption is one of Kilauea's biggest and could prove to be a bonanza for scientists.
Ball and the USGS teams are studying how the magma - molten rock from the earth's crust - tracks through a network of tubes under the volcano in what is known as the 'Lower East Rift Zone,' before ripping open ground fissures and spouting fountains of lava.
They are trying to discover what warning signs may exist for future eruptions to better protect the Big Island's communities, she said.
Fissure 8 is one of 22 around Kilauea that have destroyed over 1,000 structures and forced 2,000 people to evacuate.
They are what make this volcanic eruption a rare event, Ball said.
'They're common for Kilauea on a geologic time scale, but in a human time scale it's sort of a career event,' she said.
Dr. Jessica Ball of USGS, a geologist and volcanologist who does research at the US Geological Survey, is updating Hawaiian Volcano Observatory scientists on the ground during a helicopter overflight of the ocean entry of the fissure 8 lava flow where a laze (lava haze) plume is visible over the active parts of the flow margin near Kapoho, Hawaii, U.S., June 8, 2018.
July 6, 2018 - Kapoho, Hawaii, U.S. - Dawn at Fissure 8 glows red with steam and lava flow.
Meanwhile, the summit is erupting almost every day with steam or ash, said Janet Snyder, spokeswoman for the County of Hawaii, where Kilauea is located.
Scientists had thought the steam explosions resulted from lava at the summit dropping down the volcano's throat into groundwater. This was based on Kilauea's 1924 eruption, to which the current one is most often compared.
But the explosions this time have released lots of sulfur dioxide gas, which means magma is involved, said Michael Poland, scientist-in-charge at Yellowstone Volcano Observatory, one of many volcanologists seconded to Kilauea.
'So we have already made a conceptual leap, leading us to believe it was different from what we had understood,' he said.
Poland and other scientists pulled equipment and archives out of the abandoned observatory at the volcano summit after hundreds of small eruption-induced quakes damaged the structure, and have decamped to the University of Hawaii in Hilo on the Big Island.
The archives included photos, seismic records and samples, some 100 or more years old, Poland said. 'These materials are invaluable to someone who says, 'I have this new idea, and I want to test it using past data.''
Now the second longest Kilauea eruption on record, surpassed only by one in 1955, this eruption offers far better research opportunities than previous events, Ball said.
'We've got much better instruments and we've got longer to collect the data,' she said.
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Sorry we are not currently accepting comments on this article. | <urn:uuid:8f163748-94d3-4d70-acd8-f32cf66c88dc> | 3.109375 | 1,709 | Truncated | Science & Tech. | 48.685305 | 95,574,175 |
Water scarcity is potentially a very stressful issue in Middle East, the most water-contested region in the world. According to World Resources Institute (WRI) rankings, most water scarce countries are in the Middle East, including Bahrain, Kuwait, Yemen, Palestine, Qatar, United Arab Emirates, Israel, Saudi Arabia, Oman, and Lebanon. The region depends heavily on underground aquifers and desalinated seawater for its water supply. Given the rapid depletion of aquifers and the limited supply of desalinated water, it is bound to face exceptional water-related challenges for the foreseeable future.
Breakthrough in the search for cosmic particle accelerators: Scientists trace a single neutrino back to a galaxy billions of light years away | Science Daily
July 13, 2018 | <urn:uuid:e099f1e6-2a43-4d8b-9a4a-07610d119e8b> | 3.265625 | 158 | Truncated | Science & Tech. | 12.284712 | 95,574,184 |
New Delhi: India is making efforts to monitor and study earthquake pre-cursory phenomena in critical seismotectonic regions, the Rajya Sabha was informed on Thursday.
Minister of State for Science and Technology and Earth Sciences YS Chowdary said the government initiated a programme 'Seismicity & Earthquake Precursor' to understand the earthquake generation process, and better identify possible earthquake signs, based on which useful predictions could be made.
In a written reply to the house, Chowdary said the programme, initiated by his ministry through a multi-institutional and multi-disciplinary mechanism, would help adopt an integrated approach of generation, assimilation and analyses of a variety of earthquake signs in advance.
Also underway is a project on drilling a deep bore to study in detail the ongoing earthquake generation processes in the region of the seismically active Koyna-Warna in Maharashtra, said an official statement.
The proposed scientific deep drilling investigation seeks to provide data sets to better understand the mechanisms of faulting and the physics of reservoir triggered earthquakes.
It also intends to contribute towards earthquake hazard assessment and develop models for earthquake forecast in future. | <urn:uuid:21c0da9f-a505-47f4-a502-1efe648611f6> | 2.65625 | 233 | News Article | Science & Tech. | 2.37029 | 95,574,218 |
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What you should know about brown water polluting Indian River Lagoon, rivers, beaches
Coffee-colored water is spreading throughout area waterways and along Atlantic Coast beaches. This video shows the water at a beach on Oct. 9 in Hobe Sound about six miles south of the St. Lucie Inlet. DACIA JOHNSON/TCPALM Wochit
What waters are affected?
- Sebastian River
- St. Lucie River
- Indian River Lagoon
- Atlantic Ocean beaches
Where’s it coming from? Two sources:
- Lake Okeechobee discharges
- Rainfall runoff flowing through Florida’s drainage canal system
- C-54 Canal to the Sebastian River to the Indian River Lagoon to the Sebastian Inlet to the Atlantic Ocean
- C-25 Canal to Taylor Creek to the Indian River Lagoon to the Fort Pierce Inlet to the Atlantic Ocean
- C-24 Canal to the North Fork of the St. Lucie River to the St. Lucie Inlet to the Atlantic Ocean
- C-23 Canal to the St. Lucie River to the St. Lucie Inlet to the Atlantic Ocean
What dangers does it contain?
- Chemical-laden pesticides and herbicides
- Fertilizers containing algae-feeding nitrogen and phosphorus
- Enteric bacteria, an indication of fecal pollution from people and animals
Is a toxic algae bloom possible?
- Odds in favor: Low salinity, warm water, sunny days, lots of nutrients
- Odds against: No Lake Okeechobee bloom that could spread
In the summer of 2016, discharges from Lake Okeechobee caused widespread toxic algae blooms in the St. Lucie River. Wochit
How’s it affecting the environment?
- Killing oysters, sea grass and other plants and animals
- Nesting and hatching sea turtles likely are not affected | <urn:uuid:5ebb0311-e561-4ae7-9773-f67fa1b3c5ae> | 2.84375 | 425 | Q&A Forum | Science & Tech. | 48.711554 | 95,574,224 |
Photo credit: NASA?s Goddard Space Flight Center
Irvine, Calif., March 8, 2018 — University of California, Irvine scientists expect the world’s fisheries to be, on average, 20 percent less productive in the year 2300, with those in the North Atlantic down nearly 60 percent and those in much of the western Pacific experiencing declines of more than 50 percent.
In a study published this week in Science, UCI climatologists outline the results of computer simulations showing a world subjected to nearly three more centuries of unbridled global warming. This bleak future will be characterized by a 9.6-degree Celsius (17 degrees Fahrenheit) increase in mean surface air temperature, nearly 10 times the warming we have seen to this point. The extended climate warming will drastically alter wind patterns, boost ocean surface temperatures and melt nearly all the sea ice in polar regions.
“These conditions will cause changes in phytoplankton growth and ocean circulation around Antarctica, with the net effect of transferring nutrients from the upper ocean to the deep ocean,” said lead author J. Keith Moore, UCI professor of Earth system science. “Marine ecosystems everywhere to the north will be increasingly starved for nutrients, leading to less primary production (photosynthesis) by phytoplankton, which form the base of ocean food chains.”
In today’s ocean, nutrients are brought up to the surface around Antarctica but then move north and eventually flow into the low latitudes, supporting the plankton and fish populations there, Moore said. With increased phytoplankton growth around Antarctica, the northward transfer of nutrients will be greatly reduced.
“You end up trapping the nutrients near Antarctica,” he said.
There are three key factors driving increased phytoplankton growth around Antarctica, according to Moore: the long-term warming trend in the oceans, the changes in winds brought on by global climate warming and, most significantly, the near elimination of sea ice along the coast of Antarctica.
“Without the floating ice, which blocks much of the light today, you get increased photosynthesis,” Moore said. “Combined with warmer ocean temperatures throughout the year, this leads to a longer growing season and faster plankton growth rates. Stronger winds drive increased upwelling, bringing nutrients to the surface, resulting in higher nutrient concentrations and more plankton growth near Antarctica.”
Nitrogen and phosphorus are key nutrients that support phytoplankton growth in the ocean. As these elements are increasingly depleted everywhere to the north, phytoplankton populations decline and scarcity reverberates up through the food chain, ultimately affecting the fish that humans catch and eat. Moore and his fellow researchers used an empirical model linking plankton growth to present-day fish catches and then factored in dwindling nutrients and plankton populations due to climate warming in the coming centuries.
“By looking at the decline in fish food over time, we can estimate how much our total potential fisheries catch could be reduced,” said Moore, who helped develop the Community Earth System Model employed in this study.
He emphasized the importance of looking further into the future with climate models, something that isn’t often done because of the computational resources such modeling requires. Months of computations using thousands of central processing units were needed to simulate the climate and oceans up to 2300. But stopping climate studies at the end of our current century, as is common among scientists and policymakers, is insufficient given the amount of time it takes for the ocean to absorb and respond to heat being trapped by the Earth’s atmosphere today, Moore said.
“The climate is warming rapidly now, but in the ocean, most of that added heat is still right at the surface. It takes centuries for that heat to work its way into the deeper ocean, changing the circulation and removing the sea ice, which is a big part of this process,” he said.
“This is what’s going to happen if we don’t put the brakes on global warming, and it’s pretty catastrophic for the oceans,” Moore stressed. “There is still time to avoid most of this warming and get to a stable climate by the end of this century, but in order to do that, we have to aggressively reduce our fossil fuel use and emissions of greenhouse gas pollutants.”
Collaborating on this U.S. Department of Energy-supported study were scientists from the National Center for Atmospheric Research, the University of Virginia, Cornell University, and Oak Ridge National Laboratory.
Like this article? Click here to subscribe to free newsletters from Lab Manager | <urn:uuid:f52b1075-3226-4b34-94e8-219d6d7d970e> | 3.3125 | 963 | News Article | Science & Tech. | 34.439889 | 95,574,235 |
Displays the standard Color picker, allowing the user to choose a color.
result=SelectColor(ByRef col, prompt)
|result||Boolean||Returns True if the user clicks OK; False if the user cancels.|
|col||Color||Color passed to SelectColor and the color the user selects.
Note the usage of ByRef in the parameter list.
|prompt||String||Prompt to be displayed in the Color Picker. Shown only on Linux.|
You control the default choice of color displayed by the Color Picker by passing a value of col to SelectColor. If col is not assigned a value, black is used as the default color. The color that the user chooses is returned in col. If the user clicks Cancel without making a choice, result is set to False; otherwise it is set to True.
The following example allows the user to select a color that will be used as the fillcolor in a Rectangle control.
Dim b As Boolean
c = CMY(0.35, 0.9, 0.6) // choose the default color shown in color picker
b = SelectColor(c, "Select a Color")
Rectangle1.FillColor = c
If you don't want to test the boolean returned by SelectColor, you can call it using Call. | <urn:uuid:0293126b-fed7-4904-b060-de7694c47c25> | 2.796875 | 282 | Documentation | Software Dev. | 67.374375 | 95,574,247 |
Multicellular organisms create complex patterned structures from identical, unreliable components. Learning how to engineer such robust behavior is important to both an improved understanding of computer science and to a better understanding of the natural developmental process. Earlier work by our colleagues and ourselves on amorphous computing demonstrates in simulation how one might build complex patterned behavior in this way. This work reports on our first efforts to engineer microbial cells to exhibit this kind of multicellular pattern directed behavior. We describe a specific natural system, the Lux operon of Vibrio fischeri, which exhibits density dependent behavior using a well characterized set of genetic components. We have isolated, sequenced, and used these components to engineer intercellular communication mechanisms between living bacterial cells. In combination with digitally controlled intracellular genetic circuits, we believe this work allows us to begin the more difficult process of using these communication mechanisms to perform directed engineering of multicellular structures, using techniques such as chemical diffusion dependent behavior. These same techniques form an essential part of our toolkit for engineering with life, and are widely applicable in the field of microbial robotics, with potential applications in medicine, environmental monitoring and control, engineered crop cultivation, and molecular scale fabrication.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:9b69a802-be0f-4034-ba6f-d7695314a6e8> | 3.359375 | 263 | Academic Writing | Science & Tech. | -5.546686 | 95,574,260 |
Asked by: Will Marritt, Hampshire
Removing carbon dioxide (CO2) from the atmosphere is tricky. Some new technologies use chemical filters to extract CO2 from the air, but come with a hefty price tag. A more promising method relies on plants’ natural ability to absorb ambient CO2 as they grow, transforming it into biomass. Planting trees or crops therefore results in a net removal of CO2 from the air. Taking things one step further, this plant matter can be burned inside specially adapted power stations that produce energy while capturing the CO2 emitted and burying it underground. This technology is, however, still undergoing development.
- Are some plants better than others at sucking up carbon dioxide?
- Could captured carbon dioxide be stored in the deep ocean? | <urn:uuid:fd6e2695-89a6-4d62-b03e-99e5a3b54112> | 3.78125 | 157 | Q&A Forum | Science & Tech. | 39.64121 | 95,574,275 |
|Debugging with GDB|
By default, gdb is silent about its inner workings. If you are
running on a slow machine, you may want to use the
command. This makes gdb tell you when it does a lengthy
internal operation, so you will not think it has crashed.
Currently, the messages controlled by
set verbose are those
which announce that the symbol table for a source file is being read;
symbol-file in Commands to Specify Files.
set verbose on
set verbose off
set verboseis on or off.
By default, if gdb encounters bugs in the symbol table of an object file, it is silent; but if you are debugging a compiler, you may find this information useful (see Errors Reading Symbol Files).
(gdb) run The program being debugged has been started already. Start it from the beginning? (y or n)
set confirm off
set confirm on
If you need to debug user-defined commands or sourced files you may find it useful to enable command tracing. In this mode each command will be printed as it is executed, prefixed with one or more ‘+’ symbols, the quantity denoting the call depth of each command.
set trace-commands on
set trace-commands off | <urn:uuid:bc1f4c72-7b37-457d-a484-f4832e9fe3a7> | 2.828125 | 274 | Documentation | Software Dev. | 56.376784 | 95,574,276 |
Geochemistry of uranium and thorium
Certain chemical characteristics of uranium and thorium govern their behavior in geologic processes. Their isotopic characteristics are less related to their roles in such processes and are not considered here.
Uranium (Katz and Rabinowitch, 1951; Kirk and Othmer, 1955a)—atomic number 92 and weight 238—has an ion size of 1.05 A and six valence electrons. Quadrivalent and sexivalent occurrences are common in nature. Uranium metal has a density of 19 and a melting point of about 1,133 C (Katz and Rabinowitch, 1951, p. 152).
The ion radius is very close to that of calcium (1.06 A) and trivalent rare earths (yttrium, 1.06 A), so uranium is preferentially captured by minerals of these elements (Goldschmidt, 1954, p. 562). Fluorine captures both quadrivalent uranium and thorium.
Sexivalent uranium compounds, because of their greater ionic potential, are chemically more mobile than quadrivalent uranium (Goldschmidt, 1954, p. 565).
Uranium reacts readily with all the nonmetallic elements and many metals including Hg, Pb, Cu, Fe, Ni, Mn, Co, Zn, and Be. Reactions with elements considered to be volatile mineralizers in magmatic and mantle emanations are important. UF6 forms at room temperature and U F4 forms at 200 to 400°C. UF4 is soluble in HC1 solutions at room temperature, remaining in the quadrivalent state. It also dissolves in a mixture of dilute sulfuric acid and silica, remaining as UF4. Uranium tetrachlorides are easily formed in gas-phase reactions at elevated temperatures or by liquid-phase reactions at moderate temperatures. | <urn:uuid:815a801b-6f6a-40c5-a57f-d6e74a0ea2ca> | 3.90625 | 392 | Knowledge Article | Science & Tech. | 42.730327 | 95,574,278 |
One of the last remaining New England whaling ships has provided unexpected insights into the origin of halogenated organic compounds (HOCs) that have similar chemical and physical properties as toxic PCBs and the pesticide DDT. HOCs are found everywhere and degrade slowly, but some are naturally produced and others are produced by humans.
While large scale industrial production of HOCs did not begin until the late 1920s, scientists from the Woods Hole Oceanographic Institution (WHOI) in Massachusetts say naturally produced HOCs were bioaccumulating in marine mammals before major chemical companies like Monsanto, Dupont, and 3M were making HOCs for industrial uses. Their findings are reported in the online version of the journal Environmental Pollution.
In the past decade, scientists conducting routine analyses of animal and food samples began to discover unknown HOCs in their samples. Detective work led to their identities, but where these compounds were coming from has been a mystery. While some of these "unknown" compounds can be loosely traced to a possible industrial or natural source, the majority of these compounds have no known industrial or natural sources.
Emma Teuten and Christopher Reddy found their pre-industrial HOC samples in a most unlikely place: whale oil from the Charles W. Morgan, one of the last whaling ships operating during the 19th and early 20th century. Built in 1841 in New Bedford, Mass., the ship traveled the world looking for whales, often on voyages of three years or more. The ship is now preserved and on public display at Mystic Seaport in Mystic, Conn. The researchers received the whale oil samples from the New Bedford Whaling Museum.
Teuten and Reddy studied one sample of antique whale oil and found the HOCs in all the samples . The results provide further evidence that naturally produced HOCs were accumulating in marine mammals long before the human-produced varieties.
“What is most interesting to us is that we still find these ’natural’ compounds in recent samples from marine mammals, human breast milk, and commercially available fish in Canada,” said study co-author Christopher Reddy, an associate scientist in the WHOI Marine Chemistry and Geochemistry Department. With co-author Emma Teuten, now at the University of Plymouth, England but previously at WHOI, Reddy studied one of the previously unknown HOCs and determined that it was from a natural source, not industrial pollution. The approach was time consuming, taking more than six months of lab work to complete, and required more than ten pounds of whale blubber.
“Our main goal now is to identify who is making them, why, and how toxic they are,” said Teuten. “We suspect that many of these compounds were and are made by bacteria, plants, animals as chemical defense mechanisms.”
Reddy says the properties of these natural compounds he and Teuten found in the archived whale oil are similar to those of industrial HOCs. “Most industrial HOCs do degrade in the environment, although very slowly. With adequate regulations regarding the manufacture and release of the industrial versions, we expect in the future that natural HOCs, rather than industrial ones, will again be the only HOCs found in animal and human tissue.”
Reddy says these results should motivate science to consider the ecological role and bioactivity of these natural HOCs and how pre-exposure to these compounds prepared bacteria, plants, animals, and humans for industrial HOCs introduced during the past century. It is well known that organisms have evolved defensive mechanisms against chemicals in their environment, and until recently the sources of these chemicals were primarily natural. The importance of HOCs like those identified by Teuten and Reddy in the evolution of these defenses is not yet understood.
Industrial HOCs have been accumulating in the environment since the 1930’s. Production of PCBs began in 1929, DDT in the late 1930s. “Knowing that the natural compounds have been produced for much longer times, we can use the natural sources as tools in studying the industrial ones,” Teuten said. “For example, we may be able to use these natural HOCs as chemical tracers, just like dyes are used in medicine.”
This study was supported by the National Science Foundation, WHOI Ocean Life Institute, and The Camille and Henry Dreyfus Foundation.
Shelley Dawicki | EurekAlert!
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
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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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17.07.2018 | Power and Electrical Engineering | <urn:uuid:0d42f481-ce4a-42ef-9598-50d06266dc6f> | 3.359375 | 1,575 | Content Listing | Science & Tech. | 36.336418 | 95,574,294 |
A swarm of large jellyfish, most between 40-70 centimeters in size, has in the past few days been spotted on the northern coasts of Achziv and Nahariya, University of Haifa researchers reported on Wednesday. While jellyfish can be seen at times along Israeli shores in the winter, the quantity observed in recent days is rare, according to Dr. Dror Angel, a marine ecology expert in the maritime civilizations department.
He said one reason for the swarm’s size may be the storm that struck Israel last week. While rare, Angel stressed that this type of swarm is not unexpected.
“As long as human activity continues, including building and development on beaches, uncontrolled fishing, sea pollution, development and deep sea activities and more, marine systems will become more and more unbalanced and actually quite fragile,” he said. | <urn:uuid:abcf49b1-d4ab-485f-a827-c61827c52b40> | 2.515625 | 174 | News Article | Science & Tech. | 33.602232 | 95,574,316 |
+44 1803 865913
By: D Whittaker
262 pages, Figs
Spectroscopic data provides a great deal of useful information about organic molecules. Competently deriving structural information from such data therefore, is a requisite skill for many undergraduates studying chemistry. This work covers the basic principles of spectroscopy in as non-mathematical a way as possible. It assumes no previous knowledge of spectroscopy and avoids excessive theory, approaching the topic as an exercise in pattern recognition. Hence, the main focus of the book is in the provision on the simpler spectra, and applying techniques learned to tackle more complex examples.
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On behalf of Parque Nacional Nahuel Huapi I would like to thank NHBS. The book will be very useful for my students.
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||Ferromagnetism of metallic systems, especially those including transition metals, has been a controversial subject of modern science for a long time. This controversy stems from the apparent dual character of the rf-electrons responsible for magnetism in transition metals, i.e., they are itinerant electrons described by band theory in their ground state, while at finite temperatures they show various properties that have long been attributed to a system consisting of local magnetic moments. The most familiar example of these properties is the Curie-Weiss law of magnetic susceptibility obeyed by almost all ferromagnets above their Curie temperatures.
At first the problem seemed to be centered around whether the (/-electrons themselves are localized or itinerant. This question was settled in the 1950s and early 1960s by various experimental investigations, in particular by observations of d-electron Fermi surfaces in ferromagnetic transition metals. These observations are generally consistent with the results of band calculations.
Theoretical investigations since then have concentrated on explaining this dual character of d-electron systems, taking account of the effects of electron-electron correlations in the itinerant electron model. The problem in physical terms is to study the spin density fluctuations, which are neglected in the mean-field or one-electron theory, and their influence on the physical properties.
There have been two main streams in the research in this direction. One has been to study the local moments in metals or the possibility for the itinerant electrons to exhibit spin density fluctuations that are described at least approximately as a set of local magnetic moments. This approach attained remarkable success in the 1960s from a qualitative point of view and has been extended further since then.
The other stream of research has been to improve the mean-field theory by taking into account the spatially extended spin density fluctuations in contrast with the local moment picture. This line of approach, represented by the random-phase approximation, was, however, not successful until the early 1970s when a self-consistent theory of coupled modes of extended spin fluctuations was advanced and the difficulties of the random-phase approximation were removed. This improved theory was remarkably successful when applied to weakly ferromagnetic metals where the long-wavelength components of spin fluctuations are the predominant thermal excitations. | <urn:uuid:73fc2a15-5e2a-48c1-9786-f9f39961a92a> | 2.796875 | 463 | Academic Writing | Science & Tech. | 19.553545 | 95,574,330 |
Drawing from scientific discoveries in oceanography, meteorology, geochemistry, biology and astrophysics, author Spencer R. Weart draws you into the puzzle of climate change as it is unfolding through time. No one person had an “aha” moment and discovered global warming. Instead, today’s understanding required an accumulation of theories from disparate areas of research, shaped by the rigors of the scientific method. These discoveries convinced most scientists that global warming is a serious phenomenon. Weart outlines the scientific process that led to today’s climate diagnosis. He also relates lively stories about the people behind the discoveries. That may not be as immediately applicable, but getAbstract finds that it is illuminating and could help readers feel like insiders in this fight.
In this summary, you will learn
- How scientists discovered global warming
- How worldwide inquiry and cooperation evolved
- How greenhouse gases and other factors abet warming
About the Author
Spencer R. Weart directs the History of Physics program at the American Institute of Physics. His previous books include Nuclear Fear and Scientists in Power.
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- Open Access
MHD boundary layer flow due to a moving wedge in a parallel stream with the induced magnetic field
© Jafar et al.; licensee Springer. 2013
Received: 30 September 2012
Accepted: 14 January 2013
Published: 11 February 2013
The present analysis considers the steady magnetohydrodynamic (MHD) laminar boundary layer flow of an incompressible electrically conducting fluid caused by a continuous moving wedge in a parallel free stream with a variable induced magnetic field parallel to the wedge walls outside the boundary layer. Using a similarity transformation, the governing system of partial differential equations is first transformed into a system of ordinary differential equations in the form of a two-point boundary value problem (BVP) and then solved numerically using a finite difference scheme known as the Keller box method. Numerical results are obtained for the velocity profiles and the skin friction coefficient for various values of the moving parameter λ, the wedge parameter β, the reciprocal magnetic Prandtl number α and the magnetic parameter S. Results indicate that when the wedge and the fluid move in the opposite directions, multiple solutions exist up to a critical value of the moving parameter λ, whose value depends on the values of S and β.
MSC: 34B15, 76D10.
Magnetohydrodynamics (MHD) is a subject that studies the behavior of an electrically conducting fluid in the presence of an electromagnetic field with applications in many different fields of engineering as well as geophysics, astrophysics, manufacturing, etc. The subject of MHD has been applied, for example, in problems associated with the confinement of plasma by magnetic fields and in projects involving thermonuclear generation of energy. In recent years it has been widely used in metallurgy industries involving sheet-like materials such as production of paper, polymer sheets and wire drawing and in horizontal continuous casting of hollow billets. For examples of these applications, see Li et al. and Yan et al. . Historically, the study of the hydrodynamic behavior of the boundary layer on a semi-infinite flat plate in the presence of a uniform transverse magnetic field has been first considered by Rossow . Since then, the study of MHD flow and heat transfer fields past moving surfaces has drawn considerable attention with variations in types of geometrical surfaces and types of fluids.
The steady laminar flow of a viscous and incompressible fluid passing a fixed wedge was first analyzed in the early 1930s by Falkner and Skan to illustrate the application of Prandtl’s boundary layer theory, in which a similarity transformation was used to reduce the boundary layer equations to an ordinary differential equation known as the Falkner-Skan equation. The Falkner-Skan equation also represents the boundary layer flow with stream-wise pressure gradient. The general cases with were numerically studied by Fang and Weidman et al. independently. There are many references on the solutions of Falkner-Skan equations; for example, see Hartree , Hastings , Brodie and Banks , Pantokratoras , Alizadeh et al. , Yao , and Abbasbandy and Hayat . Similarity solutions for pressure gradient driven flow over a stretching boundary were analyzed by Riley and Weidman for the case of external velocity and boundary velocity being proportional to the same powers of the downstream coordinate. Very interesting and extensive results were reported demonstrating a rich variety of solutions available, including the existence of multiple solutions, and an exact solution was also presented for . Fang and Zhang studied a special case of the Falkner-Skan equation with in the presence of wall suction and injection. An exact solution was presented for the boundary conditions with both wall mass transfer and wall movement, with different solution behavior identified in different solution regions. On the other hand, Ishak et al. considered the steady MHD boundary layer flow in a conducting fluid flowing transverse to a variable magnetic field along a moving wedge in a free stream. The results reported were consistent with those found by Riley and Weidman and with earlier studies by the same authors Ishak et al. [17, 18]. More recent studies on similar problems were done by Van Gorder and Vajravelu , Postelnicu and Pop and Parand et al. .
The present work aims to study the boundary layer flow over a moving wedge in a parallel free stream of an electrically conducting fluid with the induced magnetic field. It considers an extension of the results reported by Riley and Weidman and Ishak et al. on the flow characteristics of a moving wedge in a parallel free stream. Both studies reported the existence of multiple solutions when the fluid and the wedge move in the opposite directions within a specific range of moving parameter λ and a critical value beyond which the solution is non-existent. The present study considers the corresponding MHD flow of the paper by Ishak et al. , but with the induced magnetic field, and investigates how this magnetic field affects the flow and the critical value . The induced magnetic field is assumed to be applied parallel to the wedge walls at the outer edge of the boundary layer. Such an induced magnetic field has been also considered by Davies , Apelblat [23, 24], Kumari et al. , Takhar et al. and more recently by Kumari and Nath . To obtain the solutions, the governing partial differential equations are first transformed into ordinary differential equations using a similarity transformation. The ordinary differential equations obtained are then solved numerically by a very efficient finite difference scheme known as the Keller box method for some values of the selected parameters. The effect of the induced magnetic field on the flow field for different values of the wedge parameter β is included in the analysis. Particular cases of the present results are compared with those reported by Riley and Weidman and Ishak et al. [16, 17].
2 Basic equations
where and are the x-velocity and magnetic field at the edge of the boundary layer, respectively. We assume here that and , where is the constant velocity at the outer edge of the boundary layer and is the value of at . Further, m is also a constant, which varies in the range .
We notice that different values of β characterize a number of main-stream flows. For , equations (9) and (10) are reduced to the MHD Blasius problem. The values and are equivalent to the flow past a wedge placed symmetrically in a stream. For MHD boundary layers, we take the values of the parameters S and α to be in the range and ; see Davies and Kumari et al. . This is the same range of magnetic parameter adopted by Takhar et al. and several earlier researchers investigating similar problems. It is also consistent with the existence of the steady-state solution of the ‘super Alfven’ flow.
where is the local Reynolds number.
We also notice that for the present problem corresponds to the MHD boundary layer flow over a static wedge, which has been considered by Apelblat , in which the MHD wedge problem was solved using the Laplace transform method to give an infinite series approximation solution for and . On the other hand, it may be noted that for (without a magnetic field), equation (9) reduces to that of Ishak et al. . Therefore, as implies the absence of a magnetic field, equation (10) governing the induced magnetic field is no longer necessary.
3 Results and discussion
Nonlinear ordinary differential equations (9) and (10) subject to the boundary conditions (11) form a two-point boundary value problem (BVP) and are solved numerically using the Keller box method as described in the book by Cebeci and Bradshaw . In this method, the solution is obtained using the following four steps:
Write the difference equations using centered differences.
Linearize the resulting algebraic equations by Newton’s method and write them in the matrix-vector form.
Solve the linear systems by the block-tridiagonal-elimination technique.
Values of for , and various β
Values of for ,
Riley and Weidman
Values of for different values of m when
Following the convention adopted by earlier researchers, we define the first two upper branches of solutions as those for which is greater for a given value of β, while the third branch is that with the smallest value of . We notice that the velocity profiles for the first two upper branches of solutions exhibit the same monotonic behavior. The boundary layer for the first branch is usually very thin and the velocity profile rapidly attains the value . In general, the third branch of solutions usually involves a much larger boundary layer thickness compared to the other two branches. It is usually characterized by starting off with a rather small value of , with a non-monotonic behavior in the development of the velocity profiles , before assuming its final asymptotic value . Similar non-monotonic behavior was reported by Riley and Weidman when they considered the velocity profiles of the upper branch solution for . Following Ishak et al. , we postulate that the upper branch of solutions with the highest value of (first solutions) are physically stable and occur in practice since it is the only solution for , i.e., when the fluid and the solid surface move in the same direction.
A reduction in the skin friction implies a reduction in the drag force. Thus, the magnetic field reduces the drag force and speeds up the separation. On the other hand, increasing the included angle of the wedge will increase the drag force, hence delaying the separation. This result is consistent with that reported by Ishak et al. .
According to the Lorenz law, the induced magnetic field will oppose the change in the original magnetic field rather than the field itself. If, for example, the original field is decreasing, then the induced magnetic field must be in the same direction as the original field to oppose the decrease. From Figures 6 and 9, we see that the induced magnetic gradient increases monotonically with the increasing value of λ. This increase is supposedly opposing a decrease in the original magnetic field. Furthermore, the induced magnetic gradient also decreases with the increase in S, which is consistent with the Lorenz law. We also notice that the effect of both S and β is more pronounced on the skin friction compared to the induced magnetic gradient .
In this paper, we have considered similarity solutions for the steady MHD boundary layer flow due to a continuous moving wedge in a parallel free stream with the induced magnetic field. We investigated the effects of the moving parameter λ, the ratio of magnetic to dynamic pressure S, the wedge parameter β and the reciprocal magnetic Prandtl number α on the flow field and the induced magnetic field characteristics. It has been found that increasing the values of the moving parameter λ and the wedge parameter β speeds up the fluid flow. In contrast, increasing the ratio of magnetic to dynamic pressure S and the reciprocal magnetic Prandtl number α slows down the fluid flow. Furthermore, the skin friction or the surface shear stress and the induced magnetic gradient decrease with the increase of the ratio of magnetic to dynamic pressure S, but increase with the wedge parameter β. We have also demonstrated the existence of a rich variety of solutions by varying the value of the wedge parameter β. We have also found that when the wedge and the fluid move in the same direction, the solution is unique for all values of the parameters β and S. However, when the wedge and the free stream move in the opposite directions, multiple solutions exist for some range of values of the moving parameter λ as soon as the value of the moving parameter is greater than a critical value . This critical value of λ is dependent on both parameters β and S. It has been found that increasing the wedge parameter β will increase the value of , while increasing the ratio of magnetic to dynamic pressure S will reduce it. Thus, increasing the ratio of magnetic to dynamic pressure speeds up the boundary layer separation, while increasing the wedge parameter β delays it.
The authors gratefully acknowledge the financial support received in the form of a FRGS research grant from the Ministry of Higher Education, Malaysia, and DIP-2012-31 from the Universiti Kebangsaan, Malaysia. They also wish to express their sincere thanks to the reviewers for the valuable comments and suggestions.
- Li X, Guo Z, Zhou X, Wei B, Chen F, Ting B: Continuous casting of copper tube billets under rotating electromagnetic field. Mater. Sci. Eng. 2007, 460-461: 648-651.View ArticleGoogle Scholar
- Yan Z, Li X, Qi ZC, Zhang X, Li T: Study on horizontal electromagnetic continuous casting of CuNi10Fe1Mn alloy hollow billets. Mater. Des. 2009, 30: 2072-2076. 10.1016/j.matdes.2008.08.047View ArticleGoogle Scholar
- Rossow, VJ: On flow of electrically conducting fluid over a flat plate in the presence of a magnetic field. NACA TR. 1358 (1958)Google Scholar
- Falkner VM, Skan SW: Some approximate solutions of the boundary-layer equations. Philos. Mag. 1931, 12: 865-896.View ArticleGoogle Scholar
- Fang T: Further study on a moving-wall boundary-layer problem with mass transfer. Acta Mech. 2003, 163: 183-188. 10.1007/s00707-002-0979-9MATHView ArticleGoogle Scholar
- Weidman PD, Kubitschek DG, Davis AMJ: The effect of transpiration on self-similar boundary layer flow over moving surfaces. Int. J. Eng. Sci. 2006, 44: 730-737. 10.1016/j.ijengsci.2006.04.005MATHView ArticleGoogle Scholar
- Hartree DR: On an equation occurring in Falkner and Skan’s approximate treatment of the equations of the boundary layer. Proc. Camb. Philos. Soc. 1937, 33: 223-239. 10.1017/S0305004100019575View ArticleGoogle Scholar
- Hastings SP: Reversed flow solutions of the Falkner-Skan equation. SIAM J. Appl. Math. 1972, 22: 329-334. 10.1137/0122031MATHMathSciNetView ArticleGoogle Scholar
- Brodie P, Banks WHH: Further properties of the Falkner-Skan equation. Acta Mech. 1986, 65: 205-211.MathSciNetView ArticleGoogle Scholar
- Pantokratoras A: The Falkner-Skan flow with constant wall temperature and variable viscosity. Int. J. Therm. Sci. 2006, 45: 378-389. 10.1016/j.ijthermalsci.2005.06.004View ArticleGoogle Scholar
- Alizadeh E, Farhadi M, Sedeghi K, Ebrahim-Kerbia HR, Ghoafourian A: Solution of the Falkner-Skan equation for wedge by Adomian decomposition method. Commun. Nonlinear Sci. Numer. Simul. 2009, 14: 724-733. 10.1016/j.cnsns.2007.11.002MATHView ArticleGoogle Scholar
- Yao B: Approximate analytical solution to the Falkner-Skan wedge flow with the permeable wall of uniform suction. Commun. Nonlinear Sci. Numer. Simul. 2009, 14: 3320-3326. 10.1016/j.cnsns.2009.01.014View ArticleGoogle Scholar
- Abbasbandy S, Hayat T: Solution of the MHD Falkner-Skan flow by homotopy analysis method. Commun. Nonlinear Sci. Numer. Simul. 2009, 14: 3591-3598. 10.1016/j.cnsns.2009.01.030MATHMathSciNetView ArticleGoogle Scholar
- Riley N, Weidman PD: Multiple solutions of the Falkner-Skan equation for flow past a stretching boundary. SIAM J. Appl. Math. 1989, 49: 1350-1358. 10.1137/0149081MATHMathSciNetView ArticleGoogle Scholar
- Fang T, Zhang J: An exact analytical solution of the Falkner-Skan equation with mass transfer and wall stretching. Int. J. Non-Linear Mech. 2008, 43: 1000-1006. 10.1016/j.ijnonlinmec.2008.05.006View ArticleGoogle Scholar
- Ishak A, Nazar R, Pop I: MHD boundary layer flow past a moving wedge. Magnetohydrodynamics 2009, 45: 3-10.Google Scholar
- Ishak A, Nazar R, Pop I: Moving wedge and flat plate in a micropolar fluid. Int. J. Eng. Sci. 2006, 44: 1225-1236. 10.1016/j.ijengsci.2006.08.005MATHMathSciNetView ArticleGoogle Scholar
- Ishak A, Nazar R, Pop I: Falkner-Skan equation for flow past a moving wedge with suction or injection. J. Appl. Math. Comput. 2007, 25: 67-83. 10.1007/BF02832339MATHMathSciNetView ArticleGoogle Scholar
- Van Gorder RA, Vajravelu K: Existence and uniqueness results for a nonlinear differential equation arising in MHD Falkner-Skan flow. Commun. Nonlinear Sci. Numer. Simul. 2010, 15: 2272-2277. 10.1016/j.cnsns.2009.09.014MATHMathSciNetView ArticleGoogle Scholar
- Postelnicu A, Pop I: Falkner-Skan boundary layer flow of a power-law fluid past a stretching wedge. Appl. Math. Comput. 2011, 217: 4359-4368. 10.1016/j.amc.2010.09.037MATHMathSciNetView ArticleGoogle Scholar
- Parand K, Rezaei AR, Ghaderi SM: A approximate solution of the MHD Falkner-Skan flow by Hermite functions pseudospectral method. Commun. Nonlinear Sci. Numer. Simul. 2011, 16: 274-283. 10.1016/j.cnsns.2010.03.022MATHMathSciNetView ArticleGoogle Scholar
- Davies TV: The magneto-hydrodynamic boundary layer in the two-dimensional steady flow past a semi-infinite flat plate I. Uniform conditions at infinity. Proc. R. Soc. Lond. Ser. A, Math. Phys. Sci. 1963, 273: 496-508. 10.1098/rspa.1963.0105MATHView ArticleGoogle Scholar
- Apelblat A: Application of the Laplace transformation to the solution of the boundary layer equations. II magneto-hydrodynamic Blasius problem. J. Phys. Soc. Jpn. 1968, 25: 888-891. 10.1143/JPSJ.25.888View ArticleGoogle Scholar
- Apelblat A: Applications of the Laplace transform to the solution of the boundary layer equations. III magnetohydrodynamic Falkner-Skan problem. J. Phys. Soc. Jpn. 1969, 27: 235-239. 10.1143/JPSJ.27.235View ArticleGoogle Scholar
- Kumari M, Takhar HS, Nath G: MHD flow and heat transfer over a stretching surface with prescribed wall temperature or heat flux. Wärme-Stoffübertrag. 1990, 25: 331-336.View ArticleGoogle Scholar
- Takhar HS, Chamka AJ, Nath G: Unsteady flow and heat transfer on a semi-infinite flat plate with aligned magnetic field. Int. J. Eng. Sci. 1999, 37: 1723-1736. 10.1016/S0020-7225(98)00144-XView ArticleGoogle Scholar
- Kumari M, Nath G: Steady mixed convection stagnation-point flow of upper convected Maxwell fluids with magnetic field. Int. J. Non-Linear Mech. 2009, 44: 1048-1055. 10.1016/j.ijnonlinmec.2009.08.002MATHView ArticleGoogle Scholar
- Cowling TG: Magnetohydrodynamics. Interscience, New York; 1957.Google Scholar
- Cebeci T, Bradshaw P: Physical and Computational Aspects of Convective Heat Transfer. Springer, New York; 1988.MATHView ArticleGoogle Scholar
- Rajagopal KR, Gupta AS, Nath TY: A note on the Falkner-Skan flows of a non-Newtonian fluid. Int. J. Non-Linear Mech. 1983, 18: 313-320. 10.1016/0020-7462(83)90028-8MATHView ArticleGoogle Scholar
- Kuo BL: Application of the differential transformation method to the solutions of Falkner-Skan wedge flow. Acta Mech. 2003, 164: 161-174. 10.1007/s00707-003-0019-4MATHView ArticleGoogle Scholar
- Klemp JB, Acrivos AA: A method for integrating the boundary-layer equations through a region of reverse flow. J. Fluid Mech. 1972, 53: 177-199. 10.1017/S0022112072000096MATHView ArticleGoogle Scholar
- Hussaini MY, Lakin WD, Nachman A: On similarity solutions for laminar boundary layer problem with an upstream moving wall. SIAM J. Appl. Math. 1987, 47: 699-709. 10.1137/0147048MATHMathSciNetView ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. | <urn:uuid:dd59731c-783f-411a-8e9f-5d3b5e0f413f> | 2.6875 | 4,668 | Academic Writing | Science & Tech. | 58.108017 | 95,574,379 |
You Gotta Know These Phyla
Taxonomists do not always agree on the usage of even the most common terms. Some textbooks and other publications will use alternate names or spellings to describe taxonomic groups, or will lump or split groups in different ways.
Under NAQT rules, unless the question states otherwise, both Latin names (Mollusca) or Anglicized names (molluscs) are acceptable for a given taxon.
Phyla of plants, algae, fungi, and sometimes bacteria are often referred to as “divisions.”
Estimates of phylal diversity vary. Because many invertebrates are inconspicuous, all estimates are probably low. Unless stated otherwise, numbers represent an estimate of the number of species that have been named.
- Porifera por-IF-ur-uh (5,000 species): The sponges are all water-dwellers (98% marine, 2% freshwater), and are sometimes classified separately from other animals because of their asymmetric bodies and lack of distinct tissues. They are sessile (immobile) except in early dispersing stages, and collect food particles via the sweeping motions of flagellated cells called choanocytes koh-AN-oh-“sites”.
- Cnidaria ny-DAIR-ee-uh (10,000 species): Also called Coelenterata see-LEN-tur-AH-tuh, the cnidarians develop from a diploblastic (two-layered) embryo, and have two separate tissue layers and radial body symmetry. Many cnidarians have two life stages, the mobile, usually bell-like medusa and the sessile polyp. All cnidarians have nematocysts, or stinging cells, for capturing prey, and some can inflict painful stings on swimmers. Examples include the hydras, sea anemones, corals, jellyfishes, and Portuguese man-o-war (which is actually an aggregation of colonial cnidarians).
- Platyhelminthes plat-ee-hel-MIN-theez (15,000 species): The flatworms are the most primitive phylum to develop from a triploblastic (three-layered) embryo. They have bilateral body symmetry, and are acoelomate (lacking a true body cavity), so that the space between the digestive tract and the body wall is filled with tissue. As the name implies, they are generally flat-bodied. They have a true head and brain, but the digestive system has only one opening, which functions as both mouth and anus. Most are hermaphroditic. This phylum includes parasites such as the tapeworms and flukes, as well as free-living (i.e., non-parasitic) organisms such as the planarians.
- Nematoda nee-muh-TOH-duh (15,000 species): The roundworms are unsegmented worms that live in a variety of habitats. They are pseudocoelomate; the three tissue layers are concentric, but the body cavity is not lined with tissue derived from the mesoderm (middle embryonic layer). They include both free-living and parasitic species; human parasites include hookworms and the causative agents of elephantiasis, trichinosis, and river blindness. Soil nematodes may be crop pests, while others are beneficial predators on other plant pests. The nematode species Caenorhabdis elegans is a common subject in genetics and developmental-biology labs.
- Annelida an-uh-LEE-duh (11,500 species): The annelids are segmented worms and represent the first lineage of truly eucoelomate (having a body cavity lined with mesoderm-derived tissue) animals; their body cavities are lined with tissue derived from the embryonic mesoderm. Annelid classes include the marine Polychaeta, as well as the mostly terrestrial Oligochaeta (including the earthworms, Lumbricus) and the mostly aquatic Hirudinea, or leeches. Characteristics of annelids include nephridia (kidney-like structures), blood vessels, and, in some classes, hermaphroditism.
- Arthropoda arth-roh-POH-duh (over 800,000 species described; estimates of actual diversity vary but go as high as 9 million species): The most diverse and successful animal phylum on earth (incorporating about 75% of all described animal species), the Arthropoda are characterized by jointed legs and a chitinous exoskeleton. Like annelids, they are segmented, but unlike annelids, their segments are usually fused into larger body parts with specialized functions (such as the head, thorax, and abdomen of an insect). Arthropods are often divided into four subphyla: Uniramia (insects, centipedes, millipedes); Chelicerata (arachnids, sea spiders, horseshoe crabs); Crustacea (shrimps, lobsters, crabs, crayfish, barnacles, pillbugs), and Trilobitomorpha (the trilobites, now extinct).
- Mollusca moh-LUS-kuh (50,000 species): The molluscs are second in diversity only to the arthropods. Body plans within this phylum are diverse, but general characteristics include a soft body covered by a thin mantle, with a muscular foot and an internal visceral mass. There are two fluid-filled body cavities derived from mesodermal tissue: a small coelom and a large hemocoel that functions as an open circulatory system. Many molluscs have a shell composed of calcium carbonate and proteins, secreted by the mantle. Familiar groups within the Mollusca include the classes Gastropoda (slugs, snails), Bivalvia (clams, oysters, scallops), and Cephalopoda (nautilus, squids, octopi).
- Echinodermata eh-KY-noh-dur-MAH-tuh (6,500 species): Characteristics of this phylum include an endoskeleton composed of many ossicles of calcium and magnesium carbonate, a water vascular system, a ring canal around the esophagus, and locomotion by tube feet connected to the water vascular system. Unique to echinoderms is the five-fold radial symmetry obvious in sea stars (starfish), sea urchins, and sea lilies. Others, like sea cucumbers, have varying degrees of bilateral symmetry. In the echinoderm body plan, a true head is absent; the anatomical terms oral (mouth-bearing) and aboral (away from the mouth) are used to describe orientation of the body surfaces. Feeding adaptations include particle feeding through the water vascular system, everting the stomach to engulf prey (sea stars), and a scraping device called Aristotle’s lantern (sea urchins).
- Chordata kor-DAH-tuh (44,000 species): The phylum that contains humans, Chordata is divided into three subphyla: Urochordata, the sea squirts; Cephalochordata, the lancelets, and Vertebrata, the true vertebrates, which is the most diverse subphylum. Defining traits of chordates include pharyngeal gill slits, a notochord, a post-anal tail, and a dorsal hollow nerve cord. In vertebrates, some of these structures are found only in embryonic stages. The lancelet Amphioxus (Branchiostoma) is often used as a demonstration organism in biology labs.
This article was contributed by former NAQT member Julie K. Stahlhut. | <urn:uuid:7316fa14-fdae-4d84-9617-420651ff1d56> | 3.578125 | 1,682 | Knowledge Article | Science & Tech. | 23.878569 | 95,574,386 |
Corals, Jellyfish, and Sea Anemones
Status/Date Listed as Endangered:
Area(s) Where Listed As Endangered:
Asia, Australia, North America (United States Territory), Oceanic
Barabattoia laddi is a species of concern belonging in the species group "corals, jellyfish, and sea anemones" and found in the following area(s): Asia, Australia, North America (United States Territory), Oceanic.
Barabattoia laddi Facts Last Updated:
January 1, 2016
To Cite This Page:
Glenn, C. R. 2006. "Earth's Endangered Creatures - Barabattoia laddi Facts" (Online).
Accessed 7/16/2018 at http://earthsendangered.com/profile.asp?sp=13674&ID=4.
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Description: This article gives a timeline of research conducted on the rare earths, 17 elements found in the f-block and Group III chemical family of the Periodic Table. It covers discoveries made after the success of Swedish chemist, Carl Gustaf Mosander. The article describes the categorization of the rare earths that took place after Mosander's time, as well as separation techniques that developed.
Date: Winter 2015
Creator: Marshall, James L., 1940- & Marshall, Virginia R.
Item Type: Refine your search to only Article
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Taking the brakes off plant production: not so good after all
- Oct 10, 2017
- Fundamental Research, Department of Energy Projects
- Igor Houwat, Atsuko Kanazawa, David Kramer
When engineers want to speed something up, they look for the “pinch points”, the slowest steps in a system, and make them faster.
Say, you want more water to flow through your plumbing. You’d find the narrowest pipe and replace it with a bigger one.
Many labs are attempting this method with photosynthesis, the process that plants and algae use to capture solar energy.
All of our food and most of our fuels have come from photosynthesis. As our population increases, we need more food and fuel, requiring that we improve the efficiency of photosynthesis.
But, Dr. Atsuko Kanazawa and the Kramer Lab are finding that, for biological systems, the "pinch point" method can potentially do more harm than good, because the pinch points are there for a reason! So, how can this be done?
ATP synthase: an amazing biological nanomachine
Atsuko and her colleagues at the MSU-DOE Plant Research Laboratory (PRL) have been working on this problem for over 15 years. They have focused on a tiny machine in the chloroplast called the ATP synthase, a complex of proteins essential to storing solar energy in “high energy molecules” that power life on Earth.
That same ATP molecule and a very similar ATP synthase are both used by animals, including humans, to grow, maintain health, and move.
In plants, the ATP synthase happens to be one of the slowest process in photosynthesis, often limiting the amount of energy plants can store.
Kicking up the gears of plant production
Atsuko thought, if the ATP synthase is such an important pinch point, what happens if it were faster? Would it be better at photosynthesis and give us faster growing plants?
Years ago, she got her hands on a mutant plant, called cfq, from a colleague. “It had an ATP synthase that worked non-stop, without slowing down, which was a curious example to investigate. In fact, under controlled laboratory conditions – very mild and steady light, temperature, and water conditions – this mutant plant grew bigger than its wild cousin.”
But when the researchers grew the plant under the more varied conditions it would experience in nature, it suffered serious damage, nearly dying.
“In nature, light and temperature quality change all the time, whether through the passing hours, or the presence of cloud cover or winds that blow through the leaves,” she says.
Plants slow photosynthesis for a reason!
Atsuko’s research now shows that the slowness of the ATP synthase is not an accident; it’s an important braking mechanism that prevents photosynthesis from producing harmful chemicals, called reactive oxygen species, which can damage or kill the plant.
“It turns out that sunlight can be damaging to plants,” says Dave Kramer, Hannah Distinguished Professor and lead investigator in the Kramer lab.
“When plants cannot use the light energy they are capturing, photosynthesis backs up and toxic chemicals accumulate, potentially destroying parts of the photosynthetic system. It is especially dangerous when light and other conditions, like temperature, change rapidly.”
"We need to figure out how the plant presses on the brakes and tune it so that it responds faster..."
The ATP synthase senses these changes and slows down light capture to prevent damage. In that light, the cfq mutant’s fast ATP is a bad idea for the plant's well-being.
“It’s as if I promised to make your car run faster by removing the brakes. In fact, it would work, but only for a short while. Then things go very wrong!” Dave says.
“In order to improve photosynthesis, what we need is not to remove the brakes completely, like in cfq, but to control them better,” Dave says. “Specifically, we need to figure out how the plant presses on the brakes and tune it so that it responds faster and more efficiently,” David says.
Atsuko adds: “Scientists are trying different methods to improve photosynthesis. Ultimately, we all want to tackle some long-term problems. Crucially, we need to continue feeding the Earth’s population, which is exploding in size.”
The study is published in the journal, Frontiers in Plant Science.
This work was primarily funded by the US Department of Energy, Office of Basic Energy Sciences.
- 'Road testing' plants reveals photosynthesis secrets
- June 22, 2016
The Kramer lab has published an article on groundbreaking technology that reveals the hidden workings of photosynthesis in living plants.
- The dangers of overcharging your plants
- October 4, 2016
Capturing light to produce energy is a dangerous business for plants. The Kramer lab has discovered one important reason why, in their search for ways to improve crop yields.
- Protecting plants from the power of sunlight
- July 13, 2017
Plants, like us, don’t like too much sunlight. The Kramer lab has figured a way to better measure how plants respond to excessive exposure, and the information might help us create more resilient plants. | <urn:uuid:a948fa84-133e-4f9a-babd-20d6a6512dc0> | 3.328125 | 1,130 | News (Org.) | Science & Tech. | 48.288627 | 95,574,438 |
Super-sharp observations with the telescope Alma have revealed what seems to be a gigantic flare on the surface of Mira, one of the closest and most famous red giant stars in the sky. Activity like this in red giants - similar to what we see in the Sun - comes as a surprise to astronomers. The discovery could help explain how winds from giant stars make their contribution to our galaxy's ecosystem.
New observations with Alma have given astronomers their sharpest ever view of the famous double star Mira. The images clearly show the two stars in the system, Mira A and Mira B, but that's not all. For the first time ever at millimetre wavelengths, they reveal details on the surface of Mira A.
"Alma's vision is so sharp that we can begin to see details on the surface of the star. Part of the stellar surface is not just extremely bright, it also varies in brightness. This must be a giant flare, and we think it's related to a flare which X-ray telescopes observed some years ago", says Wouter Vlemmings, astronomer at Chalmers University of Technology, who led the team.
The team's results were recently published in the journal Astronomy & Astrophysics.
Red giants like Mira A are crucial components of our galaxy's ecosystem. As they near the end of their lives, they lose their outer layers in the form of uneven, smoky winds. These winds carry heavy elements that the stars have manufactured - out into space where they can form new stars and planets. Most of the carbon, oxygen, and nitrogen in our bodies was formed in stars and redistributed by their winds.
Mira - the name means "Wonderful" in Latin - has been known for centuries as one of the most famous variable stars in the sky. At its brightest, it can be clearly seen with the naked eye, but when it's at its faintest a telescope is needed. The star, 420 light years away in the constellation Cetus, is in fact a binary system, made up of two stars of about the same mass as the sun: one is a dense, hot white dwarf and the other a fat, cool, red giant, orbiting each other at a distance about the same as Pluto's average distance from the Sun.
"Mira is a key system for understanding how stars like our sun reach the end of their lives, and what difference it makes for an elderly star to have a close companion", says Sofia Ramstedt, astronomer at Uppsala University and co-author on the paper.
The Sun, our closest star, shows activity powered by magnetic fields, and this activity, sometimes in the form of solar storms, drives the particles that make up the solar wind which in its turn can create auroras on Earth.
"Seeing a flare on Mira A suggests that magnetic fields also have a role to play for red giants' winds", says Wouter Vlemmings.
The new images give astronomers their sharpest ever view of Mira B, which is so close to its companion that material flows from one star to the other.
"This is our clearest view yet of gas from Mira A that is falling towards Mira B" says Eamon O'Gorman, astronomer at Chalmers and member of the team.
The observations were carried out as part of Alma's first long-baseline observations. By placing the telescope's antennas at their maximum distance from each other, Alma reached its maximum resolution for the first time. Mira was one of several targets in the campaign, alongside a young solar system, a gravitationally lensed galaxy and an asteroid. Now Wouter Vlemmings and his team plan new observations of Mira and other similar stars.
"Alma has shown us details on the surface of Mira for the first time. Now we can begin to discover our closest red giants in detail that hasn't previously been possible", he says.
Robert Cumming | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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20.07.2018 | Materials Sciences | <urn:uuid:938ea243-df2d-42ca-8909-41bf91fd0302> | 3.421875 | 1,395 | Content Listing | Science & Tech. | 48.577479 | 95,574,478 |
Impact of the Great China Fire of 1987 on the Tropospheric Chemistry of East Asia
There is a growing concern that biomass burning as a consequence of anthropogenic activities has significant impact on the atmospheric chemistry, climate and on the global biogeochemical cycles. Since the late seventies, when Crutzen et al. (1979) first proposed that the emissions of trace gases from biomass burning can make an important contribution to their budgets in the atmosphere, there has been an increase in the number of research activities in parts of the world with extensive biomass burning (Andreae, 1991). It is observed that biomass burning occurs mostly in the continental tropics coinciding with the local dry season (Crutzen et al., 1985). Trace gases such as carbon monoxide (CO), methane (CH4), nitrogen oxides (NOx = NO + NO2) and non-methane hydrocarbons (NMHCs) which are emitted from the burning fires play important roles in the production of ozone, thereby impacting the tropospheric photochemical oxidant cycle. Tropospheric ozone derived from satellite data is shown to be greater than 40 Dobson Units (DU) over southern Africa and tropical south Atlantic (Fishman et al., 1990; Fishman et al., 1991). Studies on the extent of the perturbation of this biomass signal on the composition of the atmosphere have been done in the past (Fishman et al., 1993). More recently, measurements were taken during the dry season of September-October 1992 in the Transport and Atmospheric Chemistry near the Equator (TRACE) Experiment (Fishman et al. 1996). The conclusions from this activity were that the widespread biomass burning in both South America and southern Africa is the dominant source of the precursor gases responsible for the huge amounts of ozone over the South Atlantic Ocean. Efforts in understanding the spatial and vertical distribution of the trace gases emitted from biomass burning have resulted in numerous insitu field campaigns and observational data. Measurements techniques such as satellite remote sensing, radiosondes and aircraft measurements are commonly being used to probe the atmosphere. On the other hand, synoptic-scale modeling of the influence of the fires on the atmosphere has been minimal, with the majority of work done in modeling the convective transport and redistribution of biomass burning emissions (Crutzen and Carmichael, 1993; Pickering et. al, 1996; Chatfield et. al, 1996).
KeywordsForest Fire Ozone Concentration Biomass Burning Lower Troposphere Atmospheric Chemistry
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- Andreae, M. O., 1991, Biomass Burning: Its History, Use, and Distribution and Its Impact on Environmental Quality and Global Climate, in: Global Biomass Burning 3–21, J. S. Levine, ed., MIT Press, Cambridge, Mass.Google Scholar
- Cahoon, D. R. et al., 1991, The Great Chinese Fire of 1987: A View from Space, in: Global Biomass Burning 61–66, J. S. Levine, ed., MIT Press, Cambridge, Mass.Google Scholar
- Carmichael, G. R., 1997, personal communications.Google Scholar
- Carmichael, G. R., Peters, L. K. and Saylor, R. D., 1991, The STEM-II regional scale acid deposition and photochemical oxidation model — I, An overview of model development and applications, Atmos. Environ. 25A(10):2077–2090.Google Scholar
- Crutzen, P. J. and Andreae M. O., Biomass Burning in the Tropics: Impact on Atmospheric Chemistry and Biogeochemical Cycles, Science 250:1669–1678.Google Scholar
- Crutzen, P. J. and Carmichael, G. R., 1993, Modeling the Influence of Fires on Atmospheric Chemistry, in: Fire in the Environment: The Ecological, Atmospheric and Climatic Importance of Vegetation Fires 89–105, P. J. Crutzen and J. G. Goldammer, eds., John Wiley & Sons Ltd., New York.Google Scholar
- Fishman, J. et al., 1993, Group Report: What is the Impact of Fires on Atmospheric Chemistry, Climate, and Biogeochemical Cycles?, in: Fire in the Environment: The Ecological, Atmospheric and Climatic Importance of Vegetation Fires 345–356,P. J. Crutzen and J. G. Goldammer, eds., John Wiley & Sons Ltd., New York.Google Scholar
- Fujita, S., 1992, Acid Deposition in Japan, in: Report of the Central Research Institute of Electric Power Industry, Japan.Google Scholar
- Kotamarthi, V. R. and Carmichael, G. R., 1990, The Long Range Transport of Pollutants in the Pacific Rim Region, Atmos. Environ. 24A (1990):1521–1534.Google Scholar
- Lobert, J. M. et al, 1991, Experimental evaluation of biomass burning emissions: Nitrogen and carbon containing compounds, in: Global Biomass Burning 289–404, J. S. Levine, ed., MIT Press, Cambridge, Mass.Google Scholar
- Zhang, Y., 1994, The chemical role of mineral aerosols in the troposphere in east Asia. Ph.D. Thesis, Dept. of Chem. & Biochem. Eng., Univ. of Iowa, Iowa City.Google Scholar | <urn:uuid:489b13c2-a155-496d-9b7f-a00c555b00de> | 2.90625 | 1,134 | Academic Writing | Science & Tech. | 53.657617 | 95,574,492 |
Analytical and Experimental Investigation of Thermal and Helium Lift-Pumping Recirculation Systems
Geysering is a process by which rapid vapor formation within liquid-filled vertical columns causes rapid expulsion of all or portions of the contained liquid into an overhead container. Geysering associated with space vehicle cryogenic systems is attributed to heat flow into a cryogenic suction line which is attached to a propellant tank of greater diameter. Restricted convective boundary layers in the line allow the liquid to reach local saturation temperature. Formation of vapor in the suction line causes liquid displacement into the larger diameter tank, thereby reducing the effective hydrostatic head. Reduction of hydrostatic head causes additional vapor generation which rapidly displaces more liquid into the tank. Whenever liquid refills the suction line after a geyser, detrimental pressure surge or “water hammer” frequently occurs.
KeywordsHeat Flux Feed Line Recirculation System Heat Leak Water Hammer
Unable to display preview. Download preview PDF.
- 1.P. Griffith, “Geysering in Liquid Filled Lines,” ASME, 62-HT-39 (1962).Google Scholar
- 2.S. K. Morgan and H. F. Brady, in Advances in Cryogenic Engineering, Vol. 7, Plenum Press, New York (1962), p. 206.Google Scholar
- 3.E. R. G. Eckert, The Transfer of Heat and Mass, 1st ed., International Textbook Company, Scranton, Pennsylvania (1960).Google Scholar
- 4.W. O. Randolph and J. L. Vaniman, “Subcooling of Cryogenic Liquids by Injection of Noncondensing Gas,” MTP-S and M-P-61–19.Google Scholar
- 5.J. D. Nicklin, “The Air-Lift Pump: Theory and Optimization,” Trans. Inst. Chem. Engrs. 41 (1963).Google Scholar
- 6.G. I. Taylor, Proc. Roy. Soc. (London), Ser. APP 200 (1950).Google Scholar
- 7.J. A. Clark, P. S. Larsen, W. O. Randolph, and J. L. Vaniman, in Advances in Cryogenic Engineering, Vol. 8, Plenum Press, New York (1963), p. 507.Google Scholar
- 9.A. F. Schmidt, “Experimental Investigation of Liquid-Hydrogen Cooling by Helium Gas Injection,” NASA Order Nos. H-11110 and H-12350 (August 16, 1962).Google Scholar | <urn:uuid:bb2ede3f-6fba-42dc-afde-5445c81b3274> | 3 | 555 | Academic Writing | Science & Tech. | 63.934134 | 95,574,493 |
Certain diseases such as cystic fibrosis and muscular dystrophy are linked to genetic mutations that damage the important biological process of rearranging gene sequences in pre-messenger RNA, a procedure called RNA splicing.
The single-molecule florescence microscope can view individual molecules.
Credit: Diana Hunt
These conditions are difficult to prevent because scientists are still grasping to understand how the splicing process works. Now, researchers from Brandeis University and the University of Massachusetts Medical School have teamed up to unravel a major component in understanding the process of RNA splicing.
In a recent paper published in Cell Press, research specialist Inna Shcherbakova of Brandeis and UMMS, and a team of researchers led by professors Jeff Gelles (Brandeis) and Melissa J. Moore (UMMS), explain how the molecular machine known as the spliceosome begins the process of rearranging gene sequences.
In order to convey instructions for synthesizing protein to the ribosome, RNA — a transcribed copy of DNA — must be translated into mRNA. Part of the process of translating pre-messenger RNA into mRNA involves cutting out gene segments that don't contain information relevant to protein synthesis, called introns, and connecting the remaining pieces together.
The spliceosome does the genetic cutting and pasting. It is a complicated complex, made up of four major parts and more than 100 accessory proteins that come together and break apart throughout the splicing process. Think of the spliceosome as an old Transformers robot — it has individual pieces that operate independently but can also come together to form a larger structure.
Sometimes, such as in the case of cystic fibrosis, a mutation will cause the spliceosome to snip in the wrong place, cutting out important sequences instead of introns, and resulting in the production of a faulty protein.
In studying the Transformer-like spliceosome, researchers have been unable to reconcile how the different components of the complex coordinate. To initiate the splicing process, two pieces of the spliceosome bind to the two ends of an intron. Until now, scientists believed this to be highly ordered process: first Part 1 bound, and then it would somehow tell Part 2 to attach.
In a highly ordered process in primitive organisms such as yeast, the introns are small and it's easy for Part 1 and Part 2 to communicate. But how would that process work in humans, where introns are made up of thousands of nucleotides? How could the two parts — which jumpstart the whole splicing process — communicate?
To find out, Shcherbakova aimed a single-molecule florescence microscope built in the Gelles lab at the spliceosome. By tagging the different parts of the complex with fluorescent colors, the team discovered that the process is more flexible than scientists imagined.
The two first major components of the spliceosome do not need to communicate with one another to start the splicing process, nor does it matter which piece attaches to the gene first. Either of the components, called U1 and U2, can attach first and the process works equally well.
"The process is much more sensible than we originally thought," Gelles says.
Now that scientists understand how the major components of splicing can come together, they can study how the different steps of the process are orchestrated.
"We are just scratching the surface in understanding this process, but ultimately, we hope to understand how this process goes wrong and how it can be fixed," Gelles says.
Leah Burrows | EurekAlert!
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
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An Uplifting Project—The Buoyancy of Balloons
|Time Required||Short (2-5 days)|
|Material Availability||Readily available|
|Cost||Average ($50 - $100)|
AbstractBalloons are a festive addition to many celebrations. You've probably noticed, though, that over a short period of time, helium-filled latex balloons start to lose their buoyancy. So when you're planning your next party, how soon can you buy the balloons in advance before they start deflating? In this science fair project, you will use a simple scale to measure the lift supplied by a set of balloons, and determine the rate of lift decay.
The objective of this physics science fair project is to measure how the buoyancy of helium-filled latex balloons changes over time.
David Whyte, PhD, Science Buddies
Cite This PageGeneral citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.
Last edit date: 2017-07-28
Helium-filled balloons float because the helium is lighter than the surrounding air. In other words, the weight of the air displaced by the balloon is greater than the weight of the balloon and the gas inside, so the balloon floats upward.
Figure 1. Ascending helium balloons. (Wikipedia, 2009.)
This force, or buoyancy, is exactly the difference in the weight of the balloon and its contents (plus a ribbon, if one is attached), versus the weight of the volume of air displaced.
Latex is a permeable membrane, which means it has very small holes that allow the helium atoms to escape. Helium escapes from latex balloons faster than air does, because of the small size of helium atoms. As the helium trapped inside of a latex balloon slowly escapes, the balloon starts to sink. There is a point at which the buoyancy supplied by the helium just equals the weight of the balloon and its contents (and any attached ribbon), and the balloon hovers in mid air, neither rising nor falling. This is called neutral buoyancy.
In this science fair project, you will use a simple scale and some balloons to investigate the following questions. Does the balloon lose its buoyancy at a constant rate, or does the rate change over time? What is the rate of lift decay?
Terms and Concepts
- Permeable membrane
- Neutral buoyancy
- How many latex balloons would it take to lift you off the ground? Hint: See the Bibliography.
- What other lighter-than-air gases can be used for balloons? What are their benefits and drawbacks?
- Why do latex balloons lose their buoyancy faster than Mylar® balloons do?
- University of Hawaii. (2002, May). Balloon Lift with Lighter than Air Gases. Retrieved February 27, 2009, from http://www.chem.hawaii.edu/uham/lift.html
- Neer, K. (2008). How many regular-sized helium-filled balloons would it take to lift someone? Retrieved February 27, 2009, from http://science.howstuffworks.com/question185.htm
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Materials and Equipment
- Metal spoons (3)
- Masking tape
- Permanent marker
- Digital scale, accurate to at least 1 g, such as the Fast Weigh MS-500-BLK Digital Pocket Scale, 500 by 0.1 G, available from Amazon.com
- Latex balloons, filled with helium and ribbon attached so you can hold them (9); available at party supply stores and some grocery stores
- Lab notebook
- Graph paper
Disclaimer: Science Buddies occasionally provides information (such as part numbers, supplier names, and supplier weblinks) to assist our users in locating specialty items for individual projects. The information is provided solely as a convenience to our users. We do our best to make sure that part numbers and descriptions are accurate when first listed. However, since part numbers do change as items are obsoleted or improved, please send us an email if you run across any parts that are no longer available. We also do our best to make sure that any listed supplier provides prompt, courteous service. Science Buddies does participate in affiliate programs with Home Science Tools, Amazon.com, Carolina Biological, and Jameco Electronics. Proceeds from the affiliate programs help support Science Buddies, a 501(c)(3) public charity. If you have any comments (positive or negative) related to purchases you've made for science fair projects from recommendations on our site, please let us know. Write to us at firstname.lastname@example.org.
Remember Your Display Board Supplies
Poster Making Kit
ArtSkills Trifold with Header
Performing the Experiment
- To start, label the three spoons using the masking tape and the permanent marker. Label them A, B, and C.
- Weigh each spoon and record the values in your lab notebook.
Attach three balloons to each spoon.
- Attach the balloons near the end of the ribbon, so that extra ribbon is not hanging from the spoon.
- Trim any extra ribbon with the scissors, as needed.
Weigh each spoon with the balloons attached.
- The balloons should be free to float above the scale.
- Note the weights in your lab notebook for spoons A, B, and C.
Repeat step 4 every 8 hours, until the balloons have lost most of their buoyancy.
- 8 hours is just a suggestion. Use your own judgment about how often to weigh the spoons.
- Poke a hole in each balloon to let any remaining helium escape.
- Weigh the balloons from the three sets by removing the spoons from the balloons and then weighing each balloon-and-ribbon set (a set is made up of three balloons and three ribbons). Record all data in your lab notebook.
Analyzing Your Data
Calculate the buoyancy of the balloons.
- Calculate the difference in weight between each spoon alone and each spoon with the balloons and ribbon attached.
- Add the weight of the three empty balloons and their ribbons to get the buoyancy. For example, say the weight of the spoon is 20 g, the weight of the spoon with the balloons and ribbons attached is 15 g, and the weight of the balloons and ribbons is 3 g. Then the total lift supplied by the helium gas equals 20 - 15 + 3 = 8 g. See Equation 1.
|Buoyancy =||weight of spoon − weight of spoon with balloons attached + weight of balloons and ribbon|
- Graph your data, with time on the x-axis and buoyancy on the y-axis.
- Was the rate of buoyancy loss (lift decay) linear over time, or was the rate non-constant? Explain your results.
- Repeat the experiment at least two more time so that you have three sets of data.
Communicating Your Results: Start Planning Your Display BoardCreate an award-winning display board with tips and design ideas from the experts at ArtSkills.
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- Measure the volume of the balloons during the experiment. Include these measurements in your graphs. (The equation for the volume of a balloon can be found in Katherine Neer's article in the Bibliography).
- Compare the rates at which helium and air escape from the balloons by measuring the volumes over time. Try other gases.
- Use a spreadsheet program to add a trend line to your data. Use the program to determine the equation for the trend line.
- Experiment with the effect of temperature on lift decay.
- Measure the atmospheric pressure over the course of your experiments to see if it affects the buoyancy.
- Experiment with different material for the balloon, such as mylar.
Ask an ExpertThe Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.
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10 Tips – Learn Software Development in Javahttps://secure.gravatar.com/avatar/?s=96&d=mm&r=g
10 Tips – Learn Software Development in Java
Learning Java is a great step to take since it is one of the best and most popular programming languages. Billions of devices run Java programs while millions of developers create new Java programs each year. Therefore, if you wish to learn how to code in Java, here are a few tips that will benefit you throughout your endeavors using Java.
Focus on the basics
Java is a wide programming platform and contains numerous options and features. Due to its vastness, many beginners in Java want to learn everything in the shortest time possible.
Do not let the excitement derail you. Mastering the basics in Java will give you a steady foundation that will make learning all the other components quick and easy. However, if you fail to grasp the basic workings of Java properly, the programming in the advanced levels will always prove to be frustrating.
This point is hinged on your main reason for learning Java. If your wish to stuff your brain with all the Java jargon and common code so that you can ace a test, then solely reading might do the trick. However, for a person who wishes to program using Java, gaining the theory is not enough. Practicing your theory, no matter how useless the programs you develop might be, sharpens your skill and enables you to learn even more through the errors you might make. It also gives you skills in debugging, since you have to trace your errors and fix them.
Understand the code
Simply writing code and having it perform a task will not help you much if you do not understand its inner workings. Try and figure out why the program behaves the way it does. Learn the cycle steps of a “for loop” and a “nested for loop” will be easy to understand.
Knowing how the code works enables you to manipulate it and use it in different settings.
Remember to allocate memory
If you are new to Java but not to programming languages, and you have knowledge in C or C++, then take note of this point. Since Java is a dynamic language (class files are loaded at runtime), you have to allocate memory when declaring objects and arrays. Memory is allotted using the keyword ‘new,’ and failure to assign memory results in a null pointer exception error. This feature is not present in static programming languages such as C.
Create efficient code
Since new objects need to be allocated memory when created, you should be careful when creating code to ensure you don’t hog the device’s resources. Useless objects might not affect your code, but they will affect how the program runs and how much memory it requires.
Interface over Abstract
Since Java does not have multiple inheritance, you will have to find a new way to perform multiple inheritance functions. Implementing an interface or an abstract class will help you achieve multiple inheritance-like functions. However, interface classes offer more liberty than abstract classes. Furthermore, the interface classes implement abstract methods and therefore, they can be used in place of abstract classes.
Avoid memory leaks
Java assumes automatic memory management, and hence programmers have very little control over the program’s memory consumption. However, there are some programming practices that you can adopt to ensure that your code does not hog additional memory.
Ensure that you release database connections after the function has completed querying.
Using the “finally” block also helps to limit memory usage.
Instances in static tables should be released.
The standard library is shipped with Java, and it makes the job of a programmer a lot easier. The library contains a wide collection of classes that a program developer can call instead of creating new ones. Furthermore, since the library is standard, it ensures that your program is portable and it can run on other machines that have the Java JDK. The Java library classes also consist of the most trusted reusable code since they are rigorously tested and constructed in an efficient manner making them the best option when you get the chance to use them.
Use primitive instead of wrapper classes whenever possible
Although wrapper classes offer great utility when writing code, they are not as efficient as primitive classes. The primitive classes store information about the values they hold while the wrapper classes store data on the entire class, which makes them consume more memory than the primitive classes. Moreover, since wrappers deal with objects rather than values, comparing wrapper classes tends to produce undesired results.
By now you might have realized that managing memory is essential when you are trying to create efficient programs in Java. When working with strings, always try to refrain from instantiating a string using a constructor. This is because the strings are considered as classes and actions such as concatenation result in the formation of a new string object which consumes more memory. | <urn:uuid:9954210a-4476-4ae2-ab2b-e8fdf0d94ff8> | 3.046875 | 1,006 | Listicle | Software Dev. | 43.004431 | 95,574,605 |
The ubiquity of anthropogenic chemicals in nature poses a challenge to understanding how ecological communities are impacted by them. While we are rapidly gaining an understanding of how individual contaminants affect communities, communities are exposed to suites of contaminants yet investigations of the effects of diverse contaminant mixtures in aquatic communities are rare. I examined how a single application of five insecticides (malathion, carbaryl, chlorpyrifos, diazinon, and endosulfan) and five herbicides (glyphosate, atrazine, acetochlor, metolachlor, and 2,4-D) at low concentrations (2-16 p.p.b.) affected aquatic communities composed of zooplankton, phytoplankton, periphyton, and larval amphibians (gray tree frogs, Hyla versicolor, and leopard frogs, Rana pipiens). Using outdoor mesocosms, I examined each pesticide alone, a mix of insecticides, a mix of herbicides, and a mix of all ten pesticides. Individual pesticides had a wide range of direct and indirect effects on all trophic groups. For some taxa (i.e., zooplankton and algae), the impact of pesticide mixtures could largely be predicted from the impacts of individual pesticides; for other taxa (i.e., amphibians) it could not. For amphibians, there was an apparent direct toxic effect of endosulfan that caused 84% mortality of leopard frogs and an indirect effect induced by diazinon that caused 24% mortality of leopard frogs. When pesticides were combined, the mix of herbicides had no negative effects on the survival and metamorphosis of amphibians, but the mix of insecticides and the mix of all ten pesticides eliminated 99% of leopard frogs. Interestingly, these mixtures did not cause mortality in the gray tree frogs and, as a result, the gray tree frogs grew nearly twice as large due to reduced competition with leopard frogs. In short, wetland communities can be dramatically impacted by low concentrations of pesticides (both separate and combined) and these results offer important insights for the conservation of wetland communities.
Mendeley saves you time finding and organizing research
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Chemical evolution may refer to:
- Stellar nucleosynthesis, the creation of chemical elements by stellar thermonuclear fusion or supernovae
- Abiogenesis, the transition from nonliving elements to living systems
- Molecular evolution, evolution at the scale of molecules
- Gas evolution reaction, the process of a gas bubbling out from a solution
- Oxygen evolution, the process of generating molecular oxygen through chemical reaction
- Cosmochemistry (or astrochemistry), the study of the chemical composition of matter in the universe, including complex organics, and the processes that led to those compositions.
disambiguation page lists articles associated with the title Chemical evolution.
If an internal link led you here, you may wish to change the link to point directly to the intended article. | <urn:uuid:d694b6aa-3bcd-404c-beed-0398c83699d6> | 2.546875 | 171 | Knowledge Article | Science & Tech. | -10.994242 | 95,574,616 |
Current research on groundwater vulnerability is aimed mainly at groundwater pollution vulnerability (GPV), and the vulnerability of groundwater quantity is seldom considered. It is important to carry out the groundwater vulnerability evaluation for the management of groundwater resources. This paper presents evaluation models and methods for assessing groundwater quantity and pollution vulnerability. The models and methods were used to evaluate the groundwater vulnerability in the plain area of Baotou, Inner Mongolia, China. The groundwater quantity vulnerability was assessed by computing the groundwater recharge rate, and the GPV was evaluated by simulating the migration time for pollutants traveling from ground surface to the aquifer. The research results could provide scientific support for the management of regional groundwater resources, prevention and control of groundwater pollution.
Research on the evaluation method of groundwater quantity and pollution vulnerability
Liping Bai, Yeyao Wang, Huina Fang, Li Liu, Youya Zhou, Zengguang Yan, Fasheng Li; Research on the evaluation method of groundwater quantity and pollution vulnerability. Water Science and Technology: Water Supply 1 March 2013; 13 (2): 368–375. doi: https://doi.org/10.2166/ws.2013.027
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The Omega Nebula, sometimes called the Swan Nebula, is a dazzling stellar nursery located about 5500 light-years away towards the constellation of Sagittarius (the Archer).
An active star-forming region of gas and dust about 15 light-years across, the nebula has recently spawned a cluster of massive, hot stars. The intense light and strong winds from these hulking infants have carved remarkable filigree structures in the gas and dust.When seen through a small telescope the nebula has a shape that reminds some observers of the final letter of the Greek alphabet, omega, while others see a swan with its distinctive long, curved neck. Yet other nicknames for this evocative cosmic landmark include the Horseshoe and the Lobster Nebula.
Swiss astronomer Jean-Philippe Loys de Chéseaux discovered the nebula around 1745. The French comet hunter Charles Messier independently rediscovered it about twenty years later and included it as number 17 in his famous catalogue.
In a small telescope, the Omega Nebula appears as an enigmatic ghostly bar of light set against the star fields of the Milky Way. Early observers were unsure whether this curiosity was really a cloud of gas or a remote cluster of stars too faint to be resolved. In 1866, William Huggins settled the debate when he confirmed the Omega Nebula to be a cloud of glowing gas, through the use of a new instrument, the astronomical spectrograph.
In recent years, astronomers have discovered that the Omega Nebula is one of the youngest and most massive star-forming regions in the Milky Way. Active star-birth started a few million years ago and continues through today. The brightly shining gas shown in this picture is just a blister erupting from the side of a much larger dark cloud of molecular gas. The dust that is so prominent in this picture comes from the remains of massive hot stars that have ended their brief lives and ejected material back into space, as well as the cosmic detritus from which future suns form.
The newly released image, obtained with the EMMI instrument attached to the ESO 3.58-metre New Technology Telescope (NTT) at La Silla, Chile, shows the central region of the Omega Nebula in exquisite detail. In 2000, another instrument on the NTT, called SOFI, captured another striking image of the nebula (ESO Press Photo 24a/00) in the near-infrared, giving astronomers a penetrating view through the obscuring dust, and clearly showing many previously hidden stars. The NASA/ESA Hubble Space Telescope has also imaged small parts of this nebula (heic0305a and heic0206d) in fine detail.
At the left of the image a huge and strangely box-shaped cloud of dust covers the glowing gas. The fascinating palette of subtle colour shades across the image comes from the presence of different gases (mostly hydrogen, but also oxygen, nitrogen and sulphur) that are glowing under the fierce ultraviolet light radiated by the hot young stars.More Information
Henri Boffin | EurekAlert!
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
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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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03.07.2018 | Event News
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By Gretchen Weber, KQED Climate Watch Even if the world stopped emitting all greenhouse gases today, scientists say, the climate would conti…
Floods in the Midwest and a new SolveClimate story are a reminder of nuclear power's vulnerability to climate change.
In different parts of the American West, climate influences wildfires in unexpected ways.
With heat waves on the rise, last summer's nuclear slowdown in Tennessee may be a sign of things to come.
The deadly Russian heatwave of 2010 was a more exceptional event than the 2003 European heatwave, a new study finds.
A new study finds that primarily natural causes led to last summer's soaring temperatures in Russia, but similar events are becoming more like…
Both NOAA and NASA reported today that 2010 tied with 2005 for the title of warmest year on record.
Despite two key factors that lead to cooler conditions, 2010 will go down in history as one of the warmest years on record.
A new review suggests that socioeconomic and community factors play an important role in planning for future heat waves.
A number of extreme and record breaking climate events took place in 2010. Here's our list reviewing the ten biggest newsmakers.
The Russian heat wave of 2010 contributed to the deaths of as many as 15,000 people. But just how unusual was the heat?
The average temperature in Moscow during June, July and August 2010 was significantly hotter than any year since 1950.
The average temperature in Moscow during July 2010 was significantly hotter than any year since 1950.
It's official: Washington, D.C. and New York, N.Y. both sweated through their warmest summers on record this year.
Comparison of early to mid-summer conditions along the eastern seaboard vs. the West Coast.
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CLIMATE CENTRAL - After the second warmest July on record, 2010 is shaping up to be one of the hottest years on the books.
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The Glass Transition
Most solid mineral compounds and elements form liquids of low viscosity (several centipoises) when they melt, and when the temperature is reduced, they solidify again to form a crystalline solid. Alternatively, there are materials which become liquids with a very high viscosity (105–107 P) when melted. When they are cooled below their melting point, these liquids do not solidify instantaneously but remain in a supercooled state, the viscosity of the liquid increases significantly when the temperature is reduced, and they then “freeze” in the form of a glass, which is a noncrystalline solid state. We say that the liquid has undergone a glass transition and that a glassy or vitreous state has formed.
KeywordsGlass Transition Glass Transition Temperature Supercooled Liquid Mode Coupling Theory Supercooled State
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Fans of the original, classic Star Trek will remember the “cloaking device,” a technology perfected by the warlike but technologically sophisticated Romulans, that when activated was capable of rendering an entire starship invisible.
While actual science circa 2018 may be quite some distance away from building a starship, much less rendering one invisible, a new research study published in the scientific journal Optica this week appears to show that an invisibility cloaking device may indeed soon be possible “under realistic conditions.”
The new study by scientists at the Canadian National Institute of Scientific Research in Montreal is not the first to show that the concept of invisibility cloaking can work outside of the boundaries of science fiction storytelling. But according to a summary by the site Science Daily, the NISR researchers have discovered a new, more effective invisibility technique that they call “spectral cloaking,” because it involved breaking a wave of light into all of the colors on the spectrum contained within that light wave.
The site Futurism explained the concept.
“There’s something called the electromagnetic spectrum. It contains all the different frequencies of electromagnetic radiation, a certain kind of energy. X-rays, gamma rays, and radar all fall somewhere on this spectrum,” Futurism correspondent Kristin Houser wrote. “While you can’t see an X-ray, your eyes can see one small range of frequencies on the electromagnetic spectrum. We call this visible light. As mentioned, it’s a range separated into what we perceive as colors, with violet at one end and red at the other.”
Earlier versions of invisibility cloaking relied on ways to bend light waves so they moved around an object, according to a report by the London, England, newspaper The Times. “The trouble with this approach is that it distorts the waves and struggles to cope with a range of different frequencies, such as the various colors of light,” Times science correspondent Oliver Moody explained.
The spectral cloaking method, however, alters the frequency — that is, the color — of light waves as they pass through objects. Normally, objects are visible to the eye because they reflect certain frequencies of light. A spectral cloaking device, however, changes “blocked,” or reflected, colors into a range of different colors on the wave’s spectrum, according to a summary of the findings appearing in R&D Magazine.
As a result, the light wave passes through an object without being blocked — meaning that the light would not be reflected back to human eyes, rendering the object invisible. The device then reassembles the light wave into its original frequency when it comes out the other side of the now-invisible object.
“Our work represents a breakthrough in the quest for invisibility cloaking,” said researcher José Azaña, one of the authors of the research paper, quoted by Science Daily. “We have made a target object fully invisible to observation under realistic broadband illumination by propagating the illumination wave through the object with no detectable distortion, exactly as if the object and cloak were not present.”
While rendering giant starships invisible may not exactly be right around the corner, the researchers say that spectral cloaking may have practical uses in such areas as online security. The cloaking device could be used to shield data passing through fiber-optic cables, preventing spies and other eavesdroppers from intercepting conversations and internet exchanges — because the data itself would become “invisible.” | <urn:uuid:b50dd119-3fad-43b2-85e0-a12f1db5e428> | 3.9375 | 733 | News Article | Science & Tech. | 27.364091 | 95,574,655 |
The system will be unavailable due to maintenance on Thursday July 19 from 7:00-8:30 am ET.
Range-wide Assessment of Habitat Suitability for Roanoke Logperch (Percina rex)
Anita M. Lahey
Paul L. Angermeier
MetadataShow full item record
The Roanoke logperch (Percina rex) is a federally endangered darter endemic to Virginia. Knowledge of its distribution and habitat requirements is limited. Before this study, it was known to occur in the Smith, Pigg, Roanoke and Nottoway river watersheds. We surveyed 36 sites in the Dan, Mayo, Smith, Pigg, Blackwater, Big Otter, Falling and Meherrin river and Goose Creek watersheds for new occurrences. We found Roanoke logperch in two new watersheds, Goose Creek and Big Otter River, as well as in Smith and Pigg river watersheds. We developed a screening model of reaches suitable for Roanoke logperch and assessed habitat suitability at fish-survey sites. We found reaches and sites suitable for logperch evenly distributed across the Roanoke drainage. Availability of suitable habitat was strongly correlated with logperch catch among sites. We estimate 30-40% of our observed logperch absence were false absences. Due to Roanoke logperch's low detectability, a combination of range modeling, habitat assessment, and fish surveys may be better indicators of logperch distribution than fish surveys alone. This report provides a synthesis of available knowledge on the distribution of Roanoke logperch and new insights into logperch detectability. We recommend that electrofishing generally be used rather than snorkeling to establish logperch presence/absence and that logperch detectability be more rigorously evaluated under a range of sampling conditions. In preparing for road construction or maintenance projects, we recommend that our screening model be applied to potentially impacted stream segments to help determine whether sites are suitable for logperch. | <urn:uuid:e791021f-a68d-4fdb-9faa-bd2fdbc7ba75> | 2.515625 | 423 | Academic Writing | Science & Tech. | 23.905711 | 95,574,657 |
Earthquakes can occur almost anyplace on earth.
There are two primary scales used to measure earthquakes: the Richter scale and the Mercalli scale. The Richter scale is most common in the United States while the Mercalli scale is used more globally. The moment magnitude scale is another earthquake measurement scale that is used by some seismologists. All three scales provide useful information in measuring and analyzing earthquakes across the globe.
The Richter Scale
The Richter scale was invented in the 1930s by Dr. Charles Richter, a seismologist at the California Institute of Technology. A Richter magnitude is calculated based on the amplitude of the largest seismic wave recorded for the earthquake. The Richter scale is a base-10 logarithmic scale, meaning that there is no limit to how small or large the earthquake must be to be measured by the scale. The Richter scale runs from 1 to 10, with 1 being the smallest and 10 being the largest. Since the Richter scale is logarithmic, a 5.0 earthquake measures 10 times the shaking amplitude than one that measures 4.0, for example.
The Mercalli Scale
The Mercalli scale measures the intensity of an earthquake by quantifying the effects of an earthquake on the Earth’s surface. Based on human reactions, natural objects, and man-made structures, the Mercalli scale rates earthquakes on a scale of 1 to 12, with1 denoting that nothing was felt and 12 denoting total destruction.
The Mercalli scale, invented in 1902 by Giuseppe Mercalli, isn’t considered as scientific as the Richter scale. This is because the Mercalli scale relies on witnesses to report about the earthquake, and is not defined in rigorous and objective standards like the Richter scale.
Moment Magnitude Scale
The moment magnitude scale was introduced in 1979 as a successor to the Richter scale. The moment magnitude scale compares energy released by earthquakes and is based on the moment of the earthquake, which is equal to the rigidity of the earth multiplied by the average amount of slip on the fault and the size of the area that slipped. The moment magnitude scale is more accurate in measuring large earthquakes than the Richter scale and is used to estimate magnitudes for all modern large earthquakes by the United States Geological Survey. | <urn:uuid:8f8a9a4e-d173-42bb-b4ae-91a59740b97d> | 4.4375 | 471 | Knowledge Article | Science & Tech. | 37.496316 | 95,574,663 |
Envisat guarding the planet
Envisat, whose launch is scheduled end of February 2002, will tirelessly sweep the Earth`s surface and atmosphere, using a suite of ten different scientific instruments.
Over a 35-day cycle, the satellite`s orbit will cover the entire planet, and then start all over again. Two thirds of the time it will be over water. Because of the sheer size of the oceanic currents, the complexity of thermal exchanges, and ocean-atmosphere coupling, the ocean is a crucial factor in explaining the way our planet`s climate operates and how it is changing.
Beginning with the first brief American Seasat mission in 1978, satellite observation has created a revolution in our understanding of how the ocean behaves. Since the 1990s, a continuous stream of scientific data has been flowing from ESA`s ERS satellites and the joint French-US Topex/Poseidon altimetry satellite. This first generation is now being succeeded by Envisat`s instruments designed not only to advance science but also to lead to a range of operational applications services.
The data obtained with a radar altimeter, RA-2, will ensure continuity with the original RA system on the ERS satellites. It will also provide a valuable complement to Topex/Poseidon and its follow-on, the small satellite Jason, launched on 7 December 2001. The two systems provide altimetric observation of the ocean from different orbits. A low satellite repetition ensures that Envisat, like the ERS spacecraft before it, obtains excellent spatial resolution, needed to study complex phenomena like eddies and describe the distribution of water mass with precision. Topex/Poseidon and Jason, on the other hand, with a repetitivity of just ten days, will provide better temporal resolution.
CLS, a French company, is handling the operational exploitation of altimetry measurements from both Envisat and Jason. "We will integrate data from these two sources, to get the maximum benefit," explains Philippe Gaspar, Head of satellite oceanography at CLS. "The combinatorial algorithm has been in use since 1998, allowing CLS to offer state-of-the-art data products".
Hydrosphere, atmosphere, ionosphere: a close relationship
The products developed by CLS will be of interest, first and foremost, for scientists who use them as inputs for ocean modelling and forecasting. In conjunction with atmospheric models, this forms a starting point for predicting climate change. "It is now possible to forecast some major events such as El Niño, but smaller-scale phenomena such as the North Atlantic oscillation pose much more of a problem," Gaspar said.
To obtain the best performance from a forecasting model, initial conditions must be described as precisely as possible, and this is where satellite data is indispensable. "Before the advent of satellites, forecasting of this type would have been unthinkable," as Gaspar reminds us.
Radar altimetry measurements are correlated with high-precision orbitographical data from an instrument called "DORIS", and with those of a microwave radiometer, so that errors caused by atmospheric water can be corrected. The use of a dual-frequency altimeter further makes it possible to correct for the distorting effects of the ionosphere. In this way two significant sources of error are eliminated, in the order of 40 to 50 cm for water vapour and 20 to 30 cm for the ionosphere.
The continuity of altimetry data is vital, as Gaspar explains. "The usefulness of the scientific work would be seriously impaired if the service was interrupted. And once commercial applications are on the market, continuity will become absolutely indispensable."
Managing the traffic at sea
In addition to oceanography and climate studies, the radar altimeter has an important contribution to make to marine traffic management. Dispersion of the reflected radar signal gives information on the height of waves, with a precision of ±25 cm, while the advanced synthetic aperture radar (ASAR) determines wave direction. Taken together with information on major currents, this will make it possible to optimise routing of maritime traffic for speed and fuel economy, a substantial boon to international shipping. The ASAR also tracks drifting ice and monitors the pack ice and its limits.
Two other Envisat instruments are designed primarily to study the hydrosphere. MERIS (for Medium Resolution Imaging Spectrometer) is a fifteen-band optical system spanning the visible and near-infrared spectrum, and will be used for ocean colour measurements. The AATSR radiometer covers more of the IR spectrum. It will measure ocean surface temperatures, continuing the work of earlier ATSR systems on the ERS satellites. These two instruments together will have major applications in studies of plankton and fish movements.
As instrument data comes in, Envisat puts it provisionally into its onboard mass-memory devices. Transmission may be to one of the ground stations in Kiruna, Sweden, or Svalbard, Norway or via a high-speed link to the Artemis data relay satellite, which will be positioned in geostationary orbit and forward the data to ESA`s establishment ESRIN, located in Frascati, Italy, for near-real time processing.
The data gathered will be made available to the world scientific community at archiving centres distributed throughout Europe and linked with very high speed leased lines. A data server will be put on line for access via the Internet. Two consortiums have been set up with data processing/commercialisation experts: Sarcom, led by Spot Image, and Emma, by Eurimage, will handle the commercial exploitation of the application products developed from Envisat data.
By concentrating such an array of instruments on a single orbital platform, it becomes possible to integrate the information received in near-real time. This opens exciting opportunities for new products, building on recent progress in our understanding of the mechanisms, which determine the behaviour of the Earth`s oceans and atmosphere. Thanks to a continuous flow of data, these products could revolutionise the management of our Planet and our environment.
Jacques Louet | alphagalileo
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:99623651-411f-4052-910b-3b6fc2ef8b6e> | 3.09375 | 1,825 | Content Listing | Science & Tech. | 30.974708 | 95,574,689 |
Study finds massive eruptions likely triggered mass extinction. Watch a new MIT News video about this work in the Bowring Lab.
Read this story at MIT News
Around 252 million years ago, life on Earth collapsed in spectacular and unprecedented fashion, as more than 96 percent of marine species and 70 percent of land species disappeared in a geological instant. The so-called end-Permian mass extinction — or more commonly, the “Great Dying” — remains the most severe extinction event in Earth’s history.
Scientists suspect that massive volcanic activity, in a large igneous province called the Siberian Traps, may have had a role in the global die-off, raising air and sea temperatures and releasing toxic amounts of greenhouse gases into the atmosphere over a very short period of time. However, it’s unclear whether magmatism was the main culprit, or simply an accessory to the mass extinction.
MIT researchers have now pinned down the timing of the magmatism, and determined that the Siberian Traps erupted at the right time, and for the right duration, to have been a likely trigger for the end-Permian extinction.
According to the group’s timeline, explosive eruptions began around 300,000 years before the start of the end-Permian extinction. Enormous amounts of lava both erupted over land and flowed beneath the surface, creating immense sheets of igneous rock in the shallow crust. The total volume of eruptions and intrusions was enough to cover a region the size of the United States in kilometer-deep magma. About two-thirds of this magma likely erupted prior to and during the period of mass extinction; the last third erupted in the 500,000 years following the end of the extinction event. This new timeline, the researchers say, establishes the Siberian Traps as the main suspect in killing off a majority of the planet’s species.
“We now can say it’s plausible,” says Seth Burgess, who received his PhD last year from MIT’s Department of Earth, Atmospheric, and Planetary Sciences and is now a postdoc at the U.S. Geological Survey. “The connection is unavoidable, because it’s clear these two things were happening at the same time.”
Burgess and Sam Bowring, the Robert R. Shrock Professor of Earth and Planetary Science at MIT, have published their results in the journal Science Advances.
A singular event
Around the time of the end-Permian extinction, scientists have found that the Earth was likely experiencing a sudden and massive disruption to the carbon cycle, abnormally high air and sea temperatures, and an increasingly acidic ocean — all signs of a huge and rapid addition of greenhouse gases to the atmosphere. Whatever triggered the mass extinction, scientists reasoned, must have been powerful enough to generate enormous amounts of greenhouse gases in a short period of time.
The Siberian Traps have long been a likely contender: The large igneous province bears the remains of the largest continental volcanic event in Earth’s history.
“It’s literally a singular event in Earth history — it’s a monster,” Burgess says. “It makes Yellowstone … look like the head of a pin.”
It’s thought that as the region erupted, magma rose up through the Earth’s crust, essentially cooking sediments along the way and releasing enormous amounts of greenhouse gases like carbon dioxide and methane into the atmosphere.
“The question we tried to answer is, ‘Which came first, mass extinction or the Siberian Traps? What is their overall tempo, and does the timing permit magmatism to be a trigger for mass extinction?’” Burgess says.
For the answer, Burgess, Bowring, and colleagues traveled to Siberia on multiple occasions, beginning in 2008, to sample rocks from the Siberian Traps. For each expedition, the team traveled by boat or plane to a small Siberian village, then boarded a helicopter to the Siberian Traps. From there, they paddled on inflatable boats down a wide river, chiseling out samples of volcanic rock along the way.
“We’d have a couple of hundred kilos of rocks, and would go to the market in Moscow and buy 15 sport duffle bags, and in each we’d put 10 kilos of rocks … and hope we could get them all on the plane and back to the lab,” Burgess recalls.
Back at MIT, Burgess and Bowring dated select samples using uranium/lead geochronology, in which Bowring’s lab specializes. The team looked for tiny crystals of either zircon or perovskite, each of which contain uranium and lead, the ratios of which they can measure to calculate the rock’s age. The team dated various layers of rock to determine the beginning and end of the eruptions.
They then compared the timing of the Siberian Traps to that of the end-Permian extinction, which they had previously determined using identical techniques.
“That’s important, because we can compare green apples to green apples. If everything is done the same, there’s no bias,” Burgess says. “Now we’re able to say magmatism definitely preceded mass extinction, and we can resolve those two things outside of uncertainty.”
Richard Ernst, a scientist-in-residence at Carleton University in Ottawa, Ontario, says the new timeline establishes a definitive, causal link between the Siberian Traps and the end-Permian extinction.
“This paper nails it,” says Ernst, who was not involved in the study. “Given that they have dated a portion of the Siberian Traps occurring just before, during, and only for a short time after the extinction, this is the ‘smoking gun’ for this large igneous province being fully correlated with the extinction. At this point, additional dating and other studies will simply provide more details on the link.”
Now that the team has resolved the beginning and end of the Siberian Traps eruptions, Burgess hopes others will take an even finer lens to the event, to determine the tempo of magmatism in the 300,000 years prior to the mass extinction.
“We don’t know if a little erupted for 250,000 years, and right before the extinction, boom, a vast amount did, or if it was more slow and steady, where the atmosphere reaches a tipping point, and across that point you have mass extinction, but before that you just have critically stressed biospheres,” Burgess says. “Now we’ve pinned it down in time, and others can go in with other techniques to get a more fully fleshed out timeline. But we need it to start someplace, and that’s what we’ve got.”
This research was funded, in part, by the National Science Foundation. | <urn:uuid:58c9d10e-a625-41c0-8122-ca60f2106155> | 4.28125 | 1,442 | News (Org.) | Science & Tech. | 45.246545 | 95,574,704 |
The history of the K/Ar-method for absolute dating of minerals and rocks is full of surprises and good guesses. The β-activity of potassium was discovered, together with that of rubidium, by J. J. Thomson as early as 1905. It was confirmed by a considerable number of authors (for the early literature of potassium β-activity cf. Meyer and Schweidler (1927)). The γ-activity of potassium was discovered by Kohlhörster in 1928 and studied by him in potassium-bearing salt mines. In 1935, Klemperer and, independently, Newman and Walke (1935), ascribed, from reasons of isotope systematics, the activity of potassium to a-then unknown — rare isotope K40. This was the first good guess. In 1935, A. O. Nier actually discovered this isotope and found its abundance to be 1.19 · 10-4 of the total K. Smythe and Hemmendinger (1937) found that the β--activity of K is actually due to K40.
KeywordsElectron Capture Impact Crater Good Guess Iron Meteorite Atomic Mass Unit
Unable to display preview. Download preview PDF. | <urn:uuid:d58e128e-17d8-4335-b052-8681c0dbc1d8> | 3.625 | 248 | Truncated | Science & Tech. | 60.170262 | 95,574,707 |
Human Anatomy, Physiology, and Medicine. Anything human!
Moderators: honeev, Leonid, amiradm, BioTeam
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If an organism has 12 chromosomes, how many homologous pairs will it have?
Is the answer 24?
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I hope I'm not misleading you, but usually when people talk about the number of chromosomes they actually mean the number of pairs of chromosomes. So to say an organism has 12 chromosomes probably means it has 12 homologous pairs of chromosomes, or 24 individual ones.
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Usually, the "number" of chromosomes is the total number. The number of pairs (ignoring nonmatched pairs) would be half that, not double.
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For example, humans have 46 chromosomes, and 23 homologous pairs of chromosomes.
Who is online
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In 2015, NASA, for the first time, will fly a space mission utilizing a radically different propellant—one which has reduced toxicity and is environmentally benign. This energetic ionic liquid, or EIL, is quite different from the historically employed hydrazine-based propellant, which was first used as a rocket fuel during World War II for the Messerschmitt Me 163B (the first rocket-powered fighter plane).
Within the U.S. space program, hydrazine was used on the 1970s Viking Mars program, and more recently in the Phoenix lander and Curiosity rover Mars missions, as well as in the Space Shuttle's auxiliary power units. Significantly, monopropellant hydrazine-fueled rocket engines are the norm in controlling the terminal descent of spacecraft. What makes hydrazine desirable as a propellant for this terminal descent role is that when combined with various catalysts, the result is an extremely exothermic reaction that releases significant heat in a very short time, producing energy in the form of large volumes of hot gas from a relatively small volume of hydrazine liquid.
Unfortunately, hydrazine has several significant drawbacks: it is very toxic when inhaled, corrosive on contact with skin, hazardously flammable, and falls short in providing the propulsive power required for future spacecraft systems. In 1998, driven by these challenges, Dr. Michael Berman, a Program Manager at the Arlington, Virginia-based Air Force Office of Scientific Research (AFOSR), the basic research arm of the Air Force Research Laboratory (AFRL), funded Dr. Tom Hawkins of the Propellants Branch, Rocket Propulsion Division at AFRL's Aerospace Systems Directorate, to find a more benign, yet even more powerful material to replace hydrazine.
This research effort was ultimately associated with a joint government and industry development program, the Integrated High Payoff Rocket Propulsion Technology (IHPRPT) initiative, to improve U.S. rocket propulsion systems. IHPRPT challenged the Department of Defense, the National Air and Space Administration, and the rocket propulsion industry to double U.S. rocket propulsion capability (cost and performance) by 2010. Beginning in 1996, this IHPRPT challenge meant the development of propellants that would provide far greater energy density than current state-of-the-art propellants.
Dr. Hawkins' interest in EILs began early on in his career beginning at Lehigh University when he worked on advanced propellants for the Strategic Defense Initiative in the 1980s. Knowing the untapped potential of ionic liquids to provide high energy density materials, he embarked on an effort to design and characterize the EIL family. This effort was funded by AFOSR and continues to the present day.
But it was in 2002 that Dr. Hawkins, "…thought we were on the right track when we produced an ionic liquid monopropellant that incorporated an EIL that was investigated under our AFOSR program. This propellant class, known as AF-M315, has an energy density close to twice that of the state-of-the-art spacecraft monopropellant, hydrazine." With additional support from the IHPRPT program, the Missile Defense Agency (MDA) and related USAF missile programs, a full characterization of one of these new propellants, AF-M315E, was investigated for its overall safety and hazard properties. According to Dr. Hawkins, these safety properties, coupled with the performance of AF-M315E, were "…absolutely outstanding; we found the oral toxicity of AF-M315E to be less than that of caffeine, and its vapor toxicity to be negligible. The vapor flammability of AF-M315E was essentially nil, and this made it difficult to unexpectedly ignite and sustain combustion of AF-M315E—one could even put out small fires with the propellant!"
In 2005 NASA took a keen interest in this very promising alternative to hydrazine and performed further evaluations. Follow on work performed by Aerojet, Inc. brought AF-M315E engine design to a level that was very attractive for a technology transition to the commercial sector. But for that to occur, it was necessary to find a champion to sponsor the flight demonstration that would make AF-M315E spacecraft propulsion an 'off-the-shelf' choice for future propulsion systems. NASA became that champion in 2012 with their selection of Ball Aerospace & Technologies Corporation as the lead integrator for the Green Propellant Infusion Mission—a $45 million program that will produce new AF-M315E- based thrusters for NASA's 2015 spacecraft mission. Additional program team members consist of the Air force Research Laboratory, Aerojet, Inc., the Air Force Space & Missile Systems Center and the NASA/Glenn Research Center.
The field of energetic ionic liquids is the product of AFOSR-sponsored research at AFRL that is changing the landscape of work in the energetic materials community. According to Dr. Hawkins: "The AFOSR- funded program provided the synthesis and characterization work for an EIL that enabled the experimental USAF fuel, AF-M315E, to act as a high-energy density, environmentally benign, easy-to-handle replacement for spacecraft hydrazine fuel."
Hawkins also noted that twenty years is a well-recognized time period for producing such a revolutionary propellant approach and propulsion system due to the fact that the EIL approach to liquid propulsion is completely different than that of hydrazine, and, most significantly, the performance potentials of EIL-based propellants are not small incremental improvements, but significantly larger than any state-of-the-art propellant. As EIL-based propellants are developed, they will provide lower cost and safer propulsion system operations along with greater mission flexibility and faster mission response times.
Robert P. White | EurekAlert!
A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes
20.07.2018 | Science China Press
Future electronic components to be printed like newspapers
20.07.2018 | Purdue University
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:8a89b354-0a40-41cc-bb44-a572ab7e9645> | 3.21875 | 1,771 | Content Listing | Science & Tech. | 32.555575 | 95,574,712 |
Scientists at U.S. Department of Energy’s Argonne National Laboratory are answering that call by working to chemically manipulate algae for production of the next generation of renewable fuels – hydrogen gas.
“We believe there is a fundamental advantage in looking at the production of hydrogen by photosynthesis as a renewable fuel,” senior chemist David Tiede said. “Right now, ethanol is being produced from corn, but generating ethanol from corn is a thermodynamically much more inefficient process.”
Some varieties of algae, a kind of unicellular plant, contain an enzyme called hydrogenase that can create small amounts of hydrogen gas. Tiede said many believe this is used by Nature as a way to get rid of excess reducing equivalents that are produced under high light conditions, but there is little benefit to the plant.
Tiede and his group are trying to find a way to take the part of the enzyme that creates the gas and introduce it into the photosynthesis process.
The result would be a large amount of hydrogen gas, possibly on par with the amount of oxygen created.
“Biology can do it, but it’s making it do it at 5-10 percent yield that’s the problem,” Tiede said. “What we would like to do is take that catalyst out of hydrogenase and put into the photosynthetic protein framework. We are fortunate to have Professor Thomas Rauchfuss as a collaborator from the University of Illinois at Champaign-Urbana who is an expert on the synthesis of hydrogenase active site mimics.”
Algae has several benefits over corn in fuel production. It can be grown in a closed system almost anywhere including deserts or even rooftops, and there is no competition for food or fertile soil. Algae is also easier to harvest because it has no roots or fruit and grows dispersed in water.
“If you have terrestrial plants like corn, you are restricted to where you could grow them,” Tiede said. “There is a problem now with biofuel crops competing with food crops because they are both using the same space. Algae provides an alternative, which can be grown in a closed photobioreactor analogous to a microbial fermentor that you could move any place.”
Tiede admitted the research is its beginning phases, but he is confident in his team and their research goals. The next step is to create a way to attach the catalytic enzyme to the molecule.
Brock Cooper | EurekAlert!
A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes
20.07.2018 | Science China Press
Future electronic components to be printed like newspapers
20.07.2018 | Purdue University
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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Study of Variation of Temperature of Black Holes with Respect to Mass in XRBs
International Journal of Astrophysics and Space Science
Volume 1, Issue 4, October 2013, Pages: 61-63
Received: Oct. 12, 2013;
Published: Nov. 10, 2013
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Rama Nand Mehta, University Department of Mathematics, T. M. B. U. Bhagalpur-812007, India
Umakant Prasad, Department of Physics, T.N.B. College, T. M. B. U. Bhagalpur-812007, India
Ashok Kumar, Department of Physics, M.R.J.D. College, Bishnupur, Begusarai-851101, India
Dipo Mahto, Department of Physics, Marwari College, T.M.B.U. Bhagalpur-812007, India
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In the present paper, we have derived an expression for the variation of temperature of the black holes with respect to mass using the temperature of black hole at which the black hole radiates to infinity all species of particles with a perfect black body spectrum and surface gravity for Schwarzschild black holes. We have also calculated their values of different test black holes existing only in X-ray binaries.
Surface gravity, X-ray binaries, Schwarzschild black holes
To cite this article
Rama Nand Mehta,
Study of Variation of Temperature of Black Holes with Respect to Mass in XRBs, International Journal of Astrophysics and Space Science.
Vol. 1, No. 4,
2013, pp. 61-63.
R. M. Wald: "The thermodynamics of black holes", Living reviews in relativity, 2001.
Stephen Hawking: A brief History of Time, Bantam books, 1988.
Triyanta & A. N. Bowaire: Hawking Temperature of the Reissner-Nordstrom-Vaidya Black Hole, J. Math. Fund. Sci., Vol. 45, No. 2, 2013, 114-123.
Bardeen, J.M., Carter, B., Hawking, S.W.: The four laws of black hole mechanics. Commun. Math. Phys. 31(2), 161-170(1973). doi:10.1007/BFO1645742.
P. R. Silva: "A Note on Black Hole Temperature and Entropy". General Relativity and Quantum Cosmology, arXiv.org/pdf/gr-qc/0605051, May, 2006.
B. Ram, A. Ram and N. Ram: "The quantum black hole"arXiv:gr-qc/0504030v1.April, 2005.
D. Mahto, V. Prakash, B. K. Singh, K.M. Singh: Change in entropy of Non-spinning black holes w.r.t. the radius of event horizon in XRBs., Astrophys Space Sci. DOI 10.1007/s10509-012-1219-y (2012).
J. Transchen,: "An introduction to black hole evaporation" (2000), arXiv: gr- qc/0010055V1.
R. Narayan: Black Holes In Astrophysics, New Journal Physics, Vol. 7,No. 1, 2005, pp1-31, arXiv: gr-qc/050 6078.
D. Mahto, K. Kumari, R. K. Sah & K. M. Singh: Study of non-spinning black holes with reference to the change in Energy and Entropy, Astrophys Space Sci. DOI: 10.1007/s10509-011-0883-7 (2011).
S. Kinoshita and N. Tanahashi: "Hawking temperature for near-equilibrium black holes." arXiv: 1111.2684v2 [hep-th], 27 Jan, 2012. | <urn:uuid:a881d12b-d9a6-4143-a191-489981525098> | 2.53125 | 863 | Academic Writing | Science & Tech. | 87.448087 | 95,574,779 |
Something that I often need to do in my convex integration calculations is justify why I can uniquely solve the inverse divergence. For example if we want to solve for a v such that
div v = f
where f is some given scalar valued function, if it’s possible to solve this (which it is for my fluid equations i.e. Euler 2-d, 3-d, and SQG) any solution v can have a constant vector added to it and still be a solution.
In order to ensure the uniqueness of a solution we like to impose a condition such as v must be a mean zero vector field (sometimes this act is referred to as fixing a gauge for the problem).
In my studies I was wanting of a physics explanation why any realistic fluid should satisfy a mean-zero condition and I found an answer! It’s due to the conservation of momentum and you can see in section 3 of the following notes, a calculation which justifies why a vector flow should be mean-zero (assuming a uniform density).
Roughly speaking, one checks that the time derivative of the momentum is 0, hence the momentum is constant. This means that the integral of the vector field is constant in time and up to subtracting this constant from vector field solution, we may wlog assume we have a vector field solution which is mean 0.
I just wanted to post this here so that I wouldn’t lose this reference as I go about my calculations. | <urn:uuid:fd973efd-1154-4360-8f38-861129cf6a66> | 2.640625 | 304 | Personal Blog | Science & Tech. | 53.748 | 95,574,793 |
July 14 2016 Astronomy Newsletter
Here's the latest article from the Astronomy site at BellaOnline.com.
Solar System Discoveries – Quiz
Since prehistoric times people have known the Sun, the Moon and five planets. The rest of the Solar System had to await discovery by people with telescopes. How many of the discoverers can you identify?
(1) July 18, 1921: John Glenn. On February 20, 1962, Glenn flew the Friendship 7 mission to be the first American to orbit the Earth. Thirty-six years later he became the oldest person to go into space when he flew as a payload specialist on the space shuttle Discovery.
(2) July 19, 1846: Edward Pickering. Pickering was a leading light of 19th century astronomy who made the Harvard College Observatory into an institution with an international reputation. http://www.bellaonline.com/articles/art302072.asp
(1) July 14, 1965: Mariner 4 made a flyby of Mars. It was the first successful Mars mission
(2) July 14, 2015: New Horizons made its historic flyby of Pluto. The data is still coming home.
(3) July 16, 1994: The first fragments of comet Shoemaker-Levy 9 impacted Jupiter.
(4) July 16, 2011 The Dawn spacecraft went into orbit around Vesta.
(5) July 17, 1850: The first ever photograph of a star was taken at Harvard Observatory by the Director William Cranch Bond and Boston photographer John Adams Whipple.
(6) July 20, 1969: Neil Armstrong and Buzz Aldrin were the first humans to walk on the Moon.
*A new dwarf planet*
A few days ago astronomers using the Canada-France-Hawaii Telescope announced the discovery of a new dwarf planet. Planet RR245 is around 435 miles wide, just over 5% the width of the Earth, and has one of the largest orbits of any dwarf planet, taking an estimated 700 years to travel around the sun. http://i2.cdn.turner.com/cnnnext/dam/assets/160712134738-dwarf-planet-rr245-exlarge-169.jpg
Please visit http://astronomy.bellaonline.com/Site.asp for even more great content about Astronomy.
I hope to hear from you sometime soon, either in the forum http://forums.bellaonline.com/ubbthreads.php/forums/323/1/Astronomy or in response to this email message. I welcome your feedback!
Do pass this message along to family and friends who might also be interested. Remember it's free and without obligation.
I wish you clear skies.
Mona Evans, Astronomy Editor
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Dr John Bailey of the Department of Biology has been researching the invasive weed since the 1980s. The research continues with PhD students Michelle Hollingsworth and Catherine Pashley. Research in the Leicester department established that the weed in Britain was a single clone- making it one of the biggest female organism in the world.
Dr Bailey has commented on plans announced this week to introduce a biocontrol to eradicate the weed that is plaguing Britain. The natural predator, a sap-sucking psyllid insect, is proposed to combat the weed. Plans have been submitted to the Government for approval.
University of Leicester scientists have previously liaised with the team behind the latest proposal including Dick Shaw, the lead researcher on the project, from Cabi, a not-for-profit agricultural research organisation.
Dr Bailey said: “Biological control is commonly used in the UK Glasshouse industry with a great deal of success. However, the use of predators invariably means that these die out when the prey levels get very low, and before the target is completely eliminated, so repeated applications are required.
“There is no doubt that in parts of the country Japanese Knotweed is still spreading along riversides and that in such areas it is extremely difficult to use herbicide – even supposing the will and the funding were available! Japanese Knotweed may be a big bully of a plant in Europe, but in Japan it is just one component of a giant herb community, and what we in the West think of as its almost profligate vigour is only enough to keep it in the game, struggling as it does to find somewhere to grow and to avoid the effects of the numerous predators that it attracts.
“A Biological control agent, as the developers themselves admit, is no ‘magic bullet’. Certainly such a release will weaken existing plants and slow down or hamper range extension, it may even have the effect of reducing the amount of hybrid seed produced. But it must be viewed as an invaluable aid to levelling the playfield in the fight against this alien plant, rather than as a ‘mission achieved’.
“If it is to be released it should be as part of a co-ordinated campaign which involves both public education of the dangers of inadvertently spreading the plant, and a redoubling of the use of more conventional control methods. To introduce a control agent and then sit back and let it do its work would lead to little reduction in the occurrence of the plant, and to a great increase in the unsightliness of its formerly pleasantly verdant appearance.”
• Dr Bailey travels widely on the subject of Japanese Knotweed; In September he addressed the Neobiota meeting in Prague with ‘Opening Pandora’s seed packet; unpredictable outcomes in indestructable plants?” Later this month he will be delivering ‘Japanese Knotweed here today – here tomorrow?’ at the BSBI Understanding our Alien Flora meeting in London.
Ather Mirza | alfa
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Inscrit le: 18 Avr 2016
|Posté le: Dim 9 Juil - 17:33 (2017) Sujet du message: Software Quality Plans A How To Guide For Project Staff
I N T R O D U C T I O N
How to Write Software Quality Management Plans is a plain-english, simplified version of IEEE 730 Standard for Software Quality Assurance Plans.
This how to guide specifies the format and contents of a quality plan. It identifies the practices and processes to be applied during a project to ensure that the deliverables conform to the agreed requirements.
It also identifies the quality objectives of the project, which are statements about measurable aspects of project and quality management.
The quality plan includes the:
- scope and objectives of the quality aspects of the project
- quality deliverables that the project will produce
- process by which those deliverables are produced
- organisation and staffing which will perform the quality functions
- responsibilities of those involved
S C O P E
How to Write Software Quality Management Plans applies to the medium to large scale software development projects.
O B J E C T I V E S
How to Write Software Quality Management Plans provides project and quality managers with a guide for the development of the quality plan. It addresses:
- quality related aspects of the project to be considered during the planning stage of the project
- the project's quality objectives, quality deliverables and how they are to be managed
- the need for consistent content and format
Contribution to IS Quality. As with the Project Plan, the literature of software quality recognises the importance of comprehensive planning for those aspects of a software development project that bear most closely upon its success.
Given that up to 70% of IT development projects fail (in terms of either not being completed, or completed but not used by the client due to it unsuitability), due in part to inadequate planning and execution of the project, this how to guide is an valuable aid for project planners to address the important quality-related activities. It is is an easy to use checklist, as defined by IEEE 730, and template to achieve this end.
In the same way as a systematic and comprehensive Statement of User Requirements can capture a more complete set of requirements, a project plan as provided by this how to guide allows the project manager to make sure he/she has considered all relevant quality matters in the planning stage, allowing them to avoid, as far as possible, unpleasant surprizes later. | <urn:uuid:7a64128d-143e-4c42-827c-0527295062e7> | 2.671875 | 510 | Knowledge Article | Software Dev. | 20.403636 | 95,574,821 |
A mixed-up magnetic storm
28 August 2014The Sun is a variable star, experiencing 11-year-long cycles of activity which impact our planet and near-Earth space. Forecasting the changing space weather and the effects it will have on Earth remains a challenge, as illustrated by an unusual magnetic storm that was observed by ESA's Cluster quartet and one of the Chinese-ESA Double Star spacecraft.
On 20 January 2005, the ESA/NASA SOHO spacecraft detected an explosion on the Sun which ejected a huge cloud of plasma (electrically charged gas) into space. Subsequent observations indicated that this was one of the fastest coronal mass ejections (CMEs) during solar cycle 23, with a velocity that peaked at perhaps 3000 km/s at a distance of between 3 and 50 solar radii, before slowing to 1000 km/s as it approached Earth. The typical speed of particles in the solar wind is 400-700 km/s.
As a result, the CME took only 34 hours to cross the 150 million km gulf between the Sun and Earth, compared with the typical time of 3-4 days.
The fast-moving cloud acted like a snow plough, driving into slower-moving solar wind material ahead of it and compressing the plasma so that it piled up in a high density - high temperature sheath region, preceded by an interplanetary shock.
By the time it reached Earth's vicinity, the CME exhibited two extremely unusual features. First, it was observed to contain a large amount of solar filament material. Filaments are ribbons of dense plasma that are driven upward into the Sun's outer atmosphere – the corona – by strong magnetic fields emerging from active regions. However, despite observations indicating that more than 70% of active region eruptions involve solar filaments, these structures are rarely identifiable in CMEs arriving at Earth.
Second, the filament material was displaced from its expected position in the CME. As the coronal mass ejection decelerated en route to Earth, the momentum of the massive solar filament caused it to push its way toward the front, eventually making contact with the sheath region.
What happened next was observed by a flotilla of Earth-orbiting scientific satellites, including ESA's Cluster quartet, the Chinese-ESA Double Star TC-1 spacecraft, and various US spacecraft, as well as the ground-based SuperDARN radar network. They provided a unique opportunity to study the impact and merger of the CME material with the magnetosphere – the invisible magnetic bubble which surrounds our planet.
At the time of the CME's impact with Earth's magnetosphere on 21 January 2005, Cluster was in the solar wind directly upstream of Earth, acting as a solar wind monitor.
Meanwhile, Double Star TC-1 was passing from the outer region of the planet's magnetic field (the magnetosheath) and entering the magnetosphere. This enabled it to observe the entry of the solar filament material as it crossed into the magnetosphere.
The magnetic storm that resulted from the CME impact on 21 January was moderate in intensity, since the interplanetary magnetic field was mainly northward – the same as Earth's magnetic field. (A geomagnetic storm occurs when mass, energy and momentum from the solar wind penetrate into the magnetosphere and disrupt the particles and the fields in near-Earth space. Major storms can cause damage to satellites in orbit around the Earth, and induce currents in the ground that damage or disrupt power grids.) However, the dense solar filament embedded in the incoming cloud produced a number of effects which made it behave in some ways like a superstorm.
"The data show that the dense filament material following immediately behind the sheath in the CME was directly or indirectly responsible for most of the unusual features in the geomagnetic storm which resulted," says Janet Kozyra, a researcher at the University of Michigan, Ann Arbor, USA, and lead author of a recent paper on the effects of the CME, published in the Journal of Geophysical Research, Space Physics.
"The arrival of the filament, in combination with a thin layer of southward interplanetary magnetic fields at its leading edge, resulted in a superfountain in the equatorial ionosphere. Around 18:50 UT on 21 January, near the planet's day-night boundary, Earth's ionospheric layer shot upward at a speed of more than 1000 m/s, rising above 900 km within ten minutes. The typical altitude of this layer is 300 km. Satellites in the region, now under the layer, saw a drop in ionospheric densities by a factor of 100. The development of a superfountain is highly unusual during such a moderate magnetic storm."
Within one hour of the impact, a cold, dense plasma sheet had formed out of the filament material and high density material continued to move through the magnetosphere for the entire six hours of the filament's passage. Simulated and observed plasma sheet densities exceeded tens of particles per cubic centimetre along the flanks – high enough to inflate the magnetotail under northward magnetic field conditions, despite the cool temperatures. These high densities were driven inward as the massive solar filament compressed the magnetosphere.
Other unusual effects were the equatorward spread of the auroral oval and strong heating in the polar ionosphere.
"Case studies such as this – which combine all available satellite observations in regions from Sun to Earth with linked global models – allow us to trace chains of processes and their interactions, in order to identify the drivers of the extreme features and track the changes that appear throughout the system as a consequence," remarks Kozyra.
"Predicting the impact of the Sun's activity on Earth is one of the major goals of space weather research," says Philippe Escoubet, ESA's project scientist for Cluster. "However, we are not there yet. It is well known that similar solar observations and solar wind conditions can lead to totally different consequences on the Earth's magnetic environment.
"Coordinated observations and modelling of unusual events by multiple spacecraft orbiting near Earth are essential if we are to improve our understanding of the Sun-Earth connection."
Solar filament impact on 21 January 2005: Geospace consequences, by J.U. Kozyra and colleagues is published in the Journal of Geophysical Research: Space Physics, Volume 119, Issue 7, pages 5401-5448, July 2014; DOI: 10.1002/2013JA019748.
The study is based on measurements from twelve spacecraft operating in the Earth's magnetosphere: ESA's four Cluster spacecraft, one of the Chinese-ESA Double Star spacecraft (TC-1), the Advanced Composition Explorer (ACE), the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite, and five geosynchronous satellites from Los Alamos National Laboratory. An additional nine low-altitude satellites provided measurements of the effects in the ionosphere and atmosphere.
Cluster is a constellation of four spacecraft flying in formation around Earth. It is the first space mission able to study, in three dimensions, the natural physical processes occurring within and in the near vicinity of the Earth's magnetosphere. Launched in 2000, it is composed of four identical spacecraft orbiting the Earth in a pyramidal configuration, along a nominal polar orbit of 4 × 19.6 Earth radii (1 Earth radius = 6380 km). Cluster's payload consists of state-of-the-art plasma instrumentation to measure electric and magnetic fields over wide frequency ranges, and key physical parameters characterising electrons and ions from energies of near 0 eV to a few MeV. The science operations are coordinated by the Joint Science Operations Centre (JSOC) at the Rutherford Appleton Laboratory, United Kingdom, and implemented by ESA's European Space Operations Centre (ESOC), in Darmstadt, Germany.
Janet U. Kozyra
Last Update: 05 September 2014For further information please contact: SciTech.email@example.com
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The green sea turtle is one of the largest and most widespread of all marine turtles and is found in warm tropical waters from New England to South Africa and in the Pacific from Western Africa to the Americas. Adults measure more than three feet long and weigh 220 lb on average. The green sea turtle gets its name from the green color of its body fat. The carapace is oval-shaped and varies in color from olive to brown, gray and black with swirls and irregular patterns. The undershell (plastron) is pale yellow or orange in color. Males are usually smaller than females.
Found only in tropical waters, these turtles rarely leave the water, except for when it is time to nest, or when they wish to bask in the sun to get warm. They are herbivores and feed on seagrasses and algae. When ready to mate, sea turtles migrate hundreds of miles across the ocean to the place where they hatched. The females also use the same beach to bury the eggs in the sand. Incubation lasts between 45 and 70 days. When eggs are ready to hatch, the hatchlings using a special tooth (that eventually falls off) to break the egg open, and then must use their front flippers to dig their way up to the surface. After reaching the surface, they immediately make their way back into the ocean. The young turtles are vulnerable at this time to a variety of predators, such as crabs and gulls on the beach, and to sharks and dolphins in the water.
Green sea turtles are mainly threatened by predation by animals and humans. They are overharvested for their meat and eggs in many areas. The meat is highly prized, and the cartilage underneath the plastron is used for making turtle soup. Also, some green sea turtles are accidentally caught by fishermen. This species is legally protected in the United States, and in United Kingdom protected from excess harvesting.
Copyright Notice: This article is licensed under the GNU Free
Documentation License. It uses material from the Wikipedia article "Green sea turtle".
Green Sea Turtle Facts Last Updated:
May 9, 2017
To Cite This Page:
Glenn, C. R. 2006. "Earth's Endangered Creatures - Green Sea Turtle Facts" (Online).
Accessed 7/18/2018 at http://earthsendangered.com/profile.asp?sp=821&ID=9.
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The Errera graph
|Named after||Alfred Errera|
In the mathematical field of graph theory, the Errera graph is a graph with 17 vertices and 45 edges. Alfred Errera published it in 1921 as a counterexample to Kempe's erroneous proof of the four color theorem; it was named after Errera by Hutchinson & Wagon (1998).
The Errera graph is planar and has chromatic number 4, chromatic index 6, radius 3, diameter 4 and girth 3. All its vertices are of degree 5 or 6 and it is a 5-vertex-connected graph and a 5-edge-connected graph.
The Errera graph is not a vertex-transitive graph and its full automorphism group is isomorphic to the dihedral group of order 20, the group of symmetries of a decagon, including both rotations and reflections.
The characteristic polynomial of the Errera graph is .
Application to the four color theorem
The four color theorem states that the vertices of every planar graph can be colored with four colors, so that no two adjacent vertices have equal colors. An erroneous proof was published in 1879 by Alfred Kempe, but it was discovered to be erroneous by 1890. The four color theorem was not given a valid proof until 1976. Kempe's proof can be translated into an algorithm to color planar graphs, which is also erroneous. Counterexamples to his proof were found in 1890 and 1896 (the Poussin graph), and later, the Fritsch graph and Soifer graph provided two smaller counterexamples. However, until the work of Kempe, these counterexamples did not show that the whole coloring algorithm fails. Rather, they assumed that all but one vertex of the graph had already been colored, and showed that Kempe's method (which purportedly would modify the coloring to extend it to the whole graphs) failed in those precolored instances. The Errera graph, on the other hand, provides a counterexample to Kempe's entire method. When this method is run on the Errera graph, starting with no vertices colored, it can fail to find a valid coloring for the whole graph. Additionally, unlike the Poussin graph, all vertices in the Errera graph have degree five or more. Therefore, on this graph, it is impossible to avoid the problematic cases of Kempe's method by choosing lower-degree vertices.
The figure shows an example of how Kempe's proof can fail for this graph. In the figure, the adjacencies between regions of this map form the Errera graph, partially four-colored with the outer region uncolored. Kempe's erroneous proof follows the idea of extending partial colorings such as this one by recoloring Kempe chains, connected subgraphs that have only two colors. Any such chain can be recolored, preserving the validity of the coloring, by swapping its two colors on all vertices of the chain. Kempe's proof has different cases depending on whether the next vertex to be colored has three, four, or five neighbors and on how those neighbors are colored. In the case shown, the vertex to be colored next is the one corresponding to the outer region of the map. This region cannot be colored directly, because it already has neighbors of all four different colors. The blue and yellow neighbors are connected by a single Kempe chain (shown by the dashed yellow lines in the image), preventing a swap from making them both blue or both yellow and freeing a color. Similarly, the blue and green neighbors are connected by another Kempe chain (the dashed green lines). In such a case, Kempe's proof would try to simultaneously swap the colors on two Kempe chains, the left red-yellow chain and the right red-green chain (dashed red lines). The blue-green chain blocks the left red-yellow chain from reaching the right side of the graph, and the blue-yellow chain blocks the right red-green chain from reaching the left, so it would seem that simultaneously swapping the colors on these two chains is a safe operation. But because the blue-yellow and blue-green chains cross each other rather than staying separated, there is a region in the middle of the figure where the red-yellow and red-green chains can meet. When these two chains meet in the middle, the simultaneous swap causes adjacent yellow and green vertices in this middle area (such as the vertices represented by the upper yellow and green regions in the figure) to both become red, producing an invalid coloring.
Applications in chemistry
Atoms of metals such as gold can form clusters in which a central atom is surrounded by twelve more atoms, in the pattern of an icosahedron. Another, larger, type of cluster can be formed by coalescing two of these icosahedral clusters, so that the central atom of each cluster becomes one of the boundary atoms for the other cluster. The resulting cluster of 19 atoms has two interior atoms (the centers of the two icosahedra) with 17 atoms in the outer shell in the pattern of the Errera graph.
The dual graph of the Errera graph is a fullerene with 30 vertices, designated in the chemistry literature as C30(D5h) or F30(D5h) to indicate its symmetry and distinguish it from other 30-vertex fullerenes. This shape also plays a central role in the construction of higher-dimensional fullerenes.
- Hutchinson, Joan; Wagon, Stan (1998), "Kempe revisited", American Mathematical Monthly, 105 (2): 170–174, doi:10.2307/2589650, MR 1605875.
- Errera, A. (1921), Du coloriage des cartes et de quelques questions d'analysis situs, Ph.D. thesis.
- Gethner, Ellen; Springer, William M., II (2003), "How false is Kempe's proof of the four color theorem?", Proceedings of the Thirty-Fourth Southeastern International Conference on Combinatorics, Graph Theory and Computing, Congressus Numerantium, 164: 159–175, MR 2050581.
- Michael, D.; Mingos, P. (2015), "Structural and bonding patterns in gold clusters", Dalton Trans., 44 (15): 6680–6695, doi:10.1039/c5dt00253b.
- Mathur, Rakesh Behari; Singh, Bhanu Pratap; Pande, Shailaja (2016), Carbon Nanomaterials: Synthesis, Structure, Properties and Applications, CRC Press, p. 59, ISBN 9781498702119.
- Deza, Michel; Shtogrin, Mikhail (1999), "Three-, four-, and five-dimensional fullerenes", Southeast Asian Bulletin of Mathematics, 23 (1): 9–18, arXiv: , Bibcode:1999math......6035D, MR 1810781. | <urn:uuid:88c39865-6bb1-4148-a89a-110e49f9b440> | 3.15625 | 1,466 | Knowledge Article | Science & Tech. | 55.428555 | 95,574,855 |
+44 1803 865913
By: VN Bashkin
472 pages, Figs, tabs
A wide-ranging textbook which covers problems peculiar to, or prevalent in, Asian countries. By incorporating regionally oriented knowledge, it fills a gap left by other, Western-oriented texts.
This book provides significant information on the impact of rapid industrialization and urbanization on air, soil, and water in the Asian environment. Questions at the end of each chapter are appropriately designed for undergraduate students. The author uses various combinations of expert approaches and geoinformation systems, including modelling, to predict critical load on ecosystems of Asia. This is a book for beginners intending to study the fate and behavior of contaminants in the environment. (Ravi Naidu, Centre for Environmental Risk Assessment & Remediation)
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The giant explosions, called hot flow anomalies, can be so large at Venus that they’re bigger than the entire planet and they can happen multiple times a day.
Giant perturbations called hot flow anomalies in the solar wind near Venus can pull the upper layers of its atmosphere, the ionosphere, up and away from the surface of the planet.
Image Credit: NASA
"Not only are they gigantic," said Glyn Collinson, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. "But as Venus doesn’t have a magnetic field to protect itself, the hot flow anomalies happen right on top of the planet. They could swallow the planet whole."
Collinson is the first author of a paper on these results that appeared online in the Journal of Geophysical Research in February 2014. The work is based on observations from the European Space Agency's Venus Express. The results show just how large and how frequent this kind of space weather is at Venus.
Earth is protected from the constant streaming solar wind of radiation by its magnetosphere. Venus, however, has no such luck. A barren, inhospitable planet, with an atmosphere so dense that spacecraft landing there are crushed within hours, Venus has no magnetic protection.
Scientists like to compare the two: What happened differently at Earth to make it into the life-supporting planet it is today? What would Earth be like without its magnetic field?
At Earth, hot flow anomalies do not make it inside the magnetosphere, but they release so much energy just outside that the solar wind is deflected, and can be forced to move back toward the sun. Without a magnetosphere, what happens at Venus is very different.
Venus's only protection from the solar wind is the charged outer layer of its atmosphere called the ionosphere. A sensitive pressure balance exists between the ionosphere and the solar wind, a balance easily disrupted by the giant energy rush of a hot flow anomaly. The hot flow anomalies may create dramatic, planet-scale disruptions, possibly sucking the ionosphere up and away from the surface of the planet.Karen C. Fox
Karen C. Fox | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Three species of the reef coral genus Madracis display skeletal isotopic characteristics that relate to depth, colony topography, and consequently to coral physiology. The joint interpretation of skeletal delta(13)C and delta(18)O provides information on the ecological plasticity and adaptation to depth of a coral species. Isotopic results are most easily understood in terms of "kinetic" effects, which reduce both delta(18)O and delta(13)C below isotopic equilibrium values, and "metabolic" effects, which only influence the skeletal delta(13)C. Madracis mirabilis is adapted to depths shallower than 20 m, and shows the greatest range in kinetic effects and the strongest metabolic C-13 enrichments caused by symbiont photosynthesis. Madracis formosa lives deeper than 40 m, and shows a reduced range of kinetic effects and relatively weak metabolic C-13 enrichments. Madracis pharensis inhabits depths from 5 to >60 m, and does not attain the strength of kinetic effects of either of the other two species, apparently because it is not quite as well adapted to rapid growth at either extreme.
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The Hubble Space Telescope has turned its ultraviolet, visible-light, and near-infrared eyes to the queen of galaxies, M31, capturing the biggest and sharpest image yet of our neighbor.
A bizarre set of galaxies in the Coma Cluster have lost most of their stars (or star-making material), making them especially rich in dark matter.
Astronomers are peering into a galaxy cluster’s past, using Hubble’s Frontier Fields to measure the light from ghost stars cast adrift in galaxy collisions.
Observations from several radio telescopes reveal that, when two galaxies merge, their progeny often have gaseous disks—a hypothesis that before now didn’t have solid observational evidence.
New data collected by Galaxy Zoo show early galaxies with central bars, providing implications about how galaxies grow.
Astronomers have detected a supermassive black hole in the center of a tiny galaxy — where it has no right to be.
A new diagram might link the diverse visible-light characteristics of quasars to two physical properties — essentially, their accretion rate and orientation. If the analysis holds up, it could point the way toward a long-sought unification.
Astronomers have mapped the cosmic watershed and discovered a massive supercluster that extends more than 500 million light-years and contains 100,000 large galaxies. The Milky Way sits on the edge of this humongous structure.
Astronomers are tracking down the seeds that likely grew to become today’s most massive elliptical galaxies.
Evidence from observations sheds doubt on cosmic cannibalism as a source for galaxy growth, suggesting that instead galaxies grow by pulling in gas from the intergalactic medium.
Light from the puniest galaxies played a bigger role in shaping the early universe than previously thought.
Astronomers have detected a high-speed, long-lasting gas streamer spewing from the active galactic nucleus of NGC 5548. This discovery might provide new insights into how supermassive black holes influence their host galaxies.
A neighboring galaxy’s central black hole powers strong winds, allowing astronomers — for the first time — to spot those gales pushing out star-forming gas.
A hive of stars is sailing toward Earth at more than 2 million miles per hour — and racing away from the giant galaxy it used to call home.
Amateur astronomers have teamed up with the pros to produce four stunning multiwavelength images of galaxies M101, M81, M51, and Centaurus A.
Astronomers have developed a new method to measure distances to bright but faraway galaxies, a tool which will help better constrain the expansion rate of the universe.
This year’s April Fools' provides a wealth of alarming results. Catch up on all the scientific shenanigans here.
Infrared observations of the Circinus Galaxy may help reveal the shape of the dusty region fueling its active galactic nucleus and shed light on what governs dust structures in other galaxies.
A team of astronomers claim to have the most compelling case for annihilating dark matter yet.
Researchers with an experiment based at the South Pole have discovered the long-sought "smoking gun" for inflation. The signal was hidden in polarization patterns in the cosmic microwave background and confirms physicists' audacious theory of how the Big Bang happened.
Rumors are flying that the long-sought "smoking gun" for inflation has been found in polarization patterns in the cosmic microwave background. If so, it would confirm the inflation theory for how and why the Big Bang happened.
These stunning new images of spiral galaxy ESO 137-001 highlight its violent encounter with the intracluster plasma of Abell 3627, which is stripping away its gas and forming stars in the streamers.
Asteroid debris might be bombarding a radio pulsar in the constellation Puppis.
Two teams have independently pinpointed the same key player in postponing the growth of the universe’s smaller galaxies.
Astronomers have counted up the number of galaxy clusters in the cosmos and found a problem: the number is much lower than they expected. What's going on? | <urn:uuid:266d85ed-5a18-4bee-a648-120880d7443a> | 3.5 | 848 | Content Listing | Science & Tech. | 39.138171 | 95,574,919 |
EXPR(1) User Commands EXPR(1)
expr - evaluate expressions
--help display this help and exit
output version information and exit
Print the value of EXPRESSION to standard output. A blank line below
separates increasing precedence groups. EXPRESSION may be:
ARG1 | ARG2
ARG1 if it is neither null nor 0, otherwise ARG2
ARG1 & ARG2
ARG1 if neither argument is null or 0, otherwise 0
ARG1 < ARG2
ARG1 is less than ARG2
ARG1 <= ARG2
ARG1 is less than or equal to ARG2
ARG1 = ARG2
ARG1 is equal to ARG2
ARG1 != ARG2
ARG1 is unequal to ARG2
ARG1 >= ARG2
ARG1 is greater than or equal to ARG2
ARG1 > ARG2
ARG1 is greater than ARG2
ARG1 + ARG2
arithmetic sum of ARG1 and ARG2
ARG1 - ARG2
arithmetic difference of ARG1 and ARG2
ARG1 * ARG2
arithmetic product of ARG1 and ARG2
ARG1 / ARG2
arithmetic quotient of ARG1 divided by ARG2
ARG1 % ARG2
arithmetic remainder of ARG1 divided by ARG2
STRING : REGEXP
anchored pattern match of REGEXP in STRING
match STRING REGEXP
same as STRING : REGEXP
substr STRING POS LENGTH
substring of STRING, POS counted from 1
index STRING CHARS
index in STRING where any CHARS is found, or 0
length of STRING
interpret TOKEN as a string, even if it is a
keyword like 'match' or an operator like '/'
( EXPRESSION )
value of EXPRESSION
Beware that many operators need to be escaped or quoted for shells.
Comparisons are arithmetic if both ARGs are numbers, else lexicographi-
cal. Pattern matches return the string matched between \( and \) or
null; if \( and \) are not used, they return the number of characters
matched or 0.
Exit status is 0 if EXPRESSION is neither null nor 0, 1 if EXPRESSION
is null or 0, 2 if EXPRESSION is syntactically invalid, and 3 if an
Written by Mike Parker, James Youngman, and Paul Eggert.
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Report expr translation bugs to <http://translationproject.org/team/>
Copyright (C) 2017 Free Software Foundation, Inc. License GPLv3+: GNU
GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Full documentation at: <http://www.gnu.org/software/coreutils/expr>
or available locally via: info '(coreutils) expr invocation'
GNU coreutils 8.28 October 2017 EXPR(1) | <urn:uuid:a9fff9ab-b18e-4052-bb32-6b6d818ee906> | 2.515625 | 722 | Documentation | Software Dev. | 59.480432 | 95,574,942 |
Life of Sea | Purple Striped Jelly (Chrysaora colorata) | Purple Striped Jelly is also known as Chrysaora Colorata and Mauve Stinger. It is mostly found in coastal waters. It has a wide distribution in all warm and temperate waters and is found in Bermuda, the Mediterranean Sea, the Adriatic Sea, off the coast of California, and in the Atlantic Ocean. In Bermuda, Purple striped jelly is usually found offshore, but aggregations may drift inshore, especially during winter months. Unlike sea nettles and moon jellies, purple-striped jellies are not seen in large surface aggregations.
Medusa of Purple striped jelly are pink to purple in color, having blue, brown, and magenta pigments. It has 8 tentacles, which can reach up to 10 m in length, and four large oral arms. The tentacles, oral arms, exumbrella, and gastric pouches are covered in cnidocytes, cells that eject a toxin-filled stinging thread. Purple striped jelly has 16 stomach pouches and 16 lappets, which are foldings of the exumbrella. The exumbrella is covered with wart-like clusters of stinging nematocysts. The average size of Purple striped jelly is 6.5 cm diameter across the bell but they may grow to be 10 cm or more.
Purple striped jelly feeds primarily on macrozooplankton and spend most of their time searching for food. Like all jellyfish, they have stinging nematocyst cells which they use in food capture and defense.
Purple striped jelly's stings are painful and can cause pigmented lesions and a severe allergic reaction. Although Purple striped jelly has caused no known deaths, swimmers do not want to come into contact with this species. If stung, tentacles should be removed, and pouring vinegar on the sting may prevent further discharge of nematocysts. An ice pack helps to dull the pain for most stings.
Purple striped jelly is well-known for its beautiful luminescence. If disturbed, it will bioluminesce, and this luminescence is often seen at night. Jellyfish do not have complex eyes, but they do have light receptors called ocelli so they can likely perceive luminescence in conspecifics.
find here another sea creatures | <urn:uuid:41506667-dffa-423a-b82f-98bed3c0991a> | 3.453125 | 494 | Knowledge Article | Science & Tech. | 46.097759 | 95,574,959 |
A river or stream is primarily a transport system between the land and the sea. Most of the nutrients in a river come from adjacent terrestrial ecosystems, and relatively little primary production occurs within the streams or rivers itself. The organisms that are characteristic of rivers and streams are especially adapted to feeding on organic ditritus. Some insect larvae, such as caddis flies, attach themselves to rocks and spin nets which catch food particles from the flowing waters. In slow-moving rivers and pools the biological communities are much like those in lakes and ponds. If the load of the organic material reaching a river in runoff from the land is not too great, it will be quickly converted into its inorganic constituents by an array of organisms adapted for this function.
Rivers and streams serve human society in many important ways. They provide water for drinking, irrigation, and industrial use. Rivers are used as disposal systems for sewage and industrial wastes, was well as for means of transportation and recreation. Boats and barges transport the raw materials and products of industry and society along the waterways of the world. In spite of the fact that they make up only a very small percentage of the earth's surface, man uses rivers and streams more intensively than any other natural ecosystem.
Before the industrial revolution our rivers could easily absorb the impact of man without damage to their normal functions. However, huge amounts of water used by modern society, and the heavy burdens of waste that are now emptied into these ecosystems, have placed them in a precarious state. The two categories of waste are those that consist of materials that are normally present in natural ecosystems and those that are not usually found in nature. In the first instance there are organisms in the ecosystem which are adapted to handle these products in reasonable amounts. Human sewage and fertilizers are in this category. As long the human sewage and fertilizers that enter a river do not exceed the river's capacity to use the breakdown products of these materials, the system will not be harmed. When the system is overloaded, pollution results.
Many of the chemicals in industrial wastes are in the second category. There are no organisms capable of breaking down pesticides and many industrial chemicals before they reach toxic concentrations, so these materials are poisons when they enter a natural ecosystem. | <urn:uuid:2d1b7701-8072-44d1-9c4e-a8ea73c944c8> | 3.71875 | 454 | Personal Blog | Science & Tech. | 33.465663 | 95,574,961 |
Two new studies of the seven planets orbiting TRAPPIST-1 shed light on how these worlds formed and what they look like now.
Dark matter particles may travel more slowly than we thought, hindering their detection. Dust storms may aid atmospheric loss on Mars. And a new mission is investigating magnetic fields at an unprecedented scale.
If you're not in the right place in the right time, you can still view Wednesday morning's total lunar eclipse online via several live streams. We list several options here.
Amateur astronomer Donald Bruns has received the Chambliss Amateur Achievement Award from the American Astronomical Society for his work in repeating and improving upon an iconic experiment during the August 2017 total solar eclipse.
Supermassive black holes are difficult to observe and measure, yet they have profound effects on their host galaxies. Read up on the latest black hole discoveries presented at the Washington D.C. meeting of the American Astronomical Society.
New observations of galaxies in a universe just 800 million years old show that they’ve already settled into rotating disks. They must have evolved quickly to display such surprising maturity.
Iron-rich stars host planets on closer orbits than their iron-poor siblings, astronomers find. The results could help reveal how planets form.
A new study found more massive stars than expected in an intensely star-forming region. The results beg the question whether the process of star formation really is universal.
Multiple gravitational-wave detections, a total solar eclipse, and exploration of the outer system number among the top astronomy news stories of the year.
Scientists have applied a brand of artificial intelligence to data from the exoplanet-hunting Kepler satellite, resulting in the discovery of the first eight-planet system outside our own.
New analysis from the New Horizons team suggest that the spacecraft's next target in the Kuiper Belt might have a third companion.
A combo of Hubble and Gaia data reveal the distribution of dark matter in a tiny galaxy by tracking the galaxy’s stars.
Balloon astronomy is really taking off, writes Laura Fissel (NRAO) in the February 2018 issue of Sky & Telescope. She should know — as a member of the adventure-prone Balloon-borne Large Aperture Submillimeter Telescope (BLAST) team, she has been involved in multiple balloon telescope launches, part of her effort to study magnetic fields and star…
The iconic image of faraway galaxies, and one of the most-observed regions of space, has just received a spectroscopic upgrade.
Previous studies of 55 Cancri e haven’t been able to determine whether this super-Earth hosts an atmosphere. A new study settles the question.
The Zwicky Transient Facility has taken its first image, covering an area equivalent to 247 full Moons in a single shot. This beginning is part of an ongoing sea change in astronomy.
Observations of a stellar explosion that refused to fade away have astronomers scratching their heads. What created the blast — and could it explain massive black holes?
Two telescopes — one on the ground and one in space — watched a black hole’s jet turn on, enabling astronomers to probe its origin.
The detection of a star-forming region 66,500 light-years from Earth, on the other side of our galaxy’s center, lends weight to the existence of an extended arm of the Milky Way.
The long-awaited James Webb Space Telescope — the successor to the Hubble Space Telescope — has slipped its launch date by several months. It will now launch between March and June 2019.
A few decades ago, astronomers thought they had figured out how quasars operate. Now, a new study has thrown a wrench in the works.
Date/Time of photoNovember 2015
Date/Time of photoMay 2016
Curious about machine learning? Learn about the inner workings of machine-learning algorithms without writing a line of code.
Astronomers have found what could be the closest known pair of supermassive black holes detected via direct imaging, orbiting each other only a light-year apart. | <urn:uuid:a1a73f65-a32b-4811-ad45-f5de38789623> | 2.9375 | 836 | Content Listing | Science & Tech. | 43.603723 | 95,574,965 |
It has been axiomatically accepted that the basement of a continental shelf is the offshore extension and geologically part of the same continental lithosphere. While this notion may hold true in places, our analysis of the distribution of Jurassic-Cretaceous granitoids throughout the entire eastern continental China in space and time led us to the conclusion that the basement of the Chinese continental shelf (beneath East China Sea and South China Sea) is of exotic origin geologically unrelated to the continental lithosphere of eastern China.
This exotic terrane of a sizeable mass with large compositional buoyancy could be either an oceanic plateau or a micro continent, which was transported by, or along with, the paleo-Pacific plate moving in the course of NW direction and subducting beneath the eastern margin of the continental China in the Mesozoic, responsible for the granitoids with emplacement ages of ~ 190 Ma to ~ 88 Ma.
Portion of the world topographic map, highlighting the continental China and its adjacent land and seas (Google Map, 2015) to illustrate: (1) the Chinese continental shelf (basement of the East and South China Seas) to be of exotic origin; (2) arrival of the buoyant and unsubductable oceanic plateau or micro-continent at the trench jammed the trench at ~ 100 Ma; (3) the jammed trench location is shown in red dashed curve along the southeast coast of continental China although it is unclear in the north as indicated by the dashed light blue curve with question marks; (4) The yellow "drop" dots are granitoid sample locations with ages in the literature. The thick dashed purple line labeled E-W GGL approximates the East-West Great Gradient Line topographically separating the plateau to the west from the low-land hilly plain to the east.
Credit: ©Science China Press
The termination of the granitoid magmatism throughout the vast region at ~ 88 Ma manifests the likelihood of subduction cessation at this time or more likely shortly beforehand, probably at ~ 100 Ma. Subduction stops only if the trench is jammed by a sizable terrane that is compositionally buoyant and physically unsubductable. The basement of the Chinese continental shelf is understood to be such an unsubductable mass of either an oceanic plateau or micro continent as said above that collided with the eastern margin of the continental China and jammed the trench at ~ 100 Ma.
The trench jam at ~ 100 Ma led to the Pacific plate to change its course of motion from NW to NNW and to subduct beneath the predecessors of the Kamchatka and western Aleutian trenches as manifested by the age progressive Emperor Seamount Chain of the Hawaiian hotspot origin.
This Pacific plate re-orientation produced a transform boundary between the NNW moving Pacific plate and the newly accreted eastern Asian continental plate, which explains the ~ 40 Myrs' time gap of subduction related magmatism in the greater western Pacific region before the present-day western Pacific subduction began at ~ 50 Ma. Because of the large compositional contrast across this transform boundary, it may have evolved into a trench with oblique subduction until ~ 43 Ma when the Pacific plate changed its course again back to the NW direction as manifested by the ~ 43 Ma kink and age progressive Hawaiian Seamount Chain of the Hawaiian hotspot origin.
The locus (or "suture") of the jammed trench at 100 Ma is predicted to locate on the Chinese continental shelf in the vicinity of, and parallel to, the Southeast coastal line (red dashed curve in Fig. 1). The curved arc-shape of the coastal line is inherited from the pre-100 Ma arc-shaped trench, which is similar in both curvature and size to the India-Asia collision arc (red solid curve in Fig. 1). To locate the locus in the northern section in the East China Sea and Yellow Sea is not straightforward because of the recent (< 20 Ma) tectonic re-organization associated with the opening of the Sea of Japan (see the light blue dashed line with question marks in Fig. 1).
The eastern continental China in the Mesozoic can be interpreted as an active continental margin, but NOT an Andean-Type margin as treated by many. This is because the granitoids do not define "magmatic arcs" at any given time, but distribute randomly in space and time in a wide zone in excess of > 1000 km. This observation indicates the likelihood of the presence of a stagnant paleo-Pacific slab in the mantle transition-zone beneath the region as is the case in the Cenozoic, which is seismically observed at present.
The stagnant slab under heating by the ambience above and below caused the slab dehydration. This dehydration caused a sequence of processes of geodynamic and geological significance. The released water facilitated the formation of hydrous melt within and above the transition zone, which percolated through and metasomatized the upper mantle, weakened the base of the lithosphere and transformed it into asthenosphere, hence having thinned lithosphere in the Mesozoic, accompanied by melting of the being-converted "lithospheric material" to produce basaltic melt as the heat source for crustal melting and the granitoid magmatism. Such within plate magmatism was ultimately triggered by subduction and subducted slabs, and can be readily understood as a special (vs. plate boundary zone) consequence of plate tectonics.
This new understanding on the origin of the Chinese continental shelf introduces an innovative hypothesis for consideration and testing. Basement penetration drilling on ideal sites of the shelf in collaboration with industries and IODP is expected to offer the most effective testing towards a genuine understanding of the tectonic evolution of the greater western Pacific since the Mesozoic in a global tectonic context.
This work was supported by Durham University in the UK, Chinese NSF grants (41130314, 91014003), Chinese Academy of Sciences Innovation grant (Y42217101L), grants from Chinese National Oceanography Laboratory in Qingdao, and from regional and local authorities (Shandong Province and City of Qingdao).
See the article: Niu YL, Liu Y, Xue QQ, Shao FL, Chen S, Duan M, Guo PY, Gong HM, Hu Y, Hu ZX, Kong JJ, Li JY, Liu JJ, Sun P, Sun WL, Ye L, Xiao YY, Zhang Y (2015) Exotic origin of the Chinese continental shelf: New insights into the tectonic evolution of the western Pacific and eastern China since the Mesozoic. Science Bulletin http://link.
Yaoling Niu | 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...
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+44 1803 865913
By: Heldur Nestor, Paul Copper and Carl Stock
163 pages, b/w photos, colour maps
During Late Ordovician and Early Silurian times, from 450 to 428 million years ago, stromatoporoid sponges were some of the most common and abundant fossils in shallow water tropical settings of the Anticosti Basin (Gulf of St Lawrence). They formed dense, massive coralline skeletons of calcium carbonate, some up to a meter or more across, especially in reef environments, but also in deeper waters of the Anticosti shelf, down to the margins of the photic zone, where light faded.
The Anticosti Basin reveals one of the most fossiliferous carbonate sequences worldwide for rocks of this age, straddling a global mass extinction boundary, and thus revealing not only those taxa that became extinct, but also how the seas were repopulated in an equatorial setting after the mass extinction. The mass extinction has been correlated to globally cooling climates of the time, and southern hemisphere glaciation in North Africa.
This monograph describes, for the first time, the skeletal architecture of these abundant and exquisitely preserved sponges from Anticosti, and includes more than 300 skeletons selected from ca. 2000 field localities, assigned to 14 genera, of which 4 are new, and 35 stromatoporoid species, of which 18 are new. These are illustrated by 56 figures and plates and fill a major gap in our global knowledge of the reef building stromatoporoids, especially during the Early Silurian and latest Ordovician.
All materials are precisely geographically and stratigraphically defined from the Vaureal through Chicotte formations over a nearly a kilometer thick section, and their ecologic distribution plotted across shallow to deeper water facies. Oil and gas exploratory drilling in the Gulf of St Lawrence will ultimately reveal what happened in the deeper water offshore facies, not exposed on Anticosti Island itself.
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Study finds spiders use electricity to fly
Darwin’s conjecture about static confirmed
published Thursday ended the long-running debate about whether spiders can use the silk they weave as a parachute to fly through the wind or if flight is powered by static electricity reacting with silk.
A study by University of Bristol sensory biophysicist Erica Morley confirmed what Charles Darwin notably observed watching hundred of spiders fly 60 miles across the ocean and land on his ship, the HMS Beagle.
Darwin surmised electrostatic force was involved. Morley and researchers backed this up by demonstrating for the first time in a lab how spiders use electrostatic forces to balloon.
When spiders launch off from the ground and float through the sky, sometimes for thousands of miles, it’s due to a “ballooning process” in which the spider raises its abdomen to the sky, spins 7- to 13-foot-long silk parachutes and flies away. A previous study confirmed that spiders fly by checking the wind and throwing out their silk parachutes at the right time. The study, however, could not account for why the multiple silk threads spiders use to balloon don’t tangle in the wind.
Morley’s research accounts for the lack of tangles and explains why spiders can fly thousands of miles even when it’s not windy. The strands don’t tangle because each is repelling off another in an electrostatic force. The study also concluded that the weather conditions are not the primary driver of when a spider balloons but rather if an electric field is present in the atmosphere.
“It is reasonable to surmise that if e-fields are ecologically relevant, spiders should be able to detect and respond to an e-field by changing their behavior to engage in ballooning,” the study said.
Researchers placed Linyphiid spiders into a box that limited air movement but mirrored electric fields naturally present in atmospheric conditions. When the field was turned on, spiders showed a “significant increase in ballooning.” The change in behavior demonstrated the spiders can detect when electricity is present.
Once the spiders were ballooning in the air, researchers turned the field off. The spiders would rapidly fall out of the air toward the ground, demonstrating spiders need the electricity order to balloon if air flow is limited.
Although wind does play an important role in the ballooning process and the subsequent miles spiders travel, this study shows that ballooning behavior is sparked by electric fields.
A new study says spiders’ ability to fly through the air is a function of how they use electricity. | <urn:uuid:9ebcabb5-1b20-4d84-9129-a947802d3fa8> | 3.359375 | 538 | News Article | Science & Tech. | 41.083333 | 95,575,025 |