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Wonder where the fuel will come from for tomorrows hydrogen-powered vehicles? Virginia Tech researchers are developing catalysts that will convert water to hydrogen gas. The research will be presented at the 228th American Chemical Society National Meeting in Philadelphia August 22-26, 2004
Supramolecular complexes created by Karen Brewers group at Virginia Tech convert light energy (solar energy) into a fuel that can be transported, stored, and dispensed, such as hydrogen gas.
The process has been called artificial photosynthesis, says Brewer, associate professor of chemistry. "Light energy is converted to chemical energy. Solar light is of sufficient energy to split water into hydrogen and oxygen gas, but this does not happen on its own; we need a catalysts to make this reaction occur."
Susan Trulove | EurekAlert!
A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes
20.07.2018 | Science China Press
Future electronic components to be printed like newspapers
20.07.2018 | Purdue University
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
23.07.2018 | Health and Medicine
23.07.2018 | Earth Sciences
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Finding could be used for waste treatment, energy
Researchers at Washington State University have discovered a new type of cooperative photosynthesis that could be used in engineering microbial communities for waste treatment and bioenergy production.
They report today on the unique metabolic process seen for the first time in a pair of bacteria in Nature Communications.
Photosynthetic bacteria account for nearly half of the world's food production and carbon-based organic material. The research could also improve understanding of lake ecology.
Phototroph + electron generator
Prosthecochloris aestaurii , a green-tinged, plant-like microbe, comes from the extreme environment of Hot Lake, a high salinity lake in northern Okanogan County near Oroville, Wash. Discovered and identified a few years ago by researchers at the U.S. Department of Energy's Pacific Northwest National Laboratory and Southern Illinois University, the bacterium is able to photosynthesize, using sunlight along with elemental sulfur or hydrogen sulfide to grow.
The researchers noticed that P. aestuarii tended to gather around a carbon electrode, an electricity conductor that they were operating in Hot Lake. The researchers isolated and grew P. aestuarii and determined that, similar to the way half of a battery works, the bacterium is able to grab electrons from a solid electrode and use them for photosynthesis. The pink-colored Geobacter sulfurreducens meanwhile, is known for its ability to convert waste organic matter to electricity in microbial fuel cells. The bacterium is also used in environmental cleanup.
G. sulfurreducens, like animals and humans, can't photosynthesize. It consumes organic compounds, such as acetate, and "breathes" out carbon dioxide.
The bacterium is known for its ability to donate electrons to a solid electrode. As it consumes acetate, it generates electrons, which can be collected as electricity.
Microbes paired up in WSU lab
Led by Haluk Beyenal, the Paul Hohenschuh Distinguished Professor in the WSU Gene and Linda Voiland School of Chemical Engineering and Bioengineering, and postdoctoral researcher Phuc Ha, the research team surmised that the bacteria might be able to help each other grow and put them together in the lab.
The researchers found that P. aestuarii could accept electrons generated from G. sulfurreducens and use them in a new type of anaerobic photosynthesis never before seen. Similar to how a battery or fuel cell works, the bacteria transfer electrons. They feed off each other to grow under conditions in which neither could grow independently.
From an ecological perspective, this new form of metabolism may play an important role in carbon cycling in oxygen free zones of poorly mixed freshwater lakes. It may also present new possibilities for engineering microbial communities for waste treatment and bioenergy production.
"We think this could be a common bio-electrochemical process in nature," said Beyenal, whose team is working to better understand the electron transfer mechanism.
The work was funded by the U.S. Department of Energy. Researchers from PNNL and China University of Geoscience also collaborated on the project.
The work is in keeping with WSU's Grand Challenges, a suite of research initiatives aimed at large societal issues. It is particularly relevant to the challenge of sustainable resources and its theme of meeting sustainable energy needs while protecting the environment.
Haluk Beyenal | EurekAlert!
A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes
20.07.2018 | Science China Press
Future electronic components to be printed like newspapers
20.07.2018 | Purdue University
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
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A New Form of DNA Has Been Found
News Apr 23, 2018 | Original Story from the Garvan Institute of Medical Research
This is an artist's impression of the i-motif DNA structure inside cells, along with the antibody-based tool used to detect it. Credit: Chris Hammang
It's DNA, but not as we know it.
In a world first, Australian researchers have identified a new DNA structure - called the i-motif - inside cells. A twisted 'knot' of DNA, the i-motif has never before been directly seen inside living cells.
The new findings, from the Garvan Institute of Medical Research, are published today in the leading journal Nature Chemistry.
Deep inside the cells in our body lies our DNA. The information in the DNA code - all 6 billion A, C, G and T letters - provides precise instructions for how our bodies are built, and how they work.
The iconic 'double helix' shape of DNA has captured the public imagination since 1953, when James Watson and Francis Crick famously uncovered the structure of DNA. However, it's now known that short stretches of DNA can exist in other shapes, in the laboratory at least - and scientists suspect that these different shapes might play an important role in how and when the DNA code is 'read'.
The new shape looks entirely different to the double-stranded DNA double helix.
"When most of us think of DNA, we think of the double helix," says Associate Professor Daniel Christ (Head, Antibody Therapeutics Lab, Garvan) who co-led the research. "This new research reminds us that totally different DNA structures exist - and could well be important for our cells."
"The i-motif is a four-stranded 'knot' of DNA," says Associate Professor Marcel Dinger (Head, Kinghorn Centre for Clinical Genomics, Garvan),.who co-led the research with A/Prof Christ.
"In the knot structure, C letters on the same strand of DNA bind to each other - so this is very different from a double helix, where 'letters' on opposite strands recognise each other, and where Cs bind to Gs [guanines]."
Although researchers have seen the i-motif before and have studied it in detail, it has only been witnessed in vitro - that is, under artificial conditions in the laboratory, and not inside cells.
In fact, scientists in the field have debated whether i-motif 'knots' would exist at all inside living things - a question that is resolved by the new findings.
To detect the i-motifs inside cells, the researchers developed a precise new tool - a fragment of an antibody molecule - that could specifically recognise and attach to i-motifs with a very high affinity. Until now, the lack of an antibody that is specific for i-motifs has severely hampered the understanding of their role.
Crucially, the antibody fragment didn't detect DNA in helical form, nor did it recognise 'G-quadruplex structures' (a structurally similar four-stranded DNA arrangement).
With the new tool, researchers uncovered the location of 'i-motifs' in a range of human cell lines. Using fluorescence techniques to pinpoint where the i-motifs were located, they identified numerous spots of green within the nucleus, which indicate the position of i-motifs.
"What excited us most is that we could see the green spots - the i-motifs - appearing and disappearing over time, so we know that they are forming, dissolving and forming again," says Dr Mahdi Zeraati, whose research underpins the study's findings.
The researchers showed that i-motifs mostly form at a particular point in the cell's 'life cycle' - the late G1 phase, when DNA is being actively 'read'. They also showed that i-motifs appear in some promoter regions (areas of DNA that control whether genes are switched on or off) and in telomeres, 'end sections' of chromosomes that are important in the aging process.
Dr Zeraati says, "We think the coming and going of the i-motifs is a clue to what they do. It seems likely that they are there to help switch genes on or off, and to affect whether a gene is actively read or not."
"We also think the transient nature of the i-motifs explains why they have been so very difficult to track down in cells until now," adds A/Prof Christ.
A/Prof Marcel Dinger says, "It's exciting to uncover a whole new form of DNA in cells - and these findings will set the stage for a whole new push to understand what this new DNA shape is really for, and whether it will impact on health and disease."
This article has been republished from materials provided by Garvan Institute of Medical Research. Note: material may have been edited for length and content. For further information, please contact the cited source.
Reference: Zeraati, M., Langley, D. B., Schofield, P., Moye, A. L., Rouet, R., Hughes, W. E., … Christ, D. (2018). I-motif DNA structures are formed in the nuclei of human cells. Nature Chemistry, 1. https://doi.org/10.1038/s41557-018-0046-3
House Plants an an Early Warning System?News
Researchers are exploring the future of houseplants as aesthetically pleasing and functional sirens of home health. The idea is to genetically engineer house plants to serve as subtle alarms that something is amiss in our home and office environments.READ MORE
Identical Twin Study Shows Impact of a Lifetime of Exercise on FItnessNews
When it comes to being fit, are genes or lifestyle more important? Researchers removed the nature part of the equation by studying a pair of identical twins who had taken radically different fitness paths over three decades. One became an Ironman triathlete while the other remained relatively sedentary over the last 30 years.
15th International Conference and Exhibition on Metabolomics & Systems
Apr 29 - Apr 30, 2019 | <urn:uuid:ec1ed686-e0cb-48e9-ad05-c6177d95a776> | 3.578125 | 1,301 | News Article | Science & Tech. | 51.766982 | 95,572,190 |
Do you want to learn about spatial data available to enhance conservation and sustainable development decisionmaking? Are you interested in using cutting edge spatial data to advance your NBSAP implementation and national reports to the CBD? The UN Biodiversity Lab is an online platform that allows policymakers and other partners to access global data layers, upload and manipulate their own datasets, and query multiple datasets to provide key information on the Aichi Biodiversity Targets and nature-based Sustainable Development Goals.
The search found 2 results in 1.133 seconds.
In this webinar, Dr. Jamison Ervin discusses the relevance of using Spatial Data to guide decision-makers and practitioners on biodiversity conservation. | <urn:uuid:e8f11a0c-c38d-47a4-b9fb-6c437d366162> | 2.890625 | 138 | Content Listing | Science & Tech. | 20.777838 | 95,572,192 |
Astronomers throughout the UK now have a valuable new research tool at their disposal which may lead to new discoveries and improved understanding of the physics of the Universe. Launched this week, AstroGrid provides a unique way of accessing, processing and storing astronomical data obtained from a diverse range of data archives held anywhere on Earth. AstroGrid will open the way for virtual observing on individual computers, enabling astronomers to compare and manipulate a wide range of astronomical data taken from both ground and space-based telescopes.
Astronomy is now in a golden age of discovery, with many new breakthroughs being made with the availability of high quality observations of the cosmos from major new observational facilities, such as the European Southern Observatorys Very Large Telescope [VLT] in Chile and the European Space Agencys XMM-Newton space-based observatory, which provide information across a wide range of the electro-magnetic spectrum from radio to visible light to gamma rays.
The data taken from ground and space-based observations are held in separate archives and the challenge has been to provide the astronomer with the ability to bring these various pieces of data together, enabling them to understand the wider picture. For example one astronomer may survey the sky in the optical wavelengths, using the Sloan Digital Sky Survey, whilst another astronomer may analyse data from the XMM-Newton, each resulting in different answers. Only by comparing the two sets of data, or even adding another data set (e.g. Infrared data from Spitzer), can they then discover that certain previously insignificant faint objects seen in the optical are in fact distant galaxies harbouring massive black holes at their core.
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...
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12.07.2018 | Event News
03.07.2018 | Event News
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In this chapter, you created a login system using the Log In User server behavior, and you used the Restrict Access To Page server behavior to prevent unauthorized access to all of the quotes administration system pages. You also made use of the Log Out User server behavior to provide an easy way to remove the session variables created when you log in.
You built a new user creation page that makes use of the Check New Username server behavior, ensuring that no two users in the database will have the same username and password combination, and you added code to the login form that offers to “remember” users’ login details for them using cookies stored on their computer.
Finally, you expanded upon the code that Dreamweaver writes for you in the Log In User server behavior to redirect users back to the page they tried to access without logging in first (a very user-friendly addition!), and you also added an extra session variable to those created for you by Dreamweaver’s code, expanding upon the level of complexity you can add to your own developments in future.
In the next chapter, you’ll look at creating a searchable website that uses some neat coding techniques to help bring search results to life and move you beyond the basics that the built-in server behaviors provide.
KeywordsText Field Access Level Server Behavior Design View Session Variable
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Java Industry News
Sending Data to a Java Server
Sending Data to a Java Server
By: Andrew Idsinga
Feb. 1, 1996 12:00 AM
When I read about the opportunity to submit articles to Java Developer's Journal one of the first topics that came to mind concerns the desire to be able to record or log data from a web page on the server. Every day I hear questions about outputting data to the server, be it to simply log user information in a guest book, or to have some other, more critical business data sent to the server for more processing; such as an order form.
Of course, you and I both know this is possible using some sort of CGI (considerably goofy intermediary?) program that will write the file. You could also hook your web server up to a several thousand dollar database back end and use another method to get the data there.
No, what many of us are looking for is a simple way, in Java, to send data to the server. Why in Java and not a CGI program? The simplest answer is so that we can have a cross platform solution written in a simple, stable, OO language. While we're at it we'll plop half of it into a web page so that customers or friends will have easy access from a browser!
Enter DataReceiver, DataSender and DataApplet. All three combine into a simple solution to get some formatted text from an applet in a web page to a file on your web server.
What It Looks Like at a Glance
The "Under the Hood" Basics
Meanwhile, on the server, DataReceiver is waiting for incoming connections. After accepting a connection, it reads the incoming data and writes it to a file. In the example code the file is formatted as a comma delimited text file so that it can easily be imported into your favorite spread sheet or database program (See Figure 2).
Java Sockets and How They Relate to Our Problem
To break things down further (you may want to peek at the code in Listings 2 and 3) let's talk about sockets. Sockets, simply put, are end points of communication. When using them directly, as I do with DataSender and DataReceiver, we are sending data from one "end" to the other, or from the client socket to the server socket. When programming with sockets I usually think in terms of what I have to do to get the data to the socket on the local side of the link and then how I will handle it on the other side. Whatever happens between here and there is left up to the socket implementation and network conditions. Basically, with sockets, most of the hairy details of network programming are hidden from the programmer.
In Java, sockets are quite elegant, thanks to Sun's abstraction of sockets into the Socket class and the ServerSocket class. The Socket class represents a connection to another Socket that data can be both read from and written to. By using the getInputStream() and getOutputStream() methods with an instance of Socket you can read and write data the way you would anywhere else in Java. ServerSocket, as its name implies, is meant for accepting connections, which coincidentally is accomplished by calling its accept()' method. On the server side, when accept() gets an incoming connection it returns a Socket object that can then be used to read from and write to.
In my example, DataSender uses an instance of the Socket class to connect to DataReceiver, which uses an instance of the ServerSocket class. Let's move on into the code.
On the Receiving End
It doesn't seem too difficult, and it isn't! The only tricky part is handling the "possibly many" connections. This is where that almighty concept of threaded programming comes into play. The makers of Java of course have built threads into the language and these threads are exactly what I use in DataReceiver. A thread basically does its work and then dies. A Thread class has a run()' method which is analogous to the main() method of a Java application. The run() method is where a thread's execution starts (and usually finishes).
DataReceiver's main' method creates a ServerSocket object and then starts a loop which calls the ServerSocket's accept() method. Since accept() won't return until an inbound connection is made a loop seemed like the simplest way to always be waiting for a connection. When a connection is made we create a new DataReceiver object and pass it the Socket returned by accept(). Since DataReceiver extends the Java Thread class all we have to do to get it going is call its start() method. When DataReceiver's start() method is called, the loop execution resumes at the top and the DataReceiver object starts running (concurrently) with its run() method (See Listing 2).
Now that we have an inbound connection established and a DataReceiver thread running we have to get the appropriate input stream, read the incoming data and then write it to the file.
DataReceiver's constructor handles creating a DataInputStream object by using the passed Socket's getInputStream() method. This means that any data read from this DataInputStream object will be data that has come in from the network, and hence data that needs to be written to the file. DataInputStream seemed like a good choice for this project because it provides some handy methods for reading the simple data being sent from DataSender (i.e. readLine()).
In the run() method, where thread execution actually begins, we call the DataInputStream's readLine() method. This method will stop reading when an end of line character is reached and then return a String object containing the data read. This String is then passed to the local writeData() method where it is then written to the file. You may notice that the writeData() method is declared with the synchronized' modifier. This is very important to avoid file corruption and general havoc on the server end. The reason being is that there is a good chance that many DataReceiver threads could running concurrently (possibly because of several hits to your web page), our job is to make sure that only one will be writing its data to the file at any given time. When the synchronized keyword is used, Java guarantees that only one thread will be executing that method and others will be queued and have access when it becomes available. You may also want to take note of the FILENAME' constant in DataReceiver.java. This represents a system dependent filename. If your server machine is not running on Windows NT, Windows 95, or does not otherwise understand DOS style directory names you should change this to represent a valid path + filename for your system (See Listing 3).
Sending Data with DataSender
The Socket object constructor I use in DataSender takes the above host name and also a port number. The host name argument is the name of the machine that DataReceiver is running on. This could be a DNS name such as inetserver.company.com' or an IP address string such as 22.214.171.124'. The port used with the Socket in DataSender must match the port being used by the ServerSocket in DataReceiver. If they don't match, a connection will not be made, so, be sure that the USE_PORT constants in both DataSender.java and DataReceiver.java match (see the "Additional information" section for more about ports). The Socket, on construction will attempt a connection to the server.
DataSender's constructor also creates a DataOutputStream using the newly created Socket's getOutputStream() method. The DataSender run() method simply uses DataOutputStream's writeBytes() method to write the passed String to the socket. After data has been written to the Socket I close the output stream and the Socket. The run() method then completes and exits the thread.
DataApplet is still around , so if the customer wants to enter some different information, or clicks the "Submit Request" button again another DataSender thread will start and send that data to DataReceiver.
In the example code provided in this article DataApplet manages collecting and formatting the data and then creates the DataSender object to send it. I decided it would be best to have DataSender extend from Java's Thread class so that the class could be used in more advanced situations than DataApplet (I'll leave those to you). Making use of threads in communications also makes good sense because of the wait that could occur when establishing connections or when data is being sent or received. When a thread is handling communications the main execution of the application can continue. This is especially useful in a windowed environment where we might need to accept user input while communications occur in the background.
That About Says It!
Threads are useful tools to handle communications in the "background" without interrupting the current flow of execution. The key factor to using threads is properly using the synchronized' modifier on thread methods that should only be in use by a single thread at any given time.
A Java Applet can be a quick and easy front end for user input that needs to be sent to the server. Currently, for security reasons applets can only make socket connections to the machine they were loaded from, so, in our example the DataReceiver must be running on the web server machine.
Additional Information (and the Gotchas)
The Socket.close() method is currently not working as designed on Win NT and 95 platforms. This didn't have any ill effects in my testing as the sockets eventually timed out and were cleaned up by the system (netstat -a 5' revealed this). This is listed on Sun's known bugs list and should be corrected in a future JDK release.
If you are planning on using the example code with an Internet service provider they must be using an operating system that supports a Java interpreter. This is because DataReceiver is a Java application and must be run directly on the server via the Java interpreter. These days this doesn't seem like a real problem as many OS vendors are rushing to support the wave of Java applications and applets.
Steps to run the examples as provided: First, be sure that the USE_PORT constants in DataReceiver.java and DataSender.java match. Then be sure the FILENAME constant in DataReceiver.java represents a system dependent path + filename that will work on your system. Compile the source with javac (or your favorite).
To get things running you need put the compiled .class files from DataReceiver, DataSender, and DataApplet in a directory accessible to your web server. Add the <applet> tag provided in DataApplet.html to the .html document your users/customers can access, as shown in Listing 4. Run the DataReceiver application on your server and then load the page that you added the <applet> tag to into your favorite Java aware browser.
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Through dated geological records scientists have known for decades that variations in the Earth's orbit around the sun – subtle changes in the distance between the two – control ice ages. But, for the first 2 million years of the Northern Hemisphere Ice Age there has always been a mismatch between the timing of ice sheet changes and the Earth's orbital parameters.
A new model of ice volume change developed by Boston University researchers Maureen Raymo and Lorraine Lisiecki proposes a reason for this discrepancy. Like other models, it is consistent with traditional Milankovitch theory – which holds that the three cyclical changes in the Earth's orbit around the Sun (obliquity, precession, and eccentricity) influence the severity of seasons and high latitude temperatures over time. However, the new model differs from earlier ones in that it allows for a much more dynamic Antarctic ice sheet.
According to the researchers, from 3 million years ago to about 0.8 million years ago, Northern Hemisphere ice volume appears to have varied mostly with the 41,000 year period of obliquity – the periodic shift in the direction or tilt of Earth's axis. However, summer insolation (incoming solar radiation), which is widely believed to be the major influence on high-latitude climate and ice volume change, is typically dominated by the 23,000 year precessional period – the slow "wobble" of the Earth on its axis.
"Because summer insolation is controlled by precession, and summer heating controls ice sheet mass balance, it is difficult to understand why the ice volume record is dominated by the obliquity frequency," said Dr. Raymo. "It's not a complete mismatch, but the precession frequency we think should be strong in geological records is not."
The new model proposes that during this time, ice volume changes occurred in both the Northern Hemisphere and Antarctica, each controlled by different amounts of local summer insolation paced by precession.
"The reason the frequency is not observable in records is because ice volume change occurred at both poles, but out of phase with each other. When ice was growing in the Northern Hemisphere, it was melting in the Southern," said Raymo.
The team believes scientists have been operating under the assumption that Antarctica has been exceptionally stable for 3 million years and very difficult to change climatically. "We don't tend to think of ice volume in that region as varying significantly, even on geologic time scales," said Raymo. "However, only a modest change in Antarctic ice mass is required to "cancel" a much larger Northern ice volume signal."
Records used to measure the ice volume, such as sea levels, integrate the whole world. According to Raymo, the new model demonstrates that while the precession frequency is actually strong in ice volume changes at each pole, in geologic records Northern and Southern hemisphere ice volume trends act to cancel each other out at this frequency.
The paper, which was published online today and will appear in an upcoming issue of the journal Science, proposes that the Antarctic ice sheet is more dynamic and far more capable of change than previously believed.
"If our theory holds true, it is a cause for concern with regard to climate changes not associated with orbital patterns as well," said Raymo.
Kira Edler | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine | <urn:uuid:8d58745e-3042-4d7f-bfe0-ace0d91a84bd> | 4.1875 | 1,303 | Content Listing | Science & Tech. | 38.116615 | 95,572,230 |
ESA Sea Ice Climate Change Initiative (Sea_Ice_cci): Southern hemisphere sea ice thickness from CryoSat-2 on the satellite swath (L2P), v2.0
Update Frequency: Not Planned
Online Status: ONLINE
Publication State: Citable
Publication Date: 2018-05-25
This dataset provides a Climate Data Record of Sea Ice Thickness for the SH polar region, derived from the SIRAL (SAR Interferometer Radar ALtimeter) instrument on the CryoSat-2 satellite. This product was generated in the context of the ESA Climate Change Initiative Programme (ESA CCI) by the Sea Ice CCI (Sea_Ice_cci) project.
It provides daily sea ice thickness data on the satellite measurement grid (Level 2P) at the full sensor resolution for the period November 2010 to April 2017. Note, the southern hemisphere sea ice thickness dataset is an experimental climate data record, as the algorithm does not properly considers the impact of the complex snow morphology in the freeboard retrieval. Sea ice thickness is provided for all months but needs to be considered biased high in areas with high snow depth and during the southern summer months. Please consult the Product User Guide (PUG) for more information.
Hendricks, S.; Paul, S.; Rinne, E. (2018): ESA Sea Ice Climate Change Initiative (Sea_Ice_cci): Southern hemisphere sea ice thickness from CryoSat-2 on the satellite swath (L2P), v2.0. Centre for Environmental Data Analysis, date of citation
. doi:10.5285/fbfae06e787b4fefb4b03cba2fd04bc3. http://dx.doi.org/10.5285/fbfae06e787b4fefb4b03cba2fd04bc3
Keywords: Sea Ice, ESA, CCI, Antarctic, sea ice thickness, sea ice, Level 2 Pre-processing, Level 2
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Previously used record identifiers:
No related previous identifiers.
Data were processed by the ESA CCI Sea Ice project team and were supplied to CEDA in the context of the ESA CCI Open Data Portal Project
CCI data format checked
Data are in NetCDF format
This dataset was generated by a combination of instruments deployed on platforms
and computations as detailed below. | <urn:uuid:13e66504-418c-49ee-b16c-36574a3fda30> | 2.765625 | 502 | Structured Data | Science & Tech. | 39.853104 | 95,572,251 |
(PhysOrg.com) -- A team of scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, in collaboration with researchers from the University of Delaware and Yeshiva University, has developed a new catalyst that could make ethanol-powered fuel cells feasible. The highly efficient catalyst performs two crucial, and previously unreachable steps needed to oxidize ethanol and produce clean energy in fuel cell reactions. Their results are published online in the January 25, 2009 edition of Nature Materials.
Like batteries that never die, hydrogen fuel cells convert hydrogen and oxygen into water and, as part of the process, produce electricity. However, efficient production, storage, and transport of hydrogen for fuel cell use is not easily achieved. As an alternative, researchers are studying the incorporation of hydrogen-rich compounds, for example, the use of liquid ethanol in a system called a direct ethanol fuel cell.
"Ethanol is one of the most ideal reactants for fuel cells," said Brookhaven chemist Radoslav Adzic. "It's easy to produce, renewable, nontoxic, relatively easy to transport, and it has a high energy density. In addition, with some alterations, we could reuse the infrastructure that's currently in place to store and distribute gasoline."
A major hurdle to the commercial use of direct ethanol fuel cells is the molecule's slow, inefficient oxidation, which breaks the compound into hydrogen ions and electrons that are needed to generate electricity. Specifically, scientists have been unable to find a catalyst capable of breaking the bonds between ethanol's carbon atoms.
But at Brookhaven, scientists have found a winner. Made of platinum and rhodium atoms on carbon-supported tin dioxide nanoparticles, the research team's electrocatalyst is capable of breaking carbon bonds at room temperature and efficiently oxidizing ethanol into carbon dioxide as the main reaction product. Other catalysts, by comparison, produce acetalhyde and acetic acid as the main products, which make them unsuitable for power generation.
"The ability to split the carbon-carbon bond and generate CO2 at room temperature is a completely new feature of catalysis," Adzic said. "There are no other catalysts that can achieve this at practical potentials."
Structural and electronic properties of the electrocatalyst were determined using powerful x-ray absorption techniques at Brookhaven's National Synchrotron Light Source, combined with data from transmission electron microscopy analyses at Brookhaven's Center for Functional Nanomaterials. Based on these studies and calculations, the researchers predict that the high activity of their ternary catalyst results from the synergy between all three constituents - platinum, rhodium, and tin dioxide - knowledge that could be applied to other alternative energy applications.
"These findings can open new possibilities of research not only for electrocatlysts and fuel cells but also for many other catalytic processes," Adzic said.
Next, the researchers will test the new catalyst in a real fuel cell in order to observe its unique characteristics first hand.
Provided by Brookhaven National Laboratory
Explore further: Feeding plants to this algae could fuel your car | <urn:uuid:12a2d17f-0fda-4fd9-9ad4-dda67c9feca9> | 3.359375 | 637 | News Article | Science & Tech. | 18.624335 | 95,572,268 |
forgetSQL is a Python module for accessing SQL databases by creating
|Author:||Stian Soiland <email@example.com>|
|License:||GNU Lesser General Public License (LGPL) See the file COPYING for details.|
forgetSQL is a Python module for accessing SQL databases by creating classes that maps SQL tables to objects, normally one class pr. SQL table. The idea is to forget everything about SQL and just worrying about normal classes and objects.
- What is forgetSQL?
- Normal use
- Advanced use
- Specializing the forgetters
- Wrapping SQL queries
- Framework suggestion
Installation of the forgetSQL module is pretty straight forward:
python setup.py install
This will install forgetSQL.py into site-packages/ of your Python distribution.
- Python 2.2.1 (True/False, new style classes, classmethods, iterators)
- Some database module (tested: MySQLdb, psycopg)
If using psycopg, mx.DateTime is needed to avoid a psycopg bug related to re-inserting dates. psycopg depends on mx.DateTime, so that shouldn’t be a problem.
Let’s start by showing an example using an imaginary database mydatabase:
This example is based on these SQL tables:
And should output something like:
Account details for Stian S�iland Group unix (15) Other members: Magnus Nordseth Erlend Mjaavatten
In regular SQL programming, this could be done something like this:
cursor = dbconn.cursor() cursor.execute("SELECT fullname,groupid FROM account WHERE accountid=%s", ('stain',)) fullname,groupid = cursor.fetchone() print "Account details for", fullname cursor.execute("SELECT name FROM group WHERE groupid=%s" % groupid) (groupname,) = cursor.fetchone() print "Group %s (%s)" % (groupid, name) cursor.execute("""SELECT fullname FROM account JOIN group USING (groupid) WHERE group.groupid=%s AND NOT account.accountid=%s""", (groupid, accountid)) print "Other members:" for (membername,) in cursor.fetchall(): print membername
Now, using forgetSQL:
from mydatabase import * account = Account("stain") # primary key print "Account details for", account.fullname group = account.group print "Group %s (%s)" % (group.name, group.groupid) print "Other members: " for member in group.getChildren(Account): # find Account with group as foreign key if member <> account: print member.fullname
Notice the difference in size and complexity of these two examples.
The first example is tightly bound against SQL. The programmer is forced to think about SQL instead of the real code. This programming style tends to move high-level details to SQL, even if it is not neccessary. In this example, when getting “other members”, the detail of skipping the active user is done in SQL.
This would hardly save any CPU time on modern computers, but has made the code more complex. Thinking in SQL makes your program very large, as everything can be solved by some specialized SQL. Trying to change your program or database structure at a later time would be a nightmare.
Now, forgetSQL removes all those details for the every-day-SQL tasks. It will not be hyper-effective or give you points in the largest-join-ever-possible-contest, but it will help you focus on what you should be thinking of, making your program work.
If you at a later point (when everything runs without failures) discovers that you need to optimize something with a mega-query in SQL, you could just replace that code with regular SQL operations. Of course, if you’ve been using test-driven development (like in http://c2.com/cgi/wiki?ExtremeProgramming ) your tests will show if the replaced code works.
Another alternative could be to use views and stored procedure, and layer forgetSQL on top of those views and procedures. This has never been tested, though. =)
For each table in your database, a class is created. Each instance created of these classes refer to a row in the given table. Each instance have attributes that refer to the fields in the database. Note that the instance is not created until you access that particular row.
So accessing a column of a row is simply accessing the attribute row.column. Now, if this column is a reference to another table, a foreign key, instead of an identifier you will in row.column find an instance from the other table, ie. from the other class.
This is what happens in the example above, group = account.group retrieves this instance. Further attribute access within this instance is resolved from the matching row in the group table.
If you want to change some value, you could just change the attribute value. In the example, if you want to change my name, simply run account.fullname = "Knut Carlsen" (my boss).
You can retrieve every row in some table that refers to the current object. This is what happens in group.getChildren(Account), which will return a list of those Accounts that have a foreign key refering to group.
If you retrieve the objects several times, the constructor will return the same object the second time (unless some timeout has expired). This means that changes done to the object is immediately visible to all instances. This is to reflect normal behaviour in object oriented programming.
>>> stain = Account("stain") >>> stain2 = Account("stain") >>> stain.fullname = "Knut Carlsen" >>> print stain2.fullname Knut Carlsen
forgetSQL is not a way to store objects in a database. It is a way to use databases as objects. You cannot store arbitrary objects in the database unless you use pickling.
forgetSQL does not help you with database design, although you might choose a development style that uses regular classes and objects at first, and then design the database afterwards. You could then change your classes to use forgetSQL for data retrieval and storage, and later possibly replace forgetSQL classes with even more advanced objects.
forgetSQL does not remove the need of heavy duty SQL. In some situations, SQL is simply the best solution. forgetSQL might involve many SQL operations for something that could be done in a single operations with a large magic query. If something does not scale up with forgetSQL, even if you refactored your code, you might try using SQL instead. This example would use excessive time in a table with a million rows:
for row in table.getAll(): row.backedUp = True row.save()
This would involve creating one million object instances (each row), one million SELECTs (to get the other values that needs to be saved), and one million UPDATEs. By using getAllIterator you could reduce this to just one million UPDATEs (one SELECT, reusing the same object), but still it would be far much slower than UPDATE table SET backedUp=true.
forgetSQL does not support commits/rollback. This might be implemented later, but I’m still unsure of how to actually use this in programming. Any suggestions are welcome.
forgetSQL does not ensure that objects in memory are in sync with what is stored in the database. The values in the object will be a snapshot of how the row were at the time you first tried to retrieve an attribute. If you change some value, and then save the object, the row is updated to your version, no matter what has happened in the database meanwhile. An object does not timeout while in memory, it does not refresh it’s values unless you call _loadDB() manually, as automatically updating could confuse programmers. However, a timeout value is set, and if exceeded, new objects retrieved from database (ie. Account("stain") will be fresh.
It is not easy to make a general way to ensure objects are updated. For instance, always checking it could be heavy. It could also confuse some programs if an object suddenly changes some of it’s attributes without telling, this could fuck up any updates the program is attempting to do. On the other hand, saving a changed object as forgetSQL is now, will overwrite all attributes, not just the changed ones.
Before you can use forgetSQL, you will need to generate a module containg the classes representing database tables. Luckily, forgetSQL ships with a program that can do this for you by guessing.
The program is called forgetsql-generate and should be installed by setup.py or the packaging system. You might need the devel-version of the forgetSQL package.
Create a file tables.txt, with a list of database tables, one per line. (This is needed since there is no consistent way to query a database about it’s tables)
Then generate the module representing your tables:
forgetsql-generate --dbmodule psycopg --username=johndoe --password=Jens1PuLe --database=genious --tables tables.txt --output Genious.py
Alternative, you could pipe the table list to forgetsql-generate and avoid --tables – and likewise drop --output and capture stdout from forgetsql-generate.
The generated module is ready for use, except that you need should set database connecting details. One possible way is included in the generated code, commented out and without a password.
It is recommended to set connection details from the outside instead, since the tables might be used by different parts of a system using different database passwords, connection details could be in a configuration file, you need persistent database connections, etc.
The way to do this is to set Genious._Wrapper.cursor to a cursor method, and Genious._Wrapper._dbModule to the database module used:
import Genious import psycopg conn = psycopg.connect(user="blal", pass="sdlksdlk", database="blabla") Genious._Wrapper.cursor = conn.cursor() Genious._Wrapper._dbModule = psycopg
This should be refactored to a more userfriendly interface.
We’ll call a class that is a representation of a database table a forgetter, because it inherits forgetSQL.Forgetter. This chapter will present normal usage of such forgetters by examples.
account = Account("stain") print account.fullname
If the primary key is wrong (ie. the row does not exist) accessing account.fullname will raise forgetSQL.NotFound. The object is actually not loaded from the database until a attribute is read. (delayed loading) One problem with that is that forgetSQL.NotFound will not be raised until the attribute is read.
To test if the primary key is valid, force a load:
account = Account("stain") try: account.load() except forgetSQL.NotFound(): print "Cannot find stain" return
allAccounts = Account.getAll() for account in allAccounts: print account.accountid, account.fullname
Note that getAll is a class method, so it is available even before creating some Account. The returned list will be empty if nothing is found.
Also note that if what you want to do is to iterate, using getAllIterator() would work well. This avoids creating all objects at once.
account = Account() account.accountid = "jennyme" # primary key account.fullname = "Jenny Marie Ellingsaeter" account.save()
If you have forgotten to set some required fields, save() will fail. If you don’t set the primary key, forgetSQL will try to guess the sequence name (tablename_primarykey_seq) to retrieve a new one. This might or might not work. For MySQL some other magic is involved, but it should work.
account = Account("stain") account.fullname = "Stian Stornes" # got married to a beautiful man
You can choose wether you want to call save() or not. If you don’t call save(), the object will be saved when the object reference disappaers (ie. del account, end of function, etc.) and collected by the garbage collector. Note that this might be delayed, and that any errors will be disgarded.
If you are unsure if you have used the correct datatype or want to catch save-errors, use save():
group = Group(17) group.accountid = 'itil' # a string won't work in a integer field try: group.save() except Exception, e: print "Could not save group %s: %s" % (group, e)
The exception raised will be database module specific, like psycopg.ProgrammingError, possible containing some useful information.
save() will return True if successful.
If you changed an attribute, and you don’t want to save the change to the database (as this will happen when the garbage collector kicks in), you have two choices:
reset the instance to a blank state:
This sets everything to None, including the primary key. If you have referenced the instance anywhere else, they will now experience a blank instance.
reload from database:
Note, load() will perform a new SELECT.
Note that you don’t have to reset() if you haven’t changed any attributes, the instance will only save if anything has changed.
account = Account("stain") print account.group.accountid print account.group.name
An attribute which is a foreign key to some other table will be identified by forgetsql-generate if it’s name is something like other_table_id. If the generator could not identify foreign keys correctly, modify _userClasses in the generated Forgetter definition. (See Specializing the forgetters).
To access the real primary key, use account.group.accountid or account.group._getID(). Note that the latter will return a tupple (in case the primary key contained several columns).o
You can set a foreign key attribute to a new object from the foreign class:
import random allGroups = Group.getAll() for account in Account.getAll(): # Set the group to one of the Group instances # in allGroups account.group = random.choice(allGroups) del account # Note that by reusing the account variable all of these # will be saved by the garbage collector
or to just the foreign primary key:
account.group = 18
Note that this referencing magic makes JOIN unneccessary in many cases, but be aware that due to lazy loading (attributes are not loaded from database before they are accessed for the first time), in some cases this might result in many SELECT-calls. There are ways to avoid this, see Wrapping SQL queries.
You might want to walk in reverse, finding all accounts that have a given group as a foreign key:
group = Group(15) members = group.getChildren(Account)
This is equivalent to SQL:
SELECT * FROM account WHERE groupid=15
Note that although rows are represented as instances, they will not be deleted from the database by dereferencing. Simply removing a name binding only removes the representation. (and actually forces a save() if anything has changed).
To remove a row from the database:
account = Account("stornes") account.delete()
delete() might fail if your database claims reference integrity but does not cascade delete:
group = Group(17) group.delete()
You may specify a where-sentence to be inserted into the SELECT-call of getAll-methods:
members = Account.getAll(where="groupid=17")
Note that you must take care of proper escaping on your own by using this approach. Most database modules have some form of escape functions.
In many cases, what you want to do with WHERE is probably the same as with getChildren():
group = Group(17) members = group.getChildren(Account)
This will be as effective as generating a WHERE-clasule, since group.load() won’t be run (no attributes accessed, only the primary key).
The sentence is directly inserted, so you need to use the actual SQL column names, not the attribute names. You can use AND and OR as you like.
If you have several clauses to be AND-ed together, forgetSQL can do this for you, as the where-parameter can be a list:
where = where.append("groupid=17") if something: where.append("fullname like 'Stian%'") Account.getAll(where=where)
If you have specified _orderBy (see Specializing the forgetters), the results of getAll* and getChildren will be ordered by those attributes.
If you want to specify ordering manually, you can supply a keyword argument to getAll:
all = Account.getAll(orderBy="fullname")
The value of orderBy could be either a string (representing the object attribute to be sorted) or a tupple of strings (order by A, then B, etc.). Note that you can only order by attributes defined in the given table.
If you want some other fancy sorting, sort the list after retrieval using regular list.sort():
all = Account.getAll() all.sort(lambda a,b: cmp(a.split()[-1], b.split()[-1])) # order by last name! :=)
There are specialized getAll methods for different situations.
If you just want the IDs in a table:
>>> all = Account.getAllIDs() ['stornes', 'stain', 'magnun', 'mjaavatt']
The regular getAll() actually runs getAllIDs(), and returns a list of instances based on those IDs. The real data is not loaded until attribute access. In some cases, this might be OK, for instance if you want to call getChildren and really don’t care about the attribute values.
If you are going to iterate through the list, a common case, use instead:
for account in Account.getAllIterator(): print account.fullname
This will return an iterator, not a list, returning Account objects. For each iteration, a new instance is returned, with all fields loaded. Internally in the iterator, a buffer of results from SELECT * is contained.
In Python, object creation is a bit expensive, so you might reuse the same object for each iteration by creating it first and specifying it as the keyword argument useObject:
for account in Account.getAllIterator(useObject=Account()): print account.fullname
Note that changes made to account in this case will be flushed unless you manually call save(). Do not pass this instance on, as it’s content will change for each iteration.
Finally, getAllText() will use _shortView (See Specializing the forgetters) and return tupples of (id, text). This is useful for a dropdown-list of selectors.
Sorry, this section is currently unfinished.
Sorry, this section is currently unfinished.
Sorry, this section is currently unfinished. | <urn:uuid:0233b67d-1ad1-4f36-90f2-a9b81209b723> | 2.75 | 4,149 | Documentation | Software Dev. | 51.471951 | 95,572,269 |
(photo credit: )
More than half of the dust needed for fertilizing the Brazilian rainforest is supplied by a valley in northern Chad, according to an international research team headed by Dr. Ilan Koren of the Weizmann Institute of Science's department of environmental sciences and energy research. In a study published recently in Environmental Research Letters, the scientists have explained how the Bodele valley's unique features might be responsible for making it such a major dust provider.
It has been known for more than a decade that the Amazon rainforest depends for its existence on a supply of minerals washed off by rain from the soil in the Sahara and blown across the Atlantic by dust. By combining various types of satellite data, Koren and colleagues from Israel, the United Kingdom, the US and Brazil have now for the first time managed to obtain quantitative information about the weight of this dust. Analyses of dust quantities were performed near the Bodele valley itself, on the shore of the Atlantic and at an additional spot above the ocean.
The data revealed that some 56 percent of the dust reaching the Amazon forest originates in the Bodele valley. They also showed that a total of some 50 million tons of dust make their way from Africa to the Amazon region every year, a much higher figure than the previous estimates of 13 million tons. The new estimate matches the calculations on the quantity of dust needed to supply the vital minerals for the continued existence of the Amazon rainforest.
The researchers suggest that the Bodele valley is such an important source of dust due to its shape and geographic features: It is flanked on both sides by enormous basalt mountain ridges, which create a cone-shaped crater with a narrow opening in the northeast. Winds that "drain" into the valley focus on this funnel-like opening similarly to the way light is focused by an optical lens, creating a large wind tunnel of sorts. As a result, gusts of surface wind that are accelerated and focused in the tunnel lift the dust from the ground and blow it toward the ocean, allowing the Bodele valley to export the vast amount of dust that makes a life-sustaining contribution to the Amazon rainforest.
NEW SCIENCE ACADEMY MEMBERS
Six distinguished new members have joined the Israel Academy of Sciences and Humanities. Chosen in the academy's general meeting on the basis of recommendations from its humanities and natural sciences branches, they are Prof. Moshe Oren, senior molecular biologist of the Weizmann Institute of Science; Prof. Moshe Idel, a leading Jewish philosophy expert at the Hebrew University; Prof. Gedeon Dagan, emeritus professor in Tel Aviv University's engineering faculty; Prof. Sergiu Hart, one of the world's leading mathematical economists from the Hebrew University; Prof. Shulamit Volkov, an expert in comparative European history at Tel Aviv University; and Hebrew University Prof. David Kazhdan, one of the world's most prominent mathematicians.
BRING IN THE GIRLS
Thirty 15-year-old girls from Beersheba have won a prize - a course for developing computer software that will lead to them becoming certified by Microsoft International as application developers. Beersheba's Sami Shamoon College of Engineering, in cooperation with the Ministry of Science and Technology, the Beersheba Municipality and Microsoft-Israel launched the program recently in a festive ceremony. The aim is to raise the number of women who go into scientific and engineering fields in higher education and the job market. The municipality chose the pupils among 60 studying four and five units of mathematics who took a qualifying exam. Each of the winners will be matched with female students at the college who will advise them and give them support during the 20-month course. The high-school pupils will also go on tours in industry and technological bases of the Israel Defense Forces and meet with female officers enrolled in the IDF's Atuda program.
College president Prof. Yehuda Haddad said that the course will integrate the girls into academic engineering studies and help them reach the right places in their military service and in industry. Dr. Shaul Yanai of the Science Ministry's "1,000 Scholarships" program to encourage women said that "unfortunately, the potential of half of the country's population is being wasted because few young women go into technological fields." He noted that Microsoft-Israel's Forum for Young Developers has included 800 youths, of them only two women, so far. The new Shamoon project will change this.
TAU AIMS FOR THE STARS
Tel Aviv University, in collaboration with several other Israeli universities, plans to join a large telescope facility outside Israel in a astronomical research project that will advance their researchers' ability to study the origin of galaxies and the universe, black holes, super-novae, planets and faraway stars. The exact location of the telescope has not yet been announced.
Called "New Horizons in Astronomy," the TAU effort is aimed at attracting the attention of the general public to science and talented young people to the Ramat Aviv campus, which recently hosted the British astrophysicist Prof. Stephen Hawking. Much stress will be on biological physics, which deals with physical principles underlying biological processes and molecules such as DNA, lipids and proteins. | <urn:uuid:8193b771-a518-423a-8168-b5945d47cb71> | 3.890625 | 1,082 | News Article | Science & Tech. | 30.751931 | 95,572,274 |
Three circles have a maximum of six intersections with each other. What is the maximum number of intersections that a hundred circles could have?
What size square corners should be cut from a square piece of paper to make a box with the largest possible volume?
Can you work out the dimensions of the three cubes?
Draw a square. A second square of the same size slides around the first always maintaining contact and keeping the same orientation. How far does the dot travel?
Choose a couple of the sequences. Try to picture how to make the next, and the next, and the next... Can you describe your reasoning?
Watch these videos to see how Phoebe, Alice and Luke chose to draw 7 squares. How would they draw 100?
In a right angled triangular field, three animals are tethered to posts at the midpoint of each side. Each rope is just long enough to allow the animal to reach two adjacent vertices. Only one animal. . . .
Two motorboats travelling up and down a lake at constant speeds leave opposite ends A and B at the same instant, passing each other, for the first time 600 metres from A, and on their return, 400. . . .
If you move the tiles around, can you make squares with different coloured edges?
A cheap and simple toy with lots of mathematics. Can you interpret the images that are produced? Can you predict the pattern that will be produced using different wheels?
Four rods, two of length a and two of length b, are linked to form a kite. The linkage is moveable so that the angles change. What is the maximum area of the kite?
Seven small rectangular pictures have one inch wide frames. The frames are removed and the pictures are fitted together like a jigsaw to make a rectangle of length 12 inches. Find the dimensions of. . . .
A rectangular field has two posts with a ring on top of each post. There are two quarrelsome goats and plenty of ropes which you can tie to their collars. How can you secure them so they can't. . . .
Show that all pentagonal numbers are one third of a triangular number.
How many winning lines can you make in a three-dimensional version of noughts and crosses?
Can you find a rule which connects consecutive triangular numbers?
A spider is sitting in the middle of one of the smallest walls in a room and a fly is resting beside the window. What is the shortest distance the spider would have to crawl to catch the fly?
A 10x10x10 cube is made from 27 2x2 cubes with corridors between them. Find the shortest route from one corner to the opposite corner.
A huge wheel is rolling past your window. What do you see?
Imagine a large cube made from small red cubes being dropped into a pot of yellow paint. How many of the small cubes will have yellow paint on their faces?
Square numbers can be represented as the sum of consecutive odd numbers. What is the sum of 1 + 3 + ..... + 149 + 151 + 153?
Triangular numbers can be represented by a triangular array of squares. What do you notice about the sum of identical triangle numbers?
Can you maximise the area available to a grazing goat?
If you can copy a network without lifting your pen off the paper and without drawing any line twice, then it is traversable. Decide which of these diagrams are traversable.
Euler discussed whether or not it was possible to stroll around Koenigsberg crossing each of its seven bridges exactly once. Experiment with different numbers of islands and bridges.
How many moves does it take to swap over some red and blue frogs? Do you have a method?
Use a single sheet of A4 paper and make a cylinder having the greatest possible volume. The cylinder must be closed off by a circle at each end.
If you have only 40 metres of fencing available, what is the maximum area of land you can fence off?
Imagine an infinitely large sheet of square dotty paper on which you can draw triangles of any size you wish (providing each vertex is on a dot). What areas is it/is it not possible to draw?
What is the minimum number of squares a 13 by 13 square can be dissected into?
In the game of Noughts and Crosses there are 8 distinct winning lines. How many distinct winning lines are there in a game played on a 3 by 3 by 3 board, with 27 cells?
How could Penny, Tom and Matthew work out how many chocolates there are in different sized boxes?
Find the ratio of the outer shaded area to the inner area for a six pointed star and an eight pointed star.
What would be the smallest number of moves needed to move a Knight from a chess set from one corner to the opposite corner of a 99 by 99 square board?
Can you describe this route to infinity? Where will the arrows take you next?
A right-angled isosceles triangle is rotated about the centre point of a square. What can you say about the area of the part of the square covered by the triangle as it rotates?
Can you dissect a square into: 4, 7, 10, 13... other squares? 6, 9, 12, 15... other squares? 8, 11, 14... other squares?
Have a go at this 3D extension to the Pebbles problem.
A 2 by 3 rectangle contains 8 squares and a 3 by 4 rectangle contains 20 squares. What size rectangle(s) contain(s) exactly 100 squares? Can you find them all?
Rectangles are considered different if they vary in size or have different locations. How many different rectangles can be drawn on a chessboard?
Show that among the interior angles of a convex polygon there cannot be more than three acute angles.
Can you mark 4 points on a flat surface so that there are only two different distances between them?
How efficiently can you pack together disks?
Points P, Q, R and S each divide the sides AB, BC, CD and DA respectively in the ratio of 2 : 1. Join the points. What is the area of the parallelogram PQRS in relation to the original rectangle?
A useful visualising exercise which offers opportunities for discussion and generalising, and which could be used for thinking about the formulae needed for generating the results on a spreadsheet.
The whole set of tiles is used to make a square. This has a green and blue border. There are no green or blue tiles anywhere in the square except on this border. How many tiles are there in the set?
Imagine starting with one yellow cube and covering it all over with a single layer of red cubes, and then covering that cube with a layer of blue cubes. How many red and blue cubes would you need?
The image in this problem is part of a piece of equipment found in the playground of a school. How would you describe it to someone over the phone?
A cyclist and a runner start off simultaneously around a race track each going at a constant speed. The cyclist goes all the way around and then catches up with the runner. He then instantly turns. . . .
Can you cross each of the seven bridges that join the north and south of the river to the two islands, once and once only, without retracing your steps? | <urn:uuid:a6592e23-bb94-44c0-a796-66af919d11e9> | 3.75 | 1,522 | Content Listing | Science & Tech. | 69.929435 | 95,572,288 |
NASA's TRMM satellite identified areas of heavy rainfall occurring in Hurricane Cristobal as it continued strengthening on approach to Bermuda.
NASA's Tropical Rainfall Measuring Mission or TRMM satellite flew above Hurricane Cristobal on August 26 at 11:35 UTC (7:35 a.m. EDT) gathering rainfall data. A rainfall analysis derived from TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) data instruments were overlaid on visible/infrared image from NOAA's GOES-East satellite to create a total picture of the storm.
The image was made at NASA's Goddard Space Flight Center in Greenbelt, Maryland. NASA and the Japan Aerospace Exploration Agency manage TRMM.
When TRMM captured that rainfall data, Cristobal was a category one hurricane with sustained winds estimated to be slightly above 65 knots (about 75 mph). Cristobal didn't have a clearly defined eye because vertical wind shear was still affecting the tropical cyclone's appearance and pushing clouds and storms away from the center.
TRMM PR and TMI rainfall data found heavy rain to the northeast of Cristobal's center and in intense convective storms within a feeder band streaming in from the southwest. Some of the powerful storms in the feeder band were found by TRMM PR to be dropping rain at a rate of 133.8 mm (5.2 inches) per hour.
TRMM's Precipitation Radar (PR) reflectivity data were used to create a 3-D view of precipitation within the feeder band (band of thunderstorms wrapping into the center) south of Cristobal's center. Those data showed that some energetic storms in this band were reaching heights of over 15km (about 9.3 miles) and were generating heavy rain.
Satellite imagery on August 27 showed some strong thunderstorms had redeveloped near the center of Cristobal mainly in the western semicircle. Satellite imagery also showed that dry air was wrapping south and east of the center.
At 11 a.m. EDT on Wednesday, August 27, Cristobal's maximum sustained winds were near 80 mph (130 kph) and some strengthening is possible. It was centered near latitude 31.8 north and longitude 72.2 west. That puts the center of Cristobal about 435 miles (700 km) west of Bermuda and even closer to Cape Hatteras, North Carolina at 300 miles (485 km) to the Cape's southeast.
Cristobal has a large wind field where hurricane force winds extend outward from the center up to 60 miles (95 km) and tropical storm force winds extend outward up to 205 miles (335 km). The estimated minimum central pressure is 983 millibars.
Cristobal is moving toward the north near 12 mph (19 kph) and the National Hurricane Center (NHC) expects a turn to the northeast. NHC noted that the center of Cristobal will pass well northwest of Bermuda late on August 27 and stay away from the U.S. and Canadian mainland on its track to the North Atlantic Ocean.
Cristobal is expected to become a powerful extra-tropical cyclone over the north Atlantic by Friday, August 29.
Text credit: Hal Pierce/Rob Gutro
SSAI/NASA's Goddard Space Flight Center
Rob Gutro | Eurek Alert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
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Analysis of 11,000 mammal, amphibian and bird species shows major gaps in global coverage
At least 223 bird, 140 mammal and 346 amphibian species threatened with extinction currently have no protection whatsoever over any part of their ranges, according to the most comprehensive analysis of its kind of the worlds protected area system.
In addition, many existing protected areas are so small in size as to be virtually ineffective in conserving species, placing another 943, and probably many more bird, mammal and amphibian species, at risk. Without an immediate and strategic expansion of the protected area system, scientists expect a major wave of extinctions within the next few decades.
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
23.07.2018 | Materials Sciences
23.07.2018 | Information Technology
23.07.2018 | Health and Medicine | <urn:uuid:f113606d-dbab-4961-b243-e6b4c79ce8ee> | 2.71875 | 726 | Content Listing | Science & Tech. | 37.25098 | 95,572,305 |
|The little book about OS development|
|By Thom Holwerda on 2016-12-27 21:27:24|
This text is a practical guide to writing your own x86 operating system. It is designed to give enough help with the technical details while at the same time not reveal too much with samples and code excerpts. We've tried to collect parts of the vast (and often excellent) expanse of material and tutorials available, on the web and otherwise, and add our own insights into the problems we encountered and struggled with.
- Rust 1.27.0 released - 2018-06-21
- What it was like to write a full blown Flutter application - 2018-06-18
- The land before binary - 2018-06-10
- UTC is enough for everyone... Right? - 2018-05-30
- More related articles | <urn:uuid:37efa3c4-298c-4225-95c8-e3b5f1a81391> | 2.578125 | 179 | Truncated | Software Dev. | 74.525233 | 95,572,325 |
Biology is full of stories that read like a modern day zombie apocalypse. For instance, the parasite Toxoplasma gondii has been in the news for its ability to infect the brains of rats, and reprogram their normal behavioral responses such that they lose their innate fear of cats. Previously, we reviewed the research about the parasitic fungus that infects ants, causing drastic changes in typical ant behavior to aid in distribution of the fungal spores.
In April of this year, MacLean and colleagues published research in PLOS Biology describing interactions between a phytoplasma parasite and Arabidopsis thaliana. What is nice about this particular “zombie” biology story is that the researchers present the beginnings of the genetics that underlie the plant-parasite-insect relationship, moving beyond a description of the phenotypic changes that occur to describing an actual mechanism for those changes.
Phytoplasmas are bacterial plant parasites with life cycles that require two distinct hosts, the plant and insects that feed on the vegetative structures of the plants. Phytoplasmas can effect dramatic developmental changes on plants that include converting flowers to leaf-like structures or causing a proliferation of stems known as a witches’ broom. In the study authored by Maclean, the researchers looked at the interactions among “Aster Yellows phytoplasma strain Witches’ Broom” (AY-WB), its insect vector (leafhoppers) and the wild brassica plant, Arabidopsis thaliana.
In Arabidopsis plants infected with AY-WB, flowers are transformed into leaf-like structures. The plant loses its ability to reproduce as a result, and exists solely to provide food for its phytoplasma parasite—essential becoming a “zombie” plant.
The patterning and development of the floral meristem involves an intricate sequence of gene regulation turning “on” or “off” the correct genes at the precise time in the precise place to produce the concentric whorls of flower structure: sepals, petals, stamens and carpels. In previous work, this team had identified a protein from AY-WB, SAP54, which is required for this transformation and showed that Arabidopsis plants transformed with this protein develop the same leaf-like structures seen in the infected plants.
In this paper, the researchers began by asking what Arabidopsis proteins interact with SAP54. A yeast two-hybrid screen identified Type II MADS-domain containing transcription factors (MTFs). Members of this class of proteins include AGAMOUS-LIKE 12, MADS AFFECTING FLOWERING1 and several other transcription factors that specifically regulate genes that are responsible for the conversion of vegetative to flowering meristem and the production of the flower structure. Further investigation revealed that the interaction involved the keratin-like domain of these proteins, which is unique to flowering plants and not found in the MTFs of other organisms such as the leaf hopper.
They next looked at the interactions between SAP54 and Arabidopsis proteins in infected plants using GFP tagged SAP54 transgenic plants. Immunoprecipitation and mass spectrometry analysis revealed that many of the MTFs identified in the yeast two-hybrid screen do indeed interact with SAP54 in plants.
The researchers hypothesized that SAP54 may be interfering with MTF function. Analysis of Western blots from healthy and infected plants expressing tagged MTFs indicated that MTF proteins are less abundant in the leaf-like structures of the infected plants. These and other experiments led the team to propose that SAP54 is affecting the stability of the MTF proteins either directly or by upregulating their degradation using a pathway such as the ubiquitin system. Because the treatment of samples with epoxomicin, an inhibitor of the ubiquitin degradation pathway, allowed the Type II MTFs to accumulate, the researchers concluded that SAP54 was promoting the destabilization and degradation of the Type II MTFs using the hosts normal ubiquitin tagging and protein degradation pathways.
The two-hybrid screen used to identify the interaction of Type II MTFs with SAP54, also revealed interaction between SAP54 and RAD23C and RAD23D. These proteins are believed to be proteins responsible for shuttling ubiquitin-tagged proteins to the proteasome for degradation. Thus SAP54 appears to create a “short-circuit” between two cellular pathways, flower development and protein degradation, by directly interacting with key proteins in both pathways.
But that’s not all.
The production of leaf-like structures instead of flowers has the advantage of making the plants more “attractive” to the leaf hopper insect vectors. These insects feed on the vegetative tissues of the plants, and the phytoplasma are spread from plant to plant when a leaf hopper feeds on an infected plant and then moves to another plant. The researchers performed leaf hopper “choice assays” and found that the insects were more likely to colonize both the infected plants and transgenic plants expressing SAP54, than wildtype plants or plants that produced green flowers as a result of an unrelated mutation. Furthermore this preference appears to be RAD23 dependent, although the exact nature of the RAD23 role is not understood.
This research showed how a small, bacterial parasite uses one protein to change the developmental program of a plant, converting the plant into a vegetative food-producing system on which that parasite’s vectors are more likely to lay eggs and feed. Amazing. Zombie Plant Genetics—Just another reason I love science.
MacLean, A.M. et al. (2014) Phytoplasma effector SAP54 hijacks plant reproduction by degrading MADS-box proteins and promotes insect colonization in RAD23-dependent manner. PLOS Biology 12, e1001835.
John Innes Centre News. How plants become zombies. [Internet: accessed 4/28/2014 http://news.jic.ac.uk/2014/04/how-plants-become-zombies/]
Irish, V.F. (2010) The flowering of Arabidopsis flower development. The Plant Journal 61, 1014.
Latest posts by Michele Arduengo (see all)
- Questions of Genome Privacy and Protection - June 15, 2018
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- Orchestrating the Genome: Final Thoughts for #HumanGenomeMonth - April 30, 2018 | <urn:uuid:15b34e1d-894d-41bf-86fe-6977f84c79d0> | 3.421875 | 1,367 | Nonfiction Writing | Science & Tech. | 32.941835 | 95,572,351 |
In quantum-mechanical terms, the cyclotron and electron-spin resonances originate from optical transitions of carriers between the Landau levels and magneticfield-splitted spin sublevels. Measurement of the dependence of the cyclotronresonance frequency on the magnitude and direction of magnetic field provides a direct and reliable way for determining the electron (or hole) effective mass, as well as for studying the nonparabolicity and nonsphericity of an electronic band in a semiconductor. In connection with this, we derive in Sec. 7.1 expressions for the longitudinal and transverse electron mass in a superlattice at the miniband bottom, analyze how the choice of the boundary conditions for the envelopes at the interfaces affects these masses, and discuss the nonparabolicity of the miniband spectrum.
KeywordsCyclotron Resonance Landau Level Intersubband Transition Velocity Operator Intraband Transition
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- 7.1N.F. Gashimzade, E.L. Ivchenko: Fiz. Tekh. Poluprovodn. 25, 323 (1991) [Sov. Phys. - Semicond. 25, 195 (1991)]Google Scholar
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Electron Spin Resonance, g-Factor
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Intersubband Transitions and IR Spectroscopy
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- Golub L.E., E.L. Ivchenko, R.Ya. Rasulov: Intersubband absorption of light in quantum wells for semiconductors with the complicated band structure. Fiz. Tekh. Poluprovodn. 29, 1093 (1995) [Semiconductors 29, 566 (1995)]Google Scholar | <urn:uuid:0f66b931-fc33-48cc-a041-dc7de687332c> | 2.515625 | 693 | Academic Writing | Science & Tech. | 52.243669 | 95,572,380 |
We can find the resultant force by resolving in the plane of the circle. The only force acting in the horizontal plane is the tension So by resolving T = mrω 2
Very important point! The circular force is not an additional force – it is the resultant of the forces present.
Typical exam style question Ball hangs from a light piece of inextensible string and describes a horizontal circle of radius,r and makes an angle θ with the vertical. If the mass of the ball is m kg i)calculate the tension, T in the string ii)calculate the angular velocity, ω in terms of g, r and θ. | <urn:uuid:b0471065-7f56-42a4-a93c-ead5554a4415> | 3.984375 | 136 | Content Listing | Science & Tech. | 59.748367 | 95,572,381 |
A research team led by University of Michigan evolutionary biologist Yin-Long Qiu has new findings that help resolve long-debated questions about the origin and evolution of land plants. The work will be published online this week in the Proceedings of the National Academy of Sciences.
Two major steps kicked off the chain of events that helped land plants prosper, forming the basis for modern land-based ecosystems and fundamentally altering the course of evolution of life on earth, said Qiu. The first step was the colonization of land by descendents of aquatic plants known as charophyte algae. That event opened up a vast new world where the sun's intensity was undiminished by passage through water and where carbon dioxide—another essential ingredient for plant life—was abundant.
The second event was a key change in plant life cycles. Plants exhibit a phenomenon known as alternation of generations, in which two alternating forms with different amounts of DNA make up a complete life cycle. One form, known as a sporophyte, produces spores, which grow into individuals of the other form, called gametophytes. Gametophytes produce gametes—eggs and sperm—which unite to form a fertilized egg capable of becoming a new sporophyte, thus completing a life cycle. While all plants exhibit alternation of generations, some spend most of their life cycle as sporophytes, and others spend more time in the gametophyte phase.
"Early in the history of plant evolution, a shift occurred," said Qiu, an assistant professor of ecology and evolutionary biology. "If you look at the so-called 'lower' plants such as algae, liverworts and mosses, they spend most of their life cycle as gametophytes. But if you look at plants like ferns, pines and flowering plants, they spend most of their time as sporophytes. Geneticists, developmental biologists and evolutionists have been wondering how the switch happened and have put forth two competing hypotheses."
For each hypothesis, scientists have come up with an evolutionary scheme showing how different plant lineages should be related to explain the generation shift. Studies over the last century have produced conflicting results on relationships among early land plant lineages, leaving unanswered the most critical question of how the shift in alternation of generations occurred. Qiu's group used three complementary sets of genetic data, involving more than 700 gene sequences, to resolve relationships among the four major lineages of land plants: liverworts, mosses, hornworts and vascular plants (which include ferns, pines and flowering plants). Their analysis showed that liverworts—tiny green, ribbon-like plants often found along river banks—represent the first lineage that diverged from other land plants when charophyte algae first came onto land, and an obscure group called hornworts, often found in abandoned corn fields, represents the progenitors of the vascular plants.
"Basically we captured a few major events that happened in the first few tens of millions of years of land plant evolution," Qiu said. The results make sense in light of the plants' life cycle patterns. Charophyte algae, liverworts and mosses spend most of the cycle in a free-living gametophyte phase; the sporophyte is a small, short-lived organism that lives on the gametophyte. Vascular plants, on the other hand, spend most of their time as free-living sporophytes, with small, short-lived, gametophytes that often live on the sporophytes. Hornworts may hold a clue to understanding how this shift happened, as they spend most of their life cycle in the gametophyte phase, but their sporophytes---unlike those of liverworts and mosses—show a tendency to become free-living.
Understanding evolutionary relationships among plant groups is crucial to understanding their biology, just as understanding relationships among primates advances our knowledge of human behavior, anatomy and physiology, Qiu said.
"As humans, we're always interested in knowing where we came from and why we are different from other primates," Qiu said. "Now that we know, from phylogenetic analyses, that our closest relative is the chimpanzee, we can compare the chimpanzee genome with our own genome and compare the chimpanzee brain with our own brain and compare chimpanzee behavior with human behavior.
But this all assumes we know the chimpanzee is our brother. What if we didn't know? Understanding evolutionary history really is the foundation of biology, and with today's emphasis on biofuels and medically important plants, it should be clear how important it is to learn the evolutionary history of all the organisms on our planet."
Qiu collaborated on the project with 20 other researchers from the University of Michigan; the University of Massachusetts, Amherst; the Chinese Academy of Sciences; Universitat Bonn in Germany; the University of Chicago; Southern Illinois University; the University of Akron in Ohio; Freie Universitat Berlin in Germany; Dresden University of Technology in Germany and Harvard University. The U.S. National Science Foundation, the National Natural Science Foundation of China and the Michigan Society of Fellows provided funding.
Nancy Ross-Flanigan | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
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why is scientific notation used in science
What is scientific notation? Why do we use it? How do we use it? How can we write a number in scientific notation? These are some questions that well answer in todays post. What is scientific notation and why do we use it? Working with very large or small quantities usually ends up being quite complicated. P
Scientific notation is a way to write numbers in an abbreviated way, making it easier to work with these numbers. How can you write numbers in scientific notation? A number that only has a 1s place and decimals. An exponent that indicates the power of 10. Why do we multiply by a power of 10? To the right, when the exponent is positive (when we are multiplying by a number greater than or equal to 10).
For example: 7510 = 750 =7500 35. 6910 = 356. 9 35. 69100 = 35. 6910 = 3569 To the left, when the exponent is positive (when multiplying by a number less than 1). By doing so, we make the number smaller: = 75/10 = 7. 5 P= 75/100 = 0. 75 35. 6910 P= 3. 569 35. 6910 P= 35. 69/100 = 0. 3569 Why does the decimal portion only have a 1s place and decimals? It only has a 1s place and decimals so that it follows the universal format that is understood everywhere in the world. In addition to being universal, it helps us compare quantities with a single glance as we can focus on the power of 10.
The bigger the exponent is, the bigger the number. Lets order the following numbers in scientific notation: 3. 6352P 8. 235 6. 3005 1. 3225P Carefully looking at the exponent, we can order the numbers from least to greatest: 8. 235 3. 6352P 6. 3005 PP 1. 3225 0. 8235 PP PP363. 52 PP PP6300. 5 PP PP13225 That wraps it up for scientific notation. Can you think of another reason why its useful? If you liked this post and want to keep on learning more, make an account at Pand become a math genius! Do you know this number, 300,000,000 m/sec.? It's the Speed of light! Do you recognize this number, 0. 000 000 000 753 kg. This is the mass of a dust particle!
Scientists have developed a shorter method to express very large numbers. This method is called scientific notation. Scientific Notation is based on powers of the base number 10. The number 123,000,000,000 in scientific notation is written as : The first number 1. 23 is called the coefficient. It must be greater than or equal to 1 and less than 10. The second number is called the base. It must always be 10 in scientific notation. The base number 10 is always written in exponent form. In the number 1. 23 x 10 the number 11 is referred to as the exponent or power of ten. Put the decimal after the first digit and drop the zeroes.
In the number 123,000,000,000 The coefficient will be 1. 23 To find the exponent count the number of places from the decimal to the end of the number. In 123,000,000,000 there are 11 places. Therefore we write 123,000,000,000 as: Exponents are often expressed using other notations. The number 123,000,000,000 can also be written as: 1. 23E+11 or as 1. 23 X 10^11 For small numbers we use a similar approach. Numbers less smaller than 1 will have a negative exponent. A millionth of a second is: 0. 000001 sec. or 1. 0E-6 or 1. 0^-6 For online assessment question in scientific notation (including multiplication and division problems) ---.
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why do we use x and y in math
why do we use x and y in algebra
why do we use scientific notation in chemistry
why do we use powers of ten and scientific notation
why do we use engineering notation rather than scientific notation
why do we call a decimal a decimal
why is 10 to the 0 power 1 | <urn:uuid:b0186844-8dcf-41c0-a070-930d015b6f79> | 3.828125 | 890 | Content Listing | Science & Tech. | 88.048003 | 95,572,390 |
27 May 2010
Shark attack stats highlight risk of monochromatic Speedos
by Kate Melville
An analysis of shark attacks by researchers from the University of Florida (UF) has found that attacks are most likely to occur on a Sunday, in less than 6 feet of water, during a new moon and involve surfers wearing black and white bathing suits.
The analysis was conducted using statistics from attacks that occurred in Florida's Volusia County, dubbed the "Shark Attack Capital of the World," between 1956 and 2008. The researchers also spent a year observing people between Daytona Beach and New Smyrna Beach, said George Burgess, director of the International Shark Attack File at UF.
"It's basically an analysis of why, where and when in an area that traditionally has had more shark-human interactions than any other stretch of coastline in the world," Burgess said. "One of our students, Brittany Garner, essentially camped out there, counted the number of heads on the beach and took photographs."
While this 47-mile-long section of Central Florida's Atlantic coast leads in human-shark skirmishes, making up 21 percent of all global attacks between 1999 and 2008, most are "hit and run" incidents that seldom cause serious injury and no fatalities occurred.
"Calling them attacks is probably a misnomer because the consequences are usually no more severe than a dog bite," Burgess explained. "They're not the same kind of bites made by 10- to 20-foot-long white sharks that you have off the coast of California. Here we see a different style of attack, primarily perpetrated by smaller fish-eating sharks such as spinners and blacktips that are less than 6 to 7 feet long, which because of their size normally seek smaller prey."
There have been 231 shark attacks between the first one reported in 1956 in Volusia County and 2008. According to Burgess, human, shark and environmental factors combine to create a perfect storm of favorable conditions in Volusia County for attacks, particularly near Ponce Inlet between Daytona Beach and New Smyrna Beach.
The more people in the water the greater the chances they will encounter a shark, and New Smyrna Beach south of the inlet is a "hot spot" for surfers. "Hand splashing and feet kicking provoke sharks, which bite and release what they mistake for normal prey items in the turbid waters," Burgess noted.
Young white males were attacked most because they spend the most time in the water, Burgess said. Ninety percent of victims were male, 77 percent of 196 victims were between 11 and 30 years old and in the 171 cases where race was known, 98 percent were white.
Well over half of the 220 victims were bit on the leg, more than five times the number bit on the arms, the second highest body part to be injured. Surfers were the most frequent victims, making up 61 percent of the total. They tended to be bitten more in the early morning and late afternoon when waves were highest and they spend more time surfing.
"At the time of the attack, most of the surfers were sitting or holding onto the board waiting for a wave, which explains why most surf victims were bitten on the legs," Burgess said.
Human leisure habits led to the fewest number of human encounters on Wednesdays and the highest on Sundays, followed by Saturdays. The greatest number of attacks occurred during new moons, followed by full moons, the edges of the lunar extreme when the moon has its biggest pull on the tidal phase. "Probably the moon's phases influence the movements and reproductive patterns of fish, the shark's food source, just as they affect human behavior," Burgess explained.
Most incidents involved one bite, occurred in turbid, murky or muddy waters and were at the water's surface. More victims wore swimsuits that were black and white than any other color combination, followed by black and yellow, attesting to sharks' abilities to see contrast.
Source: University of Florida | <urn:uuid:8e3c86c5-1392-42c7-9f62-5a3cde808067> | 2.671875 | 819 | News Article | Science & Tech. | 43.58375 | 95,572,406 |
The latest innovation in alternative energy? Sweat.
And no, that’s not a metaphor for hardworking scientists. Salty sweat may serve as a viable energy source to power small electronic devices, according to new research from the University of California—San Diego.
A temporary tattoo embedded with a small sensor debuted at a meeting of the American Chemical Society this week. It is capable of harnessing the lactic acid that secretes through our skin when we exercise to produce a small amount of energy.
Let’s repeat that: Science has now graced us with a sweat-battery in the form of a tattoo.
Of course, this sci-fi tech comes with a few caveats. It appears the fitter you are, the less power you are able to generate because you secrete less lactic acid. Also, the device is now only capable of producing four microWatts, just enough to power a small LED light.
So your sweat won’t power a city, but researchers expect that new versions of the tattoo/chip will be able to charge a small watch or even a smartphone.
They say good things come with a little sweat, but now thanks to science, so too does a quick recharge. | <urn:uuid:6081ece5-a15b-4173-8791-cbf839b58d21> | 2.75 | 254 | News Article | Science & Tech. | 54.637982 | 95,572,409 |
Graham's number is a gigantic natural number that was defined by a man named Ronald Graham, a mathematician credited by the American Mathematical Society as being "one of the principal architects of the rapid development worldwide of discrete mathematics in recent years".
Graham was solving a problem in an area of mathematics called Ramsey theory. He proved that the answer to his problem was smaller than Graham's number.
Ronald Graham juggling a four ball fountain (1986)
HERE ARE 5 UNUSUAL AND FASCINATING FACTS ABOUT GRAHAM'S NUMBER:
1. Guinness Book Of World Records
The number was published in the 1980 Guinness Book of World Records after the popular science writer Martin Gardner described it in the "Mathematical Games" section of Scientific American in November 1977 as "a bound so vast that it holds the record for the largest number ever used in a serious mathematical proof."
2. At The Time Of Its Creation...
Graham's number was the largest specific positive integer ever to have been used in a published mathematical proof at the time of its introduction.
3. Close Enough To Infinity
Many scientists describe it to be probably "close enough" to infinity!
4. Your Head Would Collapse Into a Black Hole?!
The basis of this mind-bending theory is that only so much information can be stored within a finite space, according to the laws of physics.
5. The Mind-Boggling Up-Arrows...
- In order to be able to write Graham's number down, we have to use Knuth's up-arrow notation in which a sequence of numbers are used to define the following ones
- When we reach the 64th number, it will be Graham's mind-boggling number
- However, what's stunning is that this process of up-arrows extends to a scale that could fill up the universe and beyond.
Conclusion: Don't try to memorize Graham's number at home folks ... this number could do some serious harm! :) | <urn:uuid:6bd54d5a-217f-49f8-b13d-ec87e496ae9f> | 3.421875 | 410 | Listicle | Science & Tech. | 57.09756 | 95,572,416 |
Research published last week in Science suggested that the makeup of the Earth's lower mantle, which makes up the largest part of the Earth by volume, is significantly different than previously thought.
The work, performed at the Advanced Photon Source at the U.S. Department of Energy’s Argonne National Laboratory, will have a significant impact on our understanding of the lower mantle, scientists said. Understanding the composition of the mantle is essential to seismology, the study of earthquakes and movement below the Earth's surface, and should shed light on unexplained seismic phenomena observed there.
We live atop the thinnest layer of the Earth: the crust. Below is the mantle (red), outer core (orange), and finally inner core (yellow-white). The lower portion of the mantle is the largest layer – stretching from 400 to 1,800 miles below the surface. Research at Argonne’s Advanced Photon Source recently suggested the makeup of the lower mantle is significantly different from what was previously thought. Image by Johan Swanepoel/Shutterstock. Click to enlarge.
Though humans haven't yet managed to drill further than seven and a half miles into the Earth, we've built a comprehensive picture of what's beneath our feet through calculations and limited observation. We all live atop the crust, the thin outer layer; just beneath is the mantle, outer core and finally inner core.
The lower portion of the mantle is the largest layer — stretching from 400 to 1,800 miles below the surface — and gives off the most heat. Until now, the entire lower mantle was thought to be composed of the same mineral throughout: ferromagnesian silicate, arranged in a type of structure called perovskite.
The pressure and heat of the lower mantle is intense — more than 3,500° Fahrenheit. Materials may have very different properties at these conditions; structures may exist there that would collapse at the surface.
To simulate these conditions, researchers use special facilities at the Advanced Photon Source, where they shine high-powered lasers to heat up the sample inside a pressure cell made of a pair of diamonds. Then they aim powerful beams of X-rays at the sample, which hit and scatter in all directions. By gathering the scatter data, scientists can reconstruct how the atoms in the sample were arranged.
The team found that at conditions that exist below about 1,200 miles underground, the ferromagnesian silicate perovskite actually breaks into two separate phases. One contains nearly no iron, while the other is full of iron. The iron-rich phase, called the H-phase, is much more stable under these conditions.
"We still don't fully understand the chemistry of the H-phase," said lead author and Carnegie Institution of Washington scientist Li Zhang. "But this finding indicates that all geodynamic models need to be reconsidered to take the H-phase into account. And there could be even more unidentified phases down there in the lower mantle as well, waiting to be identified."
The facilities at Argonne’s Advanced Photon Source were key to the findings, said Carnegie scientist Yue Meng, also an author on the paper. "Recent technological advances at our beamline allowed us to create the conditions to simulate these intense temperatures and pressures and probe the changes in chemistry and structure of the sample in situ," she said.
"What distinguished this work was the exceptional attention to detail in every aspect of the research — it demonstrates a new level for high-pressure research," Meng added.
The paper, "Disproportionation of (Mg,Fe)SiO3 perovskite in Earth’s deep lower mantle," was published in Science. Other Argonne coauthors were Wenjun Liu and Ruqing Xu.
The work was performed at the High Pressure Collaborative Access Team (HPCAT) beamline, which is run by the Geophysical Laboratory at the Carnegie Institution of Washington. Wenge Yang and Lin Wang from the APS-Carnegie Institution's High Pressure Synergetic Consortium (HPSynC) also contributed to the paper.
The research was supported by the National Science Foundation and performed at the HPCAT beamline of the Advanced Photon Source, which is supported by the U.S. Department of Energy's Office of Basic Energy Sciences, the National Nuclear Security Administration and the National Science Foundation. Portions of this work were performed at GeoSoilEnviroCARS at the APS, run by the University of Chicago and supported by the National Science Foundation and the DOE; at 34ID-E beamline; and at Shanghai Synchrotron Radiation Facility. The Advanced Photon Source is supported by DOE's Office of Basic Energy Sciences.
The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy's Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit the user facilities directory.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.
DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
Tona Kunz | Eurek Alert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:166f58b7-1a1c-4841-aa6e-57c2f2aa288e> | 4.4375 | 1,879 | Content Listing | Science & Tech. | 37.727926 | 95,572,472 |
Writing out data¶
Data contained in IntelHex can be written out in a few different formats, including HEX, bin, or python dictionaries.
You can write out HEX data contained in object by method
f should be filename or file-like object.
Note that this can include builtins like sys.stdout.
Also you can use the universal tofile.
To convert data of IntelHex object to HEX8 file format without actually saving it to disk you can use the builtin StringIO file-like object, e.g.:
>>> from cStringIO import StringIO >>> from intelhex import IntelHex >>> ih = IntelHex() >>> ih = 0x55 >>> sio = StringIO() >>> ih.write_hex_file(sio) >>> hexstr = sio.getvalue() >>> sio.close()
hexstr will contain a string with the content of a HEX8 file.
You can customize hex file output with following optional arguments
write_start_addr- you can disable start address record in new hex file;
eolstyle- you can force
CRLFline endings in new hex file.
byte_count- you can control how many bytes should be written to each data record.
To write data as a hex file with default settings you also can use
# the code below is the same as "ih.write_hex_file(sio)" >>> ih.tofile(sio, format='hex')
Class IntelHex has several methods for converting data of IntelHex objects into binary form:
tobinarray(returns array of unsigned char bytes);
tobinstr(returns string of bytes);
tobinfile(convert content to binary form and write to file).
>>> from intelhex import IntelHex >>> ih = IntelHex("foo.hex") >>> ih.tobinfile("foo.bin")
Also you can use universal method
tofile to write data as binary file:
>>> ih.tofile("foo.bin", format='bin')
Writing data in chunks¶
If you need to get binary data from IntelHex as series of chunks then you can
tobinstr methods either start/end addresses
or start address and required size of the chunk. This could be useful if
you’re creating Eeprom/Flash IC programmer or bootloader.
EEPROM_SIZE = 8192 # 8K bytes BLOCK_SIZE = 128 # 128 bytes for addr in range(0, EEPROM_SIZE, BLOCK_SIZE): eeprom.i2c_write(addr, ih.tobinarray(start=addr, size=BLOCK_SIZE)) | <urn:uuid:e002cb55-e49e-4aee-a70e-b7ed3cc5875d> | 2.640625 | 584 | Documentation | Software Dev. | 50.657005 | 95,572,478 |
The system will be unavailable due to maintenance on Thursday July 19 from 7:00-8:30 am ET.
Numerical analysis of bat noseleaf dynamics and its impact on the encoding of sensory information
Gupta, Anupam Kumar
MetadataShow full item record
Horseshoe bats possess a sophisticated biosonar system that helps them to negotiate complex unstructured environments by relying primarily on the sound as the far sense. For this, the bats emit brief ultrasonic pulses and listen to incoming echoes to learn about the environment. The sites of emission and reception in these bats are surrounded by baffle structures called "noseleaves" and "pinnae (outer ears)". These are the the only places in the biosonar system where direction-dependent information gets encoded. These baffle structures in bats unlike the engineering systems like megaphones have complex static geometry and can undergo fast deformations at the time of pulse emission/reception. However, the functional significance of the baffle motions in biosonar system is not known. The current work primarily focuses on: i) the study of the impact of noseleaf dynamics on the outgoing sound waves, ii) the study of the impact of baffle dynamics on encoding of sensory information and localization performance of bats. For this, we take a numerical approach where we use computer-animated digital models of bat noseleaves that mimic noseleaf dynamics as observed in bats. The shapes are acoustically characterized (beampatterns) numerically using a finite element implementation. These beampatterns are then analyzed using an information-theoretic approach. The followings findings were obtained: i) noseleaf dynamics altered the spatial distribution of energy, ii) baffle dynamics results in encoding of new sensory information, and iii) the new sensory information encoded due to baffle dynamics significantly improves the performance of biosonar system on the two target localization tasks evaluated here -- direction resolution and direction estimation accuracy. These results affirm the importance of dynamics in biosonar system of horseshoe bats and point at the possibility of biosonar dynamics as a key factor behind the astounding sensory capabilities of these animals that are not yet matched by engineering systems. Thus, these biosonar dynamic principles can help improve the man-made sensing systems and help close the performance gap between active sensing in biology and in engineering.
- Doctoral Dissertations | <urn:uuid:640d9f1e-43ab-44cb-978a-9d83622f6cf9> | 2.90625 | 492 | Academic Writing | Science & Tech. | 6.963546 | 95,572,483 |
Refractive index of water compared to glassRefractive index of water compared to glass Explanation density anomalies water d1 d22, explanation density anomalies water including speed sound density refractive pressibility. Gemstone mineral glossary gems jewelry information, a prehensive glossary terms describe colored stones precious semi precious gems minerals gemstone jewelry gemstone jewelry rmation gemselect. Bending light snell law refraction reflection, explore bending light media indices refraction changing air water glass bending angle play prisms shapes rainbows. Optical glass hoya optics, optical glass table 3 temperature coefficient refractive air temperature air ge 7 40 20 1 35 20 0 1 15 0 20 1 00. Handprint material attributes paints, the material attributes paints paint effectively understand material attributes paint attributes affect behavior.
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Last update Tue, 10 Jul 2018 04:46:00 GMT Read More | <urn:uuid:0db3a9ba-5e01-40af-836e-a495e738c5cc> | 2.78125 | 460 | Content Listing | Science & Tech. | 41.183033 | 95,572,491 |
Despite deleterious effects on individuals, the t haplotype is a selfish genetic element present in many house mouse populations. By distorting the transmission ratio, +/t males transmit the t haplotype to up to 90% of their offspring. However, t/t individuals perish in utero. Theoretical models based on these properties predict a much higher t frequency than observed, leading to the t paradox. Here, we use empirical field data and theoretical approaches to investigate whether polyandry is a female counterstrategy against the negative fitness consequences of such distorters. We found a significant decrease of the t frequency over a period of 5.5 years that cannot be explained by the effect of transmission ratio distortion and recessive lethals, despite significantly higher life expectancy of +/t females compared to +/+ females. We quantified life-history data and homozygous and heterozygous fitness effects. Population subdivision and inbreeding were excluded as evolutionary forces influencing the t system. The possible influence of polyandry on the t system was then investigated by applying a stochastic model to this situation. Simulations show that polyandry can explain the observed t dynamics, making it a biologically plausible explanation for low t frequencies in natural populations in general.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:0279f51d-714b-4240-8cd9-a4626d69d529> | 2.796875 | 273 | Academic Writing | Science & Tech. | 18.679291 | 95,572,499 |
Implementing InterSystems Business Intelligence
For any cube that uses more than 64,000 records (by default), the system maintains and uses a result cache. When you update a cube in any way, parts of the result cache are considered invalid and are cleared. The details depend upon options in the cube definition (see Cache Buckets and Fact Order,
later in this chapter). Therefore, it is not generally desirable to update the cubes constantly.
The result cache works as follows: Each time a user executes a query (via the Analyzer for example), the system caches the results for that query. The next time any user runs that query, the system checks to see if the cache is still valid. If so, the system then uses the cached values. Otherwise, the system re-executes the query, uses the new values, and caches the new values. The net effect is that performance improves over time as more users run more queries.
When users evaluate pivot tables, the system computes and caches aggregate values that it later reuses whenever possible. To determine whether the system can reuse a cache, the system uses the following logic:
It examines the IDs of the records used in a given scenario (for example, for a given pivot table cell).
It checks the buckets to which those IDs belong. A bucket is a large number of contiguous records in the fact table (details given later).
If the bucket has been updated (because there was a change for at least one ID in the bucket), the system discards any corresponding cache associated with that bucket and regenerates the result.
If the bucket has not been updated, the system reuses the appropriate cache (if available) or generates the result (if not).
In some scenarios, changes to the source records (and the corresponding updates to any cubes) occur primarily in the most recent source records. In such scenarios, it is useful to make sure that you build the fact table in order by age of the records, with the oldest records first. This approach means that the caches for the older rows would not be made invalid by changes to the data. (In contrast, if the older rows and newer rows were mixed throughout the fact table, all the caches would potentially become invalid when changes occurred to newer records.)
As noted earlier, when users evaluate pivot tables, the system computes and caches aggregate values that it later reuses whenever possible. This caching means that the more users work with Business Intelligence, the more quickly the system runs. (For details, see How the Analytics Engine Works,
later in this book.)
To speed up initial
performance as well, you can precompute and cache specific aggregate values that are used in your pivot tables, especially wherever performance is a concern. The feature works as follows:
Within the cube class, you specify an additional XData block (CellCache
) that specifies cube cells that should be precomputed and cached. For details, see the first subsection.
You programmatically precompute these cube cells by using a utility method. See the second subsection.
You must do this after
building the cube.
A simpler option is to simply run any queries ahead of time (that is, before any users work with them).
Your cube class can contain an additional XData block (CellCache
) that specifies cube cells that can be precomputed and cached, which speeds up the initial performance of Business Intelligence. The following shows an example:
/// This xml document defines aggregates to be precomputed.
XData CellCache [ XMLNamespace = " http://www.intersystems.com/deepsee/cellCache" ]
<cellCache xmlns= "http://www.intersystems.com/deepsee/cellCache" >
<group name= "BS">
<element >[Measures].[Big Sale Count]</element >
<group name= "G1">
<element >[UnitsPerTransaction].[H1].[UnitsSold]</ element>
<element >[Measures].[Amount Sold]</element >
<fact >DxUnitsSold</fact >
<element >[Measures].[Amount Sold]</element >
element is as follows:
It has a name
attribute, which you use later when specifying which groups of cells to precompute.
It contains one or more <item>
element represents a combination of cube indices and corresponds to the information returned by %SHOWPLAN. An <item>
element consists of one or more <element>
can include one or more of either of the following structures, in any combination:
is an MDX expression that evaluates to a member. This can be either a member of a level or it can be a measure name (each measure is a member of the special MEASURES dimension).
This expression cannot be a calculated member.
Each group defines a set of intersections. The number of intersections in a group affects the processing speed when you precompute the cube cells.
classmethod %ComputeAggregateGroup(pCubeName As %String,
pGroupName As %String,
pVerbose As %Boolean = 1) as %Status
is the name of the cube, pGroupName
is the name of the cube, and pVerbose
specifies whether to write progress information while the method is running. For pGroupName
, you can use "*"
to precompute all groups for this cube.
If you use this method, you must first build the cube.
The method processes each group by looping over the fact table and computing the intersections defined by the items within the group. Processing is faster with fewer intersections in a group. The processing is single-threaded, which allows querying in the foreground. | <urn:uuid:82f2c9f9-0b56-4667-a44a-962f7f1e8367> | 2.625 | 1,208 | Documentation | Software Dev. | 41.272223 | 95,572,508 |
37 species under national protection have been observed in the Ziwuling area, thanks to massive reforestation efforts.
A few months ago I wrote about how China is planting 16.3 million acres of forest this year alone, with plans to increase forest coverage to 23 percent of its total landmass by the end of the decade.
And you know what happens when you coax a forest back into being? Creatures great and small find a place to call home ... and begin to thrive again.
If anyone was looking for proof of this simple equation, they may need look no further than the Ziwuling Forest Area in Yan'an, Shannxi province. After two decades of "massive reforestation projects" in the area, the payoff is becoming evident.
Researchers from Beijing Normal University have been using infrared cameras to check in on Ziwuling's wildlife, and they have photographed all kinds of rare species. From golden pheasants and red foxes to roe deer, the menagerie of threatened animals adds to an earlier discovery of the largest-ever population of North-Chinese leopards in the area.
At least 28 North-Chinese #leopards, the largest wild population, have been recorded in the past year in the forest area of Ziwuling Mountains in N China’s #Shaanxi, according to State Forestry Administration's Monitoring and Research Center for the Amur Tiger and Amur Leopard pic.twitter.com/LO89ui84s5— People's Daily,China (@PDChina) June 6, 2018
"The nature reserve has a large population of wild boars and roe deer, as well as small and medium-sized carnivorous animals such as ocelots and red foxes. If it was not for environmental protection we've undertaken, it's likely none of these animals would have survived," said Feng Limin Feng, associate professor from Beijing Normal University.
The researchers say that so far they have catalogued a whopping 263 different species in Ziwuling, including eight endangered species under critically endangered first-class national protection, and another 29 under second-class national protection.
It's really not rocket science. Animals the world over are being threatened with extinction because of habitat destruction. Stop that destruction, put some effort in refurbishing the natural landscape, and give the animals a fighting chance at survival. And if we're all lucky, they may even thrive.
via China Plus | <urn:uuid:aff17500-b326-4887-a6e2-9a4851ce6621> | 3.359375 | 497 | News Article | Science & Tech. | 42.978355 | 95,572,516 |
Computational study of noise in a large signal transduction network.
Bottom Line: Although noise is often perceived as a disturbing factor, the system might actually benefit from it.In order to understand the role of noise better, its quality must be studied in a quantitative manner.We concluded that basic frequency domain techniques can be applied to the analysis of simulation results produced by the Gillespie stochastic simulation algorithm.
Affiliation: Department of Mathematics, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland. firstname.lastname@example.orgShow MeSH
Related in: MedlinePlus
Mentions: The dependence between the system volume and the quality of noise can also be studied in the frequency domain. In general, the frequency domain analysis of the simulation results shows that most of the power in these noise processes is on the low frequencies. The quality of the PSD estimates depends somewhat on the stationarity of the noise processes studied. In order to illustrate the volume dependence of the quality of noise in the frequency domain, we have selected two model species: phospholipase C (PLC), and calcium phospholipase C complex (CaPLCcomplex). Illustrative realizations of these species are shown in (Figure 5A and 5B). The realizations are simulated in four different system volumes, 5 × 10-16 l (blue), 3.5 × 10-15 l (red), 10-14 l (green), and 10-13 l (black). The realizations show how the discrete nature of reactions plays an important role in the smallest volume and how the strength of noise gets smaller when the system volume increases. The effects of noise are however still detectable also in the largest volume. By taking a look at the PLC and CaPLCcomplex noise processes in (Figure 5A and 5B), it is easy to conclude that they are somewhat different. Therefore it is interesting to see how their behavior differs in the frequency domain. We estimated PSDs of the noise in the PLC and CaPLCcomplex concentrations using 10 second realizations of these processes. The frequency content of these noise processes as a function of volume can be seen in (Figure 5C and 5D). The noise in both species seems to have most of its power on the lower frequencies. Similar behavior was also observed in other species in the network. The PSDs for PLC and CaPLCcomplex seem to have different shapes (see Figure 5C and 5D). The noise in PLC realizations clearly has the dominating power on very low frequencies whereas the frequency content of noise in CaPLCcomplex realizations is distributed more uniformly on low frequencies. An interesting observation also is that the shapes of PSDs for species PLC and CaPLCcomplex seem to be same in all studied volumes. This can be seen clearly in Figure 6, where four PSDs in different volumes for PLC and CaPLCcomplex are plotted using the log-log-scale.
Affiliation: Department of Mathematics, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland. email@example.com | <urn:uuid:85470b0a-a9a9-4264-8be6-2ce47437eb48> | 2.84375 | 659 | Academic Writing | Science & Tech. | 43.978947 | 95,572,525 |
"A surprising pattern, much like the meshed teeth of a zipper, is frequently seen when floating ice sheets collide," said John Wettlaufer, professor of geology & geophysics and of physics at Yale. He and his colleague Dominic Vella of Cambridge University in England demonstrated the underlying principle for the observation. Further, they suggest that the process can work for any materials that share particular physical characteristics of thickness and flexibility.
"When two elastic sheets floating on a liquid collide, intuition leads us to expect one of two results — one sheet might be 'subducted' under the other, as we observe with the earth's crust, or the two might crush each other forming a field of rubble, as we observe in thick ice floes," said Wettlaufer.
The researchers describe a third possibility in their study published in Physical Review Letters. They show that sheets of ice, or in their experiments, sheets of wax, form a series of interlocking blocks -– termed "finger rafting" — that alternately ride over and under one another. It is a curiosity that has vexed scientists for over 50 years.
The natural patterns look like meter-wide rectangular zigzags, and only occur when both sheets of ice are roughly the same thickness. Their theoretical analysis was confirmed experimentally using flexible layers of wax on water to simulate the phenomenon. They demonstrated the relationship between the width of the resulting fingers and the material's mechanical properties.
"We show that this striking observation is a general and robust mechanical phenomenon that we can reproduce in the laboratory with floating materials other than ice," he said. "Our experimental results were consistent with the field observations."
According to Wettlaufer, the findings are relevant for a host of physical systems and, "The same principles might be used for designing nanomachine gears from appropriate materials." He points out that Tuzo Wilson, one of the founders of the theory of plate tectonics, was inspired by the resemblance of structures on floating polar ice sheets to the transform faults and other features of the Earth's moving plates.
Janet Rettig Emanuel | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:4959471f-528f-4daa-9d71-916c566f6015> | 3.671875 | 1,015 | Content Listing | Science & Tech. | 36.824158 | 95,572,527 |
The nth term of a sequence is given by the formula n^3 + 11n . Find the first four terms of the sequence given by this formula and the first term of the sequence which is bigger than one million. . . .
The picture illustrates the sum 1 + 2 + 3 + 4 = (4 x 5)/2. Prove the general formula for the sum of the first n natural numbers and the formula for the sum of the cubes of the first n natural. . . .
Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some. . . .
Find some triples of whole numbers a, b and c such that a^2 + b^2 + c^2 is a multiple of 4. Is it necessarily the case that a, b and c must all be even? If so, can you explain why?
Three frogs started jumping randomly over any adjacent frog. Is it possible for them to finish up in the same order they started?
Take any whole number between 1 and 999, add the squares of the digits to get a new number. Make some conjectures about what happens in general.
Powers of numbers behave in surprising ways. Take a look at some of these and try to explain why they are true.
Imagine we have four bags containing a large number of 1s, 4s, 7s and 10s. What numbers can we make?
Imagine we have four bags containing numbers from a sequence. What numbers can we make now?
Carry out cyclic permutations of nine digit numbers containing the digits from 1 to 9 (until you get back to the first number). Prove that whatever number you choose, they will add to the same total.
How many noughts are at the end of these giant numbers?
Can you see how this picture illustrates the formula for the sum of the first six cube numbers?
Eight children enter the autumn cross-country race at school. How many possible ways could they come in at first, second and third places?
Liam's house has a staircase with 12 steps. He can go down the steps one at a time or two at time. In how many different ways can Liam go down the 12 steps?
This jar used to hold perfumed oil. It contained enough oil to fill granid silver bottles. Each bottle held enough to fill ozvik golden goblets and each goblet held enough to fill vaswik crystal. . . .
We have exactly 100 coins. There are five different values of coins. We have decided to buy a piece of computer software for 39.75. We have the correct money, not a penny more, not a penny less! Can. . . .
Prove that if a^2+b^2 is a multiple of 3 then both a and b are multiples of 3.
Find the smallest positive integer N such that N/2 is a perfect cube, N/3 is a perfect fifth power and N/5 is a perfect seventh power.
Some diagrammatic 'proofs' of algebraic identities and inequalities.
Consider the equation 1/a + 1/b + 1/c = 1 where a, b and c are natural numbers and 0 < a < b < c. Prove that there is only one set of values which satisfy this equation.
When number pyramids have a sequence on the bottom layer, some interesting patterns emerge...
Choose a couple of the sequences. Try to picture how to make the next, and the next, and the next... Can you describe your reasoning?
Can you discover whether this is a fair game?
In this 7-sandwich: 7 1 3 1 6 4 3 5 7 2 4 6 2 5 there are 7 numbers between the 7s, 6 between the 6s etc. The article shows which values of n can make n-sandwiches and which cannot.
How many pairs of numbers can you find that add up to a multiple of 11? Do you notice anything interesting about your results?
Caroline and James pick sets of five numbers. Charlie chooses three of them that add together to make a multiple of three. Can they stop him?
You can work out the number someone else is thinking of as follows. Ask a friend to think of any natural number less than 100. Then ask them to tell you the remainders when this number is divided by. . . .
Some puzzles requiring no knowledge of knot theory, just a careful inspection of the patterns. A glimpse of the classification of knots and a little about prime knots, crossing numbers and. . . .
Here are some examples of 'cons', and see if you can figure out where the trick is.
Find the largest integer which divides every member of the following sequence: 1^5-1, 2^5-2, 3^5-3, ... n^5-n.
From a group of any 4 students in a class of 30, each has exchanged Christmas cards with the other three. Show that some students have exchanged cards with all the other students in the class. How. . . .
Six points are arranged in space so that no three are collinear. How many line segments can be formed by joining the points in pairs?
We are given a regular icosahedron having three red vertices. Show that it has a vertex that has at least two red neighbours.
Can you use the diagram to prove the AM-GM inequality?
Problem solving is at the heart of the NRICH site. All the problems give learners opportunities to learn, develop or use mathematical concepts and skills. Read here for more information.
Prove that, given any three parallel lines, an equilateral triangle always exists with one vertex on each of the three lines.
ABCD is a square. P is the midpoint of AB and is joined to C. A line from D perpendicular to PC meets the line at the point Q. Prove AQ = AD.
Kyle and his teacher disagree about his test score - who is right?
Imagine two identical cylindrical pipes meeting at right angles and think about the shape of the space which belongs to both pipes. Early Chinese mathematicians call this shape the mouhefanggai.
The knight's move on a chess board is 2 steps in one direction and one step in the other direction. Prove that a knight cannot visit every square on the board once and only (a tour) on a 2 by n board. . . .
In how many distinct ways can six islands be joined by bridges so that each island can be reached from every other island...
Can you cross each of the seven bridges that join the north and south of the river to the two islands, once and once only, without retracing your steps?
There are four children in a family, two girls, Kate and Sally, and two boys, Tom and Ben. How old are the children?
Which of these roads will satisfy a Munchkin builder?
Points A, B and C are the centres of three circles, each one of which touches the other two. Prove that the perimeter of the triangle ABC is equal to the diameter of the largest circle.
Find the area of the annulus in terms of the length of the chord which is tangent to the inner circle.
A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.
A paradox is a statement that seems to be both untrue and true at the same time. This article looks at a few examples and challenges you to investigate them for yourself.
Prove that the internal angle bisectors of a triangle will never be perpendicular to each other.
You have been given nine weights, one of which is slightly heavier than the rest. Can you work out which weight is heavier in just two weighings of the balance? | <urn:uuid:4242dc52-5ac2-4de2-861e-58357aa47301> | 3.578125 | 1,658 | Content Listing | Science & Tech. | 78.468912 | 95,572,536 |
Transforms any GeoJSON into a data structure that can be efficiently queried to determine (roughly) where data is present or absent.
var bitgeo = ;
Given any GeoJSON data, generate a
BitBox with the provided options.
resolution- The size (width and height) of a "cell" in the same units as the input data.
A convenience function for creating a bitbox that is the union of an array of GeoJSON data objects.
A convenience function for creating a bitbox that is the intersection of an array of GeoJSON data objects.
var bitbox = ;
A bitbox is a (conceptually) rasterized representation of vector data containing information about where data is present and absent.
Returns the area of the bitbox where data is present (this will be an integer multiple of
resolution * resolution).
Test if data is present at the provided location. The
j values are offsets from the origin in terms of the bitbox resolution. For example, if a bitbox is created with
resolution: 10, then
bitbox.get(1, 2) would return
true if there is data between
[10, 20] and
[20, 30] (with upper bounds being exclusive).
bitbox.contains(minI, minJ, maxI, maxJ)
Determine if all, some, or none of a range of bits are
bitgeo.ALL if all of the bits in the provided range are
bitgeo.SOME if some bits are
true and some are
bitgeo.NONE if all of the bits in the range are
false. Ranges are inclusive (both min and max values are tested).
Return a bitbox that is the union of two bitboxes (
Return a bitbox that is the intersection of two bitboxes ( | <urn:uuid:37dde63d-badd-4973-8d1e-2222d70db12b> | 2.609375 | 389 | Documentation | Software Dev. | 51.183507 | 95,572,543 |
Authors: A. López-Trosell and R. Schomäcker
Affilation: TU Berlin, Germany
Pages: 313 - 316
Keywords: films, microemulsions
In this paper a developed methodology is presented to coat glass substrates with nanoparticles of different materials. Particles of palladium, zirconium oxide, yttrium iron garned and perovskite Ca0.5Sr0.5MnO3 were synthesized in microemulsions. The microemulsions form spontaneously and present behavior that changes systematically with temperature. These properties of the microemulsions represent a suitable medium for the deposition of the particles on the cleaned surfaces. The laboratory-scale method involved three basic steps: surface cleaning, synthesis of the nanoparticles and low-temperature heat treatment for drying and pyrolysis of the surfactant normally between (200-400°C). A fourth step was necessary for those materials that required a higher temperature for crystallization of the coating onto the desired phase. The surfaces were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Nanotech Conference Proceedings are now published in the TechConnect Briefs | <urn:uuid:fdf19a17-703f-440d-9032-dbd144dc1889> | 2.5625 | 256 | Academic Writing | Science & Tech. | 19.771184 | 95,572,544 |
A View from Susan Young Rojahn
A Near-Whole Brain Activity Map in Fish
Neuron-level whole-brain activity maps could one day help explain brain function and disfunction.
Image: Neurons glow red as they fire in this whole zebrafish larva brain. Credit: Misha Ahrens and Philipp Keller
Researchers have for the first time been able to image most of an entire vertebrate brain at the level of single cells, reports Nature.
A study from the Howard Hughes Medical Institute’s Janelia Farm Research Campus, published in Nature Methods on Monday, shows that modifications to existing microscopy techniques enable researchers to take snap shots of neuron-by-neuron activity in the whole brain of a living zebrafish larvae. The zebrafish larvae, whose bodies are transparent and brains are tiny, were genetically engineered to produce a protein in their neurons that glows in response to the chemical changes that occur when that neuron fires.
With conventional techniques, capturing the activity of even 2,000 neurons at once is difficult. With the modified fish and microscopy methods, the researchers were able to capture the activity of at least 80 percent of the baby fish’s 100,000 neurons over a time period of just 1.3 seconds.
The result is an encouraging announcement for proponents of the Brain Activity Map project, a still-developing scientific collaboration to establish new technologies that can record the activity of all individual neurons in a brain circuit simultaneously (see “The Brain Activity Map”). According to Nature News, Rafael Yuste, a neurobiologist at Columbia University in New York and leader of the Brain Activity Map project, thinks the zebrafish results are “phenomenal.”
“It is a bright star now in the literature, suggesting that it is not crazy to map every neuron in the brain of an animal,” [says Yuste].
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:e14f4752-f8a9-45e9-9c53-f838ba2370db> | 3.15625 | 427 | News Article | Science & Tech. | 31.70836 | 95,572,549 |
Can you imagine a forest giving off the same amount of energy as a power plant? Designer Ermi van Oers can. The Dutch entrepreneur and her team have created a lamp called Living Light that can harness energy from a living plant. As she continues to develop this new lighting system, her long-term goal is to power cities with green energy harnessed by plants.
So, how does this magic lamp work? The science behind this project stems from the photosynthetic process which allows plants to grow and thrive. Plants essentially generate protons and electrons which can create electricity. When the plant breaks down bacteria to develop the energy, the microbial fuel cell captures the electors in an anode compartment which transfers the electrons through a wire. Essentially, it's a form of solar energy on a very natural level. The plant, encased in a glass tube, lights up when someone touches it.
The lamp has a lot to offer by tapping back into nature. Living Light was built to be an entirely self-sufficient closed loop power source that doesn’t need electric sockets. As an off-grid light source, the lamp has the potential to help millions of people around the world who do not have reliable or environmentally safe sources of energy.
This bright idea was made possible through van Oers’ collaboration with Plant-e, a Dutch company that works on products that can harness electricity from living plants. The team is working on applying systems that can operate on a large scale. Right now the technology works with living plants that receive water.
The inspiration for Living Light began with van Oers’ desire to bring together nature and technology in a way that helped people. According to TEDxAmsterdam, van Oers believes, “Nature is full of smart solutions. I see my target as a designer to inspire people with the potential power within natural processes. I want to show the beautiful, poetic side of these living systems when they take their place in our everyday lives.”
The designer hopes to tap into the massive potential of this technology and not only light streetlights and parks but also eventually turn forests and rice fields into “power plants” which can offer natural energy. She also sees a future where cities can swap traditional electric grids with microbial energy systems.
As with many new technologies, this one’s not perfect yet. The current design for the Living Light lamp can only produce about half an hour’s worth of light after the plant can “recharge” for a day. Still, van Oer’s team is continually improving the system and already applying microbial energy to light a public park in Rotterdam.
The future looks bright for this entrepreneur who told Dezeen, "I hope we come to a point where every plant pot is provided with this technology, and we don't know any better than that plants are part of our energy system. Nature will get a higher economical value and we will start making more green places so that biodiversity can flourish, while lowering greenhouse gas emissions at the same time.” Living Lamps will be available on the market starting in 2018.
Sweden's aggressive target of generating over 40 terawatt-hours of renewable energy by 2030 could be reached nearly a decade early. A massive amount of wind power projects could hit a snag in market value with subsidies, but SWEA could push to close those up by the end of the year.
It's challenging and laborious to detect this bacteria that decimates bee populations, so an apiary inspector trained a dog to do it. They're amazing.
New technologies means that instead of sucking power off the energy grid, buildings can feed back into it, powering other buildings and even cars.
A sixth-grader in Massachusetts has begun developing a robot that's able to detect microplastics in our ocean after wanting to make a difference at the Boston Harbor. Her ultimate goal is to create a way to also pick up trash and cut costs in the process. | <urn:uuid:a6b12ea0-273e-4b5f-9a79-1f67d3513b58> | 3.4375 | 814 | News Article | Science & Tech. | 49.364918 | 95,572,562 |
Object-relational impedance mismatch
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The object-relational impedance mismatch is a set of conceptual and technical difficulties that are often encountered when a relational database management system (RDBMS) is being served by an application program (or multiple application programs) written in an object-oriented programming language or style, particularly because objects or class definitions must be mapped to database tables defined by a relational schema.
Fundamentally, objects (instances) reference one another and therefore form a graph in the mathematical sense (a network including loops and cycles). Relational schemas are, in contrast, tabular and based on the relational algebra, which defines linked heterogeneous tuples (groupings of data fields into a "row" with different types for each field).
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Object-oriented programs are designed with techniques that result in encapsulated objects whose internal representation can be hidden. In an object-oriented framework, the underlying properties of a given object are expected to be unexposed to any interface outside of the one implemented alongside the object. However, object-relational mapping necessarily exposes the underlying content of an object to interact with an interface that the object implementation cannot specify. Hence, object-relational mapping violates the encapsulation of the object.
In relational thinking, "private" versus "public" access is relative to need. In the object-oriented (OO) model it is an absolute characteristic of the data's state. The relational and OO models often have conflicts over relativity versus absolutism of classifications and characteristics.
Interface, class, inheritance and polymorphismEdit
Under an object-oriented paradigm, objects have interfaces that together provide the only access to the internals of that object. The relational model, on the other hand, utilizes derived relation variables (views) to provide varying perspectives and constraints to ensure integrity. Similarly, essential OOP concepts for classes of objects, inheritance and polymorphism, are not supported by relational database systems.
Mapping to relational conceptsEdit
A proper mapping between relational concepts and object-oriented concepts can be made if relational database tables are linked[further explanation needed] to associations found in object-oriented analysis.
Data type differencesEdit
A major mismatch between existing relational and OO languages is the type system differences. The relational model strictly prohibits by-reference attributes (or pointers), whereas OO languages embrace and expect by-reference behavior. Scalar types and their operator semantics can be vastly different between the models, causing problems in mapping.
For example, most SQL systems support string types with varying collations and constrained maximum lengths (open-ended text types tend to hinder performance), while most OO languages consider collation only as an argument to sort routines and strings are intrinsically sized to available memory. A more subtle, but related example is that SQL systems often ignore trailing white space in a string for the purposes of comparison, whereas OO string libraries do not. It is typically not possible to construct new data types as a matter of constraining the possible values of other primitive types in an OO language.
Structural and integrity differencesEdit
Another mismatch has to do with the differences in the structural and integrity aspects of the contrasted models. In OO languages, objects can be composed of other objects—often to a high degree—or specialize from a more general definition. This may make the mapping to relational schemas less straightforward. This is because relational data tends to be represented in a named set of global, unnested relation variables. Relations themselves, being sets of tuples all conforming to the same header (see tuple relational calculus) do not have an ideal counterpart in OO languages. Constraints in OO languages are generally not declared as such, but are manifested as exception raising protection logic surrounding code that operates on encapsulated internal data. The relational model, on the other hand, calls for declarative constraints on scalar types, attributes, relation variables, and the database as a whole.
The semantic differences are especially apparent in the manipulative aspects of the contrasted models, however. The relational model has an intrinsic, relatively small and well-defined set of primitive operators for usage in the query and manipulation of data, whereas OO languages generally handle query and manipulation through custom-built or lower-level, case- and physical-access-path-specific imperative operations. Some OO languages do have support for declarative query sublanguages, but because OO languages typically deal with lists and perhaps hash tables, the manipulative primitives are necessarily distinct from the set-based operations of the relational model.
The concurrency and transaction aspects are significantly different also. In particular, transactions, the smallest unit of work performed by databases, are much larger in relational databases than are any operations performed by classes in OO languages. Transactions in relational databases are dynamically bounded sets of arbitrary data manipulations, whereas the granularity of transactions in an OO language is typically on the level of individual assignments to primitive-typed fields. In general, OO languages have no analogue of isolation or durability, so atomicity and consistency are only ensured when writing to fields of those primitive types.
Solving impedance mismatchEdit
Working around the impedance mismatch problem for object-oriented programs starts with recognition of the differences in the specific logic systems being employed, then either the minimization or compensation of the mismatch.
The Object-relational impedance mismatch problem is not a universal problem between OO and databases. As the name suggests, this impedance problem only occurs with relational databases. The most common solution to this problem is to use an alternative database, such as NoSQL or XML database.
There have been some attempts at building object-oriented database management systems (OODBMS) that would avoid the impedance mismatch problem. They have been less successful in practice than relational databases however, partly due to the limitations of OO principles as a basis for a data model. There has been research performed in extending the database-like capabilities of OO languages through such notions as transactional memory.
One common solution to the impedance mismatch problem is to layer the domain and framework logic. In this scheme, the OO language is used to model certain relational aspects at runtime rather than attempt the more static mapping. Frameworks which employ this method will typically have an analogue for a tuple, usually as a "row" in a "dataset" component or as a generic "entity instance" class, as well as an analogue for a relation. Advantages of this approach may include:
- Straightforward paths to build frameworks and automation around transport, presentation, and validation of domain data.
- Smaller code size; faster compile and load times.
- Ability for the schema to change dynamically.
- Avoids the name-space and semantic mismatch issues.
- Expressive constraint checking
- No complex mapping necessary
Disadvantages may include:
- Lack of static type "safety" checks. Typed accessors are sometimes utilized as one way to mitigate this.
- Possible performance cost of runtime construction and access.
- Inability to natively utilize uniquely OO aspects, such as polymorphism.
The mixing of levels of discourse within OO application code presents problems, but there are some common mechanisms used to compensate. The biggest challenge is to provide framework support, automation of data manipulation and presentation patterns, within the level of discourse in which the domain data is being modelled. To address this, reflection and/or code generation are utilized. Reflection allows code (classes) to be addressed as data and thus provide automation of the transport, presentation, integrity, etc. of the data. Generation addresses the problem through addressing the entity structures as data inputs for code generation tools or meta-programming languages, which produce the classes and supporting infrastructure en masse. Both of these schemes may still be subject to certain anomalies where these levels of discourse merge. For instance, generated entity classes will typically have properties which map to the domain (e. g. Name, Address) as well as properties which provide state management and other framework infrastructure(e. g. IsModified).
It has been argued, by Christopher J. Date and others, that a truly relational DBMS would pose no such problem, as domains and classes are essentially one and the same thing. A naïve mapping between classes and relational schemata is a fundamental design mistake ; and that individual tuples within a database table (relation) ought to be viewed as establishing relationships between entities; not as representations for complex entities themselves. However, this view tends to diminish the influence and role of object-oriented programming, using it as little more than a field type management system.
The impedance mismatch is in programming between the domain objects and the user interface. Sophisticated user interfaces, to allow operators, managers, and other non-programmers to access and manipulate the records in the database, often require intimate knowledge about the nature of the various database attributes (beyond name and type). In particular, it's considered a good practice (from an end-user productivity point of view) to design user interfaces such that the UI prevents illegal transactions (those which cause a database constraint to be violated) from being entered; to do so requires much of the logic present in the relational schemata to be duplicated in the code.
Certain code-development frameworks can leverage certain forms of logic that are represented in the database's schema (such as referential integrity constraints), so that such issues are handled in a generic and standard fashion through library routines rather than ad hoc code written on a case-by-case basis.
It has been argued that SQL, due to a very limited set of domain types (and other alleged flaws) makes proper object and domain-modelling difficult; and that SQL constitutes a very lossy and inefficient interface between a DBMS and an application program (whether written in an object-oriented style or not). However, SQL is currently the only widely accepted common database language in the marketplace; use of vendor-specific query languages is seen as a bad practice when avoidable. Other database languages such as Business System 12 and Tutorial D have been proposed; but none of these has been widely adopted by DBMS vendors.
In current versions of mainstream "object-relational" DBMSs like Oracle and Microsoft SQL Server, the above point may be a non-issue. With these engines, the functionality of a given database can be arbitrarily extended through stored code (functions and procedures) written in a modern OO language (Java for Oracle, and a Microsoft .NET language for SQL Server), and these functions can be invoked in-turn in SQL statements in a transparent fashion: that is, the user neither knows nor cares that these functions/procedures were not originally part of the database engine. Modern software-development paradigms are fully supported: thus, one can create a set of library routines that can be re-used across multiple database schemas.
These vendors decided to support OO-language integration at the DBMS back-end because they realized that, despite the attempts of the ISO SQL-99 committee to add procedural constructs to SQL, SQL will never have the rich set of libraries and data structures that today's application programmers take for granted, and it is reasonable to leverage these as directly as possible rather than attempting to extend the core SQL language. Consequently, the difference between "application programming" and "database administration" is now blurred: robust implementation of features such as constraints and triggers may often require an individual with dual DBA/OO-programming skills, or a partnership between individuals who combine these skills. This fact also bears on the "division of responsibility" issue below.
Some, however, would point out that this contention is moot due to the fact that: (1) RDBMSes were never intended to facilitate object modelling, and (2) SQL generally should only be seen as a "lossy" or "inefficient" interface language when one is trying to achieve a solution for which RDBMSes were not designed. SQL is very efficient at doing what it was designed to do, namely, to query, sort, filter, and store large sets of data. Some would additionally point out that the inclusion of OO language functionality in the back-end simply facilitates bad architectural practice, as it admits high-level application logic into the data tier, antithetical to the RDBMS.
Here the "canonical" copy of state is located. The database model generally assumes that the database management system is the only authoritative repository of state concerning the enterprise; any copies of such state held by an application program are just that — temporary copies (which may be out of date, if the underlying database record was subsequently modified by a transaction). Many object-oriented programmers prefer to view the in-memory representations of objects themselves as the canonical data, and view the database as a backing store and persistence mechanism.
Another point of contention is the proper division of responsibility between application programmers and database administrators (DBA). It is often the case that needed changes to application code (in order to implement a requested new feature or functionality) require corresponding changes in the database definition; in most organizations, the database definition is the responsibility of the DBA. Due to the need to maintain a production database system 24 hours a day many DBAs are reluctant to make changes to database schemata that they deem gratuitous or superfluous and in some cases outright refuse to do so. Use of developmental databases (apart from production systems) can help somewhat; but when the newly developed application "goes live" the DBA will need to approve any changes. Some programmers view this as intransigence; however the DBA is frequently held responsible if any changes to the database definition cause a loss of service in a production system—as a result, many DBAs prefer to contain design changes to application code, where design defects are far less likely to have catastrophic consequences.
In organizations with a non-dysfunctional relationship between DBAs and developers, though, the above issue should not present itself, as the decision to change a database schema or not would only be driven by business needs: a new requirement to persist additional data or a performance boost of a critical application would both trigger a schema modification, for example.
Key philosophical differences between the OO and relational models can be summarized as follows:
- Declarative vs. imperative interfaces — Relational thinking tends to use data as interfaces, not behavior as interfaces. It thus has a declarative tilt in design philosophy in contrast to OO's behavioral tilt. (Some relational proponents suggest using triggers, stored procedures, etc. to provide complex behavior, but this is not a common viewpoint.)
- Schema bound — Objects do not have to follow a "parent schema" for which attributes or accessors an object has, while table rows must follow the entity's schema. A given row must belong to one and only one entity. The closest thing in OO is inheritance, but it is generally tree-shaped and optional. A dynamic form of relational tools that allows ad hoc columns may relax schema bound-ness, but such tools are currently rare.
- Access rules — In relational databases, attributes are accessed and altered through predefined relational operators, while OO allows each class to create its own state alteration interface and practices. The "self-handling noun" viewpoint of OO gives independence to each object that the relational model does not permit. This is a "standards versus local freedom" debate. OO tends to argue that relational standards limit expressiveness, while relational proponents suggest the rule adherence allows more abstract math-like reasoning, integrity, and design consistency.
- Relationship between nouns and verbs — OO encourages a tight association between verbs (actions) and the nouns (entities) that the operations operate on. The resulting tightly bound entity containing both nouns and the verbs is usually called a class, or in OO analysis, a concept. Relational designs generally do not assume there is anything natural or logical about such tight associations (outside of relational operators).
- Object identity — Objects (other than immutable ones) are generally considered to have a unique identity; two objects which happen to have the same state at a given point in time are not considered to be identical. Relations, on the other hand, have no inherent concept of this kind of identity. That said, it is a common practice to fabricate "identity" for records in a database through use of globally unique candidate keys; though many consider this a poor practice for any database record which does not have a one-to-one correspondence with a real world entity. (Relational, like objects, can use domain keys if they exist in the external world for identification purposes). Relational systems in practice strive for and support "permanent" and inspectable identification techniques, whereas object identification techniques tend to be transient or situational.
- Normalization — Relational normalization practices are often ignored by OO designs. However, this may just be a bad habit instead of a native feature of OO. An alternate view is that a collection of objects, interlinked via pointers of some sort, is equivalent to a network database; which in turn can be viewed as an extremely denormalized relational database.
- Schema inheritance — Most relational databases do not support schema inheritance. Although such a feature could be added in theory to reduce the conflict with OOP, relational proponents are less likely to believe in the utility of hierarchical taxonomies and sub-typing because they tend to view set-based taxonomies or classification systems as more powerful and flexible than trees. OO advocates point out that inheritance/subtyping models need not be limited to trees (though this is a limitation in many popular OO languages such as Java), but non-tree OO solutions are seen as more difficult to formulate than set-based variation-on-a-theme management techniques preferred by relational. At the least, they differ from techniques commonly used in relational algebra.
- Structure vs. behaviour — OO primarily focuses on ensuring that the structure of the program is reasonable (maintainable, understandable, extensible, reusable, safe), whereas relational systems focus on what kind of behaviour the resulting run-time system has (efficiency, adaptability, fault-tolerance, liveness, logical integrity, etc.). Object-oriented methods generally assume that the primary user of the object-oriented code and its interfaces are the application developers. In relational systems, the end-users' view of the behaviour of the system is sometimes considered to be more important. However, relational queries and "views" are common techniques to present information in application- or task-specific configurations. Further, relational does not prohibit local or application-specific structures or tables from being created, although many common development tools do not directly provide such a feature, assuming objects will be used instead. This makes it difficult to know whether the stated non-developer perspective of relational is inherent to relational, or merely a product of current practice and tool implementation assumptions.
- Set vs. graph relationships — The relationship between different items (objects or records) tend to be handled differently between the paradigms. Relational relationships are usually based on idioms taken from set theory, while object relationships lean toward idioms adopted from graph theory (including trees). While each can represent the same information as the other, the approaches they provide to access and manage information differ.
As a result of the object-relational impedance mismatch, it is often argued by partisans on both sides of the debate that the other technology ought to be abandoned or reduced in scope. Some database advocates view traditional "procedural" languages as more compatible with an RDBMS than many OO languages; or suggest that a less OO style ought to be used. (In particular, it is argued that long-lived domain objects in application code ought not to exist; any such objects that do exist should be created when a query is made and disposed of when a transaction or task is complete). Conversely, some OO advocates argue that more OO-friendly persistence mechanisms, such as OODBMS, ought to be developed and used, and that relational technology ought to be phased out. Many (if not most) programmers and DBAs hold neither of these viewpoints; and view the object-relational impedance mismatch as a mere fact of life that information technology has to deal with.
It is also argued that the O/R mapping is paying off in some situations, but is probably oversold: it has advantages besides drawbacks. Skeptics point out that it is worth to think carefully before using it, as it will add little value in some cases.
- C. J. Date, Relational Database Writings
- Date, Christopher ‘Chris’ J; Pascal, Fabian (2012-08-12) , "Type vs. Domain and Class", Database debunkings (World Wide Web log), Google, retrieved 12 September 2012.
- ——— (2006), "4. On the notion of logical difference", Date on Database: writings 2000–2006, The expert’s voice in database; Relational database select writings, USA: Apress, p. 39, ISBN 978-1-59059-746-0,
Class seems to be indistinguishable from type, as that term is classically understood.
- ——— (2004), "26. Object/Relational databases", An introduction to database systems (8th ed.), Pearson Addison Wesley, p. 859, ISBN 978-0-321-19784-9,
...any such rapprochement should be firmly based on the relational model.
- Date, Christopher ‘Chris’ J; Darwen, Hugh, "2. Objects and Relations", The Third Manifesto,
The first great blunder
- Neward, Ted (2006-06-26). "The Vietnam of Computer Science". Interoperability Happens. Retrieved 2010-06-02.
- Johnson, Rod (2002). J2EE Design and Development. Wrox Press. p. 256. | <urn:uuid:b17f808e-d964-42e5-bc6b-7ae205b04714> | 2.828125 | 4,589 | Knowledge Article | Software Dev. | 19.749026 | 95,572,610 |
How to find the area under a normal curve, given a z-value, shaded to the left, shaded to the right, and shaded in between.
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From David Waldo | <urn:uuid:57fcb7b4-2c28-4b10-92b9-bb3b2430173a> | 2.65625 | 359 | Content Listing | Science & Tech. | 60.748039 | 95,572,625 |
Advancing Basic Science for Humanity
Director of Communications and
The Kavli Foundation
With a telescope, scientists have for the first time identified normal star-forming galaxies at a very early stage in cosmic history.
Cambridge astronomers have made the first investigation of the sensitivity of the GAIA satellite to ultra-low frequency gravitational waves.
TU Delft investigated thin slices of SrIrO3, a material that belongs to the family of complex oxides.
The investigators compared DNA sequences of single neuronal progenitor cells in the same human brain.
Nanoscale silicon posts can reflect light differently depending on the angle of incoming light
Berkeley Lab team is leading the development of NWB:N 2.0 which is poised to become a community standard
KITP hosts a rapid-response program to explore myriad new astrophysical insights from a double neutron star merger
The group reports remarkably clear observations of excitons – electrically neutral quasiparticles – in bilayer graphene.
Origami-inspired muscles are both soft and strong, and can be made for less than $1
New approach to characterizing and understanding exotic charge-ordered phases in which electrons are ordered into periodic patterns. | <urn:uuid:a75efefc-2fd1-4637-aa76-bca50467c166> | 2.796875 | 247 | Content Listing | Science & Tech. | 13.394032 | 95,572,680 |
Quantum Dots Enable Faster, Easier Photon Detection, More Secure Data
Schematic diagram of the single photon detector. The photon is represented by the wavy multi-colored line and the red dot represents the quantum dot.
FAYETTEVILLE, Ark. – A team of researchers including U of A engineering and physics faculty has developed a new method of detecting single photons, or light particles, using quantum dots.
Single photon detection is a key element to enable use of quantum information, a method of transferring information that is much faster and more secure than current methods. This technology has other applications as well, including biological and medical imaging, spectroscopy, and astronomical observation.
Shui-Qing “Fisher” Yu, associate professor of electrical engineering; Greg Salamo, distinguished professor of physics; and Yang Zhang, a post-doctoral fellow in electrical engineering at the time, worked with colleagues from Dartmouth and the University of Wisconsin on this research, which was recently published by ACS Photonics.
Quantum information uses different quantum states of particles, such as polarization or phase, to encode information. Because quantum information is not limited to the ones and zeroes used to encode digital information, this technology can transfer a large amount of information very securely.
Since quantum information can be transmitted using an infinite variety of quantum states, the sender and receiver must both agree on which state they are using to encode and interpret the data. An outsider intercepting the signal would have little way of reading it without this knowledge.
A photon is a quantum of light. When a photon enters a detector in a quantum information system, its energy is transferred to an electron and this results in a current or a voltage. This effect is so small, though, that it is difficult to detect. Other designs for photon detectors solve this problem by using a device called an avalanche photodiode to amplify the current or voltage, but this approach tends to add delays to the detection and increases background noise.
The new approach created and modeled by these researchers uses a quantum dot, which is a semiconductor nanoscale particle, to detect single photons. Compared to other methods, the change in voltage caused by a single photon in this detector is large, with a low background noise level.
Yu compared this to adding a drop of water to a container. “If you put one drop of water in a large tank, that change is hard to see,” he said. “But if you put a drop of water into a very small container, you can see the change more easily.” In the researchers’ design, the electron is in a small container – the quantum dot.
The researchers have used computer models to demonstrate that their design can detect single photons more accurately than existing technologies.
About the University of Arkansas: The University of Arkansas provides an internationally competitive education for undergraduate and graduate students in more than 200 academic programs. The university contributes new knowledge, economic development, basic and applied research, and creative activity while also providing service to academic and professional disciplines. The Carnegie Foundation classifies the University of Arkansas among only 2 percent of universities in America that have the highest level of research activity. U.S. News & World Report ranks the University of Arkansas among its top American public research universities. Founded in 1871, the University of Arkansas comprises 10 colleges and schools and maintains a low student-to-faculty ratio that promotes personal attention and close mentoring.
Learn about plant pathology and submit your diseased plant samples for diagnosis at our bi-weekly summer booth.
The former School of Law dean will focus on the University of Arkansas’ economic and social impact on the state and beyond.
In addition to Darynne Dahlem and Reagan Grubbs, five more U of A students also won scholarships and awards at the 2018 Miss Arkansas Scholarship Pageant.
Gov. Asa Hutchinson named Sarah Moore of Stuttgart to the Arkansas Board of Education, his office announced last week. She earned a doctorate in education policy in 2015.
After more than 92 years of combined service, three faculty members in Fulbright College recently retired and were honored following the successful completion of their final academic year. | <urn:uuid:ebbfa157-6d28-49f1-8833-8fbe51fcb981> | 3.421875 | 858 | News (Org.) | Science & Tech. | 26.681925 | 95,572,688 |
New research from NASA has concluded that tropical cyclones like Gaston produce rain differently than another class of storms called "extra-tropical" cyclones. According to the study, making a proper distinction between these systems by looking at both raindrop size and abundance may be a key to assisting weather forecasters in estimating rainfall intensity. By doing so, forecasters can reduce the surprise factor of flash flooding and the unfortunate loss of property and life.
Ali Tokay, a research scientist from the Joint Center for Earth Systems Technology (JCET) at the University of Maryland Baltimore County, Baltimore, and NASA's Goddard Space Flight Center, Greenbelt, Md., compared the rain measurements collected in tropical storms and hurricanes during the past three Atlantic hurricane seasons with measurements after these storms transitioned to being extra-tropical. Tokay's study appeared in the May issue of the American Meteorological Society's Monthly Weather Review.
When a tropical cyclone -- the generic name for tropical depressions, tropical storms and hurricanes -- merges with a mid-latitude frontal storm system, measurable changes to the raindrop size and abundance occur as the system transitions to become extra-tropical. Extra-tropical cyclones also form outside the tropics without being part of a tropical system, and tend to form over land rather than over the open ocean. This category of storm can produce anything from a cloudy sky to a thunderstorm as it develops between weather fronts, the boundaries separating air masses of different densities.
Tokay looked at raindrop size, rain intensity, and the area in which rain falls in both tropical cyclones and extra-tropical cyclones using ground-based rain-measuring instruments called disdrometers. These instruments measure the range of raindrop sizes in a storm and the intensity of the rainfall. The disdrometer is an important part of the ground-based rain measuring instruments that are used to validate rainfall seen from satellites including the Tropical Rainfall Measuring Mission (TRMM), a joint mission with NASA and the Japanese Space Agency. He concluded that tropical cyclones that form over water tend to rain harder and have a greater amount of smaller drops before they transition to being extra-tropical with raindrops of larger size and mass.
"Torrents of rainfall from tropical storms are not surprising since the systems are large and move slowly. It is also true that slow moving frontal systems associated with an extra-tropical cyclone can result in abundant rainfall at a site," said Tokay. "What is less known is that the distribution of raindrops within a volume of air between the two systems differs substantially even though weather radar may measure the same returned power which is known as reflectivity." This is why disdrometer measurements of raindrop size are needed.
"Both rain intensity and reflectivity are integral products of raindrop size distribution, but they are mathematically related to different powers of the drop size," said Tokay. Weather radars cannot measure the range of raindrop sizes. As a result, rainfall estimates from weather radars must employ the use of equations that make assumptions about raindrop size. These assumptions can result in underestimation of rain intensity, and the possibility of deadly flooding.
In the study, Tokay uses disdrometer data from various sites around the U.S. and abroad. Most of the data were collected at NASA's Wallops Flight Facility, Wallops Island, Va., where Paul Bashor of Computer Sciences Corporation, Wallops Island, Va. maintains several types of disdrometers. The data from two tropical storms were collected at Orlando, Fla., and Lafayette, La. through collaborative efforts with Takis Kasparis at the University of Central Florida's Orlando campus, and Emad Habib of the University of Louisiana at Lafayette.
Lynn Chandler | EurekAlert!
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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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.
"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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Scientists: Tahoe Wolverine not from state
TAHOE NATIONAL FOREST DNA sample shows it's a male with Rocky Mountain genes
The mysterious wolverine captured in photographs from a remote camera in the Tahoe National Forest is not a native of California or Washington, U.S. Forest Service scientists revealed Wednesday.
A DNA analysis of scat collected near where the feisty predator was photographed last month revealed that the animal is a male that shares genetic traits with wolverines in the Rocky Mountains, but it was not clear exactly where it came from or how it got to California.
"This is just one gene we've looked at and this one is most prevalent in the Rocky Mountains of Idaho, Montana and Wyoming, but it can also be found in lower portions of Canada and Alaska," said Michael Schwartz, a research ecologist and the genetics team leader for the Forest Service's Rocky Mountain Research Station in Missoula, Mont.
"While we can't rule everything out, we know that this type never occurred in the historical California population and it does not occur in the contemporary Washington cascade population," he said.
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Cameras set up in the forest north of Truckee last month twice captured images of the wolverine, which some speculated could have descended from the historic population that once roamed the Southern Sierra Nevada.
The last documented California wolverine was killed off around 1922. Despite several reported sightings over the years, many believe the California wolverine is extinct.
The new findings do not shed much light on where the wolverine that was photographed came from or how it ended up in Tahoe. The nearest known resident population is about 600 miles northeast in Idaho's Sawtooth Range.
"I don't think I want to speculate at this point," Schwartz said.
Wolverines have been known to travel great distances, but the farthest any particular animal has been documented going is 235 miles, Schwartz said.
The other possibility, Schwartz said, is that the wolverine was a pet or captive that was released into the Tahoe National Forest.
The ability to rule out a connection to California wolverines was possible only because research station scientists last year extracted DNA from skulls of California wolverines.
Seven specimens were available from the National Museum of Natural History in Washington, D.C., and from the Museum of Vertebrate Zoology in Berkeley. They had been collected between 1891 and 1922 in Fresno, Tulare and Mono counties and from Yosemite National Park. Analysis done at the Wildlife Genetics Laboratory in Missoula found that the California wolverines all had the same genetic makeup unique to California, Schwartz said.
"It's just so cool to be able to go back to a skull collected by naturalists at the turn of the (last) century and extract DNA," Schwartz said. "We're still doing research, looking at other parts of the genetic code to narrow down the exact origin."
For more information about the Wildlife Genetics Laboratory: | <urn:uuid:efdbf113-6382-44e4-8ffa-762bc46b14de> | 2.859375 | 786 | News Article | Science & Tech. | 30.869621 | 95,572,719 |
Authors: George Rajna
It's ultra-thin, electrically conducting at the edge and highly insulating within—and all that at room temperature: Physicists from the University of Würzburg have developed a promising new material. An international team of researchers, working at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley, fabricated an atomically thin material and measured its exotic and durable properties that make it a promising candidate for a budding branch of electronics known as "spintronics." The emerging field of spintronics aims to exploit the spin of the electron. In a new study, researchers measure the spin properties of electronic states produced in singlet fission – a process which could have a central role in the future development of solar cells. In some chemical reactions both electrons and protons move together. When they transfer, they can move concertedly or in separate steps. Light-induced reactions of this sort are particularly relevant to biological systems, such as Photosystem II where plants use photons from the sun to convert water into oxygen. EPFL researchers have found that water molecules are 10,000 times more sensitive to ions than previously thought. Working with colleagues at the Harvard-MIT Center for Ultracold Atoms, a group led by Harvard Professor of Physics Mikhail Lukin and MIT Professor of Physics Vladan Vuletic have managed to coax photons into binding together to form molecules – a state of matter that, until recently, had been purely theoretical. The work is described in a September 25 paper in Nature. New ideas for interactions and particles: This paper examines the possibility to origin the Spontaneously Broken Symmetries from the Planck Distribution Law. This way we get a Unification of the Strong, Electromagnetic, and Weak Interactions from the interference occurrences of oscillators. Understanding that the relativistic mass change is the result of the magnetic induction we arrive to the conclusion that the Gravitational Force is also based on the electromagnetic forces, getting a Unified Relativistic Quantum Theory of all 4 Interactions.
Comments: 24 Pages.
[v1] 2017-07-10 08:37:45
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GNU C Library
The GNU C Library
The GNU C Library (glibc) is the standard C library of the GNU system. It defines the system calls and other basic functionality necessary to write programs in the C language. It handles low-level functionality that communicates with the kernel, such as process and file management, as well as higher-level functionality such as string manipulation or command-line argument handling.
The GNU C Library implements much of the POSIX.1 functionality in the GNU system, using configurations i86-*-gnu. The current GNU/Hurd support requires out-of-tree patches that will eventually be incorporated into an official GNU C Library release.
It is one of the most important components of the GNU operating system and its variants GNU/Linux. It is used by almost all C programs and provides the most essential program interface.
- IRC general channel
released on 1 February 2018
Accepts cryptocurrency donations.
git clone git://sourceware.org/git/glibc.git
|License||Verified by||Verified on||Notes|
|License:LGPLv2.1orlater||Bendikker||21 May 2010|
|License:GPLv2orlater||Bendikker||17 May 2018|
Leaders and contributors
Resources and communication
|Debian (Ref) (R)||https://tracker.debian.org/pkg/r-cran-getopt|
|VCS Repository Webview||https://sourceware.org/git/?p=glibc.git|
|Ruby (Ref) (R)||https://rubygems.org/gems/getopt|
|Python (Ref) (R)||https://pypi.org/project/glibc|
|R (Ref) (R)||https://cran.r-project.org/web/packages/getopt|
|Debian (Ref) (R)||https://tracker.debian.org/pkg/glibc|
This entry (in part or in whole) was last reviewed on 17 May 2018.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the page “GNU Free Documentation License”.
The copyright and license notices on this page only apply to the text on this page. Any software or copyright-licenses or other similar notices described in this text has its own copyright notice and license, which can usually be found in the distribution or license text itself. | <urn:uuid:aa5d72c6-05f3-43c0-8e3d-18af35708d38> | 3.484375 | 587 | Documentation | Software Dev. | 55.105328 | 95,572,763 |
It really doesn’t matter whether you are a QA engineer, developer, or a Devops. You must have a clear understanding of software testing. I know to design and developing a mobile app or a website can be a tedious task. However, it is also crucial to delivering a bug-free application. In fact, it is the most important counter-part of the software development.
In this post, we will discuss the major difference between performance testing, load testing, and Stress testing. All these terms may sound similar but they are way too different from each other. This post is here to break the common misconception in the realm of software testing.
So, without any further ado, let’s get you started
What is a Performance Testing?
Performance testing is used to determine the speed of device or network, Devices may include computers, mobile phones, and tablets.
[ Related Read: Performance Testing On Mobile Applications ]
It checks all the scenarios where the performance of the mechanisms of your system gets affected. These scenarios are technically the parameters present in different load scenarios.
What is Load Testing?
Load testing is the actual user load your software can handle. It confirms how your software will react with normal and maximum loads. When a project is almost completed, the developers put it through load testing to make sure that it can handle the unexpected excessive traffic volume.
What is Stress Testing?
If you want to determine the stability and power of your software, then you should go for stress testing. Stress testing comprises simulations that will help you in cross-checking all the hypothetical situations where your application can lag behind.
The Core Difference
Make note of these points,
- Performance testing is the superset of load and stress testing while load and stress testing are the subsets of performance testing.
- Performance testing will enhance your software and set standards while the load test is for determining the upper limit of the software. Stress testing on other hand is utilized to check how your application will behave under overload and how it will recover in the end.
- Performance testing is all about how your application will respond to the optimum parameters while load testing tells the limit and only conducted for increasing the load. Stress testing ensures that your application is ready to handle any sudden surge in traffic.
Winding It Up
In a nutshell, what you need to understand is that performance testing is one category and the other two i.e. load and stress testing is the subcategory of performance testing. They are there to ensure seamless functioning of your application in the trickiest conditions.
If you are looking for specialized services in performance testing, BugRaptors is your best bet. We offer range of tools which will help you in your cause.
Please share the word and if you have any concerns you can contact us to know more about software testing. Adios for now!!! | <urn:uuid:f3120cb6-9143-42b4-a442-5cf40eb66f84> | 2.515625 | 584 | Truncated | Software Dev. | 47.536377 | 95,572,782 |
NASA explores inflatable spacecraft technology
NORFOLK, Va. - Devising a way to one day land astronauts on Mars is a complex problem and NASA scientists think something as simple as a child's toy design might help solve the problem.
Safely landing a large spacecraft on Mars is just one of many engineering challenges the agency faces as it eyes an ambitious goal of sending humans into deep space this century.
At NASA's Langley Research Center in Hampton, Va., engineers have been working to develop an inflatable heat shield that looks a lot like a super-sized version of a stacking ring of doughnuts with which infants play. The engineers believe a lightweight, inflatable heat shield could be deployed to slow the craft to enter a Martian atmosphere much thinner than Earth's.
Such an inflatable heat shield could help a spacecraft reach the high-altitude southern plains of Mars and other areas that would otherwise be inaccessible with existing technology. The experts note that rockets alone can't be used to land a large craft on Mars as can be done on the atmosphereless moon.
Parachutes also won't work for a large spacecraft needed to send humans to Mars, they add.
Hence the inflatable rings. The rings would be filled with nitrogen and covered with a thermal blanket. Once deployed for landing, the rings would rest atop the spacecraft, somewhat resembling a giant mushroom.
"We try to not use propulsion if we don't have to," said Neil Cheatwood, the senior engineer at Langley for advanced entry, descent and landing systems. "We make use of that atmosphere as much as we can, because it means we don't have to carry all that fuel with us."
NASA's leaders acknowledge that getting humans safely to and from Mars as early as the 2030s will pose extreme challenges. The agency's scientists acknowledge they also must design new in-space propulsion systems, advanced spacesuits, long-term living habitats aboard spacecraft - even communication systems for deep space.
Work is proceeding, sometimes fitfully.
When an unmanned private rocket destined for the International Space Station exploded in October soon after liftoff from Wallops Island, Va., numerous scientific experiments went up in flames with it. But one NASA experiment that Orbital Sciences Corp. originally invited aboard - for a second-generation inflatable spacecraft - never made it for lack of time to get it together, NASA officials say.
That experiment calls for testing how second-generation inflatable spacecraft technology performs upon re-entry in Earth's atmosphere.
The test is important because NASA officials believe an inflatable heat shield could be what helps them land astronauts on Mars and return larger loads of supplies from the International Space Station.
The experiment is scheduled to go up on the next Antares rocket in 2016.
New technology is needed to get astronauts to Mars because the type of spacecraft that would land humans would be much larger than anything that has landed on the planet previously. Current heat shield technology weighs too much to be on larger spacecraft, which means scientists can't land anything much larger than the rovers that have been sent there.
NASA has relied on parachute-based deceleration on Mars since the Viking program in the 1970s.
Engineers at Langley have been working on the inflatable technology for about a decade, and believe it is close to being ready for operational use.
"If I had the budget and we had the funding to do it, I think we could get as large a scale as needed for humans in five to 10 years," Cheatwood said. | <urn:uuid:a8bc54bb-5ad4-4792-a2ac-0e723e08e734> | 3.484375 | 720 | Truncated | Science & Tech. | 44.390249 | 95,572,801 |
A gradual lengthening of the snow-free season in Alaskas tundra, and a corresponding northward progression of the growth of shrubs and trees, may be creating a cycle of warmer and longer summers in the Alaskan Arctic according to a new study to be published in the Sept. 22, 2005, issue of Science Express.
The resulting atmospheric heating in the region of northern Alaska is equivalent to what might be observed if there was a doubling of carbon dioxide in the atmosphere. Continuation of this trend could further amplify atmospheric heating in the region by two to seven times and could possibly contribute to broader changes in climate.
"We suggest that a noticeable summer warming trend in Alaska is best explained by a lengthening of the snow-free season there," said Howard E. Epstein, an associate professor of environmental sciences at the University of Virginia and a co-author of the new study. The scientists determined that the increasing summer temperatures in northern Alaska could not be attributed to regional atmospheric circulation patterns or to a reduction in sea ice in the summer or to an increase in cloud cover. The observed summer temperature increases are likely related to a global warming trend that has led to a longer snow-free season and an increase in the extent of woody vegetation. Both of these changes increase the amount of solar radiation that goes into heating rather than being reflected back to the atmosphere.
Howard Epstein | EurekAlert!
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
Drones survey African wildlife
11.07.2018 | Schweizerischer Nationalfonds SNF
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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Of all the habitable parts of our planet, one ecosystem still remains largely unexplored and unknown to science: the igneous ocean crust.
This rocky realm of hard volcanic lava exists beneath ocean sediments that lie at the bottom of much of the world's oceans.
While scientists have estimated that microbes living in deep ocean sediments may represent as much as one-third of Earth's total biomass, the habitable portion of the rocky ocean crust may be 10 times as great.
Yet biologists know very little about this ecosystem. The Integrated Ocean Drilling Program (IODP) Mid-Atlantic Ridge Microbiology Expedition set out to change that.
An international team of scientists sailing onboard the research vessel JOIDES Resolution recently returned from installing observatories beneath the seafloor in "North Pond"--a remote area in the middle of the Atlantic Ocean.
Scientists hope that data collected from these subseafloor observatories (known as CORKs, or Circulation Obviation Retrofit Kits), along with studies of rock and sediment samples collected during the expedition, will help to shed light on the role tiny subseafloor microbes play in shaping Earth's oceans and crust.
Led by co-chief scientists Wolfgang Bach of the University of Bremen in Germany and Katrina Edwards of the University of Southern California, the expedition began in Bridgetown, Barbados, on Sep. 16, 2011, and concluded in Ponta Delgada in the Azores on Nov. 17, 2011.
Two CORKs were successfully installed, and sediment and basalt core samples were recovered. CORK observatories are designed to remain in place for up to ten years.
The North Pond subseafloor observatories will allow active experiments to be conducted below the bottom of the ocean for as much as five years after deployment.
Scientists from the expedition plan to return to these observatories with the first of many submersible expeditions in early 2012.
"The innovative and novel experiments and observations from this expedition promise to greatly advance our understanding of the nature and extent of microbial life in the most widespread of environments--the Earth's ocean crust," says Jamie Allan, program director for IODP at the U.S. National Science Foundation (NSF). NSF co-funds IODP.
In the coming months and years, researchers hope to answer three main questions:
What is the nature of subseafloor microbial communities, and what is their role in the alteration of relatively young ocean crust?
Are these communities unique, particularly in comparison with seafloor and sedimentary communities?
Where do microbes in the igneous ocean crust come from (sediment, rock, seawater or another source)?
IODP is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring, and monitoring the subseafloor.
IODP is supported by two lead agencies: NSF and Japan's Ministry of Education, Culture, Sports, Science and Technology.
Additional program support comes from the European Consortium for Ocean Research Drilling, the Australia-New Zealand IODP Consortium, India's Ministry of Earth Sciences, the People's Republic of China's Ministry of Science and Technology and the Korea Institute of Geoscience and Mineral Resources.
JOIDES Resolution is a scientific research vessel managed by the U.S. Implementing Organization of IODP (USIO). Texas A&M University, Lamont-Doherty Earth Observatory of Columbia University, and the Consortium for Ocean Leadership comprise the USIO.
For more information about IODP Expedition 336--Mid-Atlantic Ridge Microbiology, please see IODP's webpage.Media Contacts
Cheryl Dybas | EurekAlert!
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
Drones survey African wildlife
11.07.2018 | Schweizerischer Nationalfonds SNF
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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So what did the Elizabethans know about software development? Well, in truth, nothing whatsoever. But what they had begun to do is codify and systematise the knowledge and experience of masters in manuals, treatises and books. Some of the earliest documents of this form refer to the martial arts or, as it was known at the time the ‘Arts of Defence’
In martial arts one learns practical skills (in this case how to defend oneself against any enemy) through practice and training. The practical skills are usually an extension of some ‘core’ principles, which form the basis of the art. These core principles state some fundamental truth about the nature of the art. Without understanding these fundamental principles one is merely performing a ‘dance’ and one will never be truly effective.
In the late 16th century George Silver, an English gentleman, wrote a martial arts treatise called ‘Paradoxes of Defence’ (A transcription of the original can be found here). The treatise is well known in the Western Martial Arts community for being one of the earliest treatises in English; and also for Silver’s prolonged and somewhat vitriolic attacks against the Italian fencing masters of his day, who he saw as frauds.
Silver followed up his ‘Paradoxes of Defence’ with a more practical publication ‘Brief Instructions Upon My Paradoxes of Defence’ where he attempted to set out his fighting principles and practices (a transcription can be found here)
Silver used the phrases ‘True Fight’ and ‘False Fight’ to describe effective fighting techniques. True fight was correct application of the principals of fighting; False Fight was to ignore, misunderstand or misuse the principals of fighting. He also talked of ‘Perfect’ and ‘Imperfect’ fighting. Perfect fighting had nothing to do with being a great fighter: as long as you used the correct technique all the time (the True Fight) then your fight was perfect; however skilled you were. So a beginner, using the principals of the True Fight, even if slow and ungainly, was fighting a Perfect fight. On the other hand, even if you were fast, skilled and deadly, if you used ‘False’ techniques Silver considered your fight to be ‘Imperfect’. In Silver’s mind using correct principles was always superior to using ineffective techniques. That didn’t mean the Perfect Fight always won; but that the Imperfect fighter was doomed, by definition, eventually to fail.
Silver based his techniques on what he called his Four Groundings and Four Governors. The Four Groundings were the fundamental principles upon which all fighting – irrespective of the weapon used – were based. The Four Groundings are tightly inter-related to each other. Ignoring one principle will affect all the others (and lead to False fight). Each Grounding must be understood, and how it affects all the others, also understood.
The Four Governors were the elements of a fight that controlled its outcome. The Governors control your actions and your approach to the fight. As the Governors change, so must your approach to the fight, and the techniques you can, or must, use.
The question is: can we apply Silver’s ideas of True Fight and False Fight to software development? What is ‘True’ development; and what is ‘False’? What are the Groundings of software development; and what are the Governors? Can we define ‘Perfect’ and ‘Imperfect’ software?
‘Imperfect’ software development
Firstly we need to make a distinction between Correctness and Intrinsic Quality. Correctness is the ability of software to fulfil its requirements. Intrinsic Quality refers to how the software is designed and built – that is, how ‘good’ or ‘bad’ the software is.
Incorrect software, irrespective of how good it is, must be considered ‘Imperfect’ by our definition. No matter how ‘good’ the software is, if it doesn’t fulfil its requirements, it’s useless (and if the requirements are wrong it’s also useless, or at least of questionable value).
Correct software must be our starting point. Is all correct software Perfect? Or should the ‘perfection’ of software be judged by its Intrinsic Quality?
If we apply Silver’s logic ‘Perfect’ software will always result from ‘True’ software development. True development is that which applies the Four Groundings and Four Governors of software development. So we need to understand what the Groundings and Governors are for software development.
The Groundings and Governors for software development must be those principles that give our software high intrinsic quality, both in its development (its static design, coding) and at runtime (its dynamic testing and execution).
What makes poor software?
It is challenging to define what makes ‘good’ software since we so rarely see it. On the other hand most engineers are used to seeing (and maintaining!) what they consider ‘bad’ software. Often engineers cannot qualify what makes the software bad; it just is. Typically, though, bad software suffers from one or more of the following maladies:
It is difficult to understand.
The code is difficult to read; variable names are unhelpful; comments are missing (or worse, incorrect); code is badly structured and laid-out; etc.
It is fragile.
Fragile code will break at the slightest provocation. Fixing a bug in one part of the code can cause a cascade of other bugs in other parts of the code; often quite un-related to the problem.
It is rigid.
Rigid code has been designed to fulfil one requirement – and that is all it will ever do. If the requirements change the software must be almost completely re-written to support the new behaviour.
It is immobile.
Engineers often build really useful software modules. However, if the useful module is so tightly intertwined with the structure of the program it’s in, the effort involved in unpicking the useful code is so great is often impractical to even try to re-use it somewhere else. Sometimes it’s just easier to write it again from scratch.
The Four Governors
In Silver’s system understanding and controlling your Governors determined how successful you were in a fight. If you fail to control your Governors you will ultimately lose the fight. In engineering terms success can be measured in terms of money. That is, failing to understand and control the software Governors will ultimately lead to spending more money (or making less money, however you want to look at it) than you need to.
Our Governors must therefore relate to the effectiveness of our software development. Effectiveness is about doing things that add value; in contrast to efficiency, which is focussed on doing more work with less resource.
If the above qualities define bad software then the opposite must define good software. Thus we can use our definition of bad software and invert them to give us our Four Governors of software development. They are:
Good software must be easy to read and understand. There should be no surprises in the code; its purpose and implementation should be obvious and equivalent.
It should require little effort to adapt existing software to new requirements.
Software should be tolerant to invalid inputs. Performance should be unhindered by incorrect inputs, or should be degraded in a known, controlled, way. The impact of change should be controlled and limited.
Software should be easily adapted to new environments, platforms or problem domains, without requiring major modification.
The Four Groundings
The Groundings are the set of (inter-related) principles upon which all actions are based. The principles are normally inter-dependent – adjusting one principle often affects the others. Thus the Groundings must be ‘balanced’ to meet the needs of the Governors. As the Governors change, so must the application of the Groundings.
In software our Groundings are the principles of good, modular, design. A module, in this case, refers to a unit of software construction (or decomposition, if you prefer). A program is constructed of one or more modules. A module should ideally be self contained, with a well-defined interface and a well-defined, localised purpose and functionality.
By correct application of the Groundings we achieve high intrinsic quality software. Once again, our Groundings are inter-dependent – focussing on any one Grounding at the expense of the others is no guarantee of producing good software.
The Four Groundings of software development are:
Coupling is the inter-dependence between modules. The inter-dependence depends on the number of, and complexity of, connection between any two modules.
Ideally, we aim for low coupling – that is, a small number of simple connections. Reducing the inter-dependency between modules allows greater flexibility in design and greater potential for re-use.
There is a compromise to be made between coupling and performance. Typically, low-coupling comes at the expense of system performance; highly-coupled systems can often be much higher performance than lower coupled systems.
The engineer’s skill is in understanding when to design for low coupling and when to design for performance.
As a rule-of-thumb always design for intrinsic quality of code, monitor the actual performance, and only then optimise the coding or coupling of the key areas that need it. Most times the problem isn’t where you think it is (dynamically).
Encapsulation literally means ‘to put in a capsule’. Encapsulation is separating ‘what’ the module does (its interface) from ‘how’ it does it (the implementation). Ideally, clients should never be able to directly access the module’s implementation – or even need to if the interface is designed well.
Strong encapsulation can reduce coupling by eliminating the ability of one module to access the internal behaviour or data of another module.
It enables the module to be easily tested in isolation before combining it with other modules that make up the program.
Encapsulation also provides ‘insulation’. By separating the interface from its implementation the implementation may be changed without affecting the client code – in other words, the client is ‘insulated’ from change.
Cohesion defines how well elements fit together. There are several models for cohesion in software (The most well known being Constantine’s 7-level scale of cohesion) but most cover the following aspects:
Functional cohesion focuses on the coherence of the interface of a module. For high cohesion the operations that form a module’s interface must be mutually self-supporting. The operations should all contribute to a unified overall behaviour for the module By contrast, the operations in a low cohesion module are independent and unrelated. Removing or replacing any operation has no effect on any other operation in the module. A highly cohesive module typically performs a single, high-level responsibility.
Temporal cohesion focuses on the concurrent or parallel execution behaviour of modules. Modules that execute in sequence with one another executing in the same thread of control are temporally cohesive. Modules that must run in parallel but are executing within the same thread of control are not temporally cohesive.
Contextual cohesion refers to design abstraction. During design engineers should organise the design into different levels of detail; each level used to focus on a different aspect of problem definition. For example, high level design should focus on architecture and design validation; lower level designs should focus on implementation and verification. A cohesive design does not mix high and low level constructs on the same design. For example, focussing on implementation artefacts during architectural design is inappropriate and therefore contextually non-cohesive.
Cohesive modules tend to limit the impact of change, since the change typically affects only the (related) operations/data in a single module; and has no impact on other modules.
Abstraction may be defined as filtering out detail that is unnecessary in the context being considered.
When we build software we are constructing models of the problem domain and manipulating them to provide some benefit to the customer. Context is important because it defines how you view the situation: what is relevant, that is, the abstractions that are useful in that context.
For any particular problem domain there are concepts that are important, and concepts that have no relevance. A good abstraction captures the relevant information about the problem domain, and ignores the superfluous. You could think of this as looking at a problem from a particular viewpoint.
Basing a design on problem domain abstractions provides resilience to change since the concepts of any particular domain are likely to remain stable over time; unlike implementation technologies which are likely to change rapidly.
The Four Groundings are all inter-dependent, but not necessarily mutually inclusive: Although a good problem domain abstraction domain is likely to be cohesive, it can be made incoherent through bad design; a coherent module should provide strong encapsulation, but that can be broken through poor design; strong encapsulation should provide lower coupling, but poor cohesion in the design and poor abstractions may lead to increased coupling.
A good engineer must understand the Four Groundings in detail and how they inter-relate.
‘Perfect’ software development
True development is one that applies the Groundings and Governors:
A design with well-chosen abstractions of problem domain elements, strongly and cohesively encapsulated with low coupling. Such a design is likely to be comprehensible, robust, flexible and mobile.
False development is one that ignores the Groundings and Governors:
An incoherent design, focussing on implementation elements, with poor encapsulation, weak cohesion and high coupling. Such a design is likely to be incomprehensible, rigid, fragile and immobile.
A Perfect development is therefore one that is always True; Imperfect development is one where we use False techniques.
Of course, we can always ignore the Groundings and Governors and still produce working software; but this will always be (in Silver’s view) Imperfect.
Even if we aren’t particularly skilled with the Groundings and Governors as long as we apply them our development will always be True. And we can always improve.
If we always choose the False development (cutting corners) our software can never be Perfect.
As it suggests Perfect development is an ideal; it is something to strive for. We will almost certainly have to compromise our development because of time, resource or money constraints. Wherever possible, though, we should aim for True development.
Perhaps those Elizabethans knew more about software development than we realise, after all.
Summary of the True development
The Four Governors
The Four Groundings
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The South Pole is an inhospitable place to do science. Temperatures can drop below minus 99 degrees Fahrenheit. The air is thin and moisture-less.
Yet physicists are flocking to an observatory there because it’s one of the best places to answer a mystery that’s been haunting their field for more than a century: What in the universe is shooting incredibly powerful beams of subatomic particles at Earth?
Scientists discovered in 1912 that subatomic particles — the building blocks of matter, such as protons, electrons, muons, neutrinos, and quarks — hit the Earth every day. They later learned they were hitting us with an energy that surpasses the power of human-built particle accelerators, like the Large Hadron Collider. Some of these particles carry so much energy that scientists have been puzzled as to which objects in space are powerful enough to create them.
Now, we have an important clue as to at least one object that may be responsible for some of these particles, often called “cosmic rays,” that hit the Earth. In two new studies appearing Thursday in Science, a large team of physicists reports that one of the sources of cosmic rays is a special type of galaxy called a blazar. Blazars have supermassive black holes at the center of them that rip apart matter into its constituent parts, and then blast subatomic particles off like a laser cannon into space.
The entire mystery of the source of cosmic rays is not solved. Scientists don’t know if there are other objects that can produce the rays, and the current results can’t yet explain the most powerful cosmic rays detected on record. They’re also not perfectly confident that the blazar is the source. (Physicists don’t use the word “certain” lightly.)
But it’s an intriguing start. Cosmic rays were first discovered in 1912. And we’re just now getting a big break to understand how they get here.
(The National Science Foundation is live streaming their press conference announcing the findings. You can watch that here.)
How a giant ice cube at the South Pole led to this discovery
There are some sources of cosmic rays that we do know about, like the sun, which is constantly spitting out bits of matter in all direction. Some cosmic rays can even be produced from atomic collision at the top of our atmosphere.
But then there are the cosmic rays being shot at us at energy levels that truly leave scientists dumbfounded. That’s the 100-year-old mystery.
The best comparison we have to explain the energy of these rays is the Large Hadron Collider near Geneva, Switzerland. The LHC is the most powerful, sophisticated particle accelerator on the planet. It can accelerate a proton to nearly the speed of light, and charge it with the energy of seven terra-electron-volts, or TEV. This is enough power to smash atoms into tiny, tiny pieces and reveal the architecture that makes up our universe.
It’s impressive. But it has nothing on the energy of the particles that rain down from space. The highest-energy cosmic ray particle ever recorded, called the “Oh-My-God” particle, was two million (!) times more energetic than the protons propelled at the LHC.
“How does nature do this?” Francis Halzen, a University of Wisconsin particle physicist and a lead collaborator on the new discovery, asks. “This has been for decades listed as one of the big open questions in astronomy and physics.”
The problem with looking for the sources of these very high energy cosmic rays is that they don’t always travel in a straight line. And that means they can’t trace it back to its source. In fact, we have the Northern and Southern Lights near the poles because the Earth’s magnetic field redirects much of the cosmic rays to these regions.
This is where the South Pole observatory comes in. There, Halzen; Naoko Kurahashi Neilson, a particle physicist at Drexel University; and several of their colleagues in physics have been looking for answers in the ice.
They work on the IceCube Neutrino Observatory, which is built directly into the ice beneath the surface of the South Pole. The observatory is funded by the National Science Foundation and is operated by the University of Wisconsin.
Basically it is a 1-cubic kilometer (about 1.3 billion cubic yards) block of crystal-clear ice surrounded by sensors. These sensors are set up to detect when subatomic particles called neutrinos — which travel along with other subatomic particles in cosmic rays — crash into the Earth.
Neutrinos are different from the other components of cosmic rays in one hugely important way: They don’t interact with other forms of matter much at all. They don’t have any electrical charge so Earth’s magnetism doesn’t deflect them. And they travel through the universe in a relatively straight line, and we can trace them back to a source.
“If I shine a flashlight through a wall, the light won’t go through,” Neilson, a co-collaborator on both of the new papers in Science, explains. “That’s because the light particles, the photons, interact with the particles in the wall and they can’t penetrate. If I had a neutrino flashlight, that stream of neutrinos would go through the wall.”
But every once in a while a neutrino — perhaps every one in 100,000 — will hit an atom in the ice at the observatory and break the atom apart.
And then something spectacular happens: The collision produces other subatomic particles, like muons, which are then propelled to a speed faster than the speed of light as they pass through the ice.
You might have heard that nothing can travel faster than light. That’s true, but only in a vacuum. The photons that make up light (a subatomic particle in their own right) actually slow down a bit when they enter a dense substance like ice. But other subatomic particles, like muons and electrons, do not slow down.
When particles are moving faster than light through a medium like ice, they glow. It’s called Cherenkov radiation. And the phenomenon is similar to that of a sonic boom. (When you go faster than the speed of sound, you produce a blast of noise.) When particles move faster than light, they leave wakes of an eerie blue light like a speedboat leaves wakes in the water.
Here’s an artist’s depiction of what this all looks like. The neutrino is the tear-drop shape in gray.
It’s an exciting finding in the “multi-messenger” age of astronomy
The light emitted from the particles is why ice is critical to the observatory. It’s crystal clear. Sensors can spot the flashes and then draw a path to where it originated in the sky. The particular neutrino — and it was just one — that led to the new discovery hit the ice cube in September 2017 with an energy of 290 terra electron-volts. Again, that’s 40 times as energetic as the particles in the LHC.
Within a minute, the computers at the observatory determined the neutrino had come from the direction of the constellation Orion, and sent out an automated alert to observatories around the world to hunt for a more precise source.
Here, the researchers caught a lucky break. Almost simultaneously, the Fermi Gamma-ray Space Telescope detected an increase in energetic activity from a galaxy in the same direction. And observatories around the world and in space picked up on it too.
The Science papers argue this likely was not a coincidence: Fermi and the other observatories picked up the same blast of cosmic rays that propelled the neutrino to the IceCube observatory and they traced it to a single blazar 4 billion light-years away. Still, the scientists are not entirely sure.
“This result doesn’t make it absolutely certain the neutrino came from the blazar,” says Kyle Cranmer, an NYU particle physicist not involved in the research. “I’d want to see another such observation.”
And the IceCube scientists agree. “I compare it to a police investigation of a murder,” Halzen says. “We just made a breakthrough and we know we’re going to find the person, but [we] didn’t get him yet.” Though the case for the blazar is made more compelling by the fact that when the IceCube team went back through their data from the past few years, they found other neutrinos that were likely spat out by the same blazar.
IceCube detects neutrinos on a regular basis, and astronomers look at blazars on a regular basis. What’s new and exciting here is that the IceCube team was able to turn to colleagues in observatories around the world to track a high-energy neutrino to its source for the first time.
As with many discoveries in physics, this one raises more questions than it answers. Scientists still don’t know how blazars actually accelerate particles to such high energies. They don’t know if all blazars are capable of doing this, or just some of them. And they don’t know what other objects in the universe could produce high-energy cosmic rays.
“This is science as usual,” Halzen says. “You solve a problem, and then it opens many more questions that are harder to solve. But that’s a perfect situation to be in to make progress.”
But perhaps more exciting than these findings is that there’s likely much more to come from these kinds of international collaborations in astronomy. “Regardless of whether or not this neutrino is actually from this blazar or not, [the results they produced are] just an incredible exercising the muscles of the whole system,” says Sarah Demers, a Yale particle physicist not involved in the research. That the IceCube lab can send out an alert that other telescopes can corroborate in the same day is an impressive accomplishment.
In recent years, astronomers have become excited by the idea of “multi-messenger” astronomy — the idea of seeing the universe with forces of nature other than light. Yes, we can see the universe in all sorts of wavelengths of electromagnetic radiation: visible light, infrared, ultraviolet, gamma, and so on. But all of these forms of radiation are different forms of light. What’s new and exciting about physics today is | <urn:uuid:a8b2e445-2c33-4d59-8ce7-d2c6a926a42e> | 3.609375 | 2,256 | News Article | Science & Tech. | 50.646137 | 95,572,855 |
Getting Prepared for Hurricane Season
At a Glance
- In August, it's almost as if a switch is flipped.
- There's a 17-day stretch from mid-August to early September during which the most intense U.S. hurricane landfalls all occurred.
Frequently in July, I am asked: "Why has the Atlantic hurricane season been so quiet?" or "When will the hurricane season ramp up?"
The Atlantic hurricane season runs from June through November, but most years, the first two months of the season are typically benign.
June averages only one named storm every other year, and July has averaged one named storm each year since 1950.
Then comes August and it's almost as if a switch is flipped.
August sees more than three times the number of named storms as July, and almost double the number of June and July storms combined.
Another way to visualize the "ramping up" of the hurricane season is through an index called accumulated cyclone energy, or ACE.
The ACE index is calculated by adding each tropical storm or hurricane's wind speed through its life cycle.
Long-lived, intense hurricanes have a high ACE index. Short-lived, weak tropical storms, a low ACE index.
The ACE of a hurricane season is the sum of each storm's ACE, thus taking into account the number, strength and duration of all the tropical storms or hurricanes in the season.
Colorado State University tropical scientist Dr. Phil Klotzbach constructed a graph of how the ACE index adds up during an avearge Atlantic hurricane season.
Where the slope of this graph is steepest, in other words, when the ACE index is increasing the fastest, generally marks out the most active stretch of the Atlantic hurricane season.
According to Klotzbach's plot, this is from the second week of August through September.
While landfalls don't necessarily correlate with numbers of named storms, there's a 17-day stretch from mid-August to early September during which the most intense U.S. hurricane landfalls all occurred.
Several factors contribute to the seasonal ramp-up in August:
- African easterly waves are most well-developed, often serving as a seed for tropical development.
- Saharan air layers, surges of dry air into the central and eastern Atlantic basin, which normally squelch tropical development in those areas tend to give way by August, as the parade of African eastely waves gradually add moisture. This effectively opens up more favorable real-estate for tropical cyclone development.
- Wind shear, the change in wind speed and/or direction with height which can rip apart a tropical cyclone wanna-be, tends to be low.
- Sea-surface temperatures rise toward a peak in early fall.
- Instability, namely, the atmosphere's ability to generate convection (t-storms) to help initiate tropical cyclones, also rises toward an early fall peak.
Of course, averages and climatology are no guarantee of an outcome in any individual hurricane season.
However, if you have plans for, say, a Caribbean cruise, and you're concerned about hurricane season, the long-term data would suggest a lower chance of a hurricane interrupting your vacation in June or July, compared to August or September.
Then again, you may be able to nab a great discount on Caribbean travel in August or September. Just make sure to buy travel insurance, just in case.
Jonathan Erdman is a senior meteorologist at weather.com and has been an incurable weather geek since a tornado narrowly missed his childhood home in Wisconsin at age 7. | <urn:uuid:48d7f401-190c-4147-9742-118937b6e130> | 3.046875 | 746 | News Article | Science & Tech. | 43.095784 | 95,572,873 |
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Forming the largest group of freshwater lakes on Earth and making up 21 percent of the world's total freshwater supply, the Great Lakes are recording all-time low water levels, posing economic threats to numerous industries that rely on the lakes water supply, including, tourism, hydroelectric generation and recreational boating.
Lakes Michigan and Huron set new record-low water levels in December of 2012, breaking the previous record set in 1964. Water levels dipped to an all-time low at 576.15 feet, according to the US Army Corps of Engineers, Detroit District. Not only did the water levels break record lows but the levels made this the longest stretch of below average levels in the lake's recorded history dating back to 1918, and thus continuing a 14 year streak of below average levels. Many factors have contributed to the significant decrease in one of the world's most important waterways but among them, one of the most notable causes is in fact, the area's weather patterns.
2012 proved to be a year of bizzare weather for the Great Lakes region. The year was warm and dry with the lakes receiving very little snow in the 2011/2012 winter and as a result, very little runoff water. However, due to the sheer size, large surface area and volume of the Great Lakes, just one year would not result in the dramatically low water levels that have been recorded.
"Water levels don't respond to just one year," said Ann Clites, a Physical Scientist at the NOAA Great Lakes Environmental Research Lab. "These low levels are not because of the precipitation for one year, the lakes are just too big and there are too many factors to say that. However, the last 15 years of low levels got the lakes ready to hit all time record lows," said Clites.
This drop in lake levels, is far more concerning due to its potential to shake economic framework. Multiple entities have invested use of the lakes and the lake water, including, commercial navigation, hydroelectric generation, coastal zoning, recreational boating and marinas, the tourism industry and the lake's ecosystems, according to the University of Michigan's School of Natural Resources & Environment. During the CILER-GLERL Great Lakes Seminar Series, hosted by the University of Michigan, Professor of Environmental Economics, Michael Moore, lectures about the potential economic impacts to come for the region.
"Does it harm experience to beach-goers?," questions Moore. Solely dependent on the lakes, the tourism industry, including restaurants and hotels could suffer, if lake levels continue to drop. Real estate value on the shores of the lakes could also take a hit. As for marinas along the lakes, they have already been affected by low levels as boats sit closer to the bottom. "Getting into a boat is now an Olympic sport," said Moore.
Shipping companies could also be at an economic loss. "The ships can not be loaded as much because if the boats sit lower in the water they can run aground," said Abrams. Rivers linked to the Great Lakes are dependent on the lakes' water sources, so they too could shallow and limit navigation for ships and boats.
It is not yet known how the lakes' wildlife will be impacted by this water level change, but it is certain that the levels have the potential to change the ecosystem cycle.
The Great Lakes are notably different than most others due to their surface size, encompassing close to 100,000 square miles. It takes years, multiple seasons, long stretches of time to influence the water levels as radically as has been recorded today.
According to the US Army Corps of Engineers, Lake Superior has seen well above average precipitation for May but it's water levels have been below average for the past 12 months. Lake Michigan and Lake Huron are not doing much better. These two lakes, despite seeing near average precipitation this year, are expected to remain 17 to 20 inches below their long term averages over the next six months. Even though rainfall amounts this year have been close to normal, the Great Lakes water levels do not appear to be improving as fast as needed.
"It's no doubt that the changes are a result of precipitation, rain and snow, said Clites. But the long term cycle seems to have entered a different regime in the early 2000's, as Lake Michigan and Lake Superior from 1998 to 2001 had an unprecedented three foot drop in water levels."
Since then, Clites explains that the upper lakes have been consistently low since 2001. If long-term lack of precipitation is only a factor into the reasoning behind the severe low water levels, then what is the culprit? One theory is evaporation.
Due to the unusually high temperatures, the temperatures of the Great Lake's surface level waters have risen. This results in higher evaporation, as AccuWeather's Elliot Abrams explains, "The warmer the water, the higher the evaporation."
Lake Superior recorded a two degree jump in water temperatures, in the end of the 90s, possibly influencing the rate of evaporation in the Great Lakes.
"A chronic increase in normal evaporation and above normal temperatures, causes a substantial drop in the levels of the lakes," said AccuWeather's Senior Meteorologist, Jim Andrews.
The low lake levels and the possible economic impacts has scientists, residents, business owners and vacationers anxious, as they wait to see what's next. However, the light of hope may be dim, as Clites explains, the difference in the balance between evaporation and precipitation is that evaporation has been consistently higher and seems to be climbing. In order for water levels to increase, the lakes need both a persistently higher amount of rainfall and evaporation rates need to slow down. How long this process could take, no one knows.
"There is little that can be done by people, nothing we can do will raise the levels. It takes years to get in the hole and it takes years to get out," said Andrews.
Comments that don't add to the conversation may be automatically or manually removed by Facebook or AccuWeather. Profanity, personal attacks, and spam will not be tolerated.
An 11-million ton iceberg hovers over the town of Innaarsuit in Greenland. The massive iceberg floats dangerously close to shore, threatening the small town.
Two people suffered shark bites while swimming in the water off Fire Island in Suffolk County, New York, according to NBC New York.
Newly formed Tropical Storm Ampil is set to strengthen as it tracks toward Japan’s Ryukyu Islands into the weekend.
A rainstorm moving up from the south will coincide with a shift in the jet stream and mark the beginning of an extended period of wet, humid conditions in the northeastern US that may last into August.
Eventualmente, la aspirante a ingeniero ambiental espera trabajar tanto con gobiernos como con corporaciones para eliminar microplásticos de los océanos de manera segura y eficiente.
Drenching thunderstorms advanced into the northeastern United States Tuesday afternoon and evening, bringing reports of flash flooding throughout the region.
Weather invariably comes into play at certain points during the Tour de France, especially when some tour stages can be greater than 100 miles in length.
Heavy spring rainfall in parts of the mid-Atlantic have triggered higher-than-average mosquito rates this season. It is estimated that mosquitoes are two to three times their normal rates. | <urn:uuid:cbdbce62-92e3-4a54-ab20-1bdea1cebb4c> | 3.53125 | 1,538 | News Article | Science & Tech. | 42.29056 | 95,572,874 |
Closely related groups can differ dramatically in their diversity, but why this happens is a fundamental question in evolutionary biology, dating back to Darwin's observation that a few hyper-diverse groups dominate the modern biota.
One of the most extreme examples of this observation is found in the comparison of rodents (Rodentia) and rabbits (Lagomorpha). These two mammalian orders are sister groups, but while rodents have diversified to over 2000 living species and an enormous range of body sizes, lagomorphs (rabbits, hares, and pikas) are limited to fewer than 100 relatively small species.
The front row from left shows: Mouse-deer (Field Museum of Natural History specimen no.68770), Andean mountain cavy (FMNH 53654), American pika (FMNH 12590), Alaskan hare (FMNH 9867). Back row shows: capybara (FMNH 79933).
Credit: Photo by S. Tomiya
A new study presented at the Society of Vertebrate Paleontology Annual Meeting shows, surprisingly, that competition with ungulates (hoofed mammals), intensified by climate change, are to blame for the lagomorphs' limited diversity.
Susumu Tomiya of the Field Museum of Natural History and Lauren Miller of the University of California at Berkeley were intrigued by the observation that lagomorphs have spread to all continents except Antarctica and inhabit a variety of environments, but the group contains only about 80 living species of small herbivores, compared to roughly 2,000 species of rodents.
According to Dr. Tomiya, "Mammalian groups that are ubiquitous at the global scale--rodents and bats, for example--tend to be species-rich and show many different ways of living. Lagomorphs are a paradox in this sense." Lagomorphs also show a much more limited range of body size and forms relative to rodents: the average weight of the largest living species (Alaskan hare) is approximately 5 kg (11 lb), whereas the largest living rodent (capybara) is twelve times larger at about 60 kg (133 lb).
Given that the two groups are each other's closest evolutionary relatives, and they have been evolving for roughly the same amount of time (~55 million years, give or take a few million years), the difference in their diversity is striking.
Importantly, fossils from Mediterranean islands show that lagomorphs are capable of becoming much larger than seen today. Nuralagus rex from the Pliocene of Minorca is estimated to have weighed about 12 kg. Ecologists and evolutionary biologists have suggested that such gigantism can take place only in absence of competitors, as is sometimes the case with island faunas.
They reasoned that, if competition were an important factor in determining body size evolution, the conspicuous absence of giant lagomorphs (by today's standards) on continents could be explained by long-standing presence of potential competitors, such as ungulates (e.g., horses, deer, cows, pigs, and their extinct relatives).
Tomiya and Miller tested this hypothesis by examining the rich North American fossil record. They compared the trajectories of maximum lagomorph body size and minimum ungulate body size over the last 30 million years, revealing two phases of body size evolution in lagomorphs. In the late Oligocene, the largest lagomorphs (comparable in body mass to medium-sized hares living today) coexisted with similar-sized and even smaller ungulates (some of which were as small as modern-day cottontails).
This body-size relationship was fundamentally altered following a major climatic transition that prompted opening-up of forests and establishment of grasslands in the early Miocene. For the next 20 million years or so, the maximum lagomorph size shifted in parallel with the minimum ungulate size, suggesting a dynamic body-size boundary between the two groups maintained by competitive interactions.
This study suggests that competitive interactions (and resulting division of resources that minimizes such interactions) may be a key factor determining diversification of mammals over millions of years. From a broader perspective, this study suggests that large-scale shifts in climate and available habitats can leave a long-lasting impact on the subsequent courses of evolution of major mammalian groups by altering their ecological interactions.
As Dr. Tomiya notes, "Much of the discussion about the current biodiversity crisis has revolved around saving species from extinctions. From a paleontological perspective, we believe that it is also important to think about the future of what will turn out to be surviving lineages, that is, how human activities are altering the courses of their evolution through modification of landscapes, seascapes, and atmosphere at the planetary scale. Millions of years from now, our own species may no longer exist, but whatever remains of life on Earth will reflect the decisions we make today about how we live as a species."
Miller, who measured modern lagomorph specimens to estimate body masses of extinct species, adds that natural history collections are crucial in this sense, "This study highlights the creative ways in which museum specimens can be used to provide data over a longer time sequence. Even something as seemingly old-fashioned as rabbit skins with handwritten weight measurements can be utilized with modern techniques to better understand current conditions and future trajectories of biodiversity."
About the Society of Vertebrate Paleontology
Founded in 1940 by thirty-four paleontologists, the Society now has more than 2,300 members representing professionals, students, artists, preparators, and others interested in VP. It is organized exclusively for educational and scientific purposes, with the object of advancing the science of vertebrate paleontology.
Society of Vertebrate Paleontology website: http://www.vertpaleo.org
Journal of Vertebrate Paleontology
The Journal of Vertebrate Paleontology (JVP) is the leading journal of professional vertebrate paleontology and the flagship publication of the Society. It was founded in 1980 by Dr. Jiri Zidek and publishes contributions on all aspects of vertebrate paleontology.
AUTHORS AND AFFILIATIONS:
Integrative Research and Collections Centers
Field Museum of Natural History
1400 South Lake Shore Drive
Chicago, IL 60605-2496
Phone (office): (312) 665 – 7006
University of California, Berkeley
OTHER EXPERTS NOT ASSOCIATED WITH THIS STUDY
BRIAN KRAATZ, PhD
Department of Anatomy
Western University of Health Sciences
Pomona, CA 91766
ALISON BOYER, PhD
Research Assistant Professor
Department of Ecology and Evolutionary Biology
569 Dabney Hall
University of Tennessee
Knoxville, TN 37996
Anthony Friscia | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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Re: origin of bats/reply 2 to TMK
David Marjanovic (email@example.com) wrote:
<No. I'm saying I expect there to be a weak correlation, composed of a
correlation between presence of quill knobs and forces on the wing feathers,
and another between those forces and the length of the wing feathers. It may
well be that other factors than the length have a much larger impact on the
forces -- well, obviously, a powered flier will almost inevitably experience
much greater forces on its wing feathers than a flightless animal with equally
long wing feathers will...>
Turner et al.s paper on the *Velociraptor* with quill knobs (2007, Science
317, pg. 1721, available free here:
http://www.sciencemag.org/cgi/content/full/317/5845/1721) has the following
"An examination of the living families of birds shows a significant
correlation between the absence of ulnar papillae and the loss and/or reduction
in volancy, even though some strong flyers lack papillae (7). This raises the
possibility that ulnar papillar reduction or absence in large-bodied derived
dromaeosaurids reflects loss of aerodynamic capabilities from the clade's
ancestral members. Quill knobs in *Velociraptor* could reflect retention of
feathers from smaller possibly volant ancestors, but such feathers may have had
other functions. Although thermoregulatory effects of secondaries on the ulna
would be negligible, such feathers could have been used for display (1), in
shielding nests for thermal control (8), or for creating negative lift during
incline running (9). Whether this feature represents retention of an ancestral
function or the cooption for other purposes, the presence of quilled feathers
on the posterior of the arms in a
medium-sized derived, clearly nonvolant dromaeosaur can now be established."
1. M. A. Norell, X. Xu, Annu. Rev. Earth Planet. Sci. 33, 277 (2005).
7. Materials and methods are available on Science Online.
8. T. P. Hopp, M. J. Oren, in Feathered Dinosaurs, P. J. Currie, E. B.
Koppelhus, M. A. Shugar, J. L. Wright, Eds. (Indiana Univ. Press,
Bloomington, IL, 2004), pp. 234â250.
9. K. P. Dial, Science 299, 402 (2003).
I would venture to state that quill knobs on an animal with a clearly
insufficient wing structure (and from the looks of it, the inability to raise
its humerus horizontally level to the perpendicular, may retard some of these
aerodynamic forces. That this animal possesses such derived features (and some
*Velociraptor* specimens do not) is further underscored by a statement in the
results of the materials and methods in the supplemental information of the
"The absence of quill knobs in several strong flyers such as the swift
*Apodus*, the hummingbird *Glaucis*, the parrots *Amazona* and *Melopsittacus*,
and the albatross *Diomedea* indicate that other factors such as perhaps body
size, wing shape, or flight styles may also affect the presence or absence of
quill knobs in birds[.]"
So while this tells us that Vel had feathers, it does not tell us it had
wings. Unless we use a definition of wing to indicate anything that sticks out
with feathers attached to it, which should therefore be true of *Microraptor*'s
feet, and the tails of a good variety of fossil taxa like *Caudipteryx*. In
which case, they were 3- to 5-winged animals, not 4-winged. | <urn:uuid:c43127f7-f294-491c-a98f-db08c3b30b51> | 2.71875 | 890 | Comment Section | Science & Tech. | 59.794882 | 95,572,908 |
Invasive plants found to be more tolerant of changes than less adaptable native species
In the battle between native and invasive wetland plants, a new Duke University study finds climate change may tip the scales in favor of the invaders -- but it's going to be more a war of attrition than a frontal assault.
"Changing surface-water temperatures, rainfall patterns and river flows will likely give Japanese knotweed, hydrilla, honeysuckle, privet and other noxious invasive species an edge over less adaptable native species," said Neal E. Flanagan, visiting assistant professor at the Duke Wetland Center, who led the research.
Increased human disturbances to watersheds and nutrient and sediment runoff into riparian wetlands over the coming century will further boost the invasive species' advantage, the study found.
"It's death by a thousand small cuts. Each change, on its own, may yield only a slight advantage for invasive species, but cumulatively they add up," said co-author Curtis J. Richardson, director of the Duke Wetland Center and professor of resource ecology at Duke's Nicholas School of the Environment.
If left unchecked, over time these change will reduce the diversity of plants found in many wetlands and could affect the wetlands' ability to mitigate flooding, store carbon, filter out water pollution and provide habitat for native wildlife, the authors said.
The scientists published their peer-reviewed findings this week in the journal Ecological Applications.
The study, funded by the U.S. Environmental Protection Agency (EPA), is the first large-scale field experiment to simulate how future environmental changes linked to global warming and land-use change will affect plant communities in major river systems in the U.S. Southeast.
It was conducted using plant species and biomass surveys, continuous real-time measurements of water levels and water temperatures, and statistical modeling of long-term plant abundance and growing conditions at 24 riparian floodplain sites in North Carolina and Virginia over a three-year period.
The Intergovernmental Panel on Climate Change (IPCC) projects that surface-water temperatures in the Southeast will increase by 1 to 5 degrees Celsius by the year 2100. Increased evaporation will reduce surface water base flows, while a 5 percent to 30 percent increase in precipitation, mostly in the form of intense storms, will cause pulsed hydrology -- sudden, short-term rises -- in water levels.
As these changes occur, the annual timing of when wetland soils warm up in spring will fluctuate and may no longer be synchronized with when river levels drop, Flanagan said.
This de-synchronization will affect all floodplain plants, but the natural phenotypic plasticity of invasive species allows them to adapt to it better than native species, which need both exposed soil and warmer temperatures to germinate.
As native species' germination rates decline, invasives will move in and fill the void, their increased abundance fueled by high levels of nutrients flowing into the wetlands in runoff from upstream agriculture and other disturbances.
"These findings underscore the need for us to better understand the interaction between climate, land use and nutrient management in maintaining the viability of native riparian plant communities," Richardson said.
"What makes this study so novel is that we used a network of natural, existing riparian wetlands to simulate the long-term impacts of IPCC-projected changes to water temperature and flow over the coming century," Richardson added.
Eighteen of the 24 wetlands used in the study were located downriver from dams or power plants built at least 50 years ago, he said. Ten of these wetlands were classified as warm sites, because water discharged back into the river by the upstream dam or power plant was heated by steam turbines or pulled from higher in a reservoir, where water temperatures were warmer.
Eight wetlands were classified as cold sites because the upstream dams pulled their outflow water from deeper in reservoirs, where temperatures were more than 5 degrees Celsius cooler than at warm sites.
"This allowed us to simulate the effect of long-term changes in water temperatures on native and invasive species abundance," Richardson said. All 18 dams regulated their outflow of water, allowing the team to simulate the effects of projected lower base flow and increased storm flows. Six wetlands in the study were located on undammed rivers and served as control sites.
Mengchi Ho, associate in research at the Duke Wetland Center, also co-authored the study, which was funded by the EPA's Science to Achieve Results (STAR) program (grant #83837010).
CITATION: "Connecting Differential Responses of Native and Invasive Riperian Plants to Climate Change and Environmental Alteration," Neal E. Flanagan, Curtis J. Richardson and Mengchi Ho, Duke University. Ecological Applications, Dec. 8, 2014. . http://dx.doi.org/10.1890/14-0767.1
Tim Lucas | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Authors: Nainan K. Varghese
Light is flow of three-dimensional matter-corpuscles, each corpuscle accompanied by separate set of distortions in universal medium. Together, they constitute radiation of photons. For existence, it is essential for matter-core of a photon to move at the highest possible linear speed, at which universal medium can move it. This limit endows light with constancy of its linear speed. Constancy of linear speed is related to and hence depends on nature of universal medium in region of space, where light is radiated. This essay very briefly describes mechanism of light’s motion and stabilizing mechanism of its linear speed, as envisaged in alternative concept, presented in the book, ‘MATTER (Re-examined)’. For details, kindly refer to same .
Comments: 10 Pages. Originally published in General Science Journal
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This is a general question, but let's talk Java for the example.
Primitive types byte and short are signed. If I'm not too wrong, the sign bit is the leftmost.
Here's some code (in Java) with simple masking:
1 byte b = -100;
2 short s = -100;
5 System.out.println(b & 0xFF);
6 System.out.println(s & 0xFF);
7 System.out.println((byte)(b & 0xFF));
8 System.out.println((byte)(s & 0xFF));
Masking with all 8 bits 'on' for the byte value, means (I think) that line 5 should print -100. But it prints 156.
Line 6 prints 156, which is more or less expected since the sign bit is lost(?)
Lines 7 and 8 print -100, which means that somehow the short's sign bit was shifted to the right by 8 positions.
So, what exactly is going on with masking and casting? Why I don't get -100 from line 5 and why I get -100 from line 8? | <urn:uuid:12b2d5d6-4334-4990-838d-388b032fac00> | 3.109375 | 245 | Q&A Forum | Software Dev. | 106.768845 | 95,572,991 |
Nearby Planet is a Target in Search For Life
Astronomers have found a cool, Earth-sized planet that's relatively close to our Solar System, reported BBC.
The properties of this newly discovered planet - called Ross 128 b - make it a prime target in the search for life elsewhere in the cosmos.
At just 11 light-years away, it's the second closest exoplanet of its kind to Earth.
But the closest one, known as Proxima b, looks to be less hospitable for life.
Found in 2016, it orbits the star Proxima Centauri, which is known to be a rather active "red dwarf" star. This means that powerful eruptions of charged particles periodically batter Proxima b with harmful radiation.
The new planet, Ross 128 b, orbits a star that's not dissimilar to Proxima Centauri (it's also a red dwarf), but is significantly less active.
The new world was discovered by a team using the High Accuracy Radial velocity Planet Searcher (Harps) instrument at the La Silla Observatory in Chile. The work will be published in the journal Astronomy & Astrophysics.
Dr Astudillo-Defru said the find was the result of more than a decade of "intensive monitoring" using the Harps instrument.
Ross 128 b orbits 20 times closer to its star than the Earth orbits the Sun. But because its parent star is much smaller and dimmer than our yellow sun, it receives only a little more solar radiation than Earth.
Consequently, it is expected to have a surface temperature close to that on our own planet.
In the search for habitable worlds beyond our Solar System, astronomers generally look for low-mass, rocky and temperate planets like our own.
But these are comparatively difficult to detect; most of the 3,500 known exoplanets are so-called Hot Jupiters - huge gas giants orbiting very close to their parent stars that don't have suitable conditions for life.
Of the smaller contingent of Earth-sized planets, the vast majority orbit red dwarf stars - the most common type in the Milky Way. Because this category of star is dim, it's easier for astronomers to detect low-mass planets when they pass in front (as viewed from Earth), blocking out a portion of the light.
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- » EU Health Commissioner: The Measures taken by Bulgaria on Rinderpest are Strictly in Line with the EC’s Recommendations | <urn:uuid:b13b5a68-8521-4861-af6c-7087b181e2eb> | 3.6875 | 584 | Truncated | Science & Tech. | 45.448387 | 95,573,008 |
Mathematical Methods for Physical Sciences II
by Christoph Kirsch
Publisher: University of North Carolina 2011
Number of pages: 209
Topics covered: Introduction to boundary value problems for the diffusion, Laplace and wave partial differential equations; Bessel functions and Legendre functions; Introduction to complex variables including the calculus of residues.
Home page url
Download or read it online for free here:
by Ivan S. Sokolnikoff - McGraw Hill
The chief purpose of the book is to help to bridge the gap which separates many engineers from mathematics by giving them a bird's-eye view of those mathematical topics which are indispensable in the study of the physical sciences.
by Jean Gallier
From the table of contents: Linear Algebra; Determinants; Basics of Affine Geometry; Polynomials, PID's and UFD's; Topology; Differential Calculus; Zorn’s Lemma and Some Applications; Gaussian elimination, LU-factoring and Cholesky-factoring.
by J. Carlson, A. Jaffe, A. Wiles - American Mathematical Society
Guided by the premise that solving the most important mathematical problems will advance the field, this book offers a fascinating look at the seven unsolved Millennium Prize problems. This work describes these problems at the professional level.
by Christopher C. Tisdell - BookBoon
This textbook takes learning to a new level by combining free written lessons with free online video tutorials. Each section within the workbook is linked to a video lesson on YouTube where the author discusses and solves problems step-by-step. | <urn:uuid:3aeaeebb-a764-44f2-baf4-51bfff3414f6> | 2.625 | 332 | Content Listing | Science & Tech. | 29.725459 | 95,573,018 |
There are two beakers each with distilled water. One has trihydrogen borate + potassium hydroxide (H3BO3 + KOH) and the other has trihydrogen borate + sodium hydroxide (H3BO3 + NaOH).
What are the products that are formed after the solutions are heated and placed in an ice water bath?
Hint: There will be a precipitate.© BrainMass Inc. brainmass.com July 17, 2018, 10:01 am ad1c9bdddf
Boric acid is not very soluble which means that it won't dissolve well without heating. When you heat the solutions all the molecules break up into their ions. So the H3BO3 breaks up into 3 hydrogen ions and (H+) and one borate ion (BO3-). The NaOH also breaks up into the sodium ion (Na+) ...
The solution briefly explains the properties of the reactants. It also describes he best way to find out if a reaction might occur and breaks up the molecules into ions to help predict the answer. | <urn:uuid:6457b058-a898-4752-98b5-7250ee21c672> | 3.546875 | 223 | Q&A Forum | Science & Tech. | 65.575526 | 95,573,076 |
As already stressed in previous chapters, there is a priori no difficulty in envisaging a numerical solution of unstationary Navier—Stokes equations for rotational flows: the various operators are represented by discrete systems relating the values taken by velocity or vorticity components, pressure, density, temperature, etc., on a space-time grid. This grid may be spatially regular or irregular, with finite-difference, finite-volume or finite-element methods. Often an orthogonal decomposition of the flow allows a spectral method to be used (see e.g. Canuto et al. ). For incompressible two-dimensional flows, the use of the stream function permits the elimination of the pressure. It is not the aim of the present monograph to describe the various numerical methods used in the so-called Computational Fluid Dynamics. We will insist rather on the physical limitations which arise when such a simulation is performed on a turbulent flow.
KeywordsEddy Viscosity Isotropic Turbulence Inertial Range Subgrid Scale Smagorinsky Model
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|Scientific Name:||Lithobates yavapaiensis (Platz and Frost, 1984)|
Rana yavapaiensis Platz and Frost, 1984
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Georgina Santos-Barrera, Geoffrey Hammerson|
|Reviewer(s):||Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)|
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.
|Range Description:||This species ranges from western and central Arizona and southwestern New Mexico, in the USA, south to northern Sonora and northwestern Chihuahua, and south-central and southeastern California and adjacent Arizona, from San Felipe Creek to the Colorado River (Painter 1985, Jennings and Hayes 1994). It usually occurs below 1,000m asl, to 1,700m asl in central Arizona (Platz and Frost 1984, Stebbins 1985). It has apparently been extirpated in Imperial Valley, California, and along the lower Colorado River, Arizona-California, though it might be extant in some areas close to the Colorado River in Arizona (Clarkson and Rorabaugh 1989, Jennings and Hayes 1994). It has been replaced by the introduced R. berlandieri along the Colorado and Gila rivers, Arizona (Clarkson and Rorabaugh 1989). In Arizona, it is found in every county except Apache and Navajo with 57% of all localities occurring in Gila, Maricopa, and Yavapai counties (Sredl et al. 1997). It is believed to be extirpated from New Mexico (New Mexico Department of Game and Fish 1997).|
Native:Mexico; United States
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||In California, historical records are from 28 locations with the most recent observation in 1965. It has not been observed during recent general herpetological surveys in California and is believed to be extirpated (Jennings and Hayes 1994). In New Mexico, it is known from 14 historical locations. A 1995 survey of 72 potential locations in New Mexico, including six historical sites that had not been surveyed in the past 10 years, resulted in no observations. New Mexico populations are now believed to be extirpated or occurring in very low numbers (Jennings 1995, New Mexico Department of Game and Fish 1997). In Arizona, the Natural Heritage Program recorded 302 populations with 90% believed to be extant (S. Schwartz pers. comm., 1998). An extensive 1991-1996 survey in Arizona resulted in the relocation of this species at 43 of the 115 historical localities surveyed and at 61 additional new sites (Sredl et al. 1997). |
It has a widespread distribution and has a large number of occurrences. Abundance information has been collected only from a small area in New Mexico and is highly variable. Mark-recapture studies were conducted annually at six New Mexico sites from 1991-1996 resulting in highly variable population estimates among sites and annually within sites. Population estimates were determined using the Lincoln-Peterson method. Individuals were observed every year at only one of the six locations. The following are the ranges of annual population estimates: 1991 (four sites), 41-704; 1992 (four sites), 19-887; 1993 (two sites), 156-1806; 1994 (two sites), 134-863; 1995 (one site), 92; and 1996 (one site), 70. See Sredl et al. (1997) for more specific individual site information.
Populations are considered stable in central Arizona, but the remainder of the USA populations are declining or extirpated. Information is not available from Mexico. In California, the species has not been observed during any recent general herpetological surveys and is believed to be extirpated (Jennings and Hayes 1994). A 1995 survey in New Mexico, where it occurred as recently as 1985, indicates that previously viable populations are now extinct or numbers are very low (Jennings 1995). A 1991-1996 survey in Arizona indicated that populations were stable in central Arizona, dramatically declining in southeastern Arizona, and extirpated from southwestern Arizona (Arizona Game and Fish Department 1997, Sredl et al. 1997).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||This species preferably inhabits rocky streams in canyon habitats surrounded by conifer forests or ponds and stream pools, usually in areas of scrub desert. Eggs and larvae develop in quiet water.|
|Major Threat(s):||The greatest threats to this species are habitat alteration and fragmentation, and the introduction of non-native predatory and competitive fishes, crayfishes, and frogs (see Jennings and Hayes 1994, Sredl et al. 1997). Habitat alteration is the result of agricultural practices, livestock grazing, development, and reservoir construction (see Jennings and Hayes 1994). Damming, draining, and the diversion of water have fragmented formerly contiguous aquatic habitats. In many areas, fragmentation has been accentuated by introduced predatory fishes, crayfish, and bullfrogs. The species has been replaced by the introduced R. berlandieri along the Colorado and Gila rivers, Arizona (Clarkson and Rorabaugh 1989). These factors result in the blockage of potential dispersal corridors for recolonisation. Populations are also vulnerable to large-scale mortality on a frequent basis due to drought, disease, and sulphur toxicity (Sredl et al. 1997). Chytridiomycosis was confirmed in this species in 1992.|
|Conservation Actions:||This species occurs in and is being managed for on several state and federally managed lands in Arizona (Sredl et al. 1997). In Mexico it was listed as rare in 1995 (New Mexico Department of Game and Fish 1997), and is also listed by the Mexican government in the "Special Protection" (Pr) category. It is listed as endangered in California and New Mexico (Jennings and Hayes 1994). It has been bred in captivity at Phoenix Zoo.|
|Citation:||Georgina Santos-Barrera, Geoffrey Hammerson. 2004. Lithobates yavapaiensis. The IUCN Red List of Threatened Species 2004: e.T19181A8848786.Downloaded on 22 July 2018.|
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+44 1803 865913
This supplement accompanies volume 91 of the Memoirs of the Entomological Society of Canada.
Part 1. Bionimic of Seven Species in Southeastern England:
For 50 years mites of the family Phytoseiidae have been recognized as predators of phytophagous orchard-inhabiting mites, though our knowledge concerning them is slight. This paper is a study of phytoseiids in southeastern England. Phytoseiids are widely distributed in the study area. None exhibits plant-specificity, though they may show a preference for certain habitats. Each species overwinters as adult females, some on evergreen plants, others in bark crevices. Winter mortality is severe.
Though Typhlodromus pyri (Scheuten) is predacious on Panonychus ulmi (Koch) and other small acarines, plant food such as fungi and pollen is acceptable and allows both development and reproduction. These activities do not occur when only apple leaves are provided as food, though a small number of P. ulmi larvae initially eaten is sufficient to permit the phytoseiids to complete development with no other food than leaves. In the absence of plant material, approximately 25 P. ulmi larvae are required for development.
Insectary rearings estabhshed the developmental times of four common species. A field population of T. pyri Scheuten was studied in 1954 and 1955 and in 1955 several other species were also studied. Various aspects of the ecology of T. pyri were studied and related to those of its prey, P. ulmi, showing that the predator is inefficient and partially ineffective. These results were substantiated by field experimentation.
Part 2 is a taxonimic review of the family and describes 38 new species.
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Found most commonly in these habitats: 1 times found in pine forest, 1 times found in shrub steppe/conifer forest edge, 1 times found in treeline with Abies, Vaccinium, 1 times found in dry alpine meadow, 1 times found in fir/pine woodland, 1 times found in open sandy soil on ridge crest.
Found most commonly in these microhabitats: 6 times under rocks, 2 times under stone, 1 times under stone, photos, 1 times nest under stone, 1 times nest under rock, 1 times ground foragers.
Collected most commonly using these methods: 5 times search, 1 times hand collecting.
Elevations: collected from 1100 - 1981 meters, 1751 meters average
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NASA’s Hubble Space Telescope has spotted a monstrous cloud of hydrogen gas that is plummeting toward our Milky Way galaxy at nearly 1.1 million km per hour.
Though hundreds of enormous, high-velocity gas clouds whiz around the outskirts of our galaxy, this so-called “Smith Cloud” is unique because its trajectory is well known.
New Hubble observations suggest it was launched from the outer regions of the galactic disk, around 70 million years ago.
The cloud was discovered in the early 1960s by doctoral astronomy student Gail Smith, who detected the radio waves emitted by its hydrogen.
The cloud is on a return collision course and is expected to plow into the Milky Way’s disk in about 30 million years.
When it does, astronomers believe it will ignite a spectacular burst of star formation, perhaps providing enough gas to make two million Suns.
“The cloud is an example of how the galaxy is changing with time. It’s telling us that the Milky Way is a bubbling, very active place where gas can be thrown out of one part of the disk and then return back down into another,” explained team leader Andrew Fox of the Space Telescope Science Institute in Baltimore, Maryland.
Our galaxy is recycling its gas through clouds, the Smith Cloud being one example, and will form stars in different places than before.
“Hubble’s measurements of the Smith Cloud are helping us to visualise how active the disks of galaxies are,” Fox added in a NASA statement.
Astronomers have measured this comet-shaped region of gas to be 11,000 light-years long and 2,500 light-years across.
If the cloud could be seen in visible light, it would span the sky with an apparent diameter 30 times greater than the size of the full moon.
The team used Hubble to measure the Smith Cloud’s chemical composition for the first time, to determine where it came from.
They observed the ultraviolet light from the bright cores of three active galaxies that reside billions of light-years beyond the cloud.
The astronomers found that the “Smith Cloud” is as rich in sulfur as the Milky Way’s outer disk, a region about 40,000 light-years from the galaxy’s centre (about 15,000 light-years farther out than our sun and solar system).
This means that the “Smith Cloud” was enriched by material from stars. This would not happen if it were pristine hydrogen from outside the galaxy, or if it were the remnant of a failed galaxy devoid of stars.
“Instead, the cloud appears to have been ejected from within the Milky Way and is now boomeranging back,” the authors noted in a paper appeared in The Astrophysical Journal Letters. | <urn:uuid:b3430bf1-d6f6-4031-8c64-f15db9064dac> | 3.734375 | 579 | Truncated | Science & Tech. | 53.197483 | 95,573,190 |
|Theorized||Murray Gell-Mann (1962)|
|Discovered||qg: 1979 at PETRA (DESY) by TASSO, MARK-J, JADE and PLUTO experiments (see diagram 1 and review)|
0 (theoretical value)|
< (experimental limit) 1.3 meV/
|Electric charge||0 e|
|Color charge||octet (8 linearly independent types)|
|Standard Model of particle physics|
A gluon (//) is an elementary particle that acts as the exchange particle (or gauge boson) for the strong force between quarks. It is analogous to the exchange of photons in the electromagnetic force between two charged particles. In layman's terms, they "glue" quarks together, forming protons and neutrons.
In technical terms, gluons are vector gauge bosons that mediate strong interactions of quarks in quantum chromodynamics (QCD). Gluons themselves carry the color charge of the strong interaction. This is unlike the photon, which mediates the electromagnetic interaction but lacks an electric charge. Gluons therefore participate in the strong interaction in addition to mediating it, making QCD significantly harder to analyze than QED (quantum electrodynamics).
The gluon is a vector boson; like the photon, it has a spin of 1. While massive spin-1 particles have three polarization states, massless gauge bosons like the gluon have only two polarization states because gauge invariance requires the polarization to be transverse. In quantum field theory, unbroken gauge invariance requires that gauge bosons have zero mass (experiments limit the gluon's rest mass to less than a few meV/c2). The gluon has negative intrinsic parity.
This may be difficult to understand intuitively. Quarks carry three types of color charge; antiquarks carry three types of anticolor. Gluons may be thought of as carrying both color and anticolor. This gives nine possible combinations of color and anticolor in gluons. The following is a list of those combinations (and their schematic names):
- red-antired (), red-antigreen (), red-antiblue ()
- green-antired (), green-antigreen (), green-antiblue ()
- blue-antired, (), blue-antigreen (), blue-antiblue ()
These are not the actual color states of observed gluons, but rather effective states. To correctly understand how they are combined, it is necessary to consider the mathematics of color charge in more detail.
Color charge and superposition
In quantum mechanics, the states of particles may be added according to the principle of superposition; that is, they may be in a "combined state" with a probability, if some particular quantity is measured, of giving several different outcomes. A relevant illustration in the case at hand would be a gluon with a color state described by:
This is read as "red–antiblue plus blue–antired". (The factor of the square root of two is required for normalization, a detail that is not crucial to understand in this discussion.) If one were somehow able to make a direct measurement of the color of a gluon in this state, there would be a 50% chance of it having red-antiblue color charge and a 50% chance of blue-antired color charge.
Color singlet states
It is often said that the stable strongly interacting particles (such as the proton and the neutron, i.e. hadrons) observed in nature are "colorless", but more precisely they are in a "color singlet" state, which is mathematically analogous to a spin singlet state. Such states allow interaction with other color singlets, but not with other color states; because long-range gluon interactions do not exist, this illustrates that gluons in the singlet state do not exist either.
The color singlet state is:
In words, if one could measure the color of the state, there would be equal probabilities of it being red-antired, blue-antiblue, or green-antigreen.
Eight gluon colors
There are eight remaining independent color states, which correspond to the "eight types" or "eight colors" of gluons. Because states can be mixed together as discussed above, there are many ways of presenting these states, which are known as the "color octet". One commonly used list is:
These are equivalent to the Gell-Mann matrices. The critical feature of these particular eight states is that they are linearly independent, and also independent of the singlet state, hence 32 − 1 or 23. There is no way to add any combination of these states to produce any other, and it is also impossible to add them to make rr, gg, or bb the forbidden singlet state. There are many other possible choices, but all are mathematically equivalent, at least equally complicated, and give the same physical results.
Group theory details
Technically, QCD is a gauge theory with SU(3) gauge symmetry. Quarks are introduced as spinors in Nf flavors, each in the fundamental representation (triplet, denoted 3) of the color gauge group, SU(3). The gluons are vectors in the adjoint representation (octets, denoted 8) of color SU(3). For a general gauge group, the number of force-carriers (like photons or gluons) is always equal to the dimension of the adjoint representation. For the simple case of SU(N), the dimension of this representation is N2 − 1.
In terms of group theory, the assertion that there are no color singlet gluons is simply the statement that quantum chromodynamics has an SU(3) rather than a U(3) symmetry. There is no known a priori reason for one group to be preferred over the other, but as discussed above, the experimental evidence supports SU(3). The U(1) group for electromagnetic field combines with a slightly more complicated group known as SU(2) – S stands for "special" – which means the corresponding matrices have determinant 1 in addition to being unitary.
Since gluons themselves carry color charge, they participate in strong interactions. These gluon-gluon interactions constrain color fields to string-like objects called "flux tubes", which exert constant force when stretched. Due to this force, quarks are confined within composite particles called hadrons. This effectively limits the range of the strong interaction to ×10−15 meters, roughly the size of an 1atomic nucleus. Beyond a certain distance, the energy of the flux tube binding two quarks increases linearly. At a large enough distance, it becomes energetically more favorable to pull a quark-antiquark pair out of the vacuum rather than increase the length of the flux tube.
Gluons also share this property of being confined within hadrons. One consequence is that gluons are not directly involved in the nuclear forces between hadrons. The force mediators for these are other hadrons called mesons.
Although in the normal phase of QCD single gluons may not travel freely, it is predicted that there exist hadrons that are formed entirely of gluons — called glueballs. There are also conjectures about other exotic hadrons in which real gluons (as opposed to virtual ones found in ordinary hadrons) would be primary constituents. Beyond the normal phase of QCD (at extreme temperatures and pressures), quark–gluon plasma forms. In such a plasma there are no hadrons; quarks and gluons become free particles.
Quarks and gluons (colored) manifest themselves by fragmenting into more quarks and gluons, which in turn hadronize into normal (colorless) particles, correlated in jets. As shown in 1978 summer conferences the PLUTO detector at the electron-positron collider DORIS (DESY) produced the first evidence that the hadronic decays of the very narrow resonance Υ(9.46) could be interpreted as three-jet event topologies produced by three gluons. Later published analyses by the same experiment confirmed this interpretation and also the spin 1 nature of the gluon (see also the recollection and PLUTO experiments).
In summer 1979 at higher energies at the electron-positron collider PETRA (DESY) again three-jet topologies were observed, now interpreted as qq gluon bremsstrahlung, now clearly visible, by TASSO, MARK-J and PLUTO experiments (later in 1980 also by JADE). The spin 1 of the gluon was confirmed in 1980 by TASSO and PLUTO experiments (see also the review). In 1991 a subsequent experiment at the LEP storage ring at CERN again confirmed this result.
The gluons play an important role in the elementary strong interactions between quarks and gluons, described by QCD and studied particularly at the electron-proton collider HERA at DESY. The number and momentum distribution of the gluons in the proton (gluon density) have been measured by two experiments, H1 and ZEUS, in the years 1996-2007. The gluon contribution to the proton spin has been studied by the HERMES experiment at HERA. The gluon density in the proton (when behaving hadronically) also has been measured.
Color confinement is verified by the failure of free quark searches (searches of fractional charges). Quarks are normally produced in pairs (quark + antiquark) to compensate the quantum color and flavor numbers; however at Fermilab single production of top quarks has been shown (technically this still involves a pair production, but quark and antiquark are of different flavor). No glueball has been demonstrated.
Deconfinement was claimed in 2000 at CERN SPS in heavy-ion collisions, and it implies a new state of matter: quark–gluon plasma, less interacting than in the nucleus, almost as in a liquid. It was found at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven in the years 2004–2010 by four contemporaneous experiments. A quark–gluon plasma state has been confirmed at the CERN Large Hadron Collider (LHC) by the three experiments ALICE, ATLAS and CMS in 2010.
The Continuous Electron Beam Accelerator Facility at Jefferson Lab, also called the Thomas Jefferson National Accelerator Facility, in Newport News, Virginia is one of 10 Department of Energy facilities doing research on gluons. The Virginia lab is competing with another facility on Long Island, New York, Brookhaven National Laboratory, for funds to build a new electron-ion collider.
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Those clues can give scientists a better understanding of what holds the universe together.
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Research reveals starfish 'dissolved' by carbon dioxide
Scientists say bursts of carbon dioxide from industry and land run off could cause irreparable damage to marine ecosystems.
Our continued monitoring of the site directly after the carbon dioxide exposure found recovery was comparably slow, which raises concern about the ability of these systems to ‘bounce back’ after repeated acute carbon dioxide events.Heidi Burdett,
Heriot-Watt University research fellow,
Tests were carried out during a four-day experiment at Loch Sween on Scotland’s west coast, to find out how whole marine ecosystems respond to short-term carbon dioxide exposure.
The results showed that calcified organisms such as the coralline algae and starfish were dissolving.
Researchers from Heriot-Watt University in Edinburgh and Glasgow University pumped water enriched with carbon dioxide into chambers placed over the coralline algal ecosystem and monitored the community’s response before, during and after exposure.
Heidi Burdett, Heriot-Watt University research fellow, said: “We found that there was a rapid, community-level shift to net dissolution, meaning that within that community, the skeletons of calcifying organisms like starfish and coralline algae were dissolving.
“If you think of pulses of carbon dioxide being carried on the tide to a particular site, it’s like a flash flood of carbon dioxide.
“Our continued monitoring of the site directly after the carbon dioxide exposure found recovery was comparably slow, which raises concern about the ability of these systems to ‘bounce back’ after repeated acute carbon dioxide events.”
Coralline algal ecosystems are very common along the west coast of Scotland, but are found in all the world’s coastal oceans. They act as nurseries for important catches like scallops, cod and pollock.
“Since coralline algae are highly calcified, we knew they would probably be quite sensitive to carbon dioxide,” said Heidi Burdett.
Dr Laura Foster is the MCS Head of Clean Seas and says that coastal algae are really important within coastal ecology, but they are facing increasing numbers of challenges from pollution: “Increased CO2 levels in the atmosphere result in it becoming increasingly difficult for them to calcify. Intertidal zones experience huge fluctuations in carbon dioxide making it a challenging environment for organisms, but are key habits for larvae. This has long term implications for the survival of a baseline species. We need to work on reducing our CO2 footprint- if we all take small actions then we can make significant reductions to CO2.”
In Scotland, the team concluded that more research is necessary and that carbon dioxide exposure should be taken into account by policymakers: “If a local authority or government agency is deciding the location of a new fish farm, forestry or carbon capture site, we should be looking at what marine ecosystems are nearby, and the potential for those ecosystems to be impacted by the new activities as a whole, rather than focusing on the impact on individual organisms, ” said Heidi Burdett.
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In this chapter, you learned how to query and modify data using the JDBC classes Statement, PreparedStatement, and OraclePreparedStatement. You also learned the reasons you should not use the Statement class in production code, as it does not support using bind variables. By using bind variables in your program, you not only make your application more performant and scaleable, but you also make it more secure by preventing SQL injection attacks.
You discovered how to boost application performance tremendously by using update batching, which in Oracle is available only when you use prepared statements. You saw a comparison of standard and Oracle update batching in terms of elapsed times and latch consumption, and you observed that Oracle update batching outperforms standard update batching in terms of elapsed time (in terms of latches, the difference between the two is negligible). You also saw how batching can dramatically reduce the latch consumption, thus improving scalability. You looked at how mixing interdependent batch statements in your application can sometimes lead to unexpected results.
A major take-away message from this chapter is that, if you are embedding SQL statements in your JDBC code, you should use a PreparedStatement object and use bind variables wherever appropriate. However, a strong case can also be made for wrapping your DML statements in PL/SQL packaged procedures and invoking them from JDBC using CallableStatement objects. This is what we will examine in the next chapter.
KeywordsStatement Interface Batch Size Execution Plan Prepared Statement Bind Variable
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The strategy promises to clarify the longstanding mystery of the role played by vast stretches of DNA sequence that do not code for the functional units—genes—that nevertheless may have a powerful regulatory influence. The research is described in the 12 February edition of the journal Nature.
"Our approach employs next generation sequencing technology to find regulatory regions, the 'switches' on a genome-wide scale and much more cost effectively," said Pennacchio. "It's the next layer of knowledge that's been missing."
The DOE JGI was founded in 1997 to accelerate the completion of the HGP and completed the DOE's commitment to sequence three (5, 16, 19) of the 23 chromosomes, totaling 11 percent of the human genome, and published the analysis in Nature back in 2004.
In this newly published study, Pennacchio, lead authors DOE scientist Axel Visel and postdoctoral fellow Matthew Blow, and their colleagues, describe a shortcut for identifying gene regulatory regions or the molecular switches that turn on or off gene expression.
Using what's called ChIP-Sequencing or ChIP-Seq, chromatin immunoprecipitation (ChIP) is combined with massively parallel DNA sequencing to identify binding sites of DNA-associated proteins.
Traditionally researchers have relied on evolution to guide them to non-coding sequences that are likely to have a function—such as enhancing the expression of genes. Via the public genome databases, they would align the entire human genome code with that of other vertebrate species (e.g. other mammals, birds, frogs, fish) and then look for sequences that are conserved in evolution.
"Most protein-coding sequences show signs of conservation between species, but there is also a large number of non-coding sequences that have been surprisingly well conserved for tens or even hundreds of millions of years," said Visel. "This suggests that these regions, formerly thought to be "junk" DNA, actually have some functional relevance and are under selection because sequence changes reduce fitness of affected individuals. Using such sequence conservation, we have in previous studies identified enhancer candidate regions and shown in transgenic mouse experiments that these conserved non-coding regions are in fact often enhancers that are active during embryonic development. Conservation-based methods are relatively good at finding enhancers in the genome, but an important limitation is that they don't tell us where and when that particular enhancer would be active and thereby drive the expression of its neighboring target gene(s).
The older methods lacked specificity, Blow said. "For example, if we have a gene that is important both for brain and for limb development, we would not have been able to specifically identify the enhancer sequences near that gene that would drive the expression in the brain or limb, the only way to find out was to test these activities in experiments one-by-one, which is slow and can't be done on a genomic scale.
"Using this new method, we can directly identify a genome-wide set of enhancers that are active in a particular anatomical region or tissue at a particular time-point, which is an important advantage over conservation-based methods because in addition to telling us where an enhancer is located in the genome, it also provides an initial experimental characterization where we should expect this enhancer to be active."
The team used ChIP linked with a particular enhancer-associated protein, p300, then directed DOE JGI's massively parallel next generation sequencing capacity to map several thousand sites in mouse embryonic forebrain, midbrain and limb tissue. Over 80 of these fragments were tested in transgenic mouse experiments indicating an almost perfect success rate of p300-ChIP-Seq for identifying enhancers active in vivo.
"Enhancers are especially important for regulating genes during embryonic development," said Pennacchio. "They can regulate genes over long distances and switch on their target genes during very specific time-points and in very specific anatomical structures during development. There are several examples of mutations in such enhancers that cause disease in humans because genes are not expressed at the right time or in the right place anymore. A fundamental problem in studying such enhancers is that until recently we did not have effective tools to even find them in the genome on a large scale.
Pennacchio said that this new method will prove useful to the greater genomics and biomedical community for characterizing the role of the vast non-coding regions—dubbed genome "dark matter"—about which little is known.
"These datasets will also help to identify mutations in enhancers that play a role in human disease," Pennacchio said. "Human genetic studies indicate that in many cases disease is caused by mutations in non-coding sequences, but it has been difficult to study this in detail because the function of most non-coding sequences is poorly understood. Eventually, this will be useful for purposes including disease detection and personalized medicine."
With the rapidly increasing efficiency and cost-savings of the next generation sequencing technologies, a deluge of data from individual human genomes are being to come to light, to the point where whole-genome sequencing of patients may soon become a standard diagnostic tool.
"While progress is being made towards this goal, it is important to keep in mind that our current understanding of the genome has focused on protein-coding sequences," said Pennacchio. "Datasets like the one provided through this study will be important to understand the remaining 98 percent of the genome and what its role in health and disease is."
The published study provides an important proof of principle to establish and validate a new method in three different mouse tissues at a single embryonic time-point, Pennacchio said. "We can now generate genome-wide enhancer datasets directly from human tissues and compare genome-wide sets of enhancer activities between healthy people and people suffering from disease, which may reveal how enhancer activities change on a global scale in these disease states."
David Gilbert | EurekAlert!
Further reports about: > ChIP-Seq > ChIP-Sequencing > DNA > DNA sequence > DNA-associated proteins > Genom > Nature Immunology > biofuels production > chromatin immunoprecipitation > embryonic development > human genome > molecular tools > multicellular organisms > non-coding sequence > on-off switches in genomes > protein-coding genes
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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.
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Atoms, Nature, and Man
by Neal O. Hines
Publisher: United States Atomic Energy Commission 1966
Number of pages: 65
This booklet describes the environmental investigations that have been conducted with the aid of the atom since the first atomic detonation near Alamogordo, New Mexico, in 1945. The story is one of beginnings that point the way, it is hoped, to a new understanding of the world in the atomic future.
Home page url
Download or read it online for free here:
by Walter Pfeifer - arXiv
This work introduces into the Interacting Boson Model, created in 1974 and then extended by numerous papers. Many-body configurations with s- and d-boson states are described and creation- and annihilation-operators for bosons are introduced.
- International Atomic Energy Agency
This reference book for graduate students provides an introduction to nuclear fusion and its prospects, and features specialized chapters written by leaders in the field, presenting the main research and development concepts in fusion physics.
by Feriz Adrovic - InTech
This book brings new research insights on the properties and behavior of gamma radiation, studies from a wide range of options of gamma radiation applications in Nuclear Physics, industrial processes, Environmental Science, Radiation Biology, etc.
by Joseph P. Hornak - Rochester Institute of Technology
Nuclear magnetic resonance, or NMR as it is abbreviated by scientists, is a phenomenon which occurs when the nuclei of certain atoms are immersed in a static magnetic field and exposed to a second oscillating magnetic field. | <urn:uuid:9ebfa0c1-1a93-4a2d-9c2b-bd7862e2cd58> | 2.515625 | 321 | Content Listing | Science & Tech. | 20.018322 | 95,573,244 |
the most basic physical constituents of the universe.
Molecules are built up from the atom, which is the basic unit of any chemical element. The atom in turn is made from the proton, neutron, and electron. It turns out that protons and neutrons are made of varieties of a still smaller particle called the quark. At this time it appears that the two basic constituents of matter are the lepton (of which the electron is one type) and quark; there are believed to be six types of each. Each type of lepton and quark also has a corresponding antiparticle: a particle that has the same mass but opposite electrical charge and magnetic moment. An isolated quark has never been found—quarks appear to almost always be found in pairs or triplets with other quarks and antiquarks (the resulting particles being classed as hadrons, more than 200 of which have been identified). Four-, five-, and six-quark particles have also been theoretically predicted; there is some experimental evidence for extremely short-lived four-quark particles in the very high-energy environments created by collisions in particle accelerators.
The most familiar lepton is the electron; the other five leptons are the muon, the tau particle, and the three types of neutrino associated with each: the electron neutrino, the muon neutrino, and the tau neutrino. The six quarks have been whimsically named up, down, charm, strange, top (or truth), and bottom (or beauty); the top quark, which has a mass greater than an entire atom of gold, is about 35 times heavier than the next biggest quark and may be the heaviest particle nature has ever created. The quarks found in ordinary matter are the up and down quarks, from which protons and neutrons are made. A proton, for instance, consists of two up quarks and a down quark, and a neutron consists of two down quarks and an up quark. The pentaquark consists of two up quarks, two down quarks, and the strange antiquark. (Quarks have fractional charges of one third or two thirds of the basic charge of the electron or proton.)
The elementary particles of matter interact with one another through four distinct types of force: gravitation, electromagnetism, and the forces from strong interactions and weak interactions. A given particle experiences certain of these forces, while it may be immune to others. The gravitational force is experienced by all particles. The electromagnetic force is experienced only by charged particles, such as the electron and muon. The strong nuclear force is responsible for the structure of the nucleus, and only particles made up of quarks participate in the strong nuclear interaction or force. Other particles, including the electron, muon, and the three neutrinos, do not participate in the strong nuclear interactions but only in the weak nuclear interactions associated with particle decay.
Each force is carried by an elementary particle. The electromagnetic force, for instance, is mediated by the photon, the basic quantum of electromagnetic radiation. The strong force is mediated by the gluon, the weak force by the W and Z particles, and gravity is thought to be mediated by the graviton. Quantum field theory applied to the understanding of the electromagnetic force is called quantum electrodynamics, and applied to the understanding of strong interactions is called quantum chromodynamics. In 1979 Sheldon Glashow, Steven Weinberg, and Abdus Salam were awarded the Nobel Prize in Physics for their work in demonstrating that the electromagnetic and weak forces are really manifestations of a single electroweak force. A unified theory that would explain all four forces as manifestations of a single force is being sought.
The behavior of all known subatomic particles can be described within a single theoretical framework called the Standard Model. This model incorporates the quarks and leptons as well as their interactions through the strong, weak and electromagnetic forces. Only gravity remains outside the Standard Model. The force-carrying particles are called gauge bosons, and they differ fundamentally from the quarks and leptons. The fundamental forces appear to behave very differently in ordinary matter, but the Standard Model indicates that they are basically very similar when matter is in a high-energy environment.
Although the Standard Model does a credible job in explaining the interactions among quarks, leptons, and bosons, the theory does not include an important property of elementary particles, their mass. The lightest particle is the electron and the heaviest particle is believed to be the top quark, which weighs at least 200,000 times as much as an electron. In 1964 several physicists working independently proposed a mechanism that provided a way to explain how these fundamental particles could have mass. They theorized that the whole of space is permeated by a field, now called the Higgs field, similar in some ways to the electromagnetic field. As particles move through space they travel through this field, and if they interact with it they acquire what appears to be mass. A basic part of quantum theory is wave-particle duality—all fields have particles associated with them. The particle associated with the Higgs field is the Higgs particle or Higgs boson, a particle with no intrinsic spin or electrical charge. Although it is called a boson, it does not mediate force as do the other bosons (see below). Finding it was the key to discovering whether the Higgs field exists, whether hypothesis for the origin of mass was indeed correct, and whether the Standard Model would survive. Data from Fermilab and CERN experiments suggested that the Higgs particle existed, and in 2012 CERN scientists announced the discovery of a new elementary particle consistent with a Higgs particle; CERN confirmed the discovery in 2013. Some theorists have proposed, as a result of experiments at Fermilab in which a greater matter-antimatter asymmetry occured than would be expected under the Standard Model, that there might be multiple Higgs particles with different charges.
Two types of statistics are used to describe elementary particles, and the particles are classified on the basis of which statistics they obey. Fermi-Dirac statistics apply to those particles restricted by the Pauli exclusion principle; particles obeying the Fermi-Dirac statistics are known as fermions. Leptons and quarks are fermions. Two fermions are not allowed to occupy the same quantum state. Bose-Einstein statistics apply to all particles not covered by the exclusion principle, and such particles are known as bosons. The number of bosons in a given quantum state is not restricted. In general, fermions compose nuclear and atomic structure, while bosons act to transmit forces between fermions; the photon, gluon, and the W and Z particles are bosons.
Basic categories of particles have also been distinguished according to other particle behavior. The strongly interacting particles were classified as either mesons or baryons; it is now known that mesons consist of quark-antiquark pairs and that baryons consist of quark triplets. The meson class members are more massive than the leptons but generally less massive than the proton and neutron, although some mesons are heavier than these particles. The lightest members of the baryon class are the proton and neutron, and the heavier members are known as hyperons. In the meson and baryon classes are included a number of particles that cannot be detected directly because their lifetimes are so short that they leave no tracks in a cloud chamber or bubble chamber. These particles are known as resonances, or resonance states, because of an analogy between their manner of creation and the resonance of an electrical circuit.
See table entitled Elementary Particles.
Some conservation laws apply both to elementary particles and to microscopic objects, such as the laws governing the conservation of mass-energy, linear momentum, angular momentum, and charge. Other conservation laws have meaning only on the level of particle physics, including the three conservation laws for leptons, which govern members of the electron, muon, and tau families respectively, and the law governing members of the baryon class.
New quantities have been invented to explain certain aspects of particle behavior. For example, the relatively slow decay of kaons, lambda hyperons, and some other particles led physicists to the conclusion that some conservation law prevented these particles from decaying rapidly through the strong interaction; instead they decayed through the weak interaction. This new quantity was named "strangeness" and is conserved in both strong and electromagnetic interactions, but not in weak interactions. Thus, the decay of a "strange" particle into nonstrange particles, e.g., the lambda baryon into a proton and pion, can proceed only by the slow weak interaction and not by the strong interaction.
Another quantity explaining particle behavior is related to the fact that many particles occur in groups, called multiplets, in which the particles are of almost the same mass but differ in charge. The proton and neutron form such a multiplet. The new quantity describes mathematically the effect of changing a proton into a neutron, or vice versa, and was given the name isotopic spin. This name was chosen because the total number of protons and neutrons in a nucleus determines what isotope the atom represents and because the mathematics describing this quantity are identical to those used to describe ordinary spin (the intrinsic angular momentum of elementary particles). Isotopic spin actually has nothing to do with spin, but is represented by a vector that can have various orientations in an imaginary space known as isotopic spin space. Isotopic spin is conserved only in the strong interactions.
Closely related to conservation laws are three symmetry principles that apply to changing the total circumstances of an event rather than changing a particular quantity. The three symmetry operations associated with these principles are: charge conjugation (C), which is equivalent to exchanging particles and antiparticles; parity (P), which is a kind of mirror-image symmetry involving the exchange of left and right; and time-reversal (T), which reverses the order in which events occur. According to the symmetry principles (or invariance principles), performing one of these symmetry operations on a possible particle reaction should result in a second reaction that is also possible. However, it was found in 1956 that parity is not conserved in the weak interactions, i.e., there are some possible particle decays whose mirror-image counterparts do not occur. Although not conserved individually, the combination of all three operations performed successively is conserved; this law is known as the CPT theorem.
The first subatomic particle to be discovered was the electron, identified in 1897 by J. J. Thomson. After the nucleus of the atom was discovered in 1911 by Ernest Rutherford, the nucleus of ordinary hydrogen was recognized to be a single proton. In 1932 the neutron was discovered. An atom was seen to consist of a central nucleus—containing protons and, except for ordinary hydrogen, neutrons—surrounded by orbiting electrons. However, other elementary particles not found in ordinary atoms immediately began to appear.
In 1928 the relativistic quantum theory of P. A. M. Dirac hypothesized the existence of a positively charged electron, or positron, which is the antiparticle of the electron; it was first detected in 1932. Difficulties in explaining beta decay (see radioactivity) led to the prediction of the neutrino in 1930, and by 1934 the existence of the neutrino was firmly established in theory (although it was not actually detected until 1956). Another particle was also added to the list: the photon, which had been first suggested by Einstein in 1905 as part of his quantum theory of the photoelectric effect.
The next particles discovered were related to attempts to explain the strong interactions, or strong nuclear force, binding nucleons (protons and neutrons) together in an atomic nucleus. In 1935 Hideki Yukawa suggested that a meson (a charged particle with a mass intermediate between those of the electron and the proton) might be exchanged between nucleons. The meson emitted by one nucleon would be absorbed by another nucleon; this would produce a strong force between the nucleons, analogous to the force produced by the exchange of photons between charged particles interacting through the electromagnetic force. (It is now known, of course, that the strong force is mediated by the gluon.) The following year a particle of approximately the required mass (about 200 times that of the electron) was discovered and named the mu meson, or muon. However, its behavior did not conform to that of the theoretical particle. In 1947 the particle predicted by Yukawa was finally discovered and named the pi meson, or pion.
Both the muon and the pion were first observed in cosmic rays. Further studies of cosmic rays turned up more particles. By the 1950s these elementary particles were also being observed in the laboratory as a result of particle collisions produced by a particle accelerator.
One of the current frontiers in the study of elementary particles concerns the interface between that discipline and cosmology. The known quarks and leptons, for instance, are typically grouped in three families (where each family contains two quarks and two leptons); investigators have wondered whether additional families of elementary particles might be found. Recent work in cosmology pertaining to the evolution of the universe has suggested that there could be no more families than four, and the cosmological theory has been substantiated by experimental work at the Stanford Linear Accelerator (now SLAC National Accelerator Laboratory) and at CERN, which indicates that there are no families of elementary particles other than the three that are known today.
- See Interactions: A Journey through the Mind of a Particle Physicist and the Matter of This World (1988). ,
- From Quarks to the Cosmos (1989). ; ,
The basic building blocks of matter. At present the only truly elementary particles containing no internal subcomponents are believed to be ...
Subatomic particles that are thought to be indivisible. Atoms that make up ordinary matter are not the smallest indivisible units of mass. Each...
A particle that, as far as is known, is not composed of other simpler particles. Elementary particles represent the most basic constituents of... | <urn:uuid:bc25eb70-3b2f-441a-87c8-fac5e2da61c6> | 4 | 2,958 | Knowledge Article | Science & Tech. | 33.408387 | 95,573,252 |
The unit of electric resistance in the centimeter-gram-second electromagnetic system of units. A conductor has a resistance of 1 abohm when the potential difference between the two ends of the conductor is 1 abvolt when a current of 1 abampere flows through it. Symbol, abΩ. One abohm = 10-9 ohm.
The prefix ab- comes from “absolute.” See ab- for the history of this prefix, which was always more popular in the United States than elsewhere. The rise of the metric system and subsequently SI eliminated any need for this unit. By the end of the 20th century, it was out of use.
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According to the current national standard in the United States¹, the abohm is not to be used. The ohm should be used instead.
1. IEEE/ASTM SI 10™-2002.
American National Standard for Use of the International System of Units (SI): The Modern Metric System.
New York: IEEE, 30 December 2002.
See Section 3.3.3.
For an excellent history of the development of the electric and magnetic units up to 1913, see U. S. Bureau of Standards Circular 60.
Dr. Kennelly has put forward an ugly system of nomenclature for absolute electromagnetic and electrostatic units which will hardly find favour in this country. [Britain] He proposes to employ the prefixes “ab” and “abstat” to designate absolute electromagnetic and electrostatic units respectively, so that abvolt represents the electromagnetic unit of potential and abstatvolt the electrostatic unit. For euphony he suggests absohm, rather than abohm for the electromagnetic unit of resistance.
All these propositions, strange to say, have been accepted by the American Institute of Electrical Engineers. Representative institutions in all other countries have been asked to consider them, and doubtless the subject will soon be opened for discussion at the Institution of Electrical Engineers.
The Electrician, vol 52, no. 1334, page 275 (Dec. 11, 1903).
Copyright © 2000-2015 Sizes, Inc. All rights reserved.
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Virginia Institute of Marine Science
Data report (Virginia Institute of Marine Science) ; no. 52.
The Chesapeake Bay Water Quality Monitoring Program (WQMP) has three main objectives: (1) characterization of water quality conditions, (2) detection of temporal and spatial trends in water quality, and (3) creation of a data base that furthers our understanding of the processes that control water quality in the Chesapeake Bay system. The purpose of this report is to characterize water quality conditions in the Virginia portion of Chesapeake Bay during the 1993 water year, which runs from October 1992 through September 1993. These monitoring efforts have been conducted with funding from the US Environmental Protection Agency and the Commonwealth of Virginia.
Water Quality, Chesapeake Bay, VA
Curling, K., & Neilson, B. (1994) Water quality in Chesapeake Bay : Virginia portion, water year 1993 : a report to the Virginia Department of Environmental Quality. Data report (Virginia Institute of Marine Science) ; no. 52.. Virginia Institute of Marine Science, College of William and Mary. https://doi.org/10.21220/V5TK5K | <urn:uuid:48ace49c-e8fc-4618-8b44-6d13726071a4> | 2.8125 | 234 | Knowledge Article | Science & Tech. | 37.396701 | 95,573,281 |
In their studies, two teams of scientists used the cosmological Lambda-Cold Dark Matter model, which stipulates that dark matter and dark energy comprise more than 95 percent of the universe, while the remaining 4.6 percent include the ordinary (Baryonic) matter consisting of protons, neutrons and electrons. Dark matter, as opposed to normal matter, is still a cosmic mystery, but at least we've solved the question of where all of this previously-theoretical normal matter is coming from. This mismatch is known as the "missing baryon problem". The particles have been studied by two different teams, and were situated at different distances from Earth. These particles serve a rather poetic role in the universe as they form a vast web, linking galaxies together through filaments of hot gas.
The scientists analyzed data obtained by the orbiting observatory Planck, created to study the cosmic microwave background (CMB), which remained after the Universe became transparent to thermal radiation. As the light travels, some of it scatters off the electrons in the gas, leaving a dim patch in the cosmic microwave background - our snapshot of the remnants from the birth of the cosmos. This phenomenon allowed the researchers to see strands of matter that are normally far too dim to observe.
Hidden cameras found in Longboat Key Airbnb
The home-sharing company has permanently banned Natt, and is working with local law enforcement in their on-going investigation. Starnes reckons the bedroom camera recorded him naked. "I hope more victims will come forward", Starnes said.
Using data from the Planck satellite, the teams were able to combine galaxy data in bulk and compare them to see the tiny differences that might highlight these filaments.
One team, led by researchers from the University of British Columbia, found out that density of these filaments is just under three times the average density of baryons in the surrounding void.
The Milky Way and Andromeda galaxies. He said the studies go "a long way" in showing that many of our fundamental ideas about space appear to be right.
Donald Trump will not meet Queen on downgraded visit
Foreign Office sources confirmed there were no current plans for a state visit but said a working visit "could happen". The first real clue that the planned State Visit would not be going ahead in 2017 came in the Queen's Speech in June .
"Everybody sort of knows that it has to be there, but this is the first time that somebody - two different groups, no less - has come up with a definitive detection", says Ralph Kraft at the Harvard-Smithsonian Center for Astrophysics in MA.
Tanimura's paper has been submitted for publication in the Monthly Notices for the Royal Astronomical Society, while de Graaff's has been submitted to the Nature journal.
Women not allowed to fly home after plastic surgery leaves them unrecognisable
Jian Hua Hua, a Chinese TV anchor, shared the photo on Weibo of the incident. However, some netizens reflected that going under the knife is not a crime. | <urn:uuid:4cca38af-b512-49d4-b5da-2df0b007b240> | 2.78125 | 624 | News Article | Science & Tech. | 40.706601 | 95,573,300 |
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel have demonstrated for the first time how electrons are transported from a superconductor through a quantum dot into a metal with normal conductivity. This transport process through a quantum dot had already been calculated theoretically in the nineties, but scientists at the University of Basel have now succeeded in proving the theory with measurements. They report on their findings in the scientific journal “Physical Review Letters”.
Transport properties such as electrical conductivity play an important role in technical applications of new materials and electronic components. Completely new phenomena occur, for example, when you combine a superconductor and nanometer-sized structures, known as quantum dots, in a component.
Researchers at the University of Basel working under Professor Christian Schönenberger have now constructed such a quantum dot between a superconductor and a metal with normal conductivity to study electron transport between the two components.
It should in fact be impossible to transport electrons from the superconductor through a quantum dot at low energies. Firstly, electrons never occur on an individual basis in a superconductor but rather always in two's or in so-called Cooper pairs, which can only be separated by relatively large amounts of energy. Secondly, the quantum dot is so small that only one particle is transported at a time due to the repulsive force between electrons.
In the past, however, scientists have repeatedly observed that a current nonetheless runs between the superconductor and the metal – in other words, electron transport does occur through the quantum dot.
First evidence of the transport mechanism through a quantum dot
On the basis of quantum mechanics, theories were developed in the nineties which indicated that the transport of Cooper pairs through a quantum dot is entirely possible under certain conditions. The prerequisite is that the second electron follows the first very quickly, namely within the time roughly stipulated by Heisenberg's uncertainty principle.
The scientists at the University of Basel have now been able to accurately measure this phenomenon. In their experiments the scientists found the exact same discrete resonances that had been calculated theoretically. In addition, the team including doctoral student Jörg Gramich and his supervisor Dr. Andreas Baumgartner was able to provide evidence that the process also works when energy is emitted into the environment or absorbed from it.
“Our results contribute to a better understanding of the transport properties of superconducting electronic nanostructures, which are of great interest for quantum technology applications”, says Dr. Andreas Baumgartner.
J. Gramich, A. Baumgartner, and C. Schönenberger
Resonant and inelastic Andreev tunneling observed on a carbon nanotube quantum dot
Physical Review Letters 115, doi: 10.1103/PhysRevLett.115.216801
Dr. Andreas Baumgartner, University of Basel, Department of Physics, tel. +41 61 267 39 06, email: firstname.lastname@example.org
Reto Caluori | Universität Basel
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine | <urn:uuid:d5ebb586-7215-45cd-9598-9dd070b06b2f> | 3.5 | 1,280 | Content Listing | Science & Tech. | 35.002209 | 95,573,323 |
Authors: Peter Horst Rehm
It is well known that the electrostatic force has infinite range, but an unheralded property of this force is that as the distance between charges approaches zero the force increases without bound. Applied to the atomic nucleus, if a positive fractional charge in one nucleon (proton or neutron) can get close enough to a negative fractional charge in a neighboring nucleon, the attractive force between them would bind these nucleons in an electrostatic bond. For example, at a distance of 5% of a nucleon radius they will experience an attractive force of -25 kN. This is orders of magnitude stronger than the repulsive force between whole protons in the nucleus. Contrary to what is normally expected from the electrostatic force, such a bond would have a short range, shorter than the radius of a nucleon. Ironically, this charge-based bond would match the nuclear force’s characteristic of charge independence (affecting both neutrons and protons), because the required positive and negative fractional charges occur inside both neutrons and protons. This electrostatic bonding of fractional charges may therefore be an overlooked factor in the search for understanding the nuclear force and may shed light upon the structure of the nucleons and the atomic nucleus.
Comments: 12 Pages.
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Resultados para: principles of mathematics
MATHEMATICS; Bulmer, M G; Bulmer,(9351133)
There are many textbooks which describe current methods of statistical analysis, while neglecting related theory. There are equally many advanced textbooks which delve into the far reaches of statistical theory, while bypassing practical...sob encomenda
Presents a uniquely balanced approach that bridges introductory and advanced topics in modern mathematics An accessible treatment of the fundamentals of modern mathematics, Principles of Mathematics: A Primer provides a unique approach to...
A precursor to Russell's famous Principa Mathematica , this is one of the most original and comprehensive treatises on the logical foundation of mathematics available today.
Shiskowski,Kenneth; CTI Reviews(4024715)
Facts101 is your complete guide to Principles of Linear Algebra. In this book, you will learn topics such as as those in your book plus much more. With key features such as key terms, people and places, Facts101 gives you all the information you need...
Keener, James P.(10270849)
This book is written for beginning graduate students in applied mathematics, science, and engineering, and is appropriate as a one-year course in applied mathematical techniques (although I have never been able to cover all of this material in one...
Mathe,National Council Of Supervisors Of(3675518)
The PRIME Leadership Framework describes the leadership principles and action indicators that the National Council of Supervisors of Mathematics endorses and that all mathematics education leaders should aspire toward to create equity and excellence...
MATHEMATICS; Friedman, Bernard(9351042)
Stimulating, thought-provoking study shows how abstract methods of pure mathematics can be used to systematize problem-solving techniques in applied mathematics. Topics include methods for solving integral equations, finding Green s function for...sob encomenda | <urn:uuid:d6248291-2a7a-445b-a6ed-bce0da5bcaf6> | 3.1875 | 399 | Content Listing | Science & Tech. | 28.512619 | 95,573,383 |
That is, it's the second tropical storm that degenerated into a remnant low pressure area only to make a comeback as a tropical storm. NASA's HS3 hurricane mission sent an unmanned Global Hawk Aircraft out to the eastern Atlantic to investigate Humberto on Sept. 16.
This GOES-East image from Sept. 16 shows Tropical Storm Humberto, the Atlantic Ocean's second "zombie storm" of the year, spinning in the eastern Atlantic. Image Credit: NASA GOES Project
On Sunday, Sept. 15, Humberto weakened to a remnant low pressure area when it hit an area of strong wind shear. The wind shear eased and Humberto regained tropical storm strength on Sept. 16, making it the second "zombie" storm in the Atlantic Ocean basin this year. The first was Tropical Storm Gabrielle that fell apart and re-formed in early September in the western Atlantic.
NASA's GOES Project at the NASA Goddard Space Flight Center uses the data gathered by NOAA's GOES series of satellites and makes them into images and animations. On Sept. 16 an image was created that showed Humberto had regained form as a tropical storm.
At 11 a.m. EDT/1500 UTC, re-born Tropical Storm Humberto had maximum sustained winds near 40 mph/65 kph. The National Hurricane Center expects slow strengthening over the next couple of days. It was centered near latitude 27.2 north and longitude 43.2 west, about 1,200 miles/1,930 km southwest of the Azores Islands. Humberto is moving toward the west-northwest near 8 mph/13 kph and is expected to move northwest and then the north-northwest
NASA's Global Hawk 872 unmanned aircraft took off at 10:42 a.m. EDT from Runway 22 at NASA's Wallops Flight Facility, Wallops Island, Va., Sept. 16 to investigate the zombie storm. NASA 872 will disperse dropsondes throughout Humberto and gather data on the environment of the storm as it did on Sept. 5 with Gabrielle, the first zombie storm of the season.
Global Hawk aircraft are well-suited for hurricane investigations because they can fly for as long as 28 hours and over-fly hurricanes at altitudes greater than 60,000 feet (18.3 km).
HS3 is a mission that brings together several NASA centers with federal and university partners to investigate the processes that underlie hurricane formation and intensity change in the Atlantic Ocean basin. Among those factors, HS3 will address the controversial role of the hot, dry and dusty Saharan Air Layer in tropical storm formation and intensification and the extent to which deep convection in the inner-core region of storms is a key driver of intensity change. The HS3 mission will operate between Aug. 20 and Sept. 23.Text credit: Rob Gutro
Rob Gutro | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:e9beb9e3-3fd3-43c6-bf76-6cfc0d1dfbaa> | 3.0625 | 1,226 | Content Listing | Science & Tech. | 51.744732 | 95,573,399 |
eventqent Struct Reference
Linked list of events. Global events are appended to the list by append_event()
. The usecount is the number
of stored pointers to the element, excluding the list pointers. So an element that is only in the list has a usecount of 0, not 1.
Clients have a pointer to the last event processed, and for each of these clients we track the usecount of the elements. If we have a pointer to an entry in the list, it is safe to navigate it forward because elements will not be deleted, but only appended. The worst that can happen is seeing the pointer still NULL.
When the usecount of an element drops to 0, and the element is the first in the list, we can remove it. Removal is done within the main thread, which is woken up for the purpose.
For simplicity of implementation, we make sure the list is never empty.
Definition at line 1337 of file manager.c.
The documentation for this struct was generated from the following file: | <urn:uuid:1900da8c-ca9f-41e4-8876-a2d3d500c490> | 2.578125 | 219 | Documentation | Software Dev. | 60.355431 | 95,573,401 |
- Potential Energy Control
User can create, shape and manipulate the potential energy, i.e., the energy of an object relating to its state of being or position. The energy is stored in the object and remains there, so long as the object remains unaltered or stationary. Potential refers to the possibility of the energy's use in the future in some capacity. Potential energy is connected to forces. When a force acts on an object with potential energy, it is transformed into a new type of energy (electricity, heat, light, sound, kinetic energy, etc.).
- Chemical Generation
- Deformation Manipulation
- Energy Containment
- Energy Conversion
- Energy Generation
- Kinetic Energy Manipulation
- Mechanical Energy Manipulation
- Physical Change Manipulation
- Potential Force Manipulation
- Process Speed Manipulation - Take underlying potential energy and use to accelerate it to its penultimate state.
- Chemical Energy Manipulation - energy stored in biomass, fuel substances.
- Elastic Energy Manipulation - energy stored in elastic substances.
- Electricity Manipulation - energy stored in object with electric charge in relation to proximity to other electrically charged objects; can also act as kinetic energy.
- Gravitational Energy Manipulation - energy stored in object in relation to it's height above ground.
- Magnetic Energy Manipulation - energy stored in object related to position within a magnetic field.
- Nuclear Manipulation - energy stored in atom's nucleus.
- Chemical Reaction Manipulation
- Gravity Manipulation
- Energy Manipulation
- Fundamental Forces Manipulation
- Physical Energy Manipulation
- Requires an acting force for the energy to be used.
- May not have control over what new energy is produced.
- May not have any more potential energy after new energy is produced.
- Altering object's state or position may affect is overall potential energy.
- Quantum Zone (Marvel Comics) | <urn:uuid:2c460c62-93bf-44ac-b90d-299eb695e7ab> | 3.4375 | 391 | Structured Data | Science & Tech. | 1.305496 | 95,573,405 |
24 March 2005
Despite the efforts deployed to understand the GOMOS instrument anomaly, the investigation team does not yet fully comprehend the problem.
The SCIAMACHY sensor aboard Envisat has performed the first space-based measurements of the global distribution of near-surface methane, one of the most important greenhouse gases. As reported in Thursday's issue of Science Express, the results show larger than expected emissions across tropical land regions.
18 March 2005
Envisat radar imagery confirms that the B-15A iceberg ? the world's largest floating object ? is adrift once more after two months aground on a shallow seamount. This latest development poses a renewed threat to the nearby pier of land-attached ice known as the Drygalski ice tongue.
11 March 2005
Spring gets off to an unseasonal start across Europe: this Envisat image from last week shows the continent covered by snow all the way down from Sweden down to Italy.
10 March 2005
Acquired from orbit 800 kilometres away, this Envisat image shows two volcanoes erupting simultaneously on Russia's snowy Kamchatka Peninsula this week.
10 March 2005
Australian researchers have found Envisat's MERIS sensor can detect coral bleaching down to ten metres deep. This means Envisat could potentially monitor impacted coral reefs worldwide on a twice-weekly basis.
Two satellite sensors work better than one for the study of Earth's oceans, atmosphere and land - that was the message of a major ESA workshop bringing together scientific users of Envisat's MERIS and AATSR instruments.
Three of the world's largest and fastest yachts are in the midst of a non-stop trans-global race, hurtling in excess of 25 knots - 46 kilometres per hour - through the Southern Ocean encircling Antarctica. Iceberg collision is a real risk, but ice-sensitive radar satellites are monitoring the area to provide advance warning to crews.
Spring starts early this year in Norway's fjords and coastal waters, with sunny weather awakening a colourful bloom of marine phytoplankton. ESA's Envisat spacecraft is being used to monitor its development.
04 March 2005
A colourful view of the Bangladesh coastline to mark the week of ESA's Envisat environmental satellite's third anniversary in orbit.
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The three-dimensional structure of the local universe may one day become as familiar as our local geography, thanks to a new generation of maps that reveal our neighborhood's rich complexity and our place within it.
Image courtesy of Courteois et al.
The geography of our world is one of the great cultural constants. There is hardly a person on this planet who is unfamiliar with the shape of the continents and the way they dovetail together, or who doesn't know that Earth is a pale blue sphere orbiting the Sun with seven other planets.
When given a three-dimensional model of the solar system, almost everyone can zoom in from beyond the Oort cloud to Earth and then even further — to the street where they live, for example. It is powerful shared knowledge.
But at greater distances, our geographical knowledge becomes a little blurred. Many people will have seen the extraordinary three-dimensional models of the filamentary structures that galaxies form on the larger scales in our universe.
And yet these structures remain strangely unfamiliar. Given an unlabeled three-dimensional model of this large-scale structure of the universe, who could point to the place we call home?
All that should begin to change in the next few years with the increasingly accurate maps that cosmologists are compiling of the three-dimensional distribution of galaxies within universe.
Today, Helene Courtois at the University of Lyon in France and her research team show off this newfound knowledge in a movie (and accompanying paper) that they've created to explore the rich structure of our galactic neighborhood.
You can view the movie here.
One of the key questions that this data can help answer is whether the distribution of visible mass in the universe is an accurate reflection of the distribution of dark matter. Courtois and co so that the data shows that this is indeed the case.
The film does a fine job of showing the three-dimensional structure of this space. It also reveals the limitations of human language in describing this complex tapestry. That's not so surprising given that our vocabulary has evolved to describe a geography that is essentially two-dimensional.
Just how to describe our position within the three-dimensional filamentary structure of the universe is a challenge that astronomers will have to wrestle with in the coming years.
And since this presents a rather different challenge than ordinary geography, researchers have coined a new term to describe this kind of intergalactic mapping — cosmography.
We can expect to see more of these kinds of 3D maps of the universe as the data becomes better and more easily accessible — and as cosmography grows into a science in its own right. Perhaps one day these depictions will appear as familiar to us as the shapes of continents on this pale blue dot.
Image courtesy of William L. Stefanov, NASA-JSC.
- China is giving Daimler the keys to test self-driving cars on its roads
- The tech behind the Thailand cave rescue
- Twitter is booting more than a million fake accounts a day
- First evidence that amino acids formed soon after the Big Bang
This article originally published at MIT Technology Review here | <urn:uuid:ee8c609f-7f1f-4ace-9eb1-41103702150f> | 3.671875 | 638 | News Article | Science & Tech. | 38.713202 | 95,573,418 |
Newtonian fluid mechanics
The previous chapter has shown how plant flowsheets can be constructed and analysed, and how the viability of a project approximately can be costed. In the flowsheets discussed in Chapter 1, no account was made of how food material moves from one plant unit to another. The next stage of design is to make accurate estimates of the size of these units and of the flows between them. The prediction of the way fluids flow is vital in engineering design, for example in the calculation of pipe sizes and pump duties. It is also necessary to have some idea of the history of the fluid during processing; in food systems, as will be seen later, the range of velocities in the flow can affect the amount and range of thermal processing a fluid receives, and thus can affect the safety and quality of the final product.
KeywordsReynolds Number Pressure Drop Laminar Flow Friction Factor Newtonian Fluid
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- Coulson, J.M. and Richardson, J.F. (1977) Chemical Engineering, Volume 1, Pergamon, London.Google Scholar
- Kay, J.M. and Nedderman, R.M. (1985) Fluid Mechanics and Transport Processes, Cambridge University Press, Cambridge.Google Scholar
- Tritton, D.J. (1988) Physical Fluid Dynamics, 2nd edn, Chapman & Hall, London.Google Scholar | <urn:uuid:13051b05-7726-4b4d-8d73-95e1799b6010> | 2.859375 | 301 | Truncated | Science & Tech. | 57.022355 | 95,573,433 |
An international research team, including University of Minnesota researcher Craig Packer, has found the first clear example of how climate extremes, such as the increased frequency of droughts and floods expected with global warming, can create conditions in which diseases that are tolerated individually may converge and cause mass die-offs of livestock or wildlife.
The study, published June 25 by PloS (Public Library of Science) ONE, an online peer-reviewed research journal, suggests that extreme climatic conditions are capable of altering normal host-pathogen relationships and causing a "perfect storm" of multiple infectious outbreaks that could trigger epidemics with catastrophic mortality.
Led by scientists at the University of California, Davis, the University of Illinois and the University of Minnesota, the research team examined outbreaks of canine distemper virus (CDV) in 1994 and 2001 that resulted in unusually high mortality of lions in Tanzania's Serengeti National Park and Ngorongoro Crater. CDV periodically strikes these ecosystems, and most epidemics have caused little or no harm to the lions.
But the fatal virus outbreaks of 1994 and 2001 were both preceded by extreme drought conditions that led to debilitated populations of Cape buffalo, a major prey species of lions. The buffalo suffered heavy tick infestations and became even more common in the lions' diet, resulting in unusually high levels of tick-borne blood parasites in the lions. (These parasites are normally present in lions at harmlessly low levels.)
The canine distemper virus suppressed the lions' immunity, which allowed the elevated levels of blood parasites to reach fatally high levels, leading to mass die-offs of lions. In 1994 the number of lions in the Serengeti study area dropped by over 35 percent after the double infection. Similar losses occurred in the Crater die-off in 2001.
The lion populations recovered within 3-4 years after each event, but most climate change models predict increasing frequency of droughts in East Africa.
"The study illustrates how ecological factors can produce unprecedented mortality events and suggests that co-infections may lie at the heart of many of the most serious die-offs in nature," said Packer, Distinguished McKnight University Professor of Ecology, Evolution and Behavior at the University of Minnesota.
The study was funded by the National Science Foundation and the Morris Animal Foundation.
Patty Mattern | EurekAlert!
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine | <urn:uuid:49a77c5f-c870-4611-a46c-cc0e4c19e294> | 3.328125 | 1,131 | Content Listing | Science & Tech. | 34.099299 | 95,573,441 |
National Nuclear Science Week (NNSW), a celebration to focus local, regional and national interest on all aspects of nuclear science, will be recognized for the fourth year on October 21-25, 2013. Observations of the week will include an array of week-long educational activities in South Carolina, mass field trips to the National Museum of Nuclear Science & History in New Mexico, and much more.
The week is a national, broadly observed recognition of how nuclear science plays a vital role in the lives of Americans - and the world. Activities during the week are intended to build awareness of the contributions of the nuclear science industry and those who work in it every day.
National Nuclear Science Week has the theme “Get to Know Nuclear.” The goal of the week is to encourage education, participation and communication around themes that are promoted on each day of the week. This year’s main National Celebration Event is a collaboration between SRS Community Reuse Organization and its affiliated Nuclear Workforce Initiative, taking place in South Carolina and Georgia. This week of activities includes education days hosted for students of all ages at institutes such as the University of South Carolina Aiken and the Ruth Patrick Science Education Center. A Workforce Development Day will also take place, hosted at the Kroc Center in Augusta, GA, on Tuesday, October 22, where high school seniors and college students can interact with current nuclear professionals, view interesting exhibits and learn about career topics in the world of nuclear technology – from nuclear medicine to emerging energy technology.
“With the nation’s spotlight on energy generation and a greener environment, it makes sense to recognize the contributions of nuclear power. Other technologies, such as nuclear medicine with its diagnostic and treatment opportunities, are also hugely important to all Americans,” states the Director of the National Museum of Nuclear Science & History, Jim Walther. “The future career opportunities in science and energy are significant as well. This week provides all of us with more information on these vital topics.”
The Web site is http://www.NuclearScienceWeek.org and features a “celebration guide” that includes free tips and tools such as a proclamation template for those wishing to create their own celebration. There are also suggestions for activities each day of the week. Followers can also access news about the week through Twitter, Facebook and a nuclear science week blogspot.
National Nuclear Science Week is a partnership between the host organization, the National Museum of Nuclear Science & History, in Albuquerque, New Mexico, and nuclear industry partners, including the SRS Community Reuse Organization, Nuclear Energy Institute, Entergy, the US Department of Energy, the American Nuclear Society, and the Society of Nuclear Medicine & Molecular Imaging.
For more information on the Museum, visit http://www.nuclearmuseum.org or call 505-245-2137.
Any individual, from a professional photographer to a student with a camera phone, is invited to share their photographic talent and eye for everything that is Science, Technology, Engineering, Art and Mathematics (STEaM) for a chance for a cash prize and to have their work on display this fall at our museum!Learn More
The National Museum of Nuclear Science & History will host "Science is Everywhere" Summer Camp 2018 for children who are 6 to 12 years old. Experience the wonders of science in week-long sessions, May 29 - August 10. Sessions include "Code of the Robot," "Chemistry and Intrigue," "Science of the X-scape," "STEMinists," "Spy Kids" and many more!Learn More
The National Museum of Nuclear Science & History will be hosting a workshop on $martPath, a new, online teaching resource for grades 1-8 geared towards economic and financial education. At the workshop, teachers will receive a walkthrough of the award-winning platform and discuss best practices for implementing $martPath in their classroom.Learn More | <urn:uuid:cc029212-c94f-4b72-937e-0fbbac440fa2> | 2.65625 | 805 | News (Org.) | Science & Tech. | 30.337195 | 95,573,489 |
Origin of Ultra-Fast Black Hole Winds Observed
Astronomers have made the most detailed observation yet of an ultra-fast wind emanating from a Black Hole at a quarter of the speed of light. Using the European Space Agency (ESA)’s XMM-Newton and NASA’s NuSTAR telescopes, the scientists observed the phenomenon in an active galaxy known as IRAS 13224-3809.
Outflowing gas is a common features of the supermassive black holes that reside at the centre of large galaxies. Often millions of times more massive than the Sun, these black holes feed off the surrounding gas that swirls around them. Space telescopes observe this as a bright light from the innermost part of the disc around the black hole.
Occasionally the black holes consume too much gas and release an ultra-fast wind. These winds are an important characteristic to study because they could have a strong influence on regulating the growth of the host galaxy by clearing the surrounding gas away and therefore suppressing the birth of stars.
Using ESA’s XMM-Newton and NASA’s NuStar telescopes, scientists have now made the most detailed observation yet of such an outflow. The winds recorded from the black hole reach 71,000 km/s, a quarter of the speed of light, putting it in the top 5% of fastest known black hole winds. XMM-Newton focused on the black hole for 17 consecutive days, revealing the extremely variable nature of the winds.
“We often only have one observation of a particular object, then several months or even years later we observe it again and see if there’s been a change,” says Dr Michael Parker of the Institute of Astronomy at the University of Cambridge, UK, lead author on a paper published in Nature this week which describes the discovery. Thanks to this long observation campaign, we observed changes in the winds on a timescale of less than an hour for the first time.”
The changes were seen in the increasing temperature of the winds, a signature of their response to greater X-ray emission from the disc right next to the black hole. Furthermore, the observations also revealed changes to the chemical fingerprints of the outflowing gas: as the X-ray emission increased, it stripped electrons in the wind from their atoms, erasing the wind signatures seen in the data.
“The chemical fingerprints of the wind changed with the strength of the X-rays in less than an hour, hundreds of times faster than ever seen before,” says co-author Professor Andrew Fabian, also from the Institute of Astronomy, and principal investigator on the project.
“It allows us to link the X-ray emission arising from the material falling into the black hole, to the variability of the outflowing wind farther away.” Dr Parker adds: “Black hole winds are one of the mechanisms for feedback, where the energy coming out from the black hole regulates the growth of the host galaxy. Understanding these winds is crucial to understanding how galaxies, including our own, grow.”
Parker, M. L., Pinto, C., Fabian, A. C., Lohfink, A., Buisson, D. J., Alston, W. N., . . . Zoghbi, A. (2017). The response of relativistic outflowing gas to the inner accretion disk of a black hole. Nature, 543(7643), 83-86. doi:10.1038/nature21385
This article has been republished from materials provided by the University of Cambridge. Note: material may have been edited for length and content. For further information, please contact the cited source.
How do Forests Respond to Atmospheric Pollution?News
How forests respond to elevated nitrogen levels from atmospheric pollution is not always the same. While a forest is filtering nitrogen as expected, a higher percentage than previously seen is leaving the system again as the potent greenhouse gas nitrous oxide, say researchers.READ MORE | <urn:uuid:102eaf2e-5f51-47d5-a761-ecc9783f8828> | 3.5625 | 830 | News Article | Science & Tech. | 52.737308 | 95,573,495 |
(CPV) - Vietnamese and Japanese researchers have been successfully completing an international project "For the Development of crop genotypes for the midlands and mountain areas of North Vietnam". They developed new rice variety with scientific guarantees of high yielding, short growth duration, disease and insect resistance by introducing useful genes and the most advanced molecular biological technology. The five-year project (from December 2010 to November 2015) is financed by Japan International Cooperation Agency (JICA), has been implemented by Vietnam National University of Agriculture (VNUA), Kyushu University and Nagoya University of Japan. "The plant breeding in Vietnam had repeated rat races for many years due to the lack of scientific proofs of improved performance. With the new technology transferred by Japan, we can make long selling product with authentic proofs of science and guarantee stable production and profit for producers," said Dr. Pham Van Cuong, Vice … [Read more...] about Japanese science and technology marks drastic change in Vietnamese plant breeding
Molecular science and technology
In a side column to the article entitled In Vietnam, genetically modified organisms find fertile ground to grow, Dr. Vandana Shiva, the Indian scientist and renowned activist on food security and food sovereignty, was quoted as follows: "When corporations claim patents [on seeds], they basically 'pirate' traits that nature and farmers have evolved. This is not innovation, it is bio-piracy." Bio-piracy On February 3, 2014, 34 farmers', breeders', environmental and development organizations from 27 European countries filed an opposition to a patent from Syngenta, the Swiss agrochemical corporation, which notably is one of the three foreign companies designated to plant their Genetically Modified Organism (GMO) corn varieties in Vietnam. Why this broad opposition to a particular patent? On May 8, 2013, the European Patent Organization (EPO) had granted a patent (EP 2140023B1) to Syngenta for insect resistant pepper (capsicum) plants. In fact, as it is stated in the press release of the … [Read more...] about Bio-piracy, defamation and the irony of history
The University of Medicine in Ho Chi Minh City January 9 organized the 23rd Youth Technology and the 31st Science and Technology conferences.As many as students and lecturers participated in the conferences reporting 351 projects in the fields of internal medicine, anatomy, nerves, and gerontology. Professor Le Van Cuong, head of the university's Science Department, students and lecturers have carried out more than 300 scientific projects at grassroots level and 12 others at municipal level. Moreover, the university has been assigned to conduct 4 additional projects. Total spending for scientific projects and science-related activities is around VND13 billion (US$616,700).In the future, the school will strengthen science-related researches and invest more in advanced technologies such as molecular biology and laparoscopic surgery. … [Read more...] about University of Medicine to enhance science-related researches
"Using every objective measurement, it seems that Vietnam's science and technology is a failure…," according to a report by the famous HarvardUniversity. Dr. Pham Duc Chinh at the Mechanics Institute analyses the weakness of science in Vietnam. In the world, the capability of scientists and nations is evaluated firstly by the number of articles published in international scientific magazines and the number of patents granted by prestigious international agencies. The US-based Institute for Scientific Information (ISI) made statistics from nearly 10,000 outstanding scientific magazines selected from over 100,000 magazines worldwide. According to ISI, in 11 years, from January 1997 to December 2007, Vietnamese scientists in 17 fields (clinical health, physics, zoology and botany, technology, biology and biochemistry, chemistry, agriculture, microorganism sciences, the environment, material sciences, immunization studies, pharmacy, molecular biology and genetics, neurology, … [Read more...] about Why is science in Vietnam underdeveloped?
By Tuong Vi - The Saigon Times Daily HCMC - The Vietnam National University of HCMC (VNU-HCM) has announced it will join forces with an American educational institution to set up a molecular and nano architectures center next year. The local university and University of California, Los Angeles expect to launch the MANAR-VN Center in March where research on sciences, and molecular and nano architectures will be conducted, said Hoang Dung, director of the Science and Technology Department at VNU-HCM. Speaking to the Daily on Monday on the sidelines of a meeting between Omar M. Yaghi, director of MANAR-USA, and students of the University of Natural Sciences in HCMC, Dung said the center would also research metal organic framework and evolving organic structures. MANAR-VN will provide postgraduate courses following international standards, and cooperate with local and foreign firms in research and technology transfers in areas such as energy, environmental protection, and biomedicine. … [Read more...] about University plans molecular and nano architectures center | <urn:uuid:d4c05e5f-e896-4c30-8af1-d4b62738a356> | 2.671875 | 1,017 | Content Listing | Science & Tech. | 23.213877 | 95,573,497 |
The planet of Vuvv has seven moons. Can you work out how long it is between each super-eclipse?
Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.
Suppose we allow ourselves to use three numbers less than 10 and multiply them together. How many different products can you find? How do you know you've got them all?
Make a pair of cubes that can be moved to show all the days of the month from the 1st to the 31st.
How many ways can you find to do up all four buttons on my coat? How about if I had five buttons? Six ...?
Six friends sat around a circular table. Can you work out from the information who sat where and what their profession were?
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.
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 use this information to work out Charlie's house number?
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!
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.
When newspaper pages get separated at home we have to try to sort them out and get things in the correct order. How many ways can we arrange these pages so that the numbering may be different?
These activities lend themselves to systematic working in the sense that it helps if you have an ordered approach.
Ten cards are put into five envelopes so that there are two cards in each envelope. The sum of the numbers inside it is written on each envelope. What numbers could be inside the envelopes?
My cube has inky marks on each face. Can you find the route it has taken? What does each face look like?
What could the half time scores have been in these Olympic hockey matches?
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!
These activities focus on finding all possible solutions so working in a systematic way will ensure none are left out.
On my calculator I divided one whole number by another whole number and got the answer 3.125. If the numbers are both under 50, what are they?
Use the clues to work out which cities Mohamed, Sheng, Tanya and Bharat live in.
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?
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?
Alice and Brian are snails who live on a wall and can only travel along the cracks. Alice wants to go to see Brian. How far is the shortest route along the cracks? Is there more than one way to go?
Lolla bought a balloon at the circus. She gave the clown six coins to pay for it. What could Lolla have paid for the balloon?
Can you create jigsaw pieces which are based on a square shape, with at least one peg and one hole?
What is the smallest number of jumps needed before the white rabbits and the grey rabbits can continue along their path?
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?
In a bowl there are 4 Chocolates, 3 Jellies and 5 Mints. Find a way to share the sweets between the three children so they each get the kind they like. Is there more than one way to do it?
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?
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.
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?
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.
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?
Find the product of the numbers on the routes from A to B. Which route has the smallest product? Which the largest?
How many shapes can you build from three red and two green cubes? Can you use what you've found out to predict the number for four red and two green?
Systematically explore the range of symmetric designs that can be created by shading parts of the motif below. Use normal square lattice paper to record your results.
In a square in which the houses are evenly spaced, numbers 3 and 10 are opposite each other. What is the smallest and what is the largest possible number of houses in the square?
In this challenge, buckets come in five different sizes. If you choose some buckets, can you investigate the different ways in which they can be filled?
The Vikings communicated in writing by making simple scratches on wood or stones called runes. Can you work out how their code works using the table of the alphabet?
The Zargoes use almost the same alphabet as English. What does this birthday message say?
I was in my car when I noticed a line of four cars on the lane next to me with number plates starting and ending with J, K, L and M. What order were they in?
This tricky challenge asks you to find ways of going across rectangles, going through exactly ten squares.
Put 10 counters in a row. Find a way to arrange the counters into five pairs, evenly spaced in a row, in just 5 moves, using the rules.
Seven friends went to a fun fair with lots of scary rides. They decided to pair up for rides until each friend had ridden once with each of the others. What was the total number rides?
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.?
Sitting around a table are three girls and three boys. Use the clues to work out were each person is sitting.
Place eight dots on this diagram, so that there are only two dots on each straight line and only two dots on each circle.
Only one side of a two-slice toaster is working. What is the quickest way to toast both sides of three slices of bread?
My cousin was 24 years old on Friday April 5th in 1974. On what day of the week was she born?
Can you arrange 5 different digits (from 0 - 9) in the cross in the way described? | <urn:uuid:5ff5fa63-792b-4071-83bb-7e1deb1cb2c6> | 3.84375 | 1,551 | Content Listing | Science & Tech. | 73.93315 | 95,573,520 |
Physico-Chemical Concepts on the Fate of Organic Compounds
The concentration, behavior, and eventual fate of an organic compound in the aquatic environment are determined by a number of physico-chemical and biological processes. These processes include sorption-desorption, volatilization, and chemical and biological transformation. Solubility, vapor pressure, and the partition coefficient of a compound determine its concentration and residence time in water and hence the subsequent processes in that phase. The movement of an organic compound is largely dependent upon the physico-chemical interactions with other components of the aquatic environment. Such components include suspended solids, sediments, and biota.
KeywordsOrganic Compound Vapor Pressure Partition Coefficient Photochemical Reaction Molecular Volume
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- Briggs, G.G. 1973. A simple relationship between soil adsorption of organic chemicals and their octanol/water partition coefficients. Proceedings of the 7th British Insecticide and Fungicide Conference 1:83–86.Google Scholar
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The cell membrane structure consist of a double layer of lipid molecules in which proteins are embedded. The major membrane lipids are phospholipids. These are amphipathic molecules: one end has a charged region, and the remainder of the molecule, which consists of two long fatty acid chains, is nonpolar. The phospholipids in cell membranes are organized into a bimolecular layer with the nonpolar fatty acid chains in the middle. The polar regions of the phospholipids are oriented toward the surfaces of the membrane as a result of their attraction to the polar water molecules in the extracellular fluid and cytosol. No chemical bonds link the phospholipids to each other or to the membrane proteins, and therefore, each molecule is free to move independently of the others. This results in considerable random lateral movement of both membrane lipids and proteins parallel to the surfaces of the bilayer. In addition, the long fatty acid chains can bend and wiggle back and forth. Thus, the lipid bilayer has the characteristics of a fluid, much like a thin layer of oil on a water surface, and this makes the membrane quite flexible. This flexibility, along with the fact that cells are filled with fluid, allows cells to undergo considerable changes in shape without disruption of their structural integrity. Like a piece of cloth, membranes can be bent and folded but cannot be stretched without being torn.
The plasma membrane also contains cholesterol (about one molecule of cholesterol for each molecule of phospholipid), whereas intracellular membranes contain very little cholesterol. Cholesterol, a steroid, is slightly amphipathic because of a single polar hydroxyl group on its nonpolar ring structure. Therefore, cholesterol, like the phospholipids, is inserted into the lipid bilayer with its polar region at a bilayer surface and its nonpolar rings in the interior in association with the fatty acid chains. Cholesterol associates with certain classes of plasma membrane phospholipids and proteins, forming organized clusters that function in the pinching off of portions of the plasma membrane to form vesicles that deliver their contents to various intracellular organelles. There are two classes of membrane proteins: integral and peripheral. Integral membrane proteins are closely associated with the membrane lipids and cannot be extracted from the membrane without disrupting the lipid bilayer. Like the phospholipids, the integral proteins are amphipathic, having polar amino acid side chains in one region of the molecule and nonpolar side chains clustered together in a separate region. Because they are amphipathic, integral proteins are arranged in the membrane with the same orientation as amphipathic lipids—the polar regions are at the surfaces in association with polar water molecules, and the nonpolar regions are in the interior in association with nonpolar fatty acid chains. Like the membrane lipids, many of the integral proteins can move laterally in the plane of the membrane, but others are immobilized because they are linked to a network of peripheral proteins located primarily at the cytosolic surface of the membrane.
Most integral proteins span the entire membrane and are referred to as transmembrane proteins. Most of these transmembrane proteins cross the lipid bilayer several times. These proteins have polar regions connected by nonpolar segments that associate with the nonpolar regions of the lipids in the membrane interior. The polar regions of transmembrane proteins may extend far beyond the surfaces of the lipid bilayer. Some transmembrane proteins form channels through which ions or water can cross the membrane, whereas others are associated with the transmission of chemical signals across the membrane or the anchoring of extracellular and intracellular protein filaments to the plasma membrane. Peripheral membrane proteins are not amphipathic and do not associate with the nonpolar regions of the lipids in the interior of the membrane. They are located at the membrane surface where they are bound to the polar regions of the integral membrane proteins. Most of the peripheral proteins are on the cytosolic surface of the plasma membrane where they are associated with cytoskeletal elements that influence cell shape and motility. | <urn:uuid:cfe78931-e9e4-4e73-94f4-fe981af6acef> | 4 | 853 | Knowledge Article | Science & Tech. | 18.871908 | 95,573,523 |
By Stephen Bucaro
Certain characters have programming meaning to the Java Script interpreter, so you
may have problems with them when using them in a string. For example a string is
enclosed in either single or double quotes. You can't use the same type of quote within
the string because when the Java Script interpreter comes upon it, it will think it has
reached the end of the string. Another example is if you want to put a new line in a
string, you just can't hit the keyboard [Enter] key.
If you need to use one of these characters in a string, you need to substitute it
with an "escape sequence". Sometimes escape sequence is called "escape characters".
The sequence of characters in an escape sequence informs the Java Script interpreter
of how to interpret the characters. Shown below are the most useful escape sequences.
|' ||\' |
|" ||\" |
|\ ||\\ |
|new line||\n |
|tab ||\t |
Shown below is an example of using escape sequences.
This will not work:
var myString = "The file you seek is in the "toys\games" folder";
The same string with characters substituted with escape sequences:
var myString = "The file you seek is in the \"toys\\games\" folder";
More Java Script Code:
• The Document Object Model (DOM)
• The do/while Loop
• Java Script Math.sin Method
• Get Webpage File Date and File Size
• Remove Blank Spaces From Ends of a String
• The Location Object
• The Conditional Operator
• Determine Absolute Value
• Java Script Events | <urn:uuid:1bb3a509-b276-4a40-a5fa-14435b7c8992> | 3.515625 | 354 | Documentation | Software Dev. | 43.727197 | 95,573,529 |
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Fitting and Averaging in cosmology: Dynamical and observational aspects George F R Ellis University of Cape Town. SIGRAV and INFN School GGI, Firenze: 2009. The Acceleration of the universe. The explanation of dark energy is a central pre-occupation of present day cosmology.
SIGRAV and INFN School
GGI, Firenze: 2009
The explanation of dark energy is a central pre-occupation of present day cosmology.
Its presence is indicated by the recent speeding up of the expansion of the universe indicated by supernova observations
confirmed by other observations such as those of the cosmic background radiation anisotropies and large scale clustering
Its nature (whether constant, or varying) is a major problem for theoretical physics
. The deduction of the existence of dark energy is based on the assumption that the universe has a Robertson-Walker geometry
- spatially homogeneous and isotropic on a large scale.
The observations can at least in principle be accounted for without the presence of any dark energy, if we consider the possibility of inhomogeneity
This can happen in two ways:
locally via backreaction associated with averaging, plus associated observational effects (this talk)
by large scale inhomogeneity (next talk)
Any mathematical description of a physical system depends on an averaging scale characterizing the nature of the
envisaged model. This averaging scale is usually hidden from view: it is taken to be understood.
Thus, when a fluid is described as a continuum, this assumes one is using an averaging scale large enough that the size of individual molecules is negligible. If the averaging scale is close to molecular scale, small changes in the position or size of the averaging volume lead to large changes in the measured density and velocity of the matter, as individual molecules are included or excluded from the reference volume. Then the fluid approximation is no longer applicable.
.Each variable definition hides an
averaging scale: e.g. density of gas
Usual work referring to the fluid density and velocity assumes a medium--size averaging scale: not so small that molecular effects matter, but not so large that spatial gradients in the properties of the fluid are significant.
The actual averaging scale, or rather the acceptable range of averaging scales, is not explicitly stated but is in fact a key--feature underlying the description used, and hence the effective macroscopic dynamical laws investigated.
Indeed, different types of physics (particle physics, atomic
physics, molecular physics, macroscopic physics, astrophysics) correspond to different assumed averaging scales. Thus, instead of referring to a density function ρ, one should really refer to a function ρ(L): the density averaged over volumes characterized by scale length L.
The key--point about the fluid approximation is that, provided this length scale is in the appropriate domain, then its actual value does not matter; i.e. when it is in this range, then changing L by a factor of 10, 100, or even much more makes no difference: the measured density and average velocity will not change.
But if you change L by a very large amount until outside this range, this is no longer true.
Hence, there is a range of validity L1 < L < L2 where the fluid approximation holds and explicit mention of the associated averaging scale may be omitted.
Relations between scales: lower level relations underlie higher ones, but
There is a non-commutativity of averaging with dynamics and observations
Averaging leads to extra terms in effective higher level equations
Cosmology: contribution to dark energy?
Multiple scales of representation of same system
Implicit averaging scale
Stars, clusters, galaxies, universe
polarization effects result from a large--scale field being applied to a medium with many microscopic charges. The macroscopic field E differs from the point--to—point microscopic field which acts on the individual charges, because of a fluctuating internal field Ei , the total internal field at each point being D = E + Ei
Spatially averaging, one regains the average field because the internal field cancels out: E = <D>, indeed this is how the macroscopic field is defined (implying invariance of the background field under averaging: E = <E> ).
On a microscopic scale, however, the detailed field D is the effective physical quantity, and so is the field ``measured'' by electrons and protons at that scale. Thus, the way different test objects respond to the field crucially depends on their scale. A macroscopic device will measure the averaged field.
Exactly the same issue arises with regard to the gravitational field. The solar system tests of general relativity theory are at solar system scales. We apply gravitational theory, however, at many other scales: to star clusters, galaxies, clusters of galaxies, and cosmology.
Cosmology utilizes the largest scale averaging envisaged in astrophysics: a representative scale is assumed that is a significant fraction of the Hubble scale, and the cosmological velocity and density functions are defined by averaging on such scales.
The General Relativistic cosmological perturbation solutions used to study structure formation embody two interacting levels: the background (zero--order) model, almost always a Robertson—Walker metric, and the perturbed (first--order) model representing the growth of inhomogeneities, represented by a perturbed Robertson--Walker metric.
Both are quite different than the solar system scale where the EFE are tested.
The question then is how do models on two or more different scales relate to each other in Einstein's gravitational theory. This is a difficult issue both because of the non--linearity of Einstein's equations, and because of the lack of a fixed background spacetime -- one of the core features of Einstein's theory. This causes major problems in defining suitable averaging processes as needed in studying these processes.
Averaging and calculating the field equations do not commute
G. F. R. Ellis: ``Relativistic cosmology: its nature, aims and problems". In General Relativity and Gravitation, Ed B Bertotti et al (Reidel, 1984), 215.
Has implications for cosmology (Kolb, Mataresse, Buchert, Wiltshire, et al.)
Averaging and calculating the field equations
do not commute
g1ab R1ab G1ab = T1abScale 1
g3ab R3ab G3ab= T3ab Scale 3
averaging gives different answer
Metric tensor: gabĝab =‹gab›
Inverse Metric tensor: gabĝab =‹gab›
but not necessarily inverse …
need correction terms to make it the inverse
Connection: Γabc‹Γabc› + Cabc
new is average plus correction terms
Curvature tensor plus correction terms
Ricci tensor plus correction terms
Field equations G ab =Tab + Pab
The problem with such averaging procedures is that they are not covariant. Can’t average tensor fields in covariant way (coordinate dependent results).
They can be defined in terms of the background unperturbed space, usually either flat spacetime or a Robertson--Walker geometry, and so will be adequate for linearized calculations where the perturbed quantities can be averaged in the background spacetime.
But the procedure is inadequate for non--linear cases, where the integral needs to be done over a generic lumpy (non--linearly perturbed) spacetime that are not ``perturbations'' of a high--symmetry background. However, it is precisely in these cases that the most interesting effects will occur.
Can’t average tensor fields in covariant way (coordinate dependent results)
Can use bitensors (Synge) for curvature and matter, but not for metric itself: and leads to complex equations
R Zalaletdinov“The Averaging Problem in Cosmology and Macroscopic Gravity” Int. J. Mod. Phys. A 23: 1173 (2008) [arXiv:0801.3256]
Scalars: can be done (Buchert),
But: usually incomplete, so hides effects
Peter Szekeres developed a polarization formulation for a
gravitational field acting in a medium, in analogy to electromagnetic polarization. He showed that the linearized Bianchi identities for an almost flat spacetime may be expressed in a form that is suggestive of Maxwell's equations with magnetic monopoles.
Assuming the medium to be molecular in structure, it is shown how, on performing an averaging process on the field
quantities, the Bianchi identities must be modified by the inclusion of polarization terms resulting from the induction of quadrupole moments on the individual ``molecules''. A model of a medium whose molecules are harmonic oscillators is discussed and constitutive equations are derived.
G ab =Tab + Pab . , Pab = Qabcd;cd
that is Pab is expressed as the double divergence of an effective quadrupole gravitational polarization tensor with suitable symmetries:
Qabcd = Q[ab][cd] = Qcdab
Gravitational waves are demonstrated to slow down in such a medium. Thus the large scale effective equations include polarisation terms, as in the case of electromagnetism
P Szekeres: “Linearised gravitational theory in macroscopic media” Ann Phys 64: 599 (1971)
Buchert equations for scalars gives modified Friedmann equation
T Buchert “Dark energy from structure: a status report”. GRG Journal 40: 467 (2008) [arXiv:0707.2153].
Expansion and averaging do not commute:
in any domain D, for any field Ψ
∂t<Ψ> - <∂tΨ> = <θΨ> - <θ><Ψ>
Buchert equations for scalars gives modified Friedmann and Raychaudhuri equations: e.g.
∂t<Θ>D = Λ - 4πGρD + 2 <II>D - <I>D2
where II = Θ2/3 - σ2 and I = Θ.
This in principle allows acceleration terms to arise from the averaging process
Claim: weak field approximation is adequate and shows effect is negligible (Peebles)
Counter claim: it certainly matters
Kolb, Mattarrese, others
NB one can check if it can explain dark energy issue fully
But if not it might still upset the cosmic concordance: it might show spatial sections are not actually flat
Fully explain it? Maybe:
B.M. Leith, S.C.C. Ng and D.L. Wiltshire
"Gravitational energy as dark energy: Concordance of cosmological tests" Astrophys. J. 672, L91 (2008) [arXiv:0709:2535].
T. Mattsson “Dark energy as a mirage” (2007) [arXiv:0711.4264]
But others disagree:
S. Rasanen: “Evaluating backreaction with the peak model of structure formation”arxiv:0801.2692 (2008).
But then it still can alter basic relations: density to curvature
Ricci focusing and Weyl focusing
B. Bertotti “The Luminosity of Distant Galaxies” Proc Royal Soc London. A294, 195 (1966).
dθ/dv = -RabKaKb - 2σ2 – θ2
d σmn/dv = - Emn
Θ = expansion
σ = shear
Rab = Ricci tensor, determined pointwise by matter
Eab = Weyl tensor, determined non-locally by matter
zero Weyl tensor and non-zero Ricci tensor.
dθ/dv = -RabKaKb
d σmn/dv = 0
Actual observations are best described by zero Ricci tensor and non-zero Weyl tensor
dθ/dv = - 2σ2 – θ2
d σmn/dv = - Emn
This averages out to FRW equations when averaged over whole sky But supernova observations are preferentially where there is no matter
Dyer Roeder equations take matter into account but not shear: allows a fraction of the uniform density
C. C Dyer. & R C Roeder, “Observations in Locally Inhomogeneous Cosmological Models” Astrophysical Journal, Vol. 189: 167 (1974)
NB: must take shear and caustics into account
Claim: averaging over whole sky leads to standard FRW form
Not obvious! It does not follow from energy conservation (Weinberg):
- depends on how area distances average out
Swiss-Cheese models: FRW regions joined to vacuum regions Exact inhomogeneous solutions
The null geodesic equations can be exactly integrated in each domain and matched. Includes shear effects.
Ron Kantowski has obtained analytic expressions for distance--redshift relations that have been corrected for the effects of inhomogeneities in the density.
The values of the density parameter and cosmological constant inferred from a given set of observations depends on the fractional amount of matter in inhomogeneities and can significantly differ from those obtained by using the Mattig relations for the FLRW universes.
applying the homogeneous distance--redshift relation to SN 1997ap at z = 0.83 could be as much as 50% lower than its true value.”
R. Kantowski “The Effects of Inhomogeneities on Evaluating the mass parameter Ωm and the cosmological constant Λ” (1998) [astro-ph/9802208]
It could be that the apparent acceleration term detected is at least partly due to this optical effect: focusing of null geodesics is different in a lumpy universe than in a smooth one. Debatable if enough to account for apparent acceleration; probably is enough to significantly influence concordance model values.
What is the best background model?
Gauge freedom with change of background model,
And of fitting of perturbed model to background model
The variables and their dynamical equations depend on this fitting, which will take presumably place by some process of averaging
Change of background model changes effects!
Which background model to use?
G.F.R. Ellis, W.R. Stoeger: ``The fitting problem in cosmology", Class. Quant. Grav. 4 (1987) 1697.
An obvious approach to fitting is some kind of averaging
But what quantities should we average?
Over what surfaces/volumes should we average?
Spacelike of null averages?
Explicit or implicit (via observational relations as in usual FLRW fitting)?
Without insufficient care, adding in a statistical distribution of density perturbations can alter the average.
e.g. in lensing models
Should use compensated inhomogeneities where each overdensity is surrounded by an equal underdensity
Else changes the average density of the universe contemplated
The original background does not give a best fit any more
Use 1+3 covariant and gauge invariant variables to describe the inhomogeneous geometry and dynamics (Dunsby)
This gives exact and perturbed equations to any desired order, at the detailed scale
2. Choose a best fitting of background to real universe when doing the averaging; use this best fitting to fix the gauge and coordinates
3.Averaging via bitensors (Zalaletdinov)
4. Use only scalars: introduce a sufficient number of scalars to completely determine the spacetime geometry
The run into the equivalence problem of GR: how do you use scalars to completely characterise a solution?
Peebles, Wald, et al; negligible
Buchert, Kolb, Mattarese, Wiltshire, et al: important
Note issue of voids in universe (Wiltshire)
Not like FRW at all!
Counter claim: as there are major voids in the expanding universe a weak-field kind of approximation is not adequate
You have to model (quasi-static) voids and junction to expanding external universe
D.L. Wiltshire "Cosmic clocks, cosmic variance and cosmic averages" New J. Phys.9, 377 (2007) [arXiv:gr-qc/0702082].
: G.F.R. Ellis, T. Buchert: "The universe seen at different scales"
G F R Ellis and W R Stoeger: ``The Fitting Problem in Cosmology". CQG 4, 1679-1690 (1987). | <urn:uuid:29f7fa49-7d32-4cc9-abb1-89e4602ee722> | 2.796875 | 3,603 | Content Listing | Science & Tech. | 35.789824 | 95,573,539 |
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The Mars Science Laboratory (MSL) is a National Aeronautics and Space Administration (NASA) mission with the aim to land and operate a rover named Curiosity on the surface of Mars. Currently in transit to Mars, it was launched November 26, 2011, at 10:02 EST and is scheduled to land on Mars at Gale Crater on August 6, 2012 (about 10pm in the evening of August 5 PDT, the time used by the mission controllers in Pasadena, California). If MSL arrives at Mars, it will attempt a more precise landing than attempted previously and then help assess Mars's habitability. A primary mission objective is to determine whether Mars is or has ever been an environment able to support life, though it will not look for any specific type of life. Rather, it is intended to chemically analyze samples in various ways, including scooping up soil, drill rocks, and with a laser and sensor system. Curiosity rover is five times larger than Spirit or Opportunity Mars Exploration Rovers and carries more than ten times the mass of scientific instruments than that design. MSL was launched by an Atlas V 541 rocket and after its journey to Mars and then landing, is designed to explore for at least 687 Earth days (1 Martian year) over a range of 5-20 km (3-12 miles). Mars Science Laboratory mission is part of NASA's Mars Exploration Program, a long-term effort of robotic exploration of Mars, and the project is managed by the Jet Propulsion Laboratory of California Institute of Technology for NASA. Doug McCuistion of NASA's Planetary Science Division is the Director of the Mars Exploration Program. The total cost of the MSL project is about US$2.5 billion. MSL launched on an Atlas V rocket from Cape Canaveral on November 26, 2011. On January 11, 2012, the spacecraft successfully refined its trajectory with a three-hour series of thruster-engine firings, advancing the rover's landing time by about 14 hours. When MSL was launched, the program's director was Doug McCuistion of NASA's Planetary Science Division. Curiosity successfully landed in the Gale Crater at 05:17:57.3 UTC on August 6, 2012, and transmitted Hazcam images confirming orientation. Due to the Mars-Earth distance at the time of landing and the limited speed of radio signals, the landing was not registered on Earth for another 14 minutes. The Mars Reconnaissance Orbiter sent a photograph of Curiosity descending under its parachute, taken by its HiRISE camera, during the landing procedure. [READ THE REST OF THIS ARTICLE]
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Studying the photochemistry has shown that ultraviolet radiation can set off harmful chemical reactions in the human body and, alternatively, can provide 'photo-protection' by dispersing extra energy. To better understand the dynamics of these photochemical processes, a group of scientists irradiated the RNA base uracil with ultraviolet light and documented its behavior on a picosecond timescale. They discuss their work this week in The Journal of Chemical Physics.
A time-resolved fluorescence resonance energy transfer-based BTK occupancy assay measures target engagement in peripheral blood mononuclear cells (PBMCs) and in lymph-node and bone-marrow samples.
A new discovery in how heart muscles maintain their shape in fruit flies sheds light on the crucial relationship between cardiac function, metabolism, and longevity. Researchers have discovered that maintaining high levels of the protein vinculin confers health benefits to fruit flies. Their work, published in APL Bioengineering, shows that fruit flies bred to produce 50 percent more vinculin enjoyed better cardiovascular health and lived a third of their average life span longer.
One object has long been known: the 13-Jupiter-mass planet beta Pictoris b, one of the first planets discovered by direct imaging, back in 2009. The new object, dubbed 2MASS 0249 c, has the same mass, brightness, and spectrum as beta Pictoris b.
A new molecule designed by University of Adelaide researchers shows great promise for future treatment of many cancers.
Researchers at Purdue University and the University of Virginia have developed a new fabrication method that makes tiny, thin-film electronic circuits peelable from a surface. The technique not only eliminates several manufacturing steps and the associated costs, but also allows any object to sense its environment or be controlled through the application of a high-tech sticker.
Defects are often observed when making borophene, the single-atom form of boron, but unlike in other two-dimensional materials, these mismatched lattices can assemble into ordered structures that preserve the material's metallic nature and electronic properties. Labs at Rice and Northwestern universities made the first detailed analysis of borophene defects.
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A new study demonstrates that a correlation also exists between cumulative carbon emissions and future sea level rise over time -- and the news isn't good. | <urn:uuid:4006e175-83bf-4d2b-a468-8186c1e17b06> | 2.546875 | 570 | Content Listing | Science & Tech. | 16.51113 | 95,573,548 |
August 10 2016 Astronomy Newsletter
Here's the latest article from the Astronomy site at BellaOnline.com.
The Moon - Quiz
The Moon has been the object of awe and fascination since our humanoid ancestors first looked up into the sky. Test your knowledge about Moon and maybe find out some interesting new facts about it.
(1) August 8, 1576: Tycho Brahe laid the cornerstone for Uraniborg (castle of the heavens). It was an observatory, a palace, a laboratory and a research institute. Scholars came from around Europe to research in astronomy and a number of other disciplines.
(2) August 10, 1990: NASA's Magellan mission went into orbit around Venus. Magellan carried out radar mapping of Venus and and made global maps of the planet's gravity field.
(3) August 12, 1877: Asaph Hall discovered Mars's moon Deimos.
(4) August 12, 2005: NASA launched the Mars Reconnaisance Orbiter.
The Perseid shower comes from the debris of comet Swift-Tuttle. The debris forms a trail of particles, and it's affected by the planets, so in any give year it might be closer to us (outburst!) or farther away from Earth (disappointment). But a predicted outburst can be a disappointment too. It might not happen. Or you might miss it, as the timing is crucial - might happen during daylight where you are, or you might not be watching at the time. But you could be lucky this year.
Whatever happens, there are plenty of meteorites in this shower, and already if you're lying back tonight and enjoying a clear night sky, you might well see some. We're already into the debris stream. The numbers will keep increasing until the August 11-12 peak, and it won't end there. You can read more here: http://www.bellaonline.com/articles/art27461.asp
Please visit http://astronomy.bellaonline.com/Site.asp for even more great content about Astronomy.
I hope to hear from you sometime soon, either in the forum http://forums.bellaonline.com/ubbthreads.php/forums/323/1/Astronomy or in response to this email message. I welcome your feedback!
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I wish you clear skies.
Mona Evans, Astronomy Editor
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Lexmark International, Inc. has released the findings from its Life Cycle Assessment (LCA) study, which reveal contributors to a printer's carbon footprint and how a user can reduce them. By shrinking your printer’s carbon footprint, you’re not only helping the environment, you’re also reducing the impact on your wallet.
Windows XP Home Page If your computer runs the Windows XP operating system you owe it to yourself to spend some time on this XP Home Page, where you can find all sorts of interesting stuff. Youu can download cool applications such as Photo story 3 and Media Player 10 or join a forum of XP users to
The Green Home Makeover so your students think they're Internet experts? They probably are. Still they might enjoy these interactive lessons from the BBC on the basics of Internet use, including browsers, searching, e-mail, safety, and online communities. Who knows, they might learn even more.
Carbon Footprint Calculator The carbon calculator allows you to enter information and determine the average level of pollutants that you release into the atmosphere. The included graphics help represent your lifestyle. This site also provides suggestions for how you can lower your ecological footprint. | <urn:uuid:fd6cbc13-9f10-4561-98cd-09c1fda193ff> | 2.703125 | 242 | Truncated | Science & Tech. | 44.962246 | 95,573,568 |
Measurements of Wet and Dry Deposition in Timis County, Romania
Our agency situated in the western part of Romania, was founded in August 1990. The activity area of the agency in Timis county is based on the following data: total area 869700 hectares; population 726000; 82 cities and villages; forest covered area 108184 hectares; 9 natural reservations. A characteristic of the Timis county is the great number of livestock (ca. 2000000 animals) which induce a high pollution level. Thus NH3 is one of the most important air pollutants in this area. The complexity of the problems is also seen on the legislative side, since Timis county is close to the border and the agency has to take into account the international laws and conventions.
Precipitation measurements, performed periodically, include: volume, pH and conductivity measurements. The atmospheric pollutant concentrations are measured by means of a stationary installation, while the wet and dry depositions are determined by photo-colorimetry and gravimetry, in several places. Heavy metal depositions were monitored in collaboration. Unfortunately the anthropogenic and biogenic emissions are not evaluated.
KeywordsPrecipitation Measurement Biogenic Emission Trace Substance High Pollution Level Heavy Metal Deposition
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Statistics is the study of the collection, organization, analysis, interpretation and presentation of data. Statistics looks at all aspects of data. Statistics is mostly application based due to its numerical roots. It is usually considered a distinct mathematical science rather than a branch of mathematics. People who study statistics are called statisticians.
Statisticians will improve data quality by developing specific experiment designs and survey samples. Statistics provides tools for both predictions and forecasting - the most important use of data and statistical models. It is applicable to a wide variety of academic disciplines. The methods can summarize a collection of data. It is useful in communicating the results of experiments and research. This method is called descriptive statistics.
Statistics is closely related to probability theory. Probability starts from the given parameters of a total population to deduce probabilities that pertain to samples. Statistical inference moves in the opposite direction; it inductively infers from samples to the parameter of a total population.
Common concepts include probability distributions, density functions, z-scores, t-tests, regression analysis, hypothesis testing, ANOVA analysis, etc.© BrainMass Inc. brainmass.com July 20, 2018, 10:22 pm ad1c9bdddf | <urn:uuid:0ab8084b-80e1-4031-93c4-3bde9780efc8> | 3.640625 | 245 | Knowledge Article | Science & Tech. | 16.05535 | 95,573,592 |