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Scientists from the Friedrich-Schiller-University Jena (Germany) were successful in improving a fabrication process for Atomic Force Microscopy (AFM) probe tips.
Atomic Force Microscopy is able to scan surfaces so that even tiniest nano structures become visible. Knowledge about these structures is for instance important for the development of new materials and carrier systems for active substances. The size of the probe is highly important for the image quality as it limits the dimensions that can be visualized – the smaller the probe, the smaller the structures that are revealed.
Carbon nanotubes are supposed to be a superior material for the improvement of such scanning probes. However, it is difficult to attach them on scanning probes, which limits their practical use.
Chemists of the Friedrich-Schiller-University Jena found a way to overcome these problems. The research team of Prof. Dr. Ulrich S. Schubert succeeded in developing a new type of process that allows the growth of carbon nanotubes on the actual scanning probe. These innovative discoveries are published in the leading scientific journal for Nano Science, “Nano Letters” and are available online under (http://pubs.acs.org/doi/pdf/10.1021/nl101934).
For this process the Jena scientists are using microwave radiation for a gentle but very fast growth of the nanotubes. The growth starts at small cobalt particles, that are being taken up with the help of the AFM tip. “The metal particles strongly heat up in the microwave and reach a temperature that is sufficient to convert alcohol vapor into carbon. The heating process works similar like a forgotten spoon in the kitchen microwave which also absorbs the microwave radiation very effectively,” explains Tamara Druzhinina from Schubert`s research team. “Carbon nanotubes can be grown very quickly due to the special conditions inside of the microwave which can generate a pressure up to 20 bar” adds her colleague Dr. Stephanie Hoeppener.
The Jena chemist Prof. Schubert points out the practical benefits of the process: “The method we developed can potentially result in a very cost-efficient production technology of for instance high resolution probes for Scanning Force Microscopy. These are already available on the market but they are very expensive at 350 Euro each. With the process we can reach a price level, that would justify the use of such tips also just for routine measurements.”
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:6a197779-e959-43cc-bbaf-3f03992039b9> | 3.546875 | 1,138 | Content Listing | Science & Tech. | 39.581648 | 95,590,607 |
The study, from University of New Hampshire professor Serita Frey and co-authors from the University of California-Davis and the Marine Biological Laboratory, sheds new light on how soil microorganisms respond to temperature and could improve predictions of how climate warming will affect the carbon dioxide flux from soils.
The activities of soil microorganisms release 10 times the carbon dioxide that human activities do on a yearly basis. Historically, this release of carbon dioxide has been kept in check by plants' uptake of the gas from the atmosphere. However, human activities are potentially upsetting this balance.Frey and co-authors Johan Six and Juhwan Lee of UC-Davis and Jerry Melillo of the Marine Biological Laboratory were curious how increased temperatures due to climate change might alter the amount of carbon released from soils. "While they're low on the charisma scale, soil microorganisms are so critically important to the carbon balance of the atmosphere," Frey says. "If we warm the soil due to climate warming, are we going to fundamentally alter the flux of carbon into the atmosphere in a way that is going to feed back to enhance climate change?"
"As you increase temperature, you decrease the efficiency – soil microorganisms release more carbon dioxide to the atmosphere – but only for the more complex food sources," Frey explains. "You could infer that as the soil warms, more carbon dioxide will be released into the atmosphere, exacerbating the climate problem."That effect diminishes, however, in the second scenario, in which soils were warmed to 5 degrees Celsius above the ambient temperature for 18 years. "When the soil was heated to simulate climate warming, we saw a change in the community to be more efficient in the longer term," Frey says, lessening the amount of carbon dioxide the soils release into the atmosphere and, in turn, their impact on the climate. "The positive feedback response may not be as strong as we originally predicted."
The researchers hypothesize that long-term warming may change the community of soil microorganisms so that it becomes more efficient. Organism adaptation, change in the species that comprise the soils, and/or changes in the availability of various nutrients could result in this increased efficiency.
This study was based on work done at the Harvard Forest Long-Term Ecological Research site in Petersham, Mass., where Frey and Melillo have been warming two sites – one 9 meters square, the other 36 meters square -- with underground cables for two versus 18 years. "It's like having a heating blanket under the forest floor," Frey says, "allowing us to examine how this particular environmental change—long-term soil warming—is altering how the soil functions."
The article, "The Temperature Response of Soil Microbial Efficiency and its Feedback to Climate," is published in the advanced online publication of Nature Climate Change on Jan. 20, 2013. To access the abstract or full text (subscribers only) of the article after the embargo lifts, use the digital object identifier (DOI) number 10.1038/NCLIMATE1796 at this link: http://dx.doi.org/.
This work was supported by an NSF Faculty Early Career Development Award, the NSF Long-term Ecological Research (LTER) Program, a DOE National Institute for Climatic Change Research (NICCR) grant, and a Harvard Forest Bullard Fellowship to Frey.Photographs available to download:
Credit: Perry Smith, UNH Photographic Serviceshttp://www.unh.edu/news/releases/2013/jan/forestplot.jpg
Credit: Alix Contosa, postdoctoral researcher at UNHhttp://www.unh.edu/news/releases/2013/jan/freyinfield.jpg
Credit: Brian Godbois, research assistant at UNHhttp://www.unh.edu/news/releases/2013/jan/freysoil.jpg
The University of New Hampshire, founded in 1866, is a world-class public research university with the feel of a New England liberal arts college. A land, sea, and space-grant university, UNH is the state's flagship public institution, enrolling 12,200 undergraduate and 2,300 graduate students.
Beth Potier | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
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Why are important see turtles to our life? We can present many answers for this questions. Sea turtles are an important and fundamental link in marine ecosystems. They help maintain the health of sea grass beds and coral reefs that benefit commercially valuable species such as shrimp, lobster and tuna. Dwindling of turtles, affect the health and survival of the world’s ocean. However, we have to take necessary steps to improve this crucial circumstance and save the beneficial turtles as we are stewards of the nature and creatures.
Causes of Crisis | <urn:uuid:1607ad9d-932f-4368-9457-9f272b580ead> | 2.921875 | 107 | About (Org.) | Science & Tech. | 47.819493 | 95,590,644 |
The purple pitcher plant: home to the changing North American mosquito.
© D. Glidden
Mosquitoes’ evolve rapidly in response to global warming.
Mosquitoes are holing up later as winters get warmer, US ecologists have shown. This is the first genetic adaptation to global warming to be identified. Less flexible animals could face extinction, they warn.
The North American mosquito Wyeomyia smithii uses shortening day length to judge when to bed down for the winter. Modern mozzies wait nine days more than their ancestors did in 1972, William Bradshaw and Christina Holzapfel of the University of Oregon in Eugene have discovered1. Warmer autumns are the most likely cause.
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
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Rubidium is a silver-white, metallic, active element, which resembles potassium. It ignites in air and reacts with water. It is used in photoelectric cells and electronic vacuum tubes. Rubidium is found world wide in carnallite and pullocite. Symbol Rb; melting point 38.89ºC; atomic weight 85.46; atomic number 37; valence 1, 2, 3, 4. | <urn:uuid:53c912fd-d523-4042-a8ff-42f8eb1b2d81> | 3.078125 | 86 | Knowledge Article | Science & Tech. | 62.750714 | 95,590,685 |
The solar wind engulves our solar system like a cocoon: This continuous plasma flow that emanates from the Sun is protecting us from the interstellar medium, especially from the cosmic rays. The boundary of this cocoon is a long-standing topic of space research.
Now the NASA spacecraft IBEX (Interstellar Boundary Explorer) has, for the first time, detected energetic hydrogen atoms from this region resulting in a surprise: The measurements indicate entirely unexpected structures in the flux of these particles.
"All scientists have, so far, modelled this outer boundary without an interstellar magnetic field - nobody has expected its strong influence", states PD Dr. Horst Fichtner (Institut für Theoretische Physik IV der RUB). He and his international colleagues present these observations and new improved models of this cocoon in two publications in Science.
Electron exchange at the boundary of the heliosphere
The IBEX spacecraft, launched in October last year into Earth orbit, has pointed its novel detectors away from Earth into outer space and records how many energetic hydrogen atoms arrive per time interval from a given direction. Step by step it has scanned the whole sky and provided the first all-sky map of this particle flux, which allows to infer the physical conditions at the outer boundary of our solar system: At the outer edge of the heliosphere - the plasma cocoon - the solar wind plasma interacts with the interstellar medium. The solar wind consists partly of fast protons, the interstellar medium to a large fraction of slow hydrogen atoms. There is a specific probability that close encounters result in a transfer of an electron from the slow hydrogen atom to the fast proton. "Thereby, the two particles exchange their roles", explains Dr. Fichtner, "the fast proton transforms into a fast hydrogen atom and vice versa. We can measure the result of this transformation."
Modelling without the interstellar magnetic field
The all-sky map measured by IBEX surprised the scientists, however. It showed only partly the theoretically predicted structures, which were obtained under the assumption that the flux of energetic atoms is mainly determined by the solar wind and not by the interstellar magnetic field. Instead an intensity ribbon - resulting from relatively many exchange processes - showed up that stretches "diagonally" across the all-sky map. "Meanwhile, we know why", explains Horst Fichtner. "This ribbon fits to the interstellar magnetic field. The latter has been neglected in the models so far."
In the second Science publication the researchers now develop scenarios to explain the newly observed data. "We assume that the magnetic field plays a dynamic role leading to a compression of the heliosphere at its boundary", says Fichtner. The magnetic field forces the plasma flow from the Sun to decelerate resulting in an accumulation of particles. Thereby, the probability for "collisions" and, hence, that for electron transfer increase.
Waiting for further measurements
"These first results of the IBEX mission are a milestone on the way to a deeper understanding of the heliosphere and its galactic environment, which also determines the conditions for life on Earth.", comments Horst Fichtner, who heads a heliospheric research group. The detailed insights into the physics of the heliosphere can be transferred to other stars and help to understand the significance of astrospheres for extrasolar planets. The IBEX observations also show first indications for a time variability of the flux of neutral atoms and, thus, of the structure of the heliosphere: "Based on our models this is what we expect as a consequence of solar activity cycle", says Dr. Fichtner. The confirmation of such variation can, however, only result from measurements over a longer period. "The further measurements by IBEX, which will be operating for at least two years but, probably, far more, are eagerly expected!"
IBEX is the latest in NASA's series of low-cost, rapidly developed Small Explorers space missions. Southwest Research Institute in San Antonio, TX, leads and developed the mission with a team of national and international partners. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the Explorers Program for NASA's Science Mission Directorate in Washington.
N. A. Schwadron, M. Bzowski, G. B. Crew, M. Gruntman, H. Fahr, H. Fichtner, P. C. Frisch, H. O. Funsten, S. Fuselier, J. Heerikhuisen, V. Izmodenov, H. Kucharek, M. Lee, G. Livadiotis, D. J. McComas, E. Moebius, T. Moore, J. Mukherjee, N. V. Pogorelov, C. Prested, D. Reisenfeld, E. Roelof, and G. P. Zank: Comparison of Interstellar Boundary Explorer Observations with 3-D Global Heliospheric Models. In: Science Express, Published online October 15 2009; 10.1126/science.1180986 (Science Express Reports)
D. J. McComas, F. Allegrini, P. Bochsler, M. Bzowski, E. R. Christian, G. B. Crew, R. DeMajistre, H. Fahr, H. Fichtner, P. C. Frisch, H. O. Funsten, S. A. Fuselier, G. Gloeckler, M. Gruntman, J. Heerikhuisen, V. Izmodenov, P. Janzen, P. Knappenberger, S. Krimigis, H. Kucharek, M. Lee, G. Livadiotis, S. Livi, R. J. MacDowall, D. Mitchell, E. Mobius, T. Moore, N. V. Pogorelov, D. Reisenfeld, E. Roelof, L. Saul, N. A. Schwadron, P. W. Valek, R. Vanderspek, P. Wurz, and G. P. Zank: Global Observations of the Interstellar Interaction from the Interstellar Boundary Explorer (IBEX), In: Science Express, Published online October 15 2009; DOI: 10.1126/science.1180906 (Science Express Reports)
PD Dr. Horst Fichtner, Institut für Theoretische Physik der Ruhr-Universität, 44780 Bochum, Tel. 0234/32-23786, E-Mail: firstname.lastname@example.org
Dr. Josef König | idw
Further reports about: > Earth's magnetic field > Galaxy Evolution Explorer > IBEX > NASA > Science Express > Science TV > Solar Decathlon > Venus Express > cosmic ray > extrasolar planet > hydrogen atom > interstellar > interstellar medium > magnetic field > observations > solar system > solar wind
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:55666242-589f-4c53-85da-a5982dfebbc2> | 3.359375 | 2,103 | Content Listing | Science & Tech. | 48.705289 | 95,590,686 |
Invisibility is Real! It is Simple Too!
Did you ever wonder what it would be like to be invisible? Are you in awe by those who use a cloaking device to infiltrate certain locations during movies? I am sure quite a few people have wondered how it would feel to walk into a room unnoticed, listen to conversations incognito and just plain feel like a superhero. We have wondered about this! The interesting thing about this idea is that it is possible. The more interesting thing about this idea is that this has been possible for a very long time.
The Invisible man
The invisible man is someone that many people want to be. In fact, these powers would change things dramatically. We could find out secrets and avoid confrontations. Unfortunately, we could also become criminals. For now, however, let’s take a look at how this is done.
Some of the accomplishments of making things invisible to the naked eye have been done with high tech equipment and exotic materials as well. This is not necessary.
Basically, becoming invisible is not as hard or expensive as it may seem. To understand how to do this, you must first understand the process. The process seems and sounds very simple.
At the University of Rochester, John Howell, professor of Physics, and graduate student Joseph Choi developed a standard procedure for cloaking. Making objects invisible is accomplished with lenses-four of them, to be exact. These lenses keep the object hidden as the viewer steps back to a certain distance, thus the object disappears. This method is not accomplished through magic, at least not with parlor tricks. This feat is made possible by simply re-directing light around something, making it appear as if it was not even there.
This process can also produce multi-directional cloaking. This is accomplished by using On/Off patterns to gain minimum information about directions and positions without affecting the momentum of the photons passing through the lenses. It may sound confusing, but trust me, it works in a very simple and inexpensive format. You could almost try this at home!
Since Science fiction has made the cloaking topic very popular, we could at least try to make it a fact. I think, this has already been done. With a bit of tweaking here and there, cloaking will become as common as catching a flight from state to state. This makes us wonder what will happen next, doesn’t it?
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- Teen Angst: 7 Signs Your Teen Is Suffering and How to Help Them - July 11, 2018
- 6 Signs of Unhealthy Safety Seeking That Reveal Avoidance and Anxiety - July 8, 2018
- 10 Ways to Use the Holistic Approach to Deal with Anxiety and Depression - July 6, 2018
- Feeling Worthless? 6 Overlooked Causes and How to Feel Good about Yourself - July 3, 2018 | <urn:uuid:23c4f35b-0705-4ce9-98ca-2f1c50c7da46> | 2.640625 | 612 | Personal Blog | Science & Tech. | 55.261491 | 95,590,687 |
Defined in header
Returns a pseudo-random integer value between 0 and RAND_MAX (0 and
srand() seeds the pseudo-random number generator used by
rand() is used before any calls to
rand() behaves as if it was seeded with
rand() is seeded with
srand(), it must produce the same sequence of values.
rand() is not guaranteed to be thread-safe.
Pseudo-random integer value between 0 and RAND_MAX, inclusive.
There are no guarantees as to the quality of the random sequence produced.
In the past, some implementations of
rand() have had serious shortcomings in the randomness, distribution and period of the sequence produced (in one well-known example, the low-order bit simply alternated between
0 between calls).
rand() is not recommended for serious random-number generation needs, like cryptography.
POSIX requires that the period of the pseudo-random number generator used by
rand is at least 232
POSIX offered a thread-safe version of rand called rand_r, which is obsolete in favor of the drand48 family of functions.
Random value on [0 2147483647]: 1373858591
- C11 standard (ISO/IEC 9899:2011):
- 184.108.40.206 The rand function (p: 346) | <urn:uuid:54206cb9-fa9a-4b94-8d27-86000e6ea958> | 3.125 | 282 | Documentation | Software Dev. | 53.971053 | 95,590,699 |
If you are looking for an answer to the question What is Artificial Intelligence? and you only have a minute, then here's the definition the Association for the Advancement of Artificial Intelligence offers on its home page: "the scientific understanding of the mechanisms underlying thought and intelligent behavior and their embodiment in machines."
However, if you are fortunate enough to have more than a minute, then please get ready to embark upon an exciting journey exploring AI (but beware, it could last a lifetime) …
Industries are investing aggressively in artificial intelligence (AI) projects to drive efficiency for better business performance. International Data Corporation predicts that AI spending will achieve a compound annual growth rate (CAGR) of 46.2% from 2016 growing to become a $52.2 billion industry by 2021. AI can significantly improve business operations by leveraging the tremendous amount of data generated by sensors monitoring the production and movement of products using IoT. The end result is AIIOT, which is the merging of AI and IoT to manage inventory, logistics, and suppliers with a higher level of awareness and precision. The supply chain is one area that can benefit the most from streamlining since it has a direct influence on profitability and customer satisfaction.
This post is part of Science of Sci-Fi, Mashable's ongoing series dissecting the science (or lack of science) in our favorite sci-fi movies, TV shows, and books. Thanks to fictional depictions, we tend to think of spaceships as well-fortified machines. But in reality, even in the emptiness of outer space, their hulls would be under threat of bombardment from near-invisible enemies. In the Star Wars and Star Trek franchises, ships are usually fitted with deflector shields -- zones of energy that absorbed beams of enemy fire. The USS Enterprise, for example, could repel an enemy's colorful phaser blasts by putting its shields up.
Intel Corporation flies 2,018 Intel Shooting Star drones over its Folsom, California, facility, in July 2018. The drone light show set a Guinness World Records title for the most unmanned aerial vehicles airborne simultaneously. SAN FRANCISCO -- Three years ago, in a hallway at Intel, a small team of people working on drones discussed whether it would be possible to fly one hundred drones over the Robert Noyce Building, Intel's headquarters in Santa Clara, and have them form the shape of the company's logo. They didn't plan on pursuing it seriously but it became a pet project for Natalie Cheung, who wondered at the time how they could fly multiple drones with one pilot. Now, Cheung is the general manager of Drone Light Shows at Intel and has helped put on hundreds of choreographed drone shows -- and the drones can make a lot more shapes than just the Intel logo.
Elon Musk and many of the world's most respected artificial intelligence researchers have committed not to build autonomous killer robots. The public pledge not to make any "lethal autonomous weapons" comes amid increasing concern about how machine learning and AI will be used on the battlefields of the future. The signatories to the new pledge – which includes the founders of DeepMind, a founder of Skype, and leading academics from across the industry – promise that they will not allow the technology they create to be used to help create killing machines. The I.F.O. is fuelled by eight electric engines, which is able to push the flying object to an estimated top speed of about 120mph. The giant human-like robot bears a striking resemblance to the military robots starring in the movie'Avatar' and is claimed as a world first by its creators from a South Korean robotic company Waseda University's saxophonist robot WAS-5, developed by professor Atsuo Takanishi and Kaptain Rock playing one string light saber guitar perform jam session A man looks at an exhibit entitled'Mimus' a giant industrial robot which has been reprogrammed to interact with humans during a photocall at the new Design Museum in South Kensington, London Electrification Guru Dr. Wolfgang Ziebart talks about the electric Jaguar I-PACE concept SUV before it was unveiled before the Los Angeles Auto Show in Los Angeles, California, U.S The Jaguar I-PACE Concept car is the start of a new era for Jaguar.
Top Pentagon official Michael Griffin sat down a few weeks ago with Air Force scientists at Wright Patterson Air Force Base in Ohio to discuss the future of quantum computing in the U.S. military. Griffin, the undersecretary of defense for research and engineering, has listed quantum computers and related applications among the Pentagon's must-do R&D investments. Quantum computing is one area where the Pentagon worries that it is playing catchup while China continues to leap ahead. The technology is being developed for many civilian applications, and the military sees it as potentially game-changing for information and space warfare. The U.S. Air Force particularly is focused on what is known as quantum information science.
A major milestone for a secretive hypersonic spaceplane the military could one day use to launch satellites at short notice have been completed. The reusable Phantom Express spaceplane will take off vertically and land horizontally, and is being built by Boeing as part of the U.S. Defense Advanced Research Projects Agency (DARPA) Experimental Spaceplane program, and its engines have now passed a key test. It is hoped it will play a crucial role in future space warfare, allowing military bosses to launch satellites and replace damaged ones within hours. The reusable Phantom Express spaceplane will take off vertically and land horizontally, and is being built by Boeing as part of the U.S. Defense Advanced Research Projects Agency (DARPA) Experimental Spaceplane program. The Pentagon's research arm now test-fired the new rocket engine 10 times in as many days, a critical step toward a space plane that can put satellites in orbit on a daily basis, project officials said.
While tracking criminal activity on dark web marketplaces, a threat intelligence team Insikt Group of the security research firm Recorded Future discovered a hacker selling classified military documents for a meager amount of $150-200 on the Deep Web and Dark Web forum. According to the research team, the hacker got a hold on the documents after they intruded by exploiting an FTP vulnerability in Netgear routers that's been known for two years. Once the hacker got an access to the router, the intruder was easily able to invade into a captain's personal computer and steal a cache of sensitive documents. "While such course books are not classified materials on their own," Recorded Future said, "in unfriendly hands, they could provide an adversary the ability to assess technical capabilities and weaknesses in one of the most technologically advanced aircrafts." The documents include contained sensitive materials, like "the M1 Abrams maintenance manual, a tank platoon training course, a crew survival course, and documentation on improvised explosive device (IED) mitigation tactics."
Top Pentagon official Michael Griffin sat down a few weeks ago with Air Force scientists at Wright Patterson Air Force Base in Ohio to discuss the future of quantum computing in the U.S. military. Griffin, the undersecretary of defense for research and engineering, has listed quantum computers and related applications among the Pentagon's must-do R&D investments. Quantum computing is one area where the Pentagon worries that it is playing catchup while China continues to leap ahead. The technology is being developed for many civilian applications and the military sees it as potentially game-changing for information and space warfare. The U.S. Air Force particularly is focused on on what is known as quantum information science.
Researchers at the cybersecurity firm Recorded Future recently released a report about one of its more interesting findings. While scouring the hacker forums on the dark web, the firm's analysts discovered someone selling MQ-9 Reaper drone documents -- maintenance books, training guides, and a list of airmen assigned to the military drone. The hacker was looking for $150-200 for the documentation. SEE ALSO: Hackers steal $23.5 million from cryptocurrency exchange Bancor That may seem a strangely low asking price, and according to Andrei Barysevich, a Recorded Future analyst, it is. The hacker was advertising the documents as classified information, but while they are only made available to military and its contractors, they aren't classified. | <urn:uuid:29c7dece-26ce-4987-92cd-8cd618c605fd> | 2.546875 | 1,693 | Content Listing | Science & Tech. | 34.722775 | 95,590,747 |
1. In the size – grain hypothesis (a) long legs allow walking organisms to step over gaps and pores in substrate but prohibit them from entering those gaps; (b) the world is more rugose for small organisms; and (c) the relative cost of long legs increases as organisms grow smaller. The hypothesis predicts a positive allometry of leg length ( = mass b where b > 0.33 of isometry), a pattern that robustly holds for ants. 2. Toward testing for leg length allometries in other taxa, arthropods were extracted from the Panama leaf litter and measured. Three common taxa (spiders, diplopods, Coleoptera) yielded b s that exceeded 0.33 while three others (Acarina, Pseudoscorpiones, and Collembola) did not. The exponent b tended to increase ( P = 0.06, n = 7) with an arthropod taxon’s average body mass. 3. Since leg length in cursorial organisms tends toward isometry in very small and very large taxa (i.e. mammals) this suggests that the size – grain hypothesis may best apply at a transition zone of intermediate body mass: the macroarthropods. 4. Body length was a robust predictor of mass in all groups despite variation in shape.
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Drying of a Polymer Sphere with Shrinkage
During the process of absorption of a liquid by a polymer, swelling very often takes place, especially when the amount of liquid absorbed is large. Shrinkage of this polymer is thus observed during the process of desorption. The process is controlled by transient diffusion of the liquid within the polymer and evaporation from the surface. To obtain analytical solutions the mathematical treatment neglects the change in the dimensions of the polymer. Very often, numerical models with finite differences are built by considering a framework of reference with constant dimensions.
KeywordsConstant Diffusivity Vinyl Acetate Small Sphere External Membrane Ethylene Vinyl Acetate
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- 3.Bakhouya A, Bouzon J, Vergnaud JM. Modelling the process of diffusion-evaporation of a liquid from a polymer sphere, by considering the shrinkage of the sphere. Plast Rubber Proc Applic 1991; 15: 263–271Google Scholar
- 4.Mouffok B, Bouzon J, Vergnaud JM. Modelling the process of evaporation of hydrocarbons out of polymers by considering diffusion-evaporation and shrinkage. J Comput Polym Sci 1991; 1: 56–62Google Scholar
- 7.David H, Bouzon J, Vergnaud JM. Modelling of desorption of liquid from an EVA polymer device composed of a core and shell. Plast Rubber Proc Applic 1989; 11: 9–16Google Scholar
- 10.Crank J. The mathematics of diffusion, 2nd edn. Clarendon Press, Oxford, 1976, p. 96Google Scholar | <urn:uuid:25ee7a90-4e93-4bc9-99ff-05aed4117b85> | 2.71875 | 359 | Truncated | Science & Tech. | 44.353804 | 95,590,770 |
Green urban oases like Hampstead Heath are absorbing about the same amount of carbon as rainforests, scientists have discovered.
Researchers at University College London have conducted a study on 85,000 trees in north London to show the importance of planting and protecting urban forests to offset fossil fuel emissions.
The team used millions of laser pulses to estimate how much carbon the trees absorb throughout their lives – which is important for helping to offset fossil fuel emissions.
The new study, published in Carbon Balance and Management, analysed trees in UCL’s local borough of Camden.
The team found that Hampstead Heath stores up to 178 tonnes of carbon per hectare, which is catching up to tropical rainforests that contain on average around 190 tonnes of carbon per hectare.
The technique used is known as LiDAR (Light Detection and Ranging) data collected both by the UK Environment Agency and their own ground-based LiDAR measurements.Paris turns to violence after France's World Cup victory over Croatia
It uses millions of laser pulses to build a very detailed picture of the 3D structure of trees, which makes the calculation of carbon stored more accurate.
This, in turn, allows them to estimate the carbon sink provided by urban trees, important for helping to offset fossil fuel emissions.
It has been estimated that the ability of urban trees to store carbon is worth £4.8m per annum in Greater London – or £17.80 per tree.
It is the first time the laser method has been used in urban forests, having previously only been used in tropical rainforests.
Previous estimates of carbon stored by urban trees have relied on measurements from trees outside of cities, which may be quite different.
The team wanted to show how protecting urban forests are central to building liveable and sustainable cities in the future.
Urban trees also provide shade, flood mitigation, habitat for birds, mammals and other plants, as well as wider recreational and aesthetic benefits, the team say.
Lead author Dr Phil Wilkes said: ‘Urban trees are a vital resource for our cities that people walk past every day.
‘Urban trees provide many ecosystem services essential for making cities liveable.
‘This includes providing shade, flood mitigation, filtering air pollution, habitat for birds, mammals and other plants, as well as wider recreational and aesthetic benefits.
‘We were able to map the size and shape of every tree in Camden, from forests in large parks to individual trees in back gardens.
‘This not only allows us to measure how much carbon is stored in these trees but also assess other important services they provide such as habitat for birds and insects.’
Co-author Dr Mat Disney said: ‘An important outcome of our work was to highlight the value of urban trees, in their various and very different settings.
‘The approach has been really successful so far, so we’re extending it across London, to other cities in the UK and internationally.’ | <urn:uuid:52668d25-4eba-4460-a1db-1b61848fc00e> | 3.484375 | 614 | News Article | Science & Tech. | 40.973343 | 95,590,771 |
A pair of relatively simple existing technologies has come out top in a fresh analysis comparing the costs of energy storage options that could be attached to wind and solar electricity generation to improve their cost-competiveness with non-intermittent rivals.
Wind and solar industries have mushroomed globally in recent years with the help of government-driven incentives and as manufacturing costs have plummeted. The installed bases of both have grown at roughly 30 percent annually over the past three decades, and offer an attractive installation speed and flexibility compared to traditional power plant construction. However, both technologies still only supply a small percentage of global electricity generation, and so do not yet substantially contribute to climate change mitigation.
The key barrier is their fluctuating supply of energy over time due to changes in weather, seasons and daylight hours. For these two renewable resources to be able to compete with fossil fuels, hydroelectric and nuclear power, which can provide ‘always on’ electricity, some form of energy storage technology will have to be developed that is both low-carbon to manufacture and, crucially, low cost.
Up to now, a range of studies have looked at the feasibility of particular storage technology options for specific locations and contexts of use, but comparing costs on a common scale that can be applied anywhere has been challenging. This is because some options are expensive on the power side of things (such as pumped-hydro generation equipment like turbines)—in other words how to get the energy back out once stored—but cheap on the energy storage side of things (the reservoir, as expensive as it is, is cheaper than other storage options), or vice versa, while no single technology is cheap for both the power and the energy side of the problem.
But last month, a trio of energy systems researchers published a paper in Nature Climate Change describing how they devised a new conceptual approach, in essence a set of equations that values from different storage options can be plugged into, in order to compare the various technology choices in terms of cost on a common scale.
Using the method, they compared nine different options, including pumped-storage hydro (PHS – in which water stored in a reservoir is released through turbines to produce electricity), compressed air energy storage (CAES – in which air is compressed and stored under pressure, then later heated and expanded in a turbine that drives a generator), and a range of batteries (lead-acid, nickel-cadmium, sodium-sulphur, lithium-ion, zinc-bromine, vanadium-redox, and flow batteries). They were compared on the basis of how much revenue and cost they added to hypothetical utility-scale renewable energy providers: a well performing solar farm, a well performing wind farm, and a pair of poorly performing wind and solar sites, in order to explore varying price dynamics and varying generation performance.
They concluded that PHS and CAES, technologies that exist today, did add value to wind and solar energy in some locations and for the lower end of cost estimates. PHS significantly out-performed lead-acid batteries for example. Nevertheless, they also concluded that further cost reductions in the technologies would still be needed to reach widespread profitability.
Hydrogen as an energy storage medium was not investigated however, as there currently are limited data on costs available.
The Climate Examiner speaks to BC-based Carbon Engineering about the technology, the business and the policies that could make direct air capture, synfuels and carbon sequestration work. | <urn:uuid:e9d1431a-9128-4f39-97a5-ca57188e84a2> | 3.90625 | 704 | News Article | Science & Tech. | 11.389188 | 95,590,779 |
- By Richard Wild
- Posted 05 Dec 2017
If you are interested in functional programming as many of our craftspeople are, you will have heard talk about tail recursion. Tail recursion refers to a recursive function call that has been made from tail position. When a function call is in tail position it... | <urn:uuid:98f9ba3a-7718-40d0-a4bb-fed26a287d88> | 2.734375 | 64 | Truncated | Software Dev. | 64.498231 | 95,590,784 |
Objects and Classes
introduces the object-oriented approach to computer programming
describes how object-oriented programs are made up of collections of interacting objects
describes how objects are defined by the class to which they belong
describes how to define a new class of objects in C#…
… and how to write a C# program that uses this class
KeywordsObject Reference Hair Colour Oriented Programming Instance Variable Shoe Size
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Marine scientists long believed that a microbe called Trichodesmium, a member of a group called the cyanobacteria, reigned over the ocean's nitrogen budget.
New research results reported on-line today in a paper in Science Express show that Trichodesmium may have to share its nitrogen-fixing throne: two others of its kind, small spherical species of nitrogen-fixing cyanobacteria called UCYN-A and Crocosphaera watsonii, are also abundant in the oceans.
One of them, UCYN-A, is more widely distributed than Trichodesmium, and can live in cooler waters.
Different nitrogen-fixing cyanobacteria, scientists have discovered, have varying preferences for water temperature and other environmental factors.
Pia Moisander and Jon Zehr of the University of California at Santa Cruz and their co-authors showed that actively nitrogen-fixing UCYN-A "can be found in great abundance at higher latitudes and deeper waters than Trichodesmium," says Moisander.
"Where Trichodesmium might be thought of as a warm-water microbe, UCYN-A likes it cooler," says Zehr. "This has far-reaching implications for the geographic distribution of the ocean's 'nitrogen fixers,' and for the process of nitrogen fixation itself."
According to co-author Joseph Montoya of the Georgia Institute of Technology, "we're now beginning to develop an appreciation for the biogeography of marine nitrogen fixation, and the broad range of oceanic habitats where nitrogen fixation makes a significant contribution to the overall nitrogen budget."
Most previous estimates of global nitrogen fixation were based on distributions of or factors that control the growth of Trichodesmium.
"The results of this study," says David Garrison, program director in the National Science Foundation (NSF)'s Directorate for Geosciences, "show that these novel microbes are found in the world's oceans in a distribution analogous to that of non-nitrogen-fixing cyanobacteria, which are widespread."
The research was also supported by NSF's Directorate for Biological Sciences and an NSF Science and Technology Center called C-MORE, the Center for Microbial Oceanography: Research and Education.
Trichodesmium, as well as UCYN-A and Crocosphaera watsonii, "fix" nitrogen in the seas, taking nitrogen gas from the air we breathe and converting it to chemical forms that other microorganisms can use to power their cellular machinery.
Nitrogen-fixing microorganisms are the key to the productivity of the oceans. Growth of microbes at the base of the food chain is dependent on nutrients like nitrogen, in the same way that agriculture on land depends on such nutrients.
Microorganisms that fix nitrogen play a central role, says Zehr, in the "vertical downward flux of organic matter to the deep ocean."
Life forms that are among our planet's smallest, he says, play a very large role. Through a series of steps in the nitrogen fixation process, they sequester carbon from the atmosphere, important in controlling Earth's climate.
Other authors of the paper are Roxanne Beinart and Ian Hewson of the University of California at Santa Cruz; Angelicque White of Oregon State University; Kenneth Johnson of the Monterey Bay Aquarium Research Institute; and Craig Carlson of the University of California at Santa Barbara.
The research received additional funding from the Gordon and Betty Moore Foundation.
Cheryl Dybas | EurekAlert!
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
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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1 Water carried into subduction zones with the down-going plate and subsequently released by dehydration reactions at depth affects the composition of the mantle wedge, triggers partial melting and affects subduction zone seismicity. Partially serpentinized peridotite may be a significant reservoir for water in the subducted plate, the mantle wedge and the overriding plate. Here we develop a model that relates the degree of serpentinization and water content of partially serpentinized peridotites to their seismic P-wave velocities. In partially-serpentinized ultramafic rocks, a 1% decrease in P-wave velocity corresponds to a 2.4% increase in serpentine content, and a 0.3% (0.18 moles/m(3)) increase in H2O content (up to a maximum of 13%). Where there is evidence of serpentinization, mantle serpentine content is typically similar to15%, corresponding to 4-5 wt% H2O (6-10 moles/m(3)).
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1) an object initially at rest reaches a velocity of 30m/s in 6 seconds, how much work is done during this time interval? 2) a roller coaster car with a mass of 1000kg starts at ground level and reaches a maximum height of 128m. what is the change in potential energy for the car? I f all the potential energy is turned into ki
Squaw Valley ski area in California claims that its lifts can move 47900 people per hour. If the average lift carries people about 200 m (vertically) higher, estimate the maximum total power needed. (Assume an average mass per person of 70 kg).
Three resistors having resistances of 1.20ohms , 2.60ohms , and 5.00 ohms are connected in series to a 26.0 V battery that has negligible internal resistance. 1) Find the equivalent resistance of the combination 2) Find the current in through 1.60, 2.50, and 5.00ohms resistors. 3) Find the total current through the ba
1. An electric d.c. circuit is attached to a 12 volt battery and has a 3-ohm resistor in it. Find the current flowing through the circuit. What is the current in an ac circuit wit 120 volts and a 60 watt light bulb? 2. A 500 kg truck moving at 30 m/s strikes a parked 300kg car. They connect together and move forward. What ki
1. Why are batteries sometimes installed as parallel circuits and other times installed as series circuits? 2. What affects the way batteries are positioned? What are the benefits for the different positions? 3.How does electricity work together with magnetism? How are the two connected? 4. What are some examples of pr
Express the van der Waals equation of state as a virial expansion in powers of 1/(V_m), and obtain expressions for B and C in terms of the parameters a and b. The expansion you will need is (1 - x)^(-1) = 1 + x + (x^2) + ... Measurements on argon gave B = -21.7 (cm^3)/mol and C = 1200 (cm^6)/(mol^2) for the virial coeffici
Chapter 7: 11. Engine 1 does twice the work of engine 2. Is it correct to conclude that engine 1 produces twice as much power as engine 2 explain? 12. Engine 1 produces twice the power of engine 2. Is it correct to conclude that engine 1 does twice as much work as engine 2? Explain. 38. You raise a bucket of wat
A linearly polarized plane wave of wavelength lembda, is travelling in air and ia incident normally on a plane sheet of glass. Show that the ratio of the reflected to the incident electric field amplitude is (n(glass)-n(air))/(n(glass)+n(air)) where n(air) and n(glass) are the refractive indices of ai
Show that the complex refractive index of a conducting medium can be expressed as n = λ0(1+i)/2 πδ and n = λ0(1-i)/2πδ where δ is the skin depth. Hence find the power reflection coefficient for an EM wave incident from free space on a good non-magnetic conductor at normal incidence. Show that the energy lost per unit area
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Any help with this problem would be great! A bungee jumper, whose mass is 82 kg, jumps from a tall platform. After reaching his lowest point, he continues to oscillate up and down, reaching the low point two more times in 9.6s. Ignoring air resistance and assuming that the bungee cord is an ideal spring, determine its spr
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Question 1 In a coal fired power plant the output from the steam turbine is 500 MW in the form of shaft power. This is connected to an electric turbine with an efficiency of 96 %. The output voltage from the electric generator is 2000 V. What is the power output from the electric generator? What is the electric current
See attached file for full problem description. 5. A 120-V rms voltage at 60.0 Hz is applied across an inductor, capacitor, and a 100-ohm resistor in series. If the maximum value of the current in this circuit is 1.60 A, what is the rms value of the current in this circuit? 6. What is the power factor of and RLC series cir
A typical adult ear has a surface area of about 1.9 10-3 m2. The sound intensity during a normal conversation is about 3.6 10-6 W/m2 at the listener's ear. Assume the sound strikes the surface of the ear perpendicularly. How much power is intercepted by the ear?
See attached file for full problem description. 18. A 120-V rms voltage at 1000 Hz is applied to a resistor and an inductor in series. If the impedance of this circuit is 110 ohms, what is the maximum value of the current? 19. A 200-ohm resistor, a 40.0-mH inductor and a 2.00-uF capacitor are connected in series with a 120
A 2.40 * 10^2 kg piano is being lifted at a steady speed from ground level straight up to an apartment 10.0 m above the ground. The crane that is doing the lifting produces a steady power of 4.00 *10^2 W. How much time does it take to lift the piano?
One kilowatt-hour (kWh) is the amount of work or energy generated when one kilowatt of power is supplied for a time of one hour. A kilowatt-hour is the unit of energy used by power companies when figuring out your electric bill. Determine the number of joules of energy in one kilowatt-hour.
Question: You are at a party with your four closest friends, Alice, Bob, Charlie, and Eve. Music is playing in the background very softly you hear it at a level of 35 dB. All of your friends are talking at once and given their volume and your proximity to them you hear Alice at 45 dB, Bob at 42 dB, Eve at 48 dB and Charlie talki
The instantaneous current and voltage in an electrical circuit are given by: i = Icos(50pi*t) v = Vcos(50*pit + pi/6) Determine an expression for the instantaneous power in the circuit p = iv, "AS THE SUM OF 2 COSINES" If I is 0.003 Amps and V is 5 volts, calculate the maximum value of p, giving the answer in watts corre
1. A battery with 12-V emf has a terminal voltage of 11.4 V. When it delivers a delivers a current of 20 A to the starter of a car. What is the internal resistance r of the battery? A) how much emf is delivered but the battery above when it delivers a current of 20 A? (b) how much of this power is delivered to the starter?
1. A solid uranium cylinder weighs 91.53 N in air and 86.63 N when submerged in water. a. The volume of the cylinder is ----------mt^3 b. The density of uranium is---------kg/mt^3 2. On each heartbeat,about 70 cm^3 of blood is forced from a human heart at an average pressure of approx 105 mm Hg. a. If the heart beats 7
(See attached file for full problem description)
Please help with the following problem. There is an old truck that has a 6 or 12-volt battery in it which has very little charge left in it. The hood cannot be opened, so to charge the battery, someone uses 3 car batteries (12 volts each) which are placed in series. The reasoning is that if it is either a 6 volt or 12-volt b
1. The 50-lb load is hoisted by the pulley system and motor M. If the crate starts from rest and by constant acceleration attains a speed of 15 ft/s after rising 6 ft, determine the power that must be applied to the motor at this instant. The motor has an efficiency ε = 0.76. Neglect the mass of the pulleys and cable. 2. Ro
Consider the observable q_u = u_1q_1+u_2q_2+u_3q_3 , where the q_i are the Pauli matrices and where u = (u_1,u_2,u_3) in R^3 and the Hamiltonian is H = q3. Compute the observable (q_u)_H (t) derived from q_u in the Heisenberg picture.
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At a distance of 3.8 m from a siren, the sound intensity is 3.6 x 10^-2 W/m^2. Assuming that the siren radiates sound uniformly in all directions, how do you find the total power radiated?
A power cycle for a piston-cylinder device is described by the following four processes: 1→2 Isothermal compression from T1 = 300K, P1 = 100 kPa to P2 = 600 kPa. 2→3 Constant pressure heat addition until the temperature is T3 = 800K. 3→4 Isentropic expansion until the volume at state 4 equals the volume at state 1. 4
I have done an example to calculate the actual max efficiency of a power plant given the temperatures of both the hot and cold reservoirs. My book, however, tells me nothing about how to calculate any of the following questions. A power plant produces 1 GW of electricity, at an efficiency of 40%. (a) At what rate does th | <urn:uuid:63f660b9-6e1a-43cc-8df7-938f4d6d58cf> | 3.15625 | 2,056 | Q&A Forum | Science & Tech. | 80.002669 | 95,590,800 |
Since 1961, hundreds of men and women from more than a dozen countries have traveled in space. Until the 1980s, however, most of those people came from the United States and the former Soviet Union. The Soviets were the first to launch an unmanned satellite, Sputnik 1, in 1957. This event marked the beginning of the space race between the United States and the Soviet Union, a campaign for superiority in space exploration.
The first living being to travel in space was a dog named Laika. She was sent into space aboard the Soviets' Sputnik 2 in 1957. Laika survived the launch and the first leg of the journey. A week after launch, however, the air supply ran out and Laika suffocated. When the spacecraft reentered Earth's atmosphere in April 1958, it burned up (it had no heat shields) and Laika's body was incinerated.
Then on April 12, 1961, Soviet cosmonaut (astronaut) Yury Gagarin rode aboard the Vostok 1, becoming the first human in space. In 108 minutes, he made a single orbit around Earth before reentering its atmosphere. At about two miles (more than three kilometers) above the ground, he parachuted to safety. Only recently did scientists from outside Russia learn that this seemingly flawless mission almost ended in disaster. During its final descent, the spacecraft had spun wildly out of control.
American-crewed space program
The Mercury program was the first phase of America's effort to put a human on the Moon by the end of the 1960s. On May 5, 1961, the first
piloted Mercury flight, Freedom 7, was launched. It took astronaut Alan Shepard on a 15-minute suborbital flight (only a partial—not complete—orbit of Earth) that went 116 miles (187 kilometers) up and 303 miles (488 kilometers) across the Atlantic Ocean at speeds up to 5,146 miles (8,280 kilometers) per hour. The capsule than parachuted safely into the Atlantic Ocean with Shepard inside.
Two months later, another U.S. suborbital flight was launched, this one carrying Virgil "Gus" Grissom. Grissom's flight was similar to Shepard's, except at splashdown his capsule took in water and sank. Grissom was unharmed, but his capsule, the Liberty Bell 7, was not recovered.
On February 20, 1962, just over nine months after Gagarin's flight, astronaut John Glenn became the first American to orbit Earth. His spacecraft, Friendship 7, completed three orbits in less than five hours.
Lunar program. The Apollo program was created for the purpose of landing American astronauts on the Moon. Engineers designed a craft consisting of three parts: a command module, in which the astronauts would travel; a service module, which contained supplies and equipment; and a lunar module, which would detach to land on the Moon.
The Apollo program was not without mishap. During a ground test in 1967, a fire engulfed the cabin of the Apollo 1 spacecraft, killing Gus Grissom, Ed White, and Roger Chaffee. This tragedy prompted a two-year delay in the launch of the first Apollo spacecraft. During this time, more than 1,500 modifications were made to the command module.
In December 1968, Apollo 8 became the first manned spacecraft to orbit both Earth and the Moon. On July 16, 1969, Apollo 11 was launched with astronauts Neil Armstrong, Edwin "Buzz" Aldrin, and Michael Collins on board. Four days later Armstrong and Aldrin landed on the Moon. When Armstrong set foot on lunar soil, he stated, "That's one small step for man, one giant leap for mankind." The Apollo 11 flight to the Moon is considered by many to be the greatest technological achievement of the modern world. Over the next three years, five more Apollo missions landed twelve more Americans on the Moon.
Soviet-crewed space program
Although the United States won the race to the Moon, the Soviet Union achieved other space race "firsts" during the 1960s. The Soviets launched the first three-person spacecraft, Voskhod ("Sunrise"), in October 1964. In March 1965, Soviet cosmonaut Alexei Leonov took the first space walk, spending ten minutes outside the Voskhod capsule connected to the craft only by telephone and telemetry cables (wires used to gather data).
The Soviet Union then began work on Soyuz ("Union"). The program proved to be a disaster. In April 1967, Soyuz 1 crashed to Earth with cosmonaut Vladimir Komarov on board. The tragedy halted the Soviet space program for 18 months. By the time they reentered the space flight quest, the Soviets had turned their attention to establishing the first orbiting space station, Salyut ("Salute").
On April 19, 1971, the Soviets launched Salyut 1, which was designed for both civilian and military purposes. The station was powered by two solar panels and divided into several different modules, three of which were pressurized for human life support. The three-person crew of Soyuz 11 successfully entered Salyut 1 on June 7, 1971. The cosmonauts' three-week stay set a new record for human endurance in space. But during their reentry into Earth's atmosphere, a cabin seal released prematurely and the spacecraft lost air pressure. The three crew members had not been issued pressure suits and suffocated instantly. As a result of this disaster, the Soviets could not refuel the station. They were forced to allow it to fall out of its orbit and burn up in reentry. Despite this major setback, the Soviets were eventually able to launch other Salyut stations as the decade progressed.
The only comparable U.S. space station has been Skylab. Launched on May 14, 1973, this two-story craft was 118 feet (36 meters) long and 21 feet (6.4 meters) in diameter and weighed nearly 100 tons (110 metric tons). Although Skylab encountered problems immediately after launch, a crew was able to repair the damage. In its six years of operation, Skylab housed three different crews for a total of 171 days. Studies on board the space station greatly increased our knowledge of the Sun and its effect on Earth's environment. In 1979, Skylab fell back to Earth.
A more advanced Soviet space station, Mir (which means both "Peace" and "World"), was launched in February 1986. Able to accommodate up to six crew members at a time, Mir was designed to afford greater comfort and privacy to its inhabitants so they would be able to remain on board for longer periods. Although plagued with technical problems in 1997, Mir continued to host Russian cosmonauts and international space travelers (a total of 104 people from 12 countries) who conducted some 23,000 experiments, including research into how humans, animals, and plants function in space. During its lengthy time in orbit, Mir attained a number of accomplishments: longest time in orbit for a space station (15 years), longest time in space for a human (437.7 days), and heaviest artificial object ever to orbit Earth. With a lone cosmonaut on board at the time, it even survived the collapse of the Soviet Union in 1991. During Mir 's lifetime, the Soviet Union and then Russia spent the equivalent of $4.2 billion to build and maintain the station. By 2001, however, the 135-ton (122-metric ton) craft had become too old to maintain properly, and Russia decided to let it fall back to Earth. On March 23, 2001, after having completed 86,330 orbits around the planet, Mir reentered the atmosphere and broke apart. Pieces of the station that did not burn up in the atmosphere splashed harmlessly into stormy waters 1,800 miles (2,896 kilometers) east of New Zealand.
The valuable knowledge scientists gained from Mir will be applied to the International Space Station (ISS), a permanent Earth-orbiting laboratory that will allow humans to perform long-term research in outer space. It draws upon the scientific and technological resources of sixteen nations. Construction of the ISS began in November 1998 with the launch of the Zarya control module from Russia. When completed in 2006, the ISS will measure about 360 feet (110 meters) in length, 290 feet (88 meters) in width, and 143 feet (44 meters) in height. It will have a mass of nearly 1 million pounds (454,000 kilograms) and will have a pressurized
living and working space of 46,000 cubic feet (1,300 cubic meters), enough for up to seven astronauts and scientists.
The U.S. space shuttle is a winged space plane designed to transport humans into space and back. It is the first and only reusable space vehicle. This 184-foot-long (56-meter-long) vessel acts like a spacecraft, but looks like an airplane. In 1981, the first space shuttle to be launched was Columbia. Challenger, Discovery, and Atlantis rounded out the initial shuttle fleet, which flew 24 consecutive missions.
The shuttle program ran smoothly until the Challenger tragedy of January 28, 1986. That shuttle exploded 73 seconds after launch, due to a faulty seal in its solid rocket booster. All seven crew members died as a result. The fleet of shuttles was grounded for 32 months while more than 400 changes in the shuttle's construction were made.
The National Aeronautics and Space Administration (NASA) resumed shuttle flights in 1988, having replaced Challenger with Endeavor. Missions of the space shuttles have included the insertion into orbit of the Galileo space probe in 1989 and the Hubble Space Telescope (HST) in 1990. A variety of communications, weather, military, and scientific satellites have also been placed into orbit by crew members aboard space shuttles. The shuttles can be configured to carry many different types of equipment, spacecraft, and scientific experiments. In addition to transporting people, materials, equipment, and spacecraft to orbit, the shuttles allow astronauts to service and repair satellites and observatories in space. In fact, shuttles flew servicing missions to the HST in 1993, 1997, and 1999.
At the beginning of the twenty-first century, the mission of many shuttle flights was the continuing construction of the ISS. In December 1998, the crew aboard Endeavor initiated the first assembly sequence of the ISS; they also became the first crew to enter the space station. In October 2000, when Discovery was launched on a mission to continue construction of the ISS, the event marked the one-hundredth flight of a U.S. space shuttle.
[See also Space station, international ]
"Spacecraft, Manned." UXL Encyclopedia of Science. . Encyclopedia.com. (July 15, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/spacecraft-manned-0
"Spacecraft, Manned." UXL Encyclopedia of Science. . Retrieved July 15, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/spacecraft-manned-0
Modern Language Association
The Chicago Manual of Style
American Psychological Association
Manned spacecraft are vehicles with the capability of maintaining life outside of Earth's atmosphere. Partially in recognition of the fact that women as well as men are active participants in space travel programs, manned spacecraft are now frequently referred to as crewed spacecraft.
In its earliest stages, crewed space flight was largely an exercise in basic research. Scientists were interested in collecting fundamental information about the Moon , the other planets in our solar system , and outer space. Today, crewed space flight is also designed to study a number of practical problems, such as the behavior of living organisms and inorganic materials in zero gravity conditions.
A very large number of complex technical problems must be solved in the construction of spacecraft that can carry humans into space. Most of these problems can be classified in one of three major categories: communication, environmental and support, and re-entry.
Communication refers to the necessity of maintaining contact with members of a space mission as well as monitoring their health and biological functions and the condition of the spacecraft in which they are traveling. Direct communication between astronauts and cosmonauts can be accomplished by means of radio and television messages transmitted between a spacecraft and ground stations. To facilitate these communications, receiving stations at various locations around Earth have been established. Messages are received and transmitted to and from a space vehicle by means of large antennas located at these stations.
Many different kinds of instruments are needed within the spacecraft to monitor cabin temperature , pressure, humidity , and other conditions as well as biological functions such as heart rate, body temperature, blood pressure, and other vital functions. Constant monitoring of spacecraft hardware is also necessary. Data obtained from these monitoring functions is converted to radio signals that are transmitted to Earth stations, allowing ground-based observers to maintain a constant check on the status of both the spacecraft and its human passengers.
The fundamental requirement of a crewed spacecraft is, of course, to provide an atmosphere in which humans can survive and carry out the jobs required of them. This means, foremost, providing the spacecraft with an Earth-like atmosphere in which humans can breathe. Traditionally, the Soviet Union has used a mixture of nitrogen and oxygen gases somewhat like that found in the earth's atmosphere. American spacecraft, however, have employed pure oxygen atmospheres at pressures of about 5 lb per square inch, roughly one-third that of normal air pressure on the earth's surface.
The level of carbon dioxide within a spacecraft must also be maintained at a healthy level. The most direct way of dealing with this problem is to provide the craft with a base, usually lithium hydroxide, which will absorb carbon dioxide exhaled by astronauts and cosmonauts. Humidity, temperature, odors, toxic gases, and sound levels are other factors that must be controlled at a level congenial to human existence.
Food and water provisions present additional problems. The space needed for the storage of conventional foodstuffs is prohibitive for spacecraft. Thus, one of the early challenges for space scientists was the development of dehydrated foods or foods prepared in other ways so that they would occupy as little space as possible. Space scientists have long recognized that food and water supplies present one of the most challenging problems of long-term space travel, as would be the case in a space station. Suggestions have been made, for example, for the purification and recycling of urine as drinking water and for the use of exhaled carbon dioxide in the growth of plants for foods in spacecraft that remain in orbit for long periods of time.
An important aspect of spacecraft design is the provision for power sources needed to operate communication, environmental, and other instruments and devices within the vehicle. The earliest crewed spacecrafts had simple power systems. The Mercury series of vehicles, for example, were powered by six conventional batteries. As spacecraft increased in size and complexity, however, so did their power needs. The Gemini spacecrafts required an additional conventional battery and two fuel cells, while the Apollo vehicles were provided with five batteries and three fuel cells.
One of the most serious on-going concerns of space scientists about crewed flights has been their potential effects on the human body. An important goal of nearly every space flight has been to determine how the human body reacts to a zero-gravity environment.
At this point, scientists have some answers to that question. For example, we know that one of the most serious dangers posed by extended space travel is the loss of calcium from bones. Also, the absence of gravitational forces results in a space traveler's blood collecting in the upper part of his or her body, especially in the left atrium. This knowledge has led to the development of special devices that modify the loss of gravitational effects during space travel.
One of the challenges posed by crewed space flight is the need for redundancy in systems. Redundancy means that there must be two or three of every instrument, device, or spacecraft part that is needed for human survival. This level of redundancy is not necessary with uncrewed spacecraft where failure of a system may result in the loss of a space probe , but not the loss of a human life. It is crucial, however, when humans travel aboard a spacecraft.
An example of the role of redundancy was provided during the Apollo 13 mission. That mission's plan of landing on the Moon had to be aborted when one of the fuel cells in the service module exploded, eliminating a large part of the spacecraft's power supply. A back-up fuel cell in the lunar module was brought on line, however, allowing the spacecraft to return to Earth without loss of life.
Space suits are designed to be worn by astronauts and cosmonauts during take-off and landing and during extravehicular activities (EVA). They are, in a sense, a space passenger's own private space vehicle and present, in miniature, most of the same environmental problems as does the construction of the spacecraft itself. For example, a space suit must be able to protect the space traveler from marked changes in temperature, pressure, and humidity, and from exposure to radiation, unacceptable solar glare, and micrometeorites. In addition, the space suit must allow the space traveler to move about with relative ease and to provide a means of communicating with fellow travelers in a spacecraft or with controllers on the earth's surface. The removal and storage of human wastes is also a problem that must be solved for humans wearing a space suit.
Ensuring that astronauts and cosmonauts are able to survive in space is only one of the problems facing space scientists. A spacecraft must also be able to return its human passengers safely to Earth's surface. In the earliest crewed spacecrafts, this problem was solved simply by allowing the vehicle to travel along a ballistic path back to Earth's atmosphere and then to settle on land or sea by means of one or more large parachutes. Later spacecraft were modified to allow pilots some control over their re-entry path. The space shuttles, for example, can be piloted back to Earth in the last stages of reentry in much the same way that a normal airplane is flown.
Perhaps the most serious single problem encountered during re-entry is the heat that develops as the spacecraft returns to Earth's atmosphere. Friction between vehicle and air produces temperatures that approach 3,092°F (1,700°C). Most metals and alloys would melt or fail at these temperatures. To deal with this problem, spacecraft designers have developed a class of materials known as ablators that absorb and then radiate large amounts of heat in brief periods of time. Ablators have been made out of a variety of materials, including phenolic resins, epoxy compounds, and silicone rubbers.
Some scientists are beginning to plan beyond space shuttle flights and the International Space Station . While NASA's main emphasis for some time will be unmanned probes and robots, the most likely target for a manned spacecraft will be Mars. Besides issues of long-term life support, any such mission will have to deal with long-term exposure to space radiation. Without sufficient protection, galactic cosmic rays would penetrate spacecraft and astronaut's bodies, damaging their DNA and perhaps disrupting nerve cells in their brains over the long-term. (Manned flights to the Moon were protected from cosmic rays by the earth's magnetosphere.) Shielding would be necessary, but it is always a trade-off between human protection and spacecraft weight. Moreover, estimates show it could add billions of dollars to the cost of any such flight.
See also Space and planetary geology; Space physiology
"Spacecraft, Manned." World of Earth Science. . Encyclopedia.com. (July 15, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/spacecraft-manned
"Spacecraft, Manned." World of Earth Science. . Retrieved July 15, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/spacecraft-manned | <urn:uuid:092bc08e-016c-4f78-9f14-6b81732fec6b> | 3.546875 | 4,181 | Knowledge Article | Science & Tech. | 46.937991 | 95,590,805 |
The current El Niño event has been predicted by an international team of scientists more than one year ago – earlier than ever before. This breakthrough in forecasting the most important phenomenon of natural climate variability has been enabled by novel approach of complex networks analysis of atmospheric temperature data from the Pacific. Such forecast can help farmers in Brazil, Australia or India to prepare and for instance seed the right crops. In an unusual move, the scientists had published their unprecedented early warning early on – fully aware of the reputational risks.
“While conventional methods are not able to yield a reasonably reliable El Niño prediction more than six months before the event, our method at least doubles the warning time,” says Armin Bunde of Justus-Liebig-Universität Gießen (JLU) who along with his colleague Josef Ludescher led the study.
The team detected evidence for the current El Niño already in September 2013. Their forecast appeared in the Proceedings of the US National Academy of Sciences in February 2014, and was now proven to be right.
Predictions by other, much bigger models wobbled up and down and as late as November 2014 gave a likelihood of only 58 percent that an El Niño will arrive. In contrast, the new and early forecast was stable over the whole period before the event and provided a significantly higher probability of 75 percent.
The US National Oceanic and Atmospheric Administration only recently declared that El Niño arrived – the event started last year, but it has to last for some time to be officially recognized. Japan’s weather bureau saw the conditions fulfilled in December last year.
**Impacts can hit hard on farmers and fishermen**
The current El Niño is very weak and will likely not have the devastating impacts it had in other years. Yet some experts think that the tropical cyclone that sadly hit Vanuatu might now enhance westerly winds in the Pacific region – and this in turn might strengthen the El Niño. Remarkably, the new methodology was able to correctly anticipate the phenomenon despite the weak signal; it cannot predict the strength or duration of the event.
Peruvian fishermen dubbed the irregular warming of the Eastern Pacific ‘El Niño’, Spanish for ‘the Christ child’ or literally the ‘boy child’, because it usually appears every few years at some time around Christmas when the birth of Jesus is celebrated. It is part of a more general pattern of the Pacific ocean-atmosphere system called ENSO, which includes anomalous cold episodes called La Niña. In the past, it linked for instance to empty fishing-nets in Peru, but also floods in Ecuador and droughts in Australia, thus affecting farmers.
**Advancing insight into how the phenomenon comes about**
“The causes of this phenomenon are so far poorly understood – our methodology might now be the key to open a door to gain insight into the intricate mechanisms that trigger El Niño,” says Hans Joachim Schellnhuber, co-author of the study and director of the Potsdam Institute for Climate Impact Research. “Using data from more than 200 points in the Pacific, we see how interactions between distant sites are building up over time in the ocean-atmosphere-system, bringing about the warming events. It is like an orchestra of 200 musicians playing together. If the different regions in the Pacific are rather playing their own tunes, like soloists, no El Niño develops. So this is what we use to derive our warning. There's a harmony building up – which collapses when the event finally arrives. So physically this might be a resonance phenomenon.”
„What we do, using modern network approaches, is at the crossroads of mathematics and physics,“ says co-author Shlomo Havlin of the Bar-Ilan University of Israel. “When we used this data to hindcast El Niños of the past, we found that the alarms are correct in three times out of four – which is a lot, given the complexity of the phenomenon. Moreover, the algorithm our team developed already correctly predicted in 2011 that in 2012 there would be no El Niño, while officials up to September of that year said there would be such an event.” The scientists will now seek to further develop their methodology. The aim is to integrate more data in order to be able to forecast even the strength and the duration of the El Niños to come.
Article in which the warning for the current El Niño is published: Ludescher, J., Gozolchiani, A., Bogachev, M.I., Bunde, A., Havlin, S., Schellnhuber, H.J. (2014): Very early warning of next El Niño. Proceedings of the National Academy of Sciences [DOI: 0.1073/pnas.1323058111]
Weblink to this article: www.pnas.org/content/early/2014/02/07/1323058111
Article in which the methodology is published: Ludescher, J., Gozolchiani, A., Bogachev, M.I., Bunde, A., Havlin, S., Schellnhuber, H.J. (2013): Improved El Niño frorecasting by cooperativity detection. Proceedings of the National Academy of Sciences [DOI:10.1073/pnas.1309353110]
Weblink to this article: www.pnas.org/cgi/doi/10.1073/pnas.1309353110
For further information please contact:
PIK press office
Jonas Viering, Sarah Messina
Phone: +49 331 288 2507
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Institut für Theoretische Physik der Justus-Liebig-Universität Gießen (JLU)
Telefon: +49 641 99-33375
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Jonas Viering | PIK Potsdam
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CHAPEL HILL, N.C. (AP) — Research at the University of North Carolina shows genetic evidence supporting how loggerhead sea turtles use the Earth’s magnetic fields to navigate back to the beaches where they were hatched.
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Probability Theory and Random Processes
In this chapter the basic results of probability theory and random processes are developed. These concepts are fundamental to most of the subsequent chapters since our methodology is generally based upon probabilistic arguments. It is recommended that this chapter is used as a reference rather than for learning about probability from scratch as it comprises mostly a list of results used later in the book without detailed discussion. The material covered is sufficient for the purposes of this text, but for further mathematical rigour and detail see for example Gray and Davisson , Papoulis or Doob .
KeywordsProbability Density Function Probability Density Function Random Process Cumulative Distribution Function Random Vector
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Python library for symbolic mathematics
SymPy is a Python library for symbolic mathematics. It aims to become a full-featured computer algebra system (CAS) while keeping the code as simple as possible in order to be comprehensible and easily extensible. SymPy is written entirely in Python and does not require any external libraries.
Source Files (show merged sources derived from linked package)
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|sympy-0.7.5.tar.gz||00060041545.73 MB||1394165630over 4 years ago| | <urn:uuid:6f5ddb57-9e7b-4f0a-92a5-6fd038b9431d> | 2.578125 | 189 | Content Listing | Software Dev. | 63.013382 | 95,590,849 |
University of Illinois at Urbana-Champaign
Extragalactic Astronomy and Cosmology
Aug 2017 - Aug 2018
Apr 14, 2016
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Aug 8, 2017
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Aug 7, 2017
What is our universe made of, and has its composition changed over time? Scientists have new insights about these fundamental questions, thanks to an international collaboration of more than 400 scientists called the Dark Energy Survey . Three scientists from NASAs Jet Propulsion Laboratory in Pasadena, California, are part of this group that is helping to further our understanding of the structure of the universe. The advances in astrophysics from DES are crucial to preparations for two upcoming space missions that will probe similar questions about the nature of the universe: ESA`s Euclid mission (which has significant NASA participation) and NASA`s Wide-Field Infrared Survey Telescope mission, both expected to launch in the 2020s.
Aug 5, 2017
New research conducted as a part of the ongoing Dark Energy Survey (DES) has used the way mass distorts light to produce a bigger, more highly detailed map of the Universe's dark matter structure. Today we can use the fact that mass changes space to "see" dark matter by measuring how light behind it distorts as it passes by, giving us a way to measure the amount and distribution of both kinds of matter across a portion of the Universe. The results are part of the Dark Energy Survey, and show how dark matter is distributed across the galaxy - scientists hitherto used models to show where it fell, largely based the Standard Model of particle physics, an incomplete theory that was nonetheless the best explanation of how matter across the universe interacts.
Aug 5, 2017
With a survey covering about 1/30th of the entire sky and spanning several billion light-years in extent, scientists have made the most accurate measurement of universe's dark matter. The results support the view that dark matter and dark energy make up most of the cosmos. The scientists unveiled the dark matter map in a presentation at the American Physical Society Division of Particles and Fields meeting at the US Department of Energy's (DOE) Fermi National Accelerator Laboratory.
Aug 5, 2017
Three scientists from NASA's Jet Propulsion Laboratory in Pasadena, California, are part of this group that is helping to further our understanding of the structure of the universe. Both will prepare scientists for future surveys, including ones with the Large Synoptic Survey Telescope (LSST). Map of dark matter made from gravitational lensing measurements of 26 million galaxies in the Dark Energy Survey.
Aug 5, 2017
Imagine planting a single seed and, with great precision, being able to predict the exact height of the tree that grows from it. Now imagine traveling to the future and snapping photographic proof that you were right. If you think of the seed as the early universe, and the tree as the universe the way it looks now, you have an idea of what the Dark Energy Survey (DES) collaboration has just done. In a presentation at the American Physical Society Division of Particles and Fields meeting at the U.S. Department of Energy’s (DOE) Fermi National Accelerator Laboratory, DES scientists unveiled the most accurate measurement ever made of the present large-scale structure of the Universe.
Aug 3, 2017
New measurements – made possible by the 570-megapixel Dark Energy Camera in Chile – of the amount and “clumpiness” of dark matter in the present-day cosmos were made with a precision that rivals that of inferences from the early universe by a space telescope, the European Space Agency’s Planck observatory. The new result by the Dark Energy Survey (DES) collaboration is close to “forecasts” made from Planck measurements of the distant past, which allow scientists to understand more about the ways the universe has evolved over 14 billion years. | <urn:uuid:34c414e3-4653-4edb-8e63-05d8ae176807> | 3.109375 | 1,107 | Content Listing | Science & Tech. | 30.215715 | 95,590,866 |
Physicists explain metallic conductivity of thin carbon nanotube films
An international team of researchers from MIPT; Lebedev Physical Institute, RAS; Prokhorov General Physics Institute, RAS; Skoltech; and Aalto University (Finland) has examined the optical and dielectric properties of thin macroscopic films based on single-walled carbon nanotubes and obtained an explanation for the metallic nature of their conductivity using infrared and terahertz spectroscopy. The research findings were published in the journals Carbon and Nanotechnology.
A single-walled carbon nanotube, or SWNT, can be pictured as a graphene sheet rolled into a cylinder. Light, strong, and resistant to high temperatures, SWNTs can be used as additives to composite materials to make them more durable, or as building blocks to fabricate aerosol filters and electrochemical sensors. Transparent and flexible carbon nanotube films — that is, 2-D structures formed by intersecting nanotubes — have a wide variety of potential applications, for example as supercapacitors or transparent electrodes in flexible electronics — electronic devices that can be bent, folded, and twisted without breaking. The study of the charge transfer mechanisms in such films is therefore important for both basic research and practical applications.
The physicists measured optical and electrical properties of the films by terahertz-infrared spectroscopy at a variety of temperatures, from -268 degrees Celsius to room temperature, and in a wide range of incident radiation wavelengths — from ultraviolet to terahertz (wavelengths of about 1 millimeter). The study of the interaction between the films and radiation yielded fundamental data on the electrodynamics of the films.
The SWNT films were synthesized by using aerosol chemical vapor deposition (CVD). Briefly, a vapor of the catalyst precursor ferrocene is supplied into the CVD reactor, where it decomposes in the atmosphere of carbon monoxide, forming nanometer-sized catalyst particles. On their surface, carbon monoxide (CO) disproportionation — simultaneous oxidation and reduction — occurs and finally SWNTs grow. The flow at the outlet of the rector is filtered, and SWNTs are collected onto the nitrocellulose filter. By varying the duration of the collection time, one could obtain the films of different thicknesses. Importantly, the SWNT films can be easily transferred to different substrates by dry deposition or used in their free-standing form, that is, without a substrate. This method enables the production of high-quality nanotubes with no amorphous carbon impurities.
"Since all carbon atoms in SWNTs are located on their surface, it is relatively easy to alter the electrical properties of this unique material. We can improve the conductivity of the films either by incorporating dopants into the nanotubes or by coating them with electron-acceptor or -donor molecules," comments Professor Albert Nasibulin of Skoltech. In their studies, the scientists coated the samples with gold chloride, whose solution acted as a doping agent, and obtained films from nanotubes filled with iodine and copper chloride by placing them in the atmosphere of the appropriate vapors. Such treatment increases charge carrier density in the filled tubes and reduces contact resistance between them, enabling flexible transparent electrodes and materials with selective charge transfer for use in optoelectronics and spintronics.
To be used in electronics, films need to be efficient charge carriers, so the physicists examined the broadband spectrum of their dielectric permittivity. But flexible electronics will also require the films to be transparent, so their optical conductivity was measured as well. Both analyses were conducted in a wide temperature range, from several degrees above absolute zero to room temperature. Of particular interest are the data obtained in the terahertz and far infrared regions of the spectrum. While prior research findings pointed to a peak in the terahertz conductivity spectrum (at frequencies between about 0.4 and 30 THz, depending on the study), this paper reports no clear indications of the phenomenon. The authors attribute such results to the high quality of their films.
Since the analysis of the optical and dielectric properties of the films at frequencies below 1,000 cm?¹ revealed spectral features that were typical for conducting materials, like metals, the team decided to employ the corresponding conductivity model that was developed by Paul Drude. According to that model, the charge in the conductors is transferred by free carriers: Like the ideal gas molecules, they move between the ions in the lattice and scatter upon collision with its vibrations, defects, or impurities. In this study, the charge carriers are also scattered by the energy barriers at the intersections of individual nanotubes. However, as the analysis suggests, these barriers are insignificant and allow the electrons to move almost freely across the film. Using the Drude model, the authors were able to quantitatively analyze the temperature dependencies of the carriers' effective parameters — namely, concentration, mobility, mean free path and time between collisions — which are responsible for the electrodynamic properties of the films.
"Our research has clearly demonstrated that terahertz spectroscopy provides an efficient tool for studying the conductivity mechanisms in macro-scale carbon nanotube films and determining the effective parameters of charge carriers in a noncontact manner. Our findings show that such films may be successfully used as components or assemblies in various micro- and nanoelectronic devices," says Elena Zhukova, deputy head of the Laboratory of Terahertz Spectroscopy at MIPT.
The study reported in this story was supported by the Ministry of Education and Science of the Russian Federation (Project 5-100, Federal Target Program Grant No. RFMEFI59417X0014) and the Russian Foundation for Basic Research (Grant No. 15-12-30041). | <urn:uuid:b6e21dbb-cef7-4bfa-8a1d-05b6bca7f8b2> | 3.46875 | 1,210 | News Article | Science & Tech. | 15.2617 | 95,590,881 |
Plants use a diverse mix of defenses against herbivores, including multiple secondary metabolites, which often affect herbivores synergistically. Chemical defenses also can affect natural enemies of herbivores via limiting herbivore populations or by affecting herbivore resistance to parasitoids. In this study, we performed feeding experiments to examine the synergistic effects of imides and amides (hereafter "amides") from Piper cenocladum and P. imperiale on specialist (Eois nympha, Geometridae) and generalist (Spodoptera frugiperda, Noctuidae) lepidopteran larvae. Each Piper species has three unique amides, and in each experiment, larvae were fed diets containing different concentrations of single amides or combinations of the three. The amides from P. imperiale had negative synergistic effects on generalist survival and specialist pupal mass, but had no effect on specialist survival. Piper cenocladum amides also acted synergistically to increase mortality caused by parasitoids, and the direct negative effects of mixtures on parasitoid resistance and pupal mass were stronger than indirect effects via changes in growth rate and approximate digestibility. Our results are consistent with plant defense theory that predicts different effects of plant chemistry on generalist versus adapted specialist herbivores. The toxicity of Piper amide mixtures to generalist herbivores are standard bottom-up effects, while specialists experienced the top-down mediated effect of mixtures causing reduced parasitoid resistance and associated decreases in pupal mass.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:c97b91ce-5de0-45ec-a0a5-dc289ac77ad7> | 3.171875 | 339 | Academic Writing | Science & Tech. | -8.521621 | 95,590,884 |
+44 1803 865913
Series: Handbook of the Mammals of the World (HMW) Volume: 8
By: Don E Wilson(Editor), Russell A Mittermeier(Editor), Toni Llobet François(Illustrator)
710 pages, 28 plates with colour illustrations; 600+ colour photos, 684 colour distribution maps
The penultimate volume of the Handbook of Mammals of the World covers all of the remaining orders (Cingulata, Pilosa, Afrosoricida, Macroscelidea, Scandentia, Dermaptera, and Eulipotyphla), other than bats (Chiroptera). From armadillos, sloths, and anteaters to shrews and moles, Volume 8 includes a wide variety of interesting small or medium-sized mammals from around the world. Most of them have different kinds of invertebrate and insectivorous diets, except sloths and colugos, which are arboreal herbivores and folivores.
Includes a Special chapter: Conservation Priorities and Actions for the Orders Cingulata, Pilosa, Afrosoricida, Macroscelidea, Eulipotyphla, Dermoptera, and Scandentia by Rosalind Kennerley, Thomas Lacher, Jr., Victor Mason, Shelby McCay, Nicolette Roach, P. J. Stephenson, Mariella Superina & Richard Young.
Family Dasypodidae (Long-nosed Armadillos) / Colleen McDonough & James Loughry
Family Chlamyphoridae (Chlamyphorid Armadillos) / Mariella Superina & Agustín Abba
Family Myrmecophagidae (Anteaters) / Alessandra Bertassoni
Family Cyclopedidae (Silky Anteaters) / Flávia Miranda
Family Megalonychidae (Two-toed Sloths) / Nadia Moraes-Barros
Family Bradypodidae (Three-toed Sloths) / Jonathan Pauli
Family Tenrecidae (Tenrecs) / Paulina Jenkins
Family Potamogalidae (Otter-shrews) / Ara Monadjem
Family Chrysochloridae (Golden Moles) / William Andrew Taylor, Samantha Mynhardt & Sarita Maree
Family Macroscelididae (Sengis) / Steven Heritage
Family Ptilocercidae (Pen-tailed Treeshrew) / Melissa Hawkins
Family Tupaiidae (Treeshrews) / Melissa Hawkins
Family Cynocephalidae (Colugos) / Jan Janecka & Mary Janecka
Family Erinaceidae (Hedgehogs, Moonrats and Gymnures) / Troy Best
Family Soricidae (Shrews) / Connor Burgin, Rudolf Haslauer, Kai He, Ardo Himckey, Stefan Hintsche, Rainer Hutterer, Paulina Jenkins, Masaharu Motokawa, Manuel Ruedi, Boris Sheftel & Neal Woodman
Family Talpidae (Moles, Desmans, Star-nosed Moles and Shrew Moles) / Boris Kryštufek & Masaharu Motokawa
Family Solenodontidae (Solenodons) / Samuel Turvey
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Hypersonic weapons are designed to give enemies little time to react. That’s the problem.
A new class of high-tech weapons is under development among the world’s major powers, and some observers worry the exact qualities that make them desirable could make wars more likely—particularly nuclear wars. The rapid development of so-called hypersonic weapons give decision makers little time to analyze an incoming attack, possibly making accidental warfare more likely.
A new study by the Rand Corp warns that hypersonic missiles, under development by the United States, Russia, and China and designed to circumvent existing ballistic missile and air defense systems through their unique flight profile, could prompt governments worldwide to set their strategic (read: nuclear) forces on a “hair-trigger state of readiness”.
Hypersonic weapons are typically missile-like weapons carried by a high altitude-capable aircraft and released or boosted by a ballistic missile to high altitude. Once released, hypersonics use scramjets or other exotic propulsion systems to attain speeds of Mach 5 or faster. Hypersonic weapons travel below the engagement envelope of most ballistic missile defense systems but fly too fast for traditional air defense systems to intercept.
The extremely high speeds hypersonic weapons travel at reduce an adversary’s ability to react to them. Suppose two nuclear-armed countries—let’s call them India and Pakistan—have hypersonic weapons and nuclear weapons. Both weapons are located in each country’s capital. A hypersonic missile launched from Pakistan’s capital, Islamabad, will reach the Indian capital of New Delhi in just over six minutes.
Under this scenario, India has just six minutes to decide whether the attack is real, what to do about it, and to do something before the missiles hit. That’s virtually no time at all. India might well choose to launch its own weapons as soon as it detects an incoming attack to prevent them from being destroyed on the ground. But what if the attack is the result of an early warning system malfunction, or was launched by accident? By the time India figures that out, the retaliatory strike —and perhaps a nuke—is already underway. The United States, China, and Russia could all have similar problems with one another.
The Rand Corp notes that although the hypersonic genie is already out of the bottle, it’s not too late for three main powers involved in hypersonic research to agree on nonproliferation rules to prevent the spread of these weapons to smaller states. The United States, China, and Russia could all agree on controls to combat the spread of hypersonic weapons and technology.
From: PM USA | <urn:uuid:ed44a88c-21dc-40a0-a749-1fb6f524c2cc> | 3.4375 | 552 | News Article | Science & Tech. | 32.790062 | 95,590,897 |
Renewable thermal energy
Renewable thermal energy is the technology of gathering thermal energy from a renewable energy source for immediate use or for storage in a thermal battery for later use. An example of Renewable Thermal is a Geothermal Heat Pump (GHP) system, where excess thermal energy due to solar heating from the sun is removed from the structure via the heating and cooling system and stored in the ground, and that same energy is then extracted from the ground to later heat the same building in another season. This example system is "renewable" because the source of excess heat energy is a reliably recurring process that occurs each summer season; in this case it is even a natural renewable energy source.
History of Renewable Thermal Systems
The outer crust of the Earth is a Thermal Battery that maintains a median temperature which is the same as the average air temperature at that location. This "average ground temperature" is a combination in balance of solar gain from the sun, thermal gain from the core of the earth, and heat loss due to conduction, evaporation, and radiation. The graphic at the right shows a map of the "average ground temperature" at locations within the United States.
Solar-based Renewable Thermal
A ground heat exchanger (GHEX) is an area of the earth that is used as an annual cycle thermal battery. These thermal batteries are un-encapsulated areas of the earth into which pipes have been placed in order to transfer thermal energy. Energy is added to the GHEX by running a higher temperature fluid through the pipes and thus raising the temperature of the local earth. Energy can also be taken from the GHEX by running a lower temperature fluid through those same pipes.
GHEX thermal batteries are implemented in two forms. The picture above depicts what is known as a "horizontal" GHEX where trenching is used to place an amount of pipe in a closed loop in the ground. GHEX's are also formed by drilling boreholes into the ground, either vertically or horizontally, and then the pipes are inserted in the form of a closed-loop with a "u-bend" fitting on the far end of the loop. These drilled GHEX thermal batteries are also sometimes called "borehole thermal energy storage systems".
Heat energy can be added to or removed from a GHEX Thermal Battery at any point in time. However, they are most often used as an "Annual-Cycle Thermal Battery" where energy is extracted from a building during the summer season to cool a building and added to the GHEX, and then that same energy is later extracted from the GHEX in the winter season to heat the building. This annual cycle of energy addition and subtraction is highly predictable based on energy modeling of the building served. A Thermal Battery used in this mode is a Renewable Energy source as the energy extracted in the winter will be restored to the GHEX the next summer in a continually repeating cycle. This Annual-Cycle Thermal Battery is a solar powered thermal storage because it is the heat from the sun in the summer that is removed from a building and stored in the ground for use in the next winter season for heating.
Process-based Renewable Thermal
There are many processes that have been created by mankind that produce thermal energy on a very reliable and repeatable basis. One giant example of such a reliable producer of thermal energy is a utility electric generator. The very process of generating electricity in a generator produces more heat than it does electricity, and this heat energy can be captured and used. When such Byproduct Thermal Energy is use immediately, this is commonly called Cogeneration. However, if heat that would have been wasted because it is not immediately needed is instead captured and stored for use at a later time, this can be an example of Renewable Thermal. The key aspect of Renewable Thermal is that it involves storing and later using energy which is reliably then available for capturing and storing again.
Renewable Thermal In The News
The state of New York took a big step in September 2015 when it created a new office titled Director of Renewable Thermal. The NY Director of Renewable Thermal will oversee a team to help companies develop and implement renewable, low-carbon cooling and heating systems. NY State considers this initiative a critical component of NYSERDA’s strategy to enable net-zero energy buildings, which produce the same amount of energy as they consume. It also will further advance New York’s progress toward creating self-sustaining energy markets for clean, renewable technologies.
Renewable Thermal has been a core resource in many states Renewable Portfolio Standards. The report says: "State Renewable Portfolio Standard (RPS) programs have historically focused on electricity generation. However, some states have started incorporating renewable thermal power for heat generation into their RPS as a way to support the development and market growth of solar thermal, biomass thermal, geothermal, and other renewable thermal technologies." Further: "Renewable thermal energy has many of the same benefits as other renewable technologies, including improved air quality, economic development and job creation, and the promotion of regional energy security."
Importance of Renewable Thermal
In a recent article, Bill Nowak, the Executive Director of the NY-GEO industry trade group, stated: "According to the recently adopted New York State energy plan, on-site combustion (largely for heating buildings) is responsible for 35 percent of fossil fuel greenhouse gas emissions in New York State. In-state electricity generation is responsible for only 18 percent. We strongly support cleaning up electricity generation in New York, but stress that renewable thermal is the next wave in resisting climate change."
- Thermal energy storage
- Seasonal thermal energy storage system
- Ground-coupled heat exchanger
- Geothermal heat pump
- , US Average Ground Temperature Map
- , NYSERDA Announces Donovan Gordon to Lead Effort to Expand Renewable Cooling and Heating Markets in New York, September 16, 2015
- , Renewable Thermal in State Renewable Portfolio Standards, April 2015
- , New Bills May Be Game Changer for New York Geothermal, September 15, 2015 | <urn:uuid:5a77ac69-568e-412c-8616-d0bad1d9849e> | 3.703125 | 1,261 | Knowledge Article | Science & Tech. | 22.602641 | 95,590,900 |
Global Ocean Circulation Appears to Be Collapsing Due to a Warming Planet
ENVIRONMENT, 7 Aug 2017
3 Aug 2017 – Scientists have long known about the anomalous “warming hole” in the North Atlantic Ocean, an area immune to warming of Earth’s oceans. This cool zone in the North Atlantic Ocean appears to be associated with a slowdown in the Atlantic Meridional Overturning Circulation (AMOC), one of the key drivers in global ocean circulation.
A recent study published in Nature outlines research by a team of Yale University and University of Southampton scientists. The team found evidence that Arctic ice loss is potentially negatively impacting the planet’s largest ocean circulation system. While scientists do have some analogs as to how this may impact the world, we will be largely in uncharted territory.
AMOC is one of the largest current systems in the Atlantic Ocean and the world. Generally speaking, it transports warm and salty water northward from the tropics to South and East of Greenland. This warm water cools to ambient water temperature then sinks as it is saltier and thus denser than the relatively more fresh surrounding water. The dense mass of water sinks to the base of the North Atlantic Ocean and is pushed south along the abyss of the Atlantic Ocean.
This process whereby water is transported into the Northern Atlantic Ocean acts to distribute ocean water globally. What’s more important, and the basis for concern of many scientists is this mechanism is one of the most efficient ways Earth transports heat from the tropics to the northern latitudes. The warm water transported from the tropics to the North Atlantic releases heat to the atmosphere, playing a key role in warming of western Europe. You likely have heard of one of the more popular components of the AMOC, the Gulf Stream which brings warm tropical water to the western coasts of Europe.
Evidence is growing that the comparatively cold zone within the Northern Atlantic could be due to a slowdown of this global ocean water circulation. Hence, a slowdown in the planet’s ability to transfer heat from the tropics to the northern latitudes. The cold zone could be due to melting of ice in the Arctic and Greenland. This would cause a cold fresh water cap over the North Atlantic, inhibiting sinking of salty tropical waters. This would in effect slow down the global circulation and hinder the transport of warm tropical waters north.
Melting of the Arctic sea ice has rapidly increased in the recent decades. Satellite image records indicate that September Arctic sea ice is 30% less today than it was in 1979. This trend of increased sea ice melting during summer months does not appear to be slowing. Hence, indications are that we will see a continued weakening of the global ocean circulation system.
This scenario of a collapse in AMOC and global ocean circulation is the premise for the movie “The Day After Tomorrow.” As a disclaimer, the plot line in which much of New England and Western Europe gets plunged into an ice age is significantly over exaggerated and unrealistic on human time scales.
While geologists have studied events in the past similar to what appears to be happening today, scientists are largely unsure of what lies ahead.
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A drinking glass creates sound when you rub your finger around its rim or strike it with an object. This sound is created when the vibrations of the glass affect the air inside the glass. Each glass vibrates at a characteristic pitch called the resonant frequency. This frequency is different based on the properties of the glass and whether or not there is liquid inside it.
The Vibrations of Glass
When a glass makes a noise, the edges of the glass move very quickly. Two opposite sides of the glass expand and contract at the same time. The sides 90 degrees away from those sides expand and contract opposite those other two sides. These rapid vibrations in the glass cause the air inside the glass to compress and expand in waves. These waves of air pressure are what we know as sound.
The pitch, or frequency, of the ringing sound changes depending on the physical characteristics of the glass. Frequency is measured in cycles per second, or hertz. The frequency at which an object vibrates is called its resonant frequency. Thicker glass will not resonate as easily as thin glass. Also, if there is liquid in a glass, this will lower the resonant frequency of the glass. This is the opposite of what happens when you blow over the top of a glass bottle. These are two different ways of making sound waves.
Rubbing Vs. Tapping
Whether you rub your finger around the rim of a glass or tap it with something will have slightly different effects on the sound produced. The frequency will be the same regardless of method, but the duration of the sound will be different. If you rub your finger around the rim of a glass, the glass alternately slips and sticks to your finger. This produces vibrations at the resonant frequency, and the glass will produce sound for the duration of the rubbing plus a little decay time afterward. If you tap the glass, it will sound and then immediately the sound will begin to decay.
A glass will not resonate very loudly or for very long on its own because its vibrations are suppressed, or damped. Not all of the glass is vibrating when you rub its edge or strike it. The glass molecules that are not vibrating will help to damp the vibrations of the rim. If the vibrations were not damped, the continuous production of increasingly strong vibrations at the resonant frequency could break the glass.
When Do Glasses Break From Sound?
The image of a powerful opera singer breaking a glass with her voice is based in the science of resonance. If a glass is exposed to sound waves at its frequency of resonance, it will vibrate in sync with those waves. The power of the sound waves coming from an external speaker can be turned up to overpower the natural damping of the glass. When this happens, the glass will not be able to sustain the stress of vibrations and it will break. | <urn:uuid:e9e032a1-f884-4bd1-9fd8-fc9efbcca690> | 3.9375 | 577 | Knowledge Article | Science & Tech. | 59.681512 | 95,590,922 |
When someone starts learning web development they usually start with HTML and CSS, and many people get stuck there without ever experiencing the wonderful work of server side scripting like PHP or ASP. I'll be talking about PHP here, but the basic rules for ASP and others are the same though.
The most important thing to understand is the difference between HTML and PHP. In HTML you write your code, upload it, and the user's will subsequently download that page along with all the code. The user's browser interprets this code and shows the user the page as you intended it (hopefully). In other words HTML is sort of what you see is what you get, in the sense that all the code goes to the user and is interpreted by the browser.
With PHP it works a bit differently because you don't actually download the code the author wrote. What happens is that if you want to download a php page the code in that file is first processed by the server, and you download the output of the code, as opposed to the whole code as is. This in turn will be HTML just as before, this is why you never see PHP code in the source of a webpage. So what happens in processing? Turn the page to find out!
With PHP the goal is to use the processing powers of the server to build (usually) dynamic webpages. A very basic example is showing the correct greeting for the time of day on a webpage. In human terms you write a script with the directions to show "Good Morning" if it is before 10am but after 5am, "Good Afternoon" if it is after 10am but before 6pm and "Good Night" after 6pm, before 5am. Instead of receiving all the code for this and processing it in your browser, this all gets processed before you download it, and you only get the result of the process, the text "Good Night" for example if it is 9pm.
This is much quicker, since if you think of bigger sites, instead of having to download 300kb (or much more) of code, it is quickly processed on the server and you might get as little as 10kb or less. Obviously your PC could process the code quickly, but downloading and handling can take a while. In addition, the code may also have database queries which can not execute if processed on your PC, they have to be processed on the server which has the database.
If you would like a more real-life example, take a look at gHacks, which has almost 5,000 posts now. In HTML world we would have to have 5,000 posts which all have the whole site code, from header to footer with the article in between. PHP makes it possible to "compress" those 5,000 files into only 1!
When you view any gHacks post on a single post page you are actually viewing a file called single.php. This file also has some additional info in the url which will tell the script which post to show, so the file you are viewing would be single.php?p=234. This tells the script that the post with the ID of 234 needs to be shown. The script queries the database for the relevant post and pulls its details (like title and post body) from the database. So in the end all you are shown is one post. WordPress has some other stuff built in to make nicer URL's and so on, but under the hood this is what is happening.
Likewise for the front page we don't always go and modify the code when posting something. Martin would be coding all day, removing the last post on the page and pasting the code of the new one. Instead, in the php file you are viewing the code gets the latest 10 posts and puts their data on the page.
There is a lot more to learn in PHP, but those are the basic mechanics, the ability to create pages based on certain criteria, as opposed to static content on each page.
Advertising revenue is falling fast across the Internet, and independently-run sites like Ghacks are hit hardest by it. The advertising model in its current form is coming to an end, and we have to find other ways to continue operating this site.
We are committed to keeping our content free and independent, which means no paywalls, no sponsored posts, no annoying ad formats or subscription fees.
If you like our content, and would like to help, please consider making a contribution:
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers. | <urn:uuid:ef6ad425-328f-4833-a349-d3cdcb99310c> | 3.109375 | 962 | Personal Blog | Software Dev. | 63.828707 | 95,590,924 |
Thursday, July 21, 2011
The Concentric Equant Model of Aryabhata
Aryabhata developed a Concentric Equant Model, in the sixth century. The Sun moves on a circle of radius R, called a deferent, whose center is the Observer on Earth. The distance between the Earth and the Sun, the Ravi Manda Karna, is constant. The motion of the Sun is uniform from a mathematical point, called the " Equant", which is located at a distance R x e from the observer in the direction of the Apogee ( e = eccentricity ).
All Indian computations are based on this Concentric Equal Model. The normal equation for computing the Manda Anomaly is R e Sin M and resembles the Kepler Equation, M = E - e Sin E.
This diagram is by courtesy of Jean-Pierre Lacroix and Robert Baywater, www.ancientcartography.net | <urn:uuid:d55ca1e4-bcea-4a0b-aee9-46b8fde98cb7> | 3.953125 | 194 | Personal Blog | Science & Tech. | 49.333542 | 95,590,941 |
Family Megalopodidae - Megalopodid Leaf Beetles
Phylogeny and classification of Cucujoidea and the recognition of a new superfamily Coccinelloidea (Coleoptera: Cucujiformia)By Robertson J.A., Ślipiński A., Moulton M., Shockley F.W., Giorgi A., Lord N.P., McKenna D.D., Tomaszewska W., Forrester J. ...
Syst. Entomol. doi: 10.1111/syen.12138, 2015
Review of the American Corylophidae, Cryptophagidae, Tritomidae and Dermestidae, with Other StudiesBy T. L. Casey
New York Entomological Society, 1900
Journal of the New York Entomological Society, 8
(2): 51-172, 1900
Abundance of herbivores on six milkweed species in Illinois.By Price, P.W. & M.F. Willson.
American Midland Naturalist 101(1): 76–86., 1979
Price, P.W. & M.F. Willson. 1979. Abundance of herbivores on six milkweed species in Illinois. American Midland Naturalist 101(1): 76–86.
To aid the understanding of the role of insect herbivores as selective agents in the evolution of their host plants a survey of herbivore abundance and impact was undertaken in central Illinois on the six milkweed species: Asclepias incarnata, A. sullivantii, A. syriaca, A. verticillata, A. amplexicaulis
, and A. tuberosa
. These species occur in this order on a moisture gradient from wet to dry soil conditions. This survey revealed that 12 species occurred at an abundance of at least one individual per 100 host stems in 1 plot-year on one host species: Oncopeltus fasciatus*, Lygaeus kalmii*, Aphis nerii*, Labidomera clivicollis*, Tetraopes tetrophthalmus*, T. femoratus, T. quinquemaculatus, Rhyssomatus lineaticollis*, Danaus plexippus, Cycnia tenera*, Euchaetias egle
and a leafminer. All but L. kalmii
are specific to milkweeds in Illinois. Seven of these species, marked with asterisks, were abundant enough to act as major selective forces on the life history patterns of the milkweed species, populations and clones concerned.
Life history evolution in seven milkweeds of the genus Asclepias.By Wilbur, H.M.
The Journal of Ecology, 64(1): 223–240., 1976
Wilbur, H.M. 1976. Life history evolution in seven milkweeds of the genus Asclepias
. The Journal of Ecology, 64(1): 223–240.
Life history differences among seven species of Asclepias
(A. exaltata, A. incarnata, A. purpurascens, A. syriaca, A. tuberosa, A. verticillata
and A. viridiflora
) in south-east Michigan are correlated with differences in microhabitat, in exposure to herbivores, and in competition. Components of each species' reproductive strategy include: number of stems per plants, number of umbels per stem, number of flowers and pods per umbel, number of seeds per pod, seed weight and annual increase in reproductive potential. Components of each species' selective regime include: the herbivore load (measured by the frequency of plants damaged by predators or animal parasites), competition (measured by the proportion of non-flowering plants and by the density of competitors), and environmental uncertainty (measured by annual mortality rates). | <urn:uuid:07d48c32-bd8c-4e6b-9da9-e472842bb0e5> | 2.71875 | 830 | Knowledge Article | Science & Tech. | 41.950867 | 95,590,942 |
Coronal holes are dark, low density regions of the sun’s outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.
The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun’s north pole on July 18, 2013, at 9:06 a.m. EDT. Image Credit: ESA&NASA/SOHO
Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun’s activity cycle. The activity cycle is currently ramping up toward what is known as solar maximum, currently predicted for late 2013.
During this portion of the cycle, the number of coronal holes decreases. During solar max, the magnetic fields on the sun reverse and new coronal holes appear near the poles with the opposite magnetic alignment.
The coronal holes then increase in size and number, extending further from the poles as the sun moves toward solar minimum again. At such times, coronal holes have appeared that are even larger than this one.
The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. While it’s unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.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....
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:109feccd-1bc5-4500-a587-010ff6b8825a> | 4.1875 | 921 | Content Listing | Science & Tech. | 40.594269 | 95,590,971 |
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The Changing Flora and Fauna of Britain was the last major report on the state of the British countryside. Twenty-five years on, this new report looks at what has happened to biodiversity in the intervening period. The 34 chapters provide specialist perspectives on changes relating to all the major groups of organisms, including algae, bacteria and fungi, vascular plants, protozoa, freshwater invertebrates, coleoptera, molluscs, lepidoptera, spiders, birds, fish, mammals and reptiles. Each contribution considers losses and declines, additions, increases and introductions. Data capture, database mapping schemes and also the availability of skilled human resources for monitoring change in each group are reviewed. Factors affecting changes in the varying kinds of organisms are also considered, including agriculture, climate, pollution and woodland management. The effectiveness of actions taken towards species protection and species recovery programmes are reviewed. A key reference.
Fifty Years of Statutory Nature Conservation in Great Britain. Flowering Plants. Ferns and Allied Plants. Mosses, Liverworts and Hornworts. Larger Fungi. Microscopic Fungi. Lichens. Terrestrial and Freshwater Eukaryotic Algae. Cyanobacteria (Blue Green Algae). Diatoms. Viruses. Protozoa. Freshwater Invertebrates. Nematodes. Mites and Ticks. Flies. True Bugs, Leaf- and Planthoppers, and their Allies. Butterflies and Moths. Grasshoppers, Crickets and Allied Insects. Dragonflies and Land
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ICESat-2 (Ice, Cloud and land Elevation Satellite-2)
ICESat-2 is a NASA follow-up mission to ICESat with the goal to continue measuring and monitoring the impacts of the changing environment. The ICESat-2 observatory contains a single instrument, an improved laser altimeter called ATLAS (Advanced Topographic Laser Altimeter System). ATLAS is designed to measure ice-sheet topography, sea ice freeboard as well as cloud and atmospheric properties and global vegetation. The requirements call for a 5-year operational mission with a goal of 7 years. 1) 2) 3) 4) 5) 6) 7)
Rational and discussion of mission goals: The mass balance of Earth's great ice sheets and their contributions to sea level are key issues in climate variability and change. The relationships between sea level and climate have been identified as critical subjects of study ib the IPCC (Intergovernmental Panel on Climate Change) assessments, the CCSP (Climate Change Science Program) strategy, and the U.S. IEOS (International Earth Observing System). Because much of the behavior of ice sheets is manifested in their shape, accurate observations of ice elevation changes are essential for understanding ice sheets' current and likely contributions to sea-level rise.
ICESat-2, with high altimetric fidelity, will provide high-quality topographic measurements that allow estimates of ice sheet volume change. High-accuracy altimetry will also prove valuable for making long-sought repeat estimates of sea ice freeboard and hence sea ice thickness change, which is used to estimate the flux of low-salinity ice out of the Arctic basin into the marginal seas. Altimetry is best (and perhaps only) technique for change studies, because sea ice areas and extends have been well observed from space since the 19070s and significant trends have been shown, but there is no such record for sea ice thickness.
As climate change proceeds, continuous measurements of both land-ice and sea-ice volume will be needed to observe trends, update assessments, and test climate models. The altimetric measurement made with the lidar instrument, along with a higher precision gravity measurement (such as GRACE-FO), would optimally characterize changes in ice sheet volume and mass and directly enhance understanding of the ice sheet contribution to sea-level rise. Coupled with the interferometric synthetic aperture radar in the DESDynI mission, the instrumentation would provide a comprehensive data set for predicting changes in Earth's ice sheets and sea ice.
In addition to studies of ice, the proposed instrument could be used to study changes in the large pool of carbon stored in terrestrial biomass. In particular, the proposed lidar could be used to measure canopy depth and thus estimate land carbon storage to aid in understanding the responses of biomass to changing climate and land management. 8) 9) 10)
Figure 1: Schematic view of mission goals (image credit: NASA)
Figure 2: Changes in Greenland ice from 1986 to 2006 (image credit: NASA)
• Quantify the polar ice sheet mass balance to determine contributions to current and recent sea level change and impacts on ocean circulation
• Determine the seasonal cycle of ice sheet changes
• Determine topographic character of ice sheet changes to assess mechanisms driving that change and constrain ice sheet models
• Estimate sea ice thickness to examine ice/ocean/atmosphere exchanges of energy, mass and moisture.
• Measuring vegetation canopy height as a basis for estimating large-scale biomass and biomass change
• Enhancing the utility of other Earth observation systems through supporting measurements.
The instrument will use micro-pulse multi-beam photon-counting approach. Science and ancillary data will be collected, stored on-board and subsequently downlinked to ground stations via an X-band communications link. This link will also include stored housekeeping telemetry. The observatory will also receive and store/execute commands and transmit real-time housekeeping telemetry via an S-band link to the NASA Ground Network.
The ICESat-2 mission is assigned to NASA/GSFC. The spacecraft is being procured under the GSFC RSDO (Rapid Spacecraft Development Office). In August 2011, NASA selected Orbital ATK, former OSC (Orbital Science Corporation of Dullas, VA, to built the ICESat-2 spacecraft. The contractor is responsible for the design and fabrication of the ICESat-2 spacecraft bus, integration of the government-furnished instrument, satellite-level testing, on-orbit satellite check-out, and continuing on-orbit engineering support. The ICESat-2 spacecraft is being designed, assembled, and tested at Orbital's satellite manufacturing and test facility in Gilbert, Arizona.
Table 1: Overview of key spacecraft parameters
Figure 3: Artist's view of the ICESat-2 spacecraft (image credit: Orbital)
Project development status:
• On 23 June 2018, ICESat-2 engineers at Vandenberg Air Force Base in California successfully finished the final ground-based test of the lasers, which are part of the satellite's sole instrument called the ATLAS (Advanced Topographic Laser Altimeter System). ICESat-2 is scheduled to launch from Vandenberg on Sept. 12, 2018. 16)
- ATLAS was built at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and trucked to a Northrop Grumman facility in Arizona where it was integrated with the spacecraft bus that provides power, navigation and communications. The completed satellite arrived at Vandenberg on June 12.
- In the Astrotech Space Operations cleanroom at Vandenberg, the ICESat-2 team tested both the spacecraft and instrument. NASA ICESat-2 launch integration manager John Satrom reports that the data from these tests have been reviewed and everything is normal.
- Meanwhile at Vandenberg's Space Launch Complex 2 along the Pacific coast, crews from United Launch Alliance are assembling the Delta II rocket that will launch ICESat-2 into space. The first and second stage, the interstage connecting them, and four solid rocket motors are in place. The ICESat-2 mission will mark the final launch for the Delta II, which will then be retired.
- After the successful completion of another round of "aliveness" tests turning on the satellite and instrument at the end of July, the ICESat-2 payload is scheduled to head to the launch pad in late August, according to Satrom.
Figure 4: ICESat-2 is uncrated inside the airlock of the Astrotech processing facility at Vandenberg Air Force Base in California, prior to a successful series of tests of the satellite and its instrument (image credit: USAF 30th Space Wing/Vanessa Valentine)
• February 28, 2018: The ATLAS (Advanced Topographic Laser Altimeter System) instrument, which was designed, built and tested at NASA's Goddard Space Flight Center in Greenbelt, Maryland, arrived in Gilbert, Arizona, at Orbital ATK's facility on Feb. 23, where it will be joined with the spacecraft structure. To deliver the instrument safely to the spacecraft for assembly and testing, the ATLAS team developed special procedures for packing, transporting and monitoring the sensitive hardware. 17)
- "There was a lot of care and feeding that went with ATLAS along the road," said Kathy Strickler, ATLAS integration and test lead.
- The trip followed a successful series of tests, designed to ensure the ATLAS instrument will function in the harsh environment of space. After the instrument passed those tests, including some in a thermal vacuum chamber, engineers inspected ATLAS to make sure it was clean and in the correct travel configuration. Then, they attached probes to the instrument that would check for vibrations as well as temperature and humidity.
- "These probes tracked what ATLAS actually sensed when going over road bumps, and what ATLAS felt as far as temperature and humidity," said Jeffrey Twum, the ATLAS transport lead.
- The team then wrapped the instrument - about the size of a Smart Car - in two layers of anti-electrostatic discharge film, to prevent any shocks en route. With its protections in place, a crane lifted ATLAS into a transporter container. The team bolted it to a platform supported by a series of wire-rope coils used to soften the ride, and the cover of the transporter was fastened shut, sealing up the cargo.
- The 2,000-mile trip took four and a half days. The ATLAS instrument is now at Orbital ATK, where engineers will attach it to the spacecraft and conduct additional testing. Then, the complete satellite will be repacked and trucked to its last stop before low-Earth orbit: Vandenberg Air Force Base in California.
• August 16, 2017: Lasers that will fly on NASA's ICESat-2, are about to be put to the test at the agency's Goddard Space Flight Center in Greenbelt, Maryland. 18)
- The sole ICESat-2 instrument, ATLAS (Advanced Topographic Laser Altimeter System) will measure the elevation of ice sheets, sea ice and glaciers by sending fast-firing laser pulses to the surface and timing how long it takes individual photons to return. With a scheduled launch date of 2018, the instrument now faces several months of testing at Goddard in which engineers will ensure it is ready to operate in the harsh environment of space. This is an intermediate stage of ICESat-2's testing regimen, and will focus on the flight lasers.
- Starting this fall, ATLAS will go into a test chamber at Goddard where engineers simulate the vacuum of space and can dial temperatures up to 50 C to - 30 C. Engineers will also turn on the two lasers — one primary and one backup — at different power levels to ensure they function correctly, said Anthony Martino, ATLAS instrument scientist at NASA Goddard. One test will include putting the instrument through its paces at different temperatures and taking pictures of the laser pulses to ensure they form a smooth, consistent circle, Martino said, with no rough edges, or dark or light spots.
- "When it's well behaved like that, it's much easier to analyze the results that we'll get," he said. Other tests involve using mirrors to reflect the laser back into the detector portions of the instrument — but only after decreasing the strength of the beam of light by 13 orders of magnitude (about 10 trillion times), to simulate the weakening of the laser beam as it is scattered by the atmosphere, bounces off Earth and returns.
• September 2016: ICESat-2 Technical Status Summary. 19)
Beyond the ATLAS instrument, all other ICESat‐2 systems are nearing completion including spacecraft, launch vehicle, algorithms, operations planning, and ground systems.
- The mission requirements remain intact through the ongoing flight Laser002 repair.
- The ATLAS management and engineering team has crafted and is implementing a conservative plan to address the recent Laser002 optical slab fracture.
Table 2: ATLAS Instrument – Technical Issue with Laser002
Figure 5: The integrated ATLAS instrument (image credit: NASA, Ref. 19)
• Feb. 18, 2016: ICESat-2 passed its Mission CDR (Critical Design Review)! Now, on to building and testing software and hardware for flight. 20)
• Jan. 17, 2016: ICESat-2 passed its Instrument Critical Design Review! The project is now moving full-speed ahead to Mission CDR and instrument I&T start.
• Dec. 10, 2015: NASA engineers tested the ATLAS instrument's pinpoint accuracy. ATLAS (Advanced Topographic Laser Altimeter System) will send laser pulses to the ground about 480 km below and then catch the handful of photons that bounce off the surface and return to its telescope mirror. There's very little margin for error when it comes to individual photons hitting on individual fiber optics - so this November, engineers conducted a series of tests on the ground, to ensure that they could hit that mark when ICESat-2 is in orbit. 21)
- This is the first time Goddard has built an automatically correcting and steering mechanism like this for flight. It was necessary for ATLAS, however, because both the receiver's field-of-view and the laser beam diameter are significantly smaller than on previous instruments, so there is less room for the laser to drift off-target. So the AMCS (Alignment Monitoring and Control System) team spent several weeks in November 2015 testing the steering mechanism and the software that controls it.
• February 2015: A NASA team tested part of the ATLAS instrument in a temperature-controlled vacuum chamber at Goddard, ensuring that its interconnected components worked together and functioned as expected. 22)
• November 3, 2014: Engineers at NASA/GSFC fitted the mirrored telescope of ICESat-2 into its place. In a Goddard cleanroom, teams are working in parallel on two sections of ATLAS: the box structure, which holds electronics that control the instrument, and the optical bench, which supports the instrument's lasers, mirrors, and the 0.8 m, 20.8 kg beryllium telescope that collects light. 23)
- Each ATLAS laser pulse contains more than 200 trillion photons, but only a dozen or so return to the telescope, where they're sent via optical fibers to the instrument's detectors. To catch those few photons, the telescope and its associated equipment, called the RTA (Receiver Telescope Assembly), need to align perfectly to the laser.
Figure 6: Engineers and technicians check the fit of ICESat-2's telescope to its sling, before moving it into place on the instrument's optical bench (image credit: NASA)
• Sept. 1, 2014: Due to cost overruns, the launch of ICESat-2 has slipped to June 2018. ICESat-2's overrun was driven primarily by technical difficulties with the ATLAS (Advanced Topographic Laser Altimeter System) instrument. 24)
• May 2014: The box structure of the ATLAS instrument was delivered to a clean room at NASA/GSFC (Figure 18). A team of 250 engineers, fabricators and scientists has now started the official integration and testing stage of the laser instrument (Ref. 37).
Figure 7: An engineer checks the ATLAS box structure, shortly after its arrival in a NASA clean room in May 2014 (image credit: NASA, Kate Ramsayer)
• February 18, 2014: ICESat-2 passed its Mission Critical Design Review! Now, on to building and testing software and hardware for flight.
• January 17, 2014: ICESat-2 passed its Instrument CDR (Critical Design Review)! The project is now moving full-speed ahead to Mission CDR and instrument I&T start.
• In December 2013, NASA notified Congress of expected budget increases ($200 million overrun) on the ICESat-2 mission. NASA is required by law to inform Congress when a mission appears likely to overrun its approved budget by more than 15%. This may cause possible launch delays. 25)
• Sept. 6, 2013: ICESat-2 passed its Ground Systems CDR (Critical Design Review). An independent review board met Sept. 3-5 , 2013at Goddard Space Flight Center in Greenbelt, MD, to examine details of the entire design of the mission's ground system, including the MOC (Mission Operations Center), the ISF (Instrument Support Facility), and the Science Investigator-led Processing System.
• The ICESat-2 mission was assigned Phase C status on December 17, 2012.
• The ICESat-2 project passed instrument PDR (Preliminary Design Review) on Nov. 18, 2011.
• The ICESat-2 team passed the SRR (System Requirements Review) on May 25, 2011.
• The ICESat-2 team passed the ISRE (Instrument System Requirements Review) on December 1, 2010.
• The ICESat-2 team passed the Key Decision Point A (KDP-A) review at HQ on December 11, 2009. Since then the project started officially in Phase A.
Launch: A launch of ICESat-2 is scheduled for September 2018 from VAFB, CA (Space Launch Complex -2W) on a Delta-2 7420 vehicle. The launch service provider is ULA (United Launch Alliance). Last flight of a Delta-2 vehicle. 26) 27)
Orbit: Near polar LEO frozen orbit, altitude =496 km, inclination = 92º, repeat cycle of 91 days with subcycles of 29, 29, and 33 days (Figure 8).
Figure 8: Illustration of monthly subcycles (image credit: NASA)
The secondary payloads on IceSat-2 are:
• ELFIN (Electron Losses and Fields Investigation), a pair of 3U CubeSats of UCLA (University of California Los Angeles). 28)
• SurSat (Surface charging Satellite), a 2U CubeSat mission developed at the UCF (University of Central Florida), Orlando, FL.
• CP-7 (CalPoly-7) or DAVE (Damping And Vibrations Experiment), a 1U CubeSat, a collaboration of Northrop Grumman Aerospace Systems and CalPoly.
ICESat-2 synergies with other atmospheric missions: 29)
ICESat-2 is expected to at least partially overlap with the operation of ADM/Aeolus and EarthCARE, during the 2018 to 2022 period. Overlap between ICESat-2 and CALIPSO and CATS is a bit more dubious: CALIPSO is already well beyond its projected mission lifetime and CATS (Cloud-Aerosol Transport System) on ISS has license to operate through February 2018, perhaps longer (it had a six-month requirement and three-year goal). There is, however, a possibility of a CATS "follow-on" mission (that would be known as CATS-I), which has been submitted in response to an Earth Venture Instrument-3 Announcement of Opportunity. Nevertheless, discussion on complimentary measurements during the meeting encompassed all instruments.
Figure 9: The bar chart shows the current projected timetables for the atmospheric missions. The circle shows the area of possible overlap with ICESat-2 (image credit: NASA, Sabrina Delgado Arias)
Sensor complement: (ATLAS)
ATLAS (Advanced Topographic Laser Altimeter System)
ICESat-2 will use a new type of laser altimeter instrument, ATLAS, for measuring elevation, and will acquire far more data. To test the instrument concept, and develop accurate software to process the data, NASA has been flying an instrument called MABEL (Multiple Altimeter Beam Experimental Lidar) on high-altitude aircraft (ER-2) to simulate measurements that the ATLAS (Advanced Topographic Laser Altimeter System) — GLAS's successor–will be making from space. 30) 31)
Table 3: ATLAS instrument science measurement requirements (Ref. 35)
MABEL and ATLAS are photon-counting laser altimeters, meaning they measure distance by detecting just a few photons from each laser pulse and timing their round-trip travel from satellite to earth and back extremely accurately. While GLAS used millions of photons to make a single distance measurement, MABEL and ATLAS gather a data set of just a few dozen photons at most, and produce a cloud of points describing the snow or land or vegetation surface structure. Sophisticated software will determine the location of the surface track, the tops of the tree canopy, or the amount of dust or fog in the air.
The original design of the ATLAS instrument for ICESat-2 evolved as a modified version of the ICESat GLAS instrument concept. More specifically, for ICESat-2, the original ATLAS design was a single-beam altimetry system with the laser transmitter operating at a slightly higher repetition rate (50 Hz), lower energy per pulse (50 mJ) and similar 6-7 ns pulse width at the near-infrared (NIR) wavelength of 1064 nm when compared to GLAS. These changes would have provided higher derating on the lasers and potentially longer mission life.
In 2009, the ATLAS instrument on ICESat-2 underwent a complete redesign during the pre-Phase A activities to accommodate more science objectives and incorporate recommendations from the ICESat-2 science workshop (June 2007). For ice sheets, improved pointing will reduce the uncertainty in the ice sheet elevations introduced by the cross-track surface slope. In addition, for land topography and vegetation, improved pointing will provide observations along exact repeat ground tracks, and sampling along uniformly spaced ground tracks will provide well-sampled grids of topography and biomass. Based on this and other recommendations, a new instrument concept was proposed and accepted by the ICESat-2 program. 32) 33) 34) 35) 36) 37) 38)
The new baselined instrument is a high repetition rate (10 kHz), micropulse laser altimeter system. GSFC has begun an in-house program to investigate various potential laser technologies to meet the laser requirements for the ATLAS instrument.
A single laser transmitter having sufficient laser energy will be split into multiple beams using a DOE (Diffractive Optical Element) similar to the one used on LOLA. The current instrument architecture consists of a 9-beam system arranged in a 3 x 3 configuration.
Figure 10: Measurement concept of the ATLAS instrument (image credit: NASA)
In contrast to the first ICESat mission, ICESat-2 will use micro-pulse multi-beam photon counting approach to provide:
- Dense cross-track sampling to resolve surface slopes on an orbit basis
- High repetition rate (10 kHz) generates dense along-track sampling (~70 cm)
- Different beam energies to provide necessary dynamic range (bright / dark surfaces)
The advantages are:
- Improved elevation estimates over high slope areas and very rough (e.g. crevassed) areas
- Improved lead detection for sea ice freeboard.
The ATLAS instrument is a multi-beam micropulse laser altimeter with the following features:
• Single laser beam split into 9 beams
• 10 m ground footprints
• 10 kHz repetition rate laser (~1 mJ)
• Multiple detector pixels per spot
• On-board boresight alignment system
• LRS (Laser Reference System) gives absolute laser pointing knowledge.
Figure 11: Schematic of the ATLAS instrument (image credit: NASA)
ATLAS will employ a micropulse laser transmitter frequency doubled to 532 nm (visible green) with a 1 ns FWHM pulse width and operating at a 10 kHz repetition rate (0.7 m along-profile footprint sampling). A narrow 20 µrad beam divergence from a 500 km orbit altitude will yield 10 m diameter footprints. To improve spatial sampling ATLAS will employ a DOE (Diffractive Optic Element) that will split the single transmit beam into 6 beams, creating a pattern consisting of 3 sets of 2 closely spaced (< 100 m) beams. The closely-spaced beam pairs will resolve local slope, enabling determination of real elevation change from a single repeat of a reference track (Ref. 4).
With ICESat-2 operating in a 91 day repeat orbit and ATLAS operating continuously, seasonal observations of inter-annual ice sheet elevation change will be possible. The beam pairs will be separated cross-track by 3 km, providing improved spatial coverage as compared to that of ICESat. Over land, rather than repeating reference tracks, spacecraft pointing will be used to systematically displace the profiles cross-track through time in order to build up dense global sampling of topography and vegetation over the course of the mission.
In the traditional analog Si:APD detection approach used by GLAS of ICESat-1, thousands of photons reflected from the Earth's surface were acquired per laser fire (for clear atmospheric conditions) in order to obtain waveforms with sufficient SNR to achieve the 3 cm ranging precision. In the ATLAS micropulse approach the transmit pulse energy will be significantly lower such that only a few to ~10 photons will be detected per footprint per laser fire using a 0.8 m diameter telescope and photon-sensitive Photomultiplier Tube (PMT) detector arrays. Laser fire times and the arrival time of each photon, those reflected from the surface as well as from solar background noise, will be time tagged with 0.15 ns precision yielding < 20 cm single-photon range precision. Post-processing on the ground will yield "point clouds" of geolocated single photon surface returns. An advantage of this approach is that the combination of small, oversampled footprints, narrow pulse width and high-precision timing can yield elevation data of higher spatial and vertical resolution. In addition the geospatial information content of the point cloud is amenable to a greater diversity of analysis approaches than afforded by analog waveforms, opening up possibilities for new ways to characterize the vertical structure of the Earth's surface (Ref. 4).
Legend to Figure 12: Single laser pulse, split into 6 beams. Redundant lasers, redundant detectors.
ATLAS carries two lasers on the optical bench – one primary and one backup. The laser light is at 532 nm, a bright green on the visible spectrum. It is fast-firing, sending 10,000 laser light pulses per second. 40)
The first step on the laser's path to the ground is just a few inches past the laser, where a fold mirror directs the light 90º around a corner, where it hits the first key component, the PBC (Polarizing Beam Combiner). The PBC has two functions: The first is to make sure that the primary and backup lasers head down the same path. Although the two lasers won't fire at the same time, the laser beams begin at different positions and need to end up at the same place. The second function is to use a periscope to pick off a fraction of the laser light and direct it to the LSA (Laser Sampling Assembly).
At the LSA, one of these fibers starts the 'stopwatch' for that photon pulse. This timing component has to be incredibly precise to get the measurements that scientists need – when a photon returns, its travel time is recorded to the billionth of a second. The LSA also uses the small fraction of the laser to measure the laser's wavelength, ensuring it remains precisely at 532.272 nm. This specific shade of bright green is what the filters on the receiving telescope let pass through to stop the stopwatch, once the laser pulse completes its journey. Any other wavelength gets filtered out as background noise. As the LSA starts the timer, the rest of the laser pulse continues to the BE (Beam Expander).
Shaping and steering the beam: The BE consists of two mirrors, facing each other but slightly angled so that the laser hits one, bounces across to the second one, and then continues on in the same direction. These mirrors are curved to make the laser beam more than four times wider once it bounces off them. Making the beam wider actually makes the photons diverge less as they travel to Earth, tightening the laser footprint on the ground and allowing for a more precise map of surface heights.
"The spot diameter on Earth's surface would have been 66 m, now it's 15 m," according to Ramos-Izquierdo. "By making the laser beam bigger in diameter before exiting the instrument, we actually decrease how much it spreads as it propagates downward through the atmosphere."
The wider laser beam now goes through the BSM (Beam Steering Mechanism), which directs the laser at the ground below, but also has fine control over where the laser is pointing. This mechanism is connected with components on the instrument's telescope receiver, which collects any photons that return. The goal is to automatically point the lasers at the exact spot on the ground, where the telescope is observing. If the telescope and laser are pointed at different spots, the BSM will make slight adjustments to correct the alignment. The BSM is key because as the satellite goes in and out of the sun, changes in temperature could slightly warp the optical bench.
Split in six: The last hurdle for the laser beam is the DOE (Diffractive Optic Element), on the far side of the beam steering mechanism. This optical component is etched with a microscopic pattern of crisscrossed lines, which splits the single laser beam into six. The beams are set at slightly different angles, so they will cover the ground in a specific formation of three pairs of beams.
Once through the Diffractive Optic Element, the photons – lined up perfectly in six beams – are off on their journey to Earth.
Figure 13: ICESat-1 observation spacing at Jakobshavn Isbræ (left) and planned ICESat-2 spacing overlay (right), (image credit: NASA, Ref. 6)
Figure 14: Schematic of analog versus photon counting (image credit: NASA)
Legend to Figure 14: It is important to note that the integrated photon-counting sample ("histogram") looks like the analog wave - but it is not - the information content is different, and the method of analyzing the data is different.
Figure 15: Overview of the ATLAS instrument (image credit: NASA)
Table 4: Current laser transmitter performance requirements for the ICESat-2 micropulse laser altimeter system
Figure 16: Block diagram of the ATLAS instrument (image credit: NASA)
Figure 17: ATLAS functional block diagram (image credit: NASA)
The ATLAS instrument has a mass of 298 kg and a power consumption of 300 W.
Just as with the original ICESat data, ICESat-2 measurements are expected to provide added value to science and applications beyond their primary purpose. NASA's Applied Sciences Program actively seeks to connect NASA's Earth-observing satellite data to societal applications and encourages each mission to come up with a plan to connect its science to user needs. To that end, the ICESat-2 mission established an ICESat-2 Applications Team to organize and develop a mission applications program that will help establish these vital links between ICESat-2 science and society.
With guidance from the Applications Team, ICESat-2 has developed and implemented a diverse range of mission-specific prelaunch applications activities and strategies for engaging end users. These activities are modeled after the highly successful application strategies implemented for NASA's SMAP (Soil Moisture Active/Passive) mission and are intended to provide a fundamental understanding of how ICESat-2's data products can be best integrated into operational procedures to improve decision-making efforts across multiple disciplines. 41)
Figure 19: Overview of ICESat-2 elements in the ground segment (image credit: NASA)
Table 5: ICESat-2 science data products. The rows are shaded light gray to dark gray to represent Level 0 (light gray), Level 1, Level 2, and Level 3 (dark gray) data products. The ICEsat-2 mission will not have a Level 4 (value-added-model) product.
ICESat-2 Preparatory Campaigns
MABEL (Multiple Altimeter Beam Experimental Lidar)
MABEL is a high-altitude airborne laser altimeter designed as a simulator for ICESat-2. The MABEL design uses multiple beams at fixed angles and allows for local slope determination. The MABEL instrument was developed to: 42) 43)
1) enable the development of ICESat-2 geophysical algorithms prior to launch
2) provide detailed error analysis of the ATLAS measurement strategy
3) provide ATLAS model validation.
MABEL is a photon-counting multibeam lidar sampling at both 532 nm and 1064 nm wavelengths using short (~1.5 ns) laser pulses. MABEL beams are arranged in a linear array, perpendicular to the direction of flight. The system allows for beam-geometry changes between flights with a maximum view angle of ±1 km from a 20 km nominal altitude achieved during the 2010–2012 deployments using a NASA ER-2 aircraft (Figure 20).
Figure 20: Schematic ICESat-2 and MABEL beam geometry (dashed lines) and reference ground tracks (grey lines along icesheet surface). ICESat-2 beam pairs (separated by ~90 m) do not have the same energy in order to keep the required laser energy low; therefore, each beam pair consists of a strong and a weak beam (as indicated by the dash difference). MABEL allows for beamgeometry changes with a maximum ground spacing of ~2 km at 20 km. However, for the 2014 AK deployment, the maximum ground spacing was 0.2 km (Ref. 43), image credit: MABEL Team
The repetition rate of MABEL is variable (between 5 and 25 kHz); most flights during the 2010–2012 deployments used 5 kHz. At this nominal altitude, repetition rate, and an aircraft speed of ~200 m/s, MABEL samples a ~2 m footprint every ~4 cm along track. During these initial MABEL deployments, beam geometry (specifically the spacing between the individual beams) was configured to mimic ICESat-2.
Following engineering test flights in December 2010 and March 2011, MABEL was deployed to Greenland in April 2012 to collect data over polar targets (Figure 21).
Operation IceBridge is a NASA airborne campaign intended to bridge the data gap between ICESat and ICESat-2. Operation IceBridge hosts a suite of instruments, including the ATM (Airborne Topographic Mapper). ATM is a lidar that conically scans at a rate of 20 Hz, with an off-nadir scanning angle of ~15º. Like GLAS, ATM digitizes returned energy as a waveform with derived surface elevations based on 532 nm wavelength pulses and a 5 kHz PRF (Pulse Repetition Frequency). The ATM flights were conducted using the NASA P-3B at an aircraft speed of ~100 m/s, with a nominal elevation of 500 m above ground level. At this air speed, elevation, and repetition frequency, ATM generates a 1 m footprint and a scanning swath width of ~250 m.
Logistics and cloud-free weather allowed for coordinated surveys between ATM and MABEL over the Greenland Ice Sheet (Figure 21). Here, the MABEL multibeam determination of the ice-sheet surface is presented and compared with that determined by ATM, including local slope assessments. These comparisons are made with consideration for the ICESat-2 planned beam geometry and relative signal strength.
Both MABEL and ATM simultaneously surveyed a 150 km "Southern Traverse" of the Greenland Ice Sheet on April 20, 2012 (Figure 21). Additionally, MABEL made three passes over a 50 km stretch of ICESat track 0412 in the vicinity of Summit Station, Greenland, on April 8, 2012. ATM made a pass of the same ground segment on April 11, 2012. This ground segment has been used as a calibration site for ICESat-2.
Figure 21: Location map of the 50 km along-track Summit Area site and the 150 km along-track Southern Traverse site on the MODIS Mosaic of Greenland. (Inset) Operation IceBridge P-3B captured in the NASA ER-2 Cirrus Digital Camera System at the black.
The NASA IceBridge ATM Level-2 Icessn Elevation, Slope, and Roughness (ILATM2) for April 11 and 20, 2012, were obtained from the National Snow and Ice Data Center (NSIDC). This is a resampled and smoothed elevation data set that provides four across-track elevations per timestamp every ~35 m along-track, which allowed for the trivial calculation of across-track slope. The total across-track span for this data set, for the flights used in this analysis, was approximately 150 m.
MABEL data (release 8) for April 8 and 20, 2012, were obtained from the NASA ICESat-2 website. Each data file contains 1 minute of data for every available beam. The data files contain photon arrival times resulting from reflected laser light (i.e., signal photons) and background photons due to sunlight (i.e., noise photons).
In order to discriminate coarse signal photons from noise photons and derive ice-sheet surface elevation, the team developed an algorithm based on histograms of the photon data. Evolving from techniques applied to other photon-counting lidars, such as the SIMPL (Slope Imaging Multi-polarization Photon-counting Lidar), a 0.125 s (~25 m; 625 shots) along-track segments of data was generated and the photon data at 10 m vertical resolution was histogrammed. Signal photons in four sequential steps were identified.
For direct comparison of the surveys, ATM tracks and MABEL beams were chosen to most closely mimic the 90 m spacing of the ICESat-2 beam geometry. ATM tracks 2 and 3 were used for this analysis because they have ground separation of ~85 m. Elevations from tracks 2 and 3 from the same along-track time were then used to calculate the ATM across-track slope. MABEL beam 6 (center of the array) and beam 5 (~85 m ground spacing from the center of the array) were chosen for analysis as they have an across-track ground separation similar to the ATM tracks used. To determine the MABEL across-track slope, signal photons from beams 5 and 6 were interpolated along track to a common time so that, similar to ATM, an across-track slope could be then calculated for each increment of along-track time. The across-track slopes for both ATM and MABEL were then compared.
MABEL beams have variable signal strengths; however, beams 5 and 6 are the most similar to the expected radiometry of the strong beams of ATLAS. The along-track data density differed within and between flights based on variables that affect reflectivity, including weather conditions, time of day, and sun-incidence angle. For the data used in this analysis, the full-rate along-track data density average for both beams was always greater than 4 signal photons/m. For the Southern Traverse flight, the along-track data densities were 3.4 and 3.9 signal photons per 70 cm for beams 5 and 6, respectively. For the Summit Area flight, data densities were 3.1 and 3.4 signal photons per 70 cm for beams 5 and 6, respectively.
A strong-beam/weak-beam pair will be used for ICESat-2 slope determination; the energy associated with the weak beam will be reduced by a factor of 4. Therefore, the expected number of signal photons per laser shot (every 70 cm along track) between the strong beam and the weak beam will also differ by a factor of 4. The current best estimates of expected signal photons per laser shot vary with season and surface type. Based on ICESat-2 engineering models, under similar conditions as the 2012 MABEL survey, the team expects ICESat-2 to record 8.5 and 2.1 signal photons every shot (or 70 cm along track) for the strong and weak beams, respectively. Thus, the MABEL full-rate data used in this analysis suggest data densities of 46% of the expected ICESat-2 data densities. MABEL engineers are currently working to increase signal strength to achieve the expected ICESat-2 data densities, which will facilitate more direct MABEL to ATLAS comparisons.
To further assess accurate ground characterization given the ICESat-2 planned configuration, all photons associated with one of the MABEL beams (beam 5) were subsampled by a factor of 4 and then reprocessed through the ground-finding algorithm, to simulate the expected radiometric relationship between the ATLAS strong and weak beams. After subsampling, the data densities were 0.9 and 0.8 signal photons per 70 cm for the Southern Traverse and Summit Area, respectively. To determine the MABEL across-track slope, the ground-signal photons from beam 6 and the subsampled ground-signal photons from beam 5 were again interpolated to a common time so that an across-track slope could be calculated as described above. Therefore, the beam with the fewest along-track samples (the weak beam, 5) limited the total number of samples that was used in the slope determination.
Antarctic Preparatory Campaign
In temperatures that can drop below -20º Fahrenheit (-29ºC), along a route occasionally blocked by wind-driven ice dunes, a hundred miles from any other people, a team led by two NASA scientists will survey an unexplored stretch of Antarctic ice. 44)
They're packing extreme cold-weather gear and scientific instruments onto sleds pulled by two tank-like snow machines called PistenBullys, and on 21 Dec. 2017, they will begin their two- to three-week traverse in an arc around the South Pole.
The 470-mile (759 km) expedition in one of the most barren landscapes on Earth will ultimately provide the best assessment of the accuracy of data collected from space by ICESat-2 (Ice Cloud and land Elevation Satellite-2), set to launch in 2018. With a fast-firing laser instrument, ICESat-2 will measure the elevation of ice sheets and track change over time. Even small amounts of melt across areas as vast as Greenland or Antarctica can result in large amounts of meltwater contributing to sea level rise.
To help document this, ICESat-2's height change measurements will have a precision of less < 2.5 cm – ground-truthed, in part, with efforts like this Antarctic campaign. The team will collect precise GPS data of the elevation at 88 degrees south, where ICESat-2's orbits converge, providing thousands of points where the survey measurements can be compared to satellite data.
"This traverse provides an extremely challenging and extremely cold way to assess the accuracy of the data," said Kelly Brunt, ICESat-2's calibration and validation lead at NASA/GSFC (Goddard Space Flight Center), and a research scientist at the University of Maryland. "ICESat-2's datasets are going to tell us incredible things about how Earth's ice is changing, and what that means for things like sea level rise."
Brunt is leading the four-person campaign from the South Pole, along with ICESat-2's deputy project scientist Tom Neumann. The NASA scientists will also be joined by a mechanic and a deep field mountaineer. The campaign to collect these key elevation measurements has been years in the making, with logistical help from the National Science Foundation's U.S. Antarctic Program.
It will be a really cold road trip, Brunt said. They'll wake up, make coffee (with beans, grounds and pour-over equipment chosen and packed with great care), turn on the snow machines and instruments, and start the day's drive. The two PistenBullys will each tow a thick plastic sled, about 8 feet wide and 60 feet long. The sleds – kind of like extra-large Flexible Flyers, Neumann noted – will carry tents as well as food, equipment and extra fuel.
The whole trek is about 750 km. The team will leave the South Pole along an established traverse line between the southernmost station and McMurdo. Just after they reach 88º south, they will turn and follow the latitude line for about 186 miles. Then, they'll turn back to the pole – creating a route like a misshapen piece of pie. At a pace of 50 to 72 km/day, it will take at least a couple weeks to complete.
"There'll be times when it's quiet and thoughtful, and there are going to be other times when you're steering around the sastrugi – the sand dunes of the ice – when you're not going to make a lot of kilometers on that day, but they'll be hard fought," Kelly Brunt said.
Figure 22: The ICESat-2 team will follow a route from the South Pole station to just north of the 88º south latitude line, then drive along the line at a pace of 50 to 72 km/day. The traverse will take two to three weeks to complete (image credit: NASA, Manrique)
Crevasses are highly unlikely in this thick, slow-moving region of the Antarctic ice sheet, she said. The campaign's deep field mountaineer will operate a ground penetrating radar that sticks out on a boom in front of the lead vehicle, looking for any gaps in the ice, but the primary safety concerns will be exposure to outside temperatures (-30ºC) and the altitude (about 3 km at South Pole).
The first few days at the South Pole station will be spent acclimatizing to the altitude, Neumann said, noting that the cold, dry air makes the environment even harsher. Once on the road, however, he plans to spend evenings out in the elements, digging holes.
"I'll measure the density of the snow along the way," he said. By shoveling out a three-foot-deep pit, he can see layers of snow that have built up over decades, some of which can be hard to dig past. "They're not super dense, but they're so old the grains of snow are bonded together like its cement."
Figure 23: The traverse follows close to the 88 degree south line, where all the orbits will converge, as seen in this visualization. This allows scientists to compare thousands of survey measurements with data collected by ICESat-2 once it is in orbit (image credit: NASA's Scientific Visualization Studio)
When ICESat-2 starts collecting elevation data, the snow density measurements and the data from the ground penetrating radar will help determine how much mass is lost when the ice sheet drops in elevation.
The 88-degree traverse is also an opportunity for Brunt and Neumann to play the odds. At three different sites along the route, they'll set up a grid of nine reflector cubes, each no bigger than the tip of a pinkie finger. They'll mark the precise latitude, longitude, and elevation of each cube.
Then, once ICESat-2 is up and running, they'll wait. If one of the satellite's six laser beams hits a cube, the mirrored material of the cube will reflect the laser light back at a much higher than normal intensity. Since they'll know the exact location and elevation of the cube, they can check the accuracy of the satellite data even more precisely than with the traverse data.
"If you hit that tiny little point, you'll know exactly where the laser hit on the ground," Brunt said. "But hitting that point is both aiming and luck. It's hard. But, by placing them at 88 degrees, where you have so many orbits crossing and so much data, it's just a statistics game."
After the traverse, the scientists will return to the United States, retracing their steps from the South Pole station, to McMurdo Station, to New Zealand and home. With them: hard drives full of data to help understand the accuracy of ICESat-2.
Figure 24: Kelly and Tom on the ice runway at McMurdo Station, Antarctica (image credit: Tom Neumann) 45)
Figure 25: Tom and Kelly inside a PistenBully, like the one they'll use for the traverse along 88 degrees south (image credit: Kelly Brunt)
NASA Operation IceBridge Campaign in Antarctica 2017
This campaign is intended to be flown by NASA's P-3 aircraft, beginning in late October and ending in late November 2017. The mission, called Operation IceBridge, is in its ninth year of flights to map the snow and ice of Antarctica. The view from above provides a tremendous amount of information about the huge expanses of snow and ice around Earth's polar regions and how they are changing. 46) 47)
Some flight lines are designed to map the ice laying atop the land, while others map the sea ice. On November 4, 2017, the IceBridge team flew its "Endurance West" mission, which specifically targets sea ice. The P3 crossed the northern tip of the Antarctic Peninsula, descended to a lower altitude, and then flew southward across the Weddell Sea. The path purposely follows a ground track of ICESat-2 —an ice-mapping satellite mission that is scheduled for launch in late 2018.
Figure 26: One of the mission's instruments, the DMS (Digital Mapping System), collects thousands of high-resolution photographs during a single flight. These images shot from a camera mounted on the belly of the plane are "visual truth," helping scientists identify features that are also detected by radar, laser, and gravity instruments (image credit: NASA Earth Observatory, map by Joshua Stevens)
Images from that day show just how varied sea ice can appear. The first photograph, shot from the aircraft by IceBridge project scientist Nathan Kurtz, shows newly formed sea ice next to a snow-covered floe in the Weddell Sea. The second and third images, both acquired by the DMS (Digital Mapping System), show sea ice off the Antarctic Peninsula. Thicker ice is white, thinner ice is gray, and open water is black or navy.
Note: Only a few images, marked in Figure 26, are provided here.
Figure 27: Newly formed sea ice (gray) in the Weddell Sea (image credit: NASA, Nathan Kurtz — image 1)
On November 12, 2017, IceBridge flew a high-priority mission over the Larsen C Ice Shelf. In July 2017, this region was significantly reshaped by the shedding of an iceberg the size of Delaware. For most of the four-hour survey, as the aircraft flew back-and-forth in parallel lines over the ice shelf, the landscape appeared flat and white. These new flight lines followed the ground tracks of the future ICESat-2, providing baseline measurements for the satellite to take over after it begins operations. This survey also increased the amount of Larsen C that has been observed with a gravimeter, an instrument that helps scientists map the bedrock below the ice shelf and the water, which radar and visual imagers cannot penetrate.
Visually, the landscape appeared more varied when the aircraft traced the edge of the ice shelf or soared over sea ice. These photographs show sea ice of various types as observed by the DMS during the November 12 flight.
Figure 28: Sea ice near the Larsen C Ice Shelf (image credit: NASA/Digital Mapping System — image 4)
Figure 29: Thin ice between the Larsen C Ice Shelf and iceberg A-68A (image credit: NASA/Digital Mapping System — image 5)
Fractures: During any given IceBridge flight, one can see areas of fractures and crevasses that attest to lumbering motion of huge slabs of ice. Its thickness on this part of the continent can vary dramatically, from no ice at all (barren bedrock) to more than a kilometer thick. The reason for the brittle appearance is similar to the phenomenon of river rapids, which become amplified as water flows through steep, narrow terrain. As ice flows through narrower areas and steeper bedrock, more fractures open up at the ice surface. But the flow of ice is so much slower than water, and fractures are often the only perceptible indication of movement. These images, acquired by the DMS on November 3, 2017, show cracks in the ice as observed while flying over the southern Antarctic Peninsula.
The image of Figure 30 shows a heavily crevassed glacier, about 13 miles long and 7 miles wide, flowing west from the Dyer Plateau to George VI Sound. The north side of this glacier merges with Meiklejohn Glacier.
Figure 30: A heavily crevassed glacier flows west from the Dyer Plateau (image credit: NASA/Digital Mapping System — image 11)
Figure 31: Proposed flight lines of the NASA P-3B aircraft during the 2017 Antarctic Field Campaign of Operation IceBridge (image credit: NASA) 48)
1) Waleed Abdalati, H. Jay Zwally, Robert Bindschadler, Bea Csatho, Sinead Louise Farrell, Helen Amanda Fricker, David Harding, Ronald Kwok, Michael Lefsky, Thorsten Markus, Allexander Marshak, Thomas Neumann, Stephen Palm, Bob Schutz, Ben Smith, James Spinhirne, Charles Webb, "The ICESat-2 Laser Altimetry Mission," Proceedings of the IEEE. Vol 98, No. 5, May 2010. Pages 735-751., URL: http://icesat.gsfc.nasa.gov/icesat2/
2) Douglas D. McLennan, "Ice, Clouds and Land Elevation (ICESat-2) Mission," Proceedings of the SPIE Remote Sensing Conference, Toulouse, France, Vol. 7826, Sept. 20-23, 2010, paper: 7826-32, 'Sensors, Systems, and Next-Generation Satellites XIV,' edited by Roland Meynart, Steven P. Neeck, Haruhisa Shimoda, doi: 10.1117/12.865200
4) David J. Harding, "NASA's Lidar measurements of the Earth's surface from space," Proceedings of IGARSS (International Geoscience and Remote Sensing Symposium), Munich, Germany, July 22-27, 2012
5) Molly Brown, Mark Carroll, Vanessa Escobar, "ICESat-2 Applications Workshop Report, NASA Goddard Space Flight Center, April 12, 2012, URL: http://icesat.gsfc.nasa.gov/icesat2/applications
6) Kelly M. Brunt, Sinéad L. Farrell, Vanessa M. Escobar, "ICESat-2: A next generation laser altimeter for space-borne determination of surface elevation," 93rd American Meteorological Society Annual Meeting, Austin, TX, USA, Jan. 6-10, 2013, URL: https://ams.confex.com/ams/93Annual/webprogramc
9) Tom Newmann, Thorsten Markus, Matthew McGill, Kelly Brunt, Tony Martino, William Cook, "MABEL and the ICESat-2 Mission: Photon-counting Altimetry from Air and Space," The Earth Observer, Sept.-Oct. 2012, Volume 24, Issue 5, pp: 4-8, URL: http://eospso.gsfc.nasa.gov/sites/default
11) S. Volz, "NASA Earth Sciience New Miissiion Concepts for the Future," 5th SORCE Science Meeting, Santa Fee, NM, Feb. 7, 2008, URL: http://lasp.colorado.edu/sorce/news/2008
12) John Loiacono, ICESat-2 Progress Report for FY08 and FY09 Plans," Feb. 11, 2009, URL: http://decadal.gsfc.nasa.gov/documents/03_ICESat_II.pdf
13) "Orbital Wins ICESat-2 Earth Science Satellite Program Contract," Space Daily, Sept. 2, 2011, URL: http://www.spacedaily.com/reports/Orbital_Wins_ICESat
14) "NASA Selects Contractor For Icesat-2 Spacecraft," NASA, Aug. 31, 2011, URL: http://www.nasa.gov/home/hqnews/2011/aug/HQ_C11-037_ICESat2.html
16) Kate Ramsayer, "ICESat-2 Lasers Pass Final Ground Test," NASA, 9 July 2018, URL: https://www.nasa.gov/feature/goddard/2018/
17) Kate Ramsayer, "NASA space laser completes 2,000-mile road trip," Space Daily, 1 March 2018, URL: http://www.spacedaily.com/reports/NASA_Space_Laser
18) Kate Ramsayer , Sara Blumberg, "NASA's ICESat-2 Preps for Laser Tests," NASA, Aug. 16, 2017, URL: https://www.nasa.gov/feature/goddard/2017/
19) Michael Freilich, "ICESat-2 Technical Status Summary," The National Academies of Sciences, Engineering, and ..., Sept. 1, 2016, URL: http://sites.nationalacademies.org/cs/groups
21) Kate Ramsayer, "NASA tests ICESat-2's laser aim," NASA, Dec. 10, 2015, URL: http://www.nasa.gov/feature/goddard/lasers-path-through-icesat-2
22) Kate Ramsayer, "NASA's ATLAS thermal testing: You're hot, then you're cold," NASA, April 21, 2015, URL: http://phys.org/news/2015-04-nasa
23) "NASA lining up ICESat-2's laser-catching telescope," NASA, Nov. 3, 2014, URL: http://phys.org/news/2014-11-nasa-lining-
24) Dan Leone, "Paying for ICESat-2 Overruns Delays International Earth Science Launches," Space News, Sept. 1, 2014, URL: http://spacenews.com/41729paying-for-icesat-2-
25) Stephen Clark, "Over-budget ICESat 2 mission under review," Spaceflight Now, Dec. 10, 2013, URL: http://spaceflightnow.com/news/
26) "2018: A Big Year for NASA's Launch Services Program," NASA, 1 Feb. 2018, URL: https://www.nasa.gov/feature/2018-a-big-
27) "About ICESat-2," NASA, 2017, URL: https://www.nasa.gov/content/goddard/about-icesat-2
29) Sabrina Delgado Arias, Molly Brown, Steve Palm, Yuekui Yang, Thomas Neumann, "NASA Missions Working Together for Improved Atmospheric Data: ICESat-2 Convenes Joint Atmospheric Tutorial," The Earth Observer, September - October 2017, Volume 29, Issue 5, pp: 20-30, URL: https://eospso.nasa.gov/sites/default/files
30) Julia M. Ruth, Sinead L. Farrell, Kelly M. Brunt, "Assessment of Arctic sea ice freeboard from photon-counting laser altimetry: Pre-launch activities for NASA's ICESat-2 Mission," URL: http://www.whoi.edu/fileserver.do?id=169388&pt=2&p=180851
31) Nicholas A. Forfinski-Sarkozi, Christopher E. Parrish, "Analysis of MABEL Bathymetry in Keweenaw Bay and Implications for ICESat-2 ATLAS," Remote Sensing, Vol. 8, 2016, doi:10.3390/rs8090772, URL: http://www.mdpi.com/2072-4292/8/9/772/pdf
32) Anthony W. Yu, Mark A. Stephen, Steve X. Li, George B. Shaw, Antonios Seas, Edward Dowdye, Elisavet Troupaki, Peter Liiva, Demetrios Poulios, Kathy Mascetti, "Space Laser Transmitter Development for ICESat-2 Mission," Proceedings of SPIE, Vol. 7578, LASE 2010, San Francisco, CA, USA, Feb. 15-18, 2010, 'Solid State Lasers XIX: Technology and Devices,' edited by W. Andrew Clarkson, doi: 10.1117/12.843342, URL: http://icesat.gsfc.nasa.gov/icesat2
34) Douglas D. McLennan, Thorsten Markus, Thomas Neumann, " URL: http://www.scribd.com/doc/76177455
35) Charon Birkett, T. Markus, T. Neumann, "The ICESat‐2 Mission - Laser altimetry of ice, clouds and land elevation ....and also ocean, coastal, and continental waters," OSTM SWT (Science Working Team), San Diego, CA, USA, October 19-21, 2011, URL: http://www.aviso.oceanobs.com/fileadmin/documents/OSTST/2011
36) Douglas D. McLennan, Thorsten Markus, Thomas Neumann, "The Vital Role of ICESat Data Products," 2011, URL: http://media.aero.und.edu/space.edu/documents/2011_0418_
37) Kate Ramsayer, "How NASA Builds a Space Laser," NASA, June 3, 2014, URL: http://www.nasa.gov/content/goddard
38) Mahsa S. Moussavi, Waleed Abdalati, Ted Scambos, Amy Neuenschwander, "Applicability of an automatic surface detection approach to micro-pulse photon-counting lidar altimetry data: implications for canopy height retrieval from future ICESat-2 data," International Journal of Remote Sensing Vol. 35 , Issue 13,2014, pp: 5263-5279
39) M. Jasinski, T. Neumann, "The ICESat‐2 Mission: Objectives, concept, and opportunities for snow," NASA Snow Remote Sensing Workshop, Boulder, CO, USA, Aug. 14-16, 2013, URL: http://nasasnowremotesensing.gi.alaska
40) Kate Ramsayer, "A Laser Beam's Path Through NASA's ICESat-2," NASA, June 30, 2015, URL: http://www.nasa.gov/feature/goddard/
41) Vanessa Escobar, Sabrina Delgado Arias, Pam Posey, Thomas, Neumann, "Improving Operational Awareness Through ICESat-2 Applications Workshops: Cross-Mission Development," The Earth Observer, May-June 2014, Volume 26, Issue 3, pp: 15-22, URL: http://eospso.gsfc.nasa.gov/earthobserver/may-jun-2014
42) Kelly M. Brunt, Thomas A. Neumann, Jason M. Amundson, Jeffrey L. Kavanaugh, Mahsa S. Moussavi, Kaitlin M. Walsh, William B. Cook, Thorsten Markus, "MABEL photon-counting laser altimetry data in Alaska for ICESat-2 simulations and development," The Cryosphere, Vol. 10, pp:1707–1719, August 2016, doi:10.5194/tc-10-1707-2016, URL: http://www.the-cryosphere.net/10/1707/2016/tc-10-1707-2016.pdf
43) Kelly M. Brunt, Thomas A. Neumann, Kaitlin M. Walsh, Thorsten Markus, "Determination of Local Slope on the Greenland Ice Sheet Using a Multibeam Photon-Counting Lidar in Preparation for the ICESat-2 Mission," IEEE Geoscience and Remote Sensing Letters, Vol. 11, No 5, May 2014, pp: 935-939, URL of abstract: http://ieeexplore.ieee.org/document/6623082/
44) Kate Ramsayer , "NASA Scientists Embark on Extreme Antarctic Trek," NASA, 14 December 2017, URL: https://www.nasa.gov/feature/goddard/2017/
45) "Archive for ‘ICESat-2 Antarctic Traverse'," NASA Earth Observatory, 12 Dec. 2017, URL: https://earthobservatory.nasa.gov/blogs/
46) Kathryn Hansen, "Antarctica from Above: Flying for Science, Finding Beauty," NASA Earth Observatory, 11 Jan. 2018, URL: https://earthobservatory.nasa.gov/Features/Operation
47) John Sonntag, "Fall 2017 IceBridge P-3 Flight Plans," 29 September 2017 Draft, URL: https://icebridge.gsfc.nasa.gov/wp-content/uploads
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org). | <urn:uuid:fe8a3a7e-09c7-4f60-9b33-cb5eb80736b7> | 3.203125 | 13,621 | Knowledge Article | Science & Tech. | 49.130056 | 95,590,977 |
Scientists are exploring oceanic ice worlds with new robots
Under the ice of the Arctic, unknown habitats conceal an unexpected variety of living beings. On October 23rd, 46 scientists are expected to return to the home port in Bremerhaven from an Arctic expedition with the research vessel Polarstern. Over the past six weeks, they had explored life in ice, ocean and seabed with new robots and camera systems.
The ice-covered, central Arctic Ocean beyond 85° North is known for its harsh climate, low productivity and poor colonisation by marine animals. Because of the difficult ice and climate conditions, only a few scientists have had the opportunity to explore this region extensively. The current Polarstern Expedition PS101 had the goal of exploring underwater sea-beds and deep-sea trenches of the central Arctic Ocean and investigating how ice, ocean and life have changed due to the massive ice decline of recent years.
Already in the year 2001 during a German-American expedition with the research breakers Polarstern and Healy, many seamounts along the Gakkel Ridge of the Central Arctic were surveyed, but until now it lacked marine technology to dive down to them. One of the largest seamounts of the Gakkel Ridge is the Karasik seamount, discovered in 2001 and rising from a depth of 5000 m to 650 m. Seamounts are generally regarded as oases of life in the ocean as they provide marine animals with a variety of habitats and food sources. But whether they are also richly populated in the icy Arctic, which is scarce in food, has so far been unexplored.
“With the first pictures of the summit of the Karasik seamount we did not believe our eyes: It is overgrown with huge globular sponges. Between the sponges lie centimetre-thick mats of needles and worm-burrows. We were able to observe different species of fish which were not to be expected here, and caught a glimpse of the northernmost corals discovered so far. There are huge white starfish, blue snails, red crabs and white and brown clams between the sponges”, reports chief scientist Prof. Dr. Antje Boetius from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), regarding the first dives under the ice. The plankton, which mainly float in the water, especially crabs, jellyfish and worms, also brought astonishment to the explorers.
The deep sea robot NUI of the American marine research institute WHOI, a prototype for the exploration of ice-covered oceanic worlds, filmed the hitherto unknown deep under the ice and collected specimens for the species determination. It dived repeatedly to the sponges of the Karasik seamount. The giant sponges are up to a metre in size, hundreds of years old and seem to be able to move on their needles. They are, in turn, a habitat for innumerable animals that find themselves at home in the sponges.
The researchers found a particularly extreme habitat under the ice at hot springs in the valley of the Gakkel Ridge. On a still unnamed volcanic lake, the team encountered ghostly structures of freshly solidified lava rock, between which hot water rose out of small vents and cracks - at an ambient temperature below the freezing point. They observed vanes of hydrogen and methane above the hot springs used by special deep-sea bacteria as a food source. In addition to swarms of crustaceans, sea anemones and bacterial mats, fish and many fish skeletons were found at the hydrothermal vents. The researchers therefore assume that the hydrothermal activity feeds energy into the food web of the deep sea.
Climate change also plays an important role in the Karasik seamount region. The AWI ice physicist Dr. Marcel Nicolaus summarises the observations: "This year's thin ice in the study region confirms the long-observed trend. While in the 1990s, the Polarstern had to sail around two or three metres thick ice floes in the investigation area, in 2001 the first surveying of the seamounts was with less than two metres in average sea ice thickness. At the moment, we have mainly found thicknesses of less than one metre and hardly any more large ice-floes." The sea ice explorers have released a series of autonomously drifting ice buoys during the expedition to monitor the sea ice and the climate of the Arctic and to improve the predictions for the change of the Arctic.
The international expedition has profited from the development of technology at the joining between deep sea and space exploration. Researchers and engineers from the Helmholtz Initiative ROBEX (Robotic Exploration of Extreme Environments) have collaborated with NASA's PSTAR program (Planetary Science and Technology Analog Research). Project leader Chris German (WHOI) notes: "The Earth is only one of up to ten planetary bodies of our solar system on which ice-covered oceans are suspected. From the PS101 expedition to the ice-covered Arctic, we were able to learn about technologies for exploring other planetary oceanic environments."
The Polarstern will spend the next two and a half weeks on routine maintenance and repair work at the Bremerhaven Lloyd shipyard. The research and supply vessel will start to the Antarctic season on the 12th of November 2016. On the transit to the south, a training course for international young scientists will take place. Until the spring of 2017, oceanographic and geoscientific expeditions as well as the supply of the Neumayer Station III will be on the agenda.
Notes for Editors:
Please find printable images in the online version of this press release at http://www.awi.de/nc/en/about-us/service/press.html.
Your scientific contact persons are Professor Antje Boetius (e-mail: Antje.Boetius(at)awi.de) and Dr Marcel Nicolaus (e-mail: Marcel.Nicolaus(at)awi.de).
Your contact person in the Dept. of Communications and Media Relations is Dr Folke Mehrtens, tel. +49 471 4831-2007 (e-mail: Folke.Mehrtens(at)awi.de).
The Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) conducts research in the Arctic, Antarctic and oceans of the high and mid-latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctica. The Alfred Wegener Institute is one of the 18 research centres of the Helmholtz Association, the largest scientific organisation in Germany.
Ralf Röchert | idw - Informationsdienst Wissenschaft
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
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Discussion of all aspects of cellular structure, physiology and communication.
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RNA in both eukaryotes and prokaryotes have a similar function of synthesizing proteins and the mechanism for synthesis, elongation and proof reading is also similar. so why is there a difference in their sedimentation number? ( 80S for eukaryotes and 70S for prokaryotes).
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Updated: January 12, 2018, 5:05 P.M. ET
When Jason Shepherd first saw the structures under a microscope, he thought they looked like viruses. The problem was: he wasn’t studying viruses.
Shepherd studies a gene called Arc which is active in neurons, and plays a vital role in the brain. A mouse that’s born without Arc can’t learn or form new long-term memories. If it finds some cheese in a maze, it will have completely forgotten the right route the next day. “They can’t seem to respond or adapt to changes in their environment,” says Shepherd, who works at the University of Utah, and has been studying Arc for years. “Arc is really key to transducing the information from those experiences into changes in the brain.”
Despite its importance, Arc has been a very difficult gene to study. Scientists often work out what unusual genes do by comparing them to familiar ones with similar features—but Arc is one-of-a-kind. Other mammals have their own versions of Arc, as do birds, reptiles, and amphibians. But in each animal, Arc seems utterly unique—there’s no other gene quite like it. And Shepherd learned why when his team isolated the proteins that are made by Arc, and looked at them under a powerful microscope.
He saw that these Arc proteins assemble into hollow, spherical shells that look uncannily like viruses. “When we looked at them, we thought: What are these things?” says Shepherd. They reminded him of textbook pictures of HIV, and when he showed the images to HIV experts, they confirmed his suspicions. That, to put it bluntly, was a huge surprise. “Here was a brain gene that makes something that looks like a virus,” Shepherd says.
That’s not a coincidence. The team showed that Arc descends from an ancient group of genes called gypsy retrotransposons, which exist in the genomes of various animals, but can behave like their own independent entities.* They can make new copies of themselves, and paste those duplicates elsewhere in their host genomes. At some point, some of these genes gained the ability to enclose themselves in a shell of proteins and leave their host cells entirely. That was the origin of retroviruses—the virus family that includes HIV.
So, Arc genes are the evolutionary cousins of these viruses, which explains why they produce shells that look so similar. Specifically, Arc is closely related to a viral gene called gag, which retroviruses like HIV use to build the protein shells that enclose their genetic material. Other scientists had noticed this similarity before. In 2006, one team searched for human genes that look like gag, and they included Arc in their list of candidates. They never followed up on that hint, and “as neuroscientists, we never looked at the genomic papers so we didn’t find it until much later,” says Shepherd.
The similarities don’t end there. When genes are activated, the instructions encoded within their DNA are first transcribed into a related molecule called RNA. Shepherd’s colleague Elissa Pastuzyn showed that the Arc shells can enclose RNA and move it from one neuron to another. And that’s basically what retroviruses do—they use protein shells to protect their own RNA as it moves between cells in a host.
So our neurons use a viral-like gene to transmit genetic information between each other in an oddly virus-like way that, until now, we had no idea about. “Why the hell do neurons want to do this?” Shepherd says. “We don’t know.” One wild possibility is that neurons are using Arc (and its cargo) to influence each other. One cell could use Arc to deliver RNA that changes the genes that are activated in a neighboring cell. Again, “that’s very similar to what a virus does—changing the state of a cell to make its own genes,” says Shepherd.
“We have way more questions now than when we started out,” he says. “What is the RNA cargo? What is the signal [that the Arc shells] are carrying? When Arc is released by a neuron, how far can it travel?” And perhaps more importantly, how does all of this influence the brain? If the team stops neurons from releasing Arc, how does that affect an animal’s ability to learn or to form new memories? “I can see what people are thinking: Is memory a virus?” Shepherd says, laughing.
As if that wasn’t weird enough, other animals seem to have independently evolved their own versions of Arc. Fruit flies have Arc genes, and Shepherd’s colleague Cedric Feschotte showed that these descend from the same group of gypsy retrotransposons that gave rise to ours. But flies and back-boned animals co-opted these genes independently, in two separate events that took place millions of years apart. And yet, both events gave rise to similar genes that do similar things: Another team showed that the fly versions of Arc also sends RNA between neurons in virus-like capsules. “It’s exciting to think that such a process can occur twice,” says Atma Ivancevic from the University of Adelaide.
This discovery has medical implications, too. Arc has been implicated in many brain disorders, like Alzheimer’s, schizophrenia, and Fragile X syndrome. It might also be involved in the mental declines that accompany aging. Shepherd says that young mice produce lots of Arc protein, and old mice make much less. If he artificially boosts Arc protein levels in the visual centers of the brains of old mice, he can make them as responsive to new experiences as those of younger rodents.
“This may be the tip of a giant iceberg,” says Harmit Malik from the Fred Hutchinson Cancer Research Center. It’s entirely possible that animals which lack Arc genes, such as fish, “use entirely different domesticated gag proteins to achieve the same purpose.” Indeed, the human genome has more than 100 gag-derived genes. What are they all doing?
This is part of a broader trend: Scientists have in recent years discovered several ways that animals have used the properties of virus-related genes to their evolutionary advantage. Gag moves genetic information between cells, so it’s perfect as the basis of a communication system. Viruses use another gene called env to merge with host cells and avoid the immune system. Those same properties are vital for the placenta—a mammalian organ that unites the tissues of mothers and babies. And sure enough, a gene called syncytin, which is essential for the creation of placentas, actually descends from env. Much of our biology turns out to be viral in nature.
* This article has been corrected to reflect the fact that Arc genes were co-opted by animals from a group of genes that also gave rise to retroviruses, and are not directly descended from retroviruses, as originally stated. We regret the error.
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If every scar has a story, the moon has quite the tale to tell. Scientists using cameras onboard NASA’s Lunar Reconnaissance Orbiter have found 222 new craters — and discovered striking blast patterns caused by the shrapnel flung out from such violent impacts.
The findings, described in the journal Nature, could help researchers better pinpoint the ages of younger surfaces on the rocky satellite — and hint that the moon is a much more active world than it may seem.
“It’s really showing that the moon is a really dynamic place,” said study lead author Emerson Speyerer, a planetary scientist at Arizona State University.
The moon may not be as intriguing as Mars or mysterious as Jupiter’s moon Europa, but it has played a key role in our understanding of the age of rocky worlds like Earth. That’s because scientists have studied the rate of crater formation on the moon to help estimate the ages of other rocky bodies that, for the most part, we cannot easily sample.
And yet, while the moon’s ancient rate of cratering is pretty well understood, there’s surprisingly little known about the contemporary rate, Speyerer said. That’s because, as you try to age-date younger and younger surfaces (around the 50-million-year mark), you have to use smaller and smaller craters — and the rates for those tiny pockmarks are not well known.
Previous work had compared images from the Apollo missions in the 1970s to images taken by the Lunar Reconnaissance Orbiter in the 2009, in order to look for craters that had formed in the intervening decades. It was painstaking work, done manually, and the researchers found just five new craters in 44 image pairs.
For those scientists, “it was really difficult to go through and actually do that comparison,” Speyerer said.
For this study, he and his colleagues streamlined that process by designing a computer program to help compare 14,092 before-and-after snapshots of random spots that altogether covered about 6.6% of the lunar surface.
“It can take up to eight hours to manually go through an image but with our automatic routine, we can analyze a temporal pair image in about two to three minutes,” he said. “So we’re really cutting down on that time and allowing us to further investigate all of these changes we’ve been finding.”
The analysis turned up 222 new craters that appeared on the “after” images, but not the “before” snapshots, 16 of which were 10 meters in diameter or larger. That’s 33% higher than the current model, which puts the formation rate of such larger craters at just 12 per year.
By comparing the pairs of images (typically taken a year or six months apart), the researchers also discovered distinctive blast patterns caused by molten and vaporized rock jetting outward from the initial impact.
“That’s actually disturbing the surface hundreds and hundreds of crater diameters away from the impact site,” Speyerer said, “and that was something that was previously not really known.”
They also found that more than 47,000 changes in the moon’s surface reflectance (dubbed “splotches” in the paper), many of which are clustered around new impact sites — and many of which lie very far from the crater that probably caused them.
The scientists think that these splotches are caused by the surface regolith (or soil) getting churned up by debris flung out from the original crater impact.
“The impressive population of splotches compared to the number of new craters (47,000 versus about 220) stresses the importance of secondary impact processes on the lunar surface,” the authors pointed out in the study.
Based on these processes, the researchers estimate that the moon’s top two centimeters of regolith gets fully churned every 81,000 years or so — which is more than 100 times faster than previous estimates based on meteoritic impacts (roughly once every 10 million years).
These adjustments could make a big difference when trying to date relatively young surfaces on the moon, he added. If the impact rate is higher than previously thought, then those ages of these areas might actually be even younger than estimated, Speyerer said. This could inform any future plans to send humans back to the moon.
“This is also important if we’re going to put a long term habitat on the moon, a lunar base or something like that,” he said. “The odds of having a direct hit from a meteor or asteroidal material would be relatively small. However, if one occurred 30, 40 kilometers away, you might be getting a lot of these secondaries that are going to be coming over, hitting your lunar base and also messing up the regolith around you.”
Speyerer said he and his colleagues plan to keep scanning the surface to accumulate even more of these before-and-after image pairs. The more they analyze, the better they’ll understand the moon’s impact rate. | <urn:uuid:c91f9fec-9e6f-4698-a8ef-f9ac2c9a6a73> | 3.625 | 1,075 | News Article | Science & Tech. | 43.177989 | 95,591,013 |
A new study published today in the Proceedings of the National Academy of Sciences says we are dramatically underestimating the role inland fisheries play in global food security.
A UW–Madison engineering professor has designed a three-credit graduate course in a virtual university format, with live online lectures delivered to remote audiences.
“It’s a generally thorny problem and we are often scrambling to react,” says lead principal investigator Monica Turner. “In fact, understanding abrupt change in ecological systems is among the biggest challenges in contemporary ecology.”
New Integrative Biology Professor Hilary Dugan once worked as a research assistant in the Canadian Arctic and fell in love with fieldwork and studying global change. At some point, her interests narrowed to water, and eventually lakes.
Steve Carpenter couldn’t believe the view from his second-floor office on the shoreline of Lake Mendota. As far as he could see, the still water looked just like teal-blue paint.
Road salt is making North America’s freshwater lakes saltier, according to a new study published in the Proceedings of the National Academy of Sciences.
More than three decades of data on the physical, chemical and biological variables in 11 Midwestern lakes show that while lake temperatures and nutrient concentrations rise within relatively expected ranges, biological organisms achieve high population extremes.
While water clarity in most Wisconsin lakes has not changed in 20 years, researchers say the fact that more lakes are getting worse signals there is work to be done.
In the last four months, UW–Madison researchers have started to find zebra mussels congregating in large numbers all over Lake Mendota.
Data reveals increasing trends toward later ice cover formation and earlier spring breakup.
According to UW researchers, a single non-native species in a single inland lake has racked up $80 million to $163 million in damage. | <urn:uuid:d6caff39-dd60-443b-aa53-53ce5eb9f9f6> | 2.71875 | 381 | Content Listing | Science & Tech. | 24.643961 | 95,591,016 |
Minimum viable densities have rarely been determined directly. Theoretical analyses, based on empirical relationships between average mammal densities, suggest that minimum densities of viable populations are lower for larger mammals. This suggestion has been cast into doubt by other field studies showing populations of small insects and birds at very low densities. We collected 143 of the closest approximations of minimum viable density available, those of minimal, rare and endangered mammal populations. We found that minimal density decreases as the -0.68 power of body mass. Minimal densities of small mammals are 1000 times those of the largest species. The correlation between minimum viable population density and body mass is negative in the majority of the mammalian taxonomic orders. Although minimum density is, on average, 10% of mean population density, viable population densities of herbivores are 13 times those of carnivores and insectivores. Populations in the wet tropics can apparently sustain themselves at densities much lower than those in temperate climates.
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Geographic Variation and Distribution of Rock Shell, Thais clavigera (Gastropoda: Muricidae) in the Korean Coasts
- Son Min-Ho, Hong Sung-Yun
- 한국어업기술학회 in 2000
- Cited Count
In general, intertidal gastropods display a considerable amount of intraspecific shell variation (De Wolf et al., 1998). Particularly, thaisid species, including Thais clavigera(=T.c.), have been shown a variety of shell variation in the world ocean (e.g. T, emerginata in Kitching, 1976). Nomura (1926) noted local variation of shell morphology based on five Japanese populations. Ahe (1985) classified Japanese T.c. into two forms (Form-C ＆. -P). In the Korean waters, a strong variation in nodule shape of T.c, shell has also been noted by Choe ＆ Park (1997). Taxonomy of T.c. is controversial so far. (omitted)
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Access a range of climate-related reports issued by government agencies and scientific organizations. Browse the reports listed below, or filter by scope, content, or focus in the boxes above. To expand your results, click the Clear Filters link.
As incomes rise and populations grow, especially in the world’s hotter regions, the use of air conditioners is becoming increasingly common. In fact, the use of air conditioners and electric fans already accounts for about a fifth of the total electricity in buildings around the world–or 10 percent of all global electricity consumption. Over the next three decades, the use of ACs is set to soar, becoming one of the top drivers of global electricity demand. This new analysis by the International Energy Agency shows how new standards can help the world avoid facing such a “cold crunch” by helping improve efficiency while also staying cool.
The first-ever Annual Report from UN Climate Change lays out key 2017 achievements and points to the future of the climate change process. Throughout 2017, UN Climate Change continued to deliver on its core tasks: supporting the intergovernmental process, bringing transparency to climate commitments, supporting parties in building resilience and adapting to climate change, facilitating the mobilization of finance and diffusion of technology, and fostering cooperation with non-party stakeholders to realize the Paris Agreement’s potential. The report also looks at the outlook for the year ahead, including increasing the number of ratifications of the Doha Amendment to the Kyoto Protocol so it can enter into force, the Talanoa Dialogue which will inform and inspire parties as they increase their commitments, and adopting the outcomes of the work programme of the Paris Agreement at the end of 2018.
In the coming decades, Indiana’s changing climate will bring with it higher temperatures, longer heat waves, more extremely hot days, and more frequent extreme storm events. Those changes will affect the health of Hoosiers in every part of the state. This report describes historical and future climate-related health impacts that affect Indian residents; the findings presented here are primarily based on the Indiana Climate change Impacts Assessment Health Working Group technical report and the report Indiana’s Past and Future Climate.
Indiana’s climate is changing. Temperatures are rising, more precipitation is falling, and the last spring frost of the year has been getting steadily earlier. This report describes historical climate trends from more than a century of data and future projections that detail the ways in which our climate will continue to change.
Each year the Global Risks Report works with experts and decision makers across the world to identify and analyze the most pressing risks that we face. As the pace of change accelerates, and as risk interconnections deepen, this year’s report highlights the growing strain we are placing on many of the global systems we rely on. The top risks listed in this year's report, which reflect the concerns of global industry leaders, include extreme weather events, natural disasters, and failure of climate change mitigation and adaptation—ranked first, second, and fifth in likelihood and second, third, and fourth in impact, respectively.
The goal of this concerted effort is to help Thurston County (Washington) and the broader South Puget Sound region prepare for and adjust to climate change. The Thurston Regional Planning Council crafted this document with a $250,000 National Estuary Program grant from the U.S. Environmental Protection Agency and significant in-kind support from the community. Partners included representatives from tribes, municipalities, universities, nonprofits, businesses, and other entities within the project area: three geographically diverse watersheds (Nisqually, Deschutes, and Kennedy-Goldsborough) within Thurston County that drain into Puget Sound. The watersheds encompass beaches, rivers, lakes, wetlands, highlands, forests, farms, ranches, cities, towns, and tribal reservations. It is the Council's hope that other communities throughout the Puget Sound region, state, and nation will replicate this project’s science-based assessments, innovative public-engagement efforts (including development of a resilience game), collaborative planning processes, economic analyses, and comprehensive actions.
In 1950, fewer than one-third of the world's people lived in cities. Today more than half do. By 2050, urban areas will be home to some two-thirds of Earth's human population. This scale and pace of urbanization has never been seen in human history.
The report provides a foundation for new scientific collaborations on how cities function, how they grow, and how they can be managed sustainably for decades to come.
During late 2016, the National Integrated Drought Information System (NIDIS), the National Drought Mitigation Center (NDMC), the Midwestern Regional Climate Center (MRCC), and other regional partners convened four stakeholder meetings in the Midwest Drought Early Warning System (DEWS). Each of these meetings included a historical drought overview and climate outlook for the region, discussion of critical drought- related needs and challenges, exploration of available tools, local drought planning and management approaches, and strategy development to improve drought early warning and resiliency in the Midwest.
The Arctic shows no sign of returning to reliably frozen region of recent past decades. Despite relatively cool summer temperatures, observations in 2017 continue to indicate that the Arctic environmental system has reached a "new normal," characterized by long-term losses in the extent and thickness of the sea ice cover, the extent and duration of the winter snow cover and the mass of ice in the Greenland Ice Sheet and Arctic glaciers, and warming sea surface and permafrost temperatures. Issued annually since 2006, the Arctic Report Card is a timely and peer-reviewed source for clear, reliable, and concise environmental information on the current state of different components of the Arctic environmental system relative to historical records. The report is intended for a wide audience, including scientists, teachers, students, decision makers, and the general public interested in the Arctic environment and science.
This report acknowledges that climate adaptation has begun to emerge as a field of practice, but states that the work is not evolving quickly or deliberately enough for communities to adequately prepare for the dangerous shocks and stresses that increasingly will be introduced by climate change.
- assesses the current state of the climate adaptation field;
- provides a vision of what a mature, effective field would look like; and
- recommends steps that should be taken to realize that vision.
This BAMS special report presents assessments of how human-caused climate change may have affected the strength and likelihood of individual extreme events. This sixth edition of explaining extreme events of the previous year (2016) from a climate perspective is the first of these reports to find that some extreme events were not possible in a pre-industrial climate.
Coastal flooding in the United States is already occurring and the risk of flooding is expected to grow in most coastal regions, in part due to climate change. The Centers for Disease Control and Prevention developed this booklet, aimed at the general public, that identifies steps people can take to prepare for the health risks associated with coastal flooding. The booklet answers some of the key questions about coastal flooding in a changing climate: why these events are on the rise; how it might affect health; and what people can do before, during, and after a coastal flooding event to stay safe. Scientific information used in the document is derived from peer-reviewed synthesis and assessment products, including those published by the U.S. Global Change Research Program and the Intergovernmental Panel on Climate Change, as well as other peer-reviewed sources and federal agency resources.
Delaware is especially vulnerable to the effects of sea level rise (SLR) due to its flat topography, low mean elevation, and significant community development and infrastructure investments along the coast. Rates of relative SLR measured at tide gauges in and around Delaware are approximately twice the rate of global mean SLR. This report provides critical information on future sea level rise for Delaware's decision makers: it can help readers gain a comprehensive understanding of risk and the likelihood of worsening coastal flooding. In addition to the report, the Delaware Geological Survey worked with others to release an updated series of coastal inundation maps that depict the extent of potential inundation from current average high tide (MHHW level) to seven feet above in one-foot increments. These maps can be used as a planning tool for understanding potential future effects of sea level rise or storm surge.
The city of Cambridge, Massachusetts, is developing a Climate Change Preparedness and Resilience Plan as a practical guide to implement specific strategies in response to climate change threats (heat, flooding from precipitation, flooding from sea level rise and storm surge). The Alewife Preparedness Plan—the first neighborhood plan to be developed—will test how the proposed strategies might create a new framework for resiliency in Alewife. It comprises two parts: a Report and a Handbook. The Report provides the context, framework, and strategies to create a prepared and resilient Alewife neighborhood; the Handbook, a companion document, is a practical compendium of specific preparedness and resiliency strategies and best practices.
As a key part of the Fourth National Climate Assessment (NCA4), the U.S. Global Change Research Program (USGCRP) oversaw the production of this stand-alone report of the state of science relating to climate change and its physical impacts. The Climate Science Special Report (CSSR) is designed to be an authoritative assessment of the science of climate change, with a focus on the United States, to serve as the foundation for efforts to assess climate-related risks and inform decision making about responses.
As Volume 1 of NCA4, CSSR serves several purposes, including providing (1) an updated and detailed analysis of the findings of how climate change is affecting weather and climate across the United States; (2) an executive summary and 15 chapters that provide the basis for the discussion of climate science found in the second volume of NCA4; and (3) foundational information and projections for climate change, including extremes, to improve “end-to-end” consistency in sectoral, regional, and resilience analyses within the second volume. CSSR integrates and evaluates the findings on climate science and discusses the uncertainties associated with these findings. It analyzes current trends in climate change, both human-induced and natural, and projects major trends to the end of this century. As an assessment and analysis of the science, CSSR provides important input to the development of other parts of NCA4, and their primary focus on the human welfare, societal, economic and environmental elements of climate change. Much of the underlying report is written at a level more appropriate for a scientific audience, though the Executive Summary is intended to be accessible to a broader audience.
This report assesses county-level crop and cash rents estimates, and offers recommendations on methods for integrating data sources to provide more precise county-level estimates of acreage and yield for major crops and of cash rents by land use. The report considers technical issues involved in using the available data sources, such as methods for integrating the data, the assumptions underpinning the use of each source, the robustness of the resulting estimates, and the properties of desirable estimates of uncertainty.
A coalition of 26 businesses, environmental organizations, community groups, and universities in the Detroit area has produced the “Detroit Climate Action Plan.” The proposition intends to address public health and environmental justice issues through a plan that individuals and businesses can practice. The 77-page report contains 20 major goals for the coming years, including calls for the reduction of greenhouse gas emissions by Detroit businesses by 10 percent in the next 5 years, and 80 percent by 2050. Additionally, the plan recommends improvements to the energy efficiency and durability of homes, better stormwater runoff management, expanded use of renewable energy, and broadened recycling and organic waste collection by 2022.
On March 13, 2017, the Roundtable on Environmental Health Sciences, Research, and Medicine and the Roundtable on Population Health Improvement jointly convened a 1-day public workshop in Washington, DC, to explore potential strategies for public health, environmental health, health care, and related stakeholders to help communities and regions to address and mitigate the health effects of climate change. Participants discussed the perspectives of civic, government, business, and health-sector leaders, and existing research, best practices, and examples that inform stakeholders and practitioners on approaches to support mitigation of and adaptation to climate change and its effects on population health. This publication summarizes the presentations and discussions from the workshop.
This assessment was a multidisciplinary research project that investigated future changes to southern Santa Barbara County climate, beaches, watersheds, wetland habitats, and beach ecosystems. The target audience is local land use planners and decision makers, and the main objective is to provide information that assists the cities of Santa Barbara, Carpinteria, and Goleta, the County of Santa Barbara, and UC Santa Barbara in climate adaptation planning with a clear focus on coastal ecosystems.
Sea level rise was a major topic of the annual meeting of the National Academy of Engineering held on October 9–10, 2016, and the second day featured a forum on sea level rise adaptation. This summary of the forum, which also incorporates material from Robert J. Nicholls’ plenary presentation, outlines a rich and challenging set of problems for engineers, scientists, and those who work with them.
This report focuses on identifying, developing, and implementing strategies to increase the power system’s resilience in the face of events that can cause large-area, long-duration outages: blackouts that extend over multiple service areas and last several days or longer. Resilience is not just about lessening the likelihood that these outages will occur; it is also about limiting the scope and impact of outages when they do occur, restoring power rapidly afterwards, and learning from these experiences to better deal with events in the future.
From Mayor Mitchell J. Landrieu's Introduction: As we marked the 10th anniversary of Hurricane Katrina in 2015, we launched the world’s first comprehensive city resilience strategy, Resilient New Orleans, combining local expertise with global best practices to confront our most urgent threats, adapt our city to our changing natural environment, invest in equity, create flexible and reliable systems, and prepare for future shocks.
It is not enough to plan for how we will adapt to climate change. We must end our contribution to it. As the world committed to action in Paris in 2015, so too did we. I signed the Global Covenant of Mayors on Climate & Energy, adding New Orleans to the team of more than 7,400 cities in 119 countries worldwide committed to taking climate action.
In the aftermath of Tropical Storms Irene and Sandy, the population centers of Greater New Haven and Bridgeport recognized significant exposure and vulnerability to their infrastructure, environment, and socioeconomic assets from extreme weather events and a changing climate. To counteract immediate and longer-term risks and broaden dialogue on community resilience building, the Southern Connecticut Regional Framework for Coastal Resilience project was launched. The overarching goal of this project was prioritizing actions and strengthening partnerships by providing proactive risk assessment, community engagement, conceptual design of on-the-ground projects, and this Final Report. The principal purpose of the project was to advance a Regional Resilience Framework—built on projects and partnerships—needed to help improve resilience for over 591,000 residents that represent over 30 percent of Connecticut’s coast. A core goal of this project was to strengthen the resilience of existing and future ecosystems, including a diverse suite of services and co-benefits, alongside existing and future development activities within a population center critical to the state of Connecticut’s future.
Forest and grassland ecosystems provide a wide range of services, including wood products, recreation, wildlife habitat, and protection of water quality. These ecosystems are also extremely valuable for their ability to store carbon, with U.S. forests absorbing more than 600 million metric tons of carbon each year. This report describes the role of forests and grasslands in the carbon cycle and outlines considerations for managing for carbon as one of many environmental benefits provided by natural ecosystems. Land management activities can influence the ability of ecosystems to absorb and sequester carbon, as well as provide other ecosystem services, and this report explores considerations for land managers interested in increasing carbon benefits on the lands that they manage.
This Technical Report presents results from a large set of sectoral impact models that quantify and monetize climate change impacts in the U.S., with a primary focus on the contiguous U.S., under moderate and severe future climates. The report summarizes and communicates the results of the second phase of quantitative sectoral impacts analysis under the Climate Change Impacts and Risk Analysis (CIRA) project. The effort is intended to inform the fourth National Climate Assessment (NCA4) of the U.S. Global Change Research Program (USGCRP). The goal of this work is to estimate climate change impacts and economic damages to multiple U.S. sectors (e.g., human health, infrastructure, and water resources) under different scenarios. Though this report does not make policy recommendations, it is designed to inform strategies to enhance resiliency and protect human health, investments, and livelihoods.
The protocol developed and used in this report is unique in that it is an asset-level assessment of the vulnerability of infrastructure to multiple coastal hazards and climate change factors (e.g., erosion, flooding, storm surge, sea-level rise, and historical flooding) over a 35-year planning horizon (2050). The protocol was applied to all buildings and roads in Cape Lookout National Seashore; the results are summarized in the report.
Green infrastructure can help to maximize the environmental, economic, and social benefits of parks. This guide from EPA encourages partnerships between park agencies and stormwater agencies to promote the use of green infrastructure on park lands to improve park lands and access to parks, better manage stormwater, increase community resiliency to shifting weather patterns, and provide funding to implement and maintain park enhancements that benefit the community. Using a stepwise approach for building relationships with potential partners, the guide includes information on how to identify and engage partners, build relationships, involve the community, leverage funding opportunities, and identify green infrastructure opportunities. It includes recommendations on the types of projects that are most likely to attract positive attention and funding and that provide a wide range of benefits. Included case studies from across the country illustrate approaches presented in the guide.
The Tampa Bay region is known as one of the most vulnerable in the world to wind damage, coastal flooding from storm surge, and rising sea levels. The City of St. Petersburg—with over 60 miles of coastal frontage—has already felt the impacts of storms. The adverse effects from these types of environmental events often impact low-income communities the hardest, as they have the most difficulty bouncing back from stresses and shocks. The City of St. Petersburg is committed to ensuring that investments in making the city resilient are equitable and create a range of opportunities that everyone can benefit from. The Urban Land Institute of Tampa Bay convened top experts in climate resilience from New Orleans, Miami, Boston, and the Tampa Bay region to provide technical assistance to the city on creating an equitable culture of resilience. A grant from the ULI Foundation and Kresge Foundation funded this effort.
This guidebook results from the culmination of a year of dialogue among diverse stakeholders in southeastern Connecticut who defined challenges and solutions from extreme weather, climate change, and shifting social and economic conditions. Participants included representatives from nine municipalities, public and private utilities, public health departments, chambers of commerce, major employers, conservation organizations, academic institutions, community non-profits, and state agencies, among others. The dialogue captured six themed planning sectors (water, food, ecosystem services, transportation, energy, and regional economy) in a process that used surface and integrated solutions to address singular and multiple challenges across planning sectors. The guidebook provides a quick reference resource to help shape and inform actions that will advance a regional resilience framework for southeastern Connecticut; an accompanying Summary of Findings captures the project's final outcomes and conclusions, as well as providing a comprehensive account of the objectives, process, and details.
This plan sets forth the 2017 federal policy platform of the Mississippi River Cities and Towns Initiative, an association of 75 U.S. mayors along the Mississippi River. The document sets forth the mayors’ recommendation of federal programs to support and strengthen the built and natural infrastructure of the Mississippi River corridor, proposing specific funding levels and support of several federal programs. Suggestions for finance mechanisms to restore Mississippi River infrastructure are also included.
The sea ice surrounding Antarctica has increased in extent and concentration from the late 1970s, when satellite-based measurements began, until 2015. Although this increasing trend is modest, it is surprising given the overall warming of the global climate and the region. Indeed, climate models, which incorporate our best understanding of the processes affecting the region, generally simulate a decrease in sea ice. Moreover, sea ice in the Arctic has exhibited pronounced declines over the same period, consistent with global climate model simulations. For these reasons, the behavior of Antarctic sea ice has presented a conundrum for global climate change science. The National Academies of Sciences, Engineering, and Medicine held a workshop in January 2016 to bring together scientists with different sets of expertise and perspectives to further explore potential mechanisms driving the evolution of recent Antarctic sea ice variability and to discuss ways to advance understanding of Antarctic sea ice and its relationship to the broader ocean-climate system. This publication summarizes the presentations and discussions from the workshop.
This guide provides recommendations for effective education and communication practices when working with different types of audiences. While effective education has been traditionally defined as the acquisition of knowledge, Climate Change Education Partnership (CCEP) Alliance programs maintain a broader definition of “effective” to include the acquisition and use of climate-change knowledge to inform decision making. The CCEP Alliance is supported by the National Science Foundation to advance exemplary climate change education through research and practice.
A private group, the Climate Leadership Council, describes "How a new climate strategy can strengthen our economy, reduce regulation, help working-class Americans, shrink government & promote national security." The group of conservative elder statesmen that authored the statement call it the first time leading Republicans have put forth a concrete, market-based climate solution. Their recommendations are built on four pillars: (1) a gradually increasing carbon tax, (2) carbon dividends for all Americans, (3) border carbon adjustments, and (4) significant regulatory rollback.
This user-friendly summary is based on the 2015 report “City of Long Beach Climate Resiliency Assessment Report" and “Appendices” prepared by the Aquarium of the Pacific at the request of Mayor Robert Garcia. The report includes clear infographics that describe current and projected conditions in the city. It also describe what the city is currently doing and what else the city and its residents can do.
This report details the 2016 collaborative assessment project of the Upper Snake River Tribes Foundation and its member tribes—the Burns Paiute Tribe, the Fort McDermitt Paiute-Shoshone Tribe, the Shoshone-Bannock Tribes, and the Shoshone-Paiute Tribes—and partners Adaptation International, the University of Washington, and Oregon State University. The project assessed climate change vulnerability for the Upper Snake River watershed in Idaho, Nevada, and Oregon, and combined the best available localized climate projections with traditional knowledge, tribal priorities, and local observations to develop quantitative vulnerability rankings for 16 species of shared concern and a qualitative assessment for an additional 12 shared concerns. The set of 28 shared concerns assessed for climate change vulnerability provided a balanced cross-section of the species, habitats, and resource issues important to the tribes. Along with this report, the project also produced eight summary sheets detailing specific species and habitat vulnerability.
This draft Regional Action Plan in support of NOAA Fisheries Climate Science Strategy helps communicate a regional vision for climate-related science in the South Atlantic, providing a framework for scientists and managers to prioritize and accomplish research on climate-related impacts to marine and coastal ecosystems. It promotes scientists working with partners and the management community to construct management approaches that ensure the development of science-based strategies to sustain marine resources and resource-dependent coastal communities in a changing climate. Highlights include establishing a NOAA Fisheries South Atlantic Climate Science Team, expanding scientific expertise and partnerships, conducting vulnerability assessments for South Atlantic species, and drafting a South Atlantic Ecosystem Status Report. The draft was available for public comment through March 24, 2017; the Plan will be finalized in summer 2017. | <urn:uuid:919527bc-b70f-4653-b7fb-7c6339ca6d20> | 2.625 | 5,021 | Content Listing | Science & Tech. | 17.566517 | 95,591,043 |
Research could pave the way for new strong, conductive materials
Researchers have discovered a way to predict which alloys will form metallic glasses. The research could pave the way for new strong, conductive materials.
Metallic glasses are sometimes formed when molten metal is cooled too fast for its atoms to arrange in a structured, crystalline order. The result is a material with numerous desirable properties. Because they are metals, metallic glasses have high hardness and toughness and good thermal conductivity. Because their structure is disorganized, they are easy to process and shape and difficult to corrode. Thanks to these characteristics, metallic glasses are used in a wide array of applications, including electrical applications, nuclear reactor engineering, medical industries, structural reinforcement and razor blades.
While metallic glass has been around for decades, scientists have no clue which combinations of elements will form them. The only way to come up with new metallic glasses to date has been to cook up new recipes in the laboratory with only a few rules of thumb for guidance and hope for the best -- a costly endeavor in both time and money.
In a new study, however, researchers from Duke University, in collaboration with groups from Harvard University and Yale University, describe a method that can predict which binary alloys will form metallic glasses. Their technique involves computing and comparing the many pockets of different structures and energies that could be found within a solidified alloy.
The results were published August 2, 2016, in Nature Communications.
"When you get a lot of structures forming next to one another that are different but still have similar internal energies, you get a sort of frustration as the material tries to crystalize," said Eric Perim, a postdoctoral researcher working in the laboratory of Stefano Curtarolo, professor of mechanical engineering and materials science and director of the Center for Materials Genomics at Duke. "The material can't decide which crystalline structure it wants to converge to, and a metallic glass emerges. What we created is basically a measure of that confusion."
To determine the likelihood of an alloy forming a glass, Curtarolo, Perim and their colleagues broke its chemistry down into numerous sections, each containing only a handful of atoms. They then turned to a prototype database to simulate the hundreds of structures each section could potentially take.
Called the AFLOW library, the database stores information on atomic structures that are commonly observed in nature. Using these examples, the program computes what a novel combination of elements would look like with these structures. For example, the atomic structure of sodium chloride -- better known as salt -- may be used to build a potential structure for copper zirconium.
These simulations produce estimations of characteristics for hundreds of structural forms that a material could take. One characteristic, called an atomic environment, looks at the geometrical arrangement of an atom's closest neighbors. Another calculates the amount of energy stored in each of these atomic structures.
To determine the likelihood of an alloy forming a metallic glass, the program compares these two characteristics between the hundreds of different structures that could be found throughout the material. If groups of atoms near one another have similar energies, they want to form similar structures. But if the rapid cooling prevents this, a metallic glass emerges.
"The big advantage to our work is that it's high-throughput, because doing this experimentally is way too time-consuming," said Cormac Toher, an assistant research professor in Curtarolo's laboratory. "You cannot check all compositions of all systems in the laboratory. That would literally take forever. The idea behind this is that we can screen a large number of materials in a couple of days and single out the most likely ones that should be checked out."
The group then put their confusion-measuring program to the test to see if it could accurately predict metallic glasses that are already known. They were able to correctly identify 73 percent -- a number they hope will improve as they continue to increase the structural information and simulations stored in their database.
Based on their initial work, they believe about one-sixth of the alloys in their system should make metallic glass. That's more than 250 potential materials, of which only about a couple dozen have been discovered.
"If you go to Venice you'll see people blowing bottles of glass," said Curtarolo. "You can do that with metallic glasses as well. You can make lightweight, very durable objects without any seams. But trying to scale these up is difficult. The larger the lump, the longer it takes its center to cool, and the more likely it is to form a normal crystalline structure. But there might be undiscovered chemical combinations that would be easier to work with, cost less, or have other, more desirable properties. We just have to figure out where to look for them."
Besides refining their results for binary alloys, the researchers plan to extend their algorithm to alloys that contain three elements, as they are more likely to form glasses but are much more difficult and time-consuming to model. Their database, however, has only about one-tenth of the entries for these alloys as it does for binary alloys, so computer clusters around the world will first need to work for some time to come.
This research was supported by the National Science Foundation (DMR-1436151, DMR-1436268, DMR-1435820).
CITATION: "Spectral Descriptors for Bulk Metallic Glasses Based on the Thermodynamics of Competing Crystalline Phases." Eric Perim, Dongwoo Lee, Yanhui Liu, Cormac Toher, Pan Gong, Yanglin Li, W. Neal Simmons, Ohad Levy, Joost J. Vlassak, Jan Schroers and Stefano Curtarolo. Nature Communications, Aug. 2, 2016. DOI: 10.1038/NCOMMS12315
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The bigger the male, the higher his chances to successfully mate – this applies, at least, to thrips, insects measuring only two to three millimetres in length that are hard to recognise with the naked eye. The larger males not only drive off their smaller rivals, they also have better immune systems and produce more sperm. This is a discovery that was made by biologists at Martin Luther University Halle-Wittenberg (MLU). Their study recently appeared in the international "Journal of Insect Behaviour".
"Larger males have better chances of procreating than their smaller rivals," says Dr Stephanie Krüger, the study’s lead author. The researcher works alongside Dr Gerald Moritz, a professor of biology from Halle who has been studying thrips for many years. Krüger has investigated a species of thrips called Echinothrips americanus which is only 1.3 millimetres in size.
This species is a pest insect that came to Europe from the USA at the end of the 20th century and is now a common occupant of Germany’s greenhouses. These small insects, which belong to the order Thysanoptera, shouldn’t be underestimated as the damage they cause to the agriculture industry and the horticulture sector can run into the millions.
There are many reasons why the larger males have a higher reproduction success rate. "For one thing, strong males drive off their smaller rivals. Their size also allows them to more easily mount females when mating," says Krüger.
Added to this is the fact that females from many different species of insect prefer larger males as they promise a higher probability of survival for the eggs and offspring. Furthermore, the animals produce more secretions, which females use as nutrients during egg production. There is even a benefit to male fertility: they produce more sperm.
Until recently little had been scientifically known about the reproductive biology of thrips. The biologists from Halle were able to refute, for example, the wide-spread hypothesis that so-called sternal glands impact mating success. The actual purpose of these glands, located on the insect’s abdomen, remains unclear. Krüger has a hypothesis, and further research should allow her to determine whether male thrips guard the pupae with the intention of being the first to mate with the hatched females.
"We presume that the males mark the territory they are guarding," says Krüger. If they have a larger pore plate, and consequently more sternal glands, they have an advantage over other males by being able to demarcate their territory. The biologist would also like to analyse whether the females actively seek out their mates or whether the larger males are more successful in finding a copulation partner due to their higher levels of aggression.
The research division "Development Biology" at MLU, led by Professor Gerald Moritz, has been studying thrips for many years. More than 6,100 species belong to their order. These micro-insects, with their stinging and sucking mouthparts, have caused a great deal of resentment in the agriculture industry. They infest cut flowers and damage fruit and vegetables by boring into the plant cells and extracting cell sap.
For instance, they have diminished harvest yields of strawberries in the USA and Germany. In addition, several species transmit major plant viruses. Thrips are also a nuisance in the living rooms of plant lovers throughout the country. Their sucking leaves behind an optically displeasing, silver-grey discoloration on indoor plants like the rubber plant and palms.
Krueger, S., Jilge, M., Mound, L., G. Moritz J Insect Behav (2017) 30: 409. doi: 10.1007/s10905-017-9627-z
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CERN experiment sets precision record in the measurement of the antiproton to electron mass ratio using a new innovative cooling technique
According to the Standard Model of elementary particle physics, to each particle exists an antiparticle that is supposed to behave exactly the same way. Thus, “anti-people” in an “anti-world” would observe the same laws of physics, or make the same experiences in general, as we do.
This postulate is, however, difficult to prove, since it is almost impossible to perform measurements on antimatter: whenever an antiparticle meets is matter-counterpart, both particles annihilate, accompanied by the creation of energy. However, a team of scientists from the Max Planck Institute of Quantum Optics and Tokyo University (Japan), and including the University of Brescia (Italy), and the Wigner Research Centre for Physics (Budapest, Hungary), has found a way to overcome this hurdle: In an experiment carried out at the European Laboratory for Particle Physics (CERN) in Geneva (Switzerland) they trap an antiproton inside a helium atom.
As due to a new cooling technique the helium atoms are almost at rest, high precision spectroscopy measurements are made possible. “For the mass of the antiproton relative to the electron we have achieved the unprecedented accuracy of 800 parts per trillion,” says Dr. Masaki Hori, leader of the research group “Antimatter Spectroscopy” which is associated with the Laser Spectroscopy Division of Prof. Theodor W. Hänsch at MPQ. (Science, 4 November, 2016).
In 1997, researchers from the Max Planck Institute of Quantum Optics in cooperation with other European, Japanese, and American groups began construction of a facility called the Antiproton Decelerator (AD) at CERN. Here antiprotons produced in high-energy collisions are collected and stored in a vacuum pipe arranged in a 190-m-long racetrack shape. The antiprotons are gradually slowed down, before being transported to several experiments.
The so-called ASACUSA (Atomic Spectroscopy and Collisions using Slow Antiprotons, named after a district in Tokyo) collaboration, of which Dr. Hori is one of the project leaders, sends the antiprotons into a helium gas target. Normal helium atoms consist of a nucleus with two electrons orbiting around it. When the antiprotons hit the helium atoms, about 3% of the antiparticles replace one of the electrons, resulting in antiprotonic helium.
The antiproton finds itself in an excited orbit some 100 picometres (10-10 m) from the nucleus. In order to determine its mass the scientists perform precision spectroscopy: they fire a laser beam onto the atom, and carefully tune its frequency until the antiproton makes a quantum jump from one energy orbit to another. By comparing this frequency with theoretical calculations, the mass of the antiproton can be determined relative to the electron.
However, an important source of imprecision remained so far, because the antiprotonic atoms move around randomly according to their thermal energy, so that atoms moving towards the laser beam experience a different frequency compared to those moving away. The new major achievement of the collaboration as reported in Science, lies in the fact that ASACUSA now managed to cool down the antiprotonic helium atoms to temperatures close to absolute zero - between 1.5 and 1.7 Kelvin.
“We cooled down the atoms using buffer-gas cooling,” explains Dr. Hori. “It is surprising that this method works at all, because normally – if you use normal matter atoms to cool a half-antimatter atom – you would expect that the atom would annihilate instead of cooling down. But here annihilation is prevented because the antiproton is safely shielded by the electron.”
The new measurements, based on data collected from 2010 to 2014, with about 2 billion atoms, showed that the antiproton is 1836.1526734(15) times heavier than the electron, the parenthesis showing the 1-standard deviation imprecision. This is in excellent agreement with a recent experimental value for the proton-to-electron mass ratio.
Physicists believe that the laws of nature obey a fundamental symmetry called “CPT” (this stands for charge conjugation, parity, and time reversal), which postulates that if all the matter in the universe were replaced with antimatter, left and right inverted as if looking into a mirror, and the flow of time reversed, this “anti-world” would be indistinguishable from our real matter world. If scientists were to experimentally detect any deviation, however small, it would indicate that this fundamental symmetry is broken. And this could possibly lead to an explanation of why the universe we live in is made entirely of matter, whereas at the beginning of the universe, in the “big bang”, matter and antimatter was created in the same amount.
“We are confident that we will be able to even improve this precision by combining buffer-gas cooling with two-photon spectroscopy, a method that by itself reduces uncertainties caused by the Doppler-effect”, resumes Masaki Hori. To this end, a new experiment at CERN named ELENA is planned. Olivia Meyer-Streng
Figure caption: Sketch of the experimental setup used at CERN for the determination of the antiproton-to-electron mass ratio. Graphic: Masaki Hori
Masaki Hori, Hossein Aghai-Khozani, Anna Sótér, Daniel Barna, Andreas Dax, Ryugo Hayano, Takumi Kobayashi, Yohei Murakami, Koichi Todoroki, Hiroyuki Yamada, Dezső Horváth, Luca Venturelli
Buffer-gas cooling of antiprotonic helium to 1.5-1.7 K, and
antiproton-to-electron mass ratio
Science, 4 November 2016, DOI: 10.1126/science.aaf6702
Dr. Masaki Hori
Max Planck Institute of Quantum Optics
Hans-Kopfermann-Str. 1, 85748 Garching, Germany
Phone: +49 (0)89 / 32 905 -268
Dr. Olivia Meyer-Streng
Press & Public Relations
Max Planck Institute of Quantum Optics
Hans-Kopfermann-Str. 1, 85748 Garching, Germany
Phone: +49 (0)89 / 32 905 -213
Dr. Olivia Meyer-Streng | Max-Planck-Institut für Quantenoptik
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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A masterly use of chemistry and physics
A little amount of appropriately prepared powder is poured in water polluted with phenol and cellulose. A bit of the sun and after fifteen minutes harmful compounds disappear, and the powder can be filtered off and reused. Sounds like a fairy tale? Perhaps, but it is not magic, only a masterly use of chemistry and physics by researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw.
Many areas worldwide are affected by the problem of growing water pollution by wastes from wood and paper industries, including cellulose and phenol derivatives. Removal of these agents from water can be easier in future due to low cost and easy-to-produce photocatalysts developed by Dr Juan Carlos Colmenares’ group from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw.
Catalysts are substances that participate in the chemical reactions, speed their courses and (almost) fully recover after the reactions are completed. In typical catalytic processes the catalysts must be activated at high temperatures, typically of several hundred degrees centigrade, often at a significantly increased pressure.
The photocatalysts designed and synthesised at the IPC PAS are much less demanding. They are activated by solar or UV light, and the actual chemical reaction can take place at a temperature of about 30°C and under normal pressure. Such conditions naturally occur in many places on Earth.
The crucial component of the new photocatalysts is titanium dioxide doped with small amount of iron or chromium atoms. All these materials are commonly available and cheap. The photocatalysts are deposited on appropriate supports – silica grains or zeolites (aluminosilicates) – using common laboratory equipment: a rotary evaporator and an ultrasonic bath.
“Ultrasonic irradiation of a solution containing precursors of titania and chromium or iron generates microbubbles of high pressure and temperature. We can manage these conditions and prepare nanocomposite materials which are very stable”, explains Dr Colmenares.
Chromium or iron doped catalytic materials so prepared have been studied and characterised in detail at the Institute of Physical Chemistry of the PAS and by the Prof. Krzysztof Kurzyd?owski’s research group from the Faculty of Materials Science and Engineering, Warsaw University of Technology.
How do the new photocatalysts clean water? In laboratory conditions the process takes only 15-20 minutes and consists in pouring powder with photocatalyst in water. Then, short exposure to solar radiation is sufficient to make disappear water polluting cellulose or phenol derivatives.
Silica supported photocatalysts turned out to be particularly effective in phenol removal, leading to a high degree of phenol oxidation and yielding water and carbon dioxide as the reaction products. Zeolite supported systems catalysed glucose partial degradation (glucose is a monomer, and thus a basic “brick” forming cellulose polymer chains) resulting in formation of, e.g., gluconic and glucaric acids, important carboxylic acids used in food, pharmaceutical and cosmetic industries.
What’s particularly important is that the analyses performed by Dr Colmenares’ group clearly prove that there is no release of chromium or iron atoms to water during the entire cleaning process.
After the reaction is completed, the photocatalyst can be easily recovered. Due to durable deposition on silica or zeolite particles of relatively large (micrometric) size, it’s enough to filter water to get the catalyst back. The recovered powder can be reused, and multiple repetition of the cycle does not significantly affect the catalyst performance.
The new catalysts can also be used outside the industry. Coatings manufactured of these materials have sufficient mechanical strength to be used, e.g., as swimming pool accessories. With good solar insolation, water in a swimming pool constructed with the use of such materials would be subject to continuous self-cleaning process.
“Essential advantages of our photocatalysts include simplicity of production, low manufacturing costs and convenience of performing chemical reactions under natural conditions. Equally important is that our materials allow to stop oxidizing water pollutants at desired stage and to obtain substances important for the industry”, stresses Dr Colmenares.
The Latest on: Photocatalysts
A futuristic way of making oxygen in zero-G could save us as we head to Mars and deep space
on July 16, 2018 at 9:29 am
An alternate method that weighs much less involves photocatalysts, which use a semiconductor submerged in water to accelerate the reaction by absorbing photons (light particles). Electrons in the semi... […]
Scientists Will Produce Oxygen From Just Water In Zero Gravity
on July 12, 2018 at 11:26 pm
On Earth, this process involves solar cells to capture sunlight and convert this into a current. The alternative is to use photocatalysts. It works by absorbing light particles into a semiconductor ma... […]
IIT-J Uses Rajasthani Clay to Clean Water In A Low-Cost & Eco-Friendly Way!
on July 12, 2018 at 2:26 am
Describing the technology, Sharma told The Times of India that when photocatalysts are exposed to sunlight, reactive oxygen is formed which destroys the contaminants present in the water. “However, pr... […]
Berkeley Lab Hosts Eight CSGF Fellows in 2018
on July 6, 2018 at 6:47 am
Recently, the group searched over tens of thousands of materials to identify a set of materials that may be promising photocatalysts for carbon dioxide (CO 2) reduction. Working with the team, Torrisi ... […]
Scanning tunneling microscopy reveals molecular dissociation induced by localized surface plasmons
on July 6, 2018 at 1:29 am
Such photocatalysts are attractive from an environmental perspective since chemical reactions could be assisted by sunlight. But to design more-efficient photocatalysts for chemical reactions requires ... […]
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Piqued Lite - 7/30/2017 - "Kepler-1625B I", The Promising New Candidate May Be The First Ever Discovered Exomoon
To Earthlings the Moon is as normal as the blueness of the sky or the rising of the sun.
We all know. The moon is there, we all see it almost every night, and it is no longer particularly exciting for the layman.
However, the moon plays a ton of important roles for the benefit of human life on Earth. It functions as a shield for space debris and it's gravity affects the winds and the tides, just to name a couple of effects.
Moreover, the moon is an amazing remnant of the Earth's violent history, probably forming in the countless millions of years following the colission of the Earth with another solar body.
Because the presence of a moon speaks to both the creation of a planet and its potential habitability, astronomers are very interested in discovering not just exoplanets, but exomoons as well.
However, this can be very hard to do. We've only just got good at looking for full planets revolving around distant stars using fairly small changes of light as our guides. To look for a moon is an even greater challenge.
Thankfully, astronomers are up to the task. Using the Kepler space telescope they have measured the transit of more than two hundred newly discovered exoplanets in search of a potential exomoon and found one tantilizing possibility, which they're calling Kepler-1625B I.
This still needs to be confirmed, but there is a plan to use the Hubble Space Telescope to do just that. If the discovery bears out, it would be another momentous achievment enabled by Kepler | <urn:uuid:dd2bd9f9-ce88-46f1-86ba-63bf8e7bcc8b> | 3.484375 | 357 | Truncated | Science & Tech. | 49.618287 | 95,591,075 |
Scientists at the Carnegie Institution determined that over a 23-year span from 1979 to 2001 the jet streams in both hemispheres have risen in altitude and shifted toward the poles. The jet stream in the northern hemisphere has also weakened. These changes fit the predictions of global warming models and have implications for the frequency and intensity of future storms, including hurricanes.
Cristina Archer and Ken Caldeira of the Carnegie Institution’s Department of Global Ecology tracked changes in the average position and strength of jet streams using records compiled by the European Centre for Medium-Range Weather Forecasts, the National Centers for Environmental Protection, and the National Center for Atmospheric Research. The data included outputs from weather prediction models, conventional observations from weather balloons and surface instruments, and remote observations from satellites. The results are published in the April 18 Geophysical Research Letters.
Jet streams twist and turn in a wide swath that changes from day to day. The poleward shift in their average location discovered by the researchers is small, about 19 kilometers (12 miles) per decade in the northern hemisphere, but if the trend continues the impact could be significant. “The jet streams are the driving factor for weather in half of the globe,” says Archer. “So, as you can imagine, changes in the jets have the potential to affect large populations and major climate systems.”
Storm paths in North America are likely to shift northward as a result of the jet stream changes. Hurricanes, whose development tends to be inhibited by jet streams, may become more powerful and more frequent as the jet streams move away from the sub-tropical zones where hurricanes are born.
The observed changes are consistent with numerous other signals of global warming found in previous studies, such as the widening of the tropical belt, the cooling of the stratosphere, and the poleward shift of storm tracks. This is the first study to use observation-based datasets to examine trends in all the jet stream parameters, however.
“At this point we can’t say for sure that this is the result of global warming, but I think it is,” says Caldeira. “I would bet that the trend in the jet streams’ positions will continue. It is something I’d put my money on.”
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Black Hole-Powered Jet of Electrons and Sub-Atomic Particles Streams From Center of Galaxy M87. Credit: NASA and The Hubble Heritage Team [STScI/AURA].
Motion of a Spinning Top
There are many forms and shapes of spinning tops, and they are put into motion in an interesting variety of ways. Some are spun by snap-twisting a center stem with your fingers and releasing. Others are spun using a cord. Regardless of how the tops are spun, they behave in a similar fashion. | <urn:uuid:4c2568f4-2109-4b89-b600-cd1754f73d5f> | 2.96875 | 111 | Knowledge Article | Science & Tech. | 56.660714 | 95,591,096 |
+44 1803 865913
Series: Environmental Education, Communication and Sustainability Series Volume: 21
Edited By: Walter Leal Filho, Dieter Greif and Bernd Delakowitz
227 pages, diagrams, b&w photos
The sustainable use of river basins is one of the top environment priorities in Europe. There are many initiatives aimed at the promotion of the sustainable development of river areas around the Baltic and around Europe as a whole, a process greatly accelerated by the introduction of the Water Framework Directive (WFD), which obliges all EU countries to improve the standards in which they use their water and river resources.
This book, prepared in the context of the Interreg IIIB Project Watersketch, is an attempt to promote a dialogue on the topic, linking aspects of sustainable biochemistry and biotechnology with elements of sustainable river management. It will serve the needs of water and river management specialists in two ways: it presents various scientific and technological approaches to river management and illustrates the epistemological breadth of the discipline, and also builds on specialised topical biotechnological and chemistry-related knowledge. The latter is especially useful to geographers and planners alike, who could perhaps adapt some of the techniques and components illustrated in the various chapters of this book to their own work.
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Applied and Economic Aspects of Sabkha Systems — Genesis of Salt, Ore and Hydrocarbon Deposits and Biotechnology
The huge salt reservoirs of the Permian (Zechstein) in Europe have very striking similarities with sabkhas. Furthermore, many of these salt systems are related to petroleum-producing strata and traps.
Recently much interest has focused on marine salt production plants mainly in the Caribbean and the Pacific. Biological factors, and among them almost exclusively those produced and controlled by prokaryotic phototrophic microorganisms, have been found to be most important in the production of large crystal-sized clear and pure salts with as little iron admixture as possible.
Practicians of applied geology have realized that many if not all of the huge or and phosphate deposits of the Precambrian and later periods of Earth history, when initially sedimentary, are at least partially interconnected with environmental conditions typical for present-day sabkhas.
Petroleum geologists and organic geochemists have concluded that many, if not most, of the hydrocarbon and gas-generating systems in the past are related to sabkha-type evaporative ocean margins.
Furthermore, the capacity of many microorganisms to develop very individual osmotic pressure regulation systems, e.g., glycerol, cation pumping, light energy driven membrane potentials (see Chap. 13), has attracted interest of biotechnologists for applications in bioengineering. Several other products and processes of halophilic microorganisms are also of applied interest.
Also several aspects of salt-water agriculture, as an alternative using marine microorganism or salt-walter plants, and the study of soil biology under saline conditions (Mykorrhyza, Rhizobium, etc.) have encountered growing interest. This interest will most probably increase in the near future.
Finally, salt-water microbiology has important aspects in the management of the growing number of desalination plants in semi-arid and arid countries. This concluding chapter thus tries to explain to some extent why the ecology and bio-geochemistry of sabkhas is an important field of research and why biochemical and biotechnological aspects have to be involved into these studies.
KeywordsSalt Deposit Spirulina Platensis Petroleum Geologist Great Salt Lake Hypersaline Environment
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These gamma rays, called MEGa-rays (for mono-energetic gamma rays), are made by using a beam of fast-moving electrons to convert laser photons (light at a lesser energy) into the gamma ray part of the spectrum.
The incoherent gamma rays can be tuned to a specific energy so that they predominantly interact with only one kind of material. A beam of MEGa-rays, for example, might be absorbed by the nuclear fuel uranium-235 while passing through other substances including the more common (but less dangerous) isotope uranium-238. That sort of precision opens the door to “nuclear photonics,” the study of nuclei with light.
“It is kind of like tunable laser absorption spectroscopy but with gamma-rays,” says Chris Barty of Lawrence Livermore National Laboratory, who will present on MEGa-rays at this year's Conference on Lasers and Electro Optics (CLEO: 2011, May 1- 6 in Baltimore) .
In the last couple of years, MEGa-ray prototypes have identified elements like lithium and lead hidden behind metal barriers. The next-generation of MEGa-ray machines, which should come on-line in a couple of years, will be a million times brighter, allowing them to see through thick materials to locate specific targets in less than a second.
Barty will present several MEGa-ray applications in use today and will describe the attributes of next-generation devices. Work is under way on a MEGa-ray technology that could be placed on a truck trailer and carried out into the field to check containers suspected of having bomb material in them. At nuclear reactors, MEGa-rays could be used to quickly identify how enriched a spent fuel rod is in uranium-235. They could also examine nuclear waste containers to assess their contents without ever opening them up. MEGa-ray technology might also be employed in medicine to track drugs that carry specific isotope markers.
Presentation ATuF2, “Mono-Energetic Gamma-rays (MEGa-rays) and the Dawn of Nuclear Photonics,” by Chris Barty is at 4:30 p.m. Tuesday, May 3.
Plenary Session keynote speakers include Donald Keck, retired vice president of Corning, talking about making the first low-loss optical fibers; James Fujimoto of MIT, talking about medical imaging using optical coherence tomography (OCT); Mordechai (Moti) Segev of the Technion-Israel Institute of Technology, speaking about the localization of light; and Susumu Noda of Kyoto University, talking about the control of photons in photonic crystals.
Online resources:• Conference program: http://www.cleoconference.org/Conference_Program
• Conference Registration: http://www.cleoconference.org/registrationPress Registration
Angela Stark | Newswise Science News
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...
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Today’s announcement by federal agriculture minister David Littleproud to establish an office of environmental biosecurity will better prepare Australia to prevent and respond to new harmful pest, weed and disease invasions.
Our case studies of dangerous invasive species that have made it into Australia or are likely to arrive illustrate the need for changes in how Australia prevents the establishment of new invasive species. The case studies are made up of our ‘dirty dozen’, 12 dangerous invasive species that have made it past Australia’s border controls…
As long as Australia has weak biosecurity laws dangerous new environmental invaders will continue to steal into our country. They come in many forms, as weedy garden species, hidden in cargo ships or even brought in and sold as ‘pets’. In the invasion timeline below we’ve listed new invasive species we know have been found…
Bulldoze trees, and you wipe out plants and animals. Introduce a new predator, competitor or disease or let a weed take over can just as effectively send species on the road to extinction.
The fifth Island Arks Symposium had many important take-home messages, but the one that stood out for our CEO Andrew Cox was that invasive species issues on Pacific islands are becoming ‘agonisingly important’.
Fact Sheets, Reports & Submissions
Habitat loss is often assumed to be the main threatening process in Australia. This compilation of evidence demonstrates that invasive species are the main threat facing Australias declining mammals and frogs and, along with habitat loss and potentially climate change, represents one of the three main threats to biodiversity.
A submission consisting of 15 case studies that form an attachment to the primary submission to the Senate inquiry into preventing new invasive species. | <urn:uuid:4bd9064d-a191-480e-97b9-93ed7a975276> | 3.046875 | 360 | Content Listing | Science & Tech. | 20.153 | 95,591,179 |
jacc in the box - extra stuff -back-
Science from the Soap Box
gravity and mass
There's a real problem in the scientific community—a lot of 'em believe that everything, by way of particles and forces, need to be symmetrical.
The stark reality is that these guys can aspire to symmetry and order on a chalk board but are faced with the undeniable fact that the universe is in actuality asymmetrical and chaotic.
For this discussion let's look at the four forces: strong, weak, electro-magnetism and gravity.
Currently there are theories that can explain all of them except for gravity, and the problem with gravity is two fold.
First, there is no observable messenger-particle like the photon is in electro-magnetism.
Secondly, gravity is so damned weak, so imperceptively feeble when compared to electro-magnetism at the nano scale, that the science geeks cannot accept it.
To them it's so not possible.
Some interesting theories have sprung up (e.g. supergravity) that require dimensions to be real for their ideas to hold true.
I almost feel sorry for the people that thought them up because here I come out of the blue to piss in their Cheerios.
It's been my contention that dimensions do not exist so, if I'm right, then the force of gravity does not percolate up through a million-billion parallel universes making gravity a force we share amongst all.
To me this is so not possible.
However, in the spirit of fair play, I'll go out on a limb here and say that maybe there is a symmetry between electro-magnetism and gravity.
We always think that symmetry must exhibit the same characteristics, but that does not necessarily have to be.
Electro-magnetism is over a million-billion times stronger than gravity, yes, but its reach is short to be sure.
On the other hand gravity has a reach that exceeds electro-magnetisms reach by that same factor and therein lies a symmetry of sorts.
It is counterintuitive but argumentatively sound.
However, and this is big, the problem with this discussion is that gravity is a totally passive force akin to vacua energy (i.e. dark energy) and is not a force in league with the strong, weak or electro-magnetic forces.
Think about it—there are no messenger particles associated with gravity that can be observed, measured or manipulated.
Whether you accept the idea from Einstein that mass warps the fabric of space and that objects "gravitate" towards one another because of said warping, or if you accept my idea of spacial displacement where mass stretches the particulate structure of space in a like manner, the same holds true.
Gravity happens to be passive, and where matter is drawn towards a vacuum the same can be said for objects with mass and how they "fall" (i.e. slide) towards one another other through their respective warp signature footprints in space.
If either of those ideas are true then gravity, like vacua, does not exist as a force as we know it.
As it is with time and dimensions we see gravity in a completely wrong light.
It is not a substantive thing like electro-magnetism and photons, but the by-product of the effect mass has on space.
If this is so then it begs to be asked...how exactly does mass factor in?
There's a problem with mass—we can't seem to find it.
We're spending billions building ever so stronger atom smashers just to shatter protons at higher energy levels all in search of the elusive Higgs Boson.
Not to say it's a wasted effort but a particle such as the Higgs should jump out at you like a Roman candle.
So far they've had no luck. (update below)
I can't seem to buy into the reintroduction of aether—what is now called the Higgs-Scalar Field.
I find it as unpalatable as branes (membranes) in string theory.
Admittedly I do not know much about the Higgs-Scalar Field and how it ties into the W and the Z bozon, but if the field has no associated force and messenger particle then go away.
Figure out how maybe photon's factor in all this and you'll have my attention.
I'll be all ears but until then...
As an alternative, and this may sound pretty crazy, but maybe mass is a force, id est a consequence of the electro-magnetic/weak processes?
If they actually find a mass particle it is logical to assume that without some force involved then mass would be inert and have no direct effect or tug on space.
Since they can't find mass per se it is my suggestion that photons, performing their electro-magnetic/weak duties, may very well be the (or part of the) mechanism(s) that is tugging on the structure of space and creating both the gravitational phenomena and mass as an expression of resistance.
Without some tangible force there would be no substantive mechanism to draw space towards what would be in fact the dynamical illusion of mass.
So, I'm calling it...
Photons of the electro-magnetic/weak force is ultimately responsible for what we perceive as mass and gravity is the by-product of its effect on the structure of space.
Since I'm not a mathematician, can't even fake it, here is where I extend the offer to some dork, who will stop giggling about what they just read, and do the math.
That dork, if he or she publishes, will win the hatred of the physics community and a trip to Sweden.
So, dork-tron, have a nice flight.
Now, if this idea here does not work for you then I have another idea that's a twist on the one above.
I've posted that at the end of the next article re EM scale and photons because it made more sense there.
The idea is pretty crazy so consider yourself warned.
nicholas ralph baum
December 4, 2010
UPDATE (7/5/2012) It appears that preliminary reports out of CERN is that they may have found the Higgs!
It would be kinda cool if they do validate the Standard Model once and for all, but I still have a problem with the Higgs Field.
As with gravity and dark energy I believe that we have a distorted view of what mass is.
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A new study based out of the University of Arizona shows that climate-prediction models are indeed good at forecasting long-term (over 30 years) climate patterns on a global scale, but deteriorate when applied to smaller, geographical regions and with time frames that are less than 30 years.
The research team evaluated 7 computer simulation models used to compile the reports that the IPCC issues every six years. The researchers fed historical climate records into the models and compared their results to the actual climate change observed between then and now, according to the story.
The team evaluated climate predictions from 1900 into the future, such as 10, 20, 30, 40 and 50 years. Then the same starting in 1901, 1902 and so forth, and applied statistics to the results.
The goal of the study was to bridge the communities of climate scientists and weather forecasters, who sometimes disagree with respect to climate change, according to Xubin Zeng, a professor in the University of Arizona department of atmospheric sciences.
Excerpts from the University of Arizona News story......
“Climate scientists are correct because we do show that on the continental scale, and for time scales of three decades or more, climate models indeed show predictive skills. But when it comes to predicting the climate for a certain area over the next 10 or 20 years, our models can’t do it," said Zeng, who serves on the Board on Atmospheric Sciences and Climate of the National Academies and the Executive Committee of the American Meteorological Society.
The skill of a climate model depends on three criteria at a minimum, Zeng explained. The model has to use reliable data, its prediction must be better than a prediction based on chance, and its prediction must be closer to reality than a prediction that only considers the internal climate variability of the Earth system and ignores processes such as variations in solar activity, volcanic eruptions, greenhouse gas emissions from fossil fuel burning and land-use change, for example urbanization and deforestation.
“Our analysis confirmed what we expected from last IPCC report in 2007,” said Koichi Sakaguchi. “Those climate models are believed to be of good skill on large scales, for example predicting temperature trends over several decades, and we confirmed that by showing that the models work well for time spans longer than 30 years and across geographical scales spanning 30 degrees or more."
------- This research was published in the Journal of Geophysical Research-Atmospheres.
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Data indicates that there has been a slight downward trend in the annual maximum extent of Great Lakes ice cover since the 1970s.
A new study concludes that global warming may eventually be twice as warm as what current climate model consensus indicates.
The increased use of air conditioning in a warming world may lead to a significant degradation of air quality in the eastern U.S. by mid-century.
Dr. James Hansen's climate model projections from the 1980s have been mostly on target.
May 2018 and the spring of 2018 both ranked in the top five warmest on record.
Rate of ice loss in Antarctica has tripled over the past decade.
A combination of a warming climate climate and increased urbanization (heat island effect) has caused a 25 to 50 percent decrease in low cloud cover in the greater Los Angeles area since the 1970s. | <urn:uuid:5d29fa48-6e84-4527-852b-60ec0e717b16> | 3.34375 | 709 | News Article | Science & Tech. | 40.469525 | 95,591,201 |
Breakpoints are locations in your code where Xcode will pause so that you can inspect the state of your program. They don’t have any impact on the final performance of your code – in fact, they don’t even exist in your code at all – so there’s no harm using them liberally.
To place a breakpoint, click to the left of a line of code you want to pause on – in the gutter, where the line numbers are visible if you use them. If you prefer keyboard shorts, press Cmd+. When you run your program now, Xcode will pause as soon as that line is reached.
To remove a breakpoint, either press Cmd+\ on it again, or drag it off the gutter.
Available from iOS 7.0 – see Hacking with Swift tutorial 18
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Filters: Tags: landscape scale conservation: Native-Aboriginal Ways (X)148 results (12ms)
Ddhaw Ghro is an isolated mountain range in central Yukon. The area has been important to Northern Tutchone people for thousands of years. It has several features of regional significance, including unglaciated alpine areas and plant communities. It is also known for the Chu Tthaw Hot Springs, the fannin sheep population, the rich cultural history of the Northern Tutchone People and the intact mountain ecosystem. In 1948, the government of Canada established the Ddhaw Ghro area as the McArthur Game Sanctuary. Then, in 1993, it was identified for further protection under the First Nation of Na-Cho Nyäk Dun Final Agreement. ... As part of the Selkirk First Nation Final Agreement, a Ddhaw Ghro steering committee was...
Categories: Data, Publication; Types: Citation, Downloadable, Map Service, OGC WFS Layer, OGC WMS Layer, Shapefile; Tags: landscape scale conservation: Native-Aboriginal Ways, Adaptation planning 1-Best Management Practices, Adaptation planning 1-Best management practices, Landscape Scale Conservation: Yukon
Concerns related to the governance of water that have emerged at the global scale have created pressure for, and an increase in, water policy reform in many countries. Simultaneously, Indigenous governance movements related to self-determination are undergoing an immense period of growth and change worldwide; the 2007 United Nations Declaration on the Rights of Indigenous Peoples has been a milestone of this growth. These movements are significant because of Indigenous peoples' asserted rights to lands, waters, and natural resources. In this paper, we explore the extent to which water policy reform efforts recognize concepts of Indigenous governance and self-determination. The extent to which these concepts are...
Categories: Data, Publication; Types: Citation, Downloadable, Map Service, OGC WFS Layer, OGC WMS Layer, Shapefile; Tags: landscape scale conservation: Native-Aboriginal Ways, Adaptation planning 1-Best Management Practices, Landscape Scale Conservation: British Columbia, Adaptation planning 1-Best management practices
Growing together: A principle-based approach to building collaborative Indigenous partnerships in Canada’s forest sector
Perceptions of change in southwest Yukon land and socialscapes: Implications for the study of cumulative effects and social thresholds
This research focuses on contemporary and historical relationships between landscape change and human impacts in southwest Yukon, Canada, in order to bring to light the nature of cumulative social effects, and culturally appropriate methodologies that may be used for their evaluation. Results were acquired through twenty eight semi-structured interviews with natural resource managers, health and social workers, First Nations, and non-First Nations residents, in which resource development, and other important local markers of change were topics of discussion. Social thresholds are also developed from these results for their use in supporting resource management decisions. Resilience theory plays a center role in...
Caribou Hunters and Researchers at the Co-management Interface: Emergent Dilemmas and the Dynamics of Legitimacy in Power Sharing
A content analysis of PCMB meeting minutes from its first meeting to 1993 reveals a repeated pattern of communication in which Native hunters pose questions about the need for caribou research requiring the use of aircraft and collars and the handling of animals, and a response by agency managers to inform community residents about the value of collars in science and/or demonstrating their application. Never discussed openly at PCMB meetings was what the Gwich'in regard as a negotiated order of power-sharing arrangement between Gwich'in and caribou, established in the time before there was time, nunh ttrotsit ultsui gwuno (when the earth was first made), when caribou were people and people were caribou. As told...
Exploring ecological changes in Cook Inlet beluga whale habitat though traditional and local ecological knowledge of contributing factors for population decline
Water hearts and cultural landscapes: Practical understanding and natural resource management in the Northwest Territories, Canada
The Canadian North finds itself in a period of Canadian history with unprecedented levels of social and environmental complexity, political uncertainty and economic change. Within the Mackenzie River valley of the Northwest Territories, major industrial resource development projects are underway. At the same time, innovative natural resource management (NRM) governance institutions are being proposed. This dissertation explores how socio-cultural and political practices enable people to become institutional bricoleurs in resource management. From Déline, Northwest Territories, I examined how outside resource managers from federal and territorial governments, environmental non-government organizations, and aboriginal...
The contents of this report include: an update on Board membership and staff; a description of the draft implementation strategy to the Plan; the Planning Board's priorities for 2004-2005; a review of land use permits and water licences issued, and an explanation of how an approved Plan has affected those acivities; a list of action items that are currently being addressed; recommendations for groups to consider in the next year; the Planning Board's work plan for 2003-2004, and; the audited financial statements for 2003-2004. ... All regulatory agencies have to ensure that all licensed, permitted, and othe authorized activities related to the use of land, water, and the deposit of waste conform with the Plan. The...
Hegemonic and emerging concepts of conservation: a critical examination of barriers to incorporating Indigenous perspectives in protected area conservation policies and practice
This page allows you to search all of the reports and publications published in the scientific and technical reporting series by ADF&G's Commercial Fisheries, Sport Fish, and Subsistence divisions. There are three approaches you can use for searching these publications - The first two search through data fields in our publications database and the third will search through the text of the PDF documents themselves. Each method offers distinct advantages - roll the cursor over each search type to find out more!
Traditional Knowledge and Wisdom: A Guide for Understanding and Shaping Alaskan Social-Ecological Change
CARIBOU RISING: DEFENDING THE PORCUPINE HERD, GWICH-'IN CULTURE, AND THE ARCTIC NATIONAL WILDLIFE REFUGE . Rick Bass. 2004. San Francisco: Sierra Club Books. xii + 164 p, hard cover. ISBN 1-57805-114-2. $19.95
Categories: Data, Publication; Types: Citation, Downloadable, Map Service, OGC WFS Layer, OGC WMS Layer, Shapefile; Tags: Porcupine Herd, Baseline 5-Baseline Data, landscape scale conservation: Native-Aboriginal Ways, Adaptation planning 1-Best management practices, R2a-Impact Climate Change Vegatation and Subsistence,
"We have to Learn to Work Together:" Current Perspectives on Incorporating Local and Traditional/Indigenous Knowledge into Alaskan Fishery Management
Categories: Data, Publication; Types: Citation, Downloadable, Map Service, OGC WFS Layer, OGC WMS Layer, Shapefile; Tags: Monitoring 1-Changes in Plant and Animal Distribution: Fauna, landscape scale conservation: Native-Aboriginal Ways, Fish, Landscape Scale Conservation: Fisheries, Adaptation Planning 1-Best Management Practices, | <urn:uuid:7061a8b5-c831-4d6d-bdd7-780caeee2d7d> | 2.828125 | 1,531 | Content Listing | Science & Tech. | 17.445727 | 95,591,231 |
Wednesday, March 06, 2013
Ancient “Egyptian blue” pigment points to new telecommunications, security ink technology
“Nanoscience of an Ancient Pigment”
Journal of the American Chemical Society
A bright blue pigment used 5,000 years ago is giving modern scientists clues toward the development of new nanomaterials with potential uses in state-of-the-art medical imaging devices, remote controls for televisions, security inks and other technology. That’s the conclusion of an article on the pigment, Egyptian blue, in the Journal of the American Chemical Society.
Tina T. Salguero and colleagues point out that Egyptian blue, regarded as humanity’s first artificial pigment, was used in paintings on tombs, statues and other objects throughout the ancient Mediterranean world. Remnants have been found, for instance, on the statue of the messenger goddess Iris on the Parthenon and in the famous Pond in a Garden fresco in the tomb of Egyptian “scribe and counter of grain” Nebamun in Thebes.
They describe surprise in discovering that the calcium copper silicate in Egyptian blue breaks apart into nanosheets so thin that thousands would fit across the width of a human hair. The sheets produce invisible infrared (IR) radiation similar to the beams that communicate between remote controls and TVs, car door locks and other telecommunications devices. “Calcium copper silicate provides a route to a new class of nanomaterials that are particularly interesting with respect to state-of-the-art pursuits like near-IR-based biomedical imaging, IR light-emitting devices (especially telecommunication platforms) and security ink formulations,” the report states. “In this way we can reimagine the applications of an ancient material through modern technochemical means.”
The authors acknowledge funding from the University of Georgia.
ACS News Service Weekly PressPac: February 20, 2013
Entre las variedades alotrópicas del carbono, se encuentran el diamante y el grafito. Ambas estructuras son sólidas y presentan propiedade...
Hace un siglo, el químico Søren Sørensen inventó lo que se convertiría en una herramienta de diagnóstico crucial: la escala pH. Desde su...
este es un trabajo ke hice para quimica general... algo ke todos hicimos hahaahhah y weno.... me dijeroooon, ke debia postiarloooo NO SE KE... | <urn:uuid:5423bbde-7025-4b16-819f-504a215017bc> | 2.859375 | 543 | Personal Blog | Science & Tech. | 34.235618 | 95,591,233 |
Lectures on Analytic Number Theory
by H. Rademacher
Publisher: Tata Institute of Fundamental Research 1955
Number of pages: 283
In mathematics, analytic number theory is a branch of number theory that uses methods from mathematical analysis to solve problems about the integers. Contents: Formal Power Series; Analysis; Analytic theory of partitions; Representation by squares.
Download or read it online for free here:
by W W L Chen - Macquarie University
These notes were used by the author at Imperial College, University of London. The contents: arithmetic functions, elementary prime number theory, Dirichlet series, primes in arithmetic progressions, prime number theorem, Riemann zeta function.
by R. D. Carmichael - John Wiley & Sons
The author's purpose has been to supply the reader with a convenient introduction to Diophantine Analysis. No attempt has been made to include all special results, but a large number of them are to be found both in the text and in the exercises.
by J.I. Igusa - Tata Institute of Fundamental Research
One of the principal objectives of modern number theory must be to develop the theory of forms of degree more than two,to the same satisfactory level in which the theory of quadratic forms is found today as the work of eminent mathematicians.
by M. Jutila - Tata Institute of Fundamental Research
The author presents a selfcontained introduction to summation and transformation formulae for exponential sums involving either the divisor function d(n) or the Fourier coefficients of a cusp form; these two cases are in fact closely analogous. | <urn:uuid:b89d747c-6b5e-460f-ad07-ea2a0578068f> | 2.671875 | 337 | Content Listing | Science & Tech. | 30.560209 | 95,591,238 |
Dinosaurs may not have been cold-blooded like modern reptiles or warm-blooded like mammals and birds — instead, they may have dominated the planet for 135 million years with blood that ran neither hot nor cold, but was a kind of in-between that's rare nowadays, researchers say.
Modern reptiles such as lizards, snakes and turtles are cold-blooded or ectothermic, meaning their body temperatures depend on their environments. Birds and mammals, on the other hand, are warm-blooded, meaning they control their own body temperatures, attempting to keep them at a safe constant — in the case of humans, at about 98.6 degrees Fahrenheit.
Dinosaurs are classified as reptiles, and so for many years scientists thought the beasts were cold-blooded, with slow metabolisms that forced them to lumber across the landscape. However, birds are modern-day dinosaurs and warm-blooded, with fast metabolic rates that give them active lifestyles, raising the question of whether or not their extinct dinosaur relatives were also warm-blooded.
To help solve this decades-old mystery, researchers developed a new method for analyzing the metabolism of extinct animals. They found "dinosaurs do not fit comfortably into either the cold-blooded or warm-blooded camp — they genuinely explored a middle way," said lead study author John Grady, a theoretical ecologist at the University of New Mexico.
Scientists often seek to deduce the metabolisms of extinct animals by looking at the rates at which their bones grow. The method resembles cutting into a tree and looking at the thickness of the rings of wood within, which can reveal how well or poorly that tree grew any given year. Similarly, looking at the way bone is deposited in layers in fossils reveals how quickly or slowly that animal might have grown.
Grady and his colleagues not only looked at growth rings in fossils, but also sought to estimate their metabolic rates by looking at changes in body size as animals grew from birth to adults. The researchers looked at a broad spectrum of animals encompassing both extinct and living species, including cold- and warm-blooded creatures, as well as dinosaurs.
The scientists found growth rate to be a good indicator of metabolic rates in living animals, ranging from sharks to birds. In general, warm-blooded mammals that grow about 10 times faster than cold-blooded reptiles also metabolize about 10 times faster.
When the researchers examined how fast dinosaurs grew, they found that the animals resembled neither mammals nor modern reptiles, and were neither ectotherms nor endotherms. Instead, dinosaurs occupied a middle ground, making them so-called "mesotherms."
Today, such energetically intermediate animals are uncommon, but they do exist. For instance, the great white shark, tuna and leatherback sea turtle are mesotherms, as is the echidna, an egg-laying mammal from Australia. Like mammals, mesotherms generate enough heat to keep their blood warmer than their environment, but like modern reptiles, they do not maintain a constant body temperature.
"For instance, tuna body temperature declines when they dive into deep, colder waters, but it always stays above the surrounding water," Grady told Live Science.
Body size may play a role in mesothermy, because larger animals can conserve heat more easily. "For instance, leatherback sea turtles are mesotherms, but smaller green sea turtles are not," Grady said. However, mesothermy does not depend just on large size. "Mako sharks are mesotherms, but whale sharks are regular ectotherms," Grady said.
Endotherms can boost their metabolisms to warm up — "for instance, we shiver when cold, which generates heat," Grady said. "Mesotherms have adaptations to conserve heat, but they do not burn fat or shiver to warm up. Unlike us, they don't boost their metabolic rate to stay warm."
Some animals are what are known as gigantotherms, meaning they are just so massive that they maintain heat even though they do not actively control their body temperature.
"Gigantotherms like crocodiles rely on basking to heat up, so they are not mesotherms," Grady said. "Gigantotherms are slower to heat up and cool down, but if they rely on external heat sources like the sun, then they are not mesotherms. In general, mesotherms produce more heat than gigantotherms and have different mechanisms for conserving it."
Advantages of being a mesotherm
Mesothermy would have permitted dinosaurs to move, grow and reproduce faster than their cold-blooded reptilian relatives, making the dinosaurs more dangerous predators and more elusive prey. This may explain why dinosaurs dominated the world until their extinction about 65 million years ago, Grady suggested.
At the same time, dinosaurs' lower metabolic rates compared to mammals allowed them to get by on less food. This may have permitted the enormous bulk that many dinosaur species attained. "For instance, it is doubtful that a lion the size of T. rex would be able to eat enough wildebeests or elephants without starving to death," Grady said. "With their lower food demands, however, a real T. rex was able to get by just fine."
All in all, Grady suspected that where direct competition occurs, warm-blooded endotherms suppress mesotherms, mesotherms suppress active but cold-blooded ectotherms, and active ectotherms suppress more lethergic sit-and-wait ectotherms
Although mesothermy appears widespread among dinosaurs, not every dinosaur was necessarily a mesotherm, Grady said. "Dinosaurs were a big and diverse bunch, and some may have been endotherms or ectotherms," he said. "In particular, feathered dinosaurs are a bit of a mystery. What do you call a metabolically intermediate animal covered in feathers? Is it like the mesothermic echidna? Or just a low-power endotherm?"
The first bird, Archaeopteryx, "was more like a regular dinosaur than any living bird," Grady said. "It grew to maturity in about two years. In contrast, a similarly sized hawk grows in about six weeks, almost 20 times faster. Despite feathers and the ability to take flight, the first birds were not the active, hot-blooded fliers their descendants came to be."
These findings could help shed light on how warm-blooded animals such as humans evolved.
"The origins of endothermy in mammals and birds are unclear," Grady said. Studying the growth rates of the ancestors of birds and mammals "will shed light on these mysterious creatures."
The scientists detailed their findings in the June 13 issue of the journal Science.
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This article originally published at LiveScience here | <urn:uuid:67075672-0a87-4f3b-9b6f-d6fed157064f> | 4.46875 | 1,474 | News Article | Science & Tech. | 38.110519 | 95,591,243 |
Research at UCLA’s Jonsson Comprehensive Cancer Center has raised that question.
It has been known for decades that reactive oxygen species (ROS) - ions or very small molecules that include free radicals - damage cells. But much to their surprise, Jonsson Cancer Center researchers found that in Drosophila, the common fruit fly, moderately elevated levels of ROS are a good thing.
These small molecules act as an internal communicator, signaling certain blood precursor cells, or blood stem cells, to differentiate into immune-bolstering cells in reaction to a threat. After the progenitor cells differentiate, the ROS levels return to normal, ensuring the safety and survival of the mature blood cells, said Utpal Banerjee, a Jonsson Cancer Center researcher and senior author of the study.
The study is published in the Sept. 24, 2009 issue of the peer-reviewed journal Nature.
The new finding was launched when Banerjee and his team set out to discover why fruit flies had naturally occurring, slightly elevated levels of ROS in their blood cell precursors, which is atypical of most other precursor cells.
“Reducing levels of reactive oxygen is usually the goal, and what we found was surprising,” said Banerjee, professor and chairman of the molecular, cell, and developmental biology department at UCLA. “Most stem cells don’t want to be damaged, so they have very low ROS levels. We wanted to know why this was different in the cells that we were investigating.”
Banerjee discovered that when ROS was taken away in the blood stem cells, they failed to differentiate into the immune-bolstering cells, called macrophages. On the other hand, when levels of ROS were further increased by genetic means, the blood stem cells “differentiated like gang busters,” Banerjee said, making a large number of macrophages.
But how did this happen? The ROS, Banerjee said, acted as a signaling mechanism that kept the blood stem cells in a certain state – when levels rose, it was a message to the cell to differentiate.
The implications from the finding are several fold, Banerjee said. The blood stem cells are stress sensing cells, their function is to sense conditions that increase oxidative stress and react with an immune response. Keeping their ROS levels slightly elevated puts the cells on alert, sensitized and ready to respond to any threat quickly.
That sparked a question: If fruit fly blood stem cells and mammalian blood stem cells operate in the same way, is it a good thing for people to be taking antioxidants? Are antioxidants dulling the immune system and its ability to react to threats?
“On the one hand, it’s good to have antioxidants to reduce the amount of reactive oxygen in our body that causes DNA damage,” Banerjee said. “But if we find that those blood stem cells aren’t primed to respond because the ROS levels are reduced, that would not be a good thing. Our findings raise the possibility that wanton overdose of antioxidant products may in fact inhibit formation of cells participating in innate immune response.”
It is known that certain types of mammalian blood stem cells, called common myeloid progenitors, do have elevated levels of ROS, but it isn’t known whether those levels operate as messengers for differentiation. Studies of mammalian systems are needed to determine why ROS levels are elevated and what, if any, function that serves in the cell. It is interesting, however, that these types of blood progenitors in mammals also give rise to macrophages, Banerjee said.
“What we found is that the fruit fly keeps its own ROS levels in the blood stem cells slightly high for its own benefit,” Banerjee said. “We do not have any direct evidence that this is true in humans, but our results suggest that further studies are needed to investigate a possible signaling role for ROS in the differentiation of precursor cells in mammalian myeloid cell development and oxidative stress response.”
UCLA's Jonsson Comprehensive Cancer Center has more than 240 researchers and clinicians engaged in disease research, prevention, detection, control, treatment and education. One of the nation's largest comprehensive cancer centers, the Jonsson center is dedicated to promoting research and translating basic science into leading-edge clinical studies. In July 2009, the Jonsson Cancer Center was named among the top 12 cancer centers nationwide by U.S. News & World Report, a ranking it has held for 10 consecutive years.
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...
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Artificial Photosynthesis Moves a Step Closer: Jülich scientists synthesise stable catalyst for water oxidation
Jülich scientists have made an important step on the long road to artificially mimicking photosynthesis. They were able to synthesise a stable inorganic metal oxide cluster, which enables the fast and effective oxidation of water to oxygen. This is reported by the German high-impact journal "Angewandte Chemie" in a publication rated as a VIP ("very important paper"). Artificial photosynthesis may decisively contribute to solving energy and climate problems, if researchers find a way to efficiently produce hydrogen with the aid of solar energy.
Hydrogen is regarded as the energy carrier of the future. The automobile industry, for example, is working hard to introduce fuel cell technology starting approximately in 2010. However, a fuel cell drive system can only be really environmentally friendly, if researchers succeed in producing hydrogen from renewable sources. Artificial photosynthesis, i.e. the splitting of water into oxygen and hydrogen with the aid of sunlight, could be an elegant way of solving this problem.
However, the road to success is littered with obstacles. One of the obstacles to be overcome is the formation of aggressive substances in the process of water oxidation. Plants solve this problem by constantly repairing and replacing their green catalysts. A technical imitation depends on more stable catalysts as developed and synthesised for the first time by a team from Research Centre Jülich, member of the Helmholtz Association, and from Emory University in Atlanta, USA. The new inorganic metal oxide cluster with a core consisting of four ions of the rare transition metal ruthenium catalyses the fast and effective oxidation of water to oxygen while remaining stable itself.
"Our water-soluble tetraruthenium complex displays its effects in aqueous solution already at ambient temperature," enthuses Prof. Paul Kögerler from the Jülich Institute of Solid State Research, who synthesised and characterised the promising cluster together with his colleague Dr. Bogdan Botar. Catalytic measurements were carried out at Emory University. "In contrast to all other molecular catalysts for water oxidation, our catalyst does not contain any organic components. This is why it is so stable".
Botar explains the next step: "Now the challenge is to integrate this ruthenium complex into photoactive systems, which efficiently convert solar energy into chemical energy". So far, energy is still obtained from a chemical oxidant.
Source: Forschungszentrum Jülich
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- Novel Terahertz Source: Potential for Scanners and Quality Control (05/27/2016) | <urn:uuid:75861bae-daab-40de-8f0f-49ab8ae98310> | 3.203125 | 615 | News Article | Science & Tech. | 22.100304 | 95,591,260 |
Mobile ectothermic animals can control their body temperatures by selecting specific thermal conditions in the environment, but embryos--trapped within an immobile egg and lacking locomotor structures--have been assumed to lack that ability. Falsifying that assumption, our experimental studies show that even early stage turtle embryos move within the egg to exploit small-scale spatial thermal heterogeneity. Behavioral thermoregulation is not restricted to posthatching life and instead may be an important tactic in every life-history stage.
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Choose a citation style from the tabs below | <urn:uuid:a55d87ed-22ef-452a-a167-c7cede53e8cc> | 3.0625 | 119 | Academic Writing | Science & Tech. | -2.268333 | 95,591,272 |
74 relations: AC power, Acoustic resonance, Amplitude, Angular frequency, Asymptote, Atomic clock, Attenuation, Bandwidth (signal processing), Bessel filter, Brass instrument, Butterworth filter, Capacitance, Capacitor, Chu–Harrington limit, Complex conjugate, Complex number, Conservative force, Crystal oscillator, Damping ratio, Dimensionless quantity, Dissipation factor, Drag (physics), Electrical resistance and conductance, Engineering, Exponential decay, Factor of safety, Frequency, Friction, Full width at half maximum, Group delay and phase delay, Harmonic oscillator, Heaviside step function, Helmholtz resonance, Hertz, Impulse response, Inductance, Inductor, Kinetic energy, Laser, Linear time-invariant theory, Low-pass filter, Negative feedback, Octave, Octave (electronics), Optical cavity, Optics, Oscillation, Oscillator linewidth, Oscillator phase noise, Phase margin, ..., Photon, Physics, Potential energy, Pulse (physics), Pure tone, Q meter, Q multiplier, Q-switching, Qualitative property, Resistor, Resonance, Resonator, RLC circuit, Sallen–Key topology, Selectivity (electronic), Sine wave, Sound box, Superconducting radio frequency, Transfer function, Tuned radio frequency receiver, Viscosity, Vuvuzela, Western Electric, Wind instrument. Expand index (24 more) » « Shrink index
Power in an electric circuit is the rate of flow of energy past a given point of the circuit.
New!!: Q factor and AC power ·
Acoustic resonance is a phenomenon where acoustic systems amplify sound waves whose frequency matches one of its own natural frequencies of vibration (its resonance frequencies).
New!!: Q factor and Acoustic resonance ·
The amplitude of a periodic variable is a measure of its change over a single period (such as time or spatial period).
New!!: Q factor and Amplitude ·
In physics, angular frequency ω (also referred to by the terms angular speed, radial frequency, circular frequency, orbital frequency, radian frequency, and pulsatance) is a scalar measure of rotation rate.
New!!: Q factor and Angular frequency ·
In analytic geometry, an asymptote of a curve is a line such that the distance between the curve and the line approaches zero as one or both of the x or y coordinates tends to infinity.
New!!: Q factor and Asymptote ·
An atomic clock is a clock device that uses an electron transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element.
New!!: Q factor and Atomic clock ·
In physics, attenuation or, in some contexts, extinction is the gradual loss of flux intensity through a medium.
New!!: Q factor and Attenuation ·
Bandwidth is the difference between the upper and lower frequencies in a continuous band of frequencies.
In electronics and signal processing, a Bessel filter is a type of analog linear filter with a maximally flat group/phase delay (maximally linear phase response), which preserves the wave shape of filtered signals in the passband.
New!!: Q factor and Bessel filter ·
A brass instrument is a musical instrument that produces sound by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips.
New!!: Q factor and Brass instrument ·
The Butterworth filter is a type of signal processing filter designed to have a frequency response as flat as possible in the passband.
New!!: Q factor and Butterworth filter ·
Capacitance is the ratio of the change in an electric charge in a system to the corresponding change in its electric potential.
New!!: Q factor and Capacitance ·
A capacitor is a passive two-terminal electrical component that stores potential energy in an electric field.
New!!: Q factor and Capacitor ·
In electrical engineering and telecommunications the Chu–Harrington limit or Chu limit sets a lower limit on the Q factor for a small radio antenna.
New!!: Q factor and Chu–Harrington limit ·
In mathematics, the complex conjugate of a complex number is the number with an equal real part and an imaginary part equal in magnitude but opposite in sign.
New!!: Q factor and Complex conjugate ·
A complex number is a number that can be expressed in the form, where and are real numbers, and is a solution of the equation.
New!!: Q factor and Complex number ·
A conservative force is a force with the property that the total work done in moving a particle between two points is independent of the taken path.
New!!: Q factor and Conservative force ·
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a precise frequency.
New!!: Q factor and Crystal oscillator ·
Damping is an influence within or upon an oscillatory system that has the effect of reducing, restricting or preventing its oscillations.
New!!: Q factor and Damping ratio ·
In dimensional analysis, a dimensionless quantity is a quantity to which no physical dimension is assigned.
New!!: Q factor and Dimensionless quantity ·
In physics, the dissipation factor (DF) is a measure of loss-rate of energy of a mode of oscillation (mechanical, electrical, or electromechanical) in a dissipative system.
New!!: Q factor and Dissipation factor ·
In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid.
New!!: Q factor and Drag (physics) ·
The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor.
Engineering is the creative application of science, mathematical methods, and empirical evidence to the innovation, design, construction, operation and maintenance of structures, machines, materials, devices, systems, processes, and organizations.
New!!: Q factor and Engineering ·
A quantity is subject to exponential decay if it decreases at a rate proportional to its current value.
New!!: Q factor and Exponential decay ·
Factors of safety (FoS), is also known as (and used interchangeably with) safety factor (SF), is a term describing the load carrying capacity of a system beyond the expected or actual loads.
New!!: Q factor and Factor of safety ·
Frequency is the number of occurrences of a repeating event per unit of time.
New!!: Q factor and Frequency ·
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.
New!!: Q factor and Friction ·
Full width at half maximum (FWHM) is an expression of the extent of function given by the difference between the two extreme values of the independent variable at which the dependent variable is equal to half of its maximum value.
In signal processing, group delay is the time delay of the amplitude envelopes of the various sinusoidal components of a signal through a device under test, and is a function of frequency for each component.
In classical mechanics, a harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force, F, proportional to the displacement, x: where k is a positive constant.
New!!: Q factor and Harmonic oscillator ·
The Heaviside step function, or the unit step function, usually denoted by or (but sometimes, or), is a discontinuous function named after Oliver Heaviside (1850–1925), whose value is zero for negative argument and one for positive argument.
New!!: Q factor and Heaviside step function ·
Helmholtz resonance or wind throb is the phenomenon of air resonance in a cavity, such as when one blows across the top of an empty bottle.
New!!: Q factor and Helmholtz resonance ·
The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second.
New!!: Q factor and Hertz ·
In signal processing, the impulse response, or impulse response function (IRF), of a dynamic system is its output when presented with a brief input signal, called an impulse.
New!!: Q factor and Impulse response ·
In electromagnetism and electronics, inductance is the property of an electrical conductor by which a change in electric current through it induces an electromotive force (voltage) in the conductor.
New!!: Q factor and Inductance ·
An inductor, also called a coil, choke or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it.
New!!: Q factor and Inductor ·
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
New!!: Q factor and Kinetic energy ·
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.
New!!: Q factor and Laser ·
Linear time-invariant theory, commonly known as LTI system theory, comes from applied mathematics and has direct applications in NMR spectroscopy, seismology, circuits, signal processing, control theory, and other technical areas.
A low-pass filter (LPF) is a filter that passes signals with a frequency lower than a certain cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency.
New!!: Q factor and Low-pass filter ·
Negative feedback (or balancing feedback) occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other disturbances.
New!!: Q factor and Negative feedback ·
In music, an octave (octavus: eighth) or perfect octave is the interval between one musical pitch and another with half or double its frequency.
New!!: Q factor and Octave ·
In electronics, an octave (symbol oct) is a doubling or halving of a frequency.
New!!: Q factor and Octave (electronics) ·
An optical cavity, resonating cavity or optical resonator is an arrangement of mirrors that forms a standing wave cavity resonator for light waves.
New!!: Q factor and Optical cavity ·
Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it.
New!!: Q factor and Optics ·
Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states.
New!!: Q factor and Oscillation ·
The concept of a linewidth is borrowed from laser spectroscopy.
New!!: Q factor and Oscillator linewidth ·
0,..., t6) one can see that the deviation in amplitude dissipates while the deviation in phase does not.| --> Oscillators inherently produce high levels of phase noise. That noise increases at frequencies close to the oscillation frequency or its harmonics. With the noise being close to the oscillation frequency, it cannot be removed by filtering without also removing the oscillation signal. And since it is predominantly in the phase, it can be removed without any limiter. All well-designed nonlinear oscillators have stable limit cycles, meaning that if perturbed, the oscillator will naturally return to its limit cycle. This is depicted in the figure on the right (removed due to unknown copyright status). Here the stable limit cycle is shown in state space as a closed orbit (the ellipse). When perturbed, the oscillator responds by spiraling back into the limit cycle. However, by observing the time stamps, it is easy to see that while the oscillation returns to its stable limit cycle, it does not return at the same phase. This is because the oscillator is autonomous; it has no stable time reference. The phase is free to drift. As a result, any perturbation of the oscillator causes the phase to drift, which explains why the noise produced by an oscillator is predominantly in phase.
New!!: Q factor and Oscillator phase noise ·
In electronic amplifiers, the phase margin (PM) is the difference between the phase and 180°, for an amplifier's output signal (relative to its input) at zero dB gain.
New!!: Q factor and Phase margin ·
The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles).
New!!: Q factor and Photon ·
Physics (from knowledge of nature, from φύσις phýsis "nature") is the natural science that studies matterAt the start of The Feynman Lectures on Physics, Richard Feynman offers the atomic hypothesis as the single most prolific scientific concept: "If, in some cataclysm, all scientific knowledge were to be destroyed one sentence what statement would contain the most information in the fewest words? I believe it is that all things are made up of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another..." and its motion and behavior through space and time and that studies the related entities of energy and force."Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves."Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. (...) You will come to see physics as a towering achievement of the human intellect in its quest to understand our world and ourselves."Physics is an experimental science. Physicists observe the phenomena of nature and try to find patterns that relate these phenomena.""Physics is the study of your world and the world and universe around you." Physics is one of the oldest academic disciplines and, through its inclusion of astronomy, perhaps the oldest. Over the last two millennia, physics, chemistry, biology, and certain branches of mathematics were a part of natural philosophy, but during the scientific revolution in the 17th century, these natural sciences emerged as unique research endeavors in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms studied by other sciences and suggest new avenues of research in academic disciplines such as mathematics and philosophy. Advances in physics often enable advances in new technologies. For example, advances in the understanding of electromagnetism and nuclear physics led directly to the development of new products that have dramatically transformed modern-day society, such as television, computers, domestic appliances, and nuclear weapons; advances in thermodynamics led to the development of industrialization; and advances in mechanics inspired the development of calculus.
New!!: Q factor and Physics ·
In physics, potential energy is the energy possessed by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.
New!!: Q factor and Potential energy ·
In physics, a pulse is a generic term describing a single disturbance that moves through a transmission medium.
New!!: Q factor and Pulse (physics) ·
A pure tone is a tone with a sinusoidal waveform; this is, a sine wave of any frequency, phase, and amplitude.
New!!: Q factor and Pure tone ·
A Q meter is a piece of equipment used in the testing of radio frequency circuits.
New!!: Q factor and Q meter ·
In electronics, a Q multiplier is a circuit added to a radio receiver to improve its selectivity and sensitivity.
New!!: Q factor and Q multiplier ·
Q-switching, sometimes known as giant pulse formation or Q-spoiling, is a technique by which a laser can be made to produce a pulsed output beam.
New!!: Q factor and Q-switching ·
Qualitative properties are properties that are observed and can generally not be measured with a numerical result.
New!!: Q factor and Qualitative property ·
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.
New!!: Q factor and Resistor ·
In physics, resonance is a phenomenon in which a vibrating system or external force drives another system to oscillate with greater amplitude at specific frequencies.
New!!: Q factor and Resonance ·
A resonator is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others.
New!!: Q factor and Resonator ·
An RLC circuit is an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C), connected in series or in parallel.
New!!: Q factor and RLC circuit ·
The Sallen–Key topology is an electronic filter topology used to implement second-order active filters that is particularly valued for its simplicity.
New!!: Q factor and Sallen–Key topology ·
Selectivity is a measure of the performance of a radio receiver to respond only to the radio signal it is tuned to (such as a radio station) and reject other signals nearby in frequency, such as another broadcast on an adjacent channel.
A sine wave or sinusoid is a mathematical curve that describes a smooth periodic oscillation.
New!!: Q factor and Sine wave ·
A sound box or sounding box (sometimes written soundbox) is an open chamber in the body of a musical instrument which modifies the sound of the instrument, and helps transfer that sound to the surrounding air.
New!!: Q factor and Sound box ·
Superconducting radio frequency (SRF) science and technology involves the application of electrical superconductors to radio frequency devices.
In engineering, a transfer function (also known as system function or network function) of an electronic or control system component is a mathematical function giving the corresponding output value for each possible value of the input to the device.
New!!: Q factor and Transfer function ·
A tuned radio frequency receiver (or TRF receiver) is a type of radio receiver that is composed of one or more tuned radio frequency (RF) amplifier stages followed by a detector (demodulator) circuit to extract the audio signal and usually an audio frequency amplifier.
The viscosity of a fluid is the measure of its resistance to gradual deformation by shear stress or tensile stress.
New!!: Q factor and Viscosity ·
The vuvuzela, also known as lepatata (its Tswana name), is a plastic horn, about long, which produces a loud monotone note, typically around flat 3 (the B below middle C).
New!!: Q factor and Vuvuzela ·
Western Electric Company (WE, WECo) was an American electrical engineering and manufacturing company that served as the primary supplier to AT&T from 1881 to 1996.
New!!: Q factor and Western Electric ·
A wind instrument is a musical instrument that contains some type of resonator (usually a tube), in which a column of air is set into vibration by the player blowing into (or over) a mouthpiece set at or near the end of the resonator.
New!!: Q factor and Wind instrument · | <urn:uuid:84305876-6e5a-462c-ba42-f35778857f7d> | 2.9375 | 4,293 | Structured Data | Science & Tech. | 37.623637 | 95,591,301 |
Exhaust from the main engines of NASA’s space shuttle, which is about 97 percent water vapor, can travel to the Arctic in the Earth’s thermosphere where it forms ice to create some of the Earth’s highest clouds that literally shine at night, according to a new study led by the Naval Research Laboratory and jointly funded by NASA and the Office of Naval Research.
This image shows the launch of space shuttle STS-85 on August 7, 1997. The orange external tank contains over 700 metric tons of liquid hydrogen and liquid oxygen. The main effluent is water. The Stevens et al. results show evidence that this water was transported to the Arctic where it formed a vast region of polar mesospheric clouds covering an area about 10% of North America. Credit: NASA
Because of their high altitude, near the edge of space, noctilucent clouds shine at night when the Suns rays hit them from below while the lower atmosphere is bathed in darkness. They typically form in the cold, summer polar mesosphere and are made of water ice crystals. Credit: Naval Research Laboratory, Washington, D.C.
The thermosphere is the highest layer in our atmosphere, occupying the region above about 55 miles (88 kilometers) altitude. The clouds settle to 51 miles (82 km) altitude in the layer directly below called the mesosphere. The stratosphere and the troposphere lie in that order below the mesosphere.
Dr. Michael H. Stevens, the paper’s lead author and a research physicist at the Naval Research Laboratory in Washington, reports that exhaust from the shuttle and other launch vehicles may help explain how some of these mysterious clouds are formed. The paper appeared on Saturday (May 31) in Geophysical Research Letters.
Krishna Ramanujan | NASA Goddard Space Flight Center
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:af098af1-7590-46c4-a6f5-f07668ab44d0> | 3.890625 | 1,001 | Content Listing | Science & Tech. | 44.157466 | 95,591,348 |
Far-off galaxy is most distant space object photographed
Astronomers took pictures of a far-off lumpy galaxy just forming 13 billion years ago, putting it among the earliest and most distant cosmic objects ever photographed.
Though the black-and-white images are fuzzy, they are the most detailed and best confirmed look back in both time and distance that humans have seen, said Johns Hopkins University astronomy professor Holland Ford. He was part of a team of scientists taking the pictures with NASA's space telescopes, Hubble and Spitzer.
The galaxy, called A1689-zD1, is from when the universe was about 700 million years old, not long after the formation of the first galaxies.
And it's different from galaxies like our Milky Way, Ford said.
"It is much smaller. It is lumpy. It has two centers instead of one, and it is undergoing extreme star formation," he said. "It is basically the building blocks for what will be a galaxy like our own in the future."
To see that far away, astronomers needed a little luck and help from the cosmos. A cluster of much closer galaxies acts as a natural zoom lens for Earth's telescopes. Strong gravitational forces bend light around that cluster of galaxies, magnifying the light from directly behind it.
In this case, the infant galaxy appeared at least 10 times brighter than it would have without the natural help, Ford said. Other places behind the cluster appear hundreds of times sharper. This natural lens has to be lined up perfectly in order to see what's behind it, he said.
When Earth gets stronger telescopes in the future, including a new space telescope to be launched in 2013, this young galaxy would be a good place to look, astronomers said.
To see photos of the galaxy: hubblesite.org/newscenter/archive/releases/2008/08/ | <urn:uuid:d9f68866-34d4-43f1-8c00-1456a8cfeecb> | 3.328125 | 382 | News Article | Science & Tech. | 54.057789 | 95,591,350 |
DNA molecules in the cells‘ nuclei are neatly folded into loops. This serves to wrap them up tightly, but also to bring distant gene regulatory sequences into close contact. In a paper published this week by NATURE, scientists at the Research Institute of Molecular Pathology (IMP) in Vienna describe how cohesin might do the trick.
Twenty years ago, the protein complex cohesin was first described by researchers at the IMP. They found that its shape strikingly corresponds to its function: when a cell divides, the ring-shaped structure of cohesin keeps sister-chromatids tied together until they are ready to separate.
Schematic illustration of the loop-extrusion mechanism (Copyright: IMP)
Apart from this important role during cell-divison, other crucial functions of cohesin have been discovered since - at the IMP and elsewhere. One of them is to help fold the DNA, which amounts to about two meters per nucleus, into a compact size by way of creating loops. “We think that the cohesin-ring clamps onto the DNA-strand to hold the loops in place”, says IMP-director Jan-Michael Peters whose team worked on the project.
The chromatin-loops are not folded at random. Their exact shape and position play an important role in gene regulation, as they bring otherwise distant areas into close contact. “For a long time, scientists were mystified by how regulatory elements – the enhancers – are able to activate distant genes. Now we think we know the trick: precisely folded loops allow enhancers to come very close to the genes they need to regulate”, says Peters. Research results point to cohesin as mediator of this process. Jan-Michael Peters and his team have already shown that the cohesin complex accumulates in areas where loops are formed.
Several scientists recently proposed a so-called “loop-extrusion mechanism” for the folding of chromatin. According to this hypothesis, cohesin is loaded onto DNA at a random site. The DNA strain is then fed through the ring-shaped complex until it encounters a molecular barrier. This element, a DNA-binding protein named CTCF, acts much like a knot tied in a rope and stops the extrusion-process at the correct position. Defined genome-sequences that were previously located far apart are now next to each other and can interact to regulate gene expression.
In NATURE online this week, IMP-researchers publish data that support the existence of such a mechanism. First author Georg Busslinger, a PhD-student in Jan-Michael Peters’ team, showed in mouse cells that cohesin is indeed translocated on DNA over long distances and that the movement depends on transcription, suggesting that this may serve as a ‘motor’.
“The loop extrusion hypothesis has opened up a whole new research area in cell biology and we will probably see many more papers published on this topic in the future”, comments Jan-Michael Peters. Understanding cohesin-function is also relevant from a medical perspective since a number of disorders, including certain cancers, are associated with malfunctions of the protein-complex.
Busslinger GA, Stocsits RR, van der Lelij P, Axelsson E, Tedeschi A, Galjart N und Peters J-M: Cohesin is positioned in mammalian genomes by transcription, CTCF and Wapl. Nature Advance Online Publication, 19 April 2017, http://rdcu.be/rsMu.
A News-Feature on the topic was published by NATURE simultaneously: http://www.nature.com/news/dna-s-secret-weapon-against-knots-and-tangles-1.21838
An illustration can be downloaded and used free of charge in connection with this press release: https://www.imp.ac.at/news-media/downloads/
Caption: Schematic illustration of the loop-extrusion mechanism (Copyright: IMP)
About the IMP
The Research Institute of Molecular Pathology (IMP) in Vienna is a basic biomedical research institute largely sponsored by Boehringer Ingelheim. With over 200 scientists from 37 nations, the IMP is committed to scientific discovery of fundamental molecular and cellular mechanisms underlying complex biological phenomena. Research areas include cell and molecular biology, neurobiology, disease mechanisms and computational biology.
Research Institute of Molecular Pathology
+43 (0)1 79730 3625
Dr. Heidemarie Hurtl | idw - Informationsdienst Wissenschaft
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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:1860c43f-02d2-4e9d-9024-8a718e5f8ee2> | 3.765625 | 1,625 | Knowledge Article | Science & Tech. | 40.385313 | 95,591,362 |
Scientists from the MIPT Department of Molecular and Chemical Physics have for the first time described the behavior of electrons in a previously unstudied analogue of graphene, two-dimensional niobium telluride, and, in the process, uncovered the nature of two-dimensionality effects on conducting properties. These findings will help in the creation of future flat and flexible electronic devices.
In recent decades, physicists have been actively studying so-called two-dimensional materials. Andrei Geim and Konstantin Novoselov received the Nobel Prize for their research on graphene, the most well-known among them.
The properties of such materials, which can be described as "sheets" with a thickness of a few atoms, strongly differ from their three-dimensional analogues. For example, graphene is transparent, conducts current better than copper and has good thermal conductivity. Scientists believe that other types of two-dimensional materials may possess even more exotic properties.
A group of scientists from Russia and the USA, including Pavel Sorokin and Liubov Antipina from MIPT, recently conducted research on the properties of the crystals of one such material,Nb3SiTe6, a compound of niobium telluride.
In their structure, the crystals resemble sandwiches with a thickness of three atoms (around 4 angstroms): a layer of tellurium, a layer of niobium mixed with silicon atoms and then another layer of tellurium. This substance belongs to a class of materials known as dichalcogenides, which many scientists view as promising two-dimensional semiconductors.
The scientists synthesized Nb3SiTe6 crystals in a laboratory at Tulane University (New Orleans). They then separated them into two-dimensional layers, taking samples for further analysis by transmission electron microscopy, X-ray crystal analysis and other methods. The goal of the researchers was to investigate electron-phonon interaction changes in two-dimensional substances.
Quasi particles, quanta of crystal lattice oscillations, are called phonons. Physicists introduced the concept of phonons because it helped simplify the description of processes in crystals, and tracking of electron-phonon interaction is fundamentally important for description of the different conducting properties in matter.
"We developed a theory that predicts that electron-phonon interaction is suppressed due to dimensional effects in two-dimensional material. In other words, these materials obstruct the flow of electrons to a lesser extent," says Pavel Sorokin, a co-author of the study, doctor of physical and mathematical sciences, and lecturer at the MIPT Section of the Physics and Chemistry of Nanostructures (DMCP).
American colleagues confirmed this predictioninrelatedexperiments. "They conducted measurements where the same effectwas observed. Our calculations allowed the ruling out of other explanations; we managed to prove that changes in electron-phonon interaction occur specifically because of the two-dimensionality of the membrane," Sorokin adds.
Full details of the research discussed above can be found in an article published in the journal Nature Physics (DOI:10.1038/NPHYS3321).
Stanislav Goryachev | 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
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A chemical once used in pesticides in Asia has accumulated thousands of miles away in Canada, according to a University of Toronto study.
High concentrations of alpha-hexachlorocyclohexane (HCH) were detected in the atmosphere of Sable Island off the coast of Nova Scotia and Newfoundland, says Professor Frank Wania of chemistry. The chemical was last used about 15 years ago in countries such as China and India but followed atmospheric and water flows across the Pacific, Arctic and Atlantic oceans to end up in eastern Canada. Frigid northern temperatures slowed its evaporation and degradation rate and trapped the chemical until it hit warmer waters where it will eventually evaporate.
"The Arctic Ocean has a lid on top in form of an ice cover," says Wania. "Over the last 20 years it acted as a sort of refrigerator preserving the chemical that is now flowing into Atlantic Canada."
Karen Kelly | University of Toronto
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
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In this chapter those mathematical tools are put together which are needed for the solution of the problems described above. Also, most of the basic notations used throughout the book will be introduced here. In the following, an attempt has been made to organise the main tools into six different domains which may be viewed as selected parts from general probability theory. Prerequisites are college mathematics only, more precisely elements of calculus and probability.
KeywordsNegative Binomial Distribution Risk Process Claim Amount Distribution Versus Total Claim
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Natural saline water, waste water, and irrigation return flow endanger the groundwater aquifers in the Rift. In the long run this will ruin the socio-economic backbone of the settlements in the area. Sustainability of the water resources will only be achieved when the process of water replenishment and its underground flow is understood and water extraction is regionally controlled. Rare earth element and spider patterns are presented as new tools for studying the hydrology. Progress in 3-D modelling of groundwater flow proved successfully the impact of pumping on the surroundings of wells and overexploitation of aquifers. | <urn:uuid:91c41d11-1c08-4981-b85a-0713903e3f0f> | 2.59375 | 120 | Product Page | Science & Tech. | 29.826714 | 95,591,409 |
- Process Termination
There are eight ways for a process to terminate. Normal termination occurs in file ways:
- Return from main
- Calling exit
- Calling _exit or _Exit
- Return of the last thread from its start routine
- Calling pthread_exit from the last thread
Abnormal termination occurs in three ways:
- Calling abort
- Receipt of a signal
- Response of the last thread to a cancellation request
2. Exit Functions
- _exit and _Exit, which return to the kernel immediately, and exit, which performs certain cleanup processing (use fclose function for all open streams) and then return to kernel.
- If any of these functions is called without an exit status, main does a return without a return value, or the main function is not declared to return a integer, the exit status of the process is undefined.
3. Memory layout of a C program
- Test segment, the machine instructions that the CPU executes. Usually, the test segment is read-only and sharable.
- Initialized data segment, containing variables that are specifically initialized in the program(ex: int data=100).
- Uninitialized data segment, data in this segment is initialized by the kernel to arithmetic 0 or NULL pointers before the program starts executing.
- Stack: where automatic variables are stored, along with information that is saved each time a function is called.
- Heap: where dynamic memory allocation usually takes place. Historically, the heap has been located between the uninitialized data and the stack.
4. Memory Allocation
- malloc, which allocates a specified number of bytes of memory. The initial value of the memory is indeterminate.
- calloc, which allocates space for a specified number of objects of a specified size. The space is initialized to all 0 bits.
- realloc, which increase or decrease the size of a previously allovated area. The initial value of the space between the old contents and the end of the new area is indeterminate.
- One additional function is also worth mentioning. The function alloca has the same calling sequence as malloc; however, instead of allocating memory from the heap, the memory is allocated from the stack frame of the current function. The advantage is that we don't have to free the space; it goes away automatically when the function returns. The disadvantage is that some system don't support alloca , it it's impossible to increase the size of the stack frame after the function has been called.
5. setjmp and longjmp functions
- In C, we can not goto a lablel that is in another function. Instead, we must use the setjmp and longjmp functions to perform this type of branching. These two functions are useful for handling error conditions that occur in a deeply rested function call.
Argument val decide return value on setjmp, we can use this to check which function call longjmp.
- The setjmp(3) manual page on one system states that variables stored in memory will have values as of the time of the longjmp, whereas variables in the CPU and floating-point registers are restored to their values when setjmp was called. If you have an automatic variable that you don't want to rolled back, define it with the volatile attribute. | <urn:uuid:6e88a5ba-6952-4d48-a637-974378fcc57a> | 3.6875 | 693 | Documentation | Software Dev. | 42.987793 | 95,591,425 |
Quantum membranes for ultraprecise mechanical measurements
Quantum mechanics dictates sensitivity limits in the measurements of displacement, velocity and acceleration. A recent experiment at the Niels Bohr Institute probes these limits, analyzing how quantum fluctuations set a sensor membrane into motion in the process of a measurement.
The membrane is an accurate model for future ultraprecise quantum sensors, whose complex nature may even hold the key to overcome fundamental quantum limits. The results are published in the prestigious scientific journal, Proceedings of the National Academy of Sciences of the USA.
Vibrating strings and membranes are at the heart of many musical instruments. Plucking a string excites it to vibrations, at a frequency determined by its length and tension. Apart from the fundamental frequency - corresponding to the musical note - the string also vibrates at higher frequencies. These overtones influence how we perceive the 'sound' of the instrument, and allow us to tell a guitar from a violin. Similarly, beating a drumhead excites vibrations at a number of frequencies simultaneously.
These matters are not different when scaling down, from the half-meter bass drum in a classic orchestra to the half-millimeter-sized membrane studied recently at the Niels Bohr Institute. And yet, some things are not the same at all: using sophisticated optical measurement techniques, a team lead by Professor Albert Schliesser could show that the membrane's vibrations, including all its overtones, follow the strange laws of quantum mechanics. In their experiment, these quantum laws implied that the mere attempt to precisely measure the membrane vibrations sets it into motion. As if looking at a drum already made it hum!
A 'drum' with many tones
Although the membrane investigated by the Niels Bohr Institute team can be seen with bare eyes, the researchers used a laser to accurately track the membrane motion. And this indeed reveals a number of vibration resonances, all of which are simultaneously measured. Their frequencies are in the Megahertz range, about a thousand times higher than the sound waves we hear, essentially because the membrane is much smaller than a musical instrument. But the analogies carry on: just like a violin sounds different depending on where the string is struck (sul tasto vs sul ponticello), the researchers could tell from the spectrum of overtones at which location their membrane was excited by the laser beam.
Yet, observing the subtle quantum effects that the researchers were most interested in, required a few more tricks. Albert Schliesser explains: "For once, there is the problem of vibrational energy loss, leading to what we call quantum decoherence. Think of it this way: in a violin, you provide a resonance body, which picks up the string vibrations and transforms them to sound waves carried away by the air. That's what you hear. We had to achieve exactly the opposite: confine the vibrations to the membrane only, so that we can follow its undisturbed quantum motion for as long as possible. For that we had to develop a special 'body' that cannot vibrate at the membrane's frequencies".
This was achieved by a so-called phononic crystal, a regular pattern of holes that exhibits a phononic bandgap, that is, a band of frequencies at which the structure cannot vibrate. Yeghishe Tsaturyan, a PhD student on the team, realized a membrane with such a special body at the Danchip nanofabrication facilities in Lyngby.
A second challenge consists in making sufficiently precise measurements. Using techniques from the field of Optomechanics, which is Schliesser's expertise, the team created a dedicated experiment at the Niels Bohr Institute, based on a laser custom-built to their needs, and a pair of highly reflecting mirrors between which the membrane is arranged. This allowed them to resolve vibrations with amplitudes much smaller than a proton's radius (1 femtometer).
"Making measurements so sensitive is not easy, in particular since pumps and other lab equipment vibrates with much larger amplitudes. So we have to make sure this doesn't show in our measurement record," adds PhD student William Nielsen.
Vacuum beats the drum
Yet it is exactly the range of ultra-precision measurements where it gets interesting. Then, it starts to matter that, according to quantum mechanics, the process of measuring the motion also influences it. In the experiment, this 'quantum measurement backaction' is caused by the inevitable quantum fluctuations of the laser light. In the framework of quantum optics, these are caused by quantum fluctuations of the electromagnetic field in empty space (vacuum). Odd as it sounds, this effect left clear signatures in the Niels Bohr Institute experiments' data, namely strong correlations between the quantum fluctuations of the light, and the mechanical motion as measured by light.
"Observing and quantifying these quantum fluctuations is important to better understand how they can affect ultraprecision mechanical measurements - that is, measurements of displacement, velocity or acceleration. And here, the multi-mode nature of the membrane comes into play: not only is it a more accurate representation of real-world sensors. It may also contain the key to overcome some of the traditional quantum limits to measurement precision with more sophisticated schemes, exploiting quantum correlations", Albert Schliesser says and adds, that in the long run, quantum experiments with ever more complex mechanical objects may also provide an answer to the question why we don't ever observe a bass drum in a quantum superposition (or will we?).
Albert Schliesser, Professor in Quantop Optics at the Niels Bohr Institute, University of Copenhagen, +45 3532-5254, email@example.com
Gertie Skaarup | 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
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
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The "scaly-foot gastropod" is a type of snail that thrives in the hydrothermal vents found deep in the Indian Ocean. And it has a unique property: a magnetic outer shell.
These snails were first discovered during a 2001 survey. It took researchers a while to find the snails because they (the snails) were at the bottom of the ocean, next to hydrothermal vents. It's those vents that gave the snails their special outer shells.
The core of the scaly-foot gastropod looks like the core of any other snail — disgusting and slimy. Go out one layer and it still looks like a common snail, with a calcium carbonate layer around the central goo. In fact, it looks just like a regular snail until you get to the outermost layer.
This layer consists of Fe3S4 and FeS2. The first is a substance called greigite, the other is the well-known pyrite, or "fool's gold." Both of them contain iron, which means that if you wanted to pick this snail up, all you'd have to do is wave a sufficiently strong magnet over it. No other gastropod on Earth has managed to make a shell out of these materials.
The key to the snail's shell is probably the sulphur. It lives near hydrothermal vents, which give off a great deal of hydrogen sulfide. The snails have used this element to make a stronger outer layer to their shells. Until a predator learns to manipulate magnetic fields, they're safe. | <urn:uuid:cee004b2-175e-4943-8a22-c9d2187f1390> | 3.84375 | 327 | Knowledge Article | Science & Tech. | 66.970179 | 95,591,444 |
It's perfectly possible to plan for droughts and minimize the losses they cause. In fact Australia has set in place policies that blaze a trail for the US follow to some extent, says Linda Botterill, a political scientist at the Australian National University in Canberra.
Botterill is presenting drought policy lessons learned in Australia at the Geological Society of America conference entitled Managing Drought and Water Scarcity in Vulnerable Environments: Creating a Roadmap for Change in the United States. The meeting takes place 18-20 September at the Radisson Hotel and Conference Center in Longmont, Colorado.
"In policy terms drought is no longer considered a disaster," said Botterill, of the fundamental change in perspective when Australia adopted a national drought policy in 1989. The shift made perfect sense because of Australia's climate, in which drought is always an issue.
"We have one of the most variable climates on Earth," said Botterill. "We really don't have a 'normal' climate." Therefore it's absurd to treat every drought as an emergency, she said. "It should be managed as any other risk. Farmers need to factor in that they are not always going to get needed rainfall."
Like Australia, the most normal thing about climate in the Central and Western U.S. is that it has no norm. Unlike Australia, however, the U.S. still reacts to droughts as if they are unexpected emergencies – which they aren't, says climatologist and drought policy specialist Donald Wilhite of the National Drought Mitigation Center at the University of Nebraska in Lincoln.
"Drought is always out there," said Wilhite, who was part of a team that built the U.S. Drought Monitor website (see: http://www.drought.unl.edu/dm/monitor.html). "It's always affecting some part of the country."
What's more, reacting to droughts is more expensive than planning for them, says Wilhite, who will speak at the meeting on what's needed for the U.S. to shift from drought crisis mode to a more proactive risk management mode. Wilhite is also serving as the technical program chair of the conference.
Climate change and increasing population are not expected to make droughts any easier in the U.S., according to Wilhite. So there is no time to lose in creating a national drought policy.
"On average, drought losses are in the neighborhood of $6 to 8 billion per year," Wilhite said. "They're right on par with hurricanes and floods." In severe drought years like 2002 and 2006, the losses run much higher.
"We're trying to bring together all the players to work on the early warning side," Wilhite said. That means states, federal agencies, tribal governments, and municipalities pouring information into one place. Data collected and monitored will include soil moisture, rainfall, snow pack, stream flows, and groundwater levels.
Two bills are pending in the House and Senate to authorize funding for the program for the next several years. Called the National Integrated Drought Information System (NIDIS), the program is currently being implemented by NOAA.
The GSA meeting is not the first time Botterill and Wilhite have addressed this subject side-by-side. They've also co-edited a book entitled From Disaster Response to Risk Management: Australia's National Drought Policy (2005).
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
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The round() method of math object is used to get the value of a number rounded to the nearest integer. If the fractional part of the number is greater than or equal to .5, the argument is rounded to the next higher integer. If the fractional part of number is less than .5, the argument is rounded to the next lower integer.
PHP Data Types : Arrays
15.09.2012 16:47 in Php | 0 comments | source: | 2574 clicks
An array in PHP is a collection of key/value pairs. This means that it maps values to keys. Array keys (or indexes) may be either an integers or a strings whereas values can be any type.
It is very important to validate the data supplied by user through a form, before you process it. Among various kind of data validation, validation of date is one.
SQL Data Type
15.09.2012 16:47 in Php | 0 comments | source: | 2194 clicks
A Data Type defines the kind of value a field (of a table) can contain. We have given a list of SQL Data Types with a short description in this page.
Etched text effect using Photoshop
11.09.2012 13:52 in Photoshop | 1 comments | source: | 2820 clicks
Here is a very easy to follow tutorial to help you easily do it for any kind of color booklet design or even for other special effects as well. Let is first start with the Initial requirements.
SQL IN operator
11.09.2012 13:52 in Php | 1 comments | source: | 2202 clicks
The IN operator checks a value within a set of values separated by commas and retrieve the rows from the table which are matching. The IN returns 1 when the search value present within the range other wise returns 0.
Install PHP on Windows
03.09.2012 10:29 in Php | 1 comments | source: | 2349 clicks
You must have a web server up and running on your Windows system, else you will not be able to run PHP Scripts. | <urn:uuid:633ab9f7-5c86-44e3-8cb3-5155dc35e02e> | 2.984375 | 435 | Content Listing | Software Dev. | 82.246455 | 95,591,461 |
There's a small amount of radioactive carbon-14 in all living organisms.
Radioactive dating fossils isotopes used debby ryan mitchel musso dating
The different methods of radiometric dating are accurate over different timescales, and they are useful for different materials.
After one half-life has elapsed, one half of the atoms of the nuclide in question will have decayed into a "daughter" nuclide, or decay product.
All rocks and minerals contain long-lived radioactive elements that were incorporated into Earth when the Solar System formed.
These radioactive elements constitute independent clocks that allow geologists to determine the age of the rocks in which they occur.
It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.
It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and it can be used to date a wide range of natural and man-made materials.
Part 1 (in the previous issue) explained how scientists observe unstable atoms changing into stable atoms in the present.
Part 2 explains how scientists run into problems when they make assumptions about what happened .
Radioactive rocks offer a similar “clock.” Radioactive atoms, such as uranium (the parent isotopes), decay into stable atoms, such as lead (the daughter isotopes), at a measurable rate. | <urn:uuid:bb78da74-7b91-4156-acaa-20ce19bda77d> | 3.984375 | 297 | Knowledge Article | Science & Tech. | 25.344107 | 95,591,463 |
K. K. Yates, L. L. Robbins, 2001. "Microbial Lime-Mud Production and Its Relation to Climate Change", Geological Perspectives of Global Climate Change, Lee C. Gerhard, William E. Harrison, Bernold M. Hanson
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Microbial calcification has been identified as a significant source of carbonate sediment production in modern marine and lacustrine environments around the globe. This process has been linked to the production of modern whitings and large, micritic carbonate deposits throughout the geologic record. Furthermore, carbonate deposits believed to be the result of cyanobacterial and microalgal calcification suggest that the potential exists for long-term preservation of microbial precipitates and storage of carbon dioxide (CO2). Recent research has advanced our understanding of the microbial-calcification mechanism as a photosynthetically driven process. However, little is known of the effects of this process on inorganic carbon cycling or of the effects of changing climate on microbial-calcification mechanisms.
Laboratory experiments on microbial cellular physiology demonstrate that cyanobacteria and green algae can utilize different carbon species for metabolism and calcification. Cyanobacterial calcification relies on bicarbonate (HCO3−) utilization while green algae use primarily CO2. Therefore, depending on which carbonate species (HCO3− or CO2) dominates in the ocean or lacustrine environments (a condition ultimately linked to atmospheric partial pressure PCO2), the origin of lime-mud production by cyanobacteria and/or algae may fluctuate through geologic time. Trends of cyanobacteria versus algal dominance in the rock record corroborate this conclusion. These results suggest that relative species abundances of calcareous cyanobacteria and algae in the Phanerozoic may serve as potential proxies for assessing paleoclimatic conditions, including fluctuations in atmospheric PCO2. | <urn:uuid:28cdd53a-d2ea-44c2-a40c-a579a7f3af10> | 2.921875 | 388 | Academic Writing | Science & Tech. | 5.779165 | 95,591,464 |
+44 1803 865913
By: Glenn B Wiggins(Author)
292 pages, b/w photos, 386 b/w illustrations
Please note: this title is also available in paperback.
Caddisflies constitute the insect order Trichoptera in which some 10 000 species are known in the world, including about 1400 in North America. Fossil evidence shows that caddisflies originated in the Triassic period, 200-250 million years ago. They are important links in the movement of energy and nutrients through freshwater ecosystems due largely to the extraordinary diversification in their larval architecture, which includes portable and stationary shelters, silken filter nets, and osmotically semipermeable cocoons. Glenn Wiggins's Caddisflies: The Underwater Architects is the foremost comprehensive reference source about these insects and is concerned with behavioural ecology, evolutionary history, biogeography, and biological diversity.
Wiggins outlines fundamental concepts of aquatic ecology, illuminating the ways in which caddisflies help to make fresh waters work. Essential features of morphology, biology, and distribution are outlined for the twenty-six North American families of caddisflies and illustrated diagnostic keys are provided for larvae, pupae, and adults. The author also brings together information on caddisflies from widely scattered sources and provides comprehensive coverage of the scientific literature.
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Glenn Wiggins is a curator emeritus (entomology) at the Royal Ontario Museum.
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Introduction to Creep Fracture and Other Fracture Modes
The acceleration of creep in the tertiary stage of the creep curve is often caused by the formation and joining of micro-cavities on grain boundaries. Creep fracture is therefore generally intergranular. The cavities may be nucleated early in the creep life, possibly even during the primary stage. Initially their effect on the creep rate is negligible but, as their number and size increase, they weaken the material progressively and finally induce failure. The nucleation and growth of cavities is studied extensively in Part II of this book.
KeywordsCreep Rate Fracture Mode Cleavage Fracture Creep Curve Rupture Time
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Andasibe-Mantadia Biodiversity Corridor
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The project will cover a total of around 5,000 hectares. It aims first at restoring forest corridors linking fragmented habitats between the Analamazaotra Special Indri Lemur Reserve, the Maromizaha Private Forest and Mantadia National Park complex in east-central Madagascar. These parks are at the core of the remaining fragments of the Malagasy rainforest, are extremely rich in terms of biodiversity, and continue to be severely deforested. Second, the project will also establish sustainable forest and fruit gardens that will provide alternative livelihoods to local communities and a buffer around the corridor. In addition, the project aims at protecting an area of 80,000 ha of prime or degraded forest north of the corridor, so as to maintain continuity up to Zahamena National Park, located approximately 100km to the north. The overall goal is to enhance the viability of the livelihoods of both people and native biodiversity, while mitigating emissions of greenhouse gases. The additional income from the carbon sequestration is essential to the realization of this goal. More specifically, the project will establish natural forest corridors allowing viable biological connectivity among several currently isolated forests and protected areas and promote sustainable cultivation systems. The forest gardens are envisioned to comprise a significant proportion of local forest plants (primarily Ravensara aromatica, which can be planted so as to mimic local forests in both structure and function). The project falls under the umbrella of the Third Environment Program of the Republic of Madagascar, a $150M program to protect natural resources in the Island supported by major environmental NGOs, bilateral and multilateral donors, including the World Bank (IDA) and the Global Environmental Facility. This Program implements the National Environmental Action Plan of the Government. | <urn:uuid:217a226b-9a8c-4f29-a13a-11631c39cb8c> | 2.75 | 383 | Knowledge Article | Science & Tech. | 10.049651 | 95,591,475 |
Describing the recent discovery of thick ice deposits on the Moon as path-breaking, former ISRO chairman G Madhavan Nair said it opens up a vast avenue for human exploration.
"This is the first time NASA and ISRO have confirmed the availability of water on moon. Huge ice sheets were found in the polar regions of the moon. This is a path-breaking finding as it was earlier believed there was a vacuum in the moon," Nair, during whose tenure unmanned lunar mission Chandrayaan I was launched, said.
"The presence of water gives many ideas.Water can be split with sunlight to get oxygen and hydrogen. While oxygen can be used by human explorers, hydrogen can be used as fuel either to generate electricity or use as rocket fuel for the return journey or even attempt a Mars mission from the Moon," he said.
This also reduces the need to carry expensive oxygen and fuel payloads by future space missions, he said, addressing the Fedbank Hormis Memorial Foundation lecture on 'Technological Challenges for National Development' here last night.
The cost of access to moon works out to about 50000 USD a kg and to go round the earth it is 20,000 USD a kg. Recently, the US had to cancel lunar exploration programmes due to the high cost, he said.
Nair said scientists have to evolve new technologies to reduce access to space by making less expensive rocket systems and to use re-useable rocket systems.A host of new systems and materials need to be developed, he said, adding by 2020, the aim was to reduce the cost of launch by half by adopting newer technologies. | <urn:uuid:1b917453-00a7-4b53-981a-6ec80cfeafd0> | 3.5 | 333 | News Article | Science & Tech. | 46.98702 | 95,591,476 |
The ductile-brittle transition zone in extensional regimes can play the role of a hydrogeological barrier. Quartz veins developed within an orthogneiss body located in the detachment footwall of a Metamorphic Core Complex (MCC) in the Nevado-Filábride units (Betics, Spain). The detachment footwall is composed mainly of gneisses, schists and metacarbonates from the Bédar-Macael sub-unit. Schist and metacarbonate bodies show evidence of ductile deformation at the time the gneiss was already undergoing brittle deformation and vein opening during exhumation. The vein system provides the opportunity to investigate the origin, composition and PVTX conditions of the fluids that circulated in the detachment footwall while the footwall units were crossing the ductile-brittle transition.The analysis of fluid inclusions reveals the presence of a single type of fluid: 30–40 mass% NaCl > KCl > CaCl2 > MgCl2 brines, with trace amounts of CO2 and N2 and tens to thousands of ppm of metals such as Fe, Sr, Li, Zn, Ba, Pb and Cu. δDfluid values between −39.8 and −16.7‰ and δ18Ofluid values between 4.4 and 11.7 ± 0.5‰ show that the brines have undergone protracted interaction with the host orthogneissic body. Coupled salinity and Cl/Br ratios (200 to 4400) indicate that the brines originate from dissolution of Triassic metaevaporites by metamorphic fluids variably enriched in Br by interaction with graphitic schists.This study highlights the absence of any record of surficial fluids within the veins, despite the brittle deformation conditions prevailing in this orthogneiss body. The fact that fluids from the detachment footwall were isolated from surficial fluid reservoirs may result from the presence of overlying schists and metacarbonates that continued to be affected by ductile deformation during vein formation in the gneiss, preventing downward circulation of surface-derived fluids.
Tectonophysics – Elsevier
Published: Mar 15, 2018
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Quantum computing is coming, so a lot of people are trying to articulate why we want it and how it works. Most of the explanations are either hardcore physics talking about spin and entanglement, or very breezy and handwaving which can be useful to get a little understanding but isn’t useful for applying the technology. Microsoft Research has a video that attempts to hit that spot in the middle — practical information for people who currently work with traditional computers. You can see the video below.
The video starts with basics you’d get from most videos talking about vector representation and operations. You have to get through about 17 minutes of that sort of thing until you get into qubits. If you glaze over on math, listen to the “index array” explanations [Andrew] gives after the math and you’ll be happier.
Continue reading “Quantum Computing For Computer Scientists”
Shared libraries are our best friends to extend the functionality of C programs without reinventing the wheel. They offer a collection of exported functions, variables, and other symbols that we can use inside our own program as if the content of the shared library was a direct part of our code. The usual way to use such libraries is to simply link against them at compile time, and let the linker resolve all external symbols and make sure everything is in place when creating our executable file. Whenever we then run our executable, the loader, a part of the operating system, will try to resolve again all the symbols, and load every required library into memory, along with our executable itself.
But what if we didn’t want to add libraries at compile time, but instead load them ourselves as needed during runtime? Instead of a predefined dependency on a library, we could make its presence optional and adjust our program’s functionality accordingly. Well, we can do just that with the concept of dynamic loading. In this article, we will look into dynamic loading, how to use it, and what to do with it — including building our own plugin system. But first, we will have a closer look at shared libraries and create one ourselves.
Continue reading “It’s All In The Libs – Building A Plugin System Using Dynamic Loading”
At this point, everyone has already heard that Microsoft is buying GitHub. Acquisitions of this scale take time, but most expect everything to be official by 2019. The general opinion online seems to be one of unease, and rightfully so. Even if we ignore Microsoft’s history of shady practices, there’s always an element of unease when somebody new takes over something you love. Sometimes it ends up being beneficial, the beginning of a new and better era. But sometimes…
Let’s not dwell on what might become of GitHub. While GitHub is the most popular web-based interface for Git, it’s not the only one. For example GitLab, a fully open source competitor to GitHub, is reporting record numbers of new repositories being created after word of the Microsoft buyout was confirmed. But even GitLab, while certainly worth checking out in these uncertain times, might be more than you strictly need.
Let’s be realistic. Most of the software projects hackers work on don’t need even half the features that GitHub/GitLab offer. Whether you’ve simply got a private project you want to maintain revisions of, or you’re working with a small group collaboratively in a hackerspace setting, you don’t need anything that isn’t already provided by the core Git software.
Let’s take a look at how quickly and easily you can setup a private Git server for you and your colleagues without having to worry about Microsoft (or anyone else) having their fingers around your code.
Continue reading “Keep it Close: A Private Git Server Crash Course”
What do you program the Arduino in? C? Actually, the Arduino’s byzantine build processes uses C++. All the features you get from the normal libraries are actually C++ classes. The problem is many people write C and ignore the C++ features other than using object already made for them. Just like traders often used pidgin English as a simplified language to talk to non-English speakers, many Arduino coders use pidgin C++ to effectively code C in a C++ environment. [Bert Hubert] has a two-part post that isn’t about the Arduino in particular, but is about moving from C to a more modern C++.
Continue reading “Arduino and Pidgin C++”
Based on [Ben Jojo’s] title — x86 Assembly Doesn’t have to be Scary — we assume that normal programmers fear assembly. Most hackers don’t mind it, but we also don’t often have an excuse to program assembly for desktop computers.
In fact, the post is really well suited for the typical hacker because it focuses the on real mode of an x86 processor after it boots. What makes this tutorial a little more interesting than the usual lecture is that it has interactive areas, where a VM runs your code in the browser after assembling with NASM.
Continue reading “Calm Down: It’s Only Assembly Language”
When the time comes to add an object recognizer to your hack, all you need do is choose from many of the available ones and retrain it for your particular objects of interest. To help with that, [Edje Electronics] has put together a step-by-step guide to using TensorFlow to retrain Google’s Inception object recognizer. He does it for Windows 10 since there’s already plenty of documentation out there for Linux OSes.
You’re not limited to just Inception though. Inception is one of a few which are very accurate but it can take a few seconds to process each image and so is more suited to a fast laptop or desktop machine. MobileNet is an example of one which is less accurate but recognizes faster and so is better for a Raspberry Pi or mobile phone.
You’ll need a few hundred images of your objects. These can either be scraped from an online source like Google’s images or you get take your own photos. If you use the latter approach, make sure to shoot from various angles, rotations, and with different lighting conditions. Fill your background with various other things and even have some things partially obscuring your objects. This may sound like a long, tedious task, but it can be done efficiently. [Edje Electronics] is working on recognizing playing cards so he first sprinkled them around his living room, added some clutter, and walked around, taking pictures using his phone. Once uploaded, some easy-to-use software helped him to label them all in around an hour. Note that he trained on 24 different objects, which are the number of different cards you get in a pinochle deck.
You’ll need to install a lot of software and do some configuration, but he walks you through that too. Ideally, you’d use a computer with a GPU but that’s optional, the difference being between three or twenty-four hours of training. Be sure to both watch his video below and follow the steps on his Github page. The Github page is kept most up-to-date but his video does a more thorough job of walking you through using the software, such as how to use the image labeling program.
Why is he training an object recognizer on playing cards? This is just one more step in making a blackjack playing robot. Previously he’d done an impressive job using OpenCV, even though the algorithm handled non-overlapping cards only. Google’s Inception, however, recognizes partially obscured cards. This is a very interesting project, one which we’ll be keeping an eye on. If you have any ideas for him, leave them in the comments below.
Continue reading “Using TensorFlow To Recognize Your Own Objects”
We’ve been talking a lot about machine learning lately. People are using it for speech generation and recognition, computer vision, and even classifying radio signals. If you’ve yet to climb the learning curve, you might be interested in a new free class from Google using TensorFlow.
Of course, we’ve covered tutorials for TensorFlow before, but this is structured as a 15 hour class with 25 lessons and 40 exercises. Of course, it is also from the horse’s mouth, so to speak. Google says the class will answer questions like:
- How does machine learning differ from traditional programming?
- What is loss, and how do I measure it?
- How does gradient descent work?
- How do I determine whether my model is effective?
- How do I represent my data so that a program can learn from it?
- How do I build a deep neural network?
Continue reading “Machine Learning Crash Course From Google” | <urn:uuid:fe166601-7dc5-4cd9-8db8-48e078bf6a8d> | 2.59375 | 1,885 | Content Listing | Software Dev. | 49.861479 | 95,591,502 |
This Summit will review progress on the implementation of the 10-year plan to create a Global Earth Observation System of Systems (GEOSS), agreed at the GEO summit held in Brussels in February 2005.
GEOSS will give policy-makers and the scientific community comprehensive and timely observation data about the Earth's physical, chemical and biological systems, which will help tackle many of today's challenges, such as the depletion of natural resources, the emergence of new diseases, climate change, the impact of migration and the loss of biodiversity. While in Cape Town, the Commissioner will celebrate with his South African counterpart 10 years of scientific co-operation between the EU and South Africa, talk to South African industrialists about the role of innovation in economic growth and visit two research centres, including the headquarters of the European and Developing Countries Clinical Trial Partnership.
"There are many areas of our future development where we will achieve much better results working together at international level than operating individually. Global Earth Observation is a prime example of this. We can work together to use science and technology to improve our decision-making on issues directly linked to the well-being of our planet and its people. I'm also pleased to be here in Cape Town celebrating 10 years of very successful scientific co-operation between the EU and South Africa."
More than 70 national governments and 50 international organisations are taking part in the Global Earth Observation Summit in Cape Town, to review progress and agree on future developments of GEOSS. The GEO summit is co-chaired by the European Commission, South Africa, US and China. GEOSS will link together many thousands of scientific observation instruments that are currently operating in isolation.
These include: floating buoys for monitoring ocean currents, temperature and salinity; land stations to record air quality and rainwater; sonar and radar systems that estimate bird and fish populations; and environmental satellites scanning the Earth from space. The 10-year plan envisages defining common technical standards, ensuring that data is inter-operable and building appropriate capacity within organisations. The European Commission supports this process through its Research Framework Programmes, the Global Monitoring for Environment and Security initiative and the African Monitoring of Environment for Sustainable Development programme. The infrastructure for Spatial Information in Europe directive promotes common spatial data and services in Europe, which can contribute to the definition of international standards.
While in Cape Town, Commissioner Potocnik will celebrate 10 years of successful scientific co-operation between South Africa and the European Union. This co-operation is thriving, with South Africa one of the top international participants in the Research Framework Programme (FP6). South African researchers took part in 117 international research projects, ranking it fourth, behind the United States of America, The People's Republic of China and the Russian Federation, in terms of successful FP6 participation by non-EU countries. The main areas of co-operation were Biotechnology and Genomics for Health, Food Safety and Quality, Global Change and Ecosystems, as well as Nanotechnology, Materials and Production. Both sides are looking to build on this positive experience for the current Framework Programme (FP7). He will meet with South African industrialists to discuss the role of innovation in economic development and the efforts being made in South Africa and the EU in this direction.
The Commissioner will also visit the International Centre for Genetic Engineering and Biotechnology at the University of Cape Town, and South Africa's Medical Research Council, which hosts the headquarters of the European and Developing Countries Clinical Trial Partnership (EDCTP), a joint effort of scientists from Europe and developing countries to undertake clinical trials for new developments in treating malaria, tuberculosis and HIV/AIDS.
Patrick Vittet-Philippe | alfa
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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173 pages, Col plates, b/w plates, illus, figs, tabs
This book provides a comprehensive overview of our current knowledge of comets. It presents a fascinating survey of the study of comets throughout history, from antiquity to the present day, and includes the most recent discoveries on the exceptional comets Hale-Bopp and Hyakutake. The authors discuss the role of comets in the formation of our Solar System and describe the links between comets, asteroids and the recently discovered Kuiper-belt objects. The book also includes new insights into the composition and nature of cometary nuclei, with results from the most up-to-date observation techniques. Written in a clear and lively style, and beautifully illustrated, this book will appeal to anyone interested in comets and astronomy, professionals and amateurs alike. It will be of particular interest to students and researchers in astronomy, astrophysics and planetary science, as well as general readers with a good background in physics.
'! a clear, succinct and authoritative narrative ! written by two French astronomers who have each contributed mightily to the modern understanding of comets. Comet Science is comprehensive yet brief, engaging yet authoritative, and fully accessible to a wide range of readers. It is well suited to student use and sufficiently detailed for astronomers wanting an overview of the state of the field, while remaining readable by the informed layperson.' Dale P. Cruikshank, Nature 'Comet Science by Jacques Crovisier and Therese Encrenaz spans the range from historical drawings to spacecraft investigations, from visual images to infrared and radio maps and spectra, and from old favourites like Comet Halley to new ones like Comet Hale-Bopp.' New Scientist 'Written in a clear and lively style, Comet Science, illustrates the vast wonders of Comets, which are the very remnants from the birth of our Solar System ! Appealing to anyone interested in the wonders of comets and astronomy, this book, which is written in a clear and straightforward style, makes it ideal for professionals and amateurs alike. Holding on to its main theme, that is, comet science, it thoroughly covers all topics with in-depth surveys into each sub-subject. Clear coloured photographs and diagrams illustrate the book throughout. As any astronomer would say, comets make a splendid introduction into the astounding and inspiring world of astronomy.' Astronomy and Space 'This is a well-written and excellently illustrated book by two world experts. it is a sheer pleasure to read. ! Both amateurs and professionals will enjoy comet browsing and studying. This book deserves an award for science appeal.' Irish Astronomical Journal 'Written in a clear and lively style, and beautifully illustrated, this book will appeal to anyone interested in comets and astronomy, professionals and amateurs alike.' Europe & Astronomy 'Readers will appreciate the happy balance between chapters devoted to observation and those devoted to techniques ! I completely agree.' Mike Moores, OUGS Journal
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Physics Question #127
Anonymous, a male from the Internet asks on January 30, 2000,
Who REALLY discovered oxygen? According to an National Public Radio program, in the 1850s 3 men at the same time discovered oxygen and its use. They named this new gas, but never got recognized for their discovery.
viewed 24340 times
answered on January 30, 2000
The discovery of oxygen happened in the 1770s, not the 1850s. It is normally credited to Joseph Priestley (1733–1804), an English clergyman and self-taught chemist. In those days chemistry was more like alchemy, or it was called apothecary. Nobody really knew what anything was made of. They thought everything was made of air, earth, water, and fire. There was no such thing as the periodic table of elements. The concept of "elements" was still evolving. Same with the idea of a gas. In 1774, during an experiment, Priestley noticed that mercuric oxide (they used to call it "mercury calx") when heated, yielded a "special air" that made a candle burn much faster, and that it would support respiration or life. He put a mouse in a vessel with his "special air" and it lived four times longer than with regular air, and was revived afterwards. Priestley published these experiments and observations in 1774.
A couple years before, in 1772 Karl W. Scheele, a Swedish apothecary discovered oxygen in a similar way, but never published his findings until 1777.
It was shortly after Priestley's discovery that he went on a trip to France and met Antoine Lavoisier, a French lawyer who was conducting scientific experiments trying to figure out what air was made of. Priestley told Lavoisier of his experiments, and this was the key Lavoisier needed to make sense of his own findings that ordinary air was made up of two major components in a ratio of about 3 to 1. Lavoiser named Priestley's special air “oxygen,” which comes from the Greek word roots that mean “acid-former.”
In summary, oxygen was probably first discovered by Scheele, but first reported by Priestley. It was not named until a bit later by the Frenchman Lavoisier. Who should get the credit?
A good explanation of the story is available at the website of the American Chemical Society although they focus on Priestley as he eventually moved to the United States and became an American.
Add to or comment on this answer using the form below.
Note: All submissions are moderated prior to posting.
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The Rosetta Lander Experiment Sesame and the New Target Comet 67P/Churyumov-Gerasimenko
SESAME is an international instrument complex carried by the Rosetta Lander. Most of the instrument sensors are mounted within the soles of the landing gear feet in order to provide good contact with or proximity to the cometary surface. The main aim of these instruments is to measure physical properties of the cometary surface layer and of emitted particles by acoustic and electrical methods. The scientific goals, the measuring principles and performance parameters are described. In addition, we discuss the impact by selecting 67P/Churyumov-Gerasimenko as the new target comet.
KeywordsLanding Gear Perihelion Distance Jupiter Family Comet Receiver Electrode Huygens Atmospheric Structure Instrument
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- Kochan, H., Feibig, W., Konopka, U., Kretschmer, M., M¨ohlmann, D., Seidensticker, K.J., Arnold, W., Gebhardt, W. and Licht, R. (2000). CASSE–The Rosetta Lander Comet Acoustic Surface Sounding Experiment-status of some aspects, the technical realisation and laboratory simulations, Planet. Space Sci., 48:385–399.Google Scholar
- Lamy, P.L., Toth, I., Weaver, H., Jorda, L. and Kaasalainen, M. (2003). The nucleus of comet 67P/Churyumov–Gerasimenko, the new target of the Rosetta mission, DPS 35th Meeting, Monterey, USA.Google Scholar
- ESA, Rosetta Lander Mission Analysis Working Group, Comet Surface Engineering Model (1999). RO–ESC–RP–5006, Issue 1.Google Scholar | <urn:uuid:ae35208d-1b9d-4b32-a6a4-46a3c14e843f> | 2.59375 | 386 | Truncated | Science & Tech. | 43.992008 | 95,591,526 |
You are wandering in the forest where you live, thinking about what you are going to have for dinner. Among the familiar calls of chickadees, you hear a foreign sound. You crouch in hiding, frightened for yourself and your family. Not until nightfall does the noise abate, allowing you to move again under the cloak of darkness. Soon you learn that the sounds come from unfamiliar beings taking over your homeland. You learn to live in hiding, believing that as soon as you let your guard down you may pay the ultimate price.
This is not the premise of a zombie apocalypse movie. It is the story of human expansion into wild places, where the wildlife that coexists with us often lives in chronic fear of humans.
Disturbance by humans changes the behavior of animals near towns, along roads and in areas that we use for mining, energy development and recreation. Although conservationists are starting to consider how the presence of humans affects the behavior of some species, they rarely analyze how these changes in animals’ behavior affects entire ecosystems. In my research examining pumas, or mountain lions, in California, I’ve found that our presence alters how they hunt for deer, which can have a significant effect on the ecosystem overall.
Fear is a powerful force in ecosystems. For decades, ecologists have acknowledged that fear can dictate when, where, and what animals eat, what habitats they use and how they communicate with one another. These behavioral changes in animals are ecologically important because they can change interactions among species. Although many animals are known to respond fearfully to their predators, we are only beginning to understand how humans elicit the same responses in wildlife.
In the Santa Cruz Mountains of California, I am studying how fear of humans in a top predator, the puma, resonates throughout the ecosystem. The Santa Cruz Mountains are isolated from other natural areas, bordered by the Pacific Ocean on the west, the San Francisco Bay metropolitan area on the north, and a major highway on the east. Like many places across the country, this region is dotted with residential developments and land utilized for mining and logging. However, it also contains open space preserves and state and county parks that provide important high-quality habitat for wildlife.
This kind of multi-use and fragmented landscape is increasingly becoming the norm in places where humans encroach on wild lands. To keep developing areas as wild as possible, we need to conserve natural animal behaviors and relationships.
With my colleagues at the Santa Cruz Puma Project, I am studying how human disturbances indirectly affect the behavior of pumas, the last remaining large carnivores in our region that roam the ravines between ridges lined with houses. We have found that pumas attempt to avoid people, but their sensitivity to disturbance depends on what the cats are doing. Although pumas consistently travel and kill prey relatively close to human developments, they make their dens and communicate with each other through scent marking in areas far from zones that humans have altered.
In many types of ecosystems, researchers have observed that animals will avoid feeding opportunities when they fear a predator. To see whether the presence of humans was having this effect on pumas, I examined behavioral changes at kill sites in areas of the Santa Cruz Mountains with varying levels of human activity. To find these kill sites, our team tracked GPS-collared pumas using their locations and searched for prey remains. I then used data from the GPS collars to learn how behavior at these kill changed near human development.
Surprisingly, I found that pumas often kill deer near human residences. However, unlike in wild areas where pumas stay close to their kills for a few days while they feed, pumas in developed areas leave their kills and move away from humans to rest, returning to feed only after dark. This causes pumas to waste energy by spending more time on the move, while losing opportunities to feed on their kills. Moreover, pumas that hunt in the most disturbed areas kill 36 percent more deer than pumas in the most rural areas. We believe that pumas ranging near developed areas kill more deer because they cannot fully consume their prey while also avoiding interactions with humans.
Our study provides evidence that the presence of humans not only changes the way top carnivores behave, but also indirectly impacts other species. Pumas that are afraid of humans but still hunt in residential areas alter their relationship with deer, their primary prey. Greater pressure on deer could possibly provide more food for scavengers or reduce deer browsing near developed areas.
Our work provides just one example of the cascading effects that human disturbance can cause in wild ecosystems. Human presence can fundamentally alter the ways in which species interact, which changes the function and composition of the animal community. By considering how humans impact the behavior of important species, we can develop conservation solutions that preserve entire functioning ecosystems.
Featured Photo Credit: Christopher Fust, Author provided. Pumas near San Jose, CA
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In this slightly dated article on Popular Science, Sarah Fecht believes that in just a few years humans could potentially set up a fully-functional and affordable moon base thanks to current technology most which has nothing at to do with space. Reportedly, self-driving cars and waste-recycling toilets are going to be "incredibly useful in space", making a moon-base an affordable reality.
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A lunar base would provide a valuable opportunity to test out new propulsion systems, habitats, communications, and life support systems before astronauts bring them to Mars--a 9-month trip away, versus just a few days to the moon.
The trouble is, NASA tends to think it can only afford to go to either the moon, or Mars. If McKay and his colleagues are right, we can afford to do both--it just takes a new way of thinking about it.
And speaking of space, NASA believes we will know about alien life within the next 20 years with a mission to Jupiter's moon, Europa:
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Dr John Rummel, a senior scientist at the Seti Institute in California, said it was important to “protect Europa for the Europans … not the Europeans”.
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From a microscopic point of view, the process of heat transport is governed by phonon-electron interaction in metallic films and by phonon scattering in dielectric films, insulators, and semiconductors. Other include the, andThe Open Library website has not been optimized for Internet Explorer 6, so some features and graphic elements may not appear correctly. Many sites, including and Facebook, have phased out support for IE6 due to security and support issues. Please consider upgrading to,,,, or to use this and other web sites to your fullest advantage. No es necesario ningún dispositivo Kindle. Descárgate una de las apps de Kindle gratuitas para comenzar a leer libros Kindle en tu smartphone, tablet u ordenador.
Haz que tu cesta sea útil: llénala de libros, DVD, productos electrónicos y mucho más. Hay un problema para ver una vista previa de tu carro de la compra en este momento. In this equation h is the heat transfer coefficient of the microscale heat exchanger, Nu is the Nusselt number which is about 8. 65, k is the thermal conductivity of the working fluid and d is the diameter of the microchannel which the fluid flows through. From this equation one can tell see how the size of the channel directly affects the heat transfer coefficient of the heat exchanger, as the diameter is decreased the heat transfer coefficient increases. The different types of microscale heat exchangers are the same as the different classifications of conventional heat exchangers.
They have either one or two passages for the fluid to flow through. When there is only one fluid and one passage in the heat exchanger the fluid is used to transfer the heat to another location. Application of this kind of heat exchangers is usually found in electronics to transfer heat into the fluid and out of the electronic device. When there are two fluids and two passages they are usually classified by the direction in which the fluids flow by each other. Microscale heat exchangers can either be cross flow or counter flow heat exchangers. Counter flow micro scale heat exchangers work the same way as macro-scale counter flow heat exchangers. In a counter flow heat exchanger the two fluids flow in opposite directions of each other.
The fluids enter the heat exchanger at opposite ends. The cooler fluids exits the counter flow microscale heat exchanger at the end where the hot fluid enters therefore the cooler fluid will approach the inlet temperature of the hot fluid. Counter flow microscale heat exchangers are more efficient than cross flow microscale heat exchangers. Department of Mechanical Engineering, University of New Mexico, Albuquerque, NM 87686A universal constitutive equation between the heat flux vector and the temperature gradient is proposed to cover the fundamental behaviors of diffusion (macroscopic in both space and time), wave (macroscopic in space but microscopic in time), phonon–electron interactions (microscopic in both space and time), and pure phonon scattering. The model is generalized from the dual-phase-lag concept accounting for the lagging behavior in the high-rate response. While the phase lag of the heat flux captures the small-scale response in time, the phase lag of the temperature gradient captures the small-scale response in space. The universal form of the energy equation facilitates identifications of the physical parameters governing the transition from one mechanism (such as diffusion or wave) to another (the phonon–electron interaction).
Sign in or create your free personal ASME account. This will give you the ability to save search results, receive TOC alerts, RSS feeds, and more. Then you can start reading Kindle books on your smartphone, tablet, or computer - no Kindle device required. Physical processes taking place in micro/nanoscale strongly depend on the material types and can be very complicated. Known approaches include kinetic theory and quantum mechanics, non-equilibrium and irreversible thermodynamics, molecular dynamics, and/or fractal theory and fraction model. Due to innately different physical bases employed, different approaches may involve different physical properties in describing micro/nanoscale heat transport. In addition, the parameters involved in different approaches, may not be mutually inclusive.
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Drilling holes on other planets and inventing novel textiles to secure large structures in space are just two of the 27 challenges that expert teams have been working on in the first year of ESA’s Innovation Triangle Initiative.
"By combining the creativity of the inventor, the needs of end users and the production experience of industry we have created strong drive and a very successful synergy to identify, demonstrate and verify novel ideas for future space technologies," says Marco Guglielmi, head of ESA’s Technology Strategy Section and one of the founders of ESA’s new Innovation Triangle Initiative.
The Innovation Triangle Initiative (ITI) started in March 2004 and in just 12 months surpassed all expectations by kicking off 27 projects, fully validating the basic objective of quickly verifying the potential of new ideas and technologies. One of its main goals is to explore technologies or services which although not designed with space in mind, do have the potential for use in space.
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Observable universe(Redirected from Large-scale structure of the universe)
The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects has had time to reach Earth since the beginning of the cosmological expansion. There are at least 2 trillion galaxies in the observable universe. Assuming the universe is isotropic, the distance to the edge of the observable universe is roughly the same in each direction. That is, the observable universe is a spherical volume (a ball) centered on the observer. Every location in the universe has its own observable universe, which may or may not overlap with the one centered on Earth.
Visualization of the whole observable universe. The scale is such that the fine grains represent collections of large numbers of superclusters. The Virgo Supercluster—home of Milky Way—is marked at the center, but is too small to be seen.
|Diameter||×1026 m 8.8(28.5 Gpc or 93 Gly)|
|Mass (ordinary matter)||1053 kg|
|Density||×10−30 g/cm3 (equivalent to 6 9.9protons per cubic meter of space)|
|Age||±0.021 billion years 13.799|
|Average temperature||2.72548 K|
Ordinary (baryonic) matter (4.9%)|
Dark matter (26.8%)
Dark energy (68.3%)
The word observable in this sense does not refer to the capability of modern technology to detect light or other information from an object, or whether there is anything to be detected. It refers to the physical limit created by the speed of light itself. Because no signals can travel faster than light, any object farther away from us than light could travel in the age of the universe (estimated as of 2015[update] around ±0.021 billion years 13.799) simply cannot be detected, as they have not reached us yet. Sometimes astrophysicists distinguish between the visible universe, which includes only signals emitted since recombination—and the observable universe, which includes signals since the beginning of the cosmological expansion (the Big Bang in traditional physical cosmology, the end of the inflationary epoch in modern cosmology).
According to calculations, the current comoving distance—proper distance, which takes into account that the universe has expanded since the light was emitted—to particles from which the cosmic microwave background radiation (CMBR) was emitted, which represent the radius of the visible universe, is about 14.0 billion parsecs (about 45.7 billion light-years), while the comoving distance to the edge of the observable universe is about 14.3 billion parsecs (about 46.6 billion light-years), about 2% larger. The radius of the observable universe is therefore estimated to be about 46.5 billion light-years and its diameter about 28.5 gigaparsecs (93 billion light-years, 8.8×1023 kilometres or 5.5×1023 miles). The total mass of ordinary matter in the universe can be calculated using the critical density and the diameter of the observable universe to be about 1.5×1053 kg.
Since the expansion of the universe is known to accelerate and will become exponential in the future, the light emitted from all distant objects past some time dependent on their current redshift will never reach the Earth. In the future all currently observable objects will slowly freeze in time while emitting progressively redder and fainter light. For instance, objects with the current redshift z from 5 to 10 will remain observable for no more than 4–6 billion years. In addition, light emitted by objects situated beyond a certain comoving distance (currently about 19 billion parsecs) will never reach Earth.
The universe versus the observable universeEdit
Some parts of the universe are too far away for the light emitted since the Big Bang to have had enough time to reach Earth, and so lie outside the observable universe. In the future, light from distant galaxies will have had more time to travel, so additional regions will become observable. However, due to Hubble's law, regions sufficiently distant from the Earth are expanding away from it faster than the speed of light (special relativity prevents nearby objects in the same local region from moving faster than the speed of light with respect to each other, but there is no such constraint for distant objects when the space between them is expanding; see uses of the proper distance for a discussion) and furthermore the expansion rate appears to be accelerating due to dark energy. Assuming dark energy remains constant (an unchanging cosmological constant), so that the expansion rate of the universe continues to accelerate, there is a "future visibility limit" beyond which objects will never enter our observable universe at any time in the infinite future, because light emitted by objects outside that limit would never reach the Earth. (A subtlety is that, because the Hubble parameter is decreasing with time, there can be cases where a galaxy that is receding from the Earth just a bit faster than light does emit a signal that reaches the Earth eventually.) This future visibility limit is calculated at a comoving distance of 19 billion parsecs (62 billion light-years), assuming the universe will keep expanding forever, which implies the number of galaxies that we can ever theoretically observe in the infinite future (leaving aside the issue that some may be impossible to observe in practice due to redshift, as discussed in the following paragraph) is only larger than the number currently observable by a factor of 2.36.
Though in principle more galaxies will become observable in the future, in practice an increasing number of galaxies will become extremely redshifted due to ongoing expansion, so much so that they will seem to disappear from view and become invisible. An additional subtlety is that a galaxy at a given comoving distance is defined to lie within the "observable universe" if we can receive signals emitted by the galaxy at any age in its past history (say, a signal sent from the galaxy only 500 million years after the Big Bang), but because of the universe's expansion, there may be some later age at which a signal sent from the same galaxy can never reach the Earth at any point in the infinite future (so, for example, we might never see what the galaxy looked like 10 billion years after the Big Bang), even though it remains at the same comoving distance (comoving distance is defined to be constant with time—unlike proper distance, which is used to define recession velocity due to the expansion of space), which is less than the comoving radius of the observable universe.[clarification needed] This fact can be used to define a type of cosmic event horizon whose distance from the Earth changes over time. For example, the current distance to this horizon is about 16 billion light-years, meaning that a signal from an event happening at present can eventually reach the Earth in the future if the event is less than 16 billion light-years away, but the signal will never reach the Earth if the event is more than 16 billion light-years away.
Both popular and professional research articles in cosmology often use the term "universe" to mean "observable universe". This can be justified on the grounds that we can never know anything by direct experimentation about any part of the universe that is causally disconnected from the Earth, although many credible theories require a total universe much larger than the observable universe. No evidence exists to suggest that the boundary of the observable universe constitutes a boundary on the universe as a whole, nor do any of the mainstream cosmological models propose that the universe has any physical boundary in the first place, though some models propose it could be finite but unbounded, like a higher-dimensional analogue of the 2D surface of a sphere that is finite in area but has no edge. It is plausible that the galaxies within our observable universe represent only a minuscule fraction of the galaxies in the universe. According to the theory of cosmic inflation initially introduced by its founder, Alan Guth (and by D. Kazanas ), if it is assumed that inflation began about 10−37 seconds after the Big Bang, then with the plausible assumption that the size of the universe before the inflation occurred was approximately equal to the speed of light times its age, that would suggest that at present the entire universe's size is at least 3×1023 times the radius of the observable universe. There are also lower estimates claiming that the entire universe is in excess of 250 times larger than the observable universe and also higher estimates implying that the universe is at least 101010122 times larger than the observable universe.
If the universe is finite but unbounded, it is also possible that the universe is smaller than the observable universe. In this case, what we take to be very distant galaxies may actually be duplicate images of nearby galaxies, formed by light that has circumnavigated the universe. It is difficult to test this hypothesis experimentally because different images of a galaxy would show different eras in its history, and consequently might appear quite different. Bielewicz et al. claims to establish a lower bound of 27.9 gigaparsecs (91 billion light-years) on the diameter of the last scattering surface (since this is only a lower bound, the paper leaves open the possibility that the whole universe is much larger, even infinite). This value is based on matching-circle analysis of the WMAP 7 year data. This approach has been disputed.
The comoving distance from Earth to the edge of the observable universe is about 14.26 gigaparsecs (46.5 billion light-years or 4.40×1026 meters) in any direction. The observable universe is thus a sphere with a diameter of about 28.5 gigaparsecs (93 Gly or 8.8×1026 m). Assuming that space is roughly flat (in the sense of being a Euclidean space), this size corresponds to a comoving volume of about ×104 Gpc3 ( 1.22×105 Gly3 or 4.22×1080 m3). 3.57
The figures quoted above are distances now (in cosmological time), not distances at the time the light was emitted. For example, the cosmic microwave background radiation that we see right now was emitted at the time of photon decoupling, estimated to have occurred about years after the Big Bang, 380,000 which occurred around 13.8 billion years ago. This radiation was emitted by matter that has, in the intervening time, mostly condensed into galaxies, and those galaxies are now calculated to be about 46 billion light-years from us. To estimate the distance to that matter at the time the light was emitted, we may first note that according to the Friedmann–Lemaître–Robertson–Walker metric, which is used to model the expanding universe, if at the present time we receive light with a redshift of z, then the scale factor at the time the light was originally emitted is given by
WMAP nine-year results combined with other measurements give the redshift of photon decoupling as z = 091.64±0.47, 1 which implies that the scale factor at the time of photon decoupling would be 1⁄1092.64. So if the matter that originally emitted the oldest CMBR photons has a present distance of 46 billion light-years, then at the time of decoupling when the photons were originally emitted, the distance would have been only about 42 million light-years.
Misconceptions on its sizeEdit
Many secondary sources have reported a wide variety of incorrect figures for the size of the visible universe. Some of these figures are listed below, with brief descriptions of possible reasons for misconceptions about them.
- 13.8 billion light-years
- The age of the universe is estimated to be 13.8 billion years. While it is commonly understood that nothing can accelerate to velocities equal to or greater than that of light, it is a common misconception that the radius of the observable universe must therefore amount to only 13.8 billion light-years. This reasoning would only make sense if the flat, static Minkowski spacetime conception under special relativity were correct. In the real universe, spacetime is curved in a way that corresponds to the expansion of space, as evidenced by Hubble's law. Distances obtained as the speed of light multiplied by a cosmological time interval have no direct physical significance.
- 15.8 billion light-years
- This is obtained in the same way as the 13.8-billion-light-year figure, but starting from an incorrect age of the universe that the popular press reported in mid-2006. For an analysis of this claim and the paper that prompted it, see the following reference at the end of this article.
- 27.6 billion light-years
- This is a diameter obtained from the (incorrect) radius of 13.8 billion light-years.
- 78 billion light-years
- In 2003, Cornish et al. found this lower bound for the diameter of the whole universe (not just the observable part), postulating that the universe is finite in size due to its having a nontrivial topology, with this lower bound based on the estimated current distance between points that we can see on opposite sides of the cosmic microwave background radiation (CMBR). If the whole universe is smaller than this sphere, then light has had time to circumnavigate it since the Big Bang, producing multiple images of distant points in the CMBR, which would show up as patterns of repeating circles. Cornish et al. looked for such an effect at scales of up to 24 gigaparsecs (78 Gly or 7.4×1026 m) and failed to find it, and suggested that if they could extend their search to all possible orientations, they would then "be able to exclude the possibility that we live in a universe smaller than 24 Gpc in diameter". The authors also estimated that with "lower noise and higher resolution CMB maps (from WMAP's extended mission and from Planck), we will be able to search for smaller circles and extend the limit to ~28 Gpc." This estimate of the maximum lower bound that can be established by future observations corresponds to a radius of 14 gigaparsecs, or around 46 billion light-years, about the same as the figure for the radius of the visible universe (whose radius is defined by the CMBR sphere) given in the opening section. A 2012 preprint by most of the same authors as the Cornish et al. paper has extended the current lower bound to a diameter of 98.5% the diameter of the CMBR sphere, or about 26 Gpc.
- 156 billion light-years
- This figure was obtained by doubling 78 billion light-years on the assumption that it is a radius. Because 78 billion light-years is already a diameter (the original paper by Cornish et al. says, "By extending the search to all possible orientations, we will be able to exclude the possibility that we live in a universe smaller than 24 Gpc in diameter," and 24 Gpc is 78 billion light-years), the doubled figure is incorrect. This figure was very widely reported. A press release from Montana State University–Bozeman, where Cornish works as an astrophysicist, noted the error when discussing a story that had appeared in Discover magazine, saying "Discover mistakenly reported that the universe was 156 billion light-years wide, thinking that 78 billion was the radius of the universe instead of its diameter." As noted above, 78 billion was also incorrect.
- 180 billion light-years
- This estimate combines the erroneous 156-billion-light-year figure with evidence that the M33 Galaxy is actually fifteen percent farther away than previous estimates and that, therefore, the Hubble constant is fifteen percent smaller. The 180-billion figure is obtained by adding 15% to 156 billion light-years.
Sky surveys and mappings of the various wavelength bands of electromagnetic radiation (in particular 21-cm emission) have yielded much information on the content and character of the universe's structure. The organization of structure appears to follow as a hierarchical model with organization up to the scale of superclusters and filaments. Larger than this (at scales between 30 and 200 megaparsecs), there seems to be no continued structure, a phenomenon that has been referred to as the End of Greatness.
Walls, filaments, nodes, and voidsEdit
The organization of structure arguably begins at the stellar level, though most cosmologists rarely address astrophysics on that scale. Stars are organized into galaxies, which in turn form galaxy groups, galaxy clusters, superclusters, sheets, walls and filaments, which are separated by immense voids, creating a vast foam-like structure sometimes called the "cosmic web". Prior to 1989, it was commonly assumed that virialized galaxy clusters were the largest structures in existence, and that they were distributed more or less uniformly throughout the universe in every direction. However, since the early 1980s, more and more structures have been discovered. In 1983, Adrian Webster identified the Webster LQG, a large quasar group consisting of 5 quasars. The discovery was the first identification of a large-scale structure, and has expanded the information about the known grouping of matter in the universe. In 1987, Robert Brent Tully identified the Pisces–Cetus Supercluster Complex, the galaxy filament in which the Milky Way resides. It is about 1 billion light-years across. That same year, an unusually large region with no galaxies was discovered, the Giant Void, which measures 1.3 billion light-years across. Based on redshift survey data, in 1989 Margaret Geller and John Huchra discovered the "Great Wall", a sheet of galaxies more than 500 million light-years long and 200 million light-years wide, but only 15 million light-years thick. The existence of this structure escaped notice for so long because it requires locating the position of galaxies in three dimensions, which involves combining location information about the galaxies with distance information from redshifts. Two years later, astronomers Roger G. Clowes and Luis E. Campusano discovered the Clowes–Campusano LQG, a large quasar group measuring two billion light-years at its widest point which was the largest known structure in the universe at the time of its announcement. In April 2003, another large-scale structure was discovered, the Sloan Great Wall. In August 2007, a possible supervoid was detected in the constellation Eridanus. It coincides with the 'CMB cold spot', a cold region in the microwave sky that is highly improbable under the currently favored cosmological model. This supervoid could cause the cold spot, but to do so it would have to be improbably big, possibly a billion light-years across, almost as big as the Giant Void mentioned above.
Another large-scale structure is the Newfound Blob, a collection of galaxies and enormous gas bubbles that measures about 200 million light-years across.
In 2011, a large quasar group was discovered, U1.11, measuring about 2.5 billion light-years across. On January 11, 2013, another large quasar group, the Huge-LQG, was discovered, which was measured to be four billion light-years across, the largest known structure in the universe at that time. In November 2013, astronomers discovered the Hercules–Corona Borealis Great Wall, an even bigger structure twice as large as the former. It was defined by the mapping of gamma-ray bursts.
End of GreatnessEdit
The End of Greatness is an observational scale discovered at roughly 100 Mpc (roughly 300 million light-years) where the lumpiness seen in the large-scale structure of the universe is homogenized and isotropized in accordance with the Cosmological Principle. At this scale, no pseudo-random fractalness is apparent. The superclusters and filaments seen in smaller surveys are randomized to the extent that the smooth distribution of the universe is visually apparent. It was not until the redshift surveys of the 1990s were completed that this scale could accurately be observed.
Another indicator of large-scale structure is the 'Lyman-alpha forest'. This is a collection of absorption lines that appear in the spectra of light from quasars, which are interpreted as indicating the existence of huge thin sheets of intergalactic (mostly hydrogen) gas. These sheets appear to be associated with the formation of new galaxies.
Caution is required in describing structures on a cosmic scale because things are often different from how they appear. Gravitational lensing (bending of light by gravitation) can make an image appear to originate in a different direction from its real source. This is caused when foreground objects (such as galaxies) curve surrounding spacetime (as predicted by general relativity), and deflect passing light rays. Rather usefully, strong gravitational lensing can sometimes magnify distant galaxies, making them easier to detect. Weak lensing (gravitational shear) by the intervening universe in general also subtly changes the observed large-scale structure.
The large-scale structure of the universe also looks different if one only uses redshift to measure distances to galaxies. For example, galaxies behind a galaxy cluster are attracted to it, and so fall towards it, and so are slightly blueshifted (compared to how they would be if there were no cluster) On the near side, things are slightly redshifted. Thus, the environment of the cluster looks a bit squashed if using redshifts to measure distance. An opposite effect works on the galaxies already within a cluster: the galaxies have some random motion around the cluster center, and when these random motions are converted to redshifts, the cluster appears elongated. This creates a "finger of God"—the illusion of a long chain of galaxies pointed at the Earth.
Cosmography of Earth's cosmic neighborhoodEdit
At the centre of the Hydra-Centaurus Supercluster, a gravitational anomaly called the Great Attractor affects the motion of galaxies over a region hundreds of millions of light-years across. These galaxies are all redshifted, in accordance with Hubble's law. This indicates that they are receding from us and from each other, but the variations in their redshift are sufficient to reveal the existence of a concentration of mass equivalent to tens of thousands of galaxies.
The Great Attractor, discovered in 1986, lies at a distance of between 150 million and 250 million light-years (250 million is the most recent estimate), in the direction of the Hydra and Centaurus constellations. In its vicinity there is a preponderance of large old galaxies, many of which are colliding with their neighbours, or radiating large amounts of radio waves.
In 1987, astronomer R. Brent Tully of the University of Hawaii's Institute of Astronomy identified what he called the Pisces–Cetus Supercluster Complex, a structure one billion light-years long and 150 million light-years across in which, he claimed, the Local Supercluster was embedded.
Mass of ordinary matterEdit
The mass of the observable universe is often quoted as 1050 tonnes or 1053 kg. In this context, mass refers to ordinary matter and includes the interstellar medium (ISM) and the intergalactic medium (IGM). However, it excludes dark matter and dark energy. This quoted value for the mass of ordinary matter in the universe can be estimated based on critical density. The calculations are for the observable universe only as the volume of the whole is unknown and may be infinite.
Estimates based on critical densityEdit
Critical density is the energy density for which the universe is flat. If there is no dark energy, it is also the density for which the expansion of the universe is poised between continued expansion and collapse. From the Friedmann equations, the value for critical density, is:
where G is the gravitational constant and H0 is the present value of the Hubble constant. The current value for H0, due to the European Space Agency's Planck Telescope, is H0 = 67.15 kilometers per second per mega parsec. This gives a critical density of ×10−26 kg/m3 (commonly quoted as about 5 hydrogen atoms per cubic meter). This density includes four significant types of energy/mass: ordinary matter (4.8%), neutrinos (0.1%), 0.85cold dark matter (26.8%), and dark energy (68.3%). Note that although neutrinos are defined as particles like electrons, they are listed separately because they are difficult to detect and so different from ordinary matter. The density of ordinary matter, as measured by Planck, is 4.8% of the total critical density or ×10−28 kg/m3. To convert this density to mass we must multiply by volume, a value based on the radius of the "observable universe". Since the universe has been expanding for 13.8 billion years, the 4.08comoving distance (radius) is now about 46.6 billion light-years. Thus, volume (4/πr3) equals ×1080 m3 and the mass of ordinary matter equals density ( 3.58×10−28 kg/m3) times volume ( 4.08×1080 m3) or 3.58×1053 kg. 1.46
Matter content – number of atomsEdit
Assuming the mass of ordinary matter is about ×1053 kg (refer to previous section) and assuming all atoms are 1.45hydrogen atoms (which in reality make up about 74% of all atoms in our galaxy by mass, see Abundance of the chemical elements), calculating the estimated total number of atoms in the observable universe is straightforward. Divide the mass of ordinary matter by the mass of a hydrogen atom (×1053 kg divided by 1.45×10−27 kg). The result is approximately 1080 hydrogen atoms. 1.67
Most distant objectsEdit
The most distant astronomical object yet announced as of January 2011 is a galaxy candidate classified UDFj-39546284. In 2009, a gamma ray burst, GRB 090423, was found to have a redshift of 8.2, which indicates that the collapsing star that caused it exploded when the universe was only 630 million years old. The burst happened approximately 13 billion years ago, so a distance of about 13 billion light-years was widely quoted in the media (or sometimes a more precise figure of 13.035 billion light-years), though this would be the "light travel distance" (see Distance measures (cosmology)) rather than the "proper distance" used in both Hubble's law and in defining the size of the observable universe (cosmologist Ned Wright argues against the common use of light travel distance in astronomical press releases on this page, and at the bottom of the page offers online calculators that can be used to calculate the current proper distance to a distant object in a flat universe based on either the redshift z or the light travel time). The proper distance for a redshift of 8.2 would be about 9.2 Gpc, or about 30 billion light-years. Another record-holder for most distant object is a galaxy observed through and located beyond Abell 2218, also with a light travel distance of approximately 13 billion light-years from Earth, with observations from the Hubble telescope indicating a redshift between 6.6 and 7.1, and observations from Keck telescopes indicating a redshift towards the upper end of this range, around 7. The galaxy's light now observable on Earth would have begun to emanate from its source about 750 million years after the Big Bang.
The limit of observability in our universe is set by a set of cosmological horizons which limit—based on various physical constraints—the extent to which we can obtain information about various events in the universe. The most famous horizon is the particle horizon which sets a limit on the precise distance that can be seen due to the finite age of the universe. Additional horizons are associated with the possible future extent of observations (larger than the particle horizon owing to the expansion of space), an "optical horizon" at the surface of last scattering, and associated horizons with the surface of last scattering for neutrinos and gravitational waves.
- Itzhak Bars; John Terning (November 2009). Extra Dimensions in Space and Time. Springer. pp. 27–. ISBN 978-0-387-77637-8. Retrieved 2011-05-01.
- What is the Universe Made Of?
- Paul Davies (2006). The Goldilocks Enigma. First Mariner Books. p. 43–. ISBN 978-0-618-59226-5.
- http://map.gsfc.nasa.gov/universe/uni_matter.html January 13, 2015
- Planck Collaboration (2015). "Planck 2015 results. XIII. Cosmological parameters (See Table 4 on page 31 of pfd)". Astronomy & Astrophysics. 594: A13. arXiv: . Bibcode:2016A&A...594A..13P. doi:10.1051/0004-6361/201525830.
- Fixsen, D. J. (December 2009). "The Temperature of the Cosmic Microwave Background". The Astrophysical Journal. 707 (2): 916–920. arXiv: . Bibcode:2009ApJ...707..916F. doi:10.1088/0004-637X/707/2/916.
- Christopher J. Conselice; et al. (2016). "The Evolution of Galaxy Number Density at z < 8 and its Implications". The Astrophysical Journal. 830 (2): 83. arXiv: . Bibcode:2016ApJ...830...83C. doi:10.3847/0004-637X/830/2/83.
- Fountain, Henry (17 October 2016). "Two Trillion Galaxies, at the Very Least". New York Times. Retrieved 17 October 2016.
- Gott III, J. Richard; Mario Jurić; David Schlegel; Fiona Hoyle; et al. (2005). "A Map of the Universe" (PDF). The Astrophysical Journal. 624 (2): 463–484. arXiv: . Bibcode:2005ApJ...624..463G. doi:10.1086/428890.
- Frequently Asked Questions in Cosmology. Astro.ucla.edu. Retrieved on 2011-05-01.
- Lineweaver, Charles; Tamara M. Davis (2005). "Misconceptions about the Big Bang". Scientific American.
- Itzhak Bars; John Terning (November 2009). Extra Dimensions in Space and Time. Springer. pp. 27–. ISBN 978-0-387-77637-8. Retrieved 1 May 2011.
- See the "Mass of ordinary matter" section in this article.
- Loeb, Abraham (2002). "Long-term future of extragalactic astronomy". Physical Review D. 65 (4). arXiv: . Bibcode:2002PhRvD..65d7301L. doi:10.1103/PhysRevD.65.047301.
- Is the universe expanding faster than the speed of light? (see the last two paragraphs)
- The comoving distance of the future visibility limit is calculated on p. 8 of Gott et al.'s A Map of the Universe to be 4.50 times the Hubble radius, given as 4.220 billion parsecs (13.76 billion light-years), whereas the current comoving radius of the observable universe is calculated on p. 7 to be 3.38 times the Hubble radius. The number of galaxies in a sphere of a given comoving radius is proportional to the cube of the radius, so as shown on p. 8 the ratio between the number of galaxies observable in the future visibility limit to the number of galaxies observable today would be (4.50/3.38)3 = 2.36.
- Krauss, Lawrence M.; Robert J. Scherrer (2007). "The Return of a Static Universe and the End of Cosmology". General Relativity and Gravitation. 39 (10): 1545–1550. arXiv: . Bibcode:2007GReGr..39.1545K. doi:10.1007/s10714-007-0472-9.
- Using Tiny Particles To Answer Giant Questions. Science Friday, 3 Apr 2009. According to the transcript, Brian Greene makes the comment "And actually, in the far future, everything we now see, except for our local galaxy and a region of galaxies will have disappeared. The entire universe will disappear before our very eyes, and it's one of my arguments for actually funding cosmology. We've got to do it while we have a chance."
- See also Faster than light#Universal expansion and Future of an expanding universe#Galaxies outside the Local Supercluster are no longer detectable.
- Loeb, Abraham (2002). "The Long-Term Future of Extragalactic Astronomy". Physical Review D. 65 (4). arXiv: . Bibcode:2002PhRvD..65d7301L. doi:10.1103/PhysRevD.65.047301.
- "Dynamics of the Universe and Spontaneous Symmetry Breaking" Kazanas, D., Ap. J. (Lett.), 241, L59-L63.
- Alan H. Guth (17 March 1998). The inflationary universe: the quest for a new theory of cosmic origins. Basic Books. pp. 186–. ISBN 978-0-201-32840-0. Retrieved 1 May 2011.
- Universe Could be 250 Times Bigger Than What is Observable – by Vanessa D'Amico on February 8, 2011 http://www.universetoday.com/83167/universe-could-be-250-times-bigger-than-what-is-observable/
- Susskind’s Challenge to the Hartle-Hawking No-Boundary Proposal and Possible Resolutions – by Don N. page on December 15, 2006 https://arxiv.org/pdf/hep-th/0610199v2.pdf
- Bielewicz, P.; Banday, A. J.; Gorski, K. M. (2013). "Constraints on the Topology of the Universe". Proceedings of the XLVIIth Rencontres de Moriond, , eds. E. Auge, J. Dumarchez and J. Tran Thanh Van, published by ARISF, p. 2012 (91). arXiv: . Bibcode:2013arXiv1303.4004B.
- Mota; Reboucas; Tavakol (2010). "Observable circles-in-the-sky in flat universes". arXiv: [astro-ph.CO].
- "WolframAlpha". Retrieved 29 November 2011.
- "WolframAlpha". Retrieved 29 November 2011.
- "WolframAlpha". Retrieved 15 February 2016.
- "Seven-Year Wilson Microwave Anisotropy Probe (WMAP) Observations: Sky Maps, Systematic Errors, and Basic Results" (PDF). nasa.gov. Retrieved 2010-12-02. (see p. 39 for a table of best estimates for various cosmological parameters)
- Abbott, Brian (May 30, 2007). "Microwave (WMAP) All-Sky Survey". Hayden Planetarium. Retrieved 2008-01-13.
- Paul Davies (28 August 1992). The new physics. Cambridge University Press. pp. 187–. ISBN 978-0-521-43831-5. Retrieved 1 May 2011.
- V. F. Mukhanov (2005). Physical foundations of cosmology. Cambridge University Press. pp. 58–. ISBN 978-0-521-56398-7. Retrieved 1 May 2011.
- Bennett, C. L.; Larson, D.; Weiland, J. L.; Jarosik, N.; et al. (1 October 2013). "Nine-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results". The Astrophysical Journal Supplement Series. 208 (2): 20. arXiv: . Bibcode:2013ApJS..208...20B. doi:10.1088/0067-0049/208/2/20.
- Ned Wright, "Why the Light Travel Time Distance should not be used in Press Releases".
- Universe Might be Bigger and Older than Expected. Space.com (2006-08-07). Retrieved on 2011-05-01.
- Big bang pushed back two billion years – space – 04 August 2006 – New Scientist. Space.newscientist.com. Retrieved on 2011-05-01.
- Edward L. Wright, "An Older but Larger Universe?"
- Cornish; Spergel; Starkman; Eiichiro Komatsu (May 2004) [October 2003 (arXiv)]. "Constraining the Topology of the Universe". Phys. Rev. Lett. 92 (20): 201302. arXiv: . Bibcode:2004PhRvL..92t1302C. doi:10.1103/PhysRevLett.92.201302. PMID 15169334. 201302.
- Levin, Janna. "In space, do all roads lead to home?". plus.maths.org. Retrieved 2012-08-15.
- "Archived copy" (PDF). Archived from the original (PDF) on 2011-09-29. Retrieved 2011-09-18.
- Bob Gardner's "Topology, Cosmology and Shape of Space" Talk, Section 7 Archived 2012-08-02 at Archive.is. Etsu.edu. Retrieved on 2011-05-01.
- Vaudrevange; Starkmanl; Cornish; Spergel (2012). "Constraints on the Topology of the Universe: Extension to General Geometries". Physical Review D. 86 (8). arXiv: . Bibcode:2012PhRvD..86h3526V. doi:10.1103/PhysRevD.86.083526.
- SPACE.com – Universe Measured: We're 156 Billion Light-years Wide!
- Roy, Robert. (2004-05-24) New study super-sizes the universe – Technology & science – Space – Space.com – msnbc.com. MSNBC. Retrieved on 2011-05-01.
- "Astronomers size up the Universe". BBC News. 2004-05-28. Retrieved 2010-05-20.
- "MSU researcher recognized for discoveries about universe". 2004-12-21. Retrieved 2011-02-08.
- Space.com – Universe Might be Bigger and Older than Expected
- Carroll, Bradley W.; Ostlie, Dale A. (2013-07-23). An Introduction to Modern Astrophysics (International ed.). Pearson. p. 1178. ISBN 9781292022932.
- Robert P Kirshner (2002). The Extravagant Universe: Exploding Stars, Dark Energy and the Accelerating Cosmos. Princeton University Press. p. 71. ISBN 0-691-05862-8.
- Carroll, Bradley W.; Ostlie, Dale A. (2013-07-23). An Introduction to Modern Astrophysics (International ed.). Pearson. pp. 1173–1174. ISBN 9781292022932.
- M. J. Geller; J. P. Huchra (1989). "Mapping the universe". Science. 246 (4932): 897–903. Bibcode:1989Sci...246..897G. doi:10.1126/science.246.4932.897. PMID 17812575.
- Biggest void in space is 1 billion light years across – space – 24 August 2007 – New Scientist. Space.newscientist.com. Retrieved on 2011-05-01.
- Wall, Mike (2013-01-11). "Largest structure in universe discovered". Fox News.
- Horváth, I; Hakkila, Jon; Bagoly, Z. (2014). "Possible structure in the GRB sky distribution at redshift two". Astronomy & Astrophysics. 561: L12. arXiv: . Bibcode:2014A&A...561L..12H. doi:10.1051/0004-6361/201323020.
- Horvath, I.; Hakkila, J.; Bagoly, Z. (2013). "The largest structure of the Universe, defined by Gamma-Ray Bursts". arXiv: [astro-ph.CO].
- Klotz, Irene (2013-11-19). "Universe's Largest Structure is a Cosmic Conundrum". Discovery.
- LiveScience.com, "The Universe Isn't a Fractal, Study Finds", Natalie Wolchover,22 August 2012
- 1Jarrett, T. H. (2004). "Large Scale Structure in the Local Universe: The 2MASS Galaxy Catalog". Publications of the Astronomical Society of Australia. 21 (4): 396–403. arXiv: . Bibcode:2004PASA...21..396J. doi:10.1071/AS04050.
- Massive Clusters of Galaxies Defy Concepts of the Universe N.Y. Times Tue. November 10, 1987:
- Map of the Pisces-Cetus Supercluster Complex:
- See Friedmann equations#Density parameter.
- Michio Kaku (2005). Parallel Worlds. Anchor Books. p. 385. ISBN 978-1-4000-3372-0. Retrieved 1 July 2013.
- Bernard F. Schutz (2003). Gravity from the ground up. Cambridge University Press. pp. 361–. ISBN 978-0-521-45506-0. Retrieved 1 May 2011.
- Planck collaboration (2013). "Planck 2013 results. XVI. Cosmological parameters". Astronomy & Astrophysics. 571: A16. arXiv: . Bibcode:2014A&A...571A..16P. doi:10.1051/0004-6361/201321591.
- New Gamma-Ray Burst Smashes Cosmic Distance Record – NASA Science. Science.nasa.gov. Retrieved on 2011-05-01.
- More Observations of GRB 090423, the Most Distant Known Object in the Universe. Universetoday.com (2009-10-28). Retrieved on 2011-05-01.
- Meszaros, Attila; et al. (2009). "Impact on cosmology of the celestial anisotropy of the short gamma-ray bursts". Baltic Astronomy. 18: 293–296. arXiv: . Bibcode:2009BaltA..18..293M.
- Hubble and Keck team up to find farthest known galaxy in the Universe|Press Releases|ESA/Hubble. Spacetelescope.org (2004-02-15). Retrieved on 2011-05-01.
- MSNBC: "Galaxy ranks as most distant object in cosmos"
- Vicent J. Martínez; Jean-Luc Starck; Enn Saar; David L. Donoho; et al. (2005). "Morphology Of The Galaxy Distribution From Wavelet Denoising". The Astrophysical Journal. 634 (2): 744–755. arXiv: . Bibcode:2005ApJ...634..744M. doi:10.1086/497125.
- Mureika, J. R. & Dyer, C. C. (2004). "Review: Multifractal Analysis of Packed Swiss Cheese Cosmologies". General Relativity and Gravitation. 36 (1): 151–184. arXiv: . Bibcode:2004GReGr..36..151M. doi:10.1023/B:GERG.0000006699.45969.49.
- Gott, III, J. R.; et al. (May 2005). "A Map of the Universe". The Astrophysical Journal. 624 (2): 463–484. arXiv: . Bibcode:2005ApJ...624..463G. doi:10.1086/428890.
- F. Sylos Labini; M. Montuori & L. Pietronero (1998). "Scale-invariance of galaxy clustering". Physics Reports. 293 (1): 61–226. arXiv: . Bibcode:1998PhR...293...61S. doi:10.1016/S0370-1573(97)00044-6.
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- Calculating the total mass of ordinary matter in the universe, what you always wanted to know
- "Millennium Simulation" of structure forming – Max Planck Institute of Astrophysics, Garching, Germany
- Visualisations of large-scale structure: animated spins of groups, clusters, filaments and voids – identified in SDSS data by MSPM (Sydney Institute for Astronomy)
- NASA Astronomy Picture of the Day: The Sloan Great Wall: Largest Known Structure? (7 November 2007)
- Cosmology FAQ
- Forming Galaxies Captured In The Young Universe By Hubble, VLT & Spitzer
- NASA featured Images and Galleries
- Star Survey reaches 70 sextillion
- Animation of the cosmic light horizon
- Inflation and the Cosmic Microwave Background by Charles Lineweaver
- Logarithmic Maps of the Universe
- List of publications of the 2dF Galaxy Redshift Survey
- The Universe Within 14 Billion Light Years – NASA Atlas of the Universe – Note, this map only gives a rough cosmographical estimate of the expected distribution of superclusters within the observable universe; very little actual mapping has been done beyond a distance of one billion light-years.
- Video: "The Known Universe", from the American Museum of Natural History
- NASA/IPAC Extragalactic Database
- Cosmography of the Local Universe at irfu.cea.fr (17:35) (arXiv)
- Size and age of the Universe – at Astronoo | <urn:uuid:144c966f-6ff5-4624-a2d7-eaa289da72c3> | 4.09375 | 9,831 | Knowledge Article | Science & Tech. | 60.281892 | 95,591,628 |
"The Marbled Murrelet (Brachyramphus marmoratus) is a small diving seabird of the Alcid family which is on the Federally Threatened Species list, and is state listed as endangered or threatened in California, Oregon, and Washington (Nelson, 1997). Because their nests are dispersed and difficult to locate within old forests on the west coast, most research on overall abundance and reproductive output is conducted at sea, where the birds are concentrated within a few km of shore on the open coast...This report summarizes population estimation and productivity indice results of the 2001 season and compares these data with earlier research in Oregon." (From Introduction)
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A cooling bath, in laboratory chemistry practice, is a liquid mixture which is used to maintain low temperatures, typically between 13 °C and −196 °C. These low temperatures are used to collect liquids after distillation, to remove solvents using a rotary evaporator, or to perform a chemical reaction below room temperature (see: kinetic control).
Cooling baths are generally one of two types: (a) a cold fluid (particularly liquid nitrogen, water, or even air) — but most commonly the term refers to (b) a mixture of 3 components: (1) a cooling agent (such as dry ice or water ice); (2) a liquid 'carrier' (such as liquid water, ethylene glycol, acetone, etc.), which transfers heat between the bath and the vessel; ; and (3) an additive to depress the melting-point of the solid/liquid system.
A familiar example of this is the use of an ice/rock-salt mixture to freeze ice cream. Adding salt lowers the freezing temperature of water, lowering the minimum temperature attainable with only ice.
|% Glycol in EtOH||Temp (°C)||% H2O in MeOH||Temp (°C)|
Mixed Solvent Cooling Baths
Mixing solvents creates cooling baths with variable freezing points. Temperatures between approximately −78 °C and −17 °C can be maintained by placing coolant into a mixture of ethylene glycol and ethanol, while mixtures of methanol and water span the −128 °C to 0 °C temperature range., Dry ice sublimes at −78 °C, while liquid nitrogen is used for colder baths.
As water or ethylene glycol freeze out of the mixture the concentration of ethanol/methanol increases. This leads to a new, lower freezing point. With dry ice these baths will never freeze solid, as pure methanol and ethanol both freeze below −78 °C (-98 °C and -114 °C, respectively).
Relative to traditional cooling baths, solvent mixtures are adaptable for a wide temperature range. In addition, the solvents necessary are cheaper and less toxic than those used in traditional baths.
Traditional cooling baths
|Cooling agent||Organic solvent or salt||Temp (°C)|
|Ice||Salts (see: above)||0 to −40|
|Dry ice||Benzyl alcohol||−15|
|Dry ice||Carbon tetrachloride||−23|
|Dry ice||Isopropyl ether||−60|
|Liquid N2||Ethyl acetate||−84|
Water and ice baths
A bath of ice and water will maintain a temperature 0 °C since the melting point of water is 0 °C. However, adding a salt such as sodium chloride will lower the temperature through the property of melting-point depression. Although the exact temperature can be hard to control, the weight ratio of salt to ice influences the temperature:
- −10 °C can be achieved with a 1 to 2.5 ratio by weight of calcium chloride hexahydrate to ice.
- −20 °C can be achieved with a 1 to 3 ratio by weight of sodium chloride to ice.
- −40 °C can be achieved with a 1 to 0.8 ratio by weight of calcium chloride hexahydrate to ice.
Dry ice baths at −78 °C
Since dry ice will sublime at −78 °C, a mixture such as acetone/dry ice will maintain −78 °C. Also, the solution will not freeze because acetone requires a temperature of about −93 °C to begin freezing. Therefore, other liquids with a lower freezing point (pentane: −95 °C, isopropyl alcohol: −89 °C) can also be used to maintain the bath at −78 °C.
Dry ice baths above −77 °C
In order to maintain temperatures above −77 °C, a solvent with a freezing point above −77 °C must be used. When dry ice is added to acetonitrile then the bath will begin cooling. Once the temperature reaches −41 °C, the acetonitrile will freeze. Therefore, dry ice must be added slowly to avoid freezing the entire mixture. In these cases, a bath temperature of −55 °C can be achieved by choosing a solvent with a similar freezing point (n-octane freezes at −56 °C).
Liquid nitrogen baths above −196 °C
Liquid nitrogen baths follow the same idea as dry ice baths. A temperature of −115 °C can be maintained by slowly adding liquid nitrogen to the organic solvent (ethanol) until it begins to freeze (ethanol freezes at −116 °C).
In water and ice-based baths, tap water is commonly used due to ease of access and the higher costs of using ultrapure water. However, tap water and ice derived from tap water can be a contaminant to biological and chemical samples. This has created a host of insulated devices aimed at creating a similar cooling or freezing effect as ice baths without the use of water or ice.
The American Chemical Society notes that the ideal organic solvents to use in a cooling baths have the following characteristics: 1. Nontoxic vapors 2. Low viscosity 3. Nonflammability 4. Low volatility 5. Suitable freezing point. In some cases, a simple substitution can give nearly identical results while lowering risks. For example, using dry ice in 2-propanol rather than acetone yields a nearly identical temperature but avoids the volatility of acetone (see Further Reading).
- Lee, Do W.; Jensen, Craig M. (2000). "Dry-Ice Bath Based on Ethylene Glycol Mixtures". J. Chem. Educ. 77: 629. doi:10.1021/ed077p629.
- Methanol/Water mixtures make great cooling baths – Chemtips. Chemtips.wordpress.com. Retrieved on 2015-02-23
- The ridiculously thorough guide to making a MeOH/Water bath - Chemtips. Chemtips.wordpress.com. Retrieved on 2015-02-23.
- Cooling baths – ChemWiki. Chemwiki.ucdavis.edu. Retrieved on 2013-06-17.
- "Benchtop ice-free cooling and freezing devices". Retrieved August 11, 2012.
- Jonathan M. Percy; Christopher J. Moody; Laurence M. Harwood (1998). Experimental Organic Chemistry: standard and microscale. Blackwell Publishing. ISBN 978-0-632-04819-9.
- Wilfred Louis Florio Armarego; Christina Li Lin Chai (2003). Purification of Laboratory Chemicals (5th ed.). Butterworth-Heinemann. ISBN 978-0-7506-7571-0.
- Kenneth P. Fivizzani (2003). Safety in Academic Chemistry Lab, by American Chemical Society, Volume 1: Accident Prevention for College and University Students (7th ed.). American Chemical Society. ISBN 9780841238633. | <urn:uuid:e59980d3-934c-41e1-8ee7-f07370c85bdb> | 3.53125 | 1,489 | Knowledge Article | Science & Tech. | 54.77435 | 95,591,633 |
Well, if it prints normally it is usually a string. The moment i write some code:
start = "hello world"
start contains a string (since i wrote it), but the moment i fetch input (with for example raw_input, or from the web) i would check which data type i am dealing with (using
You can just temporary add a
type() function, to check what you are dealing with, and then remove it, since most likely this won't change. You now know that raw_input gives unicodes, so you now know (or write it down) that raw_input gives unicode | <urn:uuid:8b0002dd-eb33-47fc-9d96-158ade05f8f2> | 2.65625 | 129 | Q&A Forum | Software Dev. | 32.015747 | 95,591,656 |