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posted by Erin
A 395.0 g block is dropped onto a vertical spring with a spring constant k = 252.0 N/m. The block becomes attached to the spring, and the spring compresses 0.29 m before momentarily stopping. While the spring is being compressed, what work is done by the block's weight?
What work is done by the spring?
What was the speed of the block just before it hit the spring?
W(block) =kx²/2=252•0.29²/2=10.6 J
W(spring) = - 10.6 J
mv²/2 = kx²/2
=0.29•sqrt(0.395/252) =0.0115 m/s | <urn:uuid:dca4952e-b3d2-490c-89b7-67ed28cffb61> | 2.796875 | 162 | Q&A Forum | Science & Tech. | 125.096786 | 95,606,528 |
- To feed the world sustainably, repair the soil
New technologies and genetically modified crops are usually invoked as the key to feeding the world's growing population. But a widely overlooked opportunity lies in reversing the soil degradation that has already taken something like a third of global farmland out of production. Simple changes in conventional farming practices offer opportunities to advance humanity's most neglected natural infrastructure project — returning health to the soil that grows our food.
- House, Senate farm bills split over conservation programs
Congress is expected to renew the so-called "farm bill" by the end of September, but lawmakers will have to reconcile some stark differences between the House and Senate versions of the sweeping legislation that governs an array of agriculture and food assistance programs. While the Senate plan would maintain the status quo in many areas, the House proposal would overhaul conservation programs that help farmers and landowners improve soil, air and water quality.
- Quick soil test aims to determine nitrogen need
Healthy soil contributes to healthy crops. Farmers know this, so they do what they can to ensure their soil is in good shape. They send samples of their soil for lab testing to find out if it is low in any important nutrients. If it is, they can take steps to improve the health of their soil. These might include adding fertilizers or growing cover crops that feed the soil. One of the essential nutrients for vigorous crop production is nitrogen. Yet most routine tests done in commercial soil testing labs do not measure available nitrogen in the soil.
- Halfway to cleanup deadline, Chesapeake Bay hits goals for phosphorus, sediment, but misses nitrogen target
Halfway to a 2025 cleanup deadline, the Chesapeake Bay is on track to meet goals for reduced phosphorus and sediment pollution, but has missed a target for nitrogen contamination. That's according to a Chesapeake Bay Program analysis of pollution controls put in place since 2009 in Maryland and six other jurisdictions in the Chesapeake watershed.
- Sinking land, poisoned water: the dark side of California's mega farms
Towns across the Central Valley region of California have had tap water arsenic levels above the federal limit for almost two decades — levels that research suggests can raise the risk of a variety of cancers and lower IQ in children. During the same period, locals and scientists have noticed another odd phenomenon: the valley is sinking, at rates as fast as 25 cm a year. Now it seems that the two problems are connected.
- Survey shows conservation is important to farmers
Many farmers and ranchers value the opportunity the Conservation Stewardship Program (CSP) offers to enhance their existing conservation efforts, according to a survey we completed last year. Eighty-seven percent of respondents, all living in an area with a strong agricultural presence, stated CSP should be supported as a priority in the farm bill.
- Agricultural nutrients targeted in Ohio's Clean Lake 2020 Bill and governor's executive order
Recent actions by the Ohio legislature and Governor Kasich will affect the management of agricultural nutrients in Ohio. The Ohio General Assembly has passed "Clean Lake 2020" legislation that will provide funding for reducing phosphorous in Lake Erie. Governor Kasich signed the Clean Lake 2020 bill on July 10, in tandem with issuing Executive Order 2018—09K, "Taking Steps to Protect Lake Erie." The two actions aim to address the impact of agricultural nutrients on water quality in Lake Erie.
- Ecuador's colonial past 'written in soil'
The arrival of European settlers in Ecuador had a profound effect on the country's population and environment. This is according to new findings from The Open University. Researchers studying soil cores from the Quijos valley found that they revealed a detailed story of the area's history after Spanish settlers arrived in the 1500s. The subsequent decimation of the region's indigenous population is told by surprising historians — plants.
- American Farmland Trust calling for increased carbon sequestration
American Farmland Trust recently joined a consortium of other conservation-centric agricultural organizations at a "Learning Lab" for the U.S. Climate Alliance Natural and Working Lands Initiative. More than 50 technical experts across industry, academia, and government worked together to draft guiding principles state governments can use to develop strategies, policy and funding projects to draw down carbon from the air and sequester it in the soils across farms, rangelands, forests and wetlands.
- Study finds urbanization and changes to climate could pack a one-two punch for watersheds in the future
Watersheds channel water from streams to oceans, and more than $450 billion in food, manufactured goods and other economic factors depend on them, according to the Environmental Protection Agency. Watersheds also are crucial to the health of surrounding ecosystems and communities. Now, researchers from the University of Missouri have found that climatic changes and urban development, when working in tandem, could have profound effects on watersheds by midcentury. | <urn:uuid:d03dde16-d895-4a5f-bd3c-2289f77dffb4> | 3.65625 | 980 | Content Listing | Science & Tech. | 30.131414 | 95,606,544 |
A cone has an altitude of 40. The volume of that cone equals the volume of a sphere. If their radii are equal, how do I find that radius?© BrainMass Inc. brainmass.com July 20, 2018, 12:48 pm ad1c9bdddf
Please see the attached file for the complete solution.
Thanks for using BrainMass.
A cone has an altitude ...
The radius of a cone is found, given height and that it has same volume as a sphere of the same radius. | <urn:uuid:c7d4cc08-912e-4080-a51b-49782cfee80c> | 3.875 | 109 | Q&A Forum | Science & Tech. | 77.840682 | 95,606,548 |
The world typically sees about 90 tropical cyclones a year, but that number could increase dramatically in the next century due to global warming, a US scientist said Monday.
Rising greenhouse gas emissions could lead to a 10 to 40 percent increase in the frequency of tropical cyclones by the year 2100, said prominent climate scientist Kerry Emanuel of the Massachusetts Institute of Technology (MIT).
Those storms could be up to 45 percent more intense, making landfall 55 percent stronger — a “substantial” increase, said the research in the Proceedings of the National Academy of Sciences.
Stronger storm surges, winds and rain would likely be felt most acutely in the southern Indian Ocean, North Pacific and North Atlantic Ocean, and could raise risks of damage in coastal areas, he said.
Satellite data has shown that cyclones — which are rotating systems of clouds and thunderstorms — have remained relatively consistent in frequency and power over the past 40 years.
But he projected a steady uptick in the future using six different climate models combined with forecasts from the Intergovernmental Panel on Climate Change (IPCC), which predicts carbon dioxide emissions will about triple by 2100.
Tropical cyclones can bring heavy rains and winds, and vary in potency from tropical depression to tropical storm to hurricane.
The Atlantic Ocean, Caribbean and Gulf of Mexico typically see about six hurricanes and 11 tropical storms per year, while the Pacific Ocean gets about 10 hurricanes and 19 tropical storms, according to US government ocean monitors.
Cyclones form in areas where there is warm deep water and cool humid air. Wind over the water pushes thermal heat upward, causing the warming air to circle and get stronger. | <urn:uuid:05180ee6-410f-4492-8057-92cd258da622> | 3.765625 | 336 | News Article | Science & Tech. | 31.148758 | 95,606,554 |
Using HTML in Android
Sometimes you may need to use html tags to format your text in android. This may be useful from the view of simplicity. Formatting with HTML is much simple than java. Therefore, if you know how to use HTML tags in android, the formatting will be much easier.
Step 1- A class named 'Html' is used for the purpose. This is a class of package 'android.text'. This class has a method 'fromHtml' which is used statically i.e. no object is needed for this.
This method returns a value of type 'Spanned'. This is also a class of package 'android.text'.
Step 2- Now this variable of class 'Spanned' can be used as a string is used. | <urn:uuid:480a7f13-dd9f-44c0-8116-0fc8df1a4602> | 3 | 159 | Tutorial | Software Dev. | 81.491639 | 95,606,561 |
London: Scientists are planning to fit radio receivers to over one thousand ants to observe their habits and ways of communication.
Researchers from the University of York in the UK will carry out this study on the National Trust`s Longshaw Estate, Derbyshire, a hotspot for the northern hairy wood ant, the `Daily Mail` reported.
The unique site has more than a thousand nests and is home to up to 50 million workers from Britain`s largest ant species, which are internationally protected.
"This research is about trying to find out how the ants communicate and commute between the vast networks of nests and how they travel in this environment," biologist and chief researcher Samuel Ellis was quoted as saying by the paper.
The researchers plan to carefully catch the ants and in a few seconds attach a 1 mm radio receiver to them. The ants are the size of an adult thumbnail but researchers say the process will not interfere with or harm them in any way.
"The way the ants use this network has important implications for how they interact with their environment. And the way information is passed through the network may even have implications for our information and telecommunications networks," Ellis said.
The findings from the research will then be used by National Trust staff on the Longshaw estate to manage the ancient woodland, made up of oak and birch trees, where the ants can be found.
The hairy wood ant is the largest native ant species of the British Isles. Workers can measure from 8-10mm in length. It has hairy `eyebrows` visible through a microscope.
They can defend themselves from predators by spraying formic acid a smelly substance about as strong as vinegar which can blister the skin. Queens can live for up to 15 years, whereas workers live for about a year.
"The study will give us a real picture of where the ants are and how we can improve the habitat for them and other wildlife without causing disturbance," National Trust Area Ranger at Longshaw Chris Millner said.
The northern hairy wood ant has an international near-threatened conservation status with the two main populations in England found in the Peak District (including Longshaw) and in the North York Moors. | <urn:uuid:d8cc4a11-eb75-48e1-bc92-cb342848dad4> | 3.421875 | 444 | News Article | Science & Tech. | 49.01753 | 95,606,562 |
Skip to Main Content
Relative effects of climate change and wildfires on stream temperatures: A simulation modeling approach in a Rocky Mountain watershedAuthor(s): Lisa Holsinger; Robert E. Keane; Daniel J. Isaak; Lisa Eby; Michael K. Young
Source: Climatic Change. 124: 191-206.
Publication Series: Scientific Journal (JRNL)
Station: Rocky Mountain Research Station
View PDF (691.01 KB)
DescriptionFreshwater ecosystems are warming globally from the direct effects of climate change on air temperature and hydrology and the indirect effects on near-stream vegetation. In fire-prone landscapes, vegetative change may be especially rapid and cause significant local stream temperature increases but the importance of these increases relative to broader changes associated with air temperature and hydrology are not well understood. We linked a spatially explicit landscape fire and vegetation model (FireBGCv2) to an empirical regression equation that predicted daily stream temperatures to explore how climate change and its impacts on fire might affect stream thermal conditions across a partially forested, mountainous landscape in the western U.S. We used the model to understand the roles that wildfire and management actions such as fuel reduction and fire suppression could play in mitigating stream thermal responses to climate change. Results indicate that air temperature increases associated with future climates could account for a much larger proportion of stream temperature increases (as much as 90% at a basin scale) than wildfire. Similarly, land management scenarios that limited wildfire prevalence had negligible effects on future stream temperature increases. These patterns emerged at broader spatial scales because wildfires typically affected only a subset of a stream's network. However, at finer spatial and temporal scales stream temperatures were sensitive to wildfire. Although wildfires will continue to cause local, short-term effects on stream temperatures, managers of aquatic systems may need to find other solutions to cope with the larger impact from climate change on future stream warming that involves adapting to the increases while developing broad strategies for riparian vegetation restoration.
- You may send email to firstname.lastname@example.org to request a hard copy of this publication.
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CitationHolsinger, Lisa; Keane, Robert E.; Isaak, Daniel J.; Eby, Lisa; Young, Michael K. 2014. Relative effects of climate change and wildfires on stream temperatures: A simulation modeling approach in a Rocky Mountain watershed. Climatic Change. 124: 191-206.
Keywordsclimate change, wildfires, stream temperatures, modeling, watershed
- Stream temperature monitoring and modeling: Recent advances and new tools for managers
- Sensitivity of summer stream temperatures to climate variability in the Pacific Northwest
- Effects of climate change and wildfire on stream temperatures and salmonid thermal habitat in a mountain river network
XML: View XML | <urn:uuid:5ae501b8-b716-40dd-908e-fcb18fefc450> | 3 | 631 | Truncated | Science & Tech. | 22.835236 | 95,606,568 |
|Keep It Simple, Stupid|
Please, please, please, call it Net::CPAN. Then we can get CGI renamed Net::CGI.
Yuck. No. I wouldn't agree with either of those names. Both CGI's and CPAN's relationship to networking is peripheral.
CPAN uses various means to retrieve modules over the network but its real job is to determine dependencies, build, and install those modules. Certainly CPAN could have the functionality to access a local archive via the filesystem rather than the network. I don't use CPAN or CPANPLUS (I answered "make" on the poll) so for all I know one or both already have that functionality. It might be especially useful where institutions keep a local CPAN mirror and make it available to their user base via NFS.
CGI is simply a platform independent interface by which information servers may run external programs. In reality, this is only true for some definitions of "platform independence" and "information servers" but that's its stated goal.1 It currently requires that the external program knows some things about the protocol that the information server is using but the actual network communication takes place through the server itself.
So, I think putting either CPAN or CGI in Net::* would be a mistake.
I wouldn't mind seeing name changes for B and O though.
1That is, its the stated goal of the draft CGI specification not of the CGI module.
-sauoq "My two cents aren't worth a dime."; | <urn:uuid:bede4197-0627-4c3e-8938-116ac1bb500d> | 2.578125 | 316 | Comment Section | Software Dev. | 57.481169 | 95,606,611 |
A small molecule inhibits jasmonic acid and helps to explain its effects
Researchers trying to get new information about the metabolism of plants can switch off individual genes and study the resulting changes. However, Erich Kombrink from the Max Planck Institute for Plant Breeding Research in Cologne and Markus Kaiser from the University of Duisburg-Essen adopt a different approach.
Jarin1 inhibits the enzyme JAR1 by displacing the natural substrate, Jasmonoyl-isoleucine (JA-Ile), from its binding site. Both substances overlap, so that JAR1 can no longer fulfil its tasks. The left panel shows an overview of the entire enzyme; the right panel a view into the active centre.
© Corey S. Westfall, Washington University, St. Louis
They identify small molecules that block specific components of the metabolic process like brake pads and prevent the downstream reactions. In their search for these molecules, they use a biological selection process involving intact plants. This strategy has long been exploited in drug research. Its application in the plant sciences, however, is relatively new.
Kombrink, Kaiser and their colleagues have identified a molecule that interferes with the effect of jasmonic acid. This plant hormone influences flower formation, root growth, defence against herbivores and infections, wound healing, ageing of plants, and much more.
Although many questions about plant metabolism can be answered through targeted gene mutations, the method has its limits. This is also demonstrated in the case of jasmonic acid and its derivatives. So far, only one signalling chain has been discovered, but this cannot explain the wide-ranging effect of this plant hormone. Therefore, other hitherto undiscovered signalling paths and action mechanisms must exist.
To find out more about them, Kombrink and Kaiser have adopted an approach that is similar to one used in medicine. Their strategy is based on the blocking of important metabolic pathways using low molecular weight compounds, which are easily assimilated by the plant. While in medical therapy such compounds are assimilated through the blood, in the plant they are introduced through the root.
The scientists embarked on their search with a screening of Arabidopsis thaliana and treating the plants with compounds in such a way that the desired selection could be identified by a conspicuous trait. Of the 1728 substances from a commercial compound library tested 16 emerged as inhibitors.
This number was further reduced using more selective tests. In the end, only one substance turned out to be a specific inhibitor of the jasmonic acid signalling pathway and was given the name Jarin-1. “In terms of its basic structure, the substance is a plant alkaloid, whose two amino groups can carry different side chains,” Kombrink explains. “However, its effect is associated with a particular side chain in one of the positions. Other side chains impair the activity of the substance. We also deliberately synthesised it once again to be certain that we had understood its chemical structure correctly.”
The scientists also looked for the target of the newly discovered inhibitor. The known signalling chain starts with the conjugation of the jasmonic acid with the amino acid isoleucine by an enzyme called JAR1. The resulting pair leads to the expression – following various detours – of the genes necessary for the relevant effect of the jasmonic acid. Kombrink and Kaiser were able to show that JAR1 is the target of the newly discovered inhibitor. Due to the inhibition, the jasmonic acid conjugated with isoleucine does no longer accumulate in the cell. As a result genes are not expressed because the jasmonic acid–isoleucine pair no longer activates the genes’ starting point.
The Jarin-1 inhibitor identified by Kombrink and Kaiser not only works in Arabidopsis but also in Cardamine hirsuta or hairy bittercress. “So we are obviously dealing with a broadly applicable molecule,” comments Kombrink. Under the effect of the inhibitor, the plants show the same features as they do following the targeted mutation of genes from the jasmonic acid signalling pathway.
The scientists also investigated the exact location where the molecule takes effect. They succeeded in demonstrating that it binds to the active centre of JAR1 and inhibits the natural substrate. “Our molecule is not a classical competitive inhibitor,” says Kombrink. “But its effect can be explained, at least in parts, by displacement of the substrate from its binding site.”
Small molecules are interesting new tools for plant research. Through their work, the researchers show how it is possible to search for them systematically and to identify their molecular mode of action.
Dr. Erich Kombrink | Max-Planck-Institute
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:bac0b16b-bde6-4757-9025-062dd29fdecd> | 3.109375 | 1,639 | Content Listing | Science & Tech. | 36.503146 | 95,606,619 |
摘要： 本文讲的是Automatic PHP Regular Expression Building Part 1: Introduction to the PHP Regex Advanced Pa...，Contents Introduction The Beginning Problem The Concept of Meta Regular Expression Matching The PHP Advanced Regex p
Some time ago I had the need to go farther than what PHP can offer regarding regular expressions. I wanted to analyze log file contents, each line being matched by a specific regular expression. I wanted that a single regular expression could be used to match a sequence of lines in a logfile using some kind of meta-matching .
This article explains the basic knowledge about regular expressions that was needed to achieve that goal. It describes the intermediate methods that I built as steps towards meta-matching.
Then it introduces this so-called "meta-matching" feature that allows you to describe text flows as sequences of meta-regular expressions involving themselves their own sets of regular expressions provided to match particular lines of text.The Beginning Problem
Let's suppose you have to scan a sequence of lines, such as in a log file. You want to recognize which sequence follows which pattern. A typical sequence in an example log file could be, for example:A line containing the string " message start " Any number of lines starting with " log: " and followed by any sequence of characters A line containing " message end "
The following example gives a layout of how such a log file could look like:xmessage startlog: message 1log: message 2...log: message nmessage end
The idea behind that is to say:Ok, I want to match the string "message start", and every string that starts with "message" and ends up with a number ; and I also want to match strings that contain "message end" But... wait... these sequences of strings can also be described by a regular expression ! If I could be able to say : I'm expecting the string "message start" as the first line Then, any number of lines containing the word "log" followed a number And finally, a line containing "message end"
Wouldn't it be better if it could be described using a regular expression ?The Concept of Meta Regular Expression Matching
Let's say that the sequence /1 references a regular expression that matches the string "message start", /2 is a reference to an expression that matches the string "log:" followed by a number, and /3 a reference to a regular expression that matches the string "message end".
Matching our example input stream with a single meta regular expression could be written as:/1 /2* /3
This means : a line containing "message start", followed by any number of lines containing the word "log" followed by an integer, and ending with a line containing "message end".
You're done! You just learned how to do meta regular expression matching. Although you do not yet know how to tell that "/1" is intended to match the string "message start", "/2" the string "log" followed by an integer, and so on, you have moved a step forward in the direction of meta-thinking (the term is humbly mine), which is an activity of choice for so many mathematicians and developers.The PHP Advanced Regex package
The PHPAdvanced Regex package is here to relieve you from the burden of this meta-something stuff.
If you feel uncomfortable with basic regular expressions, may I recommend you to read the next part of this article which is basically a survival guide to regular expressions?
Although it is not intended to provide a thorough coverage on how to be a regular expression superstar, it explains some basic concepts, introduces some habits I have taken in PHP when writing regular expressions and that saved me a lot of time.
It also contains some stuff to explain how to get proper match results from applying a regular expression to input strings. The last two items belong more to common sense rather than to rigid coding rules.Conclusion
In this part of the article you learned how to think about meta regular expression matching to match complex text sequences.
In the next part you will be guided you through basic rules for using regular expressions. It will detail the intermediary utility methods that have been implemented in the PHP dvanced Regex package to assist you into meta-regular expression matching.
The third and last part which will show you how to cope with meta-regular expression matching.
For now, if you liked this article or you have some questions, post a comment here.
|php pear-apt-get 安装p...||python正则表达式学习笔记||[Oracle] 几本重要的电子图书下载|
|... root@dev:/# sudo apt-get install php-pear Reading ...||...am-files’) ‘pro–gram files’ 二：正则表达式对象 （Regular Expr...||...e of the performance-critical internals. Download T...| | <urn:uuid:6e398f13-205b-42d4-a67d-3377c5908357> | 2.8125 | 1,068 | Truncated | Software Dev. | 55.055017 | 95,606,645 |
Large Scale Structure of the Universe
by Alison L. Coil
Publisher: arXiv 2012
Number of pages: 43
Galaxies are not uniformly distributed in space. On large scales the Universe displays coherent structure, with galaxies residing in groups and clusters, which lie at the intersections of long filaments of galaxies. Vast regions of relatively empty space, known as voids, contain very few galaxies and span the volume in between these structures.
Home page url
Download or read it online for free here:
by Richard S. Ellis - arXiv
In these lectures aimed for non-specialists, the author reviews progress in understanding how galaxies form and evolve. The first results presented here provide important guidance on how we will use more powerful future facilities.
by Halton C. Arp - California Institute of Technology
The Atlas of Peculiar Galaxies is a catalog of peculiar galaxies produced by Halton Arp. A total of 338 galaxies are presented in the atlas, which was originally published in 1966 by the California Institute of Technology.
by Regina Schulte-Ladbeck, at al. - Hindawi Publishing
Dwarf galaxies provide opportunities for drawing inferences about the processes in the early universe by observing our Local Group and its vicinity. This issue is a snapshot of the current state of the art of dwarf-galaxy cosmology.
by Jean-Paul Kneib, Priyamvada Natarajan - arXiv
Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. Given their masses, clusters strongly deform space-time in their vicinity. Clusters act as the most powerful gravitational lenses in the Universe. | <urn:uuid:5abb1694-2ad9-45ff-99d4-22a3519cd507> | 2.609375 | 349 | Content Listing | Science & Tech. | 29.752555 | 95,606,646 |
Electron and atom group transfer from a solvated donor to a solvated acceptor molecule, or between a solvated molecule and a macroscopic solid body such as an electrode or a membrane, have attracted attention since the days of Grotthuss, Davy, and Faraday(1). Such processes are of crucial importance in chemical, biological, and physical processes, which are conveniently viewed as individual or a series of consecutive reaction steps, the molecular nature of which involves electron or atom group transfer. Thus, in chemical and biological systems in liquid or solid media the elementary reaction steps most frequently consist of a synchronous bond break and bond formation in atom group transfer, or the transfer of an electron without accompanying bond breaks. Elementary chemical reaction steps are moreover conceptually closely related to such physical processes as radiative and radiationless electronic transitions in large isolated molecules(2,3) and in impurity centres in solid matrices(3,4), to defect diffusion in solids(5), and to nuclear tunnelling phenomena as manifested by ‘abnormal’ heat capacity effects(6–8) and vibrational level splitting(9,10).
KeywordsElectron Transfer Reorganization Energy Proton Transfer Reaction Transition State Theory Nuclear Mode
Unable to display preview. Download preview PDF. | <urn:uuid:4047df69-9eb7-4895-ab6e-a29a1ef9c19d> | 2.84375 | 267 | Truncated | Science & Tech. | 4.994545 | 95,606,656 |
One of the key controllers of neural development seems to depend on a simple cellular decision--whether to divide perpendicularly or in parallel to the embryonic structure called the neuroepithelium. Nevertheless, such orientation is critical, and understanding its machinery could help neuroscientists learn to control the division of adult neural stem cells to regenerate neural tissues.
Researchers know that during the earliest embryonic brain development, neural stem cells divide "symmetrically," producing identical immature progenitor cells that continue to proliferate. A bit later, however, when neural tissues need to begin to differentiate, the cells divide "asymmetrically," producing one proliferating progenitor and another that stops proliferating and differentiates into an adult neural cell. And during final brain development, the cells return to symmetric cell division, creating differentiated adult cells.
The two types of cell division seem to be governed by the orientation of the tiny bundles of fiber-like microtubules called spindles inside the dividing cell--whether the spindles are oriented parallel or perpendicular to the neuroepithelium. These spindles attach to the dividing chromosomes in the nucleus and drag the two copies apart, ensuring that each daughter cell has its fair share.
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Can continuous motion be an illusion?
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It is widely accepted that continuity is the most essential characteristic of motion; the motion of macroscopic objects is apparently continuous, and classical mechanics, which describes such motion, is also based on the assumption of continuous motion. But is motion really continuous in reality? In this paper, I will try to answer this question through a new analysis of the cause of motion. It has been argued that the standard velocity in classical mechanics cannot fulfill the causal role required for explaining continuous motion in a deterministic way. However, there is a hot debate over the solution to this causal explanation problem. The existing solutions, i.e. the "at-at" theory, the impetus view and the "no instants" view, have serious drawbacks. After reviewing their drawbacks and presenting my own objections, I propose a new solution to this causal explanation problem. It is argued that the relativity of motion or the equivalence between motion and rest demands that motion has no deterministic cause, and thus no causal explanation is needed for motion. Based on this result, I further argue that the uncaused motion is not deterministic and continuous but essentially random and discontinuous. Moreover, objects have a potential (as a probabilistic cause of motion) that determines the probabilities of their future positions. This suggests a possible connection with quantum mechanics. Lastly, I give a brief explanation for the apparent inconsistency between the suggested potential theory of motion and the appearance of continuous motion in the macroscopic world. | <urn:uuid:c7b628b5-4366-47a5-b761-179ae7c9566f> | 2.765625 | 341 | Academic Writing | Science & Tech. | 30.018333 | 95,606,671 |
A heatwave is shortly expected to hit the UK, bringing extremely warm weather and bright, clear skies.
Temperatures could rise up to 30°C by next week as the heatwave sweeps the UK, with high pressure bringing in hot Mediterranean air.
The Met Office expects this warm weather to continue over the next few weeks, but when exactly will the heatwave begin in Yorkshire?
Although tomorrow is set to be warm in Yorkshire, the temperature really begins to ramp up on Monday June 25, with temperatures starting from 24°C.
The weather this weekend will be a mixture of sun and cloud, with highs of 20°C and lows of 14°C.
Friday is set to be bright, sunny and warm for the whole day, with the temperature reaching its peak of 20°C at 15:00. The temperature will then slowly begin to dip at around 21:00.
Saturday will be slightly cooler with highs of 19°C and lows of 10°C. The weather is set to be cloudy for most of the day, reaching its peak temperature at around 16:00, before it then begins to dip at around 22:00.
The temperature on Sunday will then begin to increase again, reaching its peak of 21°C at around 16:00. Sunday morning and early afternoon will be mostly cloudy, with sunny intervals occurring at 16:00 and a burst of pure sunshine at around 19:00.
The heatwave in Yorkshire is then set to begin on Monday June 24, with pure sunshine throughout most of the day and a peak temperature of 24°C.
Tuesday and Wednesday are then expected to be similar, with pure sunshine throughout most of the day.
The temperature will then continue to climb for the rest of the week, gradually increasing at the days go on, it being expected that temperatures as high as 30°C could be reached.
This unusual warm weather is then expected to last for a few weeks, bringing unseasonably high temperatures to the UK for the first few weeks of July. | <urn:uuid:9cf186e5-14e3-40a9-819b-4cb54e25ff57> | 2.5625 | 414 | News Article | Science & Tech. | 64.314348 | 95,606,679 |
Remote Sensing of Wind Velocity from Satellite — Borne Lidar Systems
The development of stable, tunable, diffraction-limited lasers has made possible the remote measurement of atmospheric wind velocity using a pulsed coherent laser radar. The Wave Propagation Laboratory of the National Oceanic and Atmospheric Administration’s (NOAA) Environmental Research Laboratories has completed the investigation of the feasibility of measuring the global wind field using an infrared coherent laser radar under a joint program with the U.S. Air Force Space Di-vision Defense Meteorological Satellite Program (DMSP). These studies investigated both the analytical and hardware feasibility of a space-borne global wind measuring coherent laser radar. Objectives and requirements of the Air Force Defense Meteorological Satellite Program were used in the study. The vertical dis-tributions of the horizontal wind field were required throughout the troposphere with 300 km square horizontal and 1 km vertical resolution with a measurement ac-curacy of 1 m s-1. Complete global coverage was required with overlapping coverage at the equator. The lidar system should also be scalable to operational satellite conditions. The analytical studies were performed for both a 300 km altitude Space Shuttle orbit and an operational polar orbit of 800 km altitude [1, 2]. A hardware definition study was performed for a Space Shuttle demonstration test flight .
KeywordsWind Field Space Shuttle Lidar System Backscatter Coefficient Secondary Mirror
Unable to display preview. Download preview PDF.
- 1.Huffaker, R.M., Ed. Feasibility study of satellite-borne lidar global wind monitoring system, N0AA Technical Memorandum ERL WPL-37, September 1978.Google Scholar
- 2.Huffaker, R.M., T.R. Lawrence, R.J. Keeler, M.J. Post, J.T. Priestley and J.A. Korrell, Feasibility study of satellite-borne lidar global wind monitoring system Part II, NOAA Technical Memorandum ERL WPL-63, August 1980.Google Scholar
- 3.Lockheed Missiles and Space Co., Palo Alto Research Lab. Global wind measuring satellite system, Report No. LMSC-D767868, April 1981, Work conducted under NOAA contract NA 79RAC-00127.Google Scholar
- 4.National Academy of Sciences, 1980. Technological and scientific opportunities for improved weather and hydrological services in the coming decade. Select committee on the National Weather Service, 87 pp.Google Scholar
- 5.McClatchey, R.A. and J.E.A. Selby, Atmospheric attenuation of laser radiation from 0.7 to 31.27 ym, Air Force Cambridge Research Laboratories, Report No. AFCRL-TR-74-0003, January 1974.Google Scholar | <urn:uuid:71610f06-2088-4922-b24d-779797b69e91> | 2.71875 | 579 | Truncated | Science & Tech. | 40.34216 | 95,606,689 |
Analytical techniques are powerful tools in a chemist's armoury. Spectroscopic data and chemical information are used routinely in laboratories to follow a chemical reaction or elucidate a chemical structure. However, the sophistication of the analytical techniques used changes rapidly, hence the routinely used method of today can all too readily be superseded by the new technology of tomorrow. More Modern Chemical Techniques identifies some applications of the important chemical techniques in use today that are less well known in schools and colleges and which illustrate how chemistry is using state-of-the-art technology to push back the frontiers of the subject. Examples include: elemental analysis such as atomic absorption spectrometry and inductively coupled plasma techniques; separations including electrophoresis, structure determination (eg x-ray diffraction and optical microscopy); and sampling and sample preparation.
Publisher: Royal Society of Chemistry
Number of pages: 193
Weight: 900 g
Dimensions: 297 x 210 x 10 mm
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Slope dude loves to ski. He teaches us by talking while he skis the course. We learn from him that uphill slopes are positive Downhill slopes are negative flat slopes are zero and vertical "slopes" are undefined...
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Y up and down the vertical
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Can traditional gasoline-powered cars be converted to run on hydrogen fuel cells?
Yes — but it probably makes more sense to start with buses and long-haul trucks than passenger cars…By Jennifer Sutton
First of all, says John Heywood, professor of mechanical engineering, and director of the Sloan Automotive Research Laboratory, let’s define the word “convert.” A traditional vehicle can be retrofitted with a new hydrogen fuel-cell engine, he says, but it is far too challenging and costly to be worth the effort. “The only cases where a retrofit might make sense is in large diesel vehicles like buses or long-haul trucks,” Heywood says.
But the prospect of changing our gasoline-engine technology so that more and more cars run on hydrogen fuel cells, he says, is more attainable. However, don’t look for them on the road anytime soon.
Hydrogen fuel-cell vehicles, effectively run on batteries powered by hydrogen instead of the electric power grid. The fuel cell converts the hydrogen and oxygen in the air into water, and in the process it produces electricity. As long as hydrogen and oxygen keep flowing into the fuel cell, it never goes dead. Hydrogen fuel cells have the potential for reducing harmful emissions (depending on how the hydrogen is produced) and will decrease the U.S.’s dependence on foreign petroleum. The disadvantage: in order to put hydrogen-powered cars on the road, Heywood says, we must change not only our vehicle technology, but also our entire fuel supply and fuel distribution system.
Hydrogen fuel cell technology has been around for years but has yet to take root in the marketplace. “A decade ago, hydrogen was getting all the attention, and electricity was barely on the list,” Heywood says. The recent introduction of hybrids and battery-powered cars has proven more successful, he says, largely because the change they represent can happen incrementally, without having to build an entirely new system for storing and delivering fuel. “Hydrogen’s not dead,” he says. “It’s just difficult to think about such a major change.”
There are two ways to make hydrogen fuel, one clean, one not so clean. Electrolyzing water — splitting the hydrogen from the oxygen — produces no direct emissions, but the process requires more energy than it produces. Hydrogen also comes from partly burning methane gas and reacting it with steam, which separates the resulting gas into oxygen and hydrogen. In other words, in order to produce “clean” hydrogen fuel you need to start with fossil fuels (coal or natural gas), which come with the same old climate-compromising problems.
“The critical question is how can we produce hydrogen in efficient ways that also produce low emissions?” he says. “We’ve got a lot of fossil fuels around — more than we think. So we can keep being bad boys and girls, which doesn’t motivate us to make changes.”
Thanks to John Dugdale of Atlanta, GA, for this question.
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Back in July, Microsoft launched the AI for Earth program that would focus on using artificial intelligence to advance sustainability around the world. Even better, this Monday, they announced that they'll be investing an additional $50 million over the next five years into the project. More specifically, the money will go toward providing this AI technology to upcoming companies.
Brad Smith, Microsoft’s President and Chief Legal Officer, made the announcement at the One Climate Summit in Paris. In addition to further investment, they’ll be partnering with corporations as soon as possible. This isn't the only step forward they've made when it comes to the environment lately, either. For example, this news comes one month after stating that they would be cutting down on 75 percent of their own carbon emissions by 2030.
AI for Earth began with a $2 million investment from Microsoft and was used to give companies and universities grants and free use of their artificial intelligence software and Azure cloud computing. They awarded 35 grants in 10 different countries, and AI technology has already been used in products that help improve climate change, water usage, and more.
“Our approach as a company is focused on democratizing AI so its features and capabilities can be put to use by individuals and organizations around the world to improve real-world outcomes,” Smith said in a Microsoft blog post. “There are few societal areas where AI can be more impactful than in helping address the urgent work needed to monitor, model and manage the earth’s natural systems.”
Microsoft’s AI technology has been used in a number products already. Norway utility company Agder Energi uses the cloud to analyze data easier along the electrical grid as more consumers purchase electric vehicles and install solar panels. By doing this, they can more efficiently provide energy instead of just tacking on more capacity.
There’s also benefits on the other end of that spectrum. JTC in Singapore has optimized its electrical efficiency in 39 buildings. With help from the cloud and sensor data, they can patch up potential issues before they require a larger scale fix, and it’s already helped them save 15 percent in energy costs.
Other projects that Microsoft has partnered with is a high-tech mosquito trap that is able to capture specific bugs carrying diseases like the Zika virus. Called Project Premonition, these devices are able to record data such as when the bug was caught and what the conditions were. Further advancements could make the device scan the insects’ blood for potential diseases. They’ve partnered with Northeastern universities at Pittsburgh and Johns Hopkins.
It’s easy to see how much the environment can benefit with the use of artificial intelligence. With that in mind, Microsoft decided to seriously step up their game to raise up AI technology even more. With projects like Project Premonition getting more money and attention, it definitely sets the stage for more innovative developments in the near future.
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Please help with the following questions.
Chapter 2: Biology and Society, Question 14, p.34-
? One solution to the problem of acid precipitation caused by emissions from power plants is to use nuclear power to produce electricity. The proponents of nuclear power contend that it is the only way that the United States can increase its energy production while reducing air pollution, because nuclear power plants emit little or no acid-precipitation-causing pollutants. What are some of the benefits of nuclear power? What are the possible costs and dangers? Do you think we ought to increase our use of nuclear power to generate electricity? Why or why not? If a new power plant were to be built near your home, would you prefer it to be a coal-burning or nuclear plant? Why?
Chapter 3: Biology and Society, Question 15, p.53-
? Each year, industrial chemists develop and test thousands of new organic compounds for use as pesticides, such as insecticides, fungicides, and weed killers. In what ways are these chemicals useful and important to us? In what ways can they be harmful? Is your general opinion of pesticides positive or negative? What influences have shaped your feelings about these chemicals?
Chapter 4: Biology and Society, Question 12, p.71-
? Doctors at a university medical center removed John Moore's spleen, which is standard treatment for his type of leukemia. The disease did not recur. Researchers kept the spleen cells alive in a nutrient medium. They found that some of the cells produced a blood protein that showed promise as a treatment for cancer and AIDS. The researchers patented the cells. The U. S. Supreme Court ruled against Moore, stating that his lawsuit "threatens to destroy the economic incentive to conduct important medical research." Moore argued that the ruling left patients "vulnerable to exploitation at the hands of the state." Do you think Moore was treated fairly? Is there anything else you would like to know about this case that might help decide?
Chapter 5: Biology and Society, Question 14, p.87-
? Lead acts as an enzyme inhibitor, and it can interfere with the development of the nervous system. One manufacturer of lead-acid batteries instituted a "fetal protection policy" that banned female employees of childbearing age from working in areas where they might be exposed to high levels of lead. Under the policy, women were involuntarily transferred to lower-paying jobs in lower-risk areas. A group of employees challenged the policy in court, claiming that it deprived women of job opportunities available to men. The U.S. Supreme Court ruled the policy illegal. Nonetheless, many people are uncomfortable about the "right" to work in an unsafe environment. What rights and responsibilities of employers, employees, and government agencies are in conflict in this situation? Whose responsibility should it be to determine what makes a safe environment and who should it be to determine what makes a safe environment and who should or should not work there? What criteria should be used to decide?
Thank you for your help in advance!© BrainMass Inc. brainmass.com July 17, 2018, 7:25 pm ad1c9bdddf
Interesting questions! Let's take a lcoser look. I also attached two supporting articles, some of which this response and are made reference to below.
Let's take a closer look.
Chapter 2: Biology and Society, Question 14, p. 34-
One solution to the problem of acid precipitation caused by emissions from power plants is to use nuclear power to produce electricity. The proponents of nuclear power contend that it is the only way that the United States can increase its energy production while reducing air pollution, because nuclear power plants emit little or no acid-precipitation-causing pollutants.
? What are some of the benefits of nuclear power? Proponents argue that well designed, well constructed, well operated and well maintained nuclear energy is not only clean, but it is also safe, reliable, durable and competitive. It is clean: Nuclear energy produces almost no carbon dioxide, and no sulfur dioxide or nitrogen oxides whatsoever. These gases are produced in vast quantities when fossil fuels are burned. It is safe: far fewer fatalities have occurred in the civilian nuclear power industry in half a century (Chernobyl included), than occurred in any year in the fossil fuel industries. Coal mine accidents are common occurrences and often cause tens or hundreds of fatalities, reported one day and forgotten the next, adding up to about 15,000 per year worldwide, 6,000 of which are in China. It is reliable, durable and completive (see attached article for further explanations, which is also available on-line at URL:
? What are the possible costs and dangers? According to Dr. Caldicott, an opponent of nuclear energy, claims that that nuclear power adds to global warming, increases the burden of radioactive materials in the ecosphere and threatens to contribute to nuclear proliferation (see explanation at http://healthandenergy.com/nuclear_dangers.htm).
? Do you think we ought to increase our use of nuclear power to generate electricity? Why or why not? Based on ...
This solution addresses questions about biology and society on several controversial issues debating both sides of the controversies e.g. nuclear power plant emissions, the use of pesticides, controversial medical research and working in an unsafe work environment. It is supplemented with links and articles for further research on the topics. | <urn:uuid:69b1467a-eb40-4382-aeef-a909ec5979a5> | 3.03125 | 1,115 | Q&A Forum | Science & Tech. | 46.313153 | 95,606,756 |
While people in the eastern two-thirds of the U.S have been dealing with Arctic Air, the bulge in the Jet Stream over the eastern Pacific Ocean has been keeping the western third of the U.S. in warmer than normal temperatures over the last two months. Infrared data from NASA provided a look at those surface temperature extremes from west to east.
Californians have been flaunting their flip-flops and tee shirt weather at friends and relatives on the frigid East Coast. The contrast is extreme, Californians are experiencing their warmest winter since modern record keeping began and Bostonians are staggering through 8 foot and higher snowdrifts. Why?
"It's the weather-controlling polar jet stream - a fast river of wind in the upper atmosphere - that has been locked in an extreme pattern for the past few years," explained Climatologist Bill Patzert of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.
"Rather than circling in a relatively straight path, the jet stream has meandered in great north-south waves. In the west, it's been bulging northward, arguably for the past two winters - a pattern meteorologists have nick named the 'Ridiculously Resilient Ridge.' Over frigid northern Canada, the jet takes a hard right turn and plunges into the upper Midwest and East Coast, plummeting temperatures and creating punishing ice and snow storms."
Those temperatures are apparent on infrared data taken on Feb. 18 at 18:53 UTC (1:53 p.m. EST) from the Atmospheric Infrared Sounder or AIRS instrument that flies aboard NASA's Aqua satellite. AIRS data are processed and made into false-colored imagery at NASA's JPL.
In the image from Feb. 18, surface temperatures from Washington State, south to California, Nevada, Arizona, New Mexico and western Texas appeared quite warm. Surface temperatures ranged from 290K/62.3F/16.8C to 300K/80.3F/26.8 C.
On Feb. 18, when the AIRS data was taken, the high temperature in Los Angeles, California reached 75F. That was one of 10 days out of the first 20 days of February, where temperatures reached or passed that mark in the city.
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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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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Dust Bowl 2012: Hottest July on Record in U.S.
The National Oceanic and Atmospheric Administration (NOAA) reports that last month was, on average, the hottest July on record for the contiguous United States, beating the previous record set in the dust bowl of 1936. The past 12 months have been the hottest ever recorded in the US, with more than 27,000 heat records broken so far this year, more than the 26,674 for all of 2011, even with the Texas-sized drought that sizzled throughout the state last summer. Last year also saw Oklahoma setting the record for the all-time hottest average summer temperature for any state ever recorded. But that was last year.
This year, drought has extended through 63 percent of the Lower 48, according to the US Drought Monitor, with a peak (so far) on July 24 when nearly 64 percent of the contiguous states were under drought conditions, the highest ever in the Drought Monitor’s 13-year history. The areas of the country suffering “extreme to exceptional” drought conditions more than doubled, rising from 10 percent in June to 22 percent in July.
According to NOAA, the average July temperature in the contiguous United States stood at 77.6 degrees Fahrenheit, 3.3 degrees above the 20th century average and the warmest July since record keeping began in 1895. The previous hottest July was in 1936 when the average temperature was 77.4 degrees F.
In 2011, the ratio of record daily high temperatures outnumbered record daily lows by about 3-to-1. This year, that ratio has turned even more lopsided with a ratio of record daily highs to lows of 10-to-1.
As summer progresses, it may seem like the worst is over, and hopefully that is so. But in the final four months of 2010 8,636 record daily highs were tied or set. In the same period last year (Sept.-Dec.) 5,800 records were matched or beaten. | <urn:uuid:bbb72e47-b76b-4c93-949c-4e29be06953e> | 3 | 409 | News Article | Science & Tech. | 66.143831 | 95,606,777 |
Hydrozoa | Leptothecata
Environment / Climate / Range
Sessile; depth range 165 - 183 m (Ref. 116013). Subtropical
Western Atlantic: USA and Canada.
Length at first maturity / Size / Weight / Age
Maturity: Lm ? range ? - ? cm
Benthic, found the in outer continental shelf (Ref. 116013). Colonial (Ref. 19). Reproduction occurs only in hydroid stage (Ref. 1663, p. 19).
Life cycle and mating behavior
Maturity | Reproduction | Spawning | Eggs | Fecundity | Larvae
Reproduction occurs only in hydroid stage (Ref. 1663, p. 19).
Cairns, S.D., D.R. Calder, A. Brinckmann-Voss, C.B. Castro, D.G. Fautin, P.R. Pugh, C.E. Mills, W.C. Jaap, M.N. Arai, S.H.D. Haddock and D.M. Opresko. 2003. (Ref. 1663)
IUCN Red List Status (Ref. 115185)
CITES status (Ref. 108899)
Threat to humans
| FishSource |
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+44 1803 865913
By: Hans-Peter Plag(Editor), Michael Pearlman(Editor)
376 pages, 66 colour illustrations, b/w illustrations
With the provision of accurate reference frames and observations of changes in Earth's shape, gravity field and rotation, modern geodesy takes a fundamental role for improved understanding of geodynamics, geohazards, the global water cycle, global change, atmosphere and ocean dynamics, and it supports many societal applications that depend on accurate positions. Global Geodetic Observing System provides a comprehensive overview of geodesy's contribution to science and society at large, and it identifies user needs and requirements in terms of geodetic observations and products. Specifications for a global geodetic observing system that would meet these requirements lead to considerations of system design and implementation.
2 The goals, achievements, and tools of modern geodesy
3 Understanding a dynamic planet: Earth science requirements for geodesy
4 Maintaining a modern society
5 Earth observation: Serving the needs of an increasingly global society
6 Geodesy: Foundation for exploring the planets, the solar system and beyond
7 Integrated scientific and societal user requirements and functional specifications for the GGOS
8 The future geodetic reference frame
9 The future Global Geodetic Observing System
10 Towards GGOS in 2020
Acronyms and abbreviations
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In a rare move, a Houston Methodist researcher is sharing his recipe for a new, more affordable way to make nanoparticles. This will empower any laboratory in the world to easily create similar nanoparticles and could lead to a whole new way of delivering biotherapeutic drugs and do it more quickly.
“We’re the only lab in the world doing this,” said Ennio Tasciotti, Ph.D., director of the Center for Biomimetic Medicine at the Houston Methodist Research Institute and corresponding author on a paper coming out March 7 in Advanced Materials. “There are several questions about how our system works, and I can’t answer all of them. By giving away the so-called ‘recipe’ to make biomimetic nanoparticles, a lot of other labs will be able to enter this field and may provide additional solutions and applications that are beyond the reach of only one laboratory. You could say it’s the democratization of nanotechnology.”
In the article, Tasciotti and his colleagues show how to standardize nanoparticle production to guarantee stability and reproducibility, while increasing yield. Eliminating the need for multi-million-dollar facilities, Tasciotti and his team demonstrate this using a readily available and relatively affordable piece of benchtop equipment to manufacture nanoparticles in a controlled, adjustable and low-cost manner.
“Nanoparticles are generally made through cryptic protocols, and it’s very often impossible to consistently or affordably reproduce them,” Tasciotti said. “You usually need special, custom-made equipment or procedures that are available to only a few laboratories. We provide step-by-step instructions so that now everybody can do it.”
For decades nanoparticles have been made out of bioinert, or inorganic, substances that don’t interact with the body. In more recent years, nanoparticles were made to be bioactive, meaning they could respond to the environment. Now, Tasciotti is pushing the field forward by creating biomimetic nanoparticles that resemble cell composition and work in synergy with the laws that govern the physiology of the body.
“The body is so smart in the ways it defends itself. The immune system will eventually recognize nanoparticles no matter how well you make them,” Tasciotti said. “In my lab, we make nanoparticles out of the cell membrane of the very same immune cells that patrol the blood stream. When we put these biomimetic, or bioinspired, nanoparticles back in the body, the immune cells do not recognize them as something different, as they’re made of their same building blocks, so there is no adverse response.”
Despite the complexity of this new class of particles, Tasciotti says it’s incredibly simple how they put it together, which is why he decided to publish this paper.
“While our lab will remain fully devoted to this line of research, if somebody else develops some solutions using our protocols that are useful in clinical care, it’s still a good outcome,” he said. “After all, the ultimate reason why we are in translational science is for the benefit of the patients.”
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Charged particles flow through, moving energy around, creating electric currents, and producing the aurora. Many of these particles stream in from the solar wind, starting out 93 million miles away on the surface of the sun. But some areas are dominated by particles of a more local source: Earth's atmosphere.
This artist's concept drawing shows the Fast, Affordable, Science and Technology SATellite (FASTSAT) -- NASA's first microsatellite, which launched on Nov. 19, 2010 and has been collecting data on the dynamic atmosphere surrounding Earth. Credit: NASA
These are the particles being watched by FASTSAT's Miniature Imager for Neutral Ionospheric Atoms and Magnetospheric Electrons (MINI-ME) instrument. For one well-defined event, scientists have compared MINI-ME's observations to those from two other instruments. The event shows a detailed picture of this dynamic region, with a host of interrelated phenomena -- such as electric current and outflowing particles – occurring together.
"We're seeing structures that are fairly consistent throughout a handful of instruments," says Michael Collier at NASA's Goddard Space Flight Center in Greenbelt, Md., who is the principal investigator for MINI-ME. "We put all of these observations together and it tells a story greater than the sum of its parts."
Unlike the hotter hydrogen coming from the sun, Earth's upper atmosphere generally supplies cooler oxygen ions that course outward along Earth's magnetic field lines. This "ion outflow" occurs continuously, but is especially strong during periods when there is more solar activity such as solar flares and coronal mass ejections that burst off the sun and move toward Earth. Such activity drives oxygen ions out of our planet's upper atmosphere, particularly in regions where aurora displays are strong.
"These ion outflow events are important because they help us understand the space weather environment around Earth," says Goddard's Doug Rowland who is the principal investigator for FASTSAT's Plasma Impedance Spectrum Analyzer, or PISA instrument. "The heavy ions flowing away from Earth can act as a brake, or damper, on incoming energy from the solar wind. The flow also indicates ways in which planets can lose their atmospheres – something that happens slowly on Earth, but more quickly on smaller planets with weaker magnetic fields, like Mars."
MINI-ME has been successfully spotting such outflows since the instrument first began to collect data in the winter of 2010. The instrument counts ions as it moves through a part of Earth's atmosphere called the ionosphere. This is the region where the particles gain enough speed and energy to overcome Earth's gravity, so it's an ideal place to study the first step in the outflow process.
Late on March 31, 2011, the FASTSAT spacecraft flew through an ion outflow with well-defined areas of increased fast moving, or "energetic," particles.
Simultaneous observations from PISA, which measures the density of material in the atmosphere, also showed that this was a highly structured auroral zone. In addition, the scientists turned to the National Science Foundation's Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), a mission managed by the Johns Hopkins Applied Physics Laboratory, which measures current flow and magnetic features through a network of instruments placed on commercial satellites owned by Iridium Communications. AMPERE data showed current structures that were also consistent with what is expected for an auroral zone.
"This is just one event," says Collier. "But it helps confirm the idea that the current and ion-outflows are all connected. As we continue to go through the data, there will be many more events to follow. We'd like to be able to pin down the origin of all these mechanisms in the ionosphere."
Over time, data like this will allow scientists to determine where these ions come from, what drives them, and how their intensity varies with incoming solar activity.
Susan Hendrix | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
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18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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|Appearance||colorless gas, exhibiting a red-orange glow when placed in an electric field|
|Standard atomic weight (Ar, standard)||602(2)4.002|
|Helium in the periodic table|
|Atomic number (Z)||2|
|Group||group 18 (noble gases)|
|Element category||noble gas|
Electrons per shell
|Phase at STP||gas|
|Melting point||0.95 K (−272.20 °C, −457.96 °F) (at 2.5 MPa)|
|Boiling point||4.222 K (−268.928 °C, −452.070 °F)|
|Density (at STP)||0.1786 g/L|
|when liquid (at m.p.)||0.145 g/cm3|
|when liquid (at b.p.)||0.125 g/cm3|
|Triple point||2.177 K, 5.043 kPa|
|Critical point||5.1953 K, 0.22746 MPa|
|Heat of fusion||0.0138 kJ/mol|
|Heat of vaporization||0.0829 kJ/mol|
|Molar heat capacity||20.78 J/(mol·K)|
Vapor pressure (defined by ITS-90)|
|Electronegativity||Pauling scale: no data|
|Covalent radius||28 pm|
|Van der Waals radius||140 pm|
|Crystal structure||hexagonal close-packed (hcp)|
|Speed of sound||972 m/s|
|Thermal conductivity||0.1513 W/(m·K)|
|Magnetic susceptibility||−1.88·10−6 cm3/mol (298 K)|
|Naming||after Helios, Greek Titan of the Sun|
|Discovery||Pierre Janssen, Norman Lockyer (1868)|
|First isolation||William Ramsay, Per Teodor Cleve, Abraham Langlet (1895)|
|Main isotopes of helium|
Helium (from Greek: ἥλιος, translit. Helios, lit. 'Sun') is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements.
After hydrogen, helium is the second lightest and second most abundant element in the observable universe, being present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this figure in the Sun and in Jupiter, this is due to the very high nuclear binding energy (per nucleon) of helium-4 with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of both nuclear fusion and radioactive decay. Most helium in the universe is helium-4, the vast majority of which was formed during the Big Bang. Large amounts of new helium are being created by nuclear fusion of hydrogen in stars.
Helium is named for the Greek Titan of the Sun, Helios, it was first detected as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by Georges Rayet, Captain C. T. Haig, Norman R. Pogson, and Lieutenant John Herschel, and was subsequently confirmed by French astronomer Jules Janssen. Janssen is often jointly credited with detecting the element along with Norman Lockyer. Janssen recorded the helium spectral line during the solar eclipse of 1868 while Lockyer observed it from Britain. Lockyer was the first to propose that the line was due to a new element, which he named, the formal discovery of the element was made in 1895 by two Swedish chemists, Per Teodor Cleve and Nils Abraham Langlet, who found helium emanating from the uranium ore cleveite. In 1903, large reserves of helium were found in natural gas fields in parts of the United States, which is by far the largest supplier of the gas today.
Liquid helium is used in cryogenics (its largest single use, absorbing about a quarter of production), particularly in the cooling of superconducting magnets, with the main commercial application being in MRI scanners. Helium's other industrial uses—as a pressurizing and purge gas, as a protective atmosphere for arc welding and in processes such as growing crystals to make silicon wafers—account for half of the gas produced. A well-known but minor use is as a lifting gas in balloons and airships, as with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice. In scientific research, the behavior of the two fluid phases of helium-4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular the property of superfluidity) and to those looking at the phenomena, such as superconductivity, produced in matter near absolute zero.
On Earth it is relatively rare—5.2 ppm by volume in the atmosphere. Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium, although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei. This radiogenic helium is trapped with natural gas in concentrations as great as 7% by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation. Previously, terrestrial helium—a non-renewable resource, because once released into the atmosphere it readily escapes into space—was thought to be in increasingly short supply. However, recent studies suggest that helium produced deep in the earth by radioactive decay can collect in natural gas reserves in larger than expected quantities, in some cases having been released by volcanic activity.
- 1 History
- 2 Characteristics
- 3 Isotopes
- 4 Compounds
- 5 Occurrence and production
- 6 Applications
- 7 Inhalation and safety
- 8 See also
- 9 References
- 10 Bibliography
- 11 External links
The first evidence of helium was observed on August 18, 1868, as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. This line was initially assumed to be sodium, on October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in the solar spectrum, which he named the D3 because it was near the known D1 and D2 Fraunhofer line lines of sodium. He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος (helios).
In 1881, Italian physicist Luigi Palmieri detected helium on Earth for the first time through its D3 spectral line, when he analyzed a material that had been sublimated during a recent eruption of Mount Vesuvius.
On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare earth elements) with mineral acids. Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas liberated by sulfuric acid, he noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun. These samples were identified as helium by Lockyer and British physicist William Crookes, it was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight. Helium was also isolated by the American geochemist William Francis Hillebrand prior to Ramsay's discovery when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to nitrogen, his letter of congratulations to Ramsay offers an interesting case of discovery and near-discovery in science.
In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei by allowing the particles to penetrate the thin glass wall of an evacuated tube, then creating a discharge in the tube to study the spectrum of the new gas inside. In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than one kelvin, he tried to solidify it by further reducing the temperature but failed because helium does not solidify at atmospheric pressure. Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm3 of helium in 1926 by applying additional external pressure.
In 1913, Niels Bohr published his "trilogy" on atomic structure that included a reconsideration of the Pickering–Fowler series as central evidence in support of his model of the atom. This series is named for Edward Charles Pickering, who in 1896 published observations of previously unknown lines in the spectrum of the star ζ Puppis (these are now known to occur with Wolf–Rayet and other hot stars). Pickering attributed the observation (lines at 4551, 5411, and 10123 Å) to a new form of hydrogen with half-integer transition levels. In 1912, Alfred Fowler managed to produce similar lines from a hydrogen-helium mixture, and supported Pickering's conclusion as to their origin. Bohr's model does not allow for half-integer transitions (nor does quantum mechanics) and Bohr concluded that Pickering and Fowler were wrong, and instead assigned these spectral lines to ionised helium, He+. Fowler was initially skeptical but was ultimately convinced that Bohr was correct, and by 1915 "spectroscopists had transferred [the Pickering–Fowler series] definitively [from hydrogen] to helium." Bohr's theoretical work on the Pickering series had demonstrated the need for "a re-examination of problems that seemed already to have been solved within classical theories" and provided important confirmation for his atomic theory.
In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero, a phenomenon now called superfluidity. This phenomenon is related to Bose–Einstein condensation; in 1972, the same phenomenon was observed in helium-3, but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff, David M. Lee, and Robert C. Richardson. The phenomenon in helium-3 is thought to be related to pairing of helium-3 fermions to make bosons, in analogy to Cooper pairs of electrons producing superconductivity.
Extraction and use
After an oil drilling operation in 1903 in Dexter, Kansas, produced a gas geyser that would not burn, Kansas state geologist Erasmus Haworth collected samples of the escaping gas and took them back to the University of Kansas at Lawrence where, with the help of chemists Hamilton Cady and David McFarland, he discovered that the gas consisted of, by volume, 72% nitrogen, 15% methane (a combustible percentage only with sufficient oxygen), 1% hydrogen, and 12% an unidentifiable gas. With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was helium. This showed that despite its overall rarity on Earth, helium was concentrated in large quantities under the American Great Plains, available for extraction as a byproduct of natural gas.
This enabled the United States to become the world's leading supplier of helium. Following a suggestion by Sir Richard Threlfall, the United States Navy sponsored three small experimental helium plants during World War I, the goal was to supply barrage balloons with the non-flammable, lighter-than-air gas. A total of 5,700 m3 (200,000 cu ft) of 92% helium was produced in the program even though less than a cubic meter of the gas had previously been obtained. Some of this gas was used in the world's first helium-filled airship, the U.S. Navy's C-7, which flew its maiden voyage from Hampton Roads, Virginia, to Bolling Field in Washington, D.C., on December 1, 1921, nearly two years before the Navy's first rigid helium-filled airship, the Naval Aircraft Factory-built USS Shenandoah, flew in September 1923.
Although the extraction process, using low-temperature gas liquefaction, was not developed in time to be significant during World War I, production continued. Helium was primarily used as a lifting gas in lighter-than-air craft, during World War II, the demand increased for helium for lifting gas and for shielded arc welding. The helium mass spectrometer was also vital in the atomic bomb Manhattan Project.
The government of the United States set up the National Helium Reserve in 1925 at Amarillo, Texas, with the goal of supplying military airships in time of war and commercial airships in peacetime. Because of the Helium Act of 1925, which banned the export of scarce helium on which the US then had a production monopoly, together with the prohibitive cost of the gas, the Hindenburg, like all German Zeppelins, was forced to use hydrogen as the lift gas. The helium market after World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other uses) during the Space Race and Cold War. Helium use in the United States in 1965 was more than eight times the peak wartime consumption.
After the "Helium Acts Amendments of 1960" (Public Law 86–777), the U.S. Bureau of Mines arranged for five private plants to recover helium from natural gas. For this helium conservation program, the Bureau built a 425-mile (684 km) pipeline from Bushton, Kansas, to connect those plants with the government's partially depleted Cliffside gas field near Amarillo, Texas. This helium-nitrogen mixture was injected and stored in the Cliffside gas field until needed, at which time it was further purified.
By 1995, a billion cubic meters of the gas had been collected and the reserve was US$1.4 billion in debt, prompting the Congress of the United States in 1996 to phase out the reserve. The resulting Helium Privatization Act of 1996 (Public Law 104–273) directed the United States Department of the Interior to empty the reserve, with sales starting by 2005.
Helium produced between 1930 and 1945 was about 98.3% pure (2% nitrogen), which was adequate for airships. In 1945, a small amount of 99.9% helium was produced for welding use. By 1949, commercial quantities of Grade A 99.95% helium were available.
For many years, the United States produced more than 90% of commercially usable helium in the world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder; in the mid-1990s, a new plant in Arzew, Algeria, producing 17 million cubic meters (600 million cubic feet) began operation, with enough production to cover all of Europe's demand. Meanwhile, by 2000, the consumption of helium within the U.S. had risen to more than 15 million kg per year. In 2004–2006, additional plants in Ras Laffan, Qatar, and Skikda, Algeria were built. Algeria quickly became the second leading producer of helium. Through this time, both helium consumption and the costs of producing helium increased, from 2002 to 2007 helium prices doubled.
As of 2012, the United States National Helium Reserve accounted for 30 percent of the world's helium. The reserve was expected to run out of helium in 2018, despite that, a proposed bill in the United States Senate would allow the reserve to continue to sell the gas. Other large reserves were in the Hugoton in Kansas, United States, and nearby gas fields of Kansas and the panhandles of Texas and Oklahoma. New helium plants were scheduled to open in 2012 in Qatar, Russia, and the US state of Wyoming, but they were not expected to ease the shortage.
In 2013, Qatar started up the world's largest helium unit, although the 2017 Qatar diplomatic crisis severely affected helium production there. 2014 was widely acknowledged to be a year of over-supply in the helium business, following years of renowned shortages. Nasdaq reported (2015) that for Air Products, an international corporation that sells gases for industrial use, helium volumes remain under economic pressure due to feedstock supply constraints.
The helium atom
Helium in quantum mechanics
In the perspective of quantum mechanics, helium is the second simplest atom to model, following the hydrogen atom. Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons, as in Newtonian mechanics, no system that consists of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem) and helium is no exception. Thus, numerical mathematical methods are required, even to solve the system of one nucleus and two electrons, such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within < 2% of the correct value, in a few computational steps. Such models show that each electron in helium partly screens the nucleus from the other, so that the effective nuclear charge Z which each electron sees, is about 1.69 units, not the 2 charges of a classic "bare" helium nucleus.
The nucleus of the helium-4 atom is identical with an alpha particle. High-energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud, this symmetry reflects similar underlying physics: the pair of neutrons and the pair of protons in helium's nucleus obey the same quantum mechanical rules as do helium's pair of electrons (although the nuclear particles are subject to a different nuclear binding potential), so that all these fermions fully occupy 1s orbitals in pairs, none of them possessing orbital angular momentum, and each cancelling the other's intrinsic spin. Adding another of any of these particles would require angular momentum and would release substantially less energy (in fact, no nucleus with five nucleons is stable), this arrangement is thus energetically extremely stable for all these particles, and this stability accounts for many crucial facts regarding helium in nature.
For example, the stability and low energy of the electron cloud state in helium accounts for the element's chemical inertness, and also the lack of interaction of helium atoms with each other, producing the lowest melting and boiling points of all the elements.
In a similar way, the particular energetic stability of the helium-4 nucleus, produced by similar effects, accounts for the ease of helium-4 production in atomic reactions that involve either heavy-particle emission or fusion, some stable helium-3 (2 protons and 1 neutron) is produced in fusion reactions from hydrogen, but it is a very small fraction compared to the highly favorable helium-4.
The unusual stability of the helium-4 nucleus is also important cosmologically: it explains the fact that in the first few minutes after the Big Bang, as the "soup" of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. So tight was helium-4 binding that helium-4 production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and also leaving few to form heavier atoms such as lithium, beryllium, or boron. Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy) and thus, once helium had been formed, no energetic drive was available to make elements 3, 4 and 5. It was barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon, carbon. However, due to lack of intermediate elements, this process requires three helium nuclei striking each other nearly simultaneously (see triple alpha process). There was thus no time for significant carbon to be formed in the few minutes after the Big Bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible, this left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4.
All heavier elements (including those necessary for rocky planets like the Earth, and for carbon-based or other life) have thus been created since the Big Bang in stars which were hot enough to fuse helium itself. All elements other than hydrogen and helium today account for only 2% of the mass of atomic matter in the universe. Helium-4, by contrast, makes up about 23% of the universe's ordinary matter—nearly all the ordinary matter that is not hydrogen.
Gas and plasma phases
Helium is the second least reactive noble gas after neon, and thus the second least reactive of all elements, it is chemically inert and monatomic in all standard conditions. Because of helium's relatively low molar (atomic) mass, its thermal conductivity, specific heat, and sound speed in the gas phase are all greater than any other gas except hydrogen. For these reasons and the small size of helium monatomic molecules, helium diffuses through solids at a rate three times that of air and around 65% that of hydrogen.
Helium is the least water-soluble monatomic gas, and one of the least water-soluble of any gas (CF4, SF6, and C4F8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x2/10−5, respectively, versus helium's 0.70797 x2/10−5), and helium's index of refraction is closer to unity than that of any other gas. Helium has a negative Joule–Thomson coefficient at normal ambient temperatures, meaning it heats up when allowed to freely expand. Only below its Joule–Thomson inversion temperature (of about 32 to 50 K at 1 atmosphere) does it cool upon free expansion. Once precooled below this temperature, helium can be liquefied through expansion cooling.
Most extraterrestrial helium is found in a plasma state, with properties quite different from those of atomic helium; in a plasma, helium's electrons are not bound to its nucleus, resulting in very high electrical conductivity, even when the gas is only partially ionized. The charged particles are highly influenced by magnetic and electric fields, for example, in the solar wind together with ionized hydrogen, the particles interact with the Earth's magnetosphere, giving rise to Birkeland currents and the aurora.
Unlike any other element, helium will remain liquid down to absolute zero at normal pressures, this is a direct effect of quantum mechanics: specifically, the zero point energy of the system is too high to allow freezing. Solid helium requires a temperature of 1–1.5 K (about −272 °C or −457 °F) at about 25 bar (2.5 MPa) of pressure. It is often hard to distinguish solid from liquid helium since the refractive index of the two phases are nearly the same, the solid has a sharp melting point and has a crystalline structure, but it is highly compressible; applying pressure in a laboratory can decrease its volume by more than 30%. With a bulk modulus of about 27 MPa it is ~100 times more compressible than water. Solid helium has a density of ±0.006 g/cm3 at 1.15 K and 66 atm; the projected density at 0 K and 25 bar (2.5 MPa) is 0.214±0.009 g/cm3. 0.187 At higher temperatures, helium will solidify with sufficient pressure, at room temperature, this requires about 114,000 atm.
Below its boiling point of 4.22 kelvins and above the lambda point of 2.1768 kelvins, the isotope helium-4 exists in a normal colorless liquid state, called helium I. Like other cryogenic liquids, helium I boils when it is heated and contracts when its temperature is lowered. Below the lambda point, however, helium does not boil, and it expands as the temperature is lowered further.
Helium I has a gas-like index of refraction of 1.026 which makes its surface so hard to see that floats of Styrofoam are often used to show where the surface is. This colorless liquid has a very low viscosity and a density of 0.145–0.125 g/mL (between about 0 and 4 K), which is only one-fourth the value expected from classical physics. Quantum mechanics is needed to explain this property and thus both states of liquid helium (helium I and helium II) are called quantum fluids, meaning they display atomic properties on a macroscopic scale. This may be an effect of its boiling point being so close to absolute zero, preventing random molecular motion (thermal energy) from masking the atomic properties.
Liquid helium below its lambda point (called helium II) exhibits very unusual characteristics. Due to its high thermal conductivity, when it boils, it does not bubble but rather evaporates directly from its surface. Helium-3 also has a superfluid phase, but only at much lower temperatures; as a result, less is known about the properties of the isotope.
Helium II is a superfluid, a quantum mechanical state (see: macroscopic quantum phenomena) of matter with strange properties. For example, when it flows through capillaries as thin as 10−7 to 10−8 m it has no measurable viscosity. However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium was observed. Current theory explains this using the two-fluid model for helium II; in this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state, which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid.
In the fountain effect, a chamber is constructed which is connected to a reservoir of helium II by a sintered disc through which superfluid helium leaks easily but through which non-superfluid helium cannot pass. If the interior of the container is heated, the superfluid helium changes to non-superfluid helium; in order to maintain the equilibrium fraction of superfluid helium, superfluid helium leaks through and increases the pressure, causing liquid to fountain out of the container.
The thermal conductivity of helium II is greater than that of any other known substance, a million times that of helium I and several hundred times that of copper. This is because heat conduction occurs by an exceptional quantum mechanism. Most materials that conduct heat well have a valence band of free electrons which serve to transfer the heat. Helium II has no such valence band but nevertheless conducts heat well. The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air. When heat is introduced, it moves at 20 meters per second at 1.8 K through helium II as waves in a phenomenon known as second sound.
Helium II also exhibits a creeping effect. When a surface extends past the level of helium II, the helium II moves along the surface, against the force of gravity. Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates. It moves in a 30 nm-thick film regardless of surface material. This film is called a Rollin film and is named after the man who first characterized this trait, Bernard V. Rollin. As a result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine liquid helium. Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until it reaches somewhere warmer, where it will evaporate. Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity, the restoring force is the van der Waals force, these waves are known as third sound.
There are nine known isotopes of helium, but only helium-3 and helium-4 are stable. In the Earth's atmosphere, one atom is 3
He for every million that are 4
He. Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes, the most common isotope, helium-4, is produced on Earth by alpha decay of heavier radioactive elements; the alpha particles that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its nucleons are arranged into complete shells, it was also formed in enormous quantities during Big Bang nucleosynthesis.
Helium-3 is present on Earth only in trace amounts. Most of it has been present since Earth's formation, though some falls to Earth trapped in cosmic dust. Trace amounts are also produced by the beta decay of tritium. Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten, and these ratios can be used to investigate the origin of rocks and the composition of the Earth's mantle. 3
He is much more abundant in stars as a product of nuclear fusion. Thus in the interstellar medium, the proportion of 3
He to 4
He is about 100 times higher than on Earth. Extraplanetary material, such as lunar and asteroid regolith, have trace amounts of helium-3 from being bombarded by solar winds. The Moon's surface contains helium-3 at concentrations on the order of 10 ppb, much higher than the approximately 5 ppt found in the Earth's atmosphere. A number of people, starting with Gerald Kulcinski in 1986, have proposed to explore the moon, mine lunar regolith, and use the helium-3 for fusion.
Liquid helium-4 can be cooled to about 1 kelvin using evaporative cooling in a 1-K pot. Similar cooling of helium-3, which has a lower boiling point, can achieve about in a 0.2 kelvinhelium-3 refrigerator. Equal mixtures of liquid 3
He and 4
He below separate into two immiscible phases due to their dissimilarity (they follow different 0.8 Kquantum statistics: helium-4 atoms are bosons while helium-3 atoms are fermions). Dilution refrigerators use this immiscibility to achieve temperatures of a few millikelvins.
It is possible to produce exotic helium isotopes, which rapidly decay into other substances, the shortest-lived heavy helium isotope is helium-5 with a half-life of ×10−22 s. Helium-6 decays by emitting a 7.6beta particle and has a half-life of 0.8 second. Helium-7 also emits a beta particle as well as a gamma ray. Helium-7 and helium-8 are created in certain nuclear reactions. Helium-6 and helium-8 are known to exhibit a nuclear halo.
Helium has a valence of zero and is chemically unreactive under all normal conditions, it is an electrical insulator unless ionized. As with the other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge with a voltage below its ionization potential. Helium can form unstable compounds, known as excimers, with tungsten, iodine, fluorine, sulfur, and phosphorus when it is subjected to a glow discharge, to electron bombardment, or reduced to plasma by other means. The molecular compounds HeNe, HgHe10, and WHe2, and the molecular ions He+
, and HeD+
have been created this way. HeH+ is also stable in its ground state, but is extremely reactive—it is the strongest Brønsted acid known, and therefore can exist only in isolation, as it will protonate any molecule or counteranion it contacts. This technique has also produced the neutral molecule He2, which has a large number of band systems, and HgHe, which is apparently held together only by polarization forces.
Theoretically, other true compounds may be possible, such as helium fluorohydride (HHeF) which would be analogous to HArF, discovered in 2000. Calculations show that two new compounds containing a helium-oxygen bond could be stable. Two new molecular species, predicted using theory, CsFHeO and N(CH3)4FHeO, are derivatives of a metastable FHeO− anion first theorized in 2005 by a group from Taiwan. If confirmed by experiment, the only remaining element with no known stable compounds would be neon.
Helium atoms have been inserted into the hollow carbon cage molecules (the fullerenes) by heating under high pressure, the endohedral fullerene molecules formed are stable at high temperatures. When chemical derivatives of these fullerenes are formed, the helium stays inside. If helium-3 is used, it can be readily observed by helium nuclear magnetic resonance spectroscopy. Many fullerenes containing helium-3 have been reported, although the helium atoms are not attached by covalent or ionic bonds, these substances have distinct properties and a definite composition, like all stoichiometric chemical compounds.
Under high pressures helium can form compounds with various other elements. Helium-nitrogen clathrate (He(N2)11) crystals have been grown at room temperature at pressures ca. 10 GPa in a diamond anvil cell. The insulating electride Na2He has been shown to be thermodynamically stable at pressures above 113 GPa. It has a fluorite structure.
Occurrence and production
Although it is rare on Earth, helium is the second most abundant element in the known Universe (after hydrogen), constituting 23% of its baryonic mass, the vast majority of helium was formed by Big Bang nucleosynthesis one to three minutes after the Big Bang. As such, measurements of its abundance contribute to cosmological models; in stars, it is formed by the nuclear fusion of hydrogen in proton-proton chain reactions and the CNO cycle, part of stellar nucleosynthesis.
In the Earth's atmosphere, the concentration of helium by volume is only 5.2 parts per million. The concentration is low and fairly constant despite the continuous production of new helium because most helium in the Earth's atmosphere escapes into space by several processes. In the Earth's heterosphere, a part of the upper atmosphere, helium and other lighter gases are the most abundant elements.
Most helium on Earth is a result of radioactive decay. Helium is found in large amounts in minerals of uranium and thorium, including cleveite, pitchblende, carnotite and monazite, because they emit alpha particles (helium nuclei, He2+) to which electrons immediately combine as soon as the particle is stopped by the rock. In this way an estimated 3000 metric tons of helium are generated per year throughout the lithosphere. In the Earth's crust, the concentration of helium is 8 parts per billion; in seawater, the concentration is only 4 parts per trillion. There are also small amounts in mineral springs, volcanic gas, and meteoric iron, because helium is trapped in the subsurface under conditions that also trap natural gas, the greatest natural concentrations of helium on the planet are found in natural gas, from which most commercial helium is extracted. The concentration varies in a broad range from a few ppm to more than 7% in a small gas field in San Juan County, New Mexico.
As of 2011 the world's helium reserves were estimated at 40 billion cubic meters, with a quarter of that being in the South Pars / North Dome Gas-Condensate field owned jointly by Qatar and Iran. In 2015 and 2016 more probable reserves were announced to be under the Rocky Mountains in North America and in east Africa.
Modern extraction and distribution
For large-scale use, helium is extracted by fractional distillation from natural gas, which can contain as much as 7% helium, since helium has a lower boiling point than any other element, low temperature and high pressure are used to liquefy nearly all the other gases (mostly nitrogen and methane). The resulting crude helium gas is purified by successive exposures to lowering temperatures, in which almost all of the remaining nitrogen and other gases are precipitated out of the gaseous mixture. Activated charcoal is used as a final purification step, usually resulting in 99.995% pure Grade-A helium. The principal impurity in Grade-A helium is neon; in a final production step, most of the helium that is produced is liquefied via a cryogenic process. This is necessary for applications requiring liquid helium and also allows helium suppliers to reduce the cost of long distance transportation, as the largest liquid helium containers have more than five times the capacity of the largest gaseous helium tube trailers.
In 2008, approximately 169 million standard cubic meters (SCM) of helium were extracted from natural gas or withdrawn from helium reserves with approximately 78% from the United States, 10% from Algeria, and most of the remainder from Russia, Poland and Qatar. By 2013, increases in helium production in Qatar (under the company RasGas managed by Air Liquide) had increased Qatar's fraction of world helium production to 25%, and made it the second largest exporter after the United States. An estimated 54 billion cubic feet (1.5×109 m3) deposit of helium was found in Tanzania in 2016.
In the United States, most helium is extracted from natural gas of the Hugoton and nearby gas fields in Kansas, Oklahoma, and the Panhandle Field in Texas. Much of this gas was once sent by pipeline to the National Helium Reserve, but since 2005 this reserve is being depleted and sold off, and is expected to be largely depleted by 2021, under the October 2013 Responsible Helium Administration and Stewardship Act (H.R. 527).
Diffusion of crude natural gas through special semipermeable membranes and other barriers is another method to recover and purify helium; in 1996, the U.S. had proven helium reserves, in such gas well complexes, of about 147 billion standard cubic feet (4.2 billion SCM). At rates of use at that time (72 million SCM per year in the U.S.; see pie chart below) this would have been enough helium for about 58 years of U.S. use, and less than this (perhaps 80% of the time) at world use rates, although factors in saving and processing impact effective reserve numbers.
Helium must be extracted from natural gas because it is present in air at only a fraction of that of neon, yet the demand for it is far higher, it is estimated that if all neon production were retooled to save helium, that 0.1% of the world's helium demands would be satisfied. Similarly, only 1% of the world's helium demands could be satisfied by re-tooling all air distillation plants. Helium can be synthesized by bombardment of lithium or boron with high-velocity protons, or by bombardment of lithium with deuterons, but these processes are a completely uneconomical method of production.
Helium is commercially available in either liquid or gaseous form, as a liquid, it can be supplied in small insulated containers called dewars which hold as much as 1,000 liters of helium, or in large ISO containers which have nominal capacities as large as 42 m3 (around 11,000 U.S. gallons). In gaseous form, small quantities of helium are supplied in high-pressure cylinders holding as much as 8 m3 (approx. 282 standard cubic feet), while large quantities of high-pressure gas are supplied in tube trailers which have capacities of as much as 4,860 m3 (approx. 172,000 standard cubic feet).
According to helium conservationists like Nobel laureate physicist Robert Coleman Richardson, writing in 2010, the free market price of helium has contributed to "wasteful" usage (e.g. for helium balloons). Prices in the 2000s had been lowered by the decision of the U.S. Congress to sell off the country's large helium stockpile by 2015. According to Richardson, the price needed to be multiplied by 20 to eliminate the excessive wasting of helium; in their book, the Future of helium as a natural resource (Routledge, 2012), Nuttall, Clarke & Glowacki (2012) also proposed to create an International Helium Agency (IHA) to build a sustainable market for this precious commodity.
While balloons are perhaps the best known use of helium, they are a minor part of all helium use. Helium is used for many purposes that require some of its unique properties, such as its low boiling point, low density, low solubility, high thermal conductivity, or inertness. Of the 2014 world helium total production of about 32 million kg (180 million standard cubic meters) helium per year, the largest use (about 32% of the total in 2014) is in cryogenic applications, most of which involves cooling the superconducting magnets in medical MRI scanners and NMR spectrometers. Other major uses were pressurizing and purging systems, welding, maintenance of controlled atmospheres, and leak detection. Other uses by category were relatively minor fractions.
Helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography, because it is inert. Because of its inertness, thermally and calorically perfect nature, high speed of sound, and high value of the heat capacity ratio, it is also useful in supersonic wind tunnels and impulse facilities.
Gas tungsten arc welding
Helium is used as a shielding gas in arc welding processes on materials that at welding temperatures are contaminated and weakened by air or nitrogen. A number of inert shielding gases are used in gas tungsten arc welding, but helium is used instead of cheaper argon especially for welding materials that have higher heat conductivity, like aluminium or copper.
Industrial leak detection
One industrial application for helium is leak detection, because helium diffuses through solids three times faster than air, it is used as a tracer gas to detect leaks in high-vacuum equipment (such as cryogenic tanks) and high-pressure containers. The tested object is placed in a chamber, which is then evacuated and filled with helium, the helium that escapes through the leaks is detected by a sensitive device (helium mass spectrometer), even at the leak rates as small as 10−9 mbar·L/s (10−10 Pa·m3/s), the measurement procedure is normally automatic and is called helium integral test. A simpler procedure is to fill the tested object with helium and to manually search for leaks with a hand-held device.
Helium leaks through cracks should not be confused with gas permeation through a bulk material. While helium has documented permeation constants (thus a calculable permeation rate) through glasses, ceramics, and synthetic materials, inert gases such as helium will not permeate most bulk metals.
Because it is lighter than air, airships and balloons are inflated with helium for lift. While hydrogen gas is more buoyant, and escapes permeating through a membrane at a lower rate, helium has the advantage of being non-flammable, and indeed fire-retardant. Another minor use is in rocketry, where helium is used as an ullage medium to displace fuel and oxidizers in storage tanks and to condense hydrogen and oxygen to make rocket fuel. It is also used to purge fuel and oxidizer from ground support equipment prior to launch and to pre-cool liquid hydrogen in space vehicles, for example, the Saturn V rocket used in the Apollo program needed about 370,000 m3 (13 million cubic feet) of helium to launch.
Minor commercial and recreational uses
Helium as a breathing gas has no narcotic properties, so helium mixtures such as trimix, heliox and heliair are used for deep diving to reduce the effects of narcosis, which worsen with increasing depth. As pressure increases with depth, the density of the breathing gas also increases, and the low molecular weight of helium is found to considerably reduce the effort of breathing by lowering the density of the mixture, this reduces the Reynolds number of flow, leading to a reduction of turbulent flow and an increase in laminar flow, which requires less work of breathing. At depths below 150 metres (490 ft) divers breathing helium–oxygen mixtures begin to experience tremors and a decrease in psychomotor function, symptoms of high-pressure nervous syndrome. This effect may be countered to some extent by adding an amount of narcotic gas such as hydrogen or nitrogen to a helium–oxygen mixture.
Helium–neon lasers, a type of low-powered gas laser producing a red beam, had various practical applications which included barcode readers and laser pointers, before they were almost universally replaced by cheaper diode lasers.
For its inertness and high thermal conductivity, neutron transparency, and because it does not form radioactive isotopes under reactor conditions, helium is used as a heat-transfer medium in some gas-cooled nuclear reactors.
Helium, mixed with a heavier gas such as xenon, is useful for thermoacoustic refrigeration due to the resulting high heat capacity ratio and low Prandtl number, the inertness of helium has environmental advantages over conventional refrigeration systems which contribute to ozone depletion or global warming.
The use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes, due to its extremely low index of refraction. This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy.
Helium is a commonly used carrier gas for gas chromatography.
Helium at low temperatures is used in cryogenics, and in certain cryogenics applications, as examples of applications, liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging. The Large Hadron Collider at CERN uses 96 metric tons of liquid helium to maintain the temperature at 1.9 kelvin.
Inhalation and safety
Neutral helium at standard conditions is non-toxic, plays no biological role and is found in trace amounts in human blood.
The effect of helium on a human voice
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The speed of sound in helium is nearly three times the speed of sound in air, because the fundamental frequency of a gas-filled cavity is proportional to the speed of sound in the gas, when helium is inhaled there is a corresponding increase in the resonant frequencies of the vocal tract. The fundamental frequency (sometimes called pitch) does not change, since this is produced by direct vibration of the vocal folds, which is unchanged. However, the higher resonant frequencies cause a change in timbre, resulting in a reedy, duck-like vocal quality, the opposite effect, lowering resonant frequencies, can be obtained by inhaling a dense gas such as sulfur hexafluoride or xenon.
Inhaling helium can be dangerous if done to excess, since helium is a simple asphyxiant and so displaces oxygen needed for normal respiration. Fatalities have been recorded, including a youth who suffocated in Vancouver in 2003 and two adults who suffocated in South Florida in 2006; in 1998, an Australian girl (her age is not known) from Victoria fell unconscious and temporarily turned blue after inhaling the entire contents of a party balloon. Inhaling helium directly from pressurized cylinders or even balloon filling valves is extremely dangerous, as high flow rate and pressure can result in barotrauma, fatally rupturing lung tissue.
Death caused by helium is rare, the first media-recorded case was that of a 15-year-old girl from Texas who died in 1998 from helium inhalation at a friend's party; the exact type of helium death is unidentified.
In the United States only two fatalities were reported between 2000 and 2004, including a man who died in North Carolina of barotrauma in 2002. A youth asphyxiated in Vancouver during 2003, and a 27-year-old man in Australia had an embolism after breathing from a cylinder in 2000, since then two adults asphyxiated in South Florida in 2006, and there were cases in 2009 and 2010, one a Californian youth who was found with a bag over his head, attached to a helium tank, and another teenager in Northern Ireland died of asphyxiation. At Eagle Point, Oregon a teenage girl died in 2012 from barotrauma at a party. A girl from Michigan died from hypoxia later in the year.
On February 4, 2015 it was revealed that during the recording of their main TV show on January 28, a 12-year-old member (name withheld) of Japanese all-girl singing group 3B Junior suffered from air embolism, losing consciousness and falling in a coma as a result of air bubbles blocking the flow of blood to the brain, after inhaling huge quantities of helium as part of a game. The incident was not made public until a week later, the staff of TV Asahi held an emergency press conference to communicate that the member had been taken to the hospital and is showing signs of rehabilitation such as moving eyes and limbs, but her consciousness has not been sufficiently recovered as of yet. Police have launched an investigation due to a neglect of safety measures.
On July 13, 2017 CBS News reported that a political operative who reportedly attempted to recover e-mails missing from the Clinton server, Peter W. Smith, "apparently" committed suicide in May at a hotel room in Rochester, Minnesota and that his death was recorded as "asphyxiation due to displacement of oxygen in confined space with helium". More details followed in the Chicago Tribune.
The safety issues for cryogenic helium are similar to those of liquid nitrogen; its extremely low temperatures can result in cold burns, and the liquid-to-gas expansion ratio can cause explosions if no pressure-relief devices are installed. Containers of helium gas at 5 to 10 K should be handled as if they contain liquid helium due to the rapid and significant thermal expansion that occurs when helium gas at less than 10 K is warmed to room temperature.
At high pressures (more than about 20 atm or two MPa), a mixture of helium and oxygen (heliox) can lead to high-pressure nervous syndrome, a sort of reverse-anesthetic effect; adding a small amount of nitrogen to the mixture can alleviate the problem.
- Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
- Shuen-Chen Hwang, Robert D. Lein, Daniel A. Morgan (2005). "Noble Gases". Kirk Othmer Encyclopedia of Chemical Technology. Wiley. pp. 343–383. doi:10.1002/0471238961.0701190508230114.a01.
- Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
- Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
- Rayet, G. (1868) "Analyse spectral des protubérances observées, pendant l'éclipse totale de Soleil visible le 18 août 1868, à la presqu'île de Malacca"[permanent dead link] (Spectral analysis of the protuberances observed during the total solar eclipse, seen on 18 August 1868, from the Malacca peninsula), Comptes rendus … , 67 : 757–759. From p. 758: " … je vis immédiatement une série de neuf lignes brillantes qui … me semblent devoir être assimilées aux lignes principales du spectre solaire, B, D, E, b, une ligne inconnue, F, et deux lignes du groupe G." ( … I saw immediately a series of nine bright lines that … seemed to me should be classed as the principal lines of the solar spectrum, B, D, E, b, an unknown line, F, and two lines of the group G.)
- Captain C. T. Haig (1868) "Account of spectroscopic observations of the eclipse of the sun, August 18th, 1868," Proceedings of the Royal Society of London, 17 : 74–80. From p. 74: "I may state at once that I observed the spectra of two red flames close to each other, and in their spectra two broad bright bands quite sharply defined, one rose-madder and the other light golden."
- Pogson filed his observations of the 1868 eclipse with the local Indian government, but his report wasn't published. (Biman B. Nath, The Story of Helium and the Birth of Astrophysics (New York, New York: Springer, 2013), p. 8.) Nevertheless, Lockyer quoted from his report. From p. 320 of Lockyer, J. Norman (1896) "The story of helium. Prologue," Nature, 53 : 319–322 : "Pogson, in referring to the eclipse of 1868, said that the yellow line was "at D, or near D." "
- Lieutenant John Herschel (1868) "Account of the solar eclipse of 1868, as seen at Jamkandi in the Bombay Presidency," Proceedings of the Royal Society of London, 17 : 104–120. From p. 113: As the moment of the total solar eclipse approached, " … I recorded an increasing brilliancy in the spectrum in the neighborhood of D, so great in fact as to prevent any measurement of that line till an opportune cloud moderated the light. I am not prepared to offer any explanation of this." From p. 117: "I also consider that there can be no question that the ORANGE LINE was identical with D, so far as the capacity of the instrument to establish any such identity is concerned."
- In his initial report to the French Academy of Sciences about the 1868 eclipse, Janssen made no mention of a yellow line in the solar spectrum. See:
- Janssen (1868) "Indication de quelques-uns des résultats obtenus à Cocanada, pendant l'éclipse du mois d'août dernier, et à la suite de cette éclipse" (Information on some of the results obtained at Cocanada, during the eclipse of the month of last August, and following that eclipse), Comptes rendus … , 67 : 838–839.
- Wheeler M. Sears, Helium: The Disappearing Element (Heidelberg, Germany: Springer, 2015), p. 44.
- Françoise Launay with Storm Dunlop, trans., The Astronomer Jules Janssen: A Globetrotter of Celestial Physics (Heidelberg, Germany: Springer, 2012), p. 45.
- Rose, Melinda (October 2008). "Helium: Up, Up and Away?". Photonics Spectra. Retrieved February 27, 2010. For a more authoritative but older 1996 pie chart showing U.S. helium use by sector, showing much the same result, see the chart reproduced in "Applications" section of this article.
- Connor, Steve (2010-08-23). "Why the world is running out of helium". The Independent. London. Retrieved 2013-09-16.
- Siegel, Ethan (2012-12-12). "Why the World Will Run Out of Helium". Starts with a Bang. Scienceblogs.com. Retrieved 2013-09-16.
- Witchalls, Clint (18 August 2010) Nobel prizewinner: We are running out of helium. New Scientist.(subscription required)
- Szondy, David. "We may not be running out of helium after all". www.gizmag.com. Retrieved 2016-04-01.
- "Press release: The unbearable lightness of helium..." EurekAlert. European Association of Geochemistry. 19 August 2015. Archived from the original on 6 September 2015. Retrieved 2016-04-01.
- Sample, Ian (28 June 2016). "Huge helium gas find in east Africa averts medical shortage". The Guardian.
- Kochhar, R. K. (1991). "French astronomers in India during the 17th – 19th centuries". Journal of the British Astronomical Association. 101 (2): 95–100. Bibcode:1991JBAA..101...95K.
- Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 175–179. ISBN 0-19-850341-5.
- Lockyer, J. N. (October 1868). "Notice of an observation of the spectrum of a solar prominence". Proceedings of the Royal Society of London. 17: 91–92. Bibcode:1868RSPS...17...91L. doi:10.1098/rspl.1868.0011. JSTOR 112357. Retrieved 3 June 2018.
- Hampel, Clifford A. (1968). The Encyclopedia of the Chemical Elements. New York: Van Nostrand Reinhold. pp. 256–268. ISBN 0-442-15598-0.
- Harper, Douglas. "helium". Online Etymology Dictionary.
- Thomson, William (August 3, 1871). "Inaugural Address of Sir William Thomson". Nature. 4 (92): 261–278 . Bibcode:1871Natur...4..261.. doi:10.1038/004261a0. PMC .
Frankland and Lockyer find the yellow prominences to give a very decided bright line not far from D, but hitherto not identified with any terrestrial flame. It seems to indicate a new substance, which they propose to call Helium
- Palmieri, Luigi (1881). "La riga dell'Helium apparsa in una recente sublimazione vesuviana" [The line of helium appeared in a recently sublimated material [from Mt.] Vesuvius.]. Rendiconto dell'Accademia delle scienze fisiche e matematiche (Naples, Italy). 20: 223. Retrieved 1 May 2017.
Raccolsi alcun tempo fa una sostanza amorfa di consistenza butirracea e di colore giallo sbiadato sublimata sull'orlo di una fumarola prossima alla bocca di eruzione. Saggiata questa sublimazione allo spettroscopio, ho ravvisato le righe del sodio e del potassio ed una lineare ben distinta che corrisponde esattamente alla D3 che è quella dell'Helium. Do per ora il semplice annunzio del fatto, proponendomi di ritornare sopra questo argomento, dopo di aver sottoposta la sublimazione ad una analisi chimica. (I collected some time ago an amorphous substance having a buttery consistency and a faded yellow color which had sublimated on the rim of a fumarole near the mouth of the eruption. Having analyzed this sublimated substance with a spectroscope, I recognized the lines of sodium and potassium and a very distinct linear line which corresponds exactly to D3, which is that of helium. For the present, I'm making a mere announcement of the fact, proposing to return to this subject after having subjected the sublimate to a chemical analysis.)
- Kirk, Wendy L. "Cleveite [not Clevite] and helium". Museums & Collections Blog. University College London. Retrieved 18 August 2017.
- Ramsay, William (1895). "On a Gas Showing the Spectrum of Helium, the Reputed Cause of D3, One of the Lines in the Coronal Spectrum. Preliminary Note". Proceedings of the Royal Society of London. 58 (347–352): 65–67. doi:10.1098/rspl.1895.0006.
- Ramsay, William (1895). "Helium, a Gaseous Constituent of Certain Minerals. Part I". Proceedings of the Royal Society of London. 58 (347–352): 81–89. doi:10.1098/rspl.1895.0010.
- Ramsay, William (1895). "Helium, a Gaseous Constituent of Certain Minerals. Part II – Density". Proceedings of the Royal Society of London. 59 (1): 325–330. doi:10.1098/rspl.1895.0097.
- Lockyer, J. Norman (1895). "On the new gas obtained from uraninite. Preliminary note, part II". Proceedings of the Royal Society of London. 58 (347–352): 67–70. doi:10.1098/rspl.1895.0008.
- Langlet, N. A. (1895). "Das Atomgewicht des Heliums". Zeitschrift für anorganische Chemie (in German). 10 (1): 289–292. doi:10.1002/zaac.18950100130.
- Weaver, E. R. (1919). "Bibliography of Helium Literature". Industrial & Engineering Chemistry.
- Hillebrand (1890) "On the occurrence of nitrogen in uraninite and on the composition of uraninite in general," Bulletin of the U.S. Geological Survey, no. 78, pp. 43–79.
- Munday, Pat (1999). John A. Garraty; Mark C. Carnes, eds. Biographical entry for W.F. Hillebrand (1853–1925), geochemist and U.S. Bureau of Standards administrator in American National Biography. 10–11. Oxford University Press. pp. 808–9; 227–8.
- Rutherford, E.; Royds, T. (1908). "XXIV.Spectrum of the radium emanation". Philosophical Magazine. series 6. 16 (92): 313–317. doi:10.1080/14786440808636511.[permanent dead link]
- Onnes, H. Kamerlingh (1908) "The liquefaction of helium,"[permanent dead link] Communications from the Physical Laboratory at the University of Leiden, 9 (108) : 1–23.
- van Delft, Dirk (2008). "Little cup of Helium, big Science" (PDF). Physics Today. 61 (3): 36–42. Bibcode:2008PhT....61c..36V. doi:10.1063/1.2897948. Archived from the original (PDF) on June 25, 2008. Retrieved 2008-07-20.
- Preliminary notice: Keesom, W. H. (17 July 1926) Letters to the Editor: "Solidification of helium," Nature, 118 : 81.
- Preliminary notice: Keesom, W. H. (1926) "L'hélium solidifié," Comptes rendus … , 183 : 26.
- Keesom, W. H. (1926) "Solid Helium," Communications from the Physical Laboratory at the University of Leiden, 17 (184) .
- "Coldest Cold". Time Inc. 1929-06-10. Retrieved 2008-07-27.
- Hoyer, Ulrich (1981). "Constitution of Atoms and Molecules". In Hoyer, Ulrich. Niels Bohr – Collected Works: Volume 2 – Work on Atomic Physics (1912–1917). Amsterdam: North Holland Publishing Company. pp. 103–316 (esp. pp. 116–122). ISBN 0720418003.
- Kennedy, P. J. (1985). "A Short Biography". In French, A. P.; Kennedy, P. J. Niels Bohr: A Centenary Volume. Harvard University Press. pp. 3–15. ISBN 978-0-674-62415-3.
- Bohr, N. (1913). "On the constitution of atoms and molecules, part I" (PDF). Philosophical Magazine. 26 (151): 1–25. doi:10.1080/14786441308634955.
Bohr, N. (1913). "On the constitution of atoms and molecules, part II: Systems Containing Only a Single Nucleus" (PDF). Philosophical Magazine. 26 (153): 476–502. doi:10.1080/14786441308634993.
Bohr, N. (1913). "On the constitution of atoms and molecules, part III: Systems containing several nuclei". Philosophical Magazine. 26 (155): 857–875. doi:10.1080/14786441308635031.
- Robotti, Nadia (1983). "The Spectrum of ζ Puppis and the Historical Evolution of Empirical Data". Historical Studies in the Physical Sciences. 14 (1): 123–145. doi:10.2307/27757527. JSTOR 27757527.
- Pickering, E. C. (1896). "Stars having peculiar spectra. New variable stars in Crux and Cygnus". Harvard College Observatory. 12: 1–2. Bibcode:1896HarCi..12....1P. Also published as: Pickering, E. C.; Fleming, W. P. (1896). "Stars having peculiar spectra. New variable stars in Crux and Cygnus". Astrophysical Journal. 4: 369–370. Bibcode:1896ApJ.....4..369P. doi:10.1086/140291.
- Wright, W. H. (1914). "The relation between the Wolf–Rayet stars and the planetary nebulae". Astrophysical Journal. 40: 466–472. Bibcode:1914ApJ....40..466W. doi:10.1086/142138.
- Pickering, E. C. (1897). "Stars having peculiar spectra. New variable Stars in Crux and Cygnus". Astronomische Nachrichten. 142 (6): 87–90. Bibcode:1896AN....142...87P. doi:10.1002/asna.18971420605.
- Pickering, E. C. (1897). "The spectrum of zeta Puppis". Astrophysical Journal. 5: 92–94. Bibcode:1897ApJ.....5...92P. doi:10.1086/140312.
- Lakatos, Imre (1980). "Bohr: A Research Programme Progressing on Inconsistent Foundations". In Worrall, John; Currie, Gregory. The Methodology of Scientific Research Programmes. Cambridge University Press. pp. 55–68. ISBN 9780521280310.
- Fowler, A. (1912). "Observations of the Principal and other Series of Lines in the Spectrum of Hydrogen". Monthly Notices of the Royal Astronomical Society. 73 (2): 62–63. Bibcode:1912MNRAS..73...62F. doi:10.1093/mnras/73.2.62.
- Bohr, N. (1913). "The Spectra of Helium and Hydrogen". Nature. 92 (2295): 231–232. Bibcode:1913Natur..92..231B. doi:10.1038/092231d0.
- Fowler, A. (1913). "The Spectra of Helium and Hydrogen". Nature. 92 (2291): 95–96. Bibcode:1913Natur..92...95F. doi:10.1038/092095b0.
- Fowler, A. (1913). "Reply to: The Spectra of Helium and Hydrogen". Nature. 92 (2295): 232–232. Bibcode:1913Natur..92..232F. doi:10.1038/092232a0.
- Bohr, N. (1915). "The Spectra of Hydrogen and Helium". Nature. 95 (6–7): 6. Bibcode:1915Natur..95....6B. doi:10.1038/095006a0.
- Kapitza, P. (1938). "Viscosity of Liquid Helium below the λ-Point". Nature. 141 (3558): 74. Bibcode:1938Natur.141...74K. doi:10.1038/141074a0.
- Osheroff, D. D.; Richardson, R. C.; Lee, D. M. (1972). "Evidence for a New Phase of Solid He3". Phys. Rev. Lett. 28 (14): 885–888. Bibcode:1972PhRvL..28..885O. doi:10.1103/PhysRevLett.28.885.
- McFarland, D. F. (1903). "Composition of Gas from a Well at Dexter, Kan". Transactions of the Kansas Academy of Science. 19: 60–62. doi:10.2307/3624173. JSTOR 3624173.
- "Discovery of Helium in Natural Gas at the University of Kansas". National Historic Chemical Landmarks. American Chemical Society. Retrieved 2014-02-21.
- Cady, H. P.; McFarland, D. F. (1906). "Helium in Natural Gas". Science. 24 (611): 344. Bibcode:1906Sci....24..344D. doi:10.1126/science.24.611.344. PMID 17772798.
- Cady, H. P.; McFarland, D. F. (1906). "Helium in Kansas Natural Gas". Transactions of the Kansas Academy of Science. 20: 80–81. doi:10.2307/3624645. JSTOR 3624645.
- Emme, Eugene M. comp., ed. (1961). "Aeronautics and Astronautics Chronology, 1920–1924". Aeronautics and Astronautics: An American Chronology of Science and Technology in the Exploration of Space, 1915–1960. Washington, D.C.: NASA. pp. 11–19.
- Hilleret, N. (1999). "Leak Detection". In S. Turner. CERN Accelerator School, vacuum technology: proceedings: Scanticon Conference Centre, Snekersten, Denmark, 28 May – 3 June 1999 (PDF). Geneva, Switzerland: CERN. pp. 203–212.
At the origin of the helium leak detection method was the Manhattan Project and the unprecedented leak-tightness requirements needed by the uranium enrichment plants. The required sensitivity needed for the leak checking led to the choice of a mass spectrometer designed by Dr. A.O.C. Nier tuned on the helium mass.
- Williamson, John G. (1968). "Energy for Kansas". Transactions of the Kansas Academy of Science. Kansas Academy of Science. 71 (4): 432–438. doi:10.2307/3627447. JSTOR 3627447.
- "Conservation Helium Sale" (PDF). Federal Register. 70 (193): 58464. 2005-10-06. Retrieved 2008-07-20.
- Stwertka, Albert (1998). Guide to the Elements: Revised Edition. New York; Oxford University Press, p. 24. ISBN 0-19-512708-0
- Helium Privatization Act of 1996 Pub.L. 104–273
- "Executive Summary". nap.edu. Retrieved 2008-07-20.
- Mullins, P. V.; Goodling, R. M. (1951). Helium. Bureau of Mines / Minerals yearbook 1949. pp. 599–602. Retrieved 2008-07-20.
- "Helium End User Statistic" (PDF). U.S. Geological Survey. Retrieved 2008-07-20.
- Smith, E. M.; Goodwin, T. W.; Schillinger, J. (2003). "Challenges to the Worldwide Supply of Helium in the Next Decade". Advances in Cryogenic Engineering. 49. A (710): 119–138. doi:10.1063/1.1774674.
- Kaplan, Karen H. (June 2007). "Helium shortage hampers research and industry". Physics Today. American Institute of Physics. 60 (6): 31–32. Bibcode:2007PhT....60f..31K. doi:10.1063/1.2754594.
- Basu, Sourish (October 2007). Yam, Philip, ed. "Updates: Into Thin Air". Scientific American. 297 (4). Scientific American, Inc. p. 18. Retrieved 2008-08-04.
- Newcomb, Tim (2012-08-21). "There's a Helium Shortage On—and It's Affecting More than Just Balloons". Time.com. Retrieved 2013-09-16.
- "Archived copy". Archived from the original on 2014-09-14. Retrieved 2015-05-25. Air Liquide Press Release.
- "Middle East turmoil is disrupting a vital resource for nuclear energy, space flight and birthday balloons". washingtonpost.com. 26 June 2017. Retrieved 26 June 2017.
- http://www.gasworld.com/2015-what-lies-ahead-part-1/2004706.article Gasworld, 25 Dec 2014.
- Will Air Products' (APD) Earnings Surprise Estimates in Q2? – Analyst Blog
- Watkins, Thayer. "The Old Quantum Physics of Niels Bohr and the Spectrum of Helium: A Modified Version of the Bohr Model". San Jose State University.
- Lewars, Errol G. (2008). Modelling Marvels. Springer. pp. 70–71. ISBN 1-4020-6972-3.
- Weiss, Ray F. (1971). "Solubility of helium and neon in water and seawater". J. Chem. Eng. Data. 16 (2): 235–241. doi:10.1021/je60049a019.
- Scharlin, P.; Battino, R.; Silla, E.; Tuñón, I.; Pascual-Ahuir, J. L. (1998). "Solubility of gases in water: Correlation between solubility and the number of water molecules in the first solvation shell". Pure and Applied Chemistry. 70 (10): 1895–1904. doi:10.1351/pac199870101895.
- Stone, Jack A.; Stejskal, Alois (2004). "Using helium as a standard of refractive index: correcting errors in a gas refractometer". Metrologia. 41 (3): 189–197. Bibcode:2004Metro..41..189S. doi:10.1088/0026-1394/41/3/012.
- Buhler, F.; Axford, W. I.; Chivers, H. J. A.; Martin, K. (1976). "Helium isotopes in an aurora". J. Geophys. Res. 81 (1): 111–115. Bibcode:1976JGR....81..111B. doi:10.1029/JA081i001p00111.
- "Solid Helium". Department of Physics University of Alberta. 2005-10-05. Archived from the original on May 31, 2008. Retrieved 2008-07-20.
- Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
- Grilly, E. R. (1973). "Pressure-volume-temperature relations in liquid and solid 4He". Journal of Low Temperature Physics. 11 (1–2): 33–52. Bibcode:1973JLTP...11...33G. doi:10.1007/BF00655035.
- Henshaw, D. B. (1958). "Structure of Solid Helium by Neutron Diffraction". Physical Review Letters. 109 (2): 328–330. Bibcode:1958PhRv..109..328H. doi:10.1103/PhysRev.109.328.
- "Facts about helium". www.chemicool.com. chemicool.com. Retrieved 7 June 2017.
- Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. p. 6-120. ISBN 0-8493-0486-5.
- Hohenberg, P. C.; Martin, P. C. (2000). "Microscopic Theory of Superfluid Helium". Annals of Physics. 281 (1–2): 636–705 12091211. Bibcode:2000AnPhy.281..636H. doi:10.1006/aphy.2000.6019.
- Warner, Brent. "Introduction to Liquid Helium". NASA. Archived from the original on 2005-09-01. Retrieved 2007-01-05.
- Fairbank, H. A.; Lane, C. T. (1949). "Rollin Film Rates in Liquid Helium". Physical Review. 76 (8): 1209–1211. Bibcode:1949PhRv...76.1209F. doi:10.1103/PhysRev.76.1209.
- Rollin, B. V.; Simon, F. (1939). "On the 'film' phenomenon of liquid helium II". Physica. 6 (2): 219–230. Bibcode:1939Phy.....6..219R. doi:10.1016/S0031-8914(39)80013-1.
- Ellis, Fred M. (2005). "Third sound". Wesleyan Quantum Fluids Laboratory. Retrieved 2008-07-23.
- Bergman, D. (1949). "Hydrodynamics and Third Sound in Thin He II Films". Physical Review. 188 (1): 370–384. Bibcode:1969PhRv..188..370B. doi:10.1103/PhysRev.188.370.
- Weiss, Achim. "Elements of the past: Big Bang Nucleosynthesis and observation". Max Planck Institute for Gravitational Physics. Retrieved 2008-06-23.; Coc, Alain; Vangioni-Flam, Elisabeth; Descouvemont, Pierre; Adahchour, Abderrahim; Angulo, Carmen (2004). "Updated Big Bang Nucleosynthesis confronted to WMAP observations and to the Abundance of Light Elements". Astrophysical Journal. 600 (2): 544. arXiv: . Bibcode:2004ApJ...600..544C. doi:10.1086/380121.
- Anderson, Don L.; Foulger, G. R.; Meibom, A. (2006-09-02). "Helium Fundamentals". MantlePlumes.org. Retrieved 2008-07-20.
- Novick, Aaron (1947). "Half-Life of Tritium". Physical Review. 72 (10): 972–972. Bibcode:1947PhRv...72..972N. doi:10.1103/PhysRev.72.972.2.
- Zastenker, G. N.; Salerno, E.; Buehler, F.; Bochsler, P.; Bassi, M.; Agafonov, Yu. N.; Eisomont, N. A.; Khrapchenkov, V. V.; et al. (2002). "Isotopic Composition and Abundance of Interstellar Neutral Helium Based on Direct Measurements". Astrophysics. 45 (2): 131–142. Bibcode:2002Ap.....45..131Z. doi:10.1023/A:1016057812964.
- "Lunar Mining of Helium-3". Fusion Technology Institute of the University of Wisconsin-Madison. 2007-10-19. Retrieved 2008-07-09.
- Slyuta, E. N.; Abdrakhimov, A. M.; Galimov, E. M. (2007). "The estimation of helium-3 probable reserves in lunar regolith" (PDF). Lunar and Planetary Science XXXVIII. Retrieved 2008-07-20.
- Hedman, Eric R. (2006-01-16). "A fascinating hour with Gerald Kulcinski". The Space Review. Retrieved 2008-07-20.
- Hiby, Julius W. (1939). "Massenspektrographische Untersuchungen an Wasserstoff- und Heliumkanalstrahlen (H+
)". Annalen der Physik. 426 (5): 473–487. Bibcode:1939AnP...426..473H. doi:10.1002/andp.19394260506.
- Friedrich, Bretislav (8 April 2013). "A Fragile Union Between Li and He Atoms". Physics. 6: 42. Bibcode:2013PhyOJ...6...42F. doi:10.1103/Physics.6.42.
- Wong, Ming Wah (2000). "Prediction of a Metastable Helium Compound: HHeF". Journal of the American Chemical Society. 122 (26): 6289–6290. doi:10.1021/ja9938175.
- Grochala, W. (2009). "On Chemical Bonding Between Helium and Oxygen". Polish Journal of Chemistry. 83: 87–122.
- "Collapse of helium's chemical nobility predicted by Polish chemist" (PDF). Archived from the original (PDF) on 2009-03-19. Retrieved 2009-05-15.
- Saunders, Martin; Jiménez-Vázquez, Hugo A.; Cross, R. James; Poreda, Robert J. (1993). "Stable Compounds of Helium and Neon: He@C60 and Ne@C60". Science. 259 (5100): 1428–1430. Bibcode:1993Sci...259.1428S. doi:10.1126/science.259.5100.1428. PMID 17801275.
- Saunders, Martin; Jiménez-Vázquez, Hugo A.; Cross, R. James; Mroczkowski, Stanley; Freedberg, Darón I.; Anet, Frank A. L. (1994). "Probing the interior of fullerenes by 3He NMR spectroscopy of endohedral 3He@C60 and 3He@C70". Nature. 367 (6460): 256–258. Bibcode:1994Natur.367..256S. doi:10.1038/367256a0.
- Vos, W. L.; Finger, L. W.; Hemley, R. J.; Hu, J. Z.; Mao, H. K.; Schouten, J. A. (1992). "A high-pressure van der Waals compound in solid nitrogen-helium mixtures". Nature. 358 (6381): 46. Bibcode:1992Natur.358...46V. doi:10.1038/358046a0.
- Dong, Xiao; Oganov, Artem R.; Goncharov, Alexander F.; Stavrou, Elissaios; Lobanov, Sergey; Saleh, Gabriele; Qian, Guang-Rui; Zhu, Qiang; Gatti, Carlo; Deringer, Volker L.; Dronskowski, Richard; Zhou, Xiang-Feng; Prakapenka, Vitali B.; Konôpková, Zuzana; Popov, Ivan A.; Boldyrev, Alexander I.; Wang, Hui-Tian (2017). "A stable compound of helium and sodium at high pressure" (PDF). Nature Chemistry. 9 (5): 440. arXiv: . Bibcode:2017NatCh...9..440D. doi:10.1038/nchem.2716. ISSN 1755-4330. PMID 28430195.
- Oliver, B. M.; Bradley, James G. (1984). "Helium concentration in the Earth's lower atmosphere". Geochimica et Cosmochimica Acta. 48 (9): 1759–1767. Bibcode:1984GeCoA..48.1759O. doi:10.1016/0016-7037(84)90030-9.
- "The Atmosphere: Introduction". JetStream – Online School for Weather. National Weather Service. 2007-08-29. Archived from the original on January 13, 2008. Retrieved 2008-07-12.
- Lie-Svendsen, Ø.; Rees, M. H. (1996). "Helium escape from the terrestrial atmosphere: The ion outflow mechanism". Journal of Geophysical Research. 101 (A2): 2435–2444. Bibcode:1996JGR...101.2435L. doi:10.1029/95JA02208.
- Strobel, Nick (2007). "Atmospheres". Nick Strobel's Astronomy Notes. Retrieved 2007-09-25.
- G. Brent Dalrymple. "How Good Are Those Young-Earth Arguments?".
- Cook, Melvine A. (1957). "Where is the Earth's Radiogenic Helium?". Nature. 179 (4552): 213. Bibcode:1957Natur.179..213C. doi:10.1038/179213a0.
- Aldrich, L. T.; Nier, Alfred O. (1948). "The Occurrence of He3 in Natural Sources of Helium". Phys. Rev. 74 (11): 1590–1594. Bibcode:1948PhRv...74.1590A. doi:10.1103/PhysRev.74.1590.
- Morrison, P.; Pine, J. (1955). "Radiogenic Origin of the Helium Isotopes in Rock". Annals of the New York Academy of Sciences. 62 (3): 71–92. Bibcode:1955NYASA..62...71M. doi:10.1111/j.1749-6632.1955.tb35366.x.
- Zartman, R. E.; Wasserburg, G. J.; Reynolds, J. H. (1961). "Helium Argon and Carbon in Natural Gases". Journal of Geophysical Research. 66 (1): 277–306. Bibcode:1961JGR....66..277Z. doi:10.1029/JZ066i001p00277.
- Broadhead, Ronald F. (2005). "Helium in New Mexico—geology distribution resource demand and exploration possibilities" (PDF). New Mexico Geology. 27 (4): 93–101. Archived from the original (PDF) on 2012-03-30. Retrieved 2008-07-21.
- "Press release: The unbearable lightness of helium..." European Association of Geochemistry. Retrieved 5 March 2017.
- "Huge helium gas find in east Africa averts medical shortage". The Guardian. Retrieved 5 March 2017.
- Winter, Mark (2008). "Helium: the essentials". University of Sheffield. Retrieved 2008-07-14.
- Cai, Z.; et al. (2007). Modelling Helium Markets (PDF). University of Cambridge. Archived from the original (PDF) on 2009-03-26. Retrieved 2008-07-14.
- Helium (PDF). Mineral Commodity Summaries. U.S. Geological Survey. 2009. pp. 74–75. Retrieved 2009-12-19.
- "Air Liquide and Linde in Helium Hunt as Texas Reserves Dry Up". Bloomberg. 2014.
- Briggs, Helen (28 June 2016). "Helium discovery a 'game-changer'". BBC News. Retrieved 2016-06-28.
- Pierce, A. P., Gott, G. B., and Mytton, J. W. (1964). "Uranium and Helium in the Panhandle Gas Field Texas, and Adjacent Areas", Geological Survey Professional Paper 454-G, Washington:US Government Printing Office
- "Responsible Helium Administration and Stewardship Act (H.R. 527)". House Committee on Natural Resources. Committee on Natural Resources United States House of Representatives. Retrieved 5 March 2017.
- Belyakov, V. P.; Durgar'yan, S. G.; Mirzoyan, B. A. (1981). "Membrane technology—A new trend in industrial gas separation". Chemical and Petroleum Engineering. 17 (1): 19–21. doi:10.1007/BF01245721.
- Committee on the Impact of Selling, Table 4.2
- Committee on the Impact of Selling, see page 40 for the estimate of total theoretical helium production by neon and liquid air plants
- Dee, P. I.; Walton E. T. S. (1933). "A Photographic Investigation of the Transmutation of Lithium and Boron by Protons and of Lithium by Ions of the Heavy Isotope of Hydrogen". Proceedings of the Royal Society of London. 141 (845): 733–742. Bibcode:1933RSPSA.141..733D. doi:10.1098/rspa.1933.0151.
- Connor, Steve (2010-08-23). "Richard Coleman campaigning against US Congress' decision to sell all helium supplies by 2015". London: Independent.co.uk. Retrieved 2010-11-27.
- Nuttall, William J.; Clarke, Richard H.; Glowacki, Bartek A. (2012). "Resources: Stop squandering helium". Nature. 485 (7400): 573–575. Bibcode:2012Natur.485..573N. doi:10.1038/485573a. PMID 22660302.
- U.S. Department of the Interior, U.S. Geological Survey (2015). "Helium" (PDF). Mineral Commodity Summaries 2014. pp. 72–73.
- Helium sell-off risks future supply, Michael Banks, Physics World, 27 January 2010. accessed February 27, 2010.
- Beckwith, I. E.; Miller, C. G. (1990). "Aerothermodynamics and Transition in High-Speed Wind Tunnels at Nasa Langley". Annual Review of Fluid Mechanics. 22 (1): 419–439. Bibcode:1990AnRFM..22..419B. doi:10.1146/annurev.fl.22.010190.002223.
- Morris, C.I. (2001). Shock Induced Combustion in High Speed Wedge Flows (PDF). Stanford University Thesis. Archived from the original (PDF) on 2009-03-04.
- Considine, Glenn D., ed. (2005). "Helium". Van Nostrand's Encyclopedia of Chemistry. Wiley-Interscience. pp. 764–765. ISBN 0-471-61525-0.
- Hablanian, M. H. (1997). High-vacuum technology: a practical guide. CRC Press. p. 493. ISBN 0-8247-9834-1.
- Ekin, Jack W. (2006). Experimental Techniques for Low-Temperature measurements. Oxford University Press. ISBN 0-19-857054-6.
- Fowler, B.; Ackles, K. N.; G, Porlier (1985). "Effects of inert gas narcosis on behavior—a critical review". Undersea Biomedical Research. 12 (4): 369–402. PMID 4082343. Retrieved 2008-06-27.
- Thomas, J. R. (1976). "Reversal of nitrogen narcosis in rats by helium pressure". Undersea Biomed. Res. 3 (3): 249–59. PMID 969027. Retrieved 2008-08-06.
- Butcher, Scott J.; Jones, Richard L.; Mayne, Jonathan R.; Hartley, Timothy C.; Petersen, Stewart R. (2007). "Impaired exercise ventilatory mechanics with the self-contained breathing apparatus are improved with heliox". European Journal of Applied Physiology. Netherlands: Springer. 101 (6): 659–69. doi:10.1007/s00421-007-0541-5. PMID 17701048.
- "Heliox21". Linde Gas Therapeutics. 27 January 2009. Retrieved 13 April 2011.
- Hunger, W. L., Jr.; Bennett, P. B. (1974). "The causes, mechanisms and prevention of the high pressure nervous syndrome". Undersea Biomed. Res. 1 (1): 1–28. ISSN 0093-5387. OCLC 2068005. PMID 4619860. Retrieved 2008-04-07.
- Rostain, J. C.; Gardette-Chauffour, M. C.; Lemaire, C.; Naquet, R. (1988). "Effects of a H2-He-O2 mixture on the HPNS up to 450 msw". Undersea Biomed. Res. 15 (4): 257–70. OCLC 2068005. PMID 3212843. Retrieved 2008-06-24.
- Belcher, James R.; Slaton, William V.; Raspet, Richard; Bass, Henry E.; Lightfoot, Jay (1999). "Working gases in thermoacoustic engines". The Journal of the Acoustical Society of America. 105 (5): 2677–2684. Bibcode:1999ASAJ..105.2677B. doi:10.1121/1.426884. PMID 10335618.
- Makhijani, Arjun; Gurney, Kevin (1995). Mending the Ozone Hole: Science, Technology, and Policy. MIT Press. ISBN 0-262-13308-3.
- HGST balloons disk capacity with helium-filled 6TB drive | Ars Technica
- Jakobsson, H. (1997). "Simulations of the dynamics of the Large Earth-based Solar Telescope". Astronomical & Astrophysical Transactions. 13 (1): 35–46. Bibcode:1997A&AT...13...35J. doi:10.1080/10556799708208113.
- Engvold, O.; Dunn, R.B.; Smartt, R. N.; Livingston, W. C. (1983). "Tests of vacuum VS. helium in a solar telescope". Applied Optics. 22 (1): 10–12. Bibcode:1983ApOpt..22...10E. doi:10.1364/AO.22.000010. PMID 20401118.
- "LHC: Facts and Figures" (PDF). CERN. Archived from the original (PDF) on 2011-07-06. Retrieved 2008-04-30.
- Ackerman, M. J.; Maitland, G. (1975). "Calculation of the relative speed of sound in a gas mixture". Undersea Biomed Res. 2 (4): 305–10. PMID 1226588. Retrieved 2008-08-09.
- "Why does helium make your voice squeaky?". 2000-07-14. Retrieved 2013-06-08.
- Grassberger, Martin; Krauskopf, Astrid (2007). "Suicidal asphyxiation with helium: Report of three cases Suizid mit Helium Gas: Bericht über drei Fälle". Wiener Klinische Wochenschrift (in German and English). 119 (9–10): 323–325. doi:10.1007/s00508-007-0785-4. PMID 17571238.
- Montgomery B.; Hayes S. (2006-06-03). "2 found dead under deflated balloon". Tampa Bay Times.
- "Two students die after breathing helium". CBC. 2006-06-04.
- "Helium inhalation – it's no laughing matter – Article courtesy of BOC Gases". Balloon Artists & Suppliers Association of Australasia Ltd.
- "Dangers of Helium Inhalation". Lou's Balloons. Archived from the original on 2014-01-04.
- "Helium Gas Safety & Data Sheet". bouncetime.
- Engber, Daniel (2006-06-13). "Stay Out of That Balloon!". Slate.com. Retrieved 2008-07-14.
- Josefson, D. (2000). "Imitating Mickey Mouse can be dangerous". BMJ: British Medical Journal. 320 (7237): 732. PMC . PMID 10720344.
- "Teen Dies After Inhaling Helium". KTLA News. RIVERSIDE: ktla.com. January 6, 2010. Archived from the original on January 9, 2012. Retrieved 2010-11-19.
- "Tributes to 'helium death' teenager from Newtownabbey". BBC Online. 19 November 2010. Retrieved 2010-11-19.
- Mather, Kate (2012-02-24). "Parents of Eagle Point girl who died from inhaling helium hope to save others from same fate". The Oregonian. Retrieved 2013-06-08.
- Barnard, Jeff (2012-02-22). "Ashley Long, Oregon Teenager, Dies After Inhaling Helium at Wild Party (VIDEO)". Huffington Post.
- Barnard, Jeff (2012-02-23). "Teen girl dies after inhaling helium at party". Today. AP. Archived from the original on 2013-12-30. Retrieved 2013-12-30.
- The Oxford Leader Newspaper, Sherman Publications, Inc., December 3, 2012.
- "テレ朝事故で分かったヘリウム変声缶の危険性 意識を失うケースの大半が子ども" (in Japanese). 2015-02-05. Retrieved 2015-02-05.
- Rayman, Noah (2015-02-05). "J-Pop Teen Star Left in Coma After Inhaling Helium for TV Stunt". Time. Retrieved 2015-02-06.
- "アイドルが収録中に倒れ病院搬送 テレ朝、ヘリウムガス吸引" (in Japanese). 2015-02-04. Retrieved 2015-02-04.
"テレビ番組収録中、１２歳アイドルが意識失い救急搬送 ヘリウムガスが原因か" (in Japanese). 2015-02-04. Retrieved 2015-02-04.
"テレ朝謝罪、１２歳アイドルがヘリウム吸い救急搬送" (in Japanese). 2015-02-04. Archived from the original on 2015-02-04. Retrieved 2015-02-04.
"3b Junior idol in coma after inhaling helium on TV Asahi program". 2015-02-04. Retrieved 2015-02-04.
"アイドル救急搬送騒動で制作会社が実績削除の不可解" (in Japanese). 2015-02-04. Retrieved 2015-02-04.
- "Japanese child star in coma after helium stunt goes wrong". BBC. 2015-02-05. Retrieved 2015-02-06.
- Report: GOP operative who looked for Clinton emails committed suicide, CBS News, July 13, 2017
- Katherine Skiba, David Heinzmann, Todd Lighty, Peter W. Smith, GOP operative who sought Clinton's emails from Russian hackers, committed suicide, records show, Chicago Tribune, July 15, 2017
- Rostain J.C.; Lemaire C.; Gardette-Chauffour M.C.; Doucet J.; Naquet R. (1983). "Estimation of human susceptibility to the high-pressure nervous syndrome". J Appl Physiol. 54 (4): 1063–70. PMID 6853282. Retrieved 2008-08-09.
- Bureau of Mines (1967). Minerals yearbook mineral fuels Year 1965. II. U. S. Government Printing Office.
- Committee on the Impact of Selling the Federal Helium Reserve, Commission on Physical Sciences, Mathematics, and Applications, Commission on Engineering and Technical Systems, National Research Council (2000). The Impact of Selling the Federal Helium Reserve. The National Academies Press. ISBN 0-309-07038-4. Retrieved 2010-04-02.
- Emsley, John (1998). The Elements (3rd ed.). New York: Oxford University Press. ISBN 978-0-19-855818-7.
- Vercheval, J. (2003). "The thermosphere: a part of the heterosphere". Belgian Institute for Space Aeronomy. Archived from the original on 2005-01-01. Retrieved 2008-07-12.
- U.S. Government's Bureau of Land Management: Sources, Refinement, and Shortage. With some history of helium.
- U.S. Geological Survey publications on helium beginning 1996: Helium
- Where is all the helium? Aga website
- It's Elemental – Helium
- Chemistry in its element podcast (MP3) from the Royal Society of Chemistry's Chemistry World: Helium
- International Chemical Safety Cards – Helium; includes health and safety information regarding accidental exposures to helium
- Helium at The Periodic Table of Videos (University of Nottingham)
- Helium at the Helsinki University of Technology; includes pressure-temperature phase diagrams for helium-3 and helium-4
- Lancaster University, Ultra Low Temperature Physics – includes a summary of some low temperature techniques
- Physics in Speech with audio samples that demonstrate the unchanged voice pitch
- Article about helium and other noble gases
- America’s Helium Supply: Options for Producing More Helium from Federal Land: Oversight Hearing before the Subcommittee on Energy and Mineral Resources of the Committee on Natural Resources, U.S. House Of Representatives, One Hundred Thirteenth Congress, First Session, Thursday, July 11, 2013
- Helium Program: Urgent Issues Facing BLM's Storage and Sale of Helium Reserves: Testimony before the Committee on Natural Resources, House of Representatives Government Accountability Office
- Kramer, David (May 22, 2012). "Senate bill would preserve US helium reserve: Measure would give scientists first dibs on helium should a shortage develop. Physics Today web site". Archived from the original on October 27, 2012.
- Richardson, Robert C.; Chan, Moses (2009). "Helium, when will it run out?" (PDF). Archived from the original (PDF) on 2015-06-14. | <urn:uuid:efe27415-8df9-4ed5-978a-5a74c8d6d141> | 2.59375 | 22,322 | Knowledge Article | Science & Tech. | 68.045772 | 95,606,839 |
The external organs of holometabolous insects are generated through two consecutive processes: the development of imaginal primordia and their subsequent transformation into the adult structures. During the latter process, many different phenomena at the cellular level (e.g. cell shape changes, cell migration, folding and unfolding of epithelial sheets) contribute to the drastic changes observed in size and shape. Because of this complexity, the logic behind the formation of the 3D structure of adult external organs remains largely unknown. In this report, we investigated the metamorphosis of the horn in the Japanese rhinoceros beetle Trypoxylus dichotomus. The horn primordia is essentially a 2D epithelial cell sheet with dense furrows. We experimentally unfolded these furrows using three different methods and found that the furrow pattern solely determines the 3D horn structure, indicating that horn formation in beetles occurs by two distinct processes: formation of the furrows and subsequently unfolding them. We postulate that this developmental simplicity offers an inherent advantage to understanding the principles that guide 3D morphogenesis in insects.
- Journal of the Royal Society, Interface / the Royal Society
- Published about 5 years ago
Studies of model insects have greatly increased our understanding of animal development. Yet, they are limited in scope to this small pool of model species: a small number of representatives for a hyperdiverse group with highly varied developmental processes. One factor behind this narrow scope is the challenging nature of traditional methods of study, such as histology and dissection, which can preclude quantitative analysis and do not allow the development of a single individual to be followed. Here, we use high-resolution X-ray computed tomography (CT) to overcome these issues, and three-dimensionally image numerous lepidopteran pupae throughout their development. The resulting models are presented in the electronic supplementary material, as are figures and videos, documenting a single individual throughout development. They provide new insight and details of lepidopteran metamorphosis, and allow the measurement of tracheal and gut volume. Furthermore, this study demonstrates early and rapid development of the tracheae, which become visible in scans just 12 h after pupation. This suggests that there is less remodelling of the tracheal system than previously expected, and is methodologically important because the tracheal system is an often-understudied character system in development. In the future, this form of time-lapse CT-scanning could allow faster and more detailed developmental studies on a wider range of taxa than is presently possible.
Post-mortem interval (PMI) is frequently calculated using immature stages of carrion frequenting Calliphoridae (Diptera). This is based on identification to species level, followed by age estimation of the samples. These two processes depend on suitable preservation of insects for subsequent analyses, yet preservation methods for the pupal stage are poorly defined and inappropriate methods may result in discolouration or nucleic acid degradation. This study examined the effects of 21 common preservation methods on Calliphora vicina pupae of 4 and 7d old, assessing consequences of the various methods for DNA-based species identification, age estimation using morphological analyses, and differential gene expression (DGE) studies. Pupae were examined within two weeks of preservation and again after 6-8 months. Of the methods tested, hot-water-killing (HWK) followed by storage in 80% ethanol at -20°C or 4°C was the best treatment for external morphology and histological analyses respectively. DNA based species identification was possible following all methods. RNA integrity and amplification were best when pupae were stored at -80°C or in RNAlater (-20°C), however HWK and storage in 80% ethanol at -20°C was also acceptable, and thus the latter is proposed as a universal preservative method for pupae. This study proposes a preservation method for pupae that enables DNA-based species identification, internal and external morphological analysis for age estimation, and DGE study to be carried out on a single specimen, enabling a multidisciplinary approach to age estimation from a single pupa.
The brood of ants and other social insects is highly susceptible to pathogens, particularly those that penetrate the soft larval and pupal cuticle. We here test whether the presence of a pupal cocoon, which occurs in some ant species but not in others, affects the sanitary brood care and fungal infection patterns after exposure to the entomopathogenic fungus Metarhizium brunneum. We use a) a comparative approach analysing four species with either naked or cocooned pupae and b) a within-species analysis of a single ant species, in which both pupal types co-exist in the same colony.
- Proceedings. Biological sciences / The Royal Society
- Published almost 4 years ago
Explaining the taxonomic richness of the insects, comprising over half of all described species, is a major challenge in evolutionary biology. Previously, several evolutionary novelties (key innovations) have been posited to contribute to that richness, including the insect bauplan, wings, wing folding and complete metamorphosis, but evidence over their relative importance and modes of action is sparse and equivocal. Here, a new dataset on the first and last occurrences of fossil hexapod (insects and close relatives) families is used to show that basal families of winged insects (Palaeoptera, e.g. dragonflies) show higher origination and extinction rates in the fossil record than basal wingless groups (Apterygota, e.g. silverfish). Origination and extinction rates were maintained at levels similar to Palaeoptera in the more derived Polyneoptera (e.g. cockroaches) and Paraneoptera (e.g. true bugs), but extinction rates subsequently reduced in the very rich group of insects with complete metamorphosis (Holometabola, e.g. beetles). Holometabola show evidence of a recent slow-down in their high net diversification rate, whereas other winged taxa continue to diversify at constant but low rates. These data suggest that wings and complete metamorphosis have had the most effect on family-level insect macroevolution, and point to specific mechanisms by which they have influenced insect diversity through time.
Diapause is an actively induced dormancy that has evolved in Metazoa to resist environmental stresses. In temperate regions, many diapausing insects overwinter at low temperatures by blocking embryonic, larval or adult development. Despite its Afro-tropical origin, Drosophila melanogaster migrated to temperate regions of Asia and Europe where females overwinter as adults by arresting gonadal development (reproductive diapause) at temperatures <13°C. Recent work in D. melanogaster has implicated the developmental hormones dILPs-2 and/or dILP3, and dILP5, homologues of vertebrate insulin/insulin-like growth factors (IGFs), in reproductive arrest. However, polymorphisms in timeless (tim) and couch potato (cpo) dramatically affect diapause inducibility and these dILP experiments could not exclude this common genetic variation contributing to the diapause phenotype. Here, we apply an extensive genetic dissection of the insulin signaling pathway which allows us to see both enhancements and reductions in egg development that are independent of tim and cpo variations. We show that a number of manipulations dramatically enhance diapause to ~100%. These include ablating, or reducing the excitability of the insulin-producing cells (IPCs) that express dILPs-2,3,5 employing the dilp2,3,5-/- triple mutant, desensitizing insulin signaling using a chico mutation, or inhibiting dILP2 and 5 in the hemolymph by over-expressing Imaginal Morphogenesis Protein-Late 2 (Imp-L2). In addition, triple mutant dilp2,3,5-/- females maintain high levels of diapause even when temperatures are raised in adulthood to 19°C. However at 22°C, these females all show egg development revealing that the effects are conditional on temperature and not a general female sterility. In contrast, over-expression of dilps-2/5 or enhancing IPC excitability, led to levels of ovarian arrest that approached zero, underscoring dILPs-2 and 5 as key antagonists of diapause.
Butterfly wing color patterns often contain eyespots, which are developmentally determined at the late larval and early pupal stages by organizing activities of focal cells that can later form eyespot foci. In the pupal stage, the focal position of a future eyespot is often marked by a focal spot, one of the pupal cuticle spots, on the pupal surface. Here, we examined the possible relationships of the pupal focal spots with the underneath pupal wing tissues and with the adult wing eyespots using Junonia butterflies. Large pupal focal spots were found in two species with large adult eyespots, J. orithya and J. almana, whereas only small pupal focal spots were found in a species with small adult eyespots, J. hedonia. The size of five pupal focal spots on a single wing was correlated with the size of the corresponding adult eyespots in J. orithya. A pupal focal spot was a three-dimensional bulge of cuticle surface, and the underside of the major pupal focal spot exhibited a hollowed cuticle in a pupal case. Cross sections of a pupal wing revealed that the cuticle layer shows a curvature at a focal spot, and a positional correlation was observed between the cuticle layer thickness and its corresponding cell layer thickness. Adult major eyespots of J. orithya and J. almana exhibited surface elevations and depressions that approximately correspond to the coloration within an eyespot. Our results suggest that a pupal focal spot is produced by the organizing activity of focal cells underneath the focal spot. Probably because the focal cell layer immediately underneath a focal spot is thicker than that of its surrounding areas, eyespots of adult butterfly wings are three-dimensionally constructed. The color-height relationship in adult eyespots might have an implication in the developmental signaling for determining the eyespot color patterns.
Butterfly wings are covered with regularly arranged single-colored scales that are formed at the pupal stage. Understanding pupal wing development is therefore crucial to understand wing color pattern formation. Here, we successfully employed real-time in vivo imaging techniques to observe pupal hindwing development over time in the blue pansy butterfly, Junonia orithya. A transparent sheet of epithelial cells that were not yet regularly arranged was observed immediately after pupation. Bright-field imaging and autofluorescent imaging revealed free-moving hemocytes and tracheal branches of a crinoid-like structure underneath the epithelium. The wing tissue gradually became gray-white, epithelial cells were arranged regularly, and hemocytes disappeared, except in the bordering lacuna, after which scales grew. The dynamics of the epithelial cells and scale growth were also confirmed by fluorescent imaging. Fluorescent in vivo staining further revealed that these cells harbored many mitochondria at the surface of the epithelium. Organizing centers for the border symmetry system were apparent immediately after pupation, exhibiting a relatively dark optical character following treatment with fluorescent dyes, as well as in autofluorescent images. The wing tissue exhibited slow and low-frequency contraction pulses with a cycle of approximately 10 to 20 minutes, mainly occurring at 2 to 3 days postpupation. The pulses gradually became slower and weaker and eventually stopped. The wing tissue area became larger after contraction, which also coincided with an increase in the autofluorescence intensity that might have been caused by scale growth. Examination of the pattern of color development revealed that the black pigment was first deposited in patches in the central areas of an eyespot black ring and a parafocal element. These results of live in vivo imaging that covered wide wing area for a long time can serve as a foundation for studying the cellular dynamics of living wing tissues in butterflies.
The phylogeny of insects, one of the most spectacular radiations of life on earth, has received considerable attention. However, the evolutionary roots of one intriguing group of insects, the twisted-wing parasites (Strepsiptera), remain unclear despite centuries of study and debate. Strepsiptera exhibit exceptional larval developmental features, consistent with a predicted step from direct (hemimetabolous) larval development to complete metamorphosis that could have set the stage for the spectacular radiation of metamorphic (holometabolous) insects. Here we report the sequencing of a Strepsiptera genome and show that the analysis of sequence-based genomic data (comprising more than 18 million nucleotides from nearly 4,500 genes obtained from a total of 13 insect genomes), along with genomic metacharacters, clarifies the phylogenetic origin of Strepsiptera and sheds light on the evolution of holometabolous insect development. Our results provide overwhelming support for Strepsiptera as the closest living relatives of beetles (Coleoptera). They demonstrate that the larval developmental features of Strepsiptera, reminiscent of those of hemimetabolous insects, are the result of convergence. Our analyses solve the long-standing enigma of the evolutionary roots of Strepsiptera and reveal that the holometabolous mode of insect development is more malleable than previously thought.
Do miRNAs contribute to specify the germ-band type and the body structure in the insect embryo? Our goal was to address that issue by studying the changes in miRNA expression along the ontogeny of the German cockroach Blattella germanica, which is a short germ-band and hemimetabolan species. | <urn:uuid:67c0876b-93d2-4851-b429-ac9f5d31cb5c> | 2.78125 | 2,872 | Academic Writing | Science & Tech. | 16.303607 | 95,606,843 |
Graphyne is a theorized allotrope of carbon. Its structure is one-atom-thick planar sheets of sp and sp2-bonded carbon atoms arranged in crystal lattice. It can be seen as a lattice of benzene rings connected by acetylene bonds. Depending on the content of acetylene groups, graphyne can be considered a mixed hybridization, spn, where 1 < n < 2, and thus differs from the hybridization of graphene (considered pure sp2) and diamond (pure sp3).
Although not yet synthesized, periodic graphyne structures and their boron nitride analogues were shown to be stable on the basis of first-principles calculations using phonon dispersion curves and ab-initio finite temperature, quantum mechanical molecular dynamics simulations.
Graphyne has yet to be synthesized in significant quantities for study but through the use of computer models scientists have been able to predict several properties of the substance on assumed geometries of the lattice. The proposed structures of graphyne are derived from inserting acetylene bonds in place of Carbon-Carbon single bonds in a graphene lattice. Graphyne is theorized to exist in several different geometries. This variety is due to the multiple arrangements of sp and sp2 hybridized carbon. The proposed geometries include a hexagonal lattice structure and a rectangular lattice structure. It has been hypothesized as preferable to graphene for specific applications due to the potential of direction-dependent Dirac cones. Out of the theorized structures the rectangular lattice of 6,6,12-graphyne may hold the most potential for future applications.
The models for graphyne show that it has the potential for Dirac cones on its double and triple bonded carbon atoms. Due to the Dirac cones, there is a single point in the Fermi level where the conduction and valence bands meet in a linear fashion. The advantage of this scheme is that electrons behave as if they have no mass, resulting in energies that are proportional to the momentum of the electrons. Like in graphene, hexagonal graphyne has electric properties that are direction independent. However, due to the symmetry of the proposed rectangular 6,6,12-graphyne the electric properties would change along different directions in the plane of the material. This unique feature of its symmetry allows graphyne to self-dope meaning that it has two different Dirac cones lying slightly above and below the Fermi level. The self-doping effect of 6,6,12-graphyne can be effectively tuned by applying in-plane external strain. Graphyne samples synthesized to date have shown a melting point of 250-300 °C, low reactivity in decomposition reactions with oxygen, heat and light.
The directional dependency of 6,6,12-graphyne could allow for electrical grating on the nanoscale. This could lead to the development of faster transistors and nanoscale electronic devices.
The synthesis of graphdiyne was reported as a 1 mm film on a copper surface. Graphdiyne was predicted to exhibit a nanoweb-like structure, characterized by triangular and regularly distributed pores, thus forming a nanoporous membrane. Due to the effective size of its pores, which almost matches the van der Waals radius of the helium atom, graphdiyne could behave as an ideal two-dimensional membrane for helium chemical and isotopic separation. The application of a graphdiyne based membrane as an efficient two-dimensional sieve for water filtration and purification technologies has been proposed.
- Heimann, R.B.; Evsvukov, S.E.; Koga, Y. (1997). "Carbon allotropes: a suggested classification scheme based on valence orbital hybridization". Carbon. 35 (10–11): 1654–1658. doi:10.1016/S0008-6223(97)82794-7.
- Enyashin, Andrey N.; Ivanovskii, Alexander L. (2011). "Graphene Allotropes". Physica Status Solidi (b). 248 (8): 1879–1883. Bibcode:2011PSSBR.248.1879E. doi:10.1002/pssb.201046583.
- Balaban, AT; Rentia, CC; Ciupitu, E. (1968). Rev. Roum. Chim. 13: 231
- Özçelik, V. Ongun; Ciraci, S. (January 10, 2013). "Size Dependence in the Stabilities and Electronic Properties of α-Graphyne and Its Boron Nitride Analogue". The Journal of Physical Chemistry C. 117 (5): 2175–2182. doi:10.1021/jp3111869.
- Kim, Bog G.; Choi, Hyoung Joon (2012). "Graphyne: Hexagonal network of carbon with versatile Dirac cones". Physical Review B. 86 (11): 115435. arXiv: . Bibcode:2012PhRvB..86k5435K. doi:10.1103/PhysRevB.86.115435.
- Dumé, Belle (1 March 2012). "Could graphynes be better than graphene?". Physics World. Institute of Physics.
- Malko, Daniel; Neiss, Christian; Viñes, Francesc; Görling, Andreas (24 February 2012). "Competition for Graphene: Graphynes with Direction-Dependent Dirac Cones". Phys. Rev. Lett. 108 (8): 086804. Bibcode:2012PhRvL.108h6804M. doi:10.1103/PhysRevLett.108.086804. PMID 22463556.
- Schirber, Michael (24 February 2012). "Focus: Graphyne May Be Better than Graphene". Physics. 5 (24): 24. Bibcode:2012PhyOJ...5...24S. doi:10.1103/Physics.5.24.
- Wang, Gaoxue; Si, Mingsu; Kumar, Ashok; Pandey, Ravindra (May 26, 2014). "Strain engineering of Dirac cones in graphyne". Applied Physics Letters. 104 (21): 213107. Bibcode:2014ApPhL.104u3107W. doi:10.1063/1.4880635.
- Bardhan, Debjyoti (2 March 2012). "Novel new material graphyne can be a serious competitor to graphene". techie-buzz.com.
- Cartwright, J. (1 March 2012). "Graphyne could be better than graphene". news.sciencemag.org. Archived from the original on 2 October 2012.
- "Graphyne Better Than Graphene?". Materials Today. 5 March 2012.
- Li, Guoxing; Li, Yuliang; Liu, Huibiao; Guo, Yanbing; Li, Yongjun; Zhu, Daoben (2010). "Architecture of graphdiyne nanoscale films". Chemical Communications. 46 (19): 3256–3258. doi:10.1039/B922733D.
- Bartolomei, Massimiliano; Carmona-Novillo, Estela; Hernández, Marta I.; Campos-Martínez, José; Pirani, Fernando; Giorgi, Giacomo (2014). "Graphdiyne Pores: "Ad Hoc" Openings for Helium Separation Applications". Journal of Physical Chemistry C. 118 (51): 29966–29972. doi:10.1021/jp510124e.
- Bartolomei, Massimiliano; Carmona-Novillo, Estela; Hernández, Marta I.; Campos-Martínez, José; Pirani, Fernando; Giorgi, Giacomo; Yamashita, Koichi (2014). "Penetration Barrier of Water through Graphynes' Pores: First-Principles Predictions and Force Field Optimization". Journal of Physical Chemistry Letters. 5 (4): 751–755. arXiv: . doi:10.1021/jz4026563.
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Now you really can go to Tatooine! International Astronomy Union to let the public name up to 30 exoplanets next year
- Paris-based IAU will let the public vote on names for planets next year
- This is the first time they will have allowed planets to be named this way
- Previously nomenclature for exoplanets had followed strict guidelines
- But now in September astronomy clubs will be invited to submit names
- And in March next year the public will be allowed to vote on names for 20 to 30 selected planets outside the solar system
To date, nearly all planets found outside the solar system have followed a strict naming convention, which has led to rather complicated names such as OGLE235-MOA53 b.
That’s all set to change later this year, though, as the International Astronomical Union (IAU) will allow the public to vote on the names of exoplanets for the first time.
A list of 305 confirmed planets found before 31 December 2008 has been drawn up, and in October names can be submitted for consideration for some of the planets.
Paris-based IAU will let the public vote on names for planets next year. This is the first time they will have allowed planets to be named this way. Previously nomenclature for exoplanets had followed strict guidelines. But now in September astronomy clubs will be invited to submit names
The IAU, headquartered Paris, has not previously allowed many planets or stars to be named.
WHAT'S IN A NAME?
Exoplanets are currently named according to strict rules that denote their characteristics.
Take the planet HD 177830 b for example.
The first part denotes the star the planet is in orbit around, which is HD 177830.
The lowercase letter then explains where the planet sits in its system; b is the innermost planet (which would be Mercury in our solar system), followed by c, d and so on.
If the planet is in a multiple star system, the lowercase latter preceded by an uppercase one for the star.
The ‘primary star’ is labelled with an ‘A’, with its companion stars labelled B, C and so on.
So if our example planet was orbiting around the primary star in a binary system, its full name would be HD 177830 Ab
This was partly because thousands of planets have been found, and the naming process would simply be too long and complicated.
But the IAU, in association with Zooniverse, has decided to allow a select few planets to be named, owing to the large public interest in doing so, called the NameExoWorlds contest.
In September, astronomy clubs and non-profit organisations will be allowed to sign up for the IAU Directory for World Astronomy website (directory.iau.org).
Then in October, of the 305 planets 20 to 30 will be selected for naming.
Only 305 initial planets were selected as more recent discoveries haven’t been confirmed, and the IAU didn’t want to select planets that might later be proven to not exist.
In December the clubs and organisations will be invited to send proposals for names, subject to the IAU’s naming rules.
These state that a proposed name cannot be more than 16 characters, it must be pronounceable, it cannot be offensive and the names of living people will not be allowed.
This will rule out certain groups attempting to hijack the contest and submit rude, offensive or inappropriate names.
In March 2015 the public will be allowed to vote on the proposed names and finally, in August 2015, the results will be announced at a ceremony in Honolulu.
The names of planets will coexist alongside their existing scientific names, just like what is done for other celestial bodies now.
For example the Orion Nebula is also scientifically known as Messier 42.
More than 800 planets have been found outside the solar system to date, with thousands more waiting to be confirmed. The diversity of these planets has been tremendous, with some found orbiting binary stars (illustration shown) and others found in tight orbits - but few have been given 'proper' names
Exoplanets are currently named according to strict rules that denote their characteristics. First the planet is given the name of its host star, here being the star Kepler-186. Then it is given a letter denoting its order, with b being the closest, then c, d and so on
‘People have been naming celestial objects for millennia, long before any scientific system of names ever existed,’ explains the IAU.
‘Even today, almost every civilisation and culture uses common names to describe the stars and planets visible to the naked eye, as well as their apparent distribution on the sky.’
The IAU, founded in 1919, is the world’s largest professional body for astronomers with more than 11,000 members across 90 countries.
Among other roles, the IAU is tasked with deciding upon nomenclature for celestial objects.
As all the planets in the solar system are named, this first involved naming comets, asteroids and dwarf planets.
When planets started to be found, though, it was clear many names would be needed.
While the current system is useful to sift through the large numbers of planets, many have petitioned the IAU for more flexibility on certain planets, and they now have their wish.
Although the IAU doesn’t technically ‘own’ space, it still maintains the database of named objects in the night sky, making this an ‘official’ naming process for exoplanets.
The new 'official' naming system will allow planets outside the solar system to be named by members of public for the first name. This could give rise to names based on things from popular culture such as Tatooine from Star Wars (pictured), a popular choice for space enthusiasts
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Easiest Math Problems EversamuelMCL7
The Top Ten
We (my partner and I) think this question should be number one because in Preschool, what you learn is based off of the number 1. You start with 1+1 and advance to greater numbers from there. 1+1 is basically the building block of numbers, equations, and essentialy the understanding of everything that HAS surrounded us, IS surrounding us, and WILL surround us for eons to come. In conclusion, 1+1 (we feel) should number 2, but number one.
I think this is the easiest question because my niece can do and she is only 2 and if she can do anyone can do it for sure. If someone can't then they must be completely stupid.
I think this is the easiest question of all time because my cousin is hardly two and she can say the answer in a instant
I think you aren't wrong 0+0 is the easiestV 46 Comments
Laugh out loud this is the easiest of them all I wish all math was this easy!
I'm in college and there was a math problem that had times 0 in it and I wondered how they could make it any easier.
It's so easy because you're adding nothing to nothing to get nothing! NOTHING could be simpler! Laugh out loud
Also 0-0,0x0,and sqrt 0 is 0 - mathguy37V 30 Comments
My god this is so easy...
P.S. Just to say, if anyone asks you "Pick any number, don't tell me it though."
Let's say I pick 20. He would say, "Add it by 3."
I would get 23. He would get 3 because he started of with 0.
Then he says, "Now add it by 9." I would get 32, and he would get 12.
Then he would say something like "Now Subtract THAT number by the number that you started with."
Okay, well that's 32-20=12. BUT you want to know how that happened? Well what HE did was keep his number and not even subtract his, or in other words, he started out with 0 and 12-0 obviously is 12.
Then he would say to you, "Did you get 12? "
You would say "Yeah."
Then you start to freak out then start to pee your pants and all that.
So that's how you do it my friends.
I think some of you just learned something new today for those who didn't even hear about it.
It's so easy, all of the other ones are hard compared to it.
This isn't an easy thing to prove. A lot of maths can actually lead you to the (wrong) conclusion that 1 doesn't equal 1. This is silly.
This should be #1 because this is 10x easier than the top 2. EVERY PERSON IN THE WORLD (except for infants, duh) KNOWS ONE IS ONE! ( if you don't know this, I'll consider do drop you out of college or high school or whatever and put you back in the preschool level, SERIOUSLY IF YOUR'E AT that one of those levels you would know if what is arithmetic expression and decimal points.V 14 Comments
It is the easiest question because is asks if one thing is the same as the same thing. It is correct though which only rishi would get wrong
That's the most trivial thing, no proof possible, even no axiom needed.. - Flav
I bet that Babies will know this too so that's why I think it is an easiest question in math
Very easy but I still got it wrong?!?V 6 Comments
0 is simple for a toddler; even younger!
It's just so simple
You piece of bull crap you
PoopV 1 Comment
These are the easiest math problems ever
My grandma can do it and shes dead
Du stupid this is hard crap you
Well you don't add anything to the 1
Cause it's so simple but 0-0 would be easier
Its pretty self explanatory
Easy! You don't need to think. - BlueTopazIceVanillaV 2 Comments
Actually, the answer is nine. The problem is telling you to do nine - nine, so you have to take away the second nine, leaving you with the first nine. Therefore, the answer is nine. - mmarce445
Crappy you this is very hard for three-year-olds
All of these are very easy, but this is the classic "If you don't know this, you must be REALLY dumb" equation.
This should be #1, because it's the first thing a lot of people think of when they want an example of an easy math problem.
Dude I ask all my friends what is 2+2 because it is so easy
Duhh are u dumbV 4 Comments
Hey you don't no your maths bro 1+3=21 so you just got schooled fool next time check your maths dum head
No its 0101
UM... A kindergartener should be able to do this
Why is this a list?
Easy for me but not for kinder gardeners and 1st graders
Crap you this is very hardV 1 Comment
That is true
Pretty much 1+1.
Not everybody has ten fingers but I do
This is without doubt the easiest!
This is one of the easiest. - Minecraftcrazy530
hiV 6 Comments
Bruh this is so easy it's for babies who haven't even been born yet
NO IT IS 55
This is unsolvable because you don't know what the variables mean. Even though that's probably not what you're getting at.
This is too complicated.
I've learned this. It is definitely not the easiest material but it's understandable.
Pythagorean theorem! SO EASY!V 8 Comments
Make it understandable for lower primary kids.
Not that easy but okay - yanzchenthebest
X = 2 and x = 0 not that hard
I don't know.V 6 Comments
Is this delta in physics?
I did this in middle school. SO EASY!
That should be very hard to people up to 17 but I think whoever can't do this aged 19-35 are very dumb so If u don't know then GET A LIFE
It's only hard if you don't know how to expand the brackets. A six-year-old could solve it if they're taught how to do it. No reason to put others down though... - Entranced98
Not horrible. It's a general rule in mathematics that anything raised to the power of 0 is 1, and especially in calculus it's dead handy to remember it well. - Entranced98
This is horrible
You must say also. X not zero
I don't know
I think no one should know that
I think that everyone should know that math problem.
This isn't even true
Everybody should know that
then 3+6=6 - yanzchenthebest
X is 0
No duh my friend Stephanie says it’s X lol
Its obviously 0 :(
So easy it's like rocket science
Just forget it this is hard
I don't know what this is so it is not easy at all! 💕
What the crap I thought this was EASY I can think of about 1,000 easier problems than this crap
The only problem on the list I can solve - shawnmccaul22
Way too hard I can not even solve it simply - mathguy37
What?!V 4 Comments
And no, it isn't 21. - RiverClanRocks
I know the answer 21! Yo I got it right! I am so gangsta
Uhh this is wrong. The answer is 21. Heres mathematical proof:
9 + 10
3 * 3 2 * 5
This is as easy as 123
So easy its like subtracting 5
This is not THAT easy to proof only with the axioms.. everyone knows it though. - Flav
It is easy because there is 1 group of 1
Even small children will give the correct answer, because you can put any number you want up there (X) and you will get 0 as answer! OK so... it may be silly, maybe not real math :/ But it's true! *except one thing: -0, because it doesn't exist. Sorry if it's not good, not a math freak
This is easy because your just adding if you do not know this you are stupid
You are dumb
666 lucky guy
That 9+10 joke is annoying now...
21 we all know this as that one kid won't stop saying it.
I thought it was 21…
JUST KIDDING! - BlueTopazIceVanilla
Energy= Mass x (The Speed of Light)^2
E = energy m= mass c2= the square of the velocity of light in centimeters per second.
Got all that? Yeah easy as π
If you are reading this you are stupid
This problem is like 1+1!
9 to the second power
81 duh - mathguy37V 3 Comments
3.14159265...(over two quadrillion decimal places) - mathguy37
13 years old and I know this.
Pie or Pi?
Related ListsEasiest Topics in Math Top Ten Hardest Basic Math Problems Top Ten Easiest Subtraction Problems Best Math Subjects Best Math Terms
7 years, 51 days old
Top Remixes (5)
3. What is 1? 1
View All 5 | <urn:uuid:7bd1498e-2530-4b5d-b2dc-34236e2bb7d3> | 2.8125 | 2,031 | Comment Section | Science & Tech. | 88.370937 | 95,606,882 |
1. The _______ of a variable is its ________.
a. address; l-value
b. value; r-value
c. address; r-value
d. value; l-value
e. a and b
f. c and d
2. When a variable's type is determined through default conventions,
the type declaration is:
3. The goto statement is the basis for the:
a. break statement in a C switch structure.
b. exit statement in an FORTRAN 90 loop structure.
c. last statement in a Perl loop structure.
d. All of the above.
e. None of the above.
4. An advantage of dynamic scoping is that access to nonlocal variables
is considerably faster than accesses to nonlocals when static scoping
5. The idea of providing a few basic data types and methods for
programmers to design data structures to meet their needs was
d. ALGOL 68
a. can be detected and reported at runtime.
b. cannot be detected, resulting in aberrant execution.
c. results in the type of the LHS being changed to match.
d. none of the above.
7. A given variable's storage bindings are determined at runtime but
its data type is bound prior to runtime. This type of variable is
8. ALGOL 60 introduced __________, which has been copied by most
imperative languages and many non-imperative languages.
a. static scope
b. dynamic scope
c. stack-dynamic scope
d. heap-dynamic scope
9. _________ is based on the calling sequence of subprograms.
a. Dynamic scope
b. Static scope
c. Stack-dynamic scope
d. Heap-dynamic scope
10. A(n) __________ is the collection of attributes of a variable.
a. abstract data type
11. Associativity in common imperative languages is left to right.
12. Programmers can alter associativity and precedence rules by:
a. overloading operators.
b. defining constants.
c. managing heap allocation/deallocation.
d. using parenthesis.
13. The simplest of all data types is:
14. When an array's subscript ranges are determined at compile time,
but the allocation is done at runtime, the array is:
b. fixed stack-dynamic.
15. If every element of a list must be processed, a(n) ___________ is
more efficient than a(n) __________.
a. hash; array
b. array; hash
c. record; array
d. hash; record
16. A pointer that contains the address of a heap-dynamic variable that
has been deallocated is called:
a. a dangling pointer.
c. lost pointer.
d. inaccessible variable.
17. Selection statements fall into two general categories, two-way and
n-way, or single-way selection.
18. When the result of an expression is determined without evaluating
all of the operands or operators, the evaluation is said to be:
d. none of the above.
19. When selection must be based on a Boolean expression, the best
approach is a(n) ___________ control structure.
d. b or c, depending on the language
20. An iterative statement is one that causes a statement or collection of
statements to be executed one or more times.
21. When the number of iterations is dependent on the number of
_______ control structure.
22. Using the precedence rules of APL, the value of the expression
24 x 3 + 1 is 73.
23. When two pointer variables point to the same memory location, they
are said to be:
24. The association of an entity and an attribute that is done before
runtime and does not change during execution is a:
a. dynamic binding.
b. dynamic linking.
c. static binding.
d. static linking.
25. If a mathematical operation is associative, then the corresponding
floating-point operation is associative.
Solution explains some concept of programming languages like scoping, associativity, precedence, variables. etc. | <urn:uuid:15bbe03b-385f-4627-8932-9a01d7b3d5d7> | 4.0625 | 909 | Content Listing | Software Dev. | 66.256992 | 95,606,887 |
At the core of any programming language is the notion of functions, but we tend to take them for granted. Sure, there’s the obvious fact that functions allow code to be encapsulated into individual units, which can be reused rather than being duplicated all over the place. But Python takes this beyond just the notion of code, with functions being full-fledged objects that can be passed around in data structures, wrapped up in other functions or replaced entirely by new implementations.
KeywordsFunction Call Function Definition Variable Argument Positional Argument Outer Function
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"Dark Matter, Neutrinos, and Our Solar System" is a unique enterprise that portrays the connection between cosmology, particle and nuclear physics, and atmospheric and terrestrial physics. Constituents of dark matter (classified as hot, warm and cold) are studied in detail with regard to their individual structures (baryonic and non-baryonic, massive and non-massive, interacting and non-interacting) and their detection facilities. Neutrinos (an important component of dark matter) are treated as a separate entity. A detailed study describes these elusive particles researched from the year 1913, as byproducts of beta-decay - until the discovery in 2007 that their flavors were not more than three (as considered by some). The last chapter of the book is unique as it deals with real-time stories, describing the regions that were not explored thus far for lack of advanced technology. Their untold fascinating stories (which span up to 2009) are illustrated here datewise in full detail. | <urn:uuid:cba3238e-ef88-4041-978b-b51fb29820f0> | 3.046875 | 216 | Product Page | Science & Tech. | 25.373333 | 95,606,897 |
An enormous crater near the northern plains of Mars once harboured an ancient lake that could have supported microbial life, Nasa scientists claim.
The freshwater lake stood for more than one hundred thousand years at the base of Gale Crater, a 150km-wide formation that was created when a meteor punched into the red planet around 3.7bn years ago.
Tests on rock samples by Nasa’s Curiosity rover revealed the presence of fine clay minerals that formed in a standing body of water, and coarse-grained sandstones laid down by river flows that drained into the lake.
“The presence of these minerals tells us the water was likely to be fresh water, which means it’s much more conducive for microbial life,” said Sanjeev Gupta, a geologist at Imperial College, London, and a member of the Curiosity science team.
“These rocks are similar to those we would find if we walked along the Dorset or Devon coast line,” he added.
The Nasa team is not sure how deep or wide the lake was, but suspect it was deep enough not to have dried out periodically, as this would have left traces of crack marks in the rock samples.
The $2.5bn (£1.6bn) rover landed in on Mars in August 2012 on a mission to explore whether the planet may once have been habitable, though not to look for signs of ancient life itself.
Curiosity’s main objective is to trundle up nearby Mount Sharp, a 5km-high mountain that sits in the middle of Gale Crater. Through measurements of its exposed rock faces at different altitudes, researchers hope to piece together the geological history of the planet.
But Curiosity did not make for Mount Sharp immediately. After relaying details of the Martian soil near its landing site, the rover was steered towards a 5m-deep trough in the crater called Yellowknife Bay. Here, the robotic science laboratory drilled into a rock formation called Sheepbed mudstone and examined the powder with its instruments.
Though a combination of x-ray diffraction experiments and analyses of gases given off when the powder was baked in an onboard oven, researchers identified so-called smectite clay minerals that formed in water and elements crucial for life, including carbon, hydrogen, oxygen, sulphur, nitrogen and phosphorus.
The chemical makeup of the minerals showed that they formed in water with low salinity and a neutral pH, suggesting it was neither too acidic nor too alkaline for life to exist.
Writing in the journal, Science, researchers explain that the conditions in the lake were well suited to support a type of microbial life called chemolithoautotrophs. These organisms are found on Earth and can survive by breaking down rocks and minerals for energy.
The lake may have persisted on Mars for tens of thousands of years, said John Grotzinger, project scientist on the Nasa mission at Caltech in Pasadena.
Monica Grady, professor of planetary and space sciences at Open University, said the images of rocks and minerals beamed back from Mars by the Curiosity rover were “spectacular, beautiful and absolutely compelling.”
Grady said the findings were shifting scientists’ views on how life might have existed on Mars. “The life we know on Earth is largely based on photosynthesis. Grass photoynthesises, cows eat the grass, we eat the cows. We know there are other platforms for life, but they are mostly at the bottom of the ocean and in really odd places.”
Instead of relying on the sun’s energy, life in the Martian lake could have survived on energy liberated by chemical reactions. “This is really, for the first time, showing that absolutely all the ingredients are there for life based on chemistry, and that would be reactions between sulphur and iron. It says that there were absolutely environments on Mars where energy from chemical reactions could have been harvested to make nutrient pathways work. It’s so beautifully laid out.”
Grady said that even though the Martian lake may have been around for only tens of thousands of years, that may have been long enough for life to emerge there. “We don’t really know how long it took for life to get going on Earth. We don’t know if it got going once or lots of times.
“The more we know about how life developed on Earth, the more we’re beginning to understand that it didn’t take very long at all. The fact the lake might have been relatively short lived, in terms of hundreds of thousands of years, doesn’t mean that life couldn’t have got going there. It doesn’t mean that at all.”
Curiosity has found some evidence for carbonate rocks on Mars. Grady said that she and many other scientists are keen to see the rover find some of these and analyse them. The rocks form in the presence of carbon dioxide, which on Earth is a product of respiration, and is important for photosynthesis and the carbon cycle. | <urn:uuid:51d5f36f-d520-4bd0-8251-d66ab376cd3b> | 4.15625 | 1,046 | News Article | Science & Tech. | 47.710755 | 95,606,928 |
Conventional neo-Darwinian theory views organisms as infinitely sensitive and responsive to their environments, and considers them able to readily change size or shape when they adapt to selective pressures. Yet since 1863 it has been well known that Pleistocene animals and plants do not show much morphological change or speciation in response to the glacial-interglacial climate cycles. We tested this hypothesis with all of the common birds (condors, golden and bald eagles, turkeys, caracaras) and mammals (dire wolves, saber-toothed cats, giant lions, horses, camels, bison, and ground sloths) from Rancho La Brea tar pits in Los Angeles, California, which preserves large samples of many bones from many well-dated pits spanning the 35,000 years of the Last Glacial-Interglacial cycle. Pollen evidence showed the climate changed from chaparral/oaks 35,000 years ago to snowy piñon-juniper forests at the peak glacial 20,000 years ago, then back to the modern chaparral since the glacial-interglacial transition. Based on Bergmann's rule, we would expect peak glacial specimens to have larger body sizes, and based on Allen's rule, peak glacial samples should have shorter and more robust limbs. Yet statistical analysis (ANOVA for parametric samples; Kruskal-Wallis test for non-parametric samples) showed that none of the Pleistocene pit samples is statistically distinct from the rest, indicating complete stasis from 35 ka to 9 ka. The sole exception was the Pit 13 sample of dire wolves (16 ka), which was significantly smaller than the rest, but this did not occur in response to climate change. We also performed a time series analysis of the pit samples. None showed directional change; all were either static or showed a random walk. Thus, the data show that birds and mammals at Rancho La Brea show complete stasis and were unresponsive to the major climate change that occurred at 20 ka, consistent with other studies of Pleistocene animals and plants. Most explanations for such stasis (stabilizing selection, canalization) fail in this setting where climate is changing. One possible explanation is that most large birds and mammals are very broadly adapted and relatively insensitive to changes in their environments, although even the small mammals of the Pleistocene show stasis during climate change, too. © 2012 Elsevier Ltd.
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Last year, scientists with NASA's Dawn mission announced the detection of organic material -- carbon-based compounds that are necessary components for life -- exposed in patches on the surface of the dwarf planet Ceres. Now, a new analysis of the Dawn data by Brown University researchers suggests those patches may contain a much higher abundance of organics than originally thought.
The findings, published recently in Geophysical Research Letters, raise intriguing questions about how those organics got to the surface of Ceres, and the methods used in the new study could also provide a template for interpreting data for future missions, the researchers say.
"What this paper shows is that you can get really different results depending upon the type of organic material you use to compare with and interpret the Ceres data," said Hannah Kaplan, a postdoctoral researcher at the Southwest Research Institute who led the research while completing her Ph.D. at Brown. "That's important not only for Ceres, but also for missions that will soon explore asteroids that may also contain organic material."
Organic molecules are the chemical building blocks for life. Their detection on Ceres doesn't mean life exists there or ever existed there; non-biological processes can give rise to organic molecules as well. But because life as we know it can't exist without organic material, scientists are interested in how it's distributed through the solar system. The presence of organic material on Ceres raises intriguing possibilities, particularly because the dwarf planet is also rich in water ice, and water is another necessary component for life.
The original discovery of organics on Ceres was made using the Visible and Infrared (VIR) Spectrometer on the Dawn spacecraft, which went into orbit around the dwarf planet in 2015. By analyzing the patterns in which sunlight interacts with the surface -- looking carefully at which wavelengths are reflected and which are absorbed -- scientists can get an idea of what compounds are present on Ceres. The VIR instrument picked up a signal consistent with organic molecules in the region of Ernutet Crater on Ceres' northern hemisphere.
To get an initial idea of how abundant those compounds might be, the original research team compared the VIR data from Ceres with laboratory reflectance spectra of organic material formed on Earth. Based on that standard, the researchers concluded that between six and 10 percent of the spectral signature they detected on Ceres could be explained by organic matter.
But for this new research, Kaplan and her colleagues wanted to re-examine those data using a different standard. Instead of relying on Earth rocks to interpret the data, the team turned to an extraterrestrial source: meteorites. Some meteorites -- chunks of carbonaceous chondrite that have fallen to Earth after being ejected from primitive asteroids -- have been shown to contain organic material that's slightly different from what's commonly found on our own planet. And Kaplan's work shows that the spectral reflectance of the extraterrestrial organics is distinct from that of terrestrial counterparts.
"What we find is that if we model the Ceres data using extraterrestrial organics, which may be a more appropriate analog than those found on Earth, then we need a lot more organic matter on Ceres to explain the strength of the spectral absorption that we see there," Kaplan said. "We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics. That's a huge difference compared to the six to 10 percent previously reported based on terrestrial organic compounds."
If the concentration of organics on Ceres is indeed that high, it raises a host of new questions about the source of that material. There are two competing possibilities for where Ceres' organics may have come from. They could have been produced internally on Ceres and then exposed on the surface, or they could have been delivered to the surface by an impact from an organic-rich comet or asteroid.
This new study suggests that if the organics were delivered, then the potential high concentrations of the organics would be more consistent with impact by a comet rather than an asteroid. Comets are known to have significantly higher internal abundances of organics compared with primitive asteroids, potentially similar to the 40 to 50 percent figure this study suggests for these locations on Ceres. However, the heat of an impact would likely destroy a substantial amount of a comet's organics, so whether or not such high abundances could even be explained by a cometary impact remains unclear, the researchers say.
The alternative explanation, that the organics formed directly on Ceres, raises questions too. The detection of organics has so far been limited to small patches on Ceres' northern hemisphere. Such high concentrations in such small areas require an explanation.
"If the organics are made on Ceres, then you likely still need a mechanism to concentrate it in these specific locations or at least to preserve it in these spots," said Ralph Milliken, an associate professor in Brown's Department of Earth, Environmental and Planetary Sciences and a study co-author. "It's not clear what that mechanism might be. Ceres is clearly a fascinating object, and understanding the story and origin of organics in these spots and elsewhere on Ceres will likely require future missions that can analyze or return samples."
For now the researchers hope this study will be helpful in informing upcoming sample return missions to near-Earth asteroids that are also thought to host water-bearing minerals and organic compounds. The Japanese spacecraft Hayabusa2 is expected to arrive at the asteroid Ryugu in several weeks, and NASA's OSIRIS-REx mission is due to reach the asteroid Bennu in August. Kaplan is currently a science team member with the OSIRIS-REx mission.
"I think the work that went into this study, which included new laboratory measurements of important components of primitive meteorites, can provide a framework of how to better interpret data of asteroids and make links between spacecraft observations and samples in our meteorite collection," Kaplan said. "As a new member to the OSIRIS-REx team, I'm particularly interested in how this might apply to our mission."
Computer model predicts how fracturing metallic glass releases energy at the atomic level
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An estimated 1 billion people are living both without access to clean drinking water or electricity. The small photovoltaic (PV)-powered hybrid membrane system described here is designed to address the plight of some of these people. PV and membrane technologies are chosen due to suitability for operation in remote and often harsh conditions. An ultrafiltration (UF) pre-treatment is included to remove bacteria and most pathogens, while a reverse osmosis (RO) or nanofiltration (NF) membrane desalinates the brackish feedwater. Several parameters were examined in order to optimise the system performance, including (i) feed salt concentration, (ii) operating pressure, (iii) system recovery, (iv) specific energy consumption (SEC, kWh/m3), and (v) salt retention. In addition, experiments were performed over a whole day to determine system performance under varying levels of solar radiation. The minimum SEC (relatively high due to the current single-pass mode of operation) varies from 5.5 kWh/m3 at a feed concentration of 1 g/L salt to 26 kWh/m3 at a feed concentration of 7.5 g/L salt, which is the upper limit of the system in terms of salt concentration.
Performance of a small solar-powered hybrid membrane system for remote communities under varying feedwater salinities
A.I. Schäfer, C. Remy, B.S. Richards; Performance of a small solar-powered hybrid membrane system for remote communities under varying feedwater salinities. Water Science and Technology: Water Supply 1 December 2004; 4 (5-6): 233–243. doi: https://doi.org/10.2166/ws.2004.0113
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Since the beginning of time, the ocean has been regarded as boundless and untouchable by human activity. Because of its colossal size and depth, attempts at understanding the ocean are laden with difficulties. However, it has now become apparent that the ocean, despite its immense magnitude, can drastically be changed by daily activities of human beings. Unprecedented changes are occurring along coastal regions as well as into the far depths of the oceans. Our team have juxtaposed all data from scientists and wrote a paper that helps us to understand the cause of widespread pollution of world’s oceans.
While the particular causes of environmental change are multifaceted, numerous human activities and natural events are now said to be the driving forces in the alteration of the global ocean, such as marine litter.
A Rapid Decline of Ecosystems
Despite the vital role they play for the survival of fish, invertebrates, mammals, sea turtles, and waterfowl, ecosystems such as mangroves and other wetlands are in rapid decline throughout most of the coastal regions of the U.S. Occurrences such as dredging, propeller scouring, disease manifestations, pesticide and herbicide poisonings, and lack of sunlight caused by the increased turbidity of the water has lead to the destruction of these delicate habitats.
Salt marshes, which have been widely distributed along U.S. coasts, are considered one of the earth’s most biologically productive ecosystems. However, more than half of the original salt marshes and mangrove forests in the U.S. have been destroyed, according to the U.S. Fish and Wildlife Service.
It has been estimated that at least 10% of the world’s coral reefs have been degraded beyond recovery, while a good portion of the remainder is under threat from fisheries, recreational activities, mining and oil exploration, tourism, sedimentation, pollution, and disease.
Turbidity of near-shore waters due to erosion and runoff from logging, agriculture and upland development also contribute to reef degradation, says the U.S. National Oceanic and Atmospheric Administration (NOAA). They estimate that over half of all coral reef systems in the U.S., including those in U.S.-affiliated islands such as the Virgin Islands and American Samoa, are at risk and that some systems are virtually dead.
Toxicity in Oceans
In recent years, there is increasing evidence that blooms of toxic and harmful marine phytoplankton are increasing in frequency and intensity, as well as geographic distribution. Many of these algal species produce virulent toxins which either accumulate in some species, or kill outright. Pfiesteria piscicida, a recently discovered microscopic cell, produces a toxin that has killed millions of fish in the estuaries of several U.S. east coast locations.
Humans exposed to the toxin have experienced memory loss, stomach cramps and nausea, according to a 1995 article published in the Journal of Toxicology and Environmental Health.
Large “dead zones,” where no life can live due to eutrophication, have invaded significant portions of coastal waters. When fertilizer runoff from agricultural fields, wastes from livestock farms, discharges from sewage treatment plants, emissions from automobile and power plants, and seepage from septic tanks are washed out into rivers, they pollute coastal waters. The fatal outcome is the creation of large anoxic (no oxygen) or hypoxic (low-oxygen) areas where fish, invertebrates, seagrasses, and other organisms cannot live.
Salman is a prolific environmental writer, and has authored more than 300 articles in reputed journals, magazines and websites. He is proactively engaged in creating mass awareness on renewable energy, waste management, sustainability and conservation all over the world.
Salman can be reached on email@example.com.
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In 1915 the physicist Albert Einstein proposed his general theory of relativity to explain how gravity works. Since then, the theory has passed a series of high-precision tests within the solar system, but there had not been precise validation at large astronomical scales.
It has been known since 1929 that the universe is expanding, but in 1998 two teams of astronomers demonstrated that the universe is currently expanding even faster than in the past. This surprising discovery, which won the Nobel Prize in 2011, can not be explained unless the universe is composed primarily of an exotic component called dark energy. However, this interpretation is based on the fact that general relativity is also the correct theory on cosmological scales. Testing the properties of gravity over long distances is important to validate our cosmological model.
As it is, an international team of astronomers has performed the most accurate gravity test outside of our own solar system.
By combining data taken with NASA’s Hubble Space Telescope and the Very Large Telescope of the European Southern Observatory (ESO), their results show that gravity in this galaxy behaves as predicted by Albert Einstein’s general theory of relativity, confirming the validity of the galactic-scale theory.
Astronomers, led by Thomas Collett of the Institute of Cosmology and Gravitation at the University of Portsmouth (England), used a nearby galaxy as a gravitational lens to perform an accurate test of gravity on astronomical longitude scales.
“General Relativity predicts that massive objects deform space-time, this means that when light passes near another galaxy the path of light is diverted, if two galaxies are aligned along our line of sight this can give Instead of a phenomenon, called a strong gravitational lens, where we see multiple images of the background galaxy, if we know the mass of the galaxy in the foreground, then the amount of separation between the multiple images tells us if General Relativity is the correct theory of gravity on galactic scales, “explains Collett in the journal Science, which publishes the study.
A few hundred strong gravitational lenses are known, but most are too distant to accurately measure their mass, so they can not be used to evaluate accurately to validate the theory of general relativity. However, the galaxy ESO325-G004 is among the closest lenses, 500 million light-years from Earth.
“We used data from the Very Large Telescope in Chile to measure how fast the stars moved in E325, this allows us to infer how much mass there must be in E325 to keep these stars in orbit, and then we compare this mass with the gravitational lens image separations. strong that we observed with the Hubble Space Telescope and the result was just what the Theory of General Relativity predicts with a precision of 9% .This is the most accurate extrasolar test of the general relativity to date, of a single galaxy “, clarifies Collett.
As Bob Nichol, Director of the Institute of Cosmology and Gravitation says, “it is so satisfying to use the best telescopes in the world to challenge Einstein, only to discover how right he was” …
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Faster carbon dioxide emissions will overwhelm capacity of land and ocean to absorb carbon
BERKELEY – One in a new generation of computer climate models that include the effects of Earth's carbon cycle indicates there are limits to the planet's ability to absorb increased emissions of carbon dioxide.
If current production of carbon from fossil fuels continues unabated, by the end of the century the land and oceans will be less able to take up carbon than they are today, the model indicates.
(Graphics by Inez Fung/UC Berkeley)
"If we maintain our current course of fossil fuel emissions or accelerate our emissions, the land and oceans will not be able to slow the rise of carbon dioxide in the atmosphere the way they're doing now," said Inez Y. Fung at the University of California, Berkeley, who is director of the Berkeley Atmospheric Sciences Center, co-director of the new Berkeley Institute of the Environment, and professor of earth and planetary science and of environmental science, policy and management. "It's all about rates. If the rate of fossil fuel emissions is too high, the carbon storage capacity of the land and oceans decreases and climate warming accelerates."
Fung is lead author of a paper describing the climate model results that appears this week in the Early Online Edition of the Proceedings of the National Academy of Sciences (PNAS). Fung was a member of the National Academy of Sciences panel on global climate change that issued a major report for President Bush in 2001 claiming, for the first time, that global warming exists and that humans are contributing to it.
Currently, the land and oceans absorb about half of the carbon dioxide produced by human activity, most of it resulting from the burning of fossil fuels, Fung said. Some scientists have suggested that the land and oceans will continue to absorb more and more CO2 as fossil fuel emissions increase, making plants flourish and the oceans bloom.
Fung's computer model, however, indicates that the "breathing biosphere" can absorb carbon only so fast. Beyond a certain point, the planet will not be able to keep up with carbon dioxide emissions.
"The reason is very simple," Fung said. "Plants are happy growing at a certain rate, and though they can accelerate to a certain extent with more CO2, the rate is limited by metabolic reactions in the plant, by water and nutrient availability, et cetera."
In addition, increasing temperatures and drought frequencies lower plant uptake of CO2 as plants breathe in less to conserve water. A second study she and colleagues published last week in PNAS report evidence for this temperature and drought effect. Since 1982, a greening of the Northern Hemisphere has occurred each spring and summer (except for 1992 and 1993, after Mt. Pinatubo erupted) as the climate has steadily warmed. As a result, there is a small but steady decline in atmospheric CO2 each growing season due to increasing photosynthesis at temperate latitudes in the northern hemisphere. When Fung and a team of her former and current post-doctoral fellows took a detailed look at this phenomenon, however, they discovered that since 1994, enhanced uptake of CO2 as photosynthesis revved up in the warm wet springs was offset by decreasing CO2 uptake during summers, which became increasingly hot and dry - an unsuspected browning in the past 10 years.
"This negative effect of hot, dry summers completely wiped out the benefits of warm, wet springs," Fung said. "A warming climate does not necessarily lead to higher CO2 growing-season uptake, even in temperate areas such as North America."
In the climate modeling study published this week in PNAS, she and colleagues found that similar water stress could slow the uptake of CO2 by terrestrial vegetation, and at some point, the rate of fossil fuel CO2 emissions will outstrip the ability of the vegetation to keep up, leading to a rise in atmospheric CO2, increased greenhouse temperatures and increased frequency of droughts. An amplifying loop leads to ever higher temperatures, more droughts and higher CO2 levels.
The oceans exhibit a similar trend, Fung said, though less pronounced. There, mixing by turbulence in the ocean is essential for moving CO2 down into the deep ocean, away from the top 100 meters of the ocean, where carbon absorption from the atmosphere takes place. With increased temperatures, the ocean stratifies more, mixing becomes harder, and CO2 accumulates in the surface ocean instead of in the deep ocean. This accumulation creates a back pressure, lowering CO2 absorption.
In all, business as usual would lead to a 1.4 degree Celsius, or 2.5 degrees Fahrenheit, rise in global temperatures by the year 2050. This estimate is at the low range of projected increases for the 21st century, Fung said, though overall, the model is in line with others predicting large ecosystem changes, especially in the tropics.
With voluntary controls that flatten fossil fuel CO2 emission rates by the end of the century, the land and oceans could keep up with CO2 levels and continue to absorb at their current rate, the model indicates.
"This is not a prediction, but a guideline or indication of what could happen," Fung said. "Climate prediction is a work in progress, but this model tells us that, given the increases in greenhouse gases, the Earth will warm up; and given warming, hot places are likely to be drier, and the land and oceans are going to take in carbon at a slower rate; and therefore, we will see an amplification or acceleration of global warming."
"The Earth is entering a climate space we've never seen before, so we can't predict exactly what will happen," she added. "We don't know where the threshold is. A two degree increase in global temperatures may not sound like much, but if we're on the threshold, it could make a big difference."
Fung and colleagues have worked for several decades to produce a model of the Earth's carbon cycle that includes not only details of how vegetation takes up and releases carbon, but also details of decomposition by microbes in the soil, the carbon chemistry of oceans and lakes, the influence of rain and clouds, and many other sources and sinks for carbon. The model takes into account thousands of details, ranging from carbon uptake by leaves, stems and roots to the different ways that forest litter decomposes, day-night shifts in plant respiration, the salinity of oceans and seas, and effects of temperature, rainfall, cloud cover and wind speed on all these interactions.
"This is a very rough schematic of the life cycle of the ecosystem," she said.
Five years ago, she set out with colleagues Scott C. Doney of Woods Hole Oceanographic Institution in Massachusetts, Keith Lindsay of the National Center for Atmospheric Research (NCAR) in Boulder, Colo., and Jasmin John of UC Berkeley to integrate the carbon cycle model into one of the standard climate models in use today - NCAR's Community Climate System Model (CCSM). All of today's climate models are able to incorporate the climate effects of carbon dioxide in the atmosphere, but only with concentrations of CO2 specified by the modelers. Fung's model does not specify atmospheric CO2 levels, but rather predicts the levels, given fossil fuel emissions. The researchers used observations of the past two centuries to make sure that their model is "reasonable," and then used the model to project what will happen in the next 100 years, with the help of supercomputers at NCAR and the National Energy Research Scientific Computer Center at Lawrence Berkeley National Laboratory (LBNL).
The climate model coupled with the carbon cycle has been her goal for decades, as she tried to convince climate modelers that "whether plants are happy or not happy has an influence on climate projections. To include interactive biogeochemistry in climate models, which up to now embrace primarily physics and dynamics, is new."
She admits, however, that much work remains to be done to improve modeling. Methane and sulfate cycles must be included, plus effects like changes in plant distribution with rising temperatures, the possible increase in fires, disease or insect pests, and even the effects of dust in the oceans.
"We have created a blueprint, in terms of a climate modeling framework, that will allow us to go beyond the physical climate models to more sophisticated models," she said. "Then, hopefully, we can understand what is going on now and what could happen. This understanding could guide our choices for the future."
The studies were supported by the National Science Foundation, the National Aeronautics and Space Administration, LBNL and the Ocean and Climate Change Institute of the Woods Hole Oceanographic Institution.
Her colleagues on the paper looking at spring and summer CO2 uptake in northern climes were A. Angert, S. Biraud, C. Bonfils, C. C. Henning and W. Buermann of the Berkeley Atmospheric Sciences Center; and J. Pinzon and C. J. Tucker of NASA Goddard Space Flight Center in Greenbelt, Md. | <urn:uuid:d09fa78c-d834-4fcb-985c-14fe53a5c7ce> | 3.46875 | 1,852 | News Article | Science & Tech. | 38.336962 | 95,607,092 |
By P Gosselin on 24. November 2017
The Arctic is defying the alarmist melting predictions made by global warming activists and scientists. An Embarrassment!
First, Vencore Weather here writes that Greenland Summit Station “will experience high temperatures around -40°F which continues the very cold and well-below normal trend for the month of November“.
Moreover Vencore presents 2 NASA/MODIS satellite photos of Greenland’s Petermann Glacier during the past five years, which revealed growth of the glacier over the past 5 years: from a low point in August 2012 (left) to August 2017 (right):
This tells us the the dire warnings issued years ago of a melting Arctic have been in fact been met with contradictory developments.
Polar bear expert: one of the earliest Hudson Bay freezings
Meanwhile at Twitter here polar bear expert Dr. Susan Crockford recently tweeted:
CIS Hudson Bay and Eastern Arctic
#seaice for week of November 20: still way more shore-bound ice than average for this point in the season, with an unusual patch of new ice in NW Hudson Bay (dark blue).”
Also at her Polar Bear Science site here, Crockford wrote that the West Hudson Bay freeze-up was “one of earliest since 1979.”
Crockford next cited polar bear guide Kelsey Eliasson, “on the ground near Churchill“, who “noted yesterday (12 November) that virtually all bears had already left for the ice (see first comment)“.
The following charts provided by Crockford show that the “freeze up day” has been at a constant level so far this century. The “ice break-up day” in the spring has also been consistent over the past two decades. Finally, the number of ice-free days has not been trending up over the past 20 years:
According to Crockford at Twitter here:
The average date
#polarbears left the ice in the 1980s (± 5 days) vs. 2004-2008, when they left 24 November ± 8 days. Virtually all bears on the ice now, which means freeze-up this year was one of the earliest since 1979.
Arctic warming and melting? Hasn’t been any over the past 10 years!
November 24, 2017 at 10:44AM
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Meadow is a circle with radius r = 34 m. How long must a rope to tie a goat to the pin on the perimeter of the meadow to allow goat eat half of meadow?
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We want to prove the sentense: If the natural number n is divisible by six, then n is divisible by three. From what assumption we started? | <urn:uuid:e982bdb3-94bb-4670-93ba-5a6bab2a4b3a> | 3.46875 | 617 | Tutorial | Science & Tech. | 71.979736 | 95,607,107 |
How do people subjected to the endless dark days of winter in the far northern latitudes maintain normal daily rhythms? Though many might feel like hibernating, a highly regulated internal system keeps such impractical yearnings in check. From fruit flies to humans, nearly every living organism depends on an internal clock to regulate basic biological cycles such as sleep patterns, metabolism, and body temperature. And that clock runs on similar molecular mechanisms.
Specific clusters of neurons in the brain are known to control the biological clock. Scientists believed these brain "clock cells" function as independent units. But new research described in this issue show that the neurons do not act in isolation; rather they collaborate with other neurons in a cell-communication network to sustain the repeating circadian rhythm cycles.
Clock cells within the brain maintain an organisms circadian rhythms, even in the absence of cyclical environmental signals like light, in a state scientists call "free running." Though it has long been clear that the circadian rhythms of an organism persist under such free-running conditions (for example, constant darkness), it was thought that the gene-expression patterns within the cells governing these biorhythms did not require any external, or extracellular, signals to continue ticking. In experiments described here, Michael Rosbash and his colleagues show that the key brain clock cells in fruit flies, called ventral lateral neurons, do indeed support the flys circadian rhythms during periods of constant darkness, and that the molecular expression patterns associated with these rhythms continue to cycle as well within other clock cells. These sustained expression patterns, however, require intercellular communication between different groups of brain clock cells.
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
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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.
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This study presents the new aerosol assimilation system, developed at the European Centre for Medium-Range Weather Forecasts, for the Global and regional Earth-system Monitoring using Satellite and in-situ data (GEMS) project. The aerosol modeling and analysis system is fully integrated in the operational four-dimensional assimilation apparatus. Its purpose is to produce aerosol forecasts and reanalyses of aerosol fields using optical depth data from satellite sensors. This paper is the second of a series which describes the GEMS aerosol effort. It focuses on the theoretical architecture and practical implementation of the aerosol assimilation system. It also provides a discussion of the background errors and observations errors for the aerosol fields, and presents a subset of results from the 2-year reanalysis which has been run for 2003 and 2004 using data from the Moderate Resolution Imaging Spectroradiometer on the Aqua and Terra satellites. Independent data sets are used to show that despite some compromises that have been made for feasibility reasons in regards to the choice of control variable and error characteristics, the analysis is very skillful in drawing to the observations and in improving the forecasts of aerosol optical depth.
Mendeley saves you time finding and organizing research
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Non renewable resources take a long time to develop. Some examples are oil, coal, and natural gases. Renewable resources develop naturally and do not take long to do so. Some examples of these resources are wind, water, and solar power.
I think on nonrenewable resources you were talking 'bout fossil fuels.
Nonrenewable resources are thing that cannot be replaced or remade : an example could be oil for instance if other chemicals got mixed in. Renewable resources can be recreated or replaced:an example could be a phone for instance if it broke.
Renewable resources are resources that you can reuse. Some examples are water, plants, and animal fur. Nonrenewable resources are resources that cannot be reused. Some examples are food, coal, oil, and fossil fuels.
NONRENEWABLE AND RENEWABLE
Renewable resources are resources that can be made on etcetera, etcetera, and etcetera or again. An example of renewable resources are trees cause when trees produce apples or tomatoes they have seeds in them which grow other trees. Nonrenewable resources are resources that can't be made etcetera or all over again. An example of nonrenewable resources is oil cause it cant multiply, make seeds, or more.
A non-renewable resource is something that can not be used again. A renewable resource is something that goes on and on and on.A non-renewable resource is a fossil fuel like coal oil and gas.A renewable resource can be water energy solar power the sun plastic wood and a lot more objects.
NICE BRAIN $:)
A renewable recourse is when you can reuse something. For instance, water is a renewable recourse. A nonrenewable recourse is when you can't reuse something. For example, oil you cannot reuse.
A nonrenewable resource is a resource that runs out. For example fossil fuels are a nonrenewable resource. On the other hand a renewable resource is something we can always use. For example solar energy never runs out.
A nonrenewable resource is a resource that can't be used again after it runs out.Some exsamples are coal, oil, and natural gases which are fossil fuels. A renewable resource is the oppisite of a nonrenewable resource.They can be used again and again. Some exsamples are water, sun, and trees.
A nonrenewable resource is a resource that can not be replaced. One example is of this is coal. A renewable resource unlike a nonrenewable resource can be used multiple times. One example of a renewable resource would be a tree.
Renewable resources are resources can be reused like air, solar energy and a lot lot more. For instance you can renew energy by using the sun. Non renewable resources are things you can run out of. An example of that is oil and coal.
A renewable resource is something that can be replaced. A nonrenewable resource is something that cannot be replaced. Now I shall show examples. Oil is a nonrenewable resource. Paper is a renewable resource.
A renewable resource is something that can be reused For example the solar energy and wind energy. Non renewable resource is something that cannot be renewed ones it's gone its gone or it takes. Really long time for another one to come. For example oil and trees and are non renewable.
Nonrenewable resource is a resource that cannot be renewed. However renewable resources is a resource that can be renewed. And example is gasoline because It gets in a car and the car is running gasoline and turns into pollution in the air.One more example is water because it's like the lifecycle how it rains and then goes into the river and then we drink it.
A renewable resource can be used tots of times.A nonrenewable resource can only be used one time.A example of renewable resource is the suns energy.A example of nonrenewable is coal.
Nonrenewable resources are things that can not be renewed. For an example coal can not be renewed. A renewable resource is a thing that can be renewed. For an example water and solar energy can be renewed.
People with the money buy their way into the search engines with advertised links, but these can be extremely expensive depending on the keywords used, and are certainly not practical for the average person just starting out in the website business. | <urn:uuid:3258f6ff-cdde-48db-805a-ebc6415b3200> | 3.296875 | 925 | Personal Blog | Science & Tech. | 39.595403 | 95,607,149 |
Researchers from the Chinese Academy of Sciences and the Collaborative Innovation Center of Quantum Matter (Beijing), looked at the interactions of water molecules with various graphene-covered surfaces and found that graphene coatings may offer the ability to control the water evaporation process from various surfaces.
Lead author of the study, Dr. Yongfeng Huang from the Chinese Academy of Sciences, said: "Water droplet evaporation is a ubiquitous and complicated phenomenon, and plays a pivotal role in nature and industry. Understanding its mechanism at the atomic scale, and controlling evaporation rate rationally is important for applications including heat transfer and body-temperature control. However, it remains a significant challenge". The team's experiments showed that a graphene coating controls water evaporation by suppressing the evaporation rate on hydrophilic surfaces, and accelerating evaporation on hydrophobic ones. | <urn:uuid:638bfa9b-c0d2-4daf-9dfd-a7909a016708> | 3.21875 | 177 | News (Org.) | Science & Tech. | -0.185572 | 95,607,161 |
LOS ANGELES — A provocative new study of photographs taken from orbit suggests that water flowed on the surface of Mars as recently as several years ago, raising the possibility that the Red Planet could harbor an environment favorable to life.
The crisp images taken by the Mars Global Surveyor do not directly show water. Rather, they show apparently recent changes in surface features that provide the strongest evidence yet that water even now sometimes flows on the dusty, frigid world. Water and a stable heat source are considered keys for life to emerge.
Until now, the question of water in liquid form has focused on ancient Mars and on the Martian north pole, where ice has been detected. Scientists have long noted Martian features that appear to have been scoured by water or look like shorelines and have tried to prove that the Red Planet had water eons ago.
"This underscores the importance of searching for life on Mars, either present or past," said Bruce Jakosky, an astrobiologist at the University of Colorado at Boulder, who had no role in the study. "It's one more reason to think that life could be there."
The findings were published Wednesday in the journal Science, and the National Aeronautics and Space Administration scheduled a news conference for Wednesday afternoon to announce the results.Continue reading the main story
Oded Aharonson, an assistant professor of planetary science at the California Institute of Technology, said that while the interpretation of recent water activity on Mars was "compelling," it is just one possible explanation. Aharonson said further study was needed to determine whether the deposit could have been left there by the flow of dust rather than water.
The latest research emerged when the Global Surveyor spotted gullies and trenches that scientists believed were geologically young and carved by water coursing down cliffs and crater walls.
Scientists at the San Diego-based Malin Space Science Systems, who operate a camera aboard the spacecraft, decided to retake photos of thousands of gullies in search of evidence of recent water activity.
Two gullies that were originally photographed in 1999 and 2001 and re-imaged in 2004 and 2005 showed changes consistent with water flowing down crater walls, the study said. In both cases, scientists found bright, light- colored deposits that were not present in the original photos. They concluded that the deposits - possibly mud, salt or frost - were left there when water had cascaded through the channels.
The Surveyor, managed by NASA's Jet Propulsion Laboratory, abruptly lost radio contact with Earth last month. Attempts to find the spacecraft, which has mapped Mars since 1996, have failed and scientists fear it is unusable.
NASA's durable Mars rovers have sent scientists strong evidence that the planet once had water at or near the surface, based on observations of alterations in ancient rocks.
Mars formed more than 4.5 billion years ago and scientists generally believe it went through an early wet and warm era that ended after 1.5 billion to 2.5 billion years, leaving the planet extremely dry and cold. Some studies have considered the possibility of water flowing briefly on the surface through an underground water source that periodically shoots up like an aquifer.Continue reading the main story | <urn:uuid:26689f59-d095-4473-bd12-92653a05bced> | 3.765625 | 649 | Truncated | Science & Tech. | 36.007693 | 95,607,164 |
The European Union will spend about 700 million euros ($900 million) to build the world’s most powerful lasers, technology that could destroy nuclear waste and provide new cancer treatments.
The Extreme Light Infrastructure project has obtained funding for two lasers to be built in the Czech Republic and Romania, Shirin Wheeler, spokeswoman for the European Commission on regional policy, said in a phone interview. A third research center will be in Hungary.
The lasers are 10 times more powerful than any yet built and will be strong enough to create subatomic particles in a vacuum, similar to conditions that may have followed the start of the universe. Eventually, the power of the light beams could be used to deteriorate the radioactivity of nuclear waste in just a few seconds and target cancerous tumors, the projects’s Romanian coordinator Nicolae-Victor Zamfir said in an interview.
“We can’t find in nature any phenomenon with such an intense power like the one that will be generated with this laser,” Zamfir said in a phone interview from Romania. “We expect to see the first results of our research in one or two years after the centre becomes operational.”
The Magurele research center, where the Romanian laser will be located, will consume about 10 megawatts of energy, enough to supply about 2,500 average U.S. households. Most of it will come from geothermal pumps installed at the site, where the laser is expected to become operational in 2017.
“It is probably one of the largest such sites in Europe using unconventional energy,” Zamfir said.
Zamfir said companies from the computer industry have shown interest in the project, but none from the nuclear sector. “We haven’t advertised the project yet properly, possibly also because we didn’t have the EU’s approval.”
The research may replicate the same principles used in a new type of cancer radiotherapy called hadrontherapy, Zamfir said. It directly targets deep-rooted tumors, reducing the risk of recurrence or new tumors. The first results of the experiments are expected for 2018-2019.
“This treatment already exists, but requires expensive and big accelerators,” Zamfir said. “If it becomes possible by using this type of laser, it can be implemented at lower costs as technology advances and the lasers get cheaper.”
The laser technology might also be used to reduce the time it take for atomic waste to lose its radioactivity from thousands of years to a few seconds. That could remove the need to build underground stores to keep waste secure for centuries.
“It’s going to take almost 20 years until we would be able to do it, but right now many countries don’t see any solution in the near future,” Zamfir said.
The EU is basing the broject in eastern European countries to support science in former communist countries, where a tradition of research hasn’t prevented academics seeking better- paid posts outside the region.
“The hope is to create a virtuous circle that by having the infrastructure there you also attract more funds and research ,” the European Commission’s Wheeler said.
The city of Magurele is home to Romania’s National Institute of Physics and Nuclear Engineering, established in 1949 and one of the biggest nuclear physics research centers in eastern Europe during the communist era.
Although research is still being carried at the institute, Romania, it’s losing scientsits because it invests only 0.5 percent of its gross domestic product in research, compared with a European average of 2 percent.
The research center is less than 10 kilometers away from Bucharest, but the journey can take around 20 minutes on an old road that is now being enlarged.
“There’s no direct public transportation from the center of Bucharest -- you need to change the bus and then hitchhike for those private minibuses,” Zamfir said. “We now hope it will change.”
In Romania, 200 researchers will work at the project full time, with around 1,000 more expected to visit the center for experiments each year once it starts working, according to Zamfir.
The project will be followed by the construction of an even more powerful laser and any of the three countries already involved in the project, plus the U.K., might host the laser. The ELI-Ultra High Field Facility will reach 200 petawatts of power, or 100,000 times the power of the world electric grid.
“The proposal for the fourth site should have been made in 2012, but we haven’t reached maturity with the ongoing three projects to draw enough conclusions,” Zamfir said.
The EU expects to spend 550 million euros in the first phase of the project ending December 2013, Wheeler said. Further applications from Romania and Hungary for the second part of the project should raise the total funding from the organization to 700 million euro, more than 80 percent of the entire cost of the project. About 180 million will come from other sources.
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The research team – led by Durham University - including BirdLife International and the RSPB (BirdLife in the UK) looked at the effects of climate change on 815 bird species of conservation concern in sub-Saharan Africa and on the network of sites designated for them (termed Important Bird Areas).
Published in the journal Ecology Letters, the research - funded by the RSPB - demonstrates that a network of wildlife areas will be a crucial tool to help biodiversity survive future climate change. The findings suggest an urgent need for legislators to protect eco-systems and key wildlife areas in Africa. They show that, over the next 75 years, the biodiversity of some regions will suffer more than others as a result of climate change. They also underline the importance of providing 'green corridors' to help wildlife to move to find new climatically-suitable areas.
The team led by Dr Stephen Willis and Dr David Hole from the School of Biological and Biomedical Sciences at Durham University, used simulation models to see how climate change might affect birds in Important Bird Areas, in the coming decades under a scenario of moderate climate change.
The researchers looked at a network of 863 IBA sites across 42 countries and territories covering around 2,079,306 square kms (1,292,020 square miles) or 7 per cent of the African continent. The sites are identified as being critical for the conservation of birds, in particular, species that are globally threatened, restricted in range or restricted to particular biomes. Together, African IBAs are home to 875 of these species.
Climate change is not the only issue affecting wildlife in Africa. More than 40 per cent of African IBAs lack any form of legal protection under national or international law. Agricultural development, logging, invasive alien species, and unsustainable hunting and trapping are the main threats to bird species and IBAs across the African continent.
Dr Stephen Willis said: "We looked at bird species across the whole network of protected areas in Africa and the results show that wildlife conservation areas will be essential for the future survival of many species of birds.
"Important Bird Areas will provide new habitats for birds that are forced to move as temperatures and rainfall change and food sources become scarce in the areas where they currently occur. Protected areas are a vital conservation tool to help birds adapt to climate change in the 21st century."
The findings show that the biodiversity of particular areas is likely to change significantly. The turnover of species in some sites could be as high as 50 per cent, as established species leave to find more suitable climes or new food supplies, and new species move in to an area. The adaptability of birds will be an important factor, the experts say.
Dr Stephen Willis said: "The results show that 90 per cent of priority species in Africa will find suitable climate somewhere in the network of protected areas in future. However, one in ten birds will have to find new places to live and breed so new sites will have to be added to the IBA network.
"The central regions of Africa should maintain many of their current species as long as the protected areas remain intact. By contrast, areas of the Afrotropical Highlands, which occur in countries such as Cameroon, South Africa and Ethiopia, will see enormous change with more than 40 per cent of species leaving."
The findings also show that some species are likely to struggle, and may even become extinct unless new populations can be established. A priority species might be lost from a particular IBA, but there may be other climatically suitable sites in the network for the species to move to. Many species will only survive if they adapt by moving across Africa to seek out new, climatically-suitable areas to inhabit.
Dr Stuart Butchart, Global Research Coordinator at BirdLife International, said: "The survival of much of the planet's biodiversity under climate change will depend upon adequate protection for biodiverse ecosystems, the IBAs within them, and support for the people who depend on them - so that local communities can participate actively in making their environment more resilient. It is essential that policy leads to adequate protection of IBAs and takes account of the critical role that ecosystems play in helping wildlife and people adapt."
Ruth Davis, head of climate change at the RSPB, said: "Looking after IBAs is vital for the future of our wildlife. Protecting the natural resources and services provided by these ecosystems is vital for people too. Healthy ecosystems are the first line of defence against the impacts of climate change for many of the world's poorest people."
One example, is the Gola Forest Transboundary Peace Park, on the borders of Sierra Leone and Liberia, uniting existing protected IBAs and encompassing additional forest to provide corridors for the movement of wildlife between them. It protects one of the largest remaining blocks of intact forest in the Upper Guinea Area of West Africa.
Carl Stiansen | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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18.07.2018 | Information Technology | <urn:uuid:95273898-1735-43dc-a51a-2b02dfa62e41> | 3.65625 | 1,659 | Content Listing | Science & Tech. | 38.102451 | 95,607,198 |
Oligosaccharides are constructed from carbohydrate monomer units which contain multiple hydroxyl groups, along with amino and carboxyl groups. Protecting groups play a vital role in oligosaccharide synthesis as they help in differentiating not only the same type of functional groups but also the different functional groups present in the carbohydrate.
Image Credit: Yurchanka Siarhei / Shutterstock
Oligosaccharides are one of the most important class of biomolecules, playing a critical role in important biological processes like cell adhesion, immune response, bacterial and viral infection and cell differentiation and proliferation.
However, due to their low abundance in nature, it is difficult to get pure, structurally well-defined and reasonable quantities of oligosaccharides. The chemical synthesis of oligosaccharides has been instrumental in solving this problem for evaluating critical biological processes.
Desired characteristics of protecting groups
The synthesis of oligosaccharides is a challenge. This is due to the versatility of glycosylation (either alpha or beta linkages) and the presence of a large number of functional groups which necessitate the use of specific protecting groups to obtain the desired chemoselectivity and regioselectivity.
Protecting groups are used to temporarily mask a functional group that cannot survive the chemical environment. However, they can participate directly or indirectly in the glycosylation reactions altering the stereochemical outcome. Hence, an ideal protecting group should have the following characteristics:
- Readily available
- It should not introduce the formation of new stereogenic centers
- Stable in order to withstand the synthesis process
- Creates a product that is more lipophilic and crystalline
- The by-products produced should not alter other parts of the molecule and be able to be easily removed
Types of protecting groups
Classical neighboring group participation involves the participation of the acyl group at C2 position. In the glycosylation reaction, the acyl group of the donor aids in the removal of an activated leaving group leading to the formation of the stable dioxolenium ion. Therefore, the glycosyl acceptor can attack only from one side to form the 1,2-trans glycoside.
Many ester-type groups such as acetate, chloroacetate, benzoate and pivaloate have been used to make 1,2-trans glycosidic linkages. Occasionally, formation of orthoesters and harsh removal conditions prevent the formation of 1,2-trans glycosides.
Improved ester groups like 4-acetoxy-2,2-dimethylbutanoyl (ADMB) overcome these drawbacks and enable stereoselective synthesis of b-glucopyranosides.
The deprotection conditions are mild involving hydrogenolysis through intramolecular lactonization. 3-(2-Hydroxyphenyl)-3,3-dimethylpropanoate (DMBPP) and 3-(2-hydroxy-4,6-dimethylphenyl)-3,3-dimethylpropanoate groups (TMBPP), when placed at the C2 position enable synthesis of b-glucopyranosides and a-mannopyranosides in good yield. These groups are removed by hydrogenolysis in the absence of acid or base.
The glycosylation of a thioglycoside having a 2,2-dimethyltrimethylene (DMTM) phosphate group at the C2 position leads to the formation of 1,2-trans glycoside. The DMTM group is removed by sodium hydroxide in an ethanol-water solvent mixture.
Chiral auxiliary group:
A chiral auxiliary group is a substituted ethyl moiety that contains a nucleophilic group positioned at C2 of the glycosyl donor. Upon formation of a oxocarbenium ion, the participation of the nucleophilic moiety controls the stereochemical outcome of glycosylation by forming cis- or trans- decalin system depending on the configuration of the chiral auxiliary.
If the chiral auxiliary has a S-configuration, it favors the formation of 1,2-cis glycoside via a trans-decalin intermediate. If the auxiliary at C2 position of the glycosyl donor has a R-configuration, it gives 1,2-trans glycoside via a cis-decalin intermediate.
Conformation-constraining protection groups
Conformation-constraining protecting groups restrict the flexibility of the sugar ring aiding a certain conformation of the intermediate thereby making the glycosyl intermediate easily accessible from one side.
Cyclic bifunctional groups such as benzylidine, carbonyl (carbonate, oxazolidinone) and cyclic silyl groups are some examples of conformation-constraining protecting groups. The benzylidine group is used to construct a b-mannosidic linkage by the formation of an a-triflate intermediate.
Similar to the 4,6-O-benzylidene-directed mannosylation, carbonates also use the same mechanism for the synthesis of b-glucosides. The oxazolidinone group is very useful in the synthesis of a-2-amino-2-deoxyglucopyranosides and a-sialosides.
4-nitrophenyl chloroformate is used to introduce an oxazolidinone group as a non-participating group at C2 and enables the simultaneous differentiation of the 2-amino and 3-hydroxyl group from other hydroxyl groups. 5-N,4-O-carbonyl-protected sialyl donor showed high reactivity and high a-selectivity in sialylation reactions.
The glycosylation reaction with a donor having the cyclic silyl group di-tert-butylsilylene (DTBS) gives predominantly a-selective products. 3,5-O-Di-tert-butylsilylene group was introduced in an arabinosyl donor to construct b-selective arabinofuranosides which are important constituents of microbial and plant polysaccharides. A donor with 3,4-O-bisacetal protecting group was used for b-selective glucosylation.
Reviewed by Chloe Barnett, BSc
- Polyakova SM, Nizovtsev AV, Kunetskiy RA and Bovin NV “New protecting groups in the synthesis of oligosaccharides” Russ.Chem.Bull., Int.Ed., Vol 64, No. 5, May, 2015.
- Guo J and Ye Xin-Shan “Protecting groups in carbohydrate chemistry: Influence on stereoselectivity of glycosylations” Molecules, 2010, 15, 7235-7265. | <urn:uuid:33c2726d-9f3b-4aa4-b8c2-b3c033f4eb76> | 3.34375 | 1,450 | Knowledge Article | Science & Tech. | 12.681808 | 95,607,200 |
The Surprising Reason Why Neutron Stars Don’t All Collapse To Form Black Holes
“The measurements of the enormous pressure inside the proton, as well as the distribution of that pressure, show us what’s responsible for preventing the collapse of neutron stars. It’s the internal pressure inside each proton and neutron, arising from the strong force, that holds up neutron stars when white dwarfs have long given out. Determining exactly where that mass threshold is just got a great boost. Rather than solely relying on astrophysical observations, the experimental side of nuclear physics may provide the guidepost we need to theoretically understand where the limits of neutron stars actually lie.”
If you take a large, massive collection of matter and compress it down into a small space, it’s going to attempt to form a black hole. The only thing that can stop it is some sort of internal pressure that pushes back. For stars, that’s thermal, radiation pressure. For white dwarfs, that’s the quantum degeneracy pressure from the electrons. And for neutron stars, there’s quantum degeneracy pressure between the neutrons (or quarks) themselves. Only, if that last case were the only factor at play, neutron stars wouldn’t be able to get more massive than white dwarfs, and there’s strong evidence that they can reach almost twice the Chandrasekhar mass limit of 1.4 solar masses. Instead, there must be a big contribution from the internal pressure each the individual nucleon to resist collapse.
For the first time, we’ve measured that pressure distribution inside the proton, paving the way to understanding why massive neutron stars don’t all form black holes.
This Is Why The Event Horizon Telescope Still Doesn’t Have An Image Of A Black Hole
“Of all the black holes visible from Earth, the largest is at the galactic center: 37 μas.
With a theoretical resolution of 15 μas, the EHT should resolve it.
Despite the incredible news that they’ve detected the black hole’s structure at the galactic center, however, there’s still no direct image.”
Last year, data from the South Pole Telescope, a 10-meter radio telescope located at the South Pole, was added to the Event Horizon Telescope team’s overall set of information. Here we are, though, half a year later, and we still don’t have a direct image of the event horizon for the galactic center’s black hole. There aren’t any problems; the issue is that we have to successfully calibrate and error-correct the data, and that takes time and care to get it right. Science isn’t about getting the answer in the time you have to get it; it’s about getting the right answer in the time it takes to get things right. From that point of view, there’s every reason this is worth waiting for.
The Event Horizon Telescope team is on the right track; here’s where we are right now in our quest to create the first image of a black hole’s event horizon!
How Do The Most Massive Stars Die: Supernova, Hypernova, Or Direct Collapse?
“When we see a very massive star, it’s tempting to assume it will go supernova, and a black hole or neutron star will remain. But in reality, there are two other possible outcomes that have been observed, and happen quite often on a cosmic scale. Scientists are still working to understand when each of these events occurs and under what conditions, but they all happen. The next time you look at a star that’s many times the size and mass of our Sun, don’t think “supernova” as a foregone conclusion. There’s a lot of life left in these objects, and a lot of possibilities for their demise, too. We know our observable Universe started with a bang. For the most massive stars, we still aren’t certain whether they end with the ultimate bang, destroying themselves entirely, or the ultimate whimper, collapsing entirely into a gravitational abyss of nothingness.”
How do stars die? If you’re low in mass, you’ll burn through all your fuel and just contract down. If you’re mid-ranged, like our Sun, you’ll become a giant, blow off your outer layers, and then the remaining core will contract to a white dwarf. And the high-mass stars can take an even more spectacular path: going supernova to produce either a neutron star or a black hole at their core. But that’s not all a high-mass star can do. We’ve seen supernova impostors, hypernovae that are even more luminous than the brightest supernova, and direct collapse black holes, where no explosion or even ejecta exists from a star that used to be present and massive. The science behind them in incredible, and while there are still uncertainties in predicting a star’s fate, we’re learning more all the time.
Come get the fascinating physics behind how the most massive stars die. You might think “supernova” every time, but the Universe is far more intricate and complex than that!
This Is Why Our Universe Didn’t Collapse Into A Black Hole
“The level to which the expansion rate and the overall energy density must balance is insanely precise; a tiny change back then would have led to a Universe vastly different than the one we presently observe. And yet, this finely-tuned situation very much describes the Universe we have, which didn’t collapse immediately and which didn’t expand too rapidly to form complex structures. Instead, it gave rise to all the wondrous diversity of nuclear, atomic, molecular, cellular, geologic, planetary, stellar, galactic and clustering phenomena we have today. We’re lucky enough to be around right now, to have learned all we have about it, and to engage in the enterprise of learning even more: the process of science. The Universe didn’t collapse into a black hole because of the remarkably balanced conditions under which it was born, and that might just be the most remarkable fact of all.”
The Universe is a vast and complex place, full of a diversity of structure from the smallest scales to the largest. And yet, by many accounts, it’s a wonder that it came to be this way at all.
If things were just a little bit different at the very beginning, the Universe could have recollapsed in on itself in a mere fraction-of-a-second after the Big Bang. That very clearly didn’t happen, but why not? And, if it did happen, would we have formed a black hole? There must have been an incredibly perfect, finely-tuned balance between the initial expansion rate and the energy density of everything within the Universe, or this careful balance wouldn’t have existed, and we never would have arisen in this Universe.
Yet, here we are! So, what factors conspired to allow us to exist, exactly as we are? Come find out for yourself!
Einstein’s Ultimate Test: Star S0-2 To Encounter Milky Way’s Supermassive Black Hole
“The largest, closest single mass to Earth is Sagittarius A*, our Milky Way’s supermassive black hole, weighing in at 4,000,000 solar masses.
The star S0-2 makes the closest known approach to this black hole, reaching a minimum distance of just 18 billion kilometers.
That’s only three times the Sun-Pluto distance, or a meager 17 light-hours.”
After a 16 year wait, the closest star to the Milky Way’s supermassive black hole, S0-2, will make its closest approach later this year. At its closest, it should be moving at a whopping 2.5% the speed of light, enabling us to test out Einstein’s relativity in an entirely new regime. We should, for the first time, be able to measure the gravitational redshift from our galactic center, and to track the relativistic “kick” that Einstein’s theory predicts when an orbit gets modified by traveling close to an extremely large mass. New studies have recently shown that S0-2 doesn’t appear to have a binary companion, which makes it even more interesting for such an observation, which won’t come again until the year 2034. As a bonus, scientists hope to shed light on how stars form in the harsh environment of the galactic center at all.
Come find out how the newest test of Einstein could push us past the limits of relativity, or confirm it in an entirely new way!
Black Hole Mergers To Be Predicted Years In Advance By The 2030s
“When we detect black hole-black hole events with LIGO, it’s only the last few orbits that have a large enough amplitude to be seen above the background noise. The entirety of the signal’s duration lasts from a few hundred milliseconds to only a couple of seconds. By time a signal is collected, identified, processed, and localized, the critical merger event has already passed. There’s no way to point your telescopes — the ones that could find an electromagnetic counterpart to the signal — quickly enough to catch them from birth. Even inspiraling and merging neutron stars could only last tens of seconds before the critical “chirp” moment arrives. Processing time, even under ideal conditions, makes predicting the particular when-and-where a signal will occur a practical impossibility. But all of this will change with LISA.”
The past few years have ushered in the era of gravitational wave astronomy, turning a once-esoteric and controversial prediction of General Relativity into a robust, observational science. Less than a year ago, with three independent detectors online at once, the first localizations of gravitational wave signals were successfully performed. Multi-messenger astronomy, with gravitational waves and an electromagnetic follow-up, came about shortly thereafter, with the first successful neutron star-neutron star merger. But one prediction still eludes us: the ability to know where and when a merger will occur way in advance.
Thanks to LISA, launching in the 2030s, that’s all going to change. Suddenly, we’ll be able to predict these events weeks, months, or even years in advance! Here’s how.
Black Holes Must Have Singularities, Says Einstein’s Relativity
“The thing is, there’s a speed limit to how fast these force-carriers can go: the speed of light. If you want an interaction to work by having an interior particle exert an outward force on an exterior particle, there needs to be some way for a particle to travel along that outward path. If the spacetime containing your particles is below the density threshold necessary to create a black hole, that’s no problem: moving at the speed of light will allow you to take that outward trajectory.
But what if your spacetime crosses that threshold? What if you create an event horizon, and have a region of space where gravity is so intense that even if you moved at the speed of light, you couldn’t escape?”
Usually, when physicists first start teaching about black holes, the attitude they’re met with is skepticism. People can accept that as you compress a large mass into a smaller and smaller volume, it gets harder to escape its gravitational pull. As you go from a star to a white dwarf to a neutron star, you have to move closer to the speed of light to leave it’s surface. If you go even denser, you’ll create an event horizon: a region of space where the gravitational pull is so strong that nothing, not even light can escape. People are okay with that, but when you go to the next step and declare that anything that crosses the event horizon eventually falls into a central singularity, suddenly they’re not okay. Why, they reason, couldn’t there be some denser, exotic, degenerate form of matter than what we presently know? Why couldn’t that lie inside a black hole, rather than a singular point or ring? It’s a good question and an interesting bit of intuition, but there’s an answer for that.
If you wanted to hold anything up against collapse to a singularity inside a black hole, the force-carriers governing the interaction would have to travel faster than light, which is a no-go. Find out the full story on why black holes must have singularities!
Black Hole Mergers Might Actually Make Gamma-Ray Bursts, After All
“If there is a gamma-ray signal associated with black hole-black hole mergers, it heralds a revolution in physics. Black holes may have accretion disks and may often have infalling matter surrounding them, being drawn in from the interstellar medium. In the case of binary black holes, there may also be the remnants of planets and the progenitor stars floating around, as well as the potential to be housed in a messy, star-forming region. But the central black holes themselves cannot emit any radiation. If something’s emitted from their location, it must be due to the accelerated matter surrounding them. In the absence of magnetic fields anywhere near the strength of neutron stars, it’s unclear how such an energetic burst could be generated.”
In 2015, the very first black hole-black hole merger was seen by the LIGO detectors. Interestingly, the NASA Fermi team claimed the detection of a transient event well above their noise floor, beginning just 0.4 seconds after the arrival of the gravitational wave signal. On the other hand, the other gamma-ray detector in space, ESA’s Integral, not only saw nothing, but claimed the Fermi analysis was flawed. Subsequent black hole-black hole mergers showed no such signal, but they were all of far lower masses than that very first signal from September 14, 2015. Now, however, a reanalysis of the data is available from the Fermi team themselves, validating their method and indicating that, indeed, a 3-sigma result was seen during that time. It doesn’t necessarily mean that there was something real there, but it’s suggestive enough that it’s mandatory we continue to look for electromagnetic counterparts to black hole-black hole mergers.
The Universe continues to be full of surprises, and the idea that black hole mergers may make gamma-rays, after all, would be a revolutionary one! Come get the full story today.
Ask Ethan: How Do Hawking Radiation And Relativistic Jets Escape From A Black Hole?
“Everything you read about a black indicates that “nothing, not even light, can escape them”. Then you read that there is Hawking radiation, which “is blackbody radiation that is predicted to be released by black holes”. Then there are relativistic jets that “shoot out of black holes at close to the speed of light”. Obviously, something does come out of black holes, right?”
When it comes to black holes, the cardinal rule is that there exists an event horizon: a region from which nothing inside can ever escape. Once you cross over, you can never get out. No matter how fast you move, how quickly or what direction you accelerate in, or even if you travel at the speed of light, your inevitable destiny lies at the central singularity. So how, then, are things like relativistic jets and Hawking radiation emitted from black holes? The key to understanding them lies in examining the conditions that occur outside the event horizon, in the region near (but not exactly at) the black hole itself. This is the critical environment where spacetime is curved, matter achieves relativistic speeds, and the quantum fields themselves are affected by relativity.
Hawking radiation and relativistic jets may be real, but they don’t break the laws of physics to exist! Find out how they really do escape on this edition of Ask Ethan.
What Would You See As You Fell Into A Black Hole?
“But if you continue your fall towards the event horizon, you’ll eventually see the starlight compress down into a tiny dot behind you, changing color into the blue due to gravitational blueshifting. At the last moment before you cross over into the event horizon, that dot will become red, white, and then blue, as the cosmic microwave and radio backgrounds get shifted into the visible part of the spectrum for your last, final glimpse of the outside Universe, still assuming that nothing else falls in with you.”
When you fall into a black hole, terrible things happen to you. Your atoms get stretched apart in the terrifying phenomenon of spaghettification, you get sucked inevitably into the central singularity, and the entire outside Universe goes dark. But it doesn’t go dark all at once; instead, the front of the Universe gets cut off, but all the light paths converge directly behind you. What you see, as a couple of the videos within the article show, is that the entire outside Universe gets encoded in a light path that decreases to a shrinking circle directly behind you. As you try to avoid the central singularity, maximizing your survival time, you discover a terrifying phenomenon from inside the event horizon: that the singularity is everywhere, in all directions. At the last, you see the blueshifted, leftover glow from the Big Bang… and then nothing but darkness.
My words cannot do it justice (although I try!), but you’ll want to see the visualizations for yourself. They’re spectacular, and best of all, they’re accurate! Come see what you would see if you had the misfortune to fall into a black hole. | <urn:uuid:60a580b9-3685-4b38-9ed4-fc2caeb32d18> | 3.625 | 3,771 | Content Listing | Science & Tech. | 47.445327 | 95,607,210 |
An oil drum is cut in half. One half is used as a water trough. Use the dimensions; length 82cm, width 56cm to estimate the capacity of the water trough in liters.
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posted by SOS
26.Use Russell-Saunders LS coupling to derive the ground state levels of (a) Ne
(b) F (c) Sc (d) Zr (e) C.
a. Construct a Grotrian diagram for the He emission spectrum (shown on
the right) and use it to assign as much of this spectrum as you can
using the data in the table below.
b. What is the energy difference between the 3
) and 1
levels? Why are these levels not the same energy, and why is the 3
) level lower than the 1
) level, and not vice versa?
c. What is the energy difference between the 3
) and 1
levels? Compare your answer to your answer for part (c) and explain
We can't draw diagrams/structures on this forum and most of the answers to your questions can't be done easily on this site. If you can rephrase or reconstruct them perhaps we can help.
What are the Russell-Saunders LS coupling derivations of the ground state levels of (a) Ne (b) F (c) Sc (d) Zr (e) C.
Configuration Level DE (cm-1)
1s2 1S 0.0
1s1 2s1 3S 159855.97
1s1 2p1 3P2 169086.76
1s1 2p1 1P 171134.89
1s1 3s1 3S 183236.79
1s1 3p1 3P2 185564.56
1s1 3d1 3D3 186101.54
1s1 3d1 1D 186104.96
1s1 3p1 1P 186209.36
1s1 4p1 1P 191492.71 | <urn:uuid:289d0450-6fbb-4882-be9c-88ea0385d930> | 2.546875 | 389 | Q&A Forum | Science & Tech. | 110.802053 | 95,607,212 |
Teardrop-shaped mesoscale landscape features in plan view, having a tapered downstream tail.
Streamlined forms are often semi-lemniscate in plan view and may be composed of layers (Burr 2005) and so can have terrace-like benches along their margins. Some islands may be rhomboid or diamond-like shaped.
None but see also yardangs in aeolian systems
Generally interpreted to represent a shape that is hydraulically streamlined by deposition and erosion of sediment and rock by fluid flow to minimize flow resistance.
Depositional: the channel-forming flows were ponded by local...
- Baker VR, Kochel RC (1978), Morphometry of streamlined forms in terrestrial and Martian channels, In: the Proceedings of the Ninth Lunar and Planetary Science Conference. Pergamon Press, New York, pp 3193–3203Google Scholar
- Baker VR, Komatsu G, Gulick VC, Kargel JS (1991) Channels on Venus: an overview. In: Lunar Planet Sci Conf XXII, Houston pp 15–16Google Scholar
- Baker VR, Carr MH, Gluick VC, Williams CR, Marley MS (1992) Channels and valley networks. In: Kieffer HH (ed) Mars, vol I. University of Arizona Press, Tucson, pp 493–522Google Scholar
- Bridge JS, Demicco R (2012) Rivers, alluvial plains and fans. In: Earth surface processes, landforms and sediment deposits. Cambridge University Press, New York, pp 365–461Google Scholar
- Lamb H (1906) Hydrodynamics, 3rd edn. Cambridge University Press, Cambridge, UK, p 17Google Scholar
- Spitzer CR, Carr MH et al (eds) (1980) Viking orbiter views of Mars. NASA, Washington, DC, SP 441Google Scholar
- Wyrick JR (2005) Formation of fluvial islands. PhD thesis, Civil Engineering, Oregon State University, 285 ppGoogle Scholar | <urn:uuid:b907c9d5-4d68-4096-9fc3-d8d7de72172b> | 2.75 | 422 | Academic Writing | Science & Tech. | 53.591485 | 95,607,227 |
In order to avoid possible fraud in labelling, a number of different technologies have been developed in recent years to comply with the regulations of the European Union (Regulation CE No 104/2000) indicating the need to label fisheries products with their scientific name so as to ensure traceability throughout the chain of processing and marketing.
Within the European SEAFOODplus project, AZTI- Tecnalia has launched a DNA database scheme, free of charge. This database contains more than 700 references for the mitochondrial DNA sequences of the most important commercial species in Europe, including Gadidae family (e.g. cod), the Thunnus genus (e.g. tuna) and Merlucciidae family (e.g. hake).
The database is a practical tool for validating techniques of identification in species of fish. It is based on DNA analysis by means of a dynamic system that enables the simplification of the handling of DNA sequences for establishing similarities and finding polymorphisms, etc. Thus, each DNA reference sequence is characterised (with a marker at the 3’ and 5’ ends) facilitating its location on the genome.
Moreover, it is a useful source of information for developing new techniques of identification based on DNA analysis, enabling the comparison of results obtained in various laboratories.
Egoitz Etxebeste | alfa
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Tangled and drowned: a global review of penguin bycatch in fisheries
Crawford, R., Ellenberg, U., Frere, E., Hagen, C., Baird, K., Brewin, P., Crofts, S., Galss, J., Mattern, T., Pompert, J., Ross, K., Kemper, J., Ludynia, K., Asherley, R., Steinfurth, A., Suazo, C., Yorio, P., Tamini, L., Mangel, J., Bugoni, L., Jiménez Uzcategui, G., Simeone, A., Luna-Jorquera, G., Gandini, P., Woehler, E., Putz, K., Dann, P., Chiaradia, A., & Samll, C.
Penguins are the most threatened group of seabirds after albatrosses. Although penguins are regularly captured in fishing gear, the threat to penguins as a group has not yet been assessed. We reviewed both published and grey literature to identify the fishing gear types that penguins are most frequently recorded in, the most impacted species and, for these susceptible species, the relative importance of bycatch compared to other threats. While quantitative estimates of overall bycatch levels are difficult to obtain, this review highlights that, of the world’s 18 species of penguins, 14 have been recorded as bycatch in fishing gear and that gillnets, and to a lesser extent trawls, are the gear types that pose the greatest threats to penguins. Bycatch is currently of greatest concern for yellow-eyed Megadyptes antipodes (Endangered), Humboldt Spheniscus humboldti (Vulnerable) and Magellanic Spheniscus magellanicus penguins (Near Threatened). Penguins face many threats; reducing bycatch mortality in fishing gear will greatly enhance the resilience of penguin populations to threats from habitat loss and climate change that are more difficult to address in the short term. Additional data are required to quantify the true extent of penguin bycatch, particularly for the most susceptible species. In the meantime, it is crucially important to manage the fisheries operating within known penguin foraging areas to reduce the risks to this already threatened group of seabirds.
Palabras claves: Fishery, Gillnet, Seabird, Trawl, Conservation, Direct mortality
Diversification dynamics, species sorting, and changes in the functional diversity of marine benthic gastropods during the Pliocene-Quaternary at temperate western South America
Rivadeneira, M. M., & Nielsen, S. N.
Functional diversity based on species traits is a powerful tool to investigate how changes in species richness and composition affect ecosystem functioning. However, studies aimed at understanding changes in functional diversity over large temporal and spatial scales are still scant. Here we evaluate the combined effect of diversification and species sorting on functional diversity of fossil marine gastropods during the Pliocene-Quaternary transition in the Pacific coast of South America. We analyzed a total of 172 species in 29 Pliocene and 97 Quaternary sites. Each species was characterized according to six functional traits: body size, feeding type, mobility, attachment, life-habit, and larval mode. Functional diversity was estimated according to four indexes (functional richness, evenness, divergence and dispersion) based on functional traits measured. Extrapolated species richness showed a slight yet not significant decrease from the Pliocene to the Quaternary despite the fact that a large faunal turnover took place; furthermore, a large extinction of Pliocene species (61–76%) was followed by a high pulse of appearances (49–56%) during the Quaternary. Three out of four indices of functional diversity (evenness, divergence and dispersion) increased significantly towards the Quaternary which is more than expected under a random turnover of species. The increase in functional diversity is associated with a loss of large-sized carnivore forms, which tended to be replaced by small-sized grazers. Hence, this trait-selective species turnover, even in the absence of significant changes in species richness, likely had a large effect and has shaped the functional diversity of present-day assemblages.
Palabras claves: Species diversity, Species extinction, Pliocene epoch, Physiological parameters, Gastropods, Biodiversity, Malacology, Marine fossils
Holocene tephrochronology of the lower Río Cisnes valley, southern Chile
Weller, D. J., de Porras, M. E., Maldonado, A., Méndez, C., & Stern, C. R.
Sediment cores from lakes and bogs in the Río Cisnes valley contain tephra from explosive eruptions of volcanoes in the southern part of the Andean Southern Volcanic Zone (SSVZ). These tephra, which thicken and coarsen to the west, are attributed to eruptions from Melimoyu, Mentolat, Hudson, and potentially either Macá, Cay or one of the many minor eruptive centers (MEC) located both along the Liquiñe-Ofqui Fault Zone (LOFZ) and surrounding the major volcanoes. Correlation of the tephra between two new cores in the lower Río Cisnes valley, and amongst other cores previously described from the region, and source volcano identification for the tephra, has been done using lithostratigraphic data (tephra layer thickness and grain size), petrography (tephra glass color, vesicle morphology, and type and abundance of phenocryst phases), and by comparison of bulk tephra trace-element characteristics with previously published whole-rock and bulk tephra chemical analysis. Four tephras in these cores are attributed to eruptions of Mentolat, four to eruptions from Melimoyu, one possibly to Hudson, and six cannot be assigned to a specific source volcano. Some of these tephra correspond to pyroclastic tephra fall deposits previously observed in outcrop, including the MEL2 eruption of Melimoyu and the MEN1 eruption of Mentolat. However, others have not been previously observed and represent the products of newly identified small to medium sized eruptions from volcanoes of the SSVZ. These results provide new information concerning the frequency and magnitude of explosive eruption of SSVZ volcanoes and contribute to the evaluation of volcanic hazards in the region.
Palabras claves: Andean volcanism; Tephra; Tephrochronology; Chile
The combined effects of ocean warming and acidification on shallow-water meiofaunal assemblages
Lee, M. R., Torres, R., & Manríquez, P. H.
Climate change due to increased anthropogenic CO2 in the atmosphere is causing an increase in seawater temperatures referred to as ocean warming and a decrease in seawater pH, referred to as ocean acidification. The meiofauna play an important role in the ecology of marine ecosystems and the functions they provide. Using microcosms, meiofaunal assemblages were exposed to two temperatures (15 and 19 °C) and two pHs (pCO2 of 400 and 1000 ppm), both individually and in combination, for a period of 90 days. The hypothesis that increased temperature will increase meiofaunal abundance was not supported. The hypothesis that a reduced pH will reduce meiofaunal abundance and species richness was supported. The combination of future conditions of temperature and pH (19 °C and pCO2 of 1000 ppm) did not affect overall abundance but the structure of the nematode assemblage changed becoming dominated by a few opportunistic species.
Palabras claves: Meiofauna, Nematodes, Ocean warming, Ocean acidification, Microcosms, Chile
Microplastic sampling with the AVANI trawl compared to two neuston trawls in the Bay of Bengal and South Pacific
Eriksen, M., Liboiron, M., Kiessling, T., Charron, L., Alling, A., Lebreton, L., Richards, H., Roth, B., Ory, N.C., Hidalgo-Ruz, V., Meerhoff, E., Box, C., Cummins, A., & Thiel, M.
Many typical neuston trawls can only be used during relatively calm sea states and slow tow speeds. During two expeditions to the Bay of Bengal and the eastern South Pacific we investigated whether the new, high-speed AVANI trawl (All-purpose Velocity Accelerated Net Instrument) collects similar amounts and types of microplastics as two established scientific trawl designs, the manta trawl and the DiSalvo neuston net. Using a 335 μm net, the AVANI trawl can collect microplastics from the sea surface at speeds up to 8 knots as it “skis” across the surface, whereas the manta and DiSalvo neuston trawls must be towed slowly in a less turbulent sea state and often represent shorter tow lengths. Generally, the AVANI trawl collected a greater numerical abundance and weight of plastic particles in most size classes and debris types than the manta trawl and DiSalvo neuston net, likely because these trawls only skim the surface layer while the AVANI trawl, moving vertically in a random fashion, collects a “deeper” sample, capturing the few plastics that float slightly lower in the water column. However, the samples did not differ enough that results were significantly affected, suggesting that studies done with these different trawls are comparable. The advantage of the AVANI trawl over traditional research trawls is that it allows for collection on vessels underway at high speeds and during long transits, allowing for a nearly continuous sampling effort over long distances. As local surface currents make sea surface abundance widely heterogeneous, widely spaced short-tow trawls, such as the manta and DiSalvo trawls, can catch or miss hotspots or meso-scale variability of microplastic accumulations, whereas the AVANI trawl, if utilized for back-to-back tows of intermediate distances (5–10 km), can bridge variable wind conditions and debris concentrations potentially reducing variance and provide a greater resolution of spatial distribution.
Palabras claves: Plastic pollution, Marine debris, Microplastics, Bay of Bengal, South Pacific Gyre, Trawl comparison, Validation, Neuston trawls, AVANI trawl
Interactions between kelp spores and encrusting and articulated corallines: recruitment challenges for Lessonia spicata
Parada, G. M., Martínez, E. A., Aguilera, M. A., Oróstica, M. H., & Broitman, B. R.
Intertidal kelps like Lessonia spicata (Laminariales) dominate low intertidal habitats, where they coexist with morphologically diverse coralline seaweeds. We show that crustose and articulated coralline algae have contrasting effects on the settlement and recruitment of this kelp species. Crustose coralline algae significantly inhibited the settlement of kelp spores, while they readily settled on the genicula of articulated coralline algae. This pattern was observed both in laboratory experiments and in field experiments conducted in the low intertidal zone at three locations. Field surveys confirmed that L. spicata juveniles were significantly more likely to be found on articulated corallines than on crustose corallines. This pattern held in field surveys at 10 sites, where primary space occupancy of L. spicata showed a significant negative correlation with the cover of crustose coralline algae in 3 out of 4 years, across all sites. Our results provide an important ecological clue to the processes determining recruitment limitation for ecologically and economically important seaweeds, and support conservation and management actions.
Palabras claves: Facilitation; Intertidal kelps; Seaweed interactions; Spore settlement
Benthic communities under anthropogenic pressure show resilience across the Quaternary
Martinelli, J. C., Soto, L. P., González, J., & Rivadeneira, M. M.
The Southeast Pacific is characterized by rich upwelling systems that have sustained and been impacted by human groups for at least 12 ka. Recent fishing and aquaculture practices have put a strain on productive coastal ecosystems from Tongoy Bay, in north-central Chile. We use a temporal baseline to determine whether potential changes to community structure and composition over time are due to anthropogenic factors, natural climatic variations or both. We compiled a database (n = 33 194) with mollusc species abundances from the Mid-Pleistocene, Late Pleistocene, Holocene, dead shell assemblages and live-sampled communities. Species richness was not significantly different, neither were diversity and evenness indices nor rank abundance distributions. There is, however, an increase in relative abundance for the cultured scallop Argopecten, while the previously dominant clam Mulinia is locally very rare. Results suggest that impacts from both natural and anthropogenic stressors need to be better understood if benthic resources are to be preserved. These findings provide the first Pleistocene temporal baseline for the south Pacific that shows that this highly productive system has had the ability to recover from past alterations, suggesting that if monitoring and management practices continue to be implemented, moderately exploited communities from today have hopes for recovery.
Palabras claves: Conservation palaeobiology, Molluscs, Aquaculture, Overfishing, Temporal baseline, South Pacific
Development and characterization of the first 16 microsatellites loci for Panulirus pascuensis (Decapoda: Palinuridae) from Easter Island using Next Generation Sequencing
Díaz-Cabrera, E., Meerhoff, E., Rojas-Hernandez, N., Vega-Retter, C., & Veliz, D.
The spiny lobster Panulirus pascuensis stands out among the endemic species of Easter Island, due to its cultural and economic importance. A total of 16 microsatellite loci were characterized in 18 individuals, 9 of which were polymorphic. The mean number of alleles per locus was 3.44 (2-6) and the observed heterozygosity ranged from 0.11 to 0.93. None of the loci exhibited significant linkage disequilibrium or departures from HWE. These new microsatellites will be used to obtain information about migration, population structure and genetic diversity of P. pascuensis in order to improve the future sustainable management and conservation plans.
Palabras claves: Panulirus pascuensis, Easter Island, Microsatellite, Genetic marker
Characterizing stream‐aquifer exchanges with self‐potential measurements
Valois, R., Cousquer, Y., Schmutz, M., Pryet, A., Delbart, C., & Dupuy, A.
Characterizing the interactions between streams and aquifers is a major challenge in hydrology. Electrical self‐potential (SP) is sensitive to groundwater flow through the electrokinetic effect, which is proportional to Darcy velocity. SP surveys have been extensively used for the characterization of seepage flow in a variety of contexts. But to our knowledge, a model coupling SP and groundwater flow has never been implemented for the study of stream‐aquifer interactions. To address the issue, we first implemented a two‐dimensional model to a synthetic stream‐aquifer cross section. Results underline the very distinct nature of SP profiles in gaining or losing stream conditions. Second, we presented a field application in a transect crossing a stream in losing conditions. The coupled model successfully reproduced the observed SP profile. This inverse modeling of the SP signal provides quantitative data on hydrodynamic parameters (hydraulic conductivity, hydraulic heads) and geophysical parameters (coupling coefficient). Nevertheless, all relevant parameters cannot be uniquely estimated without precise prior information on at least some of these parameters. Our results confirm the potential of SP surveys on the characterization of stream‐aquifer exchanges. Recommendations on the collection of high‐quality data are also provided, along with a description of the contexts in which the methodology is likely to perform well.
First insight into the heritable variation of the resistance to infection with the bacteria causing the withering syndrome disease in Haliotis rufescens abalone
Brokordt, K., González, R., Farías, W., Winkler, F. E., & Lohrmann, K. B.
Withering syndrome disease has experienced worldwide spread in the last decade. This fatal disease for abalone is produced by a rickettsia-like organism (WS-RLO), the bacterium “Candidatus Xenohaliotis californiensis”. To evaluate the potential of the red abalone (Haliotis rufescens) to improve its resistance to infection by WS-RLO, the additive genetic component in the variation of this trait was estimated. For this, the variation in infection intensity with WS-RLOs and WS-RLOv (phage-infected RLOs) was analyzed in 56 families of full-sibs maintained for three years in a host-parasite cohabitation aquaculture system. A WS-RLO prevalence of 65% was observed in the analysed population; and from the total WS-RLO inclusions 60% were hyperparasited with the phage (WS-RLOv). The decrease in the food ingestion rate was the sole negative effect associated with increasing WS-RLO intensity of infection, suggesting that the high level of WS-RLOv load may have diminished the symptoms of WS disease in the analyzed abalones. The estimated heritabilities were moderate to mid, but significant, varying from 0.21 to 0.23 and 0.36 for WS-RLO and WS-RLOv infections, respectively. This suggests that variation in resistance to infection with WS-RLO may respond to selection in the evaluated red abalone population. Estimated response to selection (G) for the level of infection by WS-RLO indicated that if the 10% of red abalone with the lowest infection level is selected as broodstock, a 90% reduction in the intensity of infection in the progeny can be expected, even with the lowest estimation of heritability (h2 = 0.21). This strong response would be also due to the large phenotypic variance of this trait. Strong positive correlations, both phenotypic and genotypic, were observed between infection intensities with WS-RLO and WS-RLOv, indicating that selection to increase resistance to one of the types of RLOs will affect resistance in the other in the same direction. This is the first study that demonstrates the existence of additive genetic variation for resistance to WS-RLO in abalone. Consequently, it is possible to increase the resistance to WS-RLO in H. rufescens by selective breeding, which can be an economically attractive and environmentally friendly manner to reduce mortalities and growth effects caused by WS in abalone farms.
Palabras claves: Withering syndrome, Heritability, WS-RLO infection, Phage-infected WS-RLOs, Disease resistance, Abalone | <urn:uuid:aec722f3-0c4d-41b1-b582-7d49d2f245d0> | 2.734375 | 4,102 | Content Listing | Science & Tech. | 28.003502 | 95,607,265 |
Sockets in Java
A “socket” is an end point in a communication link between separate processes. In Java, sockets are objects which provide a way of exchanging information between two processes in a straightforward and platform-independent manner (see the classes in the java.net package). In fact, sockets in Java are very straightforward, as you will see in this chapter.
KeywordsHash Table Server Application Input Stream Client Application Port Number
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- Parker, T. (1994) Teach Yourself TCP/IP in 14 Days. Sams Publishing, Indianapolis.Google Scholar | <urn:uuid:f94f8c95-c732-4255-b09b-79e2577a2458> | 3.453125 | 126 | Truncated | Software Dev. | 49.888602 | 95,607,270 |
We have already introduced pointers as one of the scalar data types. In this chapter, we examine pointers more closely and introduce an aggregate type called an array. Arrays and pointers are closely related in C. Together, they represent some of the most powerful features of the C language and probably account, as much as anything, for C’s popularity.
KeywordsNull Pointer Dictionary Entry Input String Initial Element Multidimensional Array
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Application of Personal Computers to Lagrangian Modeling in Complex Terrain
Personal computers are now capable of solving complex problems related to the transport and diffusion of materials released into the atmosphere. Making such calculations rapidly and “on the spot” would be of great use in planning evacuations and cleanup activities when toxic materials are spilled as the result of some accident. It would be desirable if such calculations were not limited to the simple, steady-state assumptions usually required for such applications. A more realistic simulation, accounting for wind fields which change in space and time and variations in the meteorological conditions would be better. As personal micro-computers become ever more readily available, it is no longer unreasonable to believe that these capabilities could be supplied relatively cheaply. Mass- produced personal computers are already relatively inexpensive. In fact, their cost is, on an equivalent basis, less than that of the mechanical desk calculator of 20 years ago. Personal computers are becoming more powerful every year. However, they have limitations in the amount of core storage that is available and in their speed, so their use requires careful programming and some simplifications of the theory.
KeywordsWind Field Complex Terrain Source Strength LAGRANGIAN Modeling Potential Wind Energy
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- Ludwig, F.L., 1982, Effect of a change of atmospheric stability on the growth rate of puffs used in plume simulation models, J. Appl. Meteorol., 21 (in press).Google Scholar | <urn:uuid:0ee279fb-21a8-4e87-83e0-79b72d6328a8> | 2.875 | 305 | Truncated | Science & Tech. | 26.9561 | 95,607,274 |
New Study Sheds Light on How Cells Transport Materials Along Crowded Intercellular 'Highways'
News Feb 06, 2013
The interior of an animal cell is like a small city, with factories—called organelles—dedicated to manufacturing, energy production, waste processing, and other life functions. A network of intercellular "highways," called microtubules, enables bio-molecular complexes, products, and other cargo to move speedily about the cell to keep this vital machinery humming. A new paper published online in the journal Proceedings of the National Academy of Sciences sheds new light on how cells manage to keep traffic flowing smoothly along this busy transportation network that is vital to the survival of cells and whose failure can lead to a variety of diseases, including Alzheimer's and cancer.
The study, "Motor transport of self-assembled cargos in crowded environments" (http://www.pnas.org/content/early/2012/11/28/1209304109.abstract), is co-authored by Jennifer Ross, assistant professor of physics at the University of Massachusetts Amherst, Erkan Tüzel, assistant professor of physics at Worcester Polytechnic Institute (WPI), and Leslie Conway and Derek Wood, graduate students of physics at UMass Amherst. It examines how proteins called motors (the trucks of the intercellular transport network) cooperate to minimize traffic jams and maximize the distance traveled by cargos.
In the study, the researchers used quantum dots (nanometer-sized semiconductors that reflect brightly in microscopy images) as cargo. In the laboratory, they attached these tiny cargos to individual motor proteins and then allowed those proteins to attach to a microtubule. Motor proteins are able to "walk" along microtubules by attaching and detaching parts of their structure to the microtubule, much like the hand-over-hand motion of a person climbing a rope. The researchers observed how the quantum dots moved along the microtubule as they created more and more traffic by adding more and more motor proteins to the highways of this simplified transportation system.
They found that the dots moved more slowly as the traffic increased, but that they were able to travel farther before becoming detached from the microtubule. They also observed the pausing of the quantum dots, with the number of pauses increasing, but the length of the pauses decreasing, as the concentration of motor proteins is increased. The authors hypothesize that as the concentration of motor proteins increased, several of them became bound to each quantum dot. Much like trucks driving side-by-side down a multilane highway, the motor proteins likely became attached to different protofilaments along the microtubule (microtubules are made of 13 parallel protofilaments arranged into a hollow tube).
As an individual protein encountered an obstacle (another motor protein, for example), the motion of the dot would pause until the force exerted by the other proteins attached to the dot caused it to become detached from the blocked protein. The greater the number of proteins pulling the dot along the microtubule, the greater the force acting on it and the more quickly it would become detached from blocked proteins (and thus, the briefer the pauses in its forward motion).
In this way, motor proteins were able to cooperate to move cargo around roadblocks and to keep cargo attached to the microtubules despite heavy traffic, Tüzel says. "This is the first study to really look at the operation of the intracellular transportation system crowded conditions that are typical of living cells," he noted.
"It is important to understand how this system works and what can keep it from functioning properly because it is vital to the survival of all animal cells and motor proteins that make many fundamental biological processes, such as cell division, possible," he adds. "When the transport mechanism fails to work properly, it can lead to a variety of illnesses, including neurodegenerative diseases like Huntington's and Alzheimer's, and to cancer."
Electron Microscope Detector Achieves Record ResolutionNews
Like driving at night and being able to read the license plate of an oncoming car without being blinded by the lights.READ MORE
NIH Clinical Center Releases Data Trove of 32,000 CT ImagesNews
The National Institutes of Health’s Clinical Center has made a large-scale dataset of CT images publicly available to help the scientific community improve detection accuracy of lesions. While most publicly available medical image datasets have less than a thousand lesions, this dataset, named DeepLesion, has over 32,000.
Enabling Technology in Cell-Based Therapies: Scale-Up, Scale-Out or Program In-PlaceNews
Technologies are reducing costs and changing the ways in which researchers and clinicians process and use therapeutic cells. Two new review articles detail the status of cell bioreactors in both stem cell and tissue/organ engineering applications.READ MORE
15th International Conference and Exhibition on Metabolomics & Systems
Apr 29 - Apr 30, 2019 | <urn:uuid:4386544c-91ac-4a2b-a862-5ebf3b34db4e> | 3.59375 | 1,032 | News Article | Science & Tech. | 20.947553 | 95,607,280 |
Plate tectonic theory teaches that the Earth is divided into layers called crust, mantle and core, with continents and ocean basins made of different kinds of crust. The surface is made up of gigantic plates that move about very slowly; however, this movement does not stop at the bottom of the crust. Instead, it stops at a zone within the mantle. The rocks above this zone, including the crust and the upper part of the mantle, are called lithosphere.
Layers of the Earth
The Earth is made up of four main layers. At the surface is a thin, cool layer of highly varied rocks that make up the crust, with an average thickness of about 30 kilometers (18.6 miles). The mantle forms a layer of silicate minerals about 2,900 kilometers (1,800 miles) thick beneath the crust. At the center is the core, which is actually two layers: an outer core of molten metal about 2,250 kilometers (1,400 miles) thick and a solid metal core with a radius of about 1,220 kilometers (800 miles). Both solid and liquid core are mostly iron plus nickel, sulfur and small amounts of other elements.
The mantle accounts for about 84 percent of the Earth's volume, and the crust makes up another 1 percent. The core occupies the other 15 percent.
Upper Mantle, Lithosphere and Asthenosphere
Earth scientists divide the mantle into upper and lower mantle, placing the boundary at about 670 kilometers (416 miles) deep. They divide the uppermost few tens of kilometers of the mantle into two parts based on how the rocks behave when stress is applied, meaning when they are pushed or pulled. The very topmost layer of the mantle tends to break when stress is applied, while the layer just beneath it is soft enough to bend. Breaking is called "brittle" deformation: A breaking pencil is brittle deformation. The lower layer reacts to stress with "ductile" or "plastic" deformation, like a tube of toothpaste or a lump of modeling clay.
Scientists call the part of the upper mantle that displays plastic deformation the asthenosphere and call the combination of crust and shallower, more brittle mantle the lithosphere. The boundary between the two layers ranges from a few kilometers below the surface at oceanic spreading centers to about 70 kilometers (44 miles) under the centers of continents.
Temperature of the Earth's Interior
Scientists estimate that the solid nickel-iron alloy at the center of the Earth has a temperature in the range of 5,000 to 7,000 degrees Celsius (about 9,000 to 13,000 degrees Fahrenheit). The outer, liquid core is cooler; but the bottom of the mantle is still subjected to temperatures of around 4,000 to 5,000 degrees Celsius (7,200 to 9,000 degrees Fahrenheit). This temperature is more than hot enough to melt the mantle rocks, but the very high pressures keep them from turning to liquid. Instead, the hottest mantle rocks rise very, very slowly toward the surface. At the same time, the coolest rocks in the upper mantle sink toward the core. This constant motion creates super-slow currents circulating within the mantle.
Asthenosphere, Lithosphere and Plate Tectonics
Rocks in the lithosphere remain solid, floating on top of the mushy or partially melted rocks in the asthenosphere. The bottoms of the tectonic plates are at the boundary between asthenosphere and lithosphere, not the bottom of the crust, and it is the plastic nature of the asthenosphere that allows the tectonic plates to move.
Temperature of the Lithosphere
The lithosphere does not have a specific temperature. Instead, the temperature varies with depth and location. At the surface, the temperature is similar to the average air temperature at the location. The temperature increases with depth down to the top of the asthenosphere, where the temperature is about 1,280 degrees Celsius (2,336 degrees Fahrenheit).
The rate of change in temperature with depth is called the geothermal gradient. The gradient is higher -- temperature increases more rapidly with depth -- in ocean basins where the lithosphere is thin. Over continents, the gradient is low because the crust and lithosphere are thick. | <urn:uuid:5a1f7095-793f-4b62-9fac-72b937e8b2d3> | 4.4375 | 867 | Knowledge Article | Science & Tech. | 48.19886 | 95,607,292 |
Astronomers using the National Science Foundation’s Green Bank Telescope (GBT) -- among other telescopes -- have determined that our own Milky Way galaxy is part of a newly identified ginormous supercluster of galaxies, which they have dubbed “Laniakea,” which means “immense heaven” in Hawaiian.
This discovery clarifies the boundaries of our galactic neighborhood and establishes previously unrecognized linkages among various galaxy clusters in the local Universe.
Credit: SDvision interactive visualization software by DP at CEA/Saclay, France.
A slice of the Laniakea Supercluster in the supergalactic equatorial plane -- an imaginary plane containing many of the most massive clusters in this structure. The colors represent density within this slice, with red for high densities and blue for voids -- areas with relatively little matter. Individual galaxies are shown as white dots. Velocity flow streams within the region gravitationally dominated by Laniakea are shown in white, while dark blue flow lines are away from the Laniakea local basin of attraction. The orange contour encloses the outer limits of these streams, a diameter of about 160 Mpc. This region contains the mass of about 100 million billion suns.
“We have finally established the contours that define the supercluster of galaxies we can call home,” said lead researcher R. Brent Tully, an astronomer at the University of Hawaii at Manoa. “This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations.”
The paper explaining this work is the cover story of the September 4 issue of the journal Nature.
Superclusters are among the largest structures in the known Universe. They are made up of groups, like our own Local Group, that contain dozens of galaxies, and massive clusters that contain hundreds of galaxies, all interconnected in a web of filaments. Though these structures are interconnected, they have poorly defined boundaries.
To better refine cosmic mapmaking, the researchers are proposing a new way to evaluate these large-scale galaxy structures by examining their impact on the motions of galaxies. A galaxy between structures will be caught in a gravitational tug-of-war in which the balance of the gravitational forces from the surrounding large-scale structures determines the galaxy’s motion.
By using the GBT and other radio telescopes to map the velocities of galaxies throughout our local Universe, the team was able to define the region of space where each supercluster dominates. “Green Bank Telescope observations have played a significant role in the research leading to this new understanding of the limits and relationships among a number of superclusters,” said Tully.
The Milky Way resides in the outskirts of one such supercluster, whose extent has for the first time been carefully mapped using these new techniques. This so-called Laniakea Supercluster is 500 million light-years in diameter and contains the mass of one hundred million billion Suns spread across 100,000 galaxies.
This study also clarifies the role of the Great Attractor, a gravitational focal point in intergalactic space that influences the motion of our Local Group of galaxies and other galaxy clusters.
Within the boundaries of the Laniakea Supercluster, galaxy motions are directed inward, in the same way that water streams follow descending paths toward a valley. The Great Attractor region is a large flat bottom gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.
The name Laniakea was suggested by Nawa‘a Napoleon, an associate professor of Hawaiian Language and chair of the Department of Languages, Linguistics, and Literature at Kapiolani Community College, a part of the University of Hawaii system. The name honors Polynesian navigators who used knowledge of the heavens to voyage across the immensity of the Pacific Ocean.
The other authors are Hélène Courtois (University Claude Bernard Lyon 1, Lyon, France), Yehuda Hoffman (Racah Institute of Physics, Hebrew University, Jerusalem), and Daniel Pomarède (Institute of Research on Fundamental Laws of the Universe, CEA/Saclay, France).
The GBT is the world's largest fully steerable radio telescope. Its location in the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone protects the incredibly sensitive telescope from unwanted radio interference.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
Founded in 1967, the Institute for Astronomy at the University of Hawaii at Manoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Maunakea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaii.
Charles Blue | newswise
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 | Life Sciences
16.07.2018 | Earth Sciences
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The Dutch Ministers of Economical Affairs and of Education, Culture and Science have announced the mission name of the next Soyuz flight to the International Space Station, which has Dutch ESA astronaut André Kuipers serving as flight engineer. This mission has been christened DELTA.
Flanked by Kuipers and ESAs Director of Human Spaceflight, Mr Jörg Feustel-Büechl, on Tuesday Ministers Brinkhorst and Van der Hoeven unveiled the mission logo and also announced the experiments to be performed by Kuipers during his stay on board the International Space Station (ISS).
Kuipers will launch on a Russian Soyuz spacecraft in April 2004 to spend more than a week on ISS. While there he will carry out an extensive programme of scientific, technological and educational experiments as part of the DELTA mission. These experiments are sponsored by Dutch Ministries and therefore have a Dutch character.
| European Space Agency
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:c4478122-be5c-4231-9bcd-be8745b1b853> | 2.75 | 826 | Content Listing | Science & Tech. | 39.039403 | 95,607,312 |
If fishing around the world continues at its present pace, more and more species will vanish, marine ecosystems will unravel and there will be "global collapse" of all species currently fished, possibly as soon as midcentury, fisheries experts and ecologists are predicting.
The scientists, who report their findings Friday in the journal Science, say it is not too late to turn the situation around. As long as marine ecosystems are still biologically diverse, they can recover quickly once overfishing and other threats are reduced, the researchers say.
But they add that there must be quick, large-scale action to protect remaining diversity, including establishment of marine reserves and "no take" zones, along with restrictions on particularly destructive fishing practices.
The researchers drew their conclusion after analyzing dozens of studies and fishing data collected by the United Nations Food and Agricultural Organization and other sources. They acknowledge that much of what they are reporting amounts to correlation, rather than proven cause and effect.
And the UN agency data have come under criticism from researchers who doubt the reliability of some nations' reporting practices, said Boris Worm, a fisheries expert at Dalhousie University in Nova Scotia, who led the work.Continue reading the main story
Still, he said in an interview, "there is not a piece of evidence" that contradicts the dire conclusions.
Jane Lubchenco, a fisheries expert at Oregon State University who had no connection with the work, called the report "compelling."
"It's a meta analysis and there are challenges in interpreting those," she said in an interview, referring to the technique of analyzing a host of previous studies. "But when you get the same patterns over and over and over, that tells you something."
Twelve scientists from the United States, Canada, Sweden and Panama contributed to the work.
"We extracted all data on fish and invertebrate catches from 1950 to 2003 within all 64 large marine ecosystems worldwide," they wrote. "Collectively, these areas produced 83 percent of global fisheries yields over the past 50 years."
In an interview, Worm said, "We looked at absolutely everything - all the fish, shellfish, invertebrates, everything that people consume that comes from the ocean, all of it, globally."
The researchers found that 29 percent of species had already been fished so heavily or were so affected by pollution or habitat loss that they were down to 10 percent of previous levels, a situation the scientists called collapse.
This loss of biodiversity seems to restrict the ability of marine ecosystems as a whole to recover from overfishing, Worm said. That results in an acceleration of environmental decay.
Worm said he analyzed the data for the first time on his laptop. What he saw, he said, was "just a smooth line going down." And when he extrapolated the data into the future "to see where it ends at 100 percent collapse, you arrive at 2048."
"The hair stood up on the back of my neck and I said, 'This cannot be true,'" he recalled. So he ran the data through his computer again. And then he did calculations by hand. The results were the same.Continue reading the main story | <urn:uuid:a121de58-0c22-415a-9854-88826569a3ef> | 3.421875 | 645 | Truncated | Science & Tech. | 36.703348 | 95,607,330 |
Occurrence, Electronic Configuration, Atomic and Ionic Radii, Ionisation Enthalpy, Electron Gain Enthalpy, Electronegativity, Physical Properties and Chemical Properties (Oxidation states and trends in chemical reactivity and Anomalous behaviour of oxygen)
- P Block part 28 (Reaction with hydrogen and oxygen)
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- P Block part 26 (Group 16 trends)
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- P Block part 27 (Oxygen)
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- P Block part 24 (Group 16, oxygen family introduction)
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- P Block part 29 (Reaction with halogens and numerical)
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- P Block part 25 (Group 16 trends)
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- P Block part 38 (Numericals)
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The HNH angle value is higher than HPH, HAsH and HSbH angles. Why? [Hint: Can be explained on the basis of sp3 hybridisation in NH3 and only s−p bonding between hydrogen and other elements of the group].
Account for the following : There is large difference between the melting and boiling points of oxygen and sulphur.
Give reasons for the following : Oxygen has less electron gain enthalpy with negative sign than sulphur.
Arrange the following in the order of property indicated for each set:
F2, Cl2, Br2, I2 - increasing bond dissociation enthalpy.
Explain why inspite of nearly the same electronegativity, oxygen forms hydrogen bonding while chlorine does not.
Give reasons for the following : H2Te is the strongest reducing agent amongst all the hydrides of Group 16 elements.
Knowing the electron gain enthalpy values for O → O− and O → O2− as −141 and 702 kJ mol−1 respectively, how can you account for the formation of a large number of oxides having O2− species and not O−? (Hint: Consider lattice energy factor in the formation of compounds).
Justify the placement of O, S, Se, Te and Po in the same group of the periodic table in terms of electronic configuration, oxidation state and hydride formation. | <urn:uuid:e7d1bc95-e4cf-4abf-a97b-2a8c58d95708> | 3.390625 | 506 | Content Listing | Science & Tech. | 34.280852 | 95,607,332 |
ESA - Hubble Space Telescope logo.
28 May 2015
Large Hubble survey confirms link between mergers and supermassive black holes with relativistic jets
Image above: Artist’s illustration of galaxy with jets from a supermassive black hole
Galaxies with relativistic jets.
In the most extensive survey of its kind ever conducted, a team of scientists have found an unambiguous link between the presence of supermassive black holes that power high-speed, radio-signal-emitting jets and the merger history of their host galaxies. Almost all of the galaxies hosting these jets were found to be merging with another galaxy, or to have done so recently. The results lend significant weight to the case for jets being the result of merging black holes and will be presented in the Astrophysical Journal.
Galaxies with relativistic jets
A team of astronomers using the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 (WFC3) have conducted a large survey to investigate the relationship between galaxies that have undergone mergers and the activity of the supermassive black holes at their cores.
Radio galaxy 3C 297
The team studied a large selection of galaxies with extremely luminous centres — known as active galactic nuclei (AGNs) — thought to be the result of large quantities of heated matter circling around and being consumed by a supermassive black hole. Whilst most galaxies are thought to host a supermassive black hole, only a small percentage of them are this luminous and fewer still go one step further and form what are known as relativistic jets . The two high-speed jets of plasma move almost with the speed of light and stream out in opposite directions at right angles to the disc of matter surrounding the black hole, extending thousands of light-years into space. The hot material within the jets is also the origin of radio waves.
Radio galaxy 3C 454.1
It is these jets that Marco Chiaberge from the Space Telescope Science Institute, USA (also affiliated with Johns Hopkins University, USA and INAF-IRA, Italy) and his team hoped to confirm were the result of galactic mergers .
The team inspected five categories of galaxies for visible signs of recent or ongoing mergers — two types of galaxies with jets, two types of galaxies that had luminous cores but no jets, and a set of regular inactive galaxies .
Radio galaxy 3C 356
“The galaxies that host these relativistic jets give out large amounts of radiation at radio wavelengths,” explains Marco. “By using Hubble’s WFC3 camera we found that almost all of the galaxies with large amounts of radio emission, implying the presence of jets, were associated with mergers. However, it was not only the galaxies containing jets that showed evidence of mergers!” .
“We found that most merger events in themselves do not actually result in the creation of AGNs with powerful radio emission,” added co-author Roberto Gilli from Osservatorio Astronomico di Bologna, Italy. “About 40% of the other galaxies we looked at had also experienced a merger and yet had failed to produce the spectacular radio emissions and jets of their counterparts.”
Artist’s animation of galaxy with jets from a supermassive black hole
Although it is now clear that a galactic merger is almost certainly necessary for a galaxy to host a supermassive black hole with relativistic jets, the team deduce that there must be additional conditions which need to be met. They speculate that the collision of one galaxy with another produces a supermassive black hole with jets when the central black hole is spinning faster — possibly as a result of meeting another black hole of a similar mass — as the excess energy extracted from the black hole’s rotation would power the jets.
Fulldome clip showing animation of galaxy with jets from a supermassive black hole
“There are two ways in which mergers are likely to affect the central black hole. The first would be an increase in the amount of gas being driven towards the galaxy’s centre, adding mass to both the black hole and the disc of matter around it,” explains Colin Norman, co-author of the paper. “But this process should affect black holes in all merging galaxies, and yet not all merging galaxies with black holes end up with jets, so it is not enough to explain how these jets come about. The other possibility is that a merger between two massive galaxies causes two black holes of a similar mass to also merge. It could be that a particular breed of merger between two black holes produces a single spinning supermassive black hole, accounting for the production of jets.”
Future observations using both Hubble and ESO’s Atacama Large Millimeter/submillimeter Array (ALMA) are needed to expand the survey set even further and continue to shed light on these complex and powerful processes.
Relativistic jets travel at close to the speed of light, making them one of the fastest astronomical objects known.
The new observations used in this research were taken in collaboration with the 3CR-HST team. This international team of astronomers is currently led by Marco Chiaberge and has conducted a series of surveys of radio galaxies and quasars from the 3CR catalogue using the Hubble Space Telescope.
The team compared their observations with the swathes of archival data from Hubble. They directly surveyed twelve very distant radio galaxies and compared the results with data from a large number of galaxies observed during other observing programmes.
Other studies had shown a strong relationship between the merger history of a galaxy and the high levels of radiation at radio wavelengths that suggests the presence of relativistic jets lurking at the galaxy’s centre. However, this survey is much more extensive, and the results very clear, meaning it can now be said with almost certainty that radio-loud AGNs, that is, galaxies with relativistic jets, are the result of galactic mergers.
Notes for editors
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The international team of astronomers in this study consists of Marco Chiaberge (STScI, USA; Johns Hopkins University, USA; and INAF-IRA, Italy), Roberto Gilli (INAF Osservatorio Astronomico di Bologna, Italy), Jennifer Lotz (STScI, USA) and Colin Norman (Johns Hopkins University, USA; and STScI, USA).
Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/
Link to science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1511a.pdf
Images, Videos, Text, Credits: NASA/ESA/Hubble, L. Calçada (ESO)/M. Chiaberge (STScI). | <urn:uuid:d323b7fc-0b78-462e-b5d5-be643f2e429d> | 3.28125 | 1,431 | News (Org.) | Science & Tech. | 31.91303 | 95,607,337 |
In the course of its brilliant evolution through the twentieth century, space science brought spectacular results and led to fundamental scientific findings. In the early quest for higher altitude, cosmic rays were discovered by Viktor Hess during a balloon flight in 1912. Following the second World War, sounding rockets were used, starting in 1946, to study the structure of the terrestrial atmosphere -the threshold of space. Two landmarks of the space age stand out: the launch in 1957 of the first satellite, Sputnik 1, which sensed the near-Earth environment at orbital altitude, and in 1969 the first landing by humans on an extraterrestrial body, the Moon. Today, sophisticated space probes explore distant worlds, and space telescopes look back in time towards the early Universe.
KeywordsBlack Hole Solar System Hubble Space Telescope Terrestrial Planet Space Science
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Leatherback Sea TurtleLatin name: Dermochelys Coriacea,
Conservsation status: vulnerable (population is decreasing)
The largest of all sea turtles, the Leatherback has been on Earth since the dinosaurs—100 million years. It can grow over six feet long, weigh up to one ton, and dive over 3,000 feet—deeper than any other turtle.
Climate change impacts the Leatherback in two main ways: an increase in the temperature of nesting sands causes a greater proportion of females to hatch, destabilizing future populations; and sea level rise and stronger, more frequent storms erode nesting beaches and wash away eggs and hatchlings. The Leatherback is also threatened from fisheries by-catch, egg collection, coastal development, pollution and ingestion of floating plastics.
Other animals at risk
Koalas live in the woodlands of Australia. Thick fur and skin make it difficult for them to adapt to rising temperatures. Increased CO2 in the air produces less protein in the eucalyptus leaves, forcing the Koala to search for other sources of food and, in times of high heat, water. On the ground, the slow moving Koalas are prey to wild dingoes and domestic dogs, or are hit by cars as they cross roads. Their habitats are also being destroyed by drought, bush fires and development.
Clownfish live in the shallow waters of coral reefs where they have a mutually beneficial relation with a few species of sea anemone. The anenome protects the Clownfish, and the fish's swimming aerates the water around the anenome. Clownfish are unable to move long distances, and rising ocean temperature and acidity is a threat to their coral reef habitats. Increased acidity also seems to impair their ability to navigate to their home anemones.
Since 1960, the average summer temperature in Glacier National Park has increased by around 1 °C and glaciers have declined by 35%. By counting Stoneflies, scientists can determine how quickly glaciers are melting and the temperature of streams. In a two year search begun in 2011, scientists found the Stonefly in only one of the six streams it had previously occupied and discovered that it had retreated to two different streams at higher altitudes. Satellite data confirm that the world’s glaciers are declining, affecting the availability of fresh water for humans, animals and plants, and contributing to sea level rise.
The Arctic tundra is a region of shrubs, grasses and permanently frozen subsoil. Warming could change the tundra to boreal forest—habitat for the Red Fox. The Red Fox, a predator and a competitor for food, is already beginning to migrate north into the Arctic Fox's territory. Milder tundra weather also causes changes in the population of lemmings and rodents—main food for the Arctic Fox. | <urn:uuid:fd988228-f9c8-4f87-84eb-3e36e36e6a3c> | 4.0625 | 585 | Knowledge Article | Science & Tech. | 39.385 | 95,607,379 |
Second law of thermodynamics
From AMS Glossary
second law of thermodynamics
An inequality that is fundamentally different from the first law because it specifies the direction in which a natural process will evolve rather than merely requiring that certain quantities are conserved.
As formulated by Planck, the second law asserts that a thermodynamic state function, S, known as entropy, exists for all physical systems. For the universe and for a system isolated from its surroundings,
Equality prevails only for reversible processes or when the system is in a steady state. When the universe of a system is a maximum, no further evolution of the system is possible. The second law is often asserted in other forms, including the following.
- No device can continuously deliver mechanical work and produce no effect other than cooling a reservoir.
- In the neighborhood of every state that can be reached reversibly, there exist states that cannot be reached by a reversible, adiabatic process, or, in other words, that can be reached only irreversibly or cannot be reached at all.
Dutton, J. A. 1995. Dynamics of Atmospheric Motion. Dover Press, . 45–51, 406–410.
Sommerfeld, A. 1964. Thermodynamics and Statistical Mechanics. Academic Press, . 26–36, 39. | <urn:uuid:6da65b65-2329-4ba7-b871-bdeaeb038d78> | 3.140625 | 271 | Structured Data | Science & Tech. | 42.008222 | 95,607,388 |
Although flow meters have been in use for years, up until recently were mostly mechanical devices. However, recent advances in electronic technology have given us the the Laser flowmeter
, (sometimes referred to as an Ultrasonic flow meter) which uses two laser beams to determine the velocity of small particles almost always present in liquids and industrial gases as they pass through the flowmeter. The two laser beams, which are focused across the flow a short distance apart, are scattered by particles crossing the the beams with the amount of scattering indicative of the speed of the flow Their accuracy comes from their speed not being dependent on thermal conductivity of gases, composition of the gases or minor variations in gas flow. Since these factors have little effect on Laser flow meters measurements are quite accurate and repeatable.
Please select a journal that you would like to view papers from during the time period that you have selected. | <urn:uuid:23c5c59c-19ab-4be4-b579-98b50e2ae2df> | 3.046875 | 177 | Truncated | Science & Tech. | 21.390752 | 95,607,393 |
In an earlier chapter we looked at how different C# programs running in different processes could communicate via sockets. This approach is relatively straightforward to use and exploits the widely adopted sockets communication model. However, C# offers another way of enabling programs to communicate -.NET Remoting. Indeed, Remoting is surprisingly simple to use and may well be preferable to sockets for.NET communication. This is because the resulting software is simpler and easier to maintain than using sockets. For example, a distributed software system resembles a soft-ware system executing within a single virtual machine except for the addition of one line to a client and two lines associated with a server!
KeywordsConfiguration File Uniform Resource Identifier Remoting System Server Object Remote Object
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The discovery involves a chemical known as an acetyl group. An estimated 85 percent of human proteins have this chemical added to the amino acid at one end of the protein. The addition comes in a process known as N-terminal acetylation. N-terminal acetylation occurs shortly after proteins are assembled. Although it has long been known that proteins are N-terminally acetylated, until now it was unknown how such acetylation could serve specific functions.
The findings came from scientists studying a system cells use to regulate the fate and function of proteins. The researchers showed that much like a key must fit precisely to work a lock, the acetylated end of one enzyme fits perfectly into a deep pocket on the surface of another protein. The connection helps accelerate the activity of a protein complex that is involved in regulating cell division and that has been linked to cancer. The research appears in the November 4 print edition of the journal Science.
The findings have potential implications for drug discovery and for understanding basic mechanisms governing the interaction of possibly thousands of proteins, said the study’s senior author, Brenda Schulman, Ph.D., a member of the St. Jude Department of Structural Biology and a Howard Hughes Medical Institute investigator.
“The work presents a major new concept in protein-protein interactions,” she said. “This raises the question of whether similar ‘keys’ on thousands of different proteins also unlock doors to allow them to function.”
The research offers the first view of how N-terminal acetylation mediates protein interactions, bringing proteins together to do the work of cells. “These findings raise the possibility that N-terminal acetylation plays an important role in the function of a large number of proteins in the cell,” said first author, Daniel Scott, Ph.D. a scientist in Schulman’s laboratory.
The pocket where N-terminally acetylated proteins bind may also be a good target for small molecules designed to block protein interactions that lead to many diseases, including cancers, Schulman said.
Schulman and her colleagues discovered the pivotal role N-terminal acetylation plays while studying interactions between the proteins Ubc12 and Dcn1. Other researchers have identified human Dcn1 as an oncogene that promotes some squamous cell head, neck and lung cancers.
The focus of the current study was the role the enzymes played in regulating activity of another complex, known as cullin-RING. The cullin-RING complex is the command center of a tagging system that cells use to modify a protein’s function or to mark a protein for degradation. The cullin-RING targeted proteins include those that control such important biological processes as cell division and the immune response.
Dcn1 is bound to the cullin protein. In previous studies, Schulman and her colleagues showed that in yeast the Ubc12 and Dcn1 interaction led Ubc12 to transfer its cargo, a protein called NEDD8, to cullin. That step dramatically accelerated the activity of cullin-RING.
But a major question was how human Dcn1 and Ubc12 interact. The breakthrough came when the researchers realized that Ubc12 is among the 35 to 50 percent of proteins in which methionine is the amino acid involved in N-terminal acetylation. The investigators used a variety of laboratory techniques to demonstrate that the acetylated methionine of Ubc12 was essential to the Ubc12-Dcn1 interaction. Evidence included an X-ray image that shows Ubc12’s acetyl-methionine buried in a pocket on the surface of Dcn1.
“The size and shape of the pocket indicate it might be a completely new route to generating small- molecule inhibitors,” Schulman said. Pharmaceutical companies are already targeting other parts of the same NEDD8 pathway, and one experimental drug has entered clinical trials.
Not only does Ubc12’s acetylated tail fit perfectly into the pocket, but acetylation solved another problem that would have made the interaction of Ubc12 and Dcn1 difficult. Without acetylation, Ubc12 and the Dcn1 pocket would repel each other much like oil and water. Acetylation neutralizes the charge on Ubc12, allowing the interaction to occur, Schulman said.
Other authors are Julie Monda of St. Jude; J. Wade Harper of Harvard Medical School; and Eric Bennett, formerly of Harvard Medical School and now at University of California, San Diego.
The research was funded in part by the National Institutes of Health, Howard Hughes Medical Institute, Millennium Pharmaceuticals, Damon Runyon Cancer Research Foundation and ALSAC.St. Jude Children’s Research Hospital
Summer Freeman | Newswise Science News
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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12.07.2018 | Event News
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16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:d5d5156f-904e-43b7-90a5-2791d15cc18b> | 2.984375 | 1,657 | Content Listing | Science & Tech. | 39.644577 | 95,607,413 |
In 1972, NASA and the US Geological Survey (USGS) launched a new satellite program "aimed at gathering facts about the natural resources of the Earth."
By 2013, the programme was made up of eight satellites, collecting millions of images and documenting decades of global change.
With nearly 30 million Landsat scenes downloaded altogether, a 2014 White House-led assessment concluded that the Landsat programme was one of the most critical Earth observing systems in the US, second only to GPS and weather.
The data has been used by scientists from around the world to monitor water quality, glacier recession, coral reef health, land use change, deforestation rates, and population growth.
For the past ten years, this data has been free of charge.
But now, the Interior Department, which oversees the USGS, has directed a federal advisory committee to consider whether the agency should put a price tag on the information.
If approved, the changes could come into effect as early as 2019.
Some scientists are worried that by putting a fee on the world's longest-running data set of satellite images, the USGS could seriously hinder environmental, agricultural and public health research the world over.
"It would be just a huge setback," said Thomas Loveland, a remote-sensing scientist who recently retired from the USGS.
Loveland explained that before access to the satellite data was made free in 2008, scientific research was seriously limited by price.
"You would buy as few images as you possibly could to get an answer," he said.
On the other hand, ever since the data was made free, the rate at which users downloaded the information increased 100-fold.
If you search Landsat into Google Scholar, for instance, you will be greeted with roughly 100,000 papers that have drawn on the programme's data since 2008.
Over and above the scientific argument, there is also a compelling economic argument for keeping the data free.
A 2013 USGS survey found that free distribution of the Landsat imagery generates over $2.19 billion each year - $1.70 billion for U.S. users and $400 million for international users.
In the same year, the National Research Council found, "The economic and scientific benefits to the United States of Landsat imagery far exceed the investment in the system."
If a price tag is put on this information, the whole idea could backfire, lowering usage and the overall economic benefits.
"It costs a lot of money to charge money," argued Loveland.
Furthermore, it seems as though the idea has already been put to rest. Six year ago, an advisory committee looked into charging money for the satellite data and found "Landsat benefits far outweigh the cost."
The panel concluded that it would ultimately waste money, stifle science and innovation, and hamper the government's ability to monitor national security.
"It is in the U.S. national interest to fund and distribute Landsat data to the public without cost now and in the future," the panel wrote.
Just three years ago, a USGS report was released that was titled "Free Data Proves Its Worth for Observing Earth."
It remains unclear why the US government thinks the verdict could have changed in such a short period of time, though it may have something to do with the Trump administration's penchant for climate denial.
Secretary of the Interior under the Obama administration, Sally Jewell, fought hard in her time to reduce the financial barriers around scientific data.
"Science and reliable data need to be at the heart of policy decisions around the globe if we are to tackle climate change and other serious environmental challenges facing our world," she said in 2016.
"It is vital that we share the trusted data that comes from earth observation so citizens, scientists, and political leaders everywhere can most effectively work together to meet these most difficult challenges."
Under his leadership, the Interior has also rolled back several policies designed to elevate climate change and conservation research in policymaking.
The current trend against climate research and mitigation at the Department of Interior is certainly worrying.
This article is based on a report published in Nature. | <urn:uuid:0eb21706-d819-4032-9390-47347eb34ea6> | 3.859375 | 846 | Truncated | Science & Tech. | 41.781872 | 95,607,416 |
Gas Laws describe the behavior of gases through examining the relationships between their physical properties. Despite the wide differences in chemical properties of all gases, they more or less obey the gas laws. For example, although both H2 and O2 are very different gases, with molecular weights of 2 g/mol and 32 g/mol respectively, they will behave similarly to a change in any physical property.
Gas is one of the four fundamental states of matter, found between the liquid and plasma states, where their particles are widely separated and have very weak intermolecular bonds between the atoms. Gases are the only states of matter that can be compressed or even expand to fill a very large space. It is these properties which makes them subject to behave differently with respect to changing physical properties such as pressure, volume, temperature and amount.
The main gas laws include Avogadro’s Law, Boyle’s Law, Charles’ Law, Fick’s Law of Diffusion, Gay-Lussac’s Law and Henry’s Law. All of these examining the relationship between physical properties to help predict the overall behavior of that gas. Thus, understanding the gas laws and when to apply them is crucial to help predict how a gas will react to varying conditions.© BrainMass Inc. brainmass.com July 18, 2018, 12:40 pm ad1c9bdddf | <urn:uuid:fc7ac6ff-0a82-4d83-9dea-c331e5f667e5> | 3.984375 | 287 | Knowledge Article | Science & Tech. | 46.33594 | 95,607,433 |
Published: Fri Jul 28 2017 12:00 AM
New Zealand tsunami scientists have now published two journal papers that give a rundown on the impacts of Kaikoura tsunami
The tsunami was the biggest local-source tsunami in New Zealand since 1947 (and by local-source we mean a tsunami created close to our shore rather than a distant-source tsunami created on the other side of the Pacific Ocean, for example). It was unusual in that it was generated from an earthquake that started on land and crossed the coastline offshore – that’s pretty rare. It was also unusual because of the number of offshore faults that moved. This unique combination meant that the tsunami behaved a little differently from your more standard tsunami generated from only one fault.
The map below shows where water level gauges recorded the tsunami. The wee clock is how long after the earthquake that the first tsunami waves arrived, and the wee wave is the maximum tsunami wave recorded and the time after the earthquake that it was recorded. The maximum wave in this case is measured from peak to trough (that is, the largest change in water level from the top of a wave to the bottom, rather than the largest height above normal sea level at the time).
As you can see the first waves reached the Kaikoura coast within 10 minutes of the earthquake – a good reminder of why you need to move away from the coast quickly if you feel a long or strong earthquake (like most Kaikoura coastal residents did on the night – go you guys!). Ten minutes may not be long enough for our seismologists to confirm a tsunami has been generated, and for Civil Defence to issue an official warning to everyone – natural warnings are the best warnings.
You may have read that the tsunami was 7 metres high near Kaikoura. This sounds huge, but it’s not quite the 7 metre wall of water at the coast that it sounds like. This figure referred to the 6.9 metre ‘run up’ measured in Goose Bay, just south of Kaikoura. The tsunami wave height in the sea was probably around 3-4 metres above the normal sea level at the time when it reached Goose Bay, but the beach there is very steep and the wave pushed up against it, leaving debris up to 6.9 metres above sea level. The tsunami also pushed at least 150 metres up the Ote Makura Stream in Goose Bay and over 200 metres up Te Moto Moto stream in Oaro.
The tsunami certainly came out of left field for the seaweed and other unfortunate aquatic life, including koura (crayfish) and paua and various fish, who were also left high and dry 3-4 metres above sea level at other locations along the Kaikoura coast and at Needles Point in Marlborough.
On the whole, the damage along the Kaikoura coast from the tsunami was less than we might have expected because the tsunami arrived at mid to low tide, much of the Kaikoura coastline was uplifted during the earthquake, and the beaches along the coastline here are steep. Otherwise the damage could have been much worse.
The other unusual aspect about the tsunami was that the worst damage happened 150km away from where the tsunami started. The tsunami waves would have been almost unnoticeable as they silently travelled south through the open waters off the North Canterbury coast. But once they got to Banks Peninsula (whose narrow bays and harbours have been described in the past, by someone who shall remain nameless, as ‘a collection of funnels waiting to receive tsunamis’) 1.5 hours after the earthquake, north-facing Little Pigeon Bay sat at just the right angle for the waves to flow straight into it, and it was just the right shape for the waves to start bouncing around inside the bay. This particular mix of circumstances created tsunami surges at the head of the bay that were bigger and more forceful than those seen in other northern Banks Peninsula bays.
A historic cottage at the head of the bay was flooded by the tsunami and lifted partially off its foundations. Two verandas were torn off – one was later found floating in the bay and the other was never recovered. But it wasn’t just the water that did the damage – the cottage was battered by debris that the tsunami picked up on its way through, including some large sawn tree trunks that had been sitting on the beach. One of these logs battered down the front door and stove-in the wall beside it. The water even moved a power pole that had been lying on the ground 5 metres inland. The tsunami run-up was only 3.2 m above the sea level, but the inundation reached 140 m inland. Interestingly the cottage was also flooded, to a lesser degree, during the 1960 Chile tsunami.
The damage to the cottage is a good reminder that it’s not just the height of a tsunami wave but the sheer power behind an enormous mass of moving water, and the assorted flotsam and jetsam that it’s carrying, that can make tsunamis so dangerous.
The differing impacts from the Kaikoura tsunami along the eastern South Island and southern North Island coasts show us again what tricky little beasts tsunamis are. Scientists work really hard to understand tsunami behaviour so that they can provide better information to people both before and during a tsunami. Because this event was so complex, scientists are still working on a model to explain how the fault movements during the earthquake caused the flooding and impacts seen on land.
A very important, but not unusual, aspect of the tsunami was that in most places (apart from very close to where the tsunami started) the highest tsunami waves arrived a couple of hours after the first wave. While an official warning can’t replace the natural warning of the earthquake itself (that’s right – long OR strong earthquake, get gone!), our seismologists will still work closely with the Ministry of Civil Defence & Emergency Management (who issue tsunami warnings) to advise people of a possible local source tsunami, even if the first waves may have already arrived. This is because (a) it confirms to those coastal residents that did evacuate when they felt the long or strong earthquake that it was a good idea, and that they should stay away for the time being and (b) the largest tsunami waves may still be on their way, so for people who haven’t already evacuated, it’s still a good idea.
One last thing: we often get asked “how far up or inland am I meant to go”? Which is a really good question. You can find your region’s tsunami evacuation zones on your local authority’s CDEM website – you can find a link to these on the Ministry of Civil Defence & Emergency Management’s website. You only need to go inland far enough that you are out of the tsunami evacuation zones. If is best to go on foot or bike if you can, to leave the roads free for those who really need to drive (if you are in a car you might like to drive a wee bit further to make room for those coming behind you). Have a look at your tsunami evacuation zones – it might not be as far as you think. Or you may not even be in a tsunami evacuation zone at all, which means after you feel that long or strong earthquake you can stay put and open your doors for your friends and family who may be turning up from nearer the coast.
William Power, GNS Science, email@example.com, Emily Lane, NIWA, firstname.lastname@example.org | <urn:uuid:16f78a48-7d9b-4fc8-9bbe-4d74316df1d4> | 3.890625 | 1,570 | News (Org.) | Science & Tech. | 48.858281 | 95,607,457 |
Mangroves protect coastlines, are the beacons of hope for marine diversity, and essentially combat climate change. Saving these mangroves and growing new forests are essential tasks that we must undertake to save our planet.
Watch the video here:[embedvideo id=”91RgE_fIE34″ website=”youtube”]
Scientific evidence claim that mangroves are nature’s weapons against climate change. A buffer zone between the land & the sea, they:
- Protect the land from erosion
- Protect the coast from cyclones & storm surges
- Soak up excess CO2
And are said to be one of nature’s best carbon sinks!
#MGChangemakers - Episode 2: THE 21-YEAR JOURNEY OF CHANGE | Driving India Into Future
Live Now #MGChangemakers Episode 2 : Touched by poverty, untouchability and atrocities against Musahar- the Mahadalit community of Bihar, Padma Shri Sudha Varghese decided to dedicate her life for their upliftment. Watch the video to learn about her inspirational journey & how she is ‘Driving India Into The Future’. #MGChangemakers powered by MG Motor India and supported by United Nations India. Show your support by donating now: http://bit.ly/Milap-MGChangemakersPosted by TheBetterIndia on Wednesday, July 18, 2018
Apart from this they also serve as a haven for corals and marine diversity. A typical mangrove also has 182 tonnes of biomass above ground per hectare. Scientists claim that mangrove restoration is a conservation tool promoting ecosystems, community empowerment, climate change adaptation, carbon storage, fisheries enhancement.
A go-to for O2! | <urn:uuid:744b9d6c-eb94-41dc-b104-1fdcb6876ed1> | 3.15625 | 373 | Truncated | Science & Tech. | 25.073269 | 95,607,468 |
The mechanism of circadian oscillations in the period protein (PER) in Drosophila is investigated by means of a theoretical model. Taking into account recent experimental observations, the model for the circadian clock is based on multiple phosphorylation of PER and on the negative feedback exerted by PER on the transcription of the period (per) gene. This minimal biochemical model provides a molecular basis for circadian oscillations of the limit cycle type. During oscillations, the peak in per mRNA precedes by several hours the peak in total PER protein. The results support the view that multiple PER phosphorylation introduces times delays which strengthen the capability of negative feedback to produce oscillations. The analysis shows that the rhythm only occurs in a range bounded by two critical values of the maximum rate of PER degradation. A similar result is obtained with respect to the rate of PER transport into the nucleus. The results suggest a tentative explanation for the altered period of per mutants, in terms of variations in the rate of PER degradation.
Mendeley saves you time finding and organizing research
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Running Cars on Hydrogen Made from Starch
A new way to make hydrogen from corn or potatoes could make fuel-cell vehicles more practical.
Using a stew of enzymes culled from several organisms, researchers have developed a way to convert starch, available from numerous sources including corn and potatoes, into hydrogen gas at low temperatures and pressures. The method produces three times more hydrogen than an older enzymatic method does, suggesting that it might be practical to use such enzymes to produce hydrogen for fuel-cell vehicles.
While fuel-cell vehicles are appealing because they emit no pollutants, it’s been a challenge to find clean and affordable ways to produce, transport, and store hydrogen to fuel them. Most commonly, hydrogen is extracted from fossil fuels. Making hydrogen by electrolyzing water is energy intensive and can be expensive. The new system improves on other experimental methods for creating hydrogen from biomass by using low temperatures, making it potentially more convenient and energy efficient.
The researchers–from Virginia Tech, in Blacksburg, VA; Oak Ridge National Laboratory; and the University of Georgia, in Athens–combined 13 commercially available enzymes isolated from yeast, bacteria, spinach, and rabbit muscle. The work is available online in PLoS ONE, a journal published by the Public Library of Science. The hydrogen comes from two sources: the starch and the water used to oxidize the starch. The enzymes facilitate chemical reactions in which the water and starch can be completely converted into hydrogen and carbon dioxide, says Y. Percival Zhang, professor of biological systems at Virginia Tech. (The carbon dioxide released is offset by the carbon dioxide captured by plants that provide the starch.)
The new system produces a higher yield of hydrogen than previous experimental systems that used enzymes for converting sugars into hydrogen. But while the yield of hydrogen is high, so far the rates at which the gas is produced are extremely low. That’s in part because the researchers used off-the-shelf enzymes and have not optimized the system, Zhang says. The scientists’ next project will include analyzing each stage of the process in detail to find the rate-limiting steps.
For example, one of the enzymes may be producing a by-product that slows down later steps, says Michael Adams, professor of biochemistry and molecular biology at the University of Georgia. The researchers would then look for other enzymes, or modify current ones, to minimize the by-product. They will also look for enzymes that can operate at higher temperatures. “If you increase the temperature by 10 degrees, most times you can increase the reaction rate twofold,” Zhang says.
One of the first applications of the system, Zhang says, could be generating hydrogen for fuel cells in portable electronics. The starch could be a safer way of storing energy than using methanol, a current leading option for such small fuel-cell systems. He estimates that it will take about six to eight years to improve the rates enough for such applications. Eventually, he hopes to use his process to solve one of the biggest current problems with hydrogen fuel-cell vehicles: fitting enough hydrogen on board to compete with gasoline-powered vehicles.
But some Department of Energy (DOE) officials doubt that the entire system will be light enough for onboard use. Sunita Satyapal, the hydrogen-storage team leader at DOE, notes that the researchers’ estimates do not include the weight of the water or the other equipment needed to produce the hydrogen. These things could more than double the weight of the system, she says, even if water produced by the fuel cell is recycled. The system will probably be too heavy to give the vehicle a driving range competitive with gasoline engines, suggests Satyapal.
She also notes that the rate of hydrogen production is now orders of magnitude lower than it would need to be for use in vehicles, and it will be very difficult, if not impossible, to sufficiently improve the rate.
But even if the new system is not useful as a way of producing hydrogen in a car, it eventually could prove useful for producing hydrogen at fueling stations. One of the challenges with hydrogen production is the cost of compressing and transporting hydrogen from central locations. On-site production using enzymes at filling stations, or even in people’s homes, could get around these issues. In such applications, the hydrogen production rate can be lower than it is aboard a vehicle, as the hydrogen can be produced around the clock in relatively large tanks.
Still, some are skeptical of the basic concept of using starch to create fuel. “Making food into hydrogen is not such a great idea,” says John Deutch, a chemistry professor at MIT. Indeed, demand for corn to make ethanol is already increasing food prices. Using corn starch to make hydrogen could exacerbate the problem.
But Zhang notes that employing starch to make hydrogen would be a much better use of the available corn than turning it into ethanol: fuel cells can be three times more efficient than ethanol-burning internal combustion engines. Nevertheless, he sees starch as a temporary solution. Zhang is also developing a version of the process that starts with cellulose, found primarily in the nonfood parts of plants.
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:33ad84af-9f0c-47ad-abf4-fd0aed3a1c2c> | 3.421875 | 1,082 | Truncated | Science & Tech. | 35.486919 | 95,607,489 |
Several dating methods exist, depending on different criteria and techniques, and some very well known examples of disciplines using such techniques are, for example, history, archaeology, geology, paleontology, astronomy and even forensic science, since in the latter it is sometimes necessary to investigate the moment in the past in which the death of a cadaver occurred.
Relative dating methods are unable to determine the absolute age of an object or event, but can determine the impossibility of a particular event happening before or after another event of which the absolute date is well known.
Radiometric dating utilizes the decay rates of certain radioactive atoms to date rocks or artifacts.
Uniformitarian geologists consider this form of dating strong evidence that the Earth is billions of years old.
For example, in the The decay constant has dimensions of reciprocal seconds.
In the special case in which parent and daughter atoms are present in equal quantities, the age of the specimen is the half-life of the parent isotope: The first assumption, that the amount of the daughter isotope in the original rock is known, is the weakest assumption.
A detailed survey of the following dating methods in actual use: K-Ar, Ar-Ar, Fission track, Rb-Sr, U-Pb, Pb-Pb, Sm-Nd, Re-Os, Lu-Hf, La-Ce, etc.
Addresses and refutes the common defensive statements used by proponents of the dating methods.
Pigliucci Bio Science, 2000, 51, 411-4 AND FINALLY - About Jonathan Wells - In His Own Words!Despite very impressive and powerful measurement and characterization tools, physical and chemical analysis methods, the dating of rocks by using radioactive elements depends on very basic assumptions.The significance and relevance of these assumptions have not been demonstrated. Wells Writes About Evolution is Wrong [HTML] [PDF] - A. Gishlick Icons of Anti Evolution: Rebutals by New Mexicans for Science & Reason Legitimate Questions of Evolution, or Stealth Creationism? We will deal with carbon dating first and then with the other dating methods. | <urn:uuid:bf5a1f34-b20f-4998-90ce-3a46d9f16fc9> | 3.3125 | 440 | Spam / Ads | Science & Tech. | 27.783049 | 95,607,524 |
Add the sum of the squares of four numbers between 10 and 20 to the sum of the squares of three numbers less than 6 to make the square of another, larger, number.
Cherri, Saxon, Mel and Paul are friends. They are all different ages. Can you find out the age of each friend using the information?
This task, written for the National Young Mathematicians' Award 2016, focuses on 'open squares'. What would the next five open squares look like?
You have 5 darts and your target score is 44. How many different ways could you score 44?
Katie had a pack of 20 cards numbered from 1 to 20. She arranged the cards into 6 unequal piles where each pile added to the same total. What was the total and how could this be done?
Using the statements, can you work out how many of each type of rabbit there are in these pens?
This task, written for the National Young Mathematicians' Award 2016, invites you to explore the different combinations of scores that you might get on these dart boards.
What do the digits in the number fifteen add up to? How many other numbers have digits with the same total but no zeros?
Winifred Wytsh bought a box each of jelly babies, milk jelly bears, yellow jelly bees and jelly belly beans. In how many different ways could she make a jolly jelly feast with 32 legs?
Can you arrange 5 different digits (from 0 - 9) in the cross in the way described?
This problem is based on the story of the Pied Piper of Hamelin. Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!
You have two egg timers. One takes 4 minutes exactly to empty and the other takes 7 minutes. What times in whole minutes can you measure and how?
This challenge focuses on finding the sum and difference of pairs of two-digit numbers.
A group of children are using measuring cylinders but they lose the labels. Can you help relabel them?
Find the sum and difference between a pair of two-digit numbers. Now find the sum and difference between the sum and difference! What happens?
There are 4 jugs which hold 9 litres, 7 litres, 4 litres and 2 litres. Find a way to pour 9 litres of drink from one jug to another until you are left with exactly 3 litres in three of the jugs.
Can you use this information to work out Charlie's house number?
Use your logical-thinking skills to deduce how much Dan's crisps and ice-cream cost altogether.
This dice train has been made using specific rules. How many different trains can you make?
What do you notice about the date 03.06.09? Or 08.01.09? This challenge invites you to investigate some interesting dates yourself.
Arrange eight of the numbers between 1 and 9 in the Polo Square below so that each side adds to the same total.
Zumf makes spectacles for the residents of the planet Zargon, who have either 3 eyes or 4 eyes. How many lenses will Zumf need to make all the different orders for 9 families?
How could you put eight beanbags in the hoops so that there are four in the blue hoop, five in the red and six in the yellow? Can you find all the ways of doing this?
There are 78 prisoners in a square cell block of twelve cells. The clever prison warder arranged them so there were 25 along each wall of the prison block. How did he do it?
This magic square has operations written in it, to make it into a maze. Start wherever you like, go through every cell and go out a total of 15!
Can you find which shapes you need to put into the grid to make the totals at the end of each row and the bottom of each column?
There were chews for 2p, mini eggs for 3p, Chocko bars for 5p and lollypops for 7p in the sweet shop. What could each of the children buy with their money?
Suppose there is a train with 24 carriages which are going to be put together to make up some new trains. Can you find all the ways that this can be done?
Can you put plus signs in so this is true? 1 2 3 4 5 6 7 8 9 = 99 How many ways can you do it?
There are 44 people coming to a dinner party. There are 15 square tables that seat 4 people. Find a way to seat the 44 people using all 15 tables, with no empty places.
Look carefully at the numbers. What do you notice? Can you make another square using the numbers 1 to 16, that displays the same properties?
Exactly 195 digits have been used to number the pages in a book. How many pages does the book have?
This task follows on from Build it Up and takes the ideas into three dimensions!
Can you order the digits from 1-3 to make a number which is divisible by 3 so when the last digit is removed it becomes a 2-figure number divisible by 2, and so on?
Can you work out the arrangement of the digits in the square so that the given products are correct? The numbers 1 - 9 may be used once and once only.
Find the product of the numbers on the routes from A to B. Which route has the smallest product? Which the largest?
Tom and Ben visited Numberland. Use the maps to work out the number of points each of their routes scores.
Make a pair of cubes that can be moved to show all the days of the month from the 1st to the 31st.
This challenge, written for the Young Mathematicians' Award, invites you to explore 'centred squares'.
How many ways can you find to do up all four buttons on my coat? How about if I had five buttons? Six ...?
Can you rearrange the biscuits on the plates so that the three biscuits on each plate are all different and there is no plate with two biscuits the same as two biscuits on another plate?
When intergalactic Wag Worms are born they look just like a cube. Each year they grow another cube in any direction. Find all the shapes that five-year-old Wag Worms can be.
Tim's class collected data about all their pets. Can you put the animal names under each column in the block graph using the information?
Using all ten cards from 0 to 9, rearrange them to make five prime numbers. Can you find any other ways of doing it?
Can you use the information to find out which cards I have used?
Sitting around a table are three girls and three boys. Use the clues to work out were each person is sitting.
On a digital 24 hour clock, at certain times, all the digits are consecutive. How many times like this are there between midnight and 7 a.m.?
Find all the different shapes that can be made by joining five equilateral triangles edge to edge.
How could you put these three beads into bags? How many different ways can you do it? How could you record what you've done?
The planet of Vuvv has seven moons. Can you work out how long it is between each super-eclipse? | <urn:uuid:1c83eef2-1ce7-481d-8c4e-abfe4f2762c1> | 3.875 | 1,520 | Content Listing | Science & Tech. | 76.835976 | 95,607,530 |
The Lorentz Transformation (or Lorentz Transform) is a series of equations describing the effect of relative motion of multiple objects on the position of objects at given times. According to the transformation (unlike the Galilean Transformation), it affects relative length (Length Contraction) and time as well as position.
Henrick Lorentz produced a version in an effort to explain why Light appeared to move at the same speed no matter how fast one was traveling in relation to it, and Albert Einstein derived it from his theory of Special Relativity, his method assuming time is not invariant between frames of reference moving relative to each other.
The Lorentz Transform regarding length (Length Contraction) is:
L = L0γ(v)
The Lorentz Factor (γ or Γ) is used in probably all the Lorentz transformations as well as other related formulae, and is defined as:
1 γ = —————————— √(1-v²/c²)
In some discussions involving Relativistic Speeds, a speed is indicated by its associated Lorentz factor. Some examples; | <urn:uuid:90d1b4a9-7bdd-487b-8b00-1415e03e08af> | 4.25 | 235 | Knowledge Article | Science & Tech. | 18.460833 | 95,607,535 |
BsGCLM, when aligned with the same protein of other deuterostomes
, showed identities ranging from 34.
Until now, the earliest deuterostomes
scientists have discovered were between 510 and 520 million years old, when they had already begun to diversify into vertebrates, sea squirts, echinoderms such as starfish and sea urchins, and hemichordates.
The four new laboratory sequences (Mga lab, Oed lab, Sma lab, and Vpu lab) presented three residues that are characteristic of PG-1 proteins in deuterostomes
and protostomes, Ala29, Asn41, and Thr43 (Fig.
A newly described group of primitive soft-bodied deuterostomes
, called vetulocystids, bears similarities to some of the bizarre early echinoderms.
The central nervous system in deuterostomes
lies on the dorsal side, but on the ventral side in protostomes, such as the lobster.
Of course, eyes are characteristic of the vertebrates in the deuterostome
In protostomes, as well as in deuterostomes
, the first cleavages initially result in the separation of the cells of the presumptive ectodermal and endodermal germ layers.
While it has been variously suggested that deuterostomes
(Nursall, 1962), protostomes (Inglis, 1985), and cnidarians (Hanson, 1977) independently evolved multicellularity, the group most commonly considered to have been derived from a separate protist lineage is the sponges, phylum Porifera (as evidenced by Barnes, 1980, p.
Urochordates are monophyletic within the deuterostomes
The echinoid immune system and the phylogenetic occurrence of immune mechanisms in deuterostomes
marine), lophotrochozoans have been separated from deuterostomes
or ecdysozoans for over 550 million years and the genetic machinery has likely changed substantially.
Glycobiology of sperm-egg interactions in deuterostomes | <urn:uuid:929183af-0d55-49a4-8ea4-56232f1e2b5a> | 3.40625 | 448 | Structured Data | Science & Tech. | 2.180781 | 95,607,567 |
posted by Mary
Two slabs with parallel faces are made from different types of glass. A ray of light travels through air and enters each slab at the same angle of incidence. Which slab has the greater index of refraction and why?
slab A is a light colored glass maybe transparent. The ray of light travel through the glass at the same angle it enters the glass.
slab B is of a darker color and the ray of light at initial entry is bent slightly downwards then at then at an angle.
The sine of the angle of refraction is related to the index of refracation. A has n=1, no bending. B bends it, so n>1
If a ray of light goes through the glass at the same angle it enters, as in the case of slab A, the index of refraction would be 1.00. There is no such glass, by the way. The color or darkness by itself has nothing to do with the index. It depends upon the composition.
Slab b, which bends the light downards, has the higher value of the index. | <urn:uuid:2c4af5a9-e3cd-4b00-9010-75d9ce2c1ff5> | 3.828125 | 228 | Q&A Forum | Science & Tech. | 80.705 | 95,607,595 |
posted by Lena
Two steel blocks are at rest on a frictionless horizontal surface. Block X has a mas of 3.0 kg ans is attacthed by means of a light taut string to block Y that has a mass of 12 kg. A force of 45 N (E) is applied to block x. Calculate the force block Y exerts on block x.
I don't have any idea of how to go about do this question. I think it's related to newton's 3rd law about action-reaction forces but I don't know any else. Could someone please guide me in the right direction? Thanks
The 45N force accelerates both masses at a rate
a = 45/(3 + 12) = 3 m/s^2
The taut string between X and Y applies an accelerating force to block Y that equals f = m a = 12 kg * 3 m/s^2 = 36 N. The reaction force upon block X is 36 N in the opposite direction (West).
You are correct that Newton's third law is involved | <urn:uuid:d7382881-c635-42b5-850c-90e47dd6a95f> | 3.421875 | 221 | Q&A Forum | Science & Tech. | 90.431227 | 95,607,596 |
Fred Ciesla, assistant professor in geophysical sciences at UChicago, simulated the dynamics of the solar nebula, the cloud of gas and dust from which the sun and the planets formed. Although every dust particle within the nebula behaved differently, they all experienced the conditions needed for organics to form over a simulated million-year period.
“Whenever you make a new planetary system, these kinds of things should go on,” said Scott Sandford, a space science researcher at NASA Ames. “This potential to make organics and then dump them on the surfaces of any planet you make is probably a universal process.”
Although organic compounds are commonly found in meteorites and cometary samples, their origins presented a mystery. Now Ciesla and Sandford describe how the compounds possibly evolved in the March 29 edition of Science Express. How important a role these compounds may have played in giving rise to the origin of life remains poorly understood, however.
Sandford has devoted many years of laboratory research to the chemical processes that occur when high-energy ultraviolet radiation bombards simple ices like those seen in space. “We’ve found that a surprisingly rich mixture of organics is made,” Sandford said.
These include molecules of biological interest, such as amino acids, nucleobases and amphiphiles, which make up the building blocks of proteins, RNA and DNA, and cellular membranes, respectively. Irradiated ices should have produced these same sorts of molecules during the formation of the solar system, he said.
But a question remained: Could icy grains traveling through the outer edges of the solar nebula, in temperatures as low as minus-405 degrees Fahrenheit (less than 30 Kelvin), become exposed to UV radiation from surrounding stars?
Ciesla’s computer simulations reproduced the turbulent environment expected in the protoplanetary disk. This washing machine action mixed the particles throughout the nebula, and sometimes lofted them to high altitudes within the cloud, where they could become irradiated.
“Taking what we think we know about the dynamics of the outer solar nebula, it’s really hard for these ice particles not to spend at least part of their time where they’re going to be exposed to UV radiation,” Ciesla said.
The grains also moved in and out of warmer regions in the nebula. This completes the recipe for making organic compounds: ice, irradiation and warming.
“It was surprising how all these things just naturally fell out of the model,” Ciesla said. “It really did seem like this was a natural consequence of particle dynamics in the initial stage of planet formation.”
Citation: “Organic Synthesis via Irradiation and Warming of Ice Grains in the Solar nebula,” by Fred J. Ciesla and Scott A. Sandford, Science Express, March 29, 2012.
Funding: NASA’s Origins of the Solar Systems Program and the Astrobiology Institute.
Steve Koppes | 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.
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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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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The findings are part of a comprehensive report in this week's Science by members of the Daphnia Genomics Consortium, an international network of scientists led by the Center for Genomics and Bioinformatics (CGB) at Indiana University Bloomington and the U.S. Department of Energy's Joint Genome Institute. A bullet-point list of the Science paper's most important findings appears at the end of this release.
"Daphnia's high gene number is largely because its genes are multiplying, by creating copies at a higher rate than other species," said project leader and CGB genomics director John Colbourne. "We estimate a rate that is three times greater than those of other invertebrates and 30 percent greater than that of humans."
Daphnia Genomics Consortium projects can be found at http://daphnia.cgb.indiana.edu, as well as a link to the nearly 40 companion papers based on the data reported in the Science paper.
Scientists have studied Daphnia for centuries because of its importance in aquatic food webs and for its transformational responses to environmental stress. Predators signal some of the animals to produce exaggerated spines, neck-teeth or helmets in self-defense. And like the virgin nymph of Greek mythology that shares its name, Daphnia thrives in the absence of males -- by clonal reproduction, until harsh environmental conditions favor the benefits of sex.
Daphnia's genome is no ordinary genome.
"More than one-third of Daphnia's genes are undocumented in any other organism -- in other words, they are completely new to science," says Don Gilbert, coauthor and Department of Biology scientist at IU Bloomington.
Sequenced genomes often contain some fraction of genes with unknown functions, even among the most well-studied genetic model species for biomedical research, such as the fruit fly Drosophila. By using microarrays (containing millions of DNA strands affixed to microscope slides) that are made to measure the conditions under which these new genes are transcribed into precursors for proteins, experiments that subjected Daphnia to environmental stressors point to these unknown genes having ecologically significant functions.
"If such large fractions of genomes evolved to cope with environmental challenges, information from traditional model species used only in laboratory studies may be insufficient to discover the roles for a considerable number of animal genes," Colbourne said.
Daphnia is emerging as a model organism for a new field of science -- Environmental Genomics -- that aims to better understand how the environment and genes interact. This includes a practical need to apply scientific developments from this field toward managing our water resources and protecting human health from chemical pollutants in the environment.
James E. Klaunig, professor and chair of the School of Health, Physical Education, and Recreation's Department of Environmental Health at IU Bloomington, predicts the present work will yield a more realistic and scientifically-based risk evaluation.
"Genome research on the responses of animals to stress has important implications for assessing environmental risks to humans," Klaunig said. "The Daphnia system is an exquisite aquatic sensor, a potential high-tech and modern version of the mineshaft canary. With knowledge of its genome, and using both field sampling and laboratory studies, the possible effects of environmental agents on cellular and molecular processes can be resolved and linked to similar processes in humans."
The scientists learned that of all sequenced invertebrate genomes so far, Daphnia shares the most genes with humans.
The idea behind environmental genomics for risk assessment is fairly simple. Daphnia's gene expression patterns change depending on its environment, and the patterns indicate what state its cells are in. A water flea bobbing in water containing a chemical pollutant will express by tuning-up or tuning-down a suite of genes differently than its clonal sisters accustomed to water without the pollutant. Importantly, the health effects of most industrially produced compounds at relevant concentrations and mixtures in the environment are unknown, because current testing procedures are too slow, too costly, and unable to indicate the causes for their effects on animals, including human. The new findings suggest that Daphnia's research tools (like microarrays) and genome information can provide a higher-throughput and information-rich method of measuring the condition of our water supply.
"Until now, Daphnia has primarily been used as sentinel species for monitoring the integrity of aquatic ecosystems," said Joseph Shaw, coauthor and IU School of Public and Environmental Affairs biologist. "But with many shared genes between Daphnia and humans, we will now also apply Daphnia as a surrogate model to address issues directly related to human health. This puts us in a position to begin integrating studies of environmental quality with research of human diseases."
A requisite for reaching model system status is a large research community that contributes to its growing body of knowledge and resources. Over the course of the project, the Daphnia Genomics Consortium has grown from a handful of founding members to more than 450 investigators distributed around the globe. Nearly 200 scientists have contributed published work resulting from the genome study, many in open-source journals published as a thematic series by BioMedCentral.
A list of these publications can be found at http://www.biomedcentral.com/series/Daphnia.
"Assembling so many experts around a shared research goal is no small feat," said Peter Cherbas, director of the CGB. "We're obviously proud of the CGB's catalytic role. The genome project signals the coming-of-age of Daphnia as a research tool for investigating the molecular underpinnings of key ecological and environmental problems."
Colbourne agreed, adding, "New model systems rarely arrive on the scene with such clear and important roles to play for advancing a new field of science."
The scientists present findings on the pace at which copied genes gain new functions, including a novel theory that accounts for the apparent rapid evolution of some of Daphnia's gene families (suites of related genes that result from repeated duplication events).
"Gene functions can become distinct very quickly," said Michael Pfrender, coauthor and associate professor of biology at the University of Notre Dame. "We had all assumed that newly copied genes that code for the same proteins would initially have the same functions, and that new functions evolve slowly with age, by acquiring rare beneficial mutations. Instead, we found that half of the newly copied genes had changed their expression very soon, possibly at the time of their origin."
Like in a mystery novel, the DNA evidence presented by examining the patterns of gene duplication in the study's first chapters was combined with clues of the genes' functions in later chapters to propose a new model for how genes accumulate in genomes.
"The smoking gun in this investigation was clear," said Kelley Thomas, coauthor and Hubbard Professor in Genomics at the University of New Hampshire. "A high rate of gene duplication, which produces a steady pool of new genes that have different expressions can facilitate the preservation of some gene-copies by natural selection."
Like most theories for how new genes evolve, their common fate is to wither by disabling mutations. For a new gene to persist, its function must give an advantage to the organism -- and the earlier the better for the gene to avoid bad mutations. In Daphnia's case, there seems to be a sufficiently large pool of young gene copies that some will be expressed in novel circumstances, and by chance be compatible with expression patterns of interacting genes required to perform its new function.
"At first glance, amplified gene families in Daphnia are more likely to be functionally related than not," said Michael Lynch, coauthor and distinguished professor of biology at IU Bloomington. "This suggests that gene functions via duplication often evolve in cooperation with other genes in the genome. We are not yet prepared to generalize our findings until we broaden our investigation to include more Daphnia lineages having different population histories. However, it's quite clear that this genome project opens up enormous opportunities that are not readily accomplished using other models with poorly understood -- and not terribly accessible -- ecologies."
So what other reasons might Daphnia have so many genes compared to other animals? The coauthors of the Science paper begin addressing that issue as well as others related to the genomic architecture and evolution of the species.
"We don't yet have final answers," Pfrender said. "The sequenced isolate did originate from a naturally inbred population, which may contribute to some features of this genome -- and Daphnia's partial asexuality may have a hand to play."
Another possibility, Colbourne said, is that "since the majority of duplicated and unknown genes are sensitive to environmental conditions, their accumulation in the genome could account for Daphnia's flexible responses to environmental change."
This work received financial and material support from the Office of Science of the U.S. Department of Energy, the National Science Foundation, Lilly Endowment Inc., Roche NimbleGen Inc., the National Institutes of Health, the U.S. Department of Health and Human Services, and Indiana University.
To speak with Project Leader John Colbourne and other IU Bloomington coauthors (see below), please contact David Bricker, University Communications, at 812-856-9035 or firstname.lastname@example.org.
"The Ecoresponsive Genome of Daphnia pulex", Science (Feb. 4, 2011), by John Kenneth Colbourne et allaAuthor list
* IU Bloomington coauthors (20)Major Findings
• The overall data suggest an original hypothesis for how newly duplicated genes are retained in the genome, which depends on the condition-specific regulation of cooperatively evolving genes.
David Bricker | Newswise Science News
Further reports about: > DNA > DNA strand > Daphnia galeata > Daphnia pulex > Genom > Genomics > Tiny plants > aquatic ecosystem > crustacean > environmental conditions > environmental problem > environmental risk > gene duplication > genome sequence > health services > human health > mental conditions > mental stress > molecular process
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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It is fascinating how quantum mechanical behaviour of particles at smallest scales can give rise to strange properties that can be observed in the classical world. One example is the Fractional Quantum Hall Effect (FQH) that was discovered about 30 years ago in semiconductor devices.
It is one of the most striking phenomena in condensed matter physics and has been thoroughly investigated. Nowadays experimental physicists are able to model effects occurring in condensed matter with ultracold atoms in optical lattices. This has sparked the interest in the question under which conditions the FQH could be observed in such systems.
Now Anne Nielsen and co-workers from the Theory Division of Professor Ignacio Cirac at the Max-Planck-Institute of Quantum Optics and at the Universidad Autónoma de Madrid have developed a new lattice model which gives rise to FQH-like behaviour (Nature Communications, 28 November 2013).
The classical Hall-effect describes the behaviour of electrons or, generally spoken, charge carriers in an electrical conducting probe under the influence of a magnetic field that is directed perpendicular to the electric current. Due to the Lorentz-force a so-called Hall-voltage builds up, which increases linearly with the magnetic field.
In 1980 the German physicist Klaus von Klitzing investigated the electronic structure of so-called MOSFETs. At extremely low temperatures and extremely high magnetic fields he made the discovery that the Hall-resistivity would rise in small steps where the inverse of each plateau was an integer multiple of a combination of constants of nature. A few years later probes of gallium-arsenide, investigated under similar conditions, showed additional plateaus that would correspond to fractional multiples. These discoveries gave a completely new insight into the quantum mechanical processes that take place in flat semiconductor devices, and both were awarded with the Nobel prize in Physics: in 1985 the Nobel prize was given to Klaus von Klitzing, in 1998 to Robert Laughlin, Horst Störner and Daniel Tsui.
The FQH effect is a fascinating phenomenon and explained by theoreticians as being caused by one or more electrons forming composite states with the magnetic flux quanta. However, detailed experimental investigations of FQH are difficult to do in solids, and the states are very fragile. A cleaner implementation could be obtained by realizing the phenomenon in optical lattices in which ultracold atoms play the role of the electrons. This, and the hope to find simpler and more robust models displaying the FQH, is why theoreticians around the world seek to understand which mechanisms could lead to the observation of the FQH in lattices.
To this end the MPQ-team sets the focus on the topological properties that FQH states have. The topology of an object represents certain features of its geometrical structure: For example, a tee cup with a single hole in the handle and a bagel are topologically equivalent, because one can be transformed into the other without cutting it or punching holes in it. A bagel and a soccer ball, on the other hand, are not. In solid state systems the electrons experience the electric forces of many ions that are arranged in a periodic structure. Usually their energy levels make up straight and continuous energy ‘bands’ with a trivial topology. Instead, in systems that exhibit the fractional quantum Hall effect, the topology provides the material with exotic properties, like that the current can only be transmitted at the edge and is very robust against perturbations.
“We have developed a new lattice model where a FQH state should be observed,” Anne Nielsen says, first author of the publication. “It is defined on a two-dimensional lattice in which each site is occupied with a particle. Each particle can be either in a ‘spin up’ or a ‘spin down’ state. In addition, we imply specific, local, short range interactions between the particles.” (See figure 1.) Numerical investigations of the properties of this system showed that its topological behaviour is in accordance with the one expected for a FQH state. The system does, for example, possess long range correlations that lead to the presence of two different ground states of the system when considering periodic boundary conditions.
To obtain their model the researchers used some specific mathematical tools. These tools are by themselves interesting because they may be more widely applicable and thereby open up doors to construct further interesting models.
“The mechanism that leads to FQH in our model seems to be different from those in previous models”, Anne Nielsen points out. “And, furthermore, we have demonstrated how this model can be implemented with ultracold atoms in optical lattices. Realizing FQH states in optical lattices would give unique possibilities for detailed experimental investigations of the states under particularly well-controlled conditions and would, in addition, be a hallmark for quantum simulations.” Olivia Meyer-Streng
Figure 1: Illustration of the lattice model where each particle is either in a ‘spin up’ or a ‘spin down’ state. (Graphic: Anne Nielsen, MPQ)Original publication:
Nature Communications, 28 November 2013, DOI: 10.1038/ncomms3864Contact:
Dr. Olivia Meyer-Streng | Max-Planck-Institut
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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The long-exposure image taken with NASA's Hubble Space Telescope is the deepest-ever picture taken of a cluster of galaxies, and also contains images of some of the intrinsically faintest and youngest galaxies ever detected.
NASA, ESA, J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)
FRONTIER FIELDS IMAGE OF GALAXY CLUSTER ABELL 2744. This long-exposure Hubble Space Telescope image of massive galaxy cluster Abell 2744 is the deepest ever made of any cluster of galaxies. It shows some of the faintest and youngest galaxies ever detected in space. Abell 2744, located in the constellation Sculptor, appears in the foreground of this image. It contains several hundred galaxies as they looked 3.5 billion years ago. The immense gravity in Abell 2744 acts as a gravitational lens to warp space and brighten and magnify images of nearly 3,000 distant background galaxies. The more-distant galaxies appear as they did longer than 12 billion years ago, not long after the big bang. This image is part of an unprecedented long-distance view of the universe from an ambitious collaborative project among the NASA Great Observatories called The Frontier Fields. Over the next several years select patches of the sky will be photographed for the purpose of better understanding galaxy evolution. This visible-light and near-infrared composite image was taken with the Wide Field Camera 3.
The target is the massive cluster Abell 2744, which contains several hundred galaxies as they looked 3.5 billion years ago. The immense gravity in this foreground cluster is being used as a "gravitational lens," which warps space to brighten and magnify images of far more-distant background galaxies as they looked over 12 billion years ago, not long after the big bang.
"The Frontier Fields is an experiment; can we use Hubble's exquisite image quality and Einstein's theory of General Relativity to search for the first galaxies?," said Space Telescope Science Institute Director Matt Mountain. "With the other Great Observatories, we are undertaking an ambitious joint program to use galaxy clusters to explore the first billion years of the universe's history."
Simultaneous observations of this field are being done with NASA's two other Great Observatories, the Spitzer Space Telescope and the Chandra X-ray Observatory. The assembly of all this multispectral information is expected to provide new insights into the origin and evolution of galaxies and their accompanying black holes.
The Hubble exposure reveals nearly 3,000 of these background galaxies interleaved with images of hundreds of foreground galaxies in the cluster. The many background galaxies would otherwise be invisible without the boost from gravitational lensing. Their images not only appear brighter, but also smeared, stretched, and duplicated across the field.
Thanks to the gravitational lensing phenomenon, the background galaxies are magnified to appear up to 10 to 20 times larger than they would normally appear. What's more, the faintest of these highly magnified objects have intrinsic brightnesses roughly 10 to 20 times fainter than any galaxies ever previously observed.
The Hubble data are immediately being made available to the worldwide astronomy community where teams of researchers will do a detailed study of the visual crazy quilt of intermingled background and cluster galaxies to better understand the stages of galaxy development.
Though the foreground cluster Abell 2744 has been intensively studied as one of the most massive clusters in the universe, the Frontier Fields exposure reveals new details of the cluster population. Hubble sees dwarf galaxies in the cluster as small as 1/1,000th the mass of the Milky Way. At the other end of the size spectrum, Hubble detects the extended light from several monster central cluster galaxies that are as much as 100 times more massive than our Milky Way. Also visible is faint intra-cluster light from stars inside the cluster that have been stripped out of galaxies by gravitational interactions. These new deep images will also help astronomers map out the dark matter in the cluster with unprecedented detail, by charting its distorting effects on background light. An unseen form of matter, dark matter makes up the bulk of the mass of the cluster.
As the Abell cluster was being photographed with Hubble's Wide Field Camera 3, the telescope's Advanced Camera for Surveys was trained on a nearby parallel field that is 6 arc minutes away from the cluster. In this field, Hubble resolves roughly 10,000 galaxies seen in visible light, most of which are randomly scattered galaxies. The blue galaxies are distant star-forming galaxies seen from up to 8 billion years ago; the handful of larger, red galaxies are in the outskirts of the Abell 2744 cluster.
Hubble will again view these two Frontier Fields in May 2014, but Hubble's visible-light and infrared camera will switch targets. This will allow for both fields to be observed over a full range of colors, from ultraviolet light to near-infrared.
With each new camera installed on Hubble, the space telescope has been used to make successively deeper, groundbreaking views of the universe. To get a better assessment of whether doing more deep field observations was scientifically compelling or urgent, the Space Telescope Science Institute or STScI in Baltimore, Md. chartered a "Hubble Deep Field Initiative" working group. The Hubble Frontier Fields initiative grew out of the working group's high-level discussions at STScI concerning what important, forward-looking science Hubble should be doing in upcoming years. Despite several deep field surveys, astronomers realized that a lot was still to be learned about the far universe. Such knowledge would help in planning the observing strategy for the upcoming James Webb Space Telescope.
The astronomers also considered synergies with other observatories, such as Spitzer, Chandra, and the new Atacama Large Millimeter/submillimeter Array or ALMA. Over the coming years five more pairs of fields will be imaged. The next scheduled target is the massive cluster MACSJ 0416.1-2403, for which observations are starting this week.To see more images and information about The Frontier Fields, visit:
Ray Villard | Newswise
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
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MEDIA RELEASE - ISSUED 14th JUNE 2000
Three-month Seasonal Climate Outlook Summary: Rainfall probabilities for July to September 2000
Little shift in seasonal rainfall odds
The National Climate Centre's outlook for total July to September rainfall shows the chances of above average totals are close to 50% in most areas, including Queensland and northern N.S.W. where the outlooks are most reliable for the current season (see map below).
The largest swings in the probabilities occur in central W.A. and in South Australia near Port Augusta; in both cases the chances dip below 40%, getting less than 35% in parts of W.A. In other words, below average seasonal rainfall is the most likely outcome in these parts. This suggests a potential reduction in the number of northwest cloudbands. However, the outlook system has generally low levels of skill or reliability across these areas for July-September, requiring these probabilities to be viewed with some caution.
More information on this outlook is available during
normal office hours from 8:45am to 5:30pm (EST) Monday to
Friday by contacting the following climate meteorologists
in the National Climate Centre:
May 2000 rainfall - Decile Distribution.
March 2000 to May 2000 rainfall - Decile Distribution.
|Frequently Asked Questions|
Q: WHAT ARE THE BUREAU OF METEOROLOGY'S SEASONAL CLIMATE OUTLOOKS?|
A:General statements about the probability or risk of wetter or drier than average weather over a three-month period. The outlooks are based on the statistics of chance (the odds) taken from rainfall and sea surface temperature records. They are not, however, categorical predictions about future rainfall, and they are not about rainfall within individual months of the three-month outlook period.
Q: WHAT DO WE MEAN BY "WETTER OR DRIER THAN AVERAGE, OR "WARMER OR COOLER THAN AVERAGE""?
A:Being above or below the median rainfall, average maximum temperature, or average minimum temperature for the three-month period.
The median is a useful measure of "normal" rainfall. In the long term, rainfall is above median in one half of years, and below median in the other half.
For example, from July to September at Mackay in Queensland, one-half of 3-month rainfall totals have been below 80mm, and one-half have been above. If rainfall was above 80mm in that period it would be "wetter than average" or above median. Over the long haul there is a 50% chance of this occurring. In terms of odds this is even money.
Note that the average maximum temperature is the average of all the daily highest temperatures for the period.
Similarly, the average minimum temperature is the average of all the daily lowest temperatures for the period
Q: HOW ACCURATE ARE THE OUTLOOKS?
A: In the places and seasons where the outlooks are most skilful, the eventual outcome (above or below median) is correctly given the higher chance about 70 to 80% of the time. In the least skilful areas, the outlooks perform no better than random chance or guessing. The rainfall outlooks perform best in eastern and northern Australia between July and January, but are less useful in autumn and in the west of the continent. The skill at predicting seasonal maximum temperature peaks in early winter and drops off marginally during the second half of the year. The lowest point in skill occurs in early autumn. The skill at predicting seasonal minimum temperature peaks in late autumn and again in mid-spring. There are also two distinct periods when the skill is lowest - namely late summer and mid-winter. However, it must always be remembered that the outlooks are statements of chance or risk. For example, if you were told there was a 50:50 chance of a horse winning a race but it ran second, the original assessment of a 50:50 chance could still have been correct.
Q: WILL CATEGORICAL OUTLOOKS EVER BE ISSUED? (Eg. It WILL be drier than average.)
A: Very unlikely. There is a certain level of natural variability in the climate which is chaotic and unpredictable. This is particularly the case with rainfall. For example, rainfall in a season can be significantly above average in one region, and significantly below average less than 50km away.
Q: HOW SHOULD THE OUTLOOKS BE USED?
A: As another tool in risk management and decision making. The benefits accrue from long-term use, say over 10 years. At any given time, the probabilities may seem inaccurate, but taken over several years, the advantages of taking account of the risks will outweigh the disadvantages. For more information on the use of probabilities, farmers could contact their local departments of agriculture or primary industry.
|Definitions and Explanations....|
THE SOUTHERN OSCILLATION INDEX (SOI) is calculated using the barometric pressure difference between Tahiti and Darwin.
The SOI is one indicator of the stage of El Niņo or La Niņa events in the tropical Pacific Ocean. It is best considered in conjunction with sea-surface temperatures, which form the basis of the outlooks.
A strongly negative SOI (below -10) is characteristic of El Niņo, which is often associated with below average rainfall over eastern Australia, and a weaker than normal monsoon in the north.
A strongly positive SOI (above +10) is characteristic of La Niņa, which is often associated with above average rainfall over parts of tropical and eastern Australia, and an earlier than normal start to the northern monsoon season.
El Niño & La Niña
El Niņo translates from Spanish as "the boy-child", and refers to the extensive warming of the central and eastern Pacific Ocean.
La Niņa translates from Spanish as "the girl-child", and refers to the extensive cooling of the central and eastern Pacific Ocean. The term has recently become the conventional label for the opposite of El Niņo.
See http://www.bom.gov.au/climate/glossary/elnino.shtml for more on SOI and El Niņo. | <urn:uuid:71c49970-69c6-47f1-baee-7384ba9deffb> | 2.578125 | 1,313 | Knowledge Article | Science & Tech. | 44.680945 | 95,607,625 |
At first, the fossil was smuggled out of Mongolia, as many dinosaurs are. It found its way to Japan, then Britain, then France. In 2015, the private collector who finally bought it contacted the paleontologist Pascal Godefroit to get his opinion on the specimen.
Godefroit’s opinion was: This is one weird dinosaur.
The creature was clearly a small predator, much like Velociraptor. Its feet even had the distinctive sickle-shaped claws that clinked across the kitchen floor in Jurassic Park. But its long neck and tapering snout resembled those of a swan. Its arms and hands also had unusual proportions—something halfway between the grasping limbs of other raptors and the flattened flippers of modern penguins. It looked like a Velociraptor that had adapted for life in the water—that is, if it was even an actual dinosaur.
“It was so strange that we suspected that it might have been a chimera—a mix of different skeletons glued together. It wouldn’t be the first time,” says Andrea Cau from the University of Bologna, who joined Godefroit’s investigation. “We had to be sure that it was a real dinosaur and not a fake.”
Since most of the animal was still encased in a 15-inch block of stone, the team took it to Grenoble, and scanned it using a particle accelerator. The scans showed that the block was a solid mass that hadn’t been assembled from separate pieces. And the parts of the skull still within it were identical to those on the outside, as were the hidden arm bones. This swan-necked, duck-snouted, almost-paddle-limbed, sickle-clawed creature was assuredly weird—but it was a real dinosaur. (Cau notes that the scans are all openly available in case any other paleontologists want to check them.)
The team called the creature Halszkaraptor escuilliei. The name’s first half, pronounced “hull-shka-raptor,” honors Halszka Osmólska, a Polish paleontologist who discovered more than a dozen Mongolian dinosaurs and has at least four species named after her. The second half honors François Escuillié, the French collector who bought the fossil, alerted Godefroit, and worked to return the poached specimen to its rightful home in Mongolia. It currently sits in Brussels and will remain there for a year or so while the team finishes studying it.
Halszkaraptor is one of the theropods—a group of mostly meat-eating dinosaurs that count Tyrannosaurus and Velociraptor among their ranks. But unlike its kin, Halszkaraptor’s odd features suggest it was a strong swimmer that perhaps chased fish underwater, much like modern cormorants do. Outside of birds, “this is the first time we see that in a dinosaur,” says Cau. (Other ancient reptiles like paddle-limbed plesiosaurs and the dolphin-esque ichthyosaurs are not actually dinosaurs.)
Like many other fish-eating specialists, Halszkaraptor had a lot of teeth in the front of its snout—more than twice the number of a typical dinosaur. “The first time I saw that, I asked my colleagues to repeat the analysis because I wasn’t convinced,” says Cau. The snout also contained branching bony chambers that would have once housed a large network of blood vessels and sensory nerves. Such features are common in modern crocodiles, giving them an exquisite sense of touch.
Halszkaraptor’s neck made up half its length from snout to hip, reminiscent of plesiosaurs, several groups of freshwater turtles, and birds like swans and herons—all of which use their long necks to catch fish. Halszkaraptor’s neck bones also had more side-to-side mobility than those of the average theropod. “That might be an adaptation to swimming, or it may indicate that the animal used rapid sweeping motions of the neck to capture some sort of small prey,” says Michael Habib, from the University of Southern California.
The arms “are the most problematic part,” says Cau, because they’re not quite like anything else. The long bones are flattened, and the fingers get progressively longer from the outside in—the opposite pattern to most theropods. They’re closest in proportion to the limbs of swimming birds like puffins, murres, and penguins. But they’re not flippers. “I prefer not to say if [Halszkaraptor] used its arms propulsively,” says Cau. “We don’t have information on the shoulder girdle, which would be important to determine if it swam like a penguin.”
Despite all these adaptations for swimming, Halszkaraptor’s back half is that of a typical landlubbing theropod. It had long legs, although it wasn’t well adapted for running. It had a longish tail, although one that was too thin to effectively counterbalance the exceptionally long neck. To compensate, Halszkaraptor probably stood upright, more so than other raptors, but not quite as erect as a penguin. Cau thinks it lived in an unstable environment, with cycles of freshwater and drought. Halszkaraptor evolved to cope with both worlds.
Halszkaraptor is the first amphibious dinosaur that we know of—and that’s strange. With mammals, you have digging moles, gliding squirrels, flying bats, swimming otters, oceangoing dolphins, running gazelles, climbing monkeys, and swinging gibbons. Where’s that diversity of lifestyles among the dinosaurs? Until recently, it seemed that aside from birds, “nearly all dinosaurs are considered to be typical ground-living animals,” says Xing Xu, a prolific dino discoverer from the Chinese Academy of Sciences. That’s surprising, given how diverse they were, and how thoroughly they dominated the planet for hundreds and millions of years.
But that view has changed in recent years, thanks to new discoveries. In 2014, scientists reimagined Spinosaurus, the sail-backed giant that menaced the cast of Jurassic Park 3, as a semiaquatic, crocodile-like fish hunter. They also revealed the complete skeleton of Deinocheirus, a “horse-headed, humpbacked dinosaur that looks like something out of a bad sci-fi movie.” A year later, Xu described Yi, a small predator which had both feathers and bat-like wings, and may have glided between trees. The year after that, another team described Limusaurus, a beaked plant eater that loses its teeth as it grows up. All of these species are theropods. And all of these differ wildly in their lifestyles, diets, physiques, and more. Halszkaraptor, the first amphibious theropod, is part of that revolution.
“It’s exhilarating and yet almost embarrassing thinking back on how typecast these beasties were just a few short decades ago,” says Lindsay Zanno, from the North Carolina Museum of Natural Sciences. In particular, “the theropod section of the dinosaur family tree continues to be in flux as specimens like this one keep popping up.”
“There’s great potential for future dinosaur-fossil hunting,” Xu adds.
We want to hear what you think. Submit a letter to the editor or write to email@example.com. | <urn:uuid:401357ab-be04-4faf-b41b-ce6a9eeb7d20> | 2.8125 | 1,663 | News Article | Science & Tech. | 47.198636 | 95,607,635 |
Physicists in the College of Arts and Sciences have made several important discoveries regarding the basic structure of mesons—subatomic particles long thought to be composed of one quark and one antiquark and bound together by a strong interaction.
Recently, Professor Tomasz Skwarnicki and a team of researchers proved the existence of a meson named Z(4430), with two quarks and two antiquarks, using data from the Large Hadron Collidor beauty (LHCb) Collaboration at CERN in Geneva, Switzerland.
This tetraquark state was first discovered in Japan in 2007 but was later disputed by a team of researchers at Stanford University. Skwarnicki's finding was published earlier this month and has since garnered international publicity.
Quarks are hard, point-like objects that are found inside protons and neutrons and form the nucleus of an atom.
Now, another analysis by Syracuse University physicists—this one led by Distinguished Professor Sheldon Stone and his research associate Liming Zhang—shows two lighter, well-known mesons, originally thought to be composed of tetraquarks, that are structured like normal mesons.
Stone says that one of the particles, uniquely named the f0(980), was assumed to have four quarks because it seemed to be the only way for its mass to “make sense.”
“The four-quark states cannot be classified within the traditional quark model, where strongly interacting particles [hadrons] are formed from either quark-antiquarks pairs [mesons] or three quarks [baryons],” says Stone, who also heads up Syracuse University’s High-Energy Physics Group. “They are, therefore, called ‘exotic particles.’”
Stone points out that his and Skwarnicki's analyses are not contradictory and, together, increase what physicists know about the strong interaction that forms the basis of what holds all matter together.
Stone's finding also changes what is known about charge-parity (CP) violation, the balance of matter and antimatter in the universe. That there is a small amount of excess matter (e.g., protons, neutrons and orbiting electrons) floating around in the ether implies that something other than the Standard Model of particle physics is at play.
“Fourteen billion years ago, energy coalesced to form equal quantities of matter and antimatter,” Stone says. “But as the universe cooled and expanded, its composition changed. Antimatter all but disappeared after the Big Bang, leaving behind matter to create everything around us, from stars and galaxies to life on Earth. Something must have happened, during this process, to cause extra CP violation and, thus, form the universe as we know it. … The f0(980) is a crucial element in our studies of CP violation. Showing that it is not an exotic particle means we do not have to question the interpretation of our results."
Stone also hopes his findings may shed light on why heavy quarks are able to form four-quark particles and light ones cannot.
“How do you explain some of the interesting characteristics of f0(980), if it’s not made of four quarks?” asks Stone, whose analysis also draws on LHCb data and has been submitted for publication.
Meanwhile, the tetraquark nature of Z(4430) also has huge implications for the study of neutron stars, remnants of gravitational collapses of massive stars.
“Everything we’re doing at Syracuse University and CERN is pushing the boundaries of ‘new physics,’” Stone says. “Because we’re using large data sets, we have no choice but to use statistically powerful analyses that can measure particle properties in an unambiguous manner.”
LHCb is an international experiment, based at CERN, involving more than 800 scientists and engineers from all over the world. At CERN, Stone heads up a team of 15 physicists from Syracuse University.
Rob Enslin | Eurek Alert!
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
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20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:6a9e41ea-8336-4918-b2f2-22a349af5f2d> | 3.140625 | 1,425 | Content Listing | Science & Tech. | 39.637866 | 95,607,647 |
It may be the ideal citizen science project for a community where so many enjoy gazing at the sky.
A team at the University of Colorado Center for Environmental Technology is teaming with Boulder's National Center for Atmospheric Research and NASA on what's known as CitizenSkyView. It's all about getting to know the clouds that drift overhead — and their impact on renewable energy — much better.
"This started about eight years ago, in fact, when we saw the possibility of low-cost digital cameras and the internet, and the need for better prediction of renewable energy — in other words, better prediction of when our solar panels would be producing power," said Professor Al Gasiewski, the center's director and the project's lead investigator.
"We saw the availability of wireless in an entire community like Boulder, radiating from everybody's houses, as a unique means of communicating pictures. And we saw the need to predict whether my solar panels, or your solar panels, or Xcel's, or anybody's solar arrays, are going to be producing power," he said. "If we are going to be improving the amount of energy we're going to get from solar, we've got to be able to better predict it."
Fueled by an initial $10,000 seed grant from CU's Renewable and Sustainable Energy Institute, which was followed by a NASA grant of about $180,000, the team developed the CitizenSkyView app for iPhones or androids, then set out to enlist community volunteers.
The required app is available through both the Apple App Store and the Google Play Store.
On three Saturdays late last year, those volunteers were sent out to preselected locations around Boulder to turn on the App, put down their phones for an hour and let their phones' cameras do the rest.
During those data collection events, the apps automatically took pictures of the sky every 30 seconds, enabling scientists to create high resolution of the data for clouds as they formed and moved across the sky.
"The best photo of me participating in the event is me laying on the grass in the middle of Chautauqua Park and reading a book and munching a sandwich, with my camera next to me on a rock taking pictures," Gasiewski recalled.
An 'almost' partnership with Xcel
The data that is gathered is "stitched" together, researchers said, to produce, for the first time, three-dimensional cloud imagery.
"I think the ability to map out cloud structure from the bottom, and be able to deduce something about the vertical structure from a series of citizen-science-based cameras using their iPhones, is an interesting prospect for mapping out more generally clouds in the future," said Andy Heymsfield, co-investigator on the project and a senior scientist at NCAR's Mesoscale and Microscale Meteorology Laboratory.
"This won't only be restricted to the Boulder area, but the hope is to have it spread over a wider area," he said.
"There are two areas where this can really benefit. One would be for the estimating of, or inferring the needs of, solar charging stations. And the second would be to help in interpreting satellite data."
NCAR, he said, is involved both in choosing sites for the placement of the project's cameras, and also putting together the cloud imagery base on the collected data.
The CitizenSkyView researchers engaged in talks as far back as 2010 with Xcel Energy to enlist the utility's support of the project, and those discussions "almost" resulted in funding from Xcel, Gasiewski said.
A greater understanding of cloud structure, as a critical tool to forecasting cloud formation, can be key for utilities and providers of renewable energy to what is known as power grid load leveling, Gasiewski said.
"That's something that energy companies are concerned about," he said. "There are going to be certain amounts of energy for renewables that they have to make up for by burning more coal or natural gas or buying electricity at higher rates from other sources, if they can't predict" solar energy availability.
"And now that we want to get renewables in Boulder to levels of 40 percent and higher, it's becoming even more critical that we can predict the energy that will be produced."
'The more the merrier'
In the busy workspace that the CitizenSkyView team occupies at CU's Department for Electrical, Computer and Energy Engineering sits a prototype of the CitizenSkyCam, a unit the project members hope to deploy to rooftops across Boulder County, enabling a steady stream of the same data on clouds that is currently gathered intermittently by the phone apps.
Boulder officials have expressed interest in hosting a few permanent CitizenSkyView cameras, as has NCAR. The scientists are looking for homeowners who will also allow the units — weighing no more than about 100 pounds and requiring nothing elaborate for roof installation — to sit atop their houses.
"And I think there are about 100 sites around town that we're targeting to fill out," said Michael Hurowtiz, a member of the Center for Environmental Technology and a CitizenSkyView team member. "And we had maybe 30 percent covered last time, so the more the merrier.
"Finding permanent locations, as well as volunteers for the individual (phone-based) events, definitely could be very helpful for us, where it's just the one hour. And also for the longer term, finding homes for these as we build them up."
For homeowners who want to be a part of the project and host a CitizenSkyCam atop their houses, Gasiewski said, "Your neighbors might look at it and wonder what the little spaceship is that's up on your roof. And, you will perhaps lose about 1 percent of your internet bandwidth — a small, miniscule fraction."
As for the upside, he added, "Volunteers will have access to all the cloud pictures in real time if they wish. Volunteers will have access to the cloud forecasts, to know if the sun will be shining on them in the next hour or two. And volunteers will be part of a civic project, doing good to promote renewable energy in the Boulder County area."
Nearly three dozen CU engineering students have contributed to the project since its inception.
Meanwhile, several more hourlong data collection events are envisioned for the months ahead, with the next one expected to take place in February. Phone-carrying volunteers should contact the project team at firstname.lastname@example.org. Those throughout Boulder County with roof space and an interest in helping can contact the same address. | <urn:uuid:4d982a95-1c50-4831-98f0-6d19c4cc6c48> | 2.953125 | 1,349 | News Article | Science & Tech. | 38.634341 | 95,607,654 |
Why would humanity revive the long-extinct woolly mammoth? Atlantic senior editor Ross Andersen draws on the expertise of paleoecology professor Jacquelyn Gill and Arctic scientist Max Holmes in a panel about an unusual, extreme effort to fight climate change. getAbstract warmly recommends this innovative talk.
In this summary, you will learn
- Why the Earth needs a “climate moonshot” and
- How reviving woolly mammoths could help fight climate change.
About the Speakers
Arctic scientist Max Holmes is deputy director of the Woods Hole Research Center. Jacquelyn Gill is a professor of paleoecology at the University of Maine. Ross Andersen is a senior editor at The Atlantic.
Comment on this summary
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Penguin Press, 2017 | <urn:uuid:f8b984ce-30d9-4563-b226-95cb15a6f342> | 2.859375 | 203 | Truncated | Science & Tech. | 43.1235 | 95,607,681 |
[Yuki Nakamura] Successful plant reproduction requires a unique type of lipase found only in plant and bacteria
Plant reproduction is a key to propagate species and rich harvest of agricultural product. A research team led by Dr. Nakamura discovered in Arabidopsis thaliana that successful gametogenesis requires a pair of non-specific phospholipase C (NPC), NPC2 and NPC6, a unique family of lipase found only in seed plants and certain bacterial species. Due to its potentially toxic activity to non-specifically degrades the cellular membrane lipids, this type of enzyme was thought to function only under certain stress conditions. Our finding on the function of NPC2 and NPC6, two last uncharacterized NPC family member, shed light on critical function of phospholipid catabolism in plant reproductive development. This work was conducted in collaboration with Prof. Peter Dörmann (University of Bonn, Germany). | <urn:uuid:7af2d453-9cfd-46e2-91e5-4fc5035a77c1> | 2.828125 | 193 | Knowledge Article | Science & Tech. | 23.566331 | 95,607,687 |
Scientists have Discovered a New Giant Octopus
A new type of giant Pacific octopus was discovered by researchers at the University of Alaska, Earther said. It is believed to be the largest specimen of octopus. In 2012, scientists at the University of Alaska, and the US Geological Survey, discovered a bunch of Pacific Omonoia specimens in the Strait of Prince Wilhelm, genetically distinct from other Enteroctopus dofleini. But researchers managed to take only small samples of tissues on their tentacles and returned the animals back to the sea. In this connection, it was not clear whether they resembled Enteroctopus dofleini or were completely different. The zoologists made a detailed comparison of the two groups of animals and found that the molluscs really resembled but had different external signs. The new version had a furry leather finish along the entire length of the body, and there are two white spots instead of one in the front of the head. Temporarily, scientists have also named the giant mollusc - "frilled giant Pacific octopus".
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